Sesamol Attenuates Neuroinflammation by Regulating the AMPK/SIRT1/NF-κB Signaling Pathway after Spinal Cord Injury in Mice

Inflammation is one of the crucial mechanisms mediating spinal cord injury (SCI) progress. Sesamol, a component of sesame oil, has anti-inflammatory activity, but its mechanism in SCI remains unclear. We investigated if the AMPK/SIRT1/NF-κB pathway participated in anti-inflammation of sesamol in SCI. Sesamol could inhibit neuronal apoptosis, reduce neuroinflammation, enhance M2 phenotype microglial polarization, and improved motor function recovery in mice after SCI. Furthermore, sesamol increased SIRT1 protein expression and p-AMPK/AMPK ratio, while it downregulated the p-p65/p65 ratio, indicating that sesamol treatment upregulated the AMPK/SIRT1 pathway and inhibited NF-κB activation. However, these effects were blocked by compound C which is a specific AMPK inhibitor. Together, the study suggests that sesamol is a potential drug for antineuroinflammation and improving locomotor functional recovery through regulation of the AMPK/SIRT1/NF-κB pathway in SCI.

PPAR-γ Promotes the Polarization of Rat Retinal Microglia To M2 Phenotype By Regulating the Expression of CD200-CD200R1 Under Hypoxia

Objective Based on recent reports, peroxisome proliferator-activated receptor-γ (PPAR-γ) could promote microglial M2 polarization to inhibit inflammation. However, the specific molecular mechanisms instigate the anti-inflammatory ability of PPAR-γ in microglia have not been expounded. In the present study, we explored the molecular mechanisms of the anti-inflammatory effects of PPAR-γ in hypoxia-stimulated rat microglial cells. Methods shRNA expressing lentivirus was used to knock down PPAR-γ and CD200 genes. The hypoxia-induced polarization markers release (M1: iNOS, IL-1β, IL-6 and TNF-α; M2: Arg-1, YM1, IL-4 and IL-10) was assessed by RT-PCR, while PPAR-γ-related signals (PPAR-γ, PPAR-γ in cytoplasm or nucleus, CD200 and CD200Rs) were monitored by western blot and RT-PCR. Results Hypoxia enhanced PPAR-γ and CD200 expressions in microglial cells. In addition, PPAR-γ agonist 15d-PGJ2 elevated CD200 and CD200R1 expressions, while sh-PPAR-γ (PPAR-γ knock-down) had just the opposite effect. Following hypoxia, expressions of M1 markers increased significantly, while those of M2 markers decreased, and the above effects were attenuated by 15d-PGJ2. Conversely, knocking down PPAR-γ or CD200 inhibited the polarization of microglial cells to M2 phenotype. Conclusion Results demonstrated that PPAR-γ performed an anti-inflammatory function in hypoxia-stimulated microglial cells by promoting their polarization to M2 phenotype via CD200-CD200R1 pathway.

Melatonin Modulates Microglia Activation in Neuro-inflammation by Regulating the ER Stress/PPARd/SIRT1 Signaling Pathway

Background: Activated microglia-mediated neuro-inflammation plays a vital aspect in regulating the micromilieu of the central nervous system. Neuro-inflammation involves distinct alterations of microglial phenotypes, containing nocuous pro-inflammatory (M1) phenotype and neuroprotective anti-inflammatory (M2) phenotype. Currently, there is no effective treatment for modulating such alterations. Little evidence shows that melatonin prevents the detrimental cascade of activated microglia-mediated neuro-inflammation. Methods: The expression levels of M1/M2 marker of primary microglia influenced by Melatonin were detected via qPCR. Functional activities were explored by western blotting, luciferase activity, EMSA, and ChIP assay. Structure interaction was assessed by molecular docking and LIGPLOT analysis. ER stress detection was examined by ultrastructure TEM, calapin activity, and ERSE assay. The neurobehavioral evaluations and immunofluorescence staining in animals were used for investigation of Melatonin on the neuroinflammation in vivo. Results: Melatonin had targeted on Peroxisome Proliferator Activated Receptor Delta (PPARd) activity, boosted LPS-stimulated alterations in polarization from the M1 to the M2 phenotype, and thereby inhibited NFkB–IKKb activation in primary microglia. The PPARd agonist L-165041 or over-expression of PPARd plasmid (ov-PPARd) showed similar results. Molecular docking screening, dynamic simulation approaches, and biological studies of melatonin showed that the activated site was located at PPARd (phospho-Thr256-PPARd). Furthermore, we found that activated microglia had lowered PPARd activity as well as the downstream SIRT1 formation via enhancing ER stress. Melatonin, PPARd agonist and ov-PPARd all effectively reversed the above-mentioned effects. Melatonin blocked ER stress by regulating calapin activity and expression in LPS-activated microglia. Additionally, melatonin or L-165041 ameliorated the neurobehavioral deficits in LPS-aggravated neuroinflammatory mice through blocking microglia activities, and also promoted phenotype changes to M2-predominant microglia. Conclusions Melatonin suppressed neuro-inflammation in vitro and in vivo by tuning microglial activation through the ER stress-dependent PPARd/SIRT1 signaling cascade. We proposed that this treatment strategy is an encouraging pharmacological approach for the remedy of neuro-inflammation associated disorders.

Microglia Polarization from M1 toward M2 Phenotype Is Promoted by Astragalus Polysaccharides Mediated through Inhibition of miR-155 in Experimental Autoimmune Encephalomyelitis

Activated microglia is considered to be major mediators of the neuroinflammatory environment in demyelinating diseases of the central nervous system (CNS). Activated microglia are mainly polarized into M1 type, which plays a role in promoting inflammation and demyelinating. However, the proportion of microglia polarized into M2 type is relatively low, which cannot fully play the role of anti-inflammatory and resistance to demyelinating. Our previous study found that Astragalus polysaccharides (APS) has an immunomodulatory effect and can inhibit neuroinflammation and demyelination in experimental autoimmune encephalomyelitis (EAE), which is a classic animal model of CNS demyelinating disease. In this study, we found that APS was effective in treating EAE mice. It restored microglia balance by inhibiting the polarization of microglia to M1-like phenotype and promoting the polarization of microglia to M2-like phenotype in vivo and in vitro. miR-155 is a key factor in regulating microglia polarization. We found that APS could inhibit the expression level of miR-155 in vivo and in vitro. Furthermore, we performed transfection overexpression and blocking experiments. The results showed that miR-155 mediated the polarization of microglia M1/M2 phenotype, while the selective inhibitor of miR-155 attenuated the inhibition of APS on microglia M1 phenotype and eliminated the promotion of APS on microglia M2 phenotype. Microglia can secrete IL-1α, TNF-α, and C1q after polarizing into M1 type and induce the activation of A1 neurotoxic astrocytes, further aggravating neuroinflammation and demyelination. APS reduced the secretion of IL-1α, TNF-α, and C1q by activated microglia, thus inhibited the formation of A1 neurotoxic astrocytes. In summary, our study suggests that APS regulates the polarization of microglia from M1 to M2 phenotype by inhibiting the miR-155, reduces the secretion of inflammatory factors, and inhibits the activation of neurotoxic astrocytes, thus effectively treating EAE.

mmu-miR-145a-5p Accelerates Diabetic Wound Healing by Promoting Macrophage Polarization Toward the M2 Phenotype

Diabetic wounds are recalcitrant to healing. One of the important characteristics of diabetic trauma is impaired macrophage polarization with an excessive inflammatory response. Many studies have described the important regulatory roles of microRNAs (miRNAs) in macrophage differentiation and polarization. However, the differentially expressed miRNAs involved in wound healing and their effects on diabetic wounds remain to be further explored. In this study, we first identified differentially expressed miRNAs in the inflammation, tissue formation and reconstruction phases in wound healing using Illumina sequencing and RT-qPCR techniques. Thereafter, the expression of musculus (mmu)-miR-145a-5p (“miR-145a-5p” for short) in excisional wounds of diabetic mice was identified. Finally, expression of miR-145a-5p was measured to determine its effects on macrophage polarization in murine RAW 264.7 macrophage cells and wound healing in diabetic mice. We identified differentially expressed miRNAs at different stages of wound healing, ten of which were further confirmed by RT-qPCR. Expression of miR-145a-5p in diabetic wounds was downregulated during the tissue formation stage. Furthermore, we observed that miR-145a-5p blocked M1 macrophage polarization while promoting M2 phenotype activation in vitro. Administration of miR-145a-5p mimics during initiation of the repair phase significantly accelerated wound healing in db/db diabetic mice. In conclusion, our findings suggest that rectifying macrophage function using miR-145a-5p overexpression accelerates diabetic chronic wound healing.

Carbon Monoxide Regulates Macrophage Differentiation and Polarization toward the M2 Phenotype through Upregulation of Heme Oxygenase 1

Carbon monoxide (CO) is generated by heme oxygenase (HO), and HO-1 is highly induced in monocytes and macrophages upon stimulation. Monocytes differentiate into macrophages, including pro-inflammatory (M1) and anti-inflammatory (M2) cells, in response to environmental signals. The present study investigated whether CO modulates macrophage differentiation and polarization, by applying the CO-releasing molecule-3 (CORM-3). Results showed that murine bone marrow cells are differentiated into macrophages by CORM-3 in the presence of macrophage colony-stimulating factor. CORM-3 increases expressions of macrophage markers, including F4/80 and CD11b, and alters the cell morphology into elongated spindle-shaped cells, which is a typical morphology of M2 cells. CORM-3 upregulates the expressions of genes and molecules involved in M2 polarization and M2 phenotype markers, such as STAT6, PPARγ, Ym1, Fizz1, arginase-1, and IL-10. However, exposure to CORM-3 inhibits the iNOS expression, suggesting that CO enhances macrophage differentiation and polarization toward M2. Increased HO-1 expression is observed in differentiated macrophages, and CORM-3 further increases this expression. Hemin, an HO-1 inducer, results in increased macrophage differentiation, whereas the HO-1 inhibitor zinc protoporphyrin IX inhibits differentiation. In addition, CORM-3 increases the proportion of macrophages in peritoneal exudate cells and enhances the expression of HO-1 and arginase-1 but inhibits iNOS. Taken together, these results suggest that the abundantly produced CO in activated macrophages enhances proliferation, differentiation, and polarization toward M2. It will probably help clear apoptotic cells, resolve inflammation, and promote wound healing and tissue remodeling.

Therapeutic effect of soluble factors of M2 phenotype macrophages in children with language impairments

The aim of the present study was to assess safety and clinical efficacy of inhalation immunotherapy based on intranasal administration of bioactive factors produced by the M2 phenotype macrophages in children with language impairments, as well as to study the effect of inhalation immunotherapy on the cytokine profile in the patients' blood serum. The study was carried out according to the NCT04689282 protocol (www.ClinicalTrials.gov) and included 14 children (9 boys / 5 girls), aged 3 to 8 years, with language impairments associated with perinatal or postnatal CNS lesions of various origin. The children recruited into the study were assessed by a neurologist and speech therapist before the therapy, at the end of the course (1 month), and 6 months later. Serum samples for cytokine analysis were obtained before and 1 month after therapy. The course of intranasal inhalations by the conditioned M2 media (2 ml one time per day for 28-30 days) was safe and well tolerated. None of the 14 treated children had significant adverse reactions and severe undesirable events. Intranasal immunotherapy led to a decrease in the severity of language problems, which manifested by improved speech understanding by 45%; the sensorimotor level of speech, by 51%; word formation skills, by 72%, as well as a twofold increase in general and fine motor skills. In children with signs of autism spectrum disorders, along with a language improvement, a decrease in the severity of autistic symptoms was registered, as evidenced by statistically significant decrease in the CARS score from 42.5 to 38.5 after 1 month, and to 33 points after 6 months (p < 0.05). The clinical effect was revealed rather soon, i.e., within a month after the first procedure, being maintained or intensified during a follow-up for 6 months. At the same time, two-thirds of the children showed a clear clinical improvement, with insignificant effect in the rest of patients. Comparative analysis of the serum cytokine levels in these subgroups showed that children with a pronounced positive response to inhaled immunotherapy differed in the following parameters: (1) initially higher level of VEGF and IGF-1, and (2) decrease the level of TNFα in response to intranasal immunotherapy. In summary, we first tested a fundamentally new approach based on the use of soluble factors from M2-type macrophages and intranasal route of their administration in order to treat the children with severe language impairments, demonstrating safety and obtained preliminary data on effectiveness of such approach.

Influence of macrophage polarization on the effectiveness of surgical therapy of peri-implantitis

Purpose To evaluate the influence of macrophage expression and polarization on the effectiveness of surgical therapy of peri-implantitis over a 6 month follow-up. Methods A total of fourteen patients (n = 14 implants) diagnosed with peri-implantitis underwent access flap surgery, granulation tissue removal, implantoplasty, and augmentation at intra-bony components using a natural derived bone mineral and application of a native collagen membrane during a standardized surgical procedure. Granulation tissue biopsies were prepared for immunohistochemical characterization and macrophage polarization assessment. M1 and M2 phenotype expression was identified and quantified through immunohistochemical markers and histomorphometrical analyses. Clinical evaluation and data collection were performed initially and after a healing period of 6 months. Statistical analyses were performed to associate infiltrated area, macrophage, and M1/M2 phenotype influence on peri-implant tissue healing parameters after a 6-month follow-up. Results Mean infiltrated compartment (ICT) values occupied a total percentage of 70.3% ± 13.0 in the analyzed granulation tissue biopsies. Macrophages occupied a mean area of 15.3% ± 7.0. M1 and M2 phenotypes were present in 7.1 ± 4.1% and 5.5 ± 3.7%, respectively. No statistically significant difference was observed between M1 and M2% expression (p = 0.16). The mean M1/ M2 ratio amounted to 1.5 ± 0.8. Surgical therapy was associated with statistically significant reductions in mean bleeding on probing (BOP), probing depth (PD) and suppuration (SUPP) scores at 6 months (p < 0.05). Linear regression analyses revealed a significant correlation between macrophage expression (CD68%) and changes in PD scores and M1 (%) expression and changes in mucosal recession (MR) scores at 6 months. Conclusions The present data suggest that macrophages might influence peri-implant tissue healing mechanisms following surgical therapy of peri-implantitis over a short-term period. Particularly, changes in PD and MR scores were statistically significantly associated with macrophage expression and phenotype. Graphical Abstract