Does the Endocannabinoid Anandamide Affect Bacterial Quorum Sensing, Vitality, and Motility?

Introduction: The endocannabinoid anandamide (AEA) is a neurotransmitter produced and released "on demand." Numerous studies have been conducted on AEA and on the endocannabinoid system (ECS), but none of them have investigated their effect on prokaryotes. Quorum sensing (QS) is a process of bacteria-bacteria communication. In this cross-Talk, the bacteria secrete and recognize signal molecules termed autoinducers (AIs). It has been shown that the QS system regulates expression of many physiological and virulence factors of bacteria. Materials and Methods: QS was measured using the bioluminescence property of the bacterium Vibrio harveyi. The effect of AEA on QS-related gene expression was measured using real-Time polymerase chain reaction. 0.18% agar plates were used for surface movement assay. Results: No dose response of AEA could be determined up to 100 μg/mL on bacterial growth either wild-Type (WT) V. harveyi or mutant strains. However on addition of AEA, QS was reduced significantly for WT and other V. harveyi strains mutated at different locations of the QS cascade (BB152; HAI-1 synthase mutant, BB886; Sensor-2^-, BB170; Sensor-1^-, MM30; AI-2). Genes related to the QS pathway, such as luxS, showed significant reduction in expression in the presence of AEA. Motility tests showed that continuous exposure to AEA reduced V. harveyi ability to spread on a soft agar surface, but pre-exposure to AEA did not have any effect on its motility. Conclusions: This study presents the first evidence that the endocannabinoid AEA affects specific functions of a prokaryotic organism (e.g., QS and motility). Our results present novel, not yet been observed biological functions of the ECS, namely as a possible line of defense against bacteria.