Medium cut-off dialyzer improves erythropoiesis stimulating agent resistance in a hepcidin-independent manner in maintenance hemodialysis patients: results from a randomized controlled trial.

The response to erythropoiesis stimulating agents (ESAs) is affected by inflammation linked to middle molecules in hemodialysis (HD) patients. We evaluated the effect of a medium cut-off (MCO) dialyzer on ESA resistance in maintenance HD patients. Forty-nine patients who underwent high-flux HD were randomly allocated to the MCO or high-flux group. The primary outcome was the changes of erythropoietin resistance index (ERI; U/kg/wk/g/dL) between baseline and 12 weeks. The MCO group showed significant decrease in the ESA dose, weight-adjusted ESA dose, and ERI compared to the high-flux group at 12 weeks (p < 0.05). The generalized estimating equation models revealed significant interactions between groups and time for the ESA dose, weight-adjusted ESA dose, and ERI (p < 0.05). Serum iron and transferrin saturation were higher in the MCO group at 12 weeks (p < 0.05). The MCO group showed a greater reduction in TNF-α and lower serum TNF-α level at 12 weeks compared to the high-flux group (p < 0.05), whereas no differences were found in the reduction ratio of hepcidin and serum levels of erythropoietin, erythroferrone, soluble transferrin receptor and hepcidin between groups. HD with MCO dialyzer improves ESA resistance over time compared to high-flux HD in maintenance HD patients. The MCO dialyzer provides superior removal of the inflammatory cytokine and thus improves iron metabolism in a hepcidin-independent manner.

Randomized controlled trial of medium cut-off versus high-flux dialyzers on quality of life outcomes in maintenance hemodialysis patients.

Medium cut-off (MCO) dialyzers help remove larger middle molecules associated with symptoms related to the accumulation of uremic retention solutes. We investigated the effect of an MCO dialyzer on the improvement of quality of life (QOL) in maintenance hemodialysis (HD) patients. Forty-nine HD patients with high-flux dialysis were randomly assigned to either an MCO (Theranova 400, Baxter) or a high-flux (FX CorDiax 80 or 60, Fresenius Medical Care) dialyzer and completed the study. QOL was assessed at baseline and after 12 weeks of treatment using the Kidney Disease Quality of Life Short Form-36, and pruritus was assessed using a questionnaire and visual analog scale. The reduction ratios of middle molecules were also evaluated. Laboratory markers, including serum albumin, did not differ between the two groups after 12 weeks. Removals of kappa and lambda free light chains were greater for MCO dialyzer than high-flux dialyzer. The MCO group had higher scores than the high-flux group in the domains of physical functioning and physical role (75.2 ± 20.8 vs. 59.8 ± 30.1, P = 0.042; 61.5 ± 37.6 vs. 39.0 ± 39.6, P = 0.047, respectively), and the MCO group had lower mean scores for morning pruritus distribution and the frequency of scratching during sleep (1.29 ± 0.46 vs. 1.64 ± 0.64, P = 0.034; 0.25 ± 0.53 vs. 1.00 ± 1.47, P = 0.023, respectively). MCO dialyzers may improve patient-reported outcomes, particularly the physical components of QOL and uremic pruritus, in patients with high-flux dialyzers.

Alpha-1 antitrypsin inhibits formaldehyde-induced apoptosis of human peritoneal mesothelial cells.

BACKGROUND: The alpha-1 antitrypsin (AAT) protein has an important role in the anti-inflammatory and apoptotic response. AAT inhibits not only serine proteases but also cysteine and aspartic proteases. Apoptosis results from the sequential activation of cysteine proteases of the caspase family. This study aimed to evaluate the effect of AAT on formaldehyde-induced apoptosis of human peritoneal mesothelial cells (HPMCs). METHODS: HPMCs were cultured and treated with formaldehyde (250 µM) to induce apoptosis. In the AAT group, the cultured HPMCs were pretreated with AAT (2 mg/mL) for 1 h before formaldehyde treatment. We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays to determine cell viability, and flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assays to detect apoptosis. The MTT assays were used to find optimal concentrations of formaldehyde and AAT. We measured caspase-3 activity and used Western blotting to estimate Bcl-2 and Bad expression. RESULTS: Flow cytometry and TUNEL assays revealed that formaldehyde exposure significantly increased apoptosis compared with the control treatment, but pretreatment with AAT significantly inhibited this effect. Compared with the control, caspase-3 activity was significantly increased and the ratio of Bcl-2 to Bad expression significantly decreased following treatment with formaldehyde. However, caspase-3 activity was significantly lower and the Bcl-2 to Bad expression ratio higher in the AAT group than in the formaldehyde-only group. CONCLUSION: AAT inhibits formaldehyde-induced apoptosis of HPMCs via a caspase-mediated pathway. These data support a potential use for AAT as a therapeutic agent for the inhibition of peritoneal cell apoptosis during peritoneal dialysis.

The emerging role of xanthine oxidase inhibition for suppression of breast cancer cell migration and metastasis associated with hypercholesterolemia.

Hypercholesterolemia is reported to increase reactive oxygen species (ROS) and to promote breast cancer progression. ROS play an important role in tumor biology, and xanthine oxidase (XO) is an enzyme that generates ROS. The effects of febuxostat (FBX), an XO inhibitor, on breast cancer cell migration under LDL stimulation in vitro and metastasis of breast cancer associated with hypercholesterolemia in vivo were studied. In vitro, FBX significantly inhibited LDL-induced ROS production and cell migration. Treatment of small interfering RNA against XO was consistent with the findings of FBX treatment. In vivo, a significant increase of tumor growth and pulmonary metastasis was observed in a xenograft mouse model with 4T1 cells on a high cholesterol diet (HCD), both of which were markedly inhibited by FBX or allopurinol treatment. Moreover, ERK represented the main target-signaling pathway that was affected by FBX treatment in a xenograft mouse model on an HCD evaluated by NanoString nCounter analysis. Consistently, MEK/ERK inhibitors directly decreased the LDL-induced cell migration in vitro. In conclusion, FBX mitigates breast cancer cell migration and pulmonary metastasis in the hyperlipidemic condition, associated with decreased ROS generation and MAPK phosphorylation. The inhibition of ERK pathways is likely to underlie the XO inhibitor-mediated suppression of breast cancer cell migration.-Oh, S.-H., Choi, S.-Y., Choi, H.-J., Ryu, H.-M., Kim, Y.-J., Jung, H.-Y., Cho, J.-H., Kim, C.-D., Park, S.-H., Kwon, T.-H., Kim, Y.-L. The emerging role of xanthine oxidase inhibition for suppression of breast cancer cell migration and metastasis associated with hypercholesterolemia.

Network-based integrated analysis of omics data reveal novel players of TGF-ß1-induced EMT in human peritoneal mesothelial cells.

Long-term peritoneal dialysis is associated with progressive fibrosis of the peritoneum. Epithelial-mesenchymal transition (EMT) of mesothelial cells is an important mechanism involved in peritoneal fibrosis, and TGF-ß1 is considered central in this process. However, targeting currently known TGF-ß1-associated pathways has not proven effective to date. Therefore, there are still gaps in understanding the mechanisms underlying TGF-ß1-associated EMT and peritoneal fibrosis. We conducted network-based integrated analysis of transcriptomic and proteomic data to systemically characterize the molecular signature of TGF-ß1-stimulated human peritoneal mesothelial cells (HPMCs). To increase the power of the data, multiple expression datasets of TGF-ß1-stimulated human cells were employed, and extended based on a human functional gene network. Dense network sub-modules enriched with differentially expressed genes by TGF-ß1 stimulation were prioritized and genes of interest were selected for functional analysis in HPMCs. Through integrated analysis, ECM constituents and oxidative stress-related genes were shown to be the top-ranked genes as expected. Among top-ranked sub-modules, TNFAIP6, ZC3H12A, and NNT were validated in HPMCs to be involved in regulation of E-cadherin, ZO-1, fibronectin, and αSMA expression. The present data shows the validity of network-based integrated analysis in discovery of novel players in TGF-ß1-induced EMT in peritoneal mesothelial cells, which may serve as new prognostic markers and therapeutic targets for peritoneal dialysis patients.

Fimasartan attenuates renal ischemia-reperfusion injury by modulating inflammation-related apoptosis.

Fimasartan, a new angiotensin II receptor antagonist, reduces myocyte damage and stabilizes atherosclerotic plaque through its anti-inflammatory effect in animal studies. We investigated the protective effects of pretreatment with fimasartan on ischemia-reperfusion injury (IRI) in a mouse model of ischemic renal damage. C57BL/6 mice were pretreated with or without 5 (IR-F5) or 10 (IR-F10) mg/kg/day fimasartan for 3 days. Renal ischemia was induced by clamping bilateral renal vascular pedicles for 30 min. Histology, pro-inflammatory cytokines, and apoptosis assays were evaluated 24 h after IRI. Compared to the untreated group, blood urea nitrogen and serum creatinine levels were significantly lower in the IR-F10 group. IR-F10 kidneys showed less tubular necrosis and interstitial fibrosis than untreated kidneys. The expression of F4/80, a macrophage infiltration marker, and tumor necrosis factor (TNF)-α, decreased in the IR-F10 group. High-dose fimasartan treatment attenuated the upregulation of TNF-α, interleukin (IL)-1ß, and IL-6 in ischemic kidneys. Fewer TUNEL positive cells were observed in IR-F10 compared to control mice. Fimasartan caused a significant decrease in caspase-3 activity and the level of Bax, and increased the Bcl-2 level. Fimasartan preserved renal function and tubular architecture from IRI in a mouse ischemic renal injury model. Fimasartan also attenuated upregulation of inflammatory cytokines and decreased apoptosis of renal tubular cells. Our results suggest that fimasartan inhibited the process of tubular injury by preventing apoptosis induced by the inflammatory pathway.

Dipeptidyl peptidase-4 inhibitor gemigliptin protects against vascular calcification in an experimental chronic kidney disease and vascular smooth muscle cells.

Although dipeptidyl peptidase-4 inhibitors, a class of antidiabetic drugs, have various pleiotropic effects, it remains undetermined whether gemigliptin has a beneficial effect on vascular calcification. Therefore, this study was performed to evaluate the effect of gemigliptin on vascular calcification in a rat model of adenine-induced chronic kidney disease and in cultured vascular smooth muscle cells. Gemigliptin attenuated calcification of abdominal aorta and expression of RUNX2 in adenine-induced chronic kidney disease rats. In cultured vascular smooth muscle cells, phosphate-induced increase in calcium content was reduced by gemigliptin. Gemigliptin reduced phosphate-induced PiT-1 mRNA expression, reactive oxygen species generation, and NADPH oxidase mRNA expression (p22phox and NOX4). The reduction of oxidative stress by gemigliptin was associated with the downregulation of phospho-PI3K/AKT expression. High phosphate increased the expression of frizzled-3 (FDZ3) and decreased the expression of dickkopf-related protein-1 (DKK-1) in the Wnt pathway. These changes were attenuated by gemigliptin treatment. Gemigliptin restored the decreased expression of vascular smooth muscle cells markers (α-SMA and SM22α) and increased expression of osteogenic makers (CBFA1, OSX, E11, and SOST) induced by phosphate. In conclusion, gemigliptin attenuated vascular calcification and osteogenic trans-differentiation in vascular smooth muscle cells via multiple steps including downregulation of PiT-1 expression and suppression of reactive oxygen species generation, phospho-PI3K/AKT, and the Wnt signaling pathway.

The role of Toll-like receptor 4 in high-glucose-induced inflammatory and fibrosis markers in human peritoneal mesothelial cells.

PURPOSE: High glucose stimulates peritoneal inflammation and extracellular matrix accumulation in human peritoneal mesothelial cells (HPMCs). However, the roles of Toll-like receptor 4 (TLR4) and TLR2 in high-glucose-induced inflammation and fibrosis in peritoneal dialysis (PD) remain unclear. This study aimed to evaluate the effect of high glucose on TLR2 and TLR4 expression in HPMCs and to assess their impact on peritoneal inflammatory and fibrosis markers. METHODS: Using cultured HPMCs, TLRs expression by high-glucose (50 mM) stimulation was assessed by quantitative real-time PCR. The association of reactive oxygen species (ROS) in high-glucose-induced TLR2 and TLR4 expression was measured by 2',7'-dichlorodihydrofluorescein diacetate staining with or without ROS inhibitor. In addition, the role of TLR2 and TLR4 on high-glucose-induced inflammatory and fibrosis markers including chemoattractant protein-1 (MCP-1), NF-κB, alpha-smooth muscle actin (α-SMA), transforming growth factor-ß (TGF-ß), and fibronectin was evaluated after inhibition of TLR2 and TLR4 by small-interfering RNA (siRNA) or anti-TLR4/TLR2 antibodies, respectively. RESULTS: High glucose induced TLR1, TLR2, and TLR4 mRNAs expressions. High-glucose-induced TLR4 and TLR2 mRNAs were associated partly with the generation of ROS. Inhibition of TLR4 attenuated the high-glucose-induced expression of MCP-1 mRNA and protein, MyD88 mRNA, nuclear NF-κB p65 protein, TGF-ß, fibronectin, and α-SMA mRNA and protein. However, inhibition of TLR2 did not change the expression of MCP-1 mRNA and protein. CONCLUSIONS: High glucose induces inflammatory and fibrosis markers in HPMCs partly through the TLR4/MyD88/NF-κB signaling pathway rather than TLR2. Therefore, TLR4 might be a therapeutic target for ameliorating peritoneal inflammation and fibrosis in PD.

Phosphate-induced apoptosis in human peritoneal mesothelial cells in vitro.

BACKGROUND: It has been demonstrated that phosphate uptake through the type III sodium-dependent phosphate co-transporter, Pit-1, induced apoptosis of aortic vascular smooth muscle cells and endothelial cells in vitro. However, the apoptotic effects of high phosphate (HP) level in human peritoneal mesothelial cells (HPMCs) are not known. METHODS: To examine whether Pit-1 is expressed in HPMCs, we checked the Western blot assay of immunoreactive Pit-1 and the transcription of Pit-1 by reverse transcriptase PCR. We treated several different phosphate concentrations (1-4 mM) and calcium concentrations (1.8 and 2.8 mM) on HPMCs to assess the effects of concentration. MTT, TUNEL assays, and flow cytometry analysis using Annexin V and propidium iodide were performed to identify cell death and apoptosis. Bax and Bcl-2 by Western blot and caspase-3 activity were evaluated by colorimetric assay. In addition, phosphonoformic acid (PFA) and pan-caspase inhibitor, Z-VAD-FMK, were given to prevent phosphate-induced apoptosis. RESULTS: Pit-1 expression on HPMCs was demonstrated. Apoptosis in HPMCs significantly increased with a high concentration of phosphate in a dose- and time-dependent manner, and was enhanced in the presence of 2.8 mM calcium. HP concentrations significantly decreased the anti-apoptotic Bcl-2/Bax ratio and increased caspase-3 activity. The treatment with PFA and Z-VAD-FMK prevented cell death by HP. CONCLUSION: Phosphate uptake through Pit-1 induces apoptosis in HPMCs by a caspase-related mechanism.

Impact of low glucose degradation product bicarbonate/lactate-buffered dialysis solution on the epithelial-mesenchymal transition of peritoneum.

BACKGROUND: Epithelial-mesenchymal transition (EMT) is important in the development of peritoneal fibrosis. Glucose degradation products (GDPs) may induce EMT in human peritoneal mesothelial cells (HPMCs). METHODS: The effects of individual GDPs and GDPs derived from peritoneal dialysis fluid (PDF) in both HPMCs and peritoneal membranes were evaluated. EMT was assessed with alpha-smooth muscle actin (alpha-SMA) and E-cadherin. RESULTS: In vitro, alpha-SMA protein and mRNA levels increased in the presence of the GDPs (formaldehyde, glyoxal, methylglyoxal, and 3-deoxyglucosone), and E-cadherin decreased. Changes in the EMT markers were most prominent after exposure to 3-deoxyglucosone. Changes in both alpha-SMA and E-cadherin protein levels were less with low (L)-GDP bicarbonate/lactate-buffered PDF compared to high (H)-GDP PDF. In the rat model after 8 weeks' PDF infusion, the alpha-SMA/E-cadherin mRNA ratio increased in the H-GDP group compared with the L-GDP group (p < 0.05). The peritoneum in the H-GDP group tended to be thicker (p = 0.052) and had more blood vessels than that in the L-GDP group (p < 0.05). Tissue staining for TGF-beta1 decreased in the L-GDP group. Dual-stained cytokeratin and alpha-SMA-positive myofibroblasts in the submesothelial layer were more prominent in the H-GDP group. CONCLUSION: GDPs found in PDF induce EMT of HPMCs, which is associated with peritoneal fibrosis and vascularization. Conversely, L-GDP PDF reduces EMT and peritoneal fibrosis.

3,4-dideoxyglucosone-3-ene induces apoptosis in human peritoneal mesothelial cells.

OBJECTIVE: Glucose degradation products (GDPs) are formed during heat sterilization and storage of peritoneal dialysis (PD) fluids. 3,4-dideoxyglucosone-3-ene (3,4-DGE) has been identified as the most bioreactive GDP. 3,4-DGE induces apoptosis in leukocytes and renal tubular epithelial cells. Our aim was to evaluate the apoptotic effects of 3,4-DGE on human peritoneal mesothelial cells (HPMCs). METHODS: Primary cultured HPMCs were treated with 25 or 50 micromol/L 3,4-DGE. MTT assay was used to determine cell viability. Apoptosis was measured using TUNEL assay and flow cytometry. Expressions of procaspase-3, Bax, and Bcl-2 were estimated by Western blot. Activity of caspase-3 was measured and the effect of the caspase inhibitor zVAD-fmk (Z-Val-Ala-DL-Asp-fluoromethylketone) was evaluated by TUNEL assay. RESULTS: 3,4-DGE treatment accelerated cell death in HPMCs in a dose- and time-dependent manner. Treatment with 3,4-DGE (25 and 50 micromol/L) significantly increased apoptosis compared to control (p<0.05 and p<0.01 respectively) by TUNEL assay. Flow cytometry showed treatment with 50 micromol/L 3,4-DGE significantly increased apoptosis compared to control (p<0.05). Decreased expression of procaspase-3 and increased activity of caspase-3 were observed in the presence of 50 micromol/L 3,4-DGE compared to control and 25 micromol/L 3,4-DGE (p<0.05). 3,4-DGE-induced HPMC apoptosis was decreased after pretreatment with the pan-caspase inhibitor zVAD-fmk in the 50 micromol/L 3,4-DGE-treated group (p<0.001). The ratio of Bcl-2 to Bax expression was decreased in the 25 micromol/L and the 50 micromol/L 3,4-DGE-treated groups compared to control (p<0.05). CONCLUSIONS: 3,4-DGE promotes apoptosis in HPMCs by a caspase-related mechanism.

The TGF-beta-induced gene product, betaig-h3: its biological implications in peritoneal dialysis.

BACKGROUND: TGF-beta is involved in peritoneal changes during long-term peritoneal dialysis (PD). TGF-beta induces betaig-h3 in several cell lines, and betaig-h3 may be a marker for biologically active TGF-beta. However, no study has reported induction of betaig-h3 in human peritoneal mesothelial cells (HPMCs) or its involvement in PD-related peritoneal membrane changes. METHODS: We used cultured HPMCs to investigate the biological roles of betaig-h3 during mesothelial cell injury and repair, employing the adhesion, spreading, scratching and cell migration assays. Changes in betaig-h3 expression after high glucose exposure in vivo were also evaluated using an animal chronic PD model. RESULTS: In vitro, TGF-beta1 induced betaig-h3 in cultured HPMCs, and betaig-h3-mediated mesothelial cell adhesion occurred via alphavbeta3 integrin. betaig-h3 enhanced mesothelial cell adhesion and migration and, in part, wound healing during mesothelial cell injury. The animal study demonstrated that compared to the control group, betaig-h3 concentrations in the dialysate effluent increased in the dialysis group with alterations in peritoneal structure and function during PD, and betaig-h3 positively correlated with peritoneal solute transport. Immunohistochemical and immunoblotting results showed that betaig-h3 localizes in the mesothelium and submesothelial matrix of the parietal peritoneum, and in the vascular endothelium of omentum. betaig-h3 protein expression was higher in the dialysis group. CONCLUSION: In vitro, betaig-h3 induced by TGF-beta1 in HPMCs improved adhesion and migration of HPMCs during wound healing. In the chronic infusion model of PD, betaig-h3 played a role in the functional deterioration of the peritoneal membrane, which is associated with fibrosis.

Erythropoietin decreases renal fibrosis in mice with ureteral obstruction: role of inhibiting TGF-beta-induced epithelial-to-mesenchymal transition.

The inhibitory effects of recombinant human erythropoietin (rhEPO) were examined against (1) the progression of renal fibrosis in mice with complete unilateral ureteral obstruction and (2) the TGF-beta1-induced epithelial-to-mesenchymal transition (EMT) in MDCK cells. Unilateral ureteral obstruction was induced in BALB/c mice and rhEPO (100 or 1000 U/kg, intraperitoneally, every other day) or vehicle was administered from day 3 to day 14. Immunoblotting and immunohistochemistry revealed increased expressions of TGF-beta1, alpha-smooth muscle actin (alpha-SMA), and fibronectin and decreased expression of E-cadherin in the obstructed kidneys. In contrast, rhEPO treatment significantly attenuated the upregulation of TGF-beta1 and alpha-SMA and the downregulation of E-cadherin. MDCK cells were treated with TGF-beta1 (5 ng/ml) for 48 h to induce EMT, and the cells were then co-treated with TGF-beta1 and rhEPO for another 48 h. Increased expressions of alpha-SMA and vimentin and decreased expressions of zona occludens-1 and E-cadherin were observed after TGF-beta1 treatment, and these changes were markedly attenuated by rhEPO co-treatment. TGF-beta1 increased phosphorylated Smad-2 expression in MDCK cells, which was decreased by rhEPO co-treatment. In conclusion, rhEPO treatment inhibits the progression of renal fibrosis in obstructed kidney and attenuates the TGF-beta1-induced EMT. It is suggested that the renoprotective effects of rhEPO could be mediated, at least partly, by inhibition of TGF-beta1-induced EMT.

Effects of low glucose degradation products peritoneal dialysis fluid on the peritoneal fibrosis and vascularization in a chronic rat model.

In the present study, we examined the effects of a new peritoneal dialysis fluid (PDF) with a low level of low glucose degradation products (GDP) on the functional and structural stability of the peritoneal membrane (PM). Male Sprague-Dawley rats were divided into three groups: group C (n = 8), without dialysate infusion; group P (n = 12), infused with low-level GDP solution (4.25% Physioneal, pH 7.0-7.4); and group D (n = 12), infused with conventional solution (4.25% Dianeal, pH 5.2, adjusted to pH 7.0). In groups D and P, animals were infused through a permanent catheter with 25 mL of PDF, twice daily for 8 weeks. Lipopolysaccharide was added into the PDF immediately before infusion on days 8, 9 and 10 in the two dialysis groups. When compared with group P, group D showed a higher glucose mass transfer at weeks 6 and 8, D/P urea at week 8, TGF-beta1 at weeks 4 and 8, and VEGF level at week 8. The submesothelial matrix layer of the parietal peritoneum was significantly thickened in group D and the lectin-stained blood vessels in this layer were well-visualized in group D compared with group P. There were significantly more peritoneal blood vessels in group D than group P. The transforming growth factor-beta induced gene-h3 (betaig-h3) and TGF-beta1 levels in the peritoneal effluent correlated with the submesothelial thickness, which correlated with the dialysate-to-plasma ratio (D/P) of protein and, inversely, with the rate of glucose transport (D/D(0) glucose, where D is glucose concentration in the dialysate and D(0) is glucose concentration in the dialysis solution before it is infused into the peritoneal cavity). The present study showed that low-GDP PDF effectively attenuated the peritoneal vascularization and fibrosis related to conventional solution.