Department of Chemistry, University of Waterloo, 200 University Avenue, Waterloo, Ontario N2L 3G1, Canada.
Neuroimaging Research Section, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada.
ACS Chem Neurosci. 2020 Jun 17;11(12):1827-1840. doi: 10.1021/acschemneuro.0c00270. Epub 2020 May 29.
Analysis of brain samples obtained postmortem remains a standard approach in neuroscience, despite often being suboptimal for inferring roles of small molecules in the pathophysiology of brain diseases. Sample collection and preservation further hinders conclusive interpretation of biomarker analysis in autopsy samples. We investigate purely death-induced changes affecting rat hippocampus in the first hour of postmortem interval (PMI) by means of untargeted liquid chromatography-mass spectrometry-based metabolomics. The unique possibility of sampling the same brain area of each animal both and postmortem was enabled by employing solid phase microextraction (SPME) probes. Four millimeter probes coated with mixed mode extraction phase were used to sample awake, freely roaming animals, with 2 more sampling events performed after death. Significant changes in brain neurochemistry were found to occur as soon as 30 min after death, further progressing with increasing PMI, evidenced by relative changes in levels of metabolites and lipids. These included species from several distinct groups, which can be classified as engaged in energy metabolism-related processes, signal transduction, neurotransmission, or inflammatory response. Additionally, we perform thorough analysis of interindividual variability in response to death, which provides insights into how this aspect can obscure conclusions drawn from an untargeted study at single metabolite and pathway level. The results suggest high demand for systematic studies examining the PMI time course with sampling as a starting point to eliminate artifacts in the form of neurochemical changes assumed to occur .
尽管死后脑组织样本分析是神经科学中的一种标准方法，但通常对于推断小分子在脑疾病病理生理学中的作用并不理想。样本的采集和保存进一步阻碍了对尸检样本中生物标志物分析的明确解释。我们通过非靶向液相色谱-质谱代谢组学研究了死后第一个小时内影响大鼠海马体的纯粹由死亡引起的变化。通过使用固相微萃取（SPME）探针，我们可以实现对每个动物的同一大脑区域进行生前和死后采样的独特可能性。使用混合模式萃取相涂层的 4 毫米探针对清醒、自由活动的动物进行采样，并在死后进行了另外 2 次采样。研究发现，死后 30 分钟，大脑神经化学就发生了明显变化，随着 PMI 的增加而进一步发展，这可以通过代谢物和脂质水平的相对变化来证明。这些变化包括来自几个不同组的物质，它们可以被归类为参与能量代谢相关过程、信号转导、神经传递或炎症反应。此外，我们还对死亡后的个体间变异性进行了全面分析，这为如何在单个代谢物和途径水平的非靶向研究中消除假设的神经化学变化等方面的混淆提供了深入的见解。结果表明，需要系统研究死后时间进程，并以生前采样为起点，以消除被认为是由神经化学变化引起的假象。
