Development of organ-specific autoimmunity by dysregulated Aire expression.

Deficiency for AIRE/Aire in both humans and mice results in the development of organ-specific autoimmune disease. We tested whether augmented and/or dysregulated AIRE/Aire expression might be also prone to the breakdown of self-tolerance. To define the effect of augmented Aire expression on the development of autoimmunity, antigen-specific clonal deletion and production of clonotypic regulatory T cells (Tregs) in the thymus were examined using mice expressing two additional copies of Aire in a heterozygous state (3xAire-knockin mice: 3xAire-KI). We found that both clonal deletion of autoreactive T cells and production of clonotypic Tregs in the thymus from 3xAire-KI were impaired in a T-cell receptor-transgenic system. Furthermore, 3xAire-KI females showed higher scores of experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein than wild-type littermates, suggesting that augmented Aire expression exacerbates organ-specific autoimmunity under disease-prone conditions. In humans, we found that one patient with amyopathic dermatomyositis showed CD3- CD19- cells expressing AIRE in the peripheral blood before the treatment but not during the remission phase treated with immunosuppressive drugs. Thus, not only loss of function of AIRE/Aire but also augmented and/or dysregulated expression of AIRE/Aire should be considered for the pathogenesis of organ-specific autoimmunity. We suggest that further analyses should be pursued to establish a novel link between organ-specific autoimmune disease and dysregulated AIRE expression in clinical settings.

Differential contributions of protein kinase C isoforms in the regulation of group IIA secreted phospholipase A2 expression in cytokine-stimulated rat fibroblasts.

Protein kinase C (PKC) is a family of serine/threonine kinases involved in various signal transduction pathways. We investigated the roles of PKC in the regulation of group IIA secreted phospholipase A(2) (sPLA(2)-IIA) expression in cytokine-stimulated rat fibroblastic 3Y1 cells. Here we show that the induction of sPLA(2)-IIA by proinflammatory cytokines was under the control of both classical cPKCalpha and atypical aPKClambda/iota pathways by using PKC inhibitors, a PKC activator, and PKC knockdowns. Treatment of 3Y1 cells with PKC selective inhibitors having broad specificity, such as chelerythrine chloride and GF109203X, blocked IL-1beta/TNFalpha-dependent induction of sPLA(2)-IIA protein in a dose-dependent manner. Treatment with the PKC activator phorbol 12-myristate 13-acetate (PMA), which activates cPKC and novel nPKC isoforms, markedly attenuated the cytokine-dependent induction of sPLA(2)-IIA expression. In comparison, 24-h pretreatment with PMA, which down-regulates these PKC isoforms, markedly enhanced sPLA(2)-IIA expression. Results with short hairpin RNA (shRNA)-mediated knockdown of PKC isoforms revealed that the cytokine-induced sPLA(2)-IIA expression was markedly enhanced in cPKCalpha knockdown cells compared to those in replicate control cells. In contrast, knockdown of the aPKClambda/iota isoform reduced the cytokine-induced expression of sPLA(2)-IIA. These results suggest that the aPKClambda/iota pathway is required for the induction of sPLA(2)-IIA expression and that the cPKCalpha pathway acts as a negative regulator of sPLA(2)-IIA expression in cytokine-stimulated rat fibroblasts.