Inhibition of endothelium-dependent relaxation by Candida albicans

This study examines the effects of Candida albicans on acethylcholine-induc ed, endothelium-dependent relaxation of thoracic aorta of rabbits, precontr acted by phenylephrine (10(-7)M). Isolated vessel rings were incubated with C. albicans, Saccharomyces cerevisiae, or their mannans, and endothelium-d ependent relaxation was measured by the induction of acethylcholine. Endoth elium-dependent relaxation remained unaffected after 3 hours by either C. a lbicans or S. cerevisiae, or their mannans. After 24 hours, however, incuba tion with C. albicans had completely abolished relaxation, whereas relaxati on was decreased by mannan of C. albicans and continued unaffected by S. ce revisiae. In contrast, no change was registered with a 24 hours incubation of C. Albicans in a sodium nitroprusside-induced, endothelium-independent, vascular smooth muscle relaxation. Microscopical investigation of the morph ological structure of vessel walls revealed penetration of C. albicans on t he intimal surface after 3 hours incubation and infiltration of the yeast t hrough the vessel wall after 24 hours. No changes in vessel morphology occu rred after 3 or 24 hours with S. cerevisiae or the mannan of C. albicans. T hese results show the ability of C. albicans to inhibit endothelium-depende nt, but not endothelium-independent, relaxation of vascular smooth muscle a nd may have important implications for functional damage to endothelial cel ls and the regulation of vessel tone and blood flow.