Insight into modulators of sphingosine-1-phosphate receptor and implications for cardiovascular therapeutics

Cardiovascular disease is the leading cause of death worldwide, and it's of great importance to understand its underlying mechanisms and find new treatments. Sphingosine 1-phosphate (S1P) is an active lipid that exerts its effects through S1P receptors on the cell surface or intracellular signal, and regulates many cellular processes such as cell growth, cell proliferation, cell migration, cell survival, and so on. S1PR modulators are a class of modulators that can interact with S1PR subtypes to activate receptors or block their activity, exerting either agonist or functional antagonist effects. Many studies have shown that S1P plays a protective role in the cardiovascular system and regulates cardiac physiological functions mainly through interaction with cell surface S1P receptors (S1PRs). Therefore, S1PR modulators may play a therapeutic role in cardiovascular diseases. Here, we review five S1PRs and their functions and the progress of S1PR modulators. In addition, we focus on the effects of S1PR modulators on atherosclerosis, myocardial infarction, myocardial ischaemia/reperfusion injury, diabetic cardiovascular diseases, and myocarditis, which may provide valuable insights into potential therapeutic strategies for cardiovascular disease.

Therapeutic Strategies Targeting Mitochondrial Dysfunction in Sepsis-induced Cardiomyopathy

Sepsis is an increasingly worldwide problem; it is currently regarded as a complex life-threatening dysfunction of one or more organs as a result of dysregulated host immune response to infections. The heart is one of the most affected organs, as roughly 10% to 70% of sepsis cases are estimated to turn into sepsis-induced cardiomyopathy (SIC). SIC can be defined as a reversible myocardial dysfunction characterized by dilated ventricles, impaired contractility, and decreased ejection fraction. Mitochondria play a critical role in the normal functioning of cardiac tissues as the heart is highly dependent on its production of adenosine triphosphate (ATP), its damage during SIC includes morphology impairment, mitophagy, biogenesis disequilibrium, electron transport chain disturbance, molecular damage from the actions of pro-inflammatory cytokines and many other different impairments that are major contributing factors to the severity of SIC. Although mitochondria-targeted therapies usage is still inadequate in clinical settings, the preclinical study outcomes promise that the implementation of these therapies may effectively treat SIC. This review summarizes the different therapeutic strategies targeting mitochondria structure, quality, and quantity abnormalities for the treatment of SIC.

Targeted Mitochondrial Drugs for Treatment of Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is a complex hemodynamic pathology that is a leading cause of death worldwide and occurs in many body organs. Numerous studies have shown that mitochondria play an important role in the occurrence mechanism of ischemia-reperfusion injury and that mitochondrial structural abnormalities and dysfunction lead to the disruption of the homeostasis of the whole mitochondria. At this time, mitochondria are not just sub-organelles to produce ATP but also important targets for regulating ischemia-reperfusion injury; therefore, drugs targeting mitochondria can serve as a new strategy to treat ischemia-reperfusion injury. Based on this view, in this review, we discuss potential therapeutic agents for both mitochondrial structural abnormalities and mitochondrial dysfunction, highlighting the application and prospects of targeted mitochondrial drugs in the treatment of ischemia-reperfusion injury, and try to provide new ideas for the clinical treatment of the ischemia-reperfusion injury.

Therapeutic Implications of Targeting Pyroptosis in Cardiac-related Etiology of Heart Failure

Heart failure remains a considerable clinical and public health problem, it is the dominant cause of death from cardiovascular diseases, besides, cardiovascular diseases are one of the leading causes of death worldwide. The survival of patients with heart failure continues to be low with 45-60% reported deaths within five years. Apoptosis, necrosis, autophagy, and pyroptosis mediate cardiac cell death. Acute cell death is the hallmark pathogenesis of heart failure and other cardiac pathologies. Inhibition of pyroptosis, autophagy, apoptosis, or necrosis reduces cardiac damage and improves cardiac function in cardiovascular diseases. Pyroptosis is a form of inflammatory deliberate cell death that is characterized by the activation of inflammasomes such as NOD-like receptors (NLR), absent in melanoma 2 (AIM2), interferon-inducible protein 16 (IFI-16), and their downstream effector cytokines: Interleukin IL-1β and IL-18 leading to cell death. Recent studies have shown that pyroptosis is also the dominant cell death process in cardiomyocytes, cardiac fibroblasts, endothelial cells, and immune cells. It plays a crucial role in the pathogenesis of cardiac diseases that contribute to heart failure. This review intends to summarize the therapeutic implications targeting pyroptosis in the main cardiac pathologies preceding heart failure.

Targeted mitochondrial drugs for treatment of Myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MI/RI) refers to the further damage done to ischemic cardiomyocytes when restoring blood flow. A large body of evidence shows that MI/RI is closely associated with excessive production of mitochondrial reactive oxygen species, mitochondrial calcium overload, disordered mitochondrial energy metabolism, mitophagy, mitochondrial fission, and mitochondrial fusion. According to the way it affects mitochondria, it can be divided into mitochondrial quality abnormalities and mitochondrial quantity abnormalities. Abnormal mitochondrial quality refers to the dysfunction caused by the severe destruction of mitochondria, which then affects the balance of mitochondrial density and number, causing an abnormal mitochondrial quantity. In the past, most of the reports were limited to the study of the mechanism of myocardial ischemia-reperfusion injury, some of which involved mitochondria, but no specific countermeasures were proposed. In this review, we outline the mechanisms for treating myocardial ischemia-reperfusion injury from the direction of mitochondria and focus on targeted interventions and drugs to restore mitochondrial health during abnormal mitochondrial quality control and abnormal mitochondrial quantity control. This is an update in the field of myocardial ischemia-reperfusion injury.

S1P promotes inflammation-induced tube formation by HLECs via the S1PR1/NF-κB pathway

Inflammation-induced lymphangiogenesis is a widely accepted concept. However, most of the inflammatory factors and their related mechanisms have not been clarified. It has been reported that sphingosine-1-phosphate (S1P) is not only closely related to the chronic inflammatory process but also affects angiogenesis. Therefore, we investigated the inflammatory effects of S1P on human lymphatic endothelial cells (HLECs). Our results showed that S1P promotes tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) secretion in HLECs. We also confirmed that S1P-stimulated TNF-α and IL-1β secretion is mediated through S1P receptor 1 (S1PR1). Using TNF-α siRNA and IL-1β siRNA, we found that TNF-α and IL-1β play essential roles in S1P-induced HLEC proliferation, migration, and tube formation. S1P induces phosphorylation of NF-κB p65 and activation of NF-κB nuclear translocation. A S1PR1 antagonist (W146) and NF-κB inhibitor (BAY11-7082) inhibited S1P-induced TNF-α and IL-1β secretion and prevented NF-κB nuclear translocation. Taken together, the results demonstrated for the first time that S1P promotes the secretion of TNF-α and IL-1β in HLECs via S1PR1-mediated NF-κB signaling pathways, thus affecting lymphangiogenesis. The study provides a new strategy for finding treatments for lymphangiogenesis-related diseases.

MicroRNA-24 aggravates atherosclerosis by inhibiting selective lipid uptake from HDL cholesterol via the post-transcriptional repression of scavenger receptor class B type I

BACKGROUND AND AIMS

Liver scavenger receptor class B type I (SR-BI) exerts atheroprotective effects through selective lipid uptake (SLU) from high-density lipoprotein cholesterol (HDL-C). Low hepatic SR-BI expression leads to high HDL-C levels in the circulation and an increased risk of atherosclerosis. Furthermore, macrophage SR-BI mediates bidirectional cholesterol flux and may protect against atherogenesis. Previous studies have revealed that miR-24 is closely related to cardiovascular disease (CVD) progression. We aimed to investigate the molecular mechanisms by which miR-24 participates in SR-BI-mediated selective HDL cholesteryl ester (HDL-CE) uptake and further atherogenesis in apoE^-/- mice.

METHODS

Bioinformatic predictions and luciferase reporter assays were utilized to detect the association between miR-24 and the SR-BI 3' untranslated region (3' UTR), and RT-PCR and western blotting were used to evaluate SR-BI mRNA and protein expression, respectively. The effects of miR-24 on Dil-HDL uptake were determined by flow cytometry assay. Double-radiolabeled HDL (¹²⁵I-TC-/[³H] CEt-HDL) was utilized to measure the effects of miR-24 on HDL and CE binding and SLU in HepG2 and PMA-treated THP-1 cells. In addition, total cholesterol (TC) levels in HepG2 cells were analyzed using enzymatic methods, and macrophage lipid content was evaluated by high-performance liquid chromatography (HPLC) assay. Small interfering RNA (siRNA) and pcDNA3.1(-)-hSR-BI plasmid transfection procedures were utilized to confirm the role of SR-BI in the effects of miR-24 on Dil-HDL uptake, SLU and cholesterol levels in both cell types. Hepatic SR-BI level in apoE^-/- mice was measured by western blotting. Liver TC, FC and CE levels and plasma triglycerides (TG), TC and HDL-C levels were evaluated enzymatically using commercial test kits. Atherosclerotic lesion sizes were measured using Oil Red O and hematoxylin-eosin staining.

RESULTS

miR-24 directly repressed SR-BI expression by targeting its 3'UTR. In addition, miR-24 decreased Dil-HDL uptake and SLU in HepG2 and THP-1 macrophages. In the presence of HDL, miR-24 decreased TC levels in HepG2 cells and TC, free cholesterol (FC) and CE levels in macrophages. Overexpression and down-regulation assays showed that SR-BI mediated the effects of miR-24 on Dil-HDL uptake, SLU and cholesterol levels. Lastly, miR-24 administration decreased hepatic SR-BI expression and promoted atheromatous plaque formation in apoE^-/- mice, findings in line with those of our in vitro studies.

CONCLUSIONS

These findings indicate that miR-24 accelerates atherogenesis by repressing SR-BI-mediated SLU from HDL-C.

TGF-β Down-regulates Apolipoprotein M Expression through the TAK-1-JNK-c-Jun Pathway in HepG2 Cells

Apolipoprotein M (apoM) is a relatively novel apolipoprotein that plays pivotal roles in many dyslipidemia-associated diseases; however, its regulatory mechanisms are poorly understood. Many cytokines have been identified that down-regulate apoM expression in HepG2 cells, among which transforming growth factor-β (TGF-β) exerts the most potent effects. In addition, c-Jun, a member of the activated protein 1 (AP-1) family whose activity is modulated by c-Jun N-terminal kinase (JNK), decreases apoM expression at the transcriptional level by binding to the regulatory element in the proximal apoM promoter. In this study, we investigated the molecular mechanisms through which TGF-β decreases the apoM level in HepG2 cells. The results revealed that TGF-β inhibited apoM expression at both the mRNA and protein levels in a dose- and time-dependent manner and that it suppressed apoM secretion. These effects were attenuated by treatment of cells with either SP600125 (JNK inhibitor) or c-Jun siRNA. 5Z-7-oxozeaenol [(a TGF-β-activated kinase 1 (TAK-1) inhibitor)] also attenuated the TGF-β-mediated inhibition of apoM expression and suppressed the activation of JNK and c-Jun. These results have demonstrated that TGF-β suppresses apoM expression through the TAK-1-JNK-c-Jun pathway in HepG2 cells.

A high-density lipoprotein-mediated drug delivery system

High-density lipoprotein (HDL) is a comparatively dense and small lipoprotein that can carry lipids as a multifunctional aggregate in plasma. Several studies have shown that increasing the levels or improving the functionality of HDL is a promising target for treating a wide variety of diseases. Among lipoproteins, HDL particles possess unique physicochemical properties, including naturally synthesized physiological components, amphipathic apolipoproteins, lipid-loading and hydrophobic agent-incorporating characteristics, specific protein-protein interactions, heterogeneity, nanoparticles, and smaller size. Recently, the feasibility and superiority of using HDL particles as drug delivery vehicles have been of great interest. In this review, we summarize the structure, constituents, biogenesis, remodeling, and reconstitution of HDL drug delivery systems, focusing on their delivery capability, characteristics, applications, manufacturing, and drug-loading and drug-targeting characteristics. Finally, the future prospects are presented regarding the clinical application and challenges of using HDL as a pharmacodelivery carrier.

Involvement of the IRE1α-XBP1 pathway and XBP1s-dependent transcriptional reprogramming in metabolic diseases

The X-box binding protein 1 (XBP1) is not only an important component of the unfolded protein response (UPR), but also an important nuclear transcription factor. Upon endoplasmic reticulum stress, XBP1 is spliced by inositol-requiring enzyme 1 (IRE1), thereby generating functional spliced XBP1 (XBP1s). XBP1s functions by translocating into the nucleus to initiate transcriptional programs that regulate a subset of UPR- and non-UPR-associated genes involved in the pathophysiological processes of various diseases. Recent reports have implicated XBP1 in metabolic diseases. This review summarizes the effects of XBP1-mediated regulation on lipid metabolism, glucose metabolism, obesity, and atherosclerosis. Additionally, for the first time, we present XBP1s-dependent transcriptional reprogramming in metabolic diseases under different conditions, including pathology and physiology. Understanding the function of XBP1 in metabolic diseases may provide a basic knowledge for the development of novel therapeutic targets for ameliorating these diseases.

High-density lipoprotein induces cyclooxygenase-2 expression and prostaglandin I-2 release in endothelial cells through sphingosine kinase-2

High-density lipoprotein (HDL) has a significant cardioprotective effects. HDL induces cyclooxygenase-2 (COX-2) expression and prostacyclin I-2 (PGI-2) release in vascular endothelial cells, which contributes to its anti-atherogenic effects. However, the underlying mechanisms are not fully understood. In the present study, we observed that HDL-stimulated COX-2 expression and PGI-2 production in human umbilical vein endothelial cells (HUVECs) in a time- and dose-dependent manner. These effects triggered by HDL were inhibited by pertussis toxin (PTX), protein kinase C (PKC) inhibitor GF109203X, and ERK inhibitor PD98059, suggesting that Gαi/Gαo-coupled GPCR, PKC, and ERK pathways are involved in HDL-induced COX-2/PGI-2 activation. More importantly, we found that silencing of sphingosine kinase 2 (SphK-2) also blocked HDL-induced COX-2/PGI-2 activation. In addition, HDL-activated SphK-2 phosphorylation accompanied by increased S1P level in the nucleus. Our ChIP data demonstrated that SphK-2 is associated with CREB at the COX-2 promoter region. Collectively, these results indicate that HDL induces COX-2 expression and PGI-2 release in endothelial cells through activation of PKC, ERK1/2, and SphK-2 pathways. These findings implicate a novel mechanism underlying anti-atherothrombotic effects of HDL.

Knowledge of stroke warning signs and risk factors among patients with previous stroke or TIA in China

AIMS AND OBJECTIVES

The purpose of this study was to describe knowledge about stroke warning signs and risk factors in patients with previous stroke or transient ischaemic attacks in China and to investigate the relationship between socio-demographic characteristics & health status and patients' knowledge about stroke.

BACKGROUND

Stroke is the leading cause of death and functional impairment in China. Survivors are at high risk of new vascular events. Secondary prevention after stroke or transient ischaemic attacks is not satisfactory. Previous research suggests that awareness of stroke plays an important role in facilitating secondary prevention. However, little is known about knowledge of stroke warning signs and risk factors among patients with previous stroke/transient ischaemic attacks.

DESIGN

A cross-sectional questionnaire study.

METHODS

This study was conducted in Hunan Province, China, between July and December in 2010. Subjects were recruited using a cluster sampling method. A questionnaire was administered to 1600 patients with stroke/transient ischaemic attacks diagnose from eight hospitals, and 1200 patients (75%) responded. Patients' knowledge about stroke warning signs and risk factors were collected and analysed. Results.  Patients' knowledge about stroke warning signs was very poor (only 3.3% identified all warning signs and 28.3% identified three). Patients' knowledge about important risk factors (e.g. atrial fibrillation, diabetes, metabolic syndrome, etc.) was also very poor (<30%). Patients' action in emergency was extremely poor (only 9.2% reported to call emergency service). The age, education, stroke-related diagnoses and family history of cardiovascular disease were significantly associated with patients' knowledge about stroke.

CONCLUSIONS

Knowledge about stroke warning signs and risk factors was very poor in patients with previous stroke or transient ischaemic attacks in China.

RELEVANCE TO CLINICAL PRACTICE

Dissemination of stroke knowledge should be a core responsibility for Chinese clinical nurse. Future clinical education to improve patient's knowledge about stroke and further intervention to manage cardiovascular risk factors are indicated.

ATP citrate lyase inhibitors as novel cancer therapeutic agents

ATP citrate lyase (ACL or ACLY) is an extra-mitochondrial enzyme widely distributed in various human and animal tissues. ACL links glucose and lipid metabolism by catalyzing the formation of acetyl-CoA and oxaloacetate from citrate produced by glycolysis in the presence of ATP and CoA. ACL is aberrantly expressed in many immortalized cells and tumors, such as breast, liver, colon, lung and prostate cancers, and is correlated reversely with tumor stage and differentiation, serving as a negative prognostic marker. ACL is an upstream enzyme of the long chain fatty acid synthesis, providing acetyl-CoA as an essential component of the fatty acid synthesis. Therefore, ACL is a key enzyme of cellular lipogenesis and potent target for cancer therapy. As a hypolipidemic strategy of metabolic syndrome and cancer treatment, many small chemicals targeting ACL have been designed and developed. This review article provides an update for the research and development of ACL inhibitors with a focus on their patent status, offering a new insight into their potential application.

An involvement of SR-B1 mediated PI3K-Akt-eNOS signaling in HDL-induced cyclooxygenase 2 expression and prostacyclin production in endothelial cells

It is well-known that sphingosine-1-phosphate (S1P), the phospholipid content of HDL, binding to S1P receptors can raise COX-2 expression and PGI(2) release through p38MAPK/CREB pathway. In the present study we assess the action of SR-B1 initiated PI3K-Akt-eNOS signaling in the regulation of COX-2 expression and PGI(2) production in response to HDL. We found that apoA1 could increase PGI(2) release and COX-2 expression in ECV 304 endothelial cells. Furthermore, SR-B1 was found to be involved in HDL induced up-regulation of COX-2 and PGI(2). Over-expressed SR-B1 did not significantly increase the expression of COX-2 and the PGI(2) levels, but knock-down of SR-B1 by siRNA could significantly attenuate COX-2 expression and PGI(2) release together with p38MAPK and CREB phosphorylation. Consistently, the declines of p-p38MAPK, p-CREB, COX-2 and PGI(2) were also observed after incubation with LY294002 (25μmol/L; PI3K special inhibitor) or L-NAME (50μmol/L; eNOS special inhibitor). In addition, we demonstrated the increases of PGI(2) release, COX-2 expression and p38MAPK phosphorylation, when nitric oxide level was raised through the incubation of L-arginine (10 or 20nmol/L) in endothelial cells. Taking together, our data support that SR-B1 mediated PI3K-Akt-eNOS signaling was involved in HDL-induced COX-2 expression and PGI(2) release in endothelial cells.

NO-1886 ameliorates glycogen metabolism in insulin-resistant HepG2 cells by GSK-3β signalling

OBJECTIVES

The aim of the study was to elucidate the possible role and mechanism of NO-1886 (ibrolipim, a lipoprotein lipase activator) in ameliorating insulin resistance induced by high palmitate.

METHODS

HepG2 cells were cultured in RPMI 1640 medium and were treated with palmitate to induce insulin resistance. Free fatty acids (FFAs), glucose, glycogen, cell viability and mRNA and protein levels were analysed separately.

KEY FINDINGS

We found that HepG2 cells treated with 0.5 mm palmitate for 48 h led to a significant decrease of insulin-induced glucose consumption (from 2.89 ± 0.85 mm in the control to 0.57 ± 0.44 mm in palmitate). Insulin resistance (IR) of HepG2 cells was induced by 0.5 mm palmitate for 48 h. NO-1886 stimulated glucose consumption, glycogen synthesis and FFA absorption in insulin-resistant HepG2 cells. Maximum stimulation effects were observed with 10 µm NO-1886 for 24 h. Compared with the dimethyl sulfoxide-treated group, 2.5 µm NO-1886 or higher could induce the mRNA expression of lipoprotein lipase. Meanwhile, NO-1886 increased the protein content of P-GSK-3βser(9) and decreased the protein level of GSK-3β in insulin-resistant HepG2 cells, but NO-1886 didn't change the protein levels of PI3-Kp85 and Akt2.

CONCLUSION

Lipoprotein lipase activator NO-1886 could increase glycogen synthesis in HepG2 cells and could ameliorate the insulin resistance, which was associated with GSK-3 signalling.

[Changes of scavenger receptor class B type I and peroxisome proliferator-activated receptor gamma expression in atherosclerotic mini swine]

AIM

To study the expressions of scavenger receptor class B type I(SR-BI) and peroxisome proliferator-activated receptor gamma (PPARgamma) in atherosclerotic mini swine and provide a new mechanism for investigating the pathogenesis of atherosclerosis.

METHODS

Chinese mini swine were fed by a normal control diet or a high fat/high cholesterol diet for 12 months after common carotid artery injury induced by balloon denudation. Plasma total cholesterol(TC), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) were determined by commercially enzymatic methods every two months. The sections, which were taken from liver and abdominal aorta, were stained with hematoxylin eosin. The expressions of SR-BI and PPARgamma mRNA and protein in liver and aorta tissue were detected by reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot and immunohistochemistry respectively.

RESULTS

At the end of 12 months, plasma TC, HDL-C and TG in HFHC mini swine were increased. There were fatty liver and atherosclerotic plaque in mini swine live and aorta respectively. The expression of SR-BI was upregulated in HFHC mini swine liver and aorta tissue.

CONCLUSION

HFHC may induce atherosclerosis and the expression of SR-BI and PPARgamma. Upregulating SR-BI expression may inhibit atherosclerosis. Increasing SR-BI expression in liver and aorta may accelerate SR-BI-mediated reverse cholesterol transport and develop a new anti-atherogenic strategy.

Valsartan reduces interleukin-1beta secretion by peripheral blood mononuclear cells in patients with essential hypertension

BACKGROUND

Chronic low-grade inflammation response may contribute to the pathology of essential hypertension. Angiotensin II (Ang II) may be partly responsible for this process. Our early studies showed that individuals with essential hypertension had increased interleukin-1beta (IL-1beta) secretion by peripheral blood mononuclear cells (PBMCs). In this study, we investigated whether treatment with valsartan, an angiotensin receptor blocker, lowered IL-1beta secretion by PBMCs in patients with essential hypertension.

METHODS

Twenty-four patients with essential hypertension were randomized to treatment with valsartan (80 mg/day, group B) or matching routine therapy group (group A) for 2 weeks. PBMCs were isolated by gradient centrifugation. IL-1beta concentrations in supernatant from PBMCs were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared with routine therapy group, patients treated with valsartan had decreased secretion of IL-1beta in PBMCs after stimulated by lipopolysaccharide (2857+/-643 vs. 2146+/-508 pg/ml, P<0.05).

CONCLUSIONS

We suggest a direct anti-inflammatory effect of valsartan and a pro-inflammatory effect of Ang II in patients with essential hypertension.

[Recombinant analysis of classical swine fever virus]

To study the possible recombinant relationship among differently derived classical swine fever virus, the coding regions of 21 isolates were analyzed to detect recombination and breakpoints through gene trees comparison and quartet analyses. The results show nucleotide area corresponding to E0, E1 and E2 as a possible recombinant tract between ALD ( D49532) and GPE-(D49533) while NS5A-NS5B of the isolate 39 (AF407339) appears to be derived from a virulent Shimen strain (AF092448) sequence. This suggests that intertypic exchanges of genetic materials during mixed infections under natural or laboratorial conditions can lead classical swine fever virus to adapt to the changes of host environment.

Effect of apolipoprotein A-I on ATP binding cassette transporter A1 degradation and cholesterol efflux in THP-1 macrophage-derived foam cells

Cholesterol-loaded macrophage foam cells are a central component of atherosclerotic lesions. ATP binding cassette transporter A1 (ABCA1), the defective molecule in Tangier disease, mediates the efflux of phospholipid and cholesterol from cells to apolipoprotein A-I (apoA-I), reversing foam cell formation. This study investigated the effect of apoA-I on ABCA1 degradation and cholesterol efflux in THP-1 macrophage-derived foam cells. After exposure of the cultured THP-1 macrophage-derived foam cells to apoA-I for different time, cholesterol efflux, ABCA1 mRNA and protein levels were determined by FJ-2107P type liquid scintillator, RT-PCR and Western blot, respectively. The mean ABCA1 fluorescence intensity on THP-1 macrophage-derived foam cells was detected by flow cytometry. Results showed that apoA-I markedly increased ABCA1-mediated cholesterol efflux from THP-1 macrophage-derived foam cells. This was accompanied by an increase in the content of ABCA1. ApoA-I did not alter ABCA1 mRNA abundance. Significantly, thiol protease inhibitors increased the level of ABCA1 protein and slowed its decay in THP-1 macrophage-derived foam cells, whereas none of the proteosome-specific inhibitor lactacystin, other protease inhibitors, or the lysosomal inhibitor NH4Cl showed such effects. The apoA-I-mediated cellular cholesterol efflux was enhanced by thiol protease inhibitors. Our results suggested that thiol protease inhibitors might provide an alternative way to upregulate ABCA1 protein. This strategy is especially appealing since it may mimic the stabilizing effect of the natural ligands apoA-I.

De novo RNA synthesis by a recombinant classical swine fever virus RNA-dependent RNA polymerase

Classical swine fever virus nonstructural protein 5B (NS5B) encodes an RNA-dependent RNA polymerase, a key enzyme of the viral replication complex. To better understand the initiation of viral RNA synthesis and to establish an in vitro replication system, a recombinant NS5B protein, lacking the C-terminal 24-amino acid hydrophobic domain, was expressed in Escherichia coli. The truncated fusion protein (NS5Bdelta24) was purified on a Ni-chelating HisTrap affinity column and demonstrated to initiate either plus- or minus-strand viral RNA synthesis de novo in a primer-independent manner but not by terminal nucleotidyle transferase activity. De novo RNA synthesis represented the preferred mechanism for initiation of classical swine fever virus RNA synthesis by RNA-dependent RNA polymerase in vitro. Both Mg2+ and Mn2+ supported de novo initiation, however, RNA synthesis was more efficient in the presence of Mn2+ than in the presence of Mg2+. De novo initiation of RNA synthesis was stimulated by preincubation with 0.5 mm GTP, and a 3'-terminal cytidylate on the viral RNA template was preferred for de novo initiation. Furthermore, the purified protein was also shown, by North-Western blot analysis, to specifically interact with the 3'-end of both plus- and minus-strand viral RNA templates.

[Effects of oleate on ATP binding cassette transporter A1 expression and cholesterol efflux in THP-1 macrophage-derived foam cells]

To study the effect of oleate on ATP binding cassette transporter A1 (ABCA1) expression and cholesterol efflux in THP-1 macrophage-derived foam cells, after exposure of the cultured THP-1 macrophage-derived foam cells to oleate for different time, cholesterol efflux was determined by FJ-2107P type liquid scintillator. ABCA1 mRNA and its protein level were determined by RT-PCR and Western blot, respectively. The mean ABCA1 fluorescence intensity of THP-1 macrophage-derived foam cells was detected by flow cytometry. The results showed that oleate markedly inhibited ABCA1-mediated cholesterol efflux from THP-1 macrophage-derived foam cells. This was accompanied by a reduction in the membrane content of ABCA1. Oleate did not alter ABCA1 mRNA abundance, indicating that decreased ABCA1 transcription, enhanced mRNA decay, or impaired translation efficiency did not account for these inhibitory effects. Oleate, however, increased ABCA1 turnover when protein synthesis was blocked by cycloheximide. Oleate reduces cholesterol efflux and the level of ABCA1 protein in THP-1 macrophage-derived foam cells.

A growth factor mixture that significantly enhances angiogenesis in vivo

Studies of therapeutic angiogenesis have generally focused on single growth factor strategies. However, multiple factors participate in angiogenesis. We evaluated the angiogenic potential of a growth factor mixture (GFm) derived from bovine bone. The major components of GFm (SDS-polyacrylamide gel electrophoresis, mass spectrometry, and Western blot) include transforming growth factor-beta1-3, bone morphogenic protein-2-7, and fibroblast growth factor-1. GFm was first shown to induce an angiogenic response in chorioallantoic membranes. Next, myocardial ischemia was induced in 21 dogs (ameroid) that were randomized 3 weeks later to received GFm 1 mg/ml (I), GFm 10 mg/ml (II), or placebo (P) (with investigators blinded to conditions) injected in and adjacent to ischemic myocardium. Dogs were assessed 6 weeks later using quantitative and semiquantitative measures. There were GFm concentration-dependent improvements in distal left anterior descending artery (LAD) opacification by angiography (P: 0.4 +/- 0.2, I: 1.1 +/- 0.14, II: 1.6 +/- 0.3, angiographic score p = 0.014). Histologically, there was also concentration-dependent vascular growth response of relatively large vessels (P: 0.21 +/- 0.15, I: 1.00 +/- 0.22, II: 1.71 +/- 0.18, vascular growth score p = 0.001). Resting myocardial blood flow (colored microspheres) was not significantly impaired in any group. However, maximum blood flow (adenosine) was reduced in ischemic territories and did not improve in GFm-treated hearts. GFm, a multiple growth factor mixture, is a potent angiogenic agent that stimulates large vessel growth. Although blood flow did not improve during maximal vasodilatory stress, large intramyocardial collateral vessels developed and angiographic visualization of the occluded distal LAD improved significantly. The use of multiple growth factors may be an effective strategy for therapeutic angiogenesis provided a more effective delivery strategy is devised that can achieve improved maximum blood flow potential.

Selective renal vasodilation and active renal artery perfusion improve renal function in dogs with acute heart failure

Renal failure is common in heart failure due to renovascular constriction and hypotension. We tested whether selective pharmacological renal artery vasodilation and active renal artery perfusion (ARP) could improve renal function without adverse effects on systemic blood pressure in a canine model of acute heart failure (AHF). AHF was induced by coronary microembolization in 16 adult mongrel dogs. In five dogs, selective intrarenal (IR) papaverine (1, 2, and 4 mg/min) was administered into the left renal artery. In six dogs, ARP was performed in the left renal artery to normalize mean renal arterial pressure followed by administration of IR papaverine (2 mg/min). In five dogs, ARP plus intravenous furosemide was tested. Urine output (UO) and cortical renal blood flow decreased during AHF and were restored by 2 mg/min IR papaverine (UO: baseline 4.2 +/- 0.6, AHF 1.6 +/- 1.3, IR papaverine 5.8 +/- 1.1 ml/15 min; cortical blood flow: baseline 4.3 +/- 0.2, AHF 2.4 +/- 0.6, IR papaverine 4.2 +/- 1.2 ml/min/g) with no significant change in aortic pressure. ARP also increased urine output and cortical renal blood flow (UO: baseline 5.0 +/- 1.1, AHF 0.5 +/- 0.4, ARP 3.8 +/- 3.1 ml/15 min; cortical blood flow: baseline 4.0 +/- 0.5, AHF 2.0 +/- 0.8, ARP 3.52 +/- 1.1 ml/min/g). A combination of these methods in AHF further increased urine output to twice the normal baseline (10.5 +/- 7.5 ml/15 min). Addition of furosemide synergistically increased UO above that achieved with ARP alone (5.5 +/- 2.6 versus 40.3 +/- 24.7 ml/15 min, p = 0.03). In conclusion, ARP and selective renal vasodilation may effectively promote salt and water excretion in the setting of heart failure, particularly when systemic blood pressure is low.

Direct coronary artery perfusion from the left ventricle

OBJECTIVES

Trends in coronary bypass surgery require less invasive techniques and more conduits. We investigated the ability of direct coronary perfusion from the left ventricle to support regional and global cardiac function.

METHODS

A conduit was established between the left ventricle and left anterior descending coronary artery (n = 6) with an interposed Starling resistor that allowed for graded regulation of backward flow. Changes of coronary flow, regional function in the territory of the left anterior descending coronary artery, and reactive hyperemia were studied. In 3 separate dogs, functional tolerance to increased heart rate was tested. In another 3 dogs, left ventricle-left anterior descending and left ventricle-left circumflex coronary artery conduits were established simultaneously (double conduit), and global function was tested.

RESULTS

Without flow regulation, flow through the left ventricle-left anterior descending conduit exhibited high peaking (102 +/- 35 mL/min), midsystolic forward flow, and large pandiastolic backward flow (peaking at -47 +/- 22 mL/min). Mean coronary flow and regional function were maintained at 46.0% +/- 7.1% (35.8%-54.2%) and 45.3% +/- 29.1% (-1.8%-74.2%) of their respective normal values. When the Starling resistor was used to regulate backward flow, these values increased to 70.8% +/- 12.5% (56.8%-90.4%) and 70.2% +/- 27.8% (23.6%-107.7%), respectively. Coronary and functional reserve with a left ventricle-left anterior descending conduit were not observed. With the double conduit, global ventricular contractility indexed by end-systolic pressure-volume relation averaged 46% +/- 35% of its normal value.

CONCLUSIONS

A left ventricle-coronary artery conduit supplied approximately 45% of normal blood flow and regional function, and both were improved by regulation of backward flow. Therefore, a conduit from the left ventricle to an epicardial vessel could serve as a rapidly deployable means of revascularizing totally occluded coronary vessels for which suitable natural conduits are not available.

Maximizing hemodynamic effectiveness of biventricular assistance by direct cardiac compression studied in ex vivo and in vivo canine models of acute heart failure

OBJECTIVE

Direct cardiac compression improves effective ventricular contractility. However, associated reductions in filling volumes and increases in arterial pressure occurring at the onset of direct cardiac compression limit the degree to which cardiac output is augmented. We tested the hypothesis that active preload and afterload control maximizes the hemodynamic effectiveness of direct cardiac compression.

METHODS AND RESULTS

Studies in isolated canine hearts loaded with a computer-controlled volume servo system that mimicked heart failure were used to clearly define the hemodynamic effects of direct cardiac compression. Immediately on initiation of direct cardiac compression, ventricular end-diastolic pressure and volume decreased substantially, arterial pressure increased, but stroke volume did not change significantly. When end-diastolic pressure was restored to about 20 mm Hg, stroke volume doubled; decreasing afterload resistance further increased stroke volume by about 30%. Such load adjustments were then tested in vivo in a canine model of acute heart failure induced by coronary artery microembolizations titrated to decrease cardiac output to 33% +/- 9% of control as end-diastolic pressure rose to 20.6 +/- 2.2 mm Hg. Direct cardiac compression decreased end-diastolic pressure to 11.4 +/- 2.6 mm Hg while increasing cardiac output from 0.8 +/- 0.2 to 1. 4 +/- 0.5 L/min (to only approximately 55% of normal). Restoring end-diastolic pressure to 19.6 +/- 2.2 mm Hg by infusions of saline solution increased cardiac output to 1.9 +/- 0.5 L/min. Afterload reduction (nitroprusside), while maintaining end-diastolic pressure at 19.8 +/- 1.3 mm Hg, increased cardiac output to its baseline, 2.8 +/- 1.1 L/min.

CONCLUSIONS

Direct cardiac compression significantly improves ventricular pumping capacity and can restore cardiac output to about 60% of normal in the setting of acute heart failure. When combined with active preload and afterload manipulations, direct cardiac compression can restore cardiac output to normal.

Chronic exercise training preserves prostaglandin-induced dilation of epicardial coronary artery during development of heart failure in awake dogs

Although it has been shown that long-term exercise training preserves endothelium-mediated nitric oxide vasodilator function in chronic heart failure (CHF), whether exercise training exerts similar beneficial effects on endothelial/prostaglandin-mediated vasodilator capacity in coronary circulation during the development of CHF has not been determined. Fifteen mongrel dogs were surgically instrumented for measurement of left ventricular pressure, aortic pressure, coronary blood flow and left circumflex coronary artery diameter. Dogs (n = 5) who underwent 4 weeks of cardiac pacing (210 b/min for 3 weeks and 240 b/min for the 4th week) developed CHF as characterized by significant reduction in left ventricular systolic pressure, mean arterial pressure and left ventricular dP/dt, increases in left ventricular end-diastolic pressure and heart rate, as well as clinical signs of CHF. Endothelial prostaglandin-mediated vasodilation of the epicardial coronary artery was impaired, as manifested by an attenuated arachidonic acid (AA)-induced dilation of the artery (epicardial artery diameter increased by: 0.78 +/- 0. 84% in CHF versus 4.6 +/- 0.89% in normal, P < 0.05); however, prostacyclin (PGI(2))-induced and nitroglycerin-induced vasodilation of the coronary circulation were not altered. In contrast, dogs (n = 6) with cardiac pacing plus daily exercise training (4.4 +/- 0.3 km/h, 2 h/day) only developed mild cardiac dysfunction, and the response of the epicardial coronary artery diameter to AA was preserved (epicardial artery diameter increased by 4.2 +/- 0.98% from baseline, P 0.05 compared to its respective control). Thus, long-term exercise training preserves endothelial/prostaglandin-mediated dilation of epicardial coronary artery during development of CHF.

Physiological and hemodynamic evaluation of nonuniform direct cardiac compression

BACKGROUND

Biventricular direct cardiac compression (DCC) has the potential to support the failing heart without the complications associated with a blood/device interface encountered with the use of current ventricular assist devices. A clinically designed DCC device that provides compression pressure around the base of the heart in synchrony with native ventricular contractions was evaluated with the use of an ex vivo and in vivo canine model of heart failure.

METHODS AND RESULTS

The device was tested over a series of ventricular preloads with the use of an ex vivo canine heart preparation and computerized afterload system that mimicked the conditions of heart failure. The end-systolic pressure-volume relation of the left and right ventricles was shifted upward in parallel by DCC, with the magnitude of the shift averaging 40% of the device compression pressure. The device was tested in vivo with the use of a canine model of acute ischemic heart failure in which graded reductions in ventricular function were created through serial coronary artery embolizations. Under the most severe condition of heart failure, DCC improved cardiac output (CO) by 104% (0.80+/-0.33 to 1.63+/-0.40 L/min) and mean arterial pressure by 95% (45.6+/-11 to 89.0+/-18.2 mm Hg). The CO was typically restored to approximately 60% of the normal baseline value, despite attempts to further increase CO by increasing the amount or duration of compression pressure.

CONCLUSIONS

Nonuniform DCC significantly improves the left and right ventricular pressure-generating capability and, in the setting of acute heart failure, can increase CO and mean arterial pressure. Such DCC devices can potentially avoid the complications associated with currently available ventricular support devices that involve a blood/device interface.

Molecular analysis of rice plants harboring an Ac/Ds transposable element-mediated gene trapping system

In rice, limited efforts have been made to identify genes by the use of insertional mutagens, especially heterologous transposons such as the maize Ac/Ds. We constructed Ac and gene trap Ds vectors and introduced them into the rice genome by Agrobacterium-mediated transformation. In this report, rice plants that contained single and simple insertions of T-DNA were analysed in order to evaluate the gene-tagging efficiency. The 3' end of Ds was examined for putative splicing donor sites. As observed in maize, three splice donor sites were identified at the 3' end of the Ds in rice. Nearly 80% of Ds elements were excised from the original T-DNA sites, when Ac cDNA was expressed under a CaMV 35S promoter. Repetitive ratoon culturing was performed to induce new transpositions of Ds in new plants derived from cuttings. About 30% of the plants carried at least one Ds which underwent secondary transposition in the later cultures. Eight per cent of transposed Ds elements expressed GUS in various tissues of rice panicles. With cloned DNA adjacent to Ds, the genomic complexities of the insertion sites were examined by Southern hybridization. Half of the Ds insertion sites showed simple hybridization patterns which could be easily utilized to locate the Ds. Our data demonstrate that the Ac/Ds-mediated gene trap system could prove an excellent tool for the analysis of functions of genes in rice. We discuss genetic strategies that could be employed in a large scale mutagenesis using a heterologous Ac/Ds family in rice.

The role of angiotensin II AT1 receptor in the maintenance of hemodynamics in a canine model of coronary microembolization-induced heart failure

The purpose of this study was to determine whether Angiotensin II (Ang II) contributes to the regulation of resting hemodynamics via Ang II type 1 (AT1) receptors in awake dogs with coronary microembolization-induced heart failure. Six dogs were surgically instrumented for measurement of systemic hemodynamics and for coronary microembolization. The acute hemodynamic effects of a selective AT1-receptor antagonist, GR138950 (1 mg/kg, i.v.), were determined before and after congestive heart failure (CHF). GR138950 had no effects on hemodynamics before CHF Daily coronary microembolizations (through the previously implanted coronary catheter) resulted in CHF, as documented by hemodynamic measurements, a slight but significant increased Ang II plasma level (17.4 +/- 1.6 vs. 23 +/- 1.0 pg/ml; p < 0.05), and characteristic clinical signs of CHF. After CHF, GR138950 significantly increased left ventricular dP/dt(max) (LVdP/dt(max)) from 1,754 +/- 68 to 2,347 +/- 114 mm Hg/s and decreased LV systolic pressure (LVSP) from 118 +/- 5 to 101 +/- 7 mm Hg; meanwhile, heart rate (from 132 +/- 4 to 102 +/- 6 beats/min) and LV end-diastolic pressure (LVEDP; from 17 +/- 3 to 9 +/- 1.5 mm Hg) were significantly decreased. Mean arterial pressure (MAP) was not affected. The peak effects occurred 90 min after administration. Thus Ang II contributes significantly to resting hemodynamics via AT1 receptors in this CHF model; that is, the specific AT1 blocker inhibits the negative inotropic actions of Ang II in the CHF state.

Isolation and characterization of an anther-specific gene, RA8, from rice (Oryza sativa L.)

An anther-specific cDNA clone of rice, RA8, was isolated from an anther cDNA library by differential screening. RNA blot analysis indicated that the RA8 transcript is present specifically in anthers and the transcript level increased as flowers matured, reaching the highest level in mature flowers. The RA8 clone contains an open reading frame of 264 amino acid residues with a hydrophobic N-terminal region. The deduced amino acid sequences did not show significant homology to any known sequences. Genomic DNA blot analysis showed that RA8 is a single-copy gene. A genomic clone corresponding to the RA8 cDNA was isolated and its promoter region was fused to the beta-glucuronidase (GUS) gene. Transgenic rice plants exhibited anther-specific expression of the GUS reporter gene. Histochemical GUS analysis showed that the RA8 promoter was active in the tapetum, endothecium, and connective tissues of anthers. Experiments showed that expression of the gene starts when microspores are released from tetrads, and it reaches to the maximum level at the late vacuolated-pollen stage. The RA8 promoter may be useful for controlling gene expression in anthers of cereal plants and for generating male-sterile plants.

Hemodynamic effects of a calcium channel promoter, BAY y 5959, are preserved after chronic administration in ischemic heart failure in conscious dogs

BAY y 5959 is a dihydropyridine derivative that binds to L-type calcium channels in a voltage-dependent manner and promotes calcium entry into the cell during the plateau of the action potential by influencing mean open time. Because myofilament responsiveness to calcium is preserved in congestive heart failure (CHF), the inotropic responsiveness to this compound should be preserved in CHF, and tolerance should not develop despite long-term treatment. To test these hypotheses, CHF was induced in 14 chronically instrumented dogs by daily (30 +/- 5 days) intracoronary microsphere injections. The effects of BAY y 5959 (2-h i.v. infusions of 3 microg/kg/min and 10 microg/kg/min) were determined before heart failure, after heart failure was established and then 2 h after the end of a 5-day continuous BAY y 5959 intra-atrial infusion. Before CHF, the positive inotropic effect of BAY y 5959 at a dose of 10 microg/kg/min [left ventricular dP/dt (LVdP/dt) increased from 2955 +/- 132 mmHg to 4897 +/- 426 mmHg, P < .05] was associated with bradycardia (HR decreased from 92 +/- 4 to 78 +/- 6 b/min, P <.05), slight increases in mean arterial pressure (it increased from 100 +/- 2 mmHg to 113 +/- 5 mmHg, P <.05) and did not alter left ventricular end-diastolic pressure. In CHF, BAY y 5959 continued to induce dose-dependent increases in left ventricular systolic pressure, LVdP/dt and mean arterial pressure, as well as causing bradycardia and a significant decrease in left ventricular end-diastolic pressure. After a 5-day infusion of BAY y 5959, base-line LVdP/dt and left ventricular end-diastolic pressure improved. The responses of LVdP/dt and mean arterial pressure to BAY y 5959 were similar to those of the control state. The sustained responses in CHF and after long-term infusion suggest that BAY y 5959 may be an effective and potent inotropic agent for treatment of CHF that does not lead to tolerance to its positive inotropic effects.

Effect of BAY y 5959 on myocardial function and metabolism in normal and failing hearts

BAY y 5959 is a dihydropyridine derivative with positive inotropic actions mediated by a direct increase in intracellular calcium. We characterized the direct myocardial actions of this new agent in hearts isolated from seven normal dogs and from five dogs with repeated coronary microembolization-induced heart failure. Inotropic actions of BAY y 5959 were accompanied by little effect on duration of contraction and by prolongation of the monophasic action potential (MAP); in contrast, isoproterenol decreased contraction and MAP durations. Whereas inotropic responsiveness to isoproterenol was blunted in embolized hearts, these actions of BAY y 5959 were relatively preserved in the heart failure state. Isoproterenol increased heart rate, whereas BAY y 5959 had little effect. Changes in coronary vascular resistance also decreased similarly for isoproterenol and BAY y 5959. Finally, for comparable inotropy, increases in myocardial oxygen consumption were similar for isoproterenol and for BAY y 5959. In summary, preserved inotropic responsiveness and lack of positive chronotropic actions are two clinically favorable features of this type of inotropic agents compared with a typical beta-adrenergic agonist.

Physical training alters the pathogenesis of pacing-induced heart failure through endothelium-mediated mechanisms in awake dogs

BACKGROUND

Beneficial effects of exercise training on cardiovascular function in chronic heart failure (CHF) have been suggested previously, but the underlying mechanisms are unknown. We tested whether daily exercise training improves systemic hemodynamics and preserves endothelium-mediated vasodilator function during development of heart failure.

METHODS AND RESULTS

Fifteen dogs were surgically instrumented for hemodynamic measurements. One group of dogs underwent 4 weeks of cardiac pacing (210 bpm for 3 weeks and 240 bpm during week 4), and another group underwent pacing plus daily exercise training (4.4+/-0.3 km/h, 2 h/d). Pacing-alone dogs developed CHF characterized by typical hemodynamic abnormalities, blunted endothelium-mediated vasodilator function in coronary and femoral circulations, and decreased gene expression of endothelial constitutive nitric oxide synthase (ECNOS, normalized to GAPDH expression; normal, 1.15+/-0.31 versus CHF, 0.29+/-0.08, P<.05). Exercise training preserved normal hemodynamics at rest, endothelium-mediated vasodilator function, and gene expression of ECNOS (0.72+/-0.16 versus normal, P=NS). Inhibition of NO synthesis (nitro-L-arginine) in exercise-trained dogs abolished the preserved endothelium-mediated vasodilation of epicardial coronary arteries and elevated left ventricular end-diastolic pressure (7.7+/-0.3 to 19+/-3.4 mm Hg, P<.05), suggesting that the preservation of resting hemodynamics was in large part due to preserved endothelial function concealing the underlying CHF state.

CONCLUSIONS

Long-term exercise training altered the natural history of heart failure due to rapid cardiac pacing. One of the underlying mechanisms is through the preservation of endothelial vasodilator function.

Impact of exercise training on ventricular properties in a canine model of congestive heart failure

Exercise training improves functional class in patients with chronic heart failure (CHF) via effects on the periphery with no previously documented effect on intrinsic left ventricular (LV) properties. However, because methods used to evaluate in vivo LV function are limited, it is possible that some effects of exercise training on the failing heart have thus far eluded detection. Twelve dogs were instrumented for cardiac pacing and hemodynamic recordings. Hearts were paced rapidly for 4 wk. Six of the dogs received daily treadmill exercise (CHF(EX), 4.4 km/h, 2 h/day) concurrent with rapid pacing, while the other dogs remained sedentary (CHFs). Hemodynamic measurements taken in vivo at the end of 4 wk revealed relative preservation of maximum rate of pressure rise (2,540 +/- 440 vs. 1,720 +/- 300 mmHg/s, P < 0.05) and LV end-diastolic pressure (9 +/- 5 vs. 19 +/- 4 mmHg, P < 0.05) in CHF(EX) compared with CHFs. The hearts were then isolated and cross perfused for in vitro measurement of isovolumic pressure-volume relations; these results were compared with those of six normal dogs (N). Systolic function was similarly depressed in both groups of pacing animals [end-systolic elastance (Ees) values of 1.66 +/- 0.47 in CHFs, 1.77 +/- 0.38 in CHF(EX), and 3.05 +/- 0.81 mmHg/ml in N, with no changes in volume axis interceptors of the end-systolic pressure-volume relationship]. The diastolic myocardial stiffness constant, k, was elevated in CHFs and was normalized by exercise training (32 +/- 3 in CHFs, 21 +/- 3 in CHF(EX), 20 +/- 4 in N). Thus daily exercise training preserved in vivo hemodynamics during 4 wk of rapid cardiac pacing and was accompanied by a significant change in diastolic myocardial stiffness in vitro. These findings suggest that changes in heart function may contribute to the overall beneficial hemodynamic effects of exercise training in CHF by a significant effect on diastolic properties.

Coronary endothelial dysfunction precedes heart failure and reduction of coronary reserve in awake dogs

Endothelial dysfunction in coronary circulation is well documented in heart failure (HF). However, whether this dysfunction is a consequence of heart failure or precedes the development of HF remains unknown. To determine endothelium-dependent regulation in the remote coronary vasculature in a canine coronary microembolization-induced HF model, seven dogs were chronically instrumented for measurement of systemic hemodynamics, for selective coronary microembolization via an implanted coronary catheter and for measurement of coronary blood flow in the non-embolized coronary artery. Microembolizations were performed daily until hemodynamic and echocardiographic measurements showed HF. The responses of coronary blood flow to acetylcholine (0.25, 0.5, 5, 10 microg/kg), nitroglycerin (0.2, 0.8, 5, 25 microg/kg), adenosine (0.25, 0.5, 2, 5 micromol/kg) and brief coronary occlusions (5, 10, 15, 20, 30 s) were examined. Although no signs of HF developed and the responses of coronary blood flow to nitroglycerin, adenosine and occlusions were not altered, the response to acetylcholine was selectively reduced after 1 week of embolization (275,000+/-55,000 microspheres). Resting coronary flow increased from 21.3+/-1.4 ml/min in control state to 27.7+3.5 ml/min (P<0.001). As HF developed, characterized by an elevated left ventricular end-diastolic pressure (6.4+/-1.6 v 16+/-1.6 mmHg, P<0.001), a decreased area ejection fraction (54+/-5 v 36+/-5%, P<0.05) and a reduced beta-adrenergic response to isoproterenol, the responses of coronary blood flow to acetylcholine, nitroglycerine, adenosine and occlusions were consistently depressed. Resting coronary blood flow was decreased to 15.4+/-2.7 ml/min (P<0.01). Our results indicate, that there is a selectively impaired endothelium-mediated dilator capacity of the resistance coronary vasculature before the development of HF and a reduction of the coronary flow reserve.

Effects of levosimendan on myocardial contractility and oxygen consumption

Levosimendan is hypothesized to be primarily a calcium sensitizer in vitro. Therefore, its inotropic action may be similar in both the normal and the congestive heart failure (CHF) state, and it may be associated with a decreased energetic cost of inotropism in vivo. To test these hypotheses, we gave levosimendan to cross-circulated isolated hearts from normal (n = 11) and CHF (n = 7, 4-week rapid pacing) dogs. Peak isovolumic left ventricular pressure at an end-diastolic pressure of 5 mm Hg (Pmax,5) measured by an intraventricular balloon was 120 +/- 15 mm Hg in normal dogs, and it was increased by approximately 40% in response to approximately 0.63 microM levosimendan. In CHF dogs, base-line Pmax,5 was only 60 +/- 12 mm Hg (P < .01 compared to normals), and approximately 8.4 microM levosimendan (P < .05) was required to increase Pmax,5 by approximately 40%. The inotropic actions were associated with increases in unloaded myocardial oxygen consumption by comparable amounts in normal and falling hearts. The blunted inotropic response in CHF and the energetic cost of inotropism were also comparable to those obtained with isoproterenol. In other studies, there was no significant inotropic action of levosimendan in Langendorff-perfused rat hearts (n = 5), and intracellular calcium concentration, estimated by macroinjected aequorin, in ferret hearts (n = 2) increased dose-dependently. These findings suggest that inotropic actions of levosimendan in vivo may be mediated in part by factors other than calcium sensitization.

Prevention of postoperative gastroesophageal reflux by preservation of lower esophageal sphincter in partial esophagectomy

Postoperative reflux esophagitis is a common complication after partial removal of the esophagus and the whole gastric cardia for reconstruction through esophagogastrostomy. In 10 cases, the lower esophageal sphincter (LES) was preserved for a length of 2.05 +/- 0.33cm (mean +/- S) during partial esophagectomy for benign or malignant lesion at the middle and lower portion of the thoracic esophagus. The mean value of the LES pressures measured two weeks after operations was 2.40 +/- 0.64 kPa (18 +/- 4.8 mmHg) and the postoperative X-ray barium meal examination revealed no evidence of gastroesophageal reflux. Our study suggested that the preserved LES should effectively act as a functional barrier against the development of reflux esophagitis.