IL-10 KO Mice Research Articles

A55 INVESTIGATING THE ROLE OF ENDOGENOUS INTERLEUKIN-10 IN INTESTINAL EPITHELIAL CELLS AND HOMEOSTASIS

Abstract Background IL-10 is appreciated for its potent anti-inflammatory effects on leukocytes in mucosal immunity. However, far less attention has been paid to the impact of IL-10 on epithelial cells, which make up the crucial barrier interface between the host mucosa and the external environment. Furthermore, most studies examine the effects of exogenous IL-10, disregarding the possible presence and function of autocrine or paracrine IL-10 in the epithelium. Aims Using ex vivo organoids we aimed to examine the small intestinal epithelium for IL-10 and dissect any role for endogenously produced cytokine. Methods We growed small intestinal organoids (enteroids) from crypts isolated from C57BL/6 mice (WT) and IL-10-gene knockout mice (IL-10KO). Cellular markers were characterized through qpCR, while IL-10 and IL-10 receptor localization was characterized though immunofluorescence. Results We discovered that cells in WT enteroids expressed IL-10 and IL-10R1 constitutively throughout development. Immunofluorescent staining revealed that IL-10 localizes to Paneth cells and appears to be secreted apically. Having established that IL-10 is secreted in enteroids, we compared enteroids from IL-10KO versus WT mice. IL-10KO enteroids developed to morphologically resemble WT enteroids; however, we detected an imbalance with lower secretory cell markers over absorptive cell types in the IL-10KO enteroids, measured as less mRNA for lysozyme, cryptdins and mucin-2. Addition of IL-10 to IL-10KO enteroids did not correct these defects, but did ameliorate the lineage balance by reducing absorptive cell lineage markers (sucrose isomaltase). IL-10R1 was localized on both apical and basolateral side of cell in enteroids. We suspect that epithelial-derived IL-10 likely acts on apical IL-10R, which may conduct a different response from basolateral receptor stimulation. Conclusions In conclusion, IL-10 is present in the small intestinal epithelium; more remains to be determined regarding the role this cytokine plays in gut development and homeostasis. Funding Agencies NSERC

COMMON FOOD ADDITIVES ACCELERATE ONSET OF INFLAMMATORY BOWEL DISEASE IN MICE BY ALTERING MICROBIOME COMPOSITION AND HOST-MICROBE INTERACTION

Multiple factors contribute to inflammatory bowel disease (IBD) pathogenesis, including diet. Although correlations exist between the introduction of processed foods and a rise in IBD prevalence, it is not understood what components of processed foods drive disease pathogenesis or how. Despite a FDA classification of Generally Regarded As Safe (GRAS), food additives significantly impact microbe communities and phenotypes. We hypothesized that common food additives, such as maltodextrin (MDX) and carboxymethyl cellulose (CMC), alter intestinal microbes and increase the onset and progression of IBD. We tested this hypothesis using the interleukin-10 deficient (IL10KO) mouse model of spontaneous colitis. To standardize disease onset, IL10KO mice were pre-conditioned with fecal material from nucleotide-binding oligomerization domain 2 deficient mice (NOD2KO) to promote intestinal inflammation. Pre-conditioned IL10KO mice were randomized to chow diets containing either 1% MDX, 1% CMC, or a control diet. MDX and CMC accelerated the onset of colitis compared to the control diet. This was accompanied by elevated fecal lipocalin-2 (p<0.05) and serum amyloid A (p<0.01), intestinal infiltration of CD3+ cells, and intestinal pathology consistent with chronic inflammation (p<0.05). Although both dietary additives promote disease in this model, the molecular mechanisms involved appear to be distinct. Intestinal mucus modulates interactions of the microbiome and the host. Strikingly, goblet cells in MDX fed mice had reduced mucin granule content (∼50% of control diet) as assessed by Muc2 and Periodic Acid Schiff staining. This mucin depletion did not correlate with degree of disease activity, suggesting this deficiency is not a result of inflammation in MDX fed mice and was not observed in CMC fed mice or control diet mice. Food additives also altered the intestinal microbiome, with MDX fed mice demonstrating a significant decrease in microbiome alpha diversity (p<0.05, ANOVA), and both food additives resulting in a significant shift in beta diversity (R2=0.40, p=0.002, PERMANOVA) as compared to the control diet. Flagella expression by microbes was slightly elevated in CMC-fed mice, but not in MDX-fed mice, suggesting that these food additives have distinct actions on microbes. Magnitude of genus-level changes in microbial abundance correlated with disease severity as assessed by serum amyloid A levels. This data indicates that common food additives are not biologically inert substances, and may drive the progression of inflammatory bowel disease through additive-specific alterations of the microbiome and host-microbe interactions.

Interleukin-10 does not contribute to the anti-contractile nature of PVAT in health

Perivascular adipose tissue (PVAT) is protective and reduces contraction of blood vessels in health. PVAT is composed of adipocytes, multiple types of immune cells and stromal cells. Interleukin (IL)-10, an anti-inflammatory cytokine usually produced by T cells, B cells and macrophages, was identified as one of the highly expressed (mRNA) cytokines in the mesenteric PVAT of healthy rats. One report suggested that exogenous IL-10 causes relaxation of mouse mesenteric arteries, also suggesting that IL-10 maybe a potential anti-contractile factor. Hence, we hypothesized that PVAT-derived IL-10 causes vasorelaxation and/or reduces vasoconstriction, thus contributing to the anti-contractile nature of PVAT in health. Mesenteric arteries from rats and mice expressed the receptor for IL-10 (in tunica intima and media) as determined by immunohistochemistry. Mesenteric resistance arteries for rats and superior mesenteric artery for mice were used for isometric contractility studies. Increasing concentrations [0.4–100 ng/mL] of recombinant rat/mouse (rr/mr) IL-10 or vehicle was directly added to half-maximally constricted (phenylephrine, PE) vessels (without PVAT, with endothelium). IL-10 did not cause a direct vasorelaxation. Further, the ability of rrIL-10 to cause a rightward or downward shift of a vasoconstriction-response curve was tested in the rat. The vessels were incubated with rrIL-10 [100 ng/mL or 10 ng/mL] or vehicle for 1.5 h in the tissue bath followed by a cumulative PE [10−8–10−4 M] or U46619 [10−10–10−5 M] response curve. The maximal contractions and EC50 values were similar in IL-10 incubated vessels vs vehicle. Thus, acute exposure of exogenous IL-10 did not reduce local vasoconstriction. To further test if endogenous IL-10 from PVAT was anti-contractile, superior mesenteric arteries from IL-10 WT and KO mice, with and without PVAT, were subjected to increasing concentrations of PE. The anti-contractile nature of PVAT was preserved with both short-term and prolonged depletion (using younger and older mice, respectively) of endogenous IL-10 in males and females. Contrary to our hypothesis, PVAT-derived IL-10 neither caused vasorelaxation nor reduced local vasoconstriction directly/indirectly. Therefore, IL-10 does not contribute to the anti-contractile nature of PVAT in healthy rodents.

COMMON FOOD ADDITIVES ACCELERATE ONSET OF INFLAMMATORY BOWEL DISEASE IN MICE BY ALTERING MICROBIOME COMPOSITION AND HOST-MICROBE INTERACTION

Abstract Multiple factors contribute to inflammatory bowel disease (IBD) pathogenesis, including diet. Although correlations exist between the introduction of processed foods and a rise in IBD prevalence, it is not understood what components of processed foods drive disease pathogenesis or how. Despite a FDA classification of Generally Regarded As Safe (GRAS), food additives significantly impact microbe communities and phenotypes. We hypothesized that common food additives, such as maltodextrin (MDX) and carboxymethyl cellulose (CMC), alter intestinal microbes and increase the onset and progression of IBD. We tested this hypothesis using the interleukin-10 deficient (IL10KO) mouse model of spontaneous colitis. To standardize disease onset, IL10KO mice were pre-conditioned with fecal material from nucleotide-binding oligomerization domain 2 deficient mice (NOD2KO) to promote intestinal inflammation. Pre-conditioned IL10KO mice were randomized to chow diets containing either 1% MDX, 1% CMC, or a control diet. MDX and CMC accelerated the onset of colitis compared to the control diet. This was accompanied by elevated fecal lipocalin-2 (p&amp;lt;0.05) and serum amyloid A (p&amp;lt;0.01), intestinal infiltration of CD3+ cells, and intestinal pathology consistent with chronic inflammation (p&amp;lt;0.05). Although both dietary additives promote disease in this model, the molecular mechanisms involved appear to be distinct. Intestinal mucus modulates interactions of the microbiome and the host. Strikingly, goblet cells in MDX fed mice had reduced mucin granule content (~50% of control diet) as assessed by Muc2 and Periodic Acid Schiff staining. This mucin depletion did not correlate with degree of disease activity, suggesting this deficiency is not a result of inflammation in MDX fed mice and was not observed in CMC fed mice or control diet mice. Food additives also altered the intestinal microbiome, with MDX fed mice demonstrating a significant decrease in microbiome alpha diversity (p&amp;lt;0.05, ANOVA), and both food additives resulting in a significant shift in beta diversity (R2=0.40, p=0.002, PERMANOVA) as compared to the control diet. Flagella expression by microbes was slightly elevated in CMC-fed mice, but not in MDX-fed mice, suggesting that these food additives have distinct actions on microbes. Magnitude of genus-level changes in microbial abundance correlated with disease severity as assessed by serum amyloid A levels. This data indicates that common food additives are not biologically inert substances, and may drive the progression of inflammatory bowel disease through additive-specific alterations of the microbiome and host-microbe interactions.

Prox1-Dependent Stimulation of Lymphatic Function Ameliorates Mesenteric Lesions and Modifies the Composition of Microbiota in Experimental Crohn's Disease

Background: Prox1 is a transcription factor necessary for lymphatic function. The main aim of the current study was to investigate the potential role of Prox1 in lymphangiogenesis and lymphatic function, and analyze Prox1-dependent stimulation of lymphatic function on mesenteric lesions and the composition of microbiota in Crohn’s disease. Methods: Prox1flox/+, Tie2-CreERT2 and IL-10 KO mice were included. Disease activity and enterocolitis inflammation were assessed using a grading system. Lymphatic vessel density and lymphatic function were analyzed using immunohistochemistry and lymphangiography. The potential mechanism of Prox1 was analyzed. The effects of lymphatic function on mesenteric adipose tissue (MAT) and the composition of microbiota were evaluated. Results: Systemic delivery of AAV-Prox1 reduced disease activity index and the severity of chronic inflammation in IL-10 KO mice. Without compensatory response of Prox1, IL-10 KO+Prox1 KO mice developed serious inflammation in the colon. For lymphatic vessel, IL-10 KO+Prox1 KO mice showed lower lymphatic vessel density and less functional lymphatic vessels. IL-10 KO+AAV-Prox1 mice showed significantly increased lymphatic vessel density. Delivery of AAV-Prox1 also promoted lymphatic drainage function. The Prox1/VEGFC/VEGFR3 pathway played an important role in lymphangiogenesis and lymphatic function. Additionally, Prox1-dependent stimulation of lymphatic function ameliorated hypertrophy of MAT in IL-10 KO mice. Delivery of AAV-Prox1 also modified the composition of microbiota, the proportion of Firmicutes increased and Bacteroidetes decreased in IL-10 KO+AAV-Prox1 mice compared with IL-10 KO mice. An increase in the diversity of gut microbiota in IL-10 KO+ AAV-Prox1 mice was observed. Conclusions: Our findings demonstrated that Prox1 played the critical role in the lymphangiogenesis and lymphatic function. Additionally, Prox1-dependent stimulation of lymphatic function could ameliorate hypertrophy of MAT and modify the composition of microbiota in experimental Crohn’s disease. Funding Statement: This work was partly supported by National Natural Science Foundation of China (Grant 81670471, 81770556 and 81570500). Declaration of Interests: The authors declare that they have no conflicts of interests. Ethics Approval Statement: All animal protocols were approved by the Institutional Ethics Committee of the Jinling Hospital, Medical School of Nanjing University, Nanjing, China.

Interleukin 4 deficiency limits the development of a lupus-like disease in mice triggered by phospholipids in a non-bilayer arrangement.

Non-bilayer phospholipids arrangements (NPAs) are transient molecular associations different from lipid bilayers. When they become stable, they can trigger a disease in mice resembling human lupus, which is mainly characterized by the production of anti-NPA IgG antibodies. NPAs are stabilized on liposomes or cell bilayers by the drugs procainamide or chlorpromazine, which produce drug-induced lupus in humans. Here, we evaluated the participation of the TH 2 response, through its hallmark cytokine IL-4, on the development of the lupus-like disease in mice. Wild-type or IL-4 knockout BALB/c mice received liposomes bearing drug-induced NPAs, the drugs alone, or an anti-NPA monoclonal antibody (H308) to induce the lupus-like disease (the last two procedures stabilize NPAs on mice cells). IL-4 KO mice showed minor disease manifestations, compared to wild-type mice, with decreased production of anti-NPA IgG antibodies, no anti-cardiolipin, anti-histones and anticoagulant antibodies, and no kidney or skin lesions. In these mice, H308 was the only inducer of anti-NPA IgG antibodies. These findings indicate that IL-4 has a central role in the development of the murine lupus-like disease induced by NPA stabilization.

The role of IL-10 in immune responses against Pseudomonas aeruginosa during acute lung infection.

Pseudomonas aeruginosa is considered an opportunistic pathogen of great clinical importance. The clearance of this bacterium occurs through recognition of the pathogen by innate immune system receptors, leading to a lung inflammatory response. However, this response must be controlled via immunoregulatory pathways. In this study, we evaluate the role of endogenous murine IL-10 after acute infection with the virulent strain P. aeruginosa PA14. To assess the role of IL-10, intratracheal infection with the PA14 strain was performed in C57BL/6 or IL-10 KO mice. The PA14 strain was recovered in both types of animals, although IL-10 KO mice presented a higher number of viable bacteria in the lung when compared to the C57BL/6 group. Histopathological and stereological analyses showed that IL-10 KO mice had higher tissue damage and inflammatory infiltrate when compared to control animals. The activity of MMP-9 but not MMP-2, as well as IL-6 and TNF-α expression, were augmented in the lungs of infected animals and was much more evident in IL-10 KO animals when compared to the other analyzed groups. This work indicates that endogenous IL-10 control P. aeruginosa infection, the expression of pro-inflammatory genes, MMP-9 activity and histopathological processes of the infectious process in question.

Tissue Engineered Vascular Graft Recipient Interleukin 10 Status Is Critical for Preventing Thrombosis.

Tissue engineered vascular grafts (TEVGs) are a promising technology, but are hindered by occlusion. Seeding with bone-marrow derived mononuclear cells (BM-MNCs) mitigates occlusion, yet the precise mechanism remains unclear. Seeded cells disappear quickly and potentially mediate an anti-inflammatory effect through paracrine signaling. Here, a series of reciprocal genetic TEVG implantations plus recombinant protein treatment is reported to investigate what role interleukin-10, an anti-inflammatory cytokine, plays from both host and seeded cells. TEVGs seeded with BM-MNCs from wild-type and IL-10 KO mice, plus unseeded grafts, are implanted into wild-type and IL-10 KO mice. Wild-type mice with unseeded grafts also receive recombinant IL-10. Serial ultrasound evaluates occlusion and TEVGs are harvested at 14 d for immunohistochemical analysis. TEVGs in IL-10 KO mice have significantly higher occlusion incidence compared to wild-type mice attributed to acute (<3 d) thrombosis. Cell seeding rescues TEVGs in IL-10 KO mice comparable to wild-type patency. IL-10 from the host and seeded cells do not significantly influence graft inflammation and macrophage phenotype, yet IL-10 treatment shows interesting biologic effects including decreasing cell proliferation and increasing M2 macrophage polarization. IL-10 from the host is critical for preventing TEVG thrombosis and seeded BM-MNCs exert a significant anti-thrombotic effect in IL-10 KO mice.

IL-10-Dependent and -Independent Mechanisms Are Involved in the Cardiac Pathology Modulation Mediated by Fenofibrate in an Experimental Model of Chagas Heart Disease.

IL-10 is an anti-inflammatory cytokine that plays a significant role in the modulation of the immune response in many pathological conditions, including infectious diseases. Infection with Trypanosoma cruzi (T. cruzi), the etiological agent of Chagas disease, results in an ongoing inflammatory response that may cause heart dysfunction, ultimately leading to heart failure. Given its infectious and inflammatory nature, in this work we analyzed whether the lack of IL-10 hinders the anti-inflammatory effects of fenofibrate, a PPARα ligand, in a murine model of Chagas heart disease (CHD) using IL-10 knockout (IL-10 KO) mice. Our results show fenofibrate was able to restore the abnormal cardiac function displayed by T. cruzi-infected mice lacking IL-10. Treatment with fenofibrate reduced creatine kinase (CK) levels in sera of IL-10 KO mice infected with T. cruzi. Moreover, although fenofibrate could not modulate the inflammatory infiltrates developing in the heart, it was able to reduce the increased collagen deposition in infected IL-10 KO mice. Regarding pro-inflammatory mediators, the most significant finding was the increase in serum IL-17. These were reduced in IL-10 KO mice upon fenofibrate treatment. In agreement with this, the expression of RORγt was reduced. Infection of IL-10 KO mice increased the expression of YmI, FIZZ and Mannose Receptor (tissue healing markers) that remained unchanged upon treatment with fenofibrate. In conclusion, our work emphasizes the role of anti-inflammatory mechanisms to ameliorate heart function in CHD and shows, for the first time, that fenofibrate attains this through IL-10-dependent and -independent mechanisms.

IL-10 from dendritic cells but not from T regulatory cells protects against cisplatin-induced nephrotoxicity.

Interleukin-10 (IL-10), a cytokine with anti-inflammatory effects, is produced by renal parenchymal cells and bone marrow derived cells. Both endogenous and exogenous IL-10 are protective in cisplatin-induced acute kidney injury. However, the source of endogenous IL-10 in cisplatin-induced nephrotoxicity is not clear. Bone marrow chimera experiments in IL10-KO mice indicated that bone marrow derived cells were the primary source of IL-10 in cisplatin nephrotoxicity. Cell specific deletion of IL-10 in T regulatory cells and dendritic cells was accomplished using Foxp3 and CD11c driven cre recombination in IL10flox/flox mice, respectively. Upon treatment with cisplatin, both the IL10flox/flox and the Foxp3YFP-Cre x IL10flox/flox mice developed similar degrees of kidney injury. However, mice with the dendritic cell deletion of IL-10 showed more severe structural and functional changes in the kidney compared to the IL10flox/flox mice. These results indicate that IL-10 from dendritic cells but not from T regulatory cells offers significant endogenous protection against cisplatin induced nephrotoxicity.

Modulation of Interleukin-1 and -18 Mediated Injury in Donation after Circulatory Death Mouse Hearts

BackgroundDonation after circulatory death donors (DCD) can expand the donor pool for heart transplantation, which primarily depends on brain death donors. Ischemia and reperfusion injury are inherent to the DCD process. We hypothesize that pharmacologic inhibition of interleukin-1 (IL-1) and/or IL-18 is protective to DCD hearts. Materials and methodsFollowing clinical protocol, in-situ ischemia time in control beating-heart donor (CBD) and DCD groups was less than 5 and 40 min, respectively. Wild type (WT) C57Bl6/j, IL-1 receptor type I knockout (IL-1RI-KO), and IL-18 KO mice were used. Hearts were reanimated for 90 min on a Langendorff system with Krebs-Henseleit buffer at 37°C, to assess physiologic parameters. Recombinant IL-1 receptor antagonist (IL-1Ra) and/or IL-18 binding protein (IL-18BP) were added to the Krebs-Henseleit buffer to inhibit IL-1 and/or the IL-18 signaling, respectively. ResultsDeveloped pressure and ± dP/dt were significantly impaired in the DCD-WT group compared to CBD-WT (P ≤ 0.05). Troponin release was higher in DCD-WT groups. Functional parameters were preserved, and troponin release was significantly less in the DCD knockout groups. Heart function was improved in DCD groups treated with IL-1Ra or IL-18BP compared to the DCD-WT group. ConclusionsHeart function was significantly impaired in the DCD-WT group compared to CBD-WT. Genetic deletion or pharmacologic blockade of IL-1 or IL-18 was protective to DCD hearts.

Targeted Deletion of Interleukin-6 in a Mouse Model of Chronic Inflammation Demonstrates Opposing Roles in Aging: Benefit and Harm.

Chronic inflammation (CI) in older adults is associated with reduced health span and life span. Interleukin-6 (IL-6) is one CI marker that is strongly associated with adverse health outcomes and mortality in aging. We have previously characterized a mouse model of frailty and chronic inflammatory pathway activation (IL-10tm/tm, IL-10 KO) that demonstrates the upregulation of numerous proinflammatory cytokines, including IL-6. We sought to identify a more specific role for IL-6 within the context of CI and aging and developed a mouse with targeted deletion of both IL-10 and IL-6 (IL-10tm/tm/IL-6tm/tm, DKO). Phenotypic characteristics, cytokine measurements, cardiac myocardial oxygen consumption, physical function, and survival were measured in DKO mice and compared to age- and gender-matched IL-10 KO and wild-type mice. Our findings demonstrate that selective knockdown of IL-6 in a frail mouse with CI resulted in the reversal of some of the CI-associated changes. We observed increased protective mitochondrial-associated lipid metabolites, decreased cardiac oxaloacetic acid, improved myocardial oxidative metabolism, and better short-term functional performance in DKO mice. However, the DKO mice also demonstrated higher mortality. This work shows the pleiotropic effects of IL-6 on aging and frailty.

T cells modulate IL-4 expression by eosinophil recruitment within decellularized scaffolds to repair nerve defects

Decellularized nerve, or acellular nerve allografts (ANAs), are an increasingly used alternative to nerve autografts to repair nerve gaps to facilitate regeneration. The adaptive immune system, specifically T cells, plays a role in promoting regeneration upon these ANA scaffolds. However, how T cells promote regeneration across ANAs is not clear. Here, we show that T cells accumulate within ANAs repairing nerve gaps resulting in regulation of cytokine expression within the ANA environment. This in turn ultimately leads to robust nerve regeneration and functional recovery. Nerve regeneration across ANAs and functional recovery in Rag1KO mice was limited compared to wild-type (WT) mice. Prior to appreciable nerve regeneration, ANAs from Rag1KO mice contained fewer eosinophils and reduced IL-4 expression compared to ANAs from WT mice. During this period, both T cells and eosinophils regulated IL-4 expression within ANAs. Eosinophils represented the majority of IL-4 expressing cells within ANAs, while T cells regulated IL-4 expression. Finally, an essential role for IL-4 during nerve regeneration across ANAs was confirmed as nerves repaired using ANAs had reduced regeneration in IL-4 KO mice compared to WT mice. Our data demonstrate T cells regulate the expression of IL-4 within the ANA environment via their effects on eosinophils. Statement of significanceThe immune system has been emerging as a critical component for tissue regeneration, especially when regeneration is supported upon biomaterials. The role of T cells, and their roles in the regeneration of nerve repaired with biomaterials, is still unclear. We demonstrated that when nerves are repaired with decellularized nerve scaffolds, T cells contribute to regeneration by regulating cytokines. We focused on their regulation of cytokine IL-4. Unexpectedly, T cells do not produce IL-4, but instead regulate IL-4 by recruiting eosinophils, which are major cellular sources of IL-4 within these scaffolds. Thus, our work demonstrated how IL-4 is regulated in a model biomaterial, and has implications for improving the design of biomaterials and understanding immune responses to biomaterials.

Interleukin-6 and the Gut Microbiota Influence Melanoma Progression in Obese Mice

There is a strong correlation between obesity and cancer. Here, we investigated the influence of IL-6 and gut microbiota of obese mice in melanoma development. We first evaluated B16F10 melanoma growth in preclinical models for obesity: mice deficient for leptin (ob/ob) or adiponectin (AdpKO) and in wild-type mice (WT, C57BL/6J) fed a high-fat diet (HFD; 60% kcal from fat) for 12 weeks. The survival rates of ob/ob and HFD-fed mice were lower than those of their respective controls. AdpKO mice also died earlier than WT control mice. We then verified the involvement of IL-6 signaling in obese mice that were inoculated with melanoma cells. Both ob/ob and AdpKO mice had higher circulating IL-6 levels than wild-type mice. Melanoma tumor volumes in IL-6 KO mice fed an HFD were reduced compared to those of WT mice subjected to the same diet. Also evaluated the effect of microbiota in tumor development. Cohousing and fecal matter transfer experiments revealed that microbiota from ob/ob mice can stimulate tumor development in lean WT mice. Taken together, our data show that in some conditions IL-6 and the gut microbiota are key mediators that link obesity and melanoma.

More roles of IL-4 than being as an antagonist of IFN-γ in experimental autoimmune uveitis

Abstract IL-4 appears to be beneficial for some autoimmune diseases. Despite its role in antagonizing pathogenic Th1 response, our recent work has demonstrated IL-4 possesses functions affecting the regulatory T (Treg) cells. Here we aimed to identify the role of IL-4 in the development of experimental autoimmune uveitis (EAU). EAU was induced in WT and IL-4 KO mice via active interphotoreceptor retinoid binding protein (IRBP) immunization, and the disease development was monitored by funduscopic and histology analysis as well as the IRBP-specific immune responses by flow cytometric analysis and ELISA. It showed that the onset of disease, if the clinical score equals to 1, was day 14 and 20 in IL-4KO and WT mice, respectively. The fundoscopic images demonstrated the more and bigger size of lesions, increased leukocyte infiltration, vasculitis and neovascularization in IL-4KO mice. The histological analysis also confirmed the mononuclear cell infiltration. Moreover, Th1 effector is known as the dominant pathogenic mediators, whereas Treg cells play an important and indispensable role in control of EAU progression and disease remission. The splenic T cells from IL-4 KO EAU animals produced significantly elevated level of IFN-γ in responding to IRBP stimulation. However, there seems no significant but some alternation in the presence of Treg cells (Foxp3+) among CD4+CD25+ T cells in the spleens and lymph nodes of IL-4 KO and WT mice. These results demonstrate the lack of IL-4 disrupting the induction of EAU and leading to an increased disease severity through not only antagonizing IFN-γ but also involved mechanisms of immune-regulation. Therefore, IL-4 might play more roles than being just an antagonist of IFN-γ in autoimmune uveitis.

COX inhibition enhances allergen-induced IL-33 release and ILC2 responses in mouse lungs

Abstract The cyclooxygenase (COX) metabolic pathway has regulatory functions in immune responses and inflammation. However, the effect of the COX pathway on innate airway inflammation induced by protease-containing allergens such as Alternaria alternata is not fully defined. Here we show that COX inhibition augmented innate lung type 2 responses after repeated airway exposures to Alternaria extract in mice. We treated wild type BALB/c and IL-33 KO mice with either the COX inhibitor indomethacin or vehicle in drinking water and challenged mice intranasally with Alternaria extract for 4 consecutive days to induce innate lung inflammation. We found that indomethacin significantly increased the numbers of group 2 innate lymphoid cells (ILC2) and IL-5+IL-13+ ILC2 in the lung. Indomethacin also increased type 2 cytokine (IL-5 and IL-13) responses, the percentages of eosinophils, and mucus production in the lung. IL-33 is required for Alt-induced lung ILC2 responses, and indomethacin did not change IL-5 and IL-13 expression in IL-33 KO mice. Consistently, indomethacin increased the release of IL-33 in bronchoalveolar lavage fluid after Alternaria challenge, suggesting that more IL-33 was available for ILC2 activation. Indomethacin also increased reactive oxygen species (ROS) production in the lung, providing a possible mechanism for the increased IL-33 release. Although contrasting effects of PGD2 and PGE2/PGI2 on ILC2 responses have been previously reported, the overall effect of COX pathway on ILC2 function is inhibitory in Alternaria extract-induced airway innate type 2 responses.

Abstract B84: Decipher the role of IL-33 as an activator of NK cells’ antitumor activity

Abstract Interleukin (IL)-33 is an alarmin belonging to the IL-1 family. Through its receptor ST2, IL-33 promotes both type 1 and type 2 immune responses, depending on the type of responding cells and the microenvironment in damaged tissues. Consistently, paradoxical roles of IL-33 have been reported in the context of cancer. These observations prompted us to investigate i) the expression of IL-33/ST2 in breast tumors and ii) the role of IL-33/ST2 in NK cell activation in physiologic and tumor contexts. Using immunohistochemistry (IHC) and transcriptomic analyses, we observed that IL-33 is expressed at higher levels in ductal carcinoma in situ (DCIS) compared to invasive breast cancer (IBC), especially in the stroma and in luminal BC subtype. In situ, IL-33 was mainly detected in endothelial cells and at lower extent in scattered cells within the stroma of breast tumors. Furthermore, we unraveled a new pathway for NK cells’ activation where IL-12 upregulates ST2 on human NK cells, which in turn become responsive to IL-33 by secreting high levels of IFN-γ and increasing their cytotoxic activity. This effect was specific to a subset of human CD56dim NK cells (20%) and was dependent on STAT-4 phosphorylation. In mice, we also observed a strong activation of spleen NK cell by IL-33 in combination with IL-12 in vitro. Finally, using IL-33ko mice, preliminary results show a contribution of endogenous IL-33 in the prevention of experimental lung metastasis development following B16 iv injection in therapeutic settings using exogenous administration of IL-12. Following up on these results, our aim is now to i) better characterize IL-33-responsive NK cells subpopulation in blood, ii) understand why human CD56bright NK cells do not upregulate ST2 despite response to IL-12 by phosphorylating STAT-4, iii) characterize NK cells’ response to IL-33 in human breast tumors, iv) evaluate ST2 expression by immune cells infiltrating breast and ovarian tumors, and v) confirm the activating role of IL-33 on NK cells’ biology in tumor models in vivo. All together, our observations are in favor of an NK-mediated antitumor role of IL-33 that we are currently pursuing as a potential novel therapeutic strategy in cancer. Citation Format: Anais Eberhardt, Elena Blanc, Emilie Lardenois, Sarah Renaudineau, Jennifer Herbulot, Benoit Dumont, Isabelle Durand, Emilie Charrier, Pauline Schmitt, Jean-Philippe Girard, Antoine Marçais, Thierry Walzer, Christophe Caux, Nathalie Bendriss-Vermare. Decipher the role of IL-33 as an activator of NK cells’ antitumor activity [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B84.

Anaphylaxis induced by Thalassophryne nattereri venom in mice is an IgE/IgG1-mediated, IL-4-dependent phenomenon

We hypothesized that beyond the Thalassophryne nattereri venoms ability to induce in mice a strong specific-Th2 response with high levels of specific IgE/IgG1, it would be able to trigger anaphylaxis in sensitized individuals. To investigate whether the venom is capable of inducing an allergic reaction in mice and characterize soluble and cellular mediators involved in this process, BALB/c female mice were sensitized intraperitoneally with decreasing-dose of venom at weekly intervals for 4 weeks and challenged by intraperitoneal, oral or epicutaneous routes with venom 2 weeks later. Our data show that sensitized-mice challenged by all routes showed intense symptoms of anaphylaxis, dependent on the anaphylactic IgG1 and IgE antibodies and mast cells. The late-phase reaction developed after initial symptoms was characterized by the influx of eosinophils, dependent on IL-5, IL-17A and eotaxin produced by Th2 cells in inflamed lungs and skin draining lymph-nodes. Using C57BL/6 deficient mice we demonstrated that IL-4 KO mice failed to develop anaphylactic symptoms or local Th2 inflammation, producing low levels of IgG1 and increased levels of IgG2a. Together our results demonstrated that the venom of T. nattereri has allergenic proteins that can trigger an allergic process, a phenomenon IgE-IgG1 dependent, IL-4-mediated and negatively regulated by IFN-γ.

Dynamics of cortical progenitors and production of subcerebral neurons are altered in embryos of a maternal inflammation model for autism.

The broad impairments in cognitive and neurologic functioning found in Autism Spectrum Disorder (ASD) patients are thought to originate during early prenatal developmental stages. Indeed, postmortem and imaging studies in ASD patients detected white-matter abnormalities, as well as prefrontal and temporal cortex deficits, evident from early childhood. Here, we used Maternal Immune Activation (MIA), a mouse model for ASD, in which the offsprings exhibit Autistic-like behaviors as well as cortical abnormalities. However, the dynamics that influence the number and the identity of newly born cortical neurons following maternal inflammation remains unknown. Our study shows early changes in the duration of the S-phase of PAX6+ progenitors, leading to an increased proportion of neurogenic divisions and a reciprocal decrease in the proliferative divisions. In two different time points of maternal inflammation, MIA resulted in an overproduction of CTIP2+ cortical neurons, which remained overrepresented at the end of gestation and in postnatal mice. Interestingly, MIA-resistant IL6-KO mice did not exhibit these changes. Lastly, we propose that elevated levels of the transcription factor PAX6 following MIA supports the overproduction of CTIP2+ neurons. Taken together, our data reveals a possible link between maternal immune activation and the excess of cortical neurons found in the cortex of ASD patients.

Elucidating the Role of IL6 in Stress Erythropoiesis and in the Development of Anemia Under Inflammatory Conditions

Anemia of inflammation, also known as anemia of chronic disease is the second most common anemia after iron deficiency anemia. The predominant regulators of AI are the cytokine-interleukin-6 (IL6) and the hormone hepcidin (Hamp). IL6 has been implicated in inducing expression of hepcidin. Published data from our lab have shown that lack of IL6 or hepcidin in knockout mouse models (IL6-KO and Hamp-KO) injected with the heat-killed pathogen Brucella abortus(BA) results in recovery from anemia but interestingly the pattern of the recovery was different in IL6-KO and Hamp-KO mice, suggesting that the two proteins contribute independently to AI. Here, we validated the independent role of IL6 and Hamp in AI by generating a double-knockout (DKO) mouse model lacking the expression of both. In the first few days following BA administration, we observed severe reduction in the total number of BM cells in each model followed by a slow recovery in erythroid and multilineage hematopoietic cells. The recovery, initially, was more sustained in the BA-treated-DKO model. In particular, in the first week, BA-treated-DKO mice showed an increased number of erythroblasts in the bone marrow (BM) and spleen as seen in comparison to IL6-KO and Hamp-KO. IL6-KO mice showed an intermediate recovery profile when compared to DKO and Hamp-KO, the last one showing the worst profile in the BM. Interestingly, when the reticulocyte count in the DKO mice was compared to that of IL6-KO and Hamp-KO mice, it showed a biphasic trend, with a significant increase in number during the 2nd week, followed by a significant reduction during the 3rd week. We hypothesized that the initial surge in reticulocyte count in DKO was due to lack of hepcidin, which increases iron availability to erythroid cells, and concurrent lack of IL6, which favors BM erythropoiesis in presence of inflammatory stimuli. However, we also speculated that the excess of iron (as NTBI), which accumulates during the first two weeks, leads to oxidative stress and erythroid cell death in presence of inflammatory cytokines, despite the absence of IL6. We also surmised that, during the second week, a second wave of inflammatory cytokines is triggered by the adaptive response in response to the BA that would explain the negative effect on erythropoiesis after the initial recovery. To assess this hypothesis, we utilized an inflammation panel to analyze the cytokine expression in WT animals treated with PBS or BA at 6 hours, 24 hours and then around ~2 weeks. The cytokine levels were normalized after 24 hours. However, around two weeks, we observed a novel surge of cytokines such as IFN-g and TNFa in the BA treated mice, indicating their role in innate (immediate effect; 6 hours) and adaptive immune response, which activated a second wave of inflammation (around 2 weeks, during the recovery of hematopoiesis in the BM). Interestingly, while we observed oxidative stress and defective erythropoiesis in the bone marrow, this was not seen in the spleen, where increased and extramedullary erythropoiesis sustained some level of RBC production. Since the BA-treated-IL6-KO did not show any major defect in the BM after two weeks, we challenged them with administration of iron dextran. Upon treatment, also the IL6-KO mice treated with both BA and iron dextran shown increased production of reactive oxygen species as well as a defect in bone marrow erythropoiesis, similarly as in DKO or Hamp-KO mice, thereby explaining the plausible reason of reduced erythropoiesis in the bone-marrow. Furthermore, to identify mechanisms leading to oxidative stress, we established an in-vitro culture system where primary murine bone marrow cells were cultured for 18-20 hours in presence of serum isolated after 6hrs from either PBS treated or BA treated C57BL/6 mice. With the help of confocal microscopy, we observed an increase in mitochondrial superoxide in the cells treated with BA serum; interestingly we have also seen a decrease in Ter 119 population in the cells cultured with BA treated serum implicating that the erythroid cells are dying. To further investigate the downstream players related to the death of erythroid progenitors we are currently investigating the role caspase 1 (a major regulator in pyroptosis) and Gata-1. In conclusion, this study is elucidating some of the mechanisms associated with the anemia triggered by inflammation with the potential to identify new targets and treatments. Disclosures Rivella: Disc medicine, Protagonist, LIPC, Meira GTx: Consultancy; Meira GTx, Ionis Pharmaceutical: Membership on an entity's Board of Directors or advisory committees.