The focus of this U19 project, """"""""Immunobiology of Acute Environmental Asthma"""""""", is to conduct mechanistic studies of the role of innate immune processes in mediation of acute environmental asthma. Epidemiological studies have clearly shown that asthma exacerbation linked to air pollutants is a major cause of asthma exacerbation. Endotoxin is a commonly encountered environmental pollutant found in ambient particulate matter and in occupational and domestic settings as well. Endotoxin can induce neutrophilic inflammation at high levels, and at low levels enhance response of asthmatics to airway allergen challenge. We have shown that endotoxin causes changes in airway monocytes and macrophages (increased CD14, CD80, Fc?RI and HLA-DR) which are associated with enhanced response to either innate or acquired immune stimuli. Our team has recently identified novel regulatory molecules of inflammation in the CATERPILLER family, specifically cryopyrin (which upregulates neutrophilic inflammation and monocytic function) and monarch-1, (which downregulates response to innate activation). Cryopyrin is of particular interest as it acts through formation of a Caspase-1 based inflammasome to cleave pro-IL-l? to active IL-1? (with downstream production of IL-6 and other mediators) and IL-18. Furthermore, cryopyrin is activated after ligation of either pathogen associated molecular pattern receptors (including CD14 facilitated binding of endotoxin by TLR4) or the P2X7 receptor by ATP (which is increasingly recognized as an endogenous danger signal released by host cells following non-specific cell injury). These dual activation pathways likely account for the similar actions of a wide variety of inhaled environmental contaminants, and represent novel targets for treatment of acute asthma. We will conduct mechanistic studies of the role of the CATERPILLER family members cryopyrin and monarch-1 (Project 1-J. Ting PI), and the role of NALP-1 and the purinergic receptor P2X7 (Project 2-B. Koller, PI) in rodent models of environmental asthma, in conjunction with a translational project (Project 3-D. Peden, PI) designed to determine the effect of interaction of endotoxin- and allergen-induced inflammation on the airway biology of allergic asthmatics. Human studies will be focused on the biology of airway monocytic cells and the expression of innate immune and the CATERPILLAR family of immune regulators and P2X7 receptors in the airway. In addition to assessment of the role of innate immune processes in regulating airway inflammation, we will examine the relationship of this inflammation on airway physiology, specifically mucociliary clearance. Decreased mucociliary clearance is an understudied process which mediates asthma exacerbation and is a feature of increased asthma severity. PROJECT 1: Novel and innate immune genes in asthma (TING, J) PROJECT 1 DESCRIPTION (provided by applicant): We recently discovered the CATERPILLER family which share structural similarities with the NB-LRR (nucleotide-binding, leucine-rich repeat) super-family of disease resistance (R) proteins that constitutes the plant immune system. In the animal kingdom, this family is also known as NOD or NLR. The clinical importance of this family is underscored by the genetic linkage of family members to a number of immunologic disorders. Among the human gene family members, several of these appear to mediate negative regulatory function in controlling an overzealous inflammatory response. Most notable is the Monarch-1 protein which blocks the function of NF-?B inducing kinase (NIK). Inhibition of NIK reduces the expression of an array of chemokines with relevance in asthma. Gene profiling of induced sputum from mildly asthmatic individuals suggests that the Monarch-1 gene is reduced in these individuals relative to controls, supporting the inhibitory role of this gene during inflammation. Another group of family members regulates IL-1 production. Most notable among these is cryopyrin which mediates formation of the inflammasome complex upon stimulation with a number of inducers. The inflammasome complex is required for procaspase 1 processing to mature caspase 1. In turn, caspase-1 is required for the processing of pro-IL-1 and pro-IL-18 to their mature forms. IL-1 and IL-18 are respectively important in inflammation and TH2 skewing. Cryopyrin is also important in mediating macrophage necrosis which exacerbates inflammation. Thus there are compelling reasons to believe that Monarch-1 and cryopyrin have crucial roles in asthma, however there is no in vivo data to indicate that this is the case. Furthermore we have shown that both of these proteins are ATP-binding proteins, and they exhibit ATPase activity, thus providing ways to modulate their function, which might be important leads to drug discovery. The goals of this proposal are: (1) To study the relevance of Monarch-1 in three animal models of asthma (OVA-induced, endotoxin, and house dust mite and delineate the biochemical effects of Monarch-1 in vivo and ex vivo. (2) To study the relevance of cryopyrin and a cryopyrin-adaptor (ASC) in asthma. (3) To study and identify factors which modulate the nucleotide-binding properties and ATPase function of Monarch-1 and cryopyrin.
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