Figure 5.

IL-13 regulates Bcl-2 expression through STAT-3 activation. (A) A time-dependent increase in IL-13 secretion post infection in vitro. Data are mean ± SEM (n = 3), **P < 0.01, Mann–Whitney test. Western blot shown below demonstrates early phosphorylation of STAT-3 in response to infection. mpi, minutes post infection. (B) Blots showing increase in Bcl-2 expression and STAT-3 phosphorylation at different time points in vitro upon treatment with rIL-13 (1 ng/ml). (C) Western blot showing siRNA mediated downregulation of IL-13 receptors. Blots shown below demonstrate a reduction in STAT-3 phosphorylation in IL-13R downregulated cells or in the presence of AG490, a JAK2 inhibitor. Blot further below shows a significant decrease in rIL-13-induced Bcl-2 expression both in IL-13R knockdown cells as well as in cells treated with AG490. Cont, no treatment. Scr, scrambled siRNA; KD, knockdown; rIL-13, recombinant IL-13. (D) Blots show reduced phosphorylation of STAT-3 when expression of IL-13R was reduced (as compared to scrambled siRNA treated cells) as well as after pretreatment with AG490 at 90 min post infection. Blots below show Bcl-2 levels in infected cells with downregulated IL-13R or JAK-2 inhibition. Blot immediately below shows reduction in phosphorylated STAT-3 upon PD98059 treatment. LD, Leishmania donovani. Cont, no infection; Veh, vehicle (DMSO). Blots are representative of at least three experiments. (E) hMDMs show a time-dependent increase in secretion of IL-13 upon infection in vitro. Western blot immediately below shows increase in Bcl-2 expression upon treatment with rIL-13 (1 ng/ml). Blot below shows IL-13 receptor downregulation upon IL-13 receptor siRNA treatment. Blots further below show that both rIL-13/infection-induced STAT-3 phosphorylation as well as Bcl-2 induction are significantly reduced upon IL-13R KD or JAK-2 inhibition. LD, Leishmania donovani; KD, knockdown; rIL-13, recombinant IL-13; IL-13R KD, IL-13 receptor knockdown.