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Abstract

The effect of oxidative stress on the Ca2+-ATPase activity, lipid peroxidation and protein modification of cardiac sarcoplasmic reticulum (SR) membranes was investigated. Isolated SR vesicles were exposed to FeSO4/EDTA (0.2 micromol Fe2+ per mg of protein) at 37 degrees C for 1 h in the presence or absence of antioxidants. FeSO4/EDTA decreased the maximum velocity of Ca2+-ATPase reaction without a change of affinity for Ca2+ or Hill coefficient. Treatment with radical-generating system led also to conjugated diene formation, loss of sulfhydryl groups, changes in tryptophan and bityrosine fluorescences and to production of lysine conjugates with lipid peroxidation end-products. Lipid antioxidants butylated hydroxytoluene (BHT) and stobadine partially prevented inhibition of Ca2+-ATPase and decrease in tryptophan fluorescence, while the loss of -SH groups and formation of bityrosines or lysine conjugates were completely prevented. Glutathione also partially protected Ca2+-ATPase activity and decreased formation of bityrosine, but it was not able to prevent oxidative modification of tryptophan and lysine. These findings suggest that combination of amino acid modifications, rather than oxidation of amino acids of one kind, is responsible for inhibition of SR Ca2+-ATPase activity.

The ER mitochondria calcium cycle and ER stress response as therapeutic targets in amyotrophic lateral sclerosis

“…SERCA is very sensitive to redox state but contrary to RyR and IP 3 R, oxidation inhibits SERCA activity (Kaplan et al, 2003). SERCA is reversibly regulated through NO-dependent S-glutathiolation of specific cysteine residues (Adachi et al, 2004), where irreversible sulfonylation reduces SERCA (Ying et al, 2008).…”

Crosstalk signaling between mitochondrial Ca2+ and ROS

“…SERCA activity is sensitive to the redox state, but unlike RyR and IP 3 R, SERCA is inhibited by oxidation and ROS (201). There are three SERCA isoforms expressed differentially in different tissue types that have up to 25 cysteine residues with one or two essential catalytic cysteines (202).…”

Myocardial Ca2+handling and cell-to-cell coupling, key factors in prevention of sudden cardiac deathThis article is one of a selection of papers published in a special issue on Advances in Cardiovascular Research.

“…The larger part of the left ventricular tissue from nonstimulated (control) and stimulated young and old guinea pig hearts was taken for preparation of SR vesicles, as described previously (Kaplan et al 2003). The Ca 2+ -stimulated ATPase activity was determined photometrically from the rate of inorganic phosphate release in a reaction medium containing 20 mmol/L Hepes, pH 7.0, 100 mmol/L KCl, 5 mmol/L MgCl 2 , 5 mmol/L NaN 3 , 5 mmol/L ATP, 2 mg/mL A23187, 0.1 mmol/L EDTA, various amounts of CaCl 2 required to produce the desired concentration of free Ca 2+ , and 50 mg/mL SR protein.…”