Dose-response and mechanism of protective functions of selective alpha-2 agonist dexmedetomidine on acute lung injury in rats.

OBJECTIVES: To investigate the protective functions of dexmedetomidine on lipopolysaccharide-induced acute lung injury in the lung tissues of rats.

METHODS: The experiment was conducted from May 2008 to December 2009 in Zhongshan Hospital, Shanghai, China. Forty Sprague Dawley rats were randomized into a normal group (NS group), a lipopolysaccharide model group (LPS group), and dexmedetomidine groups in high dosages (HD), moderate dosages (MD), and low dosages (LD). After the acute lung injury model was duplicated by lipopolysaccharide, the rats in the LD, MD, and HD groups were injected with 0.5 ug/kg, 1.5 ug/kg, and 4.5 ug/kg of dexmedetomidine. The rats in the NS group were injected with normal saline. Immuno-histochemical and reverse transcription polymerase chain reaction techniques were used to assess the damage of lung tissue in each group.

RESULTS: The nuclear factor-KappaB and Toll-like receptor 4 messenger RNA expression in the lung tissues of the rats in the MD and HD groups were inhibited compared to the LPS group. The amount of tumor necrosis factor-beta, interleukin-1beta, and interleukin-6 as well as the lung tissue wet to dry weight ratio were also reduced in the MD and HD groups.

CONCLUSIONS: The inflammatory reactions in lung tissues can be effectively inhibited at doses ranging from 1.5-4.5 ug/kg, resulting in a protective effect on lung tissue.