GHK

This review synthesizes the molecular biology of GHK across multiple cellular systems relevant to dermal research. The authors describe the discovery of GHK in human plasma in 1973 at approximately 200 μg/L in young adults, declining to roughly 80 μg/L by age 60–80, and summarize the peptide's high affinity for Cu(II) which drives formation of the GHK-Cu complex in physiological conditions. Reported in vitro effects of GHK (both the free peptide and the copper complex) include modulation of extracellular matrix gene expression — collagen, elastin, glycosaminoglycan synthesis — alongside fibroblast proliferation and induction of antioxidant genes. The authors note that biological activity in most preclinical models is attributed to the copper-bound complex rather than the free peptide alone, and discuss the equilibrium between the two forms in biological media.

Researchers reviewed what is known about GHK in skin biology. GHK was discovered in human blood in 1973, and levels drop with age. The peptide on its own binds tightly to copper ions, and in most lab studies it is actually the copper-bound form (GHK-Cu) that does the work — switching on genes that build collagen and elastin, waking up the cells that produce these proteins, and turning on the cell's antioxidant defenses. The review explains that plain GHK and GHK-Cu exist in equilibrium in biological fluids depending on how much copper is present.

Using gene-expression datasets from the Broad Institute's Connectivity Map, the authors analyzed GHK's effect on the transcriptome of human cells. GHK exposure was associated with statistically significant modulation of more than 4,000 genes, with effects clustering around DNA repair pathways, ubiquitin-proteasome regulation, antioxidant defense, and inflammatory signaling. The authors discuss the relationship between the free peptide and the copper-bound complex, noting that GHK introduced into cell culture media containing trace copper will form GHK-Cu, complicating attribution of observed gene-expression changes to one form or the other.

Scientists used a large public database of gene activity to look at how GHK changes which genes are turned on or off in human cells. They found GHK affects thousands of genes — particularly ones involved in fixing DNA, recycling damaged proteins, calming inflammation, and protecting against oxidative damage. The authors point out that even when researchers add plain GHK to cells, copper already present in the growth medium can bind to it, so the observed effects may reflect the copper-bound form rather than the free peptide.