Figure 12.

l-Arginine availability and transport regulate release of pro-inflammatory and anti-inflammatory cytokines in Leishmania-infected macrophages. THP-1 monocyte-derived MΦs (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 (A). In a separate experiment, THP-1 MΦs (1 × 10⁶ cells/ml) were either left untreated or preincubated with 250 µM NEM for 10 min followed by infection with L. donovani for 48 h (B). In another experiment, THP-1 MΦs (1 × 10⁶ cells/ml) were transfected with control siRNA, CAT-1, or CAT-2 siRNA followed by infection with L. donovani for 48 h (C). Level of IL-10, IL-12, and TNF-α in the macrophage culture supernatants were quantified by sandwich ELISA (A–C). 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.