Cetirizine inhibits bradykinin-induced cutaneous wheal and flare in atopic and healthy subjects

Antipruritic effect of cold stimulation at the Quchi acupoint (LI11) in mice

Background

Acupuncture and moxibustion are used to treat pruritus and atopic dermatitis. However, whether cold stimulation (defined as that the temperature conducted under skin temperature) of acupoints affects itching in experimental murine models remains unclear.

Methods

The present study was designed to determine the therapeutic effects of different thermal stimulations at the Quchi acupoint (LI11) in a murine model in which scratching behaviour was elicited by subcutaneous injection with a pruritogenic agent (compound 48/80). Male ICR mice were divided into several groups as follows: control (saline), those receiving compound 48/80 and compound 48/80 with various thermal stimulations (5°C–45°C) at LI11 (n = 6 per group). The scratch response of each animal to these stimulations was recorded for 30 min. The antipruritic effect of the acupoint was further evaluated in LI11 and sham (non-acupoint) groups (n = 6 per group).

Results

Treatment with lower temperature (20°C) at the LI11 acupoint significantly attenuated compound 48/80-induced scratching; however, this antipruritic effect was not observed with stimulation at the sham point. The expression of c-fos in the neuron of the cervical spine induced by compound 48/80 was suppressed by cold stimulation at LI11. The antipruritic effect of cold stimulation was blocked by ruthium red (RR), a non-selective transient receptor potential (TRP) channel blocker, suggesting that TRP channels may play an important role in the antipruritic effect of cold stimulation at LI11 in mice.

Conclusions

This study demonstrated that cold stimulation at LI11 attenuated compound 48/80-induced scratching behaviour in mice, possibly by a TRP-related pathway.

Characterisation and mechanisms of bradykinin-evoked pain in man using iontophoresis

Bradykinin (BK) is an inflammatory mediator that can evoke oedema and vasodilatation, and is a potent algogen signalling via the B1 and B2 G-protein coupled receptors. In naïve skin, BK is effective via constitutively expressed B2 receptors (B2R), while B1 receptors (B1R) are purported to be upregulated by inflammation. The aim of this investigation was to optimise BK delivery to investigate the algesic effects of BK and how these are modulated by inflammation. BK iontophoresis evoked dose- and temperature-dependent pain and neurogenic erythema, as well as thermal and mechanical hyperalgesia (P < 0.001 vs saline control). To differentiate the direct effects of BK from indirect effects mediated by histamine released from mast cells (MCs), skin was pretreated with compound 4880 to degranulate the MCs prior to BK challenge. The early phase of BK-evoked pain was reduced in degranulated skin (P < 0.001), while thermal and mechanical sensitisation, wheal, and flare were still evident. In contrast to BK, the B1R selective agonist des-Arg9-BK failed to induce pain or sensitise naïve skin. However, following skin inflammation induced by ultraviolet B irradiation, this compound produced a robust pain response. We have optimised a versatile experimental model by which BK and its analogues can be administered to human skin. We have found that there is an early phase of BK-induced pain which partly depends on the release of inflammatory mediators by MCs; however, subsequent hyperalgesia is not dependent on MC degranulation. In naïve skin, B2R signaling predominates, however, cutaneous inflammation results in enhanced B1R responses.

The mast cell activator compound 48/80 is safe and effective when used as an adjuvant for intradermal immunization with Bacillus anthracis protective antigen

We evaluated the safety and efficacy of the mast cell activator compound 48/80 (C48/80) when used as an adjuvant delivered intradermally (ID) with recombinant anthrax protective antigen (rPA) in comparison with two well-known adjuvants. Mice were vaccinated in the ear pinnae with rPA or rPA+C48/80, CpG oligodeoxynucleotides (CpG), or cholera toxin (CT). All adjuvants induced similar increases in serum anti-rPA IgG and lethal toxin neutralizing antibodies. C48/80 induced a balanced cytokine production (Th1/Th2/Th17) by antigen-restimulated splenocytes, minimal injection site inflammation, and no antigen-specific IgE. Histological analysis demonstrated that vaccination with C48/80 reduced the number of resident mast cells and induced an injection site neutrophil influx within 24h. Our data demonstrate that C48/80 is a safe and effective adjuvant, when used by the intradermal route, to induce protective antibody and balanced Th1/Th2/Th17 responses.

International union of pharmacology. XLV. Classification of the kinin receptor family: from molecular mechanisms to pathophysiological consequences

Kinins are proinflammatory peptides that mediate numerous vascular and pain responses to tissue injury. Two pharmacologically distinct kinin receptor subtypes have been identified and characterized for these peptides, which are named B1 and B2 and belong to the rhodopsin family of G protein-coupled receptors. The B2 receptor mediates the action of bradykinin (BK) and lysyl-bradykinin (Lys-BK), the first set of bioactive kinins formed in response to injury from kininogen precursors through the actions of plasma and tissue kallikreins, whereas the B(1) receptor mediates the action of des-Arg9-BK and Lys-des-Arg9-BK, the second set of bioactive kinins formed through the actions of carboxypeptidases on BK and Lys-BK, respectively. The B2 receptor is ubiquitous and constitutively expressed, whereas the B1 receptor is expressed at a very low level in healthy tissues but induced following injury by various proinflammatory cytokines such as interleukin-1beta. Both receptors act through G alpha(q) to stimulate phospholipase C beta followed by phosphoinositide hydrolysis and intracellular free Ca2+ mobilization and through G alpha(i) to inhibit adenylate cyclase and stimulate the mitogen-activated protein kinase pathways. The use of mice lacking each receptor gene and various specific peptidic and nonpeptidic antagonists have implicated both B1 and B2 receptors as potential therapeutic targets in several pathophysiological events related to inflammation such as pain, sepsis, allergic asthma, rhinitis, and edema, as well as diabetes and cancer. This review is a comprehensive presentation of our current understanding of these receptors in terms of molecular and cell biology, physiology, pharmacology, and involvement in human disease and drug development.

Inhibitory effects of oral prednisolone and fexofenadine on skin responses by prick tests with histamine and compound 48/80

The prick test is a useful skin test for diagnosing immediate hypersensitivity response. Sometimes it is necessary to perform prick tests on patients who have already received antihistamines or corticosteroids. It is, however, occasionally uncertain whether the results of prick tests are reliable. In this study, the inhibitory effects of prednisolone (10 mg/day) and fexofenadine (120 mg/day) on the response to prick tests induced with histamine and compound 48/80 were examined. During a 7-day-continual drug administration, prick tests were performed 8 h after drug administration. The inhibitory effects of fexofenadine on both the histamine- and compound 48/80-induced skin responses were exhibited on the 1st day and persisted from 24 to 36 h after the final administration. The histamine-induced wheal responses were not inhibited by prednisolone, while the compound 48/80-induced flare and wheal responses were significantly inhibited on the 5th day of drug administration. These responses returned to the baseline level 24 h after the last drug administration. Thus, the results of skin tests performed during administration of antihistamines and corticosteroids should be carefully interpreted.

H1-antihistamines: inverse agonism, anti-inflammatory actions and cardiac effects

This review addresses novel concepts of histamine H1-receptor function and attempts to relate them to the anti-inflammatory effects of H1-antihistamines. Furthermore, the molecular mechanisms underlying the cardiotoxic effects of H1-antihistamines are discussed. H1-receptors are G-protein-coupled-receptors (GPCRs), the inactive and active conformations of which coexist in equilibrium. The degree receptor activation in the absence of histamine is its 'constitutive activity'. In this two-state model, histamine acts as an agonist by combining with and stabilizing the activated conformation of the H1-receptor to shift the equilibrium towards the activated state. Drugs classified previously as antagonists act as either inverse agonists or neutral antagonists. Inverse agonists combine with and stabilize the inactive conformation of the receptor to shift the equilibrium towards the inactive state. Thus, they may down-regulate constitutive receptor activity, even in the absence of histamine. Neutral antagonists combine equally with both conformations of the receptor, do not affect basal receptor activity but do interfere with agonist binding. All H1-antihistamines examined to date are inverse agonists. As the term 'H1-receptor antagonists' is obviously erroneous, we suggest that it be replaced by 'H1-antihistamines'. The observations that H1-receptors modulate NF-kappaB activation and that there are complex interactions between GPCRs, has allowed us to postulate receptor dependent-mechanisms for some anti-inflammatory effects of H1-antihistamines, e.g. inhibition of ICAM-1 expression and the effects of bradykinin. Finally, the finding that blockade of HERG1 K+ channels is the mechanism by which some H1-antihistamines may cause cardiac arrhythmias has allowed the development of preclinical tests to predict such activity.