RIP3 deficiency exacerbates inflammation in dextran sodium sulfate‐induced ulcerative colitis mice model

Ulcerative colitis (UC) is a chronic intestinal inflammatory disease. The receptor‐interacting protein kinase 3 (RIP3) was reported to be involved in many inflammatory disease. However, the mechanism of RIP3 in the pathogenesis of UC is still unclear. To investigate the effects and possible mechanism of RIP3 in UC pathogenesis, RIP3‐/‐ mice was used in dextran sulfate sodium (DSS)‐induced colitis model. It was found that by DSS‐induced colitis, RIP3‐/‐ mice showed significantly enhanced colitis symptoms, including increased weight loss, colon shortening, and colonic mucosa damage and severity, but decreased production of interleukin 6 and interleukin 1β. The results showed that RIP3 deficiency could not ameliorate but exacerbate the severity of colitis. On the mechanism, it was found that messenger RNA expressions of several repair‐associated cytokines including interleukin 6, interleukin 22, cyclooxygenase 2, epithelial growth factor receptor ligand Epiregulin and matrix metalloproteinase 10 were siginificant decreased in RIP3‐/‐ mice. Thus, RIP3‐/‐ mice exhibited an impaired tissue repair in response to DSS. In a conclusion, RIP3 deficiency exerted detrimental effects in DSS induced colitis partially because of the impaired repair‐associated cytokines expression.     

Interleukin-12 induced interferon-gamma increases inflammation in acute dextran sulfate sodium induced colitis in mice

There is increasing evidence that IL-12 and Th1-cytokines play an important role in intestinal inflammation. We therefore examined the role of IL-12 and interferon-gamma (IFN-gamma) in our model of dextran sulfate-induced acute colitis in mice. Treatment of mice with rmIL-12 during colitis induction resulted in severe aggravation as demonstrated by a greater loss of body weight, an increase of the histological parameters, and reduction of myeloperoxidase activity in colonic biopsies. Depletion of neutrophils in mice also led to aggravation of colitis. Neutralization of IFN-gamma in IL-12-treated mice with colitis inhibited these effects of IL-12. Neutralization of endogenous IFN-gamma or IL-12 with specific antibodies in DSS-treated mice, however, had only weak ameliorating effects. Since IL-12 and IFN-gamma have been shown to mediate experimental chronic colitis we conclude that the transition from a macrophage/neutrophil determined response to a Th-cell response promotes chronic intestinal inflammation.     

Involvement of nitric oxide with activation of Toll-like receptor 4 signaling in mice with dextran sodium sulfate-induced colitis

Ulcerative colitis is an inflammatory bowel disease characterized by acute inflammation, ulceration, and bleeding of the colonic mucosa. Its cause remains unknown. Increases in adhesion molecules in vascular endothelium, and activated neutrophils releasing injurious molecules such as reactive oxygen species, are reportedly associated with the pathogenesis of dextran sodium sulfate (DSS)-induced colitis. Nitric oxide (NO) production derived from inducible NO synthase (iNOS) via activation of nuclear factor κB (NF-κB) has been reported. It is also reported that stimulation of Toll-like receptor 4 (TLR4) by lipopolysaccharide can activate NF-κB. In this study, we investigated the involvement of NO production in activation of the TLR4/NF-κB signaling pathway in mice with DSS-induced colitis. The addition of 5% DSS to the drinking water of male ICR mice resulted in increases in TLR4 protein in colon tissue and NF-κB p65 subunit in the nuclear fraction on day 3, increases in colonic tumor necrosis factor-α on day 4, and increases in P-selectin, intercellular adhesion molecule-1, NO₂⁻/NO₃⁻, and nitrotyrosine in colonic mucosa on day 5. These activated inflammatory mediators and pathology of colitis were completely suppressed by treatment with a NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, as well as an iNOS inhibitor, aminoguanidine. Conversely, a NO-releasing compound, NOC-18, increased TLR4 levels and nuclear translocation of NF-κB p65 and exacerbated mucosal damage induced by DSS challenge. These data suggest that increases in TLR4 expression induced by drinking DSS-treated water might be directly or indirectly associated with NO overproduction.     

PACAP provides colonic protection against dextran sodium sulfate induced colitis

Pituitary adenylate cyclase-activating polypeptide (PACAP) plays a crucial role in immunity and inflammation. Our aim was to obtain insight in the role of PACAP in experimental colitis in mice and thus its possible role in inflammatory bowel disease. PACAP-deficient (PACAP-/-) mice and wild-type control mice were challenged by colitis-inducing agent, dextran sulfate sodium (DSS). We monitored clinical symptoms, intestinal morphology, and difference of cytokine production in the proximal and distal colon. After DSS administration, mortality was more severe in PACAP-/- mice versus wild-type control mice. The histological score and the disease activity index of PACAP-/- mice were significantly higher than those of wild-type control mice. In proximal colon, production of IL-1beta and IL-6 in PACAP-/- mice were significantly upregulated on day 8 after DSS administration, compared to wild-type control mice. In distal colon, furthermore, production of IFNgamma, IL-1beta, IL-6, IL-12, and KC were significantly higher in PACAP-/- mice than in wild-type control mice on day 4. Our findings indicate that PACAP regulates the production of pro-inflammatory cytokine in the experimental colitis.     

靛蓝对葡聚糖硫酸钠诱导的溃疡性结肠炎小鼠肠道菌群作用研究

研究靛蓝对葡聚糖硫酸钠（DSS）诱导的溃疡性结肠炎（UC）模型小鼠的干预作用,并分析对小鼠肠道菌群的影响。

实验小鼠分为对照组、模型组、柳氮磺胺吡啶组（125 mg/kg）和靛蓝组（50 mg/kg),每组小鼠各9只。观察给药后小鼠体征并进行疾病活动指数（DAI）评分,通过苏木素―伊红（HE）染色观察小鼠结肠组织切片形态变化,ELISA法检测小鼠血清中IL-6、TNF-α、IL-1β、IL-8和IL-10水平;针对16S rRNA基因V4‒V5区进行高通量测序,分析小鼠肠道内容物的菌群变化。

与模型组相比,靛蓝组小鼠DAI评分降低,病理切片结果显示靛蓝可改善UC小鼠结肠黏膜损伤,减少炎性细胞浸润,血清中促炎因子IL-6、IL-8、IL-1β和TNF-α水平显著降低（t = 4.377 0、5.374 0、12.140 0、5.508 0,P = 0.011 9、0.005 8、0.000 3、0.005 3）,抑炎因子IL-10水平显著升高（t = 3.716 0,P = 0.020 5）。16S rRNA基因测序结果显示,模型组小鼠肠道菌群多样性降低,靛蓝组小鼠肠道菌群多样性升高。

给予靛蓝干预后可有效缓解UC小鼠结肠炎症状,通过降低炎症因子水平和调节UC小鼠肠道菌群平衡达到治疗UC的效果。

     

Gender dependent importance of IRAK-1 in dextran sulfate sodium induced colitis

Toll-like receptor (TLR) signaling is important for the induction of pro-inflammatory cytokines and interferon (IFN)-inducible genes in response to bacterial and viral challenge. Interleukin-1 receptor-associated kinase-1 (IRAK-1) is a signaling kinase situated downstream of the adapter protein myeloid differentiation factor 88 (MyD88) in the TLR intracellular signaling cascade and is required for normal signal transduction through this pathway. We investigated the importance of IRAK-1 in intestinal inflammation by using the dextran sulfate sodium (DSS)-colitis model. We show that IRAK-1 deficient mice are protected against systemic signs of inflammation, i.e., weight loss and spleen enlargement compared to wild-type controls irrespective of gender. However, IRAK-1^−/y males but not IRAK-1^−/− females display significant protection against colitis and thymic atrophy compared to wild-type mice.Our results indicate a gender specific effect of IRAK-1 in the DSS-induced colitis, an interesting finding since the Irak-1 gene is located on the X-chromosome and several inflammatory diseases have a gender dependent incidence.     

Amelioration of dextran sulfate sodium-induced colitis in mice by oral administration of beta-caryophyllene, a sesquiterpene

beta-Caryophyllene (BCP), a naturally occurring plant sesquiterpene, was examined for anti-inflammatory activity in a mouse model of experimental colitis induced by dextran sulfate sodium (DSS). Colitis was induced by exposing male BALB/c mice to 5% DSS in drinking water for 7 days. BCP in doses of 30 and 300 mg/kg was administered orally once a day, beginning concurrently with exposure to DSS. The body weight and colon length were measured, and histological damage and myeloperoxidase (MPO) activity as well as inflammatory cytokines were assessed in both serum and colonic tissue after 7 days of treatment with DSS. The DSS treatment damaged the colonic tissue, increased MPO activity and inflammatory cytokines, lowered the body weight, and shortened the length of the colon. Oral administration of BCP at 300 mg/kg significantly suppressed the shortening of colon length and slightly offset the loss of body weight. BCP treatment (300 mg/kg) also significantly reduced the inflammation of colon and reversed the increase in MPO activity that had been induced by exposure to DSS. Further, BCP significantly suppressed the serum level of IL-6 protein (a 55% reduction) as well as the level of IL-6 mRNA in the tissue. These results demonstrate that BCP ameliorates DSS-induced experimental colitis, and may be useful in the prevention and treatment of colitis.     

Modulating effect of Hesperidin on experimental murine colitis induced by dextran sulfate sodium

Hesperidin, a flavanone-type flavonoid, is abundant in citrus fruit and has a wide range of pharmacological effects. Here we investigated the effect of Hesperidin on dextran sulphate sodium (DSS)-induced experimental ulcerative colitis in mice. Sulfasalazine (positive control) and Hesperidin in doses of 10, 40 and 80 mg/kg were administered orally once a day for 7 days, beginning concurrently with exposure to DSS. The symptom of ulcerative colitis was evaluated by disease activity index (DAI) and the wet weight of colon. Myeloperoxidase (MPO) activity, malondialdehyde (MDA) content and the levels of interleukin-4 (IL-4) and interleukin-6 (IL-6) in serum were measured to observe the possible mechanisms. Oral administration of Hesperidin significantly decreased DAI, MPO activity, MDA content and the level of IL-6 in serum (p<0.01), while there was no significantly effect on the level of IL-4 in serum. These results demonstrate that Hesperidin can ameliorate DSS-induced experimental colitis, and may be useful in the prevention and treatment of colitis.     

Changes in colonic mucosal permeability in mouse colitis induced with dextran sulfate sodium.

In this study we examined changes in colonic mucosal permeability induced by dextran sulfate sodium (DSS) during the acute phase of mouse colitis. To induce colitis, the mice were given drinking water containing 5% (w/v) DSS (MW = 40,000) ad libitum. Colonic mucosal permeability was evaluated by the permeation of Evans blue (EB) from the lumen into the wall of the colon on 1, 2, 3 and 7 days postadministration of DSS. Mucosal changes were also histologically examined daily for 7 days postadministration. The permeation of EB increased significantly by days 3 and 7 postadministration. Histological analysis showed that crypt loss was the initial change, with no inflammatory process and the surface mucosal epithelial cells remained morphologically intact. These histological changes developed on 2 to 3 days postadministration. Erosion was first recognized at 5 days postadministration. These findings indicated that the increase in colonic mucosal permeability may have occurred in 3 days postadministration, and the increase in mucosal permeability occurred before the appearance of the inflammatory process. This suggests that an increase in colonic mucosal permeability, leading to the destruction of mucosal barrier function, may play an important role in the induction of DSS-induced murine colitis.     

Protective role of G-CSF in dextran sulfate sodium-induced acute colitis through generating gut-homing macrophages

Granulocyte colony-stimulating factor (G-CSF) is a pleiotropic cytokine best known for its role in promoting the generation and function of neutrophils. G-CSF is also found to be involved in macrophage generation and immune regulation; however, its in vivo role in immune homeostasis is largely unknown. Here, we examined the role of G-CSF in dextran sulfate sodium (DSS)-induced acute colitis using G-CSF receptor-deficient (G-CSFR^−/−) mice. Mice were administered with 1.5% DSS in drinking water for 5 days, and the severity of colitis was measured for the next 5 days. GCSFR^−/− mice were more susceptible to DSS-induced colitis than G-CSFR^+/+ or G-CSFR^−/+ mice. G-CSFR^−/− mice harbored less F4/80⁺ macrophages, but a similar number of neutrophils, in the intestine. In vitro, bone marrow-derived macrophages prepared in the presence of both G-CSF and macrophage colony-stimulating factor (M-CSF) (G-BMDM) expressed higher levels of regulatory macrophage markers such as programmed death ligand 2 (PDL2), CD71 and CD206, but not in arginase I, transforming growth factor (TGF)-β, Ym1 (chitinase-like 3) and FIZZ1 (found in inflammatory zone 1), and lower levels of inducible nitric oxide synthase (iNOS), CD80 and CD86 than bone marrow-derived macrophages prepared in the presence of M-CSF alone (BMDM), in response to interleukin (IL)-4/IL-13 and lipopolysaccharide (LPS)/interferon (IFN)-γ, respectively. Adoptive transfer of G-BMDM, but not BMDM, protected G-CSFR^−/− mice from DSS-induced colitis, and suppressed expression of tumor necrosis factor (TNF)-α, IL-1β and iNOS in the intestine. These results suggest that G-CSF plays an important role in preventing colitis, likely through populating immune regulatory macrophages in the intestine.     

Biochemical and histological changes in the small intestine of mice with dextran sulfate sodium colitis

The dextran sulfate sodium (DSS) model of colitis has been commonly utilized in mice to assess novel treatments for ulcerative colitis. Recent studies have indicated that morphological and biochemical changes extend to the small intestine (SI). This study aimed to characterize histological and biochemical changes in the SI during DSS colitis in wild‐type (WT) and DPIV knock‐out (DPIV^?/?) mice treated with saline or the DPIV inhibitors, Ile‐Pyrr‐(2‐CN)*TFA or Ile‐Thia. Groups (n = 10) of DPIV^?/? and WT mice were orally gavaged twice daily with saline, Ile‐Pyrr‐(2‐CN)*TFA or Ile‐Thia. Mice consumed 2% DSS in drinking water for 6 days to induce colitis. Small intestinal tissue was assessed for histological changes, sucrase, and DPIV activity and neutrophil infiltration. Jejunal villus length was increased in all groups after 6 days DSS consumption (P < 0.05). Jejunal DPIV activity was significantly lower by 35% in WT mice receiving Ile‐Pyrr‐(2‐CN)*TFA compared to saline controls. Jejunal MPO activity was significantly increased in the WT + saline and DPIV^?/? + saline groups following DSS consumption, compared to WT and DPIV^?/? controls at day 0. Increased sucrase activity was apparent at day 0 in DPIV^?/? compared to WT mice (P < 0.05). We conclude that DSS‐induced damage is not restricted to the colon, but also extends to the small intestine. Furthermore, reduced or absent DPIV activity resulted in functional adaptations to brush border enzyme activity. DPIV inhibitors are now a recognized therapy for type‐II diabetes. The work presented here highlights the need to delineate any long‐term effects of DPIV inhibitors on SI function, to further validate their safety and tolerability. J. Cell. Physiol. 226: 3219–3224, 2011. © 2011 Wiley Periodicals, Inc.     

Proteomic profiling of dextran sulfate sodium induced acute ulcerative colitis mice serum exosomes and their immunomodulatory impact on macrophages

Macrophages are essential for the maintenance of intestinal homeostasis, and their activation has been proposed to be critical to the pathogenesis of inflammatory bowel disease (IBD). Although there are many recognized mediators of macrophage activation, increasing evidence suggests that macrophages respond to exosome stimulation. Exosomes are 40–150 nm microvesicles released from different cell types and are found in a variety of physiological fluids, including serum. As studies have shown that circulating exosomes participate in intercellular communication and can mediate the immune response, we hypothesized that exosomes may play a role in the pathogenesis of IBD though modulation of macrophage activity. In this study, we used the dextran sulfate sodium (DSS) induced acute colitis mice model to investigate the effect of serum exosomes on macrophages and identify exosome proteins potentially involved in macrophage activation. We treated RAW264.7 macrophages with serum exosomes isolated from dextran sulfate sodium induced mice and found that treatment induced phosphorylation of p38 and ERK and production of tumor necrosis factor α when compared to treatment with exosomes isolated from control mice. Subsequent proteomic analysis identified 56 differentially expressed proteins, a majority of which were acute‐phase proteins and immunoglobulins. Bioinformatics analysis suggested these proteins were mainly involved in the complement and coagulation cascade, which has been implicated in macrophage activation. Our findings provide new insight into the role of circulating serum exosomes in acute colitis and contribute to the understanding of macrophage activation in the pathogenesis of IBD.     

Structure guided design of a series of sphingosine kinase (SphK) inhibitors

Sphingosine-1-phosphate (S1P) signaling plays a vital role in mitogenesis, cell migration and angiogenesis. Sphingosine kinases (SphKs) catalyze a key step in sphingomyelin metabolism that leads to the production of S1P. There are two isoforms of SphK and observations made with SphK deficient mice show the two isoforms can compensate for each other’s loss. Thus, inhibition of both isoforms is likely required to block SphK dependent angiogenesis. A structure based approach was used to design and synthesize a series of SphK inhibitors resulting in the identification of the first potent inhibitors of both isoforms of human SphK. Additionally, to our knowledge, this series of inhibitors contains the only sufficiently potent inhibitors of murine SphK1 with suitable physico-chemical properties to pharmacologically interrogate the role of SphK1 in rodent models and to reproduce the phenotype of SphK1 (?/?) mice.     

High-dose green tea polyphenols induce nephrotoxicity in dextran sulfate sodium-induced colitis mice by down-regulation of antioxidant enzymes and heat-shock protein expressions

Previously, we reported that oral feeding of 1% green tea polyphenols (GTPs) aggravated the dextran sulfate sodium (DSS)-induced colitis in mice. In the present study, we assessed the toxicity of 1% GTPs in several organs from normal and DSS-exposed mice. Sixty-two male ICR mice were initially divided into four groups. Non-treated group (group 1, n = 15) was given standard diet and water, GTPs (group 2, n = 15) received 1% GTPs in diet and water, DSS (group 3, n = 15) received diet and 5% DSS in water, and GTPs + DSS group (group 4, n = 17) received 1% GTPs in diet and 5% DSS in water. We found that group 4 significantly increased (P < 0.05) kidney weight, the levels of serum creatinine and thiobarbituric acid-reactive substances in both kidney and liver, as compared with those in group 3. The mRNA expression levels of antioxidant enzymes and heat-shock proteins (HSPs) in group 4 were lower than those of group 3. For instance, heme oxygenase-1 (HO-1), HSP27, and 90 mRNA in the kidney of group 4 were dramatically down-regulated as compared with those of group 3. Furthermore, 1% GTPs diet decreased the expression of HO-1, NAD(P)H:quinone oxidoreductase 1 (NQO1) and HSP90 in kidney and liver of non-treated mice. Taken together, our results indicate that high-dose GTPs diet disrupts kidney functions through the reduction of antioxidant enzymes and heat-shock protein expressions in not only colitis but also non-treated ICR mice.     

L-arginine supplementation improves responses to injury and inflammation in dextran sulfate sodium colitis

Inflammatory bowel disease (IBD), consisting of Crohn's disease and ulcerative colitis (UC), results in substantial morbidity and is difficult to treat. New strategies for adjunct therapies are needed. One candidate is the semi-essential amino acid, L-arginine (L-Arg), a complementary medicine purported to be an enhancer of immunity and vitality in the lay media. Using dextran sulfate sodium (DSS) as a murine colonic injury and repair model with similarities to human UC, we assessed the effect of L-Arg, as DSS induced increases in colonic expression of the y(+) cationic amino acid transporter 2 (CAT2) and L-Arg uptake. L-Arg supplementation improved the clinical parameters of survival, body weight loss, and colon weight, and reduced colonic permeability and the number of myeloperoxidase-positive neutrophils in DSS colitis. Luminex-based multi-analyte profiling demonstrated that there was a marked reduction in proinflammatory cytokine and chemokine expression with L-Arg treatment. Genomic analysis by microarray demonstrated that DSS-treated mice supplemented with L-Arg clustered more closely with mice not exposed to DSS than to those receiving DSS alone, and revealed that multiple genes that were upregulated or downregulated with DSS alone exhibited normalization of expression with L-Arg supplementation. Additionally, L-Arg treatment of mice with DSS colitis resulted in increased ex vivo migration of colonic epithelial cells, suggestive of increased capacity for wound repair. Because CAT2 induction was sustained during L-Arg treatment and inducible nitric oxide (NO) synthase (iNOS) requires uptake of L-Arg for generation of NO, we tested the effect of L-Arg in iNOS(-/-) mice and found that its benefits in DSS colitis were eliminated. These preclinical studies indicate that L-Arg supplementation could be a potential therapy for IBD, and that one mechanism of action may be functional enhancement of iNOS activity.     

Soy isoflavone equol perpetuates dextran sulfate sodium-induced acute colitis in mice

The effects of the soy isoflavones, genistein, daidzein and equol, on experimental colitis were examined. Equol severely perpetrated dextran sulfate sodium (DSS)-induced colitis as evaluated by the weight loss. Production of the anti-inflammatory cytokine, IL-10, from T cells was decreased in the equol-treated mice. The results show that the soy isoflavone, equol, played an important role in the inflammatory response in the gastrointestinal tract.     

Oral nitrite ameliorates dextran sulfate sodium-induced acute experimental colitis in mice

Inflammatory bowel diseases (IBDs) such as Crohn’s disease and ulcerative colitis are chronic inflammatory disorders of the intestinal tract with excessive production of cytokines, adhesion molecules, and reactive oxygen species. Although nitric oxide (NO) is reported to be involved in the onset and progression of IBDs, it remains controversial as to whether NO is toxic or protective in experimental colitis. We investigated the effects of oral nitrite as a NO donor on dextran sulfate sodium (DSS)-induced acute colitis in mice. Mice were fed DSS in their drinking water with or without nitrite for up to 7 days. The severity of colitis was assessed by disease activity index (DAI) observed over the experimental period, as well as by the other parameters, including colon lengths, hematocrit levels, and histological scores at day 7. DSS treatment induced severe colitis by day 7 with exacerbation in DAI and histological scores. We first observed a significant decrease in colonic nitrite levels and increase in colonic TNF-α expression at day 3 after DSS treatment, followed by increased colonic myeloperoxidase (MPO) activity and increased colonic expressions of both inducible NO synthase (iNOS) and heme oxygenase-1 (HO-1) at day 7. Oral nitrite supplementation to colitis mice reversed colonic nitrite levels and TNF-α expression to that of normal control mice at day 3, resulting in the reduction of MPO activity as well as iNOS and HO-1 expressions in colonic tissues with clinical and histological improvements at day 7. These results suggest that oral nitrite inhibits inflammatory process of DSS-induced experimental colitis by supplying nitrite-derived NO instead of impaired colonic NOS activity.     

乳酸菌抑制葡聚糖硫酸钠诱导的结肠黏膜氧化应激损伤的研究

目的研究乳酸菌抗氧化活性与缓解葡聚糖硫酸钠(DSS)诱导结肠炎的关系。方法评价5株乳酸菌体外抑制大鼠肝细胞脂质过氧化活性,用DSS诱导小鼠结肠炎模型研究抗氧化性不同的菌株体内抗氧化活性;小鼠分成7组,分别是Control组、DSS组、L.plantarum Fn008+DSS组、L.casei Fn012+DSS组、L.acidophilus Fn022+DSS组、L.sakei Fn034+DSS组和L.acidophilus Fn037+DSS组。结果体外实验表明,Fn022和Fn034的丙二醛(MDA)抑制率高于LGG,但差异无统计学意义,Fn008和Fn037的MDA抑制率显著低于LGG,Fn012的MDA抑制率最低。体内实验表明,DSS可导致小鼠氧化应激,升高结肠内容物的自由基水平,降低结肠抗氧化能力;Fn008和Fn037预处理能显著降低DSS诱导结肠内容物的自由基水平,Fn008能显著降低结肠组织的髓过氧化物酶(MPO)水平,提高结肠抗氧化能力,Fn022和Fn034的干预能力居中,Fn012的干预能力最弱。相关性分析表明乳酸菌体外MDA清除率与体内MPO有负相关趋势(r=-0.862,P=0.06)。结论乳酸菌抗氧化活性与其在肠道抑制炎性细胞激活的作用有关,本实验中Fn008和Fn037具有显著的体内抗氧化作用。     

Upregulation of P-glycoprotein by probiotics in intestinal epithelial cells and in the dextran sulfate sodium model of colitis in mice

P-glycoprotein (P-gp) mediates efflux of xenobiotics and bacterial toxins from the intestinal mucosa into the lumen. Dysregulation of P-gp has been implicated in inflammatory bowel disease. Certain probiotics have been shown to be effective in treating inflammatory bowel disease. However, direct effects of probiotics on P-gp are not known. Current studies examined the effects of Lactobacilli on P-gp function and expression in intestinal epithelial cells. Caco-2 monolayers and a mouse model of dextran sulfate sodium-induced colitis were utilized. P-gp activity was measured as verapamil-sensitive [(3)H]digoxin transepithelial flux. Multidrug resistant 1 (MDR1)/P-gp expression was measured by real-time quantitative PCR and immunoblotting. Culture supernatant (CS; 1:10 or 1:50, 24 h) of Lactobacillus acidophilus or Lactobacillus rhamnosus treatment of differentiated Caco-2 monolayers (21 days postplating) increased (～3-fold) MDR1/P-gp mRNA and protein levels. L. acidophilus or L. rhamnosus CS stimulated P-gp activity (～2-fold, P < 0.05) via phosphoinositide 3-kinase and ERK1/2 MAPK pathways. In mice, L. acidophilus or L. rhamnosus treatment (3 × 10(9) colony-forming units) increased mdr1a/P-gp mRNA and protein expression in the ileum and colon (2- to 3-fold). In the dextran sulfate sodium (DSS)-induced colitis model (3% DSS in drinking water for 7 days), the degree of colitis as judged by histological damage and myeloperoxidase activity was reduced by L. acidophilus. L. acidophilus treatment to DSS-treated mice blocked the reduced expression of mdr1a/P-gp mRNA and protein in the distal colon. These findings suggest that Lactobacilli or their soluble factors stimulate P-gp expression and function under normal and inflammatory conditions. These data provide insights into a novel mechanism involving P-gp upregulation in beneficial effects of probiotics in intestinal inflammatory disorders.