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

Abstract EN

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.