IgG1 plasmacytosis in interleukin 6 transgenic mice

Suppressors of cytokine signaling: Relevance to gastrointestinal function and disease

BACKGROUND & AIMS

The suppressor of cytokine signaling (SOCS) proteins are a family of Src homology 2 domain-containing proteins. Currently, there are 8 members of the SOCS family, of which a number have been implicated strongly in the negative regulation of cytokine signal transduction pathways.

METHODS

This review focuses on recent discoveries about 4 SOCS family members, SOCS-1, -2, and -3, and cytokine-inducible SH2-domain containing (CIS), and provides more limited information about other SOCS family members.

RESULTS

A large number of cytokines and growth factors are now known to induce SOCS proteins. In turn, SOCS inhibit the actions of a growing number of cytokines and growth factors in vitro or in vivo. SOCS proteins exert their inhibitory effects at the level of activation of janus kinases (JAKs) or by competing with transcription factors for binding sites on activated cytokine receptors. SOCS proteins also may mediate the ubiquitination and subsequent degradation of the SOCS protein and its bound signaling complex. Genetic modification of SOCS genes in mice has revealed crucial roles in the negative regulation of a number of important physiologic parameters including interferon gamma activity, growth, blood cell production, and placental development.

CONCLUSIONS

Information about SOCS action in gastrointestinal function and disease is only just emerging, but available data indicate a role in growth of gastrointestinal tissues, inflammatory bowel disease, and cancer.

Endocytosis of light chains induces cytokines through activation of NF-kappaB in human proximal tubule cells

BACKGROUND

In proteinuric states increased cytokine production through endocytosis of filtered proteins by proximal tubule cells (PTCs) has been proposed as a major mechanism mediating tubulointerstitial injury and progressive kidney disease. We studied the effects of six different light chains (LCs) on the production of cytokines in cultured human PTCs.

METHODS

LCs were isolated and purified from the urine of patients with myeloma and human PTCs were exposed to either LC or human serum albumin (HSA) for up to 24 hours. LC endocytosis was monitored by immunocytochemistry. Cytokines were determined by enzyme-linked immunosorbent assay (ELISA) in the supernatants and activation of nuclear factor-kappa B (NF-kappaB) was detected by electrophoretic mobility shift assays (EMSA) and immunocytochemistry.

RESULTS

Endocytosis of LCs induced the release of interleukins (IL) IL-6, IL-8 and monocyte chemoattractant protein-1 (MCP-1); however, there was considerable variability among the six different LCs. In contrast, HSA had no effect on cytokine production even at very high concentrations. Removal of LC-containing media resulted in cessation of IL-6 release. LC-induced cytokine release was associated with nuclear translocation of NF-kappaB subunits p50 and p65, as demonstrated by both EMSA and immunocytochemistry. Inhibitors of NF-kappaB, aspirin and pyrrolidineditiocarbamate (PDTC) markedly suppressed LC-induced cytokine production.

CONCLUSION

LC endocytosis leads to production of inflammatory cytokines through activation of NF-kappaB. This may be an important mechanism of chronic tubulointerstitial inflammation process commonly seen in multiple myeloma. These findings also point out a potential role by filterable low-molecular-weight proteins, like LCs, in PTC injury during all proteinuric diseases.

The role of transsignalling via the agonistic soluble IL-6 receptor in human diseases

The activation of cells that do not express the membrane bound interleukin-6 6 receptor (IL-6R) by IL-6 and the soluble IL-6 receptor (sIL-6R) is termed transsignalling. Transsignalling may be an pathogenetic factor in human diseases as diverse as multiple myeloma (MM), Castleman's disease, prostate carcinoma, Crohn's disease, systemic sclerosis, Still's disease, osteoporosis and cardiovascular diseases. IL-6 and sIL-6R may directly or indirectly enhance their own production on endothelial or bone marrow stromal cells. Positive feedback autocrine loops thus created in affected organs may either cause or maintain disease progression. In autoimmune or vasculitic disease, the ability of the IL-6/sIL-6R complex to inhibit apoptosis of autoreactive T-cells may be central to the development of tissue specific autoimmunity. The anti-apoptotic effect of the IL-6/sIL-6R complex may be involved in tumour genesis and resistance to chemotherapy. Only in rare cases, where counterregulation has failed, there is a notable systemic effect of IL-6/sIL-6R. Appropriate animal models are necessary to establish the pathogenetic role of the IL-6/sIL-6R complex. A specific treatment option for diseases influenced by the sIL-6R could be based on gp130-Fc, a soluble gp130 (sgp130) linked to the Fc-fragment of IgG1. gp130-Fc has shown efficacy in vivo in animal models of Crohn's disease.

RNA expression profiling as prognostic tool in renal patients: toward nephrogenomics

Damage to the kidney generally elicits tissue repair mechanisms, but these processes themselves conversely may result in the progression of chronic renal disease. In a majority of patients chronic renal insufficiency progresses to a common histological end point, marked by the presence of a vast amount of scar tissue, that is, glomerulosclerosis and interstitial fibrosis. These lesions are the result of an excessive production of extracellular matrix (ECM) components. Studies on RNA expression in experimental kidney disease have shown that renal mRNA levels for ECM components and cytokines can function as prognostic tools. This suggests that mRNA levels potentially predict outcome and reaction to therapy in patients with renal diseases. Timely detection of molecular alterations could allow early therapeutic intervention that slows down or even prevents the development of sclerotic and fibrotic lesions. This review first provides a short introduction on mechanisms of initiation and progression of renal disease. Molecular techniques are available to identify renal RNA sequences potentially involved in disease progression. We discuss several molecular techniques that are being used in kidney research for quantitation and detection of mRNA. This is followed by a brief overview of investigation in experimental renal diseases, which reveal that alterations in tissue ECM mRNA levels precede histological damage and can function as predictors of clinical outcome. In particular, studies in human kidney biopsies that evaluate the prognostic value of mRNA levels with respect to renal function are examined, paying special attention to the pitfalls that potentially are encountered when interpreting the results of such studies. Then, we elaborate on ways of optimal exploitation of mRNA quantification as a prognostic tool. The potential and limitations of microarray technology in the search for genes specifically involved in progression of renal disease are reviewed, including RNA expression profiling and large-scale DNA mutation screening. Finally, the future utilities of microarray in nephrology and renal pathology are discussed.

Molecular analysis of lipid-depleting factor in a colon-26-inoculated cancer cachexia model

Cachexia in cancer is characterized by progressive emaciation involving depletion of host adipose tissue stores, the molecular mechanism of which remains largely unknown. In this study, we have attempted to clarify the biologic characteristics of lipid-depleting factor in a mouse cachexia model. Utilizing differentiated 3T3-L1 adipocytes, we established an assay method quantifying the lipid-depleting activity in plasma derived from colon-26-inoculated mice and then analyzed the associated molecular mechanism. Injection (s.c.) of a mouse colon adenocarcinoma cell line, colon-26 clone 20, induced cachexia, as evidenced by progressive weight loss. Addition of clone 20-derived cachexigenic, but not clone 5-derived noncachexigenic, plasma to the culture medium of differentiated 3T3-L1 adipocytes reduced the TG content in cultured cells. The ability of the introduced plasma to induce TG loss in 3T3-L1 cells paralleled the body weight changes of tumor-inoculated host mice. Clone 20 plasma, but not clone 5 plasma or recombinant IL-6, elicited lipolytic activity, which induced glycerol release from 3T3-L1 cells. Addition of clone 20 plasma to cultured 3T3-L1 adipocytes reduced TG synthesis from [(14)C]-glucose compared to clone 5 plasma, indicating that the lipid-depleting activity resulting from addition of clone 20 plasma depended not only on induction of lipolysis but also on inhibition of lipogenesis. Addition of clone 20 plasma to cultured 3T3-L1 adipocytes reduced the quantity of mature SREBP-1 in the nucleus of 3T3-L1 cells without affecting PPAR-gamma and C/EBP-alpha. Although TNF-alpha induced apoptosis in 3T3-L1 cells, clone 20 plasma did not. These results suggest that the lipid-depleting factor in clone 20 plasma is different from either IL-6 or TNF-alpha, and that this factor interfered with not only lipolysis but also lipogenesis through SREBP-1 of 3T3-L1 adipocytes.

IL-6 in autoimmune disease and chronic inflammatory proliferative disease

Interleukin 6 (IL-6), which was originally identified as a B-cell differentiation factor, is now known to be a multifunctional cytokine that regulates the immune response, hematopoiesis, the acute phase response, and inflammation. Deregulation of IL-6 production is implicated in the pathology of several disease processes. The expression of constitutively high levels of IL-6 in transgenic mice results in fatal plasmacytosis, which has been implicated in human multiple myeloma. Increased IL-6 levels are also observed in several diseases, including rheumatoid arthritis (RA), systemic-onset juvenile chronic arthritis (JCA), osteoporosis, and psoriasis. IL-6 is critically involved in experimentally induced autoimmune disease, such as antigen-induced arthritis (AIA), and experimental allergic encephalomyelitis. All these clinical data and animal models suggest that IL-6 plays critical roles in the pathogenesis of autoimmune diseases. Here we review the evidence for the involvement of IL-6 in the pathophysiology of autoimmune diseases and chronic inflammatory proliferative diseases (CIPD) and discuss the possible molecular mechanisms of its involvement.

B lymphocyte stimulator protein levels in systemic lupus erythematosus and other diseases

The size of the known members of the tumor necrosis factor ligand and receptor superfamilies has burgeoned in the past few years. Among the novel tumor necrosis factor ligand and receptor superfamily members recently described is B lymphocyte stimulator (BLyS; Human Genome Sciences, Rockville, MD) protein. By virtue of its ability to promote B-cell survival, expansion, and differentiation, it likely plays an important contributory role in systemic lupus erythematosus pathogenesis and propagation. In addition, it may play a similar role in other systemic immune-based rheumatic diseases, and becomes a legitimate candidate target for antagonist biologic agents.

Regulatory effects of novel neurotrophin-1/b cell-stimulating factor-3 (cardiotrophin-like cytokine) on B cell function

We describe regulatory effects that a novel neurotrophin-1/B cell-stimulating factor-3 (NNT-1/BSF-3; also reported as cardiotrophin-like cytokine) has on B cell function. NNT-1/BSF-3 stimulates B cell proliferation and Ig production in vitro. NNT-1/BSF-3-transgenic mice, engineered to express NNT-1/BSF-3 in the liver under control of the apolipoprotein E promoter, show B cell hyperplasia with particular expansion of the mature follicular B cell subset in the spleen and the prominent presence of plasma cells. NNT-1/BSF-3-transgenic mice show high serum levels of IgM, IgE, IgG2b, IgG3, anti-dsDNA Abs, and serum amyloid A. NNT-1/BSF-3-transgenic mice also show non-amyloid mesangial deposits that contain IgM, IgG, and C3 and are characterized by a distinctive ultrastructure similar to that of immunotactoid glomerulopathy. NNT-1/BSF-3-transgenic mice produce high amounts of Ag-specific IgM, IgA, and IgE and low amounts of IgG2a and IgG3. Normal mice treated with NNT-1/BSF-3 also produce high amounts of Ag-specific IgE. NNT-1/BSF-3 regulates immunity by stimulating B cell function and Ab production, with preference for Th2 over Th1 Ig types.

IL-6 rescues the hyporesponsiveness of c-Rel deficient B cells independent of Bcl-xL, Mcl-1, and Bcl-2

The hematopoietically restricted member of the NF-kappaB/Rel family, c-Rel, is essential for B cell survival and proliferation. Here we demonstrate that the production of the interleukins 6, 10, and 15 (IL-6, IL-10, and IL-15) are diminished in c-Rel(-/-) B lymphocytes. In a manner similar to that seen in IL-6(-/-) B cells, resultant STAT activation is reduced in c-Rel(-/-) B cells following B cell receptor (BCR) ligation. Addition of either exogenous IL-6 or IL-10, but not IL-15, partially restores proliferation, and this occurs through enhanced cell survival rather than promoting cell cycle progression. This increase in viability occurs independently of Bcl-xL and Mcl-1 expression though, two survival genes reported to be downstream of IL-6 signaling. Nonetheless, transgenically expressed Bcl-xL, a direct c-Rel target gene in B cells, corrects not only the survival defect of c-Rel deficiency, but also partially ameliorates hypoproliferation. Together IL-6 and Bcl-xL are additive but incomplete in the restoration of proliferation. Known deficits in the induction of several key cell cycle components in c-Rel(-/-)B cells are not corrected upon treatment with exogenous cytokine. Together, these data demonstrate that IL-6 enhances B cell responses by employing multiple survival factors.

Increased proliferation of B cells and auto-immunity in mice lacking protein kinase Cdelta

Protein kinase C (PKC), which comprises 11 closely related isoforms, has been implicated in a wide variety of cellular processes, such as growth, differentiation, secretion, apoptosis and tumour development. Among the PKC isotypes, PKC-delta is unique in that its overexpression results in inhibition of cell growth. Here we show that mice that lack PKC-delta exhibit expansion of the B-lymphocyte population with the formation of numerous germinal centres in the absence of stimulation. The rate of proliferation in response to stimulation was greater for B cells from PKC-delta-deficient mice than for those from wild-type mice. Adoptive transfer experiments suggested that the hyperproliferation phenotype is B-cell autonomous. Production of interleukin-6 was markedly increased in B cells of PKC-delta-null mice as a result of an increase in the DNA-binding activity of NF-IL6. Furthermore, the PKC-delta-deficient mice contain circulating autoreactive antibodies and display immune-complex-type glomerulonephritis, as well as lymphocyte infiltration in many organs. These results suggest that PKC-delta has an indispensable function in negative regulation of B-cell proliferation, and is particularly important for the establishment of B-cell tolerance.

IL-6 transgenic mouse model for extraosseous plasmacytoma

Plasma cell neoplasms in humans comprise plasma cell myeloma, otherwise known as multiple myeloma, Ig deposition and heavy chain diseases, and plasmacytoma (PCT). A subset of PCT, designated extramedullary PCT, is distinguished from multiple myeloma and solitary PCT of bone by its distribution among various tissue sites but not the bone marrow. Extramedullary (extraosseus) PCT are rare spontaneous neoplasms of mice but are readily induced in a susceptible strain, BALB/c, by treatment with pristane. The tumors develop in peritoneal granulomas and are characterized by Myc-activating T(12;15) chromosomal translocations and, most frequently, by secretion of IgA. A uniting feature of human and mouse plasma cell neoplasms is the critical role played by IL-6, a B cell growth, differentiation, and survival factor. To directly test the contribution of IL-6 to PCT development, we generated BALB/c mice carrying a widely expressed IL-6 transgene. All mice exhibited lymphoproliferation and plasmacytosis. By 18 months of age, over half developed readily transplantable PCT in lymph nodes, Peyer's patches, and sometimes spleen. These neoplasms also had T(12;15) translocations, but remarkably, none expressed IgA. Unexpectedly, approximately 30% of the mice developed follicular and diffuse large cell B cell lymphomas that often coexisted with PCT. These findings provide a unique model of extramedullary PCT for studies on pathogenesis and treatment and suggest a previously unappreciated role for IL-6 in the genesis of germinal center-derived lymphomas.

IL-6-like cytokines and cancer cachexia: consequences of chronic inflammation

An estimated 30% of cancer deaths are attributed to cachexia and its consequences. Cachexia (wasting syndrome) is the hypercatabolism of the body's carbon sources, proteins and lipids, for conversion into energy. It is induced by a variety of pathological conditions, including cancer. Among the inflammatory responses to cancer is the synthesis of cytokines, including IL-6 and related cytokines. These cytokines have been found to induce cachexia by altering metabolism of lipids and proteins. IL-6-like cytokines have been found to inhibit lipid biosynthesis by adipocytes, which increased the rate of lipid catabolism. Others have described the atrophy and increased catabolism of muscle protein due to IL-6. A cytokine closely-related to IL-6 is leptin, which plays a major role in lipid metabolism under normal conditions. The role of leptin in pathological conditions such as cancer cachexia has not yet been fully elucidated. Detailed mechanistic information about the induction of cancer cachexia by IL-6-like cytokines requires more research.

Distinct requirements for IL-6 in polyclonal and specific Ig production induced by microorganisms

The role of IL-6 in Ig production induced in the mouse by lactate dehydrogenase-elevating virus (LDV), Toxoplasma gondii or lipopolysaccharide (LPS) was assessed. Following infection with LDV, a strong activator of B cells, an early and transient IL-6 production was observed, that originated predominantly from macrophages. Whereas LDV-induced B lymphocyte proliferation appeared independent of IL-6, mice deficient for this cytokine showed a marked reduction in their total T-dependent IgG2a production when compared to their normal counterparts. By contrast, specific responses directed against either LDV or non-viral antigens administered at the time of infection were not decreased in the absence of IL-6. Similarly, polyclonal, but not anti-parasite IgG2a production triggered by T. gondii infection was strongly dependent on the presence of IL-6. Finally, T-independent total IgG3 secretion triggered by LPS was also markedly reduced in IL-6-deficient mice. These results suggest that IL-6 plays a major role in T-dependent and T-independent polyclonal Ig production following B lymphocyte activation by viruses, and parasites, but not in specific antibody responses induced by the same microorganisms.

Overexpression of interleukin-6 aggravates viral myocarditis: impaired increase in tumor necrosis factor-alpha

The process of inflammation and immune response is regulated by proinflammatory cytokines. Interleukin-6 (IL-6), one of the proinflammatory cytokines, plays a potentially critical role in viral-induced myocarditis. Our previous work demonstrates that exogenous IL-6 administration, given at the time of encephalomyocarditis virus (EMCV) inoculation in C3H/HeJ mice, has a protective effect on myocardium and improves survival rates. In the present study, we examined whether overexpression of IL-6 modified viral myocarditis. On day 3 and 10 after inoculation with EMCV, the ratio of heart weight to body weight and myocardial injury were significantly increased in IL-6 transgenic mice (IL-6TG). On day 3, a reduction of viral clearance was shown by the presence of elevated viral titers and viral replication in the heart of IL-6TG. The concentrations of serum tumor necrosis factor- alpha (TNF alpha) were dramatically increased in wild-type mice on day 1, in contrast, this change was not observed in IL-6TG. Treatment with recombinant human TNF (2 microg) significantly improved viral clearance in the IL-6TG hearts. Thus, overexpression of IL-6 promotes myocardial injury by interrupting both the cytokine network and viral clearance. These experiments suggest the possibility that IL-6 is one of the factors that accelerates tissue damage, including myocardial injury, in the viral myocarditis.

Strain-dependency of chromosomal abnormalities in lymphomas developed in E mu-myc transgenic mice

We previously showed that B and T cell lymphoma development in Em (immunoglobulin heavy chain enhancer)-myc transgenic mice is dependent on the mouse strain. To determine whether any non-random chromosomal abnormality that was present was caused by variations in the lymphoma cell type or by a different genetic background, we crossed C3H transgenic mice with other inbred strains of mice, C57BL / 6 or BALB / c. Cytogenetic analysis showed a high frequency of non-random chromosomal aberrations, namely, duplication or amplification of part of chromosome 5 containing the transgene and trisomy of chromosome 1, 6, or 12 in the genetic background of C3H x C57BL / 6 mouse and C3H x BALB / c mouse, respectively, regardless of cell type of lymphoma. These results suggest that non-random chromosomal abnormalities in lymphoma cells are dependent on the genetic background of mouse, not on the tumor cell type in Em-myc transgenic mouse.

Age-associated differences in cardiovascular inflammatory gene induction during endotoxic stress

Upon physiological stress, families of stress response genes are activated as natural defense mechanisms. Here, we show that induction of specific inflammatory genes is significantly dysregulated and altered in the heart of aged (24--26-month-old) versus young (4-month-old) mice experimentally challenged with a bacterial endotoxin, lipopolysaccharide (LPS, 1.5 mg/kg of body mass). Whereas the LPS-mediated induction of cardiac mRNA for tumor necrosis factor alpha or inducible nitric-oxide synthase showed no age-associated differences, the induction of interleukin-1 beta (IL-1 beta) and intracellular adhesion molecule-1 was modestly extended with aging, and the induction of IL-6 was significantly prolonged with aging. This age-associated phenomenon occurred gradually from 4 to 17 months of age and became more evident after 23 months of age. The age-associated augmentation of the cardiac IL-6 induction was also dramatic at the protein level. Immunohistochemically, the LPS-induced cardiac IL-6 was localized mainly in the microvascular walls. Aged but not young mice showed a high mortality rate during these experiments. These results demonstrate that endotoxin-mediated induction of specific inflammatory genes in cardiovascular tissues is altered with aging, which may be causally related to the increased susceptibility of aged animals to endotoxic stress.

Defective gp130-mediated signal transducer and activator of transcription (STAT) signaling results in degenerative joint disease, gastrointestinal ulceration, and failure of uterine implantation

The receptor subunit gp130 transduces multiple cell type-specific activities of the leukemia inhibitory factor (LIF)/interleukin (IL)-6 family of cytokines through the signal transducer and activator of transcription (STAT) and src homology 2 domain-bearing protein tyrosine phosphatase (SHP)-2/ras/Erk pathways. To define STAT-dependent physiological responses, we generated mice with a COOH-terminal gp130(DeltaSTAT) "knock-in" mutation which deleted all STAT-binding sites. gp130(DeltaSTAT) mice phenocopyed mice deficient for IL-6 (impaired humoral and mucosal immune and hepatic acute phase responses) and LIF (failure of blastocyst implantation). However, unlike mice with null mutations in any of the components in the gp130 signaling pathway, gp130(DeltaSTAT) mice also displayed gastrointestinal ulceration and a severe joint disease with features of chronic synovitis, cartilaginous metaplasia, and degradation of the articular cartilage. Mitogenic hyperresponsiveness of synovial cells to the LIF/IL-6 family of cyto-kines was caused by sustained gp130-mediated SHP-2/ras/Erk activation due to impaired STAT-mediated induction of suppressor of cytokine signaling (SOCS) proteins which normally limits gp130 signaling. Therefore, the joint pathology in gp130(DeltaSTAT) mice is likely to arise from the disturbance of the otherwise balanced activation of the SHP-2/ras/Erk and STAT signaling cascades emanating from gp130.

Ubiquitous transgenic expression of the IL-23 subunit p19 induces multiorgan inflammation, runting, infertility, and premature death

p19, a molecule structurally related to IL-6, G-CSF, and the p35 subunit of IL-12, is a subunit of the recently discovered cytokine IL-23. Here we show that expression of p19 in multiple tissues of transgenic mice induced a striking phenotype characterized by runting, systemic inflammation, infertility, and death before 3 mo of age. Founder animals had infiltrates of lymphocytes and macrophages in skin, lung, liver, pancreas, and the digestive tract and were anemic. The serum concentrations of the proinflammatory cytokines TNF-alpha and IL-1 were elevated, and the number of circulating neutrophils was increased. In addition, ubiquitous expression of p19 resulted in constitutive expression of acute phase proteins in the liver. Surprisingly, liver-specific expression of p19 failed to reproduce any of these abnormalities, suggesting specific requirements for production of biologically active p19. Bone marrow transfer experiments showed that expression of p19 by hemopoietic cells alone recapitulated the phenotype induced by its widespread expression, pointing to hemopoietic cells as the source of biologically active p19. These findings indicate that p19 shares biological properties with IL-6, IL-12, and G-CSF and that cell-specific expression is required for its biological activity.

Elevated serum B lymphocyte stimulator levels in patients with systemic immune-based rheumatic diseases

OBJECTIVE

To determine whether serum levels of B lymphocyte stimulator (BLyS) are elevated in patients with systemic immune-based rheumatic diseases and correlate with serum Ig levels and/or autoantibody titers.

METHODS

Sera from 185 patients with various systemic immune-based rheumatic diseases (95 with systemic lupus erythematosus [SLE], 67 with rheumatoid arthritis [RA], 23 with other diagnoses) were assayed for BLyS and Ig. In 7 patients who required arthrocentesis of a swollen knee, coincident serum and synovial fluid samples were assayed for BLyS. Medical charts were retrospectively reviewed for elevated autoantibody titers and proteinuria within a 1-month period before or after collection of sera for BLyS and Ig determination. Sera concurrently collected from 48 normal healthy subjects served as controls.

RESULTS

Serum BLyS levels were elevated in 38 of 185 patients (21%) and correlated significantly with serum IgG levels. Serum BLyS levels did not correlate with the patients' age, sex, race, or medications, but correlated positively with anti-double-stranded DNA antibody titers among SLE patients and with rheumatoid factor titers among seropositive RA patients. In contrast, serum BLyS levels correlated inversely with nephrotic-range proteinuria among SLE patients. In every case tested, BLyS levels in clinically inflamed synovial fluids were greater than those in simultaneously obtained sera.

CONCLUSION

BLyS may be an important factor in driving polyclonal hypergammaglobulinemia and elevated autoantibody titers in patients with systemic immune-based rheumatic diseases. Local production of BLyS in the joints may contribute to joint pathology. Patients with elevated serum BLyS levels may be ideal candidates for therapeutic targeting of BLyS.

A prospective study of renal disease in patients with early rheumatoid arthritis

OBJECTIVES

This prospective study was designed to clarify the frequency, causes, and clinical course of renal disease in patients with early rheumatoid arthritis (RA).

METHODS

235 patients (185 women, mean age 49.4 years) with early RA of less than one year's duration were enrolled and assessed monthly. Proteinuria was defined as a positive dipstick result and microscopic haematuria was defined as the presence of > or =5 red blood cells per high power field. Urinary abnormalities lasting three months or longer were defined as persistent abnormalities.

RESULTS

At entry, 40 patients exhibited haematuria, two had a raised serum creatinine concentration, and none had proteinuria. During the observation period (average 42 months), persistent haematuria was found in 43, persistent proteinuria in 17, and a raised serum creatinine concentration in 14 patients. Persistent proteinuria was caused by drugs in 14 of 17 patients and disappeared in most cases. Risk factors for drug induced proteinuria included a raised C reactive protein and erythrocyte sedimentation rate and age over 50 at entry. Drugs resulted in a raised serum creatinine concentration in eight of 14 patients. The incidence of haematuria at entry did not differ among patients who had been treated with non-steroidal anti-inflammatory drugs, disease modifying antirheumatic drugs, or no drugs. In some patients with isolated haematuria, the haematuria appeared when the activity of RA was high and resolved when it was low.

CONCLUSIONS

This study suggests that a raised serum creatinine concentration or persistent proteinuria in patients with early RA is predominantly drug related whereas, in contrast, isolated haematuria is more directly associated with the activity of the disease process.

Interleukin-6 is a growth factor for nonmalignant human plasmablasts

Interleukin-6 (IL-6), although often regarded as a B-cell differentiation factor, was recently described as the essential survival factor for human plasmablasts in vivo in reactive plasmacytosis. The present study reinvestigated the roles of IL-6 and IL-2 in the generation of plasma cells from human memory B cells in vitro. The cells involved in this differentiation process were identified as preplasmablasts (CD20+/-CD38+/-CD138-), plasmablasts (CD20-CD38++CD138-), and early plasma cells (CD20-CD38+++CD138+++). IL-2 or IL-10 induced a strong generation of plasmablasts and early plasma cells (PCs). Compared to IL-2 or IL-10, IL-6 alone was inefficient at PC generation. However, when combined with IL-2 or IL-10, IL-6 enhanced generation of early PCs. Moreover, anti-IL-6 monoclonal antibody markedly reduced IL-2-induced generation of early plasma cells, but not of plasmablasts. These roles of IL-2 and IL-6 were consistent with the difference in the expression of their respective receptors (R). CD25 (IL-2Ralpha) was increased 72 +/- 10-fold on activated B cells, but decreased and then disappeared on plasmablasts. Conversely, CD126 (IL-6Ralpha) was barely expressed on activated B cells, but increased 18 +/- 2-fold on preplasmablasts. Finally, IL-6 enhanced the proliferation (2-fold increase) of IL-2-generated plasmablasts. In conclusion, the data indicate that IL-6 is a growth factor for nonmalignant human plasmablasts.

Sex steroids and bone

Sex steroids are essential for skeletal development and the maintenance of bone health throughout adult life, and estrogen deficiency at menopause is a major pathogenetic factor in the development of osteoporosis in postmenopausal women. The mechanisms by which the skeletal effects of sex steroids are mediated remain incompletely understood, but in recent years there have been considerable advances in our knowledge of how estrogens and, to a lesser extent androgens, influence bone modeling and remodeling in health and disease. New insights into estrogen receptor structure and function, recent discoveries about the development and activity of osteoclasts, and lessons learned from human and animal genetic mutations have all contributed to increased understanding of the skeletal effects of estrogen, both in males and females. Studies of untreated and treated osteoporosis in postmenopausal women have also contributed to this knowledge and have provided unequivocal evidence for the potential of high-dose estrogen therapy to have anabolic skeletal effects. The development of selective estrogen receptor modulators has provided a new approach to the prevention of osteoporosis and other major diseases of menopause and has implications for the therapeutic use of other steroid hormones, including androgens. Further elucidation of the mechanisms by which sex steroids affect bone thus has the potential to improve the clinical management not only of osteoporosis, both in men and women, but also of a number of other diseases related to sex hormone status.

Immune complex-induced chronic and intense IL-4 independent IgG1-rheumatoid factor production in NZB mice

Immune complexes from the synovial fluid of rheumatoid arthritis (RA) patients, or artificial rheumatoid factors (RF)-like (antibody--antibody) immune complexes, induce a remarkably intense, sustained and selective immunoglobulin (Ig)G1 response under certain experimental conditions in mice. Because the IgG1 antibody response is extraordinarily strong, the role of interleukin (IL)-4, important for IgG1 synthesis, was investigated. Both C57BL/6 and NZB IL-4-deficient mice produced IgG1--RF antibodies after injection with RF-like immune complexes, although the antibody levels were slightly delayed compared to wild type mice. This shows that IL-4 is not obligatory in RF-like immune complex induced IgG1--RF production. A discrepancy in the decline of serum IgG1--RF was noted between NZB and C57Bl/6 mice. Serum IgG1-RF declined 43 days postinjection (p.i.), in C57BL/6 mice whereas high serum levels of IgG1--RF were maintained more than 100 days in the NZB mice, indicating different regulatory mechanisms in these mice. To study if the affinity for mouse IgG increased with time in NZB mice and thus become more directed against self, the cross-reactivity of the IgG1--RF antibodies with IgG from other species was investigated early and late after injection. It was, however, found that the cross-reactivity with IgG of human, goat and rabbit origin did not change between the two time points.

Selective enhancement of thrombopoietic activity of PEGylated interleukin 6 by a simple procedure using a reversible amino-protective reagent

We developed a novel method for the chemical modification of cytokines with synthetic polymers to increase the therapeutic efficacy of the former in vivo. A pH-reversible amino-protective reagent, dimethylmaleic anhydride (DMMAn), was used for modification of interleukin-6 (IL-6) with polyethylene glycol (PEG). The novel PEG-conjugated IL-6 (DmPEG-IL-6), which had been pretreated with DMMAn before PEGylation, showed up to a 140% increase in in vitro specific activity compared with PEG-IL-6 that had been synthesized by the previous method. Moreover, DmPEG-IL-6 caused thrombopoiesis more potently in mice than PEG-IL-6. The DmPEG-IL-6 Fr.1, having 3-4 PEG chains attached to the cytokine, showed the strongest thrombopoietic effect among the DmPEG-IL-6s with different molecular sizes that were tested. PEG-IL-6 Fr.1 had a 500-fold higher potency in stimulating thrombopoiesis than native IL-6 and DmPEG-IL-6 Fr.1 achieved a threefold higher thrombopoietic effect than PEG-IL-6 Fr.1. In addition, side-effects, such as an increase in the plasma fibrinogen level, were not observed after injection of either PEG-IL-6s or DmPEG-IL-6s. These results suggest that PEGylation with DMMAn pretreatment may become a useful means for clinical cytokine delivery.

The interleukin-6 receptor alpha-chain (CD126) is expressed by neoplastic but not normal plasma cells

Interleukin-6 (IL-6) is reported to be central to the pathogenesis of myeloma, inducing proliferation and inhibiting apoptosis in neoplastic plasma cells. Therefore, abrogating IL-6 signaling is of therapeutic interest, particularly with the development of humanized anti–IL-6 receptor (IL-6R) antibodies. The use of such antibodies clinically requires an understanding of IL-6R expression on neoplastic cells, particularly in the cycling fraction. IL-6R expression levels were determined on plasma cells from patients with myeloma (n = 93) and with monoclonal gammopathy of undetermined significance (MGUS) or plasmacytoma (n = 66) and compared with the levels found on normal plasma cells (n = 11). In addition, 4-color flow cytometry was used to assess the differential expression by stage of differentiation and cell cycle status of the neoplastic plasma cells. IL-6R alpha chain (CD126) was not detectable in normal plasma cells, but was expressed in approximately 90% of patients with myeloma. In all groups, the expression levels showed a normal distribution. In patients with MGUS or plasmacytoma, neoplastic plasma cells expressed significantly higher levels of CD126 compared with phenotypically normal plasma cells from the same marrow. VLA-5− “immature” plasma cells showed the highest levels of CD126 expression, but “mature” VLA-5+ myeloma plasma cells also overexpressed CD126 when compared with normal subjects. This study demonstrates that CD126 expression is restricted to neoplastic plasma cells, with little or no detectable expression by normal cells. Stromal cells in the bone marrow microenvironment do not induce the overexpression because neoplastic cells express higher levels of CD126 than normal plasma cells from the same bone marrow in individuals with MGUS.

The interleukin-6 receptor alpha-chain (CD126) is expressed by neoplastic but not normal plasma cells

Interleukin-6 (IL-6) is reported to be central to the pathogenesis of myeloma, inducing proliferation and inhibiting apoptosis in neoplastic plasma cells. Therefore, abrogating IL-6 signaling is of therapeutic interest, particularly with the development of humanized anti–IL-6 receptor (IL-6R) antibodies. The use of such antibodies clinically requires an understanding of IL-6R expression on neoplastic cells, particularly in the cycling fraction. IL-6R expression levels were determined on plasma cells from patients with myeloma (n = 93) and with monoclonal gammopathy of undetermined significance (MGUS) or plasmacytoma (n = 66) and compared with the levels found on normal plasma cells (n = 11). In addition, 4-color flow cytometry was used to assess the differential expression by stage of differentiation and cell cycle status of the neoplastic plasma cells. IL-6R alpha chain (CD126) was not detectable in normal plasma cells, but was expressed in approximately 90% of patients with myeloma. In all groups, the expression levels showed a normal distribution. In patients with MGUS or plasmacytoma, neoplastic plasma cells expressed significantly higher levels of CD126 compared with phenotypically normal plasma cells from the same marrow. VLA-5− “immature” plasma cells showed the highest levels of CD126 expression, but “mature” VLA-5+ myeloma plasma cells also overexpressed CD126 when compared with normal subjects. This study demonstrates that CD126 expression is restricted to neoplastic plasma cells, with little or no detectable expression by normal cells. Stromal cells in the bone marrow microenvironment do not induce the overexpression because neoplastic cells express higher levels of CD126 than normal plasma cells from the same bone marrow in individuals with MGUS.

Anti-interleukin 6 receptor antibody treatment in rheumatic disease

Interleukin 6 (IL6) is a pleiotropic cytokine with a wide range of biological activities. IL6 transgene into mice gives rise to the abnormalities such as hypergammaglobulinaemia, thrombocytosis, infiltration of inflammatory cells into the tissues, mesangial cell proliferation of the kidney as well as splenomegaly and lymphadenopathy, which are predictable by the biological functions of IL6 shown in vitro. Continuous overproduction of IL6 is observed in patients with some immune-inflammatory diseases such as Castleman's disease and rheumatoid arthritis that are frequently associated with similar abnormalities to those of IL6 transgenic mice, strongly suggesting the involvement of IL6 in the human diseases. Successful treatment of the model animals for immune-inflammatory diseases with anti-IL6 receptor (IL6R) antibody thus indicates the possible application of IL6 blocking agents to treat the IL6 related immune-inflammatory diseases of humans. In this review, the new therapeutic strategy for Castleman's disease and RA using humanized antibody to human IL6 receptor, MRA, is discussed.

gp130 Cytokine family and bone cells

Bone tissue is continually being remodelled according to physiological circumstances. Two main cell populations (osteoblasts and osteoclasts) are involved in this process, and cellular activities (including cell differentiation) are modulated by hormones, cytokines and growth factors. Within the last 20 years, many factors involved in bone tissue metabolism have been found to be closely related to the inflammatory process. More recently, a cytokine family sharing a common signal transducer (gp130) had been identified, which appears to be a key factor in bone remodelling. This family includes interleukin 6, interleukin 11, oncostatin M, leukaemia inhibitory factor, ciliary neurotrophic factor and cardiotrophin-1. This paper provides an exhaustive review of recent knowledge on the involvement of gp130 cytokine family in bone cell (osteoblast, osteoclast, etc.) differentiation/activation and in osteoarticular pathologies.

Molecular design of polyvinylpyrrolidone-conjugated interleukin-6 for enhancement of in vivo thrombopoietic activity in mice

Functional polyvinylpyrrolidone (PVP) was synthesized as a novel polymeric modifier for polymer-conjugated cytokines, and its efficiency and applicability as a drug delivery system (DDS) were evaluated. PVP with a carboxyl group at one end of the main chain was prepared by radical polymerization (M(n): 6000, M(w)/M(n): 1.14) with the aid of 4,4'-azobis(4-cyanovaleric acid) as a radical initiator and 3-mercaptopropionic acid as a transfer agent. Interleukin-6 (IL-6) was covalently conjugated via the formation of amino bonds between the lysine amino groups of IL-6 and PVP. PVP-conjugated IL-6, in which 60% of the fourteen lysine amino groups of IL-6 were estimated to be coupled with PVP (M-PVP-IL-6), showed more than 50-fold greater thrombopoietic potency in vivo than native IL-6. No side effects, such as body weight loss, were observed in the M-PVP-IL-6 treated mice. These results indicate that PVP as a polymeric modifier is a promising DDS for clinical application of cytokines and other therapeutic agents.

Induction of acute pancreatitis by cerulein in human IL-6 gene transgenic mice

Whether acute pancreatitis induced by cerulein was aggravated in human interleukin 6 (IL-6) transgenic mice and whether a specific anti-IL-6 receptor antibody improved pancreatitis were investigated. To induce acute pancreatitis, cerulein (50 microg/kg, seven injections) with or without 1 mg/kg lipopolysaccharides (LPS) was injected intraperitoneally every hour. In some mice, a monoclonal anti-IL-6 receptor antibody was administered before the first cerulein injection. The animals were killed 1 hour after the last injection. The pancreatic wet weight induced by cerulein alone was significantly higher in IL-6 transgenic mice compared with wild-type mice, but pretreatment with a specific anti-IL-6 receptor antibody did not reduce interstitial edema. When cerulein was administered with LPS, the pancreatic wet weight increased much more than when pancreatitis was induced by cerulein alone in both genotypes, and pretreatment with the anti-IL-6 receptor antibody decreased the pancreatic edema only in human-IL-6 transgenic mice. These results suggest that anticytokine antibodies may be effective in improving acute pancreatitis.

Cooperative influence of genetic polymorphisms on interleukin 6 transcriptional regulation

Interleukin 6 (IL6) plays key roles in hematopoiesis, immune, and acute phase responses. Dysregulated IL6 expression is implicated in diseases such as atherosclerosis and arthritis. We have examined the functional effect of four polymorphisms in the IL6 promoter (-597G-->A, -572G-->C, -373A(n)T(n), -174G-->C) by identifying the naturally occurring haplotypes and comparing their effects on reporter gene expression. The results indicate different transcriptional regulation in the ECV304 cell line compared with the HeLa cell line, suggesting cell type-specific regulation of IL6 expression. The haplotypes showed functional differences in the ECV304 cell line; transcription was higher from the GG9/11G haplotype and lower from the AG8/12G allele. The differences suggest that more than one of the polymorphic sites is functional; the base differences at distinct polymorphic sites do not act independently of one another, and one polymorphism influences the functional effect of variation at other polymorphic sites. These results show that genetic polymorphisms in the promoter influence IL6 transcription not by a simple additive mechanism but rather through complex interactions determined by the haplotype.

Lymph nodes and Peyer's patches of IL-6 transgenic BALB/c mice harbor T(12;15) translocated plasma cells that contain illegitimate exchanges between the immunoglobulin heavy-chain mu locus and c-myc

Hyperplastic plasmacytotic lymph nodes and Peyer's patches of 12 of 25 (48%) BALB/c mice that carried a human IL-6 transgene under the transcriptional control of the histocompatibility H-2L(D) promoter (BALB/c.IL-6 mice) were found to harbor 15 cell clones that contained in their T(12;15) translocation breakpoint regions illegitimate genetic recombinations between the upstream flank of the immunoglobulin heavy-chain C mu locus (5'-C mu) and c-myc (5'-C mu/c-myc+ clones). Similar 5'-C mu/c-myc+ clones were also detected in pristane-induced peritoneal granulomata (a significant source of IL-6 in situ) of three of 13 (13%) conventional BALB/c mice, but not in lymphoid tissues of pristane-treated BALB/c mice, nor in any tissue of untreated BALB/c mice. These findings provided strong evidence that IL-6 may be able to promote the growth and/or survival of clones that contained rearrangements between 5'-C mu and c-myc. Taken in conjunction with our previous observation that 5'-C mu/c-myc+ clones are the precursors for pristane-induced BALB/c plasmacytomas, the findings further suggested that IL-6 may play a pivotal role in the early stage of plasmacytoma development, by promoting tumor precursor cells. The BALB/c.IL-6 model of plasmacytomagenesis may be superior to the conventional BALA/c model because the putative plasmacytoma precursors appear to be more prevalent and in their development independent of treating the mice with inflammation-inducing plasmacytomagenic agents, such as pristane or silicone polymers.

Human herpes virus 8 interleukin-6 homologue triggers gp130 on neuronal and hematopoietic cells

Human herpes virus-8 (HHV8) encodes a cytokine named viral interleukin-6 (vIL-6) that shares 25% amino-acid identity with its human homologue. Human IL-6 is known to be a growth and differentiation factor of lymphatic cells and plays a potential role in the pathophysiology of various lymphoproliferative diseases. vIL-6 is expressed in HHV8-associated-diseases including Kaposi's sarcoma, Body-cavity-based-lymphoma and Castleman's disease, suggesting a pathogenetic involvement in the malignant growth of B-cell associated diseases and other malignant tumours. We expressed vIL-6 in Escherichia coli as a fusion protein with recombinant periplasmic maltose binding protein. After cleavage from the maltose binding protein moiety and purification, vIL-6 was shown to be correctly folded using circular dichroism spectroscopy. A rabbit antiserum was raised against the recombinant vIL-6 protein. vIL-6 turned out to be active on cells that expressed gp130 but no IL-6 receptor (IL-6-R) suggesting that, in contrast to human IL-6, vIL-6 stimulated gp130 directly. Accordingly, vIL-6 activity could be inhibited by a soluble gp130 Fc Fusion protein. vIL-6 was shown to induce neuronal differentiation of rat pheochromocytoma cells and to stimulate colony formation of human hematopoietic progenitor cells. Thus, vIL-6 exhibits biologic activity that has only been observed for the IL-6/soluble IL-6-R complex but not for IL-6 alone. These properties are important for the evaluation of the pathophysiological potential of vIL-6.

Roles of STAT3 in mediating the cell growth, differentiation and survival signals relayed through the IL-6 family of cytokine receptors

Members of the IL-6 cytokine family are involved in a variety of biological responses, including the immune response, inflammation, hematopoiesis, and oncogenesis by regulating cell growth, survival, and differentiation. These cytokines use gp130 as a common receptor subunit. The binding of ligand to gp130 activates the JAK/STAT signal transduction pathway, where STAT3 plays a central role in transmitting the signals from the membrane to the nucleus. STAT3 is essential for gp130-mediated cell survival and G1 to S cell-cycle-transition signals. Both c-myc and pim have been identified as target genes of STAT3 and together can compensate for STAT3 in cell survival and cell-cycle transition. STAT3 is also required for gp130-mediated maintenance of the pluripotential state of proliferating embryonic stem cells and for the gp130-induced macrophage differentiation of M1 cells. Furthermore, STAT3 regulates cell movement, such as leukocyte, epidermal cell, and keratinocyte migration. STAT3 also appears to regulate B cell differentiation into antibody-forming plasma cells. Since the IL-6/gp130/STAT3 signaling pathway is involved in both B cell growth and differentiation into plasma cells it is likely to play a central role in the generation of plasma cell neoplasias. Oncogene (2000).

Induction of chromosomal aberrations and growth-transformation of lymphoblastoid cell lines by inhibition of reactive oxygen species-induced apoptosis with interleukin-6

Etiological evidence, indicating the relationships between the onset of malignant lymphoma and pre-existing chronic inflammation, has been accumulated. For the autonomous growth of malignant tumor, genetic lesions, such as chromosomal aberrations, amplification of oncogenes, and mutations of genes involved in the cell cycle regulation, must be essential. However, how the inflammation promotes the accumulation of genetic lesions and induces the autonomous growth of lymphoid cells remains unclear. Reactive oxygen species released by polymorphonuclear leukocytes and macrophages are factors causing DNA damage in the foci of inflammation, and thus could play a role in lymphomagenesis. The xanthine/xanthine oxidase (X/XOD) system produces a mixture of hydrogen peroxide and superoxide anion extracellularly, and thus serves as an in vitro source of reactive oxygen species. Cell death of lymphoblastoid cell lines (LCLs) was induced with X/XOD treatment in a dose-dependent manner. DNA fragmentation, which is the characteristic feature of apoptosis, was observed in LCLs at 4-8 hours after X/XOD treatment. Among cytokines such as interleukin-6 (IL-6), IL-10, and interferon-gamma, only pretreatment with IL-6 gave LCLs the resistance to X/XOD-induced cell death in a dose-dependent manner. The proportion of apoptotic cells in X/XOD-treated LCL culture was decreased with IL-6 pretreatment by quantification with flow cytometric analysis. Treatment of LCLs with IL-6 for 48 hours up-regulated bcl-2 mRNA expression. Furthermore, the LCLs repeatedly treated with X/XOD and cultured with or without IL-6 showed many more structural abnormalities of chromosomes than those without X/XOD treatment. Colony forming efficiency of X/XOD-treated LCLs with IL-6 was significantly higher than those without IL-6, and even relatively higher than LCLs without X/XOD treatment. IL-6 could support the survival of non-neoplastic B cells and accelerate the malignant transformation of B lineage cells in inflammatory lesions.

Kaposi's sarcoma-associated herpesvirus-encoded interleukin-6

Since the discovery of the virus in 1994, the rapid pace with which Karposi's sarcoma-associated herpesvirus (KSHV) research has progressed has quickly led to a broad understanding of the structure of the virus and its biology and pathology in humans. Molecular piracy of potentially useful cellular genes has emerged as a characteristic feature of this virus. The viral homolog of human IL-6, vIL-6 is an example in kind. Studies in vitro and in vivo have shown that vIL-6 can stimulate the growth of KSHV-infected primary infusion lymphoma (PEL) cells, can promote hematopoiesis, and act as an angiogenic factor through the induction of vascular endothelial growth factor (VEGF). It is not difficult to envision how vIL-6, through these properties and perhaps others yet to be identified, can contribute to KSHV survival and spread in the human population.

Prominent and sustained up-regulation of gp130-signaling cytokines and the chemokine MIP-2 in murine renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a major cause of renal dysfunction in both native kidneys and renal allografts. To broaden our understanding of the inflammatory mediators involved in IRI, we used multi-probe RNase protection assays to examine the expression of 26 different cytokine genes in a murine model of renal IRI. We observed that, in addition to up-regulation of IL-1beta and to a lesser extent TNF-alpha, IRI was associated with an intense and sustained up-regulation of three gp130-signaling cytokines, IL-6, IL-11, and leukemia inhibitory factor (LIF), as well as with up-regulation of the neutrophil chemotactic and activating mediator macrophage inflammatory protein (MIP)-2. Macrophage colony-stimulating factor (M-CSF) and monocyte chemoattractant protein (MCP)-1 were also moderately up-regulated after IRI, whereas mRNA levels of several other inflammatory mediators including IL-1alpha, IL-2, IL-4, interferon (IFN)-gamma, GM-CSF, and RANTES were minimally increased or remained undetectable. These findings identify MIP-2 as an attractive target for inhibition of leukocyte recruitment in renal IRI and also suggest a potentially novel role for gp130-mediated signals in IRI.

Regulation of gingival fibroblast interleukin-6 secretion by cyclosporine A

BACKGROUND

Cyclosporine A (CsA) is a widely used immunosuppressant, with clinical applications ranging from organ transplants to chronic inflammatory diseases. One of the side effects associated with CsA treatment is the development of gingival overgrowth. Exuberant growth of connective tissue within the periodontium can result from hyperactivity of resident fibroblasts. Fibroblasts are capable of secreting interleukin-6 (IL-6), which has been shown to enhance proliferation as well as collagen and glycosaminoglycan synthesis by these cells. We tested the hypothesis that one of the pathogenetic mechanisms underlying CsA-induced fibrosis is an enhanced IL-6 secretion by gingival fibroblasts (GF) in response to this drug.

METHODS

The ability of CsA to upregulate GF IL-6 secretion alone or in combination with bacterial challenge or other inflammatory cytokines was tested in an in vitro system. Fibroblast cultures were established from systemically healthy gingival tissue donors and were challenged with CsA in the absence or presence of bacteria, IL-1beta, or tumor necrosis factor (TNF) alpha as co-stimulants. Nifedipine and phenytoin were also tested to further support findings with CsA. After 72 hours of incubation, culture supernatants were collected and analyzed for IL-6 content by ELISA.

RESULTS

We have shown that GF respond to CsA with an increase in IL-6 secretion. The magnitude of this response varies among cultures derived from different tissue donors. We have also demonstrated that GF IL-6 responses to bacterial challenge or TNFalpha are downregulated by CsA. However, CsA synergizes with IL-1beta to further upregulate IL-6 secretion, and this effect is shared by phenytoin and nifedipine.

CONCLUSIONS

We conclude that one of the pathogenetic mechanisms underlying drug-induced gingival overgrowth may be enhanced secretion of IL-6 by GF in response to these medications. This is the first report on direct and indirect effects of gingival overgrowth-related medications on GF IL-6 metabolism. This work will lay the foundation for future studies directed towards the development of prevention or treatment modalities for gingival overgrowth based on blocking the fibrogenic activities of IL-6 at the cellular level.

Cytokines and their receptors in cardiovascular diseases--role of gp130 signalling pathway in cardiac myocyte growth and maintenance

Interleukin (IL)-6-related cytokines share gp130 as the signal-transducing protein. Cardiac myocytes produce various kinds of cytokines including IL-6 and cardiotrophin-1. Activation of gp130 transduces hypertrophic and cytoprotective signals in cardiac myocytes via JAK/STAT, MAP kinase and PI-3 kinase pathways. Besides various well-established mechanisms by which cardiac growth and myocardial remodeling are regulated, gp130 signalling may be a newly discovered mechanism that regulates these events in association with cytoprotective effect in myocardial diseases.

A model that reproduces syndromes associated with human multiple myeloma in nonirradiated SCID mice

A human myeloma line was used to create a model of human multiple myeloma in vivo that would reproduce the pathophysiology of the disease, including the cachexia associated with cancer. Unirradiated severe combined immunodeficient (SCID) mice were used as surrogate hosts for in vivo experiments that allowed the effects of autocrine (human) verus paracrine (murine) cytokines on the development of myeloma to be studied. Serum levels of human paraprotein increased over time and with the number of cells transplanted. Transplanted mice developed major syndromes, cachexia and paralysis (due to invasion of bones by myeloma cells), associated with multiple myeloma. Analyses of serum samples obtained from transplanted mice revealed that when the mice were terminal, total serum protein decreased on average by 20%, whereas serum triglycerides decreased on average by 50%. These data indicate the mice were cachectic, which was confirmed by necropsy. The mice had low but measurable levels of both human and murine interleukin (IL)-6, soluble IL-6 receptor, and murine IL-10 in their sera. The presence of these cytokines and the IL-6 receptor in sera are also characteristics of human myeloma in patients. Since human cells do not respond to murine IL-6, it was possible to demonstrate clearly the importance of autocrine IL-6 in establishing myeloma in situ. By reproducing both the hallmarks of a cancer as well as the accompanying paraneoplastic syndromes, this model should be useful in designing more effective therapies for both the primary cancer as well as the accompanying secondary diseases.

Polymorphisms at - 174 and in the 3' flanking region of interleukin-6 (IL-6) gene in patients with myasthenia gravis

We examined the bi-allelic polymorphism at - 174 in the promoter region and the polymorphism in the 3' flanking AT rich region of the interleukin-6 (IL-6) gene in Swedish patients with myasthenia gravis (MG) and ethnically matched healthy individuals. There was no association between the polymorphisms and the disease. There was no relation of the polymorphisms to the clinical variables, the thymic histopathologies, the level of serum acetylcholine receptor antibodies or the concentrations of IgG and its subclasses. Our data yield no evidence for the IL-6 gene contributing to the disease susceptibility.

The effect on immunoglobulin glycosylation of altering in vivo production of immunoglobulin G

The effect on murine immunoglobulin G (IgG) glycosylation of altering IgG production in vivo was assessed in interleukin (IL)-6 transgenic and CD4 knockout mice. C57BL/6 mice carrying the IL-6 transgene showed increased levels of circulating IgG. This was associated with decreased levels of galactose on the IgG oligosaccharides. No decrease in beta4-galactosyltransferase mRNA or in enzyme activity was seen in IL-6 transgenic mice. MRL-lpr/lpr mice normally have elevated levels of circulating IgG, again accompanied by decreased levels of IgG galactose. Disruption of the CD4 gene in MRL-lpr/lpr mice led to a substantial decrease in the concentration of circulating IgG, but IgG galactose levels remained low. Thus, an enforced decrease in IgG levels in the lymphoproliferative MRL-lpr/lpr mice did not alter the percentage of agalactosyl IgG in these mice, suggesting that agalactosyl IgG production is not simply caused by excessive IgG synthesis leading to an insufficient transit time in the trans-Golgi, but rather to a molecular defect in the interaction between galactosyltransferase and the immunoglobulin heavy chain.

Adenovirus vector expressing mouse oncostatin M induces acute-phase proteins and TIMP-1 expression in vivo in mice

Mouse oncostatin M (MuOSM) regulates the production of acute-phase proteins by hepatocytes as well as tissue inhibitor of metalloproteinases-1 (TIMP-1) production by fibroblasts in vitro. We have generated an adenovirus (Ad) encoding MuOSM and tested the effects of administration of recombinant AdMuOSM to mice in vivo. On intramuscular injection, AdMuOSM (5 X 10(7) plaque-forming units, pfu) induced an increase in serum levels of interleukin-6 (IL-6) as well as the acute-phase proteins serum amyloid A (SAP) and alpha1-acid glycoprotein (AGP) at day 1. SAP and AGP concentrations were elevated to greater levels at day 3 and decreased to near control levels at day 7. Intratracheal treatment with AdMuOSM induced TIMP-1 mRNA levels (as assessed by Northern blots) that corresponded to the presence of transgene MuOSM mRNA levels. TIMP-1 was elevated at day 1 and day 3 and less consistently at day 7 after administration. Intraperitoneal treatment with AdMuOSM also resulted in elevation of TIMP-1 mRNA in lung tissue. These results show that AdMuOSM can induce both local and systemic effects and demonstrate in vivo effects of OSM that are consistent with in vitro studies on acute-phase protein and TIMP-1 expression.

Plasma cell generation from B-lymphocytes via CD27/CD70 interaction

To produce antibodies, the differentiation of B cells into antibody-secreting cells, plasma cells, is required. We describe that ligation of CD27, which belongs to the tumor necrosis factor receptor (TNFR) family and is a memory marker of B cells, yields crucial signals that positively control the entry of B cells into the pathway to plasma cells. The triggering via CD27 by CD27 ligand (CD70) on purified peripheral blood B cells yielded an increase in the number of plasma cells in the presence of interleukin-10 (IL-10). The differentiation into plasma cells by a combination of IL-10 and CD70-transfectants occurred in CD27+ B cells, but not in CD27- B cells. Moreover, the addition of IL-2 to the IL-10 and CD70-transfectants greatly induced the differentiation into plasma cells. In the presence of only IL-2, IL-4 or IL-6, CD70-transfectants did not promote the differentiation into plasma cells. On the other hand, CD40 signaling increased the expansion of a B cell pool from peripheral blood B cells primarily activated by IL-2, IL-10 and anti-CD40 mAb. These data demonstrate that CD27 ligand (CD70) is a key molecule to direct the differentiation of CD27+ memory B cells toward plasma cells in cooperation with IL-10.

Involvement of gp130-mediated signaling in pressure overload-induced activation of the JAK/STAT pathway in rodent heart

Previously, we showed that the JAK/STAT pathway was activated in pressure-overloaded rat heart, and that angiotensin II was partially involved in this activation. The present study was designed to investigate whether gp130-mediated signaling is involved in this activation, and if so, which interleukin (IL)-6 family cytokine is involved. Pressure overload was produced by ligation of the abdominal aorta of Wistar rats or ICR mice. IP-Western blot was performed to detect tyrosine phosphorylation of STATs, gp130, and the association of gp130 with JAK kinases. The serum concentration of IL-6 was measured by enzyme-linked immunosorbent assay. Expression of IL-6, IL-11, leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF), oncostatin M (OSM), and cardiotrophin-1 (CT-1) mRNA was quantitated. After pressure overload, rapid phosphorylation of STAT1 and STAT3 was observed at 5 min, STAT1 was rephosphorylated at 60 min, and intense phosphorylation of STAT3 was observed at 60 min. Both the phosphorylation of gp130 and the association of gp130 with JAK1 and JAK2 were increased after pressure overload. IL-6 was significantly increased by two-fold in the pressure-overloaded rats. Only CT-1 mRNA expression could be detected by Northern blot, and it increased after pressure overload. Reverse transcription-polymerase chain reaction revealed that IL-6 mRNA expression was increased 9.5-fold. IL-11, LIF, CNTF, and OSM expression were unaffected by pressure overload. These results suggested that gp130-mediated signaling was involved in the pressure overload-induced activation of the JAK/STAT pathway, and that IL-6 and CT-1 might be involved in this activation.

Progression of renal disease in interleukin-4 transgenic mice: involvement of transforming growth factor-beta

Recent reports have suggested the involvement of interleukin-4 (IL-4) in glomerular pathophysiology. Using immunohistochemistry and reverse transcriptase polymerase chain reaction we investigated the renal lesions in transgenic (tg) mice with widely distributed IL-4 expression including the kidney, and measured the serum levels of the cytokines transforming growth factor-beta (TGF-beta) and IL-4 by ELISA. Transgenic animals exhibited glomerular hypertrophy with progressive mesangial sclerosis leading to renal failure. Renal IL-4 transcript expression, mesangial accumulation of collagen types I, III, IV and V, and immune deposition accompanied by increased expression of TGF-beta1 protein and mRNA were observed. Seven day-old transgenic animals showed early renal fibrotic changes in the absence of immune deposits or TGF-beta1 upregulation. The sera of transgenic mice not only showed elevated levels of circulating IL-4 (tg: 76.6 pg/ml +/- 7.1 vs wildtype (wt): < 3 pg/ml), but significantly decreased TGF-beta1 levels (tg: 18.9 ng/ml +/- 4.1 vs wt: 38.7 ng/ml +/- 2.9; P < 0.005). The disease severity correlated with the serum IL-4/TGF-beta1 ratio rather than with the IL-4 concentration. These data suggest that renal IL-4 production results in matrix accumulation prior to any immunological insult, that increased circulating IL-4/TGF-beta1 ratios are associated with renal immunopathological manifestations and that upregulation of renal TGF-beta1 expression following glomerular Ig deposition accelerates the sclerosis and exacerbates disease development.

The concept of glomerular self-defense

The balance between local offense factors and defense machinery determines the fate of tissue injury: progression or resolution. In glomerular research, the most interest has been on the offensive side, for example, the roles of leukocytes, platelets, complement, cytokines, eicosanoids, and oxygen radical intermediates. There has been little focus on the defensive side, which is responsible for the attenuation and resolution of disease. The aim of this review is to address possible mechanisms of local defense that may be exerted during glomerular injury. Cytokine inhibitors, proteinase inhibitors, complement regulatory proteins, anti-inflammatory cytokines, anti-inflammatory eicosanoids, antithrombotic molecules, and extracellular matrix proteins can participate in the extracellular and/or cell surface defense. Heat shock proteins, antioxidants, protein phosphatases, and cyclin kinase inhibitors may contribute to the intracellular defense. This article outlines how the glomerulus, when faced with injurious cells or exposed to pathogenic mediators, defends itself via the intrinsic machinery that is brought into play in resident glomerular cells.

Murine plasmacytomas, carrier of the t(12;15) chromosomal translocation, develop from immature/mature B cells not from differentiated plasma cells

Dysregulation of the c-myc gene by chromosomal translocation in >95% of murine plasmacytomas (MPCs) is an obligatory requirement for the transformation of B lymphocytes into MPCs. However, it is still unknown whether sIg+ B cells or differentiated plasma cells are the legitimate precursor cells from which MPCs develop. To address this question, C.B-17 scid/scid (SCID) mice were reconstituted with splenic surface Ig-positive (sIg+) B lineage cells originating from BALB/cRb6.15 (B/cRb6.15) or human IL-6 transgene-congenic BALB/cRb8.12 mice (B/cRb8.12 IL-6-Tg). Six of 80 SCID mice reconstituted with B/cRb6.15 sIg+ B cells developed MPCs after pristane (2,6,10,14-tetramethylpentadecane) treatment followed by Abelson murine leukemia virus (A-MuLV) infection (incidence 7.5%) and four of 40 after pristane treatment alone (incidence 10%). Similarly, in 20 SCID mice reconstituted with B/cRb8.12 IL-6-Tg splenic sIg+ B cells the MPC incidence was 10%. Karyotype analysis revealed that all the translocations were of typical t(12;15) type and all tumors carried the Rb6.15 or Rb8.12 marker chromosome, indicating their donor cell origin. In contrast, none of the 48 SCID mice reconstituted with plasma cells obtained from the lymph nodes of B/cRb8.12 IL-6-Tg mice developed MPCs when treated either with pristane plus A-MuLV (20 mice) or with pristane alone (28 mice), although the transferred plasma cells were still functional in the recipient SCID mice 6 months after transfer. The findings indicate that the malignant transformation triggered by Ig/myc juxtaposition occurs more in immature (sIgM+) and/or mature (sIgM+/sIgD+, sIgG+ and sIgA+) B cells than in differentiated G0 or cycling plasma cells. We inferred that immature and/or mature B cells and not differentiated plasma cells are most likely the principal source of precursor cells from which the typical t(12;15) MPCs develop.

Transgenic mouse model of AA amyloidosis

AA amyloidosis can be induced in mice experimentally through injection of certain chemical or biological compounds. However, the usefulness of this approach is limited by its dependence on exogenous inflammatory agents that stimulate cytokines to increase the synthesis of precursor serum amyloid A (SAA) protein and the transitory nature of the pathological fibrillar deposits. We now report that transgenic mice carrying the human interleukin 6 gene under the control of the metallothionein-I promoter had markedly increased concentrations of SAA and developed amyloid in the spleen, liver, and kidneys by 3 months of age. At the time of death about 6 months later, organs obtained from these animals had extensive amyloid deposits. This disease process was apparent radiographically using small-animal computer axial tomography and magnetic resonance imaging equipment. The AA nature of the amyloid was evidenced immunohistochemically and was unequivocally established by sequence analysis of protein extracted from the fibrils. The availability of this unique in vivo experimental model of AA amyloidosis provides the means to assess the therapeutic efficacy of agents designed to reduce or prevent the fibrillar deposits found in AA and other types of amyloid-associated disease.