iNOS initiates and sustains metabolic arrest in hypoxic lung adenocarcinoma cells: mechanism of cell survival in solid tumor core

TY - JOUR

T1 - iNOS initiates and sustains metabolic arrest in hypoxic lung adenocarcinoma cells: mechanism of cell survival in solid tumor core

AU - Land, S. C.

AU - Rae, C.

N1 - dc.publisher: American Physiological Society The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. dc.description.sponsorship: Medical Research Council Wellcome Trust Tenovus (Scotland) Anonymous Trust

PY - 2005/10

Y1 - 2005/10

N2 - Nitric oxide (NO) modulates cellular metabolism by competitively inhibiting the reduction of O2 at respiratory complex IV. The aim of this study was to determine whether this effect could enhance cell survival in the hypoxic solid tumor core by inducing a state of metabolic arrest in cancer cells. Mitochondria from human alveolar type II-like adenocarcinoma (A549) cells showed a fourfold increase in NO-sensitive 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM) fluorescence and sixfold increase in Ca2+-insensitive NO synthase (NOS) activity during equilibration from PO2s of 100?23 mmHg, which was abolished by N?-nitro-L-arginine methyl ester-HCl (L-NAME) and the inducible NOS (iNOS) inhibitor, N6-(1-iminoethyl)-L-lysine dihydrochloride (L-NIL). Similarly, cytosolic and compartmented DAF-FM fluorescence increased in intact cells during a transition between ambient PO2 and 23 mmHg and was abolished by transfection with iNOS antisense oligonucleotides (AS-ODN). In parallel, mitochondrial membrane potential (??m), measured using 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolo-carbocyanine iodide (JC-1), decreased to a lower steady state in hypoxia without change in glycolytic rate, adenylate energy charge, or cell viability. However, L-NAME or iNOS AS-ODN treatment maintained ??m at normoxic levels irrespective of hypoxia and caused a marked activation of glycolysis, destabilization energy charge, and cell death. Comparison with other cancer-derived (H441) or native tissue-derived (human bronchial epithelial; alveolar type II) lung epithelial cells revealed that the hypoxic suppression of ??m was common to cells that expressed iNOS. The controlled dissipation of ??m, absence of an overt glycolytic activation, and conservation of viability suggest that A549 cells enter a state of metabolic suppression in hypoxia, which inherently depends on the activation of iNOS as PO2 falls.

AB - Nitric oxide (NO) modulates cellular metabolism by competitively inhibiting the reduction of O2 at respiratory complex IV. The aim of this study was to determine whether this effect could enhance cell survival in the hypoxic solid tumor core by inducing a state of metabolic arrest in cancer cells. Mitochondria from human alveolar type II-like adenocarcinoma (A549) cells showed a fourfold increase in NO-sensitive 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM) fluorescence and sixfold increase in Ca2+-insensitive NO synthase (NOS) activity during equilibration from PO2s of 100?23 mmHg, which was abolished by N?-nitro-L-arginine methyl ester-HCl (L-NAME) and the inducible NOS (iNOS) inhibitor, N6-(1-iminoethyl)-L-lysine dihydrochloride (L-NIL). Similarly, cytosolic and compartmented DAF-FM fluorescence increased in intact cells during a transition between ambient PO2 and 23 mmHg and was abolished by transfection with iNOS antisense oligonucleotides (AS-ODN). In parallel, mitochondrial membrane potential (??m), measured using 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolo-carbocyanine iodide (JC-1), decreased to a lower steady state in hypoxia without change in glycolytic rate, adenylate energy charge, or cell viability. However, L-NAME or iNOS AS-ODN treatment maintained ??m at normoxic levels irrespective of hypoxia and caused a marked activation of glycolysis, destabilization energy charge, and cell death. Comparison with other cancer-derived (H441) or native tissue-derived (human bronchial epithelial; alveolar type II) lung epithelial cells revealed that the hypoxic suppression of ??m was common to cells that expressed iNOS. The controlled dissipation of ??m, absence of an overt glycolytic activation, and conservation of viability suggest that A549 cells enter a state of metabolic suppression in hypoxia, which inherently depends on the activation of iNOS as PO2 falls.

KW - Cancer

KW - Oxygen conformation

KW - Mitochondrial nitric oxide synthase

KW - Mitochondrial metabolism

U2 - 10.1152/ajpcell.00476.2004

DO - 10.1152/ajpcell.00476.2004

M3 - Article

SN - 0363-6143

VL - 289

SP - C918-C933

JO - American Journal of Physiology - Cell Physiology (AJP - Cell Physiology)

JF - American Journal of Physiology - Cell Physiology (AJP - Cell Physiology)

IS - 4

ER -