Tumor necrosis factor receptor and Fas signaling mechanisms

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.

Fucoidan induces G1 phase arrest and apoptosis through caspases-dependent pathway and ROS induction in human breast cancer MCF-7 cells

Fucoidan is an active component of seaweed, which inhibits proliferation and induces apoptosis of several tumor cells while the detailed mechanisms underlying this process are still not clear. In this study, the effect of Fucoidan on the proliferation and apoptosis of human breast cancer MCF-7 cells and the molecular mechanism of Fucoidan action were investigated. Viable cell number of MCF-7 cells was decreased by Fucoidan treatment in a dose-dependent manner as measured by MTT assay. Fucoidan treatment resulted in G1 phase arrest of MCF-7 cells as revealed by flow cytometry, which was associated with the decrease in the gene expression of cyclin D1 and CDK-4. Annexin V/PI staining results showed that the number of apoptotic cells was associated with regulation of cytochrome C, caspase-8, Bax and Bcl-2 at transcriptional and translational levels. Both morphologic observation and Hoechst 33258 assay results confirmed the pro-apoptotic effect of Fucoidan. Meanwhile, the ROS production was also increased by Fucoidan treatment, which suggested that Fucoidan induced oxidative damage in MCF-7 cells. The results of present study demonstrated that Fucoidan could induce G1 phase arrest and apoptosis in MCF-7 cells through regulating the cell cycle and apoptosis-related genes or proteins expression, and ROS generation is also involved in these processes.

Expressions of tumor necrosis factor-α, its receptor I, II and receptor-associated factor 2 in the porcine corpus luteum during the estrous cycle and early pregnancy

We examined the gene and protein levels of tumor necrosis factor (TNF)-α, its receptors (types I and II, designated TNF-RI and TNF-RII, respectively), TNF receptor-associated factor 2 (TRAF2) and morphological features in the porcine corpus luteum (CL), on Days 13 and 17 (Day 0 = the last day of estrus) of the estrous cycle or of early pregnancy. Gene expression levels of TNF-α, TNF-RI, TNF-RII and TRAF2 were unaffected by the day or reproductive status. TNF-α concentration was significantly higher in the CL on Day 17 of pregnancy than on Day 13 of pregnancy and on day 17 of the estrous cycle. The TNF-RI protein level was significantly higher in the CL on Days 13 and 17 of pregnancy than those of the estrous cycle, significantly increasing on Day 17 compared with those on Day 13 in pregnancy. In relation to TNF-RII protein levels, although there were no change during pregnancy, there was a tendency (P = 0.0524) to up-regulate as pregnancy proceeded. In estrous cycle, TNF-RII protein levels decreased significantly as luteolysis proceeded. TRAF2 protein level was significantly higher in the CL on Days 13 and 17 of pregnancy than during estrous. There were few apoptotic bodies in the CL between Days 13 and 17 of pregnancy than during esrous. There were few apoptotic bodies in the CL between Days 13 and 17 of pregnancy. The number of apoptotic bodies was much greater than the CL on Day 17 of the estrous than those of pregnancy. Thus, the TNF-α and TNF-RI and TNF-RII pathways including the TRAF2 protein, known to control of cell differentiation, tissue renewal and apoptosis, might participate in maintaining the porcine CL during early pregnancy.

Arginase 1: an unexpected mediator of pulmonary capillary barrier dysfunction in models of acute lung injury

The integrity of epithelial and endothelial barriers in the lower airspaces of the lungs has to be tightly regulated, in order to prevent leakage and to assure efficient gas exchange between the alveoli and capillaries. Both G⁻ and G⁺ bacterial toxins, such as lipopolysaccharide and pneumolysin, respectively, can be released in high concentrations within the pulmonary compartments upon antibiotic treatment of patients suffering from acute respiratory distress syndrome (ARDS) or severe pneumonia. These toxins are able to impair endothelial barrier function, either directly, or indirectly, by induction of pro-inflammatory mediators and neutrophil sequestration. Toxin-induced endothelial hyperpermeability can involve myosin light chain phosphorylation and/or microtubule rearrangement. Endothelial nitric oxide synthase (eNOS) was proposed to be a guardian of basal barrier function, since eNOS knock-out mice display an impaired expression of inter-endothelial junction proteins and as such an increased vascular permeability, as compared to wild type mice. The enzyme arginase, the activity of which can be regulated by the redox status of the cell, exists in two isoforms – arginase 1 (cytosolic) and arginase 2 (mitochondrial) – both of which can be expressed in lung microvascular endothelial cells. Upon activation, arginase competes with eNOS for the substrate l-arginine, as such impairing eNOS-dependent NO generation and promoting reactive oxygen species generation by the enzyme. This mini-review will discuss recent findings regarding the interaction between bacterial toxins and arginase during acute lung injury and will as such address the role of arginase in bacterial toxin-induced pulmonary endothelial barrier dysfunction.

Downregulation of Caspase-2 Expression in Somitic Cells following Coculture with Chicken Notochord

Somites are spherical aggregations of mesodermal cells located on either sides of neural tube and are differentiated into sclerotome and dermomyotome. Notochord as an axial mesoderm has a major role in somitic cell survival and differentiation in vivo. Despite secreting the survival factors, how to notochord inhibits somitic cells apoptosis remains to be elusive. So, this study was aimed to investigate downregulation of caspase-2 expression in somitic cells upon coculturing with notochord. By using alginate system to encapsulate the isolated notochord in Somite + Notochord group, the embryonic somites were cocultured with the notochord on different days. Concurrently in somite group, the somites were cultured alone. Survival assay with MTT showed that the rate of viability in somitic cells cocultured with notochord increased from 59% on day 2 to 89.7% on day 6 but decreased to 38.5% on day 10 after coculturing. Reverse transcriptase-polymerase chain reaction and spectrophotometry analysis also confirmed these findings and showed low caspase-2 and high Bcl-2 expressions and low caspase-2 enzyme activity in somitic cells cocultured with notochord, respectively. These results clearly show that the notochord enhances survival of somitic cells in vitro through downregulating of caspase-2 expression along with triggering differentiation of somitic cells to Pax-1 expressing mesenchymal cells.

APS8, a polymeric alkylpyridinium salt blocks α7 nAChR and induces apoptosis in non-small cell lung carcinoma

Naturally occurring 3-alkylpyridinium polymers (poly-APS) from the marine sponge Reniera sarai, consisting of monomers containing polar pyridinium and nonpolar alkyl chain moieties, have been demonstrated to exert a wide range of biological activities, including a selective cytotoxicity against non-small cell lung cancer (NSCLC) cells. APS8, an analog of poly-APS with defined alkyl chain length and molecular size, non-competitively inhibits α7 nicotinic acetylcholine receptors (nAChRs) at nanomolar concentrations that are too low to be acetylcholinesterase (AChE) inhibitory or generally cytotoxic. In the present study we show that APS8 inhibits NSCLC tumor cell growth and activates apoptotic pathways. APS8 was not toxic for normal lung fibroblasts. Furthermore, in NSCLC cells, APS8 reduced the adverse anti-apoptotic, proliferative effects of nicotine. Our results suggest that APS8 or similar compounds might be considered as lead compounds to develop antitumor therapeutic agents for at least certain types of lung cancer.

Mechanisms of action of anti-tumor necrosis factor α agents in Crohn's disease

Crohn's disease (CD) is characterized by inflammation that can affect any part of the gastrointestinal tract. It is a chronic destructive condition that follows a relapsing-remitting course and can lead to disability and a poor quality of life. Lifelong pharmacotherapy with systemic immunomodulator therapies remains the cornerstone of CD management. Advances in understanding of the immunopathogenic mechanisms underlying chronic gut inflammation in CD have led to the development of effective biological therapies for patients with CD. Tumor necrosis factor α (TNF-α) is a potent proinflammatory cytokine that plays a pivotal role in the development of Crohn's inflammation. Therapies designed to target this cytokine have revolutionized treatment of CD since their introduction in the late 1990s, thanks to their ability to induce and maintain remission, heal mucosa, reduce hospital admissions and surgical procedures, and restore quality of life. Despite widespread use of these therapies in CD, their precise mechanism of action remains unclear, although several different mechanisms have been proposed. This review summarizes the biology of the TNF-α cytokine and the development of biological therapies targeting TNF-α, and updates our current understanding of mechanisms of action of the commercially available anti-TNF-α therapies used in the treatment of CD.

TNFR1 signaling kinetics: spatiotemporal control of three phases of IKK activation by posttranslational modification

TNFα is a pleotropic cytokine that plays a central role in the inflammatory response by activating the NF-κB signaling pathway, and is targeted in a range of chronic inflammatory diseases, underscoring the therapeutic importance of understanding its underlying molecular mechanisms. Although K63-linked ubiquitination of RIP1 by TRAF2/5 and cIAP1/2 was thought to serve as a scaffold to activate the NF-κB pathway, the recent accumulation of conflicting results has challenged the necessity of these proteins in NF-κB activation. In addition, several serine/threonine kinases have been implicated in TNFα-induced IKK activation; however, the targeted disruption of these kinases had no effect on transient IKK activation. The recent discovery of RIP1-dependent and -independent activation of the early and delayed phases of IKK and TRAF2 phosphorylation-dependent activation of the prolonged phase of IKK offers a reconciliatory model for the interpretation of contradictory results in the field. Notably, the TNFα-induced inflammatory response is not exclusively controlled by the NF-κB pathway but is subject to regulatory crosstalk between NF-κB and other context-dependent pathways. Thus further elucidation of these spatiotemporally-coordinated signaling mechanisms has the potential to provide novel molecular targets and therapeutic strategies for NF-κB intervention.

The role of infliximab on paracetamol-induced hepatotoxicity in rats

Paracetamol has a reasonable safety profile when consumed in therapeutic doses. However, it could induce hepatotoxicity and even acute liver failure when taken at an overdose. Infliximab is tumor necrosis factor alpha (TNF-α) inhibitor agent, which has been developed as a therapeutic agent for TNF-α-mediated disease. It acts by binding and neutralizing TNF. The aim of our study was to evaluate the hepatoprotective activity of infliximab on paracetamol-induced hepatotoxicity and to understand the relationship between the TNF-α and paracetamol-induced liver injury. Fifty-six rats were divided into eight groups as each composed of seven rats: (1) intact, (2) 7 mg/kg infliximab, (3) 140 mg/kg NAC, (4) 2 g/kg paracetamol, (5) 2 g/kg paracetamol + 140 mg/kg NAC, (6) 2 g/kg paracetamol + 3 mg/kg infliximab, (7) 2 g/kg paracetamol + 5 mg/kg infliximab and (8) 2 g/kg paracetamol + 7 mg/kg infliximab groups. Liver function tests including lipid peroxidation levels were analyzed and histopathological changes of liver were also observed. There were statistically significant increases in the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), levels of TNF-α and malondialdehyde (MDA) and decreases in the activity of superoxide dismutase (SOD) and level of glutathione (GSH) in the group treated with paracetamol. Infliximab administration dramatically reduced serum ALT, AST and TNF-α level. Also, it restored GSH, SOD and decreased MDA levels in liver. Liver histopathological examination showed that infliximab administration antagonized paracetamol-induced liver pathological damage. The results of present study suggest that infliximab has significant hepatoprotective activity on paracetamol-induced hepatotoxicity.

Effect of pulsed electromagnetic field on inflammatory pathway markers in RAW 264.7 murine macrophages

In the treatment of bacterial infections, antibiotics have proven to be very effective, but the way in which antibiotics are dosed can create a lag time between the administration of the drug and its absorption at the site of insult. The time it takes an antibiotic to reach therapeutic levels can often be significantly increased if the vascular system is compromized. Bacteria can multiply pending the delivery of the drug, therefore, developing treatments that can inhibit the inflammatory response while waiting for antibiotics to take effect could help prevent medical conditions such as septic shock. The aim of this study was to examine the effect of a pulsed electromagnetic field on the production of inflammatory markers tumor necrosis factor (TNF), transcription factor nuclear factor kappa B (NFkB), and the expression of the A20 (tumor necrosis factor-alpha-induced protein 3), in an inflamed-cell model. Lipopolysaccharide-challenged cells were exposed to a pulsed electromagnetic field at various frequencies in order to determine which, if any, frequency would affect the TNF-NFkB-A20 inflammatory response pathway. Our study revealed that cells continuously exposed to a pulsed electromagnetic field at 5 Hz demonstrated significant changes in the downregulation of TNF-α and NFkB and also showed a trend in the down regulation of A20, as compared with controls. This treatment could be beneficial in modulating the immune response, in the presence of infection.

Fas/CD95-induced chemokines can serve as "find-me" signals for apoptotic cells

Apoptosis is commonly thought to represent an immunologically silent or even anti-inflammatory mode of cell death, resulting in cell clearance in the absence of explicit activation of the immune system. However, here we show that Fas/CD95-induced apoptosis is associated with the production of an array of cytokines and chemokines, including IL-6, IL-8, CXCL1, MCP-1, and GMCSF. Fas-induced production of MCP-1 and IL-8 promoted chemotaxis of phagocytes toward apoptotic cells, suggesting that these factors serve as "find-me" signals in this context. We also show that RIPK1 and IAPs are required for optimal production of cytokines and chemokines in response to Fas receptor stimulation. Consequently, a synthetic IAP antagonist potently suppressed Fas-dependent expression of multiple proinflammatory mediators and inhibited Fas-induced chemotaxis. Thus, in addition to provoking apoptosis, Fas receptor stimulation can trigger the secretion of chemotactic factors and other immunologically active proteins that can influence immune responsiveness toward dying cells.

TNFα induces survival through the FLIP-L-dependent activation of the MAPK/ERK pathway

Activation of tumor necrosis factor receptor-1 can trigger survival or apoptosis pathways. In many cellular models, including the neuronal cell model PC12, it has been demonstrated that inhibition of protein synthesis is sufficient to render cells sensitive to apoptosis induced by TNFα. The survival effect is linked to the translocation of the transcription factor nuclear factor-kappa B (NF-κB) to the nucleus and activation of survival-related genes such as FLICE-like inhibitory protein long form (FLIP-L) or IAPs. Nonetheless, we previously reported an NF-κB-independent contribution of Bcl-xL to cell survival after TNFα treatment. Here, we demonstrate that NF-κB-induced increase in FLIP-L expression levels is essential for mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) activation. We demonstrate that FLIP-L behaves as a Raf-1 activator through both protein-protein interaction and Raf-1 kinase activation, without the requirement of the classical Ras activation. Importantly, prevention of FLIP-L increase by NF-κB inhibition or knockdown of endogenous FLIP-L blocks MAPK/ERK activation after TNFα treatment. From a functional point of view, we show that inhibition of the MAPK/ERK pathway and the NF-κB pathway are equally relevant to render PC12 cells sensitive to cell death induced by TNFα. Apoptosis induced by TNFα under these conditions is dependent on jun nuclear kinase1/2 JNK1/2-dependent Bim upregulation. Therefore, we report a previously undescribed and essential role for MAPK/ERK activation by FLIP-L in the decision between cell survival and apoptosis upon TNFα stimulation.

Electrophilic nitro-fatty acids inhibit vascular inflammation by disrupting LPS-dependent TLR4 signalling in lipid rafts

AIMS

Electrophilic fatty acid nitroalkene derivatives, products of unsaturated fatty acid nitration, exert long-term cardiovascular protection in experimental models of metabolic and cardiovascular diseases. The goal of this study is to examine the effects of nitro-fatty acids in the regulation of upstream signalling events in nuclear factor-κB (NF-κB) activation and determine whether low-dose acute administration of nitro-fatty acids reduces vascular inflammation in vivo.

METHODS AND RESULTS

Using NF-κB-luciferase transgenic mice, it was determined that pre-emptive treatment with nitro-oleic acid (OA-NO2), but not oleic acid (OA) inhibits lipopolysaccharide (LPS)-induced NF-κB activation both in vivo and in isolated macrophages. Acute intravenous administration of OA-NO2 was equally effective to inhibit leukocyte recruitment to the vascular endothelium assessed by intravital microscopy and significantly reduces aortic expression of adhesion molecules. An acute treatment with OA-NO2 in vivo yielding nanomolar concentrations in plasma, is sufficient to inhibit LPS-induced Toll-like receptor 4 (TLR4)-induced cell surface expression in leukocytes and NF-κB activation. In vitro experiments reveal that OA-NO2 suppresses LPS-induced TLR4 signalling, inhibitor of κB (IκBα) phosphorylation and ubiquitination, phosphorylation of the IκB kinase (IKK), impairing the recruitment of the TLR4 and TNF receptor associated factor 6 (TRAF6) to the lipid rafts compartments.

CONCLUSION

These studies demonstrate that acute administration of nitro-fatty acids is effective to reduce vascular inflammation in vivo. These findings reveal a direct role of nitro-fatty acids in the disruption of the TLR4 signalling complex in lipid rafts, upstream events of the NF-κB pathway, leading to resolution of pro-inflammatory activation of NF-κB in the vasculature.

Quantitative flow cytometric analysis of expression of tumor necrosis factor receptor types I and II on mononuclear cells

BACKGROUND

Tumor necrosis factor (TNF)-α is an inflammatory cytokine, the biological effects of which are mediated by the interaction with specific membrane-bound receptors. To assess TNF-α receptor (TNFR) expression, it is important to estimate both the number of cells that carry these receptors and the number of receptors per cell, because the cell fate depends on the balance between TNFRI and TNFRII signaling.

OBJECTIVE

The aim of the present study was to develop an optimized protocol to estimate the level of expression of membrane-bound TNFRI and TNFRII, using QuantiBRITE PE calibration beads.

MATERIALS AND METHODS

The percentage of cells that expressed membrane-bound TNFRI and TNFRII and the mean number of receptors per cell were determined by flow cytometry using PE-labeled antibodies against TNFR. To create a calibration curve and convert cell fluorescence intensity values to absolute numbers of receptors, we used QuantiBRITE PE beads.

RESULTS

CD19(+) B lymphocytes had the least percentage of cells expressing TNFRI and the greatest number of receptor molecules per cell, whereas CD3(+) T lymphocytes had the greatest percentage of cells expressing TNFRII and the lowest density of these receptors. We also established that stimulation of peripheral blood mononuclear cells (PBMCs) with the lipopolysaccharide (LPS) significantly increased the number of TNFRI and TNFRII on CD14(+) monocytes.

CONCLUSION

Application of the protocol-identified differences in the percentage of cells that expressed TNFRs, as well as the absolute number of receptors per cell, among different subpopulations of PBMCs, and between PBMCs cultured with and without LPS.

Functional analyses of TNFR2 in physiological and pathological retina angiogenesis

PURPOSE

To determine the function of tumor necrosis factor receptor-2 (TNFR2) in retinal development and ischemia-induced revascularization in an oxygen-induced retinopathy (OIR) model.

METHODS

Mice with a global deletion of TNFR2 (TNFR2-KO) or with a vascular endothelial cell (EC)-specific TNFR2 transgene (TNFR2-TG) were compared to wild-type C57BL/6 mice (WT). Retinal vasculature development was visualized by whole-mount and cross-sectional isolectin staining. In the OIR model, neonatal mice were subjected to 75% oxygen from postnatal day (P)7 to P12 and then returned to normoxia from P12 to P17. Immunostaining and biochemical analyses were performed to assess the effects of TNFR2 deletion and TNFR2 transgenesis on retinal vascular repair.

RESULTS

TNFR2 deletion slightly delayed, while TNFR2 transgenesis weakly promoted, intraretinal vascular development and intraretinal vessel growth. TNFR2 deletion enhanced, while TNFR2 transgene reduced, hyperoxia-induced vaso-obliteration. However, hypoxia-induced revascularization and development of deep intraretinal vessels at P17 were reduced in TNFR2-KO but increased in TNFR2-TG mice without significant increase in preretinal neovascularization (NV). Moreover, TNFR2-TG/KO mice in which only vascular EC express TNFR2 sufficiently rescued the vascular defects of TNFR2-KO in the OIR model. Biochemical analyses of retina tissues showed that the phenotypic changes in retina correlated with TNFR2-dependent activation of Nuclear factor-κB (NF-κB) survival and bone marrow kinase (Bmx)-VEGFR2 angiogenic pathways.

CONCLUSIONS

TNFR2 plays a marginal role during retinal vascular development. TNFR2 in vascular EC strongly prevents hyperoxia-induced vaso-obliteration by inhibiting cell apoptosis, and promotes retinal repair by enhancing hypoxia-induced revascularization without increasing pathological neovascular tufts. Therefore, activation of TNFR2 signaling may be an ideal strategy for the treatment of OIR.

Evidence for an association between tumor necrosis factor-alpha levels and lithium response

BACKGROUND

The role of inflammation in bipolar disorder has recently emerged as a potential pathophysiological mechanism. Tumor necrosis factor-alpha (TNF-α) modulation may represent a pathogenic molecular target and a biomarker for staging bipolar disorder. In this context, the possible association between lithium response and TNF-α level was examined.

METHODS

Sixty euthymic bipolar patients receiving lithium therapy were recruited for assessment of TNF-α level. The ALDA lithium response scale (LRS) was used to evaluate longitudinal lithium response in bipolar patients, using cut-offs of poor response, partial response and good response. TNF-α level was assessed using enzyme-linked immunosorbent assay.

RESULTS

There was a significant increase in TNF-α level in patients with poor lithium response compared to those with good response, also after controlling for a range of potential confounders (adjusted effect size: 0.47, p=0.011). Partial response showed a directionally similar, but attenuated and statistically inconclusive association (adjusted effect size: 0.16, p=0.326).

LIMITATIONS

Assessment of response was retrospective and natural course cannot be separated easily from treatment response in an observational design. Selection of additional inflammatory markers could provide for a better understanding of underlying immune changes.

CONCLUSIONS

This study strengthens the hypothesis that TNF-α level may mark or mediate lithium response, and that continuous immune imbalance in poor lithium responders may occasion treatment resistance. Further investigation of immune alterations in treatment-resistant bipolar patients may be productive.

TNFα pathway blockade ameliorates toxic effects of FSGS plasma on podocyte cytoskeleton and β3 integrin activation

BACKGROUND

In the absence of mutant genes encoding components of the podocyte slit diaphragm, about 30-50 % of children with primary glucocorticoid-resistant focal segmental glomerulosclerosis (FSGS) develop recurrent proteinuria and slowly progressive FSGS lesions following renal transplantation. Recurrence of FSGS in the allograft strongly suggests a circulating factor that disturbs normal podocyte biology. To date, the nature of the circulating factor is unclear, and there is no cure for the recurrent form of FSGS (R-FSGS).

METHODS

Cultured differentiated human podocytes were exposed to the plasmapheresis effluent or blood plasma samples from pediatric patients with recurrent or primary FSGS; in some cases, podocytes were pre-incubated with specific antibodies to block the tumor necrosis factor-alpha (TNFα) signaling pathway. Integrity of focal adhesion complexes and actin cytoskeleton were investigated by immunofluorescent microscopy.

RESULTS

Plasmapheresis effluent from an R-FSGS child or fresh plasma from two children with primary FSGS rapidly disturbed the cytoskeleton of normal human podocytes in vitro. Plasma from a child with R-FSGS also activated β3 integrin and dispersed focal adhesion complexes. The effects were reversed by pre-incubation with antibodies against TNFα or either of the two TNFα receptors. When our patient with R-FSGS became resistant to plasmapheresis, we initiated treatment with twice weekly etanercept injections and then infliximab. Within 3 weeks of regular anti-TNFα therapy, the patient achieved sustained partial remission of proteinuria, allowing us to wean her off plasmapheresis completely.

CONCLUSIONS

We suggest that in some FSGS patients, disruption of the podocyte cytoskeleton and β3 integrin-mediated podocyte attachment are driven by the TNFα pathway.

Study of apoptosis in oral pemphigus vulgaris using immunohistochemical marker Bax and TUNEL technique

BACKGROUND

Pemphigus vulgaris (PV) is an autoimmune mucocutaneous disease presenting clinically with blisters or erosions of the skin and mucous membrane. The main histopathologic characteristic of this disease is suprabasal vesicles due to loss of cell-cell adhesion between keratinocytes named acantholysis. Studies have shown that apoptosis is increased in PV. The purpose of this study is to investigate the role of apoptosis in blister formation in PV.

METHODS

This cross-sectional study was conducted on 25 specimens of oral PV. The presence of apoptosis was evaluated using the TUNEL technique in the normal perilesional region, vesicle area, and acantholytic cells. Also, the expression of Bax pro-apoptotic marker was assessed by the biotin-streptavidin immunohistochemical method. SPSS software was used for Wilcoxon test analysis. P values <0.05 were considered significant.

RESULTS

The percentage and intensity staining of TUNEL-positive cells were noteworthy. There were statistically significant differences between basal and parabasal (P = 0.05), tombstone with vesicle roof (P = 0.038) and basal with tombstone (P = 0.038). However, the expression and staining intensity of pro-apoptotic marker Bax were weak, and no statistically significant differences were observed between the various areas.

CONCLUSION

The results obtained in the present study suggest that the process of apoptosis occurs early in PV because it was observed in the perilesional normal appearing tissue. Also, the process of apoptosis may cause exacerbation or speeding of the bulla formation. In other words, inhibition of apoptosis in the patients could reduce the severity of the lesions.

Hepatitis C virus and cellular stress response: implications to molecular pathogenesis of liver diseases

Infection with hepatitis C virus (HCV) is a leading risk factor for chronic liver disease progression, including steatosis, cirrhosis, and hepatocellular carcinoma. With approximately 3% of the human population infected worldwide, HCV infection remains a global public health challenge. The efficacy of current therapy is still limited in many patients infected with HCV, thus a greater understanding of pathogenesis in HCV infection is desperately needed. Emerging lines of evidence indicate that HCV triggers a wide range of cellular stress responses, including cell cycle arrest, apoptosis, endoplasmic reticulum (ER) stress/unfolded protein response (UPR), and autophagy. Also, recent studies suggest that these HCV-induced cellular responses may contribute to chronic liver diseases by modulating cell proliferation, altering lipid metabolism, and potentiating oncogenic pathways. However, the molecular mechanism underlying HCV infection in the pathogenesis of chronic liver diseases still remains to be determined. Here, we review the known stress response activation in HCV infection in vitro and in vivo, and also explore the possible relationship of a variety of cellular responses with the pathogenicity of HCV-associated diseases. Comprehensive knowledge of HCV-mediated disease progression shall shed new insights into the discovery of novel therapeutic targets and the development of new intervention strategy.

Vasoactive intestinal peptide enhances TNF-α-induced IL-6 and IL-8 synthesis in human proximal renal tubular epithelial cells by NF-κB-dependent mechanism

Vasoactive intestinal polypeptide (VIP) is a 28-amino acid neuropeptide with vasodilator, bronchodilator, and anti-inflammatory effects. But little is known about its pro-inflammatory effects. We investigated the effect of VIP on the secretion of interleukin-6 (IL-6) and interleukin-8 (IL-8), two pro-inflammatory cytokines, in TNF-α-activated proximal renal tubular epithelial cell line (HK-2 cells). Cultured HK-2 cells were treated with TNF-α in the presence or absence of VIP with a dose range from 1 to 100 nM, followed by analysis of pro-inflammatory cytokines (IL-6 and IL-8) induction and their signal events including activation of the NF-κB pathway. We report here that tumor necrosis factor-α (TNF-α) increased IL-6 and IL-8 production, and that these effects were potentiated by VIP at 10 nM in HK-2 cells. However, VIP at 1 and 100 nM did not display this function. Consistent with these observations, we were able to show that VIP at 10 nM upregulated TNF-α-induced phosphorylation of IκB-α, leading to IκB-α degradation and the subsequent nuclear translocation of NF-κB. Furthermore, VIP-enhanced activation of NF-κB transcription activity was demonstrated using a NF-κB reporter construct upon transient transfection into HK-2 cells. These results strongly suggest that VIP synergistically enhances TNF-α-stimulated IL-6 and IL-8 synthesis via activating the NF-κB pathway in HK-2 cells.

p53 mediates TNF-induced epithelial cell apoptosis in IBD

Chronic ulcerative colitis (CUC) is characterized by increased intestinal epithelial cell (IEC) apoptosis associated with elevated tumor necrosis factor (TNF), inducible nitric oxide synthase (iNOS), and p53. We previously showed that p53 is increased in crypt IECs in human colitis and is needed for IEC apoptosis in chronic dextran sulfate sodium-colitis. Herein, we examined the roles of TNF and iNOS in regulating p53-induced IEC apoptosis in CUC. The IEC TUNEL staining, caspases 3, 8, and 9, and p53 protein levels, induced by anti-CD3 monoclonal antibody (mAb) activation of T cells, were markedly reduced in TNF receptor 1 and 2 gene knockout mice. Induction of IEC apoptosis correlated with increased p53, which was attenuated in iNOS(-/-) mice. IEC p53 levels and apoptosis were reduced in IL-10(-/-) colitic mice treated with neutralizing TNF mAb and the iNOS inhibitor, aminoguanidine, further suggesting that TNF and iNOS are upstream of p53 during colitis-induced IEC apoptosis. IEC apoptosis and p53 levels were assessed in control versus untreated or anti-TNF-treated CUC patients with equivalent levels of inflammation. Data indicated that IEC apoptosis and p53 levels were clearly higher in untreated CUC but markedly reduced in patients treated with anti-TNF mAb. Therefore, TNF-induced iNOS activates a p53-dependent pathway of IEC apoptosis in CUC. The inhibition of IEC apoptosis may be an important mechanism for mucosal healing in anti-TNF-treated CUC patients.

ARID3B induces tumor necrosis factor alpha mediated apoptosis while a novel ARID3B splice form does not induce cell death

Alternative splicing is a common occurrence in many cancers. Alternative splicing is linked with decreased apoptosis and chemoresistance in cancer cells. We previously demonstrated that ARID3B, a member of the AT-rich interactive domain (ARID) family of DNA binding proteins, is overexpressed in ovarian cancer. Therefore we wanted to assess the effect of ARID3B splice forms on cell viability. We identified a novel splice form of the ARID3B gene (designated as ARID3B Sh), which lacks the C-terminal exons 5–9 present in the full-length isoform (ARID3B Fl). ARID3B Fl is expressed in a variety of cancer cell lines. Expression of ARID3B Sh varied by cell type, but was highly expressed in most ovarian cancer lines. ARID3B is modestly transcriptionally activated by epidermal growth factor receptor (EGFR) signaling through the PEA3 transcription factor. We further found that ARID3B Fl is predominantly nuclear but is also present at the plasma membrane and in the cytosol. Endogenous ARID3B Sh is present in nuclear fractions, yet, when overexpressed ARID3B Sh accumulates in the cytosol and membrane fractions. The differential localization of these isoforms suggests they have different functions. Importantly, ARID3B Fl overexpression results in upregulation of pro-apoptotic BIM and induces Tumor Necrosis Factor alpha (TNFα) and TNF-related apoptosis inducing ligand (TRAIL) induced cell death. The ARID3B Fl-induced genes include TNFα, TRAIL, TRADD, TNF-R2, Caspase 10 and Caspase 7. Interestingly, ARID3B Sh does not induce apoptosis or expression of these genes. ARID3B Fl induces death receptor mediated apoptosis while the novel splice form ARID3B Sh does not induce cell death. Therefore alternative splice forms of ARID3B may play different roles in ovarian cancer progression.

A perspective on mammalian caspases as positive and negative regulators of inflammation

Members of the caspase family of cysteine proteases coordinate the morphological and biochemical events that typify apoptosis. However, neutralization of caspase activity in mammals fails to block death in response to most proapoptotic stimuli. This is because many cell death triggers provoke mitochondrial dysfunction upstream of caspase activation as a consequence of BAX/BAK channel opening. Although genetic or pharmacological inactivation of caspases fails to block cell death in most instances, it does convert the phenotype from apoptosis to necrosis. This has important implications for how the immune system responds to such cells, as necrotic cells provoke inflammation whereas apoptotic cells typically do not. Here, we propose an alternative perspective on apoptosis-associated caspase function by suggesting that these proteases are activated, not to kill, but to extinguish the proinflammatory properties of dying cells. This perspective unifies the mammalian caspase family as either positive or negative regulators of inflammation.

Evidence for multiple cell death pathways during development of experimental cytomegalovirus retinitis in mice with retrovirus-induced immunosuppression: apoptosis, necroptosis, and pyroptosis

AIDS-related human cytomegalovirus (HCMV) retinitis remains a major ophthalmologic problem worldwide. Although this sight-threatening disease is well characterized clinically, many pathogenic issues remain unresolved, among them a basic understanding of the relative roles of cell death pathways during development of retinal tissue destruction. Using an established model of experimental murine cytomegalovirus (MCMV) retinitis in mice with retrovirus-induced immunosuppression (MAIDS), we initially investigated MCMV-infected eyes for evidence of apoptosis-associated molecules in mice with MAIDS of 4 weeks' (MAIDS-4) and 10 weeks' (MAIDS-10) duration, which were resistant and susceptible to retinal disease, respectively, but which harbored equivalent amounts of infectious MCMV. Whereas MCMV-infected eyes of MAIDS-4 mice showed little evidence of apoptosis-associated molecules, MCMV-infected eyes of MAIDS-10 mice showed significant amounts of tumor necrosis factor alpha (TNF-α), TNF receptors 1 and 2, active caspase 8, active caspase 3, TNF-related apoptosis-inducing ligand (TRAIL), TRAIL-R(DR5), Fas, and Fas ligand mRNAs and/or proteins, all detected at peak amounts prior to development of most severe retinal disease. Immunohistochemical staining showed macrophages, granulocytes (neutrophils), Müller cells, and microglial cells as TNF-α sources. Remarkably, quantification of apoptosis by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay suggested that apoptosis contributed minimally to retinal disease in MCMV-infected eyes of MAIDS-10 mice. Subsequent studies demonstrated that MCMV-infected eyes of MAIDS-10 mice, but not MAIDS-4 mice, showed evidence of significant increases in molecules associated with two additional cell death pathways, necroptosis (receptor-interacting protein 1 [RIP1] and RIP3 mRNAs) and pyroptosis (caspase 1, interleukin 1β [IL-1β], and IL-18 mRNAs). We conclude that apoptosis, necroptosis, and pyroptosis participate simultaneously during MAIDS-related MCMV retinitis, and all may play a role during AIDS-related HCMV retinitis.

Granule exocytosis mediates immune surveillance of senescent cells

Senescence is a stable cell cycle arrest program that contributes to tumor suppression, organismal aging and certain wound healing responses. During liver fibrosis, for example, hepatic stellate cells initially proliferate and secrete extracellular matrix components that produce fibrosis; however, these cells eventually senesce and are cleared by immune cells, including natural killer (NK) cells. Here, we examine how NK cells target senescent cells and assess the impact of this process on liver fibrosis. We show that granule exocytosis, but not death-receptor-mediated apoptosis, is required for NK-cell-mediated killing of senescent cells. This pathway bias is due to upregulation of the decoy death receptor, Dcr2, an established senescence marker that attenuates NK-mediated cell death. Accordingly, mice with defects in granule exocytosis accumulate senescent stellate cells and display more liver fibrosis in response to a fibrogenic agent. Our results thus provide new insights into the immune surveillance of senescent cells and reveal how granule exocytosis has a protective role against liver fibrosis.

Both internalization and AIP1 association are required for tumor necrosis factor receptor 2-mediated JNK signaling

OBJECTIVE

The proinflammtory cytokine tumor necrosis factor (TNF), primarily via TNF receptor 1 (TNFR1), induces nuclear factor-κB (NF-κB)-dependent cell survival, and c-Jun N-terminal kinase (JNK) and caspase-dependent cell death, regulating vascular endothelial cell (EC) activation and apoptosis. However, signaling by the second receptor, TNFR2, is poorly understood. The goal of this study was to dissect how TNFR2 mediates NF-κB and JNK signaling in vascular EC, and its relevance to in vivo EC function.

METHODS AND RESULTS

We show that TNFR2 contributes to TNF-induced NF-κB and JNK signaling in EC as TNFR2 deletion or knockdown reduces the TNF responses. To dissect the critical domains of TNFR2 that mediate the TNF responses, we examine the activity of TNFR2 mutant with a specific deletion of the TNFR2 intracellular region, which contains conserved domain I, domain II, domain III, and 2 TNFR-associated factor-2-binding sites. Deletion analyses indicate that different sequences on TNFR2 have distinct roles in NF-κB and JNK activation. Specifically, deletion of the TNFR-associated factor-2-binding sites (TNFR2-59) diminishes the TNFR2-mediated NF-κB, but not JNK activation; whereas, deletion of domain II or domain III blunts TNFR2-mediated JNK but not NF-κB activation. Interestingly, we find that the TNFR-associated factor-2-binding sites ensure TNFR2 on the plasma membrane, but the di-leucine LL motif within the domain II and aa338-355 within the domain III are required for TNFR2 internalization as well as TNFR2-dependent JNK signaling. Moreover, domain III of TNFR2 is responsible for association with ASK1-interacting protein-1, a signaling adaptor critical for TNF-induced JNK signaling. While TNFR2 containing the TNFR-associated factor-2-binding sites prevents EC cell death, a specific activation of JNK without NF-κB activation by TNFR2-59 strongly induces caspase activation and EC apoptosis.

CONCLUSIONS

Our data reveal that both internalization and ASK1-interacting protein-1 association are required for TNFR2-dependent JNK and apoptotic signaling. Controlling TNFR2-mediated JNK and apoptotic signaling in EC may provide a novel strategy for the treatment of vascular diseases.

The presence of high level soluble herpes virus entry mediator in sera of gastric cancer patients

The development of gastric cancer (GC) is closely related to chronic inflammation caused by Helicobacter pylori infection, and herpes virus entry mediator (HVEM) is a receptor expressed on the surface of leukocytes that mediates potent inflammatory responses in animal models. However, the role of HVEM in human GC has not been studied. Previously, we showed that the interaction of HVEM on human leukocytes with its ligand LIGHT induces intracellular calcium mobilization, which results in inflammatory responses including induction of proinflammatory cytokine production and anti-bacterial activities. In this study, we report that leukocytes from GC patients express lower levels of membrane HVEM (mHVEM) and have lower LIGHT-induced bactericidal activities than those from healthy controls (HC). In contrast, levels of soluble HVEM (sHVEM) in the sera of GC patients were significantly higher than in those of HC. We found that monocyte membrane-bound HVEM is released into the medium when cells are activated by proinflammatory cytokines such as TNF-α and IL-8, which are elevated in the sera of GC patients. mHVEM level dropped in parallel with the release of sHVEM, and release was completely blocked by the metalloprotease inhibitor, GM6001. We also found that the low level of mHVEM on GC patient leukocytes was correlated with low LIGHT-induced bactericidal activities against H. pylori and S. aureus and production of reactive oxygen species. Our results indicate that mHVEM on leukocytes and sHVEM in sera may contribute to the development and/or progression of GC.

Fas ligand-Fas signaling participates in light-induced apoptotic death in photoreceptor cells

PURPOSE

We investigated the function of Fas in photoreceptors.

METHODS

Postmortem human eyes and mouse-derived photoreceptor cells (661W) were examined for Fas expression by in situ hybridization and immunofluorescence. 661W cells were treated with FasL or Fas agonistic antibody, or exposed to light with/without pharmacological manipulation of Fas signaling, followed by apoptosis detection by TUNEL, immunofluorescence and fluorescence activated cell scanning (FACS). Fractionated cellular extracts were used to detect protein expression or protein phosphorylation after immunoprecipitation by Western blot.

RESULTS

Fas was expressed in the photoreceptor layer of human retina. Fas and a cleaved form of FasL were found on the cell surface of 661W cells. Treatment with FasL or Fas agonistic antibody induced apoptosis in 661W cells. Blocking the activity of FasL or administration of caspase-8 inhibitor z-IETD inhibited light-induced apoptosis. However, it simultaneously caused induction of necroptosis, which could be blocked by the receptor-interacting protein 1 (RIP1) inhibitor, necrostatin-1. Light exposure in the presence of z-IETD caused hyper-phosphorylation of RIP1. Light exposure did not elevate the expression of Fas, FasL, or the Fas-associated death domain adaptor protein (FADD). Cells or conditioned medium after light exposure induced apoptosis in dark-adapted cells, which could be attenuated by blockade of Fas.

CONCLUSIONS

Fas has a pro-apoptotic role in photoreceptors. Under light stress, soluble and membrane-bound FasL can bind to Fas, inducing apoptosis via a paracrine mechanism. Although blocking Fas signaling inhibits apoptosis, it does not improve the overall photoreceptor survival due to a compensatory activation of necroptosis. Hence, prevention of photoreceptor loss from retinal photo-oxidative stress should target Fas and RIP1.

Suppression of Akt/Foxp3-mediated miR-183 expression blocks Sp1-mediated ADAM17 expression and TNFα-mediated NFκB activation in piceatannol-treated human leukemia U937 cells

To address the mechanism of piceatannol in inhibiting TNFα-mediated pathway, studies on piceatannol-treated human leukemia U937 cells were conducted. Piceatannol treatment reduced TNFα shedding and NFκB activation and decreased the release of soluble TNFα into the culture medium of U937 cells. Moreover, ADAM17 expression was down-regulated in piceatannol-treated cells. Over-expression of ADAM17 abrogated the ability of piceatannol to suppress TNFα-mediated NFκB activation. Piceatannol-evoked β-TrCP up-regulation promoted Sp1 degradation, thus reducing transcriptional level of ADAM17 gene in U937 cells. Piceatannol treatment induced p38 MAPK phosphorylation but inactivation of Akt and ERK. In contrast to p38 MAPK inhibitor or restoration of ERK activation, transfection of constitutive active Akt abolished the effect of piceatannol on β-TrCP, Sp1 and ADAM17 expression. Piceatannol-elicited down-regulation of miR-183 expression was found to cause β-TrCP up-regulation. Inactivation of Akt resulted in Foxp3 down-regulation and reduced miR-183 expression in piceatannol-treated cells. Knock-down of Foxp3 and chromatin immunoprecipitating revealed that Foxp3 genetically regulated transcription of miR-183 gene. Taken together, our data indicate that suppression of Akt/Foxp3-mediated miR-183 expression blocks Sp1-mediated ADAM17 expression in piceatannol-treated U937 cells. Consequently, piceatannol suppresses TNFα shedding, leading to inhibition of TNFα/NFκB pathway.

LPS-induced release of IL-6 from glia modulates production of IL-1β in a JAK2-dependent manner

BACKGROUND

Compelling evidence has implicated neuroinflammation in the pathogenesis of a number of neurodegenerative conditions. Chronic activation of both astrocytes and microglia leads to excessive secretion of proinflammatory molecules such as TNF α, IL-6 and IL-1 β with potentially deleterious consequences for neuronal viability. Many signaling pathways involving the mitogen-activated protein kinases (MAPKs), nuclear factor κ B (NF κ B) complex and the Janus kinases (JAKs)/signal transducers and activators of transcription (STAT)-1 have been implicated in the secretion of proinflammatory cytokines from glia. We sought to identify signaling kinases responsible for cytokine production and to delineate the complex interactions which govern time-related responses to lipopolysaccharide (LPS).

METHODS

We examined the time-related changes in certain signaling events and the release of proinflammatory cytokines from LPS-stimulated co-cultures of astrocytes and microglia isolated from neonatal rats.

RESULTS

TNF α was detected in the supernatant approximately 1 to 2 hours after LPS treatment while IL-1 β and IL-6 were detected after 2 to 3 and 4 to 6 hours, respectively. Interestingly, activation of NF κ B signaling preceded release of all cytokines while phosphorylation of STAT1 was evident only after 2 hours, indicating that activation of JAK/STAT may be important in the up-regulation of IL-6 production. Additionally, incubation of glia with TNF α induced both phosphorylation of JAK2 and STAT1 and the interaction of JAK2 with the TNF α receptor (TNFR1). Co-treatment of glia with LPS and recombinant IL-6 protein attenuated the LPS-induced release of both TNF α and IL-1 β while potentiating the effect of LPS on suppressor of cytokine signaling (SOCS)3 expression and IL-10 release.

CONCLUSIONS

These data indicate that TNF α may regulate IL-6 production through activation of JAK/STAT signaling and that the subsequent production of IL-6 may impact on the release of TNF α, IL-1 β and IL-10.

Transgenic expression of human heme oxygenase-1 in pigs confers resistance against xenograft rejection during ex vivo perfusion of porcine kidneys

BACKGROUND

The major immunological hurdle to successful porcine-to-human xenotransplantation is the acute vascular rejection (AVR), characterized by endothelial cell (EC) activation and perturbation of coagulation. Heme oxygenase-1 (HO-1) and its derivatives have anti-apoptotic, anti-inflammatory effects and protect against reactive oxygen species, rendering HO-1 a promising molecule to control AVR. Here, we report the production and characterization of pigs transgenic for human heme oxygenase-1 (hHO-1) and demonstrate significant protection in porcine kidneys against xenograft rejection in ex vivo perfusion with human blood and transgenic porcine aortic endothelial cells (PAEC) in a TNF-α-mediated apoptosis assay.

METHODS

Transgenic and non-transgenic PAEC were tested in a TNF-α-mediated apoptosis assay. Expression of adhesion molecules (ICAM-1, VCAM-1, and E-selectin) was measured by real-time PCR. hHO-1 transgenic porcine kidneys were perfused with pooled and diluted human AB blood in an ex vivo perfusion circuit. MHC class-II up-regulation after induction with IFN-γ was compared between wild-type and hHO-1 transgenic PAEC.

RESULTS

Cloned hHO-1 transgenic pigs expressed hHO-1 in heart, kidney, liver, and in cultured ECs and fibroblasts. hHO-1 transgenic PAEC were protected against TNF-α-mediated apoptosis. Real-time PCR revealed reduced expression of adhesion molecules like ICAM-1, VCAM-1, and E-selectin. These effects could be abrogated by the incubation of transgenic PAECs with the specific HO-1 inhibitor zinc protoporphorine IX (Zn(II)PPIX, 20 μm). IFN-γ induced up-regulation of MHC class-II molecules was significantly reduced in PAECs from hHO-1 transgenic pigs. hHO-1 transgenic porcine kidneys could successfully be perfused with diluted human AB-pooled blood for a maximum of 240 min (with and without C1 inh), while in wild-type kidneys, blood flow ceased after ∼60 min. Elevated levels of d-Dimer and TAT were detected, but no significant consumption of fibrinogen and antithrombin was determined. Microthrombi could not be detected histologically.

CONCLUSIONS

These results are encouraging and warrant further studies on the biological function of heme oxygenase-I expression in hHO-1 transgenic pigs in the context of xenotransplantation.

Behçet's disease: immunological relevance with arthritis of ankylosing spondylitis

Behçet's disease (BD) is a multi-system inflammatory disorder, in which cytokine balance is polarized to Th1. In this study, the cell surface molecule expression, Th1/Th2, inflammatory cytokine levels in blood, and synovial fluid of CD3(+) T lymphocytes in BD were investigated. The study group consisted of 10 BD, 10 ankylosing spondylitis (AS) patients with peripheral arthritis, and 10 healthy subjects. Expression of cell surface molecules, intracellular IL-2, IL-5, IL-8, IL-10, IL-12, IFN-γ, and TNF-α levels in CD3(+) T lymphocytes were determined by flow cytometry in synovial and peripheral blood mononuclear cells (PBMCs). Synovial and plasma cytokine levels were measured by ELISA and CBA. In PBMCs, CD4, CD25, HLA-DR expression and intracellular IL-12, and TNF-α levels of CD3(+) T lymphocytes were statistically increased in BD patients compared to healthy subjects. Compare to AS patients, CD25 and HLA-DR surface expression and intracellular IFN-γ and TNF-α levels in T cells were significantly elevated in BD patients. In BD patients, there was an increase in IL-8 secretion; however, in AS patients, both Th1- and Th2-type cytokines were increased compare to healthy subjects. Intracellular cytokine expression did not show any difference in BD patients; however, IL-12 content of synovial fluid was significantly increased compared to AS patients. Our findings revealed that Th1 polarization occurred in both peripheral blood and synovial fluid of BD patients with arthritis. It is found no difference between synovial fluid analysis of BD and AS patients, showing the similarities in the pathogenesis of both diseases.

Polyploid cells rewire DNA damage response networks to overcome replication stress-induced barriers for tumour progression

Mutations in genes involved in DNA replication, such as flap endonuclease 1 (FEN1), can cause single-stranded DNA breaks (SSBs) and subsequent collapse of DNA replication forks leading to DNA replication stresses. Persistent replication stresses normally induce p53-mediated senescence or apoptosis to prevent tumour progression. It is unclear how some mutant cells can overcome persistent replication stresses and bypass the p53-mediated pathways to develop malignancy. Here we show that polyploidy, which is often observed in human cancers, leads to overexpression of BRCA1, p19arf and other DNA repair genes in FEN1 mutant cells. This overexpression triggers SSB repair and non-homologous end-joining pathways to increase DNA repair activity, but at the cost of frequent chromosomal translocations. Meanwhile, DNA methylation silences p53 target genes to bypass the p53-mediated senescence and apoptosis. These molecular changes rewire DNA damage response and repair gene networks in polyploid tumour cells, enabling them to escape replication stress-induced senescence barriers.

Systematic review: antibodies and anti-TNF-α levels in inflammatory bowel disease

BACKGROUND

The associations between clinical efficacy and infusion reactions with anti-TNF-α drug levels and the presence of antibodies against the drug have been described. However, the clinical utility of these tests in routine clinical practice remains unclear.

AIMS

To examine the clinical significance of the development of antibodies against anti-TNF-α drugs and the relationship between the efficacy of these drugs and their serum levels. We also studied the clinical utility of testing for anti-TNF-α antibodies and measuring drug serum levels to optimise treatment of patients with inflammatory bowel disease (IBD) receiving these agents.

METHODS

A systematic review was undertaken based on electronic searches of the PubMed database from the earliest record to February 2012. The reference lists of all relevant articles and abstracts from meetings were also consulted.

RESULTS

We observed a close relationship between trough levels of anti-TNF-α drug and maintenance of response to these drugs. The role of antibodies in loss of response seems to be limited to their effect favouring the clearance of the drug. The risk of infusion reactions, but not of delayed hypersensitivity reactions, is higher in patients with antibodies against the anti-TNF-α drug. Testing anti-TNF-α drug and antibody levels, together with clinical and endoscopic or radiological assessment, seems useful when attempting to optimise therapy and prevent inappropriate management of IBD patients.

CONCLUSION

Measurement of serum anti-TNF-α trough levels and antibody titres could prove useful in therapeutic drug monitoring in IBD patients treated with anti-TNF-α agents.

The seventh ring: exploring TRAF7 functions

Tumor necrosis factor receptor-associated factors (TRAFs) have been discovered and characterized by their capacity to link tumor necrosis factor receptors (TNFR) family proteins to signaling pathways that transduce the cellular effects mediated by TNF family ligands. There are seven known mammalian TRAF proteins (TRAF1-7), that share a domain organization made of a modular structure, characteristic of adaptor proteins whose function is to link structurally dissimilar factors. Functionally, TRAF proteins mediate the assembly of cytoplasmic signal transducers and regulatory molecules downstream of receptors complexes. Despite the similarities in the signaling pathways activated by the different TRAF proteins, each appears to play distinct physiological roles. TRAF7 is the last member of the TRAF family that has been identified. Yet, the functional characterization of TRAF7 presents some aspects still obscure and poorly defined, making this protein arguably the most mysterious member of the family. In fact, recent data indicate that TRAF7 is involved in signal transduction pathways that lead either to activation or repression of NF-κB transcription factor. In addition, TRAF7 regulates activation of cellular stress pathways, as well as unconventional ubiquitination events and differentiation of muscle tissue. In this review, we try to summarize the most recent advances in our understanding of TRAF7 function and the biological processes of this protein is involved in.

Contribution of TNF receptor 1 to retinal neural cell death induced by elevated glucose

Diabetic retinopathy (DR), a leading cause of vision loss and blindness among working-age adults, holds several hallmarks of an inflammatory disease. The increase in cell death in neural retina is an early event in the diabetic retina, preceding the loss of microvascular cells. Since tumor necrosis factor-α (TNF-α) has been shown to trigger the death of perycites and endothelial cells as well as the breakdown of the blood-retinal barrier, we set out to investigate whether TNF-α acting through tumor necrosis factor receptor 1 (TNFR1), the major receptor responsible for mediating TNF-induced cell death, could also be responsible for the early neuronal cell death observed in DR. We used retinal neural cell cultures exposed to high glucose conditions, to mimic hyperglycaemia, and evaluated the contribution of TNFR1 in neural cell death. TNFR1 was found to be present to a great extent in retinal neurons and the levels of this receptor were found to be altered in cells cultured in high glucose conditions. High glucose induced an early decrease in cell viability, an increase in apoptosis and a higher immunoreactivity for the cleaved caspase-3, indicating a high glucose-induced caspase-dependent cell death. These observations were correlated with an increase in TNF-α expression. Nonetheless, inhibiting the activation of TNFR1 was sufficient to prevent the decrease in cell viability and the increase in retinal cell death by apoptosis. In conclusion, our data indicate that TNF-α acting through TNFR1 is responsible for the high glucose-induced cell death and that blocking the activity of this receptor is an adequate strategy to avoid cell loss in such conditions.

Inflammatory bone loss: pathogenesis and therapeutic intervention

Bone is a tissue undergoing continuous building and degradation. This remodelling is a tightly regulated process that can be disturbed by many factors, particularly hormonal changes. Chronic inflammation can also perturb bone metabolism and promote increased bone loss. Inflammatory diseases can arise all over the body, including in the musculoskeletal system (for example, rheumatoid arthritis), the intestine (for example, inflammatory bowel disease), the oral cavity (for example, periodontitis) and the lung (for example, cystic fibrosis). Wherever inflammatory diseases occur, systemic effects on bone will ensue, as well as increased fracture risk. Here, we discuss the cellular and signalling pathways underlying, and strategies for therapeutically interfering with, the inflammatory loss of bone.

The role of endoscopic ultrasonography in the diagnosis and management of pancreatic cancer

EUS with FNA is highly sensitive and specific for diagnosing pancreatic cancer. However, in certain situations, such as in patients with chronic pancreatitis, this high sensitivity and specificity can significantly diminish. The use of new technology, such as EUS elastography, CE-EUS, and gene mutations detection in FNA specimens, can help to differentiate chronic pancreatitis from pancreatic cancer. EUS has evolved from a diagnostic procedure to a therapeutic intervention in pancreatic cancer. EUS-guided fiducial insertion and EUS-guided delivery of antitumor agents, in addition to celiac plexus neurolysis, are the main therapeutic applications of EUS in pancreatic cancer.

Signal transduction by tumor necrosis factor receptors

Tumor necrosis factor (TNF) is a key mediator in the inflammatory response which is implicated in the onset of a number of diseases. Research on TNF led to the characterization of the largest family of cytokines known until now, the TNF superfamily, which exert their biological effects through the interaction with transmembrane receptors of the TNFR superfamily. TNF itself exerts its biological effects interacting with two different receptors: TNFR1 and TNFR2. TNFR1 presents a death domain on its intracellular region. In contrast to TNFR1, TNFR2 does not have a death domain. Activation of TNFR1 implies the consecutive formation of two different TNF receptor signalling complexes. Complex I controls the expression of antiapoptotic proteins that prevent the triggering of cell death processes, whereas Complex II triggers cell death processes. TNFR2 only signals for antiapoptotic reactions. However, recent evidence indicates that TNFR2 also signals to induce TRAF2 degradation. TRAF2 is a key mediator in signal transduction of both TNFR1 and TNFR2. Thus, this novel signalling pathway has two important implications: on one hand, it represents an auto regulatory loop for TNFR2; on the other hand, when this signal is triggered TNFR1 activity is modified so that antiapoptotic pathways are inhibited and apoptotic reactions are enhanced.

Switching from aerobic glycolysis to oxidative phosphorylation modulates the sensitivity of mantle cell lymphoma cells to TRAIL

TRAIL (TNF (tumour necrosis factor)-related apoptosis-inducing ligand) a putative anti-cancer cytokine induces apoptosis through DISC (death-inducing signalling complex)-mediated activation of caspase-8 and/or cleavage of Bid. TRAIL is relatively specific for tumour cells but primary chronic lymphocytic leukaemia and mantle cell lymphoma (MCL) cells are resistant. Herein, we show that cellular metabolism influences cell death and that MCL cells (Z138 cell line) can survive/proliferate in glucose-free media by switching from aerobic glycolysis to 'coupled' oxidative phosphorylation. Extracellular flux analysis and mitochondrial inhibitors reveal that in the absence of glycolysis, Z138 cells have enhanced respiratory capacity coupled to ATP synthesis, similar to 'classical' state 3 mitochondria. Conversely, 2-deoxyglucose (2DG) blocked glycolysis and partially inhibited glycolytic-dependent oxidative phosphorylation, resulting in a 50% reduction in cellular ATP levels. Also, 2DG sensitised Z138 cells to TRAIL and induced a marked decrease in caspase-8, -3, cFLIP(S), Bid and Mcl-1 expression but Bak remained unchanged, altering the Mcl-1/Bak ratio, facilitating cytochrome c release and cell death. Conversely, under glucose-free conditions, Z138 cells were less sensitive to TRAIL with reduced TRAIL-R1/R2 surface receptor expression and impaired DISC formation. Anti-apoptotic proteins Bcl-2 and XIAP were up-regulated while pro-apoptotic BAX was down-regulated. Additionally, mitochondria had higher levels of cytochrome c and ultrastucturally exhibited a condensed configuration with enhanced intracristal spaces. Thus, metabolic switching was accompanied by mitochondrial proteome and ultrastructural remodelling enabling enhanced respiration activity. Cytochrome c release was decreased in glucose-free cells, suggesting that either pore formation was inhibited or that cytochrome c was more tightly bound. Glucose-free Z138 cells were also resistant to intrinsic cell death stimuli (ABT-737 and ionising radiation). In summary, in MCL cells, the anti-glycolytic effects of 2DG and glucose restriction produced opposite effects on TRAIL-induced cell death, demonstrating that mitochondrial metabolism directly modulates sensitivity of tumour cells to apoptosis.

CCR5 deficiency mitigates the deleterious effects of tumor necrosis factor α antagonism in murine histoplasmosis

In murine histoplasmosis, tumor necrosis factor α (TNF-α) antagonism increases the number of regulatory T cells (Tregs) in lungs, and these cells profoundly hinder protective immunity. Because CCR5 mediates Treg homing and proliferation, we determined the outcome of antagonizing TNF-α in CCR5(-/)(-) mice infected with Histoplasma capsulatum. The absence of CCR5 attenuated the severity of infection associated with TNF-α neutralization. Infected controls given anti-TNF-α had a 10-fold increase in the number of Tregs in lungs compared with a <2-fold increase in CCR5(-/)(-) lungs. This difference was partially attributable to impaired homing in the absence of CCR5. Neutralization of TNF-α-enhanced CCR5 ligands in wild-type lungs thus promotes a gradient between lungs and the thymus. This study elucidates the interplay between TNF-α and CCR5 in histoplasmosis. The data suggest that targeting CCR5 may improve host immunity in individuals receiving TNF-α antagonists during infection.

Effects of continuous erythropoietin receptor activator in sepsis-induced acute kidney injury and multi-organ dysfunction

BACKGROUND

Despite advances in supportive care, sepsis-related mortality remains high, especially in patients with acute kidney injury (AKI). Erythropoietin can protect organs against ischemia and sepsis. This effect has been linked to activation of intracellular survival pathways, although the mechanism remains unclear. Continuous erythropoietin receptor activator (CERA) is an erythropoietin with a unique pharmacologic profile and long half-life. We hypothesized that pretreatment with CERA would be renoprotective in the cecal ligation and puncture (CLP) model of sepsis-induced AKI.

METHODS

RATS WERE RANDOMIZED INTO THREE GROUPS: control; CLP; and CLP+CERA (5 µg/kg body weight, i.p. administered 24 h before CLP). At 24 hours after CLP, we measured creatinine clearance, biochemical variables, and hemodynamic parameters. In kidney tissue, we performed immunoblotting--to quantify expression of the Na-K-2Cl cotransporter (NKCC2), aquaporin 2 (AQP2), Toll-like receptor 4 (TLR4), erythropoietin receptor (EpoR), and nuclear factor kappa B (NF-κB)--and immunohistochemical staining for CD68 (macrophage infiltration). Plasma interleukin (IL)-2, IL-1β, IL-6, IL-10, interferon gamma, and tumor necrosis factor alpha were measured by multiplex detection.

RESULTS

Pretreatment with CERA preserved creatinine clearance and tubular function, as well as the expression of NKCC2 and AQP2. In addition, CERA maintained plasma lactate at normal levels, as well as preserving plasma levels of transaminases and lactate dehydrogenase. Renal expression of TLR4 and NF-κB was lower in CLP+CERA rats than in CLP rats (p<0.05 and p<0.01, respectively), as were CD68-positive cell counts (p<0.01), whereas renal EpoR expression was higher (p<0.05). Plasma levels of all measured cytokines were lower in CLP+CERA rats than in CLP rats.

CONCLUSION

CERA protects against sepsis-induced AKI. This protective effect is, in part, attributable to suppression of the inflammatory response.

Role of tumour necrosis factor (TNF)-α and TNFRSF1A R92Q mutation in the pathogenesis of TNF receptor-associated periodic syndrome and multiple sclerosis

It has long been known that tumour necrosis factor (TNF)/TNFRSF1A signalling is involved in the pathophysiology of multiple sclerosis (MS). Different genetic and clinical findings over the last few years have generated renewed interest in this relationship. This paper provides an update on these recent findings. Genome-wide association studies have identified the R92Q mutation in the TNFRSF1A gene as a genetic risk factor for MS (odds ratio 1·6). This allele, which is also common in the general population and in other inflammatory conditions, therefore only implies a modest risk for MS and provides yet another piece of the puzzle that defines the multiple genetic risk factors for this disease. TNFRSF1A mutations have been associated with an autoinflammatory disease known as TNF receptor-associated periodic syndrome (TRAPS). Clinical observations have identified a group of MS patients carrying the R92Q mutation who have additional TRAPS symptoms. Hypothetically, the co-existence of MS and TRAPS or a co-morbidity relationship between the two could be mediated by this mutation. The TNFRSF1A R92Q mutation behaves as a genetic risk factor for MS and other inflammatory diseases, including TRAPS. Nevertheless, this mutation does not appear to be a severity marker of the disease, neither modifying the clinical progression of MS nor its therapeutic response. An alteration in TNF/TNFRS1A signalling may increase proinflammatory signals; the final clinical phenotype may possibly be determined by other genetic or environmental modifying factors that have not yet been identified.

Initiation but no execution - modulation of peripheral blood lymphocyte apoptosis in rheumatoid arthritis - a potential role for heat shock protein 70

Background

Rheumatoid arthritis (RA) is a chronic autoimmune disease, which causes synovial damage. Persistence of lymphocyte infiltrates in the rheumatoid synovium has been attributed to abnormal apoptosis. While not comprehensively investigated, perturbations in peripheral blood lymphocyte (PBL) apoptosis may also be involved in perpetuation of autoimmune processes in RA.

Methods

We investigated total, CD4+ and CD19+ PBL apoptosis in our study cohort by monitoring the translocation of phosphatidylserine using the Annexin-V assay. To examine the role of death receptor mediated apoptosis as well as activation-induced-cell-death (AICD), PBLs were labeled with CD95/Fas and CD69 markers and enumerated by flow cytometry. Proteolytic activity of initiator and executioner caspases was determined by luminometry. DNA fragmentation assays were used to examine whether apoptotic signals were transduced to the nucleus. Quantitative PCR arrays were used to investigate apoptotic pathways associated with RA-PBLs. Since heat-shock-protein-70 (HSP70) is an inducible protein which modulates apoptotic signals, we determined HSP70 levels by intra-cellular flow cytometry and western blots.

Results

The RA-PBLs showed signs of elevated apoptosis whilst in circulation. These include increases in the loss of plasma membrane asymmetry, indicated by increased externalization of phosphatidylserine (especially in B-lymphocytes). RA-PBLs showed a bias to CD95/Fas mediated apoptotic pathways, but low levels of the CD69 marker suggested that this was not associated with immune activation. Although downstream markers of apoptosis such as caspase-3/7 activity, were increased, no DNA fragmentation was observed in RA-PBLs. Interestingly, elevated levels of apoptosis did not correlate with absolute lymphocyte counts in RA patients. Levels of HSP70 were highly elevated in RA-PBLs compared to controls.

Conclusion

The results suggest that while apoptosis may be initiated in RA-PBLs, they may lack commitment to fully executing the apoptotic program. This may be related to inhibition on apoptotic transduction by HSP70. This study provides evidence that abnormalities in RA-PBLs apoptosis may occur whilst still in circulation and may contribute to pathogenesis of the disease.