TNF-alpha Binding Research Articles

Circulating Endothelial Progenitor Cells Present an Inflammatory Phenotype and Function in Patients With Alcoholic Liver Cirrhosis.

Background and Aim: Endothelial progenitor cells (EPCs) have been implicated in liver injury and repair. However, the phenotype and potential of these heterogenous EPCs remain elusive. In particular, their involvement in the pathogenesis of alcoholic liver cirrhosis (ALC) remains unclear. The current study extensively characterized the phenotype and functions of EPCs to understand their role in ALC pathogenesis.Methods: Circulating EPCs were identified as CD34+CD133+CD31+ cells by flow cytometer in ALC patients (n = 7) and healthy controls (HC, n = 7). A comprehensive characterization of circulating EPCs using more than 30 phenotype markers was performed by mass cytometer time of flight (CyTOF) in an independent cohort of age and gender matched ALC patients (n = 4) and controls (n = 5). Ex vivo cultures of circulating EPCs from ALC patients (n = 20) and controls (n = 18) were also tested for their functions, including colony formation, LDL uptake, lectin binding and cytokine secretion (ELISA).Results: Three distinct populations of circulating EPCs (CD34+CD133+CD31+) were identified, classified on their CD45 expression (negative: CD45−; intermediate: CD45int; high: CD45hi). CD45int and CD45hi EPCs significantly increased in ALC patients compared to controls (p-val = 0.006). CyTOF data showed that CD45hi EPCs were distinct from CD45− and CD45int EPCs, with higher expression of T cell and myeloid markers, including CD3, CD4, HLA-DR, and chemokine receptors, CCR2, CCR5, CCR7, and CX3CR1. Similar to circulating EPCs, percentage of CD45hiCD34+CD31+ EPCs in ex-vivo cultures from patients, were significantly higher compared to controls (p < 0.05). Cultured EPCs from patients also showed increased LDL uptake, lectin binding and release of TNF-alpha, RANTES, FGF-2, and VEGF.Conclusions: We report the first extensive characterization of circulating human EPCs with distinct EPC subtypes. Increase in CD45hi EPC subtype in ALC patients with enhanced functions, inflammatory cytokines and angiogenic mediators in patients suggests an inflammatory role for these cells in ALC.

B cell epitopes on infliximab identified by oligopeptide microarray with unprocessed patient sera

BackgroundAutoimmune diseases like rheumatoid arthritis and inflammatory bowel disease are treated with TNF-alpha-blocking antibodies such as infliximab and adalimumab. A common side effect of therapeutic antibodies is the induction of anti-drug antibodies, which may reduce therapeutic efficacy.MethodsIn order to reveal immunogenic epitopes on infliximab which are responsible for the adverse effects, sera from patients treated with infliximab were screened by ELISA for anti-infliximab antibodies. Sera containing high levels of anti-drug-antibodies (>1.25 µg/ml) were analyzed in an oligopeptide microarray system containing immobilized 15-meric oligopeptides from the infliximab amino acid sequence. Immunogenic infliximab IgG-epitopes were identified by infrared fluorescence scanning and comparison of infliximab-treated patients versus untreated controls.ResultsSix relevant epitopes on infliximab were recognized by the majority of all patient sera: 4 in the variable and 2 in the constant region. Three of the epitopes in the variable region are located in the TNF-alpha binding region of infliximab. The fourth epitope of the variable part of infliximab is located close to the TNF-alpha binding region and contains an N-glycosylation sequon. The sera positive for anti-infliximab antibodies do not contain antibodies against adalimumab as determined by ELISA. Thus, there is no infliximab–adalimumab cross-reactivity as determined by these systems.ConclusionsOur data shall contribute to a knowledge-based recommendation for a potentially necessary therapy switch from infliximab to another type of TNF-alpha-blocker. The characterization of immunogenic epitopes on therapeutic monoclonal antibodies using unprocessed patient sera shall lead to direct translational aspects for the development of less immunogenic therapeutic antibodies. Patients benefit from less adverse events and longer lasting drug effects.

Three TNFR-binding domains of PGRN act independently in inhibition of TNF-alpha binding and activity.

PGRN was previously reported to bind to TNF receptors (TNFR) and is therapeutic against inflammatory arthritis. Here we present further evidences demonstrating the PGRN inhibition of TNF-alpha binding and activity, and clarifying the distinct mechanisms underlying TNF-alpha inhibition between PGRN and classic TNF-alpha-binding inhibitors. In addition, we present evidences indicating that three TNFR binding domains of PGRN act independently in binding to TNFR. Furthermore, changing the order of three TNFR-binding domains in Atsttrin, a PGRN-derived molecule composed of these TNFR-binding domains, does not affect its anti-inflammatory and anti-TNF activities in both collagen-induced inflammatory arthritis and human TNF-alpha transgenic mouse model. Taken together, these findings provide the additional molecular basis underlying PGRN/TNFR interaction and PGRN-mediated anti-inflammatory activity in various inflammatory diseases and conditions.

Cutaneous side-effects related to treatment with infliximab

Infliximab, a chimeric human-mouse anti-tumor necrosis factor (TNF)-alpha monoclonal antibody, can inhibit the binding of TNF-alpha with its soluble and membrane receptor and inactivate TNF-alpha. Clinically, it has been used to treat TNF-alpha-associated diseases. However, it may cause the development of infection, psoriasis, lupus erythematosus, atopic dermatitis and skin neoplasms during the treatment of ankylosing spondylitis, rheumatoid arthritis and other diseases. This article describes skin manifestations related to treatment with infliximab so as to remind clinicians to pay attention to the association between skin diseases and infliximab. Key words: Skin diseases; Infliximab; Tumor necrosis factor-alpha

Lensfree holographic imaging of antibody microarrays for high-throughput detection of leukocyte numbers and function.

Characterization of leukocytes is an integral part of blood analysis and blood-based diagnostics. In the present paper, we combine lensless holographic imaging with antibody microarrays for rapid and multiparametric analysis of leukocytes from human blood. Monoclonal antibodies (Abs) specific for leukocyte surface antigens (CD4 and CD8) and cytokines (TNF-alpha, IFN-gamma, IL-2) were printed in an array so as to juxtapose cell capture and cytokine detection antibody (Ab) spots. Integration of Ab microarrays into a microfluidic flow chamber (4 muL volume) followed by incubation with human blood resulted in capture of CD4 and CD8 T-cells on specific Ab spots. On-chip mitogenic activation of these cells induced release of cytokine molecules that were subsequently captured on neighboring anticytokine Ab spots. The binding of IL-2, TNF-alpha, and IFN-gamma molecules on their respective Ab spots was detected using horseradish peroxidase (HRP)-labeled anticytokine Abs and a visible color reagent. Lensfree holographic imaging was then used to rapidly ( approximately 4 s) enumerate CD4 and CD8 T-lymphocytes captured on Ab spots and to quantify the cytokine signal emanating from IL-2, TNF-alpha, and IFN-gamma spots on the same chip. To demonstrate the utility of our approach for infectious disease monitoring, blood samples of healthy volunteers and human immunodeficiency virus (HIV)-infected patients were analyzed to determine the CD4/CD8 ratio, an important HIV/AIDS diagnostic marker. The ratio obtained by lensfree on-chip imaging of CD4 and CD8 T-cells captured on Ab spots was in close agreement with conventional microscopy-based cell counting. The present paper, describing tandem use of Ab microarrays and lensfree holographic imaging, paves the way for future development of miniature cytometry devices for multiparametric blood analysis at the point of care or in a resource-limited setting.

Generation of tumour‐necrosis‐factor‐α‐specific affibody1 molecules capable of blocking receptor binding in vitro

Affibody molecules specific for human TNF-alpha (tumour necrosis factor-alpha) were selected by phage-display technology from a library based on the 58-residue Protein A-derived Z domain. TNF-alpha is a proinflammatory cytokine involved in several inflammatory diseases and, to this day, four TNF-alpha-blocking protein pharmaceuticals have been approved for clinical use. The phage selection generated 18 unique cysteine-free affibody sequences of which 12 were chosen, after sequence cluster analysis, for characterization as proteins. Biosensor binding studies of the 12 Escherichia coli-produced and IMAC (immobilized-metal-ion affinity chromatography)-purified affibody molecules revealed three variants that demonstrated the strongest binding to human TNF-alpha. These three affibody molecules were subjected to kinetic binding analysis and also tested for their binding to mouse, rat and pig TNF-alpha. For ZTNF-alpha:185, subnanomolar affinity (KD=0.1-0.5 nM) for human TNF-alpha was demonstrated, as well as significant binding to TNF-alpha from the other species. Furthermore, the binding site was found to overlap with the binding site for the TNF-alpha receptor, since this interaction could be efficiently blocked by the ZTNF-alpha:185 affibody. When investigating six dimeric affibody constructs with different linker lengths, and one trimeric construct, it was found that the inhibition of the TNF-alpha binding to its receptor could be further improved by using dimers with extended linkers and/or a trimeric affibody construct. The potential implication of the results for the future design of affibody-based reagents for the diagnosis of inflammation is discussed.

Decrease in Tumor Necrosis Factor-α Receptor-Associated Death Domain Results from Ubiquitin-Dependent Degradation in Obstructive Renal Injury in Rats

Increased expression levels of tumor necrosis factor-alpha (TNFalpha) is involved in tubulointerstitial cell proliferation and apoptosis in obstructive renal injury. Two TNFalpha receptors (TNFRs), TNFR1 and TNFR2, are known to exist. On TNFalpha binding, TNFR1 recruits TNFR-associated death domain (TRADD), an assembly platform to mediate TNFR1 signaling. We investigated postreceptor TRADD regulation in rat kidneys with unilateral ureteral obstruction (UUO). Whereas UUO was associated with increased expression levels of TNFalpha, TNFR1, TNFR2, and TRADD mRNAs, it resulted in the marked decrease of TRADD protein levels (which appeared at day 1 and persisted thereafter) and a slight decrease in TNFR1 protein levels at days 7 and 14. Both ubiquitination and degradation of TRADD were increased in UUO kidneys, degradation of TRADD was stimulated by TNFalpha in HK-2 cells, and TRADD degradation was suppressed by proteasome inhibitor. Inhibition of TNFalpha by soluble TNFR2, etanercept, reduced significantly, although transiently, tubular and interstitial cell proliferation, fibronectin expression, and apoptosis in UUO kidneys, and also suppressed TRADD degradation. These data suggest that the decrease in TRADD resulting from enhanced ubiquitin-dependent degradation is involved in obstructive renal injury. Since TRADD is not incorporated into TNFR2-mediated TNFalpha signaling, the persistent decrease in TRADD, associated with a mild decrease in TNFR1 levels, may function, at least in part, to divert TNFalpha signals toward a TNFR2-mediated pathway in UUO kidneys.

Angiogenesis in Psoriatic Skin and its Modifications after Administration of Etanercept: Videocapillaroscopic, Histological and Immunohistochemical Evaluation

Several studies suggest that microangiopathy plays a crucial role in the pathogenesis of psoriasis. TNFalpha up-regulates the genetic transcription of VEGF, a pro-angiogenetic cytokine over-expressed in psoriatic skin, which promotes micrangiopathic modifications in psoriatic plaque. Etanercept is a chimeric protein used in the treatment of psoriasis and other immunomediated disorders, which blocks inflammatory response by interfering in the binding of TNF-alpha to its receptors. Starting from this data, we retain that etanercept can improve microangiopathy in psoriatic skin by reducing the synthesis of pro-angiogenetic chemokine VEGF. The aims of the study are: to verify the effect of etanercept on cutaneous en plaque capillaries in vivo using intra-vital videocapillaroscopy analysis, to evaluate the relation between the en plaque videocapillaroscopic pattern and the immunohistochemical cutaneous expression of VEGF in psoriasis, and finally to correlate all these in data with clinical disease activity. Eighteen patients (10 male and 8 female, mean age 51, range 21-60) suffering from stable, en plaque type psoriasis, involving at least 10 percent of body surface area (BSA), and not responsive to conventional therapy were included in the study. All the enrolled patients received etanercept 50mg/twice/week, subcutaneously, for 12 weeks, and were carefully followed up for clinical response with PASI score and DLQI index both before (T0) and after 12 weeks (T12) of treatment with etanercept. A well demarcated psoriatic plaque of the extensor surface of upper extremities was chosen to perform an intra-vital videocapillaroscopy analysis (IVCP), and a skin biopsy for immunohistochemical study both at T0 and T12 in all the included patients, in order to evaluate the presence of microangiopathy and its modification after therapy. All the patients experienced a clinical improvement of cutaneous disease with a significant decrease of PASI score (p<0.0001) and DLQI level (p<0.0001), throughout the twelve weeks of treatment. On IVCP analysis, microangiopathy dramatically decreased (p<0.0001), this modification being significantly related with PASI and DLQI decrease at T12. Immunohistochemical expression of VEGF decreased significantly from T0 to T12 (p<0.0001), and was related with a reduction of psoriatic microangiopathy at T12. The results of our videocapillaroscopic and immunohistochemical investigation confirm that the therapeutic potentiality of etanercept is based also on its capability to promote the regression of psoriatic microangiopathy. Moreover, according to these considerations, videocapillaroscopic evaluation of psoriatic plaque, both before and after treatment with etancercept, may be a useful tool to objectively demonstrate its effect on microcirculation.

A Synthetic Peptide Derived from A1 Module in CRD4 of Human TNF Receptor-1 Inhibits Binding and Proinflammatory Effect of Human TNF-α

Tumour necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine, which has been shown to be a causative factor in rheumatoid arthritis, inflammatory bowel disease and septic shock. Proinflammatory effect of TNF-alpha is activated mainly through human TNF receptor-1 (TNF-R1). However, the role of the fourth cystein-rich domain (CRD4) of TNF-R1 extracellular portion in the interaction of TNF-alpha with TNF-R1 is still unclear. In the present study, binding activity of TNF-alpha to TNF-R1 and protein levels of IkappaB-alpha and nuclear transcription factor kappa B (NF-kappaB) p65 subunit in HeLa cells were measured using enzyme-linked immunosorbent assay (ELISA) and western-blot analysis. Pep 3 (LRENECVS) which was derived from the hydrophilic region of A1 module in CRD4 remarkably inhibited the binding of TNF-alpha to TNF-R1, and also reversed TNF-alpha-induced degradation of IkappaB-alpha and nuclear translocation of NF-kappaB p65 subunit in HeLa cells. Our results confirmed that the hydrophilic region of A1 module in CRD4 participated in the interaction of TNF-alpha with TNF-R1, and demonstrated the potential of small-molecule TNF-alpha extracellular inhibitors targeting at A1 module in CRD4 of TNF-R1 in suppressing proinflammatory effect of TNF-alpha.

Effect of Ceramide on Mesenchymal Stem Cell Differentiation Toward Adipocytes

Proinflammatory cytokines such as tumor necrosis factor (TNF) alpha are well known to inhibit adipocyte differentiation. TNF-alpha triggers ceramide synthesis through binding of TNF-alpha to its p55 receptor. Therefore, ceramide is implicated in many of the multiple signaling pathways initiated by TNF-alpha. In breast tissue engineering, it is important to know how to modulate adipocyte differentiation of the stem cells with exogenous additives like ceramide in vitro. We hypothesized that stem cell adipogenesis could be retained in TNF-alpha-treated preadipocytes in which ceramide synthesis was blocked and that exogenous ceramide could inhibit adipocyte differentiation. We first studied the effect of ceramide synthase inhibitor, Fumonisin B2, on the adipogenesis of murine mesenchymal stem cells (D1 cells), treated with TNF-alpha. We then studied the effect of specific exogenous C6-ceramide on D1 cell viability and differentiation. It was found that 1 ng/ml of TNF-alpha significantly inhibited D1 cell adipogenesis. Cells treated with 5 microM of Fumonisin B2 were able to undergo adipogenesis, even when treated with TNF-alpha. High concentrations of exogenous C6-ceramide (>50 microM) had an inhibitory effect, not only on the pre-confluent proliferation of the D1 cells but also on the post-confluent cell viability. High concentrations of C6-ceramide (>50 microM) also inhibited mitotic clonal expansion when D1 cell differentiation was induced by the addition of an adipogenic hormonal cocktail. C6-ceramide at low concentrations (10-25 microM) inhibited lipid production in D1 cells, demonstrated by decreased levels of both total triglyceride content and specific fatty acid composition percentages. Genetic expression of peroxisome proliferator-activated receptor (PPAR) gamma and aP2 in D1 cells was reduced by C6-ceramide treatment. CCAAT/enhancer-binding protein (C/EBP) beta levels in D1 cells were reduced by C6-ceramide treatment during early differentiation; PPARgamma and aP2 protein levels were reduced at terminal differentiation. C6-ceramide at lower concentrations also decreased lipid accumulation of differentiating D1 cells. Our results suggest that ceramide synthase inhibitor retains the adipogenic potential of TNF-alpha-treated mesenchymal stem cells, while exogenous ceramide at lower concentrations inhibit the adipogenesis of mesenchymal stem cells. Ceramide, therefore, could be a modulator candidate in breast tissue engineering strategies.

Implication of cytokines: Roles of tumor necrosis factor‐α in liver injury

Acute liver failure caused by viruses, drugs, or liver resection, is marked by a massive degree of hepatocyte apoptosis and impaired hepatocyte proliferation, the mechanisms of which, however, still remain to be understood. The choice between life and death is associated with events in regulation of the immune system. The liver is continuously exposed to a large antigenic load that includes pathogens, toxins and dietary antigens. Bacterial toxins, including endotoxin and staphylococcal enterotoxin, have been implicated in the pathogenesis of multi-organ failure associated with liver damage through production of cytokines and chemokines. Inflammation involves the sequential activation of signaling pathways leading to the production of both pro- and anti-inflammatory mediators. Among pro-inflammatory mediators, tumor necrosis factor-alpha (TNF-alpha)/TNF receptor (TNFR) systems play central roles in the physiological regulation of apoptosis as well as inflammation and immunity. These pleiotropic biological effects of TNF-alpha result from its ability to initiate different intracellular signaling pathways, which induce both pro-apoptotic and anti-apoptotic molecules. Hepatocytes appear to be poorly responsive to pro-apoptotic stimuli by TNF-alpha. Tumor necrosis factor-alpha, however, induces excessive hepatocyte apoptosis, once cells are sensitized by D-galactosamine or actinomycin D, suggesting that TNF-alpha itself also induces molecules that protect cells from apoptosis by TNF-alpha. Besides the apoptosis-inducing signal, the binding of TNF-alpha to TNFR1 triggers a series of intracellular events that result in the activation of nuclear factor-kappaB (NF-kappaB), phosphatidylinositol 3-kinase (PI3K)/Akt, and c-Jun NH(2)-terminal kinase (JNK). Inhibition of NF-kappaB may be a two-edged sword against liver injury, which inhibits pro-inflammatory gene expression in leukocytes and causes the sensitization of hepatocytes to TNF-alpha-induced apoptosis. A variety of mechanisms exist to modulate the activity of intracellular molecules and thereby affect the ultimate outcome of a liver cell's fate.

Increased expression and occupancy of receptors for tumour necrosis factor on blood monocytes from tuberculosis patients.

Blood monocytes from tuberculosis patients release high amounts of tumour necrosis factor-alpha (TNF-alpha). Because the biological efficiency of TNF-alpha would depend on the expression of TNF-alpha receptors on target cells, we thought to analyse the capacity of blood monocytes from a group of patients with pulmonary tuberculosis to bind 125I-TNF-alpha. We report a slight but not significant enhancement in specific binding of 125I-TNF-alpha on monocytes of 15 consecutively studied patients compared with 10 controls. Per cent cell surface bound and internalized 125I-TNF-alpha was identical in the two groups. To evaluate the receptor occupancy by endogenously generated TNF-alpha, similar experiments were performed after cell exposure to low-pH glycine buffer. Under these conditions, specific binding of 125I-TNF-alpha was significantly higher on tuberculosis monocytes compared with control monocytes. Moreover, the occupancy of TNF-alpha receptors by endogenously generated TNF-alpha that was found to be significantly higher on tuberculosis monocytes than on control monocytes, was directly related to the enhanced capacity of mononuclear cells to generate TNF-alpha in vitro. It normalized after 3 months of antituberculous therapy. Scatchard analysis of the binding data revealed that tuberculosis infection caused a significant increase in high affinity 125I-TNF-alpha binding to monocytes without any significant change in the dissociation constant. Collectively, these results indicate an up-regulation of TNF-alpha generation and binding to blood monocytes in patients with pulmonary tuberculosis. They provide support to the hypothesis that TNF-alpha is of critical importance in the pathogenesis of this infection.

Exogenous tumor necrosis factor‐α rapidly alters synaptic and sensory transmission in the adult rat spinal cord dorsal horn

The proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) is involved in the generation of inflammatory and neuropathic pain. This study investigated if TNF-alpha has any effect on spinal synaptic and/or sensory transmission by using whole-cell recordings of substantia gelatinosa (SG) neurons in transverse lumbar spinal cord slices of adult rats and by using behavioral tests. After intrathecal administration of TNF-alpha in adult rats, spontaneous hind paw withdrawal behavior and thermal hyperalgesia were rapidly induced (approximately 30 min), while mechanical allodynia slowly developed. Bath application of TNF-alpha (0.1-1 nM, 8 min) depressed peak amplitude of monosynaptic Adelta and C fiber-evoked excitatory postsynaptic currents (EPSCs) without changing in holding currents and input resistances, whereas this application generally potentiated polysynaptic Adelta fiber-evoked EPSCs. Moreover, the frequencies, but not the amplitudes, of spontaneous and miniature EPSCs and spontaneous inhibitory postsynaptic currents were significantly increased by bath-applied TNF-alpha in most of the SG neurons. The effects of TNF-alpha on Adelta/C fiber-evoked monosynaptic and polysynaptic or spontaneous EPSCs were significantly blocked by 5 microM TNF-alpha antagonist that inhibits TNF-alpha binding to its type 1 receptor (TNFR1). Because this study also found high protein expression of TNFR1 in the adult dorsal root ganglion and no change of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) induced whole-cell currents by TNF-alpha, we conclude that presynaptic TNFR1 at Adelta/C primary afferent terminals contributes to the rapid alteration of synaptic transmission in the spinal SG, and the development of abnormal pain hypersensitivity by exogenous TNF-alpha.

Identification of the heparin-binding domain of TNF-alpha and its use for efficient TNF-alpha purification by heparin–Sepharose affinity chromatography

The N-terminus of the trimeric TNF-alpha molecule comprises two basic arginines within the short amino-acid sequence VRSSSR, which is here shown to be essential for binding of TNF-alpha to heparin–Sepharose. Mixed trimers containing full-length and ΔN6-truncated subunits revealed a single VRSSSR sequence to be sufficient to achieve binding. On the basis of this newly identified heparin-binding domain, a new method for efficient purification of TNF-alpha is described. Affinity chromatography on heparin–Sepharose was introduced as a key step for highly purified TNF-alpha at a high yield. With minor modifications, this procedure can be used for TNF-alpha analogues that have full-length N-termini, as shown for the less toxic analogue LK-805.

Tumor necrosis factor-α-induced sickness behavior is impaired by central administration of an inhibitor of c-jun N-terminal kinase

Tumor necrosis factor-alpha (TNFalpha) acts within the brain to induce sickness behavior, but the molecular mechanisms are still unknown. TNFalpha binding induces receptor trimerization, activation of c-Jun N-terminal kinase (JNK), and induction of downstream transcription factors. We hypothesized that TNFalpha-induced sickness behavior can be blocked by a novel JNK inhibitor. To test this idea, we used a bipartite protein consisting of a ten-amino-acid sequence of the trans-activating domain of the viral TAT protein (D-TAT) linked to a 19-amino-acid peptide that specifically inhibits JNK activation (D-JNKI-1). C57BL/6J mice were pre-treated intracerebroventricularly (i.c.v.) with D-JNKI-1 or the control peptide containing only the protein transduction domain, D-TAT. Mice were then injected centrally with an optimal amount of TNFalpha (50 ng/mouse) to induce sickness behavior. Sickness was assessed as a decrease in social exploration of a novel juvenile, an increase in duration of immobility and loss of body weight. Pre-treatment with D-JNKI-1 (10 ng/mouse), but not D-TAT, significantly inhibited all three indices of sickness induced by central TNFalpha. These findings demonstrate that D-JNKI-1 can abrogate TNFalpha-induced sickness behavior and suggest a potential therapeutic target for treating major depressive disorders that develop on a background of cytokine-induced sickness behavior.

A shed form of LDL receptor–related protein–1 regulates peripheral nerve injury and neuropathic pain in rodents

Injury to the peripheral nervous system (PNS) initiates a response controlled by multiple extracellular mediators, many of which contribute to the development of neuropathic pain. Schwann cells in an injured nerve demonstrate increased expression of LDL receptor-related protein-1 (LRP1), an endocytic receptor for diverse ligands and a cell survival factor. Here we report that a fragment of LRP1, in which a soluble or shed form of LRP1 with an intact alpha-chain (sLRP-alpha), was shed by Schwann cells in vitro and in the PNS after injury. Injection of purified sLRP-alpha into mouse sciatic nerves prior to chronic constriction injury (CCI) inhibited p38 MAPK activation (P-p38) and decreased expression of TNF-alpha and IL-1beta locally. sLRP-alpha also inhibited CCI-induced spontaneous neuropathic pain and decreased inflammatory cytokine expression in the spinal dorsal horn, where neuropathic pain processing occurs. In cultures of Schwann cells, astrocytes, and microglia, sLRP-alpha inhibited TNF-alpha-induced activation of p38 MAPK and ERK/MAPK. The activity of sLRP-alpha did not involve TNF-alpha binding, but rather glial cell preconditioning, so that the subsequent response to TNF-alpha was inhibited. Our results show that sLRP-alpha is biologically active and may attenuate neuropathic pain. In the PNS, the function of LRP1 may reflect the integrated activities of the membrane-anchored and shed forms of LRP1.

Tumor Necrosis Factor-Alpha Binding Capacity and Anti-Infliximab Antibodies Measured by Fluid-Phase Radioimmunoassays as Predictors of Clinical Efficacy of Infliximab in Crohn's Disease

To investigate if the combined assessment of anti-infliximab antibodies (Ab) and the degree of TNF-alpha binding capacity (TNF-alpha-BC) afforded by infliximab may predict the response to infliximab treatment in patients with Crohn's disease (CD). Three groups of CD patients, in total 33 patients, treated with infliximab were retrospectively selected: (a) patients with a maintained response throughout treatment; (b) patients with good initial response, but subsequent loss of response; and (c) patients with inadequate response to the first two or three doses. Blood samples were analyzed for TNF-alpha-BC and Ab using fluid-phase radioimmunoassay (RIA). At 8 wk after last infliximab infusion, TNF-alpha-BC was significantly higher (P = 0.002) in patients maintaining response (median [interquartile range] 2.9 [0.9-4.3] microg/mL), as compared to patients losing response (0.0 [0-0.1] microg/mL). Conversely, Ab levels were significantly lower (P < 0.0001) in patients maintaining response (1.3 [0-6]% bound tracer/total tracer), as compared to patients losing response (19 [14-27]%). Ab were not present and TNF-alpha-BC was high (30 [20-32]) in patients with no primary response. While secondary loss of response to infliximab is associated with high levels of Ab and low levels of TNF-alpha-BC, primary response failure may be seen in the presence of high effective levels of TNF-alpha-BC afforded by infliximab. The results suggest that combined assessment of anti-infliximab Ab and serum TNF-alpha-BC may pave the way for a more rational use of infliximab in patients with CD.

Infliximab for GVHD therapy in children

GVHD remains a significant complication of allogeneic hematopoietic stem cell transplantation. Tumor necrosis factor-alpha (TNF-alpha) is a major mediator of GVHD pathogenesis. Infliximab inhibits the binding of TNF-alpha with its cellular receptors and has been associated with encouraging responses in adults with severe GVHD. We retrospectively evaluated the efficacy and safety of infliximab 10 mg/kg i.v. once a week for a median of eight doses (range 1-162) in 24 children with steroid-resistant GVHD. The overall response rate in 22 evaluable children was 82% (12 CR+6 PR). Among those patients with acute GVHD, both skin and gastrointestinal involvement responded well to infliximab; however long-term outcome was poor. While infliximab may be useful to acutely control GVHD manifestations, GVHD recurs commonly upon discontinuation of infliximab. Within 100 days of the final infliximab dose, 77% of patients had bacterial infections, 32% had viral infections and 13.6% had probable or proven non-candidal invasive fungal infections. Infliximab appears to be well-tolerated and to have activity in steroid-resistant GVHD. Controlled studies to assess the pharmacokinetics and most effective dosing regimen of infliximab for the treatment of GVHD are warranted.

Tumor Necrosis Factor Receptor Pre-Ligand Assembly Domain is an Important Therapeutic Target in Inflammatory Arthritis

Tumor necrosis factor (TNF)-alpha is an important proinflammatory cytokine and plays a crucial role in pathogenesis of inflammatory arthritis, such as rheumatoid and septic arthritis. TNFalpha exerts its effect by binding to the extracellular domain of TNF receptor (TNFR) 1 and 2. The amino-terminal portion of the TNFR extracellular domain, known as cysteine rich domain 1 (CRD1), or the pre-ligand binding assembly domain (PLAD), plays an important role in the TNFR signaling pathway. TNFR1 PLAD and TNFR2 PLAD proteins block the actions of TNFalpha by interfering with assembly of the receptor complex required for TNFalpha binding. The TNFR1 PLAD protein have been shown to significantly inhibit inflammatory arthritis, such as arthritis induced by TNFalpha, bacterial DNA, lipopolysaccharide, and collagen. The TNFR1 PLAD protein inhibit nuclear factor (NF)-kappaB activation and osteoclastogenesis triggered by TNFalpha was able to inhibit expression of receptor activator of NF-kappaB (RANK), RANK ligand, matrix metalloproteinase and inducible nitric oxide synthase in collagen-induced arthritis. The TNFR1 PLAD protein could therefore be useful in treatment of inflammatory arthritis.

Individualized monitoring of drug bioavailability and immunogenicity in rheumatoid arthritis patients treated with the tumor necrosis factor α inhibitor infliximab

Infliximab, an anti-tumor necrosis factor alpha (anti-TNFalpha) antibody, is effective in the treatment of several immunoinflammatory diseases. However, many patients experience primary or secondary response failure, suggesting that individualization of treatment regimens may be beneficial. This study was undertaken to investigate whether serologic monitoring of infliximab bioavailability and immunogenicity in individual patients would be useful in optimizing treatment regimens to improve efficacy and tolerability. To avoid the use of solid-phase assays, two radioimmunoassays were developed: one for measurement of levels of anti-infliximab antibody, and a functional one for measurement of TNFalpha binding due to infliximab. Sera from 106 randomly selected rheumatoid arthritis patients were tested within 6 months of therapy initiation, and associations between findings of serum assays and disease activity, infusion reactions, and treatment failure occurring within 18 months were assessed. Trough serum infliximab levels after the first 2 intravenous infusions of infliximab at 3 mg/kg varied considerably between patients (range 0-22 microg/ml). At this stage, only 13% of the patients were anti-infliximab antibody positive. With subsequent infusions, the frequency of antibody positivity rose to 30% and 44% (at 3 months and 6 months, respectively), accompanied by diminished trough levels of infliximab. Indeed, low infliximab levels at 1.5 months predicted antibody development and later treatment failure. There were highly significant correlations between high levels of antibodies and later dose increases, side effects, and cessation of therapy. High baseline disease activity, judged by C-reactive protein level and Disease Activity Score, was associated with low levels of infliximab at the early stage of treatment and later development of anti-infliximab antibodies. Cotreatment with methotrexate resulted in slightly reduced antibody levels after 6 months; other disease-modifying antirheumatic drugs and prednisolone had no effect. Development of anti-infliximab antibodies, heralded by low preinfusion serum infliximab levels, is associated with increased risk of infusion reaction and treatment failure. Early monitoring may help optimize dosing regimens for individual patients, diminish side effects, and prevent prolonged use of inadequate infliximab therapy.