In vitro and in vivo inhibition of microsomal lipid peroxidation by MA-631

Oxidation Kinetics of Fluorescent Membrane Lipid Peroxidation Indicators

The oxidation of the cellular membrane through lipid peroxidation (LPO) is linked to aging and disease. Despite the physiological importance, the chemical mechanisms underlying LPO and oxidative reactions in membranes in general remain incompletely understood, and challenges exist in translating LPO inhibitor efficacies from in vitro to in vivo. The complexity of LPO, including multiple oxidation reactions in complex membrane environments and the difficulty in quantifying reaction kinetics, underlies these difficulties. In this work, we developed a robust and straightforward method for quantifying the oxidation rate kinetics of fluorescent molecules and determined the oxidation kinetics of widely fluorophores used as indicators of membrane LPO, diphenylhexatriene (DPH), BODIPY-C11, and Liperfluo. The measurement is initiated by lipoxygenase, which provides chemical specificity and enables a straightforward interpretation of oxidation kinetics. Our results reveal that the membrane composition significantly impacts the observed kinetics oxidation in DPH and BODIPY-C11 but not Liperfluo. Reaction mechanisms for their lipid peroxide-induced oxidation are proposed. This work provides a foundation for the quantitative analysis of LPO with fluorescence and extricating the complexity of oxidation reactions within membranes.

Evaluating the In Vitro Potential of Natural Extracts to Protect Lipids from Oxidative Damage

Lipid peroxidation is a chemical reaction known to have negative impacts on living organisms' health and on consumer products' quality and safety. Therefore, it has been the subject of extensive scientific research concerning the possibilities to reduce it, both in vivo and in nonliving organic matrices. It can be started by a variety of oxidants, by both ROS-dependent and -independent pathways, all of them reviewed in this document. Another feature of this reaction is the capacity of lipid peroxyl radicals to react with the non-oxidized lipids, propagating the reaction even in the absence of an external trigger. Due to these specificities of lipid peroxidation, regular antioxidant strategies-although being helpful in controlling oxidative triggers-are not tailored to tackle this challenge. Thus, more suited antioxidant compounds or technologies are required and sought after by researchers, either in the fields of medicine and physiology, or in product development and biotechnology. Despite the existence of several laboratory procedures associated with the study of lipid peroxidation, a methodology to perform bioprospecting of natural products to prevent lipid peroxidation (a Lipid Peroxidation Inhibitory Potential assay, LPIP) is not yet well established. In this review, a critical look into the possibility of testing the capacity of natural products to inhibit lipid peroxidation is presented. In vitro systems used to peroxidize a lipid sample are also reviewed on the basis of lipid substrate origin, and, for each of them, procedural insights, oxidation initiation strategies, and lipid peroxidation extent monitoring are discussed.

Difference in vulnerability of cerebral arterial bifurcation and straight portion for development of endothelial damage

Cerebral atherosclerotic changes develop most commonly on the lateral side of the bifurcation, one of the sites where the wall shear stress is lowest in the cerebral arteries. Endothelial cells exposed to the lower shear stress appear to be more vulnerable to stimuli such as free radicals. We hypothesized that the difference in endothelial vulnerability on cerebral arteries may be involved in the local preference of atherogenesis. To clarify this hypothesis, the present study was carried out by using a laser-dye technique that causes cell damage by heat and free radicals. A helium-neon laser in the presence of circulating Evans blue was used to illuminate three sites of the rat middle cerebral artery; the straight portion, the apex of the bifurcation, and the lateral side of the bifurcation. The magnitude of endothelial damage was morphologically estimated with the electron microscope. After the laser irradiation, the straight portion and the lateral side of the bifurcation developed severe endothelial damage. However, the apex of the bifurcation developed no appreciable damage, showing significantly milder changes compared with other sites. The results suggest that endothelial cells are more vulnerable to stimuli by free radicals at the straight portion and the lateral side of the bifurcation than at the apex. We conclude that the imbalance between the strength of stress stimuli, such as free radicals, and the vulnerability of endothelium is likely to be one of the key requirements for the development of cerebral atherosclerotic changes.

Inhibition of rat microsomal lipid peroxidation by the oral administration of D002

The effect of D002, a defined mixture of higher primary alcohols purified from bee wax, on in vivo and in vitro lipid peroxidation was studied. The extent of lipid peroxidation was measured on the basis of the levels of thiobarbituric acid reactive substances (TBARS). When D002 (5-100 mg/kg body weight) was administered orally to rats for two weeks, a partial inhibition of the in vitro enzymatic and non-enzymatic lipid peroxidation was observed in liver and brain microsomes. Maximal protection (46%) occurred at a dose of 25 mg/kg. D002 behaved differently depending on both the presence of NADPH and the integrity of liver microsomes, which suggests that under conditions where microsomal metabolism was favored the protective effect of D002 was increased. D002 (25 mg/kg) also completely inhibited carbon tetrachloride- and toluene-induced in vivo lipid peroxidation in liver and brain. Also, D002 significantly lowered in a dose-dependent manner the basal level of TBARS in liver (19-40%) and brain (28-44%) microsomes. We conclude that the oral administration of D002 (5, 25 and 100 mg/kg) for two weeks protected rat liver and brain microsomes against microsomal lipid peroxidation in vitro and in vivo. Thus, D002 could be useful as a dietary natural antioxidant supplement. More studies are required before these data can be extrapolated to the recommendation for the use of D002 as a dietary antioxidant supplement for humans.

Effect of herbal mixture student Rasayana on lipoxygenase activity and lipid peroxidation

Brain cellular functions are affected by free radicals. Arachidonic acid and its 12-lipoxygenase metabolites have been proposed as important in enhancing long-term potentiation associated with learning. It has been reported that Student Rasayana (SR), an herbal mixture, improves brain functions. In this study we evaluated the antioxidant capacity of SR and its effect on lipoxygenase activity. Both alcoholic and aqueous extracts of SR inhibited enzymatic- and nonenzymatic-induced microsomal lipid peroxidation in a concentration-dependent manner. The agent concentrations (micrograms/mL) that produced 50% inhibition (IC50) of enzymatic- and nonenzymatic-induced microsomal lipid peroxidation, respectively, were 99.1 +/- 3.9 and 1992.0 +/- 122.7 for the aqueous extract, and 17.7 +/- 0.9 and 646.7 +/- 79.7 for the alcoholic extract. The aqueous extract inhibited soyabean lipoxygenase (SLP)-induced LDL oxidation in a concentration-dependent manner (IC50: 515.5 +/- 11.5), whereas the alcoholic extract enhanced SLP-induced LDL oxidation. Simultaneous addition of aqueous and alcoholic extracts inhibited SLP-induced LDL oxidation. The alcoholic extract (but not the aqueous extract) enhanced the ability of SLP to induce oxidation of linoleic acid. Rats fed 2% (w:w) SR showed inhibition of toluene-induced brain microsomal lipid peroxidation. These results suggest SR improves brain functions through scavenging free radicals as well as increasing the second messenger for long-term potentiation.