Mechanism underlyinghydrogen-induced reduction of sepsis-associated encephalopathy in mice: phenotypic transformation of hippocampal microglias

Abstract

Objective To investigate the relationship between the mechanism underlying hydrogen-induced reduction of sepsis-associated encephalopathy (SAE) and phenotypic transformation of hippocampal microglias in mice. Methods Eighty-eight adult male ICR mice, aged 6-8 weeks, weighing 20-25 g, were divided into 4 groups (n=22 each) using a random number table method: sham operation group (group Sham), sham operation plus hydrogen group (group Sham+ H2), SAE group and SAE plus hydrogen group (group SAE+ H2). Sepsis was induced by cecal ligation and puncture (CLP) in anesthetized mice.Sham and Sham+ H2 groups only underwent simple laparotomy.Sham+ H2 and SAE+ H2 groups inhaled air containing 2% hydrogen for 1 h starting from 1 and 6 h after CLP, respectively.Mice were sacrificed at 24 h after CLP, and hippocampi were isolated for determination of the levels of tumor necrosis factor (TNF-α), interleukin-6 (IL-6), transforming growth factor-β (TGF-β) and IL-10 (by enzyme-linked immunosorbent assay) and expression of inducible nitric oxide synthase (iNOS) and argininase-1 (Arg-1) (by Western blot). Morris water maze test was performed on 10 mice in each group at days 4-8 after CLP. PResults Compared with group Sham, the levels of TNF-α, IL-6, TGF-β and IL-10 were significantly increased, the expression of iNOS and Arg-1 was up-regulated, the escape latency was prolonged, and the rate of time spent in the target quadrant and the number of crossing the original platform were reduced in SAE and SAE+ H2 groups (P<0.05). Compared with group SAE, the levels of TNF-α and IL-6 were significantly decreased, the expression of iNOS was down-regulated, the expression of TGF-β, IL-10 and Arg-1 was up-regulated, the escape latency was shortened, and the rate of time spent in the target quadrant and the number of crossing the original platform were increased in group SAE+ H2 (P<0.05). Conclusion Hydrogen can promote phenotypic transformation of hippocampal microglias from M1 to M2 and reduce SAE in mice. Key words: Hydrogen; Sepsis; Brain; Hippocampus; Microgila