Red Hair Pigment Linked to Cellular Protection Against Toxin

Scientists have identified that pheomelanin, a pigment found in red hair and certain bird feathers, may play a role in preventing cellular damage. The production of pheomelanin requires the amino acid cysteine. An excessive accumulation of cysteine in cells can lead to oxidative damage. Researchers at Spain's National Museum of Natural Sciences hypothesize that humans with genetic variations for red hair may possess specialized cells capable of converting surplus cysteine from diet or the environment into this pigment. Using zebra finches as a research model, the team demonstrated that pheomelanin can offer cellular protection. Male finches unable to produce pheomelanin exhibited higher levels of oxidative damage when fed excess cysteine for one month, compared to those that could produce the pigment. Female zebra finches, which do not naturally produce pheomelanin, showed a minor and statistically insignificant increase in oxidative damage when given extra cysteine compared to a control group. These findings suggest that elevated cysteine levels contribute to cellular damage and that pheomelanin production may mitigate some of this damage. In humans, pheomelanin is concentrated in areas like the lips, nipples, and genitals, and is also present in the hair and skin of individuals with red hair. While pheomelanin is associated with an increased risk of melanoma, the researchers propose that genetic variants promoting its production may assist cells in maintaining balanced cysteine levels by utilizing excess cysteine for pigment synthesis. The study authors stated, "These findings represent the first experimental demonstration of a physiological role for pheomelanin, namely avoiding the toxicity of excess cysteine, leading to a better understanding of melanoma risk and the evolution of animal coloration." The study was published in PNAS Nexus.