Dexmedetomidine Alleviates Ischemia/Reperfusion-Associated Acute Kidney Injury by Enhancing Autophagic Activity via the 2-AR/AMPK/mTOR Pathway

Background: Dexmedetomidine (DEX) reportedly protects against ischemia-reperfusion (I/R) injury and associated damage to the kidneys, but the underlying mechanisms have yet to be established. Methods: Unilateral nephrectomy was performed in Wistar rats, and the remaining kidney was clamped for 1 h prior to reperfusion to establish an experimental model system. These animals were then randomized into Sham, DEX + Sham, DEX + I/R, ATI (Altepamizole, alpha 2-adrenergic receptor inhibitor) + DEX + I/R, and 3-MA (3methyladenine, autophagy inhibitor) + DEX + I/R groups. Serum renal function biomarkers, acute kidney injury (AKI) histopathological scores, serum inflammatory factors, redox biomarkers, markers of autophagic flux, and autophagosome numbers were assessed. Levels of proteins related to the autophagic pathway, including mTOR and AMPK, were also analyzed. Results: Serum creatinine and urea nitrogen levels in the I/R group were significantly elevated over those in sham control rats, as were AKI scores, serum inflammatory cytokine concentrations (IL-6, IL-1 beta, and TNF-alpha), and serum levels of the oxidative stress biomarker malondialdehyde (MDA). All of these parameters were significantly reduced in the DEX + I/R group relative to I/R model rats. I/R group rats also exhibited significant decreases in renal levels of autophagic flux-related biomarkers and autophagosome numbers relative to sham controls, while DEX administration partially restored normal autophagic flux in these rats. Acute I/R also suppress the expression of AMPK in the kidney while increasing mTOR expression, and DEX reversed these effects. The beneficial impact of DEX on I/R-associated AKI was ablated by ATI or 3-MA administration. Conclusions: These analyses provide strong evidence for the ability of DEX to protect against I/R-associated AKI via the alpha 2-AR/AMPK/mTOR pathway-mediated enhancement of autophagic activity.