ω-Hydroxylation of farnesol by mammalian cytochromes P450

Discovery of novel diagnostic biomarkers for Sjögren-Larsson syndrome by untargeted lipidomics

AIM

Sjögren-Larsson syndrome (SLS) is a rare neurometabolic disorder that mainly affects brain, eye and skin and is caused by deficiency of fatty aldehyde dehydrogenase. Our recent finding of a profoundly disturbed brain tissue lipidome in SLS prompted us to search for similar biomarkers in plasma as no functional test in blood is available for SLS.

METHODS AND RESULTS

We performed plasma lipidomics and used a newly developed bioinformatics tool to mine the untargeted part of the SLS plasma and brain lipidome to search for SLS biomarkers. Plasma lipidomics showed disturbed ether lipid metabolism in known lipid classes. Untargeted lipidomics of both plasma and brain (white and grey matter) uncovered two new endogenous lipid classes highly elevated in SLS. The first biomarker group were alkylphosphocholines/ethanolamines containing different lengths of alkyl-chains where some alkylphosphocholines were > 600-fold elevated in SLS plasma. The second group of biomarkers were a set of 5 features of unknown structure. Fragmentation studies suggested that they contain ubiquinol and phosphocholine and one feature was also found as a glucuronide conjugate in plasma. The plasma features were highly distinctive for SLS with levels >100-1000-fold the level in controls, if present at all. We speculate on the origin of the alkylphosphocholines/ethanolamines and the nature of the ubiquinol-containing metabolites.

CONCLUSIONS

The metabolites identified in this study represent novel endogenous lipid classes thus far unknown in humans. They represent the first plasma metabolite SLS-biomarkers and may also yield more insight into SLS pathophysiology.

Concurrent administration of farnesol protects acetaminophen-induced acute hepatic necrosis in mice

Acetaminophen (APAP) is known to cause acute liver injury and acute liver failure in Western countries. This study investigates the protective role of farnesol (FAR) (C15 H26 O), a natural sesquiterpene alcohol in essential oils, against APAP-induced acute liver necrosis in mice. Mice were injected with a single dose of APAP (300 mg/kg) via an intraperitoneal route. Different groups of mice were concurrently treated with a single dose of FAR 25 mg/kg, FAR 50 mg/kg, and N-acetylcysteine. APAP administration caused a significant increase in transaminase activities and malondialdehyde (MDA) levels in the serum and liver tissue, respectively, with a concomitant decrease in intracellular antioxidants, including reduced glutathione (GSH) in the liver tissue. APAP intoxication upregulated proinflammatory cytokines such as tumor necrosis factor-α, interleukin-1β (IL-1β), IL-6, nuclear factor-κB (NF-κB), and IκB kinase β in the liver tissue. FAR and N-acetylcysteine (NAC) administrations concurrently with APAP prevented serum transaminase increase in serum and MDA levels in the liver tissue. A high dose of FAR and NAC treatments significantly inhibited GSH and other antioxidant depletion. FAR and NAC treatments also downregulated the expression of proinflammatory markers. FAR treatments protects against APAP-induced acute liver injury and offers antioxidant and anti-inflammatory effects by inhibiting the NF-κB pathway involved in the transcription of genes responsible for inflammatory cytokine synthesis.

Allosteric modulation of α1β3γ2 GABAA receptors by farnesol through the neurosteroid sites

In mammalian cells, all-trans farnesol, a 15-carbon isoprenol, is a product of the mevalonate pathway. It is the natural substrate of alcohol dehydrogenase and a substrate for CYP2E1, two enzymes implicated in ethanol metabolism. Studies have shown that farnesol is present in the human brain and inhibits voltage-gated Ca2+ channels at much lower concentrations than ethanol. Here we show that farnesol modulates the activity of γ-aminobutyric acid type A receptors (GABAARs), some of which also mediate the sedative activity of ethanol. Electrophysiology experiments performed in HEK cells expressing human α1β3γ2 or α6β3γ2 GABAARs revealed that farnesol increased chloride currents through positive allosteric modulation of these receptors and showed dependence on both the alcoholic functional group of farnesol and the length of the alkyl chain for activity. In silico studies using long-timescale unbiased all-atom molecular dynamics (MD) simulations of the human α1β3γ2 GABAA receptors revealed that farnesol modulates the channel by directly binding to the transmembrane neurosteroid-binding site, after partitioning into the surrounding membrane and reaching the receptor by lateral diffusion. Channel activation by farnesol was further characterized by several structural and dynamic variables, such as global twisting of the receptor's extracellular domain, tilting of the transmembrane M2 helices, radius, cross-sectional area, hydration status, and electrostatic potential of the channel pore. Our results expand the pharmacological activities of farnesol to yet another class of ion channels implicated in neurotransmission, thus providing a novel path for understanding and treatment of diseases involving GABAA receptor dysfunction.

Essential Oil Composition Analysis, Antimicrobial Activities, and Biosystematic Studies on Six Species of Salvia

The essential oil constituents, antimicrobial properties, and biosystematic characteristics (morphological, palynological, and anatomical features) of six Salvia species from different regions of Turkey were investigated qualitatively and quantitatively in this study. The chemical composition of the essential oils of dried aerial parts of Salvia species, i.e., S. absconditiflora, S. ceratophylla, S. multicaulis, S. verbenaca, S. viridis, and S. syriaca were analyzed by GC-MS. The main constituents of the six Salvia species studied were 1,8-cineol, caryophyllene oxide, spathulenol, and borneol in different ratios. The antimicrobial activity of the essential oil extracted from the aerial parts of species of the genus Salvia was tested by the disc diffusion method. The essential oils of Salvia species showed different antimicrobial activity against the studied microorganisms. The highest antimicrobial activity against E. coli was observed in S. multicaulis and the highest antimicrobial activity against K. pneumoniae was observed in S. verbenaca. The morphology of the stem, leaf, bract, and flower structures of the Salvia species were analyzed in this study. Anatomical investigations focused on the root, petiole, and stem in more detail. Our research has broadened the criteria of anatomical characters unique to the Salvia species. Under light microscopy, the pollen grains of the six species belonging to Salvia were isopolar and radially symmetrical. The properties of the essential oil constituents, antimicrobial properties, and biosystematic data obtained in this study contribute to the bioactive and biosystematic studies of Salvia species used for food, pharmaceutical, and cosmetic purposes.

Endophytic fungi and their bioactive secondary metabolites in medicinal leguminosae plants: Nearly untapped medical resources

There are many species of Chinese traditional leguminosae family plants that are well known for their medicinal applications, such as Astragalus membranaceus, Catsia tora, Glycyrrhiza uralensis, Sophora flavescens and Albacia acacia. Their unique bioactive composition and internal phenological environment contribute to the formation of specific and unique endophytic fungal communities, which are important resources for new compounds used in a variety of pharmacological activities. Nonetheless, they have not been systematically studied. In the last decade, nearly 64 genera and thousands of species of endophytic fungi have been discovered from leguminosae plants, as well as 138 secondary metabolites (with 34 new compounds) including flavonoid, alkaloids, phenol, anthraquinone, macrolide, terpenoid, phytohormone and many more. They were shown to have diverse applications and benefits, such as antibacterial, antitumor, antioxidative, immunoregulatory and neuroprotective properties. Here, we provide a summarized overview with the aim of raising awareness of endophytic fungi from medicinal leguminosae plants and providing a comprehensive review of the discoveries of new natural products that may be of medicinal and pharmaceutical importance.

Extracellular Vesicles Regulate Biofilm Formation and Yeast-to-Hypha Differentiation in Candida albicans

In this study, we investigated the influence of fungal extracellular vesicles (EVs) during biofilm formation and morphogenesis in Candida albicans. Using crystal violet staining and scanning electron microscopy (SEM), we demonstrated that C. albicans EVs inhibited biofilm formation in vitro. By time-lapse microscopy and SEM, we showed that C. albicans EV treatment stopped filamentation and promoted pseudohyphae formation with multiple budding sites. The ability of C. albicans EVs to regulate dimorphism was further compared to EVs isolated from different C. albicans strains, Saccharomyces cerevisiae, and Histoplasma capsulatum. C. albicans EVs from distinct strains inhibited yeast-to-hyphae differentiation with morphological changes occurring in less than 4 h. EVs from S. cerevisiae and H. capsulatum modestly reduced morphogenesis, and the effect was evident after 24 h of incubation. The inhibitory activity of C. albicans EVs on phase transition was promoted by a combination of lipid compounds, which were identified by gas chromatography-tandem mass spectrometry analysis as sesquiterpenes, diterpenes, and fatty acids. Remarkably, C. albicans EVs were also able to reverse filamentation. Finally, C. albicans cells treated with C. albicans EVs for 24 h lost their capacity to penetrate agar and were avirulent when inoculated into Galleria mellonella. Our results indicate that fungal EVs can regulate yeast-to-hypha differentiation, thereby inhibiting biofilm formation and attenuating virulence.

An epigenetic modifier induces production of 3-(4-oxopyrano)-chromen-2-ones in Aspergillus sp. AST0006, an endophytic fungus of Astragalus lentiginosus

Incorporation of the epigenetic modifier suberoylanilide hydroxamic acid (SAHA) into a potato dextrose broth culture of the endophytic fungus Aspergillus sp. AST0006 affected its polyketide biosynthetic pathway providing two new 3-(4-oxopyrano)-chromen-2-ones, aspyranochromenones A (1) and B (2), and the isocoumarin, (-)-6,7-dihydroxymellein (3). Eight additional metabolites (4-11) and two biotransformation products of SAHA (12-13) were also encountered. The planar structures and relative configurations of the new metabolites 1-2 were elucidated with the help of high-resolution mass, 1D and 2D NMR spectroscopic data and the absolute configurations of 1-3 were determined by comparison of experimental and calculated ECD data. Possible biosynthetic pathways to 1 and 2 are presented.

Synthetic Derivatives of (+)-epi-α-Bisabolol Are Formed by Mammalian Cytochromes P450 Expressed in a Yeast Reconstituted Pathway

Identification of the enzyme(s) involved in complex biosynthetic pathways can be challenging. An alternative approach might be to deliberately diverge from the original natural enzyme source and use promiscuous enzymes from other organisms. In this paper, we have tested the ability of a series of human and animal cytochromes P450 involved in xenobiotic detoxification to generate derivatives of (+)-epi-α-bisabolol and attempt to produce the direct precursor of hernandulcin, a sweetener from Lippia dulcis for which the last enzymatic steps are unknown. Screening steps were implemented in vivo in S. cerevisiae optimized for the biosynthesis of oxidized derivatives of (+)-epi-α-bisabolol by coexpressing two key enzymes: the (+)-epi-α-bisabolol synthase and the NADPH cytochrome P450 reductase. Five out of 25 cytochromes P450 were capable of producing new hydroxylated regioisomers of (+)-epi-α-bisabolol. Of the new oxidized bisabolol products, the structure of one compound, 14-hydroxy-(+)-epi-α-bisabolol, was fully elucidated by NMR while the probable structure of the second product was determined. In parallel, the production of (+)-epi-α-bisabolol derivatives was enhanced through the addition of a supplementary genomic copy of (+)-epi-α-bisabolol synthase that augmented the final titer of hydroxylated product to 64 mg/L. We thus demonstrate that promiscuous drug metabolism cytochromes P450 can be used to produce novel compounds from a terpene scaffold.

Farnesol induces fatty acid oxidation and decreases triglyceride accumulation in steatotic HepaRG cells

Non-alcoholic fatty liver disease is manifested by hepatic accumulation of triglycerides (TG) and is commonly associated with metabolic syndrome. The isoprenoid farnesol (FOH) modulates lipid metabolism and reduces hepatic TG content in rodents. This effect involves activation of at least two nuclear receptors, peroxisome proliferator-activated receptor α (PPARα) and farnesoid X receptor. We evaluated the effects of FOH (100 μM) in a cellular model of human hepatic steatosis by loading hepatocyte-like HepaRG cells with oleic acid (OA, 0.66 mM). FOH treatment decreased OA-induced TG accumulation by ~25%. Using PCR arrays, we found that FOH treatment modulated the mRNA levels of several lipid-metabolizing enzymes, both alone and when cells were loaded with OA. While FOH activated PPARα and the constitutive androstane receptor (CAR), most of the FOH-mediated effects on lipid-metabolizing genes could be attributed to activation of PPARα. In OA-loaded HepaRG cells, FOH increased fatty acid oxidation, which was accompanied by up-regulation of PPARα target genes involved in mitochondrial fatty acid oxidation, including hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase and acetyl-coenzyme A acyltransferase 2. These effects on gene expression were lost when the cells were co-treated with the PPARα antagonist, GW6471. OA treatment alone decreased the mRNA levels of the drug-metabolizing enzymes, cytochrome P450 (CYP)1A2, 2B6, and 3A4, and increased CYP2E1 expression, all of which were attenuated by FOH co-treatment. These findings show that FOH treatment increases fatty acid oxidation and decreases TG accumulation in steatotic HepaRG cells, which is likely attributable to PPARα-mediated induction of mitochondrial fatty acid oxidation.

Utilization of an intermediate of the methylerythritol phosphate pathway, (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate, as the prenyl donor substrate for various prenyltransferases

(E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate (HMBPP) is an intermediate of the methylerythritol phosphate pathway. Utilization of HMBPP by lycopene elongase from Corynebacterium glutamicum, which is a UbiA-family prenyltransferase responsible for C₅₀ carotenoid biosynthesis, was investigated using an Escherichia coli strain that contained the exogenous mevalonate pathway as well as the carotenoid biosynthetic pathway. Inhibition of the endogenous methylerythritol phosphate pathway resulted in loss of the production of C₅₀ carotenoid flavuxanthin, while C₄₀ lycopene formation was retained. Overexpression of E. coli ispH gene, which encodes HMBPP reductase, also decreased the production of flavuxanthin in E. coli cells. These results indicate the preference of lycopene elongase for HMBPP instead of the previously proposed substrate, dimethylallyl diphosphate. Furthermore, several (all-E)-prenyl diphosphate synthases, which are classified in a distinct family of prenyltransferase, were demonstrated to accept HMBPP, which implies that the compound is more widely used as a prenyl donor substrate than was previously expected.

Differential Regulation of Gene Expression by Cholesterol Biosynthesis Inhibitors That Reduce (Pravastatin) or Enhance (Squalestatin 1) Nonsterol Isoprenoid Levels in Primary Cultured Mouse and Rat Hepatocytes

Squalene synthase inhibitors (SSIs), such as squalestatin 1 (SQ1), reduce cholesterol biosynthesis but cause the accumulation of isoprenoids derived from farnesyl pyrophosphate (FPP), which can modulate the activity of nuclear receptors, including the constitutive androstane receptor (CAR), farnesoid X receptor, and peroxisome proliferator-activated receptors (PPARs). In comparison, 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (e.g., pravastatin) inhibit production of both cholesterol and nonsterol isoprenoids. To characterize the effects of isoprenoids on hepatocellular physiology, microarrays were used to compare orthologous gene expression from primary cultured mouse and rat hepatocytes that were treated with either SQ1 or pravastatin. Compared with controls, 47 orthologs were affected by both inhibitors, 90 were affected only by SQ1, and 51 were unique to pravastatin treatment (P < 0.05, ≥1.5-fold change). When the effects of SQ1 and pravastatin were compared directly, 162 orthologs were found to be differentially coregulated between the two treatments. Genes involved in cholesterol and unsaturated fatty acid biosynthesis were up-regulated by both inhibitors, consistent with cholesterol depletion; however, the extent of induction was greater in rat than in mouse hepatocytes. SQ1 induced several orthologs associated with microsomal, peroxisomal, and mitochondrial fatty acid oxidation and repressed orthologs involved in cell cycle regulation. By comparison, pravastatin repressed the expression of orthologs involved in retinol and xenobiotic metabolism. Several of the metabolic genes altered by isoprenoids were inducible by a PPARα agonist, whereas cytochrome P450 isoform 2B was inducible by activators of CAR. Our findings indicate that SSIs uniquely influence cellular lipid metabolism and cell cycle regulation, probably due to FPP catabolism through the farnesol pathway.

Cytotoxic Effect and TLC Bioautography-Guided Approach to Detect Health Properties of Amazonian Hedyosmum sprucei Essential Oil

Bioautography has been used as rapid and easy strategy to detect and identify bioactive fractions/molecules in the never before investigated Hedyosmum sprucei Solms (Chloranthaceae) essential oil (EO). The antioxidant activity, performed through DPPH bioautographic assay and spectrophotometric evaluations (IC₅₀ = 230 ± 10 µg/mL), seemed to be mainly due to α-cadinol and α-muurolol. (HP)TLC bioautography, focused on antimicrobial capacities, pointed out α-cadinol, α-muurolol, τ-muurolol, caryophyllene oxide, and methyleugenol as the most effective compounds against Staphylococcus aureus, considered as testing strain. Moreover, the microdilution method, assessed among a wide panel of microorganisms, revealed Listeria grayi and Staphylococcus aureus as the most sensitive among human tested strains and Clavibacter michiganensis among phytopathogens. GC-MS chemical profile showed that bioactive molecules represented only a small quantity of the whole EO: germacrene D (23.16%), β-caryophyllene (15.53%), δ-cadinene (5.50%), α-copaene (5.08%), and α-phellandrene (3.48%) were the main compounds, highlighting an uncommon composition among the genus Hedyosmum. Finally, H. sprucei EO was checked for cytotoxic potential against A549 (lung cancer) and MCF-7 (breast cancer) cell lines showing promising cytotoxic effects against both cell lines after 48 h (IC₅₀ A549 = 44.05 ± 2.35 µg/mL; IC₅₀ MCF-7 = 32.76 ± 4.92 µg/mL) and 72 h (IC₅₀ A549 = 43.55 ± 2.80 µg/mL; IC₅₀ MCF-7 = 33.64 ± 0.43 µg/mL).

Fatty aldehyde and fatty alcohol metabolism: review and importance for epidermal structure and function

Normal fatty aldehyde and alcohol metabolism is essential for epidermal differentiation and function. Long-chain aldehydes are produced by catabolism of several lipids including fatty alcohols, sphingolipids, ether glycerolipids, isoprenoid alcohols and certain aliphatic lipids that undergo α- or ω-oxidation. The fatty aldehyde generated by these pathways is chiefly metabolized to fatty acid by fatty aldehyde dehydrogenase (FALDH, alternately known as ALDH3A2), which also functions to oxidize fatty alcohols as a component of the fatty alcohol:NAD oxidoreductase (FAO) enzyme complex. Genetic deficiency of FALDH/FAO in patients with Sjögren-Larsson syndrome (SLS) results in accumulation of fatty aldehydes, fatty alcohols and related lipids (ether glycerolipids, wax esters) in cultured keratinocytes. These biochemical changes are associated with abnormalities in formation of lamellar bodies in the stratum granulosum and impaired delivery of their precursor membranes to the stratum corneum (SC). The defective extracellular SC membranes are responsible for a leaky epidermal water barrier and ichthyosis. Although lamellar bodies appear to be the pathogenic target for abnormal fatty aldehyde/alcohol metabolism in SLS, the precise biochemical mechanisms are yet to be elucidated. Nevertheless, studies in SLS highlight the critical importance of FALDH and normal fatty aldehyde/alcohol metabolism for epidermal function. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.

Farnesylcysteine lyase is involved in negative regulation of abscisic acid signaling in Arabidopsis

The Arabidopsis FCLY gene encodes a specific farnesylcysteine (FC) lyase, which is responsible for the oxidative metabolism of FC to farnesal and cysteine. In addition, fcly mutants with quantitative decreases in FC lyase activity exhibit an enhanced response to ABA. However, the enzymological properties of the FCLY-encoded enzyme and its precise role in ABA signaling remain unclear. Here, we show that recombinant Arabidopsis FC lyase expressed in insect cells exhibits high selectivity for FC as a substrate and requires FAD and molecular oxygen for activity. Arabidopsis FC lyase is also shown to undergo post-translational N-glycosylation. FC, which is a competitive inhibitor of isoprenylcysteine methyltransferase (ICMT), accumulates in fcly mutants. Moreover, the enhanced response of fcly mutants to ABA is reversed by ICMT overexpression. These observations support the hypothesis that the ABA hypersensitive phenotype of fcly plants is the result of FC accumulation and inhibition of ICMT.

Biochemical and structural characterization of CYP124: a methyl-branched lipid omega-hydroxylase from Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) produces a variety of methyl-branched lipids that serve important functions, including modulating the immune response during pathogenesis and contributing to a robust cell wall that is impermeable to many chemical agents. Here, we report characterization of Mtb CYP124 (Rv2266) that includes demonstration of preferential oxidation of methyl-branched lipids. Spectrophotometric titrations and analysis of reaction products indicate that CYP124 tightly binds and hydroxylates these substrates at the chemically disfavored omega-position. We also report X-ray crystal structures of the ligand-free and phytanic acid-bound protein at a resolution of 1.5 A and 2.1 A, respectively, which provide structural insights into a cytochrome P450 with predominant omega-hydroxylase activity. The structures of ligand-free and substrate-bound CYP124 reveal several differences induced by substrate binding, including reorganization of the I helix and closure of the active site by elements of the F, G, and D helices that bind the substrate and exclude solvent from the hydrophobic active site cavity. The observed regiospecific catalytic activity suggests roles of CYP124 in the physiological oxidation of relevant Mtb methyl-branched lipids. The enzymatic specificity and structures reported here provide a scaffold for the design and testing of specific inhibitors of CYP124.

Characterization of (E,E)-farnesol and its fatty acid esters from anal scent glands of nutria (Myocastor coypus) by gas chromatography–mass spectrometry and gas chromatography–infrared spectrometry

Several volatile compounds, including terpenoids, fatty alcohols, fatty acids and some of their esters, were identified from solvent extracts prepared from anal scent glands of nutria (a.k.a. coypu), a serious rodent pest ravaging wetlands in the USA. The major terpenoid constituents were identified as (E,E)-farnesol and its esters by a comparison of their gas chromatographic retention times, and electron-ionization (EI) and chemical-ionization (CI) mass spectra with those of authentic compounds. EI mass spectra of the four farnesol isomers are very similar, however, the ChemStation (Agilent) and GC-MS Solution (Shimadzu) software algorithms were able to identify the natural compound as the (E,E)-isomer, when a high-quality mass spectral library was compiled from reference samples and used for searching. Similarly, the esters were identified as those of (E,E)-farnesol. In contrast to EI spectra, the CI spectra of the (E,E)- and (E,Z)-isomers are distinctly different from those of the (Z,E)- and (Z,Z)-isomers. The intensities (I) of the peaks for the m/z 137 and 121 ions in the CI spectra offer a way of determining the configuration of the C-2 double bond of farnesols (for 2E isomers I(137)>I(121), whereas for 2Z isomers I(137)<I(121)). Moreover, the infrared spectrum of the (E,E)-isomer is distinctly different from those of the other three isomers in the 2962-2968 cm(-1) and 2918-2922 cm(-1) bands, which represent asymmetric CH(3) and CH(2) stretching vibrations, respectively. Finally, the GC retention indices of farnesol and farnesyl ester isomers determined from authentic samples were used to confirm all identifications.

Arabidopsis thaliana plants possess a specific farnesylcysteine lyase that is involved in detoxification and recycling of farnesylcysteine

In plants, prenylated proteins are involved in actin organization, calcium-mediated signal transduction, and many other biological processes. Arabidopsis thaliana mutants lacking functional protein prenyltransferase genes have also revealed roles for prenylated proteins in phytohormone signaling and meristem development. However, to date, the turnover of prenylated plant proteins and the fate of the prenylcysteine (PC) residue have not been described. We have detected an enzyme activity in Arabidopsis plants that metabolizes farnesylcysteine (FC) to farnesal, which is subsequently reduced to farnesol. Unlike its mammalian ortholog, Arabidopsis FC lyase exhibits specificity for FC over geranylgeranylcysteine (GGC), and recognizes N-acetyl-FC (AFC). FC lyase is encoded by a gene on chromosome 5 of the Arabidopsis genome (FCLY, At5g63910) and is ubiquitously expressed in Arabidopsis tissues and organs. Furthermore, T-DNA insertions into the FCLY gene cause significant decreases in FC lyase activity and an enhanced response to abscisic acid (ABA) in seed germination assays. The effects of FCLY mutations on ABA sensitivity are even greater in the presence of exogenous FC. These data suggest that plants possess a specific FC detoxification and recycling pathway.

Use of CYP2E1-Transfected Human Liver Cell Lines in Elucidating the Actions of Ethanol

This article represents the proceedings of a symposium at the 2004 RSA Meeting held in Vancouver, Canada. The chairs were Arthur I. Cederbaum and Raj Lakshman. The presentations were (1) ethanol regulates 2,6-sialyltransferase (2,6-ST) gene expression posttranscriptionally by the interaction of a cytosolic binding protein with 2,6-ST mRNA in CYP2E1- and ADH-transfected HepG2 cells, by Raj Lakshman; (2) nature versus nurture: HepG2-E47 cells as a tool to investigate mechanisms of ethanol-mediated potentiation of cell killing, by Jan B. Hoek; (3) ethanol up-regulates profibrogenic connective tissue growth factor gene expression in HepG2 cells via cytochrome P-450 2E1-mediated ethanol oxidation, by Masahiro Konishi; (4) role of calcium and calcium-activated enzymes in CYP2E1-dependent toxicity, by Arthur I Cederbaum; (5) the use of cell lines to characterize the role of CYP2E1 in the metabolism of farnesol, by Dennis Koop; and (6) studies with HepG2 cells that express the two major ethanol-metabolizing enzymes, by Terrence M. Donohue.

Monitoring farnesol-induced toxicity in tobacco BY-2 cells with a fluorescent analog

In a previous study (A. Hemmerlin, T.J. Bach, Plant Physiol. 123 (2000) 1257-1268), we have demonstrated that above a critical concentration, treatment with all-trans-farnesol induces cell-death in Nicotiana tabacum L. cv Bright Yellow-2 (TBY-2) cells. Now we used a fluorescent analog of farnesol (Fol(FLUO)), in which an isoprene unit is replaced by the fluorochrome 7-nitrobenz-2-oxa-1,3-diazol-4-yl, to visualize how cell integrity is affected. Fol(FLUO) exhibited the same toxicity as the natural compound and was shown to be readily taken up by TBY-2 cells, followed by integration into subcellular membrane structures. Although the plasma membrane seemed not to be labeled, Fol(FLUO) was associated with the tonoplast, endoplasmic reticulum, and Golgi apparatus or lipid bodies. Longer exposure times and increased Fol(FLUO) accumulation triggered the formation and proliferation of new membrane structures of as yet unknown function. Finally, at even higher and clearly cytotoxic concentrations of the analog, the cell contents became clearly disorganized, with cell swelling and ultimately plasmolysis.

Cytochrome P450 and xenobiotic receptor humanized mice

Most xenobiotics that enter the body are subjected to metabolism that functions primarily to facilitate their elimination. Metabolism of certain xenobiotics can also result in the production of electrophilic derivatives that can cause cell toxicity and transformation. Many xenobiotics can also activate receptors that in turn induce the expression of genes encoding xenobiotic-metabolizing enzymes and xenobiotic transporters. However, there are marked species differences in the way mammals respond to xenobiotics, which are due in large part to molecular differences in receptors and xenobiotic-metabolizing enzymes. This presents a problem in extrapolating data obtained with rodent model systems to humans. There are also polymorphisms in xenobiotic-metabolizing enzymes that can impact drug therapy and cancer susceptibility. In an effort to generate more reliable in vivo systems to study and predict human response to xenobiotics, humanized mice are under development.

Expanding the alkane oxygenase toolbox: new enzymes and applications

As highly reduced hydrocarbons are abundant in the environment, enzymes that catalyze the terminal or subterminal oxygenation of alkanes are relatively easy to find. A number of these enzymes have been biochemically characterized in detail, because the potential of alkane hydroxylases to catalyze high added-value reactions is widely recognized. Nevertheless, the industrial application of these enzymes is restricted owing to the complex biochemistry, challenging process requirements, and the limited number of cloned and expressed enzymes. Rational and evolutionary engineering approaches have started to yield more robust and versatile enzyme systems, broadening the alkane oxygenase portfolio. In addition, metagenomic approaches provide access to many novel alkane oxygenase sequences.

Modulation of hepatic and renal drug metabolizing enzyme activities in rats by subchronic administration of farnesol

Farnesol demonstrates antitumor activity in several animal models for human cancer and was being considered for development as a cancer chemopreventive agent. This study was performed to characterize the effects of minimally toxic doses of farnesol on the activity of phase I and II drug metabolizing enzymes. CD((R)) rats (20/sex/group) received daily gavage exposure to farnesol doses of 0, 500, or 1000 mg/kg/day for 28 days; 10 rats/sex/group were necropsied at the termination of farnesol exposure; remaining animals were necropsied after a 28-day recovery period. No deaths occurred during the study, and farnesol had no significant effects on body weight, food consumption, clinical signs, or hematology/coagulation parameters. Modest but statistically significant alterations in several clinical chemistry parameters were observed at the termination of farnesol exposure; all clinical pathology effects were reversed during the recovery period. At the termination of dosing, the activities of CYP1A, CYP2A1-3, CYP2B1/2, CYP2C11/12, CYP2E1, CYP3A1/2, CYP4A1-3, CYP19, glutathione reductase, NADPH/quinone oxidoreductase and UDP-glucuronosyltransferase were significantly increased in the livers of farnesol-treated rats; farnesol also increased the activity of glutathione S-transferase in the kidney. The effects of farnesol on hepatic and renal enzymes were reversed during the recovery period. At the end of the dosing period, increases in absolute and relative liver and kidney weights were seen in farnesol-treated rats. These increases may be secondary to induction of drug metabolizing enzymes, since organ weight increases were not associated with histopathologic alterations and were reversed upon discontinuation of farnesol exposure. Administration of farnesol at doses of up to 1000 mg/kg/day induced reversible increases in the activities of several hepatic and renal drug metabolizing enzymes in rats, while inducing only minimal toxicity. It is concluded that non-toxic or minimally toxic doses of farnesol could alter the metabolism, efficacy, and/or toxicity of drugs with which it is co-administered.