The Potential Use of Methotrexate in the Treatment of Cutaneous Leishmaniasis: In Vitro Assays against Sensitive and Meglumine Antimoniate-resistant Strains of Leishmania tropica

Background: The present study aimed to evaluate the effect of methotrexate (MTX) alone and in combination with meglumine antimoniate (MA, Glucantime) against sensitive and MA-resistant Leishmania tropica stages in vitro. Methods: The present study was carried out in 2014 in Leishmaniasis Research Center at School of Medicine, Kerman University of Medical sciences, Kerman, Iran. The effects of MTX alone and along with MA on promastigote and amastigote stages of sensitive (SS) and MA-resistant (RS) L. tropica strains have been evaluated using a colorimetric MTT assay and in a macrophage model, respectively. In addition, the inhibitory effect of MTX on the Leishmania invasion of murine macrophages was assessed in promastigotes of both strains of L. tropica. Sensitive and MA resistant L. tropica are referred to those isolates that are responsive or non-responsive to one or two courses of treatment by MA systemically and/or intralesionally, respectively. Results: The findings of OD and IC50 showed that MTX plus MA (SS: 16.1 μg/ml, RS: 39.8 μg/ml) had a higher anti-leishmanial effect than MA (SS: 52.2 μg/ml, RS: 170 μg/ml) or MTX alone (SS: 22.2 μg/ml, RS: 51.4 μg/ml) on promastigotes of both strains of L. tropica. The MTX plus MA caused a significant decrease (P<0.05) in the mean infection rate (MIR) and the mean number of amastigotes in each macrophage compared with positive control. Infectivity of promastigotes is significantly (P<0.05) reduced when it was preincubated with MTX. Conclusion: This study indicated high potency and a synergistic effect of MTX on MA in inhibiting the growth rateof promastigote and amastigote stages of sensitive and meglumine antimoniate-resistant L. tropica. Further works are needed to evaluate the anti-leishmanial effects of MTX on L. tropica using a clinical setting.