Complexity of cytokine network regulation of innate lymphoid cells in protective immunity

Immunostimulatory activity of Hovenia dulcis branches extracts through TLR4/JNK-dependent macrophage activation and TLR4-dependent macrophage autophagy in RAW264.7 cells

Hovenia dulcis, one of the traditional medicinal plants, is currently being used as a functional ingredient for the development of health functional foods that protects the liver from alcohol damage in Korea. A variety of pharmacological effects of Hovenia dulcis have been reported so far, but studies on immune-enhancing activity are insufficient. Thus, in this study, we report that Hovenia dulcis branches (HDB) induce the activation of macrophages. HDB increased the production of immunostimulatory factors and phagocytosis in RAW264.7 cells. TLR4 inhibition blocked HDB-mediated production of immunostimulatory factors. In addition, the JNK inhibition reduced the HDB-mediated production of immunostimulatory factors, and the HDB-mediated JNK activation was blocked by the TLR4 inhibition. HDB increased the level of LC3-II and p62/SQSTM1. TLR4 inhibition blocked HDB-mediated increase in the level of LC3-II and p62/SQSTM1. These findings indicate that HDB may induce TLR4/JNK-dependent macrophage activation and TLR4-dependent macrophage autophagy.

Transgenic Rice Seed Extracts Exert Immunomodulatory Effects by Modulating Immune-Related Biomarkers in RAW264.7 Macrophage Cells

Protopanaxadiol (PPD), a native active triterpenoid present in Panax ginseng, has been reported to exert immune-related effects. We previously created PPD-producing transgenic rice by introducing the P. ginseng protopanaxadiol synthase and dammarenediol-II synthase genes into Dongjin rice. In the present study, the seeds of the T₄ generation of this transgenic rice were tested for their immunomodulatory effects in RAW264.7 macrophage cells. Treatment with transgenic rice seed extract in RAW264.7 cells (i) significantly enhanced nitric oxide (NO) production in a dose-dependent manner without any cytotoxicity (up to 100 µg/mL), (ii) upregulated the expression of immune-related genes and increased production of the inflammation mediator prostaglandin E₂ (PGE₂), and (iii) activated nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) by promoting the phosphorylation of NF-κB p65, p38 MAPK, and c-Jun N-terminal protein kinase (JNK). In lipopolysaccharide (LPS)-treated RAW264.7 cells used to mimic the inflammation condition, treatment with transgenic rice seed extract significantly reduced NO production, proinflammatory cytokine expression, and PGE₂ production, all of which are LPS-induced inflammation biomarkers, by inhibiting the phosphorylation of NF-κB p65, p38 MAPK, and JNK. Collectively, these results indicate that PPD-producing transgenic rice has immunomodulatory effects.

The effective approach for the quality control of Codonopsis radix based on quality markers of immune activity

Codonopsis radix is an important edible and medicinal plant resource for immunomodulation in China and Southeast Asia. However, the chemical quality evaluation of Codonopsis radix in Chinese Pharmacopoeia (2020 Version) is still lacking; therefore, it is necessary to develop an effective method to evaluate its quality accurately and systematically. Herein, a reliable method for a comprehensive chemical analysis of bioactive compounds in Codonopsis radix by ultra-performance liquid chromatography-diode array detector was developed based on the quality marker (Q-marker) concept, which can efficiently reflect its immune activity. Our previous research explored the seven potential bioactive compounds reflecting the immune regulation activities of Codonopsis radix by spectrum-effect relationship analysis. Therefore, in this study, we researched on establishing a quality control method and selected the modern pharmacodynamic experiment of immune regulation to verify the potential bioactive compounds as quality markers. A real quality control method that reflected the traditional efficacy of Codonopsis radix in strengthening the spleen and tonifying lungs was developed. Furthermore, the Codonopsis radix extract and the seven bioactive compounds could promote the proliferation of immune-related cells and regulate the secretion of inflammatory factors, thus playing a role in immune regulation. This article is protected by copyright. All rights reserved.

Innate lymphoid cells are double-edged swords under the mucosal barrier

As the direct contacting site for pathogens and allergens, the mucosal barrier plays a vital role in the lungs and intestines. Innate lymphoid cells (ILCs) are particularly resident in the mucosal barrier and participate in several pathophysiological processes, such as maintaining or disrupting barrier integrity, preventing various pathogenic invasions. In the pulmonary mucosae, ILCs sometimes aggravate inflammation and mucus hypersecretion but restore airway epithelial integrity and maintain lung tissue homeostasis at other times. In the intestinal mucosae, ILCs can increase epithelial permeability, leading to severe intestinal inflammation on the one hand, and assist mucosal barrier in resisting bacterial invasion on the other hand. In this review, we will illustrate the positive and negative roles of ILCs in mucosal barrier immunity.

Structural characterization and immunomodulatory mechanisms of two novel glucans from Morchella importuna fruiting bodies

Two novel glucans named MIPB50-W and MIPB50-S-1 were obtained from edible Morchella importuna with molecular weights (M_w) of 939.2 kDa and 444.5 kDa, respectively. MIPB50-W has a backbone of α-(1 → 4)-d-glucan, which was substituted at O-6 position by α-d-Glcp-(1→. Moreover, MIPB50-S-1 has a backbone of α-(1 → 4)-d-glucan, which was substituted at O-6 position by α-d-Glcp-(1 → 6)-α-d-Glcp-(1→. This is the first report about glucan found in Morchella mushrooms. Furthermore, MIPB50-W and MIPB50-S-1 strengthened the phagocytosis function and the promoted secretion of interleukins (IL)-6/tumor necrosis factor-alpha (TNF-α) and nitric oxide (NO), which induced the activation of Toll-like receptor 2 (TLR2), TLR4 as well as mitogen activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways. Interestingly, MIPB50-S-1 performed the better immunomodulatory activity than that of MIPB50-W in almost all tests. Therefore, MIPB50-W and MIPB50-S-1 are potential immune-enhancing components of functional foods.

Wild simulated ginseng activates mouse macrophage, RAW264.7 cells through TRL2/4-dependent activation of MAPK, NF-κB and PI3K/AKT pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng (Panax ginseng Meyer) is a very well-known traditional herbal medicine that has long been used to enhance the body's immunity. Because it is a type of ginseng, it is believed that wild simulated ginseng (WSG) also has immune-enhancing activity. However, study on the immune-enhancing activity of WSG is quite insufficient compared to ginseng.

AIM OF THE STUDY

In this study, we evaluated immune-enhancing activity of WSG through macrophage activation to provide a scientific basis for the immune enhancing activity of WSG.

MATERIALS AND METHODS

The effect of WSG on viability of RAW264.7 cells was evaluated by MTT assay. The NO level was measured by Griess reagent. The expression levels of mRNA or protein in WSG-treated RAW264.7 cells were analyzed by RT-PCR and Western blot, respectively.

RESULTS

WSG increased the production of immunomodulators such as NO, iNOS, COX-2, IL-1β, IL-6 and TNF-α and activated phagocytosis in mouse macrophages RAW264.7 cells. Inhibition of TLR2 and TLR4 reduced the production of immunomodulators induced by WSG. WSG activated MAPK, NF-κB and PI3K/AKT signaling pathways, and inhibition of such signaling activation blocked WSG-mediated production of immunomodulators. In addition, activation of MAPK, NF-κB and PI3K/AKT signaling pathways by WSG was reversed by TLR2 or TLR4 inhibition.

CONCLUSION

Based on the results of this study, WSG is thought to activate macrophages through the production of immunomodulators and phagocytosis activation through TLR2/4-dependent MAPK, NF-κB and PI3K/AKT signaling pathways. Therefore, it is thought that WSG have the potential to be used as an agent for enhancing immunity.

Isolation, purification, characterization, and immunomodulatory effects of polysaccharide from Auricularia auricula on RAW264.7 macrophages

Auricularia auricula polysaccharide (AAP) was isolated by hot-water extraction and purified to evaluate its structural and immunomodulatory effects on RAW264.7 macrophages. The results show that three kinds of Auricularia auricula polysaccharides (c-AAP) were obtained and named as AAP-I, AAP-II, and AAP-III Their further purification found that AAP-I and AAP-II were glycoproteins, and only AAP-III was a pure polysaccharide, which we named AAP for further experiments. Structural characteristics revealed that AAP was a homogeneous galactan comprising mannose, rhamnose, gluconic acid, glucose, galactose, arabinose, and fucose in a molar ratio of 5.02:0.9:0.12:4.48:0.37:1.0:0.36, and the average molecular weight is approximately 23.51 kDa. Methylation analysis revealed that AAP mainly consisted of 1,4-linked-Glcp, 1,4,6-linked-Glcp, terminal Glcp, 1,4-linked-Manp, 1,2,6-linked-Manp, and terminal Arap. Furthermore, the in vitro immunomodulatory activities of AAP were evaluated by cell proliferation, NO production, and phagocytic ability using RAW264.7 macrophage cells. The results show that AAP not only promoted the activation of macrophages but also provided a scientific basis for the further use of AAP. PRACTICAL APPLICATIONS: Three water-soluble polysaccharides were extracted from Auricularia auricula of Changbai Mountain, two of which contained binding proteins. Determination of molecular weight, structure, and immunoreactivity of pure polysaccharide components. The result clearly demonstrated the benefits of this plant as a healthy functional food.

TGF-β induces ST2 and programs ILC2 development

The molecular pathways underlying the development of innate lymphoid cells (ILCs) are mostly unknown. Here we show that TGF-β signaling programs the development of ILC2s from their progenitors. Specifically, the deficiency of TGF-β receptor II in bone marrow progenitors results in inefficient development of ILC2s, but not ILC1s or ILC3s. Mechanistically, TGF-β signaling is required for the generation and maintenance of ILC2 progenitors (ILC2p). In addition, TGF-β upregulates the expression of the IL-33 receptor gene Il1rl1 (encoding IL-1 receptor-like 1, also known as ST2) in ILC2p and common helper-like innate lymphoid progenitors (CHILP), at least partially through the MEK-dependent pathway. These findings identify a function of TGF-β in the development of ILC2s from their progenitors.

TGF-β is thought to be important for group 2 innate lymphoid cell (ILC2) function. Here the authors show that TGF-β drives expression of ST2 specifically in ILC2 progenitors and thereby is also important for the development of ILC2s in the bone marrow.

Study on immunostimulatory activity and extraction process optimization of polysaccharides from Caulerpa lentillifera

The process of extracting polysaccharides from the green algae Caulerpa lentillifera was studied by single factor experiments and response surface methodology. Additionally, the immunostimulatory activity of Caulerpa lentillifera polysaccharides (CLP) on RAW264.7 mouse macrophage was evaluated by in vitro cell experiments. The results showed that the optimal extraction conditions consisted of ultrasonification for 30 min, extraction time of 9 h, extraction temperature of 100 °C, and a ratio of water to raw material of 40:1. RAW264.7 macrophage exhibited enhanced phagocytosis with no toxic effects after treatment with CLP. In addition, CLP effectively increased the synthesis and secretion of cytokines (IL-6, TNF-α, IL-1β, and NO), whereby the secretion levels of IL-6, TNF-α, and IL-1β were 1,840.32 ± 21.03 pg/mL (50 μg/mL), 197.17 ± 3.13 ng/mL (50 μg/mL), and 1,178.35 ± 78.82 pg/mL (25 μg/mL), respectively. The polysaccharides contained in Caulerpa lentillifera have potential value for further development due to their immunological activity.

TNF-α Contributes to Lymphoid Tissue Disorganization and Germinal Center B Cell Suppression during Intracellular Bacterial Infection

Bacterial, parasitic, and viral infections are well-known causes of lymphoid tissue disorganization, although the factors, both host and/or pathogen derived, that mediate these changes are largely unknown. Ehrlichia muris infection in mice causes a loss of germinal center (GC) B cells that is accompanied by the generation of extrafollicular T-bet⁺ CD11c⁺ plasmablasts and IgM memory B cells. We addressed a possible role for TNF-α in this process because this cytokine has been shown to regulate GC development. Ablation of TNF-α during infection resulted in an 8-fold expansion of GL7⁺ CD38^lo CD95⁺ GC B cells, and a 2.5- and 5-fold expansion of CD138⁺ plasmablasts and T-bet⁺ memory cells, respectively. These changes were accompanied by a reduction in splenomegaly, more organized T and B cell zones, and an improved response to Ag challenge. CXCL13, the ligand for CXCR5, was detected at 6-fold higher levels following infection but was much reduced following TNF-α ablation, suggesting that CXCL13 dysregulation also contributes to loss of lymphoid tissue organization. T follicular helper cells, which also underwent expansion in infected TNF-α--deficient mice, may also have contributed to the expansion of T-bet⁺ B cells, as the latter are known to require T cell help. Our findings contrast with previously described roles for TNF-α in GCs and reveal how host-pathogen interactions can induce profound changes in cytokine and chemokine production that can alter lymphoid tissue organization, GC B cell development, and extrafollicular T-bet⁺ B cell generation.

Sensing of physiological regulators by innate lymphoid cells

Maintenance of homeostasis and immune protection rely  on the coordinated action of different physiological systems. Bidirectional communication between the immune system and physiological systems is required to sense and restore any disruption of equilibrium. Recent transcriptomic analyses of innate lymphoid cells (ILCs) from different tissues have revealed that ILCs express a large array of receptors involved in the recognition of neuropeptides, hormones and metabolic signals. ILCs rapidly secrete effector cytokines that are central in the development and activation of early immune responses, but they also constitutively secrete mediators that are important for tissue homeostasis. To achieve these functions effectively, ILCs integrate intrinsic and extrinsic signals that modulate their constitutive and induced activity. Disruption of the regulation of ILCs by physiological regulators leads to altered immune responses with harmful consequences for the organism. An understanding of these complex interactions between the immune system and physiological mediators is crucial to decipher the events leading to the protective versus pathological effects of these cells.

Lineage specification in innate lymphocytes

Innate lymphoid cells (ILCs) are immune cells that lack specific antigen receptors but possess similar effector functions as T cells. Concordantly, ILCs express many transcription factors known to be important for T cell effector function. ILCs develop from lymphoid progenitors in fetal liver and adult bone marrow. However, the identification of ILC progenitor (ILCP) and other precursors in peripheral tissues raises the question of whether ILC development might occur at extramedullary sites. We discuss central and local generation in maintaining ILC abundance at peripheral sites.

Innate lymphoid cells: models of plasticity for immune homeostasis and rapid responsiveness in protection

Innate lymphoid cells (ILCs) have stormed onto the immune landscape as "newly discovered" cell types. These tissue-resident sentinels are enriched at mucosal surfaces and engage in complex cross talk with elements of the adaptive immune system and microenvironment to orchestrate immune homeostasis. Many parallels exist between innate cells and T cells leading to the initial partitioning of ILCs into rather rigid subsets that reflect their "adaptive-like" effector cytokines profiles. ILCs themselves, however, have unique attributes that are only just beginning to be elucidated. These features result in complementarity with, rather than complete duplication of, functions of the adaptive immune system. Key transcription factors determine the pathway of differentiation of progenitors towards an ILC1, ILC2, or ILC3 subset. Once formed, flexibility in the responses of these subsets to stimuli unexpectedly allows transdifferentation between the different subsets and the acquisition of altered phenotypes and function. This provides a mechanism for rapid innate immune responsiveness. Here, we discuss the models of differentiation for maintenance and activation of tissue-resident ILCs in maintaining immune homeostasis and protection.

Single-Cell Gene Expression Analyses Reveal Heterogeneous Responsiveness of Fetal Innate Lymphoid Progenitors to Notch Signaling

T and innate lymphoid cells (ILCs) share some aspects of their developmental programs. However, although Notch signaling is strictly required for T cell development, it is dispensable for fetal ILC development. Constitutive activation of Notch signaling, at the common lymphoid progenitor stage, drives T cell development and abrogates ILC development by preventing Id2 expression. By combining single-cell transcriptomics and clonal culture strategies, we characterize two heterogeneous α4β7-expressing lymphoid progenitor compartments. αLP1 (Flt3(+)) still retains T cell potential and comprises the global ILC progenitor, while αLP2 (Flt3(-)) consists of ILC precursors that are primed toward the different ILC lineages. Only a subset of αLP2 precursors is sensitive to Notch signaling required for their proliferation. Our study identifies, in a refined manner, the diversity of transitional stages of ILC development, their transcriptional signatures, and their differential dependence on Notch signaling.

Fat-associated lymphoid cluster in Cyprinus carpio: Characterisation and its relation with peritoneal haemangiosarcoma

FALC cells are natural helper cells producing Th2-type cytokines, which express c-kit, Sca-1, IL7R and CD45 in mouse and human. These cells are involved in allergic responses and contribute to the inflammatory reactions of adipose tissue; however, a lack of information prevails about the presence of these cells in other species. The aim of the study was to identify and characterise FALC cells in the common carp (Cyprinus carpio) using immunohistochemistry and molecular biology techniques as well as to explore their relationships with their microenvironment. Histological description of the FALC was performed using H&E and polyclonal antibodies were used against cell-surface markers such as c-kit, Sca-1 and CD45. Furthermore, gene expression of c-kit, Sca-1 and IL7R was assessed. C. carpio FALC cells express the same surface markers reported in FALC of the mouse at both the pre- and post-transcriptional level. By exposure to the soluble fraction of helminths, FALC cells produce abundant Th2 cytokines (IL-5, IL-6 and IL-13) but do not synthesise IL-1α. Additionally, FALC cells probably participate in vascular remodelling of the intestine vessels, inducing tumours because a malignant haemangiosarcoma in the peritoneal cavity was found. In this tumour, abundant FALC with their characteristic cell-surface markers were detected. The findings of this study suggest the involvement of some proto-oncogenes such as c-kit and Sca-1, and the deregulation of Src kinases modulated by CD45 present in C. carpio FALC with the ontogeny of peritoneal haemangiosarcoma in this fish species.

The role of brain-derived neurotrophic factor in comorbid depression: possible linkage with steroid hormones, cytokines, and nutrition

Increasing evidence demonstrates a connection between growth factor function (including brain-derived neurotrophic factor, BDNF), glucocorticoid levels (one of the steroid hormones), and the pathophysiology of depressive disorders. Because both BDNF and glucocorticoids regulate synaptic function in the central nervous system, their functional interaction is of major concern. Interestingly, alterations in levels of estrogen, another steroid hormone, may play a role in depressive-like behavior in postpartum females with fluctuations of BDNF-related molecules in the brain. BDNF and cytokines, which are protein regulators of inflammation, stimulate multiple intracellular signaling cascades involved in neuropsychiatric illness. Pro-inflammatory cytokines may increase vulnerability to depressive symptoms, such as the increased risk observed in patients with cancer and/or autoimmune diseases. In this review, we discuss the possible relationship between inflammation and depression, in addition to the cross-talk among cytokines, BDNF, and steroids. Further, since nutritional status has been shown to affect critical pathways involved in depression through both BDNF function and the monoamine system, we also review current evidence surrounding diet and supplementation (e.g., flavonoids) on BDNF-mediated brain functions.