5‐Hydroxytryptamine (5‐HT) receptors induce vasocontraction and play significant roles in vascular systems. We have previously shown that transactivation of EGFR contributes to α 1 ‐adrenergic receptor mediated vasocontraction. Here, we examined EGFR transactivation in 5‐HT induced vascular contraction and extracellular‐regulated kinase (ERK 1/2 ) activation. Aortic contraction and intracellular [Ca 2+ ] response to 5‐HT in aorta and A7R5 cells, respectively, were obtained in the absence and presence of EGFR inhibitor (AG1478). To characterize EGFR transactivation, 5‐HT stimulated‐EGFR phosphorylation was determined in the absence and presence of AG1478, Ca 2+ /Calmodulin inhibitor (W7), Src kinase inhibitor (PP2). AG1478 attenuated 5‐HT induced vasocontraction and intracellular [Ca 2+ ] response. 5‐HT mediated EGFR‐transactivation was inhibited by AG1478, W7 and PP2. 5‐HT also led to phosphorylation of myosin light chain kinase (MLCK) and ERK 1/2 which were partially inhibited by AG1478, but completely by W7 and PP2. These data suggest that 5‐HT mediated EGFR‐transactivation depends on Ca 2+ /Calmodulin and Src‐kinase and is partially involved in both vascular contractility and ERK 1/2 phosphorylation in rat aorta. Grant Funding Source : This study is supported by TUBITAK 111S131
Transactivation of epidermal growth factor receptor (EGFR) by α1-adrenoceptor (α1-AR) is implicated in contraction and hypertrophy of vascular smooth muscle (VSM). We examine whether all α1-AR subtypes transactivate EGFR and explore the mechanism of transactivation. Chinese hamster ovary (CHO) cells stably expressing one subtype of α1-AR were transiently transfected with EGFR. The transactivation mechanism was examined both by coexpression of a chimeric erythropoietin (EPO)-EGFR with an extracellular EPO and intracellular EGFR domain, and by pharmacologic inhibition of external and internal signaling routes. All three α1-AR subtypes transactivated EGFR, which was dependent on the increase in intracellular calcium. The EGFR kinase inhibitor AG1478 [4-(3′-chloroanilino)-6,7-dimethoxyquinazoline] abrogated α1A-AR and α1D-AR induced phosphorylation of EGFR, but both the inhibition of matrix metalloproteinases by GM6001 [(R)-N4-hydroxy-N1-[(S)-2-(1H-indol-3-yl)-1-methylcarbamoyl-ethyl]-2-isobutyl-succinamide] or blockade of EGFR by cetuximab did not. Stimulation of α1A-AR and α1D-AR also induced phosphorylation of EPO-EGFR chimeric receptors. Moreover, α1A-AR stimulation enhanced phosphorylation of extracellular signal regulated kinase (ERK) 1/2 and serine-threonine kinases (Akt), which were both unaffected by AG1478, indicating that ERK1/2 and Akt phosphorylation is independent of EGFR transactivation. Accordingly, inhibitors of ERK1/2 or Akt did not influence the α1A-AR–mediated EGFR transactivation. Inhibition of calcium/calmodulin-dependent kinase II (CaMKII), phosphatidylinositol 3-kinase (PI3K), and Src, however, did block EGFR transactivation by α1A-AR and α1D-AR. These findings demonstrate that all α1-AR subtypes transactivate EGFR, which is dependent on an intracellular signaling route involving an increase in calcium and activation of CaMKII, PI3K, and Src, but not the of ERK1/2 and Akt pathways.
The purpose of this study was to investigate the effects of pulsatile and non-pulsatile cardiopulmonary bypass (CPB) in high risk patients. We compared clinical, hemodynamic, biochemical and hematologic parameters, arterial and venous blood gases, urine output, complement proteins, TNF-/spl alpha/, interleukins and S100/spl beta/ protein before the initiation of CPB, at the times of aortic cross-clamping and de-clamping, at Postoperative 1/sup st/ and 24/sup th/ hours. We concluded that pulsatile blood flow during CPB has favourable influence on inflamatory, physiologic and hematologic parameters in patients who have high risk for open heart surgery.
Clinical and experimental evidence suggest that increased rates of fatty acid oxidation in the myocardium result in impaired contractile function in both normal and diabetic hearts. Glucose utilization is decreased in type 1 diabetes, and fatty acid oxidation dominates for energy production at the expense of an increase in oxygen requirement. The objective of this study was to examine the effect of chronic treatment with trimetazidine (TMZ) on cardiac mechanical function and fatty acid oxidation in streptozocin (STZ)-diabetic rats. Spontaneously beating hearts from male Sprague-Dawley rats were subjected to a 60-minute aerobic perfusion period with a recirculating Krebs-Henseleit solution containing 11 mmol/L glucose, 100 muU/mL insulin, and 0.8 mmol/L palmitate prebound to 3% bovine serum albumin (BSA). Mechanical function of the hearts, as cardiac output x heart rate (in (mL/min).(beats/min).10-2), was deteriorated in diabetic (73 +/- 4) and TMZ-treated diabetic (61 +/- 7) groups compared with control (119 +/- 3) and TMZ-treated controls (131 +/- 6). TMZ treatment increased coronary flow in TMZ-treated control (23 +/- 1 mL/min) hearts compared with untreated controls (18 +/- 1 mL/min). The mRNA expression of 3-ketoacyl-CoA thiolase (3-KAT) was increased in diabetic hearts. The inhibitory effect of TMZ on fatty acid oxidation was not detected at 0.8 mmol/L palmitate in the perfusate. Addition of 1 mumol/L TMZ 30 min into the perfusion did not affect fatty acid oxidation rates, cardiac work, or coronary flow. Our results suggest that higher expression of 3-KAT in diabetic rats might require increased concentrations of TMZ for the inhibitory effect on fatty acid oxidation. A detailed kinetic analysis of 3-KAT using different concentrations of fatty acid will determine the fatty acid inhibitory concentration of TMZ in diabetic state where plasma fatty acid levels are increased.
