Preconditioning with rHMGB1 ameliorates lung ischemia–reperfusion injury through inhibiting alveolar macrophages pyroptosis via Keap1/Nrf-2/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 (Nrf-2 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, 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. Measurement of the products of oxidative Stress (ROS, MDA, 15-F2t-Isoprostane) and the antioxidant enzymes (SOD, GSH-PX, CAT) were performed. 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, 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/Nrf-2/HO-1 pathway in LIRI. Furthermore, inhibiting Keap1/Nrf-2/HO-1 pathway through brusatol administration could aggravate lung tissue damage and inflammatory response after lung I/R. Also, brusatol administration could suppresse the antioxidant and anti-pyroptosis effects of rHMGB1 preconditioning in LIRI. Conclusions rHMGB1 preconditioning protects against LIRI through suppressing AMs pyroptosis. The mechanism is partially explained by inhibiting oxidative stress and improving the activity of antioxidative enzymes via Keap1/Nrf-2/HO-1 pathway.