Carnosine Interaction with Nitric Oxide and Astroglial Cells Protection.

The neuropeptide carnosine (b-alanyl-L-histidine; AH), present in postmitotic mammalian tissues (brain, skeletal muscle), is involved in many processes of cellular defense such as free-radical detoxification, inhibition of protein crosslinking, and glycation. Neuronal protection by carnosine through inhibition of b-amyloid peptide aggregation has been demonstrated. Carnosine protection against peroxynitrite damage is particularly relevant, but until now there has been no evidence of any direct interaction with nitric oxide. In this study we examined the protection that carnosine provides against nitric oxide (NO)-induced cell death in primary rat astroglial cell cultures treated with lipopolysaccharide (LPS) and interferon gamma (INFc), a well-known neurotoxic proinflammatory condition. A correlation was found between cell protection and NO free-radical scavenging activity of carnosine. Moreover, by competitive spectrophotometric measurement and electrospray mass spectrometry analysis in cell-free experiments, we demonstrated a direct interaction of the dipeptide with NO. A comparison of carnosine with its homologues or derivatives (homocarnosine and carcinine) as well as with its amino acid constituents (L-histidine and b-alanine) highlighted that only histidine showed significant scavenging activity. Therefore, carnosine shows direct NO-trapping ability and may be a valuable multifunctional molecule in the treatment of neurodegenerative disorders.