Protective effect of catalpol on lipopolysaccharide-induced acute lung injury in mice

Catalpol, an iridiod glucoside isolated from Rehmannia glutinosa, has been reported to have anti-inflammatory properties. Although anti-inflammatory activity of catalpol already reported, its involvement in lung protection has not been reported. Thus, we investigated the role of catalpol on lipopolysaccharide (LPS)-induced acute lung injury in this study. Mice acute lung injury model was induced by intranasal instillation of LPS. Catalpol was administrated 1 h prior to or after LPS exposure. The severity of pulmonary injury was evaluated 12 h after LPS administration. The results showed that catalpol inhibited lung W/D ratio, myeloperoxidase activity of lung samples, the amounts of inflammatory cells and TNF-α, IL-6, IL-4 and IL-1β in BALF induced by LPS. The production of IL-10 in BALF was up-regulated by catalpol. In vitro, catalpol inhibited TNF-α, IL-6, IL-4 and IL-1β production and up-regulated IL-10 expression in LPS-stimulated alveolar macrophages. Moreover, western blot analysis showed that the activation of NF-κB and MAPK signaling pathways was inhibited by catalpol. Furthermore, catalpol was found to inhibit TLR4 expression induced by LPS. In conclusion, catalpol potently protected against LPS-induced ALI. The protective effect may attribute to the inhibition of TLR4-mediated NF-κB and MAPK signaling pathways.