Khuzakhmetova Venera, Yakovleva Olga, Dmitrieva Svetlana, Khaertdinov Nail, Ziyatdinova Guzel, Giniatullin Rashid, Yakovlev Aleksey, Bukharaeva Ellya, Sitdikova Guzel
Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Kazan, Russia; Kazan Federal University, Kazan, Russia.
Kazan Federal University, Kazan, Russia.
Int J Dev Neurosci. 2019 Jun;75:1-12. doi: 10.1016/j.ijdevneu.2019.03.004. Epub 2019 Apr 1.
Enhanced levels of homocysteine during pregnancy induce oxidative stress and contribute to many age-related diseases. In this study, we analyzed age-dependent synaptic modifications in developing neuromuscular synapses of rats with prenatal hyperhomocysteinemia (hHCY). One of the main findings indicate that the intensity and the timing of transmitter release in synapses of neonatal (P6 and P10) hHCY rats acquired features of matured synaptic transmission of adult rats. The amplitude and frequency of miniature end-plate currents (MEPCs) and evoked transmitter release were higher in neonatal hHCY animals compared to the control group. Analysis of the kinetics of neurotransmitter release demonstrated more synchronized release in neonatal rats with hHCY. At the same time lower release probability was observed in adults with hHCY. Spontaneous transmitter release in neonates with hHCY was inhibited by hydrogen peroxide (HO) whereas in controls this oxidant was effective only in adult animals indicating a higher susceptibility of motor nerve terminals to oxidative stress. The morphology and the intensity of endocytosis of synaptic vesicles in motor nerve endings was assessed using the fluorescence dye FM 1-43. Adult-like synapses were found in neonates with hHCY which were characterized by a larger area of presynaptic terminals compared to controls. No difference in the intensity of FM 1-43 fluorescence was observed between two groups of animals. Prenatal hHCY resulted in reduced muscle strength assessed by the Paw Grip Endurance test. Using biochemical assays we found an increased level of HO and lipid peroxidation products in the diaphragm muscles of hHCY rats. This was associated with a lowered activity of superoxide dismutase and glutathione peroxidase. Our data indicate that prenatal hHCY induces oxidative stress and apparent faster functional and morphological "maturation" of motor synapses. Our results uncover synaptic mechanisms of disrupted muscle function observed in hHCY conditions which may contribute to the pathogenesis of motor neuronal diseases associated with enhanced level of homocysteine.
孕期同型半胱氨酸水平升高会引发氧化应激，并导致许多与年龄相关的疾病。在本研究中，我们分析了产前高同型半胱氨酸血症（hHCY）大鼠发育中的神经肌肉突触中与年龄相关的突触变化。主要发现之一表明，新生（P6和P10）hHCY大鼠突触中递质释放的强度和时间获得了成年大鼠成熟突触传递的特征。与对照组相比，新生hHCY动物的微小终板电流（MEPCs）的幅度和频率以及诱发的递质释放更高。对递质释放动力学的分析表明，hHCY新生大鼠的释放更同步。同时，在成年hHCY大鼠中观察到较低的释放概率。hHCY新生大鼠的自发递质释放受到过氧化氢（HO）的抑制，而在对照组中，这种氧化剂仅在成年动物中有效，这表明运动神经末梢对氧化应激更敏感。使用荧光染料FM 1-43评估运动神经末梢中突触小泡的内吞作用的形态和强度。在hHCY新生大鼠中发现了类似成年的突触，其特征是与对照组相比，突触前终末的面积更大。两组动物之间未观察到FM 1-43荧光强度的差异。产前hHCY导致通过握爪耐力试验评估的肌肉力量下降。通过生化分析，我们发现hHCY大鼠膈肌中HO和脂质过氧化产物的水平升高。这与超氧化物歧化酶和谷胱甘肽过氧化物酶的活性降低有关。我们的数据表明，产前hHCY会诱导氧化应激，并使运动突触出现明显更快的功能和形态“成熟”。我们的结果揭示了在hHCY条件下观察到的肌肉功能破坏的突触机制，这可能有助于与同型半胱氨酸水平升高相关的运动神经元疾病的发病机制。
