RESUMEN
Myocardial ischemia-reperfusion injury represents a combination of factors, namely the intrinsic cellular response to ischemia and the extrinsic acute inflammatory response. Recent studies in mesenteric and skeletal muscle reperfusion models identified natural IgM as a major initiator of pathology through the activation of the complement system and inflammatory cells. To determine whether a similar mechanism is involved in myocardial tissues, mice bearing an altered natural IgM repertoire (Cr2-/-) were examined in a murine model of coronary artery ischemia. Notably, these mice were significantly protected based on the reduced infarct size, limited apoptosis of cardiomyocytes, and decreased neutrophil infiltration. Protection was IgM-dependent as reconstitution of these mice with wild-type IgM restored myocardial reperfusion injury. These results support a model in which natural IgM initiates the acute inflammatory response in the myocardium following ischemia and reperfusion.
Asunto(s)
Inmunoglobulina M/fisiología , Isquemia Miocárdica/inmunología , Daño por Reperfusión Miocárdica/inmunología , Daño por Reperfusión Miocárdica/patología , Animales , Apoptosis , Modelos Animales de Enfermedad , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Ratones , Ratones Mutantes , Necrosis , Neutrófilos/patología , Receptores de Complemento/genéticaRESUMEN
The immune system of higher vertebrates consists of two components: the innate and adaptive immunity. While the adaptive immune system relies on somatically generated and clonally selected antigen receptors, the innate immune system detects the presence of pathogens by their evolutionarily highly conserved, relatively invariant structural motifs. Interestingly, recent data suggest that activation of the innate immune system could play an important role in various diseases without the direct involvement of infectious pathogens. For example, a number of inflammatory cytokines, including TNF (tumor necrosis factor), IL (interleukin)-1beta, IL-6 and IL-8, as well as iNOS (inducible nitric oxide synthase), all components of innate immunity, are also implicated in ischemia/reperfusion injury, and in the abnormal myocardial remodeling characteristic of chronic heart failure. Understanding of the regulation and activation of the innate immune system in diseases not obviously related to an immune response to specific pathogen could provide new therapeutic targets for cardiovascular diseases. Thus, in this review, we provide a general overview of the components of innate immunity with a focus on humoral factors, their role in the response to foreign pathogens, and their potential role in the response to tissue injury (i.e., the "Expanded Self-Non-Self" and the "Danger" theories of immune activation).
Asunto(s)
Cardiopatías/inmunología , Inmunidad Innata/fisiología , Miocardio/inmunología , Animales , Cardiopatías/sangre , HumanosRESUMEN
Activation of an innate immune response is among the first lines of defense after tissue injury. Restoring blood flow to the site of injured tissue is often a necessary prerequisite for mounting an initial immune response to pathogens and for subsequent initiation of a successful repair of wounded tissue. The multiple links among pathogen recognition and suppression, increased angiogenesis, and tissue repair are the topics of this review, which examines of the roles of antimicrobial peptides, mammalian toll-like receptors (TLRs), inflammatory cytokines, and putative "danger" signals, among other signaling pathways, in triggering, sustaining, and then terminating an angiogenic response.
Asunto(s)
Inmunidad Innata , Neovascularización Fisiológica , Cicatrización de Heridas/fisiología , Adenosina/fisiología , Proteínas Angiogénicas/fisiología , Animales , Péptidos Catiónicos Antimicrobianos/fisiología , Citocinas/fisiología , Sustancias de Crecimiento/fisiología , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia , Infecciones/inmunología , Infecciones/fisiopatología , Glicoproteínas de Membrana/fisiología , Ratones , Ratones Mutantes , Ratas , Receptores de Superficie Celular/fisiología , Transducción de Señal , Receptores Toll-Like , Factores de Transcripción/fisiología , Factor A de Crecimiento Endotelial Vascular/fisiología , Vasodilatación , Cicatrización de Heridas/inmunología , Heridas y Lesiones/inmunología , Heridas y Lesiones/fisiopatologíaRESUMEN
BACKGROUND: Myocardial ischemia and reperfusion-induced tissue injury involve a robust inflammatory response, but the proximal events in reperfusion injury remain incompletely defined. Toll-like receptor 4 (TLR4) is a proximal signaling receptor in innate immune responses to lipopolysaccharide of Gram-negative pathogens. TLR4 is also expressed in the heart and vasculature, but a role for TLR4 in the myocardial response to injury separate from microbial pathogens has not been examined. This study assessed the role of TLR4 in myocardial infarction and inflammation in a murine model of ischemia-reperfusion injury. METHODS AND RESULTS: Myocardial ischemia-reperfusion (MIR) was performed on 2 strains of TLR4-deficient mice (C57/BL10 ScCr and C3H/HeJ) and controls (C57/BL10 ScSn and C3H/OuJ). Mice were subjected to 1 hour of coronary ligation, followed by 24 hours of reperfusion. TLR4-deficient mice sustained significantly smaller infarctions compared with control mice given similar areas at risk. Fewer neutrophils infiltrated the myocardium of TLR4-deficient Cr mice after MIR, indicated by less myeloperoxidase activity and fewer CD45/GR1-positive cells. The myocardium of TLR4-deficient Cr mice contained fewer lipid peroxides and less complement deposition compared with control mice after MIR. Serum levels of interleukin-12, interferon-gamma, and endotoxin were not increased after ischemia-reperfusion. Neutrophil trafficking in the peritoneum was similar in all strains after injection of thioglycollate. CONCLUSIONS: TLR4-deficient mice sustain smaller infarctions and exhibit less inflammation after myocardial ischemia-reperfusion injury. The data suggest that in addition to its role in innate immune responses, TLR4 serves a proinflammatory role in murine myocardial ischemia-reperfusion injury.
Asunto(s)
Glicoproteínas de Membrana/fisiología , Daño por Reperfusión Miocárdica/inmunología , Receptores de Superficie Celular/fisiología , Animales , Inflamación/patología , Glicoproteínas de Membrana/genética , Ratones , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , Ratones Noqueados , Infarto del Miocardio/patología , Receptores de Superficie Celular/genética , Receptor Toll-Like 4 , Receptores Toll-LikeRESUMEN
We have found that neuregulin-1beta (NRG-1beta) is expressed in the cardiac microvascular endothelium, and promotes the growth and survival of cardiac myocytes in culture through the activation of erbB2 and erbB4 receptor tyrosine kinases. In this study, we examined the role of NRG-1/erbB signaling in protection of cardiac myocytes from anthracycline-induced apoptosis in vitro to determine the coupling between erbB receptor subtypes and cytoprotective signaling. Treatment of neonatal rat ventricular myocytes with NRG-1beta inhibited daunorubicin-induced apoptosis as shown by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling staining for DNA fragmentation as well as flow cytometric quantification of apoptotic myocytes. Daunorubicin-induced activation of caspase-3 in cardiomyocytes was similarly inhibited by NRG-1beta. The phosphoinositol-3-kinase (PI3-kinase) inhibitor wortmannin prevented the effects of NRG-1beta on daunorubicin-induced apoptosis and activation of caspase-3. NRG-1beta treatment induced rapid activation of Akt/PKB that was inhibited by wortmannin, and adenoviral-mediated overexpression of a dominant-negative Akt prevented the protective effect of NRG-1beta. Akt activation by NRG-1beta was prevented by the tyrphostin AG1478, which we show inhibits erbB4 activation by NRG-1beta. In contrast, the erbB2-specific tyrphostin AG879 had no effect on NRG-1beta activation of Akt. Myocyte treatment with an activating antibody to erbB2 caused phosphorylation of erbB2, and led to activation of Erk but not Akt. Treatment with the erbB2 antibody had no effect on anthracycline-induced apoptosis. Thus, NRG-1beta protects against anthracycline-induced apoptosis via erbB4-dependent activation of the PI3-kinase/Akt pathway.
Asunto(s)
Apoptosis/efectos de los fármacos , Miocitos Cardíacos/metabolismo , Neurregulina-1/metabolismo , Neurregulina-1/farmacología , Fosfatidilinositol 3-Quinasas/metabolismo , Adenoviridae/genética , Animales , Animales Recién Nacidos , Antraciclinas/farmacología , Células Cultivadas , Activación Enzimática , Receptores ErbB/metabolismo , Glicoproteínas/metabolismo , Ventrículos Cardíacos/citología , Miocardio/citología , Miocitos Cardíacos/efectos de los fármacos , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-akt , Ratas , Ratas Sprague-Dawley , Receptor ErbB-2 , Receptor ErbB-4RESUMEN
Objective. - Mice with targeted deletion of caspase-1 (interleukin-1beta (IL-1beta)-converting enzyme) lack the active forms of IL-1beta and IL-18, two cytokines implicated in maladaptive ventricular remodeling following cardiac injury. We, therefore, investigated the extent of ventricular dilation in caspase-1-knockout (KO) mice. Methods and results. - Transthoracic echocardiography was performed at days 1, 4, and 9 following left anterior descending artery ligation in caspase-1-KO and wild-type (WT) control animals, including M-mode and short-axis imaging at both mid-papillary and apical levels. Although initial post-operative mortality was lower in KO than in WT animals (21.4% WT, 12.0% KO, P < 0.001), there was no difference in mortality between 24 h and 9 d (P = n.s.). Caspase-1 KOs exhibited significantly less mid-papillary ventricular dilatation at days 4 and 9 compared to day 1 post-myocardial infarction (MI) (P < 0.05). Caspase-1 KOs also had a marked (50%) reduction in the level of matrix metalloproteinase 3 (MMP-3), although no significant changes occurred in other MMPs or in tissue inhibitors of metalloproteinase 1 levels by immunoblot analysis. Although IL-beta plasma levels were not detectable, both IL-18 levels and the rate of apoptosis in remodeling, non-infarcted muscle were significantly higher in WT compared to caspase-1-KO animals.Conclusion. - Mice lacking caspase-1 exhibited both improved peri-infarct survival and a decreased rate of ventricular dilatation, possibly due in part to a decrease in MMP-3 activity, IL-18 production, and a reduction in the rate of apoptosis after experimental MI.
Asunto(s)
Caspasa 1/genética , Infarto del Miocardio/patología , Función Ventricular Izquierda , Animales , Apoptosis , Bisbenzimidazol/farmacología , Northern Blotting , Western Blotting , Colágeno/metabolismo , Colorantes/farmacología , Ecocardiografía , Ensayo de Inmunoadsorción Enzimática , Eliminación de Gen , Inmunohistoquímica , Etiquetado Corte-Fin in Situ , Interleucina-1/genética , Interleucina-18/genética , Metaloproteinasa 1 de la Matriz/genética , Metaloproteinasa 3 de la Matriz/genética , Ratones , Ratones Noqueados , Mutagénesis Sitio-Dirigida , Infarto del Miocardio/genética , Miocardio/citología , Factores de TiempoRESUMEN
Strong evidence links cardiomyocyte loss to the pathology of some forms of heart failure. Both necrotic and apoptotic modes of cell death have been invoked as the mechanism underlying progressive cardiomyocyte dropout. Nitric oxide (NO) has received particular attention as a candidate reactive oxygen intermediate that influences not only cardiac function, but also cell death elicited by both apoptotic and necrotic mechanisms. NO is produced by resident cardiac cells under stress, and is produced in large quantities by activated immune cells that infiltrate the injured heart. A review of the literature, however, reveals that the actions of NO on apoptotic cell death are complex, especially in the context of heart disease, and that the practical contribution of NO to cell death in heart disease is yet to be defined.
Asunto(s)
Apoptosis/fisiología , Insuficiencia Cardíaca/metabolismo , Daño por Reperfusión Miocárdica/metabolismo , Óxido Nítrico/metabolismo , Disfunción Ventricular Izquierda/metabolismo , Genes Supresores de Tumor , Insuficiencia Cardíaca/fisiopatología , Trasplante de Corazón/fisiología , Humanos , Daño por Reperfusión Miocárdica/fisiopatología , Óxido Nítrico/genética , Disfunción Ventricular Izquierda/fisiopatologíaRESUMEN
The Toll-like receptor 4 (TLR4) has recently been shown to function as the major upstream sensor for LPS. In this study, a rodent model of lung injury following resuscitated hemorrhagic shock was used to examine the regulation of TLR4 gene and protein expression in vivo and in vitro. Intratracheal LPS alone induced a rapid reduction in whole lung TLR4 mRNA, an effect which is also observed in recovered alveolar macrophages. This effect appeared to be due to a lowering of TLR4 mRNA stability by approximately 69%. By contrast, while shock/resuscitation alone had no effect on TLR4 mRNA levels, it markedly altered the response to LPS. Specifically, antecedent shock prevented the LPS-induced reduction in TLR4 mRNA levels. This reversal was explained by the ability of prior resuscitated shock both to prevent the destabilization of TLR4 mRNA by LPS and also to augment LPS-stimulated TLR4 gene transcription compared with LPS alone. Oxidant stress related to shock/resuscitation appeared to contribute to the regulation of TLR4 mRNA, because supplementation of the resuscitation fluid with the antioxidant N-acetylcysteine reversed the ability of shock/resuscitation to preserve TLR4 mRNA levels following LPS. TLR4 protein levels in whole lung mirrored the changes seen for TLR4 mRNA. Considered in aggregate, these data suggest that levels of tlr4 expression are controlled both transcriptionally as well as posttranscriptionally through altered mRNA stability and that antecedent shock/resuscitation, a form of global ischemia/reperfusion, might influence regulation of this gene.
Asunto(s)
Proteínas de Drosophila , Lipopolisacáridos/toxicidad , Pulmón/inmunología , Pulmón/metabolismo , Glicoproteínas de Membrana/biosíntesis , Receptores de Superficie Celular/biosíntesis , Choque Hemorrágico/inmunología , Choque Hemorrágico/metabolismo , Animales , Líquido del Lavado Bronquioalveolar/inmunología , Modelos Animales de Enfermedad , Macrófagos Alveolares/inmunología , Macrófagos Alveolares/metabolismo , Masculino , Glicoproteínas de Membrana/genética , Estrés Oxidativo/genética , Estrés Oxidativo/inmunología , ARN Mensajero/biosíntesis , Ratas , Ratas Sprague-Dawley , Receptores de Superficie Celular/genética , Daño por Reperfusión/genética , Daño por Reperfusión/inmunología , Choque Hemorrágico/genética , Receptor Toll-Like 4 , Receptores Toll-LikeAsunto(s)
Sistema Cardiovascular/metabolismo , Caveolas/metabolismo , Membrana Celular/metabolismo , Canales Iónicos/metabolismo , Agonistas Adrenérgicos beta/farmacología , Animales , Anticuerpos/farmacología , Señalización del Calcio/fisiología , Caveolina 3 , Caveolinas/antagonistas & inhibidores , Caveolinas/metabolismo , Compartimento Celular/fisiología , Humanos , Ratones , Transporte de Proteínas/efectos de los fármacos , Transporte de Proteínas/fisiología , Sarcolema/metabolismo , Transducción de Señal/fisiología , Canales de Sodio/metabolismo , Sistema Nervioso Simpático/fisiologíaRESUMEN
The cellular response to hypoxia depends on rapid posttranslational modifications of proteins as well as regulation of gene expression. We performed serial analysis of gene expression (SAGE) on human cardiac cells under normoxia, subjected to hypoxia, or infected with Ad2/HIF-1alpha/VP16 (an adenoviral vector expressing a stable hybrid form of hypoxia-inducible factor 1alpha) or Ad2/CMVEV (an empty vector). Of the 97,646 SAGE tags that were sequenced, 27% matched GenBank entries, while an additional 32% matched expressed sequence tags (ESTs) in UniGene. We analyzed 161 characterized genes or ESTs with a putative identification. Expression of 35, 11, and 46 genes was increased by hypoxia, infection with Ad2/EVCMV, or infection with Ad2/HIF-1alpha/VP16, respectively, compared with normoxia; conversely, 20, 11, 38 genes, respectively, were expressed at lower levels. Genes regulated by hypoxia were associated with transcription, biosynthesis, extracellular matrix formation, glycolysis, energy production, cell survival, and cell stress. Changes following infection with Ad2/HIF-1alpha/VP16 mimicked the hypoxic response to a certain extent. Infection with Ad2/CMVEV affected expression of genes that were associated with extracellular matrix formation and membrane trafficking. Differential expression of select genes was confirmed using TaqMan in additional human cardiac cells and rat neonatal ventricular myocytes. These data provide insight into gene expression underlying the diverse and complex cellular response to hypoxia, expression of HIF-1alpha/VP16, or adenoviral infection.
Asunto(s)
Corazón Fetal/metabolismo , Corazón Fetal/fisiopatología , Perfilación de la Expresión Génica/métodos , Hipoxia/fisiopatología , Miocardio/metabolismo , Proteínas Recombinantes de Fusión/genética , Factores de Transcripción/genética , Adenoviridae/genética , Células Cultivadas , Regulación hacia Abajo/genética , Corazón Fetal/citología , Corazón Fetal/fisiología , Regulación de la Expresión Génica/fisiología , Vectores Genéticos/biosíntesis , Vectores Genéticos/genética , Vectores Genéticos/fisiología , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia , Miocardio/citología , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/fisiología , Factores de Transcripción/biosíntesis , Factores de Transcripción/fisiología , Regulación hacia Arriba/genéticaRESUMEN
In most cell types a family of transcriptional regulatory proteins termed hypoxia-inducible factors, of which HIF-1 is the most prevalent, mediates the physiologic response to hypoxia. Although much has been learned over the past decade since the discovery of the first HIF family member, the proximal signaling events linking a decline in oxygen concentration to the activation of HIF-dependent signaling are only now being clarified. Activation of HIF-1 in eukaryotes induces expression of many genes that assist in adapting the organism to an environment in which oxygen is limiting, such as of genes involved in new blood vessel formation, including isoforms of vascular endothelial growth factor and angiopoietins, among others. Targeted expression of constitutively active HIF transgenes to ischemic tissues may be beneficial as a form of therapeutic angiogenesis.