Enhanced intestinal inflammation induced by dextran sulfate sodium in tumor necrosis factor-alpha deficient mice

Cocoa and Polyphenol-Rich Cocoa Fractions Fail to Improve Acute Colonic Inflammation in Dextran Sulfate Sodium-Treated Mice

SCOPE

A study is conducted to determine the anti-inflammatory effects of cocoa and polyphenol-rich cocoa fractions in the dextran sulfate sodium (DSS)-induced mouse model of acute colonic inflammation.

METHODS AND RESULTS

Male C57BL/6J mice are treated with dietary cocoa powder, an extractable cocoa polyphenol fraction, or a non-extractable cocoa polyphenol fraction for 2 weeks prior to treatment with 2.5% DSS in the drinking water for 7 days to induce colonic inflammation. Cocoa treatment continues during the DSS period. Cocoa and/or cocoa fractions exacerbate DSS-induced weight loss and fail to mitigate DSS-induced colon shortening but do improve splenomegaly. Cocoa/cocoa fraction treatment fails to mitigate DSS-induced mRNA and protein markers of inflammation. Principal component analysis shows overlap between cocoa or cocoa fraction-treated mice and DSS-induced controls, but separation from mice not treated with DSS.

CONCLUSION

The results suggest cocoa and cocoa polyphenols may not be useful in mitigating acute colonic inflammation.

Solute Transporter OCTN1/Slc22a4 Affects Disease Severity and Response to Infliximab in Experimental Colitis: Role of Gut Microbiota and Immune Modulation

BACKGROUND

Inflammatory bowel diseases are chronic disabling conditions with a complex and multifactorial etiology, still incompletely understood. OCTN1, an organic cation transporter, could have a role in modulating the inflammatory response, and some genetic polymorphisms of this molecule have been associated with increased risk of inflammatory bowel diseases. Until now, limited information exists on its potential in predicting/modulating patient's response to therapies. The aim of this study was to evaluate the role of OCTN1 in modifying gut microbiota and mucosal immunity in response to infliximab therapy in murine colitis.

METHODS

A dextran sodium sulphate model of colitis was used to assess the clinical efficacy of infliximab administered intravenously in ocnt1 gene knockout mice and their C57BL/6 controls. Stool, colon, and mesenteric lymph node samples were collected to evaluate differences in gut microbiota composition, histology, and T cell populations, respectively.

RESULTS

Octn1 -/- influences the microbiota profile and is associated with a worse dysbiosis in mice with colitis. Infliximab treatment attenuates colitis-associated dysbiosis, with an increase of bacterial richness and evenness in both strains. In comparison with wild type, octn1-/- mice have milder disease and a higher baseline percentage of Treg, Tmemory, Th2 and Th17 cells.

CONCLUSIONS

Our data support the murine model to study OCTN1 genetic contribution to inflammatory bowel diseases. This could be the first step towards the recognition of this membrane transporter as a biomarker in inflammatory conditions and a predictor of response to therapies.

Epithelial TIPE1 Protein Guards against Colitis by Inhibiting TNF-α-Mediated Inflammation

Intestinal epithelial cells (IECs) at the internal/external interface orchestrate the mucosal immune response, and IEC dysfunction has been linked to multiple inflammatory diseases, including inflammatory bowel disease. In this study, we found that a member of the TNF-α-induced protein 8 (TNFAIP8 or TIPE) family called TIPE1 is indispensable for maintaining epithelial cell barrier integrity and homeostasis under inflammatory conditions. TIPE1-deficient mice, or chimeric mice that were deficient in TIPE1 in their nonhematopoietic cells, were more sensitive to dextran sulfate sodium-induced experimental colitis; however, TIPE1 deficiency had no impact on the development of inflammation-associated and sporadic colorectal cancers. Mechanistically, TIPE1 prevented experimental colitis through modulation of TNF-α-dependent inflammatory response in IECs. Importantly, genetic deletion of both TIPE1 and its related protein TNFAIP8 in mice led to the development of spontaneous chronic colitis, indicating that both of these two TIPE family members play crucial roles in maintaining intestinal homeostasis. Collectively, our findings highlight an important mechanism by which TIPE family proteins maintain intestinal homeostasis and prevent inflammatory disorders in the gut.

Terpenes: Modulating anti-inflammatory signaling in inflammatory bowel disease

Inflammatory Bowel Disease (IBD) are autoimmune diseases characterized by chronic intestinal inflammation. Considered a western disease, IBD incidence in newly developed countries is skyrocketing. Accordingly, global prevalence is steadily increasing. There are two major IBD phenotypes, ulcerative colitis (UC) and Crohn's disease (CD). UC manifests as uninterrupted inflammation localized in the colon and rectum. Meanwhile, CD presents as interrupted inflammation that can occur throughout the digestive tract. As a result, therapeutics have focused on anti-inflammatory approaches for its treatment. Unfortunately, only 50% of patients benefit from current Food and Drug Administration approved treatments, and all are associated with serious adverse effects. Thus, there is a need for safer and novel therapeutics to increase the efficacy in this population. One aspect that is critical in understanding IBD is how food and phytochemicals therein may be associated with modifying the pathogenesis of IBD. A variety of retrospective and prospective studies, and clinical trials have shown benefits of plant-rich diets on the prevention and symptomatic improvement of IBD. The Mediterranean diet is rich in vegetables, fruits, legumes, and herbs; and characterized by the abundance of anti-inflammatory phytochemicals. An understudied phytochemical class enriched in this diet is terpenes; isoprene-based molecules are widely available in Mediterranean herbs and citrus fruits. Various terpenes have been evaluated in different IBD models. However, some present contradictory or inconclusive results. Therefore, in this review we evaluated preclinical studies of terpenes modulating basic inflammatory signaling related to IBD.

Diet-induced obesity alters intestinal monocyte-derived and tissue-resident macrophages and increases intestinal permeability in female mice independent of tumor necrosis factor

Macrophages are essential for homeostatic maintenance of the anti-inflammatory and tolerogenic intestinal environment, yet monocyte-derived macrophages can promote local inflammation. Proinflammatory macrophage accumulation within the intestines may contribute to the development of systemic chronic inflammation and immunometabolic dysfunction in obesity. Using a model of high-fat diet-induced obesity in C57BL/6J female mice, we assessed intestinal paracellular permeability by in vivo and ex vivo assays and quantitated intestinal macrophages in ileum and colon tissues by multicolor flow cytometry after short (6 wk), intermediate (12 wk), and prolonged (18 wk) diet allocation. We characterized monocyte-derived CD4^-TIM4^- and CD4⁺TIM4^- macrophages, as well as tissue-resident CD4⁺TIM4⁺ macrophages. Diet-induced obesity had tissue- and time-dependent effects on intestinal permeability, as well as monocyte and macrophage numbers, surface marker phenotype, and intracellular production of the cytokines IL-10 and tumor necrosis factor (TNF). We found that obese mice had increased paracellular permeability, in particular within the ileum, but this did not elicit recruitment of monocytes nor a local proinflammatory response by monocyte-derived or tissue-resident macrophages in either the ileum or colon. Proliferation of monocyte-derived and tissue-resident macrophages was also unchanged. Wild-type and TNF^-/- littermate mice had similar intestinal permeability and macrophage population characteristics in response to diet-induced obesity. These data are unique from reported effects of diet-induced obesity on macrophages in metabolic tissues, as well as outcomes of acute inflammation within the intestines. These experiments also collectively indicate that TNF does not mediate effects of diet-induced obesity on paracellular permeability or intestinal monocyte-derived and tissue-resident intestinal macrophages in young female mice.NEW & NOTEWORTHY We found that diet-induced obesity in female mice has tissue- and time-dependent effects on intestinal paracellular permeability as well as monocyte-derived and tissue-resident macrophage numbers, surface marker phenotype, and intracellular production of the cytokines IL-10 and TNF. These changes were not mediated by TNF.

Insights into radiation carcinogenesis based on dose-rate effects in tissue stem cells

PURPOSE

Increasing epidemiological and biological evidence suggests that radiation exposure enhances cancer risk in a dose-dependent manner. This can be attributed to the 'dose-rate effect,' where the biological effect of low dose-rate radiation is lower than that of the same dose at a high dose-rate. This effect has been reported in epidemiological studies and experimental biology, although the underlying biological mechanisms are not completely understood. In this review, we aim to propose a suitable model for radiation carcinogenesis based on the dose-rate effect in tissue stem cells.

METHODS

We surveyed and summarized the latest studies on the mechanisms of carcinogenesis. Next, we summarized the radiosensitivity of intestinal stem cells and the role of dose-rate in the modulation of stem-cell dynamics after irradiation.

RESULTS

Consistently, driver mutations can be detected in most cancers from past to present, supporting the hypothesis that cancer progression is initiated by the accumulation of driver mutations. Recent reports demonstrated that driver mutations can be observed even in normal tissues, which suggests that the accumulation of mutations is a necessary condition for cancer progression. In addition, driver mutations in tissue stem cells can cause tumors, whereas they are not sufficient when they occur in non-stem cells. For non-stem cells, tissue remodeling induced by marked inflammation after the loss of tissue cells is important in addition to the accumulation of mutations. Therefore, the mechanism of carcinogenesis differs according to the cell type and magnitude of stress. In addition, our results indicated that non-irradiated stem cells tend to be eliminated from three-dimensional cultures of intestinal stem cells (organoids) composed of irradiated and non-irradiated stem cells, supporting the stem-cell competition.

CONCLUSIONS

We propose a unique scheme in which the dose-rate dependent response of intestinal stem cells incorporates the concept of the threshold of stem-cell competition and context-dependent target shift from stem cells to whole tissue. The concept highlights four key issues that should be considered in radiation carcinogenesis: i.e. accumulation of mutations; tissue reconstitution; stem-cell competition; and environmental factors like epigenetic modifications.

Acute Administration of Ojeok-san Ameliorates Pain-like Behaviors in Pre-Clinical Models of Inflammatory Bowel Diseases

(1) Background: Gastrointestinal pain and fatigue are the most reported concerns of patients with inflammatory bowel disease (IBD). Commonly prescribed drugs focus on decreasing excessive inflammation. However, up to 20% of IBD patients in an "inactive" state experience abdominal pain. The medicinal herb Ojeok-san (OJS) has shown promise in the amelioration of visceral pain. However, no research on OJS has been conducted in preclinical models of IBD. The mechanism by which OJS promotes analgesia is still elusive, and it is unclear if OJS possesses addictive properties. (2) Aims: In this study, we examined the potential of OJS to promote analgesic effects and rewarding behavior. Additionally, we investigated if tumor necrosis factor alpha (TNFα) from macrophages is a primary culprit of IBD-induced nociception. (3) Methods: Multiple animal models of IBD were used to determine if OJS can reduce visceral nociception. TNFα-macrophage deficient mice were used to investigate the mechanism of action by which OJS reduces nociceptive behavior. Mechanical sensitivity and operant conditioning tests were used to determine the analgesic and rewarding effects of OJS. Body weight, colon length/weight, blood in stool, colonic inflammation, and complete blood count were assessed to determine disease progression. (4) Results: OJS reduced the evoked mechanical nociception in the dextran sulphate sodium model of colitis and IL-10 knockout (KO) mice and delayed aversion to colorectal distension in C57BL/6 mice. No rewarding behavior was observed in OJS-treated IL-10 KO and mdr1a KO mice. The analgesic effects of OJS are independent of macrophage TNFα levels and IBD progression. (5) Conclusions: OJS ameliorated elicited mechanical and visceral nociception without producing rewarding effects. The analgesic effects of OJS are not mediated by macrophage TNFα.

The Effect of Necrosis Inhibitor on Dextran Sulfate Sodium Induced Chronic Colitis Model in Mice

Uncontrolled chronic inflammation and necrosis is characteristic of inflammatory bowel disease (IBD). This study aimed to investigate the effect of necrosis inhibitor (NI, NecroX-7) on a dextran sulfate sodium (DSS) induced chronic colitis model of mice. DSS was administered on days 1-5, and the NI was administered intraperitoneally (3 mg/kg, 30 mg/kg) on days 1, 3, and 5 as well as every other day during the first five days of a three-week cycle. Three cycles of administration were performed. Colitis was evaluated based on the disease activity index (DAI) score, colon length, and histological score. Reverse transcription polymerase chain reaction testing, the Western blot assay, and immunohistochemical staining were performed to determine inflammatory cytokine levels. The NI reduced body weight change and the DAI score. Colon length and the histological score were longer and lower in the NI-treated groups, respectively. The NI decreased the expression of pro-inflammatory cytokines, particularly in tumor necrosis factor alpha (TNF-α) and phosphorylated nuclear factor kappa B (p-NF-κB). Immunohistochemical staining revealed decreased inducible nitric oxide synthase (iNOS) and high mobility group box 1 (HMGB1) levels. Overall, the NI improved DSS induced chronic colitis by attenuating the mRNA expression of pro-inflammatory cytokines such as TNF-α. Therefore, NI use is a potential, novel treatment approach for IBD.

PR1P, a VEGF-stabilizing peptide, reduces injury and inflammation in acute lung injury and ulcerative colitis animal models

Acute Respiratory Distress Syndrome (ARDS) and Ulcerative Colitis (UC) are each characterized by tissue damage and uncontrolled inflammation. Neutrophils and other inflammatory cells play a primary role in disease progression by acutely responding to direct and indirect insults to tissue injury and by promoting inflammation through secretion of inflammatory cytokines and proteases. Vascular Endothelial Growth Factor (VEGF) is a ubiquitous signaling molecule that plays a key role in maintaining and promoting cell and tissue health, and is dysregulated in both ARDS and UC. Recent evidence suggests a role for VEGF in mediating inflammation, however, the molecular mechanism by which this occurs is not well understood. We recently showed that PR1P, a 12-amino acid peptide that binds to and upregulates VEGF, stabilizes VEGF from degradation by inflammatory proteases such as elastase and plasmin thereby limiting the production of VEGF degradation products (fragmented VEGF (fVEGF)). Here we show that fVEGF is a neutrophil chemoattractant in vitro and that PR1P can be used to reduce neutrophil migration in vitro by preventing the production of fVEGF during VEGF proteolysis. In addition, inhaled PR1P reduced neutrophil migration into airways following injury in three separate murine acute lung injury models including from lipopolysaccharide (LPS), bleomycin and acid. Reduced presence of neutrophils in the airways was associated with decreased pro-inflammatory cytokines (including TNF-α, IL-1β, IL-6) and Myeloperoxidase (MPO) in broncho-alveolar lavage fluid (BALF). Finally, PR1P prevented weight loss and tissue injury and reduced plasma levels of key inflammatory cytokines IL-1β and IL-6 in a rat TNBS-induced colitis model. Taken together, our data demonstrate that VEGF and fVEGF may each play separate and pivotal roles in mediating inflammation in ARDS and UC, and that PR1P, by preventing proteolytic degradation of VEGF and the production of fVEGF may represent a novel therapeutic approach to preserve VEGF signaling and inhibit inflammation in acute and chronic inflammatory diseases.

The spring-like effect of microRNA-31 in balancing inflammatory and regenerative responses in colitis

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders caused by the disruption of immune tolerance to the gut microbiota. MicroRNA-31 (MIR31) has been proven to be up-regulated in intestinal tissues from patients with IBDs and colitis-associated neoplasias. While the functional role of MIR31 in colitis and related diseases remain elusive. Combining mathematical modeling and experimental analysis, we systematically explored the regulatory mechanism of MIR31 in inflammatory and epithelial regeneration responses in colitis. Level of MIR31 presents an "adaptation" behavior in dextran sulfate sodium (DSS)-induced colitis, and the similar behavior is also observed for the key cytokines of p65 and STAT3. Simulation analysis predicts MIR31 suppresses the activation of p65 and STAT3 but accelerates the recovery of epithelia in colitis, which are validated by our experimental observations. Further analysis reveals that the number of proliferative epithelial cells, which characterizes the inflammatory process and the recovery of epithelia in colitis, is mainly determined by the inhibition of MIR31 on IL17RA. MIR31 promotes epithelial regeneration in low levels of DSS-induced colitis but inhibits inflammation with high DSS levels, which is dominated by the competition for MIR31 to either inhibit inflammation or promote epithelial regeneration by binding to different targets. The binding probability determines the functional transformation of MIR31, but the functional strength is determined by MIR31 levels. Thus, the role of MIR31 in the inflammatory response can be described as the "spring-like effect," where DSS, MIR31 action strength, and proliferative epithelial cell number are regarded as external force, intrinsic spring force, and spring length, respectively. Overall, our study uncovers the vital roles of MIR31 in balancing inflammation and the recovery of epithelia in colitis, providing potential clues for the development of therapeutic targets in drug design.

COVID-19 and Gut Injury

COVID-19 induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently a pandemic and it has led to more than 620 million patients with 6.56 million deaths globally. Males are more susceptible to COVID-19 infection and associated with a higher chance to develop severe COVID-19 than females. Aged people are at a high risk of COVID-19 infection, while young children have also increased cases. COVID-19 patients typically develop respiratory system pathologies, however symptoms in the gastrointestinal (GI) tract are also very common. Inflammatory cell recruitments and their secreted cytokines are found in the GI tract in COVID-19 patients. Microbiota changes are the key feature in COVID-19 patients with gut injury. Here, we review all current known mechanisms of COVID-19-induced gut injury, and the most acceptable one is that SARS-CoV-2 binds to angiotensin-converting enzyme 2 (ACE2) receptor on host cells in the GI tract. Interestingly, inflammatory bowel disease (IBD) is an inflammatory disorder, but the patients with IBD do not have the increased risk to develop COVID-19. There is currently no cure for COVID-19, but anti-viruses and monoclonal antibodies reduce viral load and shorten the recovery time of the disease. We summarize current therapeutics that target symptoms in the GI tract, including probiotics, ACE2 inhibitors and nutrients. These are promising therapeutic options for COVID-19-induced gut injury.

The Immune Change of the Lung and Bowel in an Ulcerative Colitis Rat Model and the Protective Effect of Sodium Houttuyfonate Combined With Matrine

Objective

To explore the immune change of lung injury of Ulcerative colitis (UC) by observing the changes of inherent immunity and adaptive immunity of the lung and bowel in UC rat models after the treatment of Sodium Houttuyfonate combined with Matrine.

Method

UC rat models were established with the mucous membrane of colon allergize combined with TNBS-alcohol enteroclysis for 1 week and 5 weeks. 1-week experimental rats were divided into normal group and model group, 5/each group. 5-weeks experimental rats were divided into normal group, model group, Sodium Houttuyfonate (2.9mg/ml) combined with Matrine (1.47mg/ml), and positive control sulfasalazine (10mg/ml), 5/each group. All rats were administered by gavage for 5 weeks. The histopathological and fibrotic changes in the lung and bowel were observed, and the expressions of Tumor Necrosis Factor (TNF)- α, interleukin (IL)-8 in the lung, bowel, and serum were detected by radio-immunity and immunohistochemistry, and the mRNA expressions of Toll-like receptor (TLR)-4, nuclear factor kappa (NF-κB), Macrophage migration inhibitory factor (MIF), Mucosal addressing cell adhesion molecule-1 (MadCAM1) and Pulmonary surfactant protein-A (SP-A) in the lung and bowel were detected by Real time-PCR.

Result

Compared with the normal group, the model rats had significant histopathological and fibrotic changes both in the lung and bowel, and all treatment groups were improved. After treatment, TLR4, IL-8, MIF, and TNF-α in the lung decreased (P<0.05); NF-KB, IL-8, and MIF in the bowel increased (P<0.05); MadCAM1 both in lung and bowel decreased (P<0.05); SP-A decreased in bowel and increased in the lung (P<0.05).

Conclusion

The cause of lung injury in this model was found to be related to inherent immunity and adaptive immunity, while the cause of bowel injury in this model was found to be mainly related to adaptive immunity. Sodium Houttuyfonate combined with Matrine could improve bowel and lung injury.

Macrophage orchestration of epithelial and stromal cell homeostasis in the intestine

The intestinal tract is a complex ecosystem where numerous cell types of epithelial, immune, neuronal, and endothelial origin coexist in an intertwined, highly organized manner. The functional equilibrium of the intestine relies heavily on the proper crosstalk and cooperation among each cell population. Furthermore, macrophages are versatile, innate immune cells that participate widely in the modulation of inflammation and tissue remodeling. Emerging evidence suggest that macrophages are central in orchestrating tissue homeostasis. Herein, we describe how macrophages interact with epithelial cells, neurons, and other types of mesenchymal cells under the context of intestinal inflammation, followed by the therapeutic implications of cellular crosstalk pertaining to the treatment of inflammatory bowel disease.

Crocetin Prolongs Recovery Period of DSS-Induced Colitis via Altering Intestinal Microbiome and Increasing Intestinal Permeability

Crocetin is one of the major active constituents of saffron (Crocus sativus L.) which has a reputation for facilitating blood circulation and dispersing blood stasis in traditional Chinese medicine. However, there is little evidence showing the relationship between crocetin intake and the risk of gastrointestinal diseases such as colitis. In order to investigate the effect of crocetin on the regulation of intestinal barrier function and intestinal microbiota composition, mice were treated with crocetin after 3% dextran sulfate sodium (DSS) administration for one week. We found that crocetin intake at 10 mg/kg aggravated colitis in mice, showing increased weight loss and more serious histological abnormalities compared with the DSS group. The 16s rDNA sequencing analysis of the feces samples showed that mice treated with 10 mg/kg crocetin had lower species diversity and richness than those treated with DSS. At the genus level, a higher abundance of Akkermansia and Mediterraneibacter, and a lower abundance of Muribaculaceae, Dubosiella, Paramuribaculum, Parasutterella, Allobaculum, Duncaniella, Candidatus Stoquefichus, and Coriobacteriaceae UCG-002 were observed in the crocetin group. Untargeted metabolomic analyses revealed that crocetin reduced the levels of primary and secondary bile acids such as 12-ketodeoxycholic acid, 7-ketodeoxycholic acid, 3-sulfodeoxycholic acid, 6-ethylchenodeoxycholic acid, chenodeoxycholate, glycochenodeoxycholate-7-sulfate, glycocholate, and sulfolithocholic acid in the colon. In conclusion, crocetin intake disturbed intestinal homeostasis and prolonged recovery of colitis by promoting inflammation and altering gut microbiota composition and its metabolic products in mice. Our findings suggest that patients with gastrointestinal diseases such as inflammatory bowel disease should use crocetin with caution.

Macrophage control of Crohn's disease

The intestinal tract is the body's largest mucosal surface and permanently exposed to microbial and environmental signals. Maintaining a healthy intestine requires the presence of sentinel grounds keeper cells, capable of controlling immunity and tissue homeostasis through specialized functions. Intestinal macrophages are such cells and important players in steady-state functions and during acute and chronic inflammation. Crohn's disease, a chronic inflammatory condition of the intestinal tract is proposed to be the consequence of an altered immune system through microbial and environmental stimulation. This hypothesis suggests an involvement of macrophages in the regulation of this pathology. Within this chapter, we will discuss intestinal macrophage development and highlight data suggesting their implication in chronic intestinal pathologies like Crohn's disease.

GPR35 in Intestinal Diseases: From Risk Gene to Function

Diet and gut microbial metabolites mediate host immune responses and are central to the maintenance of intestinal health. The metabolite-sensing G-protein coupled receptors (GPCRs) bind metabolites and trigger signals that are important for the host cell function, survival, proliferation and expansion. On the contrary, inadequate signaling of these metabolite-sensing GPCRs most likely participate to the development of diseases including inflammatory bowel diseases (IBD). In the intestine, metabolite-sensing GPCRs are highly expressed by epithelial cells and by specific subsets of immune cells. Such receptors provide an important link between immune system, gut microbiota and metabolic system. Member of these receptors, GPR35, a class A rhodopsin-like GPCR, has been shown to be activated by the metabolites tryptophan-derived kynurenic acid (KYNA), the chemokine CXCL17 and phospholipid derivate lysophosphatidic acid (LPA) species. There have been studies on GPR35 in the context of intestinal diseases since its identification as a risk gene for IBD. In this review, we discuss the pharmacology of GPR35 including its proposed endogenous and synthetic ligands as well as its antagonists. We elaborate on the risk variants of GPR35 implicated in gut-related diseases and the mechanisms by which GPR35 contribute to intestinal homeostasis.

Tumor Necrosis Factor's Pathway in Crohn's Disease: Potential for Intervention

Crohn’s disease (CD) is a chronic disorder characterized by full thickness patchy inflammation of the gastrointestinal tract. The pathogenesis is multifactorial and involves defective innate immune responses, microbiome alterations, and dysregulated activation of the acquired component of mucosal immunity. One of the molecular mediators that is involved at different levels in the initiation and progression of intestinal inflammation characteristic of CD is tumor necrosis factor (TNF). The present manuscript provides a comprehensive review focused on the potential role of TNF in the different phases of CD pathogenesis, particularly in light of its potential clinical implications. Currently available drugs blocking TNF are evaluated and discussed, specifically for open issues that still remain utilizing such therapy. TNF exerts a paramount role in the established phase of intestinal inflammation that characterizes CD patients, and anti-TNF biologics have definitely changed patient management, offering effective and safe options of treatment. Nonetheless, many patients still do not respond to anti-TNF therapy or experience unwanted side-effects. This could partially be due to the role that TNF plays in intestinal homeostasis that is particularly important during the early phase of the inflammatory process. In fact, emerging evidence supporting the dichotomous role of TNF and the identification of molecular markers will guide a more tailored and refined therapy for CD patients in the near future.

Lysophosphatidic Acid-Mediated GPR35 Signaling in CX3CR1+ Macrophages Regulates Intestinal Homeostasis

Single-nucleotide polymorphisms in the gene encoding G protein-coupled receptor 35 (GPR35) are associated with increased risk of inflammatory bowel disease. However, the mechanisms by which GPR35 modulates intestinal immune homeostasis remain undefined. Here, integrating zebrafish and mouse experimental models, we demonstrate that intestinal Gpr35 expression is microbiota dependent and enhanced upon inflammation. Moreover, murine GPR35⁺ colonic macrophages are characterized by enhanced production of pro-inflammatory cytokines. We identify lysophosphatidic acid (LPA) as a potential endogenous ligand produced during intestinal inflammation, acting through GPR35 to induce tumor necrosis factor (Tnf) expression in macrophages. Mice lacking Gpr35 in CX3CR1⁺ macrophages aggravate colitis when exposed to dextran sodium sulfate, which is associated with decreased transcript levels of the corticosterone-generating gene Cyp11b1 and macrophage-derived Tnf. Administration of TNF in these mice restores Cyp11b1 expression and intestinal corticosterone production and ameliorates DSS-induced colitis. Our findings indicate that LPA signals through GPR35 in CX3CR1⁺ macrophages to maintain TNF-mediated intestinal homeostasis.

Intestinal Regeneration: Regulation by the Microenvironment

Damage to the intestinal stem cell niche can result from mechanical stress, infections, chronic inflammation or cytotoxic therapies. Progenitor cells can compensate for insults to the stem cell population through dedifferentiation. The microenvironment modulates this regenerative response by influencing the activity of signaling pathways, including Wnt, Notch, and YAP/TAZ. For instance, mesenchymal cells and immune cells become more abundant after damage and secrete signaling molecules that promote the regenerative process. Furthermore, regeneration is influenced by the nutritional state, microbiome, and extracellular matrix. Here, we review how all these components cooperate to restore epithelial homeostasis in the intestine after injury.

Probiotic lactobacilli as a promising strategy to ameliorate disorders associated with intestinal inflammation induced by a non-steroidal anti-inflammatory drug

Damage to the small intestine caused by non-steroidal anti-inflammatory drugs (NSAIDs) occurs more frequently than in the upper gastrointestinal tract, is more difficult to diagnose and no effective treatments exist. Hence, we investigated whether probiotics can control the onset of this severe condition in a murine model of intestinal inflammation induced by the NSAID, indomethacin. Probiotic supplementation to mice reduce the body weight loss, anemia, shortening of the small intestine, cell infiltration into the intestinal tissue and the loss of Paneth and Goblet cells associated with intestinal inflammation. Furthermore, a high antimicrobial activity in the intestinal fluids of mice fed with probiotics compared to animals on a conventional diet was elicited against several pathogens. Interestingly, probiotics dampened the oxidative stress and several local and systemic markers of an inflammatory process, as well as increased the secretion of IL-10 by regulatory T cells. Even more importantly, probiotics induced important changes in the large intestine microbiota characterized by an increase in anaerobes and lactobacilli, and a significant decrease in total enterobacteria. We conclude that oral probiotic supplementation in NSAID-induced inflammation increases intestinal antimicrobial activity and reinforces the intestinal epithelial barrier in order to avoid pathogens and commensal invasion and maintain intestinal homeostasis.

Tumor Necrosis Factor Receptor-1 (p55) Deficiency Attenuates Tumor Growth and Intratumoral Angiogenesis and Stimulates CD8+ T Cell Function in Melanoma

The role of tumor necrosis factor-α (TNF-α) in shaping the tumor microenvironment is ambiguous. Consistent with its uncertain role in melanoma, TNF-α plays a dual role, either acting as a cytotoxic cytokine or favoring a tumorigenic inflammatory microenvironment. TNF-α signals via two cognate receptors, namely TNFR1 (p55) and TNFR2 (p75), which mediate divergent biological activities. Here, we analyzed the impact of TNFR1 deficiency in tumor progression in the B16.F1 melanoma model. Tumors developed in mice lacking TNFR1 (TNFR1 knock-out; KO) were smaller and displayed lower proliferation compared to their wild type (WT) counterpart. Moreover, TNFR1 KO mice showed reduced tumor angiogenesis. Although no evidence of spontaneous metastases was observed, conditioned media obtained from TNFR1 KO tumors increased tumor cell migration. Whereas the analysis of tumor-associated immune cell infiltrates showed similar frequency of total and M2-polarized tumor-associated macrophages (TAMs), the percentage of CD8⁺ T cells was augmented in TNFR1 KO tumors. Indeed, functional ex vivo assays demonstrated that CD8⁺ T cells obtained from TNFR1KO mice displayed an increased cytotoxic function. Thus, lack of TNFR1 attenuates melanoma growth by modulating tumor cell proliferation, migration, angiogenesis and CD8⁺ T cell accumulation and activation, suggesting that interruption of TNF-TNFR1 signaling may contribute to control tumor burden.

Exclusive enteral nutrition mediates gut microbial and metabolic changes that are associated with remission in children with Crohn's disease

A nutritional intervention, exclusive enteral nutrition (EEN) can induce remission in patients with pediatric Crohn's disease (CD). We characterized changes in the fecal microbiota and metabolome to identify the mechanism of EEN. Feces of 43 children were collected prior, during and after EEN. Microbiota and metabolites were analyzed by 16S rRNA gene amplicon sequencing and NMR. Selected metabolites were evaluated in relevant model systems. Microbiota and metabolome of patients with CD and controls were different at all time points. Amino acids, primary bile salts, trimethylamine and cadaverine were elevated in patients with CD. Microbiota and metabolome differed between responders and non-responders prior to EEN. EEN decreased microbiota diversity and reduced amino acids, trimethylamine and cadaverine towards control levels. Patients with CD had reduced microbial metabolism of bile acids that partially normalized during EEN. Trimethylamine and cadaverine inhibited intestinal cell growth. TMA and cadaverine inhibited LPS-stimulated TNF-alpha and IL-6 secretion by primary human monocytes. A diet rich in free amino acids worsened inflammation in the DSS model of intestinal inflammation. Trimethylamine, cadaverine, bile salts and amino acids could play a role in the mechanism by which EEN induces remission. Prior to EEN, microbiota and metabolome are different between responders and non-responders.

Enhancing responsiveness of human jejunal enteroids to host and microbial stimuli

KEY POINTS

Enteroids are a physiologically relevant model to examine the human intestine and its functions. Previously, the measurable cytokine response of human intestinal enteroids has been limited following exposure to host or microbial pro-inflammatory stimuli. Modifications to enteroid culture conditions facilitated robust human cytokine responses to pro-inflammatory stimuli. This new human enteroid culture methodology refines the ability to study microbiome:human intestinal epithelium interactions in the laboratory.

ABSTRACT

The intestinal epithelium is the primary interface between the host, the gut microbiome and its external environment. Since the intestinal epithelium contributes to innate immunity as a first line of defence, understanding how the epithelium responds to microbial and host stimuli is an important consideration in promoting homeostasis. Human intestinal enteroids (HIEs) are primary epithelial cell cultures that can provide insights into the biology of the intestinal epithelium and innate immune responses. One potential limitation of using HIEs for innate immune studies is the relative lack of responsiveness to factors that stimulate epithelial cytokine production. We report technical refinements, including removal of extracellular antioxidants, to facilitate enhanced cytokine responses in HIEs. Using this new method, we demonstrate that HIEs have distinct cytokine profiles in response to pro-inflammatory stimuli derived from host and microbial sources. Overall, we found that host-derived cytokines tumour necrosis factor and interleukin-1α stimulated reactive oxygen species and a large repertoire of cytokines. In contrast, microbial lipopolysaccharide, lipoteichoic acid and flagellin stimulated a limited number of cytokines and histamine did not stimulate the release of any cytokines. Importantly, HIE-secreted cytokines were functionally active, as denoted by the ability of human blood-derived neutrophil to migrate towards HIE supernatant containing interleukin-8. These findings establish that the immune responsiveness of HIEs depends on medium composition and stimuli. By refining the experimental culture medium and creating an environment conducive to epithelial cytokine responses by human enteroids, HIEs can facilitate exploration of many experimental questions pertaining to the role of the intestinal epithelium in innate immunity.

Inflammation-induced JMJD2D promotes colitis recovery and colon tumorigenesis by activating Hedgehog signaling

Histone demethylase JMJD2D can promote gene expression by specifically demethylating H3K9me2/3. The role of JMJD2D in colitis and colitis-associated colorectal cancer (CRC) progression remains unclear. Here, we show that colonic JMJD2D is induced by TNFα during dextran sulfate sodium-induced colitis. JMJD2D-deficient mice exhibit more severe colon damage and defective colon regeneration due to impaired Hedgehog signaling activation after colitis. JMJD2D knockdown in CRC cells suppresses Hedgehog signaling, resulting in reduced CRC growth and metastasis. Mechanistically, JMJD2D promotes Hedgehog target gene expression through interacting with Gli2 to reduce H3K9me3 levels at the promoter. Clinically, JMJD2D expression is upregulated and positively correlated with Gli2 expression in human inflammatory bowel disease specimens and CRC specimens. The JMJD2D inhibitor 5-c-8HQ or aspirin synergizes with Hedgehog inhibitor vismodegib to inhibit CRC cell proliferation and tumorigenesis. Collectively, our findings unveil an essential role of JMJD2D in activating the processes of colonic protection, regeneration, and tumorigenesis.

Consumption of a baked corn and bean snack reduced chronic colitis inflammation in CD-1 mice via downregulation of IL-1 receptor, TLR, and TNF-α associated pathways

Ulcerative colitis (UC) is a condition that has been rising in the number of cases around the world. Food products made from natural ingredients such as corn and common bean might serve as alternatives for the treatment of UC. This study aimed to assess the anti-inflammatory effect of the consumption of a baked corn and bean snack (CBS) in an in vivo model of UC using 2% dextran sodium sulfate (DSS) as inductor of colitis. CD-1 mice (45, n = 9/group) were randomly separated into 5 groups, treated for 6-weeks as follows: G1 (basal diet, BD), G2 (2% DSS), G3 (20 g CBS/body weight BW/day + BD), G4 (40 g CBS/BW/day + BD) and G5 (60 g CBS/BW/day + BD). BW, Disease Activity Index (DAI), and feces were collected throughout the treatment. After euthanasia, organs (spleen, liver, and colon) were excised and weighed. Feces were analyzed for β-glucuronidase (β-GLUC) activity and gas-chromatography. The colons were analyzed for histopathology, myeloperoxidase (MPO) activity, and gene analysis. At the end of treatments, among the DSS-induced groups, G3 exhibited the lowest BW losses (11.5%), MPO activity (10.4%) and β-GLUC (8.6%). G4 presented the lowest DAI (0.88), relative spleen weight, and histological inflammation score (p < 0.05). Compared to G2, CBS consumption significantly (p < 0.05) reduced serum TNF-α, IL-10, and MCP-1 levels. The fecal metabolome analysis ranked 9-decenoic acid, decane, and butyric acid as the main contributors of pathways associated with the β-oxidation of fatty acids. G4 showed the highest fecal/cecal contents of short-chain fatty acids among all the DSS-induced groups. For the gene expression, G4 was clustered with G1, showing a differential inhibition of the pro-inflammatory genes Il1r1, Il1a, Tlr4, Tlr2, and Tnfrsf1b. In conclusion, CBS consumption decreased the inflammatory state and reduced the expression of the IL-1 receptor, TLR, and TNF-α-associated pathways in DSS-induced UC in CD-1 mice.

Milk Fermented with Lactobacillus fermentum Ameliorates Indomethacin-Induced Intestinal Inflammation: An Exploratory Study

The aim of this study was to evaluate the effect of milk fermented with Lactobacillus fermentum J20 (FMJ20) or J28 (FMJ28) on ameliorating indomethacin-induced inflammation. Twenty-eight male C57Bl/6 mice were divided into four experimental groups: indomethacin, indomethacin + FMJ20, indomethacin + FMJ28, and untreated (control). Groups were fed fermented milk for 15 days, followed by administration of indomethacin supplied in three sub-doses over experimental period. Body weight, and food consumption were recorded. Additionally, spleen, kidney, and liver were weighed, and the small intestine length was measured. The cytokines in serum (IL-2, IL-4, IL-6, IL-10, IL-17, IL-23 and TNFα) and in intestinal mucosa (IL-17 and IFNγ) were also determined. Compared to the control, all indomethacin-supplemented groups lost weight (~2.7 g; p < 0.05), but no changes were found in the organ-specific morphometry analysis. FMJ28 showed better results in attenuating serum and intestinal IL-17 levels. Furthermore, showed less epithelial cell loss and inflammatory infiltrates than the other indomethacin-treated groups. These results suggest that FMJ28 may be effective in reducing intestinal and systemic acute inflammation, specifically in mice.

Synbiotics suppress colitis-induced tumorigenesis in a colon-specific cancer mouse model

Although synbiotics may be effective in maintaining remission of inflammatory bowel disease, their anticarcinogenic effects are still debated. To address this issue, we evaluated the effects of synbiotics, probiotics, and prebiotics on tumorigenesis using a CDX2P-Cre; Apc^+/flox mouse model harboring a colon-specific Apc knock out, which develops adenoma and adenocarcinoma of the colon. Dextran sodium sulfate (DSS)-administration promoted colonic tumor development in CDX2P-Cre; Apc^+/flox mice, and these tumors were associated with loss of Apc heterozygosity, as confirmed by observation of well-differentiated adenocarcinomas with β-catenin accumulation in tumor cell cytoplasm. Synbiotics-treatment suppressed dextran sodium sulfate-induced colitis in CDX2P-Cre; Apc^+/flox mice, thereby reducing mortality, and inhibited tumorigenesis accelerated by DSS-administration. Conversely, neither probiotics nor prebiotics had any effect on inflammation and tumorigenesis. Lactobacillus casei and Bifidobacterium breve were detected in the fecal microbiota of probiotics-treated mice. Synbiotics-treatment suppressed DSS-induced expression of IL-6, STAT-3, COX-2, and TNF-α gene transcripts in normal colonic epithelium, indicating the possibility of suppressing tumor development. Importantly, these genes may be potential therapeutic targets in inflammation-associated colon cancer.

Extra-Adrenal Glucocorticoid Synthesis in the Intestinal Mucosa: Between Immune Homeostasis and Immune Escape

Glucocorticoids (GCs) are steroid hormones predominantly produced in the adrenal glands in response to physiological cues and stress. Adrenal GCs mediate potent anti-inflammatory and immunosuppressive functions. Accumulating evidence in the past two decades has demonstrated other extra-adrenal organs and tissues capable of synthesizing GCs. This review discusses the role and regulation of GC synthesis in the intestinal epithelium in the regulation of normal immune homeostasis, inflammatory diseases of the intestinal mucosa, and the development of intestinal tumors.

Mucosal delivery of Lactococcus lactis carrying an anti-TNF scFv expression vector ameliorates experimental colitis in mice

Background

Anti-Tumor Necrosis Factor-alpha therapy has become clinically important for treating inflammatory bowel disease. However, the use of conventional immunotherapy requires a systemic exposure of patients and collateral side effects. Lactic acid bacteria have been shown to be effective as mucosal delivering system for cytokine and single domain antibodies, and it is amenable to clinical purposes. Therefore, lactic acid bacteria may function as vehicles for delivery of therapeutic antibodies molecules to the gastrointestinal tract restricting the pharmacological effect towards the gut. Here, we use the mucosal delivery of Lactococcus lactis carrying an anti-TNFα scFv expression plasmid on a DSS-induced colitis model in mice.

Results

Experimental colitis was induced with DSS administered in drinking water. L. lactis carrying the scFv expression vector was introduced by gavage. After four days of treatment, animals showed a significant improvement in histological score and disease activity index compared to those of untreated animals. Moreover, treated mice display IL-6, IL17A, IL1β, IL10 and FOXP3 mRNA levels similar to health control mice. Therefore, morphological and molecular markers suggest amelioration of the experimentally induced colitis.

Conclusion

These results provide evidence for the use of this alternative system for delivering therapeutic biopharmaceuticals in loco for treating inflammatory bowel disease, paving the way for a novel low-cost and site-specific biotechnological route for the treatment of inflammatory disorders.

Electronic supplementary material

The online version of this article (10.1186/s12896-019-0518-6) contains supplementary material, which is available to authorized users.

Tumour Necrosis Factor Alpha in Intestinal Homeostasis and Gut Related Diseases

The intestinal epithelium constitutes an indispensable single-layered barrier to protect the body from invading pathogens, antigens or toxins. At the same time, beneficial nutrients and water have to be absorbed by the epithelium. To prevent development of intestinal inflammation or tumour formation, intestinal homeostasis has to be tightly controlled and therefore a strict balance between cell death and proliferation has to be maintained. The proinflammatory cytokine tumour necrosis factor alpha (TNFα) was shown to play a striking role for the regulation of this balance in the gut. Depending on the cellular conditions, on the one hand TNFα is able to mediate cell survival by activating NFκB signalling. On the other hand, TNFα might trigger cell death, in particular caspase-dependent apoptosis but also caspase-independent programmed necrosis. By regulating these cell death and survival mechanisms, TNFα exerts a variety of beneficial functions in the intestine. However, TNFα signalling is also supposed to play a critical role for the pathogenesis of inflammatory bowel disease (IBD), infectious diseases, intestinal wound healing and tumour formation. Here we review the literature about the physiological and pathophysiological role of TNFα signalling for the maintenance of intestinal homeostasis and the benefits and difficulties of anti-TNFα treatment during IBD.

Inhibiting Interleukin 36 Receptor Signaling Reduces Fibrosis in Mice With Chronic Intestinal Inflammation

BACKGROUND & AIMS

Intestinal fibrosis is a long-term complication in inflammatory bowel diseases (IBD) that frequently results in functional damage, bowel obstruction, and surgery. Interleukin (IL) 36 is a group of cytokines in the IL1 family with inflammatory effects. We studied the expression of IL36 and its receptor, interleukin 1 receptor like 2 (IL1RL2 or IL36R) in the development of intestinal fibrosis in human tissues and mice.

METHODS

We obtained intestinal tissues from 92 patients with Crohn's disease (CD), 48 patients with ulcerative colitis, and 26 patients without inflammatory bowel diseases (control individuals). Tissues were analyzed by histology to detect fibrosis and by immunohistochemistry to determine the distribution of fibroblasts and levels of IL36R ligands. Human and mouse fibroblasts were incubated with IL36 or control medium, and transcriptome-wide RNA sequences were analyzed. Mice were given neutralizing antibodies against IL36R, and we studied intestinal tissues from Il1rl2^-/- mice; colitis and fibrosis were induced in mice by repetitive administration of DSS or TNBS. Bone marrow cells were transplanted from Il1rl2^-/- to irradiated wild-type mice and intestinal tissues were analyzed. Antibodies against IL36R were applied to mice with established chronic colitis and fibrosis and intestinal tissues were studied.

RESULTS

Mucosal and submucosal tissue from patients with CD or ulcerative colitis had higher levels of collagens, including type VI collagen, compared with tissue from control individuals. In tissues from patients with fibrostenotic CD, significantly higher levels of IL36A were noted, which correlated with high numbers of activated fibroblasts that expressed α-smooth muscle actin. IL36R activation of mouse and human fibroblasts resulted in expression of genes that regulate fibrosis and tissue remodeling, as well as expression of collagen type VI. Il1rl2^-/- mice and mice given injections of an antibody against IL36R developed less severe colitis and fibrosis after administration of DSS or TNBS, but bone marrow cells from Il1rl2^-/- mice did not prevent induction of colitis and fibrosis. Injection of antibodies against IL36R significantly reduced established fibrosis in mice with chronic intestinal inflammation.

CONCLUSION

We found higher levels of IL36A in fibrotic intestinal tissues from patients with IBD compared with control individuals. IL36 induced expression of genes that regulate fibrogenesis in fibroblasts. Inhibition or knockout of the IL36R gene in mice reduces chronic colitis and intestinal fibrosis. Agents designed to block IL36R signaling could be developed for prevention and treatment of intestinal fibrosis in patients with IBD.

Obesity-Induced TNFα and IL-6 Signaling: The Missing Link between Obesity and Inflammation-Driven Liver and Colorectal Cancers

Obesity promotes the development of numerous cancers, such as liver and colorectal cancers, which is at least partly due to obesity-induced, chronic, low-grade inflammation. In particular, the recruitment and activation of immune cell subsets in the white adipose tissue systemically increase proinflammatory cytokines, such as tumor necrosis factor α (TNFα) and interleukin-6 (IL-6). These proinflammatory cytokines not only impair insulin action in metabolic tissues, but also favor cancer development. Here, we review the current state of knowledge on how obesity affects inflammatory TNFα and IL-6 signaling in hepatocellular carcinoma and colorectal cancers.

Yogurt starter cultures of Streptococcus thermophilus and Lactobacillus bulgaricus ameliorate symptoms and modulate the immune response in a mouse model of dextran sulfate sodium-induced colitis

We investigated the yogurt starter cultures of Lactobacillus bulgaricus 151 and Streptococcus thermophilus MK-10 for their effect on the severity of experimental colitis, lymphocyte profile, and regulatory T-cell response. Colitis was induced in BALB/c mice via the administration of 3.5% dextran sulfate sodium salt (DSS) in drinking water for 6 d. Next, the mice were gavaged intragastrically with an active yogurt cultures (YC) mixture (∼5 × 10⁹ cfu/mouse per day) or saline (vehicle) for 8 d. Mice receiving DSS or saline alone served as positive and negative controls, respectively. The length of the colon, disease activity index, histological scores, myeloperoxidase activity, epithelium-associated microbes, short-chain fatty acid profile, total IgA antibody-forming cells, CD3⁺CD8⁺, CD3⁺CD4⁺, CD3⁺CD4⁺CD25⁺, CD3⁺CD4⁺CD25⁺Foxp3⁺ T-cell subsets, and cytokine profiles (IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ, and tumor necrosis factor) were examined after termination of the mice. Feeding mice with YC mixture reduced disease symptoms and modified intestinal microbiota and host inflammatory responsiveness to DSS. We observed limited weight loss and a decreased disease activity index score, lowered myeloperoxidase activity, and somewhat reduced damage of the intestine. The YC mixture upregulated the colon length, increased the amount and diversity of mucosa-associated microbes (enterobacteria, enterococci, and yeast), and decreased the concentration of putrefactive short-chain fatty acids in the cecal contents. It downregulated the input of cytotoxic CD3⁺CD8⁺ T cells and CD3⁺CD4⁺CD25⁺FoxP3⁺ regulatory T cells in Peyer's patches and enhanced CD3⁺CD4⁺CD25⁺ T cells in spleens and CD3⁺CD4⁺CD25⁺FoxP3⁺ cells in peripheral blood mononuclear cells. Simultaneously, IgA antibody-forming cells were downregulated in mesenteric lymph nodes (MLN) and enhanced in spleens (SPL). The cultures mostly enhanced the production of cytokines tested in MLN and SPL, except for IL-6, which was downregulated in MLN. Interleukin-2 and IL-4 were the most upregulated in MLN, whereas IL-10, IL-4, IL-2, IFN-γ, and tumor necrosis factor were most upregulated in SPL. In serum, the YC mixture downregulated IFN-γ and clearly increased IL-2. Based on these results, we recognize the high anti-inflammatory and immunomodulatory potential of the L. bulgaricus 151 and S. thermophilus MK-10 set. The strains possess the ability to modulate the intestinal mucosal and systemic immune system toward both IgA production and induction of regulatory T cells, shifting Th1/Th2 balance.

A New Venue of TNF Targeting

The first Food and Drug Administration-(FDA)-approved drugs were small, chemically-manufactured and highly active molecules with possible off-target effects, followed by protein-based medicines such as antibodies. Conventional antibodies bind a specific protein and are becoming increasingly important in the therapeutic landscape. A very prominent class of biologicals are the anti-tumor necrosis factor (TNF) drugs that are applied in several inflammatory diseases that are characterized by dysregulated TNF levels. Marketing of TNF inhibitors revolutionized the treatment of diseases such as Crohn’s disease. However, these inhibitors also have undesired effects, some of them directly associated with the inherent nature of this drug class, whereas others are linked with their mechanism of action, being pan-TNF inhibition. The effects of TNF can diverge at the level of TNF format or receptor, and we discuss the consequences of this in sepsis, autoimmunity and neurodegeneration. Recently, researchers tried to design drugs with reduced side effects. These include molecules with more specificity targeting one specific TNF format or receptor, or that neutralize TNF in specific cells. Alternatively, TNF-directed biologicals without the typical antibody structure are manufactured. Here, we review the complications related to the use of conventional TNF inhibitors, together with the anti-TNF alternatives and the benefits of selective approaches in different diseases.

Fecal Microbiota Transplantation, Commensal Escherichia coli and Lactobacillus johnsonii Strains Differentially Restore Intestinal and Systemic Adaptive Immune Cell Populations Following Broad-spectrum Antibiotic Treatment

The essential role of the intestinal microbiota in the well-functioning of host immunity necessitates the investigation of species-specific impacts on this interplay. Aim of this study was to examine the ability of defined Gram-positive and Gram-negative intestinal commensal bacterial species, namely Escherichia coli and Lactobacillus johnsonii, respectively, to restore immune functions in mice that were immunosuppressed by antibiotics-induced microbiota depletion. Conventional mice were subjected to broad-spectrum antibiotic treatment for 8 weeks and perorally reassociated with E. coli, L. johnsonii or with a complex murine microbiota by fecal microbiota transplantation (FMT). Analyses at days (d) 7 and 28 revealed that immune cell populations in the small and large intestines, mesenteric lymph nodes and spleens of mice were decreased after antibiotic treatment but were completely or at least partially restored upon FMT or by recolonization with the respective bacterial species. Remarkably, L. johnsonii recolonization resulted in the highest CD4+ and CD8+ cell numbers in the small intestine and spleen, whereas neither of the commensal species could stably restore those cell populations in the colon until d28. Meanwhile less efficient than FMT, both species increased the frequencies of regulatory T cells and activated dendritic cells and completely restored intestinal memory/effector T cell populations at d28. Furthermore, recolonization with either single species maintained pro- and anti-inflammatory immune functions in parallel. However, FMT could most effectively recover the decreased frequencies of cytokine producing CD4+ lymphocytes in mucosal and systemic compartments. E. coli recolonization increased the production of cytokines such as TNF, IFN-γ, IL-17, and IL-22, particularly in the small intestine. Conversely, only L. johnsonii recolonization maintained colonic IL-10 production. In summary, FMT appears to be most efficient in the restoration of antibiotics-induced collateral damages to the immune system. However, defined intestinal commensals such as E. coli and L. johnsonii have the potential to restore individual functions of intestinal and systemic immunity. In conclusion, our data provide novel insights into the distinct role of individual commensal bacteria in maintaining immune functions during/following dysbiosis induced by antibiotic therapy thereby shaping host immunity and might thus open novel therapeutical avenues in conditions of perturbed microbiota composition.

TREM-1 promotes intestinal tumorigenesis

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a potent amplifier of pro-inflammatory innate immune responses. Increasing evidence suggests a role for TREM-1 not only in acute pathogen-induced reactions but also in chronic and non-infectious inflammatory disorders, including various types of cancer. Here, we demonstrate that genetic deficiency in Trem1 protects from colorectal cancer. In particular, Trem1^−/− mice exhibited reduced tumor numbers and load in an experimental model of inflammation-driven tumorigenesis. Gene expression analysis of Trem1^−/− versus Trem1^+/+ tumor tissue demonstrated distinct immune signatures. Whereas Trem1^−/− tumors showed an increased abundance of transcripts linked to adaptive immunity, Trem1^+/+ tumors were characterized by overexpression of innate pro-inflammatory genes associated with tumorigenesis. Compared to adjacent tumor-free colonic mucosa, expression of Trem1 was increased in murine and human colorectal tumors. Unexpectedly, TREM-1 was not detected on tumor-associated Ly6C⁻ MHC class II⁺ macrophages. In contrast, TREM-1 was highly expressed by tumor-infiltrating neutrophils which represented the predominant myeloid population in Trem1^+/+ but not in Trem1^−/− tumors. Collectively, our findings demonstrate a clear role of TREM-1 for intestinal tumorigenesis and indicate TREM-1-expressing neutrophils as critical players in colorectal tumor development.

TNFα deficiency results in increased IL-1β in an early onset of spontaneous murine colitis

Inflammatory bowel disease (Crohn's disease (CD) and ulcerative colitis (UC)) is a multifactorial disease resulting from immune dysregulation in the gut. The underlying colitis is characterized by high levels of inflammatory cytokines, including TNFα. Biological intervention for IBD patients using anti-TNFα antibodies is often an effective therapeutic solution. However, TNFα neutralization fails to induce remission in a subgroup of IBD patients, primarily in UC patients. There is a dearth of suitable animal models representing TNFα non-responders. Here we have combined one of the best UC models currently available, namely Winnie and the TNFαKO mouse to generate a TNFα-deficient Winnie to study early onset colitis. The induced TNFα deficiency with underlying colitis does not influence general health (viability and body weight) or clinical parameters (colon weight, colon length and histological colitis) when compared with the Winnie genotype alone. The molecular characterization resulted in identification of Il1β as the major elevated cytokine during early phases of colitis. Further, in vitro functional assay using bone marrow-derived dendritic cells confirmed IL-1β as the major cytokine released in the absence of TNFα. This study has generated a successful model of colitis that remains TNFα non-responsive and has demonstrated that IL-1β expression is a major pathway for the progression of colitis in this system. These data also suggest that IL-1β can be a potential target for clinical intervention of UC patients who fail to respond to TNFα neutralization.

Amelioration of intestinal and systemic sequelae of murine Campylobacter jejuni infection by probiotic VSL#3 treatment

Background

The incidence of human Campylobacter jejuni infections is progressively increasing worldwide. Probiotic compounds might open up valuable tools to decrease pathogen burden and subsequent pro-inflammatory immune responses, but in vivo data are scarce.

Methods and results

Secondary abiotic mice generated by broad-spectrum antibiotic treatment were perorally challenged with the commercial probiotic compound VSL#3 consisting of Streptococcus thermophilus, Bifidobacterium breve, Bifidobacterium longum, Bifidobacterium infantis, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus paracasei, and Lactobacillus delbrueckii ssp. bulgaricus) either 5 days before (i.e. prophylactic regimen) or after (i.e. therapeutic regimen) peroral C. jejuni strain 81–176 infection, and analyzed 3 weeks following the initial bacterial re-association. Upon challenge, mice were colonized with the probiotic bacteria and/or C. jejuni at comparable intestinal loads, but co-colonization did not result in reduction of the pathogen burden. Remarkably, prophylactic as well as therapeutic VSL#3 treatment of C. jejuni infected mice ameliorated intestinal apoptosis and pro-inflammatory immune responses as indicated by lower numbers of innate and adaptive immune cell populations in the murine colon upon probiotic prophylaxis or treatment and reduced colonic concentrations of pro-inflammatory mediators including IL-6 and MCP-1. Importantly, concentrations of anti-inflammatory mediators such as IL-10 were significantly elevated in the colon of probiotics treated mice as compared to untreated controls. Strikingly, prophylactic VSL#3 treatment attenuated C. jejuni induced systemic pro-inflammatory responses as indicated by less TNF and IL-12p70 secretion in the spleen of VSL#3 pre-treated as compared to non-treated mice.

Conclusion

Administration of probiotic formulations such as VSL#3 might open up valuable strategies for prophylaxis and/or treatment of C. jejuni induced intestinal and systemic sequelae in vivo by the suppression of pro-inflammatory and induction of anti-inflammatory responses.

NLRP6 function in inflammatory monocytes reduces susceptibility to chemically induced intestinal injury

NLRP6 is a member of the Nod-like receptor family, whose members are involved in the recognition of microbes and/or tissue injury. NLRP6 was previously demonstrated to regulate the production of interleukin (IL)-18 and is important for protecting mice against chemically induced intestinal injury and colitis-associated colon cancer. However, the cellular mechanisms by which NLRP6 reduces susceptibility to colonic inflammation remain unclear. Here, we determined that NLRP6 expression is specifically upregulated in Ly6C^hi inflammatory monocytes that infiltrate into the colon during dextran sulfate sodium (DSS)-induced inflammation. Adoptive transfer of wild-type (WT) Ly6C^hi inflammatory monocytes into Nlrp6^-/- mice was sufficient to protect them from mortality, significantly reducing intestinal permeability and damage. NLRP6-deficient inflammatory monocytes were defective in tumor necrosis factor α (TNFα) production, which was important for reducing DSS-induced mortality and was dependent on autocrine IL-18 signaling by inflammatory monocytes. Our data reveal a previously unappreciated role for NLRP6 in inflammatory monocytes, which are recruited after DSS-induced intestinal injury to promote barrier function and limit bacteria-driven inflammation. This study highlights the importance of early cytokine responses, particularly NLRP6-dependent and IL-18-dependent TNFα production, in preventing chronic dysregulated inflammation.

Interleukin 32, inflammation and cancer

Interleukin-32 (IL-32) is a novel cytokine involved in inflammation and cancer development. IL-32 gene consists of eight small exons, and IL-32 mRNA has nine alternative spliced isoforms, and was thought to be secreted because it contains an internal signal sequence and lacks a transmembrane region. IL-32 is initially expressed selectively in activated T cells by mitogen and activated NK cells and their expression is strongly augmented by microbes, mitogens, and other cytokines. The IL-32 is induced mainly by pathogens and pro-inflammatory cytokines, but IL-32 is more prominent in immune cells than in non-immune tissues. The IL-32 transcript is expressed in various human tissues and organs such as the spleen, thymus, leukocyte, lung, small intestine, colon, prostate, heart, placenta, liver, muscle, kidney, pancreas, and brain. Cytokines are critical components of cell signaling pathways that are involved in the regulation of cell growth, metabolism, hormone signaling, immune regulation and a variety of other physiological functions. Earlier studies have demonstrated that IL-32 regulates cell growth, metabolism and immune regulation and is therefore involved in the pathologic regulator or protectant of inflammatory diseases. Previous studies defined that IL-32 is upregulated in the patients with several inflammatory diseases, and is induced by inflammatory responses. However, several reports suggested that IL-32 is downregulated in several inflammatory diseases including asthma, HIV infection disease, neuronal diseases, metabolic disorders, experimental colitis and metabolic disorders. IL-32 is also involved in various cancer malignancies including renal cancer, esophageal cancer and hepatocellular carcinoma, lung cancer, gastric cancer, breast cancer, pancreatic cancer, lymphoma, osteosarcoma, breast cancer, colon cancer and thyroid carcinoma. Other studies suggested that IL-32 decreases tumor development including cervical cancer, colon cancer and prostate cancer, melanoma, pancreatic cancer, liver cancer and chronic myeloid leukemia. Nevertheless, review articles that discuss the roles and its mechanism of IL-32 isoforms focusing on the therapeutic approaches have not yet been reported. In this review article, we will discuss recent findings regarding IL-32 in the development of diseases and further discuss therapeutic approaches targeting IL-32. Moreover, we will suggest that IL-32 could be the target of several diseases and the therapeutic agents for targeting IL-32 may have potential beneficial effects for the treatment of inflammatory diseases and cancers. Future research should open new avenues for the design of novel therapeutic approaches targeting IL-32.

Anti-inflammatory effects of infliximab in mice are independent of tumour necrosis factor α neutralization

Infliximab (IFX) has been used repeatedly in mouse preclinical models with associated claims that anti‐inflammatory effects are due to inhibition of mouse tumour necrosis factor (TNF)‐α. However, the mechanism of action in mice remains unclear. In this study, the binding specificity of IFX for mouse TNF‐α was investigated ex vivo using enzyme‐linked immunosorbent assay (ELISA), flow cytometry and Western blot. Infliximab (IFX) did not bind directly to soluble or membrane‐bound mouse TNF‐α nor did it have any effect on TNF‐α‐induced nuclear factor kappa B (NF‐κB) stimulation in mouse fibroblasts. The efficacy of IFX treatment was then investigated in vivo using a TNF‐α‐independent Trichuris muris‐induced infection model of chronic colitis. Infection provoked severe transmural colonic inflammation by day 35 post‐infection. Colonic pathology, macrophage phenotype and cell death were determined. As predicted from the in‐vitro data, in‐vivo treatment of T. muris‐infected mice with IFX had no effect on clinical outcome, nor did it affect macrophage cell phenotype or number. IFX enhanced apoptosis of colonic immune cells significantly, likely to be driven by a direct effect of the humanized antibody itself. We have demonstrated that although IFX does not bind directly to TNF‐α, observed anti‐inflammatory effects in other mouse models may be through host cell apoptosis. We suggest that more careful consideration of xenogeneic responses should be made when utilizing IFX in preclinical models.

Osteopontin and Mucosal Protection

Protection of mucosal tissues of the oral cavity, intestines, respiratory tract, and urogenital tract from the constant challenge of pathogens is achieved by the combined barrier function of the lining epithelia and specialized immune cells. Recent studies have indicated that osteopontin (OPN) has a pivotal role in the development of immune responses and in the tissue destruction and the subsequent repair processes associated with inflammatory diseases. While expression of OPN is increased in immune cells—including neutrophils, macrophages, T- and B-lymphocytes—and in epithelial, endothelial, and fibroblastic cells of inflamed tissues, deciphering the specific functions of OPN has been difficult. In part, this is due to the broad range of biological activities of OPN that are mediated by multiple receptors which recognize several signaling motifs whose activities are influenced by post-translational modifications and proteolytic processing of OPN. Understanding the role of OPN in mucosal inflammation is further complicated by its contributions to the barrier function of the lining epithelia and the complexity of the specialized mucosal immune system. In an attempt to provide some insights into the involvement of OPN in mucosal diseases, this review summarizes current knowledge of the biological activities of OPN involved in the development of inflammatory responses and in wound healing, and indicates how these activities may affect the protection of mucosal tissues.

A Randomized Phase 1 Study to Assess the Safety and Pharmacokinetics of the Subcutaneously Injected Anti-LIGHT Antibody, SAR252067

LIGHT, a member of the tumor necrosis factor superfamily, is potentially involved in mucosal inflammation associated with inflammatory bowel disease. The safety and pharmacokinetics of the fully human monoclonal anti-LIGHT antibody, SAR252067, was evaluated in healthy volunteers in a phase 1 study as a potential treatment for diseases related to LIGHT-mediated mucosal inflammation. This double-blind, randomized, placebo-controlled, sequential ascending single-dose, single-center, 16-week study randomized 48 subjects to a single subcutaneous dose of SAR252067 (40, 120, 300, 600, 900, or 1200 mg) or placebo. Safety assessments included adverse events (AEs), injection-site reactions, and antidrug antibody (ADA) titer. Pharmacokinetic end points were serum parameters of SAR252067 (C_max , AUC_0-∞ , t_max , t_1/2z ). Serum-soluble LIGHT concentrations were also determined. Safety analyses included all 48 participants; pharmacokinetic analyses included 36 subjects who received SAR252067. No serious AEs were reported, and no dose-effect relationship was apparent. Injection-site reactions were minimal. ADAs were not clinically relevant. SAR252067 exposure increased in a near-dose-proportional manner, median t_max ranged from 5.0 to 8.5 days, and t_1/2z ranged from 18.0 to 27.0 days. Serum-soluble LIGHT significantly increased after SAR252067 administration with the 40-mg dose only. SAR252067 had a good safety profile, was well tolerated in healthy humans, and displayed a predictable pharmacokinetic profile.

A Novel Role for TL1A/DR3 in Protection against Intestinal Injury and Infection

TNF-like cytokine 1A (TL1A) is expressed on APCs and provides costimulatory signals to activated lymphocytes that bear its functional receptor, death receptor 3 (DR3). TL1A/DR3 signaling is involved in the pathogenesis of human and experimental inflammatory bowel disease. In the current study, we investigated the role of this cytokine/receptor pair in acute intestinal injury/repair pathways. We demonstrate that intact DR3 signaling protected mice from acute dextran sodium sulfate colitis because DR3(-/-) mice showed more severe mucosal inflammation and increased mortality. DR3(-/-) mice were compromised in their ability to maintain adequate numbers of CD4(+)CD25(+)Foxp3(+) regulatory T cells in response to acute mucosal damage. This defect in immune regulation led to a nonspecific upregulation of effector proinflammatory pathways, which was most prominent for the Th17 immunophenotype. TL1A(-/-) mice were similarly more susceptible to dextran sodium sulfate colitis, although without mortality and with delayed kinetics compared with DR3(-/-) mice, and also displayed significantly reduced numbers of regulatory T cells. Infection of DR3(-/-) mice with Salmonella typhimurium was associated with defective microbial clearance and elevated bacterial load. Taken together, our findings indicate a novel protective role for the TL1A/DR3 axis in the regulation of mucosal homeostasis during acute intestinal injury/repair, which contrasts with its known pathogenic function during chronic intestinal inflammation.

Role of the protein annexin A1 on the efficacy of anti-TNF treatment in a murine model of acute colitis

TNF-α is involved in the mechanisms that initiate inflammatory bowel diseases (IBDs). Anti-TNF-α drugs, such as infliximab (IFX), cause non-responsiveness and side effects, indicating the need to investigate alternative therapies for these diseases. The anti-inflammatory protein, annexin A1 (AnxA1), has been associated with the protection of the gastrointestinal mucosa. To further address the role of endogenous AnxA1 on the TNF-α blockade efficacy in a murine model, we assessed colitis induced by Dextran Sulfate Sodium (DSS) in wild-type (WT) and AnxA1(-/-) Balb/c mice treated with IFX. We consistently observed endogenous AnxA1 prevented clinical and physiological manifestations of experimental colitis treated with IFX, additionally the manifestation of the disease was observed earlier in AnxA1(-)(/-) mice. Rectal bleeding, diarrhea, histological score, epithelial damages and collagen degradation caused by DSS were prevented following IFX treatment only in WT mice. IL-6 increased during colitis in WT and AnxA1(-)(/-) mice, decreasing under IFX treatment in WT. The influx of neutrophils and TNF-α secretion were largely elevated in AnxA1(-)(/-) mice when compared to WT mice. In the group WT/DSS+IFX, phagocytes were more susceptible to apoptosis following treatment with IFX. Endogenous expression of AnxA1 increased after DSS and decreased with IFX treatment, demonstrating an attenuated inflammatory response. The data indicate that AnxA1 contributes to the establishment of intestinal homeostasis after blocking of TNF-α was used as a treatment of IBD, constituting a key molecule in the mechanism of action and a potential biomarker of therapeutic efficacy.

The B-cell tumor promoter Bcl-3 suppresses inflammation-associated colon tumorigenesis in epithelial cells

Bcl-3 is an atypical member of the IκB family. It associates with p50/NF-κB1 and p52/NF-κB2 homodimers in nuclei where it modulates transcription in a context-dependent manner. A subset of B cell tumors exhibits recurrent translocations of Bcl-3, resulting in overexpression. Elevated expression without translocations is also observed in various B cell lymphomas and even some solid tumors. Here we investigated the role of Bcl-3 in AOM/DSS-induced colon tumors, a mouse model for colitis-associated colorectal cancers in humans. Contrary to expectations, Bcl-3 suppressed colorectal tumor formation: Bcl-3-deficient mice were relatively protected from DSS-induced epithelial damage and developed more polyps after AOM/DSS treatment, though polyp size was unaffected. DSS-challenged mutant mice exhibited increased recruitment of myeloid-derived suppressor cells (MDSCs), consistent with protection of the epithelium. Loss of Bcl-3 in intestinal epithelial cells was sufficient to increase tumorigenesis. The added tumor burden in mutant mice was dependent on TNFα, a tumorigenic, NF-κB-mediated signaling pathway that was dampened by Bcl-3. These findings reveal a tumor-suppressive role for Bcl-3 in this inflammation-associated cancer model. Bcl-3 thus functions as a tumor promoter or suppressor, depending on the cellular and environmental context.

5-HT3 receptors promote colonic inflammation via activation of substance P/neurokinin-1 receptors in dextran sulphate sodium-induced murine colitis

BACKGROUND AND PURPOSE

5-HT (serotonin) regulates various physiological functions, both directly and via enteric neurons. The present study investigated the role of endogenous 5-HT and 5-HT3 receptors in the pathogenic mechanisms involved in colonic inflammation, especially in relation to substance P (SP) and the neurokinin-1 (NK1 ) receptor.

EXPERIMENTAL APPROACH

The effects of 5-HT3 and NK1 receptor antagonists were examined in dextran sulphate sodium (DSS)-induced colitis in mice. Inflammatory mediator expression and the distribution of 5-HT3 and NK1 receptors were also determined.

KEY RESULTS

Daily administration of ramosetron and ondansetron (5-HT3 antagonists) dose-dependently attenuated the severity of DSS-induced colitis and up-regulation of inflammatory mediator expression. Immunohistochemical analysis showed 5-HT3 receptors are mainly expressed in vesicular ACh transporter-positive cholinergic nerve fibres in normal colon. DSS increased the number of colonic nerve fibres that were double positive for 5-HT3 receptors and SP but not of those that were double positive for 5-HT3 receptors and vesicular ACh transporter. DSS increased colonic SP levels and SP-positive nerve fibres; these responses were attenuated by ramosetron. DSS-induced colitis and up-regulation of inflammatory mediators were attenuated by aprepitant, an NK1 antagonist. Immunohistochemical studies further revealed that DSS treatment markedly increased NK1 receptor expression in CD11b-positive cells.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that the 5-HT/5-HT3 receptor and SP/NK1 receptor pathways play pathogenic roles in colonic inflammation. 5-HT acts via 5-HT3 receptors to up-regulate inflammatory mediators and promote colonic inflammation. These effects may be further mediated by activation of macrophage NK1 receptors via SP released from 5-HT3 receptor-positive nerve fibres.