Reverting Effect of Cysteine on the Suppression by Glucose or Dexamethasone of Anti-Candida Activity of Human Neutrophils

: Amino acid mixture prescribed for an hyperalimentation solution (PN-twin) diminishes suppression of anti-Candida activity of neutrophils as reported previously (Tansho, T, et al. J. Jpn. Assoc. Infect. Dis. 70: 463-469). The aim of this study was to identify the active principle in the amino acid mixture and to examine its action mechanism. Amino acid mixture (PN-twin) containing 23 amino acids neutralized the suppression of anti-Candida activity of human neutrophils by 1.0% of glucose. These amino acids were divided to several groups by their structure and effects of the groups on the suppressed anti-Candida activity neutrophils were examined. In all groups tested, amino acids containing cystein and methionine clearly neutralized the suppression, especially cysteine at the concentration more than 20 micrograms/ml significantly recovered the anti-Candida activity of neutrophils which was suppressed in the presence of 1% glucose or 10(-6) M dexamethasone. Correspondingly, cysteine augmented production of lactoferrin by stimulated neutrophils; which functions as a major effector molecule in growth inhibition of Candida by neutrophils. These results suggest that cysteine in alimentation solution augments anti-Candida defense mechanisms through recovery of neutrophil function.