Saccharomyces cerevisiae as a model to study synthetic cannabinoids: the impact of using different carbon sources

INTRODUCTION: Synthetic cannabinoids (SC) are potent agonists of cannabinoid receptors, that mime the psychoactive effect of Δ(9)-tetrahydrocannabinol (Δ(9)-THC), the principal psychoactive component of cannabis [1]. JWH-018 was the first novel psychoactive SC found in the recreational drug marketplace in 2008. A few years later, JWH-018 started to be controlled by authorities, so alternative molecules started to emerge. THJ-018 was designed to replace JWH-018, having a similar structural skeleton and also a naphthalene and pentyl chain connected via a middle core substructure. Eventually, THJ-018 was scheduled and alternatives emerged, such as EG-018 [2]. This practice makes almost impossible to characterise SC toxicological profiles on an acceptable time scale, mostly due to the time-consuming experiments that must be held in animal models or human cells by standard methods. The yeast Saccharomyces cerevisiae shares highly conserved molecular and cellular mechanisms with human cells and has been used before for synthetic cathinones [3]. The present work has studied the best carbon source (glucose or galactose) to measure the impact of synthetic cannabinoids on S. cerevisiae growth, aiming to develop a method able to profile synthetic cannabinoids toxicity in a short time scale. The difference between carbon sources is that in Crabtree-positive yeast strains, glucose induce a strong inhibition of mitochondrial oxidative phosphorylation [4]. MATERIALS AND METHODS: The effect of EG-018 was evaluated by its impact on S. cerevisiae BY4741 (WT) growth on minimal medium with 2% Glucose or 1% Galactose as sole carbon sources, in the presence and absence of the SC, followed at OD(600nm). Growth rates at each condition was fitted to a logistic equation. RESULTS: Figure 1 shows OD(600max) obtained from the non-linear regression to the logistic equation in the presence of different concentrations of EG-018. While in galactose there is no effect, in 2% Glucose the results points to a growth decrease with EG-018. Discussion and conclusions: Comparing the two carbon sources, yeast growth on glucose is more susceptible to EG-018. Recent studies points that JWH-018, a similar SC, exerts an effect on glycolytic and pentose phosphate pathway at high concentrations of glucose (personal communication). As yeast growth in galactose proceeds simultaneously via respiration and fermentation due to the “Crabtree effect” [4] an impact of EG-018 on glycolysis might be less effective. These results, suggest that glucose is the best carbon source to develop a yeast based toxicity sensor for SC.