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Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease characterized by dyspnea and progressive loss of lung function. In this study, the preventive and therapeutic effects of methanolic extract of Glycyrrhiza glabra on pulmonary fibrosis were investigated. Pulmonary fibrosis was induced by administration of bleomycin (BLM) into the left lung of rats. Methyl-prednisolone (M-pred, 4 mg/kg) and methanolic extract of G. glabra (500 mg/kg) were injected intraperitoneally from the 1st to 14th days in the preventive group and from the 14th to 28th days in the therapeutic group once every day. Pulmonary inflammatory and fibrotic indices were evaluated by hematoxylin and eosin (H&E) and Masson's trichrome, respectively. The level of hydroxyproline as an index of pulmonary fibrosis and malondialdehyde (MDA) as an oxidative stress biomarker and catalase were measured by the related ELISA Kits. Pulmonary inflammatory and fibrotic indices in the G. glabra and M-pred groups significantly reduced compared with BLM group. G. glabra decreased the level of hydroxyproline in pulmonary tissue similar to M-pred. MDA reduced in G. glabra and M-pred groups compared with BLM group. The activity of catalase increased in the G. glabra preventive group. According to the results, G. glabra prevented and treated pulmonary fibrosis and inflammation in rats. Therefore, G. glabra may be suggested for the prevention and treatment of pulmonary fibrosis and inflammation.

Context: Myrtle (Myrtus communis L) has been used widely in traditional medicine for different respiratory disorders. Idiopathic pulmonary fibrosis (IPF) is an inflammatory disease characterized by progressive loss of lung function with poor prognosis. The pathogenesis of disease has not been completely elucidated, but probably persistent epithelial damages are involved., Objective: Evaluation of biochemical and histopathological effect of preventive and therapeutic doses of myrtle against bleomycin (BLM)-induced pulmonary fibrosis (PF) in animal model., Materials and Methods: Methanolic extract of M. communis was prepared by maceration method. Total flavonoid content was determined and experimentally PF was induced in rat with intratracheal instillation of a single dose of BLM (5 mg/kg) only on day 0. Myrtle antifibrotic effect was evaluated as preventive (50 mg/kg/day, intraperitoneal (i.p.) injection, from day 0-13) and therapeutic agent (50 mg/kg, i.p., from day 14-27) in comparison with methyl prednisolone (M-pred) (4 mg/kg, i.p. for 14 days)., Results: Parenchymal inflammation and fibrotic changes significantly were reduced by myrtle and M-pred. Significant decrease in hydroxyproline content and lipid peroxidation were observed in animals receiving myrtle extract while catalase activity was increased by myrtle. Improvement in inflammation and fibrosis was observed in myrtle group especially in the early phase of fibrosis (preventive regime)., Discussion and Conclusion: Myrtle extract effectively inhibited the inflammation and fibrosis of lung parenchyma in both preventive and therapeutic methods. This effect might be due to the reduction of tissue inflammation and inhibition of oxidative stress. More studies are being carried out to find main mechanisms and separation of active compounds.