Isolation of cDNAs representing dithiolethione-responsive genes

Primiano, Thomas; Gastel, Jonathan A.; Kensler, Thomas W.; Sutter, Thomas R.

doi:10.1093/carcin/17.11.2297

Cited by 62 publications

(61 citation statements)

References 23 publications

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“…pCMV-3Tag-hPtGR-1 or pCMV-3Tag-1 plasmids were transfected into cells with Lipofectamine 2000 (Invitrogen) overnight. Rat-PtGR-1 overexpression was obtained by transfection with a pCAGGS-EGFP-rat-PtGR-1 plasmid in which rat-PtGR-1 cDNA-tagged with EGFP was ligated into the mammalian expression vector pCAGGS (41,42). Expression of recombinant as well as endogenous PtGR-1 was assessed by Western blot analysis using FLAG (Santa Cruz), GFP (Sigma), and PtGR-1 (Aviva Systems Biology) antibodies.…”

Section: Methodsmentioning

confidence: 99%

Modulation of Nitro-fatty Acid Signaling

Vitturi¹,

Chen²,

Woodcock³

et al. 2013

Journal of Biological Chemistry

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Background: Nitroalkenes are electrophilic anti-inflammatory mediators that signal via Michael addition and are metabolized in vivo. Results: Prostaglandin reductase-1 is identified as a nitroalkene reductase. Conclusion: Prostaglandin reductase-1 reduces fatty acid nitroalkenes to nitroalkanes, inactivating electrophilic reactivity. Significance: A mammalian enzyme is identified that metabolizes fatty acid nitroalkenes in vivo to silence their signaling reactions.

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Section: Methodsmentioning

confidence: 99%

Modulation of Nitro-fatty Acid Signaling

Vitturi¹,

Chen²,

Woodcock³

et al. 2013

Journal of Biological Chemistry

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“…It is coregulated in the rat with a variety of phase 2/antioxidative enzymes, including NAD(P)H:quinone reductase, glutathione S-transferases, and UDP-glucuronosyltransferases, through the Keap1/Nrf2 signaling pathway (2). ␣,␤-Unsaturated aldehydes and ketones are electrophilic and capable of reacting, via a Michael addition mechanism, with important cellular nucleophiles, which in turn leads to macromolecular (protein, DNA) dysfunction and cell death.…”

Section: Nad(p)h-dependent Alkenal/one Oxidoreductase (Aor)mentioning

confidence: 99%

“…2 Whereas the former two classes of compounds are inactive metabolites, 15-deoxy-⌬ 12,14 -prostaglandin J 2 is thought to be an endogenous activator of the Nrf2 transcription factor (8). Recently, AOR was also found to reduce the 8,9-double bond of the mycotoxins illudins S and M (9).…”

Section: Nad(p)h-dependent Alkenal/one Oxidoreductase (Aor)mentioning

confidence: 99%

“…This activity serves to virtually inactivate this potent neutrophil chemoattractant and stimulator of degranulation. It was later found that this enzyme is coordinately regulated with several antioxidative and conjugative phase 2 enzymes in the rat liver (2) and has the NAD(P)H-dependent ability to hydrogenate the 13,14-double bond of the 15-oxoprostaglandins (6). AOR was also found to catalyze the reduction of an array of smaller ␣,␤-unsaturated carbonyls, including cyto- toxic products of lipid peroxidation, at higher rates.…”

Section: Deuterium and Solvent Kinetic Isotope Effects-both [4s-2 H] mentioning

confidence: 99%

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The Catalytic and Kinetic Mechanisms of NADPH-dependent Alkenal/one Oxidoreductase

Dick

Kensler

2004

Journal of Biological Chemistry

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NADPH-dependent alkenal/one oxidoreductase (AOR) from the rat is a phase 2/antioxidative enzyme that is known to catalyze the reduction of the carbon-carbon double bond of ␣,␤-unsaturated aldehydes and ketones. It is also known for its leukotriene B 4 12-hydroxydehydrogenase activity. In order to begin to understand these dual catalytic activities and validate its classification as a reductase of the medium-chain dehydrogenase/ reductase family, an investigation of the mechanism of its NADPH-dependent activity was undertaken. Recombinant AOR and a 3-nonen-2-one substrate were used to perform steady-state initial velocity, product inhibition, and dead end inhibition experiments, which elucidated an ordered Theorell-Chance kinetic mechanism with NADPH binding first and NADP ؉ leaving last. A nearly 20-fold preference for NADPH over NADH was also observed. The dependence of kinetic parameters V and V/K on pH suggests the involvement of a general acid with a pK of 9.2. NADPH isomers stereospecifically labeled with deuterium at the 4-position were used to determine that AOR catalyzes the transfer of the pro-R hydride to the ␤-carbon of an ␣,␤-unsaturated ketone, illudin M. Two-dimensional nuclear Overhauser effect NMR spectra demonstrate that this atom becomes the R-hydrogen at this position on the metabolite. Using [4R-2 H]NADPH, small primary kinetic isotope effects of 1.16 and 1.73 for V and V/K, respectively, were observed and suggest that hydride transfer is not rate-limiting. Atomic absorption spectroscopy indicated an absence of Zn 2؉ from active preparations of AOR. Thus, AOR fits predictions made for medium-chain reductases and bears similar characteristics to well known medium-chain alcohol dehydrogenases. NAD(P)H-dependent alkenal/one oxidoreductase (AOR)1 is an enzyme that reduces the carbon-carbon double bond of a variety of ␣,␤-unsaturated aldehydes and ketones (1). It is coregulated in the rat with a variety of phase 2/antioxidative enzymes, including NAD(P)H:quinone reductase, glutathione S-transferases, and UDP-glucuronosyltransferases, through the Keap1/Nrf2 signaling pathway (2). ␣,␤-Unsaturated aldehydes and ketones are electrophilic and capable of reacting, via a Michael addition mechanism, with important cellular nucleophiles, which in turn leads to macromolecular (protein, DNA) dysfunction and cell death. Because saturated carbonyls lack this reactive moiety, they are often far less toxic. Thus, hydrogenation of the ␣,␤-double bond by AOR conceptually results in detoxication (1, 3).Of the AOR substrates identified, several are common environmental pollutants (methyl vinyl ketone and acrolein) or products of lipid peroxidation (4, 5). The latter process involves reaction of oxygen free radicals with polyunsaturated fatty acids to form aliphatic ␣,␤-unsaturated aldehydes such as 4-hydroxy-2-nonenal (4HNE), 2-hexenal, and 2,4-decadienal (5). These reactive molecules probably mediate many of the detrimental effects of oxidative stress. 4HNE is extremely cytotoxic, an abundant product of lipid perox...

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“…Subsequent studies demonstrated that oltipraz and many related dithiolethiones were potent inducers of enzymes concerned with the maintenance of reduced glutathione pools as well as enzymes important to the detoxication of electrophiles and free radicals. Genes now recognized to be induced by dithiolethiones in vivo include alpha, mu and pi isoforms of GSTs, UDP-glucuronosyl transferases, NAD(P)H: quinone reductase (NQO1), epoxide hydrolase, aflatoxin aldehyde reductase, ␥-glutamylcysteine synthase, manganese superoxide dismutase, catalase, heavy and light chains of ferritin, and leukotriene B 4 dehydrogenase [19][20][21][22].…”

Section: Role Of Enzyme Induction In Cancer Chemoprotectionmentioning

confidence: 99%

Role of phase 2 enzyme induction in chemoprotection by dithiolethiones

Kwak

Egner

Dolan

et al. 2001

Mutation Research/Fundamental and Molecular Mechanisms of Mutag

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One of the major mechanisms of protection against carcinogenesis, mutagenesis, and other forms of toxicity mediated by carcinogens is the induction of enzymes involved in their metabolism, particularly phase 2 enzymes such as glutathione S-transferases (GSTs), UDP-glucuronosyl transferases, and quinone reductases. Animal studies indicate that induction of phase 2 enzymes is a sufficient condition for obtaining chemoprevention and can be achieved by administering any of a diverse array of naturally-occurring and synthetic chemopreventive agents. Indeed, monitoring of enzyme induction has led to the recognition or isolation of novel, potent chemopreventive agents such as 1,2-dithiole-3-thiones, terpenoids and the isothiocyanate sulforaphane. For example, oltipraz, a substituted 1,2-dithiole-3-thione originally developed as an antischistosomal agent, possesses chemopreventive activity against different classes of carcinogens targeting multiple organs. Mechanistic studies in rodent models for chemoprevention of aflatoxin B 1 (AFB 1 )-induced hepatocarcinogenesis by oltipraz indicates that increased expression of phase 2 genes is of central importance, although inhibition of phase 1 activation of AFB 1 can also contribute to protection. Exposure of rodents to 1,2-dithiole-3-thiones triggers nuclear accumulation of the transcription factor Nrf2 and its enhanced binding to the "antioxidant response element" (ARE), leading to transcriptional activation of a score of genes involved in carcinogen detoxication and attenuation of oxidative stress. Nrf2-deficient mice fail to induce many of these genes in response to dithiolethiones; moreover, basal expression of these genes is typically repressed. To test the hypothesis that enzyme induction is a useful strategy for chemoprevention in humans, three key elements are necessary: a candidate agent, an at-risk population and modulatable intermediate endpoints. Towards this end, a placebo-controlled, double blind clinical trial of oltipraz was conducted in residents of Qidong, PR China who are exposed to dietary aflatoxins and who are at high risk for the development of liver cancer. Oltipraz significantly enhanced excretion of a phase 2 product, aflatoxin-mercapturic acid, a derivative of the aflatoxin-glutathione conjugate, in the urine of study participants administered 125 mg oltipraz by mouth daily. Administration of 500 mg oltipraz once a week led to a significant reduction in the excretion of the primary oxidative metabolite of AFB 1 , AFM 1 , when measured shortly after drug administration. While this study highlighted the general feasibility of inducing phase 2 enzymes in humans, a longer term intervention is addressing whether protective alterations in aflatoxin metabolism can be sustained for extended periods of time in this high-risk population.

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Isolation of cDNAs representing dithiolethione-responsive genes

Cited by 62 publications

References 23 publications

Modulation of Nitro-fatty Acid Signaling

Modulation of Nitro-fatty Acid Signaling

The Catalytic and Kinetic Mechanisms of NADPH-dependent Alkenal/one Oxidoreductase

Role of phase 2 enzyme induction in chemoprotection by dithiolethiones

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