Figure 4.

Effect of Leishmania infection on l-arginine transport. THP-1 monocyte-derived MΦs (A) and human monocyte-derived macrophages (hMDM) (B) (1 × 10⁶ cells/ml) were grown in l-arginine-supplemented and l-arginine-depleted RPMI medium followed by infection with Leishmania donovani (multiplicity of infection 1:10) for 48 h. In another experiment, THP-1 MΦs (C) and hMDM (D) were left untreated or preincubated with NEM (250 µM) for 10 min followed by infection with L. donovani for 48 h. In a separate experiment, THP-1 MΦs (E) and hMDM (F) (1 × 10⁶ cells/ml) were transfected with control siRNA, CAT-1 or CAT-2 siRNA followed by infection with L. donovani for 48 h. Arginine transport was measured after incubating the cells with 1 μCi/ml of [³H] l-arginine uptake solution for 8 min followed by counting the incorporation of [³H] l-arginine in liquid scintillation counter (A–F). Each experiment was repeated three times. Each determination was made in triplicate and the values were expressed as mean ± SD for three independent experiments. Kruskal–Wallis with Dunn’s multiple comparison test was used to evaluate statistical significance for comparing three or more groups; *p < 0.05; **p < 0.005; ns, non-significant.