Epigallocatechin-3-Gallate Attenuates Microglial Inflammation and Neurotoxicity by Suppressing the Activation of Canonical and Noncanonical Inflammasome via TLR4/NF-κB Pathway

SCOPE

In this study, it has been investigated whether the neuroprotective efficacy of epigallocatechin-3-gallate (EGCG) is mediated by inhibition of canonical and noncanonical inflammasome activation via toll-like receptor 4 (TLR4)/NF-κB pathway both in LPS+Aβ-induced microglia in vitro and in APP/PS1 mice in vivo.

METHODS AND RESULTS

In BV2 cells, EGCG inhibits the expressions of Iba-1, cleaved IL-1β, and cleaved IL-18 induced by LPS+Aβ. Then, the supernatants are used to treat SH-SY5Y cells, and EGCG treatment significantly recovers the neurotoxicity from LPS+Aβ-induced microglial conditioned media. Subsequently, it has been found that EGCG reduces the microglial expressions of caspase-1 p20, NLRP3, and caspase-11 p26. Furthermore, the expression levels of Toll-like receptor 4 (TLR4), p-IKK/IKK, and p-NF-κB/NF-κB were decreased after EGCG treatment. As expected, when a caspase-1 specific inhibitor Z-YVAD-FMK, and an IKK and caspase-11 inhibitor wedelolactone are used for blocking, Z-YVAD-FMK and wedelolactone exacerbate the inhibitory efficacy than using EGCG alone. Finally, consistent with the results obtained in BV2 cells, EGCG treatment reduces microglial inflammation and neurotoxicity by suppressing the activation of canonical NLRP3 and noncanonical caspase-11-dependent inflammasome via TLR4/NF-κB pathway in LPS+Aβ-induced rat primary microglia and hippocampus of APP/PS1 mice.

CONCLUSION

EGCG attenuates microglial inflammation and neurotoxicity by inhibition of canonical NLRP3 and noncanonical caspase-11-dependent inflammasome activation via TLR4/NF-κB pathway.

Antidepressant effects of a polysaccharide from okra (Abelmoschus esculentus (L) Moench) by anti-inflammation and rebalancing the gut microbiota

The present study aimed to evaluate the antidepressant-like effect of a polysaccharide (OP), which is isolated from okra (Abelmoschus esculentus (L) Moench), in CUMS-induced mice and its possible mechanisms. OPT, FST and TST were employed to examine the anxiety and depressive behavior in CUMS-induced mice and fecal microbiota transplantation (FMT) CUMS-induced mice, while proinflammatory cytokines, TLR4/NF-κB pathway and MAPKs signaling were detected in both CUMS-induced mice and LPS-induced BV2 cells. The results showed that anxiety- and depressive-like behaviors, gut microbiota dysbiosis and changes of SCFAs, and activation of inflammatory reactions in the colon, serum, and hippocampus of CUMS-induced mice, as well as activation of inflammatory reactions in BV2 cells, could be alleviated by the treatment of OP. The mice that were colonized by OP microbiota showed improved anxiety and depressive behaviors and lower inflammatory response. Furthermore, OP inhibited the expression of TLR4, the nuclear translocation of NF-κB and high levels of proinflammatory cytokines, and enhanced the MAPKs signaling, these effects of OP also observed in LPS-induced BV2 cells. Above all, suggested that the potential mechanism of the antidepressant-like effects of OP was closely correlated with the bidirectional communication of microbiota-gut-brain axis via regulation of inflammation response.

Chitosan oligosaccharide-mediated attenuation of LPS-induced inflammation in IPEC-J2 cells is related to the TLR4/NF-κB signaling pathway

The protective mechanism of chitosan oligosaccharide (COS) against lipopolysaccharides (LPS) -induced inflammatory responses in IPEC-J2 and in mice with DSS dextran sulfate sodium (DSS) -induced colitis is reported. Upon exposure to LPS, the proliferation rate of IPEC-J2 cells markedly decreased, and epithelial cell integrity was compromised. However, COS pretreatment significantly reduced these changes. Low-concentration (200 μg/mL) COS up-regulated Toll-like receptor 4 (TLR4) and nuclear p65 expression, but inhibited LPS-induced expression of nuclear p65, IL-6, and IL-8. Addition of the TLR4 inhibitor reduced nuclear p65, IL-6, and IL-8 expression in IPEC-J2 cells exposed to COS or LPS alone, and a slight up-regulation in nuclear p65 was observed in COS and LPS co-treated cells. Medium-dose COS (600 mg/kg/d) protected against DSS-induced colitis, in which TLR4 and nuclear p65 expression levels were decreased. We postulate that the prevention of both LPS- and DSS -induced inflammatory responses in IPEC-J2 cells and mice by COS are related to the inhibition of the TLR4/NF-κB signaling pathway.

Juglanin ameliorates LPS-induced neuroinflammation in animal models of Parkinson's disease and cell culture via inactivating TLR4/NF-κB pathway

Parkinson's disease (PD) is a common neuro-degenerative disorder, and novel therapeutic targets are required for the treatment of PD. Juglanin is a natural compound extracted from the crude Polygonum aviculare, exhibiting anti-inflammatory, anti-oxidant and anti-cancer activities. In our study, PD in mice was induced by systemic LPS treatment as evidenced by enhanced α-synuclein and reduced tyrosine hydroxylase (TH), which were reversed by juglanin treatment. Moreover, juglanin administration attenuated LPS-caused behavioral and memory impairments and reduced LPS-induced enhancement of neuro-degenerative markers, including amyloid β (Aβ) and p-Tau. Additionally, juglanin ameliorated synaptic functionality through promoting the expression of synaptic markers, such as SYP, PSD-95 and SNAP-25. Toll-like receptor 4 (TLR4) signaling in brain regulates neuroinflammation, contributing to neurodegenerative diseases. Furthermore, LPS induced neuroinflammation through the acceleration of various pro-inflammatory cytokines, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-18 (IL-18) and Cyclooxygenase-2 (COX-2), via activating TLR4/nuclear factor (NF)-κB pathway in hippocampus of mice and microglia cells. Juglanin significantly reduced LPS-induced production of pro-inflammatory cytokines and blocked TLR4/NF-κB pathway. We also found that LPS-induced astrocytes (AST) activity was prevented by juglanin through down-regulating glial fibrillary acidic protein (GFAP) and Iba1 in vivo and in vitro. Together, our results indicated that juglanin ameliorated neuroinflammation-related memory impairment, and neurodegeneration through impeding TLR4/NF-κB, indicating its potential for PD prevention.

Ginkgo diterpene lactones inhibit cerebral ischemia/reperfusion induced inflammatory response in astrocytes via TLR4/NF-κB pathway in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. (Ginkgoaceae) is a traditional Chinese medicine known to treating stroke and other cardio-cerebrovascular diseases for thousands of years in China. Ginkgo diterpene lactones (GDL) attracted much attention because of their neuroprotective properties.

AIM OF THE STUDY

To uncover the effects of GDL, which consist of ginkgolide A (GA), ginkgolide B (GB), and ginkgolide K (GK), on ischemic stroke, as well as the underlying molecular mechanisms.

MATERIALS AND METHODS

We used middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R) models mimicking the process of ischemia/reperfusion in vivo and in vitro, respectively. Anticoagulant effects of GDL were investigated on platelet activating factor (PAF), arachidonic acid (AA) and adenosine diphosphate (ADP)-induced platelet aggregation both in vivo and in vitro. We also evaluated the effects of GDL on lipopolysaccharide (LPS)-induced inflammatory response in primary cultured rats' astrocytes. Infarct size, neurological deficit score, and brain edema were measured at 72 h after MCAO. Immunohistochemistry was utilized to analyze neurons necrosis and astrocytes activation. Expression of pro-inflammatory cytokines, including tumor necrotic factor-α (TNF-α) and interleukin-1β (IL-1β) were detected using enzyme-linked immunosorbent assay (ELISA) and real time PCR. The levels of toll-like receptor 4 (TLR4) and nuclear factor κB (NF-κB) were assessed by real time PCR or Western blot.

RESULTS

Compared with MCAO/R rats, GDL significantly reduced infarct size and brain edema, improved neurological deficit score. Meanwhile, GDL suppressed platelet aggregation, astrocytes activation, pro-inflammatory cytokines releasing, TLR4 mRNA expression and transfer of NF-κB from cytoplasm to nucleus. Furthermore, GDL alleviated OGD/R injury and LPS-induced inflammatory response in primary astrocytes, characterized by promoting cell viability, decreasing lactate dehydrogenase (LDH) activity, and inhibiting IL-1β and TNF-α releasing.

CONCLUSIONS

In summary, GDL attenuate cerebral ischemic injury, inhibit platelet aggregation and astrocytes activation. The anti-inflammatory activity might be associated with the downregulation of TLR4/NF-κB signal pathway. Our present findings provide an innovative insight into the novel treatment of GDL in ischemic stroke therapy.

Protection of Anthocyanin from Myrica rubra against Cerebral Ischemia-Reperfusion Injury via Modulation of the TLR4/NF-κB and NLRP3 Pathways

Myrica rubra (MR) is rich in anthocyanins, and it has good anti-cancer, anti-aging, antioxidant, and antiviral effects. The proportion of disability and death caused by ischemic stroke gradually increased, becoming a major disease that is harmful to human health. However, research on effects of anthocyanin from MR on cerebral ischemia-reperfusion (I/R) injury is rare. In this study, we prepared eight purified anthocyanin extracts (PAEs) from different types of MR, and examined the amounts of total anthocyanin (TA) and cyanidin-3-O-glucoside (C-3-G). After one week of PAE treatment, the cerebral infarction volume, disease damage, and contents of nitric oxide and malondialdehyde were reduced, while the level of superoxide dismutase was increased in I/R mice. Altogether, our results show that Boqi¹ MR contained the most TA (22.07%) and C-3-G (21.28%), and that PAE isolated from Dongkui MR can protect the brain from I/R injury in mice, with the mechanism possibly related to the Toll-like receptor 4 (TLR4)/ nuclear factor-κB (NF-κB) and NOD-like receptor pyrin domain-containing 3 protein (NLRP3) pathways.

Histone deacetylases 3 deletion restrains PM2.5-induced mice lung injury by regulating NF-κB and TGF-β/Smad2/3 signaling pathways

Acute lung injury (ALI) as a serious disease with high mortality has been emphasized as a threat to human health and life. Accumulating studies demonstrated that PM2.5 plays a significant role in metabolic and lung diseases. Histone deacetylases 3 (HDAC3) is an important regulator in control of gene transcription, required in up-regulation of inflammation-related signaling, and has been known as a key hotpot in treating a lot of chronic inflammatory diseases. TGF-β/Smad signaling pathway has been proven to be of significance in fibrosis development. Our results found that PM2.5 induced lung function injury in WT mice with a inflammatory responses through the activation of TGF-β/Smad signaling pathways, resulting in lung injury. Of note, HDAC3-deficient mice after PM2.5 administration further promoted TGF-β/Smad signaling pathways activation. In addition, TLR4, p-NF-κB and p-IκBα indicated that HDAC3 knockout mice have a higher inflammation-related signals expression in lung tissue than WT mice after PM2.5 administration, resulting in pro-inflammatory cytokines releasing. Moreover, in vitro experiment of lung epithelial cells challenged with PM2.5, further indicated that TGF-β/Smad2/3 was involved in fibrosis development, leading to inflammation response. Also, the activation of TLR4/NF-κB could be observed in PM2.5-induced lung epithelial cells, leading to inflammation infiltration. These results indicate a new therapeutic target to protect against lung injury caused by PM2.5.

The regulation of the TLR4/NF-κB and Nrf2/HO-1 signaling pathways is involved in the inhibition of lipopolysaccharide-induced inflammation and oxidative reactions by morroniside in RAW 264.7 macrophages

Morroniside, a major iridoid glycoside isolated from Cornus officinalis, has a variety of beneficial pharmacological properties. Although morroniside has recently been reported to exhibit anti-inflammatory and antioxidant effects, the detailed mechanism has not yet been fully elucidated. In this study, we investigated the inhibitory effect of morroniside on inflammatory and oxidative stress activated by lipopolysaccharide (LPS) in RAW 264.7 macrophages. Our results indicated that morroniside pretreatment significantly inhibited the LPS-induced phagocytic activity and release of pro-inflammatory factors, which was associated with blocking the expression of their regulatory genes. Morroniside also markedly suppressed the expression of myeloid differentiation factor 88 as well as Toll-like receptor 4 (TLR4), and attenuated the translocation of nuclear factor-κB (NF-κB) to the nucleus in LPS-treated RAW 264.7 macrophages. Furthermore, morroniside prevented the binding of LPS to the TLR4 on the cell surface. In addition, morroniside abolished reactive oxygen species (ROS) generation, and enhanced the expression of heme oxygenase-1 (HO-1) following activation of nuclear factor-E2-related factor 2 (Nrf2) in LPS-stimulated RAW 264.7 macrophages. However, zinc protoporphyrin, a specific inhibitor of HO-1, reversed the morroniside-mediated inhibition of inflammatory response in LPS-treated RAW 264.7 macrophages. In conclusion, our findings suggest that morroniside exerts LPS-induced anti-inflammatory and antioxidant effects by targeting the TLR4/NF-κB and Nrf2/HO-1 signaling pathways in RAW 264.7 macrophages. Taken together, our findings suggest that morroniside interacted structurally and electrochemically with TLR4/MD2 complex, consequently can be a potential functional agent to prevent inflammatory and oxidative damage.

N-Butylphthalide (NBP) ameliorated cerebral ischemia reperfusion-induced brain injury via HGF-regulated TLR4/NF-κB signaling pathway

N-Butylphthalide (NBP) has been known to have potential neuroprotective effects in Alzheimer's disease and stroke animal models. Hepatocyte-growth factor (HGF), with strong angiogenic properties, exerted protective role in brain injury. The present study was aimed to investigate the possible anti-inflammatory effects of NBP on the brain injury of rats with cerebral ischemia reperfusion (IR) and astrocytes activation induced by lipopolysaccharide (LPS) treatment. Our results showed that cerebral IR induced brain damage with down-regulation of HGF and astrocytes activation. NBP treatment significantly increased HGF expression and activated cMet/PI3K/AKT signaling pathway, stimulating mTOR activity and suppressing apoptosis in brain tissues. Also NBP inhibited pro-inflammatory cytokines expression, including IL-6, IL-1β, and TNFα, via TLR4/NF-κB suppression. Anti-HGF treatment enhanced TLR4 expression while HGF could suppress TLR4 activation and its down-streaming signals, attenuating inflammation finally. Notably, NBP up-regulated HGF and down-regulated TLR4 expression significantly in the astrocytes combined with the treatment of TLR4 inhibitor than the cells only treated with TLR4 inhibitor, suggesting that NBP could further suppress TLR4 activation, suggesting that NBP might impede TLR4 through up-regulating HGF expression. These results suggested that NBP treatment significantly ameliorated cerebral IR-induced brain injury by inhibiting TLR4/NF-κB-associated inflammation regulated by HGF.

Inhibition of myocardial hypertrophy by magnesium isoglycyrrhizinate through the TLR4/NF-κB signaling pathway in mice

Magnesium isoglycyrrhizinate (MgIG) is a magnesium salt of the 18-α glycyrrhizic acid stereoisomer that has exhibited hepato-protective effects and has anti-inflammatory, antioxidant, and antiviral activities. Here, we have investigated the effects and potential mechanisms of action of MgIG, with respect to myocardial fibrosis induced by isoproterenol (ISO) in mice. Mice were administered MgIG for 14days, with concurrent ISO dosing, and were sacrificed two weeks later. Lactate dehydrogenase (LDH) and creatine kinase (CK) concentrations were measured in the blood. Pathological changes in the myocardium were observed via light microscopy. In addition, the expression of the Bax and Bcl-2 genes, and the basic fibroblast growth factor (bFGF) protein were measured via an immunohistochemical method. The RNA expression of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), c-fos, and c-jun mRNA were quantified by reverse transcription-polymerase chain reaction (RT-PCR) in the myocardial tissue. The protein expression of toll-like receptor (TLR) 4, and nuclear factor kappa B (NF-κB) (p65) were measured using Western blot assays. Compared with the control group, the ISO group showed significant increases in bFGF, Bax, Bcl-2, TLR4, and NF-κB (p65) expressions, as well as increased serum levels of LDH and CK. MgIG had a protective effect on ISO-induced myocardial fibrosis, which might be ascribed, at least in part, to the inhibition of the TLR4/NF-κB (p65) signaling pathway.

miR-25 inhibits sepsis-induced cardiomyocyte apoptosis by targetting PTEN

To investigate the regulatory mechanism of miR-25 in sepsis-induced cardiomyocyte apoptosis. Rats models of sepsis were established by cecal ligation and puncture (CLP). Lipopolysaccharide (LPS)-induced cardiomyocyte was used as an in vitro model of sepsis. The expressions of miR-25, tensin homolog deleted on chromosome 10 (PTEN), Toll-like receptors 4 (TLR4), and p-p65 were analyzed by quantitative real-time PCR (qRT-PCR) and Western blot, respectively. The levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were detected by ELISA. Cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated d-UTP nick end labeling (TUNEL) assay. The relationship between miR-25 and PTEN was measured by luciferase reporter assays. MiR-25 expression in serum of CLP rats and LPS-induced cardiomyocyte was decreased, while the contents of TNF-α and IL-6 were increased. Moreover, the expressions of PTEN, TLR4, and p-p65 in LPS-induced cardiomyocyte were significantly increased. Overexpression of miR-25 increased the survival rate of rats, inhibited LPS-increased cardiomyocyte apoptosis, reversed the increased expression of PTEN, TLR4, p-p65, TNF-α, and IL-6 induced by LPS. The luciferase assay demonstrated that PTEN was a target of miR-25. Additionally, pcDNA-PTEN reversed the inhibitory effect of miR-25 mimic on cardiomyocyte apoptosis, while TAK-242 (TLR-4 inhibitor) countered this effect. miR-25 reduced LPS-induced cardiomyocyte apoptosis by down-regulating PTEN/TLR4/NF-κB axis.

Obacunone Protects Against Ulcerative Colitis in Mice by Modulating Gut Microbiota, Attenuating TLR4/NF-κB Signaling Cascades, and Improving Disrupted Epithelial Barriers

Obacunone, a natural limonoid compound abundantly distributed in citrus fruits, possesses various biological properties, such as antitumor, antioxidant, and antiviral activities. Recent studies suggested an anti-inflammatory activity of obacunone in vitro, but its efficacy on intestinal inflammation remains unknown. This study was designed to evaluate the effects and mechanisms of obacunone in ameliorating intestinal inflammation in a mouse model of ulcerative colitis (UC). We found that obacunone efficiently alleviated the severity of dextran sulfate sodium (DSS)-induced mouse UC by modulating the abnormal composition of the gut microbiota and attenuating the excessive activation of toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) signaling. The intestinal epithelial barrier was disrupted in DSS colitis mice, which was associated with activation of inflammatory signaling cascades. However, obacunone promoted the expression of tight junction proteins (TJP1 and occludin) and repressed the activation of inflammatory signaling cascades. In summary, our findings demonstrated that obacunone attenuated the symptoms of experimental UC in mice through modulation of the gut microbiota, attenuation of TLR4/NF-κB signaling cascades, and restoration of intestinal epithelial barrier integrity.

Crocin attenuates isoprenaline-induced myocardial fibrosis by targeting TLR4/NF-κB signaling: connecting oxidative stress, inflammation, and apoptosis

Crocin is isolated from saffron and has multiple activities. There are many reports on its beneficial effects for cardiovascular disease, but crocin's effects on anti-myocardial fibrosis have not yet been reported. This study investigated crocin's effects and potential mechanisms on isoproterenol (ISO)-induced myocardial fibrosis (MF) in mice. Mice were infused intraperitoneally with crocin with concurrent ISO subcutaneous injections over 2 weeks. Electrocardiography, cardiac weight index (CWI), hydroxyproline content, and heart morphology changes were observed. Administration of crocin markedly decreased heart rate, J-point elevation, QRS interval, CWI, and hydroxyproline content in the myocardial tissues, and improved heart pathologic morphology. Versus the control group, the ISO group showed an increase in lactate dehydrogenase and creatine kinase activities and malondialdehyde content. Meanwhile, superoxide dismutase, catalase, and glutathione contents decreased in the ISO group; crocin caused a significant reduction in oxidative stress levels in ISO-induced MF. ISO led to a significant increase in interleukin-1 and -6 and tumor necrosis factor-α in addition to nuclear factor kappa B (NF-κB) (p65) and toll-like receptor (TLR) 4 expressions. Crocin treatment suppressed these inflammatory cytokine expressions. Moreover, crocin treatment caused a significant decrease in connective tissue growth factor and transforming growth factor-β1 mRNA levels in addition to a decrease in B cell lymphoma-2, Bcl-2-associated X protein, caspase-3, and cleaved caspase-3 expressions. Crocin has a protective effect on ISO-induced MF, which may be associated with the TLR4/NF-κB (p65) signal transduction pathway.

Gold-quercetin nanoparticles prevent metabolic endotoxemia-induced kidney injury by regulating TLR4/NF-κB signaling and Nrf2 pathway in high fat diet fed mice

High-fat diet-induced metabolic syndrome followed by chronic kidney disease caused by intestinal endotoxemia have received extensive attention. Toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) and oxidative stress-related Nrf2/Keap1 were regarded as the key target points involved in metabolic inflammation and kidney injury. However, the molecular mechanism of interaction between TLR4/NF-κB and Nrf2 activation in high-fat diet-induced renal injury is not absolutely understood. Quercetin, a natural product, has been reported to possess antitumor and anti-inflammatory effects. In this regard, this study attempted to prepare poly(d,l-lactide-co-glycolide)-loaded gold nanoparticles precipitated with quercetin (GQ) to investigate the anti-inflammatory and anti-oxidative stress effects in high-fat diet-induced kidney failure. For this study, C57BL/6 mice fed fat-rich fodder were used as the metabolic syndrome model to evaluate the protective effects of GQ on kidney injury and to determine whether TLR4/NF-κB and Nrf2 pathways were associated with the process. Moreover, histological examinations, enzyme-linked immunosorbent assay, Western blot, and basic blood tests and systemic inflammation-related indicators were used to investigate the inhibitory effects of GQ and underlying molecular mechanism by which it may reduce renal injury. Of note, podocyte injury was found to participate in endotoxin-stimulated inflammatory response. TLR4/NF-κB and Nrf2 pathways were upregulated with high-fat diet intake in mice, resulting in reduction of superoxide dismutase activity and increase in superoxide radical, H₂O₂, malondialdehyde, XO, XDH, and XO/XDH ratio. In addition, upregulation of TLR4/NF-κB and oxidative stress by endotoxin were observed in vitro, which were suppressed by GQ administration, ultimately alleviating podocyte injury. These findings indicated that GQ could restore the metabolic disorders caused by high-fat diet, which suppresses insulin resistance, lipid metabolic imbalance, and proinflammatory cytokine production. Also, it may prevent kidney injury by inhibition of TLR4/NF-κB and oxidative stress, further increasing superoxide dismutase activity.

Porcine Beta-Defensin 2 Provides Protection Against Bacterial Infection by a Direct Bactericidal Activity and Alleviates Inflammation via Interference With the TLR4/NF-κB Pathway

Porcine beta-defensin 2 (PBD-2) which is a member of the family of antimicrobial peptides, is widely expressed in pig organs with a broad spectrum of bactericidal activities confirmed in vitro. We previously demonstrated that transgenic (TG) pigs overexpressing PBD-2 could resist the infection by the porcine pathogen Actinobacillus pleuropneumoniae. In this study, the roles of PBD-2 in protecting against bacterial infection were further investigated. The biochemical indexes of the blood sample, body weights, histological morphologies, and weights of the organs of TG mice expressing PBD-2 were measured. Results confirmed that these mice showed normal physiological features. An assay of Salmonella Typhimurium infection was conducted on wild-type (WT) and TG mice. The TG mice possessed higher survival rate, less body weight loss, and pathological changes and smaller recovery rates of bacteria after infection with S. Typhimurium. The in vitro synthetic PBD-2 and the serum and tissue homogenates from the TG mice displayed a direct bactericidal activity. Moreover, PBD-2 could inhibit the release of the proinflammatory cytokines, including IL-6, TNF-α, IL-1β, and IL-12, in the TG mice infected with S. Typhimurium or treated with lipopolysaccharide (LPS). The WT mice treated with PBD-2 and S. Typhimurium or LPS showed reduced levels of proinflammatory cytokines. The mouse macrophage cell line RAW 264.7 which expressed PBD-2 was constructed to detect the signal pathways affected by PBD-2. The suppressing effect of PBD-2 on the release of the proinflammatory cytokines was confirmed using RAW 264.7 either expressing PBD-2 or supplemented with PBD-2. The promoter activity and mRNA level of NF-κB were detected, and PBD-2 was shown to significantly inhibit the activation of the NF-κB pathway induced by LPS. The direct interaction of PBD-2 with TLR4 was revealed by isothermal titration calorimetry and far-Western blot in vitro and the coimmunoprecipitation of PBD-2 with TLR4 on RAW 264.7 cells. This interaction indicates one reason for the interference of NF-κB activation. Overall, this study showed that PBD-2 protected against bacterial infection through a direct bactericidal activity and alleviated inflammation by interfering with the TLR4/NF-κB pathway.

Oxyresveratrol prevents lipopolysaccharide/d-galactosamine-induced acute liver injury in mice

Oxyresveratrol (Oxy) is a natural polyhydroxystilbene abundant in mulberry that has anti-inflammation and anti-oxidant activities. We evaluated the protective effect of Oxy in the context of the lipopolysaccharide and d-galactosamine (LPS/d-GalN) induced acute liver injury. Oxy restricted the development of histopathological changes, markedly reduced the activity of alanine transaminase (ALT) and aspartate transaminase (AST), which are indicators of impaired liver function. Oxy significantly regulated the contents of oxidative stress related enzymes and products, and inhibited expressions of inflammatory mediators and cytokines. Oxy treatment diminished the Toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-κB) signaling pathway in liver, activated the Kelch-like ECH-associated protein 1(Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, and increased expressions of heme oxygenase 1 (HO-1) and quinine oxidoreductase 1(NQO1). Pretreatment with Oxy decreased LPS/d-GalN stimulated hepatocyte apoptosis by efficaciously raising the B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X (Bax) ratio, inhibiting the expression and activation of caspases, and activating the phosphoinoside-3-kinase (PI3K)-Akt pathway. Our results demonstrate the hepatoprotective efficacy of Oxy. The protection is mainly due to the prevention of TLR4/NF-κB pathway activation, induced activation of Keap1-Nrf2 signaling pathway, and decreased hepatocyte apoptosis. Oxy warrants further study as a potential therapeutic agent candidate for the management of acute liver injury.

Melatonin protects against blood-brain barrier damage by inhibiting the TLR4/ NF-κB signaling pathway after LPS treatment in neonatal rats

Hypoxic-ischemic and inflammatory (HII) induces the disruption of blood–brain barrier (BBB) which leads to inflammatory responses and neuronal cell death, resulting in brain secondary damage. Previous studies showed that melatonin produced potent neuroprotective effects in neonatal hypoxic-ischaemic models. However, the relationship between BBB disruption and melatonin in HII was still unclear. The present study therefore investigated the beneficial effects of melatonin on BBB after HII and the underlying mechanisms. HII animal model was conducted by receiving lipopolysaccharide followed by 90 min hypoxia-ischaemia in postnatal day 2 Sprague–Dawley rat pups. Melatonin was injected intraperitoneally 1 h before lipopolysaccharide injection and then once a day for 1 week to evaluate the long-term effects. In this study, we demonstrated that melatonin administration inhibited the disruption of BBB permeability and improved the white matter recovery in HII model rats. Melatonin significantly attenuated the degradation of junction proteins and the neuroprotective role was related to the inhibition of microglial toll-like receptor 4/ nuclear factor-kappa B signaling pathway both in vivo and in vitro. Taken together, our data demonstrated that therapeutic strategies targeting inflammation might be suitable for the therapy of preserving BBB integrity after HII.

Dexmedetomidine Protects Rat Liver against Ischemia-Reperfusion Injury Partly by the α2A-Adrenoceptor Subtype and the Mechanism Is Associated with the TLR4/NF-κB Pathway

Toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) signaling plays a dominant role in the pathogenesis of liver ischemia-reperfusion (IR) injury. Dexmedetomidine (Dex) protects the liver against IR injury via α₂-adrenoceptor activation, but the contribution of TLR4 signaling remains unknown. The authors aimed to examine whether pretreatment with Dex produces hepatic protection and investigate the influence of Dex on TLR4/NF-κB signaling. Dex was given via intraperitoneal injection 30 min prior to orthotopic autologous liver transplantation (OALT) in rats, and three α₂-adrenoceptor antagonists including atipamezole (a nonselective α₂ receptor blocker), ARC-239 (a specific α_2B/C blocker) and BRL-44408 (a specific α_2A blocker) were injected intraperitoneally 10 min before Dex administration. Histopathologic evaluation of the liver and the measurement of serum alanine aminotransferase activity, TLR4/NF-κB expression in the liver, and pro-inflammatory factors (serum tumor necrosis factor-α, interleukin-1β and hepatic myeloperoxidase) concentrations were performed 8 h after OALT. Dex ameliorated liver injury after OALT probably by suppressing the TLR4/NF-κB pathway and decreasing inflammatory mediator levels. The protective effects of Dex were reversed by atipamezole and BRL-44408, but not by ARC-239, suggesting that these effects were mediated in part by the α_2A subtype. In conclusion, Dex attenuates liver injury partly via the α_2A-adrenoceptor subtype, and the mechanism is due to the suppression of the TLR4/NF-κB pathway.

Omeprazole attenuates cisplatin-induced kidney injury through suppression of the TLR4/NF-κB/NLRP3 signaling pathway

Renal toxicity is the primary factor that limits clinical use of cisplatin (CP). A previous study showed that omeprazole (OME) protected against CP-induced toxicity in human renal tubular HK-2 cells and rat kidneys. However, the protective mechanisms of OME have not been characterized. We evaluated the ability of OME to inhibit CP-induced inflammation, and characterized the pathways responsible for this effect. Rats were randomly divided into five groups (n = 10/group). The OME groups were intraperitoneally injected with 1.8 or 3.6 mg OME /kg body weight once daily for 5 days. One hour after final administration of vehicle or OME, all rats (except those in control group and OME alone group) were intraperitoneally injected with 15 mg/kg CP. Twenty-four hours after CP injection, the surgery was applied. The time points and dosing of OME and CP were calculated based on previous studies and the therapeutic dose for patients. Omeprazole attenuated CP-induced apoptosis and damage in vivo and in vitro, as evidenced by increased cell viability and prevention of structural damage. Omeprazole ameliorated CP-induced renal injury through inhibition of NF-κB activation and IκBα degradation, and down-regulation of toll-like receptor 4 (TLR4) and Nod-like receptor protein 3 (NLRP3). Lipopolysaccharide, a TLR4 agonist, was used to verify this mechanism. The results indicated that OME inhibited CP-induced expression of inflammatory proteins, and this effect was blunted by co-treatment with LPS in HK-2 cells. These findings suggested that the protective effects of OME against CP-induced kidney damage may occur through inhibition of the TLR4/NF-κB/NLRP3 signaling pathway. This study provided evidence that OME may be a promising agent to inhibit CP-induced nephrotoxicity.

NLRC5 deficiency promotes myocardial damage induced by high fat diet in mice through activating TLR4/NF-κB

The metabolic syndrome could be induced by high fat diet, leading to cardiovascular diseases, such as myocardial damage. Inflammation response and oxidative stress have been reported to be involved in high fat-induced heart injury, and the molecular mechanism is not fully understood. The NOD-like protein family member, NLRC5, could interact with IKKα to inhibit IKK complex activation. In our study, high fat diet-feeding mice showed cardiac fibrosis, inflammation and oxidative stress through collagen accumulation, TLR4/NF-κB and MAPKs signaling pathways activation. NLRC5 knockout mice fed with high fat showed accelerated fibrosis and inflammation response by promoting α-SMA, Collagen I, Collagen III, TLR4/MyD88, phosphorylated IKKα, IκBα and NF-κB expression. And no effect on oxidative stress was observed in wild type and NLRC5-deficiency samples in in vivo studies. Moreover, NLRC5-knockout and -knockdown cardiac muscle cells challenged with LPS also exhibited aggravated fibrosis levels and inflammatory response without any influences on ROS production in in vitro studies. In conclusion, the findings indicated that NLRC5 showed important effects on high fat-induced heart injury via fibrosis and inflammation modulation, providing an essential target for improving myocardial damage induced by high fat diet.

Melatonin prevents peri‑implantitis via suppression of TLR4/NF-κB

Peri‑implantitis, which is characterized by peri‑implant mucositis and alveolar bone resorption, significantly shortens the service life of dental implants. Melatonin is well-known for its anti-inflammatory and osteoprotective activities. Nevertheless, the effects and mechanisms of melatonin to prevent peri‑implantitis remain unknown. In this study, the lipopolysaccharide-induced peri‑implantitis model was established after the titanium implants were osseointegrated, and the rats received daily administrations of melatonin. The gingival fibroblasts and osteoclasts/osteoblasts were also co-cultured to simulate the inflammatory environment in vitro. We found that prophylactic administration of melatonin decreased proinflammatory cytokine levels and osteoclast numbers, attenuated alveolar bone resorption, and reduced the incidence of peri‑implantitis in vivo. Furthermore, melatonin suppressed osteoclastic formation and function in the inflammatory co-culture environment, while melatonin promoted osteoblastic differentiation and function in the in vitro model. Mechanistically, melatonin reduced TLR4 protein levels, and inhibited activation of NF-κB to downregulate the levels of TNF, IL-1β, and IL-6. These data showed that melatonin was a potent agent to prevent peri‑implantitis through inhibiting TLR4/NF-κB signaling. Our findings provide a novel strategy to prevent peri‑implantitis, and expand the applications of melatonin. STATEMENT OF SIGNIFICANCE: Dental implants have become the first choice for restoring partial and full edentulism, but its service life is seriously affected by peri‑implantitis. Exploration of novel and effective approaches to prevent peri‑implantitis is an important and urgent need. In the present study, we have reported for the first time that prophylactic administration of melatonin delayed the occurrence and reduced the incidence of peri‑implantitis by decreasing proinflammatory cytokine levels, inhibiting osteoclastogenesis, and promoting osteogenesis. The study is expected to have an important significance on the prevention of peri‑implantitis.

SIRT1 mediates improvement of cardiac surgery-induced postoperative cognitive dysfunction via the TLR4/NF-κB pathway

OBJECTIVES

Clinically, there is no effective therapy for postoperative cognitive dysfunction (POCD). Inflammation after surgery is closely associated with POCD.

METHODS

In this study, we explored the role of sirtuin 1 (SIRT1) in POCD. POCD in mice was induced by cardiac surgery. The mRNA and protein levels of related genes were determined by real-time polymerase chain reaction and western blot, respectively. Plasma concentrations of inflammatory factors were measured using an ELISA kit. Novel object and novel location recognition tests were carried out to measure recognition ability. The Morris water maze (MWM) test was performed to measure learning and memory ability.

RESULTS

There was a clear decrease in SIRT1 expression after POCD. The SIRT1 activator SRT1720 promoted recognition, learning, and memory ability of mice with POCD. Moreover, SRT1720 treatment greatly inhibited plasma inflammatory cytokine levels and TLR4 and P65 protein expression in the hippocampus of POCD mice. The effect of SRT1720 on POCD was in a TLR4-dependent manner.

CONCLUSIONS

SIRT1 mediates the improvement of cardiac surgery-induced postoperative cognitive dysfunction via the TLR4/NF-κB pathway.

Quercetin attenuates hypoxia-ischemia induced brain injury in neonatal rats by inhibiting TLR4/NF-κB signaling pathway

Neonatal hypoxic ischemia (HI) is a kind of brain damage that occurs when an infant's brain does not receive enough oxygen and blood. The unrepairable damage leads to newborn death and short/long term brain dysfunctions. Due to the complicated causes and the variety of brain damages, there is no definitive treatment of neonatal HI. In this study, we set up a HI injury model of newborn rat and administrated Quercetin (Que) to treat rat pups before and after HI injury. We performed immunohistochemistry, quantitative PCR and immunoblot experiments to examine whether Que. has a role in attenuating brain injury after HI. We found that Que. treatment could clearly attenuate cortical cell apoptosis, as well as suppress apoptosis marker Bax, and activate anti-apoptosis marker Bcl-2. Moreover, Que. treatment decreased the number of cortical cells microgliosis and astrogliosis induced by HI injury. Furthermore, Que. treatment decreased cortical inflammation. Finally, it is suggested that Que. played a neuroprotective function on HI brain injury via inhibiting the TLR4/NF-κB signaling pathway. From these results, we conclude that Que. treatment may be a used as a therapeutic drug to prevent and decrease the newborn brain damage caused by HI.

Ginkgetin exerts anti-inflammatory effects on cerebral ischemia/reperfusion-induced injury in a rat model via the TLR4/NF-κB signaling pathway

Ginkgo biloba, a natural biflavonoid isolated from Ginkgo biloba leaves, is reported to have strong anti-inflammatory and immunosuppressive properties. The aim of this study is to investigate the potential anti-inflammatory mechanisms of ginkgo flavonoids on cerebral ischemia/reperfusion (I/R) injury. Inflammatory-associated cytokines in cerebral ischemic hemispheres were determined by immunohistochemical staining, Western blot and enzyme-like immunosorbent assay (ELISA). Our results indicated that treatment with Ginkgetin significantly restored rat brain I/R-induced neurological deficit scores. Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in Ginkgetin treatment group (100 mg/kg) also significantly reduced. The expression inflammation-related protein prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and interleukin-8 (IL-8) was also decreased in Ginkgetin treatment group. However, the expression of interleukin-10 (IL-10) was remarkably increased. Thus, this study demonstrates that Ginkgetin protects neurons from I/R-induced rat injury by down-regulating pro-inflammatory cytokines and blocking the TLR4/NF-κB pathway.

Propofol attenuates inflammatory response and apoptosis to protect d-galactosamine/lipopolysaccharide induced acute liver injury via regulating TLR4/NF-κB/NLRP3 pathway

OBJECTIVE

Propofol has been reported to be protective against liver injury due to its anti-inflammatory, anti-oxidative and anti-apoptotic activities. The purpose of this study was to examine the protective effects of propofol on d-galactosamine/lipopolysaccharide (d-GalN/LPS) induced acute liver injury.

METHODS

Mice were given an intraperitoneal injection of propofol before d-GalN/LPS treatment. Liver injury was confirmed by serum biochemical analysis and liver histopathological analysis. Relevant molecular events were determined by ELISA, western blot, and test kits. Cell apoptosis were evaluated by TUNEL assay.

RESULTS

The results showed that propofol significantly prevented d-GalN/LPS-induced liver damage by preventing associated increases of serum alanine transaminase (ALT) and aspartate transaminase (AST) and restoring liver histopathological changes. Propofol markedly inhibited the production of inflammatory cytokines and oxidative stress-related factors. Propofol markedly reduced hepatocyte apoptosis, decreased Bax, Bad, cleaved caspase-3 and increased Bcl-2 expression. Besides, NLRP3 inflammasome and TLR4/NF-κB pathway were inactivated under the treatment of propofol according to the expression of pathways-related proteins.

CONCLUSION

Taken together, propofol contributed to liver protection against d-GalN/LPS-induced liver injury in mice by inhibiting inflammation, oxidative stress and hepatocyte apoptosis through regulating TLR4/NF-κB/NLRP3 pathway.