Abstract Body: Background: Mitophagy, and in particular Parkin/PINK1 dependent mitophagy, represents an essential mitochondrial quality control mechanism that mediates the lysosomal clearance of damaged mitochondria. Recent evidence remains unclear about the role of Parkin/PINK1 on metabolic and mitochondrial function in vascular smooth muscle cells (VSMCs) in aortic aneurysms (AAs). The goal of the present study is to investigate whether modulation of PINK1/Parkin-mediated mitophagy via genetic and pharmacologic approaches increases susceptibility to mitochondrial and metabolic dysfunction in VSMCs in AAs.
Approach: Single cell RNA-Seq analyses in human AAA tissue versus control revealed down-regulation of mitophagy pathways, mitochondrial structure, and function-related proteins in phenotypically modulated VSMCs with a separate but corresponding decrease in PINK1/Parkin via Western analysis using AAA vs control tissue. Mitophagy, as measured via flow cytometry in MitoQC tracker mice in 1000 ng/kg/min Angiotensin II (Ang II) treated AAs vs saline controls, demonstrated decreased mitophagy in VSMCs and endothelial cells with a corresponding decrease in PINK1/Parkin via Western blot analyses. VSMC Parkin KO male mice versus controls(n=25-30/group) treated with Ang II exhibited decreased survival and increased aortic size along with decreased coupled and uncoupled oxygen consumption rates (OCR). Metabolomics analyses in blood versus tissue in VSMC Parkin vs controls (n=6/group) demonstrates altered folate and long-chain fatty acid metabolism in AA tissue but not blood. In contrast, pre-treatment of AAs models with a USP30 antagonist named VB-08, a natural inhibitor of Parkin-dependent mitophagy whose suppression with VB-08 leads to Parkin activation, resulting in increased survival, decreased aortic size, and increased coupled and uncoupled OCR rates. Metabolomics analyses in blood and tissue in VB-08 treated AAs vs controls demonstrated recovery of long-chain fatty acid metabolism within AAA tissue but not blood. Pre-Treatment with VB-08 in VSMC Parkin KO mice demonstrated that the improved effects of VB-08 were via USP30 suppression resulting in Parkin activation in vivo.
Conclusion: These studies demonstrate that Parkin/PINK1 alterations increase susceptibility to AAs via altered mitochondrial and metabolic function. These studies offer new insight into how disturbances of the normal rate of mitophagy could contribute to the progression of AAs.