Pathological Type-2 Immune Response, Enhanced Tumor Growth, and Glucose Intolerance in Retnlß (RELMß) Null Mice: A Model of Intestinal Immune System Dysfunction in Disease Susceptibility.

Resistin, and its closely related homologs, the resistin-like molecules (RELMs) have been implicated in metabolic dysregulation, inflammation, and cancer. Specifically, RELMß, expressed predominantly in the goblet cells in the colon, is released both apically and basolaterally, and is hence found in both the intestinal lumen in the mucosal layer as well as in the circulation. RELMß has been linked to both the pathogenesis of colon cancer and type 2 diabetes. RELMß plays a complex role in immune system regulation, and the impact of loss of function of RELMß on colon cancer and metabolic regulation has not been fully elucidated. We therefore tested whether Retnlß (mouse ortholog of human RETNLß) null mice have an enhanced or reduced susceptibility for colon cancer as well as metabolic dysfunction. We found that the lack of RELMß leads to increased colonic expression of T helper cell type-2 cytokines and IL-17, associated with a reduced ability to maintain intestinal homeostasis. This defect leads to an enhanced susceptibility to the development of inflammation, colorectal cancer, and glucose intolerance. In conclusion, the phenotype of the Retnlß null mice unravels new aspects of inflammation-mediated diseases and strengthens the notion that a proper intestinal barrier function is essential to sustain a healthy phenotype.

Acidic chitinase primes the protective immune response to gastrointestinal nematodes.

Acidic mammalian chitinase (AMCase) is known to be induced by allergens and helminths, yet its role in immunity is unclear. Using AMCase-deficient mice, we show that AMCase deficiency reduced the number of group 2 innate lymphoid cells during allergen challenge but was not required for establishment of type 2 inflammation in the lung in response to allergens or helminths. In contrast, AMCase-deficient mice showed a profound defect in type 2 immunity following infection with the chitin-containing gastrointestinal nematodes Nippostrongylus brasiliensis and Heligmosomoides polygyrus bakeri. The impaired immunity was associated with reduced mucus production and decreased intestinal expression of the signature type 2 response genes Il13, Chil3, Retnlb, and Clca1. CD103(+) dendritic cells, which regulate T cell homing, were also reduced in mesenteric lymph nodes of infected AMCase-deficient mice. Thus, AMCase functions as a critical initiator of protective type 2 responses to intestinal nematodes but is largely dispensable for allergic responses in the lung.

The goblet cell-derived mediator RELM-ß drives spontaneous colitis in Muc2-deficient mice by promoting commensal microbial dysbiosis.

Intestinal goblet cells are potentially key players in controlling susceptibility to ulcerative colitis (UC). Although impaired mucin (Muc2) production by goblet cells increases microbial stimulation of the colonic mucosa, goblet cells secrete other mediators that may influence or promote UC development. Correspondingly, Muc2-deficient ((-/-)) mice develop spontaneous colitis, concurrent with the dramatic upregulation of the goblet cell mediator, resistin-like molecule-beta (RELM-ß). Testing RELM-ß's role, we generated Muc2(-/-)/Retnlb(-/-) mice, finding that RELM-ß deficiency significantly attenuated colitis development and symptoms compared with Muc2(-/-) mice. RELM-ß expression in Muc2(-/-) mice strongly induced the production/secretion of the antimicrobial lectin RegIIIß, that exerted its microbicidal effect predominantly on Gram-positive Lactobacillus species. Compared with Muc2(-/-)/Retnlb(-/-) mice, this worsened intestinal microbial dysbiosis with a selective loss of colonic Lactobacilli spp. in Muc2(-/-) mice. Orally replenishing Muc2(-/-) mice with murine Lactobacillus spp., but not with a probiotic formulation containing several human Lactobacillus spp. (VSL#3), ameliorated their spontaneous colitis in concert with increased production of short-chain fatty acids. These studies demonstrate that the goblet cell mediator RELM-ß drives colitis in Muc2(-/-) mice by depleting protective commensal microbes. The ability of selective commensal microbial replacement to ameliorate colitis suggests that personalized bacterial therapy may prove beneficial for treatment of UC.

Goblet Cell Derived RELM-ß Recruits CD4+ T Cells during Infectious Colitis to Promote Protective Intestinal Epithelial Cell Proliferation.

Enterohemorrhagic Escherichia coli and related food and waterborne pathogens pose significant threats to human health. These attaching/effacing microbes infect the apical surface of intestinal epithelial cells (IEC), causing severe diarrheal disease. Colonizing the intestinal luminal surface helps segregate these microbes from most host inflammatory responses. Based on studies using Citrobacter rodentium, a related mouse pathogen, we speculate that hosts rely on immune-mediated changes in IEC, including goblet cells to defend against these pathogens. These changes include a CD4+ T cell-dependent increase in IEC proliferation to replace infected IEC, as well as altered production of the goblet cell-derived mucin Muc2. Another goblet cell mediator, REsistin-Like Molecule (RELM)-ß is strongly induced within goblet cells during C. rodentium infection, and was detected in the stool as well as serum. Despite its dramatic induction, RELM-ß's role in host defense is unclear. Thus, wildtype and RELM-ß gene deficient mice (Retnlb-/-) were orally infected with C. rodentium. While their C. rodentium burdens were only modestly elevated, infected Retnlb-/- mice suffered increased mortality and mucosal ulceration due to deep pathogen penetration of colonic crypts. Immunostaining for Ki67 and BrDU revealed Retnlb-/- mice were significantly impaired in infection-induced IEC hyper-proliferation. Interestingly, exposure to RELM-ß did not directly increase IEC proliferation, rather RELM-ß acted as a CD4+ T cell chemoattractant. Correspondingly, Retnlb-/- mice showed impaired CD4+ T cell recruitment to their infected colons, along with reduced production of interleukin (IL)-22, a multifunctional cytokine that directly increased IEC proliferation. Enema delivery of RELM-ß to Retnlb-/- mice restored CD4+ T cell recruitment, concurrently increasing IL-22 levels and IEC proliferation, while reducing mucosal pathology. These findings demonstrate that RELM-ß and goblet cells play an unexpected, yet critical role in recruiting CD4+ T cells to the colon to protect against an enteric pathogen, in part via the induction of increased IEC proliferation.

Conditional IL-4/IL-13-deficient mice reveal a critical role of innate immune cells for protective immunity against gastrointestinal helminths.

Approximately one-third of the world population is infected with gastrointestinal helminths. Studies in mouse models have demonstrated that the cytokines interleukin (IL)-4 and IL-13 are essential for worm expulsion, but the critical cellular source of these cytokines is poorly defined. Here, we compared the immune response to Nippostrongylus brasiliensis in wild-type, T cell-specific IL-4/IL-13-deficient and general IL-4/IL-13-deficient mice. We show that T cell-derived IL-4/IL-13 promoted T helper 2 (Th2) polarization in a paracrine manner, differentiation of alternatively activated macrophages, and tissue recruitment of innate effector cells. However, innate IL-4/IL-13 played the critical role for induction of goblet cell hyperplasia and secretion of effector molecules like Mucin5ac and RELMß in the small intestine. Surprisingly, T cell-specific IL-4/IL-13-deficient and wild-type mice cleared the parasite with comparable efficiency, whereas IL-4/IL-13-deficient mice showed impaired expulsion. These findings demonstrate that IL-4/IL-13 produced by cells of the innate immune system is required and sufficient to initiate effective type 2 immune responses resulting in protective immunity against N. brasiliensis.

Resistin-like molecule ß is abundantly expressed in foam cells and is involved in atherosclerosis development.

OBJECTIVE: Resistin-like molecule (RELM) ß is a secretory protein homologous to resistin and reportedly contributes to local immune response regulation in gut and bronchial epithelial cells. However, we found that activated macrophages also express RELMß and thus investigated the role of RELMß in the development of atherosclerosis. APPROACH AND RESULTS: It was demonstrated that foam cells in atherosclerotic lesions of the human coronary artery abundantly express RELMß. RELMß knockout ((-/-)) and wild-type mice were mated with apolipoprotein E-deficient background mice. RELMß(-/-) apolipoprotein E-deficient mice exhibited less lipid accumulation in the aortic root and wall than RELMß(+/+) apolipoprotein E-deficient mice, without significant changes in serum lipid parameters. In vitro, RELMß(-/-) primary cultured peritoneal macrophages (PCPMs) exhibited weaker lipopolysaccharide-induced nuclear factor-κB classical pathway activation and inflammatory cytokine secretion than RELMß(+/+), whereas stimulation with RELMß upregulated inflammatory cytokine expressions and increased expressions of many lipid transporters and scavenger receptors in PCPMs. Flow cytometric analysis revealed inflammatory stimulation-induced RELMß in F4/80(+) CD11c(+) PCPMs. In contrast, the expressions of CD11c and tumor necrosis factor were lower in RELMß(-/-) PCPMs, but both were restored by stimulation with recombinant RELMß. CONCLUSIONS: RELMß is abundantly expressed in foam cells within plaques and contributes to atherosclerosis development via lipid accumulation and inflammatory facilitation.

IL-33 drives biphasic IL-13 production for noncanonical Type 2 immunity against hookworms.

Parasitic helminths are a major cause of chronic human disease, affecting more than 3 billion people worldwide. Host protection against most parasitic helminths relies upon Type 2 cytokine production, but the mechanisms that regulate interleukin (IL) 4 and 13 production from CD4(+) T helper 2 cells (T(H)2) and innate lymphoid type 2 cells (ILC2s) remain incompletely understood. The epithelial cell-derived cytokines IL-25 and IL-33 promote Type 2 responses, but the extent of functional redundancy between these cytokines is unclear and whether Type 2 memory relies upon either IL-25 or IL-33 is unknown. Herein, we demonstrate a pivotal role for IL-33 in driving primary and anamnestic immunity against the rodent hookworm Nippostrongylus brasiliensis. IL-33-deficient mice have a selective defect in ILC2-derived IL-13 during both primary and secondary challenge infections but generate stronger canonical CD4(+) T helper 2 cells responses (IL-4, IgE, mast cells, and basophils) than WT controls. Lack of IL-13 production in IL-33-deficient mice impairs resistin-like molecule beta (RELMß) expression and eosinophil recruitment, which are two mechanisms that eliminate N. brasiliensis parasites from infected hosts. Thus, IL-33 is requisite for IL-13 but not IL-4-driven Type 2 responses during hookworm infection.

Choosing the right antibody for resistin-like molecule (RELM/FIZZ) family members.

The family of resistin-like molecules (RELM), also known as found in inflammatory zone (FIZZ), consists of four members in mouse (RELMα/FIZZ1/HIMF, RELMß/FIZZ2, Resistin/FIZZ3, and RELMγ/FIZZ4) and two members in human (resistin and RELMß). The importance of these proteins in many aspects of physiology and pathophysiology, especially inflammatory processes, is rapidly evolving in the literature, and many investigators are beginning to work in this field. Most published studies focus on only one isoform, do not evaluate other isoforms that might be present, and have not tested for the specificity of the antibody used. Because RELM isoforms have high sequence and structural similarity and both distinct and overlapping functions, it is important to use a specific antibody to distinguish each isoform in the study. We constructed and established HEK 293 cell lines that constitutively express each isoform. Using these cell lines, we determined the specificity of antibodies (both commercially available and laboratory-made) to each isoform by Western blot and immunofluorescence. Some of the antibodies showed specificity in Western blotting but were not applicable in immunofluorescence. Others showed cross reactivity in Western blot assays. Our results indicate that RELM antibody specificity should be taken into account when using them in research and interpreting data obtained with them.

Resistin-like molecule beta (RELMbeta/FIZZ2) is highly expressed in the ileum of SAMP1/YitFc mice and is associated with initiation of ileitis.

SAMP1/Fc mice develop spontaneous ileitis that shares many features with human Crohn's disease. One of the earliest features of ileitis in SAMP1/Fc mice is an increase in the number of ileal goblet and intermediate cells. Resistin-like molecule beta (RELMbeta) is a goblet cell-specific, cysteine-rich peptide previously shown to function as part of the innate immune response. In this study, we examined the role of expression of RELMbeta in the initiation of ileal inflammation in SAMP1/Fc mice. RELMbeta was highly induced in the ilea of SAMP1/Fc mice beginning at age 5 wk, coincident with the histological appearance of inflammation. RELMbeta was found in ileal goblet cells and some intermediate and Paneth cells. Surprisingly, RELMbeta mRNA levels were significantly increased in the ilea of 80% of germ-free SAMP1/Fc mice examined compared with specific pathogen-free AKR control mice of similar age. Ileitis was observed in germfree SAMP1/Fc mice, although it was attenuated relative to specific pathogen-free SAMP1/Fc mice. These data suggest that neither the early induction of RELMbeta expression nor ileal inflammation requires the presence of viable intestinal flora. Neither was the induction of RELMbeta dependent on the major Th1 or Th2 cytokines. However, RELMbeta stimulated naive bone marrow-derived macrophages to secrete significant amounts of TNF-alpha, IL-6, and RANTES. Our data suggest that RELMbeta is involved in the initiation of ileitis in SAMP1/Fc mice and may act through the induction of proinflammatory cytokines from resident immune cells within the mucosa.

Resistin-like molecule-beta is an allergen-induced cytokine with inflammatory and remodeling activity in the murine lung.

Resistin-like molecule (RELM)-beta is a cysteine-rich cytokine implicated in insulin resistance and asthmatic responses, but its function remains an enigma. We now report that RELM-beta has a role in promoting airway inflammation and lung remodeling in the mouse lung. RELM-beta is strongly induced by diverse allergens and T helper type 2 (Th2) cytokines by an IL-13- and STAT6-dependent mechanism. To understand the in vivo role of RELM-beta, we delivered recombinant murine RELM-beta intratracheally to naïve mice. RELM-beta induced dose-dependent leukocyte accumulation (most prominently involving macrophages) and goblet cell hyperplasia. The most prominent effect induced by RELM-beta was increased perivascular and peribronchial collagen deposition. Mice genetically deficient in RELM-beta had reduced accumulation of collagen and goblet cell hyperplasia in an experimental model of allergic airway inflammation. In vitro experiments demonstrated that RELM-beta had fibroblast motogenic activity. These results identify RELM-beta as a Th2-associated cytokine with potent inflammatory and remodeling activity.

Human resistin stimulates the pro-inflammatory cytokines TNF-alpha and IL-12 in macrophages by NF-kappaB-dependent pathway.

Resistin, a recently discovered 92 amino acid protein involved in the development of insulin resistance, has been associated with obesity and type 2 diabetes. The elevated serum resistin in human diabetes is often associated with a pro-inflammatory milieu. However, the role of resistin in the development of inflammation is not well understood. Addition of recombinant human resistin protein (hResistin) to macrophages (both murine and human) resulted in enhanced secretion of pro-inflammatory cytokines, TNF-alpha and IL-12, similar to that obtained using 5 microg/ml lipopolysaccharide. Both oligomeric and dimeric forms of hResistin were able to activate these cytokines suggesting that the inflammatory action of resistin is independent of its conformation. Heat denatured hResistin abrogated cytokine induction while treatment of recombinant resistin with polymyxin B agarose beads had no effect thereby ruling out the role of endotoxin in the recombinant hResistin mediated cytokine induction. The pro-inflammatory nature of hResistin was further evident from the ability of this protein to induce the nuclear translocation of NF-kappaB transcription factor as seen from electrophoretic mobility shift assays. Induction of TNF-alpha in U937 cells by hResistin was markedly reduced in the presence of either dominant negative IkappaBalpha plasmid or PDTC, a pharmacological inhibitor of NF-kappaB. A protein involved in conferring insulin resistance is also a pro-inflammatory molecule that has important implications.

Serum resistin levels of obese and lean children and adolescents: biochemical analysis and clinical relevance.

OBJECTIVE: It was hypothesized that resistin links obesity with diabetes, but this has not been studied in children and adolescents to date. PATIENTS: We determined serum resistin levels of 135 obese (body mass index, 32.0 +/- 6.2 kg/m2; age, 12.6 +/- 3.4 yr) and 201 lean children (body mass index, 18.7 +/- 2.4 kg/m2; age, 12.5 +/- 2.5 yr) by a newly developed and extensively evaluated in-house immunoassay. These results were controlled for their association with markers of puberty, obesity, and insulin sensitivity. RESULTS: The analytical evaluation of our assay revealed different resistin isoforms with major peaks of higher than 660 and 55 kDa in the size exclusion chromatography. Using this assay system we found no difference in the resistin levels of obese compared with lean subjects (P = 0.48). However, resistin was significantly higher in girls than in boys (6.74 +/- 2.42 vs. 5.79 +/- 2.45; P < 0.001). Interestingly, in both obese and lean children, resistin correlated with age (P < 0.01), Tanner stage, and testosterone and estradiol levels (P < 0.05). In contrast, no significant correlation was found with parameters of insulin resistance such as homeostasis model assessment, insulin sensitivity index, or insulin, proinsulin, and glucose concentrations in obese subjects. CONCLUSIONS: Resistin appears to be not the main link between obesity and insulin resistance in children and adolescents but because of its association with Tanner stage, it may be related to the maturation of children during pubertal development. Additionally, we have demonstrated the presence of different molecular isoforms of resistin in human blood, and this may raise problems in comparing data from diverse assay systems.

RELMbeta/FIZZ2 is a goblet cell-specific immune-effector molecule in the gastrointestinal tract.

Gastrointestinal (GI) nematode infections are an important public health and economic concern. Experimental studies have shown that resistance to infection requires CD4(+) T helper type 2 (Th2) cytokine responses characterized by the production of IL-4 and IL-13. However, despite >30 years of research, it is unclear how the immune system mediates the expulsion of worms from the GI tract. Here, we demonstrate that a recently described intestinal goblet cell-specific protein, RELMbeta/FIZZ2, is induced after exposure to three phylogenetically distinct GI nematode pathogens. Maximal expression of RELMbeta was coincident with the production of Th2 cytokines and host protective immunity, whereas production of the Th1 cytokine, IFN-gamma, inhibited RELMbeta expression and led to chronic infection. Furthermore, whereas induction of RELMbeta was equivalent in nematode-infected wild-type and IL-4-deficient mice, IL-4 receptor-deficient mice showed minimal RELMbeta induction and developed persistent infections, demonstrating a direct role for IL-13 in optimal expression of RELMbeta. Finally, we show that RELMbeta binds to components of the nematode chemosensory apparatus and inhibits chemotaxic function of a parasitic nematode in vitro. Together, these results suggest that intestinal goblet cell-derived RELMbeta may be a novel Th2 cytokine-induced immune-effector molecule in resistance to GI nematode infection.

Enzyme-linked immunosorbent assay for circulating human resistin: resistin concentrations in normal subjects and patients with type 2 diabetes.

BACKGROUND: Resistin is a recently identified adipocyte-secreted hormone in rodents, and has been proposed to serve as a link between obesity and insulin resistance. The aim of this study was to develop a sensitive enzyme-linked immunosorbent assay (ELISA) for human resistin and evaluate serum resistin concentrations in normal subjects and patients with type 2 diabetes. METHODS: Using ELISA developed by two polyclonal antibodies, resistin concentrations were measured in 90 patients with type 2 diabetes and compared to 74 healthy control subjects. RESULTS: This ELISA has high specificity and sensitivity over the concentration of range 0.5-100 ng/ml with good percentage recovery (97.1 +/- 4.7%) and reproducibility (within-day assay, CV = 4.8-8.6%; between-day assay, CV = 5.6-9.7%). The mean concentration of resistin in sera from type 2 diabetic patients was significantly higher than that in normal subjects (mean +/- S.E.: 20.8 +/- 0.7 vs. 14.9 +/- 0.5 ng/ml, p < 0.001). A moderate positive correlation was observed between serum resistin levels and body mass indices in both normal subjects (r = 0.412, p < 0.0003) and patients with type 2 diabetes (r = 0.395, p < 0.0001). CONCLUSIONS: Our ELISA will be useful to confirm the physiological and pathophysiological role of resistin in humans.

Resistin is expressed in pancreatic islets.

Resistin, a recently described adipocyte factor, is regulated by peroxisome proliferator-activated receptor gamma (PPARgamma) agonists. While resistin has been proposed to mediate insulin resistance in rodents, little is known about human resistin and its expression in pancreatic islets has not been tested. The goal of the present study was therefore to analyze whether resistin, like PPARgamma, is expressed in islets. Human islets from seven donors were analyzed by quantitative RT-PCR revealing resistin expression in all samples. Immunohistochemistry using a resistin-specific antibody on human pancreatic sections localized resistin protein to the islets. Mouse resistin was also detected in the Min6 beta cell line. Interestingly, we found a 4-fold increase in islet resistin expression in insulin resistant A-ZIP transgenic compared to wild-type mice. Our results demonstrate that resistin is expressed in islets and up-regulated in insulin resistance and thereby shed new light on the role of resistin in mice and humans.

Human chorionic gonadotropin as a target for cancer vaccines.

Human chorionic gonadotropin (hCG) is expressed by common cancers and may play a role in cell transformation as well as angiogenic, metastatic, and immune escape phenomena that are central to cancer progression. Clinical trials with a vaccine targeting the carboxy-terminal peptide of -hCG have indicated that tolerance to this oncofetal antigen can be broken. Humoral responses that may modulate the biologic activity of tumor-associated hCG as well as cellular responses to hCG have been generated. Studies are in progress to further define the biologic significance of hCG in cancer and to develop a vaccine approach that will best target this expression.

Parathyroid hormone-related protein purified from a human lung cancer cell line.

A protein with biological activities similar to parathyroid hormone (PTH) has been purified from serum-free culture medium obtained from a human lung cancer cell line (BEN). A major protein band of 18 kDa was obtained on NaDodSO4/polyacrylamide gels, with faint bands at 35 kDa and 67 kDa. Biological activity was associated only with the 18-kDa band. Amino acid sequence analysis of the material purified by HPLC revealed that 8 of the 16 residues were identical with those of human PTH. Antibody raised to a corresponding synthetic peptide recognized the PTH-related material but showed less than 1% cross-reactivity with human PTH amino-terminal peptides. BEN cells contained PTH DNA, but not PTH messenger RNA, indicating involvement of another gene. The purified PTH-related protein had a specific biological activity approximately equal to 6 times greater than that of bovine PTH(1-34). The PTH-related protein may have a role in the syndrome of humoral hypercalcemia of malignancy.