Histamine-induced vasodilations mediated by H1- and H2-receptors in isolated rat common carotid arteries

Histamine H2 receptor antagonist exposure was related to decreased all-cause mortality in critical ill patients with heart failure: a cohort study

BACKGROUND

Previous studies reported that histamine H2 receptor antagonists (H2RAs) had cardioprotective effects. However, the effect of H2RAs on mortality of critical ill patients with heart failure (HF) remains unclear. The aim of this study was to clarify the association between H2RAs and all-cause mortality of critical ill patients with HF based on Medical Information Mart for Intensive Care III database (MIMIC-III).

METHODS

Propensity score matching (PSM) was applied to account for the baseline differences between two groups that exposed to H2RAs or not. The study primary outcome was all-cause mortality. Kaplan-Meier curves and multivariable Cox regression models were employed to estimate the effects of H2RAs on mortality of critical ill patients with HF.

RESULTS

A total of 10 387 patients were included, involving 4440 H2RAs users and 5947 non-H2RAs users. After matching, 3130 pairs of patients were matched between H2RAs users and non-H2RAs users. The results showed significant association between H2RAs exposure and decreased 30-day, 90-day and 1-year mortality in both univariate analyses and multivariate analyses (HR = 0.73, 95%CI: 0.65-0.83 for 30-day; HR = 0.80, 95%CI: 0.72-0.89 for 90-day; and HR = 0.83, 95%CI: 0.76-0.90 for 1-year mortality, respectively) by Cox regression after PSM. Furthermore, stratified analyses revealed that the 30-day, 90-day and 1-year mortality of ranitidine users were significantly lower than those of famotidine users, respectively.

CONCLUSIONS

H2RAs exposure was associated with lower mortality in critical ill patients with HF. Furthermore, ranitidine might be superior to famotidine in reducing mortality of critical ill patients with HF.

Histidine decarboxylase but not histamine receptor 1 or 2 deficiency protects from K/BxN serum-induced arthritis

Serum transfer from arthritic K/BxN mice into naive animals results in arthritis. Mast cells have been shown to be essential since mice lacking these cell type do not develop arthritis upon serum injection. Mast cell function depends on the release of granules filled with mediators such as histamine. Mice deficient in histidine decarboxylase (HDC(-/-)) that do not produce histamine and mice deficient for histamine receptor 1 (H1R(-/-)) or histamine receptor 2 (H2R(-/-)) were injected with arthritogenic sera from the K/BxN mice, and the progression of arthritis was observed through the next 2 weeks. HDC(-/-) mice that are histamine free developed a milder form of arthritis in comparison with the wild-type controls. In both receptor-deficient mice as well as in wild-type controls, the onset and severity of clinical arthritis and ankle thickening occurred during day 1 to 3. These results indicate that histamine is required but not indispensable for the development of serum-induced arthritis and histamine receptors other than those studied here may be involved.

Potentiation by neuropeptide Y of histamine H1 receptor-mediated contraction in rat blood vessels

Histamine-induced contraction and its potentiation by neuropeptide Y were investigated in rat blood vessels. Rat arteries and veins constricted with single concentrations of histamine dose-dependently (0.1-100 microM). This histamine-induced contraction immediately desensitized. Histamine H1 receptor antagonists, 1 microM mepyramine and 1 microM diphenhydramine, abolished this transient contraction completely, whereas cimetidine, phentolamine, reserpine and tetrodotoxin failed to inhibit the contraction. Histamine H1 receptor mRNA level by reverse transcription-polymerase chain reaction was quite parallel to histamine H1 receptor-mediated contraction, indicating that the contraction is mediated through histamine H1 receptors in the smooth muscle. Neuropeptide Y (10 nM in arteries and 3 nM in veins, respectively) significantly potentiated histamine H1 receptor-mediated contraction via neuropeptide Y1 receptors in most of rat blood vessels. Since the phospholipase C inhibitors, neomycin (1 mM) and 2-nitro-4-carboxyphenyl-N, N-diphenylcarbamate (NCDC, 10 microM), respectively, specifically abolished the potentiation, the potentiation by neuropeptide Y may depend on activation of phospholipase C.

Functional analysis of histamine receptor subtypes involved in endothelium-mediated relaxation of the human uterine artery

1. This work was designed to introduce human uterine arteries as a new model for cardiovascular research. Advantages of this model include considerable availability of tissue because of the appearance of uterus myomatosus in post-menopausal women who undergo surgery and the chance to work on dysfunctional and healthy vessels. 2. Histamine evoked relaxation of the uterine artery that was prevented by removal of the endothelium or by the presence of N(G)-nitro-L-arginine. 3. Receptor antagonists for histamine H(1) (mepyramine) and H(2) (ranitidine) receptors increased the EC(50) of histamine by 112- and 67-fold, respectively. 4. Remarkably, isolated uterine arteries could be stored in incubators for 5 days without any change in contractility to phenylephrine and endothelium-dependent relaxation to acetylcholine and histamine. 5. Endothelial cells could be isolated and cultured in high purity, as demonstrated by histochemical staining of factor VIII, low CD45-RO for macrophages and no smooth muscle alpha-actin. In addition, cultured human uterine artery endothelial cells could be used for single cell Ca(2+) measurements. 6. In agreement with our findings in the intact vessel, histamine-initiated elevation of the intracellular free Ca(2+) concentration was reduced in the presence of mepyramine and ranitidine by 59 and 55%, respectively. 7. These data indicate that, in the human uterine artery, H(1) and H(2) receptors are involved in histamine-induced endothelium-dependent relaxation that is mediated by nitric oxide. 8. In addition, this vessel can be stored for possible virus-mediated gene expression for 5 days without any loss of reagibility. 9. Finally, endothelial cells can be isolated and cultured from the human uterine artery and maintain their reactivity to histamine in culture.

Migraine and function of the immune system: a meta-analysis of clinical literature published between 1966 and 1999

Mechanisms underlying migraine precipitation are largely unknown. A role of the immune system in migraine precipitation is a matter of debate because of the association of atopic disorders and migraine. Recently, it was demonstrated that migraineurs benefit from eradication of a Helicobacter pylori infection, which substantiates a possible role for (sub-clinical) infections in precipitation of migraine. Since 1966, about 45 clinical investigations have reported on alterations of immune function in migraine patients, which we present in this review. Changes of serum levels of complement and immunoglobulins, histamine, cytokines and immune cells were found in some of these studies but in most cases not corroborated by others. Migraineurs suffering from comorbid atopic disorders show elevated plasma IgE levels but not patients without a type I hypersensitivity. Histamine plasma levels are chronically elevated in migraineurs, and interictally decreased lymphocyte phagocytotic function and increased plasma tumor necrosis factor alpha (TNFalpha) levels were found, and may be related to increased infection susceptibility. The cause of this increased susceptibility is unclear but most likely is a result of chronic stress, a well-known suppressor of the immune system. Stress relief enhances immune activity and triggers a burst of circulating vasoactive compounds that function as mediators of inflammation and potential precipitators of a migraine attack in vulnerable subjects. In conclusion, in the clinical literature of the past decades, there is no clear-cut evidence of an immune dysfunction in migraineurs, but we cannot totally exclude the possibility of an altered immune function in migraineurs. Discrepancies in the literature most likely are caused by the divergent patterns of sample collection relative to the time of the attack. We propose stringent definition of sample collection times for future studies of immune function in migraine patients.

Mechanisms for histamine H1 receptor-mediated vasodilation in isolated canine lingual arteries

Histamine and selective histamine receptor subtype agonists' effects on isolated and perfused canine lingual arteries were investigated with the cannula insertion method. In preparations preconstricted with phenylephrine, histamine and a selective histamine H1 receptor agonist, 2-pyridylethylamine induced a biphasic vascular response in a dose-related manner, i.e., vasoconstriction followed by vasodilatation. The biphasic responses to histamine and 2-pyridylethylamine were inhibited by diphenhydramine, a selective histamine H1 receptor antagonist, but were not influenced by cimetidine, a selective histamine H2 receptor antagonist. Dimaprit, a selective histamine H2 receptor agonist, induced only a slight vasoconstriction which was not modified by cimetidine. Dimaprit never induced vasodilation even at a large dose. A histamine H3 receptor agonist, R-alpha-methylhistamine, did not produce any significant vascular responses. Moreover, histamine-induced vasodilation was in part inhibited by removal of the endothelium, and the vasodilation remaining was abolished by H1 blockade. Thus, it is concluded that in canine lingual arteries there are abundant histamine H1 receptors which mediate both vasoconstriction and vasodilation, and that the histamine-induced vasodilation is in part due to endothelium-dependent mechanisms.

Mechanisms of augmented vascular responses to histamine in atherosclerotic rabbit common carotid arteries

The vascular responsiveness to histamine, 2-pyridylethylamine and dimaprit was investigated in isolated and perfused atherosclerotic rabbit common carotid arteries enclosed by a hollow silastic collar. The constrictor effects of histamine were significantly enhanced in atherosclerotic arteries, although those of 2-pyridylethylamine were not changed. The dilator effects of histamine and dimaprit, which were completely inhibited after pretreatment with cimetidine, were not influenced by removal of the endothelium but significantly depressed in atherosclerotic arteries. The dose-response curves for histamine in the control group pretreated with cimetidine were shifted to the left and responses reached almost the same level as those of the atherosclerotic group. From these results, it is concluded that histamine-induced vasoconstrictions are enhanced in atherosclerotic arteries, and that the mechanism of the hyperreactivity to histamine might be an attenuation of the vasodilatations mediated via histamine H2 receptors in vascular smooth muscle.