Plasma prostaglandin levels from bronchial asthmatic patients assayed by 9-anthryldiazomethane-HPLC method

Changes in erythrocyte polyunsaturated fatty acids and plasma eicosanoids level in patients with asthma

Background

To investigate the changes of polyunsaturated fatty acids (PUFAs) and their downstream eicosanoids in patients with asthma, the levels of erythrocyte membrane lipids and plasma lipid metabolites were examined.

Methods

Erythrocyte membrane lipids were extracted and esterificated, and then fatty acid compositions were determined by gas chromatography. The concentrations of six eicosanoids of PGE₂, TXA₂, LTB₄, PGE₁, 6-k-PGF_1α and PGF_2α in plasma were measured by ELISA.

Results

The results showed that the contents of erythrocyte membrane fatty acids in patients with asthma were mainly composed of C16:0, C18:0, C18:1, C18:2(n-6), and C20:4(n-6). The ratio n-6/n-3 PUFAs in patients and health persons were (4.42 ± 1.33):1 and (3.21 ± 0.79):1 (p < 0.01), showing statistically significant differences. ELISA results showed that the levels of plasma PGE₂, TXB₂, and PGE₁ in patients were higher than health persons; and the levels of eicosanoids of PGF_2α and 6-k-PGF_1α were significantly lower in patient group than healthy group (p < 0.05), but LTB₄ was no obvious difference (p = 0.09). Increased ratio of n-6/n-3 PUFAs is consistent to the increased levels of pro-inflammatory PGE₂ and TXB₂ and anti-inflammatory PGE₁ originated from C20:4(n-6) and C18:2(n-6), indicating that increased ratio of n-6/n-3 PUFAs and eicosanoids from n-6 PUFAs might promote the progress of airway inflammation of asthma.

Conclusion

Changes of erythrocyte fatty acids, n-6/n-3 PUFAs ratio and the levels of plasma PGE₂, TXB₂, and PGE₁ in patients with asthma were relevant to airway inflammation in some extent. Therefore, it could be proposed that increase of n-3/n-6 PUFAs ratio by diet supplementation of n-3 PUFAs might effectively improve airway inflammation in asthma.

Improved high-performance liquid chromatographic method for the combined analysis of phospholipase, lipoxygenase and cyclooxygenase activities

We report herein an improved method for the high-performance liquid chromatographic separation and analysis of eicosanoids formed during the stimulation of human platelets in vitro with collagen. Since the products of interest, excepting arachidonic acid, contain hydroxyl groups (one to several), our method involves the conversion of the hydroxyl groups into acetates (pyridine/acetic anhydride) after derivatization with anthryl diazomethane (ADAM) rendering the compounds with much decreased polarity for separation on a reversed-phase column. This procedure is superior to that involving ADAM esters only, i.e. with free hydroxyl groups, as it leads to the excellent separation of the desired compounds from each other and from extraneous peaks observed due to the ADAM reagent and sharpens the peak of thromboxane. We have successfully applied the method to investigate the formation of thromboxane B2 and 12-hydroxyheptadecatrienoic acid (HHT) (products of cyclooxygenase and thromboxane A2 synthase), 12-hydroxyeicosatetraenoic acid (12-HETE, a 12-lipoxygenase product) and arachidonic acid (AA, product of phospholipase A2) formed during the in vitro aggregation of human platelets induced by collagen. A correlation between the inhibition of aggregation by aspirin and thromboxane/HHT formation was observed. All four compounds can be chromatographed in a single run. We employed prostaglandin B1 (PGB1) as internal reference standard to quantify the products. The method is useful to investigate selectivity of drugs which may affect either or all of these enzyme pathways at the same time.

Role of thromboxane A2 synthetase inhibitors in the treatment of patients with bronchial asthma

Asthma results from complex interactions among inflammatory cells, mediators, and the cells and tissues resident in the airways and is characterized by airway obstruction, airway inflammation, and airway hyperresponsiveness. Treatment of asthma should address not only the airway obstruction but also the chronic inflammation that may lead to hyperresponsiveness. In Japan, where the death rate from asthma has not increased despite increasing numbers of patients, treatment of bronchial asthma relies on the use of oral prophylactic antiasthma drugs, such as thromboxane synthetase inhibitors. Thromboxanes may facilitate the effect of acetylcholine on the airways and may be involved in hyperresponsiveness. Experiments using animal models have shown that thromboxane synthetase inhibitors have prevented increased airway reactivity after exposure to allergens and irritants. Double-blind clinical trials have shown that treatment with the thromboxane A2 synthetase inhibitor ozagrel hydrochloride significantly reduced the need for concomitant steroid therapy, compared with treatment with azelastine hydrochloride. This review discusses the role of thromboxane A2 synthetase inhibitors in the treatment of patients with bronchial asthma.