THE ROLE OF TLR4-MEDIATED PTEN/PI3K/AKT/NF-κB SIGNALING PATHWAY IN NEUROINFLAMMATION IN HIPPOCAMPAL NEURONS

This study investigated a possible role for a toll-like receptor 4 (TLR4)-mediated PTEN/PI3K/AKT/NF-kappa B signaling pathway in neuroinflammation in rat hippocampal neurons. Cultured neurons were treated with lipopolysaccharide (LPS), a TLR4 ligand, or pre-treated with TLR4 antibodies to block TLR4 signaling. Neurons were also treated with dipotassium bisperoxo (pyridine-2-carboxyl) oxovanadate [bpV(pic)] and pyrrolidine dithiocarbamate (PDTC), selective inhibitors of PTEN and NF-kappa B, respectively, in the presence of LPS. The levels of PTEN, AKT, and their phosphorylated forms were evaluated, along with the nuclear localization of NF-kappa B, to assess pathway activation. The induction of a neuroinflammatory response was determined by measuring TNF-alpha and IL-1 beta mRNA and protein levels. The results indicated that while LPS stimulation had no effect on PTEN and AKT expression, the levels of phosphorylated PTEN (pPTEN) decreased, while phosphorylated AKT (pAKT) levels increased. Moreover, LPS treatment induced the nuclear translocation of NF-kappa B, and increased the expression and secretion of TNF-alpha and IL-1 beta. Blocking TLR4 increased the levels of pPTEN and decreased the levels of pAKT, while pre-treatment with bpV(pic) led to a reduction in levels of pPTEN and pAKT. Furthermore, treatment with TLR4 antibody, bpV(pic), and PDTC decreased LPS-induced nuclear translocation of NF-kappa B, and resulted in a downregulation of TNF-alpha and IL-1 beta expression. Taken together, these results provide evidence for a TLR4-mediated PTEN/PI3K/AKT/NF-kappa B signaling pathway in rat hippocampal neurons, which is associated with the activation of a neuroinflammatory response. (C) 2014 IBRO. Published by Elsevier Ltd. All rights reserved.