Concerning the decrease in cytosolic 5′-nucleotidase activity observed in SH-SY5Y cells following Xn exposure, this effect may also contribute to a protective effect against Alzheimer’s disease since a previous study conducted by our group has also revealed a significant reduction in cytosolic 5′-nucleotidase activity in the frontal cortex of human patients with Alzheimer’s [24]. Here, NT5E is linked to Alzheimer disease.