Anti-leishmanial, immunomodulatory and additive potential effect of Piperine on Leishmania major: The in silico and in vitro study of Piperine and its combination

Background: Piperine (Pn), an indole alkaloid compound found in pepper, is an effective compound with antileishmanial medications that administered alone or in combination. This study aimed to use Pn for possible biochemical targets and to assess mechanisms of anti-leishmanial action and immunomodulatory roles.Methods: The ability of Pn to bind to interleukin-12P40 (IL-12P40) and interferon-& gamma; (IFN-& gamma;) was investigated using molecular docking. The leishmanicidal effect of Pn, meglumine antimoniate (Glucantime;MA), and Pn plus MA was assessed on Leishmania major promastigotes and amastigotes. A real-time PCR was applied to quantify cytokines gene expression in drug-treated murine macrophages.Results: The molecular docking findings indicated that Pn could bind to IL-12P40/IFN-& gamma;. In silico analyses showed an affinity of Pn to IL12P40/IFN-& gamma;, with the MolDock score of -236.91 and -64.87 kcal/mol, respectively. Pn plus MA reduced the proliferation rate of promastigote and amastigote forms of L. major compared to each drug alone (IC50 = 43.22 and 19.41 & mu;g/mL, respectively). Moreover, the combination drug demonstrated no cytotoxicity as the selectivity index (SI) was 14.81. Also, Th1-related cytokines were upregulated, while Th2-related cytokines were downregulated in Pn combinationtreated murine macrophages.Conclusions: The superior effectiveness of combination therapy on L. major warrants further investigations on the clinical potential of this combination in the treatment of leishmaniasis.