Abstract: FR-PO980
Defective ATP Synthase Mediates Renal Fibrosis and Tubular Epithelial-Mesenchymal Transition
Session Information
- Pathology and Lab Medicine: Basic
November 08, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pathology and Lab Medicine
- 1601 Pathology and Lab Medicine: Basic
Author
- Sung, Junne-Ming, National Cheng-Kung University Hoispital, Tainan, Taiwan
Background
Reduced mitochondrial function is a feature of chronic kidney disease (CKD). However, there is limited understanding of various aspect of mitochondrial biology in the renal injury.
Methods
This study aims to explore the role of mitochondrion dysfunction on TGFβ1–induced tubular cell epithelio-mesenchyamal transition (EMT) in vitro and renal fibrosis in vivo and clinical renal biopsy samples from patients with various stage of CKD.
Results
We observed TGFβ1-induced EMT in cultured renal tubular HK2 cells, and found that TGFβ1-treated cells have a decrease of oxygen consumption and an increase in use of non-oxidative phosphorylation glycolysis pathway as their energy source (by seahorse assay) while undergoing EMT, which was accompanied by increased mitochondrial membrane potential (MMP) and lower complex V activity (The activities of complex 1-IV were normal). Adding a mitochondrial complex V inhibitors (oligomycin) may induce EMT and further enhances TGF-β1-induced EMT. Blue native (BN)-PAGE studies showed a defective assembly of complex V (ATP synthase) in the mitochondria of EMT cells, which was possibly attributed by attenuation of its assembly factor ATPAF1. In HK2 cells, ATPAF1 knockdown caused EMT, and restoration of ATPAF1 protects renal tubule cells from TGFβ-induced mitochondrial dysfunction and EMT. Consistently, the animal model of tubulointerstitial fibrosis caused by unilateral ureteral obstruction (UUO) demonstrated attenuations in ATPAF1 level and complex V formation, accompanied by increased MMP. Overexpression of Atpaf1 in vivo attenuated mitochondrial dysfunction of tubular cells and interstitial fibrosis in UUO animal model. Thus, restoration of ATPAF1 in the kidney is protective against injury during the progression of renal fibrosis. In clinical renal biopsy samples , we performed immunostaining for ATPAF1, MMP and α-smooth muscle actin(α-SMA, a marker of fibrosis) and found that the severity of interstitial fibrosis (α-SMA staining intensity) negatively correlated with tubular ATPAF1 and positively with MMP. In addition, tubular ATPAF1 intensity also negatively correlated with MMP staining.
Conclusion
Our study underscores ATPAF1 is an important factor in maintaining mitochondrial energy capacity in tubule cells, and is vulnerability to injury and mediates the development of renal fibrosis.