Effect of acidosis on IL-8 and MCP-1 during hypoxia and reoxygenation in human NT2-N neurons

Dexamethasone reduces bilirubin-induced toxicity and IL-8 and MCP-1 release in human NT2-N neurons

The mechanisms of neurotoxicity induced by unconjugated bilirubin (UCB) in newborns are incompletely understood. UCB may cause both necrotic and apoptotic neuronal death. We explored UCB toxicity and release of cytokines in human NT2-N neurons and the effect of dexamethasone on these processes. Cultured NT2-N neurons were exposed to UCB, and neuronal damage was evaluated by LDH release and MTT cleavage. After 96 hours, 2 μM UCB significantly increased release of IL-8 and MCP-1, but not IL-13, IP-10, PDGF, or VEGF. Dexamethasone significantly lowered the UCB-induced increase in MCP-1 release, and attenuated UCB-induced neuronal damage assessed with MTT cleavage and LDH release. For comparison, the effects of hydrogen peroxide on cytokine formation and neuronal damage were tested. Hydrogen peroxide increased MCP-1, IP-10, and VEGF, but not IL-8, IL-13, or PDGF. Dexamethasone inhibited the hydrogen peroxide-induced increase in MCP-1 and IP-10. We conclude that UCB causes release of IL-8 and MCP-1 in cultured human NT2-N neurons. Dexamethasone reduces UCB-induced cytokine release and protects against UCB-induced toxicity.

CXCL8 protects human neurons from amyloid-β-induced neurotoxicity: relevance to Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by amyloid-β (Aβ) deposition in senile plaques colocalized with activated microglia and astrocytes. Recent studies suggest that CXCL8 is involved in the AD pathogenesis. The objective of this study was to determine the cellular sources of CXCL8 in the central nervous system during AD pathogenesis, and investigate the effects of CXCL8 on neuronal survival and/or functions. Our results showed significantly higher CXCL8 levels in AD brain tissue lysates as compared to those of age-matched controls. Upon Aβ and/or pro-inflammatory cytokine stimulation, microglia, astrocytes and neurons were all capable of CXCL8 production in vitro. Although CXCL8-alone did not alter neuronal survival, it did inhibit Aβ-induced neuronal apoptosis and increased neuronal brain-derived neurotrophic factor (BDNF) production. We conclude that microglia, astrocytes and neurons, all contribute to the enhanced CXCL8 levels in the CNS upon Aβ and/or pro-inflammatory cytokine stimulation. Further, CXCL8 protects neurons possibly by paracrine or autocrine loop and regulates neuronal functions, therefore, may play a protective role in the AD pathogenesis.

Neuroprotective effects of the beta-catenin stabilization in an oxygen- and glucose-deprived human neural progenitor cell culture system

β-Catenin stabilization achieved either via GSK-3β specific inhibition or involving canonical Wnt signalling pathway, contributes to neuroprotection in an oxygen-glucose deprivation (4h OGD) in vitro hypoxia model performed on human cortical neural progenitor cells previously differentiated into neurons and glia. Neuroprotection mechanisms include both acquiring tolerance to injury throughout preconditioning (72 h prior to OGD) or being pro-survival during 24h reoxygenation after the insult. Four hours of OGD induced apoptotic cell death elevation to 73 ± 1% vs. 12% measured in control and the LDH level, indicative of necrotic cell injury, elevation by 67 ± 7% (set to 100%). A significant reduction in apoptosis occurred at 24h reoxygenation with indirubin supplement which was 49 ± 6% at 2.5 μM BIO while LDH level was only 47 ± 5% of OGD. Kenpaullone was efficient in reducing both cell deaths at 5 μM (apoptosis 38 ± 1% and necrosis 33 ± 3% less than in OGD). Wnt agonist reduced apoptosis to 45 ± 3% at 0.01 μM, while LDH value was decreased to a level of 53 ± 5% of control. Our findings suggest that GSK-3beta inhibitors/β-catenin stabilizers may ultimately be useful drugs in neuroprotection and neuroregeneration therapies in vivo.