Lysis of fibrillar collagen by neutrophils in synovial fluid. A role for surface-bound immunoglobulins

Innate Neutrophil Memory Dynamics in Disease Pathogenesis

Neutrophils, the most abundant leukocytes in circulation and the first responders to infection and inflammation, closely modulate both acute and chronic inflammatory processes. Resting neutrophils constantly patrol vasculature and migrate to tissues when challenges occur. When infection and/or inflammation recede, tissue neutrophils will be subsequently cleaned up by macrophages which collectively contribute to the resolution of inflammation. While most studies focus on the anti-microbial function of neutrophils including phagocytosis, degranulation, and neutrophil extracellular traps (NETs) formation, recent research highlighted additional contributions of neutrophils beyond simply controlling infectious agents. Neutrophils with resolving characteristics may alter the activities of neighboring cells and facilitate inflammation resolution, modulate long-term macrophage and adaptive immune responses, therefore having important impacts on host pathophysiology. The focus of this chapter is to provide an updated assessment of recent progress in the emerging field of neutrophil programming and memory in the context of both acute and chronic diseases.

Role of neutrophils in systemic autoimmune diseases

Neutrophils have emerged as important regulators of innate and adaptive immune responses. Recent evidence indicates that neutrophils display marked abnormalities in phenotype and function in various systemic autoimmune diseases, and may play a central role in initiation and perpetuation of aberrant immune responses and organ damage in these conditions. This review discusses the putative roles that neutrophils and aberrant neutrophil cell death play in the pathogenesis of various systemic autoimmune diseases, including systemic lupus erythematosus, small vessel vasculitis and rheumatoid arthritis.

Effects of laser on the synovial fluid in the inflammatory process of the knee joint of the rabbit

OBJECTIVE

The purpose of this study was to evaluate the effects of low-level laser (LLL) energy on the clinical signs of inflammation and the cellular composition of synovial fluid (SF) in the inflamed knee of the rabbit.

BACKGROUND DATA

There are few findings related to the effects of LLL on SF in inflammatory processes and there is little knowledge about the optimal parameters for reducing joint inflammation.

MATERIALS AND METHODS

Inflammation in the right knee of 36 rabbits was induced by intracapsular injection (0.2 mL) of Terebinthina commun (Tc). The animals were randomly assigned to three groups: acute experimental group (AEG), chronic experimental group (CEG), and control group (CG), which only received Tc. Each group was divided in two subgroups of six animals each. The AEG and CEG groups began to receive laser treatment 2 and 5 d after the induction of inflammation, respectively. Laser irradiation at a wavelength of 830 nm, power output of 77 mW, and power density of 27.5 W/cm(2) was applied daily for 7 d for either 0.12 sec or 0.32 sec, resulting in doses of 3.4 J/cm(2) and 8 J/cm(2), respectively. Body mass, joint perimeter, joint temperature, and the morphology of the SF were analyzed.

RESULTS

There was no statistically significant differences between groups in the body mass, joint perimeter, and SF morphology.

CONCLUSION

Laser irradiation with the selected parameters produced only a few subtle differences in the inflammatory signs and the SF. The lack of effects may have been due to the short irradiation time.

Preliminary observations on the influence of rheumatoid alpha-1-acid glycoprotein on collagen fibril formation

This study investigates the effect of alpha(1)-acid glycoprotein (AGP) isolated from both normal and rheumatoid plasma on type II collagen fibril formation. Rheumatoid samples were obtained over 2 years from two patients with early arthritis. The glycosylation of each sample was analysed to establish any correlation with fibrillogenesis. Rheumatoid AGP displays increased fucosylation compared to normal AGP. In both patients the fucosylation dipped after 1 year, then rose again over year 2. It is proposed that year 1 corresponds to the acute phase of the disease and the onset of chronic inflammation after this time produces a subsequent increase in fucosylation. Rheumatoid AGP influences type II collagen fibrillogenesis. Native fibrils were produced but with differences in the rate and extent of fibrillogenesis depending on AGP concentration and fucosylation. Low concentrations produced a decrease in fibrillogenesis rate and fibril diameter. High concentrations produced fibrils at a rate and diameter dependent on fucosylation. Highly fucosylated AGP produced narrow fibrils slowly, whereas poorly fucosylated AGP produced thicker fibrils more quickly. We propose that differences in glycosylation (especially fucosylation) of AGP are responsible for differences in collagen fibrillogenesis and this phenomenon may contribute to the exacerbation of cartilage destruction in rheumatoid arthritis.

Analysis of 16 different matrix metalloproteinases (MMP-1 to MMP-20) in the synovial membrane: different profiles in trauma and rheumatoid arthritis

OBJECTIVE

To define the pattern of mRNA expression of all human matrix metalloproteinases (MMPs) described to date in rheumatoid arthritis (RA) and traumatic synovial membrane, in order to differentiate between a physiological tissue remodelling pattern and that associated with inflammatory tissue destruction.

METHODS

Analysis of SwissProt protein and EMBL/GenBank nucleotide sequence banks, protein sequence alignment, reverse transcriptase-polymerase chain reaction and nucleotide sequencing were used.

RESULTS

MMP-2 (gelatinase A), MMP-3 (stromelysin-1), MMP-11 (stromelysin-3) and MMP-19 were constitutively expressed. MMP-1 (fibroblast type collagenase), MMP-9 (gelatinase B) and MMP-14 (MT1-MMP) were expressed in all RA, but only in 55-80% of trauma samples. MMP-13 (collagenase-3) and MMP-15 (MT2-MMP) were expressed exclusively in RA (80-90% of the samples). MMP-20 (enamelysin) was absent and MMP-8 (collagenase-2) was rarely found in RA or trauma. All other MMPs (-7, -10, -12, -16, -17) had an intermediate pattern of expression.

CONCLUSIONS

Some MMPs without interstitial collagenase activity seem to have a constitutive pattern of expression and probably participate in physiological synovial tissue remodelling. Some MMPs are exclusively associated to RA synovitis, for example, MMP-13, which preferentially degrades type II collagen and aggrecan, and MMP-15, which activates proMMP-2 and proMMP-13 and is involved in tumour necrosis factor alpha processing. This clear cut rheumatoid/inflammatory MMP profile, more complex than has been previously appreciated, may facilitate inflammatory tissue destruction in RA.

Determination of metalloproteinases, plasminogen-activators and their inhibitors in the synovial fluids of patients with rheumatoid arthritis during chemical synoviorthesis

The concentrations of matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-8 (MMP-8), matrix metalloproteinase-9 (MMP-9), lactoferrin and urokinase plasminogen activator (uPA), tissue-type plasminogen activator (tPA) and the inhibitors, tissue inhibitor of metalloproteinase-1 (TIMP-1), plasminogen activator inhibitor-1 (PAI-1), plasminogen activator inhibitor (PAI-2), and alpha2-macroglobulin in the synovial fluids of patients with rheumatoid arthritis was determined before and during chemical synoviorthesis with a sodium salt of the fatty acids from cod-liver oil (Varicocid). Synovial fluids were obtained before treatment from 37 patients with rheumatoid arthritis and, in most cases, at 8 and 24 h after injection of the agent. Well-established ELISAs were used to determine the amounts of all proteins. All patients with rheumatoid arthritis revealed very high levels of metalloproteinases (about 1-15 mu g/ml) in their synovial fluids. During the inflammation inducing treatment the granulocyte enzymes increased. In contrast to this, the level of MMP-1 decreased. All granulocyte-derived enzymes were strongly correlated with each other, whereas their dependence on the granulocyte count was only weak. uPA and PAI-2 showed good correlations with the granulocytes-derived enzymes, but were also only weakly correlating with the cell counts. t-PA was not detected by the ELISA used. The proteases, MMP-8, MMP-9 and uPA were increased 8 h after the treatment, whereas the specific inhibitors TIMP-1, PAI-1 and PAI-2 showed significant changes only 24 h after the injection. Matrix metalloproteinases are important factors in the pathogenesis of rheumatoid arthritis. The inflammatory activity in the joint could be better correlated to the granulocyte enzymes than to the granulocyte counts. The levels of uPA and PAI-2 are also parallel to the granulocyte enzyme levels and might underly the same regulatory mechanism.

Possible clearance of effete polymorphonuclear leucocytes from synovial fluid by cytophagocytic mononuclear cells: implications for pathogenesis and chronicity in inflammatory arthritis

A feature common to all forms of chronic inflammatory arthritis, irrespective of the possible underlying cause, is the persistent exudation of large numbers of polymorphonuclear leucocytes (PMNL) into synovial fluid. These cells possess potent degradative enzymes and proinflammatory mediators, and their removal is vital to normal inflammatory resolution. A major route of disposal of extravasated PMNL appears to be programmed cell death (apoptosis), followed by their rapid recognition, and intact phagocytosis, by mature tissue macrophages. Such macrophages, containing PMNL (cytophagocytic mononuclear cells (CPM)), long recognised in synovial fluid as Reiter cells, are commonly found in reactive arthritis, spondyloarthritis, and crystal arthritides, but only rarely in rheumatoid disease. In a retrospective analysis of 187 knee synovial fluid cytospins, the relation between the formation of CPM and the presence of apoptotic (pyknotic) PMNL was investigated. As long as the synovial fluid examined was fresh there was a high correlation between numbers of CPM (as a percentage of macrophages) and pyknotic numbers of PMNL in fluids containing CPM. This suggests that the formation of CPM occurs in vivo and is involved in the disposal of PMNL. Numbers of pyknotic PMNL increased rapidly in stored synovial fluid without a significant change in numbers of CPM, and were highest in synovial fluid which did not contain CPM. The presence or absence of CPM, or their disease associations, could not be explained simply by limiting numbers of macrophages, or apoptotic PMNL in synovial fluid. These findings are consistent with a regulatory role for CPM in synovial fluid, where they may be important in preventing autolysis of PMNL, and thus local tissue damage.

Degradation of human articular cartilage by neutrophils in synovial fluid

OBJECTIVE

To determine whether surface-adherent immunoglobulins are capable of mediating synovial fluid (SF) neutrophil degradation of proteoglycan and collagen in intact, normal human articular cartilage, and to define the respective roles of neutrophil serine proteases and metalloproteases in degrading these cartilage constituents.

METHODS

Pellet explants of normal human articular cartilage pretreated with bovine serum albumin (BSA) or IgG were incubated with polymorphonuclear cells suspended in SF (PMN-SF), or with supernatants derived from neutrophils stimulated with surface-associated IgG. Proteoglycan degradation was measured by assaying release of 35S-proteoglycan fragments from cartilage explants prelabeled with 35S-sulfate. Collagen degradation was measured by assaying hydroxyproline content in the PMN-SF preparations or neutrophil supernatants following their incubation with unlabeled explants.

RESULTS

Significant release of both 35S fragments and hydroxyproline was noted following incubation of PMN-SF with IgG-treated pellets, compared with pellets treated with BSA. IgG preparations derived from pooled normal serum or rheumatoid arthritis SF were equally efficacious in mediating PMN degradation of cartilage collagens. Explant release of 35S fragments during incubation with PMN supernatant was completely inhibited when serine proteases were inactivated by diisopropyl fluorophosphate (DFP); however, release of 35S fragments was enhanced when metalloprotease activity was present in the supernatant. Release of hydroxyproline during incubation of explants with PMN supernatant was comparable in the presence of DFP or EDTA, but was markedly enhanced when both serine and metalloprotease activity were present in the supernatant.

CONCLUSION

Neutrophils in SF are capable of degrading both proteoglycans and collagens in intact human articular cartilage. Degradation of these cartilage constituents is facilitated by immunoglobulins adherent to the cartilage surface and by the synergistic action of PMN serine and metalloproteases released during activation of neutrophils with surface-associated immunoglobulin.