Objective To investigate the mechanism and protective effect of Humanin (HN) on rotenone (Rot)-induced toxic damage for dopamine neurons. Methods The Rot-poisened PC12 cell model was constructed, and the control group, the Rot poisening group, the HN pretreated Rot poisening group, and the HN treatment group were set up. ELISA was used to detect the content of HN inside and outside of Rot-infected cells, CCK-8 assay was used to detect cell viability, and ATP detection kit was used to detect the intracellular ATP content. Dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay was used to detect the level of reactive oxygen species (ROS) in cells. Western blotting was performed to detect the expression level of mitochondrial autophagy regulatory proteins Pink1, Parkin, p62, LC3, mitochondrial biogenesis regulatory protein PGC1α, division/fusion regulatory proteins OPA1, MFN2, DRP1, p-DRP1 and antioxidant stress regulatory proteins Keap1 and Nrf2. HBAD-mcherry-EGFP-LC3 adenovirus transfected cells was used to observed the number of autophagosomes and autophagolysosomes. Results The results showed that the intracellular concentration of HN in PC12 in the Rot poisening group was significantly higher than that in the control group (P < 0.05);Compared with the control group, the Rot poisening group had significantly decreased activity of PC12 cells, decreased ATP content and increased production of ROS. After the poisen of Rot in PC12 cells, the expression of Pink1 and p-Parkin, the ratio of LC3Ⅱ/LC3Ⅰ and the expression of p-DRP1 in mitochondrial fusion protein was increased, while the expression of p62, the expression of mitochondrial biogenesis protein PGC1α, mitochondrial fusion proteins MFN2 and OPA1, and antioxidant stress proteins Keap1 and Nrf2 were decreased (all P < 0.05). The number of autophagosomes and autophagolysosomes in PC12 cells in the Rot poisening group was higher than that in the control group (P < 0.05), and HN pretreatment (20 μmol/L) could significantly improve the changes mentioned above caused by Rot poisening (P < 0.05). Conclusion HN ameliorates Rot-induced toxic damage for dopamine neurons by inhibiting mitophagy and mitochondrial division and promoting mitochondrial biogenesis and fusion, and anti-oxidative stress.

MOTS-c is a 16-amino acid mitochondrial-derived peptide reported to be involved in regulating energy metabolism. However, few studies have reported the role of MOTS-c on neuron degeneration. In this study, it was aimed to explore the action of MOTS-c in rotenone-induced dopaminergic neurotoxicity. In an in vitro study, it was observed that rotenone could influence the expression and localization of MOTS-c significantly in PC12 cells, with more MOTS-c translocating into the nucleus from mitochondria. Further study showed that the translocation of MOTS-c from the mitochondria into the nucleus could directly interact with Nrf2 to regulate HO-1 and NQO1 expression in PC12 cells exposed to rotenone, which had been suggested to be involved in the antioxidant defense system. In vivo and in vitro experiments demonstrated that exogenous MOTS-c pretreatment could protect PC12 cells and rats from mitochondrial dysfunction and oxidative stress induced by rotenone. Moreover, MOTS-c pretreatment significantly decreased the loss of TH, PSD95, and SYP protein expression in the striatum of rats exposed to rotenone. In addition, MOTS-c pretreatment could clearly alleviate the downregulated expression of Nrf2, HO-1, and NQO1, as well as the upregulated Keap1 protein expression in the striatum of rotenone-treated rats. Taken together, these findings suggested that MOTS-c could directly interact with Nrf2 to activate the Nrf2/HO-1/NQO1 signal pathway to defend the antioxidant system to prevent dopaminergic neurons from rotenone-induced oxidative stress and neurotoxicity in vitro and in vivo.

TDCPP is a flame retardant which has nervous and reproductive toxicity. Although there is a close association between nervous and reproductive system, the exact toxic mechanism of TDCPP in these systems is still seldom, especially in a genome scale. In this study, we explored the transcriptomic landscape of TDCPP in PC12 and GC2 cells using RNAseq method. A total of 465 co-differential expressed genes were found. These genes were mainly enriched in extra-cellular matrix, cell adhesion, cell cycle arrest, oxidoreductase activity GO terms, and PI3K/AKT, focal adhesion, ECM-receptor interaction KEGG pathways. Hub genes (ANXA1, COL27A1, GAS6, GNB4 and THBS1) were extracted using STRING and confirmed by qPCR experiment. Vimentin, HSPA5 and Caspase3 were proved to be responsible to TDCPP in GC2 and PC12 cells. Knockdown assay in PC12 cells showed that these hub genes could also affect the protein expression of vimentin, HSPA5 and Caspase3. In summary, TDCPP might exert its toxic effect through disturbing focal adhesion, ECM-receptor interaction and PI3K/Akt pathways. One of the mechanisms could be influence on the cytoskeleton (vimentin), ER stress (HSPA5) and apoptosis (Caspase3). The sequence data in this study might be a useful resource for future TDCPP related researches.