Leucine-rich repeat kinase-2 (LRRK2) modulates microglial phenotype and dopaminergic neurodegeneration

Leucine-rich repeat kinase 2 (LRRK2) is a common gene implicated in Parkinson's disease and many inflammatory processes. Thus, we assessed the role of LRRK2 in the context of endotoxin (lipopolysaccharide, LPS)-induced inflammation of the substantia nigra together with the environmental toxicant, paraquat, that has been implicated in PD. Here we found that LRRK2 ablation prevented the loss of dopaminergic neurons and behavioral deficits (motor) induced by LPS priming followed by paraquat exposure. The LRRK2 ablation also provoked a phenotypic shift in LPS-primed microglia cells. The LRRK2 deficiency reduced their "activated" morphology and upregulation of the inflammatory phagocytic regulator, WAVE2 (critical for actin remodeling), while the chemokine receptor, CX3CR1, was elevated in isolated CD11b+ myeloid cells. Furthermore, LRRK2 knockout attenuated the signs of oxidative stress and morphological changes induced in primary microglia by LPS treatment. However, induced WAVE2 expression together with LPS exposure in microglia overcame the inhibitory effects of LRRK2 knockout, suggesting WAVE2 may be acting downstream of LRRK2. Neither WAVE2 nor did LRRK2 knockout influence LPS-induced cytokine elevations in the microglia. We are the first to show the importance of LRRK2 in neurodegenerative and inflammatory processes in this multi-hit toxin model of PD. These data are consistent with the proposition that LRRK2 and WAVE2 are useful therapeutic targets for PD or other conditions with a prominent neuroinflammatory component.