Genome-wide comparison between IL-17 and combined TNF-alpha/IL-17 induced genes in primary murine hepatocytes

The Proinflammatory Role of ANGPTL8 R59W Variant in Modulating Inflammation through NF-κB Signaling Pathway under TNFα Stimulation

BACKGROUND

Angiopoietin-like protein 8 (ANGPTL8) is known to regulate lipid metabolism and inflammation. It interacts with ANGPTL3 and ANGPTL4 to regulate lipoprotein lipase (LPL) activity and with IKK to modulate NF-κB activity. Further, a single nucleotide polymorphism (SNP) leading to the ANGPTL8 R59W variant associates with reduced low-density lipoprotein/high-density lipoprotein (LDL/HDL) and increased fasting blood glucose (FBG) in Hispanic and Arab individuals, respectively. In this study, we investigate the impact of the R59W variant on the inflammatory activity of ANGPTL8.

METHODS

The ANGPTL8 R59W variant was genotyped in a discovery cohort of 867 Arab individuals from Kuwait. Plasma levels of ANGPTL8 and inflammatory markers were measured and tested for associations with the genotype; the associations were tested for replication in an independent cohort of 278 Arab individuals. Impact of the ANGPTL8 R59W variant on NF-κB activity was examined using approaches including overexpression, luciferase assay, and structural modeling of binding dynamics.

RESULTS

The ANGPTL8 R59W variant was associated with increased circulatory levels of tumor necrosis factor alpha (TNFα) and interleukin 7 (IL7). Our in vitro studies using HepG2 cells revealed an increased phosphorylation of key inflammatory proteins of the NF-κB pathway in individuals with the R59W variant as compared to those with the wild type, and TNFα stimulation further elevated it. This finding was substantiated by increased luciferase activity of NF-κB p65 with the R59W variant. Modeled structural and binding variation due to R59W change in ANGPTL8 agreed with the observed increase in NF-κB activity.

CONCLUSION

ANGPTL8 R59W is associated with increased circulatory TNFα, IL7, and NF-κB p65 activity. Weak transient binding of the ANGPTL8 R59W variant explains its regulatory role on the NF-κB pathway and inflammation.

IL-17A and TNF synergistically drive expression of proinflammatory mediators in synovial fibroblasts via IκBζ-dependent induction of ELF3

OBJECTIVE

IL-17A and TNF act in synergy to induce proinflammatory mediators in synovial fibroblasts thus contributing to diseases associated with chronic arthritis. Many of these factors are regulated by transcription factor E74-like factor-3 (ELF3). Therefore, we sought to investigate ELF3 as a downstream target of IL-17A and TNF signalling and to characterize its role in the molecular mechanism of synergy between IL-17A and TNF.

METHODS

Regulation of ELF3 expression by IL-17A and TNF was studied in synovial fibroblasts of RA and OA patients and RA synovial explants. Signalling leading to ELF3 mRNA induction and the impact of ELF3 on the response to IL-17A and TNF were studied using siRNA, transient overexpression and signalling inhibitors in synovial fibroblasts and HEK293 cells.

RESULTS

ELF3 was marginally affected by IL-17A or TNF alone, but their combination resulted in high and sustained expression. ELF3 expression was regulated by the nuclear factor-κB (NF-κB) pathway and CCAAT/enhancer-binding protein β (C/EBPβ), but its induction required synthesis of the NF-κB co-factor IκB (inhibitor of NF-κB) ζ. siRNA-mediated depletion of ELF3 attenuated the induction of cytokines and matrix metalloproteinases by the combination of IL-17A and TNF. Overexpression of ELF3 or IκBζ showed synergistic effect with TNF in upregulating expression of chemokine (C-C motif) ligand 8 (CCL8), and depletion of ELF3 abrogated CCL8 mRNA induction by the combination of IκBζ overexpression and TNF.

CONCLUSION

Altogether, our results establish ELF3 as an important mediator of the synergistic effect of IL-17A and TNF in synovial fibroblasts. The findings provide novel information of the pathogenic mechanisms of IL-17A in chronic arthritis and implicate ELF3 as a potential therapeutic target.

Liver Regeneration and Immunity: A Tale to Tell

The physiological importance of the liver is demonstrated by its unique and essential ability to regenerate following extensive injuries affecting its function. By regenerating, the liver reacts to hepatic damage and thus enables homeostasis to be restored. The aim of this review is to add new findings that integrate the regenerative pathway to the current knowledge. An optimal regeneration is achieved through the integration of two main pathways: IL-6/JAK/STAT3, which promotes hepatocyte proliferation, and PI3K/PDK1/Akt, which in turn enhances cell growth. Proliferation and cell growth are events that must be balanced during the three phases of the regenerative process: initiation, proliferation and termination. Achieving the correct liver/body weight ratio is ensured by several pathways as extracellular matrix signalling, apoptosis through caspase-3 activation, and molecules including transforming growth factor-beta, and cyclic adenosine monophosphate. The actors involved in the regenerative process are numerous and many of them are also pivotal players in both the immune and non-immune inflammatory process, that is observed in the early stages of hepatic regeneration. Balance of Th17/Treg is important in liver inflammatory process outcomes. Knowledge of liver regeneration will allow a more detailed characterisation of the molecular mechanisms that are crucial in the interplay between proliferation and inflammation.

Combination of IL-17A/F and TNF-α uniquely alters the bronchial epithelial cell proteome to enhance proteins that augment neutrophil migration

Background

The heterodimer interleukin (IL)-17A/F is elevated in the lungs in chronic respiratory disease such as severe asthma, along with the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α). Although IL-17A/F and TNF-α are known to functionally cooperate to exacerbate airway inflammation, proteins altered by their interaction in the lungs are not fully elucidated.

Results

We used Slow Off-rate Modified Aptamer-based proteomic array to identify proteins that are uniquely and/or synergistically enhanced by concurrent stimulation with IL-17A/F and TNF-α in human bronchial epithelial cells (HBEC). The abundance of 38 proteins was significantly enhanced by the combination of IL-17A/F and TNF-α, compared to either cytokine alone. Four out of seven proteins that were increased > 2-fold were those that promote neutrophil migration; host defence peptides (HDP; Lipocalin-2 (LCN-2) and Elafin) and chemokines (IL-8, GROα). We independently confirmed the synergistic increase of these four proteins by western blots and ELISA. We also functionally confirmed that factors secreted by HBEC stimulated with the combination of IL-17A/F and TNF-α uniquely enhances neutrophil migration. We further showed that PI3K and PKC pathways selectively control IL-17A/F + TNF-α-mediated synergistic production of HDPs LCN-2 and Elafin, but not chemokines IL-8 and GROα. Using a murine model of airway inflammation, we demonstrated enhancement of IL-17A/F, TNF-α, LCN-2 and neutrophil chemokine KC in the lungs, thus corroborating our findings in-vivo.

Conclusion

This study identifies proteins and signaling mediated by concurrent IL-17A/F and TNF-α exposure in the lungs, relevant to respiratory diseases characterized by chronic inflammation, especially neutrophilic airway inflammation such as severe asthma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12950-022-00323-w.

Keratinocyte Regnase-1, a Downregulator of Skin Inflammation, Contributes to Protection against Tumor Promotion by Limiting Cyclooxygenase-2 Expression

We previously showed that the ribonuclease Regnase-1 (Reg1) in keratinocytes plays a role in mitigating skin inflammation by downregulating proinflammatory cytokines. In this study, we explored whether Reg1 also has a protective role against skin carcinogenesis. The chemically induced two-stage carcinogenesis protocol revealed that epidermis-specific Reg1-deficient (Reg1-knockout [Reg1-cKO]) mice developed skin tumors with shorter latency and more multiplicity than control mice. In addition, repeated UVB irradiation readily provoked solar keratosis-like lesions in Reg1-cKO mice. Increased levels of cyclooxygenase 2, whose mRNA (Ptgs2) is reportedly a target of Reg1, have been known to be associated with the development of squamous cell carcinomas. Indeed, Ptgs2 mRNA levels were upregulated in the skin of Reg1-cKO mice after treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. The level of prostaglandin E2 was higher in 12-O-tetradecanoylphorbol-13-acetate‒treated Reg1-cKO mouse skin than in control mice skin. Moreover, in vivo inhibition of cyclooxygenase 2 attenuated the 12-O-tetradecanoylphorbol-13-acetate‒induced epidermal thickening in Reg1-cKO mice. Finally, REG1 knockdown in human squamous cell carcinomas lines enhanced PTGS2 mRNA levels after 12-O-tetradecanoylphorbol-13-acetate treatment. In conclusion, epidermal Reg1 plays a regulatory role not only in skin inflammation but also in tumor promotion through the downregulation of cyclooxygenase 2. Therefore, forced expression of Reg1 under inflammatory conditions may be relevant to preventing skin cancer.

SARS-CoV-2 infection impairs the insulin/IGF signaling pathway in the lung, liver, adipose tissue, and pancreatic cells via IRF1

BACKGROUND

COVID-19 can cause multiple organ damages as well as metabolic abnormalities such as hyperglycemia, insulin resistance, and new onset of diabetes. The insulin/IGF signaling pathway plays an important role in regulating energy metabolism and cell survival, but little is known about the impact of SARS-CoV-2 infection. The aim of this work was to investigate whether SARS-CoV-2 infection impairs the insulin/IGF signaling pathway in the host cell/tissue, and if so, the potential mechanism and association with COVID-19 pathology.

METHODS

To determine the impact of SARS-CoV-2 on insulin/IGF signaling pathway, we utilized transcriptome datasets of SARS-CoV-2 infected cells and tissues from public repositories for a wide range of high-throughput gene expression data: autopsy lungs from COVID-19 patients compared to the control from non-COVID-19 patients; lungs from a human ACE2 transgenic mouse infected with SARS-CoV-2 compared to the control infected with mock; human pluripotent stem cell (hPSC)-derived liver organoids infected with SARS-CoV-2; adipose tissues from a mouse model of COVID-19 overexpressing human ACE2 via adeno-associated virus serotype 9 (AAV9) compared to the control GFP after SARS-CoV-2 infection; iPS-derived human pancreatic cells infected with SARS-CoV-2 compared to the mock control. Gain and loss of IRF1 function models were established in HEK293T and/or Calu3 cells to evaluate the impact on insulin signaling. To understand the mechanistic regulation and relevance with COVID-19 risk factors, such as older age, male sex, obesity, and diabetes, several transcriptomes of human respiratory, metabolic, and endocrine cells and tissue were analyzed. To estimate the association with COVID-19 severity, whole blood transcriptomes of critical patients with COVID-19 compared to those of hospitalized noncritical patients with COVID-19.

RESULTS

We found that SARS-CoV-2 infection impaired insulin/IGF signaling pathway genes, such as IRS, PI3K, AKT, mTOR, and MAPK, in the host lung, liver, adipose tissue, and pancreatic cells. The impairments were attributed to interferon regulatory factor 1 (IRF1), and its gene expression was highly relevant to risk factors for severe COVID-19; increased with aging in the lung, specifically in men; augmented by obese and diabetic conditions in liver, adipose tissue, and pancreatic islets. IRF1 activation was significantly associated with the impaired insulin signaling in human cells. IRF1 intron variant rs17622656-A, which was previously reported to be associated with COVID-19 prevalence, increased the IRF1 gene expression in human tissue and was frequently found in American and European population. Critical patients with COVID-19 exhibited higher IRF1 and lower insulin/IGF signaling pathway genes in the whole blood compared to hospitalized noncritical patients. Hormonal interventions, such as dihydrotestosterone and dexamethasone, ameliorated the pathological traits in SARS-CoV-2 infectable cells and tissues.

CONCLUSIONS

The present study provides the first scientific evidence that SARS-CoV-2 infection impairs the insulin/IGF signaling pathway in respiratory, metabolic, and endocrine cells and tissues. This feature likely contributes to COVID-19 severity with cell/tissue damage and metabolic abnormalities, which may be exacerbated in older, male, obese, or diabetic patients.

Interleukin-17A pretreatment attenuates the anti-hepatitis B virus efficacy of interferon-alpha by reducing activation of the interferon-stimulated gene factor 3 transcriptional complex in hepatitis B virus-expressing HepG2 cells

Background

Some cytokine signaling pathways can interact with interferon (IFN)-α pathway and thus regulate cell responses to IFN-α. Levels of the pro-inflammatory cytokine interleukin-17A (IL-17A) were found to be elevated in both the peripheral blood and liver in chronic hepatitis B (CHB) patients. However, how IL-17A affects the anti-HBV activity of IFN-α remains unclear.

Methods

The effects of IL-17A on anti-HBV activity of IFN-α were evaluated in HBV-expressing HepG2 cells (HepG2-HBV1.3) with IL-17A pretreatment and IFN-α stimulation. Culture supernatant levels of HBsAg, HBeAg, and HBV DNA, or intracellular expression of HBsAg and HBcAg were detected by ELISA, real-time quantitative PCR (RT-qPCR), or western blotting (WB). The expression of canonical IFN-α signaling pathway components, including the interferon-α/β receptor (IFNAR), Janus Kinase 1 (JAK1), Tyrosine Kinase 2 (TYK2), the Interferon Stimulated Gene Factor 3 complex (ISGF3) and IFN-stimulated genes (ISGs), was also examined by RT-qPCR, Immunofluorescence or WB. The effects of IL-17A were further investigated by the suppression of the IL-17A pathway with a TRAF6 inhibitor.

Results

Compared to IFN-α stimulation alone, IL-17A pretreatment followed by IFN-α stimulation increased the levels of HBsAg, HBeAg, and HBV DNA, and decreased the levels of ISGF3 complex (phosphorylated (p)-signal transducer and activator of transcription (STAT1)/p-STAT2/IRF9) and antiviral-related ISGs (ISG15, ISG20 and Mx1). Interestingly, IL-17A pretreatment increased the expression of suppressor of cytokine signaling (SOCS) 1, SOCS3 and USP18, which were also the ISGs negatively regulating activity of ISGF3. Moreover, IFNAR1 protein expression declined more sharply in the group with IL-17A pretreatment than in the group with IFN-α stimulation alone. Blocking the IL-17A pathway reversed the effects of IL-17A on the IFN-α-induced activation of ISGF3 and anti-HBV efficacy.

Conclusions

Our results demonstrate that IL-17A pretreatment could attenuate IFN-α-induced anti-HBV activity by upregulating negative regulators of the critical transcriptional ISGF3 complex. Thus, this might be a potential target for improving response to IFN-α therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01753-x.

Porcine Reproductive and Respiratory Syndrome Virus nsp11 Antagonizes Broad Antiviral Effects of MCPIP1 by Inducing Interleukin-17 Expression

Monocyte chemotactic protein-induced protein 1 (MCPIP1) is an inflammatory regulator in immune response and has broad antiviral effects by targeting viral RNA. Porcine reproductive and respiratory syndrome virus (PRRSV), a major viral pathogen in pigs, causes immune suppression leading to coinfection of swine pathogens, but the mechanisms are not fully clarified. In this study, MCPIP1 expression was found to be significantly upregulated in lungs of PRRSV-infected piglets, as well as in Marc-145 and porcine pulmonary alveolar macrophage (PAM) cells upon PRRSV stimulation. MCPIP1 overexpression significantly inhibited PRRSV replication, while MCPIP1 knockdown increased the virus titer. Various mutations in RNase functional domains of MCPIP1 impaired the inhibitory activity against PRRSV, while those in deubiquitinase domains failed to do so. MCPIP1 expression started to decrease from 60 h after PRRSV infection in PAMs. Meanwhile, infection with higher dose of PRRSV further downregulated MCPIP1, indicating the antagonizing effects from PRRSV against MCPIP1. Moreover, it was confirmed that MCPIP1 expression was downregulated in 3D4 cells with either interleukin-17 (IL-17) or nsp11 overexpression, while IL-17 inhibitor abolished the decrease of MCPIP1 caused by nsp11, indicating nsp11 employs IL-17 induction to inhibit MCPIP1. Furthermore, the PRRSV nsp11 mutant with a deficiency in IL-17 induction showed the recovered expression of MCPIP1 in infected cells, inspiring a strategy for virus attenuation. This is the first report about the role of MCPIP1 against PRRSV and the function of PRRSV nsp11 against innate immunity to facilitate virus replication via IL-17. The study not only illuminates PRRSV infection machinery but also enlightens alternative antiviral strategies, such as vaccine candidates. IMPORTANCE Porcine reproductive and respiratory syndrome virus (PRRSV) suppresses the innate immunity and leads to coinfection of swine pathogens. Monocyte chemotactic protein-induced protein 1 (MCPIP1) is a broad-spectrum host antiviral protein. Therefore, to further clarify the mechanism of PRRSV against innate immunity, we explored the relationship between MCPIP1 and PRRSV infection. The results showed that MCPIP1 inhibited PRRSV infection in the early stage of virus infection. Importantly, PRRSV nsp11 subsequently employed IL-17 induction to suppress MCPIP1 expression and antagonized anti-PRRSV effects. Furthermore, PRRSV with mutation of nsp11 S74A failed to induce MCPIP1 reduction. These findings confirmed the function of MCPIP1 against PRRSV and revealed that PRRSV nsp11 plays an important role in virus against innate immunity. This study enlightens a new strategy to develop safer attenuated vaccines against PRRSV by nsp11 mutation.

Inflammation accelerates copper-mediated cytotoxicity through induction of six-transmembrane epithelial antigens of prostate 4 expression

Copper is an essential trace metal, but imbalance in copper homeostasis can induce oxidative damage. Inflammation is a fundamental element of various pulmonary diseases. Although a positive relationship between copper and chronic pulmonary diseases has been reported, the underlying reasons are still not clear. The copper level in the sputum of patients with various pulmonary diseases was measured. An inflammatory model was established to evaluate the impact of inflammation on copper uptake in the lung. We found that the level of sputum copper was increased in patients with various pulmonary diseases, especially chronic obstructive pulmonary disease and asthma. Then, we confirmed that mice with pulmonary inflammation were susceptible to copper-mediated oxidative damage because of copper overload in lung tissue. Further investigation demonstrated that interleukin (IL)-17 and tumor necrosis factor (TNF)-α exerted synergistic effects in airway epithelial cells by upregulating the expression of six-transmembrane epithelial antigens of prostate 4 (STEAP4), a metalloreductase that reduces extracellular copper ions from the cupric state to the cuprous state and facilitates copper uptake. Inhibition of STEAP4 decreased the copper uptake of cells and inhibited copper-mediated oxidative damage. Moreover, we demonstrated that the upregulation of STEAP4 by IL-17 and TNF-α was largely dependent on TNF receptor-associated factor 4 (TRAF4). Traf4^-/- mice were resistant to copper-mediated oxidative damage. Our data suggest a novel IL-17/TNF-α-TRAF4-STEAP4 axis that regulates copper homeostasis.

Treg/Th17 imbalance and its clinical significance in patients with hepatitis B-associated liver cirrhosis

Background

Recent studies have shown that T cell-mediated cellular immune mechanisms play important roles in the progression of hepatitis B to liver cirrhosis, but the underlying mechanisms remain unclear. This present study was aimed to determine the relationship between Treg/Th17 and hepatitis B-associated liver cirrhosis.

Methods

The Treg and Th17 cell frequencies in the peripheral blood of all participants, including 93 patients with hepatitis B-associated liver cirrhosis and 40 healthy subjects, were measured by flow cytometer. Cox regression model and receiver operating characteristic(ROC) curves were applied to investigate the prognostic significance of Treg/Th17 ratio in decompensated liver cirrhosis.

Results

We observed the Treg/Th17 imbalance was present in patients with hepatitis B-associated liver cirrhosis, with reduced Treg cells in their peripheral blood, increased Th17 cells and decreased Treg/Th17 ratio. Treg and Th17 cells were negatively correlated. Treg/Th17 imbalance was closely related to the clinical stage of hepatitis B-associated liver cirrhosis. The Virus load, Treg frequencies and the Treg/Th17 ratio were independent factors predicting decompensated liver cirrhosis from a Cox regression model. The ROC analysis showed that the Treg/Th17 ratio was the best marker for predicting decompensated liver cirrhosis.

Conclusions

Treg/Th17 imbalance is involved in the pathogenesis of hepatitis B-associated liver cirrhosis and the Treg/Th17 ratio can be used as a potential marker for predicting decompensated liver cirrhosis.

Systemic effects of IL-17 in inflammatory arthritis

Inflammatory arthritis occurs in many diseases and is characterized by joint inflammation and damage. However, the inflammatory state in arthritis is commonly associated with systemic manifestations, which are generally linked to a poor prognosis. The pro-inflammatory cytokine IL-17 functions within a complex network of cytokines and contributes to the pathogenesis of various inflammatory diseases. Three IL-17 inhibitors have already been approved for the treatment of psoriasis, psoriatic arthritis, and ankylosing spondylitis. After a brief description of IL-17 and its local effects on joints, this Review focuses on the systemic effects of IL-17 in inflammatory arthritis. Increased circulating concentrations of bioactive IL-17 mediate changes in blood vessels, liver and cardiac and skeletal muscles. The effects of IL-17 on vascular and cardiac cells might contribute to the increased risk of cardiovascular events that occurs in all patients with inflammatory disorders. In the liver, IL-17 contributes to the high circulating concentrations of acute-phase proteins, such as C-reactive protein, and the appearance of liver lesions. In skeletal muscle, IL-17 contributes to muscle contractibility defects and weakness. Thus, targeting IL-17 might have beneficial effects at both local and systemic levels, and could also be proposed for the treatment of a wider range of inflammatory diseases.

IL-17 and IL-17-producing cells and liver diseases, with focus on autoimmune liver diseases

The pro-inflammatory cytokine interleukin(IL)-17 and IL-17-producing cells are important players in the pathogenesis of many autoimmune / inflammatory diseases. More recently, they have been associated with liver diseases. This review first describes the general knowledge on IL-17 and IL-17 producing cells. The second part describes the in vitro and in vivo effects of IL-17 on liver cells and the contribution of IL-17 producing cells to liver diseases. IL-17 induces immune cell infiltration and liver damage driving to hepatic inflammation and fibrosis and contributes to autoimmune liver diseases. The circulating levels of IL-17 and the frequency of IL-17-producing cells are elevated in a variety of acute and chronic liver diseases. The last part focuses on the effects of IL-17 deletion or neutralization in various murine models. Some of these observed beneficial effects suggest that targeting the IL-17 axis could be a new therapeutic strategy to prevent chronicity and progression of various liver diseases.

Synergistic effect of interleukin-17 and tumour necrosis factor-α on inflammatory response in hepatocytes through interleukin-6-dependent and independent pathways

The proinflammatory cytokines interleukin (IL)-17 and tumour necrosis factor (TNF)-α are targets for treatment in many chronic inflammatory diseases. Here, we examined their role in liver inflammatory response compared to that of IL-6. Human hepatoma cells (HepaRG, Huh7.5 and HepG2 cells) and primary human hepatocytes (PHH) were cultured with IL-6, IL-17 and/or TNF-α. To determine the contribution of the IL-6 pathway in the IL-17/TNF-α-mediated effect, an anti-IL-6 receptor antibody was used. IL-17 and TNF-α increased in synergy IL-6 secretion by HepaRG cells and PHH but not by Huh7.5 and HepG2 cells. This IL-17/TNF-α synergistic cooperation enhanced the levels of C-reactive protein (CRP) and aspartate aminotransferase (ASAT) in HepaRG cell and PHH cultures through the induction of IL-6. IL-17/TNF-α also up-regulated IL-8, monocyte chemoattractant protein (MCP)-1 and chemokine (C-C motif) ligand 20 (CCL20) chemokines in synergy through an IL-6-independent pathway. Interestingly, first exposure to IL-17, but not to TNF-α, was crucial for the initiation of the IL-17/TNF-α synergistic effect on IL-6 and IL-8 production. In HepaRG cells, IL-17 enhanced IL-6 mRNA stability resulting in increased IL-6 protein levels. The IL-17A/TNF-α synergistic effect on IL-6 and IL-8 induction was mediated through the activation of extracellular signal-regulated kinase (ERK)-mitogen-activated protein kinase, nuclear factor-κB and/or protein kinase B (Akt)-phosphatidylinositol 3-kinase signalling pathways. Therefore, the IL-17/TNF-α synergistic interaction mediates systemic inflammation and cell damage in hepatocytes mainly through IL-6 for CRP and ASAT induction. Independently of IL-6, the IL-17A/TNF-α combination may also induce immune cell recruitment by chemokine up-regulation. IL-17 and/or TNF-α neutralization can be a promising therapeutic strategy to control both systemic inflammation and liver cell attraction.

RIP kinase 1-dependent endothelial necroptosis underlies systemic inflammatory response syndrome

Receptor interacting protein kinase 1 (RIPK1) has important kinase-dependent and kinase-independent scaffolding functions that activate or prevent apoptosis or necroptosis in a cell context-dependent manner. The kinase activity of RIPK1 mediates hypothermia and lethality in a mouse model of TNF-induced shock, reflecting the hyperinflammatory state of systemic inflammatory response syndrome (SIRS), where the proinflammatory "cytokine storm" has long been viewed as detrimental. Here, we demonstrate that cytokine and chemokine levels did not predict survival and, importantly, that kinase-inactive Ripk1D138N/D138N hematopoietic cells afforded little protection from TNF- or TNF/zVAD-induced shock in reconstituted mice. Unexpectedly, RIPK1 kinase-inactive mice transplanted with WT hematopoietic cells remained resistant to TNF-induced shock, revealing that a nonhematopoietic lineage mediated protection. TNF-treated Ripk1D138N/D138N mice exhibited no significant increases in intestinal or vascular permeability, nor did they activate the clotting cascade. We show that TNF administration damaged the liver vascular endothelium and induced phosphorylated mixed lineage kinase domain-like (phospho-MLKL) reactivity in endothelial cells isolated from TNF/zVAD-treated WT, but not Ripk1D138N/D138N, mice. These data reveal that the tissue damage present in this SIRS model is reflected, in part, by breaks in the vasculature due to endothelial cell necroptosis and thereby predict that RIPK1 kinase inhibitors may provide clinical benefit to shock and/or sepsis patients.

IL-17 inhibits the accumulation of myeloid-derived suppressor cells in breast cancer via activating STAT3

Breast cancer (BC) is one of the most common cancers, with high recurrence rate and poor prognosis of recurrent metastatic disease. In our study, we analyzed the markers and development of markers of myeloid-derived suppressor cells (MDSCs) for BC progression and occurrence. MDSCs is one of the major orchestrators of the immunosuppressive network, are associated with immune suppression and considered a prime target for cancer immunotherapy. Interleukin-17 (IL-17) is a signature cytokine of Th17 cells. Previous research has indicated that IL-17 plays a proinflammatory role. It was found to increase frequencies at certain tumors and involved in angiogenesis. This study aims to elucidate the biological role of IL-17 on MDSC in BC cells. Expression of MDSC in peripheral blood of 80 BCE patients and 20 healthy volunteers was compared. Our results indicate that MDSC numbers in patients with BC were higher than healthy donors. Moreover, the clinical grade and prognosis were correlate with the number of MDSC. In this study, we investigated the effect of IL-17 on MDSCs. CCK-8 assay and flow cytometry were used to assess the proliferation and apoptosis of cells. The expression of key MDSC-related molecules was detected by western blotting. We identified administration with IL-17 in vitro significantly induced MDSC differentiation, inhibited their proliferation and triggered apoptosis. In addition, Low IL-17 inhibited the activation of STAT3, leading to increase formation of MDSCs in BC. Our results from experiments suggest that the effects of IL-17 mediate activation of STAT3 signaling in BC cells. Taken together, our study shows that MDSCs can be a new type prognostic marker in BC patient. Targeting IL-17/Stat3 signaling may be a promising strategy for BC treatment.

Expression of interleukin-17 is associated with different immune phases in patients with chronic hepatitis B

Serum interleukin-17 is closely related to inflammatory liver injury after hepatitis B virus (HBV) infection. The objective is to study the expression of interleukin-17 (IL-17) in different immune phases in patients with chronic hepatitis B. Whole venous blood was obtained from normal controls (n = 20) and four patient groups (n = 213): immune tolerance phase (IT, n = 57), immune clearance phase (IC, n = 59), non (low)-replicating phase (LR, n = 44), and reactivation phase (RA, n = 53). We measured IL-17, IL-6, and tumor necrosis factor alpha (TNF-α) levels in serum samples and measured IL-17, IL-6, and TNF-α messenger RNA (mRNA) levels in peripheral blood mononuclear cell (PBMC). Compared to normal controls, IL-17, IL-6, and TNF-α protein levels in serum and mRNA levels in PBMC were significantly higher in the four groups. IL-17 protein levels in serum and mRNA levels in PBMC were positively correlated with alanine aminotransferase (ALT), aspartate aminotransferase (AST), IL-6, and TNF-α. Compared to patients in the IT phase and LR phase, patients in the IC phase exhibited the highest serum IL-17 and PBMC mRNA levels. The IL-17 mRNA levels of patients in RA phase were higher than those in patients in IT phase. IL-17 plays an important part in the various immune phases of chronic hepatitis B (CHB).

Clinical and functional significance of STEAP4-splice variant in CD14+ monocytes in patients with rheumatoid arthritis

Tumour necrosis factor alpha (TNF)-α-induced adipose-related protein (TIARP) is a negative regulator of inflammation in arthritis model mice. In humans, six-transmembrane epithelial antigen of prostate 4 (STEAP4) (human counterpart of TIARP) is also expressed in CD14⁺ monocytes from patients with rheumatoid arthritis (RA). Recently, highly levels of exon 3-spliced variant STEAP4 (v-STEAP4) expression have been observed in porcine lung. The aim of this study is to elucidate the expression and functional role of v-STEAP4, comparing it with that of STEAP4, in the pathogenesis of arthritis. We identified v-STEAP4 in CD14⁺ cells. The expression of STEAP4 and v-STEAP4 was higher in patients with RA than in healthy participants. We also found that STEAP4 and v-STEAP4 were correlated positively with C-reactive protein and that their expression was decreased after treatment with an interleukin (IL)-6 antagonist in patients with RA. To investigate further the role of STEAP4 and v-STEAP4, we produced STEAP4 and v-STEAP4 over-expressing human monocytic cell lines (THP-1) for functional analysis. In the v-STEAP4 over-expressing cells, the production of IL-6 was suppressed significantly, but TNF-α was increased significantly through lipopolysaccharide (LPS) stimulation. Immunoblot analysis revealed that phosphorylated (p-)nuclear factor kappa B (NF-κB) was increased after LPS stimulation and degradation of nuclear factor kappa B inhibitor alpha (IκBα) was sustained, whereas p-signal transducer and activator of transcription 3 (STAT-3) was decreased with v-STEAP4. We identified specific up-regulation of v-STEAP4 in RA monocytes. V-STEAP4 might play a crucial role in the production of TNF-α and IL-6 through NF-κB and STAT-3 pathways, resulting in the generation of RA.

STEAP4: its emerging role in metabolism and homeostasis of cellular iron and copper

Preserving energy homeostasis in the presence of stressors such as proinflammatory cytokines and nutrient overload is crucial to maintaining normal cellular function. Six transmembrane epithelial antigen of the prostate 4 (STEAP4), a metalloreductase involved in iron and copper homeostasis, is thought to play a potentially important role in the cellular response to inflammatory stress. Genome-wide association studies have linked various mutations in STEAP4 with the development of metabolic disorders such as obesity, metabolic syndrome and type 2 diabetes. Several studies have shown that expression of Steap4 is modulated by inflammatory cytokines, hormones and other indicators of cellular stress and that STEAP4 may protect cells from damage, helping to maintain normal metabolic function. STEAP4 appears to be particularly relevant in metabolically oriented cells, such as adipocytes, hepatocytes and pancreatic islet cells. These cells struggle to maintain their function in iron or copper overloaded states, presumably due to increased oxidative stress, suggesting STEAP4's role in metal homeostasis is critical to the maintenance of cellular homeostasis in general, and in preventing the onset of metabolic disease. In this review, we explore genetic associations of STEAP4 with metabolic disorders, and we examine STEAP4 tissue expression, subcellular localization, regulation, structure and function as it relates to metabolic diseases. We then examine how STEAP4's role as a regulator of cellular iron and copper may relate to type 2 diabetes.

Identification and functional characterization of the house finch interleukin-1β

Interleukin-1β (IL-1β), an inflammatory cytokine of the IL-1 family, is primarily produced as a precursor protein by monocytes and macrophages, then matures and becomes activated through proteolytic catalysis. Although the biological characteristics of avian IL-1β are well known, little information is available about its biological role in songbird species such as house finches that are vulnerable to naturally-occurring inflammatory diseases. In this study, house finch IL-1β (HfIL-1β) was cloned, expressed, and its biological function examined. Both precursor and mature forms of HfIL-1β consisting of 269 and 162 amino acids, respectively, were amplified from total RNA of spleen and cloned into expression vectors. HfIL-1β showed high sequential and tertiary structural similarity to chicken homologue that allowed detection of the expressed mature recombinant HfIL-1β (rHfIL-1β) with anti-ChIL-1β antibody by immunoblot analysis. For further characterization, we used primary splenocytes and hepatocytes that are predominant sources of IL-1β upon stimulation, as well as suitable targets to stimulation by IL-1β. Isolated house finch splenocytes were stimulated with rHfIL-1β in the presence and absence of concanavalin A (Con A), RNA was extracted and transcript levels of Th1/Th2 cytokines and a chemokine were measured by qRT-PCR. The addition of rHfIL-1β induced significant enhancement of IL-2 transcript, a Th1 cytokine, while transcription of IL-1β and the Th2 cytokine IL-10 was slightly enhanced by rHfIL-1β treatment. rHfIL-1β also led to elevated levels of the chemokine CXCL1 and nitric oxide production regardless of co-stimulation with Con A. In addition, the production of the acute phase protein serum amyloid A and the antimicrobial peptide LEAP2 was observed in HfIL-1β-stimulated hepatocytes. Taken together, these observations revealed the basic functions of HfIL-1β including the stimulatory effect on cell proliferation, production of Th1/Th2 cytokines and acute phase proteins by immune cells, thus providing valuable insight into how HfIL-1β is involved in regulating inflammatory response.

Analyses of caspase-1-regulated transcriptomes in various tissues lead to identification of novel IL-1β-, IL-18- and sirtuin-1-independent pathways

BACKGROUND

It is well established that caspase-1 exerts its biological activities through its downstream targets such as IL-1β, IL-18, and Sirt-1. The microarray datasets derived from various caspase-1 knockout tissues indicated that caspase-1 can significantly impact the transcriptome. However, it is not known whether all the effects exerted by caspase-1 on transcriptome are mediated only by its well-known substrates. Therefore, we hypothesized that the effects of caspase-1 on transcriptome may be partially independent from IL-1β, IL-18, and Sirt-1.

METHODS

To determine new global and tissue-specific gene regulatory effects of caspase-1, we took novel microarray data analysis approaches including Venn analysis, cooperation analysis, and meta-analysis methods. We used these statistical methods to integrate different microarray datasets conducted on different caspase-1 knockout tissues and datasets where caspase-1 downstream targets were manipulated.

RESULTS

We made the following important findings: (1) Caspase-1 exerts its regulatory effects on the majority of genes in a tissue-specific manner; (2) Caspase-1 regulatory genes partially cooperates with genes regulated by sirtuin-1 during organ injury and inflammation in adipose tissue but not in the liver; (3) Caspase-1 cooperates with IL-1β in regulating less than half of the genes involved in cardiovascular disease, organismal injury, and cancer in mouse liver; (4) The meta-analysis identifies 40 caspase-1 globally regulated genes across tissues, suggesting that caspase-1 globally regulates many novel pathways; and (5) The meta-analysis identified new cooperatively and non-cooperatively regulated genes in caspase-1, IL-1β, IL-18, and Sirt-1 pathways.

CONCLUSIONS

Our findings suggest that caspase-1 regulates many new signaling pathways potentially via its known substrates and also via transcription factors and other proteins that are yet to be identified.

TIARP attenuates autoantibody-mediated arthritis via the suppression of neutrophil migration by reducing CXCL2/CXCR2 and IL-6 expression

TNFα-induced adipose-related protein (TIARP) is a six-transmembrane protein expressed on macrophages, neutrophils and synoviocytes. We reported recently that mice deficient in TIARP (TIARP^−/−) spontaneously develop arthritis and are highly susceptible to collagen-induced arthritis (CIA) with enhanced interleukin (IL)-6 production. However, the effects of TIARP on neutrophils and fibroblast-like synoviocytes (FLS) have not been elucidated. We analyzed the roles of TIARP in K/BxN serum transfer model using TIARP^−/− mice. Arthritis in TIARP^−/− mice transferred with K/BxN serum was significantly exacerbated compared with WT mice. We characterized the differences in neutrophils between wild-type (WT) and TIARP^−/− mice by DNA microarray. Overexpression of CXCR1 and CXCR2 was noted in TIARP^−/− neutrophils. Neutrophils of TIARP^−/− mice showed strong migration activity, which was markedly facilitated by CXCL2 in vitro and in vivo. Moreover, enhanced production of CXCL2 and IL-6 and cell proliferation was noted in TIARP^−/− TNFα-stimulated FLS. Blockade of IL-6R significantly attenuated serum-transferred TIARP^−/− arthritis with diminished neutrophil recruitment in joints. Our findings suggested that TIARP independently down-regulated CXCL2 and IL-6 production by FLS, and the expression of chemokine receptors (CXCR1 and CXCR2) in neutrophils, with resultant reduction of neutrophil migration into arthritic joints.

MCPIP1 RNase Is Aberrantly Distributed in Psoriatic Epidermis and Rapidly Induced by IL-17A

ZC3H12A, which encodes the RNase monocyte chemotactic protein-induced protein 1 (MCPIP1), is up-regulated in psoriatic skin and reduced to normal levels after clinical treatments with anti-IL-17A/IL-17R neutralizing antibodies. In IL-17A-stimulated keratinocytes, MCPIP1 is rapidly increased at the transcript and protein levels. Also, IL-17A was found to be the main inducer of ZC3H12A expression in keratinocytes treated with supernatants derived from a Streptococcus pyogenes-activated psoriatic ex vivo model based on the co-culture of psoriatic cutaneous lymphocyte-associated antigen (CLA(+)) T cells and lesional epidermal cells. Moreover, MCPIP1 was aberrantly distributed in the suprabasal layers of psoriatic epidermis. In psoriatic samples, IL-17A-stimulated epidermal cell suspensions showed an increased MCPIP1 expression, especially in the mid-differentiated cellular compartment. The knockdown of ZC3H12A showed that this RNase participates in the regulation of the mRNAs present in suprabasal differentiated keratinocytes. Furthermore, JAK/STAT3 inhibition prevented the IL-17A-dependent induction of MCPIP1. In the mouse model of imiquimod-induced psoriasis, Zc3h12a expression was abrogated in Il17ra(-/-) mice. These results support the notion that IL-17A-mediated induction of MCPIP1 is involved in the regulation of local altered gene expression in suprabasal epidermal layers in psoriasis.

The balance between IL-17 and IL-22 produced by liver-infiltrating T-helper cells critically controls NASH development in mice

The mechanisms responsible for the evolution of steatosis towards NASH (non-alcoholic steatohepatitis) and fibrosis are not completely defined. In the present study we evaluated the role of CD4(+) T-helper (Th) cells in this process. We analysed the infiltration of different subsets of CD4(+) Th cells in C57BL/6 mice fed on a MCD (methionine choline-deficient) diet, which is a model reproducing all phases of human NASH progression. There was an increase in Th17 cells at the beginning of NASH development and at the NASH-fibrosis transition, whereas levels of Th22 cells peaked between the first and the second expansion of Th17 cells. An increase in the production of IL (interleukin)-6, TNFα (tumour necrosis factor α), TGFβ (transforming growth factor β) and CCL20 (CC chemokine ligand 20) accompanied the changes in Th17/Th22 cells. Livers of IL-17(-/-) mice were protected from NASH development and characterized by an extensive infiltration of Th22 cells. In vitro, IL-17 exacerbated the JNK (c-Jun N-terminal kinase)-dependent mouse hepatocyte lipotoxicity induced by palmitate. IL-22 prevented lipotoxicity through PI3K (phosphoinositide 3-kinase)-mediated inhibition of JNK, but did not play a protective role in the presence of IL-17, which up-regulated the PI3K/Akt inhibitor PTEN (phosphatase and tensin homologue deleted on chromosome 10). Consistently, livers of IL-17(-/-) mice fed on the MCD diet displayed decreased activation of JNK, reduced expression of PTEN and increased phosphorylation of Akt compared with livers of wild-type mice. Hepatic infiltration of Th17 cells is critical for NASH initiation and development of fibrosis in mice, and reflects an infiltration of Th22 cells. Th22 cells are protective in NASH, but only in the absence of IL-17. These data strongly support the potentiality of clinical applications of IL-17 inhibitors that can prevent NASH by both abolishing the lipotoxic action of IL-17 and allowing IL-22-mediated protection.

NFκBiz protein downregulation in acute kidney injury: Modulation of inflammation and survival in tubular cells

Acute kidney injury is characterized by decreased renal function, tubular cell death and interstitial inflammation. The transcription factor NF-κB is a key regulator of genes involved in cell survival and the inflammatory response. In order to better understand the regulation and role of NF-κB in acute kidney injury we explored the expression of NF-κB-related genes in experimental acute kidney injury induced by a folic acid overdose. NFκBiz, a member of the IκB family of NF-κB regulators encoding NFκBiz, was among the top up-regulated NF-κB-related genes at the mRNA level in experimental acute kidney injury. However, the NFκBiz protein was constitutively expressed by normal tubular cells but was down-regulated in experimental acute kidney injury. Kidney NFκBiz mRNA upregulation and protein downregulation was also observed in acute kidney injury induced by cisplatin or unilateral kidney injury resulting from ureteral obstruction. Thus, we studied the consequences of NFκBiz protein downregulation by specific siRNA in cultured tubular epithelial cells. NFκBiz mRNA and protein were up-regulated by inflammatory cytokines (IL-1β or TWEAK/TNFα/IFNγ) and by LPS in cultured tubular cells. However, TWEAK only induced a very mild and short lived NFκBiz upregulation. NFκBiz targeting increased chemokine production and dampened Klotho downregulation induced by TWEAK, without modulating cell proliferation. NFκBiz targeting also rendered cells more resistant to apoptosis induced by serum deprivation or inflammatory cytokines. In conclusion, NFκBiz differentially regulates NF-κB-mediated responses of tubular cells to inflammatory cytokines in a gene-specific manner, and may be of potential therapeutic interest to limit inflammation in kidney disease.

An Islet-Targeted Genome-Wide Association Scan Identifies Novel Genes Implicated in Cytokine-Mediated Islet Stress in Type 2 Diabetes

Genome-wide association studies in human type 2 diabetes (T2D) have renewed interest in the pancreatic islet as a contributor to T2D risk. Chronic low-grade inflammation resulting from obesity is a risk factor for T2D and a possible trigger of β-cell failure. In this study, microarray data were collected from mouse islets after overnight treatment with cytokines at concentrations consistent with the chronic low-grade inflammation in T2D. Genes with a cytokine-induced change of >2-fold were then examined for associations between single nucleotide polymorphisms and the acute insulin response to glucose (AIRg) using data from the Genetics Underlying Diabetes in Hispanics (GUARDIAN) Consortium. Significant evidence of association was found between AIRg and single nucleotide polymorphisms in Arap3 (5q31.3), F13a1 (6p25.3), Klhl6 (3q27.1), Nid1 (1q42.3), Pamr1 (11p13), Ripk2 (8q21.3), and Steap4 (7q21.12). To assess the potential relevance to islet function, mouse islets were exposed to conditions modeling low-grade inflammation, mitochondrial stress, endoplasmic reticulum (ER) stress, glucotoxicity, and lipotoxicity. RT-PCR revealed that one or more forms of stress significantly altered expression levels of all genes except Arap3. Thapsigargin-induced ER stress up-regulated both Pamr1 and Klhl6. Three genes confirmed microarray predictions of significant cytokine sensitivity: F13a1 was down-regulated 3.3-fold by cytokines, Ripk2 was up-regulated 1.5- to 3-fold by all stressors, and Steap4 was profoundly cytokine sensitive (167-fold up-regulation). Three genes were thus closely associated with low-grade inflammation in murine islets and also with a marker for islet function (AIRg) in a diabetes-prone human population. This islet-targeted genome-wide association scan identified several previously unrecognized candidate genes related to islet dysfunction during the development of T2D.

Regulation of alpha-1 acid glycoprotein synthesis by porcine hepatocytes in monolayer culture

Alpha-1 acid glycoprotein (AGP, orosomucoid, ORM-1) is a highly glycosylated mammalian acute-phase protein, which is synthesized primarily in the liver and represents the major serum protein in newborn pigs. Recent data have suggested that the pig is unique in that AGP is a negative acute-phase protein in this species, and its circulating concentration appears to be associated with growth rate. The purpose of the present study was to investigate the regulation of AGP synthesis in hepatocytes prepared from suckling piglets and to provide a framework to compare its regulation with that of haptoglobin (HP), a positive acute-phase protein. Hepatocytes were isolated from preweaned piglets and maintained in serum-free monolayer culture for up to 72 h. The influences of hormones, cytokines, and redox modifiers on the expression and secretion of AGP and HP were determined by relative polymerase chain reaction and by measuring the concentration of each protein secreted into culture medium. The messenger RNA abundance and/or secretion of AGP protein was enhanced by interleukin (IL)-17a, IL-1, and resveratrol and inhibited by tumor necrosis factor-α (TNF), oncostatin M, and thyroid hormone (P < 0.05). HP expression and synthesis were upregulated by oncostatin M, IL-6, and dexamethasone and downregulated by TNF (P < 0.01). The overall messenger RNA expression at 24 h was in agreement with the secreted protein patterns confirming that control of these proteins in hepatocytes is largely transcriptional. Moreover, these data support the consideration that AGP is a negative acute-phase reactant and appears to be regulated by cytokines (with the exception of TNF) and hormones primarily in a manner opposite to that of the positive acute-phase protein, HP.

Transcriptome analysis of peripheral blood mononuclear cells in human subjects following a 36 h fast provides evidence of effects on genes regulating inflammation, apoptosis and energy metabolism

There is growing interest in the potential health benefits of diets that involve regular periods of fasting. While animal studies have provided compelling evidence that feeding patterns such as alternate-day fasting can increase longevity and reduce incidence of many chronic diseases, the evidence from human studies is much more limited and equivocal. Additionally, although several candidate processes have been proposed to contribute to the health benefits observed in animals, the precise molecular mechanisms responsible remain to be elucidated. The study described here examined the effects of an extended fast on gene transcript profiles in peripheral blood mononuclear cells from ten apparently healthy subjects, comparing transcript profiles after an overnight fast, sampled on four occasions at weekly intervals, with those observed on a single occasion after a further 24 h of fasting. Analysis of the overnight fasted data revealed marked inter-individual differences, some of which were associated with parameters such as gender and subject body mass. For example, a striking positive association between body mass index and the expression of genes regulated by type 1 interferon was observed. Relatively subtle changes were observed following the extended fast. Nonetheless, the pattern of changes was consistent with stimulation of fatty acid oxidation, alterations in cell cycling and apoptosis and decreased expression of key pro-inflammatory genes. Stimulation of fatty acid oxidation is an expected response, most likely in all tissues, to fasting. The other processes highlighted provide indications of potential mechanisms that could contribute to the putative beneficial effects of intermittent fasting in humans.

IL-17A enhances the expression of profibrotic genes through upregulation of the TGF-β receptor on hepatic stellate cells in a JNK-dependent manner

Activation of hepatic stellate cells (HSCs) is a key event in the initiation of liver fibrosis, characterized by enhanced extracellular matrix production and altered degradation. Activation of HSCs can be modulated by cytokines produced by immune cells. Recent reports have implicated the proinflammatory cytokine IL-17A in liver fibrosis progression. We hypothesized that IL-17A may enhance activation of HSCs and induction of the fibrogenic signals in these cells. The human HSC line LX2 and primary human HSCs were stimulated with increasing doses of IL-17A and compared with TGF-β- and PBS-treated cells as positive and negative controls, respectively. IL-17A alone did not induce activation of HSCs. However, IL-17A sensitized HSCs to the action of suboptimal doses of TGF-β as confirmed by strong induction of α-smooth muscle actin, collagen type I (COL1A1), and tissue inhibitor of matrix metalloproteinase I gene expression and protein production. IL-17A specifically upregulated the cell surface expression of TGF-βRII following stimulation. Pretreatment of HSCs with IL-17A enhanced signaling through TGF-βRII as observed by increased phosphorylation of SMAD2/3 in response to stimulation with suboptimal doses of TGF-β. This enhanced TGF-β response of HSCs induced by IL-17A was JNK-dependent. Our results suggest a novel profibrotic function for IL-17A by enhancing the response of HSCs to TGF-β through activation of the JNK pathway. IL-17A acts through upregulation and stabilization of TGF-βRII, leading to increased SMAD2/3 signaling. These findings represent a novel example of cooperative signaling between an immune cytokine and a fibrogenic receptor.

Evolving concepts in the pathogenesis of NASH: beyond steatosis and inflammation

Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis and inflammation and, in some patients, progressive fibrosis leading to cirrhosis. An understanding of the pathogenesis of NASH is still evolving but current evidence suggests multiple metabolic factors critically disrupt homeostasis and induce an inflammatory cascade and ensuing fibrosis. The mechanisms underlying these changes and the complex inter-cellular interactions that mediate fibrogenesis are yet to be fully elucidated. Lipotoxicity, in the setting of excess free fatty acids, obesity, and insulin resistance, appears to be the central driver of cellular injury via oxidative stress. Hepatocyte apoptosis and/or senescence contribute to activation of the inflammasome via a variety of intra- and inter-cellular signalling mechanisms leading to fibrosis. Current evidence suggests that periportal components, including the ductular reaction and expansion of the hepatic progenitor cell compartment, may be involved and that the Th17 response may mediate disease progression. This review aims to provide an overview of the pathogenesis of NASH and summarises the evidence pertaining to key mechanisms implicated in the transition from steatosis and inflammation to fibrosis. Currently there are limited treatments for NASH although an increasing understanding of its pathogenesis will likely improve the development and use of interventions in the future.

Regulatory roles of tumor necrosis factor alpha-induced proteins (TNFAIPs) 3 and 9 in arthritis

Tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) have proved to be important in rheumatoid arthritis (RA) because the outcome of RA has greatly improved with the recent availability of biologics targeting them. It is well accepted that these cytokines are involved in the activation of the nuclear factor-κB (NF-κB) signaling pathway, but our understanding of the dependency of these pro-inflammatory cytokines and the link between them in RA is currently limited. Recently, we and others proved the importance of TNFα-induced protein (TNFAIP), due to the spontaneous development of arthritis in deficient animals that are dependent on IL-6. To date, nine TNFAIPs have been identified, and TNFAIP3 and TNFAIP9 were found to be clearly associated with mouse and human arthritis. In this review, we compare and discuss recent TNFAIP topics, especially focusing on TNFAIP3 and TNFAIP9 in autoimmune arthritis in mice and humans.

Progress in research of IL-10 and IL-17 in chronic hepatitis B, hepatitis B virus-related liver cirrhosis and cirrhosis with abdominal infection

Hepatitis B is a global contagious disease, posing a serious threat to human health. However, its pathogenic mechanisms and how it ultimately leads to the formation of cirrhosis are not fully understood. Elucidating the progression of hepatitis B and the mechanism responsible for liver cirrhosis formation can help develop novel antiviral treatment and anti-fibrosis therapy. In recent years, great progress has been made in understanding the pathogenesis of chronic hepatitis and liver cirrhosis and their treatment. Cytokines have become a research hotspot in this field. Emerging evidence suggests that a variety of cytokines in the liver have a quite significant role in the progressive process of HBV. Cytokines mainly mediate cell-cell interactions in paracrine, feedback or other manners to participate in the pathogenesis of chronic hepatitis B, cirrhosis and cirrhosis with infection. In recent years, many studies suggest that serum interleukin-10 (IL-10) and IL-17 levels are correlated with the development and prognosis of chronic hepatitis B, liver cirrhosis and cirrhosis with infection. In this paper, we review the progress in research of IL-10 and IL-17 in chronic hepatitis B, liver cirrhosis and cirrhosis with infection.

Microarray analysis provides new insights into the function of apolipoprotein O in HepG2 cell line

BACKGROUND

Apolipoprotein O (apoO) is a new member of the apolipoprotein family. However, data on its physiological functions are limited and inconsistent. Using a microarray expression analysis, this study explored the function of apoO in liver cells.

METHODS

HepG2 cells were treated either with oleic acid or tumor necrosis factor-α for 24 h. mRNA and protein expression of apoO were assessed by quantitative real-time PCR (qRT-PCR) and Western blot respectively. An efficient lentiviral siRNA vector targeting the human apoO gene was designed and constructed. The gene expression profile of HepG2 human hepatocellular carcinoma cells transfected with the apoO silencing vector was investigated using a whole-genome oligonucleotide microarray. The expression levels of some altered genes were validated using qRT-PCR.

RESULTS

ApoO expression in HepG2 cells was dramatically affected by lipid and inflammatory stimuli. A total of 282 differentially expressed genes in apoO-silenced HepG2 cells were identified by microarray analysis. These genes included those participating in fatty acid metabolism, such as ACSL4, RGS16, CROT and CYP4F11, and genes participating in the inflammatory response, such as NFKBIZ, TNFSF15, USP2, IL-17, CCL23, NOTCH2, APH-1B and N2N. The gene Uncoupling protein 2 (UCP2), which is involved in both these metabolic pathways, demonstrated significant changes in mRNA level after transfection.

CONCLUSIONS

It is likely that apoO participates in fatty acid metabolism and the inflammatory response in HepG2 cells, and UCP2 may act as a mediator between lipid metabolism and inflammation in apoO-silenced HepG2 cells.

Identification and characterization of a nuclear factor-κ B-p65 proteolytic fragment in nuclei of porcine hepatocytes in monolayer culture

Hepatic responses to proinflammatory signals are controlled by the activation of several transcription factors, including, nuclear factor-κ B (NF-κB). In this study, hepatocytes prepared from suckling pigs and maintained in serum-free monolayer culture were used to define a novel proinflammatory cytokine-specific NF-κB subunit modification. The immunoreactive p65 protein was detected by Western blot analysis at the appropriate molecular weight in the cytosol of control cultures and those incubated with tumor necrosis factor-α (TNF). However, in nuclei, the p65 antisera cross-reacted with a protein of approximately 38 kDa (termed p38) after TNF addition, which was not observed in the cytosol of control or cytokine-treated cells. Specifically, incubation with TNF also resulted in phosphorylation (P < 0.05) of the inhibitor complex protein (IκB), whereas incubation with other cytokines, IL-6, IL-17a, or oncostatin M was not associated with either phosphorylation of IκB or nuclear translocation of p65. Intracellular endothelial nitric oxide synthase was deceased (P < 0.05) and plasminogen activator inhibitor-1 secretion was increased (P < 0.05) after TNF incubation. The TNF-induced p38 protein was purified from hepatocyte nuclei by immunoprecipitation, concentrated by electrophoresis, and subsequently analyzed by mass spectrometry. Ten unique NF-κB p65 peptides were identified after digestion with trypsin and chymotrypsin; however, all were mapped to the N-terminus and within the first 310 amino acid residues of the intact p65 protein. Although low molecular weight immunoreactive p65 molecules were previously observed in various human and rodent systems, this is the first report to positively identify the p38 fragment within hepatocyte nuclei or after specific cytokine (TNF) induction.

Molecular mechanisms and cell targets of Th17 cells in the gastrointestinal tract: an innate sense of adaptivity

T-helper (TH) 17 activation is crucial for protective immune responses against bacteria and fungi at mucosal surfaces, but it can also be implicated in the pathogenesis of several autoimmune and chronic inflammatory diseases, such as inflammatory bowel diseases (IBD). Although rapid progress was made elucidating induction and functional heterogeneity of Th17 responses, the underlying molecular effects of Th17 response including the most relevant different cell targets of Th17 cytokines remain poorly understood. Cytokines produced by Th17 cells have broad effects on both hematopoietic and nonhematopoietic cells and can act in synergy with various inflammatory factors. In this review, we will focus on the effects of Th17-derived cytokines in the gastrointestinal tract and discuss how Th17 responses can affect both innate and adaptive immunity and may contribute to the pathogenesis of inflammatory GI processes.

The crystal structure of six-transmembrane epithelial antigen of the prostate 4 (Steap4), a ferri/cuprireductase, suggests a novel interdomain flavin-binding site

Steap4 is a cell surface metalloreductase linked to obesity-associated insulin resistance. Initial characterization of its cell surface metalloreductase activity has been reported, but thorough biochemical characterization of this activity is lacking. Here, we report detailed kinetic analysis of the Steap4 cell surface metalloreductase activities. Steap4 shows physiologically relevant Km values for both Fe(3+) and Cu(2+) and retains activity at acidic pH, suggesting it may also function within intracellular organelles to reduce these metals. Flavin-dependent NADPH oxidase activity that was much greater than the equivalent Steap3 construct was observed for the isolated N-terminal oxidoreductase domain. The crystal structure of the Steap4 oxidoreductase domain was determined, providing a structural explanation for these differing activities. Structure-function work also suggested Steap4 utilizes an interdomain flavin-binding site to shuttle electrons between the oxidoreductase and transmembrane domains, and it showed that the disordered N-terminal residues do not contribute to enzymatic activity.

Interleukin-17 (IL-17) and IL-1 activate translation of overlapping sets of mRNAs, including that of the negative regulator of inflammation, MCPIP1

Changes in gene expression during inflammation are in part caused by post-transcriptional mechanisms. A transcriptome-wide screen for changes in ribosome occupancy indicated that the inflammatory cytokine IL-17 activates translation of a group of mRNAs that overlaps partially with those affected similarly by IL-1. Included are mRNAs of IκBζ and of MCPIP1, important regulators of the quality and course of immune and inflammatory responses. Evidence for increased ribosome association of these mRNAs was also obtained in LPS-activated RAW264.7 macrophages and human peripheral blood mononuclear cells. Like IL-1, IL-17 activated translation of IκBζ mRNA by counteracting the function of a translational silencing element in its 3'-UTR defined previously. Translational silencing of MCPIP1 mRNA in unstimulated cells resulted from the combined suppressive activities of its 5'-UTR, which contains upstream open reading frames, and of its 3'-UTR, which silences independently of the 5'-UTR. Only the silencing function of the 3'-UTR was counteracted by IL-17 as well as by IL-1. Translational silencing by the 3'-UTR was dependent on a putative stem-loop-forming region previously associated with rapid degradation of the mRNA. The results suggest that translational control exerted by IL-1 and IL-17 plays an important role in the coordination of an inflammatory reaction.

Murine tumor necrosis factor α-induced adipose-related protein (tumor necrosis factor α-induced protein 9) deficiency leads to arthritis via interleukin-6 overproduction with enhanced NF-κB, STAT-3 signaling, and dysregulated apoptosis of macrophages

OBJECTIVE

To elucidate the role of tumor necrosis factor α-induced adipose-related protein (TIARP; or tumor necrosis factor α-induced protein 9 [TNFAIP-9]) in the development and pathogenesis of arthritis.

METHODS

We generated TIARP-deficient (TIARP(-/-) ) mice and investigated several organs in aged mice. Peritoneal macrophages were collected and cultured with lipopolysaccharide (LPS) and TNFα, and then the production of cytokines and subsequent NF-κB signal transduction were analyzed. We also examined the susceptibility of young TIARP(-/-) mice to collagen-induced arthritis (CIA). Draining lymph nodes and splenocytes were isolated and cultured, and serum levels of anti-type II collagen (anti-CII) antibodies, interleukin-6 (IL-6), and TNFα on day 60 were measured. We further investigated the effects of anti-IL-6 receptor monoclonal antibody (mAb) on the development of arthritis in TIARP(-/-) mice. IL-6/STAT-3 signaling was also analyzed using TIARP(-/-) macrophages.

RESULTS

TIARP(-/-) mice developed spontaneous enthesitis and synovitis, had high serum levels of IL-6, had increased CD11b+ cell counts in the spleen, and showed enhanced LPS- and TNFα-induced IL-6 expression in macrophages. Sustained degradation of IκBα with dysregulated apoptosis was also noted in TIARP(-/-) macrophages. CIA was clearly exacerbated in TIARP(-/-) mice, accompanied by marked neutrophil and macrophage infiltration in joints. The levels of anti-CII antibodies in serum were unchanged, whereas autoreactive Th1 cell and Th17 cell responses were higher in TIARP(-/-) mice. Treatment with anti-IL-6 receptor mAb prevented the development of CIA in TIARP(-/-) mice, and TIARP(-/-) macrophages showed increased IL-6-induced STAT-3 phosphorylation.

CONCLUSION

These findings suggest that TIARP acts as a negative regulator of arthritis by suppressing IL-6 production, its signaling and TNFα-induced NF-κB signaling, resulting in enhanced apoptosis in macrophages.

Effects of immunosuppressive agents on Th17 cells involved in transplantation

The lymphocyte-derived helper T (Th) cells are critical regulators of the adaptive immune response and are associated with inflammatory disease. The most recently recognized Th-cell lineage, Th17, plays an important role in host defense against extracellular pathogens by secreting the proinflammatory cytokine, interleukin 17, and recruiting reactive oxygen species (ROS)-producing monocytes to the site of infection. However, accumulating evidence has implicated Th17-cell dysregulation as an underlying cause for some immune-related pathogenic conditions, including allograft rejection. Recent studies of human transplant patients have indicated that Th17 cells exhibit resistance to current immunosuppressive therapies that would otherwise prevent allograft rejection. In this review, we will discuss the most current research findings related to Th17-cell function in various kinds of allografts.

The STEAP protein family: versatile oxidoreductases and targets for cancer immunotherapy with overlapping and distinct cellular functions

The human six-transmembrane epithelial antigen of the prostate (STEAP) protein family contains at least five homologous members. The necessity of multiple homologous STEAP proteins is still unclear, but their peculiar and tissue-specific expression suggests that they are assigned to distinct functional tasks. This concept is supported by the fact that especially STEAP1, and to a lesser extent STEAP2 and -4, are highly over-expressed in many different cancer entities, while being only minimally expressed in a few normal tissues. Despite their very similar domain organisation, STEAP3 seems to act as a potent metalloreductase essential for physiological iron uptake and turnover, while in particular STEAP4 appears to be rather involved in responses to nutrients and inflammatory stress, fatty acid and glucose metabolism. Moreover, individual STEAP proteins possess overlapping functions important for growth and survival of cancer cells. Due to their membrane-bound localisation and their high expression in many different cancers such as prostate, breast and bladder carcinoma as well as Ewing's sarcoma, STEAP proteins have been recognised and utilised as promising targets for cell- and antibody-based immunotherapy. This review summarises our present knowledge of the individual members of the human STEAP family and highlights the functional differences between them.

Monocyte chemotactic protein-1-induced protein-1 (MCPIP1) is a novel multifunctional modulator of inflammatory reactions

The generalized inflammatory response leads to activation of hundreds of genes transcribed in an established sequence in specialized cells. Transcriptome analysis of human monocyte-derived cells stimulated with IL-1beta or with monocyte chemotactic protein-1 (MCP-1) has led to the identification of a new inflammation-related gene ZC3H12A encoding a chain of 599 amino acids corresponding to a 66-kDa protein. The protein, given a provisional name of MCPIP1 (monocyte chemotactic protein-induced protein-1), is expressed in several human and murine tissues such as bone marrow, spleen, heart and placenta. In in vivo studies, mice with inactivated MCPIP1-encoding gene showed growth retardation, lymphadenopathy, splenomegaly and enhanced inflammatory symptoms. Principal molecular features of MCPIP1 include a single zinc finger motif, an RNase-like PIN domain and ubiquitin-binding domain. Reports from independent laboratories suggest that MCPIP1 may function also as a deubiquitinase. Although MCPIP1 is regarded by some authors as a new transcription factor or cell differentiation factor modulating angiogenesis or adipogenesis, its principal function appears to be downregulation of inflammatory responses through at least two independent mechanisms: increased degradation of cytokine mRNAs and inhibition of LPS- and IL-1-induced NF-kappaB signaling pathway. The interference with NF-kappaB activation is highly complex and includes TRAF6 and TANK interaction with the ubiquitin-associated (UBA) domain of MCPIP1. Purified MCPIP1 protein was reported to degrade specific mRNA and cleave K48- and K63-linked polyubiquitin chains. Although some structural features and the mechanism of action of MCPIP1 are not fully explained yet, its importance in the regulation of inflammatory reactions has been firmly established.

IL-17 induces AKT-dependent IL-6/JAK2/STAT3 activation and tumor progression in hepatocellular carcinoma

BACKGROUND

The Th17 subset and IL-17 have been found in increased frequencies within certain tumors. However, their relevance in cancer biology remains controversial. This study aimed to clarify the biological action of IL-17 on hepatocellular carcinoma (HCC).

METHODS

Effects and underlying molecular mechanisms of IL-17 on human HCC were explored in vitro using exogenous IL-17 stimulation and in nude mice by implanting IL-17 overexpressed HCC cells. The clinical significance of IL-17 was investigated in tissue microarrays containing HCC tissues from 323 patients following hepatectomy using immunohistochemistry.

RESULTS

Although exogenous IL-17 showed no direct effect on the growth rate of HCC cells in vitro, PCR and ELISA showed that IL-17 selectively augmented the secretion of diverse proinvasive factors and transwell showed a direct promotion of invasion of HCC cells by IL-17. Furthermore, transfection of IL-17 into HCC cells significantly promoted neoangiogenesis, neutrophil recruitment and tumor growth in vivo. Using siRNA mediated knockdown of AKT and STAT3, we suggested that the effects of IL-17 were operated through activation of the AKT signaling in HCC, which resulted in IL-6 production. Then, IL-6 in turn activated JAK2/STAT3 signaling and subsequently up-regulated its downstream targets IL-8, MMP2, and VEGF. Supporting these findings, in human HCC tissues, immunostaining indicated that IL-17 expression was significantly and positively associated with STAT3 phosphorylation, neutrophil infiltration and increased tumor vascularity. The clinical significance of IL-17 was authenticated by revealing that the combination of intratumoral IL-17+ cells and phospho-STAT3 served as a better prognosticator for postoperative tumor recurrence than either marker alone.

CONCLUSIONS

IL-17 mediated tumor-promoting role involves a direct effect on HCC cells through IL-6/JAK2/STAT3 induction by activating the AKT pathway.

T(H)17 cells in asthma and inflammation

BACKGROUND

The chronic airway disease asthma causes significant burden to patients as well as the healthcare system with limited options for prevention or cure. Inadequate treatment strategies are most likely due to the complex heterogeneous nature of asthma. Furthermore, the severe asthma phenotype is characterized by the lack of a response to standard medication, namely, corticosteroids.

SCOPE OF REVIEW

In the last several years it has been shown that the eosinophilic/atopic phenotype of asthma driven by T(H)2 mechanisms is not the only immunologic pathway contributing to disease. In fact, there has been evidence revealing that severe asthmatics in particular have neutrophilic inflammation, and this is associated with corticosteroid resistance. T(H)17 cells, a recently discovered lineage of T helper cells, play an important role in lung host defense against multiple pathogens via production of the cytokine IL-17. IL-17 promotes neutrophil production and chemotaxis via multiple factors.

MAJOR CONCLUSIONS

Mouse and human studies provide robust evidence that T(H)17 cells and IL-17 play a role in severe asthma and may contribute to corticosteroid resistance.

GENERAL SIGNIFICANCE

As we learn more about T(H)17 cells in severe asthma, the goal is to potentially target this pathway for treatment in the hope of significantly improving the quality of life for those children and adults affected with this disease. This article is part of a Special Issue entitled: Biochemistry of Asthma.

IL-17-induced NF-kappaB activation via CIKS/Act1: physiologic significance and signaling mechanisms

Interleukin-17 (IL-17) is essential in host defense against extracellular bacteria and fungi, especially at mucosal sites, but it also contributes significantly to inflammatory and autoimmune disease pathologies. Binding of IL-17 to its receptor leads to recruitment of adaptor protein CIKS/Act1 via heterotypic association of their respective SEFIR domains and activation of transcription factor NF-κB; it is not known whether CIKS and/or NF-κB are required for all gene induction events. Here we report that CIKS is essential for all IL-17-induced immediate-early genes in primary mouse embryo fibroblasts, whereas NF-κB is profoundly involved. We also identify a novel subdomain in the N terminus of CIKS that is essential for IL-17-mediated NF-κB activation. This domain is both necessary and sufficient for interaction between CIKS and TRAF6, an adaptor required for NF-κB activation. The ability of decoy peptides to block this interaction may provide a new therapeutic strategy for intervention in IL-17-driven autoimmune and inflammatory diseases.

Role of IL-17 and Th17 cells in liver diseases

Unbalanced Th1/Th2 T-cell responses in the liver are a characteristic of hepatic inflammation and subsequent liver fibrosis. The recently discovered Th17 cells, a subtype of CD4(+) T-helper cells mainly producing IL-17 and IL-22, have initially been linked to host defense against infections and to autoimmunity. Their preferred differentiation upon TGFβ and IL-6, two cytokines abundantly present in injured liver, makes a contribution of Th17 cells to hepatic inflammation very likely. Indeed, initial studies in humans revealed activated Th17 cells and Th17-related cytokines in various liver diseases. However, functional experiments in mouse models are not fully conclusive at present, and the pathogenic contribution of Th17 cells to liver inflammation might vary upon the disease etiology, for example, between infectious and autoimmune disorders. Understanding the chemokines and chemokine receptors promoting hepatic Th17 cell recruitment (possibly CCR6 or CCR4) might reveal new therapeutic targets interfering with Th17 migration or differentiation in liver disease.

Role of IL-17 and Th17 cells in liver diseases

Unbalanced Th1/Th2 T-cell responses in the liver are a characteristic of hepatic inflammation and subsequent liver fibrosis. The recently discovered Th17 cells, a subtype of CD4(+) T-helper cells mainly producing IL-17 and IL-22, have initially been linked to host defense against infections and to autoimmunity. Their preferred differentiation upon TGFβ and IL-6, two cytokines abundantly present in injured liver, makes a contribution of Th17 cells to hepatic inflammation very likely. Indeed, initial studies in humans revealed activated Th17 cells and Th17-related cytokines in various liver diseases. However, functional experiments in mouse models are not fully conclusive at present, and the pathogenic contribution of Th17 cells to liver inflammation might vary upon the disease etiology, for example, between infectious and autoimmune disorders. Understanding the chemokines and chemokine receptors promoting hepatic Th17 cell recruitment (possibly CCR6 or CCR4) might reveal new therapeutic targets interfering with Th17 migration or differentiation in liver disease.

ZC3H12A (MCPIP1): molecular characteristics and clinical implications

BACKGROUND

ZC3H12A is a gene whose absence is related to autoimmune disorders and to other phenotypical alterations.

METHODS

A comprehensive review of the structure, molecular functions and regulation of ZC3H12A gene and its protein MCPIP1 is done in order to understand their clinical implications.

RESULTS

ZC3H12A, at 1p34.3, has 9860bp, six exons and 61 described SNPs. Eleven are non-synonymous thus leading to changes in MCPIP1, the protein encoded by ZC3H12A. MCPIP1 is induced by MCP-1 and IL-1 whose signals are transduced through the NF-kβ and MAPkinase pathways. This protein acts as an RNAse by degrading chemokine transcripts such as IL-1 as well as its own mRNA and as a transcription factor by reducing the expression of other chemokines induced by NF-kβ such as MCP-1. It also up-regulates genes involved in several differentiation processes and apoptosis. Therefore, ZC3H12A is an equilibrium gatekeeper that not only regulates its own inducers but also controls the regulation by degrading its own mRNA.

CONCLUSION

Understanding ZC3H12A gives a comprehensive panorama that promises to improve our understanding of processes in which this gene is involved including autoimmune, infectious and cardiovascular diseases.