Role of TNFR-related 2 mediated immune responses in dextran sulfate sodium-induced inflammatory bowel disease

Alleviation of DSS-induced colitis via Lactobacillus acidophilus treatment in mice

Gut microbiota play a major role in host physiology and immunity. Inflammatory bowel diseases (IBDs), the important immune-related diseases, can occur through immune system malfunction originating due to dysregulation of the gut microbiota. The aim of this study was to investigate the capabilities and mechanisms of Lactobacillus acidophilus (L. acidophilus) KBL402 and KBL409 treatment in the alleviation of colitis using the in vivo dextran sodium sulfate (DSS)-induced colitis mice model. Various colitis symptoms of mice, including disease activity index score [4.55 ± 0.99 (P < 0.001) and 5.12 ± 0.94 (P < 0.001), respectively], colon length [6.18 ± 0.43 mm (P < 0.001) and 6.62 ± 0.47 mm (P < 0.001), respectively], and colon histological score [(5.33 ± 1.03 (P < 0.001) and 4.00 ± 0.89 (P < 0.01), respectively)], were significantly restored with L. acidophilus KBL402 or KBL409 administration (1 × 10⁹ colony-forming units) for 8 days. Moreover, inflammatory cytokines, chemokines, and myeloperoxidase were downregulated in mice with L. acidophilus treatment. Upregulation of anti-inflammatory cytokine IL-10 or regulatory T cells were discovered with L. acidophilus KBL402 (12.90 ± 7.87 pg mL^-1) (P < 0.05) or L. acidophilus KBL409 treatment (10.63 ± 2.70%) (P < 0.05), respectively. Expressions of inflammation-related micro-RNAs (miRs) were also significantly altered in mice with L. acidophilus. Finally, L. acidophilus treatment could restore the diversity of the gut microbiota. Mice with L. acidophilus KBL402 treatment showed a high relative abundance of the genus Akkermansia (0.022 ± 0.017) and Prevotella (0.010 ± 0.006) (P < 0.01). Butyrate and propionate, the major short-chain fatty acids, in the ceca of DSS + KBL402-treated mice were significantly higher than in that of the mice with DSS-induced colitis (0.03 ± 0.02 ng mg^-1 and 0.03 ± 0.01 ng mg^-1, respectively) (P < 0.05). Our study suggests that L. acidophilus KBL402 and KBL409 could be useful for the prevention or treatment of IBDs in various ways including the modulation of immune responses and miR expression, restoration of the gut microbiota, and production of metabolites.

Lactobacillus fermentum species ameliorate dextran sulfate sodium-induced colitis by regulating the immune response and altering gut microbiota

We evaluated immunometabolic functions of novel Lactobacillus fermentum strains (KBL374 and KBL375) isolated from feces of healthy Koreans. The levels of inflammatory cytokines, such as interleukin (IL)-2, interferon-γ, IL-4, IL-13, and IL-17A, were decreased, and that of the anti-inflammatory cytokine IL-10 was increased, in human peripheral blood mononuclear cells (PBMCs) treated with the L. fermentum KBL374 or KBL375 strain. When these strains were orally administered to mice with dextran sulfate sodium (DSS)-induced colitis, both L. fermentum KBL374 and KBL375 showed beneficial effects on body weight, disease activity index score, colon length, cecal weight, and histological scores. Furthermore, both L. fermentum KBL374 and KBL375 modulated the innate immune response by improving gut barrier function and reducing leukocyte infiltration. Consistent with the PBMC data, both L. fermentum KBL374- and KBL375-treated DSS mice demonstrated decreased Th1-, Th2-, and Th17-related cytokine levels and increased IL-10 in the colon compared with the DSS control mice. Administration of L. fermentum KBL374 or KBL375 to mice increased the CD4+CD25+Foxp3+Treg cell population in mesenteric lymph nodes. Additionally, L. fermentum KBL374 or KBL375 administration reshaped and increased the diversity of the gut microbiota. In particular, L. fermentum KBL375 increased the abundance of beneficial microorganisms, such as Lactobacillus spp. and Akkermansia spp. Both L. fermentum KBL374 and KBL375 may alleviate inflammatory diseases, such as inflammatory bowel disease, in the gut by regulating immune responses and altering the composition of gut microbiota.

Tipping the balance: inhibitory checkpoints in intestinal homeostasis

The small intestinal and colonic lamina propria are populated with forkhead box P3 (FOXP3)⁺CD4⁺ regulatory T cells (Tregs) and interleukin-10-producing T cells that orchestrate intestinal tolerance to harmless microbial and food antigens. Expression of co-inhibitory receptors such as CTLA-4 and PD-1 serve as checkpoints to these cells controlling their T-cell receptor (TCR)-mediated and CD28-mediated activation and modulating the phenotype of neighboring antigen presenting cells. Recent discoveries on the diversity of co-inhibitory receptors and their selective cellular expression has shed new light on their tissue-dependent function. In this review, we provide an overview of the co-inhibitory pathways and checkpoints of Treg and effector T cells and their mechanisms of action in intestinal homeostasis. Better understanding of these inhibitory checkpoints is desired as their blockade harbors clinical potential for the treatment of cancer and their stimulation may offer new opportunities to treat chronic intestinal inflammation such as inflammatory bowel disease.

Biological agents for treatment of inflammatory bowel disease: Research progress and associated risks

Inflammatory bowel disease (IBD) is a group of chronic inflammatory gastrointestinal diseases with unknown etiology, which makes it difficult to reach an ideal treatment. Fortunately, with advances in the research of pathogenesis of IBD, several biological agents aiming diverse targets have been developed, bringing good news to patients with IBD. However, these new drugs carry some new risks, which should draw the attention of clinicians. The following review discusses the research progress in biological agents utilized in IBD and the related risks, with an aim to offer a new direction for the clinical treatment of IBD in the future.

Integrating the pathogenesis of spondyloarthritis: gut and joint united?

PURPOSE OF REVIEW

The association between spondyloarthritis (SpA) and inflammatory bowel disease (IBD) is well known. Additionally, about half of SpA patients show microscopic gut inflammation. Substantial progress has been made in understanding the pathogenesis of SpA and IBD, with new therapeutic targets for either of them in clinical development.

RECENT FINDINGS

Microscopic gut inflammation was found in early forms of SpA in about 50% of cases and is associated with age, sex, disease activity and degree of MRI inflammation on sacroiliac joints. Although prospective follow-up data in men and murine animal studies show a parallelism between gut and joint evolution in SpA, therapeutic outcomes are not always the same in SpA and IBD. These differences can be ascribed to differences in not only the cytokine pathways and cells involved in disease, tissue localization and environmental factors but also in pharmacokinetics and biodistribution.

SUMMARY

A significant amount of data all point in the direction of arthritis and gut inflammation being pathogenetically closely linked in the SpA concept. However, when it comes to therapeutic effectiveness, the gut and the joints do not always react in the same way. These differences in therapeutic effect could be attributed to the different ways in which cytokine pathways are involved in SpA and IBD.

Superoxide anion-induced pain and inflammation depends on TNFα/TNFR1 signaling in mice

Inhibition of tumor necrosis factor-alpha (TNFα) and superoxide anion production reduces inflammation and pain. The present study investigated whether superoxide anion-induced pain depends on TNFα signaling and the role of superoxide anion in TNFα-induced hyperalgesia to clarify the interrelation between these two mediators in the context of pain. Intraplantar injection of a superoxide anion donor (potassium superoxide) induced mechanical hyperalgesia (0.5-5h after injection), neutrophil recruitment (myeloperoxidase activity), and overt pain-like behaviors (paw flinching, paw licking, and abdominal writhings) in wild-type mice. Tumor necrosis factor receptor 1 deficiency (TNFR1-/-) and treatment of wild-type mice with etanercept (a soluble TNFR2 receptor that inhibits TNFα actions) inhibited superoxide anion-induced pain-like behaviors. TNFR1(-/-) mice were also protected from superoxide anion donor-induced oxidative stress, suggesting the role of this pathway in the maintenance of oxidative stress. Finally, we demonstrated that Apocynin (an NADPH oxidase inhibitor) or Tempol (a superoxide dismutase mimetic) treatment inhibited TNFα-induced paw mechanical hyperalgesia and neutrophil recruitment (myeloperoxidase activity). These results demonstrate that TNFα/TNFR1 signaling is important in superoxide anion-triggered pain and that TNFα/TNFR1 signaling amplifies the oxidative stress triggered by superoxide anion, which contributes to sustaining pain and inflammation.

Update on primary sclerosing cholangitis genetics

PURPOSE OF REVIEW

The pathogenesis of primary sclerosing cholangitis (PSC) involves heritable factors. This review summarizes the recent genetic studies and discusses the implications of identified risk loci.

RECENT FINDINGS

A total of 16 PSC susceptibility loci have been identified in genome-wide association studies and related study designs. At least 33 additional loci are involved in what is increasingly acknowledged to represent a general pool of genetic risk loci for immune-mediated diseases. One important group of genes is part of well characterized immune pathways (e.g. interleukin 2 signaling), whereas for other loci the relationship to PSC pathophysiology is less evident. Importantly, the loci collectively account for only 7.3% of overall PSC liability, thus pointing to a large contribution from environmental factors to PSC development. The individual PSC risk genes cannot be interpreted within a simple cause-effect model used for monogenic traits, but need to be explored for their individual biological correlates, preferably in a disease context. To some extent, as exemplified for the human leukocyte antigen and FUT2 associations, genetic findings may guide the discovery of interacting and co-occuring environmental susceptibility factors.

SUMMARY

Multiple PSC susceptibility loci are now available for exploration in experimental model systems and patient-centered research.

TNFRSF14 deficiency protects against ovariectomy-induced adipose tissue inflammation

To elucidate the role of tumor necrosis factor receptor superfamily member 14 (TNFRSF14) in metabolic disturbance due to loss of ovarian function, ovariectomy (OVX) was performed in TNFRSF 14-knockout mice. OVX increased fat mass and infiltration of highly inflammatory CD11c cells in the adipose tissue (AT), which was analyzed by flow cytometry, and resulted in disturbance of glucose metabolism, whereas TNFRSF14 deficiency attenuated these effects. TNFRSF14 deficiency decreased recruitment of CD11c-expressing cells in AT and reduced the polarization of bone marrow-derived macrophages to M1. Upon engagement of LIGHT, a TNFRSF14 ligand, TNFRSF14 enhanced the expression of CD11c via generation of reactive oxygen species, suggesting a role of TNFRSF14 as a redox modulator. TNFRSF14 participated in OVX-induced AT inflammation via upregulation of CD11c, resulting in metabolic perturbation. TNFRSF14 could be used as a therapeutic target for the treatment of postmenopausal syndrome by reducing AT inflammation.

Herpes virus entry mediator signaling in the brain is imperative in acute inflammation-induced anorexia and body weight loss

BACKGROUND

Reduced appetite and body weight loss are typical symptoms of inflammatory diseases. A number of inflammatory stimuli are responsible for the imbalance in energy homeostasis, leading to metabolic disorders. The herpes virus entry mediator (HVEM) protein plays an important role in the development of various inflammatory diseases, such as intestinal inflammation and diet-induced obesity. However, the role of HVEM in the brain is largely unknown. This study aims to investigate whether HVEM signaling in the brain is involved in inflammation-induced anorexia and body weight loss.

METHODS

Food intake and body weight were measured at 24 hours after intraperitoneal injection of lipopolysaccharide (LPS) or intracerebroventricular injection of recombinant mouse LIGHT (also called tumor necrosis factor receptor superfamily 14, TNFSF14), an HVEM ligand, into 8- to 10-week-old male C57BL/6 mice and mice lacking HVEM expression (HVEM-/-). We also assessed LPS-induced change in hypothalamic expression of HVEM using immunohistochemistry.

RESULTS

Administration of LPS significantly reduced food intake and body weight, and moreover, increased expression of HVEM in the hypothalamic arcuate nucleus. However, LPS induced only minor decreases in food intake and body weight in HVEM-/- mice. Administration of LIGHT into the brain was very effective at decreasing food intake and body weight in wild-type mice, but was less effective in HVEM-/- mice.

CONCLUSION

Activation of brain HVEM signaling is responsible for inflammation-induced anorexia and body weight loss.

Regulation of inflammation-associated olfactory neuronal death and regeneration by the type II tumor necrosis factor receptor

BACKGROUND

Olfactory loss is a debilitating symptom of chronic rhinosinusitis. To study the impact of inflammation on the olfactory system, the inducible olfactory inflammation (IOI) transgenic mouse was created in which inflammation can be turned on and off within the olfactory epithelium. In this study, the type II tumor necrosis factor (TNF) receptor (TNFR2) was knocked out, and the effect on the olfactory loss phenotype was assessed.

METHODS

IOI mice were bred to TNFR2 knockout mice to yield progeny IOI mice lacking the TNFR2 receptor (TNFR2(-/-) ). TNF-α expression was induced within the olfactory epithelium for 6 weeks to generate chronic inflammation. Olfactory function was assayed by electro-olfactogram (EOG), and olfactory tissue was processed for histology and immunohistochemical staining.

RESULTS

Compared to IOI mice with wild-type TNFR2, IOI mice lacking the TNFR2 demonstrated similar levels of inflammatory infiltration and enlargement of the subepithelial layer. However, IOI-TNFR2(-/-) mice differed markedly in that the neuronal layer was largely preserved and active progenitor cell proliferation was present. Odorant responses were maintained in the IOI-TNFR2(-/-) mice, in contrast to IOI mice.

CONCLUSION

TNFR2 is the minor receptor for TNF-α, but appears to play an important role in mediating TNF-induced disruption of the olfactory system. This finding suggests that neuronal death and inhibition of proliferation in CRS may be mediated by TNFR2 on olfactory neurons and progenitor cells. Further studies are needed to elucidate the subcellular pathways involved and develop novel therapies for treating olfactory loss in the setting of CRS.

Absence of herpes virus entry mediator (HVEM) increases bone mass by attenuating receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis

Herpes virus entry mediator (HVEM), which is constitutively expressed at a high level on myeloid lineage cells, is also expressed on bone marrow-derived macrophages, suggesting that it may play a role in bone metabolism by affecting osteoclasts (OC) derived from bone marrow-derived macrophages. To address this question, we evaluated bone mass by micro-computed tomography and the number and activity of OC by tartrate-resistant acid phosphatase (TRAP) and pit formation on dentine slices, comparing HVEM-knockout mice with wild-type mice. The absence of HVEM led to a higher bone mass and to decreased levels of serum collagen type I fragments and serum TRACP5b in vivo. In vitro HVEM deficiency resulted in a reduced number and activity of OC and an impaired receptor activator of nuclear factor-κB ligand signaling through reduced activation of nuclear factor-κB and of nuclear factor of activated T-cells cytoplasmic 1. Exogenous soluble HVEM decreased expression of TRAP, whereas soluble LIGHT (a ligand of HVEM) increased it, indicating the occurrence of a positive signaling through HVEM during osteoclastogenesis. Our findings indicate that HVEM regulates bone remodeling via action on OC. The higher bone mass in the femurs of HVEM-knockout mice could be, at least in part, due to attenuated osteoclastogenesis and bone resorption resulting from decreased receptor activator of nuclear factor-κB ligand signaling in the OC.

LIGHT/TNFSF14 enhances adipose tissue inflammatory responses through its interaction with HVEM

Obesity-induced adipose tissue inflammation is characterized by increased macrophage infiltration and cytokine production, and is associated with metabolic disorders. LIGHT/TNFSF14, a member of the TNF superfamily, plays a role in the development of various inflammatory diseases. The purpose of this study was to examine the involvement of soluble LIGHT (sLIGHT) in obesity-induced adipose tissue inflammatory responses. LIGHT gene expression on macrophages/adipocytes was upregulated by treatment with obesity-related factors. sLIGHT displayed chemotactic activity for macrophages and T cells, and enhanced inflammatory cytokine release from macrophages, adipocytes, and adipose tissue-derived SVF cells. The sLIGHT-induced inflammatory responses were blunted by neutralizing anti-HVEM antibody or knockout of HVEM, a receptor for sLIGHT. These findings indicate that sLIGHT enhances adipose tissue inflammatory responses through its interaction with HVEM.