Anaphylactic reactions affecting the human heart

Histamine receptors in heart failure

The biogenic amine, histamine, is found predominantly in mast cells, as well as specific histaminergic neurons. Histamine exerts its many and varied actions via four G-protein-coupled receptors numbered one through four. Histamine has multiple effects on cardiac physiology, mainly via the histamine 1 and 2 receptors, which on a simplified level have opposing effects on heart rate, force of contraction, and coronary vasculature function. In heart failure, the actions of the histamine receptors are complex, the histamine 1 receptor appears to have detrimental actions predominantly in the coronary vasculature, while the histamine 2 receptor mediates adverse effects on cardiac remodeling via actions on cardiomyocytes, fibroblasts, and even endothelial cells. Conversely, there is growing evidence that the histamine 3 receptor exerts protective actions when activated. Little is known about the histamine 4 receptor in heart failure. Targeting histamine receptors as a therapeutic approach for heart failure is an important area of investigation given the over-the-counter access to many compounds targeting these receptors, and thus the relatively straight forward possibility of drug repurposing. In this review, we briefly describe histamine receptor signaling and the actions of each histamine receptor in normal cardiac physiology, before describing in more detail the known role of each histamine receptor in adverse cardiac remodeling and heart failure. This includes information from both clinical studies and experimental animal models. It is the goal of this review article to bring more focus to the possibility of targeting histamine receptors as therapy for heart failure.

Substance P-mediated cardiac mast cell activation: An in vitro study

The neuropeptide substance P can induce degranulation of cardiac mast cells at high concentrations. Herein, we seek to further understand substance P activation of cardiac mast cells in the context of other neuropeptides as well as modulation by non-neuropeptides. This is important given the increasingly recognized role of both cardiac mast cells and substance P in adverse cardiac remodeling. To address this, we isolated cardiac mast cells and compared their response to substance P as well as other members from the tachykinin family of peptides, including neurokinin A and hemokinin-1. We also tested the ability of other factors to manipulate the cardiac mast cell response to substance P. We found that while neurokinin A did not induce cardiac mast cell degranulation, both substance P and hemokinin-1 induced a concentration-dependent release of histamine; the maximal response to hemokinin-1 was greater than to substance P. Neurokinin-1 receptor blockade prevented substance P-induced histamine release, while only partially attenuating hemokinin-1-induced histamine release. The antioxidant N-acetylcysteine attenuated histamine release in response to hemokinin-1 and had no effect on substance P-induced histamine release. Selective PPAR-γ agonists attenuated histamine release in response to substance P. These data indicate that substance P activates cardiac mast cells via the neurokinin-1 receptor, and that the activation response is different to other tachykinins. That the response to substance P is receptor mediated and can be modulated by activation of other receptors (PPAR-γ), argues that substance P activation of cardiac mast cells has potential biological significance.

Prise en charge d'une réaction anaphylactique en extrahospitalier et aux urgences: revue de la littérature

Care and therapy of patients experiencing an anaphylactic reaction should be known by the physicians working in the emergency medical unit or in pre-hospital care. The epidemiology of these reactions varies according to the countries. The main aetiologies are due to food, hymenoptera or drugs. The clinical scale proposed by Ring and Messmer aims to classify the reactions in 4 grades according to their severity and is useful to stratify therapy. According to the grade of the reaction, the drug of choice for the treatment of anaphylaxis is epinephrine associated to vascular expansion. Anaphylaxis during pregnancy is described. Patients who experienced an immediate hypersensitivity reaction should undergo an allergological investigation to prove the immune mechanism and to identify the culprit allergen. Reporting to the Drug Safety Monitoring Authorities when a drug is implicated should not be forgotten.

Effects of histamine H1-receptor blockade on respiratory and cardiac manifestation of systemic anaphylaxis

In vivo anaphylaxis is associated with respiratory distress and cardiovascular failure. The present investigation was designed to further characterize respiratory and cardiac anaphylactic events. In guinea pigs, sensitization was produced by subcutaneous application of ovalbumin together with Freund's adjuvant. Fourteen days after sensitization, the effects of an intravenous infusion of ovalbumin were tested in the anesthetized artificially ventilated guinea pigs. The renewed application of the antigen induced an initial increase of left ventricular pressure which was followed by a rapid decrease 5 min after antigenic challenge. Enddiastolic left ventricular pressure increased within 3 min, thus indicating left ventricular pump failure. In the same time range, ECG recordings uniformly showed signs of acute myocardial ischemia. In addition, heart rate steadily decreased. All animals died within 15 min. Simultaneously with cardiac anaphylactic malfunction, severe arterial hypoxia and carbon dioxide retention occurred, revealing respiratory distress. Histamine is known as a potent bronchoconstrictor via histamine H1-receptor stimulation. Administration of H1-receptor antagonists to improve respiration may therefore provide further information on the contribution of pulmonary malfunction to anaphylactic cardiovascular shock. Therefore, additional experiments were performed with sensitized guinea pigs pretreated with the histamine H1-receptor blocker mepyramine. In these experiments the antigenic challenge induced a dissociation of cardiac and respiratory manifestation of anaphylaxis. Despite inhibition of hypoxia and carbon dioxide retention, left ventricular pump failure and occurrence of myocardial ischemia were delayed but not suppressed. It is concluded that histamine is an important mediator of anaphylactic respiratory distress. However, vasoactive anaphylactic mediators other than histamine are primarily involved in anaphylactic cardiac malfunction occurring during the later phase of systemic anaphylaxis.

Fatal anaphylactic reaction to suxamethonium: new screening test suggests possible prevention

A 40-year-old woman suffered cardiovascular collapse, cardiac ischaemia and arrest during induction of anaesthesia. Severe cerebral ischaemic damage was sustained during this episode and the patient died 4 days later. This fatal reaction was shown to be anaphylactic in origin; the causative agent was suxamethonium. High levels of IgE antibodies specific to the quaternary ammonium group (two of which are present in suxamethonium) were detected by the radioallergosorbent test. Results of the leucocyte histamine release test were less clear, partly as a result of steroid treatment. The two most relevant points were the absence of a history of previous anaesthesia, and involvement of the heart as the principal target of the reaction. This unfortunate and extreme case indicates the necessity for allergy testing (screening) before anaesthesia, and the need for organisation and funding of this procedure, if these fatal or near-fatal reactions are to be prevented. It is a timely reminder that action should be taken, since neuromuscular blockers have been confirmed as the most common culprits, and that specific tests for IgE antibodies are now available against haptenic groups generally common to all neuromuscular blockers.