The role of adenosine A2 receptors in the regulation of TNF-α production and PGE2 release in mouse peritoneal macrophages

The adenosine A(2) receptors are known to mediate most of the anti-inflammatory activities of adenosine. In lipopolysaccharides (LPS)-stimulated macrophages adenosine strongly inhibits TNF-alpha release, but may also enhance PGE(2) generation. The aims of this study were to determine the relative contributions of the A(2A) and A(2B) receptor subclasses in these two effects and to determine whether the enhanced release of PGE(2) contributes to the inhibition of TNF-alpha release. In LPS-stimulated mouse macrophages, adenosine potently inhibited TNF-alpha production and also potentiated PGE(2) release, though less potently (IC(50)=250 nM vs EC(50) approximately 8 microM, respectively). The non-selective adenosine receptor agonist NECA, and the selective A(2A) receptor agonist CGS21680 also inhibited TNF-alpha production even more potently (IC(50)=4.8 and 2.3 nM, respectively). NECA, but not CGS21680, also enhanced PGE(2) production. The selective A(2A) receptor antagonist ZM241385 (30 nM), but not the selective A(2B) receptor antagonist MRS1754 (30 nM), blocked the inhibitory effect of NECA and CGS21680 on TNF-alpha release. On the other hand, MRS1754, but not ZM241385, abolished the PGE(2) potentiating effect of NECA. Pre-treatment with indomethacin (1 microM) abolished adenosine-induced PGE(2) release enhancement but did not prevent the inhibition of TNF-alpha release. These results show that in this system, the inhibition of TNF-alpha release by adenosine is mediated by the A(2A) receptors whereas the enhancement of PGE(2) release appears to be mediated by the A(2B) receptors. The results also show that while exogenous PGE(2) is a potent inhibitor of TNF-alpha release, the enhanced PGE(2) release induced by adenosine does not appear to contribute to the inhibition of TNF-alpha release.

Characteristics of asthmatic children in Kuwait

This article summarizes clinical characteristics and identifies sensitizing allergens in 135 asthmatic children under 13 years of age in Kuwait, a desert environment with scant vegetation and weather conditions least associated with asthma. There were 84 males (M:F 1.65:1). Almost 70% were breast-fed (1-24 months), 59% had eczema, 52% allergic rhinitis, 78% of first-degree relatives had atopy, and 52% of parents were consanguinous. Cough was the presenting symptom in 92% and together with wheezing occurred in 76%. Most (91%) were < or = 5 years of age at diagnosis and 42% < 2 years. Mean duration of symptoms prior to diagnosis was 9.3+/-2 months (1 week-1 year). Viral upper respiratory tract infections, cigarette smoke, and exercise were the commonest triggers of symptoms (79%, 68%, 62%). Fumes of traditional Bokhour (incense) constituted a major indoor hazard. The most common sensitizing allergens were pollens of imported plants, molds, house dust mites, cockroaches, and peanuts. Management showed considerable under-treatment and included alternative medicines. In conclusion, childhood asthma in this desert environment starts at an early age, and is associated with high rate of atopy and high frequency of sensitization to aero- and food allergens. Asthmatic children are disadvantaged by delay in diagnosis, undertreatment, exposure to indoor cigarette smoke, and local traditions.

Effect of wortmannin on human eosinophil responses in vitro and on bronchial inflammation and airway hyperresponsiveness in Guinea pigs in vivo

Many mediators activate eosinophils via transduction pathways involving the enzyme phosphatidylinositol 3-kinase. The initial investigation of wortmannin, a specific inhibitor of PI3-kinase, was of its effect on human and guinea pig eosinophil superoxide (O(2)(-)) release and degranulation in vitro. Subsequently, the effect on allergen- and Sephadex-induced bronchial inflammation and airway hyperresponsiveness (AHR) in vivo in guinea pigs was investigated. Wortmannin potently inhibited complement C5a-induced O(2)(-) generation and eosinophil peroxidase (EPO) release from human eosinophils, with 50% inhibition produced by a 1-10 nM concentration. Both aerosol allergen challenge of sensitized guinea pigs and intravenous injection of Sephadex beads in normal guinea pigs caused, in 24 h, significant eosinophilia and increased EPO activity in bronchoalveolar lavage fluid (BALF) and AHR to intravenous acetylcholine and histamine. In the allergic model, intranasal pretreatment with wortmannin had no effect on BALF eosinophilia, but dose dependently inhibited BALF EPO activity. At 1 mg/kg, the drug abolished the AHR to histamine, but not acetylcholine. In the Sephadex model, the drug significantly inhibited all three parameters (eosinophilia, increased EPO activity, and AHR to both spasmogens). These results show that wortmannin is a potent inhibitor of human eosinophil degranulation and that when administered intranasally can prevent AHR in allergen-challenged guinea pigs, probably by inhibiting eosinophil degranulation, but not their accumulation in BALF. This may be relevant to the possible clinical utility of wortmannin in conditions involving eosinophilic inflammation and AHR.

Involvement of A(3) receptors in the potentiation by adenosine of the inhibitory effect of theophylline on human eosinophil degranulation: possible novel mechanism of the anti-inflammatory action of theophylline

The current use of theophylline in asthma is based on both the bronchodilatory and the anti-inflammatory effects. The exact mechanism of these actions is still controversial and may include the inhibition of adenosine 3',5'-monophosphate phosphodiesterase enzyme (PDE) and antagonism of adenosine receptors. In this study, the mechanism of the anti-inflammatory action was investigated by studying the inhibition by theophylline of complement C5a (C5a)-induced degranulation of human eosinophils and its interaction with adenosine. Theophylline (10-1000 microM) inhibited C5a-induced release of eosinophil peroxidase (EPO) in a concentration-dependent manner with an IC(50) of 233.5 microM and a maximal inhibition of 90.3 +/- 3.0%. In contrast, the PDE4 inhibitor rolipram (up to 50 microM) had no effect. The adenosine A(3) receptor agonist N(6)-(3-iodobenzyl)-5'-N-methylcarbamoyladenosine (IB-MECA) also inhibited release (IC(50) = 7.5 microM), but neither adenosine itself nor the selective A(1) and A(2) agonists and antagonists had any significant effect, even at 100 microM. The inhibition produced by clinically relevant concentration of theophylline (50 microM) was potentiated by ineffective concentrations of exogenous adenosine and additive to that produced by IB-MECA. The potent and selective A(3) antagonist MRS 1220, but not the A(1) or A(2) antagonists, significantly reversed the inhibitory effect of theophylline. These results suggest that therapeutic concentrations of theophylline inhibit human eosinophil partly by acting as an A(3) agonist. Together with the potentiation of theophylline action by adenosine, perhaps via the A(3) receptors, these novel actions may, at least in part, contribute to the mechanism of the anti-inflammatory action of this drug in vivo.

Requirement of additional adenylate cyclase activation for the inhibition of human eosinophil degranulation by phosphodiesterase IV inhibitors

Human eosinophils contain predominantly phosphodiesterase type IV, but selective inhibitors of this isoenzyme fail to inhibit certain eosinophil responses such as degranulation. In this study, the effect of activation of adenylate cyclase on the ability of several highly selective PDE IV inhibitors to inhibit complement C5a-induced O2- release and degranulation of human eosinophils in vitro was investigated. All four selective PDE IV inhibitors, N-(3,5-dichloropyrid-4-yl)-3-cyclopentyl-oxy-4-methoxybenzamide (RP 73401), rolipram, N-(3,5-dichloropyrid-4-yl)-[1-(4-fluorobenzyl)-5-hydroxy-indol-3-yl]glyoxylacidamide (AWD 12-281) and c-4-cyano-4-(3-cyclopentyloxy-4-methoxyphenyl-r-1-cyclohexane carboxylic acid) (SB 207499) potently inhibited C5a-induced O2- generation (IC50 = 0.03, 0.42, 0.55 and 0.86 microM, respectively), but generally failed to inhibit degranulation. The only exception was AWD 12-281, which inhibited degranulation (IC50 = 16.2 microM). In the presence of different AC activators (histamine, salbutamol, prostaglandin E2 and forskolin), the PDE IV inhibitors became potent inhibitors of degranulation. The interaction between the PDE IV inhibitors and the AC activators resulted in a synergistic increase in intracellular levels of adenosine 3', 5'-monophosphate (cAMP). These results show that PDE IV inhibitors generally require an additional cAMP signal to be able to inhibit eosinophil degranulation, and that this signal can be generated via both membrane receptors and direct AC activation. This may be relevant to the in vivo effectiveness of PDE IV inhibitors in eosinophilic inflammation.

Therapy of bronchial asthma with adenosine receptor agonists or antagonists

Adenosine is an endogenous nucleoside that is released under pathological conditions and interacts with four G-protein-coupled receptor subtypes. These receptors are widely distributed throughout the body. They are involved in many central and peripheral processes, including immunological and inflammatory responses. In inflammatory and asthmatic conditions, the extracellular concentration of adenosine increases in the airway tissue. It enhances mast cell degranulation and bronchoconstriction, but may also inhibit eosinophil or lymphocyte function or modulate reactive oxygen species generation in neutrophils. Despite a large number of studies clearly indicating the effects of adenosine in vitro, many aspects of the mechanisms involved in the adenosine-mediated responses are still unclear, and our knowledge is limited in understanding the complex multifactorial interactions occurring in the whole body. The discovery of adenosine receptor compounds acting with increasing selectivity will bring new approaches to the use of adenosine receptor agonists and antagonists and may clarify some of the current uncertainties. On the basis of our present knowledge, the development of adenosine A(2A)- or (A3)-receptor agonists as antiinflammatory agents or A(2B)-receptor antagonists as inhibitors of mast cell degranulation for the treatment of asthma holds promise.

Histamine H(2) receptors mediate the inhibitory effect of histamine on human eosinophil degranulation

The effect of histamine on human eosinophil degranulation and the receptor mediating such effect were studied in vitro using the complement C5a-mediated eosinophil peroxidase (EPO) release model. Following pre-treatment with 5 microg ml(-1) cytochalasin B(CB), C5a induced a concentration-dependent release of EPO from eosinophils isolated from healthy donors. Histamine (0.1-50 microM), but not L-histidine, inhibited concentration-dependently C5a-induced EPO release with IC(50) (95% CI) of 0.6 microM (0.3-1.2 microM) and maximal inhibition of approximately 60%. A similar effect was seen with the selective H(2) agonists dimaprit (IC(50) (95% CI)=6.9 microM (3.2-10.6 microM)) and amthamine (IC(50) (95% CI)=0.4 microM (0.2-0.7 microM)). Neither the selective H(1) agonist 6-(2-(4-imidazolyl)ethylamino)-N-(4-trifluoromethylphenyl) heptanecarboxamide(HTMT), nor the selective H(3) agonists imetit (up to 100 microM) had any significant effect. The inhibition by histamine was reversed by cimetidine (0.1-30 microM) and other H(2) antagonists, but not the H(1) antagonist mepyramine (1.0- 100 microM), nor the H(3) antagonist thioperamide (1.0-100 microM). Cimetidine (1-30 microM) shifted to the right the dimaprit log dose-response curve, producing a pA(2) value of 5.9 and Schild's plot slope of 0.98, thus confirming simple competitive antagonism. Histamine (10-100 microM) increased intracellular level of adenosine 3',5'-cyclic monophosphate, which was completely abolished by cimetidine (30 microM), but not mepyramine or thioperamide. The cyclic AMP analogue - dibutyryl cyclic AMP - also inhibited degranulation (IC(50) approximately 300 microM). The cyclic AMP phosphodiesterase(PDE) IV inhibitor rolipram (10 microM) synergistically enhanced the inhibition of EPO release by histamine. These results suggest that histamine, via stimulation of H(2) receptors and a consequent elevation of intracellular levels of cyclic AMP, inhibits human eosinophil degranulation.

The association of skin test reactivity, total serum IgE levels, and peripheral blood eosinophilia with asthma in Kuwait

There is evidence that elevated serum immunoglobulin E (IgE) and eosinophilia correlate well with allergic skin test reactivity. These parameters have been used as alternative methods to characterize atopic subjects. Skin test reactivity is the only measure used routinely in clinical practice in Kuwait to reflect atopy in asthma patients. This study examines the usefulness of the two other parameters of atopy in patients with asthma, and to determine the most common allergens involved in Kuwait. Between 1998 and 1999, 101 asthma patients and 33 healthy controls were recruited for this study. Skin sensitivity test, serum total and specific IgE, total blood eosinophil count (B-EOS), and eosinophil cationic protein (ECP) tests were performed in patients and controls. Nine allergens known to be prevalent in this environment were selected for the skin test and specific IgE test. Spirometry was also measured. These parameters were repeated after 4 weeks of therapy in the patients only. Skin test reaction was positive in 81% of the patients, while total IgE above 200 kU/L was obtained in 63% of cases. B-EOS above 300 x 10(3)/L was found in 75% of cases. House dust mite reactivity (positivity) was the most frequently encountered skin allergy, occurring in 28% of the patients. IgE correlated positively with B-EOS and ECP. B-EOS similarly correlated positively with ECP. There was a negative correlation between ECP and forced expiratory volume in 1 sec (FEV1) (% predicted) as expected. At least one positive parameter of atopy was found in 95% of the patients. In 48% of the patients, all three parameters of atopy were found to be positive. Skin test reactivity and elevated IgE were found together in 62% of the cases. This study reveals a significant degree of allergy among patients with asthma in this environment. Skin testing was found to be the most effective measure of atopy in this environment, and correlates well with the other more sensitive newer tests.

Allergen-induced bronchial eosinophilia in guinea-pigs is inhibited by both pre- and post-induction cyclosporin-A treatments

Repeated treatment of sensitized guinea-pigs with cyclosporin-A (CS-A) before aerosol allergen challenge is known to inhibit the subsequent bronchial eosinophilia. It is not known, however, if the drug is also effective on established/on-going bronchial eosinophilia. We have, therefore, studied the effect of CS-A on allergen-induced eosinophil recruitment into the bronchoalveolar lavage (BAL) fluid of guinea-pigs when given before or after induction.Ovalbumin-immunized guinea-pigs were treated with CS-A (20 mg/kg subcutaneously) or vehicle daily for varying periods before a single aerosol allergen challenge. In animals in which bronchial eosinophilia was maintained with repeated aerosol allergen challenge, CS-A or vehicle was given daily for varying periods after the first allergen challenge. BAL and cell count were performed 24 h after the last challenge. In vehicle-treated animals, a single allergen challenge caused a 4-5 fold increase in the number of eosinophils in the BAL fluid after 24 h, declining to baseline by 7 days. In repeatedly-challenged animals, this response was sustained throughout. Eosinophil infiltration was significantly inhibited when CS-A was given daily for 7-14 days, but not for 1 or 3 days, before allergen challenge. When given during an established/on-going eosinophil infiltration, a significant inhibition was seen after administration for 5 or 7 days, but not for 1 or 3 days.These results show that repeated CS-A administration inhibits not only the induction of allergic bronchial eosinophilia but also the maintenance of an established one. This may be relevant in the treatment of allergic diseases, such as asthma, in which drug administration often begins when eosinophilia is already established.

Sensitization to aeroallergens among patients with allergic rhinitis in a desert environment

BACKGROUND

The causative allergens of allergic rhinitis in desert environments are uncertain.

OBJECTIVE

To determine the sensitizing aeroallergens in patients with allergic rhinitis in Kuwait, a desert country.

METHODS

A total of 706 patients aged 6 to 64 years (mean 34.3 years) with allergic rhinitis were studied. Sera from the patients were screened for specific IgE to 14 inhalant allergens by the CAP-RAST method.

RESULTS

Specific IgE to any allergen was detected in 86.3% of patients. The prevalence rates for allergen groups were: pollens (77.3%), house dust (62.3%), and molds (14.7%). The individual allergens with the highest positive rates were pollens of the weed Chenopodium (64.3%); Bermuda grass (55.0%), and Prosopis tree (50.3%). These plants were all imported and cultivated for the purpose of "greening" the desert. German cockroach (48.2%) and house dust mites (32.4% to 39.2%) were the most prevalent indoor sensitizers. With the exception of the molds, sensitization rates were higher for males than females. The youngest age group (6 to 17 years) had significantly higher sensitization rates than the older ones, particularly with respect to the molds (P < .01 to .001). Severe sensitization was more common with Alternaria than the other allergens and in general mold sensitization was more frequently associated with severe symptoms. Polysensitization was very common, with 81.8% of all sensitized patients positive to more than one allergen.

CONCLUSIONS

Pollens of the local horticultural plants are the main sensitizing allergens among patients with allergic rhinitis in this desert environment. The practices that "green" the desert seem to also encourage allergen sensitization.

IgE-mediated sensitization to mould allergens among patients with allergic respiratory diseases in a desert environment

BACKGROUND

The importance of fungal allergens in the development of allergic diseases in a desert environment is uncertain. This study evaluated the prevalence of IgE sensitization to moulds among patients with allergic respiratory diseases in Kuwait - a desert country.

METHODS

A total of 810 patients (male:female ratio 1.4) with a mean age of 32.3 years (range 2-76 years) with extrinsic asthma or allergic rhinitis were studied. Sera from the patients were tested by the CAP-RAST method for specific IgE to 6 fungi (Penicillium, Cladosporium, Aspergillus, Candida, Alternaria and Helminthosporium). For comparison house dust mite and Bermuda grass were also assessed.

RESULTS

The overall positivity to at least one mould was 20.9%. Among 120 matched control subjects, the value was 5. 8%. The value was much higher among patients with asthma alone (45. 8%) or both asthma and rhinitis (28.3%) than those with rhinitis alone (11.8%; p < 0.001). Asthmatic children had the highest sensitization rate (66.0% in the 7- to 12-year age group), which declined sharply with age. Among asthmatics, Candida and Aspergillus had the highest sensitization rates (23.1 and 21.3%, respectively), followed by Helminthosporium (18.8%), Cladosporium (15.9%), Alternaria (14.6%) and Penicillium (13.9%). The values for mite and Bermuda grass were 41.2 and 54.6%, respectively. Among asthmatic children, severe asthma was significantly more frequent among mould-positive (51.6%) than mould-negative patients (17.5%; p < 0. 0001).

CONCLUSIONS

Even in this desert environment, sensitization to moulds is quite common among patients with allergic respiratory diseases, with a striking preponderance among children with asthma. Mould allergy could also be an important factor determining asthma severity in this environment.

Asthma in the desert: spectrum of the sensitizing aeroallergens

BACKGROUND

Bronchial asthma is common in Kuwait, a desert country, but the sensitizing allergens are uncertain. This study investigated the sensitizing allergens in Kuwaiti patients with extrinsic asthma.

METHODS

A total of 553 asthmatics (male:female ratio: 1.4; mean age: 31.7 years [range 3-76 years]) and 112 matched controls were studied. Sera from all patients/subjects were tested by the CAP-RAST method for specific IgE to 14 locally relevant inhalant allergens.

RESULTS

Specific IgE to at least one allergen was detected in 87.2% of the patients compared with 24.1% of controls. Among the confirmed extrinsic asthmatics, the sensitization rates for the allergen groups were as follows: pollens (87.1%), house dust (76.1%), and molds (30.3%). The three most prevalent sensitizing pollens were from Chenopodium (70.7%), Bermuda grass (62.9%), and Prosopis (62.7%), all of which are horticultural plants imported for the purpose of "greening" the desert. For all allergens, except the molds, the prevalence rate was higher in males than females, but age had only a weak effect. Severe asthma occurred significantly more frequently among mold-sensitized patients.

CONCLUSIONS

These results show that even in a desert environment, pollens and house-dust allergens may be important sensitizing allergens. They also illustrate how practices that "green" the desert can affect public health.

Serum eosinophil cationic protein as a predictor of disease activity in acute and chronic asthma

BACKGROUND

Eosinophils may contribute to airway hyper responsiveness in asthma through the effects of eosinophil derived granular proteins in the bronchial epithelium. Increased concentration of eosinophil cationic protein (ECP) has been reported in patients with acute and chronic asthma.

OBJECTIVE

To examine if ECP can serve as a marker of disease activity in acute and chronic asthma patients.

DESIGN

Prospective case control study.

PATIENTS

Sixteen non smoking asthmatics in exacerbation (group 1); twenty two in relatively stable state (group 2); and sixteen normal control subjects (group 3) were recruited into the study.

SETTING

Casuality and outpatients departments, Mubarak hospital, Kuwait between August 1997 and July 1998.

MAIN OUTCOME MEASURES

The mean serum ECP, blood eosinophil count and peak expiratory flow rate (PEFR).

RESULTS

There was a statistically significant difference between the groups in blood eosinophil count (p < 0.01) and in PEFR (p < 0.0001). At week four, the mean ECP and blood eosinophil count fell as a result of therapy in group 1. The difference in PEFR values between week 0 and 4 in group 1 reached statistical significance (p < 0.05). In group 2 patients, the mean serum ECP, blood eosinophil count and PFER values between week 0 and 4 did not show any significant difference. A correlation was observed between ECP and PEFR in group 1 (p < 0.05) and between ECP and eosinophil count in group 2 (p < 0.01).

CONCLUSION

Serum ECP has the potential to serve as a marker for predicting and monitoring the clinical course of asthma. Further studies are required to verify these baseline findings in our environment.

Adenosine A3 receptors on human eosinophils mediate inhibition of degranulation and superoxide anion release

The role of adenosine A3 receptors on human eosinophil degranulation and superoxide anion (O2-) release was studied in vitro using the complement fragment C5a as the main stimulus and employing a number of selective agonists and antagonists. In the presence of cytochalasin B (CB), C5a induced a dose-dependent release of the granular eosinophil peroxidase (EPO), but not O2-, whereas in the absence of CB O2- , but not EPO, was released. C5a-induced EPO release was inhibited dose-dependently by the selective A3 agonist N6-(3-iodobenzyl)-5'-N-methylcarbamoyladenosine (IB-MECA) and to a lesser extent by the less-selective N6-2-(4-amino-3-iodophenyl) ethyladenosine (APNEA). The IC50 (95% CI) for IB-MECA was 6.8 microM (3.1-12.0 microM). At concentrations up to 100 microM, neither adenosine nor the selective A1 agonist N-cyclopentyladenosine (CPA) and the selective A2 agonist 2-[[2-[4-(2-carboxyethyl)phenyl]ethyl]amino]-N-ethylcarboxamidoadenosine (CGS 21680) had any significant effect. The inhibitory effect of IB-MECA was almost completely abolished by pre-treatment with 1 microM of the selective A3 antagonist 9-chloro-2-(2-furyl)-5-phenylactylamino[1,2,4]triazolo[1,5-c]quina zoline (MRS 1220), but not the selective A1 antagonist 1,3-dipropyly-8-cyclopentylxanthine (DPCPX) or the selective A2 antagonist 3,7-dimethyl-1-propargylxanthine (DMPX). IB-MECA also significantly inhibited C5a-induced O2- release with IC50 (95% CI) of 9.5 microM (4.6-13.1 microM) whereas adenosine and the A1 agonist CPA potentiated this effect at low concentrations. The potentiation appeared to be a result of their direct O2- release from these cells, probably mediated via A1 receptors. The inhibition by IB-MECA was selectively reversed by MRS 1220. These results show that the A3 receptors on human eosinophils mediate inhibition of both degranulation and O2- release and suggest a therapeutic potential for A3 agonists in diseases such as asthma in which activated eosinophils are involved.

Reference values of total serum IgE and their significance in the diagnosis of allergy among the young adult Kuwaiti population

BACKGROUND

The reference total serum immunoglobulin (IgE) values and the usefulness of total IgE values in the diagnosis of allergy have not been established for the Kuwaiti population. The literature reference values may not be applicable since such values often vary among ethnic nationalities.

OBJECTIVE

The aim of this study was to establish the reference IgE values for the young adult Kuwaiti population and to determine the usefulness of such values in the diagnosis of allergic diseases in the community.

METHODS

A total of 1057 randomly selected young adults were screened for atopy using the Pharmacia CAP-PhadiatopR method. Atopy was detected in 423 individuals (40.0%). Total serum IgE was then measured in 542 randomly selected Phadiatop-negative (non-atopic) cases in the age range 18-50 years (mean 28.9 years) and male:female ratio of 1.3.

RESULTS

Serum total IgE values in non-atopics covered a very wide range (< 2-1993 kU/L) with a geometric mean (GM) value of 43.7 kU/L. The reference range, calculated as the 95% confidence interval of the log IgE (95% CI) was 3.2-602.5 kU/L. The 90% CI was 11.7-162 kU/L. The GM was significantly higher for males than females, (53.7 vs. 35.5 kU/L, P < 0.001) and for smokers than non-smokers, (64.6 vs. 40.7 kU/L, P < 0.01), but was independent of age. Although the GM for the non-atopics (43.7 kU/L) was significantly lower than those of the asymptomatic atopics (213.8 kU/L) and allergic asthmatics (626.6 kU/L), the 95% CI for the three groups showed considerable overlap.

CONCLUSIONS

These results show that the normal total IgE values in the young adult Kuwaiti population are generally high and that the distribution of the values is so wide that the diagnostic value of total serum IgE in this community is likely to be very limited.

Effects of some anti-asthma drugs on human eosinophil superoxide anions release and degranulation

BACKGROUND

Eosinophil infiltration of bronchial tissues and subsequent release of inflammatory mediators by them are the hallmarks of bronchial asthma but it has not yet been clarified whether anti-asthma drugs affect these cells directly. In this study, we investigated the direct effects of 8 clinically used anti-asthma drugs [salbutamol, salmeterol, theophylline, denbufylline, disodium cromoglycate (DSCG), azelastine, ketotifen and dexamethasone] on superoxide anions (O2-) and eosinophil peroxidase (EPO) release from human blood eosinophils in vitro.

METHODS

Highly purified eosinophils were stimulated for O2- release with platelet-activating factor (PAF) or interleukin-5 (IL-5), while for EPO release complement fragment (C5a) or N-formyl-methionyl-leucyl-phenylalanine (FMLP) was employed. Generated products were assayed by standard techniques.

RESULTS

All the drugs, except ketotifen and dexamethasone, inhibited PAF-induced O2- release in a dose-dependent manner. The IC50 values were 0.7, 5.8, 330, 3,500, 4,200 and 6,250 nM for DSCG, denbufylline, salmeterol, azelastine, salbutamol and theophylline, respectively. On IL-5-induced release, the effects were similar except that salbutamol completely failed to inhibit the release induced by this stimulus. In contrast, EPO release was generally poorly inhibited, especially when the release was induced by C5a. Only theophylline and azelastine (both at 10(-4) M or more) were able to inhibit EPO release by both C5a and FMLP. Salbutamol and, to a lesser extent, salmeterol inhibited FMLP-, but not C5a-induced EPO release, while all the other drugs tested were inactive.

CONCLUSIONS

The results show that some of the anti-asthma drugs, but not all, do exert direct effects on human blood eosinophils but these effects may be stimulus-dependent and by far more pronounced against O2- release than against degranulation.

Differential effects of salbutamol and salmeterol on human eosinophil responses

In the treatment of bronchial asthma, salmeterol is believed to have a greater anti-inflammatory activity than salbutamol. To determine whether the comparative effects of these drugs on eosinophil function are the basis of their differential anti-inflammatory properties, we studied the effect of the two drugs on interleukin-5 (IL-5) and 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF)-induced O2- release and adherence to fibronectin-coated plates, as well as the C5a- and N-formylmethionyl-leucyl-phenylalanine (FMLP)-induced degranulation of purified human blood eosinophils in vitro. Salmeterol significantly inhibited IL-5-induced O2- release in a concentration-dependent manner with an IC50 of 2.2 X 10(-6) M (95% CI, 1.6-2.7 X 10(-6) M) and a maximal inhibition of about 70%. In contrast, salbutamol had no significant effect even at 10(-5) M. Both drugs significantly inhibited PAF-induced O2- generation, but salmeterol was approximately 20 times more potent than salbutamol. Salmeterol also significantly inhibited adherence induced by both IL-5 and PAF, whereas salbutamol had no significant effect on adherence induced by both agents. Both drugs failed to block C5a-induced eosinophil peroxidase release, whereas for FMLP-induced release, salbutamol, but not salmeterol, produced significant inhibition. Unlike salbutamol, all the actions of salmeterol were independent of beta-2 adrenoceptors. These results confirm that human eosinophils can be modulated directly by beta-2 adrenoceptor agonists, but that salmeterol and salbutamol have differential effects which depend on both the stimulus used and the response being measured and that the reportedly greater in vivo anti-inflammatory effect of salmeterol may reflect its superior ability to inhibit eosinophil O2- release and adherence, rather than degranulation.

Prevalence of allergic sensitization to inhalant allergens among blood donors in Kuwait--a desert country

Kuwait is a desert country where the prevailing high temperatures, low humidity, and scant vegetation suggest a low prevalence of allergy. We evaluated the prevalence of atopic sensitization (presence of allergen-specific IgE) among young adult blood donors by screening a total of 505 subjects (male: female ratio 1.6) with mean age of 28.4 years (range 18-50 years). The Pharmacia CAP-Phadiatop test, which detects serum IgE specific to most common airborne allergens, was used. Some of the specific sensitizing allergens were also identified by the related CAP-RAST method. Sensitization was detected in 223 of the 505 subjects (44.2%) screened. Kuwaiti nationals had a significantly higher prevalence rate (50.2%) than non-Kuwaitis (34.2%) (chi 2 = 8.6, P < 0.003). The highest prevalence rate was found among male Kuwaitis (53.8%). The prevalence of current or previous allergic disease (subject-reported) was 20.6%. Bermuda grass, house-dust mite (Dermatophagoides pteronyssinus), and Chenopodium album were the most prevalent sensitizing allergens, with frequencies of 53.6%, 52.7%, and 50.9%, respectively, among the sensitized subjects (corresponding to 23.7%, 23.3%, and 22.5%, respectively) for the entire population. Sensitization increased with age, but only among the expatriates, younger Kuwaitis being as frequently sensitized as the older ones. Polysensitization was found to be common. Of the 109 CAP-RAST-positive subjects, 71 (65.1%) were sensitized to more than one allergen, and 30 of these (42.3%) were sensitized to four or more allergens. These results show that atopy is highly prevalent among young adults in Kuwait, and the higher prevalence rate among nationals than expatriates suggests the involvement of genetic or local environmental factors. The results also confirm that mite and plant pollens may be major sensitizing allergens even in a desert environment.

The effect of salmeterol on human eosinophils is both stimulus- and response-dependent

Salmeterol, a long-acting beta 2-adrenoceptor agonist, also possesses some anti-inflammatory properties, but whether eosinophils are the target of such action has been equivocal. To clarify the direct effect of salmeterol on eosinophil functions, we have studied the effect of the drug on the various responses of purified human eosinophils. Superoxide anions (O2-) release and adherence to fibronectin-coated plastic plates induced by platelet-activating factor (PAF), interleukin-5 (IL-5), leukotriene B4 (LTB4) and phorbol myristate acetate (PMA), as well as degranulation induced by C5a and formyl methionyl leucyl phenylalanine (FMLP), in the presence of cytochalasin B (CB) were studied. In the concentration range 10(-8)-10(-5) M, the drug inhibited PAF- and IL-5-induced O2- release, with an IC50 values of 3.2 +/- 1.2 x 10(-7) M and 2.2 +/- 0.4 x 10(-6) M, respectively, Superoxide anion release by LTB4 was only modestly inhibited while that due to PMA was completely unaffected. On the other hand, eosinophil adherence induced by all the 4 stimuli were significantly inhibited within the same concentration range. On eosinophil degranulation, the drug failed to significantly inhibit the release of eosinophil peroxidase (EPO) induced by either C5a or FMLP. In contrast, beta-hexoseaminidase (beta-HA) release by the same agents was significantly inhibited, the inhibition being more pronounced for FMLP-induced, than C5a-induced release. None of the effects of the drug was reversed by the selective beta 2-adrenoceptor antagonist ICI 118551 at a concentration of 10(-7) M. These results show that salmeterol may have some direct inhibitory effects on human eosinophil functions but that these effects are both stimulus- and response-dependent, and are unlikely to be mediated via beta 2 adrenoceptors.

Anti-allergic activity of cyclosporin-A metabolites and their interaction with the parent compound and FK 506

The ability of cyclosporin-A (CSA) and four of its metabolites M1, M17, M18 and M21, to inhibit antigen-stimulated release of beta-hexoseaminidase from IgE-sensitized rat basophilic leukemia cells (RBL-2H3), as an in vitro correlate of anti-allergic effect, was studied Metabolites M17, M1 and M21 were effective in inhibiting enzyme release, though less potent than the parent compound. The concentrations achieving 50% inhibition (IC50 values) were 53.3, 315.5 and 875.7 ng/ml for CSA, M17 and M1, respectively. M21 had approximately same IC50 as M1 while M18 was essentially inactive. At the highest concentration tested (1000 ng/ml) the mean maximum percentage inhibitions were 98.6, 79.5, 53.9, 48.6 and 12.2 for CSA, M17, M1, M21 and M18, respectively. The relative anti-allergic potency of the metabolites was similar to their reported relative immunosuppressive potency. Combinations of low concentrations of CSA and its metabolites were synergistic in inhibiting enzyme release whereas at higher concentrations interactions were either additive or antagonistic. Even the concentrations of the metabolites that have little or no activity when used alone also potentiated the effect of CSA. The immunosuppressor FK 506 was found to be about three times more potent than CSA in this system and the interactions between FK 506 (3, 10 and 30 ng/ml) and CSA (10, 30 and 100 ng/ml) or M17 (20, 100 and 500 ng/ml) were synergistic at all combinations. Both CSA and M17 synergized more strongly with FK 506 than they did between themselves. These results show that some metabolites of CSA, like the parent compound, possess anti-allergic effects and that at concentrations that are obtainable in transplant patients, synergistic interaction occurs between CSA and its metabolites, and this may be of some therapeutic significance.

The impact of long-term cyclosporin-A therapy on hematological and biochemical profile in renal transplant patients

With over a decade of extensive clinical use of cyclosporin A (CsA), assessment of its long-term safety implications is due. In this study the impact of long-term continuous use of CsA on a number of hematological and biochemical parameters in renal transplant patients was evaluated. Two groups of 13 patients each, one on conventional therapy (azathioprine + prednisolone) and the other on triple therapy (azathioprine + prednisolone + CsA) for 4 to 15 years post-transplantation were compared with respect to their current and overall laboratory values and clinical outcome. Laboratory values were also compared with those of 23 matched healthy subjects. No significant difference in the clinical outcome was found between conventional and triple therapy groups, however, the triple therapy group had significantly less favorable mean values compared to the conventional therapy group with respect to hemoglobin (12.1 +/- 2.2 vs 13.3 +/- 2.1 g/dl, p < 0.02), hematocrit (0.36 +/- 0.06 vs 0.42 +/- 0.03 l/l, p < 0.05), urea (13.0 +/- 3.7 vs 6.7 +/- 4.3 mmol/l, p < 0.01) and uric acid (460.0 +/- 112 vs 330 +/- 88 mumol/l, p < 0.05). The increase in serum uric acid levels in the triple therapy group was progressive throughout the post-transplant period. For the 19 other parameters measured corresponding mean values in the 2 groups were comparable. Mean laboratory values for many parameters in both groups, however, still differed from those in the control group. These results showed that kidney transplant patients on long-term triple therapy have more hematological and biochemical abnormalities and no better clinical outcome than those on conventional therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Urine methylhistamine concentrations before and after chloroquine in healthy black subjects

Urine concentrations of methylhistamine were measured in 11 subjects who experienced itching with chloroquine ('itchers') and in 14 who did not itch ('non-itchers'). In each group, urine methylhistamine concentrations were significantly greater at 12, 24 and 36 h after ingestion of 1 g chloroquine phosphate than before. There was no significant difference between itchers and non-itchers as regards urine methylhistamine concentrations at any time-point. Furthermore, there was no correlation between urine methylhistamine concentration and degree of pruritus in itchers. The findings suggest that histamine may be released by chloroquine, but it is unlikely to be the main cause of chloroquine-induced pruritus.

Anti-allergic properties of cyclosporin A: inhibition of mediator release from human basophils and rat basophilic leukemia cells (RBL-2H3)

In vitro the immunosuppressive drug cyclosporin A (CS-A) strongly inhibited histamine release from human basophils (HB) and the rat basophilic leukemia cell line (RBL) 2H3. It also inhibited leukotriene release from HB. In HB the IC50 values for inhibition of histamine release induced by Con A, anti-IgE, calcium ionophore A23187 and antigen (mite) were 0.03, 0.12, 0.36 and 2.0 microM, respectively. In fact, these figures underestimate the potency of CS-A, since studies with 3H-CS-A showed substantial adsorption to plastic experimental wares which was inversely proportional to drug concentration. With anti-IgE and A23187, the drug acted promptly when added at the same time as the inducers but, with antigen, inhibition increased with time of pre-incubation. Washing of HB after pre-incubation with CS-A did not remove the drug effect. Inhibition of histamine release was abolished by Ca2+ excess (5 mM). For TPA-induced release, the drug inhibited the Ca2(+)-dependent but not the Ca2(+)-independent component. In Ca2(+)-free conditions, ionophore A23187, which caused little or no histamine release on its own, was able to synergize with TPA in causing release, apparently by mobilizing intracellular Ca2+. CS-A blocked the synergism but not the original TPA effect. CS-A was compared with the calmodulin inhibitors, W7, TFP and ABCNS; all inhibited histamine release. CS-A also potently inhibited IgE-mediated histamine release from RBL-2H3 cells, without affecting their growth or viability.

Effect of histamine H2-receptor antagonists on acute inflammatory of the rat paw oedema

The effect of three histamine H2-antagonists, cimetidine, ranitidine, and loxtidine, on acute rat paw oedema induced by histamine, carrageenan or complete Freund's adjuvant, have been examined. Administered intraperitoneally, all three antagonists inhibited histamine-induced paw oedema dose-dependently in the range 0.5-15 mumol kg-1. The highest dose of cimetidine produced an inhibition of 92% as against 38% with the same dose of mepyramine. Analysis of the concentration-effect curves produced IC50 values of 1.66, 5.12 and 12.30 mumol kg-1 for cimetidine, loxtidine, and ranitidine, respectively, on histamine-induced oedema. In carrageenan-induced inflammation 12.3 mumol kg-1 of each of the three drugs produced significant inhibition, whereas in adjuvant-induced inflammation, (acute phase), cimetidine was very active, loxtidine less so and ranitidine inactive. Thus the relative effectiveness of the antagonists (cimetidine greater than loxtidine greater than ranitidine) appears to differ from their known potency relationship (loxtidine greater than ranitidine greater than cimetidine) on H2-mediated effects. We conclude that H2-receptors are involved in the induction of rat paw oedema, especially those induced by histamine and carrageenan, but that their relative effectiveness appears atypical.

Cardiac anaphylaxis: the role of different mediators. Part I: Histamine

The main objective of this paper is to review the literature and to present experimental evidence concerning the mediators involved in immediate hypersensitivity reactions in the heart, that is in Cardiac Anaphylaxis. In Part I, the evidence for allergic reactions occurring in the heart is briefly presented. The evidence for the role of histamine as a mediator of some of the manifestations of cardiac anaphylaxis is reviewed. These effects of histamine include a positive chronotropic effect and arrhythmias, both positive and negative inotropic effects and negative dromotropic responses, which are mediated by both classes of histamine receptors.