RESEARCH ARTICLES CURRENT SCIENCE, VOL. 119, NO. 6, 25 SEPTEMBER 2020 962 *For correspondence. (e-mail: drndsingh@gmail.com) Amelioration of bleomycin-induced acute lung injury and epithelial–mesenchymal transition by baicalein in mice Dheeraj Kumar Sharma 1 , Nittin Dev Singh 1, *, Geeta Devi Leishangthem 2 and Harmanjit Singh Banga 1 1 Department of Veterinary Pathology, and 2 Animal Disease Research Centre, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana 141 004, India During lung fibrosis, acute pulmonary inflammation and epithelial–mesenchymal transition (EMT) play im- portant roles. The present study analyses the amelio- rative effect of baicalein, a bioactive flavonoid present in the dry roots of Scutellaria baicalensis Georgi, on bleomycin-induced acute lung injury and subsequent EMT. Mice received a single intratracheal instillation of saline containing bleomycin @1 mg/kg body wt. Baicalein in different doses (0.1, 1.0, 10 mg/kg) was given intraperitoneally daily for one week. Pulmonary inflammation and EMT parameters were evaluated. Baicalein significantly attenuated bleomycin-induced pulmonary inflammatory and structural changes. Thus, treatment with baicalein ameliorates bleomycin- induced acute inflammation and subsequent early stage of EMT. Keywords: Acute lung injury, baicalein, bleomycin, epithelial–mesenchymal transition, mice. ACUTE LUNG INJURY (ALI) includes pulmonary inflam- mation characterized by alveolar epithelial cell injury, polymorphonuclear cells infiltration along with release of proinflammatory cytokines followed by proliferation of fibroblast and extracellular matrix (ECM) that results in pulmonary fibrosis. The epithelial–mesenchymal transi- tion (EMT) process has been associated with lung fibro- sis, where the epithelial cells differentiate and acquire the phenotype of myofibroblasts 1 . In pulmonary fibrosis, res- ident pulmonary fibroblasts or blood-borne fibrocytes and alveolar epithelial cells (AECs) transdifferentiate to myo- fibroblasts 2,3 . Bleomycin (BZM), an antibiotic agent isolated from the fungus Streptomyces verticillus, has been used as an anti-cancer drug, but it causes lung toxicity leading to pulmonary fibrosis as a side effect. Further, bleomycin has been widely used in animals (mice, rats and hamster) to model acute lung injury and pulmonary fibrosis, to study the mechanism involved in fibrogenesis and to potential therapies 4 . A single dose of bleomycin given intratracheally causes lung injury and fibrosis in rodents 5 . Several studies have reported that bleomycin- induced early stages of lung injury resemble human pulmonary fibrosis which includes infiltration of inflam- matory cells, higher collagen content and reduced lung volumes and compliance 5 . Further, EMT plays an impor- tant roles in the pathogenesis of bleomycin-induced lung injury 6 . Baicalein (BAIC) is a bioactive flavonoid, present in the dry roots of Scutellaria baicalensis Georgi, which is widely used in traditional Chinese herbal medicine. Evidence has shown that BAIC has many pharmacological effects, including anti-allergic, antioxidant, anti-apoptotic, anti-viral, anti-inflammatory, anti-tumour and a immune- modulatory effects 7 . Importantly, baicalein improves the dysfunction of mitochondria, thereby preventing allergic asthma 8 . It has been reported that the future therapeutic approach may focus on improvement in regeneration of alveolar epithelial cells 9 and reversal of the EMT process 10 . Few studies are available on the ameliorative effect of baicalein on pulmonary fibrosis induced by bleomy- cin 11,12 . However, all of them are on 28 days chronic pulmonary fibrosis. The present study analyses the ame- liorative effect of baicalein on acute lung injury induced by bleomycin and its subsequent EMT. Materials and methods Animals and treatments The study protocol was approved by the Institutional Animal Ethics Committee (IAEC) of Guru Angad Dev Ve- terinary and Animal Sciences University (GADVASU), Ludhiana, Punjab, India. Male albino mice (n = 30, 4–6 weeks age) were obtained from the Central Research Institute, Kasauli, Himachal Pradesh and maintained in the small animal house at GADVASU. After the