Toll-like receptor 4 siRNA attenuates LPS-induced secretion of inflammatory cytokines and chemokines by macrophages

Ginsenoside Rg1 alleviates chronic inflammation-induced neuronal ferroptosis and cognitive impairments via regulation of AIM2 - Nrf2 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng is a valuable herb in traditional Chinese medicine. Modern research has shown that it has various benefits, including tonifying vital energy, nourishing and strengthening the body, calming the mind, improving cognitive function, regulating fluids, and returning blood pressure, etc. Rg1 is a primary active component of ginseng. It protects hippocampal neurons, improves synaptic plasticity, enhances cognitive function, and boosts immunity. Furthermore, it exhibits anti-aging and anti-fatigue properties and holds great potential for preventing and managing neurodegenerative diseases (NDDs).

AIM OF THE STUDY

The objective of this study was to examine the role of Rg1 in treating chronic inflammatory NDDs and its molecular mechanisms.

MATERIALS AND METHODS

In vivo, we investigated the protective effects of Rg1 against chronic neuroinflammation and cognitive deficits in mice induced by 200 μg/kg lipopolysaccharide (LPS) for 21 days using behavioral tests, pathological sections, Western blot, qPCR and immunostaining. In vitro experiments involved the stimulation of HT22 cells with 10 μg/ml of LPS, verification of the therapeutic effect of Rg1, and elucidation of its potential mechanism of action using H2DCFDA staining, BODIPY™ 581/591 C11, JC-1 staining, Western blot, and immunostaining.

RESULTS

Firstly, it was found that Rg1 significantly improved chronic LPS-induced behavioral and cognitive dysfunction in mice. Further studies showed that Rg1 significantly attenuated LPS-induced neuronal damage by reducing levels of IL-6, IL-1β and ROS, and inhibiting AIM2 inflammasome. Furthermore, chronic LPS exposure induced the onset of neuronal ferroptosis by increasing the lipid peroxidation product MDA and regulating the ferroptosis-associated proteins Gpx4, xCT, FSP1, DMT1 and TfR, which were reversed by Rg1 treatment. Additionally, Rg1 was found to activate Nrf2 and its downstream antioxidant enzymes, such as HO1 and NQO1, both in vivo and in vitro. In vitro studies also showed that the Nrf2 inhibitor ML385 could inhibit the anti-inflammatory, antioxidant, and anti-ferroptosis effects of Rg1.

CONCLUSIONS

This study demonstrated that Rg1 administration ameliorated chronic LPS-induced cognitive deficits and neuronal ferroptosis in mice by inhibiting neuroinflammation and oxidative stress. The underlying mechanisms may be related to the inhibition of AIM2 inflammasome and activation of Nrf2 signaling. These findings provide valuable insights into the treatment of chronic neuroinflammation and associated NDDs.

Protective Role of MAVS Signaling for Murine Lipopolysaccharide-Induced Acute Kidney Injury

Despite treatment advances, acute kidney injury (AKI)-related mortality rates are still high in hospitalized adults, often due to sepsis. Sepsis and AKI could synergistically worsen the outcomes of critically ill patients. TLR4 signaling and mitochondrial antiviral signaling protein (MAVS) signaling are innate immune responses essential in kidney diseases, but their involvement in sepsis-associated AKI (SA-AKI) remains unclear. We studied the role of MAVS in kidney injury related to the TLR4 signaling pathway using a murine LPS-induced AKI model in wild-type and MAVS-knockout mice. We confirmed the importance of M1 macrophage in SA-AKI through in vivo assessment of inflammatory responses. The TLR4 signaling pathway was upregulated in activated bone marrow-derived macrophages, in which MAVS helped maintain the LPS-suppressed TLR4 mRNA level. MAVS regulated redox homeostasis via NADPH oxidase Nox2 and mitochondrial reverse electron transport in macrophages to alleviate the TLR4 signaling response to LPS. Hypoxia-inducible factor 1α (HIF-1α) and AP-1 were key regulators of TLR4 transcription and connected MAVS-dependent reactive oxygen species signaling with the TLR4 pathway. Inhibition of succinate dehydrogenase could partly reduce inflammation in LPS-treated bone marrow-derived macrophages without MAVS. These findings highlight the renoprotective role of MAVS in LPS-induced AKI by regulating reactive oxygen species generation-related genes and maintaining redox balance. Controlling redox homeostasis through MAVS signaling may be a promising therapy for SA-AKI.

Anti-inflammatory effects and molecular mechanisms of bioactive small molecule garlic polysaccharide

Although garlic polysaccharides have been found to possess anti-inflammatory activities, anti-inflammatory study on small molecule water-soluble garlic polysaccharide (WSGP) is few. In this study, a novel WSGP with a molecular weight of 1853 Da was isolated by DEAE-52 and Sephadex G-100 column and the chemical composition was identified by monosaccharide composition and methylation analysis. Furthermore, the antioxidant effects of WSGP and the potential molecular mechanisms on LPS-induced inflammatory responses in RAW264.7 macrophage cells were investigated. The results showed that WSGP has strong antioxidant activity, such as DPPH, hydroxyl, superoxide anion, ABTS radical scavenging capacity, Fe²⁺ chelating ability and reducing power. Meanwhile, WSGP could considerably suppress the manufacturing of NO and the mRNA and protein expression degrees of IL-6, TNF-α, and IL-1β in LPS inspired RAW264.7 macrophages WSGP could significantly suppress the production of NO and the mRNA and protein expression levels of IL-1β, IL-6, and TNF-α in LPS stimulated RAW264.7 macrophage cells (p < 0.05). In addition, the phosphorylated IκB-α, p65, and STAT3 proteins were significantly increased in LPS-induced macrophages, while this trend was significantly reversed by WSGP treatment in a concentration-dependent manner (p < 0.05). Consequently, WSGP supplementation might reduce LPS-induced inflammatory responses by suppressing proinflammatory cytokines and NF-κB and STAT3 pathway activation. The finding of this research would give scientific guidelines for the judicious use of small molecular garlic polysaccharide in anti-inflammatory treatments.

Lipopolysaccharide from Rhodobacter sphaeroides Attenuates Microglia-Mediated Inflammation and Phagocytosis and Directs Regulatory T Cell Response

Microglia activation and neuroinflammation are key events during the progression of neurodegenerative disorders. Microglia exhibits toll-like receptors (TLRs), with predominant expression of TLR4, inducing aberrant neuroinflammation and exacerbated neurotoxicity. Studies suggest that microglia initiate infiltration of T cells into the brain that critically influence disease conditions. We report that LPS-Rs, through TLR4 antagonism, significantly inhibit TLR4 mediated inflammatory molecules like IL-1β, IL-6, TNF-α, COX-2, iNOS, and NO. LPS-Rs regulates JNK/p38 MAPKs and p65-NF-κB signaling pathways, which we report as indispensible for LPS induced neuroinflammation. LPS-Rs mitigates microglial phagocytic activity and we are first to report regulatory role of LPS-Rs which blocked microglia mediated inflammation and apoptotic cell death. LPS-Rs significantly inhibits expression of costimulatory molecules CD80, CD86, and CD40. Chemokine receptor, CCR5, and T cell recruitment chemokines, MIP-1α and CCL5, were negatively regulated by LPS-Rs. Furthermore, LPS-Rs significantly inhibited lymphocyte proliferation with skewed regulatory T (Treg) cell response as evidenced by increased FOXP3, IL-10, and TGF-β. Additionally, LPS-Rs serves to induce coordinated immunosuppressive response and confer tolerogenic potential to activated microglia extending neurosupportive microenvironment. TLR4 antagonism can be a strategy providing neuroprotection through regulation of microglia as well as the T cells.

Establishment of a mouse model to express bovine CD14 short hairpin RNA

Background

Cluster of differentiation 14 (CD14) functions as a co-receptor for Toll-like receptor (TLR)-4 and myeloid differentiation factor (MD)-2 in detecting bacterial lipopolysaccharide. Together, these complexes promote the phagocytosis and digestion of Gram-negative bacteria, and initiate immune responses. To date, much of our understanding of CD14 function during Gram-negative bacterial inflammation comes from studies on mouse knockout models and cell transfection. To identify the effect of CD14 knockdown in this process in large livestock animals, we established a mouse model expressing bovine CD14 short hairpin (sh) RNA. shRNA fragments targeting bovine CD14 were screened by co-transfection in HEK 293 cells, and the most effective CD14 shRNA fragment was cloned into the eukaryotic expression vector pSilencer4.1-CD14 shRNA-IRES (internal ribosome entry site) and transferred into mouse zygotes by pronuclear microinjection to obtain transgenic mice. Expression of the enhanced green fluorescent protein (EGFP) reporter and genes related to the TLR4 signaling pathway was detected by immunohistochemistry (IHC) and quantitative polymerase chain reaction (PCR), respectively.

Results

One effective shRNA fragment (shRNA-674) targeting bovine CD14 was obtained, the sequence of which was shown to be conserved between cows, buffalos, sheep, and humans. Thirty-seven founder pups were obtained by pronuclear microinjection, of which three were positive for the transgene. In the F₁ generation, 11 of 33 mice (33%) were positive for the transgene as detected by PCR. IHC analysis detected exogenous EGFP expression in the liver, kidney, and spleen of transgenic F₁ mice, indicating that they were chimeric. The expression of endogenous CD14 mRNA in the heart, liver, spleen, lung, and kidney of transgenic F₁ mice was decreased 8-, 3-, 19.5-, 6-, and 11-fold, respectively. The expression patterns of endogenous MD-2, TLR4, interleukin-6 and tumor necrosis factor-α genes in transgenic mice also varied.

Conclusions

This study confirms that transgenic mice expressing bovine CD14 shRNA can be generated by pronuclear microinjection, and demonstrates inhibited endogenous mouse CD14 expression that alters gene expression related to the TLR4 signaling pathway.

Toll like receptor 4 (TLR4) mediates the stimulating activities of chitosan oligosaccharide on macrophages

The in vivo and in vitro immunostimulating properties of chitosan oligosaccharide (COS) prepared by enzymatic hydrolysis of chitosan and the mechanisms mediating the effects were investigated. Our data showed that the highly active chitosanase isolated could hydrolyze chitosan to the polymerization degree of 3-8. The resulting COS was an efficient immunostimulator. COS markedly enhanced the proliferation and neutral red phagocytosis by RAW 264.7 macrophages. The production of nitric oxide (NO) and tumor necrosis factor alpha (TNF-α) by macrophages was significantly increased after incubation with COS. Oral administration of COS in mice could increase spleen index and serum immunoglobin G (IgG) contents. COS was labeled with FITC to study the pinocytosis by macrophages. Results showed that FITC-COS was phagocyted by macrophages and anti-murine TLR4 antibody completely blocked FITC-COS pinocytosis. RT-PCR indicated that COS treatment of macrophages significantly increased TLR4 and inducible nitric oxide synthase (iNOS) mRNA levels. When cells were pretreated with anti-murine TLR4 antibody, the effect of COS on TLR4 and iNOS mRNA induction was decreased. COS-induced NO secretion by macrophages was also markedly decreased by anti-murine TLR4 antibody pretreatment. In conclusion, the present study revealed that COS possesses potent immune-stimulating properties by activating TLR4 on macrophages.

HS-23, Lonicera japonica extract, attenuates septic injury by suppressing toll-like receptor 4 signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Lonicera japonica Thunberg is a traditional herbal medicine widely used in East Asia as an anti-bacterial, anti-inflammatory, and antiviral agent. This study was designed to investigate the effects of HS-23, ethanol extract of the dried flower buds of Lonicera japonica, in experimental models of sepsis and elucidate the mechanisms of action of HS-23.

MATERIALS AND METHODS

Male ICR mice were intravenously administered HS-23 (20 and 40 mg/kg) for 0 (immediately) and 24 h after cecal ligation and puncture (CLP) for survival tests, and HS-23 (40 mg/kg) immediately after CLP for biochemical assays.

RESULTS

HS-23 improved sepsis-induced mortality, enhanced bacterial clearance, and attenuated multiple organ failure. The mechanisms of action of HS-23 included attenuation of increased toll-like receptor (TLR)4 protein and mRNA expression. HS-23 suppressed sepsis-induced increases in protein expression of myeloid differentiation primary response protein 88, p38 and c-Jun N-terminal kinase in both liver and lung, as well as TIR-domain-containing adapter-inducing interferon-β and interferon regulatory transcription factor 3 protein expression in liver.

CONCLUSION

The results of this study revealed that HS-23 attenuated sepsis through suppression of TLR signaling pathways. Therefore, our findings suggest that HS-23 might be useful as a potential therapeutic agent for treatment of sepsis.

Involvement of the Akt/NF-κB pathways in the HTNV-mediated increase of IL-6, CCL5, ICAM-1, and VCAM-1 in HUVECs

Background

Hantaan virus (HTNV) infection causes a severe form of HFRS(hemorrhagic fever with renal syndrome)in Asia. Although HTNV has been isolated for nearly forty years, the pathogenesis of HFRS is still unknown, and little is known regarding the signaling pathway that is activated by the virus.

Methodology/Principal Findings

Cardamonin was selected as a NF-κB inhibitor, and indirect immunofluorescence assays were used to detect the effect of cardamonin on HTNV-infected HUVECs. The effect of cardamonin on the HTNV-induced phosphorylation of Akt and DNA-binding activity of NF-κB were determined using Western blot analysis and electrophoretic mobility shift assays (EMSAs), respectively. Then, flow cytometric and quantitative real-time PCR analyses were performed to quantify the expression levels of the adhesion molecules ICAM-1 and VCAM-1, and the concentrations of IL-6, IL-8, and CCL5 in HUVEC supernatants were examined using ELISA. The results showed that cardamonin did not effect the proliferation of HUVECs or the replication of HTNV in HUVECs. Instead, cardamonin inhibited the phosphorylation of Akt and nuclear transduction of NF-κB and further reduced the expression of the adhesion molecules ICAM-1 and VCAM-1 in HTNV-infected HUVECs. Cardamonin also inhibited the secretion of IL-6 and CCL5, but not IL-8.

Conclusion/Significance

HTNV replication may not be dependent upon the ability of the virus to activate NF-κB in HUVECs. The Akt/NF-κB pathways may be involved in the pathogenesis of HFRS; therefore, cardamonin may serve as a potential beneficial agent for HFRS therapy.

Changes in innate and permissive immune responses after hbv transgenic mouse vaccination and long-term-siRNA treatment [corrected]

Background

Currently, no licensed therapy can thoroughly eradicate hepatitis B virus (HBV) from the body, including interferon α and inhibitors of HBV reverse-transcription. Small interfering RNA (siRNA) seem to be a promising tool for treating HBV, but had no effect on the pre-existing HBV covalently closed circular DNA. Because it is very difficult to thoroughly eradicate HBV with unique siRNAs, upgrading the immune response is the best method for fighting HBV infection. Here, we aim to explore the immune response of transgenic mice to HBV vaccination after long-term treatment with siRNAs and develop a therapeutic approach that combines siRNAs with immunopotentiators.

Methodology/Principal Findings

To explore the response of transgenic mice to hepatitis B vaccine, innate and acquired immunity were detected after long-term treatment with siRNAs and vaccination. Antiviral cytokines and level of anti-hepatitis B surface antigen antibody (HBsAg-Ab) were measured after three injections of hepatitis B vaccine.

Results

Functional analyses indicated that toll-like receptor-mediated innate immune responses were reinforced, and antiviral cytokines were significantly increased, especially in the pSilencer4.1/HBV groups. Analysis of CD80+/CD86+ dendritic cells in the mouse liver indicated that dendritic cell antigen presentation was strengthened. Furthermore, the siRNA-treated transgenic mice could produce detectable HBsAg-Ab after vaccination, especially in the CpG oligonucleotide vaccine group.

Conclusions/Significance

For the first time, our studies demonstrate that siRNAs with CpG HBV vaccine could strengthen the immune response and break the immune tolerance status of transgenic mice to HBV. Thus, siRNAs and HBV vaccine could provide a sharp double-edged sword against chronic HBV infection.

Human beta-defensin DEFB126 is capable of inhibiting LPS-mediated inflammation

β-Defensins are cationic, antimicrobial peptides that participate in antimicrobial defense as well as the regulation of innate and adaptive immunity. Human β-defensin 126 (DEFB126) is a multifunctional glycoprotein consisting of a conserved β-defensin core and a unique long glycosylated peptide tail. The long glycosylated peptide tail has been proven to be critical for efficient transport of sperm in the female reproductive tract, preventing their immune recognition, and efficient delivery of capacitated sperm to the site of fertilization. However, the functions of the conserved β-defensin core remain to be fully elucidated. In the present work, the conserved β-defensin core of the DEFB126 was expressed to explore its potential antimicrobial and anti-inflammatory activities. The DEFB126 core peptide exhibited both high potency for binding and neutralizing lipopolysaccharide (LPS) in vitro, and potent anti-inflammatory ability by down-regulating the mRNA expression of pro-inflammatory cytokines including IL-α, IL-1β, IL-6 and TNF-α in a murine macrophage cell line RAW264.7. The treatment with the DEFB126 core peptide also led to correspondingly decreased secretion of IL-6 and TNF-α. The blockade of LPS-induced p42/44 and p38 MAPK signal pathway might contribute to the anti-inflammation effects of the DEFB126 core peptide. Furthermore, fluorescence-labeled DEFB126 could enter RAW 264.7 cells and reduce the production of LPS-stimulated inflammatory factors, implying that DEFB126 might also participate in intracellular regulation beyond its direct LPS neutralization. In summary, our results demonstrate that the DEFB 126 core peptide has critical functions in parallel to its C-terminal tail by showing LPS-binding activity, anti-inflammatory effects and intracellular regulatory function.

Ginsenoside Re ameliorates inflammation by inhibiting the binding of lipopolysaccharide to TLR4 on macrophages

Ginseng (the root of Panax ginseng C.A. Meyer, family Araliaceae), which contains protopanaxadiol ginsenoside Rb1 and protopanaxatriol ginsenoside Re as main constituents, is frequently used to treat cancer, inflammation, and stress. In the preliminary study, protopanaxatriol ginsenoside Re inhibited NF-κB activation in lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages. Therefore, we investigated its anti-inflammatory effect in peptidoglycan (PGN)-, LPS-, or tumor necrosis factor-α (TNF-α)-stimulated peritoneal macrophages and, in addition, in LPS-induced systemic inflammation and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. Ginsenoside Re inhibited IKK-β phosphorylation and NF-κB activation, as well as the expression of proinflammatory cytokines, TNF-α and IL-1β, in LPS-stimulated peritoneal macrophages, but it did not inhibit them in TNF-α- or PG-stimulated peritoneal macrophages. Ginsenoside Re also inhibited IRAK-1 phosphorylation induced by LPS, as well as IRAK-1 and IRAK-4 degradations in LPS-stimulated peritoneal macrophages. Ginsenoside Re inhibited the binding of Alexa Fluor 488-conjugated LPS to TLR4 on peritoneal macrophages. Furthermore, ginsenoside Re inhibited the binding of LPS to TLR4 on peritoneal macrophages transiently transfected with MyD88 siRNAs. Orally administered ginsenoside Re significantly inhibited the expression of IL-1β and TNF-α on LPS-induced systemic inflammation and TNBS-induced colitis in mice. Ginsenoside Re inhibited colon shortening and myeloperoxidase activity in TNBS-treated mice. Ginsenoside Re reversed the reduced expression of tight-junction-associated proteins ZO-1, claudin-1, and occludin. Ginsenoside Re (20 mg/kg) inhibited the activation of NF-κB in TNBS-treated mice. On the basis of these findings, ginsenoside Re may ameliorate inflammation by inhibiting the binding of LPS to TLR4 on macrophages.

Hantaan virus triggers TLR4-dependent innate immune responses

The innate immune response induced by Hantavirus is responsible for endothelial cell dysfunction and viral pathogenicity. Recent studies demonstrate that TLR4 expression is upregulated and mediates the secretion of several cytokines in Hantaan virus (HTNV)-infected endothelial cells. To examine viral interactions with host endothelial cells and characterize the innate antiviral responses associated with Toll-like receptors, we selected TLR4 as the target molecule to investigate anti-hantavirus immunity. TLR4 mRNA-silenced EVC-304 (EVC-304 TLR4-) cells and EVC-304 cells were used to investigate signaling molecules downstream of TLR4. The expression of the adaptor protein TRIF was higher in HTNV-infected EVC-304 cells than in EVC-304 TLR4- cells. However, there was no apparent difference in the expression of MyD88 in either cell line. The transcription factors for NF-κB and IRF-3 were translocated from the cytoplasm into the nucleus in HTNV-infected EVC-304 cells, but not in HTNV-infected EVC-304 TLR4- cells. Our results demonstrate that TLR4 may play an important role in the antiviral immunity of the host against HTNV infection through an MyD88-independent signaling pathway.

Innate immunity probed by lipopolysaccharides affinity strategy and proteomics

Lipopolysaccharides (LPSs) are ubiquitous and vital components of the cell surface of Gram-negative bacteria that have been shown to play a relevant role in the induction of the immune-system response. In animal and plant cells, innate immune defenses toward microorganisms are triggered by the perception of pathogen associated molecular patterns. These are conserved and generally indispensable microbial structures such as LPSs that are fundamental in the Gram-negative immunity recognition. This paper reports the development of an integrated strategy based on lipopolysaccharide affinity methodology that represents a new starting point to elucidate the molecular mechanisms elicited by bacterial LPS and involved in the different steps of innate immunity response. Biotin-tagged LPS was immobilized on streptavidin column and used as a bait in an affinity capture procedure to identify protein partners from human serum specifically interacting with this effector. The complex proteins/lipopolysaccharide was isolated and the protein partners were fractionated by gel electrophoresis and identified by mass spectrometry. This procedure proved to be very effective in specifically binding proteins functionally correlated with the biological role of LPS. Proteins specifically bound to LPS essentially gathered within two functional groups, regulation of the complement system (factor H, C4b, C4BP, and alpha 2 macroglobulin) and inhibition of LPS-induced inflammation (HRG and Apolipoproteins). The reported strategy might have important applications in the elucidation of biological mechanisms involved in the LPSs-mediated molecular recognition and anti-infection responses.

Ultrastructural and spectrophotometric study on the effects of putative triggers on aortic valve interstitial cells in in vitro models simulating metastatic calcification

Metastatic calcification of cardiac valves is a common complication in patients affected by chronic renal failure. In this study, primary bovine aortic valve interstitial cells (AVICs) were subjected to pro-calcific treatments consisting in cell stimulation with (i) elevated inorganic phosphate (Pi = 3 mM), to simulate hyperphosphatemic conditions; (ii) bacterial endotoxin lipopolysaccharide (LPS), simulating direct effects by microbial agents; and (iii) conditioned media (CM) derived from cultures of either LPS-stimulated heterogenic macrophages (commercial murine RAW264.7 cells) or LPS-stimulated fresh allogenic monocytes/macrophages (bCM), simulating consequent inflammatory responses, alone or combined. Compared to control cultures, spectrophotometric assays revealed shared treatment-dependent higher values of both calcium amounts and alkaline phosphatase activity for cultures involving the presence of elevated Pi. Ultrastructurally, shared peculiar pro-calcific degeneration patterns were exhibited by AVICs from these latter cultures irrespectively of the additional treatments. Disappearance of all cytomembranes and concurrent formation of material showing positivity to Cuprolinic Blue and co-localizing with silver precipitation were followed by the outcropping of such a material, which transformed in layers outlining the dead cells. Subsequent budding of these layers resulted in the formation of bubbling bodies and concentrically laminated calcospherulae mirroring those in actual soft tissue calcification. In conclusion, the in vitro models employed appear to be reliable tools for simulating metastatic calcification and indicate that hyperphosphatemic-like conditions could trigger valve calcification per se, with LPS and allogenic macrophage-derived secretory products acting as possible calcific enhancers via inflammatory responses.

Effect of manassantin B, a lignan isolated from Saururus chinensis, on lipopolysaccharide-induced interleukin-1β in RAW 264.7 cells

BACKGROUND

Elevated systemic levels of pro-inflammatory cytokines cause hypotension during septic shock and induce capillary leakage in acute lung injury. Manassantin B has anti-inflammatory and anti-plasmoidal properties. This study examined the effects of manassantin B on lipopolysaccharide (LPS)-induced inflammatory response in murine macrophages.

METHODS

RAW 264.7 macrophage cells were incubated without or with (1, 3 and 10 µM) manassantin B and without or with (100 ng/ml) LPS. Manassantin B dissolved in phosphate buffered saline was added to the medium 1 h prior to the addition of LPS. The degree of activation of mitogen-activated protein kinase (MAPK) including extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun amino terminal kinases (JNK) and p38 MAPK, and the level of interleukin (IL)-1β were determined 30 min and 24 h after the addition of LPS respectively.

RESULTS

Manassantin B inhibited the production of IL-1β and attenuated the phosphorylations of ERK1/2 and p38 MAPK, but not that of JNK, in RAW 264.7 cells treated with LPS.

CONCLUSIONS

Manassantin B reduces LPS-induced IL-1β expression through effects on ERK1/2- and p38 MAPK-mediated pathways. Manassantin B has potential as a potent anti-inflammatory drug for use in pathological processes such as sepsis or acute lung injury.

Soyasaponin Ab ameliorates colitis by inhibiting the binding of lipopolysaccharide (LPS) to Toll-like receptor (TLR)4 on macrophages

Many clinical studies have shown that daily intake of soybean [ Glycine max (L.) Merr., Fabacease] or its foods may reduce the risk of osteoporosis, heart attack, hyperlipidemia, coronary heart disease, cardiovascular and chronic renal diseases, and cancers, including prostate, colon, and breast cancers. Of the soy constituents, soyasaponins exhibit anti-aging, antioxidant, apoptotic, and anti-inflammatory effects. However, the anti-inflammatory effect of soyasaponin Ab has not been thoroughly studied. Therefore, we investigated its anti-inflammatory effects in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitic mice and lipopolysaccharide (LPS)-stimulated peritoneal macrophages. Soyasaponin Ab inhibited colon shortening, myeloperoxidase activity, the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), and activation of the transcription factor nuclear factor-κB (NF-κB). Soyasaponin Ab (1, 2, 5, and 10 μM) inhibited the production of NO (IC(50) = 1.6 ± 0.1 μM) and prostaglandin E(2) (IC(50) = 2.0 ± 0.1 ng/mL), the expression of tumor necrosis factor (TNF)-α (IC(50) = 1.3 ± 0.1 ng/mL), interleukin (IL)-1β (IC(50) = 1.5 ± 0.1 pg/mL), and toll-like receptor (TLR)4, and the phosphorylation of interleukin-1 receptor-associated kinase (IRAK)-1 in LPS-stimulated peritoneal macrophages. Soyasaponin Ab weakly inhibited the phosphorylation of ERK, JNK, and p38. Soyasaponin Ab significantly reduced the binding of Alexa-Fluor-594-conjugated LPS to peritoneal macrophages. Soyasaponin Ab did not affect TLR4 expression or LPS-induced NF-κB activation in TLR4 siRNA-treated peritoneal macrophages (knockdown efficiency of TLR4 > 94%). On the basis of these findings, soyasaponin Ab may ameliorate colitis by inhibiting the binding of LPS to TLR4 on macrophages.

Immune physiology in tissue regeneration and aging, tumor growth, and regenerative medicine

The immune system plays an important role in immunity (immune surveillance), but also in the regulation of tissue homeostasis (immune physiology). Lessons from the female reproductive tract indicate that immune system related cells, such as intraepithelial T cells and monocyte-derived cells (MDC) in stratified epithelium, interact amongst themselves and degenerate whereas epithelial cells proliferate and differentiate. In adult ovaries, MDC and T cells are present during oocyte renewal from ovarian stem cells. Activated MDC are also associated with follicular development and atresia, and corpus luteum differentiation. Corpus luteum demise resembles rejection of a graft since it is attended by a massive influx of MDC and T cells resulting in parenchymal and vascular regression. Vascular pericytes play important roles in immune physiology, and their activities (including secretion of the Thy-1 differentiation protein) can be regulated by vascular autonomic innervation. In tumors, MDC regulate proliferation of neoplastic cells and angiogenesis. Tumor infiltrating T cells die among malignant cells. Alterations of immune physiology can result in pathology, such as autoimmune, metabolic, and degenerative diseases, but also in infertility and intrauterine growth retardation, fetal morbidity and mortality. Animal experiments indicate that modification of tissue differentiation (retardation or acceleration) during immune adaptation can cause malfunction (persistent immaturity or premature aging) of such tissue during adulthood. Thus successful stem cell therapy will depend on immune physiology in targeted tissues. From this point of view, regenerative medicine is more likely to be successful in acute rather than chronic tissue disorders.

The nuclear receptor Rev-erbalpha is a liver X receptor (LXR) target gene driving a negative feedback loop on select LXR-induced pathways in human macrophages

A role of the nuclear receptor Rev-erbalpha in the regulation of transcription pathways involving other nuclear receptors is emerging. Indeed, Rev-erbalpha is a negative regulator of transcription by binding to overlapping response elements shared with various nuclear receptors, including the peroxisome proliferator-activated receptors and the retinoid-related orphan receptor alpha (RORalpha). Here, we show that Rev-erbalpha is expressed in primary human macrophages and that its expression is induced by synthetic ligands for the liver X receptors (LXRs), which control cholesterol homeostasis, inflammation, and the immune response in macrophages. LXRalpha binds to a specific response element in the human Rev-erbalpha promoter, thus inducing Rev-erbalpha transcriptional expression. Interestingly, Rev-erbalpha does not influence basal or LXR-regulated cholesterol homeostasis. However, Rev-erbalpha overexpression represses the induction of toll-like receptor (TLR)-4 by LXR agonists, whereas Rev-erbalpha silencing by short interfering RNA results in enhanced TLR-4 expression upon LXR activation. Electrophoretic mobility shift, chromatin immunoprecipitation, and transient transfection experiments demonstrate that Rev-erbalpha represses human TLR-4 promoter activity by binding as a monomer to a RevRE site overlapping with the LXR response element site in the TLR-4 promoter. These data identify Rev-erbalpha as a new LXR target gene, inhibiting LXR-induction of TLR-4 in a negative transcriptional feedback loop, but not cholesterol homeostasis gene expression.