Enhancement of interferon-gamma-induced major histocompatibility complex class II gene expression by expressing an antisense RNA of poly(ADP-ribose) synthetase

Expression of histone acetyltransferases was down-regulated in poly(ADP-ribose) polymerase-1-deficient murine cells

NF-kappaB-dependent, as well as human immunodeficiency virus type-1 (HIV-1) long terminal repeat (LTR)-dependent, reporter gene expression was significantly impaired in cells derived from poly(ADP-ribose) polymerase-1 (PARP-1)-knockout (PARP-1 -/-) mice. In addition, the level of protein acetylation was markedly lower in PARP-1 -/- cells than control (PARP-1 +/+) cells. Surprisingly, the expression levels of histone acetyltransferases (HATs), p300, cAMP response element-binding protein-binding protein (CBP), and p300/CBP-associated factor (PCAF), were significantly reduced in PARP-1 -/- cells, as compared with PARP-1 +/+ cells. These results suggest that PARP-1 is required for the proper expression of particular HATs. Since p300 and CBP are coactivators of NF-kappaB, we propose here that PARP-1 participates in NF-kappaB-dependent transcription by means of maintaining the expression of HATs.

Enhancing therapeutic glycoprotein production in Chinese hamster ovary cells by metabolic engineering endogenous gene control with antisense DNA and gene targeting

Recombinant glycoprotein therapeutics have proven to be invaluable pharmaceuticals for the treatment of chronic and life-threatening diseases. Although these molecules are extraordinarily efficacious, many diseases have high dosage requirements of several hundred milligrams of protein for each administration. Multiple doses at this level are often required for treatment. One of the major challenges currently facing the biotechnology industry is the development of large-scale, cost-effective production and manufacturing processes of these biologically synthesized molecules. Metabolic engineering of animal cell expression hosts promises to address this challenge by substantially enhancing recombinant protein quality, productivity, and biological activity. In this report, we describe a novel approach to metabolic engineering in Chinese hamster ovary cells by control of endogenous gene expression. Analysis of the advantages and limitations of using antisense DNA and gene targeting as a means of control are discussed and several gene candidates for regulation with these techniques are identified. Practical considerations for using these technologies to reduce the levels of the CHO cell sialidase (Warner et al., Glycobiology, 3, 455-463, 1993) as a model gene system for regulation are also presented.

Poly (ADP-ribose) polymerase is involved in PMA-induced activation of HIV-1 in U1 cells by modulating the LTR function

Phorbol 12-myristate 13-acetate (PMA)-induced HIV-1 production in U1 cells was markedly suppressed by inhibitors of poly (ADP-ribose) polymerase (PARP). Northern blot analysis revealed that the PARP-inhibitors suppressed the virus production at a level of transcription. In order to examine the effect of PARP on transcriptional regulation of HIV-1 genes, we transfected a reporter plasmid containing HIV-1-LTR-promoted luciferase gene to L-1210 cell clones, which expressed varying decreased level of PARP. In wild type L-1210 cells, the expression of LTR-promoted luciferase gene was stimulated approximately 4-fold in response to PMA, whereas the PMA-dependent response was almost abolished in mutant cells, which expressed only 8% of PARP of the wild type cells. The effect of decrease in PARP content on the function of HIV-1-LTR was confirmed also in human wild type cells, Jurkat and J111, which were co-transfected with the reporter plasmid and a plasmid expressing a PARP-antisense RNA: Down-regulation of PARP in the cells by the expression of the antisense RNA significantly suppressed the PMA-dependent, LTR-function of the reporter plasmid in both Jurkat and J111 cells. NF-kappaB, which is known to mediate the PMA-induced activation of HIV-1 in U1 cells, was found to be activated approximately 5-fold in PMA-treated U1 cells. PARP-inhibitor, unexpectedly, did not suppress but rather stimulated (approximately 2-fold) the NF-kappaB activation. Combining the results with the finding that the LTR-function was minimum in a PARP-defective mutant cells in spite of a very high level of the activated NF-kappaB in the cells, we suggest that PARP, in addition to activated NF-kappaB, is essential for the function of HIV-1 LTR.

HIV-1 Tat protein is poly(ADP-ribosyl)ated in vitro

Purified recombinant HIV-1 Tat protein stimulated acceptor-dependent reaction of poly(ADP-ribose) polymerase in a dose-dependent manner. Analysis of the reaction products by SDS-polyacrylamide gel electrophoresis followed by immunoblotting with anti-poly(ADP-ribose) antibody revealed that recombinant Tat proteins were covalently modified with poly(ADP-ribose) in the enzyme reaction. Eventhough no significant effect of the modification was detected in the activity of Tat to form a specific complex with TAR (a viral transactivation response element) RNA, the present results raise the possibility that poly(ADP-ribose) polymerase is involved in the regulation of HIV-1 through the modification of a virus-encoded transactivator, Tat protein.

Nicotinamide potentiates TSHR and MHC class II promoter activity in FRTL-5 cells

Here we show that nicotinamide modulates the promoter activity of rat thyrotropin (TSHR) and major histocompatibility complex (MHC) class II genes in rat FRTL-5 thyroid cells, and have identified a novel mechanism for its action. TSHR and MHC class II, are potentiated through reduced expression of a common repressor of these two genes, TSEP-1 (TSHR suppressor element binding protein-1)/YB-1. Thus we show that TSHR mRNA is increased and TSHR promoter activity was concentration-dependently activated from 0 to 40 mM nicotinamide. The promoter lengths of TSHR and MHC class II containing TSEP/YB-1 binding sites were enhanced by 40 mM nicotinamide, but not the ones deleted of these binding sites. TSEP-1/YB-1 binding to the recognition sites in both TSHR and MHC class II promoters was reduced in nicotinamide-treated FRTL-5 nuclear extracts. Nicotinamide reduced the expression of TSEP-1/YB-1 mRNA and TSEP-1/YB-1 protein in the nucleus.

Genetic disruption of poly (ADP-ribose) synthetase inhibits the expression of P-selectin and intercellular adhesion molecule-1 in myocardial ischemia/reperfusion injury

The nuclear enzyme poly (ADP-ribose) synthetase (PARS) has been shown to play an important role in the pathogenesis of ischemia/reperfusion injury and circulatory shock. The aim of this study was to investigate whether PARS activity may modulate endothelial-neutrophil interaction. We present evidence that genetic disruption of PARS provides protection against myocardial ischemia and reperfusion injury by inhibiting the expression of P-selectin and intercellular adhesion molecule-1 (ICAM-1) and, consequently, by inhibiting the recruitment of neutrophils into the jeopardized tissue. Furthermore, using in vitro studies, we demonstrate that in fibroblasts lacking a functional gene for PARS, cytokine-stimulated expression of ICAM-1 is significantly reduced compared with fibroblasts from animals with a normal genotype. Similarly, in cultured human endothelial cells, oxidative- or cytokine-dependent expression of P-selectin and ICAM-1 is reduced by pharmacological inhibition of PARS by 3-aminobenzamide. These findings provide the first direct evidence that PARS activation participates in neutrophil-mediated myocardial damage by regulating the expression of P-selectin and ICAM-1 in ischemic and reperfused myocardium, and they also provide the basis for a novel therapeutic approach for the treatment of reperfusion injury.

Role of poly(ADP-ribose)synthetase in inflammation

Peroxynitrite and hydroxyl radicals are potent initiators of DNA single strand breakage, which is an obligatory stimulus for the activation of the nuclear enzyme poly(ADP-ribose)synthetase (PARS). Rapid activation of PARS depletes the intracellular concentration of its substrate, NAD+, slowing the rate of glycolysis, electron transport and ATP formation. This process can result in acute cell dysfunction and cell necrosis. Accordingly, inhibitors of PARS protect against cell death under these conditions. In addition to the direct cytotoxic pathway regulated by DNA injury and PARS activation, PARS also appears to modulate the course of inflammation by regulating the expression of a number of genes, including the gene for intercellular adhesion molecule 1, collagenase and the inducible nitric oxide synthase. The research into the role of PARS in inflammatory conditions is now supported by novel tools, such as novel, potent inhibitors of PARS, and genetically engineered animals lacking the gene for PARS. In vivo data demonstrate that inhibition of PARS protects against various forms of inflammation, including zymosan or endotoxin induced multiple organ failure, arthritis, allergic encephalomyelitis, and diabetic islet cell destruction. Pharmacological inhibition of PARS may be a promising novel approach for the experimental therapy of various forms of inflammation.

Nuclear architecture and ultrastructural distribution of poly(ADP-ribosyl)transferase, a multifunctional enzyme

A monospecific autoimmune serum for poly(ADP-ribosyl)transferase (pADPRT) was used to localise the enzyme in ultrastructural cellular compartments. We detected enzyme in mitochondria of HeLa and Sertoli cells. Within the nucleoplasm the enzyme concentration was positively correlated with the degree of chromatin condensation, with interchromatin spaces being virtually free of pADPRT. During spermatogenesis we observed a gradual increase of the chromatin associated pADPRT that parallelled chromatin condensation. The highest concentration was seen in the late stages of sperm differentiation, indicating the existence of a storage form in transcriptionally inactive nuclei. In nucleoli pADPRT is accumulated in foci within the dense fibrillar component. Such foci are seen in close spatial relationship to sites of nucleolar transcription as revealed by high resolution immunodetection of bromouridine uptake sites. It is suggested that nucleolar pADPRT plays a role in preribosome processing via the modification of nucleolus specific proteins that bind to nascent transcripts and hence indirectly regulates polymerase I activity. The persisting binding of pADPRT to ribonucleoproteins may explain the observed disperse enzyme distribution at lower concentrations in the granular component. The fibrillar centres seem to contain no pADPRT. We conclude that known compounds of fibrillar centres like polymerase I are unlikely candidates for modification via direct covalent ADP-ribosylation.

Protective effects of niacinamide in staphylococcal enterotoxin-B-induced toxicity

Staphylococcal enterotoxins (SE) interact with major histocompatibility complex (MHC) class II cell-surface receptors, eliciting signal transduction in antigen-presenting cells (APC). Subsequent toxin-class II complex interaction with specific T-cell receptors induces T-cell activation. We investigated the effect of niacinamide and interleukin (IL)-10 on SEB-induced responses. In a macrophage cell line, niacinamide (ED50--2mM) and IL-10 (ED50--7U/ml) inhibited interferon (IFN)-gamma-induced MHC class II expression in a dose-dependent manner. Also, niacinamide was a potent inhibitor of T-cell proliferation induced by SEB (ED50-- 1 mM) while IL-10 has minimal effects. In mice, the temporal responses of IL-1alpha, tumor necrosis factor (TNF)-alpha, IL-2, and IFN-gamma evoked by SEB were synergistically potentiated by lipopolysaccharide (LPS). Lethality occurred only when SEB was potentiated by LPS. Niacinamide or IL-10 improved survival of mice after lethal SEB challenge. Niacinamide reduced cytokine serum levels, although the pattern differed from that of IL-10. Niacinamide primarily reduced IL-2 and IFN-gamma, while IL-10 predominantly reduced IL-1alpha and TNF-alpha. The immunomodulatory effects of niacinamide observed on SEB-induced activation of APC and T-cells in vitro and in the LPS potentiated murine model for SEB-induced toxicity suggest it may have therapeutic value.

DNA strand breakage and activation of poly-ADP ribosyltransferase: a cytotoxic pathway triggered by peroxynitrite

Peroxynitrite is a reactive oxidant produced from nitric oxide (NO) and superoxide. Although its reactivity and decomposition are very much dependent on the constituents of the cellular environment, peroxynitrite is considered a potent oxidant that reacts with proteins, lipids, and DNA. Inasmuch as peroxynitrite is formed in many pathophysiological conditions that are associated with NO and/or superoxide overproduction, the investigation of the cytotoxic pathways triggered by peroxynitrite is of major importance. Here we review the evidence that peroxynitrite is a potent initiator of DNA strand breakage, which is an obligatory stimulus for the activation of the nuclear enzyme poly ADP ribosyl synthetase (PARS). We present an overview of experimental data that demonstrate or suggest that the peroxynitrite-PARS pathway, by leading to cell necrosis or apoptosis, contributes to cellular injury in a number of pathophysiological conditions including shock and inflammation, pancreatic islet cell destruction, and diabetes, stroke, and neurodegenerative disorders, as well as the toxic effects of various environmental oxidants or cytotoxic drugs.

Effect of poly(ADP-ribose) synthetase on the expression of major histocompatibility complex (MHC) class II genes

We have studied the effect of poly(ADP-ribose) synthetase on the interferon-gamma (IFN-gamma)-inducible expression of major histocompatibility complex (MHC) class II molecules. We constructed an expression plasmid capable of expressing either a sense RNA (MT-ARS) or an antisense RNA (pAS-FL or pAS-5') for poly(ADP-ribose) synthetase. We transfected the plasmid into mouse or human macrophage tumor cells and examined the effect on the expression of MHC class II molecules. The IFN-gamma-inducible expression of MHC class II gene was considerably reduced in transformant clones (A-2, B-2), in which the synthetase was highly expressed, whereas the depletion of the synthetase due to the expression of antisense RNA for the synthetase amplified the expression of MHC class II molecules. The results indicate that the level of the synthetase critically regulates the IFN-gamma-inducible MHC class II molecules. Next, we analyzed DNase I hypersensitive sites (DHS) of mouse MHC class II, I-A beta gene and found two sites, one in the promoter region and the other one in the first intron. The DHS in first intron was less sensitive towards DNase I attack in transformant clones (A-2, B-2) in which the synthetase was synthesized in a large quantity. Thus we constructed two beta-galactosidase reporter genes, one (A beta 2.0kb-lac z) containing the promoter region to a part of the second exon of the class II gene, and the other (A beta pro-lac z) containing the promoter region of the class II gene alone. The expression of the reporter gene was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) and found that the expression of A beta 2.0kb-lac z was suppressed in the transformant clones (A-2, B-2) relevant to control cells but the expression of A beta pro-lac z was the same level among those cells.(ABSTRACT TRUNCATED AT 250 WORDS)