The role of stress in the regulation of drug metabolizing enzymes in mice

Age-related modifications in CYP-dependent drug metabolism: role of stress

Accumulating clinical evidence indicates extensive inter-individual variations in the effectiveness and adverse effects of standard treatment protocols, which are largely attributed to the multifactorial regulation of the hepatic CYP-dependent drug metabolism that is connected with either transcriptional or post-translational modifications. Age and stress belong to the most important factors in CYP gene regulation. Alterations in neuroendocrine responses to stress, which are associated with modified hypothalamo-pituitary-adrenal axis function, usually accompany ageing. In this light, ageing followed by a decline of the functional integrity of organs, including liver, a failure in preserving homeostasis under stress, increased morbidity and susceptibility to stress, among others, holds a determinant role in the CYP-catalyzed drug metabolism and thus, in the outcome and toxicity of pharmacotherapy. Modifications in the drug metabolizing capacity of the liver with age have been reported and in particular, a decline in the activity of the main CYP isoforms in male senescent rats, indicating decreased metabolism and higher levels of the drug-substrates in their blood. These factors along with the restricted experience in the use of the most medicines in childhood and elderly, could explain at an extent the inter-individual variability in drug efficacy and toxicity outcomes, and underscore the necessity of designing the treatment protocols, accordingly.

Off-target lipid metabolism disruption by the mouse constitutive androstane receptor ligand TCPOBOP in humanized mice

The constitutive androstane receptor (CAR) controls xenobiotic clearance, regulates liver glucose, lipid metabolism, and energy homeostasis. These functions have been mainly discovered using the prototypical mouse-specific CAR ligand TCPOBOP in wild-type or CAR null mice. However, TCPOBOP is reported to result in some off-target metabolic effects in CAR null mice. In this study, we compared the metabolic effects of TCPOBOP using lipidomic, transcriptomic, and proteomic analyses in wild-type and humanized CAR-PXR-CYP3A4/3A7 mice. In the model, human CAR retains its constitutive activity in metabolism regulation; however, it is not activated by TCPOBOB. Notably, we observed that TCPOBOP affected lipid homeostasis by elevating serum and liver triglyceride levels and promoted hepatocyte hypertrophy in humanized CAR mice. Hepatic lipidomic analysis revealed a significant accumulation of triglycerides and decrease of its metabolites in humanized CAR mice. RNA-seq analysis has shown divergent gene expression levels in wild-type and humanized CAR mice. Gene expression regulation in humanized mice is mainly involved in lipid metabolic processes and in the PPAR, leptin, thyroid, and circadian clock pathways. In contrast, CAR activation by TCPOBOP in wild-type mice reduced liver and plasma triglyceride levels and induced a typical transcriptomic proliferative response in the liver. In summary, we identified TCPOBOP as a disruptor of lipid metabolism in humanized CAR mice. The divergent effects of TCPOBOP in humanized mice in comparison with the prototypical CAR-mediated response in WT mice warrant the use of appropriate model ligands and humanized animal models during the testing of endocrine disruption and the characterization of adverse outcome pathways.

Epigallocatechin-3-gallate protects immunity and liver drug-metabolism function in mice loaded with restraint stress

(-)-Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenolic compound present in green tea and has been shown to possess bio-activities. In this study, we investigated the protective effects of EGCG against restraint stress (RS)-induced liver injury and immunosuppression. EGCG (10, 20 and 40 mg/kg) was orally administered to mice daily for 7 days before modeling the restraint stress. lood, liver and broncho-alveolar lavage fluid (BALF) samples were collected and tested. We found that EGCG significantly reduced the release of stress hormones to weak restraint stress response. EGCG effectively improved hepatic damage by decreas the serum levels of alanine aminotransaminase (ALT) and aspartate transaminase (AST) in restraint-challenged mice. Furthermore, EGCG also significantly prevented the release of H₂O₂, NOS and 8-isoprostane, and reduced the levels of interleukin (IL)-1β, IL-2,and IL-6 restrained mice. EGCG can normal the level of cytochrome P450 (CYP450) 1A2, 2D22, 2E1 and 3A11 that induced by restraint stress., the inhibition status of T cells subsets in serum and gA in BALF were significantly relieved EGCG pretreatment. Taken together, our data suggest that EGCG possesse hepatic- and immune-protective properties against restraint stress through its anti-oxidant, anti-inflammatory and immunomodulatory activities.

Dopamine D2-Receptor Antagonists Down-Regulate CYP1A1/2 and CYP1B1 in the Rat Liver

Dopaminergic systems regulate the release of several hormones including growth hormone (GH), thyroid hormones, insulin, glucocorticoids and prolactin (PRL) that play significant roles in the regulation of various Cytochrome P450 (CYP) enzymes. The present study investigated the role of dopamine D₂-receptor-linked pathways in the regulation of CYP1A1, CYP1A2 and CYP1B1 that belong to a battery of genes controlled by the Aryl Hydrocarbon Receptor (AhR) and play a crucial role in the metabolism and toxicity of numerous environmental toxicants. Inhibition of dopamine D₂-receptors with sulpiride (SULP) significantly repressed the constitutive and benzo[a]pyrene (B[a]P)-induced CYP1A1, CYP1A2 and CYP1B expression in the rat liver. The expression of AhR, heat shock protein 90 (HSP90) and AhR nuclear translocator (ARNT) was suppressed by SULP in B[a]P-treated livers, whereas the AhRR expression was increased by the drug suggesting that the SULP-mediated repression of the CYP1 inducibility is due to inactivation of the AhR regulatory system. At signal transduction level, the D₂-mediated down-regulation of constitutive CYP1A1/2 and CYP1B1 expression appears to be mediated by activation of the insulin/PI3K/AKT pathway. PRL-linked pathways exerting a negative control on various CYPs, and inactivation of the glucocorticoid-linked pathways that positively control the AhR-regulated CYP1 genes, may also participate in the SULP-mediated repression of both, the constitutive and induced CYP1 expression. The present findings indicate that drugs acting as D₂-dopamine receptor antagonists can modify several hormone systems that regulate the expression of CYP1A1, CYP1A2 and CYP1B1, and may affect the toxicity and carcinogenicity outcome of numerous toxicants and pre-carcinogenic substances. Therefore, these drugs could be considered as a part of the strategy to reduce the risk of exposure to environmental pollutants and pre-carcinogens.

The effect of isoflurane anaesthesia and vasectomy on circulating corticosterone and ACTH in BALB/c mice

The use of blood corticosterone and faecal corticosterone metabolites as biomarkers of post-surgical stress and pain in laboratory animals has increased during the last decade. However, many aspects of their reliability in laboratory mice remain uninvestigated. This study investigated serum corticosterone and adrenocorticotropic hormone (ACTH) in mice subjected to isoflurane anaesthesia and vasectomy, and mice subjected to isoflurane anaesthesia without surgery. Serum levels of corticosterone and ACTH after pre-treatment with dexamethasone were analysed to provide further information about the stress hormone profiles. Vasectomy resulted in an increase in corticosterone for at least four hours after surgery with a peak 30min after the mice regained righting reflex. Mice subjected to isoflurane anaesthesia without surgery had the highest level of serum corticosterone 5min after regained righting reflex and the level returned to baseline levels four hours after the procedure. In vasectomised mice, treated with dexamethasone, high levels of corticosterone remained 30min after the procedure, whereas the anaesthetised mice, treated with dexamethasone, had significantly lower levels of corticosterone compared to anaesthetised mice not treated with dexamethasone. Thus, dexamethasone effectively inhibited the corticosterone response in the anaesthetised-only mice, but not in the mice subjected to surgery. In conclusion, both isoflurane anaesthesia and vasectomy during isoflurane anaesthesia resulted in an increase in serum glucocorticoids, but the negative feedback mechanism of newly operated mice, was altered. This may have consequences for the interpretation of glucocorticoids measurements as a biomarker of post-surgical stress in mice.

Stress is a critical player in CYP3A, CYP2C, and CYP2D regulation: role of adrenergic receptor signaling pathways

Stress is a critical player in the regulation of the major cytochrome P-450s (CYPs) that metabolize the majority of the prescribed drugs. Early in life, maternal deprivation (MD) stress and repeated restraint stress (RS) modified CYP expression in a stress-specific manner. In particular, the expression of CYP3A1 and CYP2C11 was increased in the liver of MD rats, whereas RS had no significant effect. In contrast, hepatic CYP2D1/2 activity was increased by RS, whereas MD did not affect it. The primary effectors of the stress system, glucocorticoids and epinephrine, highly induced CYP3A1/2. Epinephrine also induced the expression of CYP2C11 and CYP2D1/2. Further investigation indicated that AR-agonists may modify CYP regulation. In vitro experiments using primary hepatocyte cultures treated with the AR-agonists phenylephrine, dexmedetomidine, and isoprenaline indicated an AR-induced upregulating effect on the above-mentioned CYPs mediated by the cAMP/protein kinase A and c-Jun NH₂-terminal kinase signaling pathways. Interestingly though, in vivo pharmacological manipulations of ARs using the same AR-agonists led to a suppressed hepatic CYP expression profile, indicating that the effect of the complex network of central and peripheral AR-linked pathways overrides that of the hepatic ARs. The AR-mediated alterations in CYP3A1/2, CYP2C11, and CYP2D1/2 expressions are potentially connected with those observed in the activation of signal transducer and activator of transcription 5b. In conclusion, stress and AR-agonists may modify the expression of the major CYP genes involved in the metabolism of drugs used in a wide range of diseases, thus affecting drug efficacy and toxicity.

Drug-induced liver injury: Is it somehow foreseeable?

The classic view on the pathogenesis of drug-induced liver injury is that the so-called parent compounds are made hepatotoxic by metabolism (formation of neo-substances that react abnormally), mainly by cytochromes P-450 (CYP), with further pathways, such as mitochondrial dysfunction and apoptosis, also playing a role. Risk factors for drug-induced liver injury include concomitant hepatic diseases, age and genetic polymorphisms of CYP. However, some susceptibility can today be predicted before drug administration, working on the common substrate, by phenotyping and genotyping studies and by taking in consideration patients’ health status. Physicians should always think of this adverse effect in the absence of other clear hepatic disease. Ethical and legal problems towards operators in the health care system are always matters to consider.

Expression of cytochrome P450 2A5 in a glucose-6-phosphate dehydrogenase-deficient mouse model of oxidative stress

Murine hepatic cytochrome P450 2A5 (CYP2A5), unlike most CYP enzymes, is upregulated during hepatitis and hepatotoxic conditions, but the common stimulus for its induction remains unknown. We investigated the involvement of oxidative stress in the regulation of CYP2A5 expression using an oxidative stress-sensitive glucose-6-phosphate dehydrogenase (G6PD)-deficient mouse model. Treatment of deficient and wild-type mice with the prototypical CYP2A5-inducer pyrazole for 72h led to a significantly greater degree of induction of CYP2A5 mRNA, protein and activity in deficient mice, with the greatest increase observed in animals homozygous for the deficiency. However, markers of oxidative stress including protein carbonyl, 8-hydroxydeoxyguanosine, malondiadehyde and 4-hydroxyalkenal levels were unaltered with pyrazole treatment. Furthermore, CYP2A5 expression was not altered in G6PD-deficient mice treated with the pro-oxidant menadione whereas DNA, lipid, and protein markers of oxidative stress were significantly increased. The antioxidant polyethylene glycol-conjugated catalase, while decreasing oxidative stress in menadione-treated mice, did not prevent the induction of CYP2A5 by pyrazole. Finally, the ER stress marker protein, GRP78, was increased following pyrazole treatment in G6PD-deficient compared to wild-type mice. These findings do not support a central role for generalized cellular oxidative stress in the regulation of CYP2A5 and suggest that additional factors related to G6PD-deficiency, such as ER stress, may be involved.

Predominant role of peripheral catecholamines in the stress-induced modulation of CYP1A2 inducibility by benzo(alpha)pyrene

The potential involvement of catecholamines and in particular of alpha(2)-adrenoceptor-related signalling pathways, in the regulation of drug-metabolizing enzymes by stress was investigated in Wistar rats after exposure to the environmental pollutant benzo(alpha)pyrene. For this purpose, total cytochrome P450 content, the CYP1A2 mRNA levels, 7-methoxyresorufin-O-dealkylase (MROD), 7-pentoxyresorufin-O-dealkylase (PROD) and p-nitrophenol hydroxylase activity levels were determined in the livers of rats exposed to repeated restraint stress after treatment with benzo(alpha)pyrene coupled with pharmacological manipulations of peripheral and/or central catecholamines and alpha(2)-adrenoceptors. The data show that stress is a significant factor in the regulation of CYP1A2 induction and that catecholamines play a central role in the stress-mediated modulation of hepatic CYP1A2 inducibility by benzo(alpha)pyrene. The up-regulating effect of stress on benzo(alpha)pyrene-induced CYP1A2 gene expression was eliminated after a generalized catecholamine depletion with reserpine. Similarly, in a state where only peripheral catecholamines were depleted and central catecholamines remained intact after guanethidine administration, the up-regulating effect of stress was eliminated. It is apparent that stress up-regulates the induction of CYP1A2 by benzo(alpha)pyrene mainly via peripheral catecholamines, while central catecholamines hold a minor role in the regulation. Pharmacological manipulations of alpha(2)-adrenoceptors appear to interfere with the effect of stress on the regulation of CYP1A2 inducibility. Either blockade or stimulation of alpha(2)-adrenoceptors with atipamezole and dexmedetomidine respectively, eliminated the up-regulating effect of stress on CYP1A2 benzo(alpha)pyrene-induced expression, while it enhanced MROD activity. In contrast, stress and pharmacological manipulations of catecholamines and alpha(2)-adrenoceptors did not affect total P450 content, the CYP2B1/2-dependent PROD and the CYP2E1-dependent p-nitrophenol hydroxylase activities. In conclusion, stress is a significant factor in the regulation of the CYP1A2 inducibility by benzo(alpha)pyrene, which in turn is involved in the metabolism of a large spectrum of toxicants, drugs and carcinogenic agents. Although the mechanism underlying the stress effect on CYP1A2 induction has not been clearly elucidated, it appears that peripheral catecholamines hold a predominant role, while central catecholamines and in particular, central noradrenergic pathways hold a minor role.

Comparative cytochrome P450 proteomics in the livers of immunodeficient mice using 18O stable isotope labeling

Quantitative changes in cytochrome P450 (CYP) proteins involved in drug metabolism as a consequence of drug treatment are important parameters in predicting the fates and pharmacological consequences of xenobiotics and drugs. In this study we undertook comparative P450 proteomics using liver from control and 1,4-bis-2-(3,5-dichloropyridyloxybenzene) (TCPOBOP)-dosed mice. The method involved separation of microsomal proteins by SDS-PAGE, trypsin digestion, and postdigest 18O/16O labeling followed by nano-LC-MS/MS for peptide identification and LC-MS for relative quantification. Seventeen P450 proteins were identified from mouse liver of which 16 yielded data sufficient for relative quantification. All the P450s detected were unambiguously identified except the highly homologous CYP2A4/2A5. With the exception of CYP2A12, -2D10, and -2F2, the levels of all the P450s quantified were affected by treatment with TCPOBOP (3 mg/kg). CYP1A2, -2A4/5, -2B10, -2B20, -2C29, -2C37, -2C38, -3A11, and -39A1 were up-regulated, and CYP2C40, -2E1, -3A41, and -27A1 down-regulated. The response of CYP2B20 to stimulation has not been distinguished previously from that of CYP2B10 because of the poor discrimination between these two proteins (they share 87% sequence identity). Differential response to chemical stimulation by closely related members of the CYP2C subfamily was also observed.

Gene expression of drug metabolizing enzymes in adult and aged mouse liver: A modulation by immobilization stress

The role of stress in the regulation of enzymatic systems involved in the biotransformation of xenobiotics, as well as endogenous substrates in the liver was investigated using single immobilization stress as a model. Adult (3 months of age) and aged (26 months) C3H/a male mice were used. Cytochrome P450 1A1 and 1A2 (CYP1A1 and CYP1A2), glutathione S-transferase M1 (GSTM1), aryl hydrocarbon receptor (AHR), aryl hydrocarbon receptor nuclear translocator (ARNT) and catechol-O-methyltransferase (COMT) mRNA levels in the mouse liver were measured by a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. Excluding CYP1A1, experiments revealed significant differences in the expression of these genes between adult- and aged-control animals. The influence of stress on the expression of genes studied was shown to be higher in adult mice than in aged ones. Our results clearly demonstrate the lack of response or even the attenuation of gene expression in aged animals that may play an important role in age-related pathologies and diseases.

Stress and combined exposure to low doses of pyridostigmine bromide, DEET, and permethrin produce neurochemical and neuropathological alterations in cerebral cortex, hippocampus, and cerebellum

Exposure to a combination of stress and low doses of the chemicals pyridostigmine bromide (PB), DEET, and permethrin in adult rats, a model of Gulf War exposure, produces blood-brain barrier (BBB) disruption and neuronal cell death in the cingulate cortex, dentate gyrus, thalamus, and hypothalamus. In this study, neuropathological alterations in other areas of the brain where no apparent BBB disruption was observed was studied following such exposure. Animals exposed to both stress and chemical exhibited decreased brain acetylcholinesterase (AChE) activity in the midbrain, brainstem, and cerebellum and decreased m2 muscarinic acetylcholine (ACh) receptor ligand binding in the midbrain and cerebellum. These alterations were associated with significant neuronal cell death, reduced microtubule-associated protein (MAP-2) expression, and increased glial fibrillary acidic protein (GFAP) expression in the cerebral cortex and the hippocampal subfields CA1 and CA3. In the cerebellum, the neurochemical alterations were associated with Purkinje cell loss and increased GFAP immunoreactivity in the white matter. However, animals subjected to either stress or chemicals alone did not show any of these changes in comparison to vehicle-treated controls. Collectively, these results suggest that prolonged exposure to a combination of stress and the chemicals PB, DEET, and permethrin can produce significant damage to the cerebral cortex, hippocampus, and cerebellum, even in the absence of apparent BBB damage. As these areas of the brain are respectively important for the maintenance of motor and sensory functions, learning and memory, and gait and coordination of movements, such alterations could lead to many physiological, pharmacological, and behavioral abnormalities, particularly motor deficits and learning and memory dysfunction.

Stress-mediated modulation of B(α)P-induced hepatic CYP1A1: role of catecholamines

The present study investigated the involvement of catecholamines in stress-mediated alterations in CYP1A1 induction by benzo(alpha)pyrene (B(alpha)P) in Wistar rats. This was achieved by measuring EROD activity and CYP1A1 mRNA levels in liver tissue from rats exposed to restraint stress and B(alpha)P coupled with pharmacological modulation of peripheral and central catecholamine levels and different adrenoceptors. In a state of reserpine-induced central and peripheral catecholamine depletion, stress strongly suppressed EROD induction. Peripheral catecholamines do not appear to play a critical role in the stress-mediated modulation of EROD inducibility by B(alpha)P. Stress did not alter EROD inducibility by B(alpha)P when peripheral catecholamines were either depleted by guanethidine or supplemented by peripheral adrenaline administration. On the other hand, central noradrenergic systems appear to have a role in the stress-mediated changes in B(alpha)P-induced EROD activity and Cyp1A1 gene expression. Stimulation or blockade of noradrenaline release with atipamezole and dexmedetomidine, respectively, significantly modified the up-regulating effect of stress. Alpha1 adrenoceptors also appear to participate in the effect of stress on EROD inducibility. Alpha1-blockade with prazosin potentiated the up-regulating effect of stress, possibly preventing the down-regulating effect of noradrenaline. Beta adrenoceptors also seem to be involved directly or indirectly in the stress-mediated modulation of Cyp1A1, as propranolol (beta-antagonist) blocked the down-regulating effect of stress on B(alpha)P-induced Cyp1A1 gene expression. Plasma corticosterone alterations after stress were not related to alterations in the B(alpha)P-induced EROD activity and Cyp1A1 gene expression. In conclusion, stress appears to interfere in the regulation of B(alpha)P-induced hepatic CYP1A1 in an unpredictable manner and via signalling pathways not always directly related to catecholamines. In particular, whenever drug treatment disrupts noradrenergic neurotransmission, other stress-stimulated factors appear to modify the induction of CYP1A1. In summary, regulation of induction of hepatic CYP1A1 during stress appears to involve various components of the stress system, including central and peripheral catecholamines, which interact in a complex manner, yet to be elucidated.

Chronic exposure to a GSM-like signal (mobile phone) does not stimulate the development of DMBA-induced mammary tumors in rats: results of three consecutive studies

Certain epidemiological and experimental studies raised concerns about the safety of radiofrequency (RF) electromagnetic fields because of a possible increased risk of leukemia and lymphoma. In this study, an RF field used in mobile telecommunication was tested using 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors in female Sprague-Dawley rats as a model for human breast cancer. Three experiments were carried out under strictly standardized conditions and were started on the same day of three consecutive years. The field consisted of a GSM-like signal (900 MHz pulsed at 217 Hz, pulse width 577 micros) of relatively low power flux density (100 microW/cm(2) +/- 3 dB) and was applied continuously throughout each experiment to freely moving animals. The specific absorption rates averaged over the whole body were 17.5-70 mW/kg. The highest values in young animals were at or around the exposure limit permissible for the general public (i.e. 80 mW/kg). The animals were palpated weekly for the presence of mammary tumors and were killed humanely when tumors reached a diameter of 1-2 cm to allow a reliable histopathological classification and a distinction between malignant and benign subtypes. The overall results of the three studies are that there was no statistically significant effect of RF-field exposure on tumor latency and that the cumulative tumor incidence at the end of the experiment was unaffected as well. The risk ratios were 1.08 (95% CI: 0.91-1.29) and 0.96 (95% CI: 0.85-1.07) for benign and malignant tumors, respectively. These observations are in agreement with other published findings. In the first experiment, however, the median latency for the development of the first malignant tumor in each animal was statistically significantly extended for RF-field-exposed animals compared to controls (278 days compared to 145 days, P = 0.009). No such differences were detected in the two subsequent experiments. These results show that low-level RF radiation does not appear to possess carcinogenic or cancer-promoting effects on DMBA-induced mammary tumors. To explain the mechanisms underlying the different results obtained in the three experiments, a hypothesis is presented which is based upon the neuroendocrine control mechanisms involved in the promotion of DMBA-induced mammary tumors. Despite the apparent absence of stimulatory effects of low-level RF-field exposure on the development and growth of solid tumors, it will be necessary to verify these results for leukemias and lymphomas, which may have completely different biological control mechanisms.

Common etiology of posttraumatic stress disorder, fibromyalgia, chronic fatigue syndrome and multiple chemical sensitivity via elevated nitric oxide/peroxynitrite

Three types of overlap occur among the disease states chronic fatigue syndrome (CFS), fibromyalgia (FM), multiple chemical sensitivity (MCS) and posttraumatic stress disorder (PTSD). They share common symptoms. Many patients meet the criteria for diagnosis for two or more of these disorders and each disorder appears to be often induced by a relatively short-term stress which is followed by a chronic pathology, suggesting that the stress may act by inducing a self-perpetuating vicious cycle. Such a vicious cycle mechanism has been proposed to explain the etiology of CFS and MCS, based on elevated levels of nitric oxide and its potent oxidant product, peroxynitrite. Six positive feedback loops were proposed to act such that when peroxynitrite levels are elevated, they may remain elevated. The biochemistry involved is not highly tissue-specific, so that variation in symptoms may be explained by a variation in nitric oxide/peroxynitrite tissue distribution. The evidence for the same biochemical mechanism in the etiology of PTSD and FM is discussed here, and while less extensive than in the case of CFS and MCS, it is nevertheless suggestive. Evidence supporting the role of elevated nitric oxide/peroxynitrite in these four disease states is summarized, including induction of nitric oxide by common apparent inducers of these disease states, markers of elevated nitric oxide/peroxynitrite in patients and evidence for an inductive role of elevated nitric oxide in animal models. This theory appears to be the first to provide a mechanistic explanation for the multiple overlaps of these disease states and it also explains the origin of many of their common symptoms and similarity to both Gulf War syndrome and chronic sequelae of carbon monoxide toxicity. This theory suggests multiple studies that should be performed to further test this proposed mechanism. If this mechanism proves central to the etiology of these four conditions, it may also be involved in other conditions of currently obscure etiology and criteria are suggested for identifying such conditions.

Stress modulates the enzymatic inducibility by benzo[alpha]pyrene in the rat liver

The role of stress on the inducibility by benzo[alpha]pyrene (B[alpha]P), a representative polycyclic aromatic hydrocarbon, of several drug-metabolizing enzymes was investigated in rats, using restraint stress and mild unpredictable stress as models of psychological stress. Restraint stress was found to significantly suppress basal ethoxyresorufin 7-dealkylase (EROD) and pentoxyresorufin 7-dealkylase (PROD) activities (two-fold). In contrast, mild unpredictable stress markedly increased basal EROD activity, while PROD activity was not affected. In addition, both types of stress resulted in a significant reduction of basal p -nitrophenol hydroxylation (PNP). It is worth noting that restraint stress greatly enhanced the inducibility of EROD, methoxyresorufin 7-dealkylase (MROD) and to a lesser extent PROD activities by B[alpha]P, while mild unpredictable stress had no, or only a mild effect on the inducibility of cytochrome P450s (CYPs) by B[alpha]P. In conclusion, psychological stress may modulate different enzymatic systems which are vital elements of the detoxification mechanisms of the body. The two distinct types of psychological stress used in this study appear to affect the enzymatic systems under investigation in a stress-specific manner at the basal level and at the induced state by B[alpha]P.

Restraint as a stressor in mice: against the dopaminergic neurotoxicity of D-MDMA, low body weight mitigates restraint-induced hypothermia and consequent neuroprotection

In experimental studies of stress, restraint of laboratory rodents, perceived as easy to apply and believed to be reproducible, is a commonly used manipulation. The restraint manipulation is utilized as a technique to characterize the physiological, cellular and molecular consequences of stress as well as a tool to understand the ways in which stress may interact with toxic substances. In previous work, we utilized restraint in an examination of the effect of stress on the striatal dopaminergic neurotoxicity engendered by a series of substituted amphetamines. Contrary to our expectations, and most likely due to its body temperature-reducing properties in the mouse, restraint provided total or near total protection against the neurotoxicity of these agents. During subsequent studies utilizing C57Bl6/J female mice of varying weights and ages the degree of temperature reduction and the associated ability to block (20-100%) the dopamine depletion associated with the neurotoxic amphetamine 3,4-methylendioxyamphetamine (D-MDMA, 20 mg/kg of mouse body weight, every 2 h, s.c., total of four doses) were found to vary considerably more than had been previously observed. An in-depth analysis of the role mouse weight plays in the temperature reduction induced by restraint indicates mouse weight is a primary determinant of hypothermia and subsequent neuroprotection. It suggests the induction of stress in rodents by restraint is a complex effect that may lead to unanticipated results. The restraint manipulation is not as straight-forward a procedure as is commonly believed. Our data indicate that consistent application of restraint may require an adjustment of the restrainer device to mouse body weight.

Noradrenaline, dopamine, serotonin: different effects of psychological stress on brain biogenic amines in mice and rats

The effect of restraint stress on central neurotransmission was evaluated in mice and rats. Noradrenaline (NA), dopamine (DA) and serotonin (5-HT) levels and their primary metabolites were measured in discrete brain regions following exposure to stress. Mice and rats demonstrated a similar response to stress in some brain regions. Both species responded to stress with lower NA and 5-HT in the locus coeruleus compared to non-stressed controls. Dopaminergic activity, assessed by DA turnover, was elevated in the hypothalamus. While DA turnover was suppressed in the amygdala, 5-HT turnover was similarly elevated in both species. In most cases, however, there were differences in biogenic neurotransmission between mice and rats in response to stress. In particular, NA levels were suppressed by stress in the dorsal cortex of mice, but in the rats NA levels were decreased in the hypothalamus. While stress produced lower DA levels in the hypothalamus, DA levels demonstrated a marked increase in the amygdala of mice. Stress was also associated with a decrease in DA levels in the rat striatum and with an increase of DA turnover in the locus coeruleus of mice. On the other hand, 5-HT was suppressed in the mouse striatum and in the rat hypothalamus and amygdala, while 5-HT turnover was markedly decreased in the hippocampus and dorsal cortex of rats alone. In conclusion, the changes in the central neurotransmission which are evoked by stress appear to be species-specific in most cases, a fact which may trigger discrete alterations in homeostatic mechanisms.