Zinc-induced anti-apoptotic effects in SH-SY5Y neuroblastoma cells via the extracellular signal-regulated kinase 1/2

Zinc levels are increased in brain areas severely affected by Alzheimer's disease (AD) pathologies. Zinc has both protective and neurotoxic properties and can stimulate both phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways. Several kinases related to these pathways including protein kinase B (PKB), p70 S6 kinase (p70S6K), and extracellular signal-regulated kinase 1/2 (ERK1/2) are known cell survival factors and are overactivated in neurons bearing neurofibrillary tangles (NFTs) in AD. The present study aimed to determine whether anti-apoptotic effects of zinc are mediated via these signaling pathways. Zinc was used to treat SH-SY5Y neuroblastoma cells and effects investigated in relation to PKB, p70S6K, and ERK1/2 in the absence and presence of the pro-apoptotic agent staurosporine (STS). Cell damage was evaluated by measuring levels of DNA fragmentation as well as the WST-1 assay for cell viability. Results indicated that: (1) treatment with high doses of zinc (≥400 μM) for short time periods (≤2 h) gave rise to increased levels of DNA fragments, increased cell membrane permeability, and reduced mitochondria membrane potential; (2) treatment with 100 μM zinc for >2 h reversed an increased DNA fragmentation due to U0126 inhibition of ERK1/2; (3) increased DNA fragmentation due to STS could be protected against by 100 μM zinc; (4) the protective effects of 100 μM zinc on STS-induced DNA fragmentation could be partially reversed by U0126. These results indicate that a zinc-induced anti-apoptotic response in SH-SY5Y cells likely occurs through ERK1/2.