Temporal endothelin dynamics of the myocardial interstitium and systemic circulation in cardiopulmonary bypass

Changes in metabolism and blood flow in peripheral tissue (skeletal muscle) during cardiac surgery with cardiopulmonary bypass: the biochemical microdialysis study

The aim of this study was to monitor the metabolism and blood flow in the interstitium of the skeletal muscle during cardiac surgery with cardiopulmonary bypass (CPB) and in the early postoperative period by means of microdialysis and to compare metabolic changes during CPB at normothermia (NT) and hypothermia (HT).

Surgical revascularization using CPB was performed in 50 patients, 25 patients (group HT) were operated using hypothermic CPB, 25 (group NT) using normothermic CPB. Interstitial microdialysis was performed by two CMA 60 probes (CMA Microdialysis AB, Solna, Sweden) inserted into the patient’s deltoid muscle. Constituents analysed in the obtained dialysates, collected at intervals, were glucose, urea, glycerol and lactate. Tissue blood flow was monitored by dynamic microdialysis with gentamicin as a marker.

In both groups, NT versus HT, similar dynamics of concentrations were found. Low initial concentrations were followed by gradual increases during CPB and in the following phase of the operation. Concentrations were higher in the NT group. Immediately after the operation, the decrease in values continued, with a gradual increase in the succeeding postoperative period in both groups. Similar dynamic changes in the lactate concentration were found in both groups. The gentamicin concentrations were lower in the NT group (versus the HT group).

The results showed dynamic changes in the interstitial concentrations of glucose, urea, glycerol and lactate, which depend on the phase of the surgery in the CPB and early postoperative phase in the both groups of patients. Higher tissue perfusion of the skeletal muscle was noted in those patients operated on in normothermia. The dynamics of the concentration changes of these substances in the interstitium of the skeletal muscle has been proven to be caused by both the metabolic activity of the tissue and by the blood flow through the interstitium of the muscle.

Cardiopulmonary bypass is associated with altered vascular reactivity of isolated pulmonary artery in a porcine model: therapeutic potential of inhaled tezosentan

OBJECTIVE

Whereas it is established that endothelin-1 elicits sustained deleterious effects on the cardiovascular system during cardiopulmonary bypass (CPB), presently it remains unknown whether the inhaled administration of the dual ETA and ETB antagonist tezosentan prevents the development of pulmonary endothelial dysfunction.

DESIGN

A prospective, randomized laboratory investigation.

SETTING

University research laboratory.

PARTICIPANTS

Landrace swine.

INTERVENTIONS

Three groups of animals underwent a 90-minute period of full bypass followed by a 60-minute period of reperfusion. Among treated groups, one received tezosentan through inhalation prior to CPB, whereas the other one received it intravenously at weaning from CPB; the third group remained untreated. Pulmonary vascular reactivity studies, realized on a total of 285 rings, were performed in all groups, including 1 sham.

MEASUREMENTS AND MAIN RESULTS

The contractility of pulmonary arteries to prostaglandin F2α and to the thromboxane A2 mimetic U46619 was preserved in animals submitted to CPB. By contrast, there were significant increases both in the maximal contraction to endothelin-1 and in the plasma levels of the peptide 60 minutes after reperfusion. Tezosentan administered by inhalation or intravenously did not prevent the development of pulmonary CPB-associated endothelial dysfunction. However, while hemodynamic disturbances were improved with both routes, the inhaled administration had a beneficial effect on oxygen parameters over intravenous administration.

CONCLUSIONS

Despite the blockade of the endothelin-1 pathway with tezosentan, the development of the pulmonary endothelial dysfunction associated with CPB still occurred. However, only the inhalation route had a significant impact on gas exchange during CPB.

Off-pump myocardial revascularization attenuates endothelin-1 expression in systemic, pulmonary, and coronary circulation

OBJECTIVE

The objective of this study was to evaluate the influence of cardiopulmonary bypass (CPB) on endothelin-1 (ET-1) expression in various circulation compartments in patients undergoing myocardial revascularization.

METHODS

A total of 30 patients were randomized to undergo myocardial revascularization with (CABG, n = 15) or without (OPCAB, n = 15) CPB. Samples were taken preoperatively, after establishing CPB and after CPB (CABG group), prior to and after revascularization (OPCAB group), and 6 and 24 h postoperatively. Values of ET-1 were compared between groups at all time points and correlated with postoperative cardioselective enzyme values and clinical parameters.

RESULTS

In OPCAB group, ET-1 levels did not significantly vary between time points. In CABG group, ET-1 levels were significantly elevated vs. baseline in arterial: ART-T2 vs. ART-T0 (1.83 ± 1.81 vs. 0.76 ± 1.07 fmol/mL, p = 0.05), pulmonary: SG-T2 vs. SG-T0 (2.70 ± 2.75 vs. 0.39 ± 0.28 fmol/mL, p < 0.001) and SG-T3 vs. SG-T0 (1.56 ± 0.28 vs. 0.39 ± 0.28 fmol/mL, p < 0.001), and coronary circulation CS-T2 vs. CS-T1 (1.12 ± 0.49 vs. 0.27 ± 0.09 fmol/mL, p = 0.01). ET-1 levels were significantly higher in CABG group in all vascular compartments: ART-T2 (1.83 ± 1.81 vs. 0.17 ± 0.16 fmol/mL, p = 0.02), ART-T4 (0.99 ± 0.56 vs. 0.24 ± 0.12 fmol/mL, p = 0.01), SG-T1 (0.59 ± 0.15 vs. 0.25 ± 0.13 fmol/mL, p = 0.01), SG-T2 (2.70 ± 2.75 vs. 0.30 ± 0.24 fmol/mL, p = 0.004), SG-T3 (1.56 ± 0.28 vs. 0.35 ± 0.31 fmol/mL, p < 0.001), SG-T4 (1.34 ± 0.11 vs. 0.34 ± 0.16 fmol/mL, p < 0.001), and CS-T2 (1.12 ± 0.49 vs. 0.12 ± 0.12 fmol/mL, p = 0.004). Coronary sinus ET-1 level after CPB (CS-T2) in CABG group correlated positively with troponin-I level 24 h postoperatively (r(2) = 0.802, p = 0.02) CONCLUSION: Off-pump myocardial revascularization attenuates ET-1 expression in all investigated vascular compartments. Elevated coronary ET-1 levels after CPB in CABG group correlate with troponin-I levels 24 h postoperatively.

Effects of cardiopulmonary bypass on endothelin-1-induced contraction and signaling in human skeletal muscle microcirculation

BACKGROUND

We investigated the effects of cardiopulmonary bypass (CPB) on the contractile response of human peripheral microvasculature to endothelin-1 (ET-1), examined the role of specific ET receptors and protein kinase C-alpha (PKC-α), and analyzed ET-1-related gene/protein expression in this response.

METHODS AND RESULTS

Human skeletal muscle arterioles (90 to 180 μm in diameter) were dissected from tissue harvested before and after CPB from 30 patients undergoing cardiac surgery. In vitro contractile response to ET-1 was assessed by videomicroscopy, with and without an endothelin-A (ET-A) receptor antagonist, an endothelin-B (ET-B) antagonist, or a PKC-α inhibitor. The post-CPB contractile response of peripheral arterioles to ET-1 was significantly decreased compared with pre-CPB response. The response to ET-1 was significantly inhibited in the presence of the ET-A antagonist BQ123 but unchanged in the presence of the ET-B receptor antagonist BQ788. Pretreatment with the PKC-α inhibitor safingol reversed ET-1-induced response from contraction to relaxation. The total protein levels of ET-A and ET-B receptors were not altered after CPB. Microarray analysis showed no significant changes in the gene expression of ET receptors, ET-1-related proteins, and protein kinases after CPB.

CONCLUSIONS

CPB decreases myogenic contractile function of human peripheral arterioles in response to ET-1. The contractile response to ET-1 is through activation of ET-A receptors and PKC-α. CPB has no effects on ET-1-related gene/protein expression. These results provide novel mechanisms of ET-1-induced contraction in the setting of vasomotor dysfunction after cardiac surgery.

Endothelin-1-induced contractile responses of human coronary arterioles via endothelin-A receptors and PKC-alpha signaling pathways

BACKGROUND

We investigated the contractile function in responses to endothelin-1 (ET-1) in the human coronary microvasculature as well as the roles of endothelin receptors and protein kinase C-alpha (PKC-alpha) in these responses.

METHODS

Human atrial tissue was harvested from patients who underwent cardiac surgery pre- and post-cardioplegia (CP)/cardiopulmanory bypass (CPB). Microvascular constriction was assessed in pre- and post-CP/CPB samples in responses to ET-1, in the presence and absence of an endothelin-A (ET-A) receptor antagonist, an endothelin-B (ET-B) receptor antagonist, or a PKC-alpha inhibitor, respectively. The expression and localization of the ET-A and ET-B receptors were also examined using immunoblot and immunofluorescence photomicroscopy.

RESULTS

The post-CP/CPB contractile response of coronary arterioles to ET-1 was significantly decreased compared with the pre-CP/CPB responses. The response to ET-1 was significantly inhibited in the presence of the ET-A antagonist BQ123 (10(-7)mol/L), but these values remained unchanged with the ET-B receptor antagonist BQ788 (10(-7)mol/L). Pretreatment with the PKC-alpha inhibitor safingol (2.5 x 10(-5) mol/L) reversed the ET-1 responses from contraction into relaxation. The total polypeptide levels of ET-A and ET-B receptors were not altered post-CP/CPB. Immunoblot and immunofluorescent staining displayed strong signals for ET-A receptors and relatively weak signals for ET-B receptors localized on coronary microvasculature.

CONCLUSION

CP/CPB decreases the contractile function of human coronary microvessels in responses to ET-1. ET-A receptors are predominantly localized in the human coronary microcirculation, whereas ET-B receptors seem to be less abundant. The contractile response to ET-1 is in part through the activation of ET-A receptors and PKC-alpha. These results suggest a role of ET-1-induced contraction in the vasomotor dysfunction after cardiac surgery.

Protein Kinase C Isoform Activation and Endothelin-1 Mediated Defects in Myocyte Contractility After Cardioplegic Arrest and Reperfusion

BACKGROUND

Endothelin-1 (ET-1) is released after hyperkalemic cardioplegic arrest (CA) and reperfusion and may contribute to contractile dysfunction. ET-1 receptor transduction causes activation of protein kinase C (PKC) isoforms, which can cause differential intracellular events. The goal of this study was to determine which PKC isoforms contribute to myocyte contractile dysfunction with ET-1 and CA.

METHODS AND RESULTS

Percent shortening (PERSHORT) and the time to 50% relaxation (T50) were measured in porcine (n =22) left ventricular myocytes, randomized (minimum: 30 cells/group) to normothermia: (cell media for 2 hours/37 degrees C), and CA: (2 hours/4 degrees C, 24 mEq K+ solution followed by reperfusion in cell media), ET-1/CA: (100 pM ET-1 during CA). Studies were performed in the presence and absence of PKC inhibitors (500 nM) against the classical (Beta-I, Beta-II, Gamma) and novel (Epsilon, Eta) isoforms (myocytes from a minimum of 3 pigs per inhibitor). CA reduced PERSHORT by approximately 35% from normothermia (P<0.05), which was further reduced with ET-1. PKC-Beta-II or PKC-Gamma inhibition increased PERSHORT from ET-1/CA as well as CA only (P<0.05). CA prolonged T50 by approximately 19% from normothermia (P<0.05) and was further prolonged with ET-1. Inhibition of the classical PKC isoforms reduced T50 from ET-1/CA (P<0.05). Inhibition of novel PKC isoforms did not yield similar effects on either PERSHORT or T50 with ET-1/CA.

CONCLUSIONS

Inhibition of the classical PKC isoforms relieved the negative inotropic and lusitropic effects of ET-1 after CA. These findings provide mechanistic support for developing targeted inhibitory strategies with respect to ET-1 signaling and myocyte contractile dysfunction with cardioplegic arrest and reperfusion.

Disruptions and detours in the myocardial matrix highway and heart failure

Myocardial remodeling invariably occurs in congestive heart failure (CHF) and is a response to a prolonged cardiovascular stress, which is characterized by a cascade of compensatory structural events. Remodeling of the myocardial interstitium occurs in CHF and likely contributes to the progression of the remodeling process. The myocardial matrix can be considered a biological highway in which a large amount of signaling proteins and structural proteins are being moved within the interstitium, entering and exiting the interstitial space, and docking to cellular components. The rates at which these events occur can accelerate and decelerate depending on the particular cardiac disease state and thereby can alter the course of myocardial remodeling. Once considered merely a scaffolding to align cells, the matrix plays a complex and divergent role in influencing cell behavior. For example, the matrix has a functional role in cell migration, proliferation, adhesion, and cell-to-cell signaling. In light of this, the myocardial matrix should not be regarded as merely a static structure, but rather, as a complex system of dynamic interactions between matrix molecules, signaling proteins, and transmembrane proteins. Specific strategies that are targeted at modifying activity along this matrix highway will likely alter the course of myocardial remodeling and heart failure.

Increased endothelin-1 production in diabetic patients after cardioplegic arrest and reperfusion impairs coronary vascular reactivity: reversal by means of endothelin antagonism

OBJECTIVES

Evidence has accrued to suggest that diabetic patients face an increased risk of ischemic events and low output syndrome and might mount an inordinate response to ischemia and reperfusion. Because hyperglycemia is a potent stimulus for endothelin-1 production, we hypothesized that increased production, action, or both of endothelin-1 in diabetes might represent an important mediator of endothelial dysfunction in patients with that disease. To this aim, we compared the effects of cardioplegic arrest and reperfusion on coronary sinus effluent endothelin-1 levels and atrial arteriolar vascular responses in diabetic and case-matched nondiabetic patients undergoing coronary artery bypass grafting.

METHODS

In study 1 coronary sinus effluent endothelin-1 levels were assessed at baseline and at 1 and 10 minutes after reperfusion in 13 diabetic and 12 nondiabetic patients matched for age, ejection fraction, Parsonnet score, and crossclamp time. In study 2 vascular responses of atrial arterioles subjected to perioperative ischemia-reperfusion were evaluated with videomicroscopy. Atrial microvessels (from appendages) were obtained before and after removal of the aortic crossclamp, and vascular responses to exogenously administered endothelin-1 (10(-10) mol/L) and substance P (10(-8) mol/L) were studied in the presence or absence of BQ-123, an endothelin A receptor antagonist.

RESULTS

Diabetic patients elaborated more endothelin-1 at 1 and 10 minutes after reperfusion (P =.01). Endothelin-1-mediated vasoconstriction was similar in diabetic and nondiabetic atrial microvessels before cardioplegic arrest and cardiopulmonary bypass. After cardiopulmonary bypass and reperfusion, endothelin-1-mediated vasoconstriction was enhanced in both groups; however, this response was greater in microvessels from diabetic patients (P =.02). BQ-123, the endothelin A antagonist, attenuated the effects of bypass and reperfusion on endothelin-1-mediated vasoconstriction in both groups (P =.01). Substance P-mediated vasodilatation was similar in diabetic and nondiabetic atrial microvessels before bypass. After bypass and reperfusion, substance P-mediated vasodilatation was diminished in both groups; however, this response was more pronounced in the diabetic group (P =.003). BQ-123 coincubation restored substance P-mediated vasodilatation in both groups.

CONCLUSIONS

We determined the following: (1) the coronary effluent release of endothelin-1 is higher in diabetic than in nondiabetic patients after cardiopulmonary bypass and reperfusion; (2) diabetic coronary microvessels respond to bypass and reperfusion with greater endothelin-1-mediated vasoconstriction and diminished nitric oxide-mediated vasodilatation; and (3) these effects are attenuated by endothelin antagonism. Endothelin-1 might be an important mediator of ischemia-reperfusion injury in patients with diabetes. Furthermore, use of endothelin receptor antagonists might be a novel strategy for improving the resistance of the diabetic heart to cardioplegic arrest and reperfusion.

Hyperglycemia exaggerates ischemia-reperfusion-induced cardiomyocyte injury: reversal with endothelin antagonism

OBJECTIVES

We have previously demonstrated an importance of endothelin-1 in diabetic patients undergoing bypass surgery. Recent evidence suggests that cardiomyocytes might also produce endothelin-1, which might directly impair myocyte contractility by increasing intracellular calcium levels. Because hyperglycemia is a potent stimulus of endothelin-1 production, we hypothesized that increased production, action, or both of endothelin-1 might be a mediator of direct cardiomyocyte injury in diabetes. Therefore we studied the effects of endothelin receptor blockers (BQ-123 and bosentan) on hyperglycemia-induced endothelin-1 production and cellular injury after ischemia-reperfusion.

METHODS

Using a human ventricular heart cell model of simulated ischemia-reperfusion, we studied the effects of normoglycemia (5 mmol/L, 48 hours) and hyperglycemia (25 mmol/L, 48 hours) on cellular injury and endothelin-1 production. Furthermore, the effects of selective endothelin-A and mixed endothelin-A/B receptor antagonism (with BQ-123 and bosentan, respectively) were evaluated.

RESULTS

Cellular injury, as assessed by means of trypan blue uptake, was higher in human ventricular heart cells subjected to hyperglycemia and simulated ischemia-reperfusion injury (P =.01); this effect was prevented with both BQ-123 and bosentan (P =.01). In addition, heart cells from the hyperglycemic group elaborated more endothelin-1 after ischemia-reperfusion (P =.02).

CONCLUSIONS

Endothelin-1 production and cellular injury were greater in human ventricular heart cells subjected to hyperglycemic conditions and simulated ischemia-reperfusion. These effects are mediated by endothelin-A receptors because both BQ-123 and bosentan exerted similar degrees of protection. Endothelin receptor blockade is a novel strategy to improve the resistance of the diabetic heart to cardioplegic arrest and reperfusion.

Long-term angiotensin-converting enzyme and angiotensin I--receptor inhibition in pacing-induced heart failure: effects on myocardial interstitial bradykinin levels

BACKGROUND

We examined whether and to what degree long-term angiotensin-converting enzyme (ACE) inhibition, angiotensin type 1 (AT(1))-receptor blockade, or combined inhibition in developing congestive heart failure (CHF) alter myocardial interstitial bradykinin (BF) levels.

METHODS AND RESULTS

Pigs (27-30 kg) underwent rapid pacing-induced CHF (240 bpm, 3 weeks; n = 10); pacing CHF with concomitant ACE inhibition (benezaprilat, 3.75 mg/day; n = 10); pacing CHF and concomitant AT(1)-receptor blockade (valsartan, 60 mg/day; n = 10); pacing CHF and combined inhibition (benezaprilat/valsartan, 1.87/60 mg/day, respectively; n = 10); or served as controls (no pacing, no treatment; n = 10). Steady-state myocardial interstitial BK levels were quantitated by microdialysis. Cardiac output decreased to 1.95 +/- 0.18 L/min in pacing CHF compared with control (3.78 +/- 0.38; P < .05). Cardiac output increased from untreated CHF values with concomitant ACE inhibition (3.91 +/- 0.27 L/min), AT(1)-receptor blockade (3.30 +/- 0.41 L/min), or combined ACE/AT(1)-receptor inhibition (4.13 +/- 0.32 L/min; all P < .05 v CHF). With pacing CHF, myocardial interstitial BK levels were reduced by approximately 50% from control values and were normalized in the ACE inhibition and combined inhibition groups.

CONCLUSIONS

Long-term ACE inhibition increases myocardial interstitial BK levels with CHF; addition of AT(1)-receptor blockade does not seem to abrogate these effects.