<Emphasis Type="Italic">Clostridium difficile</Emphasis> Toxin A Induces Intestinal Epithelial Cell Apoptosis and Damage: Role of Gln and Ala-Gln in Toxin A Effects

The aim of this study was to investigate the effect of Clostridium difficile toxin A (TxA) on intestinal epithelial cell migration, apoptosis, and transepithelial resistance and to evaluate the effect of glutamine (Gln) and its stable derivative, alanyl-glutamine (Ala-Gln), on TxA-induced damage. Migration was measured in rat intestinal epithelial cells (IEC-6) 6 and 24 hr after a razor scrape of the cell monolayer. Cell proliferation was indirectly measured utilizing the tetrazolium salt WST-1. The cells were incubated with TxA (1–100 ng/ml) in medium without Gln or medium containing Gln or Ala-Gln (1–30 mM). Apoptosis was quantified in IEC-6 cells using annexin V assay. Transepithelial resistance was measured using an epithelial voltohmmeter across T84 cells seeded on a transwell filter. TxA-induced a dose-dependent reduction of migration and also caused dose and time-dependent apoptosis in IEC-6 cells. Gln and Aln-Gln significantly enhanced IEC-6 cell migration and proliferation. Gln and Ala-Gln also prevented the inhibition of migration, apoptosis, and the initial drop in transepithelial resistance induced by TxA. In conclusion, both peptides reduced toxin-induced epithelial damage and thus might play an adjunctive role in C. difficile-induced colitis therapy.This work was supported by National Institutes of Health SBIR Grant 1R43-DK58419-01A1 and ABC Grant 5D43 TW01136-04.     

RH株弓形虫速殖子体外入侵大鼠肠上皮细胞与增殖的动态观察

目的 动态观察弓形虫RH株速殖子（简称速殖子）体外入侵大鼠肠上皮细胞（IEC-6细胞）及其增殖过程。 方法 取24孔培养板,设实验组及对照组各3孔,每孔放置经预处理的盖玻片。将常规传代培养的IEC-6细胞接种于各培养孔,于37 ℃ 5% CO2培养箱培养24 h,吸弃培养液,实验组每孔加入1 ml速殖子悬液（含1×106个速殖子）,对照组每孔加入1 ml无抗生素培养液,共培养。用倒置显微镜连续观察速殖子粘附、入侵IEC-6细胞及其增殖过程,并分别于共培养5～30 min、1～48 h后取出盖玻片,经吉氏-瑞氏染色后光镜观察其入侵和增殖情况,计算入侵率。 结果 共培养5 min,速殖子即可入侵IEC-6细胞,随着共培养时间的延长入侵的速殖子逐渐增多,1 h为1～5个,入侵率为（55.0±6.6）%。2 h入侵率高达（81.8±10.2）%,有假包囊形成,速殖子可入侵细胞核并在核内增殖。4 h入侵率降为（80.8±9.2）%,假包囊破裂释出成簇排列的速殖子。6 h入侵率为（75.1±8.2）%,成簇排列的速殖子显著增多。12 h成簇排列的速殖子减少,多数速殖子游离细胞外,完整的IEC-6细胞明显减少。24 h只见部分IEC-6细胞和假包囊存在,有大量游离的速殖子。48 h见大量游离速殖子,未见贴壁细胞。 结论 体外培养的弓形虫速殖子可迅速入侵IEC-6细胞,并可在细胞质及细胞核内增殖。增殖周期为6～12 h。     

The Jagged-1/Notch-1/Hes-1 Pathway Is Involved in Intestinal Adaptation in a Massive Small Bowel Resection Rat Model

Background

Notch signaling is required for the maintenance of intestinal epithelial proliferation. Dysfunction of this signaling pathway is associated with the loss of proliferated crypt epithelial cells.

Aim

The aim of this study was to investigate the role of Notch signaling in small bowel resection (SBR)-associated crypt epithelial cell proliferation.

Methods

Male Sprague–Dawley rats were subjected to sham operation (bowel transection and reanastomosis) or 70 % mid-SBR. Intestinal tissue samples were collected at 0.5, 1, 6, 12, 24, 72, and 168 h after operation. The expression of Notch pathway mRNAs and proteins was analyzed using RT-PCR and Western blot. The expression of the Notch pathway proteins Jagged-1, NICD and Hes-1 was also determined through immunohistochemical staining using day 3 postoperative intestinal tissues. The degree of crypt epithelial cell proliferation was evaluated using the immunohistochemical staining of proliferating cell nuclear antigen (PCNA). Furthermore, IEC-6 cells were used to examine the function of the Jagged-1 signaling system.

Results

SBR led to increased crypt epithelial cell proliferation and increased expression of Jagged-1 and Hes-1 mRNA and protein along with cleaved Notch-1. Immunohistochemical staining showed that Jagged-1, cleaved Notch-1 and Hes-1 colocalized in the same proliferated crypt epithelial cell population. Recombinant Jagged-1 significantly stimulated the proliferation of IEC-6 cells. Transient upregulation of Jagged-2 expression was found 1 h after SBR, and it was accompanied by cleaved Notch-1 and Hes-1 upregulation.

Conclusion

The Jagged-1/Notch-1/Hes-1 signaling pathway is involved in intestinal adaptation through increasing crypt epithelial cell proliferation.     

Vascular endothelial growth factor (VEGF164) ameliorates intestinal epithelial injury in vitro in IEC-18 and Caco-2 monolayers via induction of TGF-beta release from epithelial cells

OBJECTIVE: VEGF is a glycoprotein with various (e.g. angiogenic) activities. So far, research has focused on its angiogenic properties. VEGF receptors are localized on epithelial cells of patients with inflammatory bowel disease (IBD) and also on Caco-2 and IEC-18 cells. Our aim was to evaluate the role of VEGF on intestinal epithelial cell (IEC) migration and proliferation by utilizing an established in vitro model. METHODS: IEC-18 and Caco-2 monolayers were wounded with a razor blade as described previously. Cells were incubated in medium w/o rat VEGF(164). After 24 h, migration was assessed by counting cells across the wound edge. Migration was blocked with neutralizing TGF-beta(1) antibodies. IEC proliferation was assessed using the MTT (3-[4, 5-Dimethylthiazol-2-yl]-2, 5-diphenyl-tetrazolium bromide) test. Semi-quantitative changes of the TGF-beta(1) mRNA expression were evaluated before and after stimulation of the cells with VEGF(164) by RT-PCR. Statistical analysis was performed with ANOVA and the Wilcoxon test. RESULTS: VEGF(164) significantly induced epithelial cell migration in Caco-2 and IEC-18 cells compared to control. TGF-beta(1) antibodies completely abolished this VEGF-induced cell migration. TGF-beta(1) mRNA significantly increased in IEC-18 and Caco-2 cells after stimulation with VEGF. VEGF significantly inhibited epithelial cell proliferation in IEC-18 and in Caco-2 cells, indicating that the observed effects on cell migration were not due to any proliferate effects. CONCLUSION: VEGF effects on epithelial cell migration play an important part in epithelial cell restitution by maintaining mucosal homeostasis after mucosal injury. This effect is mediated by TGF-beta(1). Our results obtain another possible role for increased VEGF levels in the intestinal mucosa of patients with IBD as reported recently by others.     

Differential responsiveness of intestinal epithelial cells to 1,25-dihydroxyvitamin D3--role of protein kinase C

Non-transformed rat intestinal epithelial cell (IEC) lines were used to study the action of 1,25-dihydroxyvitamin D(3) (1,25(OH)2D) in the intestine. The capacity of 1,25(OH)2D to increase the expression of the cytochrome P450 component of the vitamin D 24-hydroxylase (CYP24) was determined in IEC-6 and IEC-18 cell lines. In IEC-6 cells, which are derived from crypt cells isolated from the whole small intestine, 1,25(OH)2D markedly increased expression of CYP24 protein and mRNA within 12 h. In contrast, in IEC-18 cells, which are derived from crypt cells from the ileum only, 1,25(OH)2D did not increase expression of CYP24 until 24-48 h. The maximal levels of CYP24 mRNA seen in the IEC-18 cells were only 31% of the maximal levels seen in the IEC-6 cells. In the presence of 1,25(OH)2D, phorbol esters rapidly increased CYP24 mRNA levels in IEC-18 cells from almost undetectable to levels seen in IEC-6 cells. Protein kinase inhibitors abolished the stimulation by 1,25(OH)2D and by phorbol esters in both cell lines. Stimulation of mRNA levels by phorbol esters required new protein synthesis but stimulation by 1,25(OH)2D did not. These studies demonstrated that the rapid action of 1,25(OH)2D in IEC-6 cells is related to the activation of protein kinase C, an event which is missing in the IEC-18 cells. This differential response to 1,25(OH)2D probably takes place at a post-receptor site, since the number of vitamin D receptors in each cell line was found to be similar.     

Effect of recombinant human interleukin-11 on expressions of interleukin-11 receptor α-chain and glycoprotein 130 in intestinal epithelium cell line-6 after neutron irradiation

AIM: To explore the effect of recombinant human interleukin-11 (rhIL-11) on the expressions of interleukin-11 receptor α-chain (IL-11Rα) and an additional signal transducer glycoprotein 130 (gp130) in intestinal epithelium cell line-6 (IEC-6) after neutron irradiation.METHODS: Cultured IEC-6 cells were exposed to 4.0Gy neutron and treated with 100 ng/mL rhIL-11 12 h prior to or immediately after irradiation. The apoptosis and necrosis rates and expressions of IL-11Rα and gp130 were observed by flow cytometry, immunohistochemistry, Western blot and image analysis.RESULTS: The apoptosis rate of IEC-6 cells was increased by irradiation at 6 h (P ＜ 0.01), IL-11 stimulation resulted in a decreased apoptosis rate in irradiated IEC-6 cells (P ＜ 0.05). In normal control IEC-6 cells, intense immunoreactivity of IL-11Rα was located within the cell membrane and cytoplasm. The level of IL-11Rα expression significantly decreased at 6 h after irradiation (P ＜ 0.01) and restored at 24 h after irradiation. In IEC-6 cells treated with both radiation and rhIL-11, the level of IL-11Rα expression was higher than that of irradiated cells (P ＜ 0.05). When it came to gp130 protein, it was located in the cytoplasm of IEC-6 cells. After irradiation, we found a progressive decrease in the expression of gp130 protein (P ＜ 0.05) in 48 hours post-radiation, while in rhIL-11-stimulated cells, it came back to normal level at 24 h after irradiation and decreased at 48 h, but was still higher than that of only irradiated cells (P ＜ 0.05).CONCLUSION: rhIL-11 can protect IEC-6 cells from neutron irradiation. The protective effect of rhIL-11 might be connected with its ability to up-regulate the expressions of specific ligand-binding subunit IL-11Rα and signal-transducing subunit gp130.     

Effect of recombinant human interleukin-11 on expressions of interleukin-ll receptor α-chain and glycoprotein 130 in intestinal epithelium cell line-6 after neutron irradiation

AIM: To explore the effect of recombinant human interleukin-11 (rhIL-11) on the expressions of interleukin-11 receptor alpha-chain (IL-11Ralpha) and an additional signal transducer glycoprotein 130 (gp130) in intestinal epithelium cell line-6 (IEC-6) after neutron irradiation. METHODS: Cultured IEC-6 cells were exposed to 4.0Gy neutron and treated with 100 ng/mL rhIL-11 12 h prior to or immediately after irradiation. The apoptosis and necrosis rates and expressions of IL-11Ralpha and gp130 were observed by flow cytometry, immunohistochemistry, Western blot and image analysis. RESULTS: The apoptosis rate of IEC-6 cells was increased by irradiation at 6 h (P < 0.01), IL-11 stimulation resulted in a decreased apoptosis rate in irradiated IEC-6 cells (P < 0.05). In normal control IEC-6 cells, intense immunoreactivity of IL-11Ralpha was located within the cell membrane and cytoplasm. The level of IL-11Ralpha expression significantly decreased at 6 h after irradiation (P < 0.01) and restored at 24 h after irradiation. In IEC-6 cells treated with both radiation and rhIL-11, the level of IL-11Ralpha expression was higher than that of irradiated cells (P < 0.05). When it came to gp130 protein, it was located in the cytoplasm of IEC-6 cells. After irradiation, we found a progressive decrease in the expression of gp130 protein (P < 0.05) in 48 h post-radiation, while in rhIL-11-stimulated cells, it came back to normal level at 24 h after irradiation and decreased at 48 h, but was still higher than that of only irradiated cells (P < 0.05). CONCLUSION: rhIL-11 can protect IEC-6 cells from neutron irradiation. The protective effect of rhIL-11 might be connected with its ability to up-regulate the expressions of specific ligand-binding subunit IL-11Ralpha and signal-transducing subunit gp130.     

Contraction of collagen gels by intestinal epithelial cells depends on microfilament function

We have developed a model system to quantify the tractional forces generated by intestinal epithelial cells during organization into a confluent epithelial cell sheet. In this model system, IEC-6 cells, a rat intestinal crypt cell line, rapidly contracted collagen gels reducing the gel surface area by 97% at 24 hr. The tractional forces measured by gel contraction were directly related to the number of cells added and were inversely related to the collagen concentration of the gel. Actin microfilament function was required for gel contraction, but microtubular function was not. Fetal bovine serum and protein synthesis were required for maximal gel contraction. IEC-6 (5×10⁵) cells per gel and fibroblasts (5 ×10⁴) cells added to collagen gels resulted in contraction of the gels by 50% at 24 hr. Therefore, intestinal epithelial cells and fibroblasts generate tractional forces of similar strength capable of organizing the surrounding extracellular matrix, which should be considered in models of intestinal morphogenesis and repair.     

Proliferation of intestinal crypt cells by gastrin—induced ornithine decarboxylase

AIM: to oetermine whether the gastrin stimulated intestinalcrypt cell (IEC-6) proliferation by induction of omithinedecarboxylase (ODC).METHODS: IEC-6 cells were grown in DMEM containing50mL- L- 1 dialyzed fetal bovine serum for 24h and then weretreated with gastrin. The proliferative capablty of the cellswas monitored subsequently on d 1, 2, 3, and 4 aftertreatment with MTT assay at aborbance 570nm. The cellularODC mRNA expression, ODC activity, and putrescinecontent were examined by RT-PCR method, radiometrictechnique and high-performance liquid chromatography(HPLC) analysis respectively after 12h of treatment.RESULTS: On dl after exposure of IEC-6 cells topentagastrin, the proliferation increased initially and reacheda peak on d3 at 250μg@ L- 1 concentration. Pentagastrin 500μg@ L-1 increased cell proliferation on day 1 and day 2, andthen decreased. Compared with control group, pentagastrin250μg@ L-1 increased ODC mRNA level by 1.09-fold (P＜0.05), ODC activity by 1.71-fold(P＜ 0.01), and putrescinecontent 5.30-fold ( P ＜ 0.01 ) respectively. Similarly,pentagastrin of 500μg@ L-1 also increased ODC mRNA levelby 1.16-fold (P＜0.05), ODC activity 1.63-fold(P＜ 0.05),and putrescine content 4.41-fold ( P ＜ 0.01 ) respectively.But there was not significant difference between them.CONCLUSION: Gastrin is an agent which promotes IEC-6 cellproliferation involved in regulating ODC activity nechanism.     

Vascular endothelial growth factor (VEGF164) ameliorates intestinal epithelial injury in vitro in IEC-18 and Caco-2 monolayers via induction of TGF-β release from epithelial cells

Objective. VEGF is a glycoprotein with various (e.g. angiogenic) activities. So far, research has focused on its angiogenic properties. VEGF receptors are localized on epithelial cells of patients with inflammatory bowel disease (IBD) and also on Caco-2 and IEC-18 cells. Our aim was to evaluate the role of VEGF on intestinal epithelial cell (IEC) migration and proliferation by utilizing an established in vitro model. Methods. IEC-18 and Caco-2 monolayers were wounded with a razor blade as described previously. Cells were incubated in medium w/o rat VEGF₁₆₄. After 24?h, migration was assessed by counting cells across the wound edge. Migration was blocked with neutralizing TGF-β₁ antibodies. IEC proliferation was assessed using the MTT (3-[4, 5-Dimethylthiazol-2-yl]-2, 5-diphenyl-tetrazolium bromide) test. Semi-quantitative changes of the TGF-β₁ mRNA expression were evaluated before and after stimulation of the cells with VEGF₁₆₄ by RT-PCR. Statistical analysis was performed with ANOVA and the Wilcoxon test. Results. VEGF₁₆₄ significantly induced epithelial cell migration in Caco-2 and IEC-18 cells compared to control. TGF-β₁ antibodies completely abolished this VEGF-induced cell migration. TGF-β₁ mRNA significantly increased in IEC-18 and Caco-2 cells after stimulation with VEGF. VEGF significantly inhibited epithelial cell proliferation in IEC-18 and in Caco-2 cells, indicating that the observed effects on cell migration were not due to any proliferate effects. Conclusion. VEGF effects on epithelial cell migration play an important part in epithelial cell restitution by maintaining mucosal homeostasis after mucosal injury. This effect is mediated by TGF-β₁. Our results obtain another possible role for increased VEGF levels in the intestinal mucosa of patients with IBD as reported recently by others.     

Hepatocyte growth factor accelerates restitution of intestinal epithelial cells

Many cytokines are involved in the repair of damaged tissue, and one of these, hepatocyte growth factor (HGF), is involved not only with liver regeneration but also in the repair of other tissues. To investigate the importance of HGF in the repair of the small intestine, we evaluated its effect and that of other growth factors in IEC-6 cells, an intestinal epithelial cell line derived from normal rat small intestine. Round "wounds" were made in confluent monolayers of IEC-6 by silicon rubber-tipped steel rods and various cytokines; transforming growth factor α (TGF-α), transforming growth factor β1 (TGF-β1), keratinocyte growth factor (KGF), and HGF, were added. We photographed the repaired monolayers every 24 h and calculated the ratios of areas not covered by cells to initial areas. Cell proliferation with TGF-α, TGF-β, KGF, or HGF was examined in terms of [3H]-thymidine uptake. Finally, we determined c-met (the HGF receptor) mRNA in the IEC-6 cells by Northern blot hybridization. HGF was the most potent of the cytokines in accelerating repair of the damaged monolayer of IEC-6. HGF was also 1.34 times more effective than control the medium for inducing cell proliferation of IEC-6. By Northern blot hybridization, three bands of mRNA bound to c-met cDNA. These results suggest that HGF is important in the repair of the small intestine. (Received Feb. 21, 1997; accepted Aug. 22, 1997)     

Mesalamine promotes intestinal epithelial wound healing in vitro through a TGF-beta-independent mechanism

OBJECTIVE: Treatment with 5-aminosalicylic acid (5-ASA) derivatives is one of the main principles in the therapy of uncomplicated mild to moderate inflammatory bowel diseases (IBD). The beneficial effect of 5-ASA in the treatment of IBD is attributed to its anti-inflammatory and anti-oxidant properties within the inflamed gut. The aim of this study was to investigate whether 5-ASA also modulates intestinal epithelial wound repair in vitro. MATERIAL AND METHODS: The effects of 5-ASA on cell migration and proliferation, two key processes in mucosal healing, were studied in the non-transformed small-intestinal epithelial cell line IEC-6 using an in vitro wounding model and colorimetric MTT assays. Furthermore, the effects of 5-ASA on epithelial cell viability were determined by Trypan blue exclusion and flow cytometry-based cell cycle analysis. RESULTS: Clinically relevant concentrations of 5-ASA caused a significant dose-dependent enhancement of epithelial cell migration and proliferation in vitro. An about 2-fold enhancement of intestinal epithelial cell proliferation and migration was observed for pharmacological doses of 100 microg/ml 5-ASA. Neutralizing antibodies against TGFbeta did not modulate 5-ASA effects on IEC-6 cell proliferation and migration, indicating that the effects of 5-ASA were TGFbeta independent. Trypan blue viability tests and cell cycle analysis did not reveal any toxic or apoptotic effects of pharmacological 5-ASA concentrations on IEC-6 cells. CONCLUSIONS: 5-ASA promotes the rapid re-establishment of mucosal integrity in vitro by enhancing epithelial restitution and proliferation, suggesting that 5-ASA in addition to the well-characterized effects on the intestinal inflammatory cascade may also directly stimulate epithelial wound healing.     

Secretion of insulin-like growth factor II (IGF-II) and IGF-binding protein-2 by intestinal epithelial (IEC-6) cells: implications for autocrine growth regulation.

To identify the factors regulating the proliferation of intestinal epithelium, we examined the effects of various growth factors on [3H] thymidine incorporation into the DNA of IEC-6 cells, an intestinal epithelial cell line derived from rat jejunal crypts. Insulin-like growth factor-I (IGF-I), IGF-II, and insulin stimulated the DNA and protein synthesis of IEC-6 cells in serum-free medium supplemented with transferrin, dexamethasone, and BSA (basal medium). Concentration-response experiments demonstrated that IGF-I is approximately 10 times more potent than IGF-II or insulin in producing 2- to 3-fold stimulations of DNA and protein synthesis by IEC-6 cells. In addition, IEC-6 cells proliferated slowly in the basal medium without any added growth factors. Analysis of medium conditioned by IEC-6 cells by gel filtration chromatography, RIA, HPLC, and N-terminal sequencing revealed that IEC-6 cells synthesize and secrete mature, 7,500 mo wt (M(r)) IGF-II as well as high M(r) forms of IGF-II. In addition, ligand blot, immunoblot, and N-terminal sequence analyses showed that IEC-6 cells produce the 34,000 M(r) IGF-binding protein-2 (IGFBP-2). To determine if IGFBP-2 modulates IGF responses in IEC-6 cells, the IGF-I analogs, Des-(1-3)-IGF-I and [Gln3,Ala4,Tyr15,Leu16]IGF-I, both of which have a reduced affinity for IGFBPs, were tested for their effects on IEC-6 cell proliferation. Both analogs exhibited 10-fold greater potency than IGF-I, presumably because endogenously secreted IGFBPs depress IGF-I binding to cell surface receptors. Finally, purified IGFBP-2 attenuated the DNA synthesis of IEC-6 cells in a dose-dependent manner. We conclude that IGFBP-2 secreted by intestinal epithelial cells is capable of limiting the mitogenic activity of both exogenous and endogenous IGFs by blocking the association of the growth factors with cell surface binding sites. These results further suggest that the growth of IEC-6 cells is modulated by autocrine mechanisms involving IGF-II and IGFBP-2.     

Interleukin-1, interleukin-8, tumour necrosis factor alpha and interferon gamma stimulate DNA synthesis but have no effect on apoptosis in small-intestinal cell lines

OBJECTIVES: Cytokines stimulate lymphocyte cell proliferation and affect cell division in several other cell types. Helicobacter pylori-induced gastritis and coeliac disease are characterized by an increased cell proliferation in association with an increased production of proinflammatory cytokines, which could contribute to these cell kinetic changes. Our aim is to examine in vitro whether cytokines usually present in the gastrointestinal mucosa affect DNA synthesis and apoptosis in a rat and a human small-intestinal cell line. METHODS: IEC-6 and FHs-74 cells were incubated for 24 h with 10(-13)-10(-9) M of tumour necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), transforming growth factor-beta (TGF-beta) and interferon gamma (IFN-gamma). IEC-6 cells were also incubated with 10(-13)-10(-9) M of interleukin-1alpha (IL-1alpha) and 10(-8) M of interleukin-1 receptor antagonist (IL-1ra). The cells were labelled with 3H-methyl thymidine for the final 4 hours, and then processed for autoradiography. DNA synthesis was evaluated by the labelling index (LI%). Apoptosis was evaluated in IEC-6 cells by changes in membrane lipid asymmetry using annexin-V binding to externalized phosphatidylserine (flow cytometry) and by estimating the caspase activity. RESULTS: TNF-alpha, IL-1beta, IL-8 and IFN-gamma significantly and markedly increased the LI, even at low concentrations (P< 0.0001), in both IEC-6 and FHs-74 cells, as did IL-1alpha in IEC-6 cells. TGF-beta significantly reduced the LI in both cell lines (P< 0.0001), whereas IL-2, IL-6 and IL-1ra did not affect DNA synthesis significantly. None of IL-1beta, IL-8, TNF-alpha or IFN-gamma affected apoptosis in IEC-6 cells. CONCLUSION: TNF-alpha, IL-1alpha, IL-1beta, IL-8 and IFN-gamma stimulated DNA synthesis in a human and a rat small-intestinal cell line. The cytokines exert their mitogenic action directly on the intestinal cells via specific receptors. Our findings indicate that pro-inflammatory cytokines may participate in the regulation of the gastrointestinal epithelial cell proliferation in health and disease.     

5-FU增强TRAIL诱导的胃癌BGC823细胞凋亡的实验研究

目的 观察5-FU对TRAIL诱导的胃癌BGC823细胞凋亡的影响,明确死亡受体5(DR5)在5-FU和TRAIL诱导凋亡中的作用.方法 采用MTT法测定细胞活力、流式细胞仪检测细胞凋亡、免疫印迹检测蛋白表达.结果 TRAIL可导致BGC823细胞轻度的增殖抑制和少量的细胞凋亡.与单药TRAIL和5-FU相比,TRAIL联合5-FU对细胞的增殖抑制和诱导凋亡作用明显增强(P＜0.05).免疫印迹结果显示,TRAIL没有改变DR5的蛋白表达,而5-FU作用BGC823细胞48 h后,DR5蛋白表达上调(P＜0.05).TRAIL和5-FU联合作用后,DR5蛋白表达同样明显上调(P均＜0.05).结论 5-FU通过上调DR5蛋白表达提高了BGC823细胞对TRAIL的敏感性.     

Taurodeoxycholate Stimulates Intestinal Cell Proliferation and Protects Against Apoptotic Cell Death Through Activation of NF-κB

We hypothesized that the NF-kappaB pathway would be operative in the proliferative effect of bile salts on enterocytes. To determine this, we studied the effect of the bile salt taurodeoxycholate on cultured rat enterocyte proliferation and apoptosis and examined the role of NF-kappaB activation in these growth regulatory processes. Intestinal epithelial cells were grown for 6 days with or without taurodeoxycholate. Proliferation was measured. The cells were exposed to a known apoptotic stimulus, TNF-alpha and cyclohexamide. Apoptosis was quantified using cell number and the TUNEL stain. NF-kappaB activation was determined by an electrophoretic mobility shift assay. NF-kappaB activation was inhibited by an IkappaB superrepressor. Taurodeoxycholate stimulated cell proliferation (P < 0.01) and induced resistance to TNF-alpha induced apoptosis (P < 0.01). Taurodeoxycholate induced NF-kappaB activation. Inhibition of NF-kappaB prevented taurodeoxycholate-induced IEC-6 cell proliferation and rendered cells sensitive to TNF-alpha-induced apoptosis. Taurodeoxycholate stimulates intestinal epithelial cell proliferation and protects intestinal epithelial cells from TNF-alpha-induced apoptosis through NF-kappaB. These data support an important beneficial role of bile salts in regulation of mucosal growth and repair. Decreased enterocyte exposure to luminal bile salts, as occurs during starvation and parenteral nutrition, may have a detrimental effect on mucosal integrity.     

酒精通过抑制肠上皮干细胞增殖损伤肠上皮的更新修复能力

目的 研究酒精对肠上皮干细胞(ISC)和肠上皮更新修复能力的影响。方法 将18只C57BL/6小鼠随机分为对照组(n=9)和酒精处理组(n=9)。采用Gao-Binge法制备慢性酒精中毒模型。在造模成功后,腹腔注射5-溴-2-脱氧脲苷(BrdU),分别在注射后2 h、24 h和72 h取小肠组织,采用免疫组化法检测BrdU阳性细胞和ISC特异性标志物Lgr5表达。结果 与对照组小鼠比,酒精处理组小鼠小肠绒毛高度显著缩短、萎缩;酒精处理组小鼠ISC细胞Lgr5表达显著弱于对照组;酒精处理组小鼠每个肠隐窝BrdU阳性细胞数量为(3.50±0.65)个/肠隐窝,显著少于对照组【(7.90±1.08)个/肠隐窝,P＜0.05】;在注射BrdU 后2 h、24 h和72 h,酒精处理组小鼠小肠BrdU阳性细胞迁移距离分别为(66.67±1.60)μm、(219.40±12.11)μm和(313.90±9.76)μm,显著短于对照组【分别为(111.10±1.60)μm、(319.00±10.04)μm和(625.90±3.34)μm,P＜0.05】。结论 酒精通过抑制ISC引起肠上皮细胞增殖和迁移能力下降,从而损伤肠上皮的更新修复能力,导致肠上皮屏障功能障碍。