Abstract-Cardiac remodeling in response to pressure overload involves reorganization of the myocytes and extracellular matrix (ECM). Neurohormonal pathways have been described as effector pathways in left ventricular ECM reorganization in response to pressure overload; we now are assessing the role of the T lymphocyte in this process. Mice with defined differences in T-lymphocyte function (C57BL/6 SCID, C57BL/6 WT, and BALB/c) were treated with 50 mg/L of N G -nitro-L-arginine methyl ester in their drinking water for 30 days. The immune function of C57BL/6 WT mice was T-helper type 1 (TH1), BALB/c was TH2, and C57BL/6 SCID was null. The arterial blood pressure increased by 30% in all of the strains of mice. However, ventricular stiffness significantly decreased in the C57 SCID, significantly increased in the BALB/c, and did not change in the C57 WT. The characterization of matrix metalloproteinase induction and activation on day 30 was associated with T-lymphocyte function. The total cardiac fibrillar collagen, percentage of fibrillar collagen cross-linking, and the activity of the cross-linking enzyme lysyl oxidase-like-3 (LOXL-3) significantly decreased in the C57 SCID, significantly increased in the BALB/c, and did not change in the C57 WT. This study revealed that the LOXL-3 pathway, namely, gene expression, enzymatic activities, and LOXL-3-mediated collagen cross-linking, was associated with ventricular stiffness and incongruence with lymphocyte function. These data support the concept that the T lymphocytes may play a fundamental regulatory role in cardiac ECM composition through modulation of collagen synthesis, degradation, and cross-linking. Key Words: lymphocytes Ⅲ ventricular function Ⅲ collagen I n response to hypertension, the myocardium undergoes a series of changes, including adaptation of the extracellular matrix (ECM) composition. ECM remodeling leading to heart failure is characterized by disproportionate ECM fibrillar collagen synthesis and degradation 1 and collagen crosslinking by the enzyme lysyl oxidase (LOX). 2 These processes are mediated primarily by the cardiac fibroblast (CF), and, therefore, factors that modulate CF function will determine the nature of ECM remodeling in response to increased wall stress. It is understood that the CF function is under local as well as neurohormonal control. 3 We suggest that CF function is also affected by T-lymphocyte function.T lymphocytes participate in a regulatory role of virtually all immune responses and most nonlymphoid tissues. Several lines of evidence have shown that T lymphocytes are an essential component in the remodeling processes of noncardiac tissues, 4,5 and others have suggested a role in cardiovascular remodeling and heart failure. 2,6 The cytokine profile that has been used to describe subtypes of T-helper (CD4 ϩ ) lymphocytes is namely TH1 and TH2. 7 It is accepted that a pathological increase in neuroendocrine mediators and wall stress induce cardiac remodeling, and we proposed that, in a similar manner, a difference in TH1/TH2...

Rationale: The giant protein titin plays key roles in myofilament assembly and determines the passive mechanical properties of the sarcomere. The cardiac titin molecule has 2 mayor elastic elements, the N2B and the PEVK region. Both have been suggested to determine the elastic properties of the heart with loss of function data only available for the N2B region. Objective: The purpose of this study was to investigate the contribution of titin's proline-glutamate-valine-lysine (PEVK) region to biomechanics and growth of the heart. Methods and Results: We removed a portion of the PEVK segment (exons 219 to 225; 282 aa) that corresponds to the PEVK element of N2B titin, the main cardiac titin isoform. Adult homozygous PEVK knockout (KO) mice developed diastolic dysfunction, as determined by pressure-volume loops, echocardiography, isolated heart experiments, and muscle mechanics. Immunoelectron microscopy revealed increased strain of the N2B element, a spring region retained in the PEVK-KO. Interestingly, the PEVK-KO mice had hypertrophied hearts with an induction of the hypertrophy and fetal gene response that includes upregulation of FHL proteins. This contrasts the cardiac atrophy phenotype with decreased FHL2 levels that result from the deletion of the N2B element. Key Words: diastole Ⅲ connectin Ⅲ hypertrophy Ⅲ compliance Ⅲ FHL T itin is the largest protein in mammals and forms a continuous elastic filament along the myofibril (reviewed in 1 ). Because of its enormous size, titin is a prominent target for mutations that give rise to diseases such as familial dilated cardiomyopathy and muscular dystrophy. 2,3 Titin's extensible region resides in the I-band of the sarcomere and consists of immunoglobulin (Ig)-like domains arranged in tandem, the heart specific N2B element, and the prolineglutamate-valine-lysine (PEVK) element. 4 The PEVK element is thought to function as a largely unfolded polypeptide that extends at low force levels and that thereby provides an important source of elasticity at physiological sarcomere lengths. [5][6][7] Unlike the 1-exon heart specific N2B element, the titin gene contains 112 PEVK exons that are differentially expressed between muscle types. 8 Of these PEVK exons, 219 to 225 are expressed in the so-called N2B titin isoform, that constitutes the dominant cardiac isoform in the left ventricle of a wide range of species, including rodents and human. 9 Here we generated a mouse deficient in titin's exons 219 to 225 that results in a deletion of the c-terminal PEVK region (282 aa) and determined its role in cardiac function using echocardiography, in vivo pressure-volume loops, isolated heart physiology, muscle mechanics, immunoelectron microscopy, and expression analysis. We investigated the hypertrophy phenotype and studied members of the four-and-a-half LIM family involved in atrophy/hypertrophy signaling-FHL1 and FHL2. 10,11 Our results reveal the strong effect of the PEVK element on diastolic function but also that the role of the PEVK extends beyond that of a mechanical spr...

The induction of T helper (TH) lymphocytes by distinct TH ligands results in a differentiation to TH1/TH2 subsets based on their unique pattern of cytokine secretion and effector functions. We hypothesized that the relative proportion of TH1/TH2 directly relates to cardiac fibroblast (CF) function and thereby cardiac extracellular matrix (ECM) composition and cardiac diastolic function in the absence of injury or altered wall stress. We compared the effect of selective TH1 with TH2 inducers on cardiac gene expression, ECM composition, and diastolic function in C57BL/J mice. Twelve weeks after immune modulation, the left ventricular stiffness (beta) was significantly increased in the TH1 group and decreased in the TH2 group (P < 0.01). The TH2 group also demonstrated significantly increased end-diastolic and end-systolic volumes (P < 0.01). Cardiac gene expression patterns for pro-matrix metalloproteinase (MMP)-9 and -13 were increased by greater than fivefold in the TH2 group and significantly decreased in the TH1 group (P < 0.05). The total cardiac collagen and cross-linked collagen were significantly increased in the TH1 group and decreased in the TH2 group (P < 0.01). Coculturing lymphocytes harvested from the treated mice with naive primary CF demonstrated a direct control of the lymphocytes on CF pro-collagen, pro-MMP gene expression, and MMP activity. These results suggest that the TH phenotype differentially affects diastolic function through modulating CF pro-collagen and pro-MMP gene expression, MMP activity, and cardiac collagen cross-linking, resulting in altered ECM composition. Thus modulation of TH lymphocyte function could promote adaptive remodeling in heart failure and postmyocardial infarction.

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Osteopontin (OPN), a key component of the extracellular matrix, is associated with the fibrotic process during tissue remodeling. OPN and the cytokine interleukin (IL)-18 have been shown to be overexpressed in an array of human cardiac pathologies. In the present study, we determined the role of IL-18 in the regulation of cardiac OPN expression and the subsequent interstitial fibrosis and diastolic dysfunction. We demonstrated parallel increases in IL-18, OPN expression, and interstitial fibrosis in murine models of left ventricular pressure and volume overload. Exogenous recombinant (r)IL-18 administered for 2 wk increased cardiac OPN expression, interstitial fibrosis, and diastolic dysfunction. Stimulation of the T helper (Th)1 lymphocyte phenotype with a selective toll-like receptor (TLR)9 agonist induced cardiac IL-18 and OPN expression, which was associated with increased cardiac fibrillar collagen concentrations and interstitial fibrosis resulting in diastolic dysfunction. rIL-18 induced OPN expression and protein levels in primary of cardiac fibroblast cultures. Conditioned media from TLR9-stimulated T lymphocyte cultures induced IL-18 and OPN expression in cardiac fibroblasts, while blockade of the IL-18 receptor with a neutralizing antibody abolished the increase in OPN expression. Furthermore, a mutation in the transcriptional factor interferon regulatory factor (IRF)1 or IRF1 small interfering RNA (siRNA) resulted in the decreased expression of IL-18 and OPN in cardiac fibroblasts. With pressure overload, IRF1-mutant mice showed downregulation of IL-18 and OPN expression in cardiac tissue, reduced cardiac fibrotic development, and increased left ventricular function compared with wild type. These results provide direct evidence that the induction of IL-18 regulates OPN-mediated cardiac fibrosis and diastolic dysfunction. extracellular matrix; remodeling; T lymphocyte; interferon regulatory factor 1; toll-like receptor-9; lysyl oxidase LEFT VENTRICULAR REMODELING in response to pressure and/or volume overload is associated with myocardial hypertrophy, fibroblast hyperplasia, and increased concentrations of fibrillar collagen in the extracellular matrix. Recent studies have shown that pathological myocardial fibrosis may cause diastolic dysfunction and heart failure (24), whereas myocyte hypertrophy in the absence of fibrosis is considered physiological remodeling (22, 46) if the mass-to-volume ratio is preserved (5). In this study, we investigated whether interleukin (IL)-18 regulates the gene and protein expression of the matricellular protein osteopontin (OPN), a component and regulator of cardiac extracellular matrix fibrillar collagen concentrations.As reviewed by Okamoto (26), OPN also plays a critical role in the regulation of cellular proliferation and differentiation, interstitial fibrosis, arteriosclerosis, and angiogenesis. Although OPN is ubiquitously expressed in many tissues and is increased during stress-induced cardiac remodeling, it participates as a cytokine or humoral factor in the in...

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Autophagy is associated with both tumorigenic and protective effects in cancer. However, the role of autophagy in GC and CRC remains unclear. Although the translation of the basic science of autophagy into clinical practice is a long process, the modulation of autophagy as a potential therapeutic approach in GC and CRC merits further investigation.

Recently, the cytokine Interleukin-18 (IL-18) has been shown to be increased as a result of cardiac surgery. Elevated IL-18 has been associated with neurological dysfunction, systemic inflammatory response syndrome (SIRS), and multiple organ dysfunction syndrome (MODS) post open-heart surgery. The intent of the study contained herein was to determine the effect of IL-18 administration on cardiac function and structure. Eight C57BL/6 female mice were treated daily with 0.5microg/mouse of recombinant IL-18 for 7 days. Long axis echocardiography (ECHO) measurements of the anatomical and hemodynamic function of the heart for all mice were studied 24h after the last dose. The left ventricular wet weights increased from 84 +/- 1 to 93 +/- 3 mg when comparing the placebo (n = 8) with the IL-18 groups, respectively (p = 0.01). With ECHO analysis, IL-18 significantly increased left ventricular (LV) mass, the left atrium dimensions (LA), and the left ventricular posterior wall thickness (LVPW) over the 8-day time period (p < 0.01). There was a 5-fold increase in interstitial cardiac collagen content and a 30% increase in myocyte size in the IL-18 compared with the control groups (p < 0.01). Administration of IL-18 appears to induce interstitial fibrosis and myocyte hypertrophy, resulting in increased ventricular stiffness. Thus, increased IL-18 during and post open-heart surgical procedures may induce left ventricular diastolic dysfunction and affect post-operative outcomes.