Introduction: Parkinson’s Disease (PD) is a progressive neurodegenerative condition characterized by motor function loss. While genetic factors contribute to the development of PD, environmental influences also play a significant role. Copper (Cu)-containing pesticides have been linked with incident PD. We investigated if exposure to Cu-based pesticides is associated with an increased risk of developing PD and if this association is causal using a zebrafish (ZF) model. Methods: We investigated the association of Cu-containing pesticides to PD risk using data from the Parkinson's Environment and Gene study. Exposure was assessed using residential and occupational proximity to agricultural sites applying Cu-based pesticides over multi-decade periods. ZF larvae exposed to an environmentally relevant 500 nM dose of Cu sulfate (CuSO4) were assessed at 7 days post fertilization, with locomotion measured using ZebraBox under light-dark cycling and dopaminergic (DA) and non-DA sensory neuron numbers quantified by immunohistochemistry. Results: Exposure to ≥3 Cu-based pesticides was associated with increased PD risk (OR = 1.83 occupational; 1.46 residential). ZF larvae showed dose-dependent locomotor deficits and a 28% loss of DA neurons, with no effect on sensory neurons, indicating selective neurotoxicity. Conclusions: Exposure to Cu-based pesticides is associated with an increased risk of developing PD. ZF studies suggest that this association may be causal since larvae exposed to CuSO4 recapitulate some PD pathology.

Glioblastoma (GBM) progression is associated with alterations in extracellular pH (pHe) driven by rapid tumor growth and metabolism. Distinct pH environments exist between contrast-enhancing (CE) solid tumor and non-enhancing (NE) infiltrative regions, requiring tumor cells to adapt their pH regulatory mechanisms for survival. The sodium–bicarbonate cotransporter SLC4A4, which buffers intracellular pH in cortical astrocytes, may play a role in this adaptation. Tumor tissue from patients undergoing surgery for newly diagnosed IDH-wildtype GBM was analyzed to examine SLC4A4 expression and function in infiltrating tumor cells. Single-nucleus RNA sequencing (n=15), spatial transcriptomics (n=3), and immunohistochemistry (n=20) were used to characterize SLC4A4 expression beyond the CE margin. Functional studies were performed using SLC4A4 knockdown models in gliomaspheres and a tumor–cortical organoid model of infiltrating gliomasphere. PHe buffering was measured using pH-sensitive microelectrodes during acid titration assays. Single-nucleus and spatial transcriptomics identified SLC4A4 as highly expressed in infiltrating glioblastoma cells, with significantly increased protein expression in NE regions (p=0.0390). NE cells were sensitive to decreases in pHe (p=0.0105), and downmodulation of SLC4A4 increased tumor cell proliferation in organoid models (p=0.0410). These findings identify SLC4A4 as a regulator of pH adaptation in NE GBM and suggest that targeting pH buffering mechanisms may limit tumor invasion and recurrence.

Microglia are the immune cells of the brain. They developed from macrophage cells and are known for removing cellular debris, combating pathogenic activity and responding to neurological changes via inflammation. However, their functions are diversely significant, with research demonstrating that they contact neurons for synaptic pruning, potentiation and overall influence neuroplasticity. Microglia are also extremely heterogeneous, as found by our lab, and showcase unique gene expression patterns in different regions under different contexts. Satellite microglia are a subset of microglia that make direct contacts with neuronal bodies to regulate transmission. Our lab has found that dopamine circuitry, associated with reward, movement and motivation, especially in the midbrain regions of the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc), have heterogeneous, age-dependent and region specific interactions with satellite microglia in murine models. Our lab has found specifically, in the context of aging, satellite microglia in dopamine regions are increased, which we hypothesize is due to increased neural regulation with age. I have specifically worked on older subpopulations of mice to quantify satellite microglia. These findings have led us to develop further predictions such as the role of satellite microglia in suppressing increased neuronal activity. This can be used for studies beyond aging mice, such as murine models exposed to opioids or neurodegeneration or traumatic brain injuries (TBI).

Over a third of Alzheimer’s disease (AD) risk loci are expressed in microglia. Among these microglia-enriched AD GWAS genes, the P522R variant of PLCG2 is protective against AD, while the R47H variant of TREM2 is an AD-risk allele. PLCG2 acts downstream of TREM2, mediating signaling for recognizing and internalizing fibrillar Aβ. Prior studies, including ours, show that increasing TREM2 levels ameliorated AD phenotypes, while Trem2 deficiency impaired microglial response to amyloid plaques. Our recent study showed that the Plcg2-P522R knock-in mutation enhanced microglial function and reduced amyloid deposition. To determine if TREM2 is required for the protective effects of PLCG2-P522R, we performed epistatic genetic analysis. While loss of Trem2 did not impair the plaque-reducing effect of Plcg2-P522R in 5xFAD mice, neuropathological analyses revealed fewer plaque-associated microglia in Trem2-deficient mice. These findings suggest that while TREM2 regulates microglial recruitment to the plaques, PLCG2-P522R may independently promote microglial engagement. These results align with our prior finding that Plcg2-P522R enhances homeostatic microglial responses to Aꞵ without altering microglial states under advanced AD pathology. Additionally, we explored a translational approach by transplanting PLCG2-P522R-expressing hematopoietic stem cells into 5xFAD mice. Preliminary results indicate that exogenous Plcg2-P522R microglia lower plaque burden, though further validation is needed.