Electrical charge of the antigen determines intraarticular antigen handling and chronicity of arthritis in mice

Intestinal bacteria and rheumatic disease

The striking clinical and pathological similarities between certain naturally occurring infectious diseases in animal species and those of some human rheumatic diseases, such as rheumatoid arthritis (RA), have stimulated the search for a microbial etiology of the latter syndrome. A long series of microbial species, including aerobic and anaerobic intestinal bacteria, mycoplasma and several viruses have been put into focus. Most often, however, an initially positive report has been followed by several reports denying an etiological role of the microbial species in focus. However, the concept of a microbial trigger in the etiology and symptomatology of RA is still a subject of intense debate. Recent results have indicated a reversed effect of gram-positive vs. gram-negative intestinal bacteria on adjuvant-induced arthritis in germfree rats and microbial peptidoglycans have been shown to play a major role in this experimental model. It has been shown that the intestinal flora may include bacteria containing antigenic determinant(s) cross-reacting with some markers within the HLA-system. The intestinal flora may also influence upon several digestive and absorptive functions and thereby acting upon parameters of importance in the development of rheumatic disease.

Joint inflammations and flare-up reactions in mice induced by a helper T cell clone

Joint inflammation was induced in mice by cloned helper T cells specific for methylated bovine serum albumin (mBSA). This occurred after local injection of the helper T cells together with mBSA into the knee joint, but also when the helper T cells were intravenously injected and the antigen directly into the joint. Local injection of mBSA several weeks after waning of a joint inflammation induced by cloned helper T cells caused a flare-up reaction, indicating that the helper T cells persisted in the joint after the primary inflammation.

Monoclonal anti-Ia antibodies suppress the flare up reaction of antigen induced arthritis in mice

Intravenous injection of methylated bovine serum albumin (mBSA) in mice with a unilateral antigen-induced arthritis induced with mBSA causes a flare up of the inflammation in the arthritic but not in the contralateral joint. To study whether this phenomenon is dependent on class II antigens, we treated C57Bl/10 (H-2b) and C3H (H-2k) mice with monoclonal anti-Iab (HB26) and anti-Iak (2-2-1) antibodies on days -3, -2, -1 and 0 before induction of the flare up. Another group was treated only once on day 0 before antigen challenge. Four injections with HB26 completely suppressed the flare up reaction in C57Bl/10 mice; the same results were seen with 2-2-1 in C3H mice. One injection only partly suppressed the flare up reaction in both strains, whereas four injections with the haplotype-nonspecific antibodies did not affect the flare up. Injections with HB26 appeared to be able to completely suppress a delayed type hypersensitivity reaction but not a reversed passive Arthus reaction in C57B1/10 mice, indicating that anti-Ia antibodies have an effect on lymphocyte-dependent but not on antigen-antibody-dependent inflammatory phenomena. These results demonstrate that the flare up of antigen induced arthritis is dependent on the presence of Ia antigens, suggesting that the interaction between antigen-presenting cells and T lymphocytes plays an important role in this process.

Quantitation of glycosaminoglycan metabolism in anatomically intact articular cartilage of the mouse patella: in vitro and in vivo studies with 35S-sulfate, 3H-glucosamine, and 3H-acetate

We investigated the usefulness of the whole mouse patella to quantitate the synthesis of the glycosaminoglycan (GAG) backbone and its sulfation by intact murine articular cartilage, both in vitro and in vivo. Using 35S-sulfate, 3H-glucosamine, or 3H-acetate as precursors of GAG synthesis, it was found that more than 90% of the incorporated radioactivity was confined to the patellar cartilage layer compared to the whole patella. Overnight papain digestion was enough to liberate more than 95% of the incorporated radiolabels, except for 3H-acetate for which 15-25% was not digestible. Comparison of radioactivity in the patella and that in quantitatively isolated GAGs revealed that for 35S-sulfate incorporation studies the whole patella can be used as a reliable measure for sulfated GAG synthesis. The situation was different for the GAG backbone precursors 3H-glucosamine and 3H-acetate; more than 50% of the 3H labels were incorporated into compounds other than GAGs or non-covalently associated with matrix components. Hence, in studying GAG-backbone metabolism, polysaccharides must be isolated quantitatively from cartilage. In vivo studies made it clear that both 35S-sulfate and 3H-glucosamine are incorporated into patellar GAGs in amounts high enough to enable proper quantitation and that the route of administration (intraperitoneally or intravenously) is of minor importance. Due to its low specificity for cartilage GAGs, 3H-acetate is not suitable for such studies.

Effects of cyclosporin A on autoimmune disease in MRL/1 and BXSB mice

MRL/1 and BXSB mice were treated daily with cyclosporin A (CyA) in an oral dose of 25 mg/kg body weight. With this dose, blood levels within the therapeutic range were obtained. In normal mice CyA in this dose significantly prolonged the survival of an H-2 incompatible skin graft, and suppressed delayed-type hypersensitivity (DTH). It had no influence on the magnitude of a primary antibody response. Autoimmune mice were treated from 6 to 22 weeks of age. CyA treatment did not alter significantly the anti-DNA and anti-IgG autoantibody levels in either strain compared with control mice, who received olive oil. There was a slight but significant increase in serum IgG levels in CyA-treated MRL/1 mice. Clinical signs of glomerulonephritis (decreased kidney function and albuminuria), and glomerular proliferation were not altered by CyA treatment in either strain. The amount of mesangial IgG deposits was reduced in CyA-treated MRL/1 mice, and remained unchanged in BXSB mice. The extent of the interstitial and perivascular infiltrates and the frequency and severity of necrotizing arteritis in the kidneys of MRL/1 mice were reduced by CyA treatment. The most prominent effect of CyA was an evident reduction in lymphoproliferation in MRL/1 mice. Mortality was not reduced by CyA treatment in MRL/1 and BXSB mice.

Flare of antigen-induced arthritis in mice after intravenous challenge. Kinetics of antigen in the circulation and localization of antigen in the arthritic and noninflamed joint

Intravenous injection of methylated bovine serum albumin (mBSA) in mice with unilateral, chronic, mBSA-induced arthritis has been shown to cause a flare of smouldering arthritis without affecting the contralateral, noninflamed knee joint. We studied the kinetics of 125I-labeled mBSA in the blood, and the accumulation of antigen in both arthritic and noninflamed joints. The bulk of the antigen was eliminated from the blood within 10-30 minutes, and accumulation of antigen in the joints occurred mainly within this period. The amounts of antigen found in the arthritic joints were of the same order of magnitude as the amounts found in noninflamed joints. Autoradiography of whole joint sections revealed that, in arthritic joints, antigen was located primarily at the deep capillaries and large vessels, and in the noninflamed joints, antigen was located at the small superficial capillaries. Antigen was handled by granulocytes in the arthritic joint and by synovial lining cells in the noninflamed joint. Our data indicate that tiny amounts of antigen reach the synovial stroma in both normal and arthritic joints but cause inflammation only in the arthritic joints, because of local hyperreactivity.

Electrical charge of hyaline articular cartilage: its role in the retention of anionic and cationic proteins

The mouse patella with surrounding tissue has been used to study the influence of electrical charge of a high-molecular-weight protein on its retention at joint structures. Three proteins were used: native anionic bovine serum albumin (BSA), and charge modified BSA rendered cationic (pI 8.5) either by methylation (mBSA) or amidation (aBSA). Following a 2-hr incubation the two cationic (125I-labeled) proteins were strongly retained, both in the intact patellar cartilage and the surrounding tissue. Autoradiography revealed deep penetration of the proteins to the calcified zone of the articular cartilage, and a high labeling density of the cartilage, which is probably related to its high negative fixed charge density. Evidence for the electrostatic character of the binding emerged from studies at high pH (9.5) and ionic strength (0.5 M). The binding of aBSA, but not mBSA, could be prevented by pretreatment with the polycation protamine (pI 10). Posttreatment to remove retained aBSA was less effective. As expected, native BSA was not retained, unless the tissue was preincubated with antibodies. The antibody-mediated retention was more pronounced for the tissue compared with the dense patellar cartilage. Diffusion experiments revealed that enough BSA and IgG penetrate the surrounding tissue to permit substantial in situ immune complex (IC) formation, but the penetration of intact patellar cartilage was very low. Forty times more aBSA compared with BSA was taken up by intact cartilage; after trypsin treatment, which lowers the negative fixed charge density of the cartilage, the difference was reduced to a factor 4. Our data indicate that the fixed charge density of a tissue determines the uptake and retention of charged proteins, and may be a dominant principle in the occurrence of in situ IC formation within a tissue by allowing or preventing penetration of charged IC components.

An experimental model for hydrogen peroxide-induced tissue damage. Effects of a single inflammatory mediator on (peri)articular tissues

Hydrogen peroxide is receiving increasing attention as a mediator of tissue damage during inflammation. To evaluate its destructive potential in vivo, we devised a model in which hydrogen peroxide is, initially, the sole mediator of tissue damage. Glucose oxidase, which was made cationic to obtain good retention in tissue, was injected intraarticularly in mouse knee joints. This enzyme produces hydrogen peroxide, using endogenous glucose as a substrate. The local production of hydrogen peroxide induced drastic vascular damage, as measured by 99mTc uptake and leakage of 125I-albumin. The chondrocyte proteoglycan synthesis was severely inhibited, as measured by 35SO4 incorporation. Histologic examination showed impressive inflammatory and degenerative changes, including periarticular infiltration, chondrocyte death, subchondral erosions, and muscle necrosis. Intraarticular administration of catalase could inhibit these vascular effects and cartilage damage. Systemic administration of ebselen, a synthetic glutathione peroxidase-like compound, provided partial protection. Indomethacin and piroxicam were not effective in the acute phase. We think this model is useful both for testing drugs that are purported to act as scavengers of hydrogen peroxide and for studying chronic destructive processes.

Electrical charge of the antigen determines its localization in the mouse knee joint. Deep penetration of cationic BSA in hyaline articular cartilage

Intraarticular injection of cationic bovine serum albumin (BSA) induces a chronic arthritis in immunized mice, whereas the negatively charged native BSA fails to cause a protracted joint inflammation. In this study the authors examined the role of antigenic charge as a determinant of antigen retention and exact localization within the knee joint. Immune and nonimmune mice received an intraarticular injection of either radiolabeled native BSA (125I-BSA) or charge-modified BSA rendered cationic by amidation (aBSA), and autoradiographs were prepared of whole joint sections at various days after injection. As has been shown in the rabbit, the retention of the negatively charged native BSA is largely dependent upon the presence of antibodies. In nonimmune mice the radiolabeled antigen was hardly detectable after Day 1. In immune mice antibody-mediated retention of BSA was found in the ligaments and fibrous cartilage structures of the joint but appeared to be absent at the hyaline cartilage. In contrast, large amounts of the cationic aBSA were retained at all collagenous structures of the joint, the most striking observation being the deep penetration in the dense hyaline cartilage. This was found both in immune and nonimmune mice, which indicates that the deep penetration was not due to cartilage damage occurring under inflammatory conditions. With different dosages of aBSA it was found that the presence of antibodies may modulate the retention pattern in immune mice. Deep diffuse penetration into the dense hyaline cartilage, together with some surface labeling, was observed after injection of a high dose (60 micrograms), whereas mere surface labeling was found with the low dose (6 micrograms). Distinct superficial labeling was not seen in nonimmune mice, which suggests that this pattern represents immune complex formation at the cartilage surface. Immunofluorescence studies on undecalcified whole joint sections confirmed the deep penetration of the cationic antigen and supported the presence of immune complexes at the cartilage surface, because intense complement and Ig staining was detectable at this site. Our data indicate that antigenic charge determines the antigen retention in the joint both quantitatively and qualitatively. Negatively charged native BSA has no affinity for cartilage, high amounts of antibodies are needed for its retention in the joint, retention by this immune complex formation is largely restricted to the loose collagenous tissues, and the capacity to retain anionic antigen in the joint is therefore low.(ABSTRACT TRUNCATED AT 400 WORDS)

Cationization of catalase, peroxidase, and superoxide dismutase. Effect of improved intraarticular retention on experimental arthritis in mice

Several enzymes and other proteins were made cationic either by coupling to polylysine or by shielding of anionic sites. These cationic proteins, all having an isoelectric point greater than 8.5 exhibited excellent retention in articular structures when injected in mouse knee joints. Autoradiography and histochemistry showed that cationic forms of catalase, superoxide dismutase, and horseradish peroxidase were firmly retained by synovial and cartilaginous tissues. The half-life of these enzymes in the joint is thus significantly extended compared with native enzymes. The native enzymes and their cationic derivatives were tested for antiinflammatory properties in mice, using antigen-induced arthritis and zymosan-induced arthritis. It was found that injection of cationic catalase or peroxidase induced a marked suppression of some parameters of the inflammatory response in both types of arthritis, as measured by 99m technetium pertechnetate uptake and leakage of 125I-labeled albumin. Native catalase and peroxidase were less, or not at all effective. Cationic superoxide dismutase or cationic nonenzyme proteins did not suppress inflammation. The observed suppression of two different types of inflammation (an immune and a nonimmune arthritis) by catalase and peroxidase suggests that elimination of peroxides contributes to the suppression of an inflammatory response. We would hypothesize that cationic enzymes offer the possibility for investigating the mechanisms of inflammation and, in addition, might be interesting from a therapeutical point of view.