Staphylococcal protein A promotes osteoclastogenesis through MAPK signaling during bone infection.

Bone infection is a common and serious complication in the orthopedics field, which often leads to excessive bone destruction and non-union. Osteoclast is the only type of cells which have the function of bone resorption. Its over activation is closely related to excessive bone loss. Staphylococcus aureus (S. aureus) is a major pathogen causing bone infection, which can produce a large number of strong pathogenic substances staphylococcal protein A (SPA). However, few studies were reported about the effects of SPA on osteoclastogenesis. In our study, we observed that S. aureus activated osteoclasts and promoted bone loss in bone infection specimens. Then, we investigated the effects of SPA on RANKL-induced osteoclastogenesis in vitro, the results revealed that SPA promoted osteoclastic differentiation and fusion, and enhanced osteoclastic bone resorption. In addition, we also showed that SPA upregulated the expression of NFATc1 and c-FOS through the activation of MAPK signaling to promote osteoclastogenesis. Our findings might help us better understand the pathogenic role of S. aureus in bone infection and develop new therapeutic strategies for infectious bone diseases.

Microbiota and caspase-1/caspase-8 regulate IL-1ß-mediated bone disease.

A leucine-to-proline missense mutation at residue 98 in the proline-serine-threonine phosphatase interacting protein 2 (Pstpip2) gene leads to autoinflammatory disease that is characterized by splenomegaly, necrosis, and spontaneous development of osteomyelitis in mice (Pstpip2cmo). Disease progression in these mice resembles that of chronic recurrent multifocal osteomyelitis in humans. Our group and others have shown that disease progression in Pstpip2cmo mice is mediated by the cytokine IL-1ß, independently of inflammasomes or IL-1α. Our recent publication highlighted herein establishes that diet-induced changes in intestinal microbiota provide protection against the development of osteomyelitis in Pstpip2cmo mice. Moreover, the proteases caspase-1 and caspase-8 have redundant roles in cleaving IL-1ß and promoting disease. This addendum reviews the current literature on the Pstpip2cmo murine disease model and the clinical significance of the role of PSTPIP2 in regulating autoinflammatory osteomyelitis, which is mediated by innate components of immune cells.

The activity of paraoxonase and arylesterase in patients with osteomyelitis.

BACKGROUND: The aim of this study was to evaluate oxidative stress and to determine the activity of paraoxonase and arylesterase in patients with osteomyelitis compared to healthy controls. METHOD: In total, 30 patients diagnosed with osteomyelitis and 30 healthy volunteers were enrolled in the study. Paraoxonase and arylesterase activities were measured spectrophotometrically. Serum lipid hydroperoxide (LOOH) concentrations were measured by ferrous oxidation with xylenol orange (FOX) assay as markers of oxidative stress. RESULTS: Serum paraoxonase and arylesterase activities were significantly lower in patients with osteomyelitis compared to control individuals (all p < 0.05). Serum LOOH concentrations were significantly higher in patients with osteomyelitis than those in controls (p < 0.05). Arylesterase activity was inversely correlated with triglyceride (r =- 0.49; p = 0.005) and cholesterol concentrations (r =- 0.41; p = 0.025). CONCLUSION: In light of the findings obtained from the present study, it may be assumed that decreased activity of serum paraoxonase and increased concentrations of LOOH observed in osteomyelitis patients appear to be related to the increased oxidative stress and inflammatory conditions present in these patients, and may cause a much more severe status of the disease.

Unnecessary diagnostic investigations in benign acute childhood myositis: a case series report.

Benign acute childhood myositis (BACM) is a rare, acute, self-limiting muscle disorder, mainly affecting school-aged boys, with an excellent prognosis, requiring no therapeutic intervention. We report a series of seven previously healthy school-aged children with clinical and laboratory findings suggesting BACM where no specific diagnostic investigations were performed. All of the children were hospitalized without any specific therapeutic intervention and were discharged after two or three days free of symptoms, residual impairment or other complication. This report emphasizes that the correct diagnosis of BACM, by considering the characteristic clinical and laboratory findings of this syndrome and by recognizing more severe pathological conditions, which must be excluded from the diagnosis, can prevent unnecessary diagnostic investigations and reassure both parents and patients of the excellent prognosis.

Local antibiotic delivery with bovine cancellous chips.

Infected bone defects and osteomyelitis are encountered frequently in trauma cases. Currently, the standard of care for osteomyelitis cases is prolonged systemic antibiotic therapy and implantation of antibiotic carrier beads. However, this method requires a secondary surgery to remove the beads after the infection has cleared. In the present study a common bone void filler was investigated for its ability to be infused with an antibiotic. This study demonstrates that the xenograft material tested can be loaded with gentamicin and release clinically relevant levels of the drug for at least 14 days in vitro allowing for the inhibition of bacterial growth on the graft. This study also demonstrates that the levels of gentamicin released did not have an adverse effect on primary osteoblast cell proliferation or ability to generate alkaline phosphatase. This bone void filler may represent a viable alternative to current methods of local antibiotic delivery in orthopedic applications.

A conserved serine residue is required for the phosphatidate phosphatase activity but not the transcriptional coactivator functions of lipin-1 and lipin-2.

Mammalian lipins (lipin-1, lipin-2, and lipin-3) are Mg2+-dependent phosphatidate phosphatase (PAP) enzymes, which catalyze a key reaction in glycerolipid biosynthesis. Lipin-1 also functions as a transcriptional coactivator in conjunction with members of the peroxisome proliferator-activated receptor family. An S734L mutation in LPIN2 causes Majeed syndrome, a human inflammatory disorder characterized by recurrent osteomyelitis, fever, dyserythropoietic anemia, and cutaneous inflammation. Here we demonstrate that mutation of the equivalent serine in mouse lipin-1 and lipin-2 to leucine or aspartate abolishes PAP activity but does not impair lipin association with microsomal membranes, the major site of glycerolipid synthesis. We also determined that lipin-2 has transcriptional coactivator activity for peroxisome proliferator-activated receptor-response elements similar to lipin-1 and that this activity is not affected by mutating the conserved serine. Therefore, our results indicate that the symptoms of the Majeed syndrome result from a loss of lipin-2 PAP activity. To characterize sites of lipin-2 action, we detected lipin-2 expression by in situ hybridization on whole mouse sections and by quantitative PCR of tissues relevant to Majeed syndrome. Lipin-2 was most prominently expressed in liver, where levels were much higher than lipin-1, and also in kidney, lung, gastrointestinal tract, and specific regions of the brain. Lipin-2 was also expressed in circulating red blood cells and sites of lymphopoiesis (bone marrow, thymus, and spleen). These results raise the possibility that the loss of lipin-2 PAP activity in erythrocytes and lymphocytes may contribute to the anemia and inflammation phenotypes observed in Majeed syndrome patients.

Ubiquitin ligases MuRF1 and MAFbx in human skeletal muscle atrophy.

INTRODUCTION: Several pathological conditions can induce skeletal muscle atrophy and seem to share common enzyme pathways. In catabolic states where proteolysis is increased, two genes specific to muscle atrophy, MuRf1 and MAFbx, are upregulated. These encode ubiquitin ligases, which bind to and mediate ubiquitination of myofibrillar proteins for subsequent degradation during muscle atrophy. METHODS: Fifteen patients undergoing leg amputation were divided into two groups. Group A included 12 elderly patients (mean age 79years) amputated for vascular disease (complicated by diabetes in four), chronic osteomyelitis or squamous cell carcinoma. Group B included three car accident victims (mean age 32years) amputated due to acute arterial insufficiency. Gastrocnemius muscle biopsies were collected for a histochemical and immunohistochemical (anti-MuRf1, anti-MAFbx) study. RESULTS: Group A specimens showed a decreased cross-sectional fiber area and length, adipose tissue replacement, and MuRf1 and MAFbx immunoreactivity. Muscle cells showed MuRf1 and MAFbx subsarcolemmal immunoreactivity and weak extracellular matrix immunoreactivity. Group B samples exhibited mild muscle structural changes; they did not stain with anti-MuRf1 or anti-MAFbx, and neither did sections showing muscle degeneration and adipose tissue replacement. DISCUSSION: Results of our preliminary study showed upregulation of MuRf1 and MAFbx in atrophied muscle and support their role as regulatory peptides in various conditions that lead to muscle atrophy. Data suggest that the study of cellular pathways can help identify promising targets for effective new treatments for skeletal muscle atrophy. CONCLUSION: The treatment of several orthopedic conditions is complicated by muscle atrophy; potential treatments could be directed to specific sites where these proteins are localized.

The NOS3 (27-bp repeat, intron 4) polymorphism is associated with susceptibility to osteomyelitis.

Cytokines generate nitric oxide (NO) in osteoblasts and neutrophils through the induction of NO synthase isoforms, endothelial (NOS3) and inducible (NOS2), thereby producing bone loss. In osteomyelitis (OM), a chronic infection of the bone, homozygosity for the NOS3 (27-bp repeat, intron 4 polymorphism) 4 allele was significantly more frequent among the 80 patients than in 300 healthy controls (p=0.044). No significant differences were found for other polymorphisms of the NOS genes such as NOS3, the promoter (-786T/C), and the missense change (E298D) in exon 7, and for NOS2, the G/A substitution at position 37498 in exon 22, the (CCTTT)(n), and (TAAA)(n) micro-satellites and the -954G/C in the promoter. Serum NO levels were significantly higher only in the OM patients homozygous for the NOS3 (27-bp repeat, intron 4 polymorphism) 4 allele, compared to controls. In the presence of bacteria or bacterial products, the neutrophils of these patients produced more NO. However, immunolabelling of osteoblasts for NOS3 in biopsy tissues did not correlate with the carriage of a determined NOS polymorphism but with the presence of bone inflammation. This is the first report of an association between a NOS3 polymorphism and the risk of developing OM.

Autoantibodies to polymorphonuclear neutrophil elastase do not inhibit but enhance elastase activity.

Polymorphonuclear neutrophils (PMNs) of patients with active Wegener's granulomatosis and PMN activated in vitro express elastase on their surface as detected by autoantibodies derived from patients with ANCA-positive vasculitis or chronic staphylococcus infections. The PMN-associated elastase was enzymatically active. By affinity-purified autoantibodies to elastase, the enzymatic activity was further enhanced as measured either by a chromogenic peptide or by elastin as substrate. Antibodies to human elastase from mouse or from sheep also enhanced elastase activity, whereas unrelated immunoglobulins had no effect. Taken together, our data indicate that autoantibodies to elastase are not inhibitory but upregulate the elastase activity and thereby might contribute to tissue damage.

PMN elastase in bone and joint infections.

PMN (polymorphonuclear neutrophil) elastase is a proteolytic enzyme which is a biochemical marker for abnormal granulocyte stimulation. In inflammation and sepsis, excessive neutrophil stimulation results in significant amounts of PMN elastase being released into the plasma which indicates the severity of the disease and its prognosis. In 62 patients with osteomyelitis or suppurative arthritis, PMN elastase had a diagnostic sensitivity of 81%, which is comparable to the nonspecific erythrocyte sedimentation rate. Sensitivity of C-reactive protein (CRP) was 71%, fibrinogen 54% and leucocyte count 26%. PMN elastase was also useful in the follow up of patients with bone and joint infections; in the early post-operative period it became normal more quickly than the other findings unless the patients developed complications. Ten days after operation, PMN elastase was normal in 75% of the patients compared to the CRP which became normal in only 25%. Later both results were similar: on discharge from hospital, PMN elastase was normal in 77% and CRP in 71%.

[The effect of low-intensity radiation from a helium-neon laser on the alkaline phosphatase activity in an uncomplicated mandibular fracture and in traumatic osteomyelitis]. / Vliianie nizkointensivnogo izlucheniia gelii-neonovogo lazera na aktivnost' shchelochnoi fosfatazy pri neoslozhnennom perelome nizhnei cheliusti i travmaticheskom osteomielite.

The osteal alkaline phosphatase (AP) activity was examined in 167 Wistar rats with uncomplicated regeneration and traumatic osteomyelitis of the mandible, exposed to low-intensity He-Ne laser. Laser exposure stimulated the bone AP activity in the animals with traumatic osteomyelitis and uncomplicated regeneration, confirming the efficacy of therapy with He-Ne laser.

Myeloperoxidase secretion during phagocytosis: a case of a patient with impaired bactericidal activity.

We describe a case of a 5-year-old male patient with prolonged and extensive osteomyelitis of the left femur. Staphylococcus aureus was grown from blood cultures taken upon admission and also from pus drained from an incised hip joint. A defect in immune function was suspected and neutrophil function was assessed. Chemotaxis and phagocytosis were normal, but phagocytosed S. aureus were not killed as efficiently as in control neutrophils. No inherent defect in the ability of these neutrophils to generate reactive oxidants was observed, but an unusual luminol-dependent chemiluminescence response was obtained during phagocytosis of latex beads or opsonized S. aureus: This was characterized by an initial rapid, but transient increase occurring within 1 min of addition of phagocytic stimulus. Whereas during phagocytosis of latex beads by control neutrophils less than 1% of the total myeloperoxidase activity was detected extracellularly, up to 15% was released from the patient's neutrophils. We propose that release of myeloperoxidase from the patient's neutrophils during phagocytosis reduces the intraphagosomal concentration of this enzyme and thus impairs the efficiency of intracellular killing of S. aureus.

[The state of the microsomal oxidative system in the liver of rats with acute osteomyelitis of the mandible]. / Sostoianie mikrosomal'noi okislitel'noi sistemy pecheni krys s ostrym osteomielitom nezhnei cheliusti.

Duration of hexenal sleep and activity of main microsomal enzymes in hepatocytes were studied in experimental osteomyelitis of rat mandible. Within 7, 10 and 14 days after the osteomyelitis development content of cytochromes P-450 and b5 as well as activities of amidopyrine N-demethylase, aniline hydroxylase and NADPH cytochrome c reductase were decreased in liver cell microsomal fraction. As liver tissue monooxygenase enzymatic system is inhibited in osteomyelitis the elevated pharmacological activity and toxicity of drugs, metabolized in liver tissue, should be considered under conditions of practical use of these drugs.