PDE4A and Alzheimer disease: An AD cell model was constructed by treating SK‐N‐SH cells with Aβ1–42, and the results indicated that circAXL and PDE4A (phosphodiesterase 4A), a key regulator of cAMP (cyclic adenosine monophosphate) degradation, was upregulated, whereas the expression of miR‐1306‐5p was downregulated.