Semax, a synthetic brain-protective peptide derived from ACTH, forms stable complexes with copper(II) ions and significantly reduces copper-induced toxicity in neuronal and endothelial cell lines.
Dual neuroprotection mechanismSemax protects brain cells both through its known receptor-mediated signaling and — as this study reveals — by directly binding and neutralizing toxic copper(II) ions in a stable 4-nitrogen planar coordination complex.
What the researchers found
Semax (Met-Glu-His-Phe-Pro-Gly-Pro), an ACTH4-10 analog with a C-terminal Pro-Gly-Pro extension, demonstrated:
- Formation of three distinct copper(II) complex species
- At pH 5 and above, the predominant species [CuLH-2]2- features 4-nitrogen planar coordination around copper
- Two minor species [CuL] and [CuLH-1]- coexist at pH 3.6-5
- Significant reduction of copper-induced cytotoxicity in:
- SH-SY5Y neuroblastoma cells (brain neuron model)
- RBE4 endothelial cells (blood-brain barrier model)
- Protection assessed by MTT cell viability assay
This reveals that Semax’s neuroprotective activity may partly operate through metal ion chelation rather than solely through receptor-mediated signaling.
Why it matters
Metal ion dysregulation — particularly excess copper and zinc — is increasingly recognized as a driver of Alzheimer’s, Parkinson’s, and other neurodegenerative diseases. Semax is already approved in Russia for stroke and cognitive enhancement, and has a strong safety profile. This study reveals that Semax can serve double duty: providing cognitive benefits through its known neuroprotective signaling while also directly neutralizing toxic metal ions in the brain. This dual mechanism makes it a particularly attractive candidate for neurodegeneration research.
How the study worked
Copper(II) binding was characterized using equilibrium potentiometry and electron spin resonance (ESR) spectroscopy across a pH range. Complex speciation was determined as a function of pH. Neuroprotective activity was tested using MTT cell viability assays on SH-SY5Y neuroblastoma cells (modeling brain neurons) and RBE4 endothelial cells (modeling the blood-brain barrier), comparing copper toxicity in the presence and absence of Semax.
What this study cannot tell us
This is an in vitro study using cell lines — protection in cultured cells may not translate to in vivo neuroprotection. The copper concentrations used in toxicity assays may not reflect physiological brain copper levels. The study focused on copper only; interactions with other relevant metals (zinc, iron) were not tested. Whether Semax reaches brain copper pools at sufficient concentrations after clinical administration is unknown. The study does not determine whether metal binding or receptor signaling is the primary mechanism of Semax’s known clinical benefits.
How to read the evidence
This is an in vitro biophysical and cell biology study characterizing metal binding and cytoprotection. While it reveals an important new mechanism for a clinically used peptide, the findings require in vivo validation. Semax is approved in Russia but has limited clinical evidence by Western regulatory standards.
When this study was published
Published in 2015, this study is about a decade old. However, the bioinorganic chemistry of Semax-copper interactions and the relevance of metal chelation in neurodegeneration remain active research areas.
The bigger picture
Metal chelation therapy for neurodegenerative diseases has long been explored, but finding chelators that can cross the blood-brain barrier and are safe for long-term use has been challenging. Semax is uniquely positioned: it’s a small peptide with known brain penetration (administered intranasally), established safety in clinical use, and now demonstrated metal-binding capability. This study bridges peptide neuropharmacology with bioinorganic chemistry, suggesting that the most effective neuroprotective strategies may need to address both signaling and metal homeostasis.
Questions still open
- Does Semax’s copper-binding ability contribute to its clinical neuroprotective effects in stroke patients?
- Could Semax be effective in Alzheimer’s disease, where copper dysregulation at amyloid plaques is a recognized pathological feature?
- How do Semax-copper complexes interact with other brain proteins, and could they have additional biological activities?
Common questions
What is Semax and what is it used for?
How does copper damage the brain?
Read the original research
Semax, an ACTH4-10 peptide analog with high affinity for copper(II) ion and protective ability against metal induced cell toxicity.
Journal of inorganic biochemistry, 142, 39-46
Citation
Tabbì, Giovanni; Magrì, Antonio; Giuffrida, Alessandro; Lanza, Valeria; Pappalardo, Giuseppe; Naletova, Irina; Nicoletti, Vincenzo Giuseppe; Attanasio, Francesco; Rizzarelli, Enrico. (2015). Semax, an ACTH4-10 peptide analog with high affinity for copper(II) ion and protective ability against metal induced cell toxicity.. Journal of inorganic biochemistry, 142, 39-46. https://doi.org/10.1016/j.jinorgbio.2014.09.008