Traffic-Related Air Pollution, Blood Pressure, and Adaptive Response of Mitochondrial Abundance
Background—Exposure to black carbon (BC), a tracer of vehicular-traffic-pollution, is associated with increased blood pressure (BP). Identifying biological factors that attenuate BC effects on BP can inform prevention. We evaluated the role of mitochondrial abundance, an adaptive mechanism compensating for cellular-redox-imbalance, in the BC-BP relationship.
Methods and Results—At one or more visits among 675 older men from the Normative Aging Study (observations=1,252), we assessed daily BP and ambient BC levels from a stationary monitor. To determine blood mitochondrial abundance, we used whole blood to analyze mitochondrial-to-nuclear DNA ratio (mtDNA/nDNA) using quantitative polymerase-chain-reaction. Every standard deviation (SD) increase in 28-day BC moving average (MA) was associated with 1.97 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. 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 moderate-term ambient BC levels were associated with increased BP and blood mitochondrial abundance. Our findings indicate that increased blood mitochondrial abundance is a compensatory response and attenuates the cardiac effects of BC.
- Received August 3, 2015.
- Revision received November 20, 2015.
- Accepted December 1, 2015.