IL-12 p40 homodimer-dependent macrophage chemotaxis and respiratory viral inflammation are mediated through IL-12 receptor beta 1

IL-12p40 is essential but not sufficient for Francisella tularensis LVS clearance in chronically infected mice

IL-12p40 plays an important role in F. tularensis Live Vaccine Strain (LVS) clearance that is independent of its functions as a part of the heterodimeric cytokines IL-12p70 or IL-23. In contrast to WT, p35, or p19 knockout (KO) mice, p40 KO mice infected with LVS develop a chronic infection that does not resolve. Here, we further evaluated the role of IL-12p40 in F. tularensis clearance. Despite reduced IFN-γ production, primed splenocytes from p40 KO and p35 KO mice appeared functionally similar to those from WT mice during in vitro co-culture assays of intramacrophage bacterial growth control. Gene expression analysis revealed a subset of genes that were upregulated in re-stimulated WT and p35 KO splenocytes, but not p40 KO splenocytes, and thus are candidates for involvement in F. tularensis clearance. To directly evaluate a potential mechanism for p40 in F. tularensis clearance, we reconstituted protein levels in LVS-infected p40 KO mice using either intermittent injections of p40 homodimer (p80) or treatment with a p40-producing lentivirus construct. Although both delivery strategies yielded readily detectable levels of p40 in sera and spleens, neither treatment had a measurable impact on LVS clearance by p40 KO mice. Taken together, these studies demonstrate that clearance of F. tularensis infection depends on p40, but p40 monomers and/or dimers alone are not sufficient.

Combined testing of cerebrospinal fluid IL-12 (p40) and serum C-reactive protein as a possible discriminator of acute bacterial neuroinfections

INTRODUCTION

Central nervous system infections (CNS) are life-threatening diseases, with meningitis being the most common. Viral infections are usually self-limiting diseases but bacterial pathogens are associated with higher mortality rates and persistent neurological sequelae. We aimed to study the role of IL-6, IL-8, IL-10, IL-12(p40), TNF-α cytokines, classical cerebrospinal fluid (CSF) parameters, and serum C-reactive protein levels (CRP) for discriminating bacterial from viral central nervous system infections.

MATERIAL AND METHODS

This prospective study included 80 patients with clinical signs and abnormal cerebrospinal fluid laboratory findings typical for neuroinfection admitted to St. George University Hospital-Plovdiv. Routine methods such as direct microscopy, culturing and identification were used for microbiological analysis as well as latex-agglutination test and multiplex PCR. Cytokines' concentrations were measured by ELISA. CRP and CSF parameters were collected from the patients' medical records.

RESULTS

We observed the highest discriminatory power among cytokines for cerebrospinal IL-12(p40) (AUC = 0.925; p = 0.000). CSF protein levels were the best predictor for bacterial neuroinfection (AUC = 0.973; p = 0.000). The AUC for the serum CRP as a stand-alone biomarker was estimated to be 0.943. The discriminatory power can be increased up to 0.995 (p = 0.000) when combining cerebrospinal fluid IL-12(p40) and serum CRP, with an optimal cut-off value of 144 (Sensitivity 100%; Specificity 90.9%).

CONCLUSION

The combined testing of CSF IL-12(p40) and serum CRP is associated with the highest diagnostic accuracy.

IL-12 and IL-23-Close Relatives with Structural Homologies but Distinct Immunological Functions

Cytokines of the IL-12 family show structural similarities but have distinct functions in the immune system. Prominent members of this cytokine family are the pro-inflammatory cytokines IL-12 and IL-23. These two cytokines share cytokine subunits and receptor chains but have different functions in autoimmune diseases, cancer and infections. Accordingly, structural knowledge about receptor complex formation is essential for the development of new therapeutic strategies preventing and/or inhibiting cytokine:receptor interaction. In addition, intracellular signaling cascades can be targeted to inhibit cytokine-mediated effects. Single nucleotide polymorphisms can lead to alteration in the amino acid sequence and thereby influencing protein functions or protein–protein interactions. To understand the biology of IL-12 and IL-23 and to establish efficient targeting strategies structural knowledge about cytokines and respective receptors is crucial. A highly efficient therapy might be a combination of different drugs targeting extracellular cytokine:receptor assembly and intracellular signaling pathways.

Socheongryongtang Modulates Asthma-Related Changes via Modulation of TNF-α and T-bet as well as IFN-γ in an Asthma Murine Model

In 2017 the World Health Organization (WHO) reported that 235 million people suffered from asthma, and that 383,000 deaths were due to asthma in 2015. Asthma cannot be completely eradicated and the medications for asthma are associated with many adverse effects. Socheongryongtang is one of the prescriptions which has traditionally been used for the treatment of pulmonary disease, but the anti-asthmatic mechanism is unclear. To investigate the anti-asthmatic mechanism of socheongryongtang, BALB/c mice were divided into five groups: control, asthma-induced control, dexamethasone treatment, and 150 mg/kg or 1500 mg/kg socheongryongtang treatment and several biomarkers were analyzed, such as white blood cell (WBC) and differential counts in broncheoalveolar fluid (BALF), immunoglobulin E (IgE) in serum, and morphological changes/helper T cell-related cytokines/transcription factor in the lung. The therapeutic ingredients were also analyzed. Socheongryongtang inhibited the neutrophils differentiation in BALF, controlled interleukin (IL)-12p40 releasing, down-regulated not only GATA-3 and helper 2 T (Th2) cell transcription factors but also IL-4, and also decreased the level of tumor necrosis factor (TNF)-α in the lung. In addition, through high-performance liquid chromatography (HPLC) analysis, we confirmed that the therapeutic ingredients in socheongryongtang were paeoniflorin, liquiritin, and glycyrrhizin. The oral intake of 7.3 g of socheongryongtang is beneficial for suppressing the possibility of the occurrence of asthma via modulation of TNF-α and T-bet as well as IFN-γ.

Deciphering site 3 interactions of interleukin 12 and interleukin 23 with their cognate murine and human receptors

Interleukin (IL)-12 and IL-23 belong to the IL-12 type family and are composite cytokines, consisting of the common β subunit p40 and the specific cytokine α subunit p35 and p19, respectively. IL-12 signals via the IL-12Rβ1·IL-12Rβ2 receptor complex, and IL-23 uses also IL-12Rβ1 but engages IL-23R as second receptor. Importantly, binding of IL-12 and IL-23 to IL-12Rβ1 is mediated by p40, and binding to IL-12Rβ2 and IL-23R is mediated by p35 and p19, respectively. Previously, we have identified a W157A substitution at site 3 of murine IL-23p19 that abrogates binding to murine IL-23R. Here, we demonstrate that the analogous Y185R site 3 substitution in murine and Y189R site 3 substitution in human IL-12p35 abolishes binding to IL-12Rβ2 in a cross-species manner. Although Trp¹⁵⁷ is conserved between murine and human IL-23p19 (Trp¹⁵⁶ in the human ortholog), the site 3 W156A substitution in hIL-23p19 did not affect signaling of cells expressing human IL-12Rβ1 and IL-23R, suggesting that the interface of murine IL-23p19 required for binding to IL-23R is different from that in the human ortholog. Hence, we introduced additional hIL-23p19 substitutions within its binding interface to hIL-23R and found that the combined site 3 substitutions of W156A and L160E, which become buried at the complex interface, disrupt binding of hIL-23p19 to hIL-23R. In summary, we have identified substitutions in IL-12p35 and IL-23p19 that disrupt binding to their cognate receptors IL-12Rβ2 and IL-23R in a murine/human cross-species manner.

The IL-12 Cytokine and Receptor Family in Graft-vs.-Host Disease

Allogeneic hematopoietic cell transplantation (allo-HCT) is performed with curative intent for high- risk blood cancers and bone marrow failure syndromes; yet the development of acute and chronic graft-vs.-host disease (GVHD) remain preeminent causes of death and morbidity. The IL-12 family of cytokines is comprised of IL-12, IL-23, IL-27, IL-35, and IL-39. This family of cytokines is biologically distinct in that they are composed of functional heterodimers, which bind to cognate heterodimeric receptor chains expressed on T cells. Of these, IL-12 and IL-23 share a common β cytokine subunit, p40, as well as a receptor chain: IL-12Rβ1. IL-12 and IL-23 have been documented as proinflammatory mediators of GVHD, responsible for T helper 1 (Th1) differentiation and T helper 17 (Th17) stabilization, respectively. The role of IL-27 is less defined, seemingly immune suppressive via IL-10 secretion by Type 1 regulatory (Tr1) cells yet promoting inflammation through impairing CD4⁺ T regulatory (Treg) development and/or enhancing Th1 differentiation. More recently, IL-35 was described as a potent anti-inflammatory agent produced by regulatory B and T cells. The role of the newest member, IL-39, has been implicated in proinflammatory B cell responses but has not been explored in the context of allo-HCT. This review is directed at discussing the current literature relevant to each IL-12-family cytokine and cognate receptor engagement, as well as the consequential downstream signaling implications, during GVHD pathogenesis. Additionally, we will provide an overview of translational strategies targeting the IL-12 family cytokines, their receptors, and subsequent signal transduction to control GVHD.

The Immunobiology of the Interleukin-12 Family: Room for Discovery

The discovery of interleukin (IL)-6 and its receptor subunits provided a foundation to understand the biology of a group of related cytokines: IL-12, IL-23, and IL-27. These family members utilize shared receptors and cytokine subunits and influence the outcome of cancer, infection, and inflammatory diseases. Consequently, many facets of their biology are being therapeutically targeted. Here, we review the landmark discoveries in this field, the combinatorial biology inherent to this family, and how patient datasets have underscored the critical role of these pathways in human disease. We present significant knowledge gaps, including how similar signals from these cytokines can mediate distinct outcomes, and discuss how a better understanding of the biology of the IL-12 family provides new therapeutic opportunities.

Reversing Ongoing Chronic Intestinal Inflammation and Fibrosis by Sustained Block of IL-12 and IL-23 Using a Vaccine in Mice

Interleukin (IL)-12 and IL-23 that share subunit p40 are important cytokines in the pathogenesis of inflammatory bowel disease. We reported that mouse p40 peptide-based vaccines ameliorated intestinal inflammation in the prevention of trinitrobenzene sulfonic acid (TNBS)–induced murine colitis model. Here, we evaluated whether administration of the vaccine after establishment of colitis would be effective in modifying both TNBS-induced and dextran sulfate sodium (DSS)–induced chronic colitis and the underlying immune mechanisms. We further examined whether vaccination could exacerbate infections. Chronic colitis was developed by either intrarectally administrating TNBS or drinking 4% DSS water. Vaccination started after two TNBS administrations or 7 days of DSS treatment. Results showed that administrating p40 vaccine induced high tittered antibodies to IL-12 and IL-23, improved clinical scores, reduced intestinal inflammation and fibrosis, and down-regulated proinflammatory cytokine productions in colon tissue, compared with control mice. Furthermore, in lamina propria mononuclear cells and/or mesenteric lymph nodes, mice immunized with p40 peptide vaccine exhibited high ratios of Treg/Th1 and Treg/Th17 cells and increased IL-10 expression in CD11c⁺IL-10⁺cells. In mice infected with lung chlamydia, in which the protective role of Th1/Th17 is well documented, vaccine immunization did not increase lung bacterial burden. We conclude that p40 vaccine may provide a potential and safe approach for treatment of IBD.

Interferon induced protein 35 exacerbates H5N1 influenza disease through the expression of IL-12p40 homodimer

Pro-inflammatory cytokinemia is a hallmark of highly pathogenic H5N1 influenza virus (IAV) disease yet little is known about the role of host proteins in modulating a pathogenic innate immune response. The host Interferon Induced Protein 35 (Ifi35) has been implicated in increased susceptibility to H5N1-IAV infection. Here, we show that Ifi35 deficiency leads to reduced morbidity in mouse models of highly pathogenic H5N1- and pandemic H1N1-IAV infection. Reduced weight loss in Ifi35^-/- mice following H5N1-IAV challenge was associated with reduced cellular infiltration and decreased production of specific cytokines and chemokines including IL-12p40. Expression of Ifi35 by the hematopoietic cell compartment in bone-marrow chimeric mice contributed to increased immune cell recruitment and IL-12p40 production. In addition, Ifi35 deficient primary macrophages produce less IL-12p40 following TLR-3, TLR-4, and TLR-7 stimulation in vitro. Decreased levels of IL-12p40 and its homodimer, IL-12p80, were found in bronchoalveolar lavage fluid of H5N1-IAV infected Ifi35 deficient mice. Specific antibody blockade of IL-12p80 ameliorated weight loss and reduced cellular infiltration following H5N1-IAV infection in wild-type mice; suggesting that increased levels of IL-12p80 alters the immune response to promote inflammation and IAV disease. These data establish a role for Ifi35 in modulating cytokine production and exacerbating inflammation during IAV infection.

Highly pathogenic influenza A viruses (IAV) are an important human pathogen that cause high mortality and can acquire the ability to cause pandemics. Following highly pathogenic H5N1-IAV infection, exaggerated inflammatory responses are detrimental to the host and lead to more disease; tipping the balance between protection and pathology. Understanding the role of host genes that enhance inflammation will lead to the identification of therapeutic targets and treatments to help lessen severe disease. Here, we report that the deletion of an interferon induced gene, Ifi35 (interferon induced protein 35), in mice protects the host from severe morbidity following H5N1 infection. Ifi35 enhances inflammation following H5N1 infection by increasing pro-inflammatory cytokine production; notably, the cytokine IL-12p40 and its homodimer, IL-12p80. Blocking IL-12p80 in mice led to reduced weight loss following H5N1 infection. Thus, our results provide insights into the development of therapeutic agents against host factors, Ifi35 and IL-12p80, to help control inflammation and inflammatory disease states.

Myeloid cell expressed proprotein convertase FURIN attenuates inflammation

The proprotein convertase enzyme FURIN processes immature pro-proteins into functional end- products. FURIN is upregulated in activated immune cells and it regulates T-cell dependent peripheral tolerance and the Th1/Th2 balance. FURIN also promotes the infectivity of pathogens by activating bacterial toxins and by processing viral proteins. Here, we evaluated the role of FURIN in LysM+ myeloid cells in vivo. Mice with a conditional deletion of FURIN in their myeloid cells (LysMCre-fur^(fl/fl)) were healthy and showed unchanged proportions of neutrophils and macrophages. Instead, LysMCre-fur^(fl/fl) mice had elevated serum IL-1β levels and reduced numbers of splenocytes. An LPS injection resulted in accelerated mortality, elevated serum pro-inflammatory cytokines and upregulated numbers of pro-inflammatory macrophages. A genome-wide gene expression analysis revealed the overexpression of several pro-inflammatory genes in resting FURIN-deficient macrophages. Moreover, FURIN inhibited Nos2 and promoted the expression of Arg1, which implies that FURIN regulates the M1/M2-type macrophage balance. FURIN was required for the normal production of the bioactive TGF-β1 cytokine, but it inhibited the maturation of the inflammation-provoking TACE and Caspase-1 enzymes. In conclusion, FURIN has an anti-inflammatory function in LysM+ myeloid cells in vivo.

Defining the functional binding sites of interleukin 12 receptor β1 and interleukin 23 receptor to Janus kinases

Stimulation of cells with the IL-12–type cytokine IL-12 or IL-23 results in activation of receptor-associated Janus kinases (Jak) and phosphorylation of STAT proteins in target cells. Functional association of IL 12Rβ1 with tyrosine kinase 2 and IL-23R with Jak2 is mandatory for IL-12 and/or IL-23 signaling.

The interleukin (IL)-12–type cytokines IL-12 and IL-23 are involved in T-helper (Th) 1 and Th17 immunity, respectively. They share the IL-12 receptor β1 (IL-12Rβ1) as one component of their receptor signaling complexes, with IL-12Rβ2 as second receptor for IL-12 and IL-23R for IL-23 signal transduction. Stimulation with IL-12 and IL-23 results in activation of receptor-associated Janus kinases (Jak) and phosphorylation of STAT proteins in target cells. The Janus kinase tyrosine kinase (Tyk) 2 associates with IL-12Rβ1, whereas Jak2 binds to IL-23R and also to IL-12Rβ2. Receptor association of Jak2 is mediated by Box1 and Box2 motifs located within the intracellular domain of the receptor chains. Here we define the Box1 and Box2 motifs in IL-12Rβ1 and an unusual Jak2-binding site in IL-23R by the use of deletion and site-directed mutagenesis. Our data show that nonfunctional box motifs abolish IL-12– and IL-23–induced STAT3 phosphorylation and cytokine-dependent proliferation of Ba/F3 cells. Coimmunoprecipitation of Tyk2 by IL-12Rβ1 and Jak2 by IL‑23R supported these findings. In addition, our data demonstrate that association of Jak2 with IL-23R is mandatory for IL-12 and/or IL-23 signaling, whereas Tyk2 seems to be dispensable.

Insights into IL-23 biology: From structure to function

Interleukin (IL-)23 is a central cytokine controlling TH17 development. Overshooting IL-23 signaling contribute to autoimmune diseases. Moreover, GWAS studies have identified several SNPs within the IL-23 receptor, which are associated with autoimmune diseases. IL-23 is a member of the IL-12-type cytokine family and consists of IL-23p19 and p40. Within the IL-12 family, IL-12 and IL-23 share the p40 cytokine subunit and the IL-12Rβ1 as one chain of the receptor complex. For signaling, IL-23 triggers heterodimerization of IL-12Rβ1 and the IL-23R. Subsequently, signal transduction pathways including JAK/STAT, MAPK and PI3K are activated. Most studies have investigated the biological relevance of IL-23 in the development of TH17 cells and autoimmunity, whereas less is known about the molecular context of IL-23 biology. Therefore, we focused on IL-23 receptor complex assembly, signal transduction and functional relevance of IL-23R SNPs in the context of IL-23-inhibitory principles.

Glutathione reaction products with a chemical allergen, methylene-diphenyl diisocyanate, stimulate alternative macrophage activation and eosinophilic airway inflammation

Isocyanates have been a leading chemical cause of occupational asthma since their utility for generating polyurethane was first recognized over 60 years ago, yet the mechanisms of isocyanate asthma pathogenesis remain unclear. The present study provides in vivo evidence that a GSH mediated pathway underlies asthma-like eosinophilic inflammatory responses to respiratory tract isocyanate exposure. In naïve mice, a mixture of GSH reaction products with the chemical allergen, methylene-diphenyl diisocyanate (MDI), induced innate immune responses, characterized by significantly increased airway levels of Chitinase YM-1 and IL-12/IL-23β (but not α) subunit. However, in mice immunologically sensitized to MDI via prior skin exposure, identical GSH-MDI doses induced substantially greater inflammatory responses, including significantly increased airway eosinophil numbers and mucus production, along with IL-12/IL-23β, chitinases, and other indicators of alternative macrophage activation. The "self"-protein albumin in mouse airway fluid was uniquely modified by GSH-MDI at position (414)K, a preferred site of MDI reactivity on human albumin. The (414)K-MDI conjugation appears to covalently cross-link GSH to albumin via GSH's NH2-terminus, a unique conformation possibly resulting from cyclized mono(GSH)-MDI or asymmetric (S,N'-linked) bis(GSH)-MDI conjugates. Together, the data support a possible thiol mediated transcarbamoylating mechanism linking MDI exposure to pathogenic eosinophilic inflammatory responses.

Dendritic cells primed with HPV positive cervical tumor lysate are superior to unprimed DCs in migratory capacity and induce a potent Th1 response

In this study, we assessed the efficacy of tumor lysate primed and unprimed monocyte derived mature dendritic cells (DCs) to trigger an effective anti-tumor immune response in cervical cancer patients who tested positive for human papilloma virus (HPV) DNA. Lysate primed and unprimed DCs were assessed for the expression of CD80, CD86, CD40, HLADR and CD83. The ability of DCs to migrate in response to the chemokines CCL19 and 21 as well as their ability to secrete IL12p40 was investigated. Mixed lymphocyte proliferation assays were used to assess DC stimulatory capacity and their ability to generate a Th1 response. Our results showed no difference in phenotypic expression between primed and unprimed DCs but both had significantly increased expression of the activation marker CD83 when compared to immature DCs. Importantly, the primed DCs showed significant (P value=0.03) IL-12p40 secretion and a superior migratory capacity towards CC19 and CCL21 (P value=0.04) compared to unprimed DCs even after cytokine withdrawal. Primed DCs showed superior stimulation of T cell proliferation (allogeneic and autologous) and secretion of IFN gamma (IFN-γ) than the unprimed DCs. Hence whole tumor lysate primed mature DCs could be potent immunotherapeutic adjuvants to standard treatment for cervical cancer.

An activating NLRC4 inflammasome mutation causes autoinflammation with recurrent macrophage activation syndrome

Inflammasomes are innate immune sensors that respond to pathogen and damage-associated signals with caspase-1 activation, IL-1β and IL-18 secretion, and macrophage pyroptosis. The discovery that dominant gain-of-function mutations in NLRP3 cause the Cryopyrin Associated Periodic Syndromes (CAPS) and trigger spontaneous inflammasome activation and IL-1β oversecretion, led to successful treatment with IL-1 blocking agents¹. Herein, we report a de novo missense mutation, c.1009A>T, p.Thr337Ser, in the nucleotide-binding domain of inflammasome component NLRC4 (IPAF/CARD12) that causes early-onset recurrent fever flares and Macrophage Activation Syndrome (MAS). Functional analyses demonstrated spontaneous inflammasome formation and production of the inflammasome-dependent cytokines IL-1β and IL-18, the latter exceeding levels in CAPS. The NLRC4 mutation caused constitutive caspase-1 cleavage in transduced cells and increased production of IL-18 by both patient and NLRC4 mutant macrophages. Thus, we describe a novel monoallelic inflammasome defect that expands the monogenic autoinflammatory disease spectrum to include MAS and suggests novel targets for therapy.

Rock bream (Oplegnathus fasciatus) IL-12p40: identification, expression, and effect on bacterial infection

IL-12p40, also called IL-12β, is a subunit of the proinflammatory cytokines interleukin (IL)-12 and IL-23. In teleost, IL-12p40 homologues have been identified in several species, however, the biological function of fish IL-12p40 is essentially unknown. In this work, we reported the identification and analysis of an IL-12p40, OfIL-12p40, from rock bream (Oplegnathus fasciatus). OfIL-12p40 is composed of 361 amino acids and possesses a conserved IL-12p40 domain and a WSxWS signature motif characteristic of known IL-12p40. Constitutive expression of OfIL-12p40 occurred in multiple tissues and was highest in kidney. Experimental infection with bacterial pathogen upregulated the expression of OfIL-12p40 in kidney and spleen in a time-dependent manner. Purified recombinant OfIL-12p40 (rOfIL-12p40) stimulated the respiratory burst activity of peripheral blood leukocytes in a dose-dependent manner. rOfIL-12p40 also enhanced the resistance of rock bream against bacterial infection and upregulated the expression of innate immune genes in kidney. Taken together, these results indicate that OfIL-12p40 possesses cytokine-like property and plays a role in immune defense against bacterial infection.

Genetic contribution of CISH promoter polymorphisms to susceptibility to tuberculosis in Chinese children

Tuberculosis (TB) is the leading cause of death due to an infectious disease worldwide, particularly in developing countries. A series of candidate genes have been suggested to be associated with development of TB disease. Among them, the human Cytokine-inducible Src homology 2(SH2) domain protein (CISH) gene has been very recently reported to be involved in T cell activation and differentiation in response to Mycobacterium tuberculosis infection. Here, we studied the association between CISH promoter polymorphisms and pediatric TB. A case-control study enrolled 352 TB patients and 527 healthy controls, who were of Han Chinese ethnicity and aged from 0.2 to 18 years. CISH gene promoter SNPs rs414171, rs622502 and rs809451 were genotyped in all subjects and transcriptional activity, mRNA level, and plasma cytokine level of subjects with different genotypes were further examined. Carriers with rs414171TT homozygotes and rs809451GC heterozygotes had a 1.78-fold (95% CI,1.16–2.74) and 1.86-fold (95% CI, 1.26–2.74) excess risk of developing TB compared to those with wild-type genotypes. A greater risk of TB disease was observed in population carrying C_−809451-T_−414171-C_−622502 haplotype (OR 3.66, 95% CI:2.12–6.32). The G_−809451-A_−414171-C_−622502-containing CISH promoter drove a 5.43-fold increased reporter expression compared to the C_−809451-T_−414171-C_−622502-containing counterpart in Hela cell lines (P = 0.0009). PBMCs carrying rs414171TT homozygotes and rs809451GC heterozygotes showed a reduced CISH mRNA level compared to cells carrying wild type genotypes. Individuals with the rs414171TT genotype had significantly increased IL-12p40 and IL-10 production. In conclusion, CISH promoter rs414171 and rs809451 polymorphisms may play a vital role in mediating individual susceptibility to tuberculosis.

Interleukin (IL)-31 activates signal transducer and activator of transcription (STAT)-1, STAT-5 and extracellular signal-regulated kinase 1/2 and down-regulates IL-12p40 production in activated human macrophages

BACKGROUND

Interleukin-31 is a cytokine expressed by activated T cells. A major function of IL-31 in atopic dermatitis (AD) is the induction of pruritus in the skin. We recently showed that IL-31 induces pro-inflammatory cytokines following staphylococcal exotoxins' stimulation in human macrophages. However, signalling pathways of IL-31 in activated human macrophages still remain unclear. The aim of the study was to investigate the signalling pathways of IL-31 receptor as well as functional effects of IL-31 in activated macrophages.

METHODS

Human macrophages were prestimulated with staphylococcal exotoxins (SEB, α-toxin) to up-regulate the IL-31 receptor with and without IL-31. Phospho-signal transducer and activator of transcription (pSTAT) 1/3/5, phospho-extracellular signal-regulated kinase (ERK 1/2), β-actin as well as p21/WAF/Cip1 levels were determined by means of Western blot analysis. Interleukin-12p40, IL-12p70 and IL-23 secretions were assessed by using an enzyme-linked immunosorbent assay.

RESULTS

Interleukin-31 strongly activated STAT-1 and 5 but not STAT-3 in human macrophages after up-regulation of IL-31 receptor with staphylococcal exotoxins. p21/WAF/Cip1 expression was induced by IL-31 in activated human macrophages. Furthermore, IL-31 down-regulated. IL-12p40 secretion via ERK 1/2 phosphorylation in human macrophages following up-regulation of IL-31 receptor with staphylococcal exotoxins.

CONCLUSIONS

The T helper (Th) 2 cytokine IL-31 induces pro-inflammatory effects in activated human macrophages via STAT-1 and 5 phosphorylation. Interleukin-31-induced ERK 1/2 activation contributes to the underlying mechanism of Th1 cytokine IL-12 suppression in macrophages. This mechanism may be relevant in Th2 inflammatory responses and may help to develop therapeutic strategies in IL-31-associated diseases such as AD.

Increased production of IL-4 and IL-12p40 from bronchoalveolar lavage cells are biomarkers of Mycobacterium tuberculosis in the sputum

BACKGROUND

Tuberculosis (TB) causes 1.45 million deaths annually world wide, the majority of which occur in the developing world. Active TB disease represents immune failure to control latent infection from airborne spread. Acid-fast bacillus (AFB) seen on sputum smear is a biomarker for contagiousness.

METHODS

We enrolled 73 tuberculosis patients with extensive infiltrates into a research study using bronchoalveolar lavage (BAL) to sample lung immune cells and assay BAL cell cytokine production. All patients had sputum culture demonstrating Mycobacterium tuberculosis and 59/73 (81%) had AFB identified by microscopy of the sputum. Compared with smear negative patients, smear positive patients at presentation had a higher proportion with smoking history, a higher proportion with temperature >38.5(0) C, higher BAL cells/ml, lower percent lymphocytes in BAL, higher IL-4 and IL-12p40 in BAL cell supernatants. There was no correlation between AFB smear and other BAL or serum cytokines. Increasing IL-4 was associated with BAL PMN and negatively associated with BAL lymphocytes. Each 10-fold increase in BAL IL-4 and IL-12p40 increased the odds of AFB smear positivity by 7.4 and 2.2-fold, respectively, in a multi-variable logistic model.

CONCLUSION

Increasing IL-4 and IL-12p40 production by BAL cells are biomarkers for AFB in sputum of patients who present with radiographically advanced TB. They likely reflect less effective immune control of pathways for controlling TB, leading to patients with increased infectiousness.

Cerebrospinal fluid IL-12p40, CXCL13 and IL-8 as a combinatorial biomarker of active intrathecal inflammation

Diagnosis and management of the neuroinflammatory diseases of the central nervous system (CNS) are hindered by the lack of reliable biomarkers of active intrathecal inflammation. We hypothesized that measuring several putative inflammatory biomarkers simultaneously will augment specificity and sensitivity of the biomarker to the clinically useful range. Based on our pilot experiment in which we measured 18 inflammatory biomarkers in 10-fold concentrated cerebrospinal fluid (CSF) derived from 16 untreated patients with highly active multiple sclerosis (MS) we selected a combination of three CSF biomarkers, IL-12p40, CXCL13 and IL-8, for further validation.Concentrations of IL-12p40, CXCL13 and IL-8 were determined in a blinded fashion in CSF samples from an initial cohort (n = 72) and a confirmatory cohort (n = 167) of prospectively collected, untreated subjects presenting for a diagnostic work-up of possible neuroimmunological disorder. Diagnostic conclusion was based on a thorough clinical workup, which included laboratory assessment of the blood and CSF, neuroimaging and longitudinal follow-up. Receiver operating characteristic (ROC) curve analysis in conjunction with principal component analysis (PCA), which was used to combine information from all three biomarkers, assessed the diagnostic value of measured biomarkers.Each of the three biomarkers was significantly increased in MS and other inflammatory neurological disease (OIND) in comparison to non-inflammatory neurological disorder patients (NIND) at least in one cohort. However, considering all three biomarkers together improved accuracy of predicting the presence of intrathecal inflammation to the consistently good to excellent range (area under the ROC curve = 0.868-0.924).Future clinical studies will determine if a combinatorial biomarker consisting of CSF IL-12p40, CXCL13 and IL-8 provides utility in determining the presence of active intrathecal inflammation in diagnostically uncertain cases and in therapeutic development and management.

Inflammatory signals direct expression of human IL12RB1 into multiple distinct isoforms

IL12RB1 is essential for human resistance to multiple intracellular pathogens, including Mycobacterium tuberculosis. In its absence, the proinflammatory effects of the extracellular cytokines IL-12 and IL-23 fail to occur, and intracellular bacterial growth goes unchecked. Given the recent observation that mouse leukocytes express more than one isoform from il12rb1, we examined whether primary human leukocytes similarly express more than one isoform from IL12RB1. We observed that human leukocytes express as many as 13 distinct isoforms, the relative levels of each being driven by inflammatory stimuli both in vitro and in vivo. Surprisingly, the most abundant isoform present before stimulation is a heretofore uncharacterized intracellular form of the IL-12R (termed "isoform 2") that presumably has limited contact with extracellular cytokine. After stimulation, primary PBMCs, including the CD4(+), CD8(+), and CD56(+) lineages contained therein, alter the splicing of IL12RB1 RNA to increase the relative abundance of isoform 1, which confers IL-12/IL-23 responsiveness. These data demonstrate both a posttranscriptional mechanism by which cells regulate their IL-12/IL-23 responsiveness, and that leukocytes primarily express IL12RB1 in an intracellular form located away from extracellular cytokine.

Early control of Mycobacterium tuberculosis infection requires il12rb1 expression by rag1-dependent lineages

IL12RB1 is essential for human resistance to Mycobacterium tuberculosis infection. In the absence of a functional IL12RB1 allele, individuals exhibit susceptibility to disseminated, recurrent mycobacterial infections that are associated with defects in both RAG1-dependent and RAG1-independent hematopoietic lineages. Despite this well-established association, a causal relationship between M. tuberculosis susceptibility and IL12RB1 deficiency in either RAG1-dependent or RAG1-independent lineages has never been formally tested. Here, we use the low-dose aerosol model of experimental tuberculosis (TB) to both establish that infected il12rb1(-/-) mice recapitulate important aspects of TB in IL12RB1 null individuals and, more importantly, use radiation bone marrow chimeras to demonstrate that restriction of il12rb1 deficiency solely to rag1-dependent lineages (i.e., T and B cells) allows for the full transfer of the il12rb1(-/-) phenotype. We further demonstrate that the protection afforded by adaptive lymphocyte il12rb1 expression is mediated partially through ifng and that, within the same infection, il12rb1-sufficient T cells exhibit dominance over il12rb1-deficient T cells by enhancing ifng expression in the latter population. Collectively, our data establish a basic framework in which to understand how IL12RB1 promotes control of this significant human disease.

Interleukin-12p40 modulates human metapneumovirus-induced pulmonary disease in an acute mouse model of infection

The mechanisms that regulate the host immune response induced by human metapneumovirus (hMPV), a newly-recognized member of the Paramyxoviridae family, are largely unknown. Cytokines play an important role in modulating inflammatory responses during viral infections. IL-12p40, a known important mediator in limiting lung inflammation, is induced by hMPV and its production is sustained after the resolution phase of infection suggesting that this cytokine plays a role in the immune response against hMPV. In this work, we demonstrated that in mice deficient in IL-12p40, hMPV infection induced an exacerbated pulmonary inflammatory response and mucus production, altered cytokine response, and decreased lung function. However, hMPV infection in these mice does not have an effect on viral replication. These results identify an important regulatory role of IL-12p40 in hMPV infection.

Francisella tularensis LVS-induced Interleukin-12 p40 cytokine production mediates dendritic cell migration through IL-12 Receptor β1

Three cytokines use the IL-12p40 cytokine subunit namely: IL-12p70 (IL-12-comprised of IL-12p40 and IL-12p35), IL-23 (comprised of the IL-12p40 and IL-23p19 subunits) and homodimeric IL-12p40 (IL-12(p40)(2)). Following activation, immature dendritic cells (DCs) upregulate the chemokine receptor Chemokine-C-Receptor 7 (CCR7), and migrate in response to homeostatic chemokines such as chemokine (C-C motif) ligand 19 (CCL19). Induction of the cytokine IL-12p40 in response to pathogen-exposure, likely in its homodimeric form, is one of the primary events that mediates migration of DCs in response to CCL19. Here we show that following exposure to Francisella tularensis Live Vaccine Strain (LVS), DCs produce IL-12p40 and promote the migration of DCs to the chemokine CCL19 in an IL-12Rβ1- and IL-12p(40)(2)-dependent manner. Induction of IL-12p40 and resulting chemokine responsiveness in DCs is TLR2-dependent and coincides with the uptake of F. tularensis LVS and activation of DCs. Importantly, we show that IL-12Rβ1 signaling is required for DC migration from the lung to the draining lymph node following F. tularensis LVS exposure and coincides with accumulation of IL-12p40 expressing DCs in the draining lymph nodes. Together, these findings illustrate that IL-12p40 is induced rapidly in response to F. tularensis LVS and is required for DC migration through an IL-12Rβ1-IL-12(p40)(2) dependent mechanism.

Azithromycin attenuates airway inflammation in a mouse model of viral bronchiolitis

Background

Viral bronchiolitis is the leading cause of hospitalization in young infants. It is associated with the development of childhood asthma and contributes to morbidity and mortality in the elderly. Currently no therapies effectively attenuate inflammation during the acute viral infection, or prevent the risk of post-viral asthma. We hypothesized that early treatment of a paramyxoviral bronchiolitis with azithromycin would attenuate acute and chronic airway inflammation.

Methods

Mice were inoculated with parainfluenza type 1, Sendai Virus (SeV), and treated daily with PBS or azithromycin for 7 days post-inoculation. On day 8 and 21 we assessed airway inflammation in lung tissue, and quantified immune cells and inflammatory mediators in bronchoalveolar lavage (BAL).

Results

Compared to treatment with PBS, azithromycin significantly attenuated post-viral weight loss. During the peak of acute inflammation (day 8), azithromycin decreased total leukocyte accumulation in the lung tissue and BAL, with the largest fold-reduction in BAL neutrophils. This decreased inflammation was independent of changes in viral load. Azithromycin significantly attenuated the concentration of BAL inflammatory mediators and enhanced resolution of chronic airway inflammation evident by decreased BAL inflammatory mediators on day 21.

Conclusions

In this mouse model of paramyxoviral bronchiolitis, azithromycin attenuated acute and chronic airway inflammation. These findings demonstrate anti-inflammatory effects of azithromycin that are not related to anti-viral activity. Our findings support the rationale for future prospective randomized clinical trials that will evaluate the effects of macrolides on acute viral bronchiolitis and their long-term consequences.

Correlation between TNF-alpha and IL-12p40-containing cytokines in silicosis

The aim of the present study was to investigate the correlation between tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-12p40-containing cytokines, in silicosis patients and healthy donors exposed to silica dust, in an attempt to clarify the reason for variety of clinical outcomes between humans with similar exposure history. Serum levels of TNF-α, IL-12p40, IL-12p70 and IL-23 in total group of 62 silicosis patients, 24 healthy donors with similar exposure history like patients and 19 healthy donors without exposure were determined by enzyme-linked-immunosorbent assay (ELISA) method. The serum level of TNF-α was significantly higher in healthy donors exposed to SiO2 (22.4 ± 11.1 pg/mL) in comparison with non-exposed healthy donors (14.8 ± 8.8 pg/mL; p = 0.022) and similar to that in silicosis patients. In total, group of silicosis patients significantly elevated levels of TNF-α (20.9 ± 12.9 vs. 14.8 ± 8.8 pg/mL; p = 0.047) and IL-12p40 (94.5 ± 51.6 pg/mL vs. 68.7 ± 26.2 pg/mL; p = 0.029) compared to non-exposed healthy donors were observed. In addition, a strong positive correlation between TNF-α and IL-23 levels (r = 0.678; p = 0.022) and between TNF-α and IL-12p70 levels (r = 0.75; p = 0.0003) was detected in the group of exposed healthy donors, while in the group of silicosis patients, a significant positive correlation was observed only between TNF-α and IL-12p40 (r = 0.434; p = 0.00048), in contrast to other IL-12p40 containing cytokines. In conclusion, we could assume that the elevated serum levels of TNF-α are associated with exposition to silica particles, while the elevation of both TNF-α and IL-12p40 is associated with silicosis development and severity. Additionally, the balance between IL-12p40-containing cytokines may also contribute to the silicosis progression.

Validating 123I-metaiodobenzylguanidine as a platelet marker for non-invasive imaging in rabbits

INTRODUCTION

Recent in vitro studies in our laboratory have demonstrated that platelets are necessary for leukocyte recruitment and airway remodelling in models of allergic airway inflammation, and also migrate to lung tissues in response to anti-IgE or relevant allergens in allergic asthma. Non-invasive imaging of platelet migration in vivo would provide a further insight into the roles of platelets in inflammatory diseases such as asthma, and metaiodobenzylguanidine (MIBG) was considered as a suitable platelet marker.

METHODS

The kinetics of MIBG uptake into rabbit platelets, the effect of MIBG on platelet function and the effect of platelet activation on MIBG uptake and retention were investigated. MIBG-labelled platelets were administered intravenously into rabbits and the time course of radioactivity in the lung and blood was monitored as a function of stimulation.

RESULTS

Following a 4h incubation of MIBG in rabbit PRP, a near maximal MIBG uptake (52.4 ± 20.2%) in platelets occurred. This time point was chosen for subsequent in vitro studies. In vitro platelet function studies showed that MIBG has no effect on ADP or PAF-induced platelet aggregation, PAF-induced thromboxane production or fMLP-induced platelet chemotaxis. However, serotonin showed a significant effect on MIBG uptake and retention, but only at high concentrations. Stimulation of rabbit platelets with ADP and PAF caused a significant release of stored MIBG in vitro. Following i.v. administration of MIBG labelled platelets, the response to i.v. ADP and PAF stimulation was small but significant.

DISCUSSION

The release of MIBG from platelets in vivo, particularly following stimulation, leads to high background levels. Therefore, MIBG may have limited utility as a label for imaging platelets in vivo using PET. However, it may be a useful marker in detecting pathological conditions where platelet migration is involved.

A novel p40-independent function of IL-12p35 is required for progression and maintenance of herpes stromal keratitis

PURPOSE. Interleukin (IL)-12p40 can couple with IL-12p35 or p19 chains to form the molecules IL-12p70 and IL-23, respectively, which promote T(H)1 cytokine responses. IL-12p35 can bind to EBI3 to form the anti-inflammatory molecule IL-35, but a proinflammatory function of IL-12p35 independent of IL-12p40 has not been described. Here such a function in a mouse model of herpes stromal keratitis (HSK), a CD4(+) T(H)1 cell-dependent corneal inflammation, is demonstrated. METHODS. Corneas of wild-type (WT), IL-12p40(-/-), IL-12p35(-/-), and IL-12p35(-/-)p40(-/-) (double knockout) mice were infected with the RE strain of HSV-1, and HSK was monitored based on corneal opacity, neovascularization, leukocytic infiltrate, and cytokine/chemokine levels. RESULTS. All mouse strains developed moderate HSK by 11 days after infection (dpi). However, from 11 to 21 dpi, HSK progressed in WT and IL-12p40(-/-) mice but regressed in IL-12p35(-/-) and IL-12p35(-/-)p40(-/-) mice. HSK regression was characterized by reductions in neutrophils and CD4(+) T cells and attenuation of blood vessels, which was associated with reduced levels of the chemokines KC (CXCL3), Mip-2 (CXCL2), and MCP-1 (CCL2) and the angiogenic factor vascular endothelial growth factor. CONCLUSIONS. HSK development does not require IL-12p40 and is thus independent of IL-12p70 and IL-23. However, late HSK progression does require a previously unrecognized IL-12p40-independent, proinflammatory function of IL-12p35.

The metallopeptide antibiotic bacitracin inhibits interleukin-12 αβ and β2 secretion

The metalloantibiotic bacitracin is a known inhibitor of protein disulfide isomerase (PDI). The disulfide-linked interleukin-12 (IL-12) αβ-heterodimer and β2-homodimer forms are crucial mediators of cell-mediated immune responses and inflammatory reactions. Bacitracin was found to potently block secretion of both the αβ- and β2-dimer forms of IL-12, while it did not affect secretion of the β-monomer. This inhibition coincided with a reduction in the intracellular amount of PDI found in complex with the β-chain during intracellular transit. Bacitracin did not affect mRNA levels of the α- and β-chain. Similar to bacitracin, N-acetylcysteine blocked αβ- and β2-secretion as well as PDI-β-chain complex formation. Thus, blocking PDI or shifting the endoplasmic reticulum towards a more reduced status disrupts the oxidative folding pathway or assembly of IL-12 dimer forms. The assembly stage of cytokines in the endoplasmic reticulum may represent a novel target for pharmacological intervention.

Inhibition of secretion of interleukin (IL)-12/IL-23 family cytokines by 4-trifluoromethyl-celecoxib is coupled to degradation via the endoplasmic reticulum stress protein HERP

Interleukin-12 (IL-12), p80, and IL-23 are structurally related cytokines sharing a p40 subunit. We have recently demonstrated that celecoxib and its COX-2-independent analogue 4-trifluoromethyl-celecoxib (TFM-C) inhibit secretion but not transcription of IL-12 (p35/p40) and p80 (p40/p40). This is associated with a mechanism involving altered cytokine-chaperone interaction in the endoplasmic reticulum (ER). In the present study, we found that celecoxib and TFM-C also block secretion of IL-23 (p40/p19 heterodimers). Given the putative ER-centric mode of these compounds, we performed a comprehensive RT-PCR analysis of 23 ER-resident chaperones/foldases and associated co-factors. This revealed that TFM-C induced 1.5-3-fold transcriptional up-regulation of calreticulin, GRP78, GRP94, GRP170, ERp72, ERp57, ERdj4, and ERp29. However, more significantly, a 7-fold up-regulation of homocysteine-inducible ER protein (HERP) was observed. HERP is part of a high molecular mass protein complex involved in ER-associated protein degradation (ERAD). Using co-immunoprecipitation assays, we show that TFM-C induces protein interaction of p80 and IL-23 with HERP. Both HERP siRNA knockdown and HERP overexpression coupled to cycloheximide chase assays revealed that HERP is necessary for degradation of intracellularly retained p80 by TFM-C. Thus, our data suggest that targeting cytokine folding in the ER by small molecule drugs could be therapeutically exploited to alleviate inappropriate inflammation in autoimmune conditions.

Changes of cytokine production and cell viability of peripheral blood mononuclear cells from silicosis patients: effect of in vitro treatment with acetylsalicylic acid

In this study, IL-6 and IL-12p40 production and cell viability of peripheral blood mononuclear cells from silicosis patients after in vitro stimulation were investigated. Furthermore, the effects of introducing acetylsalicylic acid to stimulated patients’ peripheral blood mononuclear cells on cytokine production and cell viability were determined. Nine patients with moderate silicosis, 11 with severe silicosis and 14 healthy subjects were recruited for this study. The level of IL-6 produced by patients peripheral blood mononuclear cells decreased depending on the stage of the disease. The addition of acetylsalicylic acid had significantly suppressive effect on the IL-6 production by lipopolysaccharide—stimulated patients’ peripheral blood mononuclear cells. Acetylsalicylic acid treatment of C3 binding glycoprotein—stimulated patients’ peripheral blood mononuclear cells led to significant upregulation of IL-12p40 production. Results showed a stage-dependent decrease of cell viability of peripheral blood mononuclear cells from silicosis patients. Acetylsalicylic acid significantly decreased cell viability entirely in stimulated peripheral blood mononuclear cells from patients with severe silicosis. In conclusion, this study showed that the disease progression affects peripheral blood mononuclear cells in patients with silicosis and causes functional changes that became apparent after stimulation. Our study demonstrated that in severe silicosis the treatment with acetylsalicylic acid, as an anti-inflammatory agent, might not be beneficial for patients.

Interleukin 12 stimulates IFN-gamma-mediated inhibition of tumor-induced regulatory T-cell proliferation and enhances tumor clearance

To define the factors that modulate regulatory T (Treg) cells in the tumor setting, we cocultured various tumor cells with either purified Treg cells, or with unfractionated splenocytes. We found that Treg expansion occurred only with unfractionated splenocytes, suggesting that accessory cells and/or factors produced by them play an essential role in tumor-induced Treg expansion. We performed gene expression profiling on tumor-associated Treg cells to identify candidate signaling molecules and studied their effects on tumor-induced Treg expansion. We inadvertently discovered that interleukin (IL)-12 treatment blocked Treg expansion in an IL-12 receptor-dependent fashion. Additional studies showed that IL-12 acts by stimulating IFN-gamma mediated inhibition of Treg cell proliferation, which may partially account for the antitumor effects of IL-12. Furthermore, IL-12 treatment was found to decrease IL-2 production, which may lead to IFN-gamma-independent inhibition of Treg cells, as IL-2 is required for their survival and expansion. Mechanistic studies revealed that IFN-gamma signaling directly causes cell cycle arrest in Treg cells. This study shows that an IL-12-IFN-gamma axis can suppress tumor-induced Treg proliferation. This mechanism may counteract the ability of Treg cells to promote tumor growth in vivo.

12/15-lipoxygenase-dependent myeloid production of interleukin-12 is essential for resistance to chronic toxoplasmosis

Interleukin-12 (IL-12) is critical for resistance to Toxoplasma gondii during both the acute and chronic stages of infection. However, the cellular and molecular pathways that regulate IL-12 production during chronic toxoplasmosis are incompletely defined. We recently discovered that 12/15-lipoxygenase (12/15-LOX), which oxidizes unsaturated lipids in macrophages, is a novel and selective regulator of IL-12 production. We now demonstrate the essential role of this enzyme in the chronic phase of toxoplasmosis. Although 12/15-LOX-deficient mice were resistant to acute T. gondii infection, 80% of 12/15-LOX-deficient mice died during chronic toxoplasmosis, compared to no deaths in wild-type controls. The morbidity of chronically infected 12/15-LOX mice was associated with an increase in brain inflammation and parasite burden. These data suggest that the evolution of the immune response to T. gondii is accompanied by an increasing requirement for 12/15-LOX-mediated signaling. Consistent with this conclusion, 12/15-LOX activity was enhanced during chronic, but not acute, toxoplasmosis. Furthermore, the enhanced susceptibility of 12/15-LOX-deficient mice to chronic toxoplasmosis was associated with reduced production of IL-12 and gamma interferon (IFN-gamma) that was not evident during acute infection. Importantly, ex vivo IFN-gamma production by 12/15-LOX-deficient splenocytes could be rescued by the addition of recombinant IL-12. These data establish that 12/15-LOX is a critical mediator of the chronic type 1 inflammatory response and that immune mediators can be subject to distinct cellular and/or molecular mechanisms of regulation at different stages of inflammation.

Suppression of regulatory T cells by IL-12p40 homodimer via nitric oxide

Regulatory T cells (Tregs) play a pivotal role in the maintenance of homeostasis between immune response and immune tolerance. The transcription factor Foxp3 and the surface protein CD25 are the two key molecules characterizing Tregs. In autoimmune and various other chronic inflammatory diseases, the expression of Foxp3 is severely down-regulated. However, the molecular mechanism underlying the down-regulation of Foxp3 is not understood yet. Because the IL-12p40 homodimer (p40(2)) is markedly up-regulated in response to various inflammatory stimuli, the present study was undertaken to explore the role of p40(2) in the regulation of Foxp3 in naive mouse splenocytes. IL-12p40(2) dose-dependently inhibited the expression of Foxp3 and CD25, but not CD4. Interestingly, this inhibition was absent in splenocytes of IL-12Rbeta1(-/-), but not IL-12Rbeta2(-/-), mice. Moreover, suppression of Foxp3 in wild-type and IL-12Rbeta2(-/-) splenocytes was accompanied by production of NO. Consistently, l-N(6)-(1-iminoethyl)-lysine hydrochloride, an inhibitor of inducible NO synthase (iNOS), and PTIO, a scavenger of NO, restored the expression of Foxp3 and CD25 in p40(2)-stimulated splenocytes, and p40(2) was unable to down-regulate Foxp3 and CD25 in splenocytes from iNOS(-/-) mice. Furthermore, NO, but not p40(2), was able to inhibit Foxp3 in purified CD4(+)CD25(+) T cells in the absence of iNOS-expressing cells. Hence, our results clearly demonstrate that p40(2) induces NO production via IL-12Rbeta1 and that NO subsequently suppresses Tregs in naive mouse splenocytes. This study, therefore, delineates an unprecedented biological function of p40(2) in the regulation of Foxp3 via IL-12Rbeta1-mediated NO production.

Azithromycin attenuates airway inflammation in a noninfectious mouse model of allergic asthma

BACKGROUND

Definitive conclusions regarding the antiinflammatory effects of macrolide antibiotics for treatment of asthma are difficult to formulate since their beneficial effects may be related to their antimicrobial action. We hypothesized that azithromycin possesses distinct antiinflammatory properties and tested this assumption in a noninfectious mouse model of allergic asthma.

METHODS

To induce allergic airway inflammation, 7-week-old BALB/cJ mice underwent intraperitoneal ovalbumin sensitization on days 0 and 7 followed by an intranasal challenge on day 14. Mice were treated with azithromycin or phosphate-buffered saline (PBS) solution on days 13 through 16. On day 17, airway inflammation was assessed by quantifying leukocytes in the airway, expression of multiple inflammatory mediators in the BAL fluid, and mucous cell metaplasia. In a separate set of experiments, azithromycin or PBS solution treatment were initiated after the ovalbumin challenge. Each experiment was repeated 3 times (a total of 9 to 11 mice in each group).

RESULTS

Compared to treatment with PBS solution, azithromycin attenuated the ovalbumin-dependent airway inflammation. We observed a decrease in total leukocytes in the lung tissue and BAL fluid. In addition, azithromycin attenuated the expression of cytokines (eg, interleukin [IL]-13 and IL-5) and chemokines (eg, CCL2, CCL3, and CCL4) in the BAL fluid and abrogated the extent of mucous cell metaplasia. Similar antiinflammatory effects were observed when azithromycin treatment was initiated after the ovalbumin challenge.

CONCLUSION

In this noninfectious mouse model of allergic asthma, azithromycin attenuated allergic airway inflammation. These findings demonstrate an antiinflammatory effect of azithromycin and suggest azithromycin may have beneficial effects in treating noninfectious airway inflammatory diseases, including asthma.

IL-12 p40 homodimer, but not IL-12 p70, induces the expression of IL-16 in microglia and macrophages

IL-16, a leukocyte chemoattractant factor (LCF), is involved in the disease process of multiple sclerosis and other autoimmune disorders. However, mechanisms by which this LCF is expressed are poorly understood. The present study underlines the importance of IL-12 p40 homodimer (p40(2)), the so-called biologically inactive molecule, in inducing the expression of IL-16 in primary mouse and human microglia, mouse BV-2 microglial cells, mouse peritoneal macrophages, and RAW264.7 cells. In contrast, IL-12 p70, the bioactive heterodimeric cytokine, was unable to induce the expression of IL-16 in any of these cell types. Similarly IL-12 p40(2) also induced the activation of IL-16 promoter in microglia. Among various stimuli tested, p40(2) was the most potent one followed by p40 monomer, IL-16 and IL-23 in inducing the activation of IL-16 promoter in microglial cells. Furthermore, induction of IL-16 mRNA expression by over-expression of p40, but not p35, cDNA and induction of IL-16 expression by p40(2) in microglia isolated from IL-12p35 (-/-) mice confirm that p40, but not p35, is responsible for the induction of IL-16. Finally, by using primary microglia isolated from IL-12Rbeta1 (-/-) and IL-12Rbeta2 (-/-) mice, we demonstrate that p40(2) induces the expression of this LCF via IL-12Rbeta1 but not IL-12Rbeta2. These results delineate a novel biological function of p40(2) and raise the possibility that biological function of IL-12 p40(2) may be different from IL-12 p70.

IL-12 p80-dependent macrophage recruitment primes the host for increased survival following a lethal respiratory viral infection

A protective immune response to a respiratory viral infection requires a series of coordinated cellular and molecular responses. We have previously demonstrated that increased expression of airway epithelial cell interleukin (IL)-12 p80, a macrophage chemoattractant, is associated with human respiratory viral infection and mediates post-viral mortality in the mouse. To better understand the role of IL-12 p80-dependent macrophage chemotaxis in mediating viral immunity, we generated a transgenic mouse strain utilizing a promoter to drive IL-12 p40 gene expression in the airway epithelium. This transgenic strain secreted biologically active IL-12 p80 in a lung-specific manner, and demonstrated a selective increase in the number of resident, unactivated airway macrophages at baseline. Following infection with a sublethal dose of mouse parainfluenza virus type 1 (Sendai virus), the transgenic mice demonstrated an earlier peak and decline in the number of airway inflammatory cells. The transgenic mice were resistant to a lethal dose of virus and this viral resistance was dependent on the increased number of airway macrophages at baseline as partial depletion prior to infection abrogated this phenotype. The survival advantage in the transgenic mice was independent of viral load but was associated with a more rapid decline in the number of airway inflammatory cells and concentrations of multiple chemokines including the CC chemokine ligand 2 (CCL2)/JE, CCL3/macrophage inflammatory protein (MIP)-1alpha, CCL4/MIP-1beta, and CCL5/RANTES. Collectively, these results suggest that IL-12 p80-driven increases in the number of resident airway macrophages prime the host for a protective immune response that can confer increased survival following a lethal respiratory viral infection.

Differential regulation of antigen-specific CD8+ T cell responses by IL-12p40 in a dose-dependent manner

IL-12p40 is a natural antagonist which inhibits IL-12- and IL-23-mediated biological activity by blocking the binding of IL-12/23 to their receptors. Recently, IL-12p40 was also shown to have immune-enhancing activity through the activation of macrophages or dendritic cells. In this study, we investigated the effects of IL-12p40 as a genetic adjuvant on immune modulation using recombinant adenoviruses expressing IL-12p40 (rAd/IL-12p40) and OVA (rAd/OVA). Coimmunization of rAd/IL-12p40 at a low dose (1 x 10(4) PFU) with rAd/OVA resulted in OVA-specific immune enhancement, while a high dose of rAd/IL-12p40 (1 x 10(8) PFU) caused significant suppression of CD8(+) T cell responses. In addition, the enhancement and suppression of OVA-specific CD8(+) T cell responses correlated with antitumor activity against E.G7-OVA tumor challenge, which subsequently affected the survival rate. Moreover, the differential CD8(+) T cell response by IL-12p40 was still observed in IL-12Rbeta2 knockout (IL-12Rbeta2KO), but not in IL-12Rbeta1 knockout (IL-12Rbeta1KO) mice, indicating that IL-12p40 is a cytokine which can modulate Ag-specific T cell responses depending on IL-12Rbeta1. Our findings provide a novel insight on the physiological role of IL-12p40, which can be informative in the design of vaccine strategies and therapeutic regimens.

Scavenging roles of chemokine receptors: chemokine receptor deficiency is associated with increased levels of ligand in circulation and tissues

In vitro studies have implicated chemokine receptors in consumption and clearance of specific ligands. We studied the role that various signaling chemokine receptors play during ligand homeostasis in vivo. We examined the levels of ligands in serum and CNS tissue in mice lacking chemokine receptors. Compared with receptor-sufficient controls, Cx3cr1(-/-) mice exhibited augmented levels of CX3CL1 both in serum and brain, and circulating levels of CXCL1 and CXCL2 were increased in Cxcr2(-/-) mice. CCR2-deficient mice showed significantly increased amounts of circulating CCL2 compared with wild-type mice. Cxcr3(-/-) mice revealed increased levels of circulating and brain CXCL10 after experimental autoimmune encephalomyelitis (EAE) induction. CCR2-deficient peripheral blood and resident peritoneal cells exhibited reduced binding capacity and biologic responses to the CCR1 ligand CCL3, suggesting that elevated levels of CCR2 ligands had down-regulated CCR1. The results indicate that signaling chemokine receptors clear chemokines from circulation and tissues. These homeostatic functions of signaling chemokine receptors need to be integrated into safety and efficacy calculations when considering therapeutic receptor blockade.

Interleukin-12B-3'UTR polymorphism in association with IL-12p40 and IL-12p70 serum levels and silicosis severity

Susceptibility to silicosis and to disease severity is in part genetically determined. In this study, the role of IL-12B-3'UTR polymorphism in susceptibility and severity of silicosis and its influence on IL-12p40 and IL-12p70 serum level were investigated. The quantity of IL-12p40 and IL-12p70 was detected by enzyme-linked immunosorbent assay and the genotype of IL-12B was determined using the polymerase chain reaction-restriction fragment-length polymorphism method. We observed elevated IL-12p40 in contrast to IL-12p70 serum levels in a group of 62 silicosis patients compared with both control groups. In severe silicosis patients, we detected the highest IL-12p40 serum levels (129.1 +/- 67.7 pg mL(-1)); lower in patients with the moderate (94 +/- 41.6 pg mL(-1)), whereas in mild silicosis, the IL-12p40 levels (67 +/- 23.5 pg mL(-1)) was similar to these in healthy donors. According to IL-12B polymorphism, increased serum levels were observed in subjects with AA genotype (103.2 +/- 46.9 pg mL(-1)) compared to silicosis patients with AC genotype (82.7 +/- 38.3 pg mL(-1)). No significant differences of genotype and allele frequencies of the 3'UTR polymorphism were observed between silicosis patients and healthy controls. However, the heterozygous genotype was found approximately five times more frequently in patients with mild and moderate (48% and 52%) silicosis compared to patients with severe silicosis (11%), and that IL-12B polymorphism may contribute to silicosis severity rather than to susceptibility. Our data demonstrated that elevated serum IL-12p40, independently of IL-12p70 levels, is associated with severity of silicosis, and suggested that IL-12p40 profibrotic activity may contribute to silicosis severity.

Dendritic cell-derived IL-12p40 homodimer contributes to susceptibility in cutaneous leishmaniasis in BALB/c mice

Protection against Leishmania major in resistant C57BL/6 mice is mediated by Th1 cells, whereas susceptibility in BALB/c mice is the result of Th2 development. IL-12 release by L. major-infected dendritic cells (DC) is critically involved in differentiation of Th1 cells. Previously, we reported that strain differences in the production of DC-derived factors, e.g., IL-1alphabeta, are in part responsible for disparate disease outcome. In the present study, we analyzed the release of IL-12 from DC in more detail. Stimulated DC from C57BL/6 and BALB/c mice released comparable amounts of IL-12p40 and p70. In the absence of IL-4, BALB/c DC produced significantly more IL-12p40 than C57BL/6 DC. Detailed analyses by Western blot and ELISA revealed that one-tenth of IL-12p40 detected in DC supernatants was released as the IL-12 antagonist IL-12p40 homodimer (IL-12p80). BALB/c DC released approximately 2-fold more IL-12p80 than C57BL/6 DC both in vitro and in vivo. Local injection of IL-12p80 during the first 3 days after infection resulted in increased lesion volumes for several weeks in both L. major-infected BALB/c or C57BL/6 mice, in higher lesional parasite burdens, and decreased Th1-cytokine production. Finally, IL-12p40-transgenic C57BL/6 mice characterized by overexpression of p40 showed increased levels of serum IL-12p80 and enhanced disease susceptibility. Thus, in addition to IL-1alphabeta, strain-dependent differences in the release of other DC-derived factors such as IL-12p80 may influence genetically determined disease outcome.

Interleukin-12p40 overexpression promotes interleukin-12p70 and interleukin-23 formation but does not affect bacille Calmette-Guérin and Mycobacterium tuberculosis clearance

Interleukin (IL)-12p40, a subunit of IL-12p70 and IL-23, has previously been shown to inhibit IL-12p70 activity and interferon-gamma (IFN-gamma) production. However, recent evidence has suggested that the role of IL-12p40 is more complex. To study the contribution of IL-12p40 to immune responses against mycobacterial infections, we have used transgenic (tg) mice overexpressing IL-12p40 under the control of a major histocompatibility complex-II promoter. The IL-12p40 transgene was expressed during steady state at concentrations of 129 +/- 25 ng/ml of serum and 75 +/- 13 ng per spleen, while endogenous IL-12p40 was hardly detectable in control littermates. Bacille Calmette-Guérin (BCG) infection strongly induced the expression of IL-12p40 transgene in infected organs, and IL-12p40 monomeric and dimeric forms were identified in spleen of IL-12p40 tg mice. Excessive production of IL-12p40 resulted in a 14-fold increase in IL-12p70 serum levels in tg mice versus non-transgenic mice. IL-23 was also strongly elevated in the serum and spleens of IL-12p40 tg mice through BCG infection. While IFN-gamma and tumour necrosis factor protein levels were similar in IL-12p40 tg and non-transgenic mice, Th2 type immune responses were reduced in IL-12p40 tg mice. The number of BCG granulomas and macrophage expressing inducible nitric oxide synthase were similar in IL-12p40 tg and non-transgenic mice. IL-12p40 tg mice were as resistant as non-transgenic mice to BCG and Mycobacterium tuberculosis infections as they could efficiently control bacillary growth. These data show that high amounts of IL-12p40 promotes IL-12p70 and IL-23 formation, but that does not affect T helper 1 type immune responses and granuloma function, thus leading to normal mycobacterial clearance in infected organs.

IL-12p40: an inherently agonistic cytokine

IL-12p40 is known as a component of the bioactive cytokines interleukin (IL)-12 and IL-23 but it is not widely recognized as having intrinsic functional activity. Recent publications have altered this perception and support an independent role for IL-12p40. IL-12p40 is induced in excess over the other subunits of IL-12 and IL-23 and can exist in a monomeric or homodimeric form. Its most widely appreciated function is to provide a negative feedback loop by competitively binding to the IL-12 receptor. However, IL-12p40 acts as a chemoattractant for macrophages and promotes the migration of bacterially stimulated dendritic cells. It is associated with several pathogenic inflammatory responses such as silicosis, graft rejection and asthma but it is also protective in a mycobacterial model. An appreciation of the independent function of IL-12p40 is important for improving our understanding of both protective and pathogenic immune responses.

IL-23 plays a key role in Helicobacter hepaticus-induced T cell-dependent colitis

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract that is caused in part by a dysregulated immune response to the intestinal flora. The common interleukin (IL)-12/IL-23p40 subunit is thought to be critical for the pathogenesis of IBD. We have analyzed the role of IL-12 versus IL-23 in two models of Helicobacter hepaticus-triggered T cell-dependent colitis, one involving anti-IL-10R monoclonal antibody treatment of infected T cell-sufficient hosts, and the other involving CD4+ T cell transfer into infected Rag-/- recipients. Our data demonstrate that IL-23 and not IL-12 is essential for the development of maximal intestinal disease. Although IL-23 has been implicated in the differentiation of IL-17-producing CD4+ T cells that alone are sufficient to induce autoimmune tissue reactivity, our results instead support a model in which IL-23 drives both interferon gamma and IL-17 responses that together synergize to trigger severe intestinal inflammation.

Involvement of three mechanisms in the alteration of cytokine responses by sodium methyldithiocarbamate

Sodium methyldithiocarbamate (SMD) is the third most abundantly used conventional pesticide in the U.S. We recently reported that it alters the induction of cytokine production mediated though Toll-like receptor (TLR) 4 at relevant dosages in mice. Its chemical properties and evidence from the literature suggest the potential mechanisms of action for this compound. It could either act as a free radical scavenger (by means of its free S(-)group) or promote oxidation by breaking down to form methylisothiocyanate, which can deplete glutathione. It is a potent copper chelator and may affect the availability of copper to a number of copper-dependent enzymes (including some signaling molecules). SMD induces a classical neuroendocrine stress response characterized by elevated serum corticosterone concentrations, which could affect cytokine production. Although each of these mechanisms could potentially contribute to altered cytokine responses, direct evidence is lacking. The present study was conducted to obtain such evidence. The role of redox balance was investigated by pretreating mice with N-acetyl cysteine (NAC), which increases cellular glutathione concentrations, before administration of SMD. NAC exacerbated the SMD-induced suppression of IL-12 and the SMD-induced enhancement of IL-10 in the serum. The role of copper chelation was investigated by comparing the effects of SMD with an equimolar dose to SMD that was administered in the form of a copper chelation complex. Addition of copper significantly decreased the action of SMD on IL-12 production but not on IL-10 production. The role of the stress response was investigated by pretreating mice with antagonists of corticosterone and catecholamines. This treatment partially prevented the action of SMD on IL-10 and IL-12 in the peritoneal fluid. The results suggest that all of the proposed mechanisms have some role in the alteration of cytokine production by SMD.

Interleukin 12p40 is required for dendritic cell migration and T cell priming after Mycobacterium tuberculosis infection

Migration of dendritic cells (DCs) to the draining lymph node (DLN) is required for the activation of naive T cells. We show here that migration of DCs from the lung to the DLN after Mycobacterium tuberculosis (Mtb) exposure is defective in mice lacking interleukin (IL)-12p40. This defect compromises the ability of IL-12p40–deficient DCs to activate naive T cells in vivo; however, DCs that express IL-12p40 alone can activate naive T cells. Treatment of IL-12p40–deficient DCs with IL-12p40 homodimer (IL-12(p40)₂) restores Mtb-induced DC migration and the ability of IL-12p40–deficient DCs to activate naive T cells. These data define a novel and fundamental role for IL-12p40 in the pathogen-induced activation of pulmonary DCs.

Elevated interferon gamma expression in the central nervous system of tumour necrosis factor receptor 1-deficient mice with experimental autoimmune encephalomyelitis

Inflammation in the central nervous system (CNS) can be studied in experimental autoimmune encephalomyelitis (EAE). The proinflammatory cytokines interferon-gamma (IFN-gamma) and tumour necrosis factor (TNF) are implicated in EAE pathogenesis. Signals through the type 1 TNF receptor (TNFR1) are required for severe EAE to develop, whereas deficiency in IFN-gamma or its receptor result in more severe EAE. We investigated IFN-gamma expression in TNFR1-deficient (TNFR1-/-) mice. We describe here that there were more IFN-gamma-secreting T cells present in the CNS of TNFR1-/- mice during EAE compared to wild-type (WT) mice, despite that clinical symptoms were mild, with delayed onset. There was greater expression of IL-12/23p40 by antigen-presenting cells in these mice, and in vitro, TNFR1-/- antigen-presenting cells induced greater secretion of IFN-gamma but not interleukin (IL)-17 when cultured with primed T cells than did WT antigen presenting cells. TNFR1-/- mice with EAE had significantly higher expression of CXCL10 mRNA (but not CCL5 mRNA) in the CNS compared to WT mice with EAE. These data demonstrate that IFN-gamma expression is enhanced in the CNS of TNFR1-/- mice with EAE and suggest that IFN-gamma levels do not necessarily correlate with EAE severity.

IL-12 p80 is an innate epithelial cell effector that mediates chronic allograft dysfunction

RATIONALE

Bronchiolitis obliterans syndrome is the leading cause of chronic lung allograft dysfunction. We have demonstrated that respiratory viral infection is a bronchiolitis obliterans syndrome risk factor and virus-dependent injury induces expression of innate airway epithelial genes belonging to the interleukin (IL)-12 family. Thus, we hypothesized that epithelial cell IL-12 family members could mediate lung allograft dysfunction.

OBJECTIVES

We used mouse and human allograft specimens to evaluate the role of epithelial cell IL-12 family members in allograft dysfunction associated with and without viral infection.

METHODS

Murine and human IL-12 family members were characterized and manipulated in allografts and then correlated with epithelial cell injury, immune cell accumulation, and collagen deposition.

RESULTS

In a mouse model of lung transplantation, concurrent viral infection and allogeneic transplantation increased epithelial injury and this was followed by exaggerated accumulation of macrophages and collagen deposition. This virus-driven allograft dysfunction was associated with an epithelial innate response manifested by a synergistic increase in the production of the macrophage chemoattractant IL-12 p80 (p80), but not IL-12 or IL-23. Blockade or overexpression of donor epithelial p80 resulted in a corresponding abrogation or enhancement of macrophage accumulation and allograft dysfunction. We extended these findings to human recipients with viral infection and transplant bronchitis and again observed excessive epithelial p80 expression that correlated with increased macrophage accumulation.

CONCLUSIONS

These experiments support a role for an enhanced epithelial innate response as a central process in allograft dysfunction and identify the macrophage chemoattractant p80 as an innate epithelial effector of disease progression.