LIGHT/TNFSF14 enhances adipose tissue inflammatory responses through its interaction with HVEM

Cross-talk between disulfidptosis and immune check point genes defines the tumor microenvironment for the prediction of prognosis and immunotherapies in glioblastoma

Disulfidptosis is a condition where dysregulated NAPDH levels and abnormal accumulation of cystine and other disulfides occur in cells with high SLC7A11 expression under glucose deficiency. This disrupts normal formation of disulfide bonds among cytoskeletal proteins, leading to histone skeleton collapse and triggering cellular apoptosis. However, the correlation between disulfidptosis and immune responses in relation to glioblastoma survival rates and immunotherapy sensitivity remains understudied. Therefore, we utilized The Cancer Genome Atlas and The Chinese Glioma Genome Atlas to identify disulfidptosis-related immune checkpoint genes and established an overall survival (OS) prediction model comprising six genes: CD276, TNFRSF 14, TNFSF14, TNFSF4, CD40, and TNFRSF18, which could also be used for predicting immunotherapy sensitivity. We identified a cohort of glioblastoma patients classified as high-risk, which exhibited an upregulation of angiogenesis, extracellular matrix remodeling, and epithelial-mesenchymal transition as well as an immunosuppressive tumor microenvironment (TME) enriched with tumor associated macrophages, tumor associated neutrophils, CD8 + T-cell exhaustion. Immunohistochemical staining of CD276 in 144 cases further validated its negative correlation with OS in glioma. Disulfidptosis has the potential to induce chronic inflammation and an immunosuppressive TME in glioblastoma.

LIGHT/TNFSF14 Affects Adipose Tissue Phenotype

LIGHT/TNFSF14 is linked to several signaling pathways as a crucial member of a larger immunoregulatory network. It is primarily expressed in inflammatory effector cells, and high levels of LIGHT have been reported in obesity. Thus, with the aim of deepening the knowledge of the role of LIGHT on adipose tissue phenotype, we studied wild-type (WT), Tnfsf14-/-, Rag-/- and Rag-/Tnfsf14- (DKO) mice fed a normal diet (ND) or high-fat diet (HFD). Our results show that, although there is no significant weight gain between the mice with different genotypes, it is significant within each of them. We also detected an increase in visceral White Adipose Tissue (vWAT) weight in all mice fed HFD, together with the lowest levels of vWAT weight in Tnfsf14-/- and DKO mice fed ND with respect to the other strain. Inguinal WAT (iWAT) weight is significantly affected by genotype and HFD. The least amount of iWAT was detected in DKO mice fed ND. Histological analysis of vWAT showed that both the genotype and the diet significantly affect the adipocyte area, whereas the number is affected only by the genotype. In iWAT, the genotype and the diet significantly affect mean adipocyte area and number; interestingly, the area with the least adipocyte was detected in DKO mice fed ND, suggesting a potential browning effect due to the simultaneous lack of mature lymphocytes and LIGHT. Consistently, Uncoupling Protein 1 (UCP1) staining of iWAT demonstrated that few positive brown adipocytes appeared in DKO mice. Furthermore, LIGHT deficiency is associated with greater levels of UCP1, highlighting the lack of its expression in Rag-/- mice. Liver examination showed that all mice fed HFD had a steatotic liver, but it was particularly evident for DKO mice. In conclusion, our study demonstrates that the adipose tissue phenotype is affected by LIGHT levels but also much more by mature lymphocytes.

Plasma proteomic signature of fatty liver disease: The Rotterdam Study

BACKGROUND AND AIMS

Fatty liver disease (FLD) is caused by excess fat in the liver, and its global prevalence exceeds 33%. The role of protein expression on the pathogenesis of FLD and accompanied fibrosis and its potential as a disease biomarker is currently not clear. Hence, we aimed to identify plasma proteomics associated with FLD and fibrosis using population-based data.

APPROACH AND RESULTS

Blood samples were collected from 2578 participants from the population-based Rotterdam Study cohort. The proximity extension assay reliably measured plasma levels of 171 cardiometabolic and inflammatory-related proteins (Olink Proteomics). FLD was assessed by ultrasound, and fibrosis by transient elastography. Logistic regression models quantified the association of plasma proteomics with FLD and fibrosis. In addition, we aimed to validate our results in liver organoids. The cross-sectional analysis identified 27 proteins significantly associated with FLD surpassing the Bonferroni-corrected p <2.92×10 -4 . The strongest association was observed for FGF-21 (β=0.45, p =1.07×10 -18 ) and carboxylesterase 1 (CES1) protein (β=0.66, p =4.91×10 -40 ). Importantly, 15 of the 27 proteins significantly associated with FLD were also associated with liver fibrosis. Finally, consistent with plasma proteomic profiling, we found the expression levels of IL-18 receptor 1 (IL-18R1) and CES1 to be upregulated in an FLD model of 3-dimensional culture human liver organoids.

CONCLUSIONS

Among the general population, several inflammatory and cardiometabolic plasma proteins were associated with FLD and fibrosis. Particularly, plasma levels of FGF-21, IL-18R1, and CES1 were largely dependent on the presence of FLD and fibrosis and may therefore be important in their pathogenesis.

Dynamic polarization of tumor-associated macrophages and their interaction with intratumoral T cells in an inflamed tumor microenvironment: from mechanistic insights to therapeutic opportunities

Immunotherapy has brought a paradigm shift in the treatment of tumors in recent decades. However, a significant proportion of patients remain unresponsive, largely due to the immunosuppressive tumor microenvironment (TME). Tumor-associated macrophages (TAMs) play crucial roles in shaping the TME by exhibiting dual identities as both mediators and responders of inflammation. TAMs closely interact with intratumoral T cells, regulating their infiltration, activation, expansion, effector function, and exhaustion through multiple secretory and surface factors. Nevertheless, the heterogeneous and plastic nature of TAMs renders the targeting of any of these factors alone inadequate and poses significant challenges for mechanistic studies and clinical translation of corresponding therapies. In this review, we present a comprehensive summary of the mechanisms by which TAMs dynamically polarize to influence intratumoral T cells, with a focus on their interaction with other TME cells and metabolic competition. For each mechanism, we also discuss relevant therapeutic opportunities, including non-specific and targeted approaches in combination with checkpoint inhibitors and cellular therapies. Our ultimate goal is to develop macrophage-centered therapies that can fine-tune tumor inflammation and empower immunotherapy.

High levels of LIGHT/TNFSF14 in patients with Prader-Willi syndrome

PURPOSE/METHODS

Prader-Willi syndrome (PWS) is a rare genetic disorder displaying different clinical features, including obesity and bone impairment. LIGHT/TNFSF14 is a cytokine produced by immune cells affecting both fat and bone metabolism. The present study aimed to evaluate LIGHT serum levels in 28 children and 52 adult PWS patients compared to age and sex-matched controls, as well as correlations with parameters of bone and fat metabolism.

RESULTS

Median serum LIGHT levels were significantly increased in pediatric PWS with respect to controls [255.82 (284.43) pg/ml vs 168.11 (76.23) pg/ml, p ≤ 0.02] as well as in adult PWS compared to controls [296.85 (895.95) pg/ml vs 134.18 (141.18) pg/ml, p ≤ 0.001]. In pediatric PWS, LIGHT levels were positively correlated with weight-SDS, height-SDS, and glucose levels, and negatively with total 25 (OH) vitamin D, cholesterol, LDL cholesterol and triglycerides. Additionally, LIGHT levels were negatively correlated with total BMD and fat mass. In adult PWS, LIGHT levels were positively correlated with weight, HDL cholesterol and PTH, and negatively with glucose, insulin, HOMA-IR, total cholesterol, LDL cholesterol, triglycerides, calcium, phosphorus, 25(OH)Vitamin D as well as with instrumental parameters of bone and fat quality. Consistently, multiple regression analysis showed that LIGHT serum levels in pediatric and adult PWS were predicted by different parameters including 25 (OH) Vitamin D as well as DXA parameters of bone and fat quality.

CONCLUSIONS

In PWS children and adults the high levels of LIGHT could represent a marker of the altered bone and fat metabolism.

Impact of Obesity on Bone Metabolism in Children

Obesity is an epidemic disease that can increase the incidence of type 2 diabetes, cardiovascular disease, malignancy, hypertension, and other health problems that affect the musculoskeletal system. There is a complex interaction between obesity and bone metabolism. In children with obesity, the peroxisome proliferator-activated receptor gamma pathway causes the differentiation of mesenchymal stem cells into adipocytes via osteoblasts, in which results in low bone mass and osteoporosis. Systemic inflammation in obesity has negative effects on bone metabolism. An increase in the number and size of adipose tissue and adipocytokines secreted from adipocytes affect the bone mass of the whole body with hormonal and biochemical effects. The skeletal effects of obesity are mediated by higher oxidative stress and increased production of proinflammatory cytokines. Osteoporosis due to obesity has increased morbidity and mortality in recent years, resulting in important health problems in developed and developing countries.

LIGHT (TNFSF14) inhibits glucose uptake of adipocytes by downregulating GLUT4 expression via AKT signaling pathway

Glucose homeostasis of adipocytes could be regulated by immune-adipose crosstalk. In order to investigate the effects of Lymphotoxin-like inducible protein that competes with glycoprotein D for herpesvirus entry on T cells (LIGHT) on glucose metabolism, we performed the present study. Our results showed that LIGHT deficiency improved glucose tolerance and enhanced glucose consumption of inguinal white adipose tissue (iWAT) under high fat diet. Consistently, Light overexpression could inhibit glucose uptake during the process of white adipogenesis. Mechanistically, LIGHT interacted with lymphotoxin-β receptor (LTβR) to attenuate AKT pathway leading to downregulation of glucose transporter-4 (GLUT4) expression, which resulted in glucose uptake inhibition. In summary, our findings revealed LIGHT-LTβR-AKT-GLUT4 axis as a regulator of glucose uptake in adipose tissue, which suggested the pivotal role of LIGHT in maintaining glucose homeostasis.

HES5-mediated repression of LIGHT transcription may contribute to apoptosis in hepatocytes

Non-alcoholic fatty liver disease (NAFLD) is prototypical form of metabolic syndrome and has become a global pandemic. Hepatocytes undergo apoptosis in the pathogenesis of NAFLD. We report that the lymphokine LIGHT/TNFSF14 was upregulated in the murine NAFLD livers and in hepatocytes treated with free fatty acids (palmitate, PA). LIGHT knockdown or neutralization attenuated PA-induced apoptosis of hepatocytes. Similarly, knockdown or blockade of LTβR, the receptor for LIGHT, ameliorated apoptosis in hepatocytes exposed to PA. Ingenuity pathway analysis (IPA) revealed several Notch-related transcription factors as upstream regulators of LIGHT, of which HES5 expression was downregulated paralleling LIGHT induction in the pathogenesis of NAFLD. HES5 knockdown enhanced whereas HES5 over-expression weakened LIGHT induction in hepatocytes. HES5 was found to directly bind to the LIGHT promoter and repress LIGHT transcription. Mechanistically, HES5 interacted with SIRT1 to deacetylate histone H3/H4 on the LIGHT promoter to repress LIGHT transcription. SIRT1 knockdown or inhibition offset the effect of HES5 over-expression on LIGHT transcription and hepatocyte apoptosis. In conclusion, our data unveil a novel mechanism that might contribute to excessive apoptosis in hepatocyte exposed to free fatty acids.

Single-cell sequencing of human white adipose tissue identifies new cell states in health and obesity

White adipose tissue (WAT) is an essential regulator of energy storage and systemic metabolic homeostasis. Regulatory networks consisting of immune and structural cells are necessary to maintain WAT metabolism, which can become impaired during obesity in mammals. Using single-cell transcriptomics and flow cytometry, we unveil a large-scale comprehensive cellular census of the stromal vascular fraction of healthy lean and obese human WAT. We report new subsets and developmental trajectories of adipose-resident innate lymphoid cells, dendritic cells and monocyte-derived macrophage populations that accumulate in obese WAT. Analysis of cell-cell ligand-receptor interactions and obesity-enriched signaling pathways revealed a switch from immunoregulatory mechanisms in lean WAT to inflammatory networks in obese WAT. These results provide a detailed and unbiased cellular landscape of homeostatic and inflammatory circuits in healthy human WAT.

The Adipocyte and Adaptive Immunity

Not only do Adipocytes have energy storage and endocrine functions, but they also play an immunological role. Adipocytes are involved in adaptive immunity to mediate the pathological processes of a variety of chronic inflammatory diseases and autoimmune syndromes. The adaptive immune response consists of T cell-mediated cellular immunity and B cell-mediated humoral immunity. Obese adipocytes overexpress MHC class II molecules and costimulators to act as antigen-presenting cells (APCs) and promote the activation of CD4⁺ T cells. In addition, various adipokines secreted by adipocytes regulate the proliferation and differentiation of T cells. Adipokines are also involved in B cell generation, development, activation, and antibody production. Therefore, adipocytes play an important role in B cell-mediated adaptive immunity. This review describes how adipocytes participate in adaptive immunity from the perspective of T cells and B cells, and discusses their role in the pathogenesis of various diseases.

Shedding "LIGHT" on the Link between Bone and Fat in Obese Children and Adolescents

Obesity may affect bone health, but literature reports are contradictory about the correlation of body mass index (BMI) and bone markers. LIGHT, one of the immunostimulatory cytokines regulating the homeostasis of bone and adipose tissue, could be involved in obesity. The study involved 111 obese subjects (12.21 ± 3.71 years) and 45 controls. Patients underwent the evaluation of bone status by quantitative ultrasonography (QUS). LIGHT amounts were evaluated in sera by ELISA, whereas its expression on peripheral blood cells was evaluated by flow cytometry. Osteoclastogenesis was performed by culturing peripheral blood mononuclear cells (PBMCs) with or without anti-LIGHT antibodies. Obese patients showed significant high BMI-standard deviation score (SDS), weight-SDS, and Homeostatic model assessment for insulin resistance (HOMA-IR) that negatively correlated with the reduced Amplitude Dependent Speed of Sound (AD-SoS)-Z-score and Bone Transmission Time (BTT-Z)-score. They displayed significantly higher serum levels of LIGHT compared with controls (497.30 ± 363.45 pg/mL vs. 186.06 ± 101.41 pg/mL, p < 0.001). LIGHT expression on monocytes, CD3+-T-cells, and neutrophils was also higher in obese patients than in the controls. Finally, in PBMC cultures, the addition of anti-LIGHT antibodies induced a significant osteoclastogenesis inhibition. Our study highlighted the high serum levels of LIGHT in obese children and adolescents, and its relationship with both the grade of obesity and bone impairment.

Genetic inactivation of the LIGHT (TNFSF14) cytokine in mice restores glucose homeostasis and diminishes hepatic steatosis

AIMS/HYPOTHESIS

Non-alcoholic fatty liver disease (NAFLD) is frequently associated with type 2 diabetes mellitus. Progression of NAFLD is mediated, among other things, by activation of inflammatory pathways. In the present study, the role of the proinflammatory cytokine LIGHT (TNFSF14) was explored in NAFLD and type 2 diabetes mellitus in mice deficient for the cytokine.

METHODS

Light-deficient (Light^-/-) mice and WT controls were fed a regular chow diet (RCD) or a high-fat high-cholesterol diet (HFHCD) for 16 weeks. The expression of LIGHT and its receptors, herpes virus entry mediator (HVEM) and lymphotoxin β receptor (LTβR), was investigated in both dietary regimens. Glucose tolerance, insulin sensitivity, non-alcoholic fatty liver (NAFL), systemic and tissue inflammation, and metabolic gene expression were explored in Light^-/- and WT mice fed an RCD and an HFHCD. The effect of Light deficiency was also evaluated in hepatic tissue and in inflammation in HFHCD-fed Irs2^+/- mice with impaired insulin signalling.

RESULTS

Light deficiency did not have an effect on metabolism, in NAFL or in tissue and systemic inflammation, in RCD-fed WT mice. HVEM and LTβR were markedly increased in livers of HFHCD-fed WT mice compared with RCD-fed WT controls. In WT mice under HFHCD, Light deficiency improved glucose tolerance and insulin sensitivity. Non-alcoholic fatty liver disease activity (NAS) score, hepatic CD3⁺ T lymphocytes and F4/80⁺ macrophages were decreased in HFHCD-fed Light^-/- mice compared with HFHCD-fed WT controls. Consistent with a potential role of adipose tissue in hepatic homeostasis, Light^-/- mice exhibited augmented anti-inflammatory F4/80⁺CD206⁺ adipose tissue macrophages and reduced proinflammatory F4/80⁺CD11c⁺ adipose tissue macrophages. Moreover, adipose tissue explants from Light^-/- mice showed diminished secretion of monocyte chemoattractant protein 1 (MCP1), TNF-α and IL-17 cytokines. Circulating Light^-/- leucocytes consistently displayed augmented levels of the patrolling Ly6C^low monocytes, decreased Th9 T cell subset and diminished plasma TNF-α and IL-6 levels. Similarly, Light deficiency in Irs2^+/- mice, which display impaired insulin signalling, also reduced NAFL as well as systemic and adipose tissue inflammation. Analysis of hepatic gene expression in Light^-/- mouse livers showed reduced levels of Zbtb16, the transcription factor essential for natural killer T (NKT) cell function, and two genes related to NAFLD and fibrosis, Klf6 and Tlr4.

CONCLUSIONS/INTERPRETATION

These results indicate that Light deficiency in HFHCD improves hepatic glucose tolerance, and reduces hepatic inflammation and NAFL. This is accompanied by decreased systemic inflammation and adipose tissue cytokine secretion and by changes in the expression of key genes such as Klf6 and Tlr4 involved in NAFLD. These results suggest that therapies to block LIGHT-dependent signalling might be useful to restore hepatic homeostasis and to restrain NAFLD.

Plasma Cells Are Obligate Effectors of Enhanced Myelopoiesis in Aging Bone Marrow

Aging results in increased myelopoiesis, which is linked to the increased incidence of myeloid leukemias and production of myeloid-derived suppressor cells. Here, we examined the contribution of plasma cells (PCs) to age-related increases in myelopoiesis, as PCs exhibit immune regulatory function and sequester in bone marrow (BM). PC number was increased in old BM, and they exhibited high expression of genes encoding inflammatory cytokines and pathogen sensors. Antibody-mediated depletion of PCs from old mice reduced the number of myeloid-biased hematopoietic stem cells and mature myeloid cells to levels in young animals, but lymphopoiesis was not rejuvenated, indicating that redundant mechanisms inhibit that process. PCs also regulated the production of inflammatory factors from BM stromal cells, and disruption of the PC-stromal cell circuitry with inhibitors of the cytokines IL-1 and TNF-α attenuated myelopoiesis in old mice. Thus, the age-related increase in myelopoiesis is driven by an inflammatory network orchestrated by PCs.

Expression, purification, and efficient refolding of the extracellular domain of Escherichia coli-expressed signaling receptor herpesvirus entry mediator

Herpesvirus entry mediator (HVEM), a member of the TNF-receptor superfamily, plays an important role in the regulation of the immune system. It forms a complex with ligands and can either activate or inhibit the response of the immune system. Furthermore, HVEM can exhibit pro-inflammatory or anti-inflammatory effects in many human diseases. Therefore, understanding the mechanism underlying the interaction of HVEM with other receptors is extremely important to design small therapeutic molecules that can stimulate the response of the immune system. In this study, we attempted to develop the most efficient method for the expression and purification of the extracellular domain of HVEM using Escherichia coli. The soluble fraction constituted only a small portion of the E. coli-expressed protein, whereas majority of the protein was found to be accumulated in the insoluble fraction. Three different protein refolding methods were analyzed: dialysis, dilution, and using chromatographic column. The oligomeric state of the protein was determined by characterizing the obtained fractions using analytical size exclusion chromatography. All the obtained fractions were tested for their ability to form a complex with B- and T-lymphocyte attenuator using enzyme-linked immunosorbent assay. The results of this study provide crucial information regarding the production of HVEM protein in a robust, well-established, and convenient heterologous expression system using E. coli as a host. In addition, it allows for the selection of the most effective method for appropriate refolding of HVEM protein, which gets accumulated in the insoluble fraction.

Comparison of adipose‑ and bone marrow‑derived stem cells in protecting against ox‑LDL‑induced inflammation in M1‑macrophage‑derived foam cells

Adipose‑derived stem cells (ADSCs) and bone marrow‑derived stem cells (BMSCs) are considered to be prospective sources of mesenchymal stromal cells (MSCs), that can be used in cell therapy for atherosclerosis. The present study investigated whether ADSCs co‑cultured with M1 foam macrophages via treatment with oxidized low‑density lipoprotein (ox‑LDL) would lead to similar or improved anti‑inflammatory effects compared with BMSCs. ADSCs, peripheral blood monocytes, BMSCs and ox‑LDL were isolated from ten coronary heart disease (CHD) patients. After three passages, the supernatants of the ADSCs and BMSCs were collected and systematically analysed by liquid chromatography‑quadrupole time‑of‑flight‑mass spectrometry (6530; Agilent Technologies, Inc., Santa Clara, CA, USA). Cis‑9, trans‑11 was deemed to be responsible for the potential differences in the metabolic characteristics of ADSCs and BMSCs. These peripheral blood monocytes were characterized using flow cytometry. Following peripheral blood monocytes differentiation into M1 macrophages, the formation of M1 foam macrophages was achieved through treatment with ox‑LDL. Overall, 2x106 ADSCs, BMSCs or BMSCs+cis‑9, trans‑11 were co‑cultured with M1 foam macrophages. Anti‑inflammatory capability, phagocytic activity, anti‑apoptotic capability and cell viability assays were compared among these groups. It was demonstrated that the accumulation of lipid droplets decreased following ADSCs, BMSCs or BMSCs+cis‑9, trans‑11 treatment in M1 macrophages derived from foam cells. Consistently, ADSCs exhibited great advantageous anti‑inflammatory capabilities, phagocytic activity, anti‑apoptotic capability activity and cell viability over BMSCs or BMSCs+cis‑9, trans‑11. Additionally, BMSCs+cis‑9, trans‑11 also demonstrated marked improvement in anti‑inflammatory capability, phagocytic activity, anti‑apoptotic capability activity and cell viability in comparison with BMSCs. The present results indicated that ADSCs would be more appropriate for transplantation to treat atherosclerosis than BMSCs alone or BMSCs+cis‑9, trans‑11. This may be an important mechanism to regulate macrophage immune function.

Mechanisms Involved in Childhood Obesity-Related Bone Fragility

Childhood obesity is one of the major health problems in western countries. The excessive accumulation of adipose tissue causes inflammation, oxidative stress, apoptosis, and mitochondrial dysfunctions. Thus, obesity leads to the development of severe co-morbidities including type 2 diabetes mellitus, liver steatosis, cardiovascular, and neurodegenerative diseases which can develop early in life. Furthermore, obese children have low bone mineral density and a greater risk of osteoporosis and fractures. The knowledge about the interplay bone tissue and between adipose is still growing, although recent findings suggest that adipose tissue activity on bone can be fat-depot specific. Obesity is associated to a low-grade inflammation that alters the expression of adiponectin, leptin, IL-6, Monocyte Chemotactic Protein 1 (MCP1), TRAIL, LIGHT/TNFSF14, OPG, and TNFα. These molecules can affect bone metabolism, thus resulting in osteoporosis. The purpose of this review was to deepen the cellular mechanisms by which obesity may facilitate osteoporosis and bone fractures.

Characterization of different fat depots in NAFLD using inflammation-associated proteome, lipidome and metabolome

Non-alcoholic fatty liver disease (NAFLD) is recognized as a liver manifestation of metabolic syndrome, accompanied with excessive fat accumulation in the liver and other vital organs. Ectopic fat accumulation was previously associated with negative effects at the systemic and local level in the human body. Thus, we aimed to identify and assess the predictive capability of novel potential metabolic biomarkers for ectopic fat depots in non-diabetic men with NAFLD, using the inflammation-associated proteome, lipidome and metabolome. Myocardial and hepatic triglycerides were measured with magnetic spectroscopy while function of left ventricle, pericardial and epicardial fat, subcutaneous and visceral adipose tissue were measured with magnetic resonance imaging. Measured ectopic fat depots were profiled and predicted using a Random Forest algorithm, and by estimating the Area Under the Receiver Operating Characteristic curves. We have identified distinct metabolic signatures of fat depots in the liver (TAG50:1, glutamate, diSM18:0 and CE20:3), pericardium (N-palmitoyl-sphinganine, HGF, diSM18:0, glutamate, and TNFSF14), epicardium (sphingomyelin, CE20:3, PC38:3 and TNFSF14), and myocardium (CE20:3, LAPTGF-β1, glutamate and glucose). Our analyses highlighted non-invasive biomarkers that accurately predict ectopic fat depots, and reflect their distinct metabolic signatures in subjects with NAFLD.

TNFSF14/LIGHT, a Non-Canonical NF-κB Stimulus, Induces the HIF Pathway

Non-canonical NF-κB signalling plays important roles in the development and function of the immune system but it also is deregulated in a number of inflammatory diseases. Although, NF-κB and HIF crosstalk has been documented, this has only been described following canonical NF-κB stimulation, involving RelA/p50 and the HIF-1 dimer. Here, we report that the non-canonical inducer TNFSF14/LIGHT leads to HIF induction and activation in cancer cells. We demonstrate that only HIF-2α is induced at the transcriptional level following non-canonical NF-κB activation, via a mechanism that is dependent on the p52 subunit. Furthermore, we demonstrate that p52 can bind to the HIF-2α promoter in cells. These results indicate that non-canonical NF-κB can lead to HIF signalling implicating HIF-2α as one of the downstream effectors of this pathway in cells.

LIGHT is increased in patients with coronary disease and regulates inflammatory response and lipid metabolism in oxLDL-induced THP-1 macrophages

Inflammation is critical for the progression of hyperlipidemia. Although the exact mechanism through which inflammation affects hyperlipidemia is not very clear, evidence suggests that the tumor necrosis factor superfamily member 14 (TNFSF14/LIGHT)LIGHT might regulate lipid metabolism. In this study we investigated the expression of LIGHT in patients with different stages of coronary disease. The expression of lipid metabolism-related enzymes and inflammation-related proteins were further explored in oxidized low-density lipoproteins (oxLDL)-induced THP-1 macrophages. We found that LIGHT is highly expressed and companied with severe inflammations in patients with coronary disease. LIGHT significantly enhanced inflammation response in oxLDL-induced THP-1 macrophages. We further demonstrated that LIGHT markedly decreased the levels of lipolytic genes and increased the expressions of lipogenic genes in oxLDL-induced THP-1 macrophages. In addition, our results showed that LIGHT exerts its pro-inflammatory and pro-lipogenesis roles through activating nuclear factor-kappa B (NF-κB) signaling pathway. Taken together our study has demonstrated that LIGHT NF-κB-dependently exacerbates inflammation response and promotes lipid accumulation, and provided a new potential target for treatment of hyperlipidemia-related disease.

Deficiency of LIGHT signaling pathway exacerbates Chlamydia psittaci respiratory tract infection in mice

LIGHT, a costimulatory member of the immunoglobulin superfamily (Ig SF), can greatly impact T cell activation. The role of the LIGHT signaling pathway in chlamydial infection was evaluated in mice following respiratory tract infection with Chlamydia psittaci. Compared with wild type (WT) mice, LIGHT knockout (KO) mice showed significant reduction of body weight, much lower survival rate, higher bacterial burden, prolonged infection time courses and more severe pathological changes in lung tissue. The mRNA levels of IFN-γ, TNF-α, IL-17 and IL-12 in the lung tissue of LIGHT KO mice were significantly lower than those in WT mice. While there was no obvious difference in the percentages of CD4⁺ and CD8⁺ T cells in the spleens of the two groups of mice, there was a markedly elevated percentage of CD4⁺ CD25⁺ FoxP3⁺ Treg cells in LIGHT KO mice. Together, these results demonstrate that the LIGHT signaling pathway is not only required for inflammatory cytokine production as part of the host response to chlamydial infection, but also influences the differentiation of CD4⁺ CD25⁺ FoxP3⁺ Treg cells, both of which may be essential for control of C. psittaci respiratory tract infection.

LIGHT/TNFSF14 is increased in patients with type 2 diabetes mellitus and promotes islet cell dysfunction and endothelial cell inflammation in vitro

AIMS/HYPOTHESIS

Activation of inflammatory pathways is involved in the pathogenesis of type 2 diabetes mellitus. On the basis of its role in vascular inflammation and in metabolic disorders, we hypothesised that the TNF superfamily (TNFSF) member 14 (LIGHT/TNFSF14) could be involved in the pathogenesis of type 2 diabetes mellitus.

METHODS

Plasma levels of LIGHT were measured in two cohorts of type 2 diabetes mellitus patients (191 Italian and 40 Norwegian). Human pancreatic islet cells and arterial endothelial cells were used to explore regulation and relevant effects of LIGHT in vitro.

RESULTS

Our major findings were: (1) in both diabetic cohorts, plasma levels of LIGHT were significantly raised compared with sex- and age-matched healthy controls (n = 32); (2) enhanced release from activated platelets seems to be an important contributor to the raised LIGHT levels in type 2 diabetes mellitus; (3) in human pancreatic islet cells, inflammatory cytokines increased the release of LIGHT and upregulated mRNA and protein levels of the LIGHT receptors lymphotoxin β receptor (LTβR) and TNF receptor superfamily member 14 (HVEM/TNFRSF14); (4) in these cells, LIGHT attenuated the insulin release in response to high glucose at least partly via pro-apoptotic effects; and (5) in human arterial endothelial cells, glucose boosted inflammatory response to LIGHT, accompanied by an upregulation of mRNA levels of HVEM (also known as TNFRSF14) and LTβR (also known as LTBR).

CONCLUSIONS/INTERPRETATION

Our findings show that patients with type 2 diabetes mellitus are characterised by increased plasma LIGHT levels. Our in vitro findings suggest that LIGHT may contribute to the progression of type 2 diabetes mellitus by attenuating insulin secretion in pancreatic islet cells and by contributing to vascular inflammation.

The control of tissue fibrosis by the inflammatory molecule LIGHT (TNF Superfamily member 14)

The TNF Superfamily member LIGHT (TNFSF14) has recently emerged as a potential target for therapeutic interventions aiming to halt tissue fibrosis. In this perspective, we discuss how LIGHT may influence the inflammatory and remodeling steps that characterize fibrosis, relevant for many human diseases presenting with scarring such as asthma, idiopathic pulmonary fibrosis, systemic sclerosis, and atopic dermatitis. LIGHT acts through two receptors in the TNF receptor superfamily, HVEM (TNFRSF14) and LTβR (TNFRSF3), which are broadly expressed on hematopoietic and non-hematopoietic cells. LIGHT can regulate infiltrating T cells, macrophages, and eosinophils, controlling their trafficking or retention in the inflamed tissue, their proliferation, and their ability to produce cytokines that amplify fibrotic processes. More interestingly, LIGHT can act on structural cells, namely epithelial cells, fibroblasts, smooth muscle cells, adipocytes, and endothelial cells. By signaling through either HVEM or LTβR expressed on these cells, LIGHT can contribute to their proliferation and expression of chemokines, growth factors, and metalloproteinases. This will lead to hyperplasia of epithelial cells, fibroblasts, and smooth muscle cells, deposition of extracellular matrix proteins, vascular damage, and further immune alterations that in concert constitute fibrosis. Because of its early expression by T cells, LIGHT may be an initiator of fibrotic diseases, but other sources in the immune system could also signify a role for LIGHT in maintaining or perpetuating fibrotic activity. LIGHT may then be an attractive prognostic marker as well as an appealing target for fibrosis therapies relevant to humans.

Immune cell crosstalk in obesity: a key role for costimulation?

In the past two decades, numerous experimental and clinical studies have established the importance of inflammation and immunity in the development of obesity and its metabolic complications, including insulin resistance and type 2 diabetes mellitus. In this context, T cells orchestrate inflammatory processes in metabolic organs, such as the adipose tissue (AT) and liver, thereby mediating obesity-related metabolic deterioration. Costimulatory molecules, which are present on antigen-presenting cells and naïve T cells in the AT, are known to mediate the crosstalk between the adaptive and innate immune system and to direct T-cell responses in inflammation. In this Perspectives in Diabetes article, we highlight the newest insights in immune cell interactions in obesity and discuss the role of costimulatory dyads in its pathogenesis. Moreover, the potential of therapeutic strategies that target costimulatory molecules in the metabolic syndrome is explored.

TNFRSF14 deficiency protects against ovariectomy-induced adipose tissue inflammation

To elucidate the role of tumor necrosis factor receptor superfamily member 14 (TNFRSF14) in metabolic disturbance due to loss of ovarian function, ovariectomy (OVX) was performed in TNFRSF 14-knockout mice. OVX increased fat mass and infiltration of highly inflammatory CD11c cells in the adipose tissue (AT), which was analyzed by flow cytometry, and resulted in disturbance of glucose metabolism, whereas TNFRSF14 deficiency attenuated these effects. TNFRSF14 deficiency decreased recruitment of CD11c-expressing cells in AT and reduced the polarization of bone marrow-derived macrophages to M1. Upon engagement of LIGHT, a TNFRSF14 ligand, TNFRSF14 enhanced the expression of CD11c via generation of reactive oxygen species, suggesting a role of TNFRSF14 as a redox modulator. TNFRSF14 participated in OVX-induced AT inflammation via upregulation of CD11c, resulting in metabolic perturbation. TNFRSF14 could be used as a therapeutic target for the treatment of postmenopausal syndrome by reducing AT inflammation.

Herpes virus entry mediator signaling in the brain is imperative in acute inflammation-induced anorexia and body weight loss

BACKGROUND

Reduced appetite and body weight loss are typical symptoms of inflammatory diseases. A number of inflammatory stimuli are responsible for the imbalance in energy homeostasis, leading to metabolic disorders. The herpes virus entry mediator (HVEM) protein plays an important role in the development of various inflammatory diseases, such as intestinal inflammation and diet-induced obesity. However, the role of HVEM in the brain is largely unknown. This study aims to investigate whether HVEM signaling in the brain is involved in inflammation-induced anorexia and body weight loss.

METHODS

Food intake and body weight were measured at 24 hours after intraperitoneal injection of lipopolysaccharide (LPS) or intracerebroventricular injection of recombinant mouse LIGHT (also called tumor necrosis factor receptor superfamily 14, TNFSF14), an HVEM ligand, into 8- to 10-week-old male C57BL/6 mice and mice lacking HVEM expression (HVEM-/-). We also assessed LPS-induced change in hypothalamic expression of HVEM using immunohistochemistry.

RESULTS

Administration of LPS significantly reduced food intake and body weight, and moreover, increased expression of HVEM in the hypothalamic arcuate nucleus. However, LPS induced only minor decreases in food intake and body weight in HVEM-/- mice. Administration of LIGHT into the brain was very effective at decreasing food intake and body weight in wild-type mice, but was less effective in HVEM-/- mice.

CONCLUSION

Activation of brain HVEM signaling is responsible for inflammation-induced anorexia and body weight loss.

Molecular cloning and characterization of TNFSF14 (LIGHT) and its receptor TNFRSF14 (HVEM) in guinea pig (Cavia porcellus)

LIGHT (lymphotoxin-related inducible ligand that competes with herpes simplex virus (HSV) glycoprotein D for herpesvirus entry mediator on T cells) is a member of the tumor necrosis factor (TNF) ligand superfamily, which plays important roles in inflammatory and immune responses. In the present study, the cDNAs of guinea pig (Cavia porcellus) LIGHT (designated as gpLIGHT) and its receptor herpes virus entry mediator (designated as gpHVEM) were amplified from spleen by reverse transcription polymerase chain reaction (RT-PCR). The ORFs of gpLIGHT and gpHVEM cover 726 and 861 bp, encoding predicted proteins with 241 and 286 aas, respectively. The three-dimensional (3D) structure, phylogenetic relationships, and characterization of both genes were also analyzed. We also generated a 3D model to verify interaction between the two proteins. Real-time quantitative PCR (qPCR) analysis revealed that both LIGHT and HVEM are constitutively expressed in guinea pig various tissues. A fusion protein SUMO (Small Ubiquitin-like Modifier)-gpsLIGHT (the soluble mature part of gpLIGHT) was efficiently expressed in Escherichia coli BL21 (DE3) and purified using metal chelate affinity chromatography (Ni-NTA). Laser scanning confocal microscopy (LSCM) showed that gpsLIGHT can bind its receptors on T cells. The LIGHT-HVEM signaling pathway plays an important role in the immune system, and our results might provide a platform for further research into the effects of LIGHT and HVEM.

4-1BB/4-1BBL interaction promotes obesity-induced adipose inflammation by triggering bidirectional inflammatory signaling in adipocytes/macrophages

Obesity-induced adipose inflammation is characterized by recruitment of macrophages to adipose tissue and release of inflammatory cytokines. 4-1BB, a costimulatory receptor, modulates inflammatory processes through interaction with its ligand 4-1BBL on immune cell surfaces. In this study, we examined whether a 4-1BB/4-1BBL interaction between adipocytes and macrophages participates in obesity-induced adipose inflammation. We found that 4-1BB was expressed on adipocytes and was upregulated by obesity-related factors, which also enhanced 4-1BBL expression on macrophages. 4-1BB and/or 4-1BBL agonists, respectively, activated inflammatory signaling molecules (MAPK/IκBα and MAPK/Akt) in adipocytes and macrophages and enhanced the release of inflammatory cytokines (MCP-1, TNF-α, and IL-6). Moreover, disruption of the 4-1BB/4-1BBL interaction decreased the release of inflammatory cytokines from contact cocultured adipocytes/macrophages. These findings indicate that 4-1BB/4-1BBL-mediated bidirectional signaling in adipocytes/macrophages promotes adipose inflammation. 4-1BB and 4-1BBL may be useful targets for protection against obesity-induced adipose inflammation.

The signaling networks of the herpesvirus entry mediator (TNFRSF14) in immune regulation

The tumor necrosis factor (TNF) receptor superfamily member herpesvirus entry mediator (HVEM) (TNFRSF14) regulates T-cell immune responses by activating both inflammatory and inhibitory signaling pathways. HVEM acts as both a receptor for the canonical TNF-related ligands, LIGHT [lymphotoxin-like, exhibits inducible expression, and competes with herpes simplex virus glycoprotein D for HVEM, a receptor expressed on T lymphocytes] and lymphotoxin-α, and as a ligand for the immunoglobulin superfamily proteins BTLA (B and T lymphocyte attenuator) and CD160, a feature distinguishing HVEM from other immune regulatory molecules. The ability of HVEM to interact with multiple ligands in distinct configurations creates a functionally diverse set of intrinsic and bidirectional signaling pathways that control both inflammatory and inhibitory responses. The HVEM system is integrated into the larger LTβR and TNFR network through extensive shared ligand and receptor usage. Experimental mouse models and human diseases indicate that dysregulation of HVEM network may contribute to autoimmune pathogenesis, making it an attractive target for drug intervention.

HVEM-deficient mice fed a high-fat diet are protected from adipose tissue inflammation and glucose intolerance

HVEM is a member of the TNF receptor superfamily that plays a role in the development of various inflammatory diseases. In this study, we show that HVEM deficiency attenuates adipose tissue inflammatory responses and glucose intolerance in diet-induced obesity. Feeding a high-fat diet (HFD) to HVEM-deficient mice elicited a reduction in the number of macrophages and T cells infiltrated into adipose tissue. Proinflammatory cytokine levels in the adipose tissue decreased in HFD-fed HVEM-deficient mice, while levels of the anti-inflammatory cytokine IL-10 increased. Moreover, glucose intolerance and insulin sensitivity were markedly improved in the HFD-fed HVEM-deficient mice. These findings indicate that HVEM may be a useful target for combating obesity-induced inflammatory responses and insulin resistance.