Improved balance between TIMP-3 and MMP-9 after regional myocardial ischemia-reperfusion during AT1 receptor blockade

Brain-Derived Neurotrophic Factor Precursor Contributes to a Proinflammatory Program in Monocytes/Macrophages After Acute Myocardial Infarction

Background The imbalance of monocyte/macrophage polarization toward the preferential proinflammatory phenotype and a lack of normal inflammation resolution are present in acute myocardial infarction (AMI). Our previous study showed that upregulation of brain-derived neurotrophic factor precursor (proBDNF) in M2-like monocytes may contribute to the proinflammatory response in the Stanford type-A acute aortic dissection. The present study aimed to investigate the role of proBDNF signaling in monocytes/macrophages in the progress of AMI. Methods and Results We observed the upregulation of proBDNF in the proinflammatory monocytes of patients with AMI. The upregulation of proBDNF was also observed in the circulating proinflammatory Ly6C^high monocytes and cardiac F4/80⁺CD86⁺ macrophages 3 days after AMI in a mice model. To neutralize proBDNF, the mice subjected to AMI were injected intraperitoneally with a monoclonal anti-proBDNF antibody. Echocardiography, 2,3,5-triphenyltetrazolium chloride staining, and positron emission tomography/computed tomography results demonstrate that monoclonal anti-proBDNF antibody treatment further impaired cardiac functions, increased infarct size, and exacerbated the proinflammatory state. Moreover, the level of proinflammatory Ly6C^high in the blood and F4/80⁺CD86⁺ in the heart was further increased in monoclonal anti-proBDNF antibody mice. RNA sequencing revealed that matrix metalloprotease-9 protein level was dramatically increased, along with the activated proinflammatory-related cytokines. Matrix metalloprotease-9 inhibitor treatment attenuated the deteriorated effect of monoclonal anti-proBDNF antibody on cardiac function and infarct areas. Conclusions Our study shows that endogenous proBDNF in monocytes/macrophages may exert protective roles in cardiac remodeling after AMI by regulating matrix metalloprotease-9 activity.

Naoxintong capsule limits myocardial infarct expansion by inhibiting platelet activation through the ERK5 pathway

BACKGROUND

In the clinic, Naoxintong capsule (NXT) has been applied in two level prevention of ischemic disease. However, its mechanism of action requires further study.

PURPOSE

This study investigated whether NXT could affect platelet function and activation under ischemic pathological conditions.

MATERIALS AND METHODS

Wistar rats were divided into six groups, sham, saline, NXT (250, 500, 1000 mg/kg), and aspirin group (10 mg/kg). For the pre-treatment assays, MI model was established after pre-administration of saline, NXT-L, NXT-M, NXT-H, and aspirin respectively for 14 days, and after surgery, there were no continuous treatments. For the post-treatment assay, rats were orally administered for 3 days after MI. FeCl3-induced thrombosis model was applied to determine the thrombus wet weight. Bleeding time was used to assess the ability of the platelets to develop a hemostatic plug.

RESULTS

NXT decreased infarct size, decreased LDH, CK, and CK-MB values, and improved cardiac function. NXT inhibited platelets activation through reducing CD62P-positive platelets and inhibited infarct expansion by decreasing the number of CD45-positive cells and the amount of MMP9 secreted into the heart tissue. Mechanistically, NXT inhibited platelets activation through decreasing ROS levels, decreasing ERK5 phosphorylation, and increasing RAC1 phosphorylation in MI rats. Pre-treatment with NXT decreased thrombus formation and had normal bleeding times.

CONCLUSION

NXT showed obviously preventive effects, which was associated with negative control of platelet activation. The above results provide a basis for clinically expanding application of NXT.

The Gut-Brain Axis in Autism Spectrum Disorder: A Focus on the Metalloproteases ADAM10 and ADAM17

Autism Spectrum Disorder (ASD) is a spectrum of disorders that are characterized by problems in social interaction and repetitive behavior. The disease is thought to develop from changes in brain development at an early age, although the exact mechanisms are not known yet. In addition, a significant number of people with ASD develop problems in the intestinal tract. A Disintegrin And Metalloproteases (ADAMs) include a group of enzymes that are able to cleave membrane-bound proteins. ADAM10 and ADAM17 are two members of this family that are able to cleave protein substrates involved in ASD pathogenesis, such as specific proteins important for synapse formation, axon signaling and neuroinflammation. All these pathological mechanisms are involved in ASD. Besides the brain, ADAM10 and ADAM17 are also highly expressed in the intestines. ADAM10 and ADAM17 have implications in pathways that regulate gut permeability, homeostasis and inflammation. These metalloproteases might be involved in microbiota-gut-brain axis interactions in ASD through the regulation of immune and inflammatory responses in the intestinal tract. In this review, the potential roles of ADAM10 and ADAM17 in the pathology of ASD and as targets for new therapies will be discussed, with a focus on the gut-brain axis.

Comparison of the central human and mouse platelet signaling cascade by systems biological analysis

Background

Understanding the molecular mechanisms of platelet activation and aggregation is of high interest for basic and clinical hemostasis and thrombosis research. The central platelet protein interaction network is involved in major responses to exogenous factors. This is defined by systemsbiological pathway analysis as the central regulating signaling cascade of platelets (CC).

Results

The CC is systematically compared here between mouse and human and major differences were found. Genetic differences were analysed comparing orthologous human and mouse genes. We next analyzed different expression levels of mRNAs. Considering 4 mouse and 7 human high-quality proteome data sets, we identified then those major mRNA expression differences (81%) which were supported by proteome data. CC is conserved regarding genetic completeness, but we observed major differences in mRNA and protein levels between both species. Looking at central interactors, human PLCB2, MMP9, BDNF, ITPR3 and SLC25A6 (always Entrez notation) show absence in all murine datasets. CC interactors GNG12, PRKCE and ADCY9 occur only in mice. Looking at the common proteins, TLN1, CALM3, PRKCB, APP, SOD2 and TIMP1 are higher abundant in human, whereas RASGRP2, ITGB2, MYL9, EIF4EBP1, ADAM17, ARRB2, CD9 and ZYX are higher abundant in mouse. Pivotal kinase SRC shows different regulation on mRNA and protein level as well as ADP receptor P2RY12.

Conclusions

Our results highlight species-specific differences in platelet signaling and points of specific fine-tuning in human platelets as well as murine-specific signaling differences.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-020-07215-4.

Regulation and involvement of matrix metalloproteinases in vascular diseases

Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases whose main function is to degrade and deposit structural proteins within the extracellular matrix (ECM). A dysregulation of MMPs is linked to vascular diseases. MMPs are classified into collagenases, gelatinases, membrane-type, metalloelastase, stromelysins, matrilysins, enamelysins, and unclassified subgroups. The production of MMPs is stimulated by factors such as oxidative stress, growth factors and inflammation which lead to its up- or down-regulation with subsequent ECM remodeling. Normally, excess activation of MMPs is controlled by their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs). An imbalance of MMPs and TIMPs has been implicated in hypertension, atherosclerotic plaque formation and instability, aortic aneurysms and varicose vein wall remodeling. Also, recent evidence suggests epigenetic regulation of some MMPs in angiogenesis and atherosclerosis. Over the years, pharmacological inhibitors of MMPs have been used to modify or prevent the development of the disease with some success. In this review, we discuss recent advances in MMP biology, and their involvement in the manifestation of vascular disease.

Randomized placebo controlled blinded study to assess valsartan efficacy in preventing left ventricle remodeling in patients with dual chamber pacemaker--Rationale and design of the trial

BACKGROUND

Dual chamber pacing is known to have detrimental effect on cardiac performance and heart failure occurring eventually is associated with increased mortality. Experimental studies of pacing in dogs have shown contractile dyssynchrony leading to diffuse alterations in extracellular matrix. In parallel, studies on experimental ischemia/reperfusion injury have shown efficacy of valsartan to inhibit activity of matrix metalloproteinase-9, to increase the activity of tissue inhibitor of matrix metalloproteinase-3 and preserve global contractility and left ventricle ejection fraction.

PURPOSE

To present rationale and design of randomized blinded trial aimed to assess whether 12 month long administration of valsartan will prevent left ventricle remodeling in patients with preserved left ventricle ejection fraction (LVEF ≥ 40%) and first implantation of dual chamber pacemaker.

METHODS

A total of 100 eligible patients will be randomized into three parallel arms: placebo, valsartan 80 mg/daily and valsartan 160 mg/daily added to previously used drugs. The primary endpoint will be assessment of valsartan efficacy to prevent left ventricle remodeling during 12 month follow-up. We assess patients' functional capacity, blood plasma activity of matrix metalloproteinases and their tissue inhibitors, NT-proBNP, tumor necrosis factor alpha, and Troponin T. Left ventricle function and remodeling is assessed echocardiographically: M-mode, B-mode, tissue Doppler imaging.

CONCLUSION

If valsartan proves effective, it will be an attractive measure to improve long term prognosis in aging population and increasing number of pacemaker recipients. ClinicalTrials.org (NCT01805804).

Induction of autophagy contributes to the myocardial protection of valsartan against ischemia‑reperfusion injury

The mechanisms underlying the myocardial protection of valsartan against ischemia/reperfusion (I/R) injury are complicated and remain unclear. The aim of this study was to investigate whether autophagy machinery was involved in the protection against I/R injury that is induced by valsartan. In vivo rat hearts were subjected to ischemia by 30 min ligation of the left anterior descending coronary artery, followed by a 120 min reperfusion. 3‑methyladenine (3‑MA), a specific inhibitor on autophagic sequestration, was used to inhibit autophagy. The hemodynamics, infarct size of the ventricle and LC3B protein were measured. Western blot analysis was performed to investigate the mechanism by which autophagy was induced by valsartan. Valsartan preconditioning resulted in a significant decrease in infarct size and induced autophagy in the rat heart subjected to I/R injury. The hemodynamics assay showed that the valsartan‑induced cardiac functional recovery was attenuated by 3‑MA. By contrast, 3‑MA decreased the improvement induced by valsartan on the histology and infarction of the rat heart subjected to I/R injury. Valsartan preconditioning induced autophagy via the AKT/mTOR/S6K pathway, independent of Beclin1. In conclusion, valsartan preconditioning induced autophagy via the AKT/mTOR/S6K pathway, which contributed to the myocardial protection against I/R injury.

Membrane-associated matrix proteolysis and heart failure

The extracellular matrix (ECM) is a complex entity containing a large portfolio of structural proteins, signaling molecules, and proteases. Changes in the overall integrity and activational state of these ECM constituents can contribute to tissue structure and function, which is certainly true of the myocardium. Changes in the expression patterns and activational states of a family of ECM proteolytic enzymes, the matrix metalloproteinases (MMPs), have been identified in all forms of left ventricle remodeling and can be a contributory factor in the progression to heart failure. However, new clinical and basic research has identified some surprising and unpredicted changes in MMP profiles in left ventricle remodeling processes, such as with pressure or volume overload, as well as with myocardial infarction. From these studies, it has become recognized that proteolytic processing of signaling molecules by certain MMP types, particularly the transmembrane MMPs, actually may facilitate ECM accumulation and modulate fibroblast transdifferentiation; both are critical events in adverse left ventricle remodeling. Based on the ever-increasing substrates and diversity of biological actions of MMPs, it is likely that continued research about the relationship of left ventricle remodeling in this family of proteases will yield new insights into the ECM remodeling process and new therapeutic targets.

Candesartan antagonizes pressure overload-evoked cardiac remodeling through Smad7 gene-dependent MMP-9 suppression

The present study was designed to investigate the underlying molecular mechanism for Angiotensin II type 1 receptor blockers (ARBs) mediated cardio-protection against pressure overload-induced cardiac remodeling with a focus on Smad7. ROCK-1, Smad3 and fibronectin expressions were increased in male C57BL/6 mice underwent transverse aortic constriction (TAC) for 2weeks. Treatment with Candesartan (2mg/kg per day) could effectively downregulate Smad3 and fibronectin accompanied by upregulating of Smad7. Further data showed that Candesartan inhibited TGF-β1 signal-induced epithelial-to-mesenchymal transition (EMT) through attenuating matrix metalloproteinases (MMP-9), such effect was abolished by knocking-down Smad7. Moreover, TAC for 2weeks caused increased collagen deposition, thickness of left ventricular anterior and posterior wall at end-diastole (LVAWD and LVPWD) and LVEF% reduction, which were reversed by treatment with Candesartan, but failed after knocking-down Smad7. In addition, LV dP/dt(max) and dP/dt(min) were increased by TAC for 2weeks, and treatment with Candesartan or Nifedipine effectively depressed the high levels of dP/dt(min) induced by TAC. However, only Candesartan-mediated protective role in improving cardiac function was suppressed by tail-vein injection of Smad7 siRNA. This study uncovered a novel role for ARBs in preventing pressure overload-induced cardiac remodeling via Smad7 upregulation, which suppressed MMP-9 expression and TGF-β1 signal-mediated EMT progress.

Ischemia/Infarction

Myocardial infarction (MI) accounts for most incidences of heart failure (HF) and low ejection fraction. Evidence suggests that acute MI leads to early cardiac remodeling, with changes in ventricular geometry and structure that in turn lead to a vicious cycle of ventricular dilation, increased wall stress, hypertrophy and more ventricular dilation and dysfunction, and worsening of HF. The early geometric and structural changes contribute to early mechanical complications and subsequent progressive ventricular remodeling and the development of chronic HF. A clear understanding of the underlying mechanisms is helpful in developing optimal preventive and therapeutic strategies for HF.

Early activation of matrix metalloproteinases underlies the exacerbated systolic and diastolic dysfunction in mice lacking TIMP3 following myocardial infarction

Extracellular matrix (ECM) remodeling is a critical aspect of cardiac remodeling following myocardial infarction. Tissue inhibitors of metalloproteinases (TIMPs) are physiological inhibitors of matrix metalloproteinases (MMPs) that degrade the ECM proteins. TIMP3 is highly expressed in the heart, and is markedly downregulated in patients with ischemic cardiomyopathy. We therefore examined the time- and region-dependent role of TIMP3 in the cardiac response to myocardial infarction (MI). TIMP3(-/-) and wild-type (WT) mice were subjected to MI by ligation of the left anterior descending artery. TIMP3(-/-)-MI mice exhibited a significantly compromised rate of survival compared with WT-MI mice, primarily due to increased left ventricular (LV) rupture, greater infarct expansion, exacerbated LV dilation, and greater systolic and diastolic dysfunction. Second harmonic generation imaging of unfixed and unstained hearts revealed greater collagen disarray and reduced density in the TIMP3(-/-) infarct myocardium compared with the WT group. Gelatinolytic and collagenolytic activities increased in TIMP3(-/-) compared with WT hearts at 1 day post-MI but not at 3 days or 1 wk post-MI. Neutrophil infiltration and inflammatory MMPs were significantly increased in the infarct and peri-infarct regions of TIMP3(-/-)-MI hearts. Treatment of TIMP3(-/-) mice with a broad-spectrum MMP inhibitor (PD-166793) for 2 days before and 2 days after MI markedly improved post-MI infarct expansion, LV rupture incident, LV dilation, and systolic dysfunction in these mice up to 1 wk post-MI. Our data demonstrate that the initial rise in proteolytic activities early post-MI is a triggering factor for subsequent LV adverse remodeling, LV rupture, and dilated cardiomyopathy. Hence, timing of treatments to improve cardiac response to MI may be critical in producing favorable outcome.

Temporal and spatial expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases following myocardial infarction

Following a myocardial infarction (MI), the homeostatic balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) is disrupted as part of the left ventricle (LV) response to injury. The full complement of responses to MI has been termed LV remodeling and includes changes in LV size, shape and function. The following events encompass the LV response to MI: (1) inflammation and LV wall thinning and dilation, (2) infarct expansion and necrotic myocyte resorption, (3) accumulation of fibroblasts and scar formation, and (4) endothelial cell activation and neovascularization. In this review, we will summarize MMP and TIMP roles during these events, focusing on the spatiotemporal localization and MMP and TIMP effects on cellular and tissue-level responses. We will review MMP and TIMP structure and function, and discuss specific MMP roles during both the acute and chronic phases post-MI, which may provide insight into novel therapeutic targets to limit adverse remodeling in the MI setting.

Aging-related early changes in markers of ventricular and matrix remodeling after reperfused ST-segment elevation myocardial infarction in the canine model: effect of early therapy with an angiotensin II type 1 receptor blocker

BACKGROUND

Elderly patients with reperfused ST-segment-elevation myocardial infarction are at increased risk for left ventricular remodeling. Extracellular matrix damage has been implicated in early remodeling. We hypothesized that aging results in enhanced early reperfusion injury and left ventricular remodeling after reperfused ST-segment-elevation myocardial infarction and that early therapy initiated at the time of reperfusion with an angiotensin II type 1 receptor blocker such as candesartan attenuates age-related increases in reperfusion injury and remodeling.

METHODS AND RESULTS

We randomized 3 groups of dogs (age, 1 to 2, 2.1 to 5, and 5.1 to 10 years) with reperfused ST-segment-elevation myocardial infarction (90 minutes of ischemia, 2 hours of reperfusion) to therapy with placebo or candesartan (1 mg/kg CV-11974) over 30 minutes from the onset of reperfusion. Reperfusion in placebo groups was associated with aging-related changes in the ischemic zones in markers of damage (increased ischemic injury, infarct size [as percent risk], cardiomyocyte apoptosis, blood flow impairment, no reflow), structural remodeling (increased left ventricular dilation and dysfunction), extracellular matrix remodeling (increased expression of secretory leucocyte protease inhibitor, secreted protein acidic and rich in cysteine, osteopontin, a disintegrin and metalloproteinase-10 and -17, and matrix metalloproteinase-9 and -2), and inflammation (increased inducible nitric oxide synthase, proinflammatory cytokines interleukin-6 and tumor necrosis factor-alpha, and transforming growth factor-beta(1); decreased antiinflammatory cytokine interleukin-10). Compared with placebo, candesartan attenuated these age-dependent changes.

CONCLUSIONS

Aging results in age-dependent early increases in markers of damage and adverse structural and matrix remodeling after ST-segment-elevation myocardial infarction reperfused after 90 minutes of ischemia, and early therapy initiated at the time of reperfusion with the angiotensin II type 1 receptor blocker candesartan attenuates these changes. This strategy needs clinical confirmation.

Role of healing-specific-matricellular proteins and matrix metalloproteinases in age-related enhanced early remodeling after reperfused STEMI in dogs

We assessed whether aging augments left ventricular (LV) damage, remodeling, and dysfunction and alters expression of healing-specific-matricellular proteins (HSMPs), matrix metalloproteinases (MMPs) and other pertinent proteins after acute reperfused-ST-segment-elevation myocardial infarction (RSTEMI) in the dog model. The findings suggest a novel role for HSMPs, MMPs, and the other proteins in the age-related increase in LV damage, remodeling, and dysfunction. Potentially detrimental effects of the altered proteins appear to outweigh beneficial effects and contribute to adverse outcome. Deleterious changes include the increase in matrix-degrading MMPs, inducible nitric oxide synthase (iNOS) and pro-inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha, HSMPs such as secreted-protein-acidic-and-rich-in-cysteine (SPARC) and osteopontin (OPN), the blunted increase in endothelial-NOS (eNOS), and the decrease in IL-10 and neuronal NOS (nNOS). Potentially beneficial changes include increases in the HSMP secretory-leucocyte-protease-inhibitor (SLPI) and cytokine transforming growth factor (TGF)-beta(1). Targeting these proteins may mitigate enhanced LV remodeling and dysfunction with aging.

Pleiotropic effects of cardiac drugs on healing post-MI. The good, bad, and ugly

Healing after myocardial infarction (MI) is a well-orchestrated time-dependent process that involves inflammation, tissue repair with extracellular collagen matrix (ECCM) deposition and scar formation, and remodeling of myocardial structure, matrix, vasculature, and function. Rapid early ECCM degradation followed by slow ECCM replacement and maturation during post-MI healing results in a prolonged window of enhanced vulnerability to adverse remodeling. Decreased ECCM results in adverse ventricular remodeling, dysfunction, and rupture. Inflammation, a critical factor in normal healing, if impaired results in adverse remodeling and rupture. Several therapeutic drugs prescribed after MI exert pleiotropic effects that suppress ECCM and inflammation during healing and may have good, bad, or ugly consequences. This article reviews the potential impact of pleiotropic effects of some prototypic cardiac drugs such as renin-angiotensin-aldosterone system (RAAS) inhibitors, statins, and thrombolytics during healing post-ST-segment-elevation MI (STEMI), with special focus on inflammation, ECCM and remodeling, and implications in the elderly.

Angiotensin II type 1 receptor expression in human gastric cancer and induces MMP2 and MMP9 expression in MKN-28 cells

Angiotensin II (Ang II), a main effector peptide in the renin-angiotensin system, acts as a growth-promoting and angiogenic factor via angiotensin II receptor1 (AT1R). In this study, we investigated the expression of angiotensin II type1 receptor (AT1R) in gastric cancer and the effects of Ang II on the expression of MMP2 and MMP9 in the human gastric cancer cell line MKN-28 cells. The expression of the Ang II type I receptor was examined by western and immunocytochemistry in gastric cancer cell lines and detected by real-time PCR and immunohistochemistry in normal and gastric cancer tissues. The expression of MMP2 and MMP9 were detected by real-time PCR and western after treatment with Ang II and/or AT1R antagonist. AT1R were expressed in all human gastric cancer lines and the expression of AT1R was significantly higher in cancer tissues than that in normal gastric tissues (P < 0.01). Furthermore, Ang II promoted the expression of MMP2 and MMP9 in MKN-28 cells, and the stimulatory effects of Ang II could be blocked by AT1R antagonist. These results suggest that AT1R is involved in the progression of gastric cancer and may promote the angiogenesis of gastric cancer cell line (MKN-28), and these effects may be associated with the upregulation of MMP2 and MMP9.

Interruption of endothelin signaling modifies membrane type 1 matrix metalloproteinase activity during ischemia and reperfusion

The matrix metalloproteinases (MMPs), in particular, membrane type 1 MMP (MT1-MMP), are increased in the context of myocardial ischemia and reperfusion (I/R) and likely contribute to myocardial dysfunction. One potential upstream induction mechanism for MT1-MMP is endothelin (ET) release and subsequent protein kinase C (PKC) activation. Modulation of ET and PKC signaling with respect to MT1-MMP activity with I/R has yet to be explored. Accordingly, this study examined in vivo MT1-MMP activation during I/R following modification of ET signaling and PKC activation. With the use of a novel fluorogenic microdialysis system, myocardial interstitial MT1-MMP activity was measured in pigs (30 kg; n = 9) during I/R (90 min I/120 min R). Local ET(A) receptor antagonism (BQ-123, 1 microM) and PKC inhibition (chelerythrine, 1 microM) were performed in parallel microdialysis probes. MT1-MMP activity was increased during I/R by 122 +/- 10% (P < 0.05) and was unchanged from baseline with ET antagonism and/or PKC inhibition. Selective PKC isoform induction occurred such that PKC-betaII increased by 198 +/- 31% (P < 0.05). MT1-MMP phosphothreonine, a putative PKC phosphorylation site, was increased by 121 +/- 8% (P < 0.05) in the I/R region. These studies demonstrate for the first time that increased interstitial MT1-MMP activity during I/R is a result of the ET/PKC pathway and may be due to enhanced phosphorylation of MT1-MMP. These findings identify multiple potential targets for modulating a local proteolytic pathway operative during I/R.

Myocardial Matrix Remodeling and the Matrix Metalloproteinases: Influence on Cardiac Form and Function

It is now becoming apparent that dynamic changes occur within the interstitium that directly contribute to adverse myocardial remodeling following myocardial infarction (MI), with hypertensive heart disease and with intrinsic myocardial disease such as cardiomyopathy. Furthermore, a family of matrix proteases, the matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs), has been recognized to play an important role in matrix remodeling in these cardiac disease states. The purpose of this review is fivefold: 1) to examine and redefine the myocardial matrix as a critical and dynamic entity with respect to the remodeling process encountered with MI, hypertension, or cardiomyopathic disease; 2) present the remarkable progress that has been made with respect to MMP/TIMP biology and how it relates to myocardial matrix remodeling; 3) to evaluate critical translational/clinical studies that have provided a cause-effect relationship between alterations in MMP/TIMP regulation and myocardial matrix remodeling; 4) to provide a critical review and analysis of current diagnostic, prognostic, and pharmacological approaches that utilized our basic understanding of MMP/TIMPs in the context of cardiac disease; and 5) most importantly, to dispel the historical belief that the myocardial matrix is a passive structure and supplant this belief that the regulation of matrix protease pathways such as the MMPs and TIMPs will likely yield a new avenue of diagnostic and therapeutic strategies for myocardial remodeling and the progression to heart failure.

Angiotensin receptor blockade and angiotensin-converting-enzyme inhibition limit adverse remodeling of infarct zone collagens and global diastolic dysfunction during healing after reperfused ST-elevation myocardial infarction

To determine whether therapy with the angiotensin II type 1 receptor blocker (ARB) candesartan and the comparator angiotensin-converting-enzyme inhibitor (ACEI) enalapril during healing after reperfused ST-elevation myocardial infarction (RSTEMI) limit adverse remodeling of infarct zone (IZ) collagens and left ventricular (LV) diastolic dysfunction, we randomized 24 dogs surviving anterior RSTEMI (90-min coronary occlusion) to placebo, candesartan, and enalapril therapy between day 2 and 42. Six other dogs were sham. We measured regional IZ and non-infarct zone (NIZ) collagens (hydroxyproline; types I/III; cross-linking), transforming growth factor-beta (TGF-beta) and topography at 6 weeks, and hemodynamics, LV diastolic and systolic function, and remodeling over 6 weeks. Compared to sham, placebo-RSTEMI differentially altered regional collagens, with more pronounced increase in TGF-beta, hydroxyproline, and type I, insoluble, and cross-linked collagens in the IZ than NIZ, and increased IZ soluble and type III collagens at 6 weeks, and induced persistent LV filling pressure elevation, diastolic and systolic dysfunction, and LV remodeling over 6 weeks. Compared to placebo-RSTEMI, candesartan and enalapril limited adverse regional collagen remodeling, with normalization of type III, soluble and insoluble collagens and decrease in pyridinoline cross-linking in the IZ at 6 weeks, and attenuation of LV filling pressure, diastolic dysfunction, and remodeling over 6 weeks. The results suggest that candesartan and enalapril during healing after RSTEMI prevent rather than worsen adverse remodeling of IZ collagens and LV diastolic dysfunction, supporting the clinical use of ARBs and ACEIs during subacute RSTEMI.

Valsartan in the treatment of heart attack survivors

Survivors of myocardial infarction (MI) are at high risk of disability and death. This is due to infarct-related complications such as heart failure, cardiac remodeling with progressive ventricular dilation, dysfunction, and hypertrophy, and arrhythmias including ventricular and atrial fibrillation. Angiotensin (Ang) II, the major effector molecule of the renin–angiotensin–aldosterone system (RAAS) is a major contributor to these complications. RAAS inhibition, with angiotensin-converting enzyme (ACE) inhibitors were first shown to reduce mortality and morbidity after MI. Subsequently, angiotensin receptor blockers (ARBs), that produce more complete blockade of the effects of Ang II at the Ang II type 1 (AT₁) receptor, were introduced and the ARB valsartan was shown to be as effective as an ACE inhibitor in reducing mortality and morbidity in high-risk post-MI suvivors with left ventricular (LV) systolic dysfunction and and/or heart failure and in heart failure patients, respectively, in two major trials (VALIANT and Val-HeFT). Both these trials used an ACE inhibitor as comparator on top of background therapy. Evidence favoring the use of valsartan for secondary prevention in post-MI survivors is reviewed.

Pretreatment with fosinopril or valsartan reduces myocardial no-reflow after acute myocardial infarction and reperfusion

BACKGROUND

Both fosinopril and valsartan are effective in protecting endothelial function. We hypothesized that they may also reduce myocardial no-reflow. In addition, suppression of adenosine triphosphate-sensitive K (KATP) channel opening is an important mechanism for myocardial no-reflow. Therefore, this study sought to assess the effect of fosinopril and valsartan on myocardial no-reflow and explore the possible mechanism.

METHODS

Coronary ligation area and the area of no-reflow were determined with both myocardial contrast echocardiography in vivo and pathological means in 56 mini-swine randomized into seven study groups: eight in control, eight in fosinopril-pretreated (1 mg/kg/day) for 3 days, eight in fosinopril and glibenclamide (KATP channel blocker)-pretreated, eight in valsartan-pretreated (2 mg/kg/day) for 3 days, eight in valsartan and glibenclamide-pretreated, eight in glibenclamide-treated and eight in sham-operated. An acute myocardial infarction and reperfusion model was created with a 3-h occlusion of the coronary artery followed by a 2-h reperfusion. The levels of KATP channel proteins (SUR2, Kir6.1, and Kir6.2) in the reflow and no-reflow myocardium were quantified by Western blotting.

RESULTS

Compared with the control group, both fosinopril and valsartan significantly improved ventricular function, decreased area of no-reflow (myocardial contrast echocardiography: from 78.5+/-4.5 to 24.5+/-2.7 and 24.3+/-3.6%, pathological means: from 82.3+/-1.9 to 25.2+/-3.2 and 24.9+/-4.4% of ligation area, respectively; all P<0.01), reduced necrosis size from 98.5+/-1.3 to 88.9+/-3.6 and 89.1+/-3.1% of ligation area, respectively (both P<0.05). They also increased the levels of SUR2 and Kir6.2 (P<0.01), but had no effect on the level of Kir6.1 (P>0.05). A combination of fosinopril or valsartan with glibenclamide significantly increased area of no-reflow (P<0.05) and decreased the levels of SUR2 and Kir6.2 (P<0.01).

CONCLUSIONS

Pretreatment with fosinopril or valsartan can reduce myocardial no-reflow. This beneficial effect is due to activation of the KATP channel.

Growth hormone (GH) receptor knockout mice reveal actions of GH in lung development

The presence of growth hormone (GH) and GH receptors (GHRs) in the lung suggests it is an autocrine/paracrine target site for pulmonary GH action and/or an endocrine site of pituitary GH action. Roles for GH in lung growth or pulmonary function are, however, uncertain. The possibility that pituitary and/or pulmonary GH have physiological roles in lung development has therefore been investigated in GHR knockout (KO or -/-) mice, using a proteomics approach to determine if an absence of GH-signaling affects the proteome of the developing lung. More than 600 proteins were detected by 2-DE in the lungs of control [GHR (+/+)] and GHR (-/-) mice at the end of the alveolarization period (at day 14 postnatally). Of these, 39 differed significantly in protein content at the p>0.05 level [6 were of higher abundance in the GHR (-/-) group, 33 were of lower abundance] and 17 differed at the p>0.02 level [5 of higher abundance in the GHR (-/-) group, 12 of lower abundance] and 7 were definitively identified by MS. Vimentin, a protein involved in cellular proliferation, was reduced in content by approximately 75% in the lungs of the GHR (-/-) mice. Three proteins involved in oxidative protection [SH3 domain-binding glutamic acid-rich-like protein, peroxiredoxin 6 (Prdx6), and isocitrate dehydrogenase 1] were also of lower content in the GHR (-/-) lungs (by approximately 88%, 81% and 70%, respectively). Prdx6 is also involved in lipid and surfactant metabolism, as is apolipoprotein A-IV, the lung content of which was reduced by approximately 73% in these mice. Proteasome 26S ATPase subunit 4, a protein involved in the non-lysosomal degradation of intracellular proteins, and electron flavoprotein alpha subunit , involved in intracellular metabolism, were also reduced in content in the lungs of the GHR (-/-) mice (by approximately 70% and 49%, respectively). These results therefore suggest that these proteins are normally dependent upon GH signaling, and that GH is normally involved in early lung growth, oxidative protection, lipid and energy metabolism and in proteasomal activity. These roles may reflect endocrine actions of pituitary GH and/or local autocrine/paracrine actions of GH produced within the lung.