Abstract
This study revealed a new physiological function of 2-pyrrolidone-5-carboxylic acid (L-PCA), which enhanced blood circulation by modulating constitutive nitric oxide (NO) generation. It is well known that NO, generated from L-arginine (L-Arg) by catalysis of NO synthase (NOS), plays a key role in the control of vascular tone and peripheral blood flow. We found a dose-dependent enhancement of constitutive NO generation by L-PCA in the human aortic endothelial cells (HAECs). In contrast, D-PCA had no influence on NO generation. Furthermore, L-PCA stimulated L-Arg uptake into HAECs dose-dependently, while D-PCA had no effect as same as NO generation. The L-Arg uptake and its stimulation by L-PCA to HAECs were suppressed with addition of L-NMMA, an inhibitor for the cationic amino acid transporter (CAT). These results indicated that enhancement of NO generation by L-PCA is due to the increase of L-Arg uptake via the CAT pathway. In conclusion, L-PCA was found to enhance blood circulation by modulating constitutive NO generation. Then we confirmed that the occlusive patch test of L-PCA to the volar forearm skin led the redness of skin, and which in turn enhanced the blood flow temporarily. This new function of L-PCA suggests development of innovative cosmetic products to care for such problematic skin as dark circles under the eyes.
