An essential role of the JAK-STAT pathway in ischemic preconditioning

The goat of this study was to determine the role of the Janus tyrosine kina se (JAK)-signal transducers and activators of transcription (STAT) pathway in the late phase of ischemic preconditioning (PC}. A total of 230 mice wer e used. At 5 min after ischemic PC (induced with six cycles of 4-min corona ry occlusion/4-min reperfusion}, immunoprecipitation with anti-phosphotyros ine (anti-pTyr) antibodies followed by immunoblotting with anti-JAK antibod ies revealed increased tyrosine phosphorylation of JAK1 (+257 +/- 53%) and JAK2 (+238 +/- 35%). indicating rapid activation of these two kinases. Simi lar results were obtained by immunoblotting with anti-pTyr-JAK1 and anti-pT yr-JAK2 antibodies. Western analysis with anti-pTyr-STAT antibodies demonst rated a marked increase in nuclear pTyr-STAT1 (+301 +/- 61%) and pTyr-STAT3 (+253 +/- 60%) 30 min after ischemic PC, which was associated with redistr ibution of STAT1 and 5TAT3 from the cytosolic to the nuclear fraction and w ith an increase in STAT1 and STAT3 gamma -lFN activation site DNA-binding a ctivity (+606 +/- 64%), indicating activation of STAT1 and STAT3. No nuclea r translocation or tyrosine phosphorylation of STAT2, STAT4, STAT5A, STAT5B , or STATE was observed. Pretreatment with the JAK inhibitor AG-490 20 min before the six occlusion/reperfusion cycles blocked the enhanced tyrosine p hosphorylation of JAK1 and JAK2 and the increased tyrosine phosphorylation, nuclear translocation, and enhanced DNA-binding activity of STAT1 and 5TAT 3. The same dose of AG-490 abrogated the protection against myocardial infa rction and the concomitant up-regulation of inducible NO synthase (iNOS) pr otein and activity observed 24 h after ischemic PC. Taken together, these r esults demonstrate that ischemic FC induces isoform-selective activation of JAK1, JAK2, STAT1, and 5TAT3, and that ablation of this response impedes t he up-regulation of iNOS and the concurrent acquisition of ischemic toleran ce. This study demonstrates that the JAK-STAT pathway plays an essential ro le in the development of late PC. The results reveal a signaling mechanism that underlies the transcriptional up-regulation of the cardiac iNOS gene a nd the adaptation of the heart to ischemic stress.