Dexmedetomidine Preconditioning Protects Rats from Renal Ischemia–Reperfusion Injury Accompanied with Biphasic Changes of Nuclear Factor-Kappa B Signaling

Acute kidney injury (AKI) is one of the most common and troublesome perioperative complications. Dexmedetomidine (DEX) is a potent α2-adrenoceptor (α2-AR) agonist with anti-inflammatory and renoprotective effects. In this study, a rat renal ischemia–reperfusion injury (IRI) model was induced. At 24？h after reperfusion, the IRI-induced damage and the renoprotection of DEX preconditioning were confirmed both biochemically and histologically. Changes in nuclear factor-kappa B (NF-κB), as well as its downstream anti-inflammatory factor A20 and proinflammatory factor tumor necrosis factor-α (TNF-α), were detected. Atipamezole, a nonselective antagonist, was then added 5？min before the administration of DEX to further analyze DEX’s effects on NF-κB, and another anti-inflammatory medicine, methylprednisolone, was used in comparison with DEX, to further analyze DEX’s effects on NF-κB. Different concentrations of DEX (0？nM, 0.1？nM, 1？nM, 10？nM, 100？nM, 1？μM, and 10？μM) were applied to preincubated human renal tubular epithelial cell line (HK-2) cells in vitro. After anoxia and reoxygenation, the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium assay and enzyme-linked immunosorbent assay (ELISA) were performed to evaluate the levels of NF-κB downstream anti-inflammatory cytokines. The results showed that, unlike methylprednisolone, DEX preconditioning led to a time-dependent biphasic change (first activation then inhibition) of NF-κB in the rat renal IRI models that were given 25？μg/kg i.p. It was accompanied by a similarly biphasic change of TNF-α and an early and persistent upregulation of A20. In vitro, DEX’s cellular protection showed a concentration-dependent biphasic change which was protective within the range of 0 to 100？nM but became opposite when concentrations are greater than 1？μM. The changes in the A20 and NF-κB messenger RNA (mRNA) levels were consistent with the renoprotective ability of DEX. In other words, DEX preconditioning protected the rats from renal IRI via regulation biphasic change of NF-κB signaling