Bettina Heid

The NLRP1 Inflammasome Attenuates Colitis and Colitis-Associated Tumorigenesis

Nucleotide-binding domain and leucine-rich repeat (NLR) proteins are a diverse family of pattern recognition receptors that are essential mediators of inflammation and host defense in the gastrointestinal system. Recent studies have identified a subgroup of inflammasome forming NLRs that modulate the mucosal immune response during inflammatory bowel disease (IBD) and colitis associated tumorigenesis. To better elucidate the contribution of NLR family members in IBD and cancer, we conducted a retrospective analysis of gene expression metadata from human patients. These data revealed that NLRP1, an inflammasome forming NLR, was significantly dysregulated in IBD and colon cancer. To better characterize the function of NLRP1 in disease pathogenesis, we used Nlrp1b−/− mice in colitis and colitis-associated cancer models. In this paper, we report that NLRP1 attenuates gastrointestinal inflammation and tumorigenesis. Nlrp1b−/− mice demonstrated significant increases in morbidity, inflammation, and tumorigenesis compared with wild-type animals. Similar to data previously reported for related inflammsome forming NLRs, the increased inflammation and tumor burden was correlated with attenuated levels of IL-1β and IL-18. Further mechanistic studies using bone marrow reconstitution experiments revealed that the increased disease pathogenesis in the Nlrp1b−/− mice was associated with nonhematopoietic-derived cells and suggests that NLRP1 functions in the colon epithelial cell compartment to attenuate tumorigenesis. Taken together, these data identify NLRP1 as an essential mediator of the host immune response during IBD and cancer. These findings are consistent with a model whereby multiple NLR inflammasomes attenuate disease pathobiology through modulating IL-1β and IL-18 levels in the colon.

NLRX1 suppresses tumorigenesis and attenuates histiocytic sarcoma through the negative regulation of NF-κB signaling

Histiocytic sarcoma is an uncommon malignancy in both humans and veterinary species. Research exploring the pathogenesis of this disease is scarce; thus, diagnostic and therapeutic options for patients are limited. Recent publications have suggested a role for the NLR, NLRX1, in acting as a tumor suppressor. Based on these prior findings, we hypothesized that NLRX1 would function to inhibit tumorigenesis and thus the development of histiocytic sarcoma. To test this, we utilized Nlrx1−/− mice and a model of urethane-induced tumorigenesis. Nlrx1−/− mice exposed to urethane developed splenic histiocytic sarcoma that was associated with significant up-regulation of the NF-λB signaling pathway. Additionally, development of these tumors was also significantly associated with the increased regulation of genes associated with AKT signaling, cell death and autophagy. Together, these data show that NLRX1 suppresses tumorigenesis and reveals new genetic pathways involved in the pathobiology of histiocytic sarcoma.

Commercial rodent diets differentially regulate autoimmune glomerulonephritis, epigenetics and microbiota in MRL/lpr mice

The course and severity of lupus in spontaneous murine lupus models varies among laboratories, which may be due to variations in diet, housing and/or local environmental conditions. In this study, we investigated the influence of common rodent diets while keeping other factors constant. Female lupus-prone MRL/lpr (MRL/MpJ-Faslpr/J) mice were subjected to the same housing conditions and given one of the three diets: Teklad 7013 containing isoflavone-rich soy and alfalfa, Harlan 2018 isoflavone-rich soy-based diet or Research Diets Inc. D11112226 (RD) purified-ingredients diet containing casein and no phytoestrogens. While the total caloric intake was similar among all three treatment groups, mice fed on the 2018 diet developed higher levels of proteinuria and mice fed on either 7013 or 2018 developed higher levels of glomerular immune complex deposition. Remarkably, mice fed the RD diet had markedly decreased proteinuria with diminished C3, total IgG, IgG1 and IgG3 immune complex deposition, along with reduced CD11b+ cellular infiltration into the glomeruli. The type of diet intake also influenced cytokine production, fecal microbiota (increased Lachnospiraceae in mice fed on 2018), altered microRNAs (miRNAs; higher levels of lupus-associated miR-148a and miR-183 in mice fed on 7013 and/or 2018) and altered DNA methylation. This is the first study to comprehensively compare the cellular, molecular and epigenetic effects of these commercial diets in murine lupus.

A NUP98-HOXD13 leukemic fusion gene leads to impaired class switch recombination and antibody production

Myelodysplastic syndrome is a clonal process characterized by ineffective hematopoiesis and progression to acute leukemia. Although many myelodysplastic syndrome and leukemic patients have compromised immunity, the role of underlying mutations in regulating immune function is poorly understood. Recent studies show that NUP98-HOXD13 (NHD13) fusion gene results in myelodysplastic syndrome and impairs lymphocyte differentiation in transgenic mice. In our studies, we sought to elucidate the mechanism by which NHD13 affects B-lymphocyte development and function. Based on our preliminary findings that transgenic mice had increased levels of IgM and reduced IgG1 and IgE, we hypothesized that the fusion gene might impair class switch recombination (CSR). Mice were immunologically challenged with dinitrophenol. NHD13 mice showed a marked reduction in B-lymphocyte differentiation in their bone marrow and spleen following dinitrophenol stimulation and had reduced production of dinitrophenol-specific antibodies. Spleen follicles from these mice were small and hypocellular, indicating failure of clonal expansion. When isolated NHD13 B lymphocytes were stimulated in vitro using Escherichia coli lipopolysaccharide or lipopolysaccharide + interleukin-4, they failed to undergo sufficient CSR and proliferation. Taken together, our findings show that expression of NUP98-HOXD13 impairs CSR and reduces the antibody-mediated immune response, in addition to its role in leukemia. Further delineation of the NUP98-HOXD13 transgene may reveal novel pathways involved in CSR.

Noncanonical NF-κB signaling and the essential kinase NIK modulate crucial features associated with eosinophilic esophagitis pathogenesis

ABSTRACT Eosinophilic esophagitis (EoE) is an allergic disease of the esophagus driven by T cell and eosinophil responses to dietary allergens, resulting in chronic mucosal inflammation. Few spontaneous animal models of esophageal eosinophilia exist, with most studies relying on artificial sensitization procedures. NF-κB-inducing kinase (NIK; MAP3K14) is a key signaling molecule of the noncanonical NF-κB (NFKB1) pathway, an alternative signaling cascade producing chemokines involved in lymphoid stroma development and leukocyte trafficking. Nik−/− mice have been shown to develop a hypereosinophilic syndrome in peripheral blood and major filtering organs; however, the gastrointestinal mucosa of these mice has not been well characterized. We show that Nik−/− mice develop significant, localized eosinophilic esophagitis that mimics human EoE, including features such as severe eosinophil accumulation, degranulation, mucosal thickening, fibrosis and basal cell hyperplasia. The remainder of the GI tract, including the caudal stomach, small intestine and colon, in mice with active EoE are unaffected, also similar to human patients. Gene expression patterns in esophageal tissue of Nik−/− mice mimics human EoE, with thymic stromal lymphopoetin (TSLP) in particular also elevated at the protein level. In gene expression data sets from human biopsy specimens, we further show that many genes associated with noncanonical NF-κB signaling are significantly dysregulated in EoE patients, most notably a paradoxical upregulation of NIK itself with concurrent upregulation of powerful protein-level destabilizers of NIK. These findings suggest that Nik−/− mice could be useful as a spontaneous model of specific features of EoE and highlight a novel role for noncanonical NF-κB signaling in human patients. Summary: Analyses of Nik–/– mice and human gene expression data reveal a new pathway involved in the development of eosinophilic esophagitis in human patients and mouse models of the disease. This article has an associated First Person interview with the first author of the paper as part of the supplementary information.