Effects of interleukin-4 on the expression and activity of prostaglandin endoperoxide H synthase-2 in amnion-derived WISH cells

Increased prostaglandin biosynthesis during intrauterine infection may be a possible mechanism by which preterm labour is initiated. Inflammatory cyto kines and growth factors are known to stimulate prostaglandin production th rough an increase in prostaglandin endoperoxide H synthase (PGHS)-2 synthes is and activity. Interleukin-4 (IL-4), an anti-inflammatory cytokine, can d ownregulate PGHS-2 expression and inhibit prostaglandin production. Therefo re, the aims of the current study were to determine the effects of IL-4 on PGHS-1 and PGHS-2 expression in amion-derived WISH cells treated with infla mmatory cytokines and growth factors. In WISH cells, near-maximal productio n of the PGHS-2 mRNA occurred using 5 ng/ml EGF, 1 ng/ml IL-1 beta or 50 ng /ml TNF-alpha. Time-course experiments determined that the PGHS-2 mRNA was induced maximally by these stimuli by 1 h. Pretreatment of WISH cells with IL-4 reduced PGHS-2 mRNA levels at 1 h by 67% in cells treated with ECF, 62 % in cells treated with IL-1 beta and 54% in cells treated with TNF-a. Pret reatment with IL-4 more effectively inhibited PGHS-2 expression than simult aneous addition with EGF or IL-1 beta but not TNF-alpha. Immunoblot analysi s showed a correlation between inhibition of mRNA levels and levels of PGHS -2 protein, although stimulation of PGHS-2 protein production by EGF was un detectable. Levels of PGHS-1 protein and mRNA remained unchanged in all exp eriments. Increased production of prostaglandin E-2 (PGE(2)) in response to TNF-alpha and IL-1 beta treatment was attenuated by IL-4 pretreatment, by 52% and 72%, respectively. No attenuation of EGF-stimulated PGE(2) levels w as seen. We conclude that IL-4 inhibits PGHS-2 mRNA and protein production in cytokine-stimulated WISH cells, but does not affect EGF-stimulated PGE, production, suggesting that EGF can induce prostaglandin biosynthesis by a mechanism other than through increased PGHS-2 expression.