Protective effect of dexmedetomidine on endotoxin-induced acute lung injury in rats

Abstract

Objective To investigate the protective role of dexmedetomidine in rats with endotoxin-induced acute lung injury (ALI). Methods Forty-eight adult male SD rats were divided into four groups (n=12 each) according to the random number table: control group, lipopolysaccharide (LPS) group, dexmedetomidine (DEX) treatment group and DEX pretreatment group. ALI was induced in rats by femoral intravenous injection of LPS (8 mg/kg). Rats in DEX treatment group was given DEX (50 μg/kg) for 2 minutes via the femoral intravenous injection 0.5 hour after LPS injection, followed by maintenance pump injection of DEX (5 μg·kg-1·h-1). Analogously, rats in DEX pretreatment group was given DEX (50 μg/kg) for 2 min via the femoral intravenous injection 0.5 hour before LPS injection, followed by maintenance pump injection of DEX (5 μg·kg-1·h-1). By contrast, control group received the same amount of normal saline intravenously. All rats were sentenced to death and their carotid blood samples were collected6 hours after all injections. Superior lobe of the right lung was examined under light microscope and the histologic findings were tested using the difusse alveolar damage (DAD) score. Middle lobe of the right lung was used to calculate the lung tissue wet/dry weight (W/D) ratio. Samples of collected carotid blood were taken to measure levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6. Bronchoalveolar lavage fluid (BALF) obtained from bronchoalveolar lavage was collected to measure levels of TNF-α and IL-6. Results Lung tissue injury was obvious after LPS injection and DAS score was improved as well. However DEX therapy reduced the lung damage as well as the DAD score, especially obvious in DEX pretreatment group (P 0.05), but IL-6 in BALF was significantly lower in DEX pretreatment group than DEX treatment group (P 0.05). Conclusion Either preoperative injection of DEX or DEX treatment has protective effect in rats with LPS-induced ALI, while preoperative injection of DEX has been proved to be more effective. Key words: Acute lung injury; Dexmedetomidine; Endotoxemia