Aim of Thesis
~ 24 ~
Chapter 2
Aim of Thesis
Endocannabinoid system (ECs) seems to be involved in an ever-increasing number of physiological and pathological conditions, therefore interest for the ECs has been largely increased in the last years. Two G-protein-coupled receptors (GPCRs), CB1r and CB2r, have been identified to date for endocannabinoid system (Munro et al., 1993). CB1r is present predominantly in the central nervous system and it is thought to be responsible for most of the overt pharmacological effects of cannabinoids (Pertwee et al., 1999; Seltzman, 1999). Although CB2r was originally identified from macrophages present in the spleen and was initially considered to be expressed primarily by the immune system, it is now well accepted that CB2r is expressed by activated microglia and other macrophages in the brain (Lynn and Herkenham, 1994; Onaivi et al., 2006; Yiangou et al., 2006). Several studies have found that selective CB2r agonists may exhibit anti-inflammatory and analgesic properties in animal models (Guindon et al., 2008; Whiteside et al., 2007; Anand et al., 2009), and they could be useful for the treatment of neurodegenerative diseases, including Alzheimer's and Parkinson's disease (Pacher et al., 2006; Pertwee, 2005), amyotrophic lateral sclerosis (Shoemaker et al., 2007), and Huntington's disease (Sagredo et al., 2007). CB2r antagonists/inverse agonist may possess anti-inflammatory activity (Mackie et al., 2008), and may inhibit osteoclast formation and activity in vitro (Idris et al., 2008; Schuehly et al., 2011).
In literature are reported various molecules that interact selectivity with CB2r in order to minimize the psychotropic central effects mediated by CB1r. Recently, a poly-pharmacological approach has been widely considered because of the prospect synergic effect given from a single molecule interacting with different targets simultaneously.
With this point of view, my work of thesis has been performed at Biochemistry and Molecular Medicine Institute – University of Bern (Switzerland) to carry out the
Aim of Thesis
~ 25 ~
pharmacological properties of potential selective modulators of CB2r on the main endocannabinoid targets, as the endocannabinoid receptors, the enzymes responsible for endocannabinoid degradation (MAGL, FAAH, ABHDs, hCOX-2) and the specific bidirectional membrane transporter (EMT).
Molecules that I tested were synthesized in Pisa – Department of Pharmacy, from the research group of Prof.ssa Clementina Manera and they represent the last result of a long-lasting project to find new selective CB2r ligands. At first, the 1,8-naphthyridin-4(1H)-on-3-carboxamide derivatives of general structure (A) were synthesized and they displayed a remarkable affinity to both the endocannabinoid receptors (Ferrarini
et al., 2004). Afterwards, in order to increase the selectivity for CB2r, some changes
were produced and the 1,8-naphthyridin-2(1H)-on-3-carboxamide derivatives of general structure (B) were obtained with a relevant selectivity for CB2r (Manera et
al., 2009). Starting from B, was thought to simplify the structure by removing one of
the two pyridine rings and the new 1,2-dihydro-2-oxopyridine-3-carboxamide derivatives of general structure (C) were synthesized and tested on CB1r and CB2r. Results showed a decrease of CB2r affinity compared with B but better characteristics of solubility. (Manera et al., 2012).
Because of this, it was decided to investigate deeper derivatives C with [35S]GTPγS assay to evaluate the modulation of CB2r. Results interesting showed that substituent in position 5 of pyridine ring was responsible for a functional activity switch (Lucchesi et al., 2014). In particular was found that a phenyl group induced an inverse agonism behavior, a p-methoxyphenyl led to antagonism and a smaller group (as an hydrogen) to agonism (Lucchesi et al., 2014). Finally a methyl group was added in position 6 of the pyridine ring and the 1,2-dihydro-6-methyl-2-oxopyridine-3-carboxamide derivatives of general structure (D) were synthesized and the pharmacological properties screening of this compounds represents the object of my work of thesis.
In parallel a new class of molecules, structurally derived from derivatives C, in which the pyridine nucleus was replaced by a phenyl group to obtain biphenylic carboxamides derivatives of general structure (E) were synthesized and tested for binding and [35S]GTPγS. The results showed that these compounds possess a good selectivity for CB2r and a different activity modulation on the same receptor (Bertini
Aim of Thesis
~ 26 ~
et al., 2014). During my work of thesis the pharmacological properties of several
derivatives of general structure E were evaluated as well as the pharmacological properties of 1,2-dihydro-6-methyl-2-oxopyridine-3-carboxamide derivatives (D) and results will be shown separated.
A
B
C
D
E
Figure 2.1 General scaffolds directly or indirectly associated to my work of thesis: (A) 1,8-naphthyridin-4(1H)-on-3-carboxamides, (B)
1,8-naphthyridin-2(1H)-on-3-carboxamides, (C) 1,2-dihydro-2-oxopyridine-3-1,8-naphthyridin-2(1H)-on-3-carboxamides, (D) 1,2-dihydro-6-methyl-2-oxopyridine-3-carboxamides, (E) biphenyl-3-carboxamides
N O O NH R2 R3 C H3 R1 O NH R2 O R1 R3 CH3 N O R1 O NH R2 R3 N N O O NH R2 R1 N N R3 R1 O O NH R2
