Therapeutic potential of metabotropic glutamate receptor 4-positive allosteric modulator TAS-4 in rodent models of movement disorders.

Parkinson's disease (PD) is a very serious neurological disorder, and current methods of treatment fail to achieve long-term control. Previous studies suggest that stimulation of the metabotropic glutamate receptor 4 (mGluR4) represents a promising new approach to the symptomatic treatment of Parkinson's disease (PD). Preclinical models using both agonists and positive allosteric modulators of mGluR4 have demonstrated the potential for this receptor for the treatment of PD. In the present study, we describe the pharmacological characterization of an mGluR4 PAM, N-(2, 4-dichlorophenyl) pyridine-2-carboxamide (TAS-4), in several rodent PD models. TAS-4 is a potent and selective mGluR4 PAM of the human mGluR4 receptor (EC50- 287.8nM). TAS-4 showed efficacy alone or when administered in combination with l-DOPA. When administered alone, TAS-4 exhibited efficacy in reversing haloperidol-induced catalepsy. In addition, acute TAS-4 dose-dependently potentiated contralateral turning behavior induced by a threshold dose of l-3,4-dihydroxyphenylalanine (l-DOPA, 4mg/kg i.p.), a classical test for antiparkinson drug screening. Subchronic (28days, twice a day) TAS-4 (10mg/kg i.p.)+l-DOPA (4mg/kg i.p.) did not induce sensitization to turning behavior or abnormal involuntary movements during the course of treatment. Moreover, subchronic administration of a fully effective dose of l-DOPA (8mg/kg i.p.) significantly induces sensitization to turning behavior or abnormal involuntary movements. Results showed that TAS-4, in association with a low dose of l-DOPA, displayed antiparkinsonian activity similar to that produced by a full dose of l-DOPA without exacerbating abnormal motor side effects.

NS-1: a novel partial peroxisome proliferator-activated receptor γ agonist to improve insulin sensitivity and metabolic profile.

Peroxisome proliferator-activated receptor (PPAR) γ is known to be a key regulator of insulin resistance. We characterized the pharmacological profiles of NS-1 chemically known as (5Z)-5-[4-hydroxy-3-methoxy-phenyl) methylene] thiazolidine-2, 4-dione), as a selective partial activator of PPARγ. In transient transactivation assay in NIH3T3 cells, NS-1 showed a partial activation against human PPARγ with an EC (50) of 0.91 µM without activating human PPARα and PPARδ. In adipocyte differentiation assay, NS-1 induced adipocyte differentiation, which was ~25-fold weaker inducer of GPDH activities than pioglitazone and also showed weak adipogenic activity in C3H10T1/2 pluripotent stem cells using Oil Red O staining. NS-1 showed good in vivo pharmacokinetic profiles in C57BL/6J mice at 30 mg/kg oral dose with Cmax-26 µM, terminal elimination half-life- 2.5h and bioavailability of 85%. Furthermore, NS-1 significantly improved hyperglycemia and insulin resistance in DIO animals when orally administered at a dose of 30 mg/kg/day for 45 days without significant weight gain. Overall, these studies suggest that NS-1 improves insulin resistance in such animal models through activation of PPARγ-mediated transcriptional activity and that it would be a new therapeutic candidate with potential for the treatment of type 2 diabetic patients.