#5108 SUSTAINED IL-6 SECRETION CAN LEAD TO AN AMPLIFIED INFLAMMATORY RESPONSE, MEDIATED BY THE ACTIVATION OF STAT3 AND NFKB VIA THE IL-6 AMPLIFIER LOOP
Authors: Singh Mantabya , Prasad Narayan , Agarwal Vikas , Rai Mohit 
Published: June 2023

Abstract

Background and Aims
Organ transplants are the preferred treatment for end-stage organ failure. Potent and specific immunosuppressive agents have significantly decreased acute allograft rejection following renal transplantation. A significant barrier to long-term kidney allograft outcomes is chronic antibody-mediated rejection (CABMR). Chronic inflammation is a major cause of late graft loss that is mediated by soluble mediators released by immune and non-immune cells. IL-6 is a crucial cytokine that plays a central role in developing chronic inflammation. Non-immune cells, such as fibroblasts, have recently been identified as mediating chronic allograft rejection by activating the IL-6 amplifier loop (IL-6+IL-17). Our Aim of the study: -to study the effect of IL-6+IL-17 on secretion of IL-6 in the culture supernatant of fibroblasts derived from renal biopsy of chronic antibody mediated rejection (CABMR) patients; -to see the effect of anti-IL-6 (Tocilizumab)and anti-IL-17 on the secretion of IL-6 from the fibroblasts derived from kidney tissue of chronic antibody mediated rejection (CABMR) patients; and -to elucidate the pro-inflammatory pathway leading to increased IL-6 secretion by induction of Amplifier loop.

Method
Fibroblasts from grafted kidney from CABMR patients (n = 6) were cultured and stimulated with IL-6 (20ng/ µl), IL-17(50ng/ µl), IL-6 plus IL-17 for 24 hours. Levels of IL-6, MCP-1 and CCL20 were estimated in culture supernatants by ELISA as marker of IL-6 amplifier loop activation. mRNA expression of IL-6, MCP1, CCL20, and SOCS3 genes were measured in the stimulated fibroblasts. Stimulated Renal fibroblast cells from CABMR patients were lysed with Lysis buffer and subjected to SDS–PAGE and western blotting with anti-phospho-STAT3 and anti-phospho-NFκB p65. Additionally, IL-6, MCP1, and CCL20 levels were measured in Healthy control (n = 10), CABMR (n = 20), and non-CABMR (n = 30) patients.

Results
IL-6 and IL-17 synergistically induced more IL-6, CCL-20 & MCP-1 production from fibroblasts in culture supernatant. Gene expression analysis of IL-6, MCP1, and CCL20 was significantly higher with synergistic activation of IL-6 and IL-17 as compared to either IL-6 or IL-17 alone, while SOCS3 gene expression was downregulated. Our results also suggested that IL-6 Amplifier loop activation induces the NFκB and STAT3 signalling pathway activation in the non-immune cells like fibroblast derived from CABMR patients. Additionally, concentrations of IL-6, CCL-20 & MCP-1 in sera were significantly higher in CABMR patients compared to non-CABMR patients (p&lt;0.001). There was a significant reduction in IL-6 concentration in culture supernatant with IL-6 and IL-17 inhibitor together and mRNA expression of IL-6, CCL20 and MCP-1 was significantly reduced while SOCS3 gene expression was upregulated.

Conclusion
In humans after kidney transplantation, IL-6 amplifier activation plays an active role in chronic rejection responses. Inhibition of IL-6 with Anti-IL-6 (Tocilizumab) and inhibition of IL-17 with Anti-IL-17 together reduces markers of tissue injury (IL-6, MCP1, CCL20) and rejection of allografts. so, IL-6 amplifier may be a therapeutic target for Chronic transplant rejection.