Abstract P3137: Drp1-dependent Mitochondrial Fission Induces Vascular Smooth Muscle Cell Dysfunction Through Kruppel-like Factor 4 Upregulation

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Introduction: Vascular smooth muscle cell (VSMC) phenotypic switching and subsequent VSMC proliferation and migration are major events that are closely associated with progression of cardiovascular diseases. Mitochondria play key roles in regulation of cell function. Recent findings have revealed that mitochondrial fission promotes proliferation and migration of VSMCs. Hypothesis: This study aimed to explore the role of a new drug candidate, ginsenoside Rh1, in Angiotensin II (Ang II)-induced VSMC migration and proliferation and its underlying mechanisms. Methods: Sulforhodamine B and wound-healing assay were used to evaluate effects on cell proliferation and migration. Molecular mechanisms were investigated using western blotting, qRT-PCR analysis, immunofluorescence staining, and luciferase assay. Reactive oxygen species (ROS) production was measured by dihydroethidium and MitoSOX staining. Results: We found that pretreatment with 50 μM Rh1 significantly suppressed Ang II-induced cell proliferation (% of decrease vs. Ang II group: 17.41 ± 2.38%, p < 0.01, n = 5) and migration (% of decrease vs. Ang II group: 198.8 ± 2.67%, p < 0.001, n = 5). Concomitantly, Ang II-increased both protein and mRNA levels of MMP2, MMP9, PCNA, and cyclin D1 were reduced by Rh1 pretreatment. Rh1 incubation also reversed the changes in both protein and mRNA expressions of α-SMA, vimentin, and osteopontin induced by Ang II. Besides, Ang II enhanced protein expression and promoter activity of KLF4, a key regulator of phenotypic switching, whereas pretreatment with Rh1 reversed these effects. Mechanistically, inhibitory effects of Rh1 were found to be associated with inhibition of ERK1/2 signaling pathway and ROS generation. In addition, deactivation of ERK1/2 suppressed phosphorylation of DRP1 at Ser 616. Notably, inhibition of DRP1-dependent mitochondrial fission by Mdivi-1 inhibited KLF4 expression and transcriptional activity induced by Ang II. Conclusions: In conclusion, mitochondrial fission involves Ang II-induced VSMC proliferation and migration through KLF4 upregulation, and that Rh1 inhibits VSMC dysfunction by suppressing ROS-mediated ERK1/2/DRP1/KLF4 signaling pathway.