Inflammatory cell death in systemic lupus erythematosus

About This Grant

PROJECT SUMMARY/ABSTRACT Cell death plays a central role in the pathogenesis and exacerbations of systemic lupus erythematosus (SLE). Many of the best recognized autoantigens in SLE are intracellular nucleic acid-binding proteins, some of them located in the cell nucleus. While early work focused on apoptosis, the first known form of programmed cell death, attention has shifted in recent year to several more inflammatory types of programmed cell death resulting in exposure of cellular contents together with alarmins, danger signals, and damage-associated molecular patterns (DAMPs), which stimulate antigen-presenting cells to provoke a much stronger immune response. Inflammatory modes of cell death include NETosis, pyroptosis, ferroptosis, and necroptosis. These newer inflammatory pathways of cell death have been proposed to be important in SLE, but it is not known if they even occur in patients. Progress is hampered by a lack of established assays for measuring their occurrence in vivo in patients. We will use targeted, as well as unbiased, approaches to establish assays (biomarkers) that can selectively measure the presence of pyroptosis, necroptosis, and ferroptosis in patient blood samples (compared to NETosis). In brief, neutrophils and monocytes will be induced to undergo programmed inflammatory cell death and cellular and soluble constituents analyzed by microscopy, ELISA, and mass spectrometry. Our preliminary data suggest that ferroptosis is much increased in neutrophils from SLE patients. Ferroptosis will be assessed using fluorescent markers of lipid peroxides and iron accumulation and the degree of ferroptosis will be related to demographics, sex, and clinical phenotype, including disease activity. Levels of soluble ferroptosis biomarkers will be assessed by ELISA and associated with neutrophil ferroptosis as well as with clinical markers of disease activity. This is a high-risk, but high-reward proposal: a reliable quantification of the inflammatory programmed cell death pathways pyroptosis, ferroptosis, and necroptosis would have significant utility as biomarkers for patient stratification and to fill gaps in our understanding of the molecular pathology of SLE. These biomarkers would have similar utility in many additional autoimmune and autoinflammatory conditions. At present, these cell death pathways are well defined in vitro, but their presence in vivo remains a black box.