Generation of reactive oxygen species by Candida albicans in relation to morphogenesis

Abstract

Candida albicans is able to generate significant amounts of reactive oxygen species (ROS). In this study, ROS generation by yeast and hyphal forms of the strain 3153 A was analyzed to determine whether ROS generation could be a major factor in the invasive behavior of germinative cells. Furthermore, the virulent strain CA6 and its avirulent and agerminative mutant VIR3 were compared. ROS were measured by lucigenin-enhanced chemiluminescence and a cytochrome c assay. During the blastoconidial phase of all strains moderate amounts of ROS were found at cell concentrations > 1 x 10(5)/ml. However, ROS generation appeared to be specifically inhibited at cell concentrations > 1 x 10(8)/ml, and this was found in both assays. As shown in comparative experiments, the medium used for measurement markedly affected the total amount of ROS. Hyphae of strain 3153 A generated a significantly higher amount of ROS than yeast cells and cells with germ tubes (P < 0.001). The strain CA6 showed significantly higher ROS generation than the VIR3 strain for both blastoconidiae and after 30 min of induction of hypha formation (P < 0.05). In conclusion, hypha formation, usually acknowledged as a major factor in Candida pathogenicity, was associated with markedly increased ROS formation. ROS generation was not closely linked to the ability to form hyphae, but was highest in germinative cells.

Mechanisms of Resistance to Oxidative and Nitrosative Stress: Implications for Fungal Survival in Mammalian Hosts

“…Given the importance of morphological-phase transitions in fungal virulence (52) and the exposure of fungi to oxidant stress even in the early stages of mammalian host infection, it is tempting to speculate that the morphogenetic mechanisms demonstrated in N. crassa and A. nidulans may extend to fungal pathogens. In fact, evidence of ROS production by C. albicans in relation to morphogenesis has been presented, although a causal relationship has not been demonstrated (156).…”

Superoxide dismutases and glutaredoxins have a distinct role in the response of Candida albicans to oxidative stress generated by the chemical compounds menadione and diamide

“…In addition, Schroter et al (2000) analysed the amount of ROS produced when cells were incubated in 10% serum. Those authors found that ROS were produced in large amounts in a strain that formed true hyphae.…”

Glutathione levels in and total antioxidant capacity of Candida sp. cells exposed to oxidative stress caused by hydrogen peroxide

“…Consistent with this, Michán and Pueyo 33 reported that the GSH levels in C. albicans hyphae were approximately 50% of those in yeasts. Considering that oxidative stress diminishes GSH levels 33,34 , our treatment with H 2 O 2 was expected to reduce GSH content. Pacheco et al 25 demonstrated that cadmium treatment increased ROS production, depleted intracellular GSH concentrations, and increased external GSH concentrations.…”