Estimation of hydroxyl radical generation by salicylate hydroxylation method in multiple organs of mice exposed to whole-body X-ray irradiation

The role of iron-induced fibrin in the pathogenesis of Alzheimer's disease and the protective role of magnesium

Amyloid hypothesis of Alzheimer's disease (AD) has recently been challenged by the increasing evidence for the role of vascular and hemostatic components that impair oxygen delivery to the brain. One such component is fibrin clots, which, when they become resistant to thrombolysis, can cause chronic inflammation. It is not known, however, why some cerebral thrombi are resistant to the fibrinolytic degradation, whereas fibrin clots formed at the site of vessel wall injuries are completely, although gradually, removed to ensure proper wound healing. This phenomenon can now be explained in terms of the iron-induced free radicals that generate fibrin-like polymers remarkably resistant to the proteolytic degradation. It should be noted that similar insoluble deposits are present in AD brains in the form of aggregates with Abeta peptides that are resistant to fibrinolytic degradation. In addition, iron-induced fibrin fibers can irreversibly trap red blood cells (RBCs) and in this way obstruct oxygen delivery to the brain and induce chronic hypoxia that may contribute to AD. The RBC-fibrin aggregates can be disaggregated by magnesium ions and can also be prevented by certain polyphenols that are known to have beneficial effects in AD. In conclusion, we argue that AD can be prevented by: (1) limiting the dietary supply of trivalent iron contained in red and processed meat; (2) increasing the intake of chlorophyll-derived magnesium; and (3) consumption of foods rich in polyphenolic substances and certain aliphatic and aromatic unsaturated compounds. These dietary components are present in the Mediterranean diet known to be associated with the lower incidence of AD and other degenerative diseases.

Methylglyoxal augments angiotensin II-induced contraction in rat isolated carotid artery

Methylglyoxal (MGO), a metabolite of glucose, accumulates in vascular tissues of a hypertensive animal. In the present study, we examined the effect of MGO on angiotensin (Ang) II-induced contraction of rat carotid artery. Treatment of carotid artery with MGO (420 µM, 30 min) significantly augmented Ang II (0.1 to 30 nM)-induced concentration-dependent contraction. The effect was abolished by the removal of endothelium. BQ-123 (1, 5 µM), an endothelin A-receptor blocker, had no effect on the MGO-induced enhancement of Ang II-induced contraction. AL8810 (1 µM), a prostaglandin F(2α)-receptor blocker, or SQ29548 (1 µM), a thromboxane A(2)-receptor blocker, was also ineffective. However, tempol (10 µM), a superoxide scavenger, and catalase (5000 U/mL), which metabolizes hydrogen peroxide to water, significantly prevented the effect of MGO. Combined MGO and Ang II treatment increased reactive oxygen species (ROS) production. Apocynin (10 µM) or gp91ds-tat (3 µM), an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, significantly prevented the effect of MGO. Gp91ds-tat or an Ang II type 1-receptor (AT1R) blocker, losartan (10 µM), prevented the MGO-mediated increased ROS production. The present study revealed that MGO augments Ang II-induced contraction by increasing AT1R-mediated NADPH oxidase-derived superoxide and hydrogen peroxide production in endothelium of rat carotid artery.

Influences of organic solvents on CYPMPO-electron spin resonance spectra in in vitro radical generating systems

Estimation of radical scavenging capacity of lipophilic antioxidants by electron spin resonance (ESR) in vitro is a challenging issue due to their poor solubility in aqueous radical generating and measuring systems. Water-miscible organic solvents are used for this purpose. A novel radical trapping agent, 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO), that has practical advantages over well-known trapping agents was synthesized. However, no available data for the influence of solvents in an ESR system that uses CYPMPO has been presented. The influences of six water-miscible organic solvents, acetonitrile (AcN), acetone, dimethyl sulfoxide (DMSO), ethanol, polyethylene glycol (PEG), and dimethoxyethane (DME), on ESR responses to Fenton Fe(2+)/H (2)O(2 )OH· and hypoxanthine/xanthine oxidase superoxide generation systems in vitro were studied. Reduction of the ESR signal to CYPMPO-OH· adducts by 55.86 ± 5.95 and 83.17 ± 2.50% compared with the control was observed in the presence of AcN and acetone, respectively, at a final concentration of 5% (v/v). AcN of less than 1% had minimal effects. DMSO, ethanol, PEG and DME at 5% (v/v) strongly inhibited the ESR signals and/or caused derangement in the signal patterns. The six water-miscible solvents at 5% (v/v) had no influence on the ESR spectra of CYPMPO-superoxide adducts. From these results, AcN, at less than 1% (v/v), is a useful water-miscible organic solvent for assessing radical scavenging capacities of lipophilic compounds in the CYPMPO-Fenton Fe(2+)/H(2)O(2) OH· reaction system in an ESR assay. Any of the solvents used in the present study can be used in a hypoxanthine/xanthine oxidase superoxide generation system.

Towards an integrated microfluidic device for spaceflight clinical diagnostics Microchip-based solid-phase extraction of hydroxyl radical markers

A microchip-based solid-phase extraction method for biological fluid small molecule analysis has been developed. Using a commercially available copolymer packed into a microchip channel, extraction and preconcentration of 2,3-dihydroxybenzoic acid (DHBA) and 2,5-DHBA from saliva was achieved. The metabolites, formed from salicylic acid by reactive oxygen species, can be used as markers of oxidative stress. The results show high recovery of both metabolites (>90+/-15% for spiked saliva) with an 80-fold concentration enhancement possible. The eluent is directly analyzed using capillary electrophoresis, with good resolution for the two metabolites. This study demonstrates the feasibility of future integrated microdevices for spaceflight small molecule biomarker analysis.

Estimation of hydroxyl radical generation by salicylate hydroxylation method in kidney of mice exposed to ferric nitrilotriacetate and potassium bromate

Hydroxyl radical (*OH) generation in the kidney of mice treated with ferric nitrilotriacetate (Fe-NTA) or potassium bromate (KBrO3) in vivo was estimated by the salicylate hydroxylation method, using the optimal experimental conditions we recently reported. Induction of DNA lesions and lipid peroxidation in the kidney by these nephrotoxic compounds was also examined. The salicylate hydroxylation method revealed significant increases in the *OH generation after injection of Fe-NTA or KBrO3 in the kidneys. A significant increase in 8-hydroxy-2'-deoxyguanosine in nuclei of the kidney was detected only in the KBrO3 treated mice, while the comet assay showed that the Fe-NTA and KBrO3 treatments both resulted in significant increases in DNA breakage in the kidney. With respect to lipid peroxidation, the Fe-NTA treatment enhanced lipid peroxidation and ESR signals of the alkylperoxy radical adduct. These DNA breaks and lipid peroxidation mediated by *OH were diminished by pre-treatment with salicylate in vivo. These results clearly demonstrated the usefulness of the salicylate hydroxylation method as well as the comet assay in estimating the involvement of *OH generation in cellular injury induced by chemicals in vivo.