MMP-3 levels are increased in a rat model of PD induced by injection of 6-hydroxydopamine into the substantia nigra [129], and MMP-3 may play a pivotal role in the progression of PD through digestion of α-synuclein in DA neurons and modulation of α-synuclein aggregation and Lewy body formation [129, 130]. This evidence concerns the gene MMP3 and Parkinson disease.