Chronic effects of perfluorooctanesulfonate exposure on immunotoxicity in adult male C57BL/6 mice

A paucity of data exists to corroborate the few studies that report immune suppression after exposure to perfluorooctanesulfonate (PFOS). In this study, adult male C57BL/6 mice were exposed to PFOS daily via gavage for 60 days [0, 0.5, 5, 25, 50, or 125 mg/kg total administered dose (TAD)]. The results showed that liver mass was significantly increased at ≥5 mg PFOS/kg TAD and in a dose-dependent manner. Lymphocyte proliferation and natural killer cell activity were altered in male mice. Plaque forming cell (PFC) response was suppressed beginning at 5 mg/kg TAD. Based on the liver mass and PFC response, the no observed adverse effect level and lowest observed adverse effect level for male mice exposed PFOS for 60 days was 0.5 and 5 mg/kg TAD, respectively. Measured PFOS serum concentrations at these dose levels were 0.674 ± 0.166 and 7.132 ± 1.039 mg/l, respectively. These results indicate that PFOS exposure can affect the immunity function in mice at levels approximately 50-fold for highly exposed human populations.     

Sub-chronic effect of perfluorooctanesulfonate (PFOS) on the balance of type 1 and type 2 cytokine in adult C57BL6 mice

As a ubiquitous and highly persistent environmental contaminant, the clear mechanisms to explain any perfluorooctanesulfonate (PFOS)-induced immunotoxicity are still unknown. This study here sought to examine the ability of PFOS to potentially perturb T-helper (T_H)-1 and T_H-2 cell cytokine secreting activities, as well as to cause shifts in antibody isotype levels, and possible mechanisms involved in PFOS-induced immunotoxicity. Adult male C57BL/6 mice were exposed to PFOS daily via gavage for 60 days [0, 0.5, 1, 5, 25, or 50 mg/kg total administered dose (TAD)]. One day after the final exposure, the ex vivo production of the T_H1-type cytokines (IL-2 and IFN-γ), T_H2-type (IL-4), and IL-10 cytokines by isolated splenocytes, serum levels of immunoglobulin (Ig) were assessed via ELISA or ELISPOT. The results showed that IL-4 secretion was increased at exposure ≥5 mg PFOS/kg TAD in a dose-dependent manner. PFOS exposure increased IL-10 but decreased IL-2 and IFN-γ formation markedly at 50 mg PFOS/kg TAD. Serum levels of sheep red blood cells (SRBC)-specific IgM synthesis decreased significantly with PFOS exposure in a dose-related manner; serum SRBC-specific IgG, IgG1, and IgE levels increased with 50 mg PFOS/kg TAD regimens. These results indicated that, after a long-term exposure to PFOS, a host’s immune state is likely to be characterized by a shift toward a more T_H2-like state that, in turn, may lead to enhancement of their humoral response and suppression of their cellular response at levels of upper range for occupationally exposed workers or approximately 150-fold for general human population.     

Teratology of 2,3,7,8-Tetrachlorodibenzo-p-dioxin in a Complex Environmental Mixture from the Love Canal

The organic phase of a leachate (OPL) from the Love Canal chemicaldump site contains more than 100 organic compounds including2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD). The teratogenicpotential of OPL was determined in two inbred and one hybridmouse strain which differ in their sensitivity to aromatic hydrocarbon(Ah) receptor-mediated toxicity. OPL was orally administeredin corn oil on Days 6–15 of gestation to C57BL/6J mice(Ah^b/ Ah^b) at doses of 0, 0.1, 0.3, 0.5, and 0.7 g kg^–1day^–1 and to DBA/ZJ (Ah^d/Ah^d) females, which were matedwith either DBA/2J or C57BL/6J males, at 0, 0.5, 1, and 2.0g kg^–1 day^–1. In C57BL/6J mice, which express ahigh-affinity Ah receptor that avidly binds TCDD, the ED50'sof OPL for cleft palate and hydronephrosis were 0.44 and 0.11g OPL kg^–1 day^–1, respectively. Maternal mortalitywas 5% at the highest dose. In DBA/2J fetuses, which expressa low-affinity receptor, neither treatment-related cleft palatenor hydronephrosis was induced by dose levels that caused 36%maternal mortality. In hybrid D2B6F1 fetuses, the incidenceof cleft palate reached only 8% at 2 g OPL kg^–1 day^–1but the ED50 for hydronephrosis was 0.76 g OPL kg^–1 day^–1.TCDD was similarly administered to pregnant C57BL/6J mice at0, 0.5, 1, 2, and 4 µg kg^–1 day^–1 and to DBA/2Jmice at 0, 0.5, 2, 4, and 8 µg kg^–1 day^–1.In C57BL/6J fetuses, the ED50's for cleft palate and hydronephrosiswere 4.6 and 0.73 µg TCDD kg^–1 day^–1, respectively.In DBA/2J fetuses the ED50's for cleft palate and hydronephrosiswere 15.0 and 6.4 µg TCDD kg^–1 day^–1, respectively.Both the OPL and TCDD caused maternal hepatomegaly and thymicatrophy in all strains, but increased only C57BL/6J fetal weights.OPL decreased the number of fetuses per C57BL/6J dam at thetwo highest doses but there were no other reproductive effectsin any of the groups. It was concluded that the OPL is teratogenicand that hydronephrosis is a sensitive measure of TCDD toxicityin a complex organic mixture. Based on the ED50's of OPL- andTCDD-induced cleft palate and hydronephrosis in the C57BL/6Jstrain, the OPL had TCDD equivalence of 6.6 and 10.5 ppm, respectively.These values compare closely with the chemical analysis of 3ppm. The results suggest that the teratologic effects are dueprimarily to the TCDD in the OPL and that these effects aremediated through the Ah receptor, but that the maternal thymicatrophy and hepatomegaly were due primarily to the non-TCDDcomponents of the OPL.     

Antiestrogenic effect of paradichlorobenzene in immature mice and rats

A significant increase/decrease in uterine and ovarian weights was occasionally seen in immature mice and rats subcutaneously administered paradichlorobenzene (PDCB) at doses of 22–67 mg/kg/day, but the results were not necessarily reproducible. PDCB at a dose of 800 mg/kg/day always reduced uterine and ovarian weights. Intraperitoneal PDCB at doses more than 400 mg/kg/day significantly inhibited the uterotrophic effect of β-estradiol (E2) in CD-1 (ICR) mice. E2-induced uterotrophy was dose-dependently prevented by 204–400 mg PDCB/kg/day in C57BL/6N (Ah responsive) mice but not DBA/2N (Ah non-responsive) mice. While PDCB did not bind to estrogen receptor (ER_α) up to 10⁻³ M. Hepatic ethoxyresorufin-O-deethylase in adult female C57BL/6N mice was induced by ip administration of PDCB. Induction activity of PDCB may be 10⁵–10⁶ times lower than that of 2,3,7,8-tetrachlorodibenzo-p-dioxin. These results suggest that PDCB is a weak antiestrogenic/antiuterotrophic compound possibly due to ER modulation through arylhydrocarbon receptor. This study presented at the 9th annual meeting of the Japanese Society of Endocrine Disrupters Research held from 11–12 November 2006 in Tokyo, Japan.     

Amyloid Precursor Protein Expression Modulates Intestine Immune Phenotype

Amyloid precursor protein (APP) is widely expressed across many tissue and cell types. Proteolytic processing of the protein gives rise to a plethora of protein fragments with varied biological activities. Although a large amount of data has been generated describing the metabolism of the protein in neurons, its role in regulating the phenotype of other cells remains unclear. Based upon prior work demonstrating that APP regulates the activation phenotype of monocytic lineage cells, we hypothesized that APP can regulate macrophage activation phenotype in tissues other than brain. Ileums of the small intestines from C57BL6/J wild type and APP^−/− mice were compared as a representative tissue normally associated with abundant macrophage infiltration. APP^−/− intestines demonstrated diminished CD68 immunoreactivity compared to wild type mice. This correlated with significantly less cyclooxygenase-2 (cox-2), CD68, CD40, CD11c, and βIII-tubulin protein levels. Peritoneal macrophages from APP^−/− mice demonstrated decreased in vitro migratory ability compared to wild type cells and diminished basal KC cytokine secretion. Whereas, APP^−/− intestinal macrophages had an increase in basal KC cytokine secretion compared to wild type cells. Conversely, there was a significant decrease in multiple cytokine levels in APP^−/− compared to wild type ileums. Finally, APP^−/− mice demonstrated impaired absorption and increased motility compared to wild type mice. These data demonstrate the APP expression regulates immune cell secretions and phenotype and intestinal function. This data set describes a novel function for this protein or its metabolites that may be relevant not only for Alzheimer’s disease but a range of immune-related disorders.     

Attenuation of basal and cocaine-enhanced locomotion and nucleus accumbens dopamine in cannabinoid CB1-receptor-knockout mice

Rationale  Effect of cannabinoid CB1 receptor deletion on cocaine’s actions is controversial. This is partly based on findings in CB1-receptor-knockout (CB1^−/−) mice with CD1 genetic background. Objectives  In the present study, we used CB1^−/− mice with a C57BL/6J genetic background to further investigate the role of CB1 receptors in cocaine’s action. Materials and methods  Locomotor activity was assessed using AccuScan locomotor chambers. Brain extracellular dopamine (DA) levels were measured by in vivo microdialysis and by fast-scan cyclic voltammetry in the nucleus accumbens (NAc). Results  CB1^−/− mice displayed a significant reduction in basal levels of locomotion and extracellular DA, as well as in cocaine-enhanced locomotion and extracellular DA, as compared to their wild-type (CB1^+/+) littermates. The reduction in basal and cocaine-enhanced DA appears to be related to a reduction in basal DA release, not to an increase in DA clearance, as indicated by fast-scan cyclic voltammetry in brain slices. Pharmacological blockade of CB1 receptors by SR141716 inhibited locomotion and NAc DA release in CB1^+/+ mice. Conclusions  The present findings suggest an important role for CB1 receptors in mediating cocaine’s behavioral and neurochemical effects.     

EBHU18, a novel derivative of fatty acid bile acid conjugates, prevents cholesterol gallstone formation in experimental mice

In this study, we tested whether the oral administration of EBHU18, one of the newly synthesized fatty acid bile acid conjugates (FABACs), was able to prevent the development of cholesterol gallstones. In the first study, gallstone-susceptible C57BL/6 mice were fed a lithogenic diet for 8?weeks, and then treated with ursodeoxycholic acid (UDCA, 10?mg?kg^?1?day^?1, i.g.), EBHU18-L (0.5?mg?kg^?1?day^?1 i.g.), or EBHU18-H (3?mg?kg^?1?day^?1 i.g.). In the second study, C57BL/6 mice were fed the lithogenic diet for 8?weeks and then treated with EBHU18 at a daily dose of 3?mg (EBHU18-H) or 0.5?mg (EBHU18-L) or with 10?mg of UDCA for another 8?weeks. Pre-treatment or post-treatment with EBHU18 at 3?mg?kg^?1?day^?1 significantly decreased gallstone formation and the fatty liver score. In the first study, EBHU18-H significantly decreased gallstone formation compared with the control animals. The fatty liver score decreased from a mean of 1.6?±?1.02 in the controls to 0.5?±?0.67 in the EBHU18-L group (P?<?0.05) and 0.3?±?0.64 in the EBHU18-H group (P?<?0.01). In the second study, the drug significantly lowered the gallstone formation rate in the EBHU18-H group. The fatty liver score decreased from a mean of 1.6?±?0.98 in the controls to 0.67?±?0.90 in the EBHU18-L group (P?<?0.05) and 0.4?±?0.74 in the EBHU18-H group (P?<?0.01). EBHU18 can prevent and reduce gallstone formation and/or fatty liver and can be developed as a potential therapeutic candidate for anti-gallstone therapy.     

Differential effects of peripubertal exposure to perfluorooctanoic acid on mammary gland development in C57Bl/6 and Balb/c mouse strains

Perfluorooctanoic acid (PFOA), a common and persistent industrial byproduct detected in human sera, has raised health concerns. PFOA is detrimental to lactational function and postnatal mammary gland development in CD-1 mice after gestational exposure. We have examined the peripubertal period (21 through 50 days of age) as an important window of mammary gland susceptibility to environmental exposures that may affect breast cancer risk later in life. The effects of PFOA (0.1–10 mg/kg BW) were examined in Balb/c and C57BL/6 mice. PFOA treatment caused hepatocellular hypertrophy and delayed vaginal opening in both mouse strains. While Balb/c mice exhibited only inhibition of mammary gland and uterine development (5, 10 mg/kg), C57BL/6 mice exhibited stimulatory effects in both organs at low dose (5 mg/kg) and inhibition at higher dose (10 mg/kg). This underscores the need for caution when drawing conclusions about the effects of PFOA and possibly other environmental pollutants on the basis of studies in a single mouse strain.     

Discrimination and self-administration of nicotine by inbred strains of mice

These studies aim to characterize the discriminative stimulus effects of nicotine in two inbred strains of mice that differ in many pharmacological responses, and to investigate the feasibility of IV self-administration studies with nicotine in one of the strains. For discrimination studies, three groups of C57BL/6 and one group of DBA/2 mice were trained in a two-lever operant conditioning paradigm with a tandem VI-30″ FR-10 schedule of food reinforcement. After 40 training sessions, accuracy reached 57.5, 77.5 and 90.0% in C57BL/6 mice trained with (–)-nicotine (SC) in doses of 0.4, 0.8 and 1.6 mg/kg, respectively (n = 8). DBA/2 mice trained with 0.8 mg/kg nicotine attained similar (73.3%) accuracy (n = 9). Results from extinction tests showed that all groups of mice yielded orderly dose-response curves for nicotine (0.03–1.6 mg/kg), but stimulus control remained notably weaker for the mice trained with 0.4 mg/kg nicotine than for any other group. Overall rates of responding in the undrugged state were lower for DBA/2 than for C57BL/6 mice; DBA/2 mice were also slightly less sensitive than C57BL/6 mice to the response rate-reducing effect of nicotine. The nicotine antagonist mecamylamine (1.5 mg/kg SC) blocked the discriminative stimulus effect of the training dose of nicotine in all groups. The results of the IV self-administration study suggest that nicotine (0.1 mg/kg) can serve as a positive reinforcer in drug–naive C57BL/6J mice (n = 13). Behaviour maintained by 0.1 mg/kg nicotine injections was significantly greater than behaviour maintained by vehicle injections, and it was maintained under an intermittent schedule of reinforcement (FR4). The methods described provide possible approaches for genetic analyses of strain differences in sensitivity to the discriminative and reinforcing stimulus properties of nicotine. Received: 11 April 1998/Final version: 28 June 1998     

Subchronic effects of perfluorooctanesulfonate exposure on inflammation in adult male C57BL/6 mice

Previous studies indicate that exposure to perfluorooctanesulfonate (PFOS), a ubiquitous and highly persistent environmental contaminant, induces immunotoxicity in mice. However, few studies have specifically assessed the effects of PFOS on inflammation. This study utilized a standard 60‐day oral exposure period to assess the effects of PFOS on the response of inflammatory cytokines [tumor necrosis factor α (TNF‐α), interleukin‐1 β (IL‐1β), and interleukin‐6 (IL‐6)]. Adult male C57BL/6 mice were dosed daily by oral gavage with PFOS at 0, 0.0083, 0.0167, 0.0833, 0.4167, 0.8333 or 2.0833 mg/kg/day to yield a targeted Total Administered Dose (TAD) over 60 days of 0, 0.5, 1, 5, 25, 50, or 125 mg PFOS/kg, respectively. The percentage of peritoneal macrophages (CD11b⁺ cells) was significantly increased at concentrations ≥1 mg PFOS/kg TAD in a dose‐dependent manner. Ex vivo IL‐1β production by peritoneal macrophages was elevated substantially at concentrations of ≥5 mg PFOS/kg TAD. Moreover, PFOS exposure markedly enhanced the ex vivo production of TNF‐α, IL‐1β and IL‐6 by peritoneal and splenic macrophages when stimulated either in vitro or in vivo with lipopolysaccharide (LPS). The serum levels of these inflammatory cytokines observed in response to in vivo stimulation with LPS were elevated substantially by exposure to PFOS. PFOS exposure elevated the expression of pro‐inflammatory cytokines TNF‐α, IL‐1β, IL‐6, and proto‐oncogene, c‐myc, in the spleen. These data suggest that exposure to PFOS modulates the inflammatory response, and further research is needed to determine the mechanism of action. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

Pharmacokinetics of dihydroartemisinin following oral artesunate treatment of pregnant women with acute uncomplicated falciparum malaria

Objective To determine the pharmacokinetic properties of dihydroartemisinin (DHA) following oral artesunate treatment in women with recrudescent multi-drug resistant falciparum malaria, in the second and third trimesters of pregnancy.Methods Serial plasma concentrations of artesunate and DHA were measured in 24 women after the final dose of a 3 day treatment with artesunate (4 mg kg⁻¹ day⁻¹) and atovaquone (20 mg kg⁻¹ day⁻¹) plus proguanil (8 mg kg⁻¹ day⁻¹), daily. Conventional non-compartmental modelling and a population one-compartment pharmacokinetic model were applied to the data.Results Artesunate was very rapidly eliminated. For DHA the median [90% range] estimate of oral clearance (CI/F) was 4.0 [0.8–20.7] l hour⁻¹ kg⁻¹, total apparent volume of distribution (Vd/f) was 3.4 [0.9–60.7] l/kg, and terminal elimination half-life was 1.0 [0.6–2.4] h.Conclusion The kinetics of DHA are modified by pregnancy. The plasma levels of the active antimalarial metabolite DHA are lower than reported previously in non-pregnant adults. Dose-optimisation studies in pregnant women are needed.     

The effect of maternal exposure to di‐(2‐ethylhexyl)‐phthalate on fetal cardiac development in mice

Accumulating evidence has suggested a link between maternal di‐(2‐ethylhexyl)‐phthalate (DEHP) exposure and various developmental abnormalities. However, the evidence regarding the effect of maternal DEHP exposure on fetal cardiac development is scarce. The present study aimed to determine the effect of maternal DEHP exposure on fetal cardiac development in mice and explore the possible involved mechanism preliminarily. The C57BL mice were randomly divided into four groups: the vehicle group (corn oil, n = 10), 250 mg kg^–1 DEHP group (n = 15), 500 mg kg^–1 DEHP group (n = 20) and 1 g kg^–1 DEHP group (n = 20). Pregnant dams in different group received respective intervention by gavage once daily from embryonic day (E)6.5 to E14.5. Maternal weights were monitored every day and samples were collected at E15.5. Hematoxylin and eosin staining was used to examine fetal cardiac malformations. Real‐time quantitative polymerase chain reaction and western blot were applied to detect peroxisome proliferator‐activated receptor (PPAR)α/PPARγ/Nkx2.5/Gata4/Tbx5/Mef2c/Chf1 mRNA and protein expression, respectively. Maternal DEHP exposure significantly decreased maternal body weight, fetal weight and placental weight, and remarkably elevated fetal cardiac malformations rate. The phenotypes of cardiac anomalies mainly include septal defects, ventricular myocardium noncompaction and cardiac hypoplasia. Higher doses DEHP (500 mg kg^–1 and 1 g kg^–1) could significantly decreased fetal cardiac Gata4/Mef2c/Chf1 expression, while PPARγ expression was upregulated. Maternal exposure to higher doses of DEHP could result in fetal cardiac development malformations in mice and it might have resulted from the inhibition of cardiac GATA4/Mef2c/Chf1 expression via PPARγ activation.     

Further characterization of the discriminative stimulus properties of the atypical antipsychotic drug clozapine in C57BL/6 mice: role of 5-HT2A serotonergic and α1 adrenergic antagonism

Rationale  The discriminative stimulus properties of the atypical antipsychotic drug (APD) clozapine (CLZ) have recently been studied in C57BL/6 mice, a common background strain for genetic alterations. However, further evaluation is needed to fully characterize CLZ’s discriminative cue in this strain of mice. Objectives  The objectives of the study were to confirm the previous findings using a shorter pretreatment time and to further characterize the receptor mechanisms mediating the discriminative stimulus properties of CLZ by testing APDs, selective ligands, and N-desmethylclozapine (CLZ’s major metabolite) in C57BL/6 mice. Materials and methods  C57BL/6 male mice were trained to discriminate 2.5 mg/kg CLZ (s.c.) from vehicle in a two-lever drug discrimination task. Results  Generalization testing with CLZ yielded an ED₅₀ = 1.19 mg/kg. Substitution testing with APDs showed that the atypical APDs quetiapine, sertindole, zotepine, iloperidone, and melperone fully substituted for CLZ (≥80% CLZ-appropriate responding), but aripiprazole did not. The typical APDs chlorpromazine and thioridazine substituted for CLZ (fluphenazine and perphenazine did not). The serotonin (5-HT) _2A antagonist M100907 and the α₁-adrenoceptor antagonist prazosin fully substituted for CLZ. The H₁ histaminergic antagonist pyrilamine, dopamine agonist amphetamine, and the selective serotonin reuptake inhibitor fluoxetine did not substitute for CLZ. While N-desmethylclozapine did not substitute for CLZ when tested alone, N-desmethylclozapine plus a low dose of CLZ combined in an additive manner produced full substitution. Conclusions  CLZ’s discriminative cue in C57BL/6 mice is a “compound” cue mediated in part by antagonism of 5-HT_2A and α₁ receptors.     

The atrophy and changes in the cellular compositions of the thymus and spleen observed in mice subjected to short-term exposure to perfluorooctanesulfonate are high-dose phenomena mediated in part by peroxisome proliferator-activated receptor-alpha (PPARα)

We have previously shown that short-term, high-dose exposure of mice to the environmentally persistent perfluorooctanoate (PFOA) results in thymic and splenic atrophy and the attenuation of specific humoral immune responses. Here we characterize the effects of a 10-day treatment with different dietary doses (1–0.001%, w/w) of perfluorooctanesulfonate (PFOS), a similar fluorochemical, on the immune system of male C57BL/6 mice. At doses greater than 0.02%, PFOS induced clinical signs of toxicity in the animals, whereas at the concentration of 0.02%, this compound caused weight loss, hepatomegaly and atrophy of the thymus, spleen and adipose tissue without toxicity. With this latter dose, histopathological and flow-cytometric analysis revealed that (i) the thymic cortex was virtually depleted of cells; (ii) the total numbers of thymocytes and splenocytes were reduced by 84 and 43%, respectively; (iii) although all populations of thymocytes and splenocytes were smaller, the thymic CD4⁺CD8⁺ cells and the splenic B-lymphocytes were most decreased. These alterations resembled those evoked by analogous exposure to PFOA, but were less pronounced. At lower doses (less than 0.02%), PFOS induced hepatomegaly without affecting the thymus or spleen. Finally, comparison of male wild-type 129/Sv mice and the corresponding knock-outs lacking peroxisome proliferator-activated receptor-alpha (PPARα) indicated that these effects of PFOS are not strain-dependent. More importantly, hepatomegaly is independent of PPARα, the thymic changes are partially dependent on this receptor, and splenic responses are largely eliminated in its absence. Thus, immunomodulation caused by PFOS is a high-dose phenomenon partially dependent on PPARα.     

Interactive effects of ethanol and nicotine on learning in C57BL/6J mice depend on both dose and duration of treatment

Objective and rationale Alcohol and nicotine are commonly co-abused; one possible explanation for co-abuse is that each drug ameliorates the aversive effects of the other. Both drugs have dose-dependent effects on learning and memory. Thus, this study examined the interactive effects of acute ethanol and acute, chronic, or withdrawal from chronic nicotine on fear conditioning in C57BL/6J mice. Materials and methods Conditioning consisted of auditory conditioned stimulus-foot-shock unconditioned stimulus pairings. For acute studies, saline or ethanol, then saline or nicotine was administered before training, and saline or nicotine was also administered before testing. For chronic and withdrawal studies, saline or nicotine was administered chronically, and ethanol or saline was administered before training. Results Acute nicotine (0.09 mg/kg) reversed ethanol-induced deficits (1.0 and 1.5 g/kg) in contextual and cued fear conditioning, whereas a low dose of ethanol (0.25 g/kg) reversed nicotine (6.3 mg kg⁻¹ day⁻¹) withdrawal-induced deficits in contextual conditioning. Tolerance developed for the effects of nicotine on ethanol-induced deficits in conditioning and cross-tolerance between chronic nicotine and acute ethanol was seen for the enhancing effects of ethanol on conditioning. Conclusions The complex and sometimes polar actions of ethanol and nicotine on behavior may contribute to co-abuse of these drugs. Specifically, smoking may initially reduce the aversive effects of ethanol, but tolerance develops for this effect. In addition, low doses of alcohol may lessen nicotine withdrawal symptoms.     

Gestational Exposure to Perfluorooctane Sulfonate Suppresses Immune Function in B6C3F1 Mice

Perfluorinated alkyl acids (PFAAs) are used in a multitude ofapplications and are categorized as high-production volume chemicalsproduced in quantities exceeding 10,000 lbs/year. As a result,widespread exposure has been documented in adults, children,and infants. It is generally accepted that children are moresensitive to the effects of xenobiotic exposures during fetaland postnatal periods of development; therefore, considerableefforts are required to investigate the potential impact ofa model PFAA, perfluorooctane sulfonate (PFOS) on children'simmunological health. Using the pairing of female C57BL/6N micewith male C3H/HeJ, developmental immunotoxicity was evaluatedin B6C3F1 pups following oral maternal exposure to PFOS on gestationsdays 1–17. Exposure levels included 0.1, 1, and 5 mg/kg/dayPFOS. Natural killer (NK) cell activity, SRBC IgM plaque assay,CD4/8 lymphocytic subpopulations, nitrite production in peritonealmacrophages, and body/organ weights were evaluated at 4 and8 weeks of age in F1 pups. No significant dose-responsive changesin maternal or pup body weights, flow cytometry, or macrophagefunction were observed, yet hepatomegaly was indicated in F1male pups at 4 weeks of age. Functional deficits were not evidentuntil 8 weeks of age when NK cell function and IgM productionwere significantly decreased. When compared with females, malepups were more sensitive to the effects of PFOS thereby establishinga no observed adverse effect level and low observed adverseeffect level of 0.1 and 1.0 mg/kg/day (males only) followingmaternal PFOS exposure level, respectively. This study establishesthat the developing immune system is sensitive to the effectsof PFOS and results in functional deficits in innate and humoralimmunity detectable at adulthood.     

Differential susceptibility to acetaminophen-induced liver injury in sub-strains of C57BL/6 mice: 6N versus 6J

Mouse models of acetaminophen (APAP) hepatotoxicity are considered relevant for the human pathophysiology. The C57BL/6 strain is most popular because it is the background strain of gene knock-out mice. However, conflicting results in the literature may have been caused by sub-strain mismatches, e.g. C57BL/6J and C57BL/6N. This study was initiated to determine the mechanism behind the sub-strain susceptibility to APAP toxicity. C57BL/6N and C57BL/6J mice were dosed with 200 mg/kg APAP and sacrificed at different time points. C57BL/6N mice developed significantly more liver injury as measured by plasma ALT activities and histology. Although there was no difference in glutathione depletion or cytochrome P450 activity between groups, C57BL/6N had a higher glutathione disulfide-to-glutathione ratio and more APAP protein adducts. C57BL/6N showed more mitochondrial translocation of phospho-JNK and BAX, and more release of mitochondrial intermembrane proteins apoptosis-inducing factor (AIF), second mitochondria-derived activator of caspases (SMAC), which caused more DNA fragmentation. The increased mitochondrial dysfunction was confirmed in vitro as C57BL/6N hepatocytes had a more precipitous drop in JC-1 fluorescence after APAP exposure. Conclusion: C57BL/6N mice are more susceptible to APAP-induced hepatotoxicity, likely due to increased formation of APAP-protein adducts and a subsequent enhancement of mitochondrial dysfunction associated with aggravated nuclear DNA fragmentation.