Tumor necrosis factor α and interleukin-1β stimulate the expression of cyclooxygenase II but do not alter prostaglandin E2 receptor mRNA levels in cultured dorsal root ganglia cells

Turn or necrosis factor alpha (TNFalpha) and interleukin 1beta (IL- 1beta) are pro-intlammatory cytokines capable of altering the sensitivity of sensory neurons. Because sensitization elicited by IL-1beta and TNFalpha is blocked by inhibition of the inducible enzyme, cyclooxygenase-II (COX-2). we examined whether these cytokines could increase COX-2 expression in dorsal root ganglion (DRG) cultures. Treatment of cell Cultures with either IL-1beta or TNFalpha increases immunoreactive COX-2, as measured by immunoblotting, in a time-and concentration-dependent manner. A 24-h pretreatment with 10 ng/ml IL- 1beta or 50 ng/ml TNFalpha augmented COX-2 expression 50- and 8-fold over basal levels, respectively. Immunohistochemistry established the presence of COX-2-like immunoreactivity in both neuronal and non-neuronal cells ill Culture. The addition of IL-1 receptor antagonist blocked the induction of COX-2 expression by IL- 1beta, but did riot alter TNFalpha-stimulated increases in COX-2. indicating that the mechanism of TNFalpha, is not limited to increasing the expression of IL- Ibeta. The basal and TNFalpha-induced expression of COX-2 was riot dependent oil the presence of NGF in the growth media. IL-1beta and TNFalpha treatment for 24 It enhanced prosta.-landin E-2 (PGE(2)) production 2-4-fold. which was blocked by pretreatment with the COX-2 inhibitor, NS-398. Exposing cultures to PGE(2), IL-1beta, or TNFalpha. for 24 h did not alter PGE(2) receptor (EP) mRNA levels. These results indicate that TNFalpha and IL-1beta, induce the functional expression of COX-2 but not EP receptors in DRG cells in culture and suggest that cytokine-induced sensitization of sensory neurons is secondary to prostaglandin production and not alterations in EP receptors. (C) 2004 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.