Down-regulation of plasminogen activator inhibitor 1 expression promotes myocardial neovascularization by bone marrow progenitors

Cleaving Folded RNA with DNAzyme Agents

Cleavage of biological mRNA by DNAzymes (Dz) has been proposed as a variation of oligonucleotide gene therapy (OGT). The design of Dz-based OGT agents includes computational prediction of two RNA-binding arms with low affinity (melting temperatures (Tm ) close to the reaction temperature of 37 °C) to avoid product inhibition and maintain high specificity. However, RNA cleavage might be limited by the RNA binding step especially if the RNA is folded in secondary structures. This calls for the need for two high-affinity RNA-binding arms. In this study, we optimized 10-23 Dz-based OGT agents for cleavage of three RNA targets with different folding energies under multiple turnover conditions in 2 mM Mg2+ at 37 °C. Unexpectedly, one optimized Dz had each RNA-binding arm with a Tm ≥60 °C, without suffering from product inhibition or low selectivity. This phenomenon was explained by the folding of the RNA cleavage products into stable secondary structures. This result suggests that Dz with long (high affinity) RNA-binding arms should not be excluded from the candidate pool for OGT agents. Rather, analysis of the cleavage products' folding should be included in Dz selection algorithms. The Dz optimization workflow should include testing with folded rather than linear RNA substrates.

A promising nucleic acid therapy drug: DNAzymes and its delivery system

Based on the development of nucleic acid therapeutic drugs, DNAzymes obtained through in vitro selection technology in 1994 are gradually being sought. DNAzymes are single-stranded DNA molecules with catalytic function, which specifically cleave RNA under the action of metal ions. Various in vivo and in vitro models have recently demonstrated that DNAzymes can target related genes in cancer, cardiovascular disease, bacterial and viral infection, and central nervous system disease. Compared with other nucleic acid therapy drugs, DNAzymes have gained more attention due to their excellent cutting efficiency, high stability, and low cost. Here, We first briefly reviewed the development and characteristics of DNAzymes, then discussed disease-targeting inhibition model of DNAzymes, hoping to provide new insights and ways for disease treatment. Finally, DNAzymes were still subject to some restrictions in practical applications, including low cell uptake efficiency, nuclease degradation and interference from other biological matrices. We discussed the latest delivery strategy of DNAzymes, among which lipid nanoparticles have recently received widespread attention due to the successful delivery of the COVID-19 mRNA vaccine, which provides the possibility for the subsequent clinical application of DNAzymes. In addition, the future development of DNAzymes was prospected.

Transforming growth factor-β1/Thrombospondin-1/CD47 axis mediates dysfunction in CD34+ cells derived from diabetic older adults

Aging with diabetes is associated with impaired vasoprotective functions and decreased nitric oxide (NO) generation in CD34+ cells. Transforming growth factor- β1 (TGF-β1) is known to regulate hematopoietic functions. This study tested the hypothesis that transforming growth factor- β1 (TGF-β1) is upregulated in diabetic CD34+ cells and impairs NO generation via thrombospondin-1 (TSP-1)/CD47/NO pathway. CD34+ cells from nondiabetic (ND) (n=58) or diabetic older adults (DB) (both type 1 and type 2) (n=62) were isolated from peripheral blood. TGF-β1 was silenced by using an antisense delivered as phosphorodiamidate morpholino oligomer (PMO-TGF-β1). Migration and proliferation in response to stromal-derived factor-1α (SDF-1α) were evaluated. NO generation and eNOS phosphorylation were determined by flow cytometry. CD34+ cells from older, but not younger, diabetics have higher expression of TGF-β1 compared to that observed in cells derived from healthy individuals (P<0.05, n=14). TSP-1 expression was higher (n=11) in DB compared to ND cells. TGFβ1-PMO decreased the secretion of TGF-β1, which was accompanied with decreased TSP-1 expression. Impaired proliferation, migration and NO generation in response to SDF-1α in DB cells were reversed by TGF-β1-PMO (n=6). TSP-1 inhibited migration and proliferation of nondiabetic CD34+ cells that was reversed by CD47-siRNA, which also restored these responses in diabetic CD34+ cells. TSP-1 opposed SDF-1α-induced eNOS phosphorylation at Ser1177 that was reversed by CD47-siRNA. These results infer that increased TGF-β1 expression in CD34+ cells induces dysfunction in CD34+ cells from diabetic older adults via TSP-1/CD47-dependent inhibition of NO generation.

Myocardial Production of Plasminogen Activator Inhibitor-1 is Associated with Coronary Endothelial and Ventricular Dysfunction after Acute Myocardial Infarction

AIM

Although plasminogen activator inhibitor-1 (PAI-1) is abundantly expressed in infarcted myocardium, the pathogenic role of myocardial PAI-1 remains unknown. This study examined whether PAI-1 in the infarcted lesion contributes to coronary endothelial dysfunction and left ventricular (LV) dysfunction in patients with acute myocardial infarction (AMI).

METHODS

Plasma levels of PAI-1 activity and tissue-plasminogen activator (tPA) antigen were measured 2 weeks and 6 months after MI by ELISA in plasma obtained from the aortic root (AO) and anterior interventricular vein (AIV) in 28 patients with a first AMI due to occlusion of the left anterior descending coronary artery (LAD). Coronary blood flow responses in LAD to intracoronary infusion of acetylcholine (ACh) and left ventriculography were measured at the same time points: 2 weeks and 6 months after MI.

RESULTS

The trans-myocardial gradient of PAI-1 from AO to AIV, reflecting production/release of PAI-1 in the infarcted lesion, was inversely correlated with the coronary blood flow response to ACh 6 months after MI (r=-0.43, p=0.02) and with the percentage change in LV regional motion in the LAD territory from 2 weeks to 6 months after MI (r=-0.38, p=0.04). The trans-myocardial gradient of tPA level showed no significant correlations.

CONCLUSIONS

PAI-1 produced in the infarcted myocardium and released into the coronary circulation is associated with endothelial dysfunction in resistance vessels of the infarct-related coronary arteries and with progressive dysfunction of the infarcted region of the left ventricle in AMI survivors.

DNA enzymes as potential therapeutics: towards clinical application of 10-23 DNAzymes

INTRODUCTION

Ongoing studies on the inhibition of gene expression at the mRNA level have identified several types of specific inhibitors such as antisense oligonucleotides, small interfering RNA, ribozymes and DNAzymes (Dz). After its discovery in 1997, the 10-23 Dz (which can cleave RNA efficiently and site-specifically, has flexible design, is independent from cell mechanisms, does not require expensive chemical modifications for effective use in vivo) has been employed to downregulate a range of therapeutically important genes. Recently, 10-23 Dzs have taken their first steps into clinical trials.

AREAS COVERED

This review focuses predominantly on Dz applications as potential antiviral, antibacterial, anti-cancer and anti-inflammatory agents as well as for the treatment of cardiovascular disease and diseases of CNS, summarizing results of their clinical trials up to the present day.

EXPERT OPINION

In comparison with antisense oligonucleotides and small interfering RNAs, Dzs do not usually show off-target effects due to their high specificity and lack of immunogenicity in vivo. As more results of clinical trials carried out so far are gradually becoming available, Dzs may turn out to be safe and well-tolerated therapeutics in humans. Therefore, there is a good chance that we may witness a deoxyribozyme drug reaching the clinic in the near future.

Enhancing the function of CD34(+) cells by targeting plasminogen activator inhibitor-1

Previously, we showed that transient inhibition of TGF- β1 resulted in correction of key aspects of diabetes-induced CD34(+) cell dysfunction. In this report, we examine the effect of transient inhibition of plasminogen activator inhibitor-1 (PAI-1), a major gene target of TGF-β1 activation. Using gene array studies, we examined CD34(+) cells isolated from a cohort of longstanding diabetic individuals, free of microvascular complications despite suboptimal glycemic control, and found that the cells exhibited reduced transcripts of both TGF-β1 and PAI-1 compared to age, sex, and degree of glycemic control-matched diabetic individuals with microvascular complications. CD34(+) cells from diabetic subjects with microvascular complications consistently exhibited higher PAI-1 mRNA than age-matched non-diabetic controls. TGF- β1 phosphorodiamidate morpholino oligo (PMO) reduced PAI-1 mRNA in diabetic (p<0.01) and non-diabetic (p=0.05) CD34(+) cells. To reduce PAI-1 in human CD34(+) cells, we utilized PAI-1 siRNA, lentivirus expressing PAI-1 shRNA or PAI-1 PMO. We found that inhibition of PAI-1 promoted CD34(+) cell proliferation and migration in vitro, likely through increased PI3(K) activity and increased cGMP production. Using a retinal ischemia reperfusion injury model in mice, we observed that recruitment of diabetic CD34(+) cells to injured acellular retinal capillaries was greater after PAI-1-PMO treatment compared with control PMO-treated cells. Targeting PAI-1 offers a promising therapeutic strategy for restoring vascular reparative function in defective diabetic progenitors.

A phenomics-based strategy identifies loci on APOC1, BRAP, and PLCG1 associated with metabolic syndrome phenotype domains

Despite evidence of the clustering of metabolic syndrome components, current approaches for identifying unifying genetic mechanisms typically evaluate clinical categories that do not provide adequate etiological information. Here, we used data from 19,486 European American and 6,287 African American Candidate Gene Association Resource Consortium participants to identify loci associated with the clustering of metabolic phenotypes. Six phenotype domains (atherogenic dyslipidemia, vascular dysfunction, vascular inflammation, pro-thrombotic state, central obesity, and elevated plasma glucose) encompassing 19 quantitative traits were examined. Principal components analysis was used to reduce the dimension of each domain such that >55% of the trait variance was represented within each domain. We then applied a statistically efficient and computational feasible multivariate approach that related eight principal components from the six domains to 250,000 imputed SNPs using an additive genetic model and including demographic covariates. In European Americans, we identified 606 genome-wide significant SNPs representing 19 loci. Many of these loci were associated with only one trait domain, were consistent with results in African Americans, and overlapped with published findings, for instance central obesity and FTO. However, our approach, which is applicable to any set of interval scale traits that is heritable and exhibits evidence of phenotypic clustering, identified three new loci in or near APOC1, BRAP, and PLCG1, which were associated with multiple phenotype domains. These pleiotropic loci may help characterize metabolic dysregulation and identify targets for intervention.

Deoxyribozymes: new therapeutics to treat central nervous system disorders

This mini-review focuses on a knockdown technology called deoxyribozymes, which has rarely been utilized in the field of neurobiology/neuroscience. Deoxyribozymes are catalytic DNA molecules, which are also entitled DNA enzyme or DNAzyme. This mini-review presents a description of their development, structure, function, and therapeutic application. In addition, information on siRNA, ribozymes, and antisense are given. Further information on two deoxyribozymes against c-Jun and xylosyltransferase (XT) mRNA are summarized of which the first is important to influence many neurological disorders and the last potentially treats spinal cord injuries (SCIs). In particular, insults to the central nervous system (CNS) such as SCI generate an inhibitory environment (lesion scar) at the injury site that prevents the endogenous and therapy-induced axonal regeneration and thereby limits repair strategies. Presently, there are no treatments available. Hence, deoxyribozymes provide an opportunity for new therapeutics that alter the inhibitory nature of the lesion scar and thus promote axonal growth in the injured spinal cord. When used cautiously and within the limits of its ability the deoxyribozyme technology holds promise to become a major contributing factor in repair strategies of the CNS.

Sonic hedgehog-induced functional recovery after myocardial infarction is enhanced by AMD3100-mediated progenitor-cell mobilization

OBJECTIVES

This study was designed to compare the effectiveness of Sonic hedgehog (Shh) gene transfer, AMD3100-induced progenitor-cell mobilization, and Shh-AMD3100 combination therapy for treatment of surgically induced myocardial infarction (MI) in mice.

BACKGROUND

Shh gene transfer improves myocardial recovery by up-regulating angiogenic genes and enhancing the incorporation of bone marrow-derived progenitor cells (BMPCs) in infarcted myocardium. Here, we investigated whether the effectiveness of Shh gene therapy could be improved with AMD3100-induced progenitor-cell mobilization.

METHODS

Gene expression and cell function were evaluated in cells cultured with medium collected from fibroblasts transfected with plasmids encoding human Shh (phShh). MI was induced in wild-type mice, in matrix metalloproteinase (MMP)-9 knockout mice, and in mice transplanted with bone marrow that expressed green-fluorescent protein. Mice were treated with 100 μg of phShh (administered intramyocardially), 5 mg/kg of AMD3100 (administered subcutaneously), or both; cardiac function was evaluated echocardiographically, and fibrosis, capillary density, and BMPC incorporation were evaluated immunohistochemically.

RESULTS

phShh increased vascular endothelial growth factor and stromal cell-derived factor 1 expression in fibroblasts; the medium from phShh-transfected fibroblasts increased endothelial-cell migration and the migration, proliferation, and tube formation of BMPCs. Combination therapy enhanced cardiac functional recovery (i.e., left ventricular ejection fraction) in wild-type mice, but not in MMP-9 knockout mice, and was associated with less fibrosis, greater capillary density and smooth muscle-containing vessel density, and enhanced BMPC incorporation.

CONCLUSIONS

Combination therapy consisting of intramyocardial Shh gene transfer and AMD3100-induced progenitor-cell mobilization improves cardiac functional recovery after MI and is superior to either individual treatment for promoting therapeutic neovascularization.

The effects of pharmacologic plasminogen activator inhibitor-1 inhibition in acute and chronic rejection in murine cardiac allografts

BACKGROUND

Acute rejection and graft arterial disease (GAD) in cardiac transplantation limit the long-term survival of recipients; these processes are enhanced by inflammation and thrombus formation. Plasminogen activator inhibitor (PAI)-1 is critical in the inflammation and thrombus formation. However, little is known about the effect of PAI-1 in heart transplantation. Thus, the objective was to clarify the role of PAI-1 in the progression of cardiac rejection.

METHODS

Murine hearts were heterotopically transplanted using major mismatch combinations for evaluation of acute rejection and class II mismatch combinations for the GAD. We administered the specific PAI-1 inhibitor (IMD-1622) into murine recipients after cardiac allografts.

RESULTS

Nontreated allografts of the major mismatch group were acutely rejected, whereas the PAI-1 inhibitor prolonged their survival. Although severe cell infiltration and intimal thickening with enhancement of inflammatory factors were observed in untreated allografts of class II mismatch group on day 60, the PAI-1 inhibitor attenuated these changes.

CONCLUSION

The PAI-1 inhibitor is potent for the suppression of both acute rejection and GAD.

Managing drugs and devices in patients with permanent ventricular assist devices

Patients will be considered for destination mechanical circulatory support device (MCSD) implantation when all other organ-saving treatment options have failed and they are not eligible for heart transplantation. Current medical evidence suggests that only for those patients who are inotrope-dependent and therefore likely have a 1-year survival probability without MCSD implantation of less than 50%, MCSD intervention will add to survival and quality-of-life benefit. Suitable candidates for MCSD are those patients who have a high risk of dying from heart failure but acceptable noncardiac risk. Evaluation of patients for MCSD requires a systematic and critical review of all organ systems and of the psychosocial situation. Specifically, right ventricular function and risk of right ventricular failure should be evaluated before planning destination MCSD implantation. Treatment will focus on prompt recovery from MCSD implantation, maintaining optimal treatment for heart failure, and preventing/treating MCSD complications, including infection, bleeding, coagulopathy, right heart failure, and device dysfunction. MCSD programs should be organized as an advanced heart failure center directed by specialized heart failure cardiologists, surgeons expert at implant and management of MCSD, specialized nurses, social workers, psychologists, financial experts, and physical therapists. MCSD practice is based on a patient-centered theory, with an appropriate understanding of the respective roles of the physician and the patient during their iterative encounters in which the patient is an autonomous person making responsible personal health decisions while the health care team is providing continued expert and empathic counseling about various options, based on systematic outcomes research (eg, by participation in the Interagency Registry for Mechanically Assisted Circulatory Support - MCSD database ).

Role of endothelial progenitor cells during ischemia-induced vasculogenesis and collateral formation

Cell-based therapy has emerged as a promising therapeutic tool for treatment of ischemic cardiovascular disease. Both unselected bone marrow-derived mononuclear cells (BMNCs), which include stem/progenitor cells and several other cell types, and endothelial progenitor cells (EPCs), a subpopulation of BMNCs, display regenerative potential in ischemic tissue. Abundant evidence supports the involvement of EPCs in capillary growth, and EPCs also appear to participate in the formation of collateral vessels. Collectively, these effects have led to improved perfusion and functional recovery in animal models of myocardial and peripheral ischemia, and in early clinical trials, the therapeutic administration of EPCs to patients with myocardial infarction or chronic angina has been associated with positive trends in perfusion. EPCs also contribute to endothelial repair and may, consequently, impede the development or progression of arteriosclerosis. This review provides a brief summary of the preclinical and clinical evidence for the role of EPCs in blood-vessel formation and repair during ischemic cardiovascular disease.

Minimal engraftment of human CD34+ cells mobilized from healthy donors in the infarcted heart of athymic nude rats

Cell-based regenerative therapy may be useful for treatment of acute myocardial infarction (AMI). Animal xenograft models are ideally suited for preclinical studies evaluating prospective treatment regimes, identifying candidate human cell populations, and gaining mechanistic insight. Here we address whether the athymic nude rat is suitable as a xenograft model for the study of human CD34+ mobilized peripheral blood stem cells (M-PBSCs) in the repair of AMI. We injected human donor cells into the infarct border of athymic nude rats with surgically induced AMI and evaluated engraftment and functional improvement. We found no human engraftment by immunofluorescence staining at 14 days after transplantation or functional improvement at days 2 and 14 compared to controls. The lack of long-term human engraftment was furthermore confirmed in a time series study analyzing animals at 0, 24, 48, 72, and 96 h after transplantation. Although we found fluorescent microbeads coinjected with human CD34+ M-PBSCs at all time points, the number of donor cells rapidly declined and became undetectable at 96 h. CD34+ M-PBSCs from the same donor used to treat athymic nude rat hearts engrafted the bone marrow of nonobese diabetic/severe combined immunodeficient mice 8-10 weeks after transplantation. In conclusion, human CD34+ M-PBSCs with confirmed hematopoietic engraftment potential rapidly disappeared from the site of injury following intramyocardial transplantation in the athymic nude rat AMI model.

Metabolic syndrome and collateral vessel formation in patients with documented occluded coronary arteries: association with hyperglycaemia, insulin-resistance, adiponectin and plasminogen activator inhibitor-1

Aims

The metabolic syndrome (MS) is associated with an increased cardiovascular risk. Patients with the MS have endothelial dysfunction, decreased circulating adiponectin, and a high expression of angiogenic inhibitors such as plasminogen activator inhibitor-1 (PAI-1). We hypothesized that such patients, in the event of a coronary occlusion, might exhibit a less developed collateral circulation.

Methods and results

Three hundred and eighty-seven consecutive patients with at least one coronary occlusion of a major coronary vessel at diagnostic angiography were prospectively enrolled. Collateral development was graded with validated angiographic methods. The MS was defined according to the ATP-III definition. Fasting glucose, adiponectin, insulin concentrations, and PAI-1 were measured at the time of angiography. MS was associated with less developed collateral vessels (P = 0.005). In multivariable analysis adjusting for potential confounding factors including the duration of coronary occlusion (P = 0.0001), fasting glycaemia (P = 0.0007), low adiponectin concentration (P = 0.01), insulin-resistance (HOMA-IR; P = 0.01), high circulating PAI-1 concentration (P = 0.01), and hypertension (P = 0.008) were independently associated with poor coronary collateral vessel development.

Conclusion

This study shows that in patients with coronary occlusion, collateral circulation is impaired in patients with the MS. This association is partly related to fasting glycaemia and to key parameters linked to insulin resistance.

Genetic enhancement of stem cell engraftment, survival, and efficacy

Cell-based therapies for the prevention and treatment of cardiac dysfunction offer the potential to significantly modulate cardiac function and improve outcomes in patients with cardiovascular disease. To date several clinical studies have suggested the potential efficacy of several different stem cell types; however, the benefits seen in clinical trials have been inconsistent and modest. In parallel, preclinical studies have identified key events in the process of cell-based myocardial repair, including stem cell homing, engraftment, survival, paracrine factor release, and differentiation that need to be optimized to maximize cardiac repair and function. The inconsistent and modest benefits seen in clinical trials combined with the preclinical identification of mediators responsible for key events in cell-based cardiac repair offers the potential for cell-based therapy to advance to cell-based gene therapy in an attempt to optimize these key events in the hope of maximizing clinical benefit. Below we discuss potential key events in cardiac repair and the mediators of these events that could be of potential interest for genetic enhancement of stem cell-based cardiac repair.

Features of cardiomyocyte proliferation and its potential for cardiac regeneration

The human heart does not regenerate. Instead, following injury, human hearts scar. The loss of contractile tissue contributes significantly to morbidity and mortality. In contrast to humans, zebrafish and newts faithfully regenerate their hearts. Interestingly, regeneration is in both cases based on cardiomyocyte proliferation. In addition, mammalian cardiomyocytes proliferate during foetal development. Their proliferation reaches its maximum around chamber formation, stops shortly after birth, and subsequent heart growth is mostly achieved by an increase in cardiomyocyte size (hypertrophy). The underlying mechanisms that regulate cell cycle arrest and the switch from proliferation to hypertrophy are unclear. In this review, we highlight features of dividing cardiomyocytes, summarize the attempts to induce mammalian cardiomyocyte proliferation, critically discuss methods commonly used for its detection, and explore the potential and problems of inducing cardiomyocyte proliferation to improve function in diseased hearts.

DNAzymes and cardiovascular disease

Gene silencing techniques are gaining increasing popularity in the literature, both as a tool for unravelling gene function and to potentially deliver therapeutic benefit, especially in the context of cardiovascular disease. Gene-specific catalytic DNA molecules, or DNAzymes, have shown promise in ameliorating the effects of myocardial ischaemia reperfusion injury and in-stent restenosis in various animal models, demonstrating that these agents may be useful in a clinical setting. A review of the recent advances in the use of DNAzymes in treating cardiovascular disease is therefore essential given the increasing clinical burden of cardiovascular disease worldwide. We have thus sought to firstly provide background into the construct and mechanism of action of DNAzymes, with a discussion of recent improvements in design. Secondly, we have examined the effects of DNAzyme-mediated gene inhibition in in vitro studies of both endothelial and smooth muscle migration and proliferation, as well as in vivo models of acute myocardial infraction and neointima formation. Lastly we compare DNAzymes with other gene silencing tools and discuss issues involved in successfully delivering these drugs in a clinical setting.

Brothers in arms: DNA enzymes, short interfering RNA, and the emerging wave of small-molecule nucleic acid-based gene-silencing strategies

The past decade has seen the rapid evolution of small-molecule gene-silencing strategies, driven largely by enhanced understanding of gene function in the pathogenesis of disease. Over this time, many genes have been targeted by specifically engineered agents from different classes of nucleic acid-based drugs in experimental models of disease to probe, dissect, and characterize further the complex processes that underpin molecular signaling. Arising from this, a number of molecules have been examined in the setting of clinical trials, and several have recently made the successful transition from the bench to the clinic, heralding an exciting era of gene-specific treatments. This is particularly important because clear inadequacies in present therapies account for significant morbidity, mortality, and cost. The broad umbrella of gene-silencing therapeutics encompasses a range of agents that include DNA enzymes, short interfering RNA, antisense oligonucleotides, decoys, ribozymes, and aptamers. This review tracks current movements in these technologies, focusing mainly on DNA enzymes and short interfering RNA, because these are poised to play an integral role in antigene therapies in the future.

Biomarkers of obesity and subsequent cardiovascular events

Obesity is a major risk factor for cardiovascular diseases, but the mechanisms for increased cardiovascular risk in obesity are still unclear. Inflammation and increased oxidative stress are two potential mechanisms proposed to play a major role in the morbidity associated with obesity. Studies that investigate these mechanisms rely on biomarkers, but validated biomarkers for obesity-related cardiovascular outcomes are lacking. By finding optimal biomarkers, diagnostic criteria for cardiovascular diseases can be refined in the obese beyond "traditional" risk factors to identify early pathologic processes. The objective of this review is to identify potential early biomarkers resulting from obesity and associated with cardiovascular disease. Studies were initially identified through the search engine PubMed by using the keywords "obesity" and "biomarker." Subsequently, combinations of the keywords "obesity," "biomarker," "cardiovascular risk," "adipose tissue," "adipokine," "adipocytokine," and "oxidative stress" were used. The SOURCE database and Online Mendelian Inheritance in Man (OMIM) were used to obtain more information on the biomarkers. Results of the searches yielded a large number of potential biomarkers that occur in obesity and which either correlate with traditional cardiovascular risk factors or predict subsequent cardiovascular events. Several biomarkers are promising regarding their biologic properties, but they require further validation in humans.

Amelioration of hypertensive heart failure by amlodipine may occur via antioxidative effects

Although recent clinical studies have suggested that long-acting calcium channel blockers (CCBs) have beneficial effects on heart failure, the precise mechanism is unknown. In this study, Dahl salt-sensitive rats fed a high salt diet were treated with the long-acting CCB amlodipine, the low-molecular-weight membrane permeable superoxide dismutase mimetic 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (Tempol), or saline from 11 weeks after birth. The cardiac geometry and function, and gene expression profiles were determined at 17 weeks. Dahl salt-sensitive rats fed a high salt diet followed by saline as a non-treatment control (HS group) showed a marked increase in blood pressure and developed concentric hypertrophy at 11 weeks, followed by left ventricular (LV) dilation and congestive heart failure by 17 weeks. The treatment with amlodipine (AMLO group) or Tempol (TEMP group) significantly inhibited the development of LV hypertrophy and cardiac dysfunction. Analysis using an Affymetrix GeneChip U34 revealed that the expression levels of 195 genes were changed by the treatment with amlodipine. Among these 195 genes, 110 genes were increased in HS rats and decreased in AMLO rats. And of these 110 genes, 54 genes were also decreased in TEMP rats. In contrast, 85 genes were decreased in HS rats and increased in AMLO rats. Of these 85 genes, 38 genes were also increased in TEMP rats. Approximately 48% of the genes were changed in similar fashion in AMLO and TEMP rats, suggesting that amlodipine shows beneficial effects on heart failure mainly via antioxidative mechanisms.

Engraftment of engineered ES cell-derived cardiomyocytes but not BM cells restores contractile function to the infarcted myocardium

Cellular cardiomyoplasty is an attractive option for the treatment of severe heart failure. It is, however, still unclear and controversial which is the most promising cell source. Therefore, we investigated and examined the fate and functional impact of bone marrow (BM) cells and embryonic stem cell (ES cell)-derived cardiomyocytes after transplantation into the infarcted mouse heart. This proved particularly challenging for the ES cells, as their enrichment into cardiomyocytes and their long-term engraftment and tumorigenicity are still poorly understood. We generated transgenic ES cells expressing puromycin resistance and enhanced green fluorescent protein cassettes under control of a cardiac-specific promoter. Puromycin selection resulted in a highly purified (>99%) cardiomyocyte population, and the yield of cardiomyocytes increased 6-10-fold because of induction of proliferation on purification. Long-term engraftment (4-5 months) was observed when co-transplanting selected ES cell-derived cardiomyocytes and fibroblasts into the injured heart of syngeneic mice, and no teratoma formation was found (n = 60). Although transplantation of ES cell-derived cardiomyocytes improved heart function, BM cells had no positive effects. Furthermore, no contribution of BM cells to cardiac, endothelial, or smooth muscle neogenesis was detected. Hence, our results demonstrate that ES-based cell therapy is a promising approach for the treatment of impaired myocardial function and provides better results than BM-derived cells.

DNAzymes targeting the transcription factor Egr-1 reduce myocardial infarct size following ischemia-reperfusion in rats

BACKGROUND AND AIM

The transcription factor and immediate-early gene Egr-1 is widely viewed as a key upstream activator in a variety of settings within cardiovascular pathobiology. The role that Egr-1 plays in myocardial ischemia-reperfusion (IR) injury is unknown. We hypothesized that Egr-1 upregulation is of pathophysiologic importance in myocardial IR injury.

METHODS AND RESOURCES

First, abrogation of Egr-1 mRNA upregulation using Egr-1 targeting DNAzymes in a rat cardiomyocyte in vitro model was demonstrated. Egr-1 mRNA and protein upregulation following myocardial IR in rats were then selectively suppressed by locally delivered DNAzyme. Furthermore, myocardial neutrophil infiltration, intercellular adhesion molecule 1 mRNA and protein expression, and myocardial infarct size were all attenuated in DNAzyme-treated animals.

CONCLUSIONS

These data support the hypothesis that Egr-1 is a key contributor to myocardial IR injury, and that Egr-1 targeting strategies have therapeutic potential in this context.

In vitro selection, characterization, and application of deoxyribozymes that cleave RNA

Over the last decade, many catalytically active DNA molecules (deoxyribozymes; DNA enzymes) have been identified by in vitro selection from random-sequence DNA pools. This article focuses on deoxyribozymes that cleave RNA substrates. The first DNA enzyme was reported in 1994 and cleaves an RNA linkage. Since that time, many other RNA-cleaving deoxyribozymes have been identified. Most but not all of these deoxyribozymes require a divalent metal ion cofactor such as Mg²⁺ to catalyze attack by a specific RNA 2′-hydroxyl group on the adjacent phosphodiester linkage, forming a 2′,3′-cyclic phosphate and a 5′-hydroxyl group. Several deoxyribozymes that cleave RNA have utility for in vitro RNA biochemistry. Some DNA enzymes have been applied in vivo to degrade mRNAs, and others have been engineered into sensors. The practical impact of RNA-cleaving deoxyribozymes should continue to increase as additional applications are developed.

Downregulated Expression of Plasminogen Activator Inhibitor-1 Augments Myocardial Neovascularization and Reduces Cardiomyocyte Apoptosis After Acute Myocardial Infarction

OBJECTIVES

The aim of this study was to examine whether selective plasminogen activator inhibitor type 1 (PAI-1) downregulation in the acutely ischemic heart increases the myocardial microvasculature and improves cardiomyocyte (CM) survival.

BACKGROUND

Endogenous myocardial neovascularization is an important process enabling cardiac functional recovery after acute myocardial infarction. Expression of PAI-1, a potent inhibitor of angiogenesis, is induced in ischemic heart tissue.

METHODS

A sequence-specific catalytic deoxyribonucleic acid (DNA) enzyme was used to reduce PAI-1 levels in cultured endothelial cells and in ischemic myocardium. At the time of coronary artery ligation, rats were randomized into three groups, each receiving an intramyocardial injection (IMI) of a single dose at three different sites of the peri-infarct region consisting, respectively, of DNA enzyme E2 targeting rat PAI-1 (E2), scrambled control DNA enzyme (E0), or saline. Cardiomyocyte apoptosis, capillary density, and echocardiography were studied two weeks following infarction.

RESULTS

The E2 DNA enzyme, which efficiently inhibited rat PAI-1 expression in vitro, induced prolonged suppression (>2 weeks) of PAI-1 messenger ribonucleic acid and protein in rat heart tissues after a single IMI. At two weeks, hearts from experimental rats had over five-fold greater capillary density, 70% reduction in apoptotic CMs, and four-fold greater functional recovery compared with controls.

CONCLUSIONS

These results imply a causal relationship between elevated PAI-1 levels in ischemic hearts and adverse outcomes, and they suggest that strategies to reduce cardiac PAI-1 activity may augment neovascularization and improve functional recovery.