Association of Connexin37 C1019T with myocardial infarction and coronary artery disease: a meta-analysis

Connexin 37 Regulates the Kv1.3 Pathway and Promotes the Development of Atherosclerosis

Objective

To investigate the mechanism of Connexin 37 (Cx37) and Kv1.3 pathways in atherosclerosis (AS).

Methods

ApoE^−/− mice were given a high-fat diet to establish atherosclerosis (AS) model, and macrophages in mice were isolated and extracted to transfect Cx37 vectors with silencing or overexpressing, and Kv1.3 pathway blockers were used to inhibit the pathway activity. The indexes of body weight, blood glucose, and blood lipid of mice were collected. The protein and mRNA expression levels of Cx37 and Kv1.3 were detected by reverse transcription-PCR (RT-PCR), Western blot, and immunofluorescence technique. Oil red O staining was used to observe plaque area. Masson staining was used to detect collagen content. The concentrations of chemokine CCL7 were quantified using the ELISA kits. CCK8 was used to detect cell proliferation.

Results

Cx37 and Kv1.3 were highly expressed in macrophages of AS mice, and the expression of Kv1.3 and CCL7 decreased after Cx37 was silenced, and the proliferation of macrophages was also decreased. Wild-type mice and AS model mice were treated with Cx37 overexpression vectors and Kv1.3 pathway blocking, and it was found that Cx37 overexpression could improve the blood lipid and blood glucose levels and increase the area of AS in AS mice. However, blocking the activity of Kv1.3 pathway can reduce the levels of blood lipid and blood glucose, increase the body weight of mice, and reduce the area of AS mice. Blocking the activity of Kv1.3 pathway can slow down the plaque development of AS mice and make its indexes close to wild-type mice. And the use of Kv1.3 pathway blockers on the basis of overexpression of Cx37 indicated that inhibition of Kv1.3 pathway activity did not affect the expression of Cx37, but could inhibit the collagen content in the plaque area of AS mice, inhibit the expression of chemokine CCL7, and reverse the effect of Cx37 overexpression.

Conclusion

Cx37 can improve the activity of macrophages by regulating the expression of chemokines and the activity of Kv1.3 pathway in AS mice, and enrich macrophages in inflammatory tissues and expand the area of plaque formation.

Atrial Fibrillation: Focus on Myocardial Connexins and Gap Junctions

Atrial fibrillation (AF) represents the most common type of clinical cardiac arrhythmia worldwide and contributes to substantial morbidity, mortality and socioeconomic burden. Aggregating evidence highlights the strong genetic basis of AF. In addition to chromosomal abnormalities, pathogenic mutations in over 50 genes have been causally linked to AF, of which the majority encode ion channels, cardiac structural proteins, transcription factors and gap junction channels. In the heart, gap junctions comprised of connexins (Cxs) form intercellular pathways responsible for electrical coupling and rapid coordinated action potential propagation between adjacent cardiomyocytes. Among the 21 isoforms of connexins already identified in the mammal genomes, 5 isoforms (Cx37, Cx40, Cx43, Cx45 and Cx46) are expressed in human heart. Abnormal electrical coupling between cardiomyocytes caused by structural remodeling of gap junction channels (alterations in connexin distribution and protein levels) has been associated with enhanced susceptibility to AF and recent studies have revealed multiple causative mutations or polymorphisms in 4 isoforms of connexins predisposing to AF. In this review, an overview of the genetics of AF is made, with a focus on the roles of mutant myocardial connexins and gap junctions in the pathogenesis of AF, to underscore the hypothesis that cardiac connexins are a major molecular target in the management of AF.

GJA1 Gene Polymorphisms and Topographic Distribution of Cranial MRI Lesions in Cerebral Small Vessel Disease

Vascular endothelial cell (EC) and blood–brain barrier (BBB) dysfunction is the core pathogenesis of cerebral small vessel disease (CSVD). Moreover, animal experiments have shown the importance of connexin (Cx)-43 in EC and BBB function. In this study, we recruited 200 patients diagnosed with sporadic CSVD. Initially, we examined imaging scores of white matter hyperintensities (WMH), lacunar infarction (LI), and cerebral microbleeds (CMB). Additionally, we performed next-generation sequencing of the GJA1 gene (Cx43 coding gene) to examine correlation between these single-nucleotide polymorphisms and the burden and distribution of CSVD. Fourteen target loci were chosen. Of these, 13 loci (92.9%) contributed toward risk for cerebellar LI, one locus (7.1%) was shown to be a protective factor for lobar CMB after FDR adjustment. In conclusion, single-nucleotide polymorphisms in the GJA1 gene appear to affect the distribution but not severity of CSVD.

Serine 319 phosphorylation is necessary and sufficient to induce a Cx37 conformation that leads to arrested cell cycling

Connexin 37 (Cx37; protein product of GJA4) expression profoundly suppresses proliferation of rat insulinoma (Rin) cells in a manner dependent on gap junction channel (GJCh) functionality and the presence and phosphorylation status of its C-terminus (CT). In Rin cells, growth is arrested upon induced Cx37 expression and serine 319 (S319) is frequently phosphorylated. Here, we show that preventing phosphorylation at this site (alanine substitution; S319A) relieved Cx37 of its growth-suppressive effect whereas mimicking phosphorylation at this site (aspartate substitution; S319D) enhanced the growth-suppressive properties of Cx37. Like wild-type Cx37 (Cx37-WT), Cx37-S319D GJChs and hemichannels (HChs) preferred the closed state, rarely opening fully, and gated slowly. In contrast, Cx37-S319A channels preferred open states, opened fully and gated rapidly. These data indicate that phosphorylation-dependent conformational differences in Cx37 protein and channel function underlie Cx37-induced growth arrest versus growth-permissive phenotypes. That the closed state of Cx37-WT and Cx37-S319D GJChs and HChs favors growth arrest suggests that rather than specific permeants mediating cell cycle arrest, the closed conformation instead supports interaction of Cx37 with growth regulatory proteins that result in growth arrest.

Interaction between CONNEXIN37 and PDE4D gene polymorphisms with susceptibility to ischemic stroke in Chinese population

The objective of this study was to test the relationship of several single nucleotide polymorphisms (SNPs) within phosphodiesterase 4D (PDE4D ) and connexin 37 (CONNEXIN37 ) gene additional interactions with ischemic stroke (IS) risk. The online software SNPstats was used for Hardy–Weinberg equilibrium testing. Generalized multifactor dimensionality reduction (GMDR) was employed to detect the potential interactions among CONNEXIN37 gene, PDE4D g ene, and smoking. The results indicated that the rs1764391-T and rs966221-G were correlated with higher IS risk, the corresponding ORs (95% CI) were 1.66 (1.21–2.03) and 1.48 (1.11–1.92), respectively. We also found that the first two loci including rs1764391 and rs918592, and the other two-loci including rs1764391 and smoking were significant in the GMDR model. Participants with rs1764391-CT/TT and rs918592-CT/TT genotype have the highest IS risk, compared to subjects with rs1764391-CC and rs918592-CC genotype, OR (95%CI) = 3.16 (1.83–4.45); smokers with rs1764391-CT/TT genotype also have the highest IS risk, compared to never smokers with rs1764391-CC genotype, OR (95%CI) = 2.82 (1.53–4.15), but no significant interaction combinations were found between gene and alcohol drinking. So in this study, the rs1764391-T and rs966221-G, rs1764391–rs918592 interaction, rs1764391–smoking interaction were all associated with higher IS susceptibility.

How does Helicobacter pylori cause gastric cancer through connexins: An opinion review

Helicobacter pylori (H. pylori) is a Gram-negative bacterium with a number of virulence factors, such as cytotoxin-associated gene A, vacuolating cytotoxin A, its pathogenicity island, and lipopolysaccharide, which cause gastrointestinal diseases. Connexins function in gap junctional homeostasis, and their downregulation is closely related to gastric carcinogenesis. Investigations into H. pylori infection and the fine-tuning of connexins in cells or tissues have been reported in previous studies. Therefore, in this review, the potential mechanisms of H. pylori-induced gastric cancer through connexins are summarized in detail.

Differential Association of Cx37 and Cx40 Genetic Variants in Atrial Fibrillation with and without Underlying Structural Heart Disease

Atrial fibrillation (AF) appears in the presence or absence of structural heart disease. The majority of foci causing AF are located near the ostia of pulmonary veins (PVs), where cardiomyocytes and vascular smooth muscle cells interdigitate. Connexins (Cx) form gap junction channels and participate in action potential propagation. Genetic variants in genes encoding Cx40 and Cx37 affect their expression or function and may contribute to PV arrhythmogenicity. DNA was obtained from 196 patients with drug-resistant, symptomatic AF with and without structural heart disease, who were referred for percutaneous catheter ablation. Eighty-nine controls were matched for age, gender, hypertension, and BMI. Genotyping of the Cx40 -44G > A, Cx40 +71A > G, Cx40 -26A > G, and Cx37 1019C > T polymorphisms was performed. The promoter A Cx40 polymorphisms (-44G > A and +71A > G) showed no association with non-structural or structural AF. Distribution of the Cx40 promoter B polymorphism (-26A > G) was different in structural AF when compared to controls (p = 0.03). There was no significant difference with non-structural AF (p = 0.50). The distribution of the Cx37 1019C > T polymorphism was different in non-structural AF (p = 0.03) but not in structural AF (p = 0.08) when compared to controls. Our study describes for the first time an association of drug-resistant non-structural heart disease AF with the Cx37 1019C > T gene polymorphism. We also confirmed the association of the Cx40 - 26G > A polymorphism in patients with AF and structural disease.

Connexins in Cardiovascular and Neurovascular Health and Disease: Pharmacological Implications

Connexins are ubiquitous channel forming proteins that assemble as plasma membrane hemichannels and as intercellular gap junction channels that directly connect cells. In the heart, gap junction channels electrically connect myocytes and specialized conductive tissues to coordinate the atrial and ventricular contraction/relaxation cycles and pump function. In blood vessels, these channels facilitate long-distance endothelial cell communication, synchronize smooth muscle cell contraction, and support endothelial-smooth muscle cell communication. In the central nervous system they form cellular syncytia and coordinate neural function. Gap junction channels are normally open and hemichannels are normally closed, but pathologic conditions may restrict gap junction communication and promote hemichannel opening, thereby disturbing a delicate cellular communication balance. Until recently, most connexin-targeting agents exhibited little specificity and several off-target effects. Recent work with peptide-based approaches has demonstrated improved specificity and opened avenues for a more rational approach toward independently modulating the function of gap junctions and hemichannels. We here review the role of connexins and their channels in cardiovascular and neurovascular health and disease, focusing on crucial regulatory aspects and identification of potential targets to modify their function. We conclude that peptide-based investigations have raised several new opportunities for interfering with connexins and their channels that may soon allow preservation of gap junction communication, inhibition of hemichannel opening, and mitigation of inflammatory signaling.