title: Functional significance of glutamate-cysteine ligase modifier for erythrocyte survival in vitro and in vivo.
abstract: Erythrocytes endure constant exposure to oxidative stress. The major oxidative stress scavenger in erythrocytes is glutathione. The rate-limiting enzyme for glutathione synthesis is glutamate-cysteine ligase, which consists of a catalytic subunit (GCLC) and a modifier subunit (GCLM). Here, we examined erythrocyte survival in GCLM-deficient (gclm(-/-)) mice. Erythrocytes from gclm(-/-) mice showed greatly reduced intracellular glutathione. Prolonged incubation resulted in complete lysis of gclm(-/-) erythrocytes, which could be reversed by exogenous delivery of the antioxidant Trolox. To test the importance of GCLM in vivo, mice were treated with phenylhydrazine (PHZ; 0.07 mg/g b.w.) to induce oxidative stress. Gclm(-/-) mice showed dramatically increased hemolysis compared with gclm(+/+) controls. In addition, PHZ-treated gclm(-/-) mice displayed markedly larger accumulations of injured erythrocytes in the spleen than gclm(+/+) mice within 24 h of treatment. Iron staining indicated precipitations of the erythrocyte-derived pigment hemosiderin in kidney tubules of gclm(-/-) mice and none in gclm(+/+) controls. In fact, 24 h after treatment, kidney function began to diminish in gclm(-/-) mice as evident from increased serum creatinine and urea. Consequently, while all PHZ-treated gclm(+/+) mice survived, 90% of PHZ-treated gclm(-/-) mice died within 5 days of treatment. In vitro, upon incubation in the absence or presence of additional oxidative stress, gclm(-/-) erythrocytes exposed significantly more phosphatidylserine, a cell death marker, than gclm(+/+) erythrocytes, an effect at least partially due to increased cytosolic Ca(2+) concentration. Under resting conditions, gclm(-/-) mice exhibited reticulocytosis, indicating that the enhanced erythrocyte death was offset by accelerated erythrocyte generation. GCLM is thus indispensable for erythrocyte survival, in vitro and in vivo, during oxidative stress.
authors.affiliation: Department of Medical Biophysics and Immunology, The Campbell Family Institute for Breast Cancer Research at Princess Margaret Hospital, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Föller
authors.forename: I S
authors.initials: IS
authors.lastname: Harris
authors.forename: A
authors.initials: A
authors.lastname: Elia
authors.forename: R
authors.initials: R
authors.lastname: John
authors.forename: F
authors.initials: F
authors.lastname: Lang
authors.forename: T J
authors.initials: TJ
authors.lastname: Kavanagh
authors.forename: T W
authors.initials: TW
authors.lastname: Mak
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology; D004912:Erythrocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D005721:Glutamate-Cysteine Ligase / Q000097:blood*; D005978:Glutathione / Q000097:blood; D006454:Hemoglobins / Q000378:metabolism; D006461:Hemolysis; D007684:Kidney Tubules / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D018384:Oxidative Stress / Q000502:physiology; D010659:Phenylhydrazines / Q000494:pharmacology; D013154:Spleen / Q000166:cytology
chemical_list: D000975:Antioxidants; D006454:Hemoglobins; D010659:Phenylhydrazines; C030299:phenylhydrazine; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione