Association between Religious Beliefs and HPV Vaccination Attitudes among College Students.

OBJECTIVE AND PARTICIPANTS: The authors sought an updated examination of attitudes toward Human Papillomavirus (HPV) catch-up vaccination among college students at a private religious university. METHODS: A total of 1557 college students completed a 62-question survey of religious and HPV vaccination attitudes during the fall of 2021. Students' willingness to receive catch-up HPV vaccination and willingness to vaccinate a future child against HPV were recorded. RESULTS: Of the 46.8% of students who reported being unvaccinated or unaware of vaccination status, ~26% reported being uninterested in receiving catch-up HPV vaccination; ~22% of all students surveyed reported being unwilling to vaccinate a future child against HPV. The strongest predictors of vaccine hesitancy included religious concerns about sexual abstinence and safety concerns. CONCLUSIONS: College health professionals can increase the rate of HPV vaccination among college students and subsequent future generations by addressing the safety and utility of the vaccine regardless of intentions for sexual abstinence prior to marriage. Additionally, rather than a uniform approach to all students who self-identify as Christian, an effort to identify and discuss the unique religiously influenced beliefs of individual students is recommended when discussing HPV vaccination.

Evaluation of Common Use Brominated Flame Retardant (BFR) Toxicity Using a Zebrafish Embryo Model.

Brominated flame retardants (BFRs) are used to reduce the flammability of plastics, textiles, and electronics. BFRs vary in their chemical properties and structures, and it is expected that these differences alter their biological interactions and toxicity. Zebrafish were used as the model organism for assessing the toxicity of nine structurally-diverse BFRs. In addition to monitoring for overt toxicity, the rate of spontaneous movement, and acetylcholinesterase and glutathione-S-transferase (GST) activities were assessed following exposure. The toxicities of BFRs tested can be ranked by LC50 as tetrabromobisphenol A (TBBPA) < 4,4'-isopropylidenebis[2-(2,6-dibromophenoxyl)ethanol] (TBBPA-OHEE) < Pentabromochlorocyclohexane (PBCH) < 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB) < hexabromocyclododecane (HBCD) < hexabromobenzene (HBB) < Tetrabromophthalic anhydride (PHT4). No adverse effect was observed in di(2-ethylhexyl) tetrabromophthalate (TBPH) or dibromoneopentyl glycol (DBNPG)-treated embryos. The rate of spontaneous movement was decreased in a concentration-dependent manner following exposure to four of the nine compounds. GST activity was elevated following treatment with PBCH, TBBPA, HBCD, and HBB. The results indicate that exposure to several BFRs may activate an antioxidant response and alter behavior during early development. Some of the BFRs, such as TBBPA and TBBPA-OHEE, induced adverse effects at concentrations lower than chemicals that are currently banned. These results suggest that zebrafish are sensitive to exposure to BFRs and can be used as a comparative screening model, as well as to determine alterations in behavior following exposure and probe mechanisms of action.

Comparison of PBDE congeners as inducers of oxidative stress in zebrafish.

A proposed primary pathway through which polybrominated diphenyl ethers (PBDEs) disrupt normal biological functions is oxidative stress. In the present study, 4 PBDE congeners were evaluated for their potential to initiate oxidative stress in zebrafish during development: BDE 28, BDE 47, BDE 99, and BDE 100. N-acetylcysteine (NAC) was used to increase intracellular glutathione concentrations and only decreased the effects of BDE 28 at 10 ppm and 20 ppm and BDE 47 at 20 ppm. N-acetylcysteine coexposure did not alter the rates of mortality or curved body axis compared with PBDE exposure alone. The activity of glutathione-S-transferase (GST) was not altered at 24 h postfertilization (hpf), but increased following 10 ppm BDE 28 exposure at 120 hpf. Transcription of several genes associated with stress was also evaluated. At 24 hpf, cytochrome c oxidase subunit 6a (COX6a) transcription was up-regulated in embryos exposed to BDE 99, and BDE 28 exposure up-regulated the transcription of Glutathione-S-transferase-pi (GSTpi). At 24 hpf, glutamate-cysteine ligase (GCLC) was slightly down-regulated by all congeners evaluated. At 120 hpf, TNF receptor-associated protein 1 (TRAP1) and COX6A were up-regulated by all congeners, however GSTpi was down-regulated by all congeners. The results of quantitative real-time transcription polymerase chain reaction are mixed and do not strongly support a transcriptional response to oxidative stress. According to the authors' data, PBDEs do not induce oxidative stress. Oxidative stress may occur at high exposure concentrations; however, this does not appear to be a primary mechanism of action for the PBDE congeners tested.

A novel mechanism of skin tumor promotion involving interferon-gamma (IFNγ)/signal transducer and activator of transcription-1 (Stat1) signaling.

The current study was designed to explore the role of signal transducer and activator of transcription 1 (Stat1) during tumor promotion using the mouse skin multistage carcinogenesis model. Topical treatment with both 12-O-tetradecanoylphorbol-13-acetate (TPA) and 3-methyl-1,8-dihydroxy-9-anthrone (chrysarobin or CHRY) led to rapid phosphorylation of Stat1 on both tyrosine (Y701) and serine (S727) residues in epidermis. CHRY treatment also led to upregulation of unphosphorylated Stat1 (uStat1) at later time points. CHRY treatment also led to upregulation of interferon regulatory factor 1 (IRF-1) mRNA and protein, which was dependent on Stat1. Further analyses demonstrated that topical treatment with CHRY but not TPA upregulated interferon-gamma (IFNγ) mRNA in the epidermis and that the induction of both IRF-1 and uStat1 was dependent on IFNγ signaling. Stat1 deficient (Stat1(-/-) ) mice were highly resistant to skin tumor promotion by CHRY. In contrast, the tumor response (in terms of both papillomas and squamous cell carcinomas) was similar in Stat1(-/-) mice and wild-type littermates with TPA as the promoter. Maximal induction of both cyclooxygenase-2 and inducible nitric oxide synthase in epidermis following treatment with CHRY was also dependent on the presence of functional Stat1. These studies define a novel mechanism associated with skin tumor promotion by the anthrone class of tumor promoters involving upregulation of IFNγ signaling in the epidermis and downstream signaling through activated (phosphorylated) Stat1, IRF-1 and uStat1.

Fine mapping reveals that promotion susceptibility locus 1 (Psl1) is a compound locus with multiple genes that modify susceptibility to skin tumor development.

Although it is well known that the majority of human cancers occur as the result of exposure to environmental carcinogens, it is clear that not all individuals exposed to a specific environmental carcinogen have the same risk of developing cancer. Considerable evidence indicates that common allelic variants of low-penetrance, tumor susceptibility genes are responsible for this interindividual variation in risk. We previously reported a skin tumor promotion susceptibility locus, Psl1, which maps to the distal portion of chromosome 9, that modified skin tumor promotion susceptibility in the mouse. Furthermore, Psl1 was shown to consist of at least two subloci (i.e., Psl1.1 and Psl1.2) and that glutathione S-transferase alpha 4 (Gsta4), which maps to Psl1.2, is a skin tumor promotion susceptibility gene. Finally, variants of human GSTA4 were found to be associated with risk of nonmelanoma skin cancer. In the current study, a combination of nested and contiguous C57BL/6 congenic mouse strains, each inheriting a different portion of the Psl1 locus from DBA/2, were tested for susceptibility to skin tumor promotion with 12-O-tetradecanoylphorbol-13-acetate. These analyses indicate that Psl1 is a compound locus with at least six genes, including Gsta4, that modify skin tumor promotion susceptibility. More than 550 protein-coding genes map within the Psl1 locus. Fine mapping of the Psl1 locus, along with two-strain haplotype analysis, gene expression analysis, and the identification of genes with amino acid variants, has produced a list of fewer than 25 candidate skin tumor promotion susceptibility genes.

We need to talk: an observational study of the impact of electronic medical record implementation on hospital communication.

BACKGROUND: Increasing attention is being given to the importance of communication in the delivery of high-quality healthcare. We sought to determine whether communication improved in a hospital setting following the introduction of an electronic medical record (EMR). METHODS: This pre-post cohort design enrolled 75 patient-nurse-physician triads prior to the introduction of EMR, and 123 triads after the introduction of EMR. Nurses and patients reported whether they communicated with the physician that day. Patients, nurses and physicians answered several questions about the plan of care for the day. Responses were scored for degree of agreement and compared between pre-EMR and post-EMR cohorts. The primary outcome was Total Agreement Score, calculated as the sum of the agreement responses. Chart review was performed to determine patients' actual length of stay. RESULTS: Although there was no difference between the frequency of nurses reporting communication with physicians before and after EMR, face-to-face communication was significantly reduced (67% vs 51%, p=0.03). Total Agreement Score was significantly lower after the implementation of EMR (p=0.03). Additionally, fewer patients accurately predicted their expected length of stay after EMR (34% vs 26%, p=0.001). CONCLUSIONS: The implementation of EMR was associated with a decrease in face-to-face communication between physicians and nurses, and worsened overall agreement about the plan of care.

Proteomic and pathway analyses reveal a network of inflammatory genes associated with differences in skin tumor promotion susceptibility in DBA/2 and C57BL/6 mice.

Genetic susceptibility to two-stage skin carcinogenesis is known to vary significantly among different stocks and strains of mice. In an effort to identify specific protein changes or altered signaling pathways associated with skin tumor promotion susceptibility, a proteomic approach was used to examine and identify proteins that were differentially expressed in epidermis between promotion-sensitive DBA/2 and promotion-resistant C57BL/6 mice following treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA). We identified 19 differentially expressed proteins of which 5 were the calcium-binding proteins annexin A1, parvalbumin α, S100A8, S100A9, and S100A11. Further analyses revealed that S100A8 and S100A9 protein levels were also similarly differentially upregulated in epidermis of DBA/2 versus C57BL/6 mice following topical treatment with two other skin tumor promoters, okadaic acid and chrysarobin. Pathway analysis of all 19 identified proteins from the present study suggested that these proteins were components of several networks that included inflammation-associated proteins known to be involved in skin tumor promotion (e.g. TNF-α, NFκB). Follow-up studies revealed that Tnf, Nfkb1, Il22, Il1b, Cxcl1, Cxcl2 and Cxcl5 mRNAs were highly expressed in epidermis of DBA/2 compared with C57BL/6 mice at 24h following treatment with TPA. Furthermore, NFκB (p65) was also highly activated at the same time point (as measured by phosphorylation at ser276) in epidermis of DBA/2 mice compared with C57BL/6 mice. Taken together, the present data suggest that differential expression of genes involved in inflammatory pathways in epidermis may play a key role in genetic differences in susceptibility to skin tumor promotion in DBA/2 and C57BL/6 mice.

2,6-Dithiopurine, a nucleophilic scavenger, protects against mutagenesis in mouse skin treated in vivo with 2-(chloroethyl) ethyl sulfide, a mustard gas analog.

Sulfur mustard [bis(2-chloroethyl)sulfide, SM] is a well-known DNA-damaging agent that has been used in chemical warfare since World War I, and is a weapon that could potentially be used in a terrorist attack on a civilian population. Dermal exposure to high concentrations of SM produces severe, long-lasting burns. Topical exposure to high concentrations of 2-(chloroethyl) ethyl sulfide (CEES), a monofunctional analog of SM, also produces severe skin lesions in mice. Utilizing a genetically engineered mouse strain, Big Blue, that allows measurement of mutation frequencies in mouse tissues, we now show that topical treatment with much lower concentrations of CEES induces significant dose- and time-dependent increases in mutation frequency in mouse skin; the mutagenic exposures produce minimal toxicity as determined by standard histopathology and immunohistochemical analysis for cytokeratin 6 and the DNA-damage induced phosphorylation of histone H2AX (γ-H2AX). We attempted to develop a therapeutic that would inhibit the CEES-induced increase in mutation frequency in the skin. We observe that multi-dose, topical treatment with 2,6-dithiopurine (DTP), a known chemical scavenger of CEES, beginning 1h post-exposure to CEES, completely abolishes the CEES-induced increase in mutation frequency. These findings suggest the possibility that DTP, previously shown to be non-toxic in mice, may be useful as a therapeutic agent in accidental or malicious human exposures to SM.

The EP1 receptor for prostaglandin E2 promotes the development and progression of malignant murine skin tumors.

High levels of prostaglandin E2 (PGE2) synthesis resulting from the up-regulation of cyclooxygenase (COX)-2 has been shown to be critical for the development of non-melanoma skin tumors. This effect of PGE2 is likely mediated by one or more of its 4 G-protein coupled membrane receptors, EP1-4. A previous study showed that BK5.EP1 transgenic mice produced more carcinomas than wild type (WT) mice using initiation/promotion protocols, although the tumor response was dependent on the type of tumor promoter used. In this study, a single topical application of either 7,12-dimethylbenz[a]anthracene (DMBA) or benzo[a]pyrene (B[a]P), alone, was found to elicit squamous cell carcinomas (SCCs) in the BK5.EP1 transgenic mice, but not in WT mice. While the epidermis of both WT and transgenic mice was hyperplastic several days after DMBA, this effect regressed in the WT mice while proliferation continued in the transgenic mice. Several parameters associated with carcinogen initiation were measured and were found to be similar between genotypes, including CYP1B1 and aromatase expression, B[a]P adduct formation, Ras activity, and keratinocyte stem cell numbers. However, EP1 transgene expression elevated COX-2 levels in the epidermis and SCC could be completely prevented in DMBA-treated BK5.EP1 mice either by feeding the selective COX-2 inhibitor celecoxib in their diet or by crossing them onto a COX-2 null background. These data suggest that the tumor promoting/progressing effects of EP1 require the PGE2 synthesized by COX-2.

Epidural abscess caused by Mycobacterium abscessus.

BACKGROUND: Mycobacterium abscessus is a member of the Rapidly Growing Mycobacterium (RGM). The incidence of Mycobacterium abscessus infections has steadily been increasing over the last decade. We report the case of an epidural abscess caused by Mycobacterium abscessus. RGM's have infrequently been reported as spinal infections and we found no prior cases reporting M. abscessus as the definitive etiologic agent of an epidural abscess. CASE REPORT: A 50 year old female presented with significant back pain and was found to have an epidural abscess by magnetic resonance imaging. The abscess was drained via needle. Initial cultures were negative for bacterial pathogens, and the patient was discharged to a skilled nursing facility for empiric antibiotic treatment. Eventually the culture grew Mycobacterium abscessus. The patient had unfortunately left the nursing facility and was lost to follow up. CONCLUSIONS: Mycobacterium abscessus is an increasingly recognized pathogen with particular risk factors that physicians should be aware of. Central nervous system infections are rare, but do occur. Treatment is difficult, though multiple antibiotic regimens have been reported successful. Surgical debridement is often needed.

Protection against 2-chloroethyl ethyl sulfide (CEES)-induced cytotoxicity in human keratinocytes by an inducer of the glutathione detoxification pathway.

Sulfur mustard (SM or mustard gas) was first used as a chemical warfare agent almost 100years ago. Due to its toxic effects on the eyes, lungs, and skin, and the relative ease with which it may be synthesized, mustard gas remains a potential chemical threat to the present day. SM exposed skin develops fluid filled bullae resulting from potent cytotoxicity of cells lining the basement membrane of the epidermis. Currently, there are no antidotes for SM exposure; therefore, chemopreventive measures for first responders following an SM attack are needed. Glutathione (GSH) is known to have a protective effect against SM toxicity, and detoxification of SM is believed to occur, in part, via GSH conjugation. Therefore, we screened 6 potential chemopreventive agents for ability to induce GSH synthesis and protect cultured human keratinocytes against the SM analog, 2-chloroethyl ethyl sulfide (CEES). Using NCTC2544 human keratinocytes, we found that both sulforaphane and methyl-2-cyano-3,12-dioxooleana-1,9-dien-28-oate (CDDO-Me) stimulated nuclear localization of Nrf2 and induced expression of the GSH synthesis gene, GCLM. Additionally, we found that treatment with CDDO-Me elevated reduced GSH content of NCTC2544 cells and preserved their viability by ~3-fold following exposure to CEES. Our data also suggested that CDDO-Me may act additively with 2,6-dithiopurine (DTP), a nucleophilic scavenging agent, to increase the viability of keratinocytes exposed to CEES. These results suggest that CDDO-Me is a promising chemopreventive agent for SM toxicity in the skin.

Cooperation between Stat3 and Akt signaling leads to prostate tumor development in transgenic mice.

In this report, we describe the development of a transgenic mouse in which a rat probasin promoter (ARR(2)Pb) was used to direct prostate specific expression of a constitutively active form of signal transducer and activator of transcription 3 (i.e., Stat3C). ARR(2)Pb.Stat3C mice exhibited hyperplasia and prostate intraepithelial neoplasia (PIN) lesions in both ventral and dorsolateral prostate lobes at 6 and 12 months; however, no adenocarcinomas were detected. The effect of combined loss of PTEN was examined by crossing ARR(2)Pb.Stat3C mice with PTEN(+/-) null mice. PTEN(+/-) null mice on an ICR genetic background developed only hyperplasia and PIN at 6 and 12 months, respectively. ARR(2)Pb.Stat3C x PTEN(+/-) mice exhibited a more severe prostate phenotype compared with ARR(2)Pb.Stat3C and PTEN(+/-) mice. ARR(2)Pb.Stat3C x PTEN(+/-) mice developed adenocarcinomas in the ventral prostate as early as 6 months (22% incidence) that reached an incidence of 61% by 12 months. Further evaluations indicated that phospho-Stat3, phospho-Akt, phospho-nuclear factor κB, cyclin D1, and Ki67 were upregulated in adenocarcinomas from ARR(2)Pb.Stat3C x PTEN(+/-) mice. In addition, membrane staining for ß-catenin and E-cadherin was reduced. The changes in Stat3 and nuclear factor κB phosphorylation correlated most closely with tumor progression. Collectively, these data provide evidence that Stat3 and Akt signaling cooperate in prostate cancer development and progression and that ARR(2)Pb.Stat3C x PTEN(+/-) mice represent a novel mouse model of prostate cancer to study these interactions.

Upregulation of the EP1 receptor for prostaglandin E2 promotes skin tumor progression.

Prostaglandin E(2) (PGE(2) ) has been shown to promote the development of murine skin tumors. EP1 is 1 of the 4 PGE(2) G-protein-coupled membrane receptors expressed by murine keratinocytes. EP1 mRNA levels were increased ∼2-fold after topical treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) or exposure to ultraviolet (UV) light, as well as increased ∼3- to 12-fold in tumors induced by 7,12-dimethyl-benz[a]anthracene (DMBA) initiation/TPA promotion or by UV exposure. To determine the effect of EP1 levels on tumor development, we generated BK5.EP1 transgenic mice that overexpress EP1 in the basal layer of the epidermis. Skins of these mice were histologically indistinguishable from wild type (WT) mice and had similar levels of proliferation after TPA treatment. Using a DMBA/TPA carcinogenesis protocol, BK5.EP1 mice had a reduced tumor multiplicity compared to WT mice, likely due to the observed down-regulation of protein kinase C (PKC). However, the BK5.EP1 mice had an ∼8-fold higher papilloma to carcinoma conversion rate. When DMBA/anthralin was used, BK5.EP1 mice produced more tumors than WT mice, as well as a ninefold increase in carcinomas, indicating that the tumor response is dependent on the type of tumor promoter agent used. Additionally, although almost undetectable in WT mice, cyclooxygenase-2 (COX-2) was expressed in the untreated epidermis of BK5.EP1 mice. While TPA highly induced COX-2 in WT mice, COX-2 expression in the BK5.EP1 mice did not change after TPA treatment; PGE(2) levels were likewise affected. These data indicate that EP1 is more important in tumor progression than in tumor promotion and that it indirectly regulates COX-2 expression.

Evidence that Gsta4 modifies susceptibility to skin tumor development in mice and humans.

BACKGROUND: The incidence of nonmelanoma skin cancer (NMSC) is equivalent to that of all other cancers combined. Previously, we mapped the 12-O-tetradecanoylphorbol-13-acetate (TPA) skin tumor promotion susceptibility locus, Psl1, to distal chromosome 9 in crosses of sensitive DBA/2 mice with relatively resistant C57BL/6 mice. Here, we used the mouse two-stage skin carcinogenesis model to identify the gene(s) responsible for the effects of Psl1. METHODS: Interval-specific congenic mouse strains (n ≥ 59 mice per strain) were used to more precisely map the Psl1 locus. Having identified glutathione S-transferase α4 (Gsta4) as a candidate tumor promotion susceptibility gene that mapped within the delimited region, we analyzed Gsta4-deficient mice (n = 62) for susceptibility to skin tumor promotion by TPA. We used quantitative polymerase chain reaction, western blotting, and immunohistochemistry to verify induction of Gsta4 in mouse epidermis following TPA treatment and biochemical assays to associate Gsta4 activity with tumor promotion susceptibility. In addition, single-nucleotide polymorphisms (SNPs) in GSTA4 were analyzed in a case-control study of 414 NMSC patients and 450 control subjects to examine their association with human NMSC. Statistical analyses of tumor studies in mice were one-sided, whereas all other statistical analyses were two-sided. RESULTS: Analyses of congenic mice indicated that at least two loci, Psl1.1 and Psl1.2, map to distal chromosome 9 and confer susceptibility to skin tumor promotion by TPA. Gsta4 maps to Psl1.2 and was highly induced (mRNA and protein) in the epidermis of resistant C57BL/6 mice compared with that of sensitive DBA/2 mice following treatment with TPA. Gsta4 activity levels were also higher in the epidermis of C57BL/6 mice following treatment with TPA. Gsta4-deficient mice (C57BL/6.Gsta4(-/-) mice) were more sensitive to TPA skin tumor promotion (0.8 tumors per mouse vs 0.4 tumors per mouse in wild-type controls; difference = 0.4 tumors per mouse; 95% confidence interval = 0.1 to 0.7, P = .007). Furthermore, inheritance of polymorphisms in GSTA4 was associated with risk of human NMSC. Three SNPs were found to be independent predictors of NMSC risk. Two of these were associated with increased risk of NMSC (odds ratios [ORs] = 1.60 to 3.42), while the third was associated with decreased risk of NMSC (OR = 0.63). In addition, a fourth SNP was associated with decreased risk of basal cell carcinoma only (OR = 0.44). CONCLUSIONS: Gsta4/GSTA4 is a novel susceptibility gene for NMSC that affects risk in both mice and humans.

A high-throughput 1,536-well luminescence assay for glutathione S-transferase activity.

Glutathione S-transferases (GSTs) constitute a family of detoxification enzymes that catalyze the conjugation of glutathione with a variety of hydrophobic compounds, including drugs and their metabolites, to yield water-soluble derivatives that are excreted in urine or bile. Profiling the effect of small molecules on GST activity is an important component in the characterization of drug candidates and compound libraries. Additionally, specific GST isozymes have been implicated in drug resistance, especially in cancer, and thus represent potential targets for intervention. To date, there are no sensitive miniaturized high-throughput assays available for GST activity detection. A series of GST substrates containing a masked luciferin moiety have been described recently, offering the potential for configuring a sensitive screening assay via coupled luciferase reaction and standard luminescence detection. We report on the optimization and miniaturization of this homogeneous method to 1,536-well format using GSTs from 3 different species: mouse isozyme A4-4, human isozymes A1-1, M1-1, and P1-1, and the major GST from the parasitic worm Schistosoma japonicum.

Multi-stage chemical carcinogenesis in mouse skin: fundamentals and applications.

For more than 60 years, the chemical induction of tumors in mouse skin has been used to study mechanisms of epithelial carcinogenesis and evaluate modifying factors. In the traditional two-stage skin carcinogenesis model, the initiation phase is accomplished by the application of a sub-carcinogenic dose of a carcinogen. Subsequently, tumor development is elicited by repeated treatment with a tumor-promoting agent. The initiation protocol can be completed within 1-3 h depending on the number of mice used; whereas the promotion phase requires twice weekly treatments (1-2 h) and once weekly tumor palpation (1-2 h) for the duration of the study. Using the protocol described here, a highly reproducible papilloma burden is expected within 10-20 weeks with progression of a portion of the tumors to squamous cell carcinomas within 20-50 weeks. In contrast to complete skin carcinogenesis, the two-stage model allows for greater yield of premalignant lesions, as well as separation of the initiation and promotion phases.

Differential gene expression in epidermis of mice sensitive and resistant to phorbol ester skin tumor promotion.

Previous data from two-stage carcinogenesis studies in mouse skin demonstrated that genetic control of susceptibility to skin tumor promotion by the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), in crosses between susceptible DBA/2J and resistant C57BL/6J mice is a multigenic trait. Utilizing a cDNA microarray approach, we compared global gene expression profiles in the epidermis of these two mouse strains treated with TPA or vehicle (acetone). Gene expression in the epidermis was analyzed after the treatment to identify global effects of TPA, as well as potential candidate genes that modify susceptibility to skin tumor promotion. DBA/2J and C57BL/6J mice were treated topically four times with 3.4 nmol TPA or acetone over a 2-wk period, and RNA was extracted from epidermis 6 h after the final treatment. Labeled cDNA generated from each group was hybridized to commercial cDNA microarrays (Agilent) containing more than 8000 targets. More than 450 genes were significantly influenced, directly or indirectly, by TPA treatment in the epidermis of either strain. Notably, 44 genes exhibited differential expression between the tumor promotion sensitive and resistant mouse strains. Several genes that were differentially expressed in DBA/2J versus C57BL/6J epidermis after TPA treatment were located in chromosomal regions linked to TPA promotion susceptibility. Three genes, Gsta4, Nmes1 (MGC58382), and Serpinb2, located within promotion susceptibility loci Psl1 (chr 9), Psl2 (chr 2), and Psl3 (chr 1), respectively, were identified in this analysis as potential candidates for modifiers of susceptibility to skin tumor promotion by TPA.

Estradiol metabolites as isoform-specific inhibitors of human glutathione S-transferases.

Numerous studies have suggested that the lifetime dose of unopposed estrogen is a significant risk factor for breast and uterine cancer. Estradiol (E2) plays a putative role as a tumor promoter through interaction with estrogen receptors but can also be metabolized to redox active and/or mutagenic semiquinones and quinones. Similarly, equine estrogens (components of certain hormone replacement therapy preparations) are converted to quinone metabolites. The use of hormone replacement therapy has also been associated with increased breast and endometrial cancer risk. Recently, metabolites of certain equine estrogens have been shown to inhibit human glutathione S-transferases (hGSTs). Since E2 and equine estrogens share similarities in other biological interactions, we have investigated the inhibitory capacity of endogenously formed E2 metabolites toward various hGSTs. The quinone metabolite of 2-hydroxy-17-beta-estradiol (2-OH-E2) was synthesized, and inhibition of hGST-mediated biotransformation of model substrates was assessed. Inhibition of purified recombinant hGSTM1-1 and hGSTA1-1 occurred in a concentration-dependent manner with IC50-values of approximately 250 and 350 nM, respectively. hGSTs M2-2, P1-1 and T1-1 were significantly less sensitive to inhibition. Specific glutathione-conjugates of the estrogen quinone also potently inhibited hGSTM1-1 and hGSTA1-1. Mass spectrometry data indicate that the inhibition was not mediated via covalent adduction. Although we have demonstrated hGST inhibition via E2 metabolites, our findings indicate that the isoform specificity and potency of GST inhibition by endogenous E2 metabolites is different than that of equine estrogen metabolites.

Characterization of atrazine biotransformation by human and murine glutathione S-transferases.

Atrazine is one of the most widely used herbicides in the United States and has been detected, occasionally, at low levels in drinking water sources. The biotransformation of atrazine in humans has not been fully characterized. Rodent studies suggest Phase I-dominated biotransformation with minor Phase II-mediated biotransformation by glutathione S-transferase(s) (GST). In human urine, mercapturates of atrazine are significant metabolites, yet the specific GST form(s) responsible for glutathione (GSH) conjugation have not been identified. Using recombinant alpha, mu, pi and theta class human GSTs, we demonstrated that only hGSTP1-1 displays significant activity toward atrazine (7.1 nmol/min/mg protein). We also confirmed that mouse GST Pi (pi) protein is responsible for the GSH-dependent biotransformation of atrazine in mouse liver; recombinant mGSTP1-1 had a specific activity of 7.3-nmol/min/mg protein. Furthermore, cytosolic fractions from mouse and human liver conjugated atrazine with glutathione at rates of 282.3 and 3.0 pmol/min/mg, respectively. Docking studies of the atrazine-GST conjugate in the hGSTP1-1 substrate-binding site were used to elucidate a basis for the dramatic difference in activity between mouse GSTP1-1 and GSTP2-2 (7.14 versus 0.02 nmol/min/mg protein, respectively). The inactivity of mGSTP2-2 appears to be attributable to an indirect structural disruption of the G-site by Pro12. Possible effects of the hGSTP1 polymorphisms were investigated. No significant differences in catalytic-specific activity were noted among purified proteins corresponding to the four hGSTP1 variants: hGSTP1(*)A (most common form), hGSTP1(*)B (Ile105Val), hGSTP1(*)C (Ile105Val, Ala114Val), and hGSTP1(*)D (Ala114Val). Overall, this work supports a physiological role for GSTs in atrazine biotransformation and indicates a novel diagnostic substrate for human and mouse GSTP1-1 proteins.