Defects in Macrophage Specific Homeostatic Pathways in the Inflammatory Bowel Diseases

Intestinal macrophages are specialized to carry out their functions in the local antigen- and microbiota-rich environment. They are refractory to the induction of proinflammatory cytokines, yet still display potent phagocytic and bactericidal activity. These adaptations allow the intestinal macrophage to eradicate microbes that breach the intestinal epithelial barrier while maintaining local tissue homeostasis. The inflammatory bowel diseases, Crohn’s disease and ulcerative colitis, results from an inappropriately directed inflammatory response to the enteric microbiota in a genetically susceptible host. In contrast to the characteristic anti-inflammatory phenotypic and functional profile of normal intestinal macrophages, these macrophages react to luminal microbes and become potent producers of proinflammatory cytokines such as IL-12 family members. IL-12 and 23 are heterodimeric cytokines produced by macrophages and dendritic cells that are important bridges between innate and adaptive immunity. Although the molecular events that lead to the expression of IL-12 and Il-23 in macrophages through TLR signaling have been well defined, anti-inflammatory pathways that lead to inhibition of these cytokines in macrophages have not been fully elucidated. We identify two important homeostatic pathways; IFN-γ and HO-1 that regulate enteric microbiota-induced production of IL-12 and 23 by macrophages. IFN-γ inhibits TLR induced IL-23 expression in macrophages, and these events prevent the initiation and progression of spontaneous IL-23-driven experimental colitis in IL-10 deficient (IL-10-/-) mice. Moreover, we demonstrate that enteric microbiota-induced heme-oxygenase 1 (HO- 1) is critical in the prevention of experimental colitis, through inhibition of IL-12 family members and augmentation of macrophage microbicidal pathways. In our first study we demonstrate that IFN-γ has anti-inflammatory properties in murine models of Th1/Th17 mediated experimental colitis through attenuation of TLRmediated IL-23 expression in macrophages. In the second series of experiments, using germ-free WT and colitis-prone IL-10-/- mice we show that intestinal HO-1 expression induced by the enteric microbiota is an important homeostatic pathway. We also identify signaling pathways (MyDD88, MAPK and Pi3K) essential for HO-1 induction in macrophages. Finally, in our third study, protective effects of the HO-1 pathway were determined in Th2-mediated chronic colonic inflammation in T cell receptor- alpha (TCRα) deficient (-/-) mice. TCRα-/- mice exposed to carbon monoxide (CO) or treated with a pharmacologic HO-1 inducer demonstrated significant amelioration of active colitis. We demonstrate that HO-1 regulates mucosal innate immune responses in the TCRα-/- mouse through IL-10 induction in colonic macrophages

Endoscopic Third Ventriculostomy: A Comparable Alternative to Ventriculoperitoneal Shunt for Obstructive Hydrocephalus Secondary to Infratentorial Tumors

Objective: To establish ETV  as a comparable alternative to ventriculoperitoneal shunt for obstructive hydrocephalus secondary to infratentorial tumors. Methods: 40 Patients with infratentorial tumors presenting with hydrocephalus were enrolled in a prospective descriptive case series. Symptoms, neurological examinations, CT scan and intra-operative findings were used detect the complications at 03 months. Results:   Mean age = 31.98 ± 15.24 years, female to male ratio of 1:1.2. The KPS score of the participants was ? 70% and ETVSS ?80. Average operative mean time was 21 ± 2.82 minutes. Within first week, the improvement in symptoms was recorded (CI=95%): headache – 87.5% (p < 0.001), nausea vomiting - 84% (p < 0.001), gait disturbance – 59.3% (p=0.442) seizures improvement -100% (p=0.016) and urinary incontinence – 66.7% (p=0.687). Radiological improvement in hydrocephalus on CT scan was seen in one patient within 24 hours – 2.5% (p= <0.001), 12.5% (p<0.001) after two weeks and 87.5% (p= <0.001) after three months post-operatively (CI 95%). Most common of these were decrease in the size of third ventricle and decrease in the size of frontal horns of lateral ventricles.  However, complete resolution of radiologic features was observed in two patients only 5% (p<0.001). However, complete resolution of radiologic features was not observed in any patient. No intra-operative or post-operative complication of ETV was recorded. Conclusion: ETV is a quick and safe method for CSF diversion in obstructive hydrocephalus alleviating the need for placement of VP shunt hardware, thus eliminating foreign body related cranio-abdominal complications

The role of the macrophage in sentinel responses in intestinal immunity

The purpose of this review is to highlight macrophages as central mediators of intestinal immune homeostasis and inflammation

<html>Induction of Murine Intestinal Inflammation by Adoptive Transfer of Effector CD4⁺CD45RB^high T Cells into Immunodeficient Mice</html>

There are many different animal models available for studying the pathogenesis of human inflammatory bowel diseases (IBD), each with its own advantages and disadvantages. We describe here an experimental colitis model that is initiated by adoptive transfer of syngeneic splenic CD4+CD45RBhigh T cells into T and B cell deficient recipient mice. The CD4+CD45RBhigh T cell population that largely consists of naïve effector cells is capable of inducing chronic intestinal inflammation, closely resembling key aspects of human IBD. This method can be manipulated to study aspects of disease onset and progression. Additionally it can be used to study the function of innate, adaptive, and regulatory immune cell populations, and the role of environmental exposures, i.e., the microbiota, in intestinal inflammation. In this article we illustrate the methodology for inducing colitis with a step-by-step protocol. This includes a video demonstration of key technical aspects required to successfully develop this murine model of experimental colitis for research purposes

Cutting Edge: IFN- Is a Negative Regulator of IL-23 in Murine Macrophages and Experimental Colitis

IL-23 regulation is a central event in the pathogenesis of the inflammatory bowel diseases. We demonstrate that IFN-γ has anti-inflammatory properties in the initiation phase of IL-23–mediated experimental colitis. IFN-γ attenuates LPS-mediated IL-23 expression in murine macrophages. Mechanistically, IFN-γ inhibits Il23a promoter activation through altering NF-κB binding and histone modification. Moreover, intestinal inflammation is inhibited by IFN-γ signaling through attenuation of Il23a gene expression. In germ-free wild-type mice colonized with enteric microbiota, inhibition of colonic Il23a temporally correlates with induction of IFN-γ. IFN-γR1/IL-10 double-deficient mice demonstrate markedly increased colonic inflammation and IL23a expression compared with those of IL-10−/− mice. Colonic CD11b+ cells are the primary source of IL-23 and a target for IFN-γ. This study describes an important anti-inflammatory role for IFN-γ through inhibition of IL-23. Converging genetic and functional findings suggest that IL-23 and IFN-γ are important pathogenic molecules in human inflammatory bowel disease

Aberrant miR-29 is a predictive feature of severe phenotypes in pediatric Crohn’s disease

Publisher PD

Aberrant miR-29 is a predictive feature of severe phenotypes in pediatric Crohn’s disease

Funding Information: This work was supported by 5P01DK094779 (NIH/NIDDK) awarded to SZS, TSF, and PS; the NIDDK R01 DK136262 awarded to SZS; and 5R21HD104922-02 (NIH/NICHD) awarded to PS. We would also like to thank BioRender for its help in creating our graphical abstract.Peer reviewe

Molecular classification of Crohn's disease reveals two clinically relevant subtypes

The clinical presentation and course of Crohn’s disease (CD) is highly variable. We sought to better understand the cellular and molecular mechanisms that guide this heterogeneity, and characterize the cellular processes associated with disease phenotypes

Alterations to chromatin in intestinal macrophages link IL-10 deficiency to inappropriate inflammatory responses

Intestinal macrophages are uniquely programmed to tolerate exposure to bacteria without mounting potent inflammatory responses. The cytokine IL-10 maintains the macrophage anti-inflammatory response such that loss of IL-10 results in chronic intestinal inflammation. To investigate how IL-10-deficiency alters intestinal macrophage programming and bacterial tolerance, we studied changes in chromatin accessibility in response to bacteria in macrophages from two distinct niches, the intestine and bone-marrow, from both wild-type and IL-10-deficient mice. In both bone-marrow-derived and intestinal macrophages, we identified chromatin accessibility changes associated with bacterial exposure and IL-10-deficiency. Surprisingly, IL-10-deficient intestinal macrophages adopted chromatin and gene expression patterns characteristic of an inflammatory response, even in the absence of bacteria. Further, if IL-10 protein was added to cells that had previously been IL-10-deficient, it could not revert the chromatin landscape to a normal state. Our results demonstrate that IL-10 deficiency results in stable chromatin alterations in macrophages, even in the absence of bacteria. This supports a model where IL-10-deficiency leads to chromatin alterations that contribute to a loss of intestinal macrophage tolerance to bacteria, which is a primary initiating event in chronic intestinal inflammation

An Anti-Inflammatory Role for Carbon Monoxide and Heme Oxygenase-1 in Chronic Th2-Mediated Murine Colitis

Cigarette smoking is a significant environmental factor in the human inflammatory bowel diseases, remarkably, conferring protection in ulcerative colitis. We previously demonstrated that a prominent component of cigarette smoke, CO, suppresses Th17-mediated experimental colitis in IL-10−/− mice through a heme oxygenase (HO)-1–dependent pathway. In this study, homeostatic and therapeutic effects of CO and HO-1 were determined in chronic colonic inflammation in TCR-α–deficient (−/−) mice, in which colitis is mediated by Th2 cytokines, similar to the cytokine milieu described in human ulcerative colitis. TCRα−/− mice exposed to CO or treated with the pharmacologic HO-1 inducer cobalt protoporphyrin demonstrated amelioration of active colitis. CO and cobalt protoporphyrin suppressed colonic IL-1β, TNF, and IL-4 production, whereas IL-10 protein secretion was increased. CO induced IL-10 expression in macrophages and in vivo through an HO-1–dependent pathway. Bacterial products regulate HO-1 expression in macrophages through MyD88- and IL-10–dependent pathways. CO exposure and pharmacologic HO-1 induction in vivo resulted in increased expression of HO-1 and IL-10 in CD11b+ lamina propria mononuclear cells. Moreover, induction of the IL-10 family member IL-22 was demonstrated in CD11b− lamina propria mononuclear cells. In conclusion, CO and HO-1 induction ameliorated active colitis in TCRα−/− mice, and therapeutic effects correlated with induction of IL-10. This study provides further evidence that HO-1 mediates an important homeostatic pathway with pleiotropic anti-inflammatory effects in different experimental models of colitis and that targeting HO-1, therefore, is a potential therapeutic strategy in human inflammatory bowel diseases