Oxycodone and morphine have distinctly different pharmacological profiles: radioligand binding and behavioural studies in two rat models of neuropathic pain

Previously, we reported that oxycodone is a putative kappa-opioid agonist based on studies where intracerebroventricular (i.c.v.) pre-treatment of rats with the kappa-selective opioid antagonist, nor-binaltorphimine (nor-BNI), abolished i.c.v. oxycodone but not morphine antinociception, whereas pretreatment with i.c.v. naloxonazine (mu-selective antagonist) produced the opposite effects. In the present study, we used behavioural experiments in rat models of mechanical and biochemical nerve injury together with radioligand binding to further examine the pharmacology of oxycodone. Following chronic constriction injury (CCI) of the sciatic nerve in rats, the antinociceptive effects of intrathecal (i.t.) oxycodone, but not i.t. morphine, were abolished by nor-BNI. Marked differences were found in the antinociceptive properties of oxycodone and morphine in streptozotocin (STZ)-diabetic rats. While the antinociceptive efficacy of morphine was abolished at 12 and 24 weeks post-STZ administration, the antinociceptive efficacy of s.c. oxycodone was maintained over 24 weeks, albeit with an approximately 3- to 4-fold decrease in potency. In rat brain membranes irreversibly depleted of mu- and delta-opioid binding sites, oxycodone displaced [(3)H]bremazocine (kappa(2)-selective in depleted membranes) binding with relatively high affinity whereas the selective mu- and delta-opioid ligands, CTOP (D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2)) and DPDPE ([D-Pen(2,5)]-enkephalin), respectively, did not. In depleted brain membranes, the kappa(2b)-ligand, leu-enkephalin, prevented oxycodone's displacement of high-affinity [(3)H]bremazocine binding, suggesting the notion that oxycodone is a kappa(2b)-opioid ligand. Collectively, the present findings provide further support for the notion that oxycodone and morphine produce antinociception through distinctly different opioid receptor populations. Oxycodone appears to act as a kappa(2b)-opioid agonist with a relatively low affinity for mu-opioid receptors.     

The Peripheral Deletion of Autoreactive CD8+ T Cells Induced by Cross-presentation of Self-antigens Involves Signaling through CD95 (Fas,Apo-1)

Recently, we demonstrated that major histocompatibility complex class I–restricted cross-presentation of exogenous self-antigens can induce peripheral T cell tolerance by deletion of autoreactive CD8⁺ T cells. In these studies, naive ovalbumin (OVA)-specific CD8⁺ T cells from the transgenic line OT-I were injected into transgenic mice expressing membrane-bound OVA (mOVA) under the control of the rat insulin promoter (RIP) in pancreatic islets, kidney proximal tubules, and the thymus. Cross-presentation of tissue-derived OVA in the renal and pancreatic lymph nodes resulted in activation, proliferation, and then the deletion of OT-I cells. In this report, we investigated the molecular mechanisms underlying this form of T cell deletion. OT-I mice were crossed to tumor necrosis factor receptor 2 (TNFR2) knockout mice and to CD95 (Fas, Apo-1) deficient mutant lpr mice. Wild-type and TNFR2-deficient OT-I cells were activated and then deleted when transferred into RIP-mOVA mice, whereas CD95-deficient OT-I cells were not susceptible to deletion by cross-presentation. Furthermore, cross-presentation led to upregulation of the CD95 molecule on the surface of wild-type OT-I cells in vivo, consistent with the idea that this is linked to rendering autoreactive T cells susceptible to CD95-mediated signaling. This study represents the first evidence that CD95 is involved in the deletion of autoreactive CD8⁺ T cells in the whole animal.     

In situ quantitative monitoring of polyplexes and polyplex micelles in the blood circulation using intravital real-time confocal laser scanning microscopy

Surface modification using poly(ethylene glycol) (PEG) is a widely used strategy to improve the biocompatibility of cationic polymer-based nonviral gene vectors (polyplexes). A novel method based on intravital real-time confocal laser scanning microscopy (IVRTCLSM) was applied to quantify the dynamic states of polyplexes in the bloodstream, thereby demonstrating the efficacy of PEGylation to prevent their agglomeration. Blood flow in the earlobe blood vessels of experimental animals was monitored in a noninvasive manner to directly observe polyplexes in the circulation. Polyplexes formed distinct aggregates immediately after intravenous injection, followed by interaction with platelets. To quantify aggregate formation and platelet interaction, the coefficient of variation and Pearson's correlation coefficient were adopted. In contrast, polyplex micelles prepared through self-assembly of plasmid DNA with PEG-based block catiomers had dense PEG palisades, revealing no formation of aggregates without visible interaction with platelets during circulation. This is the first report of in situ monitoring and quantification of the availability of PEGylation to prevent polyplexes from agglomeration over time in the blood circulation. This shows the high utility of IVRTCLSM in drug and gene delivery research.     

Diagnostic value of DNA, (1-3)-beta-d-glucan, and galactomannan detection in serum and bronchoalveolar lavage of mice experimentally infected with Aspergillus terreus

The aim of this study was to evaluate the diagnostic value of Aspergillus terreus-specific DNA, (1-3)-beta-d-glucan (BDG), and galactomannan (GM) in immunosuppressed mice infected intravenously with A. terreus conidia and sacrificed in groups of 12 each on days 1, 3, 5, 7, and 9. A. terreus-specific DNA, BDG, and GM in serum and bronchoalveolar lavage (BAL) were detected by nested polymerase chain reaction (nPCR), Fungitell kit (Associates of Cape Cod, E. Falmouth, MA), and Aspergillus Platelia kit (Bio-Rad, Marnes-laCoquette, France), respectively. Cultures of lung homogenate of all the animals yielded A. terreus. The BDG positivity, GM positivity, and nPCR positivity in serum specimens were 43%, 78%, and 73%, respectively. Combined detection enhanced the positivity to 95% for A. terreus DNA and GM, 83% for GM and BDG, and 95% for DNA, GM, and BDG. In BAL, the GM positivity and nPCR positivity were 80% and 81%, respectively, whereas combined detection increased the positivity to 98%. Detection of GM and DNA offers a sensitive and specific diagnostic option for invasive aspergillosis.     

Non-invasive measurement of skin autofluorescence to evaluate diabetic complications

Although the accumulation of advanced glycation end-products (AGEs) of the Maillard reaction in our body is reported to increase with aging and is enhanced by the pathogenesis of lifestyle-related diseases such as diabetes, routine measurement of AGEs is not applied to regular clinical diagnoses due to the lack of conventional and reliable techniques for AGEs analyses. In the present study, a non-invasive AGEs measuring device was developed and the association between skin AGEs and diabetic complications was evaluated. To clarify the association between the duration of hyperglycemia and accumulation of skin fluorophores, diabetes was induced in mice by streptozotocin. As a result, the fluorophore in the auricle of live mice was increased by the induction of diabetes. Subsequent studies revealed that the fingertip of the middle finger in the non-dominant hand is suitable for the measurement of the fluorescence intensity by the standard deviation value. Furthermore, the fluorescence intensity was increased by the presence of diabetic microvascular complications. This study provides the first evidence that the accumulation of fluorophore in the fingertip increases with an increasing number of microvascular complications, demonstrating that the presence of diabetic microvascular complications may be predicted by measuring the fluorophore concentration in the fingertip.     

Role of N-(carboxymethyl)lysine in the development of ischemic heart disease in type 2 diabetes mellitus

This study aims to determine the levels of N(epsilon)-(carboxymethyl)lysine (CML) in patients with Type 2 diabetic patients with and without ischemic heart disease (IHD) and to find for a possible association between circulating CML and a number of clinical parameters including lipids, hemoglobin A1c (HbA1c) and malondialdehyde (MDA) in Type 2 diabetic IHD patients. Serum CML levels were measured by enzyme-linked immunosorbent assay using polyclonal anti-CML antibodies. Serum levels of CML and MDA were assessed in 60 IHD patients with Type 2 diabetes, 43 IHD patients without Type 2 diabetes, 64 Type 2 diabetics without IHD, and 80 sex- and age-matched healthy subjects. Correlations studies between CML levels and lipids, HbA1c, and lipid peroxidation were performed in Type 2 diabetes patients with and without IHD. A statistical significance was observed in the levels of serum glucose, lipids (triglyceride, total cholesterol, HDL-cholesterol), MDA, HbA1c, CML and LDL-cholesterol (p<0.05) between the groups of the study. CML levels were significantly increased in diabetic IHD patients compared with Type 2 diabetes patients but without IHD (537.1 +/- 86.1 vs 449.7 +/- 54.9, p<0.001). A positive correlation was observed between serum levels of CML and MDA, r = 0.338 (p = 0.008) in Type 2 diabetes patients with IHD. However, age, HbA1c and lipids had no significant influence on CML levels among diabetics (p>0.05). In conclusion, this study demonstrates the effect of both diabetes and oxidative stress on the higher levels of circulating CML. These results showed that increased serum levels of CML are associated with the development of IHD in Type 2 diabetes mellitus.     

The mechanism of apoptosis in human platelets during storage

BACKGROUND: Although it is usually involved only in nucleated cells (NCs), artificially enucleated cells also lose viability by a programmed process of cell death called apoptosis. Because platelets undergo loss of viability during storage, an attempt was made to determine whether platelets contained the apoptotic mechanisms and whether it was activated during platelet storage. STUDY DESIGN AND METHODS: Platelet viability was measured by reduction of a tetrazolium dye (MTS) and annexin V binding. Members of the death receptor, caspase, and Bcl-2 families were detected by RNase protection assay and Western blotting. Caspase 3 activation was measured by enzyme and Western blot assays and by cleavage of gelsolin. RESULTS: After 5 days of storage under standard blood banking conditions, platelets display biochemical signs of apoptosis by losing MTS activity and increasing the amount of phosphatidylserine on their surface. The mRNA and the proenzyme for several members of the caspase, death receptor, and Bcl-2 families are expressed at high levels in platelets. An increase in caspase 3 activity and the amount of the biologically active p17 subunit of active caspase 3 were observed to coincide with the appearance of apoptotic markers during storage. These effects were not due to platelet activation. The caspase 3 substrate, gelsolin, began to undergo proteolysis after 3 to 4 days of storage, and the addition of the caspase inhibitor z-VAD-fmt substantially inhibited this process. CONCLUSION: Platelets contain many of the components of the apoptotic mechanism and show activation of caspase 3 and consequent cleavage of gelsolin during storage, independent of platelet activation. Evaluation of the mechanism of apoptosis in platelets may provide a basis for developing novel strategies to enhance platelet viability during storage.     

Systemic delivery of BH4 anti-apoptotic peptide using CPPs prevents cardiac ischemia-reperfusion injuries in vivo

There is an obvious need to develop pharmacological strategies to protect the heart in patients suffering from acute myocardial infarction. Apoptosis was evidenced as a main contributor of myocardial ischemia-reperfusion (IR) injury. Our cardioprotective strategy was based on the use of four cell penetrating peptides (CPP: Tat, (RXR)4, Bpep and Pip2b) which were conjugated to the BH4-peptide, derived from the BH4 domain of the Bcl-xL anti-apoptotic protein. These CPP-BH4 conjugates were able to reduce staurosporine-induced apoptosis in primary cardiomyocytes in vitro. Although Pip2b-BH4 was more efficient in terms of cellular uptake, it was as efficient as Tat-BH4 for its anti-apoptotic activity. As required for potential therapeutic application their cardioprotective effects were evaluated in an in vivo mouse model of myocardial IR injury.Our results clearly show that a single low dose (1 mg/kg) injection of Tat-BH4 and Pip2b-BH4 administered intravenously 5 min before reperfusion was able to drastically reduce infarct size (~ 47%) and to inhibit apoptosis (~ 60%) in the left ventricle of treated mice. Importantly, these effects are not observed following the injection of CPP alone or scrambled version of BH4. This study evidences that the Pip2b CPP, designed for oligonucleotides translocation, as well as the widely used natural Tat CPP exhibit similar efficacy in vivo to deliver BH4 anti-apoptotic peptide to the reperfused myocardium and may thus become useful therapeutic tools to treat acute myocardial infarction in the clinical setting.     

Increased plasma anti-Xa activity and recovery of heparin from urine suggest absorption of orally administered unfractionated heparin in human subjects

Although heparin is not generally administered orally, the results of studies involving rats suggest that heparin is absorbed, with low levels in plasma but extensive distribution to the endothelium. To determine whether evidence of absorption after oral administration can also be demonstrated in human subjects, we administered unfractionated porcine heparin in a single dose of 1000 U/kg to 6 healthy human subjects. Plasma anticoagulant activity was monitored between 5 minutes and 72 hours after administration, and chemical heparin concentrations were determined in 24-hour urine samples for as long as 120 hours after administration. Plasma anticoagulant activity, determined by anti-Xa activity, increased as soon as 5 minutes after heparin administration, peaked at 120 minutes, and was still increased 72 hours after administration. Values were significantly greater 15 minutes to 48 hours after administration compared with values before administration (paired t test). Mean activated partial thromboplastin time and Heptest values in subjects given heparin were greater than those in controls 15 and 30 minutes and 5 to 120 minutes after administration, respectively. Heparin was recovered from urine as long as 120 hours after administration (the latest time point at which samples were collected); greater amounts were excreted between 48 and 120 hours than before 48 hours. Recovery from both plasma and urine suggest that unfractionated heparin administered orally is absorbed in human subjects, is widely distributed, and is found in the body at least 120 hours after administration. Because heparin is readily bound to endothelium, recovery from plasma and urine likely reflect considerable amounts with endothelium, as has been observed in other species.     

Inhibitory effects of lycopene on in vitro platelet activation and in vivo prevention of thrombus formation

Lycopene is a natural carotenoid antioxidant that is present in tomatoes and tomato products. The pharmacologic function of lycopene in platelets is not yet understood. Therefore, in this study we sought to systematically examine the effects of lycopene in the prevention of platelet aggregation and thrombus formation. We found that lycopene concentration-dependently (2-12 micromol/L) inhibited platelet aggregation in human platelets stimulated by agonists. Lycopene (6 and 12 micromol/L) inhibited phosphoinositide breakdown in platelets labeled with tritiated inositol, intracellular Ca+2 mobilization in Fura-2 AM-loaded platelets, and thromboxane B2 formation stimulated by collagen. In addition, lycopene (6 and 12 micromol/L) significantly increased the formations of cyclic GMP and nitrate but not cyclic AMP in human platelets. Rapid phosphorylation of a protein of 47,000 Da (P47), a marker of protein kinase C activation, was triggered by PDBu (60 nmol/L). This phosphorylation was markedly inhibited by lycopene (12 micromol/L) in phosphorus-32-labeled platelets. In an in vivo study, thrombus formation was induced by irradiation of mesenteric venules in mice pretreated with fluorescein sodium. Lycopene (5, 10, and 20 mg/kg) significantly prolonged the latency period for the induction of platelet-plug formation in mesenteric venules. These results indicate that the antiplatelet activity of lycopene may involve the following pathways: (1) Lycopene may inhibit the activation of phospholipase C, followed by inhibition of phosphoinositide breakdown and thromboxane B2 formation, thereby leading to inhibition of intracellular Ca+2 mobilization. (2) Lycopene also activated the formations of cyclic GMP/nitrate in human platelets, resulting in the inhibition of platelet aggregation. The results may imply that tomato-based foods are especially beneficial in the prevention of platelet aggregation and thrombosis.     

6r,a novel oxadiazole analogue of ethacrynic acid,exhibits antitumor activity both in vitro and in vivo by induction of cell apoptosis and S-phase arrest

This study investigated the in vitro and in vivo antitumor effects of 5-[2,3-Dichloro-4-(2-methylene-1-oxobutyl) phenoxymethyl]-3-methyl-1,2,4- oxadiazole (6r), a novel ethacrynic acid (EA) derivative. The in vitro effect of 6r on cell proliferation of human colon, leukemia, prostate, lung, breast, ovarian and cervical tumor cell lines was assessed using MTT assay and the in vivo effect was determined with an SW620 xenografts nude mice model. The effect of 6r on expressions of GST P1-1 and apoptosis-related proteins were measured by western blotting and the effect on cell apoptosis was analysed by Hoechst 33258 nuclear staining as well as by cell surface staining of annexin V/propidium iodide. The effect on cell cycle was assessed by flow cytometry. Results showed that 6r inhibit proliferation of a range of human cancer cells in vitro and growth of SW620 tumor xenografts in vivo. The anti-proliferative effect of 6r is associated with cell apoptosis as a result of increased ratio of cellular Bax/bcl-2 expression and subsequent cytochrome-c and caspase-3 activation. Unlike EA, 6r did not show any influence on cellular GST P1-1 expression and its anti-proliferative action was associated with cell cycle arrest in G1/S-phase. In conclusion, 6r has the potential to be developed as a chemotherapeutic agent by induction of cell apoptosis but not regulating GST P1-1.     

Selective monitoring of vitamin D2 and D3 supplementation with a highly specific 25-hydroxyvitamin D3 immunoassay with negligible cross-reactivity to 25-hydroxyvitamin D2

Background

The effects of vitamin D₂ and D₃ supplementation on circulating concentrations of 25(OH)D₃ require reliable analytical tools for specific determination of 25(OH)D₃ and 25(OH)D₂. We have developed a highly specific 25-OH Vitamin D3 ELISA with negligible cross-reactivity towards 25(OH)D₂.

Methods

25(OH)D₃ concentrations were measured in several study participants; 1) 641 healthy men and women; 2) 39 postmenopausal women receiving 400-800 IU vitamin D₃ daily for 4 months; 3) 45 men and women with hip fracture receiving 1000 IU vitamin D₂ daily for 3 months.

Results

This 25-OH Vitamin D3 ELISA had minimal cross-reactivity to 25(OH)D₂, (0.7%), and demonstrated a high correlation (r² = 0.93) with 25(OH)D₃ determined by HPLC. 25(OH)D₃ increased by 14% in subjects receiving vitamin D₃ for 4 months (p < 0.01), whereas there was no significant change in 25(OH)D₃ levels in those receiving vitamin D₂.

Conclusions

We report that 25(OH)D₃ ELISA was used for evaluation of 25(OH)D₃ concentrations in subjects receiving vitamin D₂ and D₃ supplementation. The increase of 25(OH)D₃ in circulation with vitamin D3 supplementation and lack of increase with vitamin D₂ supplementation suggest that this assay has sufficient sensitivity and specificity to be used as a reliable measurement of nutritional vitamin D₃ status in humans.     

The Effect of Insulin on the Intracellular Distribution of 14(R,S)-[18F]Fluoro-6-thia-heptadecanoic Acid in Rats

Purpose The aim of this study was to determine the effect of hyperinsulinemia on myocardial and hepatic distribution and metabolism of 14(R,S)-[¹⁸F]fluoro-6-thia-heptadecanoic acid ([¹⁸F]FTHA).Procedures Mitochondrial retention and intracellular lipid incorporation of [¹⁸F]FTHA were compared to that of [¹⁴C]-2-bromopalmitate or [¹⁴C]palmitate during hyperinsulinemic clamp vs. saline infusion in male Wistar rats.Results Mitochondrial ¹⁸F activity was increased in the heart (1.7 ± 0.4 vs. 0.5 ± 0.1% ID/g, P < 0.05), whereas it was reduced in the liver (1.1 ± 0.3 vs. 1.8 ± 0.4% ID/g, P < 0.05) during insulin vs. saline infusion, respectively. Mitochondrial [¹⁴C]-2-bromopalmitate activity was affected by insulin in a similar way in both tissues. The fractional esterification of [¹⁸F]FTHA into triglycerides was impaired compared to [¹⁴C]palmitate in both tissues, and [¹⁸F]FTHA was insensitive to the shift of esterification of fatty acids into complex lipids in response to insulin.Conclusions [¹⁸F]FTHA is sensitive to insulin-induced modifications of free fatty acid oxidative metabolism in rats but is insensitive to changes in nonoxidative fatty acid metabolism.     

Partial inefficiency of T cell receptors γ/δ composed of a heavy (55-kD) γ chain to mediate cell activation upon binding to specific monoclonal antibodies

Summary We analyzed CD8⁺ T cell receptor (TCR) γ/δ⁺ (δ-TCS-1 reactive) cell clones expressing the 55-kD γ chain for their susceptibility to triggering by monoclonal antibodies (mAbs) specific for TCR or CD3 molecules. Clones were derived by limiting dilution from CD3⁺, WT31⁻ FACS-purified peripheral blood populations or CD4⁻CD8⁻ thymocytes (a fraction of the latter cells expressingde novo CD8 surface antigen upon culture in IL-2). Clones were screened according to their reactivity with both anti-CD8 and δ-TCS-1 mAbs. Analysis of CD3-associated molecules immunoprecipitated by anti-Leu-4 (anti-CD3) mAb under conditions which preserve the CD3/TCR association (1% digitonin) showed a predominant 55–60-kD molecule both under reducing and non-reducing conditions. All clones expressing the δ-TCS-1⁺ CD8⁺ surface phenotype derived from either thymus or peripheral blood lysed the Fcγ receptor-bearing P815 target cells in the presence of anti-CD3 mAb. On the other hand, δ-TCS-1 mAb was poorly efficient in triggering the lytic machinery of these clones, while it induced target cell lysis by δ-TCS-1⁺ CD8⁻ clones. This work was supported by grants from theConsiglio Nazionale delle Ricerche (CNR), Roma, Italy,Progetto Finalizzato ‘Oncologia’ to M. C. M. and A. M., and from theAssociazione Italiana per la Ricerca sul Cancro (AIRC).     

Increased susceptibility of fat-laden Zucker-rat hepatocytes to bile acid-induced oncotic necrosis: an in vitro model of steatocholestasis

Metabolic liver disorders cause chronic liver disease and liver failure in childhood. Many of these disorders share the histologic features of steatosis and cholestasis, or steatocholestasis. In this study we sought to (1) develop an in vitro model of steatocholestasis, (2) determine the mechanisms of cell death in this model, and (3) determine the role of mitochondrial disturbances in this model. Methods: Hepatocytes were isolated from 8-week-old obese (fa/fa) and lean Zucker rats. Cell suspensions were treated with glycochenodeoxycholic acid (GCDC), after which reactive oxygen species (ROS) generation, oncotic necrosis, apoptosis, and ATP content were assessed. Isolated liver mitochondria were exposed to GCDC and analyzed for ROS generation, mitochondrial membrane-permeability transition (MPT), and cytochrome c release. Oncotic necrosis was significantly increased and apoptosis reduced in fa/fa hepatocytes exposed to GCDC compared with that in lean hepatocytes. Necrosis occurred by way of an ROS- and MPT-dependent pathway. Basal and dynamic ATP content did not differ between fa/fa and lean hepatocytes. GCDC stimulated ROS generation, MPT, and cytochrome c release to a similar extent in purified mitochondria from both fa/fa and lean rats. These findings suggest that fat-laden hepatocytes favor a necrotic rather than an apoptotic cell death when exposed to low concentrations of bile acids. The protective effects of antioxidants and MPT blockers suggest novel therapeutic strategies for the treatment of steatocholestatic metabolic liver diseases.     

Up-regulation of stanniocalcin 1 expression by 1,25-dihydroxy vitamin D(3) and parathyroid hormone in renal proximal tubular cells

Stanniocalcin 1 and stanniocalcin 2 are two glycoprotein hormones, which act as calcium phosphate-regulating factor on intestine and kidney. We have previously reported that stanniocalcin 2 expression is positively and negatively controlled by 1,25(OH)(2)D(3) and parathyroid hormone in renal proximal tubular cells. However, it has been unclear whether they regulate the stanniocalcin 1 gene expression. In this study, we identified the opossum stanniocalcin 1 cDNA sequence. The opossum stanniocalcin 1 amino acid sequence had 83% homology with human stanniocalcin 1, and has a conserved putative N-linked glycosylation site. Real-time PCR analysis using opossum kidney proximal tubular (OK-P) cells revealed that the mRNA levels of stanniocalcin 1 gene is up-regulated by both 1,25(OH)(2)D(3) and parathyroid hormone in dose-dependent and time-dependent manners. We also demonstrated that the stanniocalcin 1 expression was increased in parathyroid hormone injected rat kidney. Furthermore, the mRNA expression of stanniocalcin 1 and stanniocalcin 2 were oppositely regulated by phorbol 12,13-myristic acetate, a specific PKC activator. Interestingly, the up-regulation of stanniocalcin 1 gene by 1,25(OH)(2)D(3) and phorbol 12,13-myristic acetate were not prevented in the presence of actinomycin D, an RNA synthesis inhibitor. These results suggest that the stanniocalcin 1 gene expression is up-regulated by 1,25(OH)(2)D(3) and parathyroid hormone through mRNA stabilization in renal proximal tubular cells.     

Glutamate abnormalities in obsessive compulsive disorder: neurobiology, pathophysiology, and treatment

Obsessive compulsive disorder is prevalent, disabling, incompletely understood, and often resistant to current therapies. Established treatments consist of specialized cognitive-behavioral psychotherapy and pharmacotherapy with medications targeting serotonergic and dopaminergic neurotransmission. However, remission is rare, and more than a quarter of OCD sufferers receive little or no benefit from these approaches, even when they are optimally delivered. New insights into the disorder, and new treatment strategies, are urgently needed. Recent evidence suggests that the ubiquitous excitatory neurotransmitter glutamate is dysregulated in OCD, and that this dysregulation may contribute to the pathophysiology of the disorder. Here we review the current state of this evidence, including neuroimaging studies, genetics, neurochemical investigations, and insights from animal models. Finally, we review recent findings from small clinical trials of glutamate-modulating medications in treatment-refractory OCD. The precise role of glutamate dysregulation in OCD remains unclear, and we lack blinded, well-controlled studies demonstrating therapeutic benefit from glutamate-modulating agents. Nevertheless, the evidence supporting some important perturbation of glutamate in the disorder is increasingly strong. This new perspective on the pathophysiology of OCD, which complements the older focus on monoaminergic neurotransmission, constitutes an important focus of current research and a promising area for the ongoing development of new therapeutics.     

Past, present and future of A(2A) adenosine receptor antagonists in the therapy of Parkinson's disease

Several selective antagonists for adenosine A_2A receptors (A_2AR) are currently under evaluation in clinical trials (phases I to III) to treat Parkinson's disease, and they will probably soon reach the market. The usefulness of these antagonists has been deduced from studies demonstrating functional interactions between dopamine D₂ and adenosine A_2A receptors in the basal ganglia. At present it is believed that A_2AR antagonists can be used in combination with the dopamine precursor L-DOPA to minimize the motor symptoms of Parkinson's patients. However, a considerable body of data indicates that in addition to ameliorating motor symptoms, adenosine A_2AR antagonists may also prevent neurodegeneration. Despite these promising indications, one further issue must be considered in order to develop fully optimized antiparkinsonian drug therapy, namely the existence of (hetero)dimers/oligomers of G protein-coupled receptors, a topic that is currently the focus of intense debate within the scientific community. Dopamine D₂ receptors (D₂Rs) expressed in the striatum are known to form heteromers with A_2A adenosine receptors. Thus, the development of heteromer-specific A_2A receptor antagonists represents a promising strategy for the identification of more selective and safer drugs.