Selective DNA Demethylation Accompanies T Cell Homeostatic Proliferation and Gene Regulation in Lupus-Prone lpr Mice

Lupus nephritis: The regulatory interplay between epigenetic and MicroRNAs

MicroRNAs (miRNAs) are endogenous, small, non-coding RNA molecules that act as epigenetic modifiers to regulate the protein levels of target messenger RNAs without altering their genetic sequences. The highly complex role of miRNAs in the epigenetics of lupus nephritis (LN) is increasingly being recognized. DNA methylation and histone modifications are focal points of epigenetic research. miRNAs play a critical role in renal development and physiology, and dysregulation may result in abnormal renal cell proliferation, inflammation, and fibrosis of the kidneys in LN. However, epigenetic and miRNA-mediated regulation are not mutually exclusive. Further research has established a link between miRNA expression and epigenetic regulation in various disorders, including LN. This review summarizes the most recent evidence regarding the interaction between miRNAs and epigenetics in LN and highlights potential therapeutic and diagnostic targets.

T Cell Homeostatic Proliferation Promotes a Redox State That Drives Metabolic and Epigenetic Upregulation of Inflammatory Pathways in Lupus

Significance: Numerous abnormalities in T cells have been described in patients with systemic lupus erythematosus (SLE), including lymphopenia, DNA demethylation, expression of endogenous retroviruses (ERVs), increased cell death, enlarged mitochondria, production of reactive oxygen species (ROS), and the appearance of unusual CD4^-CD8^- T cells. Our studies propose a model in which accelerated homeostatic proliferation of T cells promotes an epigenetic and metabolic program, leading to this cluster of abnormalities. Recent Advances: Growing knowledge of the innate immune disorders in SLE has included increased mitochondrial size and ROS production that induces oligomerization of the mitochondrial antiviral signaling (MAVS) protein and type I interferon production, as well as DNA demethylation, upregulation of inflammatory genes, and expression of certain ERVs in SLE peripheral blood mononuclear cells. All these events are part of the cellular program that occurs during homeostatic proliferation of T cells. Evidence from a murine model of SLE as well as in human SLE reveals that increased T cell homeostatic proliferation may be a driving factor in these processes. Critical Issues: Despite extensive knowledge of the myriad autoantibodies in SLE and other immune abnormalities, a cogent model has been lacking to link the numerous and seemingly disparate immune aberrations. This may partly explain the general lack of new drugs specifically for SLE in over 50 years. A more coherent model of SLE would not only unify the variety of immune abnormalities is SLE but would also suggest new therapies. Future Directions: The model of augmented homeostatic proliferation leading to increased mitochondrial mass, ROS, DNA demethylation, and upregulation of inflammatory genes suggests strategic new targets for SLE, including antioxidants and certain inhibitors of metabolism. Antioxid. Redox Signal. 36, 410-422.