Increase of fibronectin and osteopontin in porcine hearts following ischemia and reperfusion

Protective Effects of Resveratrol Against Adenomyosis in a Mouse Model

Adenomyosis is a uterine condition in which endometrial glands and stroma are commonly pathologically observed in the myometrium. In this study, we sought to determine the effect of resveratrol on the progression of adenomyosis. Adenomyosis was induced in mice given tamoxifen neonatally. All mice were subjected to body weight measurement and hotplate testing every four weeks beginning four weeks after birth. All mice with adenomyosis were randomly separated into 3 groups at 16 weeks: untreated, low-dose resveratrol (25 mg/kg), and high-dose resveratrol (50 mg/kg). After 3 weeks of treatment, final hotplate test and body weight measurement were performed, and the uterine horn blood samples were collected. Adenomyosis in mice caused body weight loss and uterine weight gain, reduced hotplate latency, and progression of endometrial fibrosis. The underlying biological process could be coupled with the overexpression of many cells' proliferation and immune-regulation-related genes. Resveratrol treatment could slow the progression of adenomyosis by enhancing hotplate latency, lowering endometrial fibrosis, and restoring cell proliferation- and immune-regulation-associated gene expression levels in endometrium and plasma. However, resveratrol treatment also reduced the body weight and uterine weight. In conclusion, Resveratrol might be a potential compound for treating patients with adenomyosis.

Blockage of Fibronectin 1 Ameliorates Myocardial Ischemia/Reperfusion Injury in Association with Activation of AMP-LKB1-AMPK Signaling Pathway

Myocardial ischemia/reperfusion injury (I/RI) is closely associated with energy substrate metabolism. Fibronectin 1 (Fn1) was markedly elevated in the heart of I/R pigs and ischemic patients, but its role in myocardial I/RI is controversial and the precise mechanism involved remains elusive. Herein, we tested whether blockage of Fn1 with its inhibitor (fibronectin tetrapeptide, RGDS) would alleviate myocardial I/RI. Wild-type (WT) mice were administered with RGDS once 3 h before I/R operation and once at 24 or 48 h postreperfusion, and sacrificed at 24 or 72 h post-I/R, respectively. Cardiac function was evaluated by echocardiography. Myocardial infarction size, apoptosis, fibrosis, and inflammation were examined via histological staining. Uptake of glucose and fatty acids were detected by positron emission tomography (PET) and computer tomography (CT) with [¹⁸F]-2-fluoro-2-deoxy-D-glucose (FDG) and [¹⁸F]-fluoro-6-thia-heptadecanoic acid (FTHA), respectively. Our results showed that administration of RGDS to mice remarkably limited the I/R-induced myocardial infarct size, myocyte apoptosis, inflammation, oxidative stress, and fibrosis and improved cardiac contractile dysfunction. These protective effects were associated with upregulation of the AMP/ATP ratio and the activation of LKB1-AMPK signaling, which subsequently increased AS160-GLUT4-mediated glucose and fatty acid uptake, improved mitochondrial dynamic imbalance, and inactivated TGF-β and NF-κB signals in the I/R heart. In conclusion, the current study identified that blocking Fn1 protects against myocardial I/RI likely through activating the LKB1-AMPK-dependent signals and highlights that inhibition of Fn1 may be a novel therapeutic option for treating ischemic heart diseases.

Preparation of A Spaceflight: Apoptosis Search in Sutured Wound Healing Models

To prepare the ESA (European Space Agency) spaceflight project “Wound healing and Sutures in Unloading Conditions”, we studied mechanisms of apoptosis in wound healing models based on ex vivo skin tissue cultures, kept for 10 days alive in serum-free DMEM/F12 medium supplemented with bovine serum albumin, hydrocortisone, insulin, ascorbic acid and antibiotics at 32 °C. The overall goal is to test: (i) the viability of tissue specimens; (ii) the gene expression of activators and inhibitors of apoptosis and extracellular matrix components in wound and suture models; and (iii) to design analytical protocols for future tissue specimens after post-spaceflight download. Hematoxylin-Eosin and Elastica-van-Gieson staining showed a normal skin histology with no signs of necrosis in controls and showed a normal wound suture. TdT-mediated dUTP-biotin nick end labeling for detecting DNA fragmentation revealed no significant apoptosis. No activation of caspase-3 protein was detectable. FASL, FADD, CASP3, CASP8, CASP10, BAX, BCL2, CYC1, APAF1, LAMA3 and SPP1 mRNAs were not altered in epidermis and dermis samples with and without a wound compared to 0 day samples (specimens investigated directly post-surgery). BIRC5, CASP9, and FN1 mRNAs were downregulated in epidermis/dermis samples with and/or without a wound compared to 0 day samples. BIRC2, BIRC3 were upregulated in 10 day wound samples compared to 0 day samples in epidermis/dermis. RELA/FAS mRNAs were elevated in 10 day wound and no wound samples compared to 0 day samples in dermis. In conclusion, we demonstrate that it is possible to maintain live skin tissue cultures for 10 days. The viability analysis showed no significant signs of cell death in wound and suture models. The gene expression analysis demonstrated the interplay of activators and inhibitors of apoptosis and extracellular matrix components, thereby describing important features in ex vivo sutured wound healing models. Collectively, the performed methods defining analytical protocols proved to be applicable for post-flight analyzes of tissue specimens after sample return.

Temporal cardiac remodeling post-myocardial infarction: dynamics and prognostic implications in personalized medicine

Despite dramatic improvements in short-term mortality rates following myocardial infarction (MI), long-term survival for MI patients who progress to heart failure remains poor. MI occurs when the left ventricle (LV) is deprived of oxygen for a sufficient period of time to induce irreversible necrosis of the myocardium. The LV response to MI involves significant tissue, cellular, and molecular level modifications, as well as substantial hemodynamic changes that feedback negatively to amplify the response. Inflammation to remove necrotic myocytes and fibroblast activation to form a scar are key wound healing responses that are highly variable across individuals. Few biomarkers of early remodeling stages are currently clinically adopted. The discovery of underlying pathophysiological mechanisms and associated novel biomarkers has the potential of improving prognostic capability and therapeutic monitoring. Combining these biomarkers with other prominent ones could constitute a powerful diagnostic and prognostic tool that directly reflects the pathophysiological remodeling of the LV. Understanding temporal remodeling at the tissue, cellular, and molecular level and its link to a well-defined set of biomarkers at early stages post-MI is a prerequisite for improving personalized care and devising more successful therapeutic interventions. Here we summarize the integral mechanisms that occur during early cardiac remodeling in the post-MI setting and highlight the most prominent biomarkers for assessing disease progression.

Osteopontin is proteolytically processed by matrix metalloproteinase 9

Osteopontin is robustly upregulated following myocardial infarction (MI), which suggests that it has an important role in post-MI remodeling of the left ventricle (LV). Osteopontin deletion results in increased LV dilation and worsened cardiac function. Thus, osteopontin exerts protective effects post-MI, but the mechanisms have yet to be defined. Matrix metalloproteinases (MMPs) regulate LV remodeling post-MI, and osteopontin is a known substrate for MMP-2, -3, -7, and -9, although the cleavage sites have not been mapped. Osteopontin-derived peptides can exert distinct biological functions that may depend on their cleavage sites. We mapped the MMP-9 cleavage sites via LC-MS/MS analysis using label-free and N-terminal labeling methods, and compared them with those of MMP-2, -3, and -7. Each MMP yielded a unique cleavage profile with few overlapping cleavage sites. Using synthetic peptides, we validated 3 sites for MMP-9 cleavage at amino acid positions 151-152, 193-194, and 195-196. Four peptides were synthesized based on the upstream- and downstream-generated fragments and were tested for biological activity in isolated cardiac fibroblasts. Two peptides increased cardiac fibroblast migration rates post-wounding (p < 0.05 compared with the negative control). Our study highlights the importance of osteopontin processing, and confirms that different cleavage sites generate osteopontin peptides with distinct biological functions.

Osteopontin deficiency aggravates hepatic injury induced by ischemia-reperfusion in mice

Osteopontin (OPN) is a multifunctional protein involved in hepatic steatosis, inflammation, fibrosis and cancer progression. However, its role in hepatic injury induced by ischemia–reperfusion (I–R) has not yet been investigated. We show here that hepatic warm ischemia for 45 min followed by reperfusion for 4 h induced the upregulation of the hepatic and systemic level of OPN in mice. Plasma aspartate aminotransferase and alanine aminotransferase levels were strongly increased in Opn^−/− mice compared with wild-type (Wt) mice after I–R, and histological analysis of the liver revealed a significantly higher incidence of necrosis of hepatocytes. In addition, the expression levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNFα), interleukin 6 (IL6) and interferon-γ were strongly upregulated in Opn^−/− mice versus Wt mice after I–R. One explanation for these responses could be the vulnerability of the OPN-deficient hepatocyte. Indeed, the downregulation of OPN in primary and AML12 hepatocytes decreased cell viability in the basal state and sensitized AML12 hepatocytes to cell death induced by oxygen–glucose deprivation and TNFα. Further, the downregulation of OPN in AML12 hepatocytes caused a strong decrease in the expression of anti-apoptotic Bcl2 and in the ATP level. The hepatic expression of Bcl2 also decreased in Opn^−/− mice versus Wt mice livers after I–R. Another explanation could be the regulation of the macrophage activity by OPN. In RAW macrophages, the downregulation of OPN enhanced iNOS expression in the basal state and sensitized macrophages to inflammatory signals, as evaluated by the upregulation of iNOS, TNFα and IL6 in response to lipopolysaccharide. In conclusion, OPN partially protects from hepatic injury and inflammation induced in this experimental model of liver I–R. This could be due to its ability to partially prevent death of hepatocytes and to limit the production of toxic iNOS-derived NO by macrophages.

Danger signals in the initiation of the inflammatory response after myocardial infarction

During myocardial infarction, sterile inflammation occurs. The danger model is a solid theoretic framework that explains this inflammation as danger associated molecular patterns activate the immune system. The innate immune system can sense danger signals through different pathogen recognition receptors (PRR) such as toll-like receptors, nod-like receptors and receptors for advanced glycation endproducts. Activation of a PRR results in the production of cytokines and the recruitment of leukocytes to the site of injury. Due to tissue damage and necrosis of cardiac cells, danger signals such as extracellular matrix (ECM) breakdown products, mitochondrial DNA, heat shock proteins and high mobility box 1 are released. Matricellular proteins are non-structural proteins expressed in the ECM and are upregulated upon injury. Some members of the matricellular protein family (like tenascin-C, osteopontin, CCN1 and the galectins) have been implicated in the inflammatory and reparative responses following myocardial infarction and may function as danger signals. In a clinical setting, danger signals can function as prognostic and/or diagnostic biomarkers and for drug targeting. In this review we will provide an overview of the established knowledge on the role of danger signals in myocardial infarction and we will discuss areas of interest for future research.

Matricellular proteins in cardiac adaptation and disease

The term matricellular proteins describes a family of structurally unrelated extracellular macromolecules that, unlike structural matrix proteins, do not play a primary role in tissue architecture, but are induced following injury and modulate cell-cell and cell-matrix interactions. When released to the matrix, matricellular proteins associate with growth factors, cytokines, and other bioactive effectors and bind to cell surface receptors transducing signaling cascades. Matricellular proteins are upregulated in the injured and remodeling heart and play an important role in regulation of inflammatory, reparative, fibrotic and angiogenic pathways. Thrombospondin (TSP)-1, -2, and -4 as well as tenascin-C and -X secreted protein acidic and rich in cysteine (SPARC), osteopontin, periostin, and members of the CCN family (including CCN1 and CCN2/connective tissue growth factor) are involved in a variety of cardiac pathophysiological conditions, including myocardial infarction, cardiac hypertrophy and fibrosis, aging-associated myocardial remodeling, myocarditis, diabetic cardiomyopathy, and valvular disease. This review discusses the properties and characteristics of the matricellular proteins and presents our current knowledge on their role in cardiac adaptation and disease. Understanding the role of matricellular proteins in myocardial pathophysiology and identification of the functional domains responsible for their actions may lead to design of peptides with therapeutic potential for patients with heart disease.

Novel cardiac-specific biomarkers and the cardiovascular continuum

The concept of the cardiovascular continuum, introduced during the early 1990s, created a holistic view of the chain of events connecting cardiovascular-related risk factors with the progressive development of pathological-related tissue remodelling and ultimately, heart failure and death. Understanding of the tissue-specific changes, and new technologies developed over the last 25-30 years, enabled tissue remodelling events to be monitored in vivo and cardiovascular disease to be diagnosed more reliably than before. The tangible product of this evolution was the introduction of a number of biochemical markers such as troponin I and T, which are now commonly used in clinics to measure myocardial damage. However, biomarkers that can detect specific earlier stages of the cardiovascular continuum have yet to be generated and utilised. The majority of the existing markers are useful only in the end stages of the disease where few successful intervention options exist. Since a large number of patients experience a transient underlying developing pathology long before the signs or symptoms of cardiovascular disease become apparent, the requirement for new markers that can describe the early tissue-specific, matrix remodelling process which ultimately leads to disease is evident. This review highlights the importance of relating cardiac biochemical markers with specific time points along the cardiovascular continuum, especially during the early transient phase of pathology progression where none of the existing markers aid diagnosis.

Pretreatment of endothelial progenitor cells with osteopontin enhances cell therapy for peripheral vascular disease

Tissue necrosis resulting from critical limb ischemia (CLI) leads to amputation in a significant number of patients. Autologous cell therapy using angiogenic cells such as endothelial progenitor cells (EPCs) holds promise as a treatment for CLI but a limitation of this treatment is that the underlying disease etiology that resulted in CLI may also contribute to dysfunction of the therapeutic EPCs. This study aimed to elucidate the mechanism of EPC dysfunction using diabetes mellitus as a model and to determine whether correction of this defect in dysfunctional EPCs ex vivo would improve the outcome after cell transplantation in the murine hind limb ischemia model. EPC dysfunction was confirmed in a homogenous population of patients with type 1 diabetes mellitus and a microarray study was preformed to identify dysregulated genes. Notably, the secreted proangiogenic protein osteopontin (OPN) was significantly downregulated in diabetic EPCs. Furthermore, OPN-deficient mice showed impaired recovery following hind limb ischemia, suggesting a critical role for OPN in postnatal neovascularization. EPCs isolated from OPN KO mice showed decreased ability to adhere to endothelial cells as well as impaired angiogenic potential. However, this dysfunction was reversed upon exposure to recombinant OPN, suggesting that OPN may act in an autocrine manner on EPCs. Indeed, exposure of OPN knockout (KO) EPCs to OPN was sufficient to induce the secretion of angiogenic proteins (IL-6, TGF-α, and FGF-α). We also demonstrated that vascular regeneration following hind limb ischemia in OPN KO mice was significantly improved upon injection of EPCs preexposed to OPN. We concluded that OPN acts in an autocrine manner on EPCs to induce the secretion of angiogenic proteins, thereby playing a critical role in EPC-mediated neovascularization. Modification of cells by exposure to OPN may improve the efficacy of autologous EPC transplantation via the enhanced secretion of angiogenic proteins.

Short-term weightlessness produced by parabolic flight maneuvers altered gene expression patterns in human endothelial cells

This study focused on the effects of short-term microgravity (22 s) on the gene expression and morphology of endothelial cells (ECs) and evaluated gravisensitive signaling elements. ECs were investigated during four German Space Agency (Deutsches Zentrum für Luft- und Raumfahrt) parabolic flight campaigns. Hoechst 33342 and acridine orange/ethidium bromide staining showed no signs of cell death in ECs after 31 parabolas (P31). Gene array analysis revealed 320 significantly regulated genes after the first parabola (P1) and P31. COL4A5, COL8A1, ITGA6, ITGA10, and ITGB3 mRNAs were down-regulated after P1. EDN1 and TNFRSF12A mRNAs were up-regulated. ADAM19, CARD8, CD40, GSN, PRKCA (all down-regulated after P1), and PRKAA1 (AMPKα1) mRNAs (up-regulated) provide a very early protective mechanism of cell survival induced by 22 s microgravity. The ABL2 gene was significantly up-regulated after P1 and P31, TUBB was slightly induced, but ACTA2 and VIM mRNAs were not changed. β-Tubulin immunofluorescence revealed a cytoplasmic rearrangement. Vibration had no effect. Hypergravity reduced CARD8, NOS3, VASH1, SERPINH1 (all P1), CAV2, ADAM19, TNFRSF12A, CD40, and ITGA6 (P31) mRNAs. These data suggest that microgravity alters the gene expression patterns and the cytoskeleton of ECs very early. Several gravisensitive signaling elements, such as AMPKα1 and integrins, are involved in the reaction of ECs to altered gravity.

Differential gene regulation under altered gravity conditions in follicular thyroid cancer cells: relationship between the extracellular matrix and the cytoskeleton

Extracellular matrix proteins, adhesion molecules, and cytoskeletal proteins form a dynamic network interacting with signalling molecules as an adaptive response to altered gravity. An important issue is the exact differentiation between real microgravity responses of the cells or cellular reactions to hypergravity and/or vibrations. To determine the effects of real microgravity on human cells, we used four DLR parabolic flight campaigns and focused on the effects of short-term microgravity (22 s), hypergravity (1.8 g), and vibrations on ML-1 thyroid cancer cells. No signs of apoptosis or necrosis were detectable. Gene array analysis revealed 2,430 significantly changed transcripts. After 22 s microgravity, the F-actin and cytokeratin cytoskeleton was altered, and ACTB and KRT80 mRNAs were significantly upregulated after the first and thirty-first parabolas. The COL4A5 mRNA was downregulated under microgravity, whereas OPN and FN were significantly upregulated. Hypergravity and vibrations did not change ACTB, KRT-80 or COL4A5 mRNA. MTSS1 and LIMA1 mRNAs were downregulated/slightly upregulated under microgravity, upregulated in hypergravity and unchanged by vibrations. These data indicate that the graviresponse of ML-1 cells occurred very early, within the first few seconds. Downregulated MTSS1 and upregulated LIMA1 may be an adaptive mechanism of human cells for stabilizing the cytoskeleton under microgravity conditions.

Matrix metalloproteinases as drug targets in ischemia/reperfusion injury

Deficient blood supply (ischemia) is a common consequence of some surgical procedures and certain pathologies. Once blood circulation is re-established (reperfusion), a complex series of events results in recruitment of inflammatory cells, rearrangement of the extracellular matrix and induction of cell death, which lead to organ dysfunction. Although ischemia/reperfusion (I/R) injury is an important cause of death, there is no effective therapy targeting the molecular mechanism of disease progression. Matrix metalloproteinases (MMPs), which are important regulators of many cellular activities, have a central role in disease progression after I/R injury, as suggested by numerous studies using MMP inhibitors or MMP-deficient mice. Here, we review the involvement of MMP activity in the various processes following I/R injury and the therapeutic potential of MMP inhibition.

A proteomic approach to analysing spheroid formation of two human thyroid cell lines cultured on a random positioning machine

The human cell lines FTC-133 and CGTH W-1, both derived from patients with thyroid cancer, assemble to form different types of spheroids when cultured on a random positioning machine. In order to obtain a possible explanation for their distinguishable aggregation behaviour under equal culturing conditions, we evaluated a proteomic analysis emphasising cytoskeletal and membrane-associated proteins. For this analysis, we treated the cells by ultrasound, which freed up some of the proteins into the supernatant but left some attached to the cell fragments. Both types of proteins were further separated by free-flow IEF and SDS gel electrophoresis until their identity was determined by MS. The MS data revealed differences between the two cell lines with regard to various structural proteins such as vimentin, tubulins and actin. Interestingly, integrin α-5 chains, myosin-10 and filamin B were only found in FTC-133 cells, while collagen was only detected in CGTH W-1 cells. These analyses suggest that FTC-133 cells express surface proteins that bind fibronectin, strengthening the three-dimensional cell cohesion.

Impact of simulated microgravity on microvascular endothelial cell apoptosis

Cardiovascular deconditioning is known to occur in astronauts exposed to microgravity. Endothelial dysfunction at microcirculatory sites might contribute to cardiovascular deconditioning induced by weightlessness. Recent studies have reported changes in the morphology and gene expression of endothelial cells exposed to conditions of simulated microgravity. The present study was aimed at examining the effects of microgravity on the apoptosis of microvascular endothelial cells and the mechanism underlying these effects. We simulated a microgravity environment and found that microgravity induced microvascular endothelial cell apoptosis and that this effect was correlated with the downregulation of the PI3K/Akt pathway, increased expression of NF-κB, and depolymerization of F-actin. These findings may provide important insights into the origin of the adverse physiological changes occurring due to exposure to microgravity conditions.

The cardiokine story unfolds: ischemic stress-induced protein secretion in the heart

Intercellular communication depends on many factors, including proteins released via the classical or non-classical secretory pathways, many of which must be properly folded to be functional. Owing to their adverse effects on the secretion machinery, stresses such as ischemia can impair the folding of secreted proteins. Paradoxically, cells rely on secreted proteins to mount a response designed to resist stress-induced damage. This review examines this paradox using proteins secreted from the heart, cardiokines, as examples, and focuses on how the ischemic heart maintains or even increases the release of select cardiokines that regulate important cellular processes in the heart, including excitation-contraction coupling, hypertrophic growth, myocardial remodeling and stem cell function, in ways that moderate ischemic damage and enhance cardiac repair.

The impact of vascular endothelial growth factor and basic fibroblast growth factor on cardiac fibroblasts grown under altered gravity conditions

BACKGROUND

Myocardium is very sensitive to gravitational changes. During a spaceflight cardiovascular atrophy paired with rhythm problems and orthostatic intolerance can occur. The aim of this study was to investigate the impact of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) on cardiac fibroblasts (CF) grown under altered gravity conditions.

METHODS

We examined the influence of exposure to a Random Positioning Machine (RPM) on CF, derived from porcine hearts. We focused on growth, extracellular matrix protein (ECMP) synthesis and apoptosis.

RESULTS

When cultured on a RPM, CF began to form 3D spheroids within 24h, irrespective of growth factor treatment. Exposure to RPM induced an increased synthesis of ECMP and also resulted in elevated apoptosis in adherent CF as measured by terminal deoxynucleotidyl transferase-mediated dUTP digoxigenin nick end labeling (TUNEL) analysis, 4',6-diamidino-2-phenylindole (DAPI) staining, and caspase-3 detection. bFGF and VEGF significantly decreased the amount of ECMP (collagen type I, III, chondroitin sulfate) in 1g and RPM cultures, and also significantly reduced the amount of apoptotic CF as well as caspase-3.

CONCLUSIONS

Altered gravity conditions on a RPM induced 3D growth, elevated ECMP synthesis and apoptosis in cardiac fibroblasts. Growth factor treatment attenuated programmed cell death and ECMP secretion.

Mast cells contribute to altered vascular reactivity and ischemia-reperfusion injury following cerium oxide nanoparticle instillation

Cerium oxide (CeO₂) represents an important nanomaterial with wide ranging applications. However, little is known regarding how CeO₂ exposure may influence pulmonary or systemic inflammation. Furthermore, how mast cells would influence inflammatory responses to a nanoparticle exposure is unknown. We thus compared pulmonary and cardiovascular responses between C57BL/6 and B6.Cg-Kit(W-sh) mast cell deficient mice following CeO₂ nanoparticle instillation. C57BL/6 mice instilled with CeO₂ exhibited mild pulmonary inflammation. However, B6.Cg-Kit(W-sh) mice did not display a similar degree of inflammation following CeO₂ instillation. Moreover, C57BL/6 mice instilled with CeO₂ exhibited altered aortic vascular responses to adenosine and an increase in myocardial ischemia/reperfusion injury which was absent in B6.Cg-Kit(W-sh) mice. In vitro CeO₂ exposure resulted in increased production of PGD₂, TNF-α, IL-6 and osteopontin by cultured mast cells. These findings demonstrate that CeO₂ nanoparticles activate mast cells contributing to pulmonary inflammation, impairment of vascular relaxation and exacerbation of myocardial ischemia/reperfusion injury.

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.

Osteopontin: role in immune regulation and stress responses

Recent research has led to a better but as yet incomplete understanding of the complex roles osteopontin plays in mammalian physiology. A soluble protein found in all body fluids, it stimulates signal transduction pathways (via integrins and CD44 variants) similar to those stimulated by components of the extracellular matrix. This appears to promote the survival of cells exposed to potentially lethal insults such as ischemia/reperfusion or physical/chemical trauma. OPN is chemotactic for many cell types including macrophages, dendritic cells, and T cells; it enhances B lymphocyte immunoglobulin production and proliferation. In inflammatory situations it stimulates both pro- and anti-inflammatory processes, which on balance can be either beneficial or harmful depending on what other inputs the cell is receiving. OPN influences cell-mediated immunity and has been shown to have Th1-cytokine functions. OPN deficiency is linked to a reduced Th1 immune response in infectious diseases, autoimmunity and delayed type hypersensitivity. OPN's role in the central nervous system and in stress responses has also emerged as an important aspect related to its cytoprotective and immune functions. Evidence suggests that either OPN or anti-OPN monoclonal antibodies (depending on the circumstances) might be clinically useful in modulating OPN function. Manipulation of plasma OPN levels may be useful in the treatment of autoimmune disease, cancer metastasis, osteoporosis and some forms of stress.

Modulation of Angiotensin II–Mediated Hypertension and Cardiac Remodeling by Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 Deletion

Angiotensin II via type 1 receptor activation upregulates the expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), and LOX-1 activation, in turn, upregulates angiotensin II type 1 receptor expression. We postulated that interruption of this positive feedback loop might attenuate the genesis of angiotensin II–induced hypertension and subsequent cardiac remodeling. To examine this postulate, LOX-1 knockout and wild-type mice were infused with angiotensin II or norepinephrine (control for angiotensin II) for 4 weeks. Angiotensin II–, but not norepinephrine-, induced hypertension was attenuated in LOX-1 knockout mice. Angiotensin II–induced cardiac remodeling was also attenuated in LOX-1 knockout mice. Importantly, angiotensin II type 1 receptor expression was reduced, and the expression and activity of endothelial NO synthase were preserved in the tissues of LOX-1 knockout mice given angiotensin II. Reactive oxygen species generation, nicotinamide-adenine dinucleotide phosphate oxidase expression, and phosphorylation of p38 and p44/42 mitogen-activated protein kinases were also much less pronounced in the LOX-1 knockout mice given angiotensin II. These alterations in biochemical and structural abnormalities were associated with preservation of cardiac hemodynamics in the LOX-1 knockout mice. To confirm that fibroblast function is modulated in the absence of LOX-1, cardiac fibroblasts from wild-type and LOX-1 knockout mice were treated with angiotensin II. Indeed, LOX-1 knockout mice cardiac fibroblasts revealed an attenuated profibrotic response on treatment with angiotensin II. These observations provide strong evidence that LOX-1 is a key modulator of the development of angiotensin II–induced hypertension and subsequent cardiac remodeling.

Effects of basic fibroblast growth factor on endothelial cells under conditions of simulated microgravity

Fibroblast growth factors interact with appropriate endothelial cell (EC) surface receptors and initiate intracellular signal cascades, which participate in modulating blood vessel growth. EC, upon exposure to basic fibroblast growth factors (bFGFs) undergo profound functional alterations, which depend on their actual sensitivity and involve gene expression and de novo protein synthesis. We investigated the effects of bFGF on signaling pathways of EA.hy926 cells in different environments. EC were cultured under normal gravity (1 g) and simulated microgravity (micro g) using a three-dimensional (3D) clinostat. Microgravity induced early and late apoptosis, extracellular matrix proteins, endothelin-1 (ET-1) and TGF-beta(1) expression. Microgravity reduced eNOS mRNA within 24 h. Moreover, a six- to eightfold higher amount of IL-6 and IL-8 was secreted within 24 h micro g. In addition, microgravity induced a duplication of NF-kappaB p50, while p65 was quadrupled. At 1 g, bFGF application (4 h) reduced ET-1, TGF-beta(1) and eNOS gene expression. After 24 h, bFGF enhanced fibronectin, VEGF, Flk-1, Flt-1, the release of IL-6, IL-8, and TGF-beta(1). Furthermore, bFGF promoted apoptosis, reduced NFkB p50, but enhanced NFkB p65. After 4 h micro g, bFGF decreased TGF-beta(1), eNOS, and ET-1 gene expression. After 24 h micro g, bFGF elevated fibronectin, Flk-1 and Flt-1 protein, and reduced IL-6 and IL-8 compared with vehicle treated micro g cultures. In micro g, bFGF enhanced NF-KappaB p50 by 50%, Bax by 25% and attenuated p65, activation of caspase-3 and annexin V-positive cells. bFGF differently changes intracellular signals in ECs depending whether it is applied under microgravity or normal gravity conditions. In microgravity, bFGF contributes to protect the EC from apoptosis.

LOX-1 deletion decreases collagen accumulation in atherosclerotic plaque in low-density lipoprotein receptor knockout mice fed a high-cholesterol diet

AIMS

Collagen, as a component of the extracellular matrix, has been linked to atherosclerotic plaque formation and stability. Activation of LOX-1, a lectin-like oxidized low-density lipoprotein (LDL) receptor-1, exerts a significant role in collagen formation. We examine the hypothesis that LOX-1 deletion may inhibit collagen accumulation in atherosclerotic arteries in LDL receptor (LDLR) knockout (KO) mice.

METHODS AND RESULTS

We generated LOX-1 KO and LOX-1/LDLR double KO mice on a C57BL/6 (wild-type mice) background and fed a 4% cholesterol/10% cocoa butter diet for 18 weeks. Vessel wall collagen accumulation was increased in association with atherogenesis in the LDLR KO mice (P < 0.01 vs. wild-type mice), but much less so in the double KO mice (P < 0.01 vs. LDLR KO mice). Collagen accumulation data were corroborated with pro-collagen I measurements. Expression/activity of osteopontin, fibronectin, and matrix metalloproteinases (MMP-2 and MMP-9) was also increased in the LDLR KO mice (P < 0.01 vs. wild-type mice), but not in the mice with LOX-1 deletion (P < 0.01 vs. LDLR KO mice). The expression of NADPH oxidase (p47(phox), p22(phox), gp91(phox), and Nox-4 subunits) and nitrotyrosine was increased in the LDLR KO mice (P < 0.01 vs. wild-type mice) and not in mice with LOX-1 deletion (P < 0.01 vs. LDLR KO mice). Phosphorylation of Akt-1 and endothelial nitric oxide synthase and expression of haem-oxygenase-1 were found to be reduced in the LDLR KO mice (P < 0.01 vs. wild-type mice), but not in the mice with LOX-1 deletion (P < 0.01 vs. LDLR KO mice).

CONCLUSION

LOX-1 deletion reduces enhanced collagen deposition and MMP expression in atherosclerotic regions via inhibition of pro-oxidant signals.

Modeled gravitational unloading induced downregulation of endothelin-1 in human endothelial cells

Many space missions have shown that prolonged space flights may increase the risk of cardiovascular problems. Using a three-dimensional clinostat, we investigated human endothelial EA.hy926 cells up to 10 days under conditions of simulated microgravity (microg) to distinguish transient from long-term effects of microg and 1g. Maximum expression of all selected genes occurred after 10 min of clinorotation. Gene expression (osteopontin, Fas, TGF-beta(1)) declined to slightly upregulated levels or rose again (caspase-3) after the fourth day of clinorotation. Caspase-3, Bax, and Bcl-2 protein content was enhanced for 10 days of microgravity. In addition, long-term accumulation of collagen type I and III and alterations of the cytoskeletal alpha- and beta-tubulins and F-actin were detectable. A significantly reduced release of soluble factors in simulated microgravity was measured for brain-derived neurotrophic factor, tissue factor, vascular endothelial growth factor (VEGF), and interestingly for endothelin-1, which is important in keeping cardiovascular balances. The gene expression of endothelin-1 was suppressed under microg conditions at days 7 and 10. Alterations of the vascular endothelium together with a decreased release of endothelin-1 may entail post-flight health hazards for astronauts.

Osteopontin expression is required for myofibroblast differentiation

Osteopontin (OPN) is a multifunctional cytokine that is strongly expressed in healing wounds and fibrotic lesions, both of which are characterized by the formation of myofibroblasts. We examined the role of OPN in myofibroblast differentiation induced by the profibrotic cytokine transforming growth factor-beta1. In cultured cardiac or dermal fibroblasts treated with transforming growth factor-beta1, there was a 2- to 5-fold increase in the expression of the myofibroblast markers alpha-smooth muscle actin and extradomain A fibronectin but no significant increase of these proteins in OPN-null fibroblasts. Phalloidin staining for actin filaments and immunostaining for alpha-smooth muscle actin and focal adhesion proteins showed reduced stress fibers, focal adhesions, and lamellipodia in OPN-null fibroblasts compared with wild-type cells. OPN-null fibroblasts exhibited 40% to 60% less spreading, 50% less resistance to detachment by shear force, and a approximately 3-fold reduction in collagen gel contraction. These defects were partially rescued by ectopic expression of OPN. Mass spectrometric analysis of proteins in focal adhesions formed on collagen type I beads revealed an enrichment of HMGB1 protein in wild-type cells, whereas HMGB1 was not detected in OPN-null cells. Treatment of wild-type cells with small interfering RNA to knock down OPN reduced transforming growth factor-beta1-induced alpha-smooth muscle actin and HMGB1 to levels observed in OPN-null cells. These studies demonstrate that OPN is required for the differentiation and activity of myofibroblasts formed in response to the profibrotic cytokine transforming growth factor-beta1.

Effects of chronic therapy with cardiac contractility modulation electrical signals on cytoskeletal proteins and matrix metalloproteinases in dogs with heart failure

OBJECTIVES

Therapy with cardiac contractility modulation (CCM) electrical signals delivered to left ventricular (LV) muscle during the absolute refractory period improves LV systolic and diastolic function in dogs with heart failure (HF). This study examined the effects of CCM therapy on mRNA and protein expression of cytoskeletal proteins, matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) in the LV myocardium of dogs with HF.

METHODS

HF was produced in 14 dogs by coronary microembolizations. Dogs were randomized to 3 months of CCM therapy (n = 7) or to sham-operated controls (n = 7). LV tissue from 6 normal (NL) dogs was used for comparison. mRNA expression was measured using reverse-transcriptase polymerase chain reaction and protein expression using Western blots.

RESULTS

Compared with NL dogs, controls showed upregulation of mRNA and protein expression of the cytoskeletal proteins tubulin and fibronectin and MMP-1, MMP-2 and MMP-9, and downregulation of the cytoskeletal protein titin. Normalized expression of all these genes and proteins was seen after CCM therapy. No differences in expression of TIMP-1 and TIMP-2 were observed among groups.

CONCLUSIONS

CCM therapy normalizes expression of key cytoskeletal proteins and MMPs and may partly explain the improvement in LV function seen in HF following CCM therapy.

Expression of vascular endothelial growth factor and receptor tyrosine kinases in cardiac ischemia/reperfusion injury

INTRODUCTION

Vascular endothelial growth factor (VEGF) expression is regulated by hypoxia and cytokines, including insulin-like growth factor (IGF)-1. We examined the influence of ischemia/reperfusion (I/R) on IGF-1, VEGF, fetal liver kinase (flk-1), fms-like tyrosine kinase-1 (flt-1), and laminin using an isolated hemoperfused working porcine heart model of acute ischemia (2 h) and reperfusion (4 h).

METHODS

Twenty-three porcine hearts were randomized into the following groups: five nonischemic control hearts (Group C), five I/R hearts with occlusion of the ramus circumflexus; three I/R hearts treated with quinaprilat, a potent angiotensin-converting enzyme (ACE) inhibitor (Group Q); five I/R hearts treated with angiotensin I (Group Ang I), and 5 I/R hearts treated with Ang I and quinaprilat (Group QA).

RESULTS

Compared to C, VEGF mRNA and protein contents were significantly increased in I/R and Ang I hearts. flk-1 and flt-1 were increased in I/R (2.2-/1.95-fold) and further elevated by Ang I (3.2-/3.4-fold) compared with C. Quinaprilat application attenuated the amount of VEGF significantly and of flk-1 slightly but not that of flt-1. In contrast, IGF-1 and IGF-1 receptor (IGF-1R) proteins were elevated in I/R hearts (3-/1.4-fold vs. C) and further increased in the presence of Q. These findings were accompanied by an elevation of laminin mRNA and protein levels. Moreover, we observed an increase in collagen Type IV and chondroitin sulfate content in I/R (2.9-/1.4-fold) and Ang I (3.5-/1.5-fold) hearts. Quinaprilat significantly reduced laminin and chondroitin sulfate proteins.

CONCLUSION

These data suggest that the VEGF/VEGF receptor and IGF-1-IGF-1R systems are activated by I/R. The benefits of ACE inhibition in attenuation of cardiac remodeling may be mediated by IGF-1.

Blockade of hypoxia-reoxygenation-mediated collagen type I expression and MMP activity by overexpression of TGF-β1delivered by AAV in mouse cardiomyocytes

Transforming growth factor (TGF)-β1is one of the most pleiotropic and multifunctional peptides known. While the cardioprotective effect of TGF-β1during ischemia is well known, the specific role of TGF-β1in altering the cardiac remodeling process remains unclear. This study was designed to examine the regulation of hypoxia-reoxygenation-mediated collagen type I expression and activity of matrix metalloproteinases (MMPs) by overexpression of TGF-β1in cultured HL-1 mouse cardiomyocytes. TGF-β1was overexpressed in cardiomyocytes by transfection with adeno-associated virus (AAV)/TGF-β1Latentor with AAV/TGF-β1ACT(active TGF-β1). Twenty-four hours of hypoxia followed by 3 h of reoxygenation (H-R) markedly enhanced (pro)collagen type I expression and activity of MMPs concomitant with an increase in reactive oxygen species (ROS) release and LOX-1 expression. Overexpression of TGF-β1reduced these alterations induced by H-R. TGF-β1overexpression also blocked H-R-mediated p38 and p44/42 MAPK activation. Transfection with AAV/TGF-β1ACTwas superior to that with AAV/TGF-β1Latent. These data for the first time demonstrate that H-R induces signals for cardiac remodeling in cardiomyocytes and TGF-β1can modulate, possibly via antioxidant mechanism, these signals. These findings contribute to further understanding of the role of TGF-β1in the cardiac remodeling process.

Mesenchymal stem cells use integrin beta1 not CXC chemokine receptor 4 for myocardial migration and engraftment

Recent evidence has demonstrated the importance of bone marrow-derived mesenchymal stem cells (BM-MSCs) in the repair of damaged myocardium. The molecular mechanisms of engraftment and migration of BM-MSCs in the ischemic myocardium are unknown. In this study, we developed a functional genomics approach toward the identification of mediators of engraftment and migration of BM-MSCs within the ischemic myocardium. Our strategy involves microarray profiling (>22,000 probes) of ischemic hearts, complemented by reverse transcription-polymerase chain reaction and fluorescence-activated cell sorting of corresponding adhesion molecule and cytokine receptors in BM-MSCs to focus on the coexpressed pairs only. Our data revealed nine complementary adhesion molecules and cytokine receptors, including integrin beta1, integrin alpha4, and CXC chemokine receptor 4 (CXCR4). To examine their functional contributions, we first blocked selectively these receptors by preincubation of BM-MSCs with specific neutralizing antibodies, and then we administered these cells intramyocardially. A significant reduction in the total number of BM-MSC in the infarcted myocardium was observed after integrin beta1 blockade but not integrin alpha4 or CXCR4 blockade. The latter observation is distinctively different from that reported for hematopoietic stem cells (HSCs). Thus, our data show that BM-MSCs use a different pathway from HSCs for intramyocardial trafficking and engraftment.

Mechanisms of apoptosis after ischemia and reperfusion: role of the renin-angiotensin system

BACKGROUND

Apoptosis plays a key role in the pathogenesis of cardiac diseases. We examined the influence of the renin-angiotensin system (RAS) on different regulators of apoptosis using an isolated hemoperfused working porcine heart model of acute ischemia (2 h), followed by reperfusion (4 h).

METHODS AND RESULTS

23 porcine hearts were randomized to 5 groups: hemoperfused non-infarcted hearts (C), infarcted hearts (MI: R. circumflexus), infarcted hearts treated with quinaprilat (Q), infarcted hearts treated with angiotensin-I (Ang I), and infarcted hearts treated with angiotensin-I and quinaprilat (QA). Fas, Bax, bcl-2 and p53 proteins were increased in MI hearts and further elevated by Ang I. Quinaprilat reduced Bax and p53. Bcl-2 was elevated in Q and reduced in QA. An early upregulation of caspase-3 gene and protein expression was detected in MI and Ang I hearts compared to C. Q reduced caspase-3 gene expression, but had no effect on caspase-3 and Fas protein.

CONCLUSIONS

These data suggest that the RAS plays a pivotal role in cardiac apoptosis which is the early and predominant form of death in myocardial infarction. Ischemia/reperfusion induces programmed cell death via extrinsic and intrinsic pathways. Early treatment with quinaprilat attenuated cardiomyocyte apoptosis.

Induction of three-dimensional assembly and increase in apoptosis of human endothelial cells by simulated microgravity: impact of vascular endothelial growth factor

Endothelial cells play a crucial role in the pathogenesis of many diseases and are highly sensitive to low gravity conditions. Using a three-dimensional random positioning machine (clinostat) we investigated effects of simulated weightlessness on the human EA.hy926 cell line (4, 12, 24, 48 and 72 h) and addressed the impact of exposure to VEGF (10 ng/ml). Simulated microgravity resulted in an increase in extracellular matrix proteins (ECMP) and altered cytoskeletal components such as microtubules (alpha-tubulin) and intermediate filaments (cytokeratin). Within the initial 4 h, both simulated microgravity and VEGF, alone, enhanced the expression of ECMP (collagen type I, fibronectin, osteopontin, laminin) and flk-1 protein. Synergistic effects between microgravity and VEGF were not seen. After 12 h, microgravity further enhanced all proteins mentioned above. Moreover, clinorotated endothelial cells showed morphological and biochemical signs of apoptosis after 4 h, which were further increased after 72 h. VEGF significantly attenuated apoptosis as demonstrated by DAPI staining, TUNEL flow cytometry and electron microscopy. Caspase-3, Bax, Fas, and 85-kDa apoptosis-related cleavage fragments were clearly reduced by VEGF. After 72 h, most surviving endothelial cells had assembled to three-dimensional tubular structures. Simulated weightlessness induced apoptosis and increased the amount of ECMP. VEGF develops a cell-protective influence on endothelial cells exposed to simulated microgravity.

Effect of meiotic recombination on the production of aneuploid gametes in humans

Within the last decade, aberrant meiotic recombination has been confirmed as a molecular risk factor for chromosome nondisjunction in humans. Recombination tethers homologous chromosomes, linking and guiding them through proper segregation at meiosis I. In model organisms, mutations that disturb the recombination pathway increase the frequency of chromosome malsegregation and alterations in both the amount and placement of meiotic recombination are associated with nondisjunction. This association has been established for humans as well. Significant alterations in recombination have been found for all meiosis I-derived trisomies studied to date and a subset of so called "meiosis II" trisomy. Often exchange levels are reduced in a subset of cases where the nondisjoining chromosome fails to undergo recombination. For other trisomies, the placement of meiotic recombination has been altered. It appears that recombination too near the centromere or too far from the centromere imparts an increased risk for nondisjunction. Recent evidence from trisomy 21 also suggests an association may exist between recombination and maternal age, the most widely identified risk factor for aneuploidy. Among cases of maternal meiosis I-derived trisomy 21, increasing maternal age is associated with a decreasing frequency of recombination in the susceptible pericentromeric and telomeric regions. It is likely that multiple risk factors lead to nondisjunction, some age dependent and others age independent, some that act globally and others that are chromosome specific. Future studies are expected to shed new light on the timing and placement of recombination, providing additional clues to the link between altered recombination and chromosome nondisjunction.