Lasso Pirot Anayansi, Fritz Karen I, Ashraf Qazi M, Mishra Om P, Delivoria-Papadopoulos Maria
Division of Pulmonology, Department of Pediatrics, University of Maryland, Baltimore, MD 21201 , USA.
Neonatology. 2007;91(1):20-7. doi: 10.1159/000096967. Epub 2007 Nov 10.
Hypocapnia occurs in the newborn infant inadvertently or as a therapeutic modality and may result in neuronal and mitochondrial alterations in the newborn brain. Since mitochondria regulate apoptosis, these alterations may initiate a cascade of reactions that lead to apoptotic cell death.
This study tests the hypothesis that hypocapnia results in increased expression of the pro-apoptotic protein Bax, fragmentation of DNA and membrane lipid peroxidation in cerebral cortical mitochondria (mt) of newborn piglets.
Studies were performed in three groups of anesthetized normoxic newborn piglets: hypocapnic (H, n = 5), ventilated at a PaCO(2) of 11-15 mm Hg; normocapnic (N, n = 5), ventilated at a PaCO(2) of 40 mm Hg; and corrected normocapnic (CN, n = 4), ventilated as H with CO(2) added to maintain normocapnia. Tissue ATP and phosphocreatine levels were determined. Mitochondrial membrane proteins were separated, transblotted and probed with antibodies to Bax and Bcl-2. Bands were detected by enhanced chemiluminescence and analyzed by imaging densitometry. mtDNA was isolated. Cell and mitochondrial membrane lipid peroxidation products were measured spectrofluorometrically.
ATP and PCr concentrations were similar in the 3 groups. The ratio of Bax/Bcl-2 increased significantly in H compared to N and CN. mtDNA fragmentation was also significantly greater in H compared to N or CN. Membrane lipid peroxidation was higher in H than in N or CN; and in CN compared to N.
The data demonstrate that severe hypocapnia results in increased Bax expression, DNA fragmentation, and membrane lipid peroxidation in mitochondria of cerebral cortical neurons of newborn piglets, and may result in apoptotic cell death.
新生儿低碳酸血症可因疏忽或作为一种治疗方式而发生，可能导致新生儿脑内神经元和线粒体改变。由于线粒体调节细胞凋亡，这些改变可能引发一系列导致凋亡性细胞死亡的反应。
本研究检验如下假设：低碳酸血症会导致新生仔猪大脑皮质线粒体中促凋亡蛋白Bax表达增加、DNA片段化及膜脂质过氧化。
对三组麻醉状态下的常压氧合新生仔猪进行研究：低碳酸血症组（H，n = 5），以11 - 15 mmHg的动脉血二氧化碳分压（PaCO₂）进行通气；正常碳酸血症组（N，n = 5），以40 mmHg的PaCO₂进行通气；校正正常碳酸血症组（CN，n = 4），通气方式同H组，但添加二氧化碳以维持正常碳酸血症。测定组织ATP和磷酸肌酸水平。分离线粒体膜蛋白，进行转印并用抗Bax和抗Bcl - 2抗体进行检测。通过增强化学发光检测条带并进行图像密度测定分析。分离线粒体DNA。用荧光分光光度法测量细胞和线粒体膜脂质过氧化产物。
三组中ATP和PCr浓度相似。与N组和CN组相比，H组中Bax/Bcl - 2比值显著升高。与N组或CN组相比，H组中线粒体DNA片段化也显著更严重。H组中膜脂质过氧化高于N组或CN组；CN组高于N组。
数据表明，严重低碳酸血症会导致新生仔猪大脑皮质神经元线粒体中Bax表达增加、DNA片段化及膜脂质过氧化，并可能导致凋亡性细胞死亡。
