In Vivo Bio-Activation of JWH-175 to JWH-018: Pharmacodynamic and Pharmacokinetic Studies in Mice

3-(1-Naphthalenylmethyl)-1-pentyl-1H-indole (JWH-175) is a synthetic cannabinoid illegally marketed for its psychoactive cannabis-like effects. This study aimed to investigate and compare in vitro and in vivo pharmacodynamic activity of JWH-175 with that of 1-naphthalenyl (1-pentyl-1H-indol-3-yl)-methanone (JWH-018), as well as evaluate the in vitro (human liver microsomes) and in vivo (urine and plasma of CD-1 male mice) metabolic profile of JWH-175. In vitro binding studies showed that JWH-175 is a cannabinoid receptor agonist less potent than JWH-018 on mouse and human CB1 and CB2 receptors. In agreement with in vitro data, JWH-175 reduced the fESPS in brain hippocampal slices of mice less effectively than JWH-018. Similarly, in vivo behavioral studies showed that JWH-175 impaired sensorimotor responses, reduced breath rate and motor activity, and increased pain threshold to mechanical stimuli less potently than JWH-018. Metabolic studies demonstrated that JWH-175 is rapidly bioactivated to JWH-018 in mice blood, suggesting that in vivo effects of JWH-175 are also due to JWH-018 formation. The pharmaco-toxicological profile of JWH-175 was characterized for the first time, proving its in vivo bio-activation to the more potent agonist JWH-018. Thus, it highlighted the great importance of investigating the in vivo metabolism of synthetic cannabinoids for both clinical toxicology and forensic purposes.

Molecular mechanisms involved in the protective actions of Selective Estrogen Receptor Modulators in brain cells

Synthetic selective modulators of the estrogen receptors (SERMs) have shown to protect neurons and glial cells against toxic insults. Among the most relevant beneficial effects attributed to these compounds are the regulation of inflammation, attenuation of astrogliosis and microglial activation, prevention of excitotoxicity and as a consequence the reduction of neuronal cell death. Under pathological conditions, the mechanism of action of the SERMs involves the activation of estrogen receptors (ERs) and G protein-coupled receptor for estrogens (GRP30). These receptors trigger neuroprotective responses such as increasing the expression of antioxidants and the activation of kinase-mediated survival signaling pathways. Despite the advances in the knowledge of the pathways activated by the SERMs, their mechanism of action is still not entirely clear, and there are several controversies. In this review, we focused on the molecular pathways activated by SERMs in brain cells, mainly astrocytes, as a response to treatment with raloxifene and tamoxifen.

Kinetics of dextromethorphan-O-demethylase activity and distribution of CYP2D in four commonly-used subcellular fractions of rat brain

The purpose of this study was to compare the enzymatic kinetics and distribution of cytochrome P450 2D (CYP2D) among different rat brain subcellular fractions. Rat brains were used to prepare total membrane, crude mitochondrial, purified mitochondrial, and microsomal fractions, in addition to total homogenate. Michaelis-Menten kinetics of the brain CYP2D activity was estimated based on the conversion of dextromethorphan (DXM) to dextrorphan using UPLC-MS/MS. Protein levels of CYP2D and subcellular markers were determined by Western blot. Microsomal CYP2D exhibited high affinity and low capacity, compared with the mitochondrial CYP2D that had a much lower (∼50-fold) affinity but a higher (∼six-fold) capacity. The apparent CYP2D affinity and capacity of the crude mitochondria were in between those of the microsomes and purified mitochondria. Additionally, the CYP2D activity in the whole homogenate was much higher than that in the total membranes at higher DXM concentrations. A CYP2D immune-reactive band in the brain mitochondria appeared at a lower MW but had a much higher intensity than that in the microsomes. Mitochondrial brain CYP2D has a much higher capacity than its microsomal counterpart. Additionally, brain homogenate is more representative of the overall CYP2D activity than the widely-used total membrane fraction.

β-Naphtoflavone and Ethanol Induce Cytochrome P450 and Protect towards MPP⁺ Toxicity in Human Neuroblastoma SH-SY5Y Cells

Cytochrome P450 (CYP) isozymes vary their expression depending on the brain area, the cell type, and the presence of drugs. Some isoforms are involved in detoxification and/or toxic activation of xenobiotics in central nervous system. However, their role in brain metabolism and neurodegeneration is still a subject of debate. We have studied the inducibility of CYP isozymes in human neuroblastoma SH-SY5Y cells, treated with β-naphtoflavone (β-NF) or ethanol (EtOH) as inducers, by qRT-PCR, Western blot (WB), and metabolic activity assays. Immunohistochemistry was used to localize the isoforms in mitochondria and/or endoplasmic reticulum (ER). Tetrazolium (MTT) assay was performed to study the role of CYPs during methylphenyl pyridine (MPP⁺) exposure. EtOH increased mRNA and protein levels of CYP2D6 by 73% and 60% respectively. Both β-NF and EtOH increased CYP2E1 mRNA (4- and 1.4-fold, respectively) and protein levels (64% both). The 7-ethoxycoumarin O-deethylation and dextromethorphan O-demethylation was greater in treatment samples than in controls. Furthermore, both treatments increased by 22% and 18%, respectively, the cell viability in MPP⁺-treated cells. Finally, CYP2D6 localized at mitochondria and ER. These data indicate that CYP is inducible in SH-SY5Y cells and underline this in vitro system for studying the role of CYPs in neurodegeneration.

Atrazine Triggers Mitochondrial Dysfunction and Oxidative Stress in Quail ( Coturnix C. coturnix) Cerebrum via Activating Xenobiotic-Sensing Nuclear Receptors and Modulating Cytochrome P450 Systems

The residues from the widely used broad-spectrum environmental herbicide, atrazine (ATR), result in the exposure of nontarget organisms and persist as a global major public health hazard. ATR is neurotoxic and may cause adverse health effects in mammals, birds, and fishes. Nevertheless, the molecular mechanism of ATR induced neurotoxicity remains unclear. To assess the molecular mechanisms of ATR-induced cerebral toxicity through potential oxidative damage, quail were treated with ATR by oral gavage administration at doses of 0, 50, 250, and 500 mg/kg body weight daily for 45 days. Markedly, increases in the amount of swelling of neuronal cells, the percentage of mean damaged mitochondria, mitochondrial malformation, and mitochondrial vacuolar degeneration as well as decreases in the mitochondrial cristae and mitochondrial volume density were observed by light and electron microscopy in the cerebrum of quail. ATR induced toxicities in the expression of mitochondrial function-related genes and promoted oxidative damage, as indicated by effects on oxidative stress indices. These results indicated that ATR exposure can cause neurological disorders and cerebral injury. ATR may initiate apoptosis by activating Bcl-2, Bax, and Caspase3 protein expression but failed to induce autophagy (LC3B has not cleaved to LC3BI/II). Furthermore, ATR induced CYP-related enzymes metabolism disorders by activating the nuclear xenobiotic receptors response (NXRs including AHR, CAR, and PXR) and increased expression of several CYP isoforms (including CYP1B1 and CYP2C18) and thereby producing mitochondrial dysfunction. In this study, we observed ATR exposure resulted in oxidative stress and mitochondrial dysfunction by activating the NXR response and interfering the CYP450s homeostasis in quail cerebrum that supported the molecular mechanism of ATR induced cerebrum toxicity. In conclusion, these results provided new evidence on molecular mechanism of ATR induced neurotoxicity.

Effects of volatile anaesthetics on heme metabolism in a murine genetic model of Acute Intermittent Porphyria. A comparative study with other porphyrinogenic drugs

BACKGROUND

Acute Intermittent Porphyria (AIP) is an inherited disease produced by a deficiency of Porphobilinogen deaminase (PBG-D). The aim of this work was to evaluate the effects of Isoflurane and Sevoflurane on heme metabolism in a mouse genetic model of AIP to further support our previous proposal for avoiding their use in porphyric patients. A comparative study was performed administering the porphyrinogenic drugs allylisopropylacetamide (AIA), barbital and ethanol, and also between sex and mutation using AIP (PBG-D activity 70% reduced) and T1 (PBG-D activity 50% diminished) mice.

METHODS

The activities of 5-Aminolevulinic synthetase (ALA-S), PBG-D, Heme oxygenase (HO) and CYP2E1; the expression of ALA-S and the levels of 5-aminolevulinic acid (ALA) were measured in different tissues of mice treated with the drugs mentioned.

RESULTS

Isoflurane increased liver, kidney and brain ALA-S activity of AIP females but only affected kidney AIP males. Sevoflurane induced ALA-S activity in kidney and brain of female AIP group. PBG-D activity was further reduced by Isoflurane in liver male T1; in AIP male mice activity remained in its low basal levels. Ethanol and barbital also caused biochemical alterations. Only AIA triggered neurological signs similar to those observed during human acute attacks in male AIP being the symptoms less pronounced in females although ALA-S induction was greater. Heme degradation was affected.

DISCUSSION

Biochemical alterations caused by the porphyrinogenic drugs assayed were different in male and female mice and also between T1 and AIP being more affected the females of AIP group.

GENERAL SIGNIFICANCE

This is the first study using volatile anaesthetics in an AIP genetic model confirming Isoflurane and Sevoflurane porphyrinogenicity.

Toxicological Implications of Mitochondrial Localization of CYP2E1

Cytochrome P450 2E1 (CYP2E1) metabolizes an extensive array of pollutants, drugs, and other small molecules, often resulting in bioactivation to reactive metabolites. Therefore, it is unsurprising that it has been the subject of decades of research publications and reviews. However, while CYP2E1 has historically been studied in the endoplasmic reticulum (erCYP2E1), active CYP2E1 is also present in mitochondria (mtCYP2E1). Relatively few studies have specifically focused on mtCYP2E1, but there is growing interest in this form of the enzyme as a driver in toxicological mechanisms given its activity and location. Many previous studies have linked total CYP2E1 to conditions that involve mitochondrial dysfunction (fasting, diabetes, non-alcoholic steatohepatitis, and obesity). Furthermore, a large number of reactive metabolites that are formed by CYP2E1 through metabolism of drugs and pollutants have been demonstrated to cause mitochondrial dysfunction. Finally, there appears to be significant inter-individual variability in targeting to the mitochondria, which could constitute a source of variability in individual response to exposures. This review discusses those outcomes, the biochemical properties and toxicological consequences of mtCYP2E1, and highlights important knowledge gaps and future directions. Overall, we feel that this exciting area of research is rich with new and important questions about the relationship between mtCYP2E1, mitochondrial dysfunction, and pathology.

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.

Pleiotropic effects of 5-aminolevulinic acid in mouse brain

5-Aminolevulinic acid (ALA) seems to be responsible for the neuropsychiatric manifestations of acute intermittent porphyria (AIP). Our aim was to study the effect of ALA on the different metabolic pathways in the mouse brain to enhance our knowledge about the action of this heme precursor on the central nervous system. Heme metabolism, the cholinergic system, the defense enzyme system, and nitric oxide metabolism were evaluated in the encephalon of CF-1 mice receiving a single (40 mg/kg body mass) or multiple doses of ALA (40 mg/kg, every 48 h for 14 days). We subsequently found ALA accumulation in the encephalon of the mice. ALA also altered the brain cholinergic system. After one dose of ALA, a decrease in superoxide dismutase activity and a reduction in glutathione levels were detected, whereas malondialdehyde levels and catalase activity were increased. Heme oxygenase was also increased as an antioxidant response to protect the encephalon against injury. All nitric oxide synthase isoforms were induced by ALA, these changes were more significant for the inducible isoform in glial cells. In conclusion, ALA affected several metabolic pathways in mouse encephalon. Data indicate that a rapid response to oxidative stress was developed; however, with long-term intoxication, the redox balance was probably restored, thereby minimizing oxidative damage.

Translational Implications of the Alcohol-Metabolizing Enzymes, Including Cytochrome P450-2E1, in Alcoholic and Nonalcoholic Liver Disease

Fat accumulation (hepatic steatosis) in alcoholic and nonalcoholic fatty liver disease is a potentially pathologic condition which can progress to steatohepatitis (inflammation), fibrosis, cirrhosis, and carcinogenesis. Many clinically used drugs or some alternative medicine compounds are also known to cause drug-induced liver injury, which can further lead to fulminant liver failure and acute deaths in extreme cases. During liver disease process, certain cytochromes P450 such as the ethanol-inducible cytochrome P450-2E1 (CYP2E1) and CYP4A isozymes can be induced and/or activated by alcohol and/or high-fat diets and pathophysiological conditions such as fasting, obesity, and diabetes. Activation of these P450 isozymes, involved in the metabolism of ethanol, fatty acids, and various drugs, can produce reactive oxygen/nitrogen species directly and/or indirectly, contributing to oxidative modifications of DNA/RNA, proteins and lipids. In addition, aldehyde dehydrogenases including the mitochondrial low Km aldehyde dehydrogenase-2 (ALDH2), responsible for the metabolism of acetaldehyde and lipid aldehydes, can be inactivated by various hepatotoxic agents. These highly reactive acetaldehyde and lipid peroxides, accumulated due to ALDH2 suppression, can interact with cellular macromolecules DNA/RNA, lipids, and proteins, leading to suppression of their normal function, contributing to DNA mutations, endoplasmic reticulum stress, mitochondrial dysfunction, steatosis, and cell death. In this chapter, we specifically review the roles of the alcohol-metabolizing enzymes including the alcohol dehydrogenase, ALDH2, CYP2E1, and other enzymes in promoting liver disease. We also discuss translational research opportunities with natural and/or synthetic antioxidants, which can prevent or delay the onset of inflammation and liver disease.