Association of rs2200733 at 4q25 with atrial flutter/fibrillation diseases in an Italian population.

BACKGROUND: Atrial fibrillation (AF) and atrial flutter (AFL) are common cardiac conduction disorders affecting many people. Recent studies on sporadic cases of AF/AFL showed a significant association of the single nucleotide polymorphism rs2200733T with the disease, suggesting a genetic factor in the development of the disease. OBJECTIVES: To determine the association of rs2200733 with AF/AFL derived from an Italian population sample. SUBJECTS: 78 patients with AF/AFL and 348 controls took part in the study. DESIGN: Genetic case-control study. RESULTS: The results indicate that there is a positive, significant association between the rs2200733 T allele and patients with AF/AFL of Italian origin (allelic p<0.001 with OR = 2.17). CONCLUSION: These results derived from a sample of the Italian population agree with previously reported findings from an Icelandic study, which also found that the minor allele rs2200733 was associated with AF/AFL disease.

A reporter assay for target validation in primary neuronal cultures.

The deposition of beta-amyloid peptides (Abeta42 and Abeta40) in neuritic plaques is one of the hallmarks of Alzheimer's disease (AD), and genes modulating their brain levels and neuronal effects could result in future disease modifying therapies. The causal association of candidate targets with AD is of paramount importance in current drug discovery, as a lack of efficacy of many candidate drugs is often due to inadequate validation of their pharmacological target. In Alzheimer's as well as in other neurodegenerative diseases, in vitro target validation is hampered by the difficulty of transfecting primary neuronal cultures and assaying the effects of genes on neuronal viability. Here we describe a rapid, sensitive and simple reporter-based assay for the validation of genes putatively associated with Abeta-mediated neurotoxicity, which can in principle be extended to the validation of targets in the context of other neuronal insults. The assay is suitable for the generation of robust and reproducible data in primary neuronal cultures allowing the dissection at a molecular level of complex pathways activated by the toxic insult in a cellular context that more closely represents the real disease situation.

Heart-targeted overexpression of caspase3 in mice increases infarct size and depresses cardiac function.

Up-regulation of proapoptotic genes has been reported in heart failure and myocardial infarction. To determine whether caspase genes can affect cardiac function, a transgenic mouse was generated. Cardiac tissue-specific overexpression of the proapoptotic gene Caspase3 was induced by using the rat promoter of alpha-myosin heavy chain, a model that may represent a unique tool for investigating new molecules and antiapoptotic therapeutic strategies. Cardiac-specific Caspase3 expression induced transient depression of cardiac function and abnormal nuclear and myofibrillar ultrastructural damage. When subjected to myocardial ischemia-reperfusion injury, Caspase3 transgenic mice showed increased infarct size and a pronounced susceptibility to die. In this report, we document an unexpected property of the proapoptotic gene caspase3 on cardiac contractility. Despite inducing ultrastructural damage, Caspase3 does not trigger a full apoptotic response in the cardiomyocyte. We also implicate Caspase3 in determining myocardial infarct size after ischemia-reperfusion injury, because its cardiomyocyte-specific overexpression increases infarct size.

Pharmacological characterisation of the human small conductance calcium-activated potassium channel hSK3 reveals sensitivity to tricyclic antidepressants and antipsychotic phenothiazines.

A stable CHO-K1 cell line was developed which expresses the human small conductance calcium-activated potassium channel hSK3. Immunofluorescence microscopy using an anti-SK3 antibody and radioligand binding using [(125)I]-apamin demonstrated the presence of hSK3 channel in the recombinant cell line. This cell line was utilised in a fluorescence assay using the membrane potential-sensitive dye DiBAC(4)(3) to functionally analyse and pharmacologically characterise this potassium channel. The analysis of known blockers of calcium-activated potassium channels revealed the highest potency for apamin (IC(50)=13.2 nM). This result was confirmed by direct recordings of SK3 currents using the whole-cell patch-clamp technique. Tricyclic antidepressants such as desipramine, imipramine and nortriptyline as well as phenothiazines such as fluphenazine, promethazine, chlorpromazine and trifluoperazine blocked the hSK3 channel with micromolar potencies. These compounds also displaced [(125)I]-apamin binding to the hSK3 channel thus suggesting direct and competitive channel blocking activity. Since these compounds share a common three-ring molecular core structure, this feature seems to be important for channel blocking activity. The serine/threonine protein phosphatase inhibitors okadaic acid and calyculin A were able to abolish channel activation with nanomolar potencies, but did not displace [(125)I]-apamin binding. Thus, phosphorylation of hSK3 or an accessory channel subunit seems to be involved in its modulation.

Presynaptic localization of the small conductance calcium-activated potassium channel SK3 at the neuromuscular junction.

Small conductance, calcium-activated potassium channels (SK channels) are present in most neurons, in denervated muscles and in several non-excitable cell types. In excitable cells SK channels play a fundamental role in the generation of the afterhyperpolarization which follows an action potential, thereby modulating neuronal firing and regulating excitability. To date, three channel subunits (SK1-3) have been cloned from mammalian brain. Since SK3 only has been shown to be expressed in muscles upon denervation, this channel may be involved in hyperexcitability and afterhyperpolarization observed in muscle cells in the absence of the nerve. Using confocal microscopy and SK3 specific antibodies, we demonstrate that SK3 immunoreactivity is present at the rat neuromuscular junction in denervated but also in innervated muscles. In denervated muscle fibers, SK3 is localized in the extrajunctional as well as the junctional plasma membrane, where it appears to be less abundant in the acetylcholine receptor-rich domains, corresponding to the crests of the postsynaptic folds. In innervated muscles, SK3 is not detectable in the muscle fiber but is present at the neuromuscular junction and seems to be localized presynaptically in the motor nerve terminals. Axonal accumulation of SK3 immunoreactivity occurs above and below a ligature of rat sciatic nerve, indicating that the SK3 protein is transported in both directions along the axons of the motor neurons. During rat development SK3 immunoreactivity is not found at the neuromuscular junction until day 35 of postnatal development when SK3 first appears in the motor neuron terminals. These results indicate that SK3 channels are components of the presynaptic compartment in the mature neuromuscular junction, where they may play an important regulatory role in synaptic transmission.

Actin rearrangement-inducing factor of baculoviruses is tyrosine phosphorylated and colocalizes to F-actin at the plasma membrane.

In previous studies we have identified actin rearrangement-inducing factor 1 as an early gene product of Autographa californica multicapsid nuclear polyhedrosis virus that is involved in the remodeling of the actin cytoskeleton. We have constructed viral recombinants with a mutated Arif-1 open reading frame that confirm the causal link of Arif-1 expression and the actin rearrangement observed as accumulation of F-actin at the plasma membrane at 3 to 7 h postinfection. Infection with Arif mutant viruses leads to the loss of actin accumulation at the plasma membrane in TN-368 cells, although in the course of infection, early actin cables and nuclear F-actin are observed as in wild-type-infected cells. By immunofluorescence studies, we have demonstrated the localization of Arif-1 at the plasma membrane, and confocal imaging reveals the colocalization to F-actin. Accordingly, the approximately 47-kDa Arif-1 protein is observed exclusively in membrane fractions prepared at 4 to 48 h postinfection, with a decrease at 24 h postinfection. Phosphatase treatment suggests that Arif-1 is modified by phosphorylation. Antibodies against phosphotyrosine precipitate Arif-1 from membrane fractions, indicating that Arif-1 becomes tyrosine phosphorylated during the early and late phases of infection. In summary, our results indicate that functional Arif-1 is tyrosine phosphorylated and is located at the plasma membrane as a component of the actin rearrangement-inducing complex.

Cloning and characterization of the human phosphoinositide-specific phospholipase C-beta 1 (PLC beta 1).

Phospholipase C-beta (PLC beta) catalyses the generation of inositol 1,4,5-trisphosphate (IP(3)) and diacylglycerol (DAG) from phosphatidylinositol 4,5-bisphosphate (IP(2)), a key step in the intracellular transduction of a large number of extracellular signals, including neurotransmitters and hormones modulating diverse developmental and functional aspects of the mammalian central nervous system. Four mammalian isozymes are known (PLC beta 1-4), which differ in their function and expression patterns in vivo. We have characterized the human PLC beta 1 genomic locus (PLC beta 1), cloned two distinct PLC beta 1 cDNAs (PLC beta 1a and b) and analysed their respective expression patterns in a comprehensive panel of human tissues using quantitative TaqMan technology. The two cDNAs derive from transcripts generated through alternative splicing at their 3' end, and are predicted to encode for PLC beta 1 isoforms differing at their carboxy-terminus. The human PLC beta 1 isoforms are co-expressed in the same tissues with a distinctly CNS-specific profile of expression. Quantitative differences in PLC beta 1 isoform expression levels are observed in some tissues. Transient expression of epitope-tagged versions of the two isoforms followed by immunofluorescence revealed localization of the proteins to the cytoplasm and the inner side of the cell membrane. Finally, we characterized the structure of the PLC beta 1 locus and confirmed its mapping to human chromosome 20.

Production of Eudragit microparticles by spray-drying technique: influence of experimental parameters on morphological and dimensional characteristics.

The aim of this study was to evaluate the influence of operating parameters on the characteristics of methacrylate microparticles prepared by spray-drying technique. Eudragit microparticles were prepared by a spray-drying method. The influence of different experimental parameters (i.e., solvent, feed rate, air flow rate, air-drying temperature, and aspiration flow rate) on microparticle morphology, size distribution, and recovery was studied. In addition, different Eudragit types and Eudragit RS concentrations were employed. Optical and electron microscopy were employed to analyze microparticle morphology and dimensional distribution. Finally, prednisolone as model drug was encapsulated in Eudragit RS microparticles. Low feed rate values yielded the best results in terms of microparticle morphology. Changes in nebulizing air flow did not result in a corresponding effect on microparticle characteristics. An increase of air-drying temperature resulted in a reduction of microparticle dimension and recovery. A low flow of drying air was preferable because this resulted in microparticles with an optimal morphology. The polymer concentration affected both morphology and dimensions of microparticles. The encapsulation of prednisolone led to good incorporation efficiencies without altering percentage of recovery, morphology, and mean dimension of the microparticles. The selection of appropriate parameters yielded spray-dried Eudragit RS microparticles characterized by good morphology and narrow dimensional distribution.

Increased cardiomyocyte apoptosis and changes in proapoptotic and antiapoptotic genes bax and bcl-2 during left ventricular adaptations to chronic pressure overload in the rat.

BACKGROUND: Left ventricular hypertrophy (LVH) represents both an adaptive response to increased cardiac work load and a precursor state of heart failure. Recent evidence linked cardiac myocyte death by apoptosis with LVH and heart failure. It remained unclear, however, whether apoptosis participated in the transition from LVH to left ventricular dysfunction (LVD). METHODS AND RESULTS: Cardiac myocyte apoptotic events and changes in apoptosis-specific genes were studied in a rat model of chronic pressure overload induced by transverse aortic constriction. The changes in left ventricular geometry and function were assessed by echocardiography. Transverse aortic constriction rats progressively developed "concentric" LVH and subsequently, LVD. A similar distribution of LVH and LVD was found 18 weeks after surgery. At this time point, we determined the occurrence of myocyte apoptosis by DNA laddering, in situ DNA TUNEL labeling, and light and electron microscopy. The monitoring of proapoptotic and antiapoptotic genes was determined by Western blot and immunohistochemistry. Our data demonstrated that cardiomyocyte apoptotic events increased from virtually undetectable (in sham-operated controls, SH) to 0.8/10(3) and 1.5/10(3) positive nuclei in LVH and LVD, respectively. Fibrosis also increased in the subendocardial and midwall regions of LVH and LVD rats compared with SH. Expression of the proapoptotic gene bax increased, whereas that of antiapoptotic gene bcl-2 decreased in LVH and LVD compared with SH. CONCLUSIONS: These data suggest that in response to chronic pressure overload, cardiomyocyte-specific apoptosis contributed to the transition from LVH to LVD. LVH and LVD were accompanied by a dramatic cardiomyocyte upregulation of the proapoptotic gene bax and reduced bcl-2/bax ratio, predisposing cardiomyocytes to apoptosis.

Identification of the early actin-rearrangement-inducing factor gene, arif-1, from Autographa californica multicapsid nuclear polyhedrosis virus.

In response to Autographa californica multicapsid nuclear polyhedrosis virus (AcMNPV) infection, a sequential rearrangement of the actin cytoskeleton occurs. Previous studies suggest that the penetration of nucleocapsids induces early actin cables followed by further changes of the actin cytoskeleton which depend on early viral gene expression. By transfection of a plasmid library into Trichoplusia ni TN-368 cells, we have identified an early viral gene, designated arif-1, that is able to induce actin rearrangement. The determination of the nucleotide sequence of arif-1 revealed one open reading frame potentially encoding a gene product of 45 kDa with no significant sequence homology to known proteins. After expression of arif-1 in transfected cells, the induced actin rearrangement, visualized by fluorescence microscopy, was comparable to the changes of the actin cytoskeleton at 3 to 7 h postinfection. These changes are based on early viral gene expression during the infection cycle. A causal link between arif-1 expression and actin rearrangement in infected cells is suggested by infection studies with the AcMNPV/Spodoptera frugiperda MNPV hybrid, which carries a deletion in the arif-1 gene. In transfection experiments the presence of the known viral transactivator IE1 was required in addition to ARIF-1 to induce actin rearrangement. IE1 was needed for promoter activation of the arif-1 gene, since arif-1 expression under the control of the early pe38 promoter was sufficient to induce actin rearrangement in transfected cells. Primer extension analyses showed that the arif-1 gene is transcribed only during the early phase of AcMNPV infection in T. ni TN-368 cells. There was a delay of about 1 h compared to ie1 transcription, which is in agreement with the assumption that IE1 transactivates the arif-1 promoter during infection.

Baculovirus infection of Spodoptera exigua larvae: lacZ expression driven by promoters of early genes pe38 and me53 in larval tissue.

To follow the progression of infection of Autographa californica multicapsid nuclear polyhedrosis virus (AcMNPV) within tissues of its larval host, we have constructed AcMNPV recombinants carrying lacZ reporter genes under the control of the early virus promoters pe38 and me53, in addition to the authentic genes. The early promoter-lacZ gene cassettes were located upstream of the very late polyhedrin gene. In infected insect cell lines, pe38 transcription is initiated at an early promoter, while me53 transcripts start from both early and late sites. Transcriptional mapping of the duplicated me53 and pe38 promoters driving lacZ expression showed that they initiated at the same start sites as in the authentic genes. Expression of lacZ by these recombinants was compared to a recombinant driving beta-glucuronidase expression from the very late p10 promoter and lacZ expression from the constitutive heat shock protein 70 promoter of Drosophila melanogaster. After infection of Spodoptera exigua larvae with the different recombinants, we followed reporter gene expression and polyhedron formation in different tissues using immunohistochemistry and electron microscopy. LacZ expression, indicative of early viral transcriptional activity, was detected in nearly all larval tissues during the course of infection. In most tissues these early events were followed by pathophysiological changes associated with late and very late gene expression. However, p10 transcription and polyhedron formation were not observed in midgut goblet cells, Malpighian tubules and salivary glands. These results suggest that expression of early virus genes, such as me53 and pe38, is not restricted to larval tissues that are permissive for AcMNPV replication.

Expression of PE38 and IE2, viral members of the C3HC4 finger family, during baculovirus infection: PE38 and IE2 localize to distinct nuclear regions.

The pe38 gene of Autographa californica nuclear polyhedrosis virus represents one of the major early transcripts after viral infection. The function of the pe38 protein, which contains a C3HC4 zinc finger motif, is still not understood. We have raised polyclonal antiserum against the pe38 protein, PE38, produced in bacteria to investigate pe38 expression in the course of infection. A approximately 38-kDa polypeptide is first detectable at 2 h postinfection and decreases rapidly after 24 h. During the late phases of infection, a smaller protein of approximately 20 kDa which cross-reacts with the PE38-specific antiserum is visible at a constant level until 120 h postinfection. Since the pe38 gene shares a divergent promoter unit with the ie2 gene (formerly IEN), we have compared the expressions of the two genes. Polyclonal antibodies were raised against the bacterially expressed ie2 protein. The temporal expression pattern of the approximately 49-kDa ie2 protein is comparable to that of the approximately 38-kDa pe38 protein. Furthermore, both proteins are present in the nuclear fraction of A. californica nuclear polyhedrosis virus-infected Spodoptera frugiperda cells, but the approximately 38-kDa pe38 protein is also detectable in the cytoplasm while the smaller protein of approximately 20 kDa is exclusively present in the cytoplasmic fraction. Immunofluorescence analysis reveals that PE38 and IE2 localize to distinct regions within the nucleus mainly detected after transfection of pe38- and ie2-expressing constructs.

An aldose reductase homologous gene from barley: regulation and function.

The expression of a barley gene homologous to aldose reductase and aldehyde reductase is restricted to the embryo and temporally correlated with its acquisition of desiccation tolerance. In the work presented, two aspects of this barley gene were investigated: its transcriptional regulation and the initial characterization of the enzymatic function. The transcriptional regulation of the gene was studied in transgenic tobacco by analysing the expression of chimeric genes containing 5' sequences of the barley gene transcriptionally fused to the GUS reporter gene. This functional analysis of the promoter revealed that a 1364 bp 5' fragment confers the appropriate pattern of expression to the reporter gene in tobacco and that a short promoter fragment (-114 to +75) containing the sequence TACGTGGC, homologous to plant G-box elements, is sufficient for developmental expression during embryogenesis. To investigate the enzymatic properties of the gene product the wild-type protein and a mutant carrying a lysine 259 to methionine substitution were overexpressed in a procaryotic system and purified to homogeneity. The wild-type protein exhibits aldose reductase activity in the reduction of DL-glyceraldehyde and D-erythrose specifically using NADPH as co-factor whereas the mutant shows markedly reduced activity. However, the barley protein possesses some properties different to those of animal aldose and aldehyde reductases and its biological target still needs to be identified.

An ABA and GA modulated gene expressed in the barley embryo encodes an aldose reductase related protein.

In most higher plants a period of desiccation is the terminal event in embryogenesis. Excised barley embryos acquire desiccation tolerance at a precise developmental stage and cDNA clones have been isolated which are temporally linked with desiccation tolerance. One such clone (pG22-69) with a putative gene product of 34 kd displays high structural homology to mammalian genes encoding an NADPH dependent aldose reductase involved in the synthesis of sorbitol. This first aldose reductase gene of plants is expressed constitutively during embryo maturation and is modulated by the plant hormones abscisic acid (ABA) and gibberellic acid (GA). Immunohistochemistry showed that the protein is preferentially expressed in tissues formed at early stages in embryogenesis. Measurements of enzymatic activity indicate that pG22-69 encodes an active aldose reductase. The finding of this reductase activity and the cloning of the corresponding gene supports the existence of a metabolic pathway in plants playing a role in the synthesis of osmolytes like sorbitol. The significance of this work is that genes of related structure and functions are being used in diverse organisms to fulfil stress related biological requirements.