Abstract 087: Mitochondrial Fission Inducer, Dynamin-Related Protein 1 (DRP1), is Required for Endothelial Inflammatory Responses

Abstract

Among various cardiovascular diseases, hypertension (HTN) is considered to be a disease plagued by chronic low-grade inflammation associated with endothelial dysfunction. Interestingly, recent studies have identified mitochondrial adaptation and/or dysfunction as components to hypertensive vascular dysfunction. While mitochondria are indispensable to maintain cellular metabolism, they also participate in adaptive and maladaptive cell/tissue responses via several retro grade signaling pathways. DRP1 plays a major role in mitochondrial quality control. However, whether DRP1 is involved in mitochondrial dysfunction and endothelial inflammation during development of HTN remains unknown. In the present study, we tested the hypothesis that inflammatory stimuli, through DRP1-dependent mitochondrial alteration, enhance endothelial inflammation. In cultured rat aortic endothelial cells (RAECs), TNFα (10 μg/mL) transiently induced mitochondrial fission maximally at 3h which was inhibited using a mitochondrial fission inhibitor, Mdivi1 (10 μM) (0.16±0.04 vs 0.10±0.02 mitochondria fragmentation count with MitoTracker, p<.01 ). TNFα and FCCP (a fission agonist, 10 μM) increased THP-1 monocyte adhesion to RAECs, which was also inhibited with Mdivi1 (256±17 vs 139±16 for TNFα, 238±30 vs 156±14 for FCCP, attached cells per field scanned, p<.01 ). Likewise, mdivi1 and adenoviruses encoding siRNA for DRP1 or dominant-negative K38A DRP1 (50 moi) attenuated TNFα-induced VCAM-1 induction in RAECs. TNFα increased aerobic respiration, which was prevented by mdivi1 or ER stress inhibitor PBA (10 mM). Inhibition of ER stress, glycolysis or mitochondrial respiration using PBA, 2-DG (1 mg/mL) or oligomycin (1 μM) prevented VCAM-1 induction. However, suppression of TNFα-induced mitochondrial ROS production by mito-Tempo (25 nM) was unable to prevent VCAM-1 induction. In C57BL6 mice receiving AngII (1000 ng/kg/min, 2 weeks) infusion, treatment with Mdivi-1 (25 mg/kg ip every other day) or PBA (1g/kg/day) prevented vascular VCAM-1 induction. In conclusion, our data suggests a critical role for ER stress and subsequent functional and structural remodeling of mitochondria induced by DRP1 in mediating endothelial inflammatory activation in HTN.