Nitric oxide initiates oxidative independent apoptosis-like death in Candida albicans by lupeol

Lupeol, a dietary triterpene-type phytochemical flavonoid, was investigated for its mode of action in Candida albicans by assessing reactive species generation. While increased intracellular nitric oxide (NO) levels were detected, negligible levels were observed for other reactive oxygen species (ROS) and peroxynitrite(ONOO^-). The major NO scavenger l-NAME was applied in further experiments to determine whether NO was responsible for the observed processes. DNA damage, including fragmentation and condensation, occurred when the NO concentration increased. Additionally, G1 to S phase cell cycle arrest was induced, followed by mitochondrial dysfunction, including mitochondria mass variation and membrane depolarization. Consequently, typical apoptotic hallmarks such as caspase activation and phosphatidyl serine exposure were monitored. Thus, this study demonstrates that NO can exclusively exert lethal damage without the contribution of highly cytotoxic ROS. In conclusion, lupeol triggers downstream effects in fungal cells following DNA damage, mitochondrial dysfunction, cell cycle arrest, and caspase activation in response to apoptosis-like cell death under NO influence.