A crosstalk triggered by hypoxia and maintained by MCP-1/miR-98/IL-6/p38 regulatory loop between human aortic smooth muscle cells and macrophages leads to aortic smooth muscle cells apoptosis via Stat1 activation

Hypoxia and inflammation are central characteristics of the abdominal aortic aneurysm (AAA), but the mechanisms for their relationship and actual role remain far from full understood. Here, we showed MCP-1 (monocyte chemotactic protein-1) induced by hypoxia in primary human Aortic Smooth Muscle Cells (hASMCs) increased the chemotaxis of THP-1 macrophages and MCP-1 induced IL-6 expression in THP-1 cells via downregulating miR-98 which directly targets IL-6. In addition, IL-6 positively feedback regulated MCP-1 expression in hASMCs via p38 signal that is independent on hypoxia, and inhibition of p38 signal blocked the effect of IL-6 on MCP-1 expression regulation. Moreover, IL-6 exposure time-dependently induces phASMCs apoptosis via Stat1 activation. Collectively, our data provide compelling evidence on the association between hypoxia and inflammation triggered by hypoxia and then mediated by MCP-1/miR-98/IL-6/p38 regulatory loop, which leads to hASMCs apoptosis via Stat1 activation to contribute to AAA formation and progression.