Discovery of new MD2-targeted anti-inflammatory compounds for the treatment of sepsis and acute lung injury

Mechanisms of Sepsis-Induced Acute Lung Injury and Advancements of Natural Small Molecules in Its Treatment

Sepsis-induced acute lung injury (ALI), characterized by widespread lung dysfunction, is associated with significant morbidity and mortality due to the lack of effective pharmacological treatments available clinically. Small-molecule compounds derived from natural products represent an innovative source and have demonstrated therapeutic potential against sepsis-induced ALI. These natural small molecules may provide a promising alternative treatment option for sepsis-induced ALI. This review aims to summarize the pathogenesis of sepsis and potential therapeutic targets. It assembles critical updates (from 2014 to 2024) on natural small molecules with therapeutic potential against sepsis-induced ALI, detailing their sources, structures, effects, and mechanisms of action.

Discovery of new DHA ethanolamine derivatives as potential anti-inflammatory agents targeting Nur77

Docosahexaenoic acid (DHA) has a strong anti-inflammatory effect and is reported to bind to the ligand-binding domain (LBD) of the anti-inflammatory modulator Nur77. Recently, we have found that DHA ethanolamine (DHA-EA) exerts anti-inflammatory activity as a Nur77 modulator. Herein, using a fragment splicing-based drug design strategy, nineteen new DHA-EA derivatives were synthesized starting from DHA algae oil and then evaluated for their anti-inflammatory activity. The cell-based cytotoxicity assays showed that compounds J2, J9, and J18 had no noticeable effect on the cell morphology and viability of RAW 264.7, LO2, and MCR-5 cells. Meanwhile, J9 was identified as the most potent anti-inflammatory molecule in LPS-stimulated RAW 264.7 cells. Also, the molecular docking study and SPR assay demonstrated that J9 exhibited in vitro Nur77-binding affinity (KD = 8.58 × 10-6 M). Moreover, the mechanism studies revealed that the anti-inflammatory activity of J9 was associated with its inhibition of NF-κB activation in a Nur77-dependent manner. Notably, J9 could attenuate LPS-induced inflammation in the mouse acute lung injury (ALI) model. Overall, the DHA-EA derivative J9 targeting Nur77 is a potential candidate for developing anti-inflammatory and ALI-treating agents.

Discovery of novel TLR4/MD-2 inhibitors: Receptor structure-based virtual screening studies and anti-inflammatory evaluation

In this study, a receptor structure-based virtual screening strategy was constructed using a computer-aided drug design. First, the compounds were filtered based on the Lipinski pentad and adsorption, distribution, metabolism, excretion, and toxicity profiles. Then, receptor structure-based pharmacophore models were constructed and screened. Finally, the in vitro toxicity and anti-inflammatory activities of hit compounds were initially evaluated to investigate their in vitro anti-inflammatory effects and mechanisms of action. The results revealed that hit 94 had the best anti-inflammatory activity and low toxicity while inhibiting the activation of Toll-like receptor (TLR) 4/myeloid differentiation factor 2 (MD2)-associated signaling pathways of nuclear factor-κB and mitogen-activated protein kinase. In vivo adjuvant arthritis results also revealed that hit 94 ameliorated foot swelling to a greater extent in rats compared with the positive control drug indomethacin. These results suggest that hit 94 can be used as a potential TLR/MD2 inhibitor for inflammatory diseases.

Oxidative stress, hormones, and effects of natural antioxidants on intestinal inflammation in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing gastrointestinal (GI) disorder characterized by intestinal inflammation. The etiology of IBD is multifactorial and results from a complex interplay between mucosal immunity, environmental factors, and host genetics. Future therapeutics for GI disorders, including IBD, that are driven by oxidative stress require a greater understanding of the cellular and molecular mechanisms mediated by reactive oxygen species (ROS). In the GI tract, oxidative stressors include infections and pro-inflammatory responses, which boost ROS generation by promoting the production of pro-inflammatory cytokines. Nuclear factor kappa B (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2) represent two important signaling pathways in intestinal immune cells that regulate numerous physiological processes, including anti-inflammatory and antioxidant activities. Natural antioxidant compounds exhibit ROS scavenging and increase antioxidant defense capacity to inhibit pro-oxidative enzymes, which may be useful in IBD treatment. In this review, we discuss various polyphenolic substances (such as resveratrol, curcumin, quercetin, green tea flavonoids, caffeic acid phenethyl ester, luteolin, xanthohumol, genistein, alpinetin, proanthocyanidins, anthocyanins, silymarin), phenolic compounds including thymol, alkaloids such as berberine, storage polysaccharides such as tamarind xyloglucan, and other phytochemicals represented by isothiocyanate sulforaphane and food/spices (such as ginger, flaxseed oil), as well as antioxidant hormones like melatonin that target cellular signaling pathways to reduce intestinal inflammation occurring with IBD.

Discovery of new cinnamic derivatives as anti-inflammatory agents for treating acute lung injury in mice

The blockade of the overexpression of pro-inflammatory cytokines by anti-inflammatory natural products has been proven therapeutically beneficial in the treatment of acute lung injury (ALI). Given the fact that cinnamic acid has been proven to have significant anti-inflammatory activity, we selected it as a promising lead compound to develop more effective analogs in treating ALI. Learning from the symmetric structure of curcumin, 32 new symmetric cinnamic derivatives were designed, synthesized, and evaluated for their anti-inflammatory activity. Among them, 6h not only displayed a remarkable inhibitory activity in vitro (85.9% and 65.7% for  IL-6 and TNF-α, respectively) without cytotoxicity but also possessed chemical structure stability. Furthermore, an in vivo study in mice revealed that the administration of 6h significantly attenuated lipopolysaccharide-induced ALI, providing new lead structures for the development of anti-inflammatory drugs for the treatment of ALI.

Oral intake of xanthohumol attenuates lipoteichoic acid-induced inflammatory response in human PBMCs

PURPOSE

The aim of the study was to determine if xanthohumol, a prenylated chalcone found in Hop (Humulus lupulus), has anti-inflammatory effects in healthy humans if applied in low doses achievable through dietary intake.

METHODS

In a placebo-controlled single-blinded cross-over design study, 14 healthy young men and women either consumed a beverage containing 0.125 mg xanthohumol or a placebo. Peripheral blood mononuclear cells (PBMCs) were isolated before and 1 h after the intake of the beverages. Subsequently, PBMCs were stimulated with or without lipoteichoic acid (LTA) for 24 and 48 h. Concentrations of interleukin-1β (IL-1β), interleukin-6 (IL-6) and soluble cluster of differentiation (sCD14) protein were determined in cell culture supernatant. Furthermore, hTLR2 transfected HEK293 cells were stimulated with LTA in the presence or absence of xanthohumol and sCD14.

RESULTS

The stimulation of PBMCs with LTA for 24 and 48 h resulted in a significant induction of IL-1β, IL-6, and sCD14 protein release in PBMCs of both, fasted subjects and subjects after the ingestion of the placebo. In contrast, after ingesting xanthohumol, LTA-dependent induction of IL-1β, IL-6, and sCD14 protein release from PBMCs was not significantly higher than in unstimulated cells after 48 h. In hTLR2 transfected HEK293 cells xanthohumol significantly suppressed the LTA-dependent activation of cells, an effect attenuated when cells were co-incubated with sCD14.

CONCLUSION

The results of our study suggest that an ingestion of low doses of xanthohumol can suppress the LTA-dependent stimulation of PBMCs through mechanisms involving the interaction of CD14 with TLR2. Study registered at ClinicalTrials.gov (NCT04847193, 22.03.2022).

A Xanthohumol-Rich Hop Extract Diminishes Endotoxin-Induced Activation of TLR4 Signaling in Human Peripheral Blood Mononuclear Cells: A Study in Healthy Women

Infections with Gram-negative bacteria are still among the leading causes of infection-related deaths. Several studies suggest that the chalcone xanthohumol (XN) found in hop (Humulus lupulus) possesses anti-inflammatory effects. In a single-blinded, placebo controlled randomized cross-over design study we assessed if the oral intake of a single low dose of 0.125 mg of a XN derived through a XN-rich hop extract (75% XN) affects lipopolysaccharide (LPS)-induced immune responses in peripheral blood mononuclear cells (PBMCs) ex vivo in normal weight healthy women (n = 9) (clinicaltrials.gov: NCT04847193) and determined associated molecular mechanisms. LPS-stimulation of PBMCs isolated from participants 1 h after the intake of the placebo for 2 h resulted in a significant induction of pro-inflammatory cytokine release which was significantly attenuated when participants had consumed XN. The XN-dependent attenuation of proinflammatory cytokine release was less pronounced 6 h after the LPS stimulation while the release of sCD14 was significantly reduced at this timepoint. The LPS-dependent activation of hTLR4 transfected HEK293 cells was significantly and dose-dependently suppressed by the XN-rich hop extract which was attenuated when cells were co-challenged with sCD14. Taken together, our results suggest even a one-time intake of low doses of XN consumed in a XN-rich hop extract can suppress LPS-dependent stimulation of PBMCs and that this is related to the interaction of the hop compound with the CD14/TLR4 signaling cascade.

Neuronal MD2 induces long-term mental impairments in septic mice by facilitating necroptosis and apoptosis

Sepsis-associated encephalopathy (SAE) is a complication of sepsis with high morbidity rates. Long-lasting mental health issues in patients with SAE result in a substantial decrease in quality of life. However, its underlying mechanism is unclear, and effective treatments are not available. In the current study, we explored the role of apoptosis and necroptosis related to mental dysfunction in sepsis. In a mouse model of sepsis constructed by cecal ligation and puncture (CLP), altered behavior was detected by the open field, elevated-plus maze and forced swimming tests on the fourteenth day. Moreover, apoptosis- and necroptosis-associated proteins and morphological changes were examined in the hippocampus of septic mice. Long-lasting depression-like behaviors were detected in the CLP mice, as well as significant increases in neuronal apoptosis and necroptosis. Importantly, we found that apoptosis and necroptosis were related according to Ramsay’s rule in the brains of the septic mice. Inhibiting myeloid differentiation factor 2 (MD2), the crosstalk mediator of apoptosis and necroptosis, in neurons effectively reduced neuronal loss and alleviated depression-like behaviors in the septic mice. These results suggest that neuronal death in the hippocampus contributes to the mental impairments in SAE and that inhibiting neuronal MD2 is a new strategy for treating mental health issues in sepsis by inhibiting necroptosis and apoptosis.

CircRNA circFADS2 is under-expressed in sepsis and protects lung cells from LPS-induced apoptosis by downregulating miR-133a

Background

It has been reported that hsa_circRNA_100833 (identified as circFADS2) and miR-133a play opposite roles in LPS-induced cell apoptosis, which contributes to the development of sepsis. This study was carried out to explore the interaction between circFADS2 and miR-133a in sepsis.

Methods

Expression of circFADS2 and miR-133a in plasma from both sepsis patients (n=62) and healthy controls (n=62) was studied by RT-qPCR. Pearson’s correlation coefficient analysis was utilized to analyze the correlation between circFADS2 and miR-133a levels across plasma samples from sepsis patients. Cell viability and apoptosis, levels of proteins associated with apoptosis (cleaved caspase-3 and cleaved caspase-9), and expression of pro-inflammatory cytokines in LPS-treated HBEpCs were detected by MTT assay, cell apoptosis assay, western blot, and ELISA, respectively. In addition, a dual-luciferase reporter assay was performed to verify the interaction between circFADS2 and miR-133a.

Results

CircFADS2 was under-expressed (0.56-fold vs. control) in sepsis, and miR-133a was highly expressed (2.05-fold vs. control) in sepsis. An inverse correlation between circFADS2 and miR-133a was observed across sepsis samples. LPS decreased cell viability, increased cell apoptosis, and elevated productions of tumor necrosis factor (TNF)-α, interleukins (IL)-1β, IL-6, and IL-8 in HBEpCs in a dose-dependent manner. In addition, circFADS2 was identified as a target gene of miR-133a. The further experiment revealed that circFADS2 overexpression and miR-133a inhibition prominently promoted cell viability (1.71-fold vs. pcDNA3.1; 1.65-fold vs. NC miRNA) and decreased apoptosis of LPS-treated HBEpCs (0.44-fold vs. pcDNA3.1; 0.47-fold vs. NC miRNA). Moreover, circFADS2 knockdown and miR-133a overexpression inhibited viability (0.36-fold vs. pcDNA3.1; 0.37-fold vs. NC miRNA) and increased apoptosis (1.54-fold vs. pcDNA3.1; 1.51-fold vs. NC miRNA) of LPS-treated HBEpCs. Notably, circFADS2 overexpression reduced the effects of miR-133a on LPS-treated HBEpCs.

Conclusions

CircFADS2 is under-expressed in sepsis and may protect lung cells from LPS-induced apoptosis by downregulating miR-133a.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12950-022-00300-3.

Design and synthesis of adamantyl-substituted flavonoid derivatives as anti-inflammatory Nur77 modulators: Compound B7 targets Nur77 and improves LPS-induced inflammation in vitro and in vivo

In continuing our study on discovering new Nur77-targeting anti-inflammatory agents with natural skeletons, we combined adamantyl group and hydroxamic acid moiety with flavonoid nucleus, synthesized three series of flavonoid derivatives with a similar structure like CD437, and evaluated their activities against LPS-induced inflammation. Compound B7 was found to be an excellent Nur77 binder (K_d = 3.55 × 10^-7 M) and a potent inhibitor of inflammation, which significantly decreased the production of cytokines in vitro, such as NO, IL-6, IL-1β, and TNF-α, at concentrations of 1.25, 2.5, and 5 μM. Mechanistically, B7 modulated the colocalization of Nur77 at mitochondria and inhibited the lipopolysaccharides (LPS)-induced inflammation via the blockade of NF-κB activation in a Nur77-dependent manner. Additionally, B7 showed in vivo anti-inflammatory activity in the LPS-induced mice model of acute lung injury (ALI). These data suggest that the Nur77-targeting flavonoid derivatives can be particularly useful for further pharmaceutical development for the treatment of inflammatory diseases such as ALI.

Bioavailability and Cardiometabolic Effects of Xanthohumol: Evidence from Animal and Human Studies

Xanthohumol is the main prenylflavonoid in hops and has been associated with a wide range of health benefits, due to its anti-inflammatory, anti-oxidative, and cancer-preventive properties. Increasing evidence suggests that xanthohumol positively affects biomarkers associated with metabolic syndrome and cardiovascular diseases (CVDs). This review summarizes the effects of xanthohumol supplementation on body weight, lipid and glucose metabolism, systemic inflammation, and redox status. In addition, it provides insights into the pharmacokinetics of xanthohumol intake. Animal studies show that xanthohumol exerts beneficial effects on body weight, lipid profile, glucose metabolism, and other biochemical parameters associated with metabolic syndrome and CVDs. Although in vitro studies are increasingly elucidating the responsible mechanisms, the overall in vivo results are currently inconsistent and quantitatively insufficient. Pharmacokinetic and safety studies confirm that intake of xanthohumol is safe and well tolerated in both animals and humans. However, little is known about the metabolism of xanthohumol in the human body, and even less about its effects on body weight and CVD risk factors. There is an urgent need for studies investigating whether the effects of xanthohumol on body weight and cardiometabolic parameters observed in animal studies are reproducible in humans, and what dosage, formulation, and intervention period are required. This article is protected by copyright. All rights reserved.

MD2 contributes to the pathogenesis of perioperative neurocognitive disorder via the regulation of α5GABAA receptors in aged mice

BACKGROUND

Perioperative neurocognitive disorder (PND) is a long-term postoperative complication in elderly surgical patients. The underlying mechanism of PND is unclear, and no effective therapies are currently available. It is believed that neuroinflammation plays an important role in triggering PND. The secreted glycoprotein myeloid differentiation factor 2 (MD2) functions as an activator of the Toll-like receptor 4 (TLR4) inflammatory pathway, and α5GABA_A receptors (α5GABA_ARs) are known to play a key role in regulating inflammation-induced cognitive deficits. Thus, in this study, we aimed to investigate the role of MD2 in PND and determine whether α5GABA_ARs are involved in the function of MD2.

METHODS

Eighteen-month-old C57BL/6J mice were subjected to laparotomy under isoflurane anesthesia to induce PND. The Barnes maze was used to assess spatial reference learning and memory, and the expression of hippocampal MD2 was assayed by western blotting. MD2 expression was downregulated by bilateral injection of AAV-shMD2 into the hippocampus or tail vein injection of the synthetic MD2 degrading peptide Tat-CIRP-CMA (TCM) to evaluate the effect of MD2. Primary cultured neurons from brain tissue block containing cortices and hippocampus were treated with Tat-CIRP-CMA to investigate whether downregulating MD2 expression affected the expression of α5GABA_ARs. Electrophysiology was employed to measure tonic currents. For α5GABA_ARs intervention experiments, L-655,708 and L-838,417 were used to inhibit or activate α5GABA_ARs, respectively.

RESULTS

Surgery under inhaled isoflurane anesthesia induced cognitive impairments and elevated the expression of MD2 in the hippocampus. Downregulation of MD2 expression by AAV-shMD2 or Tat-CIRP-CMA improved the spatial reference learning and memory in animals subjected to anesthesia and surgery. Furthermore, Tat-CIRP-CMA treatment decreased the expression of membrane α5GABA_ARs and tonic currents in CA1 pyramidal neurons in the hippocampus. Inhibition of α5GABA_ARs by L-655,708 alleviated cognitive impairments after anesthesia and surgery. More importantly, activation of α5GABA_ARs by L-838,417 abrogated the protective effects of Tat-CIRP-CMA against anesthesia and surgery-induced spatial reference learning and memory deficits.

CONCLUSIONS

MD2 contributes to the occurrence of PND by regulating α5GABA_ARs in aged mice, and Tat-CIRP-CMA is a promising neuroprotectant against PND.

Discovery of Novel Pterostilbene Derivatives That Might Treat Sepsis by Attenuating Oxidative Stress and Inflammation through Modulation of MAPKs/NF-κB Signaling Pathways

Sepsis remains one of the most common life-threatening illnesses that is characterized by a systemic inflammatory response syndrome (SIRS) and usually arises following severe trauma and various septic infections. It is still in urgent need of new effective therapeutic agents, and chances are great that some candidates can be identified that can attenuate oxidative stress and inflammatory responses. Pterostilbene, which exerts attractive anti-oxidative and anti-inflammatory activities, is a homologue of natural polyphenolic derivative of resveratrol. Starting from it, we have made several rounds of rational optimizations. Firstly, based on the strategy of pharmacophore combination, indanone moiety was introduced onto the pterostilbene skeleton to generate a novel series of pterostilbene derivatives (PIF_1–PIF_16) which could possess both anti-oxidative and anti-inflammatory activities for sepsis treatment. Then, all target compounds were subjected to their structure–activity relationships (SAR) screening of anti-inflammatory activity in mouse mononuclear macrophage RAW264.7 cell line, and their cytotoxicities were determined after. Finally, an optimal compound, PIF_9, was identified. It decreased the mRNA levels of lipopolysaccharide (LPS)-induced interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS), and cyclooxygenase 2 (COX2). We also found that the anti-inflammatory effects might be contributed by its suppression on the nuclear factor-κB (NF-κB) and MAPKs signaling pathway. Moreover, PIF_9 also demonstrated potent anti-oxidative activity in RAW264.7 macrophages and the sepsis mouse model. Not surprisingly, with the benefits mentioned above, it ameliorated LPS-induced sepsis in C57BL/6J mice and reduced multi-organ toxicity. Taken together, PIF_9 was identified as a potential sepsis solution, targeting inflammation and oxidative stress through modulating MAPKs/NF-κB.

MD2 blockage prevents the migration and invasion of hepatocellular carcinoma cells via inhibition of the EGFR signaling pathway

BACKGROUND

The toll-like receptor (TLR) is an emerging signaling pathway in tumor invasion and metastasis. The activation of TLRs requires specific accessory proteins, such as the small secreted glycoprotein myeloid differentiation protein 2 (MD2), which contributes to ligand responsiveness. However, the role of MD2 in tumorigenesis and metastasis has rarely been reported. This study aimed to investigate the effects and underlying mechanisms of MD2 on the proliferation, migration, and invasion of hepatocellular carcinoma (HCC).

METHODS

Cell counting kit 8 (CCK8), cell colony formation, wound healing, and transwell assays were conducted to determine cell viability, proliferation, migration, and invasion, respectively. Quantitative real-time PCR (qRT-PCR) was performed to assess the expression of MD2 in HCC cell lines and human normal liver cell lines as well as the silencing efficiency of MD2 blockage. Western blot and qRT-PCR assays were performed to detect the protein and mRNA expression levels of epithelial mesenchymal transformation (EMT) markers and epidermal growth factor receptor (EGFR) signaling molecules.

RESULTS

MD2 was highly expressed in HCC tissues and cell lines. High expression of MD2 was associated with poor prognosis of HCC patients. In addition, MD2 silencing slightly inhibited the proliferation of HepG2 and HCCLM3, and significantly suppressed cell migration and invasion. Furthermore, MD2 blockage could distinctly prevent the EMT process by increasing the protein and mRNA levels of E-cadherin and Occludin, and decreasing the levels of Vimentin, N-cadherin, and Snail. Finally, the phosphorylation level of EGFR as well as its downstream molecular Src, Akt, I-κBα, and p65 were downregulated in HCC cells with MD2 silencing.

CONCLUSIONS

Our findings suggest that high expression of MD2 may affect the EMT, migration, and invasion via modulation of the EGFR pathway in HCC cells.

Synthesis and discovery of ω-3 polyunsaturated fatty acid- alkanolamine (PUFA-AA) derivatives as anti-inflammatory agents targeting Nur77

In this work, three series of ω-3 polyunsaturated fatty acid-alkanolamine derivatives (PUFA-AAs) were synthesized, characterized and their anti-inflammatory activity in vivo was evaluated. Compounds 4a, 4f, and 4k exhibited marked anti-inflammatory activity in LPS-stimulated RAW 264.7 cells. The most promising compound 4k dose-dependently suppressed the cytokines with IC₅₀ values in the low micromolar range. Further, 4k exhibited potential in vitro Nur77-binding affinity (K_d = 6.99 × 10^-6 M) which is consistent with the result of docking studies. Next, the anti-inflammatory mechanism of 4k was found to be through NF-κB signal pathway in a Nur77-dependent manner. Moreover, we also observed 4k significantly inhibited LPS-induced expression of cytokines (IL-6, TNF-α, and IL-1β) through suppressing NF-κB activation and attenuated LPS-induced inflammation in mouse acute lung injury (ALI) model. In conclusion, the study strongly suggests that the PUFA-AA derivatives can be particularly as new Nur77 mediators for further treatment in inflammatory diseases.

Neutrophil membranes coated, antibiotic agent loaded nanoparticles targeting to the lung inflammation

Natural cellular membranes, with the outstanding qualities of biocompatibility and specificity, have gained growing attentions in the system of drug delivery. Nanoparticles coated with cellular membranes are starting to be applied as drug-loaded-vehicles to target tumors. Here, neutrophil membranes were selected to apply in the treatment of inflammation because neutrophils can participate in various inflammatory responses and accumulate at inflammatory sites to eliminate pathogens. Through extracting neutrophil membranes from natural neutrophils without affecting their biological properties, nanoparticles loaded with sparfloxacin (SPX) were coated with these membranes and disguised as neutrophils. Compared with traditional nano-medicines, the neutrophil membrane-coated nanoparticles (NM-NP-SPX) possessed precise targeting ability just like the neutrophils could accumulate at inflammatory sites when inflammation burst. In addition, NM-NP-SPX could prolong the circulation time and had the property of controlled-release. Through in vivo experiments, we found that the concentration of three representative inflammatory cytokines in blood, bacteria and inflammatory cells in lungs of the mice with pneumonia reduced significantly in the initial 24 h after the injection of NM-NP-SPX, which meant that NM-NP-SPX could greatly reduce the risk of death for the patients with inflammation. Moreover, the infected lungs could recover rapidly without any side effects to other organs due to the low cytotoxicity of NM-NP-SPX against normal cells. Therefore, our developed drug delivery system has enormous advantages in treating inflammations. Not only that, this kind of bionic method may have greater value and application prospects in curing the inflammations arisen from cancers.

The effects and mechanisms of myeloid differentiation protein 2 on intestinal mucosal permeability in mice with chronic colitis

The present study was designed to investigate the mechanism of myeloid differentiation protein 2 (MD2) on intestinal mucosa destruction in mice with chronic colitis. Briefly, a chronic colitis mouse model was established by the administration of dextran sulfate sodium (DSS) in transgenic mice of MD2 overexpression (Transgenic, MD2-Tg) and C57BL/6 wild-type mice (MD2-WT). In addition, Caco-2 cells were cultured to form a monolayer cell model in vitro. The small interfering RNA was utilized to silence the MD2 gene in Caco-2 cells, and tumor necrosis factor-α (TNF-α) was used to establish the model of intestinal mucosal inflammation. After DSS induction, the intestinal mucosal tissue inflammation was more severe in MD2-Tg mice than MD2-WT. In addition, the intestinal mucosa was severely damaged, the intestinal mucosal permeability was increased, bacterial translocation was obvious, and the expression levels of MD2, MyD88, Toll-like receptor 4 (TLR4), and HMGB1 in mucosal tissues were significantly increased, while the expression levels of tight junction proteins, occludin, and claudin-1 were significantly lower in MD2-Tg mice compared with those in MD2-WT mice. TNF-α could induce inflammatory apoptosis in Caco-2 cell models. After MD2 silencing, the apoptotic level was decreased, the value of transepithelial electrical resistance was increased, the permeability of intestinal mucosa was decreased, the cellular expression levels of MD2, MyD88, TLR4, and HMGB1 were decreased, while the expression levels of tight junction proteins, occludin and claudin-1 were increased. MD2 could aggravate the destruction of intestinal mucosa in chronic colitis through the HMGB1-TLR4-MyD88 pathway.

The Cancer Prevention, Anti-Inflammatory and Anti-Oxidation of Bioactive Phytochemicals Targeting the TLR4 Signaling Pathway

Toll-like receptors (TLRs) are a well-known family of pattern recognition receptors that play an important role in a host immune system. TLR triggering leads to the induction of pro-inflammatory cytokines and chemokines, driving the activation of both innate and adaptive immunity. Recently, an increasing number studies have shown the link between TLRs and cancer. Among them, the toll-like receptor 4 (TLR4) signaling pathway is associated with inflammatory response and cancer progression. Dietary phytochemicals are potential modulators of immunological status with various pharmacological properties including anti-cancer, anti-oxidant and anti-inflammatory. Curcumin, 6-gingerol, 6-shogaol, 1-dehydro-10-gingerdione, epigallocatechin gallate (EGCG), luteolin, quercetin, resveratrol, caffeic acid phenethyl ester, xanthohumol, genistein, berberine, and sulforaphane can inhibit TLR4 activation. The aim of the present review is to describe the role of the TLR4 signaling pathway between inflammatory response and cancer progression. We further introduce bioactive phytochemicals with potential anti-inflammation and chemoprevention by inhibiting TLR activation.