Sulfur dioxide reduces lipopolysaccharide-induced acute lung injury in rats

Recent studies suggested that sulfur dioxide (SO2) can be produced endogenously by pulmonary vessels and attenuate acute lung injury (ALI) with vasorelaxant effects. This study was conducted to determine whether SO2 can inhibit lung inflammation and relax pulmonary arteries via inhibition of the mitogen-activated protein kinase (MAPK) pathway.

Forty-eight adult male Sprague Dawley rats (250~300 g) were randomly divided into six treatment groups: control (n = 8), control + SO2 (n = 8), control + L-aspartic acid-β-hydroxamate (HDX) (n = 8), LPS (n = 8), LPS + SO2 (n = 8) and LPS + HDX (n = 8).

Six hours after LPS treatment, rats exhibited elevated pulmonary artery hypertension (PAH), marked pulmonary structure injury with elevated pulmonary myeloperoxidase (MPO) activity and increased expression of intercellular adhesion molecule 1 (ICAM-1) and CD11b, along with decreased pulmonary SO2 production and reduced pulmonary aspartate aminotransferase (AAT) activity. Pretreatment with SO2 saline solution significantly reduced, while HDX (AAT inhibitor) aggravated, the pathogenesis of LPS-induced ALI. Moreover, SO2 saline solution significantly down-regulated expression of Raf-1, MEK-1 and phosphorylated ERK (p-ERK). It also prevented pulmonary hypertension in association with an up-regulated SO2/AAT pathway. However, HDX advanced pulmonary hypertension and inflammatory responses in the lung were associated with a down-regulated SO2/AAT pathway.

Our results suggest that SO2 markedly relieved inflammatory responses, in association with Raf-1, MEK-1 and p-ERK during ALI induced by LPS. The down-regulation of the SO2/AAT pathway may be involved in the mechanism(s) of LPS-induced lung injury.