| Objective:Corin is a type II transmembrane serine protease,which is highly expressed in cardiomyocytes.Corin proteolytic cleavages pro-atrial natriuretic peptide(pro-ANP)and pro-B-type natriuretic peptide(pro-BNP),to form mature natriuretic peptides,which can promote vasodilation,natriuresis and diuresis,and thus maintaining blood pressure and volume balance.Corin maitain sodium-water banlance by ANP and downstream signaling pathways.Corin mRNA and protein were also detected in kidney,including the proximal tubule,thick ascending limb,connecting tubule and collecting duct,but its function in kidney is still unclear.To further study the function of Corin in kidney,we analyzed the levels of Corin in urine and blood samples collected from normal individuals and patients with kidney diseases,analyzed some factors(hs-CRP,IL-1β,TNF-α and IL-6)which maybe affect Corin levels in urine and signal pathway.To further study the correlation between Corin and cytokines,we cultured two kinds cells: human embryonic kidney 293 cells(HEK293 cells)and human renal proximal tubular cells(HK2 cells),western blot was used to analyzed Corin and cytokines.These studies may help us to further understand the occurrence,development and therapy of kidney disease.Methods1.Urine and plasma samples of normal individuals and patients with chronic kidney diseases were collected.Patients with chronic kidney diseases were classified as two groups : early-stage CKD group and advanced CKD group.2.Enzyme linked immunosorbent assay(ELISA)was performed to detected urinary and plasma Corin.Besides,plasma cytokines(IL-1β,TNF-α)were also detected by ELISA.Correlation analysis was performed between urinary Corin and urinary β2-MG plasma cytokines(IL-1β,TNF-α and IL-6).3.The expressing levels of Corin in HEK293 Corin cells stimulated by cytokines(IL-1β,TNF-α,IL-6)were examined by western blot.4.Quantitative polymerase chain reaction(qPCR)was performed to detect the mRNA levels of Corin,ANP in human renal proximal tubular cells(HK2)stimulated by cytokines.Results:1.Corin can be detected in both plasma and urine,the level of plasma Corin: 627.10 ± 64.90(normal person)vs 744.90 ± 82.59(early-stage CKD group)vs 987.80 ± 59.71 pg/ml(advanced CKD group),P<0.05.The level of urinary Corin: 84.45 ±6.93(normal person)vs 114.50 ± 8.50(early-stage CKD group)vs 27.22 ± 5.00 pg/ml(advanced CKD group).In advanced CKD group,there is a positive correlation between urinary Corin and estimated glomerular filtration rate(eGFR)(R=0.69,P<0.01).2.The level of urinary Corin was positively correlated with urinary β2-MG(P=0.01)(figure 1B),but no correlation was found between urinary Corin and urinary albumin(P>0.05).3.Compared with normal person,plasma inflammation factors(IL-1β,TNF-α)didn’t change obviously,but urinary Corin of patients in early-stage CKD group correlated with plasma IL-1β(P=0.03).4.As the IL-1β concentrations(0ng/ml,0.1ng/ml,1ng/ml,10ng/ml)increased,an elevation of Corin level was observed in culture medium of HEK293 Corin cells(P<0.01).However,the amount of Corin didn’t change markedly in cells lysis(P>0.05).Only when TNF-α reached to a certain concentration(10 ng/ml),the level of Corin in medium would be augmented significantly than control group(0 ng/ml)(P=0.02),little change of Corin level in cell lysis was found neither.Conclusions:1.Soluble Corin can be detected in urine,the primary source of Corin in urine is from tubules epithelial cells,but not from plasma.2.Urinary Corin level in advanced CKD group correlated with estimated glomerular filtration rate.Along with chronic kidney diseases severity advanced,urinary Corin decreased.Urinary Corin level in patients with advanced CKD indicated kidney injury.3.Cytokines,containing IL-β and TNF-α,may accelerate Corin shedding from cell membrane,but for Corin synthesis,cytokines seemed to have no obvious effects.Inflammatory condition in patients with kidney diseases affect Corin metabolisis.Inflammatory condition in patients with kidney diseases affect Corin metabolisis. |
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