LRRK2 and Parkinson disease: Many mutational factors that cause PD, including α-syn, Leucine-rich repeat kinase 2 (LRRK2), Glucocerebrosidase (GBA), Parkin RBR E3 Ubiquitin Protein Ligase (PRKN), Parkin RBR E3 Ubiquitin Protein Ligase (PINK1), and Parkin RBR E3 Ubiquitin Protein Ligase (DJ-1), etc. They are all associated with intestinal and neuroinflammation (Keshavarzian et al., 2015; Wang L. et al., 2022b).