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Aging attenuates redox adaptive homeostasis and proteostasis in female mice exposed to traffic-derived nanoparticles ('vehicular smog').

ABSTRACT: Environmental toxicants are catalysts for protein damage, aggregation, and the aging process. Fortunately, evolution selected adaptive homeostasis as a system to mitigate such damage by expanding the normal capacity to cope with toxic stresses. Little is known about the subcellular degradative responses to proteins oxidatively damaged by air pollution. To better understand the impact of environmental toxicants upon the adaptive homeostatic response, female C57BL/6 mice were exposed for 10 weeks to filtered air or reaerosolized vehicular-derived nano-scale particulate matter (nPM), at which point tissues from young (6 month) and middle-aged (21 month) mice were studied. We found significant increases of proteolytic capacity in lung, liver, and heart. Up to two-fold increases were seen in the 20S Proteasome, the Immunoproteasome, the mitochondrial Lon protease, and NF-E2-related factor 2 (Nrf2), a major transcriptional factor for these and other stress-responsive genes. The responses were equivalent in all organs, despite the indirect input of inhaled particles to heart and liver which are downstream of lung. To our knowledge, this is the first exploration of proteostatic responses to oxidative damage by air pollution. Although, middle-aged mice had higher basal levels, their Nrf2-responsive-genes exhibited no response to nanoparticulate exposure. We also found a parallel age-associated rise in the Nrf2 transcriptional inhibitors, Bach1 and c-Myc which appear to attenuate adaptive responses in older mammals, possibly explaining the 'age-ceiling effect.' This report extends prior findings in male mice by demonstrating the involvement of proteolytic responses to traffic-related air pollution in lung, liver, and heart of female mice, with an age-dependent loss of adaptive homeostasis.

SUBMITTER: Pomatto LCD

PROVIDER: S-EPMC5987225 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Aging attenuates redox adaptive homeostasis and proteostasis in female mice exposed to traffic-derived nanoparticles ('vehicular smog').

Pomatto Laura C D LCD Cline Mayme M Woodward Nicholas N Pakbin Payam P Sioutas Constantinos C Morgan Todd E TE Finch Caleb E CE Forman Henry Jay HJ Davies Kelvin J A KJA

Free radical biology & medicine 20180427

Environmental toxicants are catalysts for protein damage, aggregation, and the aging process. Fortunately, evolution selected adaptive homeostasis as a system to mitigate such damage by expanding the normal capacity to cope with toxic stresses. Little is known about the subcellular degradative responses to proteins oxidatively damaged by air pollution. To better understand the impact of environmental toxicants upon the adaptive homeostatic response, female C57BL/6 mice were exposed for 10 weeks ...[more]

PMID: 29709705

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Project description:(1) Background: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease with still unknown etiology. Some occupational and environmental risk factors have been suggested, including long-term air pollutant exposure. We carried out a pilot case-control study in order to evaluate ALS risk due to particulate matter with a diameter of ≤10 µm (PM10) as a proxy of vehicular traffic exposure. (2) Methods: We recruited ALS patients and controls referred to the Modena Neurology ALS Care Center between 1994 and 2015. Using a geographical information system, we modeled PM10 concentrations due to traffic emissions at the geocoded residence address at the date of case diagnosis. We computed the odds ratio (OR) and 95% confidence interval (CI) of ALS according to increasing PM10 exposure, using an unconditional logistic regression model adjusted for age and sex. (3) Results: For the 132 study participants (52 cases and 80 controls), the average of annual median and maximum PM10 concentrations were 5.2 and 38.6 µg/m3, respectively. Using fixed cutpoints at 5, 10, and 20 of the annual median PM10 levels, and compared with exposure <5 µg/m3, we found no excess ALS risk at 5-10 µg/m3 (OR 0.87, 95% CI 0.39-1.96), 10-20 µg/m3 (0.94, 95% CI 0.24-3.70), and ≥20 µg/m3 (0.87, 95% CI 0.05-15.01). Based on maximum PM10 concentrations, we found a statistically unstable excess ALS risk for subjects exposed at 10-20 µg/m3 (OR 4.27, 95% CI 0.69-26.51) compared with those exposed <10 µg/m3. However, risk decreased at 20-50 µg/m3 (OR 1.49, 95% CI 0.39-5.75) and ≥50 µg/m3 (1.16, 95% CI 0.28-4.82). ALS risk in increasing tertiles of exposure showed a similar null association, while comparison between the highest and the three lowest quartiles lumped together showed little evidence for an excess risk at PM10 concentrations (OR 1.13, 95% CI 0.50-2.55). After restricting the analysis to subjects with stable residence, we found substantially similar results. (4) Conclusions: In this pilot study, we found limited evidence of an increased ALS risk due to long-term exposure at high PM10 concentration, though the high statistical imprecision of the risk estimates, due to the small sample size, particularly in some exposure categories, limited our capacity to detect small increases in risk, and further larger studies are needed to assess this relation.

Dataset Information

Aging attenuates redox adaptive homeostasis and proteostasis in female mice exposed to traffic-derived nanoparticles ('vehicular smog').

Publications

Aging attenuates redox adaptive homeostasis and proteostasis in female mice exposed to traffic-derived nanoparticles ('vehicular smog').

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