Somatic and axonal LIGHT signaling elicit degenerative and regenerative responses in motoneurons, respectively

A receptor-ligand interaction can evoke a broad range of biological activities in different cell types depending on receptor identity and cell type-specific post-receptor signaling intermediates. Here, we show that the TNF family member LIGHT, known to act as a death-triggering factor in motoneurons through LT-βR, can also promote axon outgrowth and branching in motoneurons through the same receptor. LIGHT-induced axonal elongation and branching require ERK and caspase-9 pathways. This distinct response involves a compartment-specific activation of LIGHT signals, with somatic activation-inducing death, while axonal stimulation promotes axon elongation and branching in motoneurons. Following peripheral nerve damage, LIGHT increases at the lesion site through expression by invading B lymphocytes, and genetic deletion of Light significantly delays functional recovery. We propose that a central and peripheral activation of the LIGHT pathway elicits different functional responses in motoneurons.

Increase in the mediators of asthma in obesity and obesity with type 2 diabetes: reduction with weight loss

OBJECTIVE

To determine whether the expression of key asthma related genes, IL-4, LIGHT, LTBR, MMP-9, CCR-2, and ADAM-33 in mononuclear cells and the plasma concentration of nitric oxide metabolites (NOM) and MMP-9 are increased in the obese, obese type 2 diabetics (T2DM) and in morbidly obese patients prior to and after gastric bypass surgery (RYGB).

DESIGN AND METHODS

The expression of these genes in MNC and plasma concentrations of these indices was measured in healthy lean and in obese with and without T2DM and following RYGB in obese T2DM.

RESULTS

The expression of IL-4, MMP-9, LIGHT and CCR-2 and plasma NOM concentrations was significantly higher in the obese subjects and in obese T2DM patients than in normal subjects. The expression of IL-4, LIGHT, MMP-9, and CCR-2 expression was related to BMI and HOMA-IR. The expression of IL-4, LIGHT, LTBR, ADAM-33, MMP-9, and CCR-2 fell after RYGB surgery as did plasma concentrations of MMP-9 and NOM.

CONCLUSIONS

Obesity with and without T2DM is associated with an increase in the expression of IL-4, LIGHT, MMP-9 and CCR-2; plasma NOM and MMP-9 concentrations are also increased. Following RYGB surgery and weight loss, the expression of these factors in MNC and plasma concentrations falls significantly.

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.

Reduction of decoy receptor 3 enhances TRAIL-mediated apoptosis in pancreatic cancer

Most human pancreatic cancer cells are resistant to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. However, the mechanisms by which pancreatic cancer cells utilize their extracellular molecules to counteract the proapoptotic signaling mediated by the TNF family are largely unknown. In this study, we demonstrate for the first time that DcR3, a secreted decoy receptor that malignant pancreatic cancer cells express at a high level, acts as an extracellular antiapoptotic molecule by binding to TRAIL and counteracting its death-promoting function. The reduction of DcR3 with siRNA unmasked TRAIL and greatly enhanced TRAIL-induced apoptosis. Gemcitabine, a first-line drug for pancreatic cancer, also reduced the level of DcR3. The addition of DcR3 siRNA further enhanced gemcitabine-induced apoptosis. Notably, our in vivo study demonstrated that the therapeutic effect of gemcitabine could be enhanced via further reduction of DcR3, suggesting that downregulation of DcR3 in tumor cells could tip the balance of pancreatic cells towards apoptosis and potentially serve as a new strategy for pancreatic cancer therapy.

[Study of inhibiting and killing effects of transgenic LIGHT human umbilical cord blood mesenchymal stem cells on stomach cancer]

OBJECTIVE

To study the inhibition and killing effect of transgenic LIGHT umbilical cord blood mesenchymal stem cells (UCBMSCs) on stomach carcinoma.

METHODS

The LIGHT gene was recombined to construct the transfer plasmid pGC-FU-LIGHT by infusion technique. The 293T cells were co-transfected with the transfer plasmid pGC-FU-LIGHT, the construction plasmid Helper 1.0 and the envelope plasmid Helper 2.0 with the help of lipofectamine 2000 to produce lentiviral particles. Transgenic UCBMSCs(MSC-LIGHT) and empty carrier UCBMSCs (MSC) were obtained. Human gastric cancer cell SGC-7901 was injected into nude mice subcutaneously groin. The model of transplanted human gastric cancer cell SGC-7901 in nude mice was established. Tumorigenesis nude mice were separated into three groups randomly with 5 in each group: MSC-LIGHT group, MSC group, and NS group. Three groups of nude mice were injected around the tumor with MSC-LIGHT, MSC and NS every other day for 3 times. Four weeks later, the transplanted gastric cancer volume was measured. The expressions of LIGHT in the three groups were determined by RT-PCR and ELISA method. The necrosis area in the tumors was calculated under pathological examination.

RESULTS

The average volume of transplanted tumor was(0.45±0.25) cm(3) in MSG-LIGHT group, (0.64±0.36) cm(3) in MSG group, and(1.21±0.79) cm(3) in NS group, and the difference was statistically significant(P<0.05). The LIGHT mRNA was 2.96±0.27, 1.23±0.47, and 0.73±0.10 respectively. The LIGHT protein was(167.89±2.31), (73.22±5.74), and (49.66±5.25) ng/L. The differences were all statistically significant among the three groups(both P<0.01). Pathological examination showed that the necrosis area was largest in MSC-LIGHT group.

CONCLUSION

Transgenic UCBMSCs secret LIGHT in a paracrine manner, which has inhibition and killing effects on stomach carcinoma.

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.

Critical roles for LIGHT and its receptors in generating T cell-mediated immunity during Leishmania donovani infection

LIGHT (TNFSF14) is a member of the TNF superfamily involved in inflammation and defence against infection. LIGHT signals via two cell-bound receptors; herpes virus entry mediator (HVEM) and lymphotoxin-beta receptor (LTβR). We found that LIGHT is critical for control of hepatic parasite growth in mice with visceral leishmaniasis (VL) caused by infection with the protozoan parasite Leishmania donovani. LIGHT-HVEM signalling is essential for early dendritic cell IL-12/IL-23p40 production, and the generation of IFNγ- and TNF-producing T cells that control hepatic infection. However, we also discovered that LIGHT-LTβR interactions suppress anti-parasitic immunity in the liver in the first 7 days of infection by mechanisms that restrict both CD4⁺ T cell function and TNF-dependent microbicidal mechanisms. Thus, we have identified distinct roles for LIGHT in infection, and show that manipulation of interactions between LIGHT and its receptors may be used for therapeutic advantage.

Visceral leishmaniasis (VL) is a potentially fatal human disease caused by the intracellular protozoan parasites Leishmania donovani and L. infantum (chagasi). Parasites infect macrophages throughout the viscera, though the spleen and liver are the major sites of disease. VL is responsible for significant morbidity and mortality in the developing world, particularly in India, Sudan, Nepal, Bangladesh and Brazil. Because of the intrusive techniques required to analyse tissue in VL patients, our current understanding of the host immune response during VL largely derives from studies performed in genetically susceptible mice. We have discovered that mice which are unable to produce a cytokine called LIGHT have poor control of L. donovani infection in the liver, compared with wild-type control animals. In addition, we demonstrated that LIGHT has distinct roles during VL, depending on which of its two major cell-bound receptors it engages. Finally, we identified an antibody that stimulates the lymphotoxin β receptor (one of the LIGHT receptors), that can stimulate anti-parasitic activity during an established infection, thereby identifying this receptor as a therapeutic target during disease.

Effect of LIGHT adjuvant on kinetics of T-cell responses induced by HSV-1 DNA immunization

BACKGROUND

Studies on efficacy of various vaccines that prevent or reduce the primary and recurrent HSV-1 infection have demonstrated the importance of cellular immunity for protection against the infection. We previously used DNA vaccination to induce cellular immunity against HSV-1 infection in mice.

OBJECTIVE

The aim of our study was to evaluate the effect of LIGHT; a member of TNF super family, on the kinetic of CTL response induced by HSV-1 glycoprotein B based DNA vaccine.

METHODS

Using a granzyme B ELISA for detection and analysis of CD8+ T cells, CTL activity was determined in the spleen of BALB/c mice at various time points after primary and booster dose of vaccination. The kinetics of CTL response to primary and secondary HSV-1 infection and DNA vaccination were compared to those induced by DNA vaccination in combination with LIGHT adjuvant in the present study.

RESULTS

In primary and secondary immunization, the CTL activity in the HSV injected group peaked 7 days and 12 hours post immunization, respectively. After 5 days, LIGHT could neither accelerate the CTL response compared to DNA vaccination alone nor could enhance the CTL activity in the primary and the first peak of memory response, the amount of granzyme B induced by the LIGHT containing vaccine was significantly higher than that induced by the vaccine without the adjuvant.

CONCLUSION

Although LIGHT enhances the cellular response in the booster dose of vaccination, it does not accelerate the CTL response.

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

Obesity-induced adipose tissue inflammation is characterized by increased macrophage infiltration and cytokine production, and is associated with metabolic disorders. LIGHT/TNFSF14, a member of the TNF superfamily, plays a role in the development of various inflammatory diseases. The purpose of this study was to examine the involvement of soluble LIGHT (sLIGHT) in obesity-induced adipose tissue inflammatory responses. LIGHT gene expression on macrophages/adipocytes was upregulated by treatment with obesity-related factors. sLIGHT displayed chemotactic activity for macrophages and T cells, and enhanced inflammatory cytokine release from macrophages, adipocytes, and adipose tissue-derived SVF cells. The sLIGHT-induced inflammatory responses were blunted by neutralizing anti-HVEM antibody or knockout of HVEM, a receptor for sLIGHT. These findings indicate that sLIGHT enhances adipose tissue inflammatory responses through its interaction with HVEM.

Zinc-finger protein 91 plays a key role in LIGHT-induced activation of non-canonical NF-κB pathway

LIGHT is a member of tumor necrosis factor (TNF) superfamily, and its function is mediated through lymphotoxin-β receptor (LTβR), which is known to play important roles in inflammatory and immune responses through activation of NF-κB signaling pathways. However, molecular mechanism of LTβR ligation-induced NF-κB signaling remains incompletely understood. In this report we demonstrate that a novel zinc-finger protein 91 (ZFP91) is a critical regulator in LIGHT-induced activation of non-canonical NF-κB pathway. ZFP91 appears to be required for NF-κB2 (p100) processing to p52, nuclear translocation of p52 and RelB, and DNA-binding activity of NF-κB in LIGHT-induced activation of non-canonical NF-κB pathway. Furthermore, ZFP91 knock-down by RNA interference blocks the LIGHT-induced accumulation of NIK and p100 processing, as well as the expression of non-canonical NF-κB target genes. These data clearly indicate that ZFP91 is a key regulator in LIGHT-induced activation of non-canonical NF-κB pathway in LTβR signaling.

LIGHT induces distinct signals to clear an AAV-expressed persistent antigen in the mouse liver and to induce liver inflammation

BACKGROUND

Infection with adeno-associated virus (AAV) vector with liver tropism leads to persistent expression of foreign antigens in the mouse liver, with no significant liver inflammation or pathology. This provides a model to investigate antigen persistence in the liver and strategies to modulate host immunity to reduce or clear the foreign antigen expressed from AAV vector in the liver.

METHODS/PRINCIPAL FINDINGS

We showed that expressing LIGHT with an adenovirus vector (Ad) in mice with established AAV in the liver led to clearance of the AAV. Ad-LIGHT enhanced CD8 effector T cells in the liver, correlated with liver inflammation. LTbetaR-Ig proteins blocked Ad-LIGHT in clearing AAV. Interestingly, in LTbetaR-null mice, Ad-LIGHT still cleared AAV but caused no significant liver inflammation.

CONCLUSIONS/SIGNIFICANCE

Our data suggest that LIGHT interaction with the LTbetaR plays a critical role in liver inflammation but is not required for LIGHT-mediated AAV clearance. These findings will shed light on developing novel immuno-therapeutics in treating people chronically infected with hepato-tropic viruses.

Creation of a lysine-deficient LIGHT mutant with the capacity for site-specific PEGylation and low affinity for a decoy receptor

The cytokine LIGHT is a promising candidate for cancer therapy. However, the therapeutic effect of LIGHT as a systemic anticancer agent is currently insufficient because of its instability and its binding to nonfunctional soluble decoy receptor 3 (DcR3), which is overexpressed in various tumors. Modification of proteins with polyethylene glycol (PEGylation) can improve their in vivo stability, but PEGylation may occur randomly at all lysine residues and the NH(2)-terminus; therefore, PEGylated proteins are generally heterogeneous and have decreased bioactivity. In this study, we attempted to create a lysine-deficient LIGHT mutant that could be PEGylated site-specifically and would have lower affinity for DcR3. We prepared phage libraries expressing LIGHT mutants in which all the lysine residues were replaced with other amino acids. A lysine-deficient LIGHT mutant [mLIGHT-Lys(-)] was isolated by panning against lymphotoxin beta receptor (LTbetaR). mLIGHT-Lys(-) could be site-specifically PEGylated at its NH(2)-terminus, yielding molecular uniformity and in vitro bioactivity equal to that of non-PEGylated, wild-type LIGHT. Furthermore, mLIGHT-Lys(-) was not trapped by the nonfunctional DcR3, despite binding to its functional receptors. These results suggest that mLIGHT-Lys(-) might be a useful candidate for cancer therapy.

A lymphotoxin-driven pathway to hepatocellular carcinoma

Hepatitis B and C viruses (HBV and HCV) cause chronic hepatitis and hepatocellular carcinoma (HCC) by poorly understood mechanisms. We show that cytokines lymphotoxin (LT) alpha and beta and their receptor (LTbetaR) are upregulated in HBV- or HCV-induced hepatitis and HCC. Liver-specific LTalphabeta expression in mice induces liver inflammation and HCC, causally linking hepatic LT overexpression to hepatitis and HCC. Development of HCC, composed in part of A6(+) oval cells, depends on lymphocytes and IKappa B kinase beta expressed by hepatocytes but is independent of TNFR1. In vivo LTbetaR stimulation implicates hepatocytes as the major LT-responsive liver cells, and LTbetaR inhibition in LTalphabeta-transgenic mice with hepatitis suppresses HCC formation. Thus, sustained LT signaling represents a pathway involved in hepatitis-induced HCC.

LIGHT induces cell proliferation and inflammatory responses of rheumatoid arthritis synovial fibroblasts via lymphotoxin beta receptor

OBJECTIVE

To investigate the effects of LIGHT (lymphotoxin-like, exhibits inducible expression and competes with herpes simplex virus glycoprotein D for herpes virus entry mediator, a receptor expressed by T lymphocytes) on the proliferation and gene expression of fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA).

METHODS

We measured LIGHT levels in RA synovial fluids (SF) by ELISA, and compared them with those in osteoarthritis (OA) SF. Levels of LIGHT and its receptors in RA-FLS and synovium were assessed using real-time quantitative polymerase chain reaction (PCR). RA-FLS proliferation was examined by a bromodeoxyuridine assay. Expression of intercellular adhesion molecule-1 (ICAM-1) and several chemokines, such as interleukin 8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-1alpha (MIP-1alpha), was examined by real-time quantitative PCR, ELISA, and flow cytometry. The effects of LIGHT on nuclear factor-kappaB (NF-kappaB) activation were investigated using immunofluorescence and Western blotting.

RESULTS

LIGHT was upregulated in both SF and synovium of RA patients compared with OA patients. Herpes virus entry mediator (HVEM) and lymphotoxin beta receptor (LTbetaR), but not LIGHT, were detected in RA-FLS. LIGHT significantly promoted RA-FLS proliferation and induced expression of MCP-1, IL-8, MIP-1alpha, and ICAM-1 by RA-FLS. As well, LTbetaR small interfering RNA (siRNA), but not HVEM siRNA, inhibited these effects of LIGHT. LIGHT induced IkappaBa degradation and NF-kappaB translocation, and a NF-kappaB inhibitor suppressed the effects of LIGHT on RA-FLS.

CONCLUSION

Our findings suggest that LIGHT signaling via LTbetaR plays an important role in the pathogenesis of RA by affecting key processes such as the proliferation and activation of RA-FLS. Regulation of LIGHT-LTbetaR signaling may represent a new therapeutic target for RA treatment.

Platelet-associated LIGHT (TNFSF14) mediates adhesion of platelets to human vascular endothelium

LIGHT (TNFSF 14) belongs to the tumor necrosis factor super-family and is expressed by different types of immune cells. Recently, LIGHT was found to be associated with platelets and released upon activation. Activation of endothelial cells by recombinant LIGHT results in pro-inflammatory and pro-thrombotic changes, qualitatively comparable to effects of CD40 ligand. Given the important role of platelet-associated CD40 ligand in vascular inflammatory responses we investigated the role of LIGHT for activation of endothelium and adhesion of platelets to endothelial cells. Expression of LIGHT was detected on thrombocytes upon exposure to ADP or TRAP-1. The expression of the LIGHT receptors TR2 and LTbetaR on native human endothelial cells was confirmed by FACS analysis. LIGHT mediated adhesion of platelets to endothelium significantly, occurring both under static and dynamic flow conditions. This interaction was inhibited by a monoclonal antibody to LIGHT but not a control IgG. Moreover, in-vitro stimulation of endothelial cells with recombinant soluble human LIGHT (rhLIGHT) resulted in significantly increased transcriptional and translational upregulation of inflammatory markers ICAM-1, tissue factor (TF) and IL-8. This activation of endothelial cells by LIGHT was mediated by NFkappaB activation and qualitatively comparable to that induced by membrane-bound CD40-ligand on transfected cells. Furthermore, plasma levels of patients with myocardial infarction, in those with ST-elevation myocardial infarction (STEMI), showed increased plasma levels of LIGHT compared with healthy controls. In conclusion, platelet-associated LIGHT is involved in adhesion of platelets to endothelium while soluble LIGHT induces a pro-inflammatory state in vascular endothelial cells. LIGHT may thus be implicated in the pathogenesis of atherosclerosis and acute coronary syndrome, as evidenced by serum levels.

Lymphotoxin beta receptor (Lt betaR): dual roles in demyelination and remyelination and successful therapeutic intervention using Lt betaR-Ig protein

Inflammation mediated by macrophages is increasingly found to play a central role in diseases and disorders that affect a myriad of organs, prominent among these are diseases of the CNS. The neurotoxicant-induced, cuprizone model of demyelination is ideally suited for the analysis of inflammatory events. Demyelination on exposure to cuprizone is accompanied by predictable microglial activation and astrogliosis, and, after cuprizone withdrawal, this activation reproducibly diminishes during remyelination. This study demonstrates enhanced expression of lymphotoxin beta receptor (Lt betaR) during the demyelination phase of this model, and Lt betaR is found in areas enriched with microglial and astroglial cells. Deletion of the Lt betaR gene (Lt betaR-/-) resulted in a significant delay in demyelination but also a slight delay in remyelination. Inhibition of Lt betaR signaling by an Lt betaR-Ig fusion decoy protein successfully delayed demyelination in wild-type mice. Unexpectedly, this Lt betaR-Ig decoy protein dramatically accelerated the rate of remyelination, even after the maximal pathological disease state had been reached. This strongly indicates the beneficial role of Lt betaR-Ig in the delay of demyelination and the acceleration of remyelination. The discrepancy between remyelination rates in these systems could be attributed to developmental abnormalities in the immune systems of Lt betaR-/- mice. These findings bode well for the use of an inhibitory Lt betaR-Ig as a candidate biological therapy in demyelinating disorders, because it is beneficial during both demyelination and remyelination.

LIGHT, a member of the TNF superfamily, activates Stat3 mediated by NIK pathway

Stat3, a member of the signal transducers and activators of transcription (STAT) family, is a key signal transduction protein activated by numerous cytokines, growth factors, and oncoproteins that controls cell proliferation, differentiation, development, survival, and inflammation. Constitutive activation of Stat3 has been found frequently in a wide variety of human tumors and induces cellular transformation and tumor formation. In this study, we demonstrated that LIGHT, a member of tumor necrosis factor superfamily, activates Stat3 in cancer cells. LIGHT induces dose-dependent activation of Stat3 by phosphorylation at both the tyrosine 705 and serine 727 residues. The activation of Stat3 by LIGHT appears to be mediated by NIK phosphorylation. Expression of a kinase-inactive NIK mutant abolished LIGHT induced Stat3 activation. Overexpression of an active NIK induces Stat3 activation by phosphorylation at the both tyrosine 705 and serine 727 residues. Activation of Stat3 by NIK requires NIK kinase activity as showed by kinase assays. In addition, LIGHT increases the expression of Stat3 target genes including cyclin D1, survivin, and Bcl-xL, and stimulates human LNCaP prostate cancer cell growth in vitro which can be blocked by expression of a dominant-negative Stat3 mutant. Taken together, these results indicate that in addition to activating NF-kappaB/p52, LIGHT also activates Stat3. Activation of Stat3 together with activating non-canonical NF-kappaB/p52 signaling by LIGHT may maximize its effects on cellular proliferation, survival, and inflammation.

Attenuated Salmonella engineered to produce human cytokine LIGHT inhibit tumor growth

Intravenously administered bacteria reportedly accumulate in tumors. Furthermore, systemic administration of attenuated Salmonella typhimurium has little or no significant side-effects in humans. Consequently, we engineered such bacteria to improve their oncolytic activity by stably inserting a gene encoding LIGHT, a cytokine known to promote tumor rejection. Unlike control bacteria, attenuated S. typhimurium expressing LIGHT inhibited growth of primary tumors, as well as the dissemination of pulmonary metastases, in various mouse tumor models employing murine carcinoma cell lines in immunocompetent mice. Antitumor activity was achieved without significant toxicity and was associated with infiltration of inflammatory cells and dependent on the LIGHT receptors, herpes virus entry mediator (HVEM), and lymphotoxin-beta receptor (LTbetaR). These findings provide evidence that nonvirulent bacteria can be exploited as targeting vehicles for local generation of therapeutic proteins in tumors.

[Interaction between member LIGHT of TNF superfamily and SOCS3, which respond to induce the differentiation and maturation of dendritic cell]

OBJECTIVE

To detect the relation between the member LIGHT of TNF superfamily and the suppressor of cytokine signaling 3 (SOCS3), and to investigate the effect of SOCS3 on dendritic cell (DC) maturation induced by LIGHT.

METHODS

Bone marrow-derived DC (BMDC) was generated from mouse bone marrow monocyte by culturing with rmGM-CSF, rmIL-4 in vitro. SOCS3 mRNA in BMDC was analyzed by RT-PCR, and the protein of SOCS3 was measured by Western blot. After blocking the SOCS3 expression with the specific anti-sense oligonucleotide, we applied the flow cytometry to measure the expression of CD86 and CD40 on DC for making clear whether the silence of SOCS3 would regulate the LIGHT-stimulated DC maturation.

RESULTS

With the effect of LIGHT, the level of SOCS3 mRNA and protein in BMDC sharply increased. The specific antisense oligonucleotide could effectively block SOCS3 mRNA expressing in BMDC with the ratio of 49% and block SOCS3 protein expression with the ratio of 45%. Compared with SOCS3-unblocked DC, the SOCS3-blocked BMDC with stimulation of LIGHT showed higher CD40 and CD86 (P < 0.05).

CONCLUSION

LIGHT enhances the expression of SOCS3 during stimulating BMDC maturation. As more sensitive to LIGHT, the SOCS3-blocked BMDC is driven to more mature. SOCS3 presents a negative regulation mechanism in BMDC maturation induced

LIGHT signals directly to intestinal epithelia to cause barrier dysfunction via cytoskeletal and endocytic mechanisms

BACKGROUND & AIMS

LIGHT (lymphotoxin-like inducible protein that competes with glycoprotein D for herpes virus entry on T cells) is a tumor necrosis factor core family member that regulates T-cell activation and causes experimental inflammatory bowel disease. Additional data suggest that LIGHT may be involved in the pathogenesis of human inflammatory bowel disease. The aim of this study was to determine if LIGHT is capable of signaling directly to intestinal epithelia and to define the mechanisms and consequences of such signaling.

METHODS

The effects of LIGHT and interferon-gamma on barrier function, cytoskeletal regulation, and tight junction structure were assessed in mice and intestinal epithelial monolayers.

RESULTS

LIGHT induced barrier loss in cultured epithelia via myosin II regulatory light chain (MLC) phosphorylation; both barrier loss and MLC phosphorylation were reversed by MLC kinase (MLCK) inhibition. Pretreatment with interferon-gamma, which induced lymphotoxin beta receptor (LT beta R) expression, was required for these effects, and neither barrier dysfunction nor intestinal epithelial MLC phosphorylation occurred in LT beta R knockout mice. In cultured monolayers, endocytosis of the tight junction protein occludin correlated with barrier loss. Internalized occludin colocalized with caveolin-1. LIGHT-induced occludin endocytosis and barrier loss were both prevented by inhibition of caveolar endocytosis.

CONCLUSIONS

T cell-derived LIGHT activates intestinal epithelial LT beta R to disrupt barrier function. This requires MLCK activation and caveolar endocytosis. These data suggest a novel role for LIGHT in disease pathogenesis and suggest that inhibition of MLCK-dependent caveolar endocytosis may represent an approach to restoring barrier function in inflammatory bowel disease.

LIGHT up-regulated on B lymphocytes and monocytes in rheumatoid arthritis mediates cellular adhesion and metalloproteinase production by synoviocytes

OBJECTIVE

To study the expression of LIGHT (tumor necrosis factor superfamily 14) and herpesvirus entry mediator (HVEM; tumor necrosis factor receptor superfamily 14) in rheumatoid arthritis (RA) and to determine the regulatory role of LIGHT on the effector functions of fibroblast-like synoviocytes (FLS).

METHODS

The expression of LIGHT and HVEM was assessed by immunohistochemical staining of synovial tissue and by flow cytometric analysis of mononuclear cells. The presence of HVEM and lymphotoxin beta receptor was measured by reverse transcriptase-polymerase chain reaction and by flow cytometry. The regulation of effector molecules, including matrix metalloproteinases (MMPs) and adhesion molecules, was evaluated. The adhesiveness of FLS was determined by adhesion assay.

RESULTS

HVEM was detected in most cell types within rheumatoid synovial tissue, while only a few cells were positive for LIGHT. In RA patients, LIGHT expression was significantly up-regulated only in CD20+ B cells and monocytes, whereas the mean fluorescence intensity of HVEM was down-regulated in mononuclear cells. The stimulation of FLS with LIGHT resulted in the production of MMPs and the expression of adhesion molecules, which were efficiently inhibited by dexamethasone. LIGHT-mediated up-regulation of MMPs and intercellular adhesion molecule 1 was blocked by inhibitors of NF-kappaB and JNK, whereas up-regulation of vascular cell adhesion molecule 1 was blocked by inhibitors of phosphatidylinositol 3-kinase, as well as NF-kappaB.

CONCLUSION

These data suggest that binding of LIGHT with its receptors may play a role in the progression of inflammation within rheumatoid synovium, especially by mediating the interactions between infiltrating inflammatory cells and stromal cells. These findings thus emphasize the relevance of LIGHT as a potential therapeutic target in RA.

Lymphotoxin beta receptor-dependent control of lipid homeostasis

Hyperlipidemia, one of the most important risk factors for coronary heart disease, is often associated with inflammation. We identified lymphotoxin (LT) and LIGHT, tumor necrosis factor cytokine family members that are primarily expressed on lymphocytes, as critical regulators of key enzymes that control lipid metabolism. Dysregulation of LIGHT expression on T cells resulted in hypertriglyceridemia and hypercholesterolemia. In low-density lipoprotein receptor-deficient mice, which lack the ability to control lipid levels in the blood, inhibition of LT and LIGHT signaling with a soluble lymphotoxin beta receptor decoy protein attenuated the dyslipidemia. These results suggest that the immune system directly influences lipid metabolism and that LT modulating agents may represent a novel therapeutic route for the treatment of dyslipidemia.

The TNF superfamily member LIGHT contributes to survival and activation of synovial fibroblasts in rheumatoid arthritis

OBJECTIVES

The TNF superfamily member LIGHT has a T-cell co-stimulatory role and has previously been associated with inflammation and autoimmunity. To investigate its role in rheumatoid arthritis (RA), a disease where activated T cells contribute in a prominent way, we have analysed the expression of LIGHT and its receptors in RA and analysed its effects on synovial fibroblasts in vitro.

METHODS

The expression of LIGHT was measured in synovial tissues and fluids and the receptors of LIGHT were detected on synovial fibroblasts derived from patients with RA and osteoarthritis (OA). The effects of recombinant LIGHT on the production of proinflammatory cytokines and proteases and on the apoptosis of synovial fibroblasts was assessed.

RESULTS

LIGHT mRNA was present in synovial tissues of patients with RA but not with OA. Correspondingly, soluble LIGHT protein could be detected in RA synovial fluid samples at much higher levels than in synovial fluid from patients with OA. Immunohistochemical detection of LIGHT and analysis of synovial fluid cells by flow cytometry revealed CD4 T cells as the major source of LIGHT in the rheumatoid joint. Synovial fibroblasts from RA patients were found to express the LIGHT receptors HVEM and LTbetaR. Recombinant LIGHT induced RA synovial fibroblasts to upregulate MMP-9 mRNA, CD54 and IL-6 in an NF-kappaB-dependent fashion. In vitro, exposure of cultured synovial fibroblasts to LIGHT reduced FAS-mediated apoptosis significantly, without affecting the rate of spontaneous apoptosis.

CONCLUSIONS

The results provide evidence for a novel T-cell-dependent activation of synovial fibroblasts by LIGHT in joints of patients with RA, contributing to an inflammatory and destructive phenotype.

Signaling pathways of LIGHT induced macrophage migration and vascular smooth muscle cell proliferation

The biological actions of LIGHT, a member of the tumor necrosis factor superfamily, are mediated by the interaction with lymphotoxin-beta receptor (LTbetaR) and/or herpes virus entry mediator (HVEM). Previous study demonstrated high-level expressions of LIGHT and HVEM receptors in atherosclerotic plaques. To investigate the role of LIGHT in the functioning of macrophages and vascular smooth muscle cells (VSMC) in relation to atherogenesis, we determined the effects of LIGHT on macrophage migration and VSMC proliferation. We found LIGHT through HVEM activation can induce both events. LIGHT-induced macrophage migration was associated with activation of signaling kinases, including MAPKs, PI3K/Akt, NF-kappaB, Src members, and FAK. Proliferation of VSMC was also shown relating to the activation of MAPKs, PI3K/Akt, and NF-kappaB, which consequently led to alter the expression of cell cycle regulatory molecules. Down-regulation of p21, p27, and p53, and inversely up-regulation of cyclin D and RB hyper-phosphorylation were demonstrated. In conclusion, LIGHT acts as a novel mediator for macrophage migration and VSMC proliferation, suggesting its involvement in the atherogenesis.