Dietary supplementation of camel whey protein attenuates heat stress-induced liver injury by inhibiting NLRP3 inflammasome activation through the HMGB1/RAGE signalling pathway

Abstract

• The HMGB1/RAGE/NLRP3 signaling pathway is involved in HS-induced liver injury. • CWP inhibited HS-induced liver injury by reducing activity of the NLRP3 inflammasome. • CWP inhibited the activation of NLRP3 inflammasome by restoring HMGB1 nuclear localization. • The combined application of CWP and anti-inflammatory agent completely blocked HS-induced liver injury. Inflammasomes play an important role in promoting heat stress (HS) induced liver injury. Dietary supplementation of camel whey protein (CWP) has been shown to alleviate HS-induced tissue damage. However, whether and how dietary CWP supplementation can reduce HS-induced liver injury remains unclear. Thus, we evaluated the ability of rats supplemented with CWP to resist HS-induced liver injury. To induce liver injury, Sprague-Dawley rats were exposed to HS. The mechanism of action was confirmed using an antagonist of high mobility group box 1 (HMGB1) and the NLR pyrin domain containing 3 (NLRP3) inhibitor before HS. Histological changes in the livers of the HS rats were visualised using haematoxylin and eosin staining. The protein expression of HMG1, receptor for advanced glycation end products (RAGE), NLRP3, Caspase-3, and Bcl-2 were detected using immunohistochemistry or western blotting. The content of IL-1β, the activation of Caspase-1, and the level of alanine transaminase (ALT) were determined using commercial kits. We confirmed that HS activated NLRP3 in the liver, as evidenced by enhanced Caspase-1 activity and increased IL-1β content. Inhibition of NLRP3 activation reversed abnormal expression and nuclear translocation of Caspase-3 and Bcl-2, and alleviated apoptosis, necrosis, and subsequent liver injury. HS-induced hepatocyte NLRP3 activation is dependent on elevated extracellular HMGB1 levels. Glycyrrhizic acid, an antagonist of HMGB1, which is also an anti-inflammatory agent, inhibited HS-induced NLRP3 activation. Interestingly, CWP also reversed HS-induced abnormal expression of HMGB1, RAGE, NLRP3, IL-1β, ALT, Bcl-2, and Caspase-3, inhibited Caspase-1 activity, and alleviated apoptosis and liver histological changes. More importantly, CWP combined with glycyrrhizic acid completely prevented HS-induced hepatocyte apoptosis and injury. These results indicate that CWP ameliorates HS-induced liver injury by inhibiting the HMGB1/RAGE/NLRP3 axis. Dietary supplementation with CWP may be an effective strategy to prevent serious complications from HS.