Regular articleQuantitative protein profiling of hippocampus during human aging
Introduction
Aging associated health, economic, and social issues are among the biggest challenges worldwide. Currently, there are approximately 177 million people aged ≥65 years in China. By 2050, it is estimated that >30% of Chinese or 390 million will be aged >65 years, and 100 million age >80 years (Liu et al., 2013). Thus aging-related diseases represent a major national burden for China (Liu et al., 2013). Aging is the major risk factor for a series of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (Hindle, 2010). Although much research has focused on aging-related diseases, there have been few studies on the molecular biology of the aging human brain in the setting of neurodegenerative disease. Nevertheless, limited research does suggest that healthy brain aging is associated with perturbation of the protein homeostasis or deoxyribo nucleic acid damage responses that are essential for the structure and function of the nervous system (Perry et al., 2007).
The hippocampus is critical for learning and memory and is particularly vulnerable to senescence (Verret et al., 2007). Studies have shown decreases in hippocampal volume and neuronal plasticity during aging in healthy individuals, which may underlie hippocampus-dependent functional decline (Burke and Barnes, 2006). Impaired hippocampal synaptic integrity and signaling, decreased trophic factors, decreased neurogenesis, and increased neuroinflammation may contribute to the functional decline (Ojo et al., 2015), but the underlying mechanisms need to be further elucidated.
Brain aging is accompanied by changes in protein expression in important pathways. Previous studies showed that the disruption of electron transport chain (ETC) is a major part of mitochondrial dysfunction during aging, most likely due to the perturbation of complex I and complex IV (Swerdlow, 2011). Aged brain tissue also shows evidence of increased inflammation associated with microglial activation and subsequent elevation in proinflammatory cytokines (Guest et al., 2014). Excessive proinflammatory cytokines further exacerbate oxidative stress that in turn impairs apoptosis signaling and synaptic plasticity (Dorszewska, 2013).
Proteomics is complementary to genomics. The application of quantitative proteomics using isobaric tags for relative and absolute measurements is increasingly common in neurobiological studies of aging as the field adopts more system-oriented approaches (Dayon et al., 2008, Wiese et al., 2007).
Extensive studies in animals have greatly increased our understanding of brain aging processes. However, animals generally do not develop the full spectrum of clinical or neuropathologic phenotypes of human diseases, and findings in animal models may not be replicated in human studies (Gerlach and Riederer, 1996, Nakayama et al., 2004). Furthermore, it is well recognized that genetic, environmental, and cultural factors all contribute to brain aging and disease susceptibility, and there is an extensive literature documenting Caucasian brain aging and diseases. In contrast, very limited research has been conducted with Chinese brains (Chen et al., 2003).
With the establishment of the Human Brain Bank at the Chinese Academy of Medical Sciences & Peking Union Medical College, we are now able to access fresh brain tissues with short postmortem delays from Chinese donors with well-documented clinical history and neuropathologic examinations. Here, we have used proteomic and bioinformatic strategies to investigate age-related alterations in hippocampal protein expression.
Section snippets
Brains and hippocampal specimens
All brains were obtained from the Brain Bank of Chinese Academy of Medical Sciences & Peking Union Medical College, which collects brains from donors through a whole-body donation program. All donors had given informed consent for using the donated body tissue for medical research. After death, bodies were rapidly transferred to a designated autopsy facility. Brains were removed and bisected along the sagittal plane. One hemi-brain was emersion fixed in 10% phosphate-buffered formaldehyde, the
Quantitative MS analysis of proteins in age groups
By using the LC-MS/MS analysis, a total of 4582 proteins were identified by one or more unique peptides (3222 proteins were identified by 2 or more peptides) with the false discovery rate >1% (Table S2). With the 4-plex TMT labeling, the relative abundances of identified proteins in each age group were calculated. Protein expression ratio was obtained by comparing older groups (group B, C, and D) with the youngest group A, and the ratio was then used to determine upregulated or downregulated
Discussion
Owing to cultural tradition, there have been rare studies of postmortem Chinese brains. With the newly founded Chinese human brain bank and a well-run body donor program at the Chinese Academy of Medical Sciences & Peking Union Medical College, brains with short postmortem delay and thorough neuropathologic examinations become available for medical research using modern technologies including proteomics. This study represents the first of such research effort.
The hippocampus plays critical role
Conclusion
Our proteomics study showed that, in normal aging, proteins with binding and catalytic activity were the most altered proteins in hippocampus. The ETC and synaptic vesicle fusion pathways were also affected and clearly declined during the aging process. The levels of AD biomarkers were slightly changed during normal aging process. Taken together, the data presented here provide a full protein profile of the hippocampus among different age groups, in addition to shedding light on the alteration
Disclosure statement
All authors declare that no conflicts of interest exist.
Acknowledgements
Tissue provided by Human Brain Bank, Neuroscience Center, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China. This work was supported by the Chinese Human Brain Banking Consortium. We thank Prof. Haiteng Deng for his constant support and thank Dr. Wei Liu, Yuanyuan Xu, and Ruiming Mu for their technical assistance in postmortem human brain tissue harvesting and processing.
This work was supported by the National Natural Science Foundation of China (81373150 to
References (51)
Normal aging: regionally specific changes in hippocampal synaptic transmission
Trends Neurosci.
(1994)- et al.
Proteomic comparison between human young and old brains by two-dimensional gel electrophoresis and identification of proteins
Int. J. Dev. Neurosci.
(2003) - et al.
The mitochondrial ADP/ATP carrier (SLC25 family): pathological implications of its dysfunction
Mol. Aspects Med.
(2013) Involvement of hippocampal synaptic plasticity in age-related memory decline
Brain Res. Rev.
(1999)- et al.
Astrocytic involvement in learning and memory consolidation
Neurosci. Biobehav. Rev.
(2008) - et al.
Increasing proteome coverage with offline RP HPLC coupled to online RP nanoLC–MS
J. Chromatogr. B Analyt. Technol. Biomed. Life Sci.
(2011) - et al.
The tripartite synapse: roles for gliotransmission in health and disease
Trends Mol. Med.
(2007) - et al.
Proteomic analysis of glial fibrillary acidic protein in Alzheimer's disease and aging brain
Neurobiol. Dis.
(2005) - et al.
A comparative study of age-related brain pathology - are neurodegenerative diseases present in nonhuman animals
Med. Hypotheses
(2004) - et al.
Redox proteomics and the dynamic molecular landscape of the aging brain
Ageing Res. Rev.
(2014)
Developing master keys to brain pathology, cancer and aging from the structural biology of proteins controlling reactive oxygen species and DNA repair
Neuroscience
Amyloid beta, mitochondrial dysfunction and synaptic damage: implications for cognitive decline in aging and Alzheimer's disease
Trends Mol. Med.
Mapping cellular transcriptosomes in autopsied Alzheimer's disease subjects and relevant animal models
Neurobiol. Aging
APOE-related biomarker profiles in non-pathological aging and early phases of Alzheimer's disease
Neurosci. Biobehav. Rev.
Total ApoE and ApoE4 isoform assays in an Alzheimer's disease case-control study by targeted mass spectrometry (n= 669): a pilot assay for methionine-containing proteotypic peptides
Mol. Cell Proteomics
Brain aging, Alzheimer's disease, and mitochondria
Biochim Biophys Acta
Apolipoprotein E in Alzheimer's disease and other neurological disorders
Lancet Neurol.
Hippocampal neurogenesis during normal and pathological aging
Psychoneuroendocrinology
Tau and neuron aging
Aging Dis.
Semiquantitative proteomic analysis of human hippocampal tissues from Alzheimer's disease and age-matched control brains
Clin. Proteomics
Neural plasticity in the ageing brain
Nat. Rev. Neurosci.
Thrombospondin 1 is a key mediator of transforming growth factor beta-mediated cell contractility in systemic sclerosis via a mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK)-dependent mechanism
Fibrogenesis Tissue Repair
Astrocytes in the aging brain
J. Neurosci. Res.
Drusen proteome analysis: an approach to the etiology of age-related macular degeneration
Proc. Natl. Acad. Sci. U. S. A.
Reduced expression of amyloid precursor protein, presenilin-1 and rab3a in cortical brain regions in Alzheimer's disease
Dement. Geriatr. Cogn. Disord.
Cited by (53)
The 'middle-aging' brain
2024, Trends in NeurosciencesTSPO deficiency accelerates amyloid pathology and neuroinflammation by impairing microglial phagocytosis
2021, Neurobiology of AgingInclusion of African American/Black adults in a pilot brain proteomics study of Alzheimer's disease
2020, Neurobiology of DiseaseProteome-based identification of chicken egg yolk proteins associated with antioxidant activity on the Qinghai-Tibetan Plateau
2020, International Journal of Biological Macromolecules