Proteomics as a tool to investigate ROS-related pathologies: new putative biomarkers for malignant pleural mesothelioma and neuroprotective mechanisms of oleocanthal in neurodegenerative diseases

Oxidative stress contributes to the development and progression of a broad range of syndromes and diseases, especially cancer and neurodegenerative processes. Malignant pleural mesothelioma (MPM) is a highly aggressive tumor originating from the mesothelial cells of the pleura, associated with asbestos exposure. Inhalation of long and thin asbestos fibers induces a chronic inflammatory response at sites of fibers deposition, with accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) that over time may lead to malignant cell transformation. MPM is characterized by a long latency period, a poor prognosis, and limited effective therapies. Thus, there is a real need for improvement in prognostic and diagnostic tools for MPM. In recent years the focus in the field of biomarker discovery has moved from intracellular components to secreted factors. Cancer cell secretome provides an useful source in the search for proteins involved in tumor development and can be considered a potential tool to investigate tumor properties. Proteomic approaches are increasingly used for biomarker discovery as proteins produced by cancer cells or their microenvironment may eventually enter the circulation and their expression can be assessed for diagnostic purpose. In order to obtain an inclusive overview of MPM cell protein expression, we examined through a proteomic approach the proteome and secretome profiles of two MPM cell lines (NCI-H28 and NCI-2052) and compared to those of a non malignant mesothelial cell line (Met-5A). In this study, we identified mesothelioma cells-secreted proteins prosaposin (PSAP) and quiescin sulfhydryl oxidase 1 (QSOX1) as novel biomarker candidates for mesothelioma and validated their increase in serum of MPM patients by ELISA. Our results crearly show PSAP and QSOX1 serum levels are significantly increased in MPM patients in respect to asbestos-exposed healthy subjects. The informations gained from this investigation have increased our knowledge on MPM and identified two novel potential biomarkers. Neurodegenerative diseases represent a heterogeneous group of disorders that share common features like abnormal protein aggregation, perturbed Ca2+ homeostasis, excitotoxicity, impairment of mitochondrial functions, apoptosis, inflammation, and oxidative stress. Despite recent advances in the research of biomarkers, early diagnosis and pharmacotherapy, there are no treatments that can halt the progression of these age-associated neurodegenerative diseases. Numerous epidemiological studies indicate that long-term intake of a Mediterranean diet, characterized by a high consumption of extra virgin olive oil, correlates with better cognition in aged populations. Olive oil phenolic compounds have been demonstrated to have different biological activities such as antioxidant, antithrombotic, and anti-inflammatory properties. Oleocanthal, a phenolic component of extra-virgin olive oil, is getting more and more scientific attention due to its interesting biological activities. In this study, we aimed to characterize the neuroprotective effects of oleocanthal against H2O2-induced oxidative stress in neuron-like SH-SY5Y cells. Protein expression profiling, combined with pathways analyses, was used to investigate the molecular events related to the protective effects. Oleocanthal demonstrated to counteract oxidative stress increasing cell viability, reducing ROS production and increasing GSH intracellular level. Proteomic analysis revealed that oleocanthal significantly modulates 19 proteins in the presence of H2O2. In particular, oleocanthal up-regulated proteins related to the proteasome, the chaperone heat shock protein 90, the glycolytic enzyme pyruvate kinase and the antioxidant enzyme peroxiredoxin 1. These data offer new insights in the molecular mechanisms behind oleocanthal protection against oxidative stress.