Interaction between genetic background and oxidative environmental stimuli in the pathogenesis of human lung disease has been largely unexplored. Biological response to oxidative stress is a key mechanism in numerous inflammatory diseases. In this new program, we have begun three research initiatives that evolved from our mouse modeling of inflammation and acute lung injury. In the first project, we have extablished strong collaboration with Drs. Francine Kauffmann and Rachel Nadif (INSERM, Paris) to investigate the genetic basis of susceptibility to coal workers pneumoconiosis (CWP) in individuals differentially exposed to environmental oxidants coal dust and cigarette smoke. Drs. Kauffmann and Nadif have undertaken a prospective epidemiologic study in 253 coal miners, which included quantitative phenotypes of response to environmental stimuli that may be involved in CWP, an inflammatory lung disease. Six oxidative stress markers were studied as intermediate phenotypes of response to exposure, including erythrocyte glutathione peroxidase (GSH-Px) and catalase activities. Oxidant exposures studied were smoking habits and cumulative dust exposure assessed by job history and ambient measures of exposure. Disease phenotypes included subclinical computed tomography score at the first survey and X-ray profusion grades twice 5 years apart to assess established CWP. My laboratory obtained blood from each of the individuals recruited to the study and DNA was isolated. We began to investigate the genetic basis for CWP susceptibility by evaluating association of selected phenotypes with polymorphisms in the following classes or categories of genes: innate immunity, inflammation, and antioxidant. Miners were genotyped for common functional polymorphisms in the gene for tumor necrosis factor a (TNF) and lymphotoxin a (LTA), two proinflammatory cytokines that have been implicated in the pathogenesis of chronic lung disease. We have also typed the subjects for catalase (CAT)polymorphisms. Regarding gene-environment interaction on intermediate phenotypes, our results showed interaction of the -308 promoter polymorphism in TNF with occupational exposure on erythrocyte GSH-Px activity with a significant association in those with high exposure whereas no association was observed among those with low exposure. Regarding gene-intermediate phenotype interaction on clinical outcome, our results showed an association of CWP prevalence with the NcoI polymorphism in LTA in those with low catalase activity whereas no association was observed in those with high (a priori protective) activity. We have also found significant association of CAT with blood catalase activity and disease outcome. Results suggest that interactions of genetic background with environmental exposure and intermediate response phenotypes are important components in the pathogenesis of disease (CWP) in coal miners. A second project is currently being established to investigate the genetic basis of susceptibility to adverse outcomes of acute respiratory distress syndrome (ARDS). ARDS is a major acute lung disease in adults and neonates, and is characterized by noncardiogenic edema and inflammation. The mortality rate for ARDS ranges from 50-80%. The incidence of ARDS is not well established, but approximately 2-8 cases per 100,000 are estimated. The mechanisms of susceptibility are unclear, and there are no specific therapies. Our studies in inbred mice have identified the transcription factor NRF2 as a candidate gene for susceptibility to hyperoxic lung injury, a model of ARDS. We have hypothesized, therefore, that loss-of-function polymorphisms in NRF2 predispose to oxidative lung damage associated with ALI/ARDS. To date, the genomic sequence of NRF2 is not well characterized and only a few SNPs have been localized to coding regions within the gene. In the current study, portions of the coding region and 1-kb of the promoter were amplified, sequenced and compared in order to locate NRF2polymorphisms, and to determine whether any identified SNPs have functional relevance to NRF2 activity. We are also evaluating each SNP by association with disease pathogenesis in a population of ALI patients through a collaboration with Dr. Jason Christie (University of Pennsylvania). Our third project is designed to evaluate genetic mechanisms of host response to respiratory syncytial virus and innate immunity studies in mice and humans. This project is designed to investigate the role of toll-like receptors in respiratory syncytial virus (RSV) infection and disease progression. Because TLR4 appears to be critical to protection against RSV immune challenge, a collaboration has been established with Dr. Fernando Polack (Johns Hopkins University) to test the hypothesis that loss of TLR4 function will enhance development of lower respiratory tract infection during primary RSV infection in infants.
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