A novel lipid A from Halomonas magadiensis inhibits enteric LPS-induced human monocyte activation

Lipopolysaccharide (LPS) endotoxin is the bacterial product responsible for the clinical syndrome of Gram-negative septicemia and endotoxic shock. During sepsis, microbial antigens, such as LPS, activate monocytes and macrophages to produce several pro-inflammatory cytokines, among which tumor necrosis factor-alpha (TNF-alpha) appears to be very important for the development of endotoxic shock. The endotoxic properties of LPS principally reside in the lipid A (LIP A) component, which is the primary immunostimulatory center of Gram-negative bacteria. In recent years there has been a continuous effort to identify molecules able to antagonize the deleterious effects of endotoxic shock. In this study we show that a novel LIP A fraction from the LPS of Halomonas magadiensis (Hm), a Gram-negative extremophilic and alkaliphilic bacterium, significantly inhibits the synthesis of TNF-alpha by human monocytes activated by Escherichia coli LPS. LIP A from Hm exerts these effects by interfering with E. coli LPS for activation of Toll-like receptor 4 expressed in human cells. This result defines Hm LIP A as a novel class of LPS antagonist whose structural features could be utilized for the design of compounds for the treatment of Gram-negative sepsis.     

Propensity to excessive proinflammatory response in chronic Lyme borreliosis

The clinical course of Lyme borreliosis is extremely variable. However, all the clinical manifestations, acute or chronic, are characterized by strong inflammation. Borrelia burgdorferi can induce the production of several proinflammatory and anti-inflammatory cytokines. The aim of our study was to find out whether the balance between inflammatory and regulatory mechanisms is important in determining the course of Lyme borreliosis. 13 patients with early Lyme borreliosis, 8 patients with chronic Lyme disease with neurological or joint manifestations, and 15 age- and sex-matched healthy controls were studied. Chronic forms of Lyme borreliosis were characterized by stronger TNF-alpha response by monocytes to lipopolysaccharide as well as to borrelia antigen compared to early Lyme borreliosis and the healthy state. The percentage of IL-10-secreting monocytes in response to borrelia lysate was lower in the Lyme borreliosis patients than in healthy controls. The percentage of CD4(+) CTLA-4(+) regulatory T cells showed the highest values in early Lyme borreliosis. We conclude that chronic forms of Lyme borreliosis can evolve due to an aberrant innate proinflammatory response.     

Characterization of three CpG oligodeoxynucleotide classes with distinct immunostimulatory activities

Oligodeoxynucleotides (ODN) with unmethylated deoxycytidyl-deoxyguanosine (CpG) dinucleotides (CpG ODN) mimic the immunostimulatory activity of bacterial DNA and are recognized by the Toll-like receptor 9 (TLR9). CpG ODN of the B-Class stimulate strong B cell and NK cell activation and cytokine production. The highest degrees of NK stimulation as well as IFN-alpha secretion by plasmacytoid DC were found to occur only with A-Class ODN. A third class of CpG ODN combines the immune effects of A- and B-Class CpG ODN. C-Class ODN strongly stimulate B cell or NK cell activation and IFN-alpha production. In contrast to the A-Class, the C-Class is wholly phosphorothioate, has no poly-G stretches, but has palindromic sequences combined with stimulatory CpG motifs. All classes stimulate TLR9-dependent signaling, but with strikingly different dose-response relationships that are quite in contrast to those observed for IFN-alpha. Effects similar to those on human cells were observed on mouse splenocytes. In contrast, splenocytes from TLR9-deficient mice did not show any response to the three CpG ODN classes. In vivo studies demonstrate that C-Class ODN are very potent Th1 adjuvants. C-Class ODN may represent new therapeutic drugs that combine the effects of A- and B-Class ODN for broad applications in infectious disease or cancer therapy.     

Increased expression of Toll-like receptor 4 in peripheral blood leucocytes and serum levels of some cytokines in patients with ankylosing spondylitis

Toll-like receptor 4 (TLR4) is a member of the Toll-like receptor family, which can bridge innate and adaptive immune responses. Activation of the TLR4 signalling pathway may induce the release of proinflammatory cytokines such as tumour necrosis factor (TNF)-alpha and interleukin (IL)-12, which was considered to play an important role in pathogenesis of immune-mediated diseases. Ankylosing spondylitis (AS) is an immune-mediated disease whose aetiology remains unknown. The aim of the study was to investigate the expression of TLR4 and serum TNF-alpha, IL-12 and soluble tumour necrosis factor-related apoptosis-inducing ligand (sTRAIL) level in AS patients. The results indicated that TLR4 protein and mRNA levels were significantly higher in AS patients than in healthy controls; however, there was no significant difference between human leucocyte antigen (HLA)-B27-positive and -negative AS patients, as well as serum levels of TNF-alpha, IL-12 and sTRAIL. In addition, in HLA-B27-positive AS patients, TLR4 level showed close associations with the cytokines and laboratory parameters of disease activity [erythrocyte sedimentation rate (ESR) and plasma C-reactive protein (CRP)], respectively. Similarly, the strong associations between the cytokines or between IL-12 and ESR or CRP were observed in HLA-B27-positive AS patients. Interestingly, in HLA-B27-positive AS patients, TNF-alpha correlated significantly with ESR, but did not with CRP. In contrast, sTRAIL correlated with CRP, but did not with ESR. Among HLA-B27-negative patients, no close correlation was found. In our study, it was suggested that the abnormal activation of TLR4 signalling and serum TNF-alpha, IL-12 and sTRAIL may play a key role in the development and progression of AS, which may be dependent on the status of HLA-B27 antigen.     

Secretory phospholipases A2 induce cytokine release from blood and synovial fluid monocytes.

Secretory phospholipases A2 (sPLA2) are released in the blood of patients with various inflammatory diseases and exert proinflammatory activities by releasing arachidonic acid (AA), the precursor of eicosanoids. We examined the ability of four sPLA2 to activate blood and synovial fluid monocytes in vitro. Monocytes were purified from blood of healthy donors or from synovial fluid of patients with rheumatoid arthritis by negative immunoselection and by adherence to plastic dishes, respectively. The cells were incubated with group IA, IB, IIA and III sPLA2 and the release of TNF-alpha, IL-6 and IL-12 was determined by ELISA. Group IA, IB and IIA sPLA2 induced a concentration-dependent release of TNF-alpha and IL-6 from blood monocytes. These sPLA2 activated IL-12 production only in monocytes preincubated with IFN-gamma. Group IA and IIA sPLA2 also induced TNF-alpha and IL-6 release from synovial fluid monocytes. TNF-alpha and IL-6 release paralleled an increase in their mRNA expression and was independent from the capacity of sPLA2 to mobilize AA. These results indicate that sPLA2 stimulate cytokine release from blood and synovial fluid monocytes by a mechanism at least partially unrelated to their enzymatic activity. This effect may concur with the generation of AA in the proinflammatory activity of sPLA2 released during inflammatory diseases.     

CD40-dependent and -independent activation of human tonsil B cells by CpG oligodeoxynucleotides

Immunostimulatory CpG oligodeoxynucleotide (CpG-ODN) sequences are known to directly activate B cells. We investigated the expression of the CpG receptor, Toll-like receptor 9 (TLR9), in human tonsil B cells, and determined functional responses following stimulation by a well-characterized stimulatory CpG-containing ODN sequence in the human immune system, ODN 2006. Tonsil B cells were found to express high amounts of TLR9 mRNA and protein, and exposure of B cells to CpG-ODN but not to an inactive control ODN induced a concentration- and time-dependent up-regulation of the activation markers CD23, CD25, CD40, CD54, CD80, CD86 and HLA-DR. However, significant induction of proliferation and the release of IL-6, IL-10, IgG and IgM were only noted when B cells were co-incubated with irradiated CD40L-expressing CHO cells. Endogenous IL-10 was identified as a critical mediator of Ig production, whereas all activating effects were independent of IL-6. Further, CpG-ODN counteracted IgE production induced by IL-4. Collectively, these findings suggest a synergistic role of the TLR9/CD40 system and a critical role for the immunomodulatory cytokine IL-10 in the orchestration of CpG-ODN-induced responses in B lymphocytes.     

Colonic epithelial cells induce endothelial cell expression of ICAM-1 and VCAM-1 by a NF-kappaB-dependent mechanism.

Epithelial cells are positioned in close proximity to endothelial cells. A non-contact coculture system was used to investigate whether colonic epithelial cells activated with various cytokines are able to provide signals that can modulate ICAM-1 and VCAM-1 expression on endothelial cells. Coculture of human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (HMEC-1) with TNF-alpha/IFN-gamma-stimulated human colon epithelial cell lines led to a significant up-regulation of endothelial ICAM-1 and VCAM-1 expression. Increased ICAM-1 and VCAM-1 expression by endothelial cells was accompanied by an increase in endothelial cell NF-kappaB p65 and NF-kappaB-DNA-binding activity. Inhibition of endothelial NF-kappaB activation using the proteosome inhibitors MG-132 and BAY 11-7082 resulted in a significant decrease of ICAM-1 expression, indicating an important role for NF-kappaB in this response. This cross-talk may represent a biological mechanism for the gut epithelium to control the colonic inflammatory response and the subsequent immune cell recruitment during inflammation.     

Seoul virus enhances regulatory and reduces proinflammatory responses in male Norway rats

Zoonotic pathogens, including hantaviruses, are maintained in the environment by causing persistent infection in the absence of disease in their reservoir hosts. Spillover of hantaviruses to humans can cause severe disease that is mediated by excessive proinflammatory responses. The mechanisms mediating hantaviral persistence in rodent reservoirs remain largely unknown. Male Norway rats were inoculated with their species-specific hantavirus, Seoul virus (SEOV), and viral RNA, cytokine, and chemokine responses were evaluated in spleen and lung tissue. More viral RNA was detectable in the lungs than spleen, with copies of SEOV peaking 15-30 days post-inoculation (p.i.) and persisting for 60 days p.i. In the lungs, the expression and production of proinflammatory mediators (i.e., IL-1beta, IL-6, TNF-alpha, IFN-gamma, CCL5, CCL2, CX3CL1, CXCL10, VCAM, VEGF, and NOS2) remained at or below baseline throughout SEOV infection; whereas, regulatory factors, including TGF-beta and FoxP3 were elevated. Conversely, in the spleen, proinflammatory responses were induced while regulatory responses remained unchanged during infection. To determine whether reduced proinflammatory responses mediate hantavirus persistence in the lungs, male rats were administered rIL-1beta or vehicle for 30 days during SEOV infection. SEOV persistence and shedding were not affected by IL-1beta treatment. Proinflammatory responses were elevated in rIL-1beta-treated rats, but remained within physiological levels, suggesting that supra-physiological concentrations may be necessary for viral clearance at the cost of causing disease. Elevated regulatory responses may suppress excessively high proinflammatory responses at a site of elevated SEOV replication to contribute to viral persistence and prevent proinflammatory-mediated disease in reservoir hosts.     

Ribavirin inhibits DNA,RNA, and protein synthesis in PHA-stimulated human peripheral blood mononuclear cells: possible explanation for therapeutic efficacy in patients with chronic HCV infection

The treatment of choice for patients infected chronically with HCV is the combination of IFN-alpha and ribavirin. Monotherapy with ribavirin leads to a clinical and histological improvement, but its exact mechanism of action is unknown. Therefore, the effect of ribavirin on synthesis of inflammatory cytokines and on apoptosis in stimulated peripheral blood mononuclear cells (PBMCs) was investigated. PBMCs were isolated from the blood of HCV infected patients and from healthy volunteers. The effect of ribavirin on IFN-gamma and IL-1beta release in the supernatant of unstimulated and phytohemagglutinin (PHA) stimulated PBMCs was investigated by enzyme linked immunosorbent assay (ELISA). The effect on total DNA, RNA, and protein synthesis was analyzed by measurement of 3H-thymidine, 3H-uridine and 3H-leucine incorporation into cellular macromolecules. Ribavirin led to a dose-dependent decrease of the IFN-gamma but an increase of IL-1beta release into the supernatant of PHA-stimulated PBMCs. At the same time, a dose-dependent decrease of total DNA, RNA, and protein synthesis in cultures of PHA-stimulated PBMCs was demonstrated. These effects could be compensated by the addition of equimolar amounts of guanosine. The rate of apoptotic CD45+ and CD14+ cells in PBMCs cultures increased in a dose-dependent manner. Our data suggest that ribavirin administration to chronically HCV-infected patients could lead to a decrease of the synthesis of proinflammatory cytokines (e.g., IFN-gamma) by an inhibition of total DNA-, RNA-, and protein-synthesis and by induction of apoptosis in the cells of the inflammatory infiltrate. Furthermore, ribavirin could influence the synthesis of viral particles in the hepatocytes.     

Increased expression of pro-inflammatory cytokines and metalloproteinase-1 by TGF-beta1 in synovial fibroblasts from rheumatoid arthritis and normal individuals

Transforming growth factor (TGF)-beta1 is expressed abundantly in the rheumatoid synovium. In this study, the inflammatory effect of TGF-beta1 in rheumatoid arthritis (RA) was investigated using cultured fibroblast-like synoviocytes (FLS) from RA and osteoarthritis (OA) patients, as well as non-arthritic individuals. mRNA expressions of IL-1beta, tumour necrosis factor (TNF)-alpha, IL-8, macrophage inflammatory protein (MIP)-1alpha and metalloproteinase (MMP)-1 were increased in RA and OA FLS by TGF-beta1 treatment, but not in non-arthritic FLS. Enhanced protein expression of IL-1beta, IL-8 and MMP-1 was also observed in RA FLS. Moreover, TGF-beta1 showed a synergistic effect in increasing protein expression of IL-1beta and matrix metalloproteinase (MMP)-1 with TNFalpha and IL-1beta, respectively. Biological activity of IL-1 determined by mouse thymocyte proliferation assay was also enhanced by 50% in response to TGF-beta1 in the culture supernatant of RA FLS. DNA binding activities of nuclear factor (NF)-kappaB and activator protein (AP)-1 were shown to increase by TGF-beta1 as well. These results suggest that TGF-beta1 contributes for the progression of inflammation and joint destruction in RA, and this effect is specific for the arthritic synovial fibroblasts.     

Pathogenesis of Lyme neuroborreliosis: mitogen-activated protein kinases Erk1, Erk2, and p38 in the response of astrocytes to Borrelia burgdorferi lipoproteins

Lyme borreliosis, which is prevalent both in the US and in Europe, is an infectious disease that may cause local inflammation in numerous organs. We have hypothesized that, as with some neurodegenerative diseases, the pathogenesis of the neurocognitive deficiencies associated with Lyme neuroborreliosis of the central nervous system also has an inflammatory component. Dysregulated production of pro-inflammatory cytokines such as IL-6 and TNF-alpha can lead to neuronal damage. Mitogen-activated protein kinases (MAPK) play a key role in the regulation of neuronal development, growth, and survival, as well as that of pro-inflammatory cytokine production. As a model, we explored the possibility that MAPK-mediated lipoprotein-induced apoptosis and gliosis of rhesus monkey astrocytes stimulated in vitro. Lipoproteins are the key inflammatory molecule type of Borrelia burgdorferi, the spirochete that causes Lyme disease, and we had previously shown that lipoprotein-induced TNF-alpha production in astrocytes caused astrocyte apoptosis, and IL-6 enhanced proliferation of these cells. Lipoproteins readily activated p38 and Erk1/2 MAPK, thus enlisting these pathways among the kinase pathways that spirochetes may address as they invade the central nervous system. We also investigated whether specific inhibition of p38 and Erk1/2 MAPK would inhibit TNF-alpha and IL-6 production and thus astrocyte apoptosis, and proliferation, respectively. Lipoprotein-stimulated IL-6 production was unaffected by the MAPK inhibitors. In contrast, inhibition of both p38 and Erk1/2 significantly diminished TNF-alpha production, and totally abrogated production of this cytokine when both MAPK pathways were inhibited simultaneously. MAPK inhibition thus may be considered as a strategy to control inflammation and apoptosis in Lyme neuroborreliosis.     

Detection of in vitro interferon-gamma and serum tumour necrosis factor-alpha in multidrug-resistant tuberculosis patients

Multidrug-resistant tuberculosis (MDR-TB) is known as having a poor prognosis with a weak response to therapy and very high death rates. The aim of this work was to assess the immune response to the RD1-encoded antigen ESAT-6 of Mycobacterium tuberculosis in MDR-TB patients and compare to non-resistant (NR) TB patients and healthy controls (HC). Evaluation of interferon (IFN)-gamma production showed that, although 55% of the MDR patients were responsive to ESAT-6, they produced lower IFN-gamma levels (553 +/- 11 pg/ml) when compared to NR-TB (1179 +/- 163 pg/ml; P < 0.05) but not to controls (412 +/- 65.7 pg/ml). Differences in the response to ESAT-6 and to its overlapping peptides mixture were also significant between MDR versus treated pulmonary NR-TB. Furthermore, a very low rate of response to PPD (23.5%) and to Ag85B (33.3%) was noted in MDR-TB patients as compared to the other groups. To determine the inflammatory response in patients' groups, detection of tumour necrosis factor (TNF)-alpha was assessed in their sera before and during chemotherapy. Mean TNF-alpha levels in MDR-TB (43.8 +/- 9 pg/ml) paralleled those found in treated pulmonary, and it was significantly different (P < 0.05) from the values found in untreated NR and HC. Interestingly, secretion of IFN-gamma and TNF-alpha were predominant in MDR patients who presented with bilateral pulmonary lesions and lung cavitation. The present data indicate that the overall immune response to mycobacterial antigens is decreased in resistant TB and the major role inflammatory cytokines may play in perpetuating pulmonary tissue damage.     

Beneficial effects of troglitazone on neutrophil dysfunction in multiple low-dose streptozotocin-induced diabetic mice

Patients with poorly controlled diabetes are at high risk of acquiring bacterial infections. However, conflicting results have been reported on neutrophil function in diabetes. We periodically evaluated neutrophil dysfunction in multiple low-dose streptozotocin (STZ)-induced diabetic mice, and then evaluated the effects of troglitazone and other thiazolidinediones (TZDs) on the decline of neutrophil function. Zymosan was injected intraperitoneally and neutrophil infiltration and phagocytosis were evaluated. While phagocytosis of zymosan by peritoneal neutrophils was consistently reduced in diabetic mice, neutrophil infiltration was decreased on day 30, but increased on day 40 after STZ injection. The in vitro chemotactic and phagocytic activities of blood neutrophils in mice that did not receive zymosan were consistently reduced in diabetic mice. Phorbol myristate acetate (PMA)-stimulated superoxide production by zymosan-induced peritoneal neutrophils and the levels of zymosan-induced tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta in peritoneal exudate fluids were also reduced in the diabetic mice. Treatment of the diabetic mice with troglitazone beginning 2 weeks after STZ injection did not improve hyperglycaemia but did prevent the decline of zymosan-induced neutrophil infiltration on day 30, and additionally promoted the increased infiltration on day 40. Troglitazone also promoted the chemotactic activity of blood neutrophils isolated from normal mice in vitro. Rosiglitazone but not pioglitazone induced a similar effect. Neutrophil phagocytosis was not enhanced by troglitazone either in vivo or in vitro. Taken together, neutrophil function is impaired by STZ-induced diabetes, but inflammatory infiltration does not always vary with the chemotactic disability or cytokine levels. Furthermore, troglitazone and rosiglitazone were suggested to improve at least neutrophil chemotactic activity in these animals.     

Lipopolysaccharide-induced elevation and secretion of interleukin-1beta in the submandibular gland of male mice

The intraperitoneal injection of lipopolysaccharide (LPS) (400 microg/kg body weight) induced the expression of mRNAs of inflammatory cytokines such as interleukin (IL)-1beta, IL-6 and tumour necrosis factor (TNF)-alpha in the submandibular gland (SMG) of C3H/HeN mice but not that of C3H/HeJ mice, a mutant strain for Toll-like receptor-4 (TLR-4(-) mutant). The mRNA levels of these cytokines in the SMG of the wild-type mice increased as early as 3 hr after injection, peaked at 3-6 hr, and had decreased again by 24 hr. In this study, we particularly focused on IL-1beta, and induction by this endotoxin was investigated in detail. Denervation of the superior cervical trunk and chorda tympani nerve did not diminish the LPS-induced elevation of IL-1beta mRNA in the SMG, indicating the irrelevance of the central nervous system in this induction. TLR-4 mRNA and protein were shown to be strongly expressed in the SMG, suggesting the direct action of LPS on this gland. IL-1beta proteins were localized in the secretory granules of granular convoluted tubular (GCT) cells, and their molecular weights in the gland were 17.5 and 20 kDa. IL-1beta of the same size appeared in the saliva 6 hr after LPS injection in C3H/HeN but not in C3H/HeJ mice. The present study thus suggests that IL-1beta, an inflammation cytokine, is induced and secreted into the saliva in response to endotoxin injected intraperitoneally.     

Gonadotropin treatment restores in vitro interleukin-1beta and tumour necrosis factor-alpha production by stimulated peripheral blood mononuclear cells from patients with idiopathic hypogonadotropic hypogonadism

In the present study, we aimed to investigate the effects of testosterone deficiency and gonadotropin therapy on the in vitro production of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) by peripheral blood mononuclear cells (PBMCs) from patients with idiopathic hypogonadotropic hypogonadism (IHH) in order to elucidate the modulatory role of androgen in cytokine production. Fifteen male patients with untreated IHH and 15 age-matched healthy male subjects were enrolled in the study. Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), free testosterone (FT), sex hormone binding globulin (SHBG), prolactin, and IL-2 and IL-4 levels were also measured. In unstimulated cultures, IL-1beta and TNF-alpha secretion were not significantly different between patient and control groups. However, after stimulation with lipopolysaccharide (LPS), secretion of IL-1beta and TNF-alpha was significantly higher in cultures from untreated patients with IHH than in control subjects. Mean FSH, LH and FT levels were significantly lower, whereas SHBG, IL-2 and IL-4 levels were significantly higher in patients with IHH compared than in controls. In patients with IHH, FT negatively affected the serum levels of IL-4 and in vitro secretion of IL-1beta and TNF-alpha. In addition, IL-2 and IL-4 affected the in vitro secretion of IL-1beta in a positive manner. Gonadotropin therapy decreased both TNF-alpha and IL-1beta in PBMCs from patients with IHH. The levels of serum IL-2 and IL-4 were also decreased by therapy. In conclusion, in the present study, gonadotropin treatment restored the in vitro production of IL-1beta and TNF-alpha by PBMCs from patients with IHH, suggesting that androgen modulates proinflammatory cytokine production, at least directly through its effects on PBMCs. It seems probable that this effect plays an important role in the immunosuppressive action of androgens.     

Osteoprotegerin (OPG) acts as an endogenous decoy receptor in tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis of fibroblast-like synovial cells

We examined the role of osteoprotegerin (OPG) on tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in rheumatoid fibroblast-like synovial cells (FLS). OPG protein concentrations in synovial fluid from patients with rheumatoid arthritis (RA) correlated with those of interleukin (IL)-1beta or IL-6. A similar correlation was present between IL-1beta and IL-6 concentrations. Rheumatoid FLS in vitro expressed both death domain-containing receptors [death receptor 4 (DR4) and DR5] and decoy receptors [decoy receptor 1 (DcR1) and DcR2]. DR4 expression on FLS was weak compared with the expression of DR5, DcR1 and DcR2. Recombinant TRAIL (rTRAIL) rapidly induced apoptosis of FLS. DR5 as well as DR4 were functional with regard to TRAIL-mediated apoptosis induction in FLS; however, DR5 appeared be more efficient than DR4. In addition to soluble DR5 (sDR5) and sDR4, OPG administration significantly inhibited TRAIL-induced apoptogenic activity. OPG was identified in the culture supernatants of FLS, and its concentration increased significantly by the addition of IL-1beta in a time-dependent manner. Neither IL-6 nor tumour necrosis factor (TNF)-alpha increased the production of OPG from FLS. TRAIL-induced apoptogenic activity towards FLS was reduced when rTRAIL was added without exchanging the culture media, and this was particularly noticeable in the IL-1beta-stimulated FLS culture; however, the sensitivity of FLS to TRAIL-induced apoptosis itself was not changed by IL-1beta. Interestingly, neutralization of endogenous OPG by adding anti-OPG monoclonal antibody (MoAb) to FLS culture restored TRAIL-mediated apoptosis. Our data demonstrate that OPG is an endogenous decoy receptor for TRAIL-induced apoptosis of FLS. In addition, IL-1beta seems to promote the growth of rheumatoid synovial tissues through stimulation of OPG production, which interferes with TRAIL death signals in a competitive manner.     

Toll-like receptors TLR2 and TLR4 initiate the innate immune response of the renal tubular epithelium to bacterial products

Renal tubular epithelial cells (TECs) respond diffusely to local infection, with the release of multiple cytokines, chemokines and other factors that are thought to orchestrate the cellular constituents of the innate immune response. We have investigated whether the Toll-like receptors TLR4 and TLR2, which are present on tubular epithelium and potentially detect a range of bacterial components, co-ordinate this inflammatory response acting through nuclear factor-kappa B (NF-kappaB). Primary cultures of TECs were grown from C57BL/6, C3H/HeN, C3H/HeJ, TLR2 and TLR4 knock-out mice. Cell monolayers were stimulated with lipopolysaccharide (LPS) and synthetic TLR2 and 4 agonists. The innate immune response was quantified by measurement of the cytokines tumour necrosis factor (TNF)-alpha and KC (IL-8 homologue) in cell supernatants by enzyme-linked immunosorbent assay. Cultured TECs grown from healthy mice produced the cytokines TNF-alpha and KC in response to stimulation by LPS and synthetic TLR2 and TLR4 agonists. Cells lacking the respective TLRs had a reduced response to stimulation. The TLR2- and TLR4-mediated response to stimulation was dependent on NF-kappaB signalling, as shown by curcumin pretreatment of TECs. Finally, apical stimulation of these TLRs elicited basal surface secretion of TNF-alpha and KC (as well as the reverse), consistent with the biological response in vivo. Our data highlight the potential importance of TLR-dependent mechanisms co-ordinating the innate immune response to upper urinary tract infection.