Physiologically Based Pharmacokinetics (PBPK) modeling of ayahuasca and the effects of N,N-dimethyltryptamine (DMT) and harmine on cocaine-induced neurotoxicity

Abstract

Psychedelics have received a lot of attention in recent years for the treatment of mental illnesses such as depression, anxiety, and substance use disorder. The use of cocaine is predominantly a problem in South American countries, as its production mainly occurs in Colombia, Bolivia, and Peru, with Brazil being the world's largest crack market. Ayahuasca is a psychedelic brew, with its main active compounds being N,N-dimethyltryptamine (DMT) and the beta-carbolines harmine, harmaline, and tetrahydroharmine. The presence of beta-carbolines enables the psychedelic effect of DMT when administered orally, as they reversibly inhibit monoamine oxidase (MAO), the enzyme responsible for the rapid biotransformation of DMT. Preclinical studies have shown the benefits of ayahuasca use in cases of ethanol use disorder, and it has been demonstrated that the psychedelic experience caused by DMT is essential for the benefits provided by ayahuasca. Thus, a part of this project aims to construct an in silico physiologically based pharmacokinetic (PBPK) model that allows the prediction of DMT concentration in the central nervous system. This model will, for example, assess the influence of enzyme polymorphisms involved in the biotransformation of DMT, harmine, and harmaline, such as CYP2D6, on the bioavailability of DMT. Additionally, it will be possible to evaluate the interaction between ayahuasca and antidepressants, which, by increasing serotonin availability, can trigger serotonin syndrome. Therefore, an extensive literature review will be conducted to feed the PK-Sim® software, and the need for in vitro assays to validate the obtained in silico data will be evaluated. Model validation will be performed by constructing a kinetic curve using the plasma concentrations of ayahuasca alkaloids obtained after ayahuasca administration in rats. Another aspect of the project aims to study the potential neuroprotective mechanisms produced by harmine against cocaine-induced neurotoxicity in human neuroblastoma cells (differentiated into dopaminergic neurons). Parameters of oxidative stress (antioxidant enzyme activity and reactive oxygen species generation), neuroplasticity (BDNF and its signaling pathway involved in neuroplasticity: Akt/mTOR, p70S6k, ERK 1/2), and synaptogenesis (DCX, SNAP-25, synaptophysin, and PSD-25) will be evaluated. The third aspect focuses on the kynurenine pathway, a product of tryptophan metabolism. There is evidence that drugs of abuse such as ethanol and cocaine disrupt this pathway by inhibiting the enzyme indoleamine-2,3-dioxygenase (IDO), thereby increasing the production of neurotoxic metabolites such as quinolinic acid, among others. It has already been demonstrated that DMT is an inhibitor of this enzyme in human glioma cells. Tryptophan metabolites will be quantified by LCMS/MS, and the protein expression of the main enzymes in this pathway will be evaluated. With this project, we hope to understand the kinetics of DMT in various scenarios, as well as the mechanisms associated with the neuroprotective effects of the main ayahuasca alkaloids, which may emerge as a promising alternative in the assisted therapy of cocaine use disorder. (AU)