ABSTRACT
Objective To investigate the effect of albumin on expression of NLRP3 inflammasome and its downstream cytokines IL-1β and IL-18 in tubular epithelial cells.Methods Thirty mesangioproliferative glomerulonephritis (MsPGN) patients with different levels of proteinuria were selected, and their renal biopsy samples were stained by PAS and Masson to observe tubular epithelial cells injury and inflammatory cells infiltration.NLRP3, caspase-1, IL-1β and IL-18, as well as different inflammatory cells, were detected by immunohistostaining.In vitro, Western blotting and real-time PCR were employed to detect NLRP3, caspase-1, IL-1β and IL-18 protein and mRNA in HK-2 cells stimulated by bovine serum albumin (BSA) (20 g/L).Results In MsPGN patients with high levels of proteinuria, there were obvious renal tubular epithelial cell injury and inflammatory cells infiltration (all P ＜ 0.05), and the expressions of NLRP3, caspase-1, IL-1β and IL-18 were up-regulated compared to patients with low levels of proteinuria (all P ＜ 0.05).Furthermore, IL-1β and IL-18expressions were positively correlated with the degree of proteinuria (r=0.836, P ＜ 0.05;r=0.901, P ＜0.05).NLRP3, caspase-1, IL-1β and IL-18 protein and mRNA were significantly increased in HK-2cells stimulated by BSA compared to the control group (all P ＜ 0.05).Conclusions Albumin is able to induce NLRP3 inflammasome activation in tubular epithelial cells, which may be the mechanism of tubulointerstitial injury and inflammation caused by proteinuria.
ABSTRACT
Objective To observe NLRP3 inflammasome expression and inflammatory cells infiltration in the BSA-overloaded rats kidney,and to investigate the potential mechanism of renal injury induced by proteinuria.Methods After unilateral right nephrectomy,eighteen healthy male Wistar rats were randomly divided into two groups:protein overload nephropathy model group (n=10),treated with intraperitoneal injections of bovine serum albumin (BSA); control group (n=8),treated with intraperitoneal injections of 0.9％ saline for 9 weeks.Body weigh were measured every week and 24 h urine were collected in 0,2,5,7,9 week.The plasma levels of blood total protein (TP),albumin (Alb),serum creatinine (Scr) and blood urea nitrogen (BUN) were determined by automatic analyzers.Renal pathological changes were evaluated by PAS and Masson stains.Immunohistochemical staining was used to detect the expression of NLRP3,caspase-1,IL-1β,and IL-18,as well as the types of inflammatory cells.The NLRP3,caspase-1,IL-1β,and IL-18 protein and mRNA levels were also analyzed by Western blot and real-time PCR in two groups.Results It was found that there was a significant increase of proteinuria and BUN in model group compare to that in control group (all P ＜ 0.05).However,there were no significant changes in body weight,TP,Alb and Scr between the two groups.Morphological study demonstrated that renal tubular epithelial cell injury,proteinaceous casts in tubular lumen,accompanying with the dominant macrophages and lymphocytes infiltration in interstitium in model group.The immunohistochemistry showed that there were more T (CD3+),B cells (CD20+) and macrophages (CD68+) in renal interstitium in model group than that in control group (P ＜ 0.05).Tubulointerstitial injury score was higher than that of the control group (P＜0.05).Immunohistochemistry,Western blot and real-time PCR all showed that the expression of NLRP3,caspase-1,IL-18 and IL-1 β were significantly increased compared to those in control group (P ＜ 0.05).Furthermore,there were significant correlations between proteinuria and IL-lβ/IL-18 expression (P ＜ 0.05).Conclusion NLRP3 inflammasome activation is involved in tubulointerstitial inflammation caused by proteinuria.