P2‐097: Inhibition of PLA2 inactivates GSK3B via Akt and CAMKII in primary cultures of hippocampal neurons

Abstract

Glycogen synthase kinase 3-beta (GSK3B) is overactive in Alzheimer's disease (AD), favoring the hyperphosphorylation of microtubule-associated protein Tau and the formation of neurofibrillary tangles. For this reason, GSK3B inhibition may be considered as a candidate disease-modifying approach in AD. In addition to the direct enzymatic inhibition (eg. by lithium), GSK3B can be also indirectly inactivated by phosphorylation at the Ser9 residue. This is a downstream effect of several intracellular cascades, including Akt and CaMKII signaling. Phospholipase A 2 (PLA 2) are key enzymes in membrane homeostasis and cell signaling. Reduced PLA 2 activity has been demonstrated in cerebral and peripheral tissues of patients with AD, and recent studies suggested that PLA 2 is further implicated in GSK3B homeostasis. The objective of this study is to evaluate the effect of the inhibition of PLA 2 on the GSK3B activity and to determine whether this effect involves CAMKII and Akt. Primary cultures of cortical and hippocampal neurons started from embryonic rats (E18) were treated after 4 four days in culture with different concentrations (5-250 μM) of methyl-aracdonyl-fluorophosphonate (MAFP), which is an irreversible, dual inhibitor of calcium-dependent and -independent cytosolic PLA 2. Treatment effects were evaluated by Western-blot, addressing the expression of total- and phosphorylated (Ser9) GSK3B, phosphorylated Akt (Ser473), and total CAMKII at protein level. The inhibition of GSK3B is a downstream effect of cytosolic PLA 2 inhibition, which apparently involves the activation of Akt and CAMKII. This effect seems to be specific to hippocampal neurons.