Inhibition of the PI3K-Akt signaling pathway reduces tumor necrosis factor-alpha production in response to titanium particles in vitro

Receptor activator of nuclear factor-κB ligand-mediated osteoclastogenesis signaling pathway and related therapeutic natural compounds

Osteoclast is a hematopoietic precursor cell derived from the mononuclear macrophage cell line, which is the only cell with bone resorption function. Its abnormal activation can cause serious osteolysis related diseases such as rheumatoid arthritis, Paget's disease and osteoporosis. In recent years, the adverse effects caused by anabolic anti-osteolytic drugs have increased the interest of researchers in the potential therapeutic and preventive effects of natural plant derivatives and natural compounds against osteolytic diseases caused by osteoclasts. Natural plant derivatives and natural compounds have become major research hotspots for the treatment of osteolysis-related diseases due to their good safety profile and ability to improve bone. This paper provides an overview of recent advances in the molecular mechanisms of RANKL and downstream signaling pathways in osteoclast differentiation, and briefly outlines potential natural compounds with antiosteoclast activity and molecular mechanisms.

The Antiviral Effects of Jasminin via Endogenous TNF-α and the Underlying TNF-α-Inducing Action

Previous studies have reported that recombinant tumor necrosis factor (TNF)-α has powerful antiviral activity but severe systematic side effects. Jasminin is a common bioactive component found in Chinese herbal medicine beverage “Jasmine Tea”. Here, we report that jasminin-induced endogenous TNF-α showed antiviral activity in vitro. The underlying TNF-α-inducing action of jasminin was also investigated in RAW264.7 cells. The level of endogenous TNF-α stimulated by jasminin was first analyzed by an enzyme-linked immunosorbent assay (ELISA) from the cell culture supernatant of RAW264.7 cells. The supernatants were then collected to investigate the potential antiviral effect against herpes simplex virus 1 (HSV-1). The antiviral effects of jasminin alone or its supernatants were evaluated by a plaque reduction assay. The potential activation of the PI3K–Akt pathway, three main mitogen-activated protein kinases (MAPKs), and nuclear factor (NF)–κB signaling pathways that induce TNF-α production were also investigated. Jasminin induces TNF-α protein expression in RAW264.7 cells without additional stimuli 10-fold more than the control. No significant up-expression of type I, II, and III interferons; interleukins 2 and 10; nor TNF-β were observed by the jasminin stimuli. The supernatants, containing jasminin-induced-TNF-α, showed antiviral activity against HSV-1. The jasminin-stimulated cells caused the simultaneous activation of the Akt, MAPKs, and NF–κB signal pathways. Furthermore, the pretreatment of the cells with the Akt, MAPKs, and NF–κB inhibitors effectively suppressed jasminin-induced TNF-α production. Our research provides evidence that endogenous TNF-α can be used as a strategy to encounter viral infections. Additionally, the Akt, MAPKs, and NF–κB signaling pathways are involved in the TNF-α synthesis that induced by jasminin.

Prediction of Rhizoma Drynariae Targets in the Treatment of Osteoarthritis Based on Network Pharmacology and Experimental Verification

Rhizoma Drynariae has been widely used for the treatment of osteoarthritis (OA), but its potential targets and molecular mechanisms remain to be further explored. Targets of Rhizoma Drynariae and OA were predicted by relevant databases, and a protein-protein interaction (PPI) network was constructed to identify key targets. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was performed to obtain related pathways and then select significant pathways associated with OA. The OA chondrocyte model was established by inflammatory factor-induced SW1353 chondrocytes, and molecular docking was conducted to verify the above theoretical prediction. The results showed that a total of 86 Rhizoma Drynariae-OA interaction targets were identified, among which IL-6 and AKT1 were the key targets in the PPI network. Luteolin was the most critical component of Rhizoma Drynariae. KEGG results indicated that the effects of Rhizoma Drynariae on OA are associated with the PI3K/AKT, TNF, IL-17, apoptosis, and HIF-1 signaling pathway. The PI3K/AKT pathway can activate the downstream NF-κB pathway and further regulate the transcription and expression of downstream IL-6, IL-17, HIF-1α, Bax, and TNF, suggesting that the PI3K/AKT/NF-κB pathway is the critical pathway in the treatment of OA with Rhizoma Drynariae. Active components of Rhizoma Drynariae and key proteins of the PI3K/AKT/NF-κB signaling pathway were subjected to molecular docking, whose results showed that luteolin and IKK-α played a critical role. In vitro experiments indicated that both aqueous extracts of Rhizoma Drynariae (AERD) and luteolin inhibited the expression of IL-6 and HIF-1α and suppressed the activation of PI3K/AKT/NF-κB, IL-17, and TNF pathways. The measurement of mitochondrial membrane potential (Δψm) indicated that AERD and luteolin can decrease the LPS-induced early apoptotic cells. Luteolin had a more prominent inhibitory effect than AERD in the abovementioned in vitro experiments. In conclusion, the therapeutic mechanism of Rhizoma Drynariae against OA may be closely related to the inhibition of the PI3K/AKT/NF-κB pathway and downstream pathways, and luteolin plays a vital role in the treatment.

Network Pharmacology-Based Analysis and Experimental Exploration of Antidiabetic Mechanisms of Gegen Qinlian Decoction

Type-2 diabetes mellitus (T2DM) and therapy options have been studied increasingly due to their rising incidence and prevalence. The trend of applying traditional Chinese medicine (TCM) to treat T2DM is increasing as a crucial medical care for metabolic dysfunctions. Gegen Qinlian decoction (GQL), a well-known classical TCM formula used in China, has been clinically applied to treat various types of chronic metabolic diseases. However, antidiabetic effects of GQL administration during T2DM have never been studied systematically. We assessed physiological and molecular targets associated with therapeutic effects of GQL by evaluating network topological characteristics. The GQL-related biological pathways are closely associated with antidiabetic effects, including the TNF and PI3K-AKT signaling pathways. Associated primary biological processes such as RNA polymerase II promoter transcription participate in the inflammatory response, oxidative stress reduction, and glucose metabolic process, thereby exerting multiple biological effects on the antidiabetic mechanism. Furthermore, our results showed that GQL can affect blood glycemic levels and ameliorate inflammatory symptoms, and liver and pancreas tissue injury in high-fat diet plus streptozotocin-induced diabetic mice. In vivo and in vitro experiments confirmed that antidiabetic effects of GQL were associated with a modulation of the TNF and PI3K-AKT-MTOR pathways.

The unfavorable role of titanium particles released from dental implants

Titanium is considered to be a metal material with the best biological safety. Studies have proved that the titanium implanted in the bone continuously releases titanium particles (Ti particles), significantly increasing the total titanium content in human body. Generally, Ti particles are released slowly without causing a systemic immune response. However, the continuous increased local concentration may result in damage to the intraepithelial homeostasis, aggravation of inflammatory reaction in the surrounding tissues, bone resorption and implant detachment. They also migrate with blood flow and aggregate in the distal organ. The release of Ti particles is affected by the score of the implant surface structure, microenvironment wear and corrosion, medical operation wear, and so on, but the specific mechanism is not clear. Thus, it difficult to prevent the release completely. This paper reviews the causes of the Ti particles formation, the damage to the surrounding tissue, and its mechanism, in particular, methods for reducing the release and toxicity of the Ti particles.

Role of MicroRNAs in Bone Pathology during Chikungunya Virus Infection

Chikungunya virus (CHIKV) is an alphavirus, transmitted by mosquitoes, which causes Chikungunya fever with symptoms of fever, rash, headache, and joint pain. In about 30%-40% of cases, the infection leads to polyarthritis and polyarthralgia. Presently, there are no treatment strategies or vaccine for Chikungunya fever. Moreover, the mechanism of CHIKV induced bone pathology is not fully understood. The modulation of host machinery is known to be essential in establishing viral pathogenesis. MicroRNAs (miRNAs) are small non-coding RNAs that regulate major cellular functions by modulating gene expression. Fascinatingly, recent reports have indicated the role of miRNAs in regulating bone homeostasis and altered expression of miRNAs in bone-related pathological diseases. In this review, we summarize the altered expression of miRNAs during CHIKV pathogenesis and the possible role of miRNAs during bone homeostasis in the context of CHIKV infection. A holistic understanding of the different signaling pathways targeted by miRNAs during bone remodeling and during CHIKV-induced bone pathology may lead to identification of useful biomarkers or therapeutics.

Biomechanical comparison of mono- and bicortical screws in an experimentally induced gap fracture

Objectives: To compare the bending and torsional mechanical properties of mono- and bicortical locking screws in a canine cadaveric tibial gap ostectomy bridged by a locking compression plate (LCP).

Methods: A 10-hole 3.5 mm LCP was applied medially to the tibia with a gap ostectomy using locking screws in the two proximal and distal plate holes. One tibia of each pair was randomly assigned monocortical screws and the other bicortical screws. Constructs were tested non-destructively in mediolateral and caudocranial four-point bending and torsion, and then to failure in four-point bending. Stiffness, yield and failure variables were compared between screw lengths and load conditions using analysis of variance.

Results: Caudocranial and mediolateral fourpoint bending stiffnesses were not different between screw constructs. Torsional stiffness was greater and neutral zone smaller for bicortical constructs. Constructs were stiffer and stronger in caudocranial bending than in mediolateral bending. In caudocranial bending, bicortical constructs failed by bone fracture and monocortical constructs by screw loosening.

Conclusion: Bicortical constructs were stiffer than monocortical constructs in torsion but not bending. Bicortical screw constructs failed by bone fracture under the applied loads whereas monocortical screw constructs failed at the bone-screw interface.

Clinical relevance: Bicortical screw placement may be a safer clinical alternative than monocortical screw placement for minimally invasive percutaneous osteosynthesis LCPplated canine tibiae with comminuted diaphyseal fractures.

The Role of PI3K Isoforms in Regulating Bone Marrow Microenvironment Signaling Focusing on Acute Myeloid Leukemia and Multiple Myeloma

Despite the development of novel treatments in the past 15 years, many blood cancers still remain ultimately fatal and difficult to treat, particularly acute myeloid leukaemia (AML) and multiple myeloma (MM). While significant progress has been made characterising small-scale genetic mutations and larger-scale chromosomal translocations that contribute to the development of various blood cancers, less is understood about the complex microenvironment of the bone marrow (BM), which is known to be a key player in the pathogenesis of chronic lymphocytic leukaemia (CLL), AML and MM. This niche acts as a sanctuary for the cancerous cells, protecting them from chemotherapeutics and encouraging clonal cell survival. It does this by upregulating a plethora of signalling cascades within the malignant cell, with the phosphatidylinositol-3-kinase (PI3K) pathway taking a critical role. This review will focus on how the PI3K pathway influences disease progression and the individualised role of the PI3K subunits. We will also summarise the current clinical trials for PI3K inhibitors and how these trials impact the treatment of blood cancers.

HYBRID PLATING SHOWS EQUIVALENT BIOMECHANICAL BENDING STRENGTH TO UNICORTICAL LOCKED PLATING

Locking unicortical screw fixation of diaphyseal fractures may be clinically necessary due to internal constructs or prosthetic implants. The biomechanical effects of substituting one or more bicortical nonlocking screws to create a "hybrid" construct are unknown. Use of an initial nonlocking screw may be clinically desirable for creating initial plate-to-bone fixation prior to locking. A validated transverse fracture model was used with eighteen synthetic humerus models. Plate and screw fixation was performed in three treatment groups (n = 6): Unicortical locking screws only, fixation with two unicortical locking screws and one bicortical nonlocking screw on either side of the fracture and fixation with one unicortical locking screw and two bicortical locking screws on either side of the fracture. Displacement and gap strain measurements were made with a cyclic 4-point bending test. No significant differences were noted for construct stiffness or gap micromotion among the three groups on cyclic testing. Measurements at 1000, 5000, and 10,000 cycles showed stable fixation of all construct types with no significant changes in stiffness or micromotion. Substitution of one or more bicortical nonlocking screws in a unicortical locked construct does not affect construct stiffness or fracture gap strain. Data proven through controlled laboratory study.

Clinical outcomes of locked plating of distal femoral fractures in a retrospective cohort

Purpose

Locked plating (LP) of distal femoral fractures has become very popular. Despite technique suggestions from anecdotal and some early reports, knowledge about risk factors for failure, nonunion (NU), and revision is limited. The purpose of this study was to analyze the complications and clinical outcomes of LP treatment for distal femoral fractures.

Materials and methods

From two trauma centers, 243 consecutive surgically treated distal femoral fractures (AO/OTA 33) were retrospectively identified. Of these, 111 fractures in 106 patients (53.8% female) underwent locked plate fixation. They had an average age of 54 years (range 18 to 95 years): 34.2% were obese, 18.9% were smokers, and 18.9% were diabetic. Open fractures were present in 40.5% with 79.5% Gustilo type III. Fixation constructs for plate length, working length, and screw concentration were delineated. Nonunion and/or infection, and implant failure were used as outcome complication variables. Outcome was based on surgical method and addressed according to Pritchett for reduction, range of motion, and pain.

Results

Eighty-three (74.8%) of the fractures healed after the index procedure. Twenty (18.0%) of the patients developed a NU. Four of 20 (20%) resulted in a recalcitrant NU. Length of comminution did not correlate to NU (p = 0.180). Closed injuries had a higher tendency to heal after the index procedure than open injuries (p = 0.057). Closed and minimally open (Gustilo/Anderson types I and II) fractures healed at a significantly higher rate after the index procedure compared to type III open fractures (80.0% versus 61.3%, p = 0.041). Eleven fractures (9.9%) developed hardware failure. Fewer nonunions were found in the submuscular group (10.7%) compared to open reduction (32.0%) (p = 0.023). Fractures above total knee arthroplasties had a significantly greater rate of failed hardware (p = 0.040) and worse clinical outcome according to Pritchett (p = 0.040). Loss of fixation was related to pain (F = 3.19, p = 0.046) and a tendency to worse outcome (F = 2.43, p = 0.071). No relationship was found between nonunion and working length.

Conclusion

Despite modern fixation techniques, distal femoral fractures often result in persistent disability and worse clinical outcomes. Soft tissue management seems to be important. Submuscular plate insertion reduced the nonunion rate. Preexisting total knee arthroplasty increased the risk of hardware failure. Further studies determining factors that improve outcome are warranted.

Inhibition of the PI3K/AKT pathway reduces tumor necrosis factor-alpha production in the cellular response to wear particles in vitro

Joint replacement is the most effective treatment for end-stage osteoarticular disease. However, macrophage-mediated aseptic loosening of joint prosthesis severely hampers the clinical effects of joint replacement. Until now, the mechanism by which macrophages regulate the secretion of inflammatory cytokines after particle stimulation is not clear. It is well known that the PI3K/AKT pathway participates in multiple cellular processes, including cell growth, survival, and inflammation. However, whether the PI3K/AKT pathway participates in the proinflammatory response of macrophages after particle stimulation and secondary aseptic loosening is still unknown. In this study, ceramic and titanium particles of different sizes were prepared to stimulate macrophages. LY294002, a specific inhibitor of PI3K, was pretreated prior to particle stimulation. The expression of tumor necrosis factor-alpha (TNF-α) and all the subunits of PI3K and AKT were detected by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blot. The result showed that LY294002 could suppress the RNA and protein expression of TNF-α in RAW264.7 cells after stimulation of different particles. The subunits of PI3K (p110β and p85β), followed by activation of phosphor-AKT (Ser473), participated in the regulation of activating macrophages by wear particles, ultimately resulting in the secretion of TNF-α.

Inhibitory effects of β-tricalciumphosphate wear particles on osteocytes via apoptotic response and Akt inactivation

Wear debris-induced osteolysis, a major contributing factor of orthopedic implant aseptic loosening, affects long-term survival of orthopedic prostheses following joint replacement and revision surgery. Pathogenic effects of wear debris on various cell types including macrophages/monocytes, osteoblasts, and osteoclasts have been well studied. However, the interactions between wear debris particles and osteocytes, which make up over 90% of all bone cells, have not been clearly illustrated. Here, we explored the biological effects of endotoxin-free beta-tricalciumphosphate (β-TCP) wear particles with the average diameter of 1.997 μm (range 1.3-3.2 μm) on osteocytes in vitro. Our results showed that 24 h or 48 h incubation of β-TCP particles dose-dependently inhibited cell viability of osteocytes MLO-Y4. Alternatively, β-TCP particles treatment for 24 h significantly increased the osteocytic marker SOST/sclerostin mRNA expression and the release of inflammatory cytokines including TNF-α and IL-1β into the culture media, but decreased the mRNA expression of another osteocytic marker dentin matrix protein-1 (DMP-1). Furthermore, these osteocytes dysfunctions were accompanied by F-actin disassembly, cell apoptosis, sustained enhancement of intracellular reactive oxygen species (ROS) and mitochondrial injury upon β-TCP particles stimulation. In addition, β-TCP particles also caused Akt inactivation at Ser473 resides with a dose- and time-dependent pattern. Taken together, β-TCP wear particles could cause osteocytes dysfunctions, which may be mediated by apoptotic death and Akt inactivation in MLO-Y4 cells. These findings strongly suggest that osteocytes may play an important role in the β-TCP wear particles-induced osteolysis, and provide valuable insights for understanding the molecular mechanisms of osteocytes death involved in tissue damage during bone cement and intolerance of cemented prostheses.

Clozapine protects dopaminergic neurons from inflammation-induced damage by inhibiting microglial overactivation

Increasing evidence suggests a possible involvement of neuroinflammation in some psychiatric disorders, and also pharmacological reports indicate that anti-inflammatory effects are associated with therapeutic actions of psychoactive drugs, such as anti-depressants and antipsychotics. The purpose of this study was to explore whether clozapine, a widely used antipsychotic drugs, displays anti-inflammatory and neuroprotective effects. Using primary cortical and mesencephalic neuron-glia cultures, we found that clozapine was protective against inflammation-related neurodegeneration induced by lipopolysaccharide (LPS). Pretreatment of cortical or mesencephalic neuron-glia cultures with clozapine (0.1 or 1 μM) for 24 h attenuated LPS-induced neurotoxicity. Clozapine also protected neurons against 1-methyl-4-phenylpyridinium(+) (MPP(+))-induced neurotoxicity, but only in cultures containing microglia, indicating an indispensable role of microglia in clozapine-afforded neuroprotection. Further observation revealed attenuated LPS-induced microglial activation in primary neuron-glia cultures and in HAPI microglial cell line with clozapine pretreatment. Clozapine ameliorated the production of microglia-derived superoxide and intracellular reactive oxygen species (ROS), as well as the production of nitric oxide and TNF-α following LPS. In addition, the protective effect of clozapine was not observed in neuron-glia cultures from mice lacking functional NADPH oxidase (PHOX), a key enzyme for superoxide production in immune cells. Further mechanistic studies demonstrated that clozapine pretreatment inhibited LPS-induced translocation of cytosolic subunit p47(phox) to the membrane in microglia, which was most likely through inhibiting the phosphoinositide 3-kinase (PI3K) pathway. Taken together, this study demonstrates that clozapine exerts neuroprotective effect via the attenuation of microglia activation through inhibition of PHOX-generated ROS production and suggests potential use of antipsychotic drugs for neuroprotection.

PI3Kγ deletion reduces variability in the in vivo osteolytic response induced by orthopaedic wear particles

Orthopedic wear particles activate a number of intracellular signaling pathways associated with inflammation in macrophages and we have previously shown that the phosphoinositol-3-kinase (PI3K)/Akt pathway is one of the signal transduction pathways that mediates the in vitro activation of macrophages by orthopedic wear particles. Since PI3Kγ is primarily responsible for PI3K activity during inflammation, we hypothesized that PI3Kγ mediates particle-induced osteolysis in vivo. Our results do not strongly support the hypothesis that PI3Kγ regulates the overall amount of particle-induced osteolysis in the murine calvarial model. However, our results strongly support the conclusion that variability in the amount of particle-induced osteolysis between individual mice is reduced in the PI3Kγ(-/-) mice. These results suggest that PI3Kγ contributes to osteolysis to different degrees in individual mice and that the mice, and patients, that are most susceptible to osteolysis may be so, in part, due to an increased contribution from PI3Kγ.

A retrospective study of tibial plateau translation following tibial plateau levelling osteotomy stabilisation using three different plate types

OBJECTIVE

To retrospectively evaluate mediolateral translation of the proximal tibial segment (tibial plateau) after tibial plateau levelling osteotomy (TPLO), stabilised with three types of plate.

METHOD

Pre- and postoperative radiographs of 79 dogs that had TPLO surgery using three different types of plates were reviewed. Two plate types incorporated non-locking screws: Slocum (22 cases) and Orthomed Delta (33 cases) plates. The third plate type incorporated locking screws: Synthes TPLO Locking Compression Plate (LCP) (24 cases). The radiographs were viewed by three Diplomate surgeons who were blinded to the type of implant used. Medial or lateral translation of the proximal tibial plateau relative to the tibial diaphysis was assessed and measured at the lateral tibial cortex at the osteotomy site.

RESULTS

Mean lateral translation of the tibial plateau was significantly greater when using the Synthes TPLO LCP with locking screws (+2.1 mm) compared to the non-locking Slocum (+0.4 mm) or Orthomed Delta (0.0 mm) plates.

CLINICAL SIGNIFICANCE

The use of the Synthes TPLO LCP will maintain a malalignment of the tibial plateau. Accurate alignment of the tibial plateau must be ensured prior to application of the Synthes TPLO LCP.

Proximal tibial fractures: early experience using polyaxial locking-plate technology

Between 2004 and 2009, 60 patients with proximal tibial fractures were included in this prospective study. All fractures were treated with the polyaxial locked-plate fixation system (DePuy, Warsaw, IN, USA). Clinical and radiographic data, including fracture pattern, changes in alignment, local and systemic complications, hardware failure and fracture union were analysed. The mean follow-up was 14 (12-36) months. According to the Orthopaedic Trauma Association (OTA) classification, there were five 41-A, 28 41-B and 27 41-C fractures. Fractures were treated percutaneously in 30% of cases. Double-plating was used in 11 cases. All but three fractures progressed to union at a mean of 3.2 (2.5-5) months. There was no evidence of varus collapse as a result of polyaxial screw failure. No plate fractured, and no screw cut out was noted. There was one case of lateral joint collapse (>10°) in a patient with open bicondylar plateau fracture. The mean Knee Society Score at the time of final follow-up was 91 points, and the mean functional score was 89 points. The polyaxial locking-plate system provided stable fixation of extra-articular and intra-articular proximal tibial fractures and good functional outcomes with a low complication rate.

Locked plating for femoral fractures in polio patients

BACKGROUND

Femoral fractures in polio survivors present unique challenges; the bone is often small, deformed, osteoporotic and hypovascularized. Locked compression plating aided in achieving a better construct stability of osteoporotic fractures.

METHODS

A total of 13 unilateral femoral fractures in adult polio patients were fixed with locked compression plating in a prospective study. Mean age was 49.8 years (range 34-62). In 6 cases, the small size of the bone matched only narrow plates, and in 6 cases the plate was contoured to fit the cortex. Average follow-up period was 18.4 months (range 12-24).

RESULTS

Radiological evidence of union was apparent in 12 cases after 12-20 weeks (mean 16.3). One case was considered ununited after 28 weeks and progressed to union with bone grafting after another 12 weeks. At the end of the follow-up period, 12 patients returned to their prefracture Vignos disability scale, only the case that experienced nonunion showed functional deterioration.

CONCLUSION

The locked compression plate withstood fixing femoral fractures in polio patients, addressing the challenges of a smaller, osteoporotic, less vascularized and sometimes deformed femur.

Treatment for large skeletal defects by free vascularized fibular graft combined with locking plate

BACKGROUND

Reconstruction of large skeletal defects secondary to osteomyelitis or open fracture is a challenging problem. The purpose of this study was to evaluate the results of using free vascularized fibular graft (FVFG) combined with locking plate in the treatment of large skeletal defects from open fracture and infection.

METHODS

Ten patients with a mean age of 34 years (ranged 13-57 years) and a mean length of 8.7 cm (range 6-17 cm) skeletal defect were treated with FVFG and locking plate. The mean follow-up time was 26 months.

RESULTS

Grafting union occurred in all patients, with a mean healing time of 4.5 months. No recurrence of osteomyelitis and stress fractures was observed. The mean time to full weight-bearing was 10 months, and all patients were pain-free and able to walk without supportive devices.

CONCLUSIONS

FVFG combined with locking plate is a viable option for the management of large skeletal defects from open fracture and infection.

Effect of titanium on lipoprotein lipase activity in vivo and in vitro

SUMMARY

Lipoprotein lipase (LPL) is a major lipolytic enzyme in the intravascular metabolism of postprandial triglyceride-rich lipoproteins. This enzyme is synthesized and secreted by tissues and transported to the capillary endothelial surface. Decreased activity of this enzyme is suggested to be involved in arterial sequestration of lipoproteins and thus in the progression of atherosclerosis. Titanium salts are widely used in industry, medicine, and pharmacy for tablet coating, pharmaceuticals and cosmetic products. In this study the effect of titanium on post-heparin LPL activity is reported in vivo and in vitro.

METHODS

Groups of Male Wistar rats were administered (i.p) with an acute dose of 2.5 mg/kg titanium chloride for 10 days and a chronic dose of 0.75 mg/kg for 30 and/or 60 days. Blood samples were then collected for LPL assay. For in vitro study, plasma aliquots were incubated in the presence of up to 50 mM titanium and the enzyme activity was measured.

RESULTS

Animals exposed to acute dose of titanium showed about 20% reduction in LPL activity, whereas 31% and 36% reductions were observed in animals chronically exposed for 30 and/or 60 days, respectively. Titanium in vitro also led to enzyme inhibition, so that a decrease of 28-53% was seen in the presence of 0.1-50 mM titanium. This inhibition by titanium was potentiated when citrate and/or bicarbonate was present.

CONCLUSION

Although the mechanism of titanium effect on LPL activity in vivo and in vitro demands more investigations, the inhibitory effect of titanium ion in vivo should be considered seriously in subjects exposed to this metal ion. Changes in LPL activity may affect whole body lipid metabolism, a condition favorable for development and progression of atherosclerosis.

Clinical application of locked plating system in children. An orthopaedic view

In recent years, the locked plating system has gained favour in the treatment of certain fractures in adults; however, there is not much information regarding its use in children. We think there could be some advantages and applications such as: an alternative to external fixation, the bridge plating technique, unicortical screws, removal of hardware, metadiaphyseal fractures, periarticular fractures, poor quality bone, and allograft fixation. However, there are some disadvantages to keep in mind and the final decision for using it should be based on the osteosynthesis method principle the surgeon would like to apply. In this review article we discuss the up-to-date possible clinical applications and issues of this system.

Failure of fracture plate fixation

Failure of fracture fixation after plating often leads to challenging surgical revision situations. Careful analysis of all patient and fracture variables is helpful in both determining the causes of the fixation failure and maximizing the success of subsequent interventions. Biologic and mechanical factors must be considered. Biologic considerations include traumatic soft-tissue injury and atrophic fracture site. Common mechanical reasons for failure include malreduction, inadequate plate length or strength, and excessive or insufficient construct stiffness. Reliance on laterally based implants in the presence of medial comminution may be a cause of fixation failure and subsequent deformity, particularly with conventional nonlocking implants. Management of dead space with cement or beads has been effective in conjunction with staged approaches. An antibiotic cement rod in the diaphysis may provide fracture stabilization. Locking full-length constructs should be considered for osteoporotic fractures.

Effects of NF-kappaB inhibitor on titanium particulate-induced inflammation in a murine model

BACKGROUND

Activation of nuclear factor kappa B (NF-kappaB) signaling in response to implant particulates may be critical in the pathogenesis of implant loosening after joint arthroplasty. The purpose of this study was to investigate the inhibitory effects of pyrrolidine dithiocarbamate (PDTC) in a murine model of inflammation induced by titanium (Ti) particulates.

MATERIALS AND METHODS

Ti particulates were introduced into established air pouches on C57BL/6J mice. Mice were injected intraperitoneally with either high-dose PDTC (100 mg/kg) or low-dose PDTC (50 mg/kg). Mice without drug treatment, as well as mice injected with saline alone were included. Each group consisted of sixteen mice. The membranes and lavage fluid were harvested 2 d or 7 d after injection of particulate suspension for histological and molecular analysis.

RESULTS

Histologic analysis showed that PDTC reduced inflammatory responses in air pouches, that is, thinner membrane and decreased cellular infiltration. In addition, PDTC reduced the release of inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) in the lavage fluid or supernatant of homogenates as evaluated by ELISA.

CONCLUSION

These results suggest that PDTC inhibits Ti particulate-induced inflammatory responses in the murine model; thus it represents a promising therapeutic candidate for the prevention and treatment of implant loosening.

Corrective lower limb osteotomies in children using temporary external fixation and percutaneous locking plates

BACKGROUND

We describe a new method for corrective osteotomy and the fixation of lower limb deformities in children.

METHODS

Following osteotomy, the desired position is obtained and temporarily stabilized using an external fixator. Definitive fixation is performed with a plate and locking screws inserted percutaneously under fluoroscopic guidance. The procedure was performed in 18 segments in 11 patients. Corrections were performed in all planes.

RESULTS

The mean follow up was 18 months (range 6-36 months). All patients were corrected to within 2 degrees of that which was planned. Union was obtained in 16 segments in ten patients within 6-16 weeks.

CONCLUSIONS

The method was found to be effective for the correction of deformity in the pediatric population. Advantages compared to conventional methods include minimal soft tissue dissection and the ability to adjust the position before definitive fixation.

Stimulation of macrophage TNFalpha production by orthopaedic wear particles requires activation of the ERK1/2/Egr-1 and NF-kappaB pathways but is independent of p38 and JNK

Bone loss that causes aseptic loosening of orthopedic implants is initiated by pro-inflammatory cytokines produced by macrophages in response to implant-derived wear particles. MAPK and NF-kappaB signaling pathways are activated by the particles; however, it is not clear which of the signaling pathways are important for the initial response to the wear particles and which are only involved at later steps in the process, such as osteoclast differentiation. Here, we show that the ERK1/2, p38, JNK, and NF-kappaB pathways are rapidly activated by the wear particles but that only the ERK1/2 and NF-kappaB pathways are required for the initial response to the wear particles, which include increases in TNFalpha promoter activity, TNFalpha mRNA expression, and secretion of TNFalpha protein. Moreover, ERK1/2 activation by wear particles is also required for increased expression of the transcription factor Egr-1 as well as Egr-1's ability to bind to and activate the TNFalpha promoter. These results, together with our previous studies of the PI3K/Akt pathway, demonstrate that wear particles coordinately activate multiple signaling pathways and multiple transcription factors to stimulate production of pro-inflammatory cytokines, such as TNFalpha. The current study also demonstrates that the signaling pathways are activated to a much greater extent by wear particles with adherent endotoxin than by "endotoxin-free" wear particles. These results, together with those demonstrating the requirement for ERK1/2/Egr-1 and NF-kappaB, show that activation of these signaling pathways is responsible for the ability of adherent endotoxin to potentiate cytokine production, osteoclast differentiation, and bone loss induced by wear particles.

Phosphoinositide-3 kinase-Akt pathway controls cellular entry of Ebola virus

The phosphoinositide-3 kinase (PI3K) pathway regulates diverse cellular activities related to cell growth, migration, survival, and vesicular trafficking. It is known that Ebola virus requires endocytosis to establish an infection. However, the cellular signals that mediate this uptake were unknown for Ebola virus as well as many other viruses. Here, the involvement of PI3K in Ebola virus entry was studied. A novel and critical role of the PI3K signaling pathway was demonstrated in cell entry of Zaire Ebola virus (ZEBOV). Inhibitors of PI3K and Akt significantly reduced infection by ZEBOV at an early step during the replication cycle. Furthermore, phosphorylation of Akt-1 was induced shortly after exposure of cells to radiation-inactivated ZEBOV, indicating that the virus actively induces the PI3K pathway and that replication was not required for this induction. Subsequent use of pseudotyped Ebola virus and/or Ebola virus-like particles, in a novel virus entry assay, provided evidence that activity of PI3K/Akt is required at the virus entry step. Class 1A PI3Ks appear to play a predominant role in regulating ZEBOV entry, and Rac1 is a key downstream effector in this regulatory cascade. Confocal imaging of fluorescently labeled ZEBOV indicated that inhibition of PI3K, Akt, or Rac1 disrupted normal uptake of virus particles into cells and resulted in aberrant accumulation of virus into a cytosolic compartment that was non-permissive for membrane fusion. We conclude that PI3K-mediated signaling plays an important role in regulating vesicular trafficking of ZEBOV necessary for cell entry. Disruption of this signaling leads to inappropriate trafficking within the cell and a block in steps leading to membrane fusion. These findings extend our current understanding of Ebola virus entry mechanism and may help in devising useful new strategies for treatment of Ebola virus infection.

SH-5, an AKT inhibitor potentiates apoptosis and inhibits invasion through the suppression of anti-apoptotic, proliferative and metastatic gene products regulated by IkappaBalpha kinase activation

Because the phosphatidylinositol-3-kinase-AKT pathway is emerging as an important regulator of tumor cell survival, inhibitors of this pathway have enormous potential in cancer treatment. A specific inhibitor of AKT, [d-3-deoxy-2-O-methyl-myo-inositol-1-[(R)-2-methoxy-3-(octadecyloxy)propyl hydrogen phosphate]] (SH-5) has been recently synthesized, but little is known about its effects on cytokine signaling. We found that SH-5 potentiated the apoptosis induced by tumor necrosis factor (TNF), as indicated by intracellular esterase staining, annexin V staining, and caspase-3 activation. This effect of SH-5 correlated with downregulation of various gene products that mediate cell survival, proliferation, metastasis, and invasion, all known to be regulated by NF-kappaB. SH-5 also blocked NF-kappaB activation induced by TNF-alpha, lipopolysaccharide, phorbol ester, and cigarette smoke but not that activated by hydrogen peroxide and RANK ligand, indicating differential requirement of AKT. Inhibition of NF-kappaB correlated with abrogation of phosphorylation and degradation of IkappaBalpha through the inhibition of activation of IkappaBalpha kinase (IKK). This led to suppression of the phosphorylation and translocation of p65 and also of NF-kappaB reporter activity induced by TNFR1, TRADD, TRAF2, NIK, and IKKbeta but not that induced by p65 transfection. Thus, our results clearly demonstrate that inhibition of AKT leads to potentiation of apoptosis through modulation of NF-kappaB signaling.

Formyl peptide receptor-1 activation enhances intestinal epithelial cell restitution through phosphatidylinositol 3-kinase-dependent activation of Rac1 and Cdc42

Inflammatory disorders of the gastrointestinal tract result in the breakdown of the intestinal epithelial barrier in the form of erosion and ulceration. To reestablish the epithelial barrier, the epithelium must efficiently migrate to reseal wounds. Numerous signaling cascades are involved in the induction and regulation of this complex process. N-formyl peptide receptors comprise a group of Gi-coupled receptors that regulate innate immune responses. Previously, we identified the expression of functional N-formyl peptide receptors in model SK-CO15 intestinal epithelial cells and observed a role for activation of these receptors in regulating cellular invasive behavior. In these studies, we performed formyl peptide receptor-1 (FPR) localization and evaluated its role in regulating intestinal epithelial cell wound closure. Immunolocalization studies using a recently developed specific monoclonal anti-FPR Ab demonstrated its localization along the lateral membrane of crypt epithelial cells in normal human colonic epithelium. In vitro studies using the classical FPR agonist fMLF showed that FPR activation significantly enhances model intestinal epithelial cell restitution and that FPR localized along actin filaments in lamellipodial and filopodial extrusions. The increase in cell migration was associated with activation of PI3K, Rac1, and Cdc42. Pharmacologic inhibition of PI3K activity abrogated the fMLF-induced increase in wound closure and activation of both Rac1 and Cdc42. Inhibition of Rac1 and Cdc42 using pharmacologic inhibitors and dominant negative mutants also inhibited the fMLF-induced increase in cell migration. Taken together, theses results support a novel role for FPR stimulation in enhancing intestinal epithelial cell restitution through PI3K-dependent activation of Rac1 and Cdc42.

What other biologic and mechanical factors might contribute to osteolysis?

An overwhelming consensus exists that wear particles are the primary driving force in aseptic loosening of orthopaedic implants. Nonetheless, considerable evidence has emerged demonstrating that various other factors can modulate the biologic activity of orthopaedic wear particles. Two of the most studied modulating factors are bacterial endotoxins and implant motion.