Nerve growth factor modifies the expression of inflammatory cytokines by mast cells via a prostanoid-dependent mechanism.
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Nerve growth factor (NGF) is well recognized to have a number of potent effects on mast cells, including increasing mast cell numbers in vivo and inducing mast cell degranulation in vitro. More recently, NGF has been demonstrated to induce PGD2 production by mast cells through the induction of mast cell cyclooxygenase expression. We have observed that NGF at doses as low as 10 ng/ml will induce IL-6 production and inhibit TNF-alpha release from rat peritoneal mast cells in the presence of lysophosphatidylserine as a cofactor. NGF synergizes with LPS treatment of peritoneal mast cells (PMC) for the induction of IL-6. Examination of the mechanism of this phenomenon has revealed that NGF can induce both rat PMC and mouse bone marrow-derived cultured mast cells to produce substantial levels of PGE2. This response is maximal at later time points 18-24 h after NGF activation. The ability of NGF to induce PGE2 is not dependent on mast cell degranulation. Other stimuli capable of inducing IL-6, such as LPS, do not induce production of this prostanoid. Inhibition of cyclooxygenase activity by PMC using either flurbiprofen or indomethacin inhibited both the NGF-induced PGE2 synthesis and the NGF-induced alterations in TNF-alpha and IL-6 production. These results suggest a role for mast cell-derived prostanoids in the regulation of local inflammatory responses and neuronal degeneration after tissue injury involving induction of NGF production.
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