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A total mixture of 29 persistent organic pollutants (POPs) modelled from Scandinavian blood concentrations was used to expose human A-498 kidney cells for 24 h over a concentration range spanning below to above blood level (1/10x, 1x, 50x, 100x, 500x). Its constituent submixtures (PFAA, Br, Cl) and co-mixtures (PFAA + Br, PFAA + Cl, Br + Cl) were also tested. Valinomycin (12 µM) was used as a cytotoxic comparative compound. Cell number (CN), nuclear area (NA), nuclear intensity (NI), mitochondrial membrane potential (MMP), and mitochondrial mass (MM) were assessed using high content analysis (HCA). Only the co-mixtures (PFAA + Cl, PFAA + Br) at 50x and 50x, 500x decreased CN, respectively. NI was increased by the total mixture at 500x and Cl mixture at all concentrations tested. MMP was increased by the total mixture at 100x and 500x, PFAA at 1x, Br + Cl and PFAA + Cl at 100x and 500x, respectively. MM was decreased by the total mixture at 500x. In contrast, valinomycin decreased CN and surviving cells showed a decrease in MMP and an increase in MM. In conclusion, POP exposure altered mitochondrial metabolism and induced cell death via an alternative mechanism to valinomycin. Only specific combinations of individual chemical classes, but not the total mixture, affected cell number.

The presence of environmental pollutants in our ecosystem may impose harmful health effects to wildlife and humans. Several of these toxic chemicals have a potential to interfere with the endocrine system. The adrenal cortex has been identified as the main target organ affected by endocrine disrupting chemicals. The aim of this work was to assess exposure effects of defined and environmentally relevant mixtures of chlorinated, brominated and perfluorinated chemicals on steroidogenesis, using the H295R adrenocortical cell line model in combination with a newly developed liquid chromatography tandem mass spectrometry (LC-MS/MS) method. By using this approach, we could simultaneously analyze 19 of the steroids in the steroid biosynthesis pathway, revealing a deeper insight into possible disruption of steroidogenesis. Our results showed a noticeable down-regulation in steroid production when cells were exposed to the highest concentration of a mixture of brominated and fluorinated compounds (10,000-times human blood values). In contrast, up-regulation was observed with estrone under the same experimental condition, as well as with some other steroids when cells were exposed to a perfluorinated mixture (1000-times human blood values), and the mixture of chlorinated and fluorinated compounds. Interestingly, the low concentration of the perfluorinated mixture alone produced a significant, albeit small, down-regulation of pregnenolone, and the total mixture a similar effect on 17-hydroxypregnenolone. Other mixtures resulted in only slight deviations from the control. Indication of synergistic effects were noted when we used a statistical model to improve data interpretation. A potential for adverse outcomes of human exposures is indicated, pointing to the need for further investigation into these mixtures.

Background In recent decades, the incidence of metabolic disorders has increased internationally. This increase has been linked to exposure to persistent organic pollutants (POPs) but little is known about the metabolic effects of realistic human exposure mixtures at relevant concentrations. Objectives In this study we tested if POPs, representing real life exposure profiles and concentrations, were able to disrupt development and functions of adipose tissue in a direct way. Methods The lipogenic potency of a POP mixture modelled on levels found in human blood as detected in the Scandinavian population was assessed. The Total mixture comprises 29 compounds divided over three groups: chlorinated (Cl), brominated (Br), and perfluorinated compounds (PFAA). Individual PFAA chemicals, the Total mixture, and sub-mixtures (Cl, Br, PFAA, Cl + Br, Cl + PFAA, and Br + PFAA) at five (× 1/10, × 1, × 50, × 100, and × 500) human blood levels were tested in an optimised high content analysis (HCA) 3T3-L1 adipogenesis assay. Results Individual PFAAs; perfluorohexanesulfonic acid (PFHxS), perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluoroundecanoic acid (PFUnDA) promoted lipid accumulation in 3T3-L1 cells. The Total mixture, and the Cl, PFAA, Cl + Br, and Cl + PFAA sub-mixtures, promoted adipogenic differentiation and lipid accumulation. Increased lipid accumulation promoted adipose tissue expansion. Conclusions To the authors knowledge, this is the first in vitro bioassay study assessing the adipogenic effects of POP mixtures modelled on real-life human exposure levels. The findings highlight that such exposures may alter adipose tissue development and function, thus potentially playing a role in the globally increasing escalation of metabolic disorders.

Primary cultures of cerebellar granule neurons (CGNs) derived from chicken embryos were used to explore the effects on developmental neurotoxicity by a complex defined mixture of persistent organic pollutants (POPs). Its chemical composition and concentrations were based on blood levels in the Norwegian/Scandinavian population. Perfluorooctane sulfonic acid (PFOS) alone, its most abundant compound was also evaluated. Different stages of CGNs maturation, between day in vitro (DIV) 1, 3, and 5 were exposed to the POP mixture, or PFOS alone. Their combination with glutamate, an excitatory endogenous neurotransmitter important in neurodevelopment, also known to cause excitotoxicity was evaluated. Outcomes with the mixture at 500x blood levels were compared to PFOS at its corresponding concentration of 20 µM. The POP mixture reduced tetrazolium salt (MTT) conversion at earlier stages of maturation, compared to PFOS alone. Glutamate-induced excitotoxicity was enhanced above the level of that induced by glutamate alone, especially in mature CGNs at DIV5. Glutathione (GSH) concentrations seemed to set the level of sensitivity for the toxic insults from exposures to the pollutants. The role of N-methyl-D-aspartate receptor (NMDA-R) mediated calcium influx in pollutant exposures was investigated using the non-competitive and competitive receptor antagonists MK-801 and CGP 39551. Observations indicate a calcium-independent, but still NMDA-R dependent mechanism in the absence of glutamate, and a calcium- and NMDA-R dependent one in the presence of glutamate. The outcomes for the POP mixture cannot be explained by PFOS alone, indicating that other chemicals in the mixture contribute its overall effect.

The ability of persistent organic pollutants (POPs) with endocrine disrupting properties to interfere with the developing reproductive system is of increasing concern. POPs are transferred from dams to offspring and the high sensitivity of neonates to endocrine disturbances may be caused by underdeveloped systems of metabolism and excretion. The present study aimed to characterize the effect of in utero and lactational exposure to a human relevant mixture of POPs on the female mammary gland, ovarian folliculogenesis and liver function in CD-1 offspring mice. Dams were exposed to the mixture through the diet at Control, Low or High doses (representing 0x, 5000x and 100 000x human estimated daily intake levels, respectively) from weaning and throughout mating, gestation, and lactation. Perinatally exposed female offspring exhibited altered mammary gland development and a suppressed ovarian follicle maturation. Increased hepatic cytochrome P450 enzymatic activities indirectly indicated activation of nuclear receptors and potential generation of reactive products. Hepatocellular hypertrophy was observed from weaning until 30 weeks of age and could potentially lead to hepatotoxicity. Further studies should investigate the effects of human relevant mixtures of POPs on several hormones combined with female reproductive ability and liver function.

Perfluoroalkyl acids (PFAAs) are persistent man-made chemicals, ubiquitous in nature and present in human samples. Although restrictions are being introduced, they are still used in industrial processes as well as in consumer products. PFAAs cross the blood-brain-barrier and have been observed to induce adverse neurobehavioural effects in humans and animals as well as adverse effects in neuronal in vitro studies. The sulfonated PFAA perfluorooctane sulfonic acid (PFOS), has been shown to induce excitotoxicity via the N-methyl-D-aspartate receptor (NMDA-R) in cultures of rat cerebellar granule neurons (CGNs). In the present study the aim was to further characterise PFOS-induced toxicity (1–60 μM) in rat CGNs, by examining interactions between PFOS and elements of glutamatergic signalling and excitotoxicity. Effects of the carboxylated PFAA, perfluorooctanoic acid (PFOA, 300–500 μM) on the same endpoints were also examined. During experiments in immature cultures at days in vitro (DIV) 8, PFOS increased both the potency and efficacy of glutamate, whereas in mature cultures at DIV 14 only increased potency was observed. PFOA also increased potency at DIV 14. PFOS-enhanced glutamate toxicity was further antagonised by the competitive NMDA-R antagonist 3-((R)-2-Carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) at DIV 8. At DIV 8, PFOS also induced glutamate release (9–13 fold increase vs DMSO control) after 1−3 and 24 h exposure, whereas for PFOA a large (80 fold) increase was observed, but only after 24 h. PFOS and PFOA both also increased alanine and decreased serine levels after 24 h exposure. In conclusion, our results indicate that PFOS at concentrations relevant in an occupational setting, may be inducing excitotoxicity, and potentiation of glutamate signalling, via an allosteric action on the NMDA-R or by actions on other elements regulating glutamate release or NMDA-R function. Our results further support our previous findings that PFOS and PFOA at equipotent concentrations induce toxicity via different mechanisms of action.

Perfluoroalkyl acids (PFAAs) are persistent compounds used in many industrial as well as consumer products. Despite restrictions, these compounds are found at measurable concentrations in samples of human and animal origin. In the present study we examined whether the effects on cell viability of two sulfonated and four carboxylated PFAAs in cultures of cerebellar granule neurons (CGNs), could be associated with deleterious activation of the N-methyl-d-aspartate receptor (NMDA-R). PFAA-induced effects on viability in rat CGNs and unstimulated PC12 cells were examined using the MTT assay. Cells from the PC12 rat pheochromocytoma cell line lack the expression of functional NMDA-Rs and were used to verify lower toxicity of perfluorooctanesulfonic acid (PFOS) in cells not expressing NMDA-Rs. Protective effects of NMDA-R antagonists, and extracellular as well as intracellular Ca2+ chelators were investigated. Cytosolic Ca2+ ([Ca2+]i) was measured using Fura-2. In rat CGNs the effects of the NMDA-R antagonists MK-801, memantine and CPP indicated involvement of the NMDA-R in the decreased viability induced by PFOS and perfluorohexanesulfonic acid (PFHxS). No effects were associated with the four carboxylated PFAAs studied. Further, EGTA and CPP protected against PFOS-induced decreases in cell viability, whereas no protection was afforded by BAPTA-AM. [Ca2+]i significantly increased after exposure to PFOS, and this increase was completely blocked by MK-801. In PC12 cells a higher concentration of PFOS was required to induce equivalent levels of toxicity as compared to in rat CGNs. PFOS-induced toxicity in PC12 cells was not affected by CPP. In conclusion, PFOS at the tested concentrations induces excitotoxicity in rat CGNs, which likely involves influx of extracellular Ca2+ via the NMDA-R. This effect can be blocked by specific NMDA-R antagonists.

The use of silver nanomaterials in everyday products, such as cosmetics, textiles, certain types of packaging, etc. is increasing, leading to their release into the environment, including aquatic ecosystems. This last point initiated this investigation on the toxicological effects of Ag nanoparticles (Ag NPs) in the aquatic model organism Danio rerio. For this purpose, zebrafish larvae were exposed to 20nm bare Ag NPs at different concentrations and AgNO3, used as a positive control for Ag+ ions toxicity, at the beginning of their foraging behaviour to determine adverse effects on fitness parameters. We used secondary ion mass spectrometry (SIMS) to determine the localization of Ag and transcriptomics (microarray) to determine the toxicity at the level of gene expression in fish larvae. Exposure to Ag NPs did not result in adverse effects on survival and growth of the fish. However, SIMS analysis showed that Ag NPs mainly concentrate around liver blood vessels and in the interstitial tissue between the intestine and the liver. Gene expression profiles revealed that AgNO3 and Ag NPs impacted common pathways, suggesting similar targets, such as the phototransduction system. However, the Ag NPs showed a broader set of genes impacted following the exposure, including the circadian clock regulation and the photoreception, suggesting specific particle-related effects in addition to those induced by ions.

Environmental exposure to persistent organic pollutants (POPs) has been suggested as a contributing factor for the increased rate of type 2 diabetes and obesity. A complex mixture of 29 POPs (Total mixture), based on human blood concentrations, was used to expose a glucagon-like peptide 1 (GLP-1) secreting enteroendocrine cell line (pGIP/neo: STC-1) in vitro for 3 and 24 h. Significant increases of GLP-1 occurred when cells were exposed to the Total mixture at ×500 blood levels. Six sub-mixtures representing chlorinated (Cl), brominated (Br), and perfluorinated chemicals (PFAA), and their combinations (Cl + Br, Cl + PFAA, Br + PFAA) were also tested at ×500. Secretion levels seen for these remained lower than the Total mixture, and the Br mixture had no effect. After 24 h, increased secretion was seen with all mixtures at ×1 blood levels. Cytotoxicity was present for ×100 and ×500 blood levels. When tested in a GLP-1 receptor translocation assay (U2OS-GLP1R-EGFP), neither agonistic nor antagonist effects on receptor internalization were seen for any of the mixtures. We conclude individual classes of POPs, alone or in combination, can affect GLP-1 secretion and may contribute as a molecular mechanism linking environmental toxicants and diabetes.

Persistent organic pollutants (POPs) are toxic substances, highly resistant to environmental degradation, which can bio-accumulate and have long-range atmospheric transport potential. Most studies focus on single compound effects, however as humans are exposed to several POPs simultaneously, investigating exposure effects of real life POP mixtures on human health is necessary. A defined mixture of POPs was used, where the compound concentration reflected its contribution to the levels seen in Scandinavian human serum (total mix). Several sub mixtures representing different classes of POPs were also constructed. The perfluorinated (PFC) mixture contained six perfluorinated compounds, brominated (Br) mixture contained seven brominated compounds, chlorinated (Cl) mixture contained polychlorinated biphenyls and also p,p'-dichlorodiphenyldichloroethylene, hexachlorobenzene, three chlordanes, three hexachlorocyclohexanes and dieldrin. Human hepatocarcinoma (HepG2) cells were used for 2h and 48h exposures to the seven mixtures and analysis on a CellInsight™ NXT High Content Screening platform. Multiple cytotoxic endpoints were investigated: cell number, nuclear intensity and area, mitochondrial mass and membrane potential (MMP) and reactive oxygen species (ROS). Both the Br and Cl mixtures induced ROS production but did not lead to apoptosis. The PFC mixture induced ROS production and likely induced cell apoptosis accompanied by the dissipation of MMP. Synergistic effects were evident for ROS induction when cells were exposed to the PFC+Br mixture in comparison to the effects of the individual mixtures. No significant effects were detected in the Br+Cl, PFC+Cl or total mixtures, which contain the same concentrations of chlorinated compounds as the Cl mixture plus additional compounds; highlighting the need for further exploration of POP mixtures in risk assessment.

This study describes the utilization of an LC-MS/MS based H295R assay to assess an environmentally relevant mixture of persistent organic pollutants (POPs). H295R cells were exposed to the POP mixture in two conditions stimulated with 10 μM forskolin and unstimulated. Most importantly, the unstimulated cells responded to the low concentration of the mixture with a significant down-regulation of dehydroepiandrosterone (DHEA). This response was not observed in forskolin-stimulated cells. In stimulated H295R cells, exposure to the highest concentration showed a trend towards induced production of mineralocorticoids and glucocorticoids, although this was not significant. On the other hand, in the same exposure concentration and condition, estrogen and androgen production tended to be down-regulated. In addition to these patterns of responses being different in the stimulated vs unstimulated condition, four steroids were not detectable in the unstimulated condition.

Perfluoroalkyl acids (PFAAs) are persistent compounds used in many industrial as well as consumer products. Despite restrictions, these compounds are found at measurable concentrations in samples of human and animal origin. In the present study we examined whether the effects on cell viability of two sulfonated and four carboxylated PFAAs in cultures of cerebellar granule neurons (CGNs), could be associated with deleterious activation of the N-methyl-d-aspartate receptor (NMDA-R). PFAA-induced effects on viability in rat CGNs and unstimulated PC12 cells were examined using the MTT assay. Cells from the PC12 rat pheochromocytoma cell line lack the expression of functional NMDA-Rs and were used to verify lower toxicity of perfluorooctanesulfonic acid (PFOS) in cells not expressing NMDA-Rs. Protective effects of NMDA-R antagonists, and extracellular as well as intracellular Ca

Seafood products, including fish and fish oils, are major sources of persistent organic pollutants (POPs) which may cause endocrine disruption related to reproductive dysfunction in males. Primary porcine neonatal Leydig cells were exposed to three extracts of POPs obtained from different stages in production of cod liver oil dietary supplement, in the absence and presence of luteinizing hormone (LH). No reduced viability was observed and all POP extracts showed increased testosterone and estradiol levels in unstimulated cells and decreased testosterone and estradiol secretion in LH-stimulated cells. A decrease in central steriodogenic genes including STAR, CYP11A1, HSD3B and CYP17A1 was obtained in both culture conditions with all POP extracts. We implicate both small differences in composition and concentration of compounds as well as "old" POPs to be important for the observed steroidogenic effects.

Zearalenone (ZEN) is a mycotoxin produced by Fusarium fungi. Once ingested, ZEN may be absorbed and metabolised to α- and β-zearalenol (α-ZOL, β-ZOL), and to a lesser extent α- and β-zearalanol (α-ZAL, β-ZAL). Further biotransformation to glucuronide conjugates also occurs to facilitate the elimination of these toxins from the body. Unlike ZEN and its metabolites, information regarding the estrogenic activity of these glucuronide conjugates in various tissues is lacking. ZEN-14-O-glucuronide, α-ZOL-14-O-glucuronide, α-ZOL-7-O-glucuronide, β-ZOL-14-O-glucuronide and β-ZOL-16-O-glucuronide, previously obtained as the major products from preparative enzymatic synthesis, were investigated for their potential to cause endocrine disruption through interference with estrogen receptor transcriptional activity. All five glucuronide conjugates showed a very weak agonist response in an estrogen responsive reporter gene assay (RGA), with activity ranging from 0.0001% to 0.01% of that of 17β-estradiol, and also less than that of ZEN, α-ZOL and β-ZOL which have previously shown estrogenic potencies of the order 17β-estradiol>α-ZOL>ZEN>β-ZOL. Confirmatory mass spectrometry revealed that any activity observed was likely a result of minor deconjugation of the glucuronide moiety. This study confirms that formation of ZEN and ZOL glucuronides is a detoxification reaction with regard to estrogenicity, serving as a potential host defence mechanism against ZEN-induced estrogenic activity.

The toxicity of long chained perfluoroalkyl acids (PFAAs) has previously been reported to be related to the length of the perfluorinated carbon chain and functional group attached. In the present study, we compared the cytotoxicity of six PFAAs, using primary cultures of rat cerebellar granule neurons (CGNs). Two perfluoroalkyl sulfonic acids (PFSAs, chain length C6 and C8) and four perfluoroalkyl carboxylic acids (PFCAs, chain length C8-C11) were studied. These PFAAs have been detected in human blood and the brain tissue of mammals. The cell viability trypan blue and MTT assays were used to determine toxicity potencies (based on LC50 values) after 24h exposure (in descending order): perfluoroundecanoic acid (PFUnDA)≥perfluorodecanoic acid (PFDA)>perfluorooctanesulfonic acid potassium salt (PFOS)>perfluorononanoic acid (PFNA)>perfluorooctanoic acid (PFOA)>perfluorohexanesulfonic acid potassium salt (PFHxS). Concentrations of the six PFAAs that produced equipotent effects after 24h exposure were used to further explore the dynamics of viability changes during this period. Therefore viability was assessed at 10, 30, 60, 90, 120 and 180min as well as 6, 12, 18 and 24h. A difference in the onset of reduction in viability was observed, occurring relatively quickly (30-60min) for PFOS, PFDA and PFUnDA, and much slower (12-24h) for PFHxS, PFOA and PFNA. A slight protective effect of vitamin E against PFOA, PFNA and PFOS-induced reduction in viability indicated a possible involvement of oxidative stress. PFOA and PFOS did not induce lipid peroxidation on their own, but significantly accelerated cumene hydroperoxide-induced lipid peroxidation. When distribution of the six PFAAs in the CGN-membrane was investigated using NanoSIMS50 imaging, two distinct patterns appeared. Whereas PFHxS, PFOS and PFUnDA aggregated in large hotspots, PFOA, PFNA and PFDA showed a more dispersed distribution pattern. In conclusion, the toxicity of the investigated PFAAs increased with increasing carbon chain length. For molecules with a similar chain length, a sulfonate functional group led to greater toxicity than a carboxyl group.

Polychlorinated biphenyls (PCB), synthetic, persistent organic pollutants (POP), are detected ubiquitously, in water, soil, air, and sediments, as well as in animals and humans. PCB are associated with range of adverse health effects, such as interference with the immune system and nervous system, reproductive abnormalities, fetotoxicity, carcinogenicity, and endocrine disruption. Our objective was to determine the effects of three structurally different PCB congeners, PCB118, PCB 126, and PCB 153, each at two concentrations, on the steroidogenic capacity and proteome of human adrenocortical carcinoma cell line cultures (H295R) . After 48 h of exposure, cell viability was monitored and estradiol, testosterone, cortisol and progesterone secretion measured to quantify steroidogenic capacity of the cells. Two-dimensional (2D) gel-based proteomics was used to screen for proteome alterations in H295R cells in response to the PCB. Exposure to PCB 118 increased estradiol and cortisol secretion, while exposure to PCB 153 elevated estradiol secretion. PCB 126 was the most potent congener, increasing estradiol, cortisol, and progesterone secretion in exposed H295R cells. Seventy-three of the 711 spots analyzed showed a significant difference in normalized spot volumes between controls (vehicle only) and at least one exposure group. Fourteen of these protein spots were identified by liquid chromatography with mass spectroscopy (LC-MS/MS). Exposure to three PCB congeners with different chemical structure perturbed steroidogenesis and protein expression in the H295R in vitro model. This study represents an initial analysis of the effects on proteins and hormones in the H295R cell model, and additional studies are required in order to obtain a more complete understanding of the pathways disturbed by PCB congeners in H295R cells. Overall, alterations in protein regulation and steroid hormone synthesis suggest that exposure to PCB disturbs several cellular processes, including protein synthesis, stress response, and apoptosis.

While humans are exposed to mixtures of persistent organic pollutants (POPs), their risk assessment is usually based on a chemical-by-chemical approach. To assess the health effects associated with mixed exposures, knowledge on mixture toxicity is required. Several POPs are potential ligands of the Aryl hydrocarbon receptor (AhR), which involves in xenobiotic metabolism and controls many biological pathways. This study assesses AhR agonistic and antagonistic activities of 29 POPs individually and in mixtures by using Chemical-Activated LUciferase gene eXpression bioassays with 3 transgenic cell lines (rat hepatoma DR-H4IIE, human hepatoma DR-Hep G2 and human mammary gland carcinoma DR-T47-D). Among the 29 POPs, which were selected based on their abundance in Scandinavian human blood, only 4 exerted AhR agonistic activities, while 16 were AhR antagonists in DR-H4IIE, 5 in DR-Hep G2 and 7 in DR-T47-D when tested individually. The total POP mixture revealed to be AhR antagonistic. It antagonized EC50 TCDD inducing AhR transactivation at a concentration of 125 and 250 and 500 fold blood levels in DR-H4IIE, DR-T47-D and DR-Hep G2, respectively, although each compound was present at these concentrations lower than their LOEC values. Such values could occur in real-life in food contamination incidents or in exposed populations. In DR-H4IIE, the antagonism of the total POP mixture was due to chlorinated compounds and, in particular, to PCB-118 and PCB-138 which caused 90% of the antagonistic activity in the POP mixture. The 16 active AhR antagonists acted additively. Their mixed effect was predicted successfully by concentration addition or generalized concentration addition models, rather than independent action, with only two-fold IC50 underestimation. We also attained good predictions for the full dose-response curve of the antagonistic activity of the total POP mixture.

Alternariol (AOH) is a mycotoxin commonly produced by Alternaria alternata on a wide range of foods. Few studies to date have been performed to evaluate the effects of AOH on endocrine activity. The present study makes use of in vitro mammalian cellular based assays and gene expression to investigate the ability of AOH to act as an endocrine disruptor by various modes of action. Reporter gene assays (RGAs), incorporating natural steroid hormone receptors for oestrogens, androgens, progestagens and glucocorticoids were used to identify endocrine disruption at the level of nuclear receptor transcriptional activity, and the H295R steroidogenesis assay was used to assess endocrine disruption at the level of gene expression and steroid hormone production. AOH exhibited a weak oestrogenic response when tested in the oestrogen responsive RGA and binding of progesterone to the progestagen receptor was shown to be synergistically increased in the presence of AOH. H295R cells when exposed to 0.1–1000 ng/ml AOH, did not cause a significant change in testosterone and cortisol hormones but exposure to 1000 ng/ml (3.87 μM) AOH resulted in a significant increase in estradiol and progesterone production. In the gene expression study following exposure to 1000 ng/ml (3.87 μM) AOH, only one gene NR0B1 was down-regulated, whereas expression of mRNA for CYP1A1, MC2R, HSD3B2, CYP17, CYP21, CYP11B2 and CYP19 was up-regulated. Expression of the other genes investigated did not change significantly. In conclusion AOH is a weak oestrogenic mycotoxin that also has the ability to interfere with the steroidogenesis pathway.

α- and β-zearalenol (α-ZOL and β-ZOL, respectively) are metabolites of the mycotoxin zearalenone (ZEN). All three individual mycotoxins have shown to be biological active i.e. being estrogenic and able to stimulate cellular proliferation albeit at different strengths. In this work, cytosol protein expression was determined by using stable-isotope labelling by amino acids in cell culture (SILAC) upon exposure of α-ZOL and β-ZOL to the steroidogenesis cell model H295R. A total of 14 and 5 individual proteins were found to be significantly regulated by α-ZOL and β-ZOL, respectively. Interestingly, there were no common protein regulations by the metabolites or the parent mycotoxin ZEN. Furthermore, the regulated proteins were assigned to networks and groups of actions that also differed from one another suggesting that the three individual mycotoxins may have unique biological activities.

Breed differences in steroidogenic activity between primary Leydig cells derived from neonatal purebred Duroc and Norwegian Landrace boars were investigated in vitro. Concentrations of testosterone, estradiol, androstenone, cortisol and progesterone produced into the medium were determined. To explore underlying mechanisms the cellular expression of a suite of genes relevant in steroidogenesis was measured using reverse transcription and quantitative PCR (RT-qPCR). Basal steroid concentrations indicated a larger production capacity for steroids in unstimulated Duroc cells. Stimulation of the cells with LH increased steroid hormone secretion significantly in both breeds in a dose dependent manner. Testosterone and androstenone concentrations increased approximately 50- and 15-fold, respectively, whereas concentrations of estradiol, cortisol and progesterone increased to a lesser extent. At levels of maximal LH stimulation, absolute steroid concentrations were higher in Duroc. However, the relative increase in hormone concentrations was significantly lower in Duroc cells for estradiol, progesterone and cortisol when compared to basal levels. LH exposure was associated with a general up-regulation of mRNA levels for steroidogenic genes, stronger in Duroc than in Norwegian Landrace. This was in agreement with the higher absolute concentrations of steroid hormones measured in culture medium from the LH-stimulated Duroc Leydig cells, but did not concur with the fact that the relative increase in hormone production was lower in Duroc than in Norwegian Landrace Leydig cells for some hormones. It was concluded that breed differences in steroid hormone concentrations and gene expression between Norwegian Landrace and Duroc are complex and cannot be explained by a simple mechanism of action.

Perfluorinated compounds (PFCs) comprise a large class of man-made chemicals of which some are persistent and present throughout the ecosystem. This raises concerns about potential harmful effects of such PFCs on humans and the environment. In order to investigate the effects of potentially harmful PFCs on steroid hormone production, human adrenocortical H295R cells were exposed to three persistent PFCs including perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) at six different concentrations (6nM to 600μM) for 48h. Exposure to 600μM PFOS resulted in a dose-responsive increase in oestradiol as well as a smaller dose-responsive increase in progesterone and testosterone secretion measured using radioimmunoassay. The aromatase activity was not significantly altered by PFOS. Only small changes in hormone secretion were detected following exposure to PFOA and PFNA. Gene expression of CYP11A, quantified using qRT-PCR was decreased by all exposure doses of PFOA, whereas HMGR expression was decreased by 60nM PFNA. The viability markedly decreased by exposure to 600μM of PFOA or PFNA, but not PFOS. Flow cytometric analysis demonstrated a significant increase in apoptosis following exposure to PFNA at the highest concentration. We conclude that PFOS is capable of altering steroidogenesis in the H295R in vitro model by a mechanism other than changes in gene expression or activity of aromatase. Additionally, PFCs appear to differentially affect cell viability with induction of cell death via apoptosis at high doses of PFNA.

Endocrine-disrupting chemicals (EDCs) are capable of interfering with normal hormone homeostasis by acting on several targets and through a wide variety of mechanisms. Unwanted exposure to EDCs can lead to a wide spectrum of adverse health effects, especially when exposure is during critical windows of development. Feed and food are considered to be among the main routes of inadvertent exposure to EDCs, so there is an important need for efficient detection of EDCs in these matrices. We describe in vitro bioassays that can complement current analytical chemistry in order to detect unwanted EDCs and describe their action, emphasizing assays that can measure effects on nuclear receptor signaling or hormone production. We outline both validated and unvalidated in vitro assays currently available in the scientific community for detecting and studying the effects of EDCs, and discuss their possible role in the food-safety context. We conclude by identifying gaps in the current battery of in vitro assays available for EDCs and suggest future possibilities for development and validation.

Persistent organic pollutants (POPs) are toxic substances, highly resistant to environmental degradation, which can bio-accumulate and have long-range atmospheric transport potential (UNEP 2001). The majority of studies on endocrine disruption have focused on interferences on the sexual steroid hormones and so have overlooked disruption to glucocorticoid hormones. Here the endocrine disrupting potential of individual POPs and their mixtures has been investigated in vitro to identify any disruption to glucocorticoid nuclear receptor transcriptional activity. POP mixtures were screened for glucocorticoid receptor (GR) translocation using a GR redistribution assay (RA) on a CellInsight(TM) NXT High Content Screening (HCS) platform. A mammalian reporter gene assay (RGA) was then used to assess the individual POPs, and their mixtures, for effects on glucocorticoid nuclear receptor transactivation. POP mixtures did not induce GR translocation in the GR RA or produce an agonist response in the GR RGA. However, in the antagonist test, in the presence of cortisol, an individual POP, p,p'-dichlorodiphenyldichloroethylene (DDE), was found to decrease glucocorticoid nuclear receptor transcriptional activity to 72.5% (in comparison to the positive cortisol control). Enhanced nuclear transcriptional activity, in the presence of cortisol, was evident for the two lowest concentrations of perfluorodecanoic acid (PFOS) potassium salt (0.0147mg/ml and 0.0294mg/ml), the two highest concentrations of perfluorodecanoic acid (PFDA) (0.0025mg/ml and 0.005mg/ml) and the highest concentration of 2,2',4,4'-tetrabromodiphenyl ether (BDE 47) (0.0000858mg/ml). It is important to gain a better understanding of how POPs can interact with GRs as the disruption of glucocorticoid action is thought to contribute to complex diseases.

Evidence that some of the fungal metabolites present in food and feed may act as potential endocrine disruptors is increasing. Enniatin B (ENN B) is among the emerging Fusarium mycotoxins known to contaminate cereals. In this study, the H295R and neonatal porcine Leydig cell (LC) models, and reporter gene assays (RGAs) have been used to investigate the endocrine disrupting activity of ENN B. Aspects of cell viability, cell cycle distribution, hormone production as well as the expression of key steroidogenic genes were assessed using the H295R cell model. Cell viability and hormone production levels were determined in the LC model, while cell viability and steroid hormone nuclear receptor transcriptional activity were measured using the RGAs. ENN B (0.01-100μM) was cytotoxic in the H295R and LC models used; following 48h incubation with 100μM. Flow cytometry analysis showed that ENN B exposure (0.1-25μM) led to an increased proportion of cells in the S phase at higher ENN B doses (10μM) while cells at G0/G1 phase were reduced. At the receptor level, ENN B (0.00156-15.6μM) did not appear to induce any specific (ant) agonistic responses in reporter gene assays (RGAs), however cell viability was affected at 15.6μM. Measurement of hormone levels in H295R cells revealed that the production of progesterone, testosterone and cortisol in exposed cells were reduced, but the level of estradiol was not significantly affected. There was a general reduction of estradiol and testosterone levels in exposed LC. Only the highest dose (100μM) used had a significant effect, suggesting the observed inhibitory effect is more likely associated with the cytotoxic effect observed at this dose. Gene transcription analysis in H295R cells showed that twelve of the sixteen genes were significantly modulated (p0.05) by ENN B (10μM) compared to the control. Genes HMGR, StAR, CYP11A, 3βHSD2 and CYP17 were downregulated, whereas the expression of CYP1A1, NR0B1, MC2R, CYP21, CYP11B1, CYP11B2 and CYP19 were upregulated. The reduction of hormones and modulation of genes at the lower dose (10μM) in the H295R cells suggests that adrenal endocrine toxicity is an important potential hazard.

The mycotoxin alternariol (AOH) is an important contaminant of fruits and cereal products. The current study sought to address the effect of a non-toxic AOH concentration on the proteome of the steroidogenic H295R cell model. Quantitative proteomics based on stable isotope labeling by amino acids in cell culture (SILAC) coupled to 1D-SDS-PAGE-LC-MS/MS was applied to subcellular-enriched protein samples. Gene ontology (GO) and ingenuity pathway analysis (IPA) were further carried out for functional annotation and identification of protein interaction networks. Furthermore, the effect of AOH on apoptosis and cell cycle distribution was also determined by the use of flow cytometry analysis. This work identified 22 proteins that were regulated significantly. The regulated proteins are those involved in early stages of steroid biosynthesis (SOAT1, NPC1, and ACBD5) and C21-steroid hormone metabolism (CYP21A2 and HSD3B1). In addition, several proteins known to play a role in cellular assembly, organization, protein synthesis, and cell cycle were regulated. These findings provide a new framework for studying the mechanisms by which AOH modulates steroidogenesis in H295R cell model.

The nature of hormonal involvement in pubertal brain development has attracted wide interest. Structural changes within the brain that occur during pubertal development appear mainly in regions closely linked with emotion, motivation and cognitive functions. Using a sheep model, we have previously shown that peri-pubertal pharmacological blockade of gonadotropin releasing hormone (GnRH) receptors, results in exaggerated sex-differences in cognitive executive function and emotional control, as well as sex and hemisphere specific patterns of expression of hippocampal genes associated with synaptic plasticity and endocrine signaling. In this study, we explored effects of this treatment regime on the gene expression profile of the ovine amygdala. The study was conducted with 30 same-sex twin lambs (14 female and 16 male), half of which were treated with the GnRH agonist (GnRHa) goserelin acetate every 4th week, beginning before puberty, until approximately 50 weeks of age. Gene expression profiles of the left and right amygdala were measured using 8×15 K Agilent ovine microarrays. Differential expression of selected genes was confirmed by qRT-PCR (Quantitative real time PCR). Networking analyses and Gene Ontology (GO) Term analyses were performed with Ingenuity Pathway Analysis (IPA), version 7.5 and DAVID (Database for Annotation, Visualization and integrated Discovery) version 6.7 software packages, respectively. GnRHa treatment was associated with significant sex- and hemisphere-specific differential patterns of gene expression. GnRHa treatment was associated with differential expression of 432 (|logFC|>0.3, adj. p value

Oil pollution from various sources, including exploration, production and transportation, is a growing global concern. Of particular concern is the environmental impact of produced water (PW), the main waste discharge from oil and gas platforms. In this study, we have investigated the potential of polar hydrocarbon pollutants to disrupt or modulate steroidogenesis in vitro , using a human adrenocortical carcinoma cell line, the H295R assay. Effects of two of the major groups of compounds found in the polar fraction of crude oil and PW; alkylphenols (C 2 - and C 3 -AP) and naphthenic acids (NAs), as well as the polar fraction of PW as a whole has been assessed. Endpoints include hormone (cortisol, estradiol, progesterone, testosterone) production at the functional level and key genes for steroidogenesis (17β-HSD1, 17β-HSD4, 3β-HSD2, ACTHR, CYP11A1, CYP11B1, CYP11B2, CYP17, CYP19, CYP21, DAX1, EPHX, HMGR, SF1, STAR) and metabolism (CYP1A) at the molecular level. All compounds induced the production of both estradiol and progesterone in exposed H295R cells, while the C 3 -AP and NAs decreased the production of testosterone. Exposure to C 2 -AP caused an up-regulation of DAX1 and EPHX, while exposure to NAs caused an up-regulation of ACTHR. All compounds caused an up-regulation of CYP1A1. The results indicated that these hydrocarbon pollutants, including PW, have the potential to disrupt the vitally important process of steroidogenesis.

3-Methylsulfonyl-DDE (MeSO₂-DDE) is a potent adrenal toxicant formed from the persistent insecticide DDT. MeSO₂-DDE is widely present in human plasma, milk and fat, and in tissues of marine mammals. In the present study, we investigated endocrine-disrupting properties of MeSO₂-DDE in primary neonatal porcine Leydig cells. Unstimulated and LH-stimulated cells were exposed to MeSO₂-DDE at concentrations ranging from 0.6 to 20 μM for 48 h. Cell viability, hormone secretion and expression of steroidogenesis related genes were recorded. Secretion of testosterone and estradiol was increased in a concentration-dependent fashion in unstimulated Leydig cells, while in LH-stimulated cells, secretion of testosterone, estradiol and progesterone was decreased. The expression of important steroidogenic genes was down-regulated both in unstimulated and LH-stimulated cells. Notably, no significant impairment of cell viability occurred at any exposure except the highest concentration (20 μM) in LH-stimulated cells. This indicated that the effects on hormone secretion and gene expression were not caused by cytotoxicity. We conclude that the adrenal toxicant MeSO₂-DDE disrupts hormone secretion in a complex fashion in neonatal porcine Leydig cells. The different endocrine responses in unstimulated and LH-stimulated cells imply that the endocrine disruptive activity of MeSO₂-DDE is determined by the physiological status of the Leydig cells.

Ochratoxin A (OTA) is a mycotoxin and extrolite of fungi which has been reported in a range of foods. This study uses mammalian reporter gene assays (RGAs) with natural steroid receptors and the H295R steroidogenesis assay to assess the endocrine disrupting activity of OTA. At the receptor level, OTA (within a concentration range of 0.25–2500 ng/ml) did not induce an agonistic response in an oestrogen, androgen, progestagen or glucocorticoid RGA. An antagonistic effect was observed in all of the RGAs at the highest concentration tested (2500 ng/ml). However, while there was no significant cytotoxic effect observed in the MTT (thiazolyl blue tetrazolium bromide) cell viability assay at this concentration, there was a corresponding change in cell morphology which may be related to the resulting antagonistic effect. At the hormone production level, H295R cells were used as a steroidogenesis model and exposed to OTA (within a concentration range of 0.1–1000 ng/ml). Treatment of the cells with 1000 ng/ml OTA increased the production of estradiol (117 ± 14 ng/ml) over 3 times that of the solvent control (36 ± 9 pg/ml). Western blotting confirmed an increase in aromatase protein. Overall the results indicate that OTA does not appear to interact with steroid receptors but has the potential to cause endocrine disruption by interfering with steroidogenesis. This is the first study identifying the effect OTA may have on production of the steroid hormone estradiol.

Trichothecenes are a large family of chemically related mycotoxins. Deoxynivalenol (DON), T-2 and HT-2 toxins belong to this family and are produced by various species of Fusarium. The H295R steroidogenesis assay, regulation of steroidogenic gene expression and reporter gene assays (RGAs) for the detection of androgen, estrogen, progestagen and glucocorticoid (ant)agonist responses, have been used to assess the endocrine disrupting activity of DON, T-2 and HT-2 toxins. H295R cells were used as a model for steroidogenesis and gene expression studies and exposed with either DON (0.1-1000ng/ml), T-2 toxin (0.0005-5ng/ml) or HT-2 toxin (0.005-50ng/ml) for 48h. We observed a reduction in hormone levels in media of exposed cells following radioimmunoassay. Cell viability was determined by four colorimetric assays and we observed reduced cell viability with increasing toxin concentrations partly explaining the significant reduction in hormone levels at the highest toxin concentration of all three trichothecenes. Thirteen of the 16 steroidogenic genes analyzed by quantitative real time PCR (RT-qPCR) were significantly regulated (P

Mycotoxins are secondary fungal metabolites that can cause pathological, physiological, and/or biochemical alterations in other species, including higher vertebrates. Zearalenone (ZEN) is produced by the genus Fusarium and after ingestion via contaminated cereals, may lead to animal fertility problems and reproductive pathologies. The compound has endocrine disrupting effects with a strong estrogenic action. Current data indicates that pig (hyperestrogenism) is amongst the most susceptible to ZEN, whilst in humans, this mycotoxin is suspected to be a triggering factor for central precocious puberty development in girls. Biotransformation of ZEN forms the metabolites α-zearalenol (α-ZOL) and β-zearalenol (β-ZOL), which are also produced by Fusarium in cultures, but in lower concentrations than ZEN.

The mycotoxin zearalenone (ZEN) is a secondary metabolite of fungi which is produced by certain species of the genus Fusarium and can occur in cereals and other plant products. Reporter gene assays incorporating natural steroid receptors and the H295R steroidogenesis assay have been implemented to assess the endocrine disrupting activity of ZEN and its metabolites α-zearalenol (α-ZOL) and β-zearalenol (β-ZOL). α-ZOL exhibited the strongest estrogenic potency (EC(50) 0.022±0.001 nM), slightly less potent than 17-β estradiol (EC(50) 0.015±0.002 nM). ZEN was ~70 times less potent than α-ZOL and twice as potent as β-ZOL. Binding of progesterone to the progestagen receptor was shown to be synergistically increased in the presence of ZEN, α-ZOL or β-ZOL. ZEN, α-ZOL or β-ZOL increased production of progesterone, estradiol, testosterone and cortisol hormones in the H295R steroidogenesis assay, with peak productions at 10 μM. At 100 μM, cell viability decreased and levels of hormones were significantly reduced except for progesterone. β-ZOL increased estradiol concentrations more than α-ZOL or ZEN, with a maximum effect at 10 μM, with β-ZOL (562±59 pg/ml)>α-ZOL (494±60 pg/ml)>ZEN (375±43 pg/ml). The results indicate that ZEN and its metabolites can act as potential endocrine disruptors at the level of nuclear receptor signalling and by altering hormone production.

Endocrine disruptive effects have been frequently observed in patients using antiepileptic drugs (AEDs). Two different AEDs, valproate (VPA) and levetiracetam (LEV), were tested in forskolin-stimulated human adrenal carcinoma (H295R) cells to explore their effect on steroidogenesis. VPA has a long history as an anticonvulsant and is linked with many of the endocrine disorders associated with AED use. LEV is a newer AED, and no endocrine disruptive effects have been reported in humans to date.H295R cells, which are capable of full steroidogenesis, were stimulated with forskolin and exposed to either VPA or LEV for 48 h. Medium was collected and analyzed for hormone production. For the VPA-exposed cells, steroidogenic gene expression analysis was also conducted.VPA exposure resulted in a significant reduction in progesterone and estradiol (E2) production, whereas testosterone (T) levels remained unchanged. There were also significant alterations in expression level for most genes analyzed. LEV exposure resulted in a minor, but statistically significant, reduction in T and E2 production.Exposure of forskolin-stimulated H295R cells to VPA led to an increased T/E2 ratio through a significant decrease in estradiol production. Gene analysis suggested that VPA affects NR0B1 expression. NR0B1 inhibits promoters of other genes involved in steroidogenesis, and the altered expression of NR0B1 might explain the observed down-regulation in hormone production. The effects of LEV exposure on hormone secretion were not considered to be biologically significant.

Polychlorinated biphenyls (PCB) are ubiquitous environmental pollutants that have been linked to adverse health effects including endocrine disruption. This study compared the mono-ortho-substituted PCB 118 and di-ortho-substituted PCB 153 with the non-ortho-substituted PCB 126, for possible effects on steroid hormone production and on the expression of 10 genes encoding proteins involved in steroidogenesis. The H295R human adenocarcinoma cell line was used as an in vitro model. Cells were exposed for 48 h to solvent control (dimethyl sulfoxide, DMSO) or 6 different concentrations ranging from 40 pM to 4 muM of one of the three test compounds. All three congeners significantly increased the production of estradiol-17beta. PCB 118 produced a rise in progesterone and cortisol in a concentration-dependent manner, similar to PCB 126. Testosterone was significantly reduced in response to PCB 153 but not PCB 118 or PCB 126. All three congeners elevated aldosterone at the highest concentration tested. A significant increase was observed in CYP11B2 mRNA levels in cells exposed to the three congeners. In addition, PCB 126 upregulated CYP19, 3beta-HSD2, StAR, and HMGR mRNA levels at the highest concentration tested, and downregulated CYP21 at 40 nM. In conclusion, all three PCB congeners are capable of modulating steroidogenesis in H295R in a concentration-dependent manner, whereby the hormone profile following PCB 118 exposure resembles that of PCB 126. Where changes in gene expression profile are concerned, exposure to PCB 126 showed the greatest effects.

Objectives - To better understand the interaction of antiepileptic drugs and production of sex hormones, possible effects of valproate (VPA), levetiracetam (LEV) and carbamazepine (CBZ) on steroidogenesis were investigated in the human adrenal carcinoma cell line H295R. Materials and methods - H295R cells were exposed to different concentrations of VPA, LEV or CBZ for 48 h. Sex hormone concentrations and mRNA expression levels were analyzed via radioimmunoassay and quantitative real time (RT)-PCR, respectively. Results - In VPA-exposed cells estradiol levels decreased in a dose-dependent manner, while testosterone and progesterone levels were unaffected. Expression of 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), steroidogenic acute regulatory protein (StAR), CYP11a, CYP17, CYP21, 3βHSD2, 17βHSD1 was downregulated and expression of CYP11β2 was upregulated. No effect on sex hormone production was observed under influence of LEV or CBZ. Expression of StAR, CYP17, CYP19 and 3βHSD2 was downregulated in LEVexposed cells, and expression of HMGR, CYP11β2 and CYP17 was downregulated in CBZ-exposed cells. Conclusions - VPA exposure resulted in a decrease in estradiol levels and a general downregulation of expression of genes encoding for enzymes early in steroidogenesis. No consistent changes were seen with LEV or CBZ exposure.

Cell death via apoptosis is an important event involved in a number of immunological processes. Recently, apoptosis has been associated with oxidative stress in a number of cell systems. Here we assessed the inhibitory capacity of different antioxidants on UV- and drug-induced apoptosis in the human leukemic cell line, HL-60. We found that the oxygen radical scavenger, BHA, the radioprotector cysteamine and the metal chelators, pyrrolidinedithiocarbamate (PDTC), diethyldithiocarbamate (DEDTC), and dimethyldithiocarbamate (DMDTC), were able to significantly inhibit nuclear fragmentation and reduce the formation of apoptotic bodies in UV-irradiated human leukemic cells. Both BHA and PDTC were found to reduce DNA fragmentation as assessed by in situ DNA nick-end labelling and quantification thereof using fluorescence flow cytometry. In addition to inhibiting UV-induced apoptosis, PDTC was also capable of reducing the amount of apoptosis induced by a range of cytotoxic drugs, such as actinomycin-D, camptothecin, etoposide, and melphalan, whereas BHA and cysteamine were not as effective in these cases after more than four hours in culture when compared to PDTC. To further elucidate the working mechanism of PDTC, we have looked at the effect of PDTC on DNA fragmentation in isolated nuclei, under conditions that promote activation of endogenous endonuclease involved in apoptosis. In contrast to ZnCl2, a potent inhibitor of endonuclease activity, PDTC was unable to inhibit DNA-ladder formation in this assay. Taken together, these results indicate that oxygen radicals may have a central role to play in the induction of apoptosis and that dithiocarbamates can serve as potent inhibitors of apoptosis induced by a wide variety of stimuli.

The macrophage tropism of early HIV isolates1 suggests that monocyte-derived cells may be a more general target for various HIV quasi-species. The question is thus raised whether cells of the mononuclear phagocyte lineage may be the first cells in the body to be infected with HIV. At least three forms of HIV replication have been documented to occur in monocytes2 : (i) latent infections with viral DNA but no viral RNA, (ii) low permissive infections with numerous virions accumulated within intracellular vacuoles and (iii) highly replicative infections resulting in cytopathicity and formation of multinucleated giant cells. Both latently infected macrophages and low level infected macrophages may constitute a large intracellular reservoir for HIV in the body. In fact, according to a recent study3 extraordinary large numbers of latently infected CD4+ lymphocytes and macrophages can be detected throughout the lymphatic system from early to late stages of infection.

Using an in vitro monolayer assay (MIA) we analyzed the invasive behaviour of a panel of B-cell hybridomas prepared by the fusion of non-invasive, non-metastatic NSO plasmacytoma cells and normal murine B-cells. Interaction of these hybridomas with fibroblast-like monolayers consisted mostly of adhesion on top of the monolayers, whereas only a fraction of these cells penetrated through the monolayer. This is in sharp contrast with the highly invasive properties displayed by T-cell hybridomas. Whereas T-cell hybridomas highly infiltrated monolayers of rat hepatocyte in vitro, B-cell hybridomas neither adhered to nor infiltrated hepatocyte monolayers. We found a good correlation between the degree of adhesion of B-cell hybridomas to fibroblast-like monolayers and their metastatic capabilities upon i.v. injection into syngeneic animals. Unlike T-cell hybridomas which formed diffuse metastasis in liver and spleen, B-cell hybridomas generated nodular metastatic lesions. . When normal LPS-stimulated B-lymphocytes were tested in the fibroblast-MIA, only part of the population infiltrated the monolayers. This again contrasts with T-lymphocytes where a majority of the cells penetrated through the monolayers. These results suggest that (i) B-lymphocytes express invasive properties, albeit to a lesser extent than T-lymphocytes, (ii) non-invasive B-lymphoma cells can acquire invasiveness following cell fusion with a normal B-cell, (iii) these invasive properties contribute to the malignancy of the hybridomas when tested in recipient animals.

Cell lines differing in their malignant potential have been derived from the murine BW5147 T-cell lymphosarcoma. To evalute the involvement of chromosomal aberrations in tumor progression within this model, we have analyzed the karyotypes and the in vitro invasiveness of 13 related nonmetastatic and metastatic variants. Giemsa banding revealed the presence of several marker chromosomes, one of which was of particular importance. Depending on the cell line, four variants of this marker I were found: Marker Ia corresponds to two translocated chromosomes 3, marker Ib is a deleted Ia marker, marker Ic is a Ib translocated to a small unidentified chromosome fragment, and marker Id is a further deleted Ib marker. The Ia and Id markers were characteristic for the noninvasive, nonmetastatic lines, whereas the Ib and Ic markers predominated in the invasive, metastatic variants. The results suggest that metastasis-enhancing genes are located between the D and F1 band of mouse chromosome 3 and that metastasis-suppressing genes are located between the F1 and H band of the same chromosome.

Somatic hybridization of normal somatic cells with neoplastic cells has been widely adopted as a tool to identify chromosomes or genes involved in the suppression or expression of malignancy. Originally, the neoplastic trait appeared to be dominant (1,2) but now experimental results seem to indicate that fusion of transformed cells with normal cells results in hybrids that are, initially at least, non tumorigenic (3,4). Tumorigenic lines, when they arise, are thought to do so by chromosomal segregation and the loss of specific chromosomes (5,6). This suppression of in vivo growth capacity of tumorigenic lines has often been referred to as “suppression of malignancy” and recently it has been proposed that a group of recessive genes, the socalled “tumor suppressors” or “anti-oncogenes” are implicated in this process (7).