Effects of different mouthwashes on Candida albicans adhesion, susceptibility to phagocytic cells and capacity to elicit pro-inflammatory cytokine response

Introduction. Oral candidiasis is a frequent opportunistic fungal infection, occurring especially in susceptible individuals. This pathology, mainly associated with Candida albicans species, may be prevented by a good oral hygiene, including the daily use of toothbrush and mouthwashes (MoWs). Among several virulence factors, C. albicans has the ability to adhere to epithelial surfaces, to avoid phagocytosis and/or intracellular killing and to elicit proinflammatory cytokines production. We have previously demonstrated that both C. albicans hyphal development and biofilm formation/persistence are affected by MoWs, provided that they contain chlorhexidine digluconate. Therefore, in this study we aim to expand our knowledge on MoWs effects by investigating the behaviour of MoWs-treated C. albicans, in terms of adhesion to both abiotic and biotic surfaces, susceptibility to phagocytosis and capacity to elicit pro-inflammatory immune responses. Materials and methods. C. albicans SC5314 and 6 commercial MoWs have been employed: 4 with and 2 without chlorhexidine digluconate (CHX), a component known to have antibacterial and antifungal activity. Adhesion was assessed by a bioluminescent strain of C. albicans SC5314; MoWs-treated and PBS-treated fungal cells were incubated in 96-well plates containing or not a monolayer of TR-146 oral epithelial cell line; after 60 min, plates were washed and the residual bioluminescent signal recorded. Susceptibility to phagocytosis was assessed by exposing MoWs-treated and PBS-treated C. albicans to phagocytic cell line BV2 (effector:target=1:2). Following 24 hours incubation of TR-146 cells with MoWs-treated and PBS-treated C. albicans, cytokine levels in supernatants were measured. Results. Adhesion of MoWs-treated C. albicans to abiotic surfaces was significantly lower than PBS-treated Candida. Adhesion of MoWs-treated C. albicans to TR-146 cells was significantly lower than PBS-treated Candida, in all but MoW 4. No differences could be highlighted in terms of susceptibility to phagocytosis (percent phagocytic cells and phagocytosis index) between MoWs-treated and PBS-treated Candida. On the contrary, significantly higher acidic phagolysosomes percentages were recorded from Candida treated with 4 out of 6 MoWs, with respect to PBS-treated fungi. Finally, Candida pretreatment with 4 out of 6 MoWs and 5 out of 6 MoWs impaired the production of IL-1alpha and IL-1beta respectively. Discussion and conclusions. C. albicans adhesion, susceptibility to phagocytosis and capacity to elicit pro-inflammatory cytokine response are affected by MoWs, especially those containing CHX. Thus, special attention should be used when choosing MoWs whether prevention and/or treatment of Candida-associated oral pathologies was intended.