Oxidation of endogenous N-arachidonoylserotonin by human cytochrome P450 2U1

Ninety-eight semesters of cytochrome P450 enzymes and related topics-What have I taught and learned?

This Reflection article begins with my family background and traces my career through elementary and high school, followed by time at the University of Illinois, Vanderbilt University, the University of Michigan, and then for 98 semesters as a Vanderbilt University faculty member. My research career has dealt with aspects of cytochrome P450 enzymes, and the basic biochemistry has had applications in fields as diverse as drug metabolism, toxicology, medicinal chemistry, pharmacogenetics, biological engineering, and bioremediation. I am grateful for the opportunity to work with the Journal of Biological Chemistry not only as an author but also for 34 years as an Editorial Board Member, Associate Editor, Deputy Editor, and interim Editor-in-Chief. Thanks are extended to my family and my mentors, particularly Profs. Harry Broquist and Minor J. Coon, and the more than 170 people who have trained with me. I have never lost the enthusiasm for research that I learned in the summer of 1968 with Harry Broquist, and I have tried to instill this in the many trainees I have worked with. A sentence I use on closing slides is "It's not just a laboratory-it's a fraternity."

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

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

Human Orphan Cytochrome P450 2U1 Catalyzes the ω-Hydroxylation of Leukotriene B4

Cytochrome P450 2U1 (CYP2U1) identified from the human genome remains poorly known since few data are presently available on its physiological function(s) and substrate(s) specificity. CYP2U1 mutations are associated with complicated forms of hereditary spastic paraplegia, alterations of mitochondrial architecture and bioenergetics. In order to better know the biological roles of CYP2U1, we used a bioinformatics approach. The analysis of the data invited us to focus on leukotriene B₄ (LTB₄), an important inflammatory mediator. Here, we show that CYP2U1 efficiently catalyzes the hydroxylation of LTB₄ predominantly on its ω-position. We also report docking experiments of LTB₄ in a 3D model of truncated CYP2U1 that are in agreement with this hydroxylation regioselectivity. The involvement of CYP2U1 in the metabolism of LTB₄ could have strong physiological consequences in cerebral pathologies including ischemic stroke because CYP2U1 is predominantly expressed in the brain.

Engineering indel and substitution variants of diverse and ancient enzymes using Graphical Representation of Ancestral Sequence Predictions (GRASP)

Ancestral sequence reconstruction is a technique that is gaining widespread use in molecular evolution studies and protein engineering. Accurate reconstruction requires the ability to handle appropriately large numbers of sequences, as well as insertion and deletion (indel) events, but available approaches exhibit limitations. To address these limitations, we developed Graphical Representation of Ancestral Sequence Predictions (GRASP), which efficiently implements maximum likelihood methods to enable the inference of ancestors of families with more than 10,000 members. GRASP implements partial order graphs (POGs) to represent and infer insertion and deletion events across ancestors, enabling the identification of building blocks for protein engineering. To validate the capacity to engineer novel proteins from realistic data, we predicted ancestor sequences across three distinct enzyme families: glucose-methanol-choline (GMC) oxidoreductases, cytochromes P450, and dihydroxy/sugar acid dehydratases (DHAD). All tested ancestors demonstrated enzymatic activity. Our study demonstrates the ability of GRASP (1) to support large data sets over 10,000 sequences and (2) to employ insertions and deletions to identify building blocks for engineering biologically active ancestors, by exploring variation over evolutionary time.

Anti-inflammatory dopamine- and serotonin-based endocannabinoid epoxides reciprocally regulate cannabinoid receptors and the TRPV1 channel

The endocannabinoid system is a promising target to mitigate pain as the endocannabinoids are endogenous ligands of the pain-mediating receptors—cannabinoid receptors 1 and 2 (CB1 and CB2) and TRPV1. Herein, we report on a class of lipids formed by the epoxidation of N-arachidonoyl-dopamine (NADA) and N-arachidonoyl-serotonin (NA5HT) by epoxygenases. EpoNADA and epoNA5HT are dual-functional rheostat modulators of the endocannabinoid-TRPV1 axis. EpoNADA and epoNA5HT are stronger modulators of TRPV1 than either NADA or NA5HT, and epoNA5HT displays a significantly stronger inhibition on TRPV1-mediated responses in primary afferent neurons. Moreover, epoNA5HT is a full CB1 agonist. These epoxides reduce the pro-inflammatory biomarkers IL-6, IL-1β, TNF-α and nitrous oxide and raise anti-inflammatory IL-10 cytokine in activated microglial cells. The epoxides are spontaneously generated by activated microglia cells and their formation is potentiated in the presence of anandamide. Detailed kinetics and molecular dynamics simulation studies provide evidence for this potentiation using the epoxygenase human CYP2J2. Taken together, inflammation leads to an increase in the metabolism of NADA, NA5HT and other eCBs by epoxygenases to form the corresponding epoxides. The epoxide metabolites are bioactive lipids that are potent, multi-faceted molecules, capable of influencing the activity of CB1, CB2 and TRPV1 receptors.

Endocannabinoids are ligands of cannabinoid receptors and a promising target for pain management. Here, the authors report a class of lipids formed by the epoxidation of N-arachidonoyl dopamine and N-arachidonoyl serotonin by cytochrome P450 epoxygenases, which reciprocally regulate canabinoid receptors and display anti-inflammatory activity.

Cytochrome P450 2U1 Is a Novel Independent Prognostic Biomarker in Breast Cancer Patients

Background: The susceptibility of breast cancer is largely affected by the metabolic capacity of breast tissue. This ability depends in part on the expression profile of cytochrome P450 (CYPs). CYPs are a superfamily of enzymes with related catalysis to endogenous and exogenous bioactive substances, including xenobiotic metabolism, drugs, and some endogenous substances metabolism which activate cells and stimulate cell signaling pathways, such as arachidonic acid metabolism, steroid metabolism, fatty acid metabolism. Interestingly, CYP was electively expressed in different tumors, and mediated the metabolic activation of multiple carcinogens and participated in the activation and deactivation of tumor therapeutic drugs. However, the biological action of cytochrome P450 2U1 (CYP2U1) in breast carcinoma is little understood so far.

Methods: To investigate the biological value of CYP2U1 in breast carcinoma, we performed immunohistochemical (IHC) analysis and survival analysis based on clinico-pathological data of breast cancer.

Results: IHC analysis showed that the abundance of CYP2U1 protein was inversely proportional to the state of estrogen receptor(ER) (P < 0.05), and the lower the degree of tumor differentiation, the higher the protein abundance (P < 0.001). Additionally, compared with luminal tumors, the CYP2U1 protein content was more abundant in triple negative breast cancer (P < 0.05). Importantly, survival analysis showed that higher CYP2U1 protein levels predicted poor 5-year overall survival rate (P < 0.01), 5-year disease-free survival rate (P < 0.05), and 5-year metastatic-free survival rate (P < 0.01) for the entire enrolled breast cancer patients.

Conclusions: CYP2U1 is generally closely related to the clinicopathological characteristics and is also an adverse prognostic factor for breast carcinoma patients, indicating that CYP2U1 is engaged in the malignant progression of breast carcinoma.

Lipids in the Physiopathology of Hereditary Spastic Paraplegias

Hereditary spastic paraplegias (HSP) are a group of neurodegenerative diseases sharing spasticity in lower limbs as common symptom. There is a large clinical variability in the presentation of patients, partly underlined by the large genetic heterogeneity, with more than 60 genes responsible for HSP. Despite this large heterogeneity, the proteins with known function are supposed to be involved in a limited number of cellular compartments such as shaping of the endoplasmic reticulum or endolysosomal function. Yet, it is difficult to understand why alteration of such different cellular compartments can lead to degeneration of the axons of cortical motor neurons. A common feature that has emerged over the last decade is the alteration of lipid metabolism in this group of pathologies. This was first revealed by the identification of mutations in genes encoding proteins that have or are supposed to have enzymatic activities on lipid substrates. However, it also appears that mutations in genes affecting endoplasmic reticulum, mitochondria, or endolysosome function can lead to changes in lipid distribution or metabolism. The aim of this review is to discuss the role of lipid metabolism alterations in the physiopathology of HSP, to evaluate how such alterations contribute to neurodegenerative phenotypes, and to understand how this knowledge can help develop therapeutic strategy for HSP.

Tissue distribution and characterization of feline cytochrome P450 genes related to polychlorinated biphenyl exposure

Cats have been known to be extremely sensitive to chemical exposures. To understand these model species' sensitivity to chemicals and their toxicities, the expression profiles of xenobiotic-metabolizing enzymes should be studied. Unfortunately, the characterization of cytochrome P450 (CYP), the dominant enzyme in phase I metabolism, in cats has not extensively been studied. Polychlorinated biphenyls (PCBs) are known as CYP inducers in animals, but the information regarding the PCB-induced CYP expression in cats is limited. Therefore, in the present study, we aimed to elucidate the mRNA expression of the CYP1-CYP3 families in the cat tissues and to investigate the CYP mRNA expression related to PCB exposure. In cats, the greatest abundance of CYP1-CYP3 (CYP1A2, CYP2A13, CYP2C41, CYP2D6, CYP2E1, CYP2E2, CYP2F2, CYP2F5, CYP2J2, CYP2U1, and CYP3A132) was expressed in the liver, but some extrahepatic isozymes were found in the kidney (CYP1A1), heart (CYP1B1), lung (CYP2B11 and CYP2S1) and small intestine (CYP3A131). In cats, CYP1A1, CYP1A2 and CYP1B1 were significantly upregulated in the liver as well as in several tissues exposed to PCBs, indicating that these CYPs were distinctly induced by PCBs. The strong correlations between 3,3',4,4'-tetrachlorobiphenyl (CB77) and CYP1A1 and CYP1B1 mRNA expressions were noted, demonstrating that CB77 could be a potent CYP1 inducer. In addition, these CYP isoforms could play an essential role in the PCBs biotransformation, particularly 3-4 Cl-PCBs, because a high hydroxylated metabolite level of 3-4 Cl-OH-PCBs was observed in the liver.

A Role for the Orphan Human Cytochrome P450 2S1 in Polyunsaturated Fatty Acid ω-1 Hydroxylation Using an Untargeted Metabolomic Approach

Cytochrome P450 (P450) 2S1 is one of the orphan P450s, known to be expressed but not having a defined function with an endogenous substrate or in drug oxidations. Although it has been clearly demonstrated to catalyze reductive reactions, its role in NADPH-dependent oxidations has been ambiguous. In our efforts to characterize orphan human P450 enzymes, we used an untargeted liquid chromatography-mass spectromterymetabolomic approach with recombinant human P450 2S1 and extracts of rat stomach and intestine, sites of P450 2S1 localization in humans and animals. The search yielded several candidates, including the product 19-hydroxyarachidonic acid. Subsequent 18O analysis and in vitro studies with commercial arachidonic acid and 19-hydroxyarachidonic acid were used to validate ω-1 hydroxylation of the former molecule as a NADPH- and O2-dependent reaction. Steady-state kinetic assays were done for ω-1 hydroxylation reactions of P450 2S1 with several other long-chain fatty acids, including arachidonic, linoleic, α-linolenic, eicosapentaenoic, and docosapentaenoic acids. Rates of hydroxylation were slow, but no detectable activity was seen with either medium-chain length or saturated fatty acids. P450 2S1 is known to be expressed, at least at the mRNA level, to the extent of some other non-3A subfamily P450s in the human gastrointestinal tract, and the activity may be relevant. We conclude that P450 2S1 is a fatty acid ω-1 hydroxylase, although the physiologic relevance of these oxidations remains to be established. The metabolomic approaches we employed in this study are feasible for orphan P450s and other enzymes, in regard to annotation of function, in mammals and other organisms. SIGNIFICANCE STATEMENT: An untargeted mass spectrometry approach was utilized to identify ω-1 hydroxylation of arachidonic acid as an oxidative reaction catalyzed by human cytochrome P450 2S1. The enzyme also catalyzes the relatively slow ω-1 hydroxylation of several other unsaturated long-chain fatty acids.

The role of acid-sensitive ion channels in panic disorder: a systematic review of animal studies and meta-analysis of human studies

Acid-sensitive ion channels, such as amiloride-sensitive cation channel (ACCN), transient receptor potential vanilloid-1 (TRPV1), and T-cell death-associated gene 8 (TDAG8) are highly related to the expression of fear and are expressed in several regions of the brain. These molecules can detect acidosis and maintain brain homeostasis. An important role of pH homeostasis has been suggested in the physiology of panic disorder (PD), with acidosis as an interoceptive trigger for panic attacks. To examine the effect of acid-sensitive channels on PD symptoms, we conducted a systematic review and meta-analysis of these chemosensors in rodents and humans. Following PRISMA guidelines, we systematically searched the Web of Science, Medline/Pubmed, Scopus, Science Direct, and SciELO databases. The review included original research in PD patients and animal models of PD that investigated acid-sensitive channels and PD symptoms. Studies without a control group, studies involving patients with a comorbid psychiatric diagnosis, and in vitro studies were excluded. Eleven articles met the inclusion criteria for the systematic review. The majority of the studies showed an association between panic symptoms and acid-sensitive channels. PD patients appear to display polymorphisms in the ACCN gene and elevated levels of TDAG8 mRNA. The results showed a decrease in panic-like symptoms after acid channel blockade in animal models. Despite the relatively limited data on this topic in the literature, our review identified evidence linking acid-sensitive channels to PD in humans and preclinical models. Future research should explore possible underlying mechanisms of this association, attempt to replicate the existing findings in larger populations, and develop new therapeutic strategies based on these biological features.

Cytochrome P450 2U1, a very peculiar member of the human P450s family

Cytochrome P450 2U1 (CYP2U1) exhibits several distinctive characteristics among the 57 human CYPs, such as its presence in almost all living organisms with a highly conserved sequence, its particular gene organization with only five exons, its major location in thymus and brain, and its protein sequence involving an unusually long N-terminal region containing 8 proline residues and an insert of about 20 amino acids containing 5 arginine residues after the transmembrane helix. Few substrates, including fatty acids, N-arachidonoylserotonin (AS), and some drugs, have been reported so far. However, its biological roles remain largely unknown, even though CYP2U1 mutations have been involved in some pathological situations, such as complicated forms of hereditary spastic paraplegia. These data together with its ability to hydroxylate some fatty acids and AS suggest its possible role in lipid metabolism.

Metabolomics of fescue toxicosis in grazing beef steers

Fescue toxicosis (FT) results from consumption of tall fescue (Lolium arundinaceum) infected with an endophyte (Epichloë coenophiala) that produces ergot alkaloids (EA), which are considered key etiological agents of FT. Decreased weight gains, hormonal imbalance, circulating cholesterol disruption, and decreased volatile fatty acid absorption suggest toxic (E+) fescue-induced metabolic perturbations. Employing untargeted high-resolution metabolomics (HRM) to analyze E+ grazing-induced plasma and urine metabolome changes, fescue-naïve Angus steers were placed on E+ or non-toxic (Max-Q) fescue pastures and plasma and urine were sampled before, 1, 2, 14, and 28 days after pasture assignment. Plasma and urine catecholamines and urinary EA concentrations were also measured. In E+ steers, urinary EA appeared early and peaked at 14 days. 13,090 urinary and 20,908 plasma HRM features were detected; the most significant effects were observed earlier (2 days) in the urine and later (≥14 days) in the plasma. Alongside EA metabolite detection, tryptophan and lipid metabolism disruption were among the main consequences of E+ consumption. The E+ grazing-associated metabolic pathways and signatures described herein may accelerate development of novel early FT detection and treatment strategies.

Docosahexaenoyl serotonin, an endogenously formed n-3 fatty acid-serotonin conjugate has anti-inflammatory properties by attenuating IL-23-IL-17 signaling in macrophages

Conjugates of fatty acids and amines, including endocannabinoids, are known to play important roles as endogenous signaling molecules. Among these, the ethanolamine conjugate of the n-3 poly unsaturated long chain fatty acid (PUFA) docosahexaenoic acid (22:6n-3) (DHA) was shown to possess strong anti-inflammatory properties. Previously, we identified the serotonin conjugate of DHA, docosahexaenoyl serotonin (DHA-5-HT), in intestinal tissues and showed that its levels are markedly influenced by intake of n-3 PUFAs. However, its biological roles remain to be elucidated. Here, we show that DHA-5-HT possesses potent anti-inflammatory properties by attenuating the IL-23-IL-17 signaling cascade in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Transcriptome analysis revealed that DHA-5-HT down-regulates LPS-induced genes, particularly those involved in generating a CD4+ Th17 response. Hence, levels of PGE2, IL-6, IL-1β, and IL-23, all pivotal macrophage-produced mediators driving the activation of pathogenic Th17 cells in a concerted way, were found to be significantly suppressed by concentrations as low as 100-500nM DHA-5-HT. Furthermore, DHA-5-HT inhibited the ability of RAW264.7 cells to migrate and downregulated chemokines like MCP-1, CCL-20, and gene-expression of CCL-22 and of several metalloproteinases. Gene set enrichment analysis (GSEA) suggested negative overlap with gene sets linked to inflammatory bowel disease (IBD) and positive overlap with gene sets related to the Nrf2 pathway. The specific formation of DHA-5-HT in the gut, combined with increasing data underlining the importance of the IL-23-IL-17 signaling pathway in the etiology of many chronic inflammatory diseases merits further investigation into its potential as therapeutic compound in e.g. IBD or intestinal tumorigenesis.