Host and Parasite-Targeted Mechanisms of Gedunin Against Cutaneous Leishmaniasis: In Vitro and In Vivo Evaluation.

BACKGROUND

The main pharmacological interventions for cutaneous leishmaniasis (CL) are associated with various adverse effects. The present study aims to comprehensively evaluate the antileishmanial impact of gedunin (GN) and its effects on the expression of immune and virulence-related genes.

METHODS

The antileishmanial efficacy and synergistic effects of GN, both as a monotherapy and in combination with glucantime (GT), were evaluated against the intracellular amastigote stages of Leishmania tropica. Additionally, the impact of GN on the expression of genes related to immunomodulation and virulence factors, nitric oxide (NO) and reactive oxygen species (ROS) production, and its cytotoxicity on human monocytic THP-1 cells were assessed. In addition, the expression levels of inducible nitric oxide synthase (iNOS), interferon gamma (IFN-γ), and tumor necrosis factor (TNF-α), NF-κB p65, IL-12, and IL-10 were evaluated in the Leishmania-infected macrophages. In vivo evaluation of GN, GT, and GN + GT was also performed in mice with CL through evaluating lesion size and parasite burden.

RESULTS

Investigations involving infected macrophages demonstrated that treatment with GN led to a progressive, concentration-dependent decline in the viability of intracellular amastigotes. the IC50 values for GN, GT, and the combined GN + GT formulation were 8.63, 7.42, and 3.30 μg/mL, respectively. The FICI values determined for GN and GT were 0.31 and 0.49, respectively; indicated the existence of synergistic interactions when GN is combined with GT. The treatment with GN at both IC₅₀ and half-IC₅₀ concentrations, particularly when combined with GT at half-IC₅₀, resulted in a significant downregulation of the GP63, MPI, Arg, and CP gene expression levels compared to treatment with GT alone (P < 0.001). The combination of GN at IC50 with GT at IC50 showed the highest elevation (P < 0.001) in the expression level of iNOs, TNF-α, and IL-12; whereas, markedly increased the level of NF-κB p65 and ROS generation (P < 0.001). In addition, we found that after 28 days of treatment, the cohort administered the GR + GT combination exhibited complete recovery (100%). Furthermore, the parasite load at the treated wound site was markedly diminished, with the most pronounced reduction observed in the GR + GT combination group (P < 0.001).

CONCLUSION

The current study demonstrated that GN, especially in combination with GT, showed the potential in vitro and in vivo antileishmanial effects and reducing Leishmania virulence genes and enhancing host immune response. Future studies can elucidate the detailed molecular mechanisms, long-term effects, and possible clinical applications of GN in clinical models. These data form the basis for designing novel and targeted antileishmanial therapeutic strategies.