Modulation of Inflammatory Responses After Brain Death and Syngeneic Renal Transplantation By Systemic Overexpression of esRAGE.

Abstract

Introduction: Donor brain death (BD) adversely affects organ quality. Inflammation mediated by engagement of TLR4 and RAGE may contribute to inferior outcomes. Endogenous secretory (es)RAGE is a soluble decoy receptor which sequesters HMGB1 and other RAGE ligands blocking binding to TLRs 2 and 4, as well as to RAGE. Aim: To determine whether in vivo expression of esRAGE can reduce inflammation in syngeneic KTx from BD donors. Methods: Donor and recipient C57BL/6 mice received 5×1011 VG rAAV-esRAGE or ctrl vector 7 days pre-transplant. Donor kidneys were grafted 1 hr after BD induction, and sampled at d1 and 4 post-Tx. Cellular infiltration, proliferation, and gene expression were determined. Serum and kidneys were also collected 3 hrs post-BD. Results: Serum HMGB1 levels in esRAGE-BD mice (˜10ng/ml) were significantly less than those in untreated BD mice (>25ng/ml, p=0.02). There was a trend towards reduced expression of CXCL10, MCP-1, MIP-2, CCL22, IL-10, IL-6, IL-1β and TNF-α in the kidneys of esRAGE-BD mice, but this was not consistently observed after KTx. Neutrophil and macrophage infiltrate density was substantially reduced by esRAGE (nΦ 9.1±2.0/HPF cf 23.1±6.0, p=0.03; F4/80 27.3±3.2/HPF cf 65.1±9.1, p<0.01).Figure: No Caption available.Proliferation of parenchymal cells (PCNA staining) was enhanced in esRAGE-treated mice (7.6±0.5/HPF cf 4.2±1.2, p=0.05).Figure: No Caption available.Conclusions: esRAGE significantly reduced neutrophil and macrophage infiltration following syngeneic renal Tx from BD donors. RAGE is a binding partner for the integrin MAC-1, and reduced leucocyte infiltration may reflect inhibition of this interaction. esRAGE increased proliferation of renal parenchymal cells after Tx from BD donors, similar to documented effects of soluble RAGE in liver injury. These effects may be translated into improved graft function.