Protective Functions of β-Alanyl-L-Histidine and Glycyl-L-Histidyl-L-Lysine Glycoconjugates and Copper in Concert

Two endogenous peptides, β-alanyl-L-histidine, named carnosine (Car), and glycyl-L-histidyl-L-lysine (GHK), derived from the matricellular protein Secreted Protein Acidic and Rich in Cysteine (SPARC), share many beneficial functions. The hydrolytic enzyme carnosinase for Car and the low stability for GHK can put into question their antioxidant, antiaggregating, and anti-inflammatory properties. The glycoconjugates of Car with a di- (trehalose, Tre) or polysaccharide (hyaluronan, HA) inhibit carnosinase, while the synthesis of HAGHK derivatives increases the tripeptide stability and protects/delays the biopolymer degradation. A synergic effect between the two components of the glycoconjugates is evident in their consequently preserved protective features. TreCar, HACar, and HAGHK maintain the copper-binding ability of the peptides alone, and the saccharides potentiate the Cu,Zn-superoxide dismutase-like ability of the copper(II) complexes with the glycoconjugates. These peptide derivatives behave as copper ionophores, utilizing Cu²⁺ present in the culture medium; also, an increase in the metal intracellular level occurs with a consequent stimulation of the copper-driven signaling pathways that produce the expression/release of trophic (Brain-Derived Neurotrophic Factor, BDNF, and Bone Morphogenetic Protein 2, BMP-2) and angiogenic (Vascular Endothelial Growth Factor, VEGF) proteins. Copper chaperons for SOD1, CCS, and Antioxidant 1 (Atox-1) are the copper chaperones that act as transcription factors.