title: Oxidative stress increases SNAT1 expression and stimulates cysteine uptake in freshly isolated rat cardiomyocytes.
abstract: Intracellular cysteine availability is an important rate-limiting factor governing glutathione synthesis in the heart. This is also dependent on the magnitude and rate of cysteine uptake into cardiomyocytes, which has been little studied. This study investigated the hypothesis that changes to cysteine transporter expression and activity during oxidative stress influence cardiomyocyte glutathione levels. The uptake of 0-3 mM L-[(35)S]cysteine into ventricular cardiomyocytes isolated from adult male Wistar rats was measured using oil filtration. Cysteine transporter expression was investigated by conventional and real-time quantitative reverse-transcription polymerase chain reaction and Western blotting. Glutathione levels were measured enzymatically. Oxidative stress was induced via 0-6 h incubation with 0.05 mM H(2)O(2). Cysteine uptake was greatest in sodium-containing media and was inhibited by glutamine, 2-(methylamino)-isobutyric acid (αMeAIB), serine or alanine. The K(m) and V(max) of the αMeAIB insensitive and sensitive portions were 0.133 ± 0.01 mM and 468.11 ± 9.04 pmol/μl cell vol/min, and 0.557 ± 0.096 mM and 279.87 ± 16.06 pmol/μl cell vol/min, respectively. Cardiomyocytes expressed ASCT2, SNAT1 and SNAT2 but not ASCT1. Oxidative stress significantly enhanced cysteine uptake, which was attenuated by αMeAIB. This was accompanied by significantly enhanced SNAT1 expression, whilst SNAT2 and ASCT2 were unaffected. Incubation with cysteine significantly reduced the oxidative-stress-induced decline in cardiomyocyte glutathione as compared to cells incubated without cysteine or cells incubated with cysteine and αMeAIB. In conclusion, under control conditions SNAT transporters aid in the delivery of cysteine for cardiomyocyte GSH synthesis, whilst oxidative stress increases cardiomyocyte cysteine uptake and stimulates cardiomyocyte SNAT1 expression.
authors.affiliation: Bristol Heart Institute, University of Bristol, Bristol Royal Infirmary, Bristol, BS2 8HW, UK. nking20@une.edu.au
authors.forename: Nicola
authors.initials: N
authors.lastname: King
authors.forename: Hua
authors.initials: H
authors.lastname: Lin
authors.forename: M-Saadeh
authors.initials: MS
authors.lastname: Suleiman
mesh_terms: D026924:Amino Acid Transport System A / Q000235:genetics* / Q000378:metabolism; D026962:Amino Acid Transport System ASC / Q000235:genetics / Q000378:metabolism; D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D008297:Male; D015778:Minor Histocompatibility Antigens; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000378:metabolism*; D018384:Oxidative Stress; D051381:Rats; D017208:Rats, Wistar; D015854:Up-Regulation
chemical_list: D026924:Amino Acid Transport System A; D026962:Amino Acid Transport System ASC; D026905:Amino Acid Transport Systems; D015778:Minor Histocompatibility Antigens; C498849:Slc1a5 protein, rat; C486716:Slc38a1 protein, rat; C412568:Slc38a2 protein, rat; D006861:Hydrogen Peroxide; D003545:Cysteine