Biomedical subjects

Charles Steenbergen

Publications and source records attributed to Charles Steenbergen.

At least 19 recordsLinked to original sources

PubMed2007

Detection of human CYP2C8, CYP2C9, and CYP2J2 in cardiovascular tissues.

The cytochrome P450 (P450) enzymes CYP2C8, CYP2C9, and CYP2J2 metabolize arachidonic acid to epoxyeicosatrienoic acids, which are known to be vital in regulation of vascular tone and cardiovascular homeostasis. Because there is limited information regarding the relative expression of these P450 enzymes in cardiovascular tissues, this study examined the expression of CYP2C8, CYP2C9, and CYP2J2 mRNA and protein in human heart, aorta, and coronary artery samples by real-time polymerase chain reaction, immunoblotting, and immunohistochemistry. CYP2J2 and CYP2C9 mRNA levels were highly variable in human hearts, whereas CYP2C8 mRNA was present in lower abundance. CYP2J2 mRNA was approximately 10(3) times higher than CYP2C9 or CYP2C8 in human heart. However, CYP2C9 mRNA was more abundant than CYP2J2 or CYP2C8 in one ischemic heart. In human aorta, mean CYP2C9 mRNA levels were approximately 50 times higher than that of CYP2J2 and 5-fold higher than that of CYP2C8. In human coronary artery, mean values for CYP2C9 mRNA were approximately 2-fold higher than that of CYP2J2 mRNA and 6-fold higher than that of CYP2C8 mRNA. Immunoblotting results show relatively high levels of CYP2J2 and CYP2C8 protein in human hearts, which was confirmed by immunohistochemistry. CYP2C9 protein was also detected at high levels in one ischemic heart by immunoblotting. CYP2C9 was present at higher levels than CYPJ2 in aorta and coronary artery, whereas CYP2C8 protein was below the limits of detection. The expression of CYP2J2 and CYP2C8 in human heart, and CYPC9 and CYP2J2 in aorta and coronary artery is consistent with a physiological role for these enzymes in these tissues.

Adult↗

PubMed2007

Overexpression of the Na+/H+ exchanger and ischemia-reperfusion injury in the myocardium.

In the myocardium, the Na(+)/H(+) exchanger isoform-1 (NHE1) activity is detrimental during ischemia-reperfusion (I/R) injury, causing increased intracellular Na(+) (Na(i)(+)) accumulation that results in subsequent Ca(2+) overload. We tested the hypothesis that increased expression of NHE1 would accentuate myocardial I/R injury. Transgenic mice were created that increased the Na(+)/H(+) exchanger activity specifically in the myocardium. Intact hearts from transgenic mice at 10-15 wk of age showed no change in heart performance, resting intracellular pH (pH(i)) or phosphocreatine/ATP levels. Transgenic and wild-type (WT) hearts were subjected to 20 min of ischemia followed by 40 min of reperfusion. Surprisingly, the percent recovery of rate-pressure product (%RPP) after I/R improved in NHE1-overexpressing hearts (64 +/- 5% vs. 41 +/- 5% in WT; P < 0.05). In addition, NMR spectroscopy revealed that NHE1 overexpressor hearts contained higher ATP during early reperfusion (levels P < 0.05), and there was no difference in Na(+) accumulation during I/R between transgenic and WT hearts. HOE642 (cariporide), an NHE1 inhibitor, equivalently protected both WT and NHE1-overexpressing hearts. When hearts were perfused with bicarbonate-free HEPES buffer to eliminate the contribution of HCO(3)(-) transporters to pH(i) regulation, there was no difference in contractile recovery after reperfusion between controls and transgenics, but NHE1-overexpressing hearts showed a greater decrease in ATP during ischemia. These results indicate that the basal activity of NHE1 is not rate limiting in causing damage during I/R, therefore, increasing the level of NHE1 does not enhance injury and can have some small protective effects.

Animals↗

PubMed2007

Preconditioning: the mitochondrial connection.

Over the past decade there has been considerable progress in elucidating the signaling pathways involved in cardioprotection. Considerable recent data suggest that many of these signaling pathways converge on the mitochondria, where such pathways alter the activity of key mitochondrial proteins, leading to reduced apoptosis and necrosis. Inhibition of the mitochondrial permeability transition pore is emerging as a central mechanism in cardioprotection. This review focuses on mechanisms by which cardioprotection alters mitochondrial proteins and channels that regulate cell death and survival.

Animals↗

PubMed2006

Hypercontractile female hearts exhibit increased S-nitrosylation of the L-type Ca2+ channel alpha1 subunit and reduced ischemia/reperfusion injury.

Mechanisms underlying gender differences in cardiovascular disease are poorly understood. We found previously that, under hypercontractile conditions, female hearts exhibit significantly less ischemia/reperfusion injury than males. Here we show that male wild-type (WT) mouse hearts pretreated with 10 nmol/L isoproterenol before ischemia exhibited increased injury versus female hearts, but this relative protection in females was absent in eNOS(-/-) and nNOS(-/-) hearts. In isoproterenol-treated female versus male hearts, there was also more endothelial NO synthase (eNOS) associated with cardiomyocyte caveolin-3, and more neuronal NOS (nNOS) translocation to caveolin-3 during ischemia/reperfusion. S-nitrosothiol (SNO) formation was increased in isoproterenol-treated ischemic/reperfused hearts in all mouse genotypes, but only in WT mice was SNO content significantly higher in females than males. Using the biotin switch method, we identified the L-type Ca2+ channel alpha1 subunit as the predominant S-nitrosylated protein in membrane fractions, and following isoproterenol and ischemia/reperfusion male/female differences in SNO were seen only in WT hearts, but not in constitutive NOS(-/-) genotypes. The isoproterenol-induced increase in L-type Ca2+ current (ICa) was smaller in females versus in males, but NOS blockade increased ICa in females. This gender difference in ICa in isoproterenol-treated myocytes (and abolition on NOS inhibition) was mirrored exactly in Ca2+ transients and SR Ca2+ contents. In conclusion, these data suggest that eNOS and nNOS both play roles in the gender differences observed in ischemia/reperfusion injury under adrenergic stimulation, and also demonstrate increased S-nitrosylation of the L-type Ca2+ channels in female cardiomyocytes.

Animals↗

PubMed2005

Cardiac-specific ablation of the Na+-Ca2+ exchanger confers protection against ischemia/reperfusion injury.

During ischemia and reperfusion, with an increase in intracellular Na+ and a depolarized membrane potential, Ca2+ may enter the myocyte in exchange for intracellular Na+ via reverse-mode Na+-Ca2+ exchange (NCX). To test the role of Ca2+ entry via NCX during ischemia and reperfusion, we studied mice with cardiac-specific ablation of NCX (NCX-KO) and demonstrated that reverse-mode Ca2+ influx is absent in the NCX-KO myocytes. Langendorff perfused hearts were subjected to 20 minutes of global ischemia followed by 2 hours of reperfusion, during which time we monitored high-energy phosphates using 31P-NMR and left-ventricular developed pressure. In another group of hearts, we monitored intracellular Na+ using 23Na-NMR. Consistent with Ca2+ entry via NCX during ischemia, we found that hearts lacking NCX exhibited less of a decline in ATP during ischemia, delayed ischemic contracture, and reduced maximum contracture. Furthermore, on reperfusion following ischemia, NCX-KO hearts had much less necrosis, better recovery of left-ventricular developed pressure, improved phosphocreatine recovery, and reduced Na+ overload. The improved recovery of function following ischemia in NCX-KO hearts was not attributable to the reduced preischemic contractility in NCX-KO hearts, because when the preischemic workload was matched by treatment with isoproterenol, NCX-KO hearts still exhibited improved postischemic function compared with wild-type hearts. Thus, NCX-KO hearts were significantly protected against ischemia-reperfusion injury, suggesting that Ca2+ entry via reverse-mode NCX is a major cause of ischemia/reperfusion injury.

Animals↗

PubMed2005

Recurrence of cardiac sarcoidosis in a heart transplant recipient.

We present the case of a young man who received a left ventricular assist device (LVAD) as a bridge to transplantation for end-stage heart failure, in whom the diagnosis of sarcoid cardiomyopathy was made at the time of LVAD implantation. He subsequently underwent uncomplicated heart transplantation. Nineteen months later, a routine surveillance endomyocardial biopsy specimen demonstrated recurrence of sarcoidosis in the transplanted heart.

Adult↗

PubMed2005

Protein kinase C and preconditioning: role of the sarcoplasmic reticulum.

Activation of protein kinase C (PKC) is cardioprotective, but the mechanism(s) by which PKC mediates protection is not fully understood. Inasmuch as PKC has been well documented to modulate sarcoplasmic reticulum (SR) Ca2+ and because altered SR Ca2+ handling during ischemia is involved in cardioprotection, we examined the role of PKC-mediated alterations of SR Ca2+ in cardioprotection. Using isolated adult rat ventricular myocytes, we found that addition of 1,2-dioctanoyl-sn-glycerol (DOG), to activate PKC under conditions that reduced myocyte death associated with simulated ischemia and reperfusion, also reduced SR Ca2+. Cell death was 57.9 +/- 2.9% and 47.3 +/- 1.8% in untreated and DOG-treated myocytes, respectively (P < 0.05). Using fura 2 fluorescence to monitor Ca2+ transients and caffeine-releasable SR Ca2+, we examined the effect of DOG on SR Ca2+. Caffeine-releasable SR Ca2+ was significantly reduced (by approximately 65%) after 10 min of DOG treatment compared with untreated myocytes (P < 0.05). From our examination of the mechanism by which PKC alters SR Ca2+, we present the novel finding that DOG treatment reduced the phosphorylation of phospholamban (PLB) at Ser16. This effect is mediated by PKC-epsilon, because a PKC-epsilon-selective inhibitory peptide blocked the DOG-mediated decrease in phosphorylation of PLB and abolished the DOG-induced reduction in caffeine-releasable SR Ca2+. Using immunoprecipitation, we further demonstrated that DOG increased the association between protein phosphatase 1 and PLB. These data suggest that activated PKC-epsilon reduces SR Ca2+ content through PLB dephosphorylation and that reduced SR Ca2+ may be important in cardioprotection.

Animals↗

PubMed2005

Mechanisms of erythropoietin-mediated cardioprotection during ischemia-reperfusion injury: role of protein kinase C and phosphatidylinositol 3-kinase signaling.

Langendorff-perfused rat hearts treated with EPO exhibited significantly improved postischemic recovery of left ventricular developed pressure (LVDP) and reduced infarct size compared with control hearts. Perfusion with the mitogen/extracellular signal-regulated kinase (MEK) inhibitor U0126 just before and concomitant with EPO treatment abolished EPO-induced phosphorylation of the MEK substrate extracellular signal-regulated kinase (ERK) but had no effect of EPO-mediated cardioprotection. EPO treatment of the perfused hearts induced translocation of protein kinase C (PKC) epsilon isoform to the membrane fraction of the hearts and the protective effect of EPO was significantly inhibited by the PKC catalytic inhibitor chelerythrine added before and concomitant with EPO. These data demonstrate that EPO-mediated activation of the PKC signaling pathway before or during ischemia is required for the cardioprotective effect of EPO during ischemia-reperfusion injury. Perfusion with the phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 or wortmannin just before and concomitant with EPO treatment attenuated EPO-induced phosphorylation of the PI3K substrate Akt but had no effect on EPO-mediated cardioprotection. However, when wortmannin was added during EPO treatment and continued during reperfusion, EPO-mediated cardioprotection was significantly inhibited. We also show that postischemia EPO treatment at the onset of reperfusion significantly improved recovery of LVDP and reduced infarct size. Postischemia cardioprotection by EPO required the PI3K pathway but was not affected by inhibition of PKC at the time of EPO treatment.

Alkaloids↗

PubMed2005

The role of beta-adrenergic receptor signaling in cardioprotection.

This study examines the role of the beta2-adrenergic receptor (beta2-AR) in cardioprotection. The beta2-AR couples to Gs and Gi proteins. Gs activates PKA, which phosphorylates the receptor and switches beta2-AR coupling from Gs to Gi. Prior to 20 min of global ischemia, mouse hearts were either perfused for 30 min without treatment (control), treated with 10 nmol/L of isoproterenol (ISO) for 5 min followed by 5 min washout, or preconditioned with 4 cycles of 5 min ischemia and 5 min reflow (PC). Recovery of left ventricular developed pressure (LVDP) and infarct size were measured. Intermittent ISO treatment improved post-ischemic recovery of LVDP (58.5+/-4.8% vs. 22.0+/-6.3% in control) and reduced infarct size (31.0+/-2.4% vs. 53.0+/-4.6% in control). The Gi inhibitor pertussis toxin blocked the ISO-induced improvement in postischemic LVDP and infarct size. To test the role of beta2-AR in PC, we studied mice lacking beta2-AR (beta2-AR-/-) and found that PC had no effect on postischemic LVDP or infarct size in beta2-AR-/-. To test whether PKA is required for the PC and ISO-induced protection, hearts were treated with the PKA inhibitors PKI and H-89. We found that PKI and H-89 blocked the PC- and ISO-induced improvement in postischemic LVDP and infarct size. These data show an important role for beta2-AR in cardioprotection and support the novel hypothesis that preconditioning involves switching of beta2-AR coupling from Gs to Gi.

Animals↗

PubMed2005

Estrogen receptor beta mediates gender differences in ischemia/reperfusion injury.

Under hypercontractile conditions associated with increased intracellular calcium, male hearts show enhanced ischemia/reperfusion injury compared to female hearts. Our aim in this study was to identify the specific estrogen receptor involved in this gender difference. Following brief treatment with isoproterenol, isolated mouse hearts were subjected to ischemia and reperfusion. Postischemic contractile function and infarct size were measured in wild-type (WT) male and female hearts, and female hearts lacking functional alpha estrogen receptor (alpha ERKO), or the beta estrogen receptor (beta ERKO). WT male hearts exhibited significantly less functional recovery and more necrosis than WT females. alpha ERKO female hearts exhibited ischemia/reperfusion injury similar to that observed in WT females, whereas beta ERKO females exhibited significantly less functional recovery than WT females and were similar to WT males. These data suggest that estrogen, through the beta-estrogen receptor, plays a role in the protection observed in the female heart. Furthermore, we identified genes that were differentially expressed in beta ERKO female hearts compared to alpha ERKO and WT female hearts, and found altered expression of a number of metabolism genes, which may be important in ischemic injury. We further showed that WT female hearts have increased ratio of carbohydrate to fatty acid metabolism relative to WT males.

Animals↗

PubMed2005

Bcl-2 regulation of mitochondrial energetics.

Recent data suggest that in addition to regulating apoptosis, Bcl-2 (an anti-apoptotic protein overexpressed in B-cell lymphoma) and Bcl-2 family members also regulate mitochondrial and cell physiology. t-Bid, a Bcl-2 family member, has been shown to modulate reorganization of mitochondrial cristae. Bcl-2 appears to regulate voltage-dependent anion channel permeability, which has important consequences for mitochondrial transport of adenine nucleotides, Ca(2+), and other metabolites. BAD, a pro-apoptotic Bcl-2 family member, is required for the binding of glucokinase to a mitochondrial complex, and BAD null mice have altered glucose homeostasis. It has been suggested that Bcl-2 family members may regulate important mitochondrial/cell functions and serve as sentinels to detect abnormalities in these pathways and, when the abnormalities are severe enough, to initiate or facilitate cell death. Understanding the physiologic processes controlled by Bcl-2 will be important in understanding cell regulation, and it may also provide new insights into the regulation of apoptosis.

Adenosine Triphosphate↗

PubMed2005

Inhibition of GSK-3beta as a target for cardioprotection: the importance of timing, location, duration and degree of inhibition.

Cardiovascular disease is the major cause of morbidity and mortality in western countries such as the US. Myocardial infarction leads to loss of myocytes and with extremely limited ability to replenish cardiomyocytes, the heart exhibits depressed contractility. This ultimately results in hypertrophy of the remaining viable myocytes, which is the primary predictor for heart failure. Thus, drug therapies which can reduce myocyte cell death and reduce postischaemic dysfunction would be expected to greatly reduce cardiac hypertrophy and subsequent heart failure and death. Inhibition of glycogen synthase kinase (GSK)-3beta has been proposed as a strategy to improve postischaemic cardiomyocyte survival, as inhibition of GSK-3beta has been shown to reduce myocardial cell death following ischaemia and reperfusion. Therapies for inhibiting GSK are feasible as there are a number of newly developed specific inhibitors of GSK available, although most of these drugs have not been tested in long-term animal studies.

Animals↗

PubMed2005

Graft vascular disease after cardiac transplantation and its relationship to mean acute rejection score.

CONTEXT: Graft vascular disease remains a significant source of morbidity and mortality in heart transplant patients. The influence of acute cellular rejection on the development of graft vascular disease is controversial. OBJECTIVE: To determine the relationship between mean acute cellular rejection score and the presence of atherosclerosis or fibrointimal hyperplasia in cardiac allografts at autopsy. DESIGN: This retrospective, autopsy-based study examined 27 heart transplant patients to evaluate for graft vascular disease. A rejection score for each patient was calculated as the average of all the rejection scores determined by endomyocardial biopsy. Gross and histologic examination of the heart was used to divide patients into 3 groups: no coronary artery disease, atherosclerosis, and fibrointimal hyperplasia. Mean rejection scores were calculated for each of these groups for all patients and patients who survived longer than 3 months. Mean rejection scores were compared by an analysis of variance and pairwise t tests. RESULTS: Mean rejection scores demonstrated a trend of increasing value from no coronary disease (0.323) to atherosclerosis (0.569) to fibrointimal hyperplasia (0.835). Only fibrointimal hyperplasia had a significantly higher mean rejection score compared with patients with no coronary disease when examined in all patients (P = .01) and in patients who survived longer than 3 months (P = .049). CONCLUSION: This study showed that the development of coronary artery fibrointimal hyperplasia, but not atherosclerosis, was significantly related to mean acute rejection score.

Adolescent↗

PubMed2004

Estrogen receptor-beta mediates male-female differences in the development of pressure overload hypertrophy.

The goal of this study was to determine the role of estrogen receptor subtypes in the development of pressure overload hypertrophy in mice. Epidemiological studies have suggested gender differences in the development of hypertrophy and heart disease, but the mechanism and the role of estrogen receptor subtypes are not established. We performed transverse aortic constriction (TAC) and sham operations in male and female wild-type (WT) mice and mice lacking functional estrogen receptor-alpha [alpha-estrogen receptor knockout (alpha-ERKO)] and mice lacking estrogen receptor-beta (beta-ERKO). Body, heart, and lung weights were measured 2 wk postsurgery. WT male mice subjected to TAC showed a 64% increase in the heart weight-to-body weight ratio (HW/BW) compared with sham, and WT males have increased lung weight at 2 wk. WT female mice subjected to TAC showed a 31% increase in HW/BW compared with sham, which was significantly less than their male counterparts and with no evidence of heart failure. alpha-ERKO females developed HW/BW nearly identical to that seen in WT littermate females in response to TAC, indicating that estrogen receptor-alpha is not essential for the attenuation of hypertrophy observed in WT females. In contrast, beta-ERKO females responded to TAC with a significantly greater increase in HW/BW than WT littermate females. beta-ERKO females have lower expression of lipoprotein lipase at baseline than WT or alpha-ERKO females. These data suggest an important role for estrogen receptor-beta in attenuating the hypertrophic response to pressure overload in females.

Animals↗

PubMed2004

Transgenic expression of Bcl-2 modulates energy metabolism, prevents cytosolic acidification during ischemia, and reduces ischemia/reperfusion injury.

The antiapoptotic protein Bcl-2 is targeted to the mitochondria, but it is uncertain whether Bcl-2 affects only myocyte survival after ischemia, or whether it also affects metabolic functions of mitochondria during ischemia. Hearts from mice overexpressing human Bcl-2 and from their wild-type littermates (WT) were subjected to 24 minutes of global ischemia followed by reperfusion. During ischemia, the decrease in pH(i) and the initial rate of decline in ATP were significantly reduced in Bcl-2 hearts compared with WT hearts (P<0.05). The reduced acidification during ischemia was dependent on the activity of mitochondrial F1F0-ATPase. In the presence of oligomycin (Oligo), an F1F0-ATPase inhibitor, the decrease in pH(i) was attenuated in WT hearts, but in Bcl-2 hearts, Oligo had no additional effect on pH(i) during ischemia. Likewise, addition of Oligo to WT hearts slowed the rate of decline in ATP during ischemia to a level similar to that observed in Bcl-2 hearts, but addition of Oligo had no significant effect on the rate of decline in ATP in Bcl-2 hearts during ischemia. These data are consistent with Bcl-2-mediated inhibition of consumption of glycolytic ATP. Furthermore, mitochondria from Bcl-2 hearts have a reduced rate of consumption of ATP on uncoupler addition. This could be accomplished by limiting ATP entry into the mitochondria through the voltage-dependent anion channel, and/or the adenine nucleotide transporter, or by direct inhibition of the F1F0-ATPase. Immunoprecipitation showed greater interaction between Bcl-2 and voltage-dependent anion channel during ischemia. These data indicate that Bcl-2 modulation of metabolism contributes to cardioprotection.

Adenosine Triphosphate↗

PubMed2004

Erythropoietin receptor expression in adult rat cardiomyocytes is associated with an acute cardioprotective effect for recombinant erythropoietin during ischemia-reperfusion injury.

Erythropoietin (EPO), the principal hematopoietic cytokine that regulates mammalian erythropoiesis, exhibits diverse cellular effects in non-hematopoietic tissues. The physiologic functions of EPO are mediated by its specific cell-surface receptor EPOR. In this study, we demonstrate EPOR expression in adult rat cardiac myocytes and examine the direct effects of EPO on the heart to investigate whether recombinant EPO may exert an acute cardioprotective effect during ischemia-reperfusion injury. To determine whether EPO is cardioprotective, isolated rat hearts were perfused for 10 min in the Langendorff-mode with Krebs-Henseleit buffer in the absence or presence of brief recombinant EPO treatment while left-ventricular-developed pressure (LVDP) was measured continuously to assess contractile function. The hearts were then subjected to 20 min of normothermic global ischemia followed by 25 min of reperfusion. The post-ischemic recovery of LVDP in the untreated control hearts was 26 +/- 5% of their baseline LVDP, whereas hearts pretreated with EPO exhibited significantly improved post-ischemic recovery to 57 +/- 7%. We used 31P nuclear magnetic resonance (NMR) spectroscopy to determine whether modulation of intracellular pH and/or high-energy phosphate levels during ischemia contributed to EPO-mediated cardioprotection. These experiments revealed that the rapid cardioprotective effect of EPO during ischemia-reperfusion injury was associated with preservation of ATP levels in the ischemic myocardium.

Adenosine Triphosphate↗

PubMed2004

G protein-coupled receptor internalization signaling is required for cardioprotection in ischemic preconditioning.

The present study is designed to explore the role of G protein-coupled receptors (GPCRs) in the protection afforded by ischemic preconditioning (PC). We used TG mice with cardiac-specific overexpression of a Gbetagamma-sequestering peptide, betaARKct (TG betaARKct mice), to test whether the protection of PC is Gbetagamma-dependent. To test the role of G(i) protein, we used wild-type mice pretreated with the G(i) inhibitor pertussis toxin. Recovery of left ventricular developed pressure and infarct size were measured as indices of protection. PC induced protection in wild-type mice, but this protection was blocked by pertussis toxin treatment and was also blocked in TG betaARKct mice. To determine the mechanism of Gbetagamma-induced protection in PC, we investigated one of the downstream targets of Gbetagamma, the PI3K/p70S6K pathway. PC-induced phosphorylation of p70S6K was not blocked in TG betaARKct hearts; therefore, we investigated other targets of Gbetagamma. Recent studies suggest a role for Gbetagamma in GPCR internalization. We found that betaARKct, a specific PI3K inhibitor wortmannin, and bafilomycin A1, which all block receptor recycling, all blocked the protective effect of PC. To additionally test whether PI3K is involved in PC-activated receptor internalization and endosomal signaling, we used TG mice with cardiac-specific overexpression of a catalytically inactive mutant PI3Kgamma, which disrupts the recruitment of functional PI3K to agonist-activated GPCRs in vivo. We found that the catalytically inactive mutant of PI3Kgamma blocks the protection of PC. In summary, these data suggest the novel finding that the cardioprotective effect of PC requires receptor internalization.

Androstadienes↗

PubMed2004

beta2 adrenoceptor gene therapy ameliorates left ventricular dysfunction following cardiac surgery.

OBJECTIVE: Heart surgery is associated with impairment of the myocardial beta-adrenoceptor (betaAR) system. Effective therapies for post-operative ventricular dysfunction are limited. Prolonged inotrope exposure is associated with further betaAR down-regulation. Left ventricular (LV) dysfunction and myocardial betaAR impairment were assessed following cardiopulmonary bypass (CPB) and cardioplegic arrest in a pig model. Transfer of the human beta2-adrenoceptor transgene (Adeno-beta2AR) during cardioplegic arrest was then tested as a potential therapy. METHODS: Five groups of six neonatal piglets were studied. One group did not undergo surgery (Group A). Adeno-beta2AR or phosphate buffered saline (PBS) were delivered via the aortic root during cardioplegic arrest. Groups B (PBS) and C (Adeno-beta2AR) were assessed at 2 days while Groups D (PBS) and E (Adeno-beta2AR) were assessed at 2 weeks from the time of surgery. An LV micromanometer was inserted under sedation to obtain pressure recordings following surgery. betaAR density was measured subsequently. RESULTS: Following cardiac surgery LV betaAR density was reduced (104+/-5.7 vs 135+/-6.1 fmol/mg membrane protein; P=0.007), and, in response to beta agonist stimulation, LV dP/dtmax was reduced (4337+/-405 vs 5328+/-194 mmHg/s; P<0.05) compared to animals which did not undergo surgery. Adeno-beta2AR therapy during cardiac surgery resulted in elevated LV betaAR density (520+/-250.9 fmol/mg) 2 days post-operatively compared to PBS (104+/-5.7 fmol/mg; P=0.002) and compared to the no surgery group (135+/-6.1 fmol/mg; P=0.002). Elevated LV betaAR density was also present at 2 weeks (315+/-74.1 vs 119+/-7.1 fmol/mg; P=0.002). In addition, Adeno-beta2AR therapy enhanced beta agonist stimulated LV dP/dtmax (5348+/-121 vs 4337+/-405 mmHg/s; P<0.05) and heart rate (209+/-6.9 vs 173+/-11.0 bpm; P<0.05), and reduced LVEDP (2.1+/-0.4 vs 6.4+/-1.8 mmHg; P<0.05) compared to PBS treatment. Interestingly, gene delivery was cardiac-selective and beneficial effects on function persisted for 2 weeks. Moreover, beta2AR gene transfer ameliorated LV dysfunction following surgery such that there were no significant differences between non-operated controls and animals treated with Adeno-beta2AR during CPB and cardioplegic arrest. CONCLUSIONS: Reduced betaAR density and impaired LV function were present following CPB and cardioplegic arrest. Cardiac-selective beta2AR gene transfer during CPB resulted in amelioration of LV dysfunction after cardiac surgery. Such a technique may offer a new approach to post-operative ventricular support.

Animals↗