Crosstalk control and limits of physiological c-Jun N-terminal kinase activity for cell viability and neurite stability in differentiated PC12 cells

Targeting natural antioxidant polyphenols to protect neuroinflammation and neurodegenerative diseases: a comprehensive review

Polyphenols, naturally occurring phytonutrients found in plant-based foods, have attracted significant attention for their potential therapeutic effects in neurological diseases and neuroinflammation. These compounds possess diverse neuroprotective capabilities, including antioxidant, anti-inflammatory, and anti-amyloid properties, which contribute to mitigating the progression of neurodegenerative conditions such as Alzheimer's Disease (AD), Parkinson's Disease (PD), Dementia, Multiple Sclerosis (MS), Stroke, and Huntington's Disease (HD). Polyphenols have been extensively studied for their ability to regulate inflammatory responses by modulating the activity of pro-inflammatory genes and influencing signal transduction pathways, thereby reducing neuroinflammation and neuronal death. Additionally, polyphenols have shown promise in modulating various cellular signaling pathways associated with neuronal viability, synaptic plasticity, and cognitive function. Epidemiological and clinical studies highlight the potential of polyphenol-rich diets to decrease the risk and alleviate symptoms of neurodegenerative disorders and neuroinflammation. Furthermore, polyphenols have demonstrated their therapeutic potential through the regulation of key signaling pathways such as Akt, Nrf2, STAT, and MAPK, which play critical roles in neuroprotection and the body's immune response. This review emphasizes the growing body of evidence supporting the therapeutic potential of polyphenols in combating neurodegeneration and neuroinflammation, as well as enhancing brain health. Despite the substantial evidence and promising hypotheses, further research and clinical investigations are necessary to fully understand the role of polyphenols and establish them as advanced therapeutic targets for age-related neurodegenerative diseases and neuroinflammatory conditions.

Retinoic acid-induced survival effects in SH-SY5Y neuroblastoma cells

Neuroblastoma is a malignant childhood cancer arising from the embryonic sympathoadrenal lineage of the neural crest. Retinoic acid (RA) is included in the multimodal therapy of patients with high-risk neuroblastoma to eliminate minimal residual disease. However, the formation of RA-resistant cells substantially lowers 5-year overall survival rates. To examine mechanisms that lead to treatment failure, we chose human SH-SY5Y cells, which are known to tolerate incubation with RA by activating the survival kinases Akt and extracellular signal-regulated kinase 1/2. Characterization of downstream pathways showed that both kinases increased the phosphorylation of the ubiquitin ligase mouse double minute homolog 2 (Mdm2) and thereby enhanced p53 degradation. When p53 signaling was sustained by blocking complex formation with Mdm2 or enhancing c-Jun N-terminal kinase (JNK) activation, cell viability was significantly reduced. In addition, Akt-mediated phosphorylation of the cell-cycle regulator p21 stimulated complex formation with caspase-3, which also contributed to cell protection. Thus, treatment with RA augmented survival signaling and attenuated basal apoptotic pathways in SH-SY5Y cells, which increased cell viability.