Modulating Microglia Polarization Research Articles

Therapeutic potential of EAE mice with sodium oligomannate and effects of intestinal flora and microglia polarization

Objective: To investigate the therapeutic effect of sodium oligomannate on experimental autoimmune encephalomyelitis (EAE) mice and its effect on intestinal flora and microglia polarization. Methods: Fifty female C57BL/6 mice were randomly divided by the random number table method into the control group, EAE model group and low-dose, medium-dose and high-dose group of sodium oligomannate with 10 mice each. The EAE model group and each dose group of sodium oligomannate were induced by subcutaneous multi-point injection of MOG35-55 peptide for the EAE model. Mice in the low-dose, medium-dose and high-dose group of sodium oligomannate were gavaged sodium oligomannate 40, 80, and 160 mg/kg twice a day, respectively, starting from the day after modeling. The intervention continued until the mice were euthanized. Observe the incidence of disease, infiltration of inflammatory cells in spinal cord tissue, and demyelination in each group of mice.. The mice feces were collected and tested for intestinal flora by 16S rRNA sequencing. Immunofluorescence staining was used to observe the expression of Iba-1 protein, an activation indicator of microglia, in spinal cord tissue. The protein levels of M1 type markers iNOS, CD16, and M2 type markers Arg1 and CD206 were tsested in the spinal cord by Western blotting and immunofluorescence staining. Results: None of the mice in the control group developed any disease, while the mice in other groups showed varying degrees of disease, including tail sag, unstable walking, and hind limb weakness. Compared with the EAE model group, the incubation period was prolonged, the peak was delayed and the peak neurological dysfunction score was reduced (3.6±0.6 vs 3.0±0.6, 2.8±0.5, 1.8±0.6, P<0.05) in all sodium oligomannate groups, with milder symptoms at higher doses. The differences in pairwise comparisons between the groups were all statistically significant (all P<0.05). In the control group, no inflammatory cell infiltration or demyelinating changes were observed in spinal cord tissue. In the EAE model group, inflammatory cell infiltration and demyelination changes were evident in the spinal cord tissues at the onset peak. Compared with the EAE model group, inflammatory cell infiltration and demyelination were ameliorated in all sodium oligomannate groups. Compared with the control group, the relative abundance of Bacteroidota decreased and that of Firmicutes increased in the EAE model group. Compared with the EAE model group, the relative abundance of Bacteroidota increased and that of Firmicutes decreased, the ratio of Bacteroidetes to Firmicutes increased (0.20±0.05 vs 0.37±0.02,0.61±0.03,0.91±0.08,P<0.01) in the respective dose groups. The difference in pairwise comparison between groups was statistically significant (P<0.01), with greater changes at higher doses. Compared with the control group, the levels of Iba-1、CD16 and iNOS increased, while the levels of Arg-1 and CD206 decreased in the EAE model group. Compared with the EAE model group, the levels of Iba-1、CD16 and iNOS decreased, while the levels of Arg-1 and CD206 increased in all sodium oligomannate groups(P<0.01), with greater changes at higher doses. The difference between groups was statistically significant (P<0.01). Conclusions: Sodium oligomannate has a therapeutic effect on EAE and is dose-dependent. Its mechanism of action may be related toimproving intestinal microecology and the modulation of microglial polarization.

Interleukin-4 from curcumin-activated OECs emerges as a central modulator for increasing M2 polarization of microglia/macrophage in OEC anti-inflammatory activity for functional repair of spinal cord injury

Microglia/macrophages are major contributors to neuroinflammation in the central nervous system (CNS) injury and exhibit either pro- or anti-inflammatory phenotypes in response to specific microenvironmental signals. Our latest in vivo and in vitro studies demonstrated that curcumin-treated olfactory ensheathing cells (aOECs) can effectively enhance neural survival and axonal outgrowth, and transplantation of aOECs improves the neurological outcome after spinal cord injury (SCI). The therapeutic effect is largely attributed to aOEC anti-inflammatory activity through the modulation of microglial polarization from the M1 to M2 phenotype. However, very little is known about what viable molecules from aOECs are actively responsible for the switch of M1 to M2 microglial phenotypes and the underlying mechanisms of microglial polarization. Herein, we show that Interleukin-4 (IL-4) plays a leading role in triggering the M1 to M2 microglial phenotype, appreciably decreasing the levels of M1 markers IL‑1β, IL‑6, tumour necrosis factor-alpha (TNF-α) and inducible nitric oxide synthase (iNOS) and elevating the levels of M2 markers Arg-1, TGF-β, IL-10, and CD206. Strikingly, blockade of IL-4 signaling by siRNA and a neutralizing antibody in aOEC medium reverses the transition of M1 to M2, and the activated microglia stimulated with the aOEC medium lacking IL-4 significantly decreases neuronal survival and neurite outgrowth. In addition, transplantation of aOECs improved the neurological function deficits after SCI in rats. More importantly, the crosstalk between JAK1/STAT1/3/6-targeted downstream signals and NF-κB/SOCS1/3 signaling predominantly orchestrates IL-4-modulated microglial polarization event. These results provide new insights into the molecular mechanisms of aOECs driving the M1-to-M2 shift of microglia and shed light on new therapies for SCI through the modulation of microglial polarization.

Thymoquinone regulates microglial M1/M2 polarization after cerebral ischemia-reperfusion injury via the TLR4 signaling pathway

Acute ischemic stroke followed by microglia activation, and the regulation of neuroinflammatory responses after ischemic injury involves microglia polarization. microglia polarization is involved in the regulation of neuroinflammatory responses and ischemic stroke-related brain damage. Thymoquinone (TQ) is an anti-inflammatory agent following ischemic stroke onset. However, the significance of TQ in microglia polarization following acute ischemic stroke is still unclear. We predicted that TQ might have neuroprotective properties by modulating microglia polarization. In this work, we mimicked the clinical signs of acute ischemic stroke using a mouse middle cerebral artery ischemia-reperfusion (I/R) model. It was discovered that TQ treatment decreased I/R-induced infarct volume, cerebral oedema, and promoted neuronal survival, as well as improved the histopathological changes of brain tissue. The sensorimotor function was assessed by the Garica score, foot fault test, and corner test, and it was found that TQ could improve the motor deficits caused by I/R. Secondly, real-time fluorescence quantitative PCR, immuno-fluorescence, ELISA, and western blot were used to detect the expression of M1/M2-specific markers in microglia to explore the role of TQ in the modulation of microglial cell polarization after cerebral ischemia-reperfusion. We found that TQ was able to promote the polarization of microglia with extremely secreted inflammatory factors from M1 type to M2 type. Furthermore, TQ could block the TLR4/NF-κB signaling pathway via Hif-1α activation which subsequently may attenuate microglia differentiation following the cerebral ischemia, establishing a mechanism for the TQ's beneficial effects in the cerebral ischemia-reperfusion model.

Targeted mRNA Nanoparticles Ameliorate Blood-Brain Barrier Disruption Postischemic Stroke by Modulating Microglia Polarization.

The ischemic stroke is a major global health concern, with high mortality and disability rates. Unfortunately, there is a dearth of effective clinical interventions for managing poststroke neuroinflammation and blood-brain barrier (BBB) disruption that are crucial for the brain injury evolving and neurological deficits. By leveraging the pathological progression of an ischemic stroke, we developed an M2 microglia-targeting lipid nanoparticle (termed MLNP) approach that can selectively deliver mRNA encoding phenotype-switching interleukin-10 (mIL-10) to the ischemic brain, creating a beneficial feedback loop that drives microglial polarization toward the protective M2 phenotypes and augments the homing of mIL-10-loaded MLNPs (mIL-10@MLNPs) to ischemic regions. In a transient middle cerebral artery occlusion (MCAO) mouse model of an ischemic stroke, our findings demonstrate that intravenously injected mIL-10@MLNPs induce IL-10 production and enhance the M2 polarization of microglia. The resulting positive loop reinforces the resolution of neuroinflammation, restores the impaired BBB, and prevents neuronal apoptosis after stroke. Using a permanent distal MCAO mouse model of an ischemic stroke, the neuroprotective effects of mIL-10@MLNPs have been further validated by the attenuation of the sensorimotor and cognitive neurological deficits. Furthermore, the developed mRNA-based targeted therapy has great potential to extend the therapeutic time window at least up to 72 h poststroke. This study depicts a simple and versatile LNP platform for selective delivery of mRNA therapeutics to cerebral lesions, showcasing a promising approach for addressing an ischemic stroke and associated brain conditions.

Activation of LXRs alleviates neuropathic pain-induced cognitive dysfunction by modulation of microglia polarization and synaptic plasticity via PI3K/AKT pathway.

Cognitive dysfunction is a common comorbidity in patients with chronic pain. Activation of Liver X receptors (LXRs) plays a potential role in improving cognitive disorders in central nervous diseases. In this study, we investigated the role of LXRs in cognitive deficits induced by neuropathic pain. We established the spared nerve injury (SNI) model to investigate pain-induced memory dysfunction. Pharmacological activation of LXRs with T0901317 or inhibition with GSK2033 was applied. PI3K inhibitor LY294002 was administered to explore the underlying mechanism of LXRs. Changes in neuroinflammation, microglia polarization, and synaptic plasticity were assessed using biochemical technologies. We found that SNI-induced cognitive impairment was associated with reduced LXRβ expression, increased M1-phenotype microglia, decreased synaptic proteins, and inhibition of PI3K/AKT signaling pathway in the hippocampus. Activation of LXRs using T0901317 effectively alleviated SNI-induced cognitive impairment. Additionally, T0901317 promoted the polarization of microglia from M1 to M2, reduced pro-inflammatory cytokines, and upregulated synaptic proteins in the hippocampus. However, administration of GSK2033 or LY294002 abolished these protective effects of T0901317 in SNI mice. LXRs activation alleviates neuropathic pain-induced cognitive impairment by modulating microglia polarization, neuroinflammation, and synaptic plasticity, at least partly via activation of PI3K/AKT signaling in the hippocampus. LXRs may be promising targets for addressing pain-related cognitive deficits.

Ginsenoside Rb1 attenuates mouse cerebral ischemia/reperfusion induced neurological impairments through modulation of microglial polarization

Ginsenoside Rb1 attenuates mouse cerebral ischemia/reperfusion induced neurological impairments through modulation of microglial polarization

Retraction: NOSH-NBP, a novel nitric oxide and hydrogen sulfide- releasing hybrid, attenuates ischemic stroke-induced neuroinflammatory injury by modulating microglia polarization

Retraction: NOSH-NBP, a novel nitric oxide and hydrogen sulfide- releasing hybrid, attenuates ischemic stroke-induced neuroinflammatory injury by modulating microglia polarization

I-C-F-6 attenuates chronic cerebral hypoperfusion-induced neurological injury in mice by modulating microglia polarization.

Chronic cerebral hypoperfusion (CCH) is the leading cause of chronic cerebral dysfunction syndrome with its complex pathological mechanisms involving cortical and hippocampal neuronal loss, white matter lesions, and neuroinflammation. I-C-F-6 is a septapeptide, which has anti-inflammatory and anti-fibrotic effects. This study aimed to evaluate the neuroprotective effect of I-C-F-6 in chronic cerebral hypoperfusion (CCH)-induced neurological injury. C57BL/6J mice were subjected to bilateral common carotid artery stenosis (BCAS), and BV2 microglia cells were induced with oxygen-glucose deprivation (OGD). In vivo, mice were divided randomly into four groups: Sham, BCAS, GBE (30mg/kg), and I-C-F-6 (0.5mg/kg). In vitro, microglia were divided randomly into four groups: control, OGD, I-C-F-6 (25μg/mL), and Shikonin (800nmol/L). Through LFB, TUNEL, and NeuN staining, we found that I-C-F-6 was able to mitigate myelin pathology and reduce the number of apoptotic neurons. Furthermore, immunofluorescence staining revealed that I-C-F-6 was able to reduce microglia clustering and downregulate NF-κB p65. We also observed a significant downregulation of M1 phenotype microglia signature genes, such as TNF-α, iNOS, and upregulation of anti-inflammatory cytokines, such as Arg-1 and IL-10, indicating that I-C-F-6 may mainly reduce polarization towards the M1 phenotype in microglia. Notably, I-C-F-6 downregulated the expression of NF-κB signaling pathway-related proteins IKK-β and NF-κB p65, as well as pro-inflammatory cytokines IL-1β and iNOS. In conclusion, I-C-F-6 can improve neurological damage, alleviate neuroinflammation, and inhibit microglia polarization to the M1 phenotype via the NF-κB signaling pathway.

Pseudoginsenoside GQ mitigates chronic intermittent hypoxia-induced cognitive damage by modulating microglia polarization

Obstructive sleep apnea (OSA), a state of sleep disruption, is characterized by recurrent apnea, chronic intermittent hypoxia (CIH) and hypercapnia. Previous studies have showed that CIH-induced neuroinflammatory plays a crucial role in cognitive deficits. Pseudoginsenoside GQ (PGQ) is a new oxytetracycline-type saponin formed by the oxidation and cyclization of the 20(S) Rg3 side chain. Rg3 has been found to afford anti-inflammatory effects, while whether PGQ plays a role of anti-neuroinflammatory remains unclear. The purpose of this study was to investigate whether PGQ attenuates CIH-induced neuroinflammatory and cognitive impairment and the possible mechanism it involves. We found that PGQ significantly ameliorated CIH-induced spatial learning deficits, and inhibited microglial activation, pro-inflammatory cytokine release, and neuronal apoptosis in the hippocampus of CIH mice. In addition, PGQ pretreatment promoted microglial M1 to M2 phenotypic transition in IH-induced BV-2 microglial, as well as indirectly inhibited IH-induced neuronal injury via modulation of microglia polarization. Furthermore, we noted that activation of HMGB1/TLR4/NF-κB signaling pathway induced by IH was inhibited by PGQ. Molecular docking results revealed that PGQ could bind to the active sites of HMGB1 and TLR4. Taken together, this work supports that PGQ inhibits M1 microglial polarization via the HMGB1/TLR4/NF-κB signaling pathway, and indirectly exerts neuroprotective effects, suggesting that PGQ may be a potential therapeutic strategy for cognitive impairment accompanied OSA.

Quercetin improves cerebral ischemia/reperfusion injury by promoting microglia/macrophages M2 polarization via regulating PI3K/Akt/NF-κB signaling pathway

The modulation of microglial polarization from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype shows promise as a therapeutic strategy for ischemic stroke. Quercetin, a natural flavonoid abundant in various plants, possesses anti-inflammatory, anti-apoptotic, and antioxidant properties. Nevertheless, its effect and underlying mechanism on microglia/macrophages M1/M2 polarization in the treatment of cerebral ischemia/reperfusion injury (CI/RI) remain poorly explored. In the current study, we observed that quercetin ameliorated neurological deficits, reduced infarct volume, decreased the number of M1 microglia/macrophages (CD16/32+/Iba1+), and enhanced the number of M2 microglia/macrophages (CD206+/Iba1+) after establishing the CI/RI model in rats. Subsequent in vivo and in vitro experiments indicated that quercetin downregulated M1 markers (CD86, iNOS, TNF-α, IL-1β, and IL-6) and upregulated M2 markers (CD206, Arg-1, IL-10, and TGF-β). Network pharmacology analysis and molecular docking revealed that the PI3K/Akt/NF-κB signaling pathway emerged as the core pathway. Western blot confirmed that quercetin upregulated the phosphorylation of PI3K and Akt, while alleviating the phosphorylation of IκBα and NF-κB both in vivo and in vitro. However, the PI3K inhibitor LY294002 reversed the effects of quercetin on M2 polarization and the expression of key proteins in the PI3K/Akt/NF-κB pathway in primary microglia after oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro. Collectively, our findings demonstrate that quercetin facilitates microglia/macrophages M2 polarization by modulating the PI3K/Akt/NF-κB signaling pathway in the treatment of CI/RI. These findings provide novel insights into the therapeutic mechanisms of quercetin in ischemic stroke.

Koumine ameliorates neuroinflammation by regulating microglia polarization via activation of Nrf2/HO-1 pathway

BackgroundGelsemium elegans (Gardner & Chapm.) Benth (G. elegans) has been widely used as a traditional folk medicine in China and Southeast Asia. As the most abundant alkaloid in G. elegans, Koumine (KM) has been revealed the effect of inflammatory attenuation modulating by macrophage activation and polarization. PurposeThis study aimed to explore the effect of KM on modulation of microglia polarization that led to the suppression of neuroinflammation and further improved neurodegenerative behavior. MethodsInflammatory mediators, microglia M1 and M2 phenotype markers and Nrf2/HO-1 pathway related protein were assessed in LPS-induced BV2 cells and LPS-treated mice by RT-PCR, immunohistochemistry, immunofluorescence and Western blotting. Moreover, the learning and memory abilities of mice were evaluated by Morris water maze test, and the neuronal damage was evaluated by the Nissl staining. ResultsKM attenuated LPS-induced viability and morphological changes in BV2 microglial cells. Our findings showed that KM activated the Nrf2/HO-1 signaling pathway to promote phenotypic switch from M1 to M2 phenotypes. This switch suppresses the release of inflammatory mediators in LPS-induced BV2 cells. Meanwhile, KM attenuated neuroinflammation through modulating microglia polarization and subsequently reversed the behavioral alterations in LPS-induced mice model of neuroinflammation. ConclusionsKM may alleviate neuroinflammation by regulating microglia polarization with the involvement of Nrf2/HO-1 pathway, resulting of the neuroprotective effect.

Curcumin-activated Olfactory Ensheathing Cells Improve Functional Recovery After Spinal Cord Injury by Modulating Microglia Polarization Through APOE/TREM2/NF-κB Signaling Pathway

Transplantation of curcumin-activated olfactory ensheathing cells (aOECs) improved functional recovery in spinal cord injury (SCI) rats. Nevertheless, little is known considering the underlying mechanisms. At the present study, we investigated the promotion of regeneration and functional recovery after transplantation of aOECs into rats with SCI and the possible underlying molecular mechanisms. Primary OECs were prepared from the olfactory bulb of rats, followed by treatment with 1µM CCM at 7–10 days of culture, resulting in cell activation. Concomitantly, rat SCI model was developed to evaluate the effects of transplantation of aOECs in vivo. Subsequently, microglia were isolated, stimulated with 100 ng/mL lipopolysaccharide (LPS) for 24 h to polarize to M1 phenotype and treated by aOECs conditional medium (aOECs-CM) and OECs conditional medium (OECs-CM), respectively. Changes in the expression of pro-inflammatory and anti-inflammatory phenotypic markers expression were detected using western blotting and immunofluorescence staining, respectively. Finally, a series of molecular biological experiments including knock-down of triggering receptor expressed on myeloid cells 2 (TREM2) and analysis of the level of apolipoprotein E (APOE) expression were performed to investigate the underlying mechanism of involvement of CCM-activated OECs in modulating microglia polarization, leading to neural regeneration and function recovery. CCM-activated OECs effectively attenuated deleterious inflammation by regulating microglia polarization from the pro-inflammatory (M1) to anti-inflammatory (M2) phenotype in SCI rats and facilitated functional recovery after SCI. In addition, microglial polarization to M2 elicited by aOECs-CM in LPS-induced microglia was effectively reversed when TREM2 expression was downregulated. More importantly, the in vitro findings indicated that aOECs-CM potentiating LPS-induced microglial polarization to M2 was partially mediated by the TREM2/nuclear factor kappa beta (NF-κB) signaling pathway. Besides, the expression of APOE significantly increased in CCM-treated OECs. CCM-activated OECs could alleviate inflammation after SCI by switching microglial polarization from M1 to M2, which was likely mediated by the APOE/TREM2/NF-κB pathway, and thus ameliorated neurological function. Therefore, the present finding is of paramount significance to enrich the understanding of underlying molecular mechanism of aOECs-based therapy and provide a novel therapeutic approach for treatment of SCI.

Minocycline improves autism-related behaviors by modulating microglia polarization in a mouse model of autism.

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with few pharmacological treatments. Minocycline, a tetracycline derivative that inhibits microglial activation, has been well-identified with anti-inflammatory properties and neuroprotective effects. A growing body of research suggests that ASD is associated with neuroinflammation, abnormal neurotransmitter levels, and neurogenesis. Thus, we hypothesized that minocycline could improve autism-related behaviors by inhibiting microglia activation and altering neuroinflammation. To verify our hypothesis, we used a mouse model of autism, BTBR T+Itpr3tf/J (BTBR). As expected, minocycline administration rescued the sociability and repetitive, stereotyped behaviors of BTBR mice while having no effect in C57BL/6J mice. We also found that minocycline improved neurogenesis and inhibited microglia activation in the hippocampus of BTBR mice. In addition, minocycline treatment inhibited Erk1/2 phosphorylation in the hippocampus of BTBR mice. Our findings show that minocycline administration alleviates ASD-like behaviors in BTBR mice and improves neurogenesis, suggesting that minocycline supplementation might be a potential strategy for improving ASD symptoms.

Modulation of microglial polarization by sequential targeting surface-engineered exosomes improves therapy for ischemic stroke.

Microglia are important cells that act on regulating neuroinflammation and neurofunction after the induction of ischemic stroke (IS). Consequently, the efficient accumulation of drugs within ischemic regions, particularly in microglia, serves as a valuable approach for achieving effective therapy by attenuating microglia-mediated cerebral ischemic injury. In this study, we designed mannose (man)-conjugated luteolin (lut)-loaded platelet-derived exosomes (lut/man-pEXO) as surface engineered multifunctional cascade-delivery drug carriers to target ischemic blood vessels and subsequent microglia to enhance drug accumulation and induce neuroprotection of neurovascular unit (NVU) against IS. The results revealed that as platelets naturally gathered in pathological ischemic cerebral vessels, lut/man-pEXO could bind to platelets and efficiently target ischemic injury sites. Moreover, owing to the selective binding affinity of mannose present in lut/man-pEXO towards the mannose receptor expressed on microglia, lut/man-pEXO exhibited superior microglia-targeting properties, inducing the increased uptake of lut by microglia. As a result, lut/man-pEXO regulated microglia by inhibiting the activation of detrimental M1 and promoting the transition towards the anti-inflammatory type (M2), thus attenuating ischemic damage of NVU by reducing the infarct area, rescuing the damage of blood-brain barrier (BBB) and preventing inflammatory transformation of astrocytes.

Inosine attenuates post-stroke neuroinflammation by modulating inflammasome mediated microglial activation and polarization

To date, various agents and molecules have been developed to treat post-stroke neuroinflammation; however, none of them are clinically successful. Post-stroke neuroinflammation is primarily attributed to microglial polarization as the generation of inflammasome complexes shifts microglia to their M1 phenotype and regulates the downstream cascade. Inosine, an adenosine derivative reported to maintain cellular energy homeostasis in stressed conditions. Although the exact mechanism is still unexplored, various studies have reported that it can stimulate axonal sprouting in different neurodegenerative diseases. Hence, our present study aims to decipher the molecular mechanism of inosine mediated neuroprotection by modulating inflammasome signaling towards altered microglial polarization in ischemic stroke. Inosine was administered intraperitoneally to male Sprague Dawley rats at 1 h post-ischemic stroke and was further evaluated for neurodeficit score, motor coordination and long-term neuroprotection. Brains were harvested for infarct size estimation, biochemical assays and molecular studies. Inosine administration at 1 h post ischemic stroke decreased infarct size, neurodeficit score, and improved motor co-ordination. Normalization of biochemical parameters were achieved in the treatment groups. Microglial polarization towards its anti-inflammatory phenotype and modulation of inflammation were evident by relevant gene and protein expression studies. The outcome provides preliminary evidence of inosine mediated alleviation of post-stroke neuroinflammation via modulation of microglial polarization towards its anti-inflammatory form through regulating the inflammasome activation.

ADAM17 aggravates the inflammatory response by modulating microglia polarization through the TGF-β1/Smad pathway following experimental traumatic brain injury.

Microglia-mediated neuroinflammatory responses play important roles in secondary neurological injury after traumatic brain injury (TBI). The TGF-β pathway participates in the regulation of M1/M2 phenotype transformation of microglia. TGF-β can activate the Smad pathway by binding to TGF-βRs, which is regulated by the cleavage function of A disintegrin and metalloproteinase 17 (ADAM17). However, the role of ADAM17 and the associated signaling pathways in the pathological process after TBI remain unclear. Herein, we assessed the transformation of microglia M1/M2 phenotype polarization and the neuroinflammatory response after the inhibition of ADAM17. The formation of TGF-βRs and TGF-β1/TGF-βRII complexes on microglia were detected to evaluate the effect of ADAM17 inhibition on the TGF-β1/Smad pathway. ADAM17 was highly expressed after TBI and mainly located in the microglia. the inhibition of ADAM17 improved neurological function after TBI. The neuroprotective effect of ADAM17 inhibition was related to a shift from the M1 microglial phenotype to the M2 microglial phenotype, thus reducing TBI-induced neuroinflammation. ADAM17 inhibition increased expression of TGF-βRs on the microglia membrane, promoted formation of TGF-β1/TGF-βRII complexes, and induced intranuclear translocation of Smads, which activated the TGF-β/Smad pathway. In conclusion, our study suggested that ADAM17 inhibition regulated microglia M1/M2 phenotype polarization through the TGF-β1/Smad pathway and influenced the neuroinflammatory response after TBI.

Interferon-β modulates microglial polarization to ameliorate delayed tPA-exacerbated brain injury in ischemic stroke.

Tissue plasminogen activator (tPA) is the only FDA-approved drug for the treatment of ischemic stroke. Delayed tPA administration is associated with increased risks of blood-brain barrier (BBB) disruption and hemorrhagic transformation. Studies have shown that interferon beta (IFNβ) or type I IFN receptor (IFNAR1) signaling confers protection against ischemic stroke in preclinical models. In addition, we have previously demonstrated that IFNβ can be co-administered with tPA to alleviate delayed tPA-induced adverse effects in ischemic stroke. In this study, we investigated the time limit of IFNβ treatment on the extension of tPA therapeutic window and assessed the effect of IFNβ on modulating microglia (MG) phenotypes in ischemic stroke with delayed tPA treatment. Mice were subjected to 40 minutes transient middle cerebral artery occlusion (MCAO) followed by delayed tPA treatment in the presence or absence of IFNβ at 3h, 4.5h or 6h post-reperfusion. In addition, mice with MG-specific IFNAR1 knockdown were generated to validate the effects of IFNβ on modulating MG phenotypes, ameliorating brain injury, and lessening BBB disruption in delayed tPA-treated MCAO mice. Our results showed that IFNβ extended tPA therapeutic window to 4.5h post-reperfusion in MCAO mice, and that was accompanied with attenuated brain injury and lessened BBB disruption. Mechanistically, our findings revealed that IFNβ modulated MG polarization, leading to the suppression of inflammatory MG and the promotion of anti-inflammatory MG, in delayed tPA-treated MCAO mice. Notably, these effects were abolished in MG-specific IFNAR1 knockdown MCAO mice. Furthermore, the protective effect of IFNβ on the amelioration of delayed tPA-exacerbated ischemic brain injury was also abolished in these mice. Finally, we identified that IFNβ-mediated modulation of MG phenotypes played a role in maintaining BBB integrity, because the knockdown of IFNAR1 in MG partly reversed the protective effect of IFNβ on lessening BBB disruption in delayed tPA-treated MCAO mice. In summary, our study reveals a novel function of IFNβ in modulating MG phenotypes, and that may subsequently confer protection against delayed tPA-exacerbated brain injury in ischemic stroke.

Electroacupuncture alleviates early brain injury via modulating microglia polarization and suppressing neuroinflammation in a rat model of subarachnoid hemorrhage

Subarachnoid hemorrhage refers to an uncommon but severe subtype of stroke leading to high mortality and disability rates. Electroacupuncture, a traditional Chinese medical therapy combined with modern technology, shows evident curative effects on cerebral vascular diseases. This study attempts to investigate the possible treatment effects and mechanisms of EA on early brain injury after SAH. Data were gathered among sham group, SAH-induced group, and EA-treated group of male SD rats, concerning mortality rates, weight loss, rotarod latencies, cerebral blood flow, cell apoptosis, pro-inflammatory cytokines releasing, apoptotic protein level, microglia activation and related signal pathway. All results were collected 24–72 h after SAH induction. EA treatment demonstrated significant improvement on motor function 24 h after SAH without significant changes in mortality rate, weight loss, and cerebral blood flow. Another important finding was that EA regulated Bax and Bcl-2 imbalance and reduced cleaved casepase-3 caused by SAH. Additionally, levels of TNF-α, IL-1β, IL-6 were suppressed. The neuron apoptosis was suppressed by EA. The M1 polarization of activated microglia decreased while M2 polarized phenotype increased after EA treatment. Furthermore, pSTAT3-NOX2 signal axis, the M1 phenotype related activation pathway, was depressed after EA treatment. These findings suggested that EA improved motor deficits and ameliorated early brain injury after SAH probably via decreasing neuron apoptosis and anti-inflammation, which may involve modulation of microglia polarization. Taken together, EA may be a potential therapy for SAH treatment.

Melatonin alleviates BDE-209-induced cognitive impairment and hippocampal neuroinflammation by modulating microglia polarization via SIRT1-mediated HMGB1/TLR4/NF-κB pathway.

Polybrominated diphenyl ethers (PBDEs) are persistent environmental contaminants with developmental neurotoxicity, the mechanism of which remains obscure. The present study aimed to evaluate cognitive deficits and microglia-originated neuroinflammation in the hippocampus of offspring rats exposed to BDE-209 (30 and 100mg/kg) during perinatal period. Compared to the control, BDE-209-treated rats showed significant longer escape latency and less platform crossings in tests of Morris water maze. Besides obvious hippocampal neuron damage, increased microglial activation and pro-inflammatory markers (CD86, TNFα, and IL-1β), meanwhile, decreased anti-inflammatory molecules (CD206, IL-10, and Arg1) were induced by BDE-209. Furthermore, we investigated the neuroprotection of melatonin against BDE-209 and whether through sirtuin 1 (SIRT1). Consistent with restored SIRT1 activity, enhanced deacetylation of HMGB1 and inhibited cytoplasmic translocation of HMGB1, reduced expression of proteins involved in TLR4-NF-κB pathway and nuclear transfer of phosphorylated-NF-κB p65, and ultimately suppressed microglial activation and improved spatial memory were observed in 10mg/kg melatonin-pretreated rats, compared with BDE-209-exposed alone. These results demonstrated that melatonin ameliorated BDE-209-caused cognitive impairment partially through shifting microglia polarization towards anti-inflammatory phenotype in a SIRT1-dependent manner, suggesting a potential mechanism for prevention.

Exosomes derived from mesenchymal stem cells overexpressing miR-210 inhibits neuronal inflammation and contribute to neurite outgrowth through modulating microglia polarization.

Inflammatory responses play a critical role in the progress of neurodegenerative disorders. MSC-Exos is considered to have an anti-inflammatory effect on the treatment strategy for brain injury. However, the therapeutic effect and possible mechanism of Exosomal miR-210 on microglia polarization-induced neuroinflammation and neurite outgrowth have not been reported. MSC-Exos were isolated by ultracentrifugation, identified by Nanosight NS300, transmission electron microscopy, and western bolt. In vitro, to explore the protective mechanism of MSC-Exos against neuroinflammation, the microglial BV2 cell was exposed to lipopolysaccharide to assess inflammatory changes. The intake of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil)-MSC-Exos into microglia was observed by fluorescence microscopy. The results showed that Exosomal miR-210 treatment significantly inhibited the production of nitric oxide and pro-inflammatory cytokines. Exosomal miR-210 treatment also increased the number of M2 microglia cells and inhibited M1 microglia polarization. In addition, western blot demonstrated that Exosomal miR-210 reduced neuronal apoptosis. Thus, Exosomal miR-210 attenuated neuronal inflammation and promoted neurite outgrowth. Exosomal miR-210 from MSCs attenuated neuronal inflammation and contributed to neurogenesis possibly by inhibiting microglial M1 polarization.