The role of α-tocopherol inpreventing disease

Summary. : A role of oxidative stress in atherosclerosis lies on experimental results carried out in vitro and in animal models. In humans, the supplementation with the antioxidant vitamin E has given in some cases supportive results and in others no effects. From in vitro studies, a large amount of data has shown that α-tocopherol (the major component of vitamin E) regulates key events in the cellular pathogenesis of atherosclerosis. We first described the inhibition of protein kinase C (PKC) activity by α-tocopherol to be at the basis of the vascular smooth muscle cell growth inhibition by this compound. Subsequently, PKC was recognized to be the target of α-tocopherol in different cell types, including monocytes, macrophages, neutrophils, fibroblasts and mesangial cells. Inhibiting the activity of protein kinase C by α-tocopherol results in different events in different cell types: inhibition of platelet aggregation, of nitric oxide production in endothelial cells, of superoxide production in neutrophils and macrophages as well as impairment of smooth muscle cell proliferation. Adhesion molecule expression and inflammatory cell cytokine production are also influenced by α-tocopherol. Scavenger receptors, particularly important in the formation of atherosclerotic foam cells, are also modulated by α-tocopherol. The oxidized LDL scavenger receptors SR-A and CD36 are down regulated at the transcriptional level by α-tocopherol. The relevance of CD36 expression in the onset of atherosclerosis has been indicated by the protection against atherosclerosis by CD36 knockout mice. In conclusion, the effect of α-tocopherol against atherosclerosis is not due only to the prevention of LDL oxidation but also to the down regulation of the scavenger receptor CD36 and to the inhibition of PKC activit

Fluorochrome Interaction with the Mitochondrial Membrane THE EFFECT OF ENERGY CONSERVATION

Abstract The interaction of 1-anilino-8-naphthalenesulfonate and 6-p-toluidino-2-naphthalenesulfonate with the membrane of both mitochondria and submitochondrial particles was studied. A fluorescence increase of the added fluorochromes was observed when energy was supplied to the membrane of submitochondrial particles, while a fluorescence decrease was observed with intact mitochondria. Binding studies and a comparison of the two fluorochromes have indicated that polarity changes of the membrane are not measured by 1-anilino-8-naphthalenesulfonate and 6-p-toluidino-2-naphthalenesulfonate. The fluorescence changes associated with energy conservation can be attributed to changes in the binding of the fluorochromes. Either a conformational change or a membrane potential change could account for the results

Ion transport in liver mitochondria. I. Metabolism-independent Ca++ binding and H+ release.

Abstract 1. Liver mitochondria are able to bind large amounts of Ca++ through a process which is independent of metabolism. The amount of Ca++ bound is increased by increasing the pH of the medium and is decreased by the addition of univalent cations. The binding of Ca++ to the mitochondria is a function of the concentration of Ca++ in the medium and is affected by the Ca++ to protein ratio. 2. A large part of the metabolism-independent binding of Ca++ occurs in a space which is rendered accessible to univalent cations by valinomycin or gramicidin. In fact when the mitochondria are pretreated with valinomycin or gramicidin, the binding of Ca++ is increased in a sucrose medium and decreased in a KCl or NaCl medium. The competition between Ca++ and univalent cations has been studied. 3. The metabolism-independent binding of Ca++ is coupled to a release of H+ or of K+. The conditions affecting the exchange between divalent and univalent cations are studied and data are reported on the stoichiometry of H+:Ca++ and K+:Ca++ in normal and valinomycin-treated mitochondria

Alternative splicing and gene polymorphism of the human TAP3/SEC14L4 gene

Three closely related human SEC14p-like proteins (hTAP1, hTAP2, hTAP3, or SEC14L2, SEC14L3, SEC14L4, respectively) have been described that are related to the Saccharomyces cerevisiae SEC14 protein. These proteins may participate in intracellular lipid transport and influence regulatory lipid-dependent events. Here we report the isolation of an alternatively spliced hTAP3 cDNA and a polymorphism within the coding region of the hTAP3/SEC14L4 gen

Site-directed spin labeling of the mitochondrial membrane. Synthesis and utilization of the adenosine triphosphatase inhibitor (N-(2, 2, 6, 6-tetramethyl-piperidyl-1-oxyl)-N'-(cyclohexyl)-carbodiimide).

Abstract NCCD (N-(2,2,6,6-tetramethyl-piperidyl-1-oxyl)-N'-(cyclohexyl)carbodiimide) is a spin label inhibitor of ATPase of mitochondrial membrane fragments. Upon binding (∼0.5 nmole per mg of protein) its electron paramagnetic resonance spectrum becomes highly immobilized (τc = 2.10-8 s). The bound but not the free label is reduced by succinate, indicating that electrons can be transferred from the respiratory chain to the ATPase system. The Mn++ATP complex decreases the paramagnetic signal of NCCD bound to membrane fragments about 30%. Such an interaction can be the consequence of the vicinity of the binding sites of the two species

Tocotrienol inhibits proliferation of human Tenon's fibroblasts in vitro: a comparative study with vitamin E forms and mitomycin C

Purpose: To evaluate the potential of the vitamin E compound α-tocotrienol as antifibrotic agent in vitro. Methods: Using human Tenon's capsule fibroblast cultures, the antiproliferative and cytotoxic effects of the different vitamin E forms α-tocopherol, α-tocopheryl acetate, α-tocopheryl succinate and α-tocotrienol were compared with those of mitomycin C. To mimic subconjunctival and regular oral application in vivo, exposure time of serum-stimulated and serum-restimulated fibroblasts (SF and RF, respectively) to vitamin E forms was set at 6 days. Cultures were only exposed for 5min to mitomycin C due to its known acute toxicity and to mimic the short-time intraoperative administration. Proliferation (expressed as % of control) was determined by DNA content quantification on days 2, 4 and 6, whereas cytotoxicity was assessed by cell morphology and glucose 6-phosphate dehydrogenase (G6PD) release after 24h. Results: α-Tocopherol and α-tocopheryl acetate stimulated growth of SF, but not RF. Reduction of fibroblast content by α-tocopheryl succinate was accompanied by increased G6PD release and necrosis. Contrary to α-tocopheryl succinate, 50μM or repeatedly 20μM of α-tocotrienol significantly inhibited proliferation without causing cellular toxicity (maximal effect: 46.8%). RF were more sensitive to this effect than SF. Mitomycin C 100-400μg/ml showed a stronger antiproliferative effect than α-tocotrienol (maximal effect: 13.8%). Morphologic characteristics of apoptosis were more commonly found under treatment with mitomycin C. Conclusions: Of the vitamin E forms tested, only α-tocotrienol significantly inhibited growth at non-toxic concentrations. In this in vitro study, antiproliferative effects of mitomycin C were stronger than those of α-tocotrieno