Kareem W. Shehab

Reduced colonic microbial diversity is associated with colitis in NHE3-deficient mice

Chronic inflammation and enteric infections are frequently associated with epithelial Na(+)/H(+) exchange (NHE) inhibition. Alterations in electrolyte transport and in mucosal pH associated with inflammation may represent a key mechanism leading to changes in the intestinal microbial composition. NHE3 expression is essential for the maintenance of the epithelial barrier function. NHE3(-/-) mice develop spontaneous distal chronic colitis and are highly susceptible to dextran sulfate (DSS)-induced mucosal injury. Spontaneous colitis is reduced with broad-spectrum antibiotics treatment, thus highlighting the importance of the microbiota composition in NHE3 deficiency-mediated colitis. We herein characterized the colonic microbiome of wild-type (WT) and NHE3(-/-) mice housed in a conventional environment using 454 pyrosequencing. We demonstrated a significant decrease in the phylogenetic diversity of the luminal and mucosal microbiota of conventional NHE3(-/-) mice compared with WT. Rederivation of NHE3(-/-) mice from conventional to a barrier facility eliminated the signs of colitis and decreased DSS susceptibility. Reintroduction of the conventional microflora into WT and NHE3(-/-) mice from the barrier facility resulted in the restoration of the symptoms initially described in the conventional environment. Interestingly, qPCR analysis of the microbiota composition in mice kept in the barrier facility compared with reconventionalized mice showed a significant reduction of Clostridia classes IV and XIVa. Therefore, the gut microbiome plays a prominent role in the pathogenesis of colitis in NHE3(-/-) mice, and, reciprocally, NHE3 also plays a critical role in shaping the gut microbiota. NHE3 deficiency may be a critical contributor to dysbiosis observed in patients with inflammatory bowel disease.

The role of curcumin in modulating colonic microbiota during colitis and colon cancer prevention

Background:Intestinal microbiota influences the progression of colitis-associated colorectal cancer. With diet being a key determinant of the gut microbial ecology, dietary interventions are an attractive avenue for the prevention of colitis-associated colorectal cancer. Curcumin is the most active constituent of the ground rhizome of the Curcuma longa plant, which has been demonstrated to have anti-inflammatory, antioxidative, and antiproliferative properties. Methods:Il10−/− mice on 129/SvEv background were used as a model of colitis-associated colorectal cancer. Starting at 10 weeks of age, wild-type or Il10−/− mice received 6 weekly intraperitoneal injections of azoxymethane (AOM) or phosphate-buffered saline (PBS) and were started on either a control or a curcumin-supplemented diet. Stools were collected every 4 weeks for microbial community analysis. Mice were killed at 30 weeks of age. Results:Curcumin-supplemented diet increased survival, decreased colon weight/length ratio, and, at 0.5%, entirely eliminated tumor burden. Although colonic histology indicated improvement with curcumin, no effects of mucosal immune responses have been observed in PBS/Il10−/− mice and limited effects were seen in AOM/Il10−/− mice. In wild-type and in Il10−/− mice, curcumin increased bacterial richness, prevented age-related decrease in alpha diversity, increased the relative abundance of Lactobacillales, and decreased Coriobacterales order. Taxonomic profile of AOM/Il10−/− mice receiving curcumin was more similar to those of wild-type mice than those fed control diet. Conclusions:In AOM/Il10−/− model, curcumin reduced or eliminated colonic tumor burden with limited effects on mucosal immune responses. The beneficial effect of curcumin on tumorigenesis was associated with the maintenance of a more diverse colonic microbial ecology.

T Lymphocyte Dynamics in Inflammatory Bowel Diseases: Role of the Microbiome

Humans have coevolved with a complex community of bacterial species also referred to as the microbiome, which reciprocally provides critical contributions to human metabolism and immune system development. Gut microbiome composition differs significantly between individuals depending on host genetics, diet, and environmental factors. A dysregulation of the symbiotic nature of the intestinal host-microbial relationship and an aberrant and persistent immune response are the fundamental processes involved in inflammatory bowel diseases (IBD). Considering the essential role of T cells in IBD and the contributing role of the microbiome in shaping the immune response during the pathogenesis of IBD, this review focuses on the complex relationship, interplay, and communication between the gut microbiome and T cells, including their differentiation into different subsets of effector or regulatory cells.

Transcriptional Reprogramming and Resistance to Colonic Mucosal Injury in Poly(ADP-ribose) Polymerase 1 (PARP1)-deficient Mice

Poly(ADP-ribose) polymerases (PARPs) synthesize and bind branched polymers of ADP-ribose to acceptor proteins using NAD as a substrate and participate in the control of gene transcription and DNA repair. PARP1, the most abundant isoform, regulates the expression of proinflammatory mediator cytokines, chemokines, and adhesion molecules, and inhibition of PARP1 enzymatic activity reduced or ameliorated autoimmune diseases in several experimental models, including colitis. However, the mechanism(s) underlying the protective effects of PARP1 inhibition in colitis and the cell types in which Parp1 deletion has the most significant impact are unknown. The objective of the current study was to determine the impact of Parp1 deletion on the innate immune response to mucosal injury and on the gut microbiome composition. Parp1 deficiency was evaluated in DSS-induced colitis in WT, Parp1−/−, Rag2−/−, and Rag2−/−×Parp1−/− double knock-out mice. Genome-wide analysis of the colonic transcriptome and fecal 16S amplicon profiling was performed. Compared with WT, we demonstrated that Parp1−/− were protected from dextran-sulfate sodium-induced colitis and that this protection was associated with a dramatic transcriptional reprogramming in the colon. PARP1 deficiency was also associated with a modulation of the colonic microbiota (increases relative abundance of Clostridia clusters IV and XIVa) and a concomitant increase in the frequency of mucosal CD4+CD25+ Foxp3+ regulatory T cells. The protective effects conferred by Parp1 deletion were lost in Rag2−/− × Parp1−/− mice, highlighting the role of the adaptive immune system for full protection.

Central nervous system histoplasmosis: Multicenter retrospective study on clinical features, diagnostic approach and outcome of treatment

Abstract Central nervous system (CNS) involvement occurs in 5 to 10% of individuals with disseminated histoplasmosis. Most experience has been derived from small single center case series, or case report literature reviews. Therefore, a larger study of central nervous system (CNS) histoplasmosis is needed in order to guide the approach to diagnosis, and treatment. A convenience sample of 77 patients with histoplasmosis infection of the CNS was evaluated. Data was collected that focused on recognition of infection, diagnostic techniques, and outcomes of treatment. Twenty nine percent of patients were not immunosuppressed. Histoplasma antigen, or anti-Histoplasma antibodies were detected in the cerebrospinal fluid (CSF) in 75% of patients. One year survival was 75% among patients treated initially with amphotericin B, and was highest with liposomal, or deoxycholate formulations. Mortality was higher in immunocompromised patients, and patients 54 years of age, or older. Six percent of patients relapsed, all of whom had the acquired immunodeficiency syndrome (AIDS), and were poorly adherent with treatment. While CNS histoplasmosis occurred most often in immunocompromised individuals, a significant proportion of patients were previously, healthy. The diagnosis can be established by antigen, and antibody testing of the CSF, and serum, and antigen testing of the urine in most patients. Treatment with liposomal amphotericin B (AMB-L) for at least 1 month; followed by itraconazole for at least 1 year, results in survival among the majority of individuals. Patients should be followed for relapse for at least 1 year, after stopping therapy.

Successful resolution of hyperammonemia following hematopoietic cell transplantation with directed treatment of Ureaplasma parvum infection.

Hyperammonemia following hematopoietic cell transplantation (HCT) has been characterized as idiopathic and is associated with a very high mortality. A causal relationship between Ureaplasma infection and hyperammonemia in immunocompromised lung transplant recipients has recently been described. We document the first case of hyperammonemia following HCT associated with Ureaplasma parvum. The initiation of appropriate antibiotics resulted in rapid resolution of hyperammonemic encephalopathy and eradication of the implicating organism.

Balamuthia mandrillaris Granulomatous Amebic Encephalitis With Renal Dissemination in a Previously Healthy Child: Case Report and Review of the Pediatric Literature

Balamuthia mandrillaris is a recently described ameba known to cause a subacute to chronic central nervous system infection called granulomatous amebic encephalitis. Evidence suggests that apparently immunocompetent persons are at risk for disease and show a similar nonspecific presentation to that of immunodeficient persons. However, evidence of hematogenous dissemination, which has been found in immunodeficient patients, has been lacking in immunocompetent patients. Here, we describe a previously healthy patient with B mandrillaris-associated granulomatous amebic encephalitis in whom both central nervous system and renal disease were found during autopsy, which suggests hematogenous dissemination. We also provide a comprehensive review of the pediatric literature on this disease and its clinical presentation in children.

Case 1: Progressive Hypotonia and Decreased Alertness in an 8-month-old Girl

1. Megan Paul, MD* 2. Kareem Shehab, MD* 3. Tien Nguyen, MD* 1. *Department of Pediatrics, University of Arizona, Tucson, AZ A previously healthy 8-month-old girl in southern Arizona is admitted for progressive hypotonia and decreased alertness over several weeks. She has experienced 3 months of cough and 1 week of fever. She no longer crawls, makes eye contact, visually tracks, or babbles. Her mother travels frequently with the child to Mexico and has a chronic cough for which she has neither sought nor received care. Her vital signs are as follows: temperature, 98.6°F (37°C); blood pressure, 101/57 mm Hg; heart rate, 117 beats/min; respiratory rate, 26 breaths/min; and oxygen saturation, 100% on room air. Her weight is in the 27th percentile for age, length is in the 90th percentile, and head circumference is in the 88th percentile. Physical examination reveals an alert but hypotonic infant, unable to support herself sitting, and with limited spontaneous movements. Sucking and swallowing are weak, gag reflex is intact, and deep tendon reflexes are 1+. Her anterior fontanelle is open, flat, and wide. Pupils are equal and reactive, but there is no visual fixation. Extraocular movements are intact. Fundi are normal. Examination of the lungs reveals …

Sa1764 Poly(ADP-ribose) Polymerase 1 (PARP1) Expression in iTreg Plays a Role in the Pathogenesis of Experimental Colitis

1,25-Dihydroxyvitamin D3 Decreases Th1 and Tc1 Lymphocytes From the Peripheral Blood of IBD Patients and Healthy Controls Ex Vivo but Has No Effect on IL-17 or FoxP3 Expression Michael R. Tom, Aito Ueno, Miriam Fort Gasia, Ronald Chan, Daniel Y. Hung, Shem Chenoo, Christina Hirota, Alexander Li, Ji Li, Mailin Deane, Marietta Iacucci, Remo Panaccione, Gilaad Kaplan, Paul L. Beck, Andre G. Buret, Subrata Ghosh

Sa1765 Role of Poly(ADP-ribose) Polymerase 1 (PARP1) in the Modulation of Neutrophil Function: Relevance in Inflammatory Bowel Diseases

1,25-Dihydroxyvitamin D3 Decreases Th1 and Tc1 Lymphocytes From the Peripheral Blood of IBD Patients and Healthy Controls Ex Vivo but Has No Effect on IL-17 or FoxP3 Expression Michael R. Tom, Aito Ueno, Miriam Fort Gasia, Ronald Chan, Daniel Y. Hung, Shem Chenoo, Christina Hirota, Alexander Li, Ji Li, Mailin Deane, Marietta Iacucci, Remo Panaccione, Gilaad Kaplan, Paul L. Beck, Andre G. Buret, Subrata Ghosh