Dextran sulfate sodium administered orally is depolymerized in the stomach and induces cell cycle arrest plus apoptosis in the colon in early mouse colitis

Host-microbiome orchestration of the sulfated metabolome

Recent studies have demonstrated that metabolites produced by commensal bacteria causally influence health and disease. The sulfated metabolome is one class of molecules that has recently come to the forefront due to efforts to understand the role of these metabolites in host-microbiome interactions. Sulfated compounds have canonically been classified as waste products; however, studies have revealed a variety of physiological roles for these metabolites, including effects on host metabolism, immune response and neurological function. Moreover, recent research has revealed that commensal bacteria either chemically modify or synthesize a variety of sulfated compounds. In this Review, we explore how host-microbiome collaborative metabolism transforms the sulfated metabolome. We describe bacterial and mammalian enzymes that sulfonate and desulfate biologically relevant carbohydrates, amino acid derivatives and cholesterol-derived metabolites. We then discuss outstanding questions and future directions in the field, including potential roles of sulfated metabolites in disease detection, prevention and treatment. We hope that this Review inspires future research into sulfated compounds and their effects on physiology.

Smad4 Loss in the Mouse Intestinal Epithelium Alleviates the Pathological Fibrotic Response to Injury in the Colon

Mucosal healing is associated with better clinical outcomes in patients with inflammatory bowel diseases (IBDs). Unresolved injury and inflammation, on the other hand, increases pathological fibrosis and the predisposition to cancer. Loss of Smad4, a tumor suppressor, is known to increase colitis-associated cancer in mouse models of chronic IBD. Since common biological processes are involved in both injury repair and tumor growth, we sought to investigate the effect of Smad4 loss on the response to epithelial injury. To this end, Smad4 was knocked out specifically in the intestinal epithelium and transcriptomic and morphological changes compared between wild type mice and Smad4 knock out mice after DSS-induced injury. We find that Smad4 loss alleviates pathological fibrosis and enhances mucosal repair. The transcriptomic changes specific to epithelium indicate molecular changes that affect epithelial extracellular matrix (ECM) and promote enhanced mucosal repair. These findings suggest that the biological processes that promote wound healing alleviate the pathological fibrotic response to DSS. Therefore, these mucosal repair processes could be exploited to develop therapies that promote normal wound healing and prevent fibrosis.

NEW AND NOTEWORTHY

We show that transcriptomic changes due to Smad4 loss in the colonic epithelium alleviates the pathological fibrotic response to DSS in an IBD mouse model of acute inflammation. Most notably, we find that collagen deposition in the epithelial ECM, as opposed to that in the lamina propria, correlates with epithelial changes that enhance wound healing. This is the first report on a mouse model providing alleviated fibrotic response in a DSS-IBD mouse model in vivo .

DSS treatment does not affect murine colonic microbiota in absence of the host

The prevalence of inflammatory bowel disease (IBD) is rising globally; however, its etiology is still not fully understood. Patient genetics, immune system, and intestinal microbiota are considered critical factors contributing to IBD. Preclinical animal models are crucial to better understand the importance of individual contributing factors. Among these, the dextran sodium sulfate (DSS) colitis model is the most widely used. DSS treatment induces gut inflammation and dysbiosis. However, its exact mode of action remains unclear. To determine whether DSS treatment induces pathogenic changes in the microbiota, we investigated the microbiota-modulating effects of DSS on murine microbiota in vitro. For this purpose, we cultured murine microbiota from the colon in six replicate continuous bioreactors. Three bioreactors were supplemented with 1% DSS and compared with the remaining PBS-treated control bioreactors by means of microbiota taxonomy and functionality. Using metaproteomics, we did not identify significant changes in microbial taxonomy, either at the phylum or genus levels. No differences in the metabolic pathways were observed. Furthermore, the global metabolome and targeted short-chain fatty acid (SCFA) quantification did not reveal any DSS-related changes. DSS had negligible effects on microbial functionality and taxonomy in vitro in the absence of the host environment. Our results underline that the DSS colitis mouse model is a suitable model to study host-microbiota interactions, which may help to understand how intestinal inflammation modulates the microbiota at the taxonomic and functional levels.

Inflammatory Bowel Disease Increases the Severity of Myocardial Infarction after Acute Ischemia-Reperfusion Injury in Mice

(1) Background: Increased risk of myocardial infarction (MI) has been linked to several inflammatory conditions, including inflammatory bowel disease (IBD). However, the relationship between IBD and MI remains unclear. Here, we implemented an original mouse model combining IBD and MI to determine IBD's impact on MI severity and the link between the two diseases. (2) Methods: An IBD model was established by dextran sulfate sodium (DSS) administration in drinking water, alone or with oral C. albicans (Ca) gavage. IBD severity was assessed by clinical/histological scores and intestinal/systemic inflammatory biomarker measurement. Mice were subjected to myocardial ischemia-reperfusion (IR), and MI severity was assessed by quantifying infarct size (IS) and serum cardiac troponin I (cTnI) levels. (3) Results: IBD mice exhibited elevated fecal lipocalin 2 (Lcn2) and IL-6 levels. DSS mice exhibited almost two-fold increase in IS compared to controls, with serum cTnI levels strongly correlated with IS. Ca inoculation tended to worsen DSS-induced systemic inflammation and IR injury, an observation which is not statistically significant. (4) Conclusions: This is the first proof-of-concept study demonstrating the impact of IBD on MI severity and suggesting mechanistic aspects involved in the IBD-MI connection. Our findings could pave the way for MI therapeutic approaches based on identified IBD-induced inflammatory mediators.

Capsulated Cellular Nanosponges for the Treatment of Experimental Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic gastrointestinal tract disorder characterized by uncontrolled inflammatory responses to the disrupted intestinal epithelial barrier and gut microbiome dysbiosis. Currently available small-molecule immunosuppressive agents and anticytokine biologics show limited potency, mainly due to the complexity of the inflammatory network involved in IBD. Here, we develop an oral formulation of macrophage membrane-coated nanoparticles capsulated in enteric polymer-coated gelatin capsules (denoted "cp-MΦ-NPs") for IBD treatment. The capsules protect the nanoparticles from gastric degradation and allow for targeted delivery to the colon. At the inflamed colon, cp-MΦ-NPs act as macrophage decoys that bind and neutralize pro-inflammatory cytokines. The in vivo treatment efficacy of cp-MΦ-NPs is tested in a mouse model of dextran sulfate sodium-induced colitis. In both prophylactic and delayed treatment regimens, the oral delivery of cp-MΦ-NPs significantly alleviates IBD severity, reflected by reduced intestinal inflammation and intestinal barrier restoration. Overall, cp-MΦ-NPs provide a biomimetic nanomedicine strategy for the treatment of IBD.

Protective Effects of L-Theanine on IPEC-J2 Cells Growth Inhibition Induced by Dextran Sulfate Sodium via p53 Signaling Pathway

L-theanine is a nonprotein amino acid found in tea leaves and has been widely used as a safe food additive in beverages or foods because of its varied bioactivities. The aim of this study was to reveal the in vitro gastrointestinal protective effects of L-theanine in DSS-induced intestinal porcine enterocyte (IPEC-J2) cell models using molecular and metabolic methods. Results showed that 2.5% dextran sulfate sodium (DSS) treatment inhibited the cell proliferation of IPEC-J2 and blocked the normal operation of the cell cycle, while L-theanine pretreatment significantly preserved these trends to exert protective effects. L-theanine pre-treatment also up-regulated the EGF, CDC2, FGF2, Rb genes and down-regulated p53, p21 proliferation-related mRNA expression in DSS-treated cells, in accompany with p53 signaling pathway inhibition. Meanwhile, metabolomics analysis revealed that L-theanine and DSS treated IPEC-J2 cells have different metabolomic profiles, with significant changes in the key metabolites involved in pyrimidine metabolism and amino acid metabolism, which play an important role in nucleotide metabolism. In summary, L-theanine has a beneficial protection in DSS-induced IPEC-J2 cells via promoting proliferation and regulating metabolism disorders.

Activation of the G Protein-Coupled Estrogen Receptor Prevented the Development of Acute Colitis by Protecting the Crypt Cell

G protein-coupled estrogen receptor (GPER) might be involved in ulcerative colitis (UC), but the direct effect of GPER on UC is still unclear. We used male C57BL/6 mice to establish the acute colitis model with administration of dextran sulfate sodium and explored the effect of GPER on acute colitis and its possible mechanism. The selective GPER agonist G-1 inhibited weight loss and colon shortening and decreased the disease activity index for colitis and histologic damage in mice with colitis. All of these effects were prevented by a selective GPER blocker. G-1 administration prevented the dysfunction of tight junction protein expression and goblet cells in colitis model and thus inhibited the increase of mucosal permeability in colitis-suffering mice significantly. GPER activation reduced expression of glucose-regulating peptide-78 and anti-CCAAT/enhancer-binding protein homologous protein and attenuated the three arms of the unfolded protein response in colitis. G-1 therapy inhibited the increase of cleavage caspase-3- and TUNEL-positive cells in colonic crypts in the colitis model, increased the number of Ki67- and bromodeoxyuridine-positive cells in crypts, and reversed the decrease of cyclin D1 and cyclin B1 expression in colitis, indicating its protective effect on crypt cells. In cultured CCD841 cells, G-1 treatment fought against cell injury induced by endoplasmic reticulum stress. These findings demonstrate that GPER activation prevents colitis by protecting the colonic crypt cells, which are associated with inhibition of endoplasmic reticulum stress. SIGNIFICANCE STATEMENT: We demonstrate that G protein-coupled estrogen receptor (GPER) activation prevents dextran sulfate sodium-induced acute colitis by protecting the crypt cells, showing that it inhibited the crypt cell apoptosis and protected proliferation of crypt cells, which resulted in protection of the intestinal mucosal barrier. This protective effect was achieved (at least in part) by inhibiting endoplasmic reticulum stress. Mucosal healing is regarded as a key therapeutic target for colitis, and GPER is expected to become a new therapeutic target for colitis.

Pharmacokinetics and efficacy of orally administered polymeric chloroquine as macromolecular drug in the treatment of inflammatory bowel disease

Inflammatory bowel disease is a chronic inflammation of the gastrointestinal tract with poor understanding of its pathogenesis and no effective cure. The goal of this study was to evaluate the feasibility of orally administered non-degradable polymeric chloroquine (pCQ) to locally reduce colon inflammation. The pCQ was synthesized by radical copolymerization of N-(2-hydroxypropyl)methacrylamide with methacryloylated hydroxychloroquine (HCQ). The anti-inflammatory activity of orally administered pCQ versus HCQ was tested in a mouse model of colitis induced by Citrobacter rodentium (C. rodentium). Single-dose pharmacokinetic and biodistribution studies performed in the colitis model indicated negligible systemic absorption (p ≤ 0.001) and localization of pCQ in the gastrointestinal tract. A multi-dose therapeutic study demonstrated that the localized pCQ treatment resulted in significant reduction in the colon inflammation (p ≤ 0.05). Enhanced suppression of pro-inflammatory cytokines IL-6 (p ≤ 0.01) and IL1-β and opposing upregulation of IL-2 (p ≤ 0.05) recently reported to be involved in downstream anti-inflammatory events suggested that the anti-inflammatory effects of the pCQ are mediated by altering mucosal immune homeostasis. Overall, the reported findings demonstrate a potential of pCQ as a novel polymer therapeutic option in inflammatory bowel disease with the potential of local effects and minimized systemic toxicity.

Calcium/calmodulin-dependent protein kinase IV (CaMKIV) activation contributes to the pathogenesis of experimental colitis via inhibition of intestinal epithelial cell proliferation

The incidence and prevalence of inflammatory bowel disease (IBD) are increasing worldwide. IBD is known to be multifactorial, but inflammatory signaling within the intestinal epithelium and a subsequent failure of the intestinal epithelial barrier have been shown to play essential roles in disease pathogenesis. CaMKIV is a multifunctional protein kinase associated with inflammation and cell cycle regulation. CaMKIV has been extensively studied in autoimmune diseases, but a role in idiopathic intestinal inflammation has not been described. In this study, active CaMKIV was highly expressed within the intestinal epithelium of humans with ulcerative colitis and wild-type (WT) mice with experimental induced colitis. Clinical disease severity directly correlates with CaMKIV activation, as does expression of proinflammatory cytokines and histologic features of colitis. In WT mice, CaMKIV activation is associated with increases in expression of 2 cell cycle proarrest signals: p53 and p21. Cell cycle arrest inhibits proliferation of the intestinal epithelium and ultimately results in compromised intestinal epithelial barrier integrity, further perpetuating intestinal inflammation during experimental colitis. Using a CaMKIV null mutant mouse, we demonstrate that a loss of CaMKIV protects against murine DSS colitis. Small molecules targeting CaMKIV activation may provide therapeutic benefit for patients with IBD.-Cunningham, K. E., Novak, E. A., Vincent, G., Siow, V. S., Griffith, B. D., Ranganathan, S., Rosengart, M. R., Piganelli, J. D., Mollen, K. P. Calcium/calmodulin-dependent protein kinase IV (CaMKIV) activation contributes to the pathogenesis of experimental colitis via inhibition of intestinal epithelial cell proliferation.

High Prevalence of Mansonella perstans Filariasis in Rural Senegal

Large parts of African and American countries are colonized by Mansonella, a very common but poorly described filarial nematode. Bloodsucking flies of the genus Culicoides are suspected to be the vector of Mansonella perstans, but no study in Senegal has confirmed that Culicoides can transmit the parasite. Designed specific real-time quantitative polymerase chain reaction (qPCR) can be used to identify microfilaria in stained blood smears. This study was performed in July and December 2010 in the southeastern Senegal, which is known to be endemic for M. perstans. We analyzed 297 blood smears from febrile and afebrile resident people by qPCR. The global prevalence of M. perstans was approximately 14.5% in both febrile and afebrile individuals. The age group of > 30 years had the highest prevalence (22.0%). No Culicoides among 1,159 studied specimens was positive for M. perstans and its vector in Senegal still requires identification.

Recombinant human MFG-E8 ameliorates colon damage in DSS- and TNBS-induced colitis in mice

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the digestive system and typically requires lifelong medical care. Recombinant human MFG-E8 (rhMFG-E8) is a 364-amino acid protein, which promotes apoptotic cell clearance and reduces inflammation. This study investigates the therapeutic effect of rhMFG-E8 on two well-established mouse models of IBD. Acute mucosal injury leading to colitis was caused by exposing C57BL/6 mice to 4% dextran sodium sulfate (DSS) in the drinking water over 7 days, and BALB/c mice to a single intrarectal dose of 2.75 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Upon clinical onset of colitis (day 2 in the DSS model and day 1 in the TNBS model), mice were treated with daily subcutaneous injections of rhMFG-E8 (60 or 120 μg/kg/day) or vehicle (saline) for 6 days. Treatment with rhMFG-E8 significantly attenuated colitis in both models in a dose-dependent way. Treatment of DSS-induced colitis with rhMFG-E8 (120 μg/kg/day) decreased weight loss by 59%, the colitis severity score by 71%, and colon shrinkage by 49% when compared with vehicle. Similarly, treatment of TNBS-induced colitis with rhMFG-E8 (120 μg/kg/day) decreased weight loss by 97%, the colitis severity score by 82%, and colon shrinkage by 62% when compared with vehicle. In both models, the colons of animals receiving rhMFG-E8 showed marked reduction in neutrophil infiltration, cytokine and chemokine expression, and apoptotic cell counts. In conclusion, rhMFG-E8 ameliorates DSS- and TNBS-induced colitis, suggesting that it has the potential to become a novel therapeutic agent for IBD.

Cyclooxygenase-2 silencing for the treatment of colitis: a combined in vivo strategy based on RNA interference and engineered Escherichia coli

Nonpathogenic-invasive Escherichia coli (InvColi) bacteria are suitable for genetic transfer into mammalian cells and may act as a vehicle for RNA Interference (RNAi) in vivo. Cyclooxygenase-2 (COX-2) is overexpressed in ulcerative colitis (UC) and Crohn's disease (CD), two inflammatory conditions of the colon and small intestine grouped as inflammatory bowel disease (IBD). We engineered InvColi strains for anti-COX-2 RNAi (InvColi(shCOX2)), aiming to investigate the in vivo feasibility of a novel COX-2 silencing strategy in a murine model of colitis induced by dextran sulfate sodium (DSS). Enema administrations of InvColi(shCOX2) in DSS-treated mice led to COX-2 downregulation, colonic mucosa preservation, reduced colitis disease activity index (DAI) and increased mice survival. Moreover, DSS/InvColi(shCOX2)-treated mice showed lower levels of circulating pro-inflammatory cytokines and a reduced colitis-associated shift of gut microbiota. Considering its effectiveness and safety, we propose our InvColi(shCOX2) strategy as a promising tool for molecular therapy in intestinal inflammatory diseases.

Longitudinal analysis of inflammation and microbiota dynamics in a model of mild chronic dextran sulfate sodium-induced colitis in mice

AIM: To characterize longitudinally the inflammation and the gut microbiota dynamics in a mouse model of dextran sulfate sodium (DSS)-induced colitis.

METHODS: In animal models, the most common method used to trigger colitis is based on the oral administration of the sulfated polysaccharides DSS. The murine DSS colitis model has been widely adopted to induce severe acute, chronic or semi-chronic colitis, and has been validated as an important model for the translation of mice data to human inflammatory bowel disease (IBD). However, it is now clear that models characterized by mild intestinal damage are more accurate for studying the effects of therapeutic agents. For this reason, we have developed a murine model of mild colitis to study longitudinally the inflammation and microbiota dynamics during the intestinal repair processes, and to obtain data suitable to support the recovery of gut microbiota-host homeostasis.

RESULTS: All plasma cytokines evaluated, except IL-17, began to increase (P < 0.05), after 7 d of DSS administration. IL-17 only began to increase 4 d after DSS withdrawal. IL-1β and IL-17 continue to increase during the recovery phase, even when clinical signs of colitis had disappeared. IL-6, IL-10 and IFN-γ reached their maxima 4 d after DSS withdrawal and decreased during the late recovery phase. TNFα reached a peak (a three- fold increase, P < 0.05), after which it slightly decreased, only to increase again close to the end of the recovery phase. DSS administration induced profound and rapid changes in the mice gut microbiota. After 3 d of DSS administration, we observed a major reduction in Bacteroidetes/Prevotella and a corresponding increase in Bacillaceae, with respect to control mice. In particular, Bacteroidetes/Prevotella decreased from a relative abundance of 59.42%-33.05%, while Bacillaceae showed a concomitant increase from 2.77% to 10.52%. Gut microbiota rapidly shifted toward a healthy profile during the recovery phase and returned normal 4 d after DSS withdrawal. Cyclooxygenase 2 expression started to increase 4 d after DSS withdrawal (P < 0.05), when dysbiosis had recovered, and continued to increase during the recovery phase. Taken together, these data indicated that a chronic phase of intestinal inflammation, characterized by the absence of dysbiosis, could be obtained in mice using a single DSS cycle.

CONCLUSION: Dysbiosis contributes to the local and systemic inflammation that occurs in the DSS model of colitis; however, chronic bowel inflammation is maintained even after recovery from dysbiosis.

Repeated H2 O2 exposure drives cell cycle progression in an in vitro model of ulcerative colitis

The production of hydrogen peroxide (H₂O₂) drives tumourigenesis in ulcerative colitis (UC). Recently, we showed that H₂O₂ activates DNA damage checkpoints in human colonic epithelial cells (HCEC) through c-Jun N-terminal Kinases (JNK) that induces p21^WAF1. Moreover, caspases circumvented the G1/S and intra-S checkpoints, and cells accumulated in G2/M. The latter observation raised the question of whether repeated H₂O₂ exposures alter JNK activation, thereby promoting a direct passage of cells from G2/M arrest to driven cell cycle progression. Here, we report that increased proliferation of repeatedly H₂O₂-exposed HCEC cells (C-cell cultures) was associated with (i) increased phospho-p46 JNK, (ii) decreased total JNK and phospho-p54 JNK and (iii) p21^WAF1 down-regulation. Altered JNK activation and p21^WAF1 down-regulation were accompanied by defects in maintaining G2/M and mitotic spindle checkpoints through adaptation, as well as by apoptosis resistance following H₂O₂ exposure. This may cause increased proliferation of C-cell cultures, a defining initiating feature in the inflammation-carcinoma pathway in UC. We further suggest that dysregulated JNK activation is attributed to a non-apoptotic function of caspases, causing checkpoint adaptation in C-cell cultures. Additionally, loss of cell-contact inhibition and the overcoming of senescence, hallmarks of cancer, contributed to increased proliferation. Furthermore, there was evidence that p54 JNK inactivation is responsible for loss of cell-contact inhibition. We present a cellular model of UC and suggest a sinusoidal pattern of proliferation, which is triggered by H₂O₂-induced reactive oxygen species generation, involving an interplay between JNK activation/inactivation, p21^WAF1, c-Fos, c-Jun/phospho-c-Jun, ATF2/phospho-ATF2, β-catenin/TCF4-signalling, c-Myc, CDK6 and Cyclin D2, leading to driven cell cycle progression.