Evaluation of the Sensitivity of Locally Isolated L. tropica in Macrophages to Pentostam (Ex vivo) and Study the Expression of the Resistant Genes Evaluation of the Sensitivity of Locally Isolated L. tropica in Macrophages to Pentostam (Ex vivo) and Study the Expression of the Resistant Genes

Abstract

Anthroponotic cutaneous leishmaniasis (ACL), an endemic disease in Syria, is mainly caused by Leishmania tropica. Long-term use of pentavalent antimony (Sb(V)) compounds for CL treatment has led to the emergence of locally strains with varying drug sensitivity patterns. This study aimed to

evaluate the drug susceptibility of local L. tropica isolates to pentostam and investigate the gene expression of GSH1, MRPA, AQP1, TryR, and PgpA, potential resistant genes. This study was conducted with monocytes isolated from human peripheral blood. These monocytes were then differentiated into macrophages and infected with promastigotes of four local L. tropica isolates (L1-L4). Infected macrophages were treated with three different concentrations of pentostam for 24 hours. Subsequently, the amastigote burden and IC50 values of pentostam were determined for each isolate. Total RNA was extracted from heat-transformed amastigotes and reverse-transcribed into cDNA. Relative gene expression of resistance genes was assessed using RT-qPCR. Our results showed significant differences in IC50 values among the isolates (L3 > L2 > L4 > L1), with a 1.7-fold difference in the inhibitory effect of pentostam between the most resistant (L3) and least resistant (L1) isolates. No significant differences in MRPA and AQP1 expression were observed. Only isolate L3 showed a significant increase in PgpA expression compared to other isolates. All isolates exhibited significant differences in GSH1 expression except for the L1/L4 pair. A strong positive correlation (r = 0.98) was found between GSH1 expression and IC50 values. Significant differences in TryR expression were also observed among the isolates, except for the L1/L4 and L2/L4 pairs. Increased TryR expression was associated with higher IC50 values. This study demonstrates that local L. tropica isolates exhibit varying degrees of susceptibility to antimony pentavalent compounds, associated with differential gene expression, particularly upregulation of GSH1 and TryR in more resistant isolates. Further studies are needed to elucidate the role of PgpA overexpression. These findings provide valuable insights into drug resistance dynamics in CL and highlight the need for developing targeted therapies against local isolate-specific resistance mechanisms.