DNA nanoprobe for real-time imaging and simultaneous quantification of mitochondrial Ca2+ and pH in neurons induced by superoxide anion and aggregated amyloid beta

DNA nanoprobe for real-time imaging and simultaneous quantification of mitochondrial Ca2+ and pH in neurons induced by superoxide anion and aggregated amyloid beta

Joint Event on 17^th International Conference on NEUROLOGY AND NEUROSCIENCE & 4^th International Conference on MENTAL HEALTH AND PRIMARY CARE
October 16-18, 2017 | Toronto, Canada

Zhichao Liu and Yang Tian

East China Normal University, China

Posters & Accepted Abstracts : J Neurol Neurorehabil Res

Abstract:

Mitochondria play vital roles in cellular energy production, signal transduction and Ca2+ homeostasis, as well as the cell death. Besides, mitochondrial pH and Ca2+ are closely associated with cellular functions and diseases. Thus, simultaneous imaging and biosensing are essential for understanding inter-relationship between Ca2+ and pH in physiological and pathological processes. Herein, we created a highly selective DNA nanoprobe for real-time imaging and simultaneous quantification of pH and Ca2+ in mitochondria, in which a new Ca2+ fluorescent probe was synthesized and assembled onto a DNA nanostructure together with pHresponsive, inner-reference, and mitochondria-targeted molecules. This new nanoprobe powerfully tracked pH and Ca2+ dynamics at the same localization in response to superoxide anion (O2•-)-induced oxidative stress and aggregated amyloid beta (Aβ) stimulation with a temporal resolution of milliseconds. Using this new tool, we discovered that acid-sensing ion channel 1a (ASIC1a) channel plays a vital role in O2•-- and Aβ-induced mitochondrial Ca2+ burst, which may contribute to neuron death. Moreover, psalmotoxin 1 (PcTX1) effectively protects against neuron injury, providing a potential drug for O2•- and/or Aβ-induced neuronal death. Using the DNA-assembled nanosensor for determination of pH and Ca2+ at the same localization, we demonstrated that mitochondrial Ca2+ is increased ~4-fold in neurons compared with HeLa cells, whereas mitochondrial pH exhibits no obvious difference between the two types of cells. Furthermore, experimental results demonstrated diverse mitochondrial Ca2+ and pH values in different regions of neurons. The close relationship between Ca2+ and pH in mitochondria was discovered. Mitochondrial pH value in neurons obviously increased with increasing Ca2+ concentration, which may be attributed to the function of the Ca2+/H+ antiporter in mitochondria. On the other hand, the mitochondrial Ca2+ burst can be adjusted by the ASIC1a channel during cytoplasmic acidosis. O2•- induces transitory cytoplasmic acidosis, which may activate the ASIC1a channel in the mitochondrial membrane, resulting in alkalization and Ca2+ overload in mitochondria. Mitochondrial Ca2+ overload is possibly one of the important factors in O2•--induced neuronal death. These results offer a new view for understanding the signaling pathway of ROS-induced oxidative stress and neuron injury. Aggregated Aβ is highly toxic to neurons. After stimulation by Aβ25-35, the pH value in the cytoplasm clearly decreased together with the Ca2+ burst, leading to acidification and Ca2+ overload in mitochondria through ASIC1a. PcTX1 protein protect neurons from death by preventing mitochondrial Ca2+ overload stimulated by O2•- and aggregated Aβ, suggesting that PcTX1 is a potential drug for O2•- and/or Aβ-induced neuronal death.

Biography:

Zhichao Liu, PhD is a student of Analytical Chemistry under the supervision of Prof. Tian in East China Normal University. He received his MS degree in Analytical Chemistry from Nanchang University in 2015. His doctoral research now focuses on the design, synthesis, characterization, and application of fluorescent nanomaterial for sensing and imaging in biological applications.

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