Research Black Carbon Exposures, Blood Pressure, and Interactions with Single Nucleotide Polymorphisms in MicroRNA Processing Genes Elissa H. Wilker,1,2 Andrea Baccarelli,3 Helen Suh,1 Pantel Vokonas,4 Robert O. Wright,1,5 and Joel Schwartz 1,5 1Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA; 2Cardiovascular Epidemiology Research Unit, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; 3Center of Molecular and Genetic Epidemiology, Department of Environmental and Occupational Health, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico e Università degli Studi di Milano, Milan, Italy; 4VA Normative Aging Study, Veterans Affairs Boston Healthcare System and the Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA; 5Channing Laboratory, Brigham and Women’s Hospital, Boston, Massachusetts, USA Background : Black carbon (BC) is a marker of traffic pollution that has been associated with blood pressure (BP), but findings have been inconsistent. MicroRNAs (miRNAs) are emerging as key regulators of gene expression, but whether polymorphisms in genes involved in processing of miRNAs to maturity influence susceptibility to BC has not been elucidated. o Bjectivs : We investigated the association between BC and BP, as well as potential effect modifi- cation by single nucleotide polymorphisms (SNPs) in miRNA processing genes. Methods : Repeated measures analyses were performed using data from the VA Normative Aging Study. Complete covariate data were available for 789 participants with one to six study visits between 1995 and 2008. In models of systolic and diastolic BP, we examined SNP-by-BC interactions with 19 miRNA-related variants under recessive models of inheritance. Mixed-effects models were adjusted for potential confounders including clinical characteristics, lifestyle, and meteorologic factors. r esult : A 1-SD increase in BC (0.415 µg/m3) was associated with 3.04 mmHg higher systolic (95% confidence interval (CI), 2.29–3.79) and 2.28 mmHg higher diastolic BP (95% CI, 1.88– 2.67). Interactions modifying BC associations were observed with SNPs in the DICER, GEMIN4, and DiGeorge critical region-8 (DGCR8) genes, and in GEMIN3 and GEMIN4, predicting diastolic and systolic BP, respectively. c onclusi : We observed evidence of effect modification of the association between BP and 7-day BC moving averages by SNPs associated with miRNA processing. Although the mechanisms underlying these associations are not well understood, they suggest a role for miRNA genesis and processing in influencing BC effects. k ey owrds : black carbon, blood pressure, epigenetic mechanisms, gene–environment interactions, genetic polymorphisms. Environ Health Perspect 118:943–948 (2010). doi:10.1289/ehp.0901440 [Online 8 March 2010] Exposure to particulate air pollution has been associated with cardiovascular morbidity and mortality in numerous epidemiologic studies (Brook 2008; Pope et al. 2004). Black carbon (BC), a combustion by-product, is a widely used marker of traffic pollution and has been linked to cardiac and ventricular arrhythmias (Rich et al. 2005), ST-segment depression (Gold et al. 2000), decreased flow-mediated vascular reactivity (O’Neill et al. 2005), lowered heart rate variability (Schwartz et al. 2005), and increased cardiovascular mortality (Maynard et al. 2007). Growing evidence suggests that traffic-related pollution, including BC, may be driving the cardiotoxic effects observed in response to air pollution exposures (Hoffmann et al. 2007). A few recent studies have exam- ined associations between particles and blood pressure (BP), and although positive associa- tions have been observed (Auchincloss et al. 2008; Ibald-Mulli et al. 2001; Zanobetti et al. 2004), both inverse (Harrabi et al. 2006) and (Jansen et al. 2005; Madsen and Nafstad 2006) associations have also been reported. MicroRNAs (miRNAs) are small, non- coding RNAs that repress or inhibit gene expression by targeting messenger RNA (mRNA) (Mattick and Makunin 2006; Zhang 2008). Evidence suggests that miRNAs affect pathogenic pathways including angiogene- sis (Suarez and Sessa 2009), redox signaling (Brewer and Shah 2009; Urbich et al. 2008), and stress response (van Rooij et al. 2007). Much of the existing miRNA-related litera- ture has focused on cancer outcomes (Esquela- Kerscher and Slack 2006; Hu et al. 2008, 2009; Luthra et al. 2008; Yang et al. 2008). However, there is growing evidence that the dysregulation of cell-signaling pathways asso- ciated with miRNA is a key factor affecting heart disease (Chen et al. 2008; Cheng et al. 2007; Divakaran and Mann 2008; Ikeda et al. 2007; Zhang 2008). Additionally, studies in controlled environments have demonstrated cardiovascular effects due to loss of function of miRNA processing genes (Asada et al. 2008; da Costa Martins et al. 2008; Suarez et al. 2007). For the current study, we genotyped participants for potentially functional single nucleotide polymorphisms (SNPs) involved in the processing and formation of miRNAs. We then investigated the association between air pollution and BP as well as potential dif- ferences in susceptibility by SNP carrier status. We hypothesized that polymorphisms in genes that regulate miRNA processing could modify Environmental Health Perspectives • volume 118 | number 7 | July 2010 effects of BC on BP, a marker of autonomic function and cardiovascular health. Materials and Methods Study population. Our study participants were members of the Veterans Affairs Normative Aging Study (NAS). This is an ongoing lon- gitudinal study of aging established in 1963, details of which have been published pre- viously (Bell et al. 1966). Briefly, the NAS began as a closed cohort of 2,280 male vol- unteers from the greater Boston area, 21–80 years of age at entry, who enrolled after an initial health screening determined that they were free of known chronic medical condi- tions. All participants provided informed con- sent. Collection of blood samples for genetic analysis began in the late 1990s; 942 par- ticipants were still actively participating and provided BP and blood samples for some or all miRNA-related SNPs, which were success- fully genotyped. Participants were reevaluated every 3–5 years using detailed on-site physical examinations and questionnaires. Physical parameters and medical history. Study center visits occurred after an overnight fast and abstention from smoking. Physical examination included measurement of height and weight, with body mass index (BMI) cal- culated as weight (kilograms)/height (meters squared). Questionnaires evaluated lifestyle factors and medication use. Type 2 diabetes was classified based on physician’s diagnosis or fasting blood glucose > 126 mg/dL. BP measurements. At each clinical visit, a physician measured BP using a standard Address correspondence to E. Wilker, CVERU, Beth Israel Deaconess Medical Center, 375 Longwood Ave., Boston, MA 02215 USA. Telephone: (617) 632-7654. Fax: (617) 632-7698. E-mail: ewilker@ bidmc.harvard.edu Funding for this work was provided by National Institute of Environmental Health Sciences grants ES 14663, ES 15172, ES 00002, P01 ES09825, EPA R832416, T32-07069, and T32-HL007374-30. The VA Normative Aging Study, a component of the Massachusetts Veterans Epidemiology Research and Information Center, Boston, Massachusetts, is supported by the Cooperative Studies Program/ Epidemiology Research and Information Center of the U.S. Department of Veterans Affairs. The authors declare they have no actual or potential competing financial interests. Received 8 September 2009; accepted 5 March 2010. 943