Subversion of B lymphocyte tolerance by hydralazine, a potential mechanism for drug-induced lupus

The MAPK/ERK and PI3K pathways additively coordinate the transcription of recombination-activating genes in B lineage cells

Rag-1 and Rag-2 are essential for the construction of the BCR repertoire. Regulation of Rag gene expression is tightly linked with BCR expression and signaling during B cell development. Earlier studies have shown a major role of the PI(3)K/Akt pathway in regulating the transcription of Rag genes. In this study, by using the 38c13 murine B cell lymphoma we show that transcription of Rag genes is also regulated by the MEK/ERK pathways, and that both pathways additively coordinate in this regulation. The additive effect is observed for both ligand-dependent (upon BCR ligation) and ligand independent (tonic) signals. However, whereas the PI(3)K/Akt regulation of Rag transcription is mediated by Foxo1, we show in this study that the MEK/ERK pathway coordinates with the regulation of Rag by controlling the phosphorylation and turnover of E47 and its consequential binding to the Rag enhancer regions. Our results suggest that the PI(3)K and MEK/ERK pathways additively coordinate in the regulation of Rag transcription in an independent manner.

Drug-induced autoimmunity

PURPOSE OF REVIEW

This review aims to draw attention to the increased spectrum of the features of drug-induced autoimmunity (DIA), including both clinical and autoantibody profiles in addition to the potential chronicity of the syndrome.

RECENT FINDINGS

In recent years, not only has the number of medications causing DIA increased but the spectrum of the features has broadened as well. With the use of newer medications, especially biologics, mostly directed towards immune system manipulation, the range of signs and symptoms of DIA as well as the patterns of autoantibody profiles have widened. Rashes and visceral involvement have started to be reported more often, especially with tumor necrosis factor antagonists. In addition, autoantibodies such as antidouble-stranded DNA, which are usually seen with idiopathic systemic lupus erythematosus, are appearing in place of the antihistone antibodies, typically found in drug-induced lupus. Finally, some medications have been implicated in causing the very same entity, which they may be used to treat. It is clear that progress in the field of pharmacogenetics and pharmacogenomics will help further our understanding of these and other adverse effects of medications.

SUMMARY

Even though DIA has been known for many years, the underlying mechanisms remain unclear. However, with recently described new and unexpected features, novel hypotheses have been proposed, thus opening doors to further research in understanding these mechanisms.

Signaling pathways regulating RAG expression in B lymphocytes

Development of B-cell lymphopoiesis is dependent on the presence of recombination activating genes RAG1 and RAG2 enzymes. They control the rearrangements of immunoglobulin variable, diversity and joining region segments, and allow progression of the cellular maturation. RAG1 and RAG2 are successively up- and down-regulated at each B-cell stage to progressively generate a B-cell receptor for which unforeseeable antigenic specificity results from a stochastic process. Therefore, in autoreactive immature B cells, new round of RAG re-expression can be observed to eliminate self-reactivity. In some circumstances, RAG up-regulation can also be found in peripheral mature B lymphocytes, specifically in autoimmune diseases. It is therefore of utmost importance to unravel signaling pathways that trigger RAG induction in normal and pathological conditions. Therapeutic modulation of cytokines or intracellular contacts involved in RAG expression might restrict the development of inappropriate autoimmune repertoire.

Mapping the epigenome--impact for toxicology

Recent advances in technological approaches for mapping and characterizing the epigenome are generating a wealth of new opportunities for exploring the relationship between epigenetic modifications, human disease and the therapeutic potential of pharmaceutical drugs. While the best examples for xenobiotic-induced epigenetic perturbations come from the field of non-genotoxic carcinogenesis, there is growing evidence for the relevance of epigenetic mechanisms associated with a wide range of disease areas and drug targets. The application of epigenomic profiling technologies to drug safety sciences has great potential for providing novel insights into the molecular basis of long-lasting cellular perturbations including increased susceptibility to disease and/or toxicity, memory of prior immune stimulation and/or drug exposure, and transgenerational effects.

Epigenetics in human autoimmunity. Epigenetics in autoimmunity - DNA methylation in systemic lupus erythematosus and beyond

Epigenetic mechanisms are essential for normal development and function of the immune system. Similarly, a failure to maintain epigenetic homeostasis in the immune response due to factors including environmental influences, leads to aberrant gene expression, contributing to immune dysfunction and in some cases the development of autoimmunity in genetically predisposed individuals. This is exemplified by systemic lupus erythematosus, where environmentally induced epigenetic changes contribute to disease pathogenesis in those genetically predisposed. Similar interactions between genetically determined susceptibility and environmental factors are implicated in other systemic autoimmune diseases such as rheumatoid arthritis and scleroderma, as well as in organ specific autoimmunity. The skin is exposed to a wide variety of environmental agents, including UV radiation, and is prone to the development of autoimmune conditions such as atopic dermatitis, psoriasis and some forms of vitiligo, depending on environmental and genetic influences. Herein we review how disruption of epigenetic mechanisms can alter immune function using lupus as an example, and summarize how similar mechanisms may contribute to other human autoimmune rheumatic and skin diseases.

Highlights of Mediterranean clinical immunology

The immune system continues to fascinate by the complexity of its intricacies. At the First Mediterranean Workshop on Clinical Immunology held in Evora (Portugal), recently identified mechanisms of immune defense and immunoregulation were put under a magnifying glass by an international cast of immunologists. Studies of Bacillus anthracis revealed that this anaerobic bacterium can inhibit type-II A phospholipase synthesis and secretion by alveolar macrophages, thereby subverting the pulmonary host immune response. Investigation of the mode of action of regulatory T cells indicated that FOXP3 binds the heterodimeric transcription factor AML1 and suppresses AML1-enhanced IL-2 production. In an experimental autoimmune model of prostatitis, a non-hypercalcemic vitamin D receptor agonist was able to interfere with key pathogenic events in already established disease. Other studies in the rat suggest that treating arthritis with oxidants, like phytol, may correct the deficient redox level and prevent T cell autoreactivity. With a number of other observations, the sparkling discussions opened new doors for medical immunology around the Mediterranean, but also elsewhere.