Heme oxygenase-1 protects against PM2.5 induced endothelial dysfunction through inhibition of HIF1α.

PM2.5 has been accepted as a strong risk factor for cardiovascular diseases. Activation of the renin-angiotensin system (RAS) has been proved to be a key factor in triggering vascular endothelial dysfunction upon PM2.5 exposure in our previous reports. In the current study, we observed the concurrent induction of hemoxygenase (HO)- 1 and RAS components (ANGII and AT1R) expression both in the vascular endothelial cell lines and in rat lung tissue after PM2.5 exposure. Furthermore, HO-1 inhibited RAS activation by suppressing the expression and activity of HIF1α, the upstream transcriptional activator of ANGII and AT1R. In addition, HO-1 blocked significantly increased the release of cell adhesion molecules and chemokines (VCAM-1, E-Selectin, P-Selectin, IL-8, MCP-1) that drive monocyte-endothelium adhesion, along with the enhanced the generation of oxidative stress response mediators in the vascular endothelium. These data together indicate that PM2.5 induced HO-1 upregulation functions as a self-defense response to antagonize endothelial dysfunction by inhibiting HIF1α-mediated RAS activation. Targeting endogenous protective pathway might be helpful to protect from PM2.5-induced cardiovascular injury.