Fine particulate matter catalyzes oxidative stress in the lungs

Date:
May 22, 2023
Source:
Max Planck Institute for Chemistry
Summary:
Study sheds new light on the adverse health effects of air
pollution: hydrogen peroxide production of fine particles may
not be as important as previously assumed. A new study reveals
that the adverse health effects of fine particulate matter
(PM2.5) are attributable to the conversion of peroxides into
more reactive species such as the hydroxyl radical (OH) rather
than the direct chemical production of hydrogen peroxide (H2O2)
as previously thought.


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FULL STORY ==========================================================================
In the scientific literature, the total production of reactive oxygen
species (ROS) such as H2O2 is commonly used as proxy for the toxicity
of air pollutants and their ability to induce oxidative stress and inflammation. The research team led by Thomas Berkemeier from the MPIC in
Mainz found that ROS concentrations in the epithelial lining fluid (ELF)
of the human respiratory tract may be primarily determined by the release
of endogenous H2O2 and the inhalation of ambient gas-phase H2O2, while
the chemical production of H2O2 through inhaled PM2.5 is less important.

"Based on our simulations, we think that the overall concentrations of
these reactive species in the lungs are large anyway, and not directly dependent on levels of air pollution," says Dr. Thomas Berkemeier, head
of the Chemical Kinetics & Reaction Mechanisms group at the MPIC. They
use a computer model to understand the relevant physical, chemical,
and biological processes, and quantify the health effects of different
types of air pollutants.

"Our new model simulates the chemical reactions that happen in the
respiratory tract. For the first time, we included production, diffusion,
and removal of hydrogen peroxide from cells and the blood stream into
our computer model. This was quite challenging, because it is not so
easy to put these processes in biological tissues into equations,"
explains Thomas Berkemeier.

New research directions "The findings of this study suggest that the
current paradigms for assessing the differential toxicity of individual
PM2.5 components need to be critically reassessed," says Prof. Dr. Ulrich Po"schl, Head of the Multiphase Chemistry Department at the MPIC. The
study proposes that the chemical production of superoxide and H2O2
in a cell-free assay may not be a suitable metric for assessing the differential toxicity of individual PM2.5 components, and some acellular oxidative potential assays may not capture the actual deleterious effects
of PM2.5.

Fine particulates might act through Fenton chemistry However, the
production of hydroxyl radicals (OH) was strongly correlated with Fenton chemistry of PM2.5 in the model calculations. "The model simulations
suggest that PM2.5 mostly acts by conversion of peroxides into highly
reactive OH radicals. Thus, PM2.5 is not so much the fuel, but rather
the catalyst of the chemical reactions that cause damage to cells and
tissues," says Berkemeier explaining the role of inhaled particles in
the model. Additionally, PM2.5 may stimulate the production of superoxide
from endogenous sources, which further contributes to the adverse health effects of air pollution.

The study underscores the importance of continued research to better
understand the chemical mechanisms underlying the health effects of
air pollution and to develop effective strategies to mitigate these
effects. The authors believe that this study will contribute significantly
to this important research effort. Their findings are published in the scientific journal "Environmental Science: Atmospheres." Background information Air pollution is a major health risk that affects millions
of people worldwide, but the underlying chemical mechanisms are not yet
fully understood. Fine particulate matter (PM2.5) typically contains
chemical components that can trigger oxidation reactions. When inhaled
and deposited in the human respiratory tract, they can induce and sustain radical reaction cycles that produce reactive oxygen species (ROS) in
the epithelial lining fluid (ELF) that covers the airways and alveoli in
human lungs. Numerous studies have shown that excess concentrations of
ROS like hydrogen peroxide (H2O2) and hydroxyl radicals (OH) can cause oxidative stress injuring cells and tissues in the respiratory tract.

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========================================================================== Story Source: Materials provided by
Max_Planck_Institute_for_Chemistry. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Eleni Dovrou, Steven Lelieveld, Ashmi Mishra, Ulrich Po"schl, Thomas
Berkemeier. Influence of ambient and endogenous H2O2 on reactive
oxygen species concentrations and OH radical production in the
respiratory tract. Environmental Science: Atmospheres, 2023; DOI:
10.1039/D2EA00179A ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230522131349.htm

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