Grantee Research Project Results
2016 Progress Report: The Role of Obesity in Biological Responses to Particulate Matter in Mice
EPA Grant Number: R836152C003Subproject: this is subproject number 003 , established and managed by the Center Director under grant R836152
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for the Study of Childhood Asthma in the Urban Environment
Center Director: Hansel, Nadia
Title: The Role of Obesity in Biological Responses to Particulate Matter in Mice
Investigators: Polotsky, Vsevolod Y , Mitzner, Wayne
Current Investigators: Polotsky, Vsevolod Y
Institution: The Johns Hopkins University
EPA Project Officer: Callan, Richard
Project Period: September 1, 2015 through August 31, 2019 (Extended to August 31, 2021)
Project Period Covered by this Report: September 1, 2015 through August 31,2016
RFA: Children's Environmental Health and Disease Prevention Research Centers (2014) RFA Text | Recipients Lists
Research Category: Children's Health , Human Health
Objective:
The overarching hypothesis of the Project 3 is that obesity exacerbates the particulate matter (PM)-induced airway hyperresponsiveness (AHR) due to pathogenic effects of adiposity and comorbid sleep apnea and that the effects of obesity are mediated via IL-6. Furthermore, these detrimental effects of obesity can be attenuated by weight loss and sleep apnea treatment. Our hypothesis will be addressed in two Specific Aims:
Specific Aim 1: we will test causal links between obesity and the PM-induced AHR and inflammation. (A) We will quantify the PM-induced AHR and inflammation in lean and DIO wildtype and IL-6 knockout mice; (B) To link to potential therapeutic actions, we will quantify the ability of weight loss to attenuate the PM-induced AHR and inflammation.
Specific Aim 2: we will examine effects of sleep apnea on the PM-induced AHR and inflammation. We will quantify the PM-induced AHR and inflammation in DIO mice with recurrent upper airway obstruction during sleep caused by genetically induced excessive tongue adiposity. Experiments will also assess the effects of sleep apnea treatment, which will be modeled by supplemental oxygen.
Progress Summary:
In Experiment 1, we aimed to firmly determine effects of obesity and PM on AHR and inflammation in C57BL/6J mice. We examined the effect of obesity and ambient particulate matter (PM) from urban Baltimore on AHR and inflammation. Ambient PM provided by the Environmental Core was collected from a sixth floor window in urban Baltimore during the months of March through May using a high-volume cyclone collector with a theoretical cut-point of 0.85 μm aerodynamic diameter. Baseline measurements were made at 1, 3 and 10 mg/mL. Measurements of total lung resistance (R), elastance (E), and airway resistance (Raw) (determined from the impedance variable, Rn) were recorded after each dose. Bronchoalveolar lavage (BAL) samples were collected with 2 × 1 mL of sterile phosphate-buffered saline (PBS) through a tracheal cannula. Total cell counts were measured and cell differential determined with Diff-Quik (Andwin Scientific, Tyron, NC). Lungs were collected, RNA was extracted with Trizol reagents and real time PCR was performed for IL-1β, IL-4, IL-5, IL-6, IL-13, IL-17A, and TNFα with 18S as a housekeeping gene.
Conclusions: 1) Diet-induced obesity induces airway hyperresponsiveness and neutrophilic inflammation in lung tissue. These effects may be related to the effects of pro-inflammatory cytokines IL-1β and IL-6 early in the time course of weight gain. 2) Contrary to our Preliminary Data, we found no evidence of PM and obesity interaction to increase airway reactivity. However, PM and obesity interacted to increase neutrophilic inflammation in the lung. There are several potential explanations of this phenomenon. DIO mice have higher minute ventilation than lean mice due to a higher metabolic rate. It is conceivable that a higher dose of PM is required in DIO mice to achieve a desirable effect. It also is conceivable that the current regimen of PM exposure is too short resulting predominantly in acute neutrophilic inflammation and longer exposure is needed to see an effect. We plan to modify our Research Plan in two different directions performing two new sets of experiments. First, we will adjust the dose of PM per body weight and repeat the experiment. Second, we will expose obese and lean mice to outside unfiltered air chronically mimicking human exposure to environmental pollution. These experiments will be performed during Year 2 of the grant. In Year 3, we will examine effects of IL-1 β and IL-6 knockouts on airway responsiveness in DIO mice exposed to PM.
In Experiment 2, we aimed to optimize a mouse model of obstructive sleep apnea which will be used in Experiments proposed for SA2. Obstructive sleep apnea is induced by excessive tongue adiposity. Excessive tongue adiposity has been induced by overexpressing a key transcription factor of lipid biosynthesis peroxisome proliferator-activated receptor gamma (PPARγ). Our Preliminary Data demonstrated that PPARγ overexpression using plasmid electroporation to the tongue induces sleep apnea. Major drawbacks of this experiment were a large transfection volume (200 μl), electroporation and the use of hyaluronidase inducing non-specific injury to the tongue, and high mortality (20-30%). We replaced the plasmid with adenovirus carrying the human PPAR γ gene.
Conclusion: We developed a novel approach to induce adiposity selectively in the base of the tongue. During Year 2 of the grant we will firmly establish a new transgenic mouse model of sleep apnea using this approach. During Years 3-4, we will utilize this model to study the effect of obstructive sleep apnea on PM-induced asthma.
Future Activities:
We plan to modify our Research Plan in two different directions performing two new sets of experiments. First, we will adjust the dose of PM per body weight and repeat Experiment 1 (see above). Second, we will expose obese and lean mice to outside unfiltered air chronically mimicking human exposure to environmental pollution. These experiments will be performed during Year 2 of the grant. We also will obtain initial data with IL-1β and IL-6 knockout mice.
Because we have developed a novel approach to induce adiposity selectively in the base of the tongue, we also will try to establish a new transgenic mouse model of sleep apnea using this approach.
Supplemental Keywords:
PM-induced airway hyperresponsiveness, AHR, chronic airway inflammation, overweight, asthma, obstructive sleep apnea, OSAProgress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R836152 Center for the Study of Childhood Asthma in the Urban Environment Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R836152C001 Investigating obesity as a susceptibility factor for air pollution in childhood
R836152C002 Novel exposure metrics for assessing the effects of ultrafine and fine particulate matter on asthma in children
R836152C003 The Role of Obesity in Biological Responses to Particulate Matter in Mice
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.