Effects of angiotensin II type 1 receptor antagonist and temperature on prolonged cardioplegic arrest in neonatal rat myocytes.

Cardioplegic arrest is a model of ischemia/reperfusion injury and results in the death of irreplaceable cardiac myocytes by a programmed cell death or apoptosis. Signal transducers and activators of transcription (STAT) signaling pathways play an important role in the modulation of apoptosis after ischemia and reperfusion. Angiotensin II type 1 (AT1) receptor antagonist added to cardioplegia could represent an additional modality for enhancing myocardial protection during cardioplegic arrest. To test that hypothesis, we studied the effect of AT1 receptor antagonism and cardioplegia temperature perfusion on STATs modulation during cardioplegic arrest in neonatal rat hearts. Isolated, nonworking hearts (n = 4 per group) from neonatal rats were perfused aerobically in the Langendorff mode according to the following scheme: Dulbecco's Modified Eagle's Medium solution (Group 1); cold (4°C) modified St. Thomas' Hospital no. 2 (MSTH2) cardioplegic solution (Group 2); cold (4°C) MSTH2 cardioplegic solution plus AT1 antagonist (Valsartan) (Group 3); and warm (34°C) MSTH2 cardioplegic solution (Group 4). Thus, myocytes were isolated by enzymatic digestion, and STAT1, STAT2, STAT3, and STAT5 were investigated in Western blot studies. Times to arrest after cardioplegia were 6-10 s for all groups with the exception of Group 1 (spontaneous arrest after 12-16 s). Total cardioplegia delivery volume was about 300 mL in 15 min. Perfusion with cold MSTH2 supplemented with AT1 receptor antagonist (Group 3) induced a significant reduction in STAT1, STAT2, and STAT5 tyrosine phosphorylation versus other groups (P < 0.05). The decreased activation of STAT1, STAT2, and STAT5 observed in Group 3 was accompanied by reduction of interleukin-1ß (P < 0.05). On the other hand, STAT3 activation was significantly reduced in Groups 1 and 4 (P < 0.05). Only perfusion with AT1 receptor antagonist supplemented with cold MSTH2 significantly decreases the inflammatory response of the neonatal rat cardiomyocytes without affecting antiapoptotic influence provided by activation of STAT3. Therefore, AT1 receptor antagonist could play a pivotal role in cytoprotective effect and cardiac recovery in neonates and infants.

Impaired JAK2-induced activation of STAT3 in failing human myocytes.

Although angiotensin (Ang)II-induced Janus-activated kinase (JAK)2 phosphorylation was reported to be enhanced in failing human cardiomyocytes, the downstream balance between cardio-protective (signal transducer and activator of transcription-STAT3) and the pro-inflammatory (STAT2 and STAT5) response remains unexplored. Therefore STATs phosphorylation and putative genes overexpression following JAK2 activation were investigated in isolated cardiomyocytes obtained from failing human hearts (n = 16), and from non-failing(NF) hearts of humans (putative donors, n = 6) or adult rats. In NF myocytes Ang II-induced JAK2 activation was followed by STAT3 phosphorylation (186 ± 45% at 30 min), with no STAT2 or STAT5 response. The associated B cell lymphoma (Bcl)-xL overexpression (1.05 ± 0.39 fold) was abolished by both JAK2 and extracellular signal-regulated kinase (ERK)1/2 inhibitors (AG490, 10 µM, and PD98059, 30 µM, respectively), whereas Fas ligand (Fas-L) response (0.91 ± 0.21 fold) was inhibited only by p38MAPK antagonism (SB203580, 10 µM). In failing myocytes Ang II-induced JAK2 activation was followed by STAT2 (237 ± 38%) and STAT5 (222 ± 31%) phosphorylation, with no STAT3 response. No changes in Bcl-xL expression were observed, and the associated Fas-L gene overexpression (1.14 ± 0.27 fold) being abolished by p38 mitogen-activated protein kinase (MAPK) antagonism. The altered JAK2 induced STATs response in human failing cardiomyocytes may be of relevance for the progression of cardiac dysfunction in heart failure.

Cardioplegia and angiotensin II receptor antagonists modulate signal transducers and activators of transcription activation in neonatal rat myocytes.

Previous investigations have shown that the signal transducers and activators of transcription (STATs) signaling pathway play an important role in the modulation of apoptosis after ischemia and reperfusion. The mechanism for this enhanced cardioprotection is unknown, but we believe that alterations STATs may play a role. To investigate this hypothesis, we examined the effects of angiotension II type 1 (AT1) and angiotension II type 2 (AT2) receptor antagonist added to cardioplegia on the downstream response of different STATs, connected with proinflammatory pathways (STAT2, STAT5) and prohypertrophic and antiapoptotic pathways (STAT3). Isolated, nonworking hearts (n = 3 per group) from neonatal rats were perfused aerobically (4°C) for 20 min in the Langendorff mode with the modified St. Thomas' Hospital no. 2 (MSTH2) cardioplegic solution (Group 1), the MSTH2 cardioplegic solution + AT1 receptor antagonist (Group 2), and MSTH2 cardioplegic solution + AT2 receptor antagonist (Group 3). Thus, myocytes were isolated by enzymatic digestion, and STAT2, STAT3, and STAT5 were investigated in Western blot studies. Times to arrest after cardioplegia were 8-12 s for all groups. Total cardioplegia delivery volume was about 300 mL for the 20 min. Perfusion with the MSTH2 cardioplegic solution supplemented with AT1 receptor antagonist (Group 2) induced a significant reduction in STAT2 and STAT5 tyrosine phosphorylation (-58 and -63%, respectively, vs. Group 1, P < 0.05). Conversely, STAT2 and STAT5 activation were unaffected by perfusion with the MSTH2 cardioplegic solution supplemented with AT2 receptor antagonist (Group 3). The decreased activation of STAT2 and STAT5 observed in Group 2 was accompanied by reduction of interleukin-1ß (-57% in Group 2 vs. Group 1, P < 0.05). There were no significant differences in STAT3 phosphorylation among all groups. Only the addition of AT1 receptor antagonist to MSTH2 cardioplegia significantly decreases the inflammatory response of the neonatal rat cardiomyocytes without affecting antiapoptotic influence provided by tyrosine phosphorylation of STAT3. AT1 receptor antagonist added to cardioplegia represents an additional modality for enhancing myocardial protection during cardiac surgery and could contribute to optimize the ischemia tolerance of the pediatric heart.

Index measured at an intermediate altitude to predict impending acute mountain sickness.

PURPOSE: Acute mountain sickness (AMS) is a neurological disorder that may be unpredictably experienced by subjects ascending at a high altitude. The aim of the present study was to develop a predictive index, measured at an intermediate altitude, to predict the onset of AMS at a higher altitude. METHODS: In the first part, 47 subjects were investigated and blood withdrawals were performed before ascent, at an intermediate altitude (3440 m), and after acute and chronic exposition to high altitude (Mount Everest Base Camp, 5400 m (MEBC1 and MEBC2)). Parameters independently associated to the Lake Louise scoring (LLS) system, including the self-reported and the clinical sections, and coefficients estimated from the model obtained through stepwise regression analysis were used to create a predictive index. The possibility of the index, measured after an overnight stay at intermediate altitude (Gnifetti hut, 3647 m), to predict AMS (defined as headache and LLS ≥ 4) at final altitude (Capanna Margherita, 4559 m), was then investigated in a prospective study performed on 44 subjects in the Italian Alps. RESULTS: During the expedition to MEBC, oxygen saturation, hematocrit, day of expedition, and maximum velocity of clot formation were selected as independently associated with LLS and were included in the predictive index. In the Italian Alps, subjects with a predictive index value ≥ 5.92 at an intermediate altitude had an odds ratio of 8.1 (95% confidence limits = 1.7-38.6, sensitivity = 85%, specificity = 59%) for developing AMS within 48 h of reaching high altitude. CONCLUSION: In conclusion, a predictive index combining clinical and hematological parameters measured at an intermediate step on the way to the top may provide information on impending AMS.

Response of serum proteome in patients undergoing infrarenal aortic aneurysm repair.

BACKGROUND: Postoperative organ dysfunction in conventional surgery for abdominal aortic aneurysm (AAA) is associated with a complex inflammatory reaction, with activation of coagulation and fibrinolysis. A prospective,observational study was performed to define the complex plasma proteomic changes after AAA repair and to identify factor(s) that may affect myocardial function in uncomplicated procedures. METHODS: Ten patients undergoing infrarenal AAA repair were investigated. Eight subjects subjected to major abdominal surgery served as controls. Hemodynamic changes were continuously monitored by using the pressure recording analytical method technique. The time course of plasma proteins was investigated after induction of anesthesia and at different times after surgery (6 h, 12 h, 24 h, 36 h) by using two-dimensional difference gel electrophoresis, matrix-assisted laser desorption/ionization-time of flight mass spectrometry, and Western blot. The effects of plasma on the functional properties of isolated rat ventricular myocytes were also investigated. RESULTS: In AAA patients alone, 18 spots were found to change more than two-fold in expression level, spot identification revealing an increased thrombin generation 6 h after surgery. At the same time cardiac cycle efficiency significantly reduced versus baseline (-0.5 +/- 0.9 vs. 0.18 +/- 0.3 in AAA patients, P < 0.01; 0.4 +/- 0.1 vs. 0.2 +/- 0.3 in control surgery, not significant; P < 0.01 group x time interaction at ANOVA). Plasma obtained 6 h after AAA surgery dose-dependently inhibited contractile function of control rat myocytes (percent shortening fell by 51% with 10% of AAA plasma and was abolished with 20% of AAA plasma, P < 0.001 for both). The inhibitory response was abolished by thrombin antagonism. CONCLUSIONS: These findings show for the first time the possible role of thrombin generation within the complex activation of inflammatory response in causing hemodynamic instability in the early postoperative period after AAA surgery.