Regulation of glutathione in cardiac myocytes.
Reduced glutathione (GSH) is an essential, multifunctional tripepetide that controls redox-sensitive cellular processes, but its regulation in the heart is poorly understood. The present study used a pharmocological model of GSH depletion to examine cellular mechanisms controlling cardiac GSH. Inhibition of GSH metabolism was elicited in normal rats by daily injections of buthionine sulfoximine (BSO), a blocker of gamma-glutamylcysteine synthetase, plus 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase. After 3 d of BSO/BCNU treatment, intracellular [GSH] was measured in isolated-ventricular myocytes by fluorescence microscopy using the probe monochlorobimane. Basal [GSH] in left-ventricular myocytes from BSO/BCNU-treated rats (2.0 +/- 0.05 amol/microm(3), n = 146) was 50% less than control (4.0 +/- 0.13 amol/microm(3), n = 116; P < 0.05). Incubation of myocytes from BSO/BCNU rats with 0.1 microM insulin normalized [GSH] after a delay of 3-4 h (3.6 +/- 0.29 amol/microm(3), n = 66). This effect of insulin was blocked by pre-treating myocytes with cycloheximide. A protein tyrosine phosphatase inhibitor, bis-peroxovanadium-1,10-phenanthroline (bpV(phen), 1 microM), elicited a similar effect as insulin, while neither agent altered [GSH] in myocytes from control rats. Moreover, the effect of insulin and bpV(phen) to up-regulate GSH was blocked by inhibitors of PI 3-kinase (wortmannin, LY294002), MEK (PD98059) and p38 MAP kinases (SB203580). These data suggest that the insulin-signaling cascade regulates [GSH] in ventricular myocytes by a coordinated activation of PI 3-kinase and MAP kinase pathways. These signaling mechanisms may play essential roles in controlling intracellular redox state and normal function of cardiac myocytes.
Li
Shumin
S
Department of Physiology and Biophysics, University of Nebraska College of Medicine, 984575 Nebraska Medical Center, Omaha, NE 68198-4575, USA.
Li
Xun
X
Rozanski
George J
GJ
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002330:Carmustine / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D005721:Glutamate-Cysteine Ligase / Q000037:antagonists & inhibitors / Q000378:metabolism; D005978:Glutathione / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D032383:Myocytes, Cardiac / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D018906:Antineoplastic Agents, Alkylating; D004791:Enzyme Inhibitors; D019328:Buthionine Sulfoximine; D005980:Glutathione Reductase; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D002330:Carmustine