Leptonic Model for Neutrino Emission from Active Galactic Nuclei.

It is often stated that the observation of high-energy neutrinos from an astrophysical source would constitute indisputable proof for the acceleration of hadronic cosmic rays. Here, we point out that there exists a purely leptonic mechanism to produce TeV-scale neutrinos in astrophysical environments. In particular, very high-energy synchrotron photons can scatter with x rays, exceeding the threshold for muon-antimuon pair production. When these muons decay, they produce neutrinos without any cosmic-ray protons or nuclei being involved. In order for this mechanism to be efficient, the source in question must produce very high-energy photons which interact in an environment that is dominated by keV-scale radiation. We find that such a source could potentially generate an observable neutrino flux through muon pair production for reasonable choices of physical parameters.

Alkyladenine DNA glycosylase deficiency uncouples alkylation-induced strand break generation from PARP-1 activation and glycolysis inhibition.

DNA alkylation damage is repaired by base excision repair (BER) initiated by alkyladenine DNA glycosylase (AAG). Despite its role in DNA repair, AAG-initiated BER promotes cytotoxicity in a process dependent on poly (ADP-ribose) polymerase-1 (PARP-1); a NAD+-consuming enzyme activated by strand break intermediates of the AAG-initiated repair process. Importantly, PARP-1 activation has been previously linked to impaired glycolysis and mitochondrial dysfunction. However, whether alkylation affects cellular metabolism in the absence of AAG-mediated BER initiation is unclear. To address this question, we temporally profiled repair and metabolism in wild-type and Aag-/- cells treated with the alkylating agent methyl methanesulfonate (MMS). We show that, although Aag-/- cells display similar levels of alkylation-induced DNA breaks as wild type, PARP-1 activation is undetectable in AAG-deficient cells. Accordingly, Aag-/- cells are protected from MMS-induced NAD+ depletion and glycolysis inhibition. MMS-induced mitochondrial dysfunction, however, is AAG-independent. Furthermore, treatment with FK866, a selective inhibitor of the NAD+ salvage pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT), synergizes with MMS to induce cytotoxicity and Aag-/- cells are resistant to this combination FK866 and MMS treatment. Thus, AAG plays an important role in the metabolic response to alkylation that could be exploited in the treatment of conditions associated with NAD+ dysregulation.

Synergistic and antagonistic interactions of binary mixtures of polycyclic aromatic hydrocarbons in the upregulation of CYP1 activity and mRNA levels in precision-cut rat liver slices.

The current studies investigate whether synergistic or antagonistic interactions in the upregulation of CYP1 activity occur in binary mixtures of polycyclic aromatic hydrocarbons (PAHs) involving benzo[a]pyrene and five other structurally diverse PAHs of varying carcinogenic activity. Precision-cut rat liver slices were incubated with benzo[a]pyrene alone or in combination with a range of concentrations of a second PAH, and ethoxyresorufin O-deethylase, CYP1A1 and CYP1B1 mRNA levels determined. Concurrent incubation of benzo[a]pyrene with either dibenzo[a,h]anthracene or fluoranthene in liver slices led to a synergistic interaction, at least at low concentrations, in that ethoxyresorufin O-deethylase activity was statistically higher than the added effects when the slices were incubated with the individual compounds. In contrast, benzo[b]fluoranthene and, at high doses only, dibenzo[a,l]pyrene gave rise to antagonism, whereas 1-methylphenanthrene had no effect at all concentrations studied. When CYP1A1 mRNA levels were monitored, benzo[b]fluoranthene gave rise to an antagonistic response when incubated with benzo[a]pyrene, whereas all other compounds displayed synergism, with 1-methylphenathrene being the least effective. A similar picture emerged when CYP1B1 mRNA levels were determined, though the effects were less pronounced. In conclusion, it has been demonstrated that the benzo[a]pyrene-mediated upregulation of CYP1, at the mRNA and activity levels, is synergistically and antagonistically modulated by other PAHs. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 764-775, 2017.

Supporting Caregivers of Veterans Online: A Partnership of the National Council on Aging and VA.

The National Council on Aging's Building Better Caregivers program aims to improve the well-being of caregivers of veterans.

Inhibition of prenyltransferase activity by statins in both liver and muscle cell lines is not causative of cytotoxicity.

As inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase, statins are an important first-line treatment for hypercholesterolemia. However, a recognized side-effect of statin therapy is myopathy, which in severe cases can present as potentially fatal rhabdomyolysis. This represents an important impediment to successful statin therapy, and despite decades of research the molecular mechanisms underlying this side-effect remain unclear. Current evidence supports a role for reduced levels of mevalonate pathway intermediates, with the most accepted hypothesis being a reduction in isoprenoids formation, leading to faulty post-translational modifications of membrane-associated proteins. We have undertaken a comprehensive analysis of the impact of nine statins on two human cell lines; Huh7 hepatoma and RD rhabdomyosarcoma. In both cell lines, concentration-dependent inhibition of prenylation was observed for cerivastatin and simvastatin, which could be rescued with the pathway intermediate mevalonate; in general, muscle cells were more sensitive to this effect, as measured by the levels of unprenylated Rap1A, a marker for prenylation by geranylgeranyl transferase I. Concentration-dependent toxicity was observed in both cell lines, with muscle cells again being more sensitive. Importantly, there was no correlation between inhibition of prenylation and cell toxicity, suggesting they are not causally linked. The lack of a causal relationship was confirmed by the absence of cytotoxicity in all cell lines following exposure to specific inhibitors of geranylgeranyl transferases I and II, and farnesyl transferase. As such, we provide strong evidence against the commonly accepted hypothesis linking inhibition of prenylation and statin-mediated toxicity, with the two processes likely to be simultaneous but independent.

The components of action planning and their associations with behavior and health outcomes.

BACKGROUND: Based on the works of Kiesler and Bandura, action plans have become important tools in patient self-management programs. One such program, shown effective in randomized trials, is the Internet Chronic Disease Self-Management Program. An implementation of this program, Healthy Living Canada, included detailed information on action plans and health-related outcome measures. METHODS: Action plans were coded by type, and associations between action plans, confidence in completion and completion were examined. Numbers of Action Plans attempted and competed and completion rates were calculated for participants and compared to six-month changes in outcomes using regression models. RESULTS: Five of seven outcome measures significantly improved at six-months. A total of 1136 action plans were posted by 254 participants in 12 workshops (mean 3.9 out of 5 possible); 59% of action plans involved exercise, 16% food, and 14% role management. Confidence of completion was associated with completion. Action plan completion measures were associated with improvements in activity limitation, aerobic exercise, and self-efficacy. Baseline self-efficacy was associated with at least partial completion of action plans. DISCUSSION: Action planning appears to be an important component of self-management interventions, with successful completion associated with improved health and self-efficacy outcomes.

Coding and evaluating facilitator posts for an online cancer survivor workshop.

One-hundred and forty-five people attended six online cancer survivor workshops. Each workshop was monitored by two facilitators, who generated a total of 1,537 online posts. The authors developed a scheme for coding facilitator posts, combining grounded codes with categories developed by Spiegel and Classen for coding therapist responses in cancer support groups. Participants received a mean of 10.6 facilitator posts. Improvement in two health outcomes (practice of mental relaxation and illness intrusiveness) were significantly correlated with supportive posts and total number of posts. The coding scheme was easily applied and appears reliable. The data suggests that more facilitation is better.

The South Australia health chronic disease self-management Internet trial.

OBJECTIVES: To evaluate the effectiveness of an online chronic disease self-management program for South Australia residents. METHOD: Data were collected online at baseline, 6 months, and 12 months. The intervention was an asynchronous 6-week chronic disease self-management program offered online. The authors measured eight health status measures, seven behaviors, and four utilization measures; self-efficacy; and health care satisfaction. RESULTS: Two hundred fifty-four South Australian adults with one or more chronic conditions completed baseline data. One hundred forty-four completed 6 months and 194 completed 1 year. Significant improvements (p < .05) were found at 6 months for four health status measures, six health behaviors, self-efficacy, and visits to emergency departments. At 12 months, five health status indicators, six health behaviors, self-efficacy, and visits to emergency departments remained significant. Satisfaction with health care trended toward significance. DISCUSSION: The peer-led online program was both acceptable and useful for this population. It appeared to decrease symptoms, improve health behaviors, self-efficacy, and reduce health care utilization up to 1 year. This intervention also has large potential implications for the use of a public health education model for reaching large numbers of people. It demonstrates that an Internet self-management program, which includes social media, can reach rural and underserved people as well as be effective and reduce health care costs. If this intervention can be brought to scale, it has the potential for improving the lives of large numbers of people with chronic illness. It represents a way the medical care and public health sectors can interact.

Web-based self-management support training for health professionals: a pilot study.

OBJECTIVE: To evaluate a web-based self-management training for health professionals. Patients spend 99% of their time outside the healthcare system. Thus self-management support from health professionals is central to optimal care. Our objective was to teach health professionals the skills to provide this support. METHODS: Primary care residents and practicing providers enrolled in six groups. Each group received four web-based interactive training sessions derived from self-efficacy theory. Retrospective-pre/post assessed changes in self-management beliefs and confidence. Wilcoxon signed-rank tests with Bonferroni correction compared responses. Focus groups solicited qualitative feedback. RESULTS: Fifty-seven residents and providers across the United States enrolled. Residents demonstrated positive changes on all belief questions (P 0.001-0.012). Practicing providers had a non-significant positive change on one and significant changes on the remainder (P 0.001-0.018). Both types of participants demonstrated significant increases on confidence questions regarding their ability to support self-management (P<0.01 for all). Participants described learned techniques as being useful, reducing burnout, and increasing acceptance of patient involvement in care planning. CONCLUSION: The web-based self-management support training for health professionals was feasible and changed beliefs and confidence. PRACTICE IMPLICATIONS: The program may maximize patient self-management by increasing provider self-efficacy and skill for self-management support.

The naturally occurring aliphatic isothiocyanates sulforaphane and erucin are weak agonists but potent non-competitive antagonists of the aryl hydrocarbon receptor.

As the Ah receptor target gene products play a critical role in chemical carcinogenesis, antagonists are considered as potential chemopreventive agents. It is demonstrated in this paper that the isothiocyanates R,S-sulforaphane and erucin are non-competitive antagonists of the aryl hydrocarbon (Ah) receptor. Both isothiocyanates were poor agonists for the receptor and elevated CYP1A1 mRNA levels only modestly when incubated with precision-cut rat liver slices. In contrast, the classical Ah receptor agonist benzo[a]pyrene was a potent inducer of CYP1A1 mRNA levels, with this effect being effectively antagonized by the two isothiocyanates. In further studies, it was demonstrated that R,S-sulforaphane could both prevent the interaction of and displace already bound benzo[a]pyrene from the Ah receptor, but no concentration dependency was observed with respect to the isothiocyanate. Both erucin and R,S-sulforaphane antagonized the benzo[a]pyrene-mediated increase in the CYP1A-mediated O-deethylation of ethoxyresorufin in rat precision-cut liver slices. Of the two isomers of R,S-sulforaphane, the naturally occurring R-isomer was more effective than the S-isomer in antagonizing the activation of the Ah receptor by benzo[a]pyrene. Antagonism of the Ah receptor may be a major contributor to the established chemoprevention of aliphatic isothiocyanates.

Phenethyl isothiocyanate, a naturally occurring phytochemical, is an antagonist of the aryl hydrocarbon receptor.

SCOPE: The aryl hydrocarbon (Ah) receptor is a ligand-activated transcription factor that is activated by many carcinogens, and its target gene products play a major role in tumour development, so that antagonists of the Ah receptor represent potential chemopreventive agents. METHODS AND RESULTS: Experimental evidence is presented herein that phenethyl isothiocyanate (PEITC), a phytochemical present in cruciferous vegetables, is such an antagonist. PEITC was a very weak ligand to the Ah receptor, as assessed using the chemical-activated luciferase expression (CALUX) assay, and a poor inducer of CYP1A1 mRNA levels when incubated in precision-cut rat liver slices for 24 h. It antagonised effectively, however, the interaction of benzo[a]pyrene to the receptor, being capable of preventing its binding as well as displacing it from the receptor. Moreover, PEITC suppressed in concentration-dependent manner the benzo[a]pyrene-mediated rise in rat hepatic CYP1A1 mRNA levels in rat slices. Finally, PEITC antagonised the benzo[a]pyrene-mediated increase in the O-deethylation of ethoxyresorufin in both rat and human precision-cut liver slices. CONCLUSION: It is concluded that PEITC is an effective antagonist of the Ah receptor in rat and human liver, and this potential may contribute to its established chemopreventive activity.

A PXR-mediated negative feedback loop attenuates the expression of CYP3A in response to the PXR agonist pregnenalone-16α-carbonitrile.

The nuclear receptor superfamily of ligand-activated transcription factors plays a central role in the regulation of cellular responses to chemical challenge. Nuclear receptors are activated by a wide range of both endogenous and exogenous chemicals, and their target genes include those involved in the metabolism and transport of the activating chemical. Such target gene activation, thus, acts to remove the stimulating xenobiotic or to maintain homeostatic levels of endogenous chemicals. Given the dual nature of this system it is important to understand how these two roles are balanced, such that xenobiotics are efficiently removed while not impacting negatively on homeostasis of endogenous chemicals. Using DNA microarray technology we have examined the transcriptome response of primary rat hepatocytes to two nuclear receptor ligands: Pregnenalone-16α-carbonitrile (PCN), a xenobiotic PXR agonist, and lithocholic acid, an endogenous mixed PXR/VDR/FXR agonist. We demonstrate that despite differences in the profile of activated nuclear receptors, transcriptome responses for these two ligands are broadly similar at lower concentrations, indicating a conserved general response. However, as concentrations of stimulating ligand rises, the transcriptome responses diverge, reflecting a need for specific responses to the two stimulating chemicals. Finally, we demonstrate a novel feed-back loop for PXR, whereby ligand-activation of PXR suppresses transcription of the PXR gene, acting to attenuate PXR protein expression levels at higher ligand concentrations. Through in silico simulation we demonstrate that this feed-back loop is an important factor to prevent hyperexpression of PXR target genes such as CYP3A and confirm these findings in vitro. This novel insight into the regulation of the PXR-mediated regulatory signal networks provides a potential mechanistic rationale for the robustness in steroid homeostasis within the cell.

Online diabetes self-management program: a randomized study.

OBJECTIVE: We hypothesized that people with type 2 diabetes in an online diabetes self-management program, compared with usual-care control subjects, would 1) demonstrate reduced A1C at 6 and 18 months, 2) have fewer symptoms, 3) demonstrate increased exercise, and 4) have improved self-efficacy and patient activation. In addition, participants randomized to listserve reinforcement would have better 18-month outcomes than participants receiving no reinforcement. RESEARCH DESIGN AND METHODS: A total of 761 participants were randomized to 1) the program, 2) the program with e-mail reinforcement, or 3) were usual-care control subjects (no treatment). This sample included 110 American Indians/Alaska Natives (AI/ANs). Analyses of covariance models were used at the 6- and 18-month follow-up to compare groups. RESULTS: At 6 months, A1C, patient activation, and self-efficacy were improved for program participants compared with usual care control subjects (P < 0.05). There were no changes in other health or behavioral indicators. The AI/AN program participants demonstrated improvements in health distress and activity limitation compared with usual-care control subjects. The subgroup with initial A1C >7% demonstrated stronger improvement in A1C (P = 0.01). At 18 months, self-efficacy and patient activation were improved for program participants. A1C was not measured. Reinforcement showed no improvement. CONCLUSIONS: An online diabetes self-management program is acceptable for people with type 2 diabetes. Although the results were mixed they suggest 1) that the program may have beneficial effects in reducing A1C, 2) AI/AN populations can be engaged in and benefit from online interventions, and 3) our follow-up reinforcement appeared to have no value.

The neuroprotective action of the mood stabilizing drugs lithium chloride and sodium valproate is mediated through the up-regulation of the homeodomain protein Six1.

The mood stabilizing agents lithium chloride (LiCl) and sodium valproate (VPA) have recently gained interest as potential neuroprotective therapeutics. However, exploitation of these therapeutic applications is hindered by both a lack of molecular understanding of the mode of action, and a number of sub-optimal properties, including a relatively small therapeutic window and variable patient response. Human neuroblastoma cells (SH-SY5Y) were exposed to 1 mM lithium chloride or 1 mM sodium valproate for 6 h or 72 h, and transcriptomes measured by Affymetrix U133A/B microarray. Statistically significant gene expression changes were identified using SAM software, with selected changes confirmed at transcript (TaqMan) and protein (Western blotting) levels. Finally, anti-apoptotic action was measured by an in vitro fluorescent assay. Exposure of SH-SY5Y cells to therapeutically relevant concentrations of either lithium chloride or sodium valproate elicited 936 statistically significant changes in gene expression. Amongst these changes we observed a large (maximal 31.3-fold) increase in the expression of the homeodomain protein Six1, and have characterized the time- and dose-dependent up-regulation of this gene in response to both drugs. In addition, we demonstrate that, like LiCl or VPA treatment, Six1 over-expression protects SH-SY5Y cells from staurosporine-induced apoptosis via the blockade of caspsase-3 activation, whereas removal of Six1 protein via siRNA antagonises the ability of LiCl and VPA to protect SH-SY5Y cells from STS-induced apoptosis. These results provide a novel mechanistic rationale underlying the neuroprotective mechanism of LiCl and VPA, suggesting exciting possibilities for the development of novel therapeutic agents against neurodegenerative diseases such as Alzheimer's or Parkinsonism.

The Expert Patients Programme online, a 1-year study of an Internet-based self-management programme for people with long-term conditions.

OBJECTIVES: Evaluate the effectiveness of an online self-management programme (EPP Online) for England residents with long-term conditions. METHODS: A prospective longitudinal study. Data were collected online at baseline, 6 and 12 months. The intervention was an asynchronous 6-week chronic-disease self-management programme offered online. We measured seven health status measures (health distress, self-rated health, illness intrusiveness, disability, fatigue, pain and shortness of breath), four behaviours (aerobic exercise, stretching exercise, stress management and communications with physician), and five utilization measures (GP visits, pharmacy visits, PT/OT visits, emergency visits and hospitalizations). We also measured self-efficacy and satisfaction with the health care system. RESULTS: A total of 568 completed baseline data: 546 (81%) completed 6 months and 443 (78%) completed 1 year. Significant improvements (p < 0.01) were found at 6 months for all variables except self-rated health, disability, stretching, hospitalizations and nights in hospital. At 12 months only decrease in disability, nights in hospital and hospitalizations were not significant with reduction in visits to emergency departments being marginally significant (p = 0.012). Both self-efficacy and satisfaction with the health care system improved significantly. DISCUSSION: The peer-led online programme conditions appears to decrease symptoms, improve health behaviours, self-efficacy and satisfaction with the health care system and reducing health care utilization up to 1 year.

The internet-based arthritis self-management program: a one-year randomized trial for patients with arthritis or fibromyalgia.

OBJECTIVE: To determine the efficacy of an Internet-based Arthritis Self-Management Program (ASMP) as a resource for arthritis patients unable or unwilling to attend small-group ASMPs, which have proven effective in changing health-related behaviors and improving health status measures. METHODS: Randomized intervention participants were compared with usual care controls at 6 months and 1 year using repeated-measures analyses of variance. Patients with rheumatoid arthritis, osteoarthritis, or fibromyalgia and Internet and e-mail access (n = 855) were randomized to an intervention (n = 433) or usual care control (n = 422) group. Measures included 6 health status variables (pain, fatigue, activity limitation, health distress, disability, and self-reported global health), 4 health behaviors (aerobic exercise, stretching and strengthening exercise, practice of stress management, and communication with physicians), 5 utilization variables (physician visits, emergency room visits, chiropractic visits, physical therapist visits, and nights in hospital), and self-efficacy. RESULTS: At 1 year, the intervention group significantly improved in 4 of 6 health status measures and self-efficacy. No significant differences in health behaviors or health care utilization were found. CONCLUSION: The Internet-based ASMP proved effective in improving health status measures at 1 year and is a viable alternative to the small-group ASMP.

Up-regulation of the glutathione S-transferase system in human liver by polycyclic aromatic hydrocarbons; comparison with rat liver and lung.

The cytosolic glutathione S-transferases (GSTs) comprise a pivotal enzyme system protecting the cell from electrophilic compounds. It plays a major role in the detoxication of the primary and dihydrodiol epoxides of polycyclic aromatic hydrocarbons (PAHs), so that modulation of this enzyme system by PAHs will impact on their carcinogenic activity. The potential of six structurally diverse PAHs, namely benzo[a]pyrene (B[a]P), fluoranthene, benzo[b]fluoranthene (B[b]F), dibenzo[a,l]pyrene, dibenzo[a,h]anthracene (D[a,h]A) and 1-methhylphenanthrene, to modulate hepatic GST activity was investigated in human precision-cut slices and compared to rat slices, a species frequently used in long-term carcinogenicity studies; changes were monitored at the activity, using three different substrates, protein and mRNA levels. When activity was monitored using the alpha-class selective 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, B[b]F was the only PAH that caused an increase in activity, which was accompanied by a rise in the Ya immunoreacting band. In rat slices, in addition to B[b]F, B[a]P and D[a,h]A also enhanced activity, being paralleled with increased levels of the Ya immunoreacting band. In the rat, all PAHs elevated mRNA levels. In both human and rat liver slices, only B[b]F enhanced activity when 1-chloro-2,4-dinitrobenzene (CDNB) served as substrate. To investigate tissue differences, similar studies were undertaken in precision-cut rat lung slices, incubated with PAHs under identical conditions, using CDNB, as this was the only substrate for which activity could be detected; none of the PAHs studied stimulated activity. It is concluded that some PAHs have the potential to induce GST activity in human liver tissue and that species and tissue differences exist in the induction of this enzyme system in the rat. However, the extent of induction of GST activity is very modest compared with the effect these compounds have on CYP1 expression, the family responsible for their bioactivation, and it is unlikely to compensate for the enhanced production of reactive intermediates.

Differential response of human and rat epoxide hydrolase to polycyclic aromatic hydrocarbon exposure: studies using precision-cut tissue slices.

The potential of polycyclic aromatic hydrocarbons (PAHs) to modulate microsomal epoxide hydrolase activity, determined using benzo[a]pyrene 5-oxide as substrate, in human liver, was evaluated and compared to rat liver. Precision-cut liver slices prepared from fresh human liver were incubated with six structurally diverse PAHs, at a range of concentrations, for 24h. Of the six PAHs studied, benzo[a]pyrene, dibenzo[a,h]anthracene and fluoranthene gave rise to a statistically significant increase in epoxide hydrolase activity, which was accompanied by a concomitant increase in epoxide hydrolase protein levels determined by immunoblotting. The other PAHs studied, namely dibenzo[a,l]pyrene, benzo[b]fluoranthene and 1-methylphenanthrene, influenced neither activity nor enzyme protein levels. When rat slices were incubated under identical conditions, only benzo[a]pyrene and dibenzo[a,h]anthracene elevated epoxide hydrolase activity, which was, once again accompanied by a rise in protein levels. At the mRNA level, however, all six PAHs caused an increase, albeit to different extent. In rat, epoxide hydroxylase activity in lung slices was much lower than in liver slices. In lung slices, epoxide hydrolase activity was elevated following exposure to benzo[a]pyrene and dibenzo[a,l]pyrene and, to a lesser extent, 1-methylphenanthrene; similar observations were made at the protein level. At both activity and protein levels extent of induction was far more pronounced in the lung compared with the liver. It is concluded that epoxide hydrolase activity is an inducible enzyme by PAHs, in both human and rat liver, but induction potential by individual PAHs varies enormously, depending on the nature of the compound involved. Marked tissue differences in the nature of PAHs stimulating activity in rat lung and liver were noted. Although in the rat basal lung epoxide hydrolase activity is much lower than liver, it is more markedly inducible by PAHs.

Up-regulation of CYP1A/B in rat lung and liver, and human liver precision-cut slices by a series of polycyclic aromatic hydrocarbons; association with the Ah locus and importance of molecular size.

Exposure of precision-cut rat liver slices to six structurally diverse polycyclic aromatic hydrocarbons, namely benzo[a]pyrene, benzo[b]fluoranthene, dibenzo[a,h]anthracene, dibenzo[a,l]pyrene, fluoranthene and 1-methylphenanthrene, led to induction of ethoxyresorufin O-deethylase, CYP1A apoprotein and CYP1A1 mRNA levels, but to a markedly different extent. In liver slices, constitutive CYP1A1 mRNA levels were higher, as well as being markedly more inducible by PAHs, compared with CYP1B1, a similar profile to that observed in human liver slices following exposure to the PAHs. Increase in ethoxyresorufin O-deethylase and in CYP1A1 apoprotein levels was also observed when precision-cut rat lung slices were incubated with the same PAHs, the order of induction potency being similar to that observed in liver slices. Under the same conditions of exposure, CYP1B1 apoprotein levels were elevated in the lung. Up-regulation of CYP1A1 by the six PAHs correlated with their affinity for the Ah receptor, determined using the chemical-activated luciferase expression (CALUX) assay. It may be concluded that (a) precision-cut liver and lung slices may be used to assess the CYP1 induction potential of chemicals at the activity, apoprotein and mRNA levels; (b) rat is a promising surrogate animal for human in studies to evaluate CYP1 induction potential; (c) CYP1A1 is far more inducible than CYP1B1 in both rat liver and lung; (d) CYP1 up-regulation by PAHs is related to their affinity for the Ah receptor, and finally (e) computer analysis revealed that the ratio of molecular length/width is an important determinant of CYP1 induction potency among equiplanar PAHs.

Evaluation of the precision-cut liver and lung slice systems for the study of induction of CYP1, epoxide hydrolase and glutathione S-transferase activities.

The principal objective was to ascertain whether precision-cut tissue slices can be used to evaluate the potential of chemicals to induce CYP1, epoxide hydrolase and glutathione S-transferase activities, all being important enzymes involved in the metabolism of polycyclic aromatic hydrocarbons. Precision-cut rat liver and lung slices were incubated with a range of benzo[a]pyrene concentrations for various time periods. A rise in the O-deethylation of ethoxyresorufin was seen in both liver and lung slices exposed to benzo[a]pyrene, which was accompanied by increased CYP1A apoprotein levels. Pulmonary CYP1B1 apoprotein levels and hepatic mRNA levels were similarly enhanced. Elevated epoxide hydrolase and glutathione S-transferase activities were also observed in liver slices following incubation for 24h; similarly, a rise in apoprotein levels of both enzymes was evident, peak levels occurring at the same time point. When mRNA levels were monitored, a rise in the levels of both enzymes was seen as early as 4h after incubation, but maximum levels were attained at 24 h. In lung slices, induction of epoxide hydrolase by benzo[a]pyrene was observed after a 24-h incubation, and at a concentration of 1 microM; a rise in apoprotein levels was seen at this time point. Glutathione S-transferase activity was not inducible in lung slices by benzo[a]pyrene but a modest increase was observed in hepatic slices. Collectively, these studies confirmed CYP1A induction in rat liver slices and established that CYP1B1 expression, and epoxide hydrolase and glutathione S-transferase activities are inducible in precision-cut tissue slices.