Mycoplasma arthritidis induces toxicity, arthritis, and dermal necrosis in mice. Virulence factors include a superantigen and membrane adhesins and possibly also a bacteriophage component. Here we compare the biological properties of Triton X-114 extracts derived from avirulent and virulent M. arthritidis strains. Macrophage cell lines and resident peritoneal macrophages were used to assess inflammatory potential as indicated by production of tumor necrosis factor alpha, interleukin-6, and/or nitric oxide. The activity resided exclusively within the hydrophobic detergent phase, was unaffected by heat treatment at 100°C for 30 min, and was resistant to proteinase K digestion, suggesting involvement of a lipopeptide. Contamination of extracts with endotoxin or superantigen was excluded. Extracts of the more virulent strain had higher activity than did those of the avirulent strain. Using CHO cells expressing Toll-like receptor 2 (TLR2) or TLR4, both with transfected CD14, we showed that extracts activated these cells via TLR2 but not by TLR4. Also, macrophages from C57BL/6 TLR2 ؊/؊ mice failed to respond to the extracts, whereas those from TLR2 ؉/؉ cells did respond. The preparations from the virulent strain of M. arthritidis were also more potent in activating dendritic cells, as evidenced by up-regulation of major histocompatibility complex class II, CD40, B7-1, and B7-2. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and subsequent elution of gel slices revealed the presence of three active moieties which corresponded to molecular masses of approximately 24, 28, and 40 kDa. Three active components were also found by reverse-phase chromatography. We suggest that macrophage activation by M. arthritidis could play a significant role in the inflammatory response induced in the host by this organism.
SummaryMycoplasma arthritidis mitogen (MAM) is a superantigen secreted by M. arthritidis , an agent of murine arthritis and toxicity. We previously demonstrated that C3H mouse sub-strains differing in expression of Tolllike receptor 4 (TLR4), differed in immune reactivity to MAM due to differential engagement of TLR2 and TLR4. Here we examine the role of B7 co-stimulatory molecules in immune outcome and disease manifestations resulting from these different MAM/TLR2 and MAM/TLR4 interactions. Injections of MAM into C3H/ HeJ mice upregulated expression of B7-1 but not B7-2 on peritoneal adherent cells, whereas B7-1 expression was lower on cells from C3H/HeSnJ mice. Anti-B7-1 antibody but not anti-B7-2, injected in vivo , changed the type 1 cytokines in MAM-injected C3H/ HeJ mice to a type 2 cytokines and, conversely, the type 2 response in C3H/HeSnJ mice injected with anti-B7-1 shifted to a type 1 pattern. Whereas anti-B7-2 exerted no effect on disease in either mouse strain, anti-B7-1 significantly delayed the lethal toxicity of M. arthritidis in C3H/HeJ mice but enhanced arthritis in C3H/HeSnJ mice. Thus, TLR-mediated regulation of B7-1 results in diverse cytokine profiles in C3H substrains, and that the interaction of MAM with different TLR(s) may differentially affect cytokine responses and ultimately, M. arthritidis disease.
Mycoplasma arthritidis is a naturally occurring murine pathogen, and the disease model has been used extensively to understand inflammatory mechanisms. Recently, Triton X-114 extracts of a virulent strain of M. arthritidis were found to be more potent in activating macrophages than were those from an avirulent strain, suggesting a role in disease. Here, octyl glucoside extraction of cells was used to identify four distinct bioactive moieties, with molecular masses of ϳ41, 37, 34, and 17 kDa. Their bioactivities were resistant to proteinase K but were destroyed by alkaline hydrolysis and oxidation. As for MALP-2, all were dependent upon Toll-like receptor 2, but unlike MALP-2, they were also dependent upon CD14. The M. arthritidis lipoproteins exhibited infrared absorbances at 2,900 cm ؊1 and 1,662 cm ؊1 , similar to those seen in Pam 3 -Cys-Ser-(Lys) 4 . Edman degradation failed to reveal N-terminal sequences, suggesting that they were blocked and therefore might be triacylated. However, mass spectrometry of fragments revealed that the 41-kDa moiety, which binds to serum apolipoprotein A-1, had similarity with the recently described MlpD lipoprotein of M. arthritidis.Mycoplasmas, or mollicutes, are the smallest self-replicating prokaryotes and are common parasites of humans, animals, and plants. Mycoplasma arthritidis infections in rodents serve as animal models for a chronic arthritis that closely resembles human rheumatoid arthritis, necrotizing fasciitis-like syndrome, and acute toxic shock syndrome (6). Virulence factors include a superantigen (SAg), the M. arthritidis mitogen MAM (2), which utilizes Toll-like receptor 2 (TLR2) and TLR4 (14); two membrane lipoproteins, Maa1 (32) and Maa2 (34); and bacteriophage MAV1 (28). MAM is a potent activator of T cells, B cells, and macrophages (2). Although MAM can induce arthritis when injected directly into rat joints, systemic administration into rodents is without significant clinical effects. However, major changes in immune function do occur after intravenous injection of MAM (15), and MAM can trigger and exacerbate autoimmune collagen-induced arthritis (3). The inability of MAM to cause overt clinical disease by itself supports the notion that other virulence factors participate in the inflammatory effects of whole organisms.We recently reported that Triton X-114 extracts of whole cells of a virulent strain of M. arthritidis contained components that activated macrophages through TLR2 and caused dendritic cell maturation, as evidenced by upregulation of surface expression of major histocompatibility complex class II, CD40, B7-1, and B7-2 (4). These activities were not due to contamination with MAM or lipopolysaccharide (LPS) and were significantly less potent in extracts from an avirulent strain of M.arthritidis, suggesting an association with disease. Other mycoplasmas have also been shown to possess macrophage-activating components, including MALP-2 (16), a lipopeptide derivative of MALP-404 from M. fermentans; fibroblast-and macrophage-stimulating lipopeptid...
There is increasing epidemiologic evidence implying a role for chronic infection in atherosclerosis and that microbial TLR agonists may contribute to this disease. Mycoplasma arthritidis is an agent of acute and chronic inflammatory disease in rodents, and has been used extensively as a model for defining the mechanisms involved in arthritis and other inflammatory diseases. We have purified a 28-kDa, apolipoprotein A-1 (apoA-1)-like TLR2-dependent macrophage-activating moiety from a culture of a virulent strain of M. arthritidis. ApoA-1 similarly isolated from uninoculated mycoplasma medium was without bioactivity. The activity of the mycoplasma-derived molecule was resistant to heat and to digestion with proteinase K, but was susceptible to alkaline hydrolysis and H2O2 oxidation. Infrared profiles of normal apoA-1 and that derived from mycoplasma were distinct. Unlike the activity of other mycoplasmal TLR2 agonists such as macrophage-activating lipopeptide-2, activity of the M. arthritidis-derived 28-kDa component was dependent upon CD14, a coreceptor for LPS. Finally, we showed that bioactive lipopeptides prepared from M. arthritidis grown in serum-free medium and also from a 41-kDa known bioactive lipoprotein of M. arthritidis, avidly bound to purified apoA-1 that separated out by SDS-PAGE, induced TNF-α and IL-12p40 both in vitro and in vivo. ApoA-1 is a key functional component of the high-density lipoprotein cholesterol complex by scavenging and removing unwanted lipids. Our finding that this molecule can acquire macrophage-activating properties from microbial TLR2-dependent agonists suggests a novel mechanism whereby some microbial agents might reverse the protective role of apoA-1, thus contributing to the genesis of atherosclerosis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.