Insights into the activation of oral keratinocyte cell death by Candida albicans and Staphylococcus aureus biofilms

Polymicrobial biofilms comprising Candida albicans and Staphylococcus aureus can increase the frequency and severity of oral diseases. This study assessed oral keratinocyte cell death, apoptosis and/or necrosis, promoted by soluble factors from single and dual biofilms of S. aureus and C. albicans. The soluble factors were obtained from the 16-h biofilm growth media. Cell viability was assessed by MTT and cell membrane damage by LDH. SEM was used for morphology changes. Assessment of apoptosis and necrosis was performed using annexin V and propidium iodide and caspases -2, -3, -6, -8 and -9. Statistical analysis was conducted with ANOVA and Tukey tests (α = 5%). Dual biofilms promoted the greatest harmful effect on oral cells, with a viability rate of 31.76%, damage to cell membranes and LDH released. Dual biofilms also induced higher percentages of necrotic cells (24.95%). Apoptosis was associated with caspases -2, -3, -6 and -8 activation.