[Stem cell transfer in myocardial infarction].
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Bone Marrow Transplantation↗
Biomedical subjects
S Dimmeler
Publications and source records attributed to S Dimmeler.
Normalization of coronary blood flow in the infarct-related artery after intracoronary progenitor cell therapy: intracoronary Doppler substudy of the TOPCARE-AMI trial.
BACKGROUND: Coronary microvascular dysfunction contributes to infarct extension and poor prognosis after an acute myocardial infarction (AMI). Recently, progenitor cell application has been demonstrated to improve neovascularization and myocardial function after experimental myocardial infarction. Therefore, we investigate coronary blood flow regulation in patients after AMI treated with intracoronary progenitor cell therapy. METHODS AND RESULTS: In the TOPCARE-AMI trial, patients received either bone marrow-derived or circulating progenitor cells into the infarct-related artery 3-7 days after AMI. The present substudy investigates in 40 patients coronary blood flow regulation at the time of progenitor cell therapy and at 4-month follow-up by i.c. Doppler in the infarct artery as well as a reference vessel. At the initial measurement, coronary flow reserve (CFR) was reduced in the infarct artery compared to the reference vessel (median 2.5 vs. 3.4, p<0.001). At 4-month follow-up, intracoronary progenitor cell therapy was associated with a normalization of CFR in the infarct artery (median 3.9 vs. reference vessel 3.8, p=0.15). CFR also improved in the reference vessel, but mechanisms were different: reference vessel increase in CFR was secondary to an increased basal vascular resistance, probably due to reduced need for hypercontractility. In contrast, in the infarct artery, adenosine-induced minimal vascular resistance profoundly decreased, indicating an increased maximal coronary vascular conductance capacity. In addition, in a non-randomized matched control group (n=8), minimal vascular resistance in the infarct artery was significantly elevated compared to progenitor cell treated patients 4 months after AMI (p=0.012). CONCLUSIONS: Intracoronary progenitor cell therapy after AMI is associated with complete restoration of coronary flow reserve due to a substantial improvement of maximal coronary vascular conductance capacity. The clinical importance of improved microcirculation by progenitor cell therapy in patients after AMI has to be established in further randomized trials.
Blood Flow Velocity↗
Neovascularization and cardiac repair by bone marrow-derived stem cells.
Postinfarction congestive heart failure with impaired systolic left ventricular function is a loss of cardiomyocyte disease. Adult stem or progenitor cells from the bone marrow and the peripheral blood have been experimentally shown to differentiate towards endothelial cells and cardiomyocytes under the appropriate conditions. The use of autologous adult stem cells for neovascularization and cardiac regeneration is a promising concept and has shown benefit in pilot clinical trails enrolling postinfarction patients with coronary artery disease. Cell therapy may act through differentiation into and thus replacement of cardiomyocytes and/or neovascularization, the formation of new vessels in the adult organism. Moreover, the release of factors acting in a paracrine manner may contribute to neovascularization and scar remodelling. In this review, the experimental data regarding neovascularization and cardiomyocyte formation from adult stem/progenitor cells are discussed.
Animals↗
Severity of coronary artery stenosis is associated with a polymorphism in the CXCL16/SR-PSOX gene.
OBJECTIVE: Enhanced expression of CXCL16 has been demonstrated in atherosclerotic plaques and several properties have been attributed to CXCL16 that could influence the atherosclerotic process. CXCL16 exists in transmembrane and soluble forms. The transmembrane form acts as a scavenger receptor for oxidised LDL whereas the soluble form acts a chemoattractant for mainly CD8+ T cells. In addition, the soluble form of CXCL16 influences human aortic smooth muscle cell proliferation in vitro. In the present work, a human molecular genetic approach employing a common polymorphism within exon 4 of CXCL16 (181 Ala>Val) was used to investigate whether CXCL16 may be involved in the development of coronary artery disease. The polymorphism is located within the spacer region between the chemokine and transmembrane region and potentially influences an Ala/Val cleavage site, a site commonly used for the release of chemokines by tumour necrosis factor-alpha converting enzyme. DESIGN AND SUBJECTS: We first genotyped 387 unselected survivors of a first myocardial infarction aged <60 years and 387 sex- and age-matched controls. A subset of patients (n = 236) was evaluated by quantitative coronary angiography. Secondly, a cohort of 468 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) with stent implantation was genotyped. RESULTS: No significant difference in allele frequency between patient and controls of the 181 A>V polymorphism was detected. However, the V-allele was associated with increased severity of coronary stenoses. Secondly, the V-allele was associated with smaller minimal luminal diameter in the coronary segment subjected to intervention in a second cohort of patients undergoing PTCA with stent implantation. CONCLUSIONS: The present work provides evidence that CXCL16 is involved in processes leading to enhanced stenosis in atherosclerotic coronary arteries.
Amino Acid Sequence↗
Infarct remodeling after intracoronary progenitor cell treatment in patients with acute myocardial infarction (TOPCARE-AMI): mechanistic insights from serial contrast-enhanced magnetic resonance imaging.
BACKGROUND: Experimental and initial clinical studies suggest that transplantation of circulating blood- (CPC) or bone marrow-derived (BMC) progenitor cells may beneficially affect postinfarction remodeling processes after acute myocardial infarction (AMI). To relate functional characteristics of the infused cells to quantitative measures of outcome at 4-month follow-up, we performed serial contrast-enhanced MRI and assessed the migratory capacity of the transplanted progenitor cells immediately before intracoronary infusion. METHODS AND RESULTS: In 28 patients with reperfused AMI receiving either BMCs or CPCs into the infarct artery 4.7+/-1.7 days after AMI, serial contrast-enhanced MRI performed initially and after 4 months revealed a significant increase in global ejection fraction (from 44+/-10% to 49+/-10%; P=0.003), a decrease in end-systolic volume (from 69+/-26 to 60+/-28 mL; P=0.003), and unchanged end-diastolic volumes (122+/-34 versus 117+/-37 mL; P=NS). Infarct size, measured as late enhancement (LE) volume, decreased significantly, from 46+/-32 to 37+/-28 mL (P<0.05). There was a significant correlation between the reduction in LE volume and global ejection fraction improvement. The migratory capacity of transplanted cells as assessed ex vivo toward a gradient of vascular endothelial growth factor for CPCs and stromal cell derived factor-1 for BMCs was closely correlated with the reduction of LE volume. By multivariate analysis, migratory capacity remained the most important independent predictor of infarct remodeling. CONCLUSIONS: Analysis of serial contrast-enhanced MRI suggests that intracoronary infusion of adult progenitor cells in patients with AMI beneficially affects postinfarction remodeling processes. The migratory capacity of the infused cells is a major determinant of infarct remodeling, disclosing a causal effect of progenitor cell therapy on regeneration enhancement.
Cell Movement↗
Tumor necrosis factor antagonism with etanercept improves systemic endothelial vasoreactivity in patients with advanced heart failure.
BACKGROUND: Anti-tumor necrosis factor (TNF)-alpha therapy with etanercept, a recombinant TNF receptor that binds to and functionally inactivates TNF-alpha, was shown to improve the functional status of patients with congestive heart failure (CHF). Because administration of TNF-alpha has been shown experimentally to depress endothelium-dependent relaxation, we hypothesized that TNF-alpha antagonism with etanercept might improve the depressed systemic endothelial vasodilator function, which importantly contributes to increased peripheral vascular resistance in patients with advanced CHF. METHODS AND RESULTS: Endothelium-dependent (acetylcholine, ACH; 10 to 50 microgram/min) and endothelium-independent (sodium nitroprusside, SNP; 2 to 8 microgram/min) forearm blood flow (FBF) responses were measured by venous occlusion plethysmography in 13 patients with documented CHF (New York Heart Association class III) before, 6 hours after, and 7 days after subcutaneous injection of a single dose of 25 mg etanercept. Maximum ACH-induced FBF increased significantly from 6.9+/-1.0 to 13.0+/-1.6 mL/min per 100 mL of forearm tissue (P<0.05) 6 hours after administration of etanercept and returned to 7.0+/-1.1 mL/min per 100 mL of forearm tissue after 7 days (P=NS), whereas SNP-induced FBF responses were not significantly affected. In contrast, FBF responses were not altered in control CHF patients, who did not receive etanercept (n=5). Etanercept-induced increases in ACH-mediated FBF were closely correlated with baseline TNF-alpha serum levels (r=0.66; P<0.02). CONCLUSIONS: The administration of etanercept profoundly improves systemic endothelial vasodilator capacity in patients with advanced heart failure, suggesting an important role of inflammatory mediators for impaired endothelial vasoreactivity in CHF. Improvement of systemic endothelial function might importantly contribute to the beneficial effects of etanercept on the functional status of patients with CHF.
Acetylcholine↗
Vitamin C inhibits endothelial cell apoptosis in congestive heart failure.
BACKGROUND: Proinflammatory cytokines like tumor necrosis factor-alpha and oxidative stress induce apoptotic cell death in endothelial cells (ECs). Systemic inflammation and increased oxidative stress in congestive heart failure (CHF) coincide with enhanced EC apoptosis and the development of endothelial dysfunction. Therefore, we investigated the effects of antioxidative vitamin C therapy on EC apoptosis in CHF patients. METHODS AND RESULTS: Vitamin C dose dependently suppressed the induction of EC apoptosis by tumor necrosis factor-alpha and angiotensin II in vitro as assessed by DNA fragmentation, DAPI nuclear staining, and MTT viability assay. The antiapoptotic effect of vitamin C was associated with reduced cytochrome C release from mitochondria and the inhibition of caspase-9 activity. To assess EC protection by vitamin C in CHF patients, we prospectively randomized CHF patients in a double-blind trial to vitamin C treatment versus placebo. Vitamin C administration to CHF patients markedly reduced plasma levels of circulating apoptotic microparticles to 32+/-8% of baseline levels, whereas placebo had no effect (87+/-14%, P<0.005). In addition, vitamin C administration suppressed the proapoptotic activity on EC of the serum of CHF patients (P<0.001). CONCLUSIONS: Administration of vitamin C to CHF patients suppresses EC apoptosis in vivo, which might contribute to the established functional benefit of vitamin C supplementation on endothelial function.
Administration, Oral↗
Aging enhances the sensitivity of endothelial cells toward apoptotic stimuli: important role of nitric oxide.
Advanced aging leads to impaired endothelial NO synthesis and enhanced endothelial cell apoptosis; therefore, we investigated the sensitivity of aged endothelial cells toward apoptotic stimuli and determined the role of NO. Human umbilical vein endothelial cells (HUVECs) were cultured until 14th passage. In aged cells, oxLDL and tumor necrosis factor-alpha-induced apoptosis and caspase-3-like activity were significantly enhanced more than 3-fold compared with young cells (passage 3). Because NO contributes to protection against endothelial cell death via S-nitrosylation of caspases, we determined endothelial NO synthase (eNOS) protein expression and the content of S-nitrosylated proteins. Aged HUVECs showed significantly reduced eNOS expression (35+/-10%) and a decrease in the overall S-NO content (33+/-3%), suggesting that eNOS downregulation may be involved in age-dependent increase of apoptosis sensitivity. Indeed, eNOS knockout endothelial cells showed a significantly enhanced apoptosis induction. Exogenous NO donors abolished increased apoptosis and caspase-3-like activity. In contrast, the application of shear stress, which exerts a profound apoptosis inhibitory effect via upregulation of NO synthesis in young cells, failed to inhibit apoptosis in aged cells. Moreover, no upregulation of eNOS protein expression and S-NO content in response to shear stress was detected in aged cells. Overexpression of wild-type eNOS completely restored the antiapoptotic effect of shear stress, whereas only a partial inhibitory effect was detected under steady conditions. Strikingly, transfection of constitutively active phosphomimetic eNOS (S1177D) further abrogated apoptosis in aged HUVECs. Thus, aging of endothelial cells is associated with decreased NO synthesis and concomitantly increased sensitivity of apoptosis, which may contribute to functional impairment of the endothelial monolayer.
Aging↗
TNFalpha and oxLDL reduce protein S-nitrosylation in endothelial cells.
Nitric oxide (NO) plays an important role in the regulation of the functional integrity of the endothelium. The intracellular reaction of NO with reactive cysteine groups leads to the formation of S-nitrosothiols. To investigate the regulation of S-nitrosothiols in endothelial cells, we first analyzed the composition of the S-nitrosylated molecules in endothelial cells. Gel filtration revealed that more than 95% of the detected S-nitrosothiols had a molecular mass of more than 5000 Da. Moreover, inhibition of de novo synthesis of glutathione using N-butyl-sulfoximine did not diminish the overall cellular S-NO content suggesting that S-nitrosylated glutathione quantitatively plays only a minor role in endothelial cells. Having demonstrated that most of the S-nitrosothiols are proteins, we determined the regulation of the S-nitrosylation by pro-inflammatory and pro-atherogenic factors, such as TNFalpha and mildly oxidized low density lipoprotein (oxLDL). TNFalpha and oxLDL induced denitrosylation of various proteins as assessed by Saville-Griess assay, by immunostaining with an anti-S-nitrosocysteine antibody, and by a Western blot approach. Furthermore, the caspase-3 p17 subunit, which has previously been shown to be S-nitrosylated and thereby inhibited, was denitrosylated by TNFalpha treatment suggesting that S-nitrosylation and denitrosylation are important regulatory mechanisms in endothelial cells contributing to the integrity of the endothelial cell monolayer.
Blotting, Western↗
Chronic hypoxia induces apoptosis in cardiac myocytes: a possible role for Bcl-2-like proteins.
The effect of prolonged hypoxia as well as the molecular mechanisms on cardiac cell death is not well established. A possible role of Bcl-2 and Bax in hypoxia-induced apoptosis in different cell types has been proposed. Here we demonstrate the effect of hypoxia on the induction of apoptosis and the expression of Bcl-2-like proteins in vivo and in vitro. Hearts from rats exposed to chronic hypoxia (n = 4) showed an increased rate of apoptosis compared to normoxic hearts (n = 4). The induction of apoptosis in hypoxic hearts correlated with a significant decrease of Bcl-2 protein level, whereas Bax protein expression was increased. Exposure of isolated neonatal rat cardiac myocytes to hypoxia also resulted in a significant increase in apoptosis. However, Bcl-2 and Bax protein levels essentially remained unchanged. Our results may suggest a different molecular mechanism of hypoxia-induced apoptosis in vivo and in vitro.
Animals↗
Number and migratory activity of circulating endothelial progenitor cells inversely correlate with risk factors for coronary artery disease.
Recent studies provide increasing evidence that postnatal neovascularization involves bone marrow-derived circulating endothelial progenitor cells (EPCs). The regulation of EPCs in patients with coronary artery disease (CAD) is unclear at present. Therefore, we determined the number and functional activity of EPCs in 45 patients with CAD and 15 healthy volunteers. The numbers of isolated EPCs and circulating CD34/kinase insert domain receptor (KDR)-positive precursor cells were significantly reduced in patients with CAD by approximately 40% and 48%, respectively. To determine the influence of atherosclerotic risk factors, a risk factor score including age, sex, hypertension, diabetes, smoking, positive family history of CAD, and LDL cholesterol levels was used. The number of risk factors was significantly correlated with a reduction of EPC levels (R=-0.394, P=0.002) and CD34-/KDR-positive cells (R=-0.537, P<0.001). Analysis of the individual risk factors demonstrated that smokers had significantly reduced levels of EPCs (P<0.001) and CD34-/KDR-positive cells (P=0.003). Moreover, a positive family history of CAD was associated with reduced CD34-/KDR-positive cells (P=0.011). Most importantly, EPCs isolated from patients with CAD also revealed an impaired migratory response, which was inversely correlated with the number of risk factors (R=-0.484, P=0.002). By multivariate analysis, hypertension was identified as a major independent predictor for impaired EPC migration (P=0.043). The present study demonstrates that patients with CAD revealed reduced levels and functional impairment of EPCs, which correlated with risk factors for CAD. Given the important role of EPCs for neovascularization of ischemic tissue, the decrease of EPC numbers and activity may contribute to impaired vascularization in patients with CAD. The full text of this article is available at http://www.circresaha.org.
AC133 Antigen↗
Increase in circulating endothelial progenitor cells by statin therapy in patients with stable coronary artery disease.
BACKGROUND: Therapeutic neovascularization may constitute an important strategy to salvage tissue from critical ischemia. Circulating bone marrow-derived endothelial progenitor cells (EPCs) were shown to augment the neovascularization of ischemic tissue. In addition to lipid-lowering activity, hydroxymethyl glutaryl coenzyme A reductase inhibitors (statins) reportedly promote the neovascularization of ischemic tissue in normocholesterolemic animals. Methods and Results-Fifteen patients with angiographically documented stable coronary artery disease (CAD) were prospectively treated with 40 mg of atorvastatin per day for 4 weeks. Before and weekly after the initiation of statin therapy, EPCs were isolated from peripheral blood and counted. In addition, the number of hematopoietic precursor cells positive for CD34, CD133, and CD34/kinase insert domain receptor was analyzed. Statin treatment of patients with stable CAD was associated with an approximately 1.5-fold increase in the number of circulating EPCs by 1 week after initiation of treatment; this was followed by sustained increased levels to approximately 3-fold throughout the 4-week study period. Moreover, the number of CD34/kinase insert domain receptor-positive hematopoietic progenitor cells was significantly augmented after 4 weeks of therapy. Atorvastatin treatment increased the further functional activity of EPCs, as assessed by their migratory capacity. CONCLUSION: The results of the present study define a novel mechanism of action of statin treatment in patients with stable CAD: the augmentation of circulating EPCs with enhanced functional activity. Given the well-established role of EPCs of participating in repair after ischemic injury, stimulation of EPCs by statins may contribute to the clinical benefit of statin therapy in patients with CAD.
Adult↗
Phosphorylation of Thr(495) regulates Ca(2+)/calmodulin-dependent endothelial nitric oxide synthase activity.
The activity of the endothelial nitric oxide synthase (eNOS) can be regulated independently of an increase in Ca(2+) by the phosphorylation of Ser(1177) but results only in a low nitric oxide (NO) output. In the present study, we assessed whether the agonist-induced (Ca(2+)-dependent, high-output) activation of eNOS is associated with changes in the phosphorylation of Thr(495) in the calmodulin (CaM)-binding domain. eNOS Thr(495) was constitutively phosphorylated in porcine aortic endothelial cells and was rapidly dephosphorylated after bradykinin stimulation. In the same cells, bradykinin enhanced the phosphorylation of Ser(1177), which was maximal after 5 minutes, and abolished by the CaM-dependent kinase II (CaMKII) inhibitor KN-93. Bradykinin also enhanced the association of CaMKII with eNOS. Phosphorylation of Thr(495) was attenuated by the protein kinase C (PKC) inhibitor Ro 31-8220 and after PKC downregulation using phorbol 12-myristate 13-acetate. The agonist-induced dephosphorylation of Thr(495) was completely Ca(2+)-dependent and inhibited by the PP1 inhibitor calyculin A. Little CaM was bound to eNOS immunoprecipitated from unstimulated cells, but the agonist-induced dephosphorylation of Thr(495) enhanced the association of CaM. Mutation of Thr(495) to alanine increased CaM binding to eNOS in the absence of cell stimulation, whereas the corresponding Asp(495) mutant bound almost no CaM. Accordingly, NO production by the Ala(495) mutant was more sensitive to Ca(2+)/CaM than the aspartate mutant. These results suggest that the dual phosphorylation of Ser(1177) and Thr(495) determines the activity of eNOS in agonist-stimulated endothelial cells. Moreover, the dephosphorylation of Thr(495) by PP1 precedes the phosphorylation of Ser(1177) by CaMKII. The full text of this article is available at http://www.circresaha.org.
Animals↗
Oxidized LDL inhibits vascular endothelial growth factor-induced endothelial cell migration by an inhibitory effect on the Akt/endothelial nitric oxide synthase pathway.
BACKGROUND: Oxidized LDL (oxLDL) inhibits endothelial cell (EC) migration. Stimulating ECs with vascular endothelial growth factor (VEGF) leads to the activation of Akt/protein kinase B, which in turn activates endothelial nitric oxide synthase (eNOS) by phosphorylation on serine 1177. VEGF-induced cell migration is dependent on the generation of nitric oxide (NO). Therefore, we investigated whether oxLDL affects EC migration by an inhibitory effect on the Akt/eNOS pathway. METHODS AND RESULTS: During an in vitro "scratched wound assay," oxLDL dose-dependently inhibited the VEGF-induced migration of human umbilical vein endothelial cells. Western blot analysis revealed that oxLDL dose- and time-dependently led to dephosphorylation and thus deactivation of Akt. Moreover, oxLDL inhibited the VEGF-induced generation of NO, as detected and quantified using a fluorescent NO indicator, 4,5-diaminofluorescein diacetate. Overexpression of a constitutively active Akt construct (Akt T308D/S473D) or a phosphomimetic eNOS construct (eNOS S1177D) almost completely reversed the inhibitory effect of oxLDL on VEGF-induced EC migration and NO generation. CONCLUSIONS: Our data indicate that oxLDL-induced dephosphorylation of Akt, followed by impaired eNOS activation, reduces the intracellular level of NO and thereby inhibits VEGF-induced EC migration.
Amino Acid Substitution↗
The role of toll-like receptors (TLRs) in bacteria-induced maturation of murine dendritic cells (DCS). Peptidoglycan and lipoteichoic acid are inducers of DC maturation and require TLR2.
Toll-like receptors (TLRs) have been found to be key elements in pathogen recognition by the host immune system. Dendritic cells (DCs) are crucial for both innate immune responses and initiation of acquired immunity. Here we focus on the potential involvement of TLR ligand interaction in DC maturation. TLR2 knockout mice and mice carrying a TLR4 mutation (C3H/HeJ) were investigated for DC maturation induced by peptidoglycan (PGN), lipopolysaccharide (LPS), or lipoteichoic acids (LTAs). All stimuli induced maturation of murine bone marrow-derived DCs in control mice. TLR2(-)/- mice lacked maturation upon stimulation with PGN, as assessed by expression of major histocompatibility complex class II, CD86, cytokine, and chemokine production, fluorescein isothiocyanate-dextran uptake, and mixed lymphocyte reactions, while being completely responsive to LPS. A similar lack of maturation was observed in C3H/HeJ mice upon stimulation with LPS. DC maturation induced by LTAs from two different types of bacteria was severely impaired in TLR2(-)/-, whereas C3H/HeJ mice responded to LTAs in a manner similar to wild-type mice. We demonstrate that DC maturation is induced by stimuli from Gram-positive microorganisms, such as PGN and LTA, with similar efficiency as by LPS. Finally, we provide evidence that TLR2 and TLR4 interaction with the appropriate ligand is essential for bacteria-induced maturation of DCs.
Animals↗
Pro-atherogenic factors induce telomerase inactivation in endothelial cells through an Akt-dependent mechanism.
Advanced aging may contribute to impairment of angiogenesis and development of vascular diseases. Telomerase was shown to delay endothelial cell (EC) senescence. Therefore, we determined the regulation of telomerase activity in EC. Inhibition of phosphoinositol 3-kinase (PI3K) suppressed telomerase activity, whereas inhibitors directed against ERK1/2 or protein kinase C had no effect. Dominant negative Akt significantly reduced telomerase activity. Moreover, pro-atherogenic stimuli such as oxidized low density lipoprotein led to an inactivation of Akt and diminished telomerase activity. Thus, the PI3K/Akt pathway plays an important role in the regulation of telomerase activity. Pro-atherosclerotic factors impair telomerase activity and thereby may promote EC aging.
Aging↗
Apoptosis in the vascular wall and atherosclerosis.
Apoptosis, programmed cell death, has emerged as a key element in the complex pathophysiology underlying the development as well as the progression of atherosclerosis. A number of recent reports provided evidence for both in vivo and in vitro occurrence of apoptotic cell death of vascular cells, namely endothelial cells, macrophages, and vascular smooth muscle cells. In addition, functional studies in disease models underscore the relevance of these findings for the understanding of processes which lead to lesion development, plaque rupture, and thrombus formation. Pathomechanistic in vitro investigations provided an increasingly detailed picture of the involved intracellular signaling pathways that regulate onset and execution of apoptosis. These insights offer the potential of therapeutic interventions targeted to interfere with the molecular processes involving apoptotic cell death in the vascular wall.
Animals↗
Inhibition of caspase-3 improves contractile recovery of stunned myocardium, independent of apoptosis-inhibitory effects.
OBJECTIVES: The aim of this study was to investigate whether the caspase-3 inhibitor Ac-DEVD-CHO functionally improves stunned myocardium. BACKGROUND: Degradation of troponin I contributes to the pathogenesis of myocardial stunning, whereas the role of apoptosis is unknown. Caspase-3 is an essential apoptotic protease that is specifically inhibited by Ac-DEVD-CHO. METHODS: Isolated working hearts of rats were exposed to 30 min of low-flow ischemia, followed by 30 min of reperfusion. Ac-DEVD-CHO (0.1 to 1 micromol/l) was added 15 min before ischemia/reperfusion or 5 min before reperfusion. Cardiac output, external heart power, left ventricular (LV) developing pressure and contractility (dp/dt(max)) were measured. Apoptosis was assessed by TUNEL staining and internucleosomal deoxyribonucleic acid fragmentation. Caspase-3 processing and troponin I cleavage were determined by immunoblotting. Caspase-3 activity was measured using a fluorogenic substrate. RESULTS: The addition of Ac-DEVD-CHO before ischemia/reperfusion or before reperfusion dose-dependently and significantly (p < 0.05) improved post-ischemic recovery of cardiac output, external heart power, LV developing pressure and dp/dt(max), compared with the vehicle (0.01% dimethyl sulfoxide). Ac-DEVD-CHO was similarly effective when given before reperfusion. Ac-DEVD-CHO blocked ischemia/reperfusion-induced caspase-3 activation, but cardiomyocyte apoptosis was unaffected. Troponin I cleavage was not inhibited by Ac-DEVD-CHO. CONCLUSIONS: Caspase-3 is activated in stunned myocardium. Inhibition of caspase-3 by Ac-DEVD-CHO significantly improves post-ischemic contractile recovery of stunned myocardium, even when given after the onset of ischemia. The mechanism(s) of protection by Ac-DEVD-CHO appear to be independent of apoptosis. Inhibition of caspase-3 is a novel therapeutic strategy to improve functional recovery of stunned myocardium.
Animals↗