Research Dossier on Research Dossier on GHK-Cu

(Copper Peptide / Skin Repair)

Classification & Molecular Identity

Amino acid sequence, molecular weight, structural motifs

GHK is a tripeptide (sequence: Gly-His-Lys, sometimes abbreviated GHK) that binds Cu²⁺ with high affinity to form the GHK-Cu complex. The free peptide has M_r ~ 340.4 g·mol⁻¹; the copper complex (C₁₄H₂₂CuN₆O₄) exhibits square-planar/square-pyramidal coordination around Cu(II) involving the imidazole N of His and backbone nitrogens (and, in certain models or at higher order, carboxylate oxygen participation), with nuanced speciation dependent on pH and ligand ratios. The peptide and its copper complex occur in human plasma, saliva, and urine. Wikipedia+1

Binding constants and speciation. In potentiometric/spectroscopic work, stepwise formation constants indicate high affinity for Cu(II); reported values for the dominant 1:1 complex span logK ~12.6 (conditional) up to pK ≈ 16 in analyses that compare to the albumin ATCUN site (assay- and condition-dependent). The complex is redox-silent relative to free Cu(II) and buffers copper’s redox reactivity in biological media. PMC+2American Chemical Society Publications+2

Discovery history (lab, year, species)

GHK activity was first identified in 1973 in human plasma albumin by Loren Pickart, when “youthful” plasma factors were found to shift protein synthesis patterns of aged human liver tissue toward a younger phenotype; subsequent work isolated GHK as the key peptide and established its high Cu(II) affinity. PubMed+1

Endogenous vs synthetic origin

GHK is endogenous (detectable in human plasma, saliva, urine), with plasma levels around 200 µg·L⁻¹ (~10⁻⁷ M) at ~20 years of age, declining to roughly 80 µg·L⁻¹ by ~60 years. GHK readily complexes Cu(II) to form GHK-Cu in biological fluids. Synthetic material produced via standard solid-phase methods is widely used for research. PMC+1

Homologs, analogs, derivatives

• DAHK (Asp-Ala-His-Lys)–Cu: the ATCUN motif at the N-terminus of human serum albumin (HSA) binds Cu(II) with picomolar-range affinity and is a principal extracellular Cu(II) carrier; often used as a reference in copper transport/competition studies. RSC Publishing+1

• AHK-Cu (Ala-His-Lys·Cu²⁺): a related tripeptide–copper complex used in ex vivo/in vitro hair-follicle and dermal studies. ResearchGate

• Histidine-rich and ATCUN model peptides: used to benchmark Cu(II) coordination modes and redox behavior versus GHK-Cu. PMC

Historical Development & Research Trajectory

Key milestones in discovery and study

• 1973–1988: Identification of GHK in plasma; demonstration of wound-healing and ECM remodeling actions; seminal fibroblast studies showed GHK-Cu stimulates collagen synthesis at low nanomolar concentrations (maximal at ~10⁻⁹ M). (In vitro; investigational concentrations used in Maquart 1988.) PubMed

• 1990s–2000s: Expanded cellular portfolio (glycosaminoglycans, decorin; MMP-2 modulation) and early human dermal studies in photoaged or injured skin. PubMed

• 2010s–present: Gene-expression meta-analyses indicate broad transcriptional modulation across tissue types; multiple reviews synthesize mechanistic and translational aspects (skin, connective tissues, nervous system), though large modern RCTs remain sparse. PMC+2PMC+2

Paradigm shifts and controversies

1. Copper shuttling and redox control. The field shifted from viewing GHK-Cu solely as a trophic cue to considering metal homeostasis: GHK may mobilize or deliver Cu(II) to cells while dampening copper‐driven ROS, complementing HSA’s high-affinity site; quantitative dominance of albumin in plasma means albumin is the major Cu(II) carrier, with GHK a minor but potentially signaling-relevant pool. RSC Publishing+2Nature+2

2. From single-pathway to multimodal remodeling. Evidence now spans ECM synthesis and turnover, angiogenesis/nerve outgrowth, anti-inflammatory/antioxidant actions, and gene-program resets in disease models—while the primary receptor remains undefined. PMC+1

3. Clinical translation gap. Numerous preclinical and small controlled dermal studies exist, but robust Phase II/III trials directly testing GHK-Cu for specific indications are limited/Not established; registry entries exist for broader “copper-based” wound interventions that are not peptide-specific. ClinicalTrials.gov+1

Evolution of scientific interest

Interest has broadened from dermatologic repair to systems-level protection (e.g., anti-oxidative/anti-inflammatory networks, nervous system gene expression). At the same time, analytical Cu-binding and albumin competition studies have refined our understanding of copper biochemistry in plasma and interstitial fluid. Nature+1

Mechanisms of Action

Primary and secondary interactions

• High-affinity Cu(II) binding: GHK chelates Cu(II) forming GHK-Cu; the complex is comparatively redox-inert, lowering pro-oxidant copper reactivity in vitro and in model systems. American Chemical Society Publications+1

• ECM modulation: GHK-Cu stimulates collagen synthesis in fibroblasts (10⁻¹²–10⁻⁹ M range in vitro), modulates proteoglycans (dermatan/chondroitin sulfate, decorin), and regulates matrix turnover via MMP-2/TIMP axes—consistent with tissue remodeling during repair. PubMed+2PMC+2

• Angiogenesis/innervation: Reports describe increases in markers associated with capillary and nerve outgrowthin dermal models. Mechanistic dissection (e.g., HIF/VEGF, NGF/BDNF) is supportive but not uniform across studies. PubMed

• Anti-inflammatory/antioxidant signaling: Reviews compile data showing SOD up-regulation, NF-κB pathway constraints, and mitigation of ROS in diverse tissues. PMC

• Gene-expression re-programming: Connectivity-map and transcriptomic analyses propose that GHK resets large gene sets linked to tissue protection and repair (DNA repair, proteasome/ubiquitin, copper transport, neural pathways). Direct receptor or canonical upstream sensor: Not established. PMC

Intracellular signaling pathways

Because no single cognate receptor has been validated, signaling is inferred from downstream transcriptional and functional readouts:

• ECM/repair programs (collagen I/III, elastin, decorin), MMP/TIMP balance, and growth-factor signalingrelevant to fibroblast and keratinocyte activity. PMC

• Redox defenses (SOD, catalase) and inflammation dampening (reduced TNF-α/COX products in some systems). PMC

• Copper handling: Facilitation of cellular Cu uptake consistent with GHK as a mobile Cu(II) pool that can exchange with albumin and intracellular ligands; redox-active copper is buffered in the GHK coordination environment. PMC+1

CNS vs peripheral effects

• Peripheral: Most robust evidence is dermal/connective tissue, liver, bone, and vascular repair models. PubMed

• CNS: Gene-expression analyses implicate pathways relevant to neurite outgrowth, glial/astrocytic function, and DNA repair; in vivo CNS efficacy remains preclinical and hypothesis-generating. PMC

Hormonal, metabolic, immune interactions

Indirect effects on inflammatory cytokines, ECM-associated growth factors, and wound chemotaxis(macrophages/mast cells/capillary cells) are described; firm endocrine-level effects are Not established. PubMed

Evidence grading (A–C)

• A (replicated, preclinical): Fibroblast collagen stimulation, ECM remodeling, MMP-2 modulation, and wound-healing benefits across multiple in vitro/in vivo dermal models. PubMed+1

• B (limited human / small clinical): Controlled/observational skin studies (photoaged skin, periocular skin) suggesting structural/appearance improvements; copper-oxide textiles studies (not peptide-specific) report skin-parameter changes. Large RCTs: Not established. PubMed+1

• C (hypothesis/early): Neuroprotective/cognitive implications, broad gene-program resets, and hair growthclaims remain preclinical or preliminary. PMC

Pharmacokinetics & Stability

ADME profile

• Absorption: Route-specific absorption data for GHK-Cu in humans are Not established in peer-reviewed PK monographs. In dermal models, topical penetration is formulation-dependent and under active study; systemic bioavailability by non-parenteral routes has not been quantified in modern PK terms. (Data gap.)

• Distribution: In plasma, albumin is the predominant extracellular Cu(II) carrier (ATCUN site), with GHK-Curepresenting a minor, exchangeable pool. The two ligands exhibit comparable high affinities for Cu(II) under certain conditions, but albumin is ~700-fold more abundant than GHK, making albumin the major source of Cu(II) delivery to tissues. RSC Publishing+2Nature+2

• Metabolism & excretion: Not established for human PK. Like other small peptides, proteolysis and renalelimination of peptide/metal-ligand fragments are expected, with copper reincorporated into systemic copper pools (ceruloplasmin/HSA) or excreted via hepatobiliary pathways depending on speciation. (Inference; direct kinetic mapping lacking.)

Plasma half-life & degradation pathways

Human plasma half-life of GHK-Cu is Not established. The complex exchanges copper with endogenous ligands (e.g., HSA/DAHK) based on relative concentrations and conditional stability; redox buffering by GHK reduces free-Cu reactivity, and glutathione can form ternary species with Cu(II)–GHK under physiological conditions. American Chemical Society Publications

Stability (in vitro & in vivo)

• In vitro: Potentiometric/EPR/DFT studies indicate stable coordination of Cu(II) by GHK under neutral to mildly basic conditions; the complex dampens Cu(II) redox cycling, a contributor to its antioxidant profile in cell systems. PMC+1

• In vivo: Functional effects (e.g., ECM remodeling) can persist beyond expected peptide residence, consistent with downstream gene/program effects rather than prolonged systemic exposure. (General observation across studies; quantitative PK absent.)

Storage/reconstitution considerations

Peer-reviewed literature does not provide standardized, product-agnostic shelf-life/reconstitution curves for research vials of GHK-Cu. General peptide best practices apply (lyophilizate, dryness, protect from light, low temperature). Validated stability curves: Not established.

Preclinical Evidence

In vitro and animal studies (selected)

ECM synthesis and remodeling

• Fibroblast collagen: GHK-Cu increased collagen synthesis in cultured human fibroblasts, with responses as low as 10⁻¹²–10⁻¹¹ M and maximal at ~10⁻⁹ M; effects were not due to proliferation. (In vitro; Maquart 1988). PubMed

• MMP-2 modulation: In dermal fibroblasts, GHK-Cu increased MMP-2 levels (also inducible by Cu(II) alone), consistent with controlled matrix turnover during remodeling. (In vitro; Siméon 2000). PubMed

• Proteoglycans/decorin: Reviews catalogue increases in dermatan/chondroitin sulfates and decorin synthesis in vitro. (Multiple sources summarized). PMC

Wound models & tissue protection

• Dermal repair: Multi-model animal studies and small human dermal studies report improved healing indices and structural markers with GHK-Cu exposure. (Preclinical and controlled dermal studies summarized in reviews). PubMed

• Organ protection: Experimental work suggests protective effects in liver (e.g., carbon tetrachloride injury models), GI mucosa, bone, and lung connective tissue; mechanistic details vary. (Preclinical). PubMed

Angiogenesis and nerve-related readouts

• Reports describe capillary formation and nerve outgrowth support in dermal/soft-tissue contexts. (Preclinical; mechanistic reliance on VEGF/NGF family members is incompletely mapped). PubMed

Antioxidant/anti-inflammatory actions

• Redox buffering: GHK-Cu renders Cu(II) redox-silent relative to free Cu(II) in model systems, lowering ascorbate oxidation and metal-catalyzed ROS; gene and enzyme-level data include increased SOD and reduced pro-inflammatory signaling in specific models. (Preclinical). PMC

Neuro-relevant gene programs (hypothesis-generating)

• Connectivity-map analyses indicate GHK modulates gene sets relevant to nervous system maintenance and DNA repair; functional in vivo CNS translation remains preclinical. PMC

Hair biology (early stage)

• The related AHK-Cu complex promoted ex vivo human hair-follicle elongation and dermal papilla cellproliferation at 10⁻¹²–10⁻⁹ M; apoptosis markers decreased at 10⁻⁹ M (not always significant). (Ex vivo/in vitro). ResearchGate

Dose ranges tested (investigational; illustrative)

• Fibroblast collagen assays: 10⁻¹² → 10⁻⁹ M (investigational concentrations used in study Maquart 1988). PubMed

• Dermal MMP assays: nM–µM range depending on endpoint (investigational concentrations used in study Siméon 2000). PubMed

• Hair ex vivo assays (AHK-Cu): 10⁻¹² → 10⁻⁹ M (investigational concentrations used in study cited). ResearchGate

Comparative efficacy/safety (preclinical)

Across dermal/soft-tissue models, GHK-Cu generally outperforms vehicle controls on structural and biochemical repair indices, with low acute toxicity reported at research exposures. However, GLP-style toxicology packages (repeat-dose, genotox, carcinogenicity, reproductive tox) are Not established.

Limitations (preclinical)

• Mechanistic attribution is complicated by copper biochemistry and ligand exchange with albumin and glutathione.

• Heterogeneity of models and endpoints; standardized preclinical frameworks are limited.

Human Clinical Evidence

Summary stance: GHK-Cu has small, controlled dermal studies and cosmetic-grade investigations suggesting structural/appearance benefits. Large modern Phase II/III randomized trials for specific therapeutic indications are limited/Not established. Registry records exist for copper-based wound interventions not specific to GHK-Cu.

Dermal/skin studies (controlled; cosmetic-grade)

• A 2008 field synthesis reports controlled studies on aged skin in which GHK-Cu creams improved tightness, elasticity/firmness, fine lines, clarity, and photodamage measures versus controls; details across trials (sample sizes, endpoints, randomization) vary. (Cosmetic/dermal outcomes; not drug-approval trials.) PubMed

• Reviews summarizing 12-week facial/eyecare protocols (e.g., 41–71 participants) report improved skin density/thickness and reduced wrinkles/laxity, sometimes outperforming comparator creams; original RCT manuscripts are not uniformly accessible in PubMed. (Caveat: cosmetic-grade evidence base; replication/standardization limited). PMC

• Textile copper (not peptide) trials: double-blind pillowcase textile studies (copper oxide) reported improvements in skin appearance over 4–8 weeks, indicating Cu-dependent cutaneous responses; these do not isolate GHK-Cueffects. PMC

Wound/healing trials in registries (not peptide-specific)

• NCT00673309, NCT01040104, NCT02742844: clinical-trial entries exploring wound healing mechanisms or copper-impregnated dressings; these do not constitute therapeutic RCTs of GHK-Cu itself, but are relevant to the broader copper-based wound-care context. (Investigational protocols; not peptide-specific.) ClinicalTrials.gov+2ClinicalTrials.gov+2

Investigational doses (humans)

• For GHK-Cu specifically: No standardized human dosing is supported by large, registered, peer-reviewed interventional trials. Any amounts in cosmetic studies are formulation-specific and Not established for clinical translation.

Safety signals/adverse events

• Cosmetic/dermal reports generally describe good local tolerability; systematic, modern pharmacovigilance with adjudicated adverse events is limited. Long-term safety for drug-level exposures is Not established.

ClinicalTrials.gov IDs (illustrative context)

• NCT00673309, NCT01040104, NCT02742844 (wound/copper interventions; not GHK-Cu drug trials). ClinicalTrials.gov+2ClinicalTrials.gov+2

Comparative Context

Related peptides and copper ligands

• Albumin DAHK–Cu (ATCUN): principal extracellular Cu(II) binding site; sets the competitive background for Cu(II) transport. RSC Publishing

• Other short peptides (AHK-Cu, palmitoylated pentapeptides): used in cosmetic/dermal research with varied endpoints; mechanisms differ (e.g., palmitoyl-PP-4 does not bind Cu(II)). PMC

Advantages / disadvantages (research perspective)

• Advantages: High-affinity Cu(II) chelation with redox buffering, low-nanomolar activity windows in fibroblasts, broad ECM-remodeling support, and gene-program modulation across tissues in vitro; endogenous occurrence in plasma. PubMed+1

• Disadvantages: Mechanism is multi-factorial (no single receptor), plasma copper competition dominated by albumin, and a clinical translation gap (few large, modern RCTs). RSC Publishing

Research category placement

• Copper-binding, tissue-remodeling tripeptide used to probe ECM biology, wound repair, angiogenesis/innervation, redox-inflammation coupling, and metal-homeostasis in mammalian tissues.

Research Highlights

• Collagen stimulation at picomolar–nanomolar levels in fibroblasts; consistent ECM remodeling signatures across studies. PubMed

• Matrix turnover control via MMP-2/TIMP modulation in dermal fibroblasts. PubMed

• Redox buffering of copper and anti-inflammatory actions in vitro and in vivo models. PMC

• Gene-program re-sets spanning DNA repair, proteostasis, antioxidant defenses, and neural pathways (connectivity-map analyses). (Translational significance: Hypothesis-generating.) PMC

• Conflicting/uncertain areas: precise in vivo PK, primary upstream sensor(s), extent of CNS translation, and magnitude/consistency of human clinical benefit outside cosmetic-grade endpoints. (Not established.)

Potential Research Applications (no clinical claims; research-use framing)

• Dermal/ECM biology: Dissect dose–response effects of GHK-Cu on collagens I/III, elastin, decorin, MMP/TIMP balance, and keratinocyte–fibroblast cross-talk in human skin equivalents and explants. PubMed+1

• Copper homeostasis & redox biology: Model Cu(II) exchange between albumin (DAHK), GHK, and glutathione; quantify redox silencing and ROS outcomes under physiologic buffers. RSC Publishing+1

• Angio-neuro coupling in repair: Evaluate vascular and neurite markers in wound models under GHK-Cuexposure with transcriptomic/secretomic profiling. PubMed

• Systems genomics: Use RNA-seq/ATAC-seq to map GHK-responsive networks (DNA repair, proteostasis) and validate downstream functional phenotypes (e.g., resistance to oxidative stress) in primary human cells. PMC

• Hair-follicle biology (exploratory): Confirm AHK-Cu/GHK-Cu effects on dermal papilla signaling and follicular cycling markers in 3D organoids/ex vivo follicles. (Translation to human efficacy: Not established.) ResearchGate

Safety & Toxicology

Preclinical toxicity data

• Acute tolerability at laboratory exposures is generally acceptable in dermal and soft-tissue models; systematic GLP repeat-dose, genotoxicity, carcinogenicity, reproductive, and long-term safety packages for GHK-Cu are Not established in the peer-reviewed domain.

Known/theoretical molecular risks

• Copper mis-handling: While GHK-Cu buffers copper redox activity, dysregulated copper can catalyze ROS; off-target copper redistribution in complex biological milieus is a theoretical risk that warrants in vivoPK/speciation studies (currently Not established). RSC Publishing

• Immunogenicity: As a tripeptide, immunogenic risk is expected to be low, but repeated exposure data sets are limited. (Not established.)

Human safety signals

• Cosmetic/dermal investigations report good local tolerability over 4–12 weeks; adjudicated AE datasets and long-term surveillance comparable to drug trials are limited. (Not established.)

Data gaps

• Human PK/PD, tissue distribution, drug–drug interactions, long-term exposure effects, and on-target/off-target risk profiling remain Not established.

Limitations & Controversies

• Mechanistic ambiguity: No single cognate receptor identified; actions likely multimodal (metal buffering + transcriptional re-programming + ECM effects).

• Copper competition context: In plasma, albumin (DAHK) dominates Cu(II) binding and delivery; GHK-Cu may act as a minor exchangeable/signaling pool, complicating dose scaling from in vitro to in vivo. RSC Publishing

• Clinical translation gap: Despite abundant preclinical support and cosmetic-grade human studies, large, modern, indication-specific RCTs are limited/Not established. ClinicalTrials.gov

Future Directions

• Quantitative human PK/speciation: Establish GHK-Cu pharmacokinetics, tissue partitioning, and exchange kinetics with albumin/glutathione under physiologic conditions. (Focus on LC-MS/MS + metalloproteomics.) American Chemical Society Publications

• Mechanistic deconvolution: Identify proximal sensors/targets (e.g., membrane transporters, metal-responsive transcription factors) and map cause-effect from copper buffering to ECM gene programs.

• Dermal RCTs with structural endpoints: Well-powered, blinded trials with histology/imaging and standardized biomarkers (collagen/elastin content, biomechanical measures) to quantify magnitude/consistency of effects.

• Repair neuro-vascular coupling: Multi-omics wound-healing studies to test whether angiogenesis/innervationchanges are primary or secondary under GHK-Cu exposure. PubMed

• Safety maturation: GLP-style repeat-dose tox, genotox, local tolerance, sensitization, and chronic exposurestudies; clarify oncologic risk boundaries in settings of increased cell turnover.

References

1. Maquart FX, et al. Stimulation of collagen synthesis in fibroblast cultures by the tripeptide-copper complex GHK-Cu. FEBS Lett. 1988. PMID: 3169264. PubMed

2. Siméon A, et al. GHK-Cu increases MMP-2 in dermal fibroblasts; matrix turnover during remodeling. Biochem Biophys Res Commun. 2000. PMID: 11045606. PubMed

3. Pickart L. The human tri-peptide GHK and tissue remodeling. J Biomater Sci Polym Ed. 2008;19:969–988. PMID: 18644225. PubMed

4. Pickart L, et al. The human tripeptide GHK-Cu in prevention of oxidative stress in aging. Oxid Med Cell Longev.2012. PMCID: PMC3359723. PMC

5. Pickart L, Margolina A. GHK peptide as a natural modulator of multiple cellular pathways in skin regeneration.Dermatol Res Pract. 2015. PMCID: PMC4508379. PMC

6. Pickart L, Margolina A. Regenerative and protective actions of the GHK-Cu peptide in the light of new gene data.Int J Mol Sci. 2018. PMCID: PMC6073405. PMC

7. Pickart L, Margolina A. Effect of the human peptide GHK on gene expression relevant to nervous system function.Brain Sci. 2017. PMCID: PMC5332963. PMC

8. Bossak-Ahmad K, et al. Ternary Cu(II) complex with GHK peptide and cis-Urocanic acid; binding constants and speciation. Int J Mol Sci. 2020. PMCID: PMC7503498. (Reports log cK₁ ≈ 12.62 for [Cu(GHK)] under specified conditions.) PMC

9. Kirsipuu T, et al. Copper(II)-binding equilibria in human blood; HSA ATCUN dominance. Sci Rep. 2020. doi:10.1038/s41598-020-62560-4. Nature

10. Ackermann K, et al. EPR characterization of native Cu(II) binding to human serum albumin (ATCUN). Dalton Trans. 2024. doi:10.1039/D4DT00892H. RSC Publishing

11. Frączyk T, et al. Phosphorylation impacts Cu(II) binding by ATCUN motifs; affinity benchmarks. Inorg Chem.2021. doi:10.1021/acs.inorgchem.1c00939. American Chemical Society Publications

12. Kotuniak R, et al. Buffer choice and rate of Cu²⁺–peptide complex formation; kinetic considerations. Inorg Chem.2024. doi:10.1021/acs.inorgchem.4c01797. American Chemical Society Publications

13. Noormägi A, et al. Direct competition of ATCUN peptides with HSA for Cu(II); albumin predominance. Int J Mol Sci. 2023. PMCID: PMC10515390. PMC

14. Ogórek K, et al. Are we ready to measure skin permeation of modern actives? Pharmaceutics. 2025. PMCID: PMC11721469. (Summarizes plasma GHK levels across age.) PMC

15. ClinicalTrials.gov: NCT00673309, NCT01040104, NCT02742844 (wound-healing/copper-based interventions; not GHK-Cu specific). ClinicalTrials.gov+2ClinicalTrials.gov+2

Notes on investigational amounts (examples):
• Fibroblast collagen assays: 10⁻¹² → 10⁻⁹ M — investigational concentrations used in Maquart 1988. PubMed
• Dermal MMP-2 assays: nM–µM range — investigational concentrations used in Siméon 2000. PubMed
• Hair ex vivo (AHK-Cu): 10⁻¹² → 10⁻⁹ M — investigational concentrations used in the cited human hair-follicle study. ResearchGate

⚠️ Disclaimer This peptide is intended strictly for laboratory research use. It is not FDA-approved or authorized for human use, consumption, or therapeutic application.