Submitted Successfully!
To reward your contribution, here is a gift for you: A free trial for our video production service.
Thank you for your contribution! You can also upload a video entry or images related to this topic.
Version Summary Created by Modification Content Size Created at Operation
1
David J. Kennedy
 -- 4175 2023-08-22 04:03:21

Video Upload Options

Do you have a full video?
Send video materials Upload full video

Confirm

Are you sure to Delete?
Yes No
Cite
If you have any further questions, please contact Encyclopedia Editorial Office.
Khalaf, F.K.; Dube, P.; Mohamed, A.; Tian, J.; Malhotra, D.; Haller, S.T.; Kennedy, D.J. Cardiotonic Steroids and the Sodium Trade Balance. Encyclopedia. Available online: https://encyclopedia.pub/entry/48297 (accessed on 06 August 2024).
Khalaf FK, Dube P, Mohamed A, Tian J, Malhotra D, Haller ST, et al. Cardiotonic Steroids and the Sodium Trade Balance. Encyclopedia. Available at: https://encyclopedia.pub/entry/48297. Accessed August 06, 2024.
Khalaf, Fatimah K., Prabhatchandra Dube, Amal Mohamed, Jiang Tian, Deepak Malhotra, Steven T. Haller, David J. Kennedy. "Cardiotonic Steroids and the Sodium Trade Balance" Encyclopedia, https://encyclopedia.pub/entry/48297 (accessed August 06, 2024).
Khalaf, F.K., Dube, P., Mohamed, A., Tian, J., Malhotra, D., Haller, S.T., & Kennedy, D.J. (2023, August 22). Cardiotonic Steroids and the Sodium Trade Balance. In Encyclopedia. https://encyclopedia.pub/entry/48297
Khalaf, Fatimah K., et al. "Cardiotonic Steroids and the Sodium Trade Balance." Encyclopedia. Web. 22 August, 2023.
Cardiotonic Steroids and the Sodium Trade Balance
Edit
This entry is adapted from the peer-reviewed paper 10.3390/ijms19092576

In 1972 Neal Bricker presented the “trade-off” hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990’s Xie and Askari published seminal studies indicating that the Na+/K+-ATPase (NKA) was not only an ion pump, but also a signal transducer that interacts with several signaling partners. Since this discovery, numerous studies from multiple laboratories have shown that the NKA is a central player in mediating some of these long-term “trade-offs” of the physiological adaptation processes which Bricker originally proposed in the 1970’s. In fact, NKA ligands such as cardiotonic steroids (CTS), have been shown to signal through NKA, and consequently been implicated in mediating both adaptive and maladaptive responses to volume overload such as fibrosis and oxidative stress.

cardiotonic steroids Na+/K+-ATPase inflammation fibrosis signaling

1. Introduction

The advent of the discovery of the scaffolding and signaling functions of the NKA (Na+/K+-ATPase) twenty years ago by Xie and Askari has opened up a multitude of newly appreciated roles for the NKA in both health and disease in almost every major organ system [1][2][3].

2. Structure and Function of the Na+/K+-ATPase (NKA)

The cell membrane NKA (or sodium pump) is a member of the P-type family of active cation transport proteins [4]. Initially discovered by the late Jens Skou in 1957 as an ion pump, later studies during the last few decades have shown that the NKA has an essential cell signaling role too [5]. The NKA is the driving power for renal Na+ reabsorption and is therefore critically involved in the control of extracellular volume and blood pressure [6][7][8]. The NKA consists of two noncovalently linked polypeptides, the catalytic α subunit (≈110 kDa) and the glycosylated β (≈35 kDa) subunit, and a third recently discovered subunit, the γ (≈10 kDa) subunit, which is a member of the FXYD proteins [9]. The α subunit holds both the ATP and the ligand binding sites, and regulates ATP hydrolysis. As it hydrolyzes ATP, the NKA maintains the ionic gradient via transporting sodium and potassium ions against their concentration gradients. The β subunit is necessary for the assembly of the enzyme, while the α subunit regulates the functionality of the enzyme. Different isoforms of the α and β subunits have been recognized and are believed to have different functions [10]. The α subunit of the NKA has four isoforms (α1, α2, α3, and α4), whereas, three β (β1, β2, and β3) isoforms have been identified. Different groupings of αβ complexes exhibit different functions, characteristics, and sensitivities to different CTS [11]. The α1 isoform can form a signaling complex with signaling proteins such as Src, a tyrosine kinase. This signaling cascade regulates many essential cellular functions, in addition to sodium homeostasis, such as protein trafficking, gene expression and cell growth [12]. This signaling complex can be activated by the binding of CTS [13]. The NKA is the only P-type ATPase that has the ability to bind CTS.

3. Cardiotonic Steroids: NKA Ligands Brokering the Sodium Trade Balance

An examination of the role of the NKA in these processes would not be complete without an examination of the ligands for the NKA which drive these signaling events. The digitalis-like factors or endogenous CTS are a class of endogenous volume-sensitive hormones that can be classified structurally into two groups: cardenolides (such as ouabain, digoxin, and digitoxin) and bufadienolides (such as marinobufagenin, telocinobufagin, bufalin, and proscillardin). Cardienolide’s have a five-membered unsaturated lactone/2-pyrone ring at position C17, while bufadienolide’s have a six-membered unsaturated lactone/2-pyrone ring at position C17 [14]. Functionally, it has been shown that the levels and the activity of endogenous CTS in our body vary. Nanomolar concentrations of CTS such as MBG (marinobufagenin) and TCB (telocinobufagin) have been detected in human serum from various volume expanded states [15][16][17][18][19][20][21][22][23][24][25][26][27]. Ouabain (or ouabain-like material which is immune-reactive with ouabain antibodies) has been detected in the serum of patients with hypertension [25][28], congestive heart failure [29], and terminal renal failure [30]. While both marinobufagenin and telecinobufagin were detected in the serum of patients with end stage renal failure [27], telocinobufagin (TCB) was found at a higher concentration than that of marinobufagenin. Other studies have found that TCB has the most potent activity when compared to other CTS, and has the greatest suppressive effect on NKA [31][32][33].
CTS have a natriuretic effect and they have been known to regulate renal homeostasis. Therefore, endogenous CTS levels increase in response to volume expansion states accompanying chronic diseases, such as hypertension, heart failure, and renal disease. However, unintended effects of high concentrations of these hormones potentially contribute to disease progression [34][35][36][37][38]. Long-lasting elevation of CTS may produce “off-target” effects [39], potentially including the profibrotic and the proinflammatory effects of these hormones [40]. Hence, chronic elevation of CTS signaling through NKA has implications not only for natriuretic response to high salt and volume load, but also for pathological adaptation to these conditions [41].

4. CTS (Cardiotonic Steroids), NKA, and Fibrosis

Fibrosis in its own right can be conceptualized as a trade-off imbalance between extracellular matrix production and degradation that occurs in almost all types of chronic disease [42][43]. Several pathways and mechanisms have been described in the pathogenesis of fibrosis [43][44][45][46][47]. Recent studies have examined the role of the NKA signaling in mediating organ fibrosis. In 2009, Fedorova and coworkers showed that MBG administration induces renal fibrosis in rats. MBG targets different populations of renal cells, which then activates interstitial fibroblasts and increases collagen expression [16]. The study also showed that MBG upregulates Snail, a transcription factor that has been implicated in the differentiation of epithelial cells into mesenchymal cells (epithelial–mesenchymal transition or EMT) [37][38]. This further subsidizes the expansion of fibrosis. Elkareh and colleagues further demonstrated that nanomolar concentrations of MBG stimulate collagen synthesis and induce fibrosis in kidney and cardiovascular tissues through the NKA–Src–EGFR (Na+/K+-ATPase- Src kinase-Epidermal growth factor receptor) signaling cascade [23][48]. In animal models, it has been shown that infusion of CTS to a level similar to that seen in rodents with a partial nephrectomy activates the NKA-Src-EGFR, ERK (extracellular-signal-regulated kinase) and many other biochemical and physiological features similar to those seen in patients with uremic cardiomyopathy. Interestingly, they revealed that active immunization against CTS attenuates most of the uremic cardiomyopathy features. Additionally, Haller in 2013 showed that passive immunization against MBG significantly improved renal function and markedly reduced renal fibrosis following experimental induction of renal disease [49]. This further highlighted CTS role in the pathophysiology of CKD (chronic kidney disease) and paved the road for a new therapeutic target. Immunization against CTS might serve as a potential treatment in these high risk populations. Cheng and coworkers showed that targeting the NKA-mediated signaling could attenuate renal fibrosis. He demonstrated that suppression of Src activation and its downstream ERK1/2, p38 MAPK (mitogen activated protein kinase) and Akt (protein kinase B) signaling pathways can effectively attenuate UUO (unilateral ureteral obstruction)-induced renal fibrogenesis [50]. This profibrotic pathway of MBG also involves activation of Fli-1, a nuclear transcription factor that negatively regulates collagen synthesis [51]. In addition to this, studies that have linked the association of elevated CTS levels to renal disease and decline in renal function provide many other arguments in favor of CTS role in renal disease. Komiyama and coworkers showed that patients with end stage renal disease (ESRD) have high level of CTS in their plasma as confirmed by LC-MS [27]. Kennedy and colleagues showed that animals subjected to partial nephrectomy demonstrated elevation in CTS levels similar to that seen in patients with renal failure [23]. Adding to that, other studies have highlighted the role of CTS in different renal related conditions such as hypertension. Increased levels of CTS have also been demonstrated in pregnancy and implicated in the pathogenesis of pregnancy-induced hypertension [52][53][54][55]. CTS binding to the receptor site on the α-subunit of the NKA induces EGFR-dependent cellular signaling, which is involved in the CTS mediated pathology. Further neutralizing the effects of endogenous CTS, using intravenously administered Digibind, an anti-digoxin antibody, improves renal function by reducing the NKA inhibitory activity of CTS in plasma in patients with severe preeclampsia [52][53][54][55][56].
In addition to CTS role in mediating renal fibrosis, a number of studies, in vivo and in vitro, have shown that CTS have the capacity to induce signaling cascades, which are directly involved in the development of fibrosis in other organs, such as heart, vessel, and skin. In 2007, Elkareh showed that MBG and other cardiotonic steroids, such as ouabain and digoxin, promote collagen synthesis in cardiac fibroblasts, and induce an increase in procollagen-1 mRNA expression along with an increase in collagen synthesis [48]. They revealed that, in normal animals, infusing CTS in a concentration similar to the circulating levels seen in patients with renal failure stimulates collagen synthesis in cardiac fibroblast primary culture, and that active immunization against MBG significantly attenuated the development of cardiac fibrosis in vivo. They also showed that the induction of collagen production by CTS depended on the integrity of signaling through the NKA-Src cascade, as disruption of Src kinase signaling via administration of Src kinase inhibitors diminished the CTS induced profibrotic effects. Additionally, the blockade of NKA signaling with immunization as well as pharmacologic inhibitors effectively reduced the oxidative stress seen with experimental renal failure. Grigorova and Fedorova further showed that rats on a high salt diet developed aortic fibrosis [57][58]. These studies showed that this phenotype was mediated through MBG-dependent mechanisms, and was reduced by immune-neutralization of MBG.
Furthermore, many studies [59][60][61][62] showed that in rats, chronic peripheral administration of low doses of ouabain induced cardiac hypertrophy and fibrosis. Meanwhile, passive immunization against CTS significantly ameliorates the progression of cardiac hypertrophy and fibrosis [63]. Several studies have shown an association between CTS levels and cardiac geometry and that advanced stages of hypertrophy were associated with elevated plasma CTS [62][64][65]. Pierdomenico and colleagues found that plasma CTS levels were significantly higher in patients with LV (left ventricular) hypertrophy compared to patients with normal LV geometry [28]. Interestingly, passive immunization against CTS, in animal models with myocardial infraction, significantly attenuates the progression of LV dilation and improve LV function [66]. Additional work in this same area also showed that ouabain infusion induced LV hypertrophy [62].
Importantly, while the current research has focused primarily on the non-ion dependent signaling mechanisms of the NKA, the [Na+]i/[K+]i ratio has been shown to also initiate similar signaling events. A number of important studies have shown the role of NKA inhibition and elevation of the [Na+]i/[K+]i ratio in the activation of Src-EGFR-MAPK- and Akt-mediated signaling pathways triggered by CTS, and readers are referred to a recent review which more thoroughly addresses this topic [67]. The importance of this concept is highlighted by recent data showing that NKA inhibition by CTS triggers TGFβ-induced fibrosis in cultured human lung fibroblasts via [Na+]i/[K+]i-mediated signaling which results in augmented expression of COX-2 [68] and downregulation of TGFβ2R [69]. Cumulatively, these studies have broadened the understanding of the role of CTS signaling through the NKA in human disease. Many follow up studies have linked the association of CTS signaling to other health issues, such as preeclampsia. In 2010, Fedorova showed that plasma levels of CTS in patients with preeclampsia are elevated on average, four-times that of normal patients [55]. Later studies done by Nikitina and coworkers revealed that in preeclampsia, elevated levels of endogenous MBG induce vascular fibrosis and impairment of vascular relaxation through a Fli-1-dependent mechanism [56]. The study showed that MBG induced vascular fibrosis in umbilical arteries similar to that seen in preeclampsia. Uddin and colleagues have described several studies not only confirming elevations of CTS in preeclampsia [70] but also detailing the proapoptotic and antiproliferative effects of CTS such as MBG in the disruption of normal placental function [71][72][73][74]. Recently, Lenaerts and coworkers have developed an LC-MS method to detect and definitively identify MBG in plasma samples and confirmed the presence of endogenous MBG in preeclampsia [75]. This is significant, because it was a highly specific assay, which positively identified MBG using multiple MRM (multiple reaction monitoring) transitions, providing very powerful and direct evidence of the presence of this CTS in a physiologically relevant human setting. The utility of LC-MS/MS will allow researchers to study the role of MBG and other CTS in mediating trade-off effects associated with other volume expanded states in which these hormones have been implicated.

5. CTS, NKA, and Inflammation

Inflammation and oxidant stress play a dominant role in the onset and progression of organ injury in chronic conditions [76]. Inflammation induces the release of cytokines and enhances the expression of adhesion molecules, which together contribute to recruitment of more inflammatory cells that ultimately aggravate the condition extensively. Current studies have examined the role of the CTS signaling through NKA in mediating inflammation and oxidative stress in chronic conditions.
It is well established that CTS signal through the NKA and are important in the regulation of renal sodium transport and arterial pressure [77][78][79][80]. However, recent work implicates CTS in the modulation of immunity, more specifically as mediators of inflammation. Ouabain is a well-characterized CTS and its role as a NKA inhibitor is associated with its cardiovascular effects [77][78][79][80]. Ouabain has also recently been shown to induce inflammation as a result of this inhibitory property. Goncalves-de-Albuquerque and colleagues demonstrated that intratracheal administration of ouabain induces lung inflammation in mice via inhibition of the NKA in alveolar cells [81]. Ouabain and other CTS have been associated with cell signaling mechanisms in immune cells as well. Quastel and Kaplan first identified a relationship between ouabain and the immune system when they demonstrated that ouabain inhibits lymphocyte proliferation induced by the mitogen phytohaemagglutinin [82]. This was clearly repeated using different stimuli and thus confirmed [83][84][85][86]. The studies mentioned thus far have demonstrated a relationship between CTS and inflammation [87], however, investigators are currently looking into the specific mechanisms by which chronic elevation of CTS levels induce an inflammatory response. Recent data has been collected on the effect of CTS on cells that respond to chronic inflammation such as macrophages, mast cells, and monocytes [88]. 
The transcription factor, nuclear factor kappa-light-chain-enhancer, of activated B cells (NF-κB) is considered a master regulator of immunity [89]. The NF-κB pathway is activated in macrophages when they recognize a pathogen, inducing a multitude of proinflammatory responses. Although the mechanisms related to NF-κB activation are not completely understood, activation of this pathway is associated with a proinflammatory response. Using human monocyte-derived macrophages (HMDM), as well as murine peritoneal macrophages, Chen and colleagues demonstrated that the CTS ouabain activates the NF-κB pathway leading to proinflammatory cytokine production [89]. They found that 25 nmol/L ouabain increased NF-κB-transcriptional activity up to three-fold. They then used a quantitative real time-polymerase chain reaction to show that ouabain increased expression of monocyte chemotactic protein 1 (MCP-1), TNF-α, prostaglandin endoperoxide synthase 2 (PTGS2), chemokine (CC motif) ligand (CCL5), IL-6, IL-1β, ICAM1, CXCL10, and CXCL9 [89]. Interestingly, five years prior to this publication, the sharp elevation of PTGS2 and IL6 expression triggered by ouabain was found in rat vascular smooth muscle cells, human endothelial cells, and the HeLa cell line [90]. Importantly, in these cells augmented expression of PTGS2 and IL6 was mediated by NKA inhibition and elevation of the [Na+]i/[K+]i ratio. In addition to these findings, the neurotoxicity of Venenum Bufonis has been linked to neural inflammation caused by activation of the NF-κB transcription factor [91]. However, the literature seems to be divided on this topic. Although these studies show CTS activating the pathway, others show CTS actually having an inhibitory effect on the transcription factor. For example, Wang and colleagues found that digoxin inhibited NF-κB and that TNF-α-stimulated NF-κB activity and suppressed NF-κB initiating genes (Bcl-2, Bcl-xL, cyclin D1, and c-myc) [92]. It is important to note that this study was done on Burkitt’s lymphoma cells in order to study the potential for digoxin as a therapeutic agent for cancer, while the other studies mentioned were looking at the specific immune cell response associated with elevated levels of CTS. Importantly, there are key differences between digoxin and CTS such as ouabain including the apparent inability of digoxin to activate Src kinase [93]. Additionally, according to many epidemiological studies, there is a growing relationship between digoxin treatment and increased mortality and a suggestion that volume expanded settings in which CTS are elevated may contribute to digoxin toxicity [33][94]. Some investigators believe that this link is due to the proinflammatory nature of CTS in patients with cardiac and renal disease. Kobayashi and colleagues found that ouabain induced cardiac inflammatory responses, such as macrophage infiltration and IL-1β release when mice were primed with LPS (lipopolysaccharide) [95]. They ultimately found deficiency of NLRP3 and caspase-1 attenuated ouabain dysfunction and inflammation. Given these intriguing findings, the pro-and anti-inflammatory effect of CTS on cardiac and renal disease, especially in volume expanded conditions where elevated levels of CTS persist, is a topic that warrants further investigation.

6. New Horizons for NKA Signaling: Aging, Obesity, Diabetes, and Atherosclerosis

The amplification of oxidant stress by NKA has emerged as a key theme in the role that the NKA plays in the pathophysiologic trade-off adaptations to volume expansion [41][96][97][98]. Oxidative stress has an essential role in the pathogenesis of many clinical disorders such as obesity, atherosclerosis, diabetes, and aging.
Obesity is a global epidemic, and can be defined as an abnormal or excessive accumulation of fat that impairs health. Obesity is the leading cause of morbidity and mortality associated with cardiovascular and metabolic syndrome [99][100]. Numerous studies have shown that systemic oxidative stress is a main element that generates and maintains the pathological consequences of obesity both in vitro and in vivo [101][102][103][104]. Because the NKA can amplify oxidant signaling, scientists speculate that the NKA signaling plays a role in oxidative stress related to obesity. In fact, studies have shown that a peptide designed to inhibit NKA signaling can ameliorate obesity. One of the most important developments in this field was the development of a specific peptide inhibitor of the NKA-Src signaling axis, termed pNaktide [105]. Using this specific inhibitor, Sodhi and coworkers showed that in 3T3-L1 preadipocytes, pNaKtide attenuated oxidant stress and lipid accumulation in a dose-dependent manner [97]. Additionally, they found that, in mice fed a high-fat diet, administration of pNaKtide reduced body weight, restored systemic redox and inflammatory milieu, and improved insulin sensitivity. This study highlighted the role of the NKA signaling cascade to amplify reactive oxygen species involved in adipogenesis, a process not previously linked to the NKA signaling. Earlier studies by Turaihi and colleagues showed that in obesity, the quantity of NKA sites on leucocyte membranes are significantly increased, and that this is associated with accelerated 86Rb transport [106]. Interestingly, both of these indices decreased following 4% to 5% reduction in body weight; however, this group did not specifically link the increase in NKA quantity as central component to the pathogenesis of obesity. However, a more recent study demonstrated that the NKA/ROS (reactive oxygen species) amplification loop contributes significantly to the development and progression of obesity and that visceral adipocytes create systemic oxidant stress through the feed-forward oxidant amplification loop of the NKA-Src-EGFR signaling [97]. In fact, Iannello and coworkers showed that blockade of this amplification with pNaKtide ameliorates oxidative stress and obesity in mice subjected to a high-fat diet [107]. Another study by Martin and colleagues showed that adipogenic markers PPARγ, FAS, and C/EBP in the visceral fat of western-diet fed mice was significantly reduced after lentiviral-mediated adipocyte-specific delivery of pNaKtide, which inhibits NKA signaling [108].
The NKA/ROS amplification loop is implicated in the pathogenesis of other conditions such as atherosclerosis and diabetes in addition to its role in obesity. Atherosclerosis is a worldwide epidemic and leading cause of death in developed countries. Atherosclerosis is marked by inflammation and the formation of plaque within arterial walls. Given the importance of oxidative stress in the pathophysiology of atherosclerosis, and the known ability of the NKA to act as an amplifier for ROS, several studies have investigated the role of NKA signaling in this setting. Indeed, one study demonstrated that administration of pNaKtide in ApoE−/− mice fed a western diet significantly decreased plasma ALT (alanine aminotransferase), triglycerides, FFA (free fatty acide), and LDL (low density lipoprotein) levels [109]. Further, the study showed that ApoE−/− mice fed a western diet had decreased plasma HDL (high density lipoprotein) levels, and this decrease was reversed by pNaKtide. ROS levels and plaque size were significantly reduced by pNaKtide treatment as well. Furthermore, adipocyte dysfunction in mice fed a western diet was also prevented by lentiviral-mediated adipocyte-specific delivery of pNaKtide [108]. The results showed that Lenti-adipo-pNaKtide significantly reduced western diet-induced weight gain, along with visceral and subcutaneous fat content. Additionally, the increase in cardiac hypertrophy in high fat fed animals was attenuated with lenti-adipo-pNaKtide. On this background, Sodhi and colleagues showed that the administration of pNaKtide to mice fed a western diet containing high amounts of fat and fructose significantly reduced obesity as well as hepatic steatosis, inflammation, and fibrosis [109]. The study also revealed an improvement in mitochondrial fatty acid oxidation, insulin sensitivity, dyslipidemia, and aortic streaking in their model. To further examine the role of the NKA in the development of atherosclerosis, similar studies were performed in ApoE knockout mice exposed to a western diet. In these mice, pNaKtide not only significantly improved atherosclerosis, but also ameliorated steatohepatitis, dyslipidemia, and insulin sensitivity.
Diabetes mellitus is another inflammation-related process that appears to be increasing rapidly, threatening to reduce life expectancy for humans worldwide [110][111]. Inflammation and oxidative stress have been implicated in both development and progression of diabetes [110][112][113]; although not much is known about the role of the NKA in this setting. However, studies have shown that inhibition of NKA signaling using pNaKtide improved glucose tolerance, insulin sensitivity, and HOMA-IR scores in ApoE−/− mice fed a western diet [109]. A different study showed that glucose tolerance improved in mice fed a western diet after lentiviral-mediated adipocyte-specific delivery of pNaKtide [108]. This study suggests that the NKA/ROS amplification loop may be involved in development of the diabetes phenotype as well.
The NKA oxidant amplification loop may be involved in advancing the aging process in both in vivo and in vitro models as well. In fact, mice fed a western diet showed oxidant injury and aggravated functional and morphological aging markers, whereas treating with pNaKtide reduced these changes [41]. Collectively, these studies strongly suggest that the NKA/ROS amplification loop contributes significantly to the development and progression of inflammation and oxidative stress related to obesity, atherosclerosis, diabetes, and aging. More studies are needed to unravel the development of new therapeutic targets for these conditions.

7. Novel Signaling Partners of the NKA in Inflammation and Fibrosis

The NKA has an important role in cell signaling through its interactions with endogenous CTS and signaling molecules such as Src kinase [114][115]. CTS and other ligands of this receptor complex are known to be involved in initiation and magnification of signaling cascades through the recruitment and assembly of a cell-specific NKA signalosome [116]. In the last few decades, many studies have revealed the role of the NKA and its signaling complexes in various diseases including atherosclerosis, inflammation, and fibrosis. Research efforts are being made to study different signaling partners of the pump and to unravel molecular mechanisms involved in the pathogenesis of various diseases. 
Chen and colleagues further showed that the NKA plays a significant role in oxidized LDL-CD36 signaling axis, specifically in macrophages. They confirmed the NKA as a key binding partner of CD36 in this cell type and demonstrated that oxLDL binding to CD36 recruited and activated Lyn kinase through the NKA. Here, activation of NKA associated Lyn kinase leads to foam cell formation and contributes to the development of atherosclerosis by inhibiting macrophage migration and trapping macrophages in the neointima. Macrophages deficient in the α1 subunit of the NKA resulted in a significant decrease in oxLDL uptake, foam cell formation, and oxLDL-induced inhibition of cell migration, suggesting that it is a target for anti-atherosclerotic lesion development. Chen [117] further showed that CTS trigger an inflammatory response in murine and human macrophages by activating NF-κB, causing proinflammatory cytokine production in these primary macrophages through a signaling complex, including CD36, NKA, and Toll-like receptor 4 (TLR4). TLR4 is also involved in recruiting MyD88, an adaptor protein for NF-κB activation. Their data showed that macrophages deficient in NKA, scavenger receptor CD36, or TLR4 were resistant to CTS-induced NF-κB activation, indicating the crucial role of these three receptors in the proinflammatory pathway.
A common theme emerges for both CD36 and CD40 studies in that both of these receptors (a) have little intracellular presence by which to direct signaling events, (b) lack intrinsic kinase or phosphatase activity, (c) have no known intracellular scaffolding domain(s), (d) no direct connection with GTPases, (e) reside (at least in part) in caveolae, and (f) rely on activation of Src family kinases to mediate signaling. Thus the ability of both of these receptors to interact with the signaling NKA may prove to be a common denominator which allows these receptors to activate multiple signaling pathways. If this is true, there are a host of implications not only for the signaling events and biology of these two receptors, but for a host of similarly configured receptors throughout the body. The propensity of the NKA to interact with and facilitate the signaling of multiple proteins involved in atherogenesis, inflammation, and fibrosis makes it a valuable target for therapy in different diseases.

References

  1. Xie, Z. Molecular mechanisms of Na/K-ATPase-mediated signal transduction. Ann. N. Y. Acad. Sci. 2003, 986, 497–503.
  2. Kometiani, P.; Li, J.; Gnudi, L.; Kahn, B.B.; Askari, A.; Xie, Z. Multiple Signal Transduction Pathways Link Na+/K+-ATPase to growth-related genes in cardiac myocytes the roles of Ras and mitogen-ACTIVATED protein kinases. J. Biol. Chem. 1998, 273, 15249–15256.
  3. Xie, Z.; Askari, A. Na/K-ATPase as a signal transducer. Eur. J. Biochem. 2002, 269, 2434–2439.
  4. Ogawa, H.; Motoyama, K.; Cornelius, F.; Vilsen, B.; Toyoshima, C. X-Ray Crystallographic Study of Na, K-ATPase in Complex with Cardiotonic Steroids. Biophys. J. 2015, 108, 197a.
  5. Xie, Z. Ouabain interaction with cardiac Na/K-ATPase reveals that the enzyme can act as a pump and as a signal transducer. Cell. Mol. Biol. 2001, 47, 383–390.
  6. Aperia, A.; Akkuratov, E.E.; Fontana, J.M.; Brismar, H. Na+-K+-ATPase, a new class of plasma membrane receptors. Am. J. Physiol.-Cell Physiol. 2016, 310, C491–C495.
  7. Morth, J.P.; Pedersen, B.P.; Buch-Pedersen, M.J.; Andersen, J.P.; Vilsen, B.; Palmgren, M.G.; Nissen, P. A structural overview of the plasma membrane Na+, K+-ATPase and H+-ATPase ion pumps. Nat. Rev. Mol. Cell Biol. 2011, 12, 60–70.
  8. Jørgensen, P.L. Structure, function and regulation of Na, K-ATPase in the kidney. Kidney Int. 1986, 29, 10–20.
  9. Xie, J.X.; Zhang, S.; Cui, X.; Zhang, J.; Yu, H.; Khalaf, F.K.; Malhotra, D.; Kennedy, D.J.; Shapiro, J.I.; Tian, J. Na/K-ATPase/src complex mediates regulation of CD40 in renal parenchyma. Nephrol. Dial. Transplant. 2018, 33, 1138–1149.
  10. Blanco, G.; Mercer, R.W. Isozymes of the Na-K-ATPase: Heterogeneity in structure, diversity in function. Am. J. Physiol.-Ren. Physiol. 1998, 275, F633–F650.
  11. Adams, R.J.; Schwartz, A.; Grupp, G.; Grupp, I.; Lee, S.W.; Wallick, E.T.; Powell, T.; Twist, V.W.; Gathiram, P. High-affinity ouabain binding site and low-dose positive inotropic effect in rat myocardium. Nature 1982, 296, 167–169.
  12. Kutz, L.C.; Mukherji, S.; Marck, P.; Cui, X.; Heiny, J.A.; Blanco, G.; Pierre, S.V.; Xie, Z. Isoform-specific role of Na/K-ATPase α1 in skeletal muscle growth and performance. FASEB J. 2017, 31, 1007.50.
  13. Klimanova, E.A.; Petrushanko, I.Y.; Mitkevich, V.A.; Anashkina, A.A.; Orlov, S.N.; Makarov, A.A.; Lopina, O.D. Binding of ouabain and marinobufagenin leads to different structural changes in Na, K-ATPase and depends on the enzyme conformation. FEBS Lett. 2015, 589, 2668–2674.
  14. Wolfgang, B.; Eleanor, E.B. Collection of Toad Venoms and Chemistry of the Toad Venom Steroids; Academic Press: London, UK, 1971.
  15. Bagrov, A.Y.; Fedorova, O.V.; Dmitrieva, R.I.; Howald, W.N.; Hunter, A.P.; Kuznetsova, E.A.; Shpen, V.M. Characterization of a urinary bufodienolide Na+, K+-ATPase inhibitor in patients after acute myocardial infarction. Hypertension 1998, 31, 1097–1103.
  16. Fedorova, L.V.; Raju, V.; El-Okdi, N.; Shidyak, A.; Kennedy, D.J.; Vetteth, S.; Giovannucci, D.R.; Bagrov, A.Y.; Fedorova, O.V.; Shapiro, J.I. The cardiotonic steroid hormone marinobufagenin induces renal fibrosis: Implication of epithelial-to-mesenchymal transition. Am. J. Physiol.-Ren. Physiol. 2009, 296, F922–F934.
  17. Fedorova, O.; Doris, P.; Bagrov, A. Endogenous marinobufagenin-like factor in acute plasma volume expansion. Clin. Exp. Hypertens. 1998, 20, 581–591.
  18. Gallice, P.M.; Kovacic, H.N.; Brunet, P.J.; Berland, Y.F.; Crevat, A.D. A non ouabain-like inhibitor of the sodium pump in uremic plasma ultrafiltrates and urine from healthy subjects. Clin. Chim. Acta 1998, 273, 149–160.
  19. Gonick, H.; Ding, Y.; Vaziri, N.; Bagrov, A.; Fedorova, O. Simultaneous measurement of marinobufagenin, ouabain, and hypertension-associated protein in various disease states. Clin. Exp. Hypertens. 1998, 20, 617–627.
  20. Hamlyn, J.; Blaustein, M.; Bova, S.; DuCharme, D.; Harris, D.; Mandel, F.; Mathews, W.; Ludens, J. Identification and characterization of a ouabain-like compound from human plasma. Proc. Natl. Acad. Sci. USA 1991, 88, 6259–6263.
  21. Hamlyn, J.M.; Ringel, R.; Schaeffer, J.; Levinson, P.D.; Hamilton, B.P.; Kowarski, A.A.; Blaustein, M.P. A circulating inhibitor of (Na+ K+) ATPase associated with essential hypertension. Nature 1982, 300, 650.
  22. Harwood, S.; Mullen, A.M.; McMahon, A.C.; Dawnay, A. Plasma OLC is elevated in mild experimental uremia but is not associated with hypertension. Am. J. Hypertens. 2001, 14, 1112–1115.
  23. Kennedy, D.J.; Vetteth, S.; Periyasamy, S.M.; Kanj, M.; Fedorova, L.; Khouri, S.; Kahaleh, M.B.; Xie, Z.; Malhotra, D.; Kolodkin, N.I. Central role for the cardiotonic steroid marinobufagenin in the pathogenesis of experimental uremic cardiomyopathy. Hypertension 2006, 47, 488–495.
  24. Li, S.; Liu, G.; Jia, J.; Miao, Y.; Gu, S.; Miao, P.; Shi, X.; Wang, Y.; Yu, C. Therapeutic monitoring of serum digoxin for patients with heart failure using a rapid LC-MS/MS method. Clin. Biochem. 2010, 43, 307–313.
  25. Manunta, P.; Stella, P.; Rivera, R.; Ciurlino, D.; Cusi, D.; Ferrandi, M.; Hamlyn, J.M.; Bianchi, G. Left ventricular mass, stroke volume, and ouabain-like factor in essential hypertension. Hypertension 1999, 34, 450–456.
  26. Periyasamy, S.M.; Chen, J.; Cooney, D.; Carter, P.; Omran, E.; Tian, J.; Priyadarshi, S.; Bagrov, A.; Fedorova, O.; Malhotra, D. Effects of uremic serum on isolated cardiac myocyte calcium cycling and contractile function. Kidney Int. 2001, 60, 2367–2376.
  27. Komiyama, Y.; Dong, X.H.; Nishimura, N.; Masaki, H.; Yoshika, M.; Masuda, M.; Takahashi, H. A novel endogenous digitalis, telocinobufagin, exhibits elevated plasma levels in patients with terminal renal failure. Clin. Biochem. 2005, 38, 36–45.
  28. Pierdomenico, S.D.; Bucci, A.; Manunta, P.; Rivera, R.; Ferrandi, M.; Hamlyn, J.M.; Lapenna, D.; Cuccurullo, F.; Mezzetti, A. Endogenous ouabain and hemodynamic and left ventricular geometric patterns in essential hypertension. Am. J. Hypertens. 2001, 14, 44–50.
  29. Gottlieb, S.S.; Rogowski, A.C.; Weinberg, M.; Krichten, C.M.; Hamilton, B.P.; Hamlyn, J.M. Elevated concentrations of endogenous ouabain in patients with congestive heart failure. Circulation 1992, 86, 420–425.
  30. Stella, P.; Manunta, P.; Mallamaci, F.; Melandri, M.; Spotti, D.; Tripepi, G.; Hamlyn, J.M.; Malatino, L.S.; Bianchi, G.; Zoccali, C. Endogenous ouabain and cardiomyopathy in dialysis patients. J. Intern. Med. 2008, 263, 274–280.
  31. Shimada, K.; Ishii, N.; Nambara, T. Occurrence of bufadienolides in the skin of Bufo viridis Laur. Chem. Pharm. Bull. 1986, 34, 3454–3457.
  32. Chen, K.K.; Anderson, R.C.; Henderson, F.G. Comparison of cardiac action of bufalin, cinobufotalin, and telocinobufagin with cinobufagin. Proc. Soc. Exp. Biol. Med. 1951, 76, 372–374.
  33. Touza, N.A.; Pocas, E.S.; Quintas, L.E.; Cunha-Filho, G.; Santos, M.L.; Noel, F. Inhibitory effect of combinations of digoxin and endogenous cardiotonic steroids on Na+/K+-ATPase activity in human kidney membrane preparation. Life Sci. 2011, 88, 39–42.
  34. Bricker, N.S. On the pathogenesis of the uremic state: An exposition of the trade-off hypothesis. N. Engl. J. Med. 1972, 286, 1093–1099.
  35. Hamlyn, J.M.; Manunta, P. Endogenous cardiotonic steroids in kidney failure: A review and an hypothesis. Adv. Chron. Kidney Dis. 2015, 22, 232–244.
  36. Kennedy, D.J.; Shrestha, K.; Sheehey, B.; Li, X.S.; Guggilam, A.; Wu, Y.; Finucan, M.; Gabi, A.; Medert, C.M.; Westfall, K. Elevated plasma marinobufagenin, an endogenous cardiotonic steroid, is associated with right ventricular dysfunction and nitrative stress in heart failure. Circ. Heart Fail. 2015, 8, 1068.
  37. Tomaschitz, A.; Piecha, G.; Ritz, E.; Meinitzer, A.; Haas, J.; Pieske, B.; Wiecek, A.; Rus-Machan, J.; Toplak, H.; März, W. Marinobufagenin in essential hypertension and primary aldosteronism: A cardiotonic steroid with clinical and diagnostic implications. Clin. Exp. Hypertens. 2015, 37, 108–115.
  38. Hamlyn, J.M.; Blaustein, M.P. Endogenous ouabain: Recent advances and controversies. Hypertension 2016, 68, 526–532.
  39. Xie, J.X.; Shapiro, A.P.; Shapiro, J.I. The trade-off between dietary salt and cardiovascular disease; a role for Na/K-ATPase signaling? Front. Endocrinol. 2014, 5, 97.
  40. Kennedy, D.J.; Weber, M.E.; Guggilam, A.; Westfall, K.M.; Agatisa-Boyle, B.; Bucur, P.; Lingrel, J.B.; Tang, W.W. Telecinobufagin, a novel cardiotonic steroid, promotes myocardial and renal fibrosis via Na/K-ATPase profibrotic signalling pathways. Circulation 2014, 130.
  41. Sodhi, K.; Nichols, A.; Mallick, A.; Klug, R.L.; Liu, J.; Wang, X.; Srikanthan, K.; Goguet-Rubio, P.; Nawab, A.; Pratt, R.; et al. The Na/K-ATPase Oxidant Amplification Loop Regulates Aging. Sci. Rep. 2018, 8, 9721.
  42. Lv, W.; Fan, F.; Wang, Y.; Gonzalez-Fernandez, E.; Wang, C.; Yang, L.; Booz, G.W.; Roman, R.J. Therapeutic potential of microRNAs for the treatment of renal fibrosis and CKD. Physiol. Genom. 2017, 50, 20–34.
  43. Lan, H.Y.; Nikolic-Paterson, D.J. Advances in Mechanisms of Renal Fibrosis. Front. Physiol. 2018, 9, 284.
  44. Tang, P.M.K.; Zhang, Y.Y.; Mak, T.S.K.; Tang, P.C.T.; Huang, X.R.; Lan, H.Y. TGF-β signalling in renal fibrosis: From Smads to non-coding RNAs. J. Physiol. 2018.
  45. Chang, Y.; Lau, W.L.; Jo, H.; Tsujino, K.; Gewin, L.; Reed, N.I.; Atakilit, A.; Nunes, A.C.F.; DeGrado, W.F.; Sheppard, D. Pharmacologic blockade of αvβ1 integrin ameliorates renal failure and fibrosis in vivo. J. Am. Soc. Nephrol. 2017, 28, 1998–2005.
  46. Tammaro, A.; Florquin, S.; Brok, M.; Claessen, N.; Butter, L.M.; Teske, G.J.; de Boer, O.J.; Vogl, T.; Leemans, J.C.; Dessing, M.C. S100A8/A9 promotes parenchymal damage and renal fibrosis in obstructive nephropathy. Clin. Exp. Immunol. 2018.
  47. Feng, M.; Tang, P.M.-K.; Huang, X.-R.; Sun, S.-F.; You, Y.-K.; Xiao, J.; Lv, L.-L.; Xu, A.-P.; Lan, H.-Y. TGF-β Mediates Renal Fibrosis via the Smad3-Erbb4-IR Long Noncoding RNA Axis. Mol. Therapy 2018, 26, 148–161.
  48. Elkareh, J.; Kennedy, D.J.; Yashaswi, B.; Vetteth, S.; Shidyak, A.; Kim, E.G.; Smaili, S.; Periyasamy, S.M.; Hariri, I.M.; Fedorova, L. Marinobufagenin stimulates fibroblast collagen production and causes fibrosis in experimental uremic cardiomyopathy. Hypertension 2007, 49, 215–224.
  49. Haller, S.T.; Drummond, C.A.; Yan, Y.; Liu, J.; Tian, J.; Malhotra, D.; Shapiro, J.I. Passive immunization against marinobufagenin attenuates renal fibrosis and improves renal function in experimental renal disease. Am. J. Hypertens. 2013, 27, 603–609.
  50. Cheng, X.; Song, Y.; Wang, Y. pNaKtide ameliorates renal interstitial fibrosis through inhibition of sodium-potassium adenosine triphosphatase-mediated signaling pathways in unilateral ureteral obstruction mice. Nephrol. Dial. Transplant. 2018.
  51. Elkareh, J.; Periyasamy, S.M.; Shidyak, A.; Vetteth, S.; Schroeder, J.; Raju, V.; Hariri, I.M.; El-Okdi, N.; Gupta, S.; Fedorova, L.; et al. Marinobufagenin induces increases in procollagen expression in a process involving protein kinase C and Fli-1: Implications for uremic cardiomyopathy. Am. J. Physiol. Ren. Physiol. 2009, 296, F1219–F1226.
  52. Fedorova, O.V.; Zernetkina, V.I.; Shilova, V.Y.; Grigorova, Y.N.; Juhasz, O.; Wei, W.; Marshall, C.A.; Lakatta, E.G.; Bagrov, A.Y. Synthesis of an Endogenous Steroidal Na Pump Inhibitor Marinobufagenin, Implicated in Human Cardiovascular Diseases, Is Initiated by CYP27A1 via Bile Acid Pathway. Circ. Cardiovasc. Genet. 2015, 8, 736–745.
  53. Ishkaraeva-Yakovleva, V.V.; Fedorova, O.V.; Solodovnikova, N.G.; Frolova, E.V.; Bzhelyansky, A.M.; Emelianov, I.V.; Adair, C.D.; Zazerskaya, I.E.; Bagrov, A.Y. DigiFab Interacts with Endogenous Cardiotonic Steroids and Reverses Preeclampsia-Induced Na/K.-ATPase Inhibition. Reprod Sci. 2012, 19, 1260–1267.
  54. Adair, C.D.; Buckalew, V.M.; Graves, S.W.; Lam, G.K.; Johnson, D.D.; Saade, G.; Lewis, D.F.; Robinson, C.; Danoff, T.M.; Chauhan, N.; et al. Digoxin immune fab treatment for severe preeclampsia. Am. J. Perinatol. 2010, 27, 655–662.
  55. Fedorova, O.V.; Tapilskaya, N.I.; Bzhelyansky, A.M.; Frolova, E.V.; Nikitina, E.R.; Reznik, V.A.; Kashkin, V.A.; Bagrov, A.Y. Interaction of Digibind with endogenous cardiotonic steroids from preeclamptic placentae. J. Hypertens. 2010, 28, 361–366.
  56. Nikitina, E.R.; Mikhailov, A.V.; Nikandrova, E.S.; Frolova, E.V.; Fadeev, A.V.; Shman, V.V.; Shilova, V.Y.; Tapilskaya, N.I.; Shapiro, J.I.; Fedorova, O.V.; et al. In preeclampsia endogenous cardiotonic steroids induce vascular fibrosis and impair relaxation of umbilical arteries. J. Hypertens. 2011, 29, 769–776.
  57. Grigorova, Y.N.; Juhasz, O.; Zernetkina, V.; Fishbein, K.W.; Lakatta, E.G.; Fedorova, O.V.; Bagrov, A.Y. Aortic Fibrosis, Induced by High Salt Intake in the Absence of Hypertensive Response, is Reduced by a Monoclonal Antibody to Marinobufagenin. Am. J. Hypertens. 2016, 29, 641–646.
  58. Fedorova, O.V.; Emelianov, I.V.; Bagrov, K.A.; Grigorova, Y.N.; Wei, W.; Juhasz, O.; Frolova, E.V.; Marshall, C.A.; Lakatta, E.G.; Konradi, A.O.; et al. Marinobufagenin-induced vascular fibrosis is a likely target for mineralocorticoid antagonists. J. Hypertens. 2015, 33, 1602–1610.
  59. Dostanic-Larson, I.; Lorenz, J.N.; Van Huysse, J.W.; Neumann, J.C.; Moseley, A.E.; Lingrel, J.B. Physiological role of the α1-and α2-isoforms of the Na+-K+-ATPase and biological significance of their cardiac glycoside binding site. Am. J. Physiol.-Regul. Integr. Comp. Physiol. 2006, 290, R524–R528.
  60. Cheung, W.J.; Kent, M.-A.H.; El-Shahat, E.; Wang, H.; Tan, J.; White, R.; Leenen, F.H. Central and peripheral renin-angiotensin systems in ouabain-induced hypertension. Am. J. Physiol.-Heart Circ. Physiol. 2006, 291, H624–H630.
  61. Briones, A.M.; Xavier, F.E.; Arribas, S.M.; González, M.C.; Rossoni, L.V.; Alonso, M.J.; Salaices, M. Alterations in structure and mechanics of resistance arteries from ouabain-induced hypertensive rats. Am. J. Physiol.-Heart Circ. Physiol. 2006, 291, H193–H201.
  62. Ferrandi, M.; Molinari, I.; Barassi, P.; Minotti, E.; Bianchi, G.; Ferrari, P. Organ hypertrophic signaling within caveolae membrane subdomains triggered by ouabain and antagonized by PST 2238. J. Biol. Chem. 2004, 279, 33306–33314.
  63. Haller, S.T.; Kennedy, D.J.; Shidyak, A.; Budny, G.V.; Malhotra, D.; Fedorova, O.V.; Shapiro, J.I.; Bagrov, A.Y. Monoclonal antibody against marinobufagenin reverses cardiac fibrosis in rats with chronic renal failure. Am. J. Hypertens. 2012, 25, 690–696.
  64. Schreiber, V.; Kölbel, F.; Štěpán, J.; Gregorova, I.; Přibyl, T. Digoxin-like immunoreactivity in the serum of rats with cardiac overload. J. Mol. Cell. Cardiol. 1981, 13, 107–110.
  65. Morise, T.; Okamoto, S.; Takasaki, H.; Ikeda, M.; Takeda, R.; Kiuti, F.; Tuda, Y. Biological Activity of Partially Purified Digitalis-like Substance and Na-K-ATPase Inhibitor in Rats: the 17th Conference on the Pathogenesis of Hypertension. Jpn. Circ. J. 1988, 52, 1309–1316.
  66. Leenen, F.H.; Yuan, B.; Huang, B.S. Brain “ouabain” and angiotensin II contribute to cardiac dysfunction after myocardial infarction. Am. J. Physiol.-Heart Circ. Physiol. 1999, 277, H1786–H1792.
  67. Orlov, S.N.; Klimanova, E.A.; Tverskoi, A.M.; Vladychenskaya, E.A.; Smolyaninova, L.V.; Lopina, O.D. Na+ i, K+ i-Dependent and-Independent Signaling Triggered by Cardiotonic Steroids: Facts and Artifacts. Molecules 2017, 22, 635.
  68. La, J.; Reed, E.B.; Koltsova, S.; Akimova, O.; Hamanaka, R.B.; Mutlu, G.M.; Orlov, S.N.; Dulin, N.O. Regulation of myofibroblast differentiation by cardiac glycosides. Am. J. Physiol.-Lung Cell. Mol. Physiol. 2016, 310, L815–L823.
  69. La, J.; Reed, E.; Chan, L.; Smolyaninova, L.V.; Akomova, O.A.; Mutlu, G.M.; Orlov, S.N.; Dulin, N.O. Downregulation of TGF-β Receptor-2 Expression and Signaling through Inhibition of Na/K.-ATPase. PLoS ONE 2016, 11, e0168363.
  70. Agunanne, E.; Horvat, D.; Harrison, R.; Uddin, M.N.; Jones, R.; Kuehl, T.J.; Ghanem, D.A.; Berghman, L.R.; Lai, X.; Li, J.; et al. Marinobufagenin levels in preeclamptic patients: A preliminary report. Am. J. Perinatol. 2011, 28, 509–514.
  71. Ehrig, J.C.; Afroze, S.H.; Reyes, M.; Allen, S.R.; Drever, N.S.; Pilkinton, K.A.; Kuehl, T.J.; Uddin, M.N. A p38 mitogen-activated protein kinase inhibitor attenuates cardiotonic steroids-induced apoptotic and stress signaling in a Sw-71 cytotrophoblast cell line. Placenta 2015, 36, 1276–1282.
  72. Ehrig, J.C.; Horvat, D.; Allen, S.R.; Jones, R.O.; Kuehl, T.J.; Uddin, M.N. Cardiotonic steroids induce anti-angiogenic and anti-proliferative profiles in first trimester extravillous cytotrophoblast cells. Placenta 2014, 35, 932–936.
  73. Uddin, M.N.; Horvat, D.; Demorrow, S.; Agunanne, E.; Puschett, J.B. Marinobufagenin is an upstream modulator of Gadd45a stress signaling in preeclampsia. Biochim. Biophys. Acta 2011, 1812, 49–58.
  74. Uddin, M.N.; Horvat, D.; Childs, E.W.; Puschett, J.B. Marinobufagenin causes endothelial cell monolayer hyperpermeability by altering apoptotic signaling. Am. J. Physiol. Regul. Integr. Comp. Physiol. 2009, 296, R1726–R1734.
  75. Lenaerts, C.; Bond, L.; Tuytten, R.; Blankert, B. Revealing of endogenous Marinobufagin by an ultra-specific and sensitive UHPLC-MS/MS assay in pregnant women. Talanta 2018, 187, 193–199.
  76. Vannella, K.M.; Wynn, T.A. Mechanisms of organ injury and repair by macrophages. Annu. Rev. Physiol. 2017, 79, 593–617.
  77. Manunta, P.; Maillard, M.; Tantardini, C.; Simonini, M.; Lanzani, C.; Citterio, L.; Stella, P.; Casamassima, N.; Burnier, M.; Hamlyn, J.M. Relationships among endogenous ouabain, α-adducin polymorphisms and renal sodium handling in primary hypertension. J. Hypertens. 2008, 26, 914.
  78. Rossi, G.; Manunta, P.; Hamlyn, J.M.; Pavan, E.; De, R.T.; Semplicini, A.; Pessina, A.C. Immunoreactive endogenous ouabain in primary aldosteronism and essential hypertension: Relationship with plasma renin, aldosterone and blood pressure levels. J. Hypertens. 1995, 13, 1181–1191.
  79. Fridman, A.I.; Matveev, S.A.; Agalakova, N.I.; Fedorova, O.V.; Lakatta, E.G.; Bagrov, A.Y. Marinobufagenin, an endogenous ligand of alpha-1 sodium pump, is a marker of congestive heart failure severity. J. Hypertens. 2002, 20, 1189–1194.
  80. Straub, R.; Hall, C.; Krämer, B.; Elbracht, R.; Palitzsch, K.; Lang, B.; Schölmerich, J. Atrial natriuretic factor and digoxin-like immunoreactive factor in diabetic patients: Their interrelation and the influence of the autonomic nervous system. J. Clin. Endocrinol. Metab. 1996, 81, 3385–3389.
  81. Gonçalves-de-Albuquerque, C.F.; Burth, P.; Silva, A.R.; de Moraes, I.M.M.; de Jesus Oliveira, F.M.; Santelli, R.E.; Freire, A.S.; de Lima, G.S.; da Silva, E.D.; da Silva, C.I. Murine lung injury caused by Leptospira interrogans glycolipoprotein, a specific Na/K.-ATPase inhibitor. Respir. Res. 2014, 15, 93.
  82. Quastel, M.; Kaplan, J. Inhibition by ouabain of human lymphocyte transformation induced by phytohaemagglutinin in vitro. Nature 1968, 219, 198.
  83. Cavalcante-Silva, L.H.A.; Lima, É.D.A.; Carvalho, D.M.; Sales-Neto, J.M.; Alves, A.K.D.A.; Galvão, J.G.F.M.; Silva, J.S.d.F.d.; Mascarenhas, S.R. Much More than a Cardiotonic Steroid: Modulation of Inflammation by Ouabain. Front. Physiol. 2018, 9, 895.
  84. Jensen, P.; Winger, L.; Rasmussen, H.; Nowell, P. The mitogenic effect of A23187 in human peripheral lymphocytes. Biochim. Biophys. Acta (BBA) Gen. Subj. 1977, 496, 374–383.
  85. Dornand, J.; Favero, J.; Bonnafous, J.-C.; Mani, J.-C. Mechanism whereby ouabain inhibits human T lymphocyte activation: Effect on the interleukin 2 pathway. Immunobiology 1986, 171, 436–450.
  86. Brodie, C.; Tordai, A.; Saloga, J.; Domenico, J.; Gelfand, E.W. Ouabain induces inhibition of the progression phase in human T-cell proliferation. J. Cell. Physiol. 1995, 165, 246–253.
  87. Khalaf, F.K.; Mohamed, A.; Kleinhenz, A.; Crawford, E.; Tian, J.; Xie, Z.; Malhotra, D.; Haller, S.; Kennedy, D. Cardiotonic steroid signaling through Na/K-atpase-A-1 and src kinase enhance functional interactions between immune cells and endo/epithelial cells. J. Investig. Med. 2018, 66, 859.
  88. Khalaf, F.K.; Kleinhenz, A.L.; Crawford, E.L.; Tian, J.; Malhotra, D.; Haller, S.T.; Kennedy, D.J. Cardiotonic Steroid Signaling through Na/K-ATPase-alpha-1 and Src Kinase Enhance Immune Cell Pro-Inflammatory Response. Circulation 2017.
  89. Chen, Y.; Huang, W.; Yang, M.; Xin, G.; Cui, W.; Xie, Z.; Silverstein, R.L. Cardiotonic Steroids Stimulate Macrophage Inflammatory Responses Through a Pathway Involving CD36, TLR4, and Na/K-ATPase. Arterioscler. Thromb. Vasc. Biol. 2017, 37, 1462–1469.
  90. Koltsova, S.V.; Trushina, Y.; Haloui, M.; Akimova, O.A.; Tremblay, J.; Hamet, P.; Orlov, S.N. Ubiquitous i/ i-sensitive transcriptome in mammalian cells: Evidence for Ca2+ i-independent excitation-transcription coupling. PLoS ONE 2012, 7, e38032.
  91. Bi, Q.-R.; Hou, J.-J.; Qi, P.; Ma, C.-H.; Shen, Y.; Feng, R.-H.; Yan, B.-P.; Wang, J.-W.; Shi, X.-J.; Zheng, Y.-Y. Venenum Bufonis induces rat neuroinflammation by activiating NF-κB pathway and attenuation of BDNF. J. Ethnopharmacol. 2016, 186, 103–110.
  92. Wang, T.; Xu, P.; Wang, F.; Zhou, D.; Wang, R.; Meng, L.; Wang, X.; Zhou, M.; Chen, B.; Ouyang, J. Effects of digoxin on cell cycle, apoptosis and NF-κB pathway in Burkitt’s lymphoma cells and animal model. Leuk. Lymphoma 2017, 58, 1673–1685.
  93. Zulian, A.; Linde, C.I.; Pulina, M.V.; Baryshnikov, S.G.; Papparella, I.; Hamlyn, J.M.; Golovina, V.A. Activation of c-SRC underlies the differential effects of ouabain and digoxin on Ca2+ signaling in arterial smooth muscle cells. Am. J. Physiol. Cell Physiol. 2013, 304, C324–C333.
  94. Manunta, P.; Ferrandi, M. Cardiac glycosides and cardiomyopathy. Hypertension 2006, 47, 343–344.
  95. Kobayashi, M.; Usui-Kawanishi, F.; Karasawa, T.; Kimura, H.; Watanabe, S.; Mise, N.; Kayama, F.; Kasahara, T.; Hasebe, N.; Takahashi, M. The cardiac glycoside ouabain activates NLRP3 inflammasomes and promotes cardiac inflammation and dysfunction. PLoS ONE 2017, 12, e0176676.
  96. Liu, J.; Lilly, M.N.; Shapiro, J.I. Targeting Na/K-ATPase Signaling: A New Approach to Control Oxidative Stress. Curr. Pharm. Des. 2018, 24, 359–364.
  97. Sodhi, K.; Maxwell, K.; Yan, Y.; Liu, J.; Chaudhry, M.A.; Getty, M.; Xie, Z.; Abraham, N.G.; Shapiro, J.I. pNaKtide inhibits Na/K-ATPase reactive oxygen species amplification and attenuates adipogenesis. Sci. Adv. 2015, 1, e1500781.
  98. Liu, J.; Kennedy, D.J.; Yan, Y.; Shapiro, J.I. Reactive Oxygen Species Modulation of Na/K-ATPase Regulates Fibrosis and Renal Proximal Tubular Sodium Handling. Int. J. Nephrol. 2012, 2012, 1–14.
  99. Gregg, E.W.; Shaw, J.E. Global health effects of overweight and obesity. N. Engl. J. Med. 2017, 377, 80–81.
  100. Pozza, C.; Isidori, A.M. What’s Behind the Obesity Epidemic. In Imaging in Bariatric Surgery; Springer: Berlin, Germany, 2018; pp. 1–8.
  101. Crujeiras, A.; Díaz-Lagares, A.; Carreira, M.; Amil, M.; Casanueva, F. Oxidative stress associated to dysfunctional adipose tissue: A potential link between obesity, type 2 diabetes mellitus and breast cancer. Free Radic. Res. 2013, 47, 243–256.
  102. Lafontan, M. Adipose tissue and adipocyte dysregulation. Diabetes Metab. 2014, 40, 16–28.
  103. Li, M.; Kim, D.H.; Tsenovoy, P.L.; Peterson, S.J.; Rezzani, R.; Rodella, L.F.; Aronow, W.S.; Ikehara, S.; Abraham, N.G. Treatment of obese diabetic mice with a heme oxygenase inducer reduces visceral and subcutaneous adiposity, increases adiponectin levels, and improves insulin sensitivity and glucose tolerance. Diabetes 2008, 57, 1526–1535.
  104. Burgess, A.; Li, M.; Vanella, L.; Kim, D.H.; Rezzani, R.; Rodella, L.; Sodhi, K.; Canestraro, M.; Martasek, P.; Peterson, S.J. Adipocyte heme oxygenase-1 induction attenuates metabolic syndrome in both male and female obese mice. Hypertension 2010, 56, 1124–1130.
  105. Li, Z.; Cai, T.; Tian, J.; Xie, J.X.; Zhao, X.; Liu, L.; Shapiro, J.I.; Xie, Z. NaKtide, a Na/K-ATPase-derived peptide Src inhibitor, antagonizes ouabain-activated signal transduction in cultured cells. J. Biol. Chem. 2009, 284, 21066–21076.
  106. Turaihi, K.; Baron, D.; Dandona, P. Increased leucocyte Na-K ATPase in obesity: Reversal following weight loss. Metabolism 1987, 36, 851–855.
  107. Iannello, S.; Milazzo, P.; Belfiore, F. Animal and human tissue Na, K-ATPase in obesity and diabetes: A new proposed enzyme regulation. Am. J. Med. Sci. 2007, 333, 1–9.
  108. Martin, R.; Brickman, C.; Liu, J.; Sodhi, K.; Shapiro, J.I. Abstract P203: PNaktide Targeted to Adipocytes Inhibits Na/k-atpase Reactive Oxygen Species, Systemic Inflammation, and Obesity Development in Mice Fed a Western Diet (WD). 2017. Available online: https://insights.ovid.com/hypertension/hype/2017/09/001/abstract-p203/249/00004268 (accessed on 24 August 2018).
  109. Sodhi, K.; Srikanthan, K.; Goguet-Rubio, P.; Nichols, A.; Mallick, A.; Nawab, A.; Martin, R.; Shah, P.T.; Chaudhry, M.; Sigdel, S. pNaKtide Attenuates steatohepatitis and atherosclerosis by blocking Na/K-ATPase/ROS amplification in C57Bl6 and ApoE knockout mice fed a western diet. Sci. Rep. 2017, 7, 193.
  110. Saltiel, A.R.; Olefsky, J.M. Inflammatory mechanisms linking obesity and metabolic disease. J. Clin. Investig. 2017, 127, 1–4.
  111. Zimmet, P.Z. Diabetes and its drivers: The largest epidemic in human history? Clin. Diabetes Endocrinol. 2017, 3, 1.
  112. Everett, B.M.; Donath, M.Y.; Pradhan, A.D.; Thuren, T.; Pais, P.; Nicolau, J.C.; Glynn, R.J.; Libby, P.; Ridker, P.M. Anti-inflammatory therapy with canakinumab for the prevention and management of diabetes. J. Am. Coll. Cardiol. 2018, 71, 2392–2401.
  113. Xia, C.; Rao, X.; Zhong, J. Role of T lymphocytes in type 2 diabetes and diabetes-associated inflammation. J. Diabetes Res. 2017, 2017.
  114. Bagrov, A.Y.; Shapiro, J.I.; Fedorova, O.V. Endogenous cardiotonic steroids: Physiology, pharmacology, and novel therapeutic targets. Pharmacol. Rev. 2009, 61, 9–38.
  115. Tian, J.; Xie, Z.-J. The Na-K-ATPase and calcium-signaling microdomains. Physiology 2008, 23, 205–211.
  116. Xie, J.X.; Li, X.; Xie, Z. Regulation of renal function and structure by the signaling Na/K-ATPase. IUBMB Life 2013, 65, 991–998.
  117. Chen, Y.; Kennedy, D.J.; Ramakrishnan, D.P.; Yang, M.; Huang, W.; Li, Z.; Xie, Z.; Chadwick, A.C.; Sahoo, D.; Silverstein, R.L. Oxidized LDL-bound CD36 recruits an Na+/K+-ATPase-Lyn complex in macrophages that promotes atherosclerosis. Sci. Signal. 2015, 8, ra91.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.
Upload a video for this entry
Information
Subjects: Urology & Nephrology
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :
Fatimah K. Khalaf
,
Prabhatchandra Dube
,
Amal Mohamed
,
Jiang Tian
,
Deepak Malhotra
,
Steven T. Haller
,
David J. Kennedy
View Times: 175
Revision: 1 time (View History)
Update Date: 22 Aug 2023
Table of Contents
    1000/1000
    Hot Most Recent
    Video Production Service
    Feedback