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Biomedical subjects

R Dworski

Publications and source records attributed to R Dworski.

At least 37 records · Page 2Linked to original sources
PubMed1993

Prostaglandin E2 limits arachidonic acid availability and inhibits leukotriene B4 synthesis in rat alveolar macrophages by a nonphospholipase A2 mechanism.

Prostaglandin E2 (PGE2), a potent mediator of inflammation released in large amounts by endotoxin-stimulated alveolar macrophages (AM), has been shown to inhibit leukotriene B4 (LTB4) release by activated neutrophils. We investigated the hypothesis that LTB4 synthesis by AM can be regulated by PGE2 and performed experiments to determine the biochemical site of regulation. AM obtained from Sprague-Dawley rats were preincubated with PGE2 before stimulation with the calcium ionophore A23187. LTB4, platelet-activating factor (PAF), lysoPAF, (AA), and 5-hydroxyeicosatetraenoic acid were isolated from AM cells and supernatants, then quantified by gas chromatography/electron capture negative ion mass spectrometry. Stimulated AM released 30.50 +/- 4.52 ng LTB4/10(6) cells and were inhibited by PGE2 in a dose dependent manner. PGE2 (1 microM) inhibited LTB4 synthesis by 37% and decreased release of both 5-hydroxyeicosatetraenoic acid and arachidonic acid by stimulated AM, but did not alter synthesis of PAF or lysoPAF. These mass measurements suggest that PGE2 does not affect the activity of phospholipase A2, PAF acetyltransferase, leukotriene A4 hydrolase. We conclude that PGE2 attenuates LTB4 production in alveolar macrophages by altering the activity of lipases other than phospholipase A2. PGE2-mediated inhibition of LTB4 synthesis by AM may regulate the initiation of lung inflammation.

Animals↗
PubMed1992

Thromboxane synthase inhibition in allergen challenged sheep lung: effect on eicosanoid synthesis.

We determined the effect of a novel inhibitor of thromboxane synthase, DP1904, on the baseline and allergen stimulated release of eicosanoids into the bronchoalveolar lavage fluid of sheep. DP1904 was effective in reducing the baseline and allergen stimulated production of TXB2. Inhibition of thromboxane synthase was associated with an increase in other prostaglandin endoperoxide metabolites, PGE2 and PGD2. Diversion of endoperoxide metabolism occurs in sheep lung tissue in vivo.

Allergens↗
PubMed1992

Inhaled steroids in asthma.

Inhaled corticosteroids provide a relatively trouble free means of treating the airway inflammation of asthma and can allow for the reduction of both oral steroid use and the symptoms in asthmatics using bronchodilators. Conventional doses may not be sufficient to provide control in many patients, and dosing should be tailored to the individual. These higher doses may cause systemic side effects, but these are less than those incurred by using oral prednisone.

Administration, Inhalation↗
PubMed1991

Cyclosporin for steroid-dependent asthma.

We used cyclosporin to treat 12 adult patients with severe bronchial asthma who had been on systemic steroids for an average of 16 years. During the baseline period, lasting 4-6 months, therapy with high doses of inhaled beclamethasone, aminophylline and salbutamol was standardized and a minimum necessary dose of systemic steroids was established. After 9 months' treatment with low-dose cyclosporin (average whole-blood trough levels of 105 ng/ml), in six patients the daily dose of oral prednisone could be reduced from mean 30 mg to mean 11 mg, while daily symptom scores and peak expiratory flows improved significantly. This was accompanied by a reduction in exacerbations of asthma. However, in six other patients attempts to taper the steroid doses were unsuccessful, and cyclosporin was stopped after 4 to 7 months. These preliminary results suggest that cyclosporin might be of benefit in some patients with steroid-dependent asthma.

Adult↗
PubMed1990

Salicylate pre-treatment attenuates intensity of bronchial and nasal symptoms precipitated by aspirin in aspirin-intolerant patients.

Aspirin (ASA) and other non-steroidal anti-inflammatory drugs, which are cyclooxygenase (COX) inhibitors, precipitate asthmatic attacks in ASA-intolerant patients, while sodium salicylate, hardly active on COX by itself, is well tolerated by these patients. However, salicylate moiety appears to interfere with aspirin inhibitory action on platelets and vascular COX. Such interaction, if present at the level of respiratory tract, may be of interest to pathogenesis of ASA-induced asthma. We performed a double-blind, placebo-controlled, randomized cross-over study on the effect of choline magnesium trisalicylate (CMT, trilisate) pre-treatment on ASA-induced adverse reactions in nine patients. Pulmonary function tests, nasal symptoms score, PNIF and serum salicylate levels were monitored following challenges with threshold doses of ASA. Trilisate administered at a dose of 3000 mg daily for 3 days, offered a moderate protection against ASA-induced symptoms; it diminished the severity and/or delayed the appearance of FEV1 fall. Maximal decreases in FEV1 as well as reaction intensity indexes were significantly lower (P less than 0.02 and P less than 0.002, respectively) after trilisate pre-treatment as compared to placebo. Trilisate also attenuated nasal symptoms in three out of five patients. Although the precise mechanism of the protective action of trilisate is unknown, our data support the possibility of interaction between salicylate and ASA on cyclo-oxygenase locus in the respiratory tract in ASA-intolerant patients.

Adult↗
PubMed1990

Allergen-stimulated release of thromboxane A2 and leukotriene E4 in humans. Effect of indomethacin.

Allergen-stimulated release of a cyclooxygenase product (thromboxane [TX] A2) and a 5-lipoxygenase product (leukotriene [LT] E4) into the urine was measured in 10 atopic asthmatics undergoing allergen inhalation. Because indomethacin has been reported to increase allergic-stimulated 5-lipoxygenase product formation and to inhibit the late asthmatic response, we determined the effect of indomethacin (50 mg 3 times a day) or placebo on airway and biochemical responses to inhaled allergen in a randomized, blinded study. Urinary levels of the enzymatic metabolite of TXB2, 11-dehydro-TXB2, increased from 585 +/- 330 to 1,500 +/- 250 pg/mg creatinine (mean +/- SEM, p less than 0.05) 2 h after allergen. Urinary LTE4 increased from 190 +/- 37 to 1,100 +/- 400 (p less than 0.05) 2 h after challenge. The urinary levels of these eicosanoids were not elevated during the late response. Indomethacin significantly reduced urinary 11-dehydro-TXB2 levels without affecting the excretion of LTE4 or pulmonary function. Thus, we failed to obtain evidence for enhanced leukotriene formation during allergic stimulation in vivo in the presence of cyclooxygenase inhibition. Furthermore, we conclude that cyclooxygenase products are likely to play only a marginal role in allergic bronchoconstriction.

Adult↗
PubMed1990

Choline magnesium trisalicylate in patients with aspirin-induced asthma.

Treatment of inflammatory diseases of asthmatics can be a serious problem since some patients show intolerance to aspirin and other non-steroidal, anti-inflammatory drugs that are cyclooxygenase inhibitors. Salicylates were believed to be well tolerated, but recent reports have demonstrated that diflunisal and salicylsalicylic acid can precipitate asthma attacks in aspirin-intolerant patients. This study was designed to determine the tolerance of choline magnesium trisalicylate (CMT), a nonacetylated salicylate with potent analgesic and anti-inflammatory activity, in 23 asthmatics with aspirin hypersensitivity confirmed by oral challenge. The study consisted of three phases: 1) patients received increasing doses (50-1,500 mg) of CMT under a single-blind protocol; 2) patients received either a placebo or CMT challenge in a double-blind, randomized, cross-over design; 3) patients received CMT at daily 3,000 mg doses for 1 week. Throughout the study, pulmonary function tests, peak nasal inspiratory flow, and serum salicylate and thromboxane B2 (TXB2) levels were monitored. Results showed no airway obstruction, nasal congestion or rhinorrhea after CMT. There was no significant decrease in serum TXB2 levels, indicating the absence of cyclooxygenase inhibition with CMT. We conclude that choline magnesium trisalicylate is a safe drug for treatment of different anti-inflammatory disorders in asthmatics with aspirin hypersensitivity.

Adult↗
PubMed1989

Allergen-stimulated release of mediators into sheep bronchoalveolar lavage fluid. Effect of cyclooxygenase inhibition.

Products of arachidonic acid have been implicated as potential mediators of allergic airway responses in sheep and in humans. We therefore measured the release of arachidonate metabolites into sheep bronchoalveolar lavage fluid (BALF) after local instillation of Ascaris antigen, using a highly specific and sensitive approach, gas chromatography-negative ion-chemical ionization mass spectrometry. Allergen instillation caused increases in the levels of the potent bronchoconstrictors prostaglandin (PG) D2 and thromboxane (TX) A2 (as reflected by levels of TXB2) and of their enzymatic metabolites, 9 alpha, 11 beta-PGF2 and 11-dehydro-TXB2, respectively. Potential bronchodilators, PGI2 and PGE2, were also formed in increased amounts. Levels of the 5-lipoxygenase products, leukotriene (LT) B4 and C4, were not significantly increased. Pretreatment of sheep with cyclooxygenase inhibitors was associated with a decrease in the release of cyclooxygenase products and a concomitant increase in the allergen-stimulated release of LTB4 and LTC4. Eicosanoids are formed promptly in vivo in sheep after allergen instillation: inhibition of cyclooxygenase results in augmented generation of leukotrienes in the airways of sensitive sheep in response to antigen challenge.

Allergens↗
PubMed1987

Effects of inhibition of thromboxane A2 synthesis in aspirin-induced asthma.

Since inhibition of cyclooxygenase precipitates asthmatic attacks in patients with aspirin idiosyncrasy, we have evaluated the effects of pharmacologic inhibition of thromboxane A2 (TXA2) synthetase, next to cyclooxygenase enzyme in arachidonic acid cascade. Sixteen patients with aspirin-induced asthma received increasing doses on 3 days (25 to 400 mg) of an imidazole derivative, OKY-046, which specifically blocks TXA2 synthetase. Twenty-three healthy control subjects received a single dose of 400 mg of OKY-046. In both patients and control subjects, the inhibitor at a dose of 400 mg produced (1) a pronounced fall in thromboxane B2 serum levels, (2) a rise in serum 6-keto-prostaglandin F1 alpha, and (3) a depression in platelet aggregability to arachidonic acid and adenosine diphosphate. The drug, however, neither precipitated attacks of asthma nor impaired pulmonary function tests throughout a 24-hour observation period. Five patients, but none of the control subjects, developed transient nasal congestion about 1 hour after taking the drug. Thus, inhibition of TXA2 synthetase, contrary to inhibition of cyclooxygenase, does not affect bronchopulmonary function in patients with asthma and aspirin intolerance.

Acrylates↗
PubMed1987

Effects of inhibition of thromboxane A2 synthesis in aspirin-induced asthma.

Since inhibition of cyclo-oxygenase precipitates asthmatic attacks in patients with aspirin idiosyncrasy, we have evaluated the effects of pharmacological inhibition of the next enzyme in arachidonic acid cascade, i.e., thromboxane synthetase. Twelve patients with aspirin-induced asthma received on 3 days increasing doses (25-400 mg) of an imidazole derivative, OKY-046, which specifically blocks TXA2 synthetase. Twelve healthy controls received a single dose of 400 mg OKY-046. The drug neither precipitated asthmatic attacks nor altered pulmonary function tests throughout a 24-hr observation period. Five of 12 patients, but none of the controls, developed nasal congestion, approximately 1 hr after ingestion of the inhibitor. Though initial platelet aggregation evoked by arachidonic acid or ADP did not differ between the two groups, inhibitory effects of 400 mg OKY-046 on the aggregability were more pronounced in the patients than in the controls. Thus, inhibition of TXA2 synthetase, contrary to inhibition of cyclo-oxygenase, does not affect bronchopulmonary function in patients with asthma and aspirin intolerance. It does, however, often produce nasal congestion, possibly through reorientation of prostanoid synthesis from TXA2 to PGD2. It remains to be established whether pronounced depressive effects of a TXA2 synthetase inhibitor on platelet aggregability constitute a treat of aspirin idiosyncrasy or is a more general phenomenon associated with bronchial asthma.

Adult↗