The Effects Of PACS-2 On Lipid-related Kidney Injury In Diabetic Kidney Disease

Background:Lipid accumulation in tubular cells plays a key role in the pathogenesis of diabetic kidney disease（DKD）.Targeting lipid metabolism disorders has clinical value in delaying the progression of DKD,but the precise mechanism by which molecules mediate metabolism disorders and lipid-related kidney injury remains unclear.Phosphofurin acidic cluster sorting protein 2（PACS-2）is a multifunctional sorting protein that plays a key role in lipid metabolism.But whether it mediates renal lipid metabolism disorder and the mechanism of it remains unclear.This study determined the role of PACS-2 in lipid-related kidney injury in DKD.Methods:In vivo,we chose proximal tubule-specific Pacs-2knockout mice and their control group.The experimental animals were divided into four groups:Pacs-2^fl/flmice、PT-Pacs-2^-/-mice、diabetic Pacs-2^fl/flmice、diabetic PT-Pacs-2^-/-mice.Diabetes was induced by a high-fat diet（HFD）combined with intraperitoneal injections of streptozotocin（STZ）.The physiological features of blood and urine were assessed.The histopathological changes were observed by HE,Masson and PAS staining.Lipids deposition in kidney was assessed by immunohistochemistry and Oil Red O staining.Transcriptomic analysis was performed between Pacs-2^fl/flmice and PT-Pacs-2^-/-mice to determine the changes of downstream molecules,which were verified by immunofluorescence and other methods.In vitro,HK-2 cells were stimulated by high glucose plus palmitic acid（HGPA）to mimic a diabetic state.PACS-2 plasmid、PACS-2 and SOAT1si RNA were utilized to investigate the role and related mechanisms of PACS-2 and SOAT1 in lipid metabolism and lipid deposition in HK-2 cells,Results:Diabetic PT-Pacs-2^-/-mice developed more severe tubule injury and proteinuria compared to diabetic Pacs-2^fl/flmice,which accompanied with increasing lipid synthesis,uptake and decreasing cholesterol efflux as well as lipid accumulation in tubules of the kidney.Furthermore,transcriptome analysis showed that the m RNA level of sterol O-acyltransferase 1（Soat1）was up-regulated in the kidney of control PT-Pacs-2^-/-mice.It was further verified that PACS-2 knockout could promote the expression of SOAT1 and its downstream sterol regulatory element binding proteins（SREBPs）in the kidney of diabetic mice.HGPA treatment of HK-2 cells（human renal tubular epithelial cell line）induced lipid deposition.Overexpression of PACS-2 can reduce HGPA-induced lipid deposition and the content of cellular cholesterol ester（CE）and free fatty acid（FFA）.While transfection of HK-2 cells with PACS-2 si RNA increased lipid deposition and the content of CE and FFA.In addition,silencing PACS-2 in HK-2 cells increased the expression of SOAT1 and its downstream SREBPs.Inhibition of SOAT1 expression by SOAT1 si RNA partially blocked the intracellular lipid deposition and the increased expression of SREBPs induced by PACS-2 si RNA.Conclusion:PACS-2 has a protective role against lipid-related kidney injury in DKD through SOAT1/SREBPs signaling.