Relevance of mediators to cardiac parameters of isolated anaphylactic guinea-pig heart

Immediate hypersensitivity elicits renin release from cardiac mast cells

BACKGROUND

We recently reported that murine and cavian heart mast cells are a unique extrarenal source of renin. Ischemia/reperfusion releases this renin leading to local angiotensin formation and norepinephrine release. As mast cells are a primary target of hypersensitivity, we assessed whether anaphylactic mast cell degranulation also results in renin and norepinephrine release.

METHODS

Hearts isolated from presensitized guinea pigs were challenged with antigen.

RESULTS

Cardiac anaphylaxis was characterized by mast cell degranulation, evidenced by beta-hexosaminidase release and associated with renin and norepinephrine release. Mast cell stabilization with cromolyn or lodoxamide markedly attenuated the release of beta-hexosaminidase, renin and norepinephrine. Renin inhibition with BILA2157 did not affect mast cell degranulation, but attenuated norepinephrine release.

CONCLUSIONS

Our findings disclose that immediate-type hypersensitivity elicits renin release from mast cells, activating a local renin-angiotensin system, thereby promoting norepinephrine release. As renin is stored in human heart mast cells, allergic reactions could initiate renin release, leading to local angiotensin formation and hyperadrenergic dysfunction.

Involvement of platelet-activating factor and leukotrienes in anaphylactic segmental venoconstriction in ovalbumin sensitized guinea pig livers

The hepatic anaphylactic venoconstriction is partly involved in anaphylactic hypotension, and is characterized by significant post-sinusoidal constriction and liver congestion in guinea pigs. We determined what chemical mediators are involved in anaphylaxis-induced segmental venoconstriction and liver congestion in perfused livers isolated from ovalbumin sensitized guinea pigs. Livers were perfused portally and recirculatingly at constant flow with diluted blood. The sinusoidal pressure was measured by the double occlusion pressure (Pdo), and was used to determine the pre-sinusoidal (Rpre) and post-sinusoidal (Rpost) resistances. An antigen injection increased both the portal vein pressure and Pdo, resulting in 4.1- and 2.3-fold increases in Rpre and Rpost, respectively. Hepatic congestion was observed as reflected by liver weight gain. Pretreatment with TCV-309 (10microM, platelet-activating factor (PAF) receptor antagonist) or ONO-1078 (100microM, human cysteinyl-leukotriene (Cys-LT) receptor 1 antagonist), but not indomethacin (10microM, cyclooxygenase inhibitor), ketanserin (10microM, serotonin receptor antagonist), or diphenhydramine (100microM, histamine H1 antagonist), significantly attenuated this anaphylactic hepatic venoconstriction. Anaphylaxis-induced increases in Rpre and Rpost were significantly inhibited by TCV-309 (by 48%) and ONO-1078 (by 36%), respectively. Combined TCV-309 and ONO-1078 pretreatment exerted additive inhibitory effects on anaphylactic hepatic venoconstriction. Anaphylactic hepatic weight gain was converted to weight loss when post-sinusoidal constriction was attenuated. It is concluded that anaphylaxis-induced pre-sinusoidal constriction is mainly caused by PAF and the post-sinusoidal constriction by Cys-LTs in guinea pig livers.

Involvement of CGRP in the inhibitory effect of rutaecarpine on vasoconstriction induced by anaphylaxis in guinea pig

Previous investigations have indicated that calcitonin gene-related peptide (CGRP), a principal transmitter in capsaicin-sensitive sensory nerves, could alleviate cardiac anaphylaxis injury. Rutaecarpine relaxes vascular smooth by stimulation of CGRP release via activation of vanilloid receptor subtype 1 (VR1). In the present study, we examined the role of capsaicin-sensitive sensory nerves in anaphylactic vessels and the effect of rutaecarpine on antigen-challenged constriction in the guinea pig isolated thoracic aorta. The aortas were challenged with 0.01 mg/ml bovine serum albumin, and the tension of aorta rings was continuously monitored. The amount of CGRP released from thoracic aortas was determined in the absence or presence of rutaecarpine. Antigen challenge caused a vasoconstrictor response concomitantly with an increase in the release of CGRP from the isolated thoracic aorta, and the vasoconstrictor responses were potentiated by CGRP8-37 (10 microM) or capsaicin (1 microM). Pretreatment with diphenhydramine (1 microM) markedly decreased antigen-challenged vasoconstriction. Acute application of capsaicin (0.03 or 0.1 microM) significantly inhibited vasoconstrictor responses. Pretreatment with rutaecarpine (10 or 30 microM) significantly increased CGRP release concomitantly with decrease in antigen-challenged vasoconstriction, which was abolished by CGRP8-37 (10 microM) or capsazepine (10 microM). The present results suggest that an increase in the release of CGRP during vascular anaphylaxis may be a beneficial compensatory response, and that rutaecarpine inhibits antigen-challenged vasoconstriction, which is related to stimulation of endogenous CGRP release via activation of VR1.

Cyclosporine-induced coronary artery constriction--dissociation between thromboxane release and coronary vasospasm

Cyclosporine influences vascular tone, including that of coronary arteries. But its effect on myocardial prostanoid release, which may contribute to a drug-induced coronary and/or myocardial dysfunction, remains unknown. We used the isolated perfused rat heart to study the effect of cyclosporine on both the mechanical function parameters and myocardial prostanoid release into the effluent by ELISA. Cyclosporine (5 microM) induced an increase of perfusion pressure from 40 +/- 3 to 73 +/- 4 mm Hg within 60 minutes (p < 0.001), reflecting an increase of coronary tone. Cyclosporine did not affect heart rate but contractility (+dp/dtmax) tended to decrease, although not significantly. The drug's effect on coronary tone was rapidly reversible upon withdrawal. Cyclosporine perfusion resulted in an increase of thromboxane B2 liberation from 236 +/- 150 to 1321 +/- 354 pg/ml effluent (p < 0.001), whereas the 6-keto-prostaglandin F1 alpha release was unaffected. The vehicle cremophor did not change any of these parameters. Neither inhibition of myocardial prostanoid formation with acetylsalicylic acid nor thromboxane receptor blockade prevented the cyclosporine-induced increase of perfusion pressure. However, perfusion with nitroglycerin or the voltage-sensitive calcium channel antagonist nifedipine in addition to cyclosporine were able to prevent the increase of perfusion pressure. This is the first time it has been demonstrated that cyclosporine induces an acute release of the prostanoid thromboxane within the myocardium. Despite the resulting imbalance in favor of the vasoconstrictive prostanoid, a dependency of the cyclosporine-induced increase of coronary tone on this imbalance was excluded. Conversely, nitric oxide donation or calcium channel blockade were able to prevent the negative effect of the drug on coronary tone, supporting the concept of endothelium-dependent and/or myogenic mechanism of cyclosporine toxicity on the coronary vascular bed.