GADD45A and Parkinson disease: In addition, in an in vitro model of PD, the knockdown of GADD45A was proposed to be neuroprotective against neuronal death induced by MPP (1-Methyl-4-phenylpyridinium), which is a metabolite used to mimic mitochondrial impairment in in vitro models of PD by inducing dopaminergic neuronal death [137].