Curcumin Inhibits Lipopolysaccharide-lnduced Mucin 5AC Hypersecretion and Airway Inflammation via Nuclear Factor Erythroid 2-Related Factor 2

Background： Excess mucus production is an important pathophysiological feature of chronic inflammatory airway diseases. Effective therapies are currently lacking. The aim of the study was to evaluate the effects ofcurcumin （CUR） on lipopolysaccharide （LPS）-induced mucus secretion and inflammation, and explored the underlying mechanism in vivo and in vitro. Methods： For the in vitro study, human bronchial epithelial （NCI-H292） cells were pretreated with CUR or vehicle for 30 min, and then exposed to LPS for 24 h. Next, nuclear factor erythroid 2-related factor 2 （Nrf2） was knocked down with Nrf2 small interfering RNA （siRNA） to confirm the specific role of Nrf2 in mucin regulation of CUR in NCI-H292 cells. In vivo, C57BL/6 mice were randomly assigned to three groups （n = 7 for each group）： control group, LPS group, and LPS ＋ CUR group. Mice in LPS and LPS ＋ CUR group were injected with saline or CUR （50 mg/kg） intraperitoneally 2 h before intratracheal instillation with LPS （ 100 μg/ml） for 7 days. Cell lysate and lung tissue were obtained to measured Mucin 5AC （MUC5AC） and Nrf2 mRNA and protein expression by a real-time polymerase chain reaction and Western blotting. Bronchoalveolar lavage fluid （BALF） was collected to enumerate total cells and neutrophils. HistopathologicaI changes of the lung were observed. Data were analyzed by one-way analysis of variance. Student＇s t-test was used when two groups were compared. Results： CUR significantly decreased the expression ofMUC5AC mRNA and protein in NCI-H292 cells exposed to LPS. This effect was dose dependent （2.424 ± 0.318 vs. 7.169 ± 1.785, t = 4.534, and 1.060 ± 0.197 vs. 2.340 ± 0.209, t = 7.716; both P 〈 0.05, respectively） and accompanied by increased mRNA and protein expression of Nrf2 （1.952 ± 0.340 vs. 1.142 ± 0.176, t = -3.661, and 2.010 ± 0.209 vs. 1.089 ±0. 132, t = -6.453; both P 〈 0.05, respectively）. Furthermore, knockdown of Nrf2 with siRNA increased MUC5A C mRN A expression by 47.7%, compared with levels observed in the siRNA-negative group （6.845 ± 1.478 vs. 3.391 ± 0.517, t = -3.821, P 〈 0.05）. Knockdown of Nrf2 with siRNA also markedly increased MUC5A C protein expression in NCI-H292 cells. CUR also significantly decreased LPS-induced mRNA and protein expression of MUC5A C in mouse lung （ 1.672 ± 0.721 vs. 5.961 ± 2.452, t = 2.906, and 0.480 ± 0.191 vs. 2.290 ± 0.834, t = 3.665, respectively; both P 〈 0.05）. Alcian blue/periodic acid-Schiff staining also showed that CUR suppressed mucin production. Compared with the LPS group, the numbers of inflammatory cells （247 ± 30 vs. 334 ± 24, t = 3.901, P 〈 0.05） and neutrophils （185 ± 22 vs. 246 ± 20, t = 3.566, P 〈 0.05） in BALF decreased in the LPS ＋ CUR group, as well as reduced inflammatory cell infiltration in lung tissue. Conclusion： CUR inhibits LPS-induced airway mucus hypersecretion and inflammation through activation of Nrf2 possibly.

Pyunkang-hwan (Pyunkang-Tang) ameliorates air pollutant-induced inflammatory hypersecretion of airway mucus and bleomycin-induced pulmonary fibrosis in rats

OBJECTIVE: To investigate the effect of Pyunkanghwan(Pyunkang-tang) extract(PGT) on secretion of airway mucin in an experimental animal model involving hyperplasia of goblet cells and mucus hypersecretion, and to test its effects on bleomycin(BLM)-induced pulmonary fibrosis in vivo.METHODS: The protective activity of orally administered PGT was assessed in two rat pulmonary disease models. Effects on hypersecretion of pulmonary mucin in sulfur dioxide(SO_2)-induced bronchitis in rats were assessed by quantifying the amount of mucus secreted and examining histopathology in the tracheal epithelium. In a rat model for BLMinduced pulmonary fibrosis, toxicity to the pulmonary system was examined by measuring levels of malondialdehyde and hydroxyproline,indicators of lipid peroxides and collagen,respectively, in lung tissue 28 days post-BLM treatment. Serial sections of lung tissue were stained with Masson trichrome to visualize collagen deposition. Effects of PGT on collagen synthesis were also assessed in vitro, in a cell culture model.RESULTS: PGT inhibited mucin secretion and normalized SO_2-induced increased muco- substances in goblet cells. In the BLM- induced model,PGT decreased the characteristic histopathological features of lung fibrosis and inhibited fibrotic lesions, as indicated by decreased hydroxyproline content. PGT also inhibited the BLM-induced increase in malondialdehyde levels, demonstrating its protective effect against lipid peroxidation in cell membranes of the lung. In MLg 2908 mouse lung fibroblast cells, PGT decreased transforming growth factor(TGF)-β-stimulated type I collagen synthesis.CONCLUSION: PGT can inhibit both hypersecretion of airway mucins and pulmonary fibrosis.