Diesel Exhaust and Mechanism of Asthma

Not Applicable

Completed

• Conditions: Asthma
• Interventions: Other: Filtered air; Other: Diesel exhaust; Dietary Supplement: N-acetylcysteine

• Registration Number: NCT01699204
• Lead Sponsor: University of British Columbia

Brief Summary

This experiment is designed to test the hypothesis that oxidative stress is responsible for changes in airway responsiveness in humans exposed to diesel exhaust.

Detailed Description

The specific aim is to test the hypothesis that diesel exhaust (DE) increases airway reactivity via oxidative stress, particularly in asthmatics. To test this hypothesis, we use a crossover in vivo experimental model in mild asthmatics and normal controls using a state-of-the-art diesel exhaust exposure facility.

Participants took N-acetylcysteine (600 mg) or placebo capsules three times daily for six days. On the final morning of supplementation, participants were exposed for 2 hours to either filtered air or diesel exhaust (300 µg·m-3 of particulate matter smaller than 2.5 microns). Twenty-six non-smokers between 19-49 years were studied under three experimental conditions (filtered air with placebo, diesel exhaust with placebo and diesel exhaust with N-acetylcysteine) using randomized, double-blind, crossover design, with a two week minimum washout between conditions. Methacholine challenge was performed pre-exposure (to determine baseline airway responsiveness) and post-exposure (to determine the effect of exposure).

Study Timeline

• Study Start: 2007-09
• Primary Completion: 2011-10
• Study Completion: 2011-10
• Study First Submitted: 2012-10-01
• Study First Submitted QC: 2012-10-01
• Study First Posted: 2012-10-03
• Status Verified: 2017-09
• Last Update Submitted: 2017-09-27
• Last Update Posted: 2017-09-29

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 26

Inclusion Criteria

• Between 19-49 years, non smokers, asthmatics, healthy controls

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Exclusion Criteria

• Smokers, pregnant or co-existing medical condition for which diesel exhaust would confer significant risk (i.e. coronary artery disease)

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Filtered air with placebo	Filtered air	Exposure for 2 hours to filtered air and placebo tablets 3 times daily for 6 days
Diesel exhaust with placebo	Diesel exhaust	Exposure for 2 hours to diesel exhaust and placebo tablets 3 times daily for 6 days
Diesel exhaust with N-acetylcysteine	Diesel exhaust	Exposure for 2 hours to diesel exhaust and N-acetylcysteine tablets (600 mg) 3 times daily for 6 days
Diesel exhaust with N-acetylcysteine	N-acetylcysteine	Exposure for 2 hours to diesel exhaust and N-acetylcysteine tablets (600 mg) 3 times daily for 6 days

Primary Outcome Measures

Name	Time	Method
Human airway reactivity	50 hours	Establish that oxidative stress is responsible for changes in human airway reactivity induced by DE (300 µg/m3 inhaled for two hours).

Trial Locations

Locations (1)

University of British Columbia; 🇨🇦 Vancouver, British Columbia, Canada