Novel therapies for schizophrenia: understanding the glutamatergic synapse and potential targets for altering N-methyl-D-aspartate neurotransmission.

For over fifteen years, N-methyl-D-aspartate receptor (NMDAR) mediated glutamatergic neurotransmission has generated interest because of its putative role in the pathophysiology of schizophrenia. Thus far, all antipsychotic medications have centered on manipulating the dopamine receptor to treat psychosis. These medications have limited efficacy, especially in treating the cognitive and negative symptoms of schizophrenia, and serious side effects. The NMDAR now provides an entirely new array of targets around which to focus new drug development. This paper first examines components of the glutamatergic synapse and discusses the relationship between decreased NMDAR function and schizophrenia. Then, human trials that have been conducted with agents that enhance NMDAR function, whether by molecules that activate the glycine co-agonist site (GCS), or by positive allosteric modulators (PAMs) that act on non-NMDAR are reviewed. In examining patents granted in the United States for treatment of schizophrenia based on normalizing glutamatergic neurotransmission, it seems academic researchers have focused primarily on GCS agents, and pharmaceutical industries have concentrated on synthesizing PAMs. The 21(st) century holds promise as the era in which an entirely new type of medication for schizophrenia may be created, one with more success at treating the debilitating negative and cognitive symptoms of this disease.

Multilineage engraftment with minimal graft-versus-host disease following in utero transplantation of S-59 psoralen/ultraviolet a light-treated, sensitized T cells and adult T cell-depleted bone marrow in fetal mice.

Although engraftment following in utero stem cell transplantation can readily be achieved, a major limitation is the low level of donor chimerism. We hypothesized that a lack of space for donor cells in the recipient marrow was one of the primary reasons for failure to achieve significant engraftment, and that donor T cells could make space in an allogeneic mismatched setting. We found that 3 x 10(5) C57BL/6 (B6) naive CD3(+) cells coinjected with B6 T cell-depleted bone marrow (TCDBM) into 14- to 15-day-old BALB/c fetuses resulted in multilineage engraftment (median, 68.3%) associated with severe graft-vs-host disease (GvHD; 62 vs 0% with TCDBM alone). When 1.5 x 10(5) CD4(+) or CD8(+) cells were used, low levels of engraftment were seen vs recipients of 1.5 x 10(5) CD3(+) cells (2.4 +/- 1.1 and 6.6 +/- 3.9 vs 20.4 +/- 10.4%, respectively). To test the hypothesis that proliferation of T cells in response to alloantigen resulted in GvHD and increased engraftment, we pretreated naive T cells with photochemical therapy (PCT) using S-59 psoralen and UVA light to prevent proliferation. GvHD was reduced (60-0%), but was also associated with a significant reduction in engrafted donor cells (53.4 +/- 4.2 to 1.7 +/- 0.5%). However, when B6 T cells were sensitized to BALB/c splenocytes, treated with PCT, and coinjected with TCDBM, there was a partial restoration of engraftment (13.3 +/- 2.4% H2Kb(+) cells) with only one of nine animals developing mild to moderate GvHD. In this study we have shown that PCT-treated T cells that are cytotoxic but nonproliferative can provide an engraftment advantage to donor cells, presumably by destroying host hemopoietic cells without causing GvHD.