Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Peroxynitrite is a powerful oxidant formed by the near-diffusion-limited reaction of nitric oxide with superoxide. Large doses of peroxynitrite (> 2 mM) resulted in rapid cell swelling and necrosis of undifferentiated PC12 cells. However, brief exposure to lower concentrations of peroxynitrite (EC50 = 850 microM) intially (3-4 h) caused minimal damage to low-density cultures. By 8 h, cytoplasmic shrinkage with nuclear condensation and fragmentation became increasingly evident. After 24 h, 36% of peroxynitrite-treated cells demonstrated these features associated with apoptosis. In addition, 46% of peroxynitrite-treated cells demonstrated DNA fragmentation (by terminal-deoxynucleotide transferase-mediated dUTP-digoxigenin nick end-labeling) after 7 h, which was inhibited by posttreatment with the endonuclease inhibitor aurintricarboxylic acid. Serum starvation also resulted in apoptosis in control cells (23%), the percentage of which was not altered significantly by peroxynitrite treatment. Although peroxynitrite is known to be toxic to cells, the present study provides a first indication that peroxynitrite induces apoptosis. Furthermore, pretreatment of cells with nerve growth factor or insulin, but not epidermal growth factor, was protective against peroxynitrite-induced apoptosis. However, both acidic and basic fibroblast growth factors greatly increased peroxynitrite-initiated apoptosis, to 63 and 70%, respectively. Thus, specific trophic factors demonstrate differential regulation of peroxynitrite-induced apoptosis in vitro.
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PMID:Peroxynitrite-induced cytotoxicity in PC12 cells: evidence for an apoptotic mechanism differentially modulated by neurotrophic factors. 756 48

A dramatic loss of glutamate transport has been observed in sporadic amyotrophic lateral sclerosis and has been postulated to contribute to the disease. Experimentally, this hypothesis was corroborated by mimicking the chronic loss of glutamate transport in postnatal rat spinal cord organotypic cultures through the use of glutamate transport inhibitors. This system is characterized by a relatively selective slow loss of ventral horn motor neurons resulting from glutamate transport inhibition. In this study, spinal cord organotypic cultures were used to test various drugs to evaluate their neuroprotective properties against this slow glutamate-mediated neurotoxicity The most potent neuroprotectants were drugs that altered glutamate neurotransmission, including non-NMDA receptor antagonists (GYKI-52466, PD144216, and PD13997) and drugs that could block presynaptic release or synthesis (riluzole and gabapentin). In addition, some antioxidants (U83836E and N-t-butyl-alpha-phenylnitrone) and inhibitors of nitric oxide synthesis (NG-monomethyl-L-arginine acetate) were modestly neuroprotective. The calcium endonuclease inhibitor aurintricarboxylic acid and the calcium release inhibitor dantrolene also provided partial motor neuron protection. However, several antioxidants and calcium channel antagonists had no excitotoxic neuroprotectant activity. This system provides a preclinical screening method for the burgeoning number of drugs postulated for clinical trials in motor neuron disease and a model to evaluate the mechanisms of chronic glutamate toxicity.
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PMID:Neuroprotective strategies in a model of chronic glutamate-mediated motor neuron toxicity. 761 20

Constitutively active nitric oxide synthases (NOS) are a unique class of NADPH-dependent, calcium/calmodulin-dependent enzymes that catalyze the conversion of L-arginine to nitric oxide and L-citrulline. However, little is known about the molecular similarities or differences between the two prototypical constitutive NOS enzymes, endothelial NOS (ECNOS) and brain NOS (bNOS). The aims of this study were to begin characterizing the gene structure and tissue distribution of messenger RNAs (mRNAs) for ECNOS and bNOS and to examine the immunological resemblance of the proteins by Western blotting. Full-length complementary DNAs (cDNAs) encoding bovine ECNOS and rat bNOS hybridized, under high stringency, to different-sized fragments of endonuclease-digested bovine, rat, and human genomic DNA. In addition, more than one fragment was detected with both cDNAs, suggesting that ECNOS and bNOS genes contained multiple introns. Tissue distribution of ECNOS mRNA (4.4 kb) and bNOS mRNA (9.5 kb) in the rat was detected by Northern blotting. Patterns among tissue extracts were strikingly different, with ECNOS mRNA being most abundant in aorta, heart, lung, kidney, adrenal gland, spinal cord, and urogenital tissues and bNOS mRNA most prominent in brain regions, intestine, stomach, spinal cord, adrenal gland, and aorta. Interestingly, ECNOS cDNA detected two equally abundant RNA transcripts (4.4 and 4.0 kb) in most brain regions tested, suggesting an alternative splicing of the ECNOS pre-mRNA. Western blotting, using an ECNOS monoclonal antibody, recognized ECNOS protein from native bovine endothelial cells, cultured bovine endothelial cells, and COS cells transfected with ECNOS cDNA but did not recognize purified bNOS.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Genomic analysis and expression patterns reveal distinct genes for endothelial and brain nitric oxide synthase. 768 5

Alterations of cellular functions induced by recombinant human tumor necrosis factor alpha (TNF alpha) were compared in rat hepatocytes cultured under either periportal-equivalent (10 nM insulin; 10 nM glucagon; 13% O2) or perivenous-equivalent conditions (10 nM insulin; 1 nM glucagon; 4% O2). TNF alpha induced a time- and dose-dependent increase in nitric oxide (NO) production and an acute phase response (inhibition of albumin secretion and elevation of alpha 2-macroglobulin production) under both culture conditions. NO production was more pronounced in periportal cultures, while the acute phase response was stronger in pericentral cultures. This suggests that NO production and the acute phase response are controlled by different pathways. After exposure to TNF alpha, DNA content was measured fluorimetrically and biochemically. A marked decrease in nuclear DNA content was found exclusively in pericentral cultures after an 8-h exposure, followed by an elevation of lactic dehydrogenase (LDH) release after a 12-h exposure. Aurintricarboxylic acid (100 microM), an inhibitor of endonuclease, significantly inhibited the TNF alpha-induced decrease in nuclear DNA content but only partially inhibited the LDH release. This indicates that the loss of nuclear DNA content in pericentral cultures is due to an activation of endonuclease and the resulting DNA fragmentation and does not correlate with NO production. Furthermore, the release of LDH seems to be only partially associated with DNA damage. Dexamethasone (100 nM) completely inhibited both TNF alpha-induced DNA fragmentation and the elevation of LDH release. The results clearly indicate that the toxicity of TNF alpha is influenced by the metabolic state of hepatocytes. Accordingly, the preferential perivenous cell injury observed after exposure to endotoxins in vivo seems to be due to a higher sensitivity of the pericentrally localized hepatocytes towards TNF alpha rather than a TNF alpha concentration gradient.
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PMID:Tumor necrosis factor alpha differentially modulates the cellular response of rat hepatocytes in periportal- and pericentral-equivalent cultures. 779 59

Nitric oxide is a free radical (NO) formed biologically through the oxidation of L-arginine by nitric oxide synthases. NO is produced transiently in mammalian cells for intercellular signaling and in copious quantities to cause cytostasis and cytotoxicity. In the latter situation, NO is a deliberate cytotoxic product of activated macrophages, along with other reactive oxygen species such as hydrogen peroxide (H2O2) and superoxide (O2-). Escherichia coli has a complex set of responses to H2O2 and O2- that involves approximately 80 inducible proteins; we wondered whether these bacteria might induce analogous defenses against nitric oxide. We show here that a multigene system controlled by the redox-sensitive transcriptional regulator SoxR is activated by NO in vivo. This induction confers bacterial resistance to activated murine macrophages with kinetics that parallel the production of NO by these cells. Elimination of specific SoxR-regulated genes diminishes the resistance of these bacteria to the cytotoxic macrophages. The required functions include manganese-containing superoxide dismutase, endonuclease IV (a DNA-repair enzyme for oxidative damage), and micF, an antisense regulator of the outer membrane porin OmpF. These results demonstrate that SoxR is a sensor for cellular exposure to NO, and that the soxRS response system may contribute to bacterial virulence.
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PMID:Activation by nitric oxide of an oxidative-stress response that defends Escherichia coli against activated macrophages. 823 47

Rapid and massive death of motoneurons occurs following axotomy in neonatal mammals. This likely results from the neurons being deprived of access to target-derived trophic factors, as their death can be prevented by application of a variety of neurotrophic factors to the proximal end of the cut nerve. Since trophic factor-deprived embryonic chick motoneurons undergo apoptosis in vitro, we have investigated whether axotomized neonatal rat facial motoneurons undergo apoptotic cell death in vivo. Following facial nerve transection during the first postnatal day, the dying motoneurons show characteristic morphological changes of apoptosis and undergo DNA fragmentation, as detected by an in situ end labeling technique. An initial sharp burst of DNA fragmentation, between 12 and 24 h postaxotomy, accompanies a steep decline in neuronal numbers, indicating that neuronal cell death rapidly follows endonuclease cleavage of DNA. However, the interval between axotomy and onset of DNA fragmentation varies widely. By 4 days postnatum only 38% of the lesioned motoneurons have survived an initial rapid phase of neuronal loss, whereas 11% survive to 10 days postnatum at least. NADPH-diaphorase/nitric oxide synthase activity has been implicated as having a causal role in the death of lesioned motoneurons. We have found that there is a sustained increase in the intensity of NADPH-diaphorase histochemical staining in axotomized neonatal facial motoneurons, but that this is first detectable well after the onset of DNA fragmentation and cell death. This suggests that nitric oxide, or its metabolites, does not initiate cell death in this model.
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PMID:Axotomy-induced apoptotic cell death of neonatal rat facial motoneurons: time course analysis and relation to NADPH-diaphorase activity. 859 94

Nitric oxide (NO) is a pathophysiological mediator with unique signal transducing properties. Signaling mechanisms are categorized as cGMP-dependent or cGMP-independent. Multiple interactions of NO with oxygen, superoxide, and transition metals determine the biological activity. Cyclic GMP-independent responses of NO account for the antimicrobial, the cytostatic, and the cytotoxic capacity of NO. Cytotoxicity is not only directed to harmful cells but also affects the NO-producing cell in a self-destructing loop. For macrophages and pancreatic beta-cells (RINm5F), we established NO-mediated apoptotic cell death. Endogenously generated or exogenously applied NO causes DNA cleavage after endonuclease activation. NO-mediated accumulation of the tumor suppressor p53 precedes apoptotic cell death.
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PMID:The role of nitric oxide in cell injury. 859 59

Bisphosphonates (BPs) are an important class of antiresorptive drugs used in the treatment of bone diseases, including osteoporosis. Although their mechanism of action has not been identified at the molecular level, there is substantial evidence that BPs can have a direct effect on osteoclasts by mechanisms that may lead to osteoclast cell death by apoptosis. BPs can also inhibit proliferation and cause cell death in macrophages in vitro. We have now shown that the toxic effect of BPs on macrophages is also due to the induction of apoptotic, rather than necrotic, cell death. Morphological and biochemical features that are definitive of apoptosis (chromatin condensation, nuclear fragmentation, and endonuclease-mediated internucleosomal cleavage of DNA) could be identified in mouse macrophage-like J774 and RAW264 cells, following treatment with 100 microM pamidronate, alendronate, and ibandronate for 24 h or more. Clodronate was much less potent, even at 2000 microM, while 2000 microM etidronate did not cause apoptosis. Apoptosis was not due to increased synthesis of nitric oxide and could not be prevented by inhibitors of nitric oxide synthases. Since macrophages, like osteoclasts, are particularly susceptible to BPs, these observations support the recent suggestion that the mechanism by which BPs inhibit bone resorption may involve osteoclast apoptosis. Furthermore, the macrophage-like cell lines used in this study may be a convenient model with which to identify the molecular mechanisms by which BPs promote apoptosis in osteoclasts. Induction of macrophage apoptosis by BPs in vivo may also account, at least in part, for the anti-inflammatory properties of BPs as well as the ability of BPs to cause an acute phase response.
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PMID:Bisphosphonates induce apoptosis in mouse macrophage-like cells in vitro by a nitric oxide-independent mechanism. 888 48

Oxidative stress is considered a major mediator of apoptosis in several cellular systems. Peroxynitrite is a highly toxic oxidant formed by the reaction of nitric oxide with superoxide. Primary embryonic murine fibroblasts, exposed to 1 mM peroxynitrite, resulted in delayed cell death characterized by membrane blebbing, cytoplasmic shrinkage, nuclear condensation, and DNA fragmentation that were more characteristic of apoptosis than necrosis. In addition, both morphological alterations and DNA fragmentation were inhibited by the endonuclease inhibitor aurintricarboxylic acid. Pretreatment of fibroblasts with acidic fibroblast growth factor (FGF-1) markedly enhanced peroxynitrite-induced apoptosis, an observation restricted to immediate-early transcriptional and activated tyrosine phosphorylation processes. FGF-1 pretreatment had no modulatory effect on cell death elicited by other reactive oxygen species, suggesting that enhancement of apoptosis involves a unique relationship between peroxynitrite and the growth factor. Exposure of cells to peroxynitrite resulted in immediate tyrosine nitration of several polypeptides, including major targets with estimated molecular masses of 62, 68, and 77 kDa. Pretreatment with FGF-1 did not alter targets of peroxynitrite-mediated tyrosine nitration, but rather increased the total amount of this amino acid modification. Treatment with other reactive oxygen species failed to induce tyrosine nitration. Collectively, these efforts demonstrate that FGF-1 transiently renders primary fibroblasts more sensitive to peroxynitrite-induced apoptosis. In addition, results presented here predict a pivotal role for FGF-1 and peroxynitrite-induced cytotoxicity during the resolution of inflammation and repair processes in vivo.
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PMID:Acidic fibroblast growth factor enhances peroxynitrite-induced apoptosis in primary murine fibroblasts. 891 32

All organisms have adapted to environmental changes by acquiring various functions controlled by gene regulation. In bacteria, a number of specific responses have been found to confer cell survival in various nutrient-limited conditions, and under physiological stresses such as high or low temperature, extreme pH, radiation, and oxidation (for review, see Neidhardt et al., 1987). In this article, I introduce an Escherichia coli (E. coli) global response induced by superoxide stress, the soxRS regulon. The functions controlled by this system consist of a wide variety of enzymes such as manganese-containing SOD (Mn-SOD); glucose 6-phosphate dehydrogenase (G6PD), the DNA repair enzyme endonuclease IV, fumarase C, NADPH:ferredoxin oxidoreductase, and aconitase. This response is positively regulated by a two-stage control system in which SoxR iron-sulfur protein senses exposure to superoxide and nitric oxide, and then activates transcription of the soxS gene, whose product stimulates the expression of the regulon genes. Our recent finding indicates that soxS transcription is initiated in a manner dependent on the rpoS gene encoding RNA polymerase sigma factor, theta s, in response to entering the stationary phase of growth. With this information, mechanisms for prokaryotic coordinating gene expression in response to superoxide stress and in stationary phase are discussed.
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PMID:Two-stage gene regulation of the superoxide stress response soxRS system in Escherichia coli. 895 73


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