calcimycin and 6-hydroxy-2-5-7-8-tetramethylchroman-2-carboxylic-acid

Isoprostanes are a family of prostaglandin (PG) F and E isomers generated by free-radical attack from membrane bound arachidonic acid. We measured detectable levels of 8-iso-PGF(2alpha) in the perfusates of synaptosomes obtained from different areas of the rat brain cortex. A small but significant release of this isoprostane was found under basal conditions from all the areas explored; being lower in the dorsal cortex in respect to the frontal, parietal and occipital areas. Exposure of synaptosomes to a phospholipase A(2) activator, i.e. calcium-ionophore A23187, an oxidant agent, such as hydrogen peroxide or amyloid beta-peptide did not modify 8-iso-PGF(2alpha) release when these stimuli were applied separately. However, either hydrogen peroxide or amyloid beta-peptide increased 8-iso-PGF(2alpha) release in a dose-dependent manner, when given in the presence of the calcium-ionophore A23187. Synaptosome treatment with a non-selective cyclooxygenase inhibitor (fenoprofen) did not modify 8-iso-PGF(2alpha) release in any way, but treatment with a water soluble antioxidant (Trolox C) completely suppressed isoprostane release under basal conditions, as well as after the oxidant injury induced either by hydrogen peroxide or amyloid beta-peptide. We conclude that, in neuronal endings, 8-iso-PGF(2alpha) is generated under basal conditions and its formation may be increased in a dose-dependent fashion by oxidant stimuli through a cyclooxygenase-independent mechanism involving free radical-catalyzed oxidation of arachidonic acid on membrane phospholipids.

Topics: Amyloid beta-Peptides; Animals; Brain; Calcimycin; Chromans; Dinoprost; Enzyme Activation; Enzyme Inhibitors; F2-Isoprostanes; Hydrogen Peroxide; Male; Nerve Endings; Phospholipases A; Rats; Rats, Wistar

The effects of Trolox C (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a vitamin E analogue, (60-900 microM) and SIN-1 (3-morpholino sydnonimine), a nitric oxide donor, (30-3000 microM) on arachidonic acid metabolism and on cyclic GMP formation in calcium ionophore A23187 (calcimycin)-stimulated human polymorphonuclear leukocytes were investigated. Trolox C elicited a dose dependent decrease in leukotriene B4 levels and increase in prostaglandin E2 levels but did not affect cyclic GMP levels. SIN-1 dose dependently inhibited leukotriene B4 and stimulated prostaglandin E2 and cyclic GMP formation. Dibutyryl cyclic GMP did not affect the formation of leukotriene B4 and prostaglandin E2. Trolox C (180 microM), which itself had no effect on cyclic GMP levels, enhanced the effect of SIN-1 (100 microM) on cyclic GMP levels more than 5-fold. The effects of SIN-1 on arachidonic acid metabolism seem to be independent of cyclic GMP and are probably due to nitric oxide. In this experimental model both Trolox C and SIN-1 have similar actions on the prostaglandin/leukotriene ratio, and Trolox C potentiates the SIN-1-induced increase in cyclic GMP levels.

Topics: Antioxidants; Arachidonic Acid; Calcimycin; Centrifugation, Density Gradient; Chromans; Cyclic GMP; Dibutyryl Cyclic GMP; Dinoprostone; Dose-Response Relationship, Drug; Guanylate Cyclase; Humans; Leukotriene B4; Molsidomine; Neutrophils; Radioimmunoassay; Vasodilator Agents; Vitamin E

1. Efflux of an intracellular enzyme (creatine kinase) from normal rat skeletal muscles was induced by treatment with the Ca2+ ionophore A23187. Addition of alpha-tocopherol (230 microM) to the incubation medium was found to significantly diminish this efflux, and this effect was mimicked by alpha-tocopherol acetate, phytol and isophytol, but not by Trolox C (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid). 2. Analysis of muscle cation content has shown that these protective effects of alpha-tocopherol etc. are not due to an inhibition of the Ca2+ accumulating effects of the ionophore. 3. Non-enzymic lipid peroxidation of skeletal-muscle homogenates was found to be inhibited by alpha-tocopherol and Trolox C, partially inhibited by phytol and isophytol, but unaffected by alpha-tocopherol acetate. 4. The activity of lipoxygenase enzymes was partially inhibited by alpha-tocopherol, phytol and isophytol, but not by alpha-tocopherol acetate or Trolox C. 5. Prostaglandin E2 efflux from isolated skeletal muscles was stimulated by treatment with the Ca2+ ionophore, but this was unaffected by alpha-tocopherol treatment.

Topics: alpha-Tocopherol; Animals; Calcimycin; Calcium; Chromans; Creatine Kinase; Cytosol; Dinoprostone; Lipid Peroxidation; Lipoxygenase; Muscles; Phytol; Rats; Rats, Inbred Strains; Tocopherols; Vitamin E

In the model of isolated, ventilated and perfused rabbit lungs release of arachidonic acid results in an increase of pulmonary vascular resistance and permeability. The former can be ascribed to cyclooxygenase products, the latter to lipoxygenase products of arachidonic acid. The effect of alpha-tocopherol on the increase of pulmonary vascular resistance and permeability either after the addition of arachidonic acid to the perfusion fluid or after stimulation of arachidonic acid liberation by Ca-ionophore A 23187 was investigated. It is possible to distinguish a membrane effect of the phytol side chain of alpha-tocopherol and an antioxidative effect of its chromane structure: Phytol augments the increase of pulmonary vascular resistance and permeability, whereas the chromane-structure decreases both to a large degree. The possibility of antioxidative therapy in disturbances of pulmonary vascular permeability is discussed.

Topics: Animals; Arachidonic Acids; Blood Pressure; Calcimycin; Capillary Permeability; Carboxylic Acids; Chromans; Indomethacin; Pulmonary Circulation; Rabbits; Vascular Resistance; Vitamin E