Characterizing Adversity of Lysosomal Accumulation in Nonclinical Toxicity Studies: Results from the 5th ESTP International Expert Workshop.

Lysosomes have a central role in cellular catabolism, trafficking, and processing of foreign particles. Accumulation of endogenous and exogenous materials in lysosomes represents a common finding in nonclinical toxicity studies. Histologically, these accumulations often lack distinctive features indicative of lysosomal or cellular dysfunction, making it difficult to consistently interpret and assign adverse dose levels. To help address this issue, the European Society of Toxicologic Pathology organized a workshop where representative types of lysosomal accumulation induced by pharmaceuticals and environmental chemicals were presented and discussed. The expert working group agreed that the diversity of lysosomal accumulations requires a case-by-case weight-of-evidence approach and outlined several factors to consider in the adversity assessment, including location and type of cell affected, lysosomal contents, severity of the accumulation, and related pathological effects as evidence of cellular or organ dysfunction. Lysosomal accumulations associated with cytotoxicity, inflammation, or fibrosis were generally considered to be adverse, while those found in isolation (without morphologic or functional consequences) were not. Workshop examples highlighted the importance of thoroughly characterizing the biological context of lysosomal effects, including mechanistic data and functional in vitro readouts if available. The information provided here should facilitate greater consistency and transparency in the interpretation of lysosomal effects.

Medical and ethical challenges in the case of a prenatally undiagnosed massive congenital brain tumor.

Fetal and neonatal brain tumors are rare. Prenatal ultrasound aids early tumor detection. Nonetheless, we encountered a preterm neonate born at 32 weeks gestation with a massive supratentorial glioma, which was undetected on ultrasound at 19-6/7 weeks gestation. The patient presented at birth with unanticipated massive macrocephaly. Resuscitation and stabilization were difficult, but the medical team felt that futility of care was not established and opted to transfer the baby to an academic center for further imaging and specialist consultations. Diagnosis of an extensive, inoperable tumor was confirmed and support withdrawn. Postmortem histologic examination and immunohistochemical stains identified the majority of tumor cells as glial in origin. This case report illustrates well how a severe and potentially fatal anomaly, which remained undetected prenatally, presented the medical team and family with multiple medical, ethical and emotional challenges at birth; decisions regarding futility of care in the neonatal transport setting are difficult.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Progress to Date and Future Plans.

The International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice proposal (INHAND) has been operational since 2005. A Global Editorial Steering Committee manages the overall objectives of the project, and the development of harmonized terminology for each organ system is the responsibility of the Organ Working Groups, drawing upon experts from North America, Europe, and Japan. Great progress has been made with 9 systems published to date--respiratory, hepatobiliary, urinary, central/peripheral nervous systems, male reproductive and mammary, zymbals, clitoral, and preputial glands in Toxicologic Pathology and the integument and soft tissue and female reproductive in the Journal of Toxicologic Pathology as supplements and on a Web site--www.goReni.org. INHAND nomenclature guides offer diagnostic criteria and guidelines for recording lesions observed in rodent toxicity and carcinogenicity studies. The guides provide representative photomicrographs of morphologic changes, information regarding pathogenesis, and key references. The purpose of this brief communication is to provide an update on the progress of INHAND.

Schizophrenia-risk variant rs6994992 in the neuregulin-1 gene on brain developmental trajectories in typically developing children.

The neuregulin-1 (NRG1) gene is one of the best-validated risk genes for schizophrenia, and psychotic and bipolar disorders. The rs6994992 variant in the NRG1 promoter (SNP8NRG243177) is associated with altered frontal and temporal brain macrostructures and/or altered white matter density and integrity in schizophrenic adults, as well as healthy adults and neonates. However, the ages when these changes begin and whether neuroimaging phenotypes are associated with cognitive performance are not fully understood. Therefore, we investigated the association of the rs6994992 variant on developmental trajectories of brain macro- and microstructures, and their relationship with cognitive performance. A total of 972 healthy children aged 3-20 years had the genotype available for the NRG1-rs6994992 variant, and were evaluated with magnetic resonance imaging (MRI) and neuropsychological tests. Age-by-NRG1-rs6994992 interactions and genotype effects were assessed using a general additive model regression methodology, covaried for scanner type, socioeconomic status, sex and genetic ancestry factors. Compared with the C-carriers, children with the TT-risk-alleles had subtle microscopic and macroscopic changes in brain development that emerge or reverse during adolescence, a period when many psychiatric disorders are manifested. TT-children at late adolescence showed a lower age-dependent forniceal volume and lower fractional anisotropy; however, both measures were associated with better episodic memory performance. To our knowledge, we provide the first multimodal imaging evidence that genetic variation in NRG1 is associated with age-related changes on brain development during typical childhood and adolescence, and delineated the altered patterns of development in multiple brain regions in children with the T-risk allele(s).

Common DNA methylation alterations in multiple brain regions in autism.

Autism spectrum disorders (ASD) are increasingly common neurodevelopmental disorders defined clinically by a triad of features including impairment in social interaction, impairment in communication in social situations and restricted and repetitive patterns of behavior and interests, with considerable phenotypic heterogeneity among individuals. Although heritability estimates for ASD are high, conventional genetic-based efforts to identify genes involved in ASD have yielded only few reproducible candidate genes that account for only a small proportion of ASDs. There is mounting evidence to suggest environmental and epigenetic factors play a stronger role in the etiology of ASD than previously thought. To begin to understand the contribution of epigenetics to ASD, we have examined DNA methylation (DNAm) in a pilot study of postmortem brain tissue from 19 autism cases and 21 unrelated controls, among three brain regions including dorsolateral prefrontal cortex, temporal cortex and cerebellum. We measured over 485,000 CpG loci across a diverse set of functionally relevant genomic regions using the Infinium HumanMethylation450 BeadChip and identified four genome-wide significant differentially methylated regions (DMRs) using a bump hunting approach and a permutation-based multiple testing correction method. We replicated 3/4 DMRs identified in our genome-wide screen in a different set of samples and across different brain regions. The DMRs identified in this study represent suggestive evidence for commonly altered methylation sites in ASD and provide several promising new candidate genes.

Genome-wide association study of shared components of reading disability and language impairment.

Written and verbal languages are neurobehavioral traits vital to the development of communication skills. Unfortunately, disorders involving these traits-specifically reading disability (RD) and language impairment (LI)-are common and prevent affected individuals from developing adequate communication skills, leaving them at risk for adverse academic, socioeconomic and psychiatric outcomes. Both RD and LI are complex traits that frequently co-occur, leading us to hypothesize that these disorders share genetic etiologies. To test this, we performed a genome-wide association study on individuals affected with both RD and LI in the Avon Longitudinal Study of Parents and Children. The strongest associations were seen with markers in ZNF385D (OR = 1.81, P = 5.45 × 10(-7) ) and COL4A2 (OR = 1.71, P = 7.59 × 10(-7) ). Markers within NDST4 showed the strongest associations with LI individually (OR = 1.827, P = 1.40 × 10(-7) ). We replicated association of ZNF385D using receptive vocabulary measures in the Pediatric Imaging Neurocognitive Genetics study (P = 0.00245). We then used diffusion tensor imaging fiber tract volume data on 16 fiber tracts to examine the implications of replicated markers. ZNF385D was a predictor of overall fiber tract volumes in both hemispheres, as well as global brain volume. Here, we present evidence for ZNF385D as a candidate gene for RD and LI. The implication of transcription factor ZNF385D in RD and LI underscores the importance of transcriptional regulation in the development of higher order neurocognitive traits. Further study is necessary to discern target genes of ZNF385D and how it functions within neural development of fluent language.

Liver hypertrophy: a review of adaptive (adverse and non-adverse) changes--conclusions from the 3rd International ESTP Expert Workshop.

Preclinical toxicity studies have demonstrated that exposure of laboratory animals to liver enzyme inducers during preclinical safety assessment results in a signature of toxicological changes characterized by an increase in liver weight, hepatocellular hypertrophy, cell proliferation, and, frequently in long-term (life-time) studies, hepatocarcinogenesis. Recent advances over the last decade have revealed that for many xenobiotics, these changes may be induced through a common mechanism of action involving activation of the nuclear hormone receptors CAR, PXR, or PPARα. The generation of genetically engineered mice that express altered versions of these nuclear hormone receptors, together with other avenues of investigation, have now demonstrated that sensitivity to many of these effects is rodent-specific. These data are consistent with the available epidemiological and empirical human evidence and lend support to the scientific opinion that these changes have little relevance to man. The ESTP therefore convened an international panel of experts to debate the evidence in order to more clearly define for toxicologic pathologists what is considered adverse in the context of hepatocellular hypertrophy. The results of this workshop concluded that hepatomegaly as a consequence of hepatocellular hypertrophy without histologic or clinical pathology alterations indicative of liver toxicity was considered an adaptive and a non-adverse reaction. This conclusion should normally be reached by an integrative weight of evidence approach.

Social impairments in Rett syndrome: characteristics and relationship with clinical severity.

BACKGROUND: While behavioural abnormalities are fundamental features of Rett syndrome (RTT), few studies have examined the RTT behavioural phenotype. Most of these reports have focused on autistic features, linked to the early regressive phase of the disorder, and few studies have applied standardised behavioural measures. We used a battery of standardised measures of behaviour and functioning to test the following hypotheses: (1) autistic behaviour is prominent throughout childhood in RTT; (2) autistic features are more salient in individuals with milder presentation; (3) severity of autistic behaviour is associated with a wider range of behavioural problems; and (4) specific MECP2 mutations are linked to more severe autistic behaviour. METHODS: Eighty MECP2 mutation-positive girls with RTT (aged 1.6-14.9 years) were administered: (1) the Screen for Social Interaction (SSI), a measure of autistic behaviour suited for individuals with severe communication and motor impairment; (2) the Rett Syndrome Behaviour Questionnaire (RSBQ), covering a wide range of abnormal behaviours in RTT; (3) the Vineland Adaptive Behavior Scales (VABS); and (4) a modified version of the Rett Syndrome Severity Scale (RSSS). Regression analyses examined the predictive value of age and RSSS on autistic behaviour and other behavioural abnormalities. T-tests further characterised the behavioural phenotype of individual MECP2 mutations. RESULTS: While age had no significant effect on SSI or RSBQ total scores in RTT, VABS Socialization and Composite scores decreased over time. Clinical severity (i.e. RSSS) also increased with age. Surprisingly, SSI performance was not related to either RSSS or VABS Composite scores. Autistic behaviour was weakly linked with the RSBQ Hand behaviour factor scores, but not with the RSBQ Fear/Anxiety factor. Clinical (neurological) severity did not predict RSBQ scores, as evidenced by the analysis of individual MECP2 mutations (e.g. p.R106W, p.R270X and p.R294X). CONCLUSIONS: Our data suggest that in RTT, autistic behaviour persists after the period of regression. It also demonstrated that neurological and behavioural impairments, including autistic features, are relatively independent of one another. Consistent with previous reports of the RTT phenotype, individual MECP2 mutations demonstrate complex associations with autistic features. Evidence of persistent autistic behaviour throughout childhood, and of a link between hand function and social skills, has important implications not only for research on the RTT behavioural phenotype, but also for the clinical management of the disorder.

Autism spectrum disorder in Down syndrome: cluster analysis of Aberrant Behaviour Checklist data supports diagnosis.

BACKGROUND: The diagnostic validity of autism spectrum disorder (ASD) based on Diagnostic and Statistical Manual of Mental Disorders (DSM) has been challenged in Down syndrome (DS), because of the high prevalence of cognitive impairments in this population. Therefore, we attempted to validate DSM-based diagnoses via an unbiased categorisation of participants with a DSM-independent behavioural instrument. METHODS: Based on scores on the Aberrant Behaviour Checklist - Community, we performed sequential factor (four DS-relevant factors: Autism-Like Behaviour, Disruptive Behaviour, Hyperactivity, Self-Injury) and cluster analyses on a 293-participant paediatric DS clinic cohort. The four resulting clusters were compared with DSM-delineated groups: DS + ASD, DS + None (no DSM diagnosis), DS + DBD (disruptive behaviour disorder) and DS + SMD (stereotypic movement disorder), the latter two as comparison groups. RESULTS: Two clusters were identified with DS + ASD: Cluster 1 (35.1%) with higher disruptive behaviour and Cluster 4 (48.2%) with more severe autistic behaviour and higher percentage of late onset ASD. The majority of participants in DS + None (71.9%) and DS + DBD (87.5%) were classified into Cluster 2 and 3, respectively, while participants in DS + SMD were relatively evenly distributed throughout the four clusters. CONCLUSIONS: Our unbiased, DSM-independent analyses, using a rating scale specifically designed for individuals with severe intellectual disability, demonstrated that DSM-based criteria of ASD are applicable to DS individuals despite their cognitive impairments. Two DS + ASD clusters were identified and supported the existence of at least two subtypes of ASD in DS, which deserve further characterisation. Despite the prominence of stereotypic behaviour in DS, the SMD diagnosis was not identified by cluster analysis, suggesting that high-level stereotypy is distributed throughout DS. Further supporting DSM diagnoses, typically behaving DS participants were easily distinguished as a group from those with maladaptive behaviours.

Two distinct pools of large-conductance calcium-activated potassium channels in the somatic plasma membrane of central principal neurons.

Although nerve cell membranes are often assumed to be uniform with respect to electrical properties, there is increasing evidence for compartmentalization into subdomains with heterogeneous impacts on the overall cell function. Such microdomains are characterized by specific sets of proteins determining their functional properties. Recently, clustering of large-conductance calcium-activated potassium (BK(Ca)) channels was shown at sites of subsurface membrane cisterns in cerebellar Purkinje cells (PC), where they likely participate in building a subcellular signaling unit, the 'PLasmERosome'. By applying SDS-digested freeze-fracture replica labeling (SDS-FRL) and postembedding immunogold electron microscopy, we have now studied the spatial organization of somatic BK(Ca) channels in neocortical layer 5 pyramidal neurons, principal neurons of the central and basolateral amygdaloid nuclei, hippocampal pyramidal neurons and dentate gyrus (DG) granule cells to establish whether there is a common organizational principle in the distribution of BK(Ca) channels in central principal neurons. In all cell types analyzed, somatic BK(Ca) channels were found to be non-homogenously distributed in the plasma membrane, forming two pools of channels with one pool consisting of clustered channels and the other of scattered channels in the extrasynaptic membrane. Quantitative analysis by means of SDS-FRL revealed that about two-thirds of BK(Ca) channels belong to the scattered pool and about one-third to the clustered pool in principal cell somata. Overall densities of channels in both pools differed in the different cell types analyzed, although being considerably lower compared to cerebellar PC. Postembedding immunogold labeling revealed association of clustered channels with subsurface membrane cisterns and confirmed extrasynaptic localization of scattered channels. This study indicates a common organizational principle for somatic BK(Ca) channels in central principal neurons with the formation of a clustered and a scattered pool of channels, and a cell-type specific density of this channel type.

Topoisomerase IIalpha maintains genomic stability through decatenation G(2) checkpoint signaling.

Topoisomerase IIalpha (topoIIalpha) is an essential mammalian enzyme that topologically modifies DNA and is required for chromosome segregation during mitosis. Previous research suggests that inhibition of topoII decatenatory activity triggers a G(2) checkpoint response, which delays mitotic entry because of insufficient decatenation of daughter chromatids. Here we examine the effects of both topoIIalpha and topoIIbeta on decatenatory activity in cell extracts, DNA damage and decatenation G(2) checkpoint function, and the frequencies of p16(INK4A) allele loss and gain. In diploid human fibroblast lines, depletion of topoIIalpha by small-interfering RNA was associated with severely reduced decatenatory activity, delayed progression from G(2) into mitosis and insensitivity to G(2) arrest induced by the topoII catalytic inhibitor ICRF-193. Furthermore, interphase nuclei of topoIIalpha-depleted cells showed increased frequencies of losses and gains of the tumor suppressor genetic locus p16(INK4A). This study shows that the topoIIalpha protein is required for decatenation G(2) checkpoint function, and inactivation of decatenation and the decatenation G(2) checkpoint leads to abnormal chromosome segregation and genomic instability.

The inhalation toxicity of di- and triethanolamine upon repeated exposure.

Systemic and respiratory tract (RT) toxicity of triethanolamine (TEA) was assessed in a 28-day nose-only inhalation study in Wistar rats (10animals/sex, concentrations: 0, 20, 100, 500mg/m3; 5 days/week, 6h/day). In two nose-only 90-day inhalation studies, with similar exposure design, Wistar rats were exposed to 0, 15, 150, 400mg/m3 diethanolamine (DEA) (DEA Study 1:13animals/sex, general subchronic study) and to 0, 1.5, 3, 8mg/m3 (DEA Study 2:10animals/sex) to specifically investigate respiratory tract toxicity. Only DEA induced systemic toxicity at or above 150mg/m3 (body and organ weight changes, clinical- and histo-pathological changes indicative for mild blood, liver, kidney and testicular effects). Neurotoxicity was not observed for both substances. Exposure to both substances resulted in laryngeal epithelial changes starting from 3mg/m3 for DEA (reversible metaplasia at the base of the epiglottis, inflammation at higher concentrations extending into the trachea) or from 20mg/m3 for TEA (focal inflammation, starting in single male animals). TEA appears to be less potent with respect to systemic toxicity and RT irritancy than DEA. The 90-day no adverse effect concentration" (NOAEC) for changes due to TEA exposure in the respiratory tract was 4.7mg/m3 derived by extrapolation from the NOAEC of the 28day study.

Iron deficiency causes duodenum mucosal hyperplasia in male Wistar rats.

Administration of an iron-deficient diet to Wistar rats resulted within 14 days in reduced serum iron concentrations, a microcytic hypochromic anemia, characteristic for impaired hemoglobin synthesis, and an increase of duodenal epithelial cell proliferation. After 5 weeks of iron deficiency, hypochromic microcytic anemia and a clear increase of duodenum weight but no pronounced effects on cell proliferation was observed. Increased duodenum weights corresponded to significant increases in mucosal area, indicating a diffuse, simple mucosal hyperplasia. The sequence of events following iron depletion thus appears to be: (1) reduced serum iron levels, (2) induction of hypochromic microcytic anemia, (3) increased duodenal epithelial cell proliferation, and (4) increased duodenal weight (increased mucosal area). Iron deficiency anemia was rapidly reversible after a 2-week recovery period. However, increased duodenum weights were still noted at that time. Intramuscular iron supplementation in animals fed with iron-deficient diet maintained body iron levels not below normal values, and neither anemia nor increased duodenum cell proliferation were detected after 14 days. A 5-week iron supplementation period resulted in slightly increased serum iron values, and slightly decreased duodenal epithelial cell proliferation. Thus, increased duodenum mucosal hyperplasia was shown to be secondary to depletion of body iron and anemia and reflects an attempt to increase iron absorption to counteract iron deficiency.

Investigating genotype-phenotype relationships in Rett syndrome using an international data set.

BACKGROUND: Rett syndrome is an uncommon neurodevelopmental disorder with an incidence of 1:9,000 live female births. The principal genetic cause was first reported in 1999 when the association with mutations in the methyl-CpG-binding protein 2 (or MECP2) gene was identified. This study uses data from a large international database, InterRett, to examine genotype-phenotype relationships and compares these with previous findings in a population-based cohort. METHOD: The data set for these analyses was derived from a subset of InterRett cases with subject information collected from the family, the clinician, or both. Individual phenotypic characteristics and clinical severity using three scales were compared among those with eight known recurrent pathogenic MECP2 mutations as well as those with C-terminal deletions (n = 272). RESULTS: Overall, p.R270X and p.R255X were the most severe and p.R133C and p.R294X were the mildest mutations. Significant differences by mutation were seen for individual phenotypic characteristics such as hand use, ambulation, and language. CONCLUSIONS: This multicenter investigation into the phenotypic correlates of MECP2 mutations in Rett syndrome has provided a greater depth of understanding than hitherto available about the specific phenotypic characteristics associated with commonly occurring mutations. Although the modifying influence of X inactivation on clinical severity could not be included in the analysis, the findings confirm clear genotype-phenotype relationships in Rett syndrome and show the benefits of collaboration crucial to effective research in rare disorders.

Selective cerebral volume reduction in Rett syndrome: a multiple-approach MR imaging study.

BACKGROUND AND PURPOSE: Previous studies have examined volumetric abnormalities in Rett syndrome (RTT), using MR imaging and focusing on selective changes. However, these studies preceded the identification of MECP2 as the gene mutated in most RTT cases. We studied regional brain volume changes as noted by MR imaging in girls with RTT who had mutations in the MECP2 gene and more or less severe clinical outcomes to further characterize the neuroanatomy of RTT and its correlations with clinical severity. MATERIALS AND METHODS: Complementary semiautomated Talairach- and voxel-based approaches were used to study spoiled gradient-recalled acquisition sequence MR imaging scans from 23 girls with MECP2 mutations/RTT, including a pair of discordant monozygotic twins and 25 age-matched control girls. Both absolute and relative volumetric changes were examined to account for the well-documented global reduction in brain volume seen in RTT. RESULTS: Absolute volumetric reductions were observed throughout the brain in RTT. Selective/relative decreases in parietal lobe gray matter, particularly in the dorsal parietal region, and mild, diffuse reductions in cortical white matter were observed in the RTT group compared with control subjects. In girls with RTT and a more severe phenotype, anterior frontal lobe volumes were relatively more reduced. Twin comparisons revealed selective preservation of the occipital cortex. CONCLUSION: Selective reductions of dorsal parietal gray matter and preservation of the occipital cortex seem to be basic neuroanatomic features of RTT, whereas preferential reduction of the anterior frontal lobe appears to be a correlate of clinical severity in this disorder. The most affected brain regions include those that may underlie key functional deficits observed in RTT.

Gross motor profile in rett syndrome as determined by video analysis.

Movement impairment is a fundamental but variable component of the Rett syndrome phenotype. This study used video supplemented by parent report data to describe the gross motor profile in females with Rett syndrome (n=99) and to investigate the impact of age, genotype, scoliosis and hand stereotypies. Factor analysis enabled the calculation of general and complex gross motor skills scores. Most subjects were able to sit, slightly less than half were able to walk and a minority were able to transfer without assistance. General gross motor skills declined with age and were poorer in those who had surgically treated scoliosis but not conservatively managed scoliosis. Complex gross motor skills did not decline with age and were better in those without scoliosis. Those with a p.R133C, p.R294X, or a p.R255X mutation appear to have better motor skills overall than those with a p.R270X or large deletion mutation. Motor scores were not related to the frequency of hand stereotypies. This information is useful for the clinician and family when planning support strategies and interventions.

Development of a video-based evaluation tool in Rett syndrome.

This paper describes the development of a video-based evaluation tool for use in Rett syndrome (RTT). Components include a parent-report checklist, and video filming and coding protocols that contain items on eating, drinking, communication, hand function and movements, personal care and mobility. Ninety-seven of the 169 families who initially agreed to participate returned a videotape within 8 months of the first request. Subjects whose videos were returned had a similar age profile to those who did not provide a video but were more likely to have classical than atypical RTT. Evidence of the content and social validity and inter-rater reliability on 11 videos is provided. Video may provide detailed, objective assessment of function and behaviour in RTT.

Early progressive encephalopathy in boys and MECP2 mutations.

MECP2 mutations mainly occur in females with Rett syndrome. Mutations have been described in 11 boys with progressive encephalopathy: seven of nine with affected sisters and two de novo. The authors report four de novo occurrences: three pathogenic and one potentially pathogenic. Common features include failure to thrive, respiratory insufficiency, microcephaly, and abnormal motor control. MECP2 mutations should be assessed in boys with progressive encephalopathy and one or more of respiratory insufficiency, abnormal movements or tone, and intractable seizures.

Cycloxygenase-2 activity promotes cognitive deficits but not increased amyloid burden in a model of Alzheimer's disease in a sex-dimorphic pattern.

Administration of non-steroidal anti-inflammatory agents reduces the risk of developing Alzheimer's disease in normal aging populations, an effect that may occur from inhibition of the cyclooxygenases, the rate-limiting enzymes in the formation of prostaglandins. In this study, we investigated whether increased activity of cyclooxygenase-2 (COX-2), the inducible isoform of cyclooxygenase, potentiates disease progression in a transgenic mouse model of Alzheimer's disease. To study the functional effects of COX-2 activity, male and female bigenic mice (amyloid precursor protein with Swedish mutation [APPswe]-presenilin-1 protein with deletion of exon 9 [PS1dE9] and trigenic COX-2/APPswe-PS1dE9) were behaviorally tested +/-administration of the selective COX-2 inhibitor celecoxib. Behavioral testing included a three-trial Y maze that measures spatial working and recognition memories and an open field task that tested levels of hyperactivity. Overexpression of COX-2 in APPswe-PS1dE9 mice resulted in specific deficits in spatial working memory in female but not male mice. These sex-specific deficits were abolished by pharmacological inhibition of COX-2 activity. Importantly, COX-2-associated deficits were dependent on co-expression of all three transgenes since COX-2 single transgenic and APPswe-PS1dE9 bigenic mice showed normal memory. Quantification of amyloid plaque load and total Abeta 40 and 42 peptides did not reveal significant differences in trigenic versus bigenic mice treated with either vehicle or celecoxib. Taken together, these data indicate an interaction between the effects of COX-2 and Abeta peptides on cognition that occurs in a sex-specific manner in the absence of significant changes in amyloid burden. These findings suggest that pathological activation of COX-2 may potentiate the toxicity of Abeta peptides, particularly in females, without significantly affecting Abeta accumulation.

Effects of styrene and its metabolites on different lung compartments of the mouse--cell proliferation and histomorphology.

Styrene is not carcinogenic in rats but has caused pneumotoxicity and increased lung tumors after inhalation in mice. This study investigated whether styrene-7,8-oxide, ring-oxidized, and side-chain hydroxylated styrene metabolites induce cell proliferation, apoptosis, pathological changes, and glutathione depletion in mice lungs. Intraperitoneal treatment with phenylacetaldehyde and phenylacetic acid (3 x 100 mg/kg b.w./day) increased the levels of apoptosis and cell proliferation in the alveoli without producing any effects in the terminal bronchioli, the target site of tumor formation in mice. Only styrene-oxide (SO) at 3 x 100 mg/kg b.w./day and 4-vinyl-phenol (4-VP) at 3 x 35 and 3 x 20 mg/kg b.w./day, respectively, caused up to 19-fold increases in cell proliferation in the large/medium bronchi and terminal bronchioles; marginal increases in alveolar cell proliferation were noted with SO (1.6-fold) but not with 4-VP. These compounds also caused glutathione depletion in the bronchiolar epithelium and histomorphological changes of the bronchiolar epithelium in large and medium bronchi and terminal bronchioles. Changes were characterized by flattened cells and a loss of the typical bulging of the "dome-shaped" Clara cells, suggesting that Clara cells were primary target cells. The specific reactions of mouse lung to SO and 4-VP could serve as a verifiable hypothesis for the different response of rats and mice with regard to tumor formation.