Novel function of histamine signaling in hyperlipidemia‐induced atherosclerosis: Histamine H1 receptors protect and H2 receptors accelerate atherosclerosis

Histamine is not only essential for acute inflammatory reactions, but it also participates in a chronic inflammatory disorder. We generated apolipoprotein E (apoE) and histamine receptors (HHRs), including the major H1 and H2 receptors (HH1R, HH2R) double knockout mice (DKO) to clarify the role of HHRs in hyperlipidemia‐induced atherosclerosis, in which apoE‐KO and DKO mice were fed a high cholesterol diet. We found that pronounced hyperlipidemia‐induced atherosclerotic progression occurred in HH1R/apoE‐DKO mice, but in HH2R/apoE‐DKO mice less atherosclerosis, despite pro‐atherogenic serum cholesterol levels compared with apoE‐KO mice. Furthermore, the increased expressions of scavenger receptors (SRs), such as SR‐A, CD36 and lectin‐like oxidized low‐density lipoprotein receptor 1 (LOX‐1), nuclear factor‐kappa B (NFκB), monocyte chemoattractant protein (MCP‐1), matrix metalloproteinases (MMPs) or liver X receptor (LXR)‐related inflammatory signaling factors, were consistent with the pro‐atherogenic phenotype of HH2R/apoE‐DKO mice. We hypothesize that histamine/HH1R and HH2R signaling has conflicting innate functions, inflammatory/atherogenic and anti‐inflammatory/anti‐atherogenic actions, and that there are innate links between histamine signaling and hyperlipidemia‐induced atherosclerosis, independently of serum cholesterol metabolism. Specific histamine signaling blockers, in particular, HH2R blockers, are a possible novel therapeutic target for hyperlipidemia‐induced atherosclerosis.     

Idiopathic anaphylaxis: long-term follow-up, cost, and outlook

To determine the efficacy of oral corticosteroids, antihistamines, and sympathomimetics in treating patients with idiopathic anaphylaxis, the charts of 225 patients diagnosed with idiopathic anaphylaxis from 1971 to 1990 treated at a single center were reviewed. Sixty-one patients (34 females and 27 males) were available for long-term follow-up. Ages ranged from 10 to 68 years with an average of 39 years. Patients with frequent episodes were treated with a protocol of oral corticosteroids, antihistamines, and sympathomimetics. Patients with infrequent episodes were treated for acute episodes only. The number of emergency room visits, hospitalizations, intensive care unit admissions, and length of time in remission were recorded. Sixty-five percent of patients with infrequent episodes and 91% of patients with frequent episodes of idiopathic anaphylaxis went into remission. Significant decreases in emergency room visits occurred for the idiopathic anaphylaxis-generalized-frequent group ( P< 0.016). the idiopathic-anaphylaxis-generalized-infrequent group ( P< 0.0001), and the idiopathic anaphylaxis-angioedema-infrequent group ( P <0.039). Significant decreases in the number of hospitalizations ( P < 0.022) and intensive care unit admissions ( P < 0.009) occurred for the idiopathic anaphylaxis-generalized-infrequent and frequent groups, respectively. Overall, an estimated 184740 was saved with the treatment program, for 546 patient-years. Idiopathic anaphylaxis can be controlled and remission induced in most patients. An estimated 11 million per year can be saved for patients in the USA on the basis of the estimated prevalence in this country.     

Pathophysiological mechanisms of exercise‐induced anaphylaxis: an EAACI position statement

This document is the result of a consensus on the mechanisms of exercise‐induced anaphylaxis (EIAn), an unpredictable and potentially fatal syndrome. A multidisciplinary panel of experts including exercise physiologists, allergists, lung physicians, paediatricians and a biostatistician reached the given consensus. Exercise‐induced anaphylaxis (EIAn) describes a rare and potentially fatal syndrome in which anaphylaxis occurs in conjunction with exercise. The pathophysiological mechanisms underlying EIAn have not yet been elucidated although a number of hypotheses have been proposed. This review evaluates the validity of each of the popular theories in relation to exercise physiology and immunology. On the basis of this evidence, it is concluded that proposed mechanisms lack validity, and it is recommended that a global research network is developed with a common approach to the diagnosis and treatment of EIAn in order to gain sufficient power for scientific evaluation.     

A double‐blind, single‐dose, crossover comparison of cetirizine, ebastine, epinastine, fexofenadine, terfenadine, and loratadine versus placebo: suppression of histamine‐induced wheal and flare response for 24 h in healthy male subjects

BACKGROUND: New H1-antagonists have become available, but there has been no comparison of their potency for inhibiting histamine in the skin. METHODS: Cetirizine 10 mg, ebastine 10 mg, epinastine 20 mg, fexofenadine 60 mg, terfenadine 60 mg, loratadine 10 mg, or placebo was given to 14 healthy male volunteers in a double-blind, crossover randomized manner. Inhibition of the wheal and flare response to epicutaneous histamine phosphate (100 mg/ml) challenge was measured at 0, 0.5, 1, 2, 4, 6, 8, 10, 12, and 24 h after doses. RESULTS: Epinastine inhibited the wheal and flare after 30 min. Cetirizine commenced acting at 1 h and was superior to other treatments. Ebastine was no better than placebo until 4 h, but was efficacious thereafter until 24 h. Terfenadine induced potent inhibition after 1 h and was superior to its metabolite fexofenadine. Loratadine was the least potent inhibitor. Inhibition of the flare response paralleled the patterns seen for wheals. The rank order for area under the curve (0-24 h) was cetirizine, epinastine, terfenadine, ebastine, fexofenadine, loratadine, and placebo. CONCLUSIONS: The inhibition of histamine effects in the skin may be useful in predicting the clinical utility of newly introduced antihistamines in treating allergic disorders.     

Drug-associated anaphylaxis: 20 years of reporting in the Netherlands (1974–1994) and review of the literature

Background Since 1963, the Drug Safety Unit of the Dutch Inspectorate for Health Care (DSU) holds a voluntary reporting system. Objective To analyse all reports received in the years 1974 to 1994, registered as anaphylaxis or as a diagnosis that could contain cases of anaphylaxis. Methods All reports were classified as probable or possible anaphylaxis according to previously described criteria and the causal relationship between exposure and anaphylaxis was assessed. Results Nine hundred and ninety-two reports possibly concerning anaphylaxis were received between 1974 and 1994. Fifty-six were unclassifiable. The remaining 936 reports concerned 326 men and 610 women. Three hundred and forty-five reports were classified as anaphylaxis probable, 485 as anaphylaxis possible, and 106 as anaphylaxis unlikely by previously specified criteria. Drugs frequently associated with anaphylaxis (causal relationship certain or probable) were: glafenine (326 reports classified as anaphylaxis probable or possible), combination preparations with (propy)phenazone or propyphenazone/phenacetine (39), diclofenac (30), dextran (20), ibuprofen (14), floctafenine (12), allergen extracts (12), sulfamethoxazole with trimethoprim (12), and trimethoprim (11). There is probably substantial under-reporting as well as reporting bias in these data. Furthermore, many reports were classified as possible and not as probable anaphylaxis because the temporal relationship was unknown or not reported. Conclusion Drugs that caused anaphylaxis most frequently were glafenine, NSAID and certain antibiotics. Data from a voluntary reporting system such as the DSU are valuable as an early warning system for drugs that may induce anaphylactic reactions.