Abstract 17701: Nrf2 Inhibits NF-κB Activation During Ischemia Reperfusion Injury and Suppresses Subsequent Development of Cardiac Allograft Vasculopathy in Murine Heart Transplantation

Abstract

Introduction: Recent studies suggest that ischemia reperfusion injury (IRI) activates the NF-κB pathway leading to the subsequent development of cardiac allograft vasculopathy (CAV). Nrf2 has been suggested to inhibit NF-κB activation during IRI in other organs; however, the role in myocardial IRI and CAV remains unclear. Therefore, we examined the effects of Nrf2 induction and knockout (KO) on IRI-mediated NF-κB activation as well as CAV using a murine transplant (Tx) model. Methods: Nrf2 wild-type (WT) and KO mice were used as donors, with WTs used as recipients for IRI studies and Bm12 mice for CAV studies. Donor hearts received 2hrs of cold ischemia before Tx. Twenty-five mg/kg sulforaphane (SF, a known Nrf2 agonist) was given to donors 24hrs prior to surgery and to recipients just after Tx to induce Nrf2, with saline as vehicle control (SA). Donor hearts were procured after 24hrs of reperfusion in IRI studies. In CAV studies, recipients received daily 5mg/kg SFN or saline until day 56 when donor hearts were procured (n=6/group). Results: In IRI, NF-κB activity measured by percentage of the cells with nuclear p65 (Figure A) was significantly higher in KO-SA compared with WT-SA (38±4 vs 24±4%, p<0.001). WT-SF displayed notably less NF-κB activity compared with WT-SA (13±5 vs 24±4%, p=0.002). The mRNA levels of NF-κB-mediated inflammatory cytokines were significantly higher in KO-SA compared with WT-SA, and WT-SF displayed lower levels of these mRNA compared with WT-SA (Figure B). In the chronic CAV studies, WT-SA displayed less coronary occlusion area compared with KO-SA (21±8 vs 42±12%, p=0.005). Furthermore, WT-SF showed significantly less coronary occlusion compared with WT-SA (21±8 vs 8±4%, p=0.005) (Figure C). Conclusions: Our results suggest that Nrf2 inhibits NF-κB activation during IRI and suppresses subsequent development of CAV. The Nrf2 pathway may be a promising pharmacological target to prevent development of CAV via its anti-inflammatory properties.