The attenuating effect of aqueous extract of licorice on bleomycin-induced pulmonary fibrosis in mice

Licorice has immunomodulatory and anti-asthmatic properties. This study aims to test the effect of licorice on pulmonary fibrosis (PF). PF was induced in mice through bleomycin instillation. One group of the mice received bleomycin (positive control), another one received phosphate-buffered saline and the other two received 300 mg/kg of the extracts for 20 days after the bleomycin instillation. Hematoxylin-eosin and Masson's staining were used in the lung tissues. The expression of alpha-SMA, TGF-beta 1, IL-1 beta, and TNF-alpha were evaluated using reverse-transcriptase-polymerase-chainreaction. Bleomycin led to tissue-degenerative changes, collagen deposition, and overexpression of the genes in the lung tissues. In the mice receiving the aqueous extract, the weight gain was higher (p < .004), and tissue-degenerative changes (p < .001) and collagen deposition were lower than the positive control. The expressions of the genes were lower than the positive control. These results were not observed in the hydroalcoholic extract. Aqueous extract of licorice alleviated the severity of PF.