Biology subjects

Kumbhar, R.

Publications and source records attributed to Kumbhar, R..

5 recordsLinked to original sources

bioRxiv2026

Microglial Lag3 Drives α-Synuclein--induced Neurotoxic Activated (A1) Astrocytes and Neurodegeneration

BackgroundNeuroinflammation and pathologic -synuclein (-syn) aggregation cooperate to drive dopaminergic neurodegeneration in Parkinsons disease, but the glial receptors that couple extracellular -syn to inflammatory cascades remain incompletely defined. Microglia express higher levels of lymphocyte activation gene 3 (Lag3) than neurons, yet the contribution of microglial Lag3 to -syn recognition, glial crosstalk, and neurodegeneration is unknown. MethodsBiochemical binding assays, live-cell imaging, cytokine profiling, and neuron-microglia-astrocyte co-culture paradigms were used to define Lag3-dependent -syn preformed fibril (PFF) binding, uptake, and microglial activation. To interrogate in vivo function, microglia-specific Lag3 conditional knockout mice (Lag3L/L-Cx3cr1CreER) and littermate controls received unilateral intrastriatal -syn PFF injections, followed by histological, biochemical, and behavioral assessments of -syn pathology, gliosis, nigrostriatal integrity, and motor performance. Results-syn PFFs bound microglial Lag3 with high specificity and nanomolar affinity and required Lag3 for efficient fibril internalization and induction of proinflammatory cytokines. Microglial Lag3 deficiency markedly blunted -syn PFF-evoked microglial activation, prevented cytokine-driven conversion of astrocytes into neurotoxic reactive A1 astrocytes, and abolished astrocyte-dependent neuronal death in vitro. In vivo, microglia-specific Lag3 deletion reduced cortical, striatal, and substantia nigra pS129 -syn pathology, suppressed microgliosis and A1 astrocyte induction, preserved substantia nigra dopaminergic neurons and striatal dopamine transporter/tyrosine hydroxylase expression, and ameliorated -syn PFF-induced motor deficits. ConclusionsThis study identifies microglial Lag3 as a key receptor linking extracellular -syn PFF recognition to inflammatory amplification, neurotoxic reactive A1 astrocyte conversion, and dopaminergic neurodegeneration. Together with prior work on neuronal Lag3, these findings support a cell-type-specific dual-axis model in which neuronal Lag3 mediates -syn propagation while microglial Lag3 drives glia-dependent neurotoxicity, positioning Lag3 as a promising precision therapeutic target in -synucleinopathies.

neuroscience↗

bioRxiv2025

Targeted α-Synuclein mRNA Degradation by PMO-Based RNA-Degrading Chimeras

-Synucleinopathies are devastating neurodegenerative diseases characterized by pathological accumulation of a neuronal protein, -synuclein (Syn). Lowering soluble Syn levels is a promising therapeutic strategy to limit aggregation and neurotoxicity, but directly targeting this protein is hindered by its intrinsically disordered structure and other factors, such as its conformational heterogeneity and intracellular drug delivery barriers. Consequently, increasing attention has been directed toward targeting the SNCA transcript, which encodes Syn. Here, we developed phosphorodiamidate morpholino oligonucleotide (PMO)-based RNA-degrading chimeras (RDCs) that selectively bind the 5' untranslated region of SNCA mRNA and recruit RNase L for targeted RNA degradation. Through the systematic evaluation of 10 RDCs, we identified and optimized 4-D1, which effectively reduced SNCA mRNA and Syn protein expression in HEK293T cells in an RNase L-dependent manner. 4-D1 lowered SNCA transcript and Syn protein levels in both primary cortical neurons from humanized SNCA mice and in human induced pluripotent stem cell-derived cortical neurons. This reduction prevented prion-like seeding induced by patient-derived Syn fibrils and protected neurons from fibril-induced cytotoxicity. Finally, in vivo studies confirmed the efficacy of 4-D1 in reducing Syn mRNA expression in humanized SNCA mice. These findings indicate that PMO-based RDCs may represent a promising therapeutic modality for -synucleinopathies. Significance StatementAbnormal aggregation of the neuronal protein -synuclein is central to Parkinsons disease and related disorders, yet therapeutic candidates that directly target this protein have yet to demonstrate efficacy. in clinical trials. We developed a new strategy that lowers -synuclein production at the RNA level using phosphorodiamidate morpholino oligonucleotide (PMO)-based RNA-degrading chimeras (RDCs). These molecules recruit a natural RNA-degrading enzyme to selectively destroy the RNA transcript encoding -synuclein. Our lead RDC reduced -synuclein levels in cultured cells, humanized mouse and human neurons, blocked -synuclein pathological aggregation, and protected neurons from toxicity. This study establishes RDCs as a promising therapeutic platform for Parkinsons disease and other neurodegenerative diseases driven by -synuclein.

biochemistry↗

bioRxiv2025

Copper-Containing ROS-Scavenging Nanozyme Paradoxically Drives Alpha-Synucleinopathy by Amplifying Nitrosative Stress

Reactive oxygen and nitrogen species (RONS) are implicated in neurodegeneration, but their specific pathogenic roles remain unclear. Here, we developed a pair of iridium-based nanozymes with opposing functionalities to dissect these pathways. We show that a copper-tuned iridium nanozyme (Ir{square}Cu), despite being a superior ROS scavenger, paradoxically and dramatically exacerbated -synuclein (Syn) pathology in vivo. This pathology was causally linked to its ability to amplify RNS, as pharmacological inhibition of nitric oxide synthase (NOS) with L-NAME completely abrogated the pathology and reversed a human Parkinsons disease (PD)-like transcriptomic signature. In contrast, a copper-free, broad-spectrum RONS-scavenging iridium (Ir) nanozyme demonstrated substantial therapeutic efficacy across diverse brain-first, body-first, and Alzheimers disease with Lewy body co-pathology models. Our findings uncover the importance of the RNS pathway in driving -synucleinopathies and establish a critical design principle for nanomedicine, mandating caution in the use of redox-active copper for neuroprotective applications.

pathology↗

bioRxiv2025

Neuronal LAG3 facilitates pathogenic α-synuclein neuron-to-neuron propagation

Lymphocyte activation gene 3 (LAG3) is a key receptor involved in the propagation of pathological proteins in Parkinsons disease (PD). This study investigates the role of neuronal LAG3 in mediating the binding, uptake, and propagation of -synuclein (Syn) preformed fibrils (PFFs). Using neuronal LAG3 conditional knockout mice and human induced pluripotent stem cells-derived dopaminergic (DA) neurons, we demonstrate that LAG3 expression is critical for pathogenic Syn propagation. Our results show that the absence of neuronal LAG3 significantly reduces Syn pathology, alleviates motor dysfunction, and inhibits neurodegeneration in vivo. Electrophysiological recordings revealed that Syn PFFs induce pronounced neuronal hyperactivity in wild-type (WT) neurons, increasing firing rates in cell-attached and whole-cell configurations, and reducing miniature excitatory postsynaptic currents. In contrast, neurons lacking LAG3 resisted these electrophysiological effects. Moreover, treatment with an anti-human LAG3 antibody in human DA neurons inhibited Syn PFFs binding and uptake, preventing pathology propagation. These findings confirm the essential function of neuronal LAG3 in mediating Syn propagation and associated disruptions, identifying LAG3 as a potential therapeutic target for PD and related -synucleinopathies.

neuroscience↗

bioRxiv2024

α-Synuclein Strain Dynamics Correlate with Cognitive Shifts in Parkinson's Disease

-Synuclein (-syn) strains can serve as discriminators between Parkinsons disease (PD) and related -synucleinopathies. The relationship between -syn strain dynamics and clinical performance as patients transition from normal cognition (NC) to cognitive impairment (CI) is not known. Here, we show that the biophysical properties and neurotoxicity of -syn strains change as PD cognitive status transitions from NC to mild cognitive impairment (PD-MCI) and dementia (PD-D). Both cross-sectional and longitudinal analyses reveal distinct -syn strains in PD patients correlating to their level of cognitive impairment. Machine learning (ML) was employed to achieve high classification accuracy. The combination of thioflavin T (ThT) maximal fluorescence intensity (mfi), max slope of rise curve (forming rate), lag time (tlag), 20% time (t20), and half-time (t50), dynamic light scattering (DLS) (peak number, [1/2] peak size, [1/2] peak intensity) and neurotoxicity together with demographic variables for model training yielded superior performance (89[~]99% accuracy in the 4- and 2- classification schema) compared to individual features alone in classifying cognitive status. For the longitudinal study, DLS peak number emerged as the strongest predictor of cognitive transition (HR = 0.12, P = 0.002), with the optimal predictive model combining DLS peak number, sex, education, DLS peak 1 size, and DLS peak 2 polydispersity achieving high accuracy (C-index of [~]93%). This study presents evidence that individuals with PD have different -syn strains correlating to their cognitive status and highlights the potential of -syn strain dynamics to guide future diagnosis, management, and stratification of PD patients. One Sentence SummaryDistinct features of -syn strains change with cognitive decline in Parkinsons disease and AI-based analysis incorporating these combined characteristics serves as a powerful tool for PD clinical stratification.

neuroscience↗