Abstract: TH-OR109

Macrophage Mitophagy Modulates Pro-Fibrotic Response in Renal Fibrosis

Session Information

  • Scarred for Life?
    November 02, 2017 | Location: Room 394, Morial Convention Center
    Abstract Time: 04:42 PM - 04:54 PM

Category: Chronic Kidney Disease (Non-Dialysis)

  • 308 CKD: Mechanisms of Tubulointerstitial Fibrosis

Authors

  • Bhatia, Divya, Weill Cornell Medicine, New York, New York, United States
  • Choi, Mary E., Weill Cornell Medicine, New York, New York, United States
Background

Kidney injury involves infiltration of pro-inflammatory macrophages and oxidative stress induced mitochondrial dysfunction, and pro-fibrotic macrophages driving progression of renal fibrosis. Mitophagy, the selective autophagy of dysfunctional mitochondria, is important for cellular homeostasis. We examined the role of PTEN-induced kinase1 (PINK1), major mediator of mitophagy, in regulating macrophage derived fibrotic response.

Methods

Wild type (WT) and PINK1-KO mice, subjected to unilateral ureteral obstruction (UUO), a model of progressive renal fibrosis, were sacrificed at day 3. Peritoneal and bone marrow-derived macrophages were isolated. The expression levels of CD11b, Ly6C, F4.80, CD206 and CX3CR1 were detected by flow cytometry. Arginase1 (Arg1), TGFβ type I receptor (TGFβRI), fibronectin and α-smooth muscle actin (α-SMA) expression was determined by western blot. MitoSox staining was used to assess mitochondrial derived superoxide production. Mitophagy was suppressed in RAW264.7 cells through transfection of PINK1 small interfering RNA (siRNA).

Results

UUO-induced increase in the expression of circulating Ly6C++ CD11b+ pro-inflammatory monocytes was higher in PINK1-KO mice compared to WT. PINK1-KO mice displayed higher expression of F4.80+ CD206+ pro-fibrotic macrophages and chemokine receptor CX3CR1 in obstructed kidneys compared to WT and contralateral kidneys. Flow cytometric data revealed increase in the Ly6C++ pro-inflammatory cells in kidney post-UUO at day 3. However, their expression was comparable in kidneys from KO and WT mice. The expression of Arg1 and fibronectin was higher in kidneys of KO mice after UUO. Furthermore, PINK1 deficient macrophages (both primary PINK1-KO and siRNA knockdown RAW264.7) exhibited enhanced polarization towards pro-fibrotic phenotype. Primary PINK1-KO macrophages also showed higher expression of Arg1, TGFβRI, fibronectin and α-SMA. The expression levels of Arg1, fibronectin and α-SMA were further increased after stimulation with TGFβ. In addition, PINK1 deficient macrophages displayed higher mitochondrial superoxide levels upon TGFβ stimulation compared to WT.

Conclusion

PINK1-mediated mitophagy deficiency results in increased oxidative stress and enhanced pro-fibrotic response by macrophages. Macrophage mitochondrial superoxide production might play critical role in activation of their pro-fibrotic phenotype and progression of renal fibrosis.

Funding

  • NIDDK Support