The Effects of Air Pollution on the Skin: The Price to Pay

-From 2016, articles commented in the Journal and Focus will be posted here (selection by Prof. JH Saurat M.D.)

The Effects of Air Pollution on the Skin: The Price to Pay

Postby CFH » Fri Oct 21, 2016 1:35 pm

Recognizing the impact of ambient air pollution on skin health.
Mancebo SE, Wang SQ.
J Eur Acad Dermatol Venereol. 2015 Dec;29(12):2326-32. doi: 10.1111/jdv.13250. Review.

Why read this article?
-This article reviews how Air Pollutants may act on the Skin

Introduction
-The environment where we live has an influence on our health. Beyond obvious consequences such as those on the respiratory system when inhaled, the particles in the air can also affect the skin.
-While we still know little, mechanisms of action are emerging to how air pollutants act on the Skin

How does Air pollution act on the Skin ?
Four mechanisms have been identified:
1-generation of radical oxygen species (ROS) [and depletion of antioxidants]
2-activation of inflammation
3-activation of the "dioxin pathway" via activation of Aryl Hydrocarbon Receptor (AhR)
4-changes in the organisms living on the skin


1 - Generation of ROS
-Generation of ROS generates skin damage and induces skin aging
-Ozone in the stratosphere has protective effects by filtering solar UV radiation. However, Ozone is a highly reactive compound that generates free radicals and depletes antioxidants in the epidermis

2 - Induction of inflammatory cascade and subsequent impairment of skin barrier
-Cytokines and interleukins are small proteins released from a wide variety of cells involved in cellular signalling and induction of the inflammatory cascade

3 - Activation of the Aryl-hydrocarbon Receptor (AhR)
AhR activation likely plays a role in acne-like lesions, pigmentation (melanogenesis) and atopic dermatitis (AD):

-Acne lesions induced by AhR activation: http://genevadermatology.ch/dioxin-receptor-activation-in-acne-vulgaris/
-In mice , activation of AhR creates an itchy rash resembling ad.

In more detail:
-AhR is a cytosolic ligand-activated transcription factor found in various types of skin cells that regulate cellular proliferation, inflammation and melanogenesis.
-Ligand activation of AhR results in translocation to the nucleus, where it complexes with the AhR nuclear translocator and binds to specific DNA consensus sites known as xenobiotic response element (XRE). Genes containing XREs include the cytochrome P450 detoxification enzymes (CYP).
-Activation of AhR may play a role in mediating toxic effects associated with xenobiotic exposure including air pollutants such as ozone, dioxins and PAHs.
-Several studies have examined the role of AhR activation in cutaneous mechanisms ranging from regulation of melanogenesis to the development of inflammatory skin lesions.


4 - Alterations to Skin Microflora
Ozone has a bacterical effect with exposure reducing the microflora number by half

What are air pollutants ? (non-exhaustive)
-The US Environmental Protection Agency has identified 6 criteria pollutants: ground-level ozone, particulate matter (PM), sulphur dioxide (SO2), lead, carbon monoxide (CO) and nitrogen oxides (NOx,) which includes nitric oxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O).

-Pollutants can be divided into gaseous pollutants, persistent organic pollutants (POPs), particulate matter, heavy metals, traffic related, other toxic pollutants.

-Many air pollutants are gaseous pollutants and those are mainly due to the combustion of fossil fuels (coal, petroleum, natural gas). They act mainly upon ozone levels Gas pollutants comprise NOx, CO, SO2, ozone and volatile organic compounds (VOCs)


Comments
1. While no air pollutant in itself tobacco smoke has been shown to act in aging through the AhR pathways. Follow the link to read more: http://genevadermatology.ch/role-of-the-dioxin-receptors-aryl-hydrocarbon-receptors-ahr-in-the-induction-of-the-expression-of-the-matrix-metalloproteinase-mmp-1-enzyme-by-tobacco-smoke-extracts-for-professionals/
Thus tobacco could be considered as an air pollutant, especially in some developing countries where smoking is considered as "good" social behavior and where it is therefore seldom banned.

2. Air pollution occurs in environments which tend to be urban. With that in mind, this setting tends to be overall more stressful. It is known stress has an effect on Dermatological conditions although it is not known who the chicken or the egg is.

CFH
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