Effects of infused histamine on asthmatic and normal subjects: comparison of skin test responses

Human mast cells and basophils-How are they similar how are they different?

Mast cells and basophils are key contributors to allergies and other inflammatory diseases since they are the most prominent source of histamine as well as numerous additional inflammatory mediators which drive inflammatory responses. However, a closer understanding of their precise roles in allergies and other pathological conditions has been marred by the considerable heterogeneity that these cells display, not only between mast cells and basophils themselves but also across different tissue locations and species. While both cell types share the ability to rapidly degranulate and release histamine following high-affinity IgE receptor cross-linking, they differ markedly in their ability to either react to other stimuli, generate inflammatory eicosanoids or release immunomodulating cytokines and chemokines. Furthermore, these cells display considerable pharmacological heterogeneity which has stifled attempts to develop more effective anti-allergic therapies. Mast cell- and basophil-specific transcriptional profiling, at rest and after activation by innate and adaptive stimuli, may help to unravel the degree to which these cells differ and facilitate a clearer understanding of their biological functions and how these could be targeted by new therapies.

Arjunolic acid: a new multifunctional therapeutic promise of alternative medicine

IMPORTANCE OF THE FIELD

In recent years, a number of studies describing the effective therapeutic strategies of medicinal plants and their active constituents in traditional medicine have been reported. Indeed, tremendous demand for the development and implementation of these plant derived biomolecules in complementary and alternative medicine is increasing and appear to be promising candidates for pharmaceutical industrial research. These new molecules, especially those from natural resources, are considered as potential therapeutic targets, because they are derived from commonly consumed foodstuff and are considered to be safe for humans.

AREAS COVERED IN THIS REVIEW

This review highlights the beneficial role of arjunolic acid, a naturally occurring chiral triterpenoid saponin, in various organ pathophysiology and the underlying mechanism of its protective action. Studies on the biochemistry and pharmacology suggest the potential use of arjunolic acid as a novel promising therapeutic strategy.

WHAT THE READERS WILL GAIN

The multifunctional therapeutic application of arjunolic acid has already been documented by its various biological functions including antioxidant, anti-fungal, anti-bacterial, anticholinesterase, antitumor, antiasthmatic, wound healing and insect growth inhibitor activities. The scientific basis behind its therapeutic application as a cardioprotective agent in traditional medicine is justified by its ability to prevent myocardial necrosis and apoptosis, platelet aggregation, coagulation and lowering of blood pressure, heart rate, as well as cholesterol levels. Its antioxidant property coupled with metal chelating property (by its two hydroxyl groups) protects different organs from metal and drug-induced organ pathophysiology. Arjunolic acid also plays a beneficial role in the pathogenesis of diabetes and its associated complications. The mechanism of cytoprotection of arjunolic acid, at least in part, results from the detoxification of reactive oxygen species (ROS) produced in the respective pathophysiology. In addition to its other biological functions, it also possesses vibrant insecticidal properties and it has the potential to be used as a structural molecular framework for the design of molecular receptors in the general area of supramolecular chemistry and nanochemistry. Esters of arjunolic acid function as organogelators which has wide application in designing thermochromic switches and sensor devices. Arjunolic acid derived crown ether is an attractive candidate for the design of molecular receptors, biomimetics and supramolecular systems capable of performing some biological functions.

HOME MESSAGE

This review would provide useful information about the recent progress of natural product research in the domain of clinical science. This review also aims to untie the multifunctional therapeutic application of arjunolic acid, a nanometer-long naturally occurring chiral triterpenoid biomolecule.

Inibidores de fosfodiesterases: novas perspectivas de uma antiga terapia na asma?

A asma é uma doença inflamatória crônica com níveis variados de obstrução ao fluxo aéreo e diferentes formas de apresentação. Seu tratamento vem sendo modificado com a evolução do conhecimento sobre sua patogenia. A inflamação das vias aéreas, que é modulada por determinantes genéticos e ambientais, resulta na alteração definitiva da arquitetura da via aérea (remodelamento). O padrão inflamatório da asma é de natureza multicelular, envolvendo mastócitos, neutrófilos, eosinófilos, linfócitos T, células musculares e epiteliais. Diversas citocinas e quimiocinas contribuem para a orquestração do processo inflamatório. O reconhecimento do papel crítico da inflamação, que está associada à gravidade da doença, vem direcionando o eixo do tratamento para a prevenção ou para o bloqueio das alterações inflamatórias. Nesse sentido, além dos agentes beta2-adrenérgicos, da teofilina e dos corticosteróides, novos fármacos vêm sendo estudados. Dentre eles, os inibidores específicos de fosfodiesterases vêm apresentando resultados promissores. A partir dos resultados obtidos com a segunda geração dessas substâncias, pode-se imaginar que, em breve, elas representarão uma nova opção para o tratamento da asma.

Evaluation of the anti-asthmatic property of Asystasia gangetica leaf extracts

The leaf of Asystasia gangetica T. Adams (Acanthaceae) is used in many parts of Nigeria for the management of asthma. This study was aimed at investigating the anti-asthmatic property of hexane, ethylacetate, and methanol extracts of the leaves of Asystasia gangetica, obtained by successive sohxlet extraction. The results indicated that the extracts did not exhibit contractile or relaxant activity in isolated tissue preparations; however, they inhibited the contraction evoked by spasmogens; the IC(50) were calculated, where possible. The extracts relaxed histamine-precontracted tracheal strips in the following degree of potency-ethylacetate extract>hexane extract=methanol extract. The extracts also exhibited anti-inflammatory activity in the order of magnitude-methanol extract>hexane extract>ethylacetate extract. Acute toxicity test estimated an i.p. LD(50) of 2150 mg/kg in mice for methanol extract while phytochemical screening showed the presence of carbohydrates, proteins, alkaloids, tannins, steroidal aglycones, saponins, flavonoids, reducing sugars, and triterpenoids, with the methanol extract having the highest number of constituents. The study justified the use of the leaf of Asystasia gangetica in the management of asthma in Nigerian folk medicine.

Modification by CO2 of endothelin-1-induced contraction of isolated guinea pig trachea

To investigate the effect of changes in CO2 tension on airway smooth muscle tone induced by various agonists, contractile responses to acetylcholine, histamine and endothelin-1 (ET-1) were studied in isolated guinea pig tracheae at very low PCO2 (16 +/- 0 mmHg, n = 38), moderately low PCO2 (28 +/- 0 mmHg, n = 23), normal PCO2 (38 +/- 1 mmHg, n = 70) or high PCO2 (94 +/- 1 mmHg, n = 32). The minimum concentration of ET-1 (10(-10) M) needed to induce contractions was lower than that of acetylcholine (10(-7) M) and histamine (10(-7) M) at normal PCO2. Changes in PCO2 did not significantly affect acetylcholine- or histamine-induced contractions. In contrast, very low and moderately low PCO2 attenuated the contractions induced by ET-1, but high PCO2 potentiated those induced by a high concentration of ET-1. Very low PCO2 with normal pH and with high pH attenuated the contractions caused by ET-1, whereas normal PCO2 with high pH did not. These results suggest that ET-1-induced airway smooth muscle contraction can be modified by PCO2 per se. Aspirin and indomethacin potentiated the responses to ET-1 at very low PCO2 more than at normal PCO2, but attenuated the responses to low concentration of ET-1 at high PCO2. These results also suggest that cyclooxygenase-related eicosanoids are involved in the effects of PCO2 on ET-1-induced contractions.

Histamine receptors in the lung

Histamine, which has long been implicated as a mediator of allergic airway disease, has multiple effects on airways which are mediated by at least three histamine receptors. H1-receptors mediate bronchoconstriction, vasoconstriction and dilatation, microvascular leak and activation of sensory nerves. H2-receptors mediate vasodilatation in some species and mucus secretion. H3-receptors mediate vasodilatation in some species and mucus secretion. H3-receptors modulate cholinergic neurotransmission, the release of neuropeptides from sensory nerves and allergen-induced bronchoconstriction.

The influence of ranitidine, alone and in combination with clemastine, on histamine-mediated cutaneous weal and flare reactions in human skin

Significant, (P less than 0.05) inhibition of histamine induced cutaneous weal and flare reactions by ranitidine at 10(-5) M concentration has been demonstrated in a double blind, in vivo study; the results support the evidence for cutaneous H2-histamine receptors provided by previous studies using cimetidine and metiamide. The degree of inhibition of histamine mediated cutaneous reactions achieved by clemastine was increased by the administration of clemastine and ranitidine together, for ranitidine concentrations 10(-5) M (P less than 0.001) and 10(-6) M (P less than 0.05). The magnitude of the inhibitory effect of ranitidine, both administered alone and in combination with clemastine, suggests that in the production of histamine induced cutaneous weal and flare reactions, the contribution afforded by stimulation of cutaneous H2-histamine receptors is only small.

[Change in skin reactivity in anaphylaxis to muscle relaxants and hypnotics after administration of anti H1, anti H2 and tritoqualine]

Inhibition of allergic skin reactivity was studied by the technique of thresholds in 35 patients presenting with an anaphylaxis to muscle relaxants. This method was useful to determine the anti-histamine or anti-anaphylactic effects of different substances. The best results were obtained with hydroxyzine. Associating it with an anti H2 drug (cimetidine or ranitidine) did not improve these results. Skin reactivity was never entirely abolished. This confirmed that no premedication could avoid the occurrence of an anaphylactic shock, or even reduce its magnitude. However, premedicating before general anaesthesia with anti H1 and anxiolytic drugs must be continued for all high risk patients: the prevention of non-specific histamine release appeared to be much more efficient than that of anaphylaxis.

Dopamine inhibition of histamine-mediated cutaneous responses

Several patients receiving dopamine for hypotension were skin tested for possible penicillin sensitivity. Not only were the penicillin skin tests negative but also the histamine control. On the possibility that dopamine might affect cutaneous histamine responses, we examined the effect of dopamine on histamine, antigen, morphine, and compound 48/80 skin responses. Both intradermal and intravenous dopamine selectively inhibited histamine but not antigen, morphine, or compound 48/80 skin responses, and the inhibition was in a dose-related fashion. This observation indicates that histamine should not be used to demonstrate dermal reactivity in patients receiving dopamine. The results of this study also suggest that histamine may not be the sole mast cell-derived mediator involved in the wheal-and-flare reaction characteristic of immediate-type skin tests since dopamine did not affect skin reactions caused by endogenous mast cell degranulation. Finally, the possible use of dopaminergic drugs in diseases with histamine-associated symptoms is discussed.

The pharmacokinetics and antihistaminic of the H1 receptor antagonist hydroxyzine

We studied the pharmacokinetics and the suppression of histamine-induced wheals, flares, and pruritus in the skin after administration of the histamine H1 antagonist hydroxyzine to seven healthy adults. After a single oral dose of hydroxyzine, 0.7 mg/kg (mean dose 39.0 +/- 5.4 mg), the mean maximum serum hydroxyzine concentration of 72.5 +/- 11.1 ng/ml occurred at a mean time of 2.1 +/- 0.4 hr. The mean elimination half-life calculated from the terminal linear portion of the serum hydroxyzine concentration vs. time curve was 20.0 +/- 4.1 hr. The mean clearance rate was 9.78 +/- 3.25 ml/min/kg and the mean volume of distribution was 16.0 +/- 3.0 L/kg. The single dose of hydroxyzine suppressed pruritus at the wheal and flare sites from 1 to 36 hr. Maximal suppression of the wheals was 80% and maximal suppression of the flares was 92%. Significant suppression of the wheals and flares persisted for 36 and 60 hr, respectively. Pharmacodynamic analysis of the wheal and flare suppression data and the mean serum hydroxyzine concentrations supports the prolonged terminal serum half-life value for the drug.

Measurement of plasma histamine: description of an improved method and normal values

The single isotopic-enzymatic assay of histamine was modified to increase its sensitivity and to facilitate measurement of plasma histamine levels. The modification involved extracting 3H-1-methylhistamine (generated by the enzyme N-methyltransferase acting on histamine in the presence of S-[methyl-3H]-adenosyl-L-methionine) into chloroform and isolating the 3H-1-methylhistamine by thin-layer chromatography (TLC). The TLC was developed in acetone:ammonium hydroxide (95:10), and the methylhistamine spot (Rf = 0.50) was identified with an o-phthalaldehyde spray, scraped from the plate, and assayed in a scintillation counter. The assay in plasma demonstrated a linear relationship from 200 to 5000 pg histamine/ml. Plasma always had higher readings than buffer, and dialysis of plasma returned these values to the same level as buffer, suggesting that the baseline elevations might be attributable to histamine. However, all histamine standard curves were run in dialyzed plasma to negate any additional influences plasma might exert on the assay. The arithmetic mean (+/- SEM) in normal plasma histamine was 318.4 +/- 25 pg/ml (n = 51), and the geometric mean was 280 +/- 35 pg/ml. Plasma histamine was significantly elevated by infusion of histamine at 0.05 to 1.0 micrograms/kg/min or by cold immersion of the hand of a cold-urticaria patient. Therefore this modified isotopic-enzymatic assay of histamine is extremely sensitive, capable of measuring fluctuations in plasma histamine levels within the normal range, and potentially useful in analysis of the role histamine plays in human physiology.