Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease that primarily affects young women and powerfully exemplifies the importance of sex as a determinant of immune-mediated disease. Indeed, among autoimmune and inflammatory diseases, SLE displays one of the most profound male-female differences in occurrence. As shown in studies of both patients and murine models, a signature feature of SLE is production of antinuclear antibodies (ANA). These antibodies bind to a wide array of nuclear macromolecules (antinuclear antibodies or ANA), although antibodies to nucleosomes and its DNA and histone components are the most characteristic. In SLE, the nuclear antigens inducing responses are most likely released from dead and dying cells, with the rates of cell death and dead cell clearance determining the amount of this material present. In addition to driving ANA responses, products of dead cells can function as alarmins to stimulate inflammation and promote autoreactivity. While sex has widespread effects on the immune system, its impact on the response to dead and dying cells, including the release of nuclear antigens, is not known. Studies on the effects of sex influence on conditions such as shock and sepsis suggest, however, that estrogens may modulate macrophage function and thereby influence the clearance process. To provide a platform to understand better the impact of sex on the exposure of nuclear antigens and their properties, we are proposing fundamental investigation to elucidate the mechanism for the generation and clearance of dead or dying cells and the release of nuclear antigens into the extracellular milieu. While these mechanisms may underlie autoantibody responses in SLE and their downstream effects, they may be of general significance in other states in which women have a greater disease burden. To investigate these issues, 3 specific aims are proposed:
Specific Aim 1) To elucidate sexual dimorphism in the in vivo generation of extracellular DNA and HMGB1. These studies will test the influence of sex on the generation of extracellular DNA and HMGB1 by apoptotic and necrotic cells in a mouse model;
Specific Aim 2) To elucidate the effects of sex hormones on the generation of extracellular DNA and HMGB1 in in vivo and in vitro models. These studies will the influence of sex hormones on the generation of extracellular cellular DNA and HMGB1;
and Specific Aim 3) To assess the expression of extracellular DNA in autoimmune mice using in vivo models including the expression of fetal Y chromosome DNA in the blood of pregnant mice to determine the impact of autoimmunity on the generation and clearance of DNA from the blood.
These studies will focus on the role of sex as a determinant in the pathogenesis of SLE. SLE is a prototypic autoimmune that exemplifies the importance of male-female differences in the burden of immune mediated disease. These studies will investigate in animal models the influence of sex on the release of nuclear molecules from dead and dying cells, an event considered crucial to lupus because of the effects of these molecules on immune responses as well as the formation of immune complexes that deposit in the tissues and stimulate inflammation. Understanding these mechanisms should lead to new approaches to diagnosis and treatment as well as the development of novel biomarkers relevant to both lupus and other immune-mediated diseases.
