Carnosine modulates the Sp1-Slc31a1/Ctr1 copper-sensing system and influences copper homeostasis in murine CNS-derived cells

Carnosine (CAR) is an endogenous dipeptide physiologically present in excitable tissues, such as central nervous system (CNS) and muscle. CAR is acknowledged as a substrate involved in many homeostatic pathways and mechanisms and, due to its biochemical properties, as a molecule intertwined with the homeostasis of heavy metals such as copper (Cu). In CNS, Cu excess and dysregulation imply oxidative stress, free-radical production, and functional impairment leading to neurodegeneration. Here, we report that CAR intercepts the regulatory routes of Cu homeostasis in nervous cells and tissues. Specifically, in a murine neuron-derived cell model, i.e., the B104 neuroblastoma cells, extracellular CAR exposure up to 24 h influenced intracellular Cu entry and affected (downregulated) the key Cu-sensing system, consisting of the gene coding for the Slc31a1 transmembrane Cu importer (alias Ctr1), and the gene coding for the Cu-responsive transcription factor Sp1 (Sp1). Also, CAR exposure upregulated CAR biosynthesis (Carns1), extracellular degradation (Cndp1), and transport (Slc15a4, alias Pht1) genes and elicited CAR intracellular accumulation, contributing to the outline of functional association between CAR and Cu within the cell. Interestingly, the same gene modulation scheme acting in vitro operates in vivo in brains of mice undergoing dietary administration of CAR in drinking water for 2 wk. Overall, our findings describe for the first time a regulatory interaction between CAR and Cu pathways in CNS and indicate CAR as a novel active molecule within the network of ligands and chaperones that physiologically regulate Cu homeostasis.