Mitophagy-dependent macrophage reprogramming protects against kidney fibrosis
Divya Bhatia, Kuei-Pin Chung, Kiichi Nakahira, Edwin Patino, Michelle C. Rice, Lisa K. Torres, Thangamani Muthukumar, Augustine M.K. Choi, Oleh M. Akchurin, Mary E. Choi
Divya Bhatia, Kuei-Pin Chung, Kiichi Nakahira, Edwin Patino, Michelle C. Rice, Lisa K. Torres, Thangamani Muthukumar, Augustine M.K. Choi, Oleh M. Akchurin, Mary E. Choi
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Research Article Nephrology

Mitophagy-dependent macrophage reprogramming protects against kidney fibrosis

Abstract

Mitophagy, by maintaining mitochondrial quality control, plays a key role in maintaining kidney function and is impaired in pathologic states. Macrophages are well known for their pathogenic role in kidney fibrosis. Here, we report that PINK1/Parkin-mediated mitophagy in macrophages is compromised in experimental and human kidney fibrosis. We demonstrate downregulation of mitophagy regulators mitofusin-2 (MFN2) and Parkin downstream of PINK1 in kidney fibrosis. Loss of either Pink1 or Prkn promoted renal extracellular matrix accumulation and frequency of profibrotic/M2 macrophages. Pink1–/– or Prkn–/– BM-derived macrophages (BMDMs) showed enhanced expression of rictor. Mitochondria from TGF-β1–treated Pink1–/– BMDMs exhibited increased superoxide levels, along with reduced respiration and ATP production. In addition, mitophagy in macrophages involves PINK1-mediated phosphorylation of downstream MFN2, MFN2-facilitated recruitment of Parkin to damaged mitochondria, and macrophage-specific deletion of Mfn2 aggravates kidney fibrosis. Moreover, mitophagy regulators were downregulated in human CKD kidney and TGF-β1–treated human renal macrophages, whereas Mdivi1 treatment suppressed mitophagy mediators and promoted fibrotic response. Taken together, our study is the first to our knowledge to demonstrate that macrophage mitophagy plays a protective role against kidney fibrosis via regulating the PINK1/MFN2/Parkin-mediated pathway.

Authors

Divya Bhatia, Kuei-Pin Chung, Kiichi Nakahira, Edwin Patino, Michelle C. Rice, Lisa K. Torres, Thangamani Muthukumar, Augustine M.K. Choi, Oleh M. Akchurin, Mary E. Choi

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Figure 8

Mitophagy is compromised in patients with CKD and in TGF-β1–treated human renal macrophages.

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Mitophagy is compromised in patients with CKD and in TGF-β1–treated huma...
(A–C) Relative mRNA expression levels of PINK1 (A), MFN2 (B), and PRKN (C) normalized with β-actin (ACTB) were determined by TaqMan qPCR in kidney biopsy from patients with CKD (CKD+, n = 6) and patients without CKD (CKD–, n = 9) and analyzed using Mann-Whitney U test. (D) Plasma CCL2 levels in patients with (CKD+, n = 6) or without CKD (CKD–, n = 9) were determined by ELISA and analyzed using Mann-Whitney U test. (E–G) Frequency of MFN2 (E) and Parkin (F) and median fluorescence intensity (MFI) of MitoSox dye (G) in peripheral blood mononuclear cells (PBMCs) from patients with severe CKD (n = 8) vs. mild or moderate CKD (n = 15) were determined by flow cytometry and analyzed using student’s unpaired 2-tailed t test. (H) Western blot for the expression of PINK1, MFN2, Parkin, fibronectin (FN), CX3CR1, and β-actin in human primary renal macrophages cultured in the absence (–) or presence (+) of TGF-β1 (5 ng/mL) for 24 hours. (I) Western blot for the expression of PINK1, MFN2, Parkin, TGF-β1, CD206, CX3CR1, FN, α-SMA, and β-actin in human primary renal macrophages cultured in the presence of DMSO (vehicle control) or Mdivi-1 (50 μM) for 3 hours. (J) Mitochondrial membrane potential in human primary renal macrophages treated with DMSO (vehicle control) or Mdivi-1 (50 μM) for 3 hours detected by staining with MitoTracker dye through flow cytometry. The histogram was gated from forward scatter (FSC) vs. side scatter (SSC) parent population. Data are mean ± SEM, *P < 0.05, **P < 0.01, ***P < 0.001.