The Possible Mechanisms By Which Angiotensin Ⅱ Triggers Apoptosis In A Dopaminergic Neuronal Cell Line

Aims: To investigate the effects of angiotensin II(Ang II) on the injury of dopaminergic cells and its underlying mechanisms.Materials and Methods: CATH.a cells, a dopaminergic neuronal cell line stably expressing Angiotensin II type 1 receptor(AT1R) and Angiotensin II type 2 receptor(AT2R), were exposed to Ang II alone or in combination with NADPH oxidase inhibitor or Ang II receptor blockers for 24 h. The cell survival rate was measured by methylthiazolyldiphenyl-tetrazolium bromide(MTT). The protein levels of cleaved caspase-3、gp91phoxand p67 phox detected by Western blot. The intracellular levels of reactive oxygen species(ROS) were monitored using flow cytometry. The levels of gp91 phoxand p67phox, the two main subunits of nicotinamide adenine dinucleotide phosphate(NADPH) oxidase, were examined by RT-PCR. The activity of NADPH oxidase and caspase-3 were measuredby using available kits.Results: we showed that Ang II treatment triggered cell apoptosis in a dose-dependent manner, providing the first evidence that apoptotic cell death contributed to the dopaminergic cell loss induced by Ang II. Ang II treatment also led to a significant increment in intracellular reactive oxygen species generation, which could be fully abolished by nicotinamide adenine dinucleotide phosphate(NADPH) oxidase inhibitors apocynin or diphenylene iodonium, indicating that Ang II enhanced oxidative stress via a NADPH oxidase-dependent manner. More importantly, inhibition of oxidative stress by NADPH oxidase inhibitors partially attenuated cell apoptosis caused by Ang II, implying that the enhancement of NADPH oxidase-dependent oxidative stress contributed to the cell apoptosis triggered by Ang II. Furthermore, the Ang II-induced oxidative stress and subsequent apoptosis could be completely abolished by AT1 R blocker losartan rather than AT2 R blocker PD1223319, suggesting that the aforementioned detrimental effects of Ang II are mediated by AT1 R.Conclusion: These findings indicate that Ang II interacts with AT1 R and subsequently exacerbates the injury of dopaminergic cells via elevation of ROS levels through a NADPH oxidase-dependent manner. These findings have deepened our understanding on the role of Ang II in the pathogenesis of Parkinson’s disease, and support the use of AT1 R blockers in the treatment of this devastating disease.