The synthesis of the 8 possible stereoisomeric diol epoxides (DEs) at the terminal benzo ring of carcinogenic dibenza,hanthracene (DBA) is reported. trans-3,4-Dihydroxy-3,4-dihydro-DBA (1) afforded ...the 4 bay region DEs: the enantiomeric pairs of the anti diastereomers (+)-3/(−)-3 and of the syn diastereomers (−)-4/(+)-4, respectively. trans-1,2-Dihydroxy-1,2-dihydro-DBA (2) served as precursor of the 4 reverse DEs: the enantiomeric pairs of the anti diastereomers (+)-5/(−)-5 and of the syn diastereomers (−)-6/(+)-6, respectively. The transformation of the olefinic double bond in the enantiomeric trans-dihydrodiols to epoxides was achieved by either (i) oxidation with m-chloroperoxybenzoic acid or (ii) formation of a bromohydrin with N-bromoacetamide/H2O followed by dehydrobromination with an anion exchange resin. Because of the pseudodiequatorial conformation of the hydroxyl groups in 1, both reactions proceeded highly stereoselectively, while the stereoselectivity was impaired by the pseudodiaxial conformation of the hydroxyl groups in 2. Diastereomers and racemic compounds were efficiently separated without derivatization by HPLC on achiral or chiral stationary phases, respectively. The absolute configurations of the DEs were deduced from the absolute configuration of 1 and 2 considering the regio- and stereoselectivity of the subsequent reactions and resulted in (+)-(1R,2S,3S,4R)-3/(−)-(1S,2R,3R,4S)-3, (−)-(1S,2R,3S,4R)-4/(+)-(1R,2S,3R,4S)-4, (+)-(1R,2S,3S,4R)-5/(−)-(1S,2R,3R,4S)-5, and (−)-(1R,2S,3R,4S)-6/(+)-(1S,2R,3S,4R)-6. The bacterial mutagenicity of the 8 stereoisomeric DEs was determined in histidine-dependent strains TA98 and TA100 of Salmonella typhimurium in the absence of a metabolizing system. In general, the bay region DEs of DBA were stronger mutagens than the reverse DEs. In strain TA98, the syn diastereomers of bay region DEs were stronger mutagens than their anti isomers, while in the case of reverse DEs the anti diastereomers were more potent than their syn isomers. In strain TA100, all syn diastereomers surpassed the bacterial mutagenicity of their anti isomers. Concerning the bay region DEs of DBA, this corresponds to the situation described for benzoapyrene: of the 4 enantiomeric bay region DEs of DBA and benzoapyrene, the syn diastereomer with (R,S)-diol (R,S)-epoxide absolute configuration is the most potent mutagen in both bacterial strains, while the anti isomer with (S,R)-diol (R,S)-epoxide configuration is the weakest mutagen.
Mammalian metabolism of polycyclic aromatic hydrocarbons results in the formation of vicinal diol epoxides (existing as enantiomeric pairs of two diastereomers) considered as important ultimate ...carcinogens if the oxirane ring is located in a bay or fjord region of the parent hydrocarbon. In the present study, individual stereoisomers of the bay region diol epoxides of chrysene, dibenza,h-anthracene and benzoapyrene, as well as of the fjord region diol epoxides of benzocphenanthrene, benzocchrysene and benzogchrysene, have been incubated with glutathione (GSH) in the presence or absence of human glutathione S-transferase isoenzyme GST A1-1, a class Alpha enzyme. The formation of GSH conjugates was determined and quantified by HPLC. The results demonstrate that the GST A1-1 isoenzyme catalyzes the formation of GSH conjugates of all diol epoxides tested, although a marked variation in catalytic efficiency (>20-fold) was observed. With both bay and fjord region anti-diol epoxides a significant preference for conjugation of the enantiomer with the R configuration at the benzylic position of the oxirane ring was noted. Among the syn diastereomers of the fjord region diol epoxides a similar substrate enantioselectivity was noted, i.e. the enantiomer with the corresponding R configuration was again preferentially conjugated. In contrast, for the bay region syn-diol epoxides this substrate selectivity was reversed, resulting in a preference for the enantiomer with the S configuration. The chemically more reactive syn diastereomers were in general better substrates for GST A1-1 than the corresponding anti diastereomers. However, a comparison between different diol epoxide diastereomers revealed no obvious correlation between chemical reactivity of the compounds and catalytic efficiencies. Furthermore, no significant correlation between diol epoxide lipophilicity and catalytic efficiency was observed. It is suggested that stereochemical factors, including the size and the geometry of the aromatic ring system and the preferred conformation of the diol epoxide, are involved as the major determinant for the rate of catalysis by GST A1-1.
Dihydrodiol epoxides (DEs) are important carcinogenic metabolites of polycyclic aromatic hydrocarbons (PAHs). The metabolic formation of four stereoisomeric DEs (a pair of optically active ...diastereomers termed as syn- and anti-form) is possible. Glutathione tranferases (GSTs) have been demonstrated to catalyze the detoxification of DEs. Purified GSTs display remarkable differences in catalytic efficiencies towards bay- and fjord-region DEs along with a high degree of regio- and stereoselectivity. Here we determined to which extent heterologously expressed human GSTP1-1, a major GST isoform in lung, affects the mutagenicity of stereoisomeric bay-region DEs of benzoapyrene in Chinese hamster V79 cells. To evaluate the influence of sterical crowding in the substrate on the activity of GSTP-1, the study was extended to the strongly mutagenic fjord-region (-)-anti-DEs of benzocphenanthrene and dibenzoa,lpyrene. GSTP1-1,reduced preferentially the mutagenicity (studied at the hprt locus) of (+)-anti and (+)-syn-DEs of benzoapyrene (by 66 and 67%) as compared with the corresponding (-)-anti- and (-)-syn-enantiomers (by 15 and 13%). These results are in line with previous studies on the enantioselectivity of purified GSTP1-1 towards the DE isomers of benzoapyrene and benzocphenanthrene showing that enantiomers with (R)-configuration at the benzylic oxiranyl carbon are better substrates than those with (S)-configuration. Interestingly, the (-)-anti-DEs of benzocphenanthrene and dibenzoa,lpyrene were efficiently detoxified by GSTP-1-1 in the constructed cell line (reduction of mutagenicity by 66 and 64%). This study demonstrates that differences in the caalytic activity seen for purified GST towards individual mutagens do not necessarily reflect the detoxification of DEs by the same enzyme in a living cell and provides further evidence that specific human GSTs play a role in the detoxification of DEs of PAHs.
Mammalian metabolism of polycyclic aromatic hydrocarbons results in the formation of vicinal diol epoxides (existing as enantiomeric pairs of two diastereomers) considered as important ultimate ...carcinogens if the oxirane ring is located in a bay or fjord region of the parent hydrocarbon. In the present study, individual stereoisomers of the bay region diol epoxides of chrysene, dibenza,h-anthracene and benzoapyrene, as well as of the fjord region diol epoxides of benzocphenanthrene, benzog chrysene and have beenzog incubated with glutathione (GSH) in the presence or absence of human glutathione S-transferase isoenzyme GST A1-1, a class Alpha enzyme. The formation of GSH conjugates was determined and quantified by HPLC. The results demonstrate that the GST A1-1 isoenzyme catalyzes the formation of GSH conjugates of all diol epoxides tested, although a marked variation in catalytic efficiency (>20-fold) was observed. With both bay and fjord region anti-diol epoxides a significant preference for conjugation of the enantiomer with the R configuration at the benzylic position of the oxirane ring was noted. Among the syn diastereomers of the fjord region diol epoxides a similar substrate enantiose-lectivity was noted, i.e. the enantiomer with the corresponding R configuration was again preferentially conjugated. In contrast, for the bay region syn-dioI epoxides this substrate selectivity was reversed, resulting in a preference for the enantiomer with the S configuration. The chemically more reactive syn diastereomers were in general better substrates for GST A1-1 than the corresponding anti diastereomers. However, a comparison between different diol epoxide diastereomers revealed no obvious correlation between chemical reactivity of the compounds and catalytic efficiencies. Furthermore, no significant correlation between diol epoxide lipophilicity and catalytic efficiency was observed. It is suggested that stereochemical factors, including the size and the geometry of the aromatic ring system and the preferred conformation of the diol epoxide, are involved as the major determinant for the rate of catalysis by GST A1-1.
Various parameters relevant for the formation of dG adducts produced in the reaction of individual benzoapyrene diol epoxide (BPDE) stereoisomers with oligonucleotides have been studied. Reaction ...time, temperature, pH, molar ratio of diol epoxide and oligonucleotide, base sequence, and buffer system were shown to affect the amount of (+)-anti-BPDE dG adducts formed. Optimum experimental conditions for dG adduct formation were different depending on the base sequence context of the oligonucleotide employed 5‘-d(CCTATAGATATCC) or 5‘-d(CCTATTGCTATCC). In general, low temperature to allow a longer reaction time, slightly alkaline Tris-HCl (pH 7.5−8.0) or alkaline phosphate buffer (pH 11), low concentration of organic solvent, and a molar excess of (+)-anti-BPDE promote dG adduct formation with an oligonucleotide. Low incubation temperature and Tris-HCl buffer also favor dG adduct formation of (−)-anti-BPDE and both enantiomers of syn-BPDE to both 5‘-d(CCTATAGATATCC) and 5‘-d(CCTATTGCTATCC).
A technique has been developed to probe directly RecA-DNA interactions by the use of the fluorescent chromophore, (+)anti-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), covalently attached to ...DNA. The 24-mer oligonucleotide 5′-d(CTACTAAACAT
G
TACAAATCATCC) was specifically modified on the exocyclic nitrogen of the central guanine, to yield a trans-adduct. Upon interaction of the modified oligonucleotide with RecA we find an increase in BPDE fluorescence and a rather high fluorescence anisotropy, suggesting a restricted motion of the BPDE-oligonucleotide in the protein filament. In the presence of the cofactor ATPγS, binding of two oligonuclotides, identical or complementary in sequence, in the RecA filament is possible. The RecA-DNA complex is, however, more stable when the sequences are complementary; in addition, a shift in the BPDE emission peaks is observed. In the presence of ATP (and an ATP regeneration system), the RecA-DNA interaction between two complementary oligonucleotides is changed, and we now find protein-mediated renaturation to occur.
The glutathione transferase A1-1 (GSTA1-1) isoenzyme catalyzes the formation of GSH-conjugates of the isomeric bay-region diol-epoxides (DEs) of ...trans-1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydrochrysene (CDE) and trans-3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrodibenza,hanthracene (DBADE) as well as the isomeric fjord-region DEs trans-3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzocphenanthrene (BPhDE) and trans-9,10-dihydroxy-11,12-epoxy-9,10,11,12-tetrahydro-benzocchrysene (BCDE) although with an approx. 20-fold variation in catalytic efficiency. With the anti-diastereomers and the syn-diastereomers of BPhDE and BCDE, GSTA1-1 demonstrated a significant preference for the enantiomers with R-configuration at the benzylic oxirane-carbons. However, with the syn-diastereomers of the bay-region DEs (CDE and DBADE) the enantiomers with S-configuration at the benzylic oxirane-carbons were preferentially conjugated. The more chemically reactive syn-diastereomers were in general better substrates for GSTA1-1 than the corresponding anti-diastereomers. However, no obvious correlation between catalytic efficiency and chemical reactivity (the rate of nonenzymatic conjugation of DEs and GSH) was noted. The results suggest that the stereochemical features of the DEs are the major determinant for the efficiency in GSTA1-1 catalysis.
The enzyme-catalysed conjugation of each of the four stereoisomers of trans-3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzocphenanthrene (BcPhDE) with glutathione (GSH) by HTP II, a novel isolated ...mu-class GSH transferase from the liver of untreated rat, was studied. All four stereoisomers were substrates for GSH transferase HTP II. The enzymatic reaction shows three different types of enzyme kinetics: substrate inhibition for (-)-anti-BcPhDE with (R,S,S,R)-absolute configuration, allosteric behavior using (+)-anti-BcPhDE with (S,R,R,S)-absolute configuration and Henri-Michaelis-Menten kinetics with both the (-)-syn- and (+)-syn-enantiomers, with (S,R,S,R)- and (R,S,R,S)-absolute configuration, respectively. When the concentration of these diolepoxides was varied (using 2 mM GSH), the apparent Vmax values were 1975 nmol/min x mg for (-)-anti-BcPhDE and about 60 nmol/min x mg for both (-)-syn- and (+)-syn-BcPhDE, with the corresponding Km values of 1.05 and 0.20 mM. The reaction of (+)-anti-BcPhDE determined by applying the Hill equation had an estimated Vmax value of 930 nmol/min x mg. On varying the concentration of GSH, linear Lineweaver-Burk plots were obtained. No competitive effect could be observed using a mixture of (-)-anti- and (+)-anti-enantiomers, indicating that their binding sites are different and independent. It was also shown, that the binding sites of (+)-anti- and both syn-enantiomers were different and independent of each other, while there was a small effect on the binding of the syn-enantiomers caused by (-)-anti-BcPhDE. All products of the reaction between GSH and the dihydrodiol epoxides of benzocphenanthrene could be resolved by HPLC and were identified and quantitated using the corresponding synthetic GSH conjugates.
Longevity is rightly considered one of the greatest achievements of modern society, not only as a function of lifespan, but, more importantly, as a function of healthspan. There are Longevity Blue ...Zones (LBZs), regions around the world, such as in Okinawa, Japan; the Nicoya Peninsula, Costa Rica; Loma Linda, California; Icaria, Greece; and Ogliastra, Sardinia, that are characterized by a significant percentage of residents who live exceptionally long lives, often avoiding age-related disability to a significantly higher degree than in the Western way of life. Longevity is not a universal phenomenon, so if there are places in the world with characteristics similar to the LBZs, it is important to identify them in order to better understand what other factors, in addition to the known ones, might contribute to a long and healthy life. This narrative review aims to identify common factors between Cilento and the five LBZs, taking into account environmental, nutritional, and lifestyle factors. Articles from 2004 to the present, limited to studies published in English, German, and Italian, were searched in PubMed/Medline, Scopus, and Google Scholar. The co-authors agreed on 18 final reference texts. In order to evaluate the similarities between Cilento and the LBZs, a descriptive comparative approach was used. Cilento and the LBZs share several common factors, including a hilly altitude ranging from 355 to 600 m; a mild climate throughout the year, with temperatures between 17.4 and 23.5 degrees Celsius; traditional professions, such as agriculture and animal husbandry; and a predominantly Mediterranean or plant-based diet, with typical recipes based on legumes, tubers, vegetables, and extra virgin olive oil. Additionally, maintenance of strong intergenerational family relationships, religious devotion, and social relationships within the community are also prevalent. Given the similarities to Cilento, one might wonder if this is an LBZ waiting to be discovered. The lessons learned from this discovery could be applied to the general population to protect them from non-communicable chronic diseases and help slow the aging process.
Get the Message Funk, Friederike; McGeer, Victoria; Gollwitzer, Mario
Personality & social psychology bulletin,
08/2014, Letnik:
40, Številka:
8
Journal Article
Recenzirano
Results from three studies demonstrate that victims’ justice-related satisfaction with punishment is influenced by the kind of feedback they receive from offenders after punishment. In contrast to ...previous studies that found a discrepancy between anticipated and experienced satisfaction from punishment (Carlsmith, Wilson, & Gilbert, 2008), participants were able to accurately predict their satisfaction when made aware of the presence or absence of offender feedback acknowledging the victim’s intent to punish. Results also indicate that victims were most satisfied when offender feedback not only acknowledged the victim’s intent to punish but also indicated a positive moral change in the offender’s attitude toward wrongdoing. These findings indicate that punishment per se is neither satisfying nor dissatisfying but that it is crucial to take its communicative functions and its effects on the offender into account. Implications for psychological and philosophical theories on punishment motives as well as implications for justice procedures are discussed.
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