Therapeutic Effect of Gallic Acid Against Paraquat-Induced Lung Injury in Rat

Background: Paraquat (PQ), a potent herbicide, is extremely toxic to humans when exposed orally and it is known to induce lung injury via a redox cyclic reaction. Objectives: The current study aimed at examining the effect of gallic acid (GA), a polyphenolic compound, which is a constituent of plant-derived foods, against PQ-induced lung injury and pulmonary fibrosis in association with its antioxidant activity. Methods: Male rats were randomly divided into 5 experimental groups each containing 14 rats. Group 1 received normal saline for 21 days. Group 2 received a single dose of oral administration of PQ (50 mg/kg, only on first day) for 21 days. Groups 3 to 5 were treated with different doses of GA after PQ ingestion for 21 days. Seven animals from each group were sacrificed on the days 7 and 21. Results: The results showed that paraquat gavage, significantly enhanced the inflammatory and fibrotic modifications, hydroxyproline (HP), levels of malondialdehyde (MDA), main proinflammatory cytokines such as tumor necrosis factor- (TNF-), interleukin-6 (IL-6), and transforming growth factor (TGF)-1 as a pro-fibrotic mediator in lung tissue. It also, significantly diminished enzymatic antioxidant amounts such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activity and non-enzymatic amounts such as glutathione (GSH) content in the rat lung tissue. However, after GA treatment all of these biochemical indices were diminished with a dose dependent manner and histopathological alterations were also close to normal status. Conclusions: The current study indicated that the GA improved the PQ-induced lung injury and prevented the process of pulmonary fibrosis via its antioxidant and immunomodulatory properties.