Effects of inadequate vitamin E and/or selenium nutrition on the release of arachidonic acid metabolites in rat alveolar macrophages

Malnutrition promotes prostaglandin over leukotriene production and dysregulates eicosanoid-cytokine crosstalk in activated resident macrophages

We previously described a murine model of malnutrition that mimicked features of moderate human malnutrition, and led to increased dissemination of Leishmania donovani. In this study, we investigated the effect of malnutrition on macrophage production of cytokines, prostaglandins (PGs), and leukotrienes (LTs). Using either LPS or calcium ionophore A23187 as a stimulus, macrophages from the malnourished mice produced a 3-fold higher PG/LT ((PGE(2)+6-keto-PGF(1alpha))/(LTB(4)+cysteinyl leukotrienes)) ratio than macrophages from well-nourished mice. LPS-stimulated macrophages from the malnourished mice produced decreased levels of TNF-alpha, GM-CSF, and IL-10, but similar levels of IL-6 and NO compared to well-nourished mice. A complex crosstalk between the eicosanoids and cytokines in the LPS-stimulated macrophages from the malnourished mice was evident by the following: (1) high levels of PG secretion despite low levels of TNF-alpha; (2) supplemental IL-10 modulated the excessive PG production; (3) GM-CSF rectified the PG/LT ratio, but did not correct the abnormal cytokine profile; and (4) inhibitors of cyclooxygenase decreased the PG/LT ratio, but did not affect TNF-alpha. Thus, in this model of malnutrition, there is a relative increase in anti-inflammatory PGs compared to pro-inflammatory LTs, which may contribute to immunodeficiency.

Selenium deficiency alters epithelial cell morphology and responses to influenza

It is unknown whether nutritional deficiencies affect the morphology and function of structural cells, such as epithelial cells, and modify the susceptibility to viral infections. We developed an in vitro system of differentiated human bronchial epithelial cells (BEC) grown either under selenium-adequate (Se+) or selenium-deficient (Se-) conditions, to determine whether selenium deficiency impairs host defense responses at the level of the epithelium. Se- BECs had normal SOD activity, but decreased activity of the selenium-dependent enzyme GPX1. Interestingly, catalase activity was also decreased in Se- BECs. Both Se- and Se+ BECs differentiated into a mucociliary epithelium; however, Se- BEC demonstrated increased mucus production and increased Muc5AC mRNA levels. This effect was also seen in Se+ BEC treated with 3-aminotriazole, an inhibitor of catalase activity, suggesting an association between catalase activity and mucus production. Both Se- and Se+ were infected with influenza A/Bangkok/1/79 and examined 24 h postinfection. Influenza-induced IL-6 production was greater while influenza-induced IP-10 production was lower in Se- BECs. In addition, influenza-induced apoptosis was greater in Se- BEC as compared to the Se+ BECs. These data demonstrate that selenium deficiency has a significant impact on the morphology and influenza-induced host defense responses in human airway epithelial cells.

Nutritional and botanical modulation of the inflammatory cascade--eicosanoids, cyclooxygenases, and lipoxygenases--as an adjunct in cancer therapy

Emerging on the horizon in cancer therapy is an expansion of the scope of treatment beyond cytotoxic approaches to include molecular management of cancer physiopathology. The goal in these integrative approaches, which extends beyond eradicating the affected cells, is to control the cancer phenotype. One key new approach appears to be modulation of the inflammatory cascade, as research is expanding that links cancer initiation, promotion, progression, angiogenesis, and metastasis to inflammatory events. This article presents a literature review of the emerging relationship between neoplasia and inflammatory eicosanoids (PGE2 and related prostaglandins), with a focus on how inhibition of their synthesizing oxidases, particularly cyclooxygenase (COX), offers anticancer actions in vitro and in vivo. Although a majority of this research emphasizes the pharmaceutical applications of nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors, these agents fail to address alternate pathways available for the synthesis of proinflammatory eicosanoids. Evidence is presented that suggests the inhibition of lipoxygenase and its by-products-LTB4, 5-HETE, and 12-HETE-represents an overlooked but crucial component in complementary cancer therapies. Based on the hypothesis that natural agents capable of modulating both lipoxygenase and COX may advance the efficacy of cancer therapy, an overview and discussion is presented of dietary modifications and selected nutritional and botanical agents (notably, omega-3 fatty acids, antioxidants, boswellia, bromelain, curcumin, and quercetin) that favorably influence eicosanoid production.

Micronutrients and innate immunity

Micronutrients such as zinc, selenium, iron, copper, beta-carotene, vitamins A, C, and E, and folic acid can influence several components of innate immunity. Select micronutrients play an important role in alteration of oxidant-mediated tissue injury, and phagocytic cells produce reactive oxidants as part of the defense against infectious agents. Thus, adequate micronutrients are required to prevent damage of cells participating in innate immunity. Deficiencies in zinc and vitamins A and D may reduce natural killer cell function, whereas supplemental zinc or vitamin C may enhance their activity. The specific effects of micronutrients on neutrophil functions are not clear. Select micronutrients may play a role in innate immunity associated with some disease processes. Future studies should focus on issues such as age-related micronutrient status and innate immunity, alterations of micronutrients in disease states and their effect on innate immunity, and the mechanisms by which micronutrients alter innate immunity.

Altered eicosanoid biosynthesis in selenium-deficient endothelial cells

Selenium (Se) is an integral part of the Se-dependent glutathione peroxidase (Se-GSH-Px) catalytic domain. By modulating the cellular levels of fatty acid hydroperoxides, Se-GSH-Px can influence key enzymes of arachidonic acid cascade, in this case cyclooxygenase (COX) and lipoxygenase (LOX). To investigate this phenomenon, the effects of cellular Se status on the enzymatic oxidation of arachidonic acid were investigated in bovine mammary endothelial cells (BMEC), which were cultured in either Se-deficient (-Se) or Se-adequate (+Se) media. When stimulated with calcium ionophore A23187, BMEC produced eicosanoids of both COX and LOX pathways. Compared with the Se-adequate cells, the production of prostaglandin I(2) (PGI(2)), prostaglandin F(2) (PGF(2alpha)), and prostaglandin E(2) (PGE(2)) was significantly decreased in Se-deficient cells, whereas the production of thromboxane A(2) (TXA(2)) was markedly increased in the -Se BMEC cultures. Although the enzymatic oxidation of arachidonic acid by the LOX pathway was found to be relatively less than by the COX pathway, the BMEC cultured in -Se media produced significantly more 15-hydroperoxyeicosatetraenoic acid (15-HPETE) than the +Se cells produced. Based on these results, we postulate that cellular Se status plays an important regulatory role in the enzymatic oxidation of arachidonic acid by the COX and LOX pathways. The altered eicosanoid biosynthesis, especially the overproduction of 15-HPETE, in -Se BMEC may be one of the underlying biochemical phenomena responsible for vascular dysfunction during Se deficiency.

Vitamin E exposure modulates prostaglandin and thromboxane production by avian cells of the mononuclear phagocytic system

The production of Prostaglandin E2 (PGE2) and Thromboxane B2 (TXB2) by turkey blood monocytes and a chicken mononuclear phagocytic cell line MQ-NCSU after exposure to vitamin E (VE) was examined. Turkey embryos were exposed in ovo to 0 and 10 international units (IU) of VE; blood monocytes were collected at 2 weeks of age and cultured. MQ-NCSU macrophage monolayers were exposed to 0, 0.1, 0.25, and 0.5 IU VE. The monocyte/macrophage cultures were exposed to 1 microgram/mL bacterial lipopolysaccharide (LPS). Non-stimulated parallel cultures were maintained as controls. The PGE2 and TXB2 levels were quantitated in culture supernatants by a competitive ELISA. Blood monocytes from the 10 IU VE poults produced lower PGE2 levels as compared with the 0 IU VE controls. Upon stimulation with LPS, monocytes from the 10 IU VE group exhibited levels of PGE2 that were higher than the 0 IU VE group. Levels of TXB2 were not quantitated in the poult blood monocyte culture supernatants. The PGE2 and TXB2 levels in the supernatant of the VE treated MQ-NCSU macrophage cultures were lower than the 0 IU VE controls. Stimulation with LPS resulted in increased PGE2 and TXB2 production by the VE-exposed macrophages. The results from this study suggest that in ovo or in vitro exposure with VE may either upregulate or downregulate PGE2 and TXB2 production by monocytes/macrophages, and that this production may be dependent upon the exposure to a variety of external stimuli and/or the state of macrophage activation.

Effect of vitamin E on expression of cyclooxygenase-2 in lipopolysaccharide-stimulated rat macrophages

To clarify the role of vitamin E (alpha-tocopherol) for the induction of cyclooxygenase-2 (COX-2) in rat macrophages stimulated by lipopolysaccharide (LPS), vitamin E-enriched macrophages were prepared by intraperitoneal injection of vitamin E for 6 days at a rate of 5 mg per day. The production of PGE2 was increased in dose- and time-dependent manners by addition of LPS in both control and vitamin E-enriched peritoneal macrophages. The maximum effect of LPS was observed in 12 h at concentration of 5 micrograms/ml. By analyzing COX-2 mRNA level by Northern blot and COX-2 enzyme mass and phosphotyrosine by Western blot, it was revealed that the increase of PGE2 production reflected the induction of COX-2 expression through activation of tyrosine kinase. Vitamin E failed to inhibit PGE2 production in LPS-stimulated macrophages; however, genistein, a tyrosine kinase inhibitor, completely inhibited the production at 100 microM. These results suggest that vitamin E does not inhibit COX-2 expression via LPS-mediated tyrosine kinase signal transduction pathway.

Modulation of the endogenous leukotriene production by fish oil and vitamin E

We investigated the effects of fish oil and vitamin E on the endogenous leukotriene production. 10 healthy volunteers were supplemented for 1 week with fish oil (containing 40 mg/kg body weight per day of eicosapentaenoic and docosahexaenoic acid), vitamin E (540 mg, i.e., 800 IU of D-alpha-tocopherol per day), or with both agents. Treatment resulted in a significant increase in the eicosapentaenoate concentration in red blood cell membranes and/or in the vitamin E concentration in serum. In addition, nine obese patients were investigated who were on a hypocaloric diet including 10 mg vitamin E/day for 8 weeks. This diet was associated with a significant decrease in serum vitamin E concentration. The urinary concentration of leukotriene E4 plus N-acetylleukotriene E4 served as a measure for the endogenous leukotriene production. Fish oil reduced leukotriene production in eight of the 10 healthy individuals. After vitamin E supplementation, urinary leukotrienes were significantly reduced in all of the healthy volunteers. The combination of vitamin E plus fish oil had no synergistic effect on leukotriene production in the individuals tested. The decrease in serum vitamin E concentration during the hypocaloric, 10 mg vitamin E/day diet was associated with an increase in urinary leukotrienes in 8 of the 9 obese patients. Urinary prostaglandin metabolites, determined as tetranorprostanedioic acid, increased or decreased in parallel with urinary leukotrienes in most individuals; however, changes were less pronounced than those observed with leukotrienes. We conclude that the endogenous leukotriene production can be reduced effectively by high doses of fish oil or vitamin E, whereas vitamin E depletion is associated with an increase in leukotriene generation.

Increased thromboxane A2 synthesis by rat lung neutrophils during selenium deficiency

Modulation of cellular hydroperoxide levels is considered one of the important physiological mechanisms for regulating the synthesis of prostaglandins (PGs) and leukotrienes (LTs) in mammalian cells. Both vitamin E and selenium (Se) have the potential to affect the concentration of peroxides and, thus, the biosynthesis of eicosanoids. To gain insight into some of the molecular mechanisms underlying the regulation of the arachidonic acid cascade by vitamin E and Se, we have investigated the influence of altered vitamin E and Se nutrition on the ability of polymorphonuclear leukocytes (PMNs) derived from endotoxin-challenged lung to secrete arachidonic acid metabolites. Selenium deficiency had no significant effect (p > 0.05) on lavage fluid levels of thromboxane (TX) B2, LTB4 or LTC4. Vitamin E deficiency, however, led to a significant increase in LTB4 recovered from lavage fluid while having no effect on TXB2. In contrast, Se deficiency, although producing no discernible effects on the production of LTB4, resulted in a significant increase in the release of TXB2 by PMNs. An increase in TXB2 release was seen in both in vitro-stimulated and nonstimulated PMNs. Vitamin E deficiency appeared to induce an enhancement of LTB4 release by PMNs but the increase was not statistically significant. No detectable levels of LTC4 were found in PMN cultures stimulated with either zymosan or A23187. Thus, these studies indicate that deficiencies of either Se or vitamin E lead to alterations in the metabolism of arachidonic acid in the lung.

Probucol as an antioxidant and antiatherogenic drug

Recently, interest has increased in the hypothesis that low-density lipoprotein (LDL) modified by oxidation may lead to the initiation and to the development of atherosclerosis. In vitro studies of cellular interactions with LDL have revealed that various cells, including endothelial cells and smooth muscle cells, can oxidize LDL. The biochemical changes in LDL may further enhance its atherogenic potential. In addition to these in vitro studies, there is in vivo evidence for oxidized LDL in atherosclerotic lesions and for circulating antibodies against oxidized LDL. Probucol, 4,4'-(isopropylidenedithio)bis(2,6-di-tert-butylphenol), is a widely used cholesterol-lowering drug. Recently, there has been accumulating evidence for other mechanisms of probucol's antiatherogenic effects apart from cholesterol-lowering action. Attention has especially focused on probucol's antioxidant action in the mechanism of antiatherogenesis. In the present article, we will summarize the antiatherogenic and antioxidant actions of probucol.

Modulation of the platelet thromboxane A2 and aortic prostacyclin synthesis by dietary selenium and vitamin E

Vitamin E and selenium (Se) interact synergistically as an important antioxidant defense mechanisms. Se, an essential component of glutathione peroxidase (GSH-Px) and vitamin E decompose fatty acid hydroperoxides and hydrogen peroxides generated by free radical reactions. Vitamin E and GSH-Px may modulate arachidonic acid metabolism and the activity of cyclooxygenase enzymes by affecting peroxide concentration. The balance between arterial wall prostacyclin (PGI2) production and platelet thromboxane (TX)A2 directly influences platelet activity. In order to elucidate the differential role of dietary vitamin E and Se in aortic PGI2 and platelet TXA2 synthesis, 1-mo-old F344 rats were fed semipurified diets containing different levels of vitamin E (0, 30, 200 ppm) and Se (0, 0.1, 0.2 ppm) for 2 mo. Thromboxane B2 (TXB2) and 6-keto-PGF1 alpha, were measured by radioimmunoassay (RIA) after incubation of whole blood and aortic rings at 37 degrees C for 10 and 30 min, respectively. Vitamin E deficiency reduced plasma vitamin E to 5-17% of control-fed rats, and supplementation in vitamin E-supplemented animals increased plasma GSH-Px by 17%, compared to vitamin E-deficient rats. Se and vitamin E supplementation did not have a similar effect on TXB2 and PGI2 synthesis. Se deficiency did not alter platelet TXB2 synthesis, but significantly decreased aortic PGI2 synthesis. It was necessary to supplement with both antioxidants in order to increase PGI2 synthesis. Se and vitamin E deficient groups had a higher TXB2/PGI2 ratio (0.17 +/- 0.08) compared to Se- and vitamin E-supplemented groups (0.03 +/- 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Fat-soluble vitamin nutrition for dairy cattle

The need for supplementation of dairy cow diets with fat-soluble vitamins depends on the amount of vitamins naturally present in the diet, the availability of dietary vitamins, and the vitamin utilization rate of the animal. Fresh forage contains ample amounts of the vitamin A precursor beta-carotene as well as vitamin E. Irrespective of the dietary amount, however, the availability of vitamins A, D, and E, as well as beta-carotene, can be adversely influenced by poor fat digestion, as commonly occurs due to enteric disease in young calves. In addition, high-grain diets appear to increase the amount of ruminal vitamin destruction and may thus increase vitamin requirements. The vitamin utilization rate may be increased by inflammation as well as dietary and environmental factors. The factors influencing vitamin availability and utilization rate should be considered when formulating rations. Because the vitamin requirement is variable, blood concentrations of vitamins should be monitored when conditions such as poor fertility, weak calves, and poor immune response are present.

Therapeutic potential of vitamin E in the pathogenesis of spontaneous atherosclerosis

Spontaneous atherosclerosis is largely an occlusive disease of medium-size arteries whose progression in a hyperlipidemic environment reflects chronic interactions among injury stimuli to the vessel wall and "responses to injury" by vascular tissue and certain blood components. Development of vessel lesions in animal models of spontaneous atherosclerosis and (at least in principle) in man largely reflects responses of three major cell types (vascular endothelial cells, vascular smooth muscle cells, monocytes-macrophages) as well as the content and distribution of lipids among various lipoprotein subclasses and the increased atherogenicity of modified (e.g., oxidized) lipoproteins. The severe clinical complications associated with spontaneous atherosclerosis, along with its rather common incidence in man, have focused attention on the prevention and therapy of this vascular disease state. Some pharmacological studies in animal models of spontaneous atherosclerosis and some retrospective epidemiological studies in man suggest that vitamin E, the principal (if not sole) lipid-soluble chain-breaking tissue antioxidant, might have therapeutic benefit as an antiatherosclerotic agent. This suggestion gains support from a variety of compelling in vitro evidence demonstrating direct influences of vitamin E on cells and lipoproteins likely involved in the pathogenesis of spontaneous atherosclerosis. Biochemical and cellular data indicate that the potential antiatherogenic activity of vitamin E could reflect its activities as a regulator of endothelial, smooth muscle, or monocyte-macrophage function, an inhibitor of endothelial membrane lipid peroxidation, a modulator of plasma lipid levels and lipid distribution among circulating lipoproteins, and a preventor of lipoprotein oxidative modification. On the other hand, there is a comparative lack of conclusive evidence from animal models regarding: (a) the importance to atherogenesis of vascular and cellular processes modulated by vitamin E; (b) the influence of vitamin E on these processes in vivo and, consequently, on the initiation/progression of spontaneous atherosclerosis. Therefore, pharmacologic investigation of vitamin E (and synthetic, vitamin E-like antioxidants) in nutritional and hyperlipidemic animal models of spontaneous atherosclerosis is required to establish whether any atherosclerotic impact is associated with vitamin E and, if so, what the mechanistic basis of the therapeutic benefit is. Such a line of experimental inquiry should also increase our understanding of the pathogenesis of atherosclerotic vessel disease per se.

Prostaglandin synthesis is increased in selenium supplemented human mesangial cells despite suppression of phospholipase A2-activity

Antioxidants play an important role in the regulation of phospholipid hydrolysis and arachidonate metabolism. Supplementation of cultured human mesangial cells with selenium resulted in suppression of phospholipase A2-activity and significantly increased production of three major prostaglandins. However, prostacyclin synthesis benefits most from selenium supplementation, suggesting that there is a specific action of selenium-dependent glutathione peroxidase on this pathway. Like in endothelial cells, production of platelet activating factor is significantly inhibited by selenium supplementation.