Superconductivity below 20 K in heavily electron-doped surface layer of FeSe bulk crystal

A superconducting transition temperature (T_c) as high as 100 K was recently discovered in one monolayer FeSe grown on SrTiO₃. The discovery ignited efforts to identify the mechanism for the markedly enhanced T_c from its bulk value of 8 K. There are two main views about the origin of the T_c enhancement: interfacial effects and/or excess electrons with strong electron correlation. Here, we report the observation of superconductivity below 20 K in surface electron-doped bulk FeSe. The doped surface layer possesses all the key spectroscopic aspects of the monolayer FeSe on SrTiO₃. Without interfacial effects, the surface layer state has a moderate T_c of 20 K with a smaller gap opening of 4.2 meV. Our results show that excess electrons with strong correlation cannot induce the maximum T_c, which in turn reveals the need for interfacial effects to achieve the highest T_c in one monolayer FeSe on SrTiO₃.

Thin FeSe film on SrTiO₃ substrate becomes a superconductor with a transition temperature over 100 K, yet the origin remains controversial. Here, Seo et al. show superconductivity below 20 K on the electron-doped surface of an FeSe crystal, suggesting a decisive role of interfacial effects in the enhancement of superconductivity.

Gonadotropin-releasing hormone administration to dairy cows without a corpus luteum 4 weeks after calving increases reproductive performance

This field study investigated whether the administration of a single dose of gonadotropin-releasing hormone (GnRH) to dairy cows without a corpus luteum (CL) 4 weeks after calving can improve reproductive performance. Holstein dairy cows underwent ultrasonography to assess the presence of ovarian structures at 29.2 ± 5.2 days post-partum, and cows were divided into two main groups based on the presence (CL group, n = 230) or absence (non-CL group, n = 460) of a CL. The non-CL group was further randomly divided into two subgroups based on the administration of GnRH (non-CL GnRH group, n = 230) or no GnRH (non-CL control group, n = 230). Subsets of cows from non-CL control (n = 166) and non-CL GnRH (n = 175) groups received a second ultrasonography at 44.5 ± 5.4 days post-partum to assess CL formation. The percentage of cows with CL at the second ultrasonography was greater in the non-CL GnRH group (70.9%) than in the non-CL control group (53.0%, p = 0.0006). The hazard of the first post-partum insemination by 150 days in milk (DIM) was higher in the CL group than in the non-CL control group (hazard ratio [HR]: 1.36, p = 0.001). The probability of a pregnancy to the first insemination was higher in non-CL GnRH (odds ratio [OR]: 1.50, p = 0.04) and CL groups (OR: 1.55, p = 0.03) compared to the non-CL control group. Furthermore, the hazard of pregnancy by 210 DIM was higher in non-CL GnRH (HR: 1.30, p = 0.01) and CL (HR: 1.51, p = 0.0001) groups than in the non-CL control group. In conclusion, administration of GnRH to dairy cows without a CL 4 weeks after calving was associated with an increase in ovulation and improved reproductive performance.

Microsatellite Instability in Endometrioid Type Endometrial Adenocarcinoma is Associated With Poor Prognostic Indicators

Microsatellite instability (MSI) has been reported in 25% to 45% of sporadic endometrial carcinoma. The clinicopathologic and molecular characteristics of MSI-high phenotype in colorectal and gastric carcinomas have been widely investigated; however, the clinicopathologic impact of MSI on endometrial carcinomas remained unclear. This study was performed to determine the clinicopathologic and molecular significance of MSI in endometrial carcinomas. We analyzed the MSI status using National Cancer Institute-recommended 5 microsatellite markers, and the immunohistochemical profiles of various regulatory proteins of cell cycle and apoptosis using tissue microarray in 100 endometrial carcinomas. The results were compared between MSI-high and MSI(-) groups as for the traditional clinicopathologic prognostic parameters and the immunoreactivities of various regulatory proteins. We especially focused on the endometrioid type adenocarcinoma to exclude the bias from nonendometrioid type adenocarcinomas with more aggressiveness and a close association with MSI(-) phenotype. The incidence of MSI-high phenotype was significantly higher in endometrioid type than in nonendometrioid serous type (20% vs. 0%, P<0.001). It showed orderly increase in the frequencies of MSI-high phenotype in higher histologic grade (13% vs. 21% vs. 50% in histologic grade I, II, and III, P=0.039). The MSI-high phenotype was related with the presence of lymphovascular invasion (P=0.008), deep myometrial invasion (P=0.040), and the higher clinical stages (P=0.018) independent of tumor grade. We also found a correlation between MSI-high phenotype and higher cyclin A and skp2 immunoreactivity (P=0.03 and 0.05, respectively), known to be the poor prognostic molecular indicators. According to these results, the MSI may represent the poor prognostic impact on the endometrioid type endometrial adenocarcinoma.

Genital human papillomavirus genotyping by HPV oligonucleotide microarray in Korean commercial sex workers

Because of the diversity in human papillomavirus (HPV) distribution, according to the population and region, detailed investigations of HPV genotypes are important in designing more effective HPV vaccines for any given country. HPV DNA oligonucleotide microarray was used to investigate the distribution of HPV genotypes among commercial sex workers. The prevalence of HPV in Korean commercial sex workers was 47%, with HPV-16 and HPV-51 as the dominant genotypes. HPV subtypes in 148 commercial sex workers comprised 70 with one genotype, 42 with two genotypes, 17 with three genotypes, and 19 with four or more genotypes. HPV-40, the most dominant low-risk genotype, was not detected in single-infection commercial sex workers. All women with multiple infections of low-risk genotypes had the HPV-40 genotype. This molecular epidemiological study of genital HPV will be useful for the development of a favorable strategy to prevent the spread of this potentially serious infection.

Multiple HPV infection in cervical cancer screened by HPVDNAChip

This study determined the distribution of high-risk HPV type infection in cervical cancer using newly developed oligonucleotide chips (HPVDNAChips). The study subjects included 80 cases of cervical neoplasia and 746 controls with a normal Pap smear. For HPV genotyping, the commercially available HPVDNAChips was used. The risk of cervical cancer was increased in women with a family history of cervical cancer (adjusted OR=2.3, 95% CI: 0.92-6.17) and in smokers (adjusted OR=3.2, 95% CI: 1.45-7.06). There was also a trend of increased risk with the number of full term pregnancies (P(for trend)<0.001). There were only 7.2% (54 of 746) infected high-risk HPV types in the control, whereas 54.5% (six of 11) and 76.5% (52 of 68) were infected in the CIN and cervical cancer, respectively. Multiple HPV infection was observed in 0.5% (three of 592) of the control group but in 9.1% (seven of 77) of cases. Multivariate analysis revealed that subjects infected with multiple HPV types had a 31.8-fold (95% CI: 7.50-134.75) higher risk of cervical cancer, while the single HPV type had a 19.9-fold increased risk (95% CI: 10.90-36.18) (P(for trend)<0.001). These results show that the detection and typing of HPV infection by HPVDNAChip can be a useful in clinical applications because it provides information on multiple infections and the types of HPV in addition to HPV infection status.

Detection and typing of HPV genotypes in various cervical lesions by HPV oligonucleotide microarray

OBJECTIVES

This study was conducted to evaluate a clinical efficacy of human papillomavirus (HPV) oligonucleotide microarray (Biomedlab Co., Seoul, South Korea) for the detection of HPVs in various cervical lesions.

RESULTS

HPV DNAs from 234 patients were analysed by two methods. Among those, 212 patients were classified into 5 groups according to the histologic diagnosis: chronic cervicitis, cervical intraepithelial neoplasia (CIN) I, CIN II, CIN III, and invasive cervical carcinoma. PCR-RFLP could detect 7 types of high-risk HPVs (HPV 16/18/31/33/35/52/58) and HPV microarray could detect 15 types of high-risk HPVs (HPV 16/18/31/33/35/39/45/51/52/56/58/59/66/68/69) and 7 types of low-risk HPVs (HPV 6/11/34/40/42/43/44).HPV genotyping by HPV oligonucleotide microarray revealed that HPV16 was the most frequent type (30.2%) in all specimens tested and was significantly more frequent in CIN III and invasive carcinomas than other lesions.

METHODS

HPV DNAs were detected in 158 and 174 of the 234 cervical samples by PCR-RFLP and HPV microarray, respectively. The correlation between the two methods was good in detecting HPVs in general (kappa index = 0.69) and HPVs 31 and 52 (kappa index = 0.70 and 0.70, respectively) and excellent in detecting HPVs 16, 18, 33, 35, and 58 (kappa index = 0.90, 0.88, 0.92, 0.77, and 0.84, respectively). Double HPV infection was detected in 10 cases and one triple infection was detected. By combining cytology and HPV testing, the sensitivity was improved to 87.5, 95.5, 96.1, and 97.2% in CIN I, CIN II, CIN III, and carcinoma, respectively.

CONCLUSIONS

This results suggest that HPV oligonucleotide microarray is a highly comparable method to the previously used PCR-RFLP method for the detection of HPVs in cervical specimens. Genetic informations for HPV infection in cervical specimens may offer new strategies in manipulating the patients harboring cervical intraepithelial neoplasia and cervical carcinoma.

HPV oligonucleotide microarray-based detection of HPV genotypes in cervical neoplastic lesions

BACKGROUND

In this study we examined the use of a new-human papillomavirus (HPV) detection method, the HPV oligonucleotide microarray system (Biomedlab Co., Korea), which we compared with the well-established HPV DNA detection system (Hybrid Capture II; HC-II, Digene Co.). This new method prompted us to develop a new HPV genotyping technique, using the oligonucleotide microarray, to detect the generic and type-specific sequence of HPV types. In particular, we undertook the evaluation of the clinical efficacy of the HPV oligonucleotide microarray for detecting HPV in cervical neoplastic lesions.

METHODS

One hundred forty patients were involved and classified into three groups according to their histopathologic diagnoses: Group I (nonspecific chronic cervicitis; n = 61), Group II (low-grade squamous intraepithelial lesion (SIL); koilocytosis, and mild dysplasia; n = 39), and Group III (high-grade SIL; moderate, severe dysplasia and in situ carcinoma; n = 40). Cytological diagnoses were based on the Bethesda System and cervical samples were analyzed by the two methods. The HPV oligonucleotide microarray detected 15 types of high-risk HPV (HPV-16/-18/-31/-33/-35/-39/-45/-51/-52/-56/-58/-59/-66/-68/-69) and 7 types of low-risk HPV (HPV-6/-11/-34/-40/-42/-43/-44).

RESULTS

In 105 of the 140 cervical samples (75%), HPV DNAs were examined using the HC-II method. HPV detection rates using the HPV microarray agreed with those of HC-II. One HC-II-positive, but HPV microarray-negative, case occurred in the low-grade SIL (Group II) and was later confirmed negative for HPV. The other HPV microarray-positive but HC-II-negative case was found to be HPV-18 by PCR. Low-risk types of HPV were detected in 3 of 39 low-grade SIL cases (Group II) using the HPV microarray. HPV-16 was the most frequent type (32.1%) in all specimens tested, and was significantly more frequent in low-grade or high-grade intraepithelial lesions (Groups II or III) than in normal controls (Group I) (P < 0.05). HPV-58 was the second most common type (17.5%) in Group III. The HPV microarray was found to have advantages in terms of identifying the HPV genotypes and cases of multiple HPV infection. Double HPV infections were detected in 12 cases and triple HPV infections in 7 cases. Two cases were positive for four types of HPV (HPV-16/18/33/35, HPV-16/18/58/68). The sensitivity of HPV testing (HC-II; 94.9%, HPV microarray; 93.7%) for identifying patients with squamous intraepithelial lesion was significantly better than the sensitivity of cytology (77.1%, P < 0.05). On using multiple logistic regression analysis to estimate the relative risk of SIL versus HPV type, HPV-16-positive cases were found to have a 7.5-fold risk of SIL (95% CI = 3.28-16.51; P < 0.01). HPV-33 and HPV-58 were found to be significantly related to high-grade SILs (P < 0.01).

CONCLUSIONS

Our results suggest that the HPV oligonucleotide microarray is highly comparable to HC-II for detecting HPV in cervical specimens. The HPV oligonucleotide microarray provides useful information on viral genotype and multiple HPV infections in HPV-related cervical lesions. Genetic information on HPV in cervical specimens might be a particular benefit of the new procedure in the management of cervical neoplastic lesions

Correlation of cervical carcinoma and precancerous lesions with human papillomavirus (HPV) genotypes detected with the HPV DNA chip microarray method

BACKGROUND

Human papillomavirus (HPV) infection is considered to play an important role in the development of cervical carcinoma, and it is known that certain HPV types, such as HPV-16 and HPV-18, are highly associated with cervical carcinoma. However, the pathologic behavior of other HPV types remains unclear. Recently, a new HPV detection technique, the HPV DNA chip, was introduced. The HPV DNA chip harbors 22 HPV probes and has the advantage of being able to detect 22 HPV types simultaneously. To evaluate the quality of the HPV DNA chip method and to identify HPV types related to cervical carcinoma and precancerous lesions, the authors performed HPV typing in cervical specimens from 1983 patients and compared their cytologic and histologic diagnoses.

METHODS

The HPV DNA chip was used for HPV typing. Among 1983 patients who were tested for HPV types, cervical smear cytology was performed in 1650 patients, and 677 of those patients underwent cervical biopsy.

RESULTS

Among the 1650 smears that were examined cytologically, 92.7% (114 of 123 smears) of low-grade squamous intraepithelial lesions (LSILs), 98.1% (106 of 108 smears) of high-grade squamous intraepithelial lesions (HSILs), and 96.3% (51 of 53 smears) of carcinomas were HPV positive, compared with only 35.1% of smears with normal cytology that were HPV positive. HPV-16 was the most prevalent type (chi-square test; P < 0.01) in LSILs (28.5%), in HSILs (51.9%), and in carcinomas (62.5%) followed by HPV-58 and a group of low-risk types (HPV-6, HPV-11, HPV-34, HPV-40, HPV-42, HPV-43,and HPV-44) in LSILs. HPV-58 (15.7%), HPV-18 (6.7%), and HPV-52 (4.6%) were the next most prevalent types after HPV-16 in HSILs. HPV-18 (11.4%) and HPV-58 (11.4%) were the second most common types in carcinomas. HPV-58 had the highest positive predictive value (54.9%) for the detection of histologically confirmed HSIL or carcinoma, whereas HPV 16 had the highest negative predictive value (80.6%). The sensitivity (96.0%) of the HPV test using the DNA chip method for detecting HSIL or carcinoma was superior compared with the sensitivity of cytologic diagnosis (83.6%).

CONCLUSIONS

The HPV DNA chip provides a very sensitive method for detecting 22 HPV genotypes with reasonable sensitivity (96.0%) and reasonable negative predictive value (96.9%), and it overcomes the low sensitivity of cytologic screening for the detection of HSIL or carcinoma. HPV-58, HPV-52, and HPV-56, as well as HPV-16 and HPV-18, were associated highly with HSIL and carcinoma in the current large series. In addition, multiple HPV infection was associated less frequently with cervical carcinoma and with precancerous lesions compared with normal cytology.

Genotyping of 22 human papillomavirus types by DNA chip in Korean women: comparison with cytologic diagnosis

OBJECTIVE

More sensitive and reliable methods than individual testing (such as polymerase chain reaction, restriction fragment length polymorphism, and Southern blot) should be developed as screening tools for the detection of latent human papillomavirus. Today, the new Bethesda system recommends human papillomavirus testing as an adjuvant to the conventional Papanicolaou smear for more comprehensive identification of women at certain risk of cervical neoplasia. We performed human papillomavirus genotyping with the newly designed human papillomavirus DNA chip, which is based on polymerase chain reaction for high-throughput screening power, and compared the results with the results of a Papanicolaou smear according to the new Bethesda system.

STUDY DESIGN

Polymerase chain reaction amplifications of the human papillomavirus L1 region from biologic samples were hybridized to silanized glass slides by a microarrayer, which comprised 22 specific oligonucleotide probes to their genotypes, consisting of 15 high-risk and 7 low-risk types. Two cervical cancer cell lines and 20 plasmids that contained each type of the human papillomavirus whole genome were used for the evaluation of this method; in all cases, the cancer cell lines and plasmids showed clear positive signals on their corresponding positions. A comparative study that used 685 cervicovaginal swabs was performed by human papillomavirus DNA chip microarray together with Papanicolaou diagnosis.

RESULTS

Human papillomavirus was identified as positive in 31.9% of the 414 control samples and in 78.6% of the 271 neoplastic lesions. The major prevailing human papillomavirus genotypes were human papillomavirus types 16, 58, and 18, in descending order of incidence (average overall, 78.8%). Almost all of the remaining cases were comprised of human papillomavirus types 39, 52, 56, and 51. The frequency of multiple infection of human papillomavirus was highest in low-grade squamous intraepithelial lesion but was lowest in squamous cell carcinoma. All cases that exhibited infection of single human papillomavirus type 58 were squamous cell carcinoma.

CONCLUSION

Human papillomavirus types 16, 18, and 58 were confirmed to be major causative factors for cervical carcinogenesis. Low-grade squamous intraepithelial lesion is a heterogeneous entity that is composed of different human papillomavirus subtypes and prevails in younger women (<40 years old). The human papillomavirus chip has potential use as a high-throughput screening test.

Serum deprivation increases the expression of low density lipoprotein receptor-related protein in primary cultured rat astrocytes

The low density lipoprotein receptor (LDLR)-related protein (LRP) is a multifunctional receptor which mediates the endocytic uptake of several ligands implicated in Alzheimer's disease pathophysiology. Although LRP, as a member of the LDLR family, is likely to be regulated in response to various cellular stresses, this regulation has not been fully understood yet. In the present study we studied the regulation of LRP expression in primary cultured rat astrocytes in response to serum deprivation as a general cellular stress. A significant increase in LRP expression was detected after serum deprivation and this increase was blocked by treatment of U0126, an inhibitor of MAP kinase. This serum deprivation action was partially reversed by either serum or D-glucose supplementation, but further augmented by glutamine. This result contrasted with a finding that glutamine suppressed gadd153 protein induced by serum deprivation. Taken together, the present data suggest that serum deprivation induces dramatically LRP expression in astrocytes partly by MAPK signaling pathways and by signaling pathways apparently distinct from gadd153 induction.

Depletion of mitochondrial DNA alters glucose metabolism in SK-Hep1 cells

Maternally inherited mitochondrial DNA (mtDNA) has been suggested to be a genetic factor for diabetes. Reports have shown a decrease of mtDNA content in tissues of diabetic patients. We investigated the effects of mtDNA depletion on glucose metabolism by use of rho(0) SK-Hep1 human hepatoma cells, whose mtDNA was depleted by long-term exposure to ethidium bromide. The rho(0) cells failed to hyperpolarize mitochondrial membrane potential in response to glucose stimulation. Intracellular ATP content, glucose-stimulated ATP production, glucose uptake, steady-state mRNA and protein levels of glucose transporters, and cellular activities of glucose-metabolizing enzymes were decreased in rho(0) cells compared with parental rho(+) cells. Our results suggest that the quantitative reduction of mtDNA may suppress the expression of nuclear DNA-encoded glucose transporters and enzymes of glucose metabolism. Thus this may lead to diabetic status, such as decreased ATP production and glucose utilization.

Evidence that the 5'-end cap structure is essential for encapsidation of hepatitis B virus pregenomic RNA

Hepatitis B virus (HBV) replicates by reverse transcription of an RNA intermediate, the pregenomic RNA. The first step of HBV genome replication is the encapsidation of the pregenomic RNA encoding the encapsidation signal, termed epsilon, into the core particles, which is preceded by recognition and binding of HBV DNA polymerase to epsilon. The pregenomic RNA contains two identical epsilon elements due to its terminal redundancy: one near the 5' end and another near the 3' end. Despite the fact that both epsilon elements have an identical sequence, only the 5' epsilon, but not the 3' epsilon, is functional for encapsidation. To understand the molecular nature of this position effect, we made a series of lacZ RNA expression plasmids which contain the epsilon element at various positions from the 5' end of the transcripts. Following transfection, the lacZ RNAs in cytoplasmic core particles were measured by RNase protection assay for encapsidation. The results indicated that the lacZ RNAs with epsilon positioned up to 65 nucleotides from the 5' end were encapsidated, whereas the lacZ RNAs with epsilon positioned further downstream were not. Interestingly, the cap-free lacZ RNA transcribed by T7 RNA polymerase was not encapsidated, implying that the 5' cap structure is required for encapsidation of the pregenomic RNA. We hypothesized that HBV DNA polymerase must somehow recognize the cap structure and/or its associated factors, as well as the 5' epsilon, for encapsidation to occur.

Stress- and growth-related gene expression are independent of chemical-induced prostaglandin E(2) synthesis in renal epithelial cells

Cellular stress can initiate prostaglandin (PG) biosynthesis which, through changes in gene expression, can modulate cellular functions, including cell growth. PGA(2), a metabolite of PGE(2), induces the expression of stress response genes, including gadd153 and hsp70, in HeLa cells and human diploid fibroblasts. PGs, gadd153, and hsp70 expression are also influenced by the cellular redox status. Polyphenolic glutathione conjugates retain the ability to redox cycle, with the concomitant generation of reactive oxygen species. One such conjugate, 2,3,5-tris(glutathion-S-yl)hydroquinone (TGHQ), is a potent nephrotoxic and nephrocarcinogenic metabolite of the nephrocarcinogen, hydroquinone. We therefore investigated the effects of TGHQ on PGE(2) synthesis and gene expression in a renal proximal tubular epithelial cell line (LLC-PK(1)). TGHQ (200 microM, 2 h) increases PGE(2) synthesis (2-3-fold) in LLC-PK(1) cells with only minor (5%) reductions in cell viability. This response is toxicant-specific, since another proximal tubular toxicant, S-(1, 2-dichlorovinyl)-L-cysteine (DCVC), stimulates PGE(2) synthesis only after massive (68%) reductions in cell viability. Consistent with the ability of TGHQ to generate an oxidative stress, both deferoxamine mesylate and catalase protect LLC-PK(1) cells from TGHQ-mediated cytotoxicity. Only catalase, however, completely blocks TGHQ-mediated PGE(2) synthesis, implying a major role for hydrogen peroxide in this response. TGHQ induces the early (60 min) expression of gadd153 and hsp70. However, while inhibition of cyclooxygenase with aspirin prevents TGHQ-induced PGE(2) synthesis, it does not affect TGHQ-mediated induction of gadd153 or hsp70 expression. In contrast, a stable PGE(2) analogue, 11-deoxy-16, 16-dimethyl-PGE(2) (DDM-PGE(2)), which protects LLC-PK(1) cells against TGHQ-mediated cytotoxicity, modestly elevates the levels of gadd153 and hsp70 expression. In addition, catalase and, to a lesser extent, deferoxamine mesylate block TGHQ-induced gene expression. Therefore, although TGHQ-induced generation of reactive oxygen species is required for PGE(2) synthesis and stress gene expression, acute TGHQ-mediated increases in gadd153 and hsp70 mRNA levels are independent of PGE(2) synthesis.

Nongenomic stimulation of nitric oxide release by estrogen is mediated by estrogen receptor alpha localized in caveolae

Acute administration of 17beta-estradiol (E(2)) exerts antiatherosclerotic effects in healthy postmenopausal women. The vasoprotective action of E(2) may be partly accounted for by a rapid increase in nitric oxide (NO) levels in endothelial cells (ECs). However, the signaling mechanisms producing this rise are unknown. In an attempt to address the short-term effect of E(2) on endothelial NO production, confluent bovine aortic endothelial cells (BAECs) were incubated in the absence or presence of E(2), and NO production was measured. Significant increases in NO levels were detected after only 5 min of E(2) exposure without a change in the protein levels of endothelial NO synthase (eNOS). This short-term effect of estrogen was significantly blunted by various ligands which decrease intracellular Ca(2+) concentration. Furthermore, plasma membrane-impermeable BSA-conjugated E(2) (E(2)BSA) stimulated endothelial NO release, indicating that in the current system the site of action of E(2) is on the plasma membrane rather than the classical nuclear receptor. The partial antagonist tamoxifen did not block E(2)-induced NO production; however, a pure estrogen receptor alpha (ERalpha) antagonist ICI 182,780 completely inhibited E(2)-stimulated NO release. The binding of E(2) to the membrane was confirmed using FITC-labeled E(2)BSA (E(2)BSA-FITC). Western blot analysis showed that plasmalemmal caveolae possess ERalpha in addition to well-known caveolae-associated proteins eNOS and caveolin. This study demonstrates that the nongenomic and short-term effect of E(2) on endothelial NO release is Ca(2+)-dependent and occurs via ERalpha localized in plasmalemmal caveolae.

Quinol-glutathione conjugate-induced mutation spectra in the supF gene replicated in human AD293 cells and bacterial MBL50 cells

Hydroquinone is a nephrocarcinogen in rats but generally tests negative in standard mutagenicity assays. However, 2,3,5-tris-(glutathion-S-yl)hydroquinone, a potent nephrotoxic metabolite of hydroquinone, and 2-bromo-bis-(glutathion-S-yl)hydroquinone, another cytotoxic quinol-glutathione (GSH) conjugate, cause extensive single strand breaks in DNA in a manner that is dependent on the formation of reactive oxygen species. We, therefore, investigated whether quinol-GSH conjugates have the potential to behave as genotoxicants. The shuttle vector pSP189, containing the supF gene, was treated with 2,3,5-tris-(glutathion-S-yl)hydroquinone and replicated in both human AD293 cells and Escherichia coli MBL50 cells. The mutation frequency increased 4.6- and 2.6-fold in human AD293 and bacterial MBL50 cells, respectively. Base substitutions were the major type of mutations, and they occurred predominantly at G:C sites in both cell types. A high frequency of deletions (30%), including < 10- and > 10-bp deletions, were observed in AD293-replicated plasmids. The most common types of mutations in AD293 cells were G:C to A:T transitions (33.8%) and G:C to T:A (29.4%) and G:C to C:G (19.1%) transversions. In MBL50 cells, the major mutations were G:C to T:A (33.8%) and G:C to C:G (31.3%) transversions and G:C to A:T transitions (27.5%). The mutation spectra were similar to those reported for *OH-induced mutations, suggesting that *OH generated from polyphenolic-GSH conjugates not only plays a role in cytotoxicity but also provides a basis for their mutagenicity and carcinogenicity.

Mutations induced in the supF gene of pSP189 by hydroxyl radical and singlet oxygen: relevance to peroxynitrite mutagenesis

We previously showed that the oxidant peroxynitrite (ONOO-) was strongly mutagenic in the supF shuttle vector pSP189 replicated in bacteria or human cells. Qualitative characteristics of the mutational spectra induced by ONOO- differed significantly from those reportedly caused by hydroxyl radical (OH.) in other experimental systems but showed similarities to spectra reportedly produced by singlet oxygen (1O2). The molecular mechanisms of ONOO--mediated DNA damage are unknown. The objective of the present set of experiments was to characterize mutational effects induced in the supF gene of pSP189 by OH* and 1O2 to permit direct comparison with mutational spectra induced by ONOO- in this system. Base substitutions were the major form of mutation induced in plasmids replicated in human (AD293) cells by ONOO- (84%) and 1O2 (71%), whereas OH* induced fewer of them (49%). In plasmids replicated in bacteria (Escherichia coli MBL50), frequencies of base substitutions induced by the three treatments were similar. G:C-to-T:A transversions were the most common form of base substitution induced by ONOO- (75% and 67%, respectively, in AD293- and MBL50-replicated plasmids) and 1O2 (68% and 71%); they were induced at lower frequencies by OH. (51% and 47%). G:C-to-C:G transversions or G:C-to-A:T transitions were induced at almost equal frequencies by both ONOO- and 1O2, whereas OH* induced these mutations at different frequencies in the AD293 system. Collectively, our results confirm that in several important respects mutational spectra induced by ONOO- have greater similarity to spectra induced by 1O2 than to those induced by OH* and suggest that genotoxic derivatives of ONOO- are likely to include species that have DNA-damaging properties resembling those of 1O2 in selectivity for guanine but not identical in sequence specificity.

DNA damage, gadd153 expression, and cytotoxicity in plateau-phase renal proximal tubular epithelial cells treated with a quinol thioether

2-Bromo-bis-(glutathion-S-yl)hydroquinone [2-Br-bis-(GSyl)HQ] causes DNA single-strand breaks (SSB), causes growth arrest, induces the expression of gadd153 (a gene inducible by growth arrest and DNA damage), and decreases histone H2B mRNA in log-phase renal proximal tubular epithelial cells (LLC-PK1). Renal epithelial cells in vivo normally exhibit a low mitotic index, therefore experiments in both plateau- and log-phase cells are necessary for a comprehensive understanding of the stress response to 2-Br-bis-(GSyl)HQ. In the present article we demonstrate that not all features of the stress response in log-phase cells are reproduced in plateau-phase cells. Thus, although 2-Br-bis-(GSyl)HQ causes concentration and time-dependent increases in DNA SSB, and increases the expression of gadd153, histone H2B mRNA levels are unaltered in plateau-phase cells. The relationship between reactive oxygen species, DNA damage, gene expression, and cytotoxicity was also investigated. Our findings suggest that (i) 2-Br-bis-(GSyl)HQ-mediated DNA damage in LLC-PK1 cells is mediated by the generation of H2O2; (ii) DNA damage, either directly or indirectly, contributes to cell death; and (iii) DNA damage, either directly or indirectly, provides the initial signal for gadd153 expression. In addition, DNA repair is rapid in LLC-PK1 cells, and the DNA-repair inhibitors 1-beta-D-arabinofuranosylcytosine and hydroxyurea have no effect on the amount of DNA SSB. Although the addition of 3-aminobenzamide following 2-Br-bis-(GSyl)HQ exposure has no effect on the removal of DNA SSB, it causes a slight but significant increase in gadd153 expression and cell viability, indicating that activation of poly(ADP-ribose)polymerase may exacerbate toxicity. Finally, aurintricarboxylic acid did not prevent DNA SSB or cytotoxicity in 2-Br-bis-(GSyl) HQ-treated LLC-PK1 cells, implying that activation of endonucleases does not play a role in these processes.

The response of renal tubular epithelial cells to physiologically and chemically induced growth arrest

Cells respond to a variety of stresses by activating the transcription of a battery of "acute phase" or "stress response" genes. The nature of this response is tailored to the nature of the stress. The extent to which physiologically and pathophysiologically induced growth arrest share common genomic responses is unclear. We therefore compared the effects of a physiologically induced (serum and nutrient depletion) and a chemically induced (2-Br-bis-(GSyl)HQ and 2-Br-6-(GSyl)HQ) stress in renal tubular epithelial cells (LLC-PK1). The response to physiological stress, induced by serum depletion, involves growth arrest characterized by an inhibition of DNA synthesis that occurs in the absence of a decrease in histone mRNA or an increase in gadd153 mRNA, one of the growth arrest and DNA damage inducible genes. In contrast, the chemical-induced stress involves growth arrest accompanied by a decrease in histone mRNA, particularly core histone H2B and H2A mRNA, and the induction of gadd153. Chemical-induced changes in histone mRNA inversely correlate to changes in the expression of a stress gene, hsp70, whose expression is dependent upon the maintenance of appropriate nucleosomal structure.

Quinone thioether-mediated DNA damage, growth arrest, and gadd153 expression in renal proximal tubular epithelial cells

Although the conjugation of quinones with glutathione is associated with the process of detoxication, the reaction frequently facilitates quinone-induced toxicity. Thiol conjugates of quinones retain the ability to redox cycle and generate reactive oxygen species (ROS), contributing to the biological (re)activity of a variety of polyphenolic compounds. 2-Bromo-bis(glutathion-S-yl) hydroquinone (2-Br-bis(GSyl)HQ) and 2-bromo-6-(glutathion-S-yl) hydroquinone [2-Br-6-(GSyl)HQ] are potent nephrotoxicants in rats, inducing rapid karyolysis in vivo and DNA single-strand breaks in cultured renal proximal tubular epithelial cells (LLC-PK1). We investigated the cellular and molecular responses initiated after exposure of LLC-PK1 cells to 2-Br-bis(GSyl)HQ and 2-Br-6-(GSyl)HQ. Both quinone thioethers cause the concentration-dependent formation of DNA single-strand breaks, rapidly (2-10 min) inhibit DNA synthesis, and increase the expression of gadd153, a gene responsive to growth arrest and DNA damage. The addition of catalase to LLC-PK1 cells exposed to 2-Br-6-(GSyl)HQ or 2-Br-bis(GSyl)HQ effectively prevents gadd153 induction, which is consistent with findings that the gadd153 gene is subject to redox modulation and that ROS play an important role in quinone thioether-mediated cytotoxicity. Deferoxamine pretreatment also diminishes gadd153 induction, suggesting that in renal proximal tubular epithelial cells, decreased expression of gadd153 is not dependent on the removal of hydrogen peroxide per se but rather on preventing the generation of hydroxyl radical. Chelation of intracellular calcium with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-acetoxy-methyl ester also reduces gadd153 induction by 2-Br-6-(GSyl)HQ and 2-Br-bis(GSyl)HQ, suggesting a role for calcium in the signaling process. Thus, 2-Br-6-(GSyl)HQ and 2-Br-bis(GSyl)HQ activate a genomic stress response via a signaling pathway that may include ROS, Ca2+, and DNA damage.

Local expression of a POU family transcription factor, Pit-1, in the rat placenta

A pituitary-specific trans-acting factor, Pit-1 regulates transcriptional activity of growth hormone (GH) and prolactin (PRL) genes. Pit-1 can bind and activate the promoters of human chorionic somatomammotropin (hCS-A) and placental GH variants (hGH-V) as well. However, expression of Pit-1 in the rat placenta has not yet been elucidated. The present study aims to determine whether the Pit-1 gene is locally expressed in the rat placenta using reverse transcription-polymerase chain reaction (RT-PCR), Northern blot and Western blot hybridization, in situ hybridization and immunohistochemistry. PCR products were further analyzed by Southern hybridization and DNA sequencing. The estimated size of Pit-1 mRNA in placenta was very similar to that in anterior pituitary (AP). PCR products from placenta were exactly the same size with that from AP and confirmed as Pit-1-specific by Southern hybridization. The Pit-1 specific sequence was also confirmed by sequencing of partial amplification fragments. Immunoreactive 33 kDa Pit-1 was present in the placenta as well as in AP. Pit-1 specific mRNA and protein were localized in the trophoblast cells of placenta. These data suggest that Pit-1 is locally synthesized in the rat placenta and may be involved in the regulation of GH- and/or PRL-like gene expression in the placenta.