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Abstract: TH-OR012

PINK1-MFN2-Parkin-Mediated Mitophagy Dependent Macrophage Reprogramming Protects against Renal Fibrosis

Session Information

Category: CKD (Non-Dialysis)

  • 1903 CKD (Non-Dialysis): Mechanisms

Authors

  • Bhatia, Divya, Weill Cornell Medicine, New York City, New York, United States
  • Chung, Kuei-Pin, Weill Cornell Medicine, New York City, United States
  • Muthukumar, Thangamani, Weill Cornell Medicine, New York City, New York, United States
  • Choi, Augustine MK, Weill Cornell Medicine, New York City, New York, United States
  • Choi, Mary E., Weill Cornell Medicine, New York City, New York, United States
Background

Mitophagy, by maintaining mitochondrial quality, plays critical role for normal kidney function. Kidney injury-induced mitochondrial oxidative stress triggers proinflammatory cytokine production by M1 macrophages and their reprogramming towards profibrotic/M2 phenotype. We investigated the role of mitophagy regulatory proteins: PTEN-induced kinase1 (PINK1), Mitofusin 2 (MFN2) and Parkin in macrophage reprogramming during renal fibrosis.

Methods

Renal fibrosis in wild type, PINK1 and Parkin knockout (KO) mice was induced by unilateral ureteral obstruction (UUO) (7-days) or adenine diet (14-days). Renal macrophages from mice and human kidneys were isolated by magnetic beads. Flow cytometry (F4/80, CD11b, Ly6c, CCR1, CX3CR1) and western blots (iNOS, arginase I, mannose receptor-1, fibronectin, rictor, TGFβ1, TGFβR1) were performed to determine macrophage phenotypes and fibrotic response. MitoTracker & MitoSox dyes were used to access mitochondrial membrane potential (MMP) and reactive-oxygen species (mROS). Mitophagy was suppressed by transfection of PINK1-siRNA/Mdivi1 or induced by FCCP treatment.

Results

Obstructed kidneys from PINK1/Parkin KO mice displayed higher expression of FN, MR-1, TGFβ1, TGFβRI & CD45+ mononuclear cells. Renal macrophages from obstructed kidneys of KO mice showed amplified fibrotic response. TGFβ1-treated BMDM from the KO mice displayed greater levels of mROS, rictor, Arg I but not iNOS expressing M1 macrophages. PINK1-knockdown THP-1 human macrophages showed lower phosphorylation at MFN2. Mitochondria from FCCP treated MFN2-KO macrophages showed reduced expression of Parkin and lower MMP. Inhibition of mitophagy in human primary renal macrophages resulted in: i) elevated expression of FN, MR-1, TGFβ1 & CX3CR1, ii) reduced MMP & iii) enhanced mROS production. Human fibrotic kidney showed higher relative mRNA expression of MRC1 (P=0.002), TGFβ1 (P=0.03) and a trend of decrease in Parkin (P=0.07) expression than control kidney.

Conclusion

UUO and adenine diet-induced oxidative stress and renal fibrosis were exaggerated in absence of mitophagy. Deficiency of PINK1 in macrophages resulted in decreased phosphorylation of MFN2, suppressed recruitment of Parkin to mitochondria and rictor-mediated reprogramming of macrophages towards M2/profibrotic phenotype.

Funding

  • NIDDK Support