Effects of oolonghomobisflavan A on oxidation of low-density lipoprotein.

Oxidation of low-density lipoprotein (LDL) by reactive oxygen species (ROS) and reactive nitrogen species (RNS) has been suggested to be involved in the onset of atherosclerosis. Oolong tea contains unique polyphenols including oolonghomobisflavan A (OFA). In this study, the effects of OFA on LDL oxidation by ROS and RNS were investigated in vitro. OFA suppressed formation of cholesterol ester hydroperoxides in LDL oxidized by peroxyl radical and peroxynitrite, and formation of thiobarbituric acid reactive substances in LDL oxidized by Cu2+. In addition, OFA inhibited fragmentation, carbonylation, and nitration of apolipoprotein B-100 (apo B-100) in the oxidized LDL, in which heparin-binding activity of apo B-100 was protected by OFA. Our results suggest that OFA exhibits antioxidant activity against both lipid peroxidation and oxidative modification of apo B-100 in LDL oxidized by ROS and RNS. Polyphenols in oolong tea may prevent atherosclerosis by reducing oxidative stress.

Antioxidant activity of aminodiarylamines in the thieno[3,2-b]pyridine series: radical scavenging activity, lipid peroxidation inhibition and redox profile.

The antioxidant activity of the aminodi(hetero)arylamines, prepared by C-N coupling of the methyl 3-aminothieno[3,2-b]pyridine-2-carboxylate with bromonitrobenzenes and further reduction of the obtained nitro compounds, was evaluated by chemical, biochemical and electrochemical assays. The aminodi(hetero)arylamine with the amino group ortho to the NH and a methoxy group in para, was the most efficient in radical scavenging activity (RSA, 63 µM) and reducing power (RP, 33 µM), while the aminodiarylamine with the amino group in para to the NH, gave the best results in ß-carotene-linoleate system (41 µM) and inhibition of formation of thiobarbituric acid reactive substances in porcine brain cells homogenates (7 µM), with EC50 values even lower than those obtained for the standard trolox. This diarylamine also presented the lowest oxidation potential, lower than the one of trolox, and the highest antioxidant power in the electrochemical assays. The para substitution with an amino group enables higher antioxidant potential.

Prevention of bleomycin-induced lung fibrosis in mice by a novel approach of parallel inhibition of cyclooxygenase and nitric-oxide donation using NCX 466, a prototype cyclooxygenase inhibitor and nitric-oxide donor.

Cyclooxygenase (COX)-inhibiting nitric oxide (NO) donors (CINODs) are designed to inhibit COX-1 and COX-2 while releasing NO. COX inhibition is responsible for anti-inflammatory and pain-relieving effects, whereas NO donation can improve microcirculation and exert anti-inflammatory and antioxidant actions. In an in vivo mouse model of bleomycin-induced lung fibrosis, we evaluated whether a prototype CINOD compound, (S)-(5S)-5,6-bis(nitrooxy)hexyl)2-(6-methoxynaphthalen-2-yl)propanoate (NCX 466), may show an advantage over naproxen, its congener drug not releasing NO. Bleomycin (0.05 IU) was instilled intratracheally to C57BL/6 mice, which were then treated orally with vehicle, NCX 466 (1.9 or 19 mg/kg), or an equimolar dose of naproxen (1 or 10 mg/kg) once daily for 14 days. Afterward, airway resistance, assumed as lung stiffness index, was assayed, and lung specimens were collected for analysis of lung inflammation and fibrosis. NCX 466 and naproxen dose-dependently prevented bleomycin-induced airway stiffness and collagen accumulation. NCX 466, at the highest dose, was significantly more effective than naproxen in reducing the levels of the profibrotic cytokine transforming growth factor-ß and the oxidative stress markers thiobarbituric acid reactive substance and 8-hydroxy-2'-deoxyguanosine. NCX 466 also decreased myeloperoxidase activity, a leukocyte recruitment index, to a greater extent than naproxen. A similar inhibition of prostaglandin E2 was achieved by both compounds. In conclusion, NCX 466 has shown a significantly higher efficacy than naproxen in reducing lung inflammation and preventing collagen accumulation. These findings suggest that COX inhibition along with NO donation may possess a therapeutic potential in lung inflammatory diseases with fibrotic outcome.

Protective role of tetrahydrocurcumin against erythromycin estolate-induced hepatotoxicity.

Tetrahydrocurcumin (THC), one of the major metabolites of curcumin, was investigated for its possible hepatoprotective effect in Wistar rats against erythromycin estolate-induced toxicity. Oral administration of THC significantly prevented the occurrence of erythromycin estolate-induced liver damage. The increased level of serum enzymes (aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP)), bilirubin, cholesterol, triglycerides, phospholipids, free fatty acids and plasma thiobarbituric acid reactive substances (TBARS) and hydroperoxides observed in rats treated with erythromycin estolate were very much reduced in rats treated with THC and erythromycin estolate. This biochemical observation were supplemented by histopathological examination of liver section. Results of this study revealed that THC could afford a significant protection against erthromycin estolate-induced hepatocellular damage. Tetrahydrocurcumin had a better protective effect when compared with Silymarin, a reference drug.

Inhibition of lipid peroxidation by prostaglandin oligomeric derivatives.

The inhibition of lipid peroxidation by oligomeric derivatives synthesized from prostaglandin E1 (PGE1) and PGB2 was studied using two rat models. In an in vitro model, the brain was exposed to decapitation-ischemia, the cortex was removed and homogenized, and the formation of thiobarbituric acid reactive substances (TBAR) was measured after exposing the homogenate to in vitro reoxygenation either in the presence or absence of oligomers. It was found that these oligomers could inhibit lipid peroxidation, and that their activities were higher than that of superoxide dismutase (SOD). In an in vivo administration model, either the oligomer or the vehicle was injected i.p. 30 min before decapitation. The brain was exposed to decapitation-ischemia, the cortex was homogenized and exposed to 'in vitro' reoxygenation, after which TBAR value was determined. Ester-type compounds had a greater activity than free-acid type compounds in inhibiting lipid peroxidation. A possible mechanism of the protective effect of these oligomers in ischemia/reperfusion injury may be to scavenge oxygen free radicals.

Altered antioxidant status in ischemic/reperfused rabbit myocardium: reperfusion time-course study.

A progressive impairment in antioxidant status of rabbit hearts was observed when a fixed period (40 mins) of ischemia produced by coronary artery ligation was followed by increasing periods of reperfusion. This was reflected in a reduction in myocardial glutathione levels and an increase in glutathione depletion and production of thiobarbituric acid-reactive substances following in vitro oxidative challenge with t-butylhydroperoxide. Correlation analysis, in which activities of antioxidant enzymes were viewed in relation to biochemical indices of antioxidant status, indicated the functionally relevant suppression of Cu,Zn-superoxide dismutase and glutathione reductase activities in ischemic/reperfused tissues. These results and the demonstration of significant decreases in the activity of glutathione-dependent antioxidant enzymes under acidotic conditions suggest that transient impairment in the functioning of antioxidant enzymes may be involved in the triggering of irreversible myocardial ischemia-reperfusion injury.

Release of 2-thiobarbituric acid reactive products from glutamate or deoxyribonucleic acid by 1,2,4-benzenetriol or hydroquinone in the presence of copper ions.

Cytotoxic effects of various quinone compounds are thought to be due to the formation of semiquinone free radicals. Hydroquinone and 1,2,4-benzenetriol in the presence of copper ions release from glutamate or DNA aldehydic products capable of reacting with 2-thiobarbituric acid (TBA). The formation of TBA reactive products (TBAR) was greater in the presence of 1,2,4-benzenetriol in comparison with hydroquinone. Complete inhibition of formation of TBAR from glutamate by 1,2,4-benzenetriol and copper was observed in the presence of catalase, thiourea and mannitol. Albumin and superoxide dismutase offered substantial protection. Complete protection of formation of TBAR from DNA was observed in the presence of catalase and thiourea. Presence of albumin, mannitol and superoxide dismutase caused only partial inhibition. The formation of TBAR from glutamate or DNA is dependent on copper ion concentration. The present data indicate that hydroquinone and 1,2,4-benzenetriol in the presence of copper ions can lead to the formation of reactive hydroxyl radicals which can release TBAR from glutamate or DNA.

Mutual antagonism of behavioral effects of TRH and thiobarbiturate on an operant task in rhesus monkeys.

Similar excitatory or depressant response rate dependent effects on monkeys responding on a variable interval reinforcement schedule were observed following intravenous administration of either thyrotropin releasing hormone (TRH) or thiobarbiturate. However, these agents were mutally antagonistic when given together even though the response rate altering effects of each agent were in the same direction. These findings establish an additional behavioral effect of exogenously administered TRH in primates and suggest that barbiturates might alter behavior in part through an interaction with brain TRH receptive mechanisms.