Antidepressant-like effect of the novel thiadiazolidinone NP031115 in mice

Glycogen synthase kinase-3β (GSK-3β) is an enzyme that phosphorylates glycogen synthase, thereby inhibiting glycogen synthesis. Besides this role, it is now believed that this enzyme plays an important role in the pathophysiology of many brain diseases including depression. Some inhibitors of this enzyme have shown antidepressant effects in animal models. This study investigated the effects of a novel thiadiazolidinone NP031115, a putative GSK-3β inhibitor, and the well-established GSK-3β inhibitor AR-A014418 in the mouse forced swimming test (FST), a model widely used to evaluate antidepressant activity. We found that NP031115 had an IC50 of 1.23 and 6.5 μM for GSK-3β and GSK-3α, respectively. NP031115 (0.5 and 5 mg/kg, i.p.), in a way similar to imipramine (15 mg/kg, i.p), fluoxetine (32 mg/kg, i.p), AR-A014418 (9 mg/kg, i.p.), and rosiglitazone (5 μg/site, i.c.v.), significantly reduced immobility time in the FST. NP031115 at the higher dose and AR-A014418 (9 mg/kg, i.p.) reduced locomotion in the open-field test. Rosiglitazone (30 μM), AR-A014418 (1 μM), PGJ2 (10 μM), and NP031115 (1, 10 and 25 μM) activate PPARγ in CHO transfected cells. GW-9662 (10 μg/site, i.c.v, a PPARγ antagonist) administered 15 min before NP03115 (5 mg/kg, i.p.) or co-administered with rosiglitazone (5 μg/site, i.c.v.) prevented the antidepressant-like effect of these drugs in the FST. The results of this study show that NP031115 can exhibit an antidepressant effect, likely by inhibiting GSK-3β and enhancing PPARγ activity.