Preconditioning with rHMGB1 ameliorates lung ischemia–reperfusion injury through inhibiting alveolar macrophages pyroptosis via Keap1/Nrf2/HO-1 signal pathway

Abstract Background: Lung ischemia-reperfusion injury (LIRI) is a common and complex pathophysiological process that can lead to poor patient outcomes. Inflammasome-dependent macrophage pyroptosis contributes to organ damage caused by ischemia-reperfusion (I/R). Oxidative stress reaction and antioxidant enzymes also play an important role in LIRI. This experiment was conducted to investigate whether preconditioning with rHMGB1 could ameliorate LIRI and explore the mechanisms of its protective effect in a lung I/R mice model. Methods: Adult male mice were anesthetized and the left hilus pulmonis was clamped for 60 min, followed by 120 min of reperfusion. rHMGB1 was performed by intraperitoneal injection at 2 h before anesthesia. Brusatol (Nrf2 antagonist) was given intraperitoneally every other day for a total of five times before surgery. Measurements of pathohistological lung tissue damage, pulmonary wet/dry (W/D) ratios and inflammatory mediators were performed to assess the extent of lung injury after I/R. Alveolar macrophages (AMs) pyroptosis were evaluated by LDH release, caspase-1 expression in flow cytometry, GSDMD expression in immunofluorescent staining. The products of oxidative Stress (ROS, MDA, 15-F2t-Isoprostane) and the antioxidant enzymes (SOD, GSH-PX, CAT) were detected.Results: Preconditioning with rHMGB1 significantly ameliorated I/R-induced lung injury through measuring the morphology, wet/dry weight ratio, the expressions of IL-1β, IL-6, NF-κB and HMGB1 in lung tissue. rHMGB1 preconditioning remarkably alleviated AMs pyroptosis induced by lung I/R. rHMGB1 preconditioning significantly reduced oxidative stress and restored the activity of antioxidative enzymes. In addition, rHMGB1 preconditioning mediated the activity of Keap1/Nrf2/HO-1 pathway in LIRI. Furthermore, inhibiting Keap1/Nrf2/HO-1 pathway through brusatol administration could aggravate lung tissue damage and inflammatory response after lung I/R. And these effects by brusatol administration could be alleviated by rHMGB1 preconditioning in LIRI .Conclusions : rHMGB1 preconditioning protects against LIRI through suppressing AMs pyroptosis. The molecular mechanism could be partially explained by inhibiting oxidative stress and improving the activity of antioxidative enzymes via Keap1/Nrf2/HO-1 pathway upon rHMGB1 preconditioning.