Development of haemostatic decontaminants for the treatment of wounds contaminated with chemical warfare agents. 2: evaluation of in vitro topical decontamination efficacy using undamaged skin.

The risk of penetrating, traumatic injury occurring in a chemically contaminated environment cannot be discounted. Should a traumatic injury be contaminated with a chemical warfare (CW) agent, it is likely that standard haemostatic treatment options would be complicated by the need to decontaminate the wound milieu. Thus, there is a need to develop haemostatic products that can simultaneously arrest haemorrhage and decontaminate CW agents. The purpose of this study was to evaluate a number of candidate haemostats for efficacy as skin decontaminants against three CW agents (soman, VX and sulphur mustard) using an in vitro diffusion cell containing undamaged pig skin. One haemostatic product (WoundStat™) was shown to be as effective as the standard military decontaminants Fuller's earth and M291 for the decontamination of all three CW agents. The most effective haemostatic agents were powder-based and use fluid absorption as a mechanism of action to sequester CW agent (akin to the decontaminant Fuller's earth). The envisaged use of haemostatic decontaminants would be to decontaminate from within wounds and from damaged skin. Therefore, WoundStat™ should be subject to further evaluation using an in vitro model of damaged skin.

Development of haemostatic decontaminants for the treatment of wounds contaminated with chemical warfare agents. 1: evaluation of in vitro clotting efficacy in the presence of certain contaminants.

The treatment of penetrating, haemorrhaging injuries sustained within a hazardous environment may be complicated by contamination with toxic chemicals. There are currently no specific medical countermeasures for such injuries. Haemostats with an absorbent mechanism of action have the potential to simultaneously stop bleeding and decontaminate wounds. However, a primary requirement of a 'haemostatic decontaminant' is the retention of clotting function in the presence of chemical contaminants. Thus, the aim of this study was to investigate the haemostatic efficacy of seven commercially available haemostats in the presence of toxic chemicals (soman, VX, sulphur mustard, petrol, aviation fuel and motor oil). Clot viscosity was assessed ex vivo using thrombelastography following treatment of pig blood with: (i) toxic chemical; (ii) haemostat; or (iii) haemostat in combination with toxic chemical. Several contaminants (VX, petrol and GD) were found to be pro-haemostatic and none had an adverse effect on the rate with which the test products attained haemostasis. However, the total clot strength for blood treated with certain haemostats in the presence of sulphur mustard, soman and petrol was significantly decreased. Three test products failed to demonstrate haemostatic function in this ex vivo (thrombelastography) model; this was tentatively ascribed to the products achieving haemostasis through a tamponade mechanism of action, which can only be replicated using in vivo models. Overall, this study has identified a number of commercial products that may have potential as haemostatic decontaminants and warrant further investigation to establish their decontaminant efficacy.

Silver and nanoparticles of silver in wound dressings: a review of efficacy and safety.

Wound infections present a significant clinical challenge, impacting on patient morbidity and mortality, with significant economic implications. Silver-impregnated wound dressings have the potential to reduce both wound bioburden and healing time. The silver ion Ag+ is the active antimicrobial entity; it can interfere with thiol (-SH) groups and provoke the generation of reactive oxygen species (ROS), a major contributor to its antibacterial efficacy. Recently, silver nanoparticles have gained considerable interest in wound bioburden reduction and in anti-inflammation, as they can release Ag+ ions at a greater rate than bulk silver, by virtue of their large surface area. If released from dressings, they also have the potential to cross biological compartments. This review aims to consolidate recent findings as to the efficacy and safety of different formulations of silver used as an antiseptic agent in dressings, summarising the features of silver nanomaterials, with particular attention to the dose-dependencies for biological effects, highlighting the need for information on their uptake and potential biological effects.

Induction and progression of cholangiofibrosis in rat liver injured by oral administration of furan.

Cholangiofibrosis is a structural anomaly that precedes the development of cholangiocarcinoma in some rodent models. In this article, the authors examine the contribution of the epithelial and mesenchymal cells in the pathogenesis of this complex lesion. Furan was administered to rats by gavage in corn oil at 30 mg/kg b.w. (five daily doses per week) and livers were sampled between eight hr to three months. Characteristically the administration of furan caused centrilobular injury, and restoration was accomplished by proliferation of hepatocytes. Some areas of the liver were, however, more severely affected, and here, injury extended into portal and capsular areas, which resulted in a rapid proliferation of ductular cells that extended into the parenchyma accompanied by a subtype of liver fibroblasts. These ductules either differentiated into hepatocytes, with loss of the associated fibroblasts, or progressed to form tortuous ductular structures that replaced much of the parenchyma, leading to cholangiofibrosis. Although it is unclear what determines the difference in the hepatic response, a loss of micro-environmental cues that instigate hepatocyte differentiation and termination of the hepatocyte stem cell repair response may be perturbed by continual furan administration that results in an irreversible expansile lesion that may mimic the features of cholangiocarcinoma.

Evidence of oxidative stress and associated DNA damage, increased proliferative drive, and altered gene expression in rat liver produced by the cholangiocarcinogenic agent furan.

Furan is a potent cholangiocarcinogen in rat by an as yet undefined mechanism. The risk to man remains unclear. Using a time-course stop study design, we have investigated the potential of furan to induce oxidative stress and DNA damage associated with inflammatory and regenerative responses in rat liver. Furan was administered via oral gavage (30 mg/kg b.w. 5 daily doses per week), and livers were analyzed at time points between eight hr and three months. A one-month recovery group previously treated for three months was also included. There was a marked association between CYP2E1 expression and DNA oxidation (8-oxo-dG) in areas of centrilobular hepatocyte necrosis seen after a single dose. After one-month recovery from three-month treatment, 8-oxo-dG was still observed in areas of furan-induced cholangiofibrosis. Furan-induced changes in the expression of various genes associated with oxidative stress, DNA damage, and cell cycle control were identified during treatment and recovery. We propose that furan-induced cholangiocarcinomas emerge from areas of cholangiofibrosis as a result of a combination of chronic, persistent indirect damage to DNA through oxygen radicals coupled with persistent proliferative signals, including loss of connexin 32, that act to convert this DNA damage to fixed mutations.

Multicenter study to assess potential hazards from exposure to lipid peroxidation products in soya bean oil from Trilucent breast implants.

In response to a Hazard Notice by the Medical Devices Agency of the UK in 2000 regarding the Trilucent breast implant (TBI), an expert panel was convened to implement a research program to determine whether genotoxic compounds were formed in the soybean oil filler (SOF) of TBIs and whether these could be released to produce local or systemic genotoxicity. The panel established a research program involving six laboratories. The program recruited 47 patients who had received TBIs (9 patients had received silicone implants previously). A reference group (REBI) of 34 patients who had exchanged either silicone (17 patients) implants (REBI-E) or patients (17) who were to receive primary implantation augmentation with silicone (REBI-PIA), and who were included as needed to increase either the pre- or post-explantation sample number. Of the 17 REBI-E patients, 5 had silicone implants and 12 had saline implants previously (prior to the last exchange). Investigation was undertaken before and after replacement surgery in the TBI patients and before and after replacement or augmentation surgery in the REBI patients. The pre- to post-operative sample interval was 8-12 weeks. Pre-operative samples were collected within 7 days prior to the operation. Information on a variety of demographic and behavioral features was collected. Biochemical and biological endpoints relating to genotoxic lipid peroxidation (LPO) products potentially formed in the SOF, and released locally or distributed systemically, were measured. The SOF of explanted TBIs was found to have substantial levels of LPO products, particularly malondialdehyde (MDA), and low levels of trans-4-hydroxy-2-nonenal (HNE) not found in unused implants. Mutagenicity of the SOF was related to the levels of MDA. Capsules that formed around TBIs were microscopically similar to those of reference implants, but MDA-DNA adducts were observed in capsular macrophages and fibroblasts of only TBI capsules. These cell types are not progenitors of breast carcinoma (BCa) and the location of the implants precludes LPO products reaching the mammary epithelial cells which are progenitors of BCa. Blood levels of LPO products were not increased in TBI patients compared to REBI patients and did not change with explantation. In TBI patients, white blood cells did not show evidence of increased levels of LPO-related aldehyde DNA adducts. In conclusion, based on a number of measured parameters, there was no evident effect that would contribute to breast or systemic cancer risk in the TBI patients, and the recommended treatment of TBI patients involving explantation was judged appropriate.

Hepatic transcriptomic profiles of European flounder (Platichthys flesus) from field sites and computational approaches to predict site from stress gene responses following exposure to model toxicants.

Genomic technologies offer opportunities to gain a more global assessment of the health status of an organism through an understanding of the functional pathways that are responding to pollutant exposure. We have developed a 13,000 clone cDNA toxicogenomics microarray for Platichthys flesus, the European flounder (EU-GENIPOL Project). We aimed to distinguish the origins of flounder taken from six sampling sites of different pollution status in Northern Europe according to their hepatic gene expression profile using bioinformatic approaches. To determine which gene expression differences may relate to pollutant impact, we have completed complementary laboratory exposures of flounder to selected toxicants and determined the associated gene expression profiles. Using multivariate variable selection coupled with a statistical modelling procedure (GALGO) we can predict geographical site but the accuracy is limited to specific sites. The search space for a combination of genes that effectively predicts class membership is very large, however, by combining the signatures derived from acute laboratory exposure to individual chemicals to limit the search space, a very accurate model for classification of all the different environmental sites was achieved. The final model utilised the expression profiles of 16 clones and validation with a qPCR array comprising these genes correctly assigned the site of origin for fish obtained from three of the sites in an independent sampling. These data would imply that the gene expression fingerprints obtained with these arrays are primarily attributable to variations in chemical pollutant responses at the different sites, indicating their potential utility in environmental impact assessment.

Different mechanisms of modulation of gap junction communication by non-genotoxic carcinogens in rat liver in vivo.

This is a comparative study of the mechanisms by which three different rodent non-genotoxic carcinogens modulate connexin-mediated gap junction intercellular communication in male rat liver in vivo. In the case of the peroxisome proliferating agent Wy-14,643, a non-hepatotoxic dose of 50mg/kg led to a marked loss of inter-hepatocyte dye transfer associated with a loss of both Cx32 and Cx26 protein expression. In contrast, p,p'-dichlorodiphenyltrichloroethane (DDT) at a non-hepatotoxic dose (25mg/kg) was not found to alter Cx32 or Cx26 expression or to produce a measurable Cx32 serine phosphorylation but did give a small, significant reduction of cell communication. Carbon tetrachloride (CCl(4)) did not affect cell communication (despite a small significant reduction of Cx32 content) at a non-hepatotoxic dose. Both loss of communication and Cx32 expression was observed only at a dose that caused hepatocyte toxicity as evidenced by increased serum alanine aminotransferase activity. Overall, the findings emphasise that loss of gap junctional communication in vivo can contribute to carcinogenesis by non-genotoxic carcinogens through different primary mechanism. In contrast to Wy-14,643 and DDT, the results with CCl(4) are consistent with a requirement for hepatotoxicity in its carcinogenic action.

Complex physiological traits as biomarkers of the sub-lethal toxicological effects of pollutant exposure in fishes.

Complex physiological traits, such as routine aerobic metabolic rate or exercise performance, are indicators of the functional integrity of fish that can reveal sub-lethal toxicological effects of aquatic pollutants. These traits have proved valuable in laboratory investigations of the sub-lethal effects of heavy metals, ammonia and various xenobiotics. It is not known, however, whether they can also function as biomarkers of the complex potential range of effects upon overall functional integrity caused by exposure to mixtures of chemicals in polluted natural environments. The current study used portable swimming respirometers to compare exercise performance and respiratory metabolism of fish exposed in cages for three weeks to either clean or polluted sites on three urban European river systems: the river Lambro, Milan, Italy; the rivers Blythe, Cole and Tame, Birmingham, UK; and the river Amstel, Amsterdam, The Netherlands. The UK and Italian rivers were variously polluted with high levels of both bioavailable heavy metals and organics, and the Amstel by mixtures of bioavailable organics at high concentrations. In both the UK and Italy, indigenous chub (Leuciscus cephalus) exposed to clean or polluted sites swam equally well in an initial performance test, but the chub from polluted sites could not repeat this performance after a brief recovery interval. These animals were unable to raise the metabolic rate and allocate oxygen towards exercise in the second trial, an effect confirmed in successive campaigns in Italy. Swimming performance was therefore a biomarker indicator of pollutant exposure in chub exposed at these sites. Exposure to polluted sites on the river Amstel did not affect the repeat swimming performance of cultured cloned carp (Cyprinus carpio), indicating either a species-specific tolerance or relative absence of heavy metals. However, measurements of oxygen uptake during swimming revealed increased rates of routine aerobic metabolism in both chub and carp at polluted sites in all of the rivers studied, indicating a sub-lethal metabolic loading effect. Therefore, the physiological traits of exercise performance and metabolic rate have potential as biomarkers of the overall sub-lethal toxic effects of exposure to complex mixtures of pollutants in rivers, and may also provide insight into why fish do not colonize some polluted environments.

Macromolecule oxidation and DNA repair in mussel (Mytilus edulis L.) gill following exposure to Cd and Cr(VI).

The oxidation of DNA and lipid was analysed in the marine mussel (Mytilus edulis) in response to exposure (10microg/l and 200microg/l) to cadmium (Cd) and chromium [Cr(VI)]. Concentration dependent uptake of both metals into mussel tissues was established and levels of gill ATP were not depleted at these exposure levels. DNA strand breakage in gill cells (analysed by the comet assay) was elevated by both metals, however, DNA oxidation [measured by DNA strand breakage induced by the DNA repair enzyme formamidopyrimidine glycosylase (FPG)] was not elevated. This was despite a statistically significant increase in both malondialdehyde and 4-hydroxynonenal - indicative of lipid peroxidation - following treatment with Cd. In contrast, both frank DNA stand breaks and FPG-induced DNA strand breaks (indicative of DNA oxidation) were increased following injection of mussels with sodium dichromate (10.4microgCr(VI)/mussel). The metals also showed differential inhibitory potential towards DNA repair enzyme activity with Cd exhibiting inhibition of DNA cutting activity towards an oligonucleotide containing 8-oxo-7,8-dihydro-2'-deoxyguanosine and Cr(VI) showing inhibition of such activity towards an oligonucleotide containing ethenoadenosine, both at 200microg/l. The metals thus show DNA damage activity in mussel gill with distinct mechanisms involving both direct and indirect (oxidative) DNA damage, as well as impairing different DNA repair capacities. A combination of these activities can contribute to adverse effects in these organisms.

Substrate characterisation of a recombinant sulfotransferase SULT1 and mRNA expression in chub (Leuciscus cephalus) tissues.

We have studied the role and regulation of sulfonation of xenobiotics and endogenous substrates in Leuciscus cephalus, an abundant and environmentally relevant freshwater fish. A sulfotransferase 1 (SULT1) cDNA and promoter region was cloned from chub liver and the cDNA expressed in Escherichia coli. The translated protein displayed 51% and 50% amino acid identity to mSULT1D1, hSULT1A1, respectively. We identified two conserved co-substrate binding motifs for 3'-phosphoadenosine 5'-phosphosulfate: RKGxxGDWKxxFT and YPKSGTxW. The recombinant SULT displayed a strong preference towards the isoflavones genistein (K(m)=1.7 microM) and daidzein (K(m)=4.4 microM) and lesser activity towards the endogenous substrate dopamine. Based on sequence identity and substrate preferences, the SULT was classified as SULT1,3. SULT1,3 mRNA expression was highest in the liver and kidney with low levels expressed in brain, gonad, and gill. Mature males displayed higher hepatic SULT1,3 mRNA expression compared to females. Analysis of the promoter region revealed several putative half palindromic estrogen response elements (ERE).

Activity of OGG1 variants in the repair of pro-oxidant-induced 8-oxo-2'-deoxyguanosine.

Cells are continuously exposed to damaging reactive oxygen species (ROS), which are produced from both endogenous and exogenous sources. 8-Oxodeoxyguanosine (8-oxodG) is an abundant base lesion formed during oxidative stress which, if not repaired, can give rise to G:C-->T:A transversions in DNA. The 8-oxoguanine DNA glycosylase-1 (OGG1)-initiated base excision repair (BER) pathway operates to remove 8-oxodG lesions. Ogg1 deletion and polymorphism may result in a hypermutator phenotype and susceptibility to oxidative pathologies including cancer. Limited and conflicting evidence exists regarding the repair capacity of a prevalent human OGG1 (hOGG1) polymorphism, the Cys326-hOGG1 variant. The formamidopyrimidine DNA glycosylase (FPG)-modified comet assay was used to investigate the ability of sodium dichromate, potassium bromate and Ro19-8022 (+light) to induce DNA damage in mogg1(-/-) null (KO) and wild-type (WT) mouse embryonic fibroblasts (MEFs) and to assess hOGG1 variant-initiated BER capacities under conditions of oxidative stress. Treatment of WT MEFs with these pro-oxidant agents induced direct DNA strand breaks in a concentration-dependent manner, whereas, identical treatment of KO MEFs produced no effect. In contrast, KO MEFs accumulated significantly more FPG-sensitive sites than WT MEFs. Expression of hOGG1 in KO MEFs restored the WT phenotype in response to all pro-oxidants tested. The results suggest OGG1-initiated BER generates direct DNA strand breaks detected by the conventional comet assay, thus it is important that researchers do not interpret these as direct damage per se but rather a reflection of the repair process. The data also indicate Cys326-hOGG1-initiated BER is transiently impaired with respect to Ser326-hOGG1 (wild-type)- and Gly326-hOGG1 (artificial)-initiated BER following pro-oxidant treatment, possibly via hOGG1 cysteine 326 oxidation. This finding suggests the homozygous cys326/cys326 genotype may be classified as a biomarker of disease susceptibility, which is in support of a growing body of epidemiological evidence.

Oxidative damage produced by Cr(VI) and repair in mussel (Mytilus edulis L.) gill.

This study has assessed DNA damage induced by oxidative stress and its subsequent repair in mussels. Gill was obtained from mussels collected from New Brighton, UK within 24 h and also after 1 month maintenance under laboratory conditions. The pro-oxidant sodium dichromate produced a statistically significant increase in DNA strand breaks (DSB) in these gill cells at both time points as measured by the COMET assay. The response was higher at 1 month in association with a higher concentration of GSH which is known to activate Cr(VI) producing reactive oxygen species. DSB were shown, through studies in wild type and OGG-1-null mouse fibroblasts, to be produced by repair enzymes in response to Cr(VI). In support of evidence for repair of oxidative DNA damage, we have also demonstrated for the first time repair activity in mussel gill towards 8-oxo-dG using an oligonucleotide cutting assay.

The multiple influences of glutathione on bromate genotoxicity: implications for the dose-response relationship.

Glutathione displays multiple roles in the oxidative genotoxicity of potassium bromate. On the one hand, reduced glutathione has a demonstrated role in the activation of bromate to species capable of oxidising DNA. However, if this activation should occur within the gut or extracellularly once bromate is absorbed, this may limit the ability of the chemical to oxidise cellular DNA in vivo. Moreover, glutathione may offer protection against the damaging species produced by its interaction with bromate. Finally, if bromate exposure of cells is sufficiently high to deplete glutathione, a secondary oxidative stress and associated DNA damage may occur. These observations would suggest non-linearity in the dose-response to DNA damage in vivo.

Seasonal variation in cytochrome P450 immunopositive protein levels, lipid peroxidation and genetic toxicity in digestive gland of the mussel Mytilus edulis.

The relationship between cytochrome P450 1A- and 2E-immunopositive proteins, lipid peroxidation and DNA strand breaks (SBs) was studied in Mytilus edulis digestive gland at different seasons and at different sites around the UK coast. Cytochrome P4501A (CYP1A)-immunopositive protein and DNA strand breaks were generally lowest in December but there was no correlation between PAH exposure (indicated by chemical measurement and CYP1A-immunopositive protein expression) and DNA strand breaks which was highest at the relatively non-polluted site (Port Quin). As with CYP1A, CYP2E1-immunopositive protein was maximal at most sites in May. Lipid peroxidation, in contrast, did not alter markedly throughout the year. In conclusion, DNA strand breakage was not correlated with any of the above parameters although it did correlate with "scope for growth" as did the inverse of PAH levels. The study highlights the need to establish the relative contribution of DNA damage and DNA repair processes to the production of DNA strand breaks and emphasises the need to consider seasonal variation in interpretation of biomarkers.

Gap junction communication dynamics and bystander effects from ultrasoft X-rays.

Gap junctions provide a route for small molecules to pass directly between cells. Toxic species may spread through junctions into 'bystander' cells, which may be exploited in chemotherapy and radiotherapy. However, this may be prevented by junction closure, and therefore an understanding of the dose-dependency of inhibition of communication and bystander effects is important. Low-energy ionising radiation (ultrasoft X-rays) provides a tool for the study of bystander effects because the area of exposure may be carefully controlled, and thus target cells may be clearly defined. Loss of gap junction-mediated intercellular communication between irradiated cells was dose-dependent, indicating that closure of junctions is proportional to dose. Closure was associated with hyperphosphorylation of connexin43. Inhibition of communication occurred in bystander cells but was not proportional to dose. Inhibition of communication at higher radiation doses may restrict the spread of inhibitory factors, thus protecting bystander cells. The reduction in communication that takes place in bystander cells was dependent on cells being in physical contact, and not on the release of signalling factors into the medium.

Activation of c-Jun N-terminal kinase in A549 lung carcinoma cells by sodium dichromate: role of dissociation of apoptosis signal regulating kinase-1 from its physiological inhibitor thioredoxin.

Changes in the components of the Jun N-terminal kinase (JNK) signalling pathway were investigated in human A549 lung carcinoma cells treated with sodium dichromate. Sodium dichromate (100 microM, 0-6h) failed to activate nuclear factor kappa B (NF-kappaB) as determined by a lack of nuclear translocation of p65 but resulted in Jun N-terminal kinase activation as assessed by phospho-Jun N-terminal kinase Western blotting in a dose-dependent (>25 microM) and time-dependent (>1h) manner. In addition, c-Jun, a downstream target of Jun N-terminal kinase signalling was also activated with a similar dose- and time-dependency at the level of both protein expression and degree of phosphorylation. In contrast, sodium dichromate treatment had no effect on levels of phospho-p38. Immunoprecipitation demonstrated that apoptosis signal regulating kinase-1 (ASK-1), an upstream activator of Jun N-terminal kinase was dissociated from its inhibitory partner thioredoxin (Trx) in response to sodium dichromate (100 microM, 4h) treatment. This treatment was also associated with a transient (2h) increase in cytosolic levels of thioredoxin but no nuclear translocation of thioredoxin was observed. In conclusion, sodium dichromate had a stimulatory effect on the Jun N-terminal kinase signalling pathway in A549 cells, resulting in activation of downstream effector molecules. We hypothesise that dissociation of apoptosis signal regulating kinase-1 from thioredoxin may be at least partially responsible for Jun N-terminal kinase activation.

A DNA expression array to detect toxic stress response in European flounder (Platichthys flesus).

As a first stage in developing a DNA array-based approach to investigating the effects of pollutants on an environmentally relevant European fish species, we have constructed a 160-gene custom microarray for European flounder. Degenerate primers were used to amplify 110 different fragments of stress-related and other genes from European flounder cDNA and genomic DNA. Additionally, 22 fragments were obtained by suppressive subtractive hybridisation (SSH). These fragments were cloned and sequenced, then, with additional control genes, used to create a cDNA microarray for flounder. After optimisation of the arraying process, hepatic mRNA was isolated from flounder caught in the polluted Tyne and relatively unpolluted Alde estuaries. Fluorescent cDNA probes were synthesised from the mRNA and used in dual-colour hybridisations to the microarray. A number of transcripts were differentially expressed between Tyne and Alde female flounder but these changes were not significant, due to high inter-individual variation. However, in comparisons between Tyne and Alde male flounder, 11 transcripts were found to significantly differ in expression (P<0.05). Seven transcripts were more highly expressed in the Tyne male fish (CYP1A, UDPGT, alpha-2HS-glycoprotein, dihydropyrimidine dehydrogenase, Cu/Zn SOD, aldehyde dehydrogenase and paraoxonase). Four transcripts (Elongation factor 1 (EF1), EF2, Int-6 and complement component C3) were found to be significantly less abundant in the Tyne male fish. Selected genes were assayed by real-time PCR, then normalised to alpha-tubulin. These assays confirmed the significance of the array results for CYP1A, UDPGT and EF1, but not for Cu/Zn SOD. This study provides a link between traditional single-gene biomarker studies and the emerging field of eco-toxicogenomics, demonstrating the utility of microarray studies on environmentally sampled, non-model organisms.

Characterisation of the connexin32 promoter and changes in response element complexes in rat liver and hepatocytes during culture associated with oxidative stress.

Hepatic gap junctional intercellular communication (GJIC), mediated principally by connexin 32, provides a mechanism for regulating multicellular activities between neighbouring cells. The control of Cx32 gene expression at the transcriptional level has been investigated in rat liver tissue and in primary rat hepatocytes during culture. Several response elements have been identified and characterised using the electrophoretic mobility shift assay. Nuclear protein extract prepared from rat primary hepatocytes cultured for 2 h gave a larger number of DNA-protein complexes than observed with extracts from liver in vivo, including complexes containing Sp1. In contrast, nuclear extracts prepared from primary rat hepatocytes cultured for 96 h, and subject to oxidative stress, gave altered DNA-protein complexes when compared to those from hepatocytes cultured for 2 h. These results indicate that culture conditions, known to cause a loss of connexin expression, can modulate the transcription of Cx32 in hepatocytes by affecting the regulatory trans/cis-interactions of redox-sensitive zinc finger proteins within the promoter.

Different levels of mussel (Mytilus edulis) DNA strand breaks following chronic field and acute laboratory exposure to polycyclic aromatic hydrocarbons.

Levels of polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene (B[a]P) were at least seven-fold higher in mussels sampled from a polluted site (Loch Leven, in Scotland, UK) compared to a nearby clean reference site (Loch Etive) throughout the year 2000. Levels of DNA strand breaks (alkaline COMET assay) using both gill and digestive gland nuclei were similar at both sites despite the difference in contaminant load (total PAH). In contrast, mussels collected from a reference site (Port Quin, Cornwall, UK) had an increase in DNA strand breaks in digestive gland cells following laboratory exposure to B[a]P-dosed Isochrysis galbana. However, after 14 days high dose (20 ppb-exposed diet) animals had returned to levels similar to the controls. There was no evidence of increased necrosis or apoptosis after treatments. The results from these two studies suggest that an adaptive response may prevent ongoing DNA damage in mussels exposed to high levels of B[a]P and PAH contamination.