INHIBITORY-ACTION OF PERITONEAL-MACROPHAGES ON PROGESTERONE SECRETION FROM COCULTURED RAT GRANULOSA-CELLS

Resident ovarian macrophages are recognized as potential regulators of ovarian function, and the majority of evidence suggests that such regulation is mediated through cytokine secretions, particularly interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha). In this study we examine the effects of co-cultured macrophages, stimulation and inhibition of the immune system, and IL-1 beta and TNF alpha on gonadotropin-induced progesterone secretion from rat granulosa cells. Granulosa cells were isolated from ovarian follicles of proestrous rats and were cultured for a period of 48 h. Peritoneal macrophages, obtained from untreated rats or from animals pretreated with either thioglycollate (TG) or lipopolysaccharide (LPS), were plated at concentrations of 10(5), 5 x 10(3), or 2 x 10(3) cells/ml. After their adherence to the base of the culture wells, 1 ml of serum-free McCoy's medium containing 3 x 10(5) granulosa cells/ml were added to the macrophages. Gonadotropin-induced progesterone secretion was markedly inhibited in the co-cultures, and the degree of inhibition was dependent on both the number of co-cultured macrophages and whether or not the macrophages had been pre-activated by either TG or LPS. TG-activated macrophages were most potent in this respect. Such effects were not due to cytotoxic effects of the macrophages on granulosa cells as determined by a colorimetric assay for cellular growth and survival. In fact, macrophages increased the number of viable granulosa cells after 48-h culture. Granulosa cells obtained from animals pretreated with LPS showed a reduced ability to respond to ovine LH, although suppression of the immune system with cyclosporin had no effect. There was no direct effect of either LPS or TG on progesterone secretion when the drugs were added to the granulosa cell cultures. The addition of human recombinant Il-1 beta or TNF alpha, in doses ranging from 0.5 to 20.0 ng/ml, had no effect on gonadotropin-induced progesterone secretion. Results further support the evidence that immune cells can modulate ovarian function.