Otherwise, the oral administration of P. gingivalis in leucine-rich repeat kinase (LRRK)2 mutant animals, for the emulation of late-onset PD, also led to an increase of the expression of TNF-α, IL-1β, IL-17 A and IL-17RA in the animals’ colon and brain, as well as degeneration of dopaminergic neurons in the substantia nigra [45]. This evidence concerns the gene TNF and Parkinson disease.