Effect of oxidized LDL on the expression of connexins in cultured human umbilical-vein endothelial cells

The Potential Role of Connexins in the Pathogenesis of Atherosclerosis

Connexins (Cx) are members of a protein family which enable extracellular and intercellular communication through hemichannels and gap junctions (GJ), respectively. Cx take part in transporting important cell-cell messengers such as 3',5'-cyclic adenosine monophosphate (cAMP), adenosine triphosphate (ATP), and inositol 1,4,5-trisphosphate (IP3), among others. Therefore, they play a significant role in regulating cell homeostasis, proliferation, and differentiation. Alterations in Cx distribution, degradation, and post-translational modifications have been correlated with cancers, as well as cardiovascular and neurological diseases. Depending on the isoform, Cx have been shown either to promote or suppress the development of atherosclerosis, a progressive inflammatory disease affecting large and medium-sized arteries. Cx might contribute to the progression of the disease by enhancing endothelial dysfunction, monocyte recruitment, vascular smooth muscle cell (VSMC) activation, or by inhibiting VSMC autophagy. Inhibition or modulation of the expression of specific isoforms could suppress atherosclerotic plaque formation and diminish pro-inflammatory conditions. A better understanding of the complexity of atherosclerosis pathophysiology linked with Cx could result in developing novel therapeutic strategies. This review aims to present the role of Cx in the pathogenesis of atherosclerosis and discusses whether they can become novel therapeutic targets.

Single-cell RNA sequencing of mouse left ventricle reveals cellular diversity and intercommunication

Previous studies have revealed the diversity of the whole cardiac cellulome but not refined the left ventricle, which was essential for finding therapeutic targets. Here, we characterized single-cell transcriptional profiles of the mouse left ventricular cellular landscape using single-cell RNA sequencing (10× Genomics). Detailed t-distributed stochastic neighbor embedding (tSNE) analysis revealed the cell types of left ventricle with gene markers. Left ventricular cellulome contained cardiomyocytes highly expressed Trdn, endothelial cells highly expressed Pcdh17, fibroblast highly expressed Lama2, and macrophages highly expressed Hpgds, also proved by in situ hybridization. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analysis (ListHits > 2, P < 0.05) were employed with the DAVID database to investigate subtypes of each cell type with the underlying functions of differentially expressed genes (DEGs). Endothelial cells included 5 subtypes, fibroblasts comprising 7 subtypes, and macrophages contained 11 subtypes. The key representative DEGs (P < 0.001) were Gja4 and Gja5 in cluster 3 of endothelial cells, Aqp2 and Thbs4 in cluster 2 of fibroblasts, and Clec4e and Trem-1 in cluster 3 of macrophages perhaps involved in the occurrence of atherosclerosis, heart failure, and acute myocardial infarction proved by literature review. We also revealed extensive networks of intercellular communication in left ventricle. We suggested possible therapeutic targets for cardiovascular disease and autocrine and paracrine signaling underpins left ventricular homeostasis. This study provided new insights into the structure and function of the mammalian left ventricular cellulome and offers an important resource that will stimulate studies in cardiovascular research.

Connexin43 siRNA promotes HUVEC proliferation and inhibits apoptosis induced by ox-LDL: an involvement of ERK signaling pathway

Oxidized low-density lipoprotein (ox-LDL), one of the most important risk factors of atherosclerosis, is a highly antigenic, potent chemoattractant that facilitates the development of atherosclerosis. Gap junctions also play an important in the development of atherosclerosis. In this study, we investigated the effects of ox-LDL on connexin43 and the mechanisms of connexin43 siRNA-inhibited apoptosis induced by ox-LDL in human umbilical vein endothelial cell (HUVEC), to clarify the role of connexin43 in atherosclerosis. Our results showed that ox-LDL significantly inhibited the growth and promoted apoptosis of HUVEC in a dose-dependent manner. Also, ox-LDL upregulated the expression of connexin43. Furthermore, knockdown connexin43 by siRNA promoted proliferation and inhibited apoptosis in ox-LDL-stimulated HUVEC. Moreover, the level of phosphor-ERK1/2 and connexin43 was remarkably attenuated by a ERK pathway inhibitor (PD98059). These results suggest that connexin43 siRNA promotes HUVEC proliferation and inhibits apoptosis induced by ox-LDL, and ERK signaling pathway appears to be involved in these processes.