Murine myeloid progenitor responses to GM-CSF and eosinophil precursor responses to IL-5 represent distinct targets for downmodulation by prostaglandin E(2)

Abstract

1. Because Prostaglandin E(2) (PGE(2)) and dibutiryl cyclic AMP (dbcAMP) modulate the production and effects of haemopoietic cytokines in allergy, we examined their ability to modulate responses of myeloid progenitors to GM-CSF, and of eosinophil precursors to IL-5. 2. The ability of PGE(2), dbcAMP, rolipram, forskolin, dbcGMP and PGD(2), to modulate the responses to GM-CSF and IL-5 in colony formation (progenitor) and eosinophil differentiation (precursor) assays using bone-marrow from nonsensitized or from intranasally-challenged, ovalbumin-sensitized mice of five strains was studied. 3. PGE(2) (10(-7) M) inhibited GM-CSF-stimulated colony formation in bone-marrow from BP-2 mice. This effect was duplicated by dbcAMP (0.3 - 1x10(-6) M), Rolipram (10(-5) M) and forskolin (3x10(-5) M), but not Prostaglandin D(2) (10(-6) M). Inhibition affected similarly all myeloid colony types. Progenitors from sensitized and challenged BP-2 mice were also inhibited by PGE(2) and cyclic AMP. PGE(2) inhibited progenitors from C57BL/10, CBA/J and A/J, but not BALB/c mice. However, BALB/c progenitors were sensitive to dbcAMP and Forskolin (10(-4) M). In contrast, in precursor assays, PGE(2) (10(-7) - 10(-9) M) blocked responses to IL-5 in bone-marrow from BP-2 and BALB/c mice, either naïve or sensitized and challenged, to a similar extent. PGD(2) (10(-6) M) was ineffective, as was PGE(2) (10(-7) M), if added after 48 h of culture. 4. In conclusion, PGE(2) inhibits the responses of bone-marrow myeloid progenitors to GM-CSF and of eosinophil precursors to IL-5, in naïve or ovalbumin sensitized and challenged mice. These effects are duplicated by cyclic AMP-elevating agents. In the BALB/c strain, the resistance of progenitors, but not precursors, to PGE(2) inhibition, indicates these developmental stages are separate targets for PGE(2) modulation.

Figure 1

Effect of PGE₂ and dbcAMP on GM-CSF-induced colony formation in naïve bone-marrow. The data are mean±s.e.mean of the number of myeloid colonies formed by bone-marrow from naïve BP-2 mice. GM-CSF was used at 2 ng ml⁻¹. Asterisks indicate significant differences relative to the GM-CSF controls. Data are derived from 4–19 experiments.

Figure 2

Effect of PGE₂ on GM-CSF-induced colony formation in bone-marrow from different mouse strains. The data are mean±s.e.mean of the number of myeloid colonies formed by bone-marrow from naïve mice of the indicated strains. GM-CSF was used at 2 ng ml⁻¹. Asterisks indicate significant differences relative to the respective GM-CSF controls (P<0.01 in all cases). Data are derived from 3–19 experiments.

Figure 3

Effect of PGE₂ on rmIL-5-driven eosinophil differentiation in bone-marrow from BP-2 mice. Data are mean±s.e.mean of the per cent EPO+ cells in liquid cultures established from ovalbumin-sensitized and challenged BP-2 mice, with IL-5 at the indicated concentrations, without PGE₂ (−) or with addition of PGE₂, (10⁻⁷–10⁻⁹ M) for 7 days. Inhibition was significant for all PGE₂ concentrations, relative to the respective control cultures. Data are derived from three experiments.

Figure 4

Effect of PGE₂ on IL-5-driven eosinophil differentiation in bone-marrow from BP-2 mice. Data are mean±s.e.mean of the per cent EPO+ cells in liquid cultures established from naïve BP-2 mice, in the presence of 1 ng ml⁻¹ rmIL-5, without PGE₂ (IL-5) or with addition of PGE₂, (10⁻⁷ M) for the indicated number of days. Asterisks indicate significant differences relative to the respective rmIL-5 controls. Data are derived from 4–10 experiments.

Figure 5

Effect of PGE₂ on IL-5-driven eosinophil differentiation in bone-marrow from BALB/c mice. Data are mean±s.e.mean of the per cent EPO+ cells in liquid cultures established from naïve (normal) or ovalbumin-sensitized and challenged (immune) BALB/c mice in the presence of IL-5 (1 ng ml⁻¹) alone or with PGE₂ at the indicated concentrations. Asterisks indicate significant differences relative to the respective rmIL-5 controls (P<0.003 in all cases). Data are derived from 9–10 experiments.