Elevated glucose induction of thrombospondin-1 up-regulates fibronectin synthesis in proximal renal tubular epithelial cells through TGF-β1 dependent and TGF-β1 independent pathways

Background. TGF-β1 bioactivation, consequent to the interaction of latent TGF-β1 with thrombospondin-1 (TSP-1), correlates with matrix accumulation in mesangial cells. Tubulointerstitial damage predicts poor renal survival. There is little data on TGF-β1 bioactivation and matrix synthesis in human proximal renal tubular epithelial cells under the influence of high glucose concentrations. This study thus investigates the role of TSP-1 in mediating elevated glucose-induction of TGF-β1 bioactivation and fibronectin (FN) synthesis in human proximal tubular epithelial cells. Methods. Human proximal renal tubular epithelial cells (HK-2 cells) were incubated with 5, 10, 20 or 30 mM D-glucose for up to 3 weeks either in the presence or absence of TSP-1 blocking peptide. In separate studies HK-2 cells were incubated with exogenous TSP-1 (0-10 ng/ml) or TGF-β1 (0-10 ng/ml) for 24 h. Cell proliferation was assessed by [ 3H]-thymidine incorporation. TGF-β1 transcript, secretion and bioactivity were investigated by quantitative real-time PCR, ELISA and the MLEC bioassay respectively. TSP-1 and FN synthesis were assessed by quantitative real-time PCR, ELISAs and Western blot analysis. Results. Elevated glucose concentrations increased TSP-1 synthesis, which was associated with reduced cell proliferation, increased TGF-β1 bioactivity, and stimulation of FN synthesis. The inclusion of TSP-1 blocking peptide to cells stimulated with elevated glucose concentration abrogated activation of TGF-β1 and induction of FN secretion. Exogenous TSP-1 increased bioactive TGF-β1 in HK-2 cells to initiate FN accumulation. Of interest is our observation that TSP-1 also increased matrix synthesis through a mechanism independent of TGF-β1. TGF-β1 in turn modulated TSP-1 synthesis, indicative of an autocrine loop between TSP-1 and TGF-β1. Conclusions. TSP-1 plays an important role in the induction of matrix synthesis by high glucose concentrations in human proximal renal tubular epithelial cells, through TGF-β1 dependent and TGF-β1 independent pathways. Pharmacological intervention targeting increased TSP-1 expression may interrupt the pathogenesis of diabetic nephropathy. © 2006 Oxford University Press.link_to_OA_fulltex

Elevated glucose induction of thrombospondin-1 up-regulates fibronectin synthesis in proximal renal tubular epithelial cells through TGF-β1 dependent and TGF-β1 independent pathways

Background. TGF-β1 bioactivation, consequent to the interaction of latent TGF-β1 with thrombospondin-1 (TSP-1), correlates with matrix accumulation in mesangial cells. Tubulointerstitial damage predicts poor renal survival. There is little data on TGF-β1 bioactivation and matrix synthesis in human proximal renal tubular epithelial cells under the influence of high glucose concentrations. This study thus investigates the role of TSP-1 in mediating elevated glucose-induction of TGF-β1 bioactivation and fibronectin (FN) synthesis in human proximal tubular epithelial cells. Methods. Human proximal renal tubular epithelial cells (HK-2 cells) were incubated with 5, 10, 20 or 30 mM D-glucose for up to 3 weeks either in the presence or absence of TSP-1 blocking peptide. In separate studies HK-2 cells were incubated with exogenous TSP-1 (0-10 ng/ml) or TGF-β1 (0-10 ng/ml) for 24 h. Cell proliferation was assessed by [ 3H]-thymidine incorporation. TGF-β1 transcript, secretion and bioactivity were investigated by quantitative real-time PCR, ELISA and the MLEC bioassay respectively. TSP-1 and FN synthesis were assessed by quantitative real-time PCR, ELISAs and Western blot analysis. Results. Elevated glucose concentrations increased TSP-1 synthesis, which was associated with reduced cell proliferation, increased TGF-β1 bioactivity, and stimulation of FN synthesis. The inclusion of TSP-1 blocking peptide to cells stimulated with elevated glucose concentration abrogated activation of TGF-β1 and induction of FN secretion. Exogenous TSP-1 increased bioactive TGF-β1 in HK-2 cells to initiate FN accumulation. Of interest is our observation that TSP-1 also increased matrix synthesis through a mechanism independent of TGF-β1. TGF-β1 in turn modulated TSP-1 synthesis, indicative of an autocrine loop between TSP-1 and TGF-β1. Conclusions. TSP-1 plays an important role in the induction of matrix synthesis by high glucose concentrations in human proximal renal tubular epithelial cells, through TGF-β1 dependent and TGF-β1 independent pathways. Pharmacological intervention targeting increased TSP-1 expression may interrupt the pathogenesis of diabetic nephropathy. © 2006 Oxford University Press.link_to_OA_fulltex

Membrane fouling in an anaerobic membrane bioreactor: Differences in relative abundance of bacterial species in the membrane foulant layer and in suspension

A laboratory anaerobic membrane bioreactors (AnMBRs) (10L volume) was operated at 30°C and fed with artificial sewage containing 30% protein at COD loading rate 5.1kg/m3-d to investigate membrane fouling with two membranes. Biomass attached to the membrane surface and formed a foulant layer on the membrane. The foulant layers from polyvinylidene fluoride ultrafiltration membranes coated with PEBAX (cPVDF) and an uncoated polyetherimide (PEI) ultrafiltration membranes were analyzed and compared to suspended biomass in the reactor, using terminal restriction fragments (T-RFs) of the 16S rRNA gene and a clone library. One species of OP11 bacteria was present at high relative abundance in the foulant layers of both membranes. By contrast, Bacteroidetes and Firmicutes (LGC) species were present at low relative abundance in the foulant layers but high relative abundance in the suspended biomass. Similar differences were observed for other species. The results suggest that some minority species like OP11 play a direct role in fouling by attaching to the membrane surface while others, including some that likely play a major role in the metabolism of influent organics, play a less important or indirect role. In the AnMBR, the EPS was predominately proteinaceous. EPS and microbial cells of the foulant layer contributed to membrane fouling. The results also indicate that fouling of PEI was faster than cPVDF and this reaffirm the importance of the membrane material in fouling. © 2010 Elsevier B.V.link_to_subscribed_fulltex

Simultaneous multifunctional sorption of PFOS and Cr(VI) on activated carbon prepared by one-step microwave activation

Multifunctional sorbents, activated carbons (AC), were prepared by one-step microwave activation utilizing peanut shells and sunflower seed husks. The influence of the original particle size of raw materials on the yield and specific surface area of AC was studied, which reached 33.5 % and 1133.27 m(2)/g, respectively. The repetitive and competitive uptakes of perfluorooctane sulfonate (PFOS) and chromium were applied to investigate the sorption properties of AC. The sorption mechanisms were demonstrated using sulfur Kedge X-ray absorption near edge structure analysis (XANES). In the repetitive experiment, AC made from peanut shells (AC(P05)) still retained 70 % removal efficiency of PFOS after the fourth sorption because sorbed PFOS might form a new organic phase that supplied effective sites for the hydrophobic partition of PFOS. However, the removal efficiency of Cr(VI) decreased dramatically from 60 to 11 % after the fourth uptake because electrostatic attraction was its only removal pathway. In the binary solutes system, AC(P05) possessed perfect sorption performance for both PFOS and Cr(VI), which were 885 and 192 mg/g, respectively. In the multivariate solutes system, the XANES spectra indicated that the thiol functional group existed in the resulting AC and a metal chelate was formed between thiol and Zn2+/Cu2+. Hence, the presence of Zn2+/Cu2+ further promoted the removal of PFOS and Cr(VI) through the electrostatic attraction between the anions and positive metal chelate