Ribonuclease inhibitor 1 regulates erythropoiesis by controlling GATA1 translation.

Ribosomal proteins (RP) regulate specific gene expression by selectively translating subsets of mRNAs. Indeed, in Diamond-Blackfan anemia and 5q- syndrome, mutations in RP genes lead to a specific defect in erythroid gene translation and cause anemia. Little is known about the molecular mechanisms of selective mRNA translation and involvement of ribosomal-associated factors in this process. Ribonuclease inhibitor 1 (RNH1) is a ubiquitously expressed protein that binds to and inhibits pancreatic-type ribonucleases. Here, we report that RNH1 binds to ribosomes and regulates erythropoiesis by controlling translation of the erythroid transcription factor GATA1. Rnh1-deficient mice die between embryonic days E8.5 and E10 due to impaired production of mature erythroid cells from progenitor cells. In Rnh1-deficient embryos, mRNA levels of Gata1 are normal, but GATA1 protein levels are decreased. At the molecular level, we found that RNH1 binds to the 40S subunit of ribosomes and facilitates polysome formation on Gata1 mRNA to confer transcript-specific translation. Further, RNH1 knockdown in human CD34+ progenitor cells decreased erythroid differentiation without affecting myelopoiesis. Our results reveal an unsuspected role for RNH1 in the control of GATA1 mRNA translation and erythropoiesis

IL-1β Suppresses Innate IL-25 and IL-33 Production and Maintains Helminth Chronicity.

Approximately 2 billion people currently suffer from intestinal helminth infections, which are typically chronic in nature and result in growth retardation, vitamin A deficiency, anemia and poor cognitive function. Such chronicity results from co-evolution between helminths and their mammalian hosts; however, the molecular mechanisms by which these organisms avert immune rejection are not clear. We have found that the natural murine helminth, Heligmosomoides polygyrus bakeri (Hp) elicits the secretion of IL-1β in vivo and in vitro and that this cytokine is critical for shaping a mucosal environment suited to helminth chronicity. Indeed in mice deficient for IL-1β (IL-1β(-/-)), or treated with the soluble IL-1βR antagonist, Anakinra, helminth infection results in enhanced type 2 immunity and accelerated parasite expulsion. IL-1β acts to decrease production of IL-25 and IL-33 at early time points following infection and parasite rejection was determined to require IL-25. Taken together, these data indicate that Hp promotes the release of host-derived IL-1β that suppresses the release of innate cytokines, resulting in suboptimal type 2 immunity and allowing pathogen chronicity

Diet, gut microbiota and immune responses

The fields of immunology, microbiology, nutrition and metabolism are rapidly converging. Here we expand on a diet-microbiota model as the basis for the greater incidence of asthma and autoimmunity in developed countries

Inflammasome-independent functions of NAIPs and NLRs in the intestinal epithelium

The gut relies on the complex interaction between epithelial, stromal and immune cells to maintain gut health in the face of food particles and pathogens. Innate sensing by the intestinal epithelium is critical for maintaining epithelial barrier function and also orchestrating mucosal immune responses. Numerous innate pattern recognition receptors (PRRs) are involved in such sensing. In recent years, several Nucleotide-binding-domain and Leucine-rich repeat-containing receptors (NLRs) have been found to partake in pathogen or damage sensing while also being implicated in gut pathologies, such as colitis and colorectal cancer (CRC). Here, we discuss the current literature focusing on NLR family apoptosis inhibitory proteins (NAIPs) and other NLRs that have non-inflammasome roles in the gut. The mechanisms behind NLR-mediated protection often converges on similar signalling pathways, such as STAT3, MAPK and NFκB. Further understanding of how these NLRs contribute to the maintenance of gut homeostasis will be important for understanding gut pathologies and developing new therapies

Bacterial cancer therapy in autochthonous colorectal cancer affects tumor growth and metabolic landscape

Bacterial cancer therapy (BCT) shows great promise for treatment of solid tumors, yet basic mechanisms of bacterial-induced tumor suppression remain undefined. Attenuated strains of Salmonella enterica serovar Typhimurium (STm) have commonly been used in mouse models of BCT in xenograft and orthotopic transplant cancer models. We aimed to better understand the tumor epithelium–targeted mechanisms of BCT by using autochthonous mouse models of intestinal cancer and tumor organoid cultures to assess the effectiveness and consequences of oral treatment with aromatase A–deficient STm (STm(Δ)aroA). STm(Δ)aroA delivered by oral gavage significantly reduced tumor burden and tumor load in both a colitis-associated colorectal cancer (CAC) model and in a spontaneous Apc(min/+) intestinal cancer model. STm(Δ)aroA colonization of tumors caused alterations in transcription of mRNAs associated with tumor stemness, epithelial-mesenchymal transition, and cell cycle. Metabolomic analysis of tumors demonstrated alteration in the metabolic environment of STm(Δ)aroA-treated tumors, suggesting that STm(Δ)aroA imposes metabolic competition on the tumor. Use of tumor organoid cultures in vitro recapitulated effects seen on tumor stemness, mesenchymal markers, and altered metabolome. Furthermore, live STm(Δ)aroA was required, demonstrating active mechanisms including metabolite usage. We have demonstrated that oral BCT is efficacious in autochthonous intestinal cancer models, that BCT imposes metabolic competition, and that BCT has direct effects on the tumor epithelium affecting tumor stem cells

Hp infection elicits IL-1β secretion.

<p>(<b>A–E</b>) Mice were administered 200 L3 Hp by oral gavage. IL-1β protein levels were measured by ELISA in (<b>A</b>) the peritoneal wash and (<b>B</b>) intestinal tissue culture supernatants at the indicated timepoints. (<b>C</b>) Hp worm counts were performed for defined segments of the small intestine from WT (C57BL/6) at 13 dpi. (<b>D</b>) IL-1β was measured by ELISA for duodenum tissue culture supernatants of day 6 infected bone marrow chimera mice (donor strain/recipient strain). Results are representative of at least 3 independent experiments (n = 5 per group) and expressed as mean ± SEM. (<b>E</b>) Intestinal lamina propria CD11b⁺ and CD11b⁻ cells were isolated at 6 dpi and analyzed by Western blot for IL-1β expression. Band intensity for IL-1β and β-actin was determined using Adobe Photoshop CS3. The ratio between IL-1β and the control protein β-actin band intensity was then determined. IL-1β is expressed as percent of β-actin intensity. (<b>F</b>) BMMs from WT (C57BL/6), Trif<i>^−/−</i> or MyD88<i>^−/−</i> mice were stimulated <i>in vitro</i> with HPL5 (100 µg/mL), HES (5 µg/mL) or P.HES (5 µg/mL) for 4 hours and cell extracts were analyzed for pro-IL-1β expression by Western blot. (<b>G</b>) BMMs from WT (C57BL/6), Asc<i>^−/−</i> or Nlrp<i>3^−/−</i> mice were stimulated <i>in vitro</i> with P.HES, HPL5 or LPS plus MSU and culture supernatants (SN) were analyzed for active IL-1β by ELISA. Cell extracts (XT) and SN were also analyzed for pro- or mature- IL-1β by Western blot. Pro-Casp1 was used as a control protein. XT blots for IL-1β and Casp1 demonstrate the pro-forms, and the observed lower bands in the IL-1β and Casp1 blots are cleavage products. Error bars represent means of triplicate cultures ± SEM and the experiment was repeated 3 times.</p