IL-10 inhibits apoptosis of promyeloid cells by activating insulin receptor substrate-2 and phosphatidylinositol 3 '-kinase

IL-10 is well known to be a potent inhibitor of the synthesis of proinflamm atory cytokines, but noninflammatory hemopoietic Cells also express IL-10Rs . Here we show that IL-10 directly affects progenitor myeloid cells by prot ecting them from death following the removal of growth factors. Murine fact or-dependent cell progenitors cultured in the absence of growth factors wer e 43 +/- 1% apoptotic after 12 h. Addition of IL-10 at a concentration as l ow as 100 pg/ml significantly reduced the apoptotic population to 32 +/- 3% . At 10 ng/ml, IL-10 caused a 4-fold reduction in the apoptotic population (11 +/- 1%). The anti-apoptotic activity of IL-10 was significantly inhibit ed with a neutralizing IL-10R Ab. Factor-dependent cell progenitor promyelo id cells expressed functional IL-10Rs, as assessed by precipitation of a 11 0-kDa protein with an Ab to the IL-10R and by the ability of IL-10 to activ ate Jak1 and Tyk2 and to phosphorylate tyrosine 705 on Stat-3. IL-10 increa sed tyrosyl phosphorylation of insulin receptor substrate-2 and stimulated the enzymatic activity of both phosphatidylinositol 3'-kinase and Akt. The anti-apoptotic activity of IL-10 was blocked by inhibition of phosphatidyli nositol 3'-kinase. Wortmannin and LY294002 also totally inhibited activatio n of extracellular signal-related kinase (ERK)1/2 by IL-10. Direct inhibiti on of ERK1/2 with the mitogen-activated protein kinase/ERK kinase inhibitor PD98059 partially, but significantly, impaired the anti-apoptotic activity of IL-10. These data establish that activation of the IL-10R promotes surv ival of progenitor myeloid cells. This survival-promoting activity is total ly due to IL-10 stimulating the insulin receptor substrate-2/PI 3-kinase/Ak t pathway, which increases the anti-apoptotic activity of ERK1/2.