Regulation of uterine function by cytokines in cows: Possible actions of tumor necrosis factor-alpha, interleukin-1alpha and interferon-tau
2006
Okuda, K.(Okayama Univ. (Japan)) | Sakumoto, R.
When animals do not become pregnant, regression of the corpus luteum (CL) is essential for normal cyclicity because it allows the development of a new ovulatory follicle. Luteal regression is caused by a pulsatile release of prostaglandin (PG) Fsub(2alpha) from the uterus in the late luteal phase in most mammals including cattle. Although it has been proposed in ruminants that pulsatile PGFsub(2alpha) secretion is generated by a positive feedback loop between luteal and/or hypophyseal oxytocin and uterine PGFsub(2alpha), the bovine endometrium may possess other mechanisms for initiation of luteolytic PGFsub(2alpha) secretion. There is increasing evidence that several cytokines mainly produced by immune cells modulate CL and uterine function in many species. Tumor necrosis factor-alpha (TNF-alpha) stimulates PGFsub(2alpha) output from bovine endometrium not only at the follicular phase but also at the late luteal phase. Administration of TNF-alpha at a high concentration prolongs luteal lifespan, whereas administration of a low concentration of TNF-alpha accelerates luteal regression in cows. The data obtained from the authors' previous in vitro and in vivo studies strongly suggest that TNF-alpha is a crucial factor in regulating luteolysis in cows. The authors' recent study has shown that interleukin-1alpha mediates PG secretion from bovine endometrium as a local regulator. Furthermore, interferon-tau (IFN-tau) suppresses the action of TNF-alpha on PGFsub(2alpha) synthesis by the bovine endometrium in vitro, suggesting that IFN-tau plays a luteoprotective role by inhibiting TNF-alpha-induced PGFsub(2alpha) production in early pregnancy. The purpose of the present review is to summarize current understanding of the endocrine mechanisms that regulate uterine function by cytokines during the estrous cycle and early pregnancy in cows.
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