Oxidative stress lipid hydroperoxides

Oxidative stress Lipid oxidation Oxygen absorption Manometric, polarographic Diene conjugation HPLC, spectrophotometry (234 nm) Lipid hydroperoxides HPLC, GC-MS, chemiluminescence, spectrophotometry Iodine liberation Titration Thiocyanate Spectrophotometry (500 nm) Hydrocarbons GC Cytotoxic aldehydes LPO-586, HPLC, GC, GC-MS Hexanal and related end products Sensory, physicochemical, Cu(II) induction method, GC TBARS Spectrophotometry (532-535 nm), HPLC Rancimat Conductivity F2-iP GC/MS, HPLC/MS, immunoassays... 

Mincing, cooking and maturing expose meat products to oxidative stress for a long time so that antioxidants added for lipid protection are slowly destroyed on storage. Onion juice is a powerful antioxidant in meat products, more efficient than garlic juice. Lipid hydroperoxides are reduced to inactive hydroxyl derivatives by reaction with sulphur compounds present in those juices. 

Exposure of cardiolipin to oxygen gas resulted in a substantial loss of the lipid and most of the degradation products were hydroperoxide derivatives. Even though we have not done the comparative experiment, our experience tells us that cardiolipin is more sensitive to oxidative stress than free linoleic acid or trilinolein. Taking into account that mitochondria is the site where reactive oxygen species are often produced, we propose that peroxidation of cardiolipin may easily take place once the intracellular oxidative stress occurs. 

Studies carried out with complete cells in vivo, cell membranes and other cell fractions point to the selective oxidation of phosphatidylserine (26) to a hydroperoxide (PS-OOH) on oxidative stress caused by toxic agents such as H2O2, t-BuOOH and cumyl hydroperoxide (27). Formation of PS-OOH is observed during apoptosis. These phenomena are important because of the cytotoxic effects of various peroxides used in commercial products coming into direct contact with the human body, as is the case of epidermal keratinocytes in contact with cosmetic formulations" ". The toxic effects of f-BuOOH are associated with vasoconstriction and damage to the vascular smooth muscles ". Global determination methods for primary lipid oxidation products are discussed in Section IV.B. 

Cells may show a low level of autofluorescence at 413 nm when irradiated at 324 nm. This fluorescence dramatically increases when d -parinaric acid (159) is incorporated into the cell membrane, either by intercalation or esteriflcation. Exposure to oxidation stress of cells enriched with the 159 fluorescent probe causes diminution of the fluorescence intensity and is directly correlated with formation of lipid hydroperoxides. Addition of antioxidants, such as Vitamin E (21), abates fluorescence diminution. A blanc run of cells enriched with 159 but not subjected to oxidation stress is necessary to follow the degradation of 159 when exposed to UV irradiation. This method was applied to track lipid oxidation during apoptosis and other phenomena, triggered by toxic compounds such as H2O2, f-BuOOH and cumyl hydroperoxide (27)"° 11,424... 

Lipid hydroperoxides are also generated in singlet molecular oxygen mediated oxidations and by the action of enzymes such as lipoxygenases and cyclooxygenases. Chemiluminescence (CL) arising from lipid peroxidation has been used as a sensitive detector of oxidative stress both in vitro and in vivo . Several authors have attributed ultra-weak CL associated with lipid peroxidation to the radiative deactivation of O2 and to triplet-excited carbonyls (63, 72) (equations 35 and 36) " . It has been proposed that the latter emitters arise from the thermolysis of dioxetane intermediates (61, 62) (equation 35), endoperoxide (73) (equation 37) and annihilation of aUtoxyl, as well as peroxyl radicals ... 

Perhaps the main peroxide-induced alterations, within cells and tissues, are those that affect calcium and sodium homeostasis. Na, K-ATPase, which is considered as the core of the sodium pump , is strongly affected by peroxides, and especially by lipid hydroperoxides [137-139]. This implies that oxidative stress will usually be associated with cellular edema . Alternatively, activation of the Na, K-ATPase of vascular endothelia, such as the blood-brain barrier, will result in extracellular edema on the antiluminal side of the endothelium, due to massive influx of sodium ions [119]. 

In correlation with the nature of compounds that can induce ARE-driven transcription, many of the proteins whose expression is mediated by the ARE have an endogenous role in regulating cellular redox status and protecting the cell from oxidative damage. Enzymes such as GST, NQOl, and HO-1 function to detoxify harmful by-products of oxidative stress, including lipid and DNA base hydroperoxides (29,30), quinones (31), and heme-containing molecules (32). The induction of enzymes involved in GSH biosynthesis leads to an increase in cellular GSH levels that provides a buffer against oxidative insult (2). 

There is considerable body of (indirect) evidence which makes oxidative stress one of the best accepted hypothesis for explaining the cause of Parkinson s disease. For example, the Fe(II)/Fe(III) ratio in the substantia nigra is shifted from 2 1 in the normal brain to 1 2 in Parkinsonian brain.131,132 In the Parkinsonian brain several enzymes which constitute the antioxidative defence mechanisms (glutathione peroxidase, catalase) have a decreased activity, while the activity of superoxide dismutase is increased, relative to the normal brain.133 Furthermore, specific products of radical damage, such as lipid hydroperoxides, were detected at a 10-fold increased level in the Parkinsonian brain.134... 

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