No abstract

This study investigated biphasic electric current (BEC) functions as a new type of electrical stimulation to induce rat calvarial osteoblasts to proliferate, differentiate and synthesize cytokines. The culture system was designed so that biphasic current flowed between upper and lower gold plates. BEC helps to minimize the net charge accumulation during cell exposure to the electrical stimulation. Osteoblasts were exposed to electrical stimulation of 1.5 microA/cm2 at 3000 Hz, and the effect of BEC was assessed in the interrupted mode (6 h daily) and in the continuous mode (24 h daily), depending on the interval of stimulation. Whereas proliferation increased by 31% after stimulation in the continuous mode for 2 days, it was unaffected in the interrupted mode. The transcriptional expression of osteogenesis-related genes such as alkaline phosphatase (ALP), osteopontin, and type I collagen was unchanged 4 days after stimulation in both modes, while cbfa1 was decreased under the same conditions. There was no detectable change in mRNA expression of growth factors (BMP-2, -4, IGF-2 and TGF-beta1) that promote osteoblast differentiation. However, real-time RT-PCR and ELISA demonstrated that vascular endothelial growth factor (VEGF) was markedly up-regulated by BEC. Induction of VEGF by BEC was not hypoxia driven. In conclusion, the present in vitro study demonstrates that BEC increases cell proliferation and induces the production of VEGF. The BEC was more effective with continuous stimulation than with interrupted stimulation. To confirm whether BEC can enhance osteogenesis, further in vivo studies are needed.

SummaryAuranofin (AF) is a sulphur-containing gold compound. Because of its anti-inflammatory and immunosuppressive activities, AF has been widely used for the therapeutic treatment of rheumatoid arthritis. However, little is known about its mechanism of action. To elucidate the molecular mechanism underlying the anti-inflammatory effect of AF, we studied the effects of AF on cellular responses to interleukin-6 (IL-6). In HepG2 human hepatoma cells, AF markedly inhibited IL-6-induced phosphorylation of janus kinase 1 (JAK1) and signal transducer and activator of transcription 3 (STAT3) and STAT3 translocation into the nucleus. Consistent with this, AF diminished IL-6-induced production of the acutephase proteins, haptoglobin, fibrinogen, C3 complement and a 1 -acid glycoprotein, and gene expression of vascular endothelial growth factor, all of whose transcriptional activities are regulated by STAT3. The inhibitory activity of AF on STAT3 phosphorylation was also demonstrated in primary cells, i.e. fibroblast-like synoviocytes from rheumatoid arthritis patients, human umbilical vein endothelial cells and rat astrocytes. Auranofin-mediated inhibition of STAT3 phosphorylation was recovered by pretreatment with antioxidants containing thiol groups. These findings suggest that the anti-inflammatory action of AF is associated with a blockade of JAK1/STAT3 signalling. Thiol-group-reactive proteins may be involved in AF-induced suppression of JAK1/STAT3 phosphorylation.

Electrical stimulation (ES) can activate diverse biostimulatory responses in a range of tissues. Of various forms of ES, the application of biphasic electric current (BEC) is a new approach to bone formation. This study is to investigate the effects and mechanism of action of BEC in osteoblast differentiation and cytokine production in human mesenchymal stromal cells (hMSCs). Using an in vitro culture system with a modified version of the BEC stimulator chip used in our previous study, we exposed hMSCs to a 100 Hz ES with a magnitude of 1.5/15 muA/cm(2) for 250/25 mus. hMSCs showed increased proliferation during static BEC stimulation for 5 days. However, alkaline phosphatase activity and calcium deposition were enhanced in hMSCs 7 days after the stimulation, rather than during the period of ES. BEC induced vascular endothelial growth factor (VEGF) and BMP-2 production; the former can enhance the proliferation of human umbilical vein endothelial cells in culture using conditioned media from BEC cultures. Treatment with selective inhibitors of p38 MAPK (SB203580) or Erk (PD98059), as well as calcium channel blockers (verapamil and nifedipine), reduced the BEC-mediated increase of VEGF expression and cell proliferation. These findings reveal that BEC is involved in the osteoblast differentiation of hMSCs through enhancement of cell proliferation and modulation of the local endocrine environment through VEGF and BMP-2 induction through the activation of MAPK (Erk and p38) and the calcium channel. Thus, local stimulation using BEC might be most beneficial in promoting osteogenic differentiation of hMSCs, resulting in enhanced bone formation for bone tissue engineering.

Orally administered drugs may be metabolized by intestinal microbial enzymes before absorption into the blood. Accordingly, coadministration of drugs affecting the metabolic activities of gut microbes (e.g., antibiotics) may lead to drug-drug interactions (DDI). In this study, gut microbiota-mediated DDI were investigated by studying the pharmacokinetics of lovastatin in antibiotic-treated rats. Incubation of lovastatin with human and rat fecalase preparations produced four metabolites, M1 (demethylbutyryl metabolite), M4 (hydroxylated metabolite), M8 (the active hydroxy acid metabolite), and M9 (hydroxylated M8), indicating involvement of the gut microbiota in lovastatin metabolism. The plasma concentrationtime profiles of M8 were compared after oral administration of lovastatin to control rats or those treated with either ampicillin (100 mg/kg) or an antibiotic mixture consisting of cefadroxil (150 mg/kg), oxytetracycline (300 mg/kg), and erythromycin (300 mg/kg). Pharmacokinetic analyses indicated that systemic exposure to M8 was significantly lower in antibiotic-treated rats compared with controls. In addition, fecal M8 formation decreased by 58.3 and 59.9% in the ampicillin-and antibiotic mixture-treated rats, respectively. These results suggested that antibiotic intake may reduce the biotransformation of orally administered drugs by gut microbiota and that the subsequent impact on microbiota metabolism could result in altered systemic concentrations of either the intact drug and/or its metabolite(s).