Differential Effects of Human P301L Tau Expression in Young versus Aged Mice

Age-related differences in resting glutamate levels and glutamate uptake in the hippocampus and frontal cortex of C57BL/6 mice

In normal aging, little is known in human and animal models about functional changes to glutamate neuronal systems that may contribute to age-related cognitive differences. The present studies investigated glutamate neuronal signaling in the hippocampus (dentate gyrus) and frontal cortex (infralimbic) of young adult (3-8 months), middle-aged (10-13 months), and aged (15-27 months) male and female C57BL/6 mice using microelectrode electrode array (MEA) recording technology to measure second-by-second resting levels of glutamate in anesthetized mice. Glutamate regulation was investigated in vivo by inhibiting the uptake of glutamate by local application of the competitive non-transportable blocker of excitatory amino acid transporters DL-threo-beta-benzyloxyaspartate (TBOA). Resting levels of glutamate and TBOA-induced changes in extracellular glutamate concentration were reliably measured in the hippocampus and frontal cortex of young adult, middle-aged, and aged mice and were seen to significantly increase in aging in the hippocampus. In the frontal cortex we observed an increase only in the middle-aged animals. TBOA produced robust changes in extracellular glutamate in the hippocampus and frontal cortex which showed significant changes in the kinetics of the signals in the middle-aged mice. Interestingly, the variance of the resting glutamate levels in the hippocampus of aged female mice was greater than in aged male mice, supporting a possible age-related gender difference in glutamate function. Taken together, these data support that glutamate signaling in the hippocampus and frontal cortex of aged mice is affected in normal aging with changes in glial regulation of glutamate uptake observed from the TBOA effects in the middle-aged mice.

Troriluzole rescues glutamatergic deficits, amyloid and tau pathology, and synaptic and memory impairments in 3xTg-AD mice

Alzheimer's disease (AD) is a neurodegenerative condition in which clinical symptoms are highly correlated with the loss of glutamatergic synapses. While later stages of AD are associated with markedly decreased glutamate levels due to neuronal loss, in the early stages, pathological accumulation of glutamate and hyperactivity contribute to AD pathology and cognitive dysfunction. There is increasing awareness that presynaptic dysfunction, particularly synaptic vesicle (SV) alterations, play a key role in mediating this early-stage hyperactivity. In the current study, we sought to determine whether the 3xTg mouse model of AD that exhibits both beta-amyloid (Aβ) and tau-related pathology would exhibit similar presynaptic changes as previously observed in amyloid or tau models separately. Hippocampal cultures from 3xTg mice were used to determine whether presynaptic vesicular glutamate transporters (VGlut) and glutamate are increased at the synaptic level while controlling for postsynaptic activity. We observed that 3xTg hippocampal cultures exhibited increased VGlut1 associated with an increase in glutamate release, similar to prior observations in cultures from tau mouse models. However, the SV pool size was also increased in 3xTg cultures, an effect not previously observed in tau mouse models but observed in Aβ models, suggesting the changes in pool size may be due to Aβ and not tau. Second, we sought to determine whether treatment with troriluzole, a novel 3rd generation tripeptide prodrug of the glutamate modulator riluzole, could reduce VGlut1 and glutamate release to restore cognitive deficits in 8-month-old 3xTg mice. Treatment with troriluzole reduced VGlut1 expression, decreased basal and evoked glutamate release, and restored cognitive deficits in 3xTg mice. Together, these findings suggest presynaptic alterations are early events in AD that represent potential targets for therapeutic intervention, and these results support the promise of glutamate-modulating drugs such as troriluzole in Alzheimer's disease.

Evolving alterations of structural organization and functional connectivity in feedforward neural networks after induced P301L tau mutation

Reciprocal structure-function relationships underlie both healthy and pathological behaviours in complex neural networks. Thus, understanding neuropathology and network dysfunction requires a thorough investigation of the complex interactions between structural and functional network reconfigurations in response to perturbation. Such adaptations are often difficult to study in vivo. For example, subtle, evolving changes in synaptic connectivity, transmission and the electrophysiological shift from healthy to pathological states, for example alterations that may be associated with evolving neurodegenerative disease, such as Alzheimer's, are difficult to study in the brain. Engineered in vitro neural networks are powerful models that enable selective targeting, manipulation and monitoring of dynamic neural network behaviour at the micro- and mesoscale in physiological and pathological conditions. In this study, we engineered feedforward cortical neural networks using two-nodal microfluidic devices with controllable connectivity interfaced with microelectrode arrays (mMEAs). We induced P301L mutated tau protein to the presynaptic node of these networks and monitored network dynamics over three weeks. Induced perturbation resulted in altered structural organization and extensive axonal retraction starting in the perturbed node. Perturbed networks also exhibited functional changes in intranodal activity, which manifested as an overall decline in both firing rate and bursting activity, with a progressive increase in synchrony over time and a decrease in internodal signal propagation between pre- and post-synaptic nodes. These results provide insights into dynamic structural and functional reconfigurations at the micro- and mesoscale as a result of evolving pathology and illustrate the utility of engineered networks as models of network function and dysfunction.

Leveraging mitochondrial-programmed cell death dynamics to enhance prognostic accuracy and immunotherapy efficacy in lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma (LUAD) is a highly heterogeneous disease, posing significant challenges to accurate prognosis prediction. Mitochondria play a central role in the energy metabolism of eukaryotic cells and can influence programmed cell death (PCD) mechanisms, which are critical in tumorigenesis and cancer progression. However, the prognostic significance of the interplay between mitochondrial function and PCD in LUAD requires further investigation.

METHODS

We analyzed data from 1231 LUAD patients across seven global cohorts to develop a mitochondrial-related PCD signature (MPCDS) using machine learning. Validation was done using six immunotherapy cohorts (LUAD, melanoma, clear cell renal cell carcinoma; n=935) and a pan-cancer cohort of 21 tumor types. An in-house LUAD tissue cohort (n=100) confirmed the prognostic significance of nucleoside diphosphate kinase 4 (NME4). In vivo and in vitro experiments explored NME4's role in immune exclusion.

RESULTS

The MPCDS demonstrated strong predictive performance for prognosis in LUAD patients, surpassing 114 previously published LUAD signatures. Additionally, MPCDS effectively predicted outcomes in immunotherapy patients (including those with LUAD, melanoma, and clear cell renal cell carcinoma). Biologically, MPCDS was significantly associated with immune features, with the high MPCDS group exhibiting reduced immune activity and a tendency towards cold tumors. NME4, a key gene within the MPCDS (correlation=0.55, p<0.05), was associated with poorer prognosis in LUAD patients with high expression, particularly in CD8 desert phenotypes, as validated by our in-house cohort. Multiplex immunofluorescence confirmed the spatial colocalization and exclusion relationship between NME4 and immune cells such as CD3+ T cells and CD20+ B cells. Further experiments revealed that NME4 regulated the proliferation and invasion of LUAD cells both in vitro and in vivo. Importantly, inhibiting NME4 increased the abundance and activity of CD8+ T cells and enhanced the antitumor immunity of anti-programmed cell death protein-1 therapy in vivo.

CONCLUSION

The MPCDS provides personalized risk assessment and immunotherapy interventions for individual LUAD patients. NME4, a key gene within the MPCDS, has been identified as a novel oncogene associated with immune exclusion and may serve as a new target for LUAD intervention and immunotherapy.

Molecular characterisation of lupus low disease activity state (LLDAS) and DORIS remission by whole-blood transcriptome-based pathways in a pan-European systemic lupus erythematosus cohort

OBJECTIVES

To unveil biological milieus underlying low disease activity (LDA) and remission versus active systemic lupus erythematosus (SLE).

METHODS

We determined differentially expressed pathways (DEPs) in SLE patients from the PRECISESADS project (NTC02890121) stratified into patients fulfilling and not fulfilling the criteria of (1) Lupus LDA State (LLDAS), (2) Definitions of Remission in SLE remission, and (3) LLDAS exclusive of remission.

RESULTS

We analysed data from 321 patients; 40.8% were in LLDAS, and 17.4% in DORIS remission. After exclusion of patients in remission, 28.3% were in LLDAS. Overall, 604 pathways differed significantly in LLDAS versus non-LLDAS patients with an false-discovery rate-corrected p (q)<0.05 and a robust effect size (dr)≥0.36. Accordingly, 288 pathways differed significantly between DORIS remitters and non-remitters (q<0.05 and dr≥0.36). DEPs yielded distinct molecular clusters characterised by differential serological, musculoskeletal, and renal activity. Analysis of partially overlapping samples showed no DEPs between LLDAS and DORIS remission. Drug repurposing potentiality for treating SLE was unveiled, as were important pathways underlying active SLE whose modulation could aid attainment of LLDAS/remission, including toll-like receptor (TLR) cascades, Bruton tyrosine kinase (BTK) activity, the cytotoxic T lymphocyte antigen 4 (CTLA-4)-related inhibitory signalling, and the nucleotide-binding oligomerization domain leucine-rich repeat-containing protein 3 (NLRP3) inflammasome pathway.

CONCLUSIONS

We demonstrated for the first time molecular signalling pathways distinguishing LLDAS/remission from active SLE. LLDAS/remission was associated with reversal of biological processes related to SLE pathogenesis and specific clinical manifestations. DEP clustering by remission better grouped patients compared with LLDAS, substantiating remission as the ultimate treatment goal in SLE; however, the lack of substantial pathway differentiation between the two states justifies LLDAS as an acceptable goal from a biological perspective.