The Role of Cell Death in the Pathogenesis of SLE: Is Pyroptosis the Missing Link?

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by the production of antinuclear antibodies (ANAs) in association with systemic inflammation and organ damage. In addition to genetic factors, a contribution of infection to disease induction has been proposed. In the pathogenesis of lupus, immune complexes of ANAs with nuclear antigens can form and both deposit in the tissue and stimulate cytokine production to intensify inflammation. As such, the extracellular release of nuclear antigens to form pathogenic immune complexes is an important step in the pathway to disease. This release has been considered the consequence of cell death, with apoptotic cells the relevant source of nuclear material. While apoptosis could serve this role, other death forms may act similarly. Among these death forms, pyroptosis, which can be induced by inflammasome activation during infection, has features suggesting involvement in lupus. Thus, unlike apoptosis, pyroptosis is a pro-inflammatory process. Furthermore, pyroptosis leads to the release of intracellular contents including HMGB1 and ATP, both of which can act as DAMPs (deathassociated molecular patterns) to stimulate further inflammation. Importantly, pyroptosis can lead to the release of intact nuclei, suggesting a relationship to events in the formation of LE cells. While the role of pyroptosis in SLE is hypothetical at this time, further analysis of this death form should provide new insights into lupus pathogenesis and provide the missing link between infection and the initiation of lupus by products of dead and dying cells.