NogoA-expressing astrocytes limit peripheral macrophage infiltration after ischemic brain injury in primates.
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ABSTRACT:
SUBMITTER: Boghdadi AG
PROVIDER: S-EPMC8617297 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Reactive astrocytes play critical roles after brain injury, but their precise function is not well defined, particularly in humans and nonhuman primates (NHPs). Here, we utilized single nuclei transcriptomics to characterize astrocytes after ischemic stroke in the primary visual cortex (V1) of the marmoset monkey. We observed nearly complete segregation between stroke and control astrocyte clusters. Screening the top 30 differentially expressed genes to identify candidates that might limit stroke recovery, we discovered that RTN4A/ NogoA, a neurite-outgrowth inhibitory protein previously associated specifically with oligodendrocytes but not astrocytes, was expressed in a majority of reactive astrocytes. Robust NogoA upregulation on reactive astrocytes following stroke was confirmed in both the marmoset and human brain, whereas rodents exhibited only a marginal change in NogoA expression following stroke. Further, in vivo and in vitro studies determined that NogoA mediated an anti-inflammatory response which likely contributes to limiting deeper infiltration of peripheral macrophages into the surviving parenchyma during the subacute post-stroke period. These findings are directly relevant to the development of NogoA-targeting therapies designed for clinical use shortly after ischemic stroke. In addition, our data have uncovered the complexity of astrocyte responses in primates, which highlights the importance of preclinical model selection for discovery research designed to identify novel therapeutics for brain injury.
2021-10-18 | GSE179141 | GEO
Project description:NogoA-expressing astrocytes limit peripheral macrophage infiltration after ischemic brain injury in primates
| PRJNA742407 | ENA
Project description:BACKGROUND:Peripheral nerve injury causes limb muscle/bone atrophy, leading to chronic pain. However, the mechanisms underlying muscle/bone atrophy after peripheral nerve injury remain unknown. It was recently reported that M1 macrophages are the main factors responsible for neurogenic inflammation after peripheral nerve injury. We hypothesized that M1 macrophages are important in muscle/bone atrophy after nerve injury. Therefore, we investigated the influence of M1 macrophages on muscle/bone atrophy after nerve injury in mice to prevent muscle/bone atrophy by suppressing M1 macrophages. METHODS:Hindlimb muscle weight and total bone density were measured in a chronic constriction injury (CCI) mouse model. Immunohistochemical analysis and intravital microscopy were performed to visualize hindlimb muscles/bones, and cells were quantified using flow cytometry. We compared M1 macrophage infiltration into muscles/bones and muscle/bone atrophy between macrophage depletion and untreated groups. We also investigated muscle/bone atrophy using administration models for anti-inflammatory and neuropathic pain drugs. RESULTS:Peripheral nerve injury caused significant reduction in muscle weight and total bone density at 1 and 3 weeks after CCI, respectively, compared with that in controls. Osteoclast numbers were significantly higher at 1 week after CCI in the CCI group than in the control group. M1 macrophage infiltration into muscles was observed from 2 h after CCI via intravital microscopy and 1 week after CCI, and it was significantly higher 1 week after CCI than in the control group. In the macrophage depletion group, dexamethasone, pregabalin, and loxoprofen groups, M1 macrophage infiltration into muscles/bones was significantly lower and muscle weight and total bone density were significantly higher than in the untreated group. CONCLUSIONS:M1 macrophage infiltration exacerbates muscle/bone atrophy after peripheral nerve injury. By suppressing M1 macrophages at the neural injury local site, muscle/bone atrophy could be avoided.
| S-EPMC6971979 | biostudies-literature
Project description:Acute ischemic kidney injury is a common complication in hospitalized patients. No treatment is yet available for augmenting kidney repair or preventing progressive kidney fibrosis. Animal models of acute kidney injury demonstrate that activation of the innate immune system plays a major role in the systemic response to ischemia/reperfusion injury. Macrophage depletion studies suggest that macrophages, key participants in the innate immune response, augment the initial injury after reperfusion but also promote tubular repair and contribute to long-term kidney fibrosis after ischemic injury. The distinct functional outcomes seen following macrophage depletion at different time points after ischemia/reperfusion injury suggest heterogeneity in macrophage activation states. Identifying the pathways that regulate the transitions of macrophage activation is thus critical for understanding the mechanisms that govern both macrophage-mediated injury and repair in the postischemic kidney. This review examines our understanding of the complex and intricately controlled pathways that determine monocyte recruitment, macrophage activation, and macrophage effector functions after renal ischemia/reperfusion injury. Careful delineation of repair and resolution pathways could provide therapeutic targets for the development of effective treatments to offer patients with acute kidney injury.
| S-EPMC5048744 | biostudies-literature
Project description:Cannabis legalization prompted the dilemma if plant-derived recreational drugs can have therapeutic potential and, consequently, how to address their regulation and safe distribution. In parallel, the steady worldwide decriminalization of cannabis and the enhanced content of its main psychoactive compound Δ9-tetrahydrocannabinol (THC), exposes populations to increasing amounts of cannabis and THC across all ages. While adverse effects of cannabis during critical stages of fetal neurodevelopment are investigated, these studies center on neurons alone. Thus, a gap of knowledge exists on how intercellular interactions between neighboring cell types, particularly astrocytes and neurons, could modify THC action. Here, we combine transcriptome analysis, transgenic models, high resolution microscopy and live cell imaging to demonstrate that hippocampal astrocytes accumulate in the strata radiatum and lacunosum moleculare of the CA1 subfield, containing particularly sensitive neurons to stressors, upon long term postnatal THC exposure in vivo. As this altered distribution is not dependent on cell proliferation, we propose that resident astrocytes accumulate in select areas to protect pyramidal neurons and their neurite extensions from pathological damage. Indeed, we could recapitulate the neuroprotective effect of astrocytes in vitro, as their physical presence significantly reduced the death of primary hippocampal neurons upon THC exposure (> 5 µM). Even so, astrocytes are also affected by a reduced metabolic readiness to stressors, as reflected by a downregulation of mitochondrial proteins. Thus, we find that astrocytes exert protective functions on local neurons during THC exposure, even though their mitochondrial electron transport chain is disrupted.
| S-EPMC10030412 | biostudies-literature
Project description:BackgroundWe have previously reported that nerve injury-induced neuropathic pain is attenuated in toll-like receptor 2 (TLR2) knock-out mice. In these mice, inflammatory gene expression and spinal cord microglia actvation is compromised, whereas the effects in the dorsal root ganglia (DRG) have not been tested. In this study, we investigated the role of TLR2 in inflammatory responses in the DRG after peripheral nerve injury.ResultsL5 spinal nerve transection injury induced the expression of macrophage-attracting chemokines such as CCL2/MCP-1 and CCL3/MIP-1 and subsequent macrophage infiltration in the DRG of wild-type mice. In TLR2 knock-out mice, however, the induction of chemokine expression and macrophage infiltration following nerve injury were markedly reduced. Similarly, the induction of IL-1β and TNF-α expression in the DRG by spinal nerve injury was ameliorated in TLR2 knock-out mice. The reduced inflammatory response in the DRG was accompanied by attenuation of nerve injury-induced spontaneous pain hypersensitivity in TLR2 knock-out mice.ConclusionsOur data show that TLR2 contributes to nerve injury-induced proinflammatory chemokine/cytokine gene expression and macrophage infiltration in the DRG, which may have relevance in the reduced pain hypersensitivity in TLR2 knock-out mice after spinal nerve injury.
| S-EPMC3192680 | biostudies-literature
Project description:In vertebrates, the peripheral nervous system has retained its regenerative capacity, enabling severed axons to reconnect with their original synaptic targets. While it is well documented that a favorable environment is critical for nerve regeneration, the complex cellular interactions between injured nerves with cells in their environment, as well as the functional significance of these interactions, have not been determined in vivo and in real time. Here we provide the first minute-by-minute account of cellular interactions between laser transected motor nerves and macrophages in live intact zebrafish. We show that macrophages arrive at the lesion site long before axon fragmentation, much earlier than previously thought. Moreover, we find that axon fragmentation triggers macrophage invasion into the nerve to engulf axonal debris, and that delaying nerve fragmentation in a Wld(s) model does not alter macrophage recruitment but induces a previously unknown 'nerve scanning' behavior, suggesting that macrophage recruitment and subsequent nerve invasion are controlled by separate mechanisms. Finally, we demonstrate that macrophage recruitment, thought to be dependent on Schwann cell-derived signals, occurs independently of Schwann cells. Thus, live cell imaging defines novel cellular and functional interactions between injured nerves and immune cells.
| S-EPMC3324096 | biostudies-other
Project description:BackgroundNeovascularization is an important repair mechanism in response to ischemic injury and is dependent on inflammation, angiogenesis and reactive oxygen species (ROS). IQGAP1, an actin-binding scaffold protein, is a key regulator for actin cytoskeleton and motility. We previously demonstrated that IQGAP1 mediates vascular endothelial growth factor (VEGF)-induced ROS production and migration of cultured endothelial cells (ECs); however, its role in post-ischemic neovascularization is unknown.Methodology/principal findingsIschemia was induced by left femoral artery ligation, which resulted in increased IQGAP1 expression in Mac3(+) macrophages and CD31(+) capillary-like ECs in ischemic legs. Mice lacking IQGAP1 exhibited a significant reduction in the post-ischemic neovascularization as evaluated by laser Doppler blood flow, capillary density and α-actin positive arterioles. Furthermore, IQGAP1(-/-) mice showed a decrease in macrophage infiltration and ROS production in ischemic muscles, leading to impaired muscle regeneration and increased necrosis and fibrosis. The numbers of bone marrow (BM)-derived cells in the peripheral blood were not affected in these knockout mice. BM transplantation revealed that IQGAP1 expressed in both BM-derived cells and tissue resident cells, such as ECs, is required for post-ischemic neovascularization. Moreover, thioglycollate-induced peritoneal macrophage recruitment and ROS production were inhibited in IQGAP1(-/-) mice. In vitro, IQGAP1(-/-) BM-derived macrophages showed inhibition of migration and adhesion capacity, which may explain the defective macrophage recruitment into the ischemic tissue in IQGAP1(-/-) mice.Conclusions/significanceIQGAP1 plays a key role in post-ischemic neovascularization by regulating, not only, ECs-mediated angiogenesis but also macrophage infiltration as well as ROS production. Thus, IQGAP1 is a potential therapeutic target for inflammation- and angiogenesis-dependent ischemic cardiovascular diseases.
| S-EPMC2955540 | biostudies-literature
Project description:Scutellarin, a bioactive flavone isolated from Scutellaria baicalensis, has anti-inflammatory, anti-neurotoxic, anti-apoptotic and anti-oxidative effects and has been used to treat cardiovascular and cerebrovascular diseases in China. However, the mechanisms by which scutellarin mediates neuroprotection in cerebral ischemia remain unclear. The interaction between scutellarin and nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) was assessed by molecular docking study, which showed that scutellarin selectively binds to NOX2 with high affinity. Cultures of primary astrocytes isolated from the cerebral cortex of neonatal Sprague-Dawley rats were pretreated with 2, 10 or 50 ?M scutellarin for 30 minutes. The astrocytes were then subjected to oxygen/glucose deprivation by incubation for 2 hours in glucose-free Dulbecco's modified Eagle's medium in a 95% N2/5% CO2 incubator, followed by simulated reperfusion for 22 hours. Cell viability was assessed by cell counting kit-8 assay. Expression levels of NOX2, connexin 43 and caspase-3 were assessed by western blot assay. Reactive oxygen species were measured spectrophotometrically. Pretreatment with 10 or 50 ?M scutellarin substantially increased viability, reduced the expression of NOX2 and caspase-3, increased the expression of connexin 43, and diminished the levels of reactive oxygen species in astrocytes subjected to ischemia-reperfusion. We also assessed the effects of scutellarin in vivo in the rat transient middle cerebral artery occlusion model of cerebral ischemia-reperfusion injury. Rats were given intraperitoneal injection of 100 mg/kg scutellarin 2 hours before surgery. The Bederson scale was used to assess neurological deficit, and 2,3,5-triphenyltetrazolium chloride staining was used to measure infarct size. Western blot assay was used to assess expression of NOX2 and connexin 43 in brain tissue. Enzyme-linked immunosorbent assay was used to detect 8-hydroxydeoxyguanosine (8-OHdG), 4-hydroxy-2-nonenal (4-HNE) and 3-nitrotyrosin (3-NT) in brain tissue. Immunofluorescence double staining was used to determine the co-expression of caspase-3 and NeuN. Pretreatment with scutellarin improved the neurological function of rats with focal cerebral ischemia, reduced infarct size, diminished the expression of NOX2, reduced levels of 8-OHdG, 4-HNE and 3-NT, and reduced the number of cells co-expressing caspase-3 and NeuN in the injured brain tissue. Furthermore, we examined the effect of the NOX2 inhibitor apocynin. Apocynin substantially increased connexin 43 expression in vivo and in vitro. Collectively, our findings suggest that scutellarin protects against ischemic injury in vitro and in vivo by downregulating NOX2, upregulating connexin 43, decreasing oxidative damage, and reducing apoptotic cell death.
| S-EPMC6108207 | biostudies-literature
Project description:Mitochondrial heat shock protein 70 (mtHsp70/Hsp75/Grp75/mortalin/TRAP-1/PBP74) is an essential mitochondrial chaperone and a member of the heat shock protein 70 (HSP70) family. Although many studies have shown the protective properties of overexpression of the cytosolic inducible member of the HSP70 family, Hsp72, few studies have investigated the protective potential of Hsp75 against ischemic injury. Mitochondria are one of the primary targets of ischemic injury in astrocytes. In this study, we analyzed the effects of Hsp75 overexpression on cellular levels of reactive oxygen species (ROS), mitochondrial membrane potential, ATP levels, and viability during the ischemia-like conditions of oxygen-glucose deprivation (OGD) or glucose deprivation (GD) in primary astrocytic cultures. We show that Hsp75 overexpression decreases ROS production and preserves mitochondrial membrane potential during GD, and preserves ATP levels and cell viability during OGD. These findings indicate that Hsp75 can provide protection against ischemia-like in vitro injury and suggest that it should be further studied as a potential candidate for protection against ischemic injury.
| S-EPMC2408860 | biostudies-literature