Characteristics of histamine H4 receptor agonist-induced allergic conjunctivitis model in Guinea pigs.

Histamine is strongly associated with the onset of allergic conjunctivitis. The most recent cloned histamine H4 receptor antagonist is highly expected as a new therapeutic drug candidate. As a model for a therapeutic drug targeting the histamine H4 receptor, a mouse model in which conjunctivitis symptoms are induced by instilling 4-methylhistamine, a histamine H4 receptor agonist, has been reported. However, the affinity of the H4 receptor for histamine varies in species, and it is known that the histamine binding affinity for the guinea pig H4 receptor is closer to that for human receptor than mice receptor. In this paper, we investigated a possibility that a guinea pig model would become a drug efficacy evaluation model with higher evaluation accuracy than the mouse model. As a result, hyperemia was observed in the conjunctivae and iris of guinea pigs after instillation of 4-methylhistamine and specifically suppressed by the histamine H4 receptor antagonist. Unlikely to the previously reported mouse model, however, none of edema, increased vascular permeability or scratching behavior was observed, suggesting that there may be differences between mice and guinea pigs not only in the binding affinity of histamine to the H4 receptor but also in the biological reaction to 4-methylhistamine. Although the symptoms of allergic conjunctivitis do not appear comprehensively in the guinea pig model, results of this study indicated a possibility that this model can be used as a simple screening model in the early stages of drug development.

Involvement of histamine 4 receptor in the pathogenesis and progression of rheumatoid arthritis.

Rheumatoid arthritis (RA) is one of the major autoimmune diseases with a global prevalence. Despite significant research into this disease, no drugs with acceptable safety profiles are yet available for its treatment. We investigated the possible anti-arthritic effects of the 4-methylhistamine (4-MeH) histamine 4 receptor (H4R) agonist and the JNJ77777120 (JNJ) H4R antagonist to explore the role of H4R in a mouse model of collagen antibody-induced arthritis (CAIA). Arthritis was induced via intravenous (tail vein) injection of Balb/c mice with a 5-clone cocktail of mAbs against collagen type II, followed by LPS, and the effects of treatment with 4-MeH or JNJ (30 mg kg(-1), i.p, twice daily) for 7 days (prophylactic or therapeutic regimens) were assessed. The results revealed increased paw edema, arthritic scores, joint histological inflammatory damage and matrix metalloproteinase-3 levels and high levels of Th1 pro-inflammatory cytokine mRNA and serum proteins in CAIA mice or following H4R activation via 4-MeH. Additionally, 4-MeH efficiently increased expression levels of NF-κB p65. JNJ-treated mice showed a substantial reduction in all the previously mentioned effects, with a similar trend being observed under prophylactic and therapeutic treatment regimens. The results of the present work indicate that JNJ exhibits significant anti-inflammatory and anti-arthritic activities, demonstrating the clear involvement of H4R antagonism in the pathogenesis and progression of RA.

Nalpha-methyl histamine safety and efficacy in migraine prophylaxis: phase III study.

BACKGROUND: The histamine catabolite, Nalpha-methylhistamine, possesses a selective affinity for H3 receptors. For this reason, we considered evaluating the efficacy of this histaminergic H3 agonist in migraine prophylactic treatment. OBJECTIVE: To study the therapeutic potential of the subcutaneous administration of Nalpha-methylhistamine in migraine prophylaxis, in a Phase III clinical pharmacological study. METHODS: Using a controlled double-blind, placebo controlled clinical trial for 12 weeks, 60 patients with migraine, who fit the criteria established by the International Headache Society, were selected. The efficacy of subcutaneous administration of Nalpha-methylhistamine 1 to 3 ng twice a week against placebo was studied, evaluating the outcome of headache intensity, frequency, duration, and analgesic intake. RESULTS: Comparison between the groups treated with placebo (n=30) and Nalpha-methylhistamine (n=30), on data collected for the 4th, 8th and 12th weeks of treatment, revealed that Nalpha-methylhistamine exerted a significant (p<0.0001) reduction (compared to placebo) in intensity, frequency, and duration of migraine attacks, as well as on the use of analgesic intake. No significant (p>0.05) adverse experiences or side effects developed in either group. CONCLUSIONS: The present study provides evidence of the efficacy of Nalpha-methylhistamine, given subcutaneously at doses of 1 to 3 ng twice a week, offering a new therapeutic alternative and laying the clinical and pharmacological groundwork for the use of histaminergic H3-agonists in migraine prophylaxis, which may specifically inhibit the neurogenic edema response involved in migraine pathophysiology.

Mastocytosis and adverse reactions to biogenic amines and histamine-releasing foods: what is the evidence?

BACKGROUND: It has been suggested that normal concentrations of biogenic amines and 'histamine-releasing foods' may exacerbate symptoms in mastocytosis. The purpose of this study was to look for scientific evidence in the literature on diets restricted in biogenic amines and histamine-releasing foods in the treatment of mastocytosis. METHODS: Medline (1966 to 2004), Cinahl (1982 to 2004) and the Cochraine Library were searched for double-blind placebo-controlled food challenge (DBPCFC) studies with biogenic amines and/or histamine-releasing foods in mastocytosis. RESULTS: No studies employing DBPCFC with dietary biogenic amines or histamine-releasing foods in mastocytosis were found. Only a few in vitro studies in other diseases, animal studies and studies in humans in which histamine-releasing agents were incubated directly with duodenal tissues were found. One case was reported of severe adverse reactions to alcohol in mastocytosis, objectified by an open challenge. CONCLUSION: Despite the widespread belief that biogenic amines and histamine-releasing foods may cause allergy-like, non-IgE-mediated symptoms in certain patients, the role of diets restricted in biogenic amines and histamine-releasing foods in the treatment of mastosytosis remains hypothetical but worthy of further investigation. There is some evidence for adverse reactions to alcohol in mastocytosis.

Nalpha-methylhistamine safety and efficacy in migraine prophylaxis: phase I and phase II studies.

OBJECTIVE: To study the therapeutic potential of the subcutaneous administration of Nalpha-methylhistamine in migraine prophylaxis. BACKGROUND: The histamine catabolite, Nalpha-methylhistamine, possesses a selective affinity for H3 receptors. We consequently considered it viable to conduct a clinical pharmacological study to evaluate the safety and efficacy of this histaminergic H3 agonist in migraine prophylactic treatment, which specifically may inhibit the neurogenic edema response involved in migraine pathophysiology. METHODS: Phase I.-In a clinical trial of 30 healthy volunteers, the effects of the subcutaneous administration of Nalpha-methylhistamine and placebo were studied to assess undesirable symptomatic effects. Phase II.-In a clinical open study, we evaluated the efficacy of Nalpha-methylhistamine in reducing headache intensity, frequency, and duration; and in decreasing analgesic intake in 18 patients with migraine. RESULTS: Phase I.-None of the variables studied showed significant differences (P>.05), and no secondary effects were observed at doses below 10 ng. Phase II.-Nalpha-methylhistamine, at doses of 1 to 3 ng, significantly reduced (P<.0001) the frequency, intensity, and duration of migraine attacks, as well as the need for rescue analgesics. However, at doses greater than 3 ng, patients experienced intense headache. CONCLUSIONS: The present study provides evidence of the safety and efficacy of Nalpha-methylhistamine applied subcutaneously at doses of 1 to 3 ng twice a week.

Sensory responses of human skin to synthetic histamine analogues and histamine.

The potential for itch production in human skin of the synthetic analogues of histamine, 2-methyl histamine (an H1-receptor agonist) and 4-methyl histamine and dimaprit (H2-receptor agonists) has been studied in vivo and compared with histamine. Itch thresholds for 2-methyl histamine were consistently much higher than for histamine (P < 0.001). The H1-receptor antagonist chlorpheniramine raised the itch thresholds to 2-methyl histamine and histamine significantly (P < 0.001). Pruritus was not obtained with either 4-methyl histamine or dimaprit. No evidence of synergism between 2-methyl histamine and either 4-methyl histamine or dimaprit was found. The results suggest that histamine-induced pruritus is mediated in part through the H1-receptor and in part via an additional (but probably non-H2) mechanism.