The relevance of kalikrein-kinin system via activation of B2 receptor in LPS-induced fever in rats.

PURPOSE: This study evaluated the involvement of endogenous kallikrein-kinin system and the bradykinin (BK) B1 and B2 receptors on LPS- induced fever and the POA cells involved in this response. MATERIAL AND METHODS: Male Wistar rats received either i.v. (1 mg/kg), i.c.v. (20 nmol) or i.h. (2 nmol) injections of icatibant (B2 receptor antagonist) 30 or 60 min, respectively, before the stimuli. DALBK (B1 receptor antagonist) was given either 15min before BK (i.c.v.) or 30 min before LPS (i.v.). Captopril (5 mg/kg, sc.,) was given 1 h prior LPS or BK. Concentrations of BK and total kininogenon CSF, plasma and tissue kallikrein were evaluated. Rectal temperatures (rT) were assessed by telethermometry. Ca++ signaling in POA cells was performed in rat pup brain tissue microcultures. RESULTS: Icatibant reduced LPS fever while, captopril exacerbated that response, an effect abolished by icatibant. Icatibant (i.h.) reduced fever to BK (i.h.) but not that induced by LPS (i.v.). BK increased intracellular calcium concentration in neurons and astrocytes. LPS increased levels of bradykinin, tissue kallikrein and total kininogen. BK (i.c.v.) increased rT and decreased tail skin temperature. Captopril potentiated BK-induced fever an effect abolished by icatibant. DALBK reduced the fever induced by BK. BK (i.c.v.) increased the CSF PGE2concentration. Effect abolished by indomethacin (i.p.). CONCLUSIONS: LPS activates endogenous kalikrein-kinin system leading to production of BK, which by acting on B2-receptors of POA cells causes prostaglandin synthesis that in turn produces fever. Thus, a kinin B2-receptor antagonist that enters into the brain could constitute a new and interesting strategy to treat fever.

Mediators involved in the febrile response induced by Tityus serrulatus scorpion venom in rats.

Tityus serrulatus venom (Tsv) was intraperitoneally (ip) injected at doses of 75, 150 and 300mug/kg and IL-1beta (2.0 microg/kg) was given intravenously (iv) to male Wistar rats. Rectal temperature was measured by radiotelemetry. Vagotomy was performed according to Bluthe et al. [1994. Lipopolysaccharide induces sickness behaviour in rats by a vagal mediated mechanism. C R Acad. Sci. 317(6), 499-503]. Cerebrospinal fluid (CSF) and peritoneal fluid (PF) levels of bradykinin (BK) were measured by ELISA. B(1) (des-Arg(9)-[Leu(8)]-BK; DALBK) and B(2) kinin receptor (icatibant) antagonists (1.0 mg/kg each), the induced nitric oxide synthase inhibitor aminoguanidine (50.0 mg/kg), the neuronal nitric oxide synthase inhibitor 7-nitroindazole (30.0 mg/kg), the dual cyclooxygenase inhibitor ibuprofen (10.0 mg/kg), the selective interleukin-1 receptor antagonist IL-ra (2.0 mg/kg) and dipyrone (120 mg/kg) were given ip. Celecoxib (5 mg/kg) was given per os (po). Tsv at doses of 75 microg/kg evoked no change in rectal temperature while at doses of 150 and 300 microg/kg it promoted long-lasting fever (2 degrees C+/-0.1). Tsv (150 microg/kg) increased by nearly 3 and 5 times, respectively BK concentration in the CSF and in the PF. Subdiaphragmatic vagotomy or 7-nitroindazole reduced, icatibant, DALBK, IL-1ra, aminoguanidine and dipyrone abolished, while ibuprofen and celecoxib failed to affect Tsv-induced fever. These results suggest that PGs do not play a relevant role, whereas, kinins via their B(1) and B(2) receptors, IL-1, nitric oxide and vagal neurotransmission are involved in Tsv-induced fever.

Effect of a kinin B2 receptor antagonist on LPS- and cytokine-induced neutrophil migration in rats.

1 This study examines the involvement of kinins in neutrophil migration into rat subcutaneous air pouches triggered by lipopolysaccharide (LPS), as well as the putative roles played by kinin B(1) and B(2) receptors, tumour necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1beta) and selectins in this response. 2 LPS (5 ng to 10 micro g cavity(-1)) injected into the 6-day-old pouch induced a dose- and time-dependent neutrophil migration which peaked between 4 and 6 h, and was maximal following the dose of 100 ng cavity(-1) (saline: 0.46+/-0.1; LPS: 43+/-3.70 x 10(6) cells cavity(-1) at 6 h). 3 Bradykinin (BK) (600 nmol) injected into the pouch of saline-treated rats induced only modest neutrophil migration (0.73+/-0.16 x 10(6) cells cavity(-1)). A more robust response to BK (3.2+/-0.25 x 10(6) cells cavity(-1)) was seen in animals pretreated with captopril, but this was still smaller than the responses to IL-1beta or TNF-alpha (15 pmol: 23+/-2.2 x 10(6) and 75 pmol: 29.5+/-2 x 10(6) cells cavity(-1), respectively). Nevertheless, the B(1) agonist des-Arg(9)-BK (600 nmol) failed to induce neutrophil migration. 4 HOE-140 (1 and 2 mg kg(-1)), a B(2) receptor antagonist, reduced LPS-induced neutrophil migration. HOE-140 also reduced the neutrophil migration induced by BK, but had no effect on the migration promoted by IL-1beta or TNF-alpha. des-Arg(9)-[Leu(8)]-BK, B(1) receptor antagonist was ineffective in changing neutrophil migration caused by any of these stimuli. 5 Neutrophil migration induced by LPS or BK was reduced by interleukin-1 receptor antagonist (IL-1ra) (1 mg kg(-1)), sheep anti-rat TNF serum (anti-TNF serum) (0.3 ml cavity(-1)), and the nonspecific selectin inhibitor fucoidin (10 mg kg(-1)). 6 TNF-alpha levels in the pouch fluid were increased by LPS or BK injection, peaking at 0.5-1 h and gradually declining thereafter up to 6 h. IL-1beta levels increased steadily throughout the 6 h period. HOE-140 markedly inhibited the rise in IL-1beta and TNF-alpha levels in pouch fluid triggered by both stimuli. 7 These results indicate that BK participates importantly in selectin-dependent neutrophil migration into the air pouch triggered by LPS in the rat, by stimulating B(2) receptors coupled to synthesis/release of TNF-alpha and IL-1beta.