Thiazolidinediones increase arachidonic acid release and subsequent prostanoid production in a peroxisome proliferator-activated receptor gamma-independent manner

Thiazolidinedione, peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, has been used as an anti-diabetic drug and as an useful tool to elucidate multiple PPARgamma functions by in vitro and in vivo studies. We investigated the effects of thiazolidinediones on prostanoid production in lipopolysaccharide-stimulated cells. The high concentrations (>10 microM) of rosiglitazone and pioglitazone significantly increased lipopolysaccharide-stimulated prostanoid production such as thromboxane A2 and prostaglandin E2. However, PPARgamma antagonist could not inhibit them. In PPARgamma-deficient cells, thiazolidinediones increased prostaglandin E2 production. Thiazolidinediones increased arachidonic acid (AA) release from the cell membrane by not stimulating AA releasing process involving several phospholipase A2s but inhibiting AA reuptaking process. The expression of cyclooxygenase-1 and cyclooxygenase-2 were not affected by thiazolidinediones. In this study, we demonstrated that high concentrations of TZDs increased AA release by the inhibition of AA reuptaking process, leading to subsequent increase in the prostanoid production in a PPARgamma-independent manner. This mechanism provides useful information for the elucidation of multiple PPARgamma functions and diabetic drug therapy.     

Teprenone, but not H2-receptor blocker or sucralfate, suppresses corpus Helicobacter pylori colonization and gastritis in humans: teprenone inhibition of H. pylori-induced interleukin-8 in MKN28 gastric epithelial cell lines

Background. The role of teprenone in Helicobacter pylori‐associated gastritis has yet to be determined. To investigate the effect of teprenone on inflammatory cell infiltration, and on H. pylori colonization of the gastric mucosa in H. pylori‐infected patients, we first compared the effect of teprenone with that of both histamine H2 receptor antagonists (H2‐RA) and sucralfate on the histological scores of H. pylori gastritis. We then examined its in vitro effect on H. pylori‐induced interleukin (IL)‐8 production in MKN28 gastric epithelial cells. Materials and Methods. A total of 68 patients were divided into three groups, each group undergoing a 3‐month treatment with either teprenone (150 mg/day), H2‐RA (nizatidine, 300 mg/day), or sucralfate (3 g/day). All subjects underwent endoscopic examination of the stomach before and after treatment. IL‐8 production in MKN28 gastric epithelial cells was measured by enzyme‐linked immunosorbent assay (ELISA). Results. Following treatment, the teprenone group showed a significant decrease in both neutrophil infiltration and H. pylori density of the corpus (before vs. after: 2.49 ± 0.22 vs. 2.15 ± 0.23, p = .009; 2.36 ± 0.25 vs. 2.00 ± 0.24, p = .035, respectively), with no significant differences seen in either the sucralfate or H2‐RA groups. Teprenone inhibited H. pylori‐enhanced IL‐8 production in MKN28 gastric epithelial cells in vitro, in a dose‐dependent manner. Conclusions. Teprenone may modify corpus H. pylori‐associated gastritis through its effect on neutrophil infiltration and H. pylori density, in part by its inhibition of IL‐8 production in the gastric mucosa.     

Chemical identification of serine 181 at the ATP-binding site of myosin as a residue esterified selectively by the fluorescent reagent 9-anthroylnitrile

The esterification reagent 9-anthroylnitrile (ANN) reacts with a serine residue in the NH2-terminal 23-kDa peptide segment of myosin subfragment-1 heavy chain to yield a fluorescent S1 derivative labeled by the anthroyl group (Hiratsuka, T. (1989) J. Biol. Chem. 264, 18188-18194). The labeling was highly selective and accelerated by nucleotides. In the present study, to determine the exact location of the labeled serine residue, the labeled 23-kDa peptide fragment was isolated. The subsequent extensive proteolytic digestion of the peptide fragment yielded two labeled peptides, a pentapeptide and its precursor nonapeptide. Amino acid sequence and composition analyses of both labeled peptides revealed that the anthroyl group is attached to Ser-181 involved in the phosphate binding loop for ATP (Smith, C. A., and Rayment, I. (1996) Biochemistry 35, 5404-5417). We concluded that ANN can esterify Ser-181 selectively out of over 40 serine residues in the subfragment 1 heavy chain. Thus ANN is proved to be a valuable fluorescent tool to identify peptides containing the phosphate binding loop of S1 and to detect the conformational changes around this loop.     

Maillard reaction-like lysine modification by a lipid peroxidation product: immunochemical detection of protein-bound 2-hydroxyheptanal in vivo

2-Hydroxyheptanal (2-HH) is one of the reactive aldehyde species generated during the peroxidation of n-6 polyunsaturated fatty acids, such as linoleic and arachidonic acids. Analogous to the Maillard reaction of reducing sugars, 2-HH readily reacts with lysine epsilon-amino groups. In the present study, to define the occurrence of the Maillard reaction-like lysine modification by 2-HH in vivo, we raised a monoclonal antibody directed to a trihydropyridinone (THPO) structure, 1-alkyl-4-butyl-5-pentyl-1,2,6-trihydropyridin-3-one, formed from 2-HH and lysine, and examined the presence of the antigenic structure in the human atherosclerotic aorta. Mice were immunized with the 2-HH-modified keyhole limpet hemocyanin (KLH) as the immunogen. Using a THPO-carrier protein conjugate, we screened the hybridomas and finally obtained a clone that produced the monoclonal antibody 3C8 (mAb3C8). The antibody strongly recognized bovine serum albumin (BSA) treated with 2-HH, but showed no cross-reactivity with BSAs modified with other related aldehydes. By using this antibody, it was revealed that the antigenic structure was indeed present in atherosclerotic lesions of the human aorta.     

Regulation by nectin of the velocity of the formation of adherens junctions and tight junctions

Cadherins are key Ca(2+)-dependent cell-cell adhesion molecules at adherens junctions (AJs) in fibroblasts and epithelial cells, whereas claudins are key Ca(2+)-independent cell-cell adhesion molecules at tight junctions (TJs) in epithelial cells. The formation and maintenance of TJs are dependent on the formation and maintenance of AJs. Nectins are Ca(2+)-independent immunoglobulin-like cell-cell adhesion molecules which comprise a family of four members, nectin-1, -2, -3, and -4, and are involved in the formation of AJs in cooperation with cadherins, and the subsequent formation of TJs. We show here that the velocity of the formation of the E-cadherin-based AJs is increased by overexpression of nectin-1 and is reduced by addition of the nectin-1 inhibitors to the medium in L cells stably expressing E-cadherin and Madin-Darby canine kidney cells. Moreover, the velocity of the formation of the claudin-based TJs is increased by overexpression of nectin-1 and is reduced by addition of the nectin-1 inhibitors to the medium in Madin-Darby canine kidney cells. These results indicate that nectins regulate the velocity of the formation of the E-cadherin-based AJs and the subsequent formation of the claudin-based TJs.     

Insulin activates CCAAT/enhancer binding proteins and proinflammatory gene expression through the phosphatidylinositol 3-kinase pathway in vascular smooth muscle cells

Phosphatidylinositol 3-kinase (PI3K) is a key molecule mediating signals of insulin in vascular smooth muscle cells (VSMCs). To examine the effect of chronic activation of PI3K on the gene expression of VSMCs, membrane-targeted p110CAAX, a catalytic subunit of PI3K, was overexpressed in rat VSMCs by adenovirus-mediated gene transfer. Similar to insulin's effects, cells overexpressing p110CAAX exhibited a 10- to 15-fold increase in monocyte chemoattractant protein-1 (MCP-1) mRNA expression as compared with the control cells. Electrophoretic mobility shift assay analysis showed that the overexpression of p110CAAX activated neither the NF-kappaB binding nor the activator protein (AP-1) binding activities. We found that two CCAAT/enhancer binding protein (C/EBP) binding sites located between 2.6 and 3.6 kb upstream of the MCP-1 gene were responsible for the induction by p110CAAX. The overexpression of C/EBP-beta and C/EBP-delta but not C/EBP-alpha caused 6- to 8-fold induction of MCP-1 promoter activity. Consistently, the overexpression of p110CAAX as well as insulin induced mRNA expression and nuclear expression of C/EBP-beta and C/EBP-delta in VSMCs. These results clearly indicate that the activation of PI3K induced proinflammatory gene expression through activating C/EBP-beta and C/EBP-delta but not NF-kappaB, which may explain the proinflammatory effect of insulin in the insulin-resistant state.     

Searching for genes involved in arteriosclerosis: proteomic analysis of cultured human umbilical vein endothelial cells undergoing replicative senescence

It is known that replicative senescence of endothelium in vivo contributes at least partially to age-related vascular disorders such as arteriosclerosis. However, the genes involved in this process remain to be identified. In this study, we employed a proteomics-based approach to identify candidate genes using in vitro cultured human umbilical vein endothelial cells (HUVECs) as an experimental model for replicative senescence. By comparing protein spots from young and senescent HUVECs using two-dimensional electrophoresis, we identified three up-regulated proteins and five down-regulated proteins in senescent HUVECs as compared to young HUVECs, whose alteration was not observed during replicative senescence of primary human fibroblasts. Consistent results were obtained in Western blotting analysis using specific antibodies raised against some of these proteins, whereas there were no significant changes in the mRNA levels of these genes during senescence of HUVECs. Among them, cathepsin B, a protease participating in both intracellular proteolysis and extracellular matrix remodeling was observed to be dramatically up-regulated in senescent HUVECs and whose activity is known to be up-regulated in atherosclerotic lesions with senescence-associated phenotypes in vivo. Additional proteins, including cytoskeletal proteins and proteins involved in the processes of synthesis, turnover and modification of protein, were identified, whose function in endothelium was previously unsuspected. These proteins identified by a proteomics-based approach using cultured HUVECs may be involved not only in replicative senescence but also in functional alterations in vascular endothelial cells with senescence-associated phenotypes and may serve as molecular markers for these processes.     

ATP-sensitive K+ channel-mediated glucose uptake is independent of IRS-1/phosphatidylinositol 3-kinase signaling

We previously found that disruption of Kir6.2-containing ATP-sensitive K+ (KATP) channels increases glucose uptake in skeletal muscle, but the mechanism is not clear. In the present study, we generated knockout mice lacking both Kir6.2 and insulin receptor substrate-1 (IRS-1). Because IRS-1 is the major substrate of insulin receptor kinase, we expected disruption of the IRS-1 gene to reduce glucose uptake in Kir6.2 knockout mice. However, the double-knockout mice do not develop insulin resistance or glucose intolerance. An insulin tolerance test reveals the glucose-lowering effect of exogenous insulin in double-knockout mice and in Kir6.2 knockout mice to be similarly enhanced compared with wild-type mice. The basal 2-deoxyglucose uptake rate in skeletal muscle of double-knockout mice is increased similarly to the rate in Kir6.2 knockout mice. Accordingly, disruption of the IRS-1 gene affects neither systemic insulin sensitivity nor glucose uptake in skeletal muscles of Kir6.2-deficient mice. In addition, no significant changes were observed in phosphatidylinositol 3-kinase (PI3K) activity and its downstream signal in skeletal muscle due to lack of the Kir6.2 gene. Disruption of Kir6.2-containing Katp channels clearly protects against IRS-1-associated insulin resistance by increasing glucose uptake in skeletal muscles by a mechanism separate from the IRS-1/PI3K pathway.     

Identification of a gene disrupted by inv(11)(q13.5;q25) in a patient with left-right axis malformation

An inv(11)(q13.5;q25) inversion was previously identified in a 9-month-old male patient with complex cyanotic heart defects, altered lung lobation, symmetric liver, and abnormally lobulated spleen (polysplenia). This chromosomal rearrangement was inherited from the phenotypically normal father. We termed these regions DHTX-A (disrupted in heterotaxy)-- A at 11q13.5 and DHTX-B at 11q25. Here, we report the isolation and characterization of the inversion breakpoints and the gene that is disrupted by the DHTX-A breakpoint. The putative DHTX is identical to the UVRAG gene, which was originally identified as a gene that complements the UV sensitivity of xeroderma pigmentosum complementation group C. The 4-kb mRNA was found to be encoded by a large gene, at least 300 kb long, composed of 15 exons. The function of the gene product remains largely unknown. However, the near central portion of the UVRAG protein is predicted to contain a coiled-coil domain, which has been implicated in mediating protein-protein interactions. Southern analyses and fluorescence in situ hybridization (FISH) revealed that the DHTX-A breakpoint in the patient and his father lies within the intron between exons 6 and 7 of UVRAG. Northern blot analysis indicated strong expression in human fetal and adult tissues and in mouse embryonic day-7 and adult tissues, respectively. Whole mount in situ hybridization also showed that the Uvrag gene is expressed in the presomite-stage embryo. Several hypotheses are discussed to explain the relationship between the chromosomal inversion and the accompanying phenotypes.     

The complete sequence and expression patterns of the atrial myosin heavy chain in the developing chick

We have earlier reported partial cloning of a cDNA of a chick atrial myosin heavy chain (MHC) gene, CCSV2 and its expression pattern in embryonic chick hearts (Oana et al (1995) Eur J Cell Biol 67, 42-49). In this study, five overlapping cDNA clones (including CCSV2) which together encode the entire open reading frame of the chick atrial MHC gene were characterized, and both the entire nucleotide sequence consisting of 5825 bases and the deduced amino acid sequence consisting of 1931 amino acids determined. Reinvestigation of the nucleotide sequence of the previously reported and presumably different chick atrial specific MHC cDNA clone, AMHC1 (Yutzey et al (1994) Development 120, 871-883), revealed that our clone and AMHC1 encoded the same MHC. The chick atrial MHC gene was strongly expressed in developing chick atria from a very early stage (Hamburger and Hamilton stage 9, 29-33 h) to the adult stage. This gene was also expressed, although weakly, in the ventricle, somite (the precursor to skeletal muscle) and skeletal muscle during embryonic stages but not in adults.