Free-radical scavenging by Ouratea parviflora in experimentally-induced liver injuries

Abstract

The antioxidant potential of crude extracts and fractions from leaves of Ouratea parviflora, a Brazilian medicinal plant used for the treatment of inflammatory diseases, was investigated in vitro through the scavenging of radicals 2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH), hydroxyl radical (HO^?), superoxide anion (O₂^??), and lipid peroxidation in rat liver homogenate. The crude extract (CEOP) and hydro-alcoholic fraction (OP4) showed strong inhibitory activity toward lipid peroxidation induced by tert-butyl peroxide (IC₅₀ = 2.3 ± 0.2 and 1.9 ± 0.1 μg/ml, respectively). The same products exhibited a strong concentration-dependent inhibition of deoxyribose oxidation (14.9 ± 0.2 and 0.2 ± 0.1 μg/ml, respectively), and also showed a considerable antioxidant activity against O₂^??(87.3 ± 0.1 and 73.1 ± 0.4 μg/ml, respectively) and DPPH radicals (55.4 ± 0.3 and 38.3 ± 0.4 μg/ml, respectively). The protective effects of CEOP and OP4 were also studied in mouse liver. CCl₄ significantly increased (by 90%) levels of lipid hydroperoxides, carbonyl protein content (64%), DNA damage index (133%), aspartate aminotransferase (261%), alanine aminotransferase (212%), catalase activity (23%), and also caused a decrease of 60% in GSH content. The results showed that CEOP and OP4 exerted cytoprotective effects against oxidative injury caused by CCl₄ in rat liver, probably related to the antioxidant activity showed by the in vitro free radical scavenging property.     

The role of oxidative stress in an equine model of human asthma

Abstract

Equine recurrent airway obstruction (RAO) is a naturally occurring respiratory disease in horses with many similarities to human asthma and, as a result, has been used as an animal model of this disease. Oxidative stress has been demonstrated to occur in a range of respiratory diseases in human beings including asthma. Quantitatively, horses have a greater non-enzymatic antioxidant capacity in the pulmonary epithelial lining fluid compared to human beings due to high ascorbic acid concentrations, which reflects their ability to synthesise ascorbic acid. Consequently, a greater oxidative load is likely to be required to induce oxidative stress in horses compared to human beings. Induction of acute neutrophilic airway inflammation in RAO horses by exposure to organic dust does not result in marked pulmonary oxidative stress. However, with a more prolonged inflammatory response, the antioxidant capacity is depleted and oxidative stress occurs. Despite the clear evidence of oxidative stress in RAO, there is currently limited data linking oxidative stress with a causal role in the development of the pathophysiological features of RAO, namely airway obstruction, airway hyper-responsiveness, airway inflammation and mucus accumulation. However, pathways do exist whereby oxidants could potentially augment the production of important mediators in RAO. Further work is required to ascertain the benefits of antioxidant supplementation in RAO and to determine the role of oxidative stress in the pathogenesis of the disease. Given the similarities with human asthma, results from RAO horses could enhance the understanding of the role of oxidative stress in human asthma.     

A monoclonal antibody recognizing the chlorohydrin derivatives of oleic acid for probing hypochlorous acid involvement in tissue injury

Summary

A monoclonal antibody against hypochlorous acid—modified oleic acid has been raised to investigate involvement of HOCI in tissue injury. Mice were immunized with an isomeric mixture of chlorohydrin derivatives of oleic acid (18:0-chlorohydrin) conjugated to keyhole limpet haemocyanin (CH-KLH). The chlorohydrin was formed by the treatment of oleic acid with hypochlorous acid. Monoclonal antibodies were raised and the fusion was screened with 18:0-chlorohydrin-bovine serum albumin (CH-BSA) conjugate. A number of antibody-secreting clones were identified and the supernatants were characterized by binding studies and dose-response curves. In ELISA, mAb CH-1 had an equivalent titre when either the chlorohydrin or bromohydrin derivative of oleic acid, complexed to bovine serum albumin, was used as screening antigen. The mAb CH-1 recognition of CH-BSA was competed with chlorohydrin and bromohydrin conjugates of BSA and KLH. Similarly, free 18:0-chlorohydrin and the 18:0-chlorohydrin-phosphatidyl choline treated with hypochlorous acid competed with mAb CH-1 binding. The mAb CH-1 also recognised the chlorohydrin derivative of linoleic acid and chlorohydrin formed from palmitoyl, oleyl phosphatidyl choline but with a decreased avidity. Weak cross-reactivity was observed with hydroxy-linoleic acid and linoleic acid hdroperoxide, either as free fatty acid or in phosphatidyl choline. There was minimal competitive binding of mAb CH-1 to free oleic acid, 16:0/18:1 phosphatidylcholine, cholesterol, or cholesterol chlorohydrin.

The mAb CH-1 described here may be a useful probe for assessing the involvement of hypochlorous acid in tissue injury.     

Apocynin: a potent NADPH oxidase inhibitor for the management of atrial fibrillation

Abstract

Oxidative stress in atrial tissue may be causally related to atrial fibrillation as suggested by clinical and animal studies. Reactive oxygen species (ROS) are known to play a key role in fibrosis and the induction of after-depolarization and triggered activity. Therefore, suppressing oxidative stress may have a potential beneficial role in the management of atrial fibrillation. Since increased NADPH oxidase activity is shown to play a key role in generation of ROS in atrial tissue and in atrial fibrillation, our proposed strategy to target upstream inhibition of ROS production by inhibition of NADPH oxidase activity may provide a novel approach to prevent atrial fibrillation recurrences. We hypothesize that apocynin could be effective against atrial fibrillation, by virtue of its potent inhibitory effect of a major oxidative system (i.e. NADPH oxidase) combined with its demonstrated anti-inflammatory, antifibrotic and antihypertensive effects which partially are driven from its antioxidant property. Atrial fibrillation is known to be initiated by the interaction of these multiple factors.     

Oxidative stress markers and apoptosis in the prostate of diabetic rats and the influence of vitamin C treatment

Negative consequences of diabetes on the prostate such as involution are associated with diminished testosterone, insulin deficiency, and hyperglycemia. The contributions of oxidative damage, which usually increases with diabetes, are unknown for these alterations. This study evaluated the impact of streptozotocin-induced diabetes on the biomarkers of the antioxidant system of rat ventral prostate, the influence of vitamin C supplementation on these biomarkers, and on the balance between cell proliferation and death. Diabetes (D) was induced in Wistar male rats by streptozotocin (5 mg/100 g b.w., i.p.). Control animals (C) were injected with a vehicle. Vitamin C (150 mg/kg b.w./day) supplementation was introduced by gavage in diabetes (D + V) as well as control (C + V) groups. Thirty days after diabetes onset, the rats were killed and the ventral prostates were analyzed using light microscopy, immunocytochemistry, and biochemical assays for biomarkers of oxidative stress. In comparison to control groups, the levels of circulating testosterone, proliferating, and androgen receptor-positive cells decreased in diabetic groups regardless of vitamin C treatment whereas apoptosis was increased. The levels of superoxide dismutase and glutathione peroxidase did not change, but the levels of glutathione-S-transferase (GST) were increased in diabetic prostate. Vitamin C supplementation normalized GST activity and recovered the apoptotic rates in the prostate. In conclusion, GST is a good indicator of compensatory oxidant defense in the prostate at earlier stages of diabetes and vitamin C improves its activity and attenuates apoptosis in the gland.     

Apolipoprotein A-I mimetic peptide L-4F prevents myocardial and coronary dysfunction in diabetic mice

Diabetes is a major health problem associated with adverse cardiovascular outcomes. The apolipoprotein A-I mimetic peptide L-4F is a putative anti-diabetic drug, has antioxidant and anti-inflammatory proprieties and improves endothelial function. In obese mice L-4F increases adiponectin levels, improving insulin sensitivity, and reducing visceral adiposity. We hypothesized that the pleiotropic actions of L-4F can prevent heart and coronary dysfunction in a mouse model of genetically induced Type II diabetes. We treated db/db mice with either L-4F or vehicle for 8 weeks. Trans-thoracic echocardiography was performed; thereafter, isolated hearts were subjected to ischemia/reperfusion (IR). Glucose, insulin, adiponectin, and pro-inflammatory cytokines (IL-1β, TNF-α, MCP-1) were measured in plasma and HO-1, pAMPK, peNOS, iNOS, adiponectin, and superoxide in cardiac tissue. In db/db mice L-4F decreased accumulation of subcutaneous and total fat, and increased insulin sensitivity and adiponectin levels while lowering inflammatory cytokines (P < 0.05). L-4F normalized in vivo left ventricular (LV) function of db/db mice, increasing (P < 0.05) fractional shortening and decreasing (P < 0.05) LV dimensions. In I/R experiments, L-4F prevented coronary microvascular resistance from increasing and LV function from deteriorating in the db/db mice. These changes were associated with increased cardiac expression of HO-1, pAMPK, peNOS, and adiponectin and decreased levels of superoxide and iNOS (P < 0.01). In the present study we showed that L-4F prevented myocardial and coronary functional abnormalities in db/db mice. These effects were associated with stimulation of HO-1 resulting in increased levels of anti-inflammatory, anti-oxidative, and vasodilatatory action through a mechanism involving increased levels of adiponectin, pAMPK, and peNOS.     

The acute phase protein haptoglobin and its relation to oxidative status in piglets undergoing weaning-induced stress

Abstract

Haptoglobin (Hp) prevents the hemoglobin driven generation of hydroxyl radicals and lipid peroxides. Hp can reduce the neutrophil respiratory burst and is an antioxidative molecule in its own right. We aimed to evaluate Hp concentrations, oxidative stress and antioxidative capacity in blood during weaning and to characterise potential relationships between these parameters. Two batches of 10 piglets each (2 trials) weaned at the age of 27–30 days were fed a starter feed mix ad libitum. Blood samples were taken 1 week before weaning and at weekly intervals thereafter. Oxidative stress was monitored via the D-ROM^® system, antioxidative capacity was measured with the TEAC assay and Hp concentrations were measured by ELISA. Neutrophil phagocytic activity and oxidative burst were examined via flow-cytometry. Body weights were recorded weekly. Hp concentrations were increased in both trials post-weaning (P < 0.01); oxidative stress and oxidative burst were elevated in trial I (P < 0.005). In trial I, Hp and ROM values returned to baseline levels at 6 weeks post-weaning. The piglets in trial II showed respiratory symptoms and maintained elevated Hp concentrations. ROM values and Hp were related (r = 0.58; P < 0.01). Hp and body weight gain were inversely related post-weaning.