TLR2 and Parkinson disease: Subsequent research confirmed, using different PD models, that abnormal aggregation of α-synuclein in Schwann cells in the intestine leads to gastrointestinal dysfunction and vagus inflammation via the toll-like receptor-2 (TLR2)/myeloid differentiation primary response gene 88 (MyD88)/nuclear factor kappa-B (NF-κB) signaling pathway (Cheng et al., 2023c; Jiang et al., 2023).