As displayed in Figure 3K–P, MPTP administration in PD mice led to a substantial decrease in striatal ZO-1 (Figure 3K, T (6) = 19.82, p < 0.0001), occludin (Figure 3L, T (6) = 11.41, p < 0.0001), claudin-1 (Figure 3M, T (6) = 9.672, p < 0.0001), and colon ZO-1 (Figure 3N, T (6) = 12.27, p < 0.0001), occludin (Figure 3O, T (6) = 6.899, p = 0.0005), and claudin-1 (Figure 3P, T (6) = 9.862, p < 0.0001) mRNA levels. This evidence concerns the gene CLDN1 and Parkinson disease.