HMOX1 and Parkinson disease: It has been confirmed by a series of in vitro experiments that activation of the Nrf2 signaling pathway can protect cells from PQ-induced toxicity.31 Our previous in vivo studies also showed that pretreatment with tBHQ can enhance the expression of Nrf2 and HO-1 in SN, giving a neuroprotective effect against PQ-induced PD.8 Exposure to PQ at 5 mg/kg in this study turned nuclei a blue–black color and also induced nuclear condensation and fragmentation, but did not induce significant apoptosis in either Nrf2 (+/+) or Nrf2 (−/−) mice.