The expression and significance of TIPE2 in peripheral blood mononuclear cells from asthmatic children

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.

Research progress of TIPE2 in immune-related diseases

The tumor necrosis factor α-induced protein 8 (TNFAIP8) family, which consists of TNFAIP8 (TIPE), TNFAIP8L1 (TIPE1), TNFAIP8L2 (TIPE2) and TNFAIP8L3 (TIPE3), has recently emerged as a regulatory factor involved in immune response and tumorigenesis. Among its members, TIPE2 acts as a negative regulator of both innate and adaptive immunity, playing a crucial role in maintaining immune homeostasis by negatively regulating T cell receptor (TCR) and toll-like receptor (TLR) signal transduction. Immune homeostasis is an indispensable characteristic of the immune system, which prevents harmful inflammatory reactions and ensures the proper functioning of the body. A large number of studies have shown that abnormal TIPE2 expression exists in a variety of inflammation-related diseases such as asthma, colitis, and systemic lupus erythematosus, highlighting the importance of comprehending its function for the prevention and treatment of immune-related conditions. This review aims to provide an overview of the in vivo distribution and expression of TIPE2, its regulatory role in central and peripheral immune-related diseases, and the underlying mechanisms that govern its function in the inflammatory response. By delving into these aspects, a deeper understanding of the role and functionality of TIPE2 in inflammatory responses can be achieved.

TIPE2 regulates periodontal inflammation by inhibiting NF-κB p65 phosphorylation

BACKGROUND

The roles and molecular mechanisms of tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) in periodontitis remain largely unknown.

OBJECTIVE

This study aimed to determine the expression of TIPE2 and NF-κB p65 in rat Porphyromonas gingivalis-induced periodontics in vivo.

METHODOLOGY

Periodontal inflammation and alveolar bone resorption were analyzed using western blotting, micro-computed tomography, TRAP staining, immunohistochemistry, and immunofluorescence. THP-1 monocytes were stimulated using 1 μg/ml Pg. lipopolysaccharide (Pg.LPS) to determine the expression of TIPE2 in vitro. TIPE2 mRNA was suppressed by siRNA transfection, and the transfection efficiency was proven using western blotting and real-time PCR. The NF-κB pathway was activated by treating the cells with 1 μg/ml Pg.LPS to explore related mechanisms.

RESULTS

The expression of both TIPE2 and NF-κB p65 was increased in the gingival tissues of rat periodontitis compared with normal tissues. Positive expression of TIPE2 was distributed in inflammatory infiltrating cells and osteoclasts in the marginal lacunae of the alveolar bone. However, strong positive expression of TIPE2 in THP-1 was downregulated after Pg.LPS stimulation. TIPE2 levels negatively correlated with TNF-α and IL-1β. Decreased TIPE2 in THP-1 further promoted NF-κB p65 phosphorylation. Mechanistically, TIPE2 knockdown upregulated NF-κB signaling pathway activity.

CONCLUSIONS

Taken together, these findings demonstrate that TIPE2 knockdown aggravates periodontal inflammatory infiltration via NF-κB pathway. Interventions aimed at increasing TIPE2 may help in the therapeutic applications for periodontitis.

TIPE2 attenuates neuroinflammation and brain injury through Bcl-2/Bax/cleaved caspase-3 apoptotic pathways after intracerebral hemorrhage in mice

BACKGROUND

Intracerebral hemorrhage (ICH) is a serious disease with high mortality and morbidity, and effective treatment is limited. A large amount of evidence suggests that the inflammatory response contributes to secondary brain damage following ICH. TIPE2 is an essential negative regulator of both innate and adaptive immunity, and depletion of TIPE2 causes inflammatory disease. However, the possible role of TIPE2 following ICH has not been reported.

METHODS

In this study, we investigated TIPE2 levels and inflammation in microglia treated with erythrocyte lysate in vitro. In addition, we analyzed the role of Bcl-2/Bax/cleaved caspase-3 apoptotic pathways in ICH mice. Furthermore, we observed proinflammatory cytokine production, BBB disruption, cerebral water content and neurological damage in ICH mice.

RESULTS

We found that TIPE2 levels were significantly decreased in erythrocyte lysate-treated microglia compared to control microglia.Upregulation of TIPE2 decreased microglia activation and cytokine production and accelerated brain damage in ICH mice. Furthermore, upregulation of TIPE2 decreased the higher ratio of Blc-2/Bax and increased cleaved caspase-3 levels in ICH mice. In addition, upregulation of TIPE2 attenuated proinflammatory cytokine production, BBB disruption, and severe brain inflammation after ICH.

CONCLUSION

These results demonstrated that TIPE2 was negatively correlated with the pathogenesis of ICH, which prevented brain injury and attenuated deleterious inflammatory responses following ICH. TIPE2 might serve as a novel target for ICH therapy.

TIPE2 May Target the Nrf2/HO-1 Pathway to Inhibit M1 Macrophage-Related Neutrophilic Inflammation in Asthma

Purpose

Although recent studies have highlighted the link of TIPE2 and asthma airway inflammation, its roles and molecular mechanisms in different asthma inflammatory phenotypes remain largely unknown. We evaluated sputum TIPE2 expression level and its correlation with different asthma phenotypes. Additionally, we explored the roles and mechanism of TIPE2 in M1 polarization of macrophages.

Methods

A total of 102 asthma patients who underwent sputum induction were enrolled to evaluate the expression level of TIPE2 and its association with different asthma phenotypes. To explore the roles and mechanism of TIPE2 in M1 polarization of macrophages, THP-1 monocytes stimulated with phorbol-12-myristate-13-acetate, were used as a model of undifferentiated (M0) macrophages, and M0 macrophages were treated with lipopolysaccharide to induce M1 macrophages.

Results

The sputum TIPE2 level was significantly lower in patients with neutrophilic asthma (NA) and higher in patients with eosinophilic asthma (EA) compared with patients with paucigranulocytic asthma. The levels of IL-1β, TNF-α and IL-6 were highest in NA compared with other groups. TIPE2 levels in sputum negatively correlated with IL-1β and TNF-α levels but positively correlated with IL-4, IL-5, IL-13, and IL-10 levels (P < 0.05). In vitro, TIPE2 enhanced Nrf2/HO-1 pathway activation in macrophages and inhibited LPS-induced M1 macrophage differentiation and related cytokine release. Further analysis showed that the Nrf2 inhibitor ML385 weakened TIPE2-induced activation of the Nrf2/HO-1 pathway, as well as TIPE2-induced suppression in M1 polarization of macrophage and inflammatory cytokines secretion.

Conclusions

TIPE2 expression level was highly down-regulated in NA and was negatively correlated with inflammatory factors (IL-1β and TNF-α). Aberrant expression of TIPE2 may target the Nrf2/HO-1 pathway to inhibit M1 macrophage–related neutrophilic inflammation in asthma.

TIPE2 is a checkpoint of natural killer cell maturation and antitumor immunity

The maturation process of NK cells determines their functionality during which IL-15 plays a critical role. However, very few checkpoints specifically targeting this process have been discovered. Here, we report that TIPE2 expression gradually increased during NK cell ontogenesis correlating to their maturation stages in both mice and humans. NK-specific TIPE2 deficiency increased mature NK cells in mice, and these TIPE2-deficient NK cells exhibited enhanced activation, cytotoxicity, and IFN-γ production upon stimulation and enhanced response to IL-15 for maturation. Moreover, TIPE2 suppressed IL-15–triggered mTOR activity in both human and murine NK cells. Consequently, blocking mTOR constrained the effect of TIPE2 deficiency on NK cell maturation in response to IL-15. Last, NK-specific TIPE2-deficient mice were resistant to tumor growth in vivo. Our results uncover a potent checkpoint in NK cell maturation and antitumor immunity in both mice and humans, suggesting a promising approach of targeting TIPE2 for NK cell–based immunotherapies.

TIPE2 inhibits PDGF-BB-induced phenotype switching in airway smooth muscle cells through the PI3K/Akt signaling pathway

Background

Childhood asthma is a common respiratory disease characterized by airway inflammation. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) has been found to be involved in the progression of asthma. This study aimed to explore the role of TIPE2 in the regulation of airway smooth muscle cells (ASMCs), which are one of the main effector cells in the development of asthma.

Materials and methods

ASMCs were transfected with pcDNA3.0-TIPE2 or si-TIPE2 for 48 h and then treated with platelet-derived growth factor (PDGF)-BB. Cell proliferation of ASMCs was measured using the MTT assay. Cell migration of ASMCs was determined by a transwell assay. The mRNA expression levels of calponin and smooth muscle protein 22α (SM22α) were measured using qRT-PCR. The levels of TIPE2, calponin, SM22α, PI3K, p-PI3K, Akt, and p-Akt were detected by Western blotting.

Results

Our results showed that PDGF-BB treatment significantly reduced TIPE2 expression at both the mRNA and protein levels in ASMCs. Overexpression of TIPE2 inhibited PDGF-BB-induced ASMC proliferation and migration. In addition, overexpression of TIPE2 increased the expression of calponin and SM22α in PDGF-BB-stimulated ASMCs. However, an opposite effect was observed with TIPE2 knockdown. Furthermore, TIPE2 overexpression blocked PDGF-BB-induced phosphorylation of PI3K and Akt, whereas the expression of p-PI3K and p-Akt were aggravated by TIPE2 knockdown. Additionally, the effects of TIPE2 overexpression and TIPE2 knockdown were altered by IGF-1 and LY294002 treatments, respectively.

Conclusions

Our findings demonstrate that TIPE2 inhibits PDGF-BB-induced ASMC proliferation, migration, and phenotype switching via the PI3K/Akt signaling pathway. Thus, TIPE2 may be a potential therapeutic target for the treatment of asthma.

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.

A novel prognostic factor TIPE2 inhibits cell proliferation and promotes apoptosis in pancreatic ductal adenocarcinoma (PDAC)

Background: Tumor necrosis factor (TNF)-alpha-induced protein 8-like 2 (TIPE2 or TNFAIP8L2) is a newly discovered negative immune regulator. Studies have shown that TIPE2 causes significant malignant biological effects and is differentially expressed in various malignant tumors. However, the expression and roles of TIPE2 in pancreatic ductal adenocarcinoma (PDAC) are largely unknown. Materials and Methods: The expression of TIPE2 in PDAC tissues was assessed by immunohistochemistry, qPCR and western blot analysis and related clinicopathological parameters including survival time were analyzed. After overexpression of TIPE2, cell proliferation and apoptosis analysis were conducted, and the associated underlying molecular mechanism was also explored. Results: In the present study, TIPE2 was upregulated in early PDAC tissues, and TIPE2 expression decreased as the tumor progressed (P<0.001). TIPE2 expression was negatively associated with tumor size, TNM stage and metastasis of lymph nodes. Furthermore, as an independent risk factor, TIPE2 could be used to predict the survival of patients with PDAC (P=0.035). TIPE2 overexpression significantly suppressed the viability, proliferation and induced apoptosis of PDAC cells by inhibiting survivin and increasing the activity of caspase3/7. Conclusions: For the first time, this study demonstrated that TIPE2 is an independent prognostic factor in PDAC. TIPE2 inhibited the proliferation and induced apoptosis via regulating survivin/caspase3/7 signaling pathway. These results indicated that TIPE2 is a potential biomarker for predicting the prognosis of PDAC patients and plays a pivotal role in the progression of PDAC.

Novel anti-inflammatory actions of TIPE2 in human primary amnion and myometrial cells

Inflammation plays a pivotal role in the terminal process of human labor and delivery, including myometrial contractions and membrane rupture. TNF-alpha-induced protein 8-like-2 (TIPE2) is a novel inflammation regulator; however, there are no studies on the role of TIPE2 in human labor. We report that in myometrium, there is decreased TIPE2 mRNA expression during late gestation which was further decreased in labor. In fetal membranes, TIPE2 mRNA expression was decreased with both term and preterm labor compared to no labor samples. Knockdown of TIPE2 by siRNA in primary myometrium and amnion cells was associated with an augmentation of IL1B and TNF-induced expression of pro-inflammatory cytokines and chemokines; expression of contraction-associated proteins and secretion of the uterotonic prostaglandin PGF2α and expression of extracellular matrix degrading enzymes. In TIPE2-deficient myometrial cells treated with inhibitors of NF-κB or ERK1/2, the secretion of pro-labor mediators was reduced back to control levels. In conclusion, these in vitro experiments indicate that loss of TIPE2 exacerbates the inflammatory response.

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.

Plasma BDNF and TrkB mRNA in PBMCs Are Correlated With Anti-depressive Effects of 12-Weeks Supervised Exercise During Protracted Methamphetamine Abstinence

Purpose: The aim of this study was to evaluate the potential neurotrophic factors and expression of neurotrophin receptors in peripheral blood mononuclear cells linked with the antidepressant action of exercise intervention during protracted methamphetamine (METH) abstinence.

Materials and Methods: A total of 72 male METH addicts, including 47 individuals with depression and 25 individuals without depression, were recruited in this study. Individuals with depression were divided into the depression control group and the depression exercised group. Consequently, 12 weeks of supervised exercise intervention was applied. Depression and anxiety were analyzed; plasma brain-derived neurotrophic factor (BDNF), neuronal growth factor (NGF), neurotrophin-3 (NT-3), NT-4, and proBDNF levels were tested using enzyme-linked immunosorbent assay; the mRNA expressions of TrkA, TrkB-FL, TrkB-T1, TrkCB, and P75NTR in peripheral blood mononuclear cells were detected by quantitative real-time polymerase chain reaction (qRT-PCR).

Results: NT-4 plasma levels were correlated with depression (r = −0.330, p = 0.005), which remained significant after Bonferroni correction. In addition, the BDNF and NT-3 levels in the plasma were significantly correlated with depression (r = −0.268, p = 0.023; r = −0.259, p = 0.028), but did not reach significance after Bonferroni correction. The BDNF, NT-3, and NT-4 plasma levels were significantly different between the depressive control group and the depressive exercise group using pre-exercise values as the covariate. The fold changes in TrkB-FL and TrkB-T1 mRNA in peripheral blood mononuclear cells between the post-exercise and pre-exercise demonstrated a remarkable decrease (fold change = −11.056 and −39.055).

Conclusions: Exercise intervention can alleviate depression and anxiety during protracted METH abstinence. Decrease in BDNF and the expression of TrkB in peripheral blood mononuclear cells occur following the exercise intervention.

TIPE2 suppresses atherosclerosis by exerting a protective effect on macrophages via the inhibition of the Akt signaling pathway

Macrophage apoptosis and inflammation serve pivotal roles in the occurrence of atherosclerosis. However, the detailed underlying mechanism of macrophage action during atherosclerosis is poorly understood. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) is a well-known negative regulator of the immune response. The current study assessed the association between TIPE2 and apoptosis-associated molecules in macrophages during atherosclerosis, as well as the role of TIPE2 in macrophage inflammation. RAW264.7 macrophages were subsequently transfected with a TIPE2 expression plasmid. Following oxidized low-density lipoprotein (oxLDL) induction (100 µg/m1) for 48 h, macrophage apoptosis was assessed via Annexin V/propidium iodide dual staining. The apoptosis-associated factors and Akt signaling pathway-associated factors were also evaluated via western blot analysis. The expression of inflammatory factors was determined via a reverse transcription-quantitative polymerase chain reaction assay and western blotting. Furthermore, a transwell assay was performed to test cell invasion ability. NF-κB phosphorylation and nuclear translocation were also assessed via western blotting. The results demonstrated that TIPE2 overexpression may promote oxLDL-induced RAW264.7 macrophage apoptosis by inhibiting the protein kinase B (Akt) signaling pathway. Furthermore, it was demonstrated that TIPE2 significantly reduced oxLDL-induced tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and monocyte chemoattractant protein 1 expression (MCP-1), and increased IL-10 expression by suppressing NF-κB phosphorylation and nuclear translocation in RAW264.7 macrophages. These results indicated that TIPE2 serves a protective role in oxLDL-induced RAW264.7 macrophages, and its mechanism may partly be exerted via the inhibition of the PI3K/Akt signaling pathway and the reduction of the macrophage inflammatory response achieved via the suppression of NF-κB signal activation.

Oncogenic Role of Tumor Necrosis Factor α-Induced Protein 8 (TNFAIP8)

Tumor necrosis factor (TNF)-α-induced protein 8 (TNFAIP8) is a founding member of the TIPE family, which also includes TNFAIP8-like 1 (TIPE1), TNFAIP8-like 2 (TIPE2), and TNFAIP8-like 3 (TIPE3) proteins. Expression of TNFAIP8 is strongly associated with the development of various cancers including cancer of the prostate, liver, lung, breast, colon, esophagus, ovary, cervix, pancreas, and others. In human cancers, TNFAIP8 promotes cell proliferation, invasion, metastasis, drug resistance, autophagy, and tumorigenesis by inhibition of cell apoptosis. In order to better understand the molecular aspects, biological functions, and potential roles of TNFAIP8 in carcinogenesis, in this review, we focused on the expression, regulation, structural aspects, modifications/interactions, and oncogenic role of TNFAIP8 proteins in human cancers.

TIPE2 acts as a biomarker for GIST risk category and suppresses the viability and invasiveness of GIST cells

Evaluating the risk category of gastrointestinal stromal tumors (GISTs) is crucial for predicting prognosis and choosing treatment strategies, and tumor metastasis usually represent poor prognosis. Tumor necrosis factor-alpha-induced protein 8-like 2 (TIPE2) is a novel described tumor suppressor. In the present study, TIPE2 expression was detected using a total of 96 human GIST specimens by immunohistochemistry. The effect of TIPE2 on proliferation and invasiveness of GIST cells and its related mechanisms were explored in vitro. It was found that TIPE2 expression was gradually decreased in accordance with GIST risk grades and negatively associated with tumor size, mitotic count and risk category. Moreover, TIPE2 was identified as a biomarker for evaluating the risk grade of GIST. TIPE2 markedly suppressed the viability, colony formation, migration and invasion of GIST cells. Furthermore, TIPE2 induced apoptosis and suppressed MMP-9 expression of GIST cells by targeting Rac1. In conclusion, these results indicate that TIPE2 plays a pivotal role in the progression of GIST. TIPE2 serves as a promising biomarker for evaluating GIST risk grade and a potential target for treatment of GIST.

Correlation of serum levels and gene expression of tumor necrosis factor-α-induced protein-8 like-2 with Parkinson disease severity

Different immune-mediated mechanisms involved in the pathogenesis of Parkinson disease (PD) as a neurodegenerative and inflammatory disease. According to our knowledge, there is no report evaluating Tumor necrosis factor-α-induced protein-8 like-2 (TIPE2), a cytokine maintaining immune homeostasis, in PD. We analyzed the correlation of the serum levels and circulatory gene expression of TIPE2 with severity of PD. In this case-control study, 43 patients with PD and 40 healthy subjects were enrolled. The diagnosis of PD was performed byclinical diagnostic criteria of the UK Parkinson's Disease Society Brain Bank. The severity of PD was evaluated by modified Hoehn and Yahr (H and Y) scale. Serum levels and gene expression of TIPE2 were assessed by Elisa and real time PCR, respectively. The mean serum levels and gene expression of TIPE2 in patients with PD did not have significant difference compared to healthy subjects. Linear multiple regression analysis showed that increased serum levels of TIPE2 are positively related to age and severity of PD (P ≤ 0.0001). In addition, the gene expression of TIPE2 was found to be associated with age (P < 0.0001). Our study showed that the serum levels of TIPE2 and its gene expression might be important prognostic biomarkers of PD.

TIPE2 is negatively correlated with tissue factor and thrombospondin-1 expression in patients with bronchial asthma

The interaction between inflammatory processes and a hypercoagulant state may aggravate the severity of asthma and stimulate the airway remodeling of asthma. The aim of the current study was to evaluate the association between the negative inflammatory regulator tumor necrosis factor α induced protein-8 like-2 (TIPE2) and the coagulating substances tissue factor (TF) and thrombospondin-1 (TSP-1) in patients with bronchial asthma. Compared with healthy controls, TIPE2 expression was significantly downregulated, whereas TF expression was upregulated in the peripheral blood mononuclear cells (PBMCs) of patients with bronchial asthma. In addition, levels of TF and TSP-1 in the sera were up-regulated in patients with asthma compared with healthy controls. TIPE2 expression was negatively correlated with TF in the PBMCs and sera and was negatively correlated with TSP-1 levels in the sera of patients with bronchial asthma. The results of the current study indicated that anti-inflammatory TIPE2 levels are associated with levels of the coagulation substances TF and TSP-1. However, further studies are required to determine whether TIPE2 participates in the pathogenesis of asthma by interacting with the coagulation substances TF and TSP-1.

TIPE2 Inhibits the Expression of Asthma-Related Inflammatory Factors in Hyperstretched Bronchial Epithelial Cells Through the Wnt/β-Catenin Pathway

Childhood asthma, an airway inflammatory disease, is a serious threat to the child's quality of life. Recently, TIPE2 expression was reported to be decreased in children with asthma. Therefore, additional studies focusing on TIPE2 might provide an approach for treating childhood asthma. In this study, we found that TIPE2 was poorly expressed in hyperstretched human bronchial epithelial cells (BEAS-2B). TIPE2 overexpression also significantly suppressed the stretch-induced secretion of asthma-related inflammatory factors (TNF-α, TSLP, MMP-9, and VEGF). In contrast, TIPE2 inhibition significantly promoted the secretion of TNF-α, TSLP, MMP-9, and VEGF. Furthermore, overexpression of TIPE2 remarkably inhibited the activation of Wnt/β-catenin in hyperstretched BEAS-2B cells, while siTIPE2 activated Wnt/β-catenin in hyperstretched BEAS-2B cells. Further analysis showed that the Wnt/β-catenin signal inhibitor Dkk-1 could further enhance the TIPE2-induced suppression of Wnt/β-catenin signaling, which also suppressed the siTIPE2-induced secretion of TNF-α, TSLP, MMP-9, and VEGF in hyperstretched BEAS-2B cells. Dkk-1 reversed the effects of siRNA-TIPE2 on Wnt/β-catenin signaling and inflammatory cytokines. In summary, we have exhibited that TIPE2 inhibited the expression of asthma-related inflammatory factors in hyperstretched BEAS-2B cells by suppressing the Wnt/β-catenin signaling pathway. TIPE2 may be involved in airway inflammation during asthma attack, and it may be used as a potential therapeutic target for bronchial epithelial inflammation in childhood asthma.

Direction of leukocyte polarization and migration by the phosphoinositide-transfer protein TIPE2

Leukocyte polarization toward chemoattractants is essential for directed leukocyte migration, or chemotaxis. How leukocytes acquire polarity upon encountering chemical gradients is not well understood. We report here that leukocyte polarity is generated by TIPE2 (TNFAIP8L2), a transfer protein of phosphoinositide second messengers. TIPE2 functioned as a local enhancer of phosphoinositide-dependent signaling and cytoskeleton remodeling, promoting leading edge formation. Conversely, TIPE2 acted as an inhibitor of the GTPase Rac, promoting trailing edge polarization. Consequently, TIPE2-deficient leukocytes were defective in polarization and chemotaxis, and TIPE2-deficient mice were resistant to leukocyte-mediated neural inflammation. Thus, the leukocyte polarizer is a dual-role phosphoinositide transfer protein, and a potential therapeutic target for treating inflammatory diseases.

The decreased expression of TIPE2 protein in the decidua of patients with missed abortion and possible significance

BACKGROUND

Missed abortion is a common occurrence for otherwise healthy women. Immunological factor is one of the most important reasons. Tumor necrosis factor-α-induced protein-8 like-2 (TIPE2) is a novel negative immune regulator related to several human diseases. However, the expression level and clinical significance of TIPE2 in missed abortion remain unclear.

METHODS

The expression of TIPE2 mRNA and protein in decidua and chorion from 36 missed abortion patients and 36 healthy controls was detected using quantitative real-time PCR, western blot and immunohistochemistry. In addition, serum TNF-ɑ and IL-10 levels were measured using flow cytometry. Serum estradiol and progesterone levels were measured by radioimmunoassay test. The correlations of TIPE2 protein levels with TNF-ɑ, IL-10, estradiol and progesterone were further analyzed.

RESULTS

TIPE2 protein levels were significantly lower in decidual tissues of missed abortion patients than those in healthy controls. The patients with missed abortion had significantly higher levels of serum TNF-ɑ, and lower levels of serum IL-10, estradiol and progesterone compared with healthy controls. The TIPE2 protein levels were positively related to serum IL-10 levels.

CONCLUSION

Our data indicate TIPE2 could play important roles in maintaining the maternal-fetal tolerance and decreased TIPE2 expression in the decidua may be related to the development of missed abortion.

Stable silencing of TIPE2 reduced the Poly I:C‑induced apoptosis in THP‑1 cells

The present study aimed to determine the underlying mechanism of toll‑like receptor (TLR) agonist polyinosinic:polycytidylic acid (Poly I:C)‑induced apoptosis in THP‑1 cells following silencing the expression of tumor necrosis factor α‑induced protein 8‑like 2 (TIPE2). THP‑1 cells were incubated with different concentrations of the TLR agonist. Following incubation, reverse transcription‑quantitative polymerase chain reaction was performed to quantify the mRNA expression of TIPE2. Lentiviral technology was used to silence the expression of TIPE2. MTT assay was performed to assess cell proliferation, Annexin V/PI double staining was used to evaluate the apoptosis and western blotting was used to determine the expression levels of caspase‑8 following TIPE2 silencing. The TLRs agonist Poly I:C increased the expression level of TIPE2. During the incubation, Poly I:C also inhibited the proliferation of THP‑1 cells and induced apoptosis. Following silencing of TIPE2 in THP‑1 cells, the Poly I:C‑induced TIPE2 expression was significantly downregulated. Additionally, the Poly I:C‑induced proliferation inhibition and apoptosis in THP‑1 cells were significantly reduced following silencing of TIPE2. The findings of the western blot analysis indicated that the active form of caspase‑8, p18, was downregulated following silencing of TIPE2. In conclusion, the expression of TIPE2 in THP‑1 cells may be upregulated by Poly I:C, which may also inhibit cell proliferation and induce apoptosis. Following the downregulation of TIPE2 the aforementioned effect of Poly I:C treatment was reversed and may be associated with the reduced activity of caspase‑8 that was observed in the TIPE2 silenced group.

Increased expression of TIPE2 in alternatively activated macrophages is associated with eosinophilic inflammation and disease severity in chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a multifactorial disorder characterized by exaggerated local immune responses. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) is a novel protein with potential immune modulating function. The expression and function of TIPE2 in human airway diseases are unclear.

METHODS

The expression of TIPE2 in sinonasal mucosal samples was assessed by means of quantitative reverse transcript-polymerse chain reaction, immunohistochemistry, and Western blotting. The human monocytic/macrophage cell line, THP-1 cells, was stimulated with various cytokines. Computed tomography (CT) scan images, endoscopic findings, and symptoms were scored.

RESULTS

Compared with non-eosinophilic polyps and control mucosa, the mRNA and protein expression of TIPE2 was significantly upregulated in eosinophilic polyps, with a further increase in those with asthma. The number of CD68⁺ CD163⁺ alternatively activated (M2) macrophages was increased in eosinophilic polyps. TIPE2 was mainly expressed by M2 macrophages in sinonasal mucosa and its expression was upregulated in M2 macrophages in eosinophilic polyps. Interleukin (IL)-4 and IL-13, but not interferon (IFN)-γ or IL-17A, induced TIPE2 expression in differentiated THP-1 cells. The mRNA levels of IL-4 and IL-13 correlated with the mRNA levels of TIPE2 and M2 macrophage markers in sinonasal mucosa. Importantly, the number of TIPE2⁺ cells, particularly TIPE2⁺ CD163⁺ CD68⁺ M2 macrophages, correlated positively with the number of eosinophils and total inflammatory cells in sinonasal mucosa, as well as disease duration, CT scores, hyposmia scores, and polyp size in CRSwNP.

CONCLUSION

The T-helper 2 milieu is able to induce TIPE2 expression in macrophages. TIPE2-positive M2 macrophages potentially contribute to eosinophilic inflammation and disease progression in CRSwNP.

Regulation of inflammation and tumorigenesis by the TIPE family of phospholipid transfer proteins

The TIPE (tumor necrosis factor-α-induced protein 8-like) family are newly described regulators of immunity and tumorigenesis consisting of four highly homologous mammalian proteins: TNFAIP8 (tumor necrosis factor-α-induced protein 8), TIPE1 (TNFAIP8-like 1, or TNFAIP8L1), TIPE2 (TNFAIP8L2) and TIPE3 (TNFAIP8L3). They are the only known transfer proteins of the lipid secondary messengers PIP2 (phosphatidylinositol 4,5-bisphosphate) and PIP3 (phosphatidylinositol 3,4,5-trisphosphate). Cell-surface receptors, such as G-protein-coupled receptors and receptor tyrosine kinases, regulate inflammation and cancer via several signaling pathways, including the nuclear factor (NF)-κB and phosphoinositide-3 kinase (PI3K) pathways, the latter of which is upstream of both Akt and STAT3 activation. An expression analysis in humans demonstrated that the TIPE family is dysregulated in cancer and inflammation, and studies both in mice and in vitro have demonstrated that this family of proteins plays a critical role in tumorigenesis and inflammatory responses. In this review, we summarize the current literature for all four family members, with a special focus on the phenotypic manifestations present in the various knockout murine strains, as well as the related cell signaling that has been elucidated to date.

Adenovirus-mediated TIPE2 overexpression inhibits gastric cancer metastasis via reversal of epithelial-mesenchymal transition

Tumor necrosis factor (TNF)-alpha-induced protein 8-like 2 (TNFAIP8L2; also termed TIPE2) has been shown to be involved in both the immune-negative modulation and cancer. We previously found that TIPE2 is lost in human gastric cancer, and TIPE2 restoration suppresses gastric cancer growth by induction of apoptosis and impairment of protein kinase B (PKB/AKT) and extracellular signal-regulated kinase-1/2 (ERK1/2) signaling. However, its correlation with epithelial-mesenchymal transition (EMT) in gastric cancer is largely elusive. In the present report, we carried out a gain-of-function study in AGS and HGC-27 human gastric cancer cells by adenovirus-mediated human TIPE2 gene transfer (AdVTIPE2). We then examined the effects of AdVTIPE2 on in vitro migration and invasion of AGS and HGC-27 tumor cells by wound-healing assay and Transwell invasion assay, respectively. We also investigated the effects of AdVTIPE2 on in vivo lung metastasis of AGS and HGC-27 tumor cells by intravenous (i.v.) injection in athymic BALB/c nude mice. We demonstrated that AdVTIPE2 remarkably suppressed the migratory, invasive and metastatic potential of AGS and HGC-27 tumor cells in vitro and in vivo in BALB/c nude mouse model. Mechanistically, AdVTIPE2 obviously upregulated E-cadherin epithelial marker in AGS and HGC-27 tumor cells, whereas it downregulated N-cadherin and Vimentin mesenchymal markers, Snail1, Snail2/Slug and Zeb1 EMT-inducing transcription factors (EMT-TFs), and tripartite motif-containing 29 (TRIM29) and phosphatase regenerating liver 3 (PRL-3) gastric cancer-specific metastasis markers. Importantly, glycogen synthase kinase-3β (GSK-3β) inhibitor VIII and 26S proteasome inhibitor MG132 assays revealed that TIPE2 downregulated Snail1 and Snail2/Slug in a GSK-3β- and proteasome-dependent manner possibly by impairing AKT signaling. Our data provided the first evidence that TIPE2 inhibits gastric cancer cell migration, invasion and metastasis very probably via reversal of EMT, revealing that TIPE2 may be a novel therapeutic target for human gastric cancer EMT and metastasis.

Upregulation of Tumor Necrosis Factor-α-Induced Protein 8-Like 2 mRNA Is Negatively Correlated with Serum Concentrations of Tumor Necrosis Factor-α and Interleukin 6 in Type 2 Diabetes Mellitus

BACKGROUND

Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2 or TNFAIP8L2) is a negative regulator of natural and adaptive immunity. The role of TIPE2 in type 2 diabetes mellitus (T2DM) remains unknown, although TIPE2 plays key roles in preserving inflammatory homeostasis.

METHODS

TIPE2 expression was measured by Western blotting and real-time polymerase chain reaction (RT-PCR) in peripheral blood mononuclear cells (PBMCs) isolated from T2DM patients and healthy controls, and tumor necrosis factor-α (TNF-α), high-sensitivity C-reactive protein (hsCRP), interleukin 6 (IL-6), and other related biometabolic parameters were detected using a nephelometer or by ELISA. Differentiated THP-1 cells were exposed to siTIPE2 and TIPE2 adenovirus.

RESULTS

TIPE2 was significantly increased in PBMCs from T2DM patients compared with those from healthy controls and was negatively correlated with serum TNF-α, IL-6, and hsCRP concentrations but positively correlated with HbA1c and LDL-C in T2DM patients. High glucose treatment (50 mmol/L) can upregulate the expression of TIPE2 and cytokine secretion in differentiated THP-1 cells. siTIPE2 infection exacerbated the increased TNF-α and IL-6 concentrations in differentiated THP-1 cells under high glucose conditions (50 mmol/L), while infection with TIPE2 adenovirus reversed the increased TNF-α concentration.

CONCLUSIONS

The present study indicates that TIPE2 may participate in T2DM by regulating TNF-α production.

Decreased expression of TIPE2 contributes to the hyperreactivity of monocyte to Toll-like receptor ligands in primary biliary cirrhosis

BACKGROUND AND AIM

Previous studies have shown differential TIPE2 expression in several autoimmune diseases. However, the expression levels of TIPE2 in primary biliary cirrhosis (PBC) remained unclear. The purposes of this study were to evaluate TIPE2 expression levels in patients with PBC and further investigate its role in PBC pathogenesis.

METHODS

A total of 40 PBC patients and 44 healthy controls were included in the present study. Quantitative reverse-transcription polymerase chain reaction and western blotting were used to determine the differences in mRNA and protein expression levels of TIPE2. The correlations of TIPE2 expression levels and clinical characteristics, inflammatory cytokines, and ursodeoxycholic acid treatment were also assessed. Besides, the influence of TIPE2 on the reactivity of monocyte to Toll-like receptor ligands was further analyzed.

RESULTS

The expression levels of TIPE2 were significantly decreased in PBC patients compared with normal controls (P < 0.01). The expression levels of TIPE2 were negatively correlated with alanine aminotransferase (r = -0.40, P = 0.01), alkaline phosphatase (r = -0.36, P = 0.02), gamma glutamyl transpeptidase (r = -0.53, P < 0.01), tumor necrosis factor (TNF)-α (r = -0.332, P = 0.03), interleukin (IL)-1β (r = -0.386, P = 0.01), and IL-8 (r = -0.366, P = 0.02) levels in sera from PBC patients. TIPE2 expression level could be significantly increased after ursodeoxycholic acid treatment (P < 0.01). The production of TNF-α, IL-1β, and IL-8 by monocytes from PBC patients after stimulation with lipopolysaccharide and lipoteichoic acid was significantly increased when TIPE2 was knocked down. Furthermore, TIPE2 knockdown could promote activation of nuclear factor-κB pathways through increasing phosphorylation and degradation of IκB in peripheral blood monocytes from PBC patients.

CONCLUSION

The present study reported that insufficient expression of TIPE2 might be involved in the hyperreactivity of monocyte to Toll-like receptor ligands in PBC.

Adenovirus-directed expression of TIPE2 suppresses gastric cancer growth via induction of apoptosis and inhibition of AKT and ERK1/2 signaling

Tumor necrosis factor (TNF)-α-induced protein 8-like 2 (TNFAIP8L2/TIPE2) as a novel anti-inflammatory factor plays an important role in maintaining immune homeostasis. Recently, TIPE2 has been shown to inhibit hepatocarcinoma growth and metastasis through targeting Ras and Rac1. However, its effects in human cancers are poorly understood. In the present study, we analyzed TIPE2 mRNA expression in a panel of human gastric cancer cells (AGS, HGC-27 and SGC-7901) and then examined the cell-autonomous effects of adenovirus-mediated human TIPE2 gene transfer (AdVTIPE2) on AGS and HGC-27 human gastric cancer cells. We found that compared with the GES-1 normal human gastric mucous epithelial cells, human TIPE2 was lost in the AGS, HGC-27 and SGC-7901 gastric cancer cells. Adenovirus-mediated human TIPE2 overexpression significantly inhibited AGS and HGC-27 gastric cancer cell growth and induced AGS and HGC-27 tumor cell apoptosis in vitro. Furthermore, AdVTIPE2 treatment obviously suppressed the growth of AGS gastric cancer subcutaneously xenografted tumors implanted in athymic BALB/c nude mice in vivo. Mechanistically, AdVTIPE2 exhibited marked effects on the upregulation of Bax, cleaved Caspase-9, cleaved Caspase-3, cleaved poly ADP ribose polymerase as well as the downregulation of B-cell lymphoma (Bcl)-XL, phosphorylated-protein kinase B (p-PKB/AKT), phosphorylated-extracellular signal-regulated kinase 1/2 (p-ERK1/2) in AGS gastric cancer cells in vitro and in vivo. Collectively, AdVTIPE2 suppressed gastric cancer growth very possibly by the activation of intrinsic apoptotic pathway and the attenuation of AKT and ERK1/2 signaling. Thus, our data indicated that TIPE2 may be a novel potential therapeutic target for human gastric cancer.

Critical roles of TIPE2 protein in murine experimental colitis

Both commensal bacteria and infiltrating inflammatory cells play essential roles in the pathogenesis of inflammatory bowel disease. The molecular mechanisms whereby these pathogenic factors are regulated during the disease are not fully understood. We report in this article that a member of the TNF-α-induced protein 8 (TNFAIP8) family called TIPE2 (TNFAIP8-like 2) plays a crucial role in regulating commensal bacteria dissemination and inflammatory cell function in experimental colitis induced by dextran sodium sulfate (DSS). Following DSS treatment, TIPE2-deficient mice, or chimeric mice that are deficient in TIPE2 only in their hematopoietic cells, lost less body weight and survived longer than wild-type controls. Consistent with this clinical observation, TIPE2-deficient mice exhibited significantly less severe colitis and colonic damage. This was associated with a marked reduction in the colonic expression of inflammatory cytokines, such as TNF-α, IL-6, and IL-12. Importantly, the ameliorated DSS-induced colitis in TIPE2(-/-) mice also was associated with reduced local dissemination of commensal bacteria and a weaker systemic inflammatory response. Combined with our previous report that TIPE2 is a negative regulator of antibacterial immunity, these results indicate that TIPE2 promotes colitis by inhibiting mucosal immunity to commensal bacteria.