Photosensitized Protein Damage by DiethyleneglycoxyP(V)tetrakis(p-n-butoxyphenyl)porphyrin Through Electron Transfer: Activity Control Through Self-aggregation and Dissociation.

DiethyleneglycoxyP(V)tetrakis(p-n-butoxyphenyl)porphyrin (EGP(V)TBPP) forms a self-aggregation in an aqueous solution, and the photoexcited state of this molecule was effectively deactivated. Association with human serum albumin (HSA), a water-soluble protein, causes dissociation of the self-aggregation, resulting in recovery of the photosensitizer activity of EGP(V)TBPP. Under visible light irradiation, EGP(V)TBPP photosensitized HSA oxidation. The photosensitized singlet oxygen-generating activity of EGP(V)TBPP was confirmed by near-infrared emission measurement. A singlet oxygen quencher, sodium azide, partially inhibited the HSA photodamage; however, the quenching effect was estimated to be 57%. Another 43% of the HSA photodamage could be explained by the electron transfer mechanism. The redox potential of EGP(V)TBPP and the calculated Gibbs energy of electron transfer from tryptophan to photoexcited EGP(V)TBPP demonstrated the possibility of HSA oxidation through electron extraction. Fluorescence lifetime measurements of EGP(V)TBPP verified the electron transfer from HSA. The photosensitizer activity of EGP(V)TBPP can be controlled through an association with biomolecules, such as protein, and the electron transfer-mediated biomolecule photooxidation plays an important role in photodynamic therapy under hypoxia.

Mineralization induced by phosphorylated dry baker's yeast.

We found the mineralization of Cu during long-term Cu2+ adsorption onto dry baker's yeast cells phosphorylated using sodium cyclo-triphosphate. Field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy confirmed that the elemental composition of minerals were copper, phosphorus, and oxygen. Synchrotron-based X-ray absorption fine structure showed that the local structure around Cu atoms deposited on the mineral was almost identical to that of commercial copper (II) phosphate Cu3(PO4)2∙3H2O. However, the crystallinity was low, and the structure was slightly distorted. Time profile analysis using FESEM revealed that copper phosphate mineralization was first apparent on Day 3 of adsorption, whereas mineral formation plateaued at around Day 7. It seems that mineralization occurs by the local saturation of phosphate and Cu2+ on the yeast cells. Mineralization of the rare earth ion Dy3+ was also demonstrated during long-term adsorption. Mineralization on phosphorylated yeast cells appears to follow a common path for various types of metal ions and provides a promising technique for metal recovery via irreversible adsorption.

[Factors Related to Presenteeism in Young and Middle-aged Nurses].

OBJECTIVE: Presenteeism is considered to be not only a work-related stressor but also a factor involved in the development of workaholism and error proneness, which is often described as careless. Additionally, increasing health issues arising from aging suggest the possibility that presenteeism in middle-aged nurses is different than that in young ones. Therefore, the present study aimed to identify and tease apart factors involved in presenteeism among young and middle-aged nurses. METHODS: An anonymous self-administered questionnaire survey was conducted among 2,006 nurses working at 10 hospitals. In total, 761 nurses aged <40 years and 536 nurses aged ≥40 years were enrolled in this study. Work Impairment Scores (WIS) on the Japanese version of the Stanford Presenteeism Scale were measured for presenteeism. Job stressors, workaholism, and error proneness were measured for related factors. Multiple regression analysis was conducted after determining the WIS as the dependent variable and related factors as independent variables. RESULTS: Overall, 70.8% of the young nurses reported health problems compared to 82.5% of the middle-aged nurses. However, WIS in young nurses was significantly higher than that in middle-aged ones (p < 0.001). WIS in young nurses showed a significant relationship with the degree of stressors, "difficulty of work" (ß = 0.28, p < 0.001) and tendency to "work excessively" (ß = 0.18, p < 0.001), which is a subscale of workaholism, error proneness of "action slips" (ß = 0.14, p < 0.01) and "cognitive narrowing" (ß = 0.11, p < 0.05). Conversely, WIS in middle-aged nurses showed a significant relationship with "cognitive narrowing" (ß = 0.29, p < 0.001) and to "work excessively" (ß = 0.17, p < 0.001), the degree of stressors on "difficulty of work" (ß = 0.12, p < 0.05) and "lack of communication" (ß = 0.13, p < 0.01). CONCLUSION: It was clarified that the increased health problems of middle-aged nurses does not necessarily lower their working capacity. Also, compared to young nurses, the degree of failing tendency, rather than the degree of job stressors, was more related to presenteeism for middle-aged nurses. It can be considered that middle-aged nurses simply realize that their working ability is hindered because of incidents resulting from attention narrowing. As fatigue and state of tension tend to cause narrowing of attention, it may be necessary to reduce such risks and adjust work environments so mistakes can be avoided.

Mutation screening of GRIN2B in schizophrenia and autism spectrum disorder in a Japanese population.

N-methyl-d-aspartate receptors (NMDARs) play a critical role in excitatory synaptic transmission and plasticity in the central nervous systems. Recent genetics studies in schizophrenia (SCZ) show that SCZ is susceptible to NMDARs and the NMDAR signaling complex. In autism spectrum disorder (ASD), several studies report dysregulation of NMDARs as a risk factor for ASD. To further examine the association between NMDARs and SCZ/ASD development, we conducted a mutation screening study of GRIN2B which encodes NR2B subunit of NMDARs, to identify rare mutations that potentially cause diseases, in SCZ and ASD patients (n = 574 and 152, respectively). This was followed by an association study in a large sample set of SCZ, ASD, and normal healthy controls (n = 4145, 381, and 4432, respectively). We identified five rare missense mutations through the mutation screening of GRIN2B. Although no statistically significant association between any single mutation and SCZ or ASD was found, one of its variant, K1292R, is found only in the patient group. To further examine the association between mutations in GRIN2B and SCZ/ASD development, a larger sample size and functional experiments are needed.

Identification of Rare, Single-Nucleotide Mutations in NDE1 and Their Contributions to Schizophrenia Susceptibility.

BACKGROUND: Nuclear distribution E homolog 1 (NDE1), located within chromosome 16p13.11, plays an essential role in microtubule organization, mitosis, and neuronal migration and has been suggested by several studies of rare copy number variants to be a promising schizophrenia (SCZ) candidate gene. Recently, increasing attention has been paid to rare single-nucleotide variants (SNVs) discovered by deep sequencing of candidate genes, because such SNVs may have large effect sizes and their functional analysis may clarify etiopathology. METHODS AND RESULTS: We conducted mutation screening of NDE1 coding exons using 433 SCZ and 145 pervasive developmental disorders samples in order to identify rare single nucleotide variants with a minor allele frequency ≤5%. We then performed genetic association analysis using a large number of unrelated individuals (3554 SCZ, 1041 bipolar disorder [BD], and 4746 controls). Among the discovered novel rare variants, we detected significant associations between SCZ and S214F (P = .039), and between BD and R234C (P = .032). Furthermore, functional assays showed that S214F affected axonal outgrowth and the interaction between NDE1 and YWHAE (14-3-3 epsilon; a neurodevelopmental regulator). CONCLUSIONS: This study strengthens the evidence for association between rare variants within NDE1 and SCZ, and may shed light into the molecular mechanisms underlying this severe psychiatric disorder.

Phase-dependent modulation of corticospinal excitability during the observation of the initial phase of gait.

This study was undertaken to identify the temporal characteristics of corticospinal excitability of tibialis anterior muscle during the observation of the initial phase of gait. For this purpose, using transcranial magnetic stimulation, we recorded motor evoked potentials (MEPs) during the observation of the second step of an actor's first three steps of gait initiation with (complex gait) or without (normal gait) an obstacle and unstable surface. The results demonstrate that (1) MEPs during the observation of the initial phase of normal gait were significantly increased only at early swing phase, but not other phases (mid-swing, heel contact, mid-stance, and heel off) and (2) MEPs during the observation of the initial phase of complex gait were significantly increased at early swing and also at mid-swing and heel contact phases. These findings provide the first evidence that corticospinal excitability during the observation of gait, especially the initial phase, is modulated in phase- and motor-demanded-dependent manners.

Sanguinarine as a potent and specific inhibitor of protein phosphatase 2C in vitro and induces apoptosis via phosphorylation of p38 in HL60 cells.

Sanguinarine, a plant alkaloid, was identified as a potent and specific protein phosphatase (PP) 2C inhibitor. It inhibited PP2C competitively with respect to alpha-casein (Ki=0.68 microM) and showed selectivity for PP2C as compared with PP1, PP2A, and PP2B in vitro. In vivo, sanguinarine showed cytotoxicity toward human promyelocytic leukemia cell line HL60, with an IC(50) value of 0.37 microM, and induced apoptosis through a caspase-3/7-dependent mechanism involving the phosphorylation of p38, a PP2Calpha substrate. The apoptosis activity induced by sanguinarine was partially inhibited by a p38 inhibitor, SB203580, and was involved in the phospho-p38 protein in HL60 cells.

Chemopreventive action of xanthone derivatives on photosensitized DNA damage.

Photosensitized DNA damage participates in solar-UV carcinogenesis, photogenotoxicity and phototoxicity. A chemoprevention of photosensitized DNA damage is one of the most important methods for the above phototoxic effects. In this study, the chemopreventive action of xanthone (XAN) derivatives (bellidifolin [BEL], gentiacaulein [GEN], norswertianin [NOR] and swerchirin [SWE]) on DNA damage photosensitized by riboflavin was demonstrated using [32P]-5'-end-labeled DNA fragments obtained from genes relevant to human cancer. GEN and NOR effectively inhibited the formation of piperidine-labile products at consecutive G residues by photoexcited riboflavin, whereas BEL and SWE did not show significant inhibition of DNA damage. The four XAN derivatives decrease the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), an oxidative product of G, by photoexcited riboflavin. The preventive action for the 8-oxodGuo formation of these XAN derivatives increased in the following order: GEN>NOR>>BEL>SWE. A fluorescence spectroscopic study and ab initio molecular orbital calculations suggested that the prevention of DNA photodamage is because of the quenching of the triplet excited state of riboflavin by XAN derivatives through electron transfer. This chemoprevention is based on neither antioxidation nor a physical sunscreen effect; rather, it is based on the quenching of a photosensitizer. In conclusion, XAN derivatives, especially GEN, may act as novel chemopreventive agents by the quenching mechanism of an excited photosensitizer.

Photo-irradiated titanium dioxide catalyzes site specific DNA damage via generation of hydrogen peroxide.

Titanium dioxide (TiO2) is a potential photosensitizer for photodynamic therapy. In this study, the mechanism of DNA damage catalyzed by photo-irradiated TiO2 was examined using [32P]-5'-end-labeled DNA fragments obtained from human genes. Photo-irradiated TiO2 (anatase and rutile) caused DNA cleavage frequently at the guanine residue in the presence of Cu(II) after E. coli formamidopyrimidine-DNA glycosylase treatment, and the thymine residue was also cleaved after piperidine treatment. Catalase, SOD and bathocuproine, a chelator of Cu(I), inhibited the DNA damage, suggesting the involvement of hydrogen peroxide, superoxide and Cu(I). The photocatalytic generation of Cu(I) from Cu(II) was decreased by the addition of SOD. These findings suggest that the inhibitory effect of SOD on DNA damage is due to the inhibition of the reduction of Cu(II) by superoxide. We also measured the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an indicator of oxidative DNA damage, and showed that anatase is more active than rutile. On the other hand, high concentration of anatase caused DNA damage in the absence of Cu(II). Typical free hydroxyl radical scavengers, such as ethanol, mannnitol, sodium formate and DMSO, inhibited the copper-independent DNA photodamage by anatase. In conclusion, photo-irradiated TiO2 particles catalyze the copper-mediated site-specific DNA damage via the formation of hydrogen peroxide rather than that of a free hydroxyl radical. This DNA-damaging mechanism may participate in the phototoxicity of TiO2.

Base oxidation at 5' site of GG sequence in double-stranded DNA induced by UVA in the presence of xanthone analogues: relationship between the DNA-damaging abilities of photosensitizers and their HOMO energies.

UVA contributes to skin cancer by solar UV light. Photosensitizers are believed to play an important role in UVA carcinogenesis. We investigated the mechanism of DNA damage induced by photoexcited xanthone (XAN) analogues (XAN, thioxanthone [TXAN] and acridone [ACR]), exogenous photosensitizers, and the relationship between the DNA-damaging abilities and their highest occupied molecular orbital (HOMO) energies. DNA damage by these photosensitizers was examined using 32P-labeled DNA fragments obtained from the p53 tumor suppressor gene. Photoexcited XAN caused DNA cleavage specifically at 5'-G of the GG sequence in the double-stranded DNA only when the DNA fragments were treated with piperidine, suggesting that DNA cleavage is due to base modification with little or no strand breakage. With denatured single-stranded DNA, the extent of XAN-sensitized photodamage was decreased. An oxidative product of G, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGuo), was formed by photoexcited XAN, and the 8-oxo-dGuo formation was decreased in single-stranded DNA. TXAN and ACR induced DNA photodamage as did XAN, although the order of DNA-damaging ability was XAN > TXAN > ACR. These findings suggest that photoexcited XAN analogues induce nucleobase oxidation at 5'-G of GG sequence in double-stranded DNA through electron transfer. The HOMO energies of these photosensitizers, estimated from ab initio molecular orbital (MO) calculation, decreased in the following order: XAN > TXAN > ACR. Extents of DNA damage increased exponentially with the HOMO energies of XAN analogues. This study suggests that DNA-damaging abilities of photosensitizers can be estimated from their HOMO energies.