Air Pollution (PM2.5) on Accelerated Atherosclerosis: A Montelukast Interventional Study in Modernizing China

1. Introduction Atherosclerosis related complications, in particular stroke and coronary artery disease, are the most important health issues in modernized societies, being the leading cause of death worldwide. In addition to traditional cardiovascular (CV) risk factors such as obesity, hypertension, dyslipidemia, diabetes mellitus, tobacco use and physical inactivity, particulate matter (PM) air pollution has been shown to be associated with cardiovascular morbidity and mortality in large epidemiological studies.[1-3] Long-term exposure to elevated PM levels can reduce life expectancy, especially particulate matter with an aerodynamic diameter <2.5um (PM2.5). Such PM has a causal relationship to cardiovascular morbidity and mortality.[1-4] An approximate 8-18% increase in cardiovascular mortality has been observed for every 10ug/m3 elevation in average PM2.5 exposure over the long term. [1. 3, 5] The biological mechanisms of atherogenic processes may involve direct effects of PM on cardiovascular system, and/or indirect effects mediated by oxidative stress and inflammation. [6-7] Far less research has been conducted so far on the contribution of PM to such long-term atherogenic processes in human populations. [1,2,8,9]

We have previously studied 1656 Chinese adults in southern and northern China in 1996 to 2007 with PM2.5 concentration ranging from 34 to 94 ug/m3. PM2.5 were significantly related to prognostic atherosclerotic surrogates i.e. brachial flow-mediated dilatation (FMD) and carotid intima media thickness (IMT), independent of traditional-risk factors.[10] Our CATHAY study supports a hypothesis that PM2.5 air pollution is strongly correlated with early atherosclerotic process in modernizing China.

Montelukast has been used successfully and proven safe for prevention of asthma episodes, supposed to be triggered by allergic-related inflammations of respiratory tract. Similar inflammatory process at lung and subsequently at blood vessels may be implicated in PM2.5-related accelerated atherosclerosis. [9]

1. Aims and Hypotheses to be Tested: PM2.5 air pollution has been proven accelerating atherosclerotic process in Hong Kong and mainland China (CATHAY study). To further test this initial hypothesis, this interventional substudy aims
2. To evaluate the impact of antiinflammatory agent Montelukast treatment on predictive atherosclerosis surrogates (FMD \& IMT).
3. To evaluate the mechanism involved in PM2.5-related vascular dysfunction by monitoring changes in systemic inflammatory markers (platelet counts, HsCRP and fibrinogen).
4. Plan of Investigation

4.1 The impact of interventional agents on FMD and carotid IMT in working adults Subjects (120 adults in Hong Kong and 80 adults in Chongqing)

Inclusion

• asymptomatic adults
• aged 30-60 years with
• gender: male or female
• concordance of home and workplace air pollution

High exposure group: 60 adults, with PM2.5 concentration exposure >30ug/m3, both at residence and at work.

Low exposure group: 60 sex and age-matched asymptomatic adults with PM2.5 exposure <30ug/m3 both at home and at work.

Exclusion:

• Those with family history of stroke, cardio-vascular disease
• Hypertension with blood pressure >150/90 mmHg
• Diabetes Mellitus
• Overweight/ obesity (BMI >25kg/M2)
• Cigarette smoking or ex-smoker <5 years
• Known dyslipidemia defined as LDL-C >4.1mmol/l and triglyceride >3.0mmol/l.
• Physical inactivity, with weekly leisure exercise less than 0.5 hour
• Continuous usage of vitamins or herbal medicines in recent one year.

Study design:

A flowchart figure in Annex 1 illustrates the major procedures for the proposed study. Brachial flow-mediated dilation before and after Montelukast intervention will be compared between the control and intervention group.

Methods After informed written consent, these participants (60 adults in Hong Kong, and 40 adults in Chongqing) will be randomized to take Montelukast 10mg/daily or image-matched placebo (60 adults in Hong Kong, and 40 adults in Chongqing) for 26 weeks.

Week-0 Week-13 Week-26 Health Examination + 0 + Vascular Study + 0 + Blood Test + 0 + PM2.5 Evaluation + 0 + Medicine Dispatch + + 0 Compliance Assessment 0 + +

• Collection of health data:

1. Questionnaire - All adult subjects will be interviewed and required to complete a detailed questionnaire regarding their individual and family history of cardiovascular diseases, hypertension, diabetes and current use of medications. Information on socio-economic status and lifestyle will be collected. Important factors associated with PM exposure, such as transportation between work and home, environmental tobacco use (ETS), duration of residence, home renovation, cooking/heating usage, and use of incense and mosquito coils will be recorded as well.
2. Health examination - Each participant will receive a health examination and their weight and height, blood pressures, body mass index (BMI) and wait-hip circumference ratio (WHR) will be measured when they are wearing light clothing and no shoes.
3. Blood test: 10ml of fasting blood will be taken for platelet, fasting glucose, low density cholesterol, hsC-reactive protein and fibrinogen.

• Vascular Studies

1. Endothelial function, (flow mediated dilation, FMD) of the brachial artery will be studied by using high resolution ultrasound, as described previously. [11, 12] Using a linear array transducer (L10-5) with a median frequency of 7.5MHz and a standard Advanced Technology Laboratories 3000 or Sonosite systems, and forearm tourniquet cuff placement to induce reactive hyperemia on deflation. Scans will be acquired at rest, during reactive hyperemia (to induce flow-mediated endothelium-dependent dilation, FMD). FMD will be expressed as % of dilation from baseline vessel diameter normalized with vessel strain.
2. Carotid intima-media thickness (CIMT) measurement - B-mode ultrasound examinations will be performed using X12-3 probe with a 7 MHz scanning frequency linear array transducer. All carotid scans will be performed by standardized scanning protocol for the right and left carotid arteries as described by Salonen and Salonen [13] and Touboul et al [14], using images of the far wall of the distal 10 mm of the common carotid arteries, and a verified automatic edge-detecting and measurement software package as we described previously. [11-12, 15-16] The inter-observer variability of mean IMT is 0.003 to 0.011mm (CV 0.998%).

• Collection of air pollution exposure data:

Measurement of air pollutants at home and workplace will focus on PM2.5 and PM10.

We shall measure PM2.5 and PM10 pollutant levels at homes and workplace twice (warm and cool seasons) by handy portable PM2.5 device. The micro-environment meteorological PM2.5 and PM10 data, at home and workplace, will be combined and compared with data using modeling techniques.

Estimate of PM2.5/ PM10 exposure for each participant:

Details of the methodology and its verification using PM2.5/ PM10 data from Hong Kong and China has already been published (17, 18). Change of residential address during follow-up will be taken into account.

1. Significance and Potential: The proposed study can serve as a baseline for cohort model study in near future, for comparison with other vascular epidemiological data and interventional strategies in mainland China.

Investigating the relationship between particulate matter (PM) air pollution and atherosclerosis in working adulthood will enhance our abilities to elucidate the mechanisms underlying the effects of PM on atherosclerosis disease. Subsequently, it will help to develop appropriate strategies for both the control of PM air pollution (by legislation) and the prevention of atherosclerotic diseases, such as aerosol filters, facial masks, certain health food or nutrient (Aloe), statin or leukotriene modifiers (Montelukast) medicines. A huge number of Chinese exposed to PM air pollution throughout their life courses will be expected.

1. Compliance with Declaration of Helsinki The design, methodology and conduction of project are in compliance with Declaration of Helsinki.
2. Compliance will ICH-GCP. The medicines used are freely commercially available in Hong Kong Pharmacological Registry and compliant with ICH-GCP.
3. Data processing and analysis Power Calculation: The Proc Power in the STS 9.2 statistical packages (SAS institute Inc. Comy. NC, US) was used to calculate the sample size for FMD and carotid IMT. Data from our previous studies on adults in Hong Kong and mainland China, showed that the mean FMD is 6-8%+/-1.3% in otherwise healthy adults aged 30-60 years, and carotid IMT is 0.55-0.68mm+/-0.1mm. On the assumption of post Montelukast treatment, brachial FMD will improve to 6.7-8.7+/-1.4% in adults, and carotid IMT will reduce to 0.51-0.61mm+/-0.11mm, recruitment of 114 Chinese adults (57 in each group) will be adequately powered (80%) to detect a group difference in FMD of 1.2% and in CIMT of 0.1mm (12%) between the two treatment groups. In old adults, Kunzli reported a difference in CIMT of 12.1% in exposure of 20ug/m3 difference in PM2.5 pollution.[19]

Data Analysis: Statistical Analysis System 9.2 will be used for all statistical analyses. The primary endpoints are brachial FMD and Carotid IMT, serological inflammatory biomarkers (Platelet hsCRP and Fibrinogen) are secondary endpoints. Students' T-tests will be used to detect group differences on FMD and CIMT. Multivariate linear and logistic regression will be used to calculate risk magnitude by Montelukast vs placebo, and to control for potential confounders such as various traditional cardiovascular risk factors.