Oral Administration of Taurolidine Ameliorates Chronic DSS Colitis in Mice

Taurolidine (TRD) has antimicrobial and anti-inflammatory properties. However, the anti-inflammatory effects of TRD in inflammatory bowel diseases (IBD) have not been investigated. Here, we have analyzed the toxicity of TRD after oral long-term application in mice and examined the impact of oral TRD in a dextran sulfate sodium (DSS) model of experimental colitis. Female C57/BL6 mice received TRD in various concentrations (0.1% to 0.4%) for 60 days. Toxicity was evaluated by use of a disease activity index (DAI) and histological examination of major metabolic organs. Furthermore, the impact of 0.2% TRD on a chronic DSS colitis was examined by daily DAI, histological crypt damage score (CDS), bacterial translocation into mesenteric lymph nodes (MLN), and colonic expression of tumor necrosis factor (TNF) α, transforming growth factor (TGF) β, interleukin (IL)-1β, IL-6, cytochrome oxidase (COX)-2, and monocyte chemotactic protein (MCP)-1 by real-time polymerase chain reaction (PCR). Oral TRD administration for 60 days was well tolerated by the animals and did not show any toxic effects in terms of DAI and histological changes. TRD treatment of DSS colitis led to increased survival of 100%, compared to 33% in the untreated colitis group (p ≤. 005). Clinical amelioration was mirrored by significantly reduced DAI and CDS in the TRD treated colitis. Colonic cytokine expression and bacterial translocation into MLN showed no differences between both groups.

We thus report for the first time that oral application of TRD results in amelioration of an experimental IBD model. We hypothesize direct intraluminal antimicrobial effects of TRD as well as anti-inflammatory effects during the acute phase of DSS colitis.     

Genetic deletion of JNK1 and JNK2 aggravates the DSS-induced colitis in mice.

The c-Jun N-terminal kinases (JNKs) are considered as novel targets for therapy of inflammatory bowel diseases (IBD). However, the relevant JNK isoforms have to be elucidated. Here, we analyze the individual contribution of the JNK1 and JNK2 isoforms in a dextran sulfate sodium (DSS) model of experimental colitis. JNK1 and JNK2 knockout mice (JNK1 ko, JNK2 ko) and their wild-type controls (WT1, WT2) received three cycles of DSS treatment, each consisting of 1.7% DSS for 5 days, followed by 5 days with water. Animals were daily evaluated by a disease activity index (DAI) comprising measurement of body weight, estimation of stool consistency, and test for occult blood/gross rectal bleeding. After 30 days all animals were sacrificed, and the inflamed intestine was histologically evaluated by a crypt damage score. Unexpectedly, neither JNK1 ko nor JNK2 ko prevented mice from developing a chronic colitis when compared to wild-type controls WT1 and WT2, respectively. On the contrary, DAI and mortality were aggravated in JNK2 ko compared to WT2. DAI and mortality did not differ between JNK1 ko and WT1, but the histological crypt damage score was significantly enhanced in the cecum of JNK1 ko mice. Genetic deletion of JNK2 worsens the disease outcome in an experimental model of murine colitis. We hypothesize that the functional deletion of the otherwise proapoptotic JNK2 prolongs the activity of proinflammatory immune cells with deterioration of disease activity.     

Effects of quercitrin on bacterial translocation in a rat model of experimental colitis

Background

This study aimed to analyze the effects of quercitrin, which has anti-inflammatory properties, on bacterial translocation in inflammatory bowel diseases by using an experimental colitis model.

巴柳氮对葡聚糖硫酸钠结肠炎小鼠肠黏膜通透性的影响

目的探讨巴柳氮对结肠炎小鼠肠黏膜通透性的影响及其作用机制。方法将45只C57BL／6J小鼠分成正常对照组、葡聚糖硫酸钠（DSS）模型组、巴柳氮不同剂量组（42、141、423mg／kg）,正常对照组自由饮水,其余各组自由饮用5％DSS溶液,巴柳氮灌胃给药。每日予以疾病活动指数（DAI）评分,实验结束后取结肠组织进行苏木精-伊红染色评分,匀浆检测髓过氧化物酶（MPO）、超氧化物歧化酶（SOD）、还原型谷胱甘肽活性（GSH-Px）、丙二醛（MDA）含量。小肠黏膜透射电镜检查。Evans蓝检测小肠黏膜通透性。结果与正常对照组小鼠相比,DSS组小鼠均出现明显的体质量减轻、便血和腹泻,DAI评分和病理（HI）评分增高（P〈0．01）。同时,结肠黏膜MPO活性和MDA含量明显增高（P〈0．05）,SOD和GSH-Px活性明显降低。透射电镜检查小鼠回肠黏膜绒毛变短、萎缩、稀疏和排列极不规则,细胞间连接复合体缩短、变宽及细胞间隙扩大;小肠组织中Evans蓝含量增高。巴柳氮给药组小鼠一般情况明显改善,DAI评分与HI评分降低（P〈0．05）,MPO活性减低,MDA含量降低,SOD和GSH-Px活性增高。随着巴柳氮剂量的增高,回肠黏膜微绒毛形态接近正常,小肠组织中Evans蓝含量明显减少。结论DSS模型小鼠肠黏膜通透陛增高,巴柳氮可改善结肠炎模型小鼠肠黏膜通透性。     

A vitamin D analogue inhibits colonic carcinogenesis in the AOM/DSS model

BACKGROUND: The azoxymethane (AOM) model recapitulates many features of human colon cancer, lacking an inflammatory component. Dextran sulfate sodium (DSS) induces colitis and promotes AOM-induced colon cancer in mice. Vitamin D analogues are anti-inflammatory and chemopreventive in models of colon cancer. Our aim was to evaluate the anti-inflammatory and chemopreventive efficacy of the vitamin D analogue Ro26-2198 in the AOM/DSS model and in vitro in HCA-7 colon cancer cells. MATERIALS AND METHODS: A/J mice received Ro26-2198 (0.01 microg/kg body wt/day x 28 days) or vehicle by mini-osmotic pump. Animals were treated with a single dose of AOM (5 mg/kg body wt) or vehicle 1 week after pump insertion. Mice received 3% DSS or water x 7 days beginning week 3. Animals were sacrificed after 8 weeks and colon segments were fixed in formalin or flash-frozen. Hematoxylin and eosin colonic sections were examined for dysplasia and colonic lysates were assessed for c-Myc, cyclooxygenase 2, and phospho-(active) extracellular signal regulated kinase (ERK) by Western blotting. For in vitro studies, HCA-7 cells were treated with Ro26-2198 followed by interleukin-1beta (IL-1beta). Proliferation was measured by WST-1 assay. RESULTS: Ro26-2198 delayed the onset of clinical colitis. Several dysplastic foci were present in the AOM/DSS group; none were found in the Ro26-2198 group. Compared with control, AOM/DSS significantly increased c-Myc (15-fold), cyclooxygenase 2 (COX-2) (2.5-fold), and pERK (10-fold), and Ro26-2198 abolished these increases. In vitro, Ro26-2198 inhibited IL-1beta-induced ERK activation and COX-2 induction and decreased HCA-7 cell proliferation. CONCLUSIONS: Ro26-2198 inhibited proliferative (ERK, c-Myc) and pro-inflammatory (COX-2) signals and progression to dysplasia, suggesting chemopreventive efficacy in this model of colitis-associated carcinogenesis.     

Elemental diet alters macrophage function in mice

Administration of a chemically defined liquid elemental diet (ED) induces spontaneous bacterial translocation to mesenteric lymph nodes (MLN) in animal models. The influence of this process on host immunity is unclear. This study evaluated the effects of ED on peritoneal macrophage (PM phi) antimicrobial functions. Conventional C57/BL6 mice and endotoxin-resistant C3H/HeJ mice (n = 60) were randomized to be pair-fed either an ED or regular chow diet (RD) for 14 days. Blood, spleen, liver, and MLN were cultured for bacteria. PM phi were harvested for: percentage Candida albicans (CA) phagocytosis, percentage killing of CA, PM phi superoxide anion (O2-) production, and TNF-dependent macrophage cytotoxicity. Enteral feeding of ED in conventional C57/BL6 mice caused significant bacterial translocation to MLN but not other organs. Significant impairment of CA killing by PM phi occurred in the ED group and was associated with reduced O2- production. Tumor necrosis factor (TNF)-dependent cytotoxicity of PM phi was also decreased. In endotoxin-resistant C3H/HeJ mice, bacterial translocation was not observed and PM phi antifungal functions remained similar in both RD and ED groups. Thus, enteral feeding of an elemental diet downregulates host oxidative and antimicrobial mechanisms and TNF-dependent cytotoxicity in conventional mice which may be secondary to elemental diet-induced bacterial translocation.     

Loss of the tight junction protein ZO-1 in dextran sulfate sodium induced colitis

BACKGROUND: Inflammatory bowel disease (IBD) is associated with increased intestinal permeability and decreased expression of tight junction (TJ) proteins in the inflamed mucosa. Whether this alteration in TJ expression is a prerequisite for the development of intestinal inflammation or a secondary result of that inflammation is unknown. This study looked at the expression of the TJ protein ZO-1 and the corresponding permeability changes in dextran sulfate sodium (DSS) induced colitis in a mouse model. MATERIALS AND METHODS: BALB/c mice were fed 3% DSS or water for 1, 3, 5, or 7 days. The animals were weighed, stool was checked for blood, and the colon length measured. Segments of the colon were used for histology, immunohistochemistry for ZO-1, or Western blot for TJ proteins. Colonic permeability was measured using Evan's Blue dye. RESULTS: DSS treated animals had heme positive stools, colitis by histology, significant weight loss, and colon shortening. There was an absence of ZO-1 by Western blot in the 7-day DSS treated animals, double the amount of claudin-1 and normal cytokeratin. The loss of ZO-1 started after 1 d of DSS treatment and was followed by a significant increase in permeability to Evan's blue by day 3. CONCLUSIONS: The loss of ZO-1 and increased permeability preceded the development of significant intestinal inflammation suggesting that in DSS colitis alterations in the TJ complex occur before the intestinal inflammation and not as a consequence of it. These changes in the TJ complex may facilitate the development of the inflammatory infiltrate seen in colitis.     

Antibiotic prophylaxis diminishes bacterial translocation but not mortality in experimental burn wound sepsis

Pseudomonas (PSA) burn wound sepsis results in prolonged bacterial translocation (BT) of enteric organisms such as E. coli to the mesenteric lymph nodes (MLN) and organs in rats. Intestinal decontamination with oral antibiotics may improve mortality after burn injury, perhaps due to decreased BT. To determine the effect of oral antibiotic prophylaxis effective against E. coli but not PSA on BT and subsequent mortality in a model of PSA burn wound sepsis, rats were given a 30% scald burn and wound inoculation with 10(8) PSA followed by randomization to either ampicillin (50 mg/kg/d) or saline gavage. Cultures of MLN, organs, blood, and cecal contents were obtained on days 1, 4, and 7 after injury, with additional animals observed for 14-day mortality. Although oral antibiotic prophylaxis resulted in increased cecal colony counts, the incidence of BT was unchanged. The number of organisms present in both the MLN and organs, however, was significantly reduced with prophylaxis, indicating cecal overgrowth by non-translocating bacteria. Reduction of the number of translocating organisms did not result in improved mean survival time after injury, suggesting that mortality from PSA burn wound sepsis occurs independently of bacterial translocation.     

Detection of intestinal bacterial translocation in subclinical ischemia-reperfusion using the polymerase chain reaction technique

BACKGROUND/PURPOSE: The purpose of this study was to evaluate the detection of bacterial translocation after subclinical ischemia reperfusion injuries in rats with the polymerase chain reaction (PCR) technique. METHODS: Six-week-old weaning rats were divided into 3 groups. (1) Experiment rats (n = 20) were gavaged with 10(10) Escherichia coli followed by superior mesentery artery occluded for 10 minutes, then reperfused for 30 minutes. (2) Control rats (n = 20) received bacterial gavage. (3) Group 3 were sham rats (n = 20). After the procedure, 3 mL of blood was obtained from the portal vein. The terminal ileum and mesenteric lymph node (MLN) near the terminal ileum were removed. E. coli DNA was detected in blood and MLN samples by PCR, and histological changes were examined. RESULTS: E. coli DNA detection in ischemia-reperfusion (I/R) group animals was 6 of 20 (30%) in the MLN and 2 of 20 (10%) in the blood. PCR was negative in all the rats in the control group and in the sham group (P < .05). There were no significant differences in the histological examination of rat intestines. CONCLUSION: These data suggest that subclinical intestinal I/R injury results in bacterial translocation. Also, PCR is a highly sensitive and rapid method to detect the presence of microbial DNA.     

Water-soluble ethylhydroxyethyl cellulose prevents bacterial translocation induced by major liver resection in the rat.

Enteric bacteria might act as pathogens, translocating across the intestinal barrier to extraintestinal sites after major liver resection. In the current study, water-soluble ethylhydroxyethyl cellulose (EHEC) was administered before hepatectomy to evaluate the influence on bacterial translocation induced by major liver resection, phagocytic capacity by visceral and circulating macrophages, enteric bacterial population, and bacterial adherence on the intestinal surface in rats subjected to sham operation or to 70% or 90% hepatectomy. Oral or intravenous (IV) administration of EHEC reduced the incidence of bacterial translocation to mesenteric lymph nodes (MLN) and blood after major liver resection. Oral EHEC appeared more effective than IV administration in protecting against bacterial translocation to MLN in animals with 90% hepatectomy. Ethylhydroxyethyl cellulose (oral and IV) significantly diminished intestinal macrophage uptake capacity of 125I-labeled, heat-killed Escherichia coli as compared with animals without EHEC administration. Overgrowth or colonization of enteric bacteria after major liver resection could be prevented by oral or IV EHEC. Adherence of 14C-labeled, alive E. coli on the intestinal mucosa decreased after EHEC treatment in animals subjected to major liver resection. Systemic arterial pressure and intestinal blood flow markedly decreased from 1 hour and on after 90% hepatectomy. Intravenous administration of EHEC did not improve these alterations. Bacterial hydrophobicity and surface negative charge were significantly reduced 1 hour after bacterial culture with EHEC. Thus, EHEC appears to be a potent agent preventing translocation of enteric bacteria from the gut after major liver resection, by altering the surface characters of enteric bacteria, balancing the enteric microflora, inhibiting bacterial attachment onto the intestinal surface, and blocking phagocytosis by intestinal macrophages.     

Pharmacotherapy of inflammatory bowel disease

Inflammatory bowel disease (IBD) encompasses ulcerative colitis and Crohn's disease. Since the etiology of both diseases, is undetermined the causal therapy do not exist. Medical treatment has focused on nonspecific suppressions of the inflammatory process. There are four groups of IBD drugs: anti-inflammatory medicaments, immunomodulators, antidiarrheal agents, and biologic therapy. In a last year immunosuppressives become the very essential IBD drugs. Azathioprine is drug of choice for chronically active Crohn's disease; methotrexate become the second line immunosuppressive drug. It appears that anti-TNG monoclonal antibodies, cA2 (infliximab) may produce rapid control of active Crohn's disease and achieve tissue healing. Topically acting glucocorticosteroids are a safer than standard glicocorticosteroids in ileocolonic Crohn's disease. Cyclosporin is becoming a drug of choice in severely active ulcerative colitis. Anti-inflammatory agents, sulfasalazine and 5-ASA drugs are recommended in treatment mild and moderately active IBD and as maintenance treatment in ulcerative colitis. Corticosteroids still have the main role in the treatment of active IBD. There is no convincing data for efficacy of corticosteroids as maintenance therapy.     

Gut bacterial translocation and postoperative infections: a prospective study in schistosomotic patients

BACKGROUND: Bacterial translocation (BT) across the intact intestinal mucosal barrier has been postulated as a source of sepsis in susceptible patients, including those with cirrhosis and portal hypertension. This condition has not been studied in hepatosplenic schistosomiasis, wherein portal hypertension and the presence of an immune deficiency state associated with the parasitic disease could predispose to BT into mesenteric lymph nodes (MLN). A study was conducted to determine the prevalence of aerobic bacteria in MLN (bacterial translocation) of patients with hepatosplenic schistosomiasis, and establish a possible association with postoperative infections. METHODS: In a series of 51 patients submitted to surgical treatment of schistosomotic portal hypertension with splenectomy and gastric devascularization, MLN were obtained from each patient at the beginning (MLN1) and at the end (MLN2) of the surgical procedure, and sent for bacteriological analysis. Prospective patient evaluation during the postoperative period correlated positive MLN cultures with infectious complications. RESULTS: The prevalence of aerobic bacteria was 17.6% at MLN1 and 27.5% at MLN2, however, this difference was non-significant (p = 0.24). Bacterial translocation to all MLN was 22.5%. Escherichia coli was the most frequent organism (26.1%, 6/23). The overall incidence of postoperative infections was 19.6% (10/51), with a significant association with the presence of positive cultures of MLN (p = 0.043). CONCLUSIONS: The findings of this study suggest that the presence of aerobic bacteria on MLN as a consequence of BT may play a role in the development of postoperative infectious complications, particularly in schistosomotic patients.     

Effect of total parenteral nutrition plus morphine on bacterial translocation in rats.

OBJECTIVE: This study tested the hypothesis that gut stasis induced by parenteral morphine sulfate (MS) leads to enhanced bacterial translocation in rats on total parenteral nutrition (TPN). SUMMARY BACKGROUND DATA: TPN and MS are common adjuncts in the care of critically ill patients. TPN is known to provoke a variable degree of translocation. MS induces gut stasis with an accompanying bacterial overgrowth. The effect of these two treatments in combination on translocation is not known. METHODS: Rats were provided with central and subcutaneous lines for the continuous infusion of nutrients and drugs, respectively. Intestinal transit was assessed by the caudal movement of a fluorescent marker intubated into the proximal duodenum. Quantitative bacteriology was carried out from various segments of the gut and from ileocecal mesenteric lymph nodes (MLN), spleen, liver, and systemic blood obtained by cardia puncture on sacrifice at 96 hours. RESULTS: Transit was unchanged by TPN alone but prolonged when given in combination with MS. Bacterial overgrowth was also enhanced by MS and increased the bacterial translocation to MLN from 50% of animals with TPN, to 100% in those receiving both TPN and MS; the colony-forming units per MLN increased from 33 +/- 14 with TPN alone to 2079 +/- 811 (STD) with TPN plus MS. Furthermore, no bacteria were found at systemic sites with TPN alone, but in 93.3% of animals receiving TPN and MS. In a subgroup of rates provided with glutamine in TPN, the TPN plus MS effects on translocation were not reversed. CONCLUSIONS: These observations demonstrate the important role that morphine plays in promoting translocation, presumably by disrupting fasting motility and enhancing bacterial overgrowth.     

红藤汤对小鼠溃疡性结肠炎的保护作用及机制探究

目的:观察红藤汤对葡聚糖硫酸钠(dextran sulphate sodium,DSS)诱导的溃疡性结肠炎小鼠的抗炎和抗氧化作用,分析红藤汤对溃疡性结肠炎的保护机制。方法:SPF级BALB/c小鼠30只,随机分成3组(n=10):对照组(C组)、DSS诱导的溃疡性结肠炎模型组(M组)、红藤汤治疗组(H组)。C组自由饮水,M组和H组采用自由饮用4%的DSS建立溃疡性结肠炎模型,H组从造模第1天起开始给药,连续给药10天后,采集动脉血检测TNF-α和IL-6的浓度,行结肠组织病理学评分,比色法测定MDA量及SOD和GSH-Px活性,Western blotting检测ERK1/2、P-ERK1/2、JNK、P-JNK及GADPH蛋白的表达量。结果:与M组比较,H组的结肠病理学评分和血清中炎症因子(TNF-α和IL-6)含量显著降低(P<0.05);结肠组织中MDA的含量降低(P<0.05),而SOD和GSH-Px活性升高(P<0.05),P-ERK1/2和P-JNK的表达水平也明显下调(P<0.05)。结论:红藤汤对DSS诱导的小鼠溃疡性结肠炎有保护作用,可以上调抗氧化基因,减少自由基的生成,重建氧化还原平衡,其作用机制可能与抑制JNK和ERK1/2信号通路的活化,减少炎症因子生成有关。     

Effect of T cell modulation on the translocation of bacteria from the gut and mesenteric lymph node.

Although the ability of the gut-associated lymphoid tissue (GALT) to respond to orally ingested foreign antigens has been studied extensively, its function in preventing or limiting escape of resident gut bacteria has not been assessed. The following studies were performed to examine what role cell-mediated immunity (CMI) plays in this process. The ability of suppression of CMI to induce escape of gut bacteria (translocation) to the mesenteric lymph node (MLN) in immunocompetent mice whose gut flora was unaltered was examined. Administration of cyclosporine or anti-L3T4 antibody failed to induce translocation of indigenous gut bacteria after 7 or 14 days of treatment. Antithymocyte globulin (ATG) also failed to induce translocation after 7 days of treatment, despite depletion of all Thy 1, Lyt 1, L3T4, and Lyt 2 positive cells from the spleen, MLN, and intestine as demonstrated by immunofluorescent microscopy. Finally, cultures of the MLN, spleen, liver, and peritoneum of T cell-deficient BALB/c nude mice and their heterozygous T cell-replete littermates were also sterile, demonstrating that congenital suppression of T CMI also does not lead to translocation of indigenous gut bacteria. The role of CMI in limiting systemic spread of bacteria that were already translocating to the MLN was also examined. Translocation of Escherichia coli C25 to the MLN was induced by gastrointestinal (GI) monoassociation, which leads to translocation of E. coli C25 to the MLN in 80-100% of mice. Treatment with ATG during monoassociation failed to induce spread of E. coli C25 to the spleen, liver, or peritoneum, despite the same degree of T cell depletion achieved with ATG in the previous experiment. Monoassociation of conventional T cell-deficient BALB/c nude and heterozygous mice and germ-free T cell-deficient BALB/c nude and heterozygous mice also did not lead to spread of E. coli C25 beyond the MLN. However, in ATG-treated, conventional nude, and germ-free nude mice, the average number of translocating E. coli C25 per MLN was consistently higher. In separate experiments the ability of stimulation of T cell function to inhibit translocation of E. coli C25 was examined. Recombinant interleukin-2, 25,000 units, was administered intraperitoneally every 8 hours during exposure to E. coli C25. This reduced the incidence of translocation of E. coli C25 from 85% to 51% (p = 0.02). Suppression of CMI, either systemically or within the GALT, has a minimal influence on the mechanisms by which the normal gut flora are translocated to the MLN.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of granulocyte colony-stimulating factor on bacterial translocation due to burn wound sepsis

The presence of certain defects in both cellular and humoral immunity after thermal injury has been established. Likewise, the translocation of enteric bacteria to the mesenteric lymph nodes and to distant organs has also been observed following serious thermal injury. The effects of granulocyte colony-stimulating factor (G-CSF) on bacterial translocation, the small bowel mucosa, and cecal bacterial content were investigated in a rat model of burn wound sepsis in which albino Wistar rats were scalded over 30% of their bodies, after which the lesions were infected by 1×10⁸ colony-forming units (cfu)Pseudomonas aeruginosa. The control group was treated with 5% dextrose solution subcutaneously starting 2 days preburn, while the treatment group received 100μg/kg human G-CSF subcutaneously. On the 4th day post burn all animals were killed to examine the bowel and culture of the mesenteric lymph nodes (MLN), livers, and spleens. No significant differences were observed between the groups regarding the cecal bacterial content and small bowel; however, a difference was seen in the ratio of translocation in the MLN liver and spleen and quantitative MLN cultures. Based on these findings, G-CSF was thus found to be significantly effective in reducing bacterial translocation due to burn wound sepsis.     

Abdominal radiation causes bacterial translocation

The purpose of this study was to determine if a single dose of radiation to the rat abdomen leads to bacterial translocation into the mesenteric lymph nodes (MLN). A second issue addressed was whether translocation correlates with anatomic damage to the mucosa. The radiated group (1100 cGy) which received anesthesia also was compared with a control group and a third group which received anesthesia alone but no abdominal radiation. Abdominal radiation lead to 100% positive cultures of MLN between 12 hr and 4 days postradiation. Bacterial translocation was almost nonexistent in the control and anesthesia group. Signs of inflammation and ulceration of the intestinal mucosa were not seen until Day 3 postradiation. Mucosal damage was maximal by Day 4. Bacterial translocation onto the MLN after a single dose of abdominal radiation was not apparently dependent on anatomical, histologic damage of the mucosa.     

Attenuation of NF-κB in Intestinal Epithelial Cells Is Sufficient to Mitigate the Bone Loss Comorbidity of Experimental Mouse Colitis

Skeletal abnormalities are common comorbidities of inflammatory bowel disease (IBD). Patients suffering from IBD, including ulcerative colitis and Crohn's disease, present with skeletal complications. However, the mechanism underpinning IBD-associated bone loss remains vague. Intestinal inflammation generates an inflammatory milieu at the intestinal epithelium that leads to dysregulation of mucosal immunity through gut-residing innate lymphoid cells (ILCs) and other cell types. ILCs are recently identified mucosal cells considered as the gatekeeper of gut immunity and their function is regulated by intestinal epithelial cell (IEC)-secreted cytokines in response to the inflammatory microenvironment. We first demonstrate that serum as well as IECs collected from the intestine of dextran sulfate sodium (DSS)-induced colitis mice contain high levels of inflammatory and osteoclastogenic cytokines. Mechanistically, heightened inflammatory response of IECs was associated with significant intrinsic activation of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) in IECs and increased frequency of ILC1, ILC3, and myeloid osteoclast progenitors. Validating the central role of IEC-specific NF-κB activation in this phenomenon, conditional expression of constitutively active inhibitor kappa B kinase 2 (IKK2) in IECs in mice recapitulates the majority of the cellular, inflammatory, and osteolytic phenotypes observed in the chemically induced colitis. Furthermore, conditional deletion of IKK2 from IECs significantly attenuated inflammation and bone loss in DSS-induced colitis. Finally, using the DSS-induced colitis model, pharmacologic inhibition of IKK2 was effective in reducing frequency of ILC1 and ILC3 cells, attenuated circulating levels of inflammatory cytokines, and halted colitis-associated bone loss. Our findings identify IKK2 in IECs as viable therapeutic target for colitis-associated osteopenia.     

Pretreating mesenchymal stem cells with IL-6 regulates the inflammatory response of DSS-induced ulcerative colitis in rats

The immunomodulatory properties of mesenchymal stem cells (MSCs) have been broadly investigated in research on inflammatory diseases including ulcerative colitis. Treating MSCs with an inflammatory stimulus before transplantation is an adaptive strategy that helps MSCs survive in areas of inflammation and promotes the regulation of local immune responses. This study aimed to examine the effects of pretreating bone marrow MSCs (BMSCs) with Interleukin-6 (IL-6) on attenuation of dextran sulfate sodium (DSS)-induced ulcerative colitis in rats. Experimental ulcerative colitis was induced in Wistar rats by administering 2% DSS in their water for 7 days and normal water for the next 3 days. The experimental group received 1 × 10⁶/0.4 ml of BMSCs that were treated with IL-6 for 24 h. Histological changes, colon length, and disease activity index were compared among groups, and the levels of TNF-α, IL-6, and IL-1β in homogenate supernatants were evaluated using ELISA. IL-6-pretreated BMSCs significantly reduced the colonic damage score. The colon length shortened by 6.1 ± 0.14 cm for the rats that received IL-6-pretreated BMSCs, whereas the control group rats' value was 3.8 ± 0.14 cm on the 14th day. The levels of pro-inflammatory cytokines were significantly decreased in the colons of the IL-6-pretreated BMSCs group compared with those of the control group (p < 0.05). This study revealed that IL-6-pretreated BMSCs ameliorated DSS-induced colitis via local anti-inflammatory action and suggested that IL-6-pretreated BMSCs are a promising therapeutic agent for ulcerative colitis treatment.