Analysis of Exhaled Breath Condensate in Environmental and Occupational Lung Diseases
A noninvasive method of exhaled breath testing is becoming increasingly important in health and diseases; however, exhaled breath analysis has not yet been widely used in occupational lung diseases. Although, study of fractional exhaled nitric oxide in exhaled breath condensate has evolved from a research tool into a clinical measurement, useful for diagnosing and monitoring asthma, very little is known about its use in occupational asthma. Despite significant molecular and biological advances, newer methods have not been frequently used in conjunction with noninvasive tests in occupational lung diseases.
Current new technologies, such as infrared, electrochemical, chemiluminescence, very sensitive modern mass spectrometry, gas chromatography, and gas chromatography mass spectrometry, can now identify thousands of unique substances in exhaled breath. These substances include elemental gases like nitric oxide and carbon monoxide and a multitude of volatile organic compounds. Furthermore, exhaled breath contains aerosolized droplets collected as exhaled breath condensate (EBC), which is composed of airway lining fluid mainly formed by water vapor and aerosol particles. EBC contains several biomolecules, including leukotrienes, 8-isoprostane, prostaglandins, nitric oxide-derived products, a wide range of metabolic end products, proteins, and a variety of cytokines and chemokines. This test is also suitable for longitudinal studies that can be used to monitor the disease progression or a response to therapy. EBC is a noninvasive, inexpensive, and easy to repeat test that can provide rapid analysis of biomarker levels in the setting of occupational and environmental exposure.
Specific gene expression profiling has tremendously influenced our understanding of the pathogenesis of several diseases. EBC can be used to identify gene expression profiles of target inflammatory mediators in asthma, such as IL-4, IL-17, RANTES, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, IL-8, IFNgamma-inducible protein (IP)-10, TNF-alpha, TGF-beta, and eotaxin-1.
Since occupational and environmental agents induce airway sensitization causing robust inflammatory responses, application of advanced investigative technologies could be useful in environmental and occupational lung diseases. We used polymerase chain reaction (PCR) array analysis in conjunction with noninvasive EBC tests to examine the effects of ozone on human airways. PCR array performs gene expression analysis with real-time PCR sensitivity and the multi-gene profiling capability of a microarray. Unlike conventional microarray, PCR array analysis is pathway-focused and profiles the expression of a panel of genes relevant to a pathway or disease state. In our analysis, the expressions of multiple cytokine and chemokine genes, including IL-12, IL-13, CCL-5, CCL-11, and IL-13RA, were found to be highly unregulated in EBC on exposure to high ozone levels in humans. These findings suggest that EBC can be used to study gene expression profiles induced by environmental and occupational lung diseases. Integration of newer molecular and biological technologies with noninvasive exhaled breath analysis can be used to advance investigational approaches in environmental and occupational lung diseases.
Dr. Daya Upadhyay
Steering Committee Member
