Research Letters in Physical Chemistry 
Volume 2008 (2008), Article ID 210616, 4 pages
doi:10.1155/2008/210616
Research Letter

Pigment Melanin Scavenges Nitric Oxide In Vitro: Possible Relevance to Keloid Formation

Julian M. Menter,1,2 Danita Eatman,3 Mohamed Bayorh,3 Ahmad M. Dawaghreh,4 and Isaac Willis2

 1Department of Microbiology, Biochemistry and Immunology, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA 30310-1495, USA
2Department of Internal Medicine, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA 30310-1495, USA
3Department of Pharmacology and Toxicology, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA 30310-1495, USA
4Clinical Research Center, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA 30310-1495, USA
Received 9 May 2008; Accepted 2 August 2008

Recommended by Werner Nau

Abstract

Recently, nitric oxide (NO) has been implicated in the formation of keloids, preferentially formed in dark-skinned persons, and we suspected that pigment melanin itself may play a direct role by adsorbing NO. We tested the ability of cuttlefish sepia melanin to scavenge (adsorb) NO, generated in situ by 2-(N.N Diethylamino) diazeneolate-2-oxide (DEA/NO), through a dialysis membrane. NO was measured as NO2- and NO3- by the Griess method and as N2O3 by trapping experiments with the fluorogenic substrate 4,5-diaminofluorescein (DAF-2). Initial NO2- and NO3- concentrations were significantly lower in the test dialyzates than in controls. Scavenging of NO was rapid enough to compete with DAF adduct formation. Both analytical methods gave comparable results. Adsorbed NO and/or its oxidized products may undergo interactions with melanin, adsorbed O2, and/or dermal material that may lead to keloid formation.