ATF5 Regulates Tubulointerstitial Injury In Diabetic Kidney Disease Via Mitochndrial Unfolded Protein Response

Abstract Background:Mitochondrial quality control (MQC) plays a critical role in the progression of tubulointerstitial injury in diabetic kidney disease (DKD). Mitochondrial unfolded protein response (UPRmt), an important MQC procedure, is activated to maintain mitochondrial protein homeostasis upon mitochondrial stress. Activating transcription factor 5 (ATF5) has been proved to be the key in mammalian UPRmt via its mitochondria-nuclear translocation. In this study, we investigated whether ATF5 activate UPRmt in mammalian DKD to reduce tubule injury. Methods: Eight-week-old db/db mice were injected with ATF5-shRNA lentivirus or negative control lentivirus via the tail vein. Mice were euthanized at 12 weeks, DHE and Tunel assay were performed respectively to evaluate the apoptosis and ROS production of kidney section. And we used western blotting to detect the expression relationship between ATF5 and UPRmt. ATF5-siRNA, ATF5 overexpression plasmid or HSP60-siRNA were transfected into HK-2 cells. Mitosox and DCFH-DA staining methods were used to gauging cell and mitochondial oxidative stress level, while early stage of cell apoptosis was detected by JC-1 kit. Results: We found that UPRmt intensified and exhibited opposite function in HK-2 cells in respond to high glucose intervention. We showed that compared with non-diabetic samples, renal section from patients and mice with diabetes showed increase expression of ATF5 and UPRmt related proteins (HSP60, CLpP, LONP1), which were correlated with tubule damage of kidney. We also established 12-week-old ATF5 knocking-down db/db mice, and found they presented improved biochemical and histological features and lower expression of UPRmt related proteins as compared with db/db mice. Correspondingly, HG-induced oxidative stress damage, apoptosis and UPRmt were reversed by ATF5-siRNA in HK-2 cells and aggravated by ATF5 over-expressing plasmid. Moreover, overexpressing ATF5 and down-regulating HSP60 simultaneously offset the effect of ATF5 overexpressing plasmid. Conclusions: Our findings suggest that ATF5 is closely associated with the progress of damage in diabetic kidney tubule cells by regulating UPRmt.