In vivo susceptibility to energy failure parkinsonism and LRRK2 kinase activity

Area of Science:

• Neuroscience
• Genetics
• Pharmacology

Background:

• The G2019S mutation in Leucine-Rich Repeat Kinase 2 (LRRK2) is a significant genetic risk factor for idiopathic Parkinson's disease (PD).
• LRRK2 kinase activity is implicated in PD pathogenesis, but its role in environmental toxin susceptibility remains unclear.

Purpose of the Study:

• To investigate the role of LRRK2 kinase activity in susceptibility to the neurotoxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP).
• To evaluate the neuroprotective potential of LRRK2 kinase inhibitors in an MPTP-induced parkinsonism mouse model.

Main Methods:

• Utilized G2019S knock-in mice, LRRK2 knock-out, kinase-dead, and wild-type littermates.
• Administered subacute MPTP treatment and assessed nigro-striatal degeneration.
• Tested LRRK2 kinase inhibitors (PF-06447475, MLi-2) for preventive and therapeutic effects.
• Analyzed LRRK2 Serine935 phosphorylation, striatal dopaminergic terminals, and glial fibrillary acidic protein (GFAP) expression.

Main Results:

• G2019S knock-in mice exhibited exacerbated nigro-striatal degeneration after MPTP exposure compared to controls.
• LRRK2 kinase inhibitors (PF-06447475 and MLi-2) conferred significant protection against MPTP-induced dopamine cell loss in G2019S mice.
• MLi-2 treatment rescued striatal dopaminergic terminal damage in both G2019S and wild-type mice.
• MPTP treatment increased GFAP expression, indicating neuroinflammation, similarly in wild-type and G2019S mice.

Conclusions:

• Enhanced LRRK2 kinase activity, as seen with the G2019S mutation, increases vulnerability to mitochondrial toxin-induced parkinsonism.
• LRRK2 kinase inhibitors represent a promising therapeutic strategy for mitigating neurodegeneration in LRRK2-associated parkinsonism.