Enhancement of germ tube formation in Candida albicans by beta-endorphin

Candida albicans is a dimorphic yeast that causes vaginal infections after its transition from a budding yeast to a germinating hyphal form. We report here that physiologic concentrations of beta-endorphin, a neuropeptide with immunomodulating activity produced during stress or physical exercise, stimulates germ tube formation in C. albicans. The percent of germination was proportional to the endorphin concentration, over the 5 x 10(-12) to 5 x 10(-10) mol/L range tested. beta-Endorphin modified by removal of the 4-carboxy-terminal amino acids and (D-Ala2)-beta-endorphin, a peptide with a protease-resistant amino terminal end, were equally effective in stimulating germination. In contrast, N-acetylated beta-endorphin did not stimulate germination. Antisera to beta-endorphin also completely blocked beta-endorphin-stimulated germ tube formation. Two clinical isolates of C. albicans were also responsive to beta-endorphin. Stimulation of germ tube formation by beta-endorphin occurred only in sera from ovulating women. Germination in sera from women using oral contraceptives, in sera from men, or in glucose beef extract broth was not influenced by beta-endorphin. Thus C. albicans may be able to recognize and respond to neuroendocrine signals in ovulating women.