Inhibition of tumor necrosis factor-alpha (TNF-alpha) production and arthritis in the rat by GW3333, a dual inhibitor of TNF-alpha-converting enzyme and matrix metalloproteinases

Tumor necrosis factor-alpha (TNF)-converting enzyme (TACE) cleaves the precursor form of TNF, allowing the mature form to be secreted into the extracellular space. GW3333, a dual inhibitor of TACE and matrix metalloproteinases (MMPs), was compared with an anti-TNF antibody to evaluate the importance of soluble TNF and MMPs in rat models of arthritis. Oral administration of GW3333 completely blocked increases in plasma TNF after LPS for up to 12 h. In a model wherein intrapleural zymosan injection causes an increase in TNF in the pleural cavity, GW3333 completely inhibited the increase in TNF in the pleural cavity for 12 h. Under these dosing conditions, the plasma levels of unbound GW3333 were at least 50-fold above the IC(50) values for inhibition of individual MMPs in vitro. In a model wherein bacterial peptidoglycan polysaccharide polymers reactivate a local arthritis response in the ankle, a neutralizing anti-TNF antibody completely blocked the ankle swelling over the 3-day reactivation period. GW3333 administered b.i.d. over the same period also inhibited ankle swelling, with the highest dose of 80 mg/kg being slightly less active than the anti-TNF antibody. In a 21-day adjuvant arthritis model, the anti-TNF antibody did not inhibit the ankle swelling or the joint destruction, as assessed by histology or radiology. GW3333, however, showed inhibition of both ankle swelling and joint destruction. In conclusion, GW3333 is the first inhibitor with sufficient duration of action to chronically inhibit TACE and MMPs in the rat. The efficacy of GW3333 suggests that dual inhibitors of TACE and matrix metalloproteinases may prove therapeutic as antiarthritics.

Dietary glycine prevents peptidoglycan polysaccharide-induced reactive arthritis in the rat: role for glycine-gated chloride channel

Peptidoglycan polysaccharide (PG-PS) is a primary structural component of bacterial cell walls and causes rheumatoid-like arthritis in rats. Recently, glycine has been shown to be a potential immunomodulator; therefore, the purpose of this study was to determine if glycine would be protective in a PG-PS model of arthritis in vivo. In rats injected with PG-PS intra-articularly, ankle swelling increased 21% in 24 to 48 h and recovered in about 2 weeks. Three days prior to reactivation with PG-PS given intravenously (i.v.), rats were divided into two groups and fed a glycine-containing or nitrogen-balanced control diet. After i.v. PG-PS treatment joint swelling increased 2.1 +/- 0.3 mm in controls but only 1.0 +/- 0.2 mm in rats fed glycine. Infiltration of inflammatory cells, edema, and synovial hyperplasia in the joint were significantly attenuated by dietary glycine. Tumor necrosis factor alpha (TNF-alpha) mRNA was detected in ankle homogenates from rats fed the control diet but not in ankles from rats fed glycine. Moreover, intracellular calcium was increased significantly in splenic macrophages treated with PG-PS; however, glycine blunted the increase about 50%. The inhibitory effect of glycine was reversed by low concentrations of strychnine or chloride-free buffer, and it increased radiolabeled chloride influx nearly fourfold, an effect also inhibited by strychnine. In isolated splenic macrophages, glycine blunted translocation of the p65 subunit of NF-kappaB into the nucleus, superoxide generation, and TNF-alpha production caused by PG-PS. Further, mRNA for the beta subunit of the glycine receptor was detected in splenic macrophages. This work supports the hypothesis that glycine prevents reactive arthritis by blunting cytokine release from macrophages by increasing chloride influx via a glycine-gated chloride channel.

NF-kappaB activation provides the potential link between inflammation and hyperplasia in the arthritic joint

The transcription factor NF-kappaB is a pivotal regulator of inflammatory responses. While the activation of NF-kappaB in the arthritic joint has been associated with rheumatoid arthritis (RA), its significance is poorly understood. Here, we examine the role of NF-kappaB in animal models of RA. We demonstrate that in vitro, NF-kappaB controlled expression of numerous inflammatory molecules in synoviocytes and protected cells against tumor necrosis factor alpha (TNFalpha) and Fas ligand (FasL) cytotoxicity. Similar to that observed in human RA, NF-kappaB was found to be activated in the synovium of rats with streptococcal cell wall (SCW)-induced arthritis. In vivo suppression of NF-kappaB by either proteasomal inhibitors or intraarticular adenoviral gene transfer of super-repressor IkappaBalpha profoundly enhanced apoptosis in the synovium of rats with SCW- and pristane-induced arthritis. This indicated that the activation of NF-kappaB protected the cells in the synovium against apoptosis and thus provided the potential link between inflammation and hyperplasia. Intraarticular administration of NF-kB decoys prevented the recurrence of SCW arthritis in treated joints. Unexpectedly, the severity of arthritis also was inhibited significantly in the contralateral, untreated joints, indicating beneficial systemic effects of local suppression of NF-kappaB. These results establish a mechanism regulating apoptosis in the arthritic joint and indicate the feasibility of therapeutic approaches to RA based on the specific suppression of NF-kappaB.

Targeting of SCG10 to the area of the Golgi complex is mediated by its NH2-terminal region

SCG10 is a neuronal growth-associated protein that is concentrated in the growth cones of developing neurons. SCG10 shows a high degree of sequence homology to the ubiquitous phosphoprotein stathmin, which has been recently identified as a factor that destabilizes microtubules by increasing their catastrophe rate. Whereas stathmin is a soluble cytosolic protein, SCG10 is membrane-associated, indicating that the protein acts in a distinct subcellular compartment. Identifying the precise intracellular distribution of SCG10 as well as the mechanisms responsible for its specific targeting will contribute to elucidating its function. The main structural feature distinguishing the two proteins is that SCG10 contains an NH2-terminal extension of 34 amino acids. In this study, we have examined the intracellular distribution of SCG10 in PC12 cells and in transfected COS-7 cells and the role of the NH2-terminal domain in membrane-binding and intracellular targeting. SCG10 was found to be localized to the Golgi complex region. We show that the NH2-terminal region (residues 1-34) was necessary for membrane targeting and Golgi localization. Fusion proteins consisting of the NH2-terminal 34 amino acids of SCG10 and the related protein stathmin or the unrelated protein, beta-galactosidase, accumulated in the Golgi, demonstrating that this sequence was sufficient for Golgi localization. Biosynthetic labeling of transfected COS-7 cells with [3H]palmitic acid revealed that two cysteine residues contained within the NH2-terminal domain were sites of palmitoylation.

Regulation of microtubule dynamics by the neuronal growth-associated protein SCG10

Dynamic assembly and disassembly of microtubules is essential for cell division, cell movements, and intracellular transport. In the developing nervous system, microtubule dynamics play a fundamental role during neurite outgrowth, elongation, and branching, but the molecular mechanisms involved are unknown. SCG10 is a neuron-specific protein that is membrane-associated and highly enriched in growth cones. Here we show that SCG10 binds to microtubules, inhibits their assembly, and can induce microtubule disassembly. We also show that SCG10 overexpression enhances neurite outgrowth in a stably transfected neuronal cell line. These data identify SCG10 as a key regulator of neurite extension through regulation of microtubule instability.

Inhibition of cartilage and bone destruction in adjuvant arthritis in the rat by a matrix metalloproteinase inhibitor

Considerable evidence has associated the expression of matrix metalloproteinases (MMPs) with the degradation of cartilage and bone in chronic conditions such as arthritis. Direct evaluation of MMPs' role in vivo has awaited the development of MMP inhibitors with appropriate pharmacological properties. We have identified butanediamide, N4-hydroxy-2-(2-methylpropyl)-N1-[2-[[2-(morpholinyl)ethyl]-,[S- (R*,S*)] (GI168) as a potent MMP inhibitor with sufficient solubility and stability to permit evaluation in an experimental model of chronic destructive arthritis (adjuvant-induced arthritis) in rats. In this model, pronounced acute and chronic synovial inflammation, distal tibia and metatarsal marrow hyperplasia associated with osteoclasia, severe bone and cartilage destruction, and ectopic new bone growth are well developed by 3 wk after adjuvant injection. Rats were injected with Freund's adjuvant on day 0. GI168 was was administered systemically from days 8 to 21 by osmotic minipumps implanted subcutaneously. GI168 at 6, 12, and 25 mg/kg per d reduced ankle swelling in a dose-related fashion. Radiological and histological ankle joint evaluation on day 22 revealed a profound dose related inhibition of bone and cartilage destruction in treated rats relative to rats receiving vehicle alone. A significant reduction in edema, pannus formation, periosteal new bone growth and the numbers of adherent marrow osteoclasts was also noted. However, no significant decrease in polymorphonuclear and mononuclear leukocyte infiltration of synovium and marrow hematopoietic cellularity was seen. This unique profile of antiarthritic activity indicates that GI168 is osteo- and chondro-protective, and it supports a direct role for MMP in cartilage and bone damage and pannus formation in adjuvant-induced arthritis.

Anti-inflammatory activity of phosphodiesterase (PDE)-IV inhibitors in acute and chronic models of inflammation

Inhibitors of cyclic nucleotide phosphodiesterases are known to suppress lipopolysaccharide (LPS)-induced tumour necrosis factor-alpha (TNF-alpha) production in vitro in human monocytes. The most potent of these have selectivity for type IV PDEs, suggesting that this class of PDE is the major type involved in the regulation of human TNF-alpha production. Using compounds of two distinct chemical structural classes, a quinazolinedione (CP-77059) and a 4 arylpyrrolidinone (rolipram), we show here that PDE-IV-specific inhibitors are also potent in suppressing LPS-induced TNF-alpha production in vitro in sodium periodate-elicited murine macrophages (IC50s of 1 and 33, respectively). We then report the in vivo anti-inflammatory effect of PDE-IV inhibition in five murine models of inflammation: (i) elevation of serum TNF-alpha induced by a sublethal LPS injection; (ii) LPS-induced endotoxic shock; (iii) LPS/galactosamine-induced endotoxic shock; (iv) carrageenan-induced paw oedema; and (v) adjuvant arthritis. Following a sublethal (5 micrograms/mouse) injection of LPS, serum TNF-alpha levels in mice peaked sharply, reaching concentrations of 3-12 ng/ml 90 min after injection. In this sublethal LPS assay, CP-77059 was about 30 times more potent than rolipram, with a minimum effective dose of 0.1 mg/kg versus 3 mg/kg for rolipram. This rank order is in keeping with the relative in vitro IC50s for CP-77059 and rolipram, as well as their relative Ki against the human PDE-IV enzyme (46 nM and 220 nM, respectively). In LPS-induced endotoxic shock, rolipram and CP-77059 at relatively high doses of 30 and 10 mg/kg, respectively, significantly reduced serum TNF-alpha levels, and also inhibited mortality 66%. In the LPS/galactosamine shock model, in which mice are rendered exquisitely sensitive to LPS by co-injection with galactosamine, only 0.1 microgram of LPS/mouse is necessary for serum TNF-alpha elevation and death. Both rolipram and the CP-77059 caused dose-dependent reduction of serum TNF-alpha and lethality. In the carrageenan-induced paw oedema model, in which there is a pronounced local TNF-alpha response (without a serum TNF-alpha elevation), rolipram significantly inhibited paw swelling as well as localized TNF-alpha levels in the paw. In the adjuvant arthritis model, a chronic model of inflammation also possessing localized TNF-alpha elevation in the inflamed paw, rolipram and CP-77059 suppressed ankle swelling and radiological evidence of joint damage. These data are consistent with a major role for PDE-IV in regulation of TNF-alpha production and inflammatory responses in murine systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Differential regulation of human monocyte-derived TNF alpha and IL-1 beta by type IV cAMP-phosphodiesterase (cAMP-PDE) inhibitors

Elevation of cAMP downregulates certain functions of inflammatory cells, including the release of TNF alpha and IL-1 beta by macrophages. Intracellular cAMP levels can be modulated pharmacologically by adding cell-permeable cAMP analogs, by stimulating adenylate cyclase or by inhibiting degradation of cAMP by cAMP-phosphodiesterases (cAMP-PDE). Multiple forms of cAMP-PDEs have been identified in various tissues and cells using both biochemical characterization and selective inhibitors. Therefore, we wanted to determine which of these different PDE isoforms was present in human monocytes and whether this isoform could regulate cytokine release from human monocytes by a mechanism similar to that seen with dbcAMP or PGE1. Our results demonstrate that selective inhibitors of type IV cAMP-PDE, such as rolipram and Ro20-1724, are clearly the most effective compounds at enhancing cAMP levels and inhibiting the release of TNF alpha and IL-1 beta in these cells. The type III cAMP-PDE-selective inhibitors C1930 and cilostamide and the nonselective PDE inhibitors IBMX and pentoxifylline were significantly less potent. In agreement with these data, cAMP-PDE activity in cytosolic extracts from human monocytes was also much more sensitive to inhibition by rolipram than by cilostamide. Additionally, rolipram dramatically reduced TNF alpha mRNA accumulation, which supports previous findings that cAMP regulates TNF alpha at the transcriptional level. Surprisingly, rolipram, rolipram, dbcAMP or PGE1 increased IL-1 beta was reduced, which indicates that cAMP can have both positive and negative effects on the regulation of IL-1 beta.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific endotoxic lipopolysaccharide-binding receptors on murine splenocytes. III. Binding specificity and characterization

In previously published studies, we employed a photoreactive radioiodinated derivative of LPS from Escherichia coli 0111:B4 to identify and characterize a membrane-localized specific LPS binding protein of approximately 80-kDa molecular mass. Our more recent studies demonstrating that mAb with specificity for this 80-kDa protein will act as an agonist in mediating macrophage activation have established that this protein serves as a specific receptor for LPS. In the experiments reported here, we have more accurately determined the apparent molecular mass of this protein to be 73 kDa (p73). We have also extended the sources of LPS-derivatized photo-cross-linking preparations (including Re-LPS) to determine generality of LPS binding to this receptor. Binding to the p73 LPS receptor is demonstrated with all of the LPS derivatives synthesized in our laboratory, as well as probes synthesized by other investigators. Binding of S-LPS is readily inhibited by Re chemotype LPS, and we have shown that this competitive inhibition is most likely not the result of formation of LPS aggregates. These results confirm and extend our earlier studies suggesting that the binding of LPS to the p73 receptor is lipid A specific. We further demonstrate that, in contrast to results published in a recent report, the p73 LPS receptor has no significant binding specificity for a variety peptidoglycan polymer preparations. Finally, we show that this LPS receptor can be detected on murine fibroblast, macrophage, and mastocytoma cell lines. Differences have been observed in the level of expression of LPS receptors on the various cell lines studied.

Specific endotoxic lipopolysaccharide-binding receptors on murine splenocytes. III. Binding specificity and characterization

In previously published studies, we employed a photoreactive radioiodinated derivative of LPS from Escherichia coli 0111:B4 to identify and characterize a membrane-localized specific LPS binding protein of approximately 80-kDa molecular mass. Our more recent studies demonstrating that mAb with specificity for this 80-kDa protein will act as an agonist in mediating macrophage activation have established that this protein serves as a specific receptor for LPS. In the experiments reported here, we have more accurately determined the apparent molecular mass of this protein to be 73 kDa (p73). We have also extended the sources of LPS-derivatized photo-cross-linking preparations (including Re-LPS) to determine generality of LPS binding to this receptor. Binding to the p73 LPS receptor is demonstrated with all of the LPS derivatives synthesized in our laboratory, as well as probes synthesized by other investigators. Binding of S-LPS is readily inhibited by Re chemotype LPS, and we have shown that this competitive inhibition is most likely not the result of formation of LPS aggregates. These results confirm and extend our earlier studies suggesting that the binding of LPS to the p73 receptor is lipid A specific. We further demonstrate that, in contrast to results published in a recent report, the p73 LPS receptor has no significant binding specificity for a variety peptidoglycan polymer preparations. Finally, we show that this LPS receptor can be detected on murine fibroblast, macrophage, and mastocytoma cell lines. Differences have been observed in the level of expression of LPS receptors on the various cell lines studied.

Flare-up reaction of streptococcal cell wall induced arthritis in Lewis and F344 rats: the role of T lymphocytes

One i.p. injection of a sterile suspension of streptococcal cell walls (SCW) induces chronic erosive polyarthritis in susceptible Lewis rats, but not in resistant F344 or nude Lewis rats. Because continuous exacerbations may be one possible mechanism underlying chronic disease, we studied the mechanism of these flare-up reactions in Lewis and F344 rats. Injection of SCW into the right knee joint of rats induced a transient monoarthritis in both strains. Reactivation of the subsided arthritis by i.v. administration of the same antigen could be evoked only in the Lewis rat. Even repeated i.v. challenges with SCW failed to induce a flare-up reaction in the F344 rat, while the Lewis rat went through an exacerbation after every challenge. Removal of T lymphocytes by monoclonal antibodies before induction of an exacerbation rendered Lewis rats refractory to flare-up reactions, thus indicating the T cell-dependence of this reaction. Furthermore, when cell walls from heterologous bacteria were tested for their capacity to induce exacerbations of SCW-induced monoarthritis and to induce proliferation of SCW-specific T lymphocytes in vitro, a strong correlation between both features was found, again pointing to a role for SCW-specific T cells in exacerbations. Together, these data support our hypothesis that chronic arthritis is the result from repeated reactivations of a waning arthritis which are dependent on antigen-specific T lymphocytes.

Exacerbation of arthritis by IL-1 in rat joints previously injured by peptidoglycan-polysaccharide

The arthropathic activity of mouse recombinant IL-1 (mrIL-1) after intraarticular (i.a.) injection into rat ankles was investigated. Nanogram quantities of either mrIL-1 alpha or mrIL-1 beta induced an acute transient arthritis. Arthritis induced by i.a. mrIL-1 developed more rapidly and was more severe in ankles previously injured by i.a. injection of group A streptococcal peptidoglycan-polysaccharide (PG-APS) fragments. In addition, a protracted pain response, as judged by severe limping, occurred 60 to 90 min after mrIL-1 injection into joints previously injured by PG-APS or 4 to 6 h after mrIL-1 injection into naive joints. The severity of arthritis was related to the mrIL-1 dose. Arthropathic activity of mrIL-1 alpha was neutralized by goat anti-mouse IL-1 alpha IgG, and the activity of both the alpha and beta preparations was heat labile. Repeated episodes of acute inflammation were induced by repeated i.a. injection of mrIL-1. In naive ankles this led to chronic synovitis without histologic evidence of erosions. However, in joints previously injured by PG-APS, repeated mrIL-1 injection induced a more severe chronic synovitis with a 50% incidence of early pannus formation and limited marginal erosions of cartilage and subchondral bone. Thus, mrIL-1 induces an acute exacerbation of arthritis in joints previously injured by PG-APS and repeated exposure of these joints to mrIL-1 promotes chronic erosive synovitis. These studies provide evidence for an in vivo function of IL-1 and are consistent with its role as one of the mediators in the local regulation of inflammation in recurrences of arthritis induced by bacterial cell wall polymers.

Exacerbation of arthritis by IL-1 in rat joints previously injured by peptidoglycan-polysaccharide

The arthropathic activity of mouse recombinant IL-1 (mrIL-1) after intraarticular (i.a.) injection into rat ankles was investigated. Nanogram quantities of either mrIL-1 alpha or mrIL-1 beta induced an acute transient arthritis. Arthritis induced by i.a. mrIL-1 developed more rapidly and was more severe in ankles previously injured by i.a. injection of group A streptococcal peptidoglycan-polysaccharide (PG-APS) fragments. In addition, a protracted pain response, as judged by severe limping, occurred 60 to 90 min after mrIL-1 injection into joints previously injured by PG-APS or 4 to 6 h after mrIL-1 injection into naive joints. The severity of arthritis was related to the mrIL-1 dose. Arthropathic activity of mrIL-1 alpha was neutralized by goat anti-mouse IL-1 alpha IgG, and the activity of both the alpha and beta preparations was heat labile. Repeated episodes of acute inflammation were induced by repeated i.a. injection of mrIL-1. In naive ankles this led to chronic synovitis without histologic evidence of erosions. However, in joints previously injured by PG-APS, repeated mrIL-1 injection induced a more severe chronic synovitis with a 50% incidence of early pannus formation and limited marginal erosions of cartilage and subchondral bone. Thus, mrIL-1 induces an acute exacerbation of arthritis in joints previously injured by PG-APS and repeated exposure of these joints to mrIL-1 promotes chronic erosive synovitis. These studies provide evidence for an in vivo function of IL-1 and are consistent with its role as one of the mediators in the local regulation of inflammation in recurrences of arthritis induced by bacterial cell wall polymers.

Lipopolysaccharide induces recurrence of arthritis in rat joints previously injured by peptidoglycan-polysaccharide

Rat ankle joints injected intraarticularly with 5 micrograms of group A streptococcal peptidoglycan-polysaccharide (PG-APS) developed an acute course of arthritis. Recurrence of arthritis was induced in 100% of these joints by intravenous injection of as little as 10 micrograms of Salmonella typhimurium lipopolysaccharide (LPS) 3 wk after intraarticular injection. This reaction was similar in athymic and euthymic rats. Buffalo rats were less susceptible than Lewis or Sprague-Dawley rats. Neisseria gonorrhoeae, Yersinia enterocolitica, and Escherichia coli LPS, and S. typhimurium Re mutant LPS, were also active. Re mutant LPS activity was greatly reduced by mixing with polymyxin B. E. coli lipid A was weakly active. An acute synovitis of much less incidence, severity, and duration was seen in contralateral joints injected initially with saline, and in ankle joints of naive, previously uninjected rats after intravenous LPS injection. The intravenous injection of the muramidase mutanolysin on day 0 or 7 after intraarticular PG-APS injection prevented LPS-induced recurrence of arthritis. These studies suggest that the phlogistic activities of lipid A and peptidoglycan might interact in an inflammatory disease process, and that LPS may play a role in recurrent episodes of rheumatoid arthritis or reactive arthritis.

Effect of acetylation on arthropathic activity of group A streptococcal peptidoglycan-polysaccharide fragments

Purified group A streptococcal peptidoglycan-polysaccharide (PG-PS) fragments were either de-O-acylated, or acetylated and then de-O-acylated to yield N-acetylated PG-PS. Native PG-PS was poorly degraded, N-acetylated PG-PS was extensively degraded, and de-O-acylated PG-PS was only slightly degraded by hen egg white lysozyme. N-acetylated PG-PS was also extensively degraded by human lysozyme and partially degraded by rat serum or rat liver extract. After a single intraperitoneal injection of rats with a sterile, aqueous suspension, all PG-PS preparations induced acute arthritis. The acute arthritis induced by N-acetylated PG-PS was significantly more severe than that induced by native PG-PS; that induced by de-O-acylated PG-PS was of intermediate severity. After the acute reaction, rats injected with native PG-PS developed chronic relapsing erosive synovitis which remained severe for the duration of the experiment (83 days). In contrast, joint inflammation induced by N-acetylated PG-PS resolved within 6 weeks with little evidence of recurrent disease. Chronic arthritis induced by de-O-acylated PG-PS was of intermediate severity. In another assay of arthropathic activity, the arthritis in all rat ankle joints, which had been injected directly with native PG-PS, could be reactivated 3 weeks later by the intravenous injection of a small dose of PG. In contrast, only 50% of the joints initially injected with de-O-acylated PG-PS and none of the joints injected with N-acetylated PG-PS could be reactivated. These studies support the concepts that the resistance of PG-PS to muralytic digestion is crucial for chronic arthropathic activity and that the nature and degree of PG acetylation are important molecular determinants of the phlogistic activities of PG-PS polymers.

Comparison of in vivo degradation of 125I-labeled peptidoglycan-polysaccharide fragments from group A and group D streptococci

The in vivo degradation and persistence of 125I-labeled peptidoglycan-polysaccharide (PG-PS) fragments from the cell walls of group A and D streptococci were compared by group after intraperitoneal injection into rats. The quantity of PG-PS in the livers and spleens of group D PG-PS-injected rats was less than the quantity in rats injected with group A PG-PS throughout the course of the experiment. Gel filtration analyses of liver and spleen homogenates indicated that group A PG-PS was relatively resistant to degradation, whereas group D PG-PS was extensively degraded to yield a heterogeneous mixture of fragments of lower molecular weight. There was no significant difference in the content of group A PG-PS versus that of group D in joints or blood samples. Analysis of fragment sizes in these tissues also indicated more extensive degradation of group D PG-PS. However, the majority of group A PG-PS in blood samples and joints was a lower molecular weight than that found in the livers or spleens. We conclude that group A PG-PS undergoes a significant but low level of degradation and that group D PG-PS is much less persistent and more extensively degraded than group A PG-PS is in vivo. These differences in PG-PS catabolism may account, in part, for the capacity of group A PG-PS to induce chronic, recurrent arthritis of longer duration than that induced by group D PG-PS.

Comparison of inflammatory reactions induced by intraarticular injection of bacterial cell wall polymers

Cell wall polymers isolated from group A streptococci, as well as lipopolysaccharide from Salmonella typhimurium and synthetic muramyl dipeptide, were injected into the ankle joints of rats. The inflammatory responses were assessed by gross and histologic examination, and edema was measured by accumulation of radiolabeled albumin in the limbs. The isolated group-specific polysaccharide induced extensive edema of the articular and periarticular tissue immediately after injection, and this resolved in 24 hours. The peptidoglycan moiety did not produce early edema, but induced an acute exudative reaction followed by a proliferative synovitis which resolved after 5 days. Reactions induced by covalently bound complexes of peptidoglycan and the group-specific polysaccharide (PG-APS) varied, depending on the size of the complex. Small fragments, derived from mutanolysin digestion, caused both an acute edematous reaction and transient arthritis. Larger fragments did not cause the immediate edematous reaction, but induced an acute arthritis that appeared within 24 hours and evolved into a chronic process. Episodes of recurrent inflammation, a distinctive feature of joint inflammation induced by systemic injection of PG-APS polymers, were not observed following intraarticular injection of any of the cell wall polymers. The relative susceptibility of different rat strains to arthritis induced by intraarticular injection paralleled the responses to systemic injection of PG-APS. These results demonstrate that variations in arthropathogenicity are due, in part, to inherent differences in the phlogistic activities of different cell wall polymers, and that the genetic control of susceptibility involves regulation of the inflammatory responses rather than the quantity of cell wall distributed to the joint.

Arthropathic properties of cell wall polymers from normal flora bacteria

Peptidoglycan-polysaccharide (PG-PS) fragments were purified from cell walls of group D streptococci (Streptococcus faecium, strains ATCC 9790 and F-24) with a protocol which minimizes autolytic activity and tested for ability to induce arthritis in rats. PG-PS fragments from cell walls of other normal flora bacteria (Peptostreptococcus productus, and Propionibacterium acnes), group A streptococci, and pseudomurein-PS fragments from cell walls of Methanobacterium formicicum, were similarly purified and tested. Upon intraarticular injection into rat ankles, all PG-PS polymers induced acute inflammation; pseudomurein-PS fragments were approximately five times less active than the PG-PS preparations. After intraperitoneal injection, P. acnes PG-PS induced a minimal acute arthritis, Peptostreptococcus productus PG-PS induced a moderately severe acute joint inflammation followed by a mild chronic arthritis, and both group A and group D streptococcal PG-PS induced severe acute arthritis which evolved into chronic, erosive joint disease; pseudomurein-PS fragments were without effect, consistent with a crucial role for the PG moiety of PG-PS. Chronic arthritis induced by group D streptococcal PG-PS subsided after 60 days, whereas that induced by group A streptococcal PG-PS was still active after 128 days. The arthropathic properties of this modest number of common normal flora bacteria suggest that different PG-PS structures derived from the normal flora have the potential to induce a wide range of responses, from transient acute to chronic erosive joint disease.

Reactivation of streptococcal cell wall-induced arthritis by homologous and heterologous cell wall polymers

Joint inflammation initially induced by intraarticular injection of an aqueous suspension of peptidoglycan-polysaccharide (PG-PS) fragments isolated from Streptococcus pyogenes was reactivated by systemic injection of a normally subarthropathic dose of homologous or heterologous cell wall polymers, including muramyl dipeptide and lipopolysaccharide. Reactivation was not correlated with the severity of the initial inflammatory reaction. Results of studies utilizing 125I-labeled PG-PS fragments suggested that reactivation was associated with increased localization of PG-PS fragments in the joint following reinjection. These results indicate that the initial injury of the joint by S pyogenes PG-PS fragments increases the susceptibility of the joint to subsequent injury. Furthermore, once the inflammatory reaction is initiated, it can be perpetuated by a variety of ubiquitous cell wall polymers derived from normal flora as well as from pathogenic bacteria.