Epigenetic Regulation of Immune Pathways in Sarcoidosis

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PROJECT SUMMARY/ABSTRACT The goal of this study is to define the epigenetic marks and their impact on gene expression that result in the granulomatous lung disease, sarcoidosis, and two of the most common sarcoidosis phenotypes, progressive pulmonary disease and remitting disease. The study relies on the expertise and strengths of our uniquely qualified investigative team. It will define pathogenic pathways and risk factors for sarcoidosis and two common phenotypes of disease, and have implications for similar immune mediated diseases. In sarcoidosis, it appears that exposure to an unknown inhaled antigen(s) in the setting of a genetically susceptible host, initiates a Th1 immune response, with antigen presentation occurring via HLA Class II on antigen presenting cell (APC) in the context of CD4+ T cells. Subsequently, CD4+ T cells and APCs are recruited to the lung, proliferate, produce cytokines and chemokines, and eventually form granulomas. An increased prevalence of HLA-DRB1 alleles is found in sarcoidosis, although the exact alleles vary based on an individual's race, ethnic background and disease phenotype. There are a limited number of other genetic variants associated with sarcoidosis, suggesting that other susceptibility factors or forms of genetic regulation must be important in disease pathogenesis. Growing data in other lung diseases suggests that epigenetic mechanisms in combination with genetic susceptibility and environment may help explain disease risk. Epigenetic modifications determine the Th1 versus Th2 immune response through DNA methylation and histone modifications of key genes such as FOXP3, and thus impact health and disease. To date epigenetic alterations have not been explored in sarcoidosis. Our preliminary data demonstrate significant genome-wide DNA methylation differences in pivotal immune response genes and networks at the site of exposure and disease, the lung, in sarcoidosis compared to subjects without granulomatous lung disease. Based on this information, the overarching hypothesis for this proposal is that DNA methylation changes in genes in key immune pathways impact gene expression and immune cell differentiation, and thus risk of sarcoidosis. Using an integrated genomic approach we will first define epigenetic alterations in CD4+ lung cells, in a case control study of sarcoidosis cases with progressive and remitting disease and normal controls. Subsequently, we will determine functional methylation alterations that impact gene transcription, information which will expand our understanding of the pathogenesis of sarcoidosis. As demethylating agents, such as 5-azacytidine (AZA) and decitabine are currently being used to treat immune mediated diseases, we will evaluate changes in validated methylation and gene expression targets treating sarcoidosis CD4+ lung cells with demethylating (AZA) or methylating (folic acid) agents. This study will provide data relevant to this class of agents as targets for therapy. Furthermore, the information gained from this proposal will shed light on the pathogenesis of sarcoidosis and its phenotypes and on genome-exposure relationships.