Semax Peptide

Semax peptide is a synthetic polypeptide analog of an adrenocorticotropic hormone fragment 4-7 (ACTH 4-7),⁽¹⁾ a hormone secreted by the anterior pituitary gland. This fragment has been reported by researchers not to exhibit any action characteristic of ACTH itself but may have a potentially specific action within the brain.⁽²⁾

Researchers find that naturally occurring peptides may occasionally exhibit instability and easy degradation by biological enzymes, such as those found in gastrointestinal and cerebrospinal fluids. Consequently, researchers aim to synthesize analogs of these naturally occurring but potentially unstable peptides to induce similar biological action with the added value of higher stability. Semax is one such synthetically developed derivative of an endogenous adrenocorticotropic hormone fragment. The Met-Glu-His-Phe sequence in Semax is extended by adding a Pro-Gly-Pro (PGP) sequence at its C-terminal end. This modification with PGP may potentially enhance the molecule’s ability to cross the blood-brain barrier (BBB) by increasing its lipophilicity. This increase in lipophilicity may facilitate the molecule’s passive diffusion or uptake through mechanisms such as lipid raft-mediated endocytosis, which may circumvent the tight junctions that typically restrict entry into the brain. Furthermore, the presence of PGP at the peptide’s C-terminus might also modify its interactions with specific transporters or receptors on the BBB, potentially favoring its transport via receptor-mediated transcytosis. Moreover, the acetylation of Semax may improve its stability by making it more resistant to enzymatic breakdown, thereby extending its half-life in biological settings.

Overview

Synthetically developed Semax has been widely researched for its potential mechanism of action and lauded for its apparent biological stability. Researchers suggest it may inhibit select enzymes that regulate the degradation of enkephalins, naturally released neurotransmitters secreted in the brain, which scientists consider may regulate several biological functions. Enkephalins are believed to be significantly involved in nociception (the sensory perception of pain) and stress response. Moreover, an elevation in enkephalin concentrations might potentially impact other neurotransmitter systems due to the intricate interconnections between the opioid system and neurotransmitters such as dopamine and serotonin. This interaction may manifest through modulation or alteration of neurotransmitter release, receptor activity, or signal transduction pathways, indicating a sophisticated and multifaceted relationship that remains an area of active research. In addition to enkephalins, Semax has been evaluated for its potential to inhibit other peptide-degrading secreted enzymes.

Based on one specific research study,⁽⁴⁾ Semax may induce elevated secretion and release of dopamine as well as possibly increasing the levels of brain-derived neurotrophic factor (BDNF). Based on another study,⁽⁵⁾ Semax has been speculated to also host the potential to alter gene expressions that modulate the immune system. In altering gene expression, the levels of immune cells and their mobility may be elevated. Semax was reported by researchers to exhibit altering potential in the encoding of chemokines and immunoglobulins, related to the functioning of the vascular system.

Chemical Makeup

Molecular Formula: C₃₉H₅₄N₁₀O₁₀S
Molecular Weight: 854.99 g/mol
Other Known Titles: ACTH (4-7)PGP, HY-P1146