Biology subjects

Shetty, A. K.

Publications and source records attributed to Shetty, A. K..

5 recordsLinked to original sources

bioRxiv2025

Intranasal Human NSC-derived EVs Therapy in Late Middle Age Can Restrain the Activation of NLRP3 Inflammasome and cGAS-STING Signaling in the Aged Hippocampus

Neuroinflammaging, a moderate, chronic, and sterile inflammation in the hippocampus, contributes to age-related cognitive decline. Neuroinflammaging comprises the activation of the nucleotide-binding domain, leucine-rich repeat family, and pyrin domain-containing 3 (NLRP3) inflammasomes, and the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway that triggers type 1 interferon (IFN-1) signaling. Studies have shown that extracellular vesicles from human induced pluripotent stem cell-derived neural stem cells (hiPSC-NSC-EVs) contain therapeutic miRNAs that can alleviate neuroinflammation. Therefore, this study examined the effects of late middle-aged (18-month-old) male and female C57BL6/J mice receiving two intranasal doses of hiPSC-NSC-EVs on neuroinflammaging in the hippocampus at 20.5 months of age. Compared with animals receiving vehicle treatment, the hippocampus of animals receiving hiPSC-NSC-EVs exhibited reductions in astrocyte hypertrophy, microglial clusters, and oxidative stress, along with elevated expression of antioxidant proteins and genes that maintain mitochondrial respiratory chain integrity. Moreover, hiPSC-NSC-EVs therapy decreased the levels of various proteins involved in the activation of the NLRP3 inflammasome, p38/mitogen-activated protein kinase, cGAS-STING-IFN-1, and Janus kinase and signal transducer and activator of transcription signaling pathways. Furthermore, in vitro assays using genetically engineered RAW cells and hiPSC-NSC-EVs, with or without targeted depletion of specific miRNAs, demonstrated that miRNA-30e-3p and miRNA-181a-5p, both present in hiPSC-NSC-EVs, can significantly inhibit the activation of the NLRP3 inflammasome and the STING pathway, respectively. Additionally, single-cell RNA sequencing conducted 7 days post-treatment revealed that hiPSC-NSC-EVs induce widespread transcriptomic changes in microglia, including increased expression of numerous genes that enhance oxidative phosphorylation and reduced expression of abundant genes that drive multiple proinflammatory signaling pathways. These changes mediated by hiPSC-NSC-EVs were also associated with improved cognitive and memory function. Thus, intranasal hiPSC-NSC-EVs therapy in late middle age can effectively diminish proinflammatory microglial transcriptome and signaling cascades that drive neuroinflammaging in the hippocampus, contributing to better brain function in old age.

neuroscience↗

bioRxiv2024

The Genetic Architecture of the Human Corpus Callosum and its Subregions

The corpus callosum (CC) is the largest set of white matter fibers connecting the two hemispheres of the brain. In humans, it is essential for coordinating sensorimotor responses, performing associative/executive functions, and representing information in multiple dimensions. Understanding which genetic variants underpin corpus callosum morphometry, and their shared influence on cortical structure and susceptibility to neuropsychiatric disorders, can provide molecular insights into the CCs role in mediating cortical development and its contribution to neuropsychiatric disease. To characterize the morphometry of the midsagittal corpus callosum, we developed a publicly available artificial intelligence based tool to extract, parcellate, and calculate its total and regional area and thickness. Using the UK Biobank (UKB) and the Adolescent Brain Cognitive Development study (ABCD), we extracted measures of midsagittal corpus callosum morphometry and performed a genome-wide association study (GWAS) meta-analysis of European participants (combined N = 46,685). We then examined evidence for generalization to the non-European participants of the UKB and ABCD cohorts (combined N = 7,040). Post-GWAS analyses implicate prenatal intracellular organization and cell growth patterns, and high heritability in regions of open chromatin, suggesting transcriptional activity regulation in early development. Results suggest programmed cell death mediated by the immune system drives the thinning of the posterior body and isthmus. Global and local genetic overlap, along with causal genetic liability, between the corpus callosum, cerebral cortex, and neuropsychiatric disorders such as attention-deficit/hyperactivity and bipolar disorders were identified. These results provide insight into variability of corpus callosum development, its genetic influence on the cerebral cortex, and biological mechanisms related to neuropsychiatric dysfunction.

neuroscience↗

bioRxiv2024

Residual Microglia Following Short-term PLX5622 Treatment in 5xFAD Mice Exhibit Diminished NLRP3 Inflammasome and mTOR Signaling, and Enhanced Autophagy

Chronic neuroinflammation represents a prominent hallmark of Alzheimers disease (AD). While moderately activated microglia are pivotal in clearing amyloid beta (A{beta}), hyperactivated microglia perpetuate neuroinflammation. Prior investigations have indicated that the elimination of [~]80% of microglia through a month-long inhibition of the colony-stimulating factor 1 receptor (CSF1R) during the advanced stage of neuroinflammation in 5xFamilial AD (5xFAD) mice mitigates synapse loss and neurodegeneration without impacting A{beta} levels. Furthermore, prolonged CSF1R inhibition diminished the development of parenchymal plaques. Nonetheless, the immediate effects of short-term CSF1R inhibition during the early stages of neuroinflammation on residual microglial phenotype or metabolic fitness are unknown. Therefore, we investigated the effects of 10-day CSF1R inhibition in three-month-old female 5xFAD mice, a stage characterized by the onset of neuroinflammation and minimal A{beta} plaques. We observed [~]65% microglia depletion in the hippocampus and cerebral cortex. The leftover microglia demonstrated a noninflammatory phenotype, with highly branched and ramified processes and reduced NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome complexes. Moreover, plaque-associated microglia were reduced in number with diminished Clec7a (dectin-1) expression. Additionally, both microglia and neurons displayed reduced mechanistic target of rapamycin (mTOR) signaling and autophagy. Biochemical assays validated the inhibition of NLRP3 inflammasome activation, decreased mTOR signaling, and enhanced autophagy. However, short-term CSF1R inhibition did not influence A{beta} plaques, soluble A{beta}-42 levels, or hippocampal neurogenesis. Thus, short-term CSF1R inhibition during the early stages of neuroinflammation in 5xFAD mice promotes the retention of homeostatic microglia with diminished inflammasome activation and mTOR signaling, alongside increased autophagy.

neuroscience↗

bioRxiv2024

Extracellular Vesicles from hiPSC-derived NSCs Protect Human Neurons against Abeta-42 Oligomers Induced Neurodegeneration, Mitochondrial Dysfunction and Tau Phosphorylation

BackgroundAlzheimers disease (AD) is characterized by the accumulation of amyloid beta-42 (A{beta}-42) in the brain, causing various adverse effects. Thus, therapies that reduce A{beta}-42 toxicity in AD are of great interest. One promising approach is to use extracellular vesicles from human induced pluripotent stem cell-derived neural stem cells (hiPSC-NSC-EVs) because they carry multiple therapeutic miRNAs and proteins capable of protecting neurons against A{beta}-42-induced toxicity. Therefore, this in vitro study investigated the proficiency of hiPSC-NSC-EVs to protect human neurons from A{beta}-42 oligomers (A{beta}-42o) induced neurodegeneration. MethodsWe isolated hiPSC-NSC-EVs using chromatographic methods and characterized their size, ultrastructure, expression of EV-specific markers and proficiency in getting incorporated into mature human neurons. Next, mature human neurons differentiated from two different hiPSC lines were exposed to 1 {micro}M A{beta}-42o alone or with varying concentrations of hiPSC-NSC-EVs. The protective effects of hiPSC-NSC-EVs against A{beta}-42o-induced neurodegeneration, oxidative stress, mitochondrial dysfunction, impaired autophagy, and tau phosphorylation were ascertained using multiple measures and one-way ANOVA with Newman-Keuls multiple comparisons post hoc tests. ResultsA significant neurodegeneration was observed when human neurons were exposed to A{beta}-42o alone. Neurodegeneration was associated with 1) elevated levels of reactive oxygen species (ROS), mitochondrial superoxide, malondialdehyde (MDA) and protein carbonyls (PCs), 2) increased expression of proapoptotic Bax and Bad genes and proteins, and genes encoding mitochondrial complex proteins, 3) diminished mitochondrial membrane potential and mitochondria, 4) reduced expression of the antiapoptotic gene and protein Bcl-2, and autophagy-related proteins, and 5) increased phosphorylation of tau. However, the addition of an optimal dose of hiPSC-NSC-EVs (6 x 109 EVs) to human neuronal cultures exposed to A{beta}-42o significantly reduced the extent of neurodegeneration, along with diminished levels of ROS, superoxide, MDA and PCs, normalized expressions of Bax, Bad, and Bcl-2, and autophagy-related proteins, higher mitochondrial membrane potential and mitochondria, enhanced expression of genes linked to mitochondrial complex proteins, and reduced tau phosphorylation. ConclusionsAn optimal dose of hiPSC-NSC-EVs could significantly decrease the degeneration of human neurons induced by A{beta}-42o. The results support further research into the effectiveness of hiPSC- NSC-EVs in AD, particularly their proficiency in preserving neurons and slowing disease progression.

neuroscience↗

bioRxiv2020

Innate immune signaling and sex differences contribute to neurocognitive impairment, neuroinflammation, and mitochondrial rewiring in a mouse model of Gulf War illness

Gulf War Illness (GWI) is a chronic, multi-symptom disorder affecting approximately 30 percent of the nearly 700,000 veterans of the 1991 Persian Gulf War. Recent studies have revealed that GWI-related chemical (GWIC) exposure promotes immune activation and metabolic rewiring, which correlate with neurocognitive impairments and other symptoms of GWI. However, the molecular mechanisms and signaling pathways linking GWIC to inflammation, metabolic alterations, and neurological symptoms remain unclear. Mitochondrial dysfunction has been documented in veterans with GWI and rodent models, and because mitochondria are key immune regulators, we hypothesized that alterations to mitochondria-immune crosstalk could contribute to the development of GWI-related symptoms. Here we show that acute exposure of murine macrophages to GWIC alters mitochondrial respiration and potentiates innate immune signaling and inflammatory cytokine secretion. Using an established mouse model of GWI, we report that neurobehavioral changes, neuroinflammation, and mitochondrial protein rewiring are attenuated in mice lacking the cyclic GMP-AMP synthase (cGAS)-Stimulator of Interferon Genes (STING) and NOD-, LRR- or pyrin domain-containing protein 3 (NLRP3) innate immune pathways. Finally, we report sex differences in response to GWIC, with female mice showing more pronounced cognitive impairment, neuroinflammation, and mitochondrial protein alterations in the brain compared to male mice. Our results provide novel information on sex differences in this model and suggest that STING and NLRP3 are key mediators of the cognitive impairment, inflammation, and mitochondrial dysfunction observed in GWI.

neuroscience↗