FIGURE 6.

Effect of inhibition of SOCS, thioredoxin, and PTP on MAPK activation, apoptosis, and parasite survival. A, macrophages were transfected (24 h) with either control or SOCS1 and/or SOCS3 siRNA followed by infection with L. donovani promastigotes for 6 h. Expression of various MAPKs was evaluated by immunoblot analysis. B–E, macrophages were transfected (24 h) with either control or SHP1 or PTP1B or thioredoxin siRNA followed by infection with L. donovani promastigotes for 6 h. Expression of SHP1 (B), PTP1B (C), thioredoxin (D), and various MAPKs (E) were evaluated by immunoblotting. F and G, macrophages were transfected (24 h) with either control or SOCS1 and/or SOCS3 siRNA and preincubated with either SB203580 (10 μm) or SP100625 (10 μm) or FR180204 (10 μm) followed by infection with L. donovani promastigotes for 6 h. H₂O₂ was administered as described previously. Total cellular extracts (10 μg of protein per sample) were used to determine caspase-3 activity using Ac-DEVD-pNA as substrate. H–J, cells were treated as in F and G, and the percentage of apoptotic cells was measured by flow cytometry (H), and intracellular parasite number was determined by Giemsa staining (I and J). Results are representative of three individual experiments, and the error bars represent mean ± S.D. (n = 3). ns, not significant; *, p < 0.05; **, p < 0.01; ***, p < 0.001 by Student's t test.