WKYMVm/FPR2 Alleviates Spinal Cord Injury by Attenuating the Inflammatory Response of Microglia

Mutual regulation of microglia and astrocytes after Gas6 inhibits spinal cord injury

JOURNAL/nrgr/04.03/01300535-202502000-00032/figure1/v/2024-05-28T214302Z/r/image-tiff Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury. Microglia and astrocytes play key roles in the spinal cord injury micro-environment and share a close interaction. However, the mechanisms involved remain unclear. In this study, we found that after spinal cord injury, resting microglia (M0) were polarized into pro-inflammatory phenotypes (MG1 and MG3), while resting astrocytes were polarized into reactive and scar-forming phenotypes. The expression of growth arrest-specific 6 (Gas6) and its receptor Axl were significantly down-regulated in microglia and astrocytes after spinal cord injury. In vitro experiments showed that Gas6 had negative effects on the polarization of reactive astrocytes and pro-inflammatory microglia, and even inhibited the cross-regulation between them. We further demonstrated that Gas6 can inhibit the polarization of reactive astrocytes by suppressing the activation of the Yes-associated protein signaling pathway. This, in turn, inhibited the polarization of pro-inflammatory microglia by suppressing the activation of the nuclear factor-κB/p65 and Janus kinase/signal transducer and activator of transcription signaling pathways. In vivo experiments showed that Gas6 inhibited the polarization of pro-inflammatory microglia and reactive astrocytes in the injured spinal cord, thereby promoting tissue repair and motor function recovery. Overall, Gas6 may play a role in the treatment of spinal cord injury. It can inhibit the inflammatory pathway of microglia and polarization of astrocytes, attenuate the interaction between microglia and astrocytes in the inflammatory microenvironment, and thereby alleviate local inflammation and reduce scar formation in the spinal cord.

Quercetin Regulates Microglia M1/M2 Polarization and Alleviates Retinal Inflammation via ERK/STAT3 Pathway

Retinal inflammation is a pivotal characteristic observed in various retinal degenerative disorders, notably age-related macular degeneration (AMD), primarily orchestrated by the activation of microglia. Targeting the inhibition of microglial activation has emerged as a therapeutic focal point. Quercetin (Qu), ubiquitously present in dietary sources and tea, has garnered attention for its anti-neuroinflammatory properties. However, the impact of Qu on retinal inflammation and the associated mechanistic pathways remains incompletely elucidated. In this study, retinal inflammation was induced in adult male C57BL/6 J mice through intraperitoneal administration of LPS. The results revealed that Qu pre-treatment induces a phenotypic shift in microglia from M1 phenotype to M2 phenotype. Furthermore, Qu attenuated retinal inflammation and stabilized the integrity of the blood-retina barrier (BRB). In vitro experiments revealed that Qu impedes microglial activation, proliferation, and migration, primarily via modulation the ERK/STAT3 signaling pathway. Notably, these actions of Qu significantly contributed to the preservation of photoreceptors. Consequently, Qu pre-treatment holds promise as an effective strategy for controlling retinal inflammation and preserving visual function.

Advances of the MAPK pathway in the treatment of spinal cord injury

Spinal cord injury (SCI) represents a complex pathology within the central nervous system (CNS), leading to severe sensory and motor impairments. It activates various signaling pathways, notably the mitogen-activated protein kinase (MAPK) pathway. Present treatment approaches primarily focus on symptomatic relief, lacking efficacy in addressing the underlying pathophysiological mechanisms. Emerging research underscores the significance of the MAPK pathway in neuronal differentiation, growth, survival, axonal regeneration, and inflammatory responses post-SCI. Modulating this pathway post-injury has shown promise in attenuating inflammation, minimizing apoptosis, alleviating neuropathic pain, and fostering neural regeneration. Given its pivotal role, the MAPK pathway emerges as a potential therapeutic target in SCI management. This review synthesizes current knowledge on SCI pathology, delineates the MAPK pathway's characteristics, and explores its dual roles in SCI pathology and therapeutic interventions. Furthermore, it addresses the existing challenges in MAPK research in the context of SCI, proposing solutions to overcome these hurdles. Our aim is to offer a comprehensive reference for future research on the MAPK pathway and SCI, laying the groundwork for targeted therapeutic strategies.

Upregulated miR-125b mitigates inflammation, astrocyte activation, and dysfunction of spinal cord injury by inactivating the MAPK pathway

BACKGROUND

Since the abnormal expression of miR-125b in spinal cord injury (SCI) and the regulatory effect of miR-125b on the MAPK pathway have been expounded, we attempt to investigate whether miR-125b exerts a regulatory effect on SCI by modulating the MAPK pathway.

METHOD

A SCI rat model was established. The rats were treated with miR-125b antagomir or agomir, and their motor function affected by miR-125b was further detected by Basso-Beattie-Bresnahan (BBB) scoring. The histopathological changes and neuronal loss in the spinal cord were evaluated using hematoxylin-eosin and Nissl staining. Microglia-conditioned medium (MCM) was prepared and further used to treat the astrocytes, the activation of which was evaluated via immunofluorescence staining. The expressions of miR-125b, inflammation-related factors (IL-6, IL-1β, TNF-α, and IL-10), and MAPK pathway-related proteins (p38, ERK1/2, and JNK1/2 as well as their phosphorylated (p) forms) in the spinal cord, serum, and MCM-treated astrocytes of rats were determined by reverse-transcription quantitative polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay, and Western blot.

RESULT

MiR-125b was lowly expressed in SCI-modeled rats. MiR-125b downregulation aggravated the impaired motor function, the disorder within the tissue, astrocyte activation, and neuron loss in the spinal cord tissues of SCI-modeled rats, while miR-125b upregulation did oppositely. MiR-125b downregulation enhanced the levels of IL-6, IL-1β, TNF-α, p38, p-p38, p-ERK1/2, and p-JNK1/2, whilst reducing that of IL-10. Contrarily, miR-125b upregulation exerted the opposite effects in SCI-modeled rats and MCM-treated astrocytes.

CONCLUSION

Up-regulation of miR-125b mitigates inflammation, astrocyte activation, and dysfunction in SCI by inactivating the MAPK pathway.

Apigenin Alleviates Autoimmune Uveitis by Inhibiting Microglia M1 Pro-Inflammatory Polarization

Purpose

Apigenin is a natural small molecule compound widely present in various vegetables and fruits. Recently, Apigenin was reported to inhibit lipopolysaccharide (LPS)-simulated microglial proinflammatory activation. Considering the important role of microglia in retinal disorders, we wonder whether Apigenin could exert a therapeutic effect on experimental autoimmune uveitis (EAU) through reprogramming retinal microglia to a beneficial subtype.

Methods

EAU was induced in C57BL/6J mice by immunization with interphotoreceptor retinoid-binding protein (IRBP)651-670, followed by intraperitoneal administration of Apigenin. Disease severity was assessed based on clinical and pathological scores. In vivo, Western blotting was used to quantify protein levels of classical inflammatory factors, microglial M1/M2 markers and the tight junction protein of the blood-retinal-barrier (BRB). Immunofluorescence was used to determine the Apigenin's efficacy on microglial phenotype. In vitro, Apigenin was added in LPS and IFN-γ stimulated human microglial cell line. Western blotting and Transwell assays were used to analyze the phenotype of microglia.

Results

In vivo, we found that Apigenin significantly reduced the clinical and pathological scores of EAU. The protein levels of inflammatory cytokines were significantly decreased in retina, and BRB disruption was ameliorated after Apigenin treatment. Meanwhile, Apigenin inhibited microglia M1 transition in EAU mice retina. In vitro functional studies showed that Apigenin decreased LPS and IFN-γ-induced microglial inflammatory factor production and M1-activation via the TLR4/MyD88 pathway.

Conclusions

Apigenin can ameliorate retinal inflammation in IRBP induced autoimmune uveitis through inhibiting microglia M1 pro-inflammatory polarization via TLR4/MyD88 pathway.

WKYMVm Works by Targeting Immune Cells

WKYMVm (Trp-Lys-Tyr-Met-Val-D-Met) is a synthetic hexapeptide identified as a potent agonist of FPRs. FPRs are widely expressed on the cell membrane of immune cells. Therefore, WKYMVm participates in the regulation of immune cells by activating FPRs, and plays a therapeutic role in infections, tumors, autoimmune diseases and so on. WKYMVm can promote the chemotactic migration, increase the bactericidal activity of neutrophils and monocytes. WKYMVm also regulates the number and polarization of macrophages, affects the maturation of DCs and the differentiation of T cells, and promotes the activation and chemotaxis of NK cells. These functions make WKYMVm a candidate drug for immunotherapy. In this paper, we summarize the regulatory effects and underlying mechanisms of WKYMVm on six immune cells (neutrophils, monocytes, macrophages, DCs, T cells and NK cells) to increase comprehensive understanding and promote further research on WKYMVm.