Amyloid beta-protein_1-42 increases cAMP and apolipoprotein E levels which are inhibited by β₁ and β₂-adrenergic receptor antagonists in mouse primary astrocytes

Amyloid beta-protein (Aβ) increases apolipoprotein E (apoE) levels in astrocytes which could alter lipid trafficking. The mechanism for the Aβ-induced increase in apoE levels is not well understood. It is well established that stimulation of β-adrenergic receptors (βARs) increases cAMP levels. Elevation of cAMP levels increases apoE abundance. The current study determined if Aβ_1-42 stimulation of cAMP and apoE levels could be inhibited by βAR antagonists in astrocytes. We demonstrate that Aβ_1-42 but not the reverse protein Aβ_42-1 or Aβ_1-40 stimulated cAMP formation and this stimulation was inhibited by selective βAR antagonists in mouse primary cortical astrocytes. Aβ_1-42 significantly increased apoE levels which were significantly inhibited by the βAR selective antagonists with the greatest inhibition observed with the β₂ antagonist. Separate lines of evidence have suggested that agonist-induced stimulation of βARs and increases in apoE abundance may serve a neuroprotective role in astrocytes. Our results indicate a potential interaction between βARs and apoE which may contribute to reducing Aβ_1-42 neurotoxicity.