Transient receptor potential vanilloid 1 interacts with TLR4/CD14 signaling pathway in lipopolysaccharide-mediated inflammation in macrophages

Transient receptor potential vanilloid 1 (TRPV1), a ligand-gated cation channel, is a receptor for vanilloids on sensory neurons and is also activated by capsaicin, heat, protons, arachidonic acid metabolites, and inflammatory mediators on neuronal or non-neuronal cells. However, the role of the TRPV1 receptor in pro-inflammatory cytokine secretion and its potential regulatory mechanisms in lipopolysaccharide (LPS)-induced inflammation has yet to be entirely understood. To investigate the role and regulatory mechanism of the TRPV1 receptor in regulating LPS-induced inflammatory responses, bone marrow-derived macrophages (BMDMs) harvested from wild-type (WT) and TRPV1 deficient (Trpv1-/-) mice were used as the cell model. In WT BMDMs, LPS induced an increase in the levels of tumor necrosis factor-α, interleukin-1β, inducible nitric oxide synthase (iNOS), and nitric oxide, which were attenuated in Trpv1-/- BMDMs. Additionally, the phosphorylation of IκBα and mitogen-activated protein kinases, as well as the translocation of NF-κB and AP-1, were all decreased in LPS-treated Trpv1-/- BMDMs. Immunoprecipitation assay revealed that LPS treatment increased the formation of TRPV1-TLR4-CD14 complex in WT BMDMs. Genetic deletion of TRPV1 in BMDMs impaired the LPS-triggered immune-complex formation of TLR4, MyD88, and IRAK, all of which are essential regulators in LPS-induced activation of the TLR4 signaling pathway. Moreover, genetic deletion of TRPV1 prevented the LPS-induced lethality and pro-inflammatory production in mice. In conclusion, the TRPV1 receptor may positively regulate the LPS-mediated inflammatory responses in macrophages by increasing the interaction with the TLR4-CD14 complex and activating the downstream signaling cascade.

The m6A demethylase fat mass and obesity-associated protein mitigates pyroptosis and inflammation in doxorubicin-induced heart failure via the toll-like receptor 4/NF-κB pathway

Background

Doxorubicin (Dox) can induce cardiotoxicity, thereby restricting the utility of this potent drug. Herein, the study ascertained the mechanism of the N6-methyladenosine (m6A) demethylase fat mass and obesity-associated protein (FTO) in pyroptosis and inflammation during Dox-induced heart failure (HF).

Methods

Serum samples were collected from HF patients for detection of the expression of FTO and toll-like receptor 4 (TLR4). Dox-treated H9C2 cardiomyocytes were chosen for in vitro HF modeling, followed by measurement of FTO and TLR4 expression. Cardiomyocytes were detected for viability, apoptosis, spatial distribution of NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3), and the levels of lactic dehydrogenase, inflammatory factors, oxidative stress markers, and pyroptosis-related proteins. The m6A levels of mRNA were examined. RNA immunoprecipitation (RIP) and mRNA stability measurement were used to determine mRNA and protein expression, and RNA m6A dot blot and methylated-RIP assay were performed to detect m6A methylation levels. The expression of p-NF-κB p65 and p-IκB-α was measured by western blotting.

Results

In the serum of HF patients, FTO was elevated while TLR4 was decreased. Dox treatment reduced FTO expression and increased m6A methylation levels and TLR4 expression in H9C2 cells. Overexpression of FTO and knockdown of TLR4 reduced apoptosis, cytotoxicity, inflammation, pyroptosis, oxidative stress, NLRP3 co-localization, and fluorescence intensity in Dox-induced H9C2 cells. Mechanistically, FTO resulted in reduced binding activity of YTHDF1 to TLR4 mRNA via m6A demethylation of TLR4, thus declining TLR4, p-NF-κB p65, and p-IκB-α expression. TLR4 knockdown counteracted the effects of FTO knockdown on Dox-induced H9C2 cells.

Conclusions

FTO alleviated Dox-induced HF by blocking the TLR4/NF-κB pathway.

TLR4-mediated release of heparin-binding protein in human airways: a co-stimulatory role for IL-26

Background

Bacterial infection causes accumulation of neutrophils that release antimicrobial proteins including heparin-binding protein (HBP). In human airways, this neutrophil accumulation can be re-capitulated via intrabronchial exposure to lipopolysaccharide (LPS), a Toll-like receptor 4 (TLR4) agonist, that also causes a local increase in the neutrophil-mobilizing cytokine IL-26. Although LPS is considered a weak stimulus for HBP release ex vivo, its effect on HBP release in human airways in vivo has not been characterized.

Methods

We determined whether intrabronchial exposure to LPS causes concomitant release of HBP and IL-26 in human airways, and whether IL-26 can enhance LPS-induced release of HBP in isolated human neutrophils.

Results

We found that the concentration of HBP was markedly increased in bronchoalveolar lavage (BAL) fluid 12, 24, and 48 hours after LPS exposure, and that it displayed a strong and positive correlation with that of IL-26. Moreover, the concentration of HBP in conditioned media from isolated neutrophils was enhanced only after co-stimulation with LPS and IL-26.

Conclusions

Taken together, our findings indicate that TLR4 stimulation causes concomitant release of HBP and IL-26 in human airways, and that IL-26 may constitute a required co-stimulant for HBP release in neutrophils, thus enabling the concerted action of HBP and IL-26 in local host defense.

TLR4 is one of the receptors for Chikungunya virus envelope protein E2 and regulates virus induced pro-inflammatory responses in host macrophages

Toll like receptor 4 (TLR4), a pathogen-associated molecular pattern (PAMP) receptor, is known to exert inflammation in various cases of microbial infection, cancer and autoimmune disorders. However, any such involvement of TLR4 in Chikungunya virus (CHIKV) infection is yet to be explored. Accordingly, the role of TLR4 was investigated towards CHIKV infection and modulation of host immune responses in the current study using mice macrophage cell line RAW264.7, primary macrophage cells of different origins and in vivo mice model. The findings suggest that TLR4 inhibition using TAK-242 (a specific pharmacological inhibitor) reduces viral copy number as well as reduces the CHIKV-E2 protein level significantly using p38 and JNK-MAPK pathways. Moreover, this led to reduced expression of macrophage activation markers like CD14, CD86, MHC-II and pro-inflammatory cytokines (TNF, IL-6, MCP-1) significantly in both the mouse primary macrophages and RAW264.7 cell line, in vitro. Additionally, TAK-242-directed TLR4 inhibition demonstrated a significant reduction of percent E2-positive cells, viral titre and TNF expression in hPBMC-derived macrophages, in vitro. These observations were further validated in TLR4-knockout (KO) RAW cells. Furthermore, the interaction between CHIKV-E2 and TLR4 was demonstrated by immuno-precipitation studies, in vitro and supported by molecular docking analysis, in silico. TLR4-dependent viral entry was further validated by an anti-TLR4 antibody-mediated blocking experiment. It was noticed that TLR4 is necessary for the early events of viral infection, especially during the attachment and entry stages. Interestingly, it was also observed that TLR4 is not involved in the post-entry stages of CHIKV infection in host macrophages. The administration of TAK-242 decreased CHIKV infection significantly by reducing disease manifestations, improving survivability (around 75%) and reducing inflammation in mice model. Collectively, for the first time, this study reports TLR4 as one of the novel receptors to facilitate the attachment and entry of CHIKV in host macrophages, the TLR4-CHIKV-E2 interactions are essential for efficient viral entry and modulation of infection-induced pro-inflammatory responses in host macrophages, which might have translational implication for designing future therapeutics to regulate the CHIKV infection.

Investigation of TLR4 Antagonists for Prevention of Intestinal Inflammation

Activation of toll-like receptor 4 (TLR4) has been shown to be a major influence on the inflammatory signalling pathways in intestinal mucositis (IM), as demonstrated by TLR4 knock-out mice. Pharmacological TLR4 inhibition has thus been postulated as a potential new therapeutic approach for the treatment of IM but specific TLR4 inhibitors have yet to be investigated. As such, we aimed to determine whether direct TLR4 antagonism prevents inflammation in pre-clinical experimental models of IM. The non-competitive and competitive TLR4 inhibitors, TAK-242 (10 µM) and IAXO-102 (10 µM), respectively, or vehicle were added to human T84, HT-29, and U937 cell lines and mouse colonic explants 1 h before the addition of lipopolysaccharide (LPS) (in vitro: 100 µg/mL; ex vivo: 10 µg/mL), SN-38 (in vitro: 1 µM or 1 nM; ex vivo: 2 µM), and/or tumour necrosis factor-alpha (TNF-α) (5 µg/mL). Supernatant was collected for human IL-8 and mouse IL-6 enzyme-linked immunosorbent assays (ELISAs), as a measure of inflammatory signalling. Cell viability was measured using XTT assays. Explant tissue was used in histopathological and RT-PCR analysis for genes of interest: TLR4, MD2, CD14, MyD88, IL-6, IL-6R, CXCL2, CXCR1, CXCR2. SN-38 increased cytostasis compared to vehicle (P < 0.0001). However, this was not prevented by either antagonist (P > 0.05) in any of the 3 cell lines. Quantitative histological assessment scores showed no differences between vehicle and treatment groups (P > 0.05). There were no differences in in vitro IL-8 (P > 0.05, in all 3 cells lines) and ex vivo IL-6 (P > 0.05) concentrations between vehicle and treatment groups. Transcript expression of all genes was similar across vehicle and treatment groups (P > 0.05). TLR4 antagonism using specific inhibitors TAK-242 and IAXO-102 was not effective at blocking IM in these pre-clinical models of mucositis. This work indicates that specific epithelial inhibition of TLR4 with these compounds is insufficient to manage mucositis-related inflammation. Rather, TLR4 signalling through immune cells may be a more important target to prevent IM.

M2 macrophage-derived exosomal miR-145-5p protects against the hypoxia/reoxygenation-induced pyroptosis of cardiomyocytes by inhibiting TLR4 expression

Background

Exosomes carrying micro ribonucleic acids (miRNAs) protect against myocardial ischemic injury. In the study, we sought to investigate the protective effect mechanism of M2 macrophage-derived exosome miR-145-5p in hypoxia-reoxygenation (H/R)-induced cardiomyocytes.

Methods

M2 macrophages were isolated and induced from blood donated by healthy donors. M2 macrophages were transfected with or without miR-145-5p. Exosomes derived from M2 macrophages were isolated and identified by flow cytometry, nanoparticle tracking analysis, and transmission electron microscopy (TEM). AC16 cells were used to establish an H/R model, and cell activity was detected using a Cell Counting Kit 8 (CCK-8). Western blot was used to detect the expression of gasdermin D (GSDMD), nucleotide-binding domain-like receptor protein 3 (NLRP3), and caspase-1 in the H/R-induced AC16 cells to evaluate pyroptosis. Immunofluorescence staining was used to detect the positive rates of PKH26 and caspase-1. Combined with database prediction, dual luciferase reporter assays were used to validate toll-like receptor 4 (TLR4) as a downstream target molecule of miR-145-5p. A real-time quantitative polymerase chain reaction (RT-qPCR) analysis and western blot were used to detect the expression of TLR4 in the AC16 cells.

Results

Flow cytometry, western blot, nanoparticle tracking and TEM results confirmed the successful isolation of M2 macrophage-derived exosomes. CCK-8 results showed M2 macrophage-derived exosomes decreased the viability of the H/R-induced cells. Western blot results showed the expressions of GSDMD, caspase-1, and NLRP3 were significantly downregulated in the H/R group. Moreover, CCK-8 results showed the M2 macrophage-derived exosome miR-145-5p significantly ameliorated H/R-induced AC16 cellular activity. Western blot results confirmed the expressions of GSDMD, NLRP3, and caspase-1 were significantly downregulated in the macrophage-derived exosome miR-145-5p group compared to the M2 macrophage-derived exosome NC (normal control) group. Immunofluorescence staining results displayed the same trend in terms of the caspase-1 positivity rate. Further, we demonstrated overexpression of TLR4 partially reversed the protective effect of M2 macrophage-derived exosome miR-145-5p in the H/R-induced AC16 cells. Additionally, overexpression of TLR4 reversed the protein expression associated with pyroptosis in M2 macrophage-derived exosome miR-145-5p in the H/R-induced AC16 cells.

Conclusions

Our study indicated M2 macrophage-derived exosomes carrying miR-145-5p inhibited H/R-induced cardiomyocyte pyroptosis by downregulating the expression of TLR4.

The relationship between 896A/G (rs4986790) polymorphism of TLR4 and infectious diseases: A meta-analysis

Toll-like Receptors (TLRs), such as the TLR4, are genes encoding transmembrane receptors of the same name, which induce a pro- or anti-inflammatory response according to their expression as the host's first line of defense against pathogens, such as infectious ones. Single nucleotide polymorphisms (SNPs) are the most common type of mutation in the human genome and can generate functional modification in genes. The aim of this article is to review in which infectious diseases there is an association of susceptibility or protection by the TLR4 SNP rs4986790. A systematic review and meta-analysis of the literature was conducted in the Science Direct, PUBMED, MEDLINE, and SciELO databases between 2011 and 2021 based on the dominant genotypic model of this SNP for general and subgroup analysis of infectious agent type in random effect. Summary odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated for genotypic comparison. I² statistics were calculated to assess the presence of heterogeneity between studies and funnel plots were inspected for indication of publication bias. A total of 27 articles were included, all in English. Among the results achieved, the categories of diseases that were most associated with the SNP studied were in decreasing order of number of articles: infections by bacteria (29.63%); caused by viruses (22.23%); urinary tract infection-UTI (7.4%), while 11 studies (40.74%) demonstrated a nonsignificant association. In this meta-analysis, a total of 5599 cases and 5871 controls were finalized. The present meta-analysis suggests that there is no significant association between TLR4-rs4986790 SNP and infections (OR = 1,11; 95% CI: 0,75-1,66; p = 0,59), but in the virus subgroup it was associated with a higher risk (OR = 2,16; 95% CI: 1,09-4,30; p = 0,03). The subgroups of bacteria and parasites did not show statistical significance (OR = 0,86; 95% CI: 0,56-1,30; p = 0,47, and no estimate of effects, respectively). Therefore, it has been shown that a diversity of infectious diseases is related to this polymorphism, either by susceptibility or even severity to them, and the receptor generated is also crucial for the generation of cell signaling pathways and immune response against pathogens.

Biglycan Is a Novel Mineralocorticoid Receptor Target Involved in Aldosterone/Salt-Induced Glomerular Injury

The beneficial effects of mineralocorticoid receptor (MR) antagonists (MRAs) for various kidney diseases are established. However, the underlying mechanisms of kidney injury induced by MR activation remain to be elucidated. We recently reported aldosterone-induced enhancement of proteoglycan expression in mitral valve interstitial cells and its association with fibromyxomatous valvular disorder. As the expression of certain proteoglycans is elevated in several kidney diseases, we hypothesized that proteoglycans mediate kidney injury in the context of aldosterone/MR pathway activation. We evaluated the proteoglycan expression and tissue injury in the kidney and isolated glomeruli of uninephrectomy/aldosterone/salt (NAS) mice. The MRA eplerenone was administered to assess the role of the MR pathway. We investigated the direct effects of biglycan, one of the proteoglycans, on macrophages using isolated macrophages. The kidney samples from NAS-treated mice showed enhanced fibrosis and increased expression of biglycan accompanying glomerular macrophage infiltration and enhanced expression of TNF-α, iNOS, Nox2, CCL3 (C-C motif chemokine ligand 3), and phosphorylated NF-κB. Eplerenone blunted these changes. Purified biglycan stimulated macrophages to express TNF-α, iNOS, Nox2, and CCL3. This was prevented by a toll-like receptor 4 (TLR4) or NF-κB inhibitor, indicating that biglycan stimulation is dependent on the TLR4/NF-κB pathway. We identified the proteoglycan biglycan as a novel target of MR involved in MR-induced glomerular injury and macrophage infiltration via a biglycan/TLR4/NF-κB/CCL3 cascade.

TLR4 and pSTAT3 Expression on Circulating Tumor Cells (CTCs) and Immune Cells in the Peripheral Blood of Breast Cancer Patients: Prognostic Implications

TLR4 and pSTAT3 are key players in cancer inflammation and immune evasion; however, their role in the peripheral blood (PB) is largely unexplored. Herein we evaluated their expression in the circulating tumor cells (CTCs) and peripheral-blood mononuclear cells (PBMCs) of patients with early (n = 99) and metastatic (n = 100) breast cancer (BC). PB samples obtained prior to adjuvant and first-line therapy, were immunofluorescently stained for Cytokeratins/TLR4/pSTAT3/DAPI and analyzed via Ariol microscopy. TLR4+ CTCs were detected in 50% and 68% of early and metastatic CTC-positive patients, respectively, and pSTAT3+ CTCs in 83% and 68%, respectively. In metastatic patients, CTC detection was associated with a high risk of death (HR: 1.764, p = 0.038), while TLR4+ CTCs correlated with a high risk of disease progression (HR: 1.964, p = 0.030). Regarding PBMCs, TLR4 expression prevailed in metastatic disease (p = 0.029), while pSTAT3 expression was more frequent in early disease (p = 0.014). In early BC, TLR4 expression on PBMCs independently predicted for high risk of relapse (HR: 3.549; p = 0.009), whereas in metastatic BC, TLR4+/pSTAT3- PBMCs independently predicted for high risk of death (HR: 2.925; p = 0.012). These results suggest that TLR4/pSTAT3 signaling on tumor- and immune-cell compartments in the PB could play a role in BC progression, and may hold independent prognostic implications for BC patients.

trans 10, cis 12, but Not cis 9, trans 11 Conjugated Linoleic Acid Isomer Enhances Exercise Endurance by Increasing Oxidative Skeletal Muscle Fiber Type via Toll-like Receptor 4 Signaling in Mice

Conjugated linoleic acid (CLA) has been implicated in regulating muscle fiber. However, which isomer elicits this effect and the underlying mechanisms remain unclear. Here, male C57BL6/J mice and C2C12 cells were treated with two CLA isomers, and the exercise endurance, skeletal muscle fiber type, and involvement of Toll-like receptor 4 (TLR4) signaling were assessed. The results demonstrated that dietary t10, c12, but not c9, t11-CLA isomer enhanced exercise endurance of mice (from 115.88 ± 11.21 to 130.00 ± 15.84 min, P < 0.05) and promoted the formation of oxidative muscle fiber type of gastrocnemius muscle (from 0.15 ± 0.04 to 0.24 ± 0.05, P < 0.05). Consistently, t10, c12-CLA isomer increased the mRNA expression of oxidative muscle fiber type in C2C12 myotubes (from 1.00 ± 0.08 to 2.65 ± 1.77, P < 0.05). In addition, t10, c12-CLA isomer increased TLR4 signaling expression in skeletal muscle and C2C12 myotubes. More importantly, knockdown of TLR4 eliminated the t10, c12-CLA isomer-induced enhancement of exercise endurance in mice and elevation of oxidative muscle fiber type in C2C12 myotubes and gastrocnemius muscle. Together, these findings showed that t10, c12, but not c9, t11-CLA isomer enhances exercise endurance by increasing oxidative skeletal muscle fiber type via TLR4 signaling.

Integrative analysis of long non-coding RNA and messenger RNA expression in toll-like receptor 4-primed mesenchymal stem cells of ankylosing spondylitis

Background

The precise pathogenesis of ankylosing spondylitis (AS) is still largely unknown at present. Our previous study found that toll-like receptor 4 (TLR4) downregulated and performed immunoregulatory dysfunction in mesenchymal stem cells from AS patients (AS-MSCs). The aim of this study was to explore the expression profiles of long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) in TLR4-primed AS-MSCs, and to clarify the potential mechanisms.

Methods

The immunoregulatory effects of MSCs were determined after TLR4 activation. Next, the differentially-expressed (DE) lncRNAs and mRNAs between AS-MSCs and TLR4-primed AS-MSCs [stimulated by lipopolysaccharide (LPS)] were identified via high-throughput sequencing followed by quantitative real-time PCR (qRT-PCR) confirmation. Finally, bioinformatics analyses were performed to identify the critical biological functions, signaling pathways, and associated functional networks involved in the TLR4-primed immunoregulatory function of AS-MSCs.

Results

A total of 147 DE lncRNAs and 698 DE mRNAs were identified between TLR4-primed AS-MSCs and unstimulated AS-MSCs. Of these, 107 lncRNAs were upregulated and 40 were downregulated (fold change ≥2, P<0.05), while 504 mRNAs were upregulated and 194 were downregulated (fold change ≥2, P<0.05). Five lncRNAs and five mRNAs with the largest fold changes were respectively verified by qRT-PCR. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses demonstrated that the DE mRNAs and lncRNAs were highly associated with the inflammatory response, such as NOD-like receptor (NLR) signaling pathway, the TNF signaling pathway and the NF-κB signaling pathway. Cis-regulation prediction revealed eight novel lncRNAs, while trans-regulation prediction revealed 15 lncRNAs, respectively. Eight core pairs of lncRNA and target mRNA in the lncRNA-transcription factor (TF)-mRNA network were as follows: PACERR-PTGS2, LOC105378085-SOD2, LOC107986655-HIVEP2, MICB-DT-MICB, LOC105373925-SP140L, LOC107984251-IFIT5, LOC112268267-GBP2, and LOC101926887-IFIT3, respectively.

Conclusions

TLR4 activation in AS can enhance the immunoregulatory ability of MSCs. Eight core pairs of lncRNA and target mRNA were observed in TLR4-primed AS-MSCs, which could contribute to understanding the potential mechanism of AS-MSC immunoregulatory dysfunction.

TLR4-IN-C34 Inhibits Lipopolysaccharide-Stimulated Inflammatory Responses via Downregulating TLR4/MyD88/NF-κB/NLRP3 Signaling Pathway and Reducing ROS Generation in BV2 Cells

TLR4 signal activated by lipopolysaccharide (LPS) is involved in the pathological process of the central nervous system (CNS) diseases and the suppression of TLR4 signal may become an effective treatment. TLR4-IN-C34, a TLR4 inhibitor, is expected to become a candidate compound with anti-neuroinflammatory response. In the present study, the anti-neuroinflammatory effects and possible mechanism of TLR4-IN-C34 were investigated in BV2 microglia cells stimulated by LPS. The results showed that TLR4-IN-C34 decreased the levels of pro-inflammatory factors and chemokines including NO, TNF-α, IL-1β, IL-6, and MCP-1 in the supernatant of LPS-stimulated BV2 cells. Further research indicated that TLR4-IN-C34 suppressed the expression or phosphorylation levels of inflammatory proteins regarding TLR4/MyD88/NF-κB/NLRP3 signaling pathway. In addition, TLR4-IN-C34 reduced ROS production in BV2 cells after LPS treatment. In conclusion, our findings suggest that anti-neuroinflammatory activity of TLR4-IN-C34 may be interrelated to the inhibition of TLR4/MyD88/NF-κB/NLRP3 signaling pathway and reduction of ROS generation.

Sexually Dimorphic Role of Toll-like Receptor 4 (TLR4) in High Molecular Weight Hyaluronan (HMWH)-induced Anti-hyperalgesia

High molecular weight hyaluronan (HMWH), a prominent component of the extracellular matrix binds to and signals via multiple receptors, including cluster of differentiation 44 (CD44) and toll-like receptor 4 (TLR4). We tested the hypothesis that, in the setting of inflammation, HMWH acts at TLR4 to attenuate hyperalgesia. We found that the attenuation of prostaglandin E2 (PGE2)-induced hyperalgesia by HMWH was attenuated by a TLR4 antagonist (NBP2-26245), but only in male and ovariectomized female rats. In this study we sought to evaluated the role of the TLR4 signaling pathway in anti-hyperalgesia induced by HMWH in male rats. Decreasing expression of TLR4 in nociceptors, by intrathecal administration of an oligodeoxynucleotide (ODN) antisense to TLR4 mRNA, also attenuated HMWH-induced anti-hyperalgesia, in male and ovariectomized female rats. Estrogen replacement in ovariectomized females reconstituted the gonad-intact phenotype. The administration of an inhibitor of myeloid differentiation factor 88 (MyD88), a TLR4 second messenger, attenuated HMWH-induced anti-hyperalgesia, while an inhibitor of the MyD88-independent TLR4 signaling pathway did not. Since it has previously been shown that HMWH-induced anti-hyperalgesia is also mediated, in part by CD44 we evaluated the effect of the combination of ODN antisense to TLR4 and CD44 mRNA. This treatment completely reversed HMWH-induced anti-hyperalgesia in male rats. Our results demonstrate a sex hormone-dependent, sexually dimorphic involvement of TLR4 in HMWH-induced anti-hyperalgesia, that is MyD88 dependent. PERSPECTIVE: The role of TLR4 in anti-hyperalgesia induced by HMWH is a sexually dimorphic, TLR4 dependent inhibition of inflammatory hyperalgesia that provides a novel molecular target for the treatment of inflammatory pain.

Betanin Prevents Experimental Abdominal Aortic Aneurysm Progression by Modulating the TLR4/NF-κB and Nrf2/HO-1 Pathways

Betanin, a bioactive ingredient mostly isolated from beetroots, exhibits a protective effect against cardiovascular diseases. However, its effects on abdominal aortic aneurysm (AAA) have not been elucidated. In this study, an AAA model was constructed by infusion of porcine pancreatic elastase in C57BL/6 mice. Mice were then administered with betanin or saline intragastrically once daily for 14 d. Our results showed that treatment with betanin remarkably limited AAA enlargement and mitigated the infiltration of inflammatory cells in the adventitia. The increased expression of proinflammatory cytokines and matrix metalloproteinases (MMPs) was also significantly alleviated following betanin treatment. Furthermore, betanin suppressed the activation of toll-like receptor 4 (TLR4)/nuclear factor-kappaB (NF-κB) signaling in the aortic wall, and downregulated the levels of tissue-reactive oxygen species as well as circulating 8-isoprostane by stimulating the nuclear factor-E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway. Taken together, these data suggest that betanin may attenuate AAA progression and may be used as a therapeutic drug against AAA.

MiR-135a Protects against Myocardial Injury by Targeting TLR4

Emerging evidence highlights the importance of microRNAs (miRNAs) as functional regulators in cardiovascular disease. This study aimed to investigate the functional significance of miR-135a in the regulation of cardiac injury after isoprenaline (ISO) stimulation and the underlying mechanisms of its effects. Murine models with cardiac-specific overexpression of miR-135a were constructed with an adeno-associated virus expression system. The cardiac injury model was induced by ISO injection (60 mg/kg per day for 14 d). In vitro, we used H9c2 cells to establish a cell injury model by ISO stimulation (10 µM). The results indicated that miR-135a was increased during days 0-6 of ISO injection and was then downregulated during days 8-14 of ISO injection. The expression of miR-135a was consistent with the in vivo findings. Moreover, mice with cardiac overexpression of miR-135a exhibited reduced cardiac fibrosis, lactate dehydrogenase levels, Troponin I, inflammatory response and apoptosis. Overexpression of miR-135a also ameliorated cardiac dysfunction induced by ISO. MiR-135 overexpression in H9c2 cells increased cell viability and decreased cell apoptosis and inflammation in response to ISO. Conversely, miR-135 silencing in H9c2 cells decreased cell viability and increased cell apoptosis and inflammation in response to ISO. Mechanistically, we found that miR-135a negatively regulated toll-like receptor 4 (TLR4), which was confirmed by luciferase assay. Furthermore, the TLR4 inhibitor eritoran abolished the adverse effect of miR-135 silencing. Overall, miR-135a promotes ISO-induced cardiac injury by inhibiting the TLR4 pathway. MiR-135a may be a therapeutic agent for cardiac injury.

Effect of intrathecal injection of miRNA-138 on neuropathic pain in rats undergoing partial sciatic nerve ligation and its underlying mechanism

BACKGROUND

microRNA-138 (miRNA-138) might have a promising therapeutic effect in the Neuropathic pain (NP). We aim to investigate the effects of miRNA-138 on NP and explore its underlying mechanism.

METHODS

we performed a partial sciatic nerve ligation (pSNL) surgery in rats to induce pain and inflammation. Rats were administrated by intrathecal injection of lentiviral (LV)-mediated miRNA-138. Mechanical withdrawal threshold (MWT) and paw withdrawal thermal latency (PWTL) were measured to evaluate the pain degree. The expression levels of miRNA-138, toll-like receptor 4 (TLR4), tumor necrosis factor-alpha (TNF-α), interleukin-β (IL-β), and IL-6 in the spinal cord were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Western blotting was performed to measure the expressions of macrophage inflammatory protein-1 alpha (MIP-1α) and C-C chemokine receptor type 1 (CCR1). Next, the mechanism of miRNA-138 on NP was investigated by intrathecal injection of CCR1 inhibitor or MIP-1α neutralizing antibody. Inflammatory factors, MWT, and PWTL were also measured on day 7.

RESULTS

Intrathecal injection of miRNA138 significantly reduced MWT and PWTL. qRT-PCR showed that miRNA138 mimic group significantly reduced the level of TLR4, TNF-α, Il-β, and IL-6 on day 7. Western blotting showed that the protein expressions of MIP-1α and CCR1 in pSNL + miRNA138 mimic group were significantly decreased on day 7. In addition, the miRNA138 inhibitor inversely increased MWT, PWTL and inflammatory cytokines. Further, the effect of miRNA138 inhibitor all were significantly reversed by CCR1 inhibitor or MIP-1α neutralizing antibody.

CONCLUSIONS

Intrathecal injection of miRNA-138 can remarkably alleviate NP in rats with a pSNL, which may be achieved by suppressing the TLR4 and MIP-1α/CCR1 signaling pathways.

[Effect of acupuncture on intestinal flora and TLR4 in brain and intestinal tissues in rats with stress gastric ulcer]

OBJECTIVE

To observe the effect of acupuncture at "Guanyuan" (CV 4) and "Xiajuxu" (ST 39) on intestinal flora and Toll-like receptors-4 (TLR4) in brain and intestinal tissue in rats with stress gastric ulcer (SGU), and to explore the possible mechanism of acupuncture for SGU.

METHODS

Thirty-one male SD rats were randomly divided into a blank group (n=7), a model group (n=8), an acupuncture group (n=8) and a drug group (n=8). The rats in the model group, acupuncture group and drug group were treated with modified restraint plus water-immersion stress method to establish SGU model. After modeling, the rats in the acupuncture group were treated with acupuncture at "Guanyuan" (CV 4) and "Xiajuxu" (ST 39), 20 min each time, and the needles were twirled for 30 s every 5 min. The rats in the drug group were treated with intragastric administration of 2 mL omeprazole enteric-coated tablets (20 mg/mL). Both the treatments were given once a day for 5 days. After the intervention, the gastric mucosal damage index was calculated by Guth method; the morphological changes of gastric mucosa were observed by HE staining; the diversity of intestinal flora was detected by 16S rDNA high-throughput sequencing; TLR4 contents in brain and intestinal tissues were determined by ELISA.

RESULTS

Compared with the blank group, the gastric mucosal damage index was significantly increased in the model group (P<0.01); the morphological changes of gastric mucosa were obvious; the Observed Species index and Shannon index of α diversity index of intestinal flora were decreased (P<0.05); the β diversity showed that the spatial distance between the model group and the blank group was far; the TLR4 contents in the brain and intestinal tissue were increased (P<0.05, P<0.01). Compared with the model group, the gastric mucosal damage index was decreased in the acupuncture group and the drug group (P<0.05); the morphology of gastric mucosa was improved; the Observed Species index and Shannon index of α diversity index of intestinal flora in the acupuncture group was increased (P<0.05), and the Shannon index in the drug group was increased (P<0.05); the β diversity showed that the spatial distance between the acupuncture group and the blank group was close; the TLR4 contents in the brain and intestinal tissues of the acupuncture group were decreased (P<0.01). Compared with the drug group, the contents of TLR4 in the intestinal tissue of the acupuncture group were decreased (P<0.05).

CONCLUSION

Acupuncture at "Guanyuan" (CV 4) and "Xiajuxu" (ST 39) could alleviate SGU in rats, and its mechanism may be related to increasing the diversity of intestinal flora, promoting the disorder of intestinal flora to normal, and reducing the overexpression of TLR4 in brain and intestinal tissues.

Lactobacillus delbrueckii alleviates depression-like behavior through inhibiting toll-like receptor 4 (TLR4) signaling in mice

Background

The intestinal flora can influence behavior through the microbiota-gut-brain axis and is closely related to the occurrence and development of nervous system diseases such as depression. Probiotics like Lactobacillus may regulate the balance of the intestinal flora and play an active role in preventing and treating depression.

Methods

Eight-week-old C57BL/6J mice (n=32) were randomly and equally divided into a normal control group, a control + Lac group, a model group, and a model + Lac group. The model and model + Lac groups were intraperitoneally injected with 1.2 mg/kg lipopolysaccharide for 7 days, and the behavior of the mice was assessed 24 hours later. The normal and model groups received intragastric administration of saline daily, while the control + Lac and model + Lac groups were given 10⁹ cfu Lac intragastrically daily for 7 days. The inhibitory effect of Lac and its fermentation products on depression-related bacteria were examined in vitro.

Results

Lac effectively inhibited the production of depression-like behaviors in mice. The expression levels of zonula occludens-1 (ZO-1) and E-cadherin in the small intestine in the model group were significantly decreased, but Lac abrogated this effect. Overactivation of microglia and decreased expression of dopamine transporter (DAT) in brain tissues, which are closely related to depression, were also abrogated by Lac treatment. Furthermore, the expression of toll-like receptor 4 (TLR4) and nod-like receptor protein-3 (NLRP3), as well as the level of interleukin-1 beta (IL-1β) in the intestine and brain, were all significantly increased; however, these effects were subsequently abrogated by Lac. Moreover, Lac inhibited dysbiosis through its metabolites.

Conclusions

Lac has a remarkable antidepressant function, which it performs through the inhibition of dysbiosis (via its metabolites) and pattern recognition receptor TLR4 signaling.

The role of toll-like receptor 4 (TLR4) in cancer progression: A possible therapeutic target?

The toll-like receptor (TLR) family consists of vital receptors responsible for pattern recognition in innate immunity, making them the core proteins involved in pathogen detection and eliciting immune responses. The most studied member of this family, TLR4, has been the center of attention regarding its contributory role in many inflammatory diseases including sepsis shock and asthma. Notably, mounting pieces of evidence have proved that this receptor is aberrantly expressed on the tumor cells and the tumor microenvironment in a wide range of cancer types and it is highly associated with the initiation of tumorigenesis as well as tumor progression and drug resistance. Cancer therapy using TLR4 inhibitors has recently drawn scientists' attention, and the promising results of such studies may pave the way for more investigation in the foreseeable future. This review will introduce the key proteins of the TLR4 pathway and how they interact with major growth factors in the tumor microenvironment. Moreover, we will discuss the many aspects of tumor progression affected by the activation of this receptor and provide an overview of the recent therapeutic approaches using various TLR4 antagonists.

Endotoxin Tolerance in Abdominal Aortic Aneurysm Macrophages, In Vitro: A Case-Control Study

Macrophages are implicated in the pathogenesis of abdominal aortic aneurysm (AAA). This study examined the environmentally conditioned responses of AAA macrophages to inflammatory stimuli. Plasma- and blood-derived monocytes were separated from the whole blood of patients with AAA (30–45 mm diameter; n = 33) and sex-matched control participants (n = 44). Increased concentrations of pro-inflammatory and pro-oxidant biomarkers were detected in the plasma of AAA patients, consistent with systemic inflammation and oxidative stress. However, in monocyte-derived macrophages, a suppressed cytokine response was observed in AAA compared to the control following stimulation with lipopolysaccharide (LPS) (tumor necrosis factor alpha (TNF-α) 26.9 ± 3.3 vs. 15.5 ± 3.2 ng/mL, p < 0.05; IL-6 3.2 ± 0.6 vs. 1.4 ± 0.3 ng/mL, p < 0.01). LPS-stimulated production of 8-isoprostane, a biomarker of oxidative stress, was also markedly lower in AAA compared to control participants. These findings are consistent with developed tolerance in human AAA macrophages. As Toll-like receptor 4 (TLR4) has been implicated in tolerance, macrophages were examined for changes in TLR4 expression and distribution. Although TLR4 mRNA and protein expression were unaltered in AAA, cytosolic internalization of receptors and lipid rafts was found. These findings suggest the inflamed, pro-oxidant AAA microenvironment favors macrophages with an endotoxin-tolerant-like phenotype characterized by a diminished capacity to produce pro-inflammatory mediators that enhance the immune response.

In Vitro Anti-Inflammatory Effects of Phenolic Compounds from Moraiolo Virgin Olive Oil (MVOO) in Brain Cells via Regulating the TLR4/NLRP3 Axis

Neuroinflammation is a feature of many classic neurodegenerative diseases. In the healthy brain, microglia cells are distributed throughout the brain and are constantly surveilling the central nervous system (CNS). In response to CNS injury, microglia quickly react by secreting a wide array of apoptotic molecules. Virgin olive oil (VOO) is universally recognized as a symbol of the Mediterranean diet. In the current study, using lipopolysaccharide (LPS)-stimulated BV2 microglia, the anti-inflammatory effects of VOO phenolic extracts from Moraiolo cultivar (MVOO-PE) were investigated. The results showed that low concentration of MVOO-PE prevented microglia cell death and attenuated the LPS-induced activation of toll-like receptor 4 (TLR4)/NOD-like receptor pyrin domain-containing-3 (NLRP3) signaling cascade. The levels of TLR4 and NF-kB were diminished, as well as NLRP3 inflammasome and interleukin-1β (IL-1β) production. Cyclooxygenase-2 (COX-2) isoenzyme and ionized calcium binding adaptor molecule 1 (Iba-1) inflammatory mediator were also reduced. By modulating the TLR4/NLRP3 axis, MVOO-PE pretreatment was able to significantly down-regulate the mRNA expression of inflammatory mediators and suppress the cytokine secretion. Finally, we showed protective effect of MVOO-PE in a transwell neuron-microglia co-culture system. In conclusion, these results suggest that MVOO-PE could exerts anti-inflammatory activity on brain cells and become a promising candidate for preventing several neuroinflammatory diseases.

Shikonin improve sepsis-induced lung injury via regulation of miRNA-140-5p/TLR4-a vitro and vivo study

Shikonin is an anti-inflammatory agent extracted from natural herbs. The aim of this study is to explain the treatment effects and mechanism of Shikonin in acute lung injury induced by sepsis. In this study, first, we evaluate different Shikonin concentrations for the anti-inflammation of acute lung injury induced by sepsis in an in vivo study. On the basis of the results, we confirm that 50.0 mg/kg was the best therapeutic Shikonin concentration. As a second step, we discuss the mechanism of Shikonin by a vitro cell experiment. Finaly, we validate that Shikonin has effective treatment effects on acute lung injury via regulation of microRNA-140-5p/toll-like receptor 4 (miRNA-140-5p/TLR4) in the in vivo study. The results of vitro and vivo study showed that Shikonin could improve acute lung injury induced by sepsis. The mechanism might be correlation miRNA-140-5p expression increasing, and regulated targeted gene TLR4, with TLR4 expression depressing, the downstream myeloid differentiation protein 88 and nuclear factor κB proteins expression were suppressed. In conclusion, Shikonin improved sepsis induced lung injury by regulation miRNA-140-5p/TLR4.

TLR4 and nucleolin influence cell injury, apoptosis and inflammatory factor expression in respiratory syncytial virus-infected N2a neuronal cells

Respiratory syncytial virus (RSV) infection was recently reported to be associated with central nervous system (CNS) symptoms and neurological complications; however, related studies are very limited. Moreover, the molecular mechanism underlying RSV neuropathogenesis is still unclear. Our previous study revealed that toll-like receptor 4 (TLR4) and nucleolin (C23) could be modulated and that they played a role during RSV infection in mouse neuronal-2a (N2a) cells. In the present study, the effects of silencing of TLR4 and C23 on RSV propagation and N2a cellular responses were examined by using RNA interference technology. Four N2a cell treatment groups were established, namely, a normal control group, RSV control group, TLR4 siRNA + RSV group, and C23 siRNA + RSV group. Expression changes in NeuN protein and colocalization of C23 and TLR4 with RSV F protein were assessed using confocal microscopy. Changes in TLR4 and C23 mRNA expression, TLR4, C23, TLR3, TLR7, and p-NF-κB protein expression, and interleukin (IL)-8, IL-6, and tumor necrosis factor (TNF-α) cytokine secretion was measured using quantitative real-time reverse-transcription polymerase chain reaction, Western blot analysis, and enzyme-linked immunosorbent assay, respectively. RSV titers and the apoptotic status of N2a cells were monitored using plaque formation assays and flow cytometry, respectively. The results indicated that TLR4 and C23 gene knockdown decreased the amount of F protein in RSV-infected N2a cells, inhibited RSV propagation, attenuated N2a neuronal injury, diminished cell apoptosis levels, downregulated TLR3 and TLR7 protein expression, and reduced inflammatory protein expression. Therefore, TLR4 and C23 knockdown influences cell injury, apoptosis and inflammatory protein expression in RSV-infected N2a cells.

miR-145-5p inhibits tumor occurrence and metastasis through the NF-κB signaling pathway by targeting TLR4 in malignant melanoma

Compelling evidence shows that deregulated microRNAs (miRNAs) are important regulators in the progression of melanoma. miR-145-5p has been suggested to exhibit antitumorigenic activity in melanoma. However, the molecular mechanism underlying the biological activity of miR-145-5p in melanoma remains to be further understood. Herein, quantitative real-time polymerase chain reaction was used to examine the miR-145-5p expression in malignant melanoma tissues and cells. The interaction between miR-145-5p and toll-like receptor 4 (TLR4) was explored by bioinformatics analyses, luciferase reporter assay, and Western blot. The effects of miR-145-5p or combined with TLR4 on cell proliferation, colony formation, migration, and invasion abilities were investigated by (4,5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, colony formation, wound healing, and transwell assays, respectively. The melanoma xenograft tumor models were established to determine the biological activity of miR-145-5p in melanoma in vivo. In addition, the changes of the nuclear factor kappa B (NF-κB) pathway were analyzed by detecting the NF-κB activity and the NF-κB p65 protein level. We observed that the miR-145-5p expression was underexpressed in melanoma tissues and cells. miR-145-5p suppressed the TLR4 expression by binding to its 3'untranslated region in melanoma cells. Moreover, TLR4 overexpression abolished the inhibition of cell proliferation, colony formation, migration, and invasion abilities induced by miR-145-5p in melanoma cells. Meanwhile, miR-145-5p was confirmed to restrain melanoma tumor growth in vivo by targeting TLR4. Furthermore, miR-145-5p overexpression inactivated the NF-κB pathway in melanoma in vitro and in vivo, which was reversed by TLR4 overexpression. We concluded that miR-145-5p hindered the occurrence and metastasis of melanoma cells in vitro and in vivo by targeting TLR4 via inactivation of the NF-κB pathway.

Role of Nociceptor Toll-like Receptor 4 (TLR4) in Opioid-Induced Hyperalgesia and Hyperalgesic Priming

In addition to analgesia, opioids produce opioid-induced hyperalgesia (OIH) and neuroplasticity characterized by prolongation of inflammatory-mediator-induced hyperalgesia (hyperalgesic priming). We evaluated the hypothesis that hyperalgesia and priming induced by opioids are mediated by similar nociceptor mechanisms. In male rats, we first evaluated the role of nociceptor Toll-like receptor 4 (TLR4) in OIH and priming induced by systemic low-dose morphine (LDM, 0.03 mg/kg). Intrathecal oligodeoxynucleotide antisense to TLR4 mRNA (TLR4 AS-ODN) prevented OIH and prolongation of prostaglandin E₂ hyperalgesia (priming) induced by LDM. In contrast, high-dose morphine (HDM, 3 mg/kg) increased nociceptive threshold (analgesia) and induced priming, neither of which was attenuated by TLR4 AS-ODN. Protein kinase C ε (PKCε) AS-ODN also prevented LDM-induced hyperalgesia and priming, whereas analgesia and priming induced by HDM were unaffected. Treatment with isolectin B4 (IB4)-saporin or SSP-saporin (which deplete IB4⁺ and peptidergic nociceptors, respectively), or their combination, prevented systemic LDM-induced hyperalgesia, but not priming. HDM-induced priming, but not analgesia, was markedly attenuated in both saporin-treated groups. In conclusion, whereas OIH and priming induced by LDM share receptor and second messenger mechanisms in common, action at TLR4 and signaling via PKCε, HDM-induced analgesia, and priming are neither TLR4 nor PKCε dependent. OIH produced by LDM is mediated by both IB4⁺ and peptidergic nociceptors, whereas priming is not dependent on the same population. In contrast, priming induced by HDM is mediated by both IB4⁺ and peptidergic nociceptors. Implications for the use of low-dose opioids combined with nonopioid analgesics and in the treatment of opioid use disorder are discussed.SIGNIFICANCE STATEMENT Opioid-induced hyperalgesia (OIH) and priming are common side effects of opioid agonists such as morphine, which acts at μ-opioid receptors. We demonstrate that OIH and priming induced by systemic low-dose morphine (LDM) share action at Toll-like receptor 4 (TLR4) and signaling via protein kinase C ε (PKCε) in common, whereas systemic high-dose morphine (HDM)-induced analgesia and priming are neither TLR4 nor PKCε dependent. OIH produced by systemic LDM is mediated by isolectin B4-positive (IB4⁺) and peptidergic nociceptors, whereas priming is dependent on a different class of nociceptors. Priming induced by systemic HDM is, however, mediated by both IB4⁺ and peptidergic nociceptors. Our findings may provide useful information for the use of low-dose opioids combined with nonopioid analgesics to treat pain and opioid use disorders.

TLR4 May Be Involved in the Regulation of Colonic Mucosal Microbiota by Vitamin A

Objectives: To investigate the specific role of Toll-like receptor 4 (TLR4) in the regulation of the intestinal mucosa-associated microbiota by vitamin A (VA).

Methods: Both TLR4^-/- (knockout, KO) and wild-type (WT) female mice were randomly fed a VA normal (VAN) or VA deficient (VAD) diet for 4 weeks to establish the following four mouse model groups: TLR4^-/- mice fed a VAN diet (KO VAN), TLR4^-/- mice fed a VAD diet (KO VAD), WT mice fed a VAN diet (WT VAN), and WT mice fed a VAD diet (WT VAD). Then, the mice from each experimental group were mated with male mice with the same genetic background. The pups in the KO VAD and WT VAD groups were subsequently fed the VAD diet after weaning, while the pups in the KO VAN and WT VAN groups were fed the VAN diet continuously after weaning. The serum retinol levels of 7-week-old offspring were determined using high-performance liquid chromatography, and colons were collected from mice in each group and analyzed via 16S rRNA gene sequencing using an Illumina MiSeq platform to characterize the overall microbiota of the samples.

Results: The abundance and evenness of the colon mucosa-associated microbiota were unaffected by dietary VA and TLR4 KO. VAD decreased the abundance of Anaerotruncus (Firmicutes), Oscillibacter (Firmicutes), Lachnospiraceae _NK4A136 _group (Firmicutes) and Mucispirillum (Deferribacteres) and increased the abundance of Parasutterella (Proteobacteria). TLR4 KO decreased the abundance of Bacteroides (Bacteroidetes) and Alloprevotella (Bacteroidetes). However, the abundance of Allobaculum (Firmicutes), Ruminiclostridium_9 (Firmicutes), Alistipes (Bacteroidetes), and Rikenellaceae_RC9 (Bacteroidetes) impacted the interaction between VA and TLR4.

Conclusion: TLR4 may play a pivotal role in regulation of the intestinal mucosa-associated microbiota by VA to maintain the intestinal microecology.

Farrerol attenuates MPP+ -induced inflammatory response by TLR4 signaling in a microglia cell line

Farrerol was found to possess neuroprotective effect; however, the mechanism remains unknown. The aim of the present study was to explore the effect of farrerol on MPP⁺ -induced inflammation in mouse microglial BV-2 cells and to elaborate the underlying mechanism. MTT assay was performed to measure the cell viability. The pro-inflammatory mediators and cytokines including interleukin (IL)-6, IL-1β, and tumor necrosis factor-α (TNF-α); inducible nitric oxide synthase; and cyclooxygenase 2 were measured. The expression of p-p65, p-IκBα, toll-like receptor 4 (TLR4), and myeloid differentiation primary response 88 were analyzed by western blot. We found that farrerol treatment improved cell viability in MPP⁺ -induced BV-2 cells. MPP⁺ -induced upregulation of IL-6, IL-1β, and TNF-α was inhibited by farrerol treatment. Farrerol treatment also attenuated MPP⁺ -induced expression of inducible nitric oxide synthase and cyclooxygenase 2 as well as the activation of NF-κB in BV-2 cells. MPP⁺ -induced TLR4 signaling was markedly diminished by farrerol treatment. Knockdown of TLR4 attenuated MPP⁺ -induced inflammatory response in BV-2 cells. In conclusion, farrerol treatment attenuated MPP⁺ -induced inflammatory response by inhibiting the TLR4 signaling pathway in BV-2 cells. The results indicated that farrerol could be used as a therapeutic agent for preventing or alleviating the neuroinflammation-related diseases, such as Parkinson's disease.

Platelet-neutrophil interaction aggravates vascular inflammation and promotes the progression of atherosclerosis by activating the TLR4/NF-κB pathway

Platelet-neutrophil interaction is well known for its role in inflammatory diseases; however, its biological role in atherosclerosis (AS) progression remains unclear. Human peripheral blood neutrophils were obtained to compare toll-like receptor 4 (TLR4), tumor necrosis factor α (TNF-α), interleukin (IL)-1β and myeloid-related proteins 8/14 (Mrp8/14) levels in 22 AS patients with those in 18 healthy controls using quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA). Meanwhile, mouse marrow neutrophils subjected to different treatment were collected for the ELISA assay, cell apoptosis, and Western blot analysis. Normal diet or high-fat diet ApoE^-/- mice with or without administration of Mrp8/14 antagonist paquinimod were used for plasma collection to measure total cholesterol, triglycerides, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol, TNF-α, IL-1β, Mrp8/14, TLR4, and nuclear factor (NF)-κB p65 levels. The results showed that Mrp8/14 and TLR4-mediated inflammatory pathway was activated in neutrophils of AS patients. In vitro experiments demonstrated that platelet-neutrophil interaction promoted the Mrp8/14 release and inhibited neutrophil apoptosis via P-selectin. Furthermore, platelet-neutrophil interaction upregulated TLR4/myeloid differentiation factor 88/NF-κB pathway. Conversely, Mrp8/14/TLR4/NF-κB interference alleviated AS progression. In conclusion, Mrp8/14/TLR4/NF-κB activated by platelet-neutrophil interaction is an important inflammatory signaling pathway for AS pathogenesis.

MiR-874 alleviates renal injury and inflammatory response in diabetic nephropathy through targeting toll-like receptor-4

Diabetic nephropathy (DN) is a kind of diabetic complication with capillary damage, and its pathogenesis remains obscure. Recently, microRNAs have been identified as diagnostic biomarkers in various diseases including DN. Toll-like receptor 4 (TLR4) contributes to inflammation, and it has been implicated in diabetes pathophysiology. This study was designed to investigate the role of miR-874 and TLR4 in a streptozotocin (STZ)-induced DN rat model and glucose-induced mouse podocyte model. In the current study, we reported that miR-874 was markedly downregulated in DN rats and glucose-induced mouse podocytes compared with the corresponding control groups with the activation of TLR4. In addition, we observed that overexpression of miR-874 was able to alleviate renal injury in DN rats. The cell counting kit (CCK-8) assay and 5-Ethynyl-2'-deoxyuridine (EdU) assay demonstrated that glucose simulation significantly inhibited podocyte proliferation and induced cell apoptosis, which can be reversed by miR-874 mimics significantly. Notably, miR-874 overexpression dramatically attenuated the inflammatory response, indicated by the decreased levels of interleukin-6, L-1β, and tumor necrosis factor α (TNF-α). Finally, the binding correlation between miR-874 and TLR4 was confirmed by carrying out dual-luciferase reporter assay in our study. It was found that overexpression of miR-874 depressed TLR4 levels in podocytes. These findings implied for the first time that the overexpression of miR-874 repressed glucose-triggered podocyte injury through targeting TLR4 and suggested that miR-874/TLR4 axis might represent a pathological mechanism of DN.

Heparan Sulfate Proteoglycans as Relays of Neuroinflammation

Heparan sulfate proteoglycans (HSPGs) are implicated as inflammatory mediators in a variety of settings, including chemokine activation, which is required to recruit circulating leukocytes to infection sites. Heparan sulfate (HS) polysaccharide chains are highly interactive and serve co-receptor roles in multiple ligand:receptor interactions. HS may also serve as a storage depot, sequestering ligands such as cytokines and restricting their access to binding partners. Heparanase, through its ability to fragment HS chains, is a key regulator of HS function and has featured prominently in studies of HS's involvement in inflammatory processes. This review focuses on recent discoveries regarding the role of HSPGs, HS, and heparanase during inflammation, with particular focus on the brain. HS chains emerge as critical go-betweens in multiple aspects of the inflammatory response-relaying signals between receptors and cells. The molecular interactions proposed to occur between HSPGs and the pathogen receptor toll-like receptor 4 (TLR4) are discussed, and we summarize some of the contrasting roles that HS and heparanase have been assigned in diseases associated with chronic inflammatory states, including Alzheimer's disease (AD). We conclude by briefly discussing how current knowledge could potentially be applied to augment HS-mediated events during sustained neuroinflammation, which contributes to neurodegeneration in AD.

Guggulsterone Attenuated Lipopolysaccharide-Induced Inflammatory Responses in Mouse Inner Medullary Collecting Duct-3 Cells

Guggulsterone (GS) is a phytosterol that has been used to treat inflammatory diseases such as colitis, obesity, and thrombosis. Although many previous studies have examined activities of GS, the effect of GS on lipopolysaccharide (LPS)-induced inflammatory responses in mouse inner medullary collecting duct-3 (mIMCD-3) cells have not been examined. Therefore, here, we investigated the anti-inflammatory action of GS on mIMCD-3 cells exposed to LPS. LPS treatment on mIMCD-3 cells produced pro-inflammatory molecules such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) significantly; however, GS treatment significantly inhibited the production of pro-inflammatory molecules. In addition, GS inhibited the degradation of Iκ-Bα and translocation of NF-κB on mIMCD-3 cells. These results suggest that GS could inhibit inflammatory responses in collecting duct cells which could contribute to kidney injury during systemic infection.

Expression of cartilage glycoprotein 39 in peripheral blood monocytes of septic rat and its role in TLR 4-NF-κB signaling pathways

OBJECTIVE

To investigate Cartilage glycoprotein 39 (Cgp-39) expression in peripheral blood monocytes of septic rats, and analyze the relationship between Toll-like receptor 4 (TLR4)-NF-κB signalling pathway and Cgp-39 expression.

METHODS

The ligation puncture was performed to establish rat sepsis model, and ELISA was used to measure serum Cgp-39 concentration. Peripheral blood mononuclear cells was isolated and cultured for 72 h. RNA interference technology was used to inhibit TLR4 and NF-κB gene expression, and real-time PCR and Western blot were performed to detect mRNA and protein expression of TLR4 and NF-κB.

RESULTS

At 1 h, there was no significant differences in serum Cgp-39 concentration between sepsis group and the control group (P > 0.05), however, at 6 h, 12 h, 24 h and 48 h, serum Cgp-39 concentrations in sepsis group were significantly higher than those in the control group at the corresponding time points (P < 0.05). Compared with the control group, TLR4 mRNA and protein expression were increased significantly in sepsis group and sepsis NF-κB interference group; NF-κB mRNA and protein expression were increased significantly in sepsis group and sepsis TLR4 interference group. However, compared with sepsis group, Cgp-39 concentrations decreased significantly in either sepsis TLR4 interference group or NF-κB interference group (P < 0.05 for both).

CONCLUSION

Cgp-39 is highly expressed in peripheral blood monocytes of septic rat and TLR4-NF-κB signalling pathways may be involved in the regulation of Cgp-39 expression.