Transcriptomic Profiling and Pathway Analysis of Mesenchymal Stem Cells Following Low Dose-Rate Radiation Exposure

Fucoxanthin diminishes oxidative stress damage in human placenta-derived mesenchymal stem cells through the PI3K/Akt/Nrf-2 pathway

Placenta-derived mesenchymal stem cells (PL-MSCs) have therapeutic potential in various clinical contexts due to their regenerative and immunomodulatory properties. However, with increasing age or extensive in vitro culture, their viability and function are gradually lost, thus restricting their therapeutic application. The primary cause of this deterioration is oxidative injury from free radicals. Therefore, enhancing cell viability and restoring cellular repair mechanisms of PL-MSCs in an oxidative stress environment are crucial in this context. Fucoxanthin, a carotenoid derived from brown seaweed, demonstrates antioxidant activity by increasing the production of antioxidant enzymes and lowering the levels of reactive oxygen species (ROS). This study aimed to determine whether fucoxanthin protects PL-MSCs from hydrogen peroxide (H2O2)-induced oxidative stress. After characterization, PL-MSCs were co-treated with fucoxanthin and H2O2 for 24 h (co-treatment) or pre-treated with fucoxanthin for 24 h followed by H2O2 for 24 h (pre-treatment). The effects of fucoxanthin on cell viability and proliferation were examined using an MTT assay. The expression of antioxidant enzymes, PI3K/Akt/Nrf-2 and intracellular ROS production were investigated in fucoxanthin-treated PL-MSCs compared to the untreated group. The gene expression and involvement of specific pathways in the cytoprotective effect of fucoxanthin were investigated by high-throughput NanoString nCounter analysis. The results demonstrated that co-treatment and pre-treatment with fucoxanthin restored the viability and proliferative capacity of PL-MSCs. Fucoxanthin treatment increased the expression of antioxidant enzymes in PL-MSCs cultured under oxidative stress conditions and decreased intracellular ROS accumulation. Markedly, fucoxanthin treatment could restore PI3K/Akt/Nrf-2 expression in H2O2-treated PL-MSCs. High-throughput analysis revealed up-regulation of genes involved in cell survival pathways, including cell cycle and proliferation, DNA damage repair pathways, and down-regulation of genes in apoptosis and autophagy pathways. This study demonstrated that fucoxanthin protects and rescues PL-MSCs from oxidative stress damage through the PI3K/Akt/Nrf-2 pathway. Our data provide the supporting evidence for the use of fucoxanthin as an antioxidant cytoprotective agent to improve the viability and proliferation capacity of PL-MSCs both in vitro and in vivo required to increase the effectiveness of MSC expansion for therapeutic applications.

Low-dose brain radiation: lowering hyperphosphorylated-tau without increasing DNA damage or oncogenic activation

Brain radiation has been medically used to alter the metabolism of cancerous cells and induce their elimination. Rarely, though, brain radiation has been used to interfere with the pathomechanisms of non-cancerous brain disorders, especially neurodegenerative disorders. Data from low-dose radiation (LDR) on swine brains demonstrated reduced levels of phosphorylated-tau (CP13) and amyloid precursor protein (APP) in radiated (RAD) versus sham (SH) animals. Phosphorylated-tau and APP are involved in Alzheimer's disease (AD) pathogenesis. We determined if the expression levels of hyperphosphorylated-tau, 3R-tau, 4R-tau, synaptic, intraneuronal damage, and DNA damage/oncogenic activation markers were altered in RAD versus SH swine brains. Quantitative analyses demonstrated reduced levels of AT8 and 3R-tau in hippocampus (H) and striatum (Str), increased levels of synaptophysin and PSD-95 in frontal cortex (FCtx), and reduced levels of NF-L in cerebellum (CRB) of RAD versus SH swine. DNA damage and oncogene activation markers levels did not differ between RAD and SH animals, except for histone-H3 (increased in FCtx and CRB, decreased in Str), and p53 (reduced in FCtx, Str, H and CRB). These findings confirm the region-based effects of sLDR on proteins normally expressed in larger mammalian brains and support the potential applicability of LDR to beneficially interfere against neurodegenerative mechanisms.