Clinical trial NCT02688478: The Phthalate-Allergen Immune Response Study
Official title: Effects of Phthalate Inhalation on Airway Immunology: A Controlled Human Exposure Study
Study type: INTERVENTIONAL
Overall status: UNKNOWN
Phase: NA
Conditions: Allergies
Keywords: Phthalate
Dibutylphthalate (DBP)
Airway responsiveness
Allergies
Lead sponsor: University of British Columbia
Sponsor class: OTHER
First posted: 2016-02-23
Enrollment: 20
Sex: ALL
Minimum age (years): 19
Maximum age (years): 49
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: BASIC_SCIENCE

Brief summary: Phthalates are commonly used plasticizers that have been linked to asthma in epidemiological studies. The investigators are researching effects of phthalates on airway immunology and lung function, and on allergic responses by doing an inhaled allergen challenge. After exposing participants to either filtered air or carefully controlled levels of phthalate in our exposure chamber we will collect samples from the nose and the upper airways, by rinsing the nose with saltwater or performing small brushings. The investigators will also collect a bronchial samples by bronchoscopy after each exposure. After 2 weeks, the entire procedure will be repeated with the alternate exposure.

Detailed description: 1. Purpose:

   To study the effects of phthalates on airway immunology, lung function and nasal allergic responses.
2. Hypotheses:

   Phthalate inhalation increases recruitment of immune cells to the upper airways and affects the functionality of immune and epithelial cells.

   Hypothesis 2: Phthalate inhalation alters the cellular response to an inhalation allergen challenge.
3. Justification:

   Phthalates are plasticizers or softeners, used in PVC and other plastics and a range of consumer products. Since phthalates are not chemically bound to the plastic they leak out from these products, causing routine human exposure through air, dust and food. Exposure to phthalates has been linked to worsening or development of airway diseases in epidemiological studies, but the effects of phthalates on our airways and immune responses are largely unknown. In this study we would like to investigate how one particular phthalate, dibutyl phthalate (DBP), can affect the human respiratory and immune systems. The investigators are not expecting that the responses will be noticeable to the subjects; they are expecting that any responses that may occur will only be detectable through careful examination of cells and tissues (e.g. nasal lavage and brushes (fluid from the nose), bronchial samples, blood, urine). Nasal samples will be used for measurement of nasal inflammatory responses in terms of cell recruitment and levels of inflammatory mediators. Bronchial samples will allow for a refined examination of an inflammatory responses in the lung and thus provide a much more detailed information concerning the phthalate-induced responses due to allergen challenge. Understanding these subtle changes will help us prevent health problems associated with phthalate exposure in the future.
4. Objectives:

   To establish that phthalates alter the cellular immune response in the upper airways.
5. Research Method:

   This is a blinded crossover experiment between two conditions (dibutyl phthalate, DBP, or filtered air, FA), randomized and counter-balanced to order.

   After each exposure of DBP or FA, we will deliver an inhaled allergen challenge. Data collection for each condition will be separated by a 2-week washout period.

   To evaluate the effects of the exposure on the immune response and lung function, the investigators will collect and perform the following on the day of the exposure or the following day:
   * Before each exposure, 3h and 24h post-exposure, we will collect urine and blood samples, perform NAL, and measure forced expiratory volume (FEV1) by spirometry and FeNO.
   * Methacholine challenge will be performed 24h after exposure.
   * Nasal brushing (NAB) will be performed at 3h pre-exposure on the left nostril and 3h post-exposure in the right nostril.
   * A fraction of the subjects enrolled will have a bronchoscopy performed 24h post-exposure, where bronchoalveolar samples and endobronchial biopsies will be collected.

   The literature provides conflicting data for phthalates with regard to some of the analytical endpoints. Therefore, to facilitate the choice of endpoints for the principal study, as well as to validate some study procedures, a 'Method optimization sub-study' will be performed prior to the start of the principal study. A maximum of 25 healthy subjects will be recruited for this sub-study, who will sign a modified consent that reflects their limited participation. These subjects will not be exposed to DBP or CA, but will only be recruited for collection of blood, nasal lavage, and nasal brushing, or a subset of these samples. They will only attend one visit to the Vancouver General Hospital, dedicating 1 - 3 hours of their time when participating in the sub-study. Moreover, prior starting the principal study (above), up to four healthy subjects may be recruited for a 'Pilot study' to optimize the logistics of the exposures and the experimental procedures of the principal study. These subjects will be subjected to CA exposure only and have all procedures and samples collected as described for the actual study with the exception of the bronchoscopy.

   Samples collected during the Method optimization sub-study and the Pilot study, will be used to establish analytical methods to measure immune cellular responses such as white blood or nasal epithelial cell responses to bacterial components (Toll Like Receptor (TLR) agonists) and phagocytosis assays after in vitro phthalate exposure (as described under study procedures).
6. Statistical Analysis:

A mixed effects model will be used to estimate all effects and pertinent contrasts will be used to test the hypotheses. Specifically, models will include exposure (CA or DBP), order (CA before DBP or DBP before CA) and gene variant status (e.g., GSTM1 present or GSTM1 null) as fixed effects and subject identifying number as a random effect. The inhalation allergen challenge is given during both DBP and CA exposures and will therefore not be included in the statistical analyses.

The influence of the general phthalate exposure level for 6 commonly measured phthalates, assessed in urine samples Day 1 and 2 on FeNO/blood/lung function will be analyzed by mixed effects model including exposure (DBP, CA), sampling period (Day 1, Day 2) and phthalate level (Day 1, Day 2). A one-way ANOVA will be used to compare pre- and post-exposure urinary MnBP levels for various time-points to verify phthalate exposure.

Eligibility criteria: Inclusion Criteria:

1. Age between 19 and 49 years.
2. Non-smoking.
3. Proficient in English
4. Positive skin prick test for at least one of: birch, grass, or dust.
5. Healthy, or diagnosed with mild asthma

Exclusion Criteria

1. pregnancy/breastfeeding
2. unstable asthma symptoms (eg: exacerbations in previous 2 weeks)
3. use of inhaled corticosteroids or bronchodilator medication more than 3 times a week
4. presence of co-existing medical conditions i.e. arrythmia (as assessed by the primary investigator)
5. participation in another study that involves taking medications
6. regular use of antihistamines, non-steroidal anti-inflammatories, anticoagulants, acetylsalicylic acid (ASA) or decongestants
7. allergy to salbutamol or lidocaine.

Primary outcomes:
measure: Recruitment of immune cells in airways
timeFrame: 3-24 hours
measure: Activation of immune cells in airways
timeFrame: 3-24 hours
measure: Airway responsiveness
timeFrame: 3-24 hours
measure: Airway Inflammation
timeFrame: 3-24 hours
Secondary outcomes:
measure: Allergen specific IgE
timeFrame: 24 hours
measure: Inflammatory markers in plasma and cell function after in vitro stimulation with inflammatory ligands (LPS & R848)
timeFrame: 3-24h
measure: Response of immune cells in blood
timeFrame: 3-24 hours
measure: Response of immune cells in airways
timeFrame: 3-24 hours
Other outcomes:
Locations:
city: Vancouver
country: Canada
facility: University of British columbia
state: British Columbia
Study officials:
affiliation: University of British Columbia
name: Christopher Carlsten, MD, MPH
role: PRINCIPAL_INVESTIGATOR
References:
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citation: Just AC, Whyatt RM, Miller RL, Rundle AG, Chen Q, Calafat AM, Divjan A, Rosa MJ, Zhang H, Perera FP, Goldstein IF, Perzanowski MS. Children's urinary phthalate metabolites and fractional exhaled nitric oxide in an urban cohort. Am J Respir Crit Care Med. 2012 Nov 1;186(9):830-7. doi: 10.1164/rccm.201203-0398OC. Epub 2012 Aug 23.
citation: Leung C, Ryu MH, Bolling AK, Maestre-Batlle D, Rider CF, Huls A, Urtatiz O, MacIsaac JL, Lau KS, Lin DTS, Kobor MS, Carlsten C. Peroxisome proliferator-activated receptor gamma gene variants modify human airway and systemic responses to indoor dibutyl phthalate exposure. Respir Res. 2022 Sep 16;23(1):248. doi: 10.1186/s12931-022-02174-8.
citation: Maestre-Batlle D, Huff RD, Schwartz C, Alexis NE, Tebbutt SJ, Turvey S, Bolling AK, Carlsten C. Dibutyl Phthalate Augments Allergen-induced Lung Function Decline and Alters Human Airway Immunology. A Randomized Crossover Study. Am J Respir Crit Care Med. 2020 Sep 1;202(5):672-680. doi: 10.1164/rccm.201911-2153OC.