PTEN is a dual phosphatase that negatively regulates the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway important for cell survival. We determined effects of the inflammation and oxidative stresses of tumor necrosis factor-α (TNFα) and trans-4-hydroxy-2-nonenal (HNE), respectively, on PTEN, Akt, and GSK3β signalling in rat primary cortical neurons. The inhibitors bisperoxovanadium [bpV(Pic)] and LY294002 were also used to determine PTEN and PI3K involvement in TNFα and HNE modulation of neuronal cell death. PTEN inhibition with bpV(Pic) alone did not affect Ser473Akt or Ser9GSK3β phosphorylation. Instead, effects of this inhibitor were manifest when it was used together with TNFα and to a lesser extent with HNE. TNFα together with PTEN inhibition increased phosphorylation of Ser473Akt and Ser9GSK3β. TNFα and HNE both gave decreased numbers of viable and increased numbers of early apoptotic neurons. PTEN inhibition partially reversed the toxic effect of TNFα as shown by an increased number of viable and a decreased number of early apoptotic neurons. All effects were reversed by PI3K inhibition. HNE together with inhibition of PTEN gave increased Ser473Akt but not Ser9GSK3β phosphorylation and no effects on the number of viable or early apoptotic cells. In conclusion, PTEN inhibition gives a mild reversal of TNFα- but not HNE-induced cell death via the PI3K pathway. © 2006 Wiley-Liss, Inc.