Regulation and role of REST and REST4 variants in modulation of gene expression in in vivo and in vitro in epilepsy models

Repressor element-1 silencing transcription factor (REST) is a candidate modulator of gene expression during status epilepticus in the rodent. In such models, full-length REST and the truncated REST4 variant are induced and can potentially direct differential gene expression patterns. We have addressed the regulation of these REST variants in rodent hippocampal seizure models and correlated this with expression of the proconvulsant, substance P encoding, PPT-A gene. REST and REST4 were differentially regulated following kainic acid stimulus both in in vitro and in vivo models. REST4 was more tightly regulated than REST in both models and its transient expression correlated with that of the differential regulation of PPT-A. Consistent with this, overexpression of a truncated REST protein (HZ4, lacking the C-terminal repression domain) increased expression of the endogenous PPT-A gene. Similarly the proximal PPT-A promoter reporter gene construct was differentially regulated by the distinct REST isoforms in hippocampal cells with HZ4 being the major inducer of increased reporter expression. Furthermore, REST and REST4 proteins were differentially expressed and compartmentalized within rat hippocampal cells in vitro following noxious stimuli. This differential localization of the REST isoforms was confirmed in the CA1 region following perforant path and kainic acid induction of status epilepticus in vivo. We propose that the interplay between REST and REST4 alter the expression of proconvulsant genes, as exemplified by the PPT-A gene, and may therefore regulate the progression of epileptogenesis.

Effect of reduced pH on inorganic polyphosphate accumulation by Burkholderia cepacia complex isolates

AIMS

Burkholderia cepacia complex (Bcc) isolates causing pulmonary infection in cystic fibrosis (CF) patients grow within an acidic environment in the lung. As exposure to acid pH has been shown to increase intracellular inorganic polyphosphate (polyP) formation in some bacteria, we investigated the inter-relationship between acidic pH and polyP accumulation in Bcc isolates.

METHODS AND RESULTS

The formation of polyP by one Burkholderia cenocepacia clinical isolate was initially examined at a range of pH values by measuring total intracellular polyP accumulation and phosphate uptake. The pattern of polyP accumulation corresponded with the pattern of phosphate uptake with the maximum for both occurring at pH 5.5. Phosphate uptake and formation of polyP by this isolate was further determined over 48 h at pH 5.5, 6.5 and 7.5; formation of polyP was maximal at pH 5.5 at all time points studied. Sixteen of 17 additional clinical and environmental Bcc isolates examined also exhibited maximum phosphate uptake at pH 5.5.

CONCLUSIONS

Both clinical and environmental Bcc isolates, of five genomovars, show enhanced formation of polyP in an acidic environment. Given both the speculated role of polyP in pathogenesis, cell signalling and biofilm formation and the acidic nature of the CF lung, this may be of considerable clinical importance.

SIGNIFICANCE AND IMPACT OF THE STUDY

Growth of Bcc in an acidic environment, such as that found in the lungs of CF patients may be influenced in part by polyP accumulation.

Myelodysplastic patients with raised percentage of hypochromic red cells have evidence of functional iron deficiency

Raised percentage hypochromic red cells (%HRC) were detected at diagnosis in 10 of 34 consecutive patients with low-risk myelodysplastic syndrome (MDS) [refractory anemia (RA) (4/26) and RA with ring sideroblasts (6/8)], all of whom had normal or increased serum ferritin and bone marrow iron stores. Elevated %HRC has persisted in all 10 cases and subsequently developed in another RA patient who later had a complete remission of MDS with normalisation of %HRC after a respiratory tract infection. A strong positive correlation was found between %HRC and erythrocyte zinc protoporphyrin levels in 11 MDS patients tested (p=0.01), suggesting that functional iron deficiency contributes to ineffective erythropoiesis in cases of MDS with raised %HRC. Five of seven patients with elevated %HRC had satisfactory haemoglobin responses to a trial of human recombinant erythropoietin without iron supplementation.

Nitric oxide, a biological double-faced janus--is this good or bad?

Nitric oxide (NO) is a biological messenger molecule produced by one of the essential amino acids L-arginine by the catalytic action of the enzyme NO synthase (NOS). The dual role of NO as a protective or toxic molecule is due to several factors, such as; the isoform of NOS involved, concentration of NO and the type of cells in which it is synthesised, the availability of the substrate L-arginine, generation of guanosine 3,5'-cyclic monophosphate (cGMP) from soluble guanylate cyclase and the overall extra and intracellular environment in which NO is produced. NOS activation as a result of trauma (calcium influx) or infection leads to NO production, which activates its downstream receptor sGC to synthesise cGMP and/or leads to protein nitrosylation. This may lead to one or more systemic effects including altered neurotransmission which can be protective or toxic, vaso/bronchodilatation in the cardiovascular and respiratory systems and enhanced immune activity against invading pathogens. In addition to these major functions, NO plays important role in thermoregulation, renal function, gastrointestinal motility, endocrine function, and various functions of the urogenital system ranging from renin secretion to micturation; spermatogenesis to penile erection; and ovulation to implantation and parturition. A schematic summary of the functions of NO and the various isoforms of NOS expressed in body systems is shown in figure 1. In this review, the historical background, biochemistry and biosynthesis of NO and its enzymes together with the mechanism of NO actions in physiology and pathophysiology are discussed.

Development of Daptomycin resistance in vivo in methicillin-resistant Staphylococcus aureus

Daptomycin is a new lipopeptide antibiotic that is rapidly bactericidal against Staphylococcus aureus. We report daptomycin resistance and treatment failure in 2 patients with osteomyelitis due to methicillin-resistant S. aureus. Disk diffusion susceptibility testing failed to detect resistance. Daptomycin at high concentration retained bactericidal activity against resistant isolates.

Problem pulmonary pathogens: Pseudomonas aeruinosa

Pseudomonas aeruginosa is a common and highly lethal agent of nosocomial pneumonia, especially among patients receiving mechanical ventilation. It is widespread in the environment and commonly recovered from water in nature and in hospital settings. P. aeruginosa is endowed with a formidable array of virulence factors that facilitate attachment to host cells, tissue invasion, and systemic disease. It is intrinsically resistant to many commonly used antibiotics due to a complex variety of mechanisms that we will briefly review. Recent advances in the understanding of the molecular biology of this organism have shed considerable light on its ability to form biofilms, which facilitate adherence especially in cystic fibrosis patients, and confer resistance to clearance by host immune mechanisms and antimicrobial killing. Treatment studies have demonstrated a significant risk of emergence of resistance during therapy with a variety of agents. Several studies suggest that two drugs are better than one for therapy of serious infections, although dual therapy does not always prevent emergence of resistant strains.

Bowel colonization with resistant gram-negative bacilli after antimicrobial therapy of intra-abdominal infections: observations from two randomized comparative clinical trials of ertapenem therapy

The selection of resistant gram-negative bacilli by broad-spectrum antibiotic use is a major issue in infection control. The aim of this comparative study was to assess the impact of different antimicrobial regimens commonly used to treat intra-abdominal infections on the susceptibility patterns of gram-negative bowel flora after completion of therapy. In two international randomized open-label trials with laboratory blinding, adults with complicated intra-abdominal infection requiring surgery received piperacillin-tazobactam (OASIS 1) or ceftriaxone/metronidazole (OASIS II) versus ertapenem for 4-14 days. Rectal swabs were obtained at baseline, end of therapy, and 2 weeks post-therapy. Escherichia coli and Klebsiella spp. were tested for production of extended-spectrum beta-lactamase (ESBL). Enterobacteriaceae resistant to the agent used were recovered from 19 of 156 (12.2%) piperacillin-tazobactam recipients at the end of therapy compared to 1 (0.6%) patient at baseline (p<0.001) in OASIS I, and from 33 of 193 (17.1%) ceftriaxone/metronidazole recipients at the end of therapy compared to 5 (2.6%) patients at baseline (p<0.001) in OASIS II. Ertapenem-resistant Enterobacteriaceae were recovered from 1 of 155 and 1 of 196 ertapenem recipients at the end of therapy versus 0 and 1 ertapenem recipients at baseline in OASIS I and II, respectively. Resistant Enterobacteriaceae emerged significantly less often during treatment with ertapenem than with the comparator in both OASIS I (p<0.001) and OASIS II (p<0.001). The prevalence of ESBL-producers increased significantly during therapy in OASIS II among 193 ceftriaxone/metronidazole recipients (from 4 [2.1%] to 18 [9.3%]) (p<0.001), whereas no ertapenem recipient was colonized with an ESBL-producer at the end of therapy in either study. Selection for imipenem-resistant Pseudomonas aeruginosa was uncommon in all treatment groups. In these studies, the frequency of bowel colonization with resistant Enterobacteriaceae substantially increased in patients treated with either piperacillin-tazobactam or ceftriaxone/metronidazole, but not in patients treated with ertapenem.

First nosocomial outbreak of Pseudomonas aeruginosa producing an integron-borne metallo-beta-lactamase (VIM-2) in the United States

Carbapenemases are rare in the United States. This is the first report of a United States nosocomial outbreak of pan-resistant Pseudomonas aeruginosa infections due to an integron-borne metallo-beta-lactamase, VIM-2. This emergence of carbapenemases on mobile genetic elements in the United States warrants surveillance.

An evaluation of three new-generation tetrazolium salts for the measurement of respiratory activity in activated sludge microorganisms

XTT (3'-[1-[(phenylamino)-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzenesulfonic acid hydrate), MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt), and WST-1 (4-(3-4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio)-1,3-benzenedisulfonate) are tetrazolium salts that have become commercially available only in relatively recent years; they differ from earlier such compounds in that their reduction gives rise to a formazan product that is water soluble. We have established the sites in the prokaryotic respiratory chain at which each of the dyes is reduced to its corresponding formazan and have evaluated the suitability of each for the colorimetric estimation of electron transport system activity in populations of activated sludge microorganisms. Reduction of all three tetrazolium salts was shown to be proportional to cell biomass and oxygen uptake and to be susceptible to low levels of the reference toxicant 3,5-dichlorophenol. XTT, which was not inhibitory at concentrations of up to 2 mM and was reduced by 91% of isolates from a sample of culturable activated sludge bacteria, was chosen for further assay development. XTT-formazan production was found to be stimulated by the availability of an exogenous carbon and energy source, and by the presence of the electron-coupling agent phenazine methosulfate. Less than 3% of XTT reduction by an activated sludge sample was abiotic. An assay based on this compound could be a valuable and simple tool for the routine monitoring of the performance of wastewater treatment systems.

The serotonin transporter intronic VNTR enhancer correlated with a predisposition to affective disorders has distinct regulatory elements within the domain based on the primary DNA sequence of the repeat unit

We have demonstrated that a variable number tandem repeat domain (VNTR) within intron 2 of the serotonin transporter gene is a transcriptional regulatory domain which is potentially correlated with a predisposition to affective disorders and other behavioural conditions. This correlation based on copy number of the VNTR alone (nine, 10 or 12 copies of 16/17 base-pair element) has been controversial and not reproduced in all studies. We demonstrate that individual repeat elements within the VNTR domain differ in their enhancer activity in an embryonic stem cell model. This has implications for both the mechanism by which these VNTRs are correlated with the progression of the disease and suggests that clinical analysis should now be extended to correlate sequence variation within the VNTR with the disorder. The latter may resolve some of the conflicting data published to date.

Tachykinin expression in cartilage and function in human articular chondrocyte mechanotransduction

OBJECTIVE

To assess whether substance P and the corresponding neurokinin 1 (NK1) receptor are expressed in human articular cartilage, and whether these molecules have a role in chondrocyte mechanotransduction.

METHODS

Transgenic studies, immunohistochemistry, Western blotting, and reverse transcriptase-polymerase chain reaction were used to assess the expression of the preprotachykinin (PPT) gene, substance P, and NK1 in developing mice, in adult human articular cartilage, and in human chondrocytes in culture. Chondrocytes obtained from PPT knockout mice and human articular chondrocytes were mechanically stimulated in the presence or absence of inhibitors of substance P signaling, and cell membrane potentials or relative levels of aggrecan messenger RNA (mRNA) were measured.

RESULTS

Replacing a region of the PPT gene transcriptional site that contains a dominant repressor of the proximal promoter activity with the constitutive minimal promoter of the human beta-globin promoter allowed expression of a marker gene in areas of chondrogenesis during mouse development and in adult chondrocytes grown in culture. Adult human articular chondrocytes expressed endogenous PPT mRNA, substance P, and the corresponding NK1 receptor in vivo and in vitro. Blockade of substance P signaling by a chemical antagonist to the NK1 receptor inhibited chondrocyte responses to mechanical stimulation.

CONCLUSION

Substance P is expressed in human articular cartilage and is involved in chondrocyte mechanotransduction via the NK1 receptor in an autocrine and paracrine manner. This suggests that substance P and the NK1 receptor have roles in the maintenance of articular cartilage structure and function that were previously unrecognized.

Neuron restrictive silencer factor as a modulator of neuropeptide gene expression

We hypothesize that the transcription factor neuron restrictive silencer factor (NRSF) is an important determinant of the expression of the preprotachykinin (PPTA) gene (encoding substance P and Neurokinin A) and arginine vasopressin (AVP) both in neuronal and nonneuronal cells. NRSF, a zinc finger repressor protein, binds the NRSE motif found in many neuronal specific genes at a variety of promoter locations. However, it is found in a similar location at the major transcriptional start site, within both PPTA and AVP peptide promoters. We have correlated modulation of NRSF activity with expression of AVP and PPTA in a variety of cell types, indicating the general mechanism by which this protein may regulate expression. Specifically, they are as follows:(1). Expression of NRSF dramatically represses PPTA promoter activity in reporter gene constructs in primary cultures of DRG neurons.(2). The PPTA promoter activity is regulated differentially in osteoarthritic compared to normal chondrocytes. This regulation correlates with the region containing the NRSE site.(3). We have correlated a splice variant of NRSF with the establishment and progression of small cell lung carcinoma (SCLC) and demonstrated that NRSF variants can directly affect the activity of the AVP promoter in reporter gene constructs. If the deregulated expression of peptides in these diseases point to the mechanism determining the pathology, then perhaps targeting protocols that correct this deregulation may also reverse the specific disease phenotypes. Our data would indicate that modulation of NRSF activity would be a target for such intervention.

Broad resistance due to plasmid-mediated AmpC beta-lactamases in clinical isolates of Escherichia coli

Escherichia coli that produce plasmid-mediated AmpC beta-lactamases are rare in the United States. The clinical features associated with infection with these organisms have not been well described. We identified 2 clinical isolates of E. coli that produced the plasmid-mediated AmpC enzyme beta-lactamase CMY-2. These organisms were recovered from urine specimens and were resistant to ceftazidime, ceftriaxone, and cefepime. One isolate was resistant to ertapenem but susceptible to imipenem and meropenem; the other was susceptible to imipenem, meropenem, and ertapenem. One of the 2 infected patients did not require specific therapy; the other required imipenem for cure. The presence of the CMY-2 beta-lactamase was confirmed by DNA sequencing. Hybridization studies confirmed that the bla(CMY-2) gene was on a plasmid in both isolates; in one of them, the probe also hybridized with chromosomal DNA. Infection with plasmid-mediated AmpC beta-lactamases in E. coli in the United States may be associated with treatment failure, and these strains may become a serious nosocomial threat.

Enhanced phosphate uptake and polyphosphate accumulation in Burkholderia cepacia grown under low pH conditions

Of bacterial cells in a sample of activated sludge, 34% contained detectable intracellular polyphosphate inclusions following Neisser staining, when grown on glucose/mineral salts medium at pH 5.5; at pH 7.5 only 7% of cells visibly accumulated polyphosphate. In a sludge isolate of Burkholderia cepacia chosen for further study, maximal removal of phosphate and accumulation of polyphosphate occurred at pH 5.5; levels were up to 220% and 330% higher, respectively, than in cells grown at pH 7.5. During the early stationary phase of growth at pH 5.5 a maximum level of intracellular polyphosphate that comprised 13.6% of cellular dry weight was reached. Polyphosphate kinase activity was detected in actively growing cells only when cultured at pH 5.5. The phenomenon of acid-stimulated phosphate uptake and polyphosphate accumulation in this environmental bacterial population parallels observations previously made by us in the yeast Candida humicola and may thus represent a widespread microbial response to low external pH values.

The dopamine transporter gene (SLC6A3) variable number of tandem repeats domain enhances transcription in dopamine neurons

The dopamine (DAT) and serotonin (SERT) transporter genes both contain variable number of tandem repeats (VNTR) in non-coding gene regions which have been correlated with a predisposition to a variety of CNS disorders. There is considerable homology between individual DAT and SERT repeat DNA sequences, which is reflected in their ability to compete with each other for specific protein binding as demonstrated by electrophoretic mobility shift assay. The SERT VNTR has recently been shown to act as a transcriptional enhancer. Because of the similarities between SERT and DAT VNTRs, the DAT VNTR may also enhance transcription. This study demonstrates by lipid transfection into an immortalized dopaminergic cell line and biolistic transfection into dopamine neurons in neonatal rat midbrain slices that the human nine-repeat DAT VNTR can enhance transcription. This enhancing activity suggests that the DAT VNTR may play a role in regulation of DAT gene expression.