Prostanoid production by rat aortic endothelial cells by bradykinin and histamine

Pharmacological characterization of mouse hind paw oedema induced by Bothrops insularis (jararaca ilhoa) snake venom

Bothrops snake venoms produce marked local effects, including oedema, haemorrhage and necrosis. The ability of Bothrops insularis venom to induce oedema in mice was investigated. Venom was injected into hind paws and the change in volume over time was measured by plethysmometry. B. insularis venom (0.01-2.5 microg/paw) induced paw oedema which, at high doses (>/=0.5 microg/paw), was accompanied by haemorrhage. The peak oedematogenic response occurred 3 h after venom injection with all doses and decreased gradually thereafter, but was still elevated with high doses after 24 h. Pretreating the mice with cyproheptadine (histamine H(1) and serotonin 5-HT(2) receptor antagonist), mepyramine (histamine H(1) receptor antagonist), L-NAME (inhibitor of nitric oxide synthase), indomethacin and rofecoxib (inhibitors of cyclooxygenases), and dexamethasone (indirect inhibitor of PLA(2)) significantly attenuated venom-induced oedema, whereas methysergide, a serotonin 5-HT(1)/5-HT(2) receptor antagonist, had no effect. The administration of antivenom 30 min before or immediately after venom injection also significantly inhibited venom-induced oedema. These results show that B. insularis venom causes oedema in the mouse hind paw and that this response is mediated by histamine, nitric oxide, and arachidonic acid metabolites formed by cyclooxygenases 1 and 2. The neutralization by commercial antivenom indicates that the venom components responsible for oedema are recognized by the antivenom and share immunological identity with their counterparts in the venoms of mainland Bothrops species.

Effect of inflammatory mediators on the physiology of the human Fallopian tube

The physiological basis for the use of non-steroidal anti-inflammatory drugs (NSAIDs) in the treatment of acute pelvic pain in women was examined in terms of: (i) the electrophysiological responses of epithelial cells in the human Fallopian tube; and (ii) the longitudinal and circular contractions of the myosalpinx. Epithelial cells were grown as a polarized layer in primary culture, and transepithelial potential difference (p.d.) and short-circuit current (I(scc)) were recorded using a modified Ussing chamber. The inflammatory mediators histamine (0.1-100.0 micromol l(-1)) and platelet activating factor (PAF) (1.9-1900.0 nmol l(-1)) increased p.d. and I(scc) in a dose-dependent manner. Pre-incubation with the NSAID diclofenac sodium (100 micromol l(-1)) inhibited the histamine- and PAF-induced stimulation of p.d. and I(scc). Aspirin (100 micromol l(-1)), ibuprofen (100 micromol l(-1)), indomethacin (100 micromol l(-1)) or naproxen (100 micromol l(-1)) were only partially effective. Histamine (0.1-1000.0 micromol l(-1)) increased the frequency of contractions of longitudinal and circular smooth muscle in segments of Fallopian tube in vitro, in a dose-dependent manner. Pre-incubation with diclofenac significantly reduced the histamine-induced stimulation of tubal smooth muscle contraction at the higher doses of histamine. The other NSAIDs had no effect. These data provide evidence that diclofenac downregulates acute inflammation in the human Fallopian tube and may be of use as an anti-inflammatory agent in the treatment of pelvic inflammatory disease.

Aging decreases the production of PGI2 in rat aortic endothelial cells

It has been suggested that progressive pathophysiologic modifications of endothelium are associated with aging. Aging has been shown to influence some specific functions at the cellular level. In the present study, the effects of aging on levels of prostacyclin (PGI2) production were examined in cultured rat aortic endothelial cells from young (six-week-old) and old (100-week-old) Wistar rats. The level of PGI2 production from rat aortic endothelial cells decreased significantly with increasing age, suggesting decreased function of the endothelial cells. The production of PGI2 stimulated by thrombin was decreased in old rat aortic endothelial cells compared to young rat aortic endothelial cells, whereas there was no difference in the rate of intracellular calcium mobilization caused by thrombin. These data indicate that aging nonuniformly affects both basal and agonist-induced levels of PGI2 production in rat aortic endothelial cells, and that this diminution in PGI2 production may be related to the age-related potentiation of various thrombotic events.

Interaction between nitric oxide and prostaglandin synthesis in the acute phase of allergic conjunctivitis

Both nitric oxide and prostaglandins induce vasodilatation which is an important feature of local inflammation. The purpose of the study described here was to investigate a possible interaction between these two types of mediators in an experimental model of allergic conjunctivitis. A conjunctival allergic reaction was induced with antigen in sensitized guinea pigs. Conjunctival vascular permeability changes were evaluated with the prophylactic use of an inhibitor of nitric oxide synthase (L-NAME) and a cycloxygenase inhibitor (indomethacin). To study a possible interaction between nitric oxide and prostaglandin synthesis in the acute phase of allergic conjunctivitis, the levels of nitrite and PGE2 were determined in lavage fluid. The prophylactic use of L-NAME on the formation of conjunctival edema in response to topical PGD2 administration was studied by measurement of albumin levels in lavage fluid. Both nitric oxide and PGE2 are synthesized in response to antigen provocation and after histamine administration. Nitric oxide and PGE2 are produced simultaneously in the conjunctiva and they showed identical synthesis profiles in response to antigen provocation. Pretreatment with L-NAME inhibited the synthesis of PGE2 whereas exogenous administration of nitric oxide increased the level of PGE2 in lavage fluid. Prophylactic treatment with L-NAME significantly inhibited the PGD2 induced albumin extravasation. Nitric oxide seems to play an important role in the acute phase of allergic conjunctivitis it may stimulate PGE2 production and acts as a secondary mediator in PGD2 and histamine induced conjunctival edema.

In vitro effect of cetirizine on PGE2 release by rat peritoneal macrophages and human monocytes

Cetirizine was first described as a specific anti-H1 molecule displaying potent antiallergic activity. It was later found that its pharmacological properties extended to cellular actions as on eosinophil recruitment at inflammatory sites in allergic patients. Monocytes and macrophages participate in allergic mechanisms, particularly through high affinity H1 and H2 membrane receptors and generation of pro- and anti-inflammatory agents; among them histamine-induced factors, IL-1 and prostanoids are of importance. The aim of this work was to investigate the effect exerted by various concentrations of cetirizine (0.1-10 micrograms/ml) applied in vitro to human monocytes and peritoneal rat macrophages cultured for 24 h. Peritoneal macrophages were collected either from normal or experimentally inflamed rats. Human monocytes, isolated from peripheral blood, were studied either in a resting state or after stimulation by LPS from Escherichia coli (1 and 10 micrograms/ml). Cetirizine (10 micrograms/ml) significantly enhanced IL-1 release by human monocytes stimulated by a weak LPS concentration (1 microgram/ml) but could not modify the maximal increase of IL-1 release induced by 10 micrograms/ml of LPS. It did not exert any effect on resting cells. Cetirizine (0.1-10 micrograms/ml) enhanced PGE2 release by resting human monocytes. Concentrations of 1 and 10 micrograms/ml enhanced PGE2 release by LPS-stimulated monocytes, and by healthy and inflamed rat macrophages. This effect was concentration-dependent. Our findings point to an anti-inflammatory action of cetirizine via PGE2 release and histamine H2 interactions. Cetirizine did not directly modify IL-1 generation by resting monocytes but the IL-1 production observed after LPS stimulation could promote the mechanisms by which PGE2 is released.

Evidence that endothelium-dependent relaxation to histamine in the rat common carotid artery is mediated by EDRF

The mechanism of histamine-induced relaxation in the isolated rat common carotid artery was analysed. Histamine (3 x 10(-7)-10(-4) mol/l) caused a concentration-dependent relaxation of the artery. Indomethacin, a cyclo-oxygenase inhibitor, and diethylcarbamazine, a lipoxygenase inhibitor, did not affect the relaxant response of the artery to histamine. After removal of the vascular endothelium the histamine-induced relaxation was strongly reduced. Moreover, hemoglobin and methylene blue, inhibitors of endothelium-derived relaxing factor (EDRF), prevented or reversed the relaxant effect of histamine. These findings confirm that the histamine-induced relaxation is to a greater extent endothelium dependent. It is concluded that the endothelium-dependent component in the relaxant response of the rat common carotid artery to histamine results from the release of EDRF.