Shikonin attenuates lipopolysaccharide-induced acute lung injury in mice

Shikonin, a natural naphthoquinone pigment extracted from the root of Lithospermum erythrorhizon, has shown a variety of pharmacologic properties including anti-inflammatory effect. In the present study, we analyzed the role of shikonin in acute lung injury induced by lipopolysaccharide (LPS) in mice.

Sixty male BALB/C mice were randomly allocated into six groups (n = 10, each): control group, shikonin group (50 mg/kg), LPS group, and three different doses (12.5, 25, and 50 mg/kg) for shikonin-treated groups. Shikonin or vehicle was given with an intragastric administration 1 h before an intratracheal instillation of LPS (5 mg/kg). The severity of pulmonary injury was evaluated 6 h after LPS challenge.

Shikonin pretreatment significantly attenuated LPS-induced pulmonary histopathologic changes, alveolar hemorrhage, and neutrophil infiltration. The lung wet-to-dry weight ratios, as the index of pulmonary edema, were markedly decreased by shikonin pretreatment. Moreover, shikonin decreased the productions of the proinflammatory cytokines including tumor necrosis factor alpha and interleukin 1β and the concentration of total proteins in the bronchoalveolar lavage fluid. Shikonin pretreatment also reduced the concentrations of myeloperoxidase and nitric oxide in lung tissues. In addition, shikonin pretreatment significantly suppressed LPS-induced activation of cyclooxygenase 2 and inducible nitric oxide synthase and the nuclear factor κB DNA-binding activity in lung tissues.

This study indicates that shikonin may have a protective effect against LPS-induced acute lung injury, and the potential mechanism of this action may attribute partly to the inhibition of inducible nitric oxide synthase and cyclooxygenase 2 expression by downregulating nuclear factor κB activation.