Propolis protects against bleomycin-induced pulmonary fibrosis through mitochondrial-dependent pathway: a histological study

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Pulmonary fibrosis is a chronic and progressive fibrotic lung disorder with unknown etiology and a high mortality rate. Bee propolis has shown to have antioxidant activity and modulatory impact on immune system.


The aim of the present study was to investigate the protective role of propolis against bleomycin (BLM)-induced pulmonary fibrosis.

Materials and methods

A total of 27 adult male albino rats were divided into three groups: group I, the control group; group II rats injected intravenously with BLM (7 mg/kg/day) for 5 consecutive days, and group III rats received oral propolis (140 mg/kg/day) for 7 days before BLM injection, which continued till the end of experiment. Glutathione (GSH) and malondialdehyde (MDA) enzymes were assessed. Lung sections were subjected to H&E, Masson’s trichrome stain, α-smooth muscle actin (α-SMA), inducible nitric oxide synthase (iNOS), and cytochrome c immunohistochemical stains.


Group II showed significantly decreased GSH and increased MDA, complete loss of normal lung architecture, septal thickening, congested blood vessels, inflammatory infiltration, and increased fibroblasts, with significant increase in mean area% of collagen fibers and α-SMA, iNOS, and cytochrome c immunoreactivity. Group III revealed significantly increased GSH and decreased MDA, nearly normal lung tissue with significant decrease in mean area% of collagen fibers, α-SMA, iNOS, and cytochrome c immunoreaction as compared with group II.


Propolis protects against BLM-induced pulmonary fibrosis through mitochondrial pathway.

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