Effect of dexamethasone on acute respiratory distress syndrome induced by the H5N1 virus in mice

Glucocorticoids are widely used in the treatment of different inflammatory diseases. The present study was performed to investigate the effect of dexamethasone (DEX) on acute respiratory distress syndrome (ARDS) induced by the H5N1 viral infection in mice. BALB/c mice, 6-8 weeks old, were divided into three groups with 80 mice in each. The infected group and the DEX-treated infected group were inoculated intranasally with 1 × 10² 50% mouse infectious dose of A/Chicken/Hebei/108/2002 (H5N1) viruses, with daily intraperitoneal injections of PBS, or 2.5 mg kg^-1 DEX at days 3-14 post inoculation, respectively. The control group received noninfectious allantoic fluid and a daily intraperitoneal injection of PBS. In H5N1-infected mice, DEX treatment did not improve the mortality (17 out of 20 versus 16 out of 20 deaths in the DEX-treated infected group versus the infected group), and did not alleviate clinical signs, including weight loss, decreased food intake and inactivity. There was no significant amelioration of the hypoxaemia and ARDS-associated pathological changes in DEX- treated infected mice, as assessed by blood gas analysis and histological score. Furthermore, DEX therapy did not inhibit inflammatory cellular infiltration and cytokine release (interleukin-6 and tumour necrosis factor-α) in bronchoalveolar lavage fluid induced by the H5N1 infection. In conclusion, dexamethasone treatment (2.5 mgkg ^-1) from days 3-14 post inoculation has no beneficial effect on acute respiratory distress syndrome caused by the H5N1 infection in mice.