IL-33 treatment in D-gal–administered mice significantly downregulated BACE1 protein levels in cortex (Figure 3J and K) and hippocampus (Figure 3J and K) regions, when compared with chronic D-gal–administered mice, suggesting that IL-33 has an inhibitory effect on the progression of amyloid pathology in D-gal–induced aged mice. Here, BACE1 is linked to amyloidosis.