Antenatal Administration of Betamethasone Contributes to Intimal Thickening of the Rat Ductus Arteriosus.

BACKGROUND: Antenatal betamethasone (BMZ) is a standard therapy for reducing respiratory distress syndrome in preterm infants. Recently, some reports have indicated that BMZ promotes ductus arteriosus (DA) closure. DA closure requires morphological remodeling; that is, intimal thickening (IT) formation; however, the role of BMZ in IT formation has not yet been reported. Methods and Results: First, DNA microarray analysis using smooth muscle cells (SMCs) of rat preterm DA on gestational day 20 (pDASMCs) stimulated with BMZ was performed. Among 58,717 probe sets, ADP-ribosyltransferase 3 (Art3) was markedly increased by BMZ stimulation. Quantitative reverse transcription polymerase chain reaction (RT-PCR) confirmed the BMZ-induced increase of Art3 in pDASMCs, but not in aortic SMCs. Immunocytochemistry showed that BMZ stimulation increased lamellipodia formation. BMZ significantly increased total paxillin protein expression and the ratio of phosphorylated to total paxillin. A scratch assay demonstrated that BMZ stimulation promoted pDASMC migration, which was attenuated byArt3-targeted siRNAs transfection. pDASMC proliferation was not promoted by BMZ, which was analyzed by a 5'-bromo-2'-deoxyuridine (BrdU) assay. Whether BMZ increased IT formation in vivo was examined. BMZ or saline was administered intravenously to maternal rats on gestational days 18 and 19, and DA tissues were obtained on gestational day 20. The ratio of IT to tunica media was significantly higher in the BMZ-treated group. CONCLUSIONS: These data suggest that antenatal BMZ administration promotes DA IT through Art3-mediated DASMC migration.

Mono-ADP-ribosyltransferase as a potential pharmacological drug target in the GLP-1 based therapy of obesity and diabetes mellitus type 2.

Glucagon-like peptide-1 (GLP-1) based therapy is well established for treating diabetes mellitus type 2. Moreover, GLP-1 receptor agonists influence weight loss, and have potential for treating obesity. GLP-1 receptor agonists should be administered in low doses, together with drugs that potentiate insulin release, to avoid some minor side effects. We have focused on incretin hormones, especially GLP-1 and its analogues. Here we discuss the effect of the third intracellular loop-derived peptide of GLP-1 receptor on intracellular mono-ADP-ribosyltransferase and its role in regulating the receptor. We suggest that this intracellular mono-ADP-ribosyltransferase could constitute a possible novel pharmacological target in the treatment of diabetes mellitus type 2 and obesity.

Mammalian ADP-ribosyltransferases and ADP-ribosylhydrolases.

ADP-ribosyltransferases (ARTs) and ADP-ribosylhydrolases (ARHs) catalyze opposing reactions, which are termed ADP-ribosylation and de-ADP-ribosylation. ARTs transfer the ADP-ribose unit from NAD (nicotinamide adenine dinucleotide) onto an acceptor, while ARHs release the ADP-ribose from the target. Like protein phosphorylation, ADP-ribosylation is a posttranslational modification regulating protein function. In many cases, ADP-ribosylation inactivates the target protein. Numerous bacterial toxins intoxicate cells by attaching an ADP-ribose moiety to a functionally important amino acid residue, thereby blocking the interaction of the target protein with other proteins. In other cases, ADP-ribosylation activates protein function. On the surface of T cells, ART2.2 ADP-ribosylates the P2X7 purinoceptor on arginine 125, thereby gating the P2X7 ion channel by presenting a ligand to its nucleotide-binding site. ADP-ribosylation is not limited to protein targets and ARTs have been described that ADP-ribosylate DNA, RNA, and small molecules. Mammalian cells express distinct families of ARTs and ARHs. Recently, molecular cloning, site directed mutagenesis and three-dimensional structural analyses of prototype mammalian ARTs and ARHs have shed fresh insight into the structure and function of these intriguing enzymes.

NarE: a novel ADP-ribosyltransferase from Neisseria meningitidis.

Mono ADP-ribosyltransferases (ADPRTs) are a class of functionally conserved enzymes present in prokaryotic and eukaryotic organisms. In bacteria, these enzymes often act as potent toxins and play an important role in pathogenesis. Here we report a profile-based computational approach that, assisted by secondary structure predictions, has allowed the identification of a previously undiscovered ADP-ribosyltransferase in Neisseria meningitidis (NarE). NarE shows structural homologies with E. coli heat-labile enterotoxin (LT) and cholera toxin (CT) and possesses ADP-ribosylating and NAD-glycohydrolase activities. As in the case of LT and CT, NarE catalyses the transfer of the ADP-ribose moiety to arginine residues. Despite the absence of a signal peptide, the protein is efficiently exported into the periplasm of Neisseria. The narE gene is present in 25 out of 43 strains analysed, is always present in ET-5 and Lineage 3 but absent in ET-37 and Cluster A4 hypervirulent lineages. When present, the gene is 100% conserved in sequence and is inserted upstream of and co-transcribed with the lipoamide dehydrogenase E3 gene. Possible roles in the pathogenesis of N. meningitidis are discussed.

NAD-dependent cross-linking of dinitrogenase reductase and dinitrogenase reductase ADP-ribosyltransferase from Rhodospirillum rubrum.

Chemical cross-linking of dinitrogenase reductase and dinitrogenase reductase ADP-ribosyltransferase (DRAT) from Rhodospirillum rubrum has been investigated with a cross-linking system utilizing two reagents, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and sulfo-N-hydroxysuccinimide. Cross-linking between dinitrogenase reductase and DRAT requires the presence of NAD, the cellular ADP-ribose donor, or a NAD analog containing an unmodified nicotinamide group, such as nicotinamide hypoxanthine dinucleotide. NADP, which will not replace NAD in the modification reaction, does support cross-linking between dinitrogenase reductase and DRAT. The DRAT-catalyzed ADP-ribosylation of dinitrogenase reductase is inhibited by sodium chloride, as is the cross-linking between dinitrogenase reductase and DRAT, suggesting that ionic interactions are required for the association of these two proteins. Cross-linking is specific for native, unmodified dinitrogenase reductase, in that both oxygen-denatured and ADP-ribosylated dinitrogenase reductase fail to form a cross-linked complex with DRAT. The ADP-bound and adenine nucleotide-free states of dinitrogenase reductase form cross-linked complexes with DRAT; however, cross-linking is inhibited when dinitrogenase reductase is in its ATP-bound state.

Protective effects of nicotinamide against nitric oxide-mediated delayed vascular failure in endotoxic shock: potential involvement of polyADP ribosyl synthetase.

Nitric oxide (NO) produced by the inducible isoform of nitric oxide synthase contributes to the hypotension and vascular hyporeactivity in shock. Nicotinamide is protective against the cytotoxic effects of exogenous and endogenous NO in vitro. We investigated the effect of nicotinamide on the cellular energetic and vascular failure in a rat model of endotoxin shock. Administration of nicotinamide to rats, starting at 1 h bacterial lipopolysaccharide, maintained higher blood pressure levels, without affecting induction of nitric oxide synthase. Nicotinamide treatment prevented the lipopolysaccharide-induced decrease in mitochondrial respiration and intracellular NAD+ levels in peritoneal macrophages and improved the contractility of the thoracic aorta ex vivo. Thus, nicotinamide protects against the delayed, NO-mediated vascular failure in endotoxic shock. Its actions are unrelated to inhibition of NO biosynthesis but may be related to inhibition of the NO-mediated activation of an energy-consuming DNA repair cycle triggered by polyADP ribose synthetase.

Vortex-mixing-induced inactivation of arginine-specific ADP-ribosyltransferase activity and re-activation of the less-active form by dithiothreitol plus NaCl under anaerobic conditions.

We observed dilution/vortex-mixing-induced inactivation of arginine-specific ADP-ribosyltransferase purified from chicken peripheral polymorphonuclear granulocytes (heterophils) and re-activation of the less active form by dithiothreitol plus NaCl, under anaerobic conditions. The vortex-mixing-induced inactivation of the diluted enzyme was rapid; more than 85% of the enzyme activity was lost with 1-min vortex-mixing at room temperature. When the less-active form of the enzyme was treated with 10 mM dithiothreitol plus 0.2 M NaCl, under anaerobic conditions, more than 50% of the enzyme activity was restored. Putative mechanisms of the vortex-mixing-induced inactivation and dithiothreitol/NaCl-dependent re-activation of the arginine-specific ADP-ribosyltransferase are discussed.