Post-transcriptional air pollution oxidation to the cholesterol biosynthesis pathway promotes pulmonary stress phenotypes

The impact of environmentally-induced chemical changes in RNA has been fairly unexplored. Air pollution induces oxidative modifications such as 8-oxo-7,8-dihydroguanine (8-oxoG) in RNAs of lung cells, which could be associated with premature lung dysfunction. We develop a method for 8-oxoG profiling using immunocapturing and RNA sequencing. We find 42 oxidized transcripts in bronchial epithelial BEAS-2B cells exposed to two air pollution mixtures that recreate urban atmospheres. We show that the FDFT1 transcript in the cholesterol biosynthesis pathway is susceptible to air pollution-induced oxidation. This process leads to decreased transcript and protein expression of FDFT1, and reduced cholesterol synthesis in cells exposed to air pollution. Knockdown of FDFT1 replicates alterations seen in air pollution exposure such as transformed cell size and suppressed cytoskeleton organization. Our results argue of a possible novel biomarker and of an unseen mechanism by which air pollution selectively modifies key metabolic-related transcripts facilitating cell phenotypes in bronchial dysfunction.

Abstract MP61: A Multi-pollutant, Multi-ethnic, and Methylome-wide Association Study Highlights Epigenetic Effects of Exposure to Ambient Air Pollution Mixtures

Background: Ambient air pollution mixtures including fine particulates and gases have been associated with cardiovascular disease (CVD). Although mechanisms underlying the associations remain largely uncharacterized to date, examining epigenetic responses to air pollution mixtures may identify biological systems affected by exposure and provide insight into the pathophysiology and environmental epidemiology of CVD. Therefore, we undertook a multi-pollutant, methylome-wide study of associations between DNA methylation (DNAm) at 485,000 Cytosine-phosphate-Guanine (CpG) sites and pollutants regulated by the U.S. Environmental Protection Agency under the Clean Air Act. Methods: Data from the Atherosclerosis Risk in Communities Study and three sub-studies within the Women’s Health Initiative (WHI) included information on 8,567 participants, 83% of whom were women, 46% African American, and 9% Hispanic/Latino (mean age, 61.3 years). Daily mean, geocoded participant address-specific concentrations of ambient particulate matter with diameter ≤ 10μm (PM 10 ), ≤2.5μm (PM 2.5 ), and 2.5-10μm (PM 2.5-10 ); ozone (O 3 ); nitrogen dioxide (NO 2 ); nitrogen oxides (NO x ); carbon monoxide (CO); and sulfur dioxide (SO 2 ) were averaged over 2, 7, 28, and 365 days before measurement of leukocyte DNAm in whole blood. Methylome-wide, pollutant-DNAm associations were estimated separately at each averaging period in each stratum defined by race/ethnicity and study using multi-level, linear mixed models adjusting for socio-demographic, behavioral, and meteorological characteristics; estimated leukocyte proportions; and technical covariates. Estimates were combined across strata in pollutant- and period-specific, fixed-effects, inverse-variance weighted meta-analyses. Then multi-pollutant, period-specific effects were examined using the adaptive sum of powered scores (U) test (aSPU). CpG sites associated with multi-pollutant significance (aSPU P < 1.0 x 10 -7 ) were characterized in silico to assess their putative function and biological plausibility. Results: Overall analyses identified a significant, 28-day mean, multi-pollutant association at cg15008743 near ZNF83 on chromosome 19 (p = 1x10 -7 ) and a highly-suggestive 28-day mean, multipollutant association at cg00489219 near ZNF621 on chromosome 3 (p = 5x10 -7 ). ZNF83 and ZNF621 encode zinc finger proteins with a potentially broad reach across biological systems given their transcription factor, metal, and DNA binding activities. ZNF621 also harbors rare genetic variants with large effects on blood pressure. Discussion: Methylome-wide associations of DNAm with EPA-regulated ambient air pollutants suggest biologically plausible pathways underpinning the increasingly well-documented ties between multi-pollutant mixtures and cardiovascular disease.