The Effect of Melatonin on the Expression of H19, MALAT, HOTAIR, THRIL, and NOS Activity in Leishmania major-Infected Macrophages

Background: Leishmania spp. protozoa cause leishmaniasis by infecting macrophages. Long non-coding RNAs (lncRNAs), such as H19, Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT), HOX Antisense Intergenic RNA (HOTAIR), and TNF and HNRNPL Related Immuno-regulatory lncRNA (THRIL), play a role in macrophage polarization and gene regulation. Additionally, leukocytes can synthesize and respond to melatonin, yet the regulatory role of melatonin in Leishmania major-infected macrophages is not well understood. Objectives: This study aimed to assess the impact of melatonin on the expression of lncRNAs like H19, MALAT, HOTAIR, and THRIL, as well as on nitric oxide synthase (NOS) activity in L. major-infected macrophages. Methods: Leishmania major promastigotes and U937 cell lines were cultured. Macrophages were infected with the promastigotes and subsequently treated with melatonin at concentrations of 3, 10, 30, and 100 nM for durations of 4, 24, and 48 hours. The expression levels of the lncRNAs and NOS activity were measured using quantitative Polymerase Chain Reaction (q-PCR) and spectrophotometry, respectively. Results: Melatonin treatment (100 nM) significantly increased the expression of H19 compared to the control after 48 hours (P = 0.002). There was also a significant upregulation of MALAT and HOTAIR in macrophages treated with 3 nM melatonin compared to controls after 48 hours (P = 0.02 and P = 0.003, respectively). Additionally, THRIL expression significantly increased in the melatonin group (10 nM) compared to the control after 4 hours of treatment (P = 0.003). An increase in NOS activity was observed in the melatonin group (100 nM) compared to the control at 4 hours, 24 hours, and 48 hours (P = 0.034, P = 0.011, and P = 0.014, respectively). Conclusions: The findings suggest that melatonin may enhance the expression of H19, THRIL, MALAT, and HOTAIR, as well as NOS activity in macrophages infected with L. major. The upregulation of these lncRNAs by melatonin could potentially improve the macrophages' ability to combat L. major infection.