Leptospiral lipopolysaccharide stimulates the expression of toll-like receptor 2 and cytokines in pig fibroblasts

Role of Toll-like receptor 2 during infection of Leptospira spp: A systematic review

The involvement of Toll-like receptor 2 (TLR2) in leptospirosis is poorly understood. Our systematic review examined its role across in-vitro, in-vivo, ex-vivo, and human studies. Original articles published in English up to January 2024, exploring the role of TLR2 during leptospirosis, were selected from databases including PubMed, Web of Science, Scopus, Trip, and Google Scholar. Cochrane guidelines and Preferred Reporting Items for Systematic Reviews and Meta-Analyses were followed by this systematic review. The National Institute of Health Quality Assessment tool, Systematic Review Centre for Laboratory Animal Experimentation risk of bias tool, and Office of Health Assessment and Translation extended tool were used to assess the risk of bias of the studies. Out of 2458 studies retrieved, 35 were selected for the systematic review. These comprised 3 human, 17 in-vitro, 5 in-vivo, 3 ex-vivo, and 7 studies with combined experimental models. We assessed the direct TLR2 expression and indirect TLR2 involvement via the secretion/mRNA expression of immune effectors during leptospirosis. Notably, we observed the secretion/mRNA expression of several cytokines (IL6, IL8, IL-1β, TNFα, IFNγ, IL10, CCL2/MCP-1, CCL10, COX2, CXCL1/KC, CXCL2/MIP2) and immune effectors (hBD2, iNOS, Fibronectin, Oxygen, and Nitrogen reactive species) as key aspects of host TLR2 responses during leptospirosis. Even though increased TLR2 expression in in-vivo and in-vitro studies was evident, human studies reported mixed results showing that the postulated effect of TLR2 response based on other studies may not be valid for human leptospirosis. Besides the role of TLR2 in response to leptospirosis, the involvement of TLR4 and TLR5 was identified in in-vitro and in-vivo studies. TLR2 expression is inconclusive during human leptospirosis and further studies are needed to examine the immune effector regulation, through TLR2 for mitigating the harmful effects and promoting effective immune responses.

Immunomodulatory activity of β-glucan polysaccharides isolated from different species of mushroom - A potential treatment for inflammatory lung conditions

Acute respiratory distress syndrome (ARDS) is the most common form of acute severe hypoxemic respiratory failure in the critically ill with a hospital mortality of 40%. Alveolar inflammation is one of the hallmarks for this disease. β-Glucans are polysaccharides isolated from a variety of natural sources including mushrooms, with documented immune modulating properties. To investigate the immunomodulatory activity of β-glucans and their potential as a treatment for ARDS, we isolated and measured glucan-rich polysaccharides from seven species of mushrooms. We used three models of in-vitro injury in THP-1 macrophages, Peripheral blood mononuclear cells (CD14+) (PMBCs) isolated from healthy volunteers and lung epithelial cell lines. We observed variance between β-glucan content in extracts isolated from seven mushroom species. The extracts with the highest β-glucan content found was Lentinus edodes which contained 70% w/w and Hypsizygus tessellatus which contained 80% w/w with low levels of α-glucan. The extracts had the ability to induce secretion of up to 4000 pg/mL of the inflammatory cytokine IL-6, and up to 5000 pg/mL and 500 pg/mL of the anti-inflammatory cytokines IL-22 and IL-10, respectively, at a concentration of 1 mg/mL in THP-1 macrophages. In the presence of cytokine injury, IL-8 was reduced from 15,000 pg/mL to as low as 10,000 pg/mL in THP-1 macrophages. After insult with LPS, phagocytosis dropped from 70-90% to as low 10% in CD14+ PBMCs. After LPS insult CCL8 relative gene expression was reduced, and IL-10 relative gene expression increased from 50 to 250-fold in THP-1 macrophages. In lung epithelial cells, both A549 and BEAS-2B after IL-1β insult, IL-8 levels dropped from 10,000 pg/mL to as low as 6000 pg/mL. TNF-α levels dropped 10-fold from 100 pg/mL to just below 10 pg/mL. These results demonstrate the therapeutic potential of β-glucans in inflammatory lung conditions. Findings also advance bio-based research that connects green innovation with One Health applications for the betterment of society.

β-Glucan Metabolic and Immunomodulatory Properties and Potential for Clinical Application

β-glucans are complex polysaccharides that are found in several plants and foods, including mushrooms. β-glucans display an array of potentially therapeutic properties. β-glucans have metabolic and gastro-intestinal effects, modulating the gut microbiome, altering lipid and glucose metabolism, reducing cholesterol, leading to their investigation as potential therapies for metabolic syndrome, obesity and diet regulation, gastrointestinal conditions such as irritable bowel, and to reduce cardiovascular and diabetes risk. β-glucans also have immune-modulating effects, leading to their investigation as adjuvant agents for cancers (solid and haematological malignancies), for immune-mediated conditions (e.g., allergic rhinitis, respiratory infections), and to enhance wound healing. The therapeutic potential of β-glucans is evidenced by the fact that two glucan isolates were licensed as drugs in Japan as immune-adjuvant therapy for cancer in 1980. Significant challenges exist to further clinical testing and translation of β-glucans. The diverse range of conditions for which β-glucans are in clinical testing underlines the incomplete understanding of the diverse mechanisms of action of β-glucans, a key knowledge gap. Furthermore, important differences appear to exist in the effects of apparently similar β-glucan preparations, which may be due to differences in sources and extraction procedures, another poorly understood issue. This review will describe the biology, potential mechanisms of action and key therapeutic targets being investigated in clinical trials of β-glucans and identify and discuss the key challenges to successful translation of this intriguing potential therapeutic.

The anti-inflammatory effects of low- and high-molecular-weight beta-glucans from Agrobacterium sp. ZX09 in LPS-induced weaned piglets

The physicochemical characteristics of beta-glucans determine the immune responses of the intestines and whole body. It is hypothesized that glucans with different molecular weights have diverse modes of action on LPS-mediated immune activity. This study aimed to verify the immune-modulatory effects of two types of beta-glucans in LPS-induced weaned piglets. The results indicated that dietary beta-glucan supplementation could prevent losses in body weight gain caused by LPS challenge. Supplementation with different molecular weights of beta-glucans decreased the production of IL-1β and TNF-α and increased IL-10 production, which is likely associated with key factors such as TLR4 and NF-κB. High-molecular-weight beta-glucans seemed to have a strong functional capacity to modulate the innate immune response through the Dectin-1 receptor. Therefore, the results indicate that supplementing piglets with Agrobacterium sp. ZX09 beta-glucans inhibits LPS-mediated depression in the growth performance and plays a protective role during LPS challenge possibly via the Dectin-1 receptor and the TLR4/NF-κB pathway. The results reveal the potential therapeutic activity of purified Agrobacterium sp. ZX09 beta-glucan following experimental LPS infusion.

Phagocyte Escape of Leptospira: The Role of TLRs and NLRs

The spirochetal bacteria Leptospira spp. are causative agents of leptospirosis, a globally neglected and reemerging zoonotic disease. Infection with these pathogens may lead to an acute and potentially fatal disease but also to chronic asymptomatic renal colonization. Both forms of disease demonstrate the ability of leptospires to evade the immune response of their hosts. In this review, we aim first to recapitulate the knowledge and explore the controversial data about the opsonization, recognition, intracellular survival, and killing of leptospires by scavenger cells, including platelets, neutrophils, macrophages, and dendritic cells. Second, we will summarize the known specificities of the recognition or escape of leptospire components (the so-called microbial-associated molecular patterns; MAMPs) by the pattern recognition receptors (PRRs) of the Toll-like and NOD-like families. These PRRs are expressed by phagocytes, and their stimulation by MAMPs triggers pro-inflammatory cytokine and chemokine production and bactericidal responses, such as antimicrobial peptide secretion and reactive oxygen species production. Finally, we will highlight recent studies suggesting that boosting or restoring phagocytic functions by treatments using agonists of the Toll-like or NOD receptors represents a novel prophylactic strategy and describe other potential therapeutic or vaccine strategies to combat leptospirosis.

Elevated Activation of Neutrophil Toll-Like Receptors in Patients with Acute Severe Leptospirosis: An Observational Study

Leptospirosis is the leading cause of zoonotic morbidity and mortality globally, yet little is known about the immune mechanisms that may contribute to pathogenesis and severe disease. Although neutrophils are a key component of early immune responses to infection, they have been associated with tissue damage and inflammation in some febrile infections. To assess whether neutrophils contribute to the pathogenesis observed in severe leptospirosis, we quantitated levels of neutrophil activation markers in patients with varying disease severities. Hospitalized leptospirosis patients had significantly higher levels of toll-like receptors 2 and 4 (TLR2 and TLR4, respectively) on peripheral neutrophils than healthy controls, with the highest levels detected in patients with organ dysfunction. We observed no significant differences in other neutrophil baseline activation markers (CD62L and CD11b) or activation capacity (CD62L and CD11b levels following stimulation), regardless of disease severity. Our results provide preliminary evidence supporting the hypothesis that higher initial bacterial loads or inadequate or delayed neutrophil responses, rather than TLR-driven inflammation, may drive severe disease outcomes.

Effects of cathelicidin-derived peptide from reptiles on lipopolysaccharide-induced intestinal inflammation in weaned piglets

Cathelicidins are the largest family of antimicrobial peptides. C-BF, which is short for Cathelicidin-Bungarus Fasciatus, was isolated from snake venom. C-BF was found to be the most potential substitutes for antibiotics. In this study, we analyzed the effects of cathelicidin-derived peptide C-BF, on lipopolysaccharide (LPS)-induced intestinal damage in weaned piglets, to evaluate the therapeutic effect of C-BF on infectious disease of piglets. Twenty-four piglets were randomly assigned into four groups: control, C-BF, LPS, and C-BF+LPS. The LPS and C-BF+LPS groups were intraperitoneally injected with LPS at fixed timepoints, while the control and C-BF groups were injected with equal volumes of saline. The C-BF and C-BF+LPS groups were then intraperitoneally injected with antimicrobial peptide C-BF, while the control and LPS groups were injected with equal volumes of saline. All piglets were observed for 15days and then sacrificed for analysis. The results showed that C-BF significantly improved the growth performance of weaned piglets compared with LPS-treated animals (P<0.05), and that C-BF could ameliorate the structural and developmental damage to the small intestine caused by LPS treatment. Further, the level of apoptosis in the LPS group was significantly higher than in the other three groups (P<0.05), as was the invasion of inflammatory cells into the intestinal mucosa of the jejunum (P<0.05), leading to increased secretion of pro-inflammatory cytokines. In conclusion, the study indicates that C-BF treatment may be a potential therapy for LPS/pathogen-induced intestinal injury in piglets.

Inhibitory effect of BMAP-28 on Leptospiral Lipopolysaccharide-Induced TLR2-Dependent Immune Response in Bovine Cells

Background

Bovine leptospirosis is a widespread zoonotic disease, leading to serious economic losses in animal production and causing potential hazards to human health. Leptospiral lipopolysaccharide (L-LPS) plays an important role in leptospirosis pathogenicity.

Objectives

With respect to L-LPS endotoxin-like activity, we examined bovine immune response to L-LPS and the inhibitory ability of bovine myeloid antimicrobial peptide-28 (BMAP-28) against L-LPS-induced immune activation in bovine cells.

Materials and Methods

In this study, L-LPS-induced proinflammatory cytokine production in bovine cells was quantitatively measured with real-time PCR and ELISA, and we determined which cell membrane receptors (toll-like receptor [TLR]2 and TLR4) played a major role. In addition, the ability of BMAP-28 to inhibit L-LPS-induced endotoxin-like immune activation in bovine cells was determined by the decrease in cytokine secretion.

Results

L-LPS showed the ability to induce cytokine production in bovine cells, and its induction was TLR2-dependent. BMAP-28 was used to inhibit L-LPS-induced endotoxin-like activity. The function of BMAP-28 was to inhibit LPS-induced TLR2 expression and cytokine production.

Conclusions

In this study, the L-LPS immune response of bovine cells was significant, indicating that TLR2 is the predominant receptor for L-LPS. Due to L-LPS endotoxin-like activity, we found a strategy through using BMAP-28 to prevent L-LPS-induced TLR2-dependent immune activation in bovine cells.

Interaction between Leptospiral Lipopolysaccharide and Toll-like Receptor 2 in Pig Fibroblast Cell Line, and Inhibitory Effect of Antibody against Leptospiral Lipopolysaccharide on Interaction

Leptospiral lipopolysaccharide (L-LPS) has shown potency in activating toll-like receptor 2 (TLR2) in pig fibroblasts (PEFs_NCC1), and causes the expression of proinflammatory cytokines. However, the stimulation by L-LPS was weak eliciting the function of TLR2 sufficiently in pig innate immunity responses during Leptospira infection. In this study, the immune response of pig embryonic fibroblast cell line (PEFs_SV40) was investigated and was found to be the high immune response, thus TLR2 is the predominate receptor of L-LPS in pig cells. Further, we found a strategy using the antibody against L-LPS, to prevent L-LPS interaction with TLR2 in pig cells which could impact on immune activation.