Reduced levels of intestinal neuropeptides and neurotrophins in neurotoxin-induced Parkinson disease mouse models

Abstract

Intestinal neuropeptides and neurotrophins as endocrine messengers play a key role in the bidirectional gut-brain interaction both in health and disease status. Their alterations in several neurological disorders have been reported, but whether a remarkable change occurs in Parkinson disease (PD) remains unexplored. In this study, we aimed to investigate the levels of 13 neuropeptides and 4 neurotrophins in the intestine of neurotoxin-induced PD mice. The PD mice were obtained by chronic injection of 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) or MPTP/probenecid (MPTP/p). The levels of mRNA and protein expression in mouse intestines were measured by using real-time reverse transcription polymerase chain reaction and Western blotting, respectively. We found that the mRNA expression of 2 neuropeptides (cholecystokinin [CCK] and dynorphin A [Dyn A]) and 2 neurotrophins (brain-derived neurotrophic factor [BDNF] and neurotrophin-5) was significantly decreased in the colon of MPTP group compared to the vehicle-treated group. The protein levels of CCK, Dyn A, and BDNF were reduced in the colon of MPTP- or MPTP/p-treated mice compared to those of the vehicle-treated group. These data suggest that the intestinal expression of CCK, Dyn A, and BDNF was significantly reduced in PD animal models, and may play a role in the gut-brain axis in PD.