Dysregulation of stress response in Down Syndrome

Several studies support the implication of oxidative stress (OS) in phenotypical alterations of Down Syndrome (DS) individuals; however, the mechanisms through which OS damage leads to DS pathological phenotypes need to be clarified. OS seems to be a chronic condition in DS brain and it represents a strong risk factor for neurodegeneration. The mapping of HSA21 showed the involvement of several genes, such as SOD-1, BACH-1, APP, CBR and S100B, in the over-production of ROS in DS individuals and animal models. In my thesis I focused on two main projects on the dysregulation of stress response in Down Syndrome. Project 1. To highlight novel mechanisms leading to neurodegeneration in DS phenotype we investigated the role of BACH-1 in the brain and its implication in the failure of antioxidant response. A number of studies demonstrated the importance of the nuclear balance between BACH-1 and Nrf-2 to finely tune the antioxidant response. In this scenario, using different DS models, (a) neurons and astrocytes isolated from cortex and hippocampus of Ts2cje mice, an animal model of DS; (b) hippocampus from Ts2cje mice at 3 months of age; and (c) human DS lymphoblastoid cell lines (LCLs), we demonstrated that BACH-1 triplication alters BACH-1/Nrf-2 ratio and in turn downregulate the antioxidant responses. In light of these findings, we tested the antioxidant properties of two polyphenols, Caffeic Acid Phenethyl Ester and VP961, already proved to act as inducers of Nrf-2. Our results showed the ability of these compounds to modulate BACH-1/Nrf-2 pathway in neuroblastoma cell line and in DS LCLs, proposing their targeting as a powerful strategy to reduce OS conditions in DS. Project 2. To search for biomarkers for the early detection and exploration of the disease mechanisms, we investigated the protein expression signature of peripheral blood mononuclear cells (PBMCs) from DS children compared with healthy donors (HD) by using an in-depth label-free shotgun proteomics approach. Identified proteins were 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 were consistent with published study in DS and provide evidence that increased oxidative stress and the increased induction of stress related response, are contributors to DS pathology. In addition, the expression levels of few 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