SPHK1 and Parkinson disease: Their research reported that in a PD in vitro model of MTPT/MPP+ (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-methyl-4-phenylpyridinium), Sphk1 activity was significantly reduced, which enhanced α-synuclein secretion and the activation of genes associated with apoptosis.