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

Anti-Inflammatory Properties of the SGLT2 Inhibitor Empagliflozin in Activated Primary Microglia

Sodium-glucose cotransporter 2 (SGLT2) inhibitors, including empagliflozin, are routinely used as antidiabetic drugs. Recent studies indicate that beside its beneficial effects on blood glucose level, empagliflozin may also exert vascular anti-inflammatory and neuroprotective properties. In the brain, microglia are crucial mediators of inflammation, and neuroinflammation plays a key role in neurodegenerative disorders. Dampening microglia-mediated inflammation may slow down disease progression. In this context, we investigated the immunomodulatory effect of empagliflozin on activated primary microglia. As a validated experimental model, rat primary microglial cells were activated into a pro-inflammatory state by stimulation with LPS. The influence of empagliflozin on the expression of pro-inflammatory mediators (NO, Nos2, IL6, TNF, IL1B) and on the anti-inflammatory mediator IL10 was assessed using quantitative PCR and ELISA. Further, we investigated changes in the activation of the ERK1/2 cascade by Western blot and NFkB translocation by immunostaining. We observed that empagliflozin reduces the expression of pro- and anti-inflammatory mediators in LPS-activated primary microglia. These effects might be mediated by NHE-1, rather than by SGLT2, and by the further inhibition of the ERK1/2 and NFkB pathways. Our results support putative anti-inflammatory effects of empagliflozin on microglia and suggest that SGLT2 inhibitors may exert beneficial effects in neurodegenerative disorders

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

Replacement of mouse Sox10 by the Drosophila ortholog Sox100B provides evidence for co-option of SoxE proteins into vertebrate-specific gene-regulatory networks through altered expression

AbstractNeural crest cells and oligodendrocytes as the myelinating glia of the central nervous system exist only in vertebrates. Their development is regulated by complex regulatory networks, of which the SoxE-type high-mobility-group domain transcription factors Sox8, Sox9 and Sox10 are essential components. Here we analyzed by in ovo electroporation in chicken and by gene replacement in the mouse whether the Drosophila ortholog Sox100B can functionally substitute for vertebrate SoxE proteins. Sox100B overexpression in the chicken neural tube led to the induction of neural crest cells as previously observed for vertebrate SoxE proteins. Furthermore, many aspects of neural crest and oligodendrocyte development were surprisingly normal in mice in which the Sox10 coding information was replaced by Sox100B arguing that Sox100B integrates well into the gene-regulatory networks that drive these processes. Our results therefore provide strong evidence for a model in which SoxE proteins were co-opted to these gene-regulatory networks mainly through the acquisition of novel expression patterns. However, later developmental defects in several neural crest derived lineages in mice homozygous for the Sox100B replacement allele indicate that some degree of functional specialization and adaptation of SoxE protein properties have taken place in addition to the co-option event

Effects of different ischemic preconditioning strategies on physiological and cellular mechanisms of intestinal ischemia/reperfusion injury: Implication from an isolated perfused rat small intestine model

Background Intestinal ischemia/reperfusion (I/R)-injury often results in sepsis and organ failure and is of major importance in the clinic. A potential strategy to reduce I/R-injury is the application of ischemic preconditioning (IPC) during which repeated, brief episodes of I/R are applied. The aim of this study was to evaluate physiological and cellular effects of intestinal I/R-injury and to compare the influence of in-vivo IPC (iIPC) with ex-vivo IPC (eIPC), in which blood derived factors and nerval regulations are excluded. Results I/R-injury decreased intestinal galactose uptake (iIPC group: p<0.001), increased vascular perfusion pressure (iIPC group: p<0.001; eIPC group: p<0.01) and attenuated venous flow (iIPC group: p<0.05) while lactate-to-pyruvate ratio (iIPC group, eIPC group: p<0.001), luminal flow (iIPC group: p<0.001; eIPC group: p<0.05), goblet cell ratio (iIPC group, eIPC group: p<0.001) and apoptosis (iIPC group, eIPC group: p<0.05) were all increased. Application of iIPC prior to I/R increased vascular galactose uptake (P<0.05) while eIPC had no significant impact on parameters of I/R-injury. On cellular level, I/R-injury resulted in a reduction of the phosphorylation of several MAPK signaling molecules. Application of iIPC prior to I/R increased phosphorylation of JNK2 and p38δ while eIPC enhanced CREB and GSK-3α/β phosphorylation. Conclusion Intestinal I/R-injury is associated with major physiological and cellular changes. However, the overall influence of the two different IPC strategies on the acute phase of intestinal I/R-injury is rather limited

Breaking the circulus vitiosus of neuroinflammation: Resveratrol attenuates the human glial cell response to cytokines

Neuroinflammation is both cause and effect of many neurodegenerative disorders. Activation of astrocytes and microglia leads to the release of cytokines and reactive oxygen species followed by blood-brain barrier leakage and neurotoxicity. Transient neuroinflammation is considered to be largely protective, however, chronic neuroinflammation contributes to the pathology of Alzheimer’s disease, multiple sclerosis, traumatic brain injury, and many more. In this study, we focus on the aspect of cytokine-induced neuroinflammation in human microglia and astrocytes. Here we show by mRNA and protein analysis that cytokines, released not only by microglia but also by astrocytes, lead to a circuit of proinflammatory activation. Moreover, we present how the natural compound resveratrol can stop the circuit of proinflammatory activation and facilitate return to resting conditions. These results will contribute to distinguishing between the causes and the effects of neuroinflammation, a better understanding of underlying mechanisms, and potential treatment options

Resveratrol Alleviates the Early Challenges of Implant-Based Drug Delivery in a Human Glial Cell Model

Brain diseases are oftentimes life-threatening and difficult to treat. The local administration of drug substances using brain implants can increase on-site concentrations and decrease systemic side effects. However, the biocompatibility of potential brain implant materials needs to be evaluated carefully as implants can trigger foreign body reactions, particularly by increasing the microglia and astrocyte reactivity. To date, these tests have been frequently conducted in very simple in vitro models, in particular not respecting the key players in glial cell reactions and the challenges of surgical implantation characterized by the disruption of oxygen and nutrient supply. Thus, we established an in vitro model in which we treated human glial cell lines with reduced oxygen and glucose levels. The model displayed cytokine and reactive oxygen species release from reactive microglia and an increase in a marker of reactive astrocytes, galectin-3. Moreover, the treatment caused changes in the cell survival and triggered the production of hypoxia-inducible factor 1α. In this comprehensive platform, we demonstrated the protective effect of the natural polyphenol resveratrol as a model substance, which might be included in brain implants to ease the undesired glial cell response. Overall, a glial-cell-based in vitro model of the initial challenges of local brain disease treatment may prove useful for investigating new therapy options

Limited Impact of 6-Mercaptopurine on Inflammation-Induced Chemokines Expression Profile in Primary Cultures of Enteric Nervous System

Abstract Increasing evidences indicate that the enteric nervous system (ENS) and enteric glial cells (EGC) play important regulatory roles in intestinal inflammation. Mercaptopurine (6-MP) is a cytostatic compound clinically used for the treatment of inflammatory bowel diseases (IBD), such as ulcerative colitis and Crohn’s disease. However, potential impacts of 6-MP on ENS response to inflammation have not been evaluated yet. In this study, we aimed to gain deeper insights into the profile of inflammatory mediators expressed by the ENS and on the potential anti-inflammatory impact of 6-MP in this context. Genome-wide expression analyses were performed on ENS primary cultures exposed to lipopolysaccharide (LPS) and 6-MP alone or in combination. Differential expression of main hits was validated by quantitative real-time PCR (qPCR) using a cell line for EGC. ENS cells expressed a broad spectrum of cytokines and chemokines of the C-X-C motif ligand (CXCL) family under inflammatory stress. Induction of Cxcl5 and Cxcl10 by inflammatory stimuli was confirmed in EGC. Inflammation-induced protein secretion of TNF-α and Cxcl5 was partly inhibited by 6-MP in ENS primary cultures but not in EGC. Further work is required to identify the cellular mechanisms involved in this regulation. These findings extend our knowledge of the anti-inflammatory properties of 6-MP related to the ENS and in particular of the EGC-response to inflammatory stimuli

Aldosterone exerts anti-inflammatory effects on LPS stimulated microglia

Over the last years, studies on microglia cell function in chronic neuro-inflammation and neuronal necrosis pointed towards an eminent role of these cells in Multiple Sclerosis, Parkinson's and Alzheimer's Disease. It was found, that microglia cell activity can be stimulated towards a pro- or an anti-inflammatory profile, depending on the stimulating signals. Therefore, investigation of receptors expressed by microglia cells and ligands influencing their activation state is of eminent interest.A receptor found to be expressed by microglia cells is the mineralocorticoid receptor. One of its ligands is Aldosterone, a naturally produced steroid hormone of the adrenal cortex, which mainly induces homeostatic and renal effects. We evaluated if the addition of Aldosterone to LPS stimulated microglia cells changes their inflammatory profile.Therefore, we assessed the levels of nitric oxide (NO), iNOS, IL-6, IL-1β, TNF-α and COX-2 in untreated, LPS-treated and LPS/Aldosterone-treated microglia cells. Furthermore we analyzed p38-MAP-Kinase and NFκB signaling within these cells.Our results indicate that the co-stimulation with Aldosterone leads to a decrease of the LPS-induced pro-inflammatory effect and thus renders Aldosterone an anti-inflammatory agent in our model system