Protection of myocytes against free radical-induced damage by accelerated turnover of the glutathione redox cycle

Abstract

The primary defence mechanism of myocytes against peroxides and peroxide-derived peroxyl and alkoxyl radicals is the glutathione redox cycle. The purpose of the present study was to increase the turnover rate of this cycle by stimulating the glutathione peroxidase catalysed reaction (2GSH-->GSSG), the glutathione reductase catalysed reaction (GSSG-->2GSH), or both. Neonatal rat heart cell cultures were subjected to a standardized protocol of oxidative stress using 80 mumol.l-1 cumene hydroperoxide (CHPO) for 0-90 min. The consequences of this protocol were described in terms of cellular concentrations of GSH, GSSG, NADPH and ATP, formation of malondialdehyde (MDA), release of GSSG and of ATP catabolites, depression of contraction frequency, cellular calcium overload, and enzyme release. Trolox-C, an analogue of vitamin E, accelerated the glutathione peroxidase reaction leading to lowering of GSH concentration and the GSH/GSSG ratio, less MDA formation, diminished negative chronotropy, delayed calcium overload, and less enzyme release. Glucose was used to accelerate the glutathione reductase reaction by supplying NADPH, leading to higher GSH concentration and a higher GSH/GSSG ratio, less MDA formation, diminished negative chronotropy, unchanged development of calcium overload, and less enzyme release. As a full turn of the glutathione redox cycle involves both the peroxidase and the reductase reactions, the combination of Trolox-C and glucose was superior to either of the two alone: 90 min following addition of CHPO together with Trolox-C and glucose, the GSH concentration and the GSH/GSSG ratio were almost normal, MDA formation was extremely low, calcium overload was markedly delayed, and enzyme release hardly occurred at all. Cells remained beating in the observation period of 30 min. We conclude that the capacity of the glutathione redox cycle to withstand oxidative stress can be increased by stimulation of either the peroxidase reaction or the reductase reaction, and that optimal redox cycling is achieved by stimulation of both reactions.

Functional Significance of the Pentose Phosphate Pathway and Glutathione Reductase in the Antioxidant Defenses of Human Sperm1

“…The capacity of the antioxidant pathway is limited, and defenses are overwhelmed by high levels of oxidative stress that decrease flux through both the pentose phosphate pathway and glycolysis and through reduced sperm motility. Evidence from other systems suggests that the addition of cumene hydroperoxide is an effective way to increase flux through glutathione peroxidase and to study the subsequent response of the pentose phosphate pathway [27,28]. The glutathione peroxidase-glutathione reductase-pentose phosphate pathway axis is important in limiting the oxidative damage suffered by human sperm, because blocking glutathione reductase with BiCNU made the pentose phosphate pathway unable to respond to increased demand from glutathione peroxidase and made the cells more vulnerable to lipid peroxidation and loss of motility under aerobic conditions.…”

Cardiac Function, Myocardial Glutathione, and Matrix Metalloproteinase-2 Levels in Hypoxic Newborn Pigs Reoxygenated by 21%, 50%, or 100% Oxygen

“…Glutathione (GSH) is an important cellular antioxidant that can detoxify OFRs with the resultant formation of oxidized glutathione (GSSG) (4,14), which correlates with the extent of myocardial cell death (15). Furthermore, exogenous GSH administration (16) or stimulation of the GSH redox cycle (15) has been shown to decrease OFR generation and attenuate ischemia-reperfusion-induced contractile dysfunction.…”

“…Glutathione (GSH) is an important cellular antioxidant that can detoxify OFRs with the resultant formation of oxidized glutathione (GSSG) (4,14), which correlates with the extent of myocardial cell death (15). Furthermore, exogenous GSH administration (16) or stimulation of the GSH redox cycle (15) has been shown to decrease OFR generation and attenuate ischemia-reperfusion-induced contractile dysfunction. Among the matrix metalloproteinases (MMP), MMP-2, activated by oxidants (17), can cause the detrimental effect on the contractile dysfunction after reperfusion by its action on the troponin and contractile mechanism (18,19).…”

Critical study of preanalytical and analytical phases of adenine and pyridine nucleotide assay in human whole blood

“…Recently the role of nucleotides in the cellular antioxidant system has been greatly emphasized [1,2]; intracellular pyridine nucleotides play an important role in energy transduction, signaling pathways, and the antioxidant system [3][4][5], particularly in many cardiovascular diseases in which oxidative stress is involved, such as in heart failure, myocardial ischemia, unstable angina [6][7][8], and ischemia reperfusion injury [9,10]. Nucleotide status provides biochemical and clinical information on cardiovascular diseases [1,[6][7][8][9][10][11][12][13], cellular energetic alterations, and redox metabolism disorders [4,14,15].…”