Effect And Potential Mechanism Of Calcium Binding Protein S100A16 On Chronic Renal Fibrosis

The incidence of chronic kidney disease is increasing more than 7%every year.More than 500 million people in the world have different kidney disease,and more than a million people die each year from chronic kidney disease and its associated cardiovascular disease^[1].Chronic kidney disease has become a serious threat to human health after cardiovascular and cerebrovascular disease,tumor and diabetes^[2].For the majority of patients,when come to the end-stage chronic renal failure,they will receive kidney transplant or lifelong kidney dialysis,which cause the patient’s survival quality,family and society huge burden.A large number of epidemiological studies indicate that the growth rate of patients with end-stage renal disease is increasing^[3-5].Chronic kidney disease,with various immune and hormonal factors,induces inflammatory and cytokines and result in continuous destruction of renal units and decreased renal function.The current clinical treatment principle is the treatment of original disease,remove of pathogenic factors and symptomatic treatment.However,we have not yet found a cure for renal fibrosis.The calcium binding protein S100A16 is a new member of the S100 family,which is expressed in many organs and tissues and can promote the formation of fat.In recent years,relevant studies have shown that S100A16 inhibits osteogenesis but stimulates adipogenesis by increasing the transcription of PPARγand decreasing the transcription of RUNX2.^[6].High fat is one of the chronic injury factors in the kidney,and whether S100A16,crucial in glycolipid metabolism,is related to chronic renal fibrosis.Therefore,we designed this project to explore the relationship between S100A16 and renal interstitial fibrosis.In this study,we firstly performed immunohistochemical stainning for the renal biopsy specimens of patients and found that with the aggravation of renal disease,the expression of S100A16 increased,suggesting that S100A16 may be related to renal disease.In addition,the renal interstitial fibrosis model（UUO）was established in mice,and we found that the high expression of S100A16 was positively correlated with renal interstitial fibrosis,and knockout S100A16 could reverse fibrosis.Epithelial-mesenchymal-transition（EMT）markers were detected and S100A16 was found to aggravate renal fibrosis by promoting EMT.Then EMT was induced by TGF-βin HK-2 cell line and the results were verified in vitro.At the same time,we found another cytoskeleton protein Myh9,possible participates in cell morphological change and cell movement by MS.Then the specific interaction between S100A16and Myh9 was determined by immunoprecipitation and immunofluorescence localization.When the concentration of cytoplasmic Ca²⁺increased to a certain extent,the combination of Ca²⁺-Myh9 could change the configuration of Myh9,resulting in changes in the reorganization of cytoskeleton.We use thapsigargin to reduce intracellular free calcium concentration and reverse EMT.In addition,the level of Myh9 was reduced by antibody transfection,and the effect of EMT was also reversed.Thus,it is suggested that calcium binding protein S100 A16 increases intracellular calcium concentration,thereby activating the calcium dependent cytoskeletal protein Myh9 and promoting EMT and aggravating renal fibrosis.This project explores the molecular mechanism of the molecular mechanism of S100A16 promoting EMT to aggravate fibrosis in-depth,playing much theoretical and significance role of looking for the clinical prevention and treatment of primary or secondary targets for renal interstitial fibrosis in clinic.