The potential and limitations of DOV 216,303 as a triple reuptake inhibitor for the treatment of major depression: a microdialysis study in olfactory bulbectomized rats

DOV 216,303 belongs to a new class of antidepressants, the triple reuptake inhibitors (TRIs), that blocks serotonin, norepinephrine and dopamine transporters and thereby increases extracellular brain monoamine concentrations. The aim of the present study was to measure extracellular monoamine concentrations both in the prefrontal cortex (PFC) and dorsal hippocampus (DH) after chronic administration of DOV 216,303 in the OBX animal model of depression and to compare the effects with acute drug treatment. OBX animals showed lower dopamine levels in PFC upon acute administration of DOV 216,303 than sham animals for up to five weeks after surgery. No such changes were observed in the DH. Unexpectedly, a DOV 216,303 challenge in chronic DOV 216,303 treated sham animals resulted in a blunted dopamine response in the PFC compared to the same challenge in vehicle treated animals. This blunted response probably reflects pharmacokinetic adaptations and/or pharmacodynamic changes, since brain and plasma concentrations of DOV 216,303 were significantly lower after chronic administration compared to acute administration. Surprisingly, and in contrast what we have reported earlier, chronic DOV 216,303 treatment was unable to normalize the hyperactivity of the OBX animals. Interestingly, by measuring the drug plasma and brain levels, it was demonstrated that at the time of behavioral testing (24 h after last drug treatment) DOV 216,303 was not present anymore in either plasma or brain. This seems to indicate that this putative antidepressant drug has no lasting antidepressant-like behavioral effects in the absence of the drug in the brain.

Localization and functional characterization of the human NKCC2 isoforms

AIM

Salt reabsorption across the apical membrane of cells in the thick ascending limb (TAL) of Henle is primarily mediated by the bumetanide-sensitive Na(+)/K(+)/2Cl(-) cotransporter NKCC2. Three full-length splice variants of NKCC2 (NKCC2B, NKCC2A and NKCC2F) have been described. The NKCC2 isoforms have specific localizations and transport characteristics, as assessed for rabbit, rat and mouse. In the present study, we aimed to address the localization and transport characteristics of the human NKCC2 isoforms.

METHODS

RT-PCR, in situ hybridization and uptake studies in Xenopus oocytes were performed to characterize human NKCC2 isoforms.

RESULTS

All three classical NKCC2 isoforms were detected in the human kidney; in addition, we found splice variants with tandem duplicates of the variable exon 4. Contrary to rodents, in which NKCC2F is the most abundant NKCC2 isoform, NKCC2A was the dominant isoform in humans; similarly, isoform-specific in situ hybridization showed high expression levels of human NKCC2A along the TAL. Compared to NKCC2B and NKCC2F, human NKCC2A had the lowest Cl(-) affinity as determined by (86)Rb(+) uptake studies in oocytes. All NKCC2 isoforms were more efficiently inhibited by bumetanide than by furosemide. A sequence analysis of the amino acids encoded by exon 4 variants revealed high similarities between human and rodent NKCC2 isoforms, suggesting that differences in ion transport characteristics between species may be related to sequence variations outside the highly conserved sequence encoded by exon 4.

CONCLUSION

The human NKCC2 is an example of how differential splicing forms the basis for a diversification of transporter protein function.

AMDIS Case Conference: Intrusive Medication Safety Alerts

Clinical decision support that provides enhanced patient safety at the point of care frequently encounters significant pushback from clinicians who find the process intrusive or time-consuming. We present a hypothetical medical center's dilemma about its allergy alerting system and discuss similar problems faced by real hospitals. We then share some lessons learned and best practices for institutions who wish to implement these tools themselves.

Cancer Immunoediting: Immunologic Control and Sculpting of Cancer

Cancer Immunoediting is the process by which the immune system controls and shapes cancer. We originally envisaged that cancer immunoediting would occur in three phases: Elimination (also known as cancer immunosurveillance, the host protective phase of the process), Equilibrium (the phase in which tumor cells that survive immune elimination remain under immunologic growth control resulting in a state of functional tumor dormancy) and Escape (the phase where clinically apparent tumors emerge because immune sculpting of the tumor cells has produced variants that display either reduced immunogenicity or enhanced immunosuppressive activity). Strong experimental data has now been obtained using mouse models of cancer to demonstrate the existence of each phase of the cancer immunoediting process and compelling clinical data suggests that a similar process may also occur during the evolution of certain types of human cancer. Our efforts now focus on elucidating the molecular and cellular mechanisms that underlie each phase of cancer immunoediting and identifying the critical checkpoints that regulate progression from one phase of the process to the next. This approach has led to the discovery of a new mouse cancer model that shows remarkable developmental, molecular and functional similarity to human estrogen receptor alpha positive (ERα+) luminal breast cancer. We have found that the cancers in our mice arise as a result of dysfunctional JAK-STAT pathway signaling and, interestingly, this observation has led to the discovery of a heretofore-unrecognized similar phenotype in a subset of human ERα+ luminal breast cancers. The therapeutic implications of our work will be discussed.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr BS3-1.

Mammary Tumors in STAT1-Deficient Mice Recapitulate Characteristics of Human Luminal Breast Cancers

Human breast cancer of the luminal subtype represents approximately 70% of all newly diagnosed breast cancers. This particular subtype of tumors are estrogen receptor α (ERα)-positive and/or progesterone receptor (PR)-positive. However, 50% of these patients do not derive benefit from endocrine therapy. One obstacle in the study of hormone receptor-positive breast cancer is that there is currently a deficit in murine models that can fully recapitulate the biology of this highly prevalent breast cancer subtype. Here we show that mice lacking the transcription factor signal transducers and activators of transcription 1 (STAT1) spontaneously developed mammary gland adenocarcinomas that showed remarkable similarities to human luminal breast cancer at histopathological, biological and molecular levels. More than 90% of the tumor cells in both early and advanced lesions were ERα+ and/or PR+. STAT1-/- mammary tumor cells failed to grow in ovariectomized mice, demonstrating that these tumors are addicted to ovarian hormones for proliferation. Supplementing with exogenous estrogen was sufficient to rescue tumor growth in ovariectomized mice. STAT1 functions, at least in part, as an intrinsic tumor suppressor since reconstitution of STAT1 expression in STAT1-/- mammary tumor cells induced spontaneous apoptosis. Induction of cell death required the critical tyrosine residue at position 701, suggesting that the transcriptional function of STAT1 is involved in tumor suppression.In contrast to the anti-oncogenic effect of STAT1, STAT3 was constitutively phosphorylated by JAK2 in the STAT1-/- mammary tumor cells. Inhibition of JAK2 or STAT3 activation resulted in tumor cell death, indicating that STAT3 promotes tumor cell survival. Gene expression profiles of the STAT1-/- mammary tumors showed significant overlaps with that of the human luminal breast cancers, strongly supporting that the STAT1-/- mammary tumors recapitulate the molecular signatures of human luminal breast cancers. Consistent with the results that STAT1 can act as an intrinsic tumor suppressor, approximately 10% of the human ERα+ breast cancer cases exhibit either undetectable or very low level of STAT1 in the mammary epithelial compartment. This study uncovers a unique role of STAT1 in suppressing mammary gland tumorigenesis. Importantly, this physiologically relevant model of human luminal breast cancer will provide an exceptional tool for the development and evaluation of novel therapeutics.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 65.

The neurotensin agonist NT69L improves sensorimotor gating deficits in rats induced by a glutamatergic antagonist, but not by dopaminergic agonists

An imbalance between different neurotransmitter systems is involved in the pathophysiological processes underlying schizophrenia. Since the neurotensin (NT) system modulates the activity of several of these neurotransmitters, drugs acting upon the NT system may act as novel antipsychotic drugs. This hypothesis is supported by studies with NT in animal models. For example, intracranial injection of NT improves sensorimotor gating in rats [Feifel D, Minor KL, Dulawa S, Swerdlow NR. The effects of intra-accumbens neurotensin on sensorimotor gating. Brain Research 1997;760:80-4]. NT-mimetics, such as NT69L, have been developed which are more resistant to enzymatic degradation than the native NT peptide. In the present study, the potential antipsychotic properties of NT69L were evaluated in a rat pre-pulse inhibition (PPI) paradigm. PPI is a measure of sensorimotor gating where a weak auditory stimulus, or pre-pulse, inhibits the startle response to a strong stimulus, or pulse. Schizophrenic patients exhibit deficits in their PPI response. This condition can be mimicked in rats with psychotomimetic drugs and the resulting PPI deficit is reversed by antipsychotic drugs. NT69L (0.1-10mg/kg i.p.) reversed disruptions of the PPI response induced by the NMDA antagonist dizocilpine (0.1mg/kg s.c.) for at least 1-h post-injection, but did not reverse disruptions induced by the dopaminergic agonists apomorphine and d-amphetamine (0.5 and 5mg/kg s.c., respectively). These results confirm that NT69L possesses antipsychotic-like activity and therefore could be beneficial in the treatment of schizophrenia.

European biliary atresia registries: summary of a symposium

Biliary atresia (BA) is a rare but potentially devastating disease. The European Biliary Atresia Registry (EBAR) was set up to improve data collection and to develop a pan-national and interdisciplinary strategy to improve clinical outcomes. From 2001 to 2005, 100 centers from 22 countries registered with EBAR via its website (www.biliary-atresia.com). In June 2006, the first meeting was held to evaluate results and launch further initiatives. During a 5-year period, 60 centers from 19 European countries and Israel sent completed registration forms for a total of 514 BA patients. Assuming the estimated incidence of BA in Europe is 1:18,000 live births, 35% of the expected 1488 patients from all EBAR participating countries were captured, suggesting that reporting arrangements need improvement. At the meeting, the cumulative evaluation of 928 BA patients including patients from other registries with variable follow-up revealed an overall survival of 78% (range from 41% to 92%), of whom 342 patients (37%) have had liver transplants. Survival with native liver ranged from 14% to 75%. There was a marked variance in reported management and outcome by country (e.g., referral patterns, timing of surgery, centralization of surgery). In conclusion, EBAR represents the first attempt at an overall evaluation of the outcome of BA from a pan-European perspective. The natural history and outcome of biliary atresia is of considerable relevance to a European population. It is essential that there is further support for a pan-European registry with coordination of clinical standards, further participation of parent support groups, and implementation of online data entry and multidisciplinary clinical and basic research projects.

Improving memory: a role for phosphodiesterases

During the last decennia, our understanding of the neurobiological processes underlying learning and memory has continuously improved, leading to the identification of targets for the development of memory-enhancing drugs. Here we review a class of drugs which has more recently been identified: the phosphodiesterase (PDE) inhibitors. An overview is given of the different PDEs that are known and we focus on three PDEs which have been identified as possible relevant targets for memory improvement: PDE2, PDE4 and PDE5. PDEs differ in the substrate, i.e. cyclic adenosine monophosphate (cAMP) and/or cyclic guanosine monophosphate (cGMP), being hydrolyzed. Since these cyclic nucleotides have been suggested to play distinct roles in processes of memory, selective PDE inhibitors preventing the breakdown of cAMP and/or cGMP could improve memory. The present data suggest that PDE4 (cAMP) is involved in acquisition processes, although a possible role in late consolidation processes cannot be excluded. PDE5 (cGMP) is involved in early consolidation processes. Since PDE2 inhibition affects both cAMP and cGMP, PDE2 inhibitors may improve both memory processes. The field of PDEs is highly dynamic and new isoforms of PDEs are still being described. This may lead to the discovery and development of new memory enhancing drugs that selectively inhibit such isoforms. Such drugs may exert their effects only in specific brain areas and hence possess an improved side effect profile.

Expression of cardiomyocytic markers on adipose tissue-derived cells in a murine model of acute myocardial injury

Animal and early clinical studies have provided evidence suggesting that intracoronary administration of autologous bone marrow-derived cells results in improved outcome following myocardial infarction. Animal studies with cultured marrow stromal cells (MSC) have provided similar data. Cells with properties that are similar to MSC have been identified in adipose tissue. Other groups have demonstrated in vivo differentiation of adipose tissue-derived cells (ADC) into cells exhibiting biochemical and functional markers of cardiac myocytes, including spontaneous beating. Based on these observations, the objective of the present study was to determine whether ADC might undergo similar differentiation in vivo in the context of myocardial injury.ADC were isolated from subcutaneous adipose tissue of Rosa26 mice (which express the beta-galactosidase transgene in almost every tissue) and injected into the intraventricular chamber of B6129S recipient mice immediately following induction of myocardial cryoinjury. Groups of recipients were euthanized at 24 hours, 7 and 14 days post surgery and examined for the presence of donor-derived cells within the heart.Beta-gal positive cells were identified in the infarcts of ADC-treated animals. No staining was observed in uninjured myocardium or in infarcts of control animals. Immunohistochemical analysis revealed co-expression of beta-gal with Myosin Heavy Chain, Nkx2.5 and with Troponin I. Co-expression of beta-galactosidase with Connexin 43, CD31, von Willebrand factor, MyoD or CD45 was not detected.Thus, these data indicate that adipose tissue contains a population of cells that has the ability to engraft injured myocardium and that this engraftment is associated with expression of cardiomyocytic markers by donor-derived cells.

Ca2+ signaling, intracellular pH and cell volume in cell proliferation

Mitogens control progression through the cell cycle in non-transformed cells by complex cascades of intracellular messengers, such as Ca2+ and protons, and by cell volume changes. Intracellular Ca2+ and proton concentrations are critical for linking external stimuli to proliferation, motility, apoptosis and differentiation. This review summarizes the role in cell proliferation of calcium release from intracellular stores and the Ca2+ entry through plasma membrane Ca2+ channels. In addition, the impact of intracellular pH and cell volume on cell proliferation is discussed.

5-HT1A receptors are differentially involved in the anxiolytic- and antidepressant-like effects of 8-OH-DPAT and fluoxetine in the rat

Fluoxetine, a selective serotonin reuptake inhibitor, shows moderate efficacy and potency in the rat forced swimming depression test and the shock-induced ultrasonic vocalization anxiety test, whereas the 5-HT(1A) receptor agonist (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) is highly efficient and potent in both models. Whereas the 5-HT(1A) receptor antagonist WAY 100,635 abolishes the effect of 8-OH-DPAT in both models, it only attenuates the antidepressant-like effect of fluoxetine. Pretreatment with the 5-HT-depleting agent parachlorophenylalanine attenuates the antidepressant-like effect of fluoxetine, but not that of 8-OH-DPAT. This suggests that the antidepressant-like effect of fluoxetine and 8-OH-DPAT results from indirect (via increased synaptic availability of 5-HT) and direct stimulation of postsynaptic 5-HT(1A) receptors, respectively; whereas the anxiolytic-like effect of fluoxetine is not mediated by 5-HT(1A) receptors. The data support the hypothesis that the antidepressant- and anxiolytic-like effect of 8-OH-DPAT is predominantly mediated by post- and presynaptic 5-HT(1A) receptors, respectively, and that 5-HT(1A) receptors are only partially involved in the antidepressant-like effect of fluoxetine.