Apoptosis in the left ventricle of chronic volume overload causes endocardial endothelial dysfunction in rats

NAD in pathological cardiac remodeling: Metabolic regulation and beyond

Nicotinamide adenine dinucleotide (NAD) coenzymes are carriers of high energy electrons in metabolism and also play critical roles in numerous signaling pathways. NAD metabolism is decreased in various cardiovascular diseases. Importantly, stimulation of NAD biosynthesis protects against heart disease under different pathological conditions. In this review, we describe pathways for both generation and catabolism of NAD coenzymes and the respective changes of these pathways in the heart under cardiac diseases, including pressure overload, myocardial infarction, cardiometabolic disease, cancer treatment cardiotoxicity, and heart failure. We next provide an update on the strategies and treatments to increase NAD levels, such as supplementation of NAD precursors, in the heart that prevent or reverse cardiomyopathy. We also introduce the approaches to manipulate NAD consumption enzymes to ameliorate cardiac disease. Finally, we discuss the mechanisms associated with improvements in cardiac function by NAD coenzymes, differentiating between mitochondria-dependent effects and those independent of mitochondrial metabolism.

Renal Denervation Helps Preserve the Ejection Fraction by Preserving Endocardial-Endothelial Function during Heart Failure

Renal denervation (RDN) protects against hypertension, hypertrophy, and heart failure (HF); however, it is not clear whether RDN preserves ejection fraction (EF) during heart failure (HFpEF). To test this hypothesis, we simulated a chronic congestive cardiopulmonary heart failure (CHF) phenotype by creating an aorta-vena cava fistula (AVF) in the C57BL/6J wild type (WT) mice. Briefly, there are four ways to create an experimental CHF: (1) myocardial infarction (MI), which is basically ligating the coronary artery by instrumenting and injuring the heart; (2) trans-aortic constriction (TAC) method, which mimics the systematic hypertension, but again constricts the aorta on top of the heart and, in fact, exposes the heart; (3) acquired CHF condition, promoted by dietary factors, diabetes, salt, diet, etc., but is multifactorial in nature; and finally, (4) the AVF, which remains the only one wherein AVF is created ~1 cm below the kidneys in which the aorta and vena cava share the common middle-wall. By creating the AVF fistula, the red blood contents enter the vena cava without an injury to the cardiac tissue. This model mimics or simulates the CHF phenotype, for example, during aging wherein with advancing age, the preload volume keeps increasing beyond the level that the aging heart can pump out due to the weakened cardiac myocytes. Furthermore, this procedure also involves the right ventricle to lung to left ventricle flow, thus creating an ideal condition for congestion. The heart in AVF transitions from preserved to reduced EF (i.e., HFpEF to HFrEF). In fact, there are more models of volume overload, such as the pacing-induced and mitral valve regurgitation, but these are also injurious models in nature. Our laboratory is one of the first laboratories to create and study the AVF phenotype in the animals. The RDN was created by treating the cleaned bilateral renal artery. After 6 weeks, blood, heart, and renal samples were analyzed for exosome, cardiac regeneration markers, and the renal cortex proteinases. Cardiac function was analyzed by echocardiogram (ECHO) procedure. The fibrosis was analyzed with a trichrome staining method. The results suggested that there was a robust increase in the exosomes' level in AVF blood, suggesting a compensatory systemic response during AVF-CHF. During AVF, there was no change in the cardiac eNOS, Wnt1, or β-catenin; however, during RDN, there were robust increases in the levels of eNOS, Wnt1, and β-catenin compared to the sham group. As expected in HFpEF, there was perivascular fibrosis, hypertrophy, and pEF. Interestingly, increased levels of eNOS suggested that despite fibrosis, the NO generation was higher and that it most likely contributed to pEF during HF. The RDN intervention revealed an increase in renal cortical caspase 8 and a decrease in caspase 9. Since caspase 8 is protective and caspase 9 is apoptotic, we suggest that RDN protects against the renal stress and apoptosis. It should be noted that others have demonstrated a role of vascular endothelium in preserving the ejection by cell therapy intervention. In the light of foregoing evidence, our findings also suggest that RDN is cardioprotective during HFpEF via preservation of the eNOS and accompanied endocardial-endothelial function.

Nicotinamide Adenine Dinucleotide in the Development and Treatment of Cardiac Remodeling and Aging

Background:

Recently, the beneficial effects of nicotinamide adenine dinucleotide (NAD+) as an antiaging and antioxidant molecule have become a focus of research. However, the mechanisms by which NAD+ supplementation affects the associated metabolites under physiological conditions remain unclear. Specifically, although NAD+ is involved in several processes that are dysregulated in cardiovascular diseases, some effects of NAD+ precursors and NAD+ on cardiac diseases have started to gain recognition only recently.

Objective:

To discuss the influence of NAD+ supplementation on adverse cardiac remodeling and aging.

Results:

Supplementation with NAD+ precursors or nicotinamide riboside, which enhances or supplements the NAD+ metabolome, might have a protective effect on the heart. NAD+ can alleviate chronic heart failure via a mitochondrial oxidation–reduction (redox) state mechanism. Furthermore, NAD+ replenishment can improve the life span of mice.

Conclusion:

NAD+ exerts considerable antiaging and antioxidant effects with promising therapeutic effects. However, its effect in humans and use as a dietary supplement need to be studied further.

Mechanism of Blood-Heart-Barrier Leakage: Implications for COVID-19 Induced Cardiovascular Injury

Although blood–heart-barrier (BHB) leakage is the hallmark of congestive (cardio-pulmonary) heart failure (CHF), the primary cause of death in elderly, and during viral myocarditis resulting from the novel coronavirus variants such as the severe acute respiratory syndrome novel corona virus 2 (SARS-CoV-2) known as COVID-19, the mechanism is unclear. The goal of this project is to determine the mechanism of the BHB in CHF. Endocardial endothelium (EE) is the BHB against leakage of blood from endocardium to the interstitium; however, this BHB is broken during CHF. Previous studies from our laboratory, and others have shown a robust activation of matrix metalloproteinase-9 (MMP-9) during CHF. MMP-9 degrades the connexins leading to EE dysfunction. We demonstrated juxtacrine coupling of EE with myocyte and mitochondria (Mito) but how it works still remains at large. To test whether activation of MMP-9 causes EE barrier dysfunction, we hypothesized that if that were the case then treatment with hydroxychloroquine (HCQ) could, in fact, inhibit MMP-9, and thus preserve the EE barrier/juxtacrine signaling, and synchronous endothelial-myocyte coupling. To determine this, CHF was created by aorta-vena cava fistula (AVF) employing the mouse as a model system. The sham, and AVF mice were treated with HCQ. Cardiac hypertrophy, tissue remodeling-induced mitochondrial-myocyte, and endothelial-myocyte contractions were measured. Microvascular leakage was measured using FITC-albumin conjugate. The cardiac function was measured by echocardiography (Echo). Results suggest that MMP-9 activation, endocardial endothelial leakage, endothelial-myocyte (E-M) uncoupling, dyssynchronous mitochondrial fusion-fission (Mfn2/Drp1 ratio), and mito-myocyte uncoupling in the AVF heart failure were found to be rampant; however, treatment with HCQ successfully mitigated some of the deleterious cardiac alterations during CHF. The findings have direct relevance to the gamut of cardiac manifestations, and the resultant phenotypes arising from the ongoing complications of COVID-19 in human subjects.

Remote Hind-Limb Ischemia Mechanism of Preserved Ejection Fraction During Heart Failure

During acute heart failure (HF), remote ischemic conditioning (RIC) has proven to be beneficial; however, it is currently unclear whether it also extends benefits from chronic congestive, cardiopulmonary heart failure (CHF). Previous studies from our laboratory have shown three phases describing CHF viz. (1) HF with preserved ejection fraction (HFpEF), (2) HF with reduced EF (HFrEF), and (3) HF with reversed EF. Although reciprocal organ interaction, ablation of sympathetic, and calcium signaling genes are associated with HFpEF to HFrEF, the mechanism is unclear. The HFrEF ensues, in part, due to reduced angiogenesis, coronary reserve, and leakage of endocardial endothelial (EE) and finally breakdown of the blood-heart barrier (BHB) integrity. In fact, our hypothesis states that a change in phenotype from compensatory HFpEF to decompensatory HFrEF is determined by a potential decrease in regenerative, proangiogenic factors along with a concomitant increase in epigenetic memory, inflammation that combinedly causes oxidative, and proteolytic stress response. To test this hypothesis, we created CHF by aorta-vena-cava (AV) fistula in a group of mice that were subsequently treated with that of hind-limb RIC. HFpEF vs. HFrEF transition was determined by serial/longitudinal echo measurements. Results revealed an increase in skeletal muscle musclin contents, bone-marrow (CD71), and sympathetic activation (β2-AR) by RIC. We also observed a decrease in vascular density and attenuation of EE-BHB function due to a corresponding increase in the activity of MMP-2, vascular endothelial growth factor (VEGF), caspase, and calpain. This decrease was successfully mitigated by RIC-released skeletal muscle exosomes that contain musclin, the myokine along with bone marrow, and sympathetic activation. In short, based on proteome (omics) analysis, ∼20 proteins that appear to be involved in signaling pathways responsible for the synthesis, contraction, and relaxation of cardiac muscle were found to be the dominant features. Thus, our results support that the CHF phenotype causes dysfunction of cardiac metabolism, its contraction, and relaxation. Interestingly, RIC was able to mitigate many of the deleterious changes, as revealed by our multi-omics findings.

NAD+ Metabolism in Cardiac Health, Aging, and Disease

Nicotinamide adenine dinucleotide (NAD⁺) is a central metabolite involved in energy and redox homeostasis as well as in DNA repair and protein deacetylation reactions. Pharmacological or genetic inhibition of NAD⁺-degrading enzymes, external supplementation of NAD⁺ precursors, and transgenic overexpression of NAD⁺-generating enzymes have wide positive effects on metabolic health and age-associated diseases. NAD⁺ pools tend to decline with normal aging, obesity, and hypertension, which are all major risk factors for cardiovascular disease, and NAD⁺ replenishment extends healthspan, avoids metabolic syndrome, and reduces blood pressure in preclinical models. In addition, experimental elevation of NAD⁺ improves atherosclerosis, ischemic, diabetic, arrhythmogenic, hypertrophic, or dilated cardiomyopathies, as well as different modalities of heart failure. Here, we critically discuss cardiomyocyte-specific circuitries of NAD⁺ metabolism, comparatively evaluate distinct NAD⁺ precursors for their preclinical efficacy, and raise outstanding questions on the optimal design of clinical trials in which NAD⁺ replenishment or supraphysiological NAD⁺ elevations are assessed for the prevention or treatment of major cardiac diseases. We surmise that patients with hitherto intractable cardiac diseases such as heart failure with preserved ejection fraction may profit from the administration of NAD⁺ precursors. The development of such NAD⁺-centered treatments will rely on technological and conceptual progress on the fine regulation of NAD⁺ metabolism.

Multi-organ damage by covid-19: congestive (cardio-pulmonary) heart failure, and blood-heart barrier leakage

Corona virus disease-19 (covid-19) is caused by a coronavirus that is also known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and is generally characterized by fever, respiratory inflammation, and multi-organ failure in susceptible hosts. One of the first things during inflammation is the response by acute phase proteins coupled with coagulation. The angiotensinogen (a substrate for hypertension) is one such acute phase protein and goes on to explain an association of covid-19 with that of angiotensin-converting enzyme-2 (ACE2, a metallopeptidase). Therefore, it is advisable to administer, and test the efficacy of specific blocker(s) of angiotensinogen such as siRNAs or antibodies to covid-19 subjects. Covid-19 activates neutrophils, macrophages, but decreases T-helper cells activity. The metalloproteinases promote the activation of these inflammatory immune cells, therefore; we surmise that doxycycline (a metalloproteinase inhibitor, and a safer antibiotic) would benefit the covid-19 subjects. Along these lines, an anti-acid has also been suggested for mitigation of the covid-19 complications. Interestingly, there are three primary vegetables (celery, carrot, and long-squash) which are alkaline in their pH-range as compared to many others. Hence, treatment with fresh juice (without any preservative) from these vegies or the antioxidants derived from purple carrot and cabbage together with appropriate anti-coagulants may also help prevent or lessen the detrimental effects of the covid-19 pathological outcomes. These suggested remedies might be included in the list of putative interventions that are currently being investigated towards mitigating the multi-organ damage by Covid-19 during the ongoing pandemic.

NAD+ and cardiovascular diseases

Nicotinamide adenine dinucleotide (NAD) plays pivotal roles in controlling many biochemical processes. 'NAD' refers to the chemical backbone irrespective of charge, whereas 'NAD⁺' and 'NADH' refers to oxidized and reduced forms, respectively. NAD⁺/NADH ratio is essential for maintaining cellular reduction-oxidation (redox) homeostasis and for modulating energy metabolism. As a sensing or consuming enzyme of the poly (ADP-ribose) polymerase 1 (PARP1), the cyclic ADP-ribose (cADPR) synthases (CD38 and CD157), and sirtuin protein deacetylases (sirtuins, SIRTs), NAD⁺ participates in several key processes in cardiovascular disease. For example, NAD⁺ protects against metabolic syndrome, heart failure, ischemia-reperfusion (IR) injury, arrhythmia and hypertension. Accordingly, the subsequent loss of NAD⁺ in aging or during stress results in altered metabolic status and potentially increased disease susceptibility. Therefore, it is essential to maintain NAD⁺ or reduce loss in the heart. This review focuses on the involvement of NAD⁺ in the pathogenesis of cardiovascular disease and explores the effects of NAD⁺ boosting strategies in cardiovascular health.

Epigenetic memory: gene writer, eraser and homocysteine

Naturally chromatin remodeling is highly organized, consisting of histone acetylation (opening/relaxation of the compact chromatin structure), DNA methylation (inhibition of the gene expression activity) and sequence rearrangement by shifting. All this is essentially required for proper "in-printing and off-printing" of genes thus ensuring the epigenetic memory process. Any imbalance in ratios of DNA methyltransferase (DNMT, gene writer), fat-mass obesity-associated protein (FTO, gene eraser) and product (function) homocysteine (Hcy) could lead to numerous diseases. Interestingly, a similar process also happens in stem cells during embryogenesis and development. Despite gigantic unsuccessful efforts undertaken thus far toward the conversion of a stem cell into a functional cardiomyocyte, there has been hardly any study that shows successful conversion of a stem cell into a multinucleated cardiomyocyte. We have shown nuclear hypertrophy during heart failure, however; the mechanism(s) of epigenetic memory, regulation of genes during fertilization, embryogenesis, development and during adulthood remain far from understanding. In addition, there may be a connection of aging, loosing of the memory leading to death, and presumably to reincarnation. This review highlights some of these pertinent issues facing the discipline of biology as a whole today.

NAD+ Metabolism as an Emerging Therapeutic Target for Cardiovascular Diseases Associated With Sudden Cardiac Death

In addition to its central role in mediating oxidation reduction in fuel metabolism and bioenergetics, nicotinamide adenine dinucleotide (NAD+) has emerged as a vital co-substrate for a number of proteins involved in diverse cellular processes, including sirtuins, poly(ADP-ribose) polymerases and cyclic ADP-ribose synthetases. The connection with aging and age-associated diseases has led to a new wave of research in the cardiovascular field. Here, we review the basics of NAD+ homeostasis, the molecular physiology and new advances in ischemic-reperfusion injury, heart failure, and arrhythmias, all of which are associated with increased risks for sudden cardiac death. Finally, we summarize the progress of NAD+-boosting therapy in human cardiovascular diseases and the challenges for future studies.

Both gain and loss of Nampt function promote pressure overload-induced heart failure

The heart requires high-energy production, but metabolic ability declines in the failing heart. Nicotinamide phosphoribosyl-transferase (Nampt) is a rate-limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide (NAD) synthesis. NAD is directly involved in various metabolic processes and may indirectly regulate metabolic gene expression through sirtuin 1 (Sirt1), an NAD-dependent protein deacetylase. However, how Nampt regulates cardiac function and metabolism in the failing heart is poorly understood. Here we show that pressure-overload (PO)-induced heart failure is exacerbated in both systemic Nampt heterozygous knockout (Nampt+/-) mice and mice with cardiac-specific Nampt overexpression (Tg-Nampt). The NAD level declined in Nampt+/- mice under PO (wild: 377 pmol/mg tissue; Nampt+/-: 119 pmol/mg tissue; P = 0.028). In cultured cardiomyocytes, Nampt knockdown diminished mitochondrial NAD content and ATP production (relative ATP production: wild: 1; Nampt knockdown: 0.56; P = 0.0068), suggesting that downregulation of Nampt induces mitochondrial dysfunction. On the other hand, the NAD level was increased in Tg-Nampt mice at baseline but not during PO, possibly due to increased consumption of NAD by Sirt1. The expression of Sirt1 was increased in Tg-Nampt mice, in association with reduced overall protein acetylation. PO-induced downregulation of metabolic genes was exacerbated in Tg-Nampt mice. In cultured cardiomyocytes, Nampt and Sirt1 cooperatively suppressed mitochondrial proteins and ATP production, thereby promoting mitochondrial dysfunction. In addition, Nampt overexpression upregulated inflammatory cytokines, including TNF-α and monocyte chemoattractant protein-1. Thus endogenous Nampt maintains cardiac function and metabolism in the failing heart, whereas Nampt overexpression is detrimental during PO, possibly due to excessive activation of Sirt1, suppression of mitochondrial function, and upregulation of proinflammatory mechanisms.NEW & NOTEWORTHY Nicotinamide phosphoribosyl-transferase (Nampt) is a rate-limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide synthesis. We demonstrate that pressure overload-induced heart failure is exacerbated in both systemic Nampt heterozygous knockout mice and mice with cardiac-specific Nampt overexpression. Both loss- and gain-of-function models exhibited reduced protein acetylation, suppression of metabolic genes, and mitochondrial energetic dysfunction. Thus endogenous Nampt maintains cardiac function and metabolism in the failing heart, but cardiac-specific Nampt overexpression is detrimental rather than therapeutic.

TFAM overexpression reduces pathological cardiac remodeling

Heart failure (HF) is a functional lack of myocardial performance due to a loss of molecular control over increases in calcium and ROS, resulting in proteolytic degradative advances and cardiac remodeling. Mitochondria are the molecular powerhouse of cells, shifting the sphere of cardiomyocyte stability and performance. Functional mitochondria rely on the molecular abilities of safety factors such as TFAM to maintain physiological parameters. Mitochondrial transcription factor A (TFAM) creates a mitochondrial nucleoid structure around mtDNA, protecting it from mutation, inhibiting NFAT (ROS activator/hypertrophic stimulator), and transcriptionally activates Serca2a to decrease calcium mishandling. Calpain1 and MMP9 are proteolytic degratory factors that play a major role in cardiomyocyte decline in HF. Current literature depicts major decreases in TFAM as HF progresses. We aim to assess TFAM function against Calpain1 and MMP9 proteolytic activity and its role in cardiac remodeling. To this date, no publication has surfaced describing the effects of aortic banding (AB) as a surgical HF model in TFAM-TG mice. HF models were created via AB in TFAM transgenic (TFAM-TG) and C57BLJ-6 (WT) mice. Eight weeks post AB, functional analysis revealed a successful banding procedure, resulting in cardiac hypertrophy as observed via echocardiography. Pulse wave and color doppler show increased aortic flow rates as well as turbulent flow at the banding site. Preliminary results of cardiac tissue immuno-histochemistry of HF-control mice show decreased TFAM and compensatory increases in Serca2a fluorescent expression, along with increased Calpain1 and MMP9 expression. Protein, RNA, and IHC analysis will further assess TFAM-TG results post-banding. Echocardiography shows more cardiac stability and functionality in HF-induced TFAM-TG mice than the control counterpart. These findings complement our published in vitro results. Overall, this suggests that TFAM has molecular therapeutic potential to reduce protease expression.

Emerging potential benefits of modulating NAD+ metabolism in cardiovascular disease

Nicotinamide adenine dinucleotide (NAD⁺) and related metabolites are central mediators of fuel oxidation and bioenergetics within cardiomyocytes. Additionally, NAD⁺ is required for the activity of multifunctional enzymes, including sirtuins and poly(ADP-ribose) polymerases that regulate posttranslational modifications, DNA damage responses, and Ca²⁺ signaling. Recent research has indicated that NAD⁺ participates in a multitude of processes dysregulated in cardiovascular diseases. Therefore, supplementation of NAD⁺ precursors, including nicotinamide riboside that boosts or repletes the NAD⁺ metabolome, may be cardioprotective. This review examines the molecular physiology and preclinical data with respect to NAD⁺ precursors in heart failure-related cardiac remodeling, ischemic-reperfusion injury, and arrhythmias. In addition, alternative NAD⁺-boosting strategies and potential systemic effects of NAD⁺ supplementation with implications on cardiovascular health and disease are surveyed.

NAD+ : A big player in cardiac and skeletal muscle remodeling and aging

In the past decade, NAD+ has gained importance for its beneficial effects as antioxidant and anti-aging molecule. A paper in science by Zhang et al. () has described that NAD+ when replenished, ameliorates muscle dystrophy in mice by improving mitochondrial function. NAD+ was also demonstrated by the authors to improve the life span of mice. Cox et al. () demonstrated the cardiac effects of NAD+ which mitigated chronic heart failure via mitochondrial redox state mechanism. Cox et al. () also demonstrated that NAD+ is provided in the drinking water, it improves cardiac relaxation in volume overload model of heart failure. Although NAD+ has a profound anti-aging and anti-oxidant effects, its effect on humans and use as a dietary supplement needs more exploration.

Epigenetic silencing of TIMP4 in heart failure

Tissue inhibitor of matrix metalloprotease 4 (TIMP4) is endogenously one of the key modulators of matrix metalloprotease 9 (MMP9) and we have reported earlier that cardiac specific TIMP4 instigates contractility and helps in differentiation of cardiac progenitor cells. Although studies show that the expression of TIMP4 goes down in heart failure but the mechanism is unknown. This study aims to determine the mechanism of silencing of TIMP4 in heart failure progression created by aorta-vena cava (AV) fistula. We hypothesize that there is epigenetic silencing of TIMP4 in heart failure. To validate this hypothesis, we created heart failure model by creating AV fistula in C57BL/6 mice and looked into the promoter methylation (methylation specific PCR, high resolution melting, methylation sensitive restriction enzyme and Na bisulphite treatment followed by sequencing), histone modification (ChIP assay) and microRNAs that regulate TIMP4 (mir122a) and MMP9 (mir29b and mir455-5p). The physiological parameters in terms of cardiac function after AV fistula were assessed by echocardiography. We observed that there are 7 CpG islands in the TIMP4 promoter which get methylated during the progression of heart failure which leads to its epigenetic silencing. In addition, the up-regulated levels of mir122a in part, contribute to regulation of TIMP4. Consequently, MMP9 gets up-regulated and leads to cardiac remodeling. This is a novel report to explain the epigenetic silencing of TIMP4 in heart failure.

A metabolomic study of rats with doxorubicin-induced cardiomyopathy and Shengmai injection treatment

Doxorubicin-induced cardiomyopathy (DOX-CM) is a severe complication of doxorubicin (DOX) chemotherapy. Characterized by cumulative and irreversible myocardial damage, its pathogenesis has not been fully elucidated. Shengmai Injection (SMI), a Traditional Chinese Medicine, may alleviate myocardial injury and improve heart function in the setting of DOX-CM. As a result of its multi-component and multi-target nature and comprehensive regulation, the pharmacological mechanisms underlying SMI’s effects remain obscure. The emerging field of metabolomics provides a potential approach with which to explore the pathogenesis of DOX-CM and the benefits of SMI treatment. DOX-CM was induced in rats via intraperitoneal injections of DOX. Cardiac metabolic profiling was performed via gas chromatography/mass spectrometry and ultra-performance liquid chromatography/tandem mass spectrometry. A bioinformatics analysis was conducted via Ingenuity Pathway Analysis (IPA). Eight weeks following DOX treatment, significant cardiac remodeling, dysfunction and metabolic perturbations were observed in the rats with DOX-CM. The metabolic disturbances primarily involved lipids, amino acids, vitamins and energy metabolism, and may have been indicative of both an energy metabolism disorder and oxidative stress secondary to DOX chemotherapy. However, SMI improved cardiac structure and function, as well as the metabolism of the rats with DOX-CM. The metabolic alterations induced via SMI, including the promotion of glycogenolysis, glycolysis, amino acid utilization and antioxidation, suggested that SMI exerts cardioprotective effects by improving energy metabolism and attenuating oxidative stress. Moreover, the IPA revealed that important signaling molecules and enzymes interacted with the altered metabolites. These findings have provided us with new insights into the pathogenesis of DOX-CM and the effects of SMI, and suggest that the combination of metabolomic analysis and IPA may represent a promising tool with which to explore and better understand both heart disease and TCM therapy.

Etiology-specific assessment of predictors of long-term survival in chronic systolic heart failure

BACKGROUND

We sought to identify prognostic factors of long-term mortality, specific for the underlying etiology of chronic systolic heart failure (CHF).

METHODS AND RESULTS

Between 1995 and 2009 baseline characteristics, treatment and follow-up data from 2318 CHF-patients due to ischemic (ICM; 1100 patients) or dilated cardiomyopathy (DCM; 1218 patients) were prospectively compared. To calculate hazard ratios with 95%-confidence intervals cox regression was used. We respectively established etiology-specific multivariable models of independent prognostic factors. During the follow-up period of up to 14.8 years (mean = 53.1 ± 43.5 months; 10,264 patient-years) 991 deaths (42.8%) occurred. In the ICM-cohort, 5-year-survival was 53.4% (95% CI: 49.9-56.7%), whereas in DCM-patients it was higher (68.1% (95% CI: 65.1-71.0%)). Age, ejection fraction, or hyponatremia were independent predictors for mortality in both cohorts, whereas diabetes, COPD, atrial fibrillation and a heart rate of ≥ 80/min carried independent predictive power only in ICM-patients.

CONCLUSION

This study demonstrates the disparity of prognostic value of clinically derived risk factors between the two main causes of CHF. The effects of covariables in DCM-patients were lower, suggesting a less modifiable disease through risk factors considering mortality risk. An etiology-specific prognostic model may improve accuracy of survival estimations in CHF.

Acute aortocaval fistula: role of low perfusion pressure and subendocardial remodeling on left ventricular function

The experimental model of aortocaval fistula is a useful model of cardiac hypertrophy in response to volume overload. In the present study it has been used to investigate the pathologic subendocardial remodeling associated with the development of heart failure during the early phases (day 1, 3, and 7) following volume overload. Compared with sham treated rats, aortocaval fistula rats showed lower systemic blood pressure and higher left ventricular end-diastolic pressure This resulted in lower coronary driving pressure and left ventricular systolic and diastolic dysfunction. Signs of myocyte necrosis, leukocyte cell infiltration, fibroplasia and collagen deposition appeared sequentially in the subendocardium where remodeling was more prominent than in the non-subendocardium. Accordingly, increased levels of TNF-alpha, IL-1 beta, and IL-6, and enhanced MMP-2 activity were all found in the subendocardium of rats with coronary driving pressure ≤ 60 mmHg. The coronary driving pressure was inversely correlated with MMP-2 activity in subendocardium in all time-points studied, and blood flow in this region showed positive correlation with systolic and diastolic function at day 7. Thus the predominant subendocardial remodeling that occurs in response to low myocardial perfusion pressure during the acute phases of aortocaval fistula contributes to early left ventricular dysfunction.

Physiologic and molecular characterization of a murine model of right ventricular volume overload

Pulmonary insufficiency (PI) is a common long-term sequel after repair of tetralogy of Fallot, causing progressive right ventricular (RV) dilation and failure. We describe the physiologic and molecular characteristics of the first murine model of RV volume overload. PI was created by entrapping the pulmonary valve leaflets with sutures. Imaging, catheterization, and exercise testing were performed at 1, 3, and 6 mo and compared with sham controls. RNA from the RV free wall was hybridized to Agilent whole genome oligonucleotide microarrays. Volume overload resulted in RV enlargement, decreased RV outflow tract shortening fraction at 1 mo followed by normalization at 3 and 6 mo (39 ± 2, 44 ± 2, and 41 ± 2 vs. 46 ± 3% in sham), early reversal of early and late diastolic filling velocities (E/A ratio) followed by pseudonormalization (0.87 ± 0.08, 0.82 ± 0.08, and 0.96 ± 0.08 vs. 1.04 ± 0.03; P < 0.05), elevated end-diastolic pressure (7.6 ± 0.7, 6.9 ± 0.8, and 7 ± 0.5 vs. 2.7 ± 0.2 mmHg; P < 0.05), and decreased exercise duration (26 ± 0.4, 26 ± 1, and 22 ± 1.3 vs. 30 ± 1.1 min; P < 0.05). Subendocardial RV fibrosis was evident by 1 mo. At 1 mo, 372 genes were significantly downregulated. Mitochondrial pathways and G protein-coupled receptor signaling were the most represented categories. At 3 mo, 434 genes were upregulated and 307 downregulated. While many of the same pathways continued to be downregulated, TNF-α, transforming growth factor-β(1) (TGF-β(1)), p53-signaling, and extracellular matrix (ECM) remodeling transitioned from down- to upregulated. We describe a novel murine model of chronic RV volume overload recapitulating aspects of the clinical disease with gene expression changes suggesting early mitochondrial bioenergetic dysfunction, enhanced TGF-β signaling, ECM remodeling, and apoptosis.

An elderly patient with severe aortic stenosis and myocardial infarction with a huge mobile thrombus as complication in the left ventricle

An 86-year-old woman was admitted for emergency treatment of increasing dyspnea. Transthoracic echocardiography revealed decreased left ventricular systolic function with dyskinesis at the apex, and severe aortic stenosis. The apex of the left ventricle showed a huge mobile thrombus. Coronary angiography revealed total occlusion at the middle portion of the left anterior descending coronary artery. Emergency operation was successful, and a partially calcified thrombus was observed at the site of the old myocardial infarction area. In this case, myocardial infarction and elevated intraventricular pressure due to aortic stenosis likely contributed to the wall motion abnormality and thrombus formation.

Changes in plasma profiles of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs in stress-induced cardiomyopathy

BACKGROUND

Transient changes in the composition of the myocardial extracellular matrix may contribute to the ventricular systolic dysfunction in stress-induced cardiomyopathy (SIC). We examined the changes in plasma matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) that occur early after the clinical presentation of SIC.

METHODS AND RESULTS

Ten patients with SIC were enrolled. Plasma concentrations of the 6 major MMPs (1, 2, 3, 7, 8, and 9) and all 4 TIMPs (1, 2, 3, and 4) were analyzed and compared with data from 15 control subjects. Within 24 hours of the clinical presentation, SIC patients had lower MMP-1 levels (0.41 ± 0.13 vs 0.70 ± 0.13 pg/mL; P = .048) and MMP-8 levels (1.61 ± 0.34 vs 4.84 ± 1.38 pg/mL; P = .001) and higher TIMP-4 levels (3.06 ± 0.40 vs 2.16 ± 0.18 pg/mL; P = .05) compared with control. Seven of 9 SIC patients had elevated LV end-diastolic pressures, and all had normal LV end-diastolic dimensions and volumes.

CONCLUSIONS

Patients afflicted with SIC had MMP and TIMP profiles similar to those described in hypertensive heart disease and diastolic heart failure and different from the profiles following myocardial infarction. Our findings uncovered a unique biomolecular profile in SIC during the first 24 hours of presentation.

Matrix metalloproteinase-2 in the development of diabetic retinopathy and mitochondrial dysfunction

In the pathogenesis of diabetic retinopathy, retinal mitochondria become dysfunctional resulting in accelerated apoptosis of its capillary cells. Matrix metalloproteinase-2 (MMP2) is considered critical in cell integrity and cell survival, and diabetes activates MMP2 in the retina and its capillary cells. This study aims at elucidating the mechanism by which MMP2 contributes to the development of diabetic retinopathy. Using isolated bovine retinal endothelial cells, the effect of regulation of MMP2 (by its siRNA and pharmacological inhibitor) on superoxide accumulation and mitochondrial dysfunction was evaluated. The effect of inhibiting diabetes-induced retinal superoxide accumulation on MMP2 and its regulators was investigated in diabetic mice overexpressing mitochondrial superoxide dismutase (MnSOD). Inhibition of MMP2 ameliorated glucose-induced increase in mitochondrial superoxide and membrane permeability, prevented cytochrome c leakage from the mitochondria, and inhibited capillary cell apoptosis. Overexpression of MnSOD protected the retina from diabetes-induced increase in MMP2 and its membrane activator (MT1-MMP), and decrease in its tissue inhibitor (TIMP-2). These results implicate that, in diabetes, MMP2 activates apoptosis of retinal capillary cells by mitochondrial dysfunction increasing their membrane permeability. Understanding the role of MMP2 in the pathogenesis of diabetic retinopathy should help lay ground for MMP2-targeted therapy to retard the development of retinopathy in diabetic patients.

Defects in ryanodine receptor function are associated with systolic dysfunction in rats subjected to volume overload

Cardiac hypertrophy is the compensatory enlargement of the heart aimed at reducing stress induced by either pressure overload or volume overload (VO); however, sustained hypertrophy leads to cardiac dysfunction. We hypothesize that cardiac dysfunction which develops due to VO will be associated with abnormalities in sarcoplasmic reticulum (SR) function. Volume overload was induced in rats by aortocaval shunt surgery ('VO rats'). Echocardiographic measurements were used to compare cardiac structure and function in control and VO rats. The SR was isolated from left ventricular tissue. Sarcoplasmic reticulum Ca(2+) uptake and SR Ca(2+) release were examined by the filtration method. The expression levels of SR proteins were assessed by Western immunoblotting. Rats subjected to VO developed eccentric hypertrophy. Diastolic function in VO rats was improved at all time points and was associated with elevated SR Ca(2+) uptake at 16 and 28 weeks. Sarcoendoplasmic reticulum ATPase 2a protein level was increased at 16 weeks but normalized at 28 weeks; Amounts of phospholamban protein were unaltered, but Serine16 phospholamban and Threonine17 phospholamban were reduced at 28 weeks. Systolic function was impaired in the VO rats at 16 and 28 weeks and was associated with reduced Ca(2+) release at the 28 week time point. The ryanodine receptor 2 (RyR2) protein level was reduced at 28 weeks; RyR2 phosphorylation status and the amount of FK-binding protein 12.6 were increased at 28 weeks. On the basis of the results, we conclude that the progression of hypertrophy due to VO in rats is accompanied by the impairment of systolic function, which in turn is associated with defects in RyR2 expression and function.

H2S ameliorates oxidative and proteolytic stresses and protects the heart against adverse remodeling in chronic heart failure

Reactive oxygen and nitrogen species (ROS and RNS, respectively) generate nitrotyrosine and activate latent resident myocardial matrix metalloproteinases (MMPs). Although in chronic heart failure (CHF) there is robust increase in ROS, RNS, and MMP activation, recent data suggest that hydrogen sulfide (H(2)S, a strong antioxidant gas) is cardioprotective. However, the role of H(2)S in mitigating oxidative and proteolytic stresses in cardiac remodeling/apoptosis in CHF was unclear. To test the hypothesis that H(2)S ameliorated cardiac apoptosis and fibrosis by decreasing oxidative and proteolytic stresses, arteriovenous fistula (AVF) was created in wild-type (C57BL/6J) mice. The hearts were analyzed at 0, 2, and 6 wk after AVF. To reverse the remodeling, AVF mice were treated with NaHS (an H(2)S donor, 30 micromol/l in drinking water) at 8 and 10 wk. The levels of MMPs were measured by gelatin-gel zymography. The levels of nitrotyrosine, tissue inhibitors of metalloproteinase (TIMPs), beta(1)-integrin, and a disintegrin and metalloproteinase-12 (ADAM-12) were analyzed by Western blots. The levels of pericapillary and interstitial fibrosis were identified by Masson trichrome stains. The levels of apoptosis were measured by identifying the TdT-mediated dUTP nick end labeling (TUNEL)-positive cells and caspase-3 levels. The results suggested robust nitrotyrosine and MMP activation at 2 and 6 wk of AVF. The treatment with H(2)S donor mitigated nitrotyrosine generation and MMP activation (i.e., oxidative and proteolytic stresses). The levels of TIMP-1 and TIMP-3 were increased and TIMP-4 decreased in AVF hearts. The treatment with H(2)S donor reversed this change in TIMPs levels. The levels of ADAM-12, apoptosis, and fibrosis were robust and integrin were decreased in AVF hearts. The treatment with H(2)S donor attenuated the fibrosis, apoptosis, and decrease in integrin.

The vitamin nicotinamide: translating nutrition into clinical care

Nicotinamide, the amide form of vitamin B(3) (niacin), is changed to its mononucleotide compound with the enzyme nicotinic acide/nicotinamide adenylyltransferase, and participates in the cellular energy metabolism that directly impacts normal physiology. However, nicotinamide also influences oxidative stress and modulates multiple pathways tied to both cellular survival and death. During disorders that include immune system dysfunction, diabetes, and aging-related diseases, nicotinamide is a robust cytoprotectant that blocks cellular inflammatory cell activation, early apoptotic phosphatidylserine exposure, and late nuclear DNA degradation. Nicotinamide relies upon unique cellular pathways that involve forkhead transcription factors, sirtuins, protein kinase B (Akt), Bad, caspases, and poly (ADP-ribose) polymerase that may offer a fine line with determining cellular longevity, cell survival, and unwanted cancer progression. If one is cognizant of the these considerations, it becomes evident that nicotinamide holds great potential for multiple disease entities, but the development of new therapeutic strategies rests heavily upon the elucidation of the novel cellular pathways that nicotinamide closely governs.

Oxidative stress and the development of diabetic retinopathy: contributory role of matrix metalloproteinase-2

Matrix metalloproteinases (MMPs) degrade extracellular matrix and regulate many functions including cell signaling. Oxidative stress is implicated in the development of diabetic retinopathy, and MMP-2, the most ubiquitous member of the MMP family, is sensitive to oxidative stress. This study aimed to determine the regulation of MMP-2 by oxidative stress in the development of diabetic retinopathy and the role of MMP-2 in the apoptosis of retinal capillary cells. The effects of mitochondrial superoxide scavenger on glucose-induced alterations in MMP-2, and its proenzyme activator MT1-MMP and physiological inhibitor TIMP-2, were determined in retinal endothelial cells, and the regulation of their glucose-induced accelerated apoptosis by the inhibitors of MMP-2 was accessed. To confirm in vitro results, the effects of antioxidant supplementation on MMP-2, MT1-MMP, and TIMP-2 were investigated in the retina of streptozotocin-induced diabetic rats. Glucose-induced activation of retinal capillary cell MMP-2 and MT1-MMP and decrease in TIMP-2 were inhibited by superoxide scavengers, and their accelerated apoptosis was prevented by the inhibitors of MMP-2. Antioxidant therapies, which have been shown to inhibit oxidative stress, capillary cell apoptosis, and retinopathy in diabetic rats, ameliorated alterations in retinal MMP-2 and its regulators. Thus, MMP-2 has a proapoptotic role in the loss of retinal capillary cells in diabetes, and the activation of MMP-2 is under the control of superoxide. This suggests a possible use of MMP-2-targeted therapy to inhibit the development of diabetic retinopathy.

Nitrotyrosinylation, remodeling and endothelial-myocyte uncoupling in iNOS, cystathionine beta synthase (CBS) knockouts and iNOS/CBS double knockout mice

Increased levels of homocysteine (Hcy), recognized as hyperhomocysteinemia (HHcy), were associated with cardiovascular diseases. There was controversy regarding the detrimental versus cardio protective role of inducible nitric oxide synthase (iNOS) in ischemic heart disease. The aim of this study was to test the hypothesis that the Hcy generated nitrotyrosine by inducing the endothelial nitric oxide synthase, causing endothelial-myocyte (E-M) coupling. To differentiate the role of iNOS versus constitutive nitric oxide synthase (eNOS and nNOS) in Hcy-mediated nitrotyrosine generation and matrix remodeling in cardiac dysfunction, left ventricular (LV) tissue was analyzed from cystathionine beta synthase (CBS) heterozygote knockout, iNOS homozygote knockout, CBS-/+/iNOS-/- double knockout, and wild-type (WT) mice. The levels of nitrotyrosine, MMP-2 and -9 (zymographic analysis), and fibrosis (by trichrome stain) were measured. The endothelial-myocyte function was determined in cardiac rings. In CBS-/+ mice, homocysteine was elevated and in iNOS-/- mice, nitric oxide was significantly reduced. The nitrotyrosine and matrix metalloproteinase-9 (MMP-9) levels were elevated in double knockout and CBS-/+ as compared to WT mice. Although MMP-2 levels were similar in CBS-/+, iNOS-/-, and CBS-/+/iNOS-/-, the levels were three- to fourfold higher than WT. The levels of collagen were similar in CBS-/+ and iNOS-/-, but they were threefold higher than WT. Interesting, the levels of collagen increased sixfold in double knockouts, compared to WT, suggesting synergism between high Hcy and lack of iNOS. Left ventricular hypertrophy was exaggerated in the iNOS-/- and double knockout, and mildly increased in the CBS-/+, compared to WT mice. The endothelial-dependent relaxation was attenuated to the same extent in the CBS-/+ and iNOS-/-, compared to WT, but it was robustly blunted in double knockouts. The results concluded that homocysteine generated nitrotyrosine in the vicinity of endothelium, caused MMP activation and endothelium-myocyte uncoupling. The generation of nitrotyrosine was independent of iNOS.

Triple play: promoting neurovascular longevity with nicotinamide, WNT, and erythropoietin in diabetes mellitus

Oxidative stress is a principal pathway for the dysfunction and ultimate destruction of cells in the neuronal and vascular systems for several disease entities, not promoting the ravages of oxidative stress to any less of a degree than diabetes mellitus. Diabetes mellitus is increasing in incidence as a result of changes in human behavior that relate to diet and daily exercise and is predicted to affect almost 400 million individuals worldwide in another two decades. Furthermore, both type 1 and type 2 diabetes mellitus can lead to significant disability in the nervous and cardiovascular systems, such as cognitive loss and cardiac insufficiency. As a result, innovative strategies that directly target oxidative stress to preserve neuronal and vascular longevity could offer viable therapeutic options to diabetic patients in addition to more conventional treatments that are designed to control serum glucose levels. Here we discuss the novel application of nicotinamide, Wnt signaling, and erythropoietin that modulate cellular oxidative stress and offer significant promise for the prevention of diabetic complications in the nervous and vascular systems. Essential to this process is the precise focus upon diverse as well as common cellular pathways governed by nicotinamide, Wnt signaling, and erythropoietin to outline not only the potential benefits, but also the challenges and possible detriments of these therapies. In this way, new avenues of investigation can hopefully bypass toxic complications, or at the very least, avoid contraindications that may limit care and offer both safe and robust clinical treatment for patients.

Arrhythmia and neuronal/endothelial myocyte uncoupling in hyperhomocysteinemia

Elevated levels of homocysteine (Hcy) known as hyperhomocysteinemia (HHcy) are associated with arrhythmogenesis and sudden cardiac death (SCD). Hcy decreases constitutive neuronal and endothelial nitric oxide (NO), and cardiac diastolic relaxation. Hcy increases the iNOS/NO, peroxynitrite, mitochondrial NADPH oxidase, and suppresses superoxide dismutase (SOD) and redoxins. Hcy activates matrix metalloproteinase (MMP), disrupts connexin-43 and increases collagen/elastin ratio. The disruption of connexin-43 and accumulation of collagen (fibrosis) disrupt the normal pattern of cardiac conduction and attenuate NO transport from endothelium to myocyte (E-M) causing E-M uncoupling, leading to a pro-arrhythmic environment. The goal of this review is to elaborate the mechanism of Hcy-mediated iNOS/NO in E-M uncoupling and SCD. It is known that Hcy creates arrhythmogenic substrates (i.e. increase in collagen/elastin ratio and disruption in connexin-43) and exacerbates heart failure during chronic volume overload. Also, Hcy behaves as an agonist to N-methyl-D-aspartate (NMDA, an excitatory neurotransmitter) receptor-1, and blockade of NMDA-R1 reduces the increase in heart rate-evoked by NMDA-analog and reduces SCD. This review suggest that Hcy increases iNOS/NO, superoxide, metalloproteinase activity, and disrupts connexin-43, exacerbates endothelial-myocyte uncoupling and cardiac failure secondary to inducing NMDA-R1.

Pioglitazone prevents cardiac remodeling in high-fat, high-calorie-induced Type 2 diabetes mellitus

The agonists of peroxisome proliferator-activated receptor-γ (PPARγ) ameliorate cardiovascular complications associated with diabetes mellitus. We tested the hypothesis that recovery from ailing to failing myocardium in diabetes by PPARγ agonist is in part due to decreased matrix metalloproteinase-9 (MMP-9) activation and left ventricular (LV) tissue levels of homocysteine (Hcy). C57BL/6J mice were made diabetic (D) by feeding them a high-fat calorie diet. PPARγ was activated by adding pioglitazone (Pi) to the diet. After 6 wk, mice were grouped into: normal calorie diet (N), D, N + Pi and D + Pi ( n = 6 in each group). LV variables were measured by echocardiography, endothelial-myocyte (E-M) coupling was measured in cardiac rings, and MMP-9 activation was measured by zymography. Blood glucose levels were twofold higher in D mice compared with N mice. Pi decreased the levels of glucose in D mice to the levels in N mice. LV Hcy levels were 3.5 ± 0.5 μM in N groups compared with 12.4 ± 0.6 μM in D groups. Treatment with Pi normalized the LV levels of Hcy but had no effect on plasma levels of Hcy. In the D group, LV contraction was reduced compared with that of the N group and was ameliorated by treatment with Pi. LV wall thickness was reduced to 0.25 ± 0.02 mm in the D group compared with 0.42 ± 0.01 mm in the N group. LV diastolic diameter was 3.05 ± 0.01 mm in the D group compared with 2.20 ± 0.02 mm in the N group. LV systolic diameter was 1.19 ± 0.02 mm in the D group and 0.59 ± 0.01 mm in the N group. Pi normalized the LV variables in D mice. The responses to ACh and nitroprusside were attenuated in diabetic hearts, suggesting that there was E-M uncoupling in the D group compared with the N group, which was ameliorated by Pi. Plasma and LV levels of MMP-2 and -9 activities were higher in the D group than in the N group but normalized after Pi treatment. These results suggest that E-M uncoupling in the myocardium, in part, is due to increased MMP activities secondary to suppressing PPARγ activity in high-fat, calorie-induced Type 2 diabetes mellitus.

The effect of intermittent administration of sustained release isosorbide dinitrate (sr-ISDN) in rats with volume overload heart

Recently, it has been reported that intermittent administration of nitrate, with a nitrate-free interval of 10 to 12 hr eliminated expression of tolerance, and maintained its hypotensive effect. In the present study, we evaluated whether nitrate tolerance developed or not with an intermittent administration of sr-ISDN (5 mg/kg/ once a day) in Wistar rats. The effect of this administration protocol for sr-ISDN on the volume overload heart model, aortovenous fistula, was also examined. Furthermore, blood pressure was monitored by radio telemetry during sr-ISDN (5 mg/kg/once a day) administration. Nitrate tolerance did not develop, and eccentric hypertrophy due to volume overload was moderated by sr-ISDN administration. Sr-ISDN administration maintained blood pressure lower level than the placebo group. In conclusion, prolonged intermittent administration of sr-ISDN maintained its hypotensive effect during the entire experiment period, without developing tolerance, and moderated efferent hypertrophy with attenuated volume overload.

Comparison of Gene Expression Profiling in Pressure and Volume Overload-Induced Myocardial Hypertrophies in Rats

Gene expression profiling has been conducted in rat hearts subjected to pressure overload (PO). However, pressure and volume overload produce morphologically and functionally distinct forms of cardiac hypertrophy. Surprisingly, gene expression profiling has not been reported for in an animal model of volume overload (VO). We therefore compared the gene expression profiles in the hypertrophied myocardium of rats subjected to PO and VO using DNA chip technology (Affymetrix U34A). Constriction of the abdominal aorta and abdominal aortocaval shunting were used to induce PO and VO, respectively. The gene expression profiles of the left ventricle (LV) 4 weeks after the procedure were analyzed by DNA chips. There were comparable increases in the left ventricular weight/body weight ratio in rats subjected to PO and VO. Echocardiography revealed concentric hypertrophy in the PO animals, but eccentric hypertrophy in the rats subjected to VO. The expressions of many genes were altered in VO, PO, or both. Among the genes that were upregulated in both forms of hypertrophy, greatly increased expressions of B-type natriuretic peptide, lysyl oxidase-like protein 1 and metallothionein-1 (MT) were confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR). Because free radicals are increased in the hypertrophied heart and may contribute to apoptosis, we examined the role of MT, a free radical scavenger, in apoptosis. The over-expression of MT in H9c2 cells inhibited norepinephrine-induced apoptosis, suggesting that MT may act as an anti-apoptotic molecule in cardiac hypertrophy. In conclusion, we found that many genes were regulated in VO, PO, or both. In addition, a novel role of MT in the hypertrophied myocardium was suggested.

Role of matrix metalloproteinase-9 in endothelial apoptosis in chronic heart failure in mice

Accumulation of oxidized extracellular matrix between endothelium and muscle is an important risk factor in the endothelium-myocytes uncoupling in congestive heart failure. Although ventricular remodeling is accompanied by increased matrix metalloproteinase (MMP)-9 activity, it is unclear whether MMP-9 plays a role in endothelial apoptosis in chronic volume overload congestive heart failure. We tested the hypothesis that, in chronic volume overload, myocardial dysfunction involves endocardial endothelial (EE) apoptosis in response to MMP-9 activation, extracellular matrix accumulation, and endothelium-myocytes uncoupling. Arteriovenous fistula (AVF) was created in control (FVB/NJ) and MMP-9 knockout (MMP-9KO; FVB.Cg-MMP9(tm1Tvu)/J) mice. Sham surgery was used as control. Mice were grouped as follows: wild type, n = 3 (sham control); MMP-9KO, n = 3 (sham); AVF, n = 3; and MMP-9KO + AVF (n = 3). Heart function was analyzed by M-mode and Doppler echocardiography, and with a pressure-tipped Millar catheter placed in the left ventricle of anesthetized mice 8 wk after AVF. Apoptosis was detected by measuring caspase-3, transferase-mediated dUTP nick-end labeling (TUNEL), and CD-31 by immunolabeling. Protease-activated receptors-1, connexin-43, and a disintegrin and MMP-12 (ADAM-12) expression were measured by Western blot analyses. MMP-2 and MMP-9 expression were measured by quantitative RT-PCR. Compared with control, AVF caused an increase in left ventricle end diastolic pressure and decrease in -dP/dt. In contrast, in the MMP-9KO + AVF group, these variables were changed toward control levels. Increased EE apoptosis (caspase-3 activation and TUNEL/CD-31 colabeling) in AVF mice was prevented in the MMP-9KO + AVF group. Protease-activated receptor-1, connexin-43, and ADAM-12 were induced in AVF. MMP-9 gene ablation ameliorated the induction. The results suggest that impaired cardiac function in volume overload is associated with EE apoptosis, cardiac remodeling, and endothelium-myocytes uncoupling in response to MMP-9 activation.

Protease-activated receptor and endothelial-myocyte uncoupling in chronic heart failure

We examined the hypothesis that oxidants generated nitroso derivatives, activated latent matrix metalloproteinase (MMP), and induced proteinase-activated receptor 1 (PAR-1), leading to disconnection between the endothelium and myocytes. Administration of cardiospecific tissue inhibitor of metalloproteinase-4 (TIMP-4/CIMP) ameliorated the oxidative-proteolytic stress and endothelial-myocyte uncoupling in chronic heart failure (CHF) in mice. Aortic-vena cava fistula (AVF) was created in 30 male mice (C57BL/6J) and studied at 0-, 2-, and 8-wk AVF. To reverse cardiac remodeling, as measured by MMP activation, purified CIMP was administered by an osmotic minipump subcutaneously after 8-wk AVF, and groups of mice ( n = 6 mice/group) were examined after 12 and 16 wk. Levels of PAR-1 in the left ventricle (LV) were increased at 2 and 8 wk (compared with 0 wk of no CIMP treatment) but were normal at 12 and 16 wk after CIMP treatment, as measured by Western blot analysis. Similar results were obtained for LV levels of nitrotyrosine, MMP-2 and -9 activities, and TIMP-1 and -3. However, the levels of TIMP-4, endothelial cell density, and responses of cardiac rings to acetylcholine and bradykinin were attenuated at 2 and 8 wk and normalized after CIMP administration in AVF mice. CIMP induced nitric oxide in microvascular endocardial endothelial cells. The results suggest that nitro generation activated MMP and PAR-1, leading to endothelial-myocyte uncoupling. CIMP treatment normalized PAR-1 expression and ameliorated endothelial-myocyte uncoupling by decreasing oxidant-mediated proteolytic stress in CHF.

Accelerated LV remodeling after myocardial infarction in TIMP-1-deficient mice: effects of exogenous MMP inhibition

Alterations in matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) have been implicated in adverse left ventricular (LV) remodeling after myocardial infarction (MI). However, the direct mechanistic role of TIMPs in the post-MI remodeling process has not been completely established. The goal of this project was to define the effects of altering endogenous MMP inhibitory control through combined genetic and pharmacological approaches on post-MI remodeling in mice. This study examined the effects of MMP inhibition (MMPi) with PD-166793 (30 mg.kg(-1).day(-1)) on LV geometry and function (conductance volumetry) after MI in wild-type (WT) mice and mice deficient in the TIMP-1 gene [TIMP-1 knockout (TIMP1-KO)]. At 3 days after MI (coronary ligation), mice were randomized into four groups: WT-MI/MMPi (n = 10), TIMP1-KO-MI/MMPi (n = 10), WT-MI (n = 22), and TIMP1-KO-MI (n = 23). LV end-diastolic volume (EDV) and ejection fraction were determined 14 days after MI. Age-matched WT (n = 20) and TIMP1-KO (n = 28) mice served as reference controls. LVEDV was similar under control conditions in WT and TIMP1-KO mice (36 +/- 2 and 40 +/- 2 microl, respectively) but was greater in TIMP1-KO-MI than in WT-MI mice (48 +/- 2 vs. 61 +/- 5 microl, P < 0.05). LVEDV was reduced from MI-only values in WT-MI/MMPi and TIMP1-KO-MI/MMPi mice (42 +/- 2 and 36 +/- 2 microl, respectively, P < 0.05) but was reduced to the greatest degree in TIMP1-KO mice (P < 0.05). LV ejection fraction was reduced in both groups after MI and increased in TIMP1-KO-MI/MMPi, but not in WT-MI/MMPi, mice. These unique results demonstrated that myocardial TIMP-1 plays a regulatory role in post-MI remodeling and that the accelerated myocardial remodeling induced by TIMP-1 gene deletion can be pharmacologically "rescued" by MMP inhibition. These results define the importance of local endogenous control of MMP activity with respect to regulating LV structure and function after MI.

Clinical implications of matrix metalloproteinases

Matrix metalloproteinases (MMPs) are a family of neutral proteinases that are important for normal development, wound healing, and a wide variety of pathological processes, including the spread of metastatic cancer cells, arthritic destruction of joints, atherosclerosis, pulmonary fibrosis, emphysema and neuroinflammation. In the central nervous system (CNS), MMPs have been shown to degrade components of the basal lamina, leading to disruption of the blood brain barrier and to contribute to the neuroinflammatory responses in many neurological diseases. Inhibition of MMPs have been shown to prevent progression of these diseases. Currently, certain MMP inhibitors have entered into clinical trials. A goal to the future should be to design selective synthetic inhibitors of MMPs that have minimum side effects. MMP inhibitors are designed in such a way that these can not only bind at the active site of the proteinases but also to have the characteristics to bind to other sites of MMPs which might be a promising route for therapy. To name a few: catechins, a component isolated from green tea; and Novastal, derived from extracts of shark cartilage are currently in clinical trials for the treatment of MMP-mediated diseases.

Cyclical mechanical stretch-induced apoptosis in myocytes from young rats but necrosis in myocytes from old rats

Mechanical load as stimulus for apoptosis and necrosis could be responsible for the loss of cardiomyocytes. Ventricular myocytes from young (3 mo) and old (14-24 mo) rats underwent cyclical mechanical stretch (CMS; 5% elongation, 1 Hz) for 24 h. Spontaneous apoptosis was in myocytes from young rats 0.33 +/- 0.12% and from old rats 1.05 +/- 0.35% [Tdt-mediated dUTP nick-end labeling (TUNEL) assay]; associated with a decrease of Bcl-2. CMS increased the apoptosis to 0.58 +/- 0.18% in myocytes from young rats. Western blot analysis showed that CMS reduced Bcl-2 and increased p53 (young rats). Bax was not changed by CMS. These were confirmed by cytochrome c release (31 +/- 13%) and by the enrichment of cytosolic nucleosomes (11 +/- 8%). CMS did not influence the apoptosis in myocytes from old rats (TUNEL assay, Bcl-2, Bax, or p53). CMS did not cause necrosis in myocytes from young rats. CMS increased the number of necrotic cells by showing the cell membrane rupture in myocytes from old rats (50 +/- 13% 5-hexadecanoylaminofluorescein-positive and 38 +/- 6% propidium iodide-positive cells) as well as by measuring the lactate dehydrogenase release. The results suggest that CMS-induced apoptosis in myocytes of young rats but necrosis in myocytes from old rats, which could be attributed to more stress sensitivity of cells from old rats.

Gelatinase B(MMP-9) an apoptotic factor in diabetic transgenic mice

AIMS/HYPOTHESIS

Although matrix metalloproteinase-9 (MMP-9) is specifically induced and apoptosis of endothelial cells is evidenced in diabetes mellitus, the mechanism of endocardial endothelial dysfunction in diabetes mellitus is not clear. The increase in MMP-9 activity is associated with endocardial endothelial apoptosis and dysfunction in diabetes mellitus.

METHODS

Diabetes was created by injecting 65 mg/kg alloxan in tail vein of MMP-9 knockout (-/-) and wild-type (WT, C57BL/J6) mice. At 8 weeks mice were grouped: (i) WT+saline; (ii) WT+alloxan; (iii) MMP+saline; (iv) MMP+alloxan. The MMP-9 genotype was determined by observing single PCR product of different mobility than the PCR product from wild-type in blood from tail vein.

RESULTS

MMP-9 activity, measured by zymography, increased in plasma and in the left ventricle of alloxan-induced diabetic wild-type mice. The concentrations of cardiac inhibitor of metalloproteinase, that blocks MMP-9 activity, were decreased in diabetic MMP-9 knockouts as well as in wild-type mice. Diabetes induced apoptosis, detected by TUNEL assays, in wild-type but not in MMP-9 knockouts. Endocardial endothelial function was severely impaired in diabetic wild-type mice compared with normoglycaemic animals, while non-diabetic MMP-9 knockout mice showed partial endocardial endothelial dysfunction which was not further exacerbated by the developments of diabetes.

CONCLUSION/INTERPRETATION

The results suggest an association between increased MMP-9 activity and endocardial endothelial apoptosis in diabetic mice, while genetic ablation of MMP-9 correlated with amelioration of endocardial endothelial dysfunction and apoptosis.

Matrix metalloproteinase in left ventricular remodeling and heart failure

Accumulation of oxidized matrix between the endothelium and cardiac muscle, and endocardial endothelial dysfunction, are the hallmarks of congestive heart failure. The induction of oxidative stress, decrease in endothelial cell density, activation of matrix and disintegrin metalloproteinase, collagenolysis, and repression of cardiac inhibitor of metalloproteinase (CIMP) are associated with deposition of oxidized matrix. Studies that employ CIMP as genetic or proteomic therapeutic agent may improve the heart's response to nitric oxide donors. Identification of major players involved in the control of oxidative and proteolytic stresses that ameliorate matrix deposition by integrin shading will help to develop strategies to prevent congestive heart failure.

Metalloproteinase in myocardial adaptation and maladaptation

Ventricular remodeling is a compensatory response that comprises the processes of apoptosis, muscle cell hypertrophy, and rearrangement of the extracellular matrix fibers connecting the muscles. These processes are associated with transformation of endothelium and/or fibroblasts to myofibroblasts. Neutral matrix metalloproteinases, membrane type matrix metalloproteinases, and disintegrin metalloproteinase play a significant role in these processes. The cell-extracellular matrix connections are important in maintaining and synchronizing muscle function. However, a complete extracellular matrix-cell disconnect leads to a decrease in muscle cell strength, apoptosis, and hypertrophy.