Knockdown transgenic Lrrk Drosophila resists paraquat-induced locomotor impairment and neurodegeneration: A therapeutic strategy for Parkinson's disease

Leucine-rich repeat kinase 2 (LRRK2) has been linked to familial and sporadic Parkinson's disease. However, it is still unresolved whether LRRK2 in dopaminergic (DAergic) neurons may or may not aggravate the phenotype. We demonstrate that knocking down (KD) the Lrrk gene by RNAi in DAergic neurons untreated or treated with paraquat (PQ) neither affected the number of DAergic clusters, tyrosine hydroxylase (TH) protein levels, lifespan nor locomotor activity when compared to control (i.e. TH/+) flies. KD transgenic Lrrk flies dramatically increased locomotor activity in presence of TH enzyme inhibitor alpha-methyl-para-tyrosine (aMT), whereas no effect on lifespan was observed in both fly lines. Most importantly, KD Lrrk flies had reduced lipid peroxidation (LPO) index alone or in presence of PQ and the antioxidant minocycline (MC, 0.5 mM). Taken together, these findings suggest that Lrrk appears unessential for the viability of DAergic neurons in D. melanogaster. Moreover, Lrrk might negatively regulate homeostatic levels of dopamine, thereby dramatically increasing locomotor activity, extending lifespan, and reducing oxidative stress (OS). Our data also indicate that reduced expression of Lrrk in the DAergic neurons of transgenic TH>Lrrk-RNAi/+ flies conferred PQ resistance and absence of neurodegeneration. The present findings support the notion that reduced/suppressed LRRK2 expression might delay or prevent motor symptoms and/or frank Parkinsonism in individuals at risk to suffer autosomal dominant Parkinsonism (AD-P) by blocking OS-induced neurodegenerative processes in the DAergic neurons.