Cytochrome P450 1B1 mRNA in the human central nervous system

Exploring the Genetic Landscape of Childhood Glaucoma

Childhood glaucoma, a significant cause of global blindness, represents a heterogeneous group of disorders categorized into primary or secondary forms. Primary childhood glaucoma stands as the most prevalent subtype, comprising primary congenital glaucoma (PCG) and juvenile open-angle glaucoma (JOAG). Presently, multiple genes are implicated in inherited forms of primary childhood glaucoma. This comprehensive review delves into genetic investigations into primary childhood glaucoma, with a focus on identifying causative genes, understanding their inheritance patterns, exploring essential biological pathways in disease pathogenesis, and utilizing animal models to study these mechanisms. Specifically, attention is directed towards genes such as CYP1B1 (cytochrome P450 family 1 subfamily B member 1), LTBP2 (latent transforming growth factor beta binding protein 2), TEK (TEK receptor tyrosine kinase), ANGPT1 (angiopoietin 1), and FOXC1 (forkhead box C1), all associated with PCG; and MYOC (myocilin), associated with JOAG. Through exploring these genetic factors, this review aims to deepen our understanding of the intricate pathogenesis of primary childhood glaucoma, thereby facilitating the development of enhanced diagnostic and therapeutic strategies.

The potential impact of CYP and UGT drug-metabolizing enzymes on brain target site drug exposure

Drug metabolism is one of the critical determinants of drug disposition throughout the body. While traditionally associated with the liver, recent research has unveiled the presence and functional significance of drug-metabolizing enzymes (DMEs) within the brain. Specifically, cytochrome P-450 enzymes (CYPs) and UDP-glucuronosyltransferases (UGTs) enzymes have emerged as key players in drug biotransformation within the central nervous system (CNS). This comprehensive review explores the cellular and subcellular distribution of CYPs and UGTs within the CNS, emphasizing regional expression and contrasting profiles between the liver and brain, humans and rats. Moreover, we discuss the impact of species and sex differences on CYPs and UGTs within the CNS. This review also provides an overview of methodologies for identifying and quantifying enzyme activities in the brain. Additionally, we present factors influencing CYPs and UGTs activities in the brain, including genetic polymorphisms, physiological variables, pathophysiological conditions, and environmental factors. Examples of CYP- and UGT-mediated drug metabolism within the brain are presented at the end, illustrating the pivotal role of these enzymes in drug therapy and potential toxicity. In conclusion, this review enhances our understanding of drug metabolism's significance in the brain, with a specific focus on CYPs and UGTs. Insights into the expression, activity, and influential factors of these enzymes within the CNS have crucial implications for drug development, the design of safe drug treatment strategies, and the comprehension of drug actions within the CNS. To that end, CNS pharmacokinetic (PK) models can be improved to further advance drug development and personalized therapy.

Mitochondrial cytochrome P450 1B1 is involved in pregnenolone synthesis in human brain cells

Neurosteroids, which are steroids synthesized by the nervous system, can exert neuromodulatory and neuroprotective effects via genomic and nongenomic pathways. The neurosteroid and major steroid precursor pregnenolone has therapeutical potential in various diseases, such as psychiatric and pain disorders, and may play important roles in myelination, neuroinflammation, neurotransmission, and neuroplasticity. Although pregnenolone is synthesized by CYP11A1 in peripheral steroidogenic organs, our recent study showed that pregnenolone must be synthesized by another mitochondrial cytochrome P450 (CYP450) enzyme other than CYP11A1 in human glial cells. Therefore, we sought to identify the CYP450 responsible for pregnenolone production in the human brain. Upon screening for CYP450s expressed in the human brain that have mitochondrial localization, we identified three enzyme candidates: CYP27A1, CYP1A1, and CYP1B1. We found that inhibition of CYP27A1 through inhibitors and siRNA knockdown did not negatively affect pregnenolone synthesis in human glial cells. Meanwhile, treatment of human glial cells with CYP1A1/CYP1B1 inhibitors significantly reduced pregnenolone production in the presence of 22(R)-hydroxycholesterol. We performed siRNA knockdown of CYP1A1 or CYP1B1 in human glial cells and found that only CYP1B1 knockdown significantly decreased pregnenolone production. Furthermore, overexpression of mitochondria-targeted CYP1B1 significantly increased pregnenolone production under basal conditions and in the presence of hydroxycholesterols and low-density lipoprotein. Inhibition of CYP1A1 and/or CYP1B1 via inhibitors or siRNA knockdown did not significantly reduce pregnenolone synthesis in human adrenal cortical cells, implying that CYP1B1 is not a major pregnenolone-producing enzyme in the periphery. These data suggest that mitochondrial CYP1B1 is involved in pregnenolone synthesis in human glial cells.

Benzo[a]pyrene impairs the migratory pattern of human gonadotropin-releasing-hormone-secreting neuroblasts

Benzo[a]pyrene (BaP) is a widespread pollutant that can act as an endocrine disrupting compound (EDC) and interferes with reproductive function. The central regulatory network of the reproductive system is mediated by gonadotropin-releasing hormone (GnRH) neurons, which originate in the olfactory placode and, during ontogenesis, migrate into the hypothalamus. Given the importance of the migratory process for GnRH neuron maturation, we investigated the effect of BaP (10 μM for 24 h) on GnRH neuroblasts isolated from the human fetal olfactory epithelium (FNCB4). BaP exposure significantly reduced the mRNA level of genes implicated in FNCB4 cell migration and affected their migratory ability. Our findings demonstrate that BaP may interfere with the central neuronal network controlling human reproduction affecting GnRH neuron maturation.

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.

Cytochrome P450 expression and regulation in the brain

The regulation of brain cytochrome P450 enzymes (CYPs) is different compared with respective hepatic enzymes. This may result from anatomical bases and physiological functions of the two organs. The brain is composed of a variety of functional structures built of different interconnected cell types endowed with specific receptors that receive various neuronal signals from other brain regions. Those signals activate transcription factors or alter functioning of enzyme proteins. Moreover, the blood-brain barrier (BBB) does not allow free penetration of all substances from the periphery into the brain. Differences in neurotransmitter signaling, availability to endogenous and exogenous active substances, and levels of transcription factors between neuronal and hepatic cells lead to differentiated expression and susceptibility to the regulation of CYP genes in the brain and liver. Herein, we briefly describe the CYP enzymes of CYP1-3 families, their distribution in the brain, and discuss brain-specific regulation of CYP genes. In parallel, a comparison to liver CYP regulation is presented. CYP enzymes play an essential role in maintaining the levels of bioactive molecules within normal ranges. These enzymes modulate the metabolism of endogenous neurochemicals, such as neurosteroids, dopamine, serotonin, melatonin, anandamide, and exogenous substances, including psychotropics, drugs of abuse, neurotoxins, and carcinogens. The role of these enzymes is not restricted to xenobiotic-induced neurotoxicity, but they are also involved in brain physiology. Therefore, it is crucial to recognize the function and regulation of CYP enzymes in the brain to build a foundation for future medicine and neuroprotection and for personalized treatment of brain diseases.

4-Hydroxyestrone, an Endogenous Estrogen Metabolite, Can Strongly Protect Neuronal Cells Against Oxidative Damage

Earlier studies showed that endogenous estrogens have neuroprotective effect against oxidative damage. The present study seeks to investigate the protective effect of various endogenous estrogen metabolites against oxidative neurotoxicity in vitro and in vivo. Using immortalized mouse hippocampal neuronal cells as an in vitro model, 4-hydroxyestrone, an estrone metabolite with little estrogenic activity, is found to have the strongest neuroprotective effect against oxidative neurotoxicity among 25 endogenous estrogen metabolites tested, and its protective effect is stronger than 17β-estradiol. Similarly, 4-Hydroxyestrone also exerts a stronger protective effect than 17β-estradiol against kanic acid-induced hippocampal oxidative damage in rats. Neuroprotection by 4-hydroxyestrone involves increased cytoplasmic translocation of p53 resulting from SIRT1-mediated deacetylation of p53. Analysis of brain microsomal enzymes shows that estrogen 4-hydroxylation is the main metabolic pathway in the central nervous system. Together, these results show that 4-hydroxyestrone is an endogenous neuroestrogen that can strongly protect against oxidative neuronal damage.

Central CYP1B1 (Cytochrome P450 1B1)-Estradiol Metabolite 2-Methoxyestradiol Protects From Hypertension and Neuroinflammation in Female Mice

Supplemental Digital Content is available in the text.

Previously, we showed that peripheral administration of 2-ME (2-methoxyestradiol), a CYP1B1 (cytochrome P450 1B1)-catechol-O-methyltransferase (COMT) generated metabolite of E2 (17β-Estradiol), protects against angiotensin II-induced hypertension in female mice. The demonstration that central E2 inhibits angiotensin II-induced hypertension, together with the expression of CYP1B1 in the brain, led us to hypothesize that E2-CYP1B1 generated metabolite 2-ME in the brain mediates its protective action against angiotensin II-induced hypertension in female mice. To test this hypothesis, we examined the effect of intracerebroventricularly (ICV) administered E2 in ovariectomized (OVX)-wild-type (Cyp1b1^+/+) and OVX-Cyp1b1^−/− mice on the action of systemic angiotensin II. ICV-E2 attenuated the angiotensin II-induced increase in mean arterial blood pressure, impairment of baroreflex sensitivity, and sympathetic activity in OVX-Cyp1b1^+/+ but not in ICV-injected short interfering (si)RNA-COMT or OVX-Cyp1b1^−/− mice. ICV-2-ME attenuated the angiotensin II-induced increase in blood pressure in OVX-Cyp1b1^−/− mice; this effect was inhibited by ICV-siRNA estrogen receptor-α (ERα) and G protein-coupled estrogen receptor 1 (GPER1). ICV-E2 in OVX-Cyp1b1^+/+ but not in OVX-Cyp1b1^−/− mice and 2-ME in the OVX-Cyp1b1^−/− inhibited angiotensin II-induced increase in reactive oxygen species production in the subfornical organ and paraventricular nucleus, activation of microglia and astrocyte, and neuroinflammation in paraventricular nucleus. Furthermore, central CYP1B1 gene disruption in Cyp1b1^+/+ mice by ICV-adenovirus-GFP (green fluorescence protein)-CYP1B1-short hairpin (sh)RNA elevated, while reconstitution by adenovirus-GFP-CYP1B1-DNA in the paraventricular nucleus but not in subfornical organ in Cyp1b1^−/− mice attenuated the angiotensin II-induced increase in systolic blood pressure. These data suggest that E2-CYP1B1-COMT generated metabolite 2-ME, most likely in the paraventricular nucleus via estrogen receptor-α and GPER1, protects against angiotensin II-induced hypertension and neuroinflammation in female mice.

CYP1B1: A key regulator of redox homeostasis

CYP1B1 is a member of the CYP1 subfamily of CYP superfamily of enzymes, which contains three members, CYP1A1, CYP1A2, and CYP1B1. CYP1B1 is expressed in both adult and fetal human extrahepatic tissues, including the parenchymal and stromal cells of most organs. Mutations in the CYP1B1 gene are linked to the development of primary congenital glaucoma in humans. However, the underlying mechanisms remain unknown. Using Cyp1b1-deficient mice, we showed that CYP1B1 is constitutively expressed in retinal vascular cells with a significant role in retinal neovascularization during oxygen-induced ischemic retinopathy. We also showed CYP1B1 is constitutively expressed in trabecular meshwork (TM) cells and its expression plays a significant role in the normal development and function of the TM tissue. We have observed that germline deletion of Cyp1b1 is associated with increased oxidative stress in the retinal vascular and TM cells in culture, and retinal and TM tissue in vivo. We showed increased oxidative stress was responsible for altered production of the extracellular matrix proteins and had a significant impact on cellular integrity and function of these tissues. Collectively, our studies have established an important role for CYP1B1 expression in modulation of tissue integrity and function through the regulation of cellular redox homeostasis and extracellular microenvironment.

Gene variants of CYP1A1 and CYP2D6 and the risk of childhood acute lymphoblastic leukaemia; outcome of a case control study from Kashmir, India

Studies on associations of various polymorphisms in xenobiotic metabolizing genes with different cancers including acute lymphoblastic leukaemia (ALL) are mixed and inconclusive. The current study analyzed the relationship between polymorphisms of phase I xenobiotic metabolizing enzymes, cytochromes P450 1A1 (CYP1A1) and CYP2D6 and childhood ALL in Kashmir, India. We recruited 200 confirmed ALL cases, and an equal number of controls, matched for sex, age and district of residence to the respective case. Information was obtained on various lifestyle and environmental factors in face to face interviews with the parents/attendants of each subject. Genotypes of CYP1A1 and CYP2D6 were analyzed by polymerase chain reaction and restriction fragment length polymorphism method. Logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs). Compared to the GG genotype, we found a higher ALL risk in subjects who harbored variant (AA) genotype (OR=20.9; 95% CI: 6.01-73.1, P<0.0001) and AG genotype (OR=42.6; 95% CI: 8.3-217.5, P<0.0001) of CYP2D6*4 polymorphism. Although, we found a significant association of CYP1A1*2A polymorphism with ALL risk, but the risk did not persist in the adjusted model (OR=6.76; 95% CI: 0.63-71.8, P=0.100). The study indicates that unlike CYP1A1*2A, CYP2D6*4 polymorphism is associated with ALL risk. However, more replicative studies with larger sample size are needed to substantiate our findings.

The Role of CYP2E1 in the Drug Metabolism or Bioactivation in the Brain

Organisms have metabolic pathways that are responsible for removing toxic agents. We always associate the liver as the major organ responsible for detoxification of the body; however this process occurs in many tissues. In the same way, as in the liver, the brain expresses metabolic pathways associated with the elimination of xenobiotics. Besides the detoxifying role of CYP2E1 for compounds such as electrophilic agents, reactive oxygen species, free radical products, and the bioactivation of xenobiotics, CYP2E1 is also related in several diseases and pathophysiological conditions. In this review, we describe the presence of phase I monooxygenase CYP2E1 in regions of the brain. We also explore the conditions where protein, mRNA, and the activity of CYP2E1 are induced. Finally, we describe the relation of CYP2E1 in brain disorders, including the behavioral relations for alcohol consumption via CYP2E1 metabolism.

Cell type-specific expression and localization of cytochrome P450 isoforms in tridimensional aggregating rat brain cell cultures

Within the Predict-IV FP7 project a strategy for measurement of in vitro biokinetics was developed, requiring the characterization of the cellular model used, especially regarding biotransformation, which frequently depends on cytochrome P450 (CYP) activity. The extrahepatic in situ CYP-mediated metabolism is especially relevant in target organ toxicity. In this study, the constitutive mRNA levels and protein localization of different CYP isoforms were investigated in 3D aggregating brain cell cultures. CYP1A1, CYP2B1/B2, CYP2D2/4, CYP2E1 and CYP3A were expressed; CYP1A1 and 2B1 represented almost 80% of the total mRNA content. Double-immunolabeling revealed their presence in astrocytes, in neurons, and to a minor extent in oligodendrocytes, confirming the cell-specific localization of CYPs in the brain. These results together with the recently reported formation of an amiodarone metabolite following repeated exposure suggest that this cell culture system possesses some metabolic potential, most likely contributing to its high performance in neurotoxicological studies and support the use of this model in studying brain neurotoxicity involving mechanisms of toxication/detoxication.

Polymorphisms in the human cytochrome P450 and arylamine N-acetyltransferase: susceptibility to head and neck cancers

The occurrence of head and neck cancer (HNC) is associated with smoking and alcohol drinking. Tobacco smoking exposes smokers to a series of carcinogenic chemicals. Cytochrome P450 enzymes (CYP450s), such as CYP1A1, CYP1B1, and CYP2D6, usually metabolize carcinogens to their inactive derivatives, but they occasionally convert the chemicals to more potent carcinogens. In addition, via CYP450 (CYP2E1) oxidase, alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Furthermore, two N-acetyltransferase isozymes (NATs), NAT1 and NAT2, are polymorphic and catalyze both N-acetylation and O-acetylation of aromatic and heterocyclic amine carcinogens. Genetic polymorphisms are associated with a number of enzymes involved in the metabolism of carcinogens important in the induction of HNC. It has been suggested that such polymorphisms may be linked to cancer susceptibility. In this paper, we select four cytochrome P450 enzymes (CYP1A1, CYP1BA1, CYP2D6, and CYP2E1), and two N-acetyltransferase isozymes (NAT1 and NAT2) in order to summarize and analyze findings from the literature related to HNC risk by focusing on (i) the interaction between these genes and the environment, (ii) the impact of genetic defect on protein activity and/or expression, and (iii) the eventual involvement of race in such associations.

Cytochrome P450 1B1 gene disruption minimizes deoxycorticosterone acetate-salt-induced hypertension and associated cardiac dysfunction and renal damage in mice

Previously, we showed that the cytochrome P450 1B1 inhibitor 2,3',4,5'-tetramethoxystilbene reversed deoxycorticosterone acetate (DOCA)-salt-induced hypertension and minimized endothelial and renal dysfunction in the rat. This study was conducted to test the hypothesis that cytochrome P450 1B1 contributes to cardiac dysfunction, and renal damage and inflammation associated with DOCA-salt-induced hypertension, via increased production of reactive oxygen species and modulation of neurohumoral factors and signaling molecules. DOCA-salt increased systolic blood pressure, cardiac and renal cytochrome P450 1B1 activity, and plasma levels of catecholamines, vasopressin, and endothelin-1 in wild-type (Cyp1b1(+/+)) mice that were minimized in Cyp1b1(-/-) mice. Cardiac function, assessed by echocardiography, showed that DOCA-salt increased the thickness of the left ventricular posterior and anterior walls during diastole, the left ventricular internal diameter, and end-diastolic and end-systolic volume in Cyp1b1(+/+) but not in Cyp1b1(-/-) mice; stroke volume was not altered in either genotype. DOCA-salt increased renal vascular resistance and caused vascular hypertrophy and renal fibrosis, increased renal infiltration of macrophages and T lymphocytes, caused proteinuria, increased cardiac and renal nicotinamide adenine dinucleotide phosphate-oxidase activity, caused production of reactive oxygen species, and increased activities of extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and cellular-Src; these were all reduced in DOCA-salt-treated Cyp1b1(-/-) mice. Renal and cardiac levels of eicosanoids were not altered in either genotype of mice. These data suggest that, in DOCA-salt hypertension in mice, cytochrome P450 1B1 plays a pivotal role in cardiovascular dysfunction, renal damage, and inflammation, and increased levels of catecholamines, vasopressin, and endothelin-1, consequent to generation of reactive oxygen species and activation of extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and cellular-Src independent of eicosanoids.

Genetic variability in estrogen disposition: Potential clinical implications for neuropsychiatric disorders

Variability in the physiological levels of neuroactive estrogens is widely believed to play a role in predisposition to several disorders of the central nervous system. Local biosynthesis of estrogens in the brain as well as their circulating serum levels are known to contribute to this pool of neuroactive steroids. It has been well accepted that estrogens modulate neuronal functions by affecting genesis, differentiation, excitability, and degeneration of nerve cells. These actions of estrogens appear to be more prominent in females with higher concentrations and marked variability of circulating serum levels occurring over a woman's lifetime. However, our knowledge regarding the variability of neuroactive steroid levels is very limited. Furthermore, several studies have recently reported differences in the synchronization of circulating and neuronal levels of estradiol. In the absence of reliable circulating steroid levels, knowledge of genetic variability in estrogen disposition may play a determining factor in predicting altered susceptibility or severity of neuropsychiatric disorders in women. Over the past decade, several genetic variants have been linked to both differential serum estrogen levels and predisposition to diverse types of neuropsychiatric disorders in women. Polymorphisms in genes encoding estrogen-metabolizing enzymes as well as estrogen receptors may account for this phenotypic variability. In this review, we attempt to show the contribution of genetics in determining estrogenicity in females with a particular emphasis on the central nervous system. This knowledge will further provide a driving force for unearthing the novel field of "Estrogen Pharmacogenomics." © 2010 Wiley-Liss, Inc.

2,3',4,5'-Tetramethoxystilbene prevents deoxycorticosterone-salt-induced hypertension: contribution of cytochrome P-450 1B1

Reactive oxygen species (ROS) contribute to various models of hypertension, including deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Recently, we have shown that ROS, generated by cytochrome P-450 1B1 (CYP1B1) from arachidonic acid, mediate vascular smooth muscle cell growth caused by angiotensin II. This study was conducted to determine the contribution of CYP1B1 to hypertension and associated pathophysiological changes produced by DOCA (30 mg/kg) given subcutaneously per week with 1% NaCl + 0.1% KCl in drinking water to uninephrectomized rats for 6 wk. DOCA-salt treatment increased systolic blood pressure (SBP). Injections of the selective inhibitor of CYP1B1, 2,3',4,5'-tetramethoxystilbene (TMS; 300 μg/kg ip every 3rd day) initiated at the 4th week of DOCA-salt treatment normalized SBP and decreased CYP1B1 activity but not its expression in the aorta, heart, and kidney. TMS also inhibited cardiovascular and kidney hypertrophy, prevented the increase in vascular reactivity and endothelial dysfunction, and minimized the increase in urinary protein and K(+) output and the decrease in urine osmolality, Na(+) output, and creatinine clearance associated with DOCA-salt treatment. These pathophysiological changes caused by DOCA-salt treatment and associated increase in vascular superoxide production, NADPH oxidase activity, and expression of NOX-1, and ERK1/2 and p38 MAPK activities in the aorta, heart, and kidney were inhibited by TMS. These data suggest that CYP1B1 contributes to DOCA-salt-induced hypertension and associated pathophysiological changes, most likely as a result of increased ROS production and ERK1/2 and p38 MAPK activity, and could serve as a novel target for the development of agents like TMS to treat hypertension.

Cytochrome P450 1B1 contributes to angiotensin II-induced hypertension and associated pathophysiology

Hypertension is the leading cause of cardiovascular diseases, and angiotensin II is one of the major components of the mechanisms that contribute to the development of hypertension. However, the precise mechanisms for the development of hypertension are unknown. Our recent study showing that angiotensin II-induced vascular smooth muscle cell growth depends on cytochrome P450 1B1 led us to investigate its contribution to hypertension caused by this peptide. Angiotensin II was infused via miniosmotic pump into rats (150 ng/kg per minute) or mice (1000 μg/kg per day) for 13 days resulting in increased blood pressure, increased cardiac and vascular hypertrophy, increased vascular reactivity to vasoconstrictor agents, increased vascular reactive oxygen species production, and endothelial dysfunction in both species. The increase in blood pressure and associated pathophysiological changes were minimized by the cytochrome P450 1B1 inhibitor 2,3',4,5'-tetramethoxystilbene in both species and was markedly reduced in Cyp1b1(-/-) mice. These data suggest that cytochrome P450 1B1 contributes to angiotensin II-induced hypertension and associated pathophysiological changes. Moreover, 2,3',4,5'-tetramethoxystilbene, which prevents both cytochrome P450 1B1-dependent and -independent components of angiotensin II-induced hypertension and inhibits associated pathophysiological changes could be clinically useful in the treatment of hypertension and associated cardiovascular and inflammatory diseases.

Differential induction of CYP1A1 and CYP1B1 by benzo[a]pyrene in oral squamous cell carcinoma cell lines and by tobacco smoking in oral mucosa

Polyaromatic hydrocarbons, including benzo[a]pyrene (BP), are major tobacco carcinogens. Their carcinogenic effects require metabolic activation by cytochrome p450 (CYP) enzymes. Relative CYP isoform expression is related to tissue-specific tobacco-related squamous cell carcinoma (SCC) susceptibility. There have been conflicting reports regarding relative CYP1A1 and CYP1B1 oral expression, and information regarding CYP1B1 expression in oral tissues is limited. To quantify BP- and tobacco-induced CYP1A1 and CYP1B1 expression in oral SCC cells and oral mucosa.

STUDY DESIGN

Real-time qPCR was performed to measure (1) BP-induced CYP1A1 and CYP1B1 mRNA expression in seven oral/other head and neck SCC cell lines (2) CYP1A1 and CYP1B1 mRNA expression in gingiva from 22 smokers and 24 nonsmokers. SCC lines exhibited either similar induction of both isoforms or preferential CYP1A1 induction (CYP1A1-to-CYP1B1 ratios 0.8-4.3). In contrast, gingival tissues from smokers exhibited preferential CYP1B1 induction. Marked interindividual variation in CYP1A1 and CYP1B1 expression was observed among smokers. In vitro conditions may not account for factors that modulate expression in vivo. Interindividual variation in inducible CYP1A1 and CYP1B1 expression may account in part for variation in tobacco-related oral SCC risk.

Biomedical Technologies for in vitro Screening and Controlled Delivery of Neuroactive Compounds

Cell culture models can provide information pertaining to the effective dose, toxiciology, and kinetics, for a variety of neuroactive compounds. However, many in vitro models fail to adequately predict how such compounds will perform in a living organism. At the systems level, interactions between organs can dramatically affect the properties of a compound by alteration of its biological activity or by elimination of it from the body. At the tissue level, interaction between cell types can alter the transport properties of a particular compound, or can buffer its effects on target cells by uptake, processing, or changes in chemical signaling between cells. In any given tissue, cells exist in a three-dimensional environment bounded on all sides by other cells and components of the extracellular matrix, providing kinetics that are dramatically different from the kinetics in traditional two-dimensional cell culture systems. Cell culture analogs are currently being developed to better model the complex transport and processing that occur prior to drug uptake in the CNS, and to predict blood-brain barrier permeability. These approaches utilize microfluidics, hydrogel matrices, and a variety of cell types (including lung epithelial cells, hepatocytes, adipocytes, glial cells, and neurons) to more accurately model drug transport and biological activity. Similar strategies are also being used to control both the spatial and temporal release of therapeutic compounds for targeted treatment of CNS disease.

Cytochrome P450-catalyzed pathways in human brain: Metabolism meets pharmacology or old drugs with new mechanism of action?

The true importance of cytochrome P450 enzymes, not just in drug metabolism but also in pharmacology, is only beginning to be appreciated. Though originally discovered through their role in the biotransformation of xenobiotics, the P450 enzyme super family is ubiquitous in nature and necessarily evolved around endogenous pathways. The extent of tissue- and cell-specific expression of individual P450 isoforms has led many investigators to hypothesize localized roles in endogenous biochemical pathways for isoforms traditionally thought of as drug-metabolizing. In some cases, direct evidence from humanized transgenic animal models can confirm the degree to which such enzymes modulate endogenous pathways. However, overlapping P450 substrate specificities may mask genetic or biochemical deficiencies, such that many of these reactions appear nonessential. Nonetheless, the drug-induced alteration of local biochemical concentrations in extrahepatic tissues due to metabolism by and inhibition of P450 isoforms has tremendous potential for introducing unexpected pharmacological effects. Nowhere is this truer than in the CNS. On the other hand, if we can harness the power of in silico modeling to create highly specific inhibitors of identified brain isoforms, a novel avenue for drug design using P450 as drug targets may be at hand. This article highlights some notable examples in which the catalytic state of specific P450 isoforms involved in endogenous biochemical reaction pathways are influenced by pharmacological agents. The implications of inhibition of P450-catalzyed oxidation steps that are known or speculated to influence arachadonic acid, cholesterol, and catecholamine neurotransmitters pathways in human brain will be considered.

Pharmacogenetics and regulation of human cytochrome P450 1B1: implications in hormone-mediated tumor metabolism and a novel target for therapeutic intervention

Several of the hormone-mediated cancers (breast, endometrial, ovarian, and prostate) represent major cancers in both incidence and mortality rates. The etiology of these cancers is in large part modulated by the hormones estrogen and testosterone. As advanced disease develops, the common treatment for these cancers is chemotherapy. Thus, genes that can alter tissue response to hormones and alter clinical response to chemotherapy are of major interest. The cytochrome P450 1B1 (CYP1B1) may be involved in disease progression and modulate the treatment in the above hormone-mediated cancers. This review will focus on the pharmacogenetics of CYP1B1 in relation to hormone-mediated cancers and provide an assessment of cancer risk based on CYP1B1 polymorphisms and expression. In addition, it will provide a summary of CYP1B1 gene regulation and expression in normal and neoplastic tissue.

The shared tumor-associated antigen cytochrome P450 1B1 is recognized by specific cytotoxic T cells

Cytochrome P450 1B1 (CYP1B1), a drug-metabolizing extrahepatic enzyme, was recently shown to be overexpressed in multiple types of cancer. Such tumor-associated genes may be useful targets for anticancer therapy, particularly cancer immunotherapeutics. We identified HLA-A*0201-binding peptides and a naturally processed and presented T-cell epitope capable of inducing CYP1B1-specific cytotoxic T lymphocytes (CTLs) in HLA-A2 transgenic mice. Furthermore, the induction of CYP1B1-specific T cells was demonstrated in healthy donors and cancer patients. These T cells efficiently lysed target cells pulsed with the cognate peptide. More important, HLA-A2-matched tumor cell lines and primary malignant cells were also recognized by CYP1B1-specific CTLs. These findings form the basis of a phase 1 clinical trial exploring a DNA-based vector encoding CYP1B1 for widely applicable cancer immunotherapy conducted at the Dana-Farber Cancer Institute.

Gene expression of cytochrome P450 1B1 and 2D6 in leukocytes in human pregnancy

We investigated the influence of human pregnancy on gene expression of two cytochrome P450 enzymes in white blood cells. Cytochrome P450 1B1 (CYP1B1) catalyses oestradiol 4-hydroxylation, and may participate in the endocrine regulation of oestrogens. Cytochrome P450 2D6 (CYP2D6) metabolises many commonly used drugs, and previous studies have suggested that it is induced during pregnancy. CYP1B1 and CYP2D6 were therefore considered to be of interest in human pregnancy. As it is not ethically possible to take liver biopsies from healthy mothers during pregnancy, easily accessible cells that express the genes were used as a surrogate tissue. White blood cells were collected from eighteen pregnant women, and were used to measure CYP1B1 and CYP2D6 ribonucleic acid (RNA). The analysis was repeated after pregnancy, the women, thus, serving as their own controls. Real-time reverse transcriptase - polymerase chain reaction methods were used with 18S ribosomal RNA as an internal control. A slight, but not significant, increase in gene activity of CYP1B1 was detected during pregnancy. Expression of CYP2D6 in blood was extremely low, and induction of CYP2D6 during pregnancy could not be confirmed. In conclusion, gene expression of CYP1B1 and CYP2D6 in leukocytes was not significantly up-regulated in the third trimester of pregnancy, but a trend indicating an altered metabolism during pregnancy was detected.

Drug-metabolizing cytochrome P450s in the brain

Most CYP subfamilies have been identified in brain, but there is much more information available on the distribution and metabolic activity of CYP subfamilies in brain of rodents than in humans, and what we do know still lags far behind our knowledge of hepatic CYPs. With the constant acquisition of data on the genetics, molecular structure and metabolic capacity of brain CYPs, we are increasingly able to investigate their role in the brain and the possible consequences of altered local metabolism. However, at this stage, the contribution of brain CYPs to local metabolism of drugs, toxins and endogenous compounds is still speculative, as is the role for these CYPs in modulating brain function and in the development of brain diseases. Much investigative work remains to be done to firmly establish the links between the presence of CYPs in brain, their function in this highly heterogeneous and complex organ and the consequences on overall brain function and health.

An immunohistochemical label to facilitate counting of ovarian follicles

U.S. and internationally harmonized Health Effects Test Guidelines for Reproduction and Fertility Effects include enumeration of primordial and developing ovarian follicles as endpoints of safety tests, and the number of these structures is also of interest for other aspects of reproductive biology. Performing the counts microscopically on representative hematoxylin and eosin (H&E)-stained sections of ovary is tedious and error-prone. The ability to mark oocyte nuclei distinctly with an antibody significantly increases speed and accuracy of counting. We have identified a rabbit polyclonal antibody directed against a synthetic 14-amino acid sequence from human cytochrome P-450 1B1 (CYP1B1) that unequivocally marks rodent oocyte nuclei, in addition to nuclei of some ovarian granulosa and theca cells. Follicles of all degrees of maturity are easily distinguished from ovarian background; ability to detect and identify primordial follicles is particularly enhanced. High-contrast and high-resolution labeling was achieved with routine immunohistochemical procedures using an avidin-biotin-peroxidase method on rat and mouse tissues fixed in 10% neutral buffered formalin.

Regulation, function, and tissue-specific expression of cytochrome P450 CYP1B1

Cytochrome P450 CYP1B1 is a relatively recently identified member of the CYP1 gene family. The purpose of this commentary is to review the regulatory mechanisms, metabolic specificity, and tissue-specific expression of this cytochrome P450 and to highlight its unique properties. The regulation of CYP1B1 involves a variety of both transcriptional and post-transcriptional mechanisms. CYP1B1 can metabolize a range of toxic and carcinogenic chemicals in vitro but in some cases with a unique stereoselectivity. Estradiol 4-hydroxylation appears to be a characteristic reaction catalyzed by human CYP1B1. However, there are considerable species differences regarding the regulation, metabolic specificity, and tissue-specific expression of this P450. In humans CYP1B1 is overexpressed in tumor cells, and this has important implications for tumor development and progression and the development of anticancer drugs specifically activated by CYP1B1.

In situ hybridization and immunohistochemical analysis of cytochrome P450 1B1 expression in human normal tissues

Cytochrome P450 1B1 (CYP1B1) is a recently cloned dioxin-inducible form of the cytochrome P450 supergene family of xenobiotic-metabolizing enzymes. CYP1B1 is constitutively expressed mainly in extrahepatic tissues and is inducible by aryl hydrocarbon receptor ligands. Human CYP1B1 is involved in activation of chemically diverse human procarcinogens, including polycyclic aromatic hydrocarbons and some aromatic amines, as well as the endogenous hormone 17 beta-estradiol. The metabolism of 17 beta-estradiol by CYP1B1 forms 4-hydroxyestradiol, a product believed to be important in estrogen-induced carcinogenesis. Although the distribution of CYP1B1 mRNA and protein in a number of human normal tissues has been well documented, neither the cells expressing CYP1B1 in individual tissue nor the intracellular localization of the enzyme has been thoroughly characterized. In this study, using nonradioactive in situ hybridization and immunohistochemistry, we examined the cellular localization of CYP1B1 mRNA and protein in a range of human normal tissues. CYP1B1 mRNA and protein were expressed in most samples of parenchymal and stromal tissue from brain, kidney, prostate, breast, cervix, uterus, ovary, and lymph nodes. In most tissues, CYP1B1 immunostaining was nuclear. However, in tubule cells of kidney and secretory cells of mammary gland, immunoreactivity for CYP1B1 protein was found in both nucleus and cytoplasm. This study demonstrates for the first time the nuclear localization of CYP1B1 protein. Moreover, the constitutive expression and wide distribution of CYP1B1 mRNA and protein in many human normal tissues suggest functional roles for CYP1B1 in the bioactivation of xenobiotic procarcinogens and endogenous substrates such as estrogens. (J Histochem Cytochem 49:229-236, 2001)

Human brain cytochrome P450 1B1: immunohistochemical localization in human temporal lobe and induction by dimethylbenz(a)anthracene in astrocytoma cell line (MOG-G-CCM)

CYP1B1, a new member of human cytochrome P450 family 1, is involved in the xenobiotic detoxification metabolism and possibly activation of numerous procarcinogens and promutagens. Localization of CYP1B1 in human temporal lobe and its induction in astrocytoma cell line (MOG-G-CCM) by 7,12-dimethylbenz(a)anthracene (DMBA) was investigated using antibodies against human CYP1B1. A single band of approximately 58 kDa size in both human temporal lobe and in MOG-G-CCM was detected by Western blot analysis. Treatment of MOG-G-CCM cells with DMBA resulted in approximately 2.8-fold induction of CYP1B1. CYP1B1 immunoreactivity was detected at the blood-brain interface areas of the temporal lobe as evidenced by co-localization with CD34 antigen. These results suggest that this enzyme may be important in brain xenobiotic metabolism acting as an enzymatic barrier.