Granulocyte-macrophage colony-stimulating factor augments neutrophil-mediated cartilage degradation and neutrophil adherence

Hepatocyte growth factor stimulates neutrophil degranulation but not respiratory burst

Neutrophil function is regulated in part by cytokines with growth factor activities for different cell types. Hepatocyte growth factor (HGF) is a cytokine produced during injury to the liver and other organs. Neutrophils are numerous in such tissue injury sites and may be influenced by HGF. In the present study the effect of HGF on neutrophils was investigated. The data show that HGF at 1-10 ng/ml increased lysosomal enzyme release from both specific and azurophilic granules of cytochalasin-B treated neutrophils. The release of specific granule contents in response to N-formyl-methionyl-leucylphenylalanine was also increased by HGF. In contrast there were no significant effects of HGF on neutrophil respiratory burst, adherence or locomotion. It is concluded that HGF modulates neutrophil granule exocytosis.

Granulocyte-macrophage colony stimulating factor is anabolic and interleukin-1beta is catabolic for rat articular chondrocytes

OBJECTIVE

To study the effects of GM-CSF and IL-1beta, both implicated in tissue damage in arthritis, on articular chondrocyte proliferation and metabolism, and to explore their agonist/antagonist effects.

METHODS

Chondrocytes were obtained from 1-month-old rats. First-passage monolayers were incubated for 24 h with or without GM-CSF and/or IL-1beta, and labeled with 3H-thymidine, 35S-SO4 and 14C-proline. Proteoglycan and collagen synthesis were analyzed by liquid chromatography and SDS-PAGE. Gene expression was measured by RT-PCR.

RESULTS

IL-1beta exerts potent, and GM-CSF weak, inhibitory effects on DNA synthesis. GM-CSF strongly stimulates, and IL-1beta inhibits, proteoglycan and collagen synthesis. IL-1beta suppresses the effect of GM-CSF, and increases the release of radioactive molecules from pre-labeled cartilage fragments; GM-CSF decreases the IL-1beta-induced effect. Interestingly, both cytokines induce the expression of each other's gene.

CONCLUSIONS

IL-1beta appears to be a catabolic and anti-anabolic agent for chondrocytes, whereas GM-CSF is mainly anabolic, and blocks the IL-1beta-induced catabolic effect. It is postulated that both agents are implicated in inflammation: IL-1beta promotes tissue catabolism and destruction, whereas GM-CSF enhances tissue reconstruction.

Regulation of human neutrophil-mediated cartilage proteoglycan degradation by phosphatidylinositol-3-kinase

The ability of neutrophils to degrade cartilage proteoglycan suggests that the neutrophils that accumulate in the joints of rheumatoid arthritis patients are mediators of tissue damage. The regulatory mechanisms which are relevant to the proteoglycan-degrading activity of neutrophils are poorly understood. Since phosphatidylinositol 3-kinase (PI3-K), protein kinase C (PKC), the extracellular signal-regulated protein kinase (ERK)1/ERK2 and cyclic adenosine monophosphate (cAMP) have been reported to regulate neutrophil respiratory burst and/or degranulation, a role for these signalling molecules in regulating proteoglycan degradation was investigated. Preincubation of human neutrophils with GF109203X (an inhibitor of PKC), PD98059 (an inhibitor of MEK, the upstream regulator of ERK1/ERK2) or with forskolin or dibutyryl cAMP, failed to suppress proteoglycan degradation of opsonized bovine cartilage. In contrast, preincubation of neutrophils with wortmannin or LY294002, specific inhibitors of PI3-K, inhibited proteoglycan degradation. Incubation of neutrophils with cartilage resulted in the activation of PI3-K in neutrophils, consistent with a role for PI3-K in proteoglycan degradation. Activation of PI3-K and proteoglycan degradation was enhanced by tumour necrosis factor-alpha. Degradation caused by neutrophils from the synovial fluid of rheumatoid arthritis patients was also inhibited by wortmannin. These data demonstrate that the proteoglycan degradative activity of neutrophils required PI3-K but not PKC or the ERK1/ERK2/ERK5 cascades and was insensitive to increases in intracellular cAMP concentrations.

Protection from Collagen-Induced Arthritis in Granulocyte-Macrophage Colony-Stimulating Factor-Deficient Mice

The involvement of granulocyte-macrophage CSF (GM-CSF) in collagen-induced arthritis (CIA) was examined using GM-CSF-deficient mice. Although CIA is generally considered to be restricted to mice of the H-2q or H-2r haplotypes, we examined the role of GM-CSF in the CIA model using GM-CSF-deficient (−/−) and wild-type (+/+) mice on a C57BL/6 (H-2b) background. Mice were immunized by intradermal injection at the base of the tail with chick type II collagen followed by a repeat injection 21 days later. We found, based on both clinical and histologic assessments, that wild-type mice on this background developed severe CIA, while the GM-CSF-deficient mice had virtually no disease. Mice that were heterozygous for the GM-CSF gene (+/−) collectively displayed an intermediate response between those of the GM-CSF+/+ and GM-CSF−/− groups, suggesting a gene dosage effect. GM-CSF+/+ and GM-CSF+/− mice exhibited CIA responses ranging from mild (single digits) to severe swelling of all four paws, while in the few GM-CSF−/− mice that developed CIA the disease was confined to single digits. Despite the putative role of GM-CSF in dendritic cell development, GM-CSF-deficient mice exhibited both humoral and cellular (delayed-type hypersensitivity) responses to type II collagen; however, the cellular response was significantly reduced in the GM-CSF-deficient mice compared with the wild-type controls. These findings suggest that GM-CSF is required for CIA development in mice and support the idea that GM-CSF is a key cytokine in inflammatory joint disease.

Neutrophil expression of tumour necrosis factor receptors (TNF-R) and of activation markers (CD11b, CD43, CD63) in rheumatoid arthritis

In vitro analysis of polymorphonuclear neutrophils (PMN) has allowed various stages of cell activation to be distinguished, characterized by the expression level of specific membrane markers and of functional receptors. Among those, TNF-alpha receptors (TNF-R) are modulated by various PMN activators, a mechanism which may be important to control cell responses to TNF in inflammatory reactions such as rheumatoid arthritis (RA). PMN, isolated from the blood of 36 RA patients and from the synovial fluid of 23 of them, were analysed for membrane expression of the two TNF-R (p55 and p75). Soluble p55 and p75 (sTNF-R) and TNF concentrations were measured in the plasma and synovial fluid by specific ELISA assays. Our results show that PMN from the blood of RA patients bear a normal number of TNF-R, with a normal p55/p75 ratio, compared with PMN from normal controls. Soluble TNF-R levels were similar in patients and normal plasma. In spite of high endogenous TNF concentration, patients' circulating PMN were not activated, as shown by a CD11b/CD18 expression similar to that of control resting cells. In contrast with blood neutrophils, PMN from RA patients' synovial fluids had an activated phenotype, characterized by increased expression of CD11b, decreased expression of leukosialin, CD43, and the appearance on the plasma membrane of an azurophil granule protein, CD63. High levels of soluble TNF-R were measured in RA synovial fluids. Nevertheless, membrane TNF-R levels and p55 and p75 proportions were similar to those of PMN from normal blood. These results suggest the existence of regulatory mechanisms which maintain a stable neutrophil expression of TNF-R as well as a balance between both types of receptors in inflammatory situations where neutrophils are strongly activated.

Appearance of calpain correlates with arthritis and cartilage destruction in collagen induced arthritic knee joints of mice

OBJECTIVES

To determine the relevance of calpain in murine collagen induced arthritis (CIA) and to correlate the presence of m-calpain with the appearance of arthritis and cartilage destruction.

METHODS

The immunohistochemical appearance and localisation of m-calpain at different stages of arthritis were analysed and compared with the histological changes occurring during type II CIA. The arthritic knee joint lavage was also examined for m-calpain by immunoelectrophoretic blotting.

RESULTS

Immunohistochemical staining demonstrated a clear positive correlation between the appearance of m-calpain and both a histological grade of arthritis and an acute phase of cartilage destruction. Further development of the disease showed continual presence of m-calpain but with reduced intensity. Intra-articular inflammatory cells (mainly polymorphonuclear leucocytes, synovial lining cells, and sublining fibroblasts) were found to be the most positively stained, but extracellular localisation of m-calpain on the surface of cartilage and synovium, and in the articular cartilage matrix and chondrocyte lacunae, was also observed. In the knee joint lavage obtained at the most intensive stage of acute arthritis, m-calpain was detectable by immunoelectrophoretic blotting.

CONCLUSIONS

The findings suggest that m-calpain may act at an early phase of CIA as a matrix proteinase and take part in the destruction of articular cartilage or activate other destructive enzymes.

Measurement of colony-stimulating factors in synovial fluid: potential clinical value

In this study, 100 synovial fluid (SF) samples from patients with a variety of arthritides were assayed for levels of colony-stimulating factors (CSFs) using a human bone-marrow bioassay and enzyme immunoassays for granulocyte (G-) and granulocyte-macrophage (GM-) CSFs. GM-CSF was found more frequently in samples from rheumatoid arthritis (RA) subjects (49%) than in non-RA samples (29%). Absence of GM- but not G- or bioassay CSFs characterised samples from subjects with psoriatic arthritis and ankylosing spondylitis (n = 14). There was strong evidence of an antagonistic relationship between levels of G- and GM-CSFs in samples from RA patients, an effect independent of drug treatment. However, treatment with non-steroidal anti-inflammatory agents (NSAIDs) may affect reported CSF concentrations: G-CSF levels were significantly lower in samples from subjects not taking NSAIDs. These results suggest that SF-CSF estimations using commercially available assays could provide useful diagnostic clues for clinicians, but careful interpretation is warranted particularly in patients on long-term NSAID treatment.

Immunological aspects of juvenile rheumatoid arthritis

This article reviews the evidence from recent studies on immunological abnormalities associated with pathophysiologic mechanisms operating in three clinical subtypes of juvenile rheumatoid arthritis (JRA) (polyarticular, pauciarticular and systemic). The main discussion is focused on three hallmarks of immunopathological studies. First, abnormalities in phenotype and function of lymphocytes from peripheral blood and inflamed synovium are discussed. The aberrations of lymphocytes are elucidated by T and B cells expressing phenotypic cell-markers such as CD20, CD21, CD4, CD8 and DR in association with different subtypes and disease activity. The functional imbalance and impairment of T and B cells are mainly observed by abnormal proliferation and/or in vitro Ig production in response to mitogens and alloantigens. Second, because the appearance of rheumatoid factors (RF) in serum indicates that the pathogenesis of JRA may be based on the autoimmune mechanism, the prevalence of RF including IgM, IgA and IgG isotype, hidden IgM RF and cross-reactive idiotype RF, and their characteristic properties are discussed. Moreover, specific auto-antibodies (antinuclear antibodies and others) for JRA are illustrated in this paper. Third, the production of various pro-inflammatory cytokines resulting in the release of tissue-damaging chemical mediators is also discussed. This may play a central role in the generation of systemic inflammation and joint involvement in JRA.

Albumin inhibits neutrophil spreading and hydrogen peroxide release by blocking the shedding of CD43 (sialophorin, leukosialin)

Spreading of neutrophils on protein-coated surfaces is a pivotal event in their ability to respond to soluble, physiologic agonists by releasing large amounts of hydrolases and oxidants. Using neutrophils plated on serum-, fibrinogen- or fibronectin-coated surfaces, we investigated the effect of human serum albumin (HSA) on spreading-dependent neutrophil responses. HSA suppressed the respiratory burst of neutrophils in response to tumor necrosis factor-alpha (TNF), complement component C5a or formylated peptide, but not phorbol myristate acetate. HSA was suppressive only if added before the onset of the respiratory burst, and suppression was reversed when HSA was removed. Likewise, HSA selectively and reversibly inhibited TNF-induced cell spreading and the associated fall in cAMP. However, HSA did not hinder TNF-induced cell adherence to the same protein-coated surfaces. We investigated cell surface sialoproteins as modulators of cell spreading and as targets for the anti-spreading action of HSA. Oxidation of the cell surface with periodate followed by reduction with 3H-borohydride and immunoblotting with specific mAbs helped identify the predominant sialoprotein on human neutrophils as CD43 (sialophorin, leukosialin). Treatment of neutrophils with C. perfringens sialidase desialylated CD43, markedly enhanced the ability of the cells to respond to TNF by spreading and undergoing a respiratory burst, and antagonized the ability of HSA to inhibit these responses. TNF-treated, adherent neutrophils shed CD43, and this was blocked by HSA, but not by ovalbumin. Exogenous neutrophil elastase removed CD43 from the neutrophil surface. HSA blocked the actions of both sialidase and elastase on CD43. In contrast, ovalbumin did not block the action of sialidase on CD43, and HSA did not inhibit the ability of sialidase to hydrolyze a synthetic substrate. These results suggested that HSA might bind CD43. In fact, the extracellular portion of CD43 bound to HSA-Sepharose, but not to ovalbumin- or glycylglycine-Sepharose. Finally, two mAbs recognizing different epitopes on CD43 mimicked HSA's inhibitory effects on neutrophil function. Thus, HSA can dissociate attachment of neutrophils from spreading. This dissociation may help neutrophils migrate along a chemotactic gradient, while decreasing their release of oxidants. CD43, a long, rigid molecule with a markedly negative charge, antagonizes neutrophil spreading. HSA appears to inhibit spreading-dependent neutrophil functions by binding to CD43 and interfering with the ability of neutrophils to shed it.

Inhibitory effects of hyaluronan on neutrophil-mediated cartilage degradation

The effects of hyaluronan on neutrophil-mediated cartilage degradation were studied in an in vitro model. Rat peritoneal neutrophils were incubated for up to 18 h with the neutralized cartilage of bovine nasal septa using N-formyl-L-methionyl-L-leucyl-L-phenylalanine combined with cytochalasin B, or opsonized zymosan, as a stimulation agent of neutrophils. Hyaluronan inhibited the neutrophil-mediated cartilage degradation by reducing the release of sulfated glycosaminoglycans from the cartilage. Inhibitory effects were dependent on concentration and molecular weight of hyaluronan. These results suggest that hyaluronan with a high molecular weight plays an important role in protecting the articular cartilage in inflamed joints from neutrophil injury.

Platelet-activating factor inhibits proteoglycan synthesis and enhances neutrophil-mediated proteoglycan degradation in cartilage explants

OBJECTIVE

Platelet-activating factor (PAF), which stimulates the release of tissue-destructive enzymes and reactive oxygen metabolites from neutrophils, was investigated for its role in neutrophil-mediated cartilage breakdown.

METHODS

Bovine cartilage explants were incubated with or without human neutrophils, PAF, and other reagents. Cartilage damage was measured as either proteoglycan degradation (percent release of 35S-labeled proteoglycan from 35S-labeled cartilage) or inhibition of proteoglycan synthesis (rate of incorporation of 35S into proteoglycan).

RESULTS

PAF increased neutrophil-mediated proteoglycan degradation in the 2-20 microM range. Three specific PAF-receptor antagonists, WEB2086, CV3988, and CV6209, reversed this effect of PAF. These antagonists also reduced the enhancement of neutrophil-mediated cartilage damage caused by granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor alpha (TNF alpha). The results suggest that there may be a positive feedback mechanism whereby cytokine-primed neutrophils produce PAF, which amplifies the release of other tissue-damaging substances from neutrophils. In the absence of neutrophils, PAF (2-20 microM) inhibited the synthesis of proteoglycan by bovine cartilage. Neutrophils also inhibit proteoglycan synthesis, but PAF probably is not involved in this effect of neutrophils because the PAF receptor antagonists had no consistent effect.

CONCLUSION

PAF increases neutrophil-mediated cartilage proteoglycan degradation in vitro. GM-CSF and TNF alpha enhancement of neutrophil damage to cartilage is partly due to PAF. PAF alone inhibits cartilage proteoglycan synthesis.

Analysis of intraarticular fibrinolytic pathways in patients with inflammatory and noninflammatory joint diseases

OBJECTIVE

Intraarticular activation of the fibrinolytic system has been suspected to occur in patients with arthritis. We undertook the present study to investigate the relation of this activation to clinical symptoms, and the molecular pathways involved.

METHODS

We quantitatively assessed levels of plasmin-alpha 2-antiplasmin (PAP) complexes in synovial fluid (SF) from 25 patients with rheumatoid arthritis (RA), 7 with seronegative spondylarthropathy (SSA), and 10 with osteoarthritis (OA), and conducted an analysis to determine the plasminogen-activating pathway via which these complexes were generated. In addition, we studied the relationship of intraarticular fibrinolysis to clinical and biochemical parameters.

RESULTS

All patients studied had increased SF levels of PAP complexes. Levels in patients with RA and SSA were slightly higher than those in patients with OA. These complexes were probably formed by activation of urokinase-type plasminogen activator (u-PA), and not tissue-type plasminogen activator (t-PA), since SF levels of both u-PA antigen and u-PA-plasminogen activator inhibitor (PAI) complexes were increased in 27 of the 42 patients. Conversely, SF levels of t-PA were below normal in all but 1 patient. In some patients, activation of factor XII presumably also contributed to plasminogen activation in SF, since levels of factor XIIa-C1 inhibitor in SF were increased in 8 of the 42 patients and correlated, as did u-PA-PAI levels, with levels of PAP complexes. Several of the parameters of fibrinolysis in SF, particularly u-PA antigen and u-PA-PAI-1 complexes, were found to correlate with clinical and biochemical parameters.

CONCLUSION

Our results suggest that plasminogen is frequently activated in the joints of patients with inflammatory or noninflammatory arthropathy and that this activation mainly occurs via a u-PA-, and in some cases also via a factor XII-, dependent pathway. The possible relation of this activation process to stimulation of synovial cells by cytokines is discussed.

Mediators of joint swelling and damage in rheumatoid arthritis and pristane induced arthritis

Joint swelling and tenderness in rheumatoid arthritis (RA) probably result from IgG aggregates activating complement with the consequent attraction of polymorphonuclear leucocytes (PMNs) and the liberation of their granule enzymes such as kininogenases. By contrast IL-1 and TNF are the major stimulants of cartilage and bone loss although other agents contribute. The fundamental drive for the production of these mediators is unknown but a role for heat shock proteins is suggested from work on pristane induced arthritis.