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Hypoxia-reoxygenation triggers coronary vasospasm in isolated bovine coronary arteries via tyrosine nitration of prostacyclin synthase.

Zou MH, Bachschmid M - J. Exp. Med. (1999)

Bottom Line: Hypoxia-reoxygenation selectively blunted prostacyclin (PGI2)-dependent vasorelaxation and elicited a sustained vasoconstriction that was blocked by a cyclooxygenase inhibitor, indomethacin, and SQ29548, a thromboxane (Tx)A2/prostaglandin H2 receptor antagonist, but not by CGS13080, a TxA2 synthase blocker.The inactivation of PGI2 synthase, as evidenced by suppressed 6-keto-PGF1 alpha release and a decreased conversion of 14C-prostaglandin H2 into 6-keto-PGF1 alpha, was paralleled by an increased nitration in both vascular endothelium and smooth muscle of hypoxia-reoxygenation-exposed vessels.We conclude that hypoxia-reoxygenation elicits the formation of superoxide, which causes loss of the vasodilatory action of NO and at the same time yields peroxynitrite.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Biology, University of Konstanz, Germany. zou@gkbiochem.uni-konstanz.de

ABSTRACT
The role of peroxynitrite in hypoxia-reoxygenation-induced coronary vasospasm was investigated in isolated bovine coronary arteries. Hypoxia-reoxygenation selectively blunted prostacyclin (PGI2)-dependent vasorelaxation and elicited a sustained vasoconstriction that was blocked by a cyclooxygenase inhibitor, indomethacin, and SQ29548, a thromboxane (Tx)A2/prostaglandin H2 receptor antagonist, but not by CGS13080, a TxA2 synthase blocker. The inactivation of PGI2 synthase, as evidenced by suppressed 6-keto-PGF1 alpha release and a decreased conversion of 14C-prostaglandin H2 into 6-keto-PGF1 alpha, was paralleled by an increased nitration in both vascular endothelium and smooth muscle of hypoxia-reoxygenation-exposed vessels. The administration of the nitric oxide (NO) synthase inhibitors as well as polyethylene-glycolated superoxide dismutase abolished the vasospasm by preventing the inactivation and nitration of PGI2 synthase, suggesting that peroxynitrite was implicated. Moreover, concomitant administration to the organ baths of the two precursors of peroxynitrite, superoxide, and NO mimicked the effects of hypoxia-reoxygenation, although none of them were effective when given separately. We conclude that hypoxia-reoxygenation elicits the formation of superoxide, which causes loss of the vasodilatory action of NO and at the same time yields peroxynitrite. Subsequently, peroxynitrite nitrates and inactivates PGI2 synthase, leaving unmetabolized prostaglandin H2, which causes vasospasm, platelet aggregation, and thrombus formation via the TxA2/prostaglandin H2 receptor.

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Hypoxia–reoxygenation on angiotensin II–triggered relaxation and eicosanoid metabolism in BCA. (A) Effects of indomethacin, SQ 29548, CGS13080, SOD, L-NMMA, and L-NAME on angiotensin II–triggered relaxation (white bars) and the release of 6-keto-PGF1α (black bars) and PGE2 (hatched bars) in hypoxia–reoxygenated BCA. After having obtained a reference response to angiotensin II, the coronary strip was exposed to hypoxia for 40 min after 40-min reoxygenation in presence of indomethacin (10 μM), CGS13080 (10 μM), SQ-29548 (10 μM), PEG-SOD (500 U/ml), L-NMMA (10−4 M), or L-NAME (10−4 M). PGE2 and 6-keto-PGF1α in the media were analyzed by ELISA. Data represent means ± SEM from 10 experiments. (B) Effects of superoxide, NO, and concurrent administration of superoxide and NO on angiotensin II–induced vasorelaxation and prostaglandin release in BCA. After having obtained a reference response to angiotensin II, the coronary strip was exposed to superoxide generated from 10 mU/ml xanthine oxidase/100 μM hypoxanthine or to NO generated from 20 μM DEA-NO or superoxide plus NO. PGE2 (hatched bars) and 6-keto-PGF1α (black bars) in the media were analyzed by ELISA. Data represent means ± SEM from 12 experiments. White bars, relaxation.
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Figure 1: Hypoxia–reoxygenation on angiotensin II–triggered relaxation and eicosanoid metabolism in BCA. (A) Effects of indomethacin, SQ 29548, CGS13080, SOD, L-NMMA, and L-NAME on angiotensin II–triggered relaxation (white bars) and the release of 6-keto-PGF1α (black bars) and PGE2 (hatched bars) in hypoxia–reoxygenated BCA. After having obtained a reference response to angiotensin II, the coronary strip was exposed to hypoxia for 40 min after 40-min reoxygenation in presence of indomethacin (10 μM), CGS13080 (10 μM), SQ-29548 (10 μM), PEG-SOD (500 U/ml), L-NMMA (10−4 M), or L-NAME (10−4 M). PGE2 and 6-keto-PGF1α in the media were analyzed by ELISA. Data represent means ± SEM from 10 experiments. (B) Effects of superoxide, NO, and concurrent administration of superoxide and NO on angiotensin II–induced vasorelaxation and prostaglandin release in BCA. After having obtained a reference response to angiotensin II, the coronary strip was exposed to superoxide generated from 10 mU/ml xanthine oxidase/100 μM hypoxanthine or to NO generated from 20 μM DEA-NO or superoxide plus NO. PGE2 (hatched bars) and 6-keto-PGF1α (black bars) in the media were analyzed by ELISA. Data represent means ± SEM from 12 experiments. White bars, relaxation.

Mentions: Abrupt decrease of oxygen tension from 95% O2/5% CO2 to 95% N2 /5% CO2 caused a slight decrease in tension after a transient rise. Reoxygenation (from 95% N2 /5% CO2 to 95% O2 /5% CO2) did not alter the tension of unstimulated arteries. Although hypoxia–reoxygenation did not affect the initial constriction of angiotensin II, it selectively blunted the angiotensin II–triggered relaxation phase after 30 min of hypoxia. Along with this suppression of the relaxation phase, a second constriction phase developed in parallel, with a decrease of 6-keto-PGF1α (Fig. 1 A) that closely resembled the pattern seen previously after peroxynitrite pretreatment 9.


Hypoxia-reoxygenation triggers coronary vasospasm in isolated bovine coronary arteries via tyrosine nitration of prostacyclin synthase.

Zou MH, Bachschmid M - J. Exp. Med. (1999)

Hypoxia–reoxygenation on angiotensin II–triggered relaxation and eicosanoid metabolism in BCA. (A) Effects of indomethacin, SQ 29548, CGS13080, SOD, L-NMMA, and L-NAME on angiotensin II–triggered relaxation (white bars) and the release of 6-keto-PGF1α (black bars) and PGE2 (hatched bars) in hypoxia–reoxygenated BCA. After having obtained a reference response to angiotensin II, the coronary strip was exposed to hypoxia for 40 min after 40-min reoxygenation in presence of indomethacin (10 μM), CGS13080 (10 μM), SQ-29548 (10 μM), PEG-SOD (500 U/ml), L-NMMA (10−4 M), or L-NAME (10−4 M). PGE2 and 6-keto-PGF1α in the media were analyzed by ELISA. Data represent means ± SEM from 10 experiments. (B) Effects of superoxide, NO, and concurrent administration of superoxide and NO on angiotensin II–induced vasorelaxation and prostaglandin release in BCA. After having obtained a reference response to angiotensin II, the coronary strip was exposed to superoxide generated from 10 mU/ml xanthine oxidase/100 μM hypoxanthine or to NO generated from 20 μM DEA-NO or superoxide plus NO. PGE2 (hatched bars) and 6-keto-PGF1α (black bars) in the media were analyzed by ELISA. Data represent means ± SEM from 12 experiments. White bars, relaxation.
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Related In: Results  -  Collection

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Figure 1: Hypoxia–reoxygenation on angiotensin II–triggered relaxation and eicosanoid metabolism in BCA. (A) Effects of indomethacin, SQ 29548, CGS13080, SOD, L-NMMA, and L-NAME on angiotensin II–triggered relaxation (white bars) and the release of 6-keto-PGF1α (black bars) and PGE2 (hatched bars) in hypoxia–reoxygenated BCA. After having obtained a reference response to angiotensin II, the coronary strip was exposed to hypoxia for 40 min after 40-min reoxygenation in presence of indomethacin (10 μM), CGS13080 (10 μM), SQ-29548 (10 μM), PEG-SOD (500 U/ml), L-NMMA (10−4 M), or L-NAME (10−4 M). PGE2 and 6-keto-PGF1α in the media were analyzed by ELISA. Data represent means ± SEM from 10 experiments. (B) Effects of superoxide, NO, and concurrent administration of superoxide and NO on angiotensin II–induced vasorelaxation and prostaglandin release in BCA. After having obtained a reference response to angiotensin II, the coronary strip was exposed to superoxide generated from 10 mU/ml xanthine oxidase/100 μM hypoxanthine or to NO generated from 20 μM DEA-NO or superoxide plus NO. PGE2 (hatched bars) and 6-keto-PGF1α (black bars) in the media were analyzed by ELISA. Data represent means ± SEM from 12 experiments. White bars, relaxation.
Mentions: Abrupt decrease of oxygen tension from 95% O2/5% CO2 to 95% N2 /5% CO2 caused a slight decrease in tension after a transient rise. Reoxygenation (from 95% N2 /5% CO2 to 95% O2 /5% CO2) did not alter the tension of unstimulated arteries. Although hypoxia–reoxygenation did not affect the initial constriction of angiotensin II, it selectively blunted the angiotensin II–triggered relaxation phase after 30 min of hypoxia. Along with this suppression of the relaxation phase, a second constriction phase developed in parallel, with a decrease of 6-keto-PGF1α (Fig. 1 A) that closely resembled the pattern seen previously after peroxynitrite pretreatment 9.

Bottom Line: Hypoxia-reoxygenation selectively blunted prostacyclin (PGI2)-dependent vasorelaxation and elicited a sustained vasoconstriction that was blocked by a cyclooxygenase inhibitor, indomethacin, and SQ29548, a thromboxane (Tx)A2/prostaglandin H2 receptor antagonist, but not by CGS13080, a TxA2 synthase blocker.The inactivation of PGI2 synthase, as evidenced by suppressed 6-keto-PGF1 alpha release and a decreased conversion of 14C-prostaglandin H2 into 6-keto-PGF1 alpha, was paralleled by an increased nitration in both vascular endothelium and smooth muscle of hypoxia-reoxygenation-exposed vessels.We conclude that hypoxia-reoxygenation elicits the formation of superoxide, which causes loss of the vasodilatory action of NO and at the same time yields peroxynitrite.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Biology, University of Konstanz, Germany. zou@gkbiochem.uni-konstanz.de

ABSTRACT
The role of peroxynitrite in hypoxia-reoxygenation-induced coronary vasospasm was investigated in isolated bovine coronary arteries. Hypoxia-reoxygenation selectively blunted prostacyclin (PGI2)-dependent vasorelaxation and elicited a sustained vasoconstriction that was blocked by a cyclooxygenase inhibitor, indomethacin, and SQ29548, a thromboxane (Tx)A2/prostaglandin H2 receptor antagonist, but not by CGS13080, a TxA2 synthase blocker. The inactivation of PGI2 synthase, as evidenced by suppressed 6-keto-PGF1 alpha release and a decreased conversion of 14C-prostaglandin H2 into 6-keto-PGF1 alpha, was paralleled by an increased nitration in both vascular endothelium and smooth muscle of hypoxia-reoxygenation-exposed vessels. The administration of the nitric oxide (NO) synthase inhibitors as well as polyethylene-glycolated superoxide dismutase abolished the vasospasm by preventing the inactivation and nitration of PGI2 synthase, suggesting that peroxynitrite was implicated. Moreover, concomitant administration to the organ baths of the two precursors of peroxynitrite, superoxide, and NO mimicked the effects of hypoxia-reoxygenation, although none of them were effective when given separately. We conclude that hypoxia-reoxygenation elicits the formation of superoxide, which causes loss of the vasodilatory action of NO and at the same time yields peroxynitrite. Subsequently, peroxynitrite nitrates and inactivates PGI2 synthase, leaving unmetabolized prostaglandin H2, which causes vasospasm, platelet aggregation, and thrombus formation via the TxA2/prostaglandin H2 receptor.

Show MeSH
Related in: MedlinePlus