Exploration of the selective and multitarget inhibition of the endocannabinoid system catabolic enzymes as pharmacological tools for central nervous system disorders

The endocannabinoid system (ECS) is an organized neuromodulatory network, composed by endogenous cannabinoids, cannabinoid receptors type 1 and type 2 (CB1 and CB2), and the main catabolic enzymes involved in the endocannabinoid inactivation such as fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). Indirect stimulation of ECS by using FAAH and MAGL inhibitors is emerging as a particularly attractive therapeutic target in CNS disorders and neurodegenerative diseases including Parkinson’s disease (PD), Alzheimer’s disease (AD), Huntington’s disease (HD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), stroke, traumatic brain injury (TBI), pain, and epilepsy. Epigenetic regulation orchestrates by histone deacetylase (HDAC) enzymes also play a crucial role in the several pathophysiological pathways. In this context several evidence highlight as dysregulations of the histone deacetylase 6 (HDAC6) enzymatic activity is involved in several neuroinflammatory and neurodegenerative conditions. The activity of the histaminergic system is implicated in the pathogenesis of several CNS complex diseases, such as the MS, AD or PD. Histamine receptor 3 (H3R) antagonists resulted to be effective in murine model of these complex disease. Since the multitude of potential targets involved in the pathogenesis of the nondegenerative diseases, the polypharmacologic approach is emerging as pivotal strategy to contrasts the large number of symptoms and physiological dysregulation associated at these complex conditions. In this thesis work an exploration of the selective and multitarget inhibition of the ECS catabolic enzyme was investigated with the aim to find innovative tools for the treatment of neurodegenerative diseases. A new series of carbamate based FAAH inhibitors was developed finalized at the obtainment of more soluble and stable compounds in aqueous media, compared with our previously reported analogues, maintaining a high inhibition potency against the target. The biological activity of these new inhibitors was successfully evaluated in cellular and ex vivo model of neuroinflammation. The MAGL inhibitors represent an important explored topic in our research group. Our research in this field led at the identification of high potent and selective MAGL inhibitors characterized by an azetidine-2-one scaffold. The next step in this field led us to develop new spiro β-lactam derivatives to which I contributed synthetizing two compounds. The polypharmacological investigation, object of this thesis work, started with the development of a set of dual FAAH/MAGL inhibitors for which the neuroprotective and anti-neuroinflammatory effects was evaluated in hippocampal slice cultures. Continuing in the polypharmacological exploration, a small library of innovative dual FAAH/HDAC6 was developed. Finally, a new series of dual acting compounds able to simultaneously engage MAGL and the H3R was conceived and prepared. This pioneering approach was developed in in collaboration with Professor Holger Stark (at the University of Dusseldorf) who has strong knowledge on the histaminergic system. In fact, this series of analogues was completed during a period of three months that I spent, within my PhD, in the laboratories of Professor Holger Stark.