MICROGLIAL NEUROINFLAMMATORY ACTIVITY IS MODULATED BY THE MATRIKINE GLYCINE-HISTIDINE-LYSINE-COPPER (GHK-CU)

Neuroinflammation mediated by microglia, the resident immune cells of the brain, is increasingly recognized as a critical driver of Alzheimer's disease (AD) progression. Therefore, identifying compounds that dampen microglial neuroimmune responses offers a promising drug discovery strategy for AD and other neurodegenerative diseases. The extracellular matrix-derived tripeptide glycine-histidine-lysine (GHK), a copper-binding matrikine, is known for its powerful antioxidant and anti-inflammatory activity in peripheral tissues. However, its neuroimmunomodulatory effects in the central nervous system (CNS) are largely unknown. This study investigated the effects of GHK and its copper complex, GHK-Cu, on select functions of microglia-like cells. GHK-Cu significantly reduced the production of the pro-inflammatory cytokine interleukin (IL)-6 and the cytotoxin nitric oxide (NO) by immune-stimulated murine BV-2 microglia. GHK-Cu also significantly decreased reactive oxygen species (ROS) production by primed human HL-60 microglia-like cells expressing nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Additionally, GHK-Cu significantly increased phagocytic activity of both unstimulated and lipopolysaccharide (LPS)-stimulated BV-2 microglia and reduced their circularity, indicating a shift away from a reactive ameboid morphology. While GHK-Cu protected BV-2 cells from LPS-induced toxicity, it did not significantly reduce the overall neurotoxicity of microglial supernatants toward murine NSC-34 neuronal cells. Copper-free GHK had no measurable effects, and CuSO₄ alone was ineffective or cytotoxic, highlighting the necessity of the peptide-metal complex. Collectively, our data demonstrate specific anti-neuroinflammatory and antioxidative properties of GHK-Cu, supporting this matrikine as a promising therapeutic candidate for mitigating microglia-driven neuroinflammation in AD and related CNS pathologies.