Activation of NLRP3 inflammasome in patients with renal transplantation: relation to allograft dysfunction, inflammation, and renal fibrosis

Background Chronic allograft dysfunction (CAD) represents a complex process of inflammatory response, fibrosis, and tissue restoration, mediated by a myriad of proinflammatory cytokines, enzymes, and growth factors. NOD-like receptor protein3 (NLRP3) inflammasome is one of the NLR protein families. It drives proteolysis of proinflammatory caspases which induces maturation of pro-interleukin (IL)-1β and pro-IL-18. The aim of this work is to study NLRP3 inflammasome activation in patients with renal transplantation in relation to allograft function, inflammation, and renal fibrosis.Methods Thirty renal transplant recipients (RTR): 15 patients with stable renal function (Group I), 15 patients with CAD (Group II), and 15 healthy subjects (Group III) were included. Serum and urinary NLRP3, caspase-1, and interleukin-1β were measured using an enzyme-linked immunosorbent assay (ELISA) kit. Serum high sensitivity C-reactive protein (hs-CRP) level was measured, and neutrophil-lymphocyte ratio (NLR) was calculated. Renal function was evaluated by serum creatinine (S.Cr) and estimated glomerular filtration rate (eGFR). Resistive index (RI) was calculated with Doppler ultrasonography. In patients with CAD, renal interstitial fibrosis (RIF) was graded in renal biopsies.Results Serum NLRP3, caspase-1, serum and urinary IL-1β, and hs-CRP showed a statistically significant increase in RTR, particularly in those with CAD compared to the controls with a positive correlation with each other, their urinary level, S. Cr, hs-CRP, NLR, RI, and RIF (p < 0.001). The receiver operating characteristic curve showed high diagnostic accuracy of serum NLRP3, caspase-1, and IL-1β in discriminating patients with CAD from patients with stable renal function.Conclusion The NLRP3-caspase1-IL-1β cascade is activated and upregulated in renal transplant recipients, particularly those with advanced renal impairment, and thus may play a role in developing CAD and renal fibrosis. They could be potential biomarkers for post-transplant outcome, follow-up, and early diagnosis. Moreover, their cascade could be a target for future anti-inflammatory therapeutic strategies for allograft dysfunction.