Assessment of the protective effects of tannic acid against bleomycin-induced lung fibrosis in rats

Pulmonary fibrosis (PF) is a prevalent adverse effect associated with bleomycin (Bleo) administration. Despite extensive research efforts, there is no effective treatment currently available for PF. The current study investigates the antifibrotic and antioxidant properties of tannic acid (TA), a natural polyphenol known for its potent antioxidant and anti-inflammatory activities, in the context of Bleo-induced PF in rats. Fifty Wistar rats were randomly assigned to five distinct groups for the study. Group 1 served as the control (normal saline). Group 2 received a single dose of Bleo (7.5 U/kg via intratracheal injection) on the 7th day. Groups 3, 4, and 5 were treated with 100, 200, and 400 mg/kg of TA, respectively, administered 7 days prior to and 21 days following Bleo administration. The rats were euthanized 24 hours after the last administration. The protective effects of TA were assessed through histopathological and biochemical analyses, which included measurements of lung index, hydroxyproline (HP), nitric oxide (NO), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT). Additionally, the influence of TA on tumor necrosis factor-α (TNF-α) levels was evaluated. The results indicated that TA significantly reduced the Bleo-induced increase in lung index, MDA, NO, HP, and TNF-α levels. Furthermore, TA enhanced the activities of CAT, SOD, and GPx, as well as the content of GSH. Additionally, TA mitigated the infiltration of fibroblasts and inflammatory cells and prevented alveolar thickening induced by Bleo. The findings demonstrated that TA exhibits a protective effect against PF induced by Bleo.