However, considering the increased risk of PD in older men with abnormally high Hb levels and selective vulnerability of dopaminergic A9 neurons with enriched neuronal Hb [4,8], neuronal Hb may participate in a complex and dynamic regulatory network by changing its expression, solubility, and subcellular localization during PD development, rather than a merely mitochondrial protective role. Here, GSTM1 is linked to Parkinson disease.