Participation of the endocannabinoid system in the effect of TNF-alpha on hypothalamic release of gonadotropin-releasing hormone.
It is known that Delta(9)-tetrahydrocannabinol (THC), the major active ingredient of marijuana, can suppress reproductive function. Also, we reported previously that the endocannabinoid, anandamide (AEA), inhibited gonadotropin-releasing hormone (LHRH) release from medial basal hypothalamus (MBH) of male rats incubated in vitro as well as reduced plasma LH levels after i.c.v. AEA injections into the cerebral lateral ventricle. On the other hand, it is known that during endotoxemia the hypothalamic gonadotropin axis is inhibited. Therefore, the aim of the present study was to determine whether the effect of TNF-alpha, a proinflammatory cytokine induced by lipopolysaccharide (LPS) that inhibits LHRH release, is mediated by the activation of the endocannabinoid system. The intraperitoneal injection of LPS (5 mg/kg) as well as the i.c.v. injection of tumor necrosis factor-alpha (TNF-alpha) (100 ng/rat) increased significantly the AEA synthesis measured ex vivo in MBHs removed 3 h after the treatments. To examine the possibility that TNF-alpha also acted by increasing the synthesis of AEA that was released and activated the CB1-r followed by inhibition of LHRH release, we measured the effect of TNF-alpha on the AEA synthase activity in MBHs incubated in vitro. As expected, we found that TNF-alpha (2.9 x 10(-9) M) increased the AEA synthesis. Second, we showed that TNF-alpha reduced significantly the forskolin-stimulated LHRH release and that the CB1-r antagonist AM251 (10(-5) M) blocked that inhibition, supporting the hypothesis that TNF-alpha inhibits LHRH release, acting at least in part by activating the endocannabinoid system. Therefore, our data demonstrate a key role for the endocannabinoid system in the response of the reproductive system to inflammatory signals.
Fernandez-Solari
Javier
J
Centro de Estudios Farmacológicos y Botánicos, Consejo Nacional de Investigaciones Cientificas y Técnicas, Buenos Aires, Argentina.
Prestifilippo
Juan P
JP
Bornstein
Stefan R
SR
McCann
Samuel M
SM
Rettori
Valeria
V
D000581:Amidohydrolases / Q000378:metabolism; D000818:Animals; D063385:Cannabinoid Receptor Modulators / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D063388:Endocannabinoids; D004789:Enzyme Activation / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D008070:Lipopolysaccharides; D043884:Receptor, Cannabinoid, CB1; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D007987:Gonadotropin-Releasing Hormone; D000242:Cyclic AMP; D000581:Amidohydrolases; C087226:arachidonoylethanolamide synthase