Spatiotemporal expression of sonic hedgehog signalling molecules in the embryonic mesencephalic dopaminergic neurons of mice

Background: Midbrain dopaminergic neurons (mDA) play an important role in controlling the voluntary motor movement, reward behaviour and emotion-based behaviour. Differentiation of mDA neurons from progenitors depends on several secreted proteins, such as sonic hedgehog (SHH), and transcription factors. Different groups from mDA neurons arise from the varied patterns of SHH expression during development. The present study attempted to elucidate in mice embryo model, through in situ hybridization and immunohistochemistry 1) the possible role(s) of some SHH signalling components (Ptch1, Gli1, Gli2 and Gli3) in the spatiotemporal development of mDA neurons along the rostrocaudal axis of the midbrain and their possible roles in differentiation (E12, E14) and survival of mDA neurons (E18); 2) the main role of Boc (bioregional Cdon-binding protein), and Gas1 (growth arrest-specific1) as novel accessory receptors for the SHH in the development of mDA neurons 3) the significance of using the primary culture and/or the dopaminergic cell line (MN9D) for studying the development of mDA neurons. Results: At E12 and E14, but not E18, only Ptch1 and Gli1 were expressed in ventrolateral midbrain domains. All examined SHH signalling molecules were not detected in mDA area. Whereas, in MN9D cells, many SHH signalling molecules were expressed and co-localized with the dopaminergic marker; tyrosine hydroxylase (TH), and their expression were upregulated with SHH treatment of the MN9D cells. Conclusion: These results suggest that mDA neurons differentiation and survival are independent of SHH. Besides, MN9D cell line is not the ideal in vitro model for investigating the differentiation of mesencephalic dopaminergic neurons, and hence, the ventral midbrain primary culture might be favored over MN9D line.

Spatiotemporal expression of sonic hedgehog signaling molecules in the embryonic mesencephalic dopaminergic neurons

Background Midbrain dopaminergic neurons (mDA) play an important role in controlling the voluntary motor movement, reward behavior and emotion-based behavior. Differentiation of mDA neurons from progenitors depends on a number of secreted proteins, such as sonic hedgehog (SHH), and transcription factors. Different groups from mDA neurons arise from the varied patterns of SHH expression during development. The present study attempted to elucidate 1) the possible role(s) of some SHH signaling components (Ptch1, Gli1, Gli2 and Gli3) in the spatiotemporal development of mDA neurons along the rostrocaudal axis of the midbrain and their possible roles in differentiation (E12, E14) and survival of mDA neurons (E18); 2) the main role of Boc (bioregional Cdon-binding protein), and Gas1 (growth arrest-specific 1) as novel accessory receptors for the SHH in the development of mDA neurons 3) the significance of using the primary culture and/or the dopaminergic cell line (MN9D) for studying the development of mDA neurons. Results Mice embryos from embryonic day (E)12 were used for in situ hybridization and immunohistochemistry. The primary culture and cell line MN9D were used for in vitro investigation. At E12 and E14, but not E18, only Ptch1 and Gli1 were expressed in ventrolateral midbrain domains. All examined SHH signaling molecules were not detected in mDA area. Whereas, in MN9D cells, many SHH signaling molecules were expressed and co-localized with dopaminergic marker; tyrosine hydroxylase (TH), and their expression were upregulated with SHH treatment of the MN9D cells. Conclusion These results suggest that mDA neurons differentiation and survival are independent of SHH. In addition, MN9D cell line is not the ideal in vitro model for investigating the differentiation of mesencephalic dopaminergic neurons, and hence, the ventral midbrain primary culture might be favored over MN9D line.

Salidroside Protects Dopaminergic Neurons by Enhancing PINK1/Parkin-Mediated Mitophagy

Parkinson’s disease (PD) is a common neurodegenerative disease characterized by the degeneration of nigrostriatal dopaminergic (DA) neurons. Our previous studies have suggested that salidroside (Sal) might play neuroprotective effects against PD by preserving mitochondrial Complex I activity. However, the exact mechanism of the neuroprotective effect of Sal remains unclear. Growing evidence indicates that PINK1/Parkin-mediated mitophagy is involved in the development of PD. In this study, we investigated whether Sal exerts a neuroprotective effect by modulating PINK1/Parkin-mediated mitophagy. Results showed that Sal alleviated MPTP-induced motor deficits in pole test. Moreover, Sal diminished MPTP-induced degeneration of nigrostriatal DA neurons as evidenced by upregulated TH-positive neurons in the substantia nigra, increased DAT expression, and high dopamine and metabolite levels in the striatum. Furthermore, in comparison with the MPP+/MPTP group, Sal considerably increased the mitophagosome and mitophagy flux. Moreover, in comparison with the MPP+/MPTP group, Sal evidently enhanced the mitochondrial expression of PINK1 and Parkin, accompanied by an increase in the colocalization of mitochondria with Parkin. However, transfection of MN9D cells with PINK1 siRNA reversed Sal-induced activated mitophagy and cytoprotective effect. In conclusion, Sal may confer neuroprotective effects by enhancing PINK1/Parkin-mediated mitophagy in MPP+/MPTP-induced PD models.