The level of lipopolysaccharide (LPS) is higher in the blood and brains of patients with Alzheimer's disease (AD), and this phenomenon is strongly linked to AD-related neuronal damage and β-amyloid (Aβ) generation. However, the mechanism by which LPS causes neuronal damage has still not been fully clarified. Oxidative stress, neuroinflammation, and Ca2+ overload are regarded as important factors influencing AD. NADPH oxidase 2 (NOX2) and the NOD-like receptor family protein 1 (NLRP1) inflammasome play important roles in promoting oxidative stress and inflammation in neurons. Ca2+ overload can activate calcineurin (CN), which further dephosphorylates nuclear factor of activated T cells (NFAT), leading to its translocation into the nucleus to regulate gene transcription. In the present study, LPS (250 µg/kg) exposure for 14 days was used to induce cognitive dysfunction in mice and LPS (20 µg/ml) exposure for 48 h was used to induce neuronal damage in HT22 cells. The results showed that LPS exposure activated phospholipase C (PLC), CN, and NFAT1; increased the expressions of NOX2- and NLRP1-related proteins; and promoted neuronal damage and Aβ deposition in mice and HT22 cells. However, treatment with 2-APB (SOCE inhibitor), apocynin (NOX inhibitor), or tempol (reactive oxygen species scavenger) significantly reversed these LPS-induced changes, and improved neuronal damage and Aβ deposition. Moreover, LPS exposure promoted PLC phosphorylation, increased the level of inositol-1,4,5-triphosphate, elevated the intracellular Ca2+ concentration ([Ca2+]i), and disrupted [Ca2+]i homeostasis in HT22 cells. These data indicated that the activation of SOCE-mediated NFAT1-NOX2-NLRP1 inflammasome involves in LPS-induced neuronal damage and Aβ generation.
Keywords: Alzheimer's disease; Ca2+ homeostasis; Lipopolysaccharide; NADPH oxidase 2; NLRP1 inflammasome; Nuclear factor of activated T cells.
© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.