Insulin secretory defects and impaired islet architecture in pancreatic beta-cell-specific STAT3 knockout mice.

Normal islet formation and function depends on the action of various growth factors operating in pre- and postnatal development; however, the specific physiological function of each factor is largely unknown. Loss-of-function analyses in mice have provided little information so far, perhaps due to functional redundancies of the growth factors acting on the pancreas. The present study focuses on the role of the transcription factor STAT3 in insulin-producing cells.

Oxidative stress induces nucleo-cytoplasmic translocation of pancreatic transcription factor PDX-1 through activation of c-Jun NH(2)-terminal kinase.

Oxidative stress is induced in pancreatic beta-cells under diabetic conditions and causes beta-cell dysfunction. Antioxidant treatment of diabetic animals leads to recovery of insulin biosynthesis and increases the expression of its controlling transcription factor, pancreatic duodenal homeobox-1 (PDX-1), in pancreatic beta-cells. Here, we show that PDX-1 is translocated from the nuclei to the cytoplasm of pancreatic beta-cells in response to oxidative stress.

Ectopically expressed PDX-1 in liver initiates endocrine and exocrine pancreas differentiation but causes dysmorphogenesis.

To date, the potency of pancreatic and duodenal homeobox gene 1 (PDX-1) in inducing differentiation into insulin-producing cells has been demonstrated in some cells and tissues. In order to carry out efficient screening of somatic tissues and cells that can transdifferentiate into beta-cell-like cells in response to PDX-1, we generated CAG-CAT-PDX1 transgenic mice carrying a transgene cassette composed of the chicken beta-actin gene (CAG) promoter and a floxed stuffer DNA sequence (CAT) linked to PDX-1 cDNA. When the mice were crossed with Alb-Cre mice, which express the Cre recombinase driven by the rat albumin gene promoter, PDX-1 was expressed in more than 50% of hepatocytes and cholangiocytes.

PPARgamma coactivator 1beta/ERR ligand 1 is an ERR protein ligand, whose expression induces a high-energy expenditure and antagonizes obesity.

A well balanced body energy budget controlled by limitation of calorie uptake and/or increment of energy expenditure, which is typically achieved by proper physical exercise, is most effective against obesity and diabetes mellitus. Recently, peroxisome proliferator-activated receptor (PPAR) gamma, a member of the nuclear receptor, and its cofactors have been shown to be involved in lipid metabolism and in the control of energy expenditure. Here we show that PPARgamma coactivator 1 (PGC-1) beta functions as ERRL1 (for ERR ligand 1), which can bind and activate orphan ERRs (estrogen receptor-related receptors) in vitro.

Regulation of lipocalin-type prostaglandin D synthase gene expression by Hes-1 through E-box and interleukin-1 beta via two NF-kappa B elements in rat leptomeningeal cells.

The promoter function of the rat lipocalin-type prostaglandin D synthase (L-PGDS) gene was characterized in primary cultures of leptomeningeal cells prepared from the neonatal rat brain. Luciferase reporter assays with deletion and site-directed mutation of the promoter region (-1250 to +77) showed that an AP-2 element at -109 was required for activation and an E-box at +57, for repression. Binding of nuclear factors to each of these cis-elements was demonstrated by an electrophoretic mobility shift assay.

Asymmetric random walk in a reaction intermediate of homologous recombination.

At an intermediate step of the homologous recombination between two double-stranded DNA molecules, a point (often called Holliday structure) connecting two strands coming from two recombining partners migrates along the homologous region. Assuming random walk of a connecting point, we previously explained the dependence of recombination frequency on the homology length observed in vivo. In this model, the random walk was assumed to be symmetric in that the forward transition rate equals the backward one.

In vivo and in vitro effects of SAR 943, a rapamycin analogue, on airway inflammation and remodeling.

No current therapy is considered to be satisfactory for severe asthma, and alternative approaches are still required for what is a major unmet medical need. In this study, we compared the effect of a rapamycin derivative, SAR 943, with budesonide, using a murine model of lung inflammation and remodeling. Allergen challenge of ovalbumin-sensitized BALB/c mice induced an increase in the levels of interleukin-5 and interleukin-4; numbers of eosinophil, neutrophil, and lymphocyte; cellular fibronectin; lung epithelial cell proliferation and mucus hypersecretory phenotype; as well as hyperreactivity to methacholine.

PDX-1 induces differentiation of intestinal epithelioid IEC-6 into insulin-producing cells.

A homeodomain containing transcription factor PDX-1 can induce beta-cell-specific gene expressions in some non-beta-cells and may therefore be useful for future diabetes gene/cell therapy. Among the potential target organs or tissues for transcription factor-mediated induction of beta-cell-like differentiation are the intestinal epithelial cells. They have certain merits over other tissues and organs in terms of accessibility for gene delivery and of similarity in developmental background to the pancreatic primordium.

A reaction-diffusion model for interference in meiotic crossing over.

One crossover point between a pair of homologous chromosomes in meiosis appears to interfere with occurrence of another in the neighborhood. It has been revealed that Drosophila and Neurospora, in spite of their large difference in the frequency of crossover points, show very similar plots of coincidence-a measure of the interference-against the genetic distance of the interval, defined as one-half the average number of crossover points within the interval. We here propose a simple reaction-diffusion model, where a "randomly walking" precursor becomes immobilized and matures into a crossover point.

Biochemical characterization of mouse microsomal prostaglandin E synthase-1 and its colocalization with cyclooxygenase-2 in peritoneal macrophages.

We cloned the cDNA for mouse microsomal prostaglandin (PG) E synthase-1 (mPGES-1) and expressed the recombinant enzyme in Escherichia coli. The membrane fraction containing recombinant mPGES-1 catalyzed the isomerization of PGH2 to PGE2 in the presence of GSH with K(m) values of 130 microM for PGH2 and 37 microM for GSH, a turnover number of 600 min(-1), and a k(cat)/K(m) ratio of 4.6 min(-1) microM(-1).

Protein kinase C-dependent, CCAAT/enhancer-binding protein beta-mediated expression of insulin-like growth factor I gene.

The possible involvement of the protein kinase C (PKC) pathway in transcriptional regulation of the human insulin-like growth factor-I (IGF-I) gene has been suggested. In this study, we sought to determine whether a PKC-dependent pathway is implicated in the transcriptional control, and if it is, how this occurs. Treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) caused an increase in the activity of the human IGF-I gene major promoter in HepG2 cells.

PAX6 mutation as a genetic factor common to aniridia and glucose intolerance.

A paired homeodomain transcription factor, PAX6, is a well-known regulator of eye development, and its heterozygous mutations in humans cause congenital eye anomalies such as aniridia. Because it was recently shown that PAX6 also plays an indispensable role in islet cell development, a PAX6 gene mutation in humans may lead to a defect of the endocrine pancreas. Whereas heterozygous mutations in islet-cell transcription factors such as IPF1/IDX-1/STF-1/PDX-1 and NEUROD1/BETA2 serve as a genetic cause of diabetes or glucose intolerance, we investigated the possibility of PAX6 gene mutations being a genetic factor common to aniridia and diabetes.

Pronounced eosinophilic lung inflammation and Th2 cytokine release in human lipocalin-type prostaglandin D synthase transgenic mice.

PGD(2) is a major lipid mediator released from mast cells, but little is known about its role in the development of allergic reactions. We used transgenic (TG) mice overexpressing human lipocalin-type PGD synthase to examine the effect of overproduction of PGD(2) in an OVA-induced murine asthma model. The sensitization of wild-type (WT) and TG mice was similar as judged by the content of OVA-specific IgE.

A missense mutation of Pax4 gene (R121W) is associated with type 2 diabetes in Japanese.

Pax4 is one of the transcription factors that play an important role in the differentiation of islet beta-cells. We scanned the Pax4 gene in 200 unrelated Japanese type 2 diabetic patients and found a missense mutation (R121W) in 6 heterozygous patients and 1 homozygous patient (mutant allele frequency 2.0%).

IL-5 deficiency abolishes aspects of airway remodelling in a murine model of lung inflammation.

Background And Objectives: Lung remodelling is a recognized feature of chronic asthma. In the present study, we have used IL-5-deficient mice to evaluate the role of this cytokine and eosinophilic inflammation in the initial stages of the structural changes occurring in the lung after antigen challenge.

Methods: Ovalbumin-sensitized wild type and IL-5-deficient mice were daily challenged for 5 consecutive days and killed 3 or 7 days after the last challenge to study the inflammatory and remodelling events, respectively.

Effect of a novel bifunctional endothelin receptor antagonist, IRL 3630A, on guinea pig respiratory mechanics.

This study characterized the in vitro pharmacological properties of a newly developed endothelin receptor antagonist, N-butanesulfonyl-[N-(3, 5-dimethylbenzoyl)-N-methyl-3-[4-(5-isoxazolyl)-phenyl]-(D)- alanyl]-( L)-valineamide sodium salt (IRL 3630A), and its in vivo effects on respiratory mechanics were determined. IRL 3630A showed highly balanced affinities to human endothelin ET(A) and ET(B) receptors, giving apparent K(i) values of 1.5 and 1.

Inducible nitric oxide synthase inhibitors suppress airway inflammation in mice through down-regulation of chemokine expression.

Growing evidence demonstrates that inducible NO synthase (iNOS) is induced in the airways of asthmatic patients. However, the precise role of NO in the lung inflammation is unknown. This study investigated the effect of both selective and nonselective iNOS inhibitors in an allergen-driven murine lung inflammation model.

Prolactin enhances CCAAT enhancer-binding protein-beta (C/EBP beta) and peroxisome proliferator-activated receptor gamma (PPAR gamma) messenger RNA expression and stimulates adipogenic conversion of NIH-3T3 cells.

Extracellular stimuli trigger adipocyte differentiation by inducing the complex cascades of transcription. Transcription factors CCAAT enhancer-binding proteins (C/EBPs) and peroxisome proliferator-activated receptor gamma (PPARgamma) play crucial roles in this process. Although ectopic expression of these factors in NIH-3T3 cells, a multipotential mesenchymal stem cell line, results in adipogenic conversion, little is known as to hormonal factors that regulate adipogenesis in these cells.

Induction of glycation suppresses glucokinase gene expression in HIT-T15 cells.

Aims/hypothesis: Chronic hyperglycaemia in patients with Type II (non-insulin-dependent) diabetes mellitus often leads to a decline in glucose-responsive insulin secretion from pancreatic beta cells, a phenomenon called glucose toxicity. Upon hyperglycaemia, glycation reaction occurs in the beta cells and induces oxidative stress. To understand the molecular basis of the beta-cell glucose toxicity, we investigated the possible effects of glycation on the expression and enzymatic activity of glucokinase, which plays a crucial part in glucose-responsive insulin secretion.

Effect of DNA sequence divergence on homologous recombination as analyzed by a random-walk model.

A point connecting a pair of homologous regions of DNA duplexes moves along the homology in a reaction intermediate of the homologous recombination. Formulating this movement as a random walk, we were previously successful at explaining the dependence of the recombination frequency on the homology length. Recently, the dependence of the recombination frequency on the DNA sequence divergence in the homologous region was investigated experimentally; if the methyl-directed mismatch repair (MMR) system is active, the logarithm of the recombination frequency decreases very rapidly with an increase of the divergence in a low-divergence regime.

Beneficial effects of antioxidants in diabetes: possible protection of pancreatic beta-cells against glucose toxicity.

Oxidative stress is produced under diabetic conditions and possibly causes various forms of tissue damage in patients with diabetes. The aim of this study was to examine the involvement of oxidative stress in the progression of pancreatic beta-cell dysfunction in type 2 diabetes and to evaluate the potential usefulness of antioxidants in the treatment of type 2 diabetes. We used diabetic C57BL/KsJ-db/db mice, in whom antioxidant treatment (N-acetyl-L-cysteine [NAC], vitamins C plus E, or both) was started at 6 weeks of age; its effects were evaluated at 10 and 16 weeks of age.

Identification of a portable repression domain and an E1A-responsive activation domain in Pax4: a possible role of Pax4 as a transcriptional repressor in the pancreas.

Pax4 is a paired-domain (PD)-containing transcription factor which plays a crucial role in pancreatic beta/delta-cell development. In this study, we characterized the DNA-binding and transactivation properties of mouse Pax4. Repetitive rounds of PCR-based selection led to identification of the optimal DNA-binding sequences for the PD of Pax4.

Identification of oxidative stress-regulated genes in rat aortic smooth muscle cells by suppression subtractive hybridization.

A suppression subtractive hybridization technique was used to identify reactive oxygen species (ROS)-regulated genes in rat vascular smooth muscle cells. Three genes out of 89 clones, identified as fibronectin, p105 coactivator and ECA39, showed increased expression after treatment with H(2)O(2). The mRNA expressions of these three genes were induced in a time- and dose-dependent manner, independent of protein kinase C activation.

Oxidative stress induces p21 expression in pancreatic islet cells: possible implication in beta-cell dysfunction.

Aims/hypothesis: Prolonged poor glycaemic control in patients with Type II (non-insulin-dependent) diabetes mellitus often causes pancreatic beta-cell dysfunction accompanied by decreases in insulin biosynthesis and beta-cell proliferation. This is well known as a clinical concept called glucose toxicity. Whereas oxidative stress is provoked under diabetic conditions, we examined the possible implication of cyclin-dependent kinase (Cdk) inhibitor p21 (WAF1/CIP1/Sdi1) in beta-cell dysfunction mediated by oxidative stress.

Modulation of ET-1-induced contraction of human bronchi by airway epithelium-dependent nitric oxide release via ET(A) receptor activation.

1. The purpose of this work was to investigate whether endothelin-1 (ET-1) was able to induce the release of an inhibitory factor from the airway epithelium in isolated human bronchi and to identify this mediator as well as the endothelin receptor involved in this phenomenon. 2.