Ethical and Scientific Perspectives of Placebo-controlled Trials in Schizophrenia

Clinical trials for development of new medications are essential in all fields of medicine. The requirement for a placebo arm in pharmaceutical trials presents ethical and clinical dilemmas that are especially complicated with regard to mentally ill persons whose free choice and ability to provide informed consent may be questionable. On the other hand, we do not believe that this predicament justifies unconditional rejection of placebo use in psychiatry, when the investigational drug may ultimately provide substantial benefit for some patients. At the same time it is the psychiatrist's responsibility to insure that investigators are adequately trained to conduct clinical trials and that stringent regulatory committees supervise the scientific, clinical and ethical aspects of the trials

Developmental Regulation of B Lymphocyte Immune Tolerance Compartmentalizes Clonal Selection from Receptor Selection

AbstractB lymphocyte development is a highly ordered process that involves immunoglobulin gene rearrangements, antigen receptor expression, and a learning process that minimizes the development of cells with reactivity to self tissue. Two distinct mechanisms for immune tolerance have been defined that operate during early bone marrow stages of B cell development: apoptosis, which eliminates clones of cells, and receptor editing, which spares the cells but genetically reprograms their autoreactive antigen receptors through nested immunoglobulin L chain gene rearrangements. We show here that sensitivity to antigen-induced apoptosis arises relatively late in B cell development and is preceded by a functionally distinct developmental stage capable of receptor editing. This regulation compartmentalizes clonal selection from receptor selection

A Fail-safe Mechanism for Negative Selection of Isotype-switched B Cell Precursors Is Regulated by the Fas/FasL Pathway

In B lymphocytes, immunoglobulin (Ig)M receptors drive development and construction of naive repertoire, whereas IgG receptors promote formation of the memory B cell compartment. This isotype switching process requires appropriate B cell activation and T cell help. In the absence of T cell help, activated B cells undergo Fas-mediated apoptosis, a peripheral mechanism contributing to the establishment of self-tolerance. Using Igμ-deficient μMT mouse model, where B cell development is blocked at pro-B stage, here we show an alternative developmental pathway used by isotype-switched B cell precursors. We find that isotype switching occurs normally in B cell precursors and is T independent. Ongoing isotype switching was found in both normal and μMT B cell development as reflected by detection of IgG1 germline and postswitch transcripts as well as activation-induced cytidine deaminase expression, resulting in the generation of IgG-expressing cells. These isotype-switched B cells are negatively selected by Fas pathway, as blocking the Fas/FasL interaction rescues the development of isotype-switched B cells in vivo and in vitro. Similar to memory B cells, isotype-switched B cells have a marginal zone phenotype. We suggest a novel developmental pathway used by isotype-switched B cell precursors that effectively circumvents peripheral tolerance requirements. This developmental pathway, however, is strictly controlled by Fas/FasL interaction to prevent B cell autoimmunity

IgG1 B cell receptor signaling is inhibited by CD22 and promotes the development of B cells whose survival is less dependent on Igα/β

We describe a mouse strain in which B cell development relies either on the expression of membrane-bound immunoglobulin (Ig) γ1 or μ heavy chains. Progenitor cells expressing γ1 chains from the beginning generate a peripheral B cell compartment of normal size with all subsets, but a partial block is seen at the pro– to pre–B cell transition. Accordingly, γ1-driven B cell development is disfavored in competition with developing B cells expressing a wild-type (WT) IgH locus. However, the mutant B cells display a long half-life and accumulate in the mature B cell compartment, and even though partial truncation of the Igα cytoplasmic tail compromises their development, it does not affect their maintenance, as it does in WT cells. IgG1-expressing B cells showed an enhanced Ca2+ response upon B cell receptor cross-linking, which was not due to a lack of inhibition by CD22. The enhanced Ca2+ response was also observed in mature B cells that had been switched from IgM to IgG1 expression in vivo. Collectively, these results suggest that the γ1 chain can exert a unique signaling function that can partially replace that of the Igα/β heterodimer in B cell maintenance and may contribute to memory B cell physiology

The c-Myc/miR17-92/PTEN Axis Tunes PI3K Activity to Control Expression of Recombination Activating Genes in Early B Cell Development

Appropriate PI3K signals generated by the antigen receptor are essential to promote B cell development. Regulation of recombination activating gene (RAG)-1 and RAG-2 expression is one key process that is mediated by PI3K to ensure developmental progression and selection. When PI3K signals are too high or too low, expression of RAGs does not turn off and B cell development is impaired or blocked. Yet, the mechanism which tunes PI3K activity to control RAG expression during B cell development in the bone marrow is unknown. Recently we showed that a c-Myc/miR17-92/PTEN axis regulates PI3K activity for positive and negative selection of immature B cells. Here, we show that the c-Myc/miR17-92/PTEN axis tunes PI3K activity to control the expression of RAGs in proB cells. Using different genetically engineered mouse models we show that impaired function of the c-Myc/miR17-92/PTEN axis alters the PI3K/Akt/Foxo1 pathway to result in dis-regulated expression of RAG and a block in B cell development. Studies using 38c-13 B lymphoma cells, where RAGs are constitutively expressed, suggest that this regulatory effect is mediated post-translationally through Foxo1

A Steered Molecular Dynamics Study of Binding and Translocation Processes in the GABA Transporter

The entire substrate translocation pathway in the human GABA transporter (GAT-1) was explored for the endogenous substrate GABA and the anti-convulsive drug tiagabine. Following a steered molecular dynamics (SMD) approach, in which a harmonic restraining potential is applied to the ligand, dissociation and re-association of ligands were simulated revealing events leading to substrate (GABA) translocation and inhibitor (tiagabine) mechanism of action. We succeeded in turning the transporter from the outward facing occluded to the open-to-out conformation, and also to reorient the transporter to the open-to-in conformation. The simulations are validated by literature data and provide a substrate pathway fingerprint in terms of which, how, and in which sequence specific residues are interacted with. They reveal the essential functional roles of specific residues, e.g. the role of charged residues in the extracellular vestibule including two lysines (K76 (TM1) and K448 (TM10)) and a TM6-triad (D281, E283, and D287) in attracting and relocating substrates towards the secondary/interim substrate-binding site (S2). Likewise, E101 is highlighted as essential for the relocation of the substrate from the primary substrate-binding site (S1) towards the cytoplasm