Proteomics Study of Peripheral Blood Mononuclear Cells in Down Syndrome Children

Abstract

Down syndrome (DS) is the most common chromosomal disorder and the leading genetic cause of intellectual disability in humans, which results from the triplication of chromosome 21. To search for biomarkers for the early detection and exploration of the disease mechanisms, here, we investigated the protein expression signature of peripheral blood mononuclear cells (PBMCs) in DS children compared with healthy donors (HD) by using an in-depth label-free shotgun proteomics approach. Identified proteins are found associated with metabolic pathways, cellular trafficking, DNA structure, stress response, cytoskeleton network, and signaling pathways. The results showed that a well-defined number of dysregulated pathways retain a prominent role in mediating DS pathological features. Further, proteomics results are consistent with published study in DS and provide evidences that increased oxidative stress and the increased induction of stress related response, is a participant in DS pathology. In addition, the expression levels of some key proteins have been validated by Western blot analysis while protein carbonylation, as marker of protein oxidation, was investigated. The results of this study propose that PBMCs from DS children might be in an activated state where endoplasmic reticulum stress and increased production of radical species are one of the primary events contributing to multiple DS pathological features.

Stress Responses in Down Syndrome Neurodegeneration: State of the Art and Therapeutic Molecules

“…However, the reduction of Nrf2 active form is observed very early, as an effect of Bach1 triplication. Similar data, concerning the ratio of Nrf2/Bach1 was obtained in DS mice and in PBMCs derived from children with DS [ 59 , 61 , 73 ]. On the contrary, Zamponi and collaborators reported Nrf2 activation in human astrocytes and fibroblast from DS [ 101 ].…”

“…To this regard, the analysis of autoptic brain samples from DS subjects of different ages allowed to define the profiling of alterations underlying the neurodegenerative process in DS since early stages [ 29 , 57 , 58 ]. In addition, the analysis of cells, not belonging to CNS (e.g., fibroblasts or peripheral blood mononuclear cells) from DS living individuals, allowed researchers to deeply investigate the molecular mechanisms linking trisomy 21 and aberrant proteostasis and to presume their potential involvement in brain pathology [ 59 , 60 ]. Intriguingly, a number of different DS murine models have been also employed in the study of the redox and protein homeostasis pathways of DS brain [ 61 , 62 , 63 , 64 ].…”

“…In particular, increased OS levels reported in the fetal DS brain may negatively affect development [ 84 ]. Furthermore in DS there is extensively literature describing the accumulation of 8-hydroxy-2’-deoxyguanosine (8-OHdG) oxidized protein, an increase of 3-nitrotyrosine in the cytoplasm of cerebral neurons in DS [ 85 ], an increase of protein carbonyls in peripheral blood mononucleate cells from children with DS [ 59 ], and the escalation of protein oxidation in the amniotic fluid from mothers carrying a DS fetus [ 82 ]. The alteration of redox balance was also observed early in peripheral samples from DS individuals, reinforcing the hypothesis of a pro-oxidant state occurring early in DS [ 86 , 87 ].…”

“…In turn, accumulation of H 2 O 2 , in the presence of Fe(II) or Cu(I), leads to hydroxyl radical formation that damage membrane lipids, proteins, and nucleic acids [ 17 ]. SOD1 protein levels were increased about 1.5-fold in DS brain and peripheral tissues [ 59 , 79 ]. Further, SOD1 was shown to be targeted by oxidative damage favoring its increased aggregation [ 79 ].…”

“…In the last few years, many efforts have been made to understand how the ISR and the UPR are implicated in the neurodegenerative process of DS. Accumulating evidence support the concept of dysregulated UPR and ISR as key mechanisms, [ 59 , 61 , 62 , 106 , 107 ], which due to their persistent activation could explain the long-term memory and synaptic plasticity deficits in DS. However, how the genetic of DS triggers UPR and ISR still needs to be elucidated.…”