Role of protein-tyrosine phosphatases in regulation of osteoclastic activity

Osteoclasts, the primary cell type mediating bone resorption, are multinucleated, giant cells derived from hematopoietic cells of monocyte-macrophage lineage. Osteoclast activity is, in a large part, regulated by protein-tyrosine phosphorylation. While information about functional roles of several protein-tyrosine kinases (PTK), including c-Src, in osteoclastic resorption has been accumulated, little is known about the roles of protein-tyrosine phosphatases (PTPs) in regulation of osteoclast activity. Recent evidence implicates important regulatory roles for four PTPs (SHP-1, cyt-PTP-epsilon, PTP-PEST, and PTPoc) in osteoclasts. Cyt-PTP-epsilon, PTP-PEST, and PTP-oc are positive regulators of osteoclast activity, while SHP-1 is a negative regulator. Of these PTPs in osteoclasts, only PTP-oc is a positive regulator of c-Src PTK through dephosphorylation of the inhibitory phosphotyrosine-527 residue. Although some information about mechanisms of action of these PTPs to regulate osteoclast activity is reviewed in this article, much additional work is required to provide more comprehensive details about their functions in osteoclasts.

Effects of drug transporters on volume of distribution

Recently, drug transporters have emerged as significant modifiers of a patient's pharmacokinetics. In cases where the functioning of drug transporters is altered, such as by drug-drug interactions, by genetic polymorphisms, or as evidenced in knockout animals, the resulting change in volume of distribution can lead to a significant change in drug effect or likelihood of toxicity, as well as a change in half life independent of a change in clearance. Here, we review pharmacokinetic interactions at the transporter level that have been investigated in animals and humans and reported in literature, with a focus on the changes in distribution volume. We pay particular attention to the differing effects of changes in transporter function on the three measures of volume. Further, trends are discussed as they may be used to predict volume changes given the function of a transporter and the primary location of the interaction. Because the liver and kidneys express the greatest level and variety of transporters, we denote these organs as the primary location of transporter-based interactions. We conclude that the liver is a larger contributor to distribution volume than the kidneys, in consideration of both uptake and efflux transporters. Further, while altered distribution due to secondary interactions at tissues other than the liver and kidneys may have a pharmacodynamic effect, these interactions, at least at the blood-brain barrier, do not appear to significantly influence overall distribution volume. The analysis provides a framework for understanding potential pharmacokinetic interactions rooted in drug transporters as they modify drug distribution.

Lean and obese Zucker rats exhibit different patterns of p70s6 kinase regulation in the tibialis anterior muscle in response to high-force muscle contraction

Increased phosphorylation of the 70-kDa ribosomal S6 kinase (p70S6k) signaling is strongly correlated with the degree of muscle adaptation following exercise. Herein we compare the phosphorylation of p70S6k, Akt, and mammalian target of rapamycin (mTOR) in the tibialis anterior (TA) muscles of lean and obese Zucker rats following a bout of eccentric exercise. Exercise increased p70S6k (Thr389) phosphorylation immediately after (33.3+/-7.2%) and during [1 h (24.0+/-14.9%) and 3 h (24.6+/-11.3%)] recovery in the lean TA and at 3 h (33.5+/-8.0%) in the obese TA Zucker rats. mTOR (Ser2448) phosphorylation was elevated in the lean TA immediately after exercise (96.5+/-40.3%) but remained unaltered in the obese TA. Exercise increased Akt (Thr308) and Akt (Ser473) phosphorylation in the lean but not the obese TA. These results suggest that insulin resistance is associated with alterations in the ability of muscle to activate p70S6k signaling following an acute bout of exercise.

Bioactivity of POPs and their effects in mosquitofish in Sydney Olympic Park, Australia

The site of the 2000 Olympic Games (Sydney Olympic Park (SOP), Sydney, Australia) was contaminated by persistent organic pollutants (POPs) prior to remediation in the 1990s. This study investigates the bioactivity of POPs in the sediment and water of wetlands across SOP by in vitro 2,3,7,8-TCDD equivalence (TCDDeq) measurement (H4IIE cell line bioassay). Further, it examines whether disturbance of these sediments is likely to mobilise ligands for this receptor into the water column. Exposure to aryl hydrocarbon receptor (AhR) ligands was measured in vivo using hepatic cytochrome P4501A (CYP1A) induction (EROD) in the mosquitofish (Gambusia holbrooki). Aqueous TCDDeq ranged from 0.013 to 0.057 pM in SOP wetlands which was significantly (p<0.05) less that in urban reference sites. These concentrations were not correlated to physical or chemical characteristics of the wetlands. In the sediments, TCDDeq ranged from 0.0016 to 7.06 microg/kg and these were not significantly (p>or=0.05) different to that measured in urban reference sites. Simulated disturbance of small quantities of sediment in water samples significantly (p<0.05) increased the levels of TCDDeq measured in the water. Sediment TCDDeq was correlated to sediment SigmaPAH concentration in 2006 and sediment SigmaPCB, SigmaDDT concentrations and fine sediment grain size in 2005. While fish at one SOP wetland had hepatic EROD activity elevated above the estimated basal level for this species, these were at the lower end of the range measured in urban impacted, non-remediated wetlands. EROD activity was positively correlated with both the sediment SigmaPCB load and aqueous TCDDeq. Increased catchment size was correlated with increased EROD activity suggesting an even spread of POPs throughout the residential areas of the Sydney metropolitan area. The concentration of bioactive POPs in the wetlands of SOP is therefore low relative to urban reference sites demonstrating the ongoing success of the remediation program.

Dissection of phenotype reveals possible association between schizophrenia and Glutamate Receptor Delta 1 (GRID1) gene promoter

Recent linkage and association data have implicated the Glutamate Receptor Delta 1 (GRID1) locus in the etiology of schizophrenia. In this study, we sought to test whether variants in the promoter region are associated with this disorder. The distribution of CpG islands, which are known to be relevant for transcriptional regulation, was computationally determined at the GRID1 locus, and the putative transcriptional regulatory region at the 5'-terminus was systematically tagged using HapMap data. Genotype analyses were performed with 22 haplotype-tagging single nucleotide polymorphisms (htSNPs) in a German sample of 919 schizophrenia patients and 773 controls. The study also included two SNPs in intron 2 and one in intron 3 which have been found to be significantly associated with schizophrenia in previous studies. For the transcriptional regulatory region, association was obtained with rs3814614 (p=0.0193), rs10749535 (p=0.0245), and rs11201985 (p=0.0222). For all further analyses, the patient samples were divided into more homogeneous subgroups according to sex, age at onset, positive family history of schizophrenia and lifetime history of major depression. The p-value of the schizophrenia association finding for the three markers decreased by approximately one order of magnitude, despite the reduction in the total sample size. Marker rs3814614 (unadjusted p=0.0005), located approximately 2.0 kb from the transcriptional start point, also withstood a two-step correction for multiple testing (p=0.030). No support was obtained for previously reported associations with the intronic markers. Our results suggest that genetic variants in the GRID1 transcriptional regulatory region may play a role in the etiology of schizophrenia, and that future association studies of schizophrenia may require stratification to ensure more homogeneous patient subgroups.

Metabolism of an alkyl polyamine analog by a polyamine oxidase from the microsporidian Encephalitozoon cuniculi

Encephalitozoon cuniculi is a microsporidium responsible for systemic illness in mammals. In the course of developing leads to new therapy for microsporidiosis, we found that a bis(phenylbenzyl)3-7-3 analog of spermine, 1,15-bis{N-[o-(phenyl)benzylamino}-4,12-diazapentadecane (BW-1), was a substrate for an E. cuniculi amine oxidase activity. The primary natural substrate for this oxidase activity was N'-acetylspermine, but BW-1 had activity comparable to that of the substrate. As the sole substrate, BW-1 gave linear reaction rates over 15 min and K(m) of 2 microM. In the presence of N'-acetylspermine, BW-1 acted as a competitive inhibitor of oxidase activity and may be a subversive substrate, resulting in increased peroxide production. By use of (13)C-labeled BW-1 as a substrate and nuclear magnetic resonance analysis, two products were determined to be oxidative metabolites, a hydrated aldehyde or dicarboxylate and 2(phenyl)benzylamine. These products were detected after exposure of (13)C-labeled BW-1 to E. cuniculi preemergent spore preparations and to uninfected host cells. In previous studies, BW-1 was curative in a rodent model of infection with E. cuniculi. The results in this study demonstrate competitive inhibition of oxidase activity by BW-1 and support further studies of this oxidase activity by the parasite and host.

Intrathecal injection of the neurosteroid, DHEAS, produces mechanical allodynia in mice: involvement of spinal sigma-1 and GABA receptors

BACKGROUND AND PURPOSE

The neurosteroid, dehydroepiandrosterone sulphate (DHEAS) and its non-sulphated form, DHEA, are considered as crucial endogenous modulators of a number of important physiological events. Evidence suggests that DHEAS and DHEA modulate central nervous system-related functions by activating sigma-1 receptors and/or allosterically inhibiting gamma-aminobutyric acid receptor type A (GABA(A)) receptors. As both the sigma-1 receptor and the GABA(A) receptor play important roles in spinal pain transmission, the present study was designed to examine whether intrathecally injected DHEAS or DHEA affect nociceptive signalling at the spinal cord level.

EXPERIMENTAL APPROACH

We first determined whether intrathecal (i.t.) DHEA or DHEAS injection was able to affect nociceptive thresholds to peripheral mechanical stimulation and subsequently examined whether this effect was mediated by sigma-1 or the GABA(A) receptors.

KEY RESULTS

The i.t. DHEAS injection dose-dependently decreased the nociceptive threshold to mechanical stimulation, thus producing mechanical allodynia. Moreover, this DHEAS-induced mechanical allodynia was significantly reduced by administration of the sigma-1 receptor antagonist, BD-1047 or the GABA(A) receptor agonist, muscimol. Conversely, i.t. DHEA had no effect on mechanical sensitivity. However, when i.t. DHEA was combined with the GABA(A) receptor antagonist bicuculline, DHEA dose-dependently produced mechanical allodynia similar to that of DHEAS. This effect was blocked by BD-1047 and by muscimol.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that i.t. injection of DHEAS produces mechanical allodynia and that the development of this mechanical allodynia is mediated by sigma-1 and GABA(A) receptors. The findings of this study raise several interesting questions for further investigations into the mechanisms underlying neurosteroid modulation of spinal pain transmission.

Regulation of acetylcholine receptor clustering by ADF/cofilin-directed vesicular trafficking

Postsynaptic receptor localization is crucial for synapse development and function, but the underlying cytoskeletal mechanisms remain elusive. Using Xenopus neuromuscular junctions as a model, we here report that actin depolymerizing factor (ADF)/cofilin regulates actin-dependent vesicular trafficking of acetylcholine receptors (AChRs) to the postsynaptic membrane. We found that active ADF/cofilin was concentrated in small puncta adjacent to AChR clusters and spatiotemporally correlated with the formation and maintenance of surface AChR clusters. Importantly, increased actin dynamics, vesicular markers, and intracellular AChRs were all enriched at the sites of ADF/cofilin localization. Furthermore, a substantial amount of new AChRs was detected at these ADF/cofilin-enriched sites. Manipulation of either ADF/cofilin activity through its serine-3 phosphorylation or ADF/cofilin localization via 14-3-3 proteins markedly attenuated AChR insertion and clustering. These results suggest that spatiotemporally restricted ADF/cofilin-mediated actin dynamics regulate AChR trafficking during the development of neuromuscular synapses.

Calcium-independent phospholipase A2 participates in KCl-induced calcium sensitization of vascular smooth muscle

In vascular smooth muscle, KCl not only elevates intracellular free Ca(2+) ([Ca(2+)](i)), myosin light chain kinase activity and tension (T), but also can inhibit myosin light chain phosphatase activity by activation of rhoA kinase (ROCK), resulting in Ca(2+) sensitization (increased T/[Ca(2+)](i) ratio). Precisely how KCl causes ROCK-dependent Ca(2+) sensitization remains to be determined. Using Fura-2-loaded isometric rings of rabbit artery, we found that the Ca(2+)-independent phospholipase A(2) (iPLA(2)) inhibitor, bromoenol lactone (BEL), reduced the KCl-induced tonic but not early phasic phase of T and potentiated [Ca(2+)](i), reducing Ca(2+) sensitization. The PKC inhibitor, GF-109203X (> or =3 microM) and the pseudo-substrate inhibitor of PKCzeta produced a response similar to BEL. BEL reduced basal and KCl-stimulated myosin phosphatase phosphorylation. Whereas BEL and H-1152 produced strong inhibition of KCl-induced tonic T (approximately 50%), H-1152 did not induce additional inhibition of tissues already inhibited by BEL, suggesting that iPLA(2) links KCl stimulation with ROCK activation. The cPLA(2) inhibitor, pyrrolidine-1, inhibited KCl-induced tonic increases in [Ca(2+)](i) but not T, whereas the inhibitor of 20-HETE production, HET0016, acted like the ROCK inhibitor H-1152 by causing Ca(2+) desensitization. These data support a model in which iPLA(2) activity regulates Ca(2+) sensitivity.

Loss of AMPK exacerbates experimental autoimmune encephalomyelitis disease severity

AMP-activated protein kinase (AMPK) is an energy sensing metabolic switch in mammalian cells. Here, we report our novel finding that AMPK is lost in all immune cells of experimental autoimmune encephalomyelitis (EAE), an inflammatory disease of Central Nervous System (CNS). AMPKalpha1 is predominantly expressed in T cells and antigen presenting cells (APCs), which are primarily involved in EAE disease progression. AMPK is lost at protein level in spleen macrophages, total T cells and their subsets (CD4, CD8 and regulatory T cells) isolated from EAE afflicted animals compared to control, without affecting its mRNA levels suggesting that the loss of AMPK protein is the result of posttranscriptional modification. To examine its pathological relevance in inflammatory disease, EAE was induced in wild type (+/+) and AMPKalpha1 null mice (-/-) using MOG(35-55) peptide. AMPKalpha1(-/-) mice exhibited severe EAE disease with profound infiltration of mononuclear cells compared to wild type mice however, AMPKalpha2 is not involved in enhancing the severity of the disease. Spleen cells isolated from AMPKalpha1(-/-) immunized mice exhibited a significant induction in the production of IFNgamma. Our study identifies AMPK as a down regulated target during disease in all immune cells and possibly restoring AMPK may serve as a novel therapeutic target in autoimmune diseases like multiple sclerosis (MS).

Aroclor 1254 induced cytotoxicity and mitochondrial dysfunction in isolated rat hepatocytes

Polychlorinated biphenyls (PCBs) are widespread persistent environmental contaminants that display a complex spectrum of toxicological properties, including hepatotoxicity. Although Aroclor 1254 is ubiquitous in the environment, its potential cytotoxic effect on rat hepatocytes and the mechanism underlines its cytotoxicity are not fully investigated. Therefore, the present study was conducted to investigate: (1) the potential cytotoxicity of Aroclor 1254 in rat hepatocytes, and (2) characterization of the molecular mechanisms involved in the Aroclor 1254-induced hepatotoxicity, particularly the role of mitochondria, possibly a primary target in such event, could greatly explain the cytotoxic effect of Aroclor 1254 in rat hepatocytes. Hepatocytes were isolated from adult male albino rats and incubated for 24h in a fresh media containing 0, 20, 30, 40, 50 or 60muM of Aroclor 1254. At the end of incubation, hepatocytes and hepatocyte mitochondria were used for the assay. Our results showed cytotoxicity of Aroclor 1254 in rat hepatocytes starting at a concentration of 30muM as manifested by increased lactate dehydrogenase (LDH) leakage, decreased cell viability (MTT assay) and increased lipid peroxidation. As mitochondria are known to be one possible site of the cell damage, the effects of Aroclor 1254 on hepatocyte mitochondria was investigated. Aroclor 1254 induced reactive oxygen species (ROS) generation in hepatocyte mitochondria, inhibited mitochondrial respiratory chain complexes I and III and beta-oxidation of free fatty acids, depletion of mitochondrial antioxidant enzymes GPx and GR and the non-enzymatic antioxidant reduced glutathione, inhibited mitochondrial membrane potential (Deltapsi(m)), decreased mitochondrial aconitase and cardiolipin content, and elevated levels of cytochrome P450 subfamily, CYP1A and CYP2B activities as indicated by ethoxyresorufin O-deethylase (EROD) and pentoxyresorufin O-deethylase (PROD). Therefore, we can conclude that Aroclor 1254 induced rat hepatocyte toxicity and our findings provide evidence to propose that mitochondria are one of the most important and earliest cell targets in Aroclor 1254-mediated toxicity and delineate several mitochondrial processes at least, in part, by induction of oxidative stress. These findings can be useful in future cytoprotective therapy approaches. Since mitochondrial events appear to be targeted in hepatocellular damage induced by Aroclor 1254, an antioxidant therapy targeted to mitochondria may constitute an interesting strategy to ameliorate its toxicity.

Neurogenesis mediated by gamma-aminobutyric acid and glutamate signaling

In this review, we will summarize our ongoing studies on the functionality of both gamma-aminobutyric acid (GABA) and glutamate receptors expressed by undifferentiated neural progenitor cells isolated from embryonic rodent brains. Cells were cultured with growth factors for the formation of round spheres by clustered cells under floating conditions, whereas a reverse transcription polymerase chain reaction analysis revealed expression of mRNA for particular subtypes of different ionotropic and metabotropic GABA and glutamate receptors in undifferentiated progenitors and neurospheres. Moreover, sustained exposure to either GABAergic or glutamatergic agonists not only modulated the size of neurospheres formed, but also affected spontaneous and induced differentiation of neural progenitor cells into particular progeny cell lineages such as neurons and astroglia. Both GABA and glutamate could play a pivotal role in the mechanisms underlying proliferation for self-replication along with the determination of subsequent differentiation fate toward particular progeny lineages through activation of their receptor subtypes functionally expressed by undifferentiated neural progenitor cells. Accordingly, neurogenesis seems to be also under control by GABAergic and glutamatergic signaling in developing brains as seen with neurotransmission in adult brains.

Intestinal glucuronidation metabolism may have a greater impact on oral bioavailability than hepatic glucuronidation metabolism in humans: a study with raloxifene, substrate for UGT1A1, 1A8, 1A9, and 1A10

The kinetic impact of intestinal glucuronidation metabolism on oral bioavailability (F) was assessed using reported human data of raloxifene, of which oral bioavailability was only 2%. Kinetic analysis showed that presystemic intestinal availability (Fpg) was 5.4%, whereas fraction absorbed (Ff) and hepatic availability (Fh) were 63% and 59.3%, respectively. Thus, Fpg was the lowest among factors, which affect oral bioavailability. In addition, Fpg was much lower than Fh, suggesting that intestinal glucuronidation metabolism has a greater impact on oral bioavailability than hepatic glucuronidation metabolism. It has been reported that UDP-glucuronosyltransferase (UGT) 1A1, UGT1A8, UGT1A9, and UGT1A10 are enzymes for raloxifene glucuronidation, and UGT1A8 and UGT1A10 are absent in the human liver, whereas UGT1A1, UGT1A8, UGT1A9, and UGT1A10 are present in the human intestine. Therefore, it is also suggested that intestinal glucuronidation catalyzed by UGTs, particularly UGT1A8 and UGT1A10, may play important roles in the first-pass metabolism, causing low oral bioavailability.

Sex differences in the expression of hepatic drug metabolizing enzymes

Sex differences in pharmacokinetics and pharmacodynamics characterize many drugs and contribute to individual differences in drug efficacy and toxicity. Sex-based differences in drug metabolism are the primary cause of sex-dependent pharmacokinetics and reflect underlying sex differences in the expression of hepatic enzymes active in the metabolism of drugs, steroids, fatty acids and environmental chemicals, including cytochromes P450 (P450s), sulfotransferases, glutathione transferases, and UDP-glucuronosyltransferases. Studies in the rat and mouse liver models have identified more than 1000 genes whose expression is sex-dependent; together, these genes impart substantial sexual dimorphism to liver metabolic function and pathophysiology. Sex differences in drug metabolism and pharmacokinetics also occur in humans and are due in part to the female-predominant expression of CYP3A4, the most important P450 catalyst of drug metabolism in human liver. The sexually dimorphic expression of P450s and other liver-expressed genes is regulated by the temporal pattern of plasma growth hormone (GH) release by the pituitary gland, which shows significant sex differences. These differences are most pronounced in rats and mice, where plasma GH profiles are highly pulsatile (intermittent) in male animals versus more frequent (nearly continuous) in female animals. This review discusses key features of the cell signaling and molecular regulatory mechanisms by which these sex-dependent plasma GH patterns impart sex specificity to the liver. Moreover, the essential role proposed for the GH-activated transcription factor signal transducer and activator of transcription (STAT) 5b, and for hepatic nuclear factor (HNF) 4alpha, as mediators of the sex-dependent effects of GH on the liver, is evaluated. Together, these studies of the cellular, molecular, and gene regulatory mechanisms that underlie sex-based differences in liver gene expression have provided novel insights into the physiological regulation of both xenobiotic and endobiotic metabolism.

Trace amine-associated receptor 1 as a monoaminergic modulator in brain

Brain monoaminergic systems play critical roles in mood, cognition, emotion, reward, learning and attention, and aberrance in brain monoaminergic activity is associated with a variety of neuropsychiatric disorders/diseases. The present commentary focuses on trace amine-associated receptor 1 (TAAR1) and its potential regulatory roles in brain monoaminergic systems. TAAR1 was discovered in 2001 and has been established to be a G-protein-coupled receptor signaling through the cAMP pathway. This receptor is activated by a broad spectrum of agonists, although there are notable species differences in ligand efficacy and potency. TAAR1 is expressed and widely distributed in brain monoaminergic systems and co-localized with the dopamine transporter in a subset of dopaminergic neurons in rhesus monkey and mouse brain substantia nigra. TAAR1 activation by the common biogenic amines, the trace amine beta-phenylethylamine and methamphetamine alters the monoamine transporter function in both mouse and rhesus monkey brain synaptosomes, suggesting a modulatory role for this receptor in the presynaptic regulation of monoaminergic activity. However, little is known about other functional roles of TAAR1 in the brain. With a purpose to promote further studies on this receptor, we herein discuss the recent findings that provide insights into the functional significance and biological relevance of this receptor as a modulator in brain monoaminergic systems.

Behavioral effects of agmatine in naive rats are task- and delay-dependent

The present study systematically investigated the effects of agmatine administered i.p. in several commonly used behavioral tasks. In Experiment 1, pre-test treatment of agmatine (1 and 40 mg/kg) appeared to improve animals' performance in the water maze probe test conducted 24 h, but not 120 s, after training, when the effect was evaluated within subjects. In Experiment 2, pre-test agmatine treatment (40 mg/kg) did not affect animals' performance in the open field, and the place navigation, probe tests (1-4 and 6), reversal test and cued navigation in the water maze, but significantly facilitated performance in probe 5 which was conducted 96 h after training. In Experiment 3, rats with pre-test agmatine treatment (40 mg/kg) were less anxious relative to the controls, with no performance changes in the open field. In the water maze task, post-training agmatine treatment (40 mg/kg) did not affect place and cued navigation, but significantly improved animals' performance in the probe test conducted 24 h after training and the reversal test. In the working memory version of the task, agmatine treated rats took significantly less time and generated markedly shorter path length to reach the platform at the 180 s, but not 30 s, delay relative to the controls. In the object recognition task, rats with pre-test agmatine treatment (40 mg/kg) spent significantly more time exploring displaced objects, but not novel object, as compared to the controls. In Experiment 4, pre-test agmatine treatment (40 mg/kg) had no effect on the task acquisition in the delayed non-match to position task in the T-maze, but significantly facilitated performance at the 600 s delay. These results suggest that the behavioral effects of agmatine are task- and delay-dependent, and agmatine facilitates memory particularly when the task difficulty is increased due to memory trace decay and/or greater interference.

Pharmacological properties of ketamine

Ketamine is a dissociative anaesthetic that is being used in non-medical contexts. The effects of ketamine are very similar to those of phencyclidine, another dissociative anaesthetic that has enjoyed considerable popularity as a recreational drug. The effects of ketamine include analgesia, cardiovascular and respiratory stimulation, dissociation, hallucinations and anaesthesia. The potential dangers of uncontrolled ketamine use include psychosis and violence, accidents and marked psychomotor and cognitive impairment. Although studies have shown potential for tolerance to and physical dependence on ketamine, further investigation of these phenomena is needed. Ketamine is thought to produce most of its effects through antagonist activity at the PCP site of the NMDA receptor complex. Ketamine has sympathomimetic properties resulting from enhancement of catecholamine, and particularly dopamine, activity. While opioid receptor activity has been identified, this is relatively weak and the contribution to the effects of ketamine is not clear. Although much is known of the clinical uses and effects of ketamine, as yet little is understood of ketamine as a recreational drug and potential drug of dependence.

Lived fictions: moving from pharmacology to ethnography

While positivist science dominates the drug and alcohol research sector, alternative constructivist paradigms of inquiry into drug and alcohol use are also present. The passage of individual researchers through paradigm shifts is often difficult, and rarely documented. Different paradigms of inquiry produce different types of information. The use of the psychoactive drug methylenedioxymethamphetamine (MDMA or "Ecstasy") is discussed in light of a multidisciplinary investigation into the pharmacology and use of MDMA. The role of the author in interpreting data from both positivist and constructivist paradigms is highlighted by documenting a researchers' changes in epistemology whilst undertaking multidisciplinary research. It is concluded that multidisciplinary research into drug and alcohol use could benefit from evaluation of the processes that frame how information from both research paradigms is interpreted and integrated.

TC-5619: an alpha7 neuronal nicotinic receptor-selective agonist that demonstrates efficacy in animal models of the positive and negative symptoms and cognitive dysfunction of schizophrenia

A growing body of evidence suggests that the alpha7 neuronal nicotinic receptor (NNR) subtype is an important target for the development of novel therapies to treat schizophrenia, offering the possibility to address not only the positive but also the cognitive and negative symptoms associated with the disease. In order to probe the relationship of alpha7 function to relevant behavioral correlates we employed TC-5619, a novel selective agonist for the alpha7 NNR subtype. TC-5619 binds with very high affinity to the alpha7 subtype and is a potent full agonist. TC-5619 has little or no activity at other nicotinic receptors, including the alpha4beta2, ganglionic (alpha3beta4) and muscle subtypes. The transgenic th(tk-)/th(tk-) mouse model that reflects many of the developmental, anatomical, and multi-transmitter biochemical aspects of schizophrenia was used to assess the antipsychotic effects of TC-5619. In these mice TC-5619 acted both alone and synergistically with the antipsychotic clozapine to correct impaired pre-pulse inhibition (PPI) and social behavior which model positive and negative symptoms, respectively. Antipsychotic and cognitive effects of TC-5619 were also assessed in rats. Similar to the results in the transgenic mice, TC-5619 significantly reversed apomorphine-induced PPI deficits. In a novel object recognition paradigm in rats TC-5619 demonstrated long-lasting enhancement of memory over a wide dose range. These results suggest that alpha7-selective agonists such as TC-5619, either alone or in combination with antipsychotics, could offer a new approach to treating the constellation of symptoms associated with schizophrenia, including cognitive dysfunction.

Verapamil but not calpain or creatine alters arsenate-induced cardiac cell death

The objective of this study was to examine the potential of arsenate to induce cardiomyocyte cell death and to explore the cellular mechanisms of arsenate toxicity. Isolated cardiomyocytes in culture from embryonic chick hearts were treated with a pentavalent arsenic species (H3AsO4) or arsenate. Arsenate produced a significant ( P < 0.01) concentration-dependent increase in cell death with an EC50 about 1 mM. Cardiomyocytes manifested a loss of actin structure, reduced size, and damaged nuclei. Creatine 0.1–100 uM did not significantly modify arsenate-induced cell death. In contrast, verapamil, 0.01–1 uM, produced a significant concentration-dependent accentuation of arsenate-induced cell death. The effect of verapamil was evident at low concentrations of arsenate, which produced only a small increase in cell death, and at high concentrations of arsenate, which induced a large amount of cell death. Verapamil alone did not alter cardiomyocyte cell death. By comparison, calpain inhibitor II did not modify arsenate-induced cardiomyocyte cell death. These data suggest that cardiomyocytes are vulnerable to the effects of verapamil to increase the cellular toxicity of arsenate. Two potential cellular mechanisms of arsenate toxicity, however, are likely not involved in arsenate toxicity namely calpain activation and reduction of creatine phosphate production.

Cardiac alternans induced by fibroblast-myocyte coupling: mechanistic insights from computational models

Recent experimental studies have shown that fibroblasts can electrotonically couple to myocytes via gap junctions. In this study, we investigated how this coupling affects action potential and intracellular calcium (Ca(i)) cycling dynamics in simulated fibroblast-myocyte pairs and in two-dimensional tissue with random fibroblast insertions. We show that a fibroblast coupled with a myocyte generates a gap junction current flowing to the myocyte with two main components: an early pulse of transient outward current, similar to the fast transient outward current, and a later background current during the repolarizing phase. Depending on the relative prominence of the two components, fibroblast-myoycte coupling can 1) prolong or shorten action potential duration (APD), 2) promote or suppress APD alternans due to steep APD restitution (voltage driven) and also result in a novel mechanism of APD alternans at slow heart rates, 3) promote Ca(i)-driven alternans and electromechanically discordant alternans, and 4) promote spatially discordant alternans by two mechanisms: by altering conduction velocity restitution and by heterogeneous fibroblast distribution causing electromechanically concordant and discordant alternans in different regions of the tissue. Thus, through their coupling with myocytes, fibroblasts alter repolarization and Ca(i) cycling alternans at both the cellular and tissue scales, which may play important roles in arrhythmogenesis in diseased cardiac tissue with fibrosis.

Transmitter amino acid neurochemistry in chronic alcoholism with and without cirrhosis of the liver

Neurotransmitter receptor studies are beginning to be applied more widely to human brain tissue obtained at autopsy. By taking tissue from well-documented cases which have been extensively characterized on histological and morphometric criteria, it is becoming possible to make clinicopathological correlations in studies of the effects of chronic alcohol abuse. Recent findings of alterations in the nature and amounts of amino acid neurotransmitter receptors in alcoholism are summarized, with special emphasis on the effects of chronic severe liver disease. There are selective changes in receptors in the superior frontal cortex of alcoholics. There is a marked increase in the density of the GABA binding site, and a lesser change in the density of the 'central-type' benzodiazepine site, on the GABAA-benzodiazepine receptor complex. In contrast, glutamate receptors may be much less affected. Together with morphological and cognitive studies, the results suggest that the superior frontal cortex is preferentially damaged in chronic alcoholism. An increase in 'central-type' benzodiazepine sites in both superior frontal cortex and motor cortex in cirrhotic alcoholics may reflect a more global brain damage, as observed in morphological studies. However, it should be noted the changes in [3H]GABA/muscimol binding were less pronounced in cirrhotic alcoholics than in non-cirrhotic alcoholics.

Abscisic acid activates the murine microglial cell line N9 through the second messenger cyclic ADP-ribose

Abscisic acid (ABA) is a phytohormone regulating important functions in higher plants, notably responses to abiotic stress. Recently, chemical or physical stimulation of human granulocytes was shown to induce production and release of endogenous ABA, which activates specific cell functions. Here we provide evidence that ABA stimulates several functional activities of the murine microglial cell line N9 (NO and tumor necrosis factor-alpha production, cell migration) through the second messenger cyclic ADP-ribose and an increase of intracellular calcium. ABA production and release occur in N9 cells stimulated with bacterial lipopolysaccharide, phorbol myristate acetate, the chemoattractant peptide f-MLP, or beta-amyloid, the primary plaque component in Alzheimer disease. Finally, ABA priming stimulates N9 cell migration toward beta-amyloid. These results indicate that ABA is a pro-inflammatory hormone inducing autocrine microglial activation, potentially representing a new target for anti-inflammatory therapies aimed at limiting microglia-induced tissue damage in the central nervous system.

Estradiol shapes auditory processing in the adult brain by regulating inhibitory transmission and plasticity-associated gene expression

Estradiol impacts a wide variety of brain processes, including sex differentiation, mood, and learning. Here we show that estradiol regulates auditory processing of acoustic signals in the vertebrate brain, more specifically in the caudomedial nidopallium (NCM), the songbird analog of the mammalian auditory association cortex. Multielectrode recordings coupled with local pharmacological manipulations in awake animals reveal that both exogenous and locally generated estradiol increase auditory-evoked activity in NCM. This enhancement in neuronal responses is mediated by suppression of local inhibitory transmission. Surprisingly, we also found that estradiol is both necessary and sufficient for the induction of multiple mitogen-activated protein kinase (MAPK)-dependent genes thought to be required for synaptic plasticity and memorization of birdsong. Specifically, we show that local blockade of estrogen receptors or aromatase activity in awake birds decrease song-induced MAPK-dependent gene expression. Infusions of estradiol in acoustically isolated birds induce transcriptional activation of these genes to levels comparable with song-stimulated animals. Our results reveal acute and rapid nongenomic functions for estradiol in central auditory physiology and suggest that such roles may be ubiquitously expressed across sensory systems.

Glyceraldehyde-3-phosphate dehydrogenase-monoamine oxidase B-mediated cell death-induced by ethanol is prevented by rasagiline and 1-R-aminoindan

The inhibitors of monoamine oxidase B (MAO B) are effectively used as therapeutic drugs for neuropsychiatric and neurodegenerative diseases. However, their mechanism of action is not clear, since the neuroprotective effect of MAO B inhibitors is associated with the blockage of glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-death cascade, rather than the inhibition of MAO B. Here, we provide evidence that GAPDH potentiates the ethanol-induced activity of MAO B and brain cell toxicity. The levels of nuclear GAPDH and MAO B activity are significantly increased in brain-derived cell lines upon 75 mM ethanol-induced cell death. Over-expression of GAPDH in cells enhances ethanol-induced cell death, and also increases the ethanol-induced activation of MAO B. In contrast, the MAO B inhibitors rasagiline and selegiline (0.25 nM) and the rasagiline metabolite, 1-R-aminoindan (1 muM) decreases the ethanol-induced MAO B, prevents nuclear translocation of GAPDH and reduces cell death. In addition, GAPDH interacts with transforming growth factor-beta-inducible early gene (TIEG2), a transcriptional activator for MAO B, and this interaction is increased in the nucleus by ethanol but reduced by MAO B inhibitors and 1-R-aminoindan. Furthermore, silencing TIEG2 using RNAi significantly reduces GAPDH-induced MAO B upregulation and neurotoxicity. In summary, ethanol-induced cell death, attenuated by MAO B inhibitors, may result from disrupting the movement of GAPDH with the transcriptional activator into the nucleus and secondly inhibit MAO B gene expression. Thus, the neuroprotective effects of rasagiline or 1-R-aminoindan on ethanol-induced cell death mediated by a novel GAPDH-MAO B pathway may provide a new insight in the treatment of neurobiological diseases including alcohol-use disorders.

Gene expression of synaptosomal-associated protein 25 (SNAP-25) in the prefrontal cortex of the spontaneously hypertensive rat (SHR)

Dopamine is believed to play an important role in the etiology of attention-deficit/hyperactivity disorder (ADHD). In our previous study, we showed that gene expression of dopamine D4 receptor decreased in the spontaneously hypertensive rat (SHR) in the prefrontal cortex (PFC). In the present study, we explored the potential causes of dysfunction in the dopamine system in ADHD. It is the first time that neuronal activities in both juvenile SHR and WKY rats have been measured by functional MRI (fMRI). Our results showed that in PFC the Blood Oxygenation Level Dependent (BOLD) signal response in SHR was much higher than WKY under stressful situations. We tested the effects of acute and repeated administration of amphetamine on behavioral changes in SHR combined with the expression of the neuronal activity marker, c-fos, in the PFC. Meanwhile dopamine-related gene expression was measured in the PFC after repeated administration of amphetamine. We found that potential neuronal damage occurred through deficit of D2-like receptor protective functions in the PFC of the SHR. We also measured the expression of synaptosomal-associated protein 25 (SNAP-25) in SHR in PFC. The results showed decreased expression of SNAP-25 mRNA in the PFC of SHR; this defect disappeared after repeated injection of D-AMP.

Ocular haemodynamics in cataractous eyes. A pilot study

Pulsatile ocular blood flow, systolic and diastolic intraocular pressures and ocular perfusion pressures were measured in a group of 10 patients (mean age 67 +/- 3 years) with bilateral senile cataract. Each pair of eyes comprised one phakic and one pseudophakic eye. The results are compared to a group of 8 subjects (mean age 65 +/- 4 years) with no apparent ocular pathology. The mean ocular pulsatile blood flow of 394 +/- 52 microliters min-1 in the cataractous eyes was significantly reduced P less than 0.001) compared to that of the control group (571 +/- 40 microliters min-1). Results were similar for undisturbed cataractous eyes (mean pulsatile blood flow = 400 +/- 54 microliters min-1) and pseudophakic eyes (mean pulsatile blood flow = 388 +/- 51 microliters min-1). The intraocular pressures were within normal limits (systolic intraocular pressure = 19.7 +/- 0.7 mmHg, diastolic intraocular pressure = 17.5 +/- 0.6 mmHg) as were the ocular perfusion pressures (73.7 +/- 0.5 mmHg). The results provide evidence of decreased pulsatile ocular blood flow and associated ischaemia in cataractous eyes.

Serum bilirubin levels on ICU admission are associated with ARDS development and mortality in sepsis

BACKGROUND

Hyperbilirubinaemia is a common complication of sepsis. Elevated bilirubin may induce inflammation and apoptosis. It was hypothesised that increased serum bilirubin on Intensive Care Unit (ICU) admission contributes to sepsis-related acute respiratory distress syndrome (ARDS).

METHODS

Serum bilirubin on ICU admission was measured in 1006 patients with sepsis. Serial serum bilirubin was analysed prospectively in patients with sepsis who had ARDS for a period of 28 days. The effects of clinical factors and variants of the UGT1A1 gene on serum bilirubin levels were determined. Outcomes were ARDS risk and mortality.

RESULTS

During 60-day follow-up, 326 patients with sepsis developed ARDS, of whom 144 died from ARDS. The hyperbilirubinaemia (>or=2.0 mg/dl) rate in patients with ARDS (22.4%) was higher than in those without ARDS (14.1%, p = 0.002). For each 1.0 mg/dl increase in admission bilirubin, ARDS risk and 28- and 60-day ARDS mortalities were increased by 7% (OR = 1.07; p = 0.003), 20% (OR = 1.20; p = 0.002) and 18% (OR = 1.18; p = 0.004), respectively. Compared with subjects with bilirubin levels <2.0 mg/dl, patients with hyperbilirubinaemia had higher risks of ARDS (OR = 2.12; p = 0.0007) and 28-day (OR = 2.24; p = 0.020) and 60-day ARDS mortalities (OR = 2.09; p = 0.020). In sepsis-related ARDS, serial bilirubin levels in non-survivors were consistently higher than in survivors (p<0.0001). Clinical variables explained 29.5% of the interindividual variation in bilirubin levels, whereas genetic variants of UGT1A1 contributed 7.5%.

CONCLUSION

In sepsis, a higher serum bilirubin level on ICU admission is associated with subsequent ARDS development and mortality.

Polymorphisms in genes encoding drugs and xenobiotic metabolizing enzymes in a Brazilian population

Polymorphic variations of several genes associated with drugs and xenobiotic metabolism have been linked to the factors that predispose to the carcinogenesis process. As considerable interindividual and interethnic variation in metabolizing enzyme activity has been associated with polymorphic alleles, we evaluated the frequency of the polymorphisms of CYP2D6, EPHX1 and NQO1 genes in 361 Brazilian individuals separated by ethnicity (European and African ancestry), using the polymerase chain reaction-restriction fragment length (PCR-RFLP) method. The allele frequencies of the variants *3 and *4 for the gene CYP2D6 were 0.04 and 0.14 for white subjects and 0.03 and 0.10 for black individuals, respectively. For the both variants of the gene EPHX1, we found higher allele frequencies among white individuals compared with mulatto subjects (0.62 vs 0.54 and 0.18 vs 0.14, respectively); however, these differences were not statistically significant (p = 0.39 and 0.56, respectively). For the NQO1 gene we observed a higher frequency of the homozygous genotype among black individuals (7.9%) compared with white subjects (6.3%) (p = 0.003). The genotype frequencies were within the Hardy-Weinberg equilibrium. We concluded that the allele frequencies of CYP2D6, EPHX1 and NQO1 gene polymorphisms in this Brazilian population showed ethnic variability when compared with those observed in other populations.

Acute inhibition of Ca2+/calmodulin-dependent protein kinase II reverses experimental neuropathic pain in mice

The limited data that currently exist for the role of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in neuropathic pain are conflicting. In the present study, we tested the hypothesis that CaMKII is required for the maintenance of neuropathic pain in a rodent model of experimental mononeuropathy. Spinal nerve L(5)/L(6) ligation (SNL) was found to increase the spinal activity of CaMKII (pCaMKII) on the ipsilateral (but not contralateral) side. This effect was blocked by 2-[N-(2-hydroxyethyl)-N-(4-methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine) (KN93) (intrathecal injection), a CaMKII inhibitor. Acute treatment with KN93 dose-dependently reversed SNL-induced thermal hyperalgesia and mechanical allodynia. The action of KN93 lasted for at least 2 to 4 h. 2-[N-(4-Methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine (KN92) (45 nmol i.t.), an inactive analog of KN93, showed no effect on SNL-induced CaMKII activation, allodynia, or hyperalgesia. We further examined the pharmacologic action of trifluoperazine, a clinically used antipsychotic drug that we found to be a potent CaMKII inhibitor in these assays. Trifluoperazine (administered intraperitoneally or by mouth) dose-dependently reversed SNL-induced mechanical allodynia, thermal hyperalgesia, and CaMKII activation without causing locomotor impairment in mice at the highest doses used. In conclusion, our findings support a critical role of CaMKII in neuropathic pain. Blocking CaMKII or CaMKII-mediated signaling may offer a novel therapeutic target for the treatment of neuropathic pain.

In vivo effects of 3-iodocytisine: pharmacological and genetic analysis of hypothermia and evaluation of chronic treatment on nicotinic binding sites

Several cytisine derivatives have been developed in the search for more selective drugs at nicotinic acetylcholine receptors (nAChR). Binding experiments in transfected cell lines showed that the iodination of cytisine in the position 3 of the pyridone ring increased potency at alpha7-nAChR and to a lesser extent at the alpha4beta2 subtypes, both of which are widely expressed in the brain. However, no in vivo studies have been published on this compound. Inhibition curves presented here using wild type, beta2, and beta4-null mutant mice confirm that 3-IC binds to alpha4beta2 *, alpha7 * and alpha3beta4 * receptors with higher affinity than cytisine (asterisk indicates the receptor may contain additional subunits, Lukas et al., 1999). Intraperitoneal injection of 3-iodocytisine (3-IC) induced considerable dose-dependent hypothermia in DBA/2J and C57BL/6J mice. This response was blocked by mecamylamine and partially inhibited by hexamethonium. beta4-null mice displayed significantly less 3-IC-induced hypothermia than wild-type mice, beta2-null mice were somewhat less affected than wild types, while responses of alpha7 *-null mice were similar to wild types. Mice treated chronically with 3-IC display a marked increase in alpha7 * and alpha4beta2 * binding sites determined by radioligand binding in membrane preparations from cerebral cortex and hippocampus. Quantitative autoradiographic analysis of 28 brain regions of mice treated with 3-IC was consistent with the membrane binding, detecting an increase of cytisine-sensitive [(125)I]epibatidine binding sites, while cytisine-resistant [(125)I]epibatidine sites were unchanged. [(125)I]alpha-Bungarotoxin binding sites also exhibited up-regulation. These results give a first evaluation of in vivo consequences of 3-IC as a potent agonist with marked effects on mice.

Evaluation of homology modeling of G-protein-coupled receptors in light of the A(2A) adenosine receptor crystallographic structure

Homology modeling of the human A(2A) adenosine receptor (AR) based on bovine rhodopsin predicted a protein structure that was very similar to the recently determined crystallographic structure. The discrepancy between the experimentally observed orientation of the antagonist and those obtained by previous antagonist docking is related to the loop structure of rhodopsin being carried over to the model of the A(2A) AR and was rectified when the beta(2)-adrenergic receptor was used as a template for homology modeling. Docking of the triazolotriazine antagonist ligand ZM241385 1 was greatly improved by including water molecules of the X-ray structure or by using a constraint from mutagenesis. Automatic agonists docking to both a new homology modeled receptor and the A(2A) AR crystallographic structure produced similar results. Heterocyclic nitrogen atoms closely corresponded when the docked adenine moiety of agonists and 1 were overlaid. The cumulative mutagenesis data, which support the proposed mode of agonist docking, can be reexamined in light of the crystallographic structure. Thus, homology modeling of GPCRs remains a useful technique in probing the structure of the protein and predicting modes of ligand docking.

Early atorvastatin reduces hemorrhage after acute cerebral ischemia in diabetic rats

Ischemic stroke is a leading cause of death in the United States, and diabetes mellitus is a major risk factor for stroke. Our previous work showed that type II diabetic rats [Goto-Kakizaki (GK)] have more bleeding after stroke than their normoglycemic controls (Wistar). Our aim was to evaluate the vascular protective properties of acute atorvastatin therapy after experimental ischemic stroke in diabetes and to explore the effect of stroke in GK rats compared with their normoglycemic controls. Fifty male Wistar and 40 GK rats (270-305 g) underwent 3 h of middle cerebral artery occlusion followed by reperfusion for 21 h. Animals received atorvastatin (5 mg/kg), atorvastatin (15 mg/kg), or vehicle, administered by oral gavage, one dose 5 min after reperfusion and a second dose after 12 h. At 24 h, functional outcome was measured, and brain tissue was analyzed for infarct volume, hemoglobin content, and molecular biomarkers. Plasma was collected for analysis of atorvastatin concentrations. Atorvastatin-treated groups had significantly lower bleeding rates (p = 0.0011) and infarct volume (p = 0.0007) compared with controls. There was a significant reduction in hemoglobin content and infarct volume only in the higher dose group (15 mg/kg) (p < 0.05), and these benefits were more than 4 times greater in the diabetic animals. Atorvastatin (15 mg/kg) improved neurological outcome in both Wistar and GK rats (p = 0.029) at a peak concentration of 27 to 77 ng/ml and was associated with an increase in Akt phosphorylation (p = 0.0007). We concluded that atorvastatin is a vascular protective agent after experimental ischemic stroke, especially in diabetes.

Differential receptor-mediated drug targeting to the diseased brain

The brain is not directly accessible for intravenously administered macro- and most small molecular drugs because of the presence of the blood-brain barrier (BBB). In this respect the BBB functions as a physical and metabolic barrier which is presented by the endothelial cells in brain capillaries. In order to overcome the BBB, therapeutic compounds have been targeted to internalizing receptors at the BBB. In this review we summarize the different approaches that have been described in current literature, including the possible difficulties for clinical application. Particularly, we focus on the possible impact of brain diseases on receptor-mediated transport to the BBB/brain and how this may affect various targeting strategies. Moreover, it is our opinion that a differential drug targeting/delivery approach should be applied to treat central nervous system (CNS) diseases that are related to the BBB alone, and for CNS diseases that are related to both the brain and the BBB.

Cardiac fibroblast paracrine factors alter impulse conduction and ion channel expression of neonatal rat cardiomyocytes

AIMS

The pathological proliferation of cardiac fibroblasts (CFs) in response to heart injury results in fibrosis, which correlates with arrhythmia generation and heart failure. Here we systematically examined the effect of fibroblast-derived paracrine factors on electrical propagation in cardiomyocytes.

METHODS AND RESULTS

Neonatal rat cardiac monolayers were exposed for 24 h to media conditioned by CFs. Optical mapping, sharp microelectrode recordings, quantitative RT-PCR, and immunostaining were used to assess the changes in the propagation and shape of the action potential and underlying changes in gene and protein expression. The fibroblast paracrine factors produced a 52% reduction in cardiac conduction velocity, a 217% prolongation of action potential duration, a 64% decrease of maximum capture rate, a 21% increase in membrane resting potential, and an 80% decrease of action potential upstroke velocity. These effects were dose dependent and partially reversible with removal of the conditioned media. No fibroblast proliferation, cardiomyocyte apoptosis, or decreased connexin-43 expression, phosphorylation, and function were found in conditioned cardiac cultures. In contrast, the expression of the fast sodium, inward rectifying potassium, and transient outward potassium channels were, respectively, reduced 3.8-, 6.6-fold, and to undetectable levels. The expression of beta-myosin heavy chain increased 17.4-fold. No electrophysiological changes were observed from media conditioned by CFs in the presence of cardiomyocytes.

CONCLUSION

Paracrine factors from neonatal CFs alone produced significant electrophysiological changes in neonatal rat cardiomyocytes resembling those found in several cardiac pathologies.