Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopamin-ergic neurons responsible for unintended or uncontrollable movements. Mutations in leu-cine-rich repeat kinase 2 locus, contributes to genetic forms of PD. The fruit fly Drosophila mela-nogaster carrying this mutation (LRRK2-Dm), is an in vivo model of PD that develops motor impairment and stands for an eligible non mammalian paradigm to test novel therapeutic ap-proaches. Dehydrozingerone (DHZ) is a natural phenolic compound isolated from ginger. Pre-sents anti-inflammatory, antioxidant and neuroprotective properties making it a potential therapeutic target for PD. We administered DHZ and its C2-symmetric dimer (DHZ-DIM) at 0.5 and 1mM, for 14 and 21 days, in the LRRK2-Dm, with the aim to assess changes for rescuing motor behavior, brain dopaminergic neurons, mitochondria and synapses (T-Bars). The shorter treat-ment with both molecules revealed efficacy at the higher dose improving climbing behavior with a prevention of dopaminergic neuronal demise. After 21 days, a recovery of the motor disability, dopaminergic neuron loss, mitochondrial damage and T-Bars failure was observed with the DHZ-DIM. Our data indicates that the DHZ-DIM exerts a more potent neuroprotective effect respect to the monomer in LRRK2-Dm, prompting further investigation of these compounds in rodent models of PD.

Missense mutations in the LRRK2 gene were first identified as a pathogenic cause of Parkinson’s disease (PD) in 2004. Soon thereafter, a founder mutation in LRRK2, p.Gly2019Ser (rs34637584), was described, and it is now estimated that there are approximately 100,000 people worldwide that carry this risk variant. While the clinical presentation of LRRK2 parkinsonism has been largely indistinguishable from sporadic PD, disease penetrance and age at onset can be quite variable. In addition, its neuropathological features span a wide range from nigrostriatal loss with Lewy body pathology, lack thereof, or atypical neuropathology including a large proportion of cases with concomitant Alzheimer’s pathology, hailing LRRK2 parkinsonism as the "Rosetta stone" of parkinsonian disorders. These differences may result from interactions between LRRK2 mutant protein and other proteins or environmental factors that modify LRRK2 function, and thereby influence pathobiology. This review explores how potential genetic and biochemical modifiers of LRRK2 function may contribute to the onset and clinical presentation of LRRK2 parkinsonism. We review, which genetic modifiers of LRRK2 influence clinical symptoms, age at onset, and penetrance, what LRRK2 mutations are associated with pleomorphic LRRK2 neuropathology, and which environmental modifiers can augment LRRK2 mutant pathophysiology. Understanding how LRRK2 function is influenced and modulated by other interactors and environmental factors –either increasing toxicity or providing resilience- will inform targeted therapeutic development in the years to come. This will allow developing disease-modifying therapies for PD and LRRK2-related neurodegeneration.

The movement toward prevention trials in people at-risk for Parkinson’s is rapidly becoming a reality. The authors of this article include a genetically at-risk advocate with the LRRK2 G2019S variant and two patients with rapid eye movement sleep behavior disorder (RBD), one of whom has now been diagnosed with Parkinson’s disease (PD). These authors participated as speakers, panelists, and moderators in the “Planning for Prevention of Parkinson’s: A Trial Design Forum” hosted by Massachusetts General Hospital in 2021 and 2022. Other authors include a young onset person with Parkinson’s (PwP) and retired family physician, an expert in patient engagement in Parkinson’s, and early career and veteran movement disorders clinician researchers. Several themes emerged from the at-risk participant voice concerning the importance of early intervention, the legitimacy of their input in decision-making, and the desire for transparent communication and feedback throughout the entire research study process. Challenges and opportunities in the current environment include lack of awareness among primary care physicians and general neurologists about PD risk, legal and psychological implications of risk disclosure, limited return of individual research study results, and undefined engagement and integration of individuals at-risk into the broader Parkinson’s community. Incorporating the perspectives of individuals at-risk as well as those living with PD at this early stage of prevention trial development is crucial to success.

Parkinson’s disease (PD) is characterized by motor deficits and a wide variety of non-motor symptoms. The age of onset, rate of disease progression and the precise profile of motor and non-motor symptoms display considerable individual variation. Neuropathologically, the loss of substantia nigra dopaminergic neurons is a key feature of PD. The vast majority of PD patients exhibit alpha-synuclein aggregates in several brain regions, but there is also great variability in the neuropathology between individuals. While the dopamine replacement therapies can reduce motor symptoms, current therapies do not modify the disease progression. Numerous clinical trials using a wide variety of approaches have failed to achieve disease modification. It has been suggested that the heterogeneity of PD is a major contributing factor to the failure of disease modification trials, and that it is unlikely that a single treatment will be effective in all patients. Precision medicine, using drugs designed to target the pathophysiology in a manner that is specific to each individual with PD, has been suggested as a way forward. PD patients can be stratified according to whether they carry one of the risk variants associated with elevated PD risk. In this review we assess current clinical trials targeting two enzymes, leucine-rich repeat kinase 2 (LRRK2) and glucocerebrosidase (GBA), which are encoded by two most common PD risk genes. Because the details of the pathogenic processes coupled to the different LRRK2and GBA risk variants are not fully understood, we ask if these precision medicine-based intervention strategies will prove “precise“ or “personalized“ enough to modify the disease process in PD patients. We also consider at what phases of the disease that such strategies might be effective, in light of the genes being primarily associated with the risk of developing disease in the first place, and less clearly linked to the rate of disease progression. Finally, we critically evaluate the notion that therapies targeting LRRK2 and GBA might be relevant to a wider segment of PD patients, beyond those that actually carry risk variants of these genes.