INTERLEUKIN-1-BETA AND INTERLEUKIN-6 SPECIFICALLY INCREASE THE RELEASE OF PROSTAGLANDIN-E(2) FROM RAT HYPOTHALAMIC EXPLANTS INVITRO

It has previously been shown that the cytokines interleukin-1-beta and interleukin-6 (IL-1-beta and IL-6) stimulate directly the release of corticotrophin-releasing-hormone-41 from the rat hypothalamus in vitro, while IL-1-beta can also stimulate the release of somatostatin. These effects can be antagonized by drugs which block prostaglandin (PG) synthesis. PGs are also involved in the control of hypothalamic neuropeptides by other neurotransmitters. In the present study, we have characterized the production of PGs from the rat hypothalamus in vitro, and investigated the effects of IL-1-beta and IL-6, as well as the neurotransmitters norepinephrine, acetylcholine and 5-hydroxytryptamine, on the acute release of PGs, using a well-validated acute hypothalamic incubation system. The rate of release of PGs [PGE2, PGF2-alpha, 6-keto-PGF1-alpha (6KPGF1-alpha) and thromboxane B2 (TXB2) in the medium was found to stabilize after 60 min of preincubation and thereafter remain constant, with TXB2 being the predominant species. Twenty-minute incubation in the presence of human recombinant IL-1-beta or IL-6, in the dose range 1-100 U/ml, had no effect on the release of PGF2-alpha, 6KPGF1-alpha or TXB2; however, the release of PGE2 was significantly increased by both IL-1-beta and IL-6. The effect of IL-1-beta was antagonized by both indomethacin and dexamethasone. None of the other neurotransmitters tested had any effect on the release of any of the PGs. It is concluded that the regulation of hypothalamic PG release may be investigated by means of acute rat hypothalamic explants, as has previously been shown for hypothalamic peptides and amines. Furthermore, IL-1-beta and IL-6 specifically stimulate PGE2 release, possibly implicating this PG in certain of the hypothalamic effects of IL-1-beta and IL-6.