MD-1 deficiency attenuates dextran sodium sulfate (DSS)-induced colitis through modulating the function of colonic lamina propria dendritic cells

Ameliorative effect of bound polyphenols in mung bean coat dietary fiber on DSS-induced ulcerative colitis in mice: the intestinal barrier and intestinal flora

The consumption of dietary fiber is beneficial for gut health, but the role of bound polyphenols in dietary fiber has lacked systematic study. The aim of this study is to evaluate the ameliorative effect of mung bean coat dietary fiber (MDF) on DSS-induced ulcerative colitis in mice in the presence and absence of bound polyphenols. Compared to polyphenol-removed MDF (PR-MDF), MDF and formulated-MDF (F-MDF,backfilling polyphenols by the amount of extracted from MDF into PR-MDF) alleviated symptoms such as weight loss and colonic injury in mice with colitis, effectively reduced excessive inflammatory responses, and the bound polyphenols restored the integrity of the intestinal barrier by promoting the expression of tight junction proteins. Additionally, bound polyphenols restored the expression of autophagy-related proteins (mTOR, beclin-1, Atg5 and Atg7) and inhibited the excessive expression of apoptotic-related proteins (Bax, caspase-9, and caspase-3). Furthermore, bound polyphenols could ameliorate the dysregulation of the intestinal microbiota by increasing the abundance of beneficial bacteria and inhibiting the abundance of harmful bacteria. Thus, it can be concluded that the presence of bound polyphenols in MDF plays a key role in the alleviation of DSS-induced ulcerative colitis.

Alleviative effects of natural plant polysaccharides against DSS-induced ulcerative colitis via inhibiting inflammation and modulating gut microbiota

Ulcerative colitis (UC) treatment usually involves either drug therapy or surgery. Natural food polysaccharides have showed great potential for preventing UC. In this study, the therapeutic effects of Cyclocarya paliurus (Batal.) Iljinskaja polysaccharide (CP) and Chinese yam polysaccharide (CYP) on dextran sodium sulfate (DSS)-induced mice UC model and their underlying mechanisms were explored. The results suggested that CP and CYP could improve colitis symptoms in DSS-induced mice, enhance the production of IL-10, inhibit cytokines (IL-1β, TNF-α) and reduce MPO activity. Furthermore, they maintained the integrity of intestine by improving the expression of mucin MUC-2, ZO-1 and occludin, which in turn reduced the contents of lipopolysaccharide binding protein (LBP) and endotoxin (ET) in serum and oxidative stress in liver. Finally, they modulated the composition and metabolism of gut microbiota. Notably, Alistipes and Bacteroides were the specific genera in CP and CYP groups, respectively. These findings indicated that polysaccharides might alleviate the development of colitis and inform other relevant studies.

The innate immune receptor RP105 promotes metabolic syndrome by altering gut microbiota composition and intestinal barrier function

Radioprotective 105 (RP105) plays a key role in the development of high-fat diet (HFD)-induced metabolic disorders; however, the underlying mechanisms remain to be understood. Here, we aimed to uncover whether RP105 affects metabolic syndrome through the modification of gut microbiota. We confirmed that body weight gain and fat accumulation by HFD feeding were suppressed in Rp105^-/- mice. Fecal microbiome transplantation from HFD-fed donor Rp105^-/- mice into HFD-fed recipient wild-type mice significantly improved various abnormalities associated with metabolic syndrome, including body weight gain, insulin resistance, hepatic steatosis, macrophage infiltration and inflammation in the adipose tissue. In addition, HFD-induced intestinal barrier dysfunction was attenuated by fecal microbiome transplantation from HFD-fed donor Rp105^-/- mice. A 16S rRNA sequence analysis indicated that RP105 modified gut microbiota composition and was involved in the maintenance of its diversity. Thus, RP105 promotes metabolic syndrome by altering gut microbiota composition and intestinal barrier function.

Mesona chinensis Benth Polysaccharides Alleviate DSS-Induced Ulcerative Colitis via Inhibiting of TLR4/MAPK/NF-κB Signaling Pathways and Modulating Intestinal Microbiota

SCOPE

Ulcerative colitis (UC) is a severe disease of the intestinal tract. To investigate the role of TLR4/Mitogen-activated protein kinase (MAPK)/Nuclear factor kappa-B(NF-κB) pathways and intestinal flora in UC, and the protective mechanisms of Mesona chinensis Benth polysaccharides (MBP), potential therapeutic agents due to their diabetes-relieving, cancer-suppressing, and immunomodulatory properties.

METHODS AND RESULTS

A dextran sulfate sodium (DSS)-induced mouse colitis model is used for experiments; the histopathology, immunohistochemistry, and Western blotting's results suggest that MBP can alleviate the colitis symptoms, inhibits the overproduction of TNF-α, IL-1β, promote IL-10, reduces myeloperoxidase activity, and alleviates the inflammatory response probably by inhibiting the activation of TLR4/MAPK/NF-κB pathways. Furthermore, MBP improvs the ratio of Bcl-2/BAX, maintains the intestinal integrity by promoting the levels of zonulin occludin-1 (ZO-1), occluding and mucin mucin-2 (MUC-2), reduces the levels of endotoxin (ET), lipopolysaccharide binding protein (LBP) in serum, and oxidative stress in liver. Moreover, using 16S rRNA Gene Sequencing analysis, MBP regulates gut microbiota by decreasing the abundances of Helicobacter and Prevotella and increasing the abundances of Lactobacillus and Coprococcus, reverses microbiota dysbiosis caused by DSS.

CONCLUSION

These findings confirm the anti-inflammatory effects of MBP, restoration of the intestinal barrier and intestinal flora, and have therapeutic potential to attenuate the development of UC.

Fruit and Vegetable Supplemented Diet Modulates the Pig Transcriptome and Microbiome after a Two-Week Feeding Intervention

A study was conducted to determine the effects of a diet supplemented with fruits and vegetables (FV) on the host whole blood cell (WBC) transcriptome and the composition and function of the intestinal microbiome. Nine six-week-old pigs were fed a pig grower diet alone or supplemented with lyophilized FV equivalent to half the daily recommended amount prescribed for humans by the Dietary Guideline for Americans (DGA) for two weeks. Host transcriptome changes in the WBC were evaluated by RNA sequencing. Isolated DNA from the fecal microbiome was used for 16S rDNA taxonomic analysis and prediction of metabolomic function. Feeding an FV-supplemented diet to pigs induced differential expression of several genes associated with an increase in B-cell development and differentiation and the regulation of cellular movement, inflammatory response, and cell-to-cell signaling. Linear discriminant analysis effect size (LEfSe) in fecal microbiome samples showed differential increases in genera from Lachnospiraceae and Ruminococcaceae families within the order Clostridiales and Erysipelotrichaceae family with a predicted reduction in rgpE-glucosyltransferase protein associated with lipopolysaccharide biosynthesis in pigs fed the FV-supplemented diet. These results suggest that feeding an FV-supplemented diet for two weeks modulated markers of cellular inflammatory and immune function in the WBC transcriptome and the composition of the intestinal microbiome by increasing the abundance of bacterial taxa that have been associated with improved intestinal health.

A Ganoderma atrum polysaccharide alleviated DSS-induced ulcerative colitis by protecting the apoptosis/autophagy-regulated physical barrier and the DC-related immune barrier

Polysaccharides are one of the main active substances in Ganoderma atrum (G. atrum). The purpose of this study was to explore the protective effect of a G. atrum polysaccharide (PSG-1) on DSS-induced colitis and the underlying mechanism. The results showed that PSG-1 could maintain the integrity of the intestinal structure by promoting the expression of goblet cells and levels of tight junction proteins in the colon of DSS-induced colitis mice. Furthermore, PSG-1 relieved the inhibition of Bcl-2 and the overexpression of caspase-3 and caspase-9 caused by DSS. Simultaneously, PSG-1 restored the expression of Atg5, Atg7 and beclin-1 and inhibited the p-akt and p-mTOR levels, suggesting that PSG-1 promoted autophagy via the Akt/mTOR pathway. Moreover, PSG-1 inhibited the content of DCs in the colon and modulated the expression of IL-10 in DCs. In conclusion, PSG-1 alleviated DSS-induced ulcerative colitis by protecting the apoptosis/autophagy-regulated physical barrier and the DC-related immune barrier.

MD1 deletion exaggerates cardiomyocyte autophagy induced by heart failure with preserved ejection fraction through ROS/MAPK signalling pathway

In our previous studies, we reported that myeloid differentiation protein 1 (MD1) serves as a negative regulator in several cardiovascular diseases. However, the role of MD1 in heart failure with preserved ejection fraction (HFpEF) and the underlying mechanisms of its action remain unclear. Eight‐week‐old MD1‐knockout (MD1‐KO) and wild‐type (WT) mice served as models of HFpEF induced by uninephrectomy, continuous saline or d‐aldosterone infusion and a 1.0% sodium chloride treatment in drinking water for 4 weeks to investigate the effect of MD1 on HFpEF in vivo. H9C2 cells were treated with aldosterone to evaluate the role of MD1 KO in vitro. MD1 expression was down‐regulated in the HFpEF mice; HFpEF significantly increased the levels of intracellular reactive oxygen species (ROS) and promoted autophagy; and in the MD1‐KO mice, the HFpEF‐induced intracellular ROS and autophagy effects were significantly exacerbated. Moreover, MD1 loss activated the p38‐MAPK pathway both in vivo and in vitro. Aldosterone‐mediated cardiomyocyte autophagy was significantly inhibited in cells pre‐treated with the ROS scavenger N‐acetylcysteine (NAC) or p38 inhibitor SB203580. Furthermore, inhibition with the autophagy inhibitor 3‐methyladenine (3‐MA) offset the aggravating effect of aldosterone‐induced autophagy in the MD1‐KO mice and cells both in vivo and in vitro. Our results validate a critical role of MD1 in the pathogenesis of HFpEF. MD1 deletion exaggerates cardiomyocyte autophagy in HFpEF via the activation of the ROS‐mediated MAPK signalling pathway.

FGL2 regulates IKK/NF-κB signaling in intestinal epithelial cells and lamina propria dendritic cells to attenuate dextran sulfate sodium-induced colitis

Inflammatory bowel disease (IBD) is an autoimmune disease characterized by an abnormal immune response. Fibrinogen-like protein 2 (FGL2) is known to have immunoregulatory and anti-inflammatory activity. The level of FGL2 is elevated in patients with IBD; however, its comprehensive function in IBD is almost unknown. In our study, we explored the effect of FGL2 on dextran sulfate sodium (DSS)-induced colitis in mice and on NF-κB signaling in intestinal epithelial cells (IECs) and lamina propria dendritic cells (LPDCs). We founded that FGL2^-/- mice in the colitis model showed more severe colitis manifestations than WT mice did, including weight loss, disease activity index (DAI), and colon histological scores. FGL2^-/- mice treated with DSS produced more proinflammatory cytokines (IL-1β, IL-6, TNF-α) in serum than WT mice did and demonstrated upregulated expression of TNF-α and inflammatory marker enzymes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (Cox-2) in the colon tissue. Our data suggested that DSS-treated FGL2^-/- mice showed stronger activation of NF-κB signaling, especially in IECs. Next, we demonstrated that recombinant FGL2 (rFGL2) inhibited the production of proinflammatory cytokines and the expression of inflammatory marker enzymes by downregulating the NF-κB signaling in HT-29 cells. Finally, we discovered that LPDCs from the colon of DSS-treated FGL2^-/- mice showed significantly upregulated expression of surface maturation co-stimulatory molecules, including CD80, CD86, CD40, and MHC class II molecules compared with that in WT mice. In addition, LPDCs in FGL2^-/- treated with DSS exhibited excessive NF-κB activity and the administration of rFGL2 to FGL2^-/- mice could rescue the aggravated results of FGL2^-/- mice. Taken together, our findings demonstrated that FGL2 might be a target for further therapy of IBD.

Inhibition of myeloid differentiation 1 specifically in colon with antisense oligonucleotide exacerbates dextran sodium sulfate-induced colitis

Myeloid differentiation 1 (MD-1), also known as lymphocyte antigen 86 (Ly86), is a soluble protein homologous to MD-2 and forms a complex with radioprotective 105 (RP105). RP105/MD-1 complex negatively regulates toll-like receptor 4 (TLR4) signaling and is involved in several immune disorders. However, the precise role of MD-1 in inflammatory bowel diseases (IBD) remains poorly understood. To further investigate the involvement of MD-1 in IBD, we inhibited MD-1 in colon with antisense oligonucleotide (AS-ODN) and assessed the effect of MD-1 inhibition on dextran sodium sulfate (DSS)-induced colitis. We discovered that MD-1 protein expression was remarkably decreased in both patients with ulcerative colitis and mice with DSS-induced colitis. For the first time, we showed that oral administration of MD-1 AS-ODN to mice significantly suppressed the MD-1 protein levels in colon rather than systemic tissues. Subsequently, we found that MD-1 AS-ODN treated mice were more susceptible to DSS-induced colitis based on loss of body weight, colon length, histological scores, and disease activity index. MD-1 inhibition also significantly enhanced inflammatory cytokines production such as IL-6 and IL-1β in colons. Finally, mice treated with MD-1 AS-ODN exhibited increased messenger RNA levels of TLR4 and MyD88 after DSS exposure and showed enhanced nuclear factor (NF)-κB activation compared with the control. Taken together, specifically suppression of MD-1 in colon tissues with AS-ODN exacerbates DSS-induced experimental colitis in mice, which is possibly related to activation of TLR4/NF-κB signaling.

Mouse models of inflammatory bowel disease for investigating mucosal immunity in the intestine

PURPOSE OF REVIEW

Currently several mouse models are considered representative of inflammatory bowel disease (IBD). This review presents recent developments regarding the role of animal models of intestinal inflammation as research tools in IBD.

RECENT FINDINGS

Preclinical studies in animal models of intestinal inflammation have generated novel findings in several areas of IBD research. The combination of chemical and genetically engineered models have revealed protective or harmful roles for various components of the innate immune system in response to acute injury and repair mechanisms for the intestinal mucosa. Advances in the use of endoscopic and radiologic techniques have allowed identification of inflammatory biomarkers and in-vivo monitoring of cell trafficking towards inflammatory sites. Translational research has shed light on pathogenic mechanisms through which recent biological treatments may exert their beneficial effects in patients with IBD. Finally, novel therapies are continuously tested in animal models of IBD as part of preclinical drug development programs.

SUMMARY

Animal models of intestinal inflammation continue to be important research tools with high significance for understanding the pathogenesis of IBD and exploring novel therapeutic options. Development of additional experimental models that address existing limitations, and more closely resemble the characteristics of Crohn's disease and ulcerative colitis are greatly needed.

Novel Protective Role of Myeloid Differentiation 1 in Pathological Cardiac Remodelling

Myeloid differentiation 1 (MD-1), a secreted protein interacting with radioprotective 105 (RP105), plays an important role in Toll-like receptor 4 (TLR4) signalling pathway. Previous studies showed that MD-1 may be restricted in the immune system. In this study, we demonstrated for the first time that MD-1 was highly expressed in both human and animal hearts. We also discovered that cardiac-specific overexpression of MD-1 significantly attenuated pressure overload-induced cardiac hypertrophy, fibrosis, and dysfunction, whereas loss of MD-1 had the opposite effects. Similar results were observed for in vitro angiotensin II-induced neonatal rat cardiomyocyte hypertrophy. The antihypertrophic effects of MD-1 under hypertrophic stimuli were associated with the blockage of MEK-ERK 1/2 and NF-κB signalling. Blocking MEK-ERK 1/2 signalling with a pharmacological inhibitor (U0126) greatly attenuated the detrimental effects observed in MD-1 knockout cardiomyocytes exposed to angiotensin II stimuli. Similar results were observed by blocking NF-κB signalling with a pharmacological inhibitor (BAY11–7082). Our data indicate that MD-1 inhibits cardiac hypertrophy and suppresses cardiac dysfunction during the remodelling process, which is dependent on its modulation of the MEK-ERK 1/2 and NF-κB signalling pathways. Thus, MD-1 might be a novel target for the treatment of pathological cardiac hypertrophy.