Carnosine Facilitates Nitric Oxide Production in Endothelial F-2 Cells

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We examined the effect of carnosine (β-alanyl-histidine) on nitric oxide (NO) production and endothelial NO synthase (eNOS) activation in endothelial F-2 cells. Carnosine enhanced NO production in a dose-dependent manner, and the stimulatory effect of carnosine was observed at concentrations exceeding 5 mM. The carnosine-stimulated NO production was inhibited by N^G-nitro-L-arginine methyl ester, but not by N^G-nitro-D-arginine methyl ester. In contrast, β-alanine, histidine (carnosine components) and anserine (N-methyl carnosine) failed to increase NO production. Carnosine had no effect on NO production for the initial 5 min, but thereafter resulted in a gradual increase in NO production up to 15 min. Carnosine did not induce phosphorylation of eNOS at Ser1177. The carnosine-induced increase in NO production was observed even when extracellular Ca²⁺ was depleted by ethylene glycol bis(2-aminoethyl ether)-N,N,N′-N′-tetraacetic acid however, the effect was abolished upon depletion of intracellular Ca²⁺ by BAPTA. After F-2 cells were incubated with carnosine for 4 min, intracellular Ca²⁺ concentration gradually increased. The carnosine-induced increase in intracellular Ca²⁺ concentration occurred even in the absence of extracellular Ca²⁺. These results indicate that carnosine facilitates NO production in endothelial F-2 cells. It is also suggested that eNOS is activated by Ca²⁺, which might be released from intracellular Ca²⁺ stores in response to carnosine.