Pharmacological Blockade of Hypoxia-Driven Autophagy: A Therapeutic Strategy to Limit Endothelial Activation and Thrombosis.

Thrombosis, a major underlying cause of cardiovascular disorders, is frequently initiated by endothelial cell (EC) activation, which facilitates platelet adhesion and subsequent clot formation. Although vascular injury is a well-established trigger, accumulating evidence implicates hypoxia as an additional determinant of thrombus development. In our previous study, we demonstrated that hypoxia associated with high altitude can promote autophagy-induced platelet aggregation. However, the contribution of ECs to such thrombosis under comparable hypoxic conditions (10%) remains poorly understood. In this study, using ECs isolated from rat aorta ex vivo, we show that hypoxia-inducible factor-1 alpha (HIF-1α), a key transcription factor, regulates autophagy and subsequent EC activation. Importantly, pharmacological inhibition of HIF-1α-mediated autophagy, repositioning the FDA-approved drug chloroquine (CQ), led to attenuated expression of P-Selectin, ICAM1, VCAM1 and consequent reduced platelet adhesion to ECs. Further mechanistic analysis revealed that autophagy modulates the NF-κB signaling pathway, in which P65 transcriptionally regulates the adhesion molecules ICAM1 and VCAM1 by binding to their upstream promoter elements under hypoxic conditions. In addition, using a rat IVC ligation model, we found that CQ not only attenuates thrombus formation but also suppresses VCAM1 expression, validating its antithrombotic potential. In summary, our findings suggest that hypoxia-induced HIF-1α activation promotes an autophagy-dependent NF-κB signaling cascade, thereby contributing to endothelial activation and thrombus formation. Furthermore, CQ's ability to disrupt this pathway underscores the therapeutic potential of targeting endothelial autophagy to mitigate hypoxia-associated thrombosis.