T cell activation status determines the cytokine pattern induced by zymosan and bacterial DNA both in thymocytes and splenocytes

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

Zymosan attenuates melanoma growth progression, increases splenocyte proliferation and induces TLR-2/4 and TNF-α expression in mice

Background

Melanoma is one of the most common types of skin malignancies. Since current therapies are suboptimal, considerable interest has focused on novel natural-based treatments. Toll-like receptors (TLRs) play an important role in evoking innate immunity against cancer cells. Zymosan, a known TLR-2 agonist, is a glucan derived from yeast cell walls with promising immunomodulatory effects. The aim of this study was to evaluate whether Saccharomyces cerevisiae-derived zymosan-modulated skin melanoma progression by regulation of TLR-2 and TLR-4 expression in peritoneal macrophages and serum TNF-α level.

Methods

Male C57BL/6 mice were divided into four groups: i) zymosan-treated (Z), ii) Melanoma-bearing mice (M), iii) Melanoma-bearing mice treated with zymosan (ZM) and iv) a healthy control group (negative control). 15 days after melanoma induction, mice were injected i.p. with zymosan (10 μg) daily for 4 consecutive days. Mice were CO₂-euthanized and serum TNF-α level, TLR-2 and TLR-4 expression in peritoneal macrophages and tumor growth measured. Splenocytes were treated ex-vivo with zymosan to determine viability and proliferation.

Results

Tumor weight significantly decreased following therapeutic dosing with zymosan (P < 0.05). This was associated with zymosan-induced upregulation of TLR-2, TLR-4 and TNF-α mRNA in peritoneal macrophages and enhanced serum TNF-α levels (P < 0.05). Splenocyte number and viability were increased in a concentration-dependent manner by zymosan.

Conclusions

Our study suggests that zymosan-induced upregulation of TLR-2, TLR-4 and TNF-α gene expression and of TNF-α release; together with increased level of lymphocyte proliferation may play a role in the inhibition of melanoma progression.

Zymosan-Induced Peritonitis: Effects on Cardiac Function, Temperature Regulation, Translocation of Bacteria, and Role of Dectin-1

Zymosan-induced peritonitis is a model commonly used to study systemic inflammatory response syndrome and multiple organ dysfunction syndrome. However, effects of zymosan on cardiac function have not been reported. We evaluated cardiac responses to zymosan in mice and the role of β-glucan and dectin-1 in mediating these responses. Temperature and cardiac function were evaluated before and after intraperitoneal (i.p.) injection of zymosan (100 or 500 mg/kg) or saline. Chronotropic and dromotropic functions were measured using electrocardiograms (ECGs) collected from conscious mice. Cardiac inotropic function was determined by echocardiography. High-dose zymosan caused a rapid and maintained hypothermia along with visual signs of illness. Baseline heart rate (HR) was unaffected but HR variability (HRV) increased, and there was a modest slowing of ventricular conduction. High-dose zymosan also caused prominent decreases in cardiac contractility at 4 and 24 h. Because zymosan is known to cause gastrointestinal tract pathology, peritoneal wash and blood samples were evaluated for bacteria at 24 h after zymosan or saline injection. Translocation of bacterial occurred in all zymosan-treated mice (n = 3), and two had bacteremia. Purified β-glucan (50 and 125 mg/kg, i.p.) had no effect on temperature or ECG parameters. However, deletion of dectin-1 modified the ECG responses to high-dose zymosan; slowing of ventricular conduction and the increase in HRV were eliminated but a marked bradycardia appeared at 24 h after zymosan treatment. Zymosan-treated dectin-1 knockout mice also showed hypothermia and visual signs of illness. Fecal samples from dectin-1 knockout mice contained more bacteria than wild types, but zymosan caused less translocation of bacteria. Collectively, these findings demonstrate that zymosan-induced systemic inflammation causes cardiac dysfunction in mice. The data suggest that dectin-1-dependent and -independent mechanisms are involved. Although zymosan treatment causes translocation of bacteria, this effect does not have a major role in the overall systemic response to zymosan.

Innate immune regulation of autoimmunity in multiple sclerosis: Focus on the role of Toll-like receptor 2

Innate immunity relies on a set of germline-encoded receptors including Toll-like receptors (TLRs) that enable the host to discriminate between self and non-self. Multiple sclerosis (MS) is an autoimmune inflammatory demyelinating disease of the central nervous system (CNS). Infections are thought to play an important role in disease susceptibility. The role of innate immunity in MS has been recently appreciated. TLR2, a member of the TLR family, forms heterodimers with either TLR1 or TLR6 and detects a wide range of microbial as well as self-derived molecular structures. It may thus be important both in fighting infection and in activating autoimmunity. In this review, we discuss innate regulation of autoimmunity in MS with a focus on the role of TLR2 signaling.

The influence of intrauterine exposure to immunosuppressive treatment on changes in the immune system in juvenile Wistar rats

Background

In our study, we assessed the impact of immunosuppressive drug combinations on changes in the immune system of juvenile Wistar rats exposed to these drugs during pregnancy. We primarily concentrated on changes in two organs of the immune system – the thymus and the spleen.

Methods

The study was conducted on 40 (32+8) female Wistar rats administered full and half dose of drugs, respectively, subjected to regimens commonly used in therapy of human kidney transplant recipients ([1] cyclosporine A, mycophenolate mofetil, and prednisone; [2] tacrolimus, mycophenolate mofetil, and prednisone; [3] cyclosporine A, everolimus, and prednisone). The animals received drugs by oral gavage 2 weeks before pregnancy and during 3 weeks of pregnancy.

Results

There were no statistically significant differences in the weight of the thymus and spleen, but changes were found in the results of blood hematology, cytometry from the spleen, and a histologic examination of the examined immune organs of juvenile Wistar rats. In the cytokine assay, changes in the level of interleukine 17 (IL-17) after increasing amounts of concanavaline A were dose-dependent; the increase of IL-17 was blocked after administration of higher doses of immunosuppressive drugs. However, after a reduction of doses, its increase resumed.

Conclusion

Qualitative, quantitative, and morphological changes in the immune system of infant rats born to pharmacologically immunosuppressed females were observed. Thymus structure, spleen composition, and splenocyte IL-17 production were mostly affected in a drug regimen–dependent manner.

Pseudomonas aeruginosa and Its Bacterial Components Influence the Cytokine Response in Thymocytes and Splenocytes

Infections with Pseudomonas aeruginosa may cause many different diseases. The spectrum of such infections in general includes inflammation and bacterial sepsis. Hospital-acquired pneumonia, naturally resistant to a wide range of antibiotics, is associated with a particularly high mortality rate in mechanically ventilated patients. The pathogenesis of P. aeruginosa is complex and mediated by several virulence factors, as well as cell-associated factors. We have previously demonstrated that stimulation with different bacteria triggers the cytokine response of thymocytes. In this study, we investigated the effect of P. aeruginosa and its different components on the cytokine production of immature and mature immune cells. We found that the induced cytokine pattern in the thymus and the spleen after infections with P. aeruginosa is primarily mediated by lipopolysaccharide (LPS) of the outer cell membrane, but other components of the bacterium can influence the cytokine secretion as well. Stimulation with heat-killed P. aeruginosa and LPS does not influence the amount of cytokine-producing CD4(+) T cells but instead suppresses the emergence of Th17 cells. However, stimulation with P. aeruginosa or its components triggers the interleukin-17 (IL-17) response both in thymocytes and in splenocytes. We conclude that infections with P. aeruginosa affect the cytokine secretion of immature and mature cells and that IL-17 and Th17 cells play only a minor role in the development of pathological systemic inflammatory disease conditions during P. aeruginosa infections. Therefore, other inflammatory immune responses must be responsible for septic reactions of the host.

Bacteria and their cell wall components uniformly co-activate interleukin-17-producing thymocytes

Interleukin (IL)-17-producing T cells play a critical role in the immune response against microbial pathogens. Traditionally, experimental studies have focused upon understanding the activity of IL-17-producing T cells which differentiate from naive T cells in the peripheral immune system. However, we have demonstrated previously that IL-17-producing T cells are also present in the thymus of naive wild-type mice and can be co-activated there by microbial stimuli. Other studies have supported the concept that IL-17-producing thymocytes have a specific role in the immediate defence against microbial pathogens, which is independent from the development of an adaptive immune response. Given an important role of the thymus in systemic bacterial infection and sepsis, in this study we investigate the effect of a broad spectrum of bacteria and cell wall components on thymocyte cytokine production. Surprisingly, we find that all types of bacteria investigated (including non-pathogenic species) uniformly activate IL-17-producing thymocytes upon α-CD3 stimulation. In contrast, there is a heterogeneous effect on IL-6 and interferon (IFN)-γ-production with Gram-negative bacteria inducing far higher frequencies of IL-6- and IFN-γ-producing thymocytes than Gram-positive bacteria. We conclude that IL-17-producing thymocytes constitute a 'first line of recognition', but not a 'first line of defence' against bacteria in general. Their activity might lead to immune activation, but not necessarily to a pathological inflammatory disease condition. The difference between these two states might be determined by other immunological effector molecules, such as IL-6 and IFN-γ.

Cytokine patterns in paediatric patients presenting serious gastrointestinal and respiratory bacterial infections

In the adaptive immune response, the types of cytokines produced define whether there is a cellular (T1) or a humoral (T2) response. Specifically, in the T1 response, interleukin 2 (IL-2), interferon γ (IFN-γ) and tumor necrosis factor β (TNF-β) are produced, whereas in the T2 response, IL-4, IL-5, IL- 6, IL-10 and IL-13 are primarily produced. Cytokines are primarily involved in the regulation of immune system cells. The aim of the present study was to evaluate the cytokine patterns (Type 1/Type 2) and TNF-α expression levels in children with severe gastrointestinal and respiratory bacterial infections. The enzyme-linked immunosorbent assay (ELISA) technique was used to identify the cytokines and the infectious agents. The results obtained demonstrated that, in general, children with bacterial infections experienced an increase in IL-2, IFN-γ and IL-4 concentrations and a decrease in TNF-α, IL-5 and IL-6 concentrations when compared to healthy children. Specifically, type 1 cytokines and an increased TNF-α concentration were found in children with gastrointestinal infections. However, patients with respiratory infections showed increased concentrations of both T2 (IL-4, IL-6 and IL-10) and T1 (IL-2 and IFN-γ) components. Thus, it was concluded that children with gastrointestinal infections exclusively developed a T1 response, whereas children with respiratory infections developed a T1/T2 response to fight the infection.