Relation between oxidative stress markers and antioxidant endogenous defences during exhaustive exercise

MRP1/GS-X pump ATPase expression: is this the explanation for the cytoprotection of the heart against oxidative stress-induced redox imbalance in comparison to skeletal muscle cells?

Striated muscle activity is always accompanied by oxidative stress (OxStress): the more intense muscle work and/or its duration, the more a redox imbalance may be attained. In spite of cardiac muscle functioning continuously, it is well known that the heart does not suffer from OxStress-induced damage over a broad physiological range. Although the expression of antioxidant enzymes may be of importance in defending heart muscle against OxStress, a series of combined antioxidant therapeutic approaches have proved to be mostly ineffective in avoiding cellular injury. Hence, additional mechanisms may be involved in heart cytoprotection other than antioxidant enzyme activities. The strong cardiotoxic effect of doxorubicin-induced cancer chemotherapy shed light on the possible role for multidrug resistance-associated proteins (MRP) in this context. Muscle activity-induced 'physiological' OxStress enhances the production of glutathione disulfide (GSSG) thus increasing the ratio of GSSG to glutathione (GSH) content inside the cells, which, in turn, leads to redox imbalance. Since MRP1 gene product (a GS-X pump ATPase) is a physiological GSSG transporter, adult Wistar rats were tested for MRP1 expression and activity in the heart and skeletal muscle (gastrocnemius), in as much as the latter is known to be extremely sensitive to muscle activity-induced OxS. MRP1 expression was completely absent in skeletal muscle. In contrast, the heart showed an exercise training-dependent induction of MRP1 protein expression which was further augmented (2.4-fold) as trained rats were challenged with a session of acute exercise. On the other hand, inducible expression of the 70-kDa heat shock protein (HSP70), a universal marker of cellular stress, was completely absent in the heart of sedentary and acutely exercised rats, whereas skeletal muscle showed a conspicuous exercise-dependent HSP70 expression, which decreased by 45% with exercise training. This effect was paralleled by a 58% decrease in GSH content in skeletal muscle which was even higher (an 80%-fall) after training thus leading to a marked redox imbalance ([GSSG]/[GSH] raised up to 38-fold). In the heart, GSH contents and [GSSG]/[GSH] ratio remained virtually unchanged even after exercise challenges, while GS-X pump activity was found to be 20% higher in the heart related to skeletal muscle. These findings suggest that an intrinsic higher capacity to express the MRP1/GS-X pump may dictate the redox status in the heart muscle thus protecting myocardium by preventing GSSG accumulation in cardiomyocytes as compared to skeletal muscle fibres.

Systemic antioxidant defences during acute exacerbation of chronic obstructive pulmonary disease

OBJECTIVE AND BACKGROUND

Existence of an increased oxidative stress has been confirmed in patients with acute exacerbation of COPD. This study aims to examine the extent and time-course of antioxidant defence in patients with an acute exacerbation of COPD in comparison with stable patients.

METHODS

Twelve patients with acute exacerbation were studied at admission, and then 24 h and 48 h following admission and at discharge. The antioxidants assessed were the endogenous antioxidants: glutathione peroxidase, superoxide dismutase, oxidized and reduced glutathione, albumin and exogenous antioxidants: alpha-tocopherol and retinol. Trolox equivalent antioxidant capacity as a marker of antioxidant status was also measured.

RESULTS

There was an increase in glutathione peroxidase and superoxide dismutase 48 h after admission (P<0.05). Alpha-tocopherol was the lowest 24 h after admission and increased significantly at discharge (P<0.05).

CONCLUSIONS

There is an increase in antioxidant defence during acute exacerbation of COPD reaching a maximum at 48 h after admission. This rise in the antioxidant defence is not sufficient to prevent depletion of non-enzymatic antioxidants such as alpha-tocopherol.

[Influence of regular exercise on erythrocyte catalase activity in adolescents with Down syndrome]

BACKGROUND AND OBJECTIVE

Individuals with Down syndrome have been generally described as having high levels of oxidative stress. In order to improve their redox metabolism, the present study was undertaken to ascertain the influence of regular exercise in erythrocyte catalase activity in this population.

SUBJECTS AND METHOD

31 male adolescents with Down syndrome--mean age (standard deviation): 16.1 (1.1) years--performed a 12-week training program with 3 days/week, consisting of warm up (15 min), followed by a main part (20-35 min) at a work intensity of 60-75% of peak heart rate (HRmax = 194.5 - [0.56 age]) and by a cool-down period (10 min). 7 adolescents with trisomy 21 age, sex and body mass index-matched were used as controls. Beutler's method was used to determine catalase activity in the supernatant of erythrocyte hemolysates.

RESULTS

When compared to baseline values, catalase activity was not increased significantly--1,607.0 (231) U/gHb vs 1,663.2 (280) U/gHb; (p = 0.151)- after a 12-week training program. No significant differences were found in controls.

CONCLUSIONS

Regular exercise did not increase significantly catalase activity. Further studies are required in order to highlight potential benefits of regular exercise in redox metabolism of Down syndrome individuals.

Response of antioxidant defences to oxidative stress induced by prolonged exercise: antioxidant enzyme gene expression in lymphocytes

The response of lymphocyte and plasma antioxidant defences to a prolonged exercise as a cycling stage in a professional race was analysed. Antioxidant enzyme activities and gene expression, carbonyl derivative and MDA levels were determined in lymphocytes. Plasma levels of vitamin E, carotenes, protein carbonyl derivatives and the test d-Roms were measured. Significant increases in plasmatic carbonyls and in the test d-Roms were observed after the cycling stage. No significant differences were found in the lymphocyte MDA and carbonyl derivative levels. A significant increase was found in plasma vitamin E concentration after the cycling stage; however, the lymphocyte vitamin E concentration did not change. Significant increases were observed in lymphocyte total superoxide dismutase (SOD) activity and in the levels of CuZn-SOD and Mn-SOD isoenzymes. The moderate levels of oxidative stress in the lymphocyte induced a cellular adaptation to exercise enough to counteract the negative effects of oxidative stress.

Blood cell NO synthesis in response to exercise

Nitric oxide (NO) is important for the maintenance of cardiovascular homeostasis and is also involved in immunity and inflammation. The aim of our work was to determine the effects of intense exercise on plasma and blood cell NO handling. Nine voluntary male professional cyclists participated in the study. Blood samples were taken in basal conditions and 3h after finishing a mountain cycling stage. Exercise-induced neutrophilia, lymphopenia, and hemolysis. Plasma and erythrocytes maintained basal nitrite levels, whereas neutrophils and lymphocytes decreased nitrite concentration after intense exercise. Basal iNOS levels and SOD activity were similar in neutrophils and lymphocytes. iNOS levels and SOD activity dropped in neutrophils and rose in lymphocytes after exercise. Arginase activity rose only in lymphocytes. Neutrophil nitrite was correlated with SOD activity and iNOS levels, but not in lymphocytes. iNOS levels were correlated with SOD in both neutrophils and lymphocytes. Intense exercise maintained plasma basal arginine and ornithine concentration, and decreased citrulline concentration. Intense exercise induced important changes in NO handling in neutrophils and lymphocytes, yet the basal picture was maintained in erythrocytes.