Role of Matrix Metalloproteinase-3 in Deployment-Related Pulmonary Fibrosis

Overarching Goal: The goal of this application is to determine how inhalation into the lungs of sand particles suspended in the air (particulate matter or 'desert dust') during military deployment to Iraq and Afghanistan leads to inflammation and scarring (fibrosis) of the lungs and to devise treatments for this scarring. Research Idea and Relevance to the Military: Since the onset of military operations in Afghanistan in 2001, more than 2.8 million military personnel, contractors, and US government and non-government employees have been deployed to Iraq and Afghanistan (Southwest Asia). These personnel have been exposed to high levels of dust generated by wind erosion of desert sand, movement of vehicles and troops, and combustion and construction activities with short- and long-term health consequences. Levels of sand particles in the air in Southwest Asia may exceed 1500 mu-g/m3, far higher than the World Health Organization air quality guideline of 20 mu-g/m3. In deployed military personnel, high levels of sand particles in the air are associated with an increase in respiratory symptoms, asthma, and scarring of the small airways ('bronchiolitis') and lung ('fibrosis'). In the short term, affected military personnel may be less able to carry out their duties. Over the long term, these exposures may lead to disability, chronic illness with absences from work, and increased healthcare expenditures. How these exposures lead to lung diseases and how to mitigate these pathological effects are not well understood. Our working model is that inhalation of sand particles containing silica and other toxic materials such as metals leads to inflammation that is centered on the smallest airways and air sacs and may progress to cause widespread scarring of the lung itself. Our recent publications along with our preliminary studies provide strong evidence that a member of a family of enzymes that can degrade proteins within tissues, called matrix metalloproteinase-3 (MMP-3), plays a key role in progressive lung scarring. As an example of such evidence, we found that mice with genetic deficiency in MMP-3 are protected from lung scarring. We hypothesize that exposure of deployed military personnel to sand particles from Southwest Asia ('desert dust') that are breathed into the lungs causes inflammation in the small airways that progresses to scarring of the lungs. In Specific Aim 1, we will determine how the enzyme MMP-3 participates in the development of lung scarring in mice caused by inhalation of sand particles from Iraq or of purified silica. We will compare the amount of scarring in the lungs of mice with genetic deficiency of MMP-3 to the amount of scarring in normal mice exposed to these sand particles. For part of these studies, we will use special facilities at a military base in Dayton, Ohio where the top layer of sand collected from a military base in Iraq will be suspended in air and animals subjected to the type of conditions that military personnel are exposed to. We will determine how MMP-3 breaks down structural proteins within the tissues of the lung after inhalation of sand particles and how this may liberate small fragments of these proteins that can cause lung scarring. In Specific Aim 2, we will develop chemicals that will specifically inhibit MMP-3 and then test whether they can prevent lung scarring in mice exposed to sand particles. Our long-term goal is that these treatments will be developed further for use in humans. In Specific Aim 3, we will use sensitive methods to determine if MMP-3 levels are elevated in the lungs and blood of military personnel previously deployed to Southwest Asia and whether MMP-3 levels can be used as a biomarker for the development of lung disease including lung scarring. We will also use a highly sensitive method involving laser light to measure the sand and metal content in stored lung biopsy specimens from previously deployed military personnel who were