Durham, N.C. — A new area of research may help in the development of more effective topical products to counteract polycyclic aromatic hydrocarbons, a result of air pollution which impacts skin aging.
Many different factors beyond overexposure to ultraviolet (UV) radiation are in part responsible for intrinsic as well as extrinsic skin aging, such as various forms of air pollution and even stress, begging the need for dermatologists to appropriately address these factors in their patients in terms of treatment, avoidance and advice.
Having a better handle on emotional stress and the role of psychological stress in aging is a new area of study, and although most dermatologists have considered their association, an expert says no one has actually been able to prove that there is a physiologic change associated with it, until now.
“One of the central factors that has been proven beyond any doubt to cause premature skin aging is overexposure to UV radiation. However, other potential contributors to this process can include smog, pollution, cigarette smoke as well as other particulates in the air, which behooves dermatologists to address these issues accordingly with their patients,” says Zoe Draelos, M.D., consulting professor of dermatology at Duke University School of Medicine, Durham, N.C.
Looking beyond UV
According to Dr. Draelos, many dermatologists may often stop at sunscreen and photoprotection when advising their patients in how to better protect their skin. These other non-UV sources, however, can also negatively impact the skin, Dr. Draelos says, as they operate through the same mechanism of action, which is the creation of reactive oxygen species, resulting in the premature aging of the skin.
“I do not think that a lot of people fully understand or appreciate the effects of the nanoparticles that are generated from either internal combustion engines, cigarette smoke or byproducts of industrial processes,” she says. “The truth is that these can have a profound effect on the skin in terms of premature skin aging, and we as dermatologists need not only to be aware of their action but also appropriately advise our patients in how to best avoid them.”
Cigarette smoke has long been thought to be associated with the breakdown of collagen and elastic fibers in the skin, resulting in the premature development of wrinkles and flaccid skin in individuals who smoke. Most recently, a study in Mexico City demonstrated that cigarette smoke reduces the facial blood flow in smokers, further underscoring the detrimental effects of cigarette smoke. In this yet to be published study, the perfusion between smokers and nonsmokers was compared using Doppler ultrasound and found that the test subjects who smoked demonstrated a prematurely aged microcirculation in terms of having reduced blood flow to the skin compared to those individuals who did not smoke.
“Smoking chronically deprives the skin of oxygen and arterially supplied nutrients. In my opinion, a prematurely aged microcirculation probably has just a big an effect on premature skin aging as do the nanoparticles that create reactive oxygen species that are inhaled or even touch the skin itself,” Dr. Draelos says.
Air pollution impact
In addition to cigarette smoke, Dr. Draelos says air pollution is also a major extrinsic contributing factor to premature skin aging. Research has shown that the polycyclic aromatic hydrocarbons (PAH) that are bound to the nanoparticles in the air from pollution are converted to quinones, according to Dr. Draelos. These quinones are the redox cycle chemicals that in turn produce reactive oxygen species (ROS), which result in the same type of skin aging that is seen with chronic exposure to UV light.
As air pollution will likely remain a major issue, particularly for those who reside in larger cities, Dr. Draelos says she often recommends that her patients regularly wash their face and consume antioxidants.
“Polycyclic aromatic hydrocarbons are inadvertently delivered to the skin via nanoparticles resultant from different forms of air pollution,” she says. “Washing the skin is one effective way of reducing the nanoparticle content on the skin surface. More information is needed in topical formulation development to combat this newly recognized skin aging mechanism.”
Quinones not only prematurely age the skin by creating ROS, Dr. Draelos says, but they are also thought to be a driving force behind pigmentation, which in and of itself can be considered another form of skin aging.
“Indeed, it has been shown that there is more facial dyspigmentation in individuals who dwell in high PAH environments (i.e. cities) compared to those who live in rural areas,” Dr. Draelos says.
In a recent still to be published study sponsored by L’Oréal, Dr. Draelos says the effects of PAH on the skin of 93 individuals living in a rural area in Mexico was compared to that of 93 individuals living in Mexico City. Researchers analyzed both vitamin E and the squalene content in the facial sebum of all study participants, and found that there was a decreased vitamin E as well as a decreased squalene content in the individuals who lived in the city environment.
“Lipids of all substances in the entire body are the most prone to oxidation. Vitamin E and squalene become oxidized and subsequently, their levels decrease in facial sebum because of contact with environmental pollution,” Dr. Draelos says.
New product development
This is a new area of research, she says, that hopefully will bear fruit in terms of the development of more effective topical products that can counteract the harmful PAHs. Moreover, Dr. Draelos says one of the ways of showing just how much pollution is affecting someone’s skin is to analyze and measure the squalene content in their sebum.
One of the problems in developing new topical products is that one needs to have an endpoint that can be measured, but quantifying the ROS on a patient’s skin is not possible. According to Dr. Draelos, measuring the squalene content could be one approach, as it provides an endpoint that perhaps could be used to analyze different skin appearances in individuals who are exposed to this type of environmental change.
“Perhaps in the future, you could actually just do a sebum swab of a patient’s face, analyze the squalene content, start an intervention with a topical formulation, and then look to see if more of the squalene is present in an oxidized state. If you had less oxidized squalene, that would tell you that there is less ROS being produced and that your product, if used over a lifetime, could reduce the oxidative burden of damage that prematurely ages people beyond their chronological years,” Dr. Draelos says.
Chronic psychological stress is another factor that has been recently implicated as a contributor to accelerated cellular aging, Dr. Draelos says. In a recent study, researchers showed that in individuals who have premature aging possibly due to chronic psychological stress also have decreased leukocyte telomere length (O’Donovan A, Tomiyama J, Lin J, et al. Brain Behav Immun. 2012;26(4):573-579).
The shortening of telomeres basically reflects the time clock that is ticking, Dr. Draelos says, and indicates how many more cell replications are possible. Decreased leukocyte telomere length is important because the leukocytes play a crucial role in immune function, and when the telomere length is prematurely shortened, that shortens the number of replications that each leukocyte can undergo.
“We normally lose about 100-200 telomere bases with each cell division and when you add psychological stress to the formula, you lose the telomere bases more rapidly, and telomere shortening leads to premature aging,” Dr. Draelos says.
Disclosures: Dr. Draelos is a researcher for L’Oréal.