Rosmarinic Acid Attenuates Paraquat-Induced Lung Injury by Suppressing Inflammatory Responses in Mice.

Background: Paraquat (PQ) is a commonly used herbicide known for its high toxicity. Despite its hazardous nature, there are currently no effective treatments for PQ poisoning. This study aimed to evaluate the effects of Rosmarinic acid (RA), a phenolic compound, on PQ-induced lung injury in mice. Methods: Mice were divided into ten groups for two experimental periods, 6- and 24-day periods (five groups each). The first group received normal saline daily, as the control group. Animals in the second group received a single intraperitoneal (i.p.) dose of PQ (25 mg/kg) on day 3. Groups three and four received RA (50 and 100 mg/kg, respectively) orally for 6 or 24 days. Group five received 100 mg/kg of RA daily. Animals were sacrificed 24 h after the last treatment, and lung samples were collected to determine histopathological changes and expression of TLR9, IL-1β, and TNF-α genes using RT-PCR. Results: Hematoxylin and eosin staining revealed a significant reduction in lung injury following RA treatment. RA notably reduced inflammatory cell infiltration and lung tissue congestion. Furthermore, inflammatory responses triggered by PQ were suppressed after RA treatment, as demonstrated by the downregulation of IL-1β, TNF-α, and TLR9 levels. Conclusions: These findings suggest the therapeutic potential of RA for mitigating PQ-induced lung damage and inflammation.