Interferon regulatory factor 3 plays an anti-inflammatory role in microglia by activating the PI3K/Akt pathway

Humid heat environment causes anxiety-like disorder via impairing gut microbiota and bile acid metabolism in mice

Climate and environmental changes threaten human mental health, but the impacts of specific environmental conditions on neuropsychiatric disorders remain largely unclear. Here, we show the impact of a humid heat environment on the brain and the gut microbiota using a conditioned housing male mouse model. We demonstrate that a humid heat environment can cause anxiety-like behaviour in male mice. Microbial 16 S rRNA sequencing analysis reveals that a humid heat environment caused gut microbiota dysbiosis (e.g., decreased abundance of Lactobacillus murinus), and metabolomics reveals an increase in serum levels of secondary bile acids (e.g., lithocholic acid). Moreover, increased neuroinflammation is indicated by the elevated expression of proinflammatory cytokines in the serum and cortex, activated PI3K/AKT/NF-κB signalling and a microglial response in the cortex. Strikingly, transplantation of the microbiota from mice reared in a humid heat environment readily recapitulates these abnormalities in germ-free mice, and these abnormalities are markedly reversed by Lactobacillus murinus administration. Human samples collected during the humid heat season also show a decrease in Lactobacillus murinus abundance and an increase in the serum lithocholic acid concentration. In conclusion, gut microbiota dysbiosis induced by a humid heat environment drives the progression of anxiety disorders by impairing bile acid metabolism and enhancing neuroinflammation, and probiotic administration is a potential therapeutic strategy for these disorders.

Synthetic high-density lipoprotein (sHDL): a bioinspired nanotherapeutics for managing periapical bone inflammation

Apical periodontitis (AP) is a dental-driven condition caused by pathogens and their toxins infecting the inner portion of the tooth (i.e., dental pulp tissue), resulting in inflammation and apical bone resorption affecting 50% of the worldwide population, with more than 15 million root canals performed annually in the United States. Current treatment involves cleaning and decontaminating the infected tissue with chemo-mechanical approaches and materials introduced years ago, such as calcium hydroxide, zinc oxide-eugenol, or even formalin products. Here, we present, for the first time, a nanotherapeutics based on using synthetic high-density lipoprotein (sHDL) as an innovative and safe strategy to manage dental bone inflammation. sHDL application in concentrations ranging from 25 µg to 100 µg/mL decreases nuclear factor Kappa B (NF-κB) activation promoted by an inflammatory stimulus (lipopolysaccharide, LPS). Moreover, sHDL at 500 µg/mL concentration markedly decreases in vitro osteoclastogenesis (P < 0.001), and inhibits IL-1α (P = 0.027), TNF-α (P = 0.004), and IL-6 (P < 0.001) production in an inflammatory state. Notably, sHDL strongly dampens the Toll-Like Receptor signaling pathway facing LPS stimulation, mainly by downregulating at least 3-fold the pro-inflammatory genes, such as Il1b, Il1a, Il6, Ptgs2, and Tnf. In vivo, the lipoprotein nanoparticle applied after NaOCl reduced bone resorption volume to (1.3 ± 0.05) mm3 and attenuated the inflammatory reaction after treatment to (1 090 ± 184) cells compared to non-treated animals that had (2.9 ± 0.6) mm3 (P = 0.012 3) and (2 443 ± 931) cells (P = 0.004), thus highlighting its promising clinical potential as an alternative therapeutic for managing dental bone inflammation.

Recent advances on signaling pathways and their inhibitors in spinal cord injury

Spinal cord injury (SCI) is a serious and disabling central nervous system injury. Its complex pathological mechanism can lead to sensory and motor dysfunction. It has been reported that signaling pathway plays a key role in the pathological process and neuronal recovery mechanism of SCI. Such as PI3K/Akt, MAPK, NF-κB, and Wnt/β-catenin signaling pathways. According to reports, various stimuli and cytokines activate these signaling pathways related to SCI pathology, thereby participating in the regulation of pathological processes such as inflammation response, cell apoptosis, oxidative stress, and glial scar formation after injury. Activation or inhibition of relevant pathways can delay inflammatory response, reduce neuronal apoptosis, prevent glial scar formation, improve the microenvironment after SCI, and promote neural function recovery. Based on the role of signaling pathways in SCI, they may be potential targets for the treatment of SCI. Therefore, understanding the signaling pathway and its inhibitors may be beneficial to the development of SCI therapeutic targets and new drugs. This paper mainly summarizes the pathophysiological process of SCI, the signaling pathways involved in SCI pathogenesis, and the potential role of specific inhibitors/activators in its treatment. In addition, this review also discusses the deficiencies and defects of signaling pathways in SCI research. It is hoped that this study can provide reference for future research on signaling pathways in the pathogenesis of SCI and provide theoretical basis for SCI biotherapy.

Comparative transcriptomic analysis of circulating endothelial cells in sickle cell stroke

Ischemic stroke (IS) is one of the most impairing complications of sickle cell anemia (SCA), responsible for 20% of mortality in patients. Rheological alterations, adhesive properties of sickle reticulocytes, leukocyte adhesion, inflammation and endothelial dysfunction are related to the vasculopathy observed prior to ischemic events. The role of the vascular endothelium in this complex cascade of mechanisms is emphasized, as well as in the process of ischemia-induced repair and neovascularization. The aim of the present study was to perform a comparative transcriptomic analysis of endothelial colony-forming cells (ECFCs) from SCA patients with and without IS. Next, to gain further insights of the biological relevance of differentially expressed genes (DEGs), functional enrichment analysis, protein-protein interaction network (PPI) construction and in silico prediction of regulatory factors were performed. Among the 2469 DEGs, genes related to cell proliferation (AKT1, E2F1, CDCA5, EGFL7), migration (AKT1, HRAS), angiogenesis (AKT1, EGFL7) and defense response pathways (HRAS, IRF3, TGFB1), important endothelial cell molecular mechanisms in post ischemia repair were identified. Despite the severity of IS in SCA, widely accepted molecular targets are still lacking, especially related to stroke outcome. The comparative analysis of the gene expression profile of ECFCs from IS patients versus controls seems to indicate that there is a persistent angiogenic process even after a long time this complication has occurred. Thus, this is an original study which may lead to new insights into the molecular basis of SCA stroke and contribute to a better understanding of the role of endothelial cells in stroke recovery.

Troxerutin dampened hypothalamic neuroinflammation via microglial IL-22/IL-22R1/IRF3 activation in dihydrotestosterone-induced polycystic ovary syndrome rats

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common reproductive-endocrine condition in premenopausal women. Troxerutin, a common clinical anti-coagulant agent, was shown to work as a strong IL-22 boosting agent counteracting the hyperactivated gonadotrophin releasing hormone (GnRH) neurons and heightened GnRH release, the neuroendocrine origin of PCOS with unknown mechanism in rats. Exploring the off-label use of troxerutin medication for PCOS is thus sorely needed.

METHODS

Serum IL-22 content and hypothalamic IL-22 protein were detected. Inflammatory factor levels in hypothalamo-pituitary were evaluated. Immunofluorescence staining was employed to determine the activation and M1/M2-prone polarization of microglia in arcuate hypothalamus and median eminence. RNA-sequencing and transcriptome analysis were applied to explore the potential driver of microglia M2-polarization in response to IL-22 bolstering effect. The function of microglial IL-22/IL-22R1/IRF3 system was further verified using in vivo knockdown of IL-22R1 and a potent IRF3 inhibitor in BV2 microglial cell lines in vitro.

RESULTS

Troxerutin augmented serum IL-22 content, and its consequent spillover into the hypothalamus led to the direct activation of IL-22R1/IRF3 system on microglia, thereby promoted microglia M2 polarization in arcuate hypothalamus and median eminence, dampened hypothalamic neuroinflammation, inhibited hyperactive GnRH and rescued a breadth of PCOS-like traits in dihydrotestosterone (DHT) rats. The salutary effects of troxerutin treatment on hypothalamic neuroinflammation, microglial M1/2 polarization, GnRH secretion and numerous PCOS-like features were blocked by in vivo knockdown of IL-22R1. Moreover, evidence in vitro illustrated that IL-22 supplement to BV-2 microglia cell lines promoted M2 polarization, overproduction of anti-inflammatory marker and limitation of pro-inflammatory factors, whereas these IL-22 effects were blunted by geldanamycin, a potent IRF3 inhibitor.

CONCLUSION

Here, the present study reported the potential off-label use of troxerutin medication, a common clinical anti-coagulant agent and an endogenous IL-22 enhancer, for multiple purposes in PCOS. The rational underlying the application of troxerutin as a therapeutic choice in PCOS derived from its activity as an IL-22 memetic agent targeting the neuro-endocrine origin of PCOS, and its promotive impact on microglia M2 polarization via activating microglial IL-22R1/IRF3 system in the arcuate hypothalamus and median eminence of DHT female rats.

Neurosteroid [3α,5α]-3-hydroxy-pregnan-20-one enhances IL-10 production via endosomal TRIF-dependent TLR4 signaling pathway

Background

Previous studies demonstrated the inhibitory effect of allopregnanolone (3α,5α-THP) on the activation of inflammatory toll-like receptor 4 (TLR4) signals in RAW264.7 macrophages and the brains of selectively bred alcohol-preferring (P) rats. In the current study, we investigated the impact of 3α,5α-THP on the levels of IL-10 and activation of the TRIF-dependent endosomal TLR4 pathway.

Methods

The amygdala and nucleus accumbens (NAc) of P rats, which exhibit innately activated TLR4 pathways as well as RAW264.7 cells, were used. Enzyme-linked immunosorbent assays (ELISA) and immunoblotting assays were used to ascertain the effects of 3α,5α-THP on the TRIF-dependent endosomal TLR4 pathway and endosomes were isolated to examine translocation of TLR4 and TRIF. Additionally, we investigated the effects of 3α,5α-THP and 3α,5α-THDOC (0.1, 0.3, and 1.0 µM) on the levels of IL-10 in RAW264.7 macrophages. Finally, we examined whether inhibiting TRIF (using TRIF siRNA) in RAW264.7 cells altered the levels of IL-10.

Results

3α,5α-THP administration facilitated activation of the endosomal TRIF-dependent TLR4 pathway in males, but not female P rats. 3α,5α-THP increased IL-10 levels (+13.2 ± 6.5%) and BDNF levels (+21.1 ± 11.5%) in the male amygdala. These effects were associated with increases in pTRAM (+86.4 ± 28.4%), SP1 (+122.2 ± 74.9%), and PI(3)K-p110δ (+61.6 ± 21.6%), and a reduction of TIRAP (-13.7 ± 6.0%), indicating the activation of the endosomal TRIF-dependent TLR4 signaling pathway. Comparable effects were observed in NAc of these animals. Furthermore, 3α,5α-THP enhanced the accumulation of TLR4 (+43.9 ± 11.3%) and TRIF (+64.8 ± 32.8%) in endosomes, with no significant effect on TLR3 accumulation. Additionally, 3α,5α-THP facilitated the transition from early endosomes to late endosomes (increasing Rab7 levels: +35.8 ± 18.4%). In RAW264.7 cells, imiquimod (30 µg/mL) reduced IL-10 while 3α,5α-THP and 3α,5α-THDOC (0.1, 0.3, and 1.0 µM) restored IL-10 levels. To determine the role of the TRIF-dependent TLR4 signaling pathway in IL-10 production, the downregulation of TRIF (-62.9 ± 28.2%) in RAW264.7 cells led to a reduction in IL-10 levels (-42.3 ± 8.4%). TRIF (-62.9 ± 28.2%) in RAW264.7 cells led to a reduction in IL-10 levels (-42.3 ± 8.4%) and 3α,5α-THP (1.0 µM) no longer restored the reduced IL-10 levels.

Conclusion

The results demonstrate 3α,5α-THP enhancement of the endosomal TLR4-TRIF anti-inflammatory signals and elevations of IL-10 in male P rat brain that were not detected in female P rat brain. These effects hold significant implications for controlling inflammatory responses in both the brain and peripheral immune cells.

The role and mechanisms of mesenchymal stem cells regulating macrophage plasticity in spinal cord injury

Spinal Cord Injury (SCI) is a devastating neurological disorder comprising primary mechanical injury and secondary inflammatory response-mediated injury for which an effective treatment is still unavailable. It is well known that secondary inflammatory responses are a significant cause of difficulties in neurological recovery. An immune imbalance between M1/M2 macrophages at the sites of injury is involved in developing and progressing the secondary inflammatory response. Recently, Mesenchymal Stem Cells (MSCs) have shown significant therapeutic potential in tissue engineering and regenerative medicine due to their potential multidirectional differentiation and immunomodulatory properties. Accumulating evidence shows that MSCs can regulate the balance of M1/M2 macrophage polarization, suppress downstream inflammatory responses, facilitate tissue repair and regeneration, and improve the prognosis of SCI. This article briefly overviews the impact of macrophages and MSCs on SCI and repair. It discusses the mechanisms by which MSCs regulate macrophage plasticity, including paracrine action, release of exosomes and apoptotic bodies, and metabolic reprogramming. Additionally, the article summarizes the relevant signaling pathways of MSCs that regulate macrophage polarization.

Microglia mediated neuroinflammation in neurodegenerative diseases: A review on the cell signaling pathways involved in microglial activation

Microglia, the immune sentinels of the central nervous system (CNS), have emerged to be the central players in many neurological and neurodegenerative diseases. Recent studies on large genome databases and omics studies in fact provide support to the idea that microglial cells could be the drivers of these diseases. Microglial cells have the capacity to undergo morphological and phenotypic transformations depending on its microenvironment. From the homeostatic ramified state, they can shift their phenotypes between the two extremes, known as the proinflammatory M1 and anti-inflammatory M2 phenotype, with intermediate transitional states, characterized by different transcriptional signature and release of inflammatory mediators. The temporal regulation of the release of the inflammatory factors are critical for damage control and steering the microglia back towards homeostatic conditions. A dysregulation in these can lead to excessive tissue damage and neuronal death. Therefore, targeting the cell signaling pathways that are the underpinnings of microglial modulations are considered to be an important avenue for treatment of various neurodegenerative diseases. In this review we have discussed various signaling pathways that trigger microglial activation from its ramified state and highlight the mechanisms of microglia-mediated neuroinflammation that are associated with various neurodegenerative diseases. Most of the cellular factors that drive microglia towards a proinflammatory phenotype are components of the immune system signaling pathways and cell proliferation, along with certain ion channels. The anti-inflammatory phenotype is mainly elicited by purinoceptors, metabolic receptors and other receptors that primarily suppress the production proinflammatory mediators.

The role of PI3K/AKT signaling pathway in myocardial ischemia-reperfusion injury

Myocardial ischemia has a high incidence and mortality rate, and reperfusion is currently the standard intervention. However, reperfusion may lead to further myocardial damage, known as myocardial ischemia/reperfusion injury (MIRI). There are currently no effective clinical treatments for MIRI. The PI3K/Akt signaling pathway is involved in cardiovascular health and disease and plays an important role in reducing myocardial infarct size and restoring cardiac function after MIRI. Activation of the PI3K/Akt pathway provides myocardial protection through synergistic upregulation of antioxidant, anti-inflammatory, and autophagy activities and inhibition of mitochondrial dysfunction and cardiomyocyte apoptosis. Many studies have shown that PI3K/Akt has a significant protective effect against MIRI. Here, we reviewed the molecular regulation of PI3K/Akt in MIRI and summarized the molecular mechanism by which PI3K/Akt affects MIRI, the effects of ischemic preconditioning and ischemic postconditioning, and the role of related drugs or activators targeting PI3K/Akt in MIRI, providing novel insights for the formulation of myocardial protection strategies. This review provides evidence of the role of PI3K/Akt activation in MIRI and supports its use as a therapeutic target.

Sex differences of microglia in the healthy brain from embryonic development to adulthood and across lifestyle influences

Microglia, the central nervous system innate immune cells, play a critical role in maintaining a homeostatic environment in the brain throughout life. These cells exhibit an impressive range of functions and characteristics that help to ensure proper functioning of the brain. Notably, microglia can present differences in their genetic and physical traits, which can be influenced by a range of factors, including age, environmental exposures, disease, and sex. Remarkably, microglia have been found to express receptors for sex hormones, suggesting that these hormones may play a role in modulating microglial behavior and potentially contribute to sex differences. Additionally, sex-chromosomal factors were shown to impact microglial genetics and functioning. In this review, we will examine how microglial responses in homeostasis are impacted by their interaction with sex hormones and sex chromosomes. Specifically, our investigation will focus on examining this interaction from embryonic development to adulthood, and the influence of lifestyle elements on various microglial features, including density and distribution, morphology, transcriptome, and proteome.

Regulation of intrinsic and extrinsic metabolic pathways in tumour-associated macrophages

Tumour-associated macrophages (TAMs) are highly plastic and are broadly grouped into two major functional states, namely the pro-inflammatory M1-type and the pro-tumoural M2-type. Conversion of the functional states of TAMs is regulated by various cytokines, chemokines growth factors and other secreted factors in the microenvironment. Dysregulated metabolism is a hallmark of cancer. Emerging evidence suggests that metabolism governs the TAM differentiation and functional conversation in support of tumour growth and metastasis. Aside from the altered metabolism reprogramming in TAMs, extracellular metabolites secreted by cancer, stromal and/or other cells within the tumour microenvironment have been found to regulate TAMs through passive competition for metabolite availability and direct regulation via receptor/transporter-mediated signalling reaction. In this review, we focus on the regulatory roles of different metabolites and metabolic pathways in TAM conversion and function. We also discuss if the dysregulated metabolism in TAMs can be exploited for the development of new therapeutic strategies against cancer.

Adipose tissue macrophages and their role in obesity-associated insulin resistance: an overview of the complex dynamics at play

Obesity, a major global health concern, is characterized by serious imbalance between energy intake and expenditure leading to excess accumulation of fat in adipose tissue (AT). A state of chronic low-grade AT inflammation is prevalent during obesity. The adipose tissue macrophages (ATM) with astounding heterogeneity and complex regulation play a decisive role in mediating obesity-induced insulin resistance. Adipose-derived macrophages were broadly classified as proinflammatory M1 and anti-inflammatory M2 subtypes but recent reports have proclaimed several novel and intermediate profiles, which are crucial in understanding the dynamics of macrophage phenotypes during development of obesity. Lipid-laden hypertrophic adipocytes release various chemotactic signals that aggravate macrophage infiltration into AT skewing toward mostly proinflammatory status. The ratio of M1-like to M2-like macrophages is increased substantially resulting in copious secretion of proinflammatory mediators such as TNFα, IL-6, IL-1β, MCP-1, fetuin-A (FetA), etc. further worsening insulin resistance. Several AT-derived factors could influence ATM content and activation. Apart from being detrimental, ATM exerts beneficial effects during obesity. Recent studies have highlighted the prime role of AT-resident macrophage subpopulations in not only effective clearance of excess fat and dying adipocytes but also in controlling vascular integrity, adipocyte secretions, and fibrosis within obese AT. The role of ATM subpopulations as friend or foe is determined by an intricate interplay of such factors arising within hyperlipidemic microenvironment of obese AT. The present review article highlights some of the key research advances in ATM function and regulation, and appreciates the complex dynamics of ATM in the pathophysiologic scenario of obesity-associated insulin resistance.

Exosomal miRNAs-mediated macrophage polarization and its potential clinical application

Macrophages are highly heterogeneous and plastic immune cells that play an important role in the fight against pathogenic microorganisms and tumor cells. After different stimuli, macrophages can polarize to the M1 phenotype to show a pro-inflammatory effect and the M2 phenotype to show an anti-inflammatory effect. The balance of macrophage polarization is highly correlated with disease progression, and therapeutic approaches to reprogram macrophages by targeting macrophage polarization are feasible. There are a large number of exosomes in tissue cells, which can transmit information between cells. In particular, microRNAs (miRNAs) in the exosomes can regulate the polarization of macrophages and further affect the progression of various diseases. At the same time, exosomes are also effective "drug" carriers, laying the foundation for the clinical application of exosomes. This review describes some pathways involved in M1/M2 macrophage polarization and the effects of miRNA carried by exosomes from different sources on the polarization of macrophages. Finally, the application prospects and challenges of exosomes/exosomal miRNAs in clinical treatment are also discussed.

CD36 neutralisation blunts TLR2-IRF7 but not IRF3 pathway in neonatal mouse brain and immature human microglia following innate immune challenge

Innate immune response in neonatal brain is associated with a robust microglial activation and induction of Toll-like Receptors (TLRs). To date, the role of the scavenger receptor CD36 in TLRs modulation, particularly TLR2 signaling, has been well established in adult brain. However, the crosstalk between TLR4, TLR2 and CD36 and its immunogenic influence in the neonatal brain remains unclear. In this study, using a CD36 blocking antibody (anti-CD36) at post-natal day 8, we evaluated the response of neonates to systemic endotoxin (lipopolysaccharide; LPS) challenge. We visualized the TLR2 response by bioluminescence imaging using the transgenic mouse model bearing the dual reporter system luciferase/green fluorescent protein under transcriptional control of a murine TLR2 promoter. The anti-CD36 treatment modified the LPS induced inflammatory profile in neonatal brains, causing a significant decrease in inflammatory cytokine levels and the TLR2 and TLR3 mediated signalling.The interferon regulatory factor 3 (IRF3) pathway remained unaffected. Treatment of the LPS-challenged human immature microglia with anti-CD36 induced a marked decrease in TLR2/TLR3 expression levels while TLR4 and IRF3 expression was not affected, suggesting the shared CD36 regulatory mechanisms in human and mouse microglia. Collectively, our results indicate that blocking CD36 alters LPS-induced inflammatory profile of mouse and human microglia, suggesting its role in fine-tuning of neuroinflammation.

Epigenetic regulation of macrophage polarization in wound healing

The immune microenvironment plays a critical role in regulating skin wound healing. Macrophages, the main component of infiltrating inflammatory cells, play a pivotal role in shaping the immune microenvironment in the process of skin wound healing. Macrophages comprise the classic proinflammatory M1 subtype and anti-inflammatory M2 population. In the early inflammatory phase of skin wound closure, M1-like macrophages initiate and amplify the local inflammatory response to disinfect the injured tissue. In the late tissue-repairing phase, M2 macrophages are predominant in wound tissue and limit local inflammation to promote tissue repair. The biological function of macrophages is tightly linked with epigenomic organization. Transcription factors are essential for macrophage polarization. Epigenetic modification of transcription factors determines the heterogeneity of macrophages. In contrast, transcription factors also regulate the expression of epigenetic enzymes. Both transcription factors and epigenetic enzymes form a complex network that regulates the plasticity of macrophages. Here, we describe the latest knowledge concerning the potential epigenetic mechanisms that precisely regulate the biological function of macrophages and their effects on skin wound healing.

Intranasal interferon-beta alleviates anxiety and depressive-like behaviors by modulating microglia polarization in an Alzheimer's disease model

Alzheimer's disease (AD) patients frequently experience neuropsychiatric symptoms (NPS), which are linked to a lower quality of life and a faster rate of disease progression. A growing body of research indicates that several microglial phenotypes control the inflammatory response and are crucial in the pathophysiology of AD-related NPS. Given the crucial role played by inflammatory mediators produced by microglia in developing of NPS, interferon-beta (IFNβ), a cytokine with anti-inflammatory capabilities, maybe a successful treatment for NPS caused by AD. In this investigation, using a rat model of AD, we examined the impact of intranasal treatment of IFNβ on anxious/depressive-like behavior and microglial M1/M2 polarization. The rat hippocampus was bilaterally injected with lentiviruses harboring mutant human amyloid precursor protein. Rats were given recombinant IFNβ1a (68,000 IU/rat) via the intranasal route, starting on day 23 following viral infection and continuing until day 49. On days 47-49, the elevated plus maze, forced swim, and tail suspension tests were applied to measure anxiety- and depressive-like behavior. Additionally, qPCR was utilized to quantify the expression of M1 markers (CD68, CD86, and CD40) and M2 markers (Ym1, CD206, Arg1, GDNF, BDNF, and SOCS1). Our findings demonstrated that decreased M2 marker expression is accompanied by anxious/depressive-like behavior when the mutant human APP gene is overexpressed in the hippocampus. In the rat model of AD, IFNβ therapy reduces anxious/depressive-like behaviors, at least in part by polarizing microglia towards M2. Therefore, IFNβ may be a viable therapeutic drug for reducing NPS in the context of AD.

Maltol ameliorates intervertebral disc degeneration through inhibiting PI3K/AKT/NF-κB pathway and regulating NLRP3 inflammasome-mediated pyroptosis

OBJECTIVES

As one of the major causes of low back pain, intervertebral disc degeneration (IDD) has caused a huge problem for humans. Increasing evidence indicates that NLRP3 inflammasome-mediated pyroptosis of NP cells displays an important role in the progression of IDD. Maltol (MA) is a flavoring agent extracted from red ginseng. Due to its anti-inflammatory and antioxidant effects, MA has been widely considered by researchers. Therefore, we hypothesized that MA may be a potential IVD protective agent by regulating NP cells and their surrounding microenvironment.

METHODS

In vitro, qRT-PCR, and Western blot were used to explore the effect of MA on the transcription and protein expression of the anabolic protein (ADAMTS5, MMP3, MMP9) catabolic protein (Aggrecan), and pro-inflammatory factor (iNOS COX-2). Next, the effects of MA on PI3K/AKT/NF-κB pathway and pyroptosis pathway were analyzed by Western blot and immunofluorescence. Molecular docking was used to investigate the relationship between PI3K and MA. Moreover, ELISA was also used to detect the effects of MA on inflammatory factors (TNF-α, PGE2, IL-1β, and IL-18). In vivo, the effects of MA on the vertebral structure of IDD mice were studied by HE and SO staining and the effects of MA on ECM and PI3K/AKT/NF-κB and pyroptosis pathway of IDD mice were studied by immunohistochemical staining.

RESULTS

MA can ameliorate intervertebral disc degeneration in vivo and in vitro. Specifically, the molecular docking results showed that the binding degree of MA and PI3K was significant. Second, in vitro studies showed that MA inhibited the degradation of ECM and inflammatory response by inhibiting the PI3K/AKT/NF-κB pathway and the pyroptosis mediated by NLRP3 inflammasome, which increased the expression of anabolic proteins, decreased the expression of catabolic proteins, and decreased the secretion of inflammatory mediators such as IL-18 and IL-1β. In addition, according to the study results of the mouse lumbar instability model, MA also improved the tissue disorder and degradation of the intervertebral disc, reduced the loss of proteoglycan and glycosaminoglycan, and inhibited intervertebral disc inflammation, indicating that MA has a protective effect on the intervertebral disc to intervertebral disc in mice.

CONCLUSIONS

Our results suggest that MA slowed IDD development through the PI3K/AKT/NF-κB signaling pathway and NLRP3 inflammasome-mediated pyroptosis, indicating that MA appeared to be a viable medication for IDD treatment.

The PI3K/AKT signalling pathway in inflammation, cell death and glial scar formation after traumatic spinal cord injury: Mechanisms and therapeutic opportunities

Objects

Traumatic spinal cord injury (TSCI) causes neurological dysfunction below the injured segment of the spinal cord, which significantly impacts the quality of life in affected patients. The phosphoinositide 3kinase/serine‐threonine kinase (PI3K/AKT) signaling pathway offers a potential therapeutic target for the inhibition of secondary TSCI. This review summarizes updates concerning the role of the PI3K/AKT pathway in TSCI.

Materials and Methods

By searching articles related to the TSCI field and the PI3K/AKT signaling pathway, we summarized the mechanisms of secondary TSCI and the PI3K/AKT signaling pathway; we also discuss current and potential future treatment methods for TSCI based on the PI3K/AKT signaling pathway.

Results

Early apoptosis and autophagy after TSCI protect the body against injury; a prolonged inflammatory response leads to the accumulation of pro‐inflammatory factors and excessive apoptosis, as well as excessive autophagy in the surrounding normal nerve cells, thus aggravating TSCI in the subacute stage of secondary injury. Initial glial scar formation in the subacute phase is a protective mechanism for TSCI, which limits the spread of damage and inflammation. However, mature scar tissue in the chronic phase hinders axon regeneration and prevents the recovery of nerve function. Activation of PI3K/AKT signaling pathway can inhibit the inflammatory response and apoptosis in the subacute phase after secondary TSCI; inhibiting this pathway in the chronic phase can reduce the formation of glial scar.

Conclusion

The PI3K/AKT signaling pathway has an important role in the recovery of spinal cord function after secondary injury. Inducing the activation of PI3K/AKT signaling pathway in the subacute phase of secondary injury and inhibiting this pathway in the chronic phase may be one of the potential strategies for the treatment of TSCI.

Modulating Microglia/Macrophage Activation by CDNF Promotes Transplantation of Fetal Ventral Mesencephalic Graft Survival and Function in a Hemiparkinsonian Rat Model

Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons in substantia nigra pars compacta, which leads to the motor control deficits. Recently, cell transplantation is a cutting-edge technique for the therapy of PD. Nevertheless, one key bottleneck to realizing such potential is allogenic immune reaction of tissue grafts by recipients. Cerebral dopamine neurotrophic factor (CDNF) was shown to possess immune-modulatory properties that benefit neurodegenerative diseases. We hypothesized that co-administration of CDNF with fetal ventral mesencephalic (VM) tissue can improve the success of VM replacement therapies by attenuating immune responses. Hemiparkinsonian rats were generated by injecting 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle of Sprague Dawley (SD) rats. The rats were then intrastriatally transplanted with VM tissue from rats, with/without CDNF administration. Recovery of dopaminergic function and survival of the grafts were evaluated using the apomorphine-induced rotation test and small-animal positron emission tomography (PET) coupled with [¹⁸F] DOPA or [¹⁸F] FE-PE2I, respectively. In addition, transplantation-related inflammatory response was determined by uptake of [¹⁸F] FEPPA in the grafted side of striatum. Immunohistochemistry (IHC) examination was used to determine the survival of the grated dopaminergic neurons in the striatum and to investigate immune-modulatory effects of CDNF. The modulation of inflammatory responses caused by CDNF might involve enhancing M2 subset polarization and increasing fractal dimensions of 6-OHDA-treated BV2 microglial cell line. Analysis of CDNF-induced changes to gene expressions of 6-OHDA-stimulated BV2 cells implies that these alternations of the biomarkers and microglial morphology are implicated in the upregulation of protein kinase B signaling as well as regulation of catalytic, transferase, and protein serine/threonine kinase activity. The effects of CDNF on 6-OHDA-induced alternation of the canonical pathway in BV2 microglial cells is highly associated with PI3K-mediated phagosome formation. Our results are the first to show that CDNF administration enhances the survival of the grafted dopaminergic neurons and improves functional recovery in PD animal model. Modulation of the polarization, morphological characteristics, and transcriptional profiles of 6-OHDA-stimualted microglia by CDNF may possess these properties in transplantation-based regenerative therapies.

Anti-Inflammatory Effects of Red Rice Bran Extract Ameliorate Type I Interferon Production via STING Pathway

Type I interferons (IFNs-I) are inflammatory cytokines that play an essential role in the pathogenesis of inflammation and autoimmune diseases. Signaling through nucleic acid sensors causes the production of IFNs-I. A stimulator of interferon genes (STING) is a DNA sensor that signals transduction, leading to the production of IFNs-I after their activation. This study aims to determine the anti-inflammatory effects of red rice bran extract (RRBE) on macrophages through the activation of STING signaling. RAW264.7 macrophage cells were stimulated with STING agonist (DMXAA) with and without RRBE. Cells and supernatant were collected. The level of mRNA expression was determined by qPCR, and inflammatory cytokine production was investigated by ELISA. The results indicate that RRBE significantly lowers the transcription of STING and interferon-stimulated genes (ISGs). Moreover, RRBE suppresses the phosphorylation of STING, leading to a decrease in the expression of Irf3, a transcription factor that initiates IFN-I signaling. Our results provide evidence that red rice bran extract may be a protective compound for inflammatory diseases by targeting STING signaling.

Tumour-associated macrophages heterogeneity drives resistance to clinical therapy

Tumour-associated macrophages (TAMs) constitute a plastic and heterogeneous cell population of the tumour microenvironment (TME) that can account for up to 50% of solid tumours. TAMs heterogeneous are associated with different cancer types and stages, different stimulation of bioactive molecules and different TME, which are crucial drivers of tumour progression, metastasis and resistance to therapy. In this context, understanding the sources and regulatory mechanisms of TAM heterogeneity and searching for novel therapies targeting TAM subpopulations are essential for future studies. In this review, we discuss emerging evidence highlighting the redefinition of TAM heterogeneity from three different directions: origins, phenotypes and functions. We notably focus on the causes and consequences of TAM heterogeneity which have implications for the evolution of therapeutic strategies that targeted the subpopulations of TAMs.

Protecting effect of emodin in experimental autoimmune encephalomyelitis mice by inhibiting microglia activation and inflammation via Myd88/PI3K/Akt/NF-κB signalling pathway

Experimental autoimmune encephalomyelitis (EAE) is characterised by demyelination of the central nervous system. Emodin is an anthraquinone derivative with comprehensive anti-inflammatory, anti-cancer, and immunomodulatory effects and is widely used in the treatment of inflammatory, tumour, and immune system diseases. However, none of the clinical or experimental studies have explored the therapeutic efficacy of emodin in EAE/multiple sclerosis (MS). Thus, we evaluated the protective effect of emodin on EAE mediated via inhibition of microglia activation and inflammation. Wild-type mice were randomly divided into the normal control, EAE, low-dose emodin, and high-dose emodin groups. Clinical scores and pathological changes were assessed 21 days after immunisation. The network pharmacology approach was used to elucidate underlying mechanisms by using an online database. Molecular docking, polymerase chain reaction tests, western blotting, and immunofluorescence were performed to verify the network pharmacology results. An in vivo experiment showed that high-dose emodin ameliorated clinical symptoms, inflammatory cell infiltration, and myelination. Pharmacological network analysis showed AKT1 was the main target and that emodin played a key role in MS treatment mainly via the PI3K-Akt pathway. Molecular docking showed that emodin bound well with PI3K, AKT1, and NFKB1. Emodin decreased the expression of phosphorylated(p)-PI3K, p-Akt, NF-κB, and myeloid differentiation factor 88 and the levels of markers (CD86 and CD206) in M1- and M2-phenotype microglia in EAE. Thus, emodin inhibited microglial activation and exhibited anti-inflammatory and neuroprotective effects against EAE via the Myd88/PI3K/Akt/NF-κB signalling pathway. In conclusion, emodin has a promising role in EAE/MS treatment, warranting further detailed studies.

Targeting Systemic Innate Immune Cells as a Therapeutic Avenue for Alzheimer Disease

Alzheimer disease (AD) is the first progressive neurodegenerative disease worldwide, and the disease is characterized by an accumulation of amyloid in the brain and neurovasculature that triggers cognitive decline and neuroinflammation. The innate immune system has a preponderant role in AD. The last decade, scientists focused their efforts on therapies aiming to modulate innate immunity. The latter is of great interest, since they participate to the inflammation and phagocytose the amyloid in the brain and blood vessels. We and others have developed pharmacological approaches to stimulate these cells using various ligands. These include toll-like receptor 4, macrophage colony stimulating factor, and more recently nucleotide-binding oligomerization domain-containing 2 receptors. This review will discuss the great potential to take advantage of the innate immune system to fight naturally against amyloid β accumulation and prevent its detrimental consequence on brain functions and its vascular system. SIGNIFICANCE STATEMENT: The focus on amyloid β removal from the perivascular space rather than targeting CNS plaque formation and clearance represents a new direction with a great potential. Small molecules able to act at the level of peripheral immunity would constitute a novel approach for tackling aberrant central nervous system biology, one of which we believe would have the potential of generating a lot of interest.

Exosomes derived from olfactory ensheathing cells provided neuroprotection for spinal cord injury by switching the phenotype of macrophages/microglia

Transplantation of olfactory ensheathing cells (OECs) has been demonstrated to be beneficial for spinal cord injury (SCI) by modulating neuroinflammation, supporting neuronal survival and promoting angiogenesis. Besides OECs, the conditioned medium (CM) from OECs has also been proved to have therapeutic effects for SCI, indicating that the bioactive substances secreted by OECs are essential for its protective effects. Nevertheless, there is still little information regarding the underlying mechanisms. Considering that exosomes are crucial for intercellular communication and could be secreted by different types of cells, we speculated that the therapeutic potential of OECs for SCI might be partially based on their exosomes. To examine whether OECs could secret exosomes, we isolated exosomes by polyethylene glycol‐based method, and identified them by electron microscopy study, nanoparticle tracking analysis (NTA) and western blotting. In view of phagocytic ability of microglia and its distinct roles in microenvironment regulation after SCI, we then focused the effects of OECs‐derived exosomes (OECs‐Exo) on microglial phenotypic regulation. We found that the extracted OECs‐Exo could be engulfed by microglia and partially reverse the LPS‐induced pro‐inflammatory polarization through inhibiting NF‐κB and c‐Jun signaling pathways in vitro. Furthermore, OECs‐Exo were found to inhibit the polarization of pro‐inflammatory macrophages/microglia while increased the numbers of anti‐inflammatory cells after SCI. Considering that the neuronal injury is closely related to the activation state of macrophages/microglia, co‐culture of microglia and neurons were performed. Neuronal death induced by LPS‐treated microglia could be significantly alleviated when microglia treated by LPS plus OECs‐Exo in vitro. After SCI, NeuN‐immunostaining and axonal tract‐tracing were performed to assess neuronal survival and axon preservation. Our data showed that the OECs‐Exo promoted the neuronal survival and axon preservation, and facilitated functional recovery after SCI. Our findings provide a promising therapeutic strategy for SCI based on exosome‐immunomodulation.

Dysregulated phosphoinositide 3-kinase signaling in microglia: shaping chronic neuroinflammation

Microglia are integral mediators of innate immunity within the mammalian central nervous system. Typical microglial responses are transient, intending to restore homeostasis by orchestrating the removal of pathogens and debris and the regeneration of damaged neurons. However, prolonged and persistent microglial activation can drive chronic neuroinflammation and is associated with neurodegenerative disease. Recent evidence has revealed that abnormalities in microglial signaling pathways involving phosphatidylinositol 3-kinase (PI3K) and protein kinase B (AKT) may contribute to altered microglial activity and exacerbated neuroimmune responses. In this scoping review, the known and suspected roles of PI3K-AKT signaling in microglia, both during health and pathological states, will be examined, and the key microglial receptors that induce PI3K-AKT signaling in microglia will be described. Since aberrant signaling is correlated with neurodegenerative disease onset, the relationship between maladapted PI3K-AKT signaling and the development of neurodegenerative disease will also be explored. Finally, studies in which microglial PI3K-AKT signaling has been modulated will be highlighted, as this may prove to be a promising therapeutic approach for the future treatment of a range of neuroinflammatory conditions.

Achyranthes bidentata polypeptide alleviates neurotoxicity of lipopolysaccharide-activated microglia via PI3K/Akt dependent NOX2/ROS pathway

Background

Achyranthes bidentata polypeptide fraction k (ABPPk) has been shown to protect ischemic stroke and Parkinson’s disease, and can inhibit neuroinflammation in lipopolysaccharide (LPS)-activated BV2 microglia. However, the effect of ABPPk responsible for alleviating microglial neurotoxicity remains unknown.

Methods

Primary microglia were cultured to investigate the effect of ABPPk on LPS-induced neuroinflammation. Microglia conditioned medium (MCM) was collected to stimulate primary cortical neurons and then the neuronal viability, lactate dehydrogenase (LDH) release, intracellular calcium influx, mitochondria membrane potential (MMP) were assessed, respectively. Postnatal day 5 Sprague-Dawley rat pups were intracerebral injected with LPS to establish an LPS-induced brain injury model. Double immunohistochemical staining for NeuN and Iba1 was performed to evaluate the effects of ABPPk on LPS-induced neuronal damage and microglial activation. TUNEL assay was conducted to detect cell apoptosis in LPS-injected brain. The effect of ABPPk on LPS-induced NADPH oxidase 2 (NOX2) expression and reactive oxygen species (ROS) production as well as the phosphorylation of protein kinase B (Akt) was detected. Moreover, LY294002 (a specific PI3K inhibitor) and SC79 (a specific Akt activator) were used to further reveal the underlying mechanism.

Results

ABPPk pretreatment inhibited LPS-induced NLRP3 and cleaved caspase 1 expressions as well as the mRNA levels of IL-1β and IL-18. Moreover, ABPPk inhibited glutamate release from LPS-activated microglia in a concentration-dependent manner. MCM stimulation resulted in characteristic neuronal toxicity including neuronal viability decrease, LDH release increase, calcium overload, and MMP drop. However, ABPPk pretreatment on microglia reduced the neurotoxicity of MCM. LPS intracerebral injection led to neuronal damage, microglial activation and cell apoptosis in the brain, while ABPPk preadministration significantly inhibited LPS-induced microglial activation and alleviated the brain injury. ABPPk pretreatment inhibited NOX2 expression and ROS production in LPS-activated primary microglia. Signaling pathway analysis showed that ABPPk promoted the phosphorylation of Akt in microglia and inhibited LPS-upregulated NOX2 expression, ROS production, and glutamate release, which can be eliminated by pharmacological inhibition of PI3K. Specific Akt activator could inhibit LPS-induced NOX2 expression, ROS production and glutamate release.

Conclusions

The present results suggested that ABPPk could alleviate neurotoxicity of LPS-activated microglia via PI3K/Akt dependent NOX2/ROS pathway.

Adjusting vascular permeability, leukocyte infiltration, and microglial cell activation to rescue dopaminergic neurons in rodent models of Parkinson's disease

Animal studies have indicated that increased blood-brain barrier (BBB) permeability and inflammatory cell infiltration are involved during the progression of Parkinson's disease (PD). This study used C16, a peptide that competitively binds to integrin α_vβ₃ and inhibits inflammatory cell infiltration, as well as angiopoietin-1 (Ang-1), an endothelial growth factor crucial for blood vessel protection, to reduce inflammation and improve the central nervous system (CNS) microenvironment in murine models of PD. The combination of C16 and Ang-1 yielded better results compared to the individual drugs alone in terms of reducing dopaminergic neuronal apoptosis, ameliorating cognitive impairment, and electrophysiological dysfunction, attenuating inflammation in the CNS microenvironment, and improving the functional disability in PD mice or rats. These results suggest neuroprotective and anti-inflammatory properties of the C16 peptide plus Ang-1 in PD.

Microglia and BDNF at the crossroads of stressor related disorders: Towards a unique trophic phenotype

Stressors ranging from psychogenic/social to neurogenic/injury to systemic/microbial can impact microglial inflammatory processes, but less is known regarding their effects on trophic properties of microglia. Recent studies do suggest that microglia can modulate neuronal plasticity, possibly through brain derived neurotrophic factor (BDNF). This is particularly important given the link between BDNF and neuropsychiatric and neurodegenerative pathology. We posit that certain activated states of microglia play a role in maintaining the delicate balance of BDNF release onto neuronal synapses. This focused review will address how different "activators" influence the expression and release of microglial BDNF and address the question of tropomyosin receptor kinase B (TrkB) expression on microglia. We will then assess sex-based differences in microglial function and BDNF expression, and how microglia are involved in the stress response and related disorders such as depression. Drawing on research from a variety of other disorders, we will highlight challenges and opportunities for modulators that can shift microglia to a "trophic" phenotype with a view to potential therapeutics relevant for stressor-related disorders.

On Deep Landscape Exploration of COVID-19 Patients Cells and Severity Markers

COVID-19 is a disease with a spectrum of clinical responses ranging from moderate to critical. To study and control its effects, a large number of researchers are focused on two substantial aims. On the one hand, the discovery of diverse biomarkers to classify and potentially anticipate the disease severity of patients. These biomarkers could serve as a medical criterion to prioritize attention to those patients with higher prone to severe responses. On the other hand, understanding how the immune system orchestrates its responses in this spectrum of disease severities is a fundamental issue required to design new and optimized therapeutic strategies. In this work, using single-cell RNAseq of bronchoalveolar lavage fluid of nine patients with COVID-19 and three healthy controls, we contribute to both aspects. First, we presented computational supervised machine-learning models with high accuracy in classifying the disease severity (moderate and severe) in patients with COVID-19 starting from single-cell data from bronchoalveolar lavage fluid. Second, we identified regulatory mechanisms from the heterogeneous cell populations in the lungs microenvironment that correlated with different clinical responses. Given the results, patients with moderate COVID-19 symptoms showed an activation/inactivation profile for their analyzed cells leading to a sequential and innocuous immune response. In comparison, severe patients might be promoting cytotoxic and pro-inflammatory responses in a systemic fashion involving epithelial and immune cells without the possibility to develop viral clearance and immune memory. Consequently, we present an in-depth landscape analysis of how transcriptional factors and pathways from these heterogeneous populations can regulate their expression to promote or restrain an effective immune response directly linked to the patients prognosis.

A novel miRNA-762/NFIX pathway modulates LPS-induced acute lung injury

Severe acute lung injury (ALI) cause significant morbidity and mortality worldwide. MicroRNAs (miRNAs) are possible biomarkers and therapeutic targets for ALI. We aimed to explore the role of miR-762, a known oncogenic factor, in the pathogenesis of ALI. Levels of miR-762 in lung tissues of LPS-treated ALI mice and blood cells of patients with lung injury were measured. Injury of human lung epithelial cell line A549 was induced by LPS stimulation. A downstream target of miR-762, NFIX, was predicted using online tools. Their interactions were validated by luciferase reporter assay. Effects of targeted regulation of the miR-762/NFIX axis on cell proliferation, apoptosis, and inflammatory responses were tested in vitro in A549 cells in vivo with an ALI mouse model. We found that upregulation of miR-762 expression and downregulation of NFIX expression were associated with lung injury. Either miR-762 inhibition or NFIX overexpression in A549 lung cells significantly attenuated LPS-mediated impairment of cell proliferation and viability. Notably, increasing expressions of miR-762 inhibitor or NFIX in vivo via airway lentivirus infection alleviated the LPS-induced ALI in mice. Further, targeted downregulation of miR-762 expression or upregulation of NFIX expression in A549 cells markedly down-regulates NF-κB/IRF3 activation, and substantially reduces the production of inflammatory factors, including TNF-α, IL-6, and IL-8. This study reveals a novel role for the miR-762/NFIX pathway in ALI pathogenesis and sheds new light on targeting this pathway for diagnosis, prevention, and therapy.

Triggering Innate Immune Receptors as New Therapies in Alzheimer's Disease and Multiple Sclerosis

Multiple sclerosis and Alzheimer's disease are two complex neurodegenerative diseases involving the immune system. So far, available treatments provide at best mild improvements to patients' conditions. For decades now, a new set of molecules have been used to modulate and regulate the innate immunity in these pathologies. Most studies have been carried out in rodents and some of them have reported tremendous beneficial effects on the disease course. The modulation of innate immune cells is of great interest since it provides new hope for patients. In this review, we will briefly overview the therapeutic potential of some molecules and receptors in multiple sclerosis and Alzheimer's disease and how they could be used to exploit new therapeutic avenues.

The role of macrophage polarization and associated mechanisms in regulating the anti-inflammatory action of acupuncture: a literature review and perspectives

Acupuncture is used in the treatment of a variety of inflammatory conditions and diseases. However, the mechanisms of its anti-inflammatory action are complex and have not been systematically investigated. Macrophages are key components of the innate immune system, thus, balancing the M1/M2 macrophage ratio and modulating cytokine levels in the inflammatory environment may be desirable therapeutic goals. Evidence has shown that acupuncture has anti-inflammatory actions that affect multiple body systems, including the immune, locomotory, endocrine, nervous, digestive, and respiratory systems, by downregulating pro-inflammatory M1 and upregulating anti-inflammatory M2 macrophages, as well as by modulating associated cytokine secretion. Macrophage polarization is controlled by the interlocking pathways of extrinsic factors, the local tissue microenvironment, and the neural-endocrine-immune systems. It has been suggested that polarization of T lymphocytes and cytokine secretions resulting in modulation of the autonomic nervous system and the hypothalamic–pituitary–adrenal axis, may be upstream mechanisms of acupuncture-induced macrophage polarization. We further propose that macrophage polarization could be the principal pathway involved in acupuncture immune regulation and provide the scientific basis for the clinical application of acupuncture in inflammatory conditions.

Natural Products for Regulating Macrophages M2 Polarization

Macrophages M2 polarization have been taken as an anti-inflammatory progression during inflammation. Natural plant-derived products, with potential therapeutic and preventive activities against inflammatory diseases, have received increasing attention in recent years because of their whole regulative effects and specific pharmacological activities. However, the molecular mechanisms about how different kinds of natural compounds regulate macrophages polarization still unclear. Therefore, in the current review, we summarized the detailed research progress on the active compounds derived from herbal plants with regulating effects on macrophages, especially M2 polarization. These natural occurring compounds including flavonoids, terpenoids, glycosides, lignans, coumarins, alkaloids, polyphenols and quinones. In addition, we extensively discussed the cellular mechanisms underlying the M2 polarization for each compound, which could provide potential therapeutic strategies aiming macrophages M2 polarization.

Mechanistic insights into the anti-depressant effect of emodin: an integrated systems pharmacology study and experimental validation

Depression is a complex neuropsychiatric disease involved multiple targets and signaling pathways. Systems pharmacology studies could potentially present a comprehensive molecular mechanism to delineate the anti-depressant effect of emodin (EMO). In this study, we investigated the anti-depressant effects of EMO in the chronic unpredictable mild stress (CUMS) rat model of depression and gained insights into the underlying mechanisms using systems pharmacology and molecular simulation analysis. Forty-three potential targets of EMO for treatment of depression were obtained. GO biological process analysis suggested that the biological functions of these targets mainly involve the regulation of reactive oxygen species metabolic process, response to lipopolysaccharide, regulation of inflammatory response, etc. KEGG pathway enrichment analysis showed that the PI3K-Akt signaling pathway, insulin resistance, IL-17 signaling pathway were the most significantly enriched signaling pathways. The molecular docking analysis revealed that EMO might have a strong combination with ESR1, AKT1 and GSK3B. Immunohistochemical staining and Western blotting showed that 2 weeks' EMO treatment (80 mg/kg/day) reduced depression related microglial activation, neuroinflammation and altered PI3K-Akt signaling pathway. Our findings provide a systemic pharmacology basis for the anti-depressant effects of EMO.

Intestinal guard: Human CXCL17 modulates protective response against mycotoxins and CXCL17-mimetic peptides development

Mycotoxin contamination is an ongoing and growing issue that can create health risks and even cause death. Unfortunately, there is currently a lack of specific therapy against mycotoxins with few side effects. On the other hand, the strategic expression of CXCL17 in mucosal tissues suggests that it may be involved in immune response when exposed to mycotoxins, but the exact role of CXCL17 remains largely unknown. Using Caco-2 as a cell model of the intestinal epithelial barrier (the first line of defense against mycotoxins), we showed that a strong production of ROS-dependent CXCL17 was triggered by mycotoxins via p38 and JNK pathways. Under the mycotoxins stress, CXCL17 modulated enhanced immuno-protective response with a remission of inflammation and apoptosis through PI3K/AKT/mTOR. Based on our observed feedback of CXCL17 to the mycotoxins, we developed the CXCL17-mimetic peptides in silico (CX1 and CX2) that possessed the safety and the capability to ameliorate mycotoxins-inducible inflammation and apoptosis. In this study, the identification of detoxifying feature of CXCL17 is a prominent addition to the chemokine field, pointing out a new direction for curing the mycotoxins-caused damage.

Liver macrophages and inflammation in physiology and physiopathology of non-alcoholic fatty liver disease

Non‐alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome, being a common comorbidity of type 2 diabetes and with important links to inflammation and insulin resistance. NAFLD represents a spectrum of liver conditions ranging from steatosis in the form of ectopic lipid storage, to inflammation and fibrosis in nonalcoholic steatohepatitis (NASH). Macrophages that populate the liver play important roles in maintaining liver homeostasis under normal physiology and in promoting inflammation and mediating fibrosis in the progression of NAFLD toward to NASH. Liver macrophages are a heterogenous group of innate immune cells, originating from the yolk sac or from circulating monocytes, that are required to maintain immune tolerance while being exposed portal and pancreatic blood flow rich in nutrients and hormones. Yet, liver macrophages retain a limited capacity to raise the alarm in response to danger signals. We now know that macrophages in the liver play both inflammatory and noninflammatory roles throughout the progression of NAFLD. Macrophage responses are mediated first at the level of cell surface receptors that integrate environmental stimuli, signals are transduced through multiple levels of regulation in the cell, and specific transcriptional programmes dictate effector functions. These effector functions play paramount roles in determining the course of disease in NAFLD and even more so in the progression towards NASH. The current review covers recent reports in the physiological and pathophysiological roles of liver macrophages in NAFLD. We emphasise the responses of liver macrophages to insulin resistance and the transcriptional machinery that dictates liver macrophage function.

Prolactin Attenuates Neuroinflammation in LPS-Activated SIM-A9 Microglial Cells by Inhibiting NF-κB Pathways Via ERK1/2

Prolactin (PRL) is a pleiotropic hormone with multiple functions in several tissues and organs, including the brain. PRL decreases lesion-induced microgliosis and modifies gene expression related to microglial functions in the hippocampus, thereby providing a possible mechanism through which it might participate in neuroimmune modulatory responses and prevent neuronal cell damage. However, the direct contribution of microglial cells to PRL-mediated neuroprotection is still unclear and no studies have yet documented whether PRL can directly activate cellular pathways in microglial cells. The aim of this study is to elucidate in vitro actions of PRL on the immortalized SIM-A9 microglia cell line in basal and LPS-stimulated conditions. PRL alone induced a time-dependent extracellular signal-regulated kinase 1/2 (ERK1/2) activation. Pretreatment with PRL attenuated LPS (200 ng/ml) stimulated pro-inflammatory markers: nitric oxide (NO) levels, inducible nitric oxide synthase (iNOS), interleukins (IL)-6, -1β and tumor necrosis factor (TNF-α) expression at 20 nM dosage. PRL suppressed LPS-induced nuclear factor (NF)-κappaB (NF-κB) p65 subunit phosphorylation and its upstream p-ERK1/2 activity. In conclusion, PRL exhibits anti-inflammatory effects in LPS-stimulated SIM-A9 microglia by downregulating pro-inflammatory mediators corresponding to suppression of LPS-activated ERK1/2 and NF-κB phosphorylation.

How Macrophages Become Transcriptionally Dysregulated: A Hidden Impact of Antitumor Therapy

Tumor-associated macrophages (TAMs) are the essential components of the tumor microenvironment. TAMs originate from blood monocytes and undergo pro- or anti-inflammatory polarization during their life span within the tumor. The balance between macrophage functional populations and the efficacy of their antitumor activities rely on the transcription factors such as STAT1, NF-κB, IRF, and others. These molecular tools are of primary importance, as they contribute to the tumor adaptations and resistance to radio- and chemotherapy and can become important biomarkers for theranostics. Herein, we describe the major transcriptional mechanisms specific for TAM, as well as how radio- and chemotherapy can impact gene transcription and functionality of macrophages, and what are the consequences of the TAM-tumor cooperation.

Recombinant CCL17-dependent CCR4 activation alleviates neuroinflammation and neuronal apoptosis through the PI3K/AKT/Foxo1 signaling pathway after ICH in mice

Background

Intracerebral hemorrhage (ICH), a devastating subtype of stroke, is associated with high mortality and morbidity. Neuroinflammation is an important factor leading to ICH-induced neurological injuries. C-C Chemokine Receptor 4 (CCR4) plays an important role in enhancing hematoma clearance after ICH. However, it is unclear whether CCR4 activation can ameliorate neuroinflammation and apoptosis of neurons following ICH. The aim of the present study was to examine the effects of recombinant CCL17 (rCCL17)-dependent CCR4 activation on neuroinflammation and neuronal apoptosis in an intrastriatal autologous blood injection ICH model, and to determine whether the PI3K/AKT/Foxo1 signaling pathway was involved.

Methods

Two hundred twenty-six adult (8-week-old) male CD1 mice were randomly assigned to sham and ICH surgery groups. An intrastriatal autologous blood injection ICH model was used. rCCL17, a CCR4 ligand, was delivered by intranasal administration at 1 h, 3 h, and 6 h post-ICH. CCL17 antibody was administrated by intraventricular injection at 1 h post-ICH. C021, a specific inhibitor of CCR4 and GDC0068, an AKT inhibitor were delivered intraperitoneally 1 h prior to ICH induction. Brain edema, neurobehavioral assessments, western blotting, Fluoro-Jade C staining, terminal deoxynucleotidyl transferase dUTP nick end labeling, and immunofluorescence staining were conducted.

Results

Endogenous expression of CCL17 and CCR4 were increased following ICH, peaking at 5 days post-induction. CCR4 was found to co-localize with microglia, neurons, and astrocytes. rCCL17 treatment decreased brain water content, attenuated short- and long-term neurological deficits, deceased activation of microglia/macrophages and infiltration of neutrophils, and inhibited neuronal apoptosis in the perihematomal region post-ICH. Moreover, rCCL17 treatment post-ICH significantly increased the expression of CCR4, PI3K, phosphorylated AKT, and Bcl-2, while Foxo1, IL-1β, TNF-α, and Bax expression were decreased. The neuroprotective effects of rCCL17 were reversed with the administration of C021 or GDC0068.

Conclusions

rCCL17-dependent CCR4 activation ameliorated neurological deficits, reduced brain edema, and ameliorated neuroinflammation and neuronal apoptosis, at least in part, through the PI3K/AKT/Foxo1 signaling pathway after ICH. Thus, activation of CCR4 may provide a promising therapeutic approach for the early management of ICH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02112-3.

COVID-19 and Toll-Like Receptor 4 (TLR4): SARS-CoV-2 May Bind and Activate TLR4 to Increase ACE2 Expression, Facilitating Entry and Causing Hyperinflammation

Causes of mortality from COVID-19 include respiratory failure, heart failure, and sepsis/multiorgan failure. TLR4 is an innate immune receptor on the cell surface that recognizes pathogen-associated molecular patterns (PAMPs) including viral proteins and triggers the production of type I interferons and proinflammatory cytokines to combat infection. It is expressed on both immune cells and tissue-resident cells. ACE2, the reported entry receptor for SARS-CoV-2, is only present on ~1-2% of the cells in the lungs or has a low pulmonary expression, and recently, the spike protein has been proposed to have the strongest protein-protein interaction with TLR4. Here, we review and connect evidence for SARS-CoV-1 and SARS-CoV-2 having direct and indirect binding to TLR4, together with other viral precedents, which when combined shed light on the COVID-19 pathophysiological puzzle. We propose a model in which the SARS-CoV-2 spike glycoprotein binds TLR4 and activates TLR4 signalling to increase cell surface expression of ACE2 facilitating entry. SARS-CoV-2 also destroys the type II alveolar cells that secrete pulmonary surfactants, which normally decrease the air/tissue surface tension and block TLR4 in the lungs thus promoting ARDS and inflammation. Furthermore, SARS-CoV-2-induced myocarditis and multiple-organ injury may be due to TLR4 activation, aberrant TLR4 signalling, and hyperinflammation in COVID-19 patients. Therefore, TLR4 contributes significantly to the pathogenesis of SARS-CoV-2, and its overactivation causes a prolonged or excessive innate immune response. TLR4 appears to be a promising therapeutic target in COVID-19, and since TLR4 antagonists have been previously trialled in sepsis and in other antiviral contexts, we propose the clinical trial testing of TLR4 antagonists in the treatment of severe COVID-19. Also, ongoing clinical trials of pulmonary surfactants in COVID-19 hold promise since they also block TLR4.

The role of the M1/M2 microglia in the process from cancer pain to morphine tolerance

Cancer pain, especially bone cancer pain, is a pain state often caused by inflammation or dysfunctional nerves. Moreover, in the management of cancer pain, opioid especially morphine is widely used, however, it also brings severe side effects such as morphine tolerance to the patient (Deandrea et al., 2008). A growing body of literatures demonstrated that neuroinflammation is mediated by microglia. As the macrophages like immune cells, microglia play an important role in the pathogenesis of cancer pain and morphine tolerance. Microglia acquire different activation states to regulate the function of these cells. As to M1 phenotype, microglia release pro-inflammatory cytokines and neurotoxic molecules that promote inflammation and cytotoxic reactions. Conversely, when microglia represent M2 phenotypes secreting anti-inflammatory cytokines and nutrient factors that promote the function of repair, regeneration and restore homeostasis. A better understanding of microglia activation in cancer pain and morphine tolerance is crucial for the development of hypothesized neuroprotective drugs. Targeting microglia different polarization states by the inhibition of their deleterious pro-inflammatory neurotoxicity and/or enhancing their beneficial anti-inflammatory protective function seems to be an effective treatment for cancer pain and morphine tolerance.

Role of CGRP in Neuroimmune Interaction via NF-κB Signaling Genes in Glial Cells of Trigeminal Ganglia

Activation of the trigeminal system causes the release of various neuropeptides, cytokines, and other immune mediators. Calcitonin gene-related peptide (CGRP), which is a potent algogenic mediator, is expressed in the peripheral sensory neurons of trigeminal ganglion (TG). It affects the inflammatory responses and pain sensitivity by modulating the activity of glial cells. The primary aim of this study was to use array analysis to investigate the effect of CGRP on the glial cells of TG in regulating nuclear factor kappa B (NF-κB) signaling genes and to further check if CGRP in the TG can affect neuron-glia activation in the spinal trigeminal nucleus caudalis. The glial cells of TG were stimulated with CGRP or Minocycline (Min) + CGRP. The effect on various genes involved in NF-κB signaling pathway was analyzed compared to no treatment control condition using a PCR array analysis. CGRP, Min + CGRP or saline was directly injected inside the TG and the effect on gene expression of Egr1, Myd88 and Akt1 and protein expression of cleaved Caspase3 (cleav Casp3) in the TG, and c-Fos and glial fibrillary acidic protein (GFAP) in the spinal section containing trigeminal nucleus caudalis was analyzed. Results showed that CGRP stimulation resulted in the modulation of several genes involved in the interleukin 1 signaling pathway and some genes of the tumor necrosis factor pathway. Minocycline pre-treatment resulted in the modulation of several genes in the glial cells, including anti-inflammatory genes, and neuronal activation markers. A mild increase in cleav Casp3 expression in TG and c-Fos and GFAP in the spinal trigeminal nucleus of CGRP injected animals was observed. These data provide evidence that glial cells can participate in neuroimmune interaction due to CGRP in the TG via NF-κB signaling pathway.

Interaction of inflammatorily activated retinal pigment epithelium with retinal microglia and neuronal cells

In age-related macular degeneration, inflammatory events are presumed to contribute to disease development. A primary suspect of this contribution is the microglia, the innate immune cell of the retina. In addition, retinal pigment epithelium (RPE) cells can be inflammatorily activated. In this study, we investigate the effect of activated RPE cells on retinal microglia and on neuronal cells. RPE cells and microglia were harvested from porcine eyes. In addition, a neuronal cell line (SHSY-5Y) of human origin was used. For inflammatory activation, agonists of toll-like receptors in different concentrations were used: Pam2CSK4 (Pam; TLR-2), Polyinosinic:polycytidylic acid (Poly I:C; TLR-3) and lipopolysaccharid (LPS; TLR-4). Cell viability was investigated with an MTT assay. The secretion of cytokines was assessed in an ELISA and their expression in real-time PCR. There was no effect of the agonists on cell viability in RPE cells. All agonists induced the secretion of IL-6 and IL-8 in RPE cells with the strongest effect induced by LPS. In microglia, pro-inflammatory stimulation increased the metabolic activity. All agonists induced the secretion of IL-1ß, IL-8, and TNFα in microglia cells while in real-time PCR, LPS and Pam induced the expression of IL-6, IL-1ß and iNOS. Direct stimulation of SHSY-5Y with the agonists induced only minor alterations of viability. Stimulated RPE cell supernatant reduced the secretion of TNFα and IL-8 irrespective of the inducing agent in microglia cells. Additionally a slight induction of IL-1ß was found in microglia treated with supernatant of RPE cells treated with Pam. In real time PCR, the supernatant of RPE cells stimulated with LPS significantly reduced the expression of iNOS and IL-6, but not of IL-1ß. Of note, the expression of iNOS was also reduced by naive RPE cells. The treatment of the SHSY-5Y with supernatant of microglia previously treated with RPE conditioned medium significantly decreased SHSY-5Y viability with and without pro-inflammatory treatment. In conclusion, inflammatory activated RPE cells have a regulatory effect on the pro-inflammatory activation of microglia, stressing the importance of the interaction between these two retinal cell types. Microglia treated with RPE supernatant reduced viability of a neuronal cell line, indicating a neurotoxic effect.

Neuron-derived exosomes-transmitted miR-124-3p protect traumatically injured spinal cord by suppressing the activation of neurotoxic microglia and astrocytes

Background

Spinal cord injury (SCI) is a catastrophic injury that can cause irreversible motor dysfunction with high disability. Exosomes participate in the transport of miRNAs and play an essential role in intercellular communication via transfer of genetic material. However, the miRNAs in exosomes which derived from neurons, and the underlying mechanisms by which they contribute to SCI remain unknown.

Methods

A contusive in vivo SCI model and a series of in vitro experiments were carried out to explore the therapeutic effects of exosomes. Then, a miRNA microarray analysis and rescue experiments were performed to confirm the role of neuron-derived exosomal miRNA in SCI. Western blot, luciferase activity assay, and RNA-ChIP were used to investigate the underlying mechanisms.

Results

The results indicated that neuron-derived exosomes promoted functional behavioral recovery by suppressing the activation of M1 microglia and A1 astrocytes in vivo and in vitro. A miRNA array showed miR-124-3p to be the most enriched in neuron-derived exosomes. MYH9 was identified as the target downstream gene of miR-124-3p. A series of experiments were used to confirm the miR-124-3p/MYH9 axis. Finally, it was found that PI3K/AKT/NF-κB signaling cascades may be involved in the modulation of microglia by exosomal miR-124-3p.

Conclusion

A combination of miRNAs and neuron-derived exosomes may be a promising, minimally invasive approach for the treatment of SCI.

C16 peptide and angiopoietin-1 protect against LPS-induced BV-2 microglial cell inflammation

AIMS

Pathological alterations in the brain can cause microglial activation (MA). Thus, inhibiting MA could provide a new approach for treating neurodegenerative disorders.

MAIN METHODS

To investigate the effect of C16 peptide and angiopoietin-1 (Ang1) on inflammation following MA, we stimulated microglial BV-2 cells with lipopolysaccharide (LPS) and used dexmedetomidine (DEX) as a positive control. Specific inhibitors of Tie2, αvβ3 and α5β1 integrins, and PI3K/Akt were applied to investigate the neuron-protective and anti-inflammatory effects and signaling pathway of C16 + Ang1 treatment in the LPS-induced BV-2 cells.

KEY FINDINGS

Our results showed that C16 + Ang1 treatment reduced the microglia M1 phenotype but promoted the microglia M2 phenotype. In addition, C16 + Ang1 treatment suppressed leukocyte migration across human pulmonary microvascular endothelial cells, reduced the levels of pro-inflammatory factors [inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, tumor necrosis factor (TNF-α)], and cellular apoptosis factors (caspase-3 and p53), and decreased lactate dehydrogenase (LDH) release, but promoted anti-inflammatory cytokine (IL-10) expression and cell proliferation in the LPS-activated BV-2 cells. The signaling pathways underlying the neuron-protective and anti-inflammatory effects of C16 + Ang1 may be mediated by Tie2-PI3K/Akt, Tie2-integrin and integrin-PI3K/Akt.

SIGNIFICANCE

The neuron-protective and anti-inflammatory effects of C16 + Ang1 treatment included M1 to M2 microglia phenotype switching, blocking leukocyte transmigration, decreasing apoptotic and inflammatory factors, and promoting cellular viability.

Transcriptional, Epigenetic and Metabolic Programming of Tumor-Associated Macrophages

Macrophages are key innate immune cells in the tumor microenvironment (TME) that regulate primary tumor growth, vascularization, metastatic spread and tumor response to various types of therapies. The present review highlights the mechanisms of macrophage programming in tumor microenvironments that act on the transcriptional, epigenetic and metabolic levels. We summarize the latest knowledge on the types of transcriptional factors and epigenetic enzymes that control the direction of macrophage functional polarization and their pro- and anti-tumor activities. We also focus on the major types of metabolic programs of macrophages (glycolysis and fatty acid oxidation), and their interaction with cancer cells and complex TME. We have discussed how the regulation of macrophage polarization on the transcriptional, epigenetic and metabolic levels can be used for the efficient therapeutic manipulation of macrophage functions in cancer.

Resveratrol Exerts Anti-Osteoarthritic Effect by Inhibiting TLR4/NF-κB Signaling Pathway via the TLR4/Akt/FoxO1 Axis in IL-1β-Stimulated SW1353 Cells

Purpose

Osteoarthritis (OA) is associated with chronic low-grade inflammation. Resveratrol exerts protective effects on OA through its anti-inflammatory property; however, the mechanism of resveratrol on anti-inflammatory signaling pathways has not been fully elucidated yet. The aim of the present study was to investigate whether resveratrol-mediated PI3K/Akt expression is linked to TLR4/NF-κB pathway and the role of TLR4/Akt/FoxO1 axis in the anti-osteoarthritic effect of resveratrol.

Methods

SW1353 cells stimulated by IL-1β (10 ng/mL) were cultured in the presence or absence of resveratrol (50 μM) and then treated with TLR4 siRNA, PI3K inhibitor LY294002 or FoxO1 siRNA, respectively. The associated proteins of TLR4 signaling pathways and TLR4/Akt/FoxO1 axis were evaluated by Western blot. The level of IL-6 in the supernatant was detected by ELISA.

Results

IL-1β treatment increased the expression of TLR4/NF-κB and phosphorylation of PI3K/Akt and FoxO1, while additional resveratrol further upregulated the expression of PI3K/Akt and FoxO1 phosphorylation but downregulated TLR4 signals in SW1353 cells. Further analyses by the inhibition of TLR4, PI3K/Akt and FoxO1 signaling pathways, respectively, showed that the activation of TLR4 can induce PI3K/Akt phosphorylation, which increases the phosphorylation of FoxO1 and inactivates it. Next, inactivated-FoxO1 can reduce the expression of TLR4, which forms a self-limiting mechanism of inflammation. Resveratrol treatment can upregulate PI3K/Akt phosphorylation and inactivate FoxO1, thereby reducing TLR4 and inflammation.

Conclusion

This study reveals that TLR4/Akt/FoxO1 inflammatory self-limiting mechanism may exist in IL-1β-stimulated SW1353 cells. This study reveals a novel cross-talk mechanism which is between integrated PI3K/Akt/FoxO1 signaling network and TLR4-driven innate responses in IL-1β-stimulated SW1353 cells. Resveratrol may exert anti-OA effect by enhancing the self-limiting mechanism of inflammation through TLR4/Akt/FoxO1 axis.

Immunomodulatory role of mesenchymal stem cells in Alzheimer's disease

Alzheimer's disease (AD) is one of the most common causes of dementia and is characterized by gradual loss in memory, language, and cognitive function. The hallmarks of AD include extracellular amyloid deposition, intracellular neuronal fiber entanglement, and neuronal loss. Despite strenuous efforts toward improvement of AD, there remains a lack of effective treatment and current pharmaceutical therapies only alleviate the symptoms for a short period of time. Interestingly, some progress has been achieved in treatment of AD based on mesenchymal stem cell (MSC) transplantation in recent years. MSC transplantation, as a rising therapy, is used as an intervention in AD, because of the enormous potential of MSCs, including differentiation potency, immunoregulatory function, and no immunological rejection. Although numerous strategies have focused on the use of MSCs to replace apoptotic or degenerating neurons, recent studies have implied that MSC-immunoregulation, which modulates the activity state of microglia or astrocytes and mediates neuroinflammation via several transcription factors (NFs) signaling pathways, may act as a major mechanism for the therapeutic efficacy of MSC and be responsible for some of the satisfactory results. In this review, we will focus on the role of MSC-immunoregulation in MSC-based therapy for AD.

Regulation of 8-Hydroxydaidzein in IRF3-Mediated Gene Expression in LPS-Stimulated Murine Macrophages

Cytokines and chemokines are transcriptionally regulated by inflammatory transcription factors such as nuclear factor-κB (NF-κB), activator protein-1 (AP-1), and interferon regulatory factor (IRF)-3. A daidzein derivative compound, 8-hydroxydaidzein (8-HD), isolated from soy products, has recently gained attention due to various pharmacological benefits, including anti-inflammatory activities. However, regulation of the inflammatory signaling mechanism for 8-HD is still poorly understood, particularly with respect to the IRF-3 signaling pathway. In this study, we explored the molecular mechanism of 8-HD in regulating inflammatory processes, with a focus on the IRF-3 signaling pathway using a lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid [Poly (I:C)] stimulated murine macrophage cell line (RAW264.7). The 8-HD downregulated the mRNA expression level of IRF-3-dependent genes by inhibiting phosphorylation of the IRF-3 transcription factor. The inhibitory mechanism of 8-HD in the IRF-3 signaling pathway was shown to inhibit the kinase activity of IKKε to phosphorylate IRF-3. This compound can also interfere with the TRIF-mediated complex formation composed of TRAF3, TANK, and IKKε leading to downregulation of AKT phosphorylation and reduction of IRF-3 activation, resulted in inhibition of IRF-3-dependent expression of genes including IFN-β, C-X-C motif chemokine 10 (CXCL10), and interferon-induced protein with tetratricopeptide repeats 1 (IFIT1). Therefore, these results strongly suggest that 8-HD can act as a promising compound with the regulatory function of IRF-3-mediated inflammatory responses.