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

Bioinformatic and literature assessment of toxicity and allergenicity of a CRISPR-Cas9 engineered gene drive to control Anopheles gambiae the mosquito vector of human malaria

BACKGROUND

Population suppression gene drive is currently being evaluated, including via environmental risk assessment (ERA), for malaria vector control. One such gene drive involves the dsxFCRISPRh transgene encoding (i) hCas9 endonuclease, (ii) T1 guide RNA (gRNA) targeting the doublesex locus, and (iii) DsRed fluorescent marker protein, in genetically-modified mosquitoes (GMMs). Problem formulation, the first stage of ERA, for environmental releases of dsxFCRISPRh previously identified nine potential harms to the environment or health that could occur, should expressed products of the transgene cause allergenicity or toxicity.

METHODS

Amino acid sequences of hCas9 and DsRed were interrogated against those of toxins or allergens from NCBI, UniProt, COMPARE and AllergenOnline bioinformatic databases and the gRNA was compared with microRNAs from the miRBase database for potential impacts on gene expression associated with toxicity or allergenicity. PubMed was also searched for any evidence of toxicity or allergenicity of Cas9 or DsRed, or of the donor organisms from which these products were originally derived.

RESULTS

While Cas9 nuclease activity can be toxic to some cell types in vitro and hCas9 was found to share homology with the prokaryotic toxin VapC, there was no evidence from previous studies of a risk of toxicity to humans and other animals from hCas9. Although hCas9 did contain an 8-mer epitope found in the latex allergen Hev b 9, the full amino acid sequence of hCas9 was not homologous to any known allergens. Combined with a lack of evidence in the literature of Cas9 allergenicity, this indicated negligible risk to humans of allergenicity from hCas9. No matches were found between the gRNA and microRNAs from either Anopheles or humans. Moreover, potential exposure to dsxFCRISPRh transgenic proteins from environmental releases was assessed as negligible.

CONCLUSIONS

Bioinformatic and literature assessments found no convincing evidence to suggest that transgenic products expressed from dsxFCRISPRh were allergens or toxins, indicating that environmental releases of this population suppression gene drive for malaria vector control should not result in any increased allergenicity or toxicity in humans or animals. These results should also inform evaluations of other GMMs being developed for vector control and in vivo clinical applications of CRISPR-Cas9.

Intra-articular injection of triamcinolone acetonide releasing biomaterial microspheres inhibits pain and inflammation in an acute arthritis model

Inflammation of the synovium and joint capsule is a main driver of pain in an osteoarthritic (OA) joint. Triamcinolone acetonide (TAA) is a classical corticosteroid that reduces synovitis and alleviates pain, albeit transiently. Biomaterial-based local TAA release may prolong the suppression of pain without the need for multiple injections. Polylactic-co-glycolic acid (PLGA) formulations of TAA prolong OA pain relief to a limited extent. A novel polyesteramide (PEA) microsphere platform allows for extended release in the OA joint for over 3 months. To evaluate their effect on pain and inflammation, TAA-loaded microspheres were intra-articularly delivered to the knee joint in a rat model of acute arthritis induced by intra-articular injection of streptococcal cell wall peptidoglycan-polysaccharide (PGPS) and subsequent flare-ups by intravenous PGPS injections. PEA-loaded microspheres were benchmarked with TAA-loaded PLGA microspheres and bolus TAA injection. TAA treatments were injected intra-articularly before the first induced flare-up. TAA-loaded PEA and PLGA microspheres reduced joint swelling and signs of pain-like behavior over the entire study period, as assessed by weight bearing and referred mechanical hypersensitivity, whereas bolus suspension was effective for a shorter time period. TAA-loaded PEA microspheres reduced lameness to a greater extent than TAA-loaded PLGA microspheres. In conclusion, a single intra-articular injection of TAA-loaded PEA microspheres reduced joint swelling and induced longer pain relief compared to bolus injection. Hence relief of inflammation and pain by PEA-based delivery of TAA may prove to be effective and durable.

Gut microbiota in children and altered profiles in juvenile idiopathic arthritis

Microbial diversity plays a key role in the maintenance of intestinal homeostasis and in the development of the immune system in the gut mucosa. Maybe one of the most important function of our gut microbiota is the immune system education, in particular the discrimination of friends from foes that occurs during childhood. In addition to bacterial antigens, several metabolites of microbial origin have a crucial role in training of the immune system, such as Short Chain Fatty Acids (SCFAs). There are many evidences on the role of the gut microbiota in rheumatic diseases, in particular modifications of microbiota composition causing dysbiosis that, in turn, can induce gut permeability, and thus immunological imbalance and trigger inflammation. In particular, immune cells can reach extra-intestinal sites, such as joints and trigger local inflammation. Childhood is a crucial period of life for development and evolution of the gut microbiota, especially for the acquisition of fundamental functions such as immunotolerance of commensal microorganisms. For this reason, gut dysbiosis is gaining interest as a potential pathogenetic factor for Juvenile Idiopathic Arthritis (JIA). Here we summarized the studies conducted on JIA patients in which a pro-arthritogenic microbial profiles has been observed; this, together with a depletion of microbial biodiversity, clearly distinguish patients' from healthy subjects' microbiota. Further studies are however needed to better clarify the role of microbiota in JIA pathogenesis.

Animal Models of Bone Loss in Inflammatory Arthritis: from Cytokines in the Bench to Novel Treatments for Bone Loss in the Bedside-a Comprehensive Review

Throughout life, bone is continuously remodelled. Bone is formed by osteoblasts, from mesenchymal origin, while osteoclasts induce bone resorption. This process is tightly regulated. During inflammation, several growth factors and cytokines are increased inducing osteoclast differentiation and activation, and chronic inflammation is a condition that initiates systemic bone loss. Rheumatoid arthritis (RA) is a chronic inflammatory auto-immune disease that is characterised by active synovitis and is associated with early peri-articular bone loss. Peri-articular bone loss precedes focal bone erosions, which may progress to bone destruction and disability. The incidence of generalised osteoporosis is associated with the severity of arthritis in RA and increased osteoporotic vertebral and hip fracture risk. In this review, we will give an overview of different animal models of inflammatory arthritis related to RA with focus on bone erosion and involvement of pro-inflammatory cytokines. In addition, a humanised endochondral ossification model will be discussed, which can be used in a translational approach to answer osteoimmunological questions.

Old and new therapeutics for Rheumatoid Arthritis: in vivo models and drug development

Development of novel drugs for treatment of chronic inflammatory diseases is to a large extent dependent on the availability of good experimental in vivo models in order to perform preclinical tests of new drugs and for the identification of novel drug targets. Here, we review a number of existing rodent models for Rheumatoid Arthritis in the context of how these models have been utilized for developing established therapy in Rheumatoid Arthritis and, furthermore, the present use of animal models for studies of novel drug candidates. We have studied the literature in the field for the use of in vivo models during development of anti-rheumatic drugs; from Methotrexate to various antibody treatments, to novel drugs that are, or have recently been, in clinical trials. For novel drugs, we have explored websites for clinical trials. Although a single Rheumatoid Arthritis in vivo model cannot mirror the complexity of disease development, there exist a number of good animal models for Rheumatoid Arthritis, each defining some parts in disease development, which are useful for studies of drug response. We find that many of the established drugs were not tested in in vivo models before being used in the clinic, but rather animal models have been subsequently used to find mechanisms for efficacy. Finally, we report a number of novel drugs, tested in preclinical in vivo models, presently in clinical trials.

Intra-articular (IA) ropivacaine microparticle suspensions reduce pain, inflammation, cytokine, and substance p levels significantly more than oral or IA celecoxib in a rat model of arthritis

Current therapeutic treatment options for osteoarthritis entail significant safety concerns. A novel ropivacaine crystalline microsuspension for bolus intra-articular (IA) delivery was thus developed and studied in a peptidoglycan polysaccharide (PGPS)-induced ankle swelling rat model. Compared with celecoxib controls, both oral and IA, ropivacaine IA treatment resulted in a significant reduction of pain upon successive PGPS reactivation, as demonstrated in two different pain models, gait analysis and incapacitance testing. The reduction in pain was attended by a significant reduction in histological inflammation, which in turn was accompanied by significant reductions in the cytokines IL-18 and IL-1β. This may have been due to inhibition of substance P, which was also significantly reduced. Pharmacokinetic analysis indicated that the analgesic effects outlasted measurable ropivacaine levels in either blood or tissue. The results are discussed in the context of pharmacologic mechanisms both of local anesthetics as well as inflammatory arthritis.

Otitis media induced by peptidoglycan-polysaccharide (PGPS) in TLR2-deficient (Tlr2(-/-)) mice for developing drug therapy

BACKGROUND

Toll like receptor 2 (TLR2) signaling can regulate the pathogenesis of otitis media (OM). However, the precise role of TLR2 signaling in OM has not been clarified due to the lack of an optimal animal model. Peptidoglycan-polysaccharide (PGPS) of the bacterial cell wall can induce inflammation by activating the TLR2 signaling. This study aimed at examining the pathogenic characteristics of OM induced by PGPS in Tlr2(-/-) mice, and the potential therapeutic effect of sodium aescinate (SA) in this model.

METHODS

Wild-type (WT) and Tlr2(-/-) mice were inoculated with streptococcal PGPS into their middle ears (MEs) and treated intravenously with vehicle or SA daily beginning at 3days prior to PGPS for 6 consecutive days. The pathologic changes of individual mice were evaluated longitudinally.

RESULTS

In comparison with WT mice, Tlr2(-/-) mice were susceptible to PGPS-induced OM. Tlr2(-/-) mice displayed greater hearing loss, tympanic membrane damage, ME mucosal thickening, longer inflammation state, cilia and goblet cell loss. SA-treatment decreased neutrophil infiltration, modulated TLR2-related gene expression and improved ciliary organization.

CONCLUSIONS

PGPS induced a relatively stable OM in Tlr2(-/-) mice, providing a new model for OM research. Treatment with SA mitigated the pathogenic damage in the ME and may be valuable for intervention of OM.

Sustained efficacy of a single intra-articular dose of FX006 in a rat model of repeated localized knee arthritis

OBJECTIVE

To evaluate the efficacy of a single intra-articular (IA) dose of FX006, an extended-release formulation of triamcinolone acetonide (TCA) in poly(lactic-co-glycolic acid) (PLGA) microspheres, on the sequelae of repeated episodes of synovitis.

DESIGN

Three flares of localized synovitis in the right knee of rats were induced over 4 weeks following a single IA injection of various doses of FX006, Kenalog(®) (TCA immediate release or TCA IR), or vehicle. Gait scores were employed to assess analgesic effect, and the joints were evaluated by histology at the end of the study. TCA plasma concentrations and corticosterone levels were monitored through the study.

RESULTS

A single IA dose of 0.28 mg FX006 significantly improved gait scores through all three reactivations. TCA IR at 0.06 mg (providing comparable plasma TCA exposure, 10-fold higher Cmax) demonstrated comparable benefit through the first reactivation only and reduced-to-no efficacy thereafter. Significantly improved histological joint scores were observed with effective doses of FX006 but not with TCA IR. Corticosterone levels were initially decreased following both TCA IR and FX006 treatment, but recovered by Day 14.

CONCLUSIONS

In localized, repeated synovitis in rats, sustained release of TCA following a single IA injection of FX006 significantly prolonged analgesia relative to TCA IR and significantly improved histological scores with no adverse effect on the HPA axis. Since synovitis can contribute to the pathophysiology of multiple joint diseases such as osteoarthritis (OA), RA and gout, FX006 may be an important treatment option for these conditions.

Etanercept ameliorates inflammation and pain in a novel mono-arthritic multi-flare model of streptococcal cell wall induced arthritis

Background

The impact of anti-TNF, corticosteroid and analgesic therapy on inflammation and pain was evaluated in a novel mono-arthritic multi-flare rat Streptococcal Cell Wall (SCW) model using Etanercept, Dexamethasone and Buprenorphine.

Methods

Multiple flares of arthritis were induced with an intra-articular injection of SCW in the hind ankle on day 1, followed by intravenous challenges on days 21 and 42. Inflammation and pain were monitored in the hind paws. Cytokine profiling, cell phenotyping, bioluminescence imaging and histopathological evaluation were also performed.

Results

Local injection of SCW caused a rapid onset of inflammation and pain in the injected ankle which resolved within 4 days (Flare 1). Intravenous injection 20 days after sensitization resulted in an increase in ankle diameter and pain, which partially resolved in 8 days (Flare 2). The subsequent intra-venous injection in the same animals 14 days after resulted in a more chronic disease with inflammation and pain persisting over a period of 10 days (Flare 3). In Flare 2, therapeutic administration of Dexamethasone inhibited paw swelling (95%; P<0.001) and pain (55%; P<0.05). Therapeutic administration of Buprenorphine inhibited pain (80%; P<0.001) without affecting paw swelling (0%). Prophylactic administration of Etanercept in Flare 2 inhibited paw swelling (≥60%; P<0.001) and pain by ≥30%. Expression of IL-1β, IL-6, MCP-1 and CINC was reduced by >50% (P<0.001). Treatment with Etanercept in Flare 3 inhibited paw swelling by 60% (P<0.001) and pain by 25%. Prior treatment with Etanercept in Flare 2 followed by re-administration in Flare 3 led to a complete loss in the efficacy of Etanercept. Systemic exposure of Etanercept corroborated with lack of efficacy. Dexamethasone inhibited inflammation and pain in both Flares 2 and 3 (P<0.001).

Conclusions

We established a novel multi-flare SCW arthritis model enabling drug intervention in different stages of disease. We show for the first time the evaluation of inflammation and pain simultaneously in this model. Etanercept and Dexamethasone inhibited inflammation, pain and proinflammatory cytokines in this model. Taken together, this model facilitates the assessment of anti-rheumatic agents targeting inflammation and pain in the multiple flare paradigm and offers a powerful tool for drug discovery.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-409) contains supplementary material, which is available to authorized users.

Structural variation in the glycan strands of bacterial peptidoglycan

The normal, unmodified glycan strands of bacterial peptidoglycan consist of alternating residues of beta-1,4-linked N-acetylmuramic acid and N-acetylglucosamine. In many species the glycan strands become modified after their insertion into the cell wall. This review describes the structure of secondary modifications and of attachment sites of surface polymers in the glycan strands of peptidoglycan. It also provides an overview of the occurrence of these modifications in various bacterial species. Recently, enzymes responsible for the N-deacetylation, N-glycolylation and O-acetylation of the glycan strands were identified. The presence of these modifications affects the hydrolysis of peptidoglycan and its enlargement during cell growth. Glycan strands are frequently deacetylated and/or O-acetylated in pathogenic species. These alterations affect the recognition of bacteria by host factors, and contribute to the resistance of bacteria to host defence factors such as lysozyme.

Long-term suppression of experimental arthritis following intramuscular administration of a pseudotyped AAV2/1-TNFR:Fc Vector

We previously reported that administration of an adeno-associated virus 2 (AAV2) vector encoding a rat tumor necrosis factor (TNF) receptor-immunoglobulin Fc (TNFR:Fc) fusion gene to rats with streptococcal cell wall-induced arthritis resulted in suppression of joint inflammation and cartilage and bone destruction, as well as expression of joint proinflammatory cytokines. In this study, we used an alternate rat model of arthritis to compare the serum levels and duration of TNFR:Fc protein expression following intramuscular administration of pseudotyped AAV-TNFR:Fc vectors based on serotypes 1, 2, and 5. All three pseudotyped AAV-TNFR:Fc vectors led to sustained expression of serum TNFR:Fc protein for at least one year. Serum TNFR:Fc protein levels in rats administered intramuscularly with AAV2/1-TNFR:Fc vector were up to 100- and 10-fold higher than in rats administered the AAV2-TNFR:Fc or AAV2/5-TNFR:Fc vectors, respectively. A single intramuscular administration of AAV2/1-TNFR:Fc vector at vector doses ranging from 10(10) to 10(12) DNase-resistant particles (DRP) per animal, resulted in complete and long-term suppression of recurrent joint inflammation for at least 150 days. Our results establish a proof of concept for administration of an AAV2/1-TNFR:Fc vector to the muscle to achieve long-term, sustained and therapeutically relevant levels of TNFR:Fc protein to treat chronic systemic inflammatory joint diseases.

Automatic quantification of changes in bone in serial MR images of joints

Recent innovations in drug therapies have made it highly desirable to obtain sensitive biomarkers of disease progression that can be used to quantify the performance of candidate disease modifying drugs. In order to measure potential image-based biomarkers of disease progression in an experimental model of rheumatoid arthritis (RA), we present two different methods to automatically quantify changes in a bone in in-vivo serial magnetic resonance (MR) images from the model. Both methods are based on rigid and nonrigid image registration to perform the analysis. The first method uses segmentation propagation to delineate a bone from the serial MR images giving a global measure of temporal changes in bone volume. The second method uses rigid body registration to determine intensity change within a bone, and then maps these into a reference coordinate system using nonrigid registration. This gives a local measure of temporal changes in bone lesion volume. We detected significant temporal changes in local bone lesion volume in five out of eight identified candidate bone lesion regions, and significant difference in local bone lesion volume between male and female subjects in three out of eight candidate bone lesion regions. But the global bone volume was found to be fluctuating over time. Finally, we compare our findings with histology of the subjects and the manual segmentation of bone lesions.

Arthritis imaging using a near-infrared fluorescence folate-targeted probe

A recently developed near-infrared fluorescence-labeled folate probe (NIR2-folate) was tested for in vivo imaging of arthritis using a lipopolysaccharide intra-articular injection model and a KRN transgenic mice serum induction mouse model. In the lipopolysaccharide injection model, the fluorescence signal intensity of NIR2-folate (n = 12) and of free NIR2 (n = 5) was compared between lipopolysaccharide-treated and control joints. The fluorescence signal intensity of the NIR2-folate probe at the inflammatory joints was found to be significantly higher than the control normal joints (up to 2.3-fold, P < 0.001). The NIR2-free dye injection group showed a persistent lower enhancement ratio than the NIR2-folate probe injection group. Excessive folic acid was also given to demonstrate a competitive effect with the NIR2-folate. In the KRN serum transfer model (n = 4), NIR2-folate was applied at different time points after serum transfer, and the inflamed joints could be detected as early as 30 hours after arthritogenic antibody transfer (1.8-fold increase in signal intensity). Fluorescence microscopy, histology, and immunohistochemistry validated the optical imaging results. We conclude that in vivo arthritis detection was feasible using a folate-targeted near-infrared fluorescence probe. This receptor-targeted imaging method may facilitate improved arthritis diagnosis and early assessment of the disease progress by providing an in vivo characterization of active macrophage status in inflammatory joint diseases.

Gene expression profiles in the rat streptococcal cell wall-induced arthritis model identified using microarray analysis

Experimental arthritis models are considered valuable tools for delineating mechanisms of inflammation and autoimmune phenomena. Use of microarray-based methods represents a new and challenging approach that allows molecular dissection of complex autoimmune diseases such as arthritis. In order to characterize the temporal gene expression profile in joints from the reactivation model of streptococcal cell wall (SCW)-induced arthritis in Lewis (LEW/N) rats, total RNA was extracted from ankle joints from naïve, SCW injected, or phosphate buffered saline injected animals (time course study) and gene expression was analyzed using Affymetrix oligonucleotide microarray technology (RAE230A). After normalization and statistical analysis of data, 631 differentially expressed genes were sorted into clusters based on their levels and kinetics of expression using Spotfire^® profile search and K-mean cluster analysis. Microarray-based data for a subset of genes were validated using real-time PCR TaqMan^® analysis. Analysis of the microarray data identified 631 genes (441 upregulated and 190 downregulated) that were differentially expressed (Delta > 1.8, P < 0.01), showing specific levels and patterns of gene expression. The genes exhibiting the highest fold increase in expression on days -13.8, -13, or 3 were involved in chemotaxis, inflammatory response, cell adhesion and extracellular matrix remodelling. Transcriptome analysis identified 10 upregulated genes (Delta > 5), which have not previously been associated with arthritis pathology and are located in genomic regions associated with autoimmune disease. The majority of the downregulated genes were associated with metabolism, transport and regulation of muscle development. In conclusion, the present study describes the temporal expression of multiple disease-associated genes with potential pathophysiological roles in the reactivation model of SCW-induced arthritis in Lewis (LEW/N) rat. These findings improve our understanding of the molecular events that underlie the pathology in this animal model, which is potentially a valuable comparator to human rheumatoid arthritis (RA).

Joint cytokine quantification in two rodent arthritis models: kinetics of expression, correlation of mRNA and protein levels and response to prednisolone treatment

Biomarker quantification in disease tissues from animal models of rheumatoid arthritis (RA) can help to provide insights into the mechanisms of action of novel therapeutic agents. In this study we validated the kinetics of IL-1beta, TNF-alpha and IL-6 mRNA and protein expression levels in joints from DBA/1OlaHsd murine collagen-induced arthritis (CIA) and Lewis rat Streptococcal cell wall (SCW)-induced arthritis by real-time polymerase chain reaction (PCR) TaqMan and Enzyme-linked immunosorbent assay (ELISA). Prednisolone was used as a reference to investigate any correlation between clinical response and cytokine levels at selected time-points. To our knowledge this is the first report showing a close pattern of expression between mRNA and protein for IL-1beta and IL-6, but not for TNF-alpha, in these two models of RA. The kinetics of expression for these biomarkers suggested that the optimal sampling time-points to study the effect of compounds on both inflammation and cytokine levels were day 4 postonset in CIA and day 3 after i.v challenge in SCW-induced arthritis. Prednisolone reduced joint swelling through a mechanism associated with a reduction in IL-1beta and IL-6 protein and mRNA expression levels. At the investigated time points, protein levels for TNF-alpha in arthritic joints were lower than the lower limit of detection of the ELISA, whereas mRNA levels for this cytokine were reliably detected. These observations suggest that RT-PCR TaqMan is a sensitive technique that can be successfully applied to the quantification of mRNA levels in rodent joints from experimental arthritis models providing insights into mechanisms of action of novel anti-inflammatory drugs.

PEGylated recombinant human soluble tumour necrosis factor receptor type I (r-Hu-sTNF-RI): novel high affinity TNF receptor designed for chronic inflammatory diseases

The proinflammatory cytokine, tumour necrosis factor alpha (TNFalpha) has been shown to play a pivotal part in mediating acute and chronic inflammation. The activities of TNFalpha are modulated by the proteolytic shedding of the soluble extracellular domains of the two TNF receptors, p55 sTNF-RI and p75 sTNF-RII. Amgen Inc has cloned and expressed a recombinant form of a natural inhibitor of TNFalpha, referred to as recombinant human soluble TNF receptor type I (r-Hu-sTNF-RI, sTNF-RI). sTNF-RI is an E coli recombinant, monomeric form of the soluble TNF-type I receptor. A high molecular weight polyethylene glycol (PEG) molecule is attached at the N-terminus position to form the molecule intended for clinical evaluations (PEG sTNF-RI). Preclinical studies to date demonstrate that PEG sTNF-RI is efficacious in rodent models of chronic inflammatory disease including rheumatoid arthritis and Crohn's disease at doses as low as 0.3 mg/kg given every other day. This dose results in plasma concentrations of 0.3 to 0.5 microg/ml. Higher doses with correspondingly higher plasma concentrations yield higher efficacy. It has also demonstrated efficacy in E coli lipopolysaccharide, and Staphylococcus enterotoxin B mediated models of acute inflammation in rodents and primates. Pharmacokinetic studies in mice, rats, cynomolgus monkeys, baboons, and chimpanzees have been conducted with PEG sTNF-RI. Absorption from a subcutaneous dose was slow, with the time to reach maximal plasma concentrations of 24-48 hours in rats, and in monkeys, and 3-29 hours in chimpanzees. The initial volume of distribution of PEG sTNF-RI was essentially equivalent to that of plasma (40 ml/kg). This suggests the protein does not appear to extensively distribute from the systemic circulation with a volume of distribution at steady state (Vss) less than 200 ml/kg in all species studied. These results are consistent with previous experience with PEGylated proteins in which PEGylation decreases both the rate of absorption and the plasma clearance of human recombinant proteins in animals and humans. The use of a PEG molecule will probably provide a more advantageous dosing schedule (that is, less frequent dosing) for the patient compared with a non-PEG sTNF-RI.

Systemic reactivation of otitis media with effusion in a rat model

OBJECTIVE

This study addresses the interaction of bacterial antigens, specifically peptidoglycan-polysaccharide (PG-PS) and lipopolysaccharide (LPS), in the induction and reactivation of mucoid middle ear effusions.

METHODS

Twenty-seven rats underwent eustachian tube obstruction before inoculation of the middle ear bulla with PG-PS. Three weeks later, after resolution of all middle ear effusions, 6 rats were randomly selected and euthanized as the first control group (control I). The remaining 21 animals were randomly assigned to 3 groups that received intravenous injections of Krebs Ringer (control II), PG-PS, and LPS, respectively. These rats were euthanized 2 days after intravenous injection. Middle ear mucin production and histologic changes were measured in all animals.

RESULTS

The mean concentrations of mucin were 0.94 +/- 0.52 mg/mL, 0.41 +/- 0.87 mg/mL, 16.33 +/- 3.67 mg/mL, and 1.15 +/- 0.41 mg/mL in the control I, control II, PG-PS, and LPS groups, respectively. Thus the mean concentration of mucin in the middle ear lavage samples was significantly greater in rats that were injected intravenously with PG-PS than in rats in other groups (P < 0.05). Histologic analyses demonstrated a greater degree of goblet cell hyperplasia in the PG-PS group than in other groups.

CONCLUSIONS

This is the first animal model of recurring otitis media with effusion in which a systemic injection of PG-PS was used to reactivate a middle ear effusion in rats previously primed with a transtympanic injection of PG-PS. This study suggests that after otitis media with effusion has resolved, it may be reactivated by the presence of bacterial antigens and/or cytokines in the systemic circulation.

Disease-inducible transgene expression from a recombinant adeno-associated virus vector in a rat arthritis model

Rheumatoid arthritis (RA) is a systemic autoimmune disease affecting 1% of the world's population, with significant morbidity and mortality. In this study, we investigated a recombinant adeno-associated virus (rAAV) vector for its potential application in RA gene therapy. rAAV encoding Escherichia coli beta-galactosidase was injected into rat joints which had already been induced into acute arthritis after local lipopolysaccharide (LPS) administration, and the efficiency of in vivo transduction was evaluated. We observed a striking correlation between vector transgene expression and disease severity in arthritic joints. The inflammatory reaction peaked at 3 to 7 days after LPS treatment, and, at the same time, 95% of the synoviocytes had high-level transgene expression. Gene expression diminished to the basal level (5%) when the inflammation subsided at 30 days after LPS treatment. More importantly, the diminished transgene expression could be efficiently reactivated by a repeated insult. The transgene expression in normal joints transduced with rAAV remained low for a long period of time (30 days) but could still be induced to high levels (95%) at 3 to 7 days after LPS treatment. This is the first demonstration of disease state-regulated transgene expression. These findings strongly support the feasibility of therapeutic as well as preventative gene transfer approaches for RA with rAAV vectors containing therapeutic genes, which are expected to respond primarily to the disease state of the target tissue.

Orally active indole N-oxide PDE4 inhibitors

This communication describes the synthesis and in vitro and in vivo evaluation of a novel potent series of phosphodiesterase type (IV) (PDE4) inhibitors. Several of the compounds presented possess low nanomolar IC50's for PDE4 inhibition and excellent in vivo activity for inhibition of TNF-alpha levels in LPS challenged mice (mouse endotoxemia model). Emesis studies (dog) and efficacy in a SCW arthritis model for the most potent PDE4 inhibitors are presented.

2-Substituted-4-methoxybenzimidazole-based PDE4 inhibitors

A new family of PDE4 inhibitors based on a benzimidazole framework is described. Several of these compounds are orally bioavailable and show efficacy in in vivo models of inflammatory disease.

Interleukin-1 receptor antagonist suppresses experimental autoimmune encephalomyelitis (EAE) in rats by influencing the activation and proliferation of encephalitogenic cells

Considering the role of pleiotropic interleukin-1 (IL-1) in inflammation and autoimmunity, studies were designed to examine whether specific blockade of IL-1 may influence these processes in the CNS. Although the role of CD4+ T cells in eliciting clinical signs of experimental autoimmune encephalomyelitis (EAE) has been unequivocally demonstrated, the exact mechanism by which encephalitogenic cells initiate disease process and bring about clinical signs still remains to be defined. We have evaluated the effect of human recombinant interleukin-1 receptor antagonist (IL-1Ra) in vivo on the course of actively induced EAE in highly susceptible Dark Agouti (DA) rats. The rats which were treated during the induction phase of disease (days 0-6) with IL-1Ra (350 microg/rat/day) developed milder signs of EAE, when compared to saline-treated control animals immunized with encephalitogen, which developed severe single episode disease. The transfer of lymph node cells (LNC) isolated from MBP-primed DA rats and stimulated in vitro with MBP and ConA to naive syngeneic animals resulted in the development of EAE in all recipients. However, rats injected with LNC that have been stimulated in vitro in the presence of IL-1Ra (10 microg/ml) developed significantly milder disease. Diminished encephalitogenic capacity of LNC correlated with lower proliferative response to antigen and mitogen and decreased expression of IL-2 receptors. These data provide further evidence that IL-1 is an important factor for activation of EAE inducing T lymphocytes.

Streptococcal Cell Wall-Induced Arthritis: Requirements for IL-4, IL-10, IFN-γ, and Monocyte Chemoattractant Protein-1

Intra-articular injection of streptococcal cell wall Ag followed by i.v. challenge (“reactivation”) results in a destructive lymphocyte-dependent monoarticular arthritis. To further define the role of immune mechanisms in the model, Abs to Th1 and Th2-related cytokines were evaluated. Treatment of rats with antibodies to IL-4 reduced swelling, while treatment with anti-IL-10 or anti-IFN-γ either had no effect or slightly enhanced the inflammatory response. These results suggest that Th-2 immune mechanisms may be, at least in part, operative in the model. To more precisely define the role of IL-4, the effects of anti-IL-4 on monocyte chemoattractant protein-1 (MCP-1) expression were evaluated. Initial studies demonstrated that mRNA (as determined by in situ hybridization) and protein (as determined by immunofluorescence) for MCP-1 were detectable in inflamed synovial tissue in a time-dependent manner. Anti-IL-4 treatment significantly reduced the expression of mRNA for MCP-1 24 and 72 h after reactivation. In addition, anti-MCP-1 inhibited swelling and reduced influx of 111In-labeled T cells. These data suggest that the reactivation model of streptococcal cell wall Ag-induced arthritis is Th-2 dependent, and that an inter-relationship exists between IL-4 and the expression of MCP-1.

Review article: Role of the enteric microflora in the pathogenesis of intestinal inflammation and arthritis

Strong associations exist between intestinal inflammation and arthritis, ranging from infections with enteric pathogens to idiopathic inflammatory bowel disease. Increased exposure of the lamina propia and systemic circulation to enteric microflora and their products are a result of increased proliferation of the luminal bacteria, pathogenic invasion or enhanced mucosal permeability. Data suggest that anaerobic bacteria and other constituents of the normal luminal microbial flora induce and sustain chronic intestinal inflammation and arthritis. However, the normal host develops a tolerance to such bacteria and maintains homeostasis through a controlled inflammatory response and an almost impermeable mucosal barrier.

Normal luminal bacteria, especially Bacteroides species, mediate chronic colitis, gastritis, and arthritis in HLA-B27/human beta2 microglobulin transgenic rats

Genetic and environmental factors are important in the pathogenesis of clinical and experimental chronic intestinal inflammation. We investigated the influence of normal luminal bacteria and several groups of selected bacterial strains on spontaneous gastrointestinal and systemic inflammation in HLA-B27 transgenic rats. Rats maintained germfree for 3-9 mo were compared with littermates conventionalized with specific pathogen-free bacteria. Subsequently, germfree transgenic rats were colonized with groups of five to eight bacteria that were either facultative or strictly anaerobic. Transgenic germfree rats had no gastroduodenitis, colitis, or arthritis, but developed epididymitis and dermatitis to the same degree as conventionalized rats. Colonic proinflammatory cytokine expression was increased in transgenic conventionalized rats but was undetectable in germfree and nontransgenic rats. Colitis progressively increased over the first 4 wk of bacterial exposure, then plateaued. Only transgenic rats colonized with defined bacterial cocktails which contained Bacteroides spp. had colitis and gastritis. Normal luminal bacteria predictably and uniformly induce chronic colonic, gastric and systemic inflammation in B27 transgenic F344 rats, but all bacterial species do not have equal activities.

Animal models of intestinal and joint inflammation

Recent rodent models have been exploited to explore mechanisms of intestinal and joint inflammation. HLA-B27 transgenic rats develop colitis, gastritis, and arthritis when raised in a conventional environment, but have no evidence of inflammation under germfree (sterile) conditions. Metronidazole treatment attenuates gastrointestinal inflammation, suggesting that anaerobic bacteria are important. Experimental bacterial over-growth of predominantly anaerobic bacteria reactivates arthritis in Lewis rats which have been previously injected intra-articularly with bacterial cell wall polymers. Reactivation arthritis is mediated by interleukin-1, tumour necrosis factor-alpha, and can be blocked by metronidazole. Intramural injection of the bacterial cell wall polymer, peptidoglycan-polysaccharide, leads to biphasic, chronic granulomatous enterocolitis and peripheral arthritis in Lewis rats, but only transient intestinal inflammation and no arthritis in Buffalo or MHC-matched Fischer rats. Chronic granulomatous inflammation is mediated by T lymphocytes and interleukin-1 and is dependent on persistent antigenic stimulation by poorly biodegradable bacterial polymers. Results in these models firmly incriminate resident normal enteric flora (especially anaerobes), bacterial products, and host genetic susceptibility in the pathogenesis of spondyloarthropathies. We suggest that increased uptake of luminal bacterial components across the inflamed mucosa leads to systemic distribution of these arthropathic products. The genetically susceptible host develops reactive arthritis due to defective downregulation of inflammation in response to immunologically active bacterial components.

Suppression of experimental arthritis by gene transfer of interleukin 1 receptor antagonist cDNA

Restoration of the impaired balance between pro- and antiinflammatory cytokines should provide effective treatment of rheumatoid arthritis. Gene therapy has been proposed as an approach for delivery of therapeutic proteins to arthritic joints. Here, we examined the efficacy of antiinflammatory gene therapy in bacterial cell wall-induced arthritis in rats. Human secreted interleukin 1 receptor antagonist (sIL-1ra) was expressed in joints of rats with recurrent bacterial cell wall-induced arthritis by using ex vivo gene transfer. To achieve this, primary synoviocytes were transduced in culture with a retroviral vector carrying the sIL-1ra cDNA. Transduced cells were engrafted in ankle joints of animals prior to reactivation of arthritis. Animals in control groups were engrafted with synoviocytes transduced with lacZ and neo marker genes. Cells continued to express transferred genes for at least 9 days after engraftment. We found that gene transfer of sIL-1ra significantly suppressed the severity of recurrence of arthritis, as assessed by measuring joint swelling and by the gross-observation score, and attenuated but did not abolish erosion of cartilage and bone. The effect of intraarticularly expressed sIL-1ra was essentially local, as there was no significant difference in severity of recurrence between unengrafted contralateral joints in control and experimental groups. We estimate that locally expressed sIL-1ra was about four orders of magnitude more therapeutically efficient than systemically administered recombinant sIL-1ra protein. These findings provide experimental evidence for the feasibility of antiinflammatory gene therapy for arthritis.

Role of endogenous enteric organisms in the reactivation of arthritis

Reactive arthritis is an acute form of arthritis apparently caused by a combination of bacterial infection and genetic influences. Recent experiments using an animal model suggest that certain bacterial cell wall polymers originating from endogenous enteric bacteria may be responsible for the condition.

Reactivation of arthritis induced by small bowel bacterial overgrowth in rats: role of cytokines, bacteria, and bacterial polymers

Arthritis is often associated with intestinal diseases, but the etiology is not known. We developed a rat model whereby arthritis was reactivated by experimental small bowel bacterial overgrowth (SBBO). Self-limited monoarticular arthritis was induced by intra-articular injection of 2 micrograms of rhamnose peptidoglycan-polysaccharide derived from group A streptococci into the ankle joints in female Lewis rats. Eleven days after intra-articular injection, when swelling was resolving, experimental SBBO induced by surgical creation of jejunal self-filling blind loops reactivated arthritis, but SBBO induced by creation of self-emptying blind loops, which minimally increases luminal bacteria, and sham operation did not (P < 0.001). Increased joint diameters in rats with self-filling blind loops persisted for at least 56 days after surgery. Reactivation of arthritis due to SBBO was prevented by anti-tumor necrosis factor alpha antiserum and interleukin 1 receptor antagonist (P < 0.001), indicating that these cytokines mediate joint swelling secondary to intestinal injury. Recombinant bactericidal/permeability-increasing protein, an agent which neutralizes endotoxin, and metronidazole, which is active against anaerobic bacteria, prevented arthritis (P < 0.001), but polymyxin B (which also neutralizes endotoxin) and gentamicin had no effect. Mutanolysin, an enzyme which degrades peptidoglycan-polysaccharide from group A streptococci, exacerbated arthritis for the first 6 days but then diminished joint swelling from 12 to 21 days after surgery (P < 0.001). These studies introduce a reproducible animal model of reactivation of arthritis secondary to intestinal injury and demonstrate a role for bacterial products from endogenous enteric organisms.

Inhibition of IL-1 release from human monocytes and suppression of streptococcal cell wall and adjuvant-induced arthritis in rats by an extract of Tripterygium wilfordii Hook

1. It was investigated whether an extract of Tripterygium wilfordii Hook f (TW) inhibits IL-1 production by monocytes and suppresses the development of IL-1-dependent arthritis induced in rats with streptococcal cell wall and adjuvant. 2. TW preferentially inhibited IL-1 alpha and IL-1 beta production by bacterial lipopolysaccharide (LPS)-stimulated human monocytes with IC50 of approximately 1 microgram/ml. 3. Oral administration of TW dose-dependently suppressed joint swelling and structural damage in streptococcal cell wall-induced arthritis (ED50 = 20 mg/kg/day) and in adjuvant-induced arthritis (ED50 = 46 mg/kg/day for developing and 8 mg/kg/day for established arthritis).

Group A streptococcal antigens and superantigens in the pathogenesis of autoimmune arthritis

Evidence from repeated clinical observations and from a variety of experimental approaches implicates group A streptococci in the pathogenesis of the autoimmune arthritides. Several streptococcal antigens and superantigens have now been characterized and their properties suggest that they may be involved in the mechanisms which underlie these diseases, although other antigens and superantigens yet to be discovered may also be involved. The association between group A streptococcal infection and autoimmune arthritis offers a useful model for providing a long-elusive understanding of the role of bacterial infection in the pathogenesis of autoimmune disease.

Bacterial cell wall polymers (peptidoglycan-polysaccharide) cause reactivation of arthritis

Intraperitoneal (i.p.) injection of peptidoglycan-polysaccharide derived from group A streptococci (PG-APS) causes chronic arthritis with spontaneous remissions and exacerbations. We hypothesized that, following i.p. injection, PG-APS released from hepatic stores mediated spontaneous recurrences of arthritis. We tested whether transplanted livers with large amounts of PG-APS were able to reactivate quiescent arthritis. Saline-loaded (group 1) or PG-APS-loaded (group 2) livers were transplanted into rats which had been injected intra-articularly 10 days earlier with PG-APS in one joint and saline in the other. A comparison was made with the arthritis that occurred in rats injected i.p. with PG-APS which did not receive transplants (group 3). Arthritis was monitored by serial measurement of joint diameters. Transplantation of saline-loaded livers (group 1) caused no reactivation of arthritis. However, transplantation of PG-APS-loaded livers (group 2) reactivated arthritis (P < 0.0001). Injection of PG-APS i.p. (group 3) induced the most-severe arthritis. PG-APS levels in plasma decreased with time, and PG-APS accumulated in the spleen in groups 2 and 3. Plasma and hepatic levels of PG-APS in rats injected i.p. with PG-APS were greater than levels in rats transplanted with PG-APS-loaded livers, which in turn were greater than levels in rats with saline-loaded livers. Plasma tumor necrosis factor did not correlate with recurrence of arthritis. Transplantation with PG-APS-loaded livers induced reactivation of arthritis in preinjured joints. The extent of arthritis was proportional to hepatic PG-APS content. Reactivation of arthritis may be mediated by slow release of liver-sequestered PG-APS or cytokines (not tumor necrosis factor) released by the liver.

Extent of peptidoglycan O acetylation in the tribe Proteeae

The degree of peptidoglycan O acetylation in 18 strains of the different genera of the tribe Proteeae (Proteus, Providencia, and Morganella) has been determined by high-performance liquid chromatography-based organic acid analysis of mild-base-released acetic acid and quantitation of peptidoglycan concentrations by simultaneous amino sugar-amino acid analysis using high-performance anion-exchange chromatography with pulsed amperometric detection. The N,O-diacetylmuramyl content of all isolated and purified peptidoglycans was greater than 29% and ranged up to 57% relative to total muramic acid concentration. Each of the O-acetylated peptidoglycans was found to be resistant to solubilization by hen egg white lysozyme.

Interleukin-1 receptor antagonist (IL-1ra) as a probe and as a treatment for IL-1 mediated disease

The natural human IL-1 receptor antagonist (IL-1ra) has been produced in a recombinant organism and has been used to study IL-1 action in vivo. The receptor antagonist mitigates the pathophysiology associated with animal models of ulcerative colitis through reducing IL-1 mediated neutrophil recruitment into the affected tissue. It also reduces joint swelling and damage in an animal model of rheumatoid arthritis, possibly by reducing IL-1 mediated synthesis of proteases by the synovial fibroblasts and chondrocytes of the joint. The receptor antagonist is not immunosuppressive in rodents, indicating that it is working by blocking the inflammatory reaction rather than any underlying defect in specific immunity.

Pro- and anti-inflammatory roles of interleukin-1 in recurrence of bacterial cell wall-induced arthritis in rats

A specific interleukin-1 (IL-1) receptor antagonist (IL-1ra) was used to examine the roles of IL-1 in an experimental model designed to analyze the reactivation phase of erosive arthritis, induced in rats with peptidoglycan-polysaccharide polymers (PG-APS) isolated from cell walls of group A streptococci. Monoarticular arthritis was initiated by injection of a small dose of PG-APS into an ankle joint, and reactivation was induced by intravenous injection of PG-APS 20 days later. Human recombinant IL-1ra given at a dose of 2 to 3 mg/kg at the time of reactivation of arthritis and at 6-h intervals inhibits the increase in joint swelling by at least 60%. Joint swelling is suppressed 30 to 50% when the initial treatment with IL-1ra is delayed until 6 h after reactivation. IL-1ra is not effective when the initial injection is delayed 12 or 24 h. With an injection schedule of IL-1ra given at the time of reactivation and every 6 h, treatment can be stopped at 24 h and the suppression of swelling is no different from that in rats for which injections are continued for 4 days. The results indicate that IL-1 has a prominent, although not exclusive, role in initiating inflammation in this model and is involved in the amplifying processes in progressive inflammation and chronic erosive disease. An anti-inflammatory function of IL-1 is also indicated from data showing that IL-1ra treatment limited to 6 h or less after the induction of reactivation enhances joint swelling, whereas intravenous injection of human recombinant IL-1 beta 24 h before reactivation suppresses the reactivation of arthritis.

Histology of joint inflammation induced in rats by cell wall fragments of the anaerobic intestinal bacterium Eubacterium aerofaciens

To study the arthropathic properties of human intestinal bacteria, cell wall fragments (CWF) of the anaerobic bowel bacterium Eubacterium aerofaciens were injected intraperitoneally (i.p.) in arthritis-susceptible Lewis rats. Rat paw joints were subsequently studied for histopathological changes. A persisting synovitis accompanied by marginal erosions of cartilage and bone and a marked periosteal apposition of new bone tissue were the main features of the polyarthritis induced. These results are discussed in relation to streptococcal cell wall induced arthritis and compared with histopathological findings in rheumatoid arthritis (RA) in man.

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.

Streptococcal cell wall-induced polyarthritis in the rat. Mechanisms for chronicity and regulation of susceptibility

Streptococcal cell wall (SCW)-induced arthritis is a chronic, erosive polyarthritis that can be induced in euthymic, susceptible Lewis rats by a single i.p. injection of a sterile, aqueous suspension of SCW. Nude Lewis rats and most other rats strains, including histocompatible F344 rats, are resistant to chronic disease. To study the mechanisms of chronicity and susceptibility to bacterium-induced arthritis, we compared immunological parameters in Lewis and F344 rats. A first observation was that Lewis rats mounted T-cell proliferative responses to SCW after immunisation with SCW or arthritis induction, while F344 rats were completely unable to do so. Depletion of OX8+ cells partially restored this defective response in F344 rats; it did not make them susceptible to polyarthritis, however. As SCW are present throughout the body and the disease manifests itself mainly, and sometimes uniquely as a joint inflammation, a reason for localisation had to be found. One explanation is the crossreactivity of SCW-primed T cells to cartilage components which can be demonstrated in Lewis but not in F344 rats, in vitro and in vivo. We considered this T-cell unresponsiveness in F344 rats as tolerance to threatening antigens or epitopes, so we changed the state of tolerance in both Lewis and F344 rats followed by induction of arthritis. Tolerance to bacteria was prevented in F344 rats by using them as germfree (GF) animals and was induced in Lewis rats by pretreatment with a bacterial common antigen, the 65 kD mycobacterial heat shock protein. The changed state of tolerance coincided with a reversal of the susceptibility to SCW-induced arthritis in both strains. We suggest that in arthritis-prone individuals (Lewis) tolerance to arthritogenic epitopes is defective, while in normal individuals (F344) tolerance and thus arthritis-resistance is induced and/or maintained by exogenous bacteria or gut flora. Another point to be considered is the involvement of T cells in the chronicity of joint inflammation. We demonstrated that a subsiding arthritis can be reactivated by systemic administration of a small amount of bacteria. This so called flare up is dependent on specific T cells and can therefore be induced in Lewis, but not in F344 rats. Of importance is the observation that even unrelated bacteria are able to reactivate and thus to maintain arthritis induced by streptococci.(ABSTRACT TRUNCATED AT 400 WORDS)

Protection against streptococcal cell wall-induced arthritis by pretreatment with the 65-kD mycobacterial heat shock protein

We report that streptococcal cell wall (SCW)-induced arthritis in rats, a T cell-dependent chronic, erosive polyarthritis, can be prevented by pretreatment of the rats with the mycobacterial 65-kD heat shock protein. This 65-kD protein shows extensive amino acid homology with prokaryotic and eukaryotic 65-kD heat shock proteins and is a ubiquitous bacterial common antigen. Both the clinical and histopathologic manifestations of the arthritis were prevented completely when rats were pretreated with 50 micrograms of 65-kD protein intraperitoneally at 35, 25, 15, or 5 d before administration of SCW. In such protected rats, SCW-specific T cell responses were suppressed, as compared with responses in arthritic rats. Pretreatment with 65-kD protein had no effect on the production of antibodies against SCW, on a nonspecific inflammatory reaction (zymosan-induced arthritis), or on general cellular immunity in vivo (delayed type hypersensitivity reaction to a nonrelated protein antigen). Furthermore, the protection against SCW arthritis was transferable by splenic T cells to naive recipients. Our data show that pretreatment with the 65-kD mycobacterial heat shock protein protects rats against a subsequent bacterium-induced arthritis. This protection is immunologically specific and resides in the lymphoid cell population.

Protracted anemia associated with chronic, relapsing systemic inflammation induced by arthropathic peptidoglycan-polysaccharide polymers in rats

Mild hypoproliferative anemia with abnormal iron metabolism frequently accompanies chronic inflammation and infection in humans. To determine whether anemia is associated with chronic relapsing arthritis induced by bacterial cell wall polymers, serial determinations of the hematocrit were measured in rats injected intraperitoneally with sonicated peptidoglycan-polysaccharide fragments from group A streptococci. Acute anemia peaked 5 to 10 days after injection, and chronic, spontaneously relapsing anemia persisted for 309 days. 51Cr labeling demonstrated decreased erythrocyte survival, i.e., a half-life of 8.4 days in cell wall-injected rats versus 11.8 days in controls. Erythrocytes were mildly microcytic, and leukocyte counts were elevated during early spontaneous reactivation of arthritis, 15 days after injection of peptidoglycan-polysaccharide. Bone marrow myeloid/erythroid precursor ratios were elevated in arthritic rats (P less than 0.0001). Purified peptidoglycan produced an acute anemia lasting 10 days, while injection of group A streptococcal polysaccharide and mutanolysin-digested cell wall did not affect the hematocrit. The minimal effective dose of peptidoglycan-polysaccharide was 5 micrograms of rhamnose per g (body weight). Serum iron and transferrin levels were decreased in cell wall-injected rats (P less than 0.005) and were closely correlated with hematocrit values and joint inflammatory scores. Stainable iron was increased in the liver, spleen, and mesenteric lymph nodes and unchanged in the bone marrow of cell wall-injected rats. Anemia accompanying chronic, relapsing systemic inflammation induced by peptidoglycan-polysaccharide polymers appears to be an excellent animal model of the anemia of chronic disease.

Systemic uptake and intestinal inflammatory effects of luminal bacterial cell wall polymers in rats with acute colonic injury

The systemic uptake and local intestinal inflammatory potential of luminal bacterial cell wall polymers in rats with normal and acutely inflamed colons were measured. Rats were injected intracecally with either 125I-labeled group A streptococcal peptidoglycan-polysaccharide complexes or equal amounts of Na125I, after either nonspecific colonic injury with 4% acetic acid or injection with buffer. The colons of rats injected with peptidoglycan-polysaccharide had higher inflammatory scores than Na125I-injected rats, a greater incidence of mucosal ulceration and transmural inflammation after acetic acid injury, and an increased frequency of focal accumulations of inflammatory cells in the lamina propria and submucosa after buffer injection. Radioactivity in the liver, spleen, and mesenteric lymph nodes was higher in the colon-injured rats that received peptidoglycan-polysaccharide 48 h before tissue collection than in the noninjured rats (P less than 0.002). Group A streptococcal polysaccharide antigen concentration within the liver, spleen, and mesenteric lymph nodes, measured by enzyme-linked immunosorbent assay, was significantly higher in the colon-injured rats that received cell wall polymers than in noninjured rats. These results indicate that luminal bacterial cell wall polymers with well-described inflammatory and immunoregulatory potential can cross injured colonic epithelia and are capable of initiating and potentiating intestinal inflammation.

Stimulation of rabbit synoviocyte prostaglandin E2 synthesis by lipopolysaccharides and their subunit structures

Lipopolysaccharides (LPS) induce synoviocyte activation and may lead to destruction of synovial joint tissues. We assessed the production of prostaglandin E2 (PGE2) as a measure of synoviocyte activation by LPS and their subunit structures. Diphosphoryl lipid A was the smallest portion of lipid A tested that stimulated PGE2 production. The polysaccharide fraction of LPS, containing the O antigen, was also active. Intraarticular injections of the polysaccharide resulted in a synovitis very similar to that found in association with the intact LPS molecule. These observations suggest that both parts of LPS might be involved in gram-negative, organism-associated synovitis.

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.

In vivo degradation of bacterial cell wall by the muralytic enzyme mutanolysin

The muralytic enzyme mutanolysin can act in vivo to eliminate chronic erosive arthritis induced in rats by polymers of peptidoglycan-polysaccharide isolated from group A streptococci (PG-APS). The amounts of PG-APS in the livers and spleens of rats treated with mutanolysin were significantly reduced compared with the amounts in control rats treated with phosphate-buffered saline. However, the amounts of PG-APS in the limbs of mutanolysin- and phosphate-buffered saline-treated rats were comparable. PG-APS polymers extracted from the livers, spleens, and limbs of mutanolysin-treated rats were extensively degraded, whereas PG-APS extracted from phosphate-buffered saline-treated rats had a high molecular weight. We propose that mutanolysin abrogates arthritis in rats by degrading PG-APS polymers to a size which is no longer able to induce chronic erosive arthritis, even though the polymers are still present in the limbs.

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.