TLR7 and Parkinson disease: It has been reported that let-7 was highly expressed in the PD model.509 The expression of exosomal let-7 in CSF of PD patients was upregulated.510 When exosomal let-7 is absorbed by neurons, it leads to neurodegenerative changes by activating TLR7.511 In addition, in C. elegans PD model, silence of let-7 decreases the accumulation of α-SYN protein, thereby alleviating the progression of PD.512