Colonic Bax proteins were not influenced while colonic Bcl-2 protein expression was significantly increased (p < 0.001) in response to chronic MPTP injection, the ratio of Bax/Bcl-2 in the colon was greatly lowered (p < 0.01) in PD mice (vs. Normal; Figure 2B and Supplementary Figure 4B). Here, BCL2 is linked to Parkinson disease.