INTERLEUKIN-8 EXPRESSION AND MODULATION IN HUMAN PREOVULATORY FOLLICLES AND OVARIAN-CELLS

Just before the time of ovulation, the number of neutrophils increases markedly in the thecal layer of the leading follicle. A preovulatory rise in chemotactic activity for neutrophils in human follicular fluid has also been detected. We hypothesized that interleukin-8 (IL-8), a neutrophil chemoattractant/activating factor and a potent angiogenic a gent, may be an important modulator of leukocyte chemotaxis in ovulato ry function. In this regard we investigated the expression and modulat ion of IL-8 in human follicular fluid samples from patients undergoing in vitro fertilization-embryo transfer therapy and in ovarian stromal and granulosa-lutein cell cultures. The concentration of IL-8 in pre- hCG follicular fluid samples (n = 4) was 16 +/- 12 (mean +/- SEM) pg/m l, and that in post-hCG samples (n = 101) was 262 +/- 45 pg/ml (P = 0. 001). In post-hCG samples, the concentration of IL-8 in an individual follicle correlated with the size of that follicle (r = 0.61; P = 0.02 ). We also observed a correlation between serum IL-8 levels (22 +/- 3 pg/ml) and follicular fluid levels (303 +/- 143 pg/ml), with a 14-fold gradient (r = 0.71; P = 0.01) in 11 patients tested for both. IL-8 me ssenger RNA (mRNA) and the protein were expressed constitutively in ov arian stromal cell cultures, and the level was increased by IL-1 alpha and tumor necrosis factor-alpha in a time- and concentration-dependen t manner. hCG and LH induced higher levels of IL-8 mRNA expression and protein production. Granulosalutein cells also expressed IL-8 mRNA an d protein, and the levels were increased by IL-1 alpha and tumor necro sis factor-alpha. Importantly, progesterone suppressed both basal and IL-1 alpha-stimulated IL-8 expression in stromal and granulosa-lutein cell types. In summary, we found that IL-8 levels are elevated in peri ovulatory follicular fluid, and both granulosa-lutein and ovarian stro mal cells express the mRNA and produce the protein, The modulation of IL-8 in these cell cultures by steroid and trophic hormones suggests t hat IL-8 may play an important role in the physiology of ovulation, su ch as timely follicular rupture and neovascularization of the corpus l uteum.