Interferon-gamma-inducing factor, a novel cytokine, enhances Fas ligand-mediated cytotoxicity of murine T helper 1 cells

Role of IL-18 in adipose tissue remodeling and metabolic dysfunction

BACKGROUND/OBJECTIVES

Proinflammatory cytokines are increased in obese adipose tissue, including inflammasome key masters. Conversely, IL-18 protects against obesity and metabolic dysfunction. We focused on the IL-18 effect in controlling adipose tissue remodeling and metabolism.

MATERIALS/SUBJECTS AND METHODS

We used C57BL/6 wild-type (WT) and interleukine-18 deficient (IL-18-/-) male mice fed a chow diet and samples from bariatric surgery patients.

RESULTS

IL-18-/- mice showed increased adiposity and proinflammatory cytokine levels in adipose tissue, leading to glucose intolerance. IL-18 was widely secreted by stromal vascular fraction but not adipocytes from mice's fatty tissue. Chimeric model experiments indicated that IL-18 controls adipose tissue expansion through its presence in tissues other than bone marrow. However, IL-18 maintains glucose homeostasis when present in bone marrow cells. In humans with obesity, IL-18 expression in omental tissue was not correlated with BMI or body fat mass but negatively correlated with IRS1, GLUT-4, adiponectin, and PPARy expression. Also, the IL-18RAP receptor was negatively correlated with IL-18 expression.

CONCLUSIONS

IL-18 signaling may control adipose tissue expansion and glucose metabolism, as its absence leads to spontaneous obesity and glucose intolerance in mice. We suggest that resistance to IL-18 signaling may be linked with worse glucose metabolism in humans with obesity.

Interleukin‑18 binding protein: Biological properties and roles in human and animal immune regulation (Review)

IL-18 binding protein (IL-18BP) is a natural regulatory molecule of the proinflammatory cytokine IL-18. It can regulate activity of IL-18 by high affinity binding. The present review aimed to highlight developments, characteristics and functions of IL-18BP. IL-18BP serves biological and anti-pathological roles in treating disease. In humans, it modulates progression of a number of chronic diseases, such as adult-onset Still's disease. The present review summarizes molecular structure, role of IL-18BP in disease and interaction with other proteins in important pathological processes.

Innate lymphoid cells in early tumor development

Innate and adaptive immune cells monitor, recognize, and eliminate transformed cells. Innate lymphoid cells (ILCs) are innate counterparts of T cells that play a key role in many facets of the immune response and have a profound impact on disease states, including cancer. ILCs regulate immune responses by responding and integrating a wide range of signals within the local microenvironment. As primarily tissue-resident cells, ILCs are ideally suited to sense malignant transformation and initiate anti-tumor immunity. However, as ILCs have been associated with anti-tumor and pro-tumor activities in established tumors, they could potentially have dual functions during carcinogenesis by promoting or suppressing the malignant outgrowth of premalignant lesions. Here we discuss emerging evidence that shows that ILCs can impact early tumor development by regulating immune responses against transformed cells, as well as the environmental cues that potentially induce ILC activation in premalignant lesions.

The role of Interleukin-18 in recurrent early pregnancy loss

BACKGROUND

A successful pregnancy is a unique and complex immunological state. Cytokines seem to be crucial for the implementation of a tolerogenic environment at the feto-maternal interphase towards the semi-allogenic fetus. Importantly, the switch from a Th1- to a Th2 cytokine profile might play a key role. Interestingly, Interleukin-18 (IL-18) can induce either Th1 or Th2 immune response depending on the local cytokine environment. Therefore, this study investigates the expression of IL-18 in early pregnancy loss.

PATIENTS AND METHODS

The TaqMan® Human Cytokine Network Array was carried out with placental tissue of patients with healthy pregnancies (n = 15) and recurrent miscarriage (n = 15) in order to investigate differences in IL-18 mRNA expression. Immunohistochemical staining was applied to examine the IL-18 protein expression in the syncytiotrophoblast and decidua of healthy pregnancies (n = 15), spontaneous (n = 12) and recurrent miscarriage (n = 9). The characterization of IL-18 expressing cells in the decidua was evaluated by double-immunofluorescence. Correlation analysis between IL-18 protein expression and clinical data of the study population was performed via spearman correlation coefficient.

RESULTS

Gene expression analysis revealed a 4,9-times higher expression of IL-18 in recurrent miscarriage patients. IL-18 protein expression was significantly upregulated only in the decidua in the recurrent miscarriage group (p = 0.031). We did not observe significant changes of IL-18 protein expression in spontaneous miscarriage specimens when compared to healthy controls (p = 0.172). Double-immunofluorescence identified decidual stroma cells as IL-18 expressing cells. Correlation analysis showed a significant negative correlation of IL-18 protein expression and gestational age in healthy controls (r = -,745, p = 0.034). Also, a positive correlation of IL-18 and maternal age was observed in patients suffering from recurrent pregnancy loss (r =, 894, p = 0.041).

CONCLUSION

Our results indicate that IL-18 expression might be necessary in early gestation but requires a tight regulation for a successful ongoing pregnancy. In the present study we observed that a significant upregulation of IL-18 in the decidua was restricted to patients with recurrent miscarriage and therefore might be interesting as a diagnostic marker. Further studies need to evaluate the exact pathophysiological mechanisms.

Unveiling the heterogeneity of NKT cells in the liver through single cell RNA sequencing

CD1d-dependent type I NKT cells, which are activated by lipid antigen, are known to play important roles in innate and adaptive immunity, as are a portion of type II NKT cells. However, the heterogeneity of NKT cells, especially NKT-like cells, remains largely unknown. Here, we report the profiling of NKT (NK1.1⁺CD3e⁺) cells in livers from wild type (WT), Jα18-deficient and CD1d-deficient mice by single-cell RNA sequencing. Unbiased transcriptional clustering revealed distinct cell subsets. The transcriptomic profiles identified the well-known CD1d-dependent NKT cells and defined two CD1d-independent NKT cell subsets. In addition, validation of marker genes revealed the differential organ distribution and landscape of NKT cell subsets during liver tumor progression. More importantly, we found that CD1d-independent Sca-1⁻CD62L⁺ NKT cells showed a strong ability to secrete IFN-γ after costimulation with IL-2, IL-12 and IL-18 in vitro. Collectively, our findings provide a comprehensive characterization of NKT cell heterogeneity and unveil a previously undefined functional NKT cell subset.

Psoriasis and Connective Tissue Diseases

Psoriasis is a chronic systemic inflammatory disease with various co-morbidities, having been recently considered as a comprehensive disease named psoriatic disease or psoriatic syndrome. Autoimmune diseases are one form of its co-morbidities. In addition to the genetic background, shared pathogenesis including innate immunity, neutrophil extracellular trap (NETs), and type I interferon, as well as acquitted immunity such as T helper-17 (Th17) related cytokines are speculated to play a significant role in both psoriasis and connective tissue diseases. On the other hand, there are definite differences between psoriasis and connective tissue diseases, such as their pathomechanisms and response to drugs. Therefore, we cannot expect that one stone kills two birds, and thus caution is necessary when considering whether the administered drug for one disease is effective or not for another disease. In this review, several connective tissue diseases and related diseases are discussed from the viewpoint of their coexistence with psoriasis.

Redefining the ancestral origins of the interleukin-1 superfamily

The interleukin-1 (IL-1) receptor and ligand families are components of the immune system. Knowledge of their evolutionary history is essential to understand their function. Using chromosomal anatomy and sequence similarity, we show that IL-1 receptor family members are related and nine members are likely formed from duplication and modification of a proto-IL-1R1 receptor. The IL-1 ligands have a different evolutionary history. The first proto-IL-1β gene coincided with proto-IL-1R1 and duplication events resulted in the majority of IL-1 ligand family members. However, large evolutionary distances are observed for IL-1α, IL-18 and IL-33 proteins. Further analysis show that IL-33 and IL-18 have poor sequence similarity and no chromosomal evidence of common ancestry with the IL-1β cluster and therefore should not be included in the IL-1 ligand ancestral family. IL-1α formed from the duplication of IL-1β, and moonlighting functions of pro-IL-1α acted as divergent selection pressures for the observed sequence dissimilarity.

IL18 rs360719 A>G, IL18R1 rs13015714 G>T, IL18RAP rs917997 C>T and IL28B rs8099917 T>G polymorphisms and risk of gastric cardiac adenocarcinoma

The present study was conducted to investigate the association between gastric cardiac adenocarcinoma (GCA) and four functional single-nucleotide polymorphisms (SNPs), including interleukin 18 (IL18) rs360719 A>G, IL18 receptor 1 (IL18R1) rs13015714 G>T, IL18 receptor accessory protein (IL18RAP) rs917997 C>T and interleukin 28B (IL28B) rs8099917 T>G variants. A hospital-based case-control study was performed to evaluate the genetic effects of these SNPs. A total of 243 GCA cases and 476 controls were enrolled in this study. A custom-by-design 48-Plex SNPscan™ kit was used to determine the genotypes. When the IL18 rs360719 AA homozygote genotype was used as the reference group, the AG genotype was not associated with the risk for GCA; the GG genotype was also not associated with the risk for GCA. In the dominant model, the IL18 rs360719 AG/GG variants were not associated with the risk for GCA, compared with the IL18 rs360719 AA genotype. In the recessive model, when the IL18R1 rs13015714 AA/AG genotypes were used as the reference group, the GG homozygote genotype was not associated with risk for GCA. No association was observed between IL18R1 rs13015714 G>T, IL18RAP rs917997 C>T and IL28B rs8099917 T>G polymorphisms and the risk for GCA. These results demonstrated that the functional polymorphisms IL18 rs360719 A>G, IL18R1 rs13015714 G>T, IL18RAP rs917997 C>T and IL28B rs8099917 T>G do not contribute to GCA susceptibility. However, as the statistical power of our study was limited, large well-designed studies and further functional investigations are required to confirm our findings.

Role of the inflammasome-related cytokines Il-1 and Il-18 during infection with murine coronavirus

The inflammasome, a cytosolic protein complex that mediates the processing and secretion of pro-inflammatory cytokines, is one of the first responders during viral infection. The cytokines secreted following inflammasome activation, which include IL-1 and IL-18, regulate cells of both the innate and adaptive immune system, guiding the subsequent immune responses. In this study, we used murine coronavirus, mouse hepatitis virus (MHV), infection of the central nervous system and liver to assess of the role of the inflammasome and its related cytokines on pathogenesis and host defense during viral infection. Mice lacking all inflammasome signaling due to the absence of caspase-1 and -11 were more vulnerable to infection, with poor survival and elevated viral replication compared to wild-type mice. Mice lacking IL-1 signaling experienced elevated viral replication but similar survival compared to wild-type controls. In the absence of IL-18, mice had elevated viral replication and poor survival, and this protective effect of IL-18 was found to be due to promotion of interferon gamma production in αβ T cells. These data suggest that inflammasome signaling is largely protective during murine coronavirus infection, in large part due to the pro-inflammatory effects of IL-18.

Effects of tumor vaccine expressing Granulocyte-Macrophage Colony Stimulating Factor and interleukin-18 fusion on cancer cells and its possible application for cancer immunotherapy

To access antitumor effects of a combined Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) and interleukin-18 (IL-18), cDNA fusion of murine GM-CSF and mature IL-18 (GMIL-18) was constructed and transfected in mammalian cells. GMIL-18 fusion protein was highly secreted and displayed bifunctional activities, possessing immune response initiation and cytokine roles, including IFN-γ induction in mouse splenocytes and increased proliferation of GM-CSF-dependent cells, M-NSF-60. The GMIL-18 secreting tumor vaccine was generated and it strongly stimulated differentiation of dendrite cells (DCs) and effusive CD8⁺ and CD4⁺ cell infiltration into tumor mice. Moreover, growth of CT26 mouse colon cancer cells was significantly retarded by GMIL-18 (CT26GMIL-18), but not by CT26GM-CSF- or CT26IL-18. The efficiency of prophylactic vaccination was greater than that of therapeutic vaccination in terms of tumor size and its inhibitory role in proliferation. In micrometastasis analysis of tumor models, γ-ray irradiated GMIL-18 tumor vaccine showed a smaller number of liver-meta tumor nodules in mouse liver cells. We concluded that bifunctional GMIL-18 fusion protein could be applied as an immune therapy for cancer treatments.

Correlation of plasma interleukin-18 concentration and severity of renal involvement and disease activity in systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by activation of T and polyclonal B lymphocytes. IL-18 was originally identified as a factor which enhances IFN-γ production and is a potent inducer of the inflammatory mediators by T cells, causing severe inflammatory disorders in SLE.

OBJECTIVES

This study aimed to evaluate the association of plasma interlukine-18 (IL-18) concentration and severity of lupus nephritis (LN) and disease activity in SLE patients.

PATIENTS AND METHODS

In this cross-sectional study, 113 patients with SLE and 50 healthy individuals were examined. Serum level of IL-18 was measured. The severity and activity of the disease was determined by Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score. The severity of kidney involvement was studied by renal biopsy, serum creatinine and 24 hours urine protein level.

RESULTS

The mean level of serum IL-18 was significantly higher in the patients than controls (577.67 ± 649.95 versus 60.48 ± 19.53 pg/ml; P < 0.001). In SLE patients with active disease level of serum IL-18 was significantly higher than chronic disease (622.77 ± 716.54 versus 182 ± 184.37 pg/ml; P < 0.001). The serum level of IL-18 was significantly higher in stage IV (P < 0.001) and V (P < 0.001) of patients with LN, than other stages.

CONCLUSIONS

The current study showed that the serum IL-18 is significantly higher in the patients than controls and it significantly correlated with sever renal involvement and disease activity in SLE patients.

Development of Membrane-Bound GM-CSF and IL-18 as an Effective Tumor Vaccine

The development of effective adjuvant is the key factor to boost the immunogenicity of tumor cells as a tumor vaccine. In this study, we expressed membrane-bound granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-18 (IL-18) as adjuvants in tumor cells to stimulate immune response. B7 transmembrane domain fused GM-CSF and IL-18 was successfully expressed in the cell membrane and stimulated mouse splenocyte proliferation. Co-expression of GM-CSF and IL-18 reduced tumorigenesis (P<0.05) and enhanced tumor protective efficacy (P<0.05) significantly in comparison with GM-CSF alone. These results indicated that the combination of GM-CSF andIL-18 will enhance the immunogenicity of a cell-based anti-tumor vaccine. This membrane-bound approach can be applied to other cytokines for the development of novel vaccine strategies.

Association between interleukin-18 gene promoter (- 607C/A and - 137G/C) polymorphisms and chronic hepatitis C virus infections: A meta-analysis

Objective

HCV infection has a chronicity rate of about 70%, several studies have shown that interleukin-18 (IL-18) was associated with etiology and progression of hepatitis C virus (HCV) infections. However, the association between single-nucleotide polymorphisms − 607C/A (rs1946518) and − 137G/C (rs187238) located in the IL-18 gene promoter and chronic hepatitis C virus infections was still controversial and ambiguous. To derive a more precise effect on the association between these polymorphisms and chronic hepatitis C virus infections, we performed this first meta-analysis based on the currently available evidence of the literature.

Methods

A total of 4 studies with 1222 cases and 1115 controls for − 607C/A polymorphism and 3 studies with 959 cases and 987 controls for − 137G/C polymorphism were identified to perform a meta-analysis. Summary ORs and corresponding 95% CIs for IL-18 polymorphisms and chronic hepatitis C virus infections were estimated using fixed- and random-effects models when appropriate. Heterogeneity, sensitivity analysis, and publication bias were evaluated.

Results

We found a significant association between − 137G/C polymorphism and chronic hepatitis C virus infections (CG + CC versus GG: OR = 2.157, 95% CI [1.822, 2.553]; CC versus CG + GG: OR = 2.007, 95% CI [1.441, 2.797]). However, no significant association was observed between − 607C/A polymorphism and chronic hepatitis C virus infections under different contrast models.

Conclusions

The present meta-analysis suggested that IL-18 − 137G/C polymorphism in promoter region was associated with chronic hepatitis C virus infections, but no evidence indicate association between − 607C/A polymorphism and chronic hepatitis C virus infections. High-quality studies with larger sample size and larger number are warranted.

Modulation of Th1/Th2 immune responses by killed Propionibacterium acnes and its soluble polysaccharide fraction in a type I hypersensitivity murine model: induction of different activation status of antigen-presenting cells

Propionibacterium acnes (P. acnes) is a gram-positive anaerobic bacillus present in normal human skin microbiota, which exerts important immunomodulatory effects, when used as heat- or phenol-killed suspensions. We previously demonstrated that heat-killed P. acnes or its soluble polysaccharide (PS), extracted from the bacterium cell wall, suppressed or potentiated the Th2 response to ovalbumin (OVA) in an immediate hypersensitivity model, depending on the treatment protocol. Herein, we investigated the mechanisms responsible for these effects, using the same model and focusing on the activation status of antigen-presenting cells (APCs). We verified that higher numbers of APCs expressing costimulatory molecules and higher expression levels of these molecules are probably related to potentiation of the Th2 response to OVA induced by P. acnes or PS, while higher expression of toll-like receptors (TLRs) seems to be related to Th2 suppression. In vitro cytokines production in cocultures of dendritic cells and T lymphocytes indicated that P. acnes and PS seem to perform their effects by acting directly on APCs. Our data suggest that P. acnes and PS directly act on APCs, modulating the expression of costimulatory molecules and TLRs, and these differently activated APCs drive distinct T helper patterns to OVA in our model.

IL-18 acts in synergy with IL-7 to promote ex vivo expansion of T lymphoid progenitor cells

Although IL-18 has not previously been shown to promote T lymphopoiesis, results obtained via a novel data mining algorithm (global microarray meta-analysis) led us to explore a predicted role for this cytokine in T cell development. IL-18 is a member of the IL-1 cytokine family that has been extensively characterized as a mediator of inflammatory immune responses. To assess a potential role for IL-18 in T cell development, we sort-purified mouse bone marrow-derived common lymphoid progenitor cells, early thymic progenitors (ETPs), and double-negative 2 thymocytes and cultured these populations on OP9-Delta-like 4 stromal layers in the presence or absence of IL-18 and/or IL-7. After 1 wk of culture, IL-18 promoted proliferation and accelerated differentiation of ETPs to the double-negative 3 stage, similar in efficiency to IL-7. IL-18 showed synergy with IL-7 and enhanced proliferation of both the thymus-derived progenitor cells and the bone marrow-derived common lymphoid progenitor cells. The synergistic effect on the ETP population was further characterized and found to correlate with increased surface expression of c-Kit and IL-7 receptors on the IL-18-treated cells. In summary, we successfully validated the global microarray meta-analysis prediction that IL-18 affects T lymphopoiesis and demonstrated that IL-18 can positively impact bone marrow lymphopoiesis and T cell development, presumably via interaction with the c-Kit and IL-7 signaling axis.

Successful treatment of HIV-1 infection increases the expression of a novel, short transcript for IL-18 receptor α chain

: The importance of interleukin (IL)-18 in mediating immune activation during HIV infection has recently emerged. IL-18 activity is regulated by its receptor (IL-18R), formed by an α and a β chain, the IL-18-binding protein, and the newly identified shorter isoforms of both IL-18R chains. We evaluated gene expression of the IL-18/IL-18R system in peripheral blood mononuclear cells from HIV+ patients. Compared with healthy donors, IL-18 expression decreased in patients with primary infection. The IL-18Rα short transcript expression was strongly upregulated by successful highly active antiretroviral therapy. HIV progression and its treatment can influence the expression of different components of the complex IL-18/IL-18R system.

Diet, behavior and immunity across the lifespan

It is increasingly appreciated that perinatal events can set an organism on a life-long trajectory for either health or disease, resilience or risk. One early life variable that has proven critical for optimal development is the nutritional environment in which the organism develops. Extensive research has documented the effects of both undernutrition and overnutrition, with strong links evident for an increased risk for obesity and metabolic disorders, as well as adverse mental health outcomes. Recent work has highlighted a critical role of the immune system, in linking diet with long term health and behavioral outcomes. The present review will summarize the recent literature regarding the interactions of diet, immunity, and behavior.

A novel cancer vaccine strategy with combined IL-18 and HSV-TK gene therapy driven by the hTERT promoter in a murine colorectal cancer model

A therapeutic vaccine against minimal residual cancer cells is needed for the treatment of patients with colorectal cancer. Several gene therapy studies have revealed that the combination of a suicide gene and cytokine gene might induce effective antitumor immunity. In this study, we constructed an interleukin (IL)-18 and herpes simplex virus-thymidine kinase (HSV-TK) expression vector driven by the human telomerase reverse transcriptase (hTERT) promoter to study the efficacy of combination gene therapy with IL-18 and the HSV-TK suicide gene. Low immunogenic colon 26 cells were used for transfection and inoculation into syngeneic BALB/c mice. Large established tumors of colon 26 transfectants expressing IL-18 and HSV-TK driven by the hTERT promoter were completely eradicated after GCV administration in syngeneic BALB/c mice. Immunohistochemical analysis at the tumor rejection sites revealed enormous infiltrations of CD8⁺ T lymphocytes as well as CD4⁺ T lymphocytes and CD11b⁺ monocytes. Moreover, established distant tumors were completely eradicated by vaccination with the IL-18 and HSV-TK transfectants in combination with GCV. These data suggest that the IL-18 and suicide gene therapy can elicit antitumor specific immunity. In conclusion, gene therapy with IL-18 and HSV-TK plasmid vector driven by the hTERT promoter may be useful for cancer vaccination.

Interleukin-18 as a therapeutic target in acute myocardial infarction and heart failure

Interleukin 18 (IL-18) is a proinflammatory cytokine in the IL-1 family that has been implicated in a number of disease states. In animal models of acute myocardial infarction (AMI), pressure overload, and LPS-induced dysfunction, IL-18 regulates cardiomyocyte hypertrophy and induces cardiac contractile dysfunction and extracellular matrix remodeling. In patients, high IL-18 levels correlate with increased risk of developing cardiovascular disease (CVD) and with a worse prognosis in patients with established CVD. Two strategies have been used to counter the effects of IL-18:IL-18 binding protein (IL-18BP), a naturally occurring protein, and a neutralizing IL-18 antibody. Recombinant human IL-18BP (r-hIL-18BP) has been investigated in animal studies and in phase I/II clinical trials for psoriasis and rheumatoid arthritis. A phase II clinical trial using a humanized monoclonal IL-18 antibody for type 2 diabetes is ongoing. Here we review the literature regarding the role of IL-18 in AMI and heart failure and the evidence and challenges of using IL-18BP and blocking IL-18 antibodies as a therapeutic strategy in patients with heart disease.

Regulatory effects of IL-18 on cytokine profiles and development of myocarditis during Trypanosoma cruzi infection

Chagas disease, caused by Trypanosoma cruzi (Tc), is an important cause of heart disease. Resistance to Tc infection is multifactorial and associated with Th1 response. IL-18 plays an important role in regulation of IFN-γ production/development of Th1 response. However, the role of IL-18 in the setting of Tc infection remains unclear. Therefore, we investigated the role of IL-18 in the modulation of immune response and myocarditis in Tc infection. C57BL/6 and IL-18 KO mice were infected with Tc (Y or Colombian strain) and parasitemia, immune response and pathology were evaluated. Y strain infection of IL-18 KO did not alter any parameters when compared with C57BL/6 mice. However, during the acute phase (20 and 40 days post infection-dpi), Colombian strain infected-IL-18 KO mice displayed higher serum levels of IL-12 and IFN-γ, respectively, and at the chronic phase (100 dpi) an increase in splenic IFN-γ-producing CD4(+) and CD8(+) T memory cells. There was an IL-10, FOXP3 and CD4(+)CD25(+) cells reduction during acute infection in spleen. Additionally, there was a significant reduction in leukocyte infiltration and parasite load in myocardium of chronically infected IL-18 KO mice. Collectively, these data indicate that IL-18 contributes to the pathogenesis of Tc-induced myocarditis when infected with Colombian but not Y strain. These observations also underscore that parasite and host strain differences are important in evaluation of experimental Tc infection pathogenesis.

Cellular immunotherapy using irradiated lung cancer cell vaccine co-expressing GM-CSF and IL-18 can induce significant antitumor effects

Background

Although the whole tumor cell vaccine can provide the best source of immunizing antigens, there is still a limitation that most tumors are not naturally immunogenic. Tumor cells genetically modified to secrete immune activating cytokines have been proved to be more immunogenic. IL-18 could augment proliferation of T cells and cytotoxicity of NK cells. GM-CSF could stimulate dendritic cells, macrophages and enhance presentation of tumor antigens. In our study, we used mouse GM-CSF combined with IL-18 to modify Lewis lung cancer LL/2, then investigated whether vaccination could suppress tumor growth and promote survival.

Methods

The Lewis lung cancer LL/2 was transfected with co-expressing mouse GM-CSF and IL-18 plasmid by cationic liposome, then irradiated with a sublethal dose X ray (100 Gy) to prepare vaccines. Mice were subcutaneously immunized with this inactivated vaccine and then inoculated with autologous LL/2 to estimate the antitumor efficacy.

Results

The studies reported here showed that LL/2 tumor cell vaccine modified by a co-expressing mouse GM-CSF and IL-18 plasmid could significantly inhibit tumor growth and increased survival of the mice bearing LL/2 tumor whether prophylactic or adoptive immunotherapy in vivo. A significant reduction of proliferation and increase of apoptosis were also observed in the tumor treated with vaccine of co-expressing GM-CSF and IL-18. The potent antitumor effect correlated with higher secretion levels of pro-inflammatory cytokines such as IL-18, GM-CSF, interferon-γ in serum, the proliferation of CD4⁺ IFN-γ⁺, CD8⁺ IFN-γ⁺ T lymphocytes in spleen and the infiltration of CD4⁺, CD8⁺ T in tumor. Furthermore, the mechanism of tumor-specific immune response was further proved by ⁵¹Cr cytotoxicity assay in vitro and depletion of CD4, CD8, NK immune cell subsets in vivo. The results suggested that the antitumor mechanism was mainly depended on CD4⁺, CD8⁺ T lymphocytes.

Conclusions

These results provide a new insight into therapeutic mechanisms of IL-18 plus GM-CSF modified tumor cell vaccine and provide a potential clinical cancer immunotherapeutic agent for improved antitumor immunity.

Is the inflammasome a potential therapeutic target in renal disease?

The inflammasome is a large, multiprotein complex that drives proinflammatory cytokine production in response to infection and tissue injury. Pattern recognition receptors that are either membrane bound or cytoplasmic trigger inflammasome assembly. These receptors sense danger signals including damage-associated molecular patterns and pathogen-associated molecular patterns (DAMPS and PAMPS respectively). The best-characterized inflammasome is the NLRP3 inflammasome. On assembly of the NLRP3 inflammasome, post-translational processing and secretion of pro-inflammatory cytokines IL-1β and IL-18 occurs; in addition, cell death may be mediated via caspase-1. Intrinsic renal cells express components of the inflammasome pathway. This is most prominent in tubular epithelial cells and, to a lesser degree, in glomeruli. Several primary renal diseases and systemic diseases affecting the kidney are associated with NLRP3 inflammasome/IL-1β/IL-18 axis activation. Most of the disorders studied have been acute inflammatory diseases. The disease spectrum includes ureteric obstruction, ischaemia reperfusion injury, glomerulonephritis, sepsis, hypoxia, glycerol-induced renal failure, and crystal nephropathy. In addition to mediating renal disease, the IL-1/ IL-18 axis may also be responsible for development of CKD itself and its related complications, including vascular calcification and sepsis. Experimental models using genetic deletions and/or receptor antagonists/antiserum against the NLRP3 inflammasome pathway have shown decreased severity of disease. As such, the inflammasome is an attractive potential therapeutic target in a variety of renal diseases.

The chicken TH1 response: potential therapeutic applications of ChIFN-γ

The outcomes of viral infections are costly in terms of human and animal health and welfare worldwide. The observed increase in the virulence of some viruses and failure of many vaccines to stop these infections has lead to the apparent need to develop new anti-viral strategies. One approach to dealing with viral infection may be to employ the therapeutic administration of recombinant cytokines to act as 'immune boosters' to assist in augmenting the host response to virus. With this in mind, a greater understanding of the immune response, particularly cell mediated T-helper-1 (TH1) type responses, is imperative to the development of new anti-viral and vaccination strategies. Following the release of the chicken genome, a number of TH1-type cytokines have been identified, including chicken interleukin-12 (ChIL-12), ChIL-18 and interferon-γ ChIFN-γ), highlighting the nature of the TH1-type response in this non-mammalian vertebrate. To date a detailed analysis of the in vivo biological function of these cytokines has been somewhat hampered by access to large scale production techniques. This review describes the role of TH-1 cytokines in immune responses to viruses and explores their potential use in enhancing anti-viral treatment strategies in chickens. Furthermore, this review focuses on the example of ChIFN-γ treatment of Chicken Anemia Virus (CAV) infection. CAV causes amongst other things thymocyte depletion and thymus atrophy, as well as immunosuppression in chickens. However, due to vaccination, clinical disease appears less often, nevertheless, the subclinical form of the disease is often associated with secondary complicating infections due to an immunocompromised state. Since CAV-induced immunosuppression can cause a marked decrease in the immune response against other pathogens, understanding this aspect of the disease is critically important, as well as providing insights into developing new control approaches. With increasing emphasis on developing alternative control programs for poultry diseases, novel therapeutic strategies provide one approach. We show here that the in ovo administration of ChIFN-γ impacts the depletion of T-cell precursors during CAV infection. Therefore, it appears that ChIFN-γ may have the potential to be used as a novel therapeutic reagent to impact virus infection and alter immunosuppression caused by CAV and potentially other pathogens.

Fas-mediated inflammatory response in Listeria monocytogenes infection

The molecular mechanisms of Fas (CD95/Apo-1)-mediated apoptosis are increasingly understood. However, the role of Fas-mediated production of proinflammatory cytokines such as IL-18 and IL-1β in bacterial infection is unclear. We demonstrate the importance of Fas-mediated signaling in IL-18/IL-1β production postinfection with Listeria monocytogenes without the contribution of caspase-1 inflammasome. IL-18/IL-1β production in L. monocytogenes-infected peritoneal exudate cells from Fas-deficient mice was lower than those from wild type mice, indicating that Fas signaling contributes to cytokine production. L. monocytogenes infection induced Fas ligand expression on NK cells, which stimulates Fas expressed on the infected macrophages, leading to the production of IL-18/IL-1β. This was independent of caspase-1, caspase-11, and nucleotide-binding domain and leucine-rich repeat-containing receptors (NLRs) such as Nlrp3 and Nlrc4, but dependent on apoptosis-associated speck-like protein containing a caspase recruitment domain. Wild type cells exhibited caspase-8 activation, whereas Fas-deficient cells did not. L. monocytogenes-induced caspase-8 activation was abrogated by inhibitor for intracellular reactive oxygen species, N-acetyl-L-cysteine. L. monocytogenes-infected macrophages produced type-I IFNs such as IFN-β1, which was required for Il18 gene expression. Thus, Fas signaling regulates innate inflammatory cytokine production in L. monocytogenes infection.

Stronger Correlation between Interleukin 18 and Soluble Fas in Lupus Nephritis Compared with Mild Lupus

Lupus nephritis (LN) is a major cause of morbidity in patients with systemic lupus erythematosus (SLE). Several cytokines and apoptotic markers such as IL-18 and soluble Fas (sFas) have been assumed to play a role in the pathogenesis of LN. Previous studies confirmed that serum concentrations of sFas and IL-18 are increased in SLE. However, only a few studies have suggested a possible correlation between IL-18 and sFas. This study was planned to continue our previous study on the correlation between those markers to evaluate this correlation in LN. Thirty-two patients with only LN and 46 patients without any major organ involvement participated in this study. SLEDAI score (except for scores related to nephritis) was the same in these two groups. In both groups, patients with any other major organ involvement were excluded. We found a significant rise in the serum concentrations of sFas (P = 0.03) and IL-18 (P = 0.02) in patients with proteinuria compared to those without it. This study showed that the correlation between sFas and IL-18 in LN (P < 0.001, r p = 0.5) is significantly stronger than it is in mild SLE (P < 0.001, r p = 0.4) with similar nonrenal SLEDAI score (P = 0.032, z = 1.85). Between these two serum markers, sFas is the only predictor of proteinuria.

Imbalance of interleukin-18 and interleukin-18 binding protein in children with Henoch-Schönlein purpura

The balance between interleukin-18 (IL-18) and its endogenous antagonist, IL-18 binding protein (IL-18BP), was evaluated in children with Henoch-Schönlein purpura (HSP). Plasma IL-18 and IL-18BP levels and peripheral blood mononuclear cell IL-18 mRNA expression were significantly higher in patients with active HSP (n = 30) than in healthy controls (n = 20); IL-18BP mRNA expression was similar in active HSP and controls. Plasma levels and mRNA expression of IL-18 and IL-18BP in patients in remission (n = 19) were similar to those in controls. The ratios of IL-18 / IL-18BP plasma levels and IL-18 / IL-18BP mRNA levels in active HSP were significantly higher than in patients in remission and healthy controls. Thus, adequate IL-18BP to block the proinflammatory activity of IL-18 may not be present in active HSP and regulation of the IL-18 / IL-18BP balance might provide a potential therapeutic strategy.

Role of TNF superfamily ligands in innate immunity

Natural killer (NK) cells and dendritic cells (DCs) are essential effector cells of the innate immune system that rapidly recognize and eliminate microbial pathogens and abnormal cells, and induce and regulate adaptive immune functions. While NK cells express perforin and granzymes in the lysosomal granules and transmembrane tumor necrosis factor superfamily ligands (tmTNFSFL) on the plasma membrane, DCs express only tmTNFSFL on the plasma membrane. Perforin and granzymes are cytolytic molecules, which NK cells use to mediate a secretory/necrotic killing mechanism against rare leukemia cell targets. TNFSFL are pleiotropic transmembrane molecules, which can mediate a variety of important functions such as apoptosis, development of peripheral lymphoid tissues, inflammation and regulation of immune functions. Using tmTNFSFL, NK cells and DCs mediate a cell contact-dependent non-secretory apoptotic cytotoxic mechanism against virtually all types of cancer cells, and cross talk that leads to polarization and reciprocal stimulation and amplification of Th1 type cytokines secreted by NK cells and DCs. In this paper, we review and discuss the supporting evidence of the non-secretory, tmTNFSFL-mediated innate mechanisms of NK cells and DCs, their roles in anticancer immune defense and potential of their modulation and use in prevention and treatment of cancer.

Hardy-Weinberg disequilibrium of the IL-18 C-607A SNP suggesting selective advantage of heterozygotes

Interleukin-18 (IL-18) plays a key role in autoimmune, inflammatory, and infectious diseases. The IL-18 gene contains a C to A single nucleotide polymorphism (SNP) at position -607 (C-607A) within the promoter region, which was found to affect the promoter activity and subsequently the protein level of IL-18. We investigated this SNP in a group of healthy Singaporeans and found that CA was the most common genotype and the C allele was more prevalent than the A allele, which was not always the case in other ethnic groups. In addition, Singaporean Chinese were significantly different from Singaporean Indians in both allelic and genotypic distributions. Furthermore, significant deviations from Hardy-Weinberg equilibrium of this SNP were found in all three ethnic groups studied (Chinese, Indians, and Malays) and also in other published literature, suggesting that heterozygotes of this IL-18 C-607A SNP may have certain selective advantages.

Porphyromonas gingivalis induces myocarditis and/or myocardial infarction in mice and IL-17A is involved in pathogenesis of these diseases

OBJECTIVES

Although an association between periodontitis and cardiovascular diseases has been suggested, the role of Porphyromonas gingivalis in cardiovascular diseases is not clear. In this study, we examined whether experimental bacteremia of P. gingivalis causes cardiovascular diseases and investigated the mechanism of pathogenesis of cardiovascular diseases induced by P. gingivalis.

DESIGN

C57BL/6 mice were intravenously inoculated with 2.0 × 10(8)CFU of P. gingivalis A7436 strain. Mice were sacrificed at specified days and their hearts were collected. The collected organs were divided into two halves and used for histological evaluation and cytokine analysis. IL-17A(-/-), IFN-γ(-/-) and TNF-α(-/-) mice were also intravenously inoculated and the histological changes of hearts in mice were examined.

RESULTS

Myocarditis and/or myocardial infarction were observed in mice injected with P. gingivalis. The levels of IL1-β, IL-6, IL-17A, IL-18, TNF-α and IFN-γ mRNA increased significantly after P. gingivalis injection. In particular, high levels of IL-17A and IFN-γ mRNA expression were observed in hearts of mice after P. gingivalis injection in comparison with these levels before injection. Furthermore, the production of IL-17A was detected in hearts of wild-type mice after P. gingivalis injection. In wild-type, TNF-α(-/-) and IFN-γ(-/-) mice, moderate infiltration of neutrophils and monocytes was observed in hearts at 5 days after injection. In contrast, no inflammatory findings were observed in hearts of IL-17A(-/-) mice.

CONCLUSION

We have demonstrated that an experimental bacteremia of P. gingivalis could induce myocarditis and/or myocardial infarction in mice, and IL-17A plays an important role in the pathogenesis of these diseases.

Association of polymorphisms in the Interleukin-18 gene with susceptibility to biliary atresia

BACKGROUND AND OBJECTIVE

Biliary atresia (BA) is a destructive inflammatory obliterative cholangiopathy of neonates that affects both intrahepatic and extrahepatic bile ducts. Although the etiology is unknown, immunologically mediated injury of the bile ducts triggered by as yet unidentified infectious agents is likely to play a critical role. Interleukin-18 (IL-18) is a proinflammatory cytokine that plays an important role in immune, infectious, and inflammatory diseases because of its induction of interferon-gamma. In this study, we investigated whether polymorphisms of the IL18 gene were associated with susceptibility to BA.

PATIENTS AND METHODS

Genomic DNA was extracted from whole-blood samples of 50 Taiwanese children with BA and 1117 ethnically matched healthy controls. The IL18 -1297 T/C, -607 C/A, -137 G/C, and +105 A/C polymorphisms were genotyped using the TaqMan assay.

RESULTS

No statistically significant differences of genotype, allele, carrier, and haplotype frequencies of these IL18 gene variants were found between children with BA and healthy controls.

CONCLUSIONS

Our data suggest that the IL18 gene does not play a major role in BA predisposition in Taiwanese children.

Oncolytic adenovirus co-expressing IL-12 and IL-18 improves tumor-specific immunity via differentiation of T cells expressing IL-12Rβ2 or IL-18Rα

The oncolytic adenovirus (Ad) is currently being advanced as a promising antitumor remedy as it selectively replicates in tumor cells and can transfer and amplify therapeutic genes. Interleukin (IL)-12 induces a potent antitumor effect by promoting natural killer (NK) cell and cytotoxic T cell activities. IL-18 also augments cytotoxicity of NK cells and proliferation of T cells. This effect further enhances the function of IL-12 in a synergistic manner. Therefore, we investigated for the first time an effective cancer immunogene therapy of syngeneic tumors via intratumoral administration of oncolytic Ad co-expressing IL-12 and IL-18, RdB/IL-12/IL-18. Intratumoral administration of RdB/IL-12/IL-18 improved antitumor effects, as well as increased survival, in B16-F10 murine melanoma model. The ratio of T-helper type 1/2 cytokine as well as the levels of IL-12, IL-18, interferon-γ and granulocyte–macrophage colony-stimulating factor was markedly elevated in RdB/IL-12/IL-18-treated tumors. Mice injected with RdB/IL-12/IL-18 also showed enhanced cytotoxicity of tumor-specific immune cells. Consistent with these results, immense necrosis and infiltration of NK cells, as well as CD4⁺ and CD8⁺ T cells, were observed in RdB/IL-12/IL-18-treated tumor tissues. Importantly, tumors treated with RdB/IL-12/IL-18 showed an elevated number of T cells expressing IL-12Rβ2 or IL-18Rα. These results provide a new insight into therapeutic mechanisms of IL-12 plus IL-18 and provide a potential clinical cancer immunotherapeutic agent for improved antitumor immunity.

Proinflammatory cytokines in heart failure: double-edged swords

Increased circulating and intracardiac levels of proinflammatory cytokines have been associated with chronic heart failure. Following an initial insult, the increased production of proinflammatory cytokines, including TNF-α, IL-6, IL-1, and IL-18, jeopardizes the surrounding tissue through propagation of the inflammatory response and direct effects on the cardiac myocyte structure and function. Cardiac myocyte hypertrophy, contractile dysfunction, cardiac myocyte apoptosis, and extracellular matrix remodeling contribute enormously to the development and progression of chronic heart failure. Despite the identification of efficacious pharmacological regimens and introduction of mechanical interventions, chronic heart failure remains among the leading causes of mortality worldwide. To introduce novel therapeutic strategies that modulate the inflammatory response in the context of the failing heart, it is of prime importance to determine the contributions of TNF-α, IL-6, IL-1, and IL-18 in mediating cardiac adaptive and maladaptive responses, as well as delineating their downstream intracellular signaling pathways and their potential therapeutic implications.

Role of interleukin-18 in human natural killer cell is associated with interleukin-2

Human natural killer (NK) cells constitute an important cellular component of innate immunity, capable of killing infected and transformed cells. The proliferation and activation of NK cells are regulated by various cytokines. Interleukin-18 (IL-18) promotes NK cell activation; however, whether the effects of IL-18 on NK cell are associated with other cytokines is still unknown. In this study, we observed that IL-18 induced NK cell apoptosis and inhibited NK cell expansion in the presence of low concentrations of interleukin-2 (IL-2), while high concentrations of IL-2 overcame these effects of IL-18, and high concentrations of IL-2 promoted the stimulatory activity of IL-18 on NK cells. At a low concentration of IL-2, IL-18 induced NK cell apoptosis in part through activation of the FasL/Fas- and TNFα/TNFR-mediated death receptor signaling by enhancing FasL expression and inhibiting c-FLIP(long) expression. However, high concentrations of IL-2 strongly blocked IL-18-induced NK cell apoptosis through alleviating IL-18-induced FasL expression and activation of Fas-mediated death signaling and increasing anti-apoptosis molecule (Bcl-X(L)). These results reveal that the effects of IL-18 on human NK cell are associated with IL-2 concentration and suggest the importance of IL-2 level in cytokine immunotherapy.

Oncolytic adenovirus expressing interleukin-18 induces significant antitumor effects against melanoma in mice through inhibition of angiogenesis

It has been shown that interleukin 18 (IL-18) exerts antitumor activity. In this study, we investigated whether oncolytic adenovirus-mediated gene transfer of IL-18 could induce strong antitumor activity. A tumor-selective replicating adenovirus expressing IL-18 (ZD55-IL-18) was constructed by insertion of an IL-18 expression cassette into the ZD55 vector, which is based on deletion of the adenoviral E1B 55-kDa gene. It has been shown that ZD55-IL-18 exerted a strong cytopathic effect and significant apoptosis in tumor cells. ZD55-IL-18 significantly decreased vascular endothelial growth factor and CD34 expression in the melanoma cells. Treatment of established tumors with ZD55-IL-18 showed much stronger antitumor activity than that induced by ZD55-EGFP (enhanced green fluorescent protein) or Ad-IL-18. These data indicated that oncolytic adenovirus expressing IL-18 could exert potential antitumor activity through inhibition of angiogenesis and offer a novel approach to melanoma therapy.

Resolution of inflammation-related apoptotic processes by the synthetic tellurium compound, AS101 following liver injury

BACKGROUND/AIMS

Fulminant hepatic failure is a dangerous condition, which occurs when large parts of the liver become damaged beyond repair, and the liver is no longer able to function. This syndrome is induced by inflammatory processes, resulting in acute liver failure. Recently, the organotellurium compound, trichloro(dioxoethylene-O,O(')) tellurate (AS101), has been found by our group to be able to directly inhibit caspases, due to its Te(IV)-thiol chemistry. The aim of this study was to examine the potential of AS101 as an anti-inflammatory and anti-apoptotic compound in vitro and in vivo following liver injury.

METHODS

Propionibacterium acnes-primed LPS-induced liver injury was performed in Balb/c mice. ALT/AST, cytokines, caspase-1,-3 and-8 activities, and liver histology were assessed.

RESULTS

AS101 inhibited TNFalpha or anti-FAS-induced apoptotic processes in hepatocytes in vitro. A P. acnes+LPS in vivo liver injury model revealed lower serum ALT and AST and reduced necrosis and apoptosis in AS101-treated mice. IL-18 and IL-1beta reduced levels in AS101-treated mice were associated with caspase-1 activity inhibition. Our findings suggest IL-6, IL-17 and pSTAT3 as additional novel players in the pathogenicity of FHF. Inhibition of caspase-3, and-8 activities by AS101 treatment contributed to decreased hepatocyte death, resulting in increased survival.

CONCLUSIONS

We suggest that due to its interaction with key-target cysteine residues, AS101 mediates anti-inflammatory and anti-apoptotic effects in this FHF model, which may serve as a potent treatment for mitigation of hepatic damage.

Increased Spontaneous But Decreased Mitogen-stimulated Expression and Excretion of Interleukin 18 by Mononuclear Cells in Patients with Active Systemic Lupus Erythematosus

Objective.

To measure serum concentration and analyze the expression of interleukin 18 (IL-18) mRNA in mononuclear cells of patients with systemic lupus erythematosus (SLE).

Methods.

IL-18 concentrations in sera and culture supernatants of peripheral blood mononuclear cells (PBMC) from healthy controls and patients with active SLE were measured by ELISA. PBMC and polymorphonuclear leukocytes (PMN) purified from patients with active SLE were stimulated with phytohemagglutinin (PHA), pokeweed mitogen (PWM), and lipopolysaccharide (LPS). Expression of IL-18 mRNA in cells was analyzed by RT-PCR.

Results.

Serum IL-18 levels were significantly higher in SLE patients than in controls, and correlated with disease activity in SLE patients (r2 = 0.602). Two patients receiving intravenous methylprednisolone therapy (1.0 g/day for 3 days) showed profound decreases in serum IL-18 levels after therapy. The quiescent PBMC from SLE patients (30/30) expressed IL-18 transcript more frequently than control PBMC (20/30). PBMC from SLE patients produced more IL-18 than control PBMC after 72 hours of incubation, by RT-PCR. PHA and PWM inhibited the production of IL-18 in PBMC from both SLE patients and controls. Inhibition by PWM was more pronounced than that by PHA, especially in SLE-PBMC. Control and SLE-PMN with or without LPS stimulation produced negligible IL-18.

Conclusion.

IL-18 is involved in the autoimmune derangement of leukocyte function in patients with active SLE.

Potential role of interleukin-18 in the immunopathogenesis of AIDS: involvement in fratricidal killing of NK cells

We had shown earlier that the concentrations of circulating interleukin-18 (IL-18) are increased significantly in human immunodeficiency virus (HIV)-infected persons compared to HIV-seronegative healthy subjects. In the present study, we investigated the consequences of these elevated levels of IL-18 on natural killer (NK) cells and the immunopathogenesis of AIDS. We show here an inverse correlation between IL-18 concentrations and absolute numbers of various subsets of NK cells in infected persons. Recombinant human IL-18 caused increased death of a human NK cell line, as well as of primary human NK cells in vitro. The IL-18-mediated cell death was dependent upon Fas-FasL interactions and tumor necrosis factor alpha. IL-18 induced the expression of FasL on NK cells, increased the transcription from the human FasL promoter, reduced the expression of Bcl-X(L) in NK cells, and increased their sensitivity to FasL-mediated cell death. These results suggest that increased IL-18 concentrations present in the circulation of HIV-infected persons contribute to the immunopathogenesis of AIDS by altering NK cell homeostasis.

Putative roles of hepatitis B x antigen in the pathogenesis of chronic liver disease

Under most circumstances, hepatitis B virus (HBV) is noncytopathic. However, hepatocellular regeneration that accompanies each bout of hepatitis appears to be associated with increased integration of HBV DNA fragments expressing the virus encoded hepatitis B x antigen (HBxAg). Intrahepatic HBxAg staining correlates with the intensity and progression of chronic liver disease (CLD), and additional work has shown that HBxAg blocks immune mediated killing by Fas and by tumor necrosis factor alpha (TNFalpha). This is not only associated with the blockage of caspase activities by HBxAg, but also by the constitutive stimulation of hepatoprotective pathways, such as nuclear factor kappa B (NF-kappaB), phosphoinositol 3-kinase (PI3K), and beta-catenin (beta-catenin). HBxAg also appears to promote fibrogenesis, by stimulating the production of fibronectin. HBxAg also stimulates the production and activity of transforming growth factor beta1 (TGFbeta1) by several mechanisms, thereby promoting the profibrogenic and tumorigenic properties of this important cytokine. In addition, HBxAg appears to remodel the extracellular matrix (ECM) by altering the expression of several matrix metalloproteinases (MMPs), which may promote tumor metastasis. Hence, HBxAg appears to promote chronic infection by preventing immune mediated apoptosis of infected hepatocytes, by promoting the establishment and persistence of fibrosis and cirrhosis preceding the development of HCC, and by promoting the remodeling of EMC during tumor progression.

Evidence of the involvement of caspase-1 under physiologic and pathologic cellular stress during human pregnancy: a link between the inflammasome and parturition

OBJECTIVE

Caspase-1 is a component of the NALP3 inflammasome, a cytosolic multiprotein complex that mediates the processing of pro-inflammatory caspases and cytokines. The inflammasome represents the first line of defense against cellular stress and is a crucial component of innate immunity. Caspase-1 is the enzyme responsible for the cleavage and activation of interleukin (IL)-1 beta, which is a potent pro-inflammatory cytokine, and plays a central role in the mechanisms leading to labor (preterm and term) particularly in the context of intrauterine infection/inflammation. In addition, caspase-1 cleaves IL-18 and IL-33. The objectives of this study were to determine whether there is a relationship between amniotic fluid concentrations of caspase-1 and gestational age, parturition (term and preterm), and intra-amniotic infection/inflammation (IAI).

STUDY DESIGN

A cross-sectional study was conducted including 143 pregnant women in the following groups: (1) mid-trimester of pregnancy (n = 18); (2) term not in labor (n = 25); (3) term in labor (n = 28); (4) preterm labor (PTL) who delivered at term (n = 23); (5) PTL without IAI who delivered preterm (n = 32); (6) PTL with IAI who delivered preterm neonates (n = 17). Caspase-1 concentrations in amniotic fluid were determined by a specific and sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) Caspase-1 was detected in amniotic fluid of women at term, but in none of the mid-trimester samples. (2) Patients in labor at term had a significantly higher median amniotic fluid concentration of caspase-1 than women at term not in labor (term in labor: 10.5 pg/mL, range 0.0-666.0 vs. term not in labor: 5.99 pg/mL, range 0.0-237.4; p < 0.05). (3) Among patients with spontaneous PTL, those with IAI (median 41.4 pg/mL, range 0.0-515.0) had a significantly higher median amniotic fluid caspase-1 concentration than those without IAI who delivered preterm (median 0.0 pg/mL, range 0.0-78.4) and than those who delivered at term (median 0.0 pg/mL, range 0.0-199.5); p < 0.001 for both comparisons.

CONCLUSIONS

(1) The presence and concentration of caspase-1 in the amniotic fluid varies as a function of gestational age. (2) Women with spontaneous labor at term had a higher median caspase-1 amniotic fluid concentration than women at term without labor. This suggests that the inflammasome may be activated in spontaneous parturition at term. Since most women with labor do not have intra-amniotic infection, we propose that cellular stress during labor accounts for activation of the inflammasome. (3) Preterm labor associated with infection/inflammation was also associated with a high concentration of caspase-1, suggesting that infection may induce caspase-1 production and activation of the inflammasome. (4) The sequential activation of the inflammasome and caspase-1, leading to interleukin-1 beta processing and secretion, is a candidate pathway leading to the activation of the common pathway of parturition.

Modulation of the type I hypersensitivity late phase reaction to OVA by Propionibacterium acnes-soluble polysaccharide

Late phase reaction (LPR) of immediate hypersensitivity is a Th2 response characterized by eosinophil recruitment and related to allergic asthma pathogenesis. Several strategies were developed trying to control the tissue damage observed in this reaction. Recently, we verified that killed Propionibacterium acnes (P. acnes), a Gram-positive bacillus, immunomodulated LPR in a murine model, potentiating or suppressing it depending on the treatment protocol used. However, the bacterium compounds responsible for this effect are not known, leading us to investigate if P. acnes purified soluble polysaccharide (PS) could be a major component involved on the modulation induced by the bacterium. Recently, we demonstrated that PS, like P. acnes, induces adjuvant effect on DNA vaccine, increases bone marrow dendritic cell precursors in vivo and its maturation in vitro, and modulates in vitro macrophage tumoricidal activity. Herein, we determined the chemical PS composition, which is mainly constituted by galactopyranose, ribopyranose, arabinopyranose, glucopyranose, ribofuranose and mannopyranose, and analyzed its capacity to modulate the immediate hypersensitivity in mice. Animals were subcutaneously implanted with coagulated hen's egg white (HEW) and 14 days later challenged with ovalbumin (OVA) in the footpad, developing a typical LPR after 24h. Similarly to the whole bacterium, Th2 response to OVA was potentiated when PS was administered concomitantly to HEW implantation, by increase in footpad eosinophilia and IL-4-producing spleen cells, and decrease in anti-OVA IgG2a titers and IL-12- or IFN-gamma-producing cells. On the other hand, the reaction was abrogated when HEW implantation was performed 1 week after PS-treatment, by decrease in footpad swelling, eosinophilia and anti-OVA IgG1 levels, and increase in IgG2a titers and IL-12-producing cells. These data suggest that PS seems to be the major P. acnes compound responsible for its effects on the modulation of immediate hypersensitivity reaction in mice.

Interleukin 18 in the heart

IL-18, originally termed as interferon gamma (IFN-gamma) inducing factor, is a proinflammatory cytokine that belongs to the IL-1 cytokine superfamily. IL-18 plays an important role in immune, infectious, and inflammatory diseases due to its induction of IFN-gamma. However, accumulated evidence has demonstrated that other effects of IL-18 are independent of IFN-gamma. Here, we reviewed the current literatures regarding the role of IL-18 in the heart and cardiovascular system. Infiltrated neutrophils, resident macrophages, endothelial cells, smooth muscle cells, and cardiomyocytes in the heart are able to produce IL-18 in response to injury. IL-18 is produced as a biologically inactive precursor (pro-IL-18) that is activated by caspase 1 (the IL-1beta converting enzyme). Elevated IL-18 levels have been observed in cardiac tissue and circulation after myocardial I/R and sepsis. The possible cellular and molecular mechanisms concerning IL-18-induced myocardial injury include induction of inflammation, increased apoptosis, a cardiac hypertrophy effect, modulation of mitogen activated protein kinase activation, and changes in intracellular calcium. Finally, we briefly reviewed the therapeutic strategies for inhibiting IL-18's biological activity to protect cardiac tissue from injury.

Induction of IL-33 expression and activity in central nervous system glia

IL-33 is a novel member of the IL-1 cytokine family and a potent inducer of type 2 immunity, as mast cells and Th2 CD4+ T cells respond to IL-33 with the induction of type 2 cytokines such as IL-13. IL-33 mRNA levels are extremely high in the CNS, and CNS glia possess both subunits of the IL-33R, yet whether IL-33 is produced by and affects CNS glia has not been studied. Here, we demonstrate that pathogen-associated molecular patterns (PAMPs) significantly increase IL-33 mRNA and protein expression in CNS glia. Interestingly, IL-33 was localized to the nucleus of astrocytes. Further, CNS glial and astrocyte-enriched cultures treated with a PAMP followed by an ATP pulse had significantly higher levels of supernatant IL-1beta and IL-33 than cultures receiving any single treatment (PAMP or ATP). Supernatants from PAMP + ATP-treated glia induced the secretion of IL-6, IL-13, and MCP-1 from the MC/9 mast cell line in a manner similar to exogenous recombinant IL-33. Further, IL-33 levels and activity were increased in the brains of mice infected with the neurotropic virus Theiler's murine encephalomyelitis virus. IL-33 also had direct effects on CNS glia, as IL-33 induced various innate immune effectors in CNS glia, and this induction was greatly amplified by IL-33-stimulated mast cells. In conclusion, these results implicate IL-33-producing astrocytes as a potentially critical regulator of innate immune responses in the CNS.

Measurement of human and mouse interleukin 18

IL-18, originally designated as interferon-gamma (IFN-gamma)-inducing factor (IGIF), is a pleiotropic cytokine secreted by activated macrophages and Kupffer cells. The major activity associated with this cytokine is induction of IFN-gamma production from T cells, B cells, and NK cells, especially in collaboration with IL-12. IL-18 is synthesized without a signal peptide and must be enzymatically cleaved to become active. Therefore, it is important to determine whether the produced IL-18 is an active or precursor form. This unit describes functional assays for measurement of bioactive human and mouse IL-18 and ELISAs for measurement of murine and human IL-18 proteins. The functional assays are based on the induction of IFN-gamma production by IL-18. The ELISA measures the concentration of human or mouse IL-18. Using a combination of monoclonal antibodies against human or mouse IL-18, the proform and/or mature form of IL-18 can be detected by ELISA.