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Hydroquinone: Is the Cure Worse Than the Problem?
By: Diana Howard, PhD
Posted: March 27, 2009, from the April 2009 issue of Skin Inc. magazine.
page 3 of 5
Controlling inflammation. Controlling inflammation is another strategy for treating hyperpigmentation. The use of anti-inflammatory agents, such as white tea, licorice and green tea, helps address the connection between inflammation and pigment formation. These extracts also may act as antioxidants, slowing many of the oxidation steps involved in melanin formation.
Melanin formation. Of particular interest are ingredients that impact melanin formation in multiple ways. An example is zinc glycinate, which stimulates synthesis of an antioxidant protein called metallothionein that binds the copper and reduces tyrosinase synthesis and activity; in addition, it suppresses melanocyte growth factors that stimulate melanin synthesis. Niacinamide has been shown to stop the transfer of melanosomes to neighboring keratinocytes. Glucosamine and dithiooctanediol stop the activation of the tyrosinase enzyme, a step that involves glycosylation, or the addition of a sugar molecule to the inactive proenzyme structure, converting it to the activated enzyme. Obviously, if the enzyme remains inactive, melanin formation ceases.
New studies indicate that melanin formation can also be controlled by affecting the signaling process involved in melanin biosynthesis. Sunscreens and anti-inflammatory agents work by turning off the messengers that signal melanin synthesis to commence. A brown seaweed called Ascophyllum nodosum has been shown to inhibit endothelin-1 (ET-1), a molecule synthesized and released from the keratinocytes after UV exposure. ET-1 stimulates the melanocyte and triggers tyrosinase activity. When the signal molecule ET-1 is inhibited, melanin formation is likewise inhibited. In a similar role, the use of Palmaria palmata, a red algae, has been shown to inhibit the release of stem cell factor (SCF), another signaling molecule released by keratinocytes upon exposure to UVB radiation; SCF activates the melanocyte to make melanin. Palmaria palmata inhibits the release of SCF and therefore inhibits melanocyte activation.
In the past decade, ascorbic acid (vitamin C) has been used to control melanin synthesis. Newer stabilized derivatives of vitamin C include magnesium ascorbyl phosphate (MAP), ascorbyl glucoside and tetrahexyldecyl ascorbate. These derivatives scavenge free radicals that cause erratic melanocyte activity, as well as act as antioxidants inhibiting oxidation steps along the biosynthetic pathway of melanin. They have also been shown to inhibit tyrosinase synthesis and activity.
Finally, the newest and perhaps most exciting agents to fight melanin formation are the peptides. Oligopeptide-34 is a state-of-the-art synthesized peptide that has been shown to decrease alpha-MSH activity and inhibit tyrosinase activity. Although the mechanism is not clearly understood, results indicate that it brightens skin, especially sun-induced hyperpigmentation, in half the time when compared to other brightening complexes. The use of peptides, such as oligopeptide-34 to control pigmentation, may very well be the newest and most effective approach to treating hyperpigmentation. And if safety studies are a good indicator, they are a lot safer for the end user.