Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily. PPARγ ligands, which include the naturally occurring PG metabolite 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2), as well as thiazolidinediones, have been shown to have anti-inflammatory activity. The PPARα agonists, gemfibrozil, ciprofibrate, and fenofibrate, have an excellent track history as oral agents used to treat hypertriglyceridemia. In the present study, we demonstrate that these PPARα agonists can increase the production of the Th2 cytokine, IL-4, and suppress proliferation by TCR transgenic T cells specific for the myelin basic protein Ac1–11, as well as reduce NO production by microglia. Oral administration of gemfibrozil and fenofibrate inhibited clinical signs of experimental autoimmune encephalomyelitis. More importantly, gemfibrozil was shown to shift the cytokine secretion of human T cell lines by inhibiting IFN-γ and promoting IL-4 secretion. These results suggest that PPARα agonists such as gemfibrozil and fenofibrate, may be attractive candidates for use in human inflammatory conditions such as multiple sclerosis.

As a means of developing therapies that target the pathogenic T cells in multiple sclerosis (MS) without compromising the immune system or eliciting systemic side effects, we investigated the use of T-bet-specific antisense oligonucleotides and small interfering RNAs (siRNA) to silence T-bet expression in autoreactive encephalitogenic T cells and evaluated the biological consequences of this suppression in experimental autoimmune encephalomyelitis, a model for MS. The T-bet-specific AS oligonucleotide and siRNA suppressed T-bet expression, IFNgamma production, and STAT1 levels during antigen-specific T cell differentiation. In vitro suppression of T-bet during differentiation of myelin-specific T cells and in vivo administration of a T-bet-specific antisense oligonucleotide or siRNA inhibited disease. T-bet was shown to bind the IFNgamma and STAT1 promoters, but did not regulate the IL-12/STAT4 pathway. Since T-bet regulates IFNgamma production in CD4(+) T cells, but to a lesser extent in most other IFNgamma-producing cells, T-bet may be a target for therapeutics for Th1-mediated diseases.

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Etoposide, an inhibitor of the breakage-reunion reaction associated with cellular type II DNA topoisomerases, was shown to inhibit plaque formation of vaccinia virus. This drug had a major effect on the segregation of newly replicated DNA concatemers. Gene expression and the initiation and elongation phases of viral DNA replication were essentially unaffected. Pulsed-field gel electrophoresis of viral DNA replicated in the presence of etoposide revealed two major classes of DNA: the mature monomeric linear genome and DNA that failed to enter the gel (the relative proportions depending on the concentrations of drug). Restriction enzyme analysis showed a severe defect in telomere resolution. In addition, slowly migrating restriction fragments were suggestive of a general recombination defect. We have isolated several etoposide-resistant mutants and used marker rescue and DNA sequencing to localize the resistance-causing mutation to the amino terminus of the viral DNA ligase gene. Inactivation of the DNA ligase also resulted in an etoposide-resistant phenotype, but to a lesser extent. The telomere resolution and segregation defects were corrected both in the drug-resistant mutants and in the DNA ligase knockout mutants. Reinsertion of wild-type or mutant DNA ligase in the viral thymidine kinase locus confirmed the role of the viral DNA ligase in conferring sensitivity not only to etoposide but also to another topoisomerase II inhibitor, 4-(9-acridinylamino) methanesulphon-m-anisidide (mAMSA). The data suggest that the nonessential DNA ligase is involved in telomere resolution, possibly as part of a general recombinase.

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