Morphologic Basis for Developing Diverticular Disease, Diverticulitis, and Diverticular Bleeding

Diverticula of the colon are pseudodiverticula defined by multiple outpouchings of the mucosal and submucosal layers penetrating through weak spots of the muscle coat along intramural blood vessels. A complete prolapse consists of a diverticular opening, a narrowed neck, and a thinned diverticular dome underneath the serosal covering. The susceptibility of diverticula to inflammation is explained by local ischemia, translocation of pathogens due to retained stool, stercoral trauma by fecaliths, and microperforations. Local inflammation may lead to phlegmonous diverticulitis, paracolic/mesocolic abscess, bowel perforation, peritonitis, fistula formation, and stenotic strictures. Diverticular bleeding is due to an asymmetric rupture of distended vasa recta at the diverticular dome and not primarily linked to inflammation. Structural and functional changes of the bowel wall in diverticular disease comprise: i) Altered amount, composition, and metabolism of connective tissue; ii) Enteric myopathy with muscular thickening, deranged architecture, and altered myofilament composition; iii) Enteric neuropathy with hypoganglionosis, neurotransmitter imbalance, deficiency of neurotrophic factors and nerve fiber remodeling; and iv) Disturbed intestinal motility both in vivo (increased intraluminal pressure, motility index, high-amplitude propagated contractions) and in vitro (altered spontaneous and pharmacologically triggered contractility). Besides established etiologic factors, recent studies suggest that novel pathophysiologic concepts should be considered in the pathogenesis of diverticular disease

Impaired Expression of Neuregulin 1 and Nicotinic Acetylcholine Receptor β4 Subunit in Diverticular Disease

Neuregulin 1 (NRG1) regulates the expression of the nicotinic acetylcholine receptor (nAChR) and is suggested to promote the survival and maintenance of the enteric nervous system (ENS), since deficiency of its corresponding receptor complex ErbB2/ErbB3 leads to postnatal colonic aganglionosis. As diverticular disease (DD) is associated with intestinal hypoganglionosis, the NRG1-ErbB2/ErbB3 system and the nAChR were studied in patients with DD and controls. Samples of tunica muscularis of the sigmoid colon from patients with DD (n = 8) and controls (n = 11) were assessed for mRNA expression of NRG1, ErbB2, and ErbB3 and the nAChR subunits α3, α5, α7, β2, and β4. Site-specific gene expression levels of the NRG1-ErbB2/3 system were determined in myenteric ganglia harvested by laser microdissection (LMD). Localization studies were performed by immunohistochemistry for the NRG1-ErbB2/3 system and nAChR subunit β4. Rat enteric nerve cell cultures were stimulated with NRG1 or glial-cell line derived neurotrophic factor (GDNF) for 6 days and mRNA expression of the aforementioned nAchR was measured. NRG1, ErbB3, and nAChR subunit β4 expression was significantly down-regulated in both the tunica muscularis and myenteric ganglia of patients with DD compared to controls, whereas mRNA expression of ErbB3 and nAChR subunits β2, α3, α5, and α7 remained unaltered. NRG1, ErbB3, and nAChR subunit β4 immunoreactive signals were reduced in neuronal somata and the neuropil of myenteric ganglia from patients with DD compared to control. nAChR subunit β4 exhibited also weaker immunoreactive signals in the tunica muscularis of patients with DD. NRG1 treatment but not GDNF treatment of enteric nerve cell cultures significantly enhanced mRNA expression of nAchR β4. The down-regulation of NRG1 and ErbB3 in myenteric ganglia of patients with DD supports the hypothesis that intestinal hypoganglionosis observed in DD may be attributed to a lack of neurotrophic factors. Regulation of nAChR subunit β4 by NRG1 and decreased nAChR β4 in patients with DD provide evidence that a lack of NRG1 may affect the composition of enteric neurotransmitter receptor subunits thus contributing to the intestinal motility disorders previously reported in DD

Effects of the TLR2 Agonists MALP-2 and Pam3Cys in Isolated Mouse Lungs

Background: Gram-positive and Gram-negative bacteria are main causes of pneumonia or acute lung injury. They are recognized by the innate immune system via toll-like receptor-2 (TLR2) or TLR4, respectively. Among all organs, the lungs have the highest expression of TLR2 receptors, but little is known about the pulmonary consequences of their activation. Here we studied the effects of the TLR2/6 agonist MALP-2, the TLR2/1 agonist Pam 3Cys and the TLR4 agonist lipopolysaccharide (LPS) on pro-inflammatory responses in isolated lungs. Methodology/Principal Findings: Isolated perfused mouse lungs were perfused for 60 min or 180 min with MALP-2 (25 ng/ mL), Pam3Cys (160 ng/mL) or LPS (1 mg/mL). We studied mediator release by enzyme linked immunosorbent assay (ELISA), the activation of mitogen activated protein kinase (MAPK) and AKT/protein kinase B by immunoblotting, and gene induction by quantitative polymerase chain reaction. All agonists activated the MAPK ERK1/2 and p38, but neither JNK or AKT kinase. The TLR ligands upregulated the inflammation related genes Tnf, Il1b, Il6, Il10, Il12, Ifng, Cxcl2 (MIP-2a) and Ptgs2. MALP-2 was more potent than Pam 3Cys in inducing Slpi, Cxcl10 (IP10) and Parg. Remarkable was the strong induction of Tnc by MALP2, which was not seen with Pam 3Cys or LPS. The growth factor related genes Areg and Hbegf were not affected. In addition, all three TLR agonists stimulated the release of IL-6, TNF, CXCL2 and CXCL10 protein from the lungs

Cluster analysis of the gene expression data.

<p>After 60 min of perfusion under baseline conditions, isolated mouse lungs were perfused for another 180 min with Pam₃Cys (160 ng/mL, n = 5), MALP-2 (25 ng/mL, n = 5), LPS (1 µg/mL, n = 3) or under control conditions (n = 5). The different colors (red, brown, green, blue) identify genes that clustered together.</p

Expression of genes in cluster 2.

<p>After 60 min of perfusion under baseline conditions, isolated mouse lungs were perfused for another 180 min with Pam₃Cys (160 ng/mL, n = 5), MALP-2 (25 ng/mL, n = 5), LPS (1 µg/mL, n = 3) or under control conditions (n = 5). Genes: interleukin 4 (Il4), interleukin 12p35 (Il12a), tenascin C (Tnc), interleukin 10 (Il10), cyclooxygenase 2 (<i>Ptgs2</i>), and IP10 (<i>Cxcl10</i>). Data were normalized to the experimental control and are shown as mean ± SEM. *, p<0.05 vs control; **, p<0.01 vs control; ***, p<0.001 vs control.</p

Lung functions.

<p>(<b>A</b>) Tidal volume and (B) pulmonary resistance in isolated perfused mouse lungs exposed to Pam₃Cys (160 ng/mL, black squares), MALP-2 (25 ng/mL, grey squares) or LPS (1 µg/mL, black circles) from 60 min to the end of the experiment; control lungs are shown as white circles. Data are expressed as mean ± SEM, n = 3–5.</p

Expression of genes in cluster 3 and 4.

<p>After 60 min of perfusion under baseline conditions, isolated mouse lungs were perfused for another 180 min with Pam₃Cys (160 ng/mL, n = 5), MALP-2 (25 ng/mL, n = 5), LPS (1 µg/mL, n = 3) or under control conditions (n = 5). Genes: interleukin 1β (<i>Il1b</i>), macrophage inflammatory protein 2α (<i>Cxcl2</i>), interleukin 6 (Il6), tumor necrosis factor (<i>Tnf</i>), interferon γ (Ifng), and IL12p40 (IL12b). Data were normalized to the experimental control and are shown as mean ± SEM. *, p<0.05 vs control; **, p<0.01 vs control; ***, p<0.001 vs control.</p

Expression of genes in cluster 1.

<p>After 60 min of perfusion under baseline conditions, isolated mouse lungs were perfused for another 180 min with Pam₃Cys (160 ng/mL, n = 5), MALP-2 (25 ng/mL, n = 5), LPS (1 µg/mL, n = 3) or under control conditions (n = 4). Genes: amphiregulin (Areg), angiopoietin-like 2 (Angptl2), heparin-binding epithelial growth fator (HBegf), poly(ADP-ribose)glycohydrolase (Parg), TNF receptor-associated factor 1 (Traf1), and secretory leukocyte peptidase inhibitor (<i>Slpi</i>). Data were normalized to the experimental control and are shown as mean ± SEM. *, p<0.05 vs control; **, p<0.01 vs control; ***, p<0.001 vs control.</p