Post-synaptic density
protein 95 (PSD-95) links
neuronal nitric oxide synthase (nNOS) with the
N-methyl-D-aspartic acid (
NMDA) receptor in the central nervous system, and this molecular complex has been implicated in regulating neuronal excitability in several
neurological disorders. Here, small-molecule inhibitors of the PSD-95/nNOS interaction,
IC87201 and ZL006 were tested for
neuroprotective effects in an in vitro
Parkinson's disease (PD) model. We now report that
IC87201 and ZL006 reduced MPP(+)-induced neuronal injury and apoptotic cell death in a dose-dependent manner in cultured cortical neurons. These protective effects were associated with suppressed
mitochondrial dysfunction, as evidenced by decreased
reactive oxygen species (ROS) generation,
cytochrome c release, mitochondrial membrane potential (
MMP) collapse, and the preserved mitochondrial complex I activity and
ATP synthesis.
IC87201 and ZL006 also preserved intracellular homeostasis through mitigating mitochondrial Ca(2+) uptake and promoting mitochondrial Ca(2+) buffering capacity. Moreover, treatment with
IC87201 and ZL006 significantly increased the expression of
Sirt3 after MPP(+) exposure, and knockdown of
Sirt3 using specific targeted small interfere
RNA (
siRNA) partially nullified the protective effects induced by these two inhibitors. These data strongly support the hypothesis that targeting the PSD-95/nNOS interaction produces
neuroprotective effects and may represent a novel class of
therapeutics for PD as well as other neurological diseases where detrimental
NMDA receptor signaling plays a major role.