Effects of aminoguanidine and meloxicam on nitric oxide and prostaglandin E production induced by lipopolysaccharide in the hypothalamus and anterior pituitary of the rat.
OBJECTIVE
Injection of bacterial lipopolysaccharide (LPS) into male rats activates genes that in turn induce many enzymes that participate in the animals' response to LPS. There is induction of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) in many tissues. This induction could result from combination with cell surface LPS receptors that directly induce both genes, or the nitric oxide (NO) released as a result of iNOS induction could induce COX-2.


METHODS
To distinguish between these two possibilities, specific inhibitors of iNOS and COX-2 activity, aminoguanidine (AG) and meloxicam (MLX), respectively, were injected either peripherally or intracerebroventricularly (i.c.v.), and their effect on NO and prostaglandin E (PGE) production induced by LPS in the medial basal hypothalamus (MBH) and anterior pituitary gland (AP) were determined.


RESULTS
Peripheral injection of AG blocked iNOS-derived NO production in the AP but not in the MBH. When AG was injected i.c.v., iNOS-derived NO production in the MBH was blocked. MLX injected peripherally blocked COX-2-derived PGE(2) production in the MBH and AP, whereas AG injected peripherally or i.c.v. was ineffective. Since AG was only effective in blocking iNOS-derived NO production in the MBH when injected i.c.v., AG apparently does not effectively cross the blood brain barrier, whereas MLX injected peripherally inhibited PGE production, probably by inhibiting COX-2 activity in both the MBH and AP. AG was ineffective in preventing the increase in PGE derived from COX-2 in either the MBH or AP.


CONCLUSIONS
LPS directly induces both enzymes, iNOS and COX-2, in the hypothalamus and AP.
Mohn
C
C
Centro de Estudios Farmacológicos y Botánicos, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.
Lomniczi
A
A
Faletti
A
A
Scorticati
C
C
Elverdin
J C
JC
McCann
S M
SM
Rettori
V
V
D000818:Animals; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis*; D019446:Endotoxemia / Q000150:complications*; D006146:Guanidines / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D007249:Inflammation / Q000201:enzymology* / Q000209:etiology* / Q000503:physiopathology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D000077239:Meloxicam; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013843:Thiazines / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D006146:Guanidines; D007527:Isoenzymes; D008070:Lipopolysaccharides; D013843:Thiazines; D013844:Thiazoles; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; C004479:pimagedine; D000077239:Meloxicam