Trichinella spiralis cystatin alleviates polymicrobial sepsis through activating regulatory macrophages

Macrophage polarization in sepsis: Emerging role and clinical application prospect

Sepsis is a severe, potentially fatal condition defined by organ dysfunction due to excessive inflammation. Its complex pathogenesis and poor therapeutic outcomes pose significant challenges in treatment. Macrophages, with their high heterogeneity and plasticity, play crucial roles in both the innate and adaptive immune systems. They can polarize into M1-like macrophages, which promote pro-inflammatory responses, or M2-like macrophages, which mediate anti-inflammatory responses, positioning them as critical mediators in the immune response during sepsis.Macrophages are the main regulators of inflammatory responses, and their polarization is also regulated by inflammatory signaling pathways. This review highlights recent advances in the inflammatory signaling pathways involved in sepsis, mechanism of macrophage polarization mediated by inflammation-related signaling pathways in sepsis, and the role of signaling pathway mediated macrophage polarization in organ dysfunction involved in sepsis. We also explore the therapeutic potential of targeting macrophage polarization for immunotherapy, offering new perspectives on macrophage-targeted treatments for sepsis.

Therapeutic effect of recombinant Echinococcus granulosus antigen B subunit 2 protein on sepsis in a mouse model

BACKGROUND

Sepsis is a potentially fatal systemic inflammatory response syndrome (SIRS) that threatens millions of lives worldwide. Echinococcus granulosus antigen B (EgAgB) is a protein released by the larvae of the tapeworm. This protein has been shown to play an important role in modulating host immune response. In this study we expressed EgAgB as soluble recombinant protein in E. coli (rEgAgB) and explored its protective effect on sepsis.

METHODS

The sepsis model was established by cecal ligation and puncture (CLP) procedure in BALB/c mice. The therapeutic effect of rEgAgB on sepsis was performed by interperitoneally injecting 5 µg rEgAgB in mice with CLP-induced sepsis and observing the 72 h survival rate after onset of sepsis. The proinflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-6] and regulatory cytokines [IL-10, transforming growth factor beta (TGF-β)] were measured in sera, and the histopathological change was observed in livers, kidneys, and lungs of septic mice treated with rEgAgB compared with untreated mice. The effect of rEgAgB on the macrophage polarization was performed in vitro by incubating rEgAgB with peritoneal macrophages. The levels of TLR2 and MyD88 were measured in these tissues to determine the involvement of TLR-2/MyD88 in the sepsis-induced inflammatory signaling pathway.

RESULTS

In vivo, we observed that treatment with rEgAgB significantly increased the survival rate of mice with CLP-induced sepsis up to 72 h while all mice without treatment died within the same period. The increased survival was associated with reduced pathological damage in key organs such as liver, lung, and kidneys. It was supported by the reduced proinflammatory cytokine levels and increased regulatory cytokine expression in peripheral blood and key organ tissues. Further study identified that treatment with rEgAgB promoted macrophage polarization from classically activated macrophage (M1) to regulatory M2-like macrophage via inhibiting TLR2/MyD88 signal pathway.

CONCLUSIONS

The therapeutic effects of rEgAgB on mice with sepsis was observed in a mice model that was associated with reduced inflammatory responses and increased regulatory responses, possibly through inducing polarization of macrophages from proinflammatory M1 to regulatory M2 phenotype through inhibiting TLR2/MyD88 inflammatory pathway.

Helminth-derived molecules: pathogenic and pharmacopeial roles

Parasitic helminths, taxonomically comprising trematodes, cestodes, and nematodes, are multicellular invertebrates widely disseminated in nature and have afflicted people continuously for a long time. Helminths play potent roles in the host through generating a variety of novel molecules, including some excretory/secretory products and others that are involved in intracellular material exchange and information transfer as well as the initiation or stimulation of immune and metabolic activation. The helminth-derived molecules have developed powerful and diverse immunosuppressive effects to achieve immune evasion for parasite survival and establish chronic infections. However, they also improve autoimmune and allergic inflammatory responses and promote metabolic homeostasis by promoting metabolic reprogramming of various immune functions, and then inducing alternatively activated macrophages, T helper 2 cells, and regulatory T cells-mediated immune responses. Therefore, a deeper exploration of the immunopathogenic mechanism and immune regulatory mechanisms of helminth-derived molecules exerted in the host is crucial for understanding host-helminth interactions as well as the development of therapeutic drugs for infectious or non-infectious diseases. In this review, we focus on the properties of helminth-derived molecules to give an overview of the most recent scientific knowledge about their pathogenic and pharmacopeial roles in immune-metabolic homeostasis.

Impact of resveratrol and zinc on biomarkers of oxidative stress induced by Trichinella spiralis infection

Trichinellosis is a re-emerging worldwide foodborne zoonosis. Oxidative stress is one of the most common detrimental effects caused by trichinellosis. In addition, Trichinella infection poses an infinite and major challenge to the host's immune system. Resistance and side effects limit the efficiency of the existing anti-trichinella medication. Given that concern, this work aimed to investigate the anti-helminthic, antioxidant, anti-inflammatory and immunomodulatory effects of resveratrol and zinc during both phases of Trichinella spiralis infection. Sixty-four Swiss albino mice were divided into four equal groups: non-infected control, infected control, infected and treated with resveratrol, and infected and treated with zinc. Animals were sacrificed on the 7th and 35th days post-infection for intestinal and muscular phase assessments. Drug efficacy was assessed by biochemical, parasitological, histopathological, immunological, and immunohistochemical assays. Resveratrol and zinc can be promising antiparasitic, antioxidant, anti-inflammatory, and immunomodulatory agents, as evidenced by the significant decrease in parasite burden, the significant improvement of liver and kidney function parameters, the increase in total antioxidant capacity (TAC), the reduction of malondialdehyde (MDA) level, the increase in nuclear factor (erythroid-derived 2)-like-2 factor expression, and the improvement in histopathological findings. Moreover, both drugs enhanced the immune system and restored the disturbed immune balance by increasing the interleukin 12 (IL-12) level. In conclusion, resveratrol and zinc provide protection for the host against oxidative harm and the detrimental effects produced by the host's defense response during Trichinella spiralis infection, making them promising natural alternatives for the treatment of trichinellosis.

Therapeutic effect of Echinococcus granulosus cyst fluid on bacterial sepsis in mice

BACKGROUND

The primary pathophysiological process of sepsis is to stimulate a massive release of inflammatory mediators to trigger systemic inflammatory response syndrome (SIRS), the major cause of multi-organ dysfunction and death. Like other helminths, Echinococcus granulosus induces host immunomodulation. We sought to determine whether E. granulosus cyst fluid (EgCF) displays a therapeutic effect on sepsis-induced inflammation and tissue damage in a mouse model.

METHODS

The anti-inflammatory effects of EgCF were determined by in vitro culture with bone marrow-derived macrophages (BMDMs) and in vivo treatment of BALB/C mice with cecal ligation and puncture (CLP)-induced sepsis. The macrophage phenotypes were determined by flow cytometry, and the levels of cytokines in cell supernatants or in sera of mice were measured (ELISA). The therapeutic effect of EgCF on sepsis was evaluated by observing the survival rates of mice for 72 h after CLP, and the pathological injury to the liver, kidney, and lung was measured under a microscope. The expression of TLR-2/MyD88 in tissues was measured by western blot to determine whether TLR-2/MyD88 is involved in the sepsis-induced inflammatory signaling pathway.

RESULTS

In vitro culture with BMDMs showed that EgCF promoted macrophage polarization to M2 type and inhibited lipopolysaccharide (LPS)-induced M1 macrophages. EgCF treatment provided significant therapeutic effects on CLP-induced sepsis in mice, with increased survival rates and alleviation of tissue injury. The EgCF conferred therapeutic efficacy was associated with upregulated anti-inflammatory cytokines (IL-10 and TGF-β) and reduced pro-inflammatory cytokines (TNF-α and INF-γ). Treatment with EgCF induced Arg-1-expressed M2, and inhibited iNOS-expressed M1 macrophages. The expression of TLR-2 and MyD88 in EgCF-treated mice was reduced.

CONCLUSIONS

The results demonstrated that EgCF confers a therapeutic effect on sepsis by inhibiting the production of pro-inflammatory cytokines and inducing regulatory cytokines. The anti-inflammatory effect of EgCF is carried out possibly through inducing macrophage polarization from pro-inflammatory M1 to regulatory M2 phenotype to reduce excessive inflammation of sepsis and subsequent multi-organ damage. The role of EgCF in regulating macrophage polarization may be achieved by inhibiting the TLR2/MyD88 signaling pathway.

Trichinella spiralis cathepsin L induces macrophage M1 polarization via the NF-κB pathway and enhances the ADCC killing of newborn larvae

BACKGROUND

During the early stages of Trichinella spiralis infection, macrophages predominantly undergo polarization to the M1-like phenotype, causing the host's inflammatory response and resistance against T. spiralis infection. As the disease progresses, the number of M2-type macrophages gradually increases, contributing to tissue repair processes within the host. While cysteine protease overexpression is typically associated with inflammation, the specific role of T. spiralis cathepsin L (TsCatL) in mediating macrophage polarization remains unknown. The aim of this study was to assess the killing effect of macrophage polarization mediated by recombinant T. spiralis cathepsin L domains (rTsCatL2) on newborn larvae (NBL).

METHODS

rTsCatL2 was expressed in Escherichia coli strain BL21. Polarization of the rTsCatL2-induced RAW264.7 cells was analyzed by enzyme-linked immunosorbent assay (ELISA), quantitative PCR (qPCR), western blot, immunofluorescence and flow cytometry. The effect of JSH-23, an inhibitor of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), on rTsCatL2-induced M1 polarization investigated. Cytotoxic effects of polarized macrophages on NBL were observed using in vitro killing assays.

RESULTS

Following the co-incubation of rTsCatL2 with RAW264.7 murine macrophage cells, qPCR and ELISA revealed increased transcription and secretion levels of inducible nitric oxide synthase (iNOS), interleukin (IL)-6, IL-1β and tumor necrosis factor alpha (TNF-α) in macrophages. Western blot analysis showed a significant increase in iNOS protein expression, while the expression level of arginase-1 protein remained unchanged. Flow cytometry revealed a substantial increase in the number of CD86-labeled macrophages. The western blot results also indicated that rTsCatL2 increased the expression levels of phospho-NF-κB and phospho-nuclear factor-κB inhibitor alpha (IκB-α) proteins in a dose-dependent manner, while immunofluorescence revealed that rTsCatL2 induced nuclear translocation of the p65 subunit of NF-κB (NF-κB p65) protein in macrophages. The inhibitory effect of JSH-23 suppressed and abrogated the effect of rTsCatL2 in promoting M1 macrophage polarization. rTsCatL2 mediated polarization of macrophages to the M1-like phenotype and enhanced macrophage adhesion and antibody-dependent cell-mediated cytotoxicity (ADCC) killing of NBL.

CONCLUSIONS

The results indicated that rTsCatL2 induces macrophage M1 polarization via the NF-κB pathway and enhances the ADCC killing of NBL. This study provides a further understanding of the interaction mechanism between T. spiralis and the host.

Excretory/secretory products from Trichinella spiralis adult worms ameliorate myocardial infarction by inducing M2 macrophage polarization in a mouse model

BACKGROUND

Ischemia-induced inflammatory response is the main pathological mechanism of myocardial infarction (MI)-caused heart tissue injury. It has been known that helminths and worm-derived proteins are capable of modulating host immune response to suppress excessive inflammation as a survival strategy. Excretory/secretory products from Trichinella spiralis adult worms (Ts-AES) have been shown to ameliorate inflammation-related diseases. In this study, Ts-AES were used to treat mice with MI to determine its therapeutic effect on reducing MI-induced heart inflammation and the immunological mechanism involved in the treatment.

METHODS

The MI model was established by the ligation of the left anterior descending coronary artery, followed by the treatment of Ts-AES by intraperitoneal injection. The therapeutic effect of Ts-AES on MI was evaluated by measuring the heart/body weight ratio, cardiac systolic and diastolic functions, histopathological change in affected heart tissue and observing the 28-day survival rate. The effect of Ts-AES on mouse macrophage polarization was determined by stimulating mouse bone marrow macrophages in vitro with Ts-AES, and the macrophage phenotype was determined by flow cytometry. The protective effect of Ts-AES-regulated macrophage polarization on hypoxic cardiomyocytes was determined by in vitro co-culturing Ts-AES-induced mouse bone marrow macrophages with hypoxic cardiomyocytes and cardiomyocyte apoptosis determined by flow cytometry.

RESULTS

We observed that treatment with Ts-AES significantly improved cardiac function and ventricular remodeling, reduced pathological damage and mortality in mice with MI, associated with decreased pro-inflammatory cytokine levels, increased regulatory cytokine expression and promoted macrophage polarization from M1 to M2 type in MI mice. Ts-AES-induced M2 macrophage polarization also reduced apoptosis of hypoxic cardiomyocytes in vitro.

CONCLUSIONS

Our results demonstrate that Ts-AES ameliorates MI in mice by promoting the polarization of macrophages toward the M2 type. Ts-AES is a potential pharmaceutical agent for the treatment of MI and other inflammation-related diseases.

Cystatins from the Human Liver Fluke Opisthorchis viverrini: Molecular Characterization and Functional Analysis

A high incidence of cholangiocarcinoma (bile duct cancer) has been observed in Thailand. This usually rare cancer has been associated with infection with the human liver fluke, Opisthorchis viverrini. Secretions of the parasite that interact with the host are thought to be a major component of its pathogenicity and proteolysis is a key biological activity of the secreted molecules. In this study, we present a molecular analysis of cysteine proteinase inhibitors (cystatins) of Opisthorchis viverrini. Six cDNA coding sequences of Opisthorchis viverrini cystatins, OvCys1-6, were cloned from the adult stage of the parasite using RT-PCR. Based on their sequences, OvCys1 and OvCys2 are classified as type 1 cystatins, while OvCys3-6 are classified as type 2 cystatins, with each containing a signal peptide and only one C-terminal disulfide bond. Their C-terminal region sequences are diverse compared with other cystatin members. Cystatins OvCys1, 3 and 4 were found in crude worm extracts and excretory-secretory (ES) products from the adult parasite using Western blot detection, while the other isoforms were not. Thus, OvCys1, 3 and 4 were selected for inhibition analysis and immune reactivity with Opisthorchis viverrini-infected hamster sera. OvCys1, 3, and 4 inhibited mammalian cathepsin L more effectively than cathepsin B. The pH range for their full activity was very wide (pH 3-9) and they were heat stable for at least 3 h. Unlike Fasciola gigantica cystatins, they showed no immune reactivity with infected hamster sera based on indirect ELISA. Our findings suggest that Opisthorchis viverrini cystatins are not major antigenic components in the ES product of this parasite and that other effects of Opisthorchis viverrini cystatins should be investigated.

How to train your myeloid cells: a way forward for helminth vaccines?

Soil-transmitted helminths affect approximately 1.5 billion people worldwide. However, as no vaccine is currently available for humans, the current strategy for elimination as a public health problem relies on preventive chemotherapy. Despite more than 20 years of intense research effort, the development of human helminth vaccines (HHVs) has not yet come to fruition. Current vaccine development focuses on peptide antigens that trigger strong humoral immunity, with the goal of generating neutralizing antibodies against key parasite molecules. Notably, this approach aims to reduce the pathology of infection, not worm burden, with only partial protection observed in laboratory models. In addition to the typical translational hurdles that vaccines struggle to overcome, HHVs face several challenges (1): helminth infections have been associated with poor vaccine responses in endemic countries, probably due to the strong immunomodulation caused by these parasites, and (2) the target population displays pre-existing type 2 immune responses to helminth products, increasing the likelihood of adverse events such as allergy or anaphylaxis. We argue that such traditional vaccines are unlikely to be successful on their own and that, based on laboratory models, mucosal and cellular-based vaccines could be a way to move forward in the fight against helminth infection. Here, we review the evidence for the role of innate immune cells, specifically the myeloid compartment, in controlling helminth infections. We explore how the parasite may reprogram myeloid cells to avoid killing, notably using excretory/secretory (ES) proteins and extracellular vesicles (EVs). Finally, learning from the field of tuberculosis, we will discuss how anti-helminth innate memory could be harnessed in a mucosal-trained immunity-based vaccine.

PD-L2 Blockade Exacerbates Liver Lesion in Mice Infected with Capillaria hepatica through Reducing Alternatively Activated Macrophages

Capillaria hepatica is a seriously neglected zoonotic parasite, which infects the liver of mammalian hosts, causing fibrosis or even hepatic failure. At present, the immune responses elicited by C. hepatica are not fully understood, and the role(s) of the programmed death 1 (PD-1) signaling pathway in the context of C. hepatica-induced pathology are not known. In this study, we identify that the late stage of infection with C. hepatica-especially the egg-derived antigens-modulates the host immune responses to promote alternatively activated macrophage (M2) polarization and programmed death ligand 2 (PD-L2) expression. The PD-L2-expressing alternatively activated M2 macrophages play an important role in maintaining Th2-biased regulatory immune responses, which may facilitate the survival of parasitic worms or eggs within the infected liver and reduce the liver pathology caused by the egg granulomas. Treatment with anti-PD-L2 antibody had no effect on the survival of parasitic eggs but deteriorated the pathology of egg granulomas. The obtained results suggest that PD-1/PD-L2 signaling, which is involved in alternative macrophage polarization, determines the immune response pattern and the immunopathology, consequently determining the outcome of the parasitic infection.

Ferroptosis in Macrophage Impairment in Sepsis

Sepsis is a clinical syndrome with high mortality, which can lead to multiple organ dysfunction syndrome. Nonspecific immune dysfunction and immune imbalance are its important pathological features. Macrophages are important immune cells and one of the important components of innate and adaptive immunity. Regulating the function of macrophages may be a potential method for the treatment of sepsis. Up to now, ferroptosis has been proved to be involved in the pathophysiological mechanism of many diseases, such as Alzheimer's disease, cancer, Parkinson's disease, and renal degeneration. At present, relevant studies have reported that ferroptosis may be involved in the occurrence of sepsis This paper reviews the existing mechanisms of iron ptosis in macrophages in sepsis, with a view to providing si'l for future studies on sepsis.