TIPE2 (Tumor Necrosis Factor α-induced Protein 8-like 2) Is a Novel Negative Regulator of TAK1 Signal

The deubiquitinase OTUD1 deubiquitinates TIPE2 and plays a protective role in sepsis-induced lung injury by targeting TAK1-mediated MAPK and NF-κB signaling

Ovarian tumor domain-containing protease 1 (OTUD1) is a critical negative regulator that promotes innate immune homeostasis and is extensively involved in the pathogenesis of sepsis. In this study, we performed a powerful integration of multiomics analysis and an experimental mechanistic investigation to elucidate the immunoregulatory role of OTUD1 in sepsis at the clinical, animal and cellular levels. Our study revealed the upregulation of OTUD1 expression and the related distinctive alterations observed via multiomics profiling in clinical and experimental sepsis. Importantly, in vivo and in vitro, OTUD1 was shown to negatively regulate inflammatory responses and play a protective role in sepsis-induced pathological lung injury by mechanistically inhibiting the activation of the transforming growth factor-beta-activated kinase 1 (TAK1)-mediated mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling pathways in the present study. Subsequently, we probed the molecular mechanisms underlying OTUD1's regulation of NF-κB and MAPK pathways by pinpointing the target proteins that OTUD1 can deubiquitinate. Drawing upon prior research conducted in our laboratory, it has been demonstrated that tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) performs a protective function in septic lung injury and septic encephalopathy by suppressing the NF-κB and MAPK pathways. Hence, we hypothesized that TIPE2 might be a target protein of OTUD1. Additional experiments, including Co-IP, immunofluorescence co-localization, and Western blotting, revealed that OTUD1 indeed has the ability to deubiquitinate TIPE2. In summary, OTUD1 holds potential as an immunoregulatory and inflammatory checkpoint agent, and could serve as a promising therapeutic target for sepsis-induced lung injury.

TIPE2: A Candidate for Targeting Antitumor Immunotherapy

TNF-α-induced protein 8-like 2 (TIPE2 or TNFAIP8L2) is a recently discovered negative regulator of innate and adaptive immunity. TIPE2 is expressed in a wide range of tissues, both immune and nonimmune, and is implicated in the maintenance of immune homeostasis within the immune system. Furthermore, TIPE2 has been shown to play a pivotal role in the regulation of inflammation and the development of tumor. This review focuses on the structural characteristics, expression patterns, and functional roles of TIPE proteins, with a particular emphasis on the role and underlying mechanisms of TIPE2 in immune regulation and its involvement in different diseases. However, the current body of evidence is still limited in providing a comprehensive understanding of the complex role of TIPE2 in the human body, warranting further investigation to elucidate the possible mechanisms and functions of TIPE2 in diverse disease contexts.

A Narrative Review of Cytokine Networks: Pathophysiological and Therapeutic Implications for Inflammatory Bowel Disease Pathogenesis

Inflammatory bowel disease (IBD) is a lifelong inflammatory immune mediated disorder, encompassing Crohn's disease (CD) and ulcerative colitis (UC); however, the cause and specific pathogenesis of IBD is yet incompletely understood. Multiple cytokines produced by different immune cell types results in complex functional networks that constitute a highly regulated messaging network of signaling pathways. Applying biological mechanisms underlying IBD at the single omic level, technologies and genetic engineering enable the quantification of the pattern of released cytokines and new insights into the cytokine landscape of IBD. We focus on the existing literature dealing with the biology of pro- or anti-inflammatory cytokines and interactions that facilitate cell-based modulation of the immune system for IBD inflammation. We summarize the main roles of substantial cytokines in IBD related to homeostatic tissue functions and the remodeling of cytokine networks in IBD, which may be specifically valuable for successful cytokine-targeted therapies via marketed products. Cytokines and their receptors are validated targets for multiple therapeutic areas, we review the current strategies for therapeutic intervention and developing cytokine-targeted therapies. New biologics have shown efficacy in the last few decades for the management of IBD; unfortunately, many patients are nonresponsive or develop therapy resistance over time, creating a need for novel therapeutics. Thus, the treatment options for IBD beyond the immune-modifying anti-TNF agents or combination therapies are expanding rapidly. Further studies are needed to fully understand the immune response, networks of cytokines, and the direct pathogenetic relevance regarding individually tailored, safe and efficient targeted-biotherapeutics.

TIPE2 sensitizes breast cancer cells to paclitaxel by suppressing drug-induced autophagy and cancer stem cell properties

Drug resistance is a great obstacle to the clinical application of paclitaxel (PTX) in breast cancer treatment. Chemoresistance can be either primary or acquired. Multifarious factors are related to drug resistance. Among these factors, drug-induced autophagy has been shown to contribute to acquired chemoresistance in cancer cells. Additionally, cancer stem cells (CSCs) drive primary chemoresistance. Recent advances regarding TIPE2 demonstrate that TIPE2 enhances osteosarcoma and non-small cell lung cancer cell sensitivity to cisplatin. However, the role of TIPE2 in PTX resistance in breast cancer cells has not been elucidated. Here, the in vitro and in vivo study demonstrated that TIPE2 sensitized breast cancer cells to PTX by suppressing drug-induced autophagy and CSC properties. Mechanistically, we found that TIPE2 activated the AKT/mTOR signalling pathway and inhibited the TAK1/MAPK signalling pathway to suppress drug-induced autophagy. Moreover, TIPE2 inhibited TAK1/NF-κB activation to reduce breast CSC properties. Collectively, our results first elucidated the inhibitory role of TIPE2 in breast cancer chemoresistance. Thus, TIPE2 may be a new target for breast cancer chemotherapy.

Adipose-specific deletion of the cation channel TRPM7 inhibits TAK1 kinase-dependent inflammation and obesity in male mice

Chronic inflammation of white adipose tissue is a key link between obesity and the associated metabolic syndrome. Transient receptor potential melastatin-like 7 (TRPM7) is known to be related to inflammation; however, the role of TRPM7 in adipocyte phenotype and function in obesity remains unclear. Here, we observe that the activation of adipocyte TRPM7 plays an essential role in pro-inflammatory responses. Adult male mice are used in our experiments. Adipocyte-specific deficiency in TRPM7 attenuates the pro-inflammatory phenotype, improves glucose homeostasis, and suppresses weight gain in mice fed a high-fat diet. Mechanistically, the pro-inflammatory effect of TRPM7 is dependent on Ca²⁺ signaling. Ca²⁺ influx initiated by TRPM7 enhances transforming growth factor-β activated kinase 1 activation via the co-regulation of calcium/calmodulin-dependent protein kinase II and tumor necrosis factor receptor-associated factor 6, leading to exacerbated nuclear factor kappa B signaling. Additionally, obese mice treated with TRPM7 inhibitor are protected against obesity and insulin resistance. Our results demonstrate TRPM7 as a factor in the development of adipose inflammation that regulates insulin sensitivity in obesity.

Exogenous TIPE2 Inhibit TAK1 to Improve Inflammation and Neuropathic Pain Induced by Sciatic Nerve Injury Through Inactivating NF-κB and JNK

Tumor necrosis factor-alpha-induced protein 8-like 2 (TIPE2) possesses potent anti-inflammatory effect. However, if TIPE2 ameliorates sciatic nerve injury (SNI)-induced inflammation and pain remains undiscussed, and the underlying role TAK1 in it were unknown. To verify our imagine, we performed SNI surgery, and analyzed expression and colocalization of TIPE2 and TAK1 in spinal cord and dorsal root neurons (DRG) by immunofluorescence staining and western blot. And the biological analysis, inflammatory factors, and pathological improvement were determined, and the regulation of TIPE2 in TAK1, phosphor-NF-κB, phospho-JNK was also tested by immunofluorescence staining and western blot. Experimental results showed the parabola-like change of TIPE2 and rising expression of TAK1 in spinal cord and DRG. And intrathecal TIPE2 injection could significantly improve the status of SNI rats, inhibit level of IL-6, IL-10 and TNF-α, raise the thermal withdrawal relax latency and mechanical withdrawal thresholds. Meanwhile, we also detected how TIPE2 regulated TAK1, and the downstream pathway NF-κB and JNK. The result indicated that TIPE2 could reduce TAK1 expression, and make NF-κB and JNK inactivated. To deeply discuss the potential mechanism, we injected TAK1 oligodeoxynucleotide into rats, and found that TIPE2 exerted the protective role against SNI through TAK1. In brief, TIPE2 reduced expression of TAK1, thereby inhibiting activation of NF-kB and JNK, further improving the neuroinflammation and neuropathic pain. TIPE2 played a protective role in sciatic nerve injury rats through regulating TAK1.

Examining micro-ribonucleic acids as diagnostic and therapeutic prospects in autoimmune hepatitis

INTRODUCTION

Micro-ribonucleic acids modulate the immune response by affecting the post-transcriptional expression of genes that influence the proliferation and function of activated immune cells, including regulatory T cells. Individual expressions or patterns in peripheral blood and liver tissue may have diagnostic value, reflect treatment response, or become therapeutic targets. The goals of this review are to present the properties and actions of micro-ribonucleic acids, indicate the key individual expressions in autoimmune hepatitis, and describe prospective clinical applications in diagnosis and management.

AREAS COVERED

Abstracts were identified in PubMed using the search words "microRNAs", "microRNAs in liver disease", and "microRNAs in autoimmune hepatitis". The number of abstracts reviewed exceeded 2000, and the number of full-length articles reviewed was 108.

EXPERT OPINION

Individual micro-ribonucleic acids, miR-21, miR-122, and miR-155, have been associated with biochemical severity, histological grade of inflammation, and pivotal pathogenic mechanisms in autoimmune hepatitis. Antisense oligonucleotides that down-regulate deleterious individual gene expressions, engineered molecules that impair targeting of gene products, and drugs that non-selectively up-regulate the biogenesis of potentially deficient gene regulators are feasible treatment options. Micro-ribonucleic acids constitute an under-evaluated area in autoimmune hepatitis that promises to improve diagnosis, pathogenic concepts, and therapy.

TNF-α-induced protein 8-like 2 negatively regulates the immune function of dendritic cells by suppressing autophagy via the TAK1/JNK pathway in septic mice

Tumor necrosis factor (TNF)-α-induced protein 8-like 2 (TIPE2) is a newly discovered negative immunoregulatory protein that is involved in various cellular immune responses to infections. However, the underlying mechanism by which TIPE2 affects the immune function of dendritic cells (DCs) is not yet understood. This study aimed to determine the correlations among DCs TIPE2 expression, autophagic activity and immune function in the context of sepsis. In addition, the signaling pathway by which TIPE2 regulates autophagy in DCs was investigated. We reported for the first time that TIPE2 overexpression (knock-in, KI) exerted an inhibitory effect on autophagy in DCs and markedly suppressed the immune function of DCs upon septic challenge both in vitro and in vivo. In addition, TIPE2 knockout (KO) in DCs significantly enhanced autophagy and improved the immune response of DCs in sepsis. Of note, we found that the transforming growth factor-β (TGF-β)-activated kinase-1 (TAK1)/c-Jun N-terminal kinase (JNK) pathway was inhibited by TIPE2 in DCs, resulting in downregulated autophagic activity. Collectively, these results suggest that TIPE2 can suppress the autophagic activity of DCs by inhibiting the TAK1/JNK signaling pathway and further negatively regulate the immune function of DCs in the development of septic complications.

Tumor necrosis factor α‑induced protein 8‑like 2 contributes to penehyclidine hydrochloride pretreatment against lipopolysaccharide‑induced acute lung injury in a mouse model

The aim of the present study was to investigate the effect of penehyclidine hydrochloride (PHC) pretreatment on mice with lipopolysaccharide (LPS)‑induced acute lung injury (ALI) and its possible underlying mechanisms. Mice were randomly separated into six groups: i) Sham group; ii) LPS group; iii) LPS + PHC group; iv) tumor necrosis factor a‑induced protein 8‑like protein 2 (TIPE2) group; v) LPS + TIPE2 group; and vi) LPS + TIPE2 + PHC group. The ALI model was induced using LPS through intratracheal injection. The mice received adenovirus gene to induce the overexpression of TIPE2. After mice were sacrificed, lung injury indices were assessed, and arterial blood, bronchoalveolar lavage fluid and lung tissues were collected for subsequent assays. Expression levels of related proteins were detected by using western blotting. It was found that compared with the sham group, the mice treated with LPS showed increased lung injury and dysfunctions of gas exchange. However, these trends were significantly ameliorated in the LPS + PHC group. Evaluation of protein expression in lung tissues showed that the increased expression of nuclear NF‑κB p65 and p‑c‑Jun N‑terminal kinase (JNK) induced by LPS were suppressed in the LPS + PHC group and the expression of TIPE2 was increased. The mice that received adenovirus gene to induce TIPE2 overexpression could also showed protective effects compared with the mice in the LPS group. However, the expression of TIPE2 decreased rather than increased in LPS group. In the mice pretreated with PHC, the expression of TIPE2 increased in mice with LPS‑induced ALI. To conclude, PHC pretreatment could inhibit the occurrence of inflammation and apoptosis in LPS‑induced ALI. This process may be related to the activation of TIPE2 and the inhibition of NF‑κB and JNK signaling pathway in the lungs of mice.

Tumor Necrosis Factor α-Induced Protein 8-Like 2 Alleviates Nonalcoholic Fatty Liver Disease Through Suppressing Transforming Growth Factor Beta-Activated Kinase 1 Activation

BACKGROUND AND AIMS

NAFLD prevalence has increased rapidly and become a major global health problem. Tumor necrosis factor α-induced protein 8-like 2 (TIPE2) plays a protective role in a cluster of liver diseases, such as autoimmune hepatitis, hepatitis B, and hepatocellular carcinoma. However, the function of TIPE2 in NAFLD remains unknown. Here, we investigated the role of TIPE2 in the development of NAFLD.

APPROACH AND RESULTS

Our study found that in vitro overexpression or knockout of TIPE2 significantly ameliorated or aggravated lipid accumulation and inflammation in hepatocytes exposed to metabolic stimulation, respectively. Consistently, in vivo hepatic steatosis, insulin resistance, inflammation, and fibrosis were alleviated in hepatic Tipe2-transgenic mice but exaggerated in hepatic Tipe2-knockout mice treated by metabolic challenges. RNA sequencing revealed that TIPE2 was significantly associated with the mitogen-activated protein kinase pathway. Mechanistic experiments demonstrated that TIPE2 bound with transforming growth factor beta-activated kinase 1 (TAK1), prevented tumor necrosis factor receptor-associated factor 6-mediated TAK1 ubiquitination and subsequently inhibited the TAK1 phosphorylation and activation of TAK1-c-Jun N-terminal kinase (JNK)/p38 signaling. Further investigation showed that blocking the activity of TAK1 reversed the worsening of hepatic metabolic disorders and inflammation in hepatic-specific Tipe2-knockout hepatocytes and mice treated with metabolic stimulation.

CONCLUSIONS

TIPE2 suppresses NAFLD advancement by blocking TAK1-JNK/p38 pathway and is a promising target molecule for NAFLD therapy.

Tumor Necrosis Factor-α-Induced Protein 8-Like 2 Negatively Regulates Innate Immunity Against RNA Virus by Targeting RIG-I in Macrophages

A systematic and flexible immunoregulatory network is required to ensure the proper outcome of antiviral immune signaling and maintain homeostasis during viral infection. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2), a novel immunoregulatory protein, has been extensively studied in inflammatory response, apoptosis, and cancer. However, the function of TIPE2 in antiviral innate immunity is poorly clarified. In this study, we reported that the expression of TIPE2 declined at the early period and then climbed up in macrophages under RNA virus stimulation. Knockout of TIPE2 in the macrophages enhanced the antiviral capacity and facilitated type I interferon (IFN) signaling after RNA viral infection both in vitro and in vivo. Consistently, overexpression of TIPE2 inhibited the production of type I IFNs and pro-inflammatory cytokines, and thus promoted the viral infection. Moreover, TIPE2 restrained the activation of TBK1 and IRF3 in the retinoic acid inducible gene-I (RIG-I)-like receptors (RLR) signaling pathway by directly interacting with retinoic acid inducible gene-I (RIG-I). Taken together, our results suggested that TIPE2 suppresses the type I IFN response induced by RNA virus by targeting RIG-I and blocking the activation of downstream signaling. These findings will provide new insights to reveal the immunological function of TIPE2 and may help to develop new strategies for the clinical treatment of RNA viral infections.

Decreased expression of TIPE2 in the eye under high-glucose conditions tested in vivo and in vitro

AIMS

Inflammation is important in the development of angiogenesis diabetic retinopathy (DR). Anti-inflammation is promising strategy in early DR management. This study aimed to evaluate the level of tumour necrosis factor (TNF)-α-induced protein-8 like-2 (TIPE2), a formerly anti-inflammatory factor, under high-glucose conditions.

METHODS

TIPE2 was detected in the ① retina from db/db and streptozotocin-induced diabetic mice; ② vitreous fluid of patients with proliferative diabetic retinopathy (PDR) and ③ mouse retinal microendothelial cells (RMEC) cultured in glucose of varying concentrations. In situ expression was evaluated by immunohistochemistry and immunofluorescence assay. The expression of protein was analysed by Western blot or ELISA and mRNA by qRT-PCR.

RESULTS

TIPE2 was down-regulated in the retina of the mice with diabetes. TIPE2 was present in the cytoplasm of RMEC and down-regulated in high-glucose conditions in line with concentration and time. The expression of TIPE2 in the vitreous fluid of patients with PDR was significantly lower than that without diabetes. Silencing TIPE2 by an siRNA resulted in increased expression of vascular endothelial growth factor (a vital factor in the development of DR), TNF-α and IL-1β.

CONCLUSIONS

TIPE2 down-expressed and exerted anti-VEGF and anti-inflammatory function in the high-glucose environment. TIPE2 was verified to be involved in the process of DR and might be a potential regulator for DR development.

Regulatory Roles of Tumor Necrosis Factor-α-Induced Protein 8 Like-Protein 2 in Inflammation, Immunity and Cancers: A Review

Tumor necrosis factor-alpha (TNF-α)-induced protein 8 (TNFAIP8/TIPE) family, including TNFAIP8 (TIPE), TNFAIP8 like-protein 1 (TNFAIP8L1/TIPE1), TNFAIP8 like-protein 2 (TNFAIP8L2/TIPE2), and TNFAIP8 like-protein 3 (TNFAIP8L3/TIPE3), plays a vital role in regulating inflammatory responses, immune homeostasis, and cancer development. Over the last decade, studies have shown that TIPE2 protein is differentially expressed in diverse cells and tissues. The dysregulation of TIPE2 protein can lead to dysregulation of inflammatory responses and immune homeostasis, and change the basic characteristics of cancers. In consideration of the immeasurable values of TIPE2 in diagnosis, treatment, and prognosis of various human diseases, this review will focus on the expression pattern, structure, and regulatory roles of TIPE2 in inflammation, immunity, and cancers.

Toll-like receptors in sepsis-associated cytokine storm and their endogenous negative regulators as future immunomodulatory targets

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Sepsis infects more than 48.9 million people world-wide, with 19.7 million deaths.

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Cytokine storm plays a significant role in sepsis, along with severe COVID-19.

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TLR signaling pathways plays a crucial role in generating the cytokine storm.

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Endogenous negative regulators of TLR signaling are crucial to regulate cytokine storm.

Cytokine storm generates during various systemic acute infections, including sepsis and current pandemic called COVID-19 (severe) causing devastating inflammatory conditions, which include multi-organ failure or multi-organ dysfunction syndrome (MODS) and death of the patient. Toll-like receptors (TLRs) are one of the major pattern recognition receptors (PRRs) expressed by immune cells as well as non-immune cells, including neurons, which play a crucial role in generating cytokine storm. They recognize microbial-associated molecular patterns (MAMPs, expressed by pathogens) and damage or death-associate molecular patterns (DAMPs; released and/expressed by damaged/killed host cells). Upon recognition of MAMPs and DAMPs, TLRs activate downstream signaling pathways releasing several pro-inflammatory mediators [cytokines, chemokines, interferons, and reactive oxygen and nitrogen species (ROS or RNS)], which cause acute inflammation meant to control the pathogen and repair the damage. Induction of an exaggerated response due to genetic makeup of the host and/or persistence of the pathogen due to its evasion mechanisms may lead to severe systemic inflammatory condition called sepsis in response to the generation of cytokine storm and organ dysfunction. The activation of TLR-induced inflammatory response is hardwired to the induction of several negative feedback mechanisms that come into play to conclude the response and maintain immune homeostasis. This state-of-the-art review describes the importance of TLR signaling in the onset of the sepsis-associated cytokine storm and discusses various host-derived endogenous negative regulators of TLR signaling pathways. The subject is very important as there is a vast array of genes and processes implicated in these negative feedback mechanisms. These molecules and mechanisms can be targeted for developing novel therapeutic drugs for cytokine storm-associated diseases, including sepsis, severe COVID-19, and other inflammatory diseases, where TLR-signaling plays a significant role.

Recombinant canine basic fibroblast growth factor-induced differentiation of canine bone marrow mesenchymal stem cells into voltage- and glutamate-responsive neuron-like cells

Introduction

Basic fibroblast growth factor (bFGF) is a promising cytokine in regenerative therapy for spinal cord injury. In this study, recombinant canine bFGF (rc-bFGF) was synthesized for clinical use in dogs, and the ability of rc-bFGF to differentiate canine bone marrow mesenchymal stem cells (BMSCs) into functional neurons was investigated.

Methods

The rc-bFGF was synthesized using a wheat germ cell-free protein synthesis system. The expression of rc-bFGF mRNA in the purification process was confirmed using a reverse transcription-polymerase chain reaction (RT-PCR). Western blotting was performed to confirm the antigenic property of the purified protein. To verify function of the purified protein, phosphorylation of extracellular signal-regulated kinase (ERK) was examined by in vitro assay using HEK293 cells. To compare the neuronal differentiation capacity of canine BMSCs in response to treatment with rc-bFGF, the cells were divided into the following four groups: control, undifferentiated, rh-bFGF, and rc-bFGF groups. After neuronal induction, the percentage of cells that had changed to a neuron-like morphology and the mRNA expression of neuronal markers were evaluated. Furthermore, to assess the function of the canine BMSCs after neuronal induction, changes in the intracellular Ca²⁺ concentrations after stimulation with KCl and l-glutamate were examined.

Results

The protein synthesized in this study was rc-bFGF and functioned as bFGF, from the results of RT-PCR, western blotting, and the expression of pERK in HEK293 cells. Canine BMSCs acquired a neuron-like morphology and expressed mRNAs of neuronal markers after neuronal induction in the rh-bFGF and the rc-bFGF groups. These results were more marked in the rc-bFGF group than in the other groups. Furthermore, an increase in intracellular Ca²⁺ concentrations was observed after the stimulation of KCl and l-glutamate in the rc-bFGF group, same as in the rh-bFGF group.

Conclusions

A functional rc-bFGF was successfully synthesized, and rc-bFGF induced the differentiation of canine BMSCs into voltage- and glutamate-responsive neuron-like cells. Our purified rc-bFGF may contribute, on its own, or in combination with canine BMSCs, to regenerative therapy for spinal cord injury in dogs.

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Functional rc-bFGF was successfully synthesized.

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rc-bFGF induced the differentiation of canine BMSCs into neuron-like cells.

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rc-bFGF may aid in regenerative therapy of spinal cord injury in dogs.

TIPE2 suppresses progression and tumorigenesis of the oral tongue squamous cell carcinoma by regulating FoxP3+ regulatory T cells

To discover the effect of tumor necrosis factor-alpha-induced protein 8-like 2 (TIPE2) on the oral tongue squamous cell carcinoma (OTSCC) via affecting FoxP3⁺ regulatory T (Treg) cells. Immunohistochemistry was conducted to examine TIPE2 and FoxP3 expressions in OTSCC tumor tissues and corresponding oral mucosa. Tca8113 cells were transfected with TIPE2/control lentiviral activation particles followed by the detection with qRT-PCR, Western blotting, MTT assay, Wound healing, Transwell assay and Annexin V-FITC/PI staining. In vivo experiment was carried out on the nude mice xenografts of OTSCC with TIPE2 overexpression to observe the tumor volume and survival, and the CD4⁺ T cell subgroups were detected by flow cytometry. TIPE2 was lower in the OTSCC tissues than the corresponding oral mucosa, which was correlated with T stage, N stage, TNM stage, and differentiation of patients. Patients with TIPE2-positive expression had worse prognosis and lower expression of FoxP3⁺ Treg cells than the negative ones. Furthermore, TIPE2 overexpression curbed proliferation, invasion and migration of Tca8113 cells, while cell apoptosis was increased. Besides, TIPE2 suppressed the tumor growth and extended the survival of OTSCC mice, with the decreased proportion of FoxP3⁺ Treg cells in the spleen and tumor-infiltrated lymphocytes (TILs). The clinical results showed the down-regulation of TIPE2 in OTSCC tissues. Meanwhile TIPE2 overexpression affected OTSCC cells biological behavior in vitro, as well as exhibited strong tumor-growth suppressive effects in vivo, which may be a potential therapeutic target in OTSCC via regulating FoxP3⁺ Treg cells.

The enigmatic role of TIPE2 in asthma

Unlike other members of the tumor necrosis factor (TNF)-α-induced protein 8 (TNFAIP8/TIPE) family that play a carcinogenic role and regulate apoptosis, TNFAIP8-like 2 (TIPE2) can not only maintain immune homeostasis but also regulate inflammation. TIPE2 mainly restrains the activation of T cell receptor (TCR) and Toll-like receptors (TLR), regulating its downstream signaling pathways, thereby regulating inflammation. Interestingly, TIPE2 is abnormally expressed in many inflammatory diseases and may promote or inhibit inflammation in different diseases. This review summarizes the molecular target and cellular function of TIPE2 in immune cells and inflammatory diseases and the underlying mechanism by which TIPE2 regulates inflammation. The function and mechanism of TIPE2 in asthma is also explained in detail. TIPE2 is abnormally expressed in asthma and participates in the pathogenesis of different phenotypes of asthma through regulating multiple inflammatory cells' activity and function. Considering the indispensable role of TIPE2 in asthma, TIPE2 may be an effective therapeutic target in asthma. However, the available data are insufficient to provide a full understanding of the complex role of TIPE2 in human asthma. Further study is still necessary to explore the possible mechanism and functions of TIPE2 in different asthma phenotypes.

The SCFβ-TrCP E3 Ubiquitin Ligase Regulates Immune Receptor Signaling by Targeting the Negative Regulatory Protein TIPE2

TNFAIP8-like 2 (TIPE2) is a negative regulator of immune receptor signaling that maintains immune homeostasis. Dysregulated TIPE2 expression has been observed in several types of human immunological disorders. However, how TIPE2 expression is regulated remains to be determined. We report in this study that the SCF^β-TrCP E3 ubiquitin ligase regulates TIPE2 protein abundance by targeting it for ubiquitination and subsequent degradation via the 26S proteasome. Silencing of either cullin-1 or β-TrCP1 resulted in increased levels of TIPE2 in immune cells. TAK1 phosphorylated the Ser³ in the noncanonical degron motif of TIPE2 to trigger its interaction with β-TrCP for subsequent ubiquitination and degradation. Importantly, the amount of TIPE2 protein in immune cells determined the strength of TLR 4-induced signaling and downstream gene expression. Thus, our study has uncovered a mechanism by which SCF^β-TrCP E3 ubiquitin ligase regulates TLR responses.

TIPE2 Suppresses Pseudomonas aeruginosa Keratitis by Inhibiting NF-κB Signaling and the Infiltration of Inflammatory Cells

Background

The role of tumor necrosis factor α (TNF-α) induced protein 8-like-2 (TIPE2) in Pseudomonas aeruginosa (PA) keratitis was explored.

Methods

Eight-week-old TIPE2 knockout (TIPE2−/−) C57BL/6 mice and their wild-type (WT) littermates were used. Corneal disease was graded at 1, 2, and 3 days postinfection, and slit lamp, clinical score, histopathology, and immunostaining were performed in the infected corneas. The corneas were harvested, and messenger ribonucleic acid (mRNA) levels of TNF-α, interleukin-1β (IL-1β), and interleukin-6 (IL-6) were tested. Enzyme-linked immunosorbent assay (ELISA) determined the protein levels, and nuclear factor κ-light-chain-enhancer of activated B cell (NF-κB) signaling molecules were tested by Western blot. In vitro human corneal epithelial cells (HCECs) were used to determine the relationship between TIPE2 and TAK1. The HCECs were treated with TIPE2 short hairpin ribonucleic acid (shRNA) and lipopolysaccharide (LPS) to test the NF-κB signaling molecules by Western blot.

Results

Pseudomonas aeruginosa infection induced a decreased expression of TIPE2 in mouse corneas 2 days postinfection. Compared with the control group, TIPE2-deficient mice were susceptible to infection with PA and showed increased corneal inflammation. Reduced NF-κB signaling and inflammatory cell infiltration were required in the TIPE2-mediated immune modulation.

Conclusions

TIPE2 promoted host resistance to PA infection by suppressing corneal inflammation via regulating TAK1 signaling negatively and inhibiting the infiltration of inflammatory cells.

A designed cell-penetrating human SOCS2 protein suppresses GH-dependent cancer cell proliferation

Suppressor of cytokine signaling (SOCS) 2, a negative regulator of growth hormone (GH) and insulin-like growth factor 1 (IGF-1), which is associated with acromegaly and cancers, is a promising candidate molecule for treating various diseases. To facilitate its use in protein therapy, we designed and constructed a human SOCS2 protein containing a membrane-permeable peptide sequence and expressed it in an Escherichia coli system. The partially purified recombinant protein was effectively delivered into several cancer cell lines and inhibited cell growth. Biochemical analysis showed that the recombinant SOCS2 protein interacted with growth hormone receptor (GHR) and downregulated GH-STAT5 signaling target genes. Our results suggest that the designed cell-penetrating SOCS2 protein will be useful in intercellular protein therapy to cure cancers. Abbreviations: SOCS: suppressor of cytokine signaling; GH: growth hormone; GHR: growth hormone receptor; IGF-1: insulin-like growth factor 1; CP: cell-penetrating; STAT: signal transducer and activator of transcription; JAK: Janus kinase; HNF: hepatocyte nuclear factor; MTM: membrane-translocating motif; HIV: human immunodeficiency virus.

TIPE2 sensitizes osteosarcoma cells to cis-platin by down-regulating MDR1 via the TAK1- NF-κB and - AP-1 pathways

TIPE2 participates in multiple types of cancer development. However, its mechanism underlying chemoresistance in osteosarcoma has not been elucidated. Herein, we observed the expression of TIPE2 and MDR1 in cis-platin-resistant osteosarcoma tissues and cell lines. Compared to their matched sensitive cell lines and tissues, TIPE2 was downregulated while MDR1 expression was increased. Further investigation showed that overexpression of TIPE2 effectively inhibited MDR1 expression and greatly sensitized osteosarcoma cells to cis-platin, both in vivo and in vitro. Mechanistically, TIPE2 inhibited the transcription of the MDR1 promoter by interfering with the TAK1-NF-κB and -AP-1 pathways. Overall, our results elucidated for the first time that TIPE2 sensitizes osteosarcoma cells to cis-platin through downregulation of MDR1 and may be a novel target in osteosarcoma therapy.

Emerging therapeutic biomarkers of autoimmune hepatitis and their impact on current and future management

Autoimmune hepatitis lacks a quantifiable biomarker that is close to its pathogenic mechanisms and that accurately reflects inflammatory activity, correlates with treatment response, and ensures inactive disease before treatment withdrawal. Areas covered: Micro-ribonucleic acids, programmed death-1 protein and its ligands, macrophage migration inhibitory factor, soluble CD163, B cell activating factor, and metabolite patterns in blood were considered the leading candidates as therapeutic biomarkers after search of PubMed from August 1981 to August 2017 using the search words 'biomarkers of autoimmune hepatitis'. Expert commentary: Each of the candidate biomarkers is close to the putative pathogenic mechanisms of autoimmune hepatitis, and each has attributes that support its potential role as a surrogate marker of inflammatory activity that can be monitored during treatment. Future studies must demonstrate the superiority of each biomarker to conventional indices of inflammatory activity and validate their correlation with treatment response and outcome. A reliable therapeutic biomarker would facilitate the individualization of current management algorithms, ensure that pathogenic mechanisms were disrupted or eliminated prior to treatment withdrawal, and reduce the frequency of relapse or unnecessary protracted therapy. The biomarker might also prove to be a target of next-generation therapies.

TIPE2 governs macrophage polarization via negative regulation of mTORC1

Macrophages can be polarized into the inflammatory M1 lineage or the immunomodulatory M2 lineage, depending on the differential tissue microenvironment signaling, specific pathogens or cytokine stimulation. Tumor necrosis factor α-induced protein 8-like protein 2 (TIPE2) has been demonstrated to negatively regulate inflammation by inhibiting the Toll-like receptor (TLR) pathway. The present study utilized murine bone marrow derived macrophages (BMDMs) as the model of undifferentiated (M0) macrophages to study the roles of TIPE2 in the differential polarization status of BMDMs. It was observed that the expression levels of TIPE2 were diminished in M1 macrophages treated with lipopolysaccharide/interferon γ, and elevated in M2 macrophages treated with interleukin (IL)-4. BMDMs with TIPE2 overexpression exhibited defective M1 polarization and enhanced responses to IL-4 stimulation. TIPE2 impeded M1 polarization by interfering with mitogen-activated protein kinase kinase kinase 7-inhibitor of nuclear factor-κB kinase subunit β and B cell receptor-associated protein-serine/threonine-protein kinase mTOR complex 1 (mTORC1) activation. TIPE2 overexpression accelerated IL-4 induced M2 polarization by dampening mTORC1 activation via the accelerated process of arginine to urea. Overall, these results define a key role for TIPE2 in macrophage polarization by impeding mTORC1 response.