Tumor Necrosis Factor a Inhibits the Hormonal Response of the Pituitary Gland to Hypothalamic Releasing Factors*

Abstract

Tumor necrosis factor α (TNFα), a monokine produced by activated macrophages and monocytes, may be an essential mediator of the pathogenesis and of the hormonal response to endotoxic shock. It has been suggested that an elevated level of TNFα is a marker for morbidity and mortality during septic shock, and that treatment with antibodies against TNFα decreases mortality. Because monokines have been shown to interact at the hypothalamic-pituitary level, we have studied the effect of TNFα on basal and stimulated hormone release from normal rat anterior pituitary cells. After 3 days of incubation, primary cultures of rat anterior pituitary cells were stimulated with either 0.5 ng/ml CRF, 3 ng/ml AVP, 10 ng/ml angiotensin II (All), 10-6 M TRF, 10-8 M LHRH, or 10-8 M GHRH, alone or in the presence of 20 or 50 ng/ml human or murine recombinant TNFα. The culture media were analyzed for ACTH, GH, LH, and PRL content. Each experiment was performed in triplicate and was repeated 3 to 8 times. Timecourse experiments (n = 3) demonstrated that TNFα inhibited CRF-stimulated ACTH production over a period of 8, 16, and 24 h, but had no effect before a period of 4 h. At doses ranging from 1 to 100 ng/ml, TNFα did not affect basal ACTH secretion but inhibited CRF-stimulated ACTH release in a dose-dependent manner (ED50 - 10 ng/ml). At a dose of 50 ng/ml, TNFα inhibited AVP-stimulated ACTH release by 30% and blocked the effect of AIL TNFα (20 and 50 ng/ml) completely prevented the CRF-AVP potentiation of ACTH release. Similarly, TNFα inhibited the stimulated release of GH (100% inhibition), LH (35% inhibition), and PRL (100% inhibition). TNFα had no effect on the basal secretion of GH or LH but inhibited basal PRL in a dose-dependent manner. The administration of the monokine did not cause any cellular damage because 48 h after removal of the TNFα treatment the cells showed normal basal and stimulated hormone levels in response to their specific stimuli. Incubation of TNFα solutions with antibody to TNFα reversed all TNFα actions. These data suggest that TNFα inhibits the secretion of pituitary hormones and particularly suppresses the response of the corticotroph cells. This inhibitory effect may contribute to the increased mortality observed in cases of severe septic shock with high circulating TNFα levels. (Endocrinology127: 101–106, 1990)