Interleukin-33 (IL-33) (NF-HEV) is a chromatin-associated nuclear cytokine from the IL-1 family, which has been linked to important diseases, including asthma, rheumatoid arthritis, ulcerative colitis, and cardiovascular diseases. IL-33 signals through the ST2 receptor and drives cytokine production in type 2 innate lymphoid cells (ILCs) (natural helper cells, nuocytes), T-helper (Th)2 lymphocytes, mast cells, basophils, eosinophils, invariant natural killer T (iNKT), and natural killer (NK) cells. We and others recently reported that, unlike IL-1β and IL-18, full-length IL-33 is biologically active independently of caspase-1 cleavage and that processing by caspases results in IL-33 inactivation. We suggested that IL-33, which is released upon cellular damage, may function as an endogenous danger signal or alarmin, similar to IL-1α or high-mobility group box 1 protein (HMGB1). Here, we investigated the possibility that IL-33 activity may be regulated by proteases released during inflammation. Using a combination of in vitro and in vivo approaches, we demonstrate that neutrophil serine proteases cathepsin G and elastase can cleave full-length human IL-33 1-270 and generate mature forms IL-33 , and IL-33 . These forms are produced by activated human neutrophils ex vivo, are biologically active in vivo, and have a ∼10-fold higher activity than full-length IL-33 in cellular assays. Murine IL-33 is also cleaved by neutrophil cathepsin G and elastase, and both fulllength and cleaved endogenous IL-33 could be detected in the bronchoalveolar lavage fluid in an in vivo model of acute lung injury associated with neutrophil infiltration. We propose that the inflammatory microenvironment may exacerbate disease-associated functions of IL-33 through the generation of highly active mature forms.innate immunity | inflammatory protease | serine protease inhibitor | alveolar epithelium C ytokines of the IL-1 family (IL-1α, IL-1β, IL-18) play a major role in inflammatory, infectious, and autoimmune diseases (1-3). IL-33 [previously known as nuclear factor from high endothelial venule or NF-HEV (4, 5)], is a chromatin-associated nuclear cytokine from the IL-1 family (6, 7), which has been linked to important diseases (8-10), including asthma (11), rheumatoid arthritis (12, 13), ulcerative colitis (14), and cardiovascular diseases (15).IL-33 signals through the ST2 receptor (4), a member of the IL-1 receptor family, which is expressed (or induced) on various immune cell types, including mast cells, basophils, eosinophils, Thelper (Th)2 lymphocytes, invariant natural killer T (iNKT) and natural killer (NK) cells, macrophages, dendritic cells, and neutrophils (8-10). IL-33 stimulation of ST2 on Th2 cells induces secretion of the Th2 cytokines IL-5 and IL-13 (4, 16). Recently, IL-33 has been shown to drive production of extremely high amounts of these Th2 cytokines by type 2 innate lymphoid cells (ILCs) (natural helper cells, nuocytes, innate helper 2 cells), which play important roles in innate immune responses, after helminth infec...

Urine has become one of the most attractive biofluids in clinical proteomics as it can be obtained non-invasively in large quantities and is stable compared with other biofluids. The urinary proteome has been studied by almost any proteomics technology, but mass spectrometry-based urinary protein and peptide profiling has emerged as most suitable for clinical application. After a period of descriptive urinary proteomics the field is moving out of the discovery phase into an era of validation of urinary biomarkers in larger prospective studies. Although mainly due to the site of production of urine, the majority of these studies apply to the kidney and the urinary tract, but recent data show that analysis of the urinary proteome can also be highly informative on non-urogenital diseases and used in their classification. Despite this progress in urinary biomarker discovery, the contribution of urinary proteomics to the understanding of the pathophysiology of disease upon analysis of the urinary proteome is still modest mainly because of problems associated to sequence identification of the biomarkers. Until now, research has focused on the highly abundant urinary proteins and peptides, but analysis of the less abundant and naturally existing urinary proteins and peptides still remains a challenge. In conclusion, urine has evolved as one of the most attractive body fluids in clinical proteomics with potentially a rapid application in the clinic.