Biology subjects

Wood, L. B.

Publications and source records attributed to Wood, L. B..

32 records · Page 2Linked to original sources

bioRxiv2023

Profiling the neuroimmune cascade in 3xTg mice exposed to successive mild traumatic brain injuries

Repetitive mild traumatic brain injuries (rmTBI) sustained within a window of vulnerability can result in long term cognitive deficits, depression, and eventual neurodegeneration associated with tau pathology, amyloid beta (A{beta}) plaques, gliosis, and neuronal and functional loss. However, we have limited understanding of how successive injuries acutely affect the brain to result in these devastating long-term consequences. In the current study, we addressed the question of how repeated injuries affect the brain in the acute phase of injury (<24hr) by exposing the 3xTg-AD mouse model of tau and A{beta} pathology to successive (1x, 3x, 5x) once-daily weight drop closed-head injuries and quantifying immune markers, pathological markers, and transcriptional profiles at 30min, 4hr, and 24hr after each injury. We used young adult mice (2-4 months old) to model the effects of rmTBI relevant to young adult athletes, and in the absence of significant tau and A{beta} pathology. Importantly, we identified pronounced sexual dimorphism, with females eliciting more differentially expressed proteins after injury compared to males. Specifically, females showed: 1) a single injury caused a decrease in neuron-enriched genes inversely correlated with inflammatory protein expression as well as an increase in AD-related genes within 24hr, 2) each injury significantly increased expression of a group of cortical cytokines (IL-1, IL-1{beta}, IL-2, IL-9, IL-13, IL-17, KC) and MAPK phospho-proteins (phospho-Atf2, phospho-Mek1), several of which were co-labeled with neurons and correlated with phospho-tau, and 3) repetitive injury caused increased expression of genes associated with astrocyte reactivity and immune function. Collectively our data suggest that neurons respond to a single injury within 24h, while other cell types including astrocytes transition to inflammatory phenotypes within days of repetitive injury.

neuroscience↗

bioRxiv2023

Native-state proteomics of Parvalbumin interneurons identifies novel molecular signatures and metabolic vulnerabilities to early Alzheimer's disease pathology

One of the earliest pathophysiological perturbations in Alzheimers Disease (AD) may arise from dysfunction of fast-spiking parvalbumin (PV) interneurons (PV-INs). Defining early protein-level (proteomic) alterations in PV-INs can provide key biological and translationally relevant insights. Here, we use cell-type-specific in vivo biotinylation of proteins (CIBOP) coupled with mass spectrometry to obtain native-state proteomes of PV interneurons. PV-INs exhibited proteomic signatures of high metabolic, mitochondrial, and translational activity, with over-representation of causally linked AD genetic risk factors. Analyses of bulk brain proteomes indicated strong correlations between PV-IN proteins with cognitive decline in humans, and with progressive neuropathology in humans and mouse models of A{beta} pathology. Furthermore, PV-IN-specific proteomes revealed unique signatures of increased mitochondrial and metabolic proteins, but decreased synaptic and mTOR signaling proteins in response to early A{beta} pathology. PV-specific changes were not apparent in whole-brain proteomes. These findings showcase the first native state PV-IN proteomes in mammalian brain, revealing a molecular basis for their unique vulnerabilities in AD.

neuroscience↗

bioRxiv2023

Brain rhythms control microglial response and cytokine expression via NFkappaB signaling

Microglia, the brains primary immune cells, transform in response to changes in sensory or neural activity, like sensory deprivation. However, little is known about how specific frequencies of neural activity, or brain rhythms, impact microglia and cytokine signaling. Using visual noninvasive flickering sensory stimulation (flicker) to induce electrical neural activity at different frequencies, 40Hz, within the gamma band and 20Hz, within the beta band, we discovered these brain rhythms differentially affect microglial morphology and cytokine expression in healthy animals. We found that flicker induced expression of certain cytokines, including IL-10 and M-CSF, that was independent of microglia. Because NF{kappa}B is activated by synaptic activity and regulates cytokines, we hypothesized this pathway plays a causal role in frequency-specific cytokine and microglial responses. Indeed, we found that after flicker, phospho-NF{kappa}B co-labeled with neurons more than microglia. Furthermore, inhibition of NF{kappa}B signaling by a small molecule inhibitor down-regulated flicker-induced cytokine expression and attenuated flicker-induced changes in microglia morphology. These results reveal a new mechanism through which brain rhythms affect brain function by altering microglia morphology and cytokines via NF{kappa}B. TeaserFrequency-specific brain rhythms regulate cytokine expression, microglia morphology, and microglia-independent expression of M-CSF and IL10 via NF{kappa}B.

neuroscience↗

bioRxiv2022

Defective neuritogenesis in Abcd1/2 deficient rat neurons due to intrinsic and astrocyte-dependent mechanisms

X-linked adrenoleukodystrophy (X-ALD) is a rare neurometabolic and demyelinating disorder caused by loss of function mutations of the ABCD1 transporter that imports very-long-chain fatty acids (VLCFA) into the peroxisome for beta-oxidation. Impaired ABCD1 function results in VLCFA accumulation, which ultimately causes lethal forms of X-ALD in children (CCALD) and adults (CAMN). Because X-ALD is a genetic disorder, we looked for signs of altered neurodevelopmental pathways in the transcriptomes of brain cortical tissues free of pathology from patients that died of CALD or CAMN. Several categories related to brain development, axonal growth, synaptic signaling and synaptic compartments were significantly dysregulated in both CALD and CAMN, suggesting that congenital circuit abnormalities might be structural in brains of mutated ABCD1 carriers. We partially dissected the cellular origin of dysregulated pathways using rat neuronal and astrocytic cultures in which X-ALD was modeled by silencing of Abcd1 and Abcd2 by RNA interference. Abcd2 was silenced lest it compensated for Abcd1 loss. Abcd1/2 deficient neurons presented higher rates of death, reduced sizes and defective formation of spines, dendrites and axons. The aberrant neuron development was caused by cell-autonomous and astrocyte-dependent mechanisms, and involved Wnt signaling, as suggested by the rescue of the expression of a synaptic gene upon pharmacological activation of the Wnt pathway. As recently proposed for neurogenetic disorders such as Huntingtons disease, our data suggest that X-ALD has a neurodevelopmental component that may cause psychiatric alterations and prime neural circuits for neurodegeneration. If this is the case, therapies aimed at restoring neural-circuit function in neurodevelopmental disorders may be reprofiled for X-ALD therapeutics.

neuroscience↗

bioRxiv2021

Cell type-specific biotin labeling in vivo resolves regional neuronal proteomic differences in mouse brain

Isolation and proteomic profiling of brain cell types, particularly neurons, pose several technical challenges which limit our ability to resolve distinct cellular phenotypes in neurological diseases. Therefore, we generated a novel mouse line that enables cell type-specific expression of a biotin ligase, TurboID, via Cre-lox strategy for in vivo proximity-dependent biotinylation of proteins. Using adenoviral-based and transgenic approaches, we show striking protein biotinylation in neuronal cell bodies and axons throughout the mouse brain. We quantified more than 2,000 neuron-derived proteins following enrichment that mapped to numerous subcellular compartments. Synaptic, transmembrane transporters, ion channel subunits, and disease-relevant druggable targets were among the most significantly enriched proteins. Remarkably, we resolved brain region-specific proteomic profiles of Camk2a neurons with distinct functional molecular signatures and disease associations that may underlie regional neuronal vulnerability. Leveraging the neuronal specificity of this in vivo biotinylation strategy, we used an antibody-based approach to uncover regionally unique patterns of neuron-derived signaling phospho-proteins and cytokines, particularly in the cortex and cerebellum. Our work provides a proteomic framework to investigate cell type-specific mechanisms driving physiological and pathological states of the brain as well as complex tissues beyond the brain.

neuroscience↗

bioRxiv2020

Biomaterial encapsulation of human mesenchymal stromal cells modulates paracrine signaling response and enhances efficacy for treatment of established osteoarthritis

Mesenchymal stromal cells (MSCs) have shown promise as a treatment for osteoarthritis (OA); however, effective translation has been limited by numerous factors ranging from high variability and heterogeneity of hMSCs, to suboptimal delivery strategies, to poor understanding of critical quality and potency attributes. The objective of the current study was to assess the effects of biomaterial encapsulation in alginate microcapsules on human MSC (hMSC) secretion of immunomodulatory cytokines in an OA microenvironment and therapeutic efficacy in treating established OA. Lewis rats underwent Medial Meniscal Transection (MMT) surgery to induce OA. Three weeks post-surgery, after OA was established, rats received intra-articular injections of either encapsulated hMSCs or controls (saline, empty capsules, or non-encapsulated hMSCs). Six weeks post-surgery, microstructural changes in the knee joint were quantified using contrast enhanced microCT. Encapsulated hMSCs attenuated progression of OA including articular cartilage degeneration (swelling and cartilage loss) and subchondral bone remodeling (thickening and hardening). A multiplexed immunoassay panel (41 cytokines) was used to profile the in vitro secretome of encapsulated and non-encapsulated hMSCs in response to IL-1{square}, a key cytokine involved in OA. Non-encapsulated hMSCs showed an indiscriminate increase in all cytokines in response to IL-1{square} while encapsulated hMSCs showed a highly targeted secretory response with increased expression of some pro-inflammatory (IL-1{beta}, IL-6, IL-7, IL-8), anti-inflammatory (IL-1RA), and chemotactic (G-CSF, MDC, IP10) cytokines. These data show that biomaterial encapsulation using alginate microcapsules can modulate hMSC paracrine signaling in response to OA cytokines and enhance the therapeutic efficacy of the hMSCs in treating established OA.

bioengineering↗

bioRxiv2020

Effects of osteogenic ambulatory mechanical stimulation on early stages of BMP-2mediated bone repair

Mechanical loading of bone defects through rehabilitation is a promising therapeutic approach to stimulate repair and reduce the risk of non-union; however, little is known about how therapeutic mechanical stimuli modulate early stages of repair before mineralized bone formation. In a previous study, we established an osteogenic mechanical loading protocol using early ambulatory rehabilitation and a compliant, load-sharing fixator in a rat model of BMP-2 mediated bone defect repair. The objective of this study was to investigate the early effects of osteogenic loading on cytokine expression, tissue composition, and angiogenesis during the first 3 weeks of repair in this model. Using a wireless implantable strain sensor for local measurements of mechanical boundary conditions, finite element simulations showed that osteogenic mechanical loading increased mean compressive strain in defect soft tissue during rehabilitative ambulation at 1 week (load-sharing: -1.54 {+/-} 0.17% vs. load-shielded: -0.76 {+/-} 0.06%), and that strain was amplified in remaining soft tissue regions at 3 weeks as mineralization progressed (load-sharing: -1.89 {+/-} 0.35% vs. load-shielded: -1.38 {+/-} 0.35%). Multivariate analysis of multiplex cytokine arrays revealed that loading significantly altered cytokine expression profiles in the defect tissue at 2 weeks compared to load-shielded defects. Specifically, loading reduced VEGF and increased CXCL5 (LIX) levels. Subsequently, vascular volume in loaded defects was reduced relative to load-shielded defects but similar to intact bone at 3 weeks. Endochondral bone repair was also observed histologically in loaded defects only at 3 weeks. Together, these results demonstrate that moderate ambulatory strains previously shown to stimulate functional bone regeneration significantly alter early angiogenic and cytokine signaling and may promote endochondral ossification in large segmental bone defects. Authors ContributionsB.S.K., N.J.W., and R.E.G. designed the research and performed surgeries; B.S.K., C.E.V., and J.K. performed experiments; B.S.K., C.E.V., J.K., and L.B.W., analyzed data; B.S.K., C.E.V., N.J.W., and R.E.G. wrote the manuscript; All authors interpreted data, critically edited, and have read and approved the final manuscript.

bioengineering↗

bioRxiv2020

JAGGED1 Stimulates Cranial Neural Crest Cell Osteoblast Commitment Pathways and Bone Regeneration Independent of Canonical NOTCH Signaling

Craniofacial bone loss is a complex clinical problem with limited regenerative solutions. Currently, BMP2 is used as a bone-regenerative therapy in adults, but in pediatric cases of bone loss, it is not FDA-approved due to concerns of life-threatening inflammation and cancer. Development of a bone-regenerative therapy for children will transform our ability to reduce the morbidity associated with current autologous bone grafting techniques. We discovered that JAGGED1 (JAG1) induces cranial neural crest (CNC) cell osteoblast commitment during craniofacial intramembranous ossification, suggesting that exogenous JAG1 delivery is a potential craniofacial bone-regenerative approach. In this study, we found that JAG1 delivery using synthetic hydrogels containing O9-1 cells, a CNC cell line, into critical-sized calvarial defects in C57BL/6 mice provided robust bone-regeneration. Since JAG1 signals through canonical (Hes1/Hey1) and non-canonical (JAK2) NOTCH pathways in CNC cells, we used RNAseq to analyze transcriptional pathways activated in CNC cells treated with JAG1{+/-}DAPT, a NOTCH-canonical pathway inhibitor. JAG1 upregulated expression of multiple NOTCH canonical pathway genes (Hes1), which were downregulated in the presence of DAPT. JAG1 also induced bone chemokines (Cxcl1), regulators of cytoskeletal organization and cell migration (Rhou), signaling targets (STAT5), promoters of early osteoblast cell proliferation (Prl2c2, Smurf1 and Esrra), and, inhibitors of osteoclasts (Id1). In the presence of DAPT, expression levels of Hes1 and Cxcl1 were decreased, whereas, Prl2c2, Smurf1, Esrra, Rhou and Id1 remain elevated, suggesting that JAG1 induces osteoblast proliferation through these non-canonical genes. Pathway analysis of JAG1+DAPT-treated CNC cells revealed significant upregulation of multiple non-canonical pathways, including the cell cycle, tubulin pathway, regulators of Runx2 initiation and phosphorylation of STAT5 pathway. In total, our data show that JAG1 upregulates multiple pathways involved in osteogenesis, independent of the NOTCH canonical pathway. Moreover, our findings suggest that JAG1 delivery using a synthetic hydrogel, is a bone-regenerative approach with powerful translational potential.

genomics↗

bioRxiv2020

Regenerating motor neurons prime muscle stem cells for myogenesis by enhancing protein synthesis and mitochondrial bioenergetics

Throughout life, skeletal muscle, the arbiter of voluntary movements, is maintained by a population of skeletal muscle-dedicated stem cells, called muscle satellite cells (MuSCs). Similar to other adult stem cells, the function of MuSCs is tightly coordinated by the cellular and acellular components of their microenvironment, or the niche. While the processes that control the coupling of neurotransmission and muscle contraction have been well characterized, little is known on the reciprocal crosstalk between neural cells and MuSCs within the muscle microenvironment. Here, we report that mild peripheral nerve injury enhances MuSC myogenic function and muscle regeneration by synergistically augmenting MuSC mitochondrial bioenergetics and upregulating anabolic protein synthesis pathways. We also demonstrate that chronic disruption or degeneration of neuromuscular synapses, such as in muscular dystrophy and biological aging, abolishes MuSC and motor neuron interactions, causing significant deficits in muscle regeneration following injury. These results underscore the importance of neuromuscular junction and neural network as an essential niche of MuSCs. Determining the significance of MuSC-nerve interactions and their functional outcomes, as well as the possibility of modulating these connections, have important implications for our understanding of neuromuscular disease pathology and development of therapeutic interventions. HighlightsO_LIMild peripheral nerve injury increases muscle stem cell bioavailability of healthy muscle. C_LIO_LINerve perturbation stimulates myogenesis by enhancing protein synthesis and mitochondrial metabolism in young, healthy muscle. C_LIO_LISynergistic crosstalk within neuromuscular niche boosts muscle regeneration in young, healthy muscle. C_LIO_LIPositive influences from the neural network on muscle stem cells are abolished in pathological denervation manifested in dystrophic and aging muscle. C_LI

cell biology↗

bioRxiv2020

Engineered Heterochronic Parabiosis in 3D Microphysiological System for Identification of Muscle Rejuvenating Factors

Exposure of aged mice to a young systemic milieu revealed remarkable rejuvenation effects on aged tissues, including skeletal muscle. Although some candidate factors have been identified, the exact identity and the underlying mechanisms of putative rejuvenating factors remain elusive, mainly due to the complexity of in vivo parabiosis. Here, we present an in vitro muscle parabiosis system that integrates young- and old-muscle stem cell vascular niche on a three-dimensional microfluidic platform designed to recapitulate key features of native muscle stem cell microenvironment. This innovative system enables mechanistic studies of cellular dynamics and molecular interactions within the muscle stem cell niche, especially in response to conditional extrinsic stimuli of local and systemic factors. We demonstrate that vascular endothelial growth factor (VEGF) signaling from endothelial cells and myotubes synergistically contribute to the rejuvenation of the aged muscle stem cell function. Moreover, with the adjustable on-chip system, we can mimic both blood transfusion and parabiosis and detect the time-varying effects of anti-geronic and pro-geronic factors in a single organ or multi-organ systems. Our unique approach presents a complementary in vitro model to supplement in vivo parabiosis for identifying potential anti-geronic factors responsible for revitalizing aging organs.

cell biology↗

bioRxiv2020

Mechanical Regulation of Microvascular Angiogenesis

Neovascularization is a critical early step toward successful tissue regeneration during wound healing. While vasculature has long been recognized as highly mechanosensitive (to fluid shear, pulsatile luminal pressure, etc.), the effects of extracellular matrix strains on angiogenesis are poorly understood. Previously, we found that dynamic matrix compression in vivo potently regulated neovascular growth during tissue regeneration; however, whether matrix deformations directly regulate00 angiogenesis remained unknown. Here, we tested the effects of load initiation time, strain magnitude, and mode of compressive deformation (uniform compression vs. compressive indentation that also introduced shear stress) on neovascularization and key angiogenic and mechanotransduction signaling pathways by microvascular fragments in vitro. We hypothesized that neovascularization would be enhanced by delayed, moderate compression and inhibited by early, high magnitude compression and by compressive indentation. Consistent with our hypothesis, early, high magnitude loading inhibited vessel growth, while delayed loading enhanced vessel growth. Compressive indentation led to longer, more branched networks than uniform compression - particularly at high strain magnitude. Gene expression was differentially regulated by time of load initiation; genes associated with active angiogenic sprouts were downregulated by early loading but upregulated by delayed loading. Canonical gene targets of the YAP/TAZ mechanotransduction pathway were increased by loading and abrogated by pharmacological YAP inhibition. Together, these data demonstrate that neovascularization is directly responsive to dynamic matrix strain and is particularly sensitive to the timing of load initiation. This work further identifies putative mechanoregulatory angiogenic mechanisms and implicates a critical role for dynamic mechanical cues in vascularized tissue regeneration. Statement of SignificanceMechanical cues influence tissue regeneration, and although vasculature is known to be mechanically sensitive, remarkably little is known about the effects of bulk extracellular matrix deformation on the nascent vessel networks found in healing tissues. Here, we demonstrated that load initiation time, magnitude, and mode all regulate microvascular growth, as well as upstream angiogenic and mechanotransduction signaling pathways. Across all tested magnitudes and modes, microvascular network formation and upstream signaling were powerfully regulated by the timing of load initiation. This work provides a new foundational understanding of how extracellular matrix mechanics regulate angiogenesis and has critical implications for clinical translation of new regenerative medicine therapies and physical rehabilitation strategies designed to enhance revascularization during tissue regeneration.

bioengineering↗

bioRxiv2020

Development of Systemic Immune Dysregulation in a Rat Trauma Model with Biomaterial-Associated Infection

Orthopedic biomaterial-associated infections remain a large clinical challenge, particularly with open fractures and segmental bone loss. Invasion and colonization of bacteria within immune-privileged canalicular networks of the bone can lead to local, indolent infections that can persist for years without symptoms before eventual catastrophic hardware failure. Host immunity is essential for bacterial clearance and an appropriate healing response, and recent evidence has suggested an association between orthopedic trauma and systemic immune dysregulation and immunosuppression. However, the impact of a local infection on this systemic immune response and subsequent effects on the local response is poorly understood and has not been a major focus for addressing orthopedic injuries and infections. Therefore, this study utilized a model of orthopedic biomaterial-associated infection to investigate the effects of infection on the long-term immune response. Here, despite persistence of a local, indolent infection lacking outward symptoms, there was still evidence of long-term immune dysregulation with systemic increases in MDSCs and decreases in T cells compared to non-infected trauma. Further, the trauma only group exhibited a regulated and coordinated systemic cytokine response, which was not present in the infected trauma group. Locally, the infection group had attenuated macrophage infiltration in the local soft tissue compared to the non-infected group. Our results demonstrate widespread impacts of a localized orthopedic infection on the systemic and local immune responses. Characterization of the immune response to orthopedic biomaterial-associated infection may identify key targets for immunotherapies that could optimize both regenerative and antibiotic interventions, ultimately improving outcomes for these patients.

bioengineering↗

bioRxiv2019

Experimental control of macrophage pro-inflammatory dynamics using predictive models

Macrophage activity is a major component of the healthy response to infection and injury that consists of tightly regulated early pro-inflammatory activation followed by anti-inflammatory and regenerative activity. In numerous diseases, however, macrophage polarization becomes dysregulated and can not only impair recovery, but can also promote further injury and pathogenesis, e.g. after injury, in diabetes, or in Alzheimers disease. Dysregulated macrophages may either fail to polarize or become chronically polarized, resulting in increased production of cytotoxic factors, diminished capacity to clear pathogens, or failure to promote tissue regeneration. In these cases, a method of predicting and dynamically controlling macrophage polarization will enable a new strategy for treating diverse inflammatory diseases. In this work, we developed a model-predictive control framework to temporally regulate macrophage polarization. Using RAW 264.7 macrophages as a model system, we enabled temporal control by identifying transfer function models relating the polarization marker iNOS to exogenous pro- and anti-inflammatory stimuli. These stimuli-to-iNOS response models were identified using linear autoregressive with exogenous input terms (ARX) equations and were coupled with nonlinear elements to account for experimentally identified supra-additive and hysteretic effects. Using this model architecture, we were able to reproduce experimentally observed temporal iNOS dynamics induced with lipopolysaccharides (LPS) and interferon gamma (IFN-{gamma}). Moreover, the identified model enabled the design of time-varying input trajectories to experimentally sustain the duration and magnitude of iNOS expression. By designing transfer function models with the intent to predict cell behavior, we were able to predict and experimentally obtain temporal regulation of iNOS expression using LPS and IFN-{gamma} from both naive and non-naive initial states. Moreover, our data driven models revealed decaying magnitude of iNOS response to LPS stimulation over time that could be recovered using combined treatment with both LPS and IFN-{gamma}. Given the importance of dynamic tissue macrophage polarization and overall inflammatory regulation to a broad number of diseases, the temporal control methodology presented here will have numerous applications for regulating immune activity dynamics in chronic inflammatory diseases.

bioengineering↗

bioRxiv2019

Microglial ERK activation is a critical regulator of pro-inflammatory immune responses in Alzheimer’s disease

BackgroundThe mitogen-activated protein kinase (MAPK) pathway is a central regulator of gene expression, pro-survival signaling, and inflammation. However, the importance of MAPK pathway signaling in regulating microglia-mediated neuroinflammation in Alzheimers Disease (AD) remains unclear. Here we examined the role of MAPK signaling in microglia using pre-clinical in-vitro and in-vivo models of AD pathology integrated with quantitative proteomics studies of post-mortem human brains.\n\nMethodsWe performed multiplexed immunoassay analyses of MAPK phosphoproteins, particularly ERK1/2, in acutely-isolated microglia and brain tissue from wild-type and 5xFAD mice. Neuropathological studies of mouse and human brain tissues were performed to quantify total and phosphorylated ERK protein in AD. The importance of ERK signaling in unstimulated and interferon {gamma} (IFN{gamma})-stimulated primary microglia cultures was investigated using NanoString transcriptomic profiling, coupled with functional assays of amyloid {beta} (A{beta}) and neuronal phagocytosis. Receptor tyrosine kinases (RTKs) likely responsible for ERK signaling in homeostatic microglia and disease-associated-microglia (DAM) states and ERK-regulated human AD risk genes were identified using gene expression data. Total and phosphorylated MAPKs in human post-mortem brain tissues were measured in quantitative proteomic datasets.\n\nResultsPhosphorylated ERK was the most strongly up-regulated signaling protein within the MAPK pathway in microglia acutely isolated from 5xFAD brains. Neuroinflammatory transcriptomic and phagocytic profiling of mouse microglia confirmed that ERK is a critical regulator of IFN{gamma}-mediated pro-inflammatory activation of microglia, although it was also important for constitutive microglial functions. Phospho-ERK was an upstream regulator of disease-associated microglia (DAM) gene expression (Trem2, Tyrobp), as well as of several human AD risk genes (Bin1, Cd33, Trem2, Cnn2). Among RTKs that signal via ERK, CSF1R and MERTK were primarily expressed by homeostatic microglia while AXL and FLT1 were likely regulators of ERK signaling in DAM. Within DAM, FLT4 and IGF1R were specifically expressed by pro- and anti-inflammatory DAM sub-profiles respectively. In quantitative proteomic analyses of post-mortem human brains from non-disease, asymptomatic and cognitively-impaired AD cases, ERK1 and ERK2 were the only MAPK pathway signaling proteins with increased protein expression and positive associations with neuropathological grade. Moreover, in a phospho-proteomic study of post-mortem human brains from controls, asymptomatic and symptomatic AD cases, we found evidence for a progressive increased flux through the ERK signaling pathway.\n\nConclusionsOur integrated analyses using pre-clinical models and human proteomic data strongly suggest that ERK phosphorylation in microglia is a critical regulator of pro-inflammatory immune response in AD pathogenesis and that modulation of ERK via upstream RTKs may reveal novel avenues for immunomodulation.

neuroscience↗