In vitro assessment of Dracocephalum lindbergii for growth inhibition, apoptosis induction, and cytokine modulation against Leishmania major

Leishmaniasis is a vector-borne disease caused by several species of flagellate protozoan parasites belonging to the genus <i>Leishmania</i>, which are part of the Trypanosomatidae family. This study aims to evaluate the <i>in vitro</i> anti-<i>Leishmania</i> activity of <i>Dracocephalum lindbergii</i> Rech.f (<i>D. lindbergii</i>) on the growth, apoptosis induction, and proliferation of <i>Leishmania major</i>. To conduct this study, the aerial parts of <i>D. lindbergii</i> were collected during the flowering stage in May 2022 from North Khorasan province, Iran. The plant material was extracted using various solvents, starting with those of lower polarity and progressing to those of higher polarity. To assess the impact of the <i>D. lindbergii</i> fraction on <i>L. major</i> promastigotes, amastigotes, and macrophages (THP-1), cell viability was determined using the MTT assay. Additionally, flow cytometry with the Annexin V-PE apoptosis detection kit was employed to distinguish between viable, necrotic, and apoptotic promastigotes in response to treatment with the 100 % methanolic fraction of <i>D. lindbergii</i> (D). The expression levels of TNF-α, IFN-γ, IL-12, IL-10, TGF-β, IL4, iNOS, and GAPDH were quantified using real-time PCR (qPCR) on the macrophage cell line. Each treatment approach exhibited marked anti-leishmanial effects across different concentrations over 24, 48, and 72 h of incubation, showing statistically significant differences compared to the untreated control group (P < 0.001). Different concentrations of D, MAT, and AmpB, both individually and in combination, significantly reduced the total number of intramacrophage amastigotes compared to the untreated control groups at 24, 48, and 72 h. The results also showed time-dependent variations in the anti-<i>Leishmania</i> activity of the fraction. In terms of cellular morphology, treated cells exhibited changes such as shrinkage, cytoplasmic condensation, and reduced mobility, particularly noticeable after 24 h of treatment. Additionally, fraction D demonstrated significant antioxidant properties. This study highlights the potential of <i>D. lindbergii</i> as an anti-<i>Leishmania</i> agent, with the 100 % methanolic fraction emerging as a promising candidate for the development of novel treatments for leishmaniasis.