Effect of hydrogen-rich saline on TLR4/MyD88 signaling pathway in rats with endotoxin-induced acute lung injury

Objective To evaluate the effects of hydrogen-rich saline on Toll-like receptor 4(TLR4)/myeloid differentiation factor 88(MyD88)pathway in rats with endotoxin-induced acute lung injury (ALI). Methods Forty pathogen-free male Sprague-Dawley rats, aged 3 months, weighing 250-300 g, were randomly divided into 4 groups (n=10 each) using a random number table: control group (group C); ALI group; hydrogen-rich saline group (group H); ALI + hydrogen-rich saline group (ALI + H group). ALI was induced by intratracheal instillation of lipopolysaccharide (LPS) 5 mg/kg.At 1 and 6 h after LPS instillation, 0.6 mmol/L hydrogen-rich saline 10 ml/kg was injected intraperitoneally in H2 and ALI + H2 groups, while the equal volume of normal saline was given in the other two groups.At 12 h after LPS instillation, bronchoalveolar lavage fluid (BALF) was collected for determination of the concentrations of tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β) and IL-6 by enzyme-linked immunosorbent assay.The animals were then sacrificed, and lungs were removed for examination of the pathological changes which were scored and for determination of wet to dry lung weight ratio (W/D ratio), and expression of TLR4, MyD88 and nuclear factor kappa B (NF-κB) (by Western blot). Results Compared with group C, the concentrations of TNF-α, IL-1β and IL-6 in BALF, lung injury score and W/D ratio were significantly increased, and the expression of TLR4, MyD88 and NF-κB was up-regulated in ALI and ALI + H groups (P<0.05). Compared with group ALI, the concentrations of TNF-α, IL-1β and IL-6 in BALF, lung injury score and W/D ratio were significantly decreased, and the expression of TLR4, MyD88 and NF-κB was down-regulated in ALI + H group (P<0.05). Conclusion Hydrogen-rich saline can reduce endotoxin-induced ALI through inhibiting TLR4/MyD88 signaling pathway in the lung tissues of rats. Key words: Hydrogen; Toll-like receptor 4; Myeloid differentiation factor 88; Respiratory distress syndrome, adult; Endotoxemia