The novel adenosine A2A antagonist prodrug MSX-4 is effective in animal models related to motivational and motor functions
Highlights
► MSX-4 is a novel adenosine A2A antagonist prodrug, converted into MSX-2 in vivo. ► MSX-4 reversed the effects of eticlopride on effort-related choice behavior. ► MSX-4 increased locomotion in eticlopride-treated rats. ► MSX-4 suppressed galantamine-induced tremulous jaw movements in rats. ► MSX-4 may be useful for treating parkinsonism and depression.
Introduction
A growing body of evidence indicates that the neuromodulator adenosine plays an important role in regulating the functional circuitry of the basal ganglia (Ferré et al., 1997, Ferré et al., 2001, Ferré et al., 2004, Stromberg et al., 2000, Hauber et al., 2001, Morelli and Pinna, 2002, Bara-Jimenez et al., 2003, Simola et al., 2006, Salamone et al., 2008). A1 and A2A adenosine receptor subtypes are involved in striatal function, and anatomical studies have shown that adenosine A2A receptors have a very high level of expression within both the neostriatum and the nucleus accumbens (Wang et al., 2000, Hettinger et al., 2001, Chen et al., 2001). In these striatal areas, adenosine A2A receptors are present largely on enkephalin-positive ventral and dorsal striatopallidal neurons, and are co-localized with DA D2 receptors (Fink et al., 1992, Rosin et al., 1998, Hillion et al., 2002, Chen et al., 2001, Fuxe et al., 2003, Fuxe et al., 2007, Mingote et al., 2008). Adenosine A2A and DA D2 receptors are thought to form heteromeric complexes that influence neurotransmitter binding, and these receptors also converge onto the same cAMP-related signal transduction pathways (Ferré, 1997, Ferré et al., 2008). A number of behavioral pharmacology studies have shown that drugs acting on adenosine A2A receptors can affect both motivational and motor functions. Adenosine A2A agonists such as CGS 21680 produce effects that resemble DA antagonism or depletion on tests of locomotor activity (Barraco et al., 1993), operant lever pressing (Mingote et al., 2008), effort-related choice behavior (Font et al., 2008) and tremor (Collins-Praino et al., 2011). Furthermore, adenosine A2A antagonists have been shown to act as psychomotor stimulants (Randall et al., 2011), and to reverse many of the behavioral effects of DA D2 antagonists (Farrar et al., 2007, Farrar et al., 2010, Salamone et al., 2008, Salamone et al., 2009a, Mott et al., 2009, Worden et al., 2009, Trevitt et al., 2009, Nunes et al., 2010, Collins et al., 2010a, Collins et al., 2012, Pereira et al., 2011) and cholinomimetics (Collins et al., 2010b, Collins et al., 2011). Based upon preclinical research, it has been suggested that adenosine A2A receptor antagonists could be useful as antiparkinsonian drugs (Ferré et al., 1997, Wardas et al., 2001, Morelli and Pinna, 2002, Hodgson et al., 2009, Salamone et al., 2008), and antidepressants (El Yacoubi et al., 2003, Hanff et al., 2010, Hodgson et al., 2009), or as treatments for motivational or effort-related psychiatric symptoms such as psychomotor retardation, anergia, apathy and fatigue (Salamone et al., 2007, Salamone et al., 2010), which are core symptoms of depression and other disorders (Marin, 1996, Demyttenaere et al., 2005, Salamone et al., 2006, Friedman, 2009).
In view of the preclinical research described above, and the growing clinical interest in adenosine A2A antagonists (LeWitt et al., 2008, Pinna, 2009, Hodgson et al., 2009, Salamone, 2010a), the development and testing of novel adenosine A2A antagonists is becoming an important research priority. One of the main considerations in drug discovery is the development of novel ligands with useful in vivo characteristics. For example, many drugs have difficulties in terms of absorption properties, solubility and blood brain barrier penetrability (Müller, 2009). An effective way of alleviating some of these problems is the use of prodrugs, which are bioreversible derivatives of drug molecules that must undergo a chemical or enzymatic biotransformation to the active forms prior to exerting a pharmacological action (Rautio et al., 2008, Müller, 2009). Prodrugs are traditionally developed by attaching an inactive promoiety to a pharmacologically active parent drug. The drug and promoiety are covalently linked via bioreversible groups that are chemically or enzymatically labile. The ideal prodrug yields the parent drug with high recovery ratios, with the promoiety being non-toxic (Rautio et al., 2008). Ultimately, the drug and promoiety are cleaved by chemical and/or enzymatic transformations, thus releasing the pharmacologically active parent drug. By employing this methodology, the clinical relevance of a drug molecule may be enhanced without modifying the pharmacological activity of a parent drug (Rautio et al., 2008). An example of an adenosine A2A antagonist parent compound that has been used in prodrug development is MSX-2. MSX-2, like other adenosine receptor antagonists and xanthine derivatives, suffers from poor water solubility (Müller, 2009). One approach to increase water solubility is to attach a polar moiety to the drug, which can be cleaved off by an enzymatic reaction to release the active drug. MSX-3 was developed several years ago as a pro-drug of MSX-2 (Hockemeyer et al., 2004), and previous studies have shown that MSX-3 can reverse the behavioral effects of DA D2 antagonists (Farrar et al., 2007, Salamone et al., 2008, Worden et al., 2009, Mott et al., 2009, Collins et al., 2010a, Collins et al., 2010b, Pardo et al., 2012). More recently, a novel valine ester amino acid promoiety for MSX-2 was developed (Vollmann et al., 2008). The new compound, MSX-4, was developed by condensing the carboxylate function of valine with the OH group of MSX-2, resulting in a prodrug with a basic amino group that can be protonated, which leads to a large increase in water solubility. MSX-4 was found to be stable in artificial gastric acid, and readily cleaved by pig liver esterase into MSX-2 (Vollmann et al., 2008).
Although MSX-3 has been widely used in vivo, the behavioral effects of MSX-4 have not been reported; thus, the present studies focused upon the characterization of the behavioral actions of MSX-4. The first group of studies compared MSX-4 and MSX-3 in terms of their ability to reverse the effects of the D2 antagonist eticlopride on effort-related choice behavior using a concurrent lever pressing/chow feeding choice task (Salamone et al., 1991, Salamone et al., 2002, Salamone et al., 2009a, Salamone et al., 2009b, Cagniard et al., 2006, Farrar et al., 2007, Nunes et al., 2010). It has been suggested that tests of effort-based choice behavior are useful for assessing motivational functions that are related to some of the activational or effort-based motivational symptoms of depression and other disorders (Salamone et al., 2006, Salamone et al., 2007, Salamone et al., 2009a, Salamone et al., 2009b, Salamone et al., 2010, Treadway and Zald, 2011). For these experiments, both intraperitoneal (IP) and oral administration were used. Additional studies focused upon the ability of MSX-4 to reverse the suppression of open field locomotion induced by eticlopride, and also used relative inner activity as a marker of any potential anxiogenic effects of MSX-4 (Prut and Belzung, 2003). To provide a cellular marker of the interaction between eticlopride and MSX-4, immunoreactivity of two markers of signal transduction activity (c-Fos and DARPP-32 phosphorylated at the threonine 34 residue, i.e., pDARPP-32(Thr34)) was determined in brain sections of nucleus accumbens. Finally, the ability of MSX-4 to suppress the oral tremor induced by the anticholinesterase galantamine (Collins et al., 2011) was assessed using the tremulous jaw movement test, which is a widely used rodent model of drug-induced parkinsonian tremor (Salamone et al., 1998, Salamone et al., 2005, Salamone et al., 2008, Rodriguez Diaz et al., 2001, Correa et al., 2004, Simola et al., 2004, Miwa et al., 2011, Collins-Praino et al., 2011, Collins et al., 2012). It was hypothesized that MSX-4 would show the behavioral and neurochemical characteristics of an adenosine A2A antagonist, by reversing the operant and locomotor effects of eticlopride, attenuating eticlopride-induced increases in c-Fos and pDARPP-32(Thr34) expression, and suppressing galantamine-induced oral tremor.
Section snippets
Animals
Across all experiments, a total of 140 male Sprague–Dawley rats (Harlan–Sprague–Dawley, Indianapolis, IN, USA) were used. Rats were housed in pairs in a colony maintained at 22–24 °C with a 12 h light/12 h dark cycle (lights on at 0700). Water was available ad libitum in the home cages at all times. The rats that were tested in operant boxes were food restricted to 85% of their free-feeding weight for initial operant training and allowed modest weight gain during the studies. Animal protocols have
Experiments 1 and 2: MSX-3 and MSX-4 reversed the effort-related effects of eticlopride
In experiment 1, there was an overall significant effect of drug treatment on lever pressing (Fig. 1A; F (5,30) = 11.466, p < 0.001). Planned comparisons showed that eticlopride produced a significant reduction in lever pressing compared to vehicle control (p < 0.05). In addition, co-administration of MSX-3 with eticlopride produced a significant increase in lever pressing compared to eticlopride plus vehicle, with the 0.5, 1.0 and 2.0 mg/kg doses of MSX-3 producing significant differences relative to
Discussion
The present studies were conducted to characterize the behavioral effects of the novel adenosine A2A antagonist prodrug MSX-4. MSX-4 was compared to a previously characterized prodrug (MSX-3) in the first 5 experiments, which employed a concurrent lever pressing/chow feeding task. Furthermore, we studied the MSX-4-induced reversal of the locomotor suppression induced by eticlopride, and the ability of MSX-4 to attenuate the signal transduction effects of eticlopride using c-Fos and
Acknowledgments
This work was supported by a grant to J.S. from the National Institute of Mental Health (MH078023), and to M.C. from Conselleria de Empresa, Universitat i Ciència. Generalitat Valenciana (BEST/2009/157). Y.B. and C.E.M. were supported by the BMBF, Germany (01EW0911) in the frame of ERA-NET NEURON.
References (92)
- et al.
Adenosine A2a receptors in the nucleus accumbens mediate locomotor depression
Brain Res Bull
(1993) - et al.
Effects of the adenosine A2A antagonist KW-6002 (istradefylline) on pimozide-induced oral tremor and striatal c-Fos expression: Comparisons with the muscarinic antagonist tropicamide
Neuroscience
(2009) - et al.
Interactions between adenosine and dopamine receptor antagonists with different selectivity profiles: Effects on locomotor activity
Behav Brain Res
(2010) - et al.
Oral tremor induced by the muscarinic agonist pilocarpine is suppressed by the adenosine A2A antagonists MSX-3 and SCH58261, but not the adenosine A1 antagonist DPCPX
Pharmacol Biochem Behav
(2010) - et al.
Oral tremor induced by galantamine in rats: a model of the parkinsonian side effects of cholinomimetics used to treat Alzheimer's disease
Pharmacol Biochem Behav
(2011) - et al.
The novel adenosine A2A antagonist Lu AA47070 reverses the motor and motivational effects produced by dopamine D2 receptor blockade
Pharmacol Biochem Behav
(2012) - et al.
The adenosine A2A antagonist KF17837 reverses the locomotor suppression and tremulous jaw movements induced by haloperidol in rats: Possible relevance to parkinsonism
Behav Brain Res
(2004) - et al.
Different effects of nucleus accumbens and ventrolateral striatal dopamine depletions on instrumental response selection in the rat
Pharmacol Biochem Behav
(1993) - et al.
Nucleus accumbens and effort-related functions: behavioral and neural markers of the interactions between adenosine A2A and dopamine D2 receptors
Neuroscience
(2010) - et al.
Adenosine–dopamine receptor–receptor interactions as an integrative mechanism in the basal ganglia
Trends Neurosci
(1997)
Adenosine/dopamine interaction: implications for the treatment of Parkinson's disease
Parkinsonism Relat Disord
Adenosine A2A–dopamine D2 receptor–receptor heteromers. Targets for neuro-psychiatric disorders
Parkinsonism Relat Disord
Molecular cloning of the rat A2 adenosine receptor: Selective co-expression with D2 dopamine receptors in rat striatum
Brain Res Mol Brain Res
Adenosine receptor–dopamine receptor interactions in the basal ganglia and their relevance for brain function
Physiol Behav
Coaggregation, cointernalization, and codesensitization of adenosine A2A receptors and dopamine D2 receptors
J Biol Chem
Injections of the selective adenosine A2A antagonist MSX-3 into the nucleus accumbens core attenuate the locomotor suppression induced by haloperidol in rats
Behav Brain Res
Corticostriatal-hypothalamic circuitry and food motivation: integration of energy, action and reward
Physiol Behav
Effects of T-type calcium channel blockers on a parkinsonian tremor model in rats
Pharmacol Biochem Behav
D1 or D2 antagonism in nucleus accumbens core or dorsomedial shell suppresses lever pressing for food but leads to compensatory increases in chow consumption
Pharmacol Biochem Behav
Differential effects of selective adenosine antagonists on the effort-related impairments induced by dopamine D1 and D2 antagonist
Neuroscience
Adenosine A(2A) receptor antagonism and genetic deletion attenuate the effects of dopamine D(2) antagonism on effort-based decision making in mice
Neuropharmacology
Involvement of adenosine A2A receptors in the induction of c-fos expression by clozapine and haloperidol
Neuropsychopharmacology
A new ethyladenine antagonist of adenosine A(2A) receptors: behavioral and biochemical characterization as an antiparkinsonian drug
Neuropharmacology
The open field as a paradigm to measure the effects of drugs on anxiety-like behaviors: a review
Eur J Pharmacol
Neuroleptics increase c-fos expression in the forebrain: contrasting effects of haloperidol and clozapine
Neuroscience
Motor behavioural changes after intracerebroventricular injection of 6-hydroxydopamine in the rat: an animal model of Parkinson's disease
Behav Brain Res
Motivational views of reinforcement: implications for understanding the behavioral functions of nucleus accumbens dopamine
Behav Brain Res
Dopamine/adenosine interactions involved in effort-related aspects of food motivation
Appetite
Tremulous jaw movements in rats: a model of parkinsonian tremor
Prog Neurobiol
Nucleus accumbens dopamine depletions make animals highly sensitive to high fixed ratio requirements but do not impair primary food reinforcement
Neuroscience
Beyond the reward hypothesis: alternative functions of nucleus accumbens dopamine
Curr Opin Pharmacol
Differential actions of adenosine A1 and A2A antagonists on the effort-related effects of dopamine D2 antagonism
Behav Brain Res
Blockade of adenosine A2A receptors antagonizes parkinsonian tremor in the rat tacrine model by an action on specific striatal regions
Exp Neurol
Dopamine and adenosine receptor interaction as basis for the treatment of Parkinson's disease
J Neurol Sci
The role of accumbens dopamine in lever pressing and response allocation: Effects of 6-OHDA injected into core and dorsomedial shell
Pharmacol Biochem Behav
Reconsidering anhedonia in depression: lessons from translational neuroscience
Neurosci Biobehav Rev
Adenosine antagonists reverse the cataleptic effects of haloperidol: Implications for the treatment of Parkinson's disease
Pharmacol Biochem Behav
Characterization of the antiparkinsonian effects of the new adenosine A2A receptor antagonist ST1535: acute and subchronic studies in rats
Eur J Pharmacol
Acute administration of typical and atypical antipsychotic drugs induces distinctive patterns of Fos expression in the rat forebrain
Brain Res
Carbon-11-labeled KF21213: a highly selective ligand for mapping CNS adenosine A(2A) receptors with positron emission tomography
Nucl Med Biol
Adenosine A(2A) receptor antagonist treatment of Parkinson's disease
Neurology
Involvement of adenosine and glutamate receptors in the induction of c-fos in the striatum by haloperidol
Synapse
Deciphering the actions of antiparkinsonian and antipsychotic drugs on cAMP/DARPP-32
Signal Front Neuroanat
Mice with chronically elevated dopamine exhibit enhanced motivation, but not learning, for a food reward
Neuropsychopharmacology
The role of the D2 dopamine receptor (D2R) in A2a adenosine-receptor (A2aR) mediated behavioral and cellular responses as revealed by A2a and D2 receptor knockout mice
Proc Natl Acad Sci
Pharmacological and physiological characterization of the tremulous jaw movement model of parkinsonian tremor: Potential insights into the pathophysiology of tremor
Front Syst Neurosci
Cited by (41)
Adolescent high-fructose corn syrup consumption leads to dysfunction in adult affective behaviors and mesolimbic proteins in male Sprague-Dawley rats
2022, Behavioural Brain ResearchCitation Excerpt :These findings suggest an important role for D2 receptors in neuroplastic changes induced by reinforcing stimuli, such as highly palatable foods. In addition to reinforcement, DA transmission has also been well established to modulate effort-related decision making that is required for the acquisition of food [25–28]. Both D1 and D2 receptor antagonism have been shown to produce low-effort bias in effort-related tasks [25,29,30].
Of adenosine and the blues: The adenosinergic system in the pathophysiology and treatment of major depressive disorder
2021, Pharmacological ResearchThe non-selective adenosine antagonist theophylline reverses the effects of dopamine antagonism on tremor, motor activity and effort-based decision-making
2020, Pharmacology Biochemistry and BehaviorCitation Excerpt :As noted above, it is hypothesized that adenosine A2A receptor blockade is able to strongly reverse the signal transduction effects of DA D2 receptor antagonism because both receptors are located on the same neurons, and converge on to the same signal transduction mechanisms (Worden et al., 2009; Santerre et al., 2012; Nunes et al., 2010, 2013). This suggestion is consistent with studies that use c-Fos or DARPP-32 as markers of the cellular effects of D2 antagonism; across several drug combinations, it has been shown that adenosine A2A antagonism is able to reverse the expression of c-Fos and DARPP-32 (phosphorylated at the threonine 34 site) in nucleus accumbens that is induced by D2 antagonism (Betz et al., 2009; Farrar et al., 2010; Santerre et al., 2012; Nunes et al., 2013). Theophylline also can reverse the expression of nucleus accumbens c-Fos that is induced by DA D2 antagonism (Pardo et al., 2013).
Adenosine A<inf>2A</inf> receptor as potential therapeutic target in neuropsychiatric disorders
2019, Pharmacological Research
- 1
Present address: Cognitive Neuroscience Division, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University College of Physicians and Surgeons, NY, USA.