Cigarette smoke exposure alters [14C]arachidonic acid metabolism in aortas and platelets of rats fed various levels of selenium and vitamin E

Methods for imaging and detecting modification of proteins by reactive lipid species

Products of lipid peroxidation are generated in a wide range of pathologies associated with oxidative stress and inflammation. Many oxidized lipids contain reactive functional groups that can modify proteins, change their structure and function, and affect cell signaling. However, intracellular localization and protein adducts of reactive lipids have been difficult to detect, and the methods of detection rely largely on antibodies raised against specific lipid-protein adducts. As an alternative approach to monitoring oxidized lipids in cultured cells, we have tagged the lipid peroxidation substrate arachidonic acid and an electrophilic lipid, 15-deoxy-Delta(12,14)-prostaglandin-J2 (15d-PGJ2), with either biotin or the fluorophore BODIPY. Tagged arachidonic acid can be used in combination with conditions of oxidant stress or inflammation to assess the subcellular localization and protein modification by oxidized lipids generated in situ. Furthermore, we show that reactive lipid oxidation products such as 15d-PGJ2 can also be labeled and used in fluorescence and Western blotting applications. This article describes the synthesis, purification, and selected application of these tagged lipids in vitro.

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.

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.

Selenium deficiency inhibits prostacyclin release and enhances production of platelet activating factor by human endothelial cells

Selenium is an essential component of glutathione peroxidase, an enzyme which protects cells against peroxidation and controls concentrations of intracellular peroxides. Since selenium deficiency is clinically associated with an increased degree of atherosclerosis, the effects of selenium deficiency on prostacyclin (PGI2) and platelet activating factor (PAF) production by cultured human umbilical vein endothelial cells (HUVEC) were investigated. In selenium-deficient HUVEC, histamine-induced PGI2 synthesis was significantly decreased when compared to selenium-supplemented HUVEC; in contrast, histamine-induced PAF production was increased by selenium deficiency. Histamine-induced inositol trisphosphate and [Ca2+]i responses and the conversion of PGG2 and PGH2 to PGI2 were not altered by selenium deficiency. However, selenium deficiency decreased the conversion of exogenous arachidonate to PGI2 and markedly suppressed glutathione peroxidase activity. These results suggest that selenium deficiency, by decreasing glutathione peroxidase activity, makes HUVEC susceptible to peroxide-induced inhibition of the cyclooxygenase activity of PGH2 synthase, resulting in decreased PGI2 production. These changes may alter platelet function in vivo and thus play a role in the increased incidence of atherosclerosis reported in selenium-deficient individuals.

[Thromboxane concentrations in the arterial blood of cigarette smokers]

Thromboxane concentrations were investigated in the arterial plasma of 44 patients (25 smokers, 19 nonsmokers) with chronic obstructive arterial disease (COAD) of the lower extremities, documented by angiography. The thromboxane levels were measured by radioimmunoassay. The results indicate that smokers with COAD have significantly higher thromboxane levels than nonsmokers with COAD. The potential effect of nicotine on thromboxane is discussed.