Dong Yan, Ning Gang, Ewing Andrew G, Heien Michael L
Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, Shanghai, China; Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
PLoS One. 2014 Mar 6;9(3):e91132. doi: 10.1371/journal.pone.0091132. eCollection 2014.
A number of efforts have been made to understand how pituitary adenylate cyclase activating polypeptide (PACAP) functions as a neurotrophic and neuroprotective factor in Parkinson's disease (PD). Recently its effects on neurotransmission and underlying mechanisms have generated interest. In the present study, we investigate the effects of PACAP on catecholamine storage and secretion in PC12 cells with amperometry and transmission electron microscopy (TEM). PACAP increases quantal release induced by high K+ without significantly regulating the frequency of vesicle fusion events. TEM data indicate that the increased volume of the vesicle is mainly the result of enlargement of the fluidic space around the dense core. Moreover, the number of docked vesicles isn't modulated by PACAP. When cells are acutely treated with L-DOPA, the vesicular volume and quantal release both increase dramatically. It is likely that the characteristics of amperometric spikes from L-DOPA treated cells are associated with increased volume of individual vesicles rather than a direct effect on the mechanics of exocytosis. Treatment with PACAP versus L-DOPA results in different profiles of the dynamics of exocytosis. Release via the fusion pore prior to full exocytosis was observed with the same frequency following treatment with PACAP and L-DOPA. However, release events have a shorter duration and higher average current after PACAP treatment compared to L-DOPA. Furthermore, PACAP reduced the proportion of spikes having rapid decay time and shortened the decay time of both fast and slow spikes. In contrast, the distributions of the amperometric spike decay for both fast and slow spikes were shifted to longer time following L-DOPA treatment. Compared to L-DOPA, PACAP may produce multiple favorable effects on dopaminergic neurons, including protecting dopaminergic neurons against neurodegeneration and potentially regulating dopamine storage and release, making it a promising therapeutic agent for the treatment of PD.
人们已做出多项努力来了解垂体腺苷酸环化酶激活多肽（PACAP）在帕金森病（PD）中作为神经营养和神经保护因子的作用机制。最近，其对神经传递的影响及潜在机制引起了人们的关注。在本研究中，我们运用安培法和透射电子显微镜（TEM）研究了PACAP对PC12细胞中儿茶酚胺储存和分泌的影响。PACAP增加了高钾诱导的量子释放，但对囊泡融合事件的频率没有显著调节作用。TEM数据表明，囊泡体积的增加主要是由于致密核心周围流体空间的扩大。此外，停靠囊泡的数量不受PACAP的调节。当细胞用左旋多巴（L-DOPA）急性处理时，囊泡体积和量子释放均显著增加。L-DOPA处理细胞的安培信号特征可能与单个囊泡体积的增加有关，而不是对胞吐作用机制的直接影响。PACAP与L-DOPA处理导致了不同的胞吐动力学特征。在用PACAP和L-DOPA处理后，观察到在完全胞吐之前通过融合孔释放的频率相同。然而，与L-DOPA相比，PACAP处理后的释放事件持续时间更短，平均电流更高。此外，PACAP降低了具有快速衰减时间的信号比例，并缩短了快速和慢速信号的衰减时间。相比之下，L-DOPA处理后，快速和慢速信号的安培信号衰减分布均向更长时间偏移。与L-DOPA相比，PACAP可能对多巴胺能神经元产生多种有益作用，包括保护多巴胺能神经元免受神经退行性变，并可能调节多巴胺的储存和释放，使其成为治疗PD的一种有前景的治疗药物。
