New insights of CYP1A in endogenous metabolism: a focus on single nucleotide polymorphisms and diseases

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.

Toxicity and biomarkers of micro-plastic in aquatic environment: a review

Microplastics (MPs; <5 mm) are found in all aquatic environments. Due to harmful impacts, MPs pose a great threat to the aquatic ecology. Therefore, this review aims to provide an overview of the risk, bioavailability, and toxicity of MPs in aquatic organisms. Various factors affecting MPs bioavailability and level of risks at cellular and molecular level on aquatic organisms are comprehensively discussed. More specifically biomarkers for antioxidant response (superoxide dismutase, catalase, glutathione peroxidase, reductase, and glutathione S-transferase), neurotoxic impairment (acetylcholinesterase), lysosomal activity alteration, and genotoxicity have been discussed in detail. Biomarkers are powerful tool in the monitoring programme, but the collection of literature on biomarkers for MPs is limited. Thus, here we demonstrate how to evaluate MPs impact, in monitoring programme, on organisms using biomarkers in aquatic environment. This review would broaden the existing knowledge on the toxic effect and biomarkers of MPs and offer research priorities for future studies.

The role of cytochrome P450 (CYP) enzymes in hyperoxic lung injury

INTRODUCTION

Hyperoxic lung injury is a condition that can occur in patients in need of supplemental oxygen, such as premature infants with bronchopulmonary dysplasia or adults with acute respiratory distress syndrome. Cytochrome P450 (CYP) enzymes play critical roles in the metabolism of endogenous and exogenous compounds.

AREAS COVERED

Through their complex pathways, some subfamilies of these enzymes may contribute to or protect against hyperoxic lung injury. Oxidative stress from reactive oxygen species (ROS) production is most likely a major contributor of hyperoxic lung injury. CYP1A enzymes have been shown to protect against hyperoxic lung injury while CYP1B enzymes seem to contribute to it. CYP2J2 enzymes help protect against hyperoxic lung injury by triggering EET production, thereby, increasing antioxidant enzymes. The metabolism of arachidonic acid to ω-terminal hydroxyeicosatetraenoic acid (20-HETEs) by CYP4A and CYP4F enzymes could impact hyperoxic lung injury via the vasodilating effects of 20-HETE. CYP2E1 and CYP2A enzymes may contribute to the oxidative stress in the lungs caused by ethanol- and nicotine-metabolism, respectively.

EXPERT OPINION

Overall, the CYP enzymes, depending upon the isoform, play a contributory or protective role in hyperoxic lung injury, and are, therefore, ideal candidates for developing drugs that can treat oxygen-mediated lung injury.

Drug interaction of ningetinib and gefitinib involving CYP1A1 and efflux transporters in non-small cell lung cancer patients

AIMS

Ningetinib is a tyrosine kinase inhibitor for the treatment of non-small cell lung cancer (NSCLC). The present study aims to investigate the drug interaction of ningetinib and gefitinib and the mechanism of high plasma exposure of N-demethylated ningetinib (M1) in NSCLC patients.

METHODS

Patients with NSCLC were recruited. Metabolism and transport assays were performed using in vitro models. Deuterated M1 was used to study the effects of ningetinib and gefitinib on M1 efflux in Institute of Cancer Research (ICR) mice.

RESULTS

Upon co-administration of ningetinib with gefitinib, the plasma exposure of M1 was reduced by 80%, whereas that of ningetinib was not affected. In vitro experiments indicated that CYP1A1 was primarily responsible for M1 formation. Gefitinib was demonstrated to be a strong inhibitor of CYP1A1 with K_i value of 0.095 μM. M1 was identified as a substrate of efflux transporters P-gp and BCRP, while ningetinib and gefitinib were demonstrated to be their inhibitors, which was consistent with the results in mice. However, the inhibitory effect of gefitinib on efflux in vivo was negligible in the presence of ningetinib.

CONCLUSION

The high plasma exposure of M1 in patients was attributed to the inhibition of M1 efflux by ningetinib and its low tissue affinity. When co-administered, gefitinib inhibited the formation of M1, but due to the low metabolic yield of M1 in vivo, the pharmacokinetics of ningetinib was not influenced. Inhibition of CYP1A1 may increase the concentration of ningetinib in target tissues, and the long-term safety and efficacy of ningetinib combined with gefitinib should be evaluated.

Expression and localization of the aryl hydrocarbon receptors and cytochrome P450 1A during early development of Atlantic cod (Gadus morhua)

The aryl hydrocarbon receptor (Ahr) is a ligand-activated transcription factor that mediates the toxicity of dioxins and dioxin-like compounds (DLCs) in vertebrates. Two clades of the Ahr family exist in teleosts (Ahr1 and Ahr2), and it has been demonstrated that Ahr2 is the main protein involved in mediating the toxicity of dioxins and DLCs in most teleost species. Recently, we characterized the Atlantic cod (Gadus morhua) Ahr1a and Ahr2a receptors. To further explore a possible subfunction partitioning of Ahr1a and Ahr2a in Atlantic cod we have mapped the expression and localization of ahr1a and ahr2a in early developmental stages. Atlantic cod embryos were continuously exposed in a passive-dosing exposure system to the Ahr agonist, benzo[a]pyrene (B[a]P), from five days post fertilization (dpf) until three days post hatching (dph). Expression of ahr1a, ahr2a, and the Ahr-target genes, cyp1a and ahrrb, was assessed in embryos (8 dpf and 10 dpf) and larvae (3 dph) with quantitative real-time PCR analyses (qPCR), while in situ hybridization was used to assess the localization of expression of ahr1a, ahr2a and cyp1a. Quantitative measurements showed an increased cyp1a expression in B[a]P-exposed samples at all sampling points, and for ahr2a at 10 dpf, confirming the activation of the Ahr-signalling pathway. Furthermore, B[a]P strongly induced ahr2a and cyp1a expression in the cardiovascular system and skin, respectively, of embryos and larvae. Induced expression of both ahr2a and cyp1a was also revealed in the liver of B[a]P-exposed larvae. Our results suggest that Ahr2a is the major subtype involved in mediating responses to B[a]P in early developmental stages of Atlantic cod, which involves transcriptional regulation of biotransformation genes, such as cyp1a. The focused expression of ahr1a in the eye of embryos and larvae, and the presence of ahr2a transcripts in the jaws and fin nodes, further indicate evolved specialized roles of the two Ahrs in ontogenesis.

New insights into the role of mitochondria in cardiac microvascular ischemia/reperfusion injury

As reperfusion therapies have become more widely used in acute myocardial infarction patients, ischemia-induced myocardial damage has been markedly reduced, but reperfusion-induced cardiac injury has become increasingly evident. The features of cardiac ischemia-reperfusion (I/R) injury include microvascular perfusion defects, platelet activation and sequential cardiomyocyte death due to additional ischemic events at the reperfusion stage. Microvascular obstruction, defined as a no-reflow phenomenon, determines the infarct zone, myocardial function and peri-operative mortality. Cardiac microvascular endothelial cell injury may occur much earlier and with much greater severity than cardiomyocyte injury. Endothelial cells contain fewer mitochondria than other cardiac cells, and several of the pathological alterations during cardiac microvascular I/R injury involve mitochondria, such as increased mitochondrial reactive oxygen species (mROS) levels and disturbed mitochondrial dynamics. Although mROS are necessary physiological second messengers, high mROS levels induce oxidative stress, endothelial senescence and apoptosis. Mitochondrial dynamics, including fission, fusion and mitophagy, determine the shape, distribution, size and function of mitochondria. These adaptive responses modify extracellular signals and orchestrate intracellular processes such as cell proliferation, migration, metabolism, angiogenesis, permeability transition, adhesive molecule expression, endothelial barrier function and anticoagulation. In this review, we discuss the involvement of mROS and mitochondrial morphofunction in cardiac microvascular I/R injury.

Molecular role of cytochrome P4501A enzymes inoxidative stress

Cytochrome P4501A (CYP1A) enzymes play important roles in xenobiotic and endobiotic metabolism. Due to uncoupling reactions during the enzymatic cycle, CYP1A enzymes can release reactive oxidative species (ROS) in the form of superoxide radical, hydrogen peroxide, hydroxyl radical etc. An imbalance between production of free radicals and the ability of antioxidants to detoxify the free radicals can lead to accumulation of ROS, which in turn can lead to oxidative stress. Oxidative stress can lead to inflammation and toxicity, which in turn can cause human diseases such as bronchopulmonary disease (BPD), ARDS, renal hypertension, etc. CYP1A enzymes, depending on the organ system, they either contribute or protect against oxidative injury. Thus, they have dual roles in regard to oxidative stress. This review presents an overview of the mechanistic relationship between CYP1A enzymes and oxidative stress in relation to various diseases in different organs (e.g., liver, lungs, heart, kidneys, and reproductive organs).