Researchers investigated whether glycyl-L-histidyl-L-lysine (GHK), a tripeptide, could prevent protein aggregation and cell death caused by excess copper and zinc in cultured central nervous system cells (in vitro study). The study found that GHK demonstrated protective effects against both copper- and zinc-induced protein aggregation and cellular toxicity in these cell culture models. This is in vitro evidence and does not establish clinical efficacy in human subjects.