# Connexome-Associated Pathways in Atherosclerosis

## Overview

The connexome refers to the coordinated network of connexins, pannexins, gap junctions, hemichannels, and interacting proteins that mediate electrical, metabolic, and paracrine communication among vascular cells. This communication is essential for maintaining endothelial integrity, vascular tone, inflammatory balance, and smooth muscle phenotype. Atherosclerosis profoundly disturbs these communication systems, leading to endothelial dysfunction, leukocyte recruitment, maladaptive smooth muscle remodeling, chronic inflammation, and ultimately plaque destabilization (1, 2, 14). Regions of disturbed flow exhibit marked upregulation of pro-atherogenic connexins—particularly connexin 43 (Cx43)—which amplifies ATP release, immune activation, and endothelial permeability (7, 15, 19, 21).

## Connexome Components

Connexins form hexameric hemichannels that pair to create gap junctions enabling direct cytoplasmic exchange. Connexin 37 (Cx37) is enriched in the arterial endothelium and plays a protective role by limiting monocyte adhesion and supporting endothelial quiescence (15, 28). Connexin 40 (Cx40) promotes nitric oxide production, maintains anti-inflammatory signaling, and supports vascular homeostasis (28, 46). In contrast, connexin 43 (Cx43) is strongly induced under oscillatory shear stress and inflammatory conditions (7, 15, 21), where it promotes leukocyte adhesion, macrophage infiltration, foam cell formation, and smooth muscle migration (18, 30). Connexin 45 (Cx45) participates in vascular development and smooth muscle electrical communication (35).

Pannexin 1 (Panx1) functions predominantly as a mechanosensitive ATP-release channel activated by cytokines, oxidative stress, and mechanical strain (22, 24). Panx1-mediated ATP release triggers purinergic P2X7 receptor activation and NLRP3 inflammasome assembly, escalating inflammatory signaling in atherosclerosis (22, 31).

## Connexome Remodeling in Atherosclerosis

Atherosclerotic lesions preferentially develop in arterial branches or curvatures where blood flow is disturbed. Here, endothelial cells lose protective flow-dependent transcriptional programs and move toward an inflammatory phenotype characterized by reduced KLF2 and KLF4 expression (28, 46, 49). This shift decreases protective Cx37 and Cx40 expression (15, 28) and increases the expression and phosphorylation of Cx43 (7, 18, 21).

Enhanced ATP release through Cx43 and Panx1 amplifies endothelial activation and leukocyte recruitment (22, 24, 31). Smooth muscle cells respond to increased Cx43 signaling by adopting a synthetic, proliferative phenotype conducive to neointimal growth (18, 30).

Panx1-dependent ATP release activates the NLRP3 inflammasome, leading to caspase-1 activation and IL-1β secretion, processes that contribute to necrotic core expansion and plaque vulnerability (22, 31, 40).

# Regulatory Pathways Governing the Connexome

## 1. The KLF2/KLF4 Shear-Stress Axis

Laminar shear stress activates the MEKK2–MEK5–ERK5 pathway, stimulating MEF2 and resulting in the upregulation of KLF2 and KLF4 (28, 46, 49). These transcription factors enhance expression of Cx37 and Cx40 (15, 28) while suppressing Cx43 (7, 21). Loss of KLF2/KLF4 signaling under disturbed flow fosters endothelial inflammation and connexome dysregulation.

## 2. NF-κB Pathway

Inflammatory cytokines—including TNF-α and IL-1β—activate NF-κB signaling, which increases Cx43 transcription and drives phosphorylation patterns favoring hemichannel opening (7, 21, 20). This promotes endothelial activation, barrier dysfunction, and leukocyte recruitment (1, 14).

## 3. MAPK Pathways

ERK, JNK, and p38 MAPKs modify connexin behavior through transcriptional and post-translational mechanisms. ERK promotes Cx43 internalization and turnover (20), JNK elevates Cx43 expression during oxidative stress (30), and p38 increases hemichannel opening and inflammatory coupling (31).

## 4. PI3K–Akt/eNOS Signaling

Akt promotes endothelial homeostasis and supports Cx40 expression (28). Reduced nitric oxide bioavailability—common in atherosclerosis—enhances Cx43 hemichannel opening and promotes endothelial dysfunction (35).

## 5. Notch Signaling

Laminar shear stimulates Notch1–RBPJ signaling, which suppresses Cx43 expression and maintains endothelial quiescence (49). Loss of Notch activity in disturbed flow promotes endothelial-mesenchymal transition and enhances vascular inflammation (18).

## 6. TGF-β/SMAD Pathway

TGF-β induces Cx43 through SMAD2/3 activation (20, 30). Crosstalk with RhoA/ROCK and YAP/TAZ mechanotransduction pathways intensifies cytoskeletal tension, enhances matrix remodeling, and promotes connexin trafficking (48, 52).

## 7. Oxidative Stress & Nrf2

Reactive oxygen species oxidize Cx43 and Panx1, increasing hemichannel activity and weakening endothelial integrity (31). Nrf2 activation counters these effects by restoring antioxidant defenses and supporting Cx37 and Cx40 expression (24). However, Nrf2 is often suppressed in plaques (31).

## 8. NLRP3 Inflammasome Activation

Panx1-mediated ATP release activates P2X7 and the NLRP3 inflammasome (22, 31). This leads to caspase-1 activation and IL-1β maturation, key contributors to plaque expansion and inflammation (39, 40).

## 9. RhoA/ROCK Mechanotransduction

RhoA/ROCK enhances actomyosin tension and increases trafficking of Cx43 to the plasma membrane under disturbed flow, promoting inflammatory remodeling (48).

## 10. YAP/TAZ Mechanotransduction

YAP and TAZ respond to matrix stiffness and oscillatory shear by entering the nucleus and increasing Cx43 transcription (52). This activation promotes smooth muscle proliferation and migration, contributing to plaque progression (53).

# Nanomedicine and Therapeutic Modulation of the Connexome

Nanotechnology offers new tools for imaging, modulating, and repairing connexome signaling. Targeted nanoparticles that bind VCAM-1, ICAM-1, macrophages, or oxidized lipids provide highly sensitive plaque imaging (37, 38, 42). Therapeutic delivery systems—including siRNA, miRNA mimics/inhibitors, and mRNA nanoparticles—are being developed to restore KLF2/KLF4 signaling or suppress Cx43 and Panx1 activation (27, 39). Connexin-modulating peptides such as Gap26, Gap27, and TAT-Gap19 can selectively inhibit Cx43 hemichannels when delivered via nanoparticles (47). Multifunctional theranostic platforms combine real-time imaging with connexome-targeted therapy (40, 52, 53).

# Future Directions

Emerging technologies—including single-cell transcriptomics, spatial proteomics, and computational flow modeling—are revealing cell-specific patterns of connexome regulation in unprecedented detail (49). The integration of mechanobiology, inflammation, and nanotherapeutics is guiding next-generation strategies aimed at normalizing Cx37, Cx40, Cx43, and Panx1 activity. Precision modulation of connexome signaling is increasingly seen as a promising approach for stabilizing plaques and reducing the burden of atherosclerotic cardiovascular disease (27, 52, 53).

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This entry is adapted from: 10.1080/17435889.2025.2587712