The present disclosure describes that the 15-
lipoxygenase (15-LO) product 4-hydroxynonenal (4HNE or 4-HNE) post-translationally modifies LRRK2 and is believed to induce a pathologically elevated, chronic LRRK2
kinase activity associated with a LRRK2 mediated
disease or condition, e.g., Parkinson's
disease or
frontotemporal dementia. Production of LRRK2-4HNE adducts, e.g., LRRK2 Cys2024-4HNE and / or LRRK2 Cys2025-4HNE
adduct described herein, may be an indication of a LRRK2 mediated
disease or condition. Inhibiting the production of excessive 4HNE in cells by 15-LO inhibitors converted an elevated LRRK2 activity to a normal basal LRRK2
activity level as demonstrated in cellular experiments in the Examples. The 15-LO inhibition of 4HNE production is believed to only remove elevated LRRK2 activity associated with LRRK2 mediated diseases or conditions and not normal LRRK2 activity that may be required for other
cellular functions. Accordingly, 15-LO inhibition of elevated LRRK2 activity and / or expression may afford a safe and
effective treatment for LRRK2 mediated diseases or conditions.