Experimental Exposure to Air Pollutants and Sympathetic Nerve Activity in Human Subjects

Study Overview
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Brief Summary
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The primary hypothesis of the study is that in healthy elderly subjects experimental exposure to air pollutants increases sympathetic nervous system activity compared with sham (clean air) exposure. The secondary hypothesis of the study is that combined experimental exposure to air pollutants (particles + ozone) increases sympathetic nervous system activity to a greater extent than does the exposure to particles alone.

Detailed Description
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In a randomized, double-blind, and cross-over fashion, the participants will be exposed to clean air, ultrafine particles, or ultrafine particles and ozone in an exposure chamber. The investigators will determine blood pressure, heart rate, respiration as well as cardiac output and directly record sympathetic vasomotor tone using the microneurography technique. To elucidate the underlying mechanisms through which particles and ozone affect the autonomic nervous system, the investigators will assess the local and systemic inflammatory response as well as the changes in neurotrophic factors in sputum and blood. In addition, the activation of inflammatory cells in sputum and blood will be analyzed at different points in time after exposures. Changes in sympathetic activity will be correlated with the degree of airway inflammation and oxidative stress assessed in induced sputum and blood. This study will provide important insight in the mechanisms through which air pollution, particularly ultrafine particle exposure, increases cardiovascular risk in human subjects and generate a human model for mechanistic and therapeutic studies.

Official Title
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Experimental Exposure to Air Pollutants and Sympathetic Nerve Activity in Human Subjects

Conditions
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Cardiovascular Morbidity

Intervention / Treatment
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* Other: ultrafine particles
* Other: ultrafine particles and ozone
* Other: clean air


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Elderly man or postmenopausal woman older than 50 years of age. Signed written informed consent. Exclusion Criteria: Smoker. Cardiovascular and/or pulmonary disease. Medication with relevant impact on autonomic system function, e. g. norepinephrine reuptake inhibitors. Stable medication with slight to moderate autonomic effects is tolerable. Subject is the investigator or any sub-investigator, research assistant, pharmacist, study coordinator, other staff or relative thereof directly involved in the conduct of the protocol. Mental condition rendering the subject unable to understand the nature, scope, and possible consequences of the study. Subject unlikely to comply with protocol, e. g. uncooperative attitude or unlikelihood of completing the study. Known hypersensitivity to ozone. History of drug or alcohol abuse. Particles Study - Protocol version: October 19, 2012 14 Blood donation of more than 500 mL during the previous 3 months.

Ages Eligible for Study
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Minimum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Supportive Care
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: ultrafine particles<br>Subjects will be exposed to ultrafine particles for three hours in an exposure chamber. During that time participants will perform intermittent bicycle ergometer training. Training intensity is adjusted individually to increase ventilation to 20 l/min/m². During exposure, heart rate will be monitored continuously via ECG. Blood pressure will be measured every 15 minutes. Ultrafine elemental carbon black particles are generated using a commercially available electric spark generator. Particle number, mass, and size distribution will be monitored during exposure. | Other: ultrafine particles<br>* exposure to ultrafine particles<br>|
| Active Comparator: ultrafine particles and ozone<br>Subjects will be exposed to ultrafine particles for three hours in an exposure chamber. During that time participants will perform intermittent bicycle ergometer training. Training intensity is adjusted individually to increase ventilation to 20 l/min/m². During exposure, heart rate will be monitored continuously via ECG. Blood pressure will be measured every 15 minutes. Ultrafine elemental carbon black particles are generated using a commercially available electric spark generator. Particle number, mass, and size distribution will be monitored during exposure.Ozone is generated from medical oxygen in order to maintain a concentration of 250 ppb. | Other: ultrafine particles and ozone<br>* exposure to ultrafine particles and ozone<br>|
| Placebo Comparator: clean air<br>Subjects will be exposed to clean air for three hours in an exposure chamber controlled for temperature, humidity, and gas/particle composition. During that time they will perform intermittent bicycle ergometer training for 15 minutes alternating with 15 minutes rest. Training intensity is adjusted individually to increase ventilation to 20 l/min/m². During exposure, heart rate will be monitored continuously via ECG. The blood pressure will be measured in time intervals of 15 minutes. | Other: clean air<br>* Exposure to clean air.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Muscle sympathetic nerve activity (MSNA) | Change of sympathetic vasoconstrictor nerve activity directed to skeletal muscle expressed as sympathetic bursts per minute. The primary hypothesis of the study is that in healthy elderly subjects experimental exposure to air pollutants increases sympathetic nervous system activity compared with sham (clean air) exposure. | 2.5 hours after exposure to clean air, to ultrafine particles, or to a combination of ultrafine particles and ozone | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| MSNA burst incidence | Change of MSNA expressed as bursts/100 heart beats. | 2.5 hours after exposure to clean air, to ultrafine particles, or to a combination of ultrafine particles and ozone | 
| total MSNA | Change of MSNA expressed as burst area/min. | 2.5 hours after exposure to clean air, to ultrafine particles, or to a combination of ultrafine particles and ozone | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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air pollution, ozone, fine particle, cytokine, chemokine, oxidative stress, inflammation, heart rate variability, autonomic nervous system, sympathetic nerve activity, plasma catecholamine