Effects of interleukin-8 on estradiol and progesterone production by bovine granulosa cells from large follicles and progesterone production by luteinizing granulosa cells in culture.

Interleukin 8 (IL-8) is a chemoattractant involved in the recruitment and activation of neutrophils and is associated with the ovulate process. We examined the possible role of IL-8 in steroid production by bovine granulosa cells before and after ovulation. The concentration of IL-8 in the follicular fluid of estrogen-active dominant (EAD) and pre-ovulatory follicles (POF) was higher than that of small follicles (SF). CXCR1 mRNA expression was higher in the granulosa cells of EAD and POF than that of SF. In contrast, CXCR2 mRNA expression was lower in granulosa cells of EAD and POF than in SF. IL-8 inhibited estradiol (E2) production in follicle-stimulating hormone (FSH)-treated granulosa cells at 48 h of culture. IL-8 also suppressed CYP19A1 mRNA expression in FSH-treated granulosa cells. IL-8 stimulated progesterone (P4) production in luteinizing hormone (LH)-treated granulosa cells at 48 h of culture. Although IL-8 did not alter the expression of genes associated with P4 production, it induced StAR protein expression in LH-treated granulosa cells. The expression of CXCR1 mRNA in corpus luteum (CL) did not change during the luteal phase. In contrast, the expression of CXCR2 mRNA in middle CL was significantly higher than in early and regression CL during the luteal phase. In luteinizing granulosa cells, an in vitro model of granulosa cell luteinization, CXCR2 mRNA expression was downregulated, whereas CXCR1 mRNA expression was unchanged. IL-8 also stimulated P4 production in luteinizing granulosa cells. These data provide evidence that IL-8 functions not only as a chemokine, but also act as a regulator of steroid synthesis in granulosa cells to promote luteinization after ovulation.

Effect of VEGF (vascular endothelial growth factor) on expression of IL-8 (interleukin-8), IL-1beta and their receptors in bovine theca cells.

Cytokines such as VEGF (vascular endothelial growth factor) and ILs (interleukins) are involved in follicular development in the mammalian ovary. The aim of the present study is to examine the transcripts of IL-8 and -1 that differ during follicular development; the relationships between IL-8, IL-1 and VEGF in theca cells is still unknown. We first examined the gene expression of IL-8, IL-1beta and their respective receptors, CXCR1 and IL-1R1 in the theca cells of PRF (preselection) and POF (postselection follicles) from the bovine ovary. Expression of IL-8 and CXCR1 genes were observed in POF, whereas expression of IL-1beta and IL-1R1 genes was observed in both follicles. Secondly, we examined the effects of VEGF on the expression of IL-8, IL-1beta and their receptors genes in cultured bovine theca cells. mRNA expression was quantified by using real-time PCR methods. VEGF stimulates the expression of IL-8 and CXCR1 mRNA. However, VEGF down-regulates the expression of CXCR2 mRNA during the culture period. Expression of IL-1beta and -1R1 mRNA was induced in the cultured theca cells at 48 h. Our data demonstrate that VEGF stimulated the expression of the IL-8 and CXCR1 genes and that CXCR2 expression was suppressed by VEGF, suggesting a follicle stage-dependent expression pattern for the IL-8 system. Furthermore, our results suggest that the transcription system for CXCR genes may have different pathways of VEGF stimulation in bovine theca cells. Taken together, our data suggested that VEGF is associated with the IL system in theca cells in bovine ovary.