p38α MAPK inhibits stretch-induced JNK activation in cardiac myocytes through MKP-1.

Mechanical stretch is a major determinant that leads to heart failure, which is associated with a steady increase in myocardial angiotensinogen (Aogen) expression and formation of the biological peptide angiotensin II (Ang II). c-jun NH2-terminal kinase (JNK) and p38α have been found to have opposing roles on stretch-induced Aogen gene expression in neonatal rat ventricular myocytes (NRVM). JNK negatively regulated Aogen expression in NRVM following acute stretch, whereas with prolonged stretch, JNK phosphorylation was downregulated and p38α was found responsible for upregulation of Aogen expression.

Mechanosensing and Regulation of Cardiac Function.

The role of mechanical force as an important regulator of structure and function of mammalian cells, tissues, and organs has recently been recognized. However, mechanical overload is a pathogenesis or comorbidity existing in a variety of heart diseases, such as hypertension, aortic regurgitation and myocardial infarction. Physical stimuli sensed by cells are transmitted through intracellular signal transduction pathways resulting in altered physiological responses or pathological conditions.

Paracrine communication between mechanically stretched myocytes and fibroblasts.

Mechanical stretch is a major factor for myocardial hypertrophy and heart failure. Stretch activates mechanical sensors from cardiac myocytes, leading to a series of signal transduction cascades, which can result in cell malfunction and remodeling. It is well known that mechanical stretch also induces the release of paracrine factors from cardiac fibroblasts, as well as myocytes.

Production of spontaneously beating neonatal rat heart tissue for calcium and contractile studies.

Neonatal rat ventricular myocytes (NRVM) and fibroblasts (FB) serve as in vitro models for studying fundamental mechanisms underlying cardiac pathologies, as well as identifying potential therapeutic targets. Typically, these cell types are separated using Percoll density gradient procedures. Cells located between the Percoll bands (interband cells [IBCs]), which contain less mature NRVM and a variety of non-myocytes, including coronary vascular smooth muscle cells and endothelial cells (ECs), are routinely discarded.

Anthrax lethal toxin induces acute diastolic dysfunction in rats through disruption of the phospholamban signaling network.

Background: Anthrax lethal toxin (LT), secreted by Bacillus anthracis, causes severe cardiac dysfunction by unknown mechanisms. LT specifically cleaves the docking domains of MAPKK (MEKs); thus, we hypothesized that LT directly impairs cardiac function through dysregulation of MAPK signaling mechanisms.

Methods And Results: In a time-course study of LT toxicity, echocardiography revealed acute diastolic heart failure accompanied by pulmonary regurgitation and left atrial dilation in adult Sprague-Dawley rats at time points corresponding to dysregulated JNK, phospholamban (PLB) and protein phosphatase 2A (PP2A) myocardial signaling.

Caveolin and β1-integrin coordinate angiotensinogen expression in cardiac myocytes.

Background: The cardiac renin-angiotensin system (RAS) has been implicated in mediating myocyte hypertrophy and remodeling, although the biochemical mechanisms responsible for regulating the local RAS are poorly understood. Caveolin-1 (Cav-1)/Cav-3 double-knockout mice display cardiac hypertrophy, and in vitro disruption of lipid rafts/caveolae using methyl-β-cyclodextrin (MβCD) abolishes cardiac protection.

Methods: In this study, neonatal rat ventricular myocytes (NRVM) were used to determine whether lipid rafts/caveolae may be involved in the regulation of angiotensinogen (Ao) gene expression, a substrate of the RAS system.

In utero assessment of cardiovascular function in the embryonic mouse heart using high-resolution ultrasound biomicroscopy.

Murine models are currently the preferred approach for studying the molecular mechanisms of cardiac dysfunction resulting from changes in gene expression. Transgenic and gene-targeting methods can be used to generate mice with altered cardiac size and function, and as a result, in vivo techniques are indispensible in evaluating cardiac phenotype. Traditionally, the pathologic assessment of sacrificed hearts was used to study cardiac pathophysiology in small animals.

Isolation of cardiac myocytes and fibroblasts from neonatal rat pups.

Neonatal rat ventricular myocytes (NRVM) and fibroblasts (FBs) serve as in vitro models for studying fundamental mechanisms underlying cardiac pathologies, as well as identifying potential therapeutic targets. Both cell types are relatively easy to culture as monolayers and can be manipulated using molecular and pharmacological tools. Because NRVM cease to proliferate after birth, and FBs undergo phenotypic changes and senescence after a few passages in tissue culture, primary cultures of both cell types are required for experiments.

Modulation of myocardial mitochondrial mechanisms during severe polymicrobial sepsis in the rat.

Background: We tested the hypothesis that 5-Hydroxydecanoic acid (5HD), a putative mitoK(ATP) channel blocker, will reverse sepsis-induced cardiodynamic and adult rat ventricular myocyte (ARVM) contractile dysfunction, restore mitochondrial membrane permeability alterations and improve survival.

Methodology/principal Findings: Male Sprague-Dawley rats (350-400 g) were made septic using 400 mg/kg cecal inoculum, ip. Sham animals received 5% dextrose water, ip.

Rac1 and RhoA differentially regulate angiotensinogen gene expression in stretched cardiac fibroblasts.

Aims: Angiotensin II (Ang II) stimulates cardiac remodelling and fibrosis in the mechanically overloaded myocardium. Although Rho GTPases regulate several cellular processes, including myocardial remodelling, involvement in mediating mechanical stretch-induced regulation of angiotensinogen (Ao), the precursor to Ang II, remains to be determined. We, therefore, examined the role and associated signalling mechanisms of Rho GTPases (Rac1 and RhoA) in regulation of Ao gene expression in a stretch model of neonatal rat cardiac fibroblasts (CFs).

Norepinephrine induces systolic failure and inhibits antiapoptotic genes in a polymicrobial septic rat model.

Aims: We examined the effect of norepinephrine (NE) infusion on left ventricular function and apoptotic genes during progression of polymicrobial sepsis.

Methods: Male Sprague-Dawley rats (350-400 g) were made septic by intraperitoneal (i.p.

Anthrax toxin: pathologic effects on the cardiovascular system.

Anthrax is a disease caused by infection with spores from the bacteria Bacillus anthracis. After entering the body, the spores germinate into bacteria and secrete a toxin that causes local edema and, in systemic infections, cardiovascular collapse and death. The toxin is a tripartite polypeptide, consisting of protective antigen (PA), lethal factor (LF) and edema factor (EF), which have key roles in the bacterial pathogenesis and disease progression.

Integrins and proximal signaling mechanisms in cardiovascular disease.

Integrins are heterodimeric cell-surface molecules, which act as the principle mediators of molecular dialog between a cell and its extracellular matrix environment. In addition to their structural functions, integrins mediate signaling from the extracellular space into the cell through integrin-associated signaling and adaptor molecules such as FAK (focal adhesion kinase), ILK (integrin-linked kinase), PINCH (particularly interesting new cysteine-histidine rich protein) and Nck2 (non-catalytic (region of) tyrosine kinase adaptor protein-2). Via these molecules, integrin signaling tightly and cooperatively interacts with receptor tyrosine kinases (RTKs) signaling to regulate survival, proliferation and cell shape as well as polarity, adhesion, migration and differentiation.

Stretch-induced regulation of angiotensinogen gene expression in cardiac myocytes and fibroblasts: opposing roles of JNK1/2 and p38alpha MAP kinases.

The cardiac renin-angiotensin system (RAS) has been implicated in mediating myocyte hypertrophy, remodeling, and fibroblast proliferation in the hemodynamically overloaded heart. However, the intracellular signaling mechanisms responsible for regulation of angiotensinogen (Ao), a substrate of the RAS system, are largely unknown. Here we report the identification of JNK1/2 as a negative, and p38alpha as a major positive regulator of Ao gene expression.

Competing interactions between micro-RNAs determine neural progenitor survival and proliferation after ethanol exposure: evidence from an ex vivo model of the fetal cerebral cortical neuroepithelium.

The fetal brain is sensitive to a variety of teratogens, including ethanol. We showed previously that ethanol induced mitosis and stem cell maturation, but not death, in fetal cerebral cortex-derived progenitors. We tested the hypothesis that micro-RNAs (miRNAs) could mediate the teratogenic effects of ethanol in a fetal mouse cerebral cortex-derived neurosphere culture model.