Abstract 12781: Traffic-related Air Pollution, Blood Pressure, and Adaptive Response of Mitochondrial Abundance

Abstract

Introduction: Black carbon (BC) exposure - a tracer of vehicular traffic pollution - is associated with increased blood pressure (BP). Identifying biological factors that attenuate BC effects on BP can aid effective prevention. Hypothesis: We aimed to evaluate the role of mitochondrial abundance, an adaptive mechanism compensating for cellular-redox-unbalance, in the BC-BP relationship. Methods: At one or more visits among 675 older men from the Normative Aging Study (1,252 observations), we assessed BP and ambient BC levels (2-day to 28-day prior to visit, from a stationary monitor). Mitochondrial abundance was determined as blood mitochondrial-to-nuclear DNA ratio (mtDNA/nDNA) using quantitative polymerase-chain-reaction. Results: Every standard deviation (SD) increase in 28-day BC moving average (MA) was associated with 1.94 mm Hg (95%CI, 1.23-2.72; P<0.0001) and 3.46 mm Hg (95%CI, 2.06-4.87; P<0.0001) higher diastolic and systolic (SBP) BP, respectively. Positive BC-BP associations existed throughout all time windows. Likewise, BC MAs (5-day to 28-day) were associated with increased mtDNA/nDNA. Every SD increase in 28-day BC MA was associated with 0.12 SD (95%CI, 0.03-0.20; P=0.007) higher mtDNA/nDNA. High mtDNA/nDNA significantly attenuated the BC-SBP association throughout all time windows. The estimated effect of 28-day BC MA on SBP was 1.95-fold larger for individuals at the lowest mtDNA/nDNA quartile midpoint (4.68 mm Hg; 95%CI, 3.03-6.33; P<0.0001), compared to the top quartile midpoint (2.40 mm Hg; 95%CI, 0.81-3.99; P=0.003). Conclusions: In older adults, short- to moderated-term ambient BC levels were associated with increased BP and mitochondrial abundance. Increased mitochondrial abundance may represent a compensatory response that attenuates the adverse cardiac effects of BC.