Suppression of lung inflammation in an LPS-induced acute lung injury model by the fruit hull of Gleditsia sinensis

Background: The fruit hull of Gleditsia sinensis (FGS) used in traditional Asian medicine was reported to have a preventive effect on lung inflammation in an acute lung injury (ALI) mouse model. Here, we explored FGS as a possible therapeutics against inflammatory lung diseases including ALI, and examined an underlying mechanism for the effect of FGS. Methods: The decoction of FGS in water was prepared and fingerprinted. Mice received an intra-tracheal (i.t.) FGS 2 h after an intra-peritoneal (i.p.) injection of lipopolysaccharide (LPS). The effect of FGS on lung inflammation was determined by chest imaging of NF-kappa B reporter mice, counting inflammatory cells in bronchoalveolar lavage fluid, analyzing lung histology, and performing semi-quantitative RT-PCR analysis of lung tissue. Impact of Nrf2 on FGS effect was assessed by comparing Nrf2 knockout (KO) and wild type (WT) mice that were treated similarly. Results: Bioluminescence from the chest of the reporter mice was progressively increased to a peak at 16 h after an i.p. LPS treatment. FGS treatment 2 h after LPS reduced the bioluminescence and the expression of pro-inflammatory cytokine genes in the lung. While suppressing the infiltration of inflammatory cells to the lungs of WT mice, FGS post-treatment failed to reduce lung inflammation in Nrf2 KO mice. FGS activated Nrf2 and induced Nrf2-dependent gene expression in mouse lung. Conclusions: FGS post-treatment suppressed lung inflammation in an LPS-induced ALI mouse model, which was mediated at least in part by Nrf2. Our results suggest a therapeutic potential of FGS on inflammatory lung diseases.