The protective role of antioxidants in the defence against ROS/RNS-mediated environmental pollution

Our plain-English summary of The protective role of antioxidants in the defence against ROS/RNS-mediated environmental pollution, by B. Poljšak, R. Fink (Oxidative Medicine and Cellular Longevity, 2014).

The study

• Authors: B. Poljšak, R. Fink
• Journal: Oxidative Medicine and Cellular Longevity
• Published: 2014;2014:671539
• Type of article: Review
• Cited by: 143 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Overproduction of reactive oxygen and nitrogen species can result from exposure to environmental pollutants, such as ionising and nonionising radiation, ultraviolet radiation, elevated concentrations of ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, asbestos, particulate matter, pesticides, dioxins and furans, polycyclic aromatic hydrocarbons, and many other compounds present in the environment. It appears that increased oxidative/nitrosative stress is often neglected mechanism by which environmental pollutants affect human health. Oxidation of and oxidative damage to cellular components and biomolecules have been suggested to be involved in the aetiology of several chronic diseases, including cancer, cardiovascular disease, cataracts, age-related macular degeneration, and aging. Several studies have demonstrated that the human body can alleviate oxidative stress using exogenous antioxidants. However, not all dietary antioxidant supplements display protective effects, for example, β-carotene for lung cancer prevention in smokers or tocopherols for photooxidative stress. In this review, we explore the increases in oxidative stress caused by exposure to environmental pollutants and the protective effects of antioxidants.

In plain English

This was a review article. It summarised published studies on whether environmental pollutants increase oxidative stress, meaning an excess of reactive oxygen and nitrogen species that can damage cells, and whether antioxidants protect against this. The pollutants covered included air pollutants, radiation, pesticides, household chemicals, water pollutants and noise. Asbestos was one of many pollutants covered, and the article did not name asbestos fiber types. Its tables listed cited studies reporting oxidative stress markers linked to asbestos, such as 8-isoprostane. It also described a cited rat study (Luo et al.) that found an inhibitory effect of green tea extract on cancer development induced by asbestos combined with benzo(a)pyrene. A table of adverse or insignificant antioxidant effects listed beta-carotene for asbestos, citing van Helden et al. The authors concluded that there is substantial evidence that pollution increases oxidative stress. They also concluded that dietary antioxidants or more fruit and vegetables may help buffer this, but that synthetic supplements cannot give complete protection under normal conditions. They called for more research and noted that not all studies could be covered.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: narrative review of published studies
• Who was studied: Published laboratory, animal and human studies on oxidative stress caused by environmental pollutants and on protection by antioxidants. The number of studies reviewed is not stated.
• Exposure: A wide range of environmental pollutants that produce reactive oxygen and nitrogen species. These included ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, particulate matter, asbestos (fiber types not specified), radiation, pesticides, dioxins, household chemicals, water disinfection byproducts and noise.
• Main results:
  • The review cited Luo et al., who found an inhibitory effect of green tea extract on cancer development induced by asbestos plus benzo(a)pyrene in rats drinking 2% green tea extract throughout their lives.
  • Table 1 listed cited studies reporting oxidative stress markers linked to asbestos. These were ROS formation, hydrogen peroxide, hydroxyl radical and superoxide anion, activation of phagocytic cells, increased 8-isoprostane (Pelclová et al. 2008) and 8-hydroxy-2'-deoxyguanosine (Marczynski et al. 2000). The same table listed green tea extract and SOD as antioxidants exerting a protective effect against asbestos.
  • Table 5, which lists studies showing adverse or insignificant effects of antioxidants, listed beta-carotene for asbestos, citing van Helden et al. (2009).
  • The review cited evidence that, in smokers, high doses of beta-carotene increased the rate of lung cancer.
• The authors' conclusion: The authors concluded that there is substantial evidence that environmental pollution increases oxidative stress. They concluded that dietary antioxidant supplementation and/or eating more fruit and vegetables may play a role in buffering these effects. They also concluded that synthetic antioxidant supplements cannot provide appropriate or complete protection under normal conditions, and that more research is needed.
• Limitations the authors state:
  • Because of space constraints and the breadth of the scientific data, not all studies could be covered in the review.
  • The authors stated that results of clinical trials of antioxidant intake are conflicting and contradictory.
  • The authors stated that more research is needed to strengthen the evidence for dietary supplements as modulators of pollution effects.

Topics

Medical terms in this study, explained in our Lexicon: Oxidative Stress, Lung Cancer.

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