Selective uptake of intraluminal dextran sulfate sodium and senna by macrophages in the cecal mucosa of the guinea pig

Review on melanosis coli and anthraquinone-containing traditional Chinese herbs that cause melanosis coli

Backgrounds: The incidence of melanosis coli (MC) has gradually increased annually, attracting significant attention and efforts into this field. A potential risk for MC is the long-term use of anthraquinone laxatives in patients with constipation. Most traditional cathartic drugs are made from herbs containing anthraquinone compounds. This review aims to provide guidance for the application of traditional Chinese herbs containing anthraquinones for physicians and researchers. Materials and methods: We reviewed risk factors and pathogenesis of MC, and natural anthraquinones isolated from TCM herbs. We searched Pubmed and CNKI databases for literature related to MC with keywords such as"traditional Chinese medicine", "Chinese herbs", "anthraquinones", and "melanosis coli". The literature is current to January 2023 when the searches were last completed. After the literature retrieval, the TCM herbs containing anthraquinones (including component identification and anthraquinone content determination) applied in clinical were selected. According to the collected evidence, we provide a list of herbs containing anthraquinones that could cause MC. Results: We identified 20 herbs belonging to 7 families represented by Polygonaceae, Fabaceae, Rhamnaceae, and Rubiaceae, which may play a role in the pathogenesis of MC. Among these, the herbs most commonly used include Dahuang (Rhei Radix et Rhizome), Heshouwu (Radix Polygoni Multiflori), Huzhang (Rhizoma Polygoni Cuspidati), Juemingzi (Semen Cassiae), Luhui (Aloe) and Qiancao (Rubiae Radix et Rhizoma). Conclusion: Due to a lack of awareness of the chemical composition of TCM herbs, many patients with constipation and even some TCM physicians take cathartic herbal remedies containing abundant anthraquinones to relieve defecation disturbances, resulting in long-term dependence on these herbs, which is potentially associated with most cases of MC. When such treatments are prescribed, TCM physicians should avoid long-term use in large doses to reduce their harm on colonic health. Individuals who take healthcare products containing these herbs should also be under the supervision of a doctor.

Disposal of intestinal apoptotic epithelial cells and their fate via divergent routes

Gut epithelial cells are characterized by rapid, constant cell renewal. The disposal of aging epithelial cells around the villus tips of the small intestine occurs so regularly that it has been regarded as a consequence of well-controlled cell death, designated as apoptosis. However, the notion of live cell extrusion in the intestine has been intensively built among researchers, and the disposal processes of effete epithelial cells display species and regional differences. Chemical mediators and mechanical forces rising from surrounding cells contribute to the regulated cell replacement. Cytotoxic intraepithelial lymphocytes and lamina propria macrophages play a leading role in the selection of disposal cells and their extrusion to maintain fully the epithelial homeostasis in tandem with the dynamic reconstruction of junctional devices. Lymphocyte-mediated cell killing is predominant in the mouse and rat, while the disposal of epithelial cells in the guinea pig, monkey, and human is characterized by active phagocytosis by subepithelially gathering macrophages. The fenestrated basement membrane formed by immune cells supports their involvement and explains species differences in the disposal of epithelial cells. Via these fenestrations, macrophages and dendritic cells can engulf apoptotic epithelial cells and debris and convey substantial information to regional lymph nodes. In this review, we attempt to focus on morphological aspects concerning the apoptosis and disposal process of effete epithelial cells; in vitro or ex vivo analyses using cultured monolayer has become predominant in recent studies concerning the exfoliation of apoptotic enterocytes. Furthermore, we give attention to their species differences, which is controversial but crucial to our understanding.

A murine colitis model developed using a combination of dextran sulfate sodium and Citrobacter rodentium

Adult mice were treated with dextran sulfate sodium (DSS) and infected with Citrobacter rodentium for developing a novel murine colitis model. C57BL/6N mice (7-week-old) were divided into four groups. Each group composed of control, dextran sodium sulfate-treated (DSS), C. rodentium-infected (CT), and DSS-treated and C. rodentium-infected (DSS-CT) mice. The DSS group was administered 1% DSS in drinking water for 7 days. The CT group was supplied with normal drinking water for 7 days and subsequently infected with C. rodentium via oral gavage. The DSS-CT group was supplied with 1% DSS in drinking water for 7 days and subsequently infected with C. rodentium via oral gavage. The mice were sacrificed 10 days after the induction of C. rodentium infection. The DSS-CT group displayed significantly shorter colon length, higher spleen to body weight ratio, and higher histopathological score compared to the other three groups. The mRNA expression levels of tumor necrosis factor (TNF)-α and interferon (INF)-γ were significantly upregulated; however, those of interleukin (IL)-6 and IL-10 were significantly downregulated in the DSS-CT group than in the control group. These results demonstrated that a combination of low DSS concentration (1%) and C. rodentium infection could effectively induce inflammatory bowel disease (IBD) in mice. This may potentially be used as a novel IBD model, in which colitis is induced in mice by the combination of a chemical and a pathogen.

Dextran sulphate sodium (DSS) causes intestinal histopathology and inflammatory changes consistent with increased gut leakiness in chickens

1. The clinical severity, histological changes, indicators of gut leakiness and inflammatory cytokine profiles were studied in chickens with dextran sulphate sodium (DSS)-induced intestinal inflammation. 2. The experimental groups (1.25%, 1.5% and 2.5% DSS) showed clinical signs, such as loose stools and weight loss, which increased with additional treatment days and, as expected, the effects of DSS-induced intestinal inflammation were time and dose-dependent. 3. After 10 d, histological manifestations were evident, including goblet cell depletion, mucus layer loss, significantly shorter villi and a thinner total ileal mucosa. 4. The d(-)-lactate value, which was used as a gut leakiness indicator, was significantly increased in the 2.5% DSS group. 5. Expression of the inflammatory cytokines interleukin-1Beta, tumour necrosis factor alpha and interleukin-10 in the serum significantly increased with DSS treatment. 6. This study indicates that the experimental intestinal inflammation induced by DSS is an ideal model to study the pathogenic mechanisms of intestinal inflammation in chickens and to test the efficacy of therapies.

Arhgap17, a RhoGTPase activating protein, regulates mucosal and epithelial barrier function in the mouse colon

Coordinated regulation of the actin cytoskeleton by the Rho GTPase family is required for the maintenance of polarity in epithelial cells as well as for their proliferation and migration. A RhoGTPase-activating protein 17 (Arhgap17) is known to be involved in multiple cellular processes in vitro, including the maintenance of tight junctions and vesicle trafficking. However, the function of Arhgap17 has not been studied in the physiological context. Here, we generated Arhgap17-deficient mice and examined the effect in the epithelial and mucosal barriers of the intestine. Reporter staining revealed that Arhgap17 expression is limited to the luminal epithelium of intestine. Arhgap17-deficient mice show an increased paracellular permeability and aberrant localization of the apical junction complex in the luminal epithelium, but do not develop spontaneous colitis. The inner mucus layer is impervious to the enteric bacteria irrespective of Tff3 downregulation in the Arhgap17-deficient mice. Interestingly however, treatment with dextran sulfate sodium (DSS) causes an increased accumulation of DSS and TNF production in intraluminal cells and rapid destruction of the inner mucus layer, resulting in increased severity of colitis in mutant mice. Overall, these data reveal that Arhgap17 has a novel function in regulating transcellular transport and maintaining integrity of intestinal barriers.

Oral administration of dextran sodium sulphate induces a caecum-localized colitis in rabbits

Trichuris suis ova (TSO) have shown promising results in the treatment of inflammatory bowel disease (IBD) but the mechanisms which underlies this therapeutic effect cannot be studied in mice and rats as T. suis fails to colonize the rodent intestine, whilst hatching in humans and rabbits. As a suitable rabbit IBD model is currently not available, we developed a rabbit colitis model by administration of dextran sodium sulphate (DSS). White Himalayan rabbits (n = 12) received 0.1% DSS in the daily water supply for five days. Clinical symptoms were monitored daily, and rabbits were sacrificed at different time points. A genomewide expression analysis was performed with RNA isolated from caecal lamina propria mononuclear cells (LPMC) and intestinal epithelial cells (IEC). The disease activity index of DSS rabbits increased up to 2.1 ± 0.4 (n = 6) at day 10 (controls <0.5). DSS induced a caecum-localized pathology with crypt architectural distortion, stunted villous surface and inflammatory infiltrate in the lamina propria. The histopathology score reached a peak of 14.2 ± 4.9 (n = 4) at day 10 (controls 7.7 ± 0.9, n = 5). Expression profiling revealed an enrichment of IBD-related genes in both LPMC and IEC. Innate inflammatory response, Th17 signalling and chemotaxis were among the pathways affected significantly. We describe a reproducible and reliable rabbit model of DSS colitis. Localization of the inflammation in the caecum and its similarities to IBD make this model particularly suitable to study TSO therapy in vivo.

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

The mechanisms responsible for human inflammatory bowel disease remain poorly understood. The pathogenic factors for dextran sulfate sodium (DSS)-induced colitis, one of the experimental animal colitis models, also remain unknown. Furthermore, detailed studies on DSS metabolism in the gut lumen have not been reported. Therefore, we investigated DSS metabolism in the mouse gut lumen and report the mechanisms which induce colitis. DSS was labeled with 2-aminopyridine (pyridylamino-DSS, PA-DSS). PA-DSS was administered orally to male BALB/cA Jcl mice. The metabolites and histological findings were observed using HPLC and light or fluorescence microscopy. PA-DSS with Mr 5000 was depolymerized rapidly in the gastric lumen, and the depolymerized PA-DSS was absorbed in the small intestine. Therefore, the majority of the PA-DSS in the cecal contents returned to Mr 5000 PA-DSS, escaping absorption in the small intestine. Mr 5000 DSS induced severe colitis, and immunostaining using an anti-mouse Ki-67 antibody and the TUNEL assay showed that DSS arrested the cell cycle at the G0 phase and induced apoptosis of the colonic epithelium. Mr 2500 PA-DSS, however, induced these same effects weakly. During these processes, we observed that the epithelial cells can depolymerize DSS themselves. An in vitro study using Caco-2 cells also showed similar effects. Mr 5000 DSS was depolymerized in the gut lumen and epithelial cells. Therefore, the molecular mass distribution of the DSS differed between each part in the lumen. As an early stage event, DSS induced colitis through cell cycle arrest and apoptosis according to its molecular mass.

Factors influencing the development of animal models of dextran sulphate sodium-induced colitis

The animal models of dextran sulphate sodium (DSS)-induced colitis have demonstrated several correlations with human ulcerative colitis (UC) since the first report of DSS-induced colitis in hamsters in 1985. These animal models have similarities to human UC in etiology, pathology, pathogenesis and therapeutic response, and are deemed suitable for investigating the pathogenesis and therapeutic options of UC and UC-related dysplasia-adenocarcinoma sequence. Although induction of colitis with DSS is relatively cheap and simple, the development of this model is influenced by many factors, such as DSS concentration, administration duration, DSS molecular weight and animal species. These factors are important for successful development of DSS-induced colitis. In this paper we summarize factors influencing the development of animal models of DSS-induced colitis.

Lack of Modifying Effects of Intratracheal Instillation of Quartz or Dextran Sulfate Sodium (DSS) in Drinking Water on Lung Tumor Development Initiated with 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in Female A/J Mice

The purpose of the present study was to investigate the effects of inflammation, induced by intratracheal instillation (i.t.) of quartz as an environmental factor in the lung or drinking of dextran sulfate sodium (DSS) as an environmental factor in the colon on lung tumors in female A/J mice initiated with NNK. For comparison, colonic preneoplastic lesions, aberrant crypt foci (ACF), were also assessed. A/J mice at 6 weeks of age were divided into 5 groups, and Groups 1, 2 and 3 were pretreated with NNK (2 mg / 0.1 ml saline / mouse, intraperitoneal injection) at week 0. For a week, 2% DSS in drinking water was administered to the mice in Groups 2 and 4 beginning in week 1. In week 2, the mice of Groups 3 and 5 were exposed to intratracheal instillation of quartz (0.1 mg/rat) suspended in 25 μl saline. The experiment was terminated after 16 weeks. The results for the lung tumors and colonic ACFs showed a lack of modifying effects of the inflammation in either site. Hematologically and histopathologically, the inflammation induced by 0.1 mg quartz in the lung and 2% DSS in the colon was lacking or only mild at the end of 16 weeks. These results suggest that there may be differences in sensitivity to inflammation that determine tumor promoting potential.

Mouse strain differences in inflammatory responses of colonic mucosa induced by dextran sulfate sodium cause differential susceptibility to PhIP-induced large bowel carcinogenesis

In mice, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induces a high incidence of malignant lymphoma and leukemia, but exhibits little, if any, carcinogenic activity in the large intestine after long-term exposure. However, recent studies have revealed that colonic adenocarcinomas can be efficiently and rapidly induced by combined treatment with PhIP and dextran sulfate sodium (DSS), a potent inducer of colitis. In the present study, the authors investigated the effects of inflammation on PhIP-induced carcinogenesis using two mouse strains, C57BL/6J and MSM/Ms, showing distinct temporal profiles of inflammatory responses to DSS. A long-term carcinogenesis experiment conducted with a single i.g. administration of PhIP (200 mg/kg body weight), followed by DSS treatment in drinking water for 4-6 days, revealed an increase in tumor incidence in C57BL/6J mice in accordance with the DSS intake. In contrast, neoplastic lesions were rarely observed in the MSM/Ms strain. From the short-term exposure to DSS for 4 days, C57BL/6J mice demonstrated severe chronic colitis, accompanied by hyperplastic cryptal epithelium and extensive cellular infiltration. Splenomegaly and swelling of mesenteric lymph nodes were also evident for over 1 month as chronic symptoms of systemic immunological disturbance. However, no inflammatory lesions were detected in MSM/Ms mice. The present results provide strong evidence that prolonged chronic inflammatory responses induced by DSS are directly responsible for the observed enhancement of PhIP-induced large bowel carcinogenicity.

Dextran sodium sulfate-induced colitis in germ-free IQI/Jic mice

This study presents a histological examination of dextran sodium sulfate (DSS)-induced colitis in germ-free (GF) mice. A comparison of the pathology between GF and conventionalized mice (CVz) was made to determine the role that intestinal microflora play in DSS-induced colitis. To induce colitis, GF and CVz IQI/Jic mice were given either 5% or 1% DSS orally. Administration of 5% DSS, a common concentration used to induce colitis in mice, caused gross rectal bleeding and a marked decrease in hematocrit as early as day one in GF mice. These mice died on day three due to massive bleeding into the intestinal lumen. In contrast, CVz mice did not die during the seven-day experimental period. Histopathological examination three days after administration of 5% DSS did not reveal any colitis lesions in GF mice, but CVz mice had developed moderate colitis in the large intestine. Administration of a low concentration of DSS (1%), which only induces mild basal crypt loss in CVz mice, caused severe colitis in the distal colon in GF mice, and they died on day 14. These data suggest that intestinal microflora are not necessary for the induction of colitis. Furthermore, DSS may be highly toxic to GF mice, and when given at a concentration of 5% it causes massive bleeding into the intestinal lumen resulting in death prior to development of colitis.

Adverse effects of laxatives

Laxatives are among the most commonly used drugs or additives. Most are quite safe when used judiciously, intermittently when possible, and in the absence of contraindications. Bulking agents and nonabsorbable compounds such as lactulose can cause bloating but have very few serious adverse effects except for the allergic reaction to psyllium preparations. Osmotic laxatives containing poorly absorbable ions such as magnesium or phosphate can cause metabolic disturbances, particularly in the presence of renal impairment. However, if taken intermittently, in the absence of conditions such as ileus or bowel obstruction, they have few adverse effects. Polyethylene glycol solutions are emerging as an effective and safe mode of treatment for chronic constipation. Of stimulant laxatives, senna compounds and bisacodyl are the most commonly used. Although there are data to support the neoplastic potential of this class of drugs in in vitro studies, epidemiologic data in humans so far has not established a clear link between these laxatives and colonic neoplasia. The link between stimulant laxatives and structural changes, such as the "cathartic colon" or enteric nerve damage, is not well established either. Danthron compounds should be avoided because of hepatotoxicity.

Histological analysis of murine colitis induced by dextran sulfate sodium of different molecular weights

In this study, we examined the relationship between the molecular weight of dextran sulfate sodium (DSS) and the features of colitis in a DSS-induced mouse model of human ulcerative colitis. DSS at three different molecular weights, 5 kD, 40 kD and 500 kD, was used in this study. DSS was administered in drinking water at 5% (w/v) to 6-7-week-old female BALB/c mice. After 7 days of treatment with DSS, the large intestine was examined histopathologically. Colitis was characterized by a loss of crypts, infiltration of inflammatory cells into the mucosa and submucosa, edema of the submucosa, erosion and ulceration and was observed in mice given the 5 kD and 40 kD forms but not the 500 kD. In the 5 kD group, colitis was observed predominantly in the cecum and upper colon. Colitis in the 40 kD group was more severe than that in the 5 kD group, and in the 40 kD group it was more severe in the lower colon than in the upper colon. These findings suggest the molecular weight of DSS to be an important factor in the murine model of colitis.

Tissue distribution of dextran sulfate sodium (DSS) in the acute phase of murine DSS-induced colitis

In the present study, we examined histochemically the tissue distribution of dextran sulfate sodium (DSS) in the acute phase of murine colitis induced by administering DSS in the drinking water. DSS was mainly observed in the Kupffer cells of the liver, in the macrophages of the mesenteric lymph node (MLN) and in the lamina propria of the large intestine after administration of DSS. We followed the time course of DSS distribution and found that DSS, which was considered as a large and negatively charged molecule that can not easily cross membranes, was distributed in the liver, the MLN, and the large intestine 1 day after the start of administration of DSS.

Differential susceptibility of inbred mouse strains to dextran sulfate sodium-induced colitis

Dextran sulfate sodium (DSS)-induced murine colitis represents an experimental model for human inflammatory bowel disease. The aim of this study was to screen various inbred strains of mice for genetically determined differences in susceptibility to DSS-induced colitis. Mice of strains C3H/HeJ, C3H/HeJBir, C57BL/6J, DBA/2J, NOD/LtJ, NOD/LtSz-Prkdc(scid)/Prkdc(scid), 129/SvPas, NON/LtJ, and NON.NOD-H2g7 were fed 3.5% DSS in drinking water for 5 days and necropsied 16 days later. Ceca and colons were scored for histological lesions based on severity, ulceration, hyperplasia, and area involved. Image analysis was used to quantitate the proportion of cecum ulcerated. Histological examination revealed significant differences among inbred strains for all parameters scored. In both cecum and colon, C3H/HeJ and a recently selected substrain, C3H/HeJBir, were highly DSS susceptible. NOD/LtJ, an autoimmune-prone strain, and NOD/LtSz-Prkdc(scid)/Prkdc(scid), a stock with multiple defects in innate and adoptive immunity, were also highly DSS susceptible. NON/LtJ, a strain closely related to NOD, was quite DSS resistant. The major histocompatibility (MHC) haplotype of NOD mice (H2g7), a major component of the NOD autoimmune susceptibility, was not crucial in determining DSS susceptibility, since NON mice congenic for this MHC haplotype retained resistance. C57BL/6J, 129/SvPas, and DBA/2J mice showed various degrees of susceptibility, depending upon the anatomical site. A greater male susceptibility to DSS-induced colonic but not cecal lesions was observed. In summary, this study demonstrates major differences in genetic susceptibility to DSS-induced colitis among inbred strains of mice. Knowledge of these strain differences in genetic responsiveness to acute inflammatory stress in the large intestine will permit design of genetic crosses to elucidate the genes involved.