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J S Beckman

Publications and source records attributed to J S Beckman.

At least 55 records · Page 3Linked to original sources
PubMed1997

Superoxide dismutase catalyzes nitration of tyrosines by peroxynitrite in the rod and head domains of neurofilament-L.

Superoxide dismutase (SOD) catalyzes the nitration of specific tyrosine residues in proteins by peroxynitrite (ONOO-), which may be the damaging gain-of-function resulting from mutations to SOD associated with familial amyotrophic lateral sclerosis (ALS). We found that disassembled neurofilament-L (light subunit) was more susceptible to tyrosine nitration catalyzed by SOD in vitro. Neurofilament-L was selectively nitrated compared with the majority of other proteins present in brain homogenates. Assembled neurofilament-L was more resistant to nitration, suggesting that the susceptible tyrosine residues were protected by intersubunit contacts in assembled neurofilaments. Electrospray mass spectrometry of trypsin-digested neurofilament-L showed that tyrosine 17 in the head region and tyrosines 138, 177, and 265 in alpha-helical coil regions of the rod domain of neurofilament-L were particularly susceptible to SOD-catalyzed nitration. Nitrated neurofilament-L inhibited the assembly of unmodified neurofilament subunits, suggesting that the affected tyrosines are located in regions important for intersubunit contacts. Neurofilaments are major structural proteins expressed in motor neurons and known to be important for their survival in vivo. We suggest that SOD-catalyzed nitration of neurofilament-L may have a significant role in the pathogenesis of ALS.

Amino Acid Sequence↗
PubMed1997

Extensive tyrosine nitration in human myocardial inflammation: evidence for the presence of peroxynitrite.

OBJECTIVES: Production of nitric oxide via the cytokine-mediated activation of myocardial inducible nitric oxide synthase decreases myocardial contractility. Whether myocardial dysfunction is mediated directly by nitric oxide or indirectly through the formation of secondary reaction products, such as peroxynitrite, has not been established. Peroxynitrite, but not nitric oxide, reacts with the phenolic ring of tyrosine to form the stable product 3-nitro-L-tyrosine. Demonstration of tissue nitrotyrosine residues, therefore, infers the presence of peroxynitrite or related nitrogen-centered oxidants. DESIGN: Retrospective analysis of human autopsy specimens. SETTING: University pathology and basic science laboratories. PATIENTS: Formalin-fixed, paraffin-embedded myocardial tissue samples were obtained from 11 patients with a diagnosis of sepsis, seven patients with a diagnosis of viral myocarditis, and five control patients without clinical or pathologic cardiac disease. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Specific antibodies to nitrotyrosine were utilized to detect nitrotyrosine residues in human autopsy specimens. Cardiac tissue obtained from patients with myocarditis or sepsis demonstrated intense nitrotyrosine immunoreactivity in the endocardium, myocardium, and coronary vascular endothelium and smooth muscle. In contrast, connective tissue elements were without appreciable immunohistochemical staining. Nitrotyrosine antibody binding was blocked by coincubation with nitrotyrosine or nitrated bovine serum albumin, but not by aminotyrosine, phosphotyrosine, or bovine serum albumin. In situ reduction of tissue nitrotyrosine to aminotyrosine by sodium hydrosulfite also blocked antibody binding. Densitometric analysis of nitrotyrosine immunoreactivity demonstrated significantly higher values for specimens from myocarditis and sepsis patients when compared with control tissue specimens. CONCLUSION: These results demonstrate the formation of peroxynitrite within the myocardium during inflammatory disease states, suggesting a role for peroxynitrite in inflammation-associated myocardial dysfunction.

Adolescent↗
PubMed1996

Acidic fibroblast growth factor enhances peroxynitrite-induced apoptosis in primary murine fibroblasts.

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.

Animals↗
PubMed1996

Nitration and inactivation of manganese superoxide dismutase in chronic rejection of human renal allografts.

Inflammatory processes in chronic rejection remain a serious clinical problem in organ transplantation. Activated cellular infiltrate produces high levels of both superoxide and nitric oxide. These reactive oxygen species interact to form peroxynitrite, a potent oxidant that can modify proteins to form 3-nitrotyrosine. We identified enhanced immunostaining for nitrotyrosine localized to tubular epithelium of chronically rejected human renal allografts. Western blot analysis of rejected tissue demonstrated that tyrosine nitration was restricted to a few specific polypeptides. Immunoprecipitation and amino acid sequencing techniques identified manganese superoxide dismutase, the major antioxidant enzyme in mitochondria, as one of the targets of tyrosine nitration. Total manganese superoxide dismutase protein was increased in rejected kidney, particularly in the tubular epithelium; however, enzymatic activity was significantly decreased. Exposure of recombinant human manganese superoxide dismutase to peroxynitrite resulted in a dose-dependent (IC50 = 10 microM) decrease in enzymatic activity and concomitant increase in tyrosine nitration. Collectively, these observations suggest a role for peroxynitrite during development and progression of chronic rejection in human renal allografts. In addition, inactivation of manganese superoxide dismutase by peroxynitrite may represent a general mechanism that progressively increases the production of peroxynitrite, leading to irreversible oxidative injury to mitochondria.

Amino Acid Sequence↗
PubMed1996

Nitric oxide, superoxide, and peroxynitrite: the good, the bad, and ugly.

Nitric oxide contrasts with most intercellular messengers because it diffuses rapidly and isotropically through most tissues with little reaction but cannot be transported through the vasculature due to rapid destruction by oxyhemoglobin. The rapid diffusion of nitric oxide between cells allows it to locally integrate the responses of blood vessels to turbulence, modulate synaptic plasticity in neurons, and control the oscillatory behavior of neuronal networks. Nitric oxide is not necessarily short lived and is intrinsically no more reactive than oxygen. The reactivity of nitric oxide per se has been greatly overestimated in vitro because no drain is provided to remove nitric oxide. Nitric oxide persists in solution for several minutes in micromolar concentrations before it reacts with oxygen to form much stronger oxidants like nitrogen dioxide. Nitric oxide is removed within seconds in vivo by diffusion over 100 microns through tissues to enter red blood cells and react with oxyhemoglobin. The direct toxicity of nitric oxide is modest but is greatly enhanced by reacting with superoxide to form peroxynitrite (ONOO-). Nitric oxide is the only biological molecule produced in high enough concentrations to out-compete superoxide dismutase for superoxide. Peroxynitrite reacts relatively slowly with most biological molecules, making peroxynitrite a selective oxidant. Peroxynitrite modifies tyrosine in proteins to create nitrotyrosines, leaving a footprint detectable in vivo. Nitration of structural proteins, including neurofilaments and actin, can disrupt filament assembly with major pathological consequences. Antibodies to nitrotyrosine have revealed nitration in human atherosclerosis, myocardial ischemia, septic and distressed lung, inflammatory bowel disease, and amyotrophic lateral sclerosis.

Animals↗
PubMed1996

Mechanisms of cerebral vasodilation by superoxide, hydrogen peroxide, and peroxynitrite.

We investigated the role of potassium channels in the vasodilator action of hydrogen peroxide, peroxynitrite, and superoxide on cerebral arterioles. We studied the effect of topical application of these agents in anesthetized cats equipped with cranial windows. Hydrogen peroxide and peroxynitrite induced dose-dependent dilation that was inhibited by glyburide, an inhibitor of ATP-sensitive potassium channels. Superoxide, generated by xanthine oxidase acting on xanthine in the presence of catalase, also induced dose-dependent dilation of cerebral arterioles that was unaffected by glyburide but inhibited completely by tetraethylammonium chloride, an inhibitor of calcium-activated potassium channels. The vasodilations from hydrogen peroxide, peroxynitrite, or superoxide were unaffected by inhibition of soluble guanylate cyclase with LY-83583. The findings provide pharmacological evidence that hydrogen peroxide and peroxynitrite reversibly dilate cerebral arterioles by activating ATP-sensitive potassium channels, probably through an oxidant mechanism, whereas superoxide dilates cerebral arterioles by opening calcium-activated potassium channels. Activation of soluble guanylate cyclase is not a mediator of the vasodilator action of these agents in cerebral arterioles.

Aminoquinolines↗
PubMed1995

Peroxynitrite stimulates vascular smooth muscle cell cyclic GMP synthesis.

Peroxynitrite stimulated the synthesis of cyclic GMP by rat aortic smooth muscle in a time- and dose-dependent manner. Peak formation of cyclic GMP occurred at 1 min with 100 microM peroxynitrite and was inhibited by oxyhemoglobin. Peroxynitrite was less potent than nitric oxide in stimulating cyclic GMP synthesis. Peroxynitrite also enhanced endothelial-dependent cyclic GMP synthesis, via generation of a long-lived substance, which was prevented by inhibition of glutathione synthesis. These data show that peroxynitrite stimulates cyclic GMP synthesis, inferring production of low yields of nitric oxide or associated derivatives. Additionally, vascular exposure to peroxynitrite potentiates endothelial-dependent activation of guanylate cyclase.

Animals↗
PubMed1995

Sensitivity of the essential zinc-thiolate moiety of yeast alcohol dehydrogenase to hypochlorite and peroxynitrite.

Disruption of the zinc-thiolate center at the active site of yeast alcohol dehydrogenase results in inactivation and zinc release. Measurements of activity, zinc release, and thiol/thiolate oxidation were used to assess the effects of biologically relevant oxidants on alcohol dehydrogenase. Alcohol dehydrogenase was inactivated by 1 mM hydrogen peroxide at a rate of 1.3 M-1 s-1. Peroxynitrite, the near diffusion-limited reaction product of nitric oxide and superoxide, inactivated alcohol dehydrogenase with an IC50 = 0.95 microM when catalytic concentrations of alcohol dehydrogenase subunit (0.074 microM) were present. Slow, continuous production of peroxynitrite from decomposition of SIN-1 inactivated alcohol dehydrogenase as effectively as bolus addition. The rate constants for reaction of peroxynitrite with alcohol dehydrogenase at 23 degrees C as determined by two different competition assays were 2.6 x 10(5) M-1 s-1 and 5.2 x 10(5) M-1 s-1. The reaction with alcohol dehydrogenase represents one of the fastest reactions yet determined for peroxynitrite. Hypochlorite inactivated alcohol dehydrogenase at a rate of 4 x 10(3) M-1 s-1. The rate constant for inactivation by taurine choramine, the reaction product of taurine and hypochlorite, was only slightly slower at 2.7 x 10(3) M-1 s-1. Zinc release and thiol/thiolate oxidation were correlated with inactivation by either peroxynitrite or hypochlorite. At the concentrations of peroxynitrite or hypochlorite producing total inactivation, 0.85 zinc atom was released per subunit and 3 thiol/thiolates per subunit were oxidized.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Dehydrogenase↗
PubMed1995

The comparative toxicity of nitric oxide and peroxynitrite to Escherichia coli.

The reactivity and toxicity of nitric oxide is modest in comparison to oxidants derived from nitric oxide. Exposure of Escherichia coli to 1 mM nitric oxide under aerobic or anaerobic conditions did not decrease viability of the bacteria. Peroxynitrite (1 mM), the reaction product of superoxide and nitric oxide, was completely bactericidal after 5 s. The nitrovasodilator, 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1), slowly decomposes to release both nitric oxide and superoxide and thereby produces peroxynitrite. SIN-1 killed E. coli in direct proportion to its concentration with an LD50 of 0.5 mM. Copper, zinc superoxide dismutase (50-400 units/ml) provided substantial but not complete protection against SIN-1 killing. Catalase (500-10,000 units/ml) partially protected in direct proportion to its concentration, while inactivated catalase was not protective. Superoxide dismutase and catalase together completely protected E. coli against SIN-1 toxicity. Oxy-hemoglobin eliminated both SIN-1 and peroxynitrite toxicity. The bactericidal activity of SIN-1 was further enhanced by pterin plus xanthine oxidase. Pterin plus xanthine oxidase alone or together with Fe3+ ethylenediamine tetraacetate produced no significant decrease in E. coli viability. Hydrogen peroxide was not directly toxic to the bacteria, but E. coli pretreated with hydrogen peroxide were more susceptible to peroxynitrite, SIN-1, and the aerobic oxidation products of nitric oxide. Hydrogen peroxide pretreatment did not increase significantly the toxicity of nitric oxide under anaerobic conditions. Our results suggest that peroxynitrite is far more toxic to E. coli than nitric oxide or its by products from aerobic oxidation.

Escherichia coli↗
PubMed1995

Role of inducible nitric oxide synthase expression and peroxynitrite formation in guinea pig ileitis.

BACKGROUND & AIMS: Inflammatory bowel disease is characterized by increased synthesis of nitric oxide. The aim of this study was to determine if inducible NO synthase (iNOS) was responsible for tissue injury, potentially via peroxynitrite formation, in the guinea pig model of gut inflammation. METHODS: Inflammation was induced in guinea pig ileum by intraluminal administration of the hapten trinitrobenzene sulfonic acid in 50% ethanol. iNOS gene expression was assessed by reverse-transcriptase polymerase chain reaction and Western blotting, immunohistochemistry was determined by its localization, and activity was inhibited with the specific inhibitor aminoguanidine administered via the drinking water for 7 days. Nitration of tyrosines was assessed by immunohistochemistry. RESULTS: In control animals, iNOS gene expression was minimal to absent, whereas, in hapten, inflammation-marked iNOS gene expression was evident from day 1 to 7. Nitrotyrosine and iNOS immunohistochemistry were colocalized, and positive staining was most intense in epithelia and neurons. Inhibition of NO formation prevented nitrotyrosine formation. Aminoguanidine inhibited the inflammatory response and restored morphology. CONCLUSIONS: The colocalization of tyrosine nitration with iNOS immunoreactivity suggests that iNOS may be responsible for tissue injury and the formation of NO-dependent nitrating species, potentially peroxynitrite. Inhibition of iNOS may afford a new therapeutic approach to the treatment of inflammatory bowel disease.

Amino Acid Sequence↗