Treatment with 5-methoxytryptophan attenuates microglia-induced neuroinflammation in spinal cord trauma

Blockade of the ADAM8-Fra-1 complex attenuates neuroinflammation by suppressing the Map3k4/MAPKs axis after spinal cord injury

BACKGROUND

Mechanical spinal cord injury (SCI) is a deteriorative neurological disorder, causing secondary neuroinflammation and neuropathy. ADAM8 is thought to be an extracellular metalloproteinase, which regulates proteolysis and cell adherence, but whether its intracellular region is involved in regulating neuroinflammation in microglia after SCI is unclear.

METHODS

Using animal tissue RNA-Seq and clinical blood sample examinations, we found that a specific up-regulation of ADAM8 in microglia was associated with inflammation after SCI. In vitro, microglia stimulated by HMGB1, the tail region of ADAM8, promoted microglial inflammation, migration and proliferation by directly interacting with ERKs and Fra-1 to promote activation, then further activated Map3k4/JNKs/p38. Using SCI mice, we used BK-1361, a specific inhibitor of ADAM8, to treat these mice.

RESULTS

The results showed that administration of BK-1361 attenuated the level of neuroinflammation and reduced microglial activation and recruitment by inhibiting the ADAM8/Fra-1 axis. Furthermore, treatment with BK-1361 alleviated glial scar formation, and also preserved myelin and axonal structures. The locomotor recovery of SCI mice treated with BK-1361 was therefore better than those without treatment.

CONCLUSIONS

Taken together, the results showed that ADAM8 was a critical molecule, which positively regulated neuroinflammatory development and secondary pathogenesis by promoting microglial activation and migration. Mechanically, ADAM8 formed a complex with ERK and Fra-1 to further activate the Map3k4/JNK/p38 axis in microglia. Inhibition of ADAM8 by treatment with BK-1361 decreased the levels of neuroinflammation, glial formation, and neurohistological loss, leading to favorable improvement in locomotor functional recovery in SCI mice.

Predictive Value of 5-Methoxytryptophan on Long-Term Clinical Outcome after PCI in Patients with Acute Myocardial Infarction-a Prospective Cohort Study

BACKGROUND

In recent years, 5-Methoxytryptophan (5-MTP) has been identified as an endothelial factor with vaso-protective and anti-inflammatory properties.

METHODS

In this prospective cohort study, a total of 407 patients with acute myocardial infarction (AMI) who underwent percutaneous coronary intervention (PCI) successfully were enrolled. A 1-year follow-up Kaplan-Meier survival analysis was used for evaluating the correlation between 5-MTP and major adverse cardiovascular event (MACE) while Cox proportional-hazards regression was used to identify predictive values of 5-MTP on MACE after AMI.

RESULTS

Increased 5-MTP level led to a significant downtrend in the incidence of MACE (All Log-rank p < 0.05). Thus, a high baseline 5-MTP could reduce the 1-year incidence of MACE (HR = 0.33, 95%Cl 0.17-0.64, p = 0.001) and heart failure (HF) (HR = 0.28, 95% Cl 0.13-0.62, p = 0.002). Subgroup analysis indicated the predictive value of 5-MTP was more significant in patients aged ≤ 65 years and those with higher baseline NT-proBNP, T2DM, STEMI, and baseline HF with preserved LVEF (HFpEF) characteristics.

CONCLUSIONS

Plasma 5-MTP is an independent and protective early biomarker for 1-year MACE and HF events in patients with AMI, especially in younger patients and those with T2DM, STEMI, and baseline HFpEF characteristics.

5-Methoxytryptophan ameliorates endotoxin-induced acute lung injury in vivo and in vitro by inhibiting NLRP3 inflammasome-mediated pyroptosis through the Nrf2/HO-1 signaling pathway

BACKGROUND AND AIM

Endotoxin-induced acute lung injury (ALI) is a complicated and fatal condition with no specific or efficient clinical treatments. 5-Methoxytryptophan (5-MTP), an endogenous metabolite of tryptophan, was revealed to block systemic inflammation. However, the specific mechanism by which 5-MTP affects ALI still needs to be clarified. The purpose of this study was to determine whether 5-MTP protected the lung by inhibiting NLRP3 inflammasome-mediated pyroptosis through the Nrf2/HO-1 signaling pathway.

METHODS AND RESULTS

We used lipopolysaccharide (LPS)-stimulated C57BL/6 J mice and MH-S alveolar macrophages to create models of ALI, and 5-MTP (100 mg/kg) administration attenuated pathological lung damage in LPS-exposed mice, which was associated with decreased inflammatory cytokines and oxidative stress levels, upregulated protein expression of Nrf2 and HO-1, and suppressed Caspase-1 activation and NLRP3-mediated pyroptosis protein levels. Moreover, Nrf2-deficient mice or MH-S cells were treated with 5-MTP to further confirm the protective effect of the Nrf2/HO-1 pathway on lung damage. We found that Nrf2 deficiency partially eliminated the beneficial effect of 5-MTP on reducing oxidative stress levels and inflammatory responses and abrogating the inhibition of NLRP3-mediated pyroptosis induced by LPS.

CONCLUSION

These findings suggested that 5-MTP could effectively ameliorate ALI by inhibiting NLRP3-mediated pyroptosis via the Nrf2/HO-1 signaling pathway.

Novel Functional Peptide for Next-Generation Vital Pulp Therapy

Although vital pulp therapy should be performed by promoting the wound-healing capacity of dental pulp, existing pulp-capping materials were not developed with a focus on the pulpal repair process. In previous investigations of wound healing in dental pulp, we found that organic dentin matrix components (DMCs) were degraded by matrix metalloproteinase-20, and DMC degradation products containing protein S100A7 (S100A7) and protein S100A8 (S100A8) promoted the pulpal wound-healing process. However, the direct use of recombinant proteins as pulp-capping materials may cause clinical problems or lead to high medical costs. Thus, we hypothesized that functional peptides derived from recombinant proteins could solve the problems associated with direct use of such proteins. In this study, we identified functional peptides derived from the protein S100 family and investigated their effects on dental pulp tissue. We first performed amino acid sequence alignments of protein S100 family members from several mammalian sources, then identified candidate peptides. Next, we used a peptide array method that involved human dental pulp stem cells (hDPSCs) to evaluate the mineralization-inducing ability of each peptide. Our results supported the selection of 4 candidate functional peptides derived from proteins S100A8 and S100A9. Direct pulp-capping experiments in a rat model demonstrated that 1 S100A8-derived peptide induced greater tertiary dentin formation compared with the other peptides. To investigate the mechanism underlying this induction effect, we performed liquid chromatography-tandem mass spectrometry analysis using hDPSCs and the S100A8-derived peptide; the results suggested that this peptide promotes tertiary dentin formation by inhibiting inflammatory responses. In addition, this peptide was located in a hairpin region on the surface of S100A8 and could function by direct interaction with other molecules. In summary, this study demonstrated that a S100A8-derived functional peptide promoted wound healing in dental pulp; our findings provide insights for the development of next-generation biological vital pulp therapies.

Role of statins in regulating molecular pathways following traumatic brain injury: A system pharmacology study

Traumatic brain injury (TBI) is a serious disorder with debilitating physical and psychological complications. Previous studies have indicated that genetic factors have a critical role in modulating the secondary phase of injury in TBI. Statins have interesting pleiotropic properties such as antiapoptotic, antioxidative, and anti-inflammatory effects, which make them a suitable class of drugs for repurposing in TBI. In this study, we aimed to explore how statins modulate proteins and pathways involved in TBI using system pharmacology. We first explored the target associations with statins in two databases to discover critical clustering groups, candidate hub and critical hub genes in the network of TBI, and the possible connections of statins with TBI-related genes. Our results showed 1763 genes associated with TBI. Subsequently, the analysis of centralities in the PPI network displayed 55 candidate hub genes and 15 hub genes. Besides, MCODE analysis based on threshold score:10 determined four modular clusters. Intersection analysis of genes related to TBI and statins demonstrated 204 shared proteins, which suggested that statins influence 31 candidate hub and 9 hub genes. Moreover, statins had the highest interaction with MCODE1. The biological processes of the 31 shared proteins are related to gene expression, inflammation, antioxidant activity, and cell proliferation. Biological enriched pathways showed Programmed Cell Death proteins, AGE-RAGE signaling pathway, C-type lectin receptor signalling pathway, and MAPK signaling pathway as top clusters. In conclusion, statins could target several critical post-TBI genes mainly involved in inflammation and apoptosis, supporting the previous research results as a potential therapeutic agent.

Ruxolitinib attenuates secondary injury after traumatic spinal cord injury

Excessive inflammation post-traumatic spinal cord injury (SCI) induces microglial activation, which leads to prolonged neurological dysfunction. However, the mechanism underlying microglial activation-induced neuroinflammation remains poorly understood. Ruxolitinib (RUX), a selective inhibitor of JAK1/2, was recently reported to inhibit inflammatory storms caused by SARS-CoV-2 in the lung. However, its role in disrupting inflammation post-SCI has not been confirmed. In this study, microglia were treated with RUX for 24 hours and then activated with interferon-γ for 6 hours. The results showed that interferon-γ-induced phosphorylation of JAK and STAT in microglia was inhibited, and the mRNA expression levels of pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1β, interleukin-6, and cell proliferation marker Ki67 were reduced. In further in vivo experiments, a mouse model of spinal cord injury was treated intragastrically with RUX for 3 successive days, and the findings suggest that RUX can inhibit microglial proliferation by inhibiting the interferon-γ/JAK/STAT pathway. Moreover, microglia treated with RUX centripetally migrated toward injured foci, remaining limited and compacted within the glial scar, which resulted in axon preservation and less demyelination. Moreover, the protein expression levels of tumor necrosis factor-α, interleukin-1β, and interleukin-6 were reduced. The neuromotor function of SCI mice also recovered. These findings suggest that RUX can inhibit neuroinflammation through inhibiting the interferon-γ/JAK/STAT pathway, thereby reducing secondary injury after SCI and producing neuroprotective effects.

BAY61‑3606 attenuates neuroinflammation and neurofunctional damage by inhibiting microglial Mincle/Syk signaling response after traumatic brain injury

Neuroinflammatory processes mediated by microglial activation and subsequent neuronal damage are the hallmarks of traumatic brain injury (TBI). As an inhibitor of the macrophage‑inducible C‑type lectin (Mincle)/spleen tyrosine kinase (Syk) signaling pathway, BAY61‑3606 (BAY) has previously demonstrated anti‑inflammatory effects on some pathological processes, such as acute kidney injury, by suppressing the inflammatory macrophage response. In the present study, the potential effects of BAY on microglial phenotype and neuroinflammation after TBI were investigated. BAY (3 mg/kg) was first administered into mice by intraperitoneal injection after TBI induction in vivo and microglia were also treated with BAY (2 µM) in vitro. The levels of inflammatory factors in microglia were assessed using reverse transcription‑quantitative PCR and ELISA. Cortical neuron, myelin sheath, astrocyte and cerebrovascular endothelial cell markers were detected using immunofluorescence. The levels of components of the Mincle/Syk/NF‑κB signaling pathway [Mincle, phosphorylated (p)‑Syk and NF‑κB], in addition to proteins associated with inflammation (ASC, caspase‑1, TNF‑α, IL‑1β and IL‑6), apoptosis (Bax and Bim) and tight junctions (Claudin‑5), were measured via western blotting and ELISA. Migration and chemotaxis of microglial cells were evaluated using Transwell and agarose spot assays. Neurological functions of the mice were determined in vivo using the modified neurological severity scoring system and a Morris water maze. The results of the present study revealed that the expression levels of proteins in the Mincle/Syk/NF‑κB signaling pathway (including Mincle, p‑Syk and p‑NF‑κB), inflammatory cytokines (TNF‑α, IL‑1β and IL‑6), proteins involved in inflammation (ASC and caspase‑1), apoptotic markers (Bax and Bim) and the tight junction protein Claudin‑5 were significantly altered post‑TBI. BAY treatment reversed these effects in both the cerebral cortex extract‑induced cell model and the controlled cortical impact mouse model. BAY was also revealed to suppress activation of the microglial proinflammatory phenotype and microglial migration. In addition, BAY effectively attenuated TBI‑induced neurovascular unit damage and neurological function deficits. Taken together, these findings provided evidence that BAY may inhibit the Mincle/Syk/NF‑κB signaling pathway in microglia; this in turn could attenuate microglia‑mediated neuroinflammation and improve neurological deficits following TBI.

Disrupting RhoA activity by blocking Arhgef3 expression mitigates microglia-induced neuroinflammation post spinal cord contusion

Excess inflammatory microglia activation deteriorates the pathological degree of spinal cord injury (SCI). We here employed microglia samples in vitro and murine model in vivo to trace the role of inhibition of Arhgef3 in inflammatory response post SCI. From the specimen analysis of lipopolysaccharide (LPS)-induced inflammatory microglia, we found that Arhgef3 expression was positively relative to microglia activation. In vitro, LPS caused the microglia inflammatory activation and induced upregulation of the Arhgef3 expression. Interestingly, presence of Arhgef3 could activate RhoA through promoting Rho GTPases, but silencing of Arhgef3 decreased RhoA activation and inhibited the microglia inflammation. Moreover, disruption of Arhgef3 inhibited the GTP-RhoA, resulted in a suppression of proinflammatory cytokines, and alleviated the LPS-elicited inflammatory genes expression. Moreover, artificially decreasing Arhgef3 expression remarkedly reduced ROS generation after LPS treatment. In vivo of a mouse mechanical contusion-induced SCI model, inhibition of Arhgef3 reduced the ratio of GTP-RhoA/Total-RhoA, and prevented SCI via mitigating the microglial inflammatory phenotype and decreased secondary neurological injury. Besides, inhibition of Arhgef3 prevented alleviated the degree of demyelination but did not affect neuronal regeneration. Meaningfully, absence of Arhgef3 improved mouse locomotor recovery post SCI. Taken together, Arhgef3 involves the microglial activation and inflammatory response following neural injury, and targeted disrupting of which may indicate a promising therapeutic direction in preventing SCI.

Silencing TAK1 reduces MAPKs-MMP2/9 expression to reduce inflammation-driven neurohistological disruption post spinal cord injury

Microglia activation post traumatic spinal cord injury (SCI) provokes accumulation of inflammatory metabolites, leading to increasing neurological disruption. Our previous studies demonstrated that blocking MAPKs pathway mitigated microglia inflammatory activation and prevented cords from neuroinflammation-induced secondary injury. Transforming growth factor-β-activated kinase 1 (TAK1) is an upstream gate regulating activation of MAPKs signaling. To validate the therapeutic effect of TAK1 inhibition in neuroinflammation post SCI, in the current study, cultures of microglia BV2 line was undergone lipopolysaccharide (LPS) stimulation in the presence of TAK1 inhibitor 5Z-7-Oxozeaenol (ZO), LPS, or control. LPS triggered inflammatory level, cell migration, and matrix metalloproteinase (MMP) 2/9 production, which was reduced in ZO-treated cultures. TAK1 inhibition by ZO also decreased activation of MAPKs pathway, indicating that ZO-mediated alleviation of neuroinflammation is likely modulated via TAK1/MAPKs axis. In vivo, neuroinflammatory level and tissue destruction were assessed in adult male mice that were undergone SCI by mechanical trauma, and treated with ZO by intraperitoneal injection. Compared with SCI mice, ZO-treated mice exhibited less microglia pro-inflammatory activation and accumulation adjacent to injured core linked to reduced MMP2/9 expression, leading to minor tissue damage and better locomotor recovery. To sum up, the obtained data proved that in the early phase post SCI, TAK1 inhibition impedes microglia biological activities including activation, enzymatic synthesis, and migration via downregulation of MAPKs pathway, and the effects may be accurately characterized as potent anti-inflammation.

Beneficial Impacts of Alpha-Eleostearic Acid from Wild Bitter Melon and Curcumin on Promotion of CDGSH Iron-Sulfur Domain 2: Therapeutic Roles in CNS Injuries and Diseases

Neuroinflammation and abnormal mitochondrial function are related to the cause of aging, neurodegeneration, and neurotrauma. The activation of nuclear factor κB (NF-κB), exaggerating these two pathologies, underlies the pathogenesis for the aforementioned injuries and diseases in the central nervous system (CNS). CDGSH iron-sulfur domain 2 (CISD2) belongs to the human NEET protein family with the [2Fe-2S] cluster. CISD2 has been verified as an NFκB antagonist through the association with peroxisome proliferator-activated receptor-β (PPAR-β). This protective protein can be attenuated under circumstances of CNS injuries and diseases, thereby causing NFκB activation and exaggerating NFκB-provoked neuroinflammation and abnormal mitochondrial function. Consequently, CISD2-elevating plans of action provide pathways in the management of various disease categories. Various bioactive molecules derived from plants exert protective anti-oxidative and anti-inflammatory effects and serve as natural antioxidants, such as conjugated fatty acids and phenolic compounds. Herein, we have summarized pharmacological characters of the two phytochemicals, namely, alpha-eleostearic acid (α-ESA), an isomer of conjugated linolenic acids derived from wild bitter melon (Momordica charantia L. var. abbreviata Ser.), and curcumin, a polyphenol derived from rhizomes of Curcuma longa L. In this review, the unique function of the CISD2-elevating effect of α-ESA and curcumin are particularly emphasized, and these natural compounds are expected to serve as a potential therapeutic target for CNS injuries and diseases.