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Biomedical subjects

Kenneth R Chien

Publications and source records attributed to Kenneth R Chien.

At least 55 records · Page 3Linked to original sources
PubMed2003

IL-6 induces an anti-inflammatory response in the absence of SOCS3 in macrophages.

Whereas interleukin-6 (IL-6) is a proinflammatory cytokine, IL-10 is an anti-inflammatory cytokine. Although signal transducer and activator of transcription 3 (STAT3) is essential for the function of both IL-6 and IL-10, it is unclear how these two cytokines have such opposing functions. Here we show that suppressor of cytokine signaling 3 (SOCS3) is a key regulator of the divergent action of these two cytokines. In macrophages lacking the Socs3 gene or carrying a mutation of the SOCS3-binding site in gp130, the lipopolysaccharide-induced production of tumor necrosis factor (TNF) and IL-12 is suppressed by both IL-10 and IL-6. SOCS3 specifically prevents activation of STAT3 by IL-6 but not IL-10. Taken together, these data indicate that SOCS3 selectively blocks signaling by IL-6, thereby preventing its ability to inhibit LPS signaling.

Animals↗
PubMed2003

Atrial chamber-specific expression of sarcolipin is regulated during development and hypertrophic remodeling.

Intracellular Ca2+ regulation is critical in the normal cardiac function and development of pathologic hearts. Phospholamban, an endogenous inhibitor of sarcoplasmic reticulum Ca2+ ATPase in the sarcoplasmic reticulum, plays an important role in Ca2+ cycling in heart. Recently, sarcolipin has been identified as having a similar function as phospholamban in skeletal muscle. Because phospholamban is differentially expressed in atrial and ventricular myocardia and its expression is often altered in diseased hearts, we investigated the cardiac chamber specificity of sarcolipin expression and its regulation during development and hypertrophic remodeling. Northern blot analysis revealed that the expression of mouse sarcolipin mRNA was most abundant in the atria and was undetectable in the ventricles, indicating an atrial chamber-specific expression pattern. Atrial chamber-specific expression of sarcolipin mRNA was increased during development. These findings were confirmed by in situ hybridization studies. In addition, sarcolipin expression was down-regulated in the atria of hypertrophic heart when induced by ventricular specific overexpression of the activated H-ras gene. In humans, sarcolipin mRNA was also expressed in the atria but not detected in the ventricles, although sarcolipin expression was most abundant in skeletal muscle. Taken together, sarcolipin is likely to be an atrial chamber-specific regulator of Ca2+ cycling in heart.

Animals↗
PubMed2003

Anisotropic stretch-induced hypertrophy in neonatal ventricular myocytes micropatterned on deformable elastomers.

Because cell shape and alignment, cell-matrix adhesion, and cell-cell contact can all affect growth, and because mechanical strains in vivo are multiaxial and anisotropic, we developed an in vitro system for engineering aligned, rod-shaped, neonatal cardiac myocyte cultures. Photolithographic and microfluidic techniques were used to micropattern extracellular matrices in parallel lines on deformable silicone elastomers. Confluent, elongated, aligned myocytes were produced by varying the micropattern line width and collagen density. An elliptical cell stretcher applied 2:1 anisotropic strain statically to the elastic substrate, with the axis of greatest stretch (10%) either parallel or transverse to the myofibrils. After 24 h, the principal strain parallel to myocytes did not significantly alter myofibril accumulation or expression of atrial natriuretic factor (ANF), connexin-43 (Cx-43), or N-cadherin (by indirect immunofluorescent antibody labeling and immunoblotting) compared with unstretched controls. In contrast, 10% transverse principal strain resulted in continuous staining of actin filaments (rhodamine phalloidin); increased immunofluorescent labeling of ANF, Cx-43, and N-cadherin; and upregulation of protein signal intensity by western blotting. By using microfabrication and microfluidics to control cell shape and alignment on an elastic substrate, we found greater effects for transverse than for longitudinal stretch in regulating sarcomere organization, hypertrophy, and cell-to-cell junctions.

Actins↗
PubMed2003

Absence epilepsy and sinus dysrhythmia in mice lacking the pacemaker channel HCN2.

Hyperpolarization-activated cation (HCN) channels are believed to be involved in the generation of cardiac pacemaker depolarizations as well as in the control of neuronal excitability and plasticity. The contributions of the four individual HCN channel isoforms (HCN1-4) to these diverse functions are not known. Here we show that HCN2-deficient mice exhibit spontaneous absence seizures. The thalamocortical relay neurons of these mice displayed a near complete loss of the HCN current, resulting in a pronounced hyperpolarizing shift of the resting membrane potential, an altered response to depolarizing inputs and an increased susceptibility for oscillations. HCN2-null mice also displayed cardiac sinus dysrhythmia, a reduction of the sinoatrial HCN current and a shift of the maximum diastolic potential to hyperpolarized values. Mice with cardiomyocyte- specific deletion of HCN2 displayed the same dysrhythmia as mice lacking HCN2 globally, indicating that the dysrhythmia is indeed caused by sinoatrial dysfunction. Our results define the physiological role of the HCN2 subunit as a major determinant of membrane resting potential that is required for regular cardiac and neuronal rhythmicity.

Animals↗
PubMed2003

Genetic modifiers of cardiac arrhythmias.

Rhythmic contraction of a four-chambered mammalian heart is a highly coordinated process, requiring a functional conduction system. Both acquired and inherited forms of arrhythmia can be life threatening, and are major causes of mortality and morbidity in developed nations. Knowledge derived from human genetics and from studies of mouse genetic models has led to the discovery of multiple molecular defects responsible for arrhythmogenesis, including mutations in ion channels, cytoplasmic ion-channel-interacting proteins, gap-junction proteins, transcription factors and, most recently, a kinase subunit. However, phenotypic expression of a given mutation does not always appear to be uniform in human patients, implying a contribution from environmental factors and/or the presence of other genetic modifiers. Accumulating evidence suggests that 'multiple hits' affecting the interaction and integrity of multiple pathways might be responsible for many forms of arrhythmia.

AMP-Activated Protein Kinase Kinases↗
PubMed2003

The suppressor of cytokine signaling-1 (SOCS1) is a novel therapeutic target for enterovirus-induced cardiac injury.

Enteroviral infections of the heart are among the most commonly identified causes of acute myocarditis in children and adults and have been implicated in dilated cardiomyopathy. Although there is considerable information regarding the cellular immune response in myocarditis, little is known about innate signaling mechanisms within the infected cardiac myocyte that contribute to the host defense against viral infection. Here we show the essential role of Janus kinase (JAK) signaling in cardiac myocyte antiviral defense and a negative role of an intrinsic JAK inhibitor, the suppressor of cytokine signaling (SOCS), in the early disease process. Cardiac myocyte-specific transgenic expression of SOCS1 inhibited enterovirus-induced signaling of JAK and the signal transducers and activators of transcription (STAT), with accompanying increases in viral replication, cardiomyopathy, and mortality in coxsackievirus-infected mice. Furthermore, the inhibition of SOCS in the cardiac myocyte through adeno-associated virus-mediated (AAV-mediated) expression of a dominant-negative SOCS1 increased the myocyte resistance to the acute cardiac injury caused by enteroviral infection. These results indicate that strategies directed at inhibition of SOCS in the heart and perhaps other organs can augment the host-cell antiviral system, thus preventing viral-mediated end-organ damage during the early stages of infection.

Animals↗
PubMed2003

Defects in cardiac conduction system lineages and malignant arrhythmias: developmental pathways and disease.

To unravel the complex disease phenotype of heart failure, we are utilizing an integrative approach employing genomics, physiology, and mouse genetics to identify nodal pathways for specific physiological end points such as myocyte stretch activation responses, contractility and electrical conduction. A new class of genetic pathways for cardiac sudden death and associated arrhythmias has been based on transcription factors that control conduction system lineages, including HF1b/SP4 and NKX2.5. Previous studies have established that HF1b plays a critical role in conduction system lineage formation and the loss of HF1b leads to a confused electrophysiological identity in Purkinje and ventricular cell lineages, resulting in cardiac sudden death and marked tachy and brady arrhythmias. Utilizing Hf1b and Nkx2.5 floxed alleles, we now have identified the primary pathways which link these transcription factors with cardiac arrythmogenesis. Mice which harbour a neural crest restricted knockout of HF1b display marked arrhythmogenesis and conduction system defects, implicating neural crest cues in conduction system development and disease. Mice which harbour a ventricular-restricted knockout of Nkx2.5 display completely normal conduction at birth, but a hypoplastic atrioventricular (AV) node. During maturation, progressive complete heart block ensues, associated with a selective dropout of distal AV nodal cell lineages at the boundaries of the penetrating His bundle. Single cell analyses examining individual nodal cells within AV node of ventricular restricted Nkx2.5 knockout mice clearly document a cell autonomous requirement for NKX2.5 within AV nodal lineages per se. Micro-electrophysiological AV nodal mapping indicates a selective conduction defect at the boundary of the distal AV node and His bundle. HF1b and NKX2.5 reflect new cardiac cell non-autonomous and autonomous pathways for conduction system lineage defects and associated cardiac arrythmogenesis.

Animals↗
PubMed2002

The cardiac mechanical stretch sensor machinery involves a Z disc complex that is defective in a subset of human dilated cardiomyopathy.

Muscle cells respond to mechanical stretch stimuli by triggering downstream signals for myocyte growth and survival. The molecular components of the muscle stretch sensor are unknown, and their role in muscle disease is unclear. Here, we present biophysical/biochemical studies in muscle LIM protein (MLP) deficient cardiac muscle that support a selective role for this Z disc protein in mechanical stretch sensing. MLP interacts with and colocalizes with telethonin (T-cap), a titin interacting protein. Further, a human MLP mutation (W4R) associated with dilated cardiomyopathy (DCM) results in a marked defect in T-cap interaction/localization. We propose that a Z disc MLP/T-cap complex is a key component of the in vivo cardiomyocyte stretch sensor machinery, and that defects in the complex can lead to human DCM and associated heart failure.

Adult↗
PubMed2002

Defects in caveolin-1 cause dilated cardiomyopathy and pulmonary hypertension in knockout mice.

Caveolins are important components of caveolae, which have been implicated in vesicular trafficking and signal transduction. To investigate the in vivo significance of Caveolins in mammals, we generated mice deficient in the caveolin-1 (cav-1) gene and have shown that, in the absence of Cav-1, no caveolae structures were observed in several nonmuscle cell types. Although cav-1(-/-) mice are viable, histological examination and echocardiography identified a spectrum of characteristics of dilated cardiomyopathy in the left ventricular chamber of the cav-1-deficient hearts, including an enlarged ventricular chamber diameter, thin posterior wall, and decreased contractility. These animals also have marked right ventricular hypertrophy, suggesting a chronic increase in pulmonary artery pressure. Direct measurement of pulmonary artery pressure and histological analysis revealed that the cav-1(-/-) mice exhibit pulmonary hypertension, which may contribute to the right ventricle hypertrophy. In addition, the loss of Cav-1 leads to a dramatic increase in systemic NO levels. Our studies provided in vivo evidence that cav-1 is essential for the control of systemic NO levels and normal cardiopulmonary function.

Animals↗
PubMed2002

Chronic suppression of heart-failure progression by a pseudophosphorylated mutant of phospholamban via in vivo cardiac rAAV gene delivery.

The feasibility of gene therapy for cardiomyopathy, heart failure and other chronic cardiac muscle diseases is so far unproven. Here, we developed an in vivo recombinant adeno-associated virus (rAAV) transcoronary delivery system that allows stable, high efficiency and relatively cardiac-selective gene expression. We used rAAV to express a pseudophosphorylated mutant of human phospholamban (PLN), a key regulator of cardiac sarcoplasmic reticulum (SR) Ca(2+) cycling in BIO14.6 cardiomyopathic hamsters. The rAAV/S16EPLN treatment enhanced myocardial SR Ca(2+) uptake and suppressed progressive impairment of left ventricular (LV) systolic function and contractility for 28-30 weeks, thereby protecting cardiac myocytes from cytopathic plasma-membrane disruption. Low LV systolic pressure and deterioration in LV relaxation were also largely prevented by rAAV/S16EPLN treatment. Thus, transcoronary gene transfer of S16EPLN via rAAV vector is a potential therapy for progressive dilated cardiomyopathy and associated heart failure.

Adenosine Triphosphatases↗
PubMed2002

Conditional mutation of the ErbB2 (HER2) receptor in cardiomyocytes leads to dilated cardiomyopathy.

The ErbB2 (Her2) proto-oncogene encodes a receptor tyrosine kinase, which is frequently amplified and overexpressed in human tumors. ErbB2 provides the target for a novel and effective antibody-based therapy (Trastuzumab/Herceptin) used for the treatment of mammary carcinomas. However, cardiomyopathies develop in a proportion of patients treated with Trastuzumab, and the incidence of such complications is increased by combination with standard chemotherapy. Gene ablation studies have previously demonstrated that the ErbB2 receptor, together with its coreceptor ErbB4 and the ligand Neuregulin-1, are essential for normal development of the heart ventricle. We use here Cre-loxP technology to mutate ErbB2 specifically in ventricular cardiomyocytes. Conditional mutant mice develop a severe dilated cardiomyopathy, with signs of cardiac dysfunction generally appearing by the second postnatal month. We infer that signaling from the ErbB2 receptor, which is enriched in T-tubules in cardiomyocytes, is crucial for adult heart function. Conditional ErbB2 mutant mice provide a model of dilated cardiomyopathy. In particular, they will allow a rigorous assessment of the role of ErbB2 in the heart and provide insight into the molecular mechanisms that underlie the adverse effects of anti-ErbB2 antibodies.

Animals↗
PubMed2002

Restoration of deficient membrane proteins in the cardiomyopathic hamster by in vivo cardiac gene transfer.

BACKGROUND: One of the most important problems in developing in vivo cardiac gene transfer has been low transfection efficiency. A novel in vivo technique was developed, tested in normal hamsters, and the feasibility of restoring a deficient structural protein (delta-sarcoglycan) in the cardiomyopathic (CM) hamster evaluated. METHODS AND RESULTS: Adenoviral (AdV) vectors encoding either the lacZ gene or delta-sarcoglycan gene were constructed. Hypothermia was achieved in hamsters by external body cooling to a rectal temperature of 18 to 25 degrees C. Through a small thoracotomy, the ascending aorta and the main pulmonary artery were occluded with snares, and cardioplegic solution containing histamine was injected into the aortic root; viral constructs were delivered 3 to 5 minutes later followed by release of the occluders and rewarming. Four days later, homogeneous beta-galactosidase expression was detected throughout the ventricles of the normal hearts (average 77.3+/-9.0% [SEM] of left ventricular myocytes). At 1 and 3 weeks after transfection, immunostaining showed extensive restoration of delta-sarcoglycan as well as alpha- and beta-sarcoglycan proteins to the myocyte membranes, despite loss of beta-galactosidase expression at 3 weeks. Also, at 3 weeks after gene transfer, there was significantly less progression of left ventricular dysfunction assessed as percent change in fractional shortening compared with controls. CONCLUSIONS: This study demonstrates the feasibility of high efficiency in vivo myocardial gene transfer and shows application in improving the level of a deficient cardiac structural protein and cardiac function in CM hamsters. The approach should be useful for assessing effects of expressing other genes that influence the structure or function of the normal and failing heart.

Adenoviridae↗
PubMed2002

Fibulin-5/DANCE is essential for elastogenesis in vivo.

The elastic fibre system has a principal role in the structure and function of various types of organs that require elasticity, such as large arteries, lung and skin. Although elastic fibres are known to be composed of microfibril proteins (for example, fibrillins and latent transforming growth factor (TGF)-beta-binding proteins) and polymerized elastin, the mechanism of their assembly and development is not well understood. Here we report that fibulin-5 (also known as DANCE), a recently discovered integrin ligand, is an essential determinant of elastic fibre organization. fibulin-5-/- mice generated by gene targeting exhibit a severely disorganized elastic fibre system throughout the body. fibulin-5-/- mice survive to adulthood, but have a tortuous aorta with loss of compliance, severe emphysema, and loose skin (cutis laxa). These tissues contain fragmented elastin without an increase of elastase activity, indicating defective development of elastic fibres. Fibulin-5 interacts directly with elastic fibres in vitro, and serves as a ligand for cell surface integrins alphavbeta3, alphavbeta5 and alpha9beta1 through its amino-terminal domain. Thus, fibulin-5 may provide anchorage of elastic fibres to cells, thereby acting to stabilize and organize elastic fibres in the skin, lung and vasculature.

Animals↗