Endothelial mitochondrial oxidative stress determines podocyte depletion in segmental glomerulosclerosis
Ilse Daehn, Gabriella Casalena, Taoran Zhang, Shaolin Shi, Franz Fenninger, Nicholas Barasch, Liping Yu, Vivette D’Agati, Detlef Schlondorff, Wilhelm Kriz, Borje Haraldsson, Erwin P. Bottinger
Ilse Daehn, Gabriella Casalena, Taoran Zhang, Shaolin Shi, Franz Fenninger, Nicholas Barasch, Liping Yu, Vivette D’Agati, Detlef Schlondorff, Wilhelm Kriz, Borje Haraldsson, Erwin P. Bottinger
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Research Article Nephrology

Endothelial mitochondrial oxidative stress determines podocyte depletion in segmental glomerulosclerosis

Abstract

Focal segmental glomerular sclerosis (FSGS) is a primary kidney disease that is commonly associated with proteinuria and progressive loss of glomerular function, leading to development of chronic kidney disease (CKD). FSGS is characterized by podocyte injury and depletion and collapse of glomerular capillary segments. Progression of FSGS is associated with TGF-β activation in podocytes; however, it is not clear how TGF-β signaling promotes disease. Here, we determined that podocyte-specific activation of TGF-β signaling in transgenic mice and BALB/c mice with Adriamycin-induced glomerulosclerosis is associated with endothelin-1 (EDN1) release by podocytes, which mediates mitochondrial oxidative stress and dysfunction in adjacent endothelial cells via paracrine EDN1 receptor type A (EDNRA) activation. Endothelial dysfunction promoted podocyte apoptosis, and inhibition of EDNRA or scavenging of mitochondrial-targeted ROS prevented podocyte loss, albuminuria, glomerulosclerosis, and renal failure. We confirmed reciprocal crosstalk between podocytes and endothelial cells in a coculture system. Biopsies from patients with FSGS exhibited increased mitochondrial DNA damage, consistent with EDNRA-mediated glomerular endothelial mitochondrial oxidative stress. Our studies indicate that segmental glomerulosclerosis develops as a result of podocyte-endothelial crosstalk mediated by EDN1/EDNRA-dependent mitochondrial dysfunction and suggest that targeting the reciprocal interaction between podocytes and endothelia may provide opportunities for therapeutic intervention in FSGS.

Authors

Ilse Daehn, Gabriella Casalena, Taoran Zhang, Shaolin Shi, Franz Fenninger, Nicholas Barasch, Liping Yu, Vivette D’Agati, Detlef Schlondorff, Wilhelm Kriz, Borje Haraldsson, Erwin P. Bottinger

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Figure 3

TGF-β signaling in podocytes decreased mitochondrial genes and function and increased mtDNA damage in glomerular epithelial cells.

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TGF-β signaling in podocytes decreased mitochondrial genes and function ...
(A) mRNA expression of mitochondrial proteins in isolated glomeruli from PodTgfbr1 mice after Dox for 0 to 14 days (n = 3; mean ± SEM). (B) Mitochondrial respiratory reserve capacity was measured by OCR of isolated glomeruli and tubules in single transgenic mice (stg) or double-transgenic PodTgfbr1 mice (+) treated with Dox for the days indicated (values are mean percentage reduction in OCR ± SEM; n = 8 mice per time point). (C) Immunoperoxidase detecting 3-nitrotyrosine in control untreated PodTgfbr1 (–Dox) and (D) day 4 Dox-treated PodTgfbr1 (+Dox) mice. (E) Quantification of lesion frequencies in mtDNA and nuclear DNA by QPCR in isolated glomeruli of stg or PodTgfbr1 mice treated with Dox for up to day 14 relative to untreated day 0 controls (n = 6; mean ± SEM relative amplification normalized to nondamaged day 0 controls). (F) Representative images of double immunofluorescence detection of 8-oxoG (green) and mitochondrial transcription factor A (mTFA; red) in glomeruli of a day 4 Dox-treated PodTgfbr1 mouse. (G) Urine 8-oxodG relative to urine creatinine in PodTgfbr1 mice left untreated (control) or treated with Dox for up to 21 days (n = 6; mean ± SEM). (H) Quantification of 8-oxoG staining of glomeruli from Dox control PodTgfbr1 mice, mice fed Dox chow for 7 days, or Dox-fed PodTgfbr1 mice treated with 1 mg/kg LY364947 from day 4 to day 7 (mean ± SEM). *P < 0.05, **P < 0.01 versus controls. Original magnification, ×40 (C and D); ×100 (F).