IgG1 plasmacytosis in interleukin 6 transgenic mice

Pyrano-isochromanones as IL-6 inhibitors: synthesis, in vitro and in vivo antiarthritic activity

Bergenin (1), a unique fused C-glycoside isolated from Bergenia species, possesses interesting anti-inflammatory and antipain activities. To study SAR of this scaffold, first-generation derivatives were synthesized and evaluated for inhibition of lymphocyte proliferation and production of pro-inflammatory cytokines. The C-7 substituted derivatives showed inhibition of IL-6 as well as TNF-α production. Bergenin and its most potent IL-6 inhibitor derivatives 4e and 4f were then investigated in a panel of in vitro and in vivo inflammation/arthritis models. These compounds significantly decreased the expression of NF-kB and IKK-β in THP-1 cells. In in vivo study in BALB/c mice, a dose-dependent inhibition of SRBC-induced cytokines, reduction in humoral/cell-mediated immunity, and antibody titer was observed. The CIA study in DBA/1J mice indicated that compounds led to reduction in swelling of paws, cytokine levels, and anticollagen IgG1/IgG2a levels. The significant in vivo immunosuppressive efficacy of pyrano-isochromanones demonstrates the promise of this scaffold for development of next-generation antiarthritic drugs.

The tyrosine kinase Lyn limits the cytokine responsiveness of plasma cells to restrict their accumulation in mice

Maintenance of an appropriate number of plasma cells, long-lived antibody-producing cells that are derived from B cells, is essential for maintaining immunological memory while limiting disease. Plasma cell survival relies on extrinsic factors, the limited availability of which determines the size of the plasma cell population. Mice deficient in the nonreceptor tyrosine kinase Lyn are prone to an autoimmune disease that is characterized by inflammation and an excess of plasma cells (plasmacytosis). We demonstrated that the plasmacytosis was intrinsic to B cells and independent of inflammation. We also showed that Lyn attenuated signaling by signal transducer and activator of transcription 3 (STAT3) and STAT5 in response to the cytokines interleukin-6 (IL-6) and IL-3, respectively, in two previously uncharacterized plasma cell signaling pathways. Thus, in the absence of Lyn, the survival of plasma cells was improved, which enabled the plasma cells to become established in excess numbers in niches in vivo. These data identify Lyn as a key regulator of survival signaling in plasma cells, limiting plasma cell accumulation and autoimmune disease susceptibility.

A new era for the treatment of inflammatory autoimmune diseases by interleukin-6 blockade strategy

Interleukin-6 (IL-6) is a cytokine with redundant and pleiotropic activities, and its synthesis is tightly regulated by transcriptional and posttranscriptional mechanisms. When infections and tissue injuries occur, IL-6 synthesis is promptly induced and provides an emergent signal that contributes to host defense through the stimulation of acute-phase responses, immune reactions, and hematopoiesis. After the environmental stress is removed from the host, the production of IL-6 is terminated. However, dysregulated continual synthesis of IL-6 is involved in the development of chronic inflammatory autoimmune diseases. For this reason, tocilizumab, a humanized anti-IL-6 receptor antibody, was developed. Worldwide clinical trials have demonstrated the outstanding efficacy of tocilizumab in rheumatoid arthritis, systemic juvenile idiopathic arthritis, and Castleman's disease; thus, a new era has come for the treatment of these diseases, which were previously considered intractable. Moreover, favorable results from off-label use of tocilizumab strongly suggest that it will be widely applicable for various refractory inflammatory autoimmune diseases. In this context, the mechanism for the continual synthesis of IL-6 needs to be elucidated in order to investigate the pathogenesis of specific diseases and to facilitate the development of more specific therapeutic strategies.

Emerging therapeutic paradigms to target the dysregulated Janus kinase/signal transducer and activator of transcription pathway in hematological malignancies

Over the past decade, there has been increasing biochemical evidence that the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is aberrantly activated in malignant cells from patients with a wide spectrum of cancers of the blood and immune systems. The emerging availability of small molecule inhibitors of JAK and other signaling molecules in the JAK/STAT pathway has allowed preclinical studies validating an important role of this pathway in the pathogenesis of many hematologic malignancies, and provided motivation for new strategies for treatment of these diseases. Here, a round-table panel of experts review the current preclinical and clinical landscape of the JAK/STAT pathway in acute lymphoid and myeloid leukemias, lymphomas and myeloma, and chronic myeloid neoplasms.

Interleukin 6 and rheumatoid arthritis

Interleukin-6 (IL-6) is a representative cytokine featuring pleiotropic activity and redundancy. A transient synthesis of IL-6 contributes to host defense against infectious agents and tissue injuries by inducing acute phase reactions and immunological and hematopoietic responses. However, uncontrolled persistent production of IL-6 may lead to the development of several immune-mediated diseases. Rheumatoid arthritis (RA) is a chronic disease with joint and systemic inflammation resulting from immunological abnormalities and it has been found that IL-6 plays a key role in the development of this disease. Clinical trials in various parts of the world of tocilizumab, a humanized anti-IL-6 receptor antibody, have proved its efficacy and tolerable safety either as monotherapy or in combination with disease-modifying antirheumatic drugs. As a result, it is currently used as a first-line biologic for the treatment of moderate-to-severe RA in more than 100 countries. Clarification of the mechanism(s) through which tocilizumab exerts its effect on RA and of the reason(s) why IL-6 is continuously produced in RA can be expected to lead to the best use of this agent for RA patients and aid in investigations into the pathogenesis of RA.

(18)F-FDG-PET/CT imaging in an IL-6- and MYC-driven mouse model of human multiple myeloma affords objective evaluation of plasma cell tumor progression and therapeutic response to the proteasome inhibitor ixazomib

(18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) and computed tomography (CT) are useful imaging modalities for evaluating tumor progression and treatment responses in genetically engineered mouse models of solid human cancers, but the potential of integrated FDG-PET/CT for assessing tumor development and new interventions in transgenic mouse models of human blood cancers such as multiple myeloma (MM) has not been demonstrated. Here we use BALB/c mice that contain the newly developed iMyc(ΔEμ) gene insertion and the widely expressed H2-L(d)-IL6 transgene to demonstrate that FDG-PET/CT affords an excellent research tool for assessing interleukin-6- and MYC-driven plasma cell tumor (PCT) development in a serial, reproducible and stage- and lesion-specific manner. We also show that FDG-PET/CT permits determination of objective drug responses in PCT-bearing mice treated with the investigational proteasome inhibitor ixazomib (MLN2238), the biologically active form of ixazomib citrate (MLN9708), that is currently in phase 3 clinical trials in MM. Overall survival of 5 of 6 ixazomib-treated mice doubled compared with mice left untreated. One outlier mouse presented with primary refractory disease. Our findings demonstrate the utility of FDG-PET/CT for preclinical MM research and suggest that this method will play an important role in the design and testing of new approaches to treat myeloma.

Interleukin-6 expands homeostatic space for peripheral T cells

T cell homeostasis and survival is dependent on interleukin-7 (IL-7). Immune activation, however, downregulates IL-7 receptor expression on T cells so that T cell survival during activation must be maintained independently of IL-7. The pro-inflammatory cytokine IL-6 shares common signaling pathways with IL-7 and can promote T cell survival in vitro. But whether IL-6 promotes T cell survival and homeostasis in vivo is not clear. Notably, IL-6 overexpression results in massive plasmacytosis and autoimmunity so that an IL-6 effect on in vivo T cell survival has remained untested. To overcome this limitation, here we generated IL-6 transgenic mice on an immunoglobulin heavy chain (IgH) deficient background which rendered them B cell deficient. Notably, such IgH(KO)IL6(Tg) mice were free of any signs of inflammation or autoimmunity and remained healthy throughout the course of analysis. In these mice, we found that IL-6 overexpression significantly increased peripheral T cell numbers, but importantly without increasing thymopoiesis. Moreover, IL-6 signaled T cells maintained their naïve phenotype and did not express activation/memory markers, suggesting that increased T cell numbers were due to increased T cell survival and not because of expansion of activated T cells. Mechanistically, we found that IL-6 signaling induced expression of pro-survival factors Mcl-1 and Pim-1/-2 but not Bcl-2. Thus, IL-6 is a T cell homeostatic cytokine that expands T cell space and can maintain the naïve T cell pool.

Interleukin 5 immunotherapy depletes alloreactive plasma cells

BACKGROUND

Long-lived plasma cells (PCs) that form after alloantigen sensitization produce donor-specific alloantibodies that generate a positive serum crossmatch and preclude transplantation. New approaches for desensitization, including PC depletion with proteasome inhibition, show promise but carry considerable toxicity. Recently, eosinophils have been shown to govern PC persistence. Interleukin 5 (IL-5) depletion is known to reduce eosinophils in human asthmatics. We hypothesized that treatment with an anti-IL-5 antibody can deplete alloreactive PCs, reduce donor-specific alloantibodies, and serve as a less toxic alternative to proteasome inhibition.

METHODS

BALB/c mice were sensitized with B6 skin allografts. Starting at 8 wk after sensitization, control mice received injections of phosphate-buffered saline, whereas experimental mice received weekly injections of an anti-IL-5 antibody. PCs were enumerated by enzyme-linked immunosorbent spot after 8 wk.

RESULTS

All control and experimental recipients of skin allografts developed positive crossmatches when screened at 8 wk after sensitization. All experimental mice treated with anti-IL-5 showed a reduction in their total PC numbers. Also, in contrast to the known adverse effects of proteasome inhibition, experimental mice treated with anti-IL-5 exhibited negligible weight loss or lymphopenia.

CONCLUSIONS

Treatment with anti-IL-5 is sufficient to reduce, but not eliminate, alloreactive PCs in the bone marrow. This is because of the targeted reduction of eosinophils leading to a reduction in the PC survival factors a proliferation-inducing ligand and IL-6. Generalized toxicity was not observed in experimental mice. Overall, IL-5 directed immunotherapy can eliminate PC's but is unlikely to be a clinically significant desensitization strategy given the persistence of DSA.

Tocilizumab: An Updated Review of Its Use in the Treatment of Rheumatoid Arthritis and Its Application for Other Immune-Mediated Diseases

Interleukin-6 (IL-6), produced by a variety of cells, is a typical cytokine featuring redundancy and pleiotropic activity. IL-6 is promptly and transiently synthesized in response to infections or injuries, and participates in host defense by inducing immune responses, hematopoiesis, and acute-phase reactions. However, since its abnormal persistent production of mostly unknown etiology plays an important pathological role in the development of various immune-mediated diseases, a humanized anti-IL-6 receptor monoclonal antibody, tocilizumab, was developed and is now used as an innovative biologic for rheumatoid arthritis in more than 90 countries. Several factors strongly suggest that a IL-6 blockade strategy may have a broad application for the treatment of various immune-mediated diseases. These factors include favorable results of pilot or case studies with off-label use of tocilizumab, pathological analyses of the contribution of IL-6 to the development of immune-mediated diseases, and the potential capability of tocilizumab to both repair an imbalance of effector T cell subsets and to suppress pathologic autoantibody production. However, clinical trials to evaluate the efficacy and safety of tocilizumab for these diseases are essential. Furthermore, clarification of the cell source of IL-6 production and of the mechanisms through which dysregulated continuous IL-6 synthesis is induced constitutes an important issue for future studies into the pathogenesis of diseases.

Targeting interleukin-6: all the way to treat autoimmune and inflammatory diseases

Interleukin (IL)-6, a cytokine featuring redundancy and pleiotropic activity, contributes to host defense against acute environmental stress, while dysregulated persistent IL-6 production has been demonstrated to play a pathological role in various autoimmune and chronic inflammatory diseases. Targeting IL-6 is thus a rational approach to the treatment of these diseases. Indeed, clinical trials of tocilizumab, a humanized anti-IL-6 receptor antibody have verified its efficacy and tolerable safety for patients with rheumatoid arthritis, Castleman's disease and systemic juvenile idiopathic arthritis, resulting in approval of this innovative biologic for treatment of these diseases. Moreover, a considerable number of case reports and pilot studies of off-label use of tocilizumab point to the beneficial effects of tocilizumab for a variety of other phenotypically different autoimmune and chronic inflammatory diseases. Elucidation of the source of IL-6 and of mechanisms through which IL-6 production is dysregulated can thus be expected to lead to clarification of the pathogenesis of various diseases.

FK506 and Cyclosporin A Enhance IL-6 Production in Monocytes: A single-Cell Assay

The effect of FK506 and cyclosporin A (CsA) on the production of interleukin 6 (IL-6) in adherent monocytes was studied at a single-cell level by the avidinbiotin- peroxidase complex methods. The percentage of IL-6-producing monocytes increased when stimulated with lipopolysaccharide (LPS) at concentrations between 10 ng/ml and 10 μg/ml, in a dose dependent manner. Both FK506 and CsA enhanced the percentage of IL-6- producing monocytes stimulated with 100 pg/ml-1 μg/ml of LPS up to values near those obtained with 10 μg/ml of LPS. The enhancement by FK506 and CsA was not seen when monocytes were stimulated with a high concentration of LPS (10 μg/ml). When monocytes were stimulated with a low concentration of LPS (10 ng/ml), FK506 and CsA enhanced IL-6 production in a dose dependent manner, at a drug concentration of 0.12 nM–1.2 μM (0.1–1 000 ng/ml) for FK506 and 0.83 nM–8.3 μM (1–10 000 ng/ml) for CsA. The optimal effect of FK506 was achieved at a concentration 7-fold lower than that of CsA. In contrast, production of turnout necrosis factor-α (TNFα and interleukin 1β (IL-1β) was slightly suppressed by FK506 and CsA at the concentrations tested. Moreover, pretreatment of monocytes with FK506 and CsA had a significant enhancing effect on LPS-induced IL-6 production, while treatment with FK506 or CsA after LPS stimulation had no effects on IL-6 production, suggesting that the enhancing effect of each drug is exerted before LPS stimulation or at an early stage of the post-receptor pathway after LPS stimulation. These experiments demonstrate that FK506 and CsA can selectively enhance IL-6 production in monocytes under certain conditions in vitro and, possibly, also in vivo.

Dimeric and polymeric IgA, but not monomeric IgA, enhance the production of IL-6 by human renal mesangial cells

Depositions of IgA in the renal glomerular mesangial area are a hallmark of IgA nephropathy, and are thought to be crucial for the onset of inflammation processes in IgA nephropathy. In this report we show that human mesangial cells (MC) in vitro bind IgA and that binding of IgA enhances the production of IL-6 by MC. Furthermore we show that the size of IgA is crucial in its capability to enhance IL-6 production. Monomeric IgA does not affect basic IL-6 production, whereas dimeric and polymeric IgA enhance IL-6 production up to 3- to 9-fold respectively. Additional studies demonstrate that enhanced IL-6 production by MC is not accompanied by increased proliferation of human mesangial cells, a finding which is distinct from that found with rat mesangial cells. Taken together, these fmdings suggest that deposition of dimeric and polymeric IgA in the mesangial area of human kidneys in IgA nephropathy may amplify local inflammation.

Interleukin-6 stimulates gene expression of extracellular matrix components in bovine mesangial cells in culture

The effect of interleukin-6 (IL-6) on gene expression of extracellular matrix components in bovine mesangial cells in culture has been investigated. IL-6 (100 U/ml) time dependently increased the steady state expression of mRNAs coding for alpha1 collagen III and fibronectin, both transcripts being 1.5- and 2.5-fold higher than basal level at 24 and 48 h, respectively. In contrast, IL-6 stimulated laminin mRNA expression only after 48 h incubation (2.5-fold upon basal level). These results suggest that IL-6 could favour glomerular matrix accumulation thus contributing to the development of glomerulosclerosis.

Overexpression of RORγt under control of the CD2 promoter induces polyclonal plasmacytosis and autoantibody production in transgenic mice

Retinoic acid related orphan receptor gamma-t (RORγt) is known to be a master regulator of Th17-cell development. In this study, we generated RORγt-overexpressing transgenic (RORγt Tg) mice in which transgene expression was driven by the CD2 promoter, and found that these mice developed polyclonal plasmacytosis and autoantibody production. RORγt Tg mice were generated on a C57BL/6 background, and also were intercrossed with BALB/c mice. BALB/c F1 (BALB/F1) RORγt Tg mice developed massive polyclonal plasma-cytosis, and had shorter life spans. Splenomegaly and infiltration of plasma cells into the lung were observed. Hyperglobulinemia, anti-double-stranded DNA antibodies, anti-erythrocyte antibodies, and anti-platelet antibodies were detected in BALB/F1 RORγt Tg mice. In the present study, polyclonal plasmacytosis in BALB/F1 RORγt Tg mice appeared to be due to the induction of excessive IL-6 production by IL-17. We detected increased numbers of CD11b(+) cells that produced IL-6. We also generatedIL-6-deficient RORγt Tg BALB/F1 background mice, which displayed high levels of serum IL-17, but did not develop severe hyperglobulinemia. Excessive IL-6 production by several cell types, including macrophages, in BALB/F1 RORγt Tg mice, might effect the development of plasma-cytosis. These results suggest that RORγt plays important roles in the development of plasmacytosis and autoantibody production.

Differential role of gp130-dependent STAT and Ras signalling for haematopoiesis following bone-marrow transplantation

Introduction

Bone marrow transplantation (BMT) is a complex process regulated by different cytokines and growth factors. The pleiotropic cytokine IL-6 (Interleukin-6) and related cytokines of the same family acting on the common signal transducer gp130 are known to play a key role in bone marrow (BM) engraftment. In contrast, the exact signalling events that control IL-6/gp130-driven haematopoietic stem cell development during BMT remain unresolved.

Methods

Conditional gp130 knockout and knockin mice were used to delete gp130 expression (gp130^ΔMx), or to selectively disrupt gp130-dependent Ras (gp130^ΔMxRas) or STAT signalling (gp130^ΔMxSTAT) in BM cells. BM derived from the respective strains was transplanted into irradiated wildtype hosts and repopulation of various haematopoietic lineages was monitored by flow cytometry.

Results

BM derived from gp130 deficient donor mice (gp130^ΔMx) displayed a delayed engraftment, as evidenced by reduced total white blood cells (WBC), marked thrombocytopenia and anaemia in the early phase after BMT. Lineage analysis unravelled a restricted development of CD4(+) and CD8(+) T-cells, CD19(+) B-cells and CD11b(+) myeloid cells after transplantation of gp130-deficient BM grafts. To further delineate the two major gp130-induced signalling cascades, Ras-MAPK and STAT1/3-signalling respectively, we used gp130^ΔMxRas and gp130^ΔMxSTAT donor BM. BMT of gp130^ΔMxSTAT cells significantly impaired engraftment of CD4(+), CD8(+), CD19(+) and CD11b(+) cells, whereas gp130^ΔMxRas BM displayed a selective impairment in early thrombopoiesis. Importantly, gp130-STAT1/3 signalling deficiency in BM grafts severely impaired survival of transplanted mice, thus demonstrating a pivotal role for this pathway in BM graft survival and function.

Conclusion

Our data unravel a vital function of IL-6/gp130-STAT1/3 signals for BM engraftment and haematopoiesis, as well as for host survival after transplantation. STAT1/3 and ras-dependent pathways thereby exert distinct functions on individual bone-marrow-lineages.

HHV-8-encoded viral IL-6 collaborates with mouse IL-6 in the development of multicentric Castleman disease in mice

Human herpes virus 8 (HHV-8) or Kaposi sarcoma-associated herpes virus is the etiologic agent of Kaposi sarcoma, primary effusion lymphoma, and plasma cell-type multicentric Castleman disease (MCD). HHV-8 encodes a viral homolog of human IL-6, called viral IL-6 (vIL-6), which does not require the cellular IL-6 receptor for binding to the ubiquitously expressed gp130 receptor subunit and subsequent JAK-STAT signaling. Thus, in contrast to IL-6, vIL-6 can stimulate virtually all cells in the body. To elucidate the mechanism by which vIL-6 drives human diseases, we generated transgenic mice that constitutively express vIL-6 under control of the MHC class I promoter. The mice were found to exhibit vIL-6 serum levels comparable with those observed in HHV-8-infected patients, to contain elevated amounts of phosphorylated STAT3 in spleen and lymph nodes, where vIL-6 was produced, and to spontaneously develop key features of human plasma cell-type MCD, including splenomegaly, multifocal lymphadenopathy, hypergammaglobulinemia, and plasmacytosis. Transfer of the vIL-6 transgene onto an IL-6-deficient genetic background abrogated MCD-like phenotypes, indicating that endogenous mouse IL-6 is a crucial cofactor in the natural history of the disease. Our results in mice suggest that human IL-6 plays an important role in the pathogenesis of HHV-8-associated MCD.

Efficacy of tocilizumab, a humanized neutralizing antibody against interleukin-6 receptor, in progressive renal injury associated with Castleman's disease

Castleman's disease is a benign lymphoproliferative disorder in which interleukin-6 (IL-6), a pleiotropic proinflammatory cytokine, is thought to play a pathogenetic role. Presented is the case of a 72-year-old man with Castleman's disease who exhibited progressive renal dysfunction with proteinuria. Renal biopsy revealed mesangial hypercellularity and matrix expansion in most glomeruli and peritubular inflammatory cell infiltration. Immunofluorescence studies showed intense deposition of IgG in a granular pattern along the glomerular basement membrane. Histological features were compatible with membranoproliferative glomerulonephritis accompanied by interstitial inflammatory cell infiltration. Immunohistological analysis showed that IL-6 was abundantly expressed by tubular cells and interstitial macrophages, suggesting involvement of IL-6 in the renal injury. As a result of administration of tocilizumab, a humanized anti-IL-6 receptor antibody, the patient experienced clinical and biochemical improvement of Castleman's disease, including marked reduction of proteinuria and stabilization of renal function. These findings suggest the efficacy of tocilizumab against Castleman's disease and its renal complications.

Prolonged renal allograft survival by donor interleukin-6 deficiency: association with decreased alloantibodies and increased intragraft T regulatory cells

Both humoral and cellular immune responses are involved in renal allograft rejection. Interleukin (IL)-6 is a regulatory cytokine for both B and Foxp3 (forkhead box P3)-expressing regulatory T (Treg) cells. This study was designed to investigate the impact of donor IL-6 production on renal allograft survival. Donor kidneys from IL-6 knockout (KO) vs. wild-type (WT) C57BL/6 mice (H-2b) were orthotopically transplanted to nephrotomized BALB/c mice (H-2d). Alloantibodies and Treg cells were examined by fluorescence-activated cell sorting analysis. Graft survival was determined by the time to graft failure. Here, we showed that a deficiency in IL-6 expression in donor kidneys significantly prolonged renal allograft survival compared with WT controls. IL-6 protein was upregulated in renal tubules and endothelium of renal allografts following rejection, which correlated with an increase in serum IL-6 compared with that in those receiving KO grafts or naive controls. The absence of graft-producing IL-6 or lower levels of serum IL-6 in the recipients receiving IL-6 KO allografts was associated with decreased circulating anti-graft alloantibodies and increased the percentage of intragraft CD4+CD25+Foxp3+ Treg cells compared with those with WT allografts. In conclusion, the lack of graft-producing IL-6 significantly prolongs renal allograft survival, which is associated with reduced alloantibody production and/or increased intragraft Treg cell population, implying that targeting donor IL-6 may effectively prevent both humoral and cellular rejection of kidney transplants.

IL-6/IL-6 receptor system and its role in physiological and pathological conditions

IL (interleukin)-6, which was originally identified as a B-cell differentiation factor, is a multifunctional cytokine that regulates the immune response, haemopoiesis, the acute phase response and inflammation. IL-6 is produced by various types of cell and influences various cell types, and has multiple biological activities through its unique receptor system. IL-6 exerts its biological activities through two molecules: IL-6R (IL-6 receptor) and gp130. When IL-6 binds to mIL-6R (membrane-bound form of IL-6R), homodimerization of gp130 is induced and a high-affinity functional receptor complex of IL-6, IL-6R and gp130 is formed. Interestingly, sIL-6R (soluble form of IL-6R) also binds with IL-6, and the IL-6-sIL-6R complex can then form a complex with gp130. The homodimerization of receptor complex activates JAKs (Janus kinases) that then phosphorylate tyrosine residues in the cytoplasmic domain of gp130. The gp130-mediated JAK activation by IL-6 triggers two main signalling pathways: the gp130 Tyr759-derived SHP-2 (Src homology 2 domain-containing protein tyrosine phosphatase-2)/ERK (extracellular-signal-regulated kinase) MAPK (mitogen-activated protein kinase) pathway and the gp130 YXXQ-mediated JAK/STAT (signal transducer and activator of transcription) pathway. Increased IL-6 levels are observed in several human inflammatory diseases, such as rheumatoid arthritis, Castleman's disease and systemic juvenile idiopathic arthritis. IL-6 is also critically involved in experimentally induced autoimmune diseases. All clinical findings and animal models suggest that IL-6 plays a number of critical roles in the pathogenesis of autoimmune diseases. In the present review, we first summarize the IL-6/IL-6R system and IL-6 signal transduction, and then go on to discuss the physiological and pathological roles of IL-6.

Cutaneous and systemic plasmacytosis vs. cutaneous plasmacytic castleman disease: review and speculations about pathogenesis

Cutaneous and systemic plasmacytosis (C/SP), human herpes virus-8 (HHV8), negative multicentric plasmacytic Castleman disease (MPCD), and idiopathic plasmacytic lymphadenopathy are polyclonal plasma cell proliferations of unknown etiology that predominantly affect Asian individuals. Herein, we present our experience with a Vietnamese man with typical C/SP limited to the skin but, after 10 years, may have developed perirenal involvement, and with a white man with human immunodeficiency virus and HHV8 negative MPCD with involvement of skin, lymph nodes, and kidneys at presentation, and who later succumbed to gastric carcinoma. Based on a review of the literature, we suggest that C/SP, cutaneous MPCD, and idiopathic plasmacytic lymphadenopathy with skin involvement are part of a continuum rather than distinct entities and, as such, may be regarded as variants of HHV8-negative MPCD. Although the majority of patients with C/SP run a chronic benign course, special attention should be given to monitoring for pulmonary and renal involvement. We hypothesize that long-lived plasma cells originate and survive in the environment of the skin akin to other stromal "survival" niches due to the local production of interleukin 6 and that such patients might respond to agents that interfere with interleukin-6 activity.

Positive regulators of osteoclastogenesis and bone resorption in rheumatoid arthritis

Bone destruction is a frequent and clinically serious event in patients with rheumatoid arthritis (RA). Local joint destruction can cause joint instability and often necessitates reconstructive or replacement surgery. Moreover, inflammation-induced systemic bone loss is associated with an increased fracture risk. Bone resorption is a well-controlled process that is dependent on the differentiation of monocytes to bone-resorbing osteoclasts. Infiltrating as well as resident synovial cells, such as T cells, monocytes and synovial fibroblasts, have been identified as sources of osteoclast differentiation signals in RA patients. Pro-inflammatory cytokines are amongst the most important mechanisms driving this process. In particular, macrophage colony-stimulating factor, RANKL, TNF, IL-1 and IL-17 may play dominant roles in the pathogenesis of arthritis-associated bone loss. These cytokines activate different intracellular pathways to initiate osteoclast differentiation. Thus, over the past years several promising targets for the treatment of arthritic bone destruction have been defined.

Viral interleukin-6: role in Kaposi's sarcoma-associated herpesvirus: associated malignancies

Viral interleukin-6 (vIL-6) is a product of Kaposi's sarcoma-associated herpesvirus (KSHV) expressed in latently infected cells and to a higher degree during viral replication. A distinctive feature of vIL-6 is the ability to directly bind and activate gp130 signaling in the absence of other receptor subunits. Secretion of vIL-6 is generally poor, but vIL-6 can activate gp130 from inside the cell. Due to the wide cell distribution of gp130, vIL-6 has the potential to induce a wide range of biological effects. Expression of vIL-6 is variable in KSHV-associated Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), multicentric Castleman's disease (MCD), and in a newly described MCD-like systemic inflammatory syndrome observed in human immunodeficiency virus-positive patients. PEL effusions usually contain vIL-6 at high concentrations; since vIL-6 induces vascular endothelial growth factor, vIL-6 likely contributes to vascular permeability and formation of PEL effusions. Lymph nodes affected with MCD contain vIL-6-positive cells, and vIL-6 levels rise in conjunction with flares of the disease and likely contribute to symptoms of inflammation. The development of vIL-6 inhibitors is a potentially important advance in the treatment of KSHV-associated malignancies where vIL-6 is expressed.

Expression of HLA class II molecules in humanized NOD.Rag1KO.IL2RgcKO mice is critical for development and function of human T and B cells

BACKGROUND

Humanized mice able to reconstitute a surrogate human immune system (HIS) can be used for studies on human immunology and may provide a predictive preclinical model for human vaccines prior to clinical trials. However, current humanized mouse models show sub-optimal human T cell reconstitution and limited ability to support immunoglobulin class switching by human B cells. This limitation has been attributed to the lack of expression of Human Leukocyte Antigens (HLA) molecules in mouse lymphoid organs. Recently, humanized mice expressing HLA class I molecules have been generated but showed little improvement in human T cell reconstitution and function of T and B cells.

METHODS

We have generated NOD.Rag1KO.IL2RγcKO mice expressing HLA class II (HLA-DR4) molecules under the I-E(d) promoter that were infused as adults with HLA-DR-matched human hematopoietic stem cells (HSC). Littermates lacking expression of HLA-DR4 molecules were used as control.

RESULTS

HSC-infused HLA-DR4.NOD.Rag1KO.IL-2RγcKO mice developed a very high reconstitution rate (>90%) with long-lived and functional human T and B cells. Unlike previous humanized mouse models reported in the literature and our control mice, the HLA-DR4 expressing mice reconstituted serum levels (natural antibodies) of human IgM, IgG (all four subclasses), IgA, and IgE comparable to humans, and elicited high titers of specific human IgG antibodies upon tetanus toxoid vaccination.

CONCLUSIONS

Our study demonstrates the critical role of HLA class II molecules for development of functional human T cells able to support immunoglobulin class switching and efficiently respond to vaccination.

Decreased leukocyte accumulation and delayed Bordetella pertussis clearance in IL-6-/- mice

IL-6, a pleiotropic cytokine primarily produced by the innate immune system, has been implicated in the development of acquired immune responses, though its roles are largely undefined and may vary in the context of different diseases. Using a murine model of infection, we established that IL-6 influences the adaptive immune responses against the endemic human respiratory pathogen Bordetella pertussis. IL-6 was induced in the lungs of C57BL/6 mice by B. pertussis. IL-6(-/-) mice showed a protracted infectious course and were less efficiently protected by B. pertussis vaccination than wild-type mice. Abs from IL-6(-/-) mice, though lower in titer, efficiently reduced B. pertussis numbers in IL-6-sufficient mice. Pulmonary leukocyte recruitment and splenic or pulmonary T cell cytokine responses to B. pertussis, including Th1 and Th17 cytokine production, were lower in IL-6(-/-) mice than in wild-type mice. Adoptive transfer of immune wild-type CD4(+) cells ameliorated the defect of IL-6(-/-) mice in the control of B. pertussis numbers. Together, these results reveal the dysregulation of multiple aspects of adaptive immune responses in B. pertussis-infected IL-6(-/-) mice and suggest that IL-6 is involved in regulating Ab generation, pulmonary leukocyte accumulation, and T cell cytokine production in response to B. pertussis as well as the generation of effective vaccine-induced immunity against this pathogen.

The pro- and anti-inflammatory properties of the cytokine interleukin-6

Interleukin-6 is a cytokine not only involved in inflammation and infection responses but also in the regulation of metabolic, regenerative, and neural processes. In classic signaling, interleukin-6 stimulates target cells via a membrane bound interleukin-6 receptor, which upon ligand binding associates with the signaling receptor protein gp130. Gp130 dimerizes, leading to the activation of Janus kinases and subsequent phosphorylation of tyrosine residues within the cytoplasmic portion of gp130. This leads to the engagement of phosphatase Src homology domains containing tyrosin phosphatase-2 (SHP-2) and activation of the ras/raf/Mitogen-activated protein (MAP) kinase (MAPK) pathway. In addition, signal transducer and activator of transcription factors are recruited, which are phosphorylated, and consequently dimerize whereupon they translocate into the nucleus and activate target genes. Interestingly, only few cells express membrane bound interleukin-6 receptor whereas all cells display gp130 on the cell surface. While cells, which only express gp130, are not responsive to interleukin-6 alone, they can respond to a complex of interleukin-6 bound to a naturally occurring soluble form of the interleukin-6 receptor. Therefore, the generation of soluble form of the interleukin-6 receptor dramatically enlarges the spectrum of interleukin-6 target cells. This process has been named trans-signaling. Here, we review the involvement of both signaling modes in the biology of interleukin-6. It turns out that regenerative or anti-inflammatory activities of interleukin-6 are mediated by classic signaling whereas pro-inflammatory responses of interleukin-6 are rather mediated by trans-signaling. This is important since therapeutic blockade of interleukin-6 by the neutralizing anti-interleukin-6 receptor monoclonal antibody tocilizumab has recently been approved for the treatment of inflammatory diseases. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.

Molecular pathogenesis of multiple myeloma: chromosomal aberrations, changes in gene expression, cytokine networks, and the bone marrow microenvironment

This chapter focuses on two aspects of myeloma pathogenesis: (1) chromosomal aberrations and resulting changes in gene and protein expression with a special focus on growth and survival factors of malignant (and normal) plasma cells and (2) the remodeling of the bone marrow microenvironment induced by accumulating myeloma cells. We begin this chapter with a discussion of normal plasma cell generation, their survival, and a novel class of inhibitory factors. This is crucial for the understanding of multiple myeloma, as several abilities attributed to malignant plasma cells are already present in their normal counterpart, especially the production of survival factors and interaction with the bone marrow microenvironment (niche). The chapter closes with a new model of pathogenesis of myeloma.

Alternate mechanisms of initial pattern recognition drive differential immune responses to related poxviruses

Vaccinia immunization was pivotal to successful smallpox eradication. However, the early immune responses that distinguish poxvirus immunization from pathogenic infection remain unknown. To address this, we developed a strategy to map the activation of key signaling networks in vivo and applied this approach to define and compare the earliest signaling events elicited by immunizing (vaccinia) and lethal (ectromelia) poxvirus infections in mice. Vaccinia induced rapid TLR2-dependent responses, leading to IL-6 production, which then initiated STAT3 signaling in dendritic and T cells. In contrast, ectromelia did not induce TLR2 activation, and profound mouse strain-dependent responses were observed. In resistant C57BL/6 mice, the STAT1 and STAT3 pathways were rapidly activated, whereas in susceptible BALB/c mice, IL-6-dependent STAT3 activation did not occur. These data link early immune signaling events to infection outcome and suggest that activation of different pattern-recognition receptors early after infection may be important in determining vaccine efficacy.

Separate checkpoints regulate splenic plasma cell accumulation and IgG autoantibody production in Lyn-deficient mice

Accumulation of plasma cells and autoantibodies against nuclear antigens characterize both human and murine lupus. Understanding how these processes are controlled may reveal novel therapeutic targets for this disease. Mice deficient in Lyn, a negative regulator of B and myeloid cell activity, develop lupus-like autoimmune disease. Here, we show that lyn(-) (/) (-) mice exhibit increased splenic plasmablasts and plasma cells and produce IgM against a wide range of self-antigens. Both events require Btk, a target of Lyn-dependent inhibitory pathways. A Btk-dependent increase in the expression of the plasma cell survival factor IL-6 by lyn(-) (/) (-) splenic myeloid cells was also observed. Surprisingly, IL-6 was not required for plasma cell accumulation or polyclonal IgM autoreactivity in lyn(-/-) mice. IL-6 was, however, necessary for the production of IgG autoantibodies, which we show are focused towards a limited set of nucleic acid-containing and glomerular autoantigens in lyn(-) (/) (-) mice. A similar uncoupling of plasma cell accumulation from IgG autoantibodies was seen in lyn(+/-) mice. Plasma cell accumulation and polyclonal IgM autoreactivity are therefore controlled separately from, and are insufficient for, the production of IgG against lupus-associated autoantigens. Regulators of either of these two checkpoints may be attractive therapeutic targets for lupus.

The immortality of humoral immunity

Decades of high-titered antibody are sustained due to the persistence of memory B cells and long-lived plasma cells (PCs). The differentiation of each of these subsets is antigen- and T-cell driven and is dependent on signals acquired and integrated during the germinal center response. Inherent in the primary immune response must be the delivery of signals to B cells to create these populations, which have virtual immortality. Differences in biology and chemotactic behavior disperse memory B cells and long-lived PCs to a spectrum of anatomic sites. Each subset must rely on survival factors that can support their longevity. This review focuses on the generation of each of these subsets, their survival, and renewal, which must occur to sustain serological memory. In this context, we discuss the role of antigen, bystander inflammation, and cellular niches. The contribution of BAFF (B-cell activating factor belonging to the tumor necrosis factor family) and APRIL (a proliferation-inducing ligand) to the persistence of memory B cells and PCs are also detailed. Insights that have been provided over the past few years in the regulation of long-lived B-cell responses will have profound impact on vaccine development, the treatment of pre-sensitized patients for organ transplantation, and therapeutic interventions in both antibody- and T-cell-mediated autoimmunity.

Potential immunological adjuvant of `K'-type CpG-oligodeoxynucleotides enhanced the cell proliferation and IL-6 mRNA transcription in canine B cells

CpG oligodeoxynucleotides (CpG-ODNs) are ligands for toll-like receptor 9 (TLR9), signaling of which plays a role in innate immunity by inducing T helper 1 (TH1)-cell responses and pro-inflammatory cytokine production. The activation of TLR9 signaling is considered to be effective for the therapy of cancer, infectious diseases, and allergies and preclinical studies using CpG-ODNs have been performed in dogs and humans. In order to investigate the precise mechanisms responsible for the effect of CpG-ODNs in dogs, we examined their role in cell proliferation and cytokine gene expression in canine B cells. Canine B cells were collected by a magnetic cell isolation method using anti-CD21 antibody. Flow cytometric analysis for the intracellular CD79α revealed the purity of canine B cells to be as high as 90.2 ± 2.1%. Transcription of TLR2, TLR4, and TLR9 mRNA on canine CD21(+) cells was confirmed by reverse-transcript polymerase chain reaction (RT-PCR). CpG-ODNs induced dose-dependent proliferation of canine CD21(+) cells (P<0.05 compared with control-ODNs) detected by BrdU incorporation. Quantification of IL-6, IL-10, and IL-12p40 mRNA transcription on canine CD21(+) cells revealed that CpG-ODNs enhanced IL-6 mRNA transcription but not IL-10 and IL-12p40 mRNA transcription (P<0.05 compared with control-ODNs). These responses to CpG-ODNs in the canine B cells indicated that CpG-ODNs would be useful as an immunological adjuvant for vaccine in dogs.

Transcriptional modulation of heat-shock protein gene expression

Heat-shock proteins (Hsps) are molecular chaperones that are ubiquitously expressed but are also induced in cells exposed to stressful stimuli. Hsps have been implicated in the induction and propagation of several diseases. This paper focuses on regulatory factors that control the transcription of the genes encoding Hsps. We also highlight how distinct transcription factors are able to interact and modulate Hsps in different pathological states. Thus, a better understanding of the complex signaling pathways regulating Hsp expression may lead to novel therapeutic targets.

Renal involvement in Castleman disease

BACKGROUND

Castleman disease (CD), or angiofollicular lymph-node hyperplasia, is an atypical lymphoproliferative disorder with heterogeneous clinical manifestations. Renal involvement in CD has been described in only single-case reports, which have included various types of renal diseases.

METHODS

Nineteen patients with histologically documented CD and renal biopsies available were included. Clinical features and renal histological findings were reviewed, and the available samples were immunolabelled with anti-vascular endothelial growth factor (VEGF) antibody.

RESULTS

Nineteen CD cases were identified: 89% were multicentric, and 84% were of the plasma-cell or mixed type. Four cases (21%) were associated with human immunodeficiency virus (HIV) infection. Among HIV-negative patients, two main patterns of renal involvement were found: (i) a small-vessel lesions group (SVL) (60%) with endotheliosis and glomerular double contours in all patients and with superimposed glomerular/arteriolar thrombi or mesangiolysis in most; and (ii) AA amyloidosis (20%). Renal histology was more heterogeneous among HIV-positive patients. Decreases in glomerular VEGF were observed only in some patients with SVL, whereas VEGF staining was normal in all other histological groups. Interestingly, glomerular VEGF loss associated with SVL was correlated with plasma C-reactive protein levels, a marker of CD activity.

CONCLUSIONS

Small-vessel lesions are the most frequent renal involvement in CD, whereas loss of glomerular VEGF is correlated with CD activity and could have a role in SVL pathophysiology.

gp130 at the nexus of inflammation, autoimmunity, and cancer

Glycoprotein 130 (gp130) is a shared receptor utilized by several related cytokines, including IL-6, IL-11, IL-27, Leukemia Inhibitory Factor (LIF), Oncostatin M (OSM), Ciliary Neurotrophic Factor (CNTF), Cardiotrophin 1 (CT-1) and Cardiotrophin-like Cytokine (CLC). Gp130 plays critical roles during development and gp130-deficient mice are embryonically lethal. However, the best characterized facet of this receptor and its associated cytokines is the ability to promote or suppress inflammation. The aim of this review is to discuss the role of gp130 in promoting or preventing the development of autoimmunity and cancer, two processes that are associated with aberrant inflammatory responses.

In vivo regulation of Bcl6 and T follicular helper cell development

Follicular helper T (T(FH)) cells, defined by expression of the surface markers CXCR5 and programmed death receptor-1 (PD-1) and synthesis of IL-21, require upregulation of the transcriptional repressor Bcl6 for their development and function in B cell maturation in germinal centers. We have explored the role of B cells and the cytokines IL-6 and IL-21 in the in vivo regulation of Bcl6 expression and T(FH) cell development. We found that T(FH) cells are characterized by a Bcl6-dependent downregulation of P-selectin glycoprotein ligand 1 (PSGL1, a CCL19- and CCL21-binding protein), indicating that, like CXCR5 and PD-1 upregulation, modulation of PSGL1 expression is part of the T(FH) cell program of differentiation. B cells were neither required for initial upregulation of Bcl6 nor PSGL1 downregulation, suggesting these events preceded T-B cell interactions, although they were required for full development of the T(FH) cell phenotype, including CXCR5 and PD-1 upregulation, and IL-21 synthesis. Bcl6 upregulation and T(FH) cell differentiation were independent of IL-6 and IL-21, revealing that either cytokine is not absolutely required for development of Bcl6(+) T(FH) cells in vivo. These data increase our understanding of Bcl6 regulation in T(FH) cells and their differentiation in vivo and identifies a new surface marker that may be functionally relevant in this subset.

Role for interleukin-6 in structural joint damage and systemic bone loss in rheumatoid arthritis

Interleukin-6 (IL-6) plays a key role in the local and systemic manifestations of rheumatoid arthritis (RA). IL-6 is not only a proinflammatory cytokine, but also interacts in complex ways with the cells involved in bone remodeling. In RA, IL-6 may indirectly promote osteoclastogenesis by increasing the release of RANK-L by osteoblasts and synovial cells. However, IL-6 inhibits osteoclastogenesis in vitro, via a direct mechanism. The effects of IL-6 on osteoblasts may vary with the cell differentiation stage: thus, IL-6 may promote the differentiation of pre-osteoblasts to mature osteoblasts while also diminishing the proliferation of osteoblasts at late differentiation stages. Thus, the effects of IL-6 on bone remodeling are complex and may occur in opposite directions depending on the model or experimental conditions. Nevertheless, results from studies in animal models and humans support a negative effect of IL-6 on bone. Thus, in patients with RA, blocking IL-6 may be effective both in diminishing the inflammatory manifestations and in preventing the bone complications of the disease.

IL-6: from its discovery to clinical applications

In the late 1960s, the essential role of T cells in antibody production was reported. This led to our hypothesis that T-cell-derived soluble factors would have to be involved in the activation of B cells. The factor that induced B cells to produce immunoglobulins was initially named B-cell stimulatory factor-2. In 1986, we successfully cloned the complementary DNA encoding B-cell stimulatory factor-2, now known as IL-6. At the same time, IFN-beta2 and a 26-kDa protein found in fibroblasts were independently cloned and found to be identical to IL-6. Later, a hybridoma/plasmacytoma growth factor and a hepatocyte-stimulating factor were also proven to be the same molecule as IL-6. Now, we know that IL-6 is a pleiotropic cytokine with a wide range of biological activities in immune regulation, hematopoiesis, inflammation and oncogenesis. Since the discovery of IL-6, we have further clarified its activities, the IL-6R system and the IL-6 signal transduction mechanism. On the basis of the findings, a new therapeutic approach to block the actions of IL-6 by use of a humanized anti-IL-6R antibody has been proven to be therapeutically effective for rheumatoid arthritis, systemic juvenile idiopathic arthritis and Castleman's disease. In this review, I discuss the history of IL-6 research as a paradigm of progress from basic science to clinical applications.

IL-6 increases B-cell IgG production in a feed-forward proinflammatory mechanism to skew hematopoiesis and elevate myeloid production

Src homology 2 domain-containing inositol 5-phosphatase (SHIP(-/-)) animals display an age-related increase in interleukin-6 (IL-6), a decrease in B lymphopoiesis, and an elevation in myelopoiesis. We investigated the origin of the IL-6 production and show that it is largely produced by peritoneal and splenic macrophages. IL-6 production by these macrophages is not a direct result of the loss of SHIP: IL-6 production is not spontaneous, is absent from bone marrow-derived macrophages, declines with prolonged culture of macrophages, and requires a stimulus present in vivo. The IL-6-rich peritoneal cavity of SHIP(-/-) mice shows more than 700-fold more immunoglobulin G (IgG) than wild-type, approximately 20% of which is aggregated or in an immune complex and contains B220(+) cells that secrete IgG. The SHIP-deficient peritoneal macrophages show evidence of IgG receptor stimulation. Animals lacking both the signal-transducing gamma-chain of IgG receptors and SHIP or Ig and SHIP produce less IL-6. The data indicate a feed-forward process in which peripheral macrophages, responding through IgG receptors to secreted IgG, produce IL-6, to support further B-cell production of IgG. Because of the proinflammatory phenotype of SHIP(-/-) animals, these findings emphasize the importance of IL-6-neutralizing strategies in autoimmune and proinflammatory diseases.

Neurotrophins regulate bone marrow stromal cell IL-6 expression through the MAPK pathway

BACKGROUND

The host's response to infection is characterized by altered levels of neurotrophins and an influx of inflammatory cells to sites of injured tissue. Progenitor cells that give rise to the differentiated cellular mediators of inflammation are derived from bone marrow progenitor cells where their development is regulated, in part, by cues from bone marrow stromal cells (BMSC). As such, alteration of BMSC function in response to elevated systemic mediators has the potential to alter their function in biologically relevant ways, including downstream alteration of cytokine production that influences hematopoietic development.

METHODOLOGY/PRINCIPAL FINDINGS

In the current study we investigated BMSC neurotrophin receptor expression by flow cytometric analysis to determine differences in expression as well as potential to respond to NGF or BDNF. Intracellular signaling subsequent to neurotrophin stimulation of BMSC was analyzed by western blot, microarray analysis, confocal microscopy and real-time PCR. Analysis of BMSC Interleukin-6 (IL-6) expression was completed using ELISA and real-time PCR.

CONCLUSION

BMSC established from different individuals had distinct expression profiles of the neurotrophin receptors, TrkA, TrkB, TrkC, and p75(NTR). These receptors were functional, demonstrated by an increase in Akt-phosphorylation following BMSC exposure to recombinant NGF or BDNF. Neurotrophin stimulation of BMSC resulted in increased IL-6 gene and protein expression which required activation of ERK and p38 MAPK signaling, but was not mediated by the NFkappaB pathway. BMSC response to neurotrophins, including the up-regulation of IL-6, may alter their support of hematopoiesis and regulate the availability of inflammatory cells for migration to sites of injury or infection. As such, these studies are relevant to the growing appreciation of the interplay between neurotropic mediators and the regulation of hematopoiesis.

Human IL6 enhances leptin action in mice

AIMS/HYPOTHESIS

Interleukin-6 is an inflammatory cytokine with pleiotropic effects upon nutrient homeostasis. Many reports show that circulating IL6 correlates with obesity and contributes to insulin resistance; however, IL6 can promote energy expenditure that improves glucose homeostasis.

METHODS

We investigated nutrient homeostasis in C57BL/6J mice with sustained circulating human IL6 (hIL6) secreted predominantly from brain and lung (hIL6(tg) mice).

RESULTS

The hIL6(tg) mice displayed no features of systemic inflammation and were more insulin-sensitive than wild-type mice. On a high-fat diet, hIL6(tg) mice were lean, had low leptin concentrations, consumed less food and expended more energy than wild-type mice. Like ob/ob mice, the ob/ob (IL6) mice (generated by intercrossing ob/ob and hIL6(tg) mice) were obese and glucose-intolerant. However, low-dose leptin injections increased physical activity and reduced both body weight and food intake in ob/ob (IL6) mice, but was ineffective in ob/ob mice. Leptin increased hypothalamic signal transducer and activator of transcription-3 phosphorylation in ob/ob (IL6) mice, whereas ob/ob mice barely responded.

CONCLUSIONS/INTERPRETATION

Human IL6 enhanced central leptin action in mice, promoting nutrient homeostasis and preventing diet-induced obesity.

Epidermal loss of JunB leads to a SLE phenotype due to hyper IL-6 signaling

Systemic lupus erythematosus (SLE) is a complex autoimmune disease affecting various tissues. Involvement of B and T cells as well as increased cytokine levels have been associated with disease manifestation. Recently, we demonstrated that mice with epidermal loss of JunB (JunB(Deltaep)) develop a myeloproliferative syndrome (MPS) due to high levels of G-CSF which are secreted by JunB-deficient keratinocytes. In addition, we show that JunB(Deltaep) mice develop a SLE phenotype linked to increased epidermal interleukin 6 (IL-6) secretion. Intercrosses with IL-6-deficient mice could rescue the SLE phenotype. Furthermore, we show that JunB binds to the IL-6 promoter and transcriptionally suppresses IL-6. Facial skin biopsies of human SLE patients similarly revealed low JunB protein expression and high IL-6, activated Stat3, Socs-1, and Socs-3 levels within lupus lesions. Thus, keratinocyte-induced IL-6 secretion can cause SLE and systemic autoimmunity. Our results support trials to use alpha-IL-6 receptor antibody therapy for treatment of SLE.

Dichloroacetate alleviates development of collagen II-induced arthritis in female DBA/1 mice

INTRODUCTION

Dichloroacetate (DCA) has been in clinical use for the treatment of lactacidosis and inherited mitochondrial disorders. It has potent anti-tumor effects both in vivo and in vitro, facilitating apoptosis and inhibiting proliferation. The pro-apoptotic and anti-proliferative properties of DCA prompted us to investigate the effects of this compound in arthritis.

METHODS

In the present study, we used DCA to treat murine collagen type II (CII)-induced arthritis (CIA), an experimental model of rheumatoid arthritis. DBA/1 mice were treated with DCA given in drinking water.

RESULTS

Mice treated with DCA displayed much slower onset of CIA and significantly lower severity (P < 0.0001) and much lower frequency (36% in DCA group vs. 86% in control group) of arthritis. Also, cartilage and joint destruction was significantly decreased following DCA treatment (P = 0.005). Moreover, DCA prevented arthritis-induced cortical bone mineral loss. This clinical picture was also reflected by lower levels of anti-CII antibodies in DCA-treated versus control mice, indicating that DCA affected the humoral response. In contrast, DCA had no effect on T cell- or granulocyte-mediated responses. The beneficial effect of DCA was present in female DBA/1 mice only. This was due in part to the effect of estrogen, since ovariectomized mice did not benefit from DCA treatment to the same extent as sham-operated controls (day 30, 38.7% of ovarectomized mice had arthritis vs. only 3.4% in sham-operated group).

CONCLUSION

Our results indicate that DCA delays the onset and alleviates the progression of CIA in an estrogen-dependent manner.

TANK is a negative regulator of Toll-like receptor signaling and is critical for the prevention of autoimmune nephritis

The intensity and duration of immune responses are controlled by multiple proteins that modulate Toll-like receptor (TLR) signaling. TRAF family member-associated NF-κB activator (TANK) has been implicated in positive regulation of interferon-regulatory factor-3 as well as NF-κB. Here we demonstrate that TANK is not involved in interferon responses, and is a negative regulator of proinflammatory cytokine production induced by TLR signaling. TLR-induced polyubiquitination of TRAF6 was upregulated in Tank^−/−macrophages. Notably, Tank^−/− mice spontaneously developed fatal glomerulonephritis owing to deposition of immune complexes. Autoantibody production in Tank^−/− mice was rescued by antibiotic treatment or the absence of interleukin (IL)-6 or MyD88. These results demonstrate that constitutive TLR signaling by intestinal commensal microflora is suppressed by TANK.

Effect of interleukin-6 receptor blockage on renal injury in apolipoprotein E-deficient mice

Hyperlipidemia has been demonstrated to be associated with renal disease, yet the mechanism of renal injury is still poorly understood. Inflammation that occurs with the hyperlipidemia has been considered to play an important role in development of glomerular injury. In the present study, we investigated the role of interleukin-6 (IL-6), a key inflammatory molecule, on renal injury in apolipoprotein E-deficient (ApoE(-/-)) mice with severe hypercholesterolemia. The 6-wk-old mice were fed a high-fat diet and administered weekly rat anti-IL-6 receptor monoclonal antibody (MR16-1), control rat IgG, or saline for a total of 4 wk. We examined histopathological changes in the kidney and urinary excretion of protein and albumin. Saline- and IgG-treated mice showed remarkable proteinuria at 10 wk of age, whereas MR16-1-treated mice exhibited significantly lower levels. Renal histopathology of saline- and IgG-treated mice revealed striking lipid deposits and foam cells in the glomerular tuft, juxtaglomerular area, and arteriolar wall along with range of mesangial cell proliferation and matrix expansion. Notably, the severity of lipid deposits and mesangial cell proliferation were significantly reduced in MR16-1-treated mice. Immunohistochemistry demonstrated that mesangial IL-6 expression was dramatically reduced in MR16-1-treated mice compared with IgG-treated mice. Blocking the IL-6 receptor prevented progression of proteinuria and renal lipid deposit, as well as the mesangial cell proliferation associated with severe hyperlipoproteinemia. These results clearly demonstrate that IL-6 plays an essential role in the pathogenesis of hyperlipidemia-induced glomerular injury in ApoE(-/-) mice and suggests the usefulness of anti-IL-6 receptor antibody in treatments for hyperlipidemia-induced organ damage.