Genetic Susceptibility to Ozone in Mild Asthmatic Volunteers

Overview

Recent reports have shown that people with asthma who have a particular gene, known as the GSTM1 null gene, are more susceptible to the effect of air pollutants. The purpose of this research study is to learn if volunteers who have asthma and have a GSTM1 null gene have increased response (change in lung function and increase in lung cells collected from sputum) compared to volunteers with asthma who have the GSTM1 sufficient gene when challenged with 0.4 ppm ozone during intermittent exercise. The principal purpose of this study is to identify hyper-responsive, responsive and non-responsive groups of human subjects with mild asthma based on their airway neutrophilic response to ozone exposure, and to perform analyses on DNA from airway cells to explore possible differences in genetic profiles between the three groups. An additional pilot aim is to compare expression of a small number of specific genes of interest in a subset of ozone-responsive and ozone-non-responsive subjects with mild asthma.

Fifty volunteers with mild asthma will be recruited to undergo ozone challenge in the controlled exposure facility of the US EPA Human Studies Division (104 Mason Farm Road, Chapel Hill, NC) with 0.4ppm for 2 hours with moderate exercise alternating with rest. Endpoints will include genetic analysis for the GSTM1 genotype, sputum and spirometry changes pre and post exposure, and blood endpoints pre and post exposure. TRAINING DAY: (at least 3 days prior to the ozone challenge) Eligible subjects will report to the research lab for a 3 hour training session. * All female volunteers will undergo a urine pregnancy test. * After informed consent is obtained, Measurement of orally exhaled nitric oxide will be obtained * Subjects will perform spirometry. * Subjects will exercise on a treadmill to determine the workload for the actual exposure. * Finally the subject will undergo sputum induction following pretreatment with albuterol. The sputum will be assessed for quality to determine continued eligibility. If a subject has provided an acceptable sputum sample within the prior 6 months this may be used as inclusion criteria rather than repeating the induction at this point. After subjects have demonstrated production of an adequate sputum sample, they will be scheduled for the ozone exposure visit. 24 HOURS PRIOR to the exposure day (Day 1): Subjects will be asked to refrain from smoking as well as drinking alcohol for 24 hours prior to Day 1 until after completion of Day 3. * Subjects will have vital signs and oxygen saturation checked, including the symptom questionnaire. * They will also undergo a physical examination of the ears, nose, throat and chest (lung sounds). * Female volunteers will undergo urine pregnancy testing. * Measurement of orally exhaled nitric oxide will be obtained. * Spirometry testing will be performed. * Subjects will have a sputum induction preceded by administration of 2 puffs of albuterol. EXPOSURE DAY (at least 3 days after the training day): * Subjects will be asked to arrive at the study site at approximately 8 AM and will undergo assessment of vital signs (temperature, pulse, respiratory rate, blood pressure), oxygen saturation, and symptom score assessment. * A telemetry unit will be placed for cardiac monitoring during the exposure. * Measurement of orally exhaled nitric oxide will be obtained prior to exposure and 4 hours after the end of the exposure * Spirometry testing to rule out acute illness prior to the exposure. * They will also undergo a physical examination of the ears, nose, throat and chest. * Exposure sessions: The 0.4 ppm ozone exposure will be conducted in an ozone exposure chamber. Each subject will be exposed to 0.4 ppm ozone for 2 hours. During exposures, subjects will perform four 15 minute bouts of moderate exercise (minute ventilation or VE = 30 40 L/min) on a treadmill, each separated by 15 minutes of seated rest. Minute ventilation is measured for 2 to 3 minutes after about 4 minutes of exercise during the first exercise period, and again at about 12 minutes of exercise. It is then measured at about 12 minutes into each exercise period. Two subjects may be exposed simultaneously, in which case the exercise/rest periods will be alternated. * Immediately post exposure and 4 hours after completion of exposure, subjects will have an assessment of vital signs, oxygen saturation, symptom score assessment and undergo spirometry evaluation. * Venipuncture: 20 ml of blood will be collected for a CBC/ differential, assessment of blood monocyte phagocytic function and cell surface markers just prior to the exposure and 4 hours after the end of exposure. A portion of the sample will be used for genotyping. * Induced sputum will be collected 6 hours after initiation of exposure after subjects have been premedicated with albuterol. The subjects will be observed at the study site until sputum induction is complete. Subjects will not be discharged home following the post-exposure sputum induction until FEV1 is within 90% of baseline values and vital signs are normal. Subjects not meeting safety criteria at the end of the exposure day will be admitted to the GCRC for overnight observation. 24 HOURS POST EXPOSURE (Day 3): The following morning, approximately 24 hours after exposure, the volunteer subject will be assessed directly at the study site. The subject will undergo spirometry, vital sign monitoring and symptom scoring. STUDY DISCONTINUATION VISIT (5-10 days after exposure): The volunteer subject will again be assessed directly at the study site. The subject will undergo spirometry, vital sign monitoring and symptom scoring.