NADPH oxidase elevations in pyramidal neurons drive psychosocial stress-induced neuropathology.

Oxidative stress is thought to be involved in the development of behavioral and histopathological alterations in animal models of psychosis. Here we investigate the causal contribution of reactive oxygen species generation by the phagocyte NADPH oxidase NOX2 to neuropathological alterations in a rat model of chronic psychosocial stress. In rats exposed to social isolation, the earliest neuropathological alterations were signs of oxidative stress and appearance of NOX2. Alterations in behavior, increase in glutamate levels and loss of parvalbumin were detectable after 4 weeks of social isolation. The expression of the NOX2 subunit p47(phox) was markedly increased in pyramidal neurons of isolated rats, but below detection threshold in GABAergic neurons, astrocytes and microglia. Rats with a loss of function mutation in the NOX2 subunit p47(phox) were protected from behavioral and neuropathological alterations induced by social isolation. To test reversibility, we applied the antioxidant/NOX inhibitor apocynin after initiation of social isolation for a time period of 3 weeks. Apocynin reversed behavioral alterations fully when applied after 4 weeks of social isolation, but only partially after 7 weeks. Our results demonstrate that social isolation induces rapid elevations of the NOX2 complex in the brain. Expression of the enzyme complex was strongest in pyramidal neurons and a loss of function mutation prevented neuropathology induced by social isolation. Finally, at least at early stages, pharmacological targeting of NOX2 activity might reverse behavioral alterations.

Definition of arthritis candidate risk genes by combining rat linkage-mapping results with human case-control association data.

OBJECTIVE: To define genomic regions that link to rat arthritis and to determine the potential association with rheumatoid arthritis (RA) of the corresponding human genomic regions. METHODS: Advanced intercross lines (AIL) between arthritis susceptible DA rats and arthritis resistant PVG.1AV1 rats were injected with differently arthritogenic oils to achieve an experimental situation with substantial phenotypic variation in the rat study population. Genotyping of microsatellite markers was performed over genomic regions with documented impact on arthritis, located on rat chromosomes 4, 10 and 12. Linkage between genotypes and phenotypes were determined by R/quantitative trait loci (QTL). Potential association with RA of single nucleotide polymorphisms (SNPs) in homologous human chromosome regions was evaluated from public Wellcome Trust Case Control Consortium (WTCCC) data derived from 2000 cases and 3000 controls. RESULTS: A high frequency of arthritis (57%) was recorded in 422 rats injected with pristane. Maximum linkage to pristane-induced arthritis occurred less than 130 kb from the known genetic arthritis determinants Ncf1 and APLEC, demonstrating remarkable mapping precision. Five novel quantitative trait loci were mapped on rat chromosomes 4 and 10, with narrow confidence intervals. Some exerted sex-biased effects and some were linked to chronic arthritis. Human homologous genomic regions contain loci where multiple nearby SNPs associate nominally with RA (eg, at the genes encoding protein kinase Calpha and interleukin 17 receptor alpha). CONCLUSIONS: High-resolution mapping in AIL populations defines limited sets of candidate risk genes, some of which appear also to associate with RA and thus may give clues to evolutionarily conserved pathways that lead to arthritis.

Cellular distribution of the C-type II lectin dendritic cell immunoreceptor (DCIR) and its expression in the rheumatic joint: identification of a subpopulation of DCIR+ T cells.

OBJECTIVE: An association to variations in the dendritic cell immunoreceptor (DCIR) gene with rheumatoid arthritis (RA) was recently shown. However, protein expression of DCIR has so far not been assessed in a disease setting. In the present work, we aimed to determine the cellular and tissue distribution of this receptor in healthy controls and in patients with RA before and after local glucocorticoid administration. METHODS: DCIR mRNA expression was evaluated by quantitative PCR (n=3) and protein expression by flow cytometry (n=18), immunohistochemistry (n=14) and double immunofluorescence (n=5). RESULTS: DCIR protein was not detected in healthy synovia. By contrast, expression was abundant on cells from rheumatic joints in synovial fluid and in tissue. Following corticosteroid treatment this expression was downregulated. Interestingly, DCIR could be detected on natural killer (NK) cells and T cells, and CD4+ and CD8+, as well as on monocytes, B cells, dendritic cells and granulocytes. The frequency of DCIR+ T cells and the level of surface expression were increased in the rheumatic joint compared to blood. In synovial fluid the typical DCIR+ T cells were large activated cells, whereas blasted DCIR+ T cells were not detected in blood. CONCLUSIONS: We demonstrate increased protein and mRNA expression of DCIR in RA, especially in the rheumatic joint. Expression was widespread and included a subpopulation of T cells. This suggests that the inflammatory synovial environment induces DCIR expression, and this may be related to synovial T cell function. Ligation of DCIR, or lack thereof, could contribute to the chronic inflammation characterising autoimmune diseases such as RA.