Ke Peng

The Canonical Notch Signaling Was Involved in the Regulation of Intestinal Epithelial Cells Apoptosis after Intestinal Ischemia/Reperfusion Injury

Notch signaling plays a critical role in the maintenance of intestinal homeostasis. The aim of the present study was to investigate the role of Notch signaling in the apoptosis of intestinal epithelial cells after intestinal ischemia reperfusion (I/R) injury. Male C57BL/6 mice were subjected to sham operation or I/R injury. Intestinal tissue samples were collected at 12 h after reperfusion. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling) staining showed that intestinal I/R injury induced significantly increased apoptosis of intestinal epithelial cells. Meanwhile, the mRNA expression of Jagged1, DLL1, Notch2, and Hes5, and protein expression of NICD2 and Hes5 were increased significantly after I/R injury in intestinal epithelial cells. In an in vitro IEC-6 culture model, flow cytometry analyses showed that inhibition of Notch signaling by γ-secretase inhibitor DAPT and the suppression of Hes5 expression using siRNA both significantly increased the apoptosis of IEC-6 cells under the condition of hypoxia/reoxygenation (H/R). In conclusion, the Notch2/Hes5 signaling pathway was activated and involved in the regulation of intestinal epithelial cells apoptosis in intestinal I/R injury.

CD8αα TCRαβ Intraepithelial Lymphocytes in the Mouse Gut

The epithelium of the mouse small intestine harbors an abundant CD8αα+TCRαβ+ intraepithelial lymphocyte (IEL) population. This unique IEL subset is a self-reactive population that requires exposure to self-agonists for selection in the thymus, similarly to other regulatory T cell populations. After leaving the thymus, these cells directly seed the intestinal epithelium, which provides a unique combination of cellular interactions together with cytokines, nutrients, and antigens that guide the lineage-specific differentiation and function of these IELs. For instance, epithelial cells and nearby immune cells secrete a number of cytokines, including interleukin-15 (IL-15), IL-7, and transforming growth factor-β, resulting in an assortment of cellular responses, including activation of master transcription factors, cell proliferation, and cytokine secretion. Recent advances have also highlighted the importance of diet-derived substances and commensal metabolites, such as the aryl hydrocarbon receptor ligands and vitamin D, in controlling the survival and gene expression of CD8αα+TCRαβ+ IELs. Furthermore, these cells function in the epithelium and require constant communication between cells in the form of cell-to-cell contacts. These interactions tune the antigen sensitivity of the TCR and maintain the quiescence of the CD8αα+TCRαβ+ IELs. Finally, we discuss how these cells might contribute to tolerance and immunopathological responses in the gut. Therefore, an increased understanding of CD8αα+TCRαβ+ IELs in the gut will help us understand how these cells participate in immune regulation and protection.

Hypoxia-inducible factor-1 modulates upregulation of mutT homolog-1 in colorectal cancer

AIM To investigate the roles and interactions of mutT homolog (MTH)-1 and hypoxia-inducible factor (HIF)-1α in human colorectal cancer (CRC). METHODS The expression and distribution of HIF-1α and MTH-1 proteins were detected in human CRC tissues by immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). SW480 and HT-29 cells were exposed to normoxia or hypoxia. Protein and mRNA levels of HIF-1α and MTH-1 were analyzed by western blotting and qRT-PCR, respectively. In order to determine the effect of HIF-1α on the expression of MTH-1 and the amount of 8-oxo-deoxyguanosine triphosphate (dGTP) in SW480 and HT-29 cells, HIF-1α was silenced with small interfering RNA (siRNA). Growth studies were conducted on cells with HIF-1α inhibition using a xenograft tumor model. Finally, MTH-1 protein was detected by western blotting in vivo. RESULTS High MTH-1 mRNA expression was detected in 64.2% of cases (54/84), and this was significantly correlated with tumor stage (P = 0.023) and size (P = 0.043). HIF-1α protein expression was correlated significantly with MTH-1 expression (R = 0.640; P < 0.01) in human CRC tissues. Hypoxic stress induced mRNA and protein expression of MTH-1 in SW480 and HT-29 cells. Inhibition of HIF-1α by siRNA decreased the expression of MTH-1 and led to the accumulation of 8-oxo-dGTP in SW480 and HT-29 cells. In the in vivo xenograft tumor model, expression of MTH-1 was decreased in the HIF-1α siRNA group, and the tumor volume was much smaller than that in the mock siRNA group. CONCLUSION MTH-1 expression in CRC cells was upregulated via HIF-1α in response to hypoxic stress, emphasizing the crucial role of HIF-1α-induced MTH-1 in tumor growth.

Intracellular Adhesion Molecule-1 K469E Gene Polymorphism and the Risk of Inflammatory Bowel Disease: A Meta-Analysis

Background and objective: Several studies have evaluated the association of the K469E (rs5498, A/G) gene polymorphism in Intracellular Adhesion Molecule-1 (ICAM-1) with Inflammatory Bowel Disease (IBD), including Crohn’s Disease (CD) and Ulcerative Colitis (UC), in different populations. However, the results of these individual studies have been inconsistent. Therefore, a meta-analysis was performed. Methods: The current meta-analysis, which involved 3260 subjects from nine separate studies, was conducted to explore the relationship between the ICAM-1 K469E gene polymorphism and IBD. The pooled odds ratios (OR) and 95% Confidence Intervals (CI) were assessed using the random effect model. Data were analyzed using STATA software. Results: Overall, we observed no significant association between the ICAM-1 K469E gene polymorphism and IBD, CD, or UC. Stratification of cases by ethnicity revealed that the ICAM-1 K469E gene polymorphism was significantly associated with IBD only in the East Asian population (KK+KE vs. EE: OR=2.586, 95% CI=1.411-4.742; KK vs. KE+EE: OR=1.828, 95% CI=1.081-3.092; K vs. E: OR=1.739, 95% CI=1.240-2.439; EE vs. KK: OR=0.305, 95% CI=0.151-0.615). Conclusions: This meta-analysis suggested that the K469E polymorphism in ICAM-1 likely does not represent a major factor affecting susceptibility to IBD. However, additional large case-control studies should be performed to clarify the possible role of ICAM-1 in IBD, especially studies examining potential ethnic differences and/or genotypephenotype interactions.

A Novel Role of OS-9 in the Maintenance of Intestinal Barrier Function from Hypoxia-induced Injury via p38-dependent Pathway

OS-9 is a lectin required for efficient ubquitination of glycosylated substrates of endoplasmic reticulum-associated degradation (ERAD). OS-9 has previously been implicated in ER-to-Golgi transport and transcription factor turnover. However, we know very little about other functions of OS-9 under endoplasmic reticulum stress. Here, we used gene knockdown and overexpression approaches to study the protective effect of OS-9 on intestinal barrier function of intestinal epithelial cell Caco-2 monolayer. We found that OS-9 attenuated intestinal epithelial barrier dysfunction under hypoxia through up-regulating occludin and claudin-1 protein expression. Furthermore, we showed that the up-regulation of occludin and claudin-1 induced by OS-9 was mediated by p38 and ERK1/2 phosphorylation and did not involve HIF-1α. In summary, our results demonstrate that OS-9 up-regulates occludin and claudin-1 by activating the MAP kinase (MAPK) pathway, and thus protects the epithelial barrier function of Caco-2 monolayer under hypoxia condition.

Su1879 SIRT1 Antagonizes Distinct Effects of TNF-α on Intestinal Epithelial Barrier

G A A b st ra ct s with siRNA os-9 obviously decreased the TER (806.6±49.9V/cm2). Consistently, os-9 knockdown in hypoxia significantly reduced the TER (333.3±31.5V/cm2) compared to in hypoxia only (736.6±39.8V/cm2). Conclusion: Os-9 knockdown significantly aggratated hypoxiainduced intestinal epithelium injury. These findings indicate that os-9 may play an important role in maintaining the epithelial barrier function through occludin and claudin-1.

Mo1955 Notch Signaling Pathway Protects Intestine From Ischemia/Reperfusion Injury in Rats Through STAT3 Signaling

Background: Notch signaling has been shown to play an important role in the maintenance of intestinal homeostasis. The purpose of the present study was to investigate the role of Notch signaling in the regulation of intestinal injury in an ischemia reperfusion (I/R) rat model. Method: Male Sprague-Dawley rats were subjected to sham operation or I/R by occlusion of the superior mesenteric artery (SMA) for 30 min. DAPT (a γ-secretase inhibitor, 500μg/100g) or DMSO was given intraperitoneally 2 h before I/R. Intestinal tissue samples were collected at 12 h after reperfusion. The expression of Notch signaling pathway and phosphorylation of STAT were examined by Real-time PCR, Western blot, immunofluorescence and Co-Immunoprecipitation. Apoptosis of intestinal epithelial cells were examined by TUNEL staining. Neutrophil infiltration was assessed by examining myeloperoxidase (MPO) activity in the gut. Finally, an in vitro IEC-6 culture system was further applied to investigate the role of Notch signaling in the regulation of intestinal epithelal apoptosis after I/R injury. Results: In this study, Notch signaling was activated after intestinal I/R injury. The proteins expression of NICD-1 and Hes-5 were increased significantly (NICD-1: 0.35±0.12 vs 0.79±0.27, p<0.05; Hes-5:0.42±0.15 vs 0.93±0.31, p<0.05 ) and immunofluorescence results showed that the proteins were colocalized mainly in the intestinal epithelial cells after I/R injury. Blocking Notch signaling by DAPT led to aggravated intestinal I/R injury, as manifested by deteriorated intestinal barrier function (TER: 78±9.5V.cm2 vs 62±7.3V.cm2), increased inflammation and intestinal epithelial cells apoptosis (18±1.9 cells/100crypts vs 32±2.2 cells/ 100crypts). Notch signaling blockade also resulted in down-regulation of Hes5, leading to reduced formation of the Hes5-STAT3 complex and hypophosphorylation of STAT3 both in vivo and in vitro. Overexpression of a constitutively active STAT3 attenuated I/R injury by reducing apoptosis. Furthermore, IEC-6 cells were protected from I/R injury induced apoptosis after the activation of Notch signaling by ligand stimulation through increased activation of STAT3. Conclusion: Notch signaling was activated and played an important role in the protection of intestine from I/R injury through Hes-5 dependent activation of STAT3.