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Introduction Heart function depends on the extracellular matrix (ECM) to transmit mechanical forces to cardiomyocytes, where they are converted into biochemical signals that regulate muscle activity to maintain homeostasis (1-3). [...], Patients with Marfan syndrome (MFS), a multisystem disorder caused by mutations in the gene encoding the extracellular matrix (ECM) protein fibrillin 1, are unusually vulnerable to stress-induced cardiac dysfunction. The prevailing view is that MFS-associated cardiac dysfunction is the result of aortic and/or valvular disease. Here, we determined that dilated cardiomyopathy (DCM) in fibrillin 1--deficient mice is a primary manifestation resulting from ECM-induced abnormal mechanosignaling by cardiomyocytes. MFS mice displayed spontaneous emergence of an enlarged and dysfunctional heart, altered physical properties of myocardial tissue, and biochemical evidence of chronic mechanical stress, including increased angiotensin II type I receptor (AT1R) signaling and abated focal adhesion kinase (FAK) activity. Partial fibrillin 1 gene inactivation in cardiomyocytes was sufficient to precipitate DCM in otherwise phenotypically normal mice. Consistent with abnormal mechanosignaling, normal cardiac size and function were restored in MFS mice treated with an AT1R antagonist and in MFS mice lacking AT1R or β-arrestin 2, but not in MFS mice treated with an angiotensin-converting enzyme inhibitor or lacking angiotensinogen. Conversely, DCM associated with abnormal AT1R and FAK signaling was the sole abnormality in mice that were haploinsufficient for both fibrillin 1 and β1 integrin. Collectively, these findings implicate fibrillin 1 in the physiological adaptation of cardiac muscle to elevated workload.

Bian Y, Sun M, Silver M, Ho KK, Marchionni MA, Caggiano AO, Stone JR, Amende I, Hampton TG, Morgan JP, Yan X. Neuregulin-1 attenuated doxorubicin-induced decrease in cardiac troponins. Am J Physiol Heart Circ Physiol 297: H1974-H1983, 2009. First published October 2, 2009; doi: 10.1152/ajpheart.01010.2008.--Neuregulin-1 (NRG1) is a potential therapeutic agent for the treatment of doxorubicin (Dox)-induced heart failure. NRG1, however, activates the erbB2 receptor, which is frequently overexpressed in breast cancers. It is, therefore, important to understand how NRG1, via erbB2, protects the heart against Dox cardiotoxicity. Here, we studied NRG1-erbB2 signaling in Dox-treated mice hearts and in isolated neonatal rat ventricular myocytes (NRVM). Male C57BL/6 mice were treated with recombinant NRG1 before and daily after a single dose of Dox. Cardiac function was determined by catheterization. Two-week survival was analyzed by the Kaplan-Meier method. Cardiac troponins [cardiac troponin I (cTnI) and cardiac troponin T (cTnT)] and phosphorylated Akt protein levels were determined in mice hearts and in NRVM by Western blot analysis. Activation of caspases and ubiquitinylation of troponins were determined in NRVM by caspase assay and immunoprecipitation. NRG1 significantly improved survival and cardiac function in Dox-treated mice. NRG1 reduced the decrease in cTnI, cTnT, and cardiac troponin C (cTnC) and maintained Akt phosphorylation in Dox-treated mice hearts. NRG1 reduced the decrease in cTnI and cTnT mRNA and proteins in Dox-treated NRVM. Inhibition of erbB2, phosphoinositide 3-kinase (PI3K), Akt, and mTOR blocked the protective effects of NRG1 on cTnI and cTnT in NRVM. NRG1 significantly reduced Dox-induced caspase activation, which degraded troponins, in NRVM. NRG1 reduced Dox-induced proteasome degradation of cTnI. NRG1 attenuates Dox-induced decrease in cardiac troponins by increasing transcription and translation and by inhibiting caspase activation and proteasome degradation of troponin proteins. NRG1 maintains cardiac troponins by the erbB2-PI3K pathway, which may lessen Dox-induced cardiac dysfunction. ErbB2; troponin proteins; signaling doi: 10.1152/ajpheart.01010.2008

Embryonic stem cells (ESCs) overexpressing the vascular endothelial growth factor (VEGF) improve cardiac function in mouse models of myocardial ischemia and infarction by mechanisms that are poorly understood. Here we studied the effects of VEGF on cardiomyocyte differentiation of mouse ESCs in vitro. We used flow cytometry to determine the expression of ct-myosin heavy chain ([alpha]-MHC), cardiac troponin I (cTn-I), and Nkx2.5 in differentiated ESCs. VEGF (20 ng/ml) significantly enhanced [alpha]-MHC, cTn-I, and Nkx2.5 expression in differentiated ESCs. Western blot analysis confirmed these findings. We found that VEGF receptor FMS-like tyrosine kinase-1 (Flt-1) and fetal liver kinase-1 (Flk-1) expression increased during ESC differentiation. Antibodies against Flk-1 totally blocked and against Fit-1 partially blocked VEGF-induced NKx2.5-positive-stained cells. The ERK inhibitor PD-098059 abolished VEGF-induced cardiomyocyte differentiation of ESCs. Our results suggest that VEGF promotes cardiomyocyte differentiation predominantly by ERK-mediated Flk-1 activation and, to a lesser extent, by Flt-1 activation. These findings may be of significance for stem cell and growth factor therapies to regenerate failing cardiomyocytes. cardiac-specific proteins; Flt-1 and Flk-1; extracellular signal-regulated kinase

Recent studies point to important interactions between proinflammatory cytokines and neurohumoral mediators in heart failure. Here we investigate the influence of the [beta]-adrenergic system on cytokines and neurohumoral factors and the sequelae of viral myocarditis. In an experimental model with virus-infected BALB/c mice, we studied the acute and chronic effects of epinephrine and propranolol on myocardial morphology, cytokine gene expression, and survival. BALB/c mice were inoculated with the encephalomyocarditis virus (EMCV) or sham inoculated with saline and followed for 30 days. Epinephrine increased the severity of inflammatory cell infiltration and myocardial necrosis induced by EMCV. Gene expression of TNF-[alpha], IL-6, and IL-10 was markedly enhanced by epinephrine in EMCV-inoculated mice. Survival rate after 30 days was reduced to 40% in epinephrine-treated EMCV-inoculated mice compared with 70% in untreated EMCV-inoculated mice (P < 0.05). Treatment with the [beta]-blocker propranolol significantly decreased mortality, myocardial necrosis, and infiltration of inflammatory cells in EMCV-inoculated mice. Propranolol also suppressed gene expression of TNF-a, IL-6, and IL-10. A single dose of epinephrine 120 days after EMCV inoculation caused sudden death in 70% of infected mice; propranolol significantly reduced incidence of death to 33%. These results indicate that acute and chronic stages of viral myocarditis are modulated by the [beta]-adrenergic system and its interactions with proinflammatory cytokines. heart failure; arrhythmia; [beta]adrenergic receptor stimulation; [beta]locker; proinflammatory cytokines; encephalomyocarditis virus

Cocaine treatment of mice with viral myocarditis significantly increases neutrophil infiltration into the myocardium and exacerbates the inflammatory response. The mechanisms of these effects are unknown; however, it may be that cocaine increases circulating catecholamines and consequently increases inflammatory cell adhesion to the coronary endothelium. Here, we examined the hypothesis that cocaine enhances inflammatory cell infiltration via catecholamine-induced upregulation of cell adhesion molecule (CAM) expression in adult BALB/c mouse hearts. Intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), endothelial leukocyte adhesion molecule-1 (E-selectin), and leukocyte adhesion molecule-1 (L-selectin) were detected by gene array analysis, RT-PCR, Western blotting, and immunohistochemical staining. CAMs were significantly upregulated in cocaine-treated mouse hearts. [beta]-Adrenergic stimulation with epinephrine also upregulated CAM expression, confirming the effects obtained with cocaine. [beta]-Adrenergic blockade with propranolol inhibited epinephrine-induced CAM expression. In hearts infused with polymorphonuclear neutrophils (PMN), an increased adhesion of PMN to the coronary endothelium was observed in cocaine-treated and epinephrine-treated mouse hearts compared with control hearts. Blocking antibodies against ICAM-1, E-selectin, and L-selectin significantly inhibited epinephrine-enhanced PMN adhesion, whereas anti-VCAM-1 had lesser effects. Our findings suggest that cocaine-induced neutrophil infiltration is mediated by [beta]-adrenergic stimulation through upregulation of CAM expression, which enhances PMN adhesion. Conversely, [beta]-adrenergic blockade with propranolol inhibits the effects of cocaine and epinephrine on CAM expression and decreases PMN adhesion to the coronary endothelium. These observations may be of significance for the development of preventative and therapeutic approaches to patients with cocaine- or catecholamine-induced myocarditis. epinephrine; propranolol; cell adhesion molecules; polymorphonuclear neutrophils; heart perfusion

Author(s): Jian Li [1]; Mark Post [1]; Rudiger Volk [1]; Youhe Gao [1]; Min Li [1]; Caroline Metais [1, 3]; Kaori Sato [1, 3]; Jo Tsai [2]; William Aird [2]; [...]

Intracellular calcium and left ventricular (LV) function were determined in the coronary-perfused mouse heart to investigate intracellular calcium-related mechanisms of injury from myocardial ischemia and reperfusion. Findings in the mouse heart showed that stunning is not due to deficiency of intracellular calcium but rather from a decreased myofilament responsiveness to intracellular calcium.

Abstract Background Gait is impaired in patients with Parkinson's disease (PD) and Huntington's disease (HD), but gait dynamics in mouse models of PD and HD have not been described. Here we quantified temporal and spatial indices of gait dynamics in a mouse model of PD and a mouse model of HD. Methods Gait indices were obtained in C57BL/6J mice treated with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 30 mg/kg/day for 3 days) for PD, the mitochondrial toxin 3-nitropropionic acid (3NP, 75 mg/kg cumulative dose) for HD, or saline. We applied ventral plane videography to generate digital paw prints from which indices of gait and gait variability were determined. Mice walked on a transparent treadmill belt at a speed of 34 cm/s after treatments. Results Stride length was significantly shorter in MPTP-treated mice (6.6 ± 0.1 cm vs. 7.1 ± 0.1 cm, P < 0.05) and stride frequency was significantly increased (5.4 ± 0.1 Hz vs. 5.0 ± 0.1 Hz, P < 0.05) after 3 administrations of MPTP, compared to saline-treated mice. The inability of some mice treated with 3NP to exhibit coordinated gait was due to hind limb failure while forelimb gait dynamics remained intact. Stride-to-stride variability was significantly increased in MPTP-treated and 3NP-treated mice compared to saline-treated mice. To determine if gait disturbances due to MPTP and 3NP, drugs affecting the basal ganglia, were comparable to gait disturbances associated with motor neuron diseases, we also studied gait dynamics in a mouse model of amyotrophic lateral sclerosis (ALS). Gait variability was not increased in the SOD1 G93A transgenic model of ALS compared to wild-type control mice. Conclusion The distinct characteristics of gait and gait variability in the MPTP model of Parkinson's disease and the 3NP model of Huntington's disease may reflect impairment of specific neural pathways involved.

1. Introduction Muscular dystrophy includes loss of muscle strength and muscle mass and leads to gait disturbances resulting in compensatory kinematic and postural adaptation [1-3]. Eventually, patients lose their ability [...], The delta-sarcoglycan-deficient hamster is an excellent model to study muscular dystrophy. Gait disturbances, important clinically, have not been described in this animal model. We applied ventral plane videography (DigiGait) to analyze gait in BIO TO-2 dystrophic and BIO F1B control hamsters walking on a transparent treadmill belt. Stride length was -13% shorter (P < .05) in TO-2 hamsters at 9 months of age compared to F1B hamsters. Hindlimb propulsion duration, an indicator of muscle strength, was shorter in 9-month-old TO-2 (247 ± 8 ms) compared to F1B hamsters (272 ± 11 ms; P

Hampton, Thomas G., Ju-Feng Wang, Joseph DeAngelis, Ivo Amende, Kenneth D. Philipson, and James P. Morgan. Enhanced gene expression of [Na.sup.+]/[Ca.sup.2+] exchanger attenuates ischemic and hypoxic contractile dysfunction. Am J Physiol Heart Circ Physiol 279: H2846-H2854, 2000.--Enhanced gene expression of the [Na.sup.+]/[Ca.sup.2+] exchanger in failing hearts may be a compensatory mechanism to promote influx and efflux of [Ca.sup.2+], despite impairment of the sarcoplasmic reticulum (SR). To explore this, we monitored intracellular calcium ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]) and cardiac function in mouse hearts engineered to overexpress the [Na.sup.+]/[Ca.sup.2+] exchanger and subjected to ischemia and hypoxia, conditions known to impair SR [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] transport and contractility. Although baseline [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and function were similar between transgenic and wild-type hearts, significant differences were observed during ischemia and hypoxia. During early ischemia, [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was preserved in transgenic hearts but significantly altered in wild-type hearts. Transgenic hearts maintained 40% of pressure-generating capacity during early ischemia, whereas wild-type hearts maintained only 25% (P [is less than] 0.01). During hypoxia, neither peak nor diastolic [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] decreased in transgenic hearts. In contrast, both peak and diastolic [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] decreased significantly in wild-type hearts. The decline of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was abbreviated in hypoxic transgenic hearts but prolonged in wild-type hearts. Peak systolic pressure decreased by nearly 10% in hypoxic transgenic hearts and [is greater than] 25% in wild-type hearts (P [is less than] 0.001). These data demonstrate that enhanced gene expression of the [Na.sup.+]/[Ca.sup.2+] exchanger preserves [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] homeostasis during ischemia and hypoxia, thereby preserving cardiac function in the acutely failing heart. ischemia; hypoxia; sodium; calcium; heart failure; excitation-contraction

Basic FGF reduces stunning via an NOS2-dependent pathway in coronary-perfused mouse hearts. Am J Physiol Heart Circ Physiol 279: H260-H268, 2000.--Basic fibroblast growth factor (FGF-2) may protect the heart from ischemia-reperfusion injury (stunning) by stimulating nitric oxide (NO) production. To test this hypothesis, we pretreated coronary-perfused mouse hearts with 1 [micro]g/ml FGF-2 or vehicle control before the onset of ischemia. Intracellular calcium [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was estimated by aequorin, and NO release was measured with an NO-selective electrode. Hearts perfused with FGF-2 maintained significantly better left ventricular (LV) function during ischemia than hearts perfused with vehicle. FGF-2 significantly delayed the onset of ischemic contracture and improved LV recovery during reperfusion. [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was similar in both groups at baseline during ischemia and reperfusion. L-[N.sup.6]-(1-iminoethyl)lysine, a selective inhibitor of inducible NO synthase (NOS2), obliterated the protective effects of FGF-2. In transgenic hearts deficient in the expression of NOS2 (NOS2-/-), FGF-2 did not attenuate ischemia-induced LV dysfunction. Measurements of NO release demonstrated that FGF-2 perfusion significantly increased NO in wild-type but not in NOS2-/- hearts. We conclude that basic FGF attenuates myocardial stunning independent of alterations in [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] by stimulating NO production via an NOS2-dependent pathway. ischemia; nitric oxide; intracellular calcium; myocardial function

Depressed tolerance to fluorocarbon-simulated ischemia in failing myocardium due to impaired [[[Ca.sup.2+]].sub.i] modulation. Am J Physiol Heart Circ Physiol 278: H1446-H1456, 2000.--The aim of this study was to investigate the tolerance of failing myocardium from postinfarction rats to simulated ischemia. Myocardial infarction (MI) was induced by ligation of the left coronary artery in male Wistar rats. Isometric force and free intracellular [Ca.sup.2+] concentration ([[fCa.sup.2+]].sub.i]) were measured in isolated left ventricular papillary muscles from shamoperated and post-MI animals 6 wk after surgery. Ischemia was simulated by using fluorocarbon immersion with hypoxia. Results showed that mechanical performance was depressed during the period of hypoxia in physiological salt solution (44 [+ or -] 7% of baseline in sham vs. 30 [+ or -] 6% of baseline in MI, P [is less than] 0.05) or ischemia (16 [+ or -] 2% of baseline in sham vs. 9 [+ or -] 1% of baseline in MI, P [is less than] 0.01) accompanied by no corresponding decrease of peak [[[Ca.sup.2+]].sub.i] (hypoxia: 51 [+ or -] 8% of baseline in sham vs. 46 [+ or -] 7% of baseline in MI, P = NS; ischemia: 47 [+ or -] 5% of baseline in sham, 39 [+ or -] 7% of baseline in MI, P = NS). After reoxygenation, [[[Ca.sup.2+]][sub.i] rapidly returned to near preischemic basal levels, whereas developed tension in fluorocarbon remained significantly lower. This dissociation between peak [[[Ca.sup.2+]].sub.i] and isometric contractility was more pronounced in the failing myocardium from postinfarction rats. In conclusion, more severe impairment of [[[Ca.sup.2+]].sub.i] homeostasis in the failing myocardium from postinfarction rats increases susceptibility to ischemia-reperfusion injury. myocardial infarction; intracellular [Ca.sup.2+]; contractility