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Nitrite augments tolerance to ischemia/reperfusion injury via the modulation of mitochondrial electron transfer.

Shiva S, Sack MN, Greer JJ, Duranski M, Ringwood LA, Burwell L, Wang X, MacArthur PH, Shoja A, Raghavachari N, Calvert JW, Brookes PS, Lefer DJ, Gladwin MT - J. Exp. Med. (2007)

Bottom Line: Although the mechanism of nitrite-mediated cytoprotection is unknown, NO is a mediator of the ischemic preconditioning cell-survival program.This cytoprotection is associated with increases in mitochondrial oxidative phosphorylation.These data suggest that nitrite dynamically modulates mitochondrial resilience to reperfusion injury and may represent an effector of the cell-survival program of ischemic preconditioning and the Mediterranean diet.

View Article: PubMed Central - PubMed

Affiliation: Vascular Medicine Branch, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.

ABSTRACT
Nitrite (NO(2)(-)) is an intrinsic signaling molecule that is reduced to NO during ischemia and limits apoptosis and cytotoxicity at reperfusion in the mammalian heart, liver, and brain. Although the mechanism of nitrite-mediated cytoprotection is unknown, NO is a mediator of the ischemic preconditioning cell-survival program. Analogous to the temporally distinct acute and delayed ischemic preconditioning cytoprotective phenotypes, we report that both acute and delayed (24 h before ischemia) exposure to physiological concentrations of nitrite, given both systemically or orally, potently limits cardiac and hepatic reperfusion injury. This cytoprotection is associated with increases in mitochondrial oxidative phosphorylation. Remarkably, isolated mitochondria subjected to 30 min of anoxia followed by reoxygenation were directly protected by nitrite administered both in vitro during anoxia or in vivo 24 h before mitochondrial isolation. Mechanistically, nitrite dose-dependently modifies and inhibits complex I by posttranslational S-nitrosation; this dampens electron transfer and effectively reduces reperfusion reactive oxygen species generation and ameliorates oxidative inactivation of complexes II-IV and aconitase, thus preventing mitochondrial permeability transition pore opening and cytochrome c release. These data suggest that nitrite dynamically modulates mitochondrial resilience to reperfusion injury and may represent an effector of the cell-survival program of ischemic preconditioning and the Mediterranean diet.

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Nitrite-dependent cytoprotection does not modulate mitochondrial biogenesis. Rats were given one intraperitoneal injection (480 nmol) of saline or nitrite daily for nine consecutive days. (A and B) Recovery of respiration (A) and ATP (B) generation rates of mitochondria isolated from these rats after 30 min of anoxia in vitro (white, saline; green, nitrite). (C) Relative expression of genes in the livers of nitrite-treated rats on day 9 presented as the fold change in gene expression compared with saline-treated rats. (D) Protein expression of the 39-kD subunit of complex I, cytochrome c, and ATPase subunit B in the livers of rats after 9 d of nitrite or saline treatment. All experiments are means ± SEM of at least n = 3 independent experiments. *, P < 0.01.
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fig3: Nitrite-dependent cytoprotection does not modulate mitochondrial biogenesis. Rats were given one intraperitoneal injection (480 nmol) of saline or nitrite daily for nine consecutive days. (A and B) Recovery of respiration (A) and ATP (B) generation rates of mitochondria isolated from these rats after 30 min of anoxia in vitro (white, saline; green, nitrite). (C) Relative expression of genes in the livers of nitrite-treated rats on day 9 presented as the fold change in gene expression compared with saline-treated rats. (D) Protein expression of the 39-kD subunit of complex I, cytochrome c, and ATPase subunit B in the livers of rats after 9 d of nitrite or saline treatment. All experiments are means ± SEM of at least n = 3 independent experiments. *, P < 0.01.

Mentions: Because the half-life of nitrite in blood is only 11 min (33), we considered that nitrite may mimic delayed preconditioning through the transcriptional regulation of nuclear-encoded mitochondrial functioning genes (34, 35). Moreover, recent studies have shown that NO activates the mitochondrial biogenesis regulatory program (28, 29). To explore this possibility, we evaluated the gene expression profiles in response to daily nitrite administration for 1, 2, 3, and 9 d before mRNA extraction. The gene expression profiles of the nuclear genes encoding mitochondrial biogenesis regulatory proteins, antioxidant enzymes, uncoupling proteins, and respiratory chain enzymes were quantified. Although nitrite-dependent protection was maintained in the mitochondria throughout this exposure time (Fig. 3, A and B), nitrite-treated rats showed no change in mRNA expression of genes encoding transcriptional regulators of the mitochondrial biogenesis program (PGC-1α and NRF2), respiratory proteins (cytochrome c oxidase, cytochrome c, and adenine nucleotide translocase), or in antioxidant defense mediators (catalase, superoxide dismutase, and uncoupling protein 2) in comparison with saline-treated rats (Fig. 3 C). Mitochondrial protein expression (Fig. 3 D) and mitochondrial number and morphology (unpublished data) remained constant despite nine consecutive days of nitrite treatment. These data show that nitrite-dependent protection is not mediated by changes in gene transcription or translation that directly modulate the mitochondrial biogenesis program. Similarly, a single dose of nitrite administered 5 h before the extraction of hepatic tissue demonstrated no significant up-regulation of genes encoding cyclooxygenase-2 and inducible NO synthase (iNOS; 1.66 ± 0.02 fold change [P = 0.08] and 1.335 ± 0.09 fold change [P = 0.23], respectively; n = 10). As cyclooxygenase-2 and iNOS are established mediators of delayed preconditioning (36), a partial role of this signaling cascade in nitrite-dependent delayed cytoprotection cannot be completely excluded without further study.


Nitrite augments tolerance to ischemia/reperfusion injury via the modulation of mitochondrial electron transfer.

Shiva S, Sack MN, Greer JJ, Duranski M, Ringwood LA, Burwell L, Wang X, MacArthur PH, Shoja A, Raghavachari N, Calvert JW, Brookes PS, Lefer DJ, Gladwin MT - J. Exp. Med. (2007)

Nitrite-dependent cytoprotection does not modulate mitochondrial biogenesis. Rats were given one intraperitoneal injection (480 nmol) of saline or nitrite daily for nine consecutive days. (A and B) Recovery of respiration (A) and ATP (B) generation rates of mitochondria isolated from these rats after 30 min of anoxia in vitro (white, saline; green, nitrite). (C) Relative expression of genes in the livers of nitrite-treated rats on day 9 presented as the fold change in gene expression compared with saline-treated rats. (D) Protein expression of the 39-kD subunit of complex I, cytochrome c, and ATPase subunit B in the livers of rats after 9 d of nitrite or saline treatment. All experiments are means ± SEM of at least n = 3 independent experiments. *, P < 0.01.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2118713&req=5

fig3: Nitrite-dependent cytoprotection does not modulate mitochondrial biogenesis. Rats were given one intraperitoneal injection (480 nmol) of saline or nitrite daily for nine consecutive days. (A and B) Recovery of respiration (A) and ATP (B) generation rates of mitochondria isolated from these rats after 30 min of anoxia in vitro (white, saline; green, nitrite). (C) Relative expression of genes in the livers of nitrite-treated rats on day 9 presented as the fold change in gene expression compared with saline-treated rats. (D) Protein expression of the 39-kD subunit of complex I, cytochrome c, and ATPase subunit B in the livers of rats after 9 d of nitrite or saline treatment. All experiments are means ± SEM of at least n = 3 independent experiments. *, P < 0.01.
Mentions: Because the half-life of nitrite in blood is only 11 min (33), we considered that nitrite may mimic delayed preconditioning through the transcriptional regulation of nuclear-encoded mitochondrial functioning genes (34, 35). Moreover, recent studies have shown that NO activates the mitochondrial biogenesis regulatory program (28, 29). To explore this possibility, we evaluated the gene expression profiles in response to daily nitrite administration for 1, 2, 3, and 9 d before mRNA extraction. The gene expression profiles of the nuclear genes encoding mitochondrial biogenesis regulatory proteins, antioxidant enzymes, uncoupling proteins, and respiratory chain enzymes were quantified. Although nitrite-dependent protection was maintained in the mitochondria throughout this exposure time (Fig. 3, A and B), nitrite-treated rats showed no change in mRNA expression of genes encoding transcriptional regulators of the mitochondrial biogenesis program (PGC-1α and NRF2), respiratory proteins (cytochrome c oxidase, cytochrome c, and adenine nucleotide translocase), or in antioxidant defense mediators (catalase, superoxide dismutase, and uncoupling protein 2) in comparison with saline-treated rats (Fig. 3 C). Mitochondrial protein expression (Fig. 3 D) and mitochondrial number and morphology (unpublished data) remained constant despite nine consecutive days of nitrite treatment. These data show that nitrite-dependent protection is not mediated by changes in gene transcription or translation that directly modulate the mitochondrial biogenesis program. Similarly, a single dose of nitrite administered 5 h before the extraction of hepatic tissue demonstrated no significant up-regulation of genes encoding cyclooxygenase-2 and inducible NO synthase (iNOS; 1.66 ± 0.02 fold change [P = 0.08] and 1.335 ± 0.09 fold change [P = 0.23], respectively; n = 10). As cyclooxygenase-2 and iNOS are established mediators of delayed preconditioning (36), a partial role of this signaling cascade in nitrite-dependent delayed cytoprotection cannot be completely excluded without further study.

Bottom Line: Although the mechanism of nitrite-mediated cytoprotection is unknown, NO is a mediator of the ischemic preconditioning cell-survival program.This cytoprotection is associated with increases in mitochondrial oxidative phosphorylation.These data suggest that nitrite dynamically modulates mitochondrial resilience to reperfusion injury and may represent an effector of the cell-survival program of ischemic preconditioning and the Mediterranean diet.

View Article: PubMed Central - PubMed

Affiliation: Vascular Medicine Branch, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.

ABSTRACT
Nitrite (NO(2)(-)) is an intrinsic signaling molecule that is reduced to NO during ischemia and limits apoptosis and cytotoxicity at reperfusion in the mammalian heart, liver, and brain. Although the mechanism of nitrite-mediated cytoprotection is unknown, NO is a mediator of the ischemic preconditioning cell-survival program. Analogous to the temporally distinct acute and delayed ischemic preconditioning cytoprotective phenotypes, we report that both acute and delayed (24 h before ischemia) exposure to physiological concentrations of nitrite, given both systemically or orally, potently limits cardiac and hepatic reperfusion injury. This cytoprotection is associated with increases in mitochondrial oxidative phosphorylation. Remarkably, isolated mitochondria subjected to 30 min of anoxia followed by reoxygenation were directly protected by nitrite administered both in vitro during anoxia or in vivo 24 h before mitochondrial isolation. Mechanistically, nitrite dose-dependently modifies and inhibits complex I by posttranslational S-nitrosation; this dampens electron transfer and effectively reduces reperfusion reactive oxygen species generation and ameliorates oxidative inactivation of complexes II-IV and aconitase, thus preventing mitochondrial permeability transition pore opening and cytochrome c release. These data suggest that nitrite dynamically modulates mitochondrial resilience to reperfusion injury and may represent an effector of the cell-survival program of ischemic preconditioning and the Mediterranean diet.

Show MeSH
Related in: MedlinePlus