Innate CD8αα+ cells promote ILC1-like intraepithelial lymphocyte homeostasis and intestinal inflammation.

Innate CD8αα+ cells, also referred to as iCD8α cells, are TCR-negative intraepithelial lymphocytes (IEL) possessing cytokine and chemokine profiles and functions related to innate immune cells. iCD8α cells constitute an important source of osteopontin in the intestinal epithelium. Osteopontin is a pleiotropic cytokine with diverse roles in bone and tissue remodeling, but also has relevant functions in the homeostasis of immune cells. In this report, we present evidence for the role of iCD8α cells in the homeostasis of TCR-negative NKp46+NK1.1+ IEL (ILC1-like). We also show that the effect of iCD8α cells on ILC1-like IEL is enhanced in vitro by osteopontin. We show that in the absence of iCD8α cells, the number of NKp46+NK1.1+ IEL is significantly reduced. These ILC1-like cells are involved in intestinal pathogenesis in the anti-CD40 mouse model of intestinal inflammation. Reduced iCD8α cell numbers results in a milder form of intestinal inflammation in this disease model, whereas treatment with osteopontin increases disease severity. Collectively, our results suggest that iCD8α cells promote survival of NKp46+NK1.1+ IEL, which significantly impacts the development of intestinal inflammation

Interaction of Helicobacter pylori With Gastric Epithelial Cells Is Mediated by the p53 Protein Family

Background & Aims: Although the p53 tumor suppressor has been extensively studied, many critical questions remain unanswered about the biological functions of p53 homologs, p73 and p63. Accumulating evidence suggests that both p73 and p63 play important roles in regulation of apoptosis, cell differentiation, and therapeutic drug sensitivity. Methods: Gastric epithelial cells were cocultured with Helicobacter pylori, and the roles of p63 and p73 proteins were assessed by luciferase reporter, real-time polymerase chain reaction, immunoblotting, and cell survival assays. Short hairpin RNA and dominant-negative mutants were used to inhibit activity of p73 and p63 isoforms. Human and murine gastric tissues were analyzed by immunohistochemistry with p73 and p63 antibodies and modified Steiner's silver method. Results: Interaction of H pylori with gastric epithelial cells leads to robust up-regulation of p73 protein in vitro and in vivo in human gastritis specimens and H pylori–infected mice. The p73 increase resulted in up-regulation of pro-apoptotic genes, NOXA, PUMA, and FAS receptor in gastric epithelial cells. Down-regulation of p73 activity suppressed cell death and Fas receptor induced by H pylori. Bacterial virulence factors within the cag pathogenicity island, c-Abl tyrosine kinase, and interaction with p63 isoforms control the activity of p73. Conclusion: Our findings implicate p73 in H pylori–induced apoptosis and more generally suggest that the p53 family may play a role in the epithelial cell response to H pylori infection

Frequent overexpression of Aurora Kinase A in upper gastrointestinal adenocarcinomas correlates with potent antiapoptotic functions

Upper gastrointestinal adenocarcinomas are a common cause of cancer-related deaths. In this study, the authors investigated the prevalence and biological significance of Aurora Kinase A (AURKA) overexpression in upper gastrointestinal adenocarcinomas. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical staining on tumor tissue microarrays (TMA) were used to study the expression of AURKA in upper gastrointestinal adenocarcinomas. To investigate the biological and signaling impact of AURKA, the authors used multiple in vitro assays that included 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), TUNEL (terminal deoxynucleotidyl transferase-mediated nick-end labeling), cytochrome C release, flow cytometry, luciferase reporter, and Western blot analysis. Frequent overexpression of AURKA transcript in upper gastrointestinal adenocarcinomas was detected compared with normal samples (47%; P= .001). The immunohistochemical analysis of 130 tumors demonstrated moderate-to-strong immunostaining of AURKA in >50% of upper gastrointestinal adenocarcinomas. By using camptothecin as a drug-induced apoptosis in vitro model, the authors demonstrated that the expression of AURKA provided protection against apoptosis to gastrointestinal cancer cells (AGS and RKO) (P= .006) and RIE-1 primary intestinal epithelial cells (P= .001). The AURKA overexpression mediated an increase in phosphorylation of AKT(Ser473) with an increase in HDM2 level. The shRNA-knockdown of AKT in AURKA-overexpressing cells reversed this effect and showed a significant increase in the p53 protein level, indicating a possible nexus of AURKA/AKT/p53. Indeed, overexpression of AURKA led to a remarkable reduction in the transcription activity of p53, with subsequent reductions in transcript and protein levels of its downstream proapoptotic transcription targets (p21, BAX, NOXA, and PUMA). Study results indicated that AURKA provides potent antiapoptotic properties to gastrointestinal cells by regulating levels of p53 through the AKT/HDM2 axis

Immune evasion by helicobacter pylori Is mediated by induction of macrophage arginase II

Helicobacter pylori infection persists for the life of the host due to the failure of the immune response to eradicate the bacterium. Determining how H. pylori escapes the immune response in its gastric niche is clinically important. We have demonstrated in vitro that macrophage NO production can kill H. pylori, but induction of macrophage arginase II (Arg2) inhibits inducible NO synthase (iNOS) translation, causes apoptosis, and restricts bacterial killing. Using a chronic H. pylori infection model, we determined whether Arg2 impairs host defense in vivo. In C57BL/6 mice, expression of Arg2, but not arginase I, was abundant and localized to gastric macrophages. Arg2(-/-) mice had increased histologic gastritis and decreased bacterial colonization compared with wild-type (WT) mice. Increased gastritis scores correlated with decreased colonization in individual Arg2(-/-) mice but not in WT mice. When mice infected with H. pylori were compared, Arg2(-/-) mice had more gastric macrophages, more of these cells were iNOS(+), and these cells expressed higher levels of iNOS protein, as determined by flow cytometry and immunofluorescence microscopy. There was enhanced nitrotyrosine staining in infected Arg2(-/-) versus WT mice, indicating increased NO generation. Infected Arg2(-/-) mice exhibited decreased macrophage apoptosis, as well as enhanced IFN-gamma, IL-17a, and IL-12p40 expression, and reduced IL-10 levels consistent with a more vigorous Th1/Th17 response. These studies demonstrate that Arg2 contributes to the immune evasion of H. pylori by limiting macrophage iNOS protein expression and NO production, mediating macrophage apoptosis, and restraining proinflammatory cytokine responses

Regulation of p53 Tumor Suppressor by Helicobacter pylori in Gastric Epithelial Cells

Infection with the gastric mucosal pathogen Helicobacter pylori is the strongest identified risk factor for distal gastric cancer. These bacteria colonize a significant part of the world's population. We investigated the molecular mechanisms of p53 regulation in H pylori–infected cells. Mongolian gerbils were challenged with H pylori and their gastric tissues were analyzed by immunohistochemistry and immunoblotting with p53 antibodies. Gastric epithelial cells were co-cultured with H pylori and the regulation of p53 was assessed by real-time polymerase chain reaction, immunoblotting, immunofluorescence, and cell survival assays. Short hairpin RNA and dominant-negative mutants were used to inhibit activities of Human Double Minute 2 (HDM2) and AKT1 proteins. We found that in addition to previously reported up-regulation of p53, H pylori can also negatively regulate p53 by increasing ubiquitination and proteasomal degradation via activation of the serine/threonine kinase AKT1, which phosphorylates and activates the ubiquitin ligase HDM2. These effects were mediated by the bacterial virulence factor CagA; ectopic expression of CagA in gastric epithelial cells increased phosphorylation of HDM2 along with the ubiquitination and proteasomal degradation of p53. The decrease in p53 levels increased survival of gastric epithelial cells that had sustained DNA damage. H pylori is able to inhibit the tumor suppressor p53. H pylori activates AKT1, resulting in phosphorylation and activation of HDM2 and subsequent degradation of p53 in gastric epithelial cells. H pylori–induced dysregulation of p53 is a potential mechanism by which the microorganism increases the risk of gastric cancer in infected individuals