Biomedical subjects

Kenneth D Bloch

Publications and source records attributed to Kenneth D Bloch.

At least 19 recordsLinked to original sources

PubMed2016

Androgen-sensitive hypertension associated with soluble guanylate cyclase-α1 deficiency is mediated by 20-HETE.

Dysregulated nitric oxide (NO) signaling contributes to the pathogenesis of hypertension, a prevalent and often sex-specific risk factor for cardiovascular disease. We previously reported that mice deficient in the α1-subunit of the NO receptor soluble guanylate cyclase (sGCα1 (-/-) mice) display sex- and strain-specific hypertension: male but not female sGCα1 (-/-) mice are hypertensive on an 129S6 (S6) but not a C57BL6/J (B6) background. We aimed to uncover the genetic and molecular basis of the observed sex- and strain-specific blood pressure phenotype. Via linkage analysis, we identified a suggestive quantitative trait locus associated with elevated blood pressure in male sGCα1 (-/-)S6 mice. This locus encompasses Cyp4a12a, encoding the predominant murine synthase of the vasoconstrictor 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE). Renal expression of Cyp4a12a in mice was associated with genetic background, sex, and testosterone levels. In addition, 20-HETE levels were higher in renal preglomerular microvessels of male sGCα1 (-/-)S6 than of male sGCα1 (-/-)B6 mice. Furthermore, treating male sGCα1 (-/-)S6 mice with the 20-HETE antagonist 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (20-HEDE) lowered blood pressure. Finally, 20-HEDE rescued the genetic background- and testosterone-dependent impairment of acetylcholine-induced relaxation in renal interlobar arteries associated with sGCα1 deficiency. Elevated Cyp4a12a expression and 20-HETE levels render mice susceptible to hypertension and vascular dysfunction in a setting of sGCα1 deficiency. Our data identify Cyp4a12a as a candidate sex-specific blood pressure-modifying gene in the context of deficient NO-sGC signaling.

Androgens↗

PubMed2007

FSTL3 deletion reveals roles for TGF-beta family ligands in glucose and fat homeostasis in adults.

Activin and myostatin are related members of the TGF-beta growth factor superfamily. FSTL3 (Follistatin-like 3) is an activin and myostatin antagonist whose physiological role in adults remains to be determined. We found that homozygous FSTL3 knockout adults developed a distinct group of metabolic phenotypes, including increased pancreatic islet number and size, beta cell hyperplasia, decreased visceral fat mass, improved glucose tolerance, and enhanced insulin sensitivity, changes that might benefit obese, insulin-resistant patients. The mice also developed hepatic steatosis and mild hypertension but exhibited no alteration of muscle or body weight. This combination of phenotypes appears to arise from increased activin and myostatin bioactivity in specific tissues resulting from the absence of the FSTL3 antagonist. Thus, the enlarged islets and beta cell number likely result from increased activin action. Reduced visceral fat is consistent with a role for increased myostatin action in regulating fat deposition, which, in turn, may be partly responsible for the enhanced glucose tolerance and insulin sensitivity. Our results demonstrate that FSTL3 regulation of activin and myostatin is critical for normal adult metabolic homeostasis, suggesting that pharmacological manipulation of FSTL3 activity might simultaneously reduce visceral adiposity, increase beta cell mass, and improve insulin sensitivity.

Animals↗

PubMed2006

Sildenafil improves exercise hemodynamics and oxygen uptake in patients with systolic heart failure.

BACKGROUND: Heart failure (HF) is frequently associated with dysregulation of nitric oxide-mediated pulmonary vascular tone. Sildenafil, a type 5 phosphodiesterase inhibitor, lowers pulmonary vascular resistance in pulmonary hypertension by augmenting intracellular levels of the nitric oxide second messenger, cyclic GMP. We tested the hypothesis that a single oral dose of sildenafil (50 mg) would improve exercise capacity and exercise hemodynamics in patients with chronic systolic HF through pulmonary vasodilation. METHODS AND RESULTS: Thirteen patients with New York Heart Association class III HF underwent assessment of right heart hemodynamics, gas exchange, and first-pass radionuclide ventriculography at rest and with cycle ergometry before and 60 minutes after administration of 50 mg of oral sildenafil. Sildenafil reduced resting pulmonary arterial pressure, systemic vascular resistance, and pulmonary vascular resistance, and increased resting and exercise cardiac index (P<0.05 for all) without altering mean arterial pressure, heart rate, or pulmonary capillary wedge pressure. Sildenafil reduced exercise pulmonary arterial pressure, pulmonary vascular resistance, and pulmonary vascular resistance/systemic vascular resistance ratio, which indicates a selective pulmonary vasodilator effect with exercise. Peak VO2 increased (15+/-9%) and ventilatory response to CO2 output (VE/VCO2 slope) decreased (16+/-5%) after sildenafil treatment. Improvements in right heart hemodynamics and exercise capacity were confined to patients with secondary pulmonary hypertension (rest pulmonary arterial pressure >25 mm Hg). CONCLUSIONS: The present study shows that in patients with systolic HF, type 5 phosphodiesterase inhibition with sildenafil improves peak VO2, reduces VE/VCO2 slope, and acts as a selective pulmonary vasodilator during rest and exercise in patients with HF and pulmonary hypertension.

Adult↗

PubMed2006

Cardiomyocyte-specific overexpression of nitric oxide synthase 3 prevents myocardial dysfunction in murine models of septic shock.

Myocardial dysfunction contributes to the high mortality of patients with endotoxemia. Although nitric oxide (NO) has been implicated in the pathogenesis of septic cardiovascular dysfunction, the role of myocardial NO synthase 3 (NOS3) remains incompletely defined. Here we show that mice with cardiomyocyte-specific NOS3 overexpression (NOS3TG) are protected from myocardial dysfunction and death associated with endotoxemia. Endotoxin induced more marked impairment of Ca(2+) transients and cellular contraction in wild-type than in NOS3TG cardiomyocytes, in part, because of greater total sarcoplasmic reticulum Ca(2+) load and myofilament sensitivity to Ca(2+) in the latter during endotoxemia. Endotoxin increased reactive oxygen species production in wild-type but not NOS3TG hearts, in part, because of increased xanthine oxidase activity. Inhibition of NOS by N(G)-nitro-l-arginine-methyl ester restored the ability of endotoxin to increase reactive oxygen species production and xanthine oxidase activity in NOS3TG hearts to the levels measured in endotoxin-challenged wild-type hearts. Allopurinol, a xanthine oxidase inhibitor, attenuated endotoxin-induced reactive oxygen species accumulation and myocardial dysfunction in wild-type mice. The protective effects of cardiomyocyte NOS3 on myocardial function and survival were further confirmed in a murine model of polymicrobial sepsis. These results suggest that increased myocardial NO levels attenuate endotoxin-induced reactive oxygen species production and increase total sarcoplasmic reticulum Ca(2+) load and myofilament sensitivity to Ca(2+), thereby reducing myocardial dysfunction and mortality in murine models of septic shock.

Actin Cytoskeleton↗

PubMed2006

Nitric oxide-dependent suppression of thioredoxin-interacting protein expression enhances thioredoxin activity.

OBJECTIVE: Cellular redox balance is regulated by enzymatic and nonenzymatic systems and freely diffusible nitric oxide (NO) promotes antioxidative mechanisms. We show the NO-dependent transcriptional regulation of the antioxidative thioredoxin system. METHODS AND RESULTS: Incubation of rat pulmonary artery smooth muscle cells (RPaSMC) with the NO donor compound S-nitroso-glutathione (GSNO, 100 micromol/L) suppressed thioredoxin-interacting protein (Txnip), an inhibitor of thioredoxin function, by 71+/-18% and enhanced thioredoxin reductase 2.7+/-0.2 fold (n=6; both P<0.001 versus control). GSNO increased thioredoxin activity (1.9+/-0.5-fold after 4 hours; P<0.05 versus control). Promoter deletion analysis revealed that NO suppression of Txnip transcription is mediated by cis-regulatory elements between -1777 and -1127 bp upstream of the start codon. Hyperglycemia induced Txnip promoter activity (3.9+/-0.2-fold; P<0.001) and abolished NO effects (-37.4+/-1.0% at 5.6 mmol/L glucose versus 12.4+/-2.1% at 22.4 mmol/L glucose; P<0.05). Immunoprecipitation experiments demonstrated that GSNO stimulation and mutation of thioredoxin at Cys69, a site of nitrosylation, had no effect on the Txnip/thioredoxin interaction. CONCLUSIONS: NO can regulate cellular redox state by changing expression of Txnip and thioredoxin reductase. This represents a novel antioxidative mechanism of NO independent of posttranslational protein S-nitrosylation of thioredoxin.

Animals↗

PubMed2006

Tissue Doppler imaging predicts left ventricular dysfunction and mortality in a murine model of cardiac injury.

AIMS: Currently available non-invasive imaging methods frequently fail to detect alterations in left ventricular (LV) function despite histological evidence of injury. Tissue Doppler imaging (TDI) can detect subtle LV dysfunction. The aim of this study was to investigate whether TDI indices can predict LV systolic dysfunction and mortality following exposure to doxorubicin (DOX) in mice. METHODS AND RESULTS: TDI-derived peak endocardial systolic velocity (V(ENDO)) and strain rate (SR), as well as M-mode and two-dimensional indices of LV systolic function, were measured serially in mice after receiving DOX as a single dose (20 mg/kg). Haemodynamic measurements were obtained invasively before and at 1, 2, 4, and 5 days after the single DOX dose. Cardiac apoptosis was measured before and at 1 day after DOX. V(ENDO) and SR decreased after 1 and 2 days, respectively, whereas changes in fractional shortening (FS) and LV ejection fraction (LVEF) were not detected before 5 days. The reduction in both V(ENDO) and SR correlated with the decrease in dP/dt(MAX), and the change in V(ENDO) correlated with the early increase in cardiac cell apoptosis. In a subsequent experiment, DOX was administered at 4 mg/kg/week for 5 weeks, and LV function was followed serially for 16 weeks. In this chronic experiment, TDI indices decreased before FS and LVEF, correlated with late LV dysfunction, and predicted DOX-induced mortality. CONCLUSION: In a murine model of DOX-induced cardiac injury, TDI detects LV dysfunction prior to alterations in conventional echocardiographic indices and predicts mortality. This study suggests that TDI may be a reliable tool to detect early subtle changes in DOX-induced cardiac dysfunction.

Animals↗

PubMed2006

MyD88 and NOS2 are essential for toll-like receptor 4-mediated survival effect in cardiomyocytes.

Innate immune system such as Toll-like receptor 4 (TLR4) represents the first line of defense against infection. In addition to its pivotal role in host immunity, recent studies have suggested that TLR4 may play a broader role in mediating tissue inflammation and cell survival in response to noninfectious injury. We and other investigators have reported that cardiac TLR4 signaling is dynamically modulated in ischemic myocardium and that activation of TLR4 confers a survival benefit in the heart and in isolated cardiomyocytes. However, the signaling pathways leading to these effects are not completely understood. Here, we investigate the role of MyD88, an adaptor protein of TLR4 signaling, and inducible nitric oxide synthase (NOS2) in mediating TLR4-induced cardiomyocyte survival in an in vitro model of apoptosis. Serum deprivation induced a significant increase in the number of apoptotic cardiomyocytes as demonstrated by transferase-mediated dUTP nick-end labeling (TUNEL) assay, nuclear morphology, DNA laddering, and DNA-histone ELISA. Lipopolysaccharide (LPS), a TLR4 agonist, activated TLR4 signaling and led to significant reduction in apoptotic cardiomyocytes and improved cellular function of surviving cardiomyocytes with enhanced Ca(2+) transients and cell shortening. We found that both TLR4 and MyD88 are required for the LPS-induced beneficial effects as demonstrated by improved survival and function in wild-type but not in TLR4(-/-) or MyD88(-/-) cardiomyocytes. Moreover, genetic deletion or pharmacological inhibition of NOS2 abolished survival and functional rescue of cardiomyocytes treated with LPS. Taken together, these data suggest that TLR4 protects cardiomyocytes from stress-induced injury through MyD88- and NOS2-dependent mechanisms.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Sildenafil improves coronary artery patency in a canine model of platelet-mediated cyclic coronary occlusion after thrombolysis.

OBJECTIVES: We sought to assess the effect of sildenafil, a highly-specific type 5 phosphodiesterase (PDE5) inhibitor, on platelet-mediated cyclic coronary flow reductions occurring in a canine model of coronary thrombosis despite aspirin therapy. BACKGROUND: The PDE5 inhibitors augment the antithrombotic effects of nitric oxide in vitro and in vivo, but it has been proposed that the PDE5 inhibitor sildenafil is prothrombotic. METHODS: Cyclic coronary flow reductions were induced in the left anterior descending coronary artery by creation of a stenosis, endothelial injury, and thrombus formation followed by treatment with aspirin, heparin, and tissue plasminogen activator. After an initial observation period, dogs were treated with or without sildenafil (100 microg/kg bolus followed by 4 microg/kg/min infusion). RESULTS: Cyclic coronary flow reductions ceased in five of six animals 18 +/- 5 min after initiation of sildenafil but continued in all six control animals. The portion of the observation period during which the coronary artery was patent increased from 52 +/- 9% to 83 +/- 5% after sildenafil administration (p = 0.008) but did not differ between the first and second observation periods in untreated dogs (49 +/- 11% vs. 44 +/- 11%, respectively). Among animals with plasma free sildenafil levels > or =20 nmol/l, cyclic coronary flow reductions were 73 +/- 12% less frequent and the time to cessation of cycling 72 +/- 14% shorter than in animals with levels <20 nmol/l (p < 0.05 for both). Sildenafil transiently decreased blood pressure 7 +/- 1% but did not change heart rate. Sildenafil treatment reduced ex vivo thrombin-induced platelet aggregation by 39 +/- 3% (p < 0.005). CONCLUSIONS: Sildenafil improves coronary patency in a canine model of platelet-mediated coronary artery thrombosis, likely via inhibition of platelet aggregation.

Animals↗

PubMed2006

Nitric oxide synthase 2 and pressure-overload-induced left ventricular remodelling in mice.

Nitric oxide synthase 2 (NOS2) has been reported to increase in hypertrophied cardiomyocytes; however, whether NOS2 plays a role in the development of hypertrophy is unknown. To investigate the relationship of NOS2 with left ventricular (LV) remodelling and hypertrophy following prolonged pressure overload, we studied 18 male wild-type (WT) and 20 male NOS2-deficient (NOS2-/-) mice before and 7, 14 and 28 days after transverse aortic constriction (TAC) using echocardiography. A subgroup of eight WT and eight NOS2-/- mice were studied 42 days after TAC. Haemodynamic measurements were obtained before killing. Left ventricular size and function were similar for both genotypes at baseline. After TAC for 28 days, both groups developed LV hypertrophy, with echo-derived LV mass increasing from 78 +/- 2 to 147 +/- 10 mg in WT and from 86 +/- 3 to 142 +/- 10 mg in NOS2-/- mice. Twenty-eight days after TAC, LV weight and cardiomyocyte width were also similar in both genotypes. Fractional shortening (FS) decreased on day 7 from 57 +/- 1 to 48 +/- 2% in WT and from 59 +/- 1 to 49 +/- 2% in NOS2-/- mice. Although this decrease in FS was transient in WT mice, it persisted in NOS2-/- mice. Invasively measured parameters of systolic and diastolic function, however, were similar in the two genotypes both 28 and 42 days after TAC. A load-independent index of contractility, Emax, was similar in both strains 42 days after TAC. In conclusion, NOS2 does not appear to have a critical role in the development of LV hypertrophy after chronic pressure overload.

Animals↗

PubMed2006

RNA-associated protein 55 (RAP55) localizes to mRNA processing bodies and stress granules.

The mRNA processing body (P-body) is a cellular structure that has an important role in mRNA degradation. P-bodies have also been implicated in RNAi-mediated post-transcriptional gene silencing. The objective of this study was to identify and characterize novel components of the mammalian P-body. Approximately 5% of patients with the autoimmune disease primary biliary cirrhosis have antibodies directed against this structure. Serum from one of these patients was used to identify a cDNA encoding RAP55, a 463-amino acid protein. RAP55 colocalized with previously identified P-body components DCP1a and Ge-1. RAP55 contains an N-terminal Sm-like domain and two C-terminal RGG-rich domains separated by an FDF motif. The two RGG domains and the FDF domain were necessary and sufficient to target the protein to P-bodies. A fragment of RAP55 consisting of the FDF and the second RGG domains did not localize to P-bodies, but was able to displace other P-body components from this structure. After cells were subjected to arsenite-induced stress, RAP55 was detected in TIA-containing stress granules. The second RGG domain was necessary and sufficient for stress granule localization. siRNA-mediated knock-down of RAP55 resulted in loss of P-bodies, suggesting that RAP55 acts prior to the 5'-decapping step in mRNA degradation. The results of this study show that RAP55 is a component of P-bodies in cells at rest and localizes in stress granules in arsenite-treated cells. RAP55 may serve to shuttle mRNAs between P-bodies and stress granules.

Blotting, Western↗

PubMed2006

Inhaled nitric oxide decreases infarction size and improves left ventricular function in a murine model of myocardial ischemia-reperfusion injury.

To learn whether nitric oxide (NO) inhalation can decrease myocardial ischemia-reperfusion (I/R) injury, we studied a murine model of myocardial infarction (MI). Anesthetized mice underwent left anterior descending coronary artery ligation for 30, 60, or 120 min followed by reperfusion. Mice breathed NO beginning 20 min before reperfusion and continuing thereafter for 24 h. MI size and area at risk were measured, and left ventricular (LV) function was evaluated using echocardiography and invasive hemodynamic measurements. Inhalation of 40 or 80 ppm, but not 20 ppm, NO decreased the ratio of MI size to area at risk. NO inhalation improved LV systolic function, as assessed by echocardiography 24 h after reperfusion, and systolic and diastolic function, as evaluated by hemodynamic measurements 72 h after reperfusion. Myocardial neutrophil infiltration was reduced in mice breathing NO, and neutrophil depletion prevented inhaled NO from reducing myocardial I/R injury. NO inhalation increased arterial nitrite levels but did not change myocardial cGMP levels. Breathing 40 or 80 ppm NO markedly and significantly decreased MI size and improved LV function after ischemia and reperfusion in mice. NO inhalation may represent a novel method to salvage myocardium at risk of I/R injury.

Administration, Inhalation↗

PubMed2006

Processing body autoantibodies reconsidered.

Processing bodies (P-bodies) are cellular structures that have critical roles in mRNA degradation and post-transcriptional gene silencing. Some patients with autoimmune disease have high titer antibodies directed against P-bodies, and certain sera have been used as markers for the GW182 component of these structures. This study shows that available reference sera are unreliable markers for GW182 because the sera contain antibodies directed against Ge-1, a second P-body autoantigen.

Argonaute Proteins↗

PubMed2005

Inhaled nitric oxide does not reduce systemic vascular resistance in mice.

Inhaled nitric oxide (NO) is a highly selective pulmonary vasodilator. It was recently reported that inhaled NO causes peripheral vasodilatation after treatment with a NO synthase (NOS) inhibitor. These findings suggested the possibility that inhibition of endogenous NOS uncovered the systemic vasodilating effect of NO or NO adducts absorbed via the lungs during NO inhalation. To learn whether inhaled NO reduces systemic vascular resistance in the absence of endothelial NOS, we studied the systemic vascular effects of NO breathing in wild-type mice treated without and with the NOS inhibitor N(omega)-nitro-l-arginine methyl ester and in NOS3-deficient (NOS3(-/-)) mice. During general anesthesia, the cardiac output, left ventricular function, and systemic vascular resistance were not altered by NO breathing at 80 parts/million in both genotypes. Breathing NO in air did not alter blood pressure and heart rate, as measured by tail-cuff and telemetric methods, in either awake wild-type mice (whether or not they were treated with N(omega)-nitro-l-arginine methyl ester), or in awake NOS3(-/-) mice. Our findings suggest that absorption of NO or adducts during NO breathing is insufficient to cause systemic vasodilation in mice, even when endogenous endothelial NO production is congenitally absent.

Administration, Inhalation↗

PubMed2005

Nitric oxide induces phosphodiesterase 4B expression in rat pulmonary artery smooth muscle cells.

Phosphodiesterases (PDE) metabolize cyclic nucleotides limiting the effects of vasodilators such as prostacyclin and nitric oxide (NO). In this study, DNA microarray techniques were used to assess the impact of NO on expression of PDE genes in rat pulmonary arterial smooth muscle cells (rPASMC). Incubation of rPASMC with S-nitroso-l-glutathione (GSNO) increased expression of a PDE isoform that specifically metabolizes cAMP (PDE4B) in a dose- and time-dependent manner. GSNO increased PDE4B protein levels, and rolipram-inhibitable PDE activity was 2.3 +/- 1.0-fold greater in GSNO-treated rPASMC than in untreated cells. The soluble guanylate cyclase (sGC) inhibitor, 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one, and the cAMP-dependent protein kinase inhibitor, H89, prevented induction of PDE4B gene expression by GSNO, but the protein kinase G (PKG) inhibitors, Rp-8-pCPT-cGMPs and KT-5823, did not. Incubation of rPASMC with IL-1beta and tumor necrosis factor-alpha induced PDE4B gene expression, an effect that was inhibited by l-N(6)-(1-iminoethyl)lysine, an antagonist of NO synthase 2 (NOS2). The GSNO-induced increase in PDE4B mRNA levels was blocked by actinomycin D but augmented by cycloheximide. Infection of rPASMC with an adenovirus specifying a dominant negative cAMP response element binding protein (CREB) mutant inhibited the GSNO-induced increase of PDE4B gene expression. These results suggest that exposure of rPASMC to NO induces expression of PDE4B via a mechanism that requires cGMP synthesis by sGC but not PKG. The GSNO-induced increase of PDE4B gene expression is CREB dependent. These findings demonstrate that NO increases expression of a cAMP-specific PDE and provide evidence for a novel "cross talk" mechanism between cGMP and cAMP signaling pathways.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2005

Inhibition of phosphodiesterase 1 augments the pulmonary vasodilator response to inhaled nitric oxide in awake lambs with acute pulmonary hypertension.

Phosphodiesterase 1 (PDE1) modulates vascular tone and the development of tolerance to nitric oxide (NO)-releasing drugs in the systemic circulation. Any role of PDE1 in the pulmonary circulation remains largely uncertain. We measured the expression of genes encoding PDE1 isozymes in the pulmonary vasculature and examined whether or not selective inhibition of PDE1 by vinpocetine attenuates pulmonary hypertension and augments the pulmonary vasodilator response to inhaled NO in lambs. Using RT-PCR, we detected PDE1A, PDE1B, and PDE1C mRNAs in pulmonary arteries and veins isolated from healthy lambs. In 13 lambs, the thromboxane A(2) analog U-46619 was infused intravenously to increase mean pulmonary arterial pressure to 35 mmHg. Four animals received an intravenous infusion of vinpocetine at incremental doses of 0.3, 1, and 3 mg.kg(-1).h(-1). In nine lambs, inhaled NO was administered in a random order at 2, 5, 10, and 20 ppm before and after an intravenous infusion of 1 mg.kg(-1).h(-1) vinpocetine. Administration of vinpocetine did not alter pulmonary and systemic hemodynamics or transpulmonary cGMP or cAMP release. Inhaled NO selectively reduced mean pulmonary arterial pressure, pulmonary capillary pressure, and pulmonary vascular resistance index, while increasing transpulmonary cGMP release. The addition of vinpocetine enhanced pulmonary vasodilation and transpulmonary cGMP release induced by NO breathing without causing systemic vasodilation but did not prolong the duration of pulmonary vasodilation after NO inhalation was discontinued. Our findings demonstrate that selective inhibition of PDE1 augments the therapeutic efficacy of inhaled NO in an ovine model of acute chemically induced pulmonary hypertension.

Acute Disease↗

PubMed2005

Mediation of Epstein-Barr virus EBNA-LP transcriptional coactivation by Sp100.

The Epstein-Barr virus (EBV) EBNA-LP protein is important for EBV-mediated B-cell immortalization and is a potent gene-specific coactivator of the viral transcriptional activator, EBNA2. The mechanism(s) by which EBNA-LP functions as a coactivator remains an important question in the biology of EBV-induced B-cell immortalization. In this study, we found that EBNA-LP interacts with the promyelocytic leukemia nuclear body (PML NB)-associated protein Sp100 and displaces Sp100 and heterochromatin protein 1alpha (HP1alpha) from PML NBs. Interaction between EBNA-LP and Sp100 was mediated through conserved region 3 in EBNA-LP and the PML NB targeting domain in Sp100. Overexpression of Sp100 lacking the N-terminal PML NB targeting domain, but not a mutant form of Sp100 lacking the HP1alpha interaction domain, was sufficient to coactivate EBNA2 in a gene-specific manner independent of EBNA-LP. These findings suggest that Sp100 is a major mediator of EBNA-LP coactivation. These studies indicate that modulation of PML NB-associated proteins may be important for establishment of latent viral infections, and also identify a convenient model system to investigate the functions of Sp100.

Antigens, Nuclear↗

PubMed2005

Combined administration of intravenous dipyridamole and inhaled nitric oxide to assess reversibility of pulmonary arterial hypertension in potential cardiac transplant recipients.

BACKGROUND: Irreversible, severe pulmonary hypertension (PH) can produce right heart failure and early mortality after cardiac transplantation. We hypothesized that dipyridamole, an inhibitor of Type 5 phosphodiesterase, would augment the ability of inhaled nitric oxide (NO) to identify reversibility of PH. METHODS: In 9 patients with congestive heart failure (CHF) and severe PH who were breathing 100% oxygen during right heart catheterization, we administered inhaled NO (80 ppm) alone and in combination with intravenous dipyridamole (0.2-mg/kg bolus, with an infusion of 0.0375 mg/kg/min). RESULTS: Compared with breathing oxygen alone, NO inhalation decreased pulmonary artery pressure and pulmonary vascular resistance (PVR) (by 10 +/- 4% and 26 +/- 12% [mean +/- SEM], respectively; both p < 0.05). The combination of NO and dipyridamole reduced PVR (43 +/- 7%; p < 0.05) to a greater extent than did administration of NO alone, and increased the duration of pulmonary vasodilation produced by NO inhalation. Combined administration of inhaled NO and intravenous dipyridamole increased cardiac index (by 23 +/- 10%) and reduced SVR (by 19 +/- 6%, both p < 0.05) without changing systemic arterial pressure. NO inhalation reduced PVR to <200 dyne x s/cm5 in 3 of 7 patients who had a PVR of >200 dyne x s/cm5 when breathing oxygen alone, whereas the combination of NO and dipyridamole decreased PVR to <200 dyne.s/cm(5) in 2 additional patients. CONCLUSIONS: Intravenous dipyridamole augments and prolongs the pulmonary vasodilator effects of inhaled NO in CHF patients with severe PH and, when administered in combination with NO inhalation, can identify PH reversibility in potential cardiac transplant recipients in whom a pulmonary vasodilator response to inhalation of NO alone is not observed.

Administration, Inhalation↗

PubMed2005

Quantitative assessment of regional myocardial function in mice by tissue Doppler imaging: comparison with hemodynamics and sonomicrometry.

BACKGROUND: Tissue Doppler imaging (TDI) is a novel echocardiographic method to quantify regional myocardial function. The objective of this study was to assess whether myocardial velocities and strain rate (SR) could be obtained by TDI in mice and whether these indices accurately quantified alterations in left ventricular (LV) systolic function. METHODS AND RESULTS: TDI was performed in 10 healthy mice to measure endocardial (v(endo)) and epicardial systolic velocities and SR. In further experiments, TDI indices were compared with dP/dt(max) and with sonomicrometer-derived regional velocities, at rest and after administration of dobutamine or esmolol. TDI indices were also studied serially in 8 mice before and 4 and 7 hours after endotoxin challenge. Myocardial velocities and SR were obtained in all mice with low measurement variability. TDI indices increased with administration of dobutamine (v(endo) from 2.2+/-0.3 to 3.8+/-0.2 cm/s [P<0.01]; SR from 12+/-2 to 20+/-2 s(-1) [P<0.05]) and decreased with administration of esmolol (v(endo) 1.4+/-0.2 cm/s [P<0.05]; SR 6+/-1 s(-1) [P<0.01]). Both indices correlated strongly with dP/dt(max) (r2=0.79 for SR and r2= 0.69 for v(endo); both P<0.0001). SR and shortening fraction were predictors of dP/dt(max) even after adjustment for the confounding effect of the other variables. V(endo) correlated closely with sonomicrometer-measured velocity (r2=0.71, P<0.0005). After endotoxin challenge, decreases in both v(endo) and SR were detected before decreases in shortening fraction became manifest. CONCLUSIONS: Myocardial velocities and SR can be measured noninvasively in mice with the use of TDI. Both indices are sensitive markers for quantifying LV global and regional function in mice.

Animals↗