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Jarrod Bailey

Publications and source records attributed to Jarrod Bailey.

12 recordsLinked to original sources
PubMed2006

Animal carcinogenicity studies: 1. Poor human predictivity.

The regulation of human exposure to potentially carcinogenic chemicals constitutes society's most important use of animal carcinogenicity data. Environmental contaminants of greatest concern within the USA are listed in the Environmental Protection Agency's (EPA's) Integrated Risk Information System (IRIS) chemicals database. However, of the 160 IRIS chemicals lacking even limited human exposure data but possessing animal data that had received a human carcinogenicity assessment by 1 January 2004, we found that in most cases (58.1%; 93/160), the EPA considered animal carcinogenicity data inadequate to support a classification of probable human carcinogen or non-carcinogen. For the 128 chemicals with human or animal data also assessed by the World Health Organisation's International Agency for Research on Cancer (IARC), human carcinogenicity classifications were compatible with EPA classifications only for those 17 having at least limited human data (p = 0.5896). For those 111 primarily reliant on animal data, the EPA was much more likely than the IARC to assign carcinogenicity classifications indicative of greater human risk (p < 0.0001). The IARC is a leading international authority on carcinogenicity assessments, and its significantly different human carcinogenicity classifications of identical chemicals indicate that: 1) in the absence of significant human data, the EPA is over-reliant on animal carcinogenicity data; 2) as a result, the EPA tends to over-predict carcinogenic risk; and 3) the true predictivity for human carcinogenicity of animal data is even poorer than is indicated by EPA figures alone. The EPA policy of erroneously assuming that tumours in animals are indicative of human carcinogenicity is implicated as a primary cause of these errors.

Animals↗
PubMed2006

Animal carcinogenicity studies: 2. Obstacles to extrapolation of data to humans.

Due to limited human exposure data, risk classification and the consequent regulation of exposure to potential carcinogens has conventionally relied mainly upon animal tests. However, several investigations have revealed animal carcinogenicity data to be lacking in human predictivity. To investigate the reasons for this, we surveyed 160 chemicals possessing animal but not human exposure data within the US Environmental Protection Agency chemicals database, but which had received human carcinogenicity assessments by 1 January 2004. We discovered the use of a wide variety of species, with rodents predominating, and of a wide variety of routes of administration, and that there were effects on a particularly wide variety of organ systems. The likely causes of the poor human predictivity of rodent carcinogenicity bioassays include: 1) the profound discordance of bioassay results between rodent species, strains and genders, and further, between rodents and human beings; 2) the variable, yet substantial, stresses caused by handling and restraint, and the stressful routes of administration common to carcinogenicity bioassays, and their effects on hormonal regulation, immune status and predisposition to carcinogenesis; 3) differences in rates of absorption and transport mechanisms between test routes of administration and other important human routes of exposure; 4) the considerable variability of organ systems in response to carcinogenic insults, both between and within species; and 5) the predisposition of chronic high dose bioassays toward false positive results, due to the overwhelming of physiological defences, and the unnatural elevation of cell division rates during ad libitum feeding studies. Such factors render profoundly difficult any attempts to accurately extrapolate human carcinogenic hazards from animal data.

Animals↗
PubMed2006

Animal carcinogenicity studies: 3. Alternatives to the bioassay.

Conventional animal carcinogenicity tests take around three years to design, conduct and interpret. Consequently, only a tiny fraction of the thousands of industrial chemicals currently in use have been tested for carcinogenicity. Despite the costs of hundreds of millions of dollars and millions of skilled personnel hours, as well as millions of animal lives, several investigations have revealed that animal carcinogenicity data lack human specificity (i.e. the ability to identify human non-carcinogens), which severely limits the human predictivity of the bioassay. This is due to the scientific inadequacies of many carcinogenicity bioassays, and numerous serious biological obstacles, which render profoundly difficult any attempts to accurately extrapolate animal data in order to predict carcinogenic hazards to humans. Proposed modifications to the conventional bioassays have included the elimination of mice as a second species, and the use of genetically-altered or neonatal mice, decreased study durations, initiation-promotion models, the greater incorporation of toxicokinetic and toxicodynamic assessments, structure-activity relationship (computerised) systems, in vitro assays, cDNA microarrays for detecting changes in gene expression, limited human clinical trials, and epidemiological research. The potential advantages of non-animal assays when compared to bioassays include the superior human specificity of the results, substantially reduced time-frames, and greatly reduced demands on financial, personnel and animal resources. Inexplicably, however, the regulatory agencies have been frustratingly slow to adopt alternative protocols. In order to decrease the enormous cost of cancer to society, a substantial redirection of resources away from excessively slow and resource-intensive rodent bioassays, into the further development and implementation of non-animal assays, is both strongly justified and urgently required.

Animal Testing Alternatives↗
PubMed2006

Animal carcinogenicity studies: implications for the REACH system.

The 2001 European Commission proposal for the Registration, Evaluation and Authorisation of Chemicals (REACH) aims to improve public and environmental health by assessing the toxicity of, and restricting exposure to, potentially toxic chemicals. The greatest benefits are expected to accrue from decreased cancer incidences. Hence the accurate identification of chemical carcinogens must be a top priority for the REACH system. Due to a paucity of human clinical data, the identification of potential human carcinogens has conventionally relied on animal tests. However, our survey of the US Environmental Protection Agency's (EPAs) toxic chemicals database revealed that, for a majority of the chemicals of greatest public health concern (93/160, i.e. 58.1%), the EPA found animal carcinogenicity data to be inadequate to support classifications of probable human carcinogen or non-carcinogen. A wide variety of species were used, with rodents predominating; a wide variety of routes of administration were used; and a particularly wide variety of organ systems were affected. These factors raise serious biological obstacles that render accurate extrapolation to humans profoundly difficult. Furthermore, significantly different International Agency for Research on Cancer assessments of identical chemicals, indicate that the true human predictivity of animal carcinogenicity data is even poorer than is indicated by the EPA figures alone. Consequently, we propose the replacement of animal carcinogenicity bioassays with a tiered combination of non-animal assays, which can be expected to yield a weight-of-evidence characterisation of carcinogenic risk with superior human predictivity. Additional advantages include substantial savings of financial, human and animal resources, and potentially greater insights into mechanisms of carcinogenicity.

Animals↗
PubMed2005

The switch in alternative splicing of cyclic AMP-response element modulator protein CREM{tau}2{alpha} (activator) to CREM{alpha} (repressor) in human myometrial cells is mediated by SRp40.

The transcription factor cAMP-response element modulator (CREM) protein, plays a major role in cAMP-responsive gene regulation. Biological consequences resulting from the transcriptional stimuli of CREM are dictated by the expression of multiple protein isoforms generated by extensive alternative splicing of its precursor mRNA. We have previously shown that alternative splicing enables the expression of the CREM gene to be "switched" within the human myometrium during pregnancy from the production of CREMtau(2alpha), a potent transcriptional activator to the synthesis of CREMalpha, a transcriptional repressor. Furthermore we have recently reported that this change in the expression of CREM spliced variants is likely to have important ramifications on the regulation of downstream cAMP-response element-responsive target genes involved in uterine activity during gestation. We have investigated the splicing factors involved in controlling the expression of myometrial CREM splice variants. Data presented here from transient transfections indicate that the switch in the synthesis of CREMtau(2)alpha to CREMalpha that occurs during pregnancy is regulated primarily by an SR protein family member, SRp40. We also show that expression of this splicing factor is tightly regulated in the myometrium during pregnancy. SRp40 regulates the splicing of CREM via its interactions with multiple ESE motifs present in the alternatively exons of CREM. In vitro splicing and electrophoretic mobility shift assays were employed to confirm the functionality of the SRp40-binding ESEs, thus providing a mechanistic explanation of how SRp40 regulates the switch in splicing from production of CREMtau(2)alpha to CREMalpha.

Alternative Splicing↗
PubMed2005

Regulation of expression of the chorionic gonadotropin/luteinizing hormone receptor gene in the human myometrium: involvement of specificity protein-1 (Sp1), Sp3, Sp4, Sp-like proteins, and histone deacetylases.

At present there is little information on the regulatory processes by which the chorionic gonadotropin (CG)/LH receptor gene is regulated in the human myometrium during pregnancy and labor. Employing human primary myometrial cell cultures in conjunction with DNA affinity purification assays/Western analysis, DNA binding studies, CG/LH promoter luciferase reporter gene deletion constructs in transfection assays, and measurement of endogenous mRNA levels in vivo by duplex RT-PCR, we have determined the role that the major transcriptional regulatory sequences from the +1 ATG codon to -2678 bp play in modulating expression of the CG/LH receptor gene in the myometrium. We report that the distal -180 to -2678 bp region of the promoter, although capable of binding members of the Jun family via the multiple activator protein-1 sites within this region, has no significant role in regulating the expression of the CG/LH receptor gene in myometrial cells. In contrast, the two specificity protein-1 to -4 (Sp1-4) GC boxes within the +1 to -180 bp proximal promoter are central to expression of the gene in the myometrium. However, not only are Sp1/Sp3 proteins involved in this process, but Sp4 and a novel Sp-like factor(s) also have an intimate part in transcriptional regulation of the gene. It would appear that Sp1/Sp3/Sp4 and Sp-like proteins are involved in recruiting histone deacetylase complexes to the proximal promoter, preventing chromatin remodeling resulting in transcriptional repression of the gene. Our data suggest that administration of the histone deacetylase inhibitor trichostatin A to human myometrial cells in vitro and in vivo substantially removes this silencing effect on expression of the gene and may implicate the use of this and similar agents in increasing myometrial CG/LH receptor levels and subsequent maintenance of uterine relaxation during fetal maturation.

Base Sequence↗
PubMed2005

Spatial and temporal expression of the myometrial mitogen-activated protein kinases p38 and ERK1/2 in the human uterus during pregnancy and labor.

OBJECTIVE: We have recently identified a novel putative spliced variant of the activating transcription factor 2 (ATF2) in the human myometrium during pregnancy and labor. This protein, termed ATF2-sm like full-length ATF2, acts as a potent transactivator of cyclic adenosine monophosphate response element (CRE)-containing promoter reporter genes. Similarly, employing microarray gene profiling in myometrial cells, we have shown ATF2-sm to affect the expression of several specific myometrial genes associated with regulating uterine activity during pregnancy and labor. At some point after conception this transcription factor becomes spatially expressed within the body of the uterus, with significantly higher levels detected in the upper (corpus) compared to the lower uterine segment. Because ATF2 species are the primary substrate for phosphorylation by the mitogen-activated protein kinases (MAPKs) p38 and ERK1/2, the purpose of the current investigation was to define the expression levels of these kinases in upper and lower segment myometrium during pregnancy and labor to see if they also correlated with expression of ATF2-sm. METHODS: Paired myometrial samples were collected from the upper (corpus) and lower uterine segments from term nonlaboring and spontaneously laboring women undergoing elective and emergency cesarean deliveries, respectively. Non-pregnant myometrial samples were collected from premenopausal women having hysterectomies for benign gynecologic disorders. The MAPKs p38 and ERK1/2 present in individual myometrial homogenates were resolved using sodium dodecyl sulfate polacrylamide gel electropheresis (SDS-PAGE) with subsequent Western blotting with specific antibodies and scanning densitometry. Expression of the individual MAPKs in myometrial tissues was confirmed in situ using immunohistochemistry. RESULTS: In non-pregnant tissues, p38 and ERK1/2 expression was uniform throughout the uterus. In term pregnant nonlaboring and spontaneously laboring samples expression of p38 and ERK1 was significantly elevated in the upper uterine segment compared to the lower segment, respectively. In contrast, there was no difference in ERK2 expression. CONCLUSION: The data from this study indicate that both p38 and ERK1 are spatially regulated in different uterine regions during pregnancy/labor and suggest that they may be involved in regulating the activity of ATF2 isoforms and their subsequent effects on myometrial function.

Activating Transcription Factor 2↗
PubMed2005

Identification of human myometrial target genes of the cAMP pathway: the role of cAMP-response element binding (CREB) and modulator (CREMalpha and CREMtau2alpha) proteins.

cAMP-response element (CRE) binding (CREB) and modulator (CREM) proteins, activated by protein kinase A-mediated phosphorylation, bind as homo- and heterodimers to promoters containing CRE and activator protein 1 (AP-1) sites to alter target-gene expression. We have previously reported differential expression of CREB and CREM splice variants CREMalpha and CREMtau2alpha in human myometrium during pregnancy and labour. Via microarray studies with cultured myometrial cells stably transfected with CREB, CREMalpha and CREMtau2alpha cDNAs, CREB affected the expression of 958 genes; 522 being up-regulated and 436 down-regulated. CREMalpha altered the expression of 118 genes; 71 were increased and 47 decreased. CREMtau2alpha affected 220 genes; 148 were activated and 72 repressed. Notably, genes affected by CREB, CREMalpha and CREMtau2alpha belong to largely discrete groups: less than 9% were affected by more than one factor. Genes involved in regulation of cell death and apoptosis, growth and maintenance, signal transduction, physiological and developmental processes, protein kinase cascades, extracellular matrix, cytoskeleton, cell-cycle regulation, transport, and a variety of enzymes, intracellular components and nucleic acid-binding proteins have been described, many of which are involved in the modulation of myometrial activity during pregnancy and parturition.

Cyclic AMP↗
PubMed2005

Identification of human myometrial target genes of the c-Jun NH2-terminal kinase (JNK) pathway: the role of activating transcription factor 2 (ATF2) and a novel spliced isoform ATF2-small.

Activating transcription factor 2 (ATF2), a ubiquitously expressed member of the basic region leucine zipper (bZIP) family of transcription factors activated by mitogen activated protein kinase (MAPK) pathways, is important in the mediation of cellular stress responses, development and transformation. We have previously reported the differential expression of active ATF2 in the human myometrium throughout pregnancy and labour, and identified and partially characterized a novel splice variant ATF2-small (ATF2-sm). To further understand the role of these factors in the myometrium, we have used gene microarrays to define the target genes in cultured myometrial cells stably-transfected with ATF2 and ATF2-sm cDNAs. Many of the genes identified appear to have potential roles in regulating myometrial function and include proteins involved in G-protein receptor signalling, cytokine signalling, transcriptional regulation, cell-cycle control, formation of the extracellular matrix and cytoskeletal architecture. ATF2 was found to affect the expression of 204 genes; 113 being up-regulated and 91 down-regulated whereas the novel ATF2-sm factor altered the expression of 55 genes; expression was increased in 29 cases and decreased in 26. A further 25 genes affected by ATF2-sm were identified by suppression subtractive hybridisation (SSH). Notably, the genes affected by ATF2 and ATF2-sm appear to belong to discrete groups: only two genes were affected by both factors.

Activating Transcription Factor 2↗
PubMed2002

Differential expression of the adenylyl cyclase-stimulatory guanosine triphosphate-binding protein G(s)alpha in the human myometrium during pregnancy and labor involves transcriptional regulation by cyclic adenosine 3',5'-monophosphate and binding of phosphorylated nuclear proteins to multiple GC boxes within the promoter.

G(s)alpha is the G protein subunit that stimulates adenylyl cyclase activity in the myometrium during pregnancy, raising intracellular levels of the smooth muscle relaxant cAMP. The promoter region of the gene encoding G(s)alpha is GC rich and contains multiple putative binding sites for the specificity protein (Sp) transcription factor family. In electrophoretic mobility shift assays, four of these Sp sites were bound by recombinant Sp1 protein. Binding was dependent on phosphorylation of Sp1 by protein kinase A. Phosphorylated Sp1-4 proteins were observed in extracts of cultured human myometrial cells, but in electrophoretic mobility shift assays G(s)alpha promoter sequence binding by Sp1 was not apparent. Instead, these assays showed phosphorylation-dependent G(s)alpha promoter binding by lower molecular weight myometrial proteins that could not be supershifted by antibodies specific to Sp1-4 proteins. To investigate the regulation of G(s)alpha expression, the GC-rich promoter region was used to direct transcription of a firefly luciferase reporter gene in transient transfection assays of primary human myometrial cell cultures, COS-7 and HEK 293 cells. Reporter gene expression was found to follow a biphasic response to forskolin and 8-bromo-cAMP, with an initial, concentration-dependent increase in luciferase activity, followed by a prolonged decrease. In myometrial cells, this pattern was also seen in response to treatment with human chorionic gonadotropin.

Adenylyl Cyclases↗
PubMed2002

Characterization and functional analysis of cAMP response element modulator protein and activating transcription factor 2 (ATF2) isoforms in the human myometrium during pregnancy and labor: identification of a novel ATF2 species with potent transactivation properties.

There is now extensive evidence to indicate that components of the cAMP signaling pathway are up-regulated in the human myometrium during pregnancy so as to potentiate the maintenance of uterine quiescence until term. In many tissue and cell types, increased signaling of the cAMP pathway results in profound changes in gene expression that are catalyzed via stimulation of PKA and activation of cAMP-dependent transcription factors that bind cAMP response elements (CREs) within the promoter regions of affected genes. In the myometrium, these CRE containing genes include beta2-adrenoceptor, cyclo-oxygenase 2, oxytocin receptor, and connexin-43. In preliminary investigations, we reported the differential expression of members of the cAMP bZIP protein family in the myometrium during pregnancy and labor. In this present study, we have now identified and functionally characterized these proteins with respect to myometrial gene expression. We report the identification of a 39,000 mol wt CRE response element modulator protein (CREM)tau2alpha protein having both transactivation and transrepressor properties whose expression is sequentially decreased in the myometrium during gestation and parturition. In contrast, expression of a myometrial 28,000 mol wt CREMalpha protein having only transrepressor actions progressively increased in the myometrium during pregnancy and labor. Similarly, we have isolated two ATF2 proteins of 60,000 and 28,000 mol wts, which represent full-length ATF2 and a novel small isoform of ATF2 that we have termed ATF2-small (ATF2-sm). These proteins are potent transactivators of gene expression and appear to be spatially expressed within the myometrium of the upper and lower uterine regions. The identification and functional characterization of these basic region/leucine zipper proteins in the myometrium may provide further insight into the molecular mechanisms regulating uterine activity during fetal maturation and parturition.

Activating Transcription Factor 2↗