Low dose LPS does not increase TLR4 expression on monocytes in a human in vivo model

Exposure to normobaric hypoxia shapes the acute inflammatory response in human whole blood cells in vivo

Cells of the immune defence, especially leukocytes, often have to perform their function in tissue areas that are characterized by oxygen deficiency, so-called hypoxia. Physiological hypoxia significantly affects leukocyte function and controls the innate and adaptive immune response mainly through transcriptional gene regulation via the hypoxia-inducible factors (HIFs). Multiple pathogens including components of bacteria, such as lipopolysaccharides (LPS) trigger the activation of leukocytes. HIF pathway activation enables immune cells to adapt to both hypoxic environments in physiological and inflammatory settings and modulates immune cell responses through metabolism changes and crosstalk with other immune-relevant signalling pathways. To study the mutual influence of both processes in vivo, we used a human endotoxemia model, challenging participants with an intravenous LPS injection post or prior to a 4-h stay in a hypoxic chamber with normobaric hypoxia of 10.5% oxygen. We analysed changes in gene expression in whole blood cells and determined inflammatory markers to unveil the crosstalk between both processes. Our investigations showed differentially altered gene expression patterns of HIF and target genes upon in vivo treatment with LPS and hypoxia. Further, we found evidence for effects of hypoxic priming upon inflammation in combination with immunomodulatory effects in whole blood cells in vivo. Our work elucidates the complex interplay of hypoxic and inflammatory HIF regulation in human immune cells and offers new perspectives for further clinical research.

Endotoxin Translocation Is Increased in Broiler Chickens Fed a Fusarium Mycotoxin-Contaminated Diet

Broiler chickens in livestock production face numerous challenges that can impact their health and welfare, including mycotoxin contamination and heat stress. In this study, we aimed to investigate the combined effects of two mycotoxins, deoxynivalenol (DON) and fumonisins (FBs), along with short-term heat stress conditions, on broiler gut health and endotoxin translocation. An experiment was conducted to assess the impacts of mycotoxin exposure on broilers, focusing on intestinal endotoxin activity, gene expression related to gut barrier function and inflammation, and the plasma concentration of the endotoxin marker 3-OH C14:0 either at thermoneutral conditions or short-term heat stress conditions. Independently of heat stress, broilers fed DON-contaminated diets exhibited reduced body weight gain during the starter phase (Day 1-12) compared to the control group, while broilers fed FB-contaminated diets experienced decreased body weight gain throughout the entire trial period (Day 1-24). Furthermore, under thermoneutral conditions, broilers fed DON-contaminated diets showed an increase in 3-OH C14:0 concentration in the plasma. Moreover, under heat stress conditions, the expression of genes related to gut barrier function (Claudin 5, Zonulin 1 and 2) and inflammation (Toll-like receptor 4, Interleukin-1 beta, Interleukin-6) was significantly affected by diets contaminated with mycotoxins, depending on the gut segment. This effect was particularly prominent in broilers fed diets contaminated with FBs. Notably, the plasma concentration of 3-OH C14:0 increased in broilers exposed to both DON- and FB-contaminated diets under heat stress conditions. These findings shed light on the intricate interactions between mycotoxins, heat stress, gut health, and endotoxin translocation in broiler chickens, highlighting the importance of understanding these interactions for the development of effective management strategies in livestock production to enhance broiler health and welfare.

The BCG Moreau Vaccine Upregulates In Vitro the Expression of TLR4, B7-1, Dectin-1 and EP2 on Human Monocytes

Background: Tuberculosis (TB) is currently the second greatest killer worldwide and is caused by a single infectious agent. Since Bacillus Calmette−Guérin (BCG) is the only vaccine currently in use against TB, studies addressing the protective role of BCG in the context of inducible surface biomarkers are urgently required for TB control. Methods: In this study, groups of HIV-negative adult healthy donors (HD; n = 22) and neonate samples (UCB; n = 48) were voluntarily enrolled. The BCG Moreau strain was used for the in vitro mononuclear cell infections. Subsequently, phenotyping tools were used for surface biomarker detection. Monocytes were assayed for TLR4, B7-1, Dectin-1, EP2, and TIM-3 expression levels. Results: At 48 h, the BCG Moreau induced the highest TLR4, B7-1, and Dectin-1 levels in the HD group only (p-value < 0.05). TIM-3 expression failed to be modulated after BCG infection. At 72 h, BCG Moreau equally induced the highest EP2 levels in the HD group (p-value < 0.005), and higher levels were also found in HD when compared with the UCB group (p-value < 0.05). Conclusions: This study uncovers critical roles for biomarkers after the instruction of host monocyte activation patterns. Understanding the regulation of human innate immune responses is critical for vaccine development and for treating infectious diseases.

Effect of Lipopolysaccharides (LPS) and Lipoteichoic Acid (LTA) on the Inflammatory Response in Rumen Epithelial Cells (REC) and the Impact of LPS on Claw Explants

Simple Summary

Endotoxins, often referred to as lipopolysaccharides (LPS), are bacterial toxins and play an essential role in several diseases in ruminants. One of the most common disorders in dairy cows, sub-acute rumen acidosis (SARA), is associated with a substantial increase of ruminal and intestinal endotoxin load. Other potentially harmful substances, e.g., lipoteichoic acid (LTA), derived from the cell wall of Gram-positive bacteria, might play an essential role during SARA as well. Besides the potential local effect of LPS, translocation to the blood can induce a strong immune response in cattle. Furthermore, LPS might reach the claw tissue after translocation. In our study, we used a cell culture model with epithelial cells isolated from rumen tissue to assess the effects of LPS and LTA. Furthermore, we evaluated the effects of LPS on claw tissue with an explant model. LPS and LTA could induce an inflammatory response in rumen epithelial cells. However, the effect of LPS was more substantial and seen at an earlier time point compared to LTA. Furthermore, in claw explants, LPS negatively affected the separation force, an indicator for tissue integrity, which decreased with increasing LPS concentrations. Overall, our data suggest that especially endotoxins can impact local inflammatory response in the rumen. Furthermore, if endotoxins reach the claw tissue, it might affect claw health.

Abstract

Endotoxins play a crucial role in ruminant health due to their deleterious effects on animal health. The study aimed to evaluate whether LPS and LTA can induce an inflammatory response in rumen epithelial cells. For this purpose, epithelial cells isolated from rumen tissue (REC) were stimulated with LPS and LTA for 1, 2, 4, and 24 h. Thereafter, the expression of selected genes of the LPS and LTA pathway and inflammatory response were evaluated. Furthermore, it was assessed whether LPS affects inflammatory response and structural integrity of claw explants. Therefore, claw explants were incubated with LPS for 4 h to assess the expression of selected genes and for 24 h to evaluate tissue integrity via separation force. LPS strongly affected the expression of genes related to inflammation (NFkB, TNF-α, IL1B, IL6, CXCL8, MMP9) in REC. LTA induced a delayed and weaker inflammatory response than LPS. In claw explants, LPS affected tissue integrity, as there was a concentration-dependent decrease of separation force. Incubation time had a strong effect on inflammatory genes in claw explants. Our data suggest that endotoxins can induce a local inflammatory response in the rumen epithelium. Furthermore, translocation of LPS might negatively impact claw health.

Comparing the protective effects of resveratrol, curcumin and sulforaphane against LPS/IFN-γ-mediated inflammation in doxorubicin-treated macrophages

Doxorubicin (DOX) chemotherapy is associated with the release of inflammatory cytokines from macrophages. This has been suggested to be, in part, due to DOX-mediated leakage of endotoxins from gut microflora, which activate Toll-like receptor 4 (TLR4) signaling in macrophages, causing severe inflammation. However, the direct function of DOX on macrophages is still unknown. In the present study, we tested the hypothesis that DOX alone is incapable of stimulating inflammatory response in macrophages. Then, we compared the anti-inflammatory effects of curcumin (CUR), resveratrol (RES) and sulforaphane (SFN) against lipopolysaccharide/interferon-gamma (LPS/IFN-γ)-mediated inflammation in the absence or presence of DOX. For this purpose, RAW 264.7 cells were stimulated with LPS/IFN-γ (10 ng/mL/10 U/mL) in the absence or presence of DOX (0.1 µM). Our results showed that DOX alone is incapable of stimulating an inflammatory response in RAW 264.7 macrophages. Furthermore, after 24 h of incubation with LPS/IFN-γ, a significant increase in tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS) mRNA levels was observed. Similarly, nitric oxide (NO) production and TNF-α and IL-6 protein levels were significantly upregulated. Moreover, in LPS/IFN-γ-treated macrophages, the microRNAs (miRNAs) miR-146a, miR-155, and miR-21 were significantly overexpressed. Interestingly, upon testing CUR, RES, and SFN against LPS/IFN-γ-mediated inflammation, only SFN was able to significantly reverse the LPS/IFN-γ-mediated induction of iNOS, TNF-α and IL-6 and attenuate miR-146a and miR-155 levels. In conclusion, SFN, at the transcriptional and posttranscriptional levels, exhibits potent immunomodulatory action against LPS/IFN-γ-stimulated macrophages, which may indicate SFN as a potential treatment for DOX-associated inflammation.

Euxanthone inhibits traumatic spinal cord injury via anti-oxidative stress and suppression of p38 and PI3K/Akt signaling pathway in a rat model

BACKGROUND

Owing to neurite promoting, antioxidant and anti-inflammatory effects of Euxanthone (Eux), the investigation was aimed to probe the neuroprotective efficacy of Eux against traumatic spinal cord injury (t-SCI) in rats and whether Eux can improve neuropathic function in t-SCI.

METHOD

Sprague-Dawley (SD) rats were randomized in - Sham, t-SCI, Eux30, and Eux60 (t-SCI + 30 and 60 mg/kg respectively). Animals with compression force-induced t-SCI were subjected to estimation of locomotor functions. Spinal cord water content and Evans blue (EB) effusion were determined for quantifying edema and intactness of the spinal cord. Oxidative stress and immunochemical markers were quantified by ELISA and western blotting.

RESULTS

Findings revealed that Eux60 group animals had greater Basso, Beattie, and Bresnahan (BBB) and (incline plane test) IPT score indicating improved locomotor functions. There was a reduction in the spinal edema and water content after Eux treatment, together with lowering of oxidative stress markers. The expression of IL-6, IL-12, IL-1β, caspase-3, RANKL, TLR4, NF-κB, p-38, PI3K, and Akt in spinal cord tissues of t-SCI-induced rats was lowered after Eux treatment.

CONCLUSION

Overall, the investigation advocates that Eux attenuates t-SCI and associated inflammation, oxidative damage, and resulting apoptosis via modulation of TLR4/NF-κB/p38 and PI3K/Akt signaling cascade.

Endotoxin Translocation and Gut Inflammation Are Increased in Broiler Chickens Receiving an Oral Lipopolysaccharide (LPS) Bolus during Heat Stress

Lipopolysaccharides (LPS), also termed endotoxins, are the major component of the outer membrane of Gram-negative bacteria. In general, endotoxins in the intestine are considered harmless in healthy animals. However, different stressors, such as heat stress, can lead to a compromised gut barrier, resulting in endotoxin translocation. Chickens are considered to be less sensitive to the effects of LPS compared with other species, for example, humans, pigs, or calves, probably because of the lack of the functional-specific TRAM-TRIF signalling pathway (MyD88-independent). Therefore, six LPS preparations (three different strains with two different preparation methods each) were compared in murine macrophages and characterized according to their MyD88-dependent pathway activation. All tested LPS preparations induced a strong inflammatory response after 4 and 24 h on a murine macrophage cell line. However, there was a similar strong response in the gene expression profile as well as production of nitrite oxide and TNF-alpha from LPS of different strains and preparation methods. On the basis of the results of the in vitro study, one LPS preparation was chosen for the subsequent in vivo study with broilers to assess the effect of an oral LPS bolus (E. coli O55:B5 phenol extracted; 2 mg/kg b.w.) during heat stress conditions (10 h, 36 °C). The most pronounced effects were seen in broilers receiving the oral LPS bolus during heat stress conditions. The endotoxin activity in the intestine as well as the serum concentration of the 3-OH C14 (part of LPS) were increased. In addition, an increased expression of genes related to inflammation and stress response (e.g., IL-6, IL-1beta, HSP70) was observed, whereas the expression of genes associated with gut health (e.g., MUC2, FABP2) was decreased. To conclude, an increase of intestinal LPS combined with heat stress can pose a risk to animal health.

Safety, Pharmacokinetics, and Pharmacodynamics of the TLR4 Agonist GSK1795091 in Healthy Individuals: Results from a Randomized, Double-blind, Placebo-controlled, Ascending Dose Study

PURPOSE

Interest in Toll-like receptor (TLR) agonists for cancer treatment has been renewed after promising preliminary clinical data in combination with checkpoint inhibitors. This first-in-human study assessed the safety, tolerability, and pharmacokinetic (PK) and pharmacodynamic (PD) properties of intravenous GSK1795091, a synthetic TLR4 agonist, in healthy volunteers as a precursor to evaluation in patients with cancer.

METHODS

Healthy participants were randomized (1:3; double-blinded manner) to receive placebo or a single intravenous injection of GSK1795091 at doses of 7-100 ng. The primary objective was to evaluate the safety and tolerability of GSK1795091; secondary and exploratory objectives were to characterize GSK1795091 PK and PD properties.

FINDINGS

Forty participants received study treatment (10 received placebo and 30 received GSK1795091). Overall, 3 of the 10 participants (30%) who received placebo and 16 of the 30 (53%) who received GSK1795091 experienced ≥1 adverse event (AE). The most common AEs were influenza-like illness, headache, back pain, and increased body temperature. One participant experienced late-occurring AEs (alanine aminotransferase and aspartate aminotransferase increases), considered possibly related to GSK1795091. No serious AEs were reported. GSK1795091 PK properties were characterized by dose proportional increase in exposure. Transient and dose-dependent changes in induced cytokine and chemokine concentrations and immune cell counts were observed 1-4 h after GSK1795091 administration and returned to baseline within 24 h.

IMPLICATIONS

Intravenously administered GSK1795091 was acceptably tolerated in healthy volunteers, had favorable PK properties, and stimulated immune cell changes in a dose-dependent manner, providing evidence of target engagement and downstream pharmacology. These results supported the design and initiation of a repeat-dose study of intravenous GSK1795091 in combination with other immunotherapies in patients with advanced cancer. ClinicalTrials.gov identifier: NCT02798978.

Sickle Cell Anemia Patients Display an Intricate Cellular and Serum Biomarker Network Highlighted by TCD4+CD69+ Lymphocytes, IL-17/MIP-1β, IL-12/VEGF, and IL-10/IP-10 Axis

BACKGROUND

Sickle cell anemia (SCA) is associated with a chronic proinflammatory state characterized by elevated leukocyte count, mortality from severe recurrent infections, and subsequent vasoocclusive complications with leukocyte adhesion to the endothelium and increased plasma levels of inflammatory cytokines. The immune system has a close connection with morbidity in SCA, but further studies are needed to uncover the involvement of innate and adaptive immunities in modulating the SCA physiopathology. We performed measurements of the frequency of innate and adaptive immunity cells, cytokines, chemokines, and growth factors and immunophenotyping of Toll-like receptor and adhesion molecule expression in the blood of SCA patients and healthy donors to evaluate the different profiles of these biomarkers, the relationship among them, and their correlation to laboratory records and death risk. Material and Methods. Immunophenotyping of cells, Toll-like receptors, and adhesion molecules were performed from peripheral blood samples of SCA patients and healthy donors by flow cytometry and cytokine/chemokine/growth factor measurement by the Luminex technique performed from the serum of the same subjects.

RESULTS

Cells of adaptive immunity such as IL-12, IL-17, and IL-10 cytokines; IL-8, IP-10, MIP-1α, MIP-1β, and RANTES chemokines; and VEGF, FGF-basic, and GM-CSF growth factors were higher in SCA patients than healthy donors regardless of any laboratorial and clinical condition. However, high death risk appears to have relevant biomarkers.

CONCLUSION

In the SCA pathophysiology at steady state, there is a broad immunological biomarker crosstalk highlighted by TCD4+CD69+ lymphocytes, IL-12 and IL-17 inflammatory and IL-10 regulatory cytokines, MIP-1α, MIP-1β, and IP-10 chemokines, and VEGF growth factor. High expression of TLR2 in monocytes and VLA-4 in TCD8+ lymphocytes and high levels of MIP-1β and RANTES appear to be relevant in high death risk conditions. The high reticulocytosis and high death risk conditions present common correlations, and there seems to be a balance by the Th2 profile.

Minor C allele of the SNP rs7873784 associated with rheumatoid arthritis and type-2 diabetes mellitus binds PU.1 and enhances TLR4 expression

Toll-like receptor 4 (TLR4) is an innate immunity receptor predominantly expressed on myeloid cells and involved in the development of various diseases, many of them with complex genetics. Here we present data on functionality of single nucleotide polymorphism rs7873784 located in the 3'-untranslated region (3'-UTR) of TLR4 gene and associated with various pathologies involving chronic inflammation. We demonstrate that TLR4 3'-UTR strongly enhanced the activity of TLR4 promoter in U937 human monocytic cell line while minor rs7873784(C) allele created a binding site for transcription factor PU.1 (encoded by SPI1 gene), a known regulator of TLR4 expression. Increased binding of PU.1 further augmented the TLR4 transcription while PU.1 knockdown or complete disruption of the PU.1 binding site abrogated the effect. We hypothesize that additional functional PU.1 site may increase TLR4 expression in individuals carrying minor C variant of rs7873784 and modulate the development of certain pathologies, such as rheumatoid arthritis and type-2 diabetes mellitus.

TLR4 Signaling Pathway Modulators as Potential Therapeutics in Inflammation and Sepsis

Toll-Like Receptor 4 (TLR4) signal pathway plays an important role in initiating the innate immune response and its activation by bacterial endotoxin is responsible for chronic and acute inflammatory disorders that are becoming more and more frequent in developed countries. Modulation of the TLR4 pathway is a potential strategy to specifically target these pathologies. Among the diseases caused by TLR4 abnormal activation by bacterial endotoxin, sepsis is the most dangerous one because it is a life-threatening acute system inflammatory condition that still lacks specific pharmacological treatment. Here, we review molecules at a preclinical or clinical phase of development, that are active in inhibiting the TLR4-MyD88 and TLR4-TRIF pathways in animal models. These are low-molecular weight compounds of natural and synthetic origin that can be considered leads for drug development. The results of in vivo studies in the sepsis model and the mechanisms of action of drug leads are presented and critically discussed, evidencing the differences in treatment results from rodents to humans.

Differential in vivo activation of monocyte subsets during low-grade inflammation through experimental endotoxemia in humans

Human monocytes are a heterogeneous cell population, which can be divided into a classical (CD14++CD16−), a non-classical (CD14+CD16+), and an intermediate (CD14++CD16+) subset. We hypothesized that low-grade inflammation may differentially affect monocyte subsets. We used a human lipopolysaccharide (LPS) infusion model to mimic low-grade inflammation to identify, which monocyte subsets are preferentially activated under these conditions. Monocyte subsets were identified by staining for CD14 and CD16, activation status of monocytes was analyzed by staining for CD11b and a novel in situ mRNA hybridization approach to detect IL-6 and IL-8 specific mRNA at the single-cell level by flow cytometry. After LPS challenge, cell numbers of monocyte subsets dropped after 2 h with cell numbers recovering after 6 h. Distribution of monocyte subsets was skewed dramatically towards the intermediate subset after 24 h. Furthermore, intermediate monocytes displayed the largest increase of CD11b expression after 2 h. Finally, IL-6 and IL-8 mRNA levels increased in intermediate and non-classical monocytes after 6 h whereas these mRNA levels in classical monocytes changed only marginally. In conclusion, our data indicates that the main responding subset of monocytes to standardized low-grade inflammation induced by LPS in humans is the CD14++CD16+ intermediate subset followed by the CD14+CD16+ non-classical monocyte subset. Circulating classical monocytes showed comparably less reaction to LPS challenge in vivo.

Naringin ameliorates cognitive deficits via oxidative stress, proinflammatory factors and the PPARγ signaling pathway in a type 2 diabetic rat model

Naringenin is a flavonoid polyphenolic compound, which facilitates the removal of free radicals, oxidative stress and inflammation. The present study aimed to obtain a better understanding of the effects of curcumin on the regulation of diabetes‑associated cognitive decline, and its underlying mechanisms. An experimental diabetes mellitus (DM) rat model was induced by streptozoticin (50 mg/kg). Following treatment with naringin (100 and 200 mg/kg) for 16 weeks, the body weight and blood glucose levels of the DM rats were measured. A morris water maze test was used to analyze the effects of naringin on the cognitive deficit of the DM rats. The levels of oxidative stress, proinflammatory factors, caspase‑3 and caspase‑9, and the protein expression of peroxisome proliferator‑activated receptor γ (PPARγ) were quantified in the DM rats using a commercially‑available kit and western blot assay, respectively. In addition, a GW9662 PPARγ inhibitor (0.3 mg/kg) was administered to the DM rats to determine whether PPARγ affected the effects of naringin on the cognitive deficit of the DM rats. The results demonstrated that naringin increased the body weight, blood glucose levels, and cognitive deficits of the DM rats. The levels of oxidative stress and proinflammatory factors in the naringin‑treated rats were significantly lower, compared with those of the DM rats. In addition, naringin activated the protein expression of PPARγ, and administration of the PPARγ inhibitor decreased the protein expression of PPARγ, and attenuated the effects of naringin on cognitive deficit. The results also demonstrated that naringin decreased the expression levels of caspase‑3 and caspase‑9 in the DM rats. These results suggested that naringin ameliorated cognitive deficits via oxidative stress, proinflammatory factors and the PPARγ signaling pathway in the type 2 diabetic rat model. Furthermore, oxidative stress, proinflammatory factors and PPARγ signaling may be involved in mediating these effects.

Receptors involved in cell activation by antiphospholipid antibodies

The antiphospholipid syndrome (APS) is an autoimmune disease associated with arterial or venous thrombosis and/or recurrent fetal loss and is caused by pathogenic antiphospholipid antibodies (aPLA). The plasma protein β2-glycoprotein 1 (β2GP1) has been identified as a major target of aPLA associated with APS. Cell activation by aPLA appears to be a major pathogenic cause in the pathogenesis of APS. Receptors, co-receptors and accessory molecules are known to assist the pathogenic effects of aPLA. Members of the TLR family and the platelet receptor apolipoprotein E receptor 2' (apoER2'), a receptor belonging to the low-density lipoprotein receptor (LDL-R) family, as well as GPIbα, were identified as putative candidates for aPLA recognition. CD14, a co-receptor for TLR2 and TLR4, and annexin A2, a ubiquitous Ca2+ -binding protein that is essential for actin-dependent vesicle transport, could serve as important accessory molecules in mediating the pathogenic effects of aPLA. Finally, complement activation has been reported in association with the pathogenicity of APS. The relative contribution of these different mechanisms in the pathogenesis of APS is controversial. Here, we review the various in vivo and in vitro models that have been used to investigate the pathogenic mechanisms of aPLA in APS.