Colon impairments and inflammation driven by an altered gut microbiota leads to social behavior deficits rescued by hyaluronic acid and celecoxib

BACKGROUND

The exact mechanisms linking the gut microbiota and social behavior are still under investigation. We aimed to explore the role of the gut microbiota in shaping social behavior deficits using selectively bred mice possessing dominant (Dom) or submissive (Sub) behavior features. Sub mice exhibit asocial, depressive- and anxiety-like behaviors, as well as systemic inflammation, all of which are shaped by their impaired gut microbiota composition.

METHODS

An age-dependent comparative analysis of the gut microbiota composition of Dom and Sub mice was performed using 16S rRNA sequencing, from early infancy to adulthood. Dom and Sub gastrointestinal (GI) tract anatomy, function, and immune profiling analyses were performed using histology, RT-PCR, flow cytometry, cytokine array, and dextran-FITC permeability assays. Short chain fatty acids (SCFA) levels in the colons of Dom and Sub mice were quantified using targeted metabolomics. To support our findings, adult Sub mice were orally treated with hyaluronic acid (HA) (30 mg/kg) or with the non-steroidal anti-inflammatory agent celecoxib (16 mg/kg).

RESULTS

We demonstrate that from early infancy the Sub mouse gut microbiota lacks essential bacteria for immune maturation, including Lactobacillus and Bifidobacterium genera. Furthermore, from birth, Sub mice possess a thicker colon mucin layer, and from early adulthood, they exhibit shorter colonic length, altered colon integrity with increased gut permeability, reduced SCFA levels and decreased regulatory T-cells, compared to Dom mice. Therapeutic intervention in adult Sub mice treated with HA, celecoxib, or both agents, rescued Sub mice phenotypes. HA treatment reduced Sub mouse gut permeability, increased colon length, and improved mouse social behavior deficits. Treatment with celecoxib increased sociability, reduced depressive- and anxiety-like behaviors, and increased colon length, and a combined treatment resulted in similar effects as celecoxib administered as a single agent.

CONCLUSIONS

Overall, our data suggest that treating colon inflammation and decreasing gut permeability can restore gut physiology and prevent social deficits later in life. These findings provide critical insights into the importance of early life gut microbiota in shaping gut immunity, functionality, and social behavior, and may be beneficial for the development of future therapeutic strategies.

Adverse effect of oxidized cholesterol exposure on colitis is mediated by modulation of gut microbiota

Both cholesterol and oxidized cholesterol (OXC) are present in human diets. The incidence of inflammatory bowel diseases (IBDs) is increasing in the world. The present study was to investigate the mechanism by which OXC promotes colitis using C57BL/6 mice as a model. Results shown that more severe colitis was developed in OXC-treated mice with the administration of dextran sulfate sodium (DSS) in water. Direct effects of short-term OXC exposure on gut barrier or inflammation were not observed in healthy mice. However, OXC exposure could cause gut microbiota dysbiosis with a decrease in the relative abundance of short-train fatty acids (SCFAs)-producing bacteria (Lachnospiraceae_NK4A136_group and Blautia) and an increase in the abundance of some potential harmful bacteria (Bacteroides). OXC-induced symptoms of colitis were eliminated when mice were administered with antibiotic cocktails, indicating the promoting effect of OXC on DSS-induced colitis was mediated by its effect on gut microbiota. Moreover, bacteria-depleted mice colonized with gut microbiome from OXC-DSS-exposed mice exhibited a severe colitis, further proving the gut dysbiosis caused by OXC exposure was the culprit in exacerbating the colitis. It was concluded that dietary OXC exposure increased the susceptibility of colitis in mice by causing gut microbiota dysbiosis.

Colonic mechanism of serum NAD+ depletion induced by DEHP during pregnancy

Di (2-ethylhexyl) phthalate (DEHP) is a widely used plasticizer in polyvinyl chloride products such as feed piping, packing bag, and medical consumable. Our previous studies have demonstrated that DEHP exposure reduced the concentration of nicotinamide adenine dinucleotide (NAD⁺) in pregnant mice serum, which cuts off the source of NAD⁺ to placenta and results fetal growth restriction. However, the mechanism of serum NAD⁺ depletion by DEHP remains elusive. This study investigated the intestinal mechanism of NAD⁺ shortage-induced by DEHP in pregnant mice. The transcriptome results implicated that the mRNA level of oxidative response genes Cyp1a1, Gsto2, Trpv1 and Trpv3 were upregulated in colon. These changes induced intestinal inflammation. Transmission Electron Microscopy results displayed that DEHP destroyed the tight junctions and cell polarity of colonic epithelial cells. These dysfunctions diminished the expression of NAD⁺ precursor transporters SLC12A8, SLC5A8, SLC7A5, and the NAD⁺ biosynthetic key enzymes NAMPT, NMNAT1-3, and TDO2 in colonic epithelial cells. Analysis of the gut microbiota showed that DEHP led to the dysbiosis of gut microbiota, reducing the relative abundance of Prevotella copri which possesses the VB3 biosynthetic pathway. Therefore, maternal DEHP exposure during pregnancy decreased the transportation of NAD⁺ precursors from enteric cavity to colonic epithelial cells, and inhibited the synthesis of NAD⁺ in colonic epithelial cells. Meanwhile, DEHP reduced the NAD⁺ precursors provided by gut microbiota. Eventually, serum NAD⁺ content was lowered. Taken together, our findings provide a new insight for understanding the intestinal mechanisms by which DEHP affects serum NAD⁺ levels.

ROS-triggered self-disintegrating and pH-responsive astaxanthin nanoparticles for regulating the intestinal barrier and colitis

Smart delivery systems with stimuli-responsive capability are able to improve the bioaccessibility through increasing the solubility, physicochemical stability and biocompatibility of bioactive compounds. In this study, the astaxanthin nanoparticles with reactive oxygen species (ROS) and pH dual-response function were design and constructed using poly (propylene sulfide) covalently modified sodium alginate as carriers based on ultrasonic assisted self-assembly strategy. Atomic force microscope and scanning electron microscope analysis showed that the nanoparticles were spherical in shape with a size of around 260 nm. Meanwhile, the astaxanthin nanoparticles showed both pH and ROS stimuli-responsive release characteristics. In vitro cell experiments showed that astaxanthin nanoparticles significantly inhibited the production of ROS and mitochondrial depolarization induced by oxidative stress. In vivo colitis experiment of mice revealed that astaxanthin nanoparticles could significantly relieve colitis, protect the integrity of colon tissue and restore the expression of tight junction proteins ZO-1 and occludin. The abundance of Lactobacillus and Lachnospiraceae, and the ratio of Firmicutes/Bacteroidota of gut microbiota were significantly improved after intervention of the stimuli-responsive astaxanthin nanoparticles. This work provided a simple strategy for constructing ROS/pH dual response delivery system, which provided an experimental basis for improving the oral bioavailability of hydrophobic active compounds.

Oral delivery of folate-targeted resveratrol-loaded nanoparticles for inflammatory bowel disease therapy in rats

AIMS

In the current study, resveratrol-loaded PLGA nanoparticles targeted with folate were developed in order to protect resveratrol from fast degradation, modify its pharmacokinetics and increase its intestinal permeation. Then, the therapeutic efficacy of the prepared system was evaluated in suppression of colon inflammation on TNBS-induced colitis model.

MAIN METHODS

In this regard, resveratrol was encapsulated in PLGA and FA-conjugated PLGA in order to prepare non-targeted (PLGA-RSV) and targeted (PLGA-FA-RSV) platforms, respectively.

KEY FINDINGS

Obtained results demonstrated that the prepared formulations encapsulated the resveratrol with high encapsulation efficiency of 90.7% ± 5.1% for PLGA-RSV and 59.1% ± 3.3% for PLGA-FA-RSV. In vitro release experiment showed that the prepared formulations were capable of retaining good amount of resveratrol under the simulated gastric condition (HCl 0.1 N, pH 1.2), while significant amount of resveratrol was released under simulated intestinal condition (PBS, pH 7.4). The trans-well permeability rates through Caco-2 monolayer during 180 min, was determined to be 4.5%, 61% and 99% for resveratrol, PLGA-RSV and PLGA-FA-RSV respectively. The pathological analysis of the rat intestinal sections (hematoxylin & eosin staining) at 7th day post-TNBS colonic inflammation induction illustrated that the oral administrations of FA-PLGA-RSV and PLGA-RSV were able to significantly inhibit the inflammation and reduce neutrophil and lymphocytes accumulation. It is worth noting that the folate-targeted system demonstrated highest efficacy in suppressing colon inflammation.

SIGNIFICANCE

It could be concluded that the encapsulation of resveratrol into biodegradable folate-targeted PLGA nanoparticles could introduce a potent platform in suppressing colonic inflammation thus offering a great capability for clinical translation.

Tissue-specific effect of colitis on protein synthesis in mice: impact of the dietary protein content

PURPOSE

Inflammatory bowel diseases are associated with an increase in the whole-body protein turnover, thus possibly requiring an additional supply of dietary proteins. Our aim was to evaluate whether increasing dietary protein content could alleviate protein metabolism alterations in the injured splanchnic and peripheral tissues during colitis and spontaneous mucosal healing.

METHODS

Mice with acute chemically induced colitis received either a normal protein (P14, 14% as energy), a moderately (P30, 30%) and a very high-protein (P53, 55%) diets. At different times after the challenge, protein synthesis rate was determined in tissues using a flooding dose of ¹³C valine.

RESULTS

Colon, liver and spleen protein synthesis rates were significantly increased after colitis induction, while being decreased in the caecum, kidneys and muscle. Contrastingly to the two other diets, P30 diet consumption allowed faster recovery of the animals, and this coincided with a rapid resaturation of the initial protein synthesis in the colon. In the other tissues studied, the high-protein diets show different effects depending on the dietary protein content consumed and on the examined tissues, with a general trend of P53 in lowering anabolism rates.

CONCLUSION

This study highlights the severe impact of acute colonic inflammation on protein metabolism in different organs. In addition, dietary protein content modulated the recovery of the initial protein synthesis rate in the various tissues following colitis induction. P30 diet consumption notably showed a better ability to alleviate protein metabolism perturbations induced by colitis, that may explain its documented beneficial effect on colon mucosal healing.

Alcohol-Induced Immune Dysregulation in the Colon Is Diurnally Variable

Introduction

Alcohol increases the risk of colon cancer. Colonic inflammation mediates the effects of alcohol on colon carcinogenesis. Circadian rhythm disruption enhances the alcohol's effect on colonic inflammation and cancer.

Objective

Here, we investigate the diurnal variation of lymphocyte infiltration in the colonic mucosa in response to alcohol.

Methods

Sixty C57BL6/J mice were fed a chow diet, and gavaged with alcohol at a specific time once per day for 3 consecutive days. Immunohistochemistry and immunofluorescence staining were used to quantify total, effector, and regulatory T cells in the colon. Student's t test, one-way ANOVA, and two-way ANOVA were used to determine significance.

Results

Following the alcohol binge, the composition of immune T cell subsets in the mouse colon was time-dependent. Alcohol did not alter the total number of CD3⁺ T cells. However, upon alcohol treatment, T-bet⁺ T helper 1 (Th1) cells appeared to dominate the T cell population following a reduction in Foxp3⁺ regulatory T cell (Treg) numbers. Depletion of Tregs was time-dependent, and their numbers were dramatically reduced when alcohol was administered during the rest phase. A reduction in Tregs significantly increased the Th1/Treg ratio, resulting in a more proinflammatory milieu.

Conclusions

Alcohol enhanced the proinflammatory profile in the colon mucosa, as demonstrated by a higher T-bet⁺/Foxp3⁺ ratio, especially during the rest phase. These findings may partly account for the interaction of circadian rhythm disruption with alcohol in colon inflammation and cancer.

TRIM34 attenuates colon inflammation and tumorigenesis by sustaining barrier integrity

Loss of the colonic inner mucus layer leads to spontaneously severe colitis and colorectal cancer. However, key host factors that may control the generation of the inner mucus layer are rarely reported. Here, we identify a novel function of TRIM34 in goblet cells (GCs) in controlling inner mucus layer generation. Upon DSS treatment, TRIM34 deficiency led to a reduction in Muc2 secretion by GCs and subsequent defects in the inner mucus layer. This outcome rendered TRIM34-deficient mice more susceptible to DSS-induced colitis and colitis-associated colorectal cancer. Mechanistic experiments demonstrated that TRIM34 controlled TLR signaling-induced Nox/Duox-dependent ROS synthesis, thereby promoting the compound exocytosis of Muc2 by colonic GCs that were exposed to bacterial TLR ligands. Clinical analysis revealed that TRIM34 levels in patient samples were correlated with the outcome of ulcerative colitis (UC) and the prognosis of rectal adenocarcinoma. This study indicates that TRIM34 expression in GCs plays an essential role in generating the inner mucus layer and preventing excessive colon inflammation and tumorigenesis.

Dietary Extra-Virgin Olive Oil Polyphenols Do Not Attenuate Colon Inflammation in Transgenic HLAB-27 Rats but Exert Hypocholesterolemic Effects through the Modulation of HMGCR and PPAR-α Gene Expression in the Liver

BACKGROUND

Human studies have demonstrated that olive oil phenolic compounds reduce inflammatory markers associated with chronic diseases.

OBJECTIVES

To explore the anti-inflammatory effects of extra-virgin olive oil polyphenols in an experimental model of inflammatory bowel disease (IBD).

METHODS

HLA-B27 transgenic rats were fed an AIN-76 diet containing 10% corn oil (CO) or extra-virgin olive oil with high (EVOO) or low phenolic content (ROO) for 3 months. Wild-type rats (WT) were fed the CO diet.

RESULTS

CO-fed HLA-B27 animals developed intestinal inflammation characterized by diarrhea, increased myeloperoxidase activity, and mucosal injury. None of these parameters were influenced by EVOO. Gene expression profiling indicated that proinflammatory pathways were upregulated in the colon mucosa of CO-fed HLA-B27 rats compared to WT, and this was further confirmed by RT-PCR for the iNOS, TNFα, and IL1β genes. EVOO significantly reduced TNFα gene expression in the colon mucosa and decreased total cholesterol blood levels compared to CO HLA-B27 rats (89.43 ± 3.66 vs. 111.5 ± 8.10 mg/dL, p < 0.05). This latter effect with EVOO was associated with reduced HMGCR and increased PPAR-α hepatic gene expression, compared to ROO.

CONCLUSION

These data indicate that olive oil polyphenols do not control colon inflammation in HLA-B27 transgenic rats but exert a positive effect on blood lipids by reducing total cholesterol levels. This preliminary result suggests the need to explore the efficacy of EVOO rich in polyphenols as a complementary strategy for managing hypercholesterolemia and to potentially limit statin-associated myotoxicity.

Disruption of GPR35 Exacerbates Dextran Sulfate Sodium-Induced Colitis in Mice

BACKGROUND

G protein-coupled receptor 35 (GPR35) is an orphan receptor and is vastly expressed in immune cells and gastrointestinal cells, suggesting the potential physiological importance of GPR35 in these cells. Here, we tested the hypothesis that the lack of GPR35 expression in the colon mucosa exacerbates the severity of dextran sulfate sodium (DSS)-induced experimental colitis in mice.

METHODS

Colitis was induced in GPR35 wild-type (GPR35^+/+) and GPR35 knockout (GPR35^-/-) mice through the administration of DSS in drinking water for 5 days followed by regular facility water for 1 day. Induction of colitis was evaluated by measuring relative body weight loss, clinical illness scores, and morphological changes in the colon. Abolition of Gpr35 gene expression in the colon mucosa of GPR35^-/- mice was confirmed by quantitative real-time PCR (qPCR). Gene expressions of inflammatory and tissue remodeling cytokines were detected by qPCR. Human colorectal epithelial Caco cells were transfected with siRNA against GPR35 before treated with 1% DSS in vitro. Protein expressions were measured using Western blot.

RESULTS

GPR35^-/- mice receiving DSS showed a significantly worsened colitis disease with profound loss of body weight and a considerable amount of severe clinical illness compared to GPR35^+/+ mice that received DSS. The histology of colon sections from GPR35^-/- mice showed extensive pathological changes including submucosal edema, diffuse ulcerations, and evidence of complete loss of crypts compared to wild-type mice. The mean histopathological score was significantly higher in GPR35^-/- mice as compared to GPR35^+/+ mice. The qPCR data revealed significant expression of pro-inflammatory and tissue remodeling cytokines in GPR35^-/- colon mucosa, including IL-1β, CXCL1, CXCL2, CCL2, HMGB1, TGFβ1, TGFβ3, MMP1/9/12. The protein expressions of Zonula occludens-1, E-cadherin, Claudin1 were decreased upon knocking down GPR35 with or without 1% DSS treatment.

CONCLUSIONS

Our experimental data suggest that lack of GPR35 resulted in worsened disease outcome in DSS-induced experimental colitis, indicating that GPR35 could play a crucial role in protecting from colonic inflammation and serve as a therapeutic target.

Acute infection with Strongyloides venezuelensis increases intestine production IL-10, reduces Th1/Th2/Th17 induction in colon and attenuates Dextran Sulfate Sodium-induced colitis in BALB/c mice

Helminth infection can reduce the severity of inflammatory bowel disease. However, the modulatory mechanisms elicited by helminth infection are not yet fully understood and vary depending on the experimental model. Herein we evaluated the effect of acute infection of BALB/c mice with Strongyloides venezuelensis on the clinical course of ulcerative colitis induced by Dextran Sulfate Sodium (DSS) treatment of these animals. For the experiments, S. venezuelensis-infected BALB/c mice were treated orally with 4% DSS solution for seven days. As controls, we used untreated S. venezuelensis infected, DSS-treated uninfected, and untreated/uninfected BALB/c mice. During DSS treatment, mice from the different groups were compared with regards to the clinical signs related to the severity of colitis and intestinal inflammation. Mice acutely infected with S. venezulensis and treated with DSS had reduced clinical score, shortening of the colon, and tissue inflammation. Moreover, DSS-treated and infected mice showed reduced IL-4, INF-γ, and IL-17 levels and increase of IL-10 production in the colon and/or in the supernatant of mesenteric lymph nodes cell cultures that resulted in lower eosinophil peroxidase and myeloperoxidase activity in colon homogenates, when compared with DSS-treated uninfected mice. DSS-treated infected mice also preserved the intestine architecture and had normal differentiation of goblet cells and mucus production in the colon mucosa. In conclusion, the data indicate that the clinical improvement reported in DSS-treated infected mice was accompanied by the lower production of Th1/Th2/Th17 pro-inflammatory cytokines, stimulation of IL-10, and induction of mucosal repair mechanisms.

Cyclin D1 Gene Silencing by siRNA in Ex Vivo Human Tissue Cultures

BACKGROUND

Short interfering RNAs (siRNAs) are double-stranded RNA molecules able to specifically targeting genes products responsible for human diseases. Cyclin D1 (CyD1) is a cell cycleregulatory molecule, up-regulated at sites of inflammation in several tissues. CyD1 is a very interesting potential target in lung and colon inflammatory diseases.

OBJECTIVE

The aim of this paper was testing CyD1 expression in human lung and colon tissues after the application of an inflammatory stimulus, and verifying its gene silencing by using siRNA for CyD1 (siCyD1).

METHOD

Colon and pulmonary biopsies were treated with siCyD1 by using two different transfection carriers: a) invivofectamine and b) ad hoc produced nanoliposomes. After 24 hours of incubation with nanoliposomes encapsulating siRNA or invivofectamine-CyD1siRNA, in presence or absence of ECLPS, we analysed the protein expression of CyD1 through Western-Blotting.

RESULTS

After EC-LPS treatment, in both colon and pulmonary biopsies, an overexpression of CyD1was found (about 64% and 40% respectively). Invivofectamine-CyD1 siRNA reduced the expression of CyD1 approximately by 46% compared to the basal condition, and by around 65% compared to EC-LPS treated colon samples. In lung, following in vivo fectamine siRNA silencing in the presence of EC-LPS, no reduction was observed. Ad hoc nanoliposomes were able to enter colon and lung tissues, but CyD1 silencing was reported in 2 colon samples out of 4 and no efficacy was demonstrated in the only lung sample we studied.

CONCLUSION

The silencing of Cyclin D1 expression in vitro "organ culture" model is possible. Our preliminary results encourage further investigations, using different siRNA concentrations delivered by nanoliposomes.

HIF1α deficiency reduces inflammation in a mouse model of proximal colon cancer

Hypoxia-inducible factor 1α (HIF1α) is a transcription factor that regulates the adaptation of cells to hypoxic microenvironments, for example inside solid tumours. Stabilisation of HIF1α can also occur in normoxic conditions in inflamed tissue or as a result of inactivating mutations in negative regulators of HIF1α. Aberrant overexpression of HIF1α in many different cancers has led to intensive efforts to develop HIF1α-targeted therapies. However, the role of HIF1α is still poorly understood in chronic inflammation that predisposes the colon to carcinogenesis. We have previously reported that the transcription of HIF1α is upregulated and that the protein is stabilised in inflammatory lesions that are caused by the non-steroidal anti-inflammatory drug (NSAID) sulindac in the mouse proximal colon. Here, we exploited this side effect of long-term sulindac administration to analyse the role of HIF1α in colon inflammation using mice with a Villin-Cre-induced deletion of Hif1α exon 2 in the intestinal epithelium (Hif1α^ΔIEC). We also analysed the effect of sulindac sulfide on the aryl hydrocarbon receptor (AHR) pathway in vitro in colon cancer cells. Most sulindac-treated mice developed visible lesions, resembling the appearance of flat adenomas in the human colon, surrounded by macroscopically normal mucosa. Hif1α^ΔIEC mice still developed lesions but they were smaller than in the Hif1α-floxed siblings (Hif1α^F/F). Microscopically, Hif1α^ΔIEC mice had significantly less severe colon inflammation than Hif1α^F/F mice. Molecular analysis showed reduced MIF expression and increased E-cadherin mRNA expression in the colon of sulindac-treated Hif1α^ΔIEC mice. However, immunohistochemistry analysis revealed a defect of E-cadherin protein expression in sulindac-treated Hif1α^ΔIEC mice. Sulindac sulfide treatment in vitro upregulated Hif1α, c-JUN and IL8 expression through the AHR pathway. Taken together, HIF1α expression augments inflammation in the proximal colon of sulindac-treated mice, and AHR activation by sulindac might lead to the reduction of E-cadherin protein levels through the mitogen-activated protein kinase (MAPK) pathway.

Summary: HIF1α deficiency reduces inflammation in the mouse proximal colon but is associated with defective E-cadherin expression in colon epithelial cells when mice lacking intestinal epithelium expression of Hif1α are challenged with sulindac.