The immunobiology of toll-like receptor 4 agonists: from endotoxin tolerance to immunoadjuvants

Structural insight into TLR4/MD-2 activation by synthetic LPS mimetics with distinct binding modes

The mammalian pattern-recognition receptor TLR4/MD-2 (Toll-like receptor 4/myeloid differentiation factor-2) can be activated by a wide variety of pathogen-associated and endogenous molecules, with Gram-negative bacterial lipopolysaccharide (LPS) being the primary natural TLR4 agonist. Activation of TLR4 triggers cellular signaling that enables the beneficial innate immune responses and enhances adaptive immunity, thereby emphasizing the potential of TLR4 agonists for the management of diseases with an immunopathological background and for use as vaccine adjuvants. Given the challenges associated with LPS-derived products, including structural complexity, heterogeneity, toxicity, and species specificity, synthetic molecules targeting TLR4/MD-2 offer a promising alternative. Here, we elucidate the structural basis for the recognition of synthetic LPS-mimicking glycolipids, Disaccharide Lipid A Mimetics (DLAMs), by human and mouse TLR4/MD-2 through cryo-EM structures of six dimeric [TLR4/MD-2/ligand]2 complexes resolved at 2.2-3.1 Å. We reveal that the specific binding modes of DLAMs, distinct from those of LPS, are essential for the species-independent TLR4 agonistic activity. DLAMs function as a molecular bridge, effectively induce the dimerization of TLR4/MD-2 complexes through specific carbohydrate structure-relevant ligand-protein interactions. Our findings reveal the distinct molecular modes of TLR4 activation, and provide a structural basis for the rationale design and development of innovative, highly potent TLR4-targeting immunotherapeutics and adjuvants.

Network Pharmacology and Experimental Validation of the Therapeutic Effect of Baji Capsule on LPS-Induced Osteoporosis

Purpose

Osteoporosis is a common skeletal disease characterized by impaired bone microarchitecture, decreased bone mineral density and increased bone fragility, leading to a heavy physical and economic burden due to its greatly increased risk of fracture. Baji capsule is a proprietary medicine that can treat menstrual disorders and postmenopausal osteoporosis. However, the efficacy of Baji capsule has not been reported for osteoporosis caused by oxidative stress and inflammation. Therefore, the aim of this study was to evaluate whether Baji capsule has a therapeutic effect on lipopolysaccharide (LPS)-induced inflammatory osteoporosis and to explore the underlying mechanisms through network pharmacology.

Patients and Methods

Osteoporosis model in ICR mice induced with LPS. Mice were treated with vitamin E (100mg/kg), PBS, high-dose Baji capsule (810mg/kg) and low-dose Baji capsule (90mg/kg), respectively. The therapeutic effect of Baji capsule was evaluated by high-resolution micro-computed tomography (Micro-CT) and tissue section staining, serum inflammatory factor levels were assessed by ELISA, serum oxidative stress-related marker levels were determined by kits, and finally the mechanism was explored by network pharmacology and then verified by immunohistochemistry.

Results

Micro-CT results showed that Baji capsule attenuated LPS-induced inflammatory bone loss.Baji capsule also reduced serum inflammatory factor levels and oxygen free radical production. Target screening by network pharmacology yielded a total of 236 active ingredients of Baji capsule, as well as 278 common targets after taking the intersection of Baji capsule active ingredient targets and osteoporosis disease-related targets.

Conclusion

Baji capsule can treat osteoporosis by reducing inflammation and oxidative stress. The therapeutic effects of Baji capsule were shown to be multi-targeted and multi-pathway through network pharmacology. In the future, its anti-inflammatory and antioxidant properties can be utilized to further explore its therapeutic effects on inflammatory diseases, as well as a prospective study for the clinical treatment of osteoporosis.

The fermentation of Cordyceps militaris polysaccharide influenced gut bacterial LPS structure formation and changed its antigenicity

Gut bacterial lipopolysaccharide (LPS) could be released into the circulatory system via the gut-liver axis and cause inflammatory immune response, while Cordyceps militaris polysaccharide (CMP40) has been reported to be effective in alleviating this inflammatory response. In this study, the effects of CMP40 gut fermentation on internal LPS structure formation and the subsequent immune response were explored. Results showed that CMP40 could change antigenicity of LPS of Vibrio parahaemolyticus, Salmonella enterica, and enterotoxigenic Escherichia coli, indicated by a reduced level of NO, IL-1β, IL-6, and TNF-α. The LPS structure of these three strains were further elucidated. ESI/MS results revealed that CMP40 fermentation could alter the LPS structure by removing phosphate group from a single Kdo sugar or removing additional sided fatty acid chain. The gene expressions of enzymes that are responsible for group transfer further confirmed this structure modification process. This study focused on the regulation of polysaccharide on gut bacteria LPS and provided a new insight into health effect of CMP40.

Lipopolysaccharide preconditioning augments the antibacterial activity of renal macrophages and ameliorates acute kidney injury caused by Staphylococcus aureus bacteremia in mice

IntroductionRepeated injections of low-dose lipopolysaccharide (LPS preconditioning) augment the antibacterial activity of liver macrophages. In this study, a mouse model of acute kidney injury (AKI) induced by Staphylococcus aureus (S. aureus) bacteremia was used to investigate the effects of LPS preconditioning on renal macrophages.MethodsEight-week-old C57BL/6J mice were preconditioned with either low-dose LPS (5 μg/kg) or the vehicle for three consecutive days. Kidney immune cells were isolated, and the antibacterial activity of renal macrophages was assessed by pHrodoTM-labeled S. aureus in vitro. Twenty-four hours after the last LPS injection, the mice were intravenously challenged with S. aureus (2 × 107 CFU) and their renal function was evaluated to identify the changes.ResultsMouse renal macrophages exhibited a weak antibacterial activity against S. aureus compared with the liver and spleen macrophages. LPS preconditioning elevated the count of F4/80low CD11bhigh bone marrow-derived macrophages (BMDM) and augmented their antibacterial activities in the mouse kidney. It also enhanced the antibacterial activity of F4/80high CD11blow tissue-resident macrophages (TRM) without altering their abundance. LPS preconditioning lowered the bacterial propagation in the kidney in the challenged mice and ameliorated sepsis-associated AKI compared with the control. LPS preconditioning upregulated the CD80/CD206 expression (M1/M2) ratio in BMDMs in the kidney before bacterial challenge and reduced their M1/M2 ratio following S. aureus challenge compared with the control.ConclusionLPS preconditioning enhanced the antibacterial activity of the renal macrophages against S. aureus and suppressed the excessive activation of M1 macrophages following S. aureus challenge, resulting in the amelioration of AKI caused by S. aureus bacteremia.

Polyphenols have unique cellular effects that are distinct from antioxidant function in Toll-like receptor 4-mediated inflammation in RAW264.7 macrophage-like cells

Plant polyphenols are bioactive compounds touted for their antioxidant effects, and this is often the primary attribute used to explain their health benefits. However, we hypothesize that polyphenols have molecular properties independent of antioxidant function. The objective of this study was to investigate whether polyphenols had distinct molecular effects compared to pure antioxidants. RAW 264.7 macrophages were pretreated with either TEMPOL, a superoxide scavenger, N-acetyl cysteine, a hydroxyl radical and hydrogen peroxide scavenger, or polyphenol extracts from blackberry, blueberry, raspberry, strawberry, kale, and baru nut. After 1 hour of pretreatment, cells were treated with lipopolysaccharides (100 ng/mL) for an additional 6 hour. Antioxidants and polyphenol extracts elicited antioxidant effects in vitro; however, polyphenols regulated redox proteins in a distinct, protective manner, whereas antioxidants, TEMPOL, and N-acetyl cysteine, did not. Additionally, distinct effects were observed in downstream Toll-like receptor 4 signaling and transcriptional activity of inflammatory proteins. We conclude that polyphenols have unique molecular effects that are independent of just their free radical scavenging capacity. This work advances our molecular understanding of how polyphenols act to target inflammation.

Zoledronic Acid Inhibits Lipopolysaccharide-Induced Osteoclastogenesis by Suppressing Macrophage NLRP3-Mediated Autophagy Pathway

INTRODUCTION

Inflammatory factors leading to bone loss significantly increase the risk of tooth loosening or implantation failure. Zoledronic acid (ZOL) is a widely used medication for effectively inhibiting excessive bone destruction, but its effect on alleviating inflammatory bone loss remains to be elucidated. In this study, we investigated whether ZOL alleviates inflammatory bone resorption through immunomodulatory effect.

METHODS

The viability of the cells was evaluated by Cell Counting Kit 8 (CCK8) assay. Osteoclast (OC) differentiation and function were determined by tartrate-resistant acid phosphatase (TRAP) staining and bone resorption pits assays, respectively. Autophagosomes and actin ring structures of OC were observed using transmission electron microscopy (TEM) and F-actin ring staining, respectively. The microstructure in mice maxillary alveolar bone model was observed by micro computed tomography (Miro-CT). Reverse transcription-quantitative PCR (RT-qPCR) to detect the mRNA expression of osteoclast-related genes and Western blot (WB) analysis to evaluate the protein expression levels of autophagy-related proteins and the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3)-related proteins in pre-OCs.

RESULTS

The findings indicated that ZOL hindered lipopolysaccharide (LPS)-mediated OC differentiation, formation, bone resorption activity and autophagosome levels. Furthermore, ZOL diminished the expression of genes associated with OC. And the expression of proteins ATG7, LC3II, Beclin1, NLRP3-related proteins and tumor necrosis factor-α (TNF-α) protein were markedly decreased while P62 was increased, especially in the 1 μM ZOL group or MCC950 + ZOL group.

CONCLUSIONS

ZOL has a certain immunomodulatory effect that exhibits anti-inflammatory properties at lower concentrations, which can weaken LPS-induced OCs differentiation and function, and NLRP3-mediated autophagy pathway may participate in this process.

Nonreducing Sugar Scaffold Enables the Development of Immunomodulatory TLR4-specific LPS Mimetics with Picomolar Potency

Innate immune defense mechanisms against infection and cancer encompass the modulation of pattern recognition receptor (PRR)-mediated inflammation, including upregulation of various transcription factors and the activation of pro-inflammatory pathways important for immune surveillance. Dysfunction of PRRs-mediated signaling has been implicated in cancer and autoimmune diseases, while the overactivation of PRRs-driven responses during infection can lead to devastating consequences such as acute lung injury or sepsis. We used crystal structure-based design to develop immunomodulatory lipopolysaccharide (LPS) mimetics targeting one of the ubiquitous PRRs, Toll-like Receptor 4 (TLR4). Taking advantage of an exo-anomeric conformation and specific molecular shape of synthetic nonreducing β,β-diglucosamine, which was investigated by NMR, we developed two sets of lipid A mimicking glycolipids capable of either potently activating innate immune responses or inhibiting pro-inflammatory signaling. Stereoselective 1,1'-glycosylation towards fully orthogonally protected nonreducing GlcNβ(1↔1')βGlcN followed by stepwise assembly of differently functionalised phosphorylated glycolipids provided biologically active molecules that were evaluated for their ability to trigger or to inhibit cellular innate immune responses. Two LPS mimetics, identified as potent TLR4-specific inducers of the intracellular signaling pathways, serve as vaccine adjuvant- and immunotherapy candidates, while anionic glycolipids with TLR4-inhibitory potential hold therapeutic promise for the management of acute or chronic inflammation.

The critical role of toll-like receptor 4 in bone remodeling of osteoporosis: from inflammation recognition to immunity

Osteoporosis is a common chronic metabolic bone disorder. Recently, increasing numbers of studies have demonstrated that Toll-like receptor 4 (TLR4, a receptor located on the surface of osteoclasts and osteoblasts) plays a pivotal role in the development of osteoporosis. Herein, we performed a comprehensive review to summarize the findings from the relevant studies within this topic. Clinical data showed that TLR4 polymorphisms and aberrant TLR4 expression have been associated with the clinical significance of osteoporosis. Mechanistically, dysregulation of osteoblasts and osteoclasts induced by abnormal expression of TLR4 is the main molecular mechanism underlying the pathological processes of osteoporosis, which may be associated with the interactions between TLR4 and NF-κB pathway, proinflammatory effects, ncRNAs, and RUNX2. In vivo and in vitro studies demonstrate that many promising substances or agents (i.e., methionine, dioscin, miR-1906 mimic, artesunate, AEG-1 deletion, patchouli alcohol, and Bacteroides vulgatus) have been able to improve bone metabolism (i.e., inhibits bone resorption and promotes bone formation), which may partially attribute to the inhibition of TLR4 expression. The present review highlights the important role of TLR4 in the clinical significance and the pathogenesis of osteoporosis from the aspects of inflammation and immunity. Future therapeutic strategies targeting TLR4 may provide a new insight for osteoporosis treatment.

TIFA contributes to periodontitis in diabetic mice via activating the NF‑κB signaling pathway

Diabetic periodontitis (DP) refers to destruction of periodontal tissue and absorption of bone tissue in diabetic patients. Tumor necrosis factor receptor‑associated factor (TRAF)‑interacting protein with forkhead‑associated domain (TIFA) as a crucial regulator of inflammation activates the NF‑κB signaling pathway to regulate cell biological behavior. However, the function and mechanism of TIFA on DP suffer from a lack of research. In the present study, TIFA was upregulated in the periodontal tissue of a DP mouse model. In addition, the expression of TIFA in RAW264.7 cells was induced by high glucose (HG) culture and increased by lipopolysaccharide (LPS) from Porphyromonas gingivalis treatment in a time‑dependent manner. Knockdown of TIFA significantly reduced the levels of inflammatory cytokines, including TNF‑α, IL‑6, IL‑1β and monocyte chemoattractant protein‑1, in HG and LPS‑induced RAW264.7 cells. The nuclear translocation of NF‑κB p65 was induced by HG and LPS and was clearly suppressed by absence of TIFA. The expression of downstream factors Nod‑like receptor family pyrin domain‑containing 3 and apoptosis‑associated speck‑like protein was inhibited by silencing TIFA. Moreover, TIFA was increased by receptor activator of NF‑κB (RANK) ligand (RANKL) in a concentration dependent manner. The expression of cathepsin K, MMP9 and nuclear factor of activated T cells cytoplasmic 1 was downregulated by depletion of TIFA. RANKL‑induced osteoclast differentiation was inhibited by silencing of TIFA. Meanwhile, the decrease of TIFA blocked activation of the NF‑κB pathway in RANKL‑treated RAW264.7 cells. In conclusion, TIFA as a promoter regulates the inflammation and osteoclast differentiation via activating the NF‑κB signaling pathway.

Bacteria- and fungus-derived PAMPs induce innate immune memory via similar functional, metabolic, and transcriptional adaptations

Exposure to pathogen-associated molecular patterns (PAMPs) induces an augmented, broad-spectrum antimicrobial response to subsequent infection, a phenomenon termed innate immune memory. This study examined the effects of treatment with β-glucan, a fungus-derived dectin-1 ligand, or monophosphoryl lipid A (MPLA), a bacteria-derived Toll-like receptor 4 ligand, on innate immune memory with a focus on identifying common cellular and molecular pathways activated by these diverse PAMPs. Treatment with either PAMP prepared the innate immune system to respond more robustly to Pseudomonas aeruginosa infection in vivo by facilitating mobilization of innate leukocytes into blood, recruitment of leukocytes to the site of infection, augmentation of microbial clearance, and attenuation of cytokine production. Examination of macrophages ex vivo showed amplification of metabolism, phagocytosis, and respiratory burst after treatment with either agent, although MPLA more robustly augmented these activities and more effectively facilitated killing of bacteria. Both agents activated gene expression pathways in macrophages that control inflammation, antimicrobial functions, and protein synthesis and suppressed pathways regulating cell division. β-glucan treatment minimally altered macrophage differential gene expression in response to lipopolysaccharide (LPS) challenge, whereas MPLA attenuated the magnitude of the LPS-induced transcriptional response, especially cytokine gene expression. These results show that β-glucan and MPLA similarly augment the innate response to infection in vivo. Yet, MPLA more potently induces alterations in macrophage metabolism, antimicrobial functions, gene transcription and the response to LPS.

The role of autophagy in SIM mediated anti-inflammatory osteoclastogenesis through NLRP3 signaling pathway

BACKGROUND

Inflammatory bone resorption is a prominent risk factor for implantation failure. Simvastatin (SIM) has anti-inflammatory effects independent of cholesterol lowering and reduces osteoclastogenesis by decreasing both the number and activity of osteoclasts. However, the specific mechanism of inflammatory bone loss alleviation by SIM remains to be elucidated. We hypothesized that SIM relieves inflammatory bone loss by modulating autophagy and suppressing the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) signaling pathway.

METHODS AND RESULTS

RAW264.7 cells were stimulated by lipopolysaccharide (LPS) after being pretreated with various concentrations of SIM. Osteoclast (OC) differentiation, formation and activity were evaluated by tartrate-resistant acid phosphatase staining, F-actin ring staining and bone resorption pit assays, respectively. We observed autophagosomes by transmission electron microscopy. Then NLRP3 inhibitor MCC950 was used to further explore the corresponding molecular mechanism underlying anti-inflammatory bone resorption, the expression of autophagy-related proteins and NLRP3 signaling pathway factors in pre-OCs were evaluated by western blot analysis, and the expression of OC-specific molecules was analyzed using reverse transcription-quantitative polymerase chain reaction. The results showed that SIM decreased the expression of tumor necrosis factor-α, whereas increased Interleukin-10. In addition, SIM inhibited LPS-induced OC differentiation, formation, bone resorption activity, the level of autophagosomes, and OC-specific markers. Furthermore, SIM significantly suppressed autophagy by downregulating LC3II, Beclin1, ATG7, and NLRP3-related proteins expression while upregulating P62 under inflammatory conditions.

CONCLUSIONS

SIM may reduce autophagy secretion to attenuate LPS-induced osteoclastogenesis and the NLRP3 signaling pathway participates in this process, thus providing theoretical basis for the application of this drug in peri-implantitis.

Macrophages derived from LPS-stimulated monocytes from individuals with subclinical atherosclerosis were characterized by increased pro-inflammatory activity

OBJECTIVE

Atherosclerosis is characterized by chronic inflammation in the vascular wall. Currently the violation of immune tolerance of innate immune cells is considered as a possible mechanism of chronification of inflammation. The aim of this study is to assess the inflammatory activity and tolerance of monocytes and macrophages in subclinical atherosclerosis.

METHODS

A total of 55 individuals free from clinical manifestations of atherosclerosis-associated cardiovascular disease with a presence or absence of atherosclerotic plaques in the carotid arteries were included in this study. CD14+ monocytes were isolated from individuals' blood and stimulated with a single dose of lipopolysaccharide (LPS) on day 1 or with double doses of LPS on day 1 and day 6. The secretion of cytokines TNF, IL-1β, IL-6, IL-8, IL-10 and CCL2 were evaluated using ELISA.

RESULTS

Our findings demonstrate that macrophages derived from LPS-stimulated monocytes in individuals with subclinical atherosclerosis exhibited increased secretion of IL-6, IL-10 and CCL2, which was associated with intima-media thickness, body mass index, but not with individuals' age. Moreover, macrophages from individuals with atherosclerotic plaques exhibited impaired tolerance towards the second LPS stimulation manifested by elevated secretion of the chemoattractant CCL2.

CONCLUSION

Increased secretion of these cytokines by macrophages may contribute to chronic local inflammation in the vascular wall by recruiting other immune cells.

Nanovaccines: A game changing approach in the fight against infectious diseases

The field of nanotechnology has revolutionised global attempts to prevent, treat, and eradicate infectious diseases in the foreseen future. Nanovaccines have proven to be a valuable pawn in this novel technology. Nanovaccines are made up of nanoparticles that are associated with or prepared with components that can stimulate the host's immune system. In addition to their delivery capabilities, the nanocarriers have been demonstrated to possess intrinsic adjuvant properties, working as immune cell stimulators. Thus, nanovaccines have the potential to promote rapid as well as long-lasting humoral and cellular immunity. The nanovaccines have several possible benefits, including site-specific antigen delivery, increased antigen bioavailability, and a diminished adverse effect profile. To avail these benefits, several nanoparticle-based vaccines are being developed, including virus-like particles, liposomes, polymeric nanoparticles, nanogels, lipid nanoparticles, emulsion vaccines, exomes, and inorganic nanoparticles. Inspired by their distinctive properties, researchers are working on the development of nanovaccines for a variety of applications, such as cancer immunotherapy and infectious diseases. Although a few challenges still need to be overcome, such as modulation of the nanoparticle pharmacokinetics to avoid rapid elimination from the bloodstream by the reticuloendothelial system, The future prospects of this technology are also assuring, with multiple options such as personalised vaccines, needle-free formulations, and combination nanovaccines with several promising candidates.

Podocin, mTOR, and CHOP dysregulation contributes to nephrotoxicity induced of lipopolysaccharide/diclofenac combination in rats: Curcumin and silymarin could afford protective effect

AIM

Sepsis is a common cause of acute kidney injury (AKI). Lipopolysaccharides (LPS) are the main gram-negative bacterial cell wall component with a well-documented inflammatory impact. Diclofenac (DIC) is a non-steroidal anti-inflammatory drug with a potential nephrotoxic effect. Curcumin (CUR) and silymarin (SY) are natural products with a wide range of pharmacological activities, including antioxidant and anti-inflammatory ones. The objective of this study was to examine the protective impact of CUR and SY against kidney damage induced by LPS/DIC co-exposure.

MATERIALS AND METHODS

Four groups of rats were used; control; LPS/DIC, LPS/DIC + CUR, and LPS/DIC + SY group. LPS/DIC combination induced renal injury at an LPS dose much lower than a nephrotoxic one.

KEY FINDING

Nephrotoxicity was confirmed by histopathological examination and significant elevation of renal function markers. LPS/DIC induced oxidative stress in renal tissues, evidenced by decreasing reduced glutathione and superoxide dismutase, and increasing lipid peroxidation. Inflammatory response of LPS/DIC was associated with a significant increase of renal IL-1β and TNF-α. Treatment with either CUR or SY shifted measured parameters to the opposite side. Moreover, LPS/DIC exposure was associated with upregulation of mTOR and endoplasmic reticulum stress protein (CHOP) and downregulation of podocin These effects were accompanied by reduced gene expression of cystatin C and KIM-1. CUR and SY ameliorated LPS/DIC effect on the aforementioned genes and protein significantly.

SIGNIFICANCE

This study confirms the potential nephrotoxicity; mechanisms include upregulation of mTOR, CHOP, cystatin C, and KIM-1 and downregulation of podocin. Moreover, both CUR and SY are promising nephroprotective products against LPS/DIC co-exposure.

Intranasal Monophosphoryl Lipid a Administration Ameliorates depression-like Behavior in Chronically Stressed Mice Through Stimulation of Microglia

We and others have reported that systematic stimulation of the central innate immune system by a low dose of lipopolysaccharide (LPS) can improve depression-like behavior in chronically stressed animals. However, it is unclear whether similar stimulation by intranasal administration could improve depression-like behavior in animals. We investigated this question using monophosphoryl lipid A (MPL), a derivative of LPS that lacks the adverse effects of LPS but is still immuno-stimulatory. We found that a single intranasal administration of MPL at a dose of 10 or 20 µg/mouse, but not at a dose of 5 µg/mouse, ameliorated chronic unpredictable stress (CUS)-induced depression-like behavior in mice, as evidenced by the decrease in immobility time in tail suspension test and forced swimming test and the increase in sucrose intake in sucrose preference test. In the time-dependent analysis, the antidepressant-like effect of a single intranasal MPL administration (20 µg/mouse) was observed 5 and 8 h but not 3 h after drug administration and persisted for at least 7 days. Fourteen days after the first intranasal MPL administration, a second intranasal MPL administration (20 µg/mouse) still showed an antidepressant-like effect. The innate immune response mediated by microglia might mediate the antidepressant-like effect of intranasal MPL administration, because both inhibition of microglial activation by pretreatment with minocycline and depletion of microglia by pretreatment with PLX3397 prevented the antidepressant-like effect of intranasal MPL administration. These results suggest that intranasal administration of MPL can produce significant antidepressant-like effects in animals under chronic stress conditions via stimulation of microglia.

A TLR4 Agonist Induces Osteosarcoma Regression by Inducing an Antitumor Immune Response and Reprogramming M2 Macrophages to M1 Macrophages

Osteosarcoma (OsA) has limited treatment options and stagnant 5-year survival rates. Its immune microenvironment is characterized by a predominance of tumor-associated macrophages (TAMs), whose role in OsA progression remain unclear. Nevertheless, immunotherapies aiming to modulate macrophages activation and polarization could be of interest for OsA treatment. In this study, the antitumor effect of a liposome-encapsulated chemically detoxified lipopolysaccharide (Lipo-MP-LPS) was evaluated as a therapeutic approach for OsA. Lipo-MP-LPS is a toll-like receptor 4 (TLR4) agonist sufficiently safe and soluble to be IV administered at effective doses. Lipo-MP-LPS exhibited a significant antitumor response, with tumor regression in 50% of treated animals and delayed tumor progression in the remaining 50%. The agent inhibited tumor growth by 75%, surpassing the efficacy of other immunotherapies tested in OsA. Lipo-MP-LPS modulated OsA's immune microenvironment by favoring the transition of M2 macrophages to M1 phenotype, creating a proinflammatory milieu and facilitating T-cell recruitment and antitumor immune response. Overall, the study demonstrates the potent antitumor effect of Lipo-MP-LPS as monotherapy in an OsA immunocompetent model. Reprogramming macrophages and altering the immune microenvironment likely contribute to the observed tumor control. These findings support the concept of immunomodulatory approaches for the treatment of highly resistant tumors like OsA.

ATF4 knockdown in macrophage impairs glycolysis and mediates immune tolerance by targeting HK2 and HIF-1α ubiquitination in sepsis

Strengthened glycolysis is crucial for the macrophage pro-inflammatory response during sepsis. Activating transcription factor 4 (ATF4) plays an important role in regulating glucose and lipid metabolic homeostasis in hepatocytes and adipocytes. However, its immunometabolic role in macrophage during sepsis remains largely unknown. In the present study, we found that the expression of ATF4 in peripheral blood mononuclear cells (PBMCs) was increased and associated with glucose metabolism in septic patients. Atf4 knockdown specifically decreased LPS-induced spleen macrophages and serum pro-inflammatory cytokines levels in mice. Moreover, Atf4 knockdown partially blocked LPS-induced pro-inflammatory cytokines, lactate accumulation and glycolytic capacity in RAW264.7. Mechanically, ATF4 binds to the promoter region of hexokinase II (HK2), and interacts with hypoxia inducible factor-1α (HIF-1α) and stabilizes HIF-1α through ubiquitination modification in response to LPS. Furthermore, ATF4-HIF-1α-HK2-glycolysis axis launches pro-inflammatory response in macrophage depending on the activation of mammalian target of rapamycin (mTOR). Importantly, Atf4 overexpression improves the decreased level of pro-inflammatory cytokines and lactate secretion and HK2 expression in LPS-induced tolerant macrophages. In conclusion, we propose a novel function of ATF4 as a crucial glycolytic activator contributing to pro-inflammatory response and improving immune tolerant in macrophage involved in sepsis. So, ATF4 could be a potential new target for immunotherapy of sepsis.

Pretreatment with a novel Toll-like receptor 4 agonist attenuates renal ischemia-reperfusion injury

Acute kidney injury (AKI) is common in surgical and critically ill patients. This study examined whether pretreatment with a novel Toll-like receptor 4 agonist attenuated ischemia-reperfusion injury (IRI)-induced AKI (IRI-AKI). We performed a blinded, randomized-controlled study in mice pretreated with 3-deacyl 6-acyl phosphorylated hexaacyl disaccharide (PHAD), a synthetic Toll-like receptor 4 agonist. Two cohorts of male BALB/c mice received intravenous vehicle or PHAD (2, 20, or 200 µg) at 48 and 24 h before unilateral renal pedicle clamping and simultaneous contralateral nephrectomy. A separate cohort of mice received intravenous vehicle or 200 µg PHAD followed by bilateral IRI-AKI. Mice were monitored for evidence of kidney injury for 3 days postreperfusion. Kidney function was assessed by serum blood urea nitrogen and creatinine measurements. Kidney tubular injury was assessed by semiquantitative analysis of tubular morphology on periodic acid-Schiff (PAS)-stained kidney sections and by kidney mRNA quantification of injury [neutrophil gelatinase-associated lipocalin (Ngal), kidney injury molecule-1 (Kim-1), and heme oxygenase-1 (Ho-1)] and inflammation [interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (Tnf-α)] using quantitative RT-PCR. Immunohistochemistry was used to quantify proximal tubular cell injury and renal macrophages by quantifying the areas stained with Kim-1 and F4/80 antibodies, respectively, and TUNEL staining to detect the apoptotic nuclei. PHAD pretreatment yielded dose-dependent kidney function preservation after unilateral IRI-AKI. Histological injury, apoptosis, Kim-1 staining, and Ngal mRNA were lower in PHAD-treated mice and IL-1β mRNA was higher in PHAD-treated mice. Similar pretreatment protection was noted with 200 mg PHAD after bilateral IRI-AKI, with significantly reduced Kim-1 immunostaining in the outer medulla of mice treated with PHAD after bilateral IRI-AKI. In conclusion, PHAD pretreatment leads to dose-dependent protection from renal injury after unilateral and bilateral IRI-AKI in mice.NEW & NOTEWORTHY Pretreatment with 3-deacyl 6-acyl phosphorylated hexaacyl disaccharide; a novel synthetic Toll-like receptor 4 agonist, preserves kidney function during ischemia-reperfusion injury-induced acute kidney injury.

RIPK1 in the inflammatory response and sepsis: Recent advances, drug discovery and beyond

Cytokine storms are an important mechanism of sepsis. TNF-α is an important cytokine. As a regulator of TNF superfamily receptors, RIPK1 not only serves as the basis of the scaffold structure in complex I to promote the activation of the NF-κB and MAPK pathways but also represents an important protein in complex II to promote programmed cell death. Ubiquitination of RIPK1 is an important regulatory function that determines the activation of cellular inflammatory pathways or the activation of death pathways. In this paper, we introduce the regulation of RIPK1, RIPK1 PANoptosome's role in Inflammatory and sepsis, and perspectives.

Multi-Epitope Vaccine Candidates Associated with Mannosylated Chitosan and LPS Conjugated Chitosan Nanoparticles Against Brucella Infection

One promising approach to increase protection against infectious diseases is to use adjuvants that can selectively stimulate the immune responses. In this study, multi-epitope antigens associated with LPS loaded chitosan (LLC) as toll-like receptor agonist or mannosylated chitosan nanoparticle (MCN) as vaccine delivery system were evaluated for their ability to stimulate immune responses to Brucella infection in mice model. Our results indicated that the addition of MCN to our vaccine formulations significantly elicited IFN-γ and IL-2 cytokines and antibody titers, in comparison with the non-adjuvanted vaccine candidates. The present results indicated that multi-epitopes and their administration with LLC or MCN induced Th1 immune response. In addition, vaccine candidates containing MCN provided high percentage of protection against B. melitensis and B. abortus infection. Our results provided support to previous reports indicating that MCNs are attractive adjuvants and addition of this adjuvant to multi-epitopes antigens play an important role in the development of vaccine against Brucella.

TLR4 agonist activity of Alcaligenes lipid a utilizes MyD88 and TRIF signaling pathways for efficient antigen presentation and T cell differentiation by dendritic cells

Alcaligenes faecalis was previously identified as an intestinal lymphoid tissue-resident commensal bacteria, and our subsequent studies showed that lipopolysaccharide and its core active element (i.e., lipid A) have a potent adjuvant activity to promote preferentially antigen-specific Th17 response and antibody production. Here, we compared A. faecalis lipid A (ALA) with monophosphoryl lipid A, a licensed lipid A-based adjuvant, to elucidate the immunological mechanism underlying the adjuvant properties of ALA. Compared with monophosphoryl lipid A, ALA induced higher levels of MHC class II molecules and costimulatory CD40, CD80, and CD86 on dendritic cells (DCs), which in turn resulted in strong T cell activation. Moreover, ALA more effectively promoted the production of IL-6 and IL-23 from DCs than did monophosphoryl lipid A, thus leading to preferential induction of Th17 and Th1 cells. As underlying mechanisms, we found that the ALA-TLR4 axis stimulated both MyD88- and TRIF-mediated signaling pathways, whereas monophosphoryl lipid A was biased toward TRIF signaling. These findings revealed the effects of ALA on DCs and T cells and its induction pattern on signaling pathways.

Distinct Immune Reconstitution Profiles Captured by Immune Functional Assays at 6 Months Post Allogeneic Hematopoietic Stem Cell Transplantation

Immune reconstitution after allogeneic-hematopoietic-stem-cell transplantation (allo-HSCT) is a complex and individual process. In this cross-sectional study, whole-blood (WB) immune functional assay (IFA) was used to characterize immune function by assessing immune-related gene/pathway alterations. The usefulness of this tool in the context of infection, 6 months after transplantation, was evaluated. Sixty allo-HSCT recipients at 6 months after transplantation and 10 healthy volunteers (HV) were included. WB was stimulated in standardized TruCulture tubes using lipopolysaccharides and Staphylococcal enterotoxin B. Gene expression was quantified using a custom 144-gene panel using NanoString nCounter technology and analyzed using Ingenuity Pathway Analysis. The relationships between immune function and clinical characteristics, immune cell counts, and post-transplantation infections were assessed. Allo-HSCT recipients were able to activate similar networks of the innate and adaptive immune response compared to HV, with, nevertheless, a lower intensity. A reduced number and a lower expression of genes associated with immunoregulatory and inflammatory processes were observed in allo-HSCT recipients. The use of immunosuppressive treatments was associated with a protracted immune reconstitution revealed by transcriptomic immunoprofiling. No difference in immune cell counts was observed among patients receiving or not receiving immunosuppressive treatments using a large immunophenotyping panel. Moreover, the expression of a set of genes, including CCL3/CCL4, was significantly lower in patients with Herpesviridae reactivation (32%, 19/60), which once again was not identified using classical immune cell counts. Transcriptional IFA revealed the heterogeneity among allo-HSCT recipients with a reduced immune function, a result that could not be captured by circulating immune cell counts. This highlights the potential added value of this tool for the personalized care of immunocompromised patients.

Microbiota-Associated HAF-EVs Regulate Monocytes by Triggering or Inhibiting Inflammasome Activation

In pregnancy, human amniotic fluid extracellular vesicles (HAF-EVs) exert anti-inflammatory effects on T cells and on monocytes, supporting their immunoregulatory roles. The specific mechanisms are still not completely defined. The aim of this study was to investigate the ability of HAF-EVs, isolated from pregnant women who underwent amniocentesis and purified by gradient ultracentrifugation, to affect inflammasome activation in the human monocytes. Proteomic studies revealed that HAF-EV samples expressed several immunoregulatory molecules as well as small amounts of endotoxin. Surprisingly, metagenomic analysis shows the presence of specific bacterial strain variants associated with HAF-EVs as potential sources of the endotoxin. Remarkably, we showed that a single treatment of THP-1 cells with HAF-EVs triggered inflammasome activation, whereas the same treatment followed by LPS and ATP sensitization prevented inflammasome activation, a pathway resembling monocyte refractories. A bioinformatics analysis of microbiota-HAF-EVs functional pathways confirmed the presence of enzymes for endotoxin biosynthesis as well as others associated with immunoregulatory functions. Overall, these data suggest that HAF-EVs could serve as a source of the isolation of a specific microbiota during early pregnancy. Moreover, HAF-EVs could act as a novel system to balance immune training and tolerance by modulating the inflammasome in monocytes or other cells.

Inflammatory phenotype, clinicopathologic variables, and effects of long-term methylene blue in dogs with hereditary methemoglobinemia caused by cytochrome b5 reductase deficiency

OBJECTIVE

To determine whether dogs with cytochrome b5 reductase (CYB5R) deficiency have a constitutive proinflammatory phenotype, characterize hematologic and serum chemistry results, and describe changes in methemoglobin (MetHb) levels and serum C-reactive protein (CRP) concentrations after long-term per os (PO) methylene blue (MB) therapy.

ANIMALS

21 client-owned dogs (CYB5R deficient, n = 10; healthy controls, 11).

PROCEDURES

In this prospective, case-control study, methemoglobin levels were measured using a blood gas analyzer with co-oximetry. Plasma tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10) concentrations were measured using a canine-specific multiplex bead-based assay. Serum CRP concentrations were measured with a canine-specific commercial ELISA kit. Serum CRP concentration and MetHb levels were measured in 6 dogs with CYB5R deficiency after ≥ 60 days of PO MB therapy.

RESULTS

As expected, MetHb levels were higher in dogs with CYB5R deficiency compared to controls (P < .001). Plasma TNF-α, IL-6, IL-10, and serum CRP concentrations were no different between CYB5R-deficient and control dogs. Dogs with CYB5R deficiency had lower absolute lymphocyte (P = .005) and eosinophil counts (P = .04) and higher alanine transaminase (P = .04) and alkaline phosphatase activity (P = .02) than controls, but these changes were not clinically relevant. Methemoglobin levels decreased after PO MB therapy (P = .03).

CLINICAL RELEVANCE

These results suggest that otherwise healthy dogs with CYB5R deficiency do not have a constitutive proinflammatory phenotype and clinically relevant abnormalities in hematologic and serum chemistry panels are not expected. Dogs with decreased quality of life attributed to methemoglobinemia from CYB5R deficiency might benefit from PO MB therapy.

TIMP-1 is a novel ligand of Amyloid Precursor Protein and triggers a proinflammatory phenotype in human monocytes

The emerging cytokine tissue inhibitor of metalloproteinases-1 (TIMP-1) correlates with the progression of inflammatory diseases, including cancer. However, the effects of TIMP-1 on immune cell activation and underlying molecular mechanisms are largely unknown. Unbiased ligand-receptor-capture-screening revealed TIMP-1-interaction with Amyloid Precursor Protein (APP) family members, namely APP and Amyloid Precursor-like Protein-2 (APLP2), which was confirmed by pull-down assays and confocal microscopy. We found that TIMP-1 triggered glucose uptake and proinflammatory cytokine expression in human monocytes. In cancer patients, TIMP-1 expression positively correlated with proinflammatory cytokine expression and processes associated with monocyte activation. In pancreatic cancer, TIMP-1 plasma levels correlated with the monocyte activation marker sCD163, and the combined use of both clinically accessible plasma proteins served as a powerful prognostic indicator. Mechanistically, TIMP-1 triggered monocyte activation by its C-terminal domain and via APP as demonstrated by in vitro interference, in silico docking, and the employment of recombinant TIMP-1 variants. Identification of TIMP-1 as a trigger of monocyte activation opens new therapeutic perspectives for inflammatory diseases.

Salvia miltiorrhiza Extract Prevents the Occurrence of Early Atherosclerosis in Apoe -/- Mice via TLR4/ NF-kB Pathway

OBJECTIVE

Salvia miltiorrhiza (SM) contains four major aqueous active ingredients, which have been isolated, purified and identified as danshensu (DSS), salvianolic acid A (Sal-A), salvianolic acid B (Sal-B) and protocatechuic aldehyde (PAL), A mixture of these four ingredients is called SABP. Although aqueous extract from Salvia miltiorrhiza has been traditionally used to treat cardiovascular diseases, the efficacy and function of the optimal ratio of SABP in preventing and treating cardiovascular diseases remain unknown. This study aims to explore the antiinflammatory mechanisms underlying the attenuation of atherosclerosis development by aqueous extract from Salvia miltiorrhiza.

METHODS

Male ApoE-/- mice (6 weeks) were randomly allocated into three groups: the model group (Model), the SABP group (SABP), and the rosuvastatin calcium group (RC). Male C57BL/6 mice (6 weeks) were used as a control group. All mice were fed with an ordinary diet. After 8 weeks of treatment, the lipid profiles in serum and the lactate dehydrogenase (LDH) and creatine kinase (CK) in heart tissue were measured using an automatic biochemical analyzer. Alterations of the thoracic aorta and the heart were assessed using Hematoxylin and eosin staining. The protein expression of Toll-like receptor 4 (TLR4), TGF beta-activated kinase 1 (TAK1), nuclear factor kappa-B (NF-κB), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the heart tissue were determined though immunohistochemistry and western blotting analysis.

RESULTS

The serum low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and total cholesterol (TC) levels were increased, and the high-density lipoprotein cholesterol (HDL-C) level was decreased in ApoE-/- mice. SABP significantly decreased serum lipid levels and improved histopathology in the thoracic aorta. In addition. SABP treatment inhibited the expression of TLR4, TAK1, NF-κB, IL-6 and TNF-α in the heart in ApoE-/- mice. The LDH and CK in the heart did not differ significantly among different groups, and the heart did not have obvious pathological changes.

CONCLUSION

These findings indicated that SABP may exert an anti-atherosclerotic effect by lowering blood lipids and inhibiting inflammatory response via TLR4/ NF-κB signaling pathway.

Breaking the niche: multidimensional nanotherapeutics for tumor microenvironment modulation

Most of the current antitumor therapeutics were developed targeting the cancer cells only. Unfortunately, in the majority of tumors, this single-dimensional therapy is found to be ineffective. Advanced research has shown that cancer is a multicellular disorder. The tumor microenvironment (TME), which is made by a complex network of the bulk tumor cells and other supporting cells, plays a crucial role in tumor progression. Understanding the importance of the TME in tumor growth, different treatment modalities have been developed targeting these supporting cells. Recent clinical results suggest that simultaneously targeting multiple components of the tumor ecosystem with drug combinations can be highly effective. This type of "multidimensional" therapy has a high potential for cancer treatment. However, tumor-specific delivery of such multi-drug combinations remains a challenge. Nanomedicine could be utilized for the tumor-targeted delivery of such multidimensional therapeutics. In this review, we first give a brief overview of the major components of TME. We then highlight the latest developments in nanoparticle-based combination therapies, where one drug targets cancer cells and other drug targets tumor-supporting components in the TME for a synergistic effect. We include the latest preclinical and clinical studies and discuss innovative nanoparticle-mediated targeting strategies.

Therapeutic Targeting of TLR4 for Inflammation, Infection, and Cancer: A Perspective for Disaccharide Lipid A Mimetics

The Toll-like receptor 4 (TLR4) signaling pathway plays a central role in the prompt defense against infectious challenge and provides immediate response to Gram-negative bacterial infection. The TLR4/MD-2 complex can sense and respond to various pathogen-associated molecular patterns (PAMPs) with bacterial lipopolysaccharide (LPS) being the most potent and the most frequently occurring activator of the TLR4-mediated inflammation. TLR4 is believed to be both a friend and foe since improperly regulated TLR4 signaling can result in the overactivation of immune responses leading to sepsis, acute lung injury, or pathologic chronic inflammation involved in cancer and autoimmune disease. TLR4 is also considered a legitimate target for vaccine adjuvant development since its activation can boost the adaptive immune responses. The dual action of the TLR4 complex justifies the efforts in the development of both TLR4 antagonists as antisepsis drug candidates or remedies for chronic inflammatory diseases and TLR4 agonists as vaccine adjuvants or immunotherapeutics. In this review, we provide a brief overview of the biochemical evidences for possible pharmacologic applications of TLR4 ligands as therapeutics and report our systematic studies on the design, synthesis, and immunobiological evaluation of carbohydrate-based TLR4 antagonists with nanomolar affinity for MD-2 as well as disaccharide-based TLR4 agonists with picomolar affinity for the TLR4/MD-2 complex.

Spatio-temporal delivery of both intra- and extracellular toll-like receptor agonists for enhancing antigen-specific immune responses

For cancer immunotherapy, triggering toll-like receptors (TLRs) in dendritic cells (DCs) can potentiate antigen-based immune responses. Nevertheless, to generate robust and long-lived immune responses, a well-designed nanovaccine should consider different locations of TLRs on DCs and co-deliver both antigens and TLR agonist combinations to synergistically induce optimal antitumor immunity. Herein, we fabricated lipid-polymer hybrid nanoparticles (LPNPs) to spatio-temporally deliver model antigen ovalbumin (OVA) on the surface of the lipid layer, TLR4 agonist monophosphoryl lipid A (MPLA) within the lipid layer, and TLR7 agonist imiquimod (IMQ) in the polymer core to synergistically activate DCs by both extra- and intra-cellular TLRs for enhancing adaptive immune responses. LPNPs-based nanovaccines exhibited a narrow size distribution at the mean diameter of 133.23 nm and zeta potential of -2.36 mV, showed a high OVA loading (around 70.83 μg/mg) and IMQ encapsulation efficiency (88.04%). Our data revealed that LPNPs-based nanovaccines showed great biocompatibility to immune cells and an excellent ability to enhance antigen internalization, thereby promoting DCs maturation and cytokines production. Compared to Free OVA, OVA-LPNPs promoted antigen uptake, lysosome escape, depot effect and migration to secondary lymphatic organs. In vivo immunization showed that IMQ-MPLA-OVA-LPNPs with dual agonists induced more powerful cellular and humoral immune responses. Moreover, prophylactic vaccination by IMQ-MPLA-OVA-LPNPs effectively suppressed tumor growth and increased survival efficacy. Hence, the nanovaccines we fabricated can effectively co-deliver antigens and different TLR agonists and realize coordinated stimulation of DCs in a spatio-temporal manner for enhanced immune responses, which provides a promising strategy for cancer immunotherapy.

Regulatory Effect of JAK2/STAT3 on the Immune Function of Endotoxin-tolerant Dendritic Cells and its Involvement in Acute Liver Failure

BACKGROUND AND AIMS

Acute liver failure (ALF) is a potentially fatal clinical syndrome with no effective treatment. This study aimed to explore the role of Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway in modulating the phenotype and immune function of endotoxin-tolerant dendritic cells (ETDCs). In addition, we explored the use of EDTCs in an experimental model of ALF and investigated the associated mechanisms.

METHODS

In the in vitro experiment, ETDCs were transfected with adenovirus to induce SOCS1+/+ETDCs and SOCS1-/-ETDCs. Thereafter, costimulatory molecules and mixed lymphocyte reaction were assessed. Experimental mice were randomly divided into normal control, ALF, ALF+mock-ETDCs, ALF+SOCS1+/+ETDCs, ALF+AG490, and ALF+AG490+SOCS1+/+ETDCs groups. We examined the therapeutic effect of adoptive cellular immunotherapy by tail-vein injection of target ETDCs 12 h before ALF modeling. AG490, a JAK2/STAT3 inhibitor, was used in the in vivo experiment to further explore the protective mechanism of SOCS1+/+ETDCs.

RESULTS

Compared with control ETDCs, SOCS1+/+ETDCs had lower expression of costimulatory molecules, weaker allostimulatory ability, lower levels of IL-6 and TNF-α expression and higher IL-10 secretion. SOCS1-/-ETDCs showed the opposite results. In the in vivo experiments, the ALF+SOCS1+/+ETDCs and ALF+AG490+SOCS1+/+ETDCs groups showed less pathological damage and suppressed activation of JAK2/STAT3 pathway. The changes were more pronounced in the ALF+AG490+SOCS1+/+ETDCs group. Infusion of SOCS1+/+ETDCs had a protective effect against ALF possibly via inhibition of JAK2 and STAT3 phosphorylation.

CONCLUSIONS

The SOCS1 gene had an important role in induction of endotoxin tolerance. SOCS1+/+ETDCs alleviated lipopolysaccharide/D-galactosamine-induced ALF by downregulating the JAK2/STAT3 signaling pathway.

Glycoconjugates: Synthesis, Functional Studies, and Therapeutic Developments

Glycoconjugates are major constituents of mammalian cells that are formed via covalent conjugation of carbohydrates to other biomolecules like proteins and lipids and often expressed on the cell surfaces. Among the three major classes of glycoconjugates, proteoglycans and glycoproteins contain glycans linked to the protein backbone via amino acid residues such as Asn for N-linked glycans and Ser/Thr for O-linked glycans. In glycolipids, glycans are linked to a lipid component such as glycerol, polyisoprenyl pyrophosphate, fatty acid ester, or sphingolipid. Recently, glycoconjugates have become better structurally defined and biosynthetically understood, especially those associated with human diseases, and are accessible to new drug, diagnostic, and therapeutic developments. This review describes the status and new advances in the biological study and therapeutic applications of natural and synthetic glycoconjugates, including proteoglycans, glycoproteins, and glycolipids. The scope, limitations, and novel methodologies in the synthesis and clinical development of glycoconjugates including vaccines, glyco-remodeled antibodies, glycan-based adjuvants, glycan-specific receptor-mediated drug delivery platforms, etc., and their future prospectus are discussed.

Erythropoietin mediates re-programming of endotoxin-tolerant macrophages through PI3K/AKT signaling and protects mice against secondary infection

Initial lipopolysaccharide (LPS) exposure leads to a hypo-responsive state by macrophages to a secondary stimulation of LPS, known as endotoxin tolerance. However, recent findings show that functions of endotoxin-tolerant macrophages are not completely suppressed, whereas they undergo a functional re-programming process with upregulation of a panel of molecules leading to enhanced protective functions including antimicrobial and tissue-remodeling activities. However, the underlying molecular mechanisms are still elusive. Erythropoietin (EPO), a glycoprotein regulated by hypoxia-inducible factor 1α (HIF-1α), exerts anti-inflammatory and tissue-protective activities. Nevertheless, the potential effects of EPO on functional re-programming of endotoxin-tolerant macrophages have not been investigated yet. Here, we found that initial LPS exposure led to upregulation of HIF-1α/EPO in macrophages and that EPO enhanced tolerance in tolerized macrophages and mice as demonstrated by suppressed proinflammatory genes such as Il1b, Il6, and Tnfa after secondary LPS stimulation. Moreover, we showed that EPO improved host protective genes in endotoxin-tolerant macrophages and mice, such as the anti-bacterial genes coding for cathelicidin-related antimicrobial peptide (Cnlp) and macrophage receptor with collagenous structure (Marco), and the tissue-repairing gene vascular endothelial growth factor C (Vegfc). Therefore, our findings indicate that EPO mediates the functional re-programming of endotoxin-tolerant macrophages. Mechanistically, we found that PI3K/AKT signaling contributed to EPO-mediated re-programming through upregulation of Irak3 and Wdr5 expression. Specifically, IL-1 receptor-associated kinase 3 (IRAK3) was responsible for inhibiting proinflammatory genes Il1b, Il6, and Tnfa in tolerized macrophages after LPS rechallenge, whereas WDR5 contributed to the upregulation of host beneficial genes including Cnlp, Marco, and Vegfc. In a septic model of mice, EPO pretreatment significantly promoted endotoxin-tolerant re-programming, alleviated lung injury, enhanced bacterial clearance, and decreased mortality in LPS-tolerized mice after secondary infection of Escherichia coli. Collectively, our results reveal a novel role for EPO in mediating functional re-programming of endotoxin-tolerant macrophages; thus, targeting EPO appears to be a new therapeutic option in sepsis and other inflammatory disorders.

Design of Multi-Epitope Vaccine for Staphylococcus saprophyticus: Pan-Genome and Reverse Vaccinology Approach

Staphylococcus saprophyticus is a Gram-positive coccus responsible for the occurrence of cystitis in sexually active, young females. While effective antibiotics against this organism exist, resistant strains are on the rise. Therefore, prevention via vaccines appears to be a viable solution to address this problem. In comparison to traditional techniques of vaccine design, computationally aided vaccine development demonstrates marked specificity, efficiency, stability, and safety. In the present study, a novel, multi-epitope vaccine construct was developed against S. saprophyticus by targeting fully sequenced proteomes of its five different strains, which were examined using a pangenome and subtractive proteomic strategy to characterize prospective vaccination targets. The three immunogenic vaccine targets which were utilized to map the probable immune epitopes were verified by annotating the entire proteome. The predicted epitopes were further screened on the basis of antigenicity, allergenicity, water solubility, toxicity, virulence, and binding affinity towards the DRB*0101 allele, resulting in 11 potential epitopes, i.e., DLKKQKEKL, NKDLKKQKE, QDKLKDKSD, NVMDNKDLE, TSGTPDSQA, NANSDGSSS, GSDSSSSNN, DSSSSNNDS, DSSSSDRNN, SSSDRNNGD, and SSDDKSKDS. All these epitopes have the efficacy to cover 99.74% of populations globally. Finally, shortlisted epitopes were joined together with linkers and three different adjuvants to find the most stable and immunogenic vaccine construct. The top-ranked vaccine construct was further scrutinized on the basis of its physicochemical characterization and immunological profile. The non-allergenic and antigenic features of modeled vaccine constructs were initially validated and then subjected to docking with immune receptor major histocompatibility complex I and II (MHC-I and II), resulting in strong contact. In silico cloning validations yielded a codon adaptation index (CAI) value of 1 and an ideal percentage of GC contents (46.717%), indicating a putative expression of the vaccine in E. coli. Furthermore, immune simulation demonstrated that, after injecting the proposed MEVC, powerful antibodies were produced, resulting in the sharpest peaks of IgM + IgG formation (>11,500) within 5 to 15 days. Experimental testing against S. saprophyticus can evaluate the safety and efficacy of these prophylactic vaccination designs.

A Potential Interplay between HDLs and Adiponectin in Promoting Endothelial Dysfunction in Obesity

Obesity is an epidemic public health problem that has progressively worsened in recent decades and is associated with low-grade chronic inflammation (LGCI) in metabolic tissues and an increased risk of several diseases. In particular, LGCI alters metabolism and increases cardiovascular risk by impairing endothelial function and altering the functions of adiponectin and high-density lipoproteins (HDLs). Adiponectin is an adipokine involved in regulating energy metabolism and body composition. Serum adiponectin levels are reduced in obese individuals and negatively correlate with chronic sub-clinical inflammatory markers. HDLs are a heterogeneous and complex class of lipoproteins that can be dysfunctional in obesity. Adiponectin and HDLs are strictly interdependent, and the maintenance of their interplay is essential for vascular function. Since such a complex network of interactions is still overlooked in clinical settings, this review aims to highlight the mechanisms involved in the impairment of the HDLs/adiponectin axis in obese patients to predict the risk of cardiovascular diseases and activate preventive countermeasures. Here, we provide a narrative review of the role of LGCI in altering HDLs, adiponectin and endothelial functions in obesity to encourage new studies about their synergic effects on cardiovascular health and disease.

Possible Mechanisms Underlying the Effects of Glucagon-Like Peptide-1 Receptor Agonist on Cocaine Use Disorder

Cocaine use disorder (CUD) is a major public health challenge with a high relapse rate and lack of effective pharmacotherapies; therefore, there is a substantial need to identify novel medications to treat this epidemic. Since the advent of glucagon-like peptide-1 (GLP-1) receptors (GLP-1Rs) agonists (GLP-1RAs), their potential has been extensively explored and expanded. In this review, we first summarized the biological effects of GLP-1, GLP-1Rs, and GLP-1RAs. Subsequently, the recent literature examining the behavioral effects and the possible pharmacological mechanisms of GLP-1RAs on CUD was reviewed. Increasing preclinical evidence suggests that GLP-1RAs are promising in regulating dopamine release, dopamine transporter (DAT) surface expression and function, mesolimbic reward system and GABAergic neurons, and maladaptive behaviors in animal models of self-administration and conditioned place preference. In addition, the emerging role of GLP-1RAs in inhibiting inflammatory cytokines was reported. These findings indicate that GLP-1RAs perform essential functions in the modulation of cocaine-seeking and cocaine-taking behaviors likely through multifaceted mechanisms. Although the current preclinical evidence provides convincing evidence to support GLP-1RA as a promising pharmacotherapy for CUD, other questions concerning clinical availability, impact and specific mechanisms remain to be addressed in further studies.

Neuron–Microglia Contacts Govern the PGE2 Tolerance through TLR4-Mediated de Novo Protein Synthesis

Cellular and molecular mechanisms of the peripheral immune system (e.g., macrophage and monocyte) in programming endotoxin tolerance (ET) have been well studied. However, regulatory mechanism in development of brain immune tolerance remains unclear. The inducible COX-2/PGE₂ axis in microglia, the primary innate immune cells of the brain, is a pivotal feature in causing inflammation and neuronal injury, both in acute excitotoxic insults and chronic neurodegenerative diseases. This present study investigated the regulatory mechanism of PGE₂ tolerance in microglia. Multiple reconstituted primary brain cells cultures, including neuron–glial (NG), mixed glial (MG), neuron-enriched, and microglia-enriched cultures, were performed and consequently applied to a treatment regimen for ET induction. Our results revealed that the levels of COX-2 mRNA and supernatant PGE₂ in NG cultures, but not in microglia-enriched and MG cultures, were drastically reduced in response to the ET challenge, suggesting that the presence of neurons, rather than astroglia, is required for PGE₂ tolerance in microglia. Furthermore, our data showed that neural contact, instead of its soluble factors, is sufficient for developing microglial PGE₂ tolerance. Simultaneously, this finding determined how neurons regulated microglial PGE₂ tolerance. Moreover, by inhibiting TLR4 activation and de novo protein synthesis by LPS-binding protein (LBP) manipulation and cycloheximide, our data showed that the TLR4 signal and de novo protein synthesis are necessary for microglia to develop PGE₂ tolerance in NG cells under the ET challenge. Altogether, our findings demonstrated that neuron–microglia contacts are indispensable in emerging PGE₂ tolerance through the regulation of TLR4-mediated de novo protein synthesis.

Induction of Endotoxin Tolerance Delays Acute Rejection in a Hindlimb Transplantation Model in Rats

BACKGROUND

Acute rejection is seen in 85 percent of composite vascular allogeneic transplants despite long-term immunosuppression. Recently, it was reported that the induction of endotoxin tolerance prolonged heart allograft survival in mice. However, it produced side effects in all the animals secondary to the inflammatory reaction. Galactomannan has shown endotoxin tolerance without this side effect in vitro. The authors hypothesized that galactomannan-induced endotoxin tolerance delays acute rejection in vascular allogeneic transplantation without the side effects produced by lipopolysaccharide.

METHODS

Twenty-four rat hindlimb transplants were divided into four groups according to the preconditioning received: control, lipopolysaccharide (0.16 ml/kg), galactomannan 72 hours before (galactomannan-72) (8 ml/kg), and galactomannan 24 hours before (galactomannan-24) (8 ml/kg). Median acute rejection time, weight loss, and diarrheal episodes were monitored. Blood samples were collected at 0, 7, 21, 30, 45, and 60 days. Plasma cytokines (i.e., tumor necrosis factor alpha, interferon gamma), peripheral chimerism, and lymphocyte percentages were analyzed.

RESULTS

Median allograft survival was 40 days (range, 40 to 44 days) in the control group, 68 days (range, 61 to 71 days) in the lipopolysaccharide group, and 70 days (range, 69 to 73 days) in both galactomannan groups (p = 0.001). Weight loss was higher in the lipopolysaccharide group (p < 0.001), as was the 83.3 percent rate of diarrheal episodes (control, 0 percent, p = 0.015; galactomannan-72, 0 percent, p = 0.015; and galactomannan-24, 16.7 percent, p = 0.02). Preconditioned rats had higher peripheral blood chimerism (lipopolysaccharide, 2.30 ± 0.13 percent; galactomannan-72, 2.63 ±1.46 percent; and galactomannan-24, 2.47 ± 0.19 percent) compared to the control group (2.06 ± 0.36 percent) (lipopolysaccharide, p = 0.04; galactomannan-72, p = 0.002; and galactomannan-24, p = 0.002).

CONCLUSIONS

Induction of endotoxin tolerance delays acute rejection in the rat hindlimb transplantation model. Galactomannan preconditioning has no lipopolysaccharide side effects and was equally effective in delaying acute rejection.

CLINICAL RELEVANCE STATEMENT

The contributions of this experimental work are very incipient. Although the use of galactomannan in clinical practice requires more studies to assess its safety, there is no doubt that immunomodulation may be one of the responses that solve the problem of long-term immunosuppression.

Nanoflow LC-MS Method Allowing In-Depth Characterization of Natural Heterogeneity of Complex Bacterial Lipopolysaccharides

The variable modification of the outer membrane lipopolysaccharide (LPS) in Gram-negative bacteria contributes to bacterial pathogenesis through various mechanisms, including the development of antibiotic resistance and evasion of the immune response of the host. Characterizing the natural structural repertoire of LPS is challenging due to the high heterogeneity, branched architecture, and strong amphipathic character of these glycolipids. To address this problem, we have developed a method enabling the separation and structural profiling of complex intact LPS mixtures by using nanoflow reversed-phase high-performance liquid chromatography (nLC) coupled to electrospray ionization Fourier transform mass spectrometry (ESI-FT-MSⁿ). Nanogram quantities of rough-type LPS mixtures from Neisseria meningitidis could be separated and analyzed by nLC-ESI-FT-MS. Furthermore, the method enabled the analysis of highly heterogeneous smooth (S)-type LPS from pathogenic enteric bacteria such as Salmonella enterica serotype Typhimurium and Escherichia coli serotype O111:B4. High-resolution, accurate mass spectra of intact LPS containing various lengths of the O-specific polysaccharide in the range of 3 and 15 kDa were obtained. In addition, MS/MS experiments with collision-induced dissociation of intact LPS provided detailed information on the composition of oligo/polysaccharides and lipid A domains of single S-type LPS species. The structural heterogeneity of S-type LPS was characterized by unprecedented details. Our results demonstrate that nLC-ESI-FT-MSⁿ is an attractive strategy for the structural profiling of small quantities of complex bacterial LPS mixtures in their intact form.

TLRs in COVID-19: How they drive immunopathology and the rationale for modulation

COVID-19 is both a viral illness and a disease of immunopathology. Proximal events within the innate immune system drive the balance between deleterious inflammation and viral clearance. We hypothesize that a divergence between the generation of excessive inflammation through over activation of the TLR associated myeloid differentiation primary response (MyD88) pathway relative to the TIR-domain-containing adaptor-inducing IFN-β (TRIF) pathway plays a key role in COVID-19 severity. Both viral elements and damage associated host molecules act as TLR ligands in this process. In this review, we detail the mechanism for this imbalance in COVID-19 based on available evidence, and we discuss how modulation of critical elements may be important in reducing severity of disease.

Immunotherapeutic Role of NOD-2 and TLR-4 Signaling as an Adjunct to Antituberculosis Chemotherapy

Tuberculosis (TB) treatment is lengthy and inflicted with severe side-effects. Here, we attempted a novel strategy to reinforce host immunity through NOD-like receptor (NOD-2) and Toll-like receptor (TLR-4) signaling in the murine model of TB. Intriguingly, we noticed that it not only bolstered the immunity but also reduced the dose and duration of rifampicin and isoniazid therapy. Further, we observed expansion in the pool of effector (CD44^hi, CD62L^lo, CD127^hi) and central (CD44^hi, CD62L^hi, CD127^hi) memory CD4 T cells and CD8 T cells and increased the intracellular killing of Mycobacterium tuberculosis (Mtb) by activated dendritic cells [CD86^hi, CD40^hi, IL-6^hi, IL-12^hi, TNF-α^hi, nitric oxide (NO)^hi] with significant reduction in Mtb load in the lungs and spleen of infected animals. We infer that the signaling through NOD-2 and TLR-4 may be an important approach to reduce the dose and duration of the drugs to treat TB.

Two Faces of Macrophages: Training and Tolerance

Macrophages are present in almost all body tissues. They detect and quickly respond to “environmental signals” in the tissue. Macrophages have been associated with numerous beneficial roles, such as host defense, wound healing, and tissue regeneration; however, they have also been linked to the development of diverse illnesses, particularly cancers and autoimmune disorders. Complex signaling, epigenetic, and metabolic pathways drive macrophage training and tolerance. The induced intracellular program differs depending on the type of initial stimuli and the tissue microenvironment. Due to the essential roles of macrophages in homeostatic and their association with the pathogenesis of inflammatory diseases, recent studies have investigated the molecular mechanisms of macrophage training and tolerance. This review discusses the role of factors involved in macrophage training and tolerance, along with the current studies in human diseases.

Case of acute onset ataxia caused by Klebsiella pneumoniae sepsis with the appearance of anti-GD1b antibody

Various disorders can cause acute onset ataxia including those that have toxic/metabolic, traumatic, neoplastic, vascular, demyelinating/dysmyelinating, infectious, postinfectious and genetic features. We present a case of postseptic acute ataxia. A 72-year-old woman was diagnosed with septic shock secondary to acute obstructive suppurative cholangitis. A blood sample for bacterial culture was positive for Klebsiella pneumoniae Thus, we initiated antibiotics and intravenous immunoglobulin therapies to control the infection. We later added extracorporeal endotoxin removal with a polymyxin B immobilised fibre cartridge for endotoxin shock. The patient's condition improved soon after endotoxin removal. Mildly slurred and explosive speech with limb and truncal ataxia, which improved gradually, developed shortly afterwards. Serum samples obtained on day 15 after admission were positive for anti-GD1b IgG antibody. The clinical course of monophasic illness with good recovery, neurological findings and the appearance of anti-GD1b antibody suggest that this case is a variant of Miller-Fisher syndrome.

Cumulative Signaling Through NOD-2 and TLR-4 Eliminates the Mycobacterium Tuberculosis Concealed Inside the Mesenchymal Stem Cells

For a long time, tuberculosis (TB) has been inflicting mankind with the highest morbidity and mortality. Although the current treatment is extremely potent, a few bacilli can still hide inside the host mesenchymal stem cells (MSC). The functional capabilities of MSCs are known to be modulated by TLRs, NOD-2, and RIG-1 signaling. Therefore, we hypothesize that modulating the MSC activity through TLR-4 and NOD-2 can be an attractive immunotherapeutic strategy to eliminate the Mtb hiding inside these cells. In our current study, we observed that MSC stimulated through TLR-4 and NOD-2 (N2.T4) i) activated MSC and augmented the secretion of pro-inflammatory cytokines; ii) co-localized Mtb in the lysosomes; iii) induced autophagy; iv) enhanced NF-κB activity via p38 MAPK signaling pathway; and v) significantly reduced the intracellular survival of Mtb in the MSC. Overall, the results suggest that the triggering through N2.T4 can be a future method of immunotherapy to eliminate the Mtb concealed inside the MSC.

Natural and synthetic carbohydrate-based vaccine adjuvants and their mechanisms of action

Modern subunit vaccines based on homogeneous antigens offer more precise targeting and improved safety compared with traditional whole-pathogen vaccines. However, they are also less immunogenic and require an adjuvant to increase the immunogenicity of the antigen and potentiate the immune response. Unfortunately, few adjuvants have sufficient potency and low enough toxicity for clinical use, highlighting the urgent need for new, potent and safe adjuvants. Notably, a number of natural and synthetic carbohydrate structures have been used as adjuvants in clinical trials, and two have recently been approved in human vaccines. However, naturally derived carbohydrate adjuvants are heterogeneous, difficult to obtain and, in some cases, unstable. In addition, their molecular mechanisms of action are generally not fully understood, partly owing to the lack of tools to elucidate their immune-potentiating effects, thus hampering the rational development of optimized adjuvants. To address these challenges, modification of the natural product structure using synthetic chemistry emerges as an attractive approach to develop well-defined, improved carbohydrate-containing adjuvants and chemical probes for mechanistic investigation. This Review describes selected examples of natural and synthetic carbohydrate-based adjuvants and their application in synthetic self-adjuvanting vaccines, while also discussing current understanding of their molecular mechanisms of action.

Lipopolysaccharide directly inhibits bicarbonate absorption by the renal outer medullary collecting duct

Acidosis is associated with E. coli induced pyelonephritis but whether bacterial cell wall constituents inhibit HCO₃ transport in the outer medullary collecting duct from the inner stripe (OMCDi) is not known. We examined the effect of lipopolysaccharide (LPS), on HCO₃ absorption in isolated perfused rabbit OMCDi. LPS caused a ~ 40% decrease in HCO₃ absorption, providing a mechanism for E. coli pyelonephritis-induced acidosis. Monophosphoryl lipid A (MPLA), a detoxified TLR4 agonist, and Wortmannin, a phosphoinositide 3-kinase inhibitor, prevented the LPS-mediated decrease, demonstrating the role of TLR4-PI3-kinase signaling and providing proof-of-concept for therapeutic interventions aimed at ameliorating OMCDi dysfunction and pyelonephritis-induced acidosis.

Commensal Microbiota Modulation of Natural Resistance to Virus Infection

Interferon (IFN)-Is are crucial mediators of antiviral immunity and homeostatic immune system regulation. However, the source of IFN-I signaling under homeostatic conditions is unclear. We discovered that commensal microbes regulate the IFN-I response through induction of IFN-β by colonic DCs. Moreover, the mechanism by which a specific commensal microbe induces IFN-β was identified. Outer membrane (OM)-associated glycolipids of gut commensal microbes belonging to the Bacteroidetes phylum induce expression of IFN-β. Using Bacteroides fragilis and its OM-associated polysaccharide A, we determined that IFN-β expression was induced via TLR4-TRIF signaling. Antiviral activity of this purified microbial molecule against infection with either vesicular stomatitis virus (VSV) or influenza was demonstrated to be dependent on the induction of IFN-β. In a murine VSV infection model, commensal-induced IFN-β regulated natural resistance to virus infection. Due to the physiological importance of IFN-Is, discovery of an IFN-β-inducing microbial molecule represents a potential approach for the treatment of some human diseases.

Deciphering heterogeneity of septic shock patients using immune functional assays: a proof of concept study

The complexity of sepsis pathophysiology hinders patient management and therapeutic decisions. In this proof-of-concept study we characterised the underlying host immune response alterations using a standardised immune functional assay (IFA) in order to stratify a sepsis population. In septic shock patients, ex vivo LPS and SEB stimulations modulated, respectively, 5.3% (1/19) and 57.1% (12/21) of the pathways modulated in healthy volunteers (HV), highlighting deeper alterations induced by LPS than by SEB. SEB-based clustering, identified 3 severity-based groups of septic patients significantly different regarding mHLA-DR expression and TNFα level post-LPS, as well as 28-day mortality, and nosocomial infections. Combining the results from two independent cohorts gathering 20 HV and 60 patients, 1 cluster grouped all HV with 12% of patients. The second cluster grouped 42% of patients and contained all non-survivors. The third cluster grouped 46% of patients, including 78% of those with nosocomial infections. The molecular features of these clusters indicated a distinctive contribution of previously described genes defining a “healthy-immune response” and a “sepsis-related host response”. The third cluster was characterised by potential immune recovery that underlines the possible added value of SEB-based IFA to capture the sepsis immune response and contribute to personalised management.