Lead-induced cardiomyocytes apoptosis by inhibiting gap junction intercellular communication via autophagy activation

Lead (Pb) is one of the most common heavy metal contaminants in the environment. Pb can cause pathophysiological changes in several organ systems, including the cardiovascular system, but the molecular mechanism remains elusive. The study aimed to study the effects of Pb on Gap junction intercellular communication (GJIC) and its role in Pb-induced apoptosis. The present study aims to determine whether Pb-induced autophagy promotes apoptosis of rat cardiac myocytes (H9c2 cells) by downregulating GJIC using CCK-8 Kit, scrape loading/dye transfer assay, Annexin V/PI assays, Western blot analysis and double-immunofluorescence experiments. The results showed that Pb elicited cytotoxicity in a time- and concentration-dependent manner and led to increased apoptosis in a concentration-dependent manner in H9c2 cells. Pb also reduced GJIC in H9c2 cells in a concentration-dependent manner through the downregulation of connexin (Cx) 43. Inhibition of gap junctions by gap junction blocker carbenoxolone disodium (CBX) resulted in increased apoptosis. Furthermore, Pb increased autophagy in a concentration-dependent manner in H9c2 cells, decreasing the distribution of Cx43 on the cell membrane, and targeted Cx43 to autophagosome via light chain 3 (LC3). However, autophagy inhibitor 3-Methyladenine (3-MA) can slow down the downregulation of Cx43 induced by Pb in H9c2 cells. In conclusion, our results provide evidence that Pb-decreased GJIC promotes apoptosis in cardiomyocytes. This is probably because of the fact that Pb-induced autophagy exacerbates GJIC inhibition and downregulation of Cx43.