Nora E. Gray

Background: Inflammation is an early event that substantially influences Alzheimer’s disease (AD) pathogenesis, making it a compelling target for therapeutic intervention. Sob-AM2 is a brain-penetrating thyromimetic drug capable of inducing the expression of microglial cell surface receptor TREM2, which mediates the switch from pro-inflammatory to a more restorative microglial state. Objective: Evaluate the effects of Sob-AM2 on cognition, AD pathology and microglial activity in the 5xFAD mouse model of amyloid-beta (Aβ) accumulation. Methods: Seven-month-old 5xFAD mice and their wild-type littermates were administered Sob-AM2 subcutaneously three times per week for 12 weeks. In the last two weeks of treatment mice underwent behavioral tests to assess cognition and monitor for off-target mobility effects. At the end of treatment, brain tissue was harvested for gene and protein expression analyses. Results: Sob-AM2 treatment increased TREM2 expression in the brains of 5xFAD mice. This was accompanied by an improvement in both spatial and associative memory as well as an increase in the expression of synaptic genes synaptophysin and PSD-95. No significant changes were detected in Aβ plaque burden or the expression of microglial activation marker Iba1 in Sob-AM2 treated animals, however, the expression of the phagocytic marker CD68 was significantly increased in the hippocampus, but not the cortex, in Sob-AM2 treated 5xFAD mice. Conclusion: These results suggest that the cognitive-enhancing effects of Sob-AM2 are not the result of reduced overall plaque burden. Future work is needed to further investigate the neuroprotective mechanism of Sob-AM2 and how it may be affecting microglial phenotypes.

Parkinson’s Disease (PD) is the second most diagnosed neurological disorder globally, affecting millions of people worldwide. Oxidative stress is implicated in the progression of PD, yet its direct effects on motor function, particularly in the context of synucleinopathy, are not fully understood. Here, we investigated the effects of the loss of the antioxidant regulatory transcription factor NRF2 in the A53TSyn mouse model of synucleinopathy. Motor function was evaluated in separate cohorts of A53TSyn mice without NRF2 (A53TSyn/NRF2KO), as well as A53TSyn mice expressing NRF2 (A53TSyn/NRF2+) and healthy wild-type (WT) mice at four, six, and eight months of age. The overall mobility decreased in A53TSyn/NRF2KO mice relative to WT mice at all ages. Significant alterations in gait were also apparent in A53TSyn/NRF2KO mice compared to A53TSyn mice without NRF2 deletion. Expression of tyrosine hydroxylase (TH) was also quantified in the brains of those mice. While there were no differences in cortical pSyn expression between A53TSyn/NRF2+ and A53TSyn/NRF2KO mice, a reduction in TH abundance in the striatum was evident in A53TSyn/NRF2KO mice at all ages. In summary, our data suggest that NRF2 plays a role in maintaining mobility and gait in the context of synucleinopathy and may represent a therapeutic target to mitigate mobility decline in PD-affected individuals.

Heterozygote carriers of Gaucher's disease mutations and other polymorphisms in the glucocerebrosidase (GBA) gene show an increased incidence of Parkinson's disease. We hypothesized that common GBA polymorphisms would be associated with subtle parkinsonian features, mild cognitive impairment, and “silent” Lewy body (LB) pathology in aging individuals without a clinical diagnosis of parkinsonism. The most prevalent GBA variants, T369M and E326K, appear in the general population at rates of approximately 0.6% and 1%, respectively. We evaluated 845 participants from the Oregon Alzheimer's Disease Research Center (OADRC) with SNP data generated by the National Centralized Repository of Alzheimer's Disease (NCRAD). Twenty-one subjects were E326K carriers and eighteen were T369M carriers. Clinical measures and postmortem neuropathology were compared between each SNP group and non-carriers. Although there were no statistically significant clinical differences related to synucleinopathy across groups, neuropathological analyses revealed a significantly higher prevalence of LB pathology in E326K carriers compared to T369M carriers. When stratifying each genetic group by LB status (LB+ or LB−), LB+ E326K carriers demonstrated a significant reduction in Mini-Mental State Examination (MMSE) scores compared with LB− non-carriers and a modest decrease compared with T369M carriers. These preliminary findings from a small, uni-center cohort suggest that the E326K GBA polymorphism may predict LB pathology and subtle cognitive decline in aging individuals who lack overt parkinsonian symptoms. Further validation in a larger cohort is warranted. Identifying at-risk individuals through targeted genetic screening may ultimately support earlier intervention and preventative care strategies.

Background/objectives: A water extract of the plant Centella asiatica (CAW) has been shown to improve cognitive deficits in aged mice when administered for 5 weeks in drinking water. However, the contribution of the constituent compounds within CAW to the beneficial effects of the extract remains unelucidated. This study evaluated the effects of triterpene (TT) and caffeoylquinic acids (CQA) found within CAW, on learning, cognitive flexibility, memory, and anxiety-like behaviors in aged C57BL6 mice. Methods: Eighteen-month-old male and female C57BL6 mice were administered either TT, CQA, or the combination (TT+CQA) in their drinking water for a total of 5 weeks, at concentrations corresponding to their presence in CAW. During the final two weeks of treatment learning, executive function, memory, and anxiety were assessed. Results: Aged mice of both sexes showed significant improvement in learning when treated with TT and CQA separately and in combination. Treatment with TT also improved cognitive flexibility in aged mice of both sexes, but CQA and the combination of TT+CQA did not alter cognitive flexibility in aged male mice. There was no effect on recognition memory or anxiety in any of the treatment groups (TT, CQA, TT+CQA) relative to mice treated with the vehicle control although there was a trend towards improved recognition memory with TT treatment. Conclusions: These results suggest that the TT and CQA present in CAW likely contribute to its previously reported amelioration of age-related cognitive changes, especially in learning and cognitive flexibility, while other constituents may be responsible for CAW’s anxiolytic effects.

Mitochondrial dysfunction is increasingly recognized as a key driver of pathology in patients with Parkinson's disease (PD). Peripheral blood mononuclear cells (PBMCs) have emerged as an accessible way to characterize mitochondrial function in PD. The aim of this study was to conduct a preliminary evaluation of the clinical relevance of PBMC mitochondrial function as a biomarker in early PD. PBMC mitochondrial bioenergetics were measured using the Seahorse XF platform in individuals with de novo, untreated PD (n = 13) and compared to age- and sex-matched healthy controls (n = 15). Correlations between mitochondrial endpoints and clinical outcomes were assessed in the PD group. Basal and ATP-linked respiration were elevated in the PD group (p = 0.002, p = 0.004), while spare capacity, or the cell's ability to handle an unexpected energetic stress, was decreased (p = 0.045), relative to controls. Notably, the variability within basal respiratory measurements was markedly increased in the PD group compared to controls (p = 0.002). Further analyses revealed significant correlations between spare capacity and clinical motor function scores within the PD group. These findings support the potential of PBMC bioenergetics as a biomarker for early-stage PD as well as disease progression.

Background/Objectives: Extracts of the plant Centella asiatica can enhance mitochondrial function, promote antioxidant activity and improve cognitive deficits. Asiatic acid (AA) is one of the constituent triterpene compounds present in the plant. In this study, we explore the effects of AA on brain mitochondrial function, antioxidant response and cognition in a beta-amyloid (Aβ)-overexpressing 5xFAD mouse line. Methods: Six- to seven-month-old 5xFAD mice were treated with 1% AA for 4 weeks. In the last week of treatment, associative memory was assessed along with mitochondrial bioenergetics and the expression of mitochondrial and antioxidant response genes from isolated cortical synaptosomes. The Aβ plaque burden was also evaluated. Results: AA treatment resulted in improvements in associative memory in female 5xFAD mice without altering the Aβ plaque burden. Cortical mitochondrial function and mitochondrial gene expression were increased in the AA-treated female 5xFAD mice, as was the expression of antioxidant genes. More modest effects of AA on cortical mitochondrial function and mitochondrial and antioxidant gene expression were observed in male 5xFAD mice. Conclusions: Oral AA treatment improved cognitive and mitochondrial function and activated antioxidant in Aβ-overexpressing mice. These changes occurred independent of alterations in Aβ plaque burden, suggesting that AA could have translational therapeutic relevance in later-stage AD when plaques are well established.

Neuroinflammation and mitochondrial dysfunction are early events in Alzheimer’s disease (AD) and contribute to neurodegeneration and cognitive impairment. Evidence suggests that the inflammatory axis mediated by macrophage migration inhibitory factor (MIF) binding to its receptor, CD74, plays an important role in many central nervous system (CNS) disorders such as AD. Our group has developed DRhQ, a novel CD74 binding construct which competitively inhibits MIF binding, blocks macrophage activation and migration into the CNS, enhances anti-inflammatory microglia cell numbers and reduces pro-inflammatory gene expression. Here, we evaluate its effects in amyloid-β (Aβ) overexpressing mice. 5xFAD mice and their wild type littermates were treated with DRhQ (100 µg) or vehicle for 4 weeks. DRhQ improved cognition and cortical mitochondrial function in both male and female 5xFAD mice. Aβ plaque burden in 5xFAD animals was not robustly impacted by DRhQ treatment in either the hippocampus or the cortex. Cortical microglial activation was similarly not apparently affected by DRhQ treatment, although in the hippocampus there was evidence of a reduction in activated microglia for female 5xFAD mice. Future studies are needed to confirm this possible sex-dependent response on microglial activation, as well as to optimize the dose and timing of DRhQ treatment and gain a better understanding of its mechanism of action in AD.

Alterations in epigenetic modifications, like DNA methylation, in peripheral blood could serve as a useful, minimally invasive biomarker of the effects of anti-aging interventions. This study explores this potential with a water extract of the botanical Centella asiatica (CAW). Eighteen-month-old mice were treated with CAW in their drinking water for 5 weeks alongside vehicle-treated eighteen-month-old C57BL6 mice. Reduced representation bisulfite sequencing (RRBS) was used to identify genome-wide differential methylation in the blood of CAW-treated aged mice compared to vehicle-treated aged mice. Our results showed a distinct enrichment of differentially methylated regions (DMRs) nearby genes involved in biological processes relevant to aging (i.e., antioxidant response, metabolic regulation, cellular metabolism). A distinct difference was observed between males and females in both the number of methylation sites and the state of methylation. Moreover, genes nearby or overlapping DMRs were found to be enriched for biological processes related to previously described cellular effects of CAW in the mouse brain (i.e., antioxidant response, metabolic regulation, calcium regulation, and circadian rhythm). Together, our data suggest that the peripheral blood methylation signature of CAW in the blood could be a useful, and readily accessible, biomarker of CAW’s effects in aging.

Background: A water extract of the Ayurvedic plant Centella asiatica (L.) Urban, family Apiaceae (CAW), improves cognitive function in mouse models of aging and Alzheimer’s disease and affects dendritic arborization, mitochondrial activity, and oxidative stress in mouse primary neurons. Triterpenes (TT) and caffeoylquinic acids (CQA) are constituents associated with these bioactivities of CAW, although little is known about how interactions between these compounds contribute to the plant’s therapeutic benefit. Methods: Mouse primary cortical neurons were treated with CAW or equivalent concentrations of four TT combined, eight CQA combined, or these twelve compounds combined (TTCQA). Treatment effects on the cell transcriptome (18,491 genes) and metabolome (192 metabolites) relative to vehicle control were evaluated using RNAseq and metabolomic analyses, respectively. Results: Extensive differentially expressed genes (DEGs) were seen with all treatments, as well as evidence of interactions between compounds. Notably, many DEGs seen with TT treatment were not observed in the TTCQA condition, possibly suggesting CQA reduced the effects of TT. Moreover, additional gene activity seen with CAW as compared to TTCQA indicates the presence of additional compounds in CAW that further modulate TTCQA interactions. Weighted Gene Correlation Network Analysis (WGCNA) identified 4 gene co-expression modules altered by treatments that were associated with extracellular matrix organization, fatty acid metabolism, cellular response to stress and stimuli, and immune function. Compound interaction patterns were seen at the eigengene level in these modules. Interestingly, in metabolomics analysis, the TTCQA treatment saw the highest number of changes in individual metabolites (20), followed by CQA (15), then TT (8), and finally CAW (3). WGCNA analysis found two metabolomics modules with significant eigenmetabolite differences for TT and CQA and possible compound interactions at this level. Conclusions: Four gene expression modules and two metabolite modules were altered by the four treatment types applied. This methodology demonstrated the existence of both negative and positive interactions between TT, CQA, and additional compounds found in CAW on the transcriptome and metabolome of mouse primary cortical neurons.

Background/Objectives: Centella asiatica (L.) Urban (family Apiaceae) (C. asiatica) is a traditional botanical medicine used in aging and dementia. Water extracts of C. asiatica (CAW) have been used to treat neuropsychiatric symptoms in related animal models and are associated with increases in antioxidant response element (ARE) genes and improvements in mitochondrial respiratory function and neuronal health. Because multiple sclerosis (MS) shares its neurogenerative pathology of oxidative stress and mitochondrial dysfunction with aging and dementia, neuropsychiatric symptoms in MS may also benefit from C. asiatica. To determine whether CAW similarly benefits neuropsychiatric symptoms, ARE gene expression, and mitochondrial respiration in inflammatory models of MS, and to determine the effects of CAW on clinical disability and inflammation, we tested CAW using experimental autoimmune encephalomyelitis (EAE). Methods: C57BL/6J mice induced with EAE were treated with CAW or a placebo for 2 weeks. The outcomes were clinical disability, signs of anxiety (open field test), ARE gene expression, mitochondrial respiration, and inflammation and demyelination. Results: At the dosing schedule and concentrations tested, CAW-treated mice with EAE demonstrated increased ARE gene expression and mitochondrial respiratory activity compared to those of placebo-treated mice with EAE. CAW was also associated with reduced inflammatory infiltrates in the spinal cord, but the differences between the populations of activated versus quiescent microglia were equivocal. CAW did not improve behavioral performance, EAE motor disability, or demyelination. Conclusions: In the inflammatory EAE model of MS, CAW demonstrates similar neuroprotective effects to those it exhibits in aging and dementia mouse models. These benefits, along with the anti-inflammatory effects of CAW, support further investigation of its neuropsychiatric effects in people with MS.