Soyasaponin Bb inhibits the recruitment of toll-like receptor 4 (TLR4) into lipid rafts and its signaling pathway by suppressing the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent generation of reactive oxygen species

Hepatoprotective Action Mechanism and Quantification of Soyasaponin Bb in Abri Herba by HPLC and Network Pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

The herb of Abrus cantoniensis Hance (AC) is an important Traditional Chinese Medicine (TCM) and is also used as an herbal tea with hepatoprotective action. Soyasaponin Bb is one of the pharmacodynamic substances of AC for the herb's effective pharmacological activity. This study aims to investigate the anti-fibrotic and hepatoprotective activities of soyasaponin Bb in vivo and in vitro experiments, mechanism by network pharmacology and quantification by HPLC.

MATERIALS AND METHODS

High-performance liquid chromatography (HPLC) was applied to evaluate the quality of the herb and determine the contents of soyasaponin Bb from different sources and parts of the AC. In vivo experiments were conducted to induce an acute liver injury model by injecting CCl4 into mice, and an in vitro liver fibrosis model was established by cultivating LX-2 cells with TGF-β1. These models were used to explore the anti-fibrotic and hepatoprotective effects of soyasaponin Bb and its underlying mechanisms.. In addition, the potential target genes corresponding to soyasaponin Bb were identified using the Swiss Target Prediction database through network pharmacology methods. Meanwhile, hepatic fibrosis targets were screened using the GeneCards, TTD, and OMIM disease databases. The STING database was used to construct the protein-protein interaction (PPI) network of soyasaponin Bb-Liver fibrosis. The soyasaponin Bb-hepatic fibrosis disease target-pathway network was constructed using Cytoscape 3.9.1 software. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to enrich and analyze the common targets of the drug and the disease, aiming to identify the potential targets and pathways involved in the anti-fibrotic and hepatoprotective effects of soyasaponin Bb.

RESULTS

The content of soyasaponin Bb varied across different sources, with the roots containing the highest concentration, up to 0.2480%. In vivo experiments showed that soyasaponin Bb had a protective effect against CCl4-induced acute liver injury, effectively inhibiting the increase in ALT and AST levels and slowing down the hepatocyte inflammatory damage caused by CCl4. Soyasaponin Bb also down-regulated MDA levels and up-regulated SOD levels, indicating a certain antioxidant capacity. In vitro cell experiments showed that soyasaponin Bb could effectively inhibit the proliferation of HSC-LX2 cells induced by TGF-β1 by regulating the TGF-β1/α-SMA pathway, significantly down-regulate the protein expression of TGF-β1 and α-SMA, while also reducing the levels of inflammatory cytokines IL-6 and IL-1β. Further network pharmacology analysis suggested that soyasaponin Bb can exert anti-fibrosis activity by regulating the IBD signaling pathway, Th17 signaling pathway, Hepatitis B signaling pathway, and JAK-STAT signaling pathway.

CONCLUSION

Soyasaponin Bb is primarily distributed in the root of AC, and it has a strong protective effect against CCl4-induced acute liver injury. It can reduce the level of inflammatory factors, relieve inflammation, and exert anti-fibrotic activity by regulating the TGF-β1/α-SMA pathway. Its potential anti-liver fibrosis mechanism has been investigated through network pharmacology.

Protective Effects of Glycine soja Leaf and Stem Extract against Chondrocyte Inflammation and Osteoarthritis

Wild soybean, also known as Glycine soja Sieb. et Zucc. (GS), has long been known for its various health benefits. Although various pharmacological effects of G. soja have been studied, the effects of GS leaf and stem (GSLS) on osteoarthritis (OA) have not been evaluated. Here, we examined the anti-inflammatory effects of GSLS in interleukin-1β (IL-1β)-stimulated SW1353 human chondrocytes. GSLS inhibited the expression of inflammatory cytokines and matrix metalloproteinases and ameliorated the degradation of collagen type II in IL-1β-stimulated chondrocytes. Furthermore, GSLS played a protective role in chondrocytes by inhibiting the activation of NF-κB. In addition, our in vivo study demonstrated that GSLS ameliorated pain and reversed cartilage degeneration in joints by inhibiting inflammatory responses in a monosodium iodoacetate (MIA)-induced OA rat model. GSLS remarkably reduced the MIA-induced OA symptoms, such as joint pain, and decreased the serum levels of proinflammatory mediators, cytokines, and matrix metalloproteinases (MMPs). Our findings show that GSLS exerts anti-osteoarthritic effects and reduces pain and cartilage degeneration by downregulating inflammation, suggesting that it is a useful therapeutic candidate for OA.

Advances in the Bioactivities of Phytochemical Saponins in the Prevention and Treatment of Atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease characterized by hardening and narrowing of arteries. AS leads to a number of arteriosclerotic vascular diseases including cardiovascular diseases, cerebrovascular disease and peripheral artery disease, which pose a big threat to human health. Phytochemicals are a variety of intermediate or terminal low molecular weight secondary metabolites produced during plant energy metabolism. Phytochemicals from plant foods (vegetables, fruits, whole grains) and traditional herb plants have been shown to exhibit multiple bioactivities which are beneficial for prevention and treatment against AS. Many types of phytochemicals including polyphenols, saponins, carotenoids, terpenoids, organic sulfur compounds, phytoestrogens, phytic acids and plant sterols have already been identified, among which saponins are a family of glycosidic compounds consisting of a hydrophobic aglycone (sapogenin) linked to hydrophilic sugar moieties. In recent years, studies have shown that saponins exhibit a number of biological activities such as anti-inflammation, anti-oxidation, cholesterol-lowering, immunomodulation, anti-platelet aggregation, etc., which are helpful in the prevention and treatment of AS. This review aims to summarize the recent advances in the anti-atherosclerotic bioactivities of saponins such as ginsenoside, soyasaponin, astra-galoside, glycyrrhizin, gypenoside, dioscin, saikosaponin, etc.

Biosynthesis, distribution, nutritional and organoleptic properties of bitter compounds in fruit and vegetables

Compounds that confer a bitter taste on fruits and vegetables (FAVs) play crucial roles in both plant defense and health promotion. This review details the current knowledge of the distribution, properties (toxicity, pharmacological effects and receptors) and environmental plant responses relating to the biosynthesis, catabolism and transcriptional regulation of 53 bitter plant metabolites in diverse species of FAVs. Some bitter compounds, such as flavonoids, are common in all plant species and make a minor contribution to bitter flavor, but many are synthesized only in specific taxa. They make major contributions to the bitter taste of the corresponding species and some also have significant pharmacological effects. Levels of bitter metabolites are genetically determined, but various environmental cues can affect their final concentration during preharvest development and postharvest storage processes. Molecular approaches are helping to unravel the mechanisms of biosynthesis and regulation of bitter compounds in diverse crop species. This review not only discusses the theoretical basis for utilizing breeding programs and other agricultural technologies to produce FAVs with improved safety, favorable taste and healthier profiles, but also suggests new directions for the utilization of bitter compounds in FAVs for the development of natural pesticides and health-promoting medicines.

Metabolic Profiling of Soyasaponin Bb in Rat Plasma, Urine, Bile and Feces after Intragastric Administration

Soyasaponin Bb is one of the bioactive oleanolic acid type triterpenoid saponin mainly isolated from soybean. It possessed significant antithrombosis, hypolipidemic, anticancer and antioxidant activities. However, the metabolic profiles of soyasaponin Bb remains unknown. In the present study, the metabolites of soyasaponin Bb in plasma, bile, urine, and feces samples after intragastric (i.g.) administration were investigated by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), and its possible metabolic pathways were subsequently proposed. With the metabolite profiling strategy, a total of 11 metabolites were first recognized from urine, plasma, bile and feces of rats after i.g. administration of soyasaponin Bb. The hydroxylation and hydrolysis were the major metabolic pathway of soyasaponins Bb in rat. The results expand our knowledge about the metabolism of soyasaponins Bb, which could provide valuable information for better comprehension of the future pharmacological research.

Bridging the Gaps between Plant and Human Health: A Systematic Review of Soyasaponins

Saponins, prominent secondary plant metabolites, are recognized for their roles in plant defense and medicinal benefits. Soyasaponins, commonly derived from legumes, are a class of triterpenoid saponins that demonstrate significant potential for plant and human health applications. Previous research and reviews largely emphasize human health effects of soyasaponins. However, the biological effects of soyasaponins and their implications for plants in the context of human health have not been well-discussed. This review provides comprehensive discussions on the biological roles of soyasaponins in plant defense and rhizosphere microbial interactions; biosynthetic regulation and compound production; immunological effects and potential for therapeutics; and soyasaponin acquisition attributed to processing effects, bioavailability, and biotransformation processes based on recent soyasaponin research. Given the multifaceted biological effects elicited by soyasaponins, further research warrants an integrated approach to understand molecular mechanisms of regulations in their production as well as their applications in plant and human health.

Effects of glutamine on the IKK/IκB/NF-кB system in the enterocytes of turbot Scophthalmus maximus L. stimulated with soya-saponins

Soya-saponins represent key anti-nutritional factors that contribute to soybean meal-induced enteritis, and glutamine is an effective fish intestine protectant that combats the negative effects of soya-saponins. Nuclear transcription factor-kappa B (NF-кB) systems are involved in the interactions between soya-saponins and glutamine, and the goal of the present work was to clarify the related molecular mechanisms used by the NF-кB kinase (IKK)/inhibitor of NF-κB (IκB)/NF-кB system. Primary cultured turbot (Scophthalmus maximus L.) intestinal epithelial cells were concurrently administrated with 1 mg/mL of soya-saponins and several levels of glutamine (0, 0.5, 1.0 and 2.0 mM) for 12 h and then subjected to real-time PCR and Western blot assays. Compared with cells treated with soya-saponins alone, glutamine significantly decreased the expression of interleukin-1 beta, interleukin 8 and tumor necrosis factor α genes, significantly reduced nuclear and cytosolic NF-κB p65 abundance levels in a dose-dependent manner, increased the IκBα protein level but decreased its phosphorylation, and down-regulated the IKKα/β and phosphorylated IKKα/β levels. In conclusion, this in vitro work confirmed that glutamine attenuated soya-saponin-induced inflammatory responses in turbot intestines. Moreover, it identified molecular pathways in which glutamine first decreased the p65 level and then prevented its nuclear translocation. In addition, glutamine reduced IκBα phosphorylation and maintained its level. Finally, glutamine decreased IKK expression and phosphorylation.

Inhibition of vascular adhesion protein 1 protects dopamine neurons from the effects of acute inflammation and restores habit learning in the striatum

Background

Changes in dopaminergic neural function can be induced by an acute inflammatory state that, by altering the integrity of the neurovasculature, induces neuronal stress, cell death and causes functional deficits. Effectively blocking these effects of inflammation could, therefore, reduce both neuronal and functional decline. To test this hypothesis, we inhibited vascular adhesion protein 1 (VAP-1), a membrane-bound protein expressed on the endothelial cell surface, that mediates leukocyte extravasation and induces oxidative stress.

Method

We induced dopaminergic neuronal loss by infusing lipopolysaccharide (LPS) directly into the substantia nigra (SN) in rats and administered the VAP-1 inhibitor, PXS-4681A, daily.

Results

LPS produced: an acute inflammatory response, the loss of dopaminergic neurons in the SN, reduced the dopaminergic projection to SN target regions, particularly the dorsolateral striatum (DLS), and a deficit in habit learning, a key function of the DLS. In an attempt to protect SN neurons from this inflammatory response we found that VAP-1 inhibition not only reduced neutrophil infiltration in the SN and striatum, but also reduced the associated striatal microglia and astrocyte response. We found VAP-1 inhibition protected dopamine neurons in the SN, their projections to the striatum and promoted the functional recovery of habit learning. Thus, we reversed the loss of habitual actions, a function usually dependent on dopamine release in DLS and sensitive to striatal dysfunction.

Conclusions

We establish, therefore, that VAP-1 inhibition has an anti-inflammatory profile that may be beneficial in the treatment of dopamine neuron dysfunction caused by an acute inflammatory state in the brain.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02288-8.

BIG1 mediates sepsis-induced lung injury by modulating lipid raft-dependent macrophage inflammatory responses

Sepsis is a systemic inflammatory response syndrome with high mortality. It has been reported that brefeldin A-inhibited guanine nucleotide-exchange factor 1 (BIG1) is involved in the pathogenesis of sepsis. However, the mechanism is not fully elucidated. In the present study, we explored the role of BIG1 in mediating lipid raft-dependent macrophage inflammatory response and its impact on lung injury in murine sepsis. In vitro studies revealed that BIG1 deficiency reduces the upregulation and secretion of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and IL-1β and inhibits the activation of the toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88-dependent nuclear factor kappa-B signaling pathway induced by the lipopolysaccharide (LPS) treatment. Further experiments revealed that the inhibitory effects of BIG1 deficiency on LPS-induced inflammation are due to the upregulation of adenosine triphosphate-binding cassette transporter A1. This promotes the free-cholesterol efflux from lipid rafts and results in the reduction of lipid raft TLR4 content. The decrease in TLR4 content in lipid raft thereby inhibits the LPS-induced inflammatory response. Furthermore, using the cecal ligation and puncture-induced polymicrobial sepsis mouse model, we found that conditional knockout (cKO) of the myeloid cell BIG1 significantly reduced the serum concentrations of TNF-α, IL-6, and IL-1β, and downregulated their mRNA expressions in the lungs. Pathological analysis confirmed that the BIG1 cKO alleviated the sepsis-induced lung injury. These results revealed the crucial new role of BIG1 in mediating lipid raft-dependent macrophage inflammatory response. Hence, BIG1 may be a potential promising therapeutic target for the treatment of septic lung injury.

Soyasaponin A2 Alleviates Steatohepatitis Possibly through Regulating Bile Acids and Gut Microbiota in the Methionine and Choline-Deficient (MCD) Diet-induced Nonalcoholic Steatohepatitis (NASH) Mice

SCOPE

Nonalcoholic steatohepatitis (NASH) is a chronic progressive disease with complex pathogenesis of which the bile acids (BAs) and gut microbiota are involved. Soyasaponins (SS) exhibits many health-promoting effects including hepatoprotection, but its prevention against NASH is unclear. This study aims to investigate the preventive bioactivities of SS monomer (SS-A₂ ) against NASH and further clarify its mechanism by targeting the BAs and gut microbiota.

METHODS AND RESULTS

The methionine and choline deficient (MCD) diet-fed male C57BL/6 mice were intervened with obeticholic acid or SS-A₂ for 16 weeks. Hepatic pathology is assessed by hematoxylin-eosin and Masson's trichrome staining. BAs in serum, liver, and colon are measured by ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-TQMS). Gut microbiota in caecum are determined by 16S rDNA amplicon sequencing. In the MCD diet-induced NASH mice, SS-A₂ significantly reduces hepatic steatosis, lobular inflammation, ballooning, nonalcoholic fatty liver disease activity score (NAS) scores, and fibrosis, decreases Erysipelotrichaceae (Faecalibaculum) and Lactobacillaceae (Lactobacillus) and increases Desulfovibrionaceae (Desulfovibrio). Moreover, SS-A₂ reduces serum BAs accumulation and promotes fecal BAs excretion. SS-A₂ changes the BAs profiles in both liver and serum and specifically increases the taurohyodeoxycholic acid (THDCA) level. Faecalibaculum is negatively correlated with serum THDCA.

CONCLUSION

SS-A₂ alleviates steatohepatitis possibly through regulating BAs and gut microbiota in the MCD diet-induced NASH mice.

Germinated Soybean Embryo Extract Ameliorates Fatty Liver Injury in High-Fat Diet-Fed Obese Mice

Soybean is known to have diverse beneficial effects against human diseases, including obesity and its related metabolic disorders. Germinated soybean embryos are enriched with bioactive phytochemicals and known to inhibit diet-induced obesity in mice, but their effect on non-alcoholic fatty liver disease (NAFLD) remains unknown. Here, we germinated soybean embryos for 24 h, and their ethanolic extract (GSEE, 15 and 45 mg/kg) was administered daily to mice fed with a high-fat diet (HFD) for 10 weeks. HFD significantly increased the weight of the body, liver and adipose tissue, as well as serum lipid markers, but soyasaponin Ab-rich GSEE alleviated these changes. Hepatic injury and triglyceride accumulation in HFD-fed mice were attenuated by GSEE via decreased lipid synthesis (SREBP1c) and increased fatty acid oxidation (p-AMPKα, PPARα, PGC1α, and ACOX) and lipid export (MTTP and ApoB). HFD-induced inflammation (TNF-α, IL-6, IL-1β, CD14, F4/80, iNOS, and COX2) was normalized by GSEE in mice livers. In adipose tissue, GSEE downregulated white adipose tissue (WAT) differentiation and lipogenesis (PPARγ, C/EBPα, and FAS) and induced browning genes (PGC1α, PRDM16, CIDEA, and UCP1), which could also beneficially affect the liver via lowering adipose tissue-related circulating lipid levels. Thus, our results suggest that GSEE can prevent HFD-induced NAFLD via inhibition of hepatic inflammation and restoration of lipid metabolisms in both liver and adipose tissue.

The Budesonide-Hydroxypropyl-β-Cyclodextrin Complex Attenuates ROS Generation, IL-8 Release and Cell Death Induced by Oxidant and Inflammatory Stress. Study on A549 and A-THP-1 Cells

Synthetic glucocorticoids such as budesonide (BUD) are potent anti-inflammatory drugs commonly used to treat patients suffering from chronic inflammatory diseases. A previous animal study reported a higher anti-inflammatory activity with a 2-hydroxypropyl-β-cyclodextrin (HPβCD)-based formulation of BUD (BUD:HPβCD). This study investigated, on cellular models (A549 and A-THP-1), the effect of BUD:HPβD in comparison with BUD and HPβCD on the effects induced by oxidative and inflammatory stress as well as the role of cholesterol. We demonstrated the protective effect afforded by BUD:HPβCD against cytotoxicity and ROS generation induced by oxidative and inflammatory stress. The effect observed for BUD:HPβCD was comparable to that observed with HPβCD with no major effect of cholesterol content. We also demonstrated (i) the involvement of the canonical molecular pathway including ROS generation, a decrease in PI3K/Akt activation, and decrease in phosphorylated/unphosphorylated HDAC2 in the effect induced by BUD:HPβCD, (ii) the maintenance of IL-8 decrease with BUD:HPβCD, and (iii) the absence of improvement in glucocorticoid insensitivity with BUD:HPβCD in comparison with BUD, in conditions where HDAC2 was inhibited. Resulting from HPβCD antioxidant and anticytotoxic potential and protective capacity against ROS-induced PI3K/Akt signaling and HDAC2 inhibition, BUD:HPβCD might be more beneficial than BUD alone in a context of concomitant oxidative and inflammatory stress.

Proposed mechanisms for the extracellular release of PD-L1 by the anticancer saponin platycodin D

Platycodin D (PTD) is an oleanane-type terpenoid saponin, isolated from the plant Platycodon grandiflorus. PTD displays multiple pharmacological effects, notably significant anticancer activities in vitro and in vivo. Recently, PTD was shown to trigger the extracellular release of the immunologic checkpoint glycoprotein PD-L1. The reduction of PD-L1 expression at the surface of cancer cells leads to interleukin-2 secretion and T cells activation. In the present review, we have analyzed the potential origin of this atypical PTD-induced PD-L1 release to propose a mechanistic explanation. For that, we considered all published scientific information, as well as the physicochemical characteristics of the natural product (a modeling analysis of PTD and the related saponin β -escin is provided). On this basis, we raise the hypothesis that the capacity of PTD to induce PD-L1 extracellular release derives from two main mechanisms: (i) a drug-promoted shedding of membrane PD-L1 by metalloproteases or more likely, (ii) a cholesterol binding-related effect, that would lead to perturbation of membrane raft domains, limiting the recruitment of proteins like TLR4. The drug-induced membrane effects (frequently observed with saponin drugs), associated with a production of interferon-γ,can favor the release of proteins like PD-L1 into membrane vesicles. Our analysis supports the hypothesis that PTD is a cholesterol-dependent lipid raft-modulating agent able to promote the formation of PD-L1 containing extracellular vesicles. The anticancer potential of PTD and its capacity to modulate the functioning of the PD-1/PD-L1 checkpoint should be further considered.

Soyasaponins reduce inflammation by downregulating MyD88 expression and suppressing the recruitments of TLR4 and MyD88 into lipid rafts

Background

Previous studies indicate that soyasaponins may reduce inflammation via modulating toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88) signaling. However, its underlying mechanisms are still not fully understood.

Methods

Lipopolysaccharide (LPS)-challenged inflamed male ICR mice were intervened by intragastrical administration with 10 and 20 μmol/kg·BW of soyasaponin A₁, A₂ or I for 8 weeks. The serum inflammatory markers were determined by commercial kits and the expression of molecules in TLR4/MyD88 signaling pathway in liver by real-time PCR and western blotting. The recruitments of TLR4 and MyD88 into lipid rafts of live tissue lysates were detected by sucrose gradient ultracentrifugation and western blotting. LPS-stimulated RAW264.7 macrophages were treated with 10, 20 and 40 μmol/L of soyasaponin A₁, A₂ or I for 2 h. MyD88-overexpressed HEK293T cells were treated with 20 and 40 μmol/L of soyasaponins (A₁, A₂ or I) or 20 μmol/L of ST2825 (a MyD88 inhibitor) for 6 h. The expression of molecules in TLR4/MyD88 signaling pathway were determined by western blotting. Data were analyzed by using one way analysis of variance or t-test by SPSS 20.0 statistical software.

Results

Soyasaponins A₁, A₂ or I significantly reduced the levels of tumor necrosis factor alpha (TNFα), interleukin (IL)-6 and nitric oxide (NO) in serum (p < 0.05), and decreased the mRNA levels of TNFα, IL-6, IL-1β, cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS) (p < 0.05), the protein levels of myeloid differentiation protein 2 (MD-2), TLR4, MyD88, toll-interleukin1 receptor domain containing adaptor protein (TIRAP), phosphorylated interleukin-1 receptor-associated kinase 4 (p-IRAK-4), phosphorylated interleukin-1 receptor-associated kinase 1 (p-IRAK-1) and TNF receptor associated factor 6 (TRAF6) (p < 0.05), and the recruitments of TLR4 and MyD88 into lipid rafts in liver (p < 0.05). In LPS-stimulated macrophages, soyasaponins A₂ or I significantly decreased MyD88 (p < 0.05), soyasaponins A₁, A₂ or I reduced p-IRAK-4 and p-IRAK-1 (p < 0.05), and soyasaponin I decreased TRAF6 (p < 0.05). In MyD88-overexpressed HEK293T cells, soyasaponins (A₁, A₂ or I) and ST2825 significantly decreased MyD88 and TRAF6 (p < 0.05).

Conclusion

Soyasaponins can reduce inflammation by downregulating MyD88 expression and suppressing the recruitments of TLR4 and MyD88 into lipid rafts. This study provides novel understanding about the anti-inflammatory mechanism of soyasaponins.

Soyasaponins A1 and A2 exert anti-atherosclerotic functionalities by decreasing hypercholesterolemia and inflammation in high fat diet (HFD)-fed ApoE-/- mice

Atherosclerosis is a chronic inflammatory disease causing coronary heart attacks and strokes. Soyasaponins (SS), the phytochemicals naturally existing in soybeans and their products, have been shown to reduce hypercholesterolemia and inflammation, which are intimately related to the genesis and development of atherosclerosis. However, the anti-atherosclerotic functionality of soyasaponins remains unknown. The aim of this study was to investigate the effects of the supplementation of two types of soyasaponin monomers (A1 and A2) on atherosclerotic plaque formation, serum lipid profiles, and inflammation in ApoE gene knockout (ApoE-/-) mice. Sixty 5-week-old ApoE-/- male mice were fed with a high-fat diet (HFD) and intervened by SSA1 and SSA2 (10 and 20 μmol per kg BW, respectively) or simvastatin (10 μmol per kg BW) for 24 weeks. The atherosclerotic lesions in the aorta, aortic root, and innominate artery, lipid profile and inflammatory markers in serum, and TLR4/MyD88/NF-κB signaling in arterial tissues were determined. SSA1 and SSA2 decreased the plaque ratio in the aortic root and innominate artery but not in the entire aorta. In serum, SSA1 reduced TG, TC, and LDL-C but increased HDL-C; SSA2 decreased TC, TG, and LDL-C but did not affect HDL-C. Meanwhile, SSA1 increased TG, SSA2 increased TC, and both of them increased bile acids in the feces. SSA1 and SSA2 lowered TNF-α, MCP-1, and hs-crp in serum. Furthermore, SSA1 and SSA2 reduced the TLR4 and MyD88 expressions in the aorta and innominate artery and inhibited NF-κB p65 and IκBα phosphorylation in the aorta. These results suggest that SSA1 and SSA2 exert anti-atherosclerotic functionalities by decreasing hypercholesterolemia and inflammation in HFD-fed ApoE-/- mice.

Sphingomyelin Synthase 2 Inhibition Ameliorates Cerebral Ischemic Reperfusion Injury Through Reducing the Recruitment of Toll-Like Receptor 4 to Lipid Rafts

Background

Inflammation is recognized as an important contributor of ischemia/reperfusion (I/R) damage after ischemic stroke. Sphingomyelin synthase 2 (SMS2), the key enzyme for the biosynthesis of sphingomyelin, can function as a critical mediator of inflammation. In the present study, we investigated the role of SMS2 in a mouse model of cerebral I/R.

Methods and Results

Cerebral I/R was induced by 60‐minute transient middle cerebral artery occlusion in SMS2 knockout (SMS2^‐/‐) mice and wild‐type mice. Brain injury was determined by neurological deficits and infarct volume at 24 and 72 hours after transient middle cerebral artery occlusion. Microglia activation and inflammatory factors were detected by immunofluorescence staining, flow cytometry, western blot, and RT‐PCR. SMS2 deficiency significantly improved neurological function and minimized infarct volume at 72 hours after transient middle cerebral artery occlusion. The neuroprotective effects of SMS2 deficiency were associated with (1) suppression of microglia activation through Toll‐like receptor 4/nuclear factor kappa‐light‐chain‐enhancer of activated B cells pathway and (2) downregulation of the level of galactin‐3 and other proinflammatory cytokines. The mechanisms underlying the beneficial effects of SMS2 deficiency may include altering sphingomyelin components in lipid raft fractions, thus impairing the recruitment of Toll‐like receptor 4 to lipid rafts and subsequently reducing Toll‐like receptor 4/myeloid differentiation factor 2 complex formation on the surface of microglia.

Conclusions

SMS2 deficiency ameliorated inflammatory injury after cerebral I/R in mice, and SMS2 may be a key modulator of Toll‐like receptor 4/nuclear factor kappa‐light‐chain‐enhancer of activated B cells activation by disturbing the membrane component homeostasis during cerebral I/R.

Cav-1 participates in the development of diabetic neuropathy pain through the TLR4 signaling pathway

This study aims to determine whether caveolin-1 (Cav-1) participates in the process of diabetic neuropathic pain by directly regulating the expression of toll-like receptor 4 (TLR4) and the subsequent phosphorylation of N-methyl-D-aspartate receptor 2B subunit (NR2B) in the spinal cord. Male Sprague-Dawley rats (120-150 g) were continuously fed with high-fat and high-sugar diet for 8 weeks, and received a single low-dose of intraperitoneal streptozocin injection in preparation for the type-II diabetes model. Then, these rats were divided into five groups according to the level of blood glucose, and the mechanical withdrawal threshold and thermal withdrawal latency values. The pain thresholds were measured at 3, 7, and 14 days after animal grouping. Then, eight rats were randomly chosen from each group and killed. Lumbar segments 4-6 of the spinal cord were removed for western blot analysis and immunofluorescence assay. Cav-1 was persistently upregulated in the spinal cord after diabetic neuropathic pain in rats. The downregulation of Cav-1 through the subcutaneous injection of Cav-1 inhibitor daidzein ameliorated the pain hypersensitivity and TLR4 expression in the spinal cord in diabetic neuropathic pain (DNP) rats. Furthermore, it was found that Cav-1 directly bound with TLR4, and the subsequent phosphorylation of NR2B in the spinal cord contributed to the modulation of DNP. These findings suggest that Cav-1 plays a vital role in DNP processing at least in part by directly regulating the expression of TLR4, and through the subsequent phosphorylation of NR2B in the spinal cord.

Indirubin improves antioxidant and anti-inflammatory functions in lipopolysaccharide-challenged mice

Indirubin, a traditional Chinese medicine formulation from the Muricidae family, has been reported to exhibit abroad anti-cancer and anti-inflammation activities and mediate nuclear factor-κB (NF-κB) signal. Thus, this study aimed to investigate the protective effects of indirubin on LPS-induced acute lung injury and the potential mechanism in mice. The results showed that LPS treatment caused oxidative stress and inflammation in mice. Indirubin alleviated LPS-caused oxidative stress and inflammation via reducing MDA abundance and IL-1β and TNF-α expressions in mice. Meanwhile, indirubin improved lung NO production and inhibited NF-κB activation caused by LPS exposure. In conclusion, indirubin alleviated LPS-induced acute lung injury via improving antioxidant and anti-inflammatory functions, which might be associated with the NO and NF-κB signals.

TLR4-NOX2 axis regulates the phagocytosis and killing of Mycobacterium tuberculosis by macrophages

Background

Macrophages stand at the forefront of both innate and adapted immunity through their capacities to recognize, engulf, and eliminate foreign particles, and to stimulate adapted immune cells. They are also involved in controlling pro- and anti-inflammatory pathways. Macrophage activity against Mycobacterium tuberculosis (M. tuberculosis) has been shown to involve Toll-like receptor (TLR) activation and ROS production. Previous studies have shown that lipopolysaccharide (LPS), through TLR4, could activate macrophages, improve their bactericidal ROS production, and facilitate anti-infective immune responses. We sought to better understand the role of the TLR4-NOX2 axis in macrophage activation during M. tuberculosis infection.

Methods

THP-1 macrophages and PMA primed THP-1 macrophages [THP-1(A)] were treated with LPS and infected by M. tuberculosis. Cells were analyzed by flow cytometry for TLR4 expression, ROS production, phagocytosis, and killing of M. tuberculosis. Western blotting was used to analyze NOX2 expression. Inhibitors of the TLR4-NOX2 pathway were used to assess this pathway’s role in these processes, and their role in LPS activation of macrophages.

Results

We found that THP1-derived macrophages or PMA primed THP-1 macrophages exhibit higher surface TLR4 levels and increased NOX2 expression levels following LPS treatment. M. tuberculosis infection reduced these levels, but LPS was able to limit the negative effects of M.tb. Additionally, LPS increases THP-1(A) cells’ bactericidal activities including phagocytosis, ROS production, and destruction of M. tuberculosis. Significantly, all of these activities are impaired when TLR4 or NOX2 are inhibited.

Conclusion

These studies demonstrate the importance of the TLR4-NOX2 axis in M. tuberculosis elimination by macrophages and may lead to novel therapies for tuberculosis and other bacterial infections.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0517-0) contains supplementary material, which is available to authorized users.