Neuroinflammatory and Motor Alterations in LRRK2*G2019S Transgenic Mice Without Enhanced Vulnerability to Aging or Chronic MPTP-Induced Nigrostriatal Neurodegeneration.
García-Swinburn R, Morón-Márquez L, et al. • Journal of neurochemistry • 2026
The G2019S mutation modulates the neuroimmune response but does not exacerbate nigrostriatal neurodegeneration in response to mitochondrial dysfunction, highlighting the mutation's complex role in PD pathophysiology.
Key Findings
Results
Young adult hLRRK2*G2019S mice showed significant microglial activation compared to wild-type controls without accompanying nigrostriatal neurodegeneration.
Microglial activation was detected using histological analysis in young adult transgenic mice
Despite the neuroinflammatory signal, no dopaminergic neuron loss was observed in the substantia nigra or striatum
This dissociation between neuroinflammation and neurodegeneration was a key finding in the young adult cohort
Analysis included both histological and neurochemical measures to assess nigrostriatal integrity
Results
Young adult hLRRK2*G2019S mice exhibited deficits in motor coordination compared to wild-type littermates.
Motor coordination deficits were identified through behavioral analysis in young adult transgenic mice
These motor alterations occurred in the absence of detectable nigrostriatal neurodegeneration
The behavioral phenotype was part of a complete characterization using histological, neurochemical, and behavioral analyses
Motor coordination was specifically highlighted as distinct from the hyperactive phenotype seen in aged animals
Results
Aged hLRRK2*G2019S transgenic mice displayed a hyperactive phenotype rather than a hypokinetic parkinsonian phenotype.
Aged transgenic mice showed hyperactivity as assessed by behavioral analysis
No evidence of nigrostriatal neurodegeneration was found in aged transgenic animals
This hyperactive phenotype contrasts with the motor coordination deficits seen in young adult transgenic mice
The absence of neurodegeneration in aged animals indicates the G2019S mutation alone does not confer enhanced vulnerability to aging-related nigrostriatal decline
Results
hLRRK2*G2019S mice did not show exacerbated nigrostriatal neurodegeneration following chronic MPTP exposure compared to wild-type mice.
MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) was administered chronically as a mitochondrial complex I inhibitor to model parkinsonism
No exacerbation of nigrostriatal neurodegeneration was observed in hLRRK2*G2019S mice relative to wild-type counterparts after MPTP treatment
This finding suggests the G2019S mutation does not increase sensitivity to mitochondrial stress
Both dopaminergic neuron counts and neurochemical markers were used to assess neurodegeneration
Results
hLRRK2*G2019S mice treated with MPTP showed altered glial responses compared to wild-type MPTP-treated mice.
Alterations in the glial response induced by MPTP neurotoxic treatment were observed in transgenic mice relative to WT counterparts
This suggests the G2019S mutation modulates the neuroimmune response to mitochondrial toxin exposure
The altered glial response occurred independently of any exacerbation of neurodegeneration
This finding parallels the baseline microglial activation seen in untreated young adult transgenic mice, suggesting a consistent effect of the mutation on neuroinflammatory signaling
Discussion
The LRRK2 G2019S mutation modulates neuroinflammatory responses across multiple contexts without enhancing nigrostriatal neurodegeneration.
Neuroinflammatory alterations were observed both at baseline in young adult mice and in response to MPTP in treated mice
Neither aging nor chronic mitochondrial complex I inhibition exacerbated dopaminergic neurodegeneration in transgenic animals
The authors conclude that the mutation's role in PD pathophysiology is complex and cannot be reduced to simple vulnerability enhancement
Findings are based on a complete characterization using histological, neurochemical, and behavioral analyses across age groups and treatment conditions
What This Means
This research suggests that carrying the LRRK2 G2019S gene mutation — the most common genetic cause of Parkinson's disease — does not make the brain's dopamine-producing neurons more vulnerable to dying, either with aging or when exposed to a toxin that damages mitochondria (the energy factories of cells). Scientists studied mice engineered to carry this human mutation at different ages and after treatment with a chemical called MPTP that causes Parkinson's-like damage. Surprisingly, despite being a major genetic risk factor for Parkinson's disease, the mutation alone did not cause the loss of dopamine neurons that is the hallmark of the disease, and it did not worsen the damage caused by the toxin.
However, the mutation was not without effects. Young adult mice with the mutation showed signs of brain inflammation (specifically activation of immune cells called microglia) and had trouble with motor coordination, even without neuron loss. Older mice with the mutation became abnormally hyperactive rather than showing the slow movement typical of Parkinson's disease. When treated with the MPTP toxin, transgenic mice showed a different pattern of brain immune cell response compared to normal mice, again suggesting the mutation alters how the brain's immune system responds to stress.
This research suggests that the LRRK2 G2019S mutation's contribution to Parkinson's disease may work primarily through changes in brain inflammation and immune signaling rather than by directly making dopamine neurons fragile. This has potential implications for how therapies targeting this mutation are developed, as treatments focused purely on protecting dopamine neurons may not address the mutation's primary biological effects.
García-Swinburn R, Morón-Márquez L, Conde-Naranjo C, García-Roldán E, Espadas I, Rodríguez-Gil A, et al.. (2026). Neuroinflammatory and Motor Alterations in LRRK2*G2019S Transgenic Mice Without Enhanced Vulnerability to Aging or Chronic MPTP-Induced Nigrostriatal Neurodegeneration.. Journal of neurochemistry. https://doi.org/10.1111/jnc.70547