Lipidomic identification of plasma lipids associated with pain behaviour and pathology in a mouse model of osteoarthritis.

INTRODUCTION: Osteoarthritis (OA) is the most common form of joint disease, causing pain and disability. Previous studies have demonstrated the role of lipid mediators in OA pathogenesis. OBJECTIVES: To explore potential alterations in the plasma lipidomic profile in an established mouse model of OA, with a view to identification of potential biomarkers of pain and/or pathology. METHODS: Pain behaviour was assessed following destabilisation of the medial meniscus (DMM) model of OA (n = 8 mice) and compared to sham controls (n = 7). Plasma and knee joints were collected at 16 weeks post-surgery. Plasma samples were analysed using ultra-high performance liquid chromatography accurate mass high resolution mass spectrometry (UHPLC-HR-MS) to identify potential differences in the lipidome, using multivariate and univariate statistical analyses. Correlations between pain behaviour, joint pathology and levels of lipids were investigated. RESULTS: 24 lipids, predominantly from the lipid classes of cholesterol esters (CE), fatty acids (FA), phosphatidylcholines (PC), N-acylethanolamines (NAE) and sphingomyelins (SM), were differentially expressed in DMM plasma compared to sham plasma. Six of these lipids which were increased in the DMM model were identified as CE(18:2), CE(20:4), CE(22:6), PC(18:0/18:2), PC(38:7) and SM(d34:1). CEs were positively correlated with pain behaviour and all six lipid species were positively correlated with cartilage damage. Pathways shown to be involved in altered lipid homeostasis in OA were steroid biosynthesis and sphingolipid metabolism. CONCLUSION: We identify plasma lipid species associated with pain and/or pathology in a DMM model of OA.

Human C-reactive protein aggravates osteoarthritis development in mice on a high-fat diet.

OBJECTIVE: C-reactive protein (CRP) levels can be elevated in osteoarthritis (OA) patients. In addition to indicating systemic inflammation, it is suggested that CRP itself can play a role in OA development. Obesity and metabolic syndrome are important risk factors for OA and also induce elevated CRP levels. Here we evaluated in a human CRP (hCRP)-transgenic mouse model whether CRP itself contributes to the development of 'metabolic' OA. DESIGN: Metabolic OA was induced by feeding 12-week-old hCRP-transgenic males (hCRP-tg, n = 30) and wild-type littermates (n = 15) a 45 kcal% high-fat diet (HFD) for 38 weeks. Cartilage degradation, osteophytes and synovitis were graded on Safranin O-stained histological knee joint sections. Inflammatory status was assessed by plasma lipid profiling, flow cytometric analyses of blood immune cell populations and immunohistochemical staining of synovial macrophage subsets. RESULTS: Male hCRP-tg mice showed aggravated OA severity and increased osteophytosis compared with their wild-type littermates. Both classical and non-classical monocytes showed increased expression of CCR2 and CD86 in hCRP-tg males. HFD-induced effects were evident for nearly all lipids measured and indicated a similar low-grade systemic inflammation for both genotypes. Synovitis scores and synovial macrophage subsets were similar in the two groups. CONCLUSIONS: Human CRP expression in a background of HFD-induced metabolic dysfunction resulted in the aggravation of OA through increased cartilage degeneration and osteophytosis. Increased recruitment of classical and non-classical monocytes might be a mechanism of action through which CRP is involved in aggravating this process. These findings suggest interventions selectively directed against CRP activity could ameliorate metabolic OA development.

Local and systemic inflammatory lipid profiling in a rat model of osteoarthritis with metabolic dysregulation.

OBJECTIVE: Bioactive oxidised lipids (oxylipins) are important signalling mediators, capable of modulating the inflammatory state of the joint and anticipated to be of importance in joint homeostasis and status of osteoarthritis. The aim of this study was to quantify oxylipin levels in plasma and synovial fluid from rats with experimentally induced osteoarthritis to investigate the potential role of oxylipins as a marker in the disease process of early osteoarthritis. DESIGN: Forty rats were randomly allocated to a standard or high-fat diet group. After 12 weeks, local cartilage damage was induced in one knee joint in 14 rats of each diet group. The remaining 6 rats per group served as controls. At week 24, samples were collected. Oxylipin levels were quantified by liquid chromatography-mass spectrometry. RESULTS: Overall, 31 lipid-derived inflammatory mediators were detected in fasted plasma and synovial fluid. Principal component analysis identified four distinct clusters associated with histopathological changes. Diet induced differences were evident for 13 individual plasma oxylipins, as well as 5,6-EET in synovial fluid. Surgical-model induced differences were evident for three oxylipins in synovial fluid (15-HETE, 8,9-DHET and 17R-ResolvinD1) with a different response in lipid concentrations for synovial fluid and plasma. CONCLUSIONS: We demonstrate the quantification of oxidised lipids in rat plasma and synovial fluid in a model of early experimental osteoarthritis. Oxylipins in the synovial fluid that were altered as consequence of the surgically induced osteoarthritis were not represented in the plasma. Our findings suggest differential roles of the oxylipins in the local versus peripheral compartment.

The fitness burden imposed by synthesising quorum sensing signals.

It is now well established that bacterial populations utilize cell-to-cell signaling (quorum-sensing, QS) to control the production of public goods and other co-operative behaviours. Evolutionary theory predicts that both the cost of signal production and the response to signals should incur fitness costs for producing cells. Although costs imposed by the downstream consequences of QS have been shown, the cost of QS signal molecule (QSSM) production and its impact on fitness has not been examined. We measured the fitness cost to cells of synthesising QSSMs by quantifying metabolite levels in the presence of QSSM synthases. We found that: (i) bacteria making certain QSSMs have a growth defect that exerts an evolutionary cost, (ii) production of QSSMs negatively correlates with intracellular concentrations of QSSM precursors, (iii) the production of heterologous QSSMs negatively impacts the production of a native QSSM that shares common substrates, and (iv) supplementation with exogenously added metabolites partially rescued growth defects imposed by QSSM synthesis. These data identify the sources of the fitness costs incurred by QSSM producer cells, and indicate that there may be metabolic trade-offs associated with QS signaling that could exert selection on how signaling evolves.

Partial restoration of protein synthesis rates by the small molecule ISRIB prevents neurodegeneration without pancreatic toxicity.

Activation of the PERK branch of the unfolded protein response (UPR) in response to protein misfolding within the endoplasmic reticulum (ER) results in the transient repression of protein synthesis, mediated by the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2α). This is part of a wider integrated physiological response to maintain proteostasis in the face of ER stress, the dysregulation of which is increasingly associated with a wide range of diseases, particularly neurodegenerative disorders. In prion-diseased mice, persistently high levels of eIF2α cause sustained translational repression leading to catastrophic reduction of critical proteins, resulting in synaptic failure and neuronal loss. We previously showed that restoration of global protein synthesis using the PERK inhibitor GSK2606414 was profoundly neuroprotective, preventing clinical disease in prion-infected mice. However, this occured at the cost of toxicity to secretory tissue, where UPR activation is essential to healthy functioning. Here we show that pharmacological modulation of eIF2α-P-mediated translational inhibition can be achieved to produce neuroprotection without pancreatic toxicity. We found that treatment with the small molecule ISRIB, which restores translation downstream of eIF2α, conferred neuroprotection in prion-diseased mice without adverse effects on the pancreas. Critically, ISRIB treatment resulted in only partial restoration of global translation rates, as compared with the complete restoration of protein synthesis seen with GSK2606414. ISRIB likely provides sufficient rates of protein synthesis for neuronal survival, while allowing some residual protective UPR function in secretory tissue. Thus, fine-tuning the extent of UPR inhibition and subsequent translational de-repression uncouples neuroprotective effects from pancreatic toxicity. The data support the pursuit of this approach to develop new treatments for a range of neurodegenerative disorders that are currently incurable.

Increased function of pronociceptive TRPV1 at the level of the joint in a rat model of osteoarthritis pain.

OBJECTIVES: Blockade of transient receptor potential vanilloid 1 (TRPV1) with systemic antagonists attenuates osteoarthritis (OA) pain behaviour in rat models, but on-target-mediated hyperthermia has halted clinical trials. The present study investigated the potential for targeting TRPV1 receptors within the OA joint in order to produce analgesia. METHODS: The presence of TRPV1 receptors in human synovium was detected using western blotting and immunohistochemistry. In a rat model of OA, joint levels of an endogenous ligand for TRPV1, 12-hydroxy-eicosatetraenoic acid (12-HETE), were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Effects of peripheral administration of the TRPV1 receptor antagonist JNJ-17203212 on afferent fibre activity, pain behaviour and core body temperature were investigated. Effects of a spinal administration of JNJ-17203212 on dorsal horn neuronal responses were studied. RESULTS: We demonstrate increased TRPV1 immunoreactivity in human OA synovium, confirming the diseased joint as a potential therapeutic target for TRPV1-mediated analgesia. In a model of OA pain, we report increased joint levels of 12-HETE, and the sensitisation of joint afferent neurones to mechanical stimulation of the knee. Local administration of JNJ-17203212 reversed this sensitisation of joint afferents and inhibited pain behaviour (weight-bearing asymmetry), to a comparable extent as systemic JNJ-17203212, in this model of OA pain, but did not alter core body temperature. There was no evidence for increased TRPV1 function in the spinal cord in this model of OA pain. CONCLUSIONS: Our data provide a clinical and mechanistic rationale for the future investigation of the therapeutic benefits of intra-articular administration of TRPV1 antagonists for the treatment of OA pain.

Chemically diverse polymer microarrays and high throughput surface characterisation: a method for discovery of materials for stem cell culture†Electronic supplementary information (ESI) available. See DOI: 10.1039/c4bm00054dClick here for additional data file.

Materials discovery provides the opportunity to identify novel materials that are tailored to complex biological environments by using combinatorial mixing of monomers to form large libraries of polymers as micro arrays. The materials discovery approach is predicated on the use of the largest chemical diversity possible, yet previous studies into human pluripotent stem cell (hPSC) response to polymer microarrays have been limited to 20 or so different monomer identities in each study. Here we show that it is possible to print and assess cell adhesion of 141 different monomers in a microarray format. This provides access to the largest chemical space to date, allowing us to meet the regenerative medicine challenge to provide scalable synthetic culture ware. This study identifies new materials suitable for hPSC expansion that could not have been predicted from previous knowledge of cell-material interactions.

Spinal administration of the monoacylglycerol lipase inhibitor JZL184 produces robust inhibitory effects on nociceptive processing and the development of central sensitization in the rat.

BACKGROUND AND PURPOSE: The cannabinoid receptor-mediated analgesic effects of 2-arachidonoylglycerol (2-AG) are limited by monoacylglycerol lipase (MAGL). 4-nitrophenyl 4-[bis (1,3-benzodioxol-5-yl) (hydroxy) methyl] piperidine-1-carboxylate (JZL184) is a potent inhibitor of MAGL in the mouse, though potency is reportedly reduced in the rat. Here we have assessed the effects of spinal inhibition of MAGL with JZL184 on nociceptive processing in rats. EXPERIMENTAL APPROACH: In vivo spinal electrophysiological assays in anaesthetized rats were used to determine the effects of spinal administration of JZL184 on spinal nociceptive processing in the presence and absence of hindpaw inflammation. Contributions of CB(1) receptors to these effects was assessed with AM251. Inhibition of 2-oleoylglycerol hydrolytic activity and alterations of 2-AG in the spinal cord after JZL 184 were also assessed. KEY RESULTS: Spinal JZL184 dose-dependently inhibited mechanically evoked responses of wide dynamic range (WDR) neurones in naïve anaesthetized rats, in part via the CB(1) receptor. A single spinal administration of JZL184 abolished inflammation-induced expansion of the receptive fields of spinal WDR neurones. However, neither spinal nor systemic JZL184 altered levels of 2-AG, or 2-oleoylglycerol hydrolytic activity in the spinal cord, although JZL184 displayed robust inhibition of MAGL when incubated with spinal cord tissue in vitro. CONCLUSIONS AND IMPLICATIONS: JZL184 exerted robust anti-nociceptive effects at the level of the spinal cord in vivo and inhibited rat spinal cord MAGL activity in vitro. The discordance between in vivo and in vitro assays suggests that localized sites of action of JZL184 produce these profound functional inhibitory effects. LINKED ARTICLES: This article is part of a themed section on Cannabinoids. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.167.issue-8.

Surface analysis using a new plasma assisted desorption/ionisation source for mass spectrometry in ambient air.

The authors report on a modified micro-plasma assisted desorption/ionisation (PADI) device which creates plasma through the breakdown of ambient air rather than utilising an independent noble gas flow. This new micro-PADI device is used as an ion source for ambient mass spectrometry to analyse species released from the surfaces of polytetrafluoroethylene, and generic ibuprofen and paracetamol tablets through remote activation of the surface by the plasma. The mass spectra from these surfaces compare favourably to those produced by a PADI device constructed using an earlier design and confirm that the new ion source is an effective device which can be used to achieve ambient mass spectrometry with improved spatial resolution.

Effects of COX-2 inhibition on spinal nociception: the role of endocannabinoids.

BACKGROUND AND PURPOSE: Recent studies suggest that the effects of cyclooxygenase-2 (COX-2) inhibition are mediated by cannabinoid receptor activation. However, some non-steroidal anti-inflammatory drugs inhibit the enzyme fatty acid amide hydrolase, which regulates levels of some endocannabinoids. Whether COX-2 directly regulates levels of endocannabinoids in vivo is unclear. Here, the effect of the COX-2 inhibitor nimesulide, which does not inhibit fatty acid amide hydrolase, on spinal nociceptive processing was determined. Effects of nimesulide on tissue levels of endocannabinoids and related compounds were measured and the role of cannabinoid 1 (CB(1)) receptors was determined. EXPERIMENTAL APPROACH: Effects of spinal and peripheral administration of nimesulide (1-100 microg per 50 microL) on mechanically evoked responses of rat dorsal horn neurones were measured, and the contribution of the CB(1) receptor was determined with the antagonist AM251 (N-(piperidin-1-yl)-5-(-4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide), in anaesthetized rats. Effects of nimesulide on spinal levels of endocannabinoids and related compounds were quantified using liquid chromatography-tandem mass spectrometry. KEY RESULTS: Spinal, but not peripheral, injection of nimesulide (1-100 microg per 50 microL) significantly reduced mechanically evoked responses of dorsal horn neurones. Inhibitory effects of spinal nimesulide were blocked by the CB(1) receptor antagonist AM251 (1 microg per 50 microL), but spinal levels of endocannabinoids were not elevated. Indeed, both anandamide and N-oleoylethanolamide (OEA) were significantly decreased by nimesulide. CONCLUSIONS AND IMPLICATIONS: Although the inhibitory effects of COX-2 blockade on spinal neuronal responses by nimesulide were dependent on CB(1) receptors, we did not detect a concomitant elevation in anandamide or 2-AG. Further understanding of the complexities of endocannabinoid catabolism by multiple enzymes is essential to understand their contribution to COX-2-mediated analgesia.

Involvement of 2-arachidonoyl glycerol in the increased consumption of and preference for ethanol of mice treated with neurotoxic doses of methamphetamine.

BACKGROUND AND PURPOSE: Methamphetamine (METH) is a psychostimulant amphetamine that causes long-term dopaminergic neurotoxicity in mice. Hypodopaminergic states have been demonstrated to increase voluntary ethanol (EtOH) consumption and preference. In addition, the endocannabinoid system has been demonstrated to modulate EtOH drinking behaviour. Thus, we investigated EtOH consumption in METH-lesioned animals and the role of cannabinoid (CB) signalling in this EtOH drinking. EXPERIMENTAL APPROACH: Mice were treated with a neurotoxic regimen of METH, and 7 days later exposed to increasing concentrations of drinking solutions of EtOH (3, 6, 10 and 20%). Seven days after neurotoxic METH, the following biochemical determinations were carried out in limbic forebrain: CB(1) receptor density and stimulated activity, 2-arachidonoyl glycerol (2-AG) and monoacylglycerol lipase (MAGL) activity, dopamine levels and dopamine transporter density. KEY RESULTS: EtOH consumption and preference were increased in METH-treated mice. Seven days after METH, a time at which both dopamine levels and density of dopamine transporters in limbic forebrain were decreased, CB(1) receptor density and activity were unaltered, but 2-AG levels were increased. At this same time-point, MAGL activity was reduced. The CB(1) receptor antagonist AM251 prevented the METH-induced increase in EtOH consumption and preference, while N-arachidonoyl maleimide, an inhibitor of MAGL, increased EtOH consumption and preference in both saline- and METH-treated mice. CONCLUSIONS AND IMPLICATIONS: An increase in endocannabinoid tone may be involved in the increased consumption of and preference for EtOH displayed by METH-lesioned mice as blockade of the CB(1) receptor decreased EtOH-seeking behaviours, whereas the MAGL inhibitor increased EtOH consumption.

Quantitative liquid chromatography-tandem mass spectrometry profiling of activated methyl cycle metabolites involved in LuxS-dependent quorum sensing in Escherichia coli.

A rapid, selective, and sensitive liquid chromatography-tandem mass spectrometry assay has been developed and validated for the simultaneous quantification of the metabolites and precursors of the activated methyl cycle, reported in preliminary form by Heurlier et al. (2009) [43]. Analytes were extracted from Escherichia coli MG1655 and chemically derivatized as N(O,S)-iso-butyloxycarbonyl iso-butyl esters using iso-butyl chloroformate in an aqueous iso-butanol/pyridine environment. S-Adenosylmethionine, S-adenosylhomocysteine, S-ribosylhomocysteine, homocysteine, methionine, cystathionine, cysteine, and homoserine were quantified by liquid chromatography-positive ion tandem electrospray ionization mass spectrometry. Internal standards were isotopically labeled [(13)CD(3)]methionine and S-adenosylcysteine. Linearity of the assay was established up to a concentration of 700 microg/g cell dry weight for each analyte. The validated assay was used to quantitatively profile the intracellular activated methyl cycle metabolites as a function of growth in E. coli MG1655 and its derivative Deltapfs and DeltaluxS mutants to determine the metabolic consequences of a disruption to the activated methyl cycle and, hence, LuxS-dependent quorum sensing.

Plasma endocannabinoid levels in multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a chronic inflammatory disease of the CNS. Therapies that affect the endocannabinoid (EC) system may have immunomodulatory, symptomatic and neuroprotective effects. AIM: The aim of this study was to determine how levels of EC and related compounds are altered in MS. METHODS: Plasma and whole blood were collected from 24 MS patients (10 relapsing-remitting (RR); 8 secondary-progressive (SP); 6 primary-progressive (PP); 19 females; 25-66 years) and 17 controls (10 females; 22-62 years). Plasma EC and related compounds were quantified by liquid chromatography-tandem mass spectrometry. Fatty acid amide hydrolase (FAAH), cannabinoid receptors CB(1) and CB(2) mRNA were measured by quantitative reverse transcriptase-polymerase chain reaction. RESULTS: Anandamide (AEA) and palmitoylethanolamide (PEA) were higher in RRMS compared to controls (p=0.001 and p=0.027). AEA, PEA and oleoylethanolamide were also increased in SPMS plasma (p=0.001, p=0.004, and p=0.005). PPMS patients had higher AEA plasma levels compared to controls (p=0.009). FAAH mRNA was decreased in SPMS (p=0.04) but not in RRMS or PPMS blood. CB(1) (p=0.012) and CB(2) mRNA (p=0.003) were increased in the PPMS. CONCLUSION: The EC system is altered in MS. It may be dynamically modulated depending on the subtype of the disease, but further studies with larger subgroups are needed to confirm this.

Preclinical toxicokinetic evaluation of phortress [2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole lysylamide dihydrochloride] in two rodent species.

BACKGROUND AND AIMS: The 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole prodrug Phortress exerts potent and selective antitumour activity in vitro and in vivo. Preclinical toxicokinetic studies in 2 rodent species were undertaken to determine Phortress' maximum tolerated dose and advise a safe starting dose for clinical evaluation. METHODS: Plasma pharmacokinetic parameters were determined by high-performance liquid chromatography and fluorescence detection following Phortress administration to mice (10 mg/kg, intravenously on days 1 and 8). Phortress (20 mg/kg, on days 1 and 8) was administered to CYP1A1/betaGAL reporter mice; tissues were examined macro- and microscopically. Toxicological and pharmacodynamic endpoints were examined in organs of rodents receiving Phortress (10 mg/kg or 20 mg/kg, on days 1 and 8). CYP1A1 expression and Phortress-derived DNA adducts were determined in lungs and livers (on days 11 and 36). RESULTS: No accumulation of Phortress was detected in murine plasma. beta-Galactosidase activity inferred Phortress-derived induction of cyp1a1 transcription in the livers of transgenic mice; no total body weight loss was encountered in these animals. However, a fall in lung:body weight and kidney:body weight ratios, raised serum alkaline phosphatase levels and hepatic histopathological disturbances in animals receiving 20 mg/kg Phortress indicate organ sites of potential toxicity. CYP1A1 protein was induced transiently in the lungs of both species and in the livers of rats. Elimination of hepatic DNA adducts and rat pulmonary adducts was evident; however, murine pulmonary adducts persisted. CONCLUSION: Rodent preclinical toxicology established that mice represent the more sensitive rodent species, resolving a maximum tolerated dose of 10 mg/kg Phortress.

'Entourage' effects of N-palmitoylethanolamide and N-oleoylethanolamide on vasorelaxation to anandamide occur through TRPV1 receptors.

BACKGROUND AND PURPOSE: The endocannabinoid N-arachidonoylethanolamide (anandamide) is co-synthesized with other N-acylethanolamides, namely N-palmitoylethanolamide (PEA) and N-oleoylethanolamide (OEA), which have been shown to potentiate anandamide responses (so-called 'entourage effects') in non-vascular tissues. It remains unclear whether such interactions occur in the circulation. EXPERIMENTAL APPROACH: In rat isolated small mesenteric arteries, the effects of PEA and OEA on relaxation to anandamide and tissue contents of the N-acylethanolamides were examined under myographic conditions. KEY RESULTS: Anandamide-induced relaxation was potentiated by pretreatment with PEA (10 microM) or OEA (1 microM), or in combination. The potentiation by PEA and OEA was endothelium-independent and abolished by treatment with capsaicin (10 microM), which desensitizes the transient receptor potential vanilloid type 1 (TRPV1) receptor system, or by the TRPV1 receptor antagonist, N-(3-methoxyphenyl)-4-chlorocinnamide (SB366791) (2 microM). It was also observed at molar ratios of anandamide and PEA (or OEA) similar to those found in mesenteric arteries. PEA and inhibition of anandamide hydrolysis by 3'-carbamoyl-biphenyl-3-yl-cyclohexylcarbamate (URB597) (1 microM) additively potentiated anandamide responses. On the other hand, PEA and OEA also induced vasorelaxation per se (rank order of potency: anandamide>OEA>PEA), but relaxation to the three N-acylethanolamides displayed different sensitivity to treatment with capsaicin, SB366791 and URB597. For example, relaxations to anandamide and OEA, but not PEA, were attenuated by both capsaicin and SB366791. CONCLUSION AND IMPLICATIONS: This study shows that PEA and OEA potentiate relaxant responses to anandamide through TRPV1 receptors in rat small mesenteric arteries. The congeners also induce vasorelaxation per se, suggesting a function for the N-acylethanolamides in vascular control.

Evidence for a novel functional role of cannabinoid CB(2) receptors in the thalamus of neuropathic rats.

Cannabinoid CB(1) receptors have analgesic effects in models of neuropathic pain, but can also produce psychoactive side-effects. A supraspinal location of CB(2) receptors has recently been described. CB(2) agonists are also antinociceptive, although the functional role of supraspinal CB(2) receptors in the control of nociception is unknown. Herein, we provide evidence that CB(2) receptors in the thalamus play a functional role in the modulation of responses of neurons in the ventral posterior nucleus (VPL) of the thalamus in neuropathic, but not sham-operated, rats. Spontaneous and mechanically evoked activity of VPL neurons was recorded with a multichannel electrode array in anaesthetized spinal nerve-ligated (SNL) rats and compared to sham-operated rats. Intra-VPL administration of the CB(2) agonist JWH-133 (30 ng in 500 nL) significantly reduced spontaneous (P < 0.05), non-noxious (P < 0.001) and noxious (P < 0.01) mechanically evoked responses of VPL neurons in SNL rats, but not in sham-operated rats. Inhibitory effects of JWH-133 on spontaneous (P < 0.01) and noxious-evoked (P < 0.001) responses of neurons were blocked by the CB(2) antagonist SR144528. Local administration of SR144528 alone did not alter spontaneous or evoked responses of VPL neurons, but increased burst activity of VPL neurons in SNL rats. There were, however, no differences in levels of the endocannabinoids anandamide and 2AG in the thalamus of SNL and sham-operated rats. These data suggest that supraspinal CB(2) receptors in the thalamus may contribute to the modulation of neuropathic pain responses.

The Arabidopsis thaliana/Myzus persicae model system demonstrates that a single gene can influence the interaction between a plant and a sap-feeding insect.

We have developed an Arabidopsis thaliana/Myzus persicae model system to allow the dissection of plant/insect interactions at a molecular genetic level. This allows the examination of the role of single plant genes in the interaction between the plant and an aphid. Our initial studies have exploited an Arabidopsis genotype in which the function of the amino acid transporter ANT1 has been abolished. This mutation results in a change in the proportions of several amino acids within the phloem sieve elements (SEs) resulting in an increase in the proportion of essential amino acids. This has been measured using aphid stylectomy to collect SE samples, followed by a novel micellar electrokinetic chromatography method for amino acid analysis. The SE content represents the aphid's diet, and use of electrical penetration graph technology and honeydew clocks have demonstrated that this altered diet results in a change in the feeding rate of the aphid. Balance sheets can be produced to show the amount (nmoles/24 h) of each of 18 amino acids taken up and excreted by aphids feeding on wild type and ant1 mutant plants. The data show that aphids feeding on the ant1 mutant take up larger amounts of amino acids. However, we could not detect any effect on the reproductive rate of the aphids. The results show that, under experimental conditions, this model system can be used to identify plant genes that control the behaviour and fecundity of an insect pest.

Methotrexate induced differentiation in colon cancer cells is primarily due to purine deprivation.

The folate antagonist methotrexate (MTX) inhibits synthesis of tetrahydrofolate (THF), pyrimidines and purines, and induces differentiation in several cell types. At 1 microM, MTX reduced proliferation and induced differentiation in HT29 colon cancer cells; the latter effect was augmented (P < 0.001) by thymidine (100 microM) but was reversed (P < 0.001) by the purines, hypoxanthine (Hx; 100 microM) and adenosine (100 microM). In contrast 5-fluoro-uracil (5-FU), a specific thymidylate synthase (TS) inhibitor, had no effect on differentiation, suggesting that MTX-induced differentiation is not due to a reduction in thymidine but to the inhibition of purine biosynthesis. Inhibition of cyclic AMP (cAMP) by RpcAMP (25 microM) further enhanced (P < 0.001) MTX induced differentiation, whereas the cAMP activator forskolin (10 microM) reversed (P < 0.001) MTX induced differentiation. These observations implicate a central role of adenosine and cAMP in MTX induced differentiation. By combining Western blot analysis with liquid chromatography-mass spectrometry (LC-MS)and HPLC analyses we also reveal both the expression and activity of key enzymes (i.e. methionine synthase (MS), s-adenosylhomocysteinase, cystathionine beta-synthase and ornithine decarboxylase) regulating methyl cycle, transsulfuration and polyamine pathways in HT29 colon cancer cells. At 1 microM, MTX induced differentiation was associated with a marked reduction in the intracellular concentrations of adenosine and, consequently, S-adenosylmethionine (SAM), S-adenosylhomocysteine, polyamines and glutathione (GSH). Importantly, the marked reduction in methionine that accompanied MS inhibition following MTX treatment was non-limiting with respect to SAM synthesis. Collectively, these findings indicate that the effects of MTX on cellular differentiation and single carbon metabolism are primarily due to the intracellular depletion of purines.

Quantification of clarithromycin, its 14-hydroxy and decladinose metabolites in rat plasma, gastric juice and gastric tissue using high-performance liquid chromatography with electrochemical detection.

A rapid, selective and sensitive HPLC assay has been developed for the simultaneous analysis of clarithromycin, its 14-hydroxy-clarithromycin metabolite, and its decladinose acid degradation product, in small volumes of rat gastric juice aspirate, plasma and gastric tissue. Sample were extracted with n-hexane/2-butanol (4:1) and the internal standard was roxithromycin. A Kromasil ODS 5 micrometer(75x4.6 mm I.D.) column was used with a mobile phase consisting of acetonitrile/aqueous phosphate buffer (pH 7, 0.086 M) (45:55 v/v). The column temperature was 30 degrees C and coulometric detection was used at 850 mV using a screen voltage of 600 mV. The analysis time was less than 8 min. The limits of quantitation for clarithromycin, 14-OH clarithromycin and decladinose clarithromycin were 0.15 microgram ml(-1) or lower in plasma (0.05 ml); 0.16 microgram ml(-1) or lower in gastric juice (0.2 ml); and 0.51 microgram g(-1) or lower for gastric tissue (0.25 g). The method was linear up to at least 20.3, 15.4 and 12.5 microgram ml(-1) for clarithromycin, 14-OH-clarithromycin and decladinose, respectively, in gastric juice aspirate and plasma and up to 40.6, 30.9 and 25.0 microgram g(-1) in gastric tissue. The assay was applied to the measurement of clarithromycin, 14-OH-clarithromycin and, for the first time, decladinose clarithromycin in pharmacokinetic studies of gastric transfer of clarithromycin in individual rats.