Protein kinase C alpha modulates microvascular reactivity in the human coronary and skeletal microcirculation

Role of Protein Kinase C in Metabolic Regulation of Coronary Endothelial Small Conductance Calcium-Activated Potassium Channels

BACKGROUND

Small conductance calcium-activated potassium (SK) channels are largely responsible for endothelium-dependent coronary arteriolar relaxation. Endothelial SK channels are downregulated by the reduced form of nicotinamide adenine dinucleotide (NADH), which is increased in the setting of diabetes, yet the mechanisms of these changes are unclear. PKC (protein kinase C) is an important mediator of diabetes-induced coronary endothelial dysfunction. Thus, we aimed to determine whether NADH signaling downregulates endothelial SK channel function via PKC.

METHODS AND RESULTS

SK channel currents of human coronary artery endothelial cells were measured by whole cell patch clamp method in the presence/absence of NADH, PKC activator phorbol 12-myristate 13-acetate, PKC inhibitors, or endothelial PKCα/PKCβ knockdown by using small interfering RNA. Human coronary arteriolar reactivity in response to the selective SK activator NS309 was measured by vessel myography in the presence of NADH and PKCβ inhibitor LY333531. NADH (30-300 μmol/L) or PKC activator phorbol 12-myristate 13-acetate (30-300 nmol/L) reduced endothelial SK current density, whereas the selective PKCᵦ inhibitor LY333531 significantly reversed the NADH-induced SK channel inhibition. PKCβ small interfering RNA, but not PKCα small interfering RNA, significantly prevented the NADH- and phorbol 12-myristate 13-acetate-induced SK inhibition. Incubation of human coronary artery endothelial cells with NADH significantly increased endothelial PKC activity and PKCβ expression and activation. Treating vessels with NADH decreased coronary arteriolar relaxation in response to the selective SK activator NS309, and this inhibitive effect was blocked by coadministration with PKCβ inhibitor LY333531.

CONCLUSIONS

NADH-induced inhibition of endothelial SK channel function is mediated via PKCβ. These findings may provide insight into novel therapeutic strategies to preserve coronary microvascular function in patients with metabolic syndrome and coronary disease.

Increased Coronary Contraction to Thromboxane A2 in Cardiac Surgery Patients With Poorly Controlled Hypertension

INTRODUCTION

Cardioplegia and cardiopulmonary bypass (CP/CPB) alters coronary arteriolar response to thromboxane A2 (TXA2) in patients undergoing cardiac surgery. Comorbidities, including hypertension (HTN), can further alter coronary vasomotor tone. This study investigates the effects of HTN on coronary arteriolar response to TXA2 pre and post-CP/CPB and cardiac surgery.

MATERIALS AND METHODS

Coronary arterioles pre and post-CP/CPB were dissected from atrial tissue samples in patients with no HTN (NH, n = 9), well-controlled HTN (WC, n = 12), or uncontrolled HTN (UC, n = 12). In-vitro coronary microvascular reactivity was examined in the presence of TXA2 analog U46619 (10-9-10-4M). Protein expression of TXA2 receptor in the harvested right atrial tissue samples were measured by immunoblotting.

RESULTS

TXA2 analog U46619 induced dose-dependent contractile responses of coronary arterioles in all groups. Pre-CPB contractile responses to U46619 were significantly increased in microvessels in the UC group compared to the NH group (P < 0.05). The pre-CP/CPB contractile responses of coronary arterioles were significantly diminished post-CP/CPB among the three groups (P < 0.05), but there remained an increased contractile response in the microvessels of the UC group compared to the WC and NH groups (P < 0.05). There were no significant differences in U46619-induced vasomotor tone between patients in the NH and WC groups (P > 0.05). There were no differences in expression of TXA2R among groups.

CONCLUSIONS

Poorly controlled HTN is associated with increased contractile response of coronary arterioles to TXA2. This alteration may contribute to worsened recovery of coronary microvascular function in patients with poorly controlled HTN after CP/CPB and cardiac surgery.

Acute protein kinase C beta inhibition preserves coronary endothelial function after cardioplegic hypoxia/reoxygenation

Objective

Protein kinase C (PKC) influences myocardial contractility and susceptibility to long-term cardiac dysfunction after ischemia-reperfusion injury. In diabetes, PKC inhibition has a protective effect in terms of microvascular dysfunction. SK-channel dysfunction also influences endothelial dysfunction in cardioplegic hypoxia-reoxygenation (CP-H/R). Here, we examine whether acute inhibition of PKC beta protects against CP-H/R-induced coronary endothelial and SK channel dysfunction.

Methods

Isolated mouse coronary arterioles, half pretreated with selective PKC inhibitor ruboxistaurin (RBX), were subjected to hyperkalemic, cardioplegic hypoxia (1 hour), and reoxygenation (1 hour) with Krebs buffer. Sham control vessels were continuously perfused with oxygenated Krebs buffer without CP-H/R. After 1 hour of reoxygenation, responses to the endothelium-dependent vasodilator adenosine-diphosphate (ADP) and the SK-channel activator NS309 were examined. Endothelial SK-specific potassium currents from mouse heart endothelial cells were examined using whole-cell path clamp configurations in response to NS309 and SK channel blockers apamin and TRAM34.

Results

CP-H/R significantly decreased coronary relaxation responses to ADP (P = .006) and NS309 (P = .0001) compared with the sham control group. Treatment with selective PKC beta inhibitor RBX significantly increased recovery of coronary relaxation responses to ADP (P = .031) and NS309 (P = .004) after CP-H/R. Treatment with RBX significantly increased NS309-mediated potassium currents following CP-H/R (P = .0415). Apamin and TRAM34 sensitive currents were significantly greater in CP-H/R + RBX versus CP-H/R mouse heart endothelial cells (P = .0027).

Conclusions

Acute inhibition of PKC beta significantly protected mouse coronary endothelial function after CP-H/R injury. This suggests that acute PKC beta inhibition may be a novel approach for preventing microvascular dysfunction during CP-H/R.

Poorly controlled hypertension is associated with increased coronary myogenic tone in patients undergoing cardiac surgery with cardiopulmonary bypass

OBJECTIVE

Cardioplegia and cardiopulmonary bypass dysregulate coronary vasomotor tone, which can be further affected by common comorbidities in patients undergoing cardiac surgery. This study investigates differences in coronary myogenic tone and vasomotor responses to phenylephrine before and after cardioplegia and cardiopulmonary bypass based on hypertension history.

METHODS

Coronary arterioles before and after cardioplegia and cardiopulmonary bypass were dissected from atrial tissue samples in patients with no hypertension, well-controlled hypertension, or uncontrolled hypertension, as determined by documented history of hypertension, antihypertensive agent use, and clinical blood pressure measurements averaged over 1 year. Myogenic tone in response to stepwise increases in intraluminal pressure was studied between pressure steps. Microvascular reactivity in response to phenylephrine was assessed via vessel myography. Protein expression was measured with immunoblotting.

RESULTS

Coronary myogenic tone was significantly increased in the uncontrolled hypertension group compared with the no hypertension and well-controlled hypertension groups before cardioplegia and cardiopulmonary bypass at higher intraluminal pressures, and after cardioplegia and cardiopulmonary bypass across all intraluminal pressures (P < .05). Contractile responses to phenylephrine were significantly enhanced in patients in the uncontrolled hypertension group compared with the well-controlled hypertension group before cardioplegia and cardiopulmonary bypass, and in the uncontrolled hypertension group compared with the no hypertension and well-controlled hyertension groups after cardioplegia and cardiopulmonary bypass (P < .05). There were no differences in myogenic tone or phenylephrine-induced reactivity between the no hypertension and well-controlled hypertension groups (P > .05). There was increased expression of phosphorylated protein kinase C alpha in the uncontrolled hypertension group after cardiopulmonary bypass compared with before cardiopulmonary bypass and increased phosphorylated extracellular signal-regulated kinase 1/2 in the uncontrolled hypertension compared with the no hypertension group after cardiopulmonary bypass (P < .05).

CONCLUSIONS

Uncontrolled hypertension is associated with increased coronary myogenic tone and vasoconstrictive response to phenylephrine that persists after cardioplegia and cardiopulmonary bypass.

Prenatal hypoxia attenuated contraction of offspring coronary artery associated with decreased PKCβ Ser660 phosphorylation and intracellular calcium

AIMS

Prenatal hypoxia (PH) could affect peripheral vascular tone of the offspring, thus increasing the risk of cardiovascular diseases in adult. However, it's still unknown whether functions of coronary arteries (COA) in adult offspring would be influenced by PH. The present study aimed at effects of PH on vascular tone of COA and its related mechanisms.

METHODS

Coronary arteries of adult offspring exposed to hypoxic or normoxic circumstances during gestational day 5 to 21 were collected. Wire myograph system, whole-cell patch clamp technique, IonOptix MyoCam system, PCR, and western blot were used to detect vascular function of adult offspring COA.

KEY FINDINGS

PH significantly attenuated serotonin- and phorbol 12, 13-dibutyrate (PDBu)-induced constriction. Iberiotoxin potentiated PDBu-induced constriction and the effect was augmented by PH, however, no significant differences were found in whole-cell BK_Ca channel currents and its protein expression. Nifedipine inhibited PDBu-mediated constriction and the inhibitory effect was reduced in PH group, and whole-cell calcium channel current was decreased in offspring COA. Besides, PH reduced the capability of calcium release from the endoplasmic reticulum in COA. The phosphorylated PKCβ protein expression at Ser⁶⁶⁰ site, not Thr⁶⁴¹ site, was significantly decreased in PH offspring. Chronic hypoxia during pregnancy attenuated PDBu-mediated constriction in offspring COA, presumably through decreased phosphorylated PKCβ at serine⁶⁶⁰ sites and decreased intracellular calcium-related weaker PKC activation.

SIGNIFICANCE

The findings provided new information on the influence of prenatal hypoxia on COA, and suggested potential use of PKCβ-serine⁶⁶⁰ for early prevention of coronary heart diseases in developmental origins.

Skeletal muscle microvasculature response to β-adrenergic stimuli is diminished with cardiac surgery

BACKGROUND

Cardiac surgery and cardiopulmonary bypass are associated with alterations in blood pressure in the perioperative period, which, if uncontrolled, can result in end organ damage or dysfunction. Microvessels, significant contributors to blood pressure, both in the myocardium and peripheral skeletal muscle, have diminished responsiveness to major mediators of vascular tone, including thromboxane and serotonin after cardiopulmonary bypass. Responsiveness of these vessels to β-adrenergic stimulation, a major mediator of vascular tone, has not yet been studied. In this report, we investigated the role of β-adrenergic receptors in vascular tone regulation in human skeletal muscle microvessels before and after β-adrenergic stimulation.

METHODS

Skeletal muscle microvessels were isolated from patients undergoing cardiac surgery before and after cardiopulmonary bypass. Vessels were exposed in an ex vivo model to the β-adrenergic agonist isoproterenol, or the direct adenylyl cyclase activator, forskolin, and the selective β-receptor antagonist ICI18.551 hydrochloride plus isoproterenol. Immunofluorescence of β receptors and Western blotting were also performed.

RESULTS

Microvessels showed diminished responsiveness to isoproterenol (10^-6 to 10^-4M) after cardiopulmonary bypass (n = 8/group, P = .01). Pretreatment with the selective β-2 blocker ICI18.551 (10^-6M) prevented isoproterenol-induced microvascular relaxation (P = .001). Forskolin-induced relaxation response was also significantly diminished after cardiopulmonary bypass (n = 4/group, P < .05 versus before cardiopulmonary bypass). No significant changes in the total protein expression of β-1, β-2, and β-3 receptors were detected by western blotting or immunofluorescence.

CONCLUSION

Microvessels isolated from human skeletal muscle show diminished responsiveness to isoproterenol and its downstream activator forskolin after cardiopulmonary bypass, suggesting there is an alteration in β-adrenergic receptor responsive in adenylate cyclase. The relaxation response to isoproterenol was via activation β-2 receptors without changes in β-adrenergic receptor abundance.

Enhanced coronary arteriolar contraction to vasopressin in patients with diabetes after cardiac surgery

OBJECTIVE

Cardioplegic arrest (CP) and cardiopulmonary bypass (CPB) are associated with vasomotor dysfunction of coronary arterioles in patients with diabetes (DM) undergoing cardiac surgery. We hypothesized that DM may up-regulate vasopressin receptor expression and alter the contractile response of coronary arterioles to vasopressin in the setting of CP/CPB.

METHODS

Right atrial tissue samples of patients with DM and without (ND) (n = 8 in each group) undergoing cardiac surgery were harvested before and after CP/CPB. The isolated coronary arterioles (80-150 μm) dissected from the harvested right atrial tissue samples were cannulated and pressurized (40 mm Hg) in a no-flow state. The changes in diameter were measured with video microscopy. The protein expression/localization of vasopressin 1A receptors (V1A) and vasopressin 1B receptors (V1B) in the atrial tissue were measured by immune-blotting and immunohistochemistry.

RESULTS

The pre-CP/CPB contractile responses of the coronary arterioles to vasopressin were significantly increased post-CP/CPB in both the ND and DM groups. This effect was more pronounced in the vessels from patients in the DM group than that of vessels from patients in the ND group (P < .05). Vasopressin-induced contractile response of the coronary arterioles was inhibited in the presence of the specific V1A antagonist SR 49059 (10-7 M) in both ND and DM vessels (P < .05). The post-CP/CPB protein levels of V1A were significantly increased compared with pre-CP/CPB values in both the ND and DM groups (P < .05), whereas this increase was greater in DM than that of ND (P < .05). Immunohistochemistry staining further indicates that V1B were mainly expressed in the myocardium but not in vascular smooth muscle.

CONCLUSIONS

CP/CPB and DM are both associated with up-regulation in V1 receptor expression/localization in human myocardium. Vasopressin may induce coronary arteriolar constriction via V1A. This alteration may lead to increased coronary arteriolar spasm in patients with DM undergoing CP/CPB and cardiac surgery.

Impaired coronary contraction to phenylephrine after cardioplegic arrest in diabetic patients

BACKGROUND

We have previously found that hyperkalemic cardioplegic arrest in the setting of cardiopulmonary bypass (CP/CPB) is associated with impairment of the coronary arteriolar response to phenylephrine in nondiabetic (ND) patients. We hypothesized that diabetes may alter coronary arteriolar response to alpha-1 adrenergic agonist in the setting of CP/CPB. In this study, we further investigated the effects of diabetes on the altered coronary arteriolar response to phenylephrine in patients undergoing cardiac surgery.

METHODS

Coronary arterioles (90-150 μm in diameter) were harvested pre- and post-CP/CPB from the ND and diabetic mellitus (DM) patients (n = 8/group) undergoing cardiac surgery. In-vitro microvascular reactivity was examined in response to phenylephrine. The protein expression/localization of the alpha-1 adrenergic receptors in the atrial myocardium was measured by Western blotting and immunohistochemistry.

RESULTS

Phenylephrine (10-9 to 10-4 M) induced a dose-dependent contractile response in both ND and DM vessels pre- and post-CP/CPB. There was no significant difference in the pre-CP/CPB contractile responses to phenylephrine between ND and DM groups. The post-CP/CPB contractile response was significantly diminished in both ND and DM groups compared with the respective pre-CP/CPB response (P < 0.05 versus pre-CP/CPB). This diminished contractile response was more pronounced in vessels from DM patients compared with vessels from ND patients (P < 0.05 versus ND). There were no significant differences in the protein expression of alpha-1A and alpha-1B receptors in the atrial myocardium between the ND and DM groups or tissue harvested pre- or post-CP/CPB.

CONCLUSIONS

Diabetes is associated with a decreased contractile response of coronary arterioles to phenylephrine in the setting of CP/CPB versus that observed in ND patients. This alteration may contribute to the vasomotor dysfunction of coronary microcirculation seen early after CP/CPB in patients with diabetes.

Identify Cross Talk Between Circadian Rhythm and Coronary Heart Disease by Multiple Correlation Analysis

Disorder in circadian rhythm has been revealed as a risk factor for coronary heart disease. Several studies in molecular biology established a gene interaction network using coronary heart susceptibility genes and the circadian rhythm pathway. However, cross talk between genes was mostly discovered in single gene pairs. There might be combination sets of genes intergraded as a unit to regulate the network. To resolve multiple variables in coronary heart susceptibility genes controlling circadian rhythm pathways, a multiple correlation analysis was applied to the transcriptome. Nine genes, including CUGBP, Elav-like family member (CELF); sodium leak channel, nonselective (NALCN); protein phosphatase 2 regulatory subunit B gamma (PPP2R2C); tubulin alpha 1c (TUBA1C); microtubule-associated protein 4 (MAP4); cofilin 1 (CFL1); myosin heavy chain 7 (MYH7); QKI, KH domain containing RNA binding (QKI); and maternal embryonic leucine zipper kinase (MELK), from coronary heart susceptibility were identified to predict the outcome of a linear combination of circadian rhythm pathway genes with R factor more than 0.7. G protein subunit alpha o1 (GNAO1), protein kinase C gamma (PRKCG), RBX, and G protein subunit beta 1 (GNB1) in the circadian rhythm pathway are characterized as combination variables to coexpress with coronary heart susceptibility genes.

Decreased contractile response of peripheral arterioles to serotonin after CPB in patients with diabetes

BACKGROUND

Regulation of coronary vasomotor tone by serotonin is significantly changed after cardioplegic arrest and reperfusion. The current study investigates whether cardiopulmonary bypass may also affect peripheral arteriolar response to serotonin in patients with or without diabetes.

METHODS

Human peripheral microvessels (90-180 µm diameter) were dissected from harvested skeletal muscle tissues from diabetic and non-diabetic patients before and after cardiopulmonary bypass and cardiac surgery (n = 8/group). In vitro contractile response to serotonin was assessed by videomicroscopy in the presence or absence of serotonin alone (10^-9-10^-5M) or combined with the selective serotonin 1B receptor (5-HT1B) antagonist, SB224289 (10^-6M). 5-HT1A/1B protein expression in the skeletal muscle was measured by Western-blot and immunohistochemistry.

RESULTS

There were no significant differences in contractile response of peripheral arterioles to serotonin (10^-5M) pre-cardiopulmonary bypass between diabetic and non-diabetic patients. After cardiopulmonary bypass, contractile response to serotonin was significantly impaired in both diabetic and non-diabetic patients compared to their pre-cardiopulmonary bypass counterparts (P < .05). This effect was more pronounced in diabetic patients than non-diabetic patients (P < .05 versus non-diabetic). The contractile response to serotonin was significantly inhibited by the 5-HT1B antagonist in both diabetic and non-diabetic vessels (P < .05 versus serotonin alone). There were no significant differences in the expression/distribution of 5-HT1A/1B between non-diabetic and diabetic groups or between pre- versus post- cardiopulmonary bypass vessels.

CONCLUSIONS

Cardiopulmonary bypass is associated with decreased contractile response of peripheral arterioles to serotonin and this effect was exaggerated in the presence of diabetes. Serotonin-induced contractile response of the peripheral arterioles was via 5-HT1B in both diabetic and non-diabetic patients.

Microvascular dysfunction in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass

PURPOSE OF REVIEW

The purpose of the current review is to describe the changes of microvascular function in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass (CPB) and cardiac surgery.

RECENT FINDINGS

Cardiac surgery, especially that involving cardioplegia and CPB, is associated with significant changes in vascular reactivity of coronary/peripheral microcirculation, vascular permeability, gene/protein expression, and programmed cell death, as well as with increased morbidity and mortality after surgical procedures. In particular, these changes are more profound in patients with poorly controlled diabetes.

SUMMARY

Because alterations in vasomotor regulation are critical aspects of mortality and morbidity of cardioplegia/CPB, a better understanding of diabetic regulation of microvascular function may lead to improved postoperative outcomes of patients with diabetes after cardioplegia/CPB and cardiac surgery.

Decreased coronary arteriolar response to KCa channel opener after cardioplegic arrest in diabetic patients

We have recently found that diabetes is associated with the inactivation of the calcium-activated potassium channels (K_Ca) in endothelial cells, which may contribute to endothelial dysfunction in diabetic patients at baseline. In the current study, we further investigated the effects of diabetes on coronary arteriolar responses to the small (SK) and intermediate (IK) K_Ca opener NS309 in diabetic and non-diabetic patients and correlated that data with the changes in the SK/IK protein expression/distribution in the setting of cardioplegic ischemia and reperfusion (CP) and cardiopulmonary bypass (CPB). Coronary arterioles from the harvested right atrial tissue samples from diabetic and non-diabetic patients (n = 8/group) undergoing cardiac surgery were dissected pre- and post-CP/CPB. The in vitro relaxation response of pre-contracted arterioles was examined in the presence of the selective SK/IK opener NS309 (10⁻⁹–10⁻⁵ M). The protein expression/localization of K_Ca channels in the harvested atrial tissue samples, coronary microvessels, and primary cultured human coronary endothelial cells were assayed by Western blotting and immunohistochemistry. The relaxation response to NS309 post-CP/CPB was significantly decreased in diabetic and non-diabetic groups compared to their pre-CP/CPB responses, respectively (P < 0.05). Furthermore, this decrease was greater in the diabetic group than that of the non-diabetic group (P < 0.05). There were no significant differences in the total protein expression/distribution of SK/IK in the human myocardium, coronary microvessels or coronary endothelial cells between diabetic and non-diabetic groups or between pre- and post-CP/CPB (P > 0.05). Our results suggest that diabetes further inactivates SK/IK channels of coronary microvasculature early after CP/CPB and cardiac surgery. The lack of diabetic changes in SK/IK protein abundances in the setting of CP/CPB suggests that the effect is post-translational. This alteration may contribute to post-operative endothelial dysfunction in the diabetic patients early after CP/CPB and cardiac surgery.

Dexmedetomidine-Induced Contraction in the Isolated Endothelium-Denuded Rat Aorta Involves PKC-δ-mediated JNK Phosphorylation

Vasoconstriction mediated by the highly selective alpha-2 adrenoceptor agonist dexmedetomidine leads to transiently increased blood pressure and severe hypertension. The dexmedetomidine-induced contraction involves the protein kinase C (PKC)-mediated pathway. However, the main PKC isoform involved in the dexmedetomidine-induced contraction remains unknown. The goal of this in vitro study was to examine the specific PKC isoform that contributes to the dexmedetomidine-induced contraction in the isolated rat aorta. The endothelium-denuded rat aorta was suspended for isometric tension recording. Dexmedetomidine dose-response curves were generated in the presence or absence of the following inhibitors: the pan-PKC inhibitor, chelerythrine; the PKC-α and -β inhibitor, Go6976; the PKC-α inhibitor, safingol; the PKC-β inhibitor, ruboxistaurin; the PKC-δ inhibitor, rottlerin; the c-Jun NH2-terminal kinase (JNK) inhibitor, SP600125; and the myosin light chain kinase inhibitor, ML-7 hydrochloride. Western blot analysis was used to examine the effect of rottlerin on dexmedetomidine-induced PKC-δ expression and JNK phosphorylation in rat aortic vascular smooth muscle cells (VSMCs) and to investigate the effect of dexmedetomidine on PKC-δ expression in VSMCs transfected with PKC-δ small interfering RNA (siRNA) or control siRNA. Chelerythrine as well as SP600125 and ML-7 hydrochloride attenuated the dexmedetomidine-induced contraction. Go6976, safingol, and ruboxistaurin had no effect on the dexmedetomidine-induced contraction, whereas rottlerin inhibited the dexmedetomidine-induced contraction. Dexmedetomidine induced PKC-δ expression, whereas rottlerin and PKC-δ siRNA transfection inhibited dexmedetomidine-induced PKC-δ expression. Dexmedetomidine also induced JNK phosphorylation, which was inhibited by rottlerin. Taken together, these results suggest that the dexmedetomidine-induced contraction involves PKC-δ-dependent JNK phosphorylation in the isolated rat aorta.

S1P1 receptor modulation preserves vascular function in mesenteric and coronary arteries after CPB in the rat independent of depletion of lymphocytes

Background

Cardiopulmonary bypass (CPB) may induce systemic inflammation and vascular dysfunction. Sphingosine 1-phosphate (S1P) modulates various vascular and immune responses. Here we explored whether agonists of the S1P receptors, FTY720 and SEW2871 improve vascular reactivity after CPB in the rat.

Methods

Experiments were done in male Wistar rats (total n = 127). Anesthesia was induced by isoflurane (2.5–3%) and maintained by fentanyl and midazolam during CPB. After catheterization of the left femoral artery, carotid artery and the right atrium, normothermic extracorporeal circulation was instituted for 60 minutes. In the first part of the study animals were euthanized after either 1 hour, 1 day, 2 or 5 days of the recovery period. In second part of the study animals were euthanized after 1 day of postoperative period. We evaluated the contractile response to phenylephrine (mesenteric arteries) or to serotonin (coronary artery) and vasodilatory response to acethylcholine (both arteries).

Results

Contractile responses to phenylephrine were reduced at 1 day recovery after CPB and Sham as compared to healthy control animals (Emax, mN: 7.9±1.9, 6.5±1.5, and 11.3±1.3, respectively). Mainly FTY720, but not SEW2871, caused lymphopenia in both Sham and CPB groups. In coronary and mesenteric arteries, both FTY720 and SEW2871 normalized serotonin and phenylephrine-mediated vascular reactivity after CPB (p<0.05) and FTY720 increased relaxation to acetylcholine as compared with untreated rats that underwent CPB.

Conclusion

Pretreatment with FTY720 or SEW2871 preserves vascular function in mesenteric and coronary artery after CPB. Therefore, pharmacological activation of S1P₁ receptors may provide a promising therapeutic intervention to prevent CPB-related vascular dysfunction in patients.

Altered expression and activation of mitogen-activated protein kinases in diabetic heart during cardioplegic arrest and cardiopulmonary bypass

BACKGROUND

We investigated whether mitogen-activated protein kinases (MAPKs) are changed in the hearts of patients with diabetes after cardioplegia and cardiopulmonary bypass (CP/CPB) operations.

METHODS

Biopsies from the right atrial appendage were harvested pre- and post-CP/CPB from nondiabetic (ND) patients (n = 8, hemoglobin A1c (HbA1c) = 5.4 ± 0.12); patients with controlled diabetes (CDM) (n = 8, HbA1c = 6.5 ± 0.15); and patients with uncontrolled diabetes (UDM) (n = 8, HbA1c = 9.6 ± 0.3) undergoing coronary artery bypass grafting. The expression and/or activation of the p38-MAPK, ERK1/2, JNK, and MKP-1 in the right-atrial tissues were analyzed by Western blotting. The vasomotor function of coronary arterioles was measured by videomicroscopy.

RESULTS

The post-CP/CPB levels of total p38-MAPK were decreased in the 3 groups as compared with their pre-CP/CPB levels (P < .05). There were increases in phospho-p38-MAPK, phospho-ERK1/2, and MKP-1 in UDM patients as compared with ND and CDM patients at baseline (P < .05). Compared to pre-CP/CPB, the post-CP/CPB levels of phospho-p38-MAPK decreased in the UDM group but were unaltered in the ND and CDM groups; however, the post-CP/CPB levels of phospho-p38-MAPK still remained greater than the post-CP/CPB levels of the other 2 groups. Post-CP/CPB levels of phospho-ERK1/2 were increased in the ND and CDM groups but were decreased in the UDM group compared to their pre-CP/CPB levels, respectively (P < .05). There were no significant differences in phospho-JNK in 3 groups at baseline. Post-CP/CPB levels of phospho-JNK, however, were increased in the 3 groups and were more pronounced in the myocardium of the UDM group (P < .05). After CP/CPB, the protein levels of MKP-1 were unchanged in the 3 groups when compared with their pre-CP/CPB levels. Post-CP/CPB levels of MKP-1, however, remained greater in the UDM group than in the ND and CDM groups. The post-CP/CPB contractile responses to the thromboxane A2 analog U46619 were significantly impaired in all 3 groups compared with pre-CP/CPB contractile responses. These impairments were more pronounced in the UDM group.

CONCLUSION

Uncontrolled diabetes is associated with changes in expression of and activation of MAPKs and vasomotor dysfunction in the setting of CP/CPB.

Changes in microvascular reactivity after cardiopulmonary bypass in patients with poorly controlled versus controlled diabetes

BACKGROUND

We investigated the effects of cardiopulmonary bypass (CPB) on peripheral arteriolar reactivity and associated signaling pathways in poorly controlled (UDM), controlled (CDM), and case-matched nondiabetic (ND) patients undergoing coronary artery bypass grafting (CABG).

METHODS AND RESULTS

Skeletal muscle arterioles were harvested before and after CPB from the UDM patients (hemoglobin A1c [HbA1c]=9.0 ± 0.3), the CDM patients (HbA1c=6.3 ± 0.15), and the ND patients (HbA1c=5.2 ± 0.1) undergoing CABG surgery (n=10/group). In vitro relaxation responses of precontracted arterioles to endothelium-dependent vasodilators adenosine 5'-diphosphate (ADP) and substance P and the endothelium-independent vasodilator sodium nitroprusside (SNP) were examined. The baseline responses to ADP, substance P, and SNP of arterioles from the UDM patients were decreased as compared with microvessels from the ND or CDM patients (P<0.05). The post-CPB relaxation responses to ADP and substance P were significantly decreased in all 3 groups compared with pre-CPB responses (P<0.05). However, these decreases were more pronounced in the UDM group (P<0.05). The post-CPB response to SNP was significantly decreased only in the UDM group, not in the other 2 groups compared with pre-CPB. The expression of protein kinase C (PKC)-α, PKC-β, protein oxidation, and nitrotyrosine in the skeletal muscle were significantly increased in the UDM group as compared with those of ND or CDM groups (P<0.05).

CONCLUSIONS

Poorly controlled diabetes results in impaired arteriolar function before and after CPB. These alterations are associated with the increased expression/activation of PKC-α and PKC-β and enhanced oxidative and nitrosative stress.

Decreased coronary microvascular reactivity after cardioplegic arrest in patients with uncontrolled diabetes mellitus

BACKGROUND

We investigated the effects of cardioplegic arrest and reperfusion on coronary arteriolar responses to endothelium-dependent and -independent vasodilators and associated signaling pathways in uncontrolled diabetic, well controlled diabetic, and case-matched nondiabetic patients undergoing coronary artery bypass graft surgery.

METHODS

Coronary arterioles from harvested right atrial tissues were dissected pre- and post-cardioplegic arrest and reperfusion from uncontrolled diabetic (n = 10; hemoglobin A1c = 9.3 ± 0.3), well controlled diabetic (n = 10; hemoglobin A1c = 6.2 ± 0.2), and nondiabetic patients (n = 10; hemoglobin A1c = 5.1 ± 0.1) undergoing coronary artery bypass graft surgery.

RESULTS

The baseline microvascular response to adenosine 5'-diphosphate, substance P, and sodium nitroprusside of arterioles from uncontrolled diabetic patients were decreased compared to the respective response from nondiabetic or well controlled diabetic patients (P < .05). The vasodilatory responses to adenosine 5'-diphosphate and substance P after cardioplegic arrest and reperfusion were significantly decreased in all 3 groups compared to pre-cardioplegic arrest and reperfusion responses (P < .05). However, these decreases were more pronounced in the uncontrolled diabetic group (P < .05). The expression of protein kinase C-α, protein kinase C-β, and protein oxidation in atrial tissues was significantly increased in the uncontrolled diabetic group compared to the nondiabetic or controlled diabetes groups.

CONCLUSION

Uncontrolled diabetes is associated with endothelium-dependent and -independent vascular dysfunction of coronary arterioles. In addition, uncontrolled diabetes worsens the recovery of coronary arteriolar function after cardioplegic arrest and reperfusion. These alterations are associated with an increased expression/activation of protein kinase C-α and protein kinase C-β and enhanced oxidative stress.

Impaired contractile response of human peripheral arterioles to thromboxane A-2 after cardiopulmonary bypass

BACKGROUND

We studied the contractile response of human peripheral microvasculature to thromboxane A-2 (TXA-2) before and after cardiopulmonary bypass (CPB), with and without the blockade of TXA-2 receptors, or the inhibition of phospholipase C (PLC), phospholipase A-2 (PLA-2) or protein kinase C (PKC)-α. We also examined the protein/gene expression and localization of TXA-2 receptors, TXA-2 synthase, PLC, and other TXA-2-related proteins.

METHODS

Skeletal muscle arterioles (90-180 μm in diameter) were harvested pre- and post-CPB from patients (n = 28) undergoing cardiac surgery.

RESULTS

The post-CPB contractile response of skeletal muscle arterioles to TXA-2 analog U-46619 was impaired compared with pre-CPB (P < .05). The presence of TXA-2 receptor antagonist SQ-29548 (10(-6)mol/L) prevented the contractile response to U-46619 (P < .05). Pretreatment with the PLC inhibitor U-73122 (10(-6)mol/L) significantly inhibited the U-46619-induced contractile response (P < .01). Administration of the PLA-2 inhibitor quinacrine (10(-6)mol/L) or PKC-α inhibitor safingol (2 × 10(-5)mol/L), however, failed to affect U-46619-induced contraction. Total protein levels and gene expression of TXA-2 receptors, and TXA-2 synthase of skeletal muscle, were not altered post-CPB. Confocal microscopy showed no differences in the expression of PLCβ-3 in the microcirculation. PLCβ-3 was localized to both smooth muscle and endothelium.

CONCLUSION

CPB decreases the contractile response of human peripheral arterioles to TXA-2 soon after cardiac surgery. This response may be in part responsible for the decrease in vascular tone, and accompanying hypotension sometimes observed after cardiac operations utilizing CPB.

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.

Decreased contractile response to endothelin-1 of peripheral microvasculature from diabetic patients

BACKGROUND

We compared the contractile responses to endothelin-1 (ET-1) with and without the inhibition of ET-A receptors and protein kinase C-alpha (PKC-α) in the human peripheral microvasculature of diabetic and case-matched, nondiabetic patients.

METHODS

Chest wall skeletal muscle was harvested from patients with and without diabetics undergoing cardiac surgery. Peripheral arterioles (90-180 μm in diameter) were dissected from the harvested tissue. Microvascular constriction was assessed by videomicroscopy in response to ET-1 with and without an endothelin-A (ET-A) receptor antagonist, an endothelin B (ET-B) antagonist, or a PKC-α inhibitor.

RESULTS

ET-1 induced a dose-dependent contractile response of skeletal muscle arterioles from diabetic and nondiabetic patients. The contractile response of diabetic arterioles from both prebypass and postbypass to ET-1 (10(-9) mol/L) was decreased compared with those of nondiabetic patients (P < .05). The contractile responses of microvessels of both diabetics and nondiabetics to ET-1 were inhibited in the presence of either ET-A receptor antagonist BQ123 (10(-7) mol/L) or the PKC-α inhibitor safingol (2 × 10(-5) mol/L, P < .05, respectively). In contrast, the ET-1-induced vasoconstriction was not affected by the administration of the ET-B receptor antagonist BQ788 (10(-7) mol/L). There were no differences in skeletal muscle levels of the ET-A and ET-B receptors between diabetic and nondiabetic groups.

CONCLUSION

Diabetic patients demonstrated a decreased contractile response to ET-1 in human peripheral microvasculature. The contractile response of diabetic vessels to ET-1 occurs via activation of ET-A receptors and PKC-α. These results provide novel mechanisms of ET-1-induced contraction in vasomotor dysfunction in patients with diabetes.

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.

Hypercholesterolemia is associated with hyperactive cardiac mTORC1 and mTORC2 signaling

Nutritional excess and hyperlipidemia increase the heart's susceptibility to ischemic injury. Mammalian target of rapamycin (mTOR) controls the cellular response to nutritional status and may play a role in ischemic injury. To explore the effect of hypercholesterolemia on cardiac mTOR signaling, we assessed mTOR signaling in hypercholesterolemic swine (HC) that are also susceptible to increased cardiac ischemia-reperfusion injury. Yucatan pigs were fed a high-fat/high-cholesterol diet for 4 weeks to induce hypercholesterolemia, and mTOR signaling was measured by immunoblotting and immunofluorescence in the non-ischemic left ventricular area. Total myocardial mTOR and raptor levels were markedly increased in the HC group compared to the normocholesterolemic group, and directly correlated with serum cholesterol levels. mTOR exhibited intense perinuclear staining in myocytes only in the HC group. Hypercholesterolemia was associated with hyperactive signaling upstream and downstream of both mTOR complexes, including myocardial Akt, S6K1, 4EBP1, S6 and PKC-alpha, increased levels of cardiac hypertrophy markers, and a trend toward lower levels of myocardial autophagy. Hypercholesterolemia can now be added to the growing list of conditions associated with aberrant mTOR signaling. Hypercholesterolemia produces a unique profile of alterations in cardiac mTOR signaling, which is a potential target in cardiac diseases associated with hypercholesterolemia and nutritional excess.