Acetylcholine Protects against Candida albicans Infection by Inhibiting Biofilm Formation and Promoting Hemocyte Function in a Galleria mellonella Infection Model

Abstract

dBoth neuronal acetylcholine and nonneuronal acetylcholine have been demonstrated to modulate inflammatory responses. Studies investigating the role of acetylcholine in the pathogenesis of bacterial infections have revealed contradictory findings with regard to disease outcome. At present, the role of acetylcholine in the pathogenesis of fungal infections is unknown. Therefore, the aim of this study was to determine whether acetylcholine plays a role in fungal biofilm formation and the pathogenesis of Candida albicans infection. The effect of acetylcholine on C. albicans biofilm formation and metabolism in vitro was assessed using a crystal violet assay and phenotypic microarray analysis. Its effect on the outcome of a C. albicans infection, fungal burden, and biofilm formation were investigated in vivo using a Galleria mellonella infection model. In addition, its effect on modulation of host immunity to C. albicans infection was also determined in vivo using hemocyte counts, cytospin analysis, larval histology, lysozyme assays, hemolytic assays, and real-time PCR. Acetylcholine was shown to have the ability to inhibit C. albicans biofilm formation in vitro and in vivo. In addition, acetylcholine protected G. mellonella larvae from C. albicans infection mortality. The in vivo protection occurred through acetylcholine enhancing the function of hemocytes while at the same time inhibiting C. albicans biofilm formation. Furthermore, acetylcholine also inhibited inflammation-induced damage to internal organs. This is the first demonstration of a role for acetylcholine in protection against fungal infections, in addition to being the first report that this molecule can inhibit C. albicans biofilm formation. Therefore, acetylcholine has the capacity to modulate complex host-fungal interactions and plays a role in dictating the pathogenesis of fungal infections.

Exopolysaccharide-Repressing Small Molecules with Antibiofilm and Antivirulence Activity against Pseudomonas aeruginosa

“…Of the four lead compounds I7, I9, I10, and I11, only I9, the natural product brazilin, possesses antibacterial activity against the unrelated bacterium Propionibacterium acnes (45). Compound I10 (acetylcholine) was recently reported to have antibiofilm and antivirulence activity against Candida albicans (46), and several choline analogs were reported to reduce biofilm activity in P. aeruginosa without inhibiting growth (43). The identification of acetylcholine in this study, a known antibiofilm compound, validates the screening approach used.…”

Clinical associations between acetylcholine levels and cholinesterase activity in saliva and gingival crevicular fluid and periodontal diseases

“…It is now well established that non-neuronal ACh, acting via the α7nAChR, can also negatively regulate proinflammatory mediator expression by both professional and non-professional immune cells (de Jonge et al, 2005;Macpherson et al, 2014;Yoshikawa et al, 2006). However, evidence from in vivo and in vitro infection models suggests that it is too simplistic to state that within complex mucosal tissues ACh acts purely in an anti-inflammatory capacity (Giebelen, Leendertse, Florquin, & van der Poll, 2009;Giebelen et al, 2008;Rajendran et al, 2015). There is indeed evidence to support a role for ACh in promoting neutrophil recruitment, activation and neutrophil extracellular trap (NET) formation (Carmona-Rivera et al, 2017;Giebelen et al, 2008;Rajendran et al, 2015;Ruhnau et al, 2014;Xu et al, 2008).…”

“…However, evidence from in vivo and in vitro infection models suggests that it is too simplistic to state that within complex mucosal tissues ACh acts purely in an anti-inflammatory capacity (Giebelen, Leendertse, Florquin, & van der Poll, 2009;Giebelen et al, 2008;Rajendran et al, 2015). There is indeed evidence to support a role for ACh in promoting neutrophil recruitment, activation and neutrophil extracellular trap (NET) formation (Carmona-Rivera et al, 2017;Giebelen et al, 2008;Rajendran et al, 2015;Ruhnau et al, 2014;Xu et al, 2008). A plausible explanation for these differential findings is the fact that immune cells possess a plethora of nicotinic and muscarinic receptors which may differentially regulate immune responses.…”

Anti-inflammatory action of seed extract and polymeric nanoparticles of Syzygium cumini in diabetic rats infected with Candida albicans

“…We observed an increase in AChE activity in lymphocyte suspensions in DM, CA and DM+CA groups. ASc and NPASc were equally able to decrease the activity of AChE in DM+CA+ASc and DM+CA+NPASc, increasing ACh levels, which has recently been shown to be an inhibitor of C. albicans biofilm formation and pathogenicity (Rajendran et al, 2015).…”