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J Mol Cell Cardiol. 2003 May;35(5):525-37.

Mechanism of cyclooxygenase-2 upregulation in late preconditioning.

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Experimental Research Laboratory, Division of Cardiology, University of Louisville and the Jewish Hospital Heart and Lung Institute, Louisville, KY 40292, USA.


Although the cardioprotection of late preconditioning (PC) is known to be mediated by both inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), the signaling mechanism responsible for COX-2 upregulation and the interaction between iNOS and COX-2 remain unknown. A total of 122 mice were used to address this issue. In wild-type mice preconditioned with six cycles of 4-min coronary occlusion-4-min reperfusion, ischemic PC resulted in rapid activation of nuclear STAT1/3 through tyrosine phosphorylation (STAT1: 339 +/- 48% of control; STAT3: 389 +/- 46% of control) and increased STAT1/3-DNA binding activity (687 +/- 58% of control) at 30 min after PC, with subsequent upregulation of COX-2 protein (373 +/- 60% of control) and activity(increased myocardial levels of PGE2, PGF(2alpha), and 6-keto-PGF(1alpha)) at 24 h. However, COX-1 protein was not changed 24 h after ischemic PC. Pretreatment with the Janus tyrosine kinase (JAK) inhibitor AG-490 before the six occlusion-reperfusion cycles blocked both the tyrosine phosphorylation of STAT1/3 and the subsequent upregulation of COX-2 protein, demonstrating a necessary role of the JAK-STAT pathway in the induction of COX-2. Targeted disruption of the iNOS gene (iNOS-/-) did not block the increased expression of COX-2 protein 24 h after ischemic PC but completely blocked the increase in COX-2 activity, whereas targeted disruption of the COX-2 gene (COX-2-/-) did not alter ischemic PC-induced iNOS induction. Immunoprecipitation of preconditioned heart tissues with anti-COX-2 antibodies followed by immunoblotting with anti-iNOS antibodies revealed that the increased iNOS protein co-precipitated with COX-2. We conclude that (i) the upregulation of COX-2 protein expression after ischemic PC is mediated by a JAK1/2-STAT1/3-signaling cascade; (ii) COX-2 activity requires upregulated iNOS and iNOS-derived NO; and (iii) COX-2 forms complexes with iNOS, supporting a direct interaction between these two proteins. To our knowledge, this is the first evidence that myocardial COX-2 is upregulated via a JAK1/2-STAT1/3 pathway.

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