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Abstract-Left ventricular (LV) remodeling leads to congestive heart failure and is a main determinant of morbidity and mortality following myocardial infarction. Therapeutic options to prevent LV remodeling are limited, which necessitates the exploration of alternative therapeutic targets. Toll-like receptors (TLRs) serve as pattern recognition receptors within the innate immune system. Activation of TLR4 results in an inflammatory response and is involved in extracellular matrix degradation, both key processes of LV remodeling following myocardial infarction. To establish the role of TLR4 in postinfarct LV remodeling, myocardial infarction was induced in wild-type BALB/c mice and TLR4-defective C3H-Tlr4 LPSϪd mice. Without affecting infarct size, TLR4 defectiveness reduced the extent of LV remodeling (end-diastolic volume: 103.7Ϯ6.8 L versus 128.5Ϯ5.7 L; PϽ0.01) and preserved systolic function (ejection fraction: 28.2Ϯ3.1% versus 16.6Ϯ1.3%; PϽ0.01), as assessed by MRI. In the noninfarcted area, interstitial fibrosis, and myocardial hypertrophy were reduced in C3H-Tlr4LPSϪd mice. In the infarcted area, however, collagen density was increased, which was accompanied by fewer macrophages, reduced inflammation regulating cytokine expression levels (interleukin [IL]-1␣, IL-2, IL-4, IL-5, IL-6, IL-10, IL-17, tumor necrosis factor-␣, interferon-␥, granulocyte/macrophage colony-stimulating factor), and reduced matrix metalloproteinase-2 (4684Ϯ515 versus 7573Ϯ611; Pϭ0.002) and matrix metalloproteinase-9 activity (76.0Ϯ14.3 versus 168.0Ϯ36.2; Pϭ0.027). These data provide direct evidence for a causal role of TLR4 in postinfarct maladaptive LV remodeling, probably via inflammatory cytokine production and matrix degradation. TLR4 may therefore constitute a novel target in the treatment of ischemic heart failure.

Myotonic dystrophy (DM) is commonly associated with CTG repeat expansions within the gene for DM-protein kinase (DMPK). The effect of altered expression levels of DMPK, which is ubiquitously expressed in all muscle cell lineages during development, was examined by disrupting the endogenous Dmpk gene and overexpressing a normal human DMPK transgene in mice. Nullizygous (-/-) mice showed only inconsistent and minor size changes in head and neck muscle fibres at older age, animals with the highest DMPK transgene expression showed hypertrophic cardiomyopathy and enhanced neonatal mortality. However, both models lack other frequent DM symptoms including the fibre-type dependent atrophy, myotonia, cataract and male-infertility. These results strengthen the contention that simple loss- or gain-of-expression of DMPK is not the only crucial requirement for development of the disease.

BackgroundWomen are at great risk for mood and anxiety disorders during their childbearing years and may become pregnant while taking antidepressant drugs. In the treatment of depression and anxiety disorders, selective serotonin reuptake inhibitors (SSRIs) are the most frequently prescribed drugs, while it is largely unknown whether this medication affects the development of the central nervous system of the fetus. The possible effects are the product of placental transfer efficiency, time of administration and dose of the respective SSRI.Methodology/Principal FindingsIn order to attain this information we have setup a study in which these parameters were measured and the consequences in terms of physiology and behavior are mapped. The placental transfer of fluoxetine and fluvoxamine, two commonly used SSRIs, was similar between mouse and human, indicating that the fetal exposure of these SSRIs in mice is comparable with the human situation. Fluvoxamine displayed a relatively low placental transfer, while fluoxetine showed a relatively high placental transfer. Using clinical doses of fluoxetine the mortality of the offspring increased dramatically, whereas the mortality was unaffected after fluvoxamine exposure. The majority of the fluoxetine-exposed offspring died postnatally of severe heart failure caused by dilated cardiomyopathy. Molecular analysis of fluoxetine-exposed offspring showed long-term alterations in serotonin transporter levels in the raphe nucleus. Furthermore, prenatal fluoxetine exposure resulted in depressive- and anxiety-related behavior in adult mice. In contrast, fluvoxamine-exposed mice did not show alterations in behavior and serotonin transporter levels. Decreasing the dose of fluoxetine resulted in higher survival rates and less dramatic effects on the long-term behavior in the offspring.ConclusionsThese results indicate that prenatal fluoxetine exposure affects fetal development, resulting in cardiomyopathy and a higher vulnerability to affective disorders in a dose-dependent manner.

Background-Endoglin, an accessory receptor for transforming growth factor-␤ in vascular endothelial cells, is essential for angiogenesis during mouse development. Mutations in the human gene cause hereditary hemorrhagic telangiectasia type 1 (HHT1), a disease characterized by vascular malformations that increase with age. Although haploinsufficiency is the underlying cause of the disease, HHT1 individuals show great heterogeneity in age of onset, clinical manifestations, and severity. Methods and Results-In situ hybridization and immunohistochemical analysis of mouse and human hearts revealed that endoglin is upregulated in neoangiogenic vessels formed after myocardial infarction. Microvascularity within the infarct zone was strikingly lower in mice with reduced levels of endoglin (Eng ϩ/Ϫ ) compared with wild-type mice, which resulted in a greater deterioration in cardiac function as measured by magnetic resonance imaging. This did not appear to be because of defects in host inflammatory cell numbers in the infarct zone, which accumulated to a similar extent in wild-type and heterozygous mice. However, defects in vessel formation and heart function in Eng ϩ/Ϫ mice were rescued by injection of mononuclear cells from healthy human donors but not by mononuclear cells from HHT1 patients. Conclusions-These results establish defective vascular repair as a significant component of the origin of HHT1. Because vascular damage or inflammation occurs randomly, it may also explain disease heterogeneity. More generally, the efficiency of vascular repair may vary between individuals because of intrinsic differences in their mononuclear cells.

A new type of lipid organization is observed in mixtures of phosphatidyl-choline with cardiolipin (in the presence of Ca2+), monoglycosyldiglyceride and phosphatidylethanolamine (in the presence of cholesterol). This phase is characterised by an isotropic 31P NMR signal and is visualised by freeze-fracturing as particles and pits on the fracture faces of the lipid bilayer. As the most favourable model for this phase we propose the inverted micelle sandwiched in between the two monolayers of the lipid bilayer.

Background-Hypertrophic growth, a risk factor for mortality in heart disease, is driven by reprogramming of cardiac gene expression. Although the transcription factor myocyte enhancer factor-2 (MEF2) is a common end point for several hypertrophic pathways, its precise cardiac gene targets and function in cardiac remodeling remain to be elucidated. Methods and Results-We report the existence of synergistic interactions between the nuclear factor of activated T cells and MEF2 transcription factors triggered by calcineurin signaling. To circumvent the embryonic lethality and mitochondrial deficiency associated with germ-line null mutations for MEF2C and MEF2A respectively, we used conditional transgenesis to express a dominant-negative form of MEF2 in the murine postnatal heart and combined this with magnetic resonance imaging to assess MEF2 transcriptional function in Ca 2ϩ /calcineurin-induced cardiac remodeling. Surprisingly, end-diastolic and end-systolic ventricular dimensions and contractility were normalized in the presence of severely hypertrophied left ventricular walls on MEF2 inhibition in calcineurin transgenic mice. In line, we generated lines of transgenic mice expressing MEF2A in the heart, which displayed primarily chamber dilation. Microarray profiling indicated that MEF2 promotes a gene profile functioning primarily to or at the nucleus, cytoskeletal and microtubular networks, and mitochondria. Conclusions-These findings assign a novel function to MEF2 transcription factors in the postnatal heart, where they activate a genetic program that minimally affects cardiac growth yet promotes chamber dilation, mechanical dysfunction, and dilated cardiomyopathy.

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