Dexmedetomidine ameliorates renal ischemia reperfusion-mediated activation of the NLRP3 inflammasome in alveolar macrophages

Renal ischemia-reperfusion (rI/R) is a risk factor for acute lung injury (ALI). Alveolar macrophages (AMs) activation mediated by rI/R-induced ALI is one of the pathogeneses associated with the development of ALI. In rI/ R, alpha(2)-adrenergic receptor agonists have been indicated to be effective in decreasing urea nitrogen concentrations. In this study, we explored the underlying pathogenesis of the clinically obtainable alpha(2)-adrenergic receptor agonist dexmedetomidine (DEX) in protecting against rI/R-mediated AMs activation. We incubated AMs with the serum of sham and rI/R rats in the presence or absence of various concentrations of DEX. We used an enzyme-linked immunosorbent assay to detect the secretion levels of GSH, LDH, IL-18, IL-1 beta, and HMGB1 in the culture supernatant. We employed real-time polymerase chain reaction to assess the expression of NOX-4 mRNA, and western blotting to observe the protein levels of NOX-4, the NLRP3 inflammasome, AMPK, and eNOS. In addition, we used immunofluorescence to analyze ROS and MMP activity. Incubation of AMs with DEX suppressed rI/R-mediated cellular LDH production and ROS release. DEX also abolished the rI/R-mediated decrease in the activity of GSH and increased the levels of the rI/R-related NADPH oxidase protein NOX-4. Furthermore, DEX reduced the amelioration of the mitochondrial potential induced by rI/R. Our study showed that DEX inhibits rI/R-mediated levels of the NLRP3 inflammasome proteins ASC, NLRP3, HMGB1 and p20, and ameliorates rI/R-mediated AMPK signaling inactivation. Therefore, DEX reduces the levels of two mediators that are activated by the NLRP3 inflammasome: IL-18 and IL-1 beta. Finally, our study established that DEX mitigates the rI/ R-mediated decrease in eNOS, demonstrating its protective functions against AMs activation. In conclusion, our study demonstrated that the protective action of DEX in AMs is induced through amelioration of HMGB1-NLRP3 inflammasome-AMPK signaling. Our results suggest that the anesthetic reagent DEX exerts beneficial effects to ameliorate rI/R-induced ALI.