Stem cell factor and interleukin-4 increase responsiveness of mast cells to Substance P

Objective. The response of mast cells (MC) to non-IgE-mediated stimulation is critically dependent on the population of MC examined. The neuropeptide Substance P (SP) has been reported to activate connective tissue-type MC (C TMC), while mucosal MC (MMC) are not activated by SP. We examined the effec t of stem cell factor (SCF) plus interleukin-4 (IL-4) on SP-initiated activ ation of bone marrow-derived MC (BMMC). Materials and Methods. Mouse MC, derived from a culture of BM cells with IL -3, were subsequently treated with recombinant SCF plus IL-4 for 6 days. Re sponsiveness to SP was monitored measuring beta-hexosaminidase and lipid me diator release. Histochemical staining, histamine analysis, and granule pro tease expression were achieved to characterize the cells. Results. In contrast to IL-3 grown cells, SCF/IL-4-exposed cells showed fun ctional responsiveness to release beta-hexosaminidase (42.25% +/- 1.46% at SP concentration of 100 mu M) and produce leukotriene C-4 (LTC4) (7.4 +/- 1 .5 ng/10(6) cells)/prostaglandin D-2 (PGD(2)) (2.0 +/- 0.3 ng/10(6) cells) upon stimulation by SP. The increase in sensitivity of the cells to SP was not due to differentiation into CTMC, as the cells remained heparin negativ e. Both SCF and IL-4 were needed because SCF or IL-4 alone were insufficien t to keep cells viable after 3 to 4 days post coculture. SP-induced secreti on from BMMC cultured in medium containing SCF plus IL-4 (25.76% +/- 1.83%) was higher in comparison with cells cultured with SCF plus IL-3 (8.85% +/- 0.68%). Conclusion. These findings indicate that temporal changes in cytokine expre ssion can influence the sensitivity of MC to non-immunologic stimuli. Local cytokine production leading to an increase in MC responsiveness to SP and inducing secretion of granule content and lipid generation may, therefore, propagate and worsen inflammatory conditions. (C) 2000 International Societ y for Experimental Hematology. Published by Elsevier Science Inc.