NADPH-cytochrome P450 oxidoreductase: roles in physiology, pharmacology, and toxicology

Cytochrome P450 monooxygenase systems: Diversity and plasticity for adaptive stress response

Superfamily of cytochromes P450 (CYPs) is composed of heme-thiolate-containing monooxygenase enzymes, which play crucial roles in the biosynthesis, bioactivation, and detoxification of a variety of organic compounds, both endogenic and exogenic. Majority of CYP monooxygenase systems are multi-component and contain various redox partners, cofactors and auxiliary proteins, which contribute to their diversity in both prokaryotes and eukaryotes. Recent progress in bioinformatics and computational biology approaches make it possible to undertake whole-genome and phylogenetic analyses of CYPomes of a variety of organisms. Considerable variations in sequences within and between CYP families and high similarity in secondary and tertiary structures between all CYPs along with dramatic conformational changes in secondary structure elements of a substrate binding site during catalysis have been reported. This provides structural plasticity and substrate promiscuity, which underlie functional diversity of CYPs. Gene duplication and mutation events underlie CYP evolutionary diversity and emergence of novel selectable functions, which provide the involvement of CYPs in high adaptability to changing environmental conditions and dietary restrictions. In our review, we discuss the recent advancements and challenges in the elucidating the evolutionary origin and mechanisms underlying the CYP monooxygenase system diversity and plasticity. Our review is in the view of hypothesis that diversity of CYP monooxygenase systems is translated into the broad metabolic profiles, and this has been acquired during the long evolutionary time to provide structural plasticity leading to high adaptative capabilities to environmental stress conditions.

Complete correction of murine phenylketonuria by selection-enhanced hepatocyte transplantation

BACKGROUND AND AIMS

Hepatocyte transplantation for genetic liver diseases has several potential advantages over gene therapy. However, the low efficiency of cell engraftment has limited its clinical implementation. This problem could be overcome by selectively expanding transplanted donor cells until they replace enough of the liver mass to achieve therapeutic benefit. We previously described a gene therapy method to selectively expand hepatocytes deficient in cytochrome p450 reductase (Cypor) using acetaminophen (APAP). Because Cypor is required for the transformation of APAP to a hepatotoxic metabolite, Cypor-deficient cells are protected from toxicity and are able to expand following APAP-induced liver injury. Here, we apply this selection system to correct a mouse model of phenylketonuria by cell transplantation.

APPROACH AND RESULTS

Hepatocytes from a wild-type donor animal were edited in vitro to create Cypor deficiency and then transplanted into phenylketonuric animals. Following selection with APAP, blood phenylalanine concentrations were fully normalized and remained stable following APAP withdrawal. Cypor-deficient hepatocytes expanded from < 1% to ~14% in corrected animals, and they showed no abnormalities in blood chemistries, liver histology, or drug metabolism.

CONCLUSIONS

We conclude that APAP-mediated selection of transplanted hepatocytes is a potential therapeutic for phenylketonuria with long-term efficacy and a favorable safety profile.

Engineering of redox partners and cofactor NADPH supply of CYP68JX for efficient steroid two-step ordered selective hydroxylation activity

CYP68JX, a P450 hydroxylase, derived from Colletotrichum lini ST-1 is capable of biotransforming dehydroepiandrosterone (DHEA) to 3β,7α,15α-trihydroxy-5-androstene-17-one (7α,15α-diOH-DHEA). Redox partners and cofactor supply are important factors affecting the catalytic activity of CYP68JX. In this study, the heterologous expression of CYP68JX in Saccharomyces cerevisiae BY4741 was realized resulting in a 17.1% target product yield. In order to increase the catalytic efficiency of CYP68JX in S. cerevisiae BY4741, a complete cytochrome P450 redox system was constructed. Through the combination of CYP68JX and heterologous CPRs, the yield of the target product 7α,15α-diOH-DHEA in CYP68JX recombinant system was increased to 37.8%. Furthermore, by adding NADPH coenzyme precursor tryptophan of 40 mmol/L and co-substrate fructose of 20 g/L during the conversion process, the catalytic efficiency of CYP68JX was further improved, the target product yield reached 57.9% which was 3.39-fold higher than initial yield. Overall, this study provides a reference for improving the catalytic activity of P450s.

Computational identification and analysis of deleterious non-synonymous single nucleotide polymorphisms (nsSNPs) in the human POR gene: a structural and functional impact

Cytochrome P450 oxidoreductase (POR) protein is essential for steroidogenesis, and POR gene mutations are frequently associated with P450 Oxidoreductase Deficiency (PORD), a disorder of hormone production. To our knowledge, no previous attempt has been made to identify and analyze the deleterious/pathogenic non-synonymous single nucleotide polymorphisms (nsSNPs) in the human POR gene through an extensive computational approach. Computational algorithms and tools were employed to identify, characterize, and validate the pathogenic SNPs associated with certain diseases. To begin with, all the high-confidence SNPs were collected, and their structural and functional impacts on the protein structures were explored. The results of various in silico analyses affirm that the A287P and R457H variants of POR could destabilize the interactions between the amino acids and the hydrogen bond networks, resulting in functional deviations of POR. The literature study further confirms that the pathogenic mutations (A287P and R457H) are associated with the onset of PORD. Molecular dynamics simulations (MDS) and essential dynamics (ED) studies characterized the structural consequences of prioritized deleterious mutations, representing the structural destabilization that might disrupt POR biological function. The identified deleterious mutations at the cofactor's binding domains might interfere with the essential interactions between the protein and cofactors, thus inhibiting POR catalytic activity. The consolidated insights from the computational analyses can be used to predict potential deleterious mutants and understand the disease's pathological basis and the molecular mechanism of drug metabolism for the application of personalized medication. HIGHLIGHTSNADPH cytochrome P450 oxidoreductase (POR) mutations are associated with a broad spectrum of human diseasesIdentified and analyzed the most deleterious nsSNPs of POR through the sequence and structure-based prediction toolsInvestigated the structural and functional impacts of the most significant mutations (A287P and R457H) associated with PORDMolecular dynamics and PCA-based FEL analysis were utilized to probe the mutation-induced structural alterations in PORCommunicated by Ramaswamy H. Sarma.

Vitamin E/Coenzyme Q-Dependent "Free Radical Reductases": Redox Regulators in Ferroptosis

Significance: Lipid peroxidation and its products, oxygenated polyunsaturated lipids, act as essential signals coordinating metabolism and physiology and can be deleterious to membranes when they accumulate in excessive amounts. Recent Advances: There is an emerging understanding that regulation of polyunsaturated fatty acid (PUFA) phospholipid peroxidation, particularly of PUFA-phosphatidylethanolamine, is important in a newly discovered type of regulated cell death, ferroptosis. Among the most recently described regulatory mechanisms is the ferroptosis suppressor protein, which controls the peroxidation process due to its ability to reduce coenzyme Q (CoQ). Critical Issues: In this study, we reviewed the most recent data in the context of the concept of free radical reductases formulated in the 1980-1990s and focused on enzymatic mechanisms of CoQ reduction in different membranes (e.g., mitochondrial, endoplasmic reticulum, and plasma membrane electron transporters) as well as TCA cycle components and cytosolic reductases capable of recycling the high antioxidant efficiency of the CoQ/vitamin E system. Future Directions: We highlight the importance of individual components of the free radical reductase network in regulating the ferroptotic program and defining the sensitivity/tolerance of cells to ferroptotic death. Complete deciphering of the interactive complexity of this system may be important for designing effective antiferroptotic modalities. Antioxid. Redox Signal. 40, 317-328.

Anthracycline Toxicity: Light at the End of the Tunnel?

Anthracycline-induced cardiotoxicity (AIC) is a serious and common side effect of anthracycline therapy. Identification of genes and genetic variants associated with AIC risk has clinical potential as a cardiotoxicity predictive tool and to allow the development of personalized therapies. In this review, we provide an overview of the function of known AIC genes identified by association studies and categorize them based on their mechanistic implication in AIC. We also discuss the importance of functional validation of AIC-associated variants in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to advance the implementation of genetic predictive biomarkers. Finally, we review how patient-specific hiPSC-CMs can be used to identify novel patient-relevant functional targets and for the discovery of cardioprotectant drugs to prevent AIC. Implementation of functional validation and use of hiPSC-CMs for drug discovery will identify the next generation of highly effective and personalized cardioprotectants and accelerate the inclusion of approved AIC biomarkers into clinical practice.

Altered gene expression linked to germline dysfunction following exposure of Caenorhabditis elegans to DEET

N,N-diethyl-meta-toluamide (DEET) is a commonly used synthetic insect repellent. Although the neurological effects of DEET have been widely investigated, its effects on the germline are less understood. Here, we show that exposure of the nematode Caenorhabditis elegans, which is highly predictive of mammalian reprotoxicity, resulting in internal DEET levels within the range detected in human biological samples, causes activation of p53/CEP-1-dependent germ cell apoptosis, altered meiotic recombination, chromosome abnormalities, and missegregation. RNA-sequencing analysis links DEET-induced alterations in the expression of genes related to redox processes and chromatin structure to reduced mitochondrial function, impaired DNA double-strand break repair progression, and defects during early embryogenesis. We propose that Caenorhabditis elegans exposure to DEET interferes with gene expression, leading to increased oxidative stress and altered chromatin structure, resulting in germline effects that pose a risk to reproductive health.

Synthesis of mono Cytochrome P450 in a modified CHO-CPR cell-free protein production platform

Cytochromes P450 (CYPs) are a group of monooxygenases that can be found in almost all kinds of organisms. For CYPs to receive electrons from co-substrate NADPH, the activity of NADPH-Cytochrome-P450-oxidoreductase (CPR) is required as well. In humans, CYPs are an integral part of liver-based phase-1 biotransformation, which is essential for the metabolization of multiple xenobiotics and drugs. Consequently, CYPs are important players during drug development and therefore these enzymes are implemented in diverse screening applications. For these applications it is usually advantageous to use mono CYP microsomes containing only the CYP of interest. The generation of mono-CYP containing mammalian cells and vesicles is difficult since endogenous CYPs are present in many cell types that contain the necessary co-factors. By obtaining translationally active lysates from a modified CHO-CPR cell line, it is now possible to generate mono CYPs in a cell-free protein synthesis process in a straightforward manner. As a proof of principle, the synthesis of active human CYPs from three different CYP450 gene families (CYP1A2, CYP2B6 and CYP3A4), which are of outstanding interest in industry and academia was demonstrated. Luciferase based activity assays confirm the activity of the produced CYPs and enable the individual adaptation of the synthesis process for efficient cell-free enzyme production. Furthermore, they allow for substrate and inhibitor screenings not only for wild-type CYPs but also for mutants and further CYP isoforms and variants. As an example, the turnover of selected CYP substrates by cell-free synthesized CYPs was demonstrated via an indirect luciferase assay-based screening setup.

Exploring Novel Variants of the Cytochrome P450 Reductase Gene (POR) from the Genome Aggregation Database by Integrating Bioinformatic Tools and Functional Assays

Cytochrome P450 oxidoreductase (POR) is an essential redox partner for steroid and drug-metabolizing cytochromes P450 located in the endoplasmic reticulum. Mutations in POR lead to metabolic disorders, including congenital adrenal hyperplasia, and affect the metabolism of steroids, drugs, and xenobiotics. In this study, we examined approximately 450 missense variants of the POR gene listed in the Genome Aggregation Database (gnomAD) using eleven different in silico prediction tools. We found that 64 novel variants were consistently predicted to be disease-causing by most tools. To validate our findings, we conducted a population analysis and selected two variations in POR for further investigation. The human POR wild type and the R268W and L577P variants were expressed in bacteria and subjected to enzyme kinetic assays using a model substrate. We also examined the activities of several cytochrome P450 proteins in the presence of POR (WT or variants) by combining P450 and reductase proteins in liposomes. We observed a decrease in enzymatic activities (ranging from 35% to 85%) of key drug-metabolizing enzymes, supported by POR variants R288W and L577P compared to WT-POR. These results validate our approach of curating a vast amount of data from genome projects and provide an updated and reliable reference for diagnosing POR deficiency.

The mechanism of ferroptosis and its related diseases

Ferroptosis, a regulated form of cellular death characterized by the iron-mediated accumulation of lipid peroxides, provides a novel avenue for delving into the intersection of cellular metabolism, oxidative stress, and disease pathology. We have witnessed a mounting fascination with ferroptosis, attributed to its pivotal roles across diverse physiological and pathological conditions including developmental processes, metabolic dynamics, oncogenic pathways, neurodegenerative cascades, and traumatic tissue injuries. By unraveling the intricate underpinnings of the molecular machinery, pivotal contributors, intricate signaling conduits, and regulatory networks governing ferroptosis, researchers aim to bridge the gap between the intricacies of this unique mode of cellular death and its multifaceted implications for health and disease. In light of the rapidly advancing landscape of ferroptosis research, we present a comprehensive review aiming at the extensive implications of ferroptosis in the origins and progress of human diseases. This review concludes with a careful analysis of potential treatment approaches carefully designed to either inhibit or promote ferroptosis. Additionally, we have succinctly summarized the potential therapeutic targets and compounds that hold promise in targeting ferroptosis within various diseases. This pivotal facet underscores the burgeoning possibilities for manipulating ferroptosis as a therapeutic strategy. In summary, this review enriched the insights of both investigators and practitioners, while fostering an elevated comprehension of ferroptosis and its latent translational utilities. By revealing the basic processes and investigating treatment possibilities, this review provides a crucial resource for scientists and medical practitioners, aiding in a deep understanding of ferroptosis and its effects in various disease situations.

Complete correction of murine phenylketonuria by selection-enhanced hepatocyte transplantation

Hepatocyte transplantation for genetic liver diseases has several potential advantages over gene therapy. However, low efficiency of cell engraftment has limited its clinical implementation. This problem could be overcome by selectively expanding transplanted donor cells until they replace enough of the liver mass to achieve therapeutic benefit. We previously described a gene therapy method to selectively expand hepatocytes deficient in cytochrome p450 reductase (Cypor) using acetaminophen (APAP). Because Cypor is required for the transformation of APAP to a hepatotoxic metabolite, Cypor deficient cells are protected from toxicity and are able to expand following APAP-induced liver injury. Here, we apply this selection system to correct a mouse model of phenylketonuria (PKU) by cell transplantation. Hepatocytes from a wildtype donor animal were edited in vitro to create Cypor deficiency and then transplanted into PKU animals. Following selection with APAP, blood phenylalanine concentrations were fully normalized and remained stable following APAP withdrawal. Cypor-deficient hepatocytes expanded from <1% to ~14% in corrected animals, and they showed no abnormalities in blood chemistries, liver histology, or drug metabolism. We conclude that APAP-mediated selection of transplanted hepatocytes is a potential therapeutic for PKU with long-term efficacy and a favorable safety profile.

Diagnostic challenges and management advances in cytochrome P450 oxidoreductase deficiency, a rare form of congenital adrenal hyperplasia, with 46, XX karyotype

Cytochrome P450 oxidoreductase deficiency (PORD) is a rare form of congenital adrenal hyperplasia that can manifest with skeletal malformations, ambiguous genitalia, and menstrual disorders caused by cytochrome P450 oxidoreductase (POR) mutations affecting electron transfer to all microsomal cytochrome P450 and some non-P450 enzymes involved in cholesterol, sterol, and drug metabolism. With the advancement of molecular biology and medical genetics, increasing numbers of PORD cases were reported, and the clinical spectrum of PORD was extended with studies on underlying mechanisms of phenotype-genotype correlations and optimum treatment. However, diagnostic challenges and management dilemma still exists because of unawareness of the condition, the overlapping manifestations with other disorders, and no clear guidelines for treatment. Delayed diagnosis and management may result in improper sex assignment, loss of reproductive capacity because of surgical removal of ruptured ovarian macro-cysts, and life-threatening conditions such as airway obstruction and adrenal crisis. The clinical outcomes and prognosis, which are influenced by specific POR mutations, the presence of additional genetic or environmental factors, and management, include early death due to developmental malformations or adrenal crisis, bilateral oophorectomies after spontaneous rupture of ovarian macro-cysts, genital ambiguity, abnormal pubertal development, and nearly normal phenotype with successful pregnancy outcomes by assisted reproduction. Thus, timely diagnosis including prenatal diagnosis with invasive and non-invasive techniques and appropriate management is essential to improve patients' outcomes. However, even in cases with conclusive diagnosis, comprehensive assessment is needed to avoid severe complications, such as chromosomal test to help sex assignment and evaluation of adrenal function to detect partial adrenal insufficiency. In recent years, it has been noted that proper hormone replacement therapy can lead to decrease or resolve of ovarian macro-cysts, and healthy babies can be delivered by in vitro fertilization and frozen embryo transfer following adequate control of multiple hormonal imbalances. Treatment may be complicated with adverse effects on drug metabolism caused by POR mutations. Unique challenges occur in female PORD patients such as ovarian macro-cysts prone to spontaneous rupture, masculinized genitalia without progression after birth, more frequently affected pubertal development, and impaired fertility. Thus, this review focuses only on 46, XX PORD patients to summarize the potential molecular pathogenesis, differential diagnosis of classic and non-classic PORD, and tailoring therapy to maintain health, avoid severe complications, and promote fertility.

DNA Methylation of Genes Participating in Hepatic Metabolisms and Function in Fetal Calf Liver Is Altered by Maternal Undernutrition during Gestation

This study aimed to elucidate the effects of maternal undernutrition (MUN) on epigenetic modification of hepatic genes in Japanese Black fetal calves during gestation. Using a previously established experimental design feeding the dams with 60% (LN) or 120% (HN) of their global nutritional requirements during the 8.5-month gestational period, DNA methylation in the fetal liver was analyzed with reduced representation bisulfite sequencing (RRBS). The promoters and gene bodies in the LN fetuses were hypomethylated compared to HN fetuses. Pathway analysis showed that the genes with DMR in the exon/intron in the LN group were associated with pathways involved in Cushing syndrome, gastric acid secretion, and aldosterone synthesis and secretion. Promoter hypomethylation in the LN group was frequently observed in genes participating in various signaling pathways (thyroid hormone, Ras/Rap1, PIK3-Akt, cAMP), fatty acid metabolism, and cholesterol metabolism. The promoter hypomethylated genes ALPL and GNAS were upregulated in the LN group, whereas the promoter hypermethylated genes GRB10 and POR were downregulated. The intron/exon hypomethylated genes IGF2, IGF2R, ACAD8, TAT, RARB, PINK1, and SOAT2 were downregulated, whereas the hypermethylated genes IGF2BP2, NOS3, and NR2F1 were upregulated. Collectively, MUN alters the promoter and gene body methylation of genes associated with hepatic metabolisms (energy, cholesterol, mitochondria) and function, suggesting an impact of altered gene methylation on the dysregulation of gene expression in the fetal liver.

Variation in pentose phosphate pathway-associated metabolism dictates cytotoxicity outcomes determined by tetrazolium reduction assays

Tetrazolium reduction and resazurin assays are the mainstay of routine in vitro toxicity batteries. However, potentially erroneous characterization of cytotoxicity and cell proliferation can arise if verification of baseline interaction of test article with method employed is neglected. The current investigation aimed to demonstrate how interpretation of results from several standard cytotoxicity and proliferation assays vary in dependence on contributions from the pentose phosphate pathway (PPP). Non-tumorigenic Beas-2B cells were treated with graded concentrations of benzo[a]pyrene (B[a]P) for 24 and 48 h prior to cytotoxicity and proliferation assessment with commonly used MTT, MTS, WST1, and Alamar Blue assays. B[a]P caused enhanced metabolism of each dye assessed despite reductions in mitochondrial membrane potential and was reversed by 6-aminonicotinamide (6AN)-a glucose-6-phosphate dehydrogenase inhibitor. These results demonstrate differential sensitivity of standard cytotoxicity assessments on the PPP, thus (1) decoupling "mitochondrial activity" as an interpretation of cellular formazan and Alamar Blue metabolism, and (2) demonstrating the implicit requirement for investigators to sufficiently verify interaction of these methods in routine cytotoxicity and proliferation characterization. The nuances of method-specific extramitochondrial metabolism must be scrutinized to properly qualify specific endpoints employed, particularly under the circumstances of metabolic reprogramming.

Oxidative stress, free radicals and antioxidants: potential crosstalk in the pathophysiology of human diseases

Introduction: Free radicals are reactive oxygen species that constantly circulate through the body and occur as a side effect of many reactions that take place in the human body. Under normal conditions, they are removed from the body by antioxidant processes. If these natural mechanisms are disrupted, radicals accumulate in excess and contribute to the development of many diseases. Methodology: Relevant recent information on oxidative stress, free radicals, reactive oxidative species, and natural and synthetic antioxidants was collected by researching electronic databases such as PubMed / Medline, Web of Science, and Science Direct. Results: According to the analysed studies, this comprehensive review provided a recent update on oxidative stress, free radicals and antioxidants and their impact on the pathophysiology of human diseases. Discussion: To counteract the condition of oxidative stress, synthetic antioxidants must be provided from external sources to supplement the antioxidant defense mechanism internally. Because of their therapeutic potential and natural origin, medicinal plants have been reported as the main source of natural antioxidants phytocompounds. Some non-enzymatic phytocompounds such as flavonoids, polyphenols, and glutathione, along with some vitamins have been reported to possess strong antioxidant activities in vivo and in vitro studies. Thus, the present review describes, in brief, the overview of oxidative stress-directed cellular damage and the unction of dietary antioxidants in the management of different diseases. The therapeutic limitations in correlating the antioxidant activity of foods to human health were also discussed.

Multitarget-Directed Gallium(III) Tris(acyl-pyrazolonate) Complexes Induce Ferroptosis in Cancer Cells via Dysregulation of Cell Redox Homeostasis and Inhibition of the Mevalonate Pathway

A series of Ga(Q_n)₃ coordination compounds have been synthesized, where HQ_n is 1-phenyl-3-methyl-4-RC(═O)-pyrazolo-5-one. The complexes have been characterized through analytical data, NMR and IR spectroscopy, ESI mass spectrometry, elemental analysis, X-ray crystallography, and density functional theory (DFT) studies. Cytotoxic activity against a panel of human cancer cell lines was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, with interesting results in terms of both cell line selectivity and toxicity values compared with cisplatin. The mechanism of action was explored by spectrophotometric, fluorometric, chromatographic, immunometric, and cytofluorimetric assays, SPR biosensor binding studies, and cell-based experiments. Cell treatment with gallium(III) complexes promoted several cell death triggering signals (accumulation of p27, PCNA, PARP fragments, activation of the caspase cascade, and inhibition of the mevalonate pathway) and induced changes in cell redox homeostasis (decreased levels of GSH/GPX4 and NADP(H), increased reactive oxygen species (ROS) and 4-hydroxynonenal (HNE), mitochondrial damage, and increased activity of CPR and CcO), identifying ferroptosis as the mechanism responsible for cancer cell death.

Melatonin Activation by Cytochrome P450 Isozymes: How Does CYP1A2 Compare to CYP1A1?

Cytochrome P450 enzymes are versatile enzymes found in most biosystems that catalyze mono-oxygenation reactions as a means of biosynthesis and biodegradation steps. In the liver, they metabolize xenobiotics, but there are a range of isozymes with differences in three-dimensional structure and protein chain. Consequently, the various P450 isozymes react with substrates differently and give varying product distributions. To understand how melatonin is activated by the P450s in the liver, we did a thorough molecular dynamics and quantum mechanics study on cytochrome P450 1A2 activation of melatonin forming 6-hydroxymelatonin and N-acetylserotonin products through aromatic hydroxylation and O-demethylation pathways, respectively. We started from crystal structure coordinates and docked substrate into the model, and obtained ten strong binding conformations with the substrate in the active site. Subsequently, for each of the ten substrate orientations, long (up to 1 μs) molecular dynamics simulations were run. We then analyzed the orientations of the substrate with respect to the heme for all snapshots. Interestingly, the shortest distance does not correspond to the group that is expected to be activated. However, the substrate positioning gives insight into the protein residues it interacts with. Thereafter, quantum chemical cluster models were created and the substrate hydroxylation pathways calculated with density functional theory. These relative barrier heights confirm the experimental product distributions and highlight why certain products are obtained. We make a detailed comparison with previous results on CYP1A1 and identify their reactivity differences with melatonin.

POR overexpression induces tamoxifen-resistance in breast cancer through the STAT1/c-Myc pathway

Breast cancer is the most common cancer in women worldwide. Although tamoxifen (TAM), a selective estrogen receptor (ER) modulator, is widely used to treat ER-positive breast cancers, resistance to TAM remains a major clinical problem. NADPH-dependent cytochrome P450 reductase (POR) is known to participate in drug metabolism and steroid metabolism. Recent studies showed that high POR expression was correlated with poor outcomes in triple-negative breast cancer (TNBC), and POR might be a prognostic biomarker in TNBC. However, the role of POR in TAM resistance is still elusive. In this study, we found that high POR expression was associated with poor prognosis of ER-positive and TAM-treated breast cancer patients. In addition, COX analysis showed that POR expression was an independent prognostic biomarker for ER-positive as well as TAM-treated breast cancer patients. Furthermore, our results suggested that POR overexpression promoted TAM resistance by activating the STAT1/c-Myc pathway in ER-positive breast cancer cells. Immunohistochemical analysis showed that high POR/STAT1 expression was correlated with poor prognosis in TAM-treated breast cancer patients. Notably, combined treatment with TAM and a specific STAT1 inhibitor Fludarabine was more effective for inhibiting TAM-resistant breast cancer cells. Altogether, our findings suggested that POR overexpression induced TAM resistance through STAT1/c-Myc pathway and might serve as an independent prognostic biomarker in TAM-treated breast cancer patients. Combining TAM and STAT1 inhibitors might be an effective strategy for treating POR-induced TAM-resistant breast cancer.

Drug Metabolism: A Half-Century Plus of Progress, Continued Needs, and New Opportunities

The systematic study of drug metabolism began in the 19th Century, but most of what we know now has been learned in the last 50 years. Drug metabolism continues to play a critical role in pharmaceutical development and clinical practice, as well as contributing to toxicology, chemical carcinogenesis, endocrinology, and drug abuse. The importance of the field will continue, but its nature will continue to develop with changes in analytical chemistry, structural biology, and artificial intelligence. Challenges and opportunities include toxicology, defining roles of genetic variations, and application to clinical issues. Although the focus of this Minireview is cytochrome P450, the same principles apply to other enzymes and transporters involved in drug metabolism. SIGNIFICANCE STATEMENT: Progress in the field of drug metabolism over the past 50 years has helped make the pharmaceutical enterprise what it is today. Drug metabolism will continue to be important. Challenges and opportunities for the future are discussed.

Metabolomic Signatures of Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is associated with many variations in metabolism, but the ex-act correlates of these metabolic disturbances with behavior and development and their links to other core metabolic disruptions are understudied. In this study, large-scale targeted LC-MS/MS metabolomic analysis was conducted on fasting morning plasma samples from 57 children with ASD (29 with neurodevelopmental regression, NDR) and 37 healthy controls of similar age and gender. Linear model determined the metabolic signatures of ASD with and without NDR, measures of behavior and neurodevelopment, as well as markers of oxidative stress, inflammation, redox, methylation, and mitochondrial metabolism. MetaboAnalyst ver 5.0 (the Wishart Research Group at the University of Alberta, Edmonton, Canada) identified the pathways associated with altered metabolic signatures. Differences in histidine and glutathione metabolism as well as aromatic amino acid (AAA) biosynthesis differentiated ASD from controls. NDR was associated with disruption in nicotinamide and energy metabolism. Sleep and neurodevelopment were associated with energy metabolism while neurodevelopment was also associated with purine metabolism and aminoacyl-tRNA biosynthesis. While behavior was as-sociated with some of the same pathways as neurodevelopment, it was also associated with alternations in neurotransmitter metabolism. Alterations in methylation was associated with aminoacyl-tRNA biosynthesis and branched chain amino acid (BCAA) and nicotinamide metabolism. Alterations in glutathione metabolism was associated with changes in glycine, serine and threonine, BCAA and AAA metabolism. Markers of oxidative stress and inflammation were as-sociated with energy metabolism and aminoacyl-tRNA biosynthesis. Alterations in mitochondrial metabolism was associated with alterations in energy metabolism and L-glutamine. Using behavioral and biochemical markers, this study finds convergent disturbances in specific metabolic pathways with ASD, particularly changes in energy, nicotinamide, neurotransmitters, and BCAA, as well as aminoacyl-tRNA biosynthesis.

Loss of Protein Stability and Function Caused by P228L Variation in NADPH-Cytochrome P450 Reductase Linked to Lower Testosterone Levels

Cytochrome P450 oxidoreductase (POR) is the redox partner of steroid and drug-metabolising cytochromes P450 located in the endoplasmic reticulum. Mutations in POR cause a broad range of metabolic disorders. The POR variant rs17853284 (P228L), identified by genome sequencing, has been linked to lower testosterone levels and reduced P450 activities. We expressed the POR wild type and the P228L variant in bacteria, purified the proteins, and performed protein stability and catalytic functional studies. Variant P228L affected the stability of the protein as evidenced by lower unfolding temperatures and higher sensitivity to urea denaturation. A significant decline in the rate of electron transfer to cytochrome c and thiazolyl blue tetrazolium (MTT) was observed with POR P228L, while activities of CYP3A4 were reduced by 25% and activities of CYP3A5 and CYP2C9 were reduced by more than 40% compared with WT POR. The 17,20 lyase activity of CYP17A1, responsible for the production of the main androgen precursor dehydroepiandrosterone, was reduced to 27% of WT in the presence of the P228L variant of POR. Based on in silico and in vitro studies, we predict that the change of proline to leucine may change the rigidity of the protein, causing conformational changes in POR, leading to altered electron transfer to redox partners. A single amino acid change can affect protein stability and cause a severe reduction in POR activity. Molecular characterisation of individual POR mutations is crucial for a better understanding of the impact on different redox partners of POR.

Characterization of POR haplotype distribution in African populations and comparison with other global populations

Background & aim: POR is an enzyme that mediates electron transfer to enable the drug-metabolizing activity of CYP450 proteins. However, POR has been understudied in pharmacogenomics despite this vital role. This study aimed to characterize the genetic variation in POR across African populations and to compare the star allele (haplotype) distribution with that in other global populations. Materials & methods: POR star alleles were called from whole-genome sequencing data using the StellarPGx pipeline. Results: In addition to the common POR*1 and *28 (defined by rs1057868), five novel rare haplotypes were computationally inferred. No significant frequency differences were observed among the majority of African populations. However, POR*28 was observed at a higher frequency in individuals of non-African ancestry. Conclusion: This study highlights the distribution of POR alleles in Africa and across global populations with a view toward informing future precision medicine implementation.

Humanized liver TK-NOG mice with functional deletion of hepatic murine cytochrome P450s as a model for studying human drug metabolism

Chimeric TK-NOG mice with a humanized liver (normal Hu-liver) are a unique animal model for predicting drug metabolism in humans. However, residual mouse hepatocytes occasionally prevent the precise evaluation of human drug metabolism. Herein, we developed a novel humanized liver TK-NOG mouse with a conditional knockout of liver-specific cytochrome P450 oxidoreductase (POR cKO Hu-liver). Immunohistochemical analysis revealed only a few POR-expressing cells around the portal vein in POR cKO mouse livers. NADPH-cytochrome c reductase and cytochrome P450 (P450)-mediated drug oxidation activity in liver microsomes from POR cKO mice was negligible. After the intravenous administration of S-warfarin, high circulating and urinary levels of S-7-hydroxywarfarin (a major human metabolite) were observed in POR cKO Hu-liver mice. Notably, the circulating and urinary levels of S-4′-hydroxywarfarin (a major warfarin metabolite in mice) were much lower in POR cKO Hu-liver mice than in normal Hu-liver mice. POR cKO Hu-liver mice with minimal interference from mouse hepatic P450 oxidation activity are a valuable model for predicting human drug metabolism.

Cytochrome P450 oxidoreductase variant A503V contributes to the increased CYP3A5 activity with tacrolimus in vitro

BACKGROUND

Tacrolimus is a calcineurin inhibitor with a strong efficacy in prevention of graft rejection after transplantation. It is well known that cytochrome P450 3A5 (CYP3A5) has a high metabolic capacity for tacrolimus, and mutations in human cytochrome P450 oxidoreductase (POR) cause altered CYP3A5 activity. Recently, clinical studies have revealed that POR*28 contributes enhanced tacrolimus clearance in CYP3A5 expressers. A503V is an amino acid sequence variant encoded by POR*28. In this study, we first evaluated the impact of A503V on CYP3A5 activity with tacrolimus as the substrate in vitro.

RESEARCH DESIGN & METHODS

Wild-type (WT) and A503V POR, with WT CYP3A5 were expressed in recombinant HepG2 cells and reconstituted proteins. Michaelis constant (K_m) and maximum velocity (V_max) of CYP3A5 with tacrolimus as substrates were determined, and catalytic efficiency is expressed as V_max/K_m.

RESULTS

WT and A503V POR both down-regulated the CYP3A5 mRNA expression, and WT POR rather than A503V down-regulated the protein expression of CYP3A5 in recombinant HepG2 cells. Compared with WT POR, A503V increased metabolism of tacrolimus by CYP3A5 in both cellular and protein level.

CONCLUSION

A503V can affect CYP3A5-catalyzed tacrolimus metabolism in vitro, which suggests that A503V has the potential to serve as a biomarker for tacrolimus treatment in transplantation recipients.

A large-scale polygenic risk score analysis identified candidate proteins associated with anxiety, depression and neuroticism

Psychiatric disorders and neuroticism are closely associated with central nervous system, whose proper functioning depends on efficient protein renewal. This study aims to systematically analyze the association between anxiety / depression / neuroticism and each of the 439 proteins. 47,536 pQTLs of 439 proteins in brain, plasma and cerebrospinal fluid (CSF) were collected from recent genome-wide association study. Polygenic risk scores (PRS) of the 439 proteins were then calculated using the UK Biobank cohort, including 120,729 subjects of neuroticism, 255,354 subjects of anxiety and 316,513 subjects of depression. Pearson correlation analyses were performed to evaluate the correlation between each protein and each of the mental traits by using calculated PRSs as the instrumental variables of protein. In general population, six correlations were identified in plasma and CSF such as plasma protease C1 inhibitor (C1-INH) with neuroticism score (r = - 0.011, P = 2.56 × 10^- 9) in plasma, C1-INH with neuroticism score (r = -0.010, P = 3.09 × 10^- 8) in CSF, and ERBB1 with self-reported depression (r = - 0.012, P = 4.65 × 10^- 5) in CSF. C1-INH and ERBB1 may induce neuroticism and depression by affecting brain function and synaptic development. Gender subgroup analyses found that BST1 was correlated with neuroticism score in male CSF (r = - 0.011, P = 1.80 × 10^- 5), while CNTN2 was correlated with depression score in female brain (r = - 0.013, P = 6.43 × 10^- 4). BST1 and CNTN2 may be involved in nervous system metabolism and brain health. Six common candidate proteins were associated with all three traits (P < 0.05) and were confirmed in relevant proteomic studies, such as C1-INH in plasma, CNTN2 and MSP in the brain. Our results provide novel clues for revealing the roles of proteins in the development of anxiety, depression and neuroticism.

Central Nervous System Metabolism in Autism, Epilepsy and Developmental Delays: A Cerebrospinal Fluid Analysis

Neurodevelopmental disorders are associated with metabolic pathway imbalances; however, most metabolic measurements are made peripherally, leaving central metabolic disturbances under-investigated. Cerebrospinal fluid obtained intraoperatively from children with autism spectrum disorder (ASD, n = 34), developmental delays (DD, n = 20), and those without known DD/ASD (n = 34) was analyzed using large-scale targeted mass spectrometry. Eighteen also had epilepsy (EPI). Metabolites significantly related to ASD, DD and EPI were identified by linear models and entered into metabolite-metabolite network pathway analysis. Common disrupted pathways were analyzed for each group of interest. Central metabolites most involved in metabolic pathways were L-cysteine, adenine, and dodecanoic acid for ASD; nicotinamide adenine dinucleotide phosphate, L-aspartic acid, and glycine for EPI; and adenosine triphosphate, L-glutamine, ornithine, L-arginine, L-lysine, citrulline, and L-homoserine for DD. Amino acid and energy metabolism pathways were most disrupted in all disorders, but the source of the disruption was different for each disorder. Disruption in vitamin and one-carbon metabolism was associated with DD and EPI, lipid pathway disruption was associated with EPI and redox metabolism disruption was related to ASD. Two microbiome metabolites were also detected in the CSF: shikimic and cis-cis-muconic acid. Overall, this study provides increased insight into unique metabolic disruptions in distinct but overlapping neurodevelopmental disorders.

Role of Lung P450 Oxidoreductase in Paraquat-Induced Collagen Deposition in the Lung

Paraquat (PQ) is an agrochemical known to cause pulmonary fibrosis. PQ-induced collagen deposition in the lung is thought to require enzymatic formation of PQ radicals, but the specific enzymes responsible for this bioactivation event in vivo have not been identified. We tested the hypothesis that lung P450 oxidoreductase (POR or CPR) is important in PQ-induced lung fibrosis in mice. A lung-Cpr-null mouse model was utilized, which undergoes doxycycline-induced, Cre recombinase-mediated deletion of the Por gene specifically in airway Club cells and alveolar type 2 cells in the lung. The lungs of lung-Cpr-null mice and their wild-type littermates were collected on day 15 after a single intraperitoneal injection of saline (control) or PQ (20 mg/kg). Lung tissue sections were stained with picrosirius red for detection of collagen fibrils. Fibrotic lung areas were found to be significantly smaller (1.6-fold for males and 1.4-fold for females) in PQ-treated lung-Cpr-null mice than in sex- and treatment-matched wild-type mice. The levels of collagen in lung tissue homogenate were also lower (1.4-2.3-fold; p < 0.05) in PQ-treated lung-Cpr-null mice compared to PQ-treated wild-type mice. In contrast, plasma PQ toxicokinetic profiles were not different between sex-matched wild-type and lung-Cpr-null mice. Taken together, these results indicate that lung POR plays an important role in PQ-induced pulmonary fibrosis.

Cytochrome P450s in algae: Bioactive natural product biosynthesis and light-driven bioproduction

Algae are a large group of photosynthetic organisms responsible for approximately half of the earth's total photosynthesis. In addition to their fundamental ecological roles as oxygen producers and as the food base for almost all aquatic life, algae are also a rich source of bioactive natural products, including several clinical drugs. Cytochrome P450 enzymes (P450s) are a superfamily of biocatalysts that are extensively involved in natural product biosynthesis by mediating various types of reactions. In the post-genome era, a growing number of P450 genes have been discovered from algae, indicating their important roles in algal life-cycle. However, the functional studies of algal P450s remain limited. Benefitting from the recent technical advances in algae cultivation and genetic manipulation, the researches on P450s in algal natural product biosynthesis have been approaching to a new stage. Moreover, some photoautotrophic algae have been developed into “photo-bioreactors” for heterologous P450s to produce high-value added pharmaceuticals and chemicals in a carbon-neutral or carbon-negative manner. Here, we comprehensively review these advances of P450 studies in algae from 2000 to 2021.

Ferroptosis: The Silver Lining of Cancer Therapy

Regulatory cell death has been a major focus area of cancer therapy research to improve conventional clinical cancer treatment (e.g. chemotherapy and radiotherapy). Ferroptosis, a novel form of regulated cell death mediated by iron-dependent lipid peroxidation, has been receiving increasing attention since its discovery in 2012. Owing to the highly iron-dependent physiological properties of cancer cells, targeting ferroptosis is a promising approach in cancer therapy. In this review, we summarised the characteristics of ferroptotic cells, associated mechanisms of ferroptosis occurrence and regulation and application of the ferroptotic pathway in cancer therapy, including the use of ferroptosis in combination with other therapeutic modalities. In addition, we presented the challenges of using ferroptosis in cancer therapy and future perspectives that may provide a basis for further research.

Effects of Diminished NADPH:cytochrome P450 Reductase in Human Hepatocytes on Lipid and Bile Acid Homeostasis

NADPH:cytochrome P450 oxidoreductase (POR) is the obligate electron donor for microsomal cytochrome P450 (CYP) enzymes involved in the biosynthesis of endogenous substances like bile acids and other steroids as well as in the oxidative metabolism of xenobiotics. P450 oxidoreductase also supports other redox enzymes in fatty acid and cholesterol pathways. Recently, we have established CRISPR/Cas9-mediated POR knockdown in a human hepatic cell model, HepaRG, and demonstrated the differential effects of limited POR expression on CYP activity. The aim of the present work was to systematically investigate the impact of POR knockdown with a focus on the expression of ADME (absorption, distribution, metabolism, and excretion) genes and related regulators. Functional consequences have been assessed using quantitative mass spectrometry for targeted metabolomics covering bile acids, and cholesterol and its precursors, and for untargeted proteomics. In addition to the previously described alteration of RNA expression of CYP genes, we showed significant downregulation of transcriptional regulators of drug metabolism and transport, including NR1I3 (CAR), NR1I2 (PXR), NR1H4 (FXR), and NR1H3 (LXRα) in cells with POR gene disruption. Furthermore, POR knockdown resulted in deregulated bile acid and cholesterol biosynthesis demonstrated by low levels of cholic acid derivates and increased concentrations of chenodeoxycholic acid derivates, respectively. Systemic effects of POR knockdown on global protein expression were indicated by downregulation of several metabolic pathways including lipid metabolism and biological oxidation reactions. The deduced protein network map corroborates CYP enzymes as direct interaction partners, whereas changes in lipid metabolism and homeostasis are the result of indirect effects. In summary, our results emphasize a widespread role of POR in various metabolic pathways and provide the first human data on the effects of diminished POR expression on drug and endogenous metabolism in a genomeedited HepaRG cell model.

Molecular Cloning and Identification of NADPH Cytochrome P450 Reductase from Panax ginseng

Ginseng (Panax ginseng C.A. Mey.) is a precious Chinese traditional medicine, for which ginsenosides are the most important medicinal ingredients. Cytochrome P450 enzymes (CYP450) and their primary redox molecular companion NADPH cytochrome P450 reductase (CPR) play a key role in ginsenoside biosynthesis pathway. However, systematic studies of CPR genes in ginseng have not been reported. Numerous studies on ginsenoside synthesis biology still use Arabidopsis CPR (AtCPR1) as a reductase. In this study, we isolated two CPR genes (PgCPR1, PgCPR2) from ginseng adventitious roots. Phylogenetic tree analysis showed that both PgCPR1 and PgCPR2 are grouped in classⅡ of dicotyledonous CPR. Enzyme experiments showed that recombinant proteins PgCPR1, PgCPR2 and AtCPR1 can reduce cytochrome c and ferricyanide with NADPH as the electron donor, and PgCPR1 had the highest enzymatic activities. Quantitative real-time PCR analysis showed that PgCPR1 and PgCPR2 transcripts were detected in all examined tissues of Panax ginseng and both showed higher expression in stem and main root. Expression levels of the PgCPR1 and PgCPR2s were both induced after a methyl jasmonate (MeJA) treatment and its pattern matched with ginsenoside accumulation. The present investigation suggested PgCPR1 and PgCPR2 are associated with the biosynthesis of ginsenoside. This report will assist in future CPR family studies and ultimately improving ginsenoside production through transgenic engineering and synthetic biology.

Inhibition of phase-1 biotransformation and cytostatic effects of diphenyleneiodonium on hepatoblastoma cell line HepG2 and a CYP3A4-overexpressing HepG2 cell clone

Cell-based in vitro liver models are an important tool in the development and evaluation of new drugs in pharmacological and toxicological drug assessment. Hepatic microsomal enzyme complexes, consisting of cytochrome P450 oxidoreductase (CPR) and cytochrome P450 monooxygenases (CYPs), play a decisive role in catalysing phase-1 biotransformation of pharmaceuticals and xenobiotics. For a comprehensive understanding of the phase-1 biotransformation of drugs, the availability of well-characterized substances for the targeted modulation of in vitro liver models is essential. In this study, we investigated diphenyleneiodonium (DPI) for its ability to inhibit phase-1 enzyme activity and further its toxicological profile in an in vitro HepG2 cell model with and without recombinant expression of the most important drug metabolization enzyme CYP3A4.

Aim of the study was to identify effective DPI concentrations for CPR/CYP activity modulation and potentially associated dose and time dependent hepatotoxic effects. The cells were treated with DPI doses up to 5,000nM (versus vehicle control) for a maximum of 48 h and subsequently examined for CYP3A4 activity as well as various toxicological relevant parameters such as cell morphology, integrity and viability, intracellular ATP level, and proliferation. Concluding, the experiments revealed a time- and concentration-dependent DPI mediated partial and complete inhibition of CYP3A4 activity in CYP3A4 overexpressing HepG2-cells (HepG2-CYP3A4). Other cell functions, including ATP synthesis and consequently the proliferation were negatively affected in both in vitro cell models. Since neither cell integrity nor cell viability were reduced, the effect of DPI in HepG2 can be assessed as cytostatic rather than cytotoxic.

New Target in an Old Enemy: Herbicide (R)-Dichlorprop Induces Ferroptosis-like Death in Plants

Iron is an essential microelement in plants that is involved in several growth processes. The use of herbicides may cause the abnormal aggregation of iron in leaves, but the regulatory mechanisms underlying this phenomenon remain unclear. Here, we show that chiral herbicide (R)-dichlorprop ((R)-DCPP) triggers ferroptosis-like death in Arabidopsis thaliana. (R)-DCPP led to reactive oxygen species (ROS) accumulation and iron aggregation, and these processes were iron dependent. Under (R)-DCPP treatment, ROS, lipid hydrogen peroxides, and malondialdehyde were significantly accumulated. In addition, (R)-DCPP induced the depletion of glutathione, ascorbic acid, and glutathione peroxidase as well as the accumulation of toxic lipid peroxides. Thus, oxidation imbalance led to cell death, and this mode of action could be inhibited by the ferroptosis inhibitor ferrostatin-1 or ciclopirox olamine. NADPH oxidases were found to be involved in herbicide-induced ROS accumulation, and lipoxygenase and NADPH cytochrome P450 oxidase were shown to positively regulate (R)-DCPP-induced lipid peroxidation. Overall, these results indicate that the iron- and ROS-dependent signaling cascades were involved in the (R)-DCPP-induced phytotoxicity pathway, which disrupted the structure of plant cell membranes and triggered ferroptosis. Generally, this study provides new insight into the mechanisms of pesticide phytotoxicity and suggests new therapeutic directions to protect nontarget plants.

The Controversial Role of Glucose-6-Phosphate Dehydrogenase Deficiency on Cardiovascular Disease: A Narrative Review

Cardiovascular disorders (CVD) are highly prevalent and the leading cause of death worldwide. Atherosclerosis is responsible for most cases of CVD. The plaque formation and subsequent thrombosis in atherosclerosis constitute an ongoing process that is influenced by numerous risk factors such as hypertension, diabetes, dyslipidemia, obesity, smoking, inflammation, and sedentary lifestyle. Among the various risk and protective factors, the role of glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common inborn enzyme disorder across populations, is still debated. For decades, it has been considered a protective factor against the development of CVD. However, in the recent years, growing scientific evidence has suggested that this inherited condition may act as a CVD risk factor. The role of G6PD deficiency in the atherogenic process has been investigated using in vitro or ex vivo cellular models, animal models, and epidemiological studies in human cohorts of variable size and across different ethnic groups, with conflicting results. In this review, the impact of G6PD deficiency on CVD was critically reconsidered, taking into account the most recent acquisitions on molecular and biochemical mechanisms, namely, antioxidative mechanisms, glutathione recycling, and nitric oxide production, as well as their mutual interactions, which may be impaired by the enzyme defect in the context of the pentose phosphate pathway. Overall, current evidence supports the notion that G6PD downregulation may favor the onset and evolution of atheroma in subjects at risk of CVD. Given the relatively high frequency of this enzyme deficiency in several regions of the world, this finding might be of practical importance to tailor surveillance guidelines and facilitate risk stratification.

Recent advances in the ontogeny of drug disposition

Developmental changes that occur throughout childhood have long been known to impact drug disposition. However, pharmacokinetic studies in the paediatric population have historically been limited due to ethical concerns arising from incorporating children into clinical trials. As such, much of the early work in the field of developmental pharmacology was reliant on difficult-to-interpret in vitro and in vivo animal studies. Over the last 2 decades, our understanding of the mechanistic processes underlying age-related changes in drug disposition has advanced considerably. Progress has largely been driven by technological advances in mass spectrometry-based methods for quantifying proteins implicated in drug disposition, and in silico tools that leverage these data to predict age-related changes in pharmacokinetics. This review summarizes our current understanding of the impact of childhood development on drug disposition, particularly focusing on research of the past 20 years, but also highlighting select examples of earlier foundational research. Equally important to the studies reviewed herein are the areas that we cannot currently describe due to the lack of research evidence; these gaps provide a map of drug disposition pathways for which developmental trends still need to be characterized.

Lipid Metabolism and Ferroptosis

Simple Summary

Ferroptosis is a type of cell death, which is morphologically and mechanistically distinct from other type of cell death pathways such as apoptosis and necroptosis. Lipid peroxidation is a hallmark of ferroptosis and directly destroys cellular membranes, thereby causing ferroptosis. Since lipid peroxidation, which induces ferroptosis, occurs in polyunsaturated fatty acid on specific phospholipids, various lipid metabolic pathways are involved in lipid peroxidation and ferroptosis. Besides, various metabolic and signaling pathways directly and indirectly regulate lipid peroxidation and ferroptosis. Since ferroptosis is associated with a variety of human diseases such as cancer, myocardial infarction, atherosclerosis, kidney diseases, liver diseases, and neuronal diseases, a better understanding of the regulatory mechanisms of ferroptosis can provide insights and treatment strategies for related diseases.

Abstract

Ferroptosis is a type of iron-dependent regulated necrosis induced by lipid peroxidation that occurs in cellular membranes. Among the various lipids, polyunsaturated fatty acids (PUFAs) associated with several phospholipids, such as phosphatidylethanolamine (PE) and phosphatidylcholine (PC), are responsible for ferroptosis-inducing lipid peroxidation. Since the de novo synthesis of PUFAs is strongly restricted in mammals, cells take up essential fatty acids from the blood and lymph to produce a variety of PUFAs via PUFA biosynthesis pathways. Free PUFAs can be incorporated into the cellular membrane by several enzymes, such as ACLS4 and LPCAT3, and undergo lipid peroxidation through enzymatic and non-enzymatic mechanisms. These pathways are tightly regulated by various metabolic and signaling pathways. In this review, we summarize our current knowledge of how various lipid metabolic pathways are associated with lipid peroxidation and ferroptosis. Our review will provide insight into treatment strategies for ferroptosis-related diseases.

Vascular biotransformation of organic nitrates is independent of cytochrome P450 monooxygenases

BACKGROUND AND PURPOSE

Organic nitrates such as nitroglycerin (NTG) or pentaerythritol tetranitrate (PETN) have been used for over a century in the treatment of angina or ischaemic heart disease. These compounds are prodrugs which release their nitrovasodilators upon enzymic bioactivation by aldehyde dehydrogenase (ALDH2) or cytochromes P450 (CYP). Whereas ALDH2 is known to directly activate organic nitrates in vessels, the contribution of vascular CYPs is unknown and was studied here.

EXPERIMENTAL APPROACH

As all CYPs depend on cytochrome P450 reductase (POR) as electron donor, we generated a smooth muscle cell-specific, inducible knockout mouse of POR (smcPOR^-/- ) to investigate the contribution of POR/CYP to vascular biotransformation of organic nitrates.

KEY RESULTS

Microsomes containing recombinant CYPs expressed in human vascular tissues released nitrite from NTG and PETN with CYP2C9 and CYP2C8 being most efficient. SFK525, a CYP suicide inhibitor, blocked this effect. smcPOR^-/- mice exhibited no obvious cardiovascular phenotype (normal cardiac weight and endothelium-dependent relaxation) and plasma and vascular nitrite production was similar to control (CTL) animals. NTG- and PETN-induced relaxation of isolated endothelium-intact or endothelium-denuded vessels were identical between CTL and smcPOR^-/- . Likewise, nitrite release from organic nitrates in aortic rings was not affected by deletion of POR in smooth muscle cells (SMCs). In contrast, inhibition of ALDH2 by benomyl (10 μM) inhibited NTG-induced nitrite production and relaxation. Deletion of POR did not modulate this response.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that metabolism by vascular CYPs does not contribute to the pharmacological function of organic nitrates.

Ferroptosis-Related Flavoproteins: Their Function and Stability

Ferroptosis has been described recently as an iron-dependent cell death driven by peroxidation of membrane lipids. It is involved in the pathogenesis of a number of diverse diseases. From the other side, the induction of ferroptosis can be used to kill tumor cells as a novel therapeutic approach. Because of the broad clinical relevance, a comprehensive understanding of the ferroptosis-controlling protein network is necessary. Noteworthy, several proteins from this network are flavoenzymes. This review is an attempt to present the ferroptosis-related flavoproteins in light of their involvement in anti-ferroptotic and pro-ferroptotic roles. When available, the data on the structural stability of mutants and cofactor-free apoenzymes are discussed. The stability of the flavoproteins could be an important component of the cellular death processes.

Membrane Damage during Ferroptosis Is Caused by Oxidation of Phospholipids Catalyzed by the Oxidoreductases POR and CYB5R1

Ferroptosis is a form of necrotic cell death caused by iron-dependent peroxidation of polyunsaturated phospholipids on cell membranes and is actively suppressed by the cellular antioxidant systems. We report here that oxidoreductases, including NADPH-cytochrome P450 reductase (POR) and NADH-cytochrome b5 reductase (CYB5R1), transfer electrons from NAD(P)H to oxygen to generate hydrogen peroxide, which subsequently reacts with iron to generate reactive hydroxyl radicals for the peroxidation of the polyunsaturated fatty acid (PUFA) chains of membrane phospholipids, thereby disrupting membrane integrity during ferroptosis. Genetic knockout of POR and CYB5R1 decreases cellular hydrogen peroxide generation, preventing lipid peroxidation and ferroptosis. Moreover, POR knockdown in mouse liver prevents ConA-induced liver damage. Ferroptosis, therefore, is a result of incidental electron transfer carried out by POR/CYB5R1 oxidoreductase and thus needs to be constitutively countered by the antioxidant systems.

Proximal Tubular Vacuolization and Hypersensitivity to Drug-Induced Nephrotoxicity in Male Mice With Decreased Expression of the NADPH-Cytochrome P450 Reductase

The effect of variations in the expression of cytochrome P450 reductase (CPR or POR) is determined in mice with decreased POR expression to identify potential vulnerabilities in people with low POR expression. There is an age-dependent appearance of increasing vacuolization in the proximal tubules of the renal cortex in 4- to 9-month-old male (but not female) Cpr-low (CL) mice. These mice have low POR expression in all cells of the body and upregulation of lysosome-associated membrane protein 1 expression in the renal cortex. Vacuolization is also seen in extrahepatic CL and extrarenal CL male mice, but not in mice with tissue-specific Por deletion in liver, intestinal epithelium, or kidney. The occurrence of vacuolization is accompanied by increases in serum blood-urea-nitrogen levels. Male CL mice are hypersensitive to cisplatin- and gentamicin-induced renal toxicity at 3 months of age, before proximal tubular (PT) vacuoles are detectable. At doses that do not cause renal toxicity in wild-type mice, both drugs cause substantial increases in serum blood-urea-nitrogen levels and PT vacuolization in male but not female CL mice. The hypersensitivity to drug-induced renal toxicity is accompanied by increases in circulating drug levels. These novel findings demonstrate deficiency of renal function in mice with globally reduced POR expression and suggest that low POR expression may be a risk factor for drug-induced nephrotoxicity in humans.

Molecular Docking of 4-ethoxychalcones on Oxidoreductase/Pirin Inhibitors and Cytotoxic Evaluation on Breast/Skin Cancer Cell Lines

Background:

The role of α, β unsaturated propenone derivatives, has attracted the chemists for its biological importance. An attempt is made to reveal the interaction between breast and skin cancer cell lines with the help of molecular docking studies.

Objective:

The study aimed to synthesize and characterize 4-ethoxychalcones for testing breast and skin cancer targets.

Methods:

A series of chalcone analogues starting from 4-ethoxyacetophenone and substituted aromatic aldehydes were synthesized, well-characterized and evaluated for their in vitro anticancer activities against human breast cancer (MDA-MB-231) and human metastatic melanoma (A-375) cell lines by MTT assay. Docking simulation was performed to study the drug-receptor interaction of chalcone scaffold on the active site of target inhibitor bound to cytochrome P450 family oxidoreductase for breast cancer and Pirin inhibiting target for skin cancer, respectively.

Results and Discussion:

After performing cytotoxic evaluation, it was observed that compounds having a substitution at the para position showed better results compared to ortho and meta positions for both the cell lines. Molecular docking studies revealed different types of interactions with selected oxidoreductase and Pirin inhibiting targets. Ligand-protein interactions and morphological changes are monitored by molecular dynamics.

Conclusion:

The presence of electron-withdrawing and donating groups on ring B marginally affected IC50 and docking scores. The stability of the binding mode of ligands having high inhibitory efficiency for compounds 8 and 10 predicted by docking studies was confirmed by molecular dynamics simulation. The pharmacokinetic parameters were found to be within the acceptable range. Further molecular dynamics study would provide the necessary information.

Oxidative Damage and Antioxidant Defense in Ferroptosis

Many new types of regulated cell death have been recently implicated in human health and disease. These regulated cell deaths have different morphological, genetic, biochemical, and functional hallmarks. Ferroptosis was originally described as a carcinogenic RAS-dependent non-apoptotic cell death, and is now defined as a type of regulated necrosis characterized by iron accumulation, lipid peroxidation, and the release of damage-associated molecular patterns (DAMPs). Multiple oxidative and antioxidant systems, acting together autophagy machinery, shape the process of lipid peroxidation during ferroptosis. In particular, the production of reactive oxygen species (ROS) that depends on the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) and the mitochondrial respiratory chain promotes lipid peroxidation by lipoxygenase (ALOX) or cytochrome P450 reductase (POR). In contrast, the glutathione (GSH), coenzyme Q10 (CoQ10), and tetrahydrobiopterin (BH4) system limits oxidative damage during ferroptosis. These antioxidant processes are further transcriptionally regulated by nuclear factor, erythroid 2-like 2 (NFE2L2/NRF2), whereas membrane repair during ferroptotic damage requires the activation of endosomal sorting complexes required for transport (ESCRT)-III. A further understanding of the process and function of ferroptosis may provide precise treatment strategies for disease.

Stereoselective Bupropion Hydroxylation by Cytochrome P450 CYP2B6 and Cytochrome P450 Oxidoreductase Genetic Variants

Bioactivation of the antidepressant and smoking cessation drug bupropion is catalyzed predominantly by CYP2B6. The metabolite hydroxybupropion derived from t-butylhydroxylation is considered to contribute to the antidepressant and smoking-cessation effects of the parent drug. Bupropion hydroxylation is the canonical in vitro and in vivo probe for CYP2B6 activity. P450 also requires obligate partnership with P450 oxidoreductase (POR). Human CYP2B6 and POR genes are highly polymorphic. Some CYP2B6 variants affect bupropion disposition. This investigation evaluated the influence of several human CYP2B6 and POR genetic variants on stereoselective bupropion metabolism, using an insect cell coexpression system containing CYP2B6, POR, and cytochrome b ₅ Based on intrinsic clearances (Cl_ints), relative activities for S,S-hydroxybupropion formation were in the order CYP2B6.4 > CYP2B6.1 > CYP2B6.17 > CYP2B6.5 > CYP2B6.6 ≈ CYP2B6.26 ≈ CYP2B6.19 > CYP2B6.7 > CYP2B6.9 > > CYP2B6.16 and CYP2B6.18; relative activities for R,R-hydroxybupropion formation were in the order CYP2B6.17 > CYP2B6.4 > CYP2B6.1 > CYP2B6.5 ≈ CYP2B6.19 ≈ CYP2B6.26 > CYP2B6.6 > CYP2B6.7 ≈ CYP2B6.9 > > CYP2B6.16 and CYP2B6.18. Bupropion hydroxylation was not influenced by POR variants. CYP2B6-catalyzed bupropion hydroxylation is stereoselective. Though V_max and K_m varied widely among CYP2B6 variants, stereoselectivity was preserved, reflected by similar Cl_int(S,S-hydroxybupropion)/Cl_int(R,R-hydroxybupropion) ratios (1.8-2.9), except CYP2B6.17, which was less enantioselective. Established concordance between human bupropion hydroxylation in vitro and in vivo, together with these new results, suggests additional CYP2B6 variants may influence human bupropion disposition. SIGNIFICANCE STATEMENT: Bupropion pharmacokinetics, metabolism, and clinical effects are affected by the CYP2B6*6 polymorphism. Other expressed CYP2B6 polymorphisms had diminished (*5, *6, *7, *9, *19, *26) or defective (*16, *18) in vitro bupropion hydroxylation. P450 oxidoreductase genetic variants had no effect on metabolism, suggesting no clinical consequence of this polymorphism. These CYP2B6 polymorphisms may portend diminished in vivo bupropion hydroxylation and predict additional clinically important variant alleles.

Cytochrome P450 oxidoreductase contributes to phospholipid peroxidation in ferroptosis

Ferroptosis is widely involved in degenerative diseases in various tissues including kidney, liver and brain, and is a targetable vulnerability in multiple primary and therapy-resistant cancers. Accumulation of phospholipid hydroperoxides in cellular membranes is the hallmark and rate-limiting step of ferroptosis; however, the enzymes contributing to lipid peroxidation remain poorly characterized. Using genome-wide, CRISPR-Cas9-mediated suppressor screens, we identify cytochrome P450 oxidoreductase (POR) as necessary for ferroptotic cell death in cancer cells exhibiting inherent and induced susceptibility to ferroptosis. By genetic depletion of POR in cancer cells, we reveal that POR contributes to ferroptosis across a wide range of lineages and cell states, and in response to distinct mechanisms of ferroptosis induction. Using systematic lipidomic profiling, we further map POR's activity to the lipid peroxidation step in ferroptosis. Hence, our work suggests that POR is a key mediator of ferroptosis and potential druggable target for developing antiferroptosis therapeutics.

NADPH-cytochrome P450 reductase expression and enzymatic activity in primary-like human hepatocytes and HepG2 cells for in vitro biotransformation studies

BACKGROUND:

Human hepatocyte in vitro cell culture systems are important models for drug development and toxicology studies in the context of liver xenobiotic metabolism. Often, such culture systems are used to elucidate the biotransformation of xenobiotics or drugs and further investigate drug and drug metabolite effects on biological systems in terms of potential therapeutic benefit or toxicity. Human hepatocytes currently used for such in vitro studies are mostly primary cells or cell lines derived from liver cancers. Both approaches have limitations such as low proliferation capacity and progressive dedifferentiation found in primary cells or lack of liver functions in cell lines, which makes it difficult to reliably predict biotransformation of xenobiotics in patients. In order to overcome these limitations, HepaFH3 cells and Upcyte^® hepatocytes representing primary-like hepatocytes of the first and second generation are increasingly used. Based on primary human hepatocyte cells transduced for stable expression of Upcyte^® proliferation genes, they are mitotically active and exhibit liver functions over an extended period, making them comparable to primary human hepatocytes. These hepatocyte models show active liver metabolism such as urea and glycogen formation as well as biotransformation of xenobiotics. The latter is based on the expression, activity and inducibility of cytochrome P450 enzymes (CYP) as essential phase I reaction components. However, for further characterisation in terms of performance and existing limitations, additional studies are needed to elucidate the mechanisms involved in phase I reactions. One prerequisite is sufficient activity of microsomal NADPH-cytochrome P450 reductase (POR) functionally connected as electron donor to those CYP enzymes.

OBJECTIVE:

For Upcyte^® hepatocytes and HepaFH3 cells, it is so far unknown to what extent POR is expressed, active, and may exert CYP-modulating effects. Here we studied POR expression and corresponding enzyme activity in human hepatoblastoma cell line HepG2 and compared this with HepaFH3 and Upcyte^® hepatocytes representing proliferating primary-like hepatocytes.

METHODS:

POR expression of those hepatocyte models was determined at mRNA and protein level using qRT-PCR, Western Blot and immunofluorescence staining. Kinetic studies on POR activity in isolated microsomes were performed by a colorimetric method.

RESULTS:

The investigated hepatocyte models showed remarkable differences at the level of POR expression. Compared to primary-like hepatocytes, POR expression of HepG2 cells was 4-fold higher at mRNA and 2-fold higher at protein level. However, this higher expression did not correlate with corresponding enzyme activity levels in isolated microsomes, which were comparable between all cell systems tested. A tendency of higher POR activity in HepG2 cells compared to HepaFH3

(p = 0.0829) might be present. Compared to primary human hepatocyte microsomes, POR activity was considerably lower in all hepatocyte models.

CONCLUSION:

In summary, our study revealed that POR expression and activity were clearly detectable in all in vitro hepatocyte models with the highest POR expression in cancer cell line HepG2. However, POR activity was lower in tested hepatocyte models when compared to human primary hepatocyte microsomes. Whether this was caused by e.g. polymorphisms or metabolic differences of investigated hepatocyte models will be target for future studies.

A deeper understanding of intestinal organoid metabolism revealed by combining fluorescence lifetime imaging microscopy (FLIM) and extracellular flux analyses

Stem cells and the niche in which they reside feature a complex microenvironment with tightly regulated homeostasis, cell-cell interactions and dynamic regulation of metabolism. A significant number of organoid models has been described over the last decade, yet few methodologies can enable single cell level resolution analysis of the stem cell niche metabolic demands, in real-time and without perturbing integrity. Here, we studied the redox metabolism of Lgr5-GFP intestinal organoids by two emerging microscopy approaches based on luminescence lifetime measurement - fluorescence-based FLIM for NAD(P)H, and phosphorescence-based PLIM for real-time oxygenation. We found that exposure of stem (Lgr5-GFP) and differentiated (no GFP) cells to high and low glucose concentrations resulted in measurable shifts in oxygenation and redox status. NAD(P)H-FLIM and O2-PLIM both indicated that at high 'basal' glucose conditions, Lgr5-GFP cells had lower activity of oxidative phosphorylation when compared with cells lacking Lgr5. However, when exposed to low (0.5 mM) glucose, stem cells utilized oxidative metabolism more dynamically than non-stem cells. The high heterogeneity of complex 3D architecture and energy production pathways of Lgr5-GFP organoids were also confirmed by the extracellular flux (XF) analysis. Our data reveals that combined analysis of NAD(P)H-FLIM and organoid oxygenation by PLIM represents promising approach for studying stem cell niche metabolism in a live readout.

Congenital Adrenal Hyperplasias Presenting in the Newborn and Young Infant

Congenital adrenal hyperplasia includes autosomal recessive conditions that affect the adrenal cortex steroidogenic enzymes (cholesterol side-chain cleavage enzyme; 3β-hydroxysteroid dehydrogenase; 17α-hydroxylase/17,20 lyase; P450 oxidoreductase; 21-hydroxylase; and 11β-hydroxylase) and proteins (steroidogenic acute regulatory protein). These are located within the three major pathways of the steroidogenic apparatus involved in the production of mineralocorticoids, glucocorticoids, and androgens. Many countries have introduced newborn screening program (NSP) based on 17-OH-progesterone (17-OHP) immunoassays on dried blood spots, which enable faster diagnosis and treatment of the most severe forms of 21-hydroxylase deficiency (21-OHD). However, in several others, the use of this diagnostic tool has not yet been implemented and clinical diagnosis remains challenging, especially for males. Furthermore, less severe classic forms of 21-OHD and other rarer types of CAHs are not identified by NSP. The aim of this mini review is to highlight both the main clinical characteristics and therapeutic options of these conditions, which may be useful for a differential diagnosis in the neonatal period, while contributing to the biochemical evolution taking place in the steroidogenic field. Currently, chromatographic techniques coupled with tandem mass spectrometry are gaining attention due to an increase in the reliability of the test results of NPS for detecting 21-OHD. Furthermore, the possibility of identifying CAH patients that are not affected by 21-OHD but presenting elevated levels of 17-OHP by NSP and the opportunity to include the recently investigated 11-oxygenated androgens in the steroid profiles are promising tools for a more precise diagnosis and monitoring of some of these conditions.