Browsing by Subject "Intestinal Mucosa"
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Item Open Access Characterization of basal pseudopod-like processes in ileal and colonic PYY cells.(J Mol Histol, 2011-02) Bohórquez, Diego V; Chandra, Rashmi; Samsa, Leigh Ann; Vigna, Steven R; Liddle, Rodger AThe peptide tyrosine tyrosine (PYY) is produced and secreted from L cells of the gastrointestinal mucosa. To study the anatomy and function of PYY-secreting L cells, we developed a transgenic PYY-green fluorescent protein mouse model. PYY-containing cells exhibited green fluorescence under UV light and were immunoreactive to antibodies against PYY and GLP-1 (glucagon-like peptide-1, an incretin hormone also secreted by L cells). PYY-GFP cells from 15 μm thick sections were imaged using confocal laser scanning microscopy and three-dimensionally (3D) reconstructed. Results revealed unique details of the anatomical differences between ileal and colonic PYY-GFP cells. In ileal villi, the apical portion of PYY cells makes minimal contact with the lumen of the gut. Long pseudopod-like basal processes extend from these cells and form an interface between the mucosal epithelium and the lamina propria. Some basal processes are up to 50 μm in length. Multiple processes can be seen protruding from one cell and these often have a terminus resembling a synapse that appears to interact with neighboring cells. In colonic crypts, PYY-GFP cells adopt a spindle-like shape and weave in between epithelial cells, while maintaining contact with the lumen and lamina propria. In both tissues, cytoplasmic granules containing the hormones PYY and GLP-1 are confined to the base of the cell, often filling the basal process. The anatomical arrangement of these structures suggests a dual function as a dock for receptors to survey absorbed nutrients and as a launching platform for hormone secretion in a paracrine fashion.Item Open Access Elevated C-peptide and insulin predict increased risk of colorectal adenomas in normal mucosa.(BMC Cancer, 2012-09-05) Vidal, Adriana C; Lund, Pauline Kay; Hoyo, Cathrine; Galanko, Joseph; Burcal, Lauren; Holston, Rachel; Massa, Berri; Omofoye, Oluwaseun; Sandler, Robert S; Keku, Temitope OBACKGROUND: Lower concentrations of the insulin-like growth factor binding protein-1 (IGFBP-1) and elevated concentrations of insulin or C-peptide have been associated with an increase in colorectal cancer risk (CRC). However few studies have evaluated IGFBP-1 and C-peptide in relation to adenomatous polyps, the only known precursor for CRC. METHODS: Between November 2001 and December 2002, we examined associations between circulating concentrations of insulin, C-peptide, IGFBP-1 and apoptosis among 190 individuals with one or more adenomatous polyps and 488 with no adenomatous polyps using logistic regression models. RESULTS: Individuals with the highest concentrations of C-peptide were more likely to have adenomas (OR = 2.2, 95% CI 1.4-4.0) than those with the lowest concentrations; associations that appeared to be stronger in men (OR = 4.4, 95% CI 1.7-10.9) than women. Individuals with high insulin concentrations also had a higher risk of adenomas (OR = 3.5, 95% CI 1.7-7.4), whereas higher levels of IGFBP-1 were associated with a reduced risk of adenomas in men only (OR = 0.3, 95% CI 0.1-0.7). Overweight and obese individuals with higher C-peptide levels (>1(st) Q) were at increased risk for lower apoptosis index (OR = 2.5, 95% CI 0.9-7.1), an association that remained strong in overweight and obese men (OR = 6.3, 95% CI 1.0-36.7). Higher levels of IGFBP-1 in overweight and obese individuals were associated with a reduced risk of low apoptosis (OR = 0.3, 95% CI 0.1-1.0). CONCLUSIONS: Associations between these peptides and the apoptosis index in overweight and obese individuals, suggest that the mechanism by which C-peptide could induce adenomas may include its anti-apoptotic properties. This study suggests that hyperinsulinemia and IGF hormones predict adenoma risk, and that outcomes associated with colorectal carcinogenesis maybe modified by gender.Item Open Access Human Non-neutralizing HIV-1 Envelope Monoclonal Antibodies Limit the Number of Founder Viruses during SHIV Mucosal Infection in Rhesus Macaques.(PLoS Pathog, 2015-08) Santra, Sampa; Tomaras, Georgia D; Warrier, Ranjit; Nicely, Nathan I; Liao, Hua-Xin; Pollara, Justin; Liu, Pinghuang; Alam, S Munir; Zhang, Ruijun; Cocklin, Sarah L; Shen, Xiaoying; Duffy, Ryan; Xia, Shi-Mao; Schutte, Robert J; Pemble Iv, Charles W; Dennison, S Moses; Li, Hui; Chao, Andrew; Vidnovic, Kora; Evans, Abbey; Klein, Katja; Kumar, Amit; Robinson, James; Landucci, Gary; Forthal, Donald N; Montefiori, David C; Kaewkungwal, Jaranit; Nitayaphan, Sorachai; Pitisuttithum, Punnee; Rerks-Ngarm, Supachai; Robb, Merlin L; Michael, Nelson L; Kim, Jerome H; Soderberg, Kelly A; Giorgi, Elena E; Blair, Lily; Korber, Bette T; Moog, Christiane; Shattock, Robin J; Letvin, Norman L; Schmitz, Joern E; Moody, MA; Gao, Feng; Ferrari, Guido; Shaw, George M; Haynes, Barton FHIV-1 mucosal transmission begins with virus or virus-infected cells moving through mucus across mucosal epithelium to infect CD4+ T cells. Although broadly neutralizing antibodies (bnAbs) are the type of HIV-1 antibodies that are most likely protective, they are not induced with current vaccine candidates. In contrast, antibodies that do not neutralize primary HIV-1 strains in the TZM-bl infection assay are readily induced by current vaccine candidates and have also been implicated as secondary correlates of decreased HIV-1 risk in the RV144 vaccine efficacy trial. Here, we have studied the capacity of anti-Env monoclonal antibodies (mAbs) against either the immunodominant region of gp41 (7B2 IgG1), the first constant region of gp120 (A32 IgG1), or the third variable loop (V3) of gp120 (CH22 IgG1) to modulate in vivo rectal mucosal transmission of a high-dose simian-human immunodeficiency virus (SHIV-BaL) in rhesus macaques. 7B2 IgG1 or A32 IgG1, each containing mutations to enhance Fc function, was administered passively to rhesus macaques but afforded no protection against productive clinical infection while the positive control antibody CH22 IgG1 prevented infection in 4 of 6 animals. Enumeration of transmitted/founder (T/F) viruses revealed that passive infusion of each of the three antibodies significantly reduced the number of T/F genomes. Thus, some antibodies that bind HIV-1 Env but fail to neutralize virus in traditional neutralization assays may limit the number of T/F viruses involved in transmission without leading to enhancement of viral infection. For one of these mAbs, gp41 mAb 7B2, we provide the first co-crystal structure in complex with a common cyclical loop motif demonstrated to be critical for infection by other retroviruses.Item Open Access PDGFRα+ pericryptal stromal cells are the critical source of Wnts and RSPO3 for murine intestinal stem cells in vivo.(Proceedings of the National Academy of Sciences of the United States of America, 2018-04) Greicius, Gediminas; Kabiri, Zahra; Sigmundsson, Kristmundur; Liang, Chao; Bunte, Ralph; Singh, Manvendra K; Virshup, David MWnts and R-spondins (RSPOs) support intestinal homeostasis by regulating crypt cell proliferation and differentiation. Ex vivo, Wnts secreted by Paneth cells in organoids can regulate the proliferation and differentiation of Lgr5-expressing intestinal stem cells. However, in vivo, Paneth cell and indeed all epithelial Wnt production is completely dispensable, and the cellular source of Wnts and RSPOs that maintain the intestinal stem-cell niche is not known. Here we investigated both the source and the functional role of stromal Wnts and RSPO3 in regulation of intestinal homeostasis. RSPO3 is highly expressed in pericryptal myofibroblasts in the lamina propria and is several orders of magnitude more potent than RSPO1 in stimulating both Wnt/β-catenin signaling and organoid growth. Stromal Rspo3 ablation ex vivo resulted in markedly decreased organoid growth that was rescued by exogenous RSPO3 protein. Pdgf receptor alpha (PdgfRα) is known to be expressed in pericryptal myofibroblasts. We therefore evaluated if PdgfRα identified the key stromal niche cells. In vivo, Porcn excision in PdgfRα+ cells blocked intestinal crypt formation, demonstrating that Wnt production in the stroma is both necessary and sufficient to support the intestinal stem-cell niche. Mice with Rspo3 excision in the PdgfRα+ cells had decreased intestinal crypt Wnt/β-catenin signaling and Paneth cell differentiation and were hypersensitive when stressed with dextran sodium sulfate. The data support a model of the intestinal stem-cell niche regulated by both Wnts and RSPO3 supplied predominantly by stromal pericryptal myofibroblasts marked by PdgfRα.Item Open Access Role of mast cells in inflammatory bowel disease and inflammation-associated colorectal neoplasia in IL-10-deficient mice.(PLoS One, 2010-08-17) Chichlowski, Maciej; Westwood, Greg S; Abraham, Soman N; Hale, Laura PBACKGROUND: Inflammatory bowel disease (IBD) is hypothesized to result from stimulation of immune responses against resident intestinal bacteria within a genetically susceptible host. Mast cells may play a critical role in IBD pathogenesis, since they are typically located just beneath the intestinal mucosal barrier and can be activated by bacterial antigens. METHODOLOGY/PRINCIPAL FINDINGS: This study investigated effects of mast cells on inflammation and associated neoplasia in IBD-susceptible interleukin (IL)-10-deficient mice with and without mast cells. IL-10-deficient mast cells produced more pro-inflammatory cytokines in vitro both constitutively and when triggered, compared with wild type mast cells. However despite this enhanced in vitro response, mast cell-sufficient Il10(-/-) mice actually had decreased cecal expression of tumor necrosis factor (TNF) and interferon (IFN)-gamma mRNA, suggesting that mast cells regulate inflammation in vivo. Mast cell deficiency predisposed Il10(-/-) mice to the development of spontaneous colitis and resulted in increased intestinal permeability in vivo that preceded the development of colon inflammation. However, mast cell deficiency did not affect the severity of IBD triggered by non-steroidal anti-inflammatory agents (NSAID) exposure or helicobacter infection that also affect intestinal permeability. CONCLUSIONS/SIGNIFICANCE: Mast cells thus appear to have a primarily protective role within the colonic microenvironment by enhancing the efficacy of the mucosal barrier. In addition, although mast cells were previously implicated in progression of sporadic colon cancers, mast cells did not affect the incidence or severity of colonic neoplasia in this inflammation-associated model.Item Open Access Ubc9 overexpression and SUMO1 deficiency blunt inflammation after intestinal ischemia/reperfusion.(Laboratory investigation; a journal of technical methods and pathology, 2018-06) Karhausen, Jörn; Bernstock, Joshua D; Johnson, Kory R; Sheng, Huaxin; Ma, Qing; Shen, Yuntian; Yang, Wei; Hallenbeck, John M; Paschen, WulfThe intestinal epithelium constitutes a crucial defense to the potentially life-threatening effects of gut microbiota. However, due to a complex underlying vasculature, hypoperfusion and resultant tissue ischemia pose a particular risk to function and integrity of the epithelium. The small ubiquitin-like modifier (SUMO) conjugation pathway critically regulates adaptive responses to metabolic stress and is of particular significance in the gut, as inducible knockout of the SUMO-conjugating enzyme Ubc9 results in rapid intestinal epithelial disintegration. Here we analyzed the pattern of individual SUMO isoforms in intestinal epithelium and investigated their roles in intestinal ischemia/reperfusion (I/R) damage. Immunostaining revealed that epithelial SUMO2/3 expression was almost exclusively limited to crypt epithelial nuclei in unchallenged mice. However, intestinal I/R or overexpression of Ubc9 caused a remarkable enhancement of epithelial SUMO2/3 staining along the crypt-villus axis. Unexpectedly, a similar pattern was found in SUMO1 knockout mice. Ubc9 transgenic mice, but also SUMO1 knockout mice were protected from I/R injury as evidenced by better preserved barrier function and blunted inflammatory responses. PCR array analysis of microdissected villus-tip epithelia revealed a specific epithelial contribution to reduced inflammatory responses in Ubc9 transgenic mice, as key chemotactic signaling molecules such as IL17A were significantly downregulated. Together, our data indicate a critical role particularly of the SUMO2/3 isoforms in modulating responses to I/R and provide the first evidence that SUMO1 deletion activates a compensatory process that protects from ischemic damage.Item Open Access Wnt signaling suppresses MAPK-driven proliferation of intestinal stem cells.(The Journal of clinical investigation, 2018-08) Kabiri, Zahra; Greicius, Gediminas; Zaribafzadeh, Hamed; Hemmerich, Amanda; Counter, Christopher M; Virshup, David MIntestinal homeostasis depends on a slowly proliferating stem cell compartment in crypt cells, followed by rapid proliferation of committed progenitor cells in the transit amplifying (TA) compartment. The balance between proliferation and differentiation in intestinal stem cells (ISCs) is regulated by Wnt/β-catenin signaling, although the mechanism remains unclear. We previously targeted PORCN, an enzyme essential for all Wnt secretion, and demonstrated that stromal production of Wnts was required for intestinal homeostasis. Here, a PORCN inhibitor was used to acutely suppress Wnt signaling. Unexpectedly, the treatment induced an initial burst of proliferation in the stem cell compartment of the small intestine, due to conversion of ISCs into TA cells with a loss of intrinsic ISC self-renewal. This process involved MAPK pathway activation, as the proliferating cells in the base of the intestinal crypt contained phosphorylated ERK1/2, and a MEK inhibitor attenuated the proliferation of ISCs and their differentiation into TA cells. These findings suggest a role for Wnt signaling in suppressing the MAPK pathway at the crypt base to maintain a pool of ISCs. The interaction between Wnt and MAPK pathways in vivo has potential therapeutic applications in cancer and regenerative medicine.