Brain Cytochrome P450 Research Articles

Exploring the Regulation of Cytochrome P450 in SH-SY5Y Cells: Implications for the Onset of Neurodegenerative Diseases.

Human individual differences in brain cytochrome P450 (CYP) metabolism, including induction, inhibition, and genetic variation, may influence brain sensitivity to neurotoxins and thus participate in the onset of neurodegenerative diseases. The aim of this study was to explore the modulation of CYPs in neuronal cells. The experimental approach was focused on differentiating human neuroblastoma SH-SY5Y cells into a phenotype resembling mature dopamine neurons and investigating the effects of specific CYP isoform induction. The results demonstrated that the differentiation protocols using retinoic acid followed by phorbol esters or brain-derived neurotrophic factor successfully generated SH-SY5Y cells with morphological neuronal characteristics and increased neuronal markers (NeuN, synaptophysin, β-tubulin III, and MAO-B). qRT-PCR and Western blot analysis showed that expression of the CYP 1A1, 3A4, 2D6, and 2E1 isoforms was detectable in undifferentiated cells, with subsequent increases in CYP 2E1, 2D6, and 1A1 following differentiation. Further increases in the 1A1, 2D6, and 2E1 isoforms following β-naphthoflavone treatment and 1A1 and 2D6 isoforms following ethanol treatment were evident. These results demonstrate that CYP isoforms can be modulated in SH-SY5Y cells and suggest their potential as an experimental model to investigate the role of CYPs in neuronal processes involved in the development of neurodegenerative diseases.

Identification of Neurotransmission and Synaptic Biological Processes Disrupted in Autism Spectrum Disorder Using Interaction Networks and Community Detection Analysis.

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by communication deficits and repetitive behavioral patterns. Hundreds of candidate genes have been implicated in ASD, including neurotransmission and synaptic (NS) genes; however, the genetic architecture of this disease is far from clear. In this study, we seek to clarify the biological processes affected by NS gene variants identified in individuals with ASD and the global networks that link those processes together. For a curated list of 1216 NS candidate genes, identified in multiple databases and the literature, we searched for ultra-rare (UR) loss-of-function (LoF) variants in the whole-exome sequencing dataset from the Autism Sequencing Consortium (N = 3938 cases). Filtering for population frequency was carried out using gnomAD (N = 60,146 controls). NS genes with UR LoF variants were used to construct a network of protein-protein interactions, and the network's biological communities were identified by applying the Leiden algorithm. We further explored the expression enrichment of network genes in specific brain regions. We identified 356 variants in 208 genes, with a preponderance of UR LoF variants in the PDE11A and SYTL3 genes. Expression enrichment analysis highlighted several subcortical structures, particularly the basal ganglia. The interaction network defined seven network communities, clustering synaptic and neurotransmitter pathways with several ubiquitous processes that occur in multiple organs and systems. This approach also uncovered biological pathways that are not usually associated with ASD, such as brain cytochromes P450 and brain mitochondrial metabolism. Overall, the community analysis suggests that ASD involves the disruption of synaptic and neurotransmitter pathways but also ubiquitous, but less frequently implicated, biological processes.

Alzheimer's Precision Neurology: Epigenetics of Cytochrome P450 Genes in Circulating Cell-Free DNA for Disease Prediction and Mechanism.

Precision neurology combines high-throughput technologies and statistical modeling to identify novel disease pathways and predictive biomarkers in Alzheimer's disease (AD). Brain cytochrome P450 (CYP) genes are major regulators of cholesterol, sex hormone, and xenobiotic metabolism, and they could play important roles in neurodegenerative disorders. Increasing evidence suggests that epigenetic factors contribute to AD development. We evaluated cytosine ('CpG')-based DNA methylation changes in AD using circulating cell-free DNA (cfDNA), to which neuronal cells are known to contribute. We investigated CYP-based mechanisms for AD pathogenesis and epigenetic biomarkers for disease detection. We performed a case-control study using 25 patients with AD and 23 cognitively healthy controls using the cfDNA of CYP genes. We performed a logistic regression analysis using the MetaboAnalyst software computer program and a molecular pathway analysis based on epigenetically altered CYP genes using the Cytoscape program. We identified 130 significantly (false discovery rate correction q-value < 0.05) differentially methylated CpG sites within the CYP genes. The top two differentially methylated genes identified were CYP51A1 and CYP2S1. The significant molecular pathways that were perturbed in AD cfDNA were (i) androgen and estrogen biosynthesis and metabolism, (ii) C21 steroid hormone biosynthesis and metabolism, and (iii) arachidonic acid metabolism. Existing evidence suggests a potential role of each of these biochemical pathways in AD pathogenesis. Next, we randomly divided the study group into discovery and validation sub-sets, each consisting of patients with AD and control patients. Regression models for AD prediction based on CYP CpG methylation markers were developed in the discovery or training group and tested in the independent validation group. The CYP biomarkers achieved a high predictive accuracy. After a 10-fold cross-validation, the combination of cg17852385/cg23101118 + cg14355428/cg22536554 achieved an AUC (95% CI) of 0.928 (0.787~1.00), with 100% sensitivity and 92.3% specificity for AD detection in the discovery group. The performance remained high in the independent validation or test group, achieving an AUC (95% CI) of 0.942 (0.905~0.979) with a 90% sensitivity and specificity. Our findings suggest that the epigenetic modification of CYP genes may play an important role in AD pathogenesis and that circulating CYP-based cfDNA biomarkers have the potential to accurately and non-invasively detect AD.

The Effect of the Selective N-methyl-D-aspartate (NMDA) Receptor GluN2B Subunit Antagonist CP-101,606 on Cytochrome P450 2D (CYP2D) Expression and Activity in the Rat Liver and Brain.

The CYP2D enzymes of the cytochrome P450 superfamily play an important role in psychopharmacology, since they are engaged in the metabolism of psychotropic drugs and endogenous neuroactive substrates, which mediate brain neurotransmission and the therapeutic action of those drugs. The aim of this work was to study the effect of short- and long-term treatment with the selective antagonist of the GluN2B subunit of the NMDA receptor, the compound CP-101,606, which possesses antidepressant properties, on CYP2D expression and activity in the liver and brain of male rats. The presented work shows time-, organ- and brain-structure-dependent effects of 5-day and 3-week treatment with CP-101,606 on CYP2D. Five-day treatment with CP-101,606 increased the activity and protein level of CYP2D in the hippocampus. That effect was maintained after the 3-week treatment and was accompanied by enhancement in the CYP2D activity/protein level in the cortex and cerebellum. In contrast, a 3-week treatment with CP-101,606 diminished the CYP2D activity/protein level in the hypothalamus and striatum. In the liver, CP-101,606 decreased CYP2D activity, but not the protein or mRNA level, after 5-day or 3-week treatment. When added in vitro to liver microsomes, CP-101,606 diminished the CYP2D activity during prolonged incubation. While in the brain, the observed decrease in the CYP2D activity after short- and long-term treatment with CP-101,606 seems to be a consequence of the drug effect on enzyme regulation. In the liver, the direct inhibitory effect of reactive metabolites formed from CP-101,606 on the CYP2D activity may be considered. Since CYP2Ds are engaged in the metabolism of endogenous neuroactive substances, it can be assumed that apart from antagonizing the NMDA receptor, CP-101,606 may modify its own pharmacological effect by affecting brain cytochrome P450. On the other hand, an inhibition of the activity of liver CYP2D may slow down the metabolism of co-administered substrates and lead to pharmacokinetic drug-drug interactions.

The effect of short and long-term treatment with the NMDA receptor GluN2B subunit antagonist CP-101,606 on brain cytochrome P450 2D

The effect of short and long-term treatment with the NMDA receptor GluN2B subunit antagonist CP-101,606 on brain cytochrome P450 2D

P.0865 The effect of the NMDA receptor GluN2B subunit antagonist CP-101,606 on brain and liver cytochrome P450 2D (CYP2D)

P.0865 The effect of the NMDA receptor GluN2B subunit antagonist CP-101,606 on brain and liver cytochrome P450 2D (CYP2D)

P.0906 The effects of aging and cerebral serotonin deficiency on brain and liver cytochrome P450 2D in female rats – sex differences

P.0906 The effects of aging and cerebral serotonin deficiency on brain and liver cytochrome P450 2D in female rats – sex differences

Unveiling the Role of Cytochrome P450 (2E1) in Human Brain Specifically in Parkinson's Disease - Literature Review.

In recent years, the significance of cytochrome P450 enzymes (CYPs) has expanded beyond their role in the liver. Factors such as genetics, environmental toxins, drug biotransformation and underlying diseases mediate the expression of these enzymes. Among the CYP enzymes, CYP2E1, a well-recognized monooxygenase enzyme involved in the metabolism of various endogenous and exogenous substances, plays a crucial role in the brain concerning the development of Parkinson's disease. The expression of CYP2E1 varies in different brain regions making certain regions more vulnerable than others. CYP2E1 expression is inducible which generates tissuedamaging radicals leading to oxidative stress, mitochondrial dysfunction and ultimately neurodegeneration. Less is understood about the role of CYP2E1 in the central nervous system, therefore the purpose of the study was to investigate the relationship between the expression and activity of CYP2E1 enzyme relevant to Parkinson's disease and to identify whether an increase in the expression of CYP2E1 is associated with neurodegeneration. The objectives of the study were achieved by implicating an unsystematic integrative literature review approach in which the literature was qualitatively analysed, critically evaluated and a new theory with an overall view of the mechanism was presented. The contribution of CYP2E1 in the development of Parkinson's disease was found to be significant as the negative effects of CYP2E1 overshadowed its protective detoxifying role. Overexpression of CYP2E1 seems detrimental to dopaminergic neurons, therefore, to overcome this, a synthetic biochemical is required, which paves the way for further research and development of valuable biomolecules.

The effect of ageing and cerebral serotonin deficit on the activity of cytochrome P450 2D (CYP2D) in the brain and liver of male rats

Brain cytochrome P450 (CYP) contributes to the local metabolism of endogenous substrates and drugs. The aim of present study was to ascertain whether the cytochrome P450 2D (CYP2D) activity changes with ageing and in cerebral serotonin deficit. Kinetics of 5-methoxytryptamine O-demethylation to serotonin was studied and the CYP2D activity was measured in brain and liver microsomes of Dark Agouti wild type (WT) rats (mature 3.5-month-old and senescent 21-month-old rats) and in tryptophan hydroxylase 2 (TPH2)-deficient senescent rats. The CYP2D activity and protein level decreased in the frontal cortex of senescent WT rats, but increased in senescent TPH2-deficient rats (compared to senescent WT). In contrast, in the hippocampus, hypothalamus and striatum the CYP2D activity/protein level increased with ageing, but did not change in senescent TPH2-deficient animals (compared to senescent WT). The activity and protein level of liver CYP2D was lower in senescent WT rats than in the mature animals and further decreased in senescent TPH2-deficient rats. In conclusion, ageing and TPH2-deficit affect the CYP2D activity and protein level, which may have a positive impact on neurotransmitter synthesis in brain structures involved in cognitive, emotional or motor functions, but a negative effect on drug metabolism in the liver.

Effect of copper nanoparticles on brain cytochromeP450 enzymes in rats.

The aim of the present study was to evaluate the long‑term effect of copper nanoparticles (CuNPs) on cytochromeP450 (CYP450) enzymes in the rat brain. Rats were repeatedly gavaged with different forms of copper sources for 28days, and the levels of oxidative stress and CYP450 mRNA and protein expression in the rat brain were subsequently analyzed. The results demonstrated that a high dose of CuNPs (200mg/kg) induced severe oxidative stress in the rat brain along with a decrease in the levels of total superoxide dismutase and glutathione, and an increase in hydroxyl radicals and malondialdehyde. A medium dose of CuNPs reduced CYP4502C11 and CYP4503A1 protein expression in the rat brain, whereas high doses of CuNPs resulted in decreased expression of most CYP450 enzyme proteins, and inhibition of pregnaneX receptor and constitutive androstane receptor expression. The results suggested that CuNPs may inhibit CYP450 enzyme expression by increasing the levels of oxidative stress and decreasing the expression of nuclear receptors in the rat brain, which affects the metabolism of drugs and endogenous hormones in the brain.

Abstract 041: Brain Cytochrome P450 1B1-Testosterone Generated Metabolite 6Beta-Hydroxytestosterone Contributes to Angiotensin II-Induced Increased Sympathetic Outflow and Blood Pressure

Cytochrome P450 1B1 (CYP1B1)-generated testosterone (T) metabolite 6β-hydroxytestosterone (6β-OHT) contributes to angiotensin (Ang) II-induced hypertension in the male mice. However, the site of action of CYP1B1-testosterone metabolite 6β-OHT in Ang II-induced hypertension is unknown. The demonstration that Ang II increases blood pressure by its action in the subfornical organ and the presence of CYP1B1 in the brain led us to hypothesize that T contributes to Ang II-induced hypertension via its metabolism to 6β-OHT in the brain. To test this hypothesis, we examined the effect of intracerebroventricularly (ICV) administered T in castrated (Cas) wild-type ( Cyp1b1 +/+ ) and Cas Cyp1b1 -/- mice on the action of systemic Ang II (700 ng/kg/min) for 14 days. T (3 μg/2μL/injection/every 2nd day) or its vehicle (2-Hydroxypropyl-β-cyclodextrin dissolved in artificial CSF) was injected via a cannula implanted in the brain. Mean arterial blood pressure (MAP, mmHg) was measured by radiotelemetry (n=4-5). Ang II increased MAP in T but not its vehicle-injected Cas Cyp1b1 +/+ mice on Day 12 (159±2 vs. 98±2, P&lt;0.05). In Cas Cyp1b1 -/- mice Ang II increased MAP in ICV injected 6β-OHT (1.5 μg/2μL/injection every 2nd day) but not T (151±3 vs. 123±5, P&lt;0.05). Power spectral analysis of the data on day 12 showed that Ang II increased the low to high-frequency ratio of heart rate variability, index of sympathetic outflow modulation in ICV T injected Cas Cyp1b1 +/+ but not Cas Cyp1b1 -/- mice (3.8±0.0.4 vs. 1.9±0.0); whereas ICV 6β-OHT in the later mice increased this ratio (4.7±0.6). Ganglionic blocker hexamethonium (30 mg/Kg, ip) on day 14 of Ang II infusion resulted in greater reduction in MAP (P&lt;0.05) in centrally 6β-OHT injected Cas Cyp1b1 -/- , and T-injected Cas Cyp1b1 +/+ (Δ81±11 and Δ87±10) than in T injected Cas Cyp1b1 -/- mice (Δ50±8). Furthermore, in intact Cyp1b1 -/- , but not Cas Cyp1b1 -/- mice transduction with adenovirus (Ad) of CYP1B1-DNA (ICV 2μL of 1.0 X 10 12 particles/mL) increased Ang II-induced systolic blood pressure (P&lt;0.05, n=5/group) measured by tail-cuff on Day12 (176±11 vs. 120±2, mm Hg). These data suggest that T contributes to Ang II-induced hypertension most likely via generation by the brain CYP1B1 to 6β-OHT, which increases sympathetic outflow in male mice.

Role of the brain in adaptation of the common and golden carps to adverse factors of chemical origin

Using an indirect solid-phase immunoassay (ELISA test), cytochrome P-450, serotoninmodulated anticonsolidation protein (SMAP) and 70-kDa heat shock protein (HSP70) levels were analyzed in the brain and liver of the common carp Cyprinus carpio L. and golden carp Carassius auratus caught in reservoirs of the Arpachay river (clean zone) and Araks river (polluted zone) in Nakhchivan Autonomous Republic of Azerbaijan. Upregulation of cytochrome P-450 (p < 0.05) and SMAP (p < 0.01) in the common carp brain and downregulation of cytochrome P-450 (p < 0.05) and HSP70 (p < 0.05) in the golden carp liver were detected in fish caught in the Araks river reservoir as compared to levels of the same substances in fish from the Arpachay river reservoir. It is concluded that the brain plays a regulatory role in adaptation of animals to adverse environmental conditions and in protection of tissues from negative effects of pollutants.

CYP-mediated drug metabolism in the brain impacts drug response.

The functional role of cytochrome P450 (CYP) enzymes in the brain is an exciting and evolving field of research. CYPs are present and active in the brain, with heterogeneous patterns of expression, activity, and sensitivity to modulation across cell types, regions, and species. Despite total brain CYP expression being a fraction of hepatic CYP expression, the expanding literature of in vitro and in vivo experiments has provided evidence that brain CYPs can impact acute and chronic drug response, susceptibility to damage by neurotoxins, and are associated with altered personality, behaviour, and risk of neurological disease. They may also play a role in endogenous neurotransmitter and neurosteroid homeostasis. This review goes through the characterization of brain CYPs across species, the patterns of susceptibility of brain CYPs to exogenous induction, and recent preclinical evidence of the potential role of brain CYPs in vivo (e.g. CYP2D), along with the development of experiment paradigms that allow modulation of brain CYP activity without affecting CYP activity in the liver. Understanding brain CYP function, and changes therein, may provide unique strategies for the development of CNS-acting therapeutics metabolized locally in the brain, as well as therapeutics to target brain CYPs directly.

Effect of genetic polymorphism on the inhibition of dopamine formation from p-tyramine catalyzed by brain cytochrome P450 2D6

The inhibitory effects of steroid hormones, including glucocorticoids such as cortisol, and related compounds on dopamine formation from p-tyramine, catalyzed by cytochrome P450 (CYP) 2D6.2 (Arg296Cys, Ser486Thr) and CYP2D6.10 (Pro34Ser, Ser486Thr) were compared with the effects of those catalyzed by CYP2D6.1 (wild type), to investigate the effect of a CYP2D6 polymorphism on neuroactive amine metabolism in the brain. Inhibition constants (Ki) or 50% inhibitory concentrations of six steroid hormones (cortisol, cortisone, corticosterone, dehydroepiandrosterone, progesterone, and pregnenolone) and quinidine and quinine—typical potent inhibitors of the human CYP2D6 and rat CYP2D subfamily, respectively—toward dopamine formation catalyzed by CYP2D6.1, CYP2D6.2, and CYP2D6.10 expressed in recombinant Escherichia coli were compared. Although most steroid hormones had no or minor inhibitory effects on the dopamine formation by all CYP2D6 variants, progesterone inhibited the metabolism and Ki value against CYP2D6.10 was approximately twice that for CYP2D6.1 and CYP2D6.2. Quinidine exhibited stronger inhibition than quinine; however, these two compounds inhibited the CYP2D6.10-mediated reaction more weakly than the CYP2D6.1 and CYP2D6.2 reactions. These results suggest that CYP2D6 polymorphism would affect drug interaction through dopamine formation in the brain.

Effects of alkylphenols on the biotransformation of diuron and enzymes involved in the synthesis and clearance of sex steroids in juvenile male tilapia (Oreochromus mossambica)

Previous studies using in vivo bioassay guided fractionation indicated that the herbicide diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) and alkylphenol (AP)-containing surfactants were detected in fractions of extracts that induced the estrogenic biomarker, vitellogenin in fish exposed to surface water extracts from the United States. However, when the compounds were evaluated individually using in vivo estrogenic assays or in vitro estrogen receptor assays, estrogenic activity was not observed. Since APs have been shown to alter activity and content of cytochrome P450s (CYP) which convert diuron to potential estrogenic metabolites, the hepatic biotransformation of diuron was measured with and without a 7day pretreatment of p-Octylphenol (OP) and p-Nonylphenol (NP) at low (OP 13ng/L+NP 91ng/L), and high concentrations (OP 65ng/L+NP 455ng/L) in juvenile male Nile tilapia (Oreochromus niloticus). Pre-treatment with the OP/NP (AP) mixture caused elevated levels of NADPH-catalyzed formation of 3,4-dichlorophenyl-N-methylurea (DCPMU) but not 3,4-dichlorophenylurea (DCPU). Fish were also treated with nominal concentrations of low (40ng/L) and high (200ng/L) diuron and each of its three degradates/metabolites: DCPMU, DCPU and 3,4-dichloroaniline (DCA). Additional treatments were conducted with APs and Diuron as a mixture at the low concentrations which mimicked concentrations observed in surface waters. Hepatic vitellogenin (Vtg) mRNA was induced by exposure to the high concentrations of Diuron, as well as DCPMU and DCPU in both concentrations. Brain cytochrome P450 aromatase activity was generally diminished by diuron, its metabolites, and the AP/diuron mixtures. 17β-Hydroxysteroid dehydrogenase (17βHSD) levels were also reduced by DCPMU and DCA in the lower concentrations, but not by higher concentrations. While the AP mixture reduced 17βHSD, the AP/diuron mixture induced testosterone (T) biosynthesis at the single concentration tested. Although CYP3A expression was induced by all diuron metabolites, it was unchanged by the AP mixture. These data indicate that mixtures of AP and diuron enhanced the formation of the metabolite (DCPMU) which induced vitellogenin, and reduced T biosynthetic enzymes (17βHSD inhibition). Overall, these data showed that APs may have induced the biotransformation of diuron to at least one metabolite, that may disrupt androgen biosynthesis and potentially alter steroid feedback pathways in the central nervous system.

Effects of Chronic Renal Failure on Brain Cytochrome P450 in Rats.

Chronic renal failure (CRF) impedes renal excretion of drugs and their metabolism by reducing the expression of liver cytochrome P450 (P450). Uremic serum contains factors, such as parathyroid hormone (PTH), that decrease liver P450s. The P450s are also involved in the metabolism of xenobiotics in the brain. This study investigates: 1) the effects of CRF on rat brain P450, 2) the role of PTH in the downregulation of brain P450s in CRF rats, and 3) the effects of PTH on P450s in astrocytes. Protein and mRNA expression of P450s were assessed in the brain of CRF and control (CTL) rats, as well as from CTL or CRF rats that underwent parathyroidectomy (PTX) 1 week before nephrectomy. CYP3A activity was measured using 3-[(3, 4-difluorobenzyl) oxy]-5, 5-dimethyl-4-[4-methylsulfonyl) phenyl] furan-2(5H)-1 metabolism in brain microsomal preparation. CYP3A protein expression was assessed in primary cultured astrocytes incubated with serum obtained from CRF or CTL rats or with PTH. Significant downregulations (≥40%) of CYP1A, CYP2C11, and CYP3A proteins were observed in microsomes from CRF rat brains. CYP3A activity reduction was also observed. CYP3A expression and activity were unaffected in PTX-pretreated CRF rats. Serum of PTX-treated CRF rats had no impact on CYP3A levels in astrocytes compared with that of untreated CRF rats. Finally, PTH addition to normal calf serum induced a reduction in CYP3A protein similar to CRF serum, suggesting that CRF-induced hyperparathyroidism is associated with a significant decrease in P450 drug-metabolizing enzymes in the brain, which may have implications in drug response.

Sex hormones regulate cerebral drug metabolism via brain miRNAs: down-regulation of brain CYP2D by androgens reduces the analgesic effects of tramadol.

Brain cytochrome P450 2D (CYP2D) metabolises exogenous neurotoxins, endogenous substances and neurotransmitters. Brain CYP2D can be regulated in an organ-specific manner, but the possible regulatory mechanisms are poorly understood. We investigated the involvement of miRNAs in the selective regulation of brain CYP2D by testosterone and the corresponding alteration of the pharmacological profiles of tramadol by testosterone. The regulation of CYP2D and brain-enriched miRNAs by testosterone was investigated using SH-SY5Y cells, U251 cells, and HepG2 cells as well as orchiectomized growth hormone receptor knockout (GHR-KO) mice and rats. Concentration-time curves of tramadol in rat brain were determined using a microdialysis technique. The analgesic action of tramadol was assessed by the tail-flick test in rats. miR-101 and miR-128-2 bound the 3'-untranslated region of the CYP2D6 mRNA and decreased its level. Testosterone decreased CYP2D6 catalytic function via the up-regulation of miR-101 and miR-128-2 in SH-SY5Y and U251 cells, but not in HepG2 cells. Orchiectomy decreased the levels of miR-101 and miR-128-2 in the hippocampus of male GHR-KO mice, indicating that androgens regulate miRNAs directly, not via the alteration of growth hormone secretion patterns. Changes in the pharmacokinetic and pharmacodynamic profiles of tramadol by orchiectomy was attenuated by either testosterone supplementation or a specific brain CYP2D inhibitor. The selective regulation of brain CYP2D via brain-enriched miRNAs, following changes in androgen levels, such as in testosterone therapy, androgen deprivation therapy and/or ageing may alter the response to centrally active substances.

Brain Cytochrome p450 enzymes: a possible Therapeutic Targets for Neurological Diseases

Neurological diseases (ND) afflict hundreds of millions of people worldwide and constitute 12% of total deaths of the population all around the world. According to a global study conducted by the World Health Organization, 8 out of 10 disorders in the 3 rd highest disability classes are neurologic problems. Commonly they have disabling consequences, compromising severely the quality of the life of affected subjects. Often therapeutic strategies are limited in efficacy. Limitations lie with the enormous fragility of the so complex structure and functions accomplished by the central nervous system, together with the presence of the barrier between the tissue and the blood limiting the penetration of drugs. For these reason new strategies to protect the brain are essential. One way might be the enhancement of local biomolecular mechanisms (metabolizing enzymes, transporters, etc.). However, increasing evidence underline that our knowledge of the brain is still partial, and information cannot simply be derived from other well-known organs such as the liver. This is the case for the brain cytochrome P450 enzymes, showing differential cellular localization, brain regional expression and modulation.

Role of brain cytochrome P450 mono-oxygenases in bilirubin oxidation-specific induction and activity.

In the Crigler-Najjar type I syndrome, the genetic absence of efficient hepatic glucuronidation of unconjugated bilirubin (UCB) by the uridine 5'-diphospho-glucuronosyltransferase1A1 (UGT1A1) enzyme produces the rise of UCB level in blood. Its entry to central nervous system could generate toxicity and neurological damage, and even death. In the past years, a compensatory mechanism to liver glucuronidation has been indicated in the hepatic cytochromes P450 enzymes (Cyps) which are able to oxidize bilirubin. Cyps are expressed also in the central nervous system, the target of bilirubin toxicity, thus making them theoretically important to confer a protective activity toward bilirubin accumulation and neurotoxicity. We therefore investigated the functional induction (mRNA, EROD/MROD) and the ability to oxidize bilirubin of Cyp1A1, 1A2, and 2A3 in primary astrocytes cultures obtained from two rat brain region (cortex: Cx and cerebellum: Cll). We observed that Cyp1A1 was the Cyp isoform more easily induced by beta-naphtoflavone (βNF) in both Cx and Cll astrocytes, but oxidized bilirubin only after uncoupling by 3, 4,3',4'-tetrachlorobiphenyl (TCB). On the contrary, Cyp1A2 was the most active Cyp in bilirubin clearance without uncoupling, but its induction was confined only in Cx cells. Brain Cyp2A3 was not inducible. In conclusion, the exposure of astrocytes to βNF plus TCB significantly enhanced Cyp1A1 mediating bilirubin clearance, improving cell viability in both regions. These results may be a relevant groundwork for the manipulation of brain Cyps as a therapeutic approach in reducing bilirubin-induced neurological damage.

Effect of Gestational Exposure of Cypermethrin on Postnatal Development of Brain Cytochrome P450 2D1 and 3A1 and Neurotransmitter Receptors.

Oral administration of low doses (1.25, 2.5, or 5 mg/kg) of cypermethrin to pregnant Wistar rats from gestation days 5 to 21 led to dose-dependent differences in the induction of cytochrome P450 2D1 (CYP2D1) and 3A1 messenger RNA (mRNA) and protein in brain regions isolated from the offsprings postnatally at 3 weeks that persisted up to adulthood (12 weeks). Similar alterations were observed in the expression of GABAergic, muscarinic, dopaminergic, and serotonergic neurotransmitter receptors in brain regions of rat offsprings. Rechallenge of the prenatally exposed offsprings at adulthood (12 weeks old) with cypermethrin (p.o., 10 mg/kg for 6 days) led to a greater magnitude of alterations in the expression of CYPs, neurotransmitter receptors, and neurotransmitter receptor binding in the brain regions when compared to the control offsprings treated at adulthood with cypermethrin or prenatally exposed offsprings. A greater magnitude of decrease was also observed in the spontaneous locomotor activity (SLA) in prenatally exposed offsprings rechallenged with cypermethrin. The present data indicating similarities in the alterations in the expression of CYPs (2D1 and 3A1) and neurotransmitter receptors in brain has led us to suggest that endogenous function regulating CYPs is possibly associated with neurotransmission processes. A greater magnitude of alterations in CYP2D1, 3A1, neurotransmitter receptors, and SLA in rechallenged animals has further provided evidence that alterations in CYPs are possibly linked with neurotransmission processes.