Check out our New Publishers' Select for Free Articles

Biochemical Pharmacology (v.81, #6)

Editorial Advisory Board (pp. iii).

Strategies for the identification of allosteric modulators of G-protein-coupled receptors by Neil T. Burford; John Watson; Robert Bertekap; Andrew Alt (pp. 691-702).

Once considered a pharmacological curiosity, allosteric modulation of seven transmembrane domain G-protein-coupled receptors (GPCRs) has emerged as a potentially powerful means to affect receptor function for therapeutic purposes. Allosteric modulators, which interact with binding sites topologically distinct from the orthosteric ligand binding sites, can potentially provide improved selectivity and safety, along with maintenance of spatial and temporal aspects of GPCR signaling. Accordingly, drug discovery efforts for GPCRs have increasingly focused on the identification of allosteric modulators. This review is devoted to an examination of the strategies, challenges, and opportunities for high-throughput screening for allosteric modulators of GPCRs, with particular focus on the identification of positive allosteric modulators.

Keywords: Abbreviations; GPCR; G-protein-coupled receptor; PAM; positive allosteric modulator; NAM; negative allosteric modulator; SAM; silent allosteric modulator; NAL; neutral allosteric ligand; HTS; high-throughput screening; cAMP; 3′-5′-cyclic adenosine monophosphate; mGluR; metabotropic glutamate receptor; CaSR; calcium-sensing receptor; MAPK; mitogen-activated protein kinaseG-protein-coupled receptors; Allosteric modulators; High-throughput screening; Ca; ²⁺; signaling

Plasma membrane repair and cellular damage control: The annexin survival kit by Annette Draeger; Katia Monastyrskaya; Eduard B. Babiychuk (pp. 703-712).

Plasmalemmal injury is a frequent event in the life of a cell. Physical disruption of the plasma membrane is common in cells that operate under conditions of mechanical stress. The permeability barrier can also be breached by chemical means: pathogens gain access to host cells by secreting pore-forming toxins and phospholipases, and the host's own immune system employs pore-forming proteins to eliminate both pathogens and the pathogen-invaded cells. In all cases, the influx of extracellular Ca²⁺ is being sensed and interpreted as an “immediate danger” signal.Various Ca²⁺-dependent mechanisms are employed to enable plasma membrane repair. Extensively damaged regions of the plasma membrane can be patched with internal membranes delivered to the cell surface by exocytosis. Nucleated cells are capable of resealing their injured plasmalemma by endocytosis of the permeabilized site. Likewise, the shedding of membrane microparticles is thought to be involved in the physical elimination of pores. Membrane blebbing is a further damage-control mechanism, which is triggered after initial attempts at plasmalemmal resealing have failed.The members of the annexin protein family are ubiquitously expressed and function as intracellular Ca²⁺ sensors. Most cells contain multiple annexins, which interact with distinct plasma membrane regions promoting membrane segregation, membrane fusion and – in combination with their individual Ca²⁺-sensitivity – allow spatially confined, graded responses to membrane injury.

Keywords: Plasmalemma; Annexins; Calcium; Blebbing; Microparticles; Pore-forming toxins

Effects of hippuristanol, an inhibitor of eIF4A, on adult T-cell leukemia by Tomoyuki Tsumuraya; Chie Ishikawa; Yoshiaki Machijima; Sawako Nakachi; Masachika Senba; Junichi Tanaka; Naoki Mori (pp. 713-722).

We evaluated the anti-adult T-cell leukemia (ATL) effects of hippuristanol, an eukaryotic translation initiation inhibitor from the coral Isis hippuris. Hippuristanol inhibited proliferation of HTLV-1-infected T-cell lines and ATL cells, but not normal peripheral blood mononuclear cells. It induced cell cycle arrest during G₁ phase by reducing the expression of cyclin D1, cyclin D2, CDK4 and CDK6, and induced apoptosis by reducing the expression of Bcl-x_L, c-IAP2, XIAP and c-FLIP. The induced apoptosis was associated with activation of caspase-3, -8 and -9. Hippuristanol also suppressed IkappaBalpha phosphorylation and depleted IKKalpha, IKKgamma, JunB and JunD, resulting in inactivation of NF-kappaB and AP-1. It also suppressed carbonic anhydrase type II expression. In addition to its in vitro effects, hippuristanol suppressed tumor growth in mice with severe combined immunodeficiency harboring tumors induced by inoculation of HTLV-1-infected T cells. These preclinical data suggest that hippuristanol could be a potentially useful therapeutic agent for patients with ATL.

Keywords: ATL; Hippuristanol; NF-kappaB; AP-1; eIF4A

Molecular docking and pharmacogenomics of Vinca alkaloids and their monomeric precursors, vindoline and catharanthine by Serkan Sertel; Yujie Fu; Yuangang Zu; Blanka Rebacz; Badireenath Konkimalla; Peter K. Plinkert; Alwin Krämer; Jürg Gertsch; Thomas Efferth (pp. 723-735).

Vinblastine produced high fractions of mono- and multipolar mitotic spindles, while its monomeric precursor molecules, vindoline and catharanthine did only weakly affect spindle formation.Vinblastine and vincristine are dimeric indole alkaloids derived from Catharanthus roseus (formerly: Vinca rosea). Their monomeric precursor molecules are vindoline and catharanthine. While vinblastine and vincristine are well-known mitotic spindle poisons, not much is known about vindoline and catharanthine. Vindoline and catharanthine showed weak cytotoxicity, while vinblastine, vincristine, and the semisynthetic vindesine and vinorelbine revealed high cytotoxicity towards cancer cells. This may reflect a general biological principle of poisonous plants. Highly toxic compounds are not only active towards predators, but also towards plant tissues. Hence, plants need mechanisms to protect themselves from their own poisons. One evolutionary strategy to solve this problem is to generate less toxic precursors, which are dimerized to toxic end products when needed. As shown by in silico molecular docking and biochemical approaches, vinblastine, vincristine and vinorelbine bound with high affinity to α/β-tubulin and inhibited tubulin polymerization, whereas the effects of vindoline and catharanthine were weak. Similarly, vinblastine produced high fractions of mono- and multipolar mitotic spindles, while vindoline and catharanthine did only weakly affect bipolar mitotic spindle formation. Here, we show that vinblastine contributes to cell death by interference with spindle polarity. P-glycoprotein-overexpressing multidrug-resistant CEM/VCR1000 cells were highly resistant towards vincristine and cross-resistant to vinblastine, vindesine, and vinorelbine, but not or only weakly cross-resistant to vindoline and catharanthine. In addition to tubulin as primary target, microarray-based mRNA signatures of responsiveness of these compounds have been identified by COMPARE and signaling pathway profiling.

Keywords: Abbreviations; ABC transporter; ATP-binding cassette transporter; HNSCC; head and neck squamous cell carcinoma; IC; ₅₀; 50% inhibition concentration; RMSD; root mean square deviations; mRNA; messenger RNA; NCI; national cancer instituteCentrosomal clustering; Molecular docking; Multidrug resistance; Pharmacogenomics; Vinca alkaloids

Bj-PRO-5a, a natural angiotensin-converting enzyme inhibitor, promotes vasodilatation mediated by both bradykinin B₂ and M1 muscarinic acetylcholine receptors by K.L.P. Morais; M.A.F. Hayashi; F.M. Bruni; M. Lopes-Ferreira; A.C.M. Camargo; H. Ulrich; C. Lameu (pp. 736-742).

Bradykinin-potentiating peptides (BPPs) or proline-rich oligopeptides (PROs) isolated from the venom glands of Bothrops jararaca ( Bj) were the first natural inhibitors of the angiotensin-converting enzyme (ACE) described. Bj-PRO-5a (Bj-PROs have been identified with higher ACE inhibition potency compared to Bj-PRO-5a. However, despite its modest inhibitory effect of ACE inhibition, Bj-PRO-5a reveals strong bradykinin-potentiating activity, suggesting the participation of other mechanisms for this peptide. In the present study, we have shown that Bj-PRO-5a induced nitric oxide (NO) production depended on muscarinic acetylcholine receptor M1 subtype (mAchR-M1) and bradykinin B₂ receptor activation, as measured by a chemiluminescence assay using a NO analyzer. Intravital microscopy based on transillumination of mice cremaster muscle also showed that both bradykinin B₂ receptor and mAchR-M1 contributed to the vasodilatation induced by Bj-PRO-5a. Moreover, Bj-PRO-5a-mediated vasodilatation was completely blocked in the presence of a NO synthase inhibitor. The importance of this work lies in the definition of novel targets for Bj-PRO-5a in addition to ACE, the structural model for captopril development.

Keywords: Abbreviations; ACE; angiotensin-converting enzyme; ASS; argininosuccinate synthase; Bj; Bothrops jararaca; BK; bradykinin; BPPs; bradykinin-potentiating peptides; Bj; -PROs; proline-rich oligopeptides from the venom glands of; Bothrops jararaca; venom glands; HEK; human embryonic kidney; CHO; Chinese hamster ovarian; [Ca; ²⁺; ]; _i; intracellular calcium concentration; eNOS; endothelial nitric oxide synthase; l; -NMMA; N; ^G; -methyl-; l; -arginine acetate salt; mAchR; muscarinic acetylcholine receptor; mAchR-M1; muscarinic acetylcholine receptor M1 subtype; NO; nitric oxide; PLC-γ; phospholipase C-γKey words; Bradykinin-potentiating peptides; Bradykinin B; ₂; receptor; Muscarinic acetylcholine receptor; Nitric oxide; Proline-rich oligopeptide

Anti-inflammatory actions of a taurine analogue, ethane β-sultam, in phagocytic cells, in vivo and in vitro by Roberta J. Ward; Frederic Lallemand; Philippe de Witte; Robert R. Crichton; Jacques Piette; Keith Tipton; Karl Hemmings; Arnaud Pitard; Mike Page; Laura Della Corte; Deanna Taylor; David Dexter (pp. 743-751).

The ability of a taurine prodrug, ethane β-sultam, to reduce cellular inflammation has been investigated, in vitro, in primary cultures of alveolar macrophages and an immortilised N9 microglial cell line and in vivo in an animal model of inflammation and control rats. Ethane β-sultam showed enhanced ability to reduce the inflammatory response in alveolar macrophages, as assayed by the lipopolysaccharide-stimulated–nitric oxide release, (LPS stimulated-NO), in comparison to taurine both in vitro (10nM, 50nM) and in vivo (0.15mmol/kg/day by gavage). In addition, ethane β-sultam, (50, 100 and 1000nM) significantly reduced LPS-stimulated glutamate release from N9 microglial cells to a greater extent than taurine. The anti-inflammatory response of taurine was shown to be mediated via stabilisation of IkBα. The use of a taurine prodrug as therapeutic agents, for the treatment of neurological conditions, such as Parkinson's and Alzheimer's disease and alcoholic brain damage, where activated phagocytic cells contribute to the pathogenesis, may be of great potential.

Keywords: Abbreviations; NO; nitric oxide; TauT; taurine transporter; LPS; lipopolysaccharide; ROS; reactive oxygen species; IκB; IkappaB; IκBα; IκBalpha; NFκB; nuclear factor kappaB; TNFα; tumor necrosis factor alphaTaurine; Anti-inflammatory action; Ethane-β sultam; Nitric oxide; Glutamate

1,3,5-Trihydroxy-4-prenylxanthone represses lipopolysaccharide-induced iNOS expression via impeding posttranslational modification of IRAK-1 by Wen-Fei Chiou; Chien-Chih Chen; I.-Hsin Lin; Jen-Hwey Chiu; Yi-Ju Chen (pp. 752-760).

TH-4-PX inhibited LPS-induced iNOS expression by interference with the posttranslational modification of IRAK-1 resulted in blocking TAK1-mediated activation of IKK and MAPKs signal transduction to down-regulate NF-κB and AP-1 activation.Both high level of nitric oxide (NO) and its generating enzyme, inducible NO synthase (iNOS), play important roles in pathophysiological conditions such as inflammatory processes. We previously found that 1,3,5-trihydroxy-4-prenylxanthone (TH-4-PX) isolated from Cudrania cochinchinensis repressed lipopolysaccharide (LPS)-induced NO production in RAW264.7 macrophages. Here we further examined the underlying mechanisms using RT-PCR and Western blot analyses. Consistent with NO inhibition, suppression of LPS-induced iNOS expression by TH-4-PX through abolishing IκB kinase (IKK) phosphorylation, IκB degradation and nuclear factor-κB (NF-κB) nuclear translocation was observed. After LPS stimulation, the increased nuclear level of c-Fos and c-Jun (major components of activator protein-1, AP-1) and the phosphorylated level of upstream signal molecules, such as c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase, (ERK) were all significantly suppressed by TH-4-PX, while p38 remained unaffected. A further experiment revealed that TH-4-PX inhibited the phosphorylation of transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1), an upstream signaling molecule required for IKK and mitogen-activated protein kinases (MAPKs) activation. Stimulation with LPS also triggered the modification (phosphorylation and ubiquitination) and eventually the proteasomal degradation of membrane-associated interleukin (IL)-1 receptor-associated serine/threonine kinase 1 (IRAK-1), an essential signaling component to toll-like receptor (TLR)-mediated TAK-1 activation. Interestingly, the modified pattern of IRAK-1 in the presence LPS was significantly attenuated by TH-4-PX treatment. In conclusion, TH-4-PX inhibited LPS-induced NF-κB and AP-1 activations by interfering with the posttranslational modification (phosphorylation and/or ubiquitinylation) of IRAK-1 in the cell membrane to impede TAK1-mediated activation of IKK and MAPKs signal transduction.

Keywords: 1,3,5-Trihydroxy-4-prenylxanthone; Lipopolysaccharide; Inducible nitric oxide synthase; Interleukin (IL)-1 receptor-associated serine/threonine kinase 1; Transforming growth factor β -activated kinase-1

In vitro liver metabolism of aclidinium bromide in preclinical animal species and humans: Identification of the human enzymes involved in its oxidative metabolism by Joan J. Albertí; Sònia Sentellas; Miquel Salvà (pp. 761-776).

The metabolism of aclidinium bromide, a novel long-acting antimuscarinic drug for the maintenance treatment of chronic obstructive pulmonary disorder, has been investigated in liver microsomes and hepatocytes of mice, rats, rabbits, dogs, and humans. Due to the rapid hydrolysis of this ester compound, two distinct radiolabeled forms of aclidinium were studied. The main biotransformation route of aclidinium was the hydrolytic cleavage of the ester moiety, resulting in the formation of the alcohol metabolite (M2, LAS34823) and carboxylic acid metabolite (m3, LAS34850), which mainly occurred non-enzymatically. By comparison, the oxidative metabolism was substantially lower and the metabolite profiles were similar across all five species examined. Aclidinium was metabolized oxidatively to four minor primary metabolites that were identified as monohydroxylated derivatives of aclidinium at the phenyl (M4) and glycolyl (m6 and m7) moieties of the molecule. The NADPH-dependent metabolite m4 involved the loss of one of the thiophene rings of aclidinium. Incubations with human recombinant P450 isoforms and inhibition studies with selective chemical inhibitors and antibodies of human P450 enzymes demonstrated that the oxidative metabolism of aclidinium is primarily mediated by CYP3A4 and CYP2D6. Additionally, up to eight secondary metabolites were also characterized, involving further hydrolysis, oxidation, or glucuronidation of the primary metabolites. Also, the liver oxidative metabolism of the alcohol metabolite (LAS34823) resulted in the production of one hydroxylated metabolite (M1) mediated by human CYP2D6, whereas the acid metabolite (LAS34850) was not metabolized enzymatically, although a minor non-enzymatic and NADPH-dependent reduction was observed.

Keywords: Abbreviations; AB; aclidinium bromide; BChE; butyrylcholinesterase; CID; collision-induced dissociation; P450; cytochrome P450; ESI; electrospray ionization; FMO; flavin-containing monooxigenases; glyc; glycolyl; K; _h; hydrolysis rate constant; LC; liquid chromatography; MRM; multiple reaction monitoring; MS; mass spectrometry; m; /; z; mass-to-charge ratio; phe; phenyl; SPE; solid-phase extraction; TEA; triethylamineAclidinium bromide; In vitro metabolism; Interspecies differences; Enzyme identification

Isoform-specific regulation of cytochrome P450 expression and activity by estradiol in female rats by Su-Young Choi; Liam Fischer; Kyunghee Yang; Hyejin Chung; Hyunyoung Jeong (pp. 777-782).

Estradiol may not be responsible for the changes in drug metabolism by major CYP enzymes during human pregnancy.Estradiol (E2) is the major endogenous estrogen, and its plasma concentration increases up to 100-fold during pregnancy in humans. Accumulating evidence suggests that an elevated level of E2 may influence hepatic drug metabolism, potentially being responsible for altered drug metabolism during pregnancy. We characterized effects of E2 on expression and activities of cytochrome P450 enzymes (CYPs) in an in vivo system using rats. To this end, female rats were treated with estradiol benzoate (EB) or known CYP inducers. Liver tissues were obtained after 5 days of treatment, and mRNA and protein expression levels as well as activities of major hepatic CYPs were determined by qRT-PCR, immunoblot, and microsomal assay. E2 increased CYP1A2 expression and activity to a smaller extent than β-naphthoflavone did. E2 also enhanced CYP2C expression (CYP2C6, CYP2C7, and CYP2C12) to levels comparable to those observed by phenobarbital. E2 upregulated CYP3A9 expression, while expression of CYP3A1 was downregulated. Expression of hepatic nuclear receptors (PXR and CAR) and the obligate redox partner of CYPs (POR) was downregulated in EB-treated rats, suggesting their potential involvement in regulation of CYP expression and activity by E2. In summary, in female rats E2 regulates expression of hepatic CYPs in a CYP isoform-specific manner although the directional changes are different from those clinically observed during human pregnancy. Further study is warranted to determine whether the changes in drug metabolism during human pregnancy are attributable to involvement of hormones other than E2.

Keywords: Abbreviations; AhR; aryl hydrocarbon receptor; BNF; β-naphthoflavone; CAR; constitutive androstane receptor; CYP; cytochrome P450; DX; dexamethasone; E2; 17β-estradiol; EB; estradiol benzoate; PB; phenobarbital; POR; P450 oxidoreductase; PXR; pregnane X receptorCytochrome P450; Estradiol; Nuclear receptors; p450 oxidoreductase; Pregnancy; Rat

Breast cancer resistance protein BCRP/ABCG2 regulatory microRNAs (hsa-miR-328, -519c and -520h) and their differential expression in stem-like ABCG2+ cancer cells by Xin Li; Yu-Zhuo Pan; Gail M. Seigel; Zi-Hua Hu; Min Huang; Ai-Ming Yu (pp. 783-792).

Hsa-miR-519c and -328 showed a more profound impact on BCRP/ABCG2 expression than miR-520h in human breast cancer cells.Recent studies have shown that a number of microRNAs (miRNA or miR) may regulate human breast cancer resistance protein (BCRP/ABCG2), an important efflux transporter responsible for cellular drug disposition, whereas their effects on ABCG2 protein expression are not compared. In this study, we first identified a new proximal miRNA response element (MRE) for hsa-miR-519c within ABCG2 3′-untranslated region (3′UTR) through computational analyses. This miR-519c MRE site was confirmed using dual luciferase reporter assay and site-directed mutagenesis. Immunoblot analyses indicated that ABCG2 protein expression was significantly down-regulated in MCF-7/MX100 cells after transfection with hsa-miR-328- or -519c expression plasmids, and was markedly up-regulated in MCF-7 cells after transfection with miR-328 or -519c antagomir. However, ABCG2 protein expression was unchanged in MCF-7/MX100 cells after transfection with hsa-miR-520h expression plasmids, which was associated with undetectable miR-520h expression. Furthermore, ABCG2 mRNA degradation was accelerated dramatically in cells transfected with miR-519c expression plasmid, suggesting the involvement of mRNA degradation mechanism. Intervention of miR-328 or -519c signaling led to significant change in intracellular mitoxantrone accumulation, as determined by flow cytometry analyses. In addition, we separated RB143 human retinoblastoma cells into stem-like (ABCG2+) and non-stem-like (ABCG2−) populations through immunomagnetic selection, and found that miR-328, -519c and -520h levels were 9-, 15- and 3-fold lower in the ABCG2+ cells, respectively. Our data suggest that miR-519c and -328 have greater impact on ABCG2 expression than miR-520h in MCF-7 human breast cancer cells, and the presence of proximal miR-519c MRE explains the action of miR-519c on shortened ABCG2 3′UTR.

Keywords: Abbreviations; miRNA; microRNA; BCRP/ABCG2; breast cancer resistance protein/ATP-binding cassette, subfamily G (white), member 2; hsa-miR-328; human microRNA-328; miR-519c; microRNA-519c; miR-520 h; microRNA-520h; MRE; microRNA response element; 3′UTR; 3′-untranslated region; ALDH1A1; aldehyde dehydrogenase 1A1; MDR1/ABCB1; P-glycoprotein; MRP1/ABCC1; multidrug resistance-associated protein 1; FTC; fumitremorgin C; PBS; phosphate-buffered salinemiRNA; BCRP/ABCG2; Drug disposition; Gene regulation; Epigenetic; Multidrug resistance; Stem cell; Breast cancer; Retinoblastoma

Carboxyl-terminus of Hsc70 interacting protein mediates 2,5-hexanedione-induced neurofilament medium chain degradation by Qingshan Wang; Fuyong Song; Cuili Zhang; Xiulan Zhao; Zhenping Zhu; Sufang Yu; Keqin Xie (pp. 793-799).

Neurofilaments (NFs), the most abundant cytoskeletal components in large neurons and myelinated axons, are the targets of n-hexane-induced neuropathy, in which a specific loss of NFs protein has been frequently observed. However, the precise mechanisms regulating NFs contents are not well understood. The aim of this study was to elucidate the role of ubiquitin–proteasome system (UPS) in NFs degradation. We first demonstrated that the E3 ligase carboxyl-terminus of Hsc70 interacting protein (CHIP), originally identified as a co-chaperone of Hsc70, directly interacted with NFs medium chain (NF-M) and then enhanced NF-M ubiquitination and degradation after 2,5-hexanedione (HD) treatment. Consistent with this result, the application of proteasome inhibitor MG132 partly reversed HD-induced decrease of NF-M. Finally, we found that other components of UPS system (e.g. ubiquitin-activating enzyme E1, CHIP and proteasome) were significantly increased in sciatic nerve of HD-intoxicated rats. In conclusion, this study indicated that the CHIP ubiquitin ligase complex interacted with and repressed NFs by targeting NFs for ubiquitin-mediated proteolysis, which led to reduction of NFs contents in HD-induced neuropathy.

Keywords: Abbreviations; NFs; neurofilaments; HD; 2,5-hexanedione; CHIP; carboxyl-terminus of Hsc70 interacting protein; NF-M; neurofilament medium chain; UPS; ubiquitin proteasome system; IFs; intermediate filaments; CHX; cycloheximide; TPR; tetratricopeptide repeat; UbmE1; ubiquitin-activating enzyme 1; AD; Alzheimer's disease; PD; Parkinson's disease; Aβ; β-amyloid; CaMKII; Ca; ²⁺; /calmodulin-dependent protein kinase II; PKC; protein kinase Cn-Hexane; Ubiquitin–proteasome system; Neurofilaments; Neurotoxicity

Protective efficacy of catalytic bioscavenger, paraoxonase 1 against sarin and soman exposure in guinea pigs by Manojkumar Valiyaveettil; Yonas Alamneh; Peter Rezk; Lionel Biggemann; Michael W. Perkins; Alfred M. Sciuto; Bhupendra P. Doctor; Madhusoodana P. Nambiar (pp. 800-809).

Human paraoxonase 1 (PON1) has been portrayed as a catalytic bioscavenger which can hydrolyze large amounts of chemical warfare nerve agents (CWNAs) and organophosphate (OP) pesticides compared to the stoichiometric bioscavengers such as butyrylcholinesterase. We evaluated the protective efficacy of purified human and rabbit serum PON1 against nerve agents sarin and soman in guinea pigs. Catalytically active PON1 purified from human and rabbit serum was intravenously injected to guinea pigs, which were 30min later exposed to 1.2×LCt₅₀ sarin or soman using a microinstillation inhalation exposure technology. Pre-treatment with 5 units of purified human and rabbit serum PON1 showed mild to moderate increase in the activity of blood PON1, but significantly increased the survival rate with reduced symptoms of CWNA exposure. Although PON1 is expected to be catalytic, sarin and soman exposure resulted in a significant reduction in blood PON1 activity. However, the blood levels of PON1 in pre-treated animals after exposure to nerve agent were higher than that of untreated control animals. The activity of blood acetylcholinesterase and butyrylcholinesterase and brain acetylcholinesterase was significantly higher in PON1 pre-treated animals and were highly correlated with the survival rate. Blood O₂ saturation, pulse rate and respiratory dynamics were normalized in animals treated with PON1 compared to controls. These results demonstrate that purified human and rabbit serum PON1 significantly protect against sarin and soman exposure in guinea pigs and support the development of PON1 as a catalytic bioscavenger for protection against lethal exposure to CWNAs.

Keywords: Abbreviations; PON1; paraoxonase 1; HPON1; human PON1; RPON1; rabbit PON1; OP; organophosphate; CWNA; chemical warfare nerve agent; DFP; diisopropylfluorophosphate; CPO; chlorpyrifos oxon; AChE; acetylcholinesterase; ACh; acetylcholine; BChE; butyrylcholinesterase; p-NPA; p-nitrophenyl acetate; DTNB; dithionitrobenzoic acid; DTP; 44′-dipyridyl disulfide, 4,4′-dithiodipyridine; Iso-OMPA; tetra monoisopropyl pyrophosphor-tetramide; SDS-PAGE; sodium dodecyl sulfate polyacrylamide gel electrophoresis; Sarin; 2-(fluoro-methylphosphoryl)oxypropane; Soman; 2-(fluoromethylphosphoryl) oxy-3,3-dimethylbutaneChemical warfare nerve agents; Sarin; Soman; Catalytic bioscavenger; Paraoxonase 1

The food colorant erythrosine is a promiscuous protein–protein interaction inhibitor by Lakshmi Ganesan; Emilio Margolles-Clark; Yun Song; Peter Buchwald (pp. 810-818).

Following our observation that erythrosine B (FD&C Red No. 3) is a relatively potent inhibitor of the TNF-R–TNFα and CD40–CD154 protein–protein interactions, we investigated whether this inhibitory activity extends to any other protein–protein interactions (PPI) as well as whether any other approved food colors possess such inhibitory activity. We found erythrosine, a poly-iodinated xanthene dye, to be a non-specific promiscuous inhibitor of a number of PPIs within the tumor necrosis factor superfamily (TNF-R–TNFα, CD40–CD154, BAFF-R–BAFF, RANK–RANKL, OX40–OX40L, 4-1BB–4-1BBL) as well as outside of it (EGF-R–EGF) with a remarkably consistent median inhibitory concentration (IC₅₀) in the 2–20μM (approximately 2–20mg/L) range. In agreement with this, erythrosine also showed cellular effects including clear cytotoxic effects around this concentration range (IC₅₀≈50μM). Among the seven FDA-approved food colorants, only erythrosine showed consistent PPI inhibitory activity in the sub-100μM range, which might also explain (at least partially) why it also has the lowest approved acceptable daily intake (ADI) (0.1mg/kg body weight/day). Among a number of xanthene structural analogs of erythrosine tested for activity, rose Bengal, a food colorant approved in Japan, showed similar, maybe even more pronounced, promiscuous inhibitory activity, whereas fluorescein was inactive and gallein, phloxine, and eosin were somewhat active in some of the assays.

Keywords: Abbreviations; ADI; acceptable daily intake; BAFF; B-cell activating factor (CD257); BrdU; bromodeoxyuridine; BSA; bovine serum albumin; DAPI; 4′,6-diamidino-2-phenylindole; EGF; epidermal growth factor; FBS; fetal bovine serum; HRP; horseradish peroxidase; IC; ₅₀; median inhibitory concentration; K; _d; equilibrium dissociation constant of a ligand–receptor complex; PBS; phosphate buffered saline; PPI; protein–protein interaction; RT; room temperature; TNF; tumor necrosis factorErythrosine; Food color; THP-1 cells; TNF superfamily; Xanthene dyes

Tributyltin chloride induces ABCA1 expression and apolipoprotein A-I-mediated cellular cholesterol efflux by activating LXRalpha/RXR by Hongyan Cui; Keiichiro Okuhira; Nobumichi Ohoka; Mikihiko Naito; Hiroyuki Kagechika; Akihiko Hirose; Tomoko Nishimaki-Mogami (pp. 819-824).

Organotins, including tri-butyltin chloride (TBTC), are widely used in agricultural and chemical industries and cause persistent and widespread pollution. TBTC has been shown to activate nuclear receptor retinoid X receptor (RXR)/PPARγ signaling by interacting with RXR to modulate adipogenesis. However, whether TBTC affects liver X receptor (LXR)/RXR activity and subsequently the expression of cholesterol mobilizing genes is not known. In this study, we evaluated the ability of TBTC to activate LXR/RXR and ABC transporter A1 (ABCA1) expression. ABCA1 plays a critical role in HDL generation, maintaining cholesterol homeostasis, and cholesterol accumulation-induced diseases, such as atherosclerosis and pancreatic islet dysfunction. In a reporter gene assay, TBTC activated LXRα/RXR but not LXRβ/RXR. In mouse macrophage RAW264 cells, TBTC activated the ABCA1 promoter in an LXR-responsive element dependent manner and increased ABCA1 mRNA expression. TBTC augmented ABCA1 protein levels and apolipoprotein A-I-dependent cellular cholesterol efflux (HDL generation). The LXR-target fatty acid synthase and Spα mRNA levels were also increased by TBTC exposure. We conclude that TBTC has the ability to activate permissive LXRα/RXR signaling and thereby modulate cellular cholesterol efflux.

Keywords: Tributyltin chloride; Retinoid X receptor; Liver X receptor; ABCA1; HDL

Sections

Personal tools

Biochemical Pharmacology (v.81, #6)

Sections

Personal tools

Local resources

Biochemical Pharmacology (v.81, #6)