RP220, a Renalase Peptide, Attenuates Lupus Nephritis by Anti-Inflammatory in MRL/lpr Mice

Background: Lupus nephritis (LN) is a common and serious complication of systemic lupus erythematosus (SLE), which inflammation plays an important role in the progression of the disease. RP220, an active peptide of renalase, was proved previously to be effective in protecting kidney against ischemic and toxic injury by anti-inflammatory effect. We aimed to investigate the therapeutic effect of RP220 in lupus nephritis and its possible mechanism.   Methods: MRL/lpr mice were treated by RP220, cyclophosphamide (CP) and saline respectively. Urine albumin creatinine ratio, serum creatinine and blood urea nitrogen, circulating autoantibody levels and renal histopathological assessment was done to evaluate the renal damage and immunology status for all the mice. Renal pro-inflammatory cytokines including IL-1β, IL-6, CCL-2, TNF-α and NLRP3 inflammasome were assessed by real-time PCR and western blotting. Mouse macrophage cell line (RAW264.7) were treated by renalase-siRNA and RP220 to verify its antiinflammatory effects in vitro. Results: Urinary albumin creatinine ratio, blood urea nitrogen (BUN) and serum anti-dsDNA antibody were significantly lower in RP220 and CP group compared with saline group at the end of the experiment. Renal immune complex deposition and the injury score of glomerular, tubular and perivascular were significantly lower in RP220 and CP treated group as well as inflammatory cytokines such as TNF-α, IL-6 and IL-1β and NLRP3. The increase of renal expression of NLRP3, ASC and caspase-1 was reversed by RP220 but not by CP. Moreover, RP220 treated mice has no significant adverse effect such as body weight loss, bone marrow arrest and immune over inhibition in CP group. In vitro study of macrophage cell found that the expression of TNF-α, IL-6, IL-1β and CCL-2 induced by LPS were significantly aggravated by RP220 targeted siRNA and the effects were reversed by RP220 administration. Conclusion: Administration of RP220 ameliorated proteinuria, renal injury and inflammatory status in LN murine model without adverse effects. The renal protective effect of RP220 might be associated with NLRP3-IL1 β pathway. Development of pharmacologic peptide would be helpful in providing novel therapeutic strategies for human SLE. Funding Statement: This work was supported by the National Science and Technology Major Project (No. 81770666), Shanghai Municipal Health Commission Project (ZY(2018-2020)-FWTX-1001, 20154Y0003) and research funding to LING WANG from Shanghai Shenkang Hospital Development Center(16CR3022A). Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: All experiments were approved by the Institutional Animal Care Committee of Shanghai Jiaotong University.