A masked gene concealed hand in glove in the forkhead protein crocodile regulates the predominant detoxification CYP6DA1 in Aphis gossypii Glover

Cytochrome P450-mediated metabolism is an important mechanism of insecticide resistance, most studies show upregulated transcript levels of P450s in resistant insect strains. Our previous studies illustrated that some upregulated P450s were associated with cyantraniliprole resistance, and it is more comprehensive to use the tissue specificity of transcriptomes to compare resistant (CyR) and susceptible (SS) strains. In this study, the expression profiles of P450s in a CyR strain compared with a SS strain in remaining carcass or midgut were investigated by RNA sequencing, and candidate genes were selected for functional study. Drosophila melanogaster bioassays suggested that ectopic overexpression of CYP4CK1, CYP6CY5, CYP6CY9, CYP6CY19, CYP6CZ1 and CYP6DA1 in flies was sufficient to confer cyantraniliprole resistance, among which CYP6DA1 was the predominant contributor to resistance (12.24-fold). RNAi suppression of CYP4CK1, CYP6CY5, CYP6CY9 and CYP6DA1 significantly increased CyR aphid sensitivity to cyantraniliprole. The CYP6DA1 promoter had two predicted binding sites for crocodile (CROC), an intron-free ORF with bidirectional transcription yielding CROC (+) and CROC (-). Y1H, RNAi and EMSA found that CROC (-) was a transcription factor directly regulating CYP6DA1 expression. In conclusion, P450 genes contribute to cyantraniliprole resistance, and the transcription factor CROC (-) regulates the expression of CYP6DA1 in A. gossypii.

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.

The Effects of AT-533 and AT-533 gel on Liver Cytochrome P450 Enzymes in Rats

BACKGROUND AND OBJECTIVES

AT-533 is a novel heat shock protein 90 inhibitor, which exhibits various biological activities in vitro and in vivo. Cytochrome P450 (CYP) enzymes in the liver are involved in the biotransformation of drugs and considered to be essential indicators of liver toxicity. The aim of this study was to assess the effect of AT-533, either as active pharmaceutical ingredient or in gel form, on liver CYP enzymes.

METHODS

The effect of AT-533 or AT-533 gel on rat liver cytochrome P450 enzymes, including CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, was analyzed using LC-MS/MS.

RESULTS

AT-533 and AT-533 gel did not significantly increase or reduce the enzymatic activity of CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 at any treatment dose.

CONCLUSIONS

AT-533 and AT-533 gel did not have any effect on CYP activity and may be considered safe for external use in gel form, as an alternative to conventional treatment.

Chronic treatment with asenapine affects cytochrome P450 2D (CYP2D) in rat brain and liver. Pharmacological aspects

Neuroleptics have to be used for a long time to produce a therapeutic effect. Cytochrome P450 2D (CYP2D) enzymes mediate alternative pathways of neurotransmitter synthesis (i.e. tyramine hydroxylation to dopamine and 5-methoxytryptamine O-demethylation to serotonin), and metabolism of neurosteroids. The aim of our present study was to examine the influence of chronic treatment with the new atypical neuroleptic asenapine on CYP2D in rat brain. In parallel, liver CYP2D was investigated for comparison. Asenapine added in vitro to microsomes of control rats competitively, but weakly inhibited the activity of CYP2D (brain: Ki = 385 μM; liver: Ki = 36 μM). However, prolonged administration of asenapine (0.3 mg/kg sc. for 2 weeks) significantly diminished the activity and protein level of CYP2D in the frontal cortex, nucleus accumbens, hippocampus and cerebellum, but did not affect the enzyme in the hypothalamus, brain stem, substantia nigra and the remainder of the brain. In contrast, asenapine enhanced the enzyme activity and protein level in the striatum. In the liver, chronically administered asenapine reduced the activity and protein level of CYP2D, and the CYP2D1 mRNA level. In conclusion, prolonged administration of asenapine alters the CYP2D expression in the brain structures and in the liver. Through affecting the CYP2D activity in the brain, asenapine may modify its pharmacological effect. By increasing the CYP2D expression/activity in the striatum, asenapine may accelerate the synthesis of dopamine (via tyramine hydroxylation) and serotonin (via 5-methoxytryptamine O-demethylation), and thus alleviate extrapyramidal symptoms. By reducing the CYP2D expression/activity in other brain structures asenapine may diminish the 21-hydroxylation of neurosteroids and thus have a beneficial influence on the symptoms of schizophrenia. In the liver, by reducing the CYP2D activity, asenapine may slow the biotransformation of concomitantly administered CYP2D substrates (drugs) during continuous treatment of schizophrenia or bipolar disorders.

Oleuropein-Induced Acceleration of Cytochrome P450-Catalyzed Drug Metabolism: Central Role for Nuclear Receptor Peroxisome Proliferator-Activated Receptor α

Oleuropein (OLE), the main constituent of Olea europaea, displays pleiotropic beneficial effects in health and disease, which are mainly attributed to its anti-inflammatory and cardioprotective properties. Several food supplements and herbal medicines contain OLE and are available without a prescription. This study investigated the effects of OLE on the main cytochrome P450s (P450s) catalyzing the metabolism of many prescribed drugs. Emphasis was given to the role of peroxisome proliferator-activated receptor α (PPARα), a nuclear transcription factor regulating numerous genes including P450s. 129/Sv wild-type and Ppara-null mice were treated with OLE for 6 weeks. OLE induced Cyp1a1, Cyp1a2, Cyp1b1, Cyp3a14, Cyp3a25, Cyp2c29, Cyp2c44, Cyp2d22, and Cyp2e1 mRNAs in liver of wild-type mice, whereas no similar effects were observed in Ppara-null mice, indicating that the OLE-induced effect on these P450s is mediated by PPARα. Activation of the pathways related to phosphoinositide 3-kinase/protein kinase B (AKT)/forkhead box protein O1, c-Jun N-terminal kinase, AKT/p70, and extracellular signal-regulated kinase participates in P450 induction by OLE. These data indicate that consumption of herbal medicines and food supplements containing OLE could accelerate the metabolism of drug substrates of the above-mentioned P450s, thus reducing their efficacy and the outcome of pharmacotherapy. Therefore, OLE-induced activation of PPARα could modify the effects of drugs due to their increased metabolism and clearance, which should be taken into account when consuming OLE-containing products with certain drugs, in particular those of narrow therapeutic window. SIGNIFICANCE STATEMENT: This study indicated that oleuropein, which belongs to the main constituents of the leaves and olive drupes of Olea europaea, induces the synthesis of the major cytochrome P450s (P450s) metabolizing the majority of prescribed drugs via activation of peroxisome proliferator-activated receptor α. This effect could modify the pharmacokinetic profile of co-administered drug substrates of the P450s, thus altering their therapeutic efficacy and toxicity.

Anatomical distribution and expression of CYP in humans: Neuropharmacological implications

The cytochrome P450 (CYP450) superfamily is responsible for the metabolism of most xenobiotics and pharmacological treatments generally used in clinical settings. Genetic factors as well as environmental determinants acting through fine epigenetic mechanisms modulate the expression of CYP over the lifespan (fetal vs. infancy vs. adult phases) and in diverse organs. In addition, pathological processes might alter the expression of CYP. In this selective review, we sought to summarize the evidence on the expression of CYP focusing on three specific aspects: (a) the anatomical distribution of the expression in body districts relevant in terms of drug pharmacokinetics (liver, gut, and kidney) and pharmacodynamics, focusing for the latter on the brain, since this is the target organ of psychopharmacological agents; (b) the patterns of expression during developmental phases; and (c) the expression of CYP450 enzymes during pathological processes such as cancer. We showed that CYP isoforms show distinct patterns of expression depending on the body district and the specific developmental phases. Of particular relevance for neuropsychopharmacology is the complex regulatory mechanisms that significantly modulate the complexity of the pharmacokinetic regulation, including the concentration of specific CYP isoforms in distinct areas of the brain, where they could greatly affect local substrate and metabolite concentrations of drugs.

Sex steroid hormones differentially regulate CYP2D in female wild-type and CYP2D6-humanized mice

The CYP2D subfamily catalyses the metabolism of about 25% of prescribed drugs, including the majority of antidepressants and antipsychotics. At present, the mechanism of hepatic CYP2D regulation remains largely unknown. This study investigated the role of sex steroid hormones in CYP2D regulation. For this purpose, Cyp2d22 expression was assessed in the distinct phases of the estrous cycle of normocyclic C57BL/6J (WT) female mice. Cyp2d22 was also evaluated in ovariectomised WT and CYP2D6-humanized (hCYP2D6) mice that received hormonal supplementation with either 17β-estradiol (E2) and/or progesterone. Comparisons were also made to male mice. The data revealed that hepatic Cyp2d22 mRNA, protein and activity levels were higher at estrous compared to the other phases of the estrous cycle and that ovariectomy repressed Cyp2d22 expression in WT mice. Tamoxifen, an anti-estrogenic compound, also repressed hepatic Cyp2d22 via activation of GH/STAT5b and PI3k/AKT signaling pathways. Both hormones prevented the ovariectomy-mediated Cyp2d22 repression. In case of progesterone, this may be mediated by inhibition of the PI3k/AKT/FOX01 pathway. Notably, Cyp2d22 mRNA levels in WT males were similar to those in ovariectomised mice and were markedly lower compared to females at estrous, a differentiation potentially regulated by the GH/STAT5b pathway. Sex steroid hormone-related alterations in Cyp2d22 mRNA expression were highly correlated with Hnf1a mRNA. Interestingly, fluctuations in Cyp2d22 in hippocampus and cerebellum followed those in liver. In contrast to WT mice, ovariectomy induced hepatic CYP2D6 expression in hCYP2D6 mice, whereas E2 and/or progesterone prevented this induction. Apparently, sex steroid hormones display a significant gender- and species-specific role in the regulation of CYP2D.

Role of glucocorticoid- and monoamine-metabolizing enzymes in stress-related psychopathological processes

Glucocorticoid signaling is fundamental in healthy stress coping and in the pathophysiology of stress-related diseases, such as post-traumatic stress disorder (PTSD). Glucocorticoids are metabolized by cytochrome P450 (CYP) as well as 11-β-hydroxysteroid dehydrogenase type 1 (11βHSD1) and 2 (11βHSD2). Acute stress-induced increase in glucocorticoid concentrations stimulates the expression of several CYP sub-types. CYP is primarily responsible for glucocorticoid metabolism and its increased activity can result in decreased circulating glucocorticoids in response to repeated stress stimuli. In addition, repeated stress-induced glucocorticoid release can promote 11βHSD1 activation and 11βHSD2 inhibition, and the 11βHSD2 suppression can lead to apparent mineralocorticoid excess. The activation of CYP and 11βHSD1 and the suppression of 11βHSD2 may at least partly contribute to development of the blunted glucocorticoid response to stressors characteristic in high trait anxiety, PTSD, and other stress-related disorders. Glucocorticoids and glucocorticoid-metabolizing enzymes interact closely with other biomolecules such as inflammatory cytokines, monoamines, and some monoamine-metabolizing enzymes, namely the monoamine oxidase type A (MAO-A) and B (MAO-B). Glucocorticoids boost MAO activity and this decreases monoamine levels and induces oxidative tissue damage which then activates inflammatory cytokines. The inflammatory cytokines suppress CYP expression and activity. This dynamic cross-talk between glucocorticoids, monoamines, and their metabolizing enzymes could be a critical factor in the pathophysiology of stress-related disorders.Lay summaryGlucocorticoids, which are produced and released under the control by brain regulatory centers, are fundamental in the stress response. This review emphasizes the importance of glucocorticoid metabolism and particularly the interaction between the brain and the liver as the major metabolic organ in the body. The activity of enzymes involved in glucocorticoid metabolism is proposed to play not only an important role in positive, healthy glucocorticoid effects, but also to contribute to the development and course of stress-related diseases.

Fatty acids modulate the expression of pyruvate kinase and arachidonate-lipoxygenase through PPARγ/CYP2C45 pathway: a link to goose fatty liver

Cytochrome P-450 2C45 (CYP2C45) is the most highly expressed cytochrome P-450 isoform in chicken liver, and may play an important role in avian liver biology. However, information regarding the function of CYP2C45 in fatty liver is generally limited. The aim of this study was to investigate the role of CYP2C45 during the development of goose fatty liver. Our result indicated that the transcription of CYP2C45, together with PK and ALOX5, was increased in goose liver upon overfeeding for 19 D (P < 0.05). In goose primary hepatocytes, CYP2C45 RNA expression was also upgraded by the treatment with various chemicals like insulin, the fatty acids, and PPAR agonists (P < 0.05). We also found that both CYP2C45 overexpression and troglitazone treatment could increase the expression of pyruvate kinase (PK) and arachidonate 5-lipoxygenase (ALOX5), and furthermore, showed that the up-regulation of PK and ALOX5 induced by troglitazone could be suppressed by small interfering RNAs targeting CYP2C45 (P < 0.05). These findings suggest that fatty acids treatment and the overfeeding can induce the up-regulation of CYP2C45 expression possibly via PPARγ and that the induction of PK and ALOX5 in goose fatty liver is at least partially attributed to fatty acid-induced expression of CYP2C45. Thus, our data provides an insight into the mechanism by which glycolysis and arachidonic acid metabolism are modulated in goose fatty liver.

Age-associated changes of cytochrome P450 and related phase-2 gene/proteins in livers of rats

Cytochrome P450s (CYPs) are phase-I metabolic enzymes playing important roles in drug metabolism, dietary chemicals and endogenous molecules. Age is a key factor influencing P450s expression. Thus, age-related changes of CYP 1–4 families and bile acid homeostasis-related CYPs, the corresponding nuclear receptors and a few phase-II genes were examined. Livers from male Sprague-Dawley rats at fetus (−2 d), neonates (1, 7, and 14 d), weanling (21 d), puberty (28 and 35 d), adulthood (60 and 180 d), and aging (540 and 800 d) were collected and subjected to qPCR analysis. Liver proteins from 14, 28, 60, 180, 540 and 800 days of age were also extracted for selected protein analysis by western blot. In general, there were three patterns of their expression: Some of the drug-metabolizing enzymes and related nuclear receptors were low in fetal and neonatal stage, increased with liver maturation and decreased quickly at aging (AhR, Cyp1a1, Cyp2b1, Cyp2b2, Cyp3a1, Cyp3a2, Ugt1a2); the majority of P450s (Cyp1a2, Cyp2c6, Cyp2c11, Cyp2d2, Cyp2e1, CAR, PXR, FXR, Cyp7a1, Cyp7b1. Cyp8b1, Cyp27a1, Ugt1a1, Sult1a1, Sult1a2) maintained relatively high levels throughout the adulthood, and decreased at 800 days of age; and some had an early peak between 7 and 14 days (CAR, PXR, PPARα, Cyp4a1, Ugt1a2). The protein expression of CYP1A2, CYP2B1, CYP2E1, CYP3A1, CYP4A1, and CYP7A1 corresponded the trend of mRNA changes. In summary, this study characterized three expression patterns of 16 CYPs, five nuclear receptors, and four phase-II genes during development and aging in rat liver, adding to our understanding of age-related CYP expression changes and age-related disorders.

Targeting Dopamine D2, Adenosine A2A, and Glutamate mGlu5 Receptors to Reduce Repetitive Behaviors in Deer Mice

Repetitive behaviors are seemingly purposeless patterns of behavior that vary little in form and are characteristic of many neurodevelopmental, psychiatric, and neurologic disorders. Our work has identified an association between hypofunctioning of the indirect basal ganglia pathway and the expression of repetitive behavior in the deer mouse model. In this study, we targeted indirect pathway cells of the striatum with single drugs and drug combinations that bind to dopamine D₂, adenosine A_2A, and glutamate mGlu₅ receptors. These receptors function both individually and as receptor heteromers. We found that only the triple drug cocktail (L-741,626+CGS21680+CDPPB) that was designed to increase striatal indirect basal ganglia pathway cell function reduced repetitive behavior in adult male deer mice. No single drug or double drug combinations were effective at selectively reducing repetitive behavior. We found this triple drug cocktail reduced repetitive behavior in both short-acting and long-acting formulations and was effective throughout 7 days of daily administration. Conversely, another triple drug cocktail (quinpirole+SCH58261+MTEP) that was designed to further reduce striatal indirect basal ganglia pathway cell function caused a significant increase in repetitive behavior. Significant and behaviorally selective effects on repetitive behavior were only achieved with the triple drug cocktails that included doses of L-741,626 and quinpirole that have off-target effects (e.g., dopamine D₃ receptors). These data further a role for decreased indirect basal ganglia pathway activation in repetitive behavior and suggest that targeting these receptors and/or heteromeric complexes on the indirect pathway neurons of the striatum may offer pharmacotherapeutic benefit for individuals with repetitive behavior disorders.

Effect of Prolactin on Biochemical and Morphological Parameters of Rabbit Liver in Warm Ischemia

BACKGROUND

The aim of the study was to assess the degree of liver damage in a rabbit perfused with histidine-tryptophan-ketoglutarate (HTK [Custodiol]) solution with and without the presence of prolactin (PRL) based on biochemical studies in perfundate and ultrastructural analysis of hepatocytes.

MATERIALS AND METHODS

The experiment was carried out on rabbits. Liver ischemia was used in the study, based on Pringle's maneuver. About 70% of the rabbit liver lobes were perfused with HTK with or without the addition of PRL (2.5μg/g liver/h) under ischemic conditions for 2 hours. In the perfundate, the activity of enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), γ-glutamyl transpeptidase (GGT), and lactate concentration were determined. Liver biopsies were collected for histopathologic evaluation under an electron microscope.

RESULTS

The addition of PRL to the HTK significantly reduced the leakage of enzymes from the liver to perfundate compared with the control group without PRL. The activity of ALT, AST, LDH, and GGT in the perfundates obtained after 2-hour perfusion with HTK-PRL solution was lower when compared with activity of the same parameters determined in perfundates with liver perfused with HTK without PRL. The area under the curve (AUC_0-2h) calculated for GGT, LDH, and lactates was significantly higher after perfusion with the HTK than with HTK with the addition of PRL. In the study group, bile was secreted throughout the whole experiment. The morphological confirmation of these results was obtained by means of transmission microscopy.

CONCLUSION

PRL added to the preservation solution significantly inhibits the process of liver cell cytolysis, which may suggest its hepatoprotective effect.

Access to the CNS: Biomarker Strategies for Dopaminergic Treatments

Despite substantial research carried out over the last decades, it remains difficult to understand the wide range of pharmacological effects of dopaminergic agents. The dopaminergic system is involved in several neurological disorders, such as Parkinson's disease and schizophrenia. This complex system features multiple pathways implicated in emotion and cognition, psychomotor functions and endocrine control through activation of G protein-coupled dopamine receptors. This review focuses on the system-wide effects of dopaminergic agents on the multiple biochemical and endocrine pathways, in particular the biomarkers (i.e., indicators of a pharmacological process) that reflect these effects. Dopaminergic treatments developed over the last decades were found to be associated with numerous biochemical pathways in the brain, including the norepinephrine and the kynurenine pathway. Additionally, they have shown to affect peripheral systems, for example the hypothalamus-pituitary-adrenal (HPA) axis. Dopaminergic agents thus have a complex and broad pharmacological profile, rendering drug development challenging. Considering the complex system-wide pharmacological profile of dopaminergic agents, this review underlines the needs for systems pharmacology studies that include: i) proteomics and metabolomics analysis; ii) longitudinal data evaluation and mathematical modeling; iii) pharmacokinetics-based interpretation of drug effects; iv) simultaneous biomarker evaluation in the brain, the cerebrospinal fluid (CSF) and plasma; and v) specific attention to condition-dependent (e.g., disease) pharmacology. Such approach is considered essential to increase our understanding of central nervous system (CNS) drug effects and substantially improve CNS drug development.

Altered tolbutamide pharmacokinetics by a decrease in hepatic expression of CYP2C6/11 in rats pretreated with 5-fluorouracil

1. We investigated the change in the pharmacokinetic profile of tolbutamide (TB), a substrate for CYP2C6/11, 4 days after single administration of 5-fluorouracil (5-FU), and the hepatic gene expression and activity of CYP2C6/11 were also examined in 5-FU-pretreated rats. 2. Regarding the pharmacokinetic parameters of the 5-FU group, the area under the curve (AUC) was significantly increased, and correspondingly, the elimination rate constant at the terminal phase (k_e) was significantly decreased without significant change in the volume of distribution at the steady state (Vd_ss). 3. The metabolic production of 4-hydroxylated TB in hepatic microsomes was significantly reduced by the administration of 5-FU. 4. The expression level of mRNAs for hepatic CYP2C6 and CYP2C11 was significantly lower than in the control group when the rats were pretreated with 5-FU. 5. These results demonstrated that the pharmacokinetic profile of TB was altered by the treatment with 5-FU through a metabolic process, which may be responsible for the decreased CYP2C6/11 expression at mRNA levels.

Parameters of Calcium Metabolism Fluctuated during Initiation or Changing of Antipsychotic Drugs

OBJECTIVE

Serum parameters of calcium homeostasis were measured based on previously published evidence linking osteoporotic fractures and/or bone/mineral loss with antipsychotics.

METHODS

Prospective, four-week, time-series trial was conducted and study population consisted of patients of both genders, aged 35-85 years, admitted within the routine practice, with acute psychotic symptoms, to whom an antipsychotic drug was either introduced or substituted. Serial measurements of serum calcium, phosphorous, magnesium, 25(OH)D, parathyroid hormone, calcitonin, osteocalcin and C-telopeptide were made from patient venous blood samples.

RESULTS

Calcium serum concentrations significantly decreased from baseline to the fourth week (2.42±0.12 vs. 2.33±0.16 mmol/L, p=0.022, n=25). The mean of all calcemia changes from the baseline was -2.6±5.7% (-24.1 to 7.7) with more decreases than increases (78 vs. 49, p=0.010) and more patents having negative sum of calcemia changes from baseline (n=28) than positive ones (n=10) (p=0.004). There were simultaneous falls of calcium and magnesium from baseline (63/15 vs. 23/26, p<0.001; OR=4.75, 95% CI 2.14-10.51), phosphorous (45/33 vs. 9/40, p<0.001; 6.06, 2.59-14.20) and 25(OH)D concentrations (57/21 vs. 13/35, p<0.001; 7.31, 3.25-16.42), respectively. Calcemia positively correlated with magnesemia, phosphatemia and 25(OH)D values. Parathyroid hormone and C-telopeptide showed only subtle oscillations of their absolute concentrations or changes from baseline; calcitonin and osteocalcin did not change. Adjustment of final calcemia trend (depletion/accumulation) for relevant risk factors, generally, did not change the results.

CONCLUSION

In patients with psychotic disorders and several risks for bone metabolism disturbances antipsychotic treatment was associated with the decrease of calcemia and changes in levels of the associated ions.

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.

Pituitary and brain dopamine D2 receptors regulate liver gene sexual dimorphism

Liver sexual gene dimorphism, which depends mainly on specific patterns of GH secretion, may underlie differential susceptibility to some liver diseases. Because GH and prolactin secretion are regulated by dopaminergic pathways, we studied the participation of brain and lactotrope dopamine 2 receptors (D2Rs) on liver gene sexual dimorphism, to explore a link between the brain and liver gene expression. We used global D2R knockout mice (Drd2(-/-)) and conducted a functional dissection strategy based on cell-specific Drd2 inactivation in neurons (neuroDrd2KO) or pituitary lactotropes. Disruption of neuronal D2Rs (which impaired the GH axis) decreased most of male or female-predominant class I liver genes and increased female-predominant class II genes in males, consistent with the positive (class I) or negative (class II) regulation of these genes by GH. Notably, sexual dimorphism was lost for class I and II genes in neuroDrd2KO mice. Disruption of lactotrope D2Rs did not modify class I or II genes in either sex, because GH axis was preserved. But surprisingly, 1 class II gene (Prlr) and female-predominant class I genes were markedly up-regulated in lacDrd2KO females, pointing to direct or indirect effects of prolactin in the regulation of selected female-predominant liver genes. This suggestion was strengthened in the hyperprolactinemic Drd2(-/-) female mouse, in which increased expression of the same 4 liver genes was observed, despite a decreased GH axis. We hereby demonstrate endocrine-mediated D2R actions on sexual dimorphic liver gene expression, which may be relevant during chronic dopaminergic medications in psychiatric disease.