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Background & objectives: Pentavalent antimonials are the first-line drugs for treatment of leishmaniasis, which have multiple side effects such as drug toxicity. Moreover, parasite resistance to these drugs is rising around the world. Second-line drugs, including Amphotericin B and pantamidine have also side effects and expensive for patients. According to the cytotoxic effects of paraquat, this study was conducted to evaluate the effect of paraquat on Leishmania major promastigotes and HUVECs viability.
Methods: A number of 2.5×10⁶ of Leishmania major promastigotes were treated in each well of 96 well plates with different concentrations of paraquat. Cells were incubated for 48 hours in 24 °C. MTT test was performed for evaluating paraquat impact on promastigotes. The absorbance was measured using a microplate reader at 570 nm.  The trypan blue staining assay was performed to evaluate the number of viable Leishmania major promastigotes following paraquat treatment. Furthermore, the effect of paraquat concentrations on HUVECs viability was evaluated under the cell culture condition.
Results: The results of the MTT test showed that increasing concentrations of paraquat could significantly reduce the viability and the number of Leishmania major promastigotes in comparison to control group (p<0.05). In this study, the IC₅₀ for Leishmania major promastigotes was calculated as 272.46 µg/ml. Trypan blue results were in line with the finding of MTT assay. Moreover, we found that HUVECs were susceptible to paraquat (IC₅₀=188.99 µg/ml).
Conclusion: Paraquat has a strong inhibitory effect on Leishmania major promastigotes and human endothelial cells. Although more comprehensive studies on the effects of the topical use of paraquat on Leishmania major lesions in animal model and its side effects are necessary.

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Background & objectives: Paraquat is a toxic herbicide that is widely used in many countries. Paraquat selectively accumulates in the lung tissue and leads to severe pulmonary injury through the oxidative and inflammatory processes. The plant Rosa canina L. has been used for long years as an herbal medicine throughout the world. Rosa canina L. is a member of Rosacea family and shows therapeutic effects against numerous disorders by its antioxidant and anti-inflammatory properties. The aim of this study was to evaluate the antioxidant effect of Rosa canina fruits on the paraquat induced lung injury in a mouse model.
Methods: Animal experiments were performed on male NMRI mice. Paraquat was injected at a single dose (20 mg/kg, ip) to induce pulmonary damage in mice. The extract of Rosa canina fruits (200 and 400 mg/kg/day, orally) administered by gavage for four days after the injection of paraquat. The treated mice were compared to normal mice as a control group. At the end of the experiment, lung tissue samples were collected for biochemical analysis.
Results: The results showed that administration of paraquat caused an oxidant-antioxidant imbalance in the lung tissue. However, treatment with Rosa canina increased the levels of glutathione (GSH) and catalase (CAT) antioxidants and decreased the levels of malondialdehyde (MDA) and myeloperoxidase (MPO) in the lung tissues compared with those in the paraquat group.
Conclusion: Treatment of paraquat-exposed mice with the extract of Rosa canina fruits improved oxidant-antioxidant balance in the lung tissue of mice. In other words, the present study demonstrated that Rosa canina has remarkable antioxidant effects against paraquat induced oxidative damage.