Strain Differences In Susceptibility Research Articles

Toxoplasma GRA15 limits parasite growth in IFNγ-activated fibroblasts through TRAF ubiquitin ligases.

The protozoan parasite Toxoplasma gondii lives inside a vacuole in the host cytosol where it is protected from host cytoplasmic innate immune responses. However, IFNγ-dependent cell-autonomous immunity can destroy the vacuole and the parasite inside. Toxoplasma strain differences in susceptibility to human IFNγ exist, but the Toxoplasma effector(s) that determine these differences are unknown. We show that in human primary fibroblasts, the polymorphic Toxoplasma-secreted effector GRA15 mediates the recruitment of ubiquitin ligases, including TRAF2 and TRAF6, to the vacuole membrane, which enhances recruitment of ubiquitin receptors (p62/NDP52) and ubiquitin-like molecules (LC3B, GABARAP). This ultimately leads to lysosomal degradation of the vacuole. In murine fibroblasts, GRA15-mediated TRAF6 recruitment mediates the recruitment of immunity-related GTPases and destruction of the vacuole. Thus, we have identified how the Toxoplasma effector GRA15 affects cell-autonomous immunity in human and murine cells.

Mouse model demonstrates strain differences in susceptibility to opioid side effects

Individual differences have been observed in responses to opioid drugs, including common side effects. In this study, the inbred mouse strains A/J and C57BL/6J were used to determine whether their specific strain differences correlate with differences in susceptibility to respiratory depression and constipation. To measure the effects of morphine on respiration, morphine at 15 and 40 mg/kg was injected subcutaneously. Respiratory parameters were then measured 30 and 60 min later. To measure the effects on constipation, 5, 15, 40, and 60 mg/kg doses were administered subcutaneously three times daily for three days. Gastrointestinal transit distance was then measured using the charcoal bolus test. C57BL/6J mice showed a greater degree of change in several respiratory parameters, resulting in more pronounced respiratory depression. C57BL6J mice also showed significantly more constipation than A/J mice with 40 and 60 mg/kg morphine doses. This study demonstrates that the strain differences between A/J and C57BL/6J mice have a major effect on opioid-induced constipation and respiratory depression. These correlations are of great clinical interest, as they could lead to the development of methods for reducing side effects.

Strain- and sex-dependent pulmonary toxicity of waterpipe smoke in mouse.

Waterpipe smoking is emerging as a form of tobacco smoking, but its lung health/risks is not known. It has been shown that different mouse strains show differences in susceptibility to tobacco smoke. However, the effect of waterpipe smoke (WPS) exposure and strain differences in susceptibility to oxidative and inflammatory responses is not known. Here, we showed acute WPS exposure induced oxidative stress and inflammatory response in C57BL/6J and BALB/cJ mouse strains. WPS exposure induced inflammatory cell influx (neutrophils and T‐lymphocytes) in bronchoalveolar lavage fluid (BAL fluid), which varied among mouse strains. Proinflammatory cytokines release differed among both the strains, but was significantly increased in C57BL/6J mice. Myeloperoxidase levels in BAL fluid were increased significantly in both the strains. Total reduced glutathione (GSH) level was decreased, whereas the level of oxidized or glutathione disulfide (GSSG) increased in lungs of both the strains. Similarly, the level of lipid peroxidation markers, 15‐isoprostane (plasma), malondialdehyde and 4‐hydroxy‐2‐nonenal (lung homogenates) were increased by WPS. Our data suggest that, oxidative stress and inflammatory responses are influenced by strain characteristics during acute WPS exposure. Overall, C57BL/6J mice showed more susceptibility to oxidative stress and inflammatory responses compared to BALB/cJ mice. Acute WPS mediated pulmonary toxicity is differentially regulated in different mouse strains.

Double-hit mouse model of cigarette smoke priming for acute lung injury.

Epidemiological studies indicate that cigarette smoking (CS) increases the risk and severity of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). The mechanism is not understood, at least in part because of lack of animal models that reproduce the key features of the CS priming process. In this study, using two strains of mice, we characterized a double-hit mouse model of ALI induced by CS priming of injury caused by lipopolysaccharide (LPS). C57BL/6 and AKR mice were preexposed to CS briefly (3 h) or subacutely (3 wk) before intratracheal instillation of LPS and ALI was assessed 18 h after LPS administration by measuring lung static compliance, lung edema, vascular permeability, inflammation, and alveolar apoptosis. We found that as little as 3 h of exposure to CS enhanced LPS-induced ALI in both strains of mice. Similar exacerbating effects were observed after 3 wk of preexposure to CS. However, there was a strain difference in susceptibility to CS priming for ALI, with a greater effect in AKR mice. The key features we observed suggest that 3 wk of CS preexposure of AKR mice is a reproducible, clinically relevant animal model that is useful for studying mechanisms and treatment of CS priming for a second-hit-induced ALI. Our data also support the concept that increased susceptibility to ALI/ARDS is an important adverse health consequence of CS exposure that needs to be taken into consideration when treating critically ill individuals.

Strain differences in the proteome of dioxin-sensitive and dioxin-resistant mice treated with 2,3,7,8-tetrabromodibenzo-p-dioxin.

Dioxins cause various toxic effects through the aryl hydrocarbon receptor (AHR) in vertebrates, with dramatic species and strain differences in susceptibility. Although inbred mouse strains C3H/HeJ-lpr/lpr (C3H/lpr) and MRL/MpJ-lpr/lpr (MRL/lpr) are known as dioxin-sensitive and dioxin-resistant mice, respectively, the molecular mechanism underlying this difference remains unclear. The difference in the hepatic proteome of the two mouse strains treated with vehicle or 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) was investigated by a proteomic approach of two-dimensional electrophoresis (2-DE) coupled with matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF). To confirm the strain-difference in response to TBDD treatment, cytochrome P450 (CYP) 1A1 and 1A2 protein levels were measured in both strains. A dose of 10µg/kg body weight of TBDD induced hepatic CYP1A1 and CYP1A2 expression in both strains, but the expression levels of both CYP1A proteins were higher in C3H/lpr mice than in MRL/lpr mice, supporting that C3H/lpr mice are more sensitive to dioxins than MRL/lpr mice. Proteins that were more induced or suppressed by TBDD treatment in C3H/lpr mice were successfully identified by 2-DE and MALDI-TOF/TOF, including proteins responsible for AHR activation through production of endogenous ligands such as aspartate aminotransferase, indolethylamine N-methyltransferase, and aldehyde dehydrogenases, as well as proteins reducing oxidative stress, such as superoxide dismutase and peroxiredoxins. Taken together, our results provide insights into the molecular mechanism underlying the high dioxin susceptibility of the C3H/lpr strain, in which AHR activation by TBDD is more prompted by the production of endogenous ligands, but the adaptation to oxidative stress is also acquired.

Susceptibility of different mice strains to okadaic acid, a diarrhetic shellfish poisoning toxin

The mouse bioassay is widely used to detect diarrhetic shellfish poisoning (DSP) toxins. To the best of our knowledge, however, there have been no reports specifically on strain differences in susceptibility to DSP toxins. In this study, we investigated the susceptibility of different mice strains to okadaic acid (OA), one of the representative DSP toxins. A lethal dose of OA was injected intraperitoneally (i.p.) into mice. The mice were observed until 24 h after injection. Five inbred strains (A/J, BALB/c, C3H/He, C57BL/6, and DBA/2) and two non-inbred strains (ddY, and ICR) of mice were compared. All the mice were male, weighed 16–20 g, and were 4–5 weeks old. The lethality was 90–100% in the A/J, BALB/c, ddY, and ICR strains, 70–80% in the C3H/He and C57BL/6 strains, and 40% in DBA/2 strain. Survival analysis showed that the BALB/c, C57BL/6, ddY, and ICR strains died earlier and the A/J, C3H/He and DBA/2 strains survived longer. These results indicate that significant differences may exist in the susceptibility of mice strains to OA.

Strain differences in seizure-induced cell death following pilocarpine-induced status epilepticus

Mouse strains differ from one another in their susceptibility to seizure-induced excitotoxic cell death. Previously, we have demonstrated that mature inbred strains of mice show remarkable genetic differences in susceptibility to the neuropathological consequences of seizures in the kainate model of status epilepticus. At present, while the cellular mechanisms underlying strain-dependent differences in susceptibility remain unclear, some of this variation is assumed to have a genetic basis. However, it remains unclear whether strain differences in susceptibility to seizure-induced cell death observed following kainate administration are observed following systemic administration of other chemoconvulsants. In rodents, the cholinomimetic convulsant pilocarpine is widely used to induce status epilepticus (SE), followed by hippocampal damage and spontaneous recurrent seizures, resembling temporal lobe epilepsy. This model has initially been described in rats, but is increasingly used in mice. We characterized neuronal pathologies after pilocarpine-induced status epilepticus (SE) in eight inbred strains of mice focusing on the hippocampus. A ramping-up dose protocol for pilocarpine was used and behavior was monitored for 4–5h. While we did not observe any significant differences in seizure latency or duration to pilocarpine among the inbred strains, we did observe a significant difference in susceptibility to the neuropathological consequences of pilocarpine-induced SE. Of the eight genetically diverse mouse strains screened for pilocarpine-induced status, BALB/cJ and BALB/cByJ were the only two strains that were resistant to the neuropathological consequences of seizure-induced cell death. Additional studies of these murine strains may be useful for investigating genetic influences on pilocarpine-induced status epilepticus.

Use of transgenic animals in understanding molecular mechanisms of toxicity.

Understanding molecular mechanisms of chemical toxicity and the potential risks of drugs to man is a pivotal part of the drug development process. With the dramatic increase in the number of new chemical entities arising from high throughput screening, there is an urgent need to develop systems for the rapid evaluation of potential drugs so that those agents which are most likely to be free of adverse effects can be identified at the earliest possible stage in drug development. The complex mechanisms of action of chemical toxins has made it extremely difficult to evaluate the precise toxic mechanism and also the relative role of specific genes in either potentiating or ameliorating the toxic effect. This problem can be addressed by the application of genetic strategies. Such strategies can exploit strain differences in susceptibility to specific toxic agents or, with the rapidly developing technologies, can exploit the use of transgenic animals where specific genes can be manipulated and subsequent effects on chemical toxicity evaluated. Transgenic animals can be exploited in a variety of ways to understand mechanisms of chemical toxicity. For example, a human gene encoding a drug metabolizing enzyme can be directly introduced and the effects on toxic response evaluated. Alternatively, specific genes can be deleted from the mouse genome and the consequences on toxicological response determined. Many toxic chemical agents modulate patterns of gene expression within target cells. This can be used to screen for responses to different types of toxic insult. In such experiments the promotor of a stress-regulated gene can be ligated to a suitable reporter gene, such as lacZ, or green fluorescent protein, and inserted into the genome of an appropriate test species. On administration of a chemical agent, cells which are sensitive to the toxic effects of that chemical will express the reporter, which can then be identified using an appropriate assay system. This latter strategy provides the potential for screening a large number of compounds rapidly for their potential toxic effects and also provides information on tissue and cellular specificity. Experiments using transgenic animals can be complex, and care must be taken to ensure that the results are not affected by background activities within the species being used. For example, the introduction of a specific human cytochrome P450 gene may have no effect on the metabolic disposition of a drug or toxin because of the background activity within the mouse. As the toxicity of a chemical agent is determined by a wide range of different factors including drug uptake, metabolism, detoxification and repair, differences between man and the species being used could potentially generate a toxic response in the animal model whereas no toxicity may be observed in man. In spite of these confounding factors, the application of transgenic animals to toxicological issues has enormous potential for speeding up the drug discovery process and will undoubtedly become part of this process in the future.

MPTP Mouse Models of Parkinson's Disease: An Update

Among the most widely used models of Parkinson's disease (PD) are those that employ toxins, especially 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Depending on the protocol used, MPTP yields large variations in nigral cell loss, striatal dopamine loss and behavioral deficits. Motor deficits do not fully replicate those seen in PD. Nonetheless, MPTP mouse models mimic many aspects of the disease and are therefore important tools for understanding PD. In this review, we will discuss the ability of MPTP mouse models to replicate the pathophysiology of PD, the mechanisms of MPTP-induced neurotoxicity, strain differences in susceptibility to MPTP, and the models' roles in testing therapeutic approaches.

Rat strain differences in susceptibility to alcohol-induced chronic liver injury and hepatic insulin resistance.

The finding of more severe steatohepatitis in alcohol fed Long Evans (LE) compared with Sprague Dawley (SD) and Fisher 344 (FS) rats prompted us to determine whether host factors related to alcohol metabolism, inflammation, and insulin/IGF signaling predict proneness to alcohol-mediated liver injury. Adult FS, SD, and LE rats were fed liquid diets containing 0% or 37% (calories) ethanol for 8 weeks. Among controls, LE rats had significantly higher ALT and reduced GAPDH relative to SD and FS rats. Among ethanol-fed rats, despite similar blood alcohol levels, LE rats had more pronounced steatohepatitis and fibrosis, higher levels of ALT, DNA damage, pro-inflammatory cytokines, ADH, ALDH, catalase, GFAP, desmin, and collagen expression, and reduced insulin receptor binding relative to FS rats. Ethanol-exposed SD rats had intermediate degrees of steatohepatitis, increased ALT, ADH and profibrogenesis gene expression, and suppressed insulin receptor binding and GAPDH expression, while pro-inflammatory cytokines were similarly increased as in LE rats. Ethanol feeding in FS rats only reduced IL-6, ALDH1–3, CYP2E1, and GAPDH expression in liver. In conclusion, susceptibility to chronic steatohepatitis may be driven by factors related to efficiency of ethanol metabolism and degree to which ethanol exposure causes hepatic insulin resistance and cytokine activation.

Comparative Study on Susceptibility to 1-Bromopropane in Three Mice Strains

Previous studies indicate that 1-bromopropane (1BP) has neurotoxicity and reproductive toxicity both in humans and animals. The present study investigated strain differences in susceptibility to 1BP and identified possible biological factors that determine such susceptibility. Twenty-four male mice of each of the three strains (C57BL/6J, DBA/2J, and BALB/cA) were divided into four groups of six each and exposed to 1BP at 0, 50, 110, and 250 ppm for 8 h/day for 28 days by inhalation. At the end of exposure period, the relative susceptibilities of each strain to 1BP-mediated hepatotoxicity and male reproductive toxicity were evaluated. The contributing factors to strain-dependent susceptibility were assessed by determination of hepatic CYP2E1 levels, glutathione-S-transferase (GST) activity, glutathione (GSH) status, and NAD(P)H:quinone oxidoreductase and heme oxygenase-1 mRNA levels. Liver histopathology showed significantly larger area of liver necrosis and more degenerative lobules in BALB/cA in the order of BALB/cA > C57BL/6J > DBA/2J. BALB/cA showed higher CYP2E1 protein level and lower total GSH content and GST activity in the liver than DBA/2J. These results indicate that BALB/cA mice are the most susceptible to hepatotoxicity of 1BP among the three strains tested, and that CYP2E1, GSH level/GST activity may contribute to the susceptibility to 1BP hepatotoxicity. Exposure to > or = 50 ppm of 1BP also decreased sperm count and sperm motility and increased sperms with abnormal heads in all three strains mice in a dose-dependent manner. Comparison with previous studies in rats indicates that mice are far more susceptible than rats to 1BP regarding hepatotoxicity and reproductive toxicity.

Strain difference in susceptibility to experimental autoimmune encephalomyelitis in rats correlates with T H1 and T H17-inducing cytokine profiles

Albino Oxford (AO) rats are resistant to induction of experimental autoimmune encephalomyelitis (EAE), in contrast to susceptible Dark Agouti (DA) rats. We have previously shown that draining lymph node cells (DLNC) obtained from immunized DA rats before the onset of the clinical disease produced more interferon (IFN)-γ and interleukin (IL)-17 (signature cytokines of T H1 and T H17 responses, respectively) compared to DLNC from AO rats. In this study, we extend our analysis to entire induction phase of EAE with the emphasis on the T H1 and T H17-inducing cytokines. As a result, we show that throughout the inductive phase of the disease DLNC of DA rats, not only expressed higher levels of IFN-γ and IL-17, but also of T H1-inducing cytokine—IL-12. As for T H17-inducing cytokines, DLNC of DA rats expressed more mRNA for p19, specific subunit of IL-23, but the expression of transforming growth factor (TGF)-β in both strains was similar. Interestingly, the analysis of IL-6 expression revealed striking difference: while all DA DLNC were positive for IL-6 mRNA, cells from none of AO rats expressed detectable levels of mRNA for this cytokine. Taken together, our data suggest that the differential regulation of production of T H1 and T H17 cytokines, and IL-6 in particular, during the induction phase of disease could be responsible for the discrepancy in susceptibility to EAE between these two rat strains.

Strain difference in susceptibility to Trichinella spiralis infection between dark agouti and albino oxford rats

The influence of host genetics on the susceptibility to primary Trichinella spiralis infection has been extensively studied in a mouse model, but has not been clarified for rats. Analyses of interstrain and intrastrain genetic variation in response to infectious agents could be beneficial not only for elucidating the genetic basis of host resistance/susceptibility, but for revealing immune response mechanisms as well. The aim of this study was to analyse interstrain differences in worm burdens and cytokine production between Albino Oxford (AO) and Dark Agouti (DA) rats in muscle phase of T. spiralis infection. Clear strain-dependent variation was observed in the number of T. spiralis larvae per gram (lpg) of muscle tissue where values for DA rats (626.7±171lpg) vastly exceeded those found in AO rats (49.8±25.9lpg, p<0.001). Differences between the strains were also noticed in key cytokine levels. In infected AO rats, the cytokine production remained in favor of Th1 type response, while infected DA rats showed a shift towards a Th2 type response. The level of regulatory IL-10 was significantly increased only in T. spiralis infected DA rats. Our results provide evidence that DA rats express higher susceptibility to T. spiralis infection in comparison to AO rats with respect to muscle larvae burden. The infection in DA rats was accompanied by the production of anti-inflammatory cytokines, while the response of AO rats was characterized by a proinflammatory type of immune response.

Circulating immune complexes may play a regulatory and pathogenic role in experimental autoimmune uveoretinitis.

We compared the time course of changes in serum levels of circulating immune complexes (CICs) and of IgG antibody after sensitization of albino Lewis and pigmented Lister strain rats with uveitogenic (retinal S-antigen) and non-uveitogenic (ovalbumin) protein antigens of comparable molecular weight. Normal levels of CICs were far lower in Lewis rats in which experimental autoimmune uveoretinitis (EAU) takes the form of a severe panuveitis, than in Lister rats, in which the disease is mild, focal, confined to the posterior segment, and of lower incidence. After sensitization with either S-antigen or ovalbumin, polyethylene-glycol-precipitable CIC (PEG-CIC) peaked and fell as IgG antibody levels rose in both rat strains. However, peak levels of PEG-CIC were lower and subsequent IgG antibody levels were higher in the Lewis strain than in the less susceptible Lister strain. In both strains of rat these linked PEG-CIC/IgG antibody responses occurred earlier after sensitization with uveitogenic (S-) antigen than with ovalbumin, whether or not individual S-antigen-sensitized Lister rats developed EAU. In contrast, complement-binding CIC rose substantially only in those rats of both strains displaying EAU in response to S-antigen and not in response to ovalbumin. We suggest that immune complex (idiotypic) regulation of IgG antibody responses may be more readily perturbed by a pathogenic autoantigen (S-antigen) than by a bland antigen (ovalbumin). We also suggest that differences between the balance of regulatory and pathogenic CIC responses to uveitogenic retinal antigen may underlie or reflect strain differences in susceptibility to and severity of EAU.

Strain Differences in Susceptibility to In Vivo Erectile Dysfunction Following 6 weeks of Induced Hyperglycemia in the Mouse

With the large-scale availability of transgenic and knockout mouse models, the use of mice may greatly facilitate the examination of the mechanisms underlying diabetic erectile dysfunction (ED). Although in vitro studies of the mouse cavernosum show impairment of vasoreactivity, to date, no studies have demonstrated the in vivo impairment of erectile function in diabetic mice. To establish whether mouse models of type I diabetes exhibit in vivo ED. Hyperglycemia was induced by injection with streptozotocin (STZ, 125 mg/kg x 2 days) in two mouse strains, C57BLKS (BKS) and BALB/c. Six weeks after injection, the cavernosum was removed from some mice for the in vitro assessment of the endothelium and nerve-mediated dilatory responses of the cavernosal strips. The in vivo assessment of intracorporal pressure normalized to mean arterial pressure, in response to the electrical stimulation of the cavernosal nerve, was performed in the remaining mice. The main outcome measure of this study was the in vivo assessment of erectile function following diabetic induction in mice. Despite similar levels of sustained hyperglycemia following STZ injection, the phenotype of diabetic ED was observed only in BKS and not BALB/c mice. The cavernosum from diabetic BKS mice showed decreased endothelium-dependent dilation in response to acetylcholine (ACh), as well as impaired parasympathetic nerve-mediated relaxation. There was no change in ACh or nerve-mediated relaxation in the cavernousum from diabetic vs. control BALB/c mice. Further, in vivo physiologic assessment of erectile activity revealed a significant decrease in erectile function in diabetic BKS but not in BALB/c mice. Together these data first established in vivo ED in a mouse model of type I diabetes (BKS mouse) and importantly demonstrated that certain inbred strains may be protected from hyperglycemia-induced erectile impairment. Further study of the strain-dependent effects may offer important clues into the mechanisms of ED as it relates to type I diabetes.

Development of a Novel Mouse Anaphylaxis Model Produced by Intermittent Intravenous Injections of Ovalbumin without Adjuvant

This study was performed to develop mouse anaphylaxis model using ovalbumin (OA) as an antigen, with no adjuvant, and an intravenous route of administration. OA at dose levels from 0.5 to 500 mg/kg was injected 3 times into the tail vein of female CD-1 (ICR) mice at 4-day intervals. Clinical signs and extravasation of Evans blue dye (vascular permeability) were observed, serum histamine levels and airway resistance were measured, and histopathological examinations were performed. Furthermore, to detect serum IgE and IgG, heterologous and homologous passive cutaneous anaphylaxis tests were performed. Additionally, strain differences in susceptibility to OA anaphylaxis was examined with 3 mouse strains: ICR, BALB/c and C57BL/6 mice. Shortly after the 3rd injection, most of the animals exhibited systemic anaphylactic signs including death, and this was accompanied by increases in vascular permeability, plasma histamine levels, and airway resistance. Four days after the 2nd injection, anti-OA IgE and IgG were detected in sera of mice injected with 0.5 and 5.0 mg/kg or higher doses of OA, respectively. Histological findings included: congestion in many tissues; detachment of mucosal epithelial cells in the gastrointestinal tract; enhanced death, decreased numbers of lymphocytes, and increased numbers of macrophages in the lymphoid tissues. ICR mice were shown to be most susceptible to the OA anaphylaxis of the 3 mouse strains examined. In conclusion, the results demonstrate that 3 intermittent intravenous injections of OA without adjuvant at 4-day intervals can induce anaphylactic shock in mice, in particular, most effectively in ICR mice, and that the anaphylaxis is characterized by specific IgE and IgG production.

P.1.a.015 Strain differences in susceptibility to unpredictable chronic mild stress as assessed by hippocampal gene expression profiling

Major depression is a common long-lasting or recurrent psychiatric disease with high lifetime prevalence and high incidence of suicide. The main purpose of the current study was to verify whether liquiritigenin conferred an antidepressant-like effect on the depressive mouse model established by unpredictable chronic mild stress (UCMS) and explore its possible mechanism. The results of depression-related behaviors including sucrose preference test (SPT), open field test (OFT), forced swimming test (FST) and tail suspension test (TST) indicated that both liquiritigenin (7.5 mg/kg, 15 mg/kg) and fluoxetine (20 mg/kg) dramatically improved the depression symptoms. Enzyme-linked immunosorbent assay (ELISA) revealed that treatment with liquiritigenin significantly reduced the concentrations of pro-inflammatory cytokines including interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)-α in serum and hippocampus. Compared with the UCMS group, the administrations of liquiritigenin, increased levels of superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), and decreased Malondialdehyde (MDA) content. Meanwhile, glucocorticoids (GC) content was reduced in the liquiritigenin group, which suggested that liquiritigenin exhibiting the ameliorative effect on activated hypothalamic-pituitary-adrenal (HPA) axis stimulated with UCMS. Mice treated with liquiritigenin showed restored levels of neurotransmitter norepinephrine (NE) and serotonin (5-HT). Western blot analysis displayed up-regulated expressions of p-phosphatidylinositol 3-kinase (PI3 K), p-Akt, p- mammalian target of rapamycin (mTOR), p-tropomyosin-related kinase B (TrkB), brain-derived neurotrophic factor (BDNF). Thus, it was supposed that liquiritigenin might be useful for the treatment of chronic depression possibly through PI3 K/Akt/mTOR mediated BDNF/TrkB pathway.

Strain difference in susceptibility to experimental autoimmune encephalomyelitis between Albino Oxford and Dark Agouti rats correlates with disparity in production of IL-17, but not nitric oxide

Albino Oxford (AO) rats, unlike Dark Agouti (DA) rats are resistant to the induction of experimental autoimmune encephalomyelitis (EAE). The reason for the resistance could be some restraining mechanism preventing auto-aggressive cell activation at the level of draining lymph nodes (DLN) during the induction phase of the disease. Such a mechanism could be anti-proliferative action of nitric oxide (NO), which has already been shown of importance for the resistance of several rat strains to the induction of the disease. Importantly, number of AO DLN cells (DLNC) is markedly lower and with lower proliferative response to myelin basic protein (MBP) ex vivo in comparison to DA DLNC in the inductive phase of EAE, thus implying that in AO rats DLNC do not proliferate as extensively as in DA rats. We show that AO rats do not produce larger quantities of NO than DA rats after immunization. Further, DLNC of immunized AO rats have significantly lower mRNA expression and synthesis of interferon (IFN)-gamma and interleukin (IL)-17 compared to DLNC of DA rats. Collectively, these results suggest that there is a substantial difference between EAE-resistant AO rats and EAE-prone DA rats in the initiation of autoimmune response. This difference seems to be independent of anti-proliferative actions of NO, but correlates with impaired IL-17 production in AO rats.

A major quantitative trait locus on mouse chromosome 3 is involved in disease susceptibility in different colitis models

Mice with a disrupted gene for the G-protein alpha inhibitory 2 chain ( Gnai2 -/- ) develop a spontaneous colitis resembling human inflammatory bowel disease. Disease expression differs markedly between inbred strains of mice, indicating genetic control of disease susceptibility. We performed a genome-wide screen to localize the chromosomal regions regulating disease expression. A total of 284 F2 mice derived from resistant C57BL/6J Gnai2 -/- mice and susceptible C3H/HeN Gnai2 -/- mice were analyzed in a genome-wide screen for colitis susceptibility and severity. A highly significant locus on chromosome 3 (Gpdc1) contributed to colitis susceptibility and severity (likelihood ratio statistics [LRS] = 32.4; LOD score = 7; P < 1.0 x 10(-5)). The peak linkage of this locus at 62 cM colocalizes exactly with a previously identified locus controlling colitis susceptibility in interleukin-10-deficient mice. In addition, evidence for linkage with a locus on chromosome 1 (Gpdc2 ; LRS = 19.7; LOD = 4.3) was found, and the 2 loci interacted epistatically (combined LRS = 68.2). A third locus (Gpdc3) was found on chromosome 9 and this locus interacted epistatically with a locus on chromosome 7, which by itself did not have an effect on the trait. The identification of a major locus on chromosome 3 that controls susceptibility to spontaneous colitis in 2 different gene-knockout models indicates that this locus harbors a gene(s) that plays a key role in maintaining mucosal homeostasis. Identification of this gene(s) may contribute to further understanding of the mechanisms underlying human inflammatory bowel disease.

Comparison of the susceptibility of wild-type and CYP2E1 knockout mice to the hepatotoxic and pneumotoxic effects of styrene and styrene oxide

Styrene causes both liver and lung damage in non-Swiss albino, CD-1, and other strains of mice. This is considered to be due to the bioactivation of styrene to styrene oxide by cytochromes P450, principally CYP2E1 and CYP2F2. If so, one would expect CYP2E1 knockout mice to be less susceptible to styrene-induced toxicity than wild-type mice. However, previous in vitro and in vivo studies demonstrated little difference in the metabolism of styrene to styrene oxide between wild-type and CYP2E1 knockout mice. These findings would suggest that there should be no difference in the toxic responses to styrene between these two strains. To determine which of these possibilities was correct, styrene (600 mg/kg) or styrene oxide (300 mg/kg) was administered i.p. 24 h prior to measurement of serum sorbitol dehydrogenase as a biomarker of hepatotoxicity or lactate dehydrogenase activity, protein, and cells in bronchoalveolar lavage fluid as biomarkers for pneumotoxicity. Styrene was more hepatotoxic in the wild-type mice than in the knockout mice suggesting CYP2E1 activity is important. Strain differences were not observed with styrene oxide indicating no difference in intrinsic susceptibility. For lung, the response was similar in both strains to both styrene and styrene oxide supporting the idea that CYP2F2 is important in the bioactivation of styrene in this tissue and that there is no strain difference in susceptibility to the active metabolite.