The Mechanism Of YWHAZ Affecting The Transformation Of Renal Tubular Epithelial Cells After Acute Kidney Injury

Background and Objective:Acute kidney injury(AKI)is the most common acute kidney disease with a high risk of death.The progression of AKI to chronic kidney disease(CKD)has brought a huge health and economic burden to the world.At present,there is no effective method to prevent the progression of AKI to CKD.Poor regeneration and repair of renal tubular epithelial cells after AKI is the central link in the progression of AKI to CKD.Therefore,reducing the damage of renal tubular epithelial cells and inhibiting their conversion to myofibroblasts are the keys to preventing or delaying the transformation of AKI-CKD.It is reported in the literature that the transcription coactivator Yes-associated protein(YAP)is involved in the poor repair process of renal tubular epithelial cells.This subject takes YWHAZ,an important regulatory protein of YAP,as the research object.By establishing a unilateral renal ischemia-reperfusion induced AKI-CKD model(IR-AKI-CKD)model combined with in vitro studies on the intervention of YWHAZ expression to prove that YWHAZ inhibits renal tubular epithelial cells maladaptive repair and affects the specific mechanism of action of AKI-CKD transition.Methods:(1)In vivo study:The experimental mice were divided into sham operation group,IR-AKI group,including three time points of 24h,48h and 72h after operation,and IR-AKI-CKD group,including two time points 21 d and 28d after operation.Pathological PAS,Masson,Sirius Red staining and detection of serum creatinine and urea nitrogen to verify whether the model is established;Use immunofluorescence and Western Blot to detect the expression of YWHAZ,Kim-1,active YAP and fibrosis-related proteins.(2)In vitro studies:Using human renal tubular epithelial cells to establish YWHAZ low expression and overexpression cell models,detect cell proliferation under normal oxygen and hypoxia-reoxygenation conditions,and the cell phenotype changes were detected after treating cells with the classic fibroblast growth factor TGF-β1.Results:In vivo experiments,the serum creatinine and urea nitrogen levels in the model group showed a trend of first increasing and then decreasing,peaking at 24h,and the CKD phase was higher than that of normal group mice;pathological results showed that the renal tubules in the Sham group were intact and the renal tubular epithelial cells were neatly arranged,in the model group,renal tubules in the AKI phase were damaged and regenerated,and the degree of fibrosis in the CKD phase was aggravated.Immunofluorescence and Western Blot results showed that the expression level of YWHAZ in AKI kidney increased,and the CKD phase decreased,and the active YAP showed a significant increase trend in CKD phase.In the model of knockdown expression of YWHAZ in renal tubular epithelial cells,the expression of phosphorylated YAP decreased,active YAP was increased,and knockdown expression of YWHAZ under normal and hypoxic conditions reduced cell proliferation.The expression of fibrosis-related indicators after TGF-β1 treatment was significantly increased.In the YWHAZ overexpression model,expression of phosphorylated YAP increased,active YAP was decreased,and the expression of fibrosis-related indexes decreased after TGF-β1 treatment.Conclusion:In vivo experimental results illustrated that the expression level of YWHAZ in the renal tubules of mice in the AKI phase of the IR-AKI-CKD model was higher than that of the control mice,the expression of YWHAZ in the renal tubules of the CKD phase model group was decreased,the level of activation YAP which promotes the transformation of renal tubular epithelial cells was increased under the regulation of YWHAZ.In vitro studies,it was confirmed that YWHAZ negatively regulated active YAP,suppressed the expression of downstream fibrosis-related proteins,and inhibited the transformation of renal tubular epithelial cells.These results provide clues for the prevention and cure of AKI-CKD transition.