Fisetin Suppresses Pulmonary Inflammatory Responses Through Heme Oxygenase-1 Mediated Downregulation of Inducible Nitric Oxide Synthase.

The effects of a mixture of fisetin on cytokine-mediated pulmonary damages have not been studied, despite its known antiviral, neuroprotective, and anti-inflammatory activities. Using lipopolysaccharide (LPS)-activated human pulmonary artery endothelial cells (HPAECs), we determined the effects of fisetin on the induction of heme oxygenase-1 (HO-1), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). In the lung tissue of LPS-treated mice, fisetin was also evaluated for its effect on the regulation of iNOS and tumor necrosis factor (TNF)-α. In LPS-activated HPAECs, fisetin increased nuclear factor erythrocyte 2-related factor 2-antioxidant response element (Nrf2-ARE) reporter activity through the nuclear translocation of Nrf2, and the expression of HO-1, and decreased IL-1ß and iNOS/NO production. In particular, the suppression of iNOS/NO expression by the administration of fisetin was dependent on HO-1. Current findings indicate that the anti-inflammatory activity of fisetin was due to its HO-1 dependent downregulation of p-STAT-1 and nuclear factor kappa B (NF-κB) and the resultant inhibition of iNOS, and also suggest TNF-α as a potential target for HO-1. We propose that administration of fisetin may be a novel approach, ideal for the treatment of inflammatory pulmonary disease.

Inhibitory functions of cardamonin against particulate matter-induced lung injury through TLR2,4-mTOR-autophagy pathways.

Particulate matter with an aerodynamic diameter equal to or less than 2.5 µm (PM2.5) is a form of air pollutant that causes significant lung damage when inhaled. Cardamonin, a flavone found in Alpinia katsumadai Heyata seeds, has been reported to have anti-inflammatory and anticoagulative activity. The aim of this study was to determine the protective effects of cardamonin on PM2.5-induced lung injury. Mice were treated with cardamonin via tail-vein injection 30 min after the intratracheal instillation of PM2.5. The results showed that cardamonin markedly reduced the pathological lung injury, lung wet/dry weight ratio, and hyperpermeability caused by PM2.5. Cardamonin also significantly inhibited PM2.5-induced myeloperoxidase (MPO) activity in lung tissue, decreased the levels of PM2.5-induced inflammatory cytokines and effectively attenuated PM2.5-induced increases in the number of lymphocytes in the bronchoalveolar lavage fluid (BALF). And, cardamonin increased the phosphorylation of mammalian target of rapamycin (mTOR) and dramatically suppressed the PM2.5-stimulated expression of toll-like receptor 2 and 4 (TLR 2,4), MyD88, and the autophagy-related proteins LC3 II and Beclin 1. In conclusion, these findings indicate that cardamonin has a critical anti-inflammatory effect due to its ability to regulate both the TLR2,4-MyD88 and mTOR-autophagy pathways and may thus be a potential therapeutic agent against PM2.5-induced lung injury.