More recently, the use of a chelating agent to protect the skin specifically against environmental pollutants was measured.33 Healthy human Caucasian skin explants were assigned to 4 different preventive regimens: no treatment, a commercially available cosmetic antioxidant alone, the chelating agent deferoxamine alone, or both the antioxidant and deferoxamine. The explants were then exposed to diesel engine exhaust (DEE) for up to 4 days. DEE is not only one of the most abundant pollutants, but also the most noxious to human health; in addition to oxides of nitrogen, sulfur dioxide, and various hydrocarbons, DEE contains significant levels of metals that can induce oxidative stress and inflammation.
The beneficial effects of topical deferoxamine were demonstrated by improvement in several measures of skin integrity. In the stratum corneum, DEE exposure leads to the formation of several lipid oxidation products, of which 4HNE is one of the most harmful. The combined application of antioxidant and deferoxamine was found to have an additive effect, reducing 4HNE levels to a greater extent than either treatment alone.33
Type I collagen is an interstitial matrix collagen that is essential for the competence of the skin. Depletion of type I collagen, which is one of the most evident signs of skin aging, has been linked with premature aging due to various factors, including pollution exposure. Whereas levels of type I collagen in untreated skin fell by more than 40% following DEE exposure, no decrease at all was seen in skin that had been treated with antioxidant and/or deferoxamine (Figure 2).33
Filaggrin and involucrin are key proteins involved in skin structure. Levels of these proteins in untreated skin also fell by approximately 40% to 50% following DEE exposure. The antioxidant and deferoxamine both protected tissues from depletion of these proteins and, in skin that had been treated with both agents, levels of filaggrin and involucrin increased (Figure 3).33
SUMMARY
The importance of regular use of sunscreen to protect the skin from the harmful effects of UV radiation is now universally accepted. However, other environmental stressors, including ozone and PM, also cause damage to the skin and promote premature aging. Transition metals, in particular, compromise the integrity of the
