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31.
Abstract— Ultraviolet B irradiation has been believed to decrease or impair the activity of reactive oxygen species (ROS) scavenging enzymes such as superoxide dismutase (SOD) in the skin. It has been recently reported that two isozymes of SOD, namely copper-zinc SOD (Cu-Zn SOD) and manganese SOD (Mn SOD), exist in mammalian cells and that the two enzymes play different roles in living systems. The aim of this study was to investigate changes in SOD activities and protein levels in cultured human keratinocytes after acute UVB irradiation. In addition, the protein levels of Cu-Zn SOD and Mn SOD were quantified separately. A single exposure to UVB irradiation produced an increase in SOD activity and protein level that peaked immediately after UVB irradiation, after which a decline was observed, with subsequent recovery to baseline levels 24 h after irradiation. In individual assays of Mn SOD and Cu-Zn SOD, the amount of Mn SOD protein decreased and then gradually recovered 24 h after irradiation. In contrast, the amount of Cu-Zn SOD protein increased immediately after UVB irradiation, and then gradually declined. To evaluate the mechanisms of these changes, we examined the effects of the cytokines, interleukin-1α (IL-1α) and tumor necrosis factor-α (TNF-α), which can be secreted from keratinocytes after UVB irradiation, on the SOD activity and protein levels in keratinocytes. Interleukin-la and TNF-α enhanced both the SOD activity and protein level of Mn SOD, while these cytokines had no effect on Cu-Zn SOD protein levels in cultured human keratinocytes after incubation for 24 h. Furthermore, when neutralizing antibodies against IL-1α and TNF-α were added separately or together to the culture medium before UVB irradiation, the recovery of total SOD activity and Mn SOD protein level were markedly inhibited 24 h after irradiation. Our results suggest that significant increases in SOD activity and protein level occur as a cutaneous antioxidant defense mechanism that protects against the cytotoxicity as a result of UVB irradiation, and that this increase in SOD is attributed to Cu-Zn SOD. The Cu-Zn SOD and Mn SOD protein levels changed in a different manner after UVB irradiation. The former may participate in an early phase and the latter in a late phase defense mechanism directed against oxidant cytotoxicity through UVB irradiation. In addition, the recovery of Mn SOD to baseline levels 24 h after UVB irradiation seems to be mediated through cytokines such as IL-1α and TNF-α, which are secreted from keratinocytes. 相似文献
32.
Jyunichi Koyanagi Katsumi Yamamoto Kouji Nakayama Akira Tanaka 《Journal of heterocyclic chemistry》1997,34(2):407-412
4,9-Dimethoxynaphtho[2,3-b]furan 9 was obtained in 91% yield via the reductive methylation of naphtho[2,3-b]furan-4,9-dione 2 . After treatment of 9 with butyllithium, the mixture was allowed to react with N,N-dimethylacetamide, followed by oxidization with cerium(IV) diammonium nitrate to give 2-acetylnaphtho[2,3-b]furan-4,9-dione 1 . 2-Formylnaphtho[2,3-b]furan-4,9-dione 13 and 2-trimethylsilyl-naphtho[2,3-b]furan-4,9-dione 14 were also obtained from 9 by a similar method. The halodesilylations of 14 easily gave 2-iodonaphtho[2,3-b]furan-4,9-dione 16 , 2-bromonaphtho[2,3-b]furan-4,9-dione 17 , and 2-chloronaphtho[2,3-b]furan-4,9-dione 18 in 82%, and 93% and 83% yield, respectively. Furthermore, the nitrodesilylation of 14 gave 2-nitronaphtho[2,3-b]furan-4,9-dione 3 in 77% yield. 相似文献
33.
Otani T Takayama J Sugihara Y Ishii A Nakayama J 《Journal of the American Chemical Society》2003,125(27):8255-8263
3,4-Di-tert-butylthiophene 1-oxide (1a) reacted with a series of electron-deficient alkenic dienophiles at its syn-pi-face relating to the S=O bond to give [4+2] adducts in excellent yields. The 1-oxide 1a also reacted even with angle-strained dienophiles acenaphthylene and norbornene at its syn-pi-face to afford [4+2] adducts; in the latter case, norbornene reacted exclusively at its exo-pi-face. The oxide 1a reacted with dimethyl acetylenedicarboxylate to produce dimethyl 4,5-di-tert-butylphthalate in high yield with spontaneous extrusion of SO from the initial adduct even at room temperature. Similarly, 3,4-di-tert-butylthiophene 1-(p-toluenesulfonyl)imide (3a) reacted with alkenic dienophiles at its syn-pi-face relating to the S=N bond to give [4+2] adducts in good yields. The reaction of 3a with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) afforded a 1,2-thiazetidine 12a, the first example of S-unoxidized 1,2-thiazetidine, in good yield, through rearrangement of the initial [4+2] adduct. The molecular structure of 12a is discussed on the basis of the X-ray crystallographic analysis. Comparison of the foregoing reactions leads to the conclusion that the 1-oxide 1a is more reactive as a diene than the 1-imide 3a, which is more reactive than 3,4-di-tert-butylthiophene 1,1-dioxide. The origin of the syn-pi-face selectivities of 1a and 3a in Diels-Alder reactions is discussed in terms of the orbital mixing rule and steric effect and also based on B3LYP/6-31G(d) calculations. 相似文献
34.
Takashi Hirota Kenji Sasaki Yohsuke Tashima Taiji Nakayama 《Journal of heterocyclic chemistry》1991,28(2):263-267
Syntheses of 2,3-dihydrobenzofuro[2,3-e]imidazo[1,2-c]pyrimidine and its 5-substituted derivatives, corresponding to B-nor-6-oxa-11,13,15-triazasteroids, are described. These products and their precursors were screened to evaluate the antidepressive activity. 相似文献
35.
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37.
Ishii Y Iwahama T Sakaguchi S Nakayama K Nishiyama Y 《The Journal of organic chemistry》1996,61(14):4520-4526
A novel class of catalysts for alkane oxidation with molecular oxygen was examined. N-Hydroxyphthalimide (NHPI) combined with Co(acac)(n)() (n = 2 or 3) was found to be an efficient catalytic system for the aerobic oxidation of cycloalkanes and alkylbenzenes under mild conditions. Cycloalkanes were successfully oxidized with molecular oxygen in the presence of a catalytic amount of NHPI and Co(acac)(2) in acetic acid at 100 degrees C to give the corresponding cycloalkanones and dicarboxylic acids. Alkylbenzenes were also oxidized with dioxygen using this catalytic system. For example, toluene was converted into benzoic acid in excellent yield under these conditions. Ethyl- and butylbenzenes were selectively oxidized at their alpha-positions to form the corresponding ketones, acetophenone, and 1-phenyl-1-butanone, respectively, in good yields. A key intermediate in this oxidation is believed to be the phthalimide N-oxyl radical generated from NHPI and molecular oxygen using a Co(II) species. The isotope effect (k(H)/k(D)) in the oxidation of ethylbenzene and ethylbenzene-d(10) with dioxygen using NHPI/Co(acac)(2) was 3.8. 相似文献
38.
Kawai K Yoshida H Sugimoto A Fujitsuka M Majima T 《Journal of the American Chemical Society》2005,127(38):13232-13237
The formation of the pyrene (Py) dimer radical cation (Py(2)(*+)) was used to measure the kinetics of the intrastrand end-to-end contact rates of single-stranded DNAs (ssDNAs) in the 10 nanoseconds to the tens of microseconds time range. ssDNAs labeled with Py at both ends with the lengths of 3, 6, and 9 mer were synthesized, and the two-photon ionization method was employed to generate a Py(*+), which enables the measurements of the end-to-end contact rates from 10 ns. The formation rate of Py(2)(*+) depended on the length and the sequence of the ssDNAs, and about 1 order of magnitude faster rates were observed for the T-rich ssDNAs compared to those for the corresponding length of A-rich ssDNAs, showing that ssDNA made from adenines is much more rigid than that composed of thymidines. As for the T-rich ssDNAs, the formation of Py(2)(*+) attributed to the misfolded structures was also observed, which is consistent with the configurational diffusion model suggested by Ansari and co-workers. 相似文献
39.
Poly(ethylene oxide-)-poly(1, 1-dimethyl-2, 2-dihexyldisilene) block copolymers (PEO-b-PMHS) were synthesized by the anionic polymerization of masked disilenes initiated with the potassium alkoxide of poly(ethylene glycol). The block copolymer self-assembled into polymer micelles in water accompanied by a transition in the polysilane conformation. 相似文献
40.
The steric hindrance between the oxygen and halogen atoms results in the structural deformation of α-haloanthraquinones and their lowest excited triplet (T1) states are of mixed nπ *-ππ * or ππ * character with unusually short lifetimes. Moreover, the rates of hydrogen-atom abstraction from ethanol by the T1 states decrease with their increasing ππ * character, and the proximity of the halogen atom to the hydroxy group causes the photochemical intramolecular elimination of hydrogen halide from the initial photoproducts (α-haloanthrahydroquinones) yielding α-haloanthraquinones (or anthraquinone) with one less halogen atom than the original molecule; the final product is anthrahydroquinone. The remarkably large structural deformation of 1,8-dihaloanthrasemiquinone radicals which gives rise to the simultaneous formation of 1,8-dihaloanthrahydroquinones and the original anthraquinones. Of particular interest is observation of the absorption band(s) attributable to the second excited triplet (T2) states of 1,8-dihaloanthraquinones. However, the electron transfer from triethylamine (TEA) to these T2 states generating the radical anions is observed only in acetonitrile, while that to the T1 states generating their exciplexes with TEA is observed not only in acetonitrile but also in toluene and ethanol. 相似文献