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The lack of a clonal renin-secreting cell line has greatly hindered the investigation of the regulatory mechanisms of renin secretion at the cellular, biochemical, and molecular levels. In the present study, we investigated whether it was possible to induce phenotypic switching of the renin-expressing clonal cell line As4.1 from constitutive inactive renin secretion to regulated active renin secretion. When grown to postconfluence for at least two days in media containing fetal bovine serum or insulin-like growth factor-1, the formation of cell-cell contacts via N-cadherin triggered downstream cellular signaling cascades and activated smooth muscle-specific genes, culminating in phenotypic switching to a regulated active renin secretion phenotype, including responding to the key stimuli of active renin secretion. With the use of phenotype-switched As4.1 cells, we provide the first evidence that active renin secretion via exocytosis is regulated by phosphorylation/dephosphorylation of the 20 kDa myosin light chain. The molecular mechanism of phenotypic switching in As4.1 cells described here could serve as a working model for full phenotypic modulation of other secretory cell lines with incomplete phenotypes. [ABSTRACT FROM AUTHOR]

Background: We investigated the impact of a transvenous cardiac implantable electronic device (CIED) placement on outcomes and arteriovenous vascular access (VA) patency among chronic hemodialysis patients.Methods: This is a single-center, observational comparative study between chronic hemodialysis patients with ipsilateral and contralateral CIED and VA. Forty-two consecutive patients who underwent both CIED placement and upper-extremity VA for hemodialysis, regardless of the sequence and time interval between these 2 procedures, were identified between January 2001 and December 2017. Patients with ipsilateral (n = 22, 52%, the ipsilateral group) and contralateral (n = 20, 48%, the contralateral group) CIED and VA were compared retrospectively; the primary outcome was any-cause mortality and cardiac mortality or the composite of any systemic complications, defined as central venous stenosis or occlusion, any device infections or tricuspid regurgitation; the secondary outcome was CIED or VA malfunction.Results: During the median follow-up period of 101 months, primary outcome incidence was significantly higher in the ipsilateral group than the contralateral group (73% vs 40%, P = 0.03), although the incidences of any-cause mortality (P = 0.28) and cardiac mortality (P > 0.99) were similar between the groups. Secondary outcome incidence did not differ significantly between the 2 groups (55% vs 30%, P = 0.36). Kaplan-Meier survival analysis revealed similar primary and secondary VA patency rates in both groups. On subgroup analysis, patients with upper arm VA had similar primary and secondary patency to those with forearm VA.Conclusions: Despite some notable limitations of the study, the retrospective study design and small sample size, we found that the any-cause mortality incidence and VA patency did not differ between the 2 groups, but primary outcome incidence was significantly higher among patients with ipsilateral CIED and VA. [ABSTRACT FROM AUTHOR]

Background: Volume overload results in higher mortality rates in patients on continuous ambulatory peritoneal dialysis (CAPD). The ratio of bioimpedance (RBI) might be a helpful parameter in adjusting dry body weight in CAPD patients. This study examined whether it is possible to distinguish between non-hypervolemic status and hypervolemic status in CAPD patients by using only RBI. Methods: RBI was calculated as follows: RBI = impedance at 50 kHz/impedance at 500 kHz. Based on the experts' judgements, a total of 64 CAPD patients were divided into two groups, a non-hypervolemic group and a hypervolemic group. The RBI was measured from right wrist to right ankle (rw-raRBI) by bioimpedance spectroscopy (BCM®, Fresenius Medical Care) before and after the peritosol was emptied. Other RBIs were measured from the right side of the anterior superior iliac spine to the ipsilateral ankle (rasis-raRBI) to control for the electro-physiological effects of peritoneal dialysate. Results: The mean rw-raRBI of non-hypervolemic patients was higher than that of hypervolemic patients in the presence (1.141 ± 0.022 vs. 1.121 ± 0.021, P < 0.001) of a peritosol. Likewise, the mean rasis-raRBI of nonhypervolemic patients was higher than that of hypervolemic patients (presence of peritosol: 1.136 ± 0.026 vs. 1.109 ± 0.022, P < 0.001; absence of peritosol: 1.131 ± 0.022 vs. 1.107 ± 0.022, P < 0.001). Conclusion: The volume status of CAPD patients was able to be simply expressed by RBI. Therefore, this study suggests that when patients cannot be analyzed using BCM, RBI could be an alternative. [ABSTRACT FROM AUTHOR]

Endoplasmic reticulum (ER) stress is increasingly identified as modulator of fibrosis. Losartan, an angiotensin II receptor blocker, has been widely used as the first choice of treatment in chronic renal diseases. We postulated that anti-fibrotic effect of losartan is mediated through inhibition of ER stress via SIRT1 (silent mating type information regulation 2 homolog 1) hemeoxygenase-1 (HO-1)/thioredoxin pathway. Renal tubular cells, tunicamycin (TM)-induced ER stress, and unilateral ureteral obstruction (UUO) mouse model were used. Expression of ER stress was assessed byWestern blot analysis and immunohistochemical stain. ER stress was induced by chemical ER stress inducer, tunicamycin, and non-chemical inducers such as TGF-β, angiotensin II, high glucose, and albumin. Losartan suppressed the TM-induced ER stress, as shown by inhibition of TM-induced expression of GRP78 (glucose related protein 78) and p-eIF2α (phosphospecific-eukaryotic translation initiation factor-2α), through up-regulation of SIRT1 via HO-1 and thioredoxin. Losartan also suppressed the ER stress by non-chemical inducers. In both animal models, losartan reduced the tubular expression of GRP78, which were abolished by pretreatment with sirtinol (SIRT1 inhibitor). Sirtinol also blocked the inhibitory effect of losartan on the UUO-induced renal fibrosis. These findings provide new insights into renoprotective effects of losartan and suggest that SIRT1, HO-1, and thioredoxin may be potential pharmacological targets in kidney diseases under excessive ER stress condition. [ABSTRACT FROM AUTHOR]

The epithelial- mesenchymal transition (EMT) is a novel mechanism that promotes renal fibrosis. Transforming growth factor-β(TGF-β), angiotensin II, aldosterone, high glucose, and urinary albumin are well-known causes of EMT and renal fibrosis. We examined whether and how activation of AMP-activated protein kinase (AMPK) suppressed EMT induced by the above agents in tubular epithelial cells. All experiments were performed using HK-2 cells. Protein expression was measured by Western blot analysis. Intracellular reactive oxygen species (ROS) were analyzed by flow cytometry. Exposure of tubular cells to TGF-β (10 ng/ml), angiotensin II (1 μM), aldosterone (100 nM), high glucose (30 mM), and albumin (5 mg/ml) for 5 days induced EMT, as shown by upregulation of smooth muscle actin and downregulation of E-cadherin. ROS and NADPH oxidase 4 (Nox4) expression were increased, and antioxidants such as tiron and N-acetylcysteine inhibited EMT induction. Metformin (the best known clinical activator of AMPK) suppressed EMT induction through inhibition of ROS via induction of heme oxygenase-1 and endogenous antioxidant thioredoxin. An AMPK inhibitor (compound C) and AMPK small interfering RNA blocked the effect of metformin, and another AMPK activator [5- aminoimidazole-4-carboxamide-1β riboside (AICAR)] exerted the same effects as metformin. In conclusion, AMPK activation might be beneficial in attenuating the tubulointerstitial fibrosis induced by TGF-β, angiotensin II, aldosterone, high glucose, and urinary albumin. [ABSTRACT FROM AUTHOR]

Background: Serum phosphorus concentrations are associated with an increased risk of cardiovascular disease (CVD) and mortality in patients with renal insufficiency. This association has also been reported in Western individuals without chronic kidney disease (CKD). Objective: It is unclear, however, whether this correlation occurs in Korean individuals without CKD, who usually ingest less phosphorus than do Western individuals. Design: We reviewed the findings in 402 healthy Korean adults with a mean (±SD) age of 50.8 ± 8.5 y (n = 257 men and 145 women) and a glomerular filtration rate of 83.5 ± 14.1 mL/min, who underwent health screening with electron-beam computed tomography (EBCT). The study population was separated into 4 groups on the basis of the coronary calcium concentration (Agatston score: 0, >0 to ≤10, >10 to ≤100, and >100). Mean serum phosphorus concentrations, measured ≥10 y before EBCT, were compared. Results: Multivariate analysis showed that age (P = 0.001), male sex (P = 0.002), family history of CVD (P = 0.006), serum glucose (P = 0.003), and serum phosphorus >3.6 mg/dL (P = 0.008) were significant factors influencing the coronary calcification group with an Agatston score >100, when those with an Agatston score of 0 were considered as the reference group. Compared with the group with a serum phosphorus concentration ≤3.3 mg/dL, the OR of an Agatston score >100 in individuals with a serum phosphorus concentration >3.6 to ≤3.9 mg/dL was 3.89 (95% CI: 1.43, 10.63; P = 0.008) and in those with a serum phosphorus concentration >3.9 mg/dL was 3.17 (95% CI: 1.19, 8.41; P = 0.021). Conclusion: A lower concentration of serum phosphorus within the normal range could be associated with less calcification of the coronary artery in Koreans with normal renal function. [ABSTRACT FROM AUTHOR]

The epithelial-mesenchymal transition (EMT) and endoplasmic reticulum (ER) stress induced by urinary protein, particularly albumin, play an important role in tubulointerstitial injury. However, signaling pathways regulating both albumin-induced EMT and ER stress are not precisely known. We postulated that reactive oxygen species (ROS), c-Src kinase, and mammalian target of rapamysin (mTOR) would act as upstream signaling molecules. We further examined the effect of imatinib mesylate on these processes. All experiments were performed using HK-2 cells, a human proximal tubular cell line. Protein and mRNA expression were measured by Western blot analysis and real-time PCR, respectively. Exposure of tubular cells to albumin (5 mg/ml) for up to 5 days induced EMT in a time-dependent manner, as shown by conversion to the spindle-like morphology, loss of E-cadherin protein, and upregulation of α-smooth muscle actin mRNA and protein. Albumin also induced ER stress as evidenced by phosphorylation of eukaryotic translation initiation factor-2α and increased expression of GRP78 mRNA and protein. Albumin induced ROS, c-Src kinase, and mTOR as well. Antioxidants, c-Src kinase inhibitor (PP2), and mTOR inhibitor (rapamycin) suppressed the albumin-induced EMT and ER stress. Antioxidants and PP2 inhibited the albumin-induced c-Src kinase and mTOR, respectively. Imatinib suppressed the albumin-induced EMT and ER stress via inhibition of ROS and c-Src kinase. Imatinib also inhibited the albumin-induced mRNA expression of MCP-1, VCAM-1, transforming growth factor (TGF)-β1, and collagen I (α1). In conclusion, the ROS-c-Src kinase-mTOR pathway played a central role in the signaling pathway that linked albumin to EMT and ER stress. Imatinib might be beneficial in attenuating the albumin-induced tubular injury. [ABSTRACT FROM AUTHOR]

Background: Fatty acid-bearing albumin [FA(+) albumin] exerts more deleterious effects in tubular cells than albumin alone. We investigated the effect of FA(+) albumin on the vascular cell adhesion molecule-1 (VCAM-1) expression and elucidated the underlying signaling pathways. We further examined the effect of L-carnitine, since it was known to modulate intracellular fatty acid concentration. Methods: Activation of AP-1 and NF-κB was assessed by electrophoretic mobility shift assay. Phosphorylation of protein kinase was examined by Western blot analysis. VCAM-1 mRNA and protein expression were measured by Northern blot analysis and cell ELISA. Results: FA(+) albumin induced VCAM-1 expression via activation of AP-1 and NF-κB, which was mediated through activation of c-Src kinase, followed by MAP kinases (p38, ERK 1/2, JNK-1) and IκB kinase and IκB-α, respectively. Inhibitors of protein kinase C and tyrosine kinase, anti-oxidants and intracellular calcium chelator suppressed the FA(+) albumin-induced activation of c-Src kinase. L-Carnitine suppressed the FA(+) albumin-induced VCAM-1 expression via inhibition of c-Src kinase. Conclusions: VCAM-1 expression with activation of c-Src kinase-AP-1/NFκB pathways might be one of the possible mechanisms that linked FA(+) albumin to tubulointerstitial injury. L-Carnitine might be beneficial in attenuating FA(+) albumin-induced tubular injury. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Aim: i.v. iron therapy is more effective in maintaining adequate iron status in haemodialysis (HD) patients than oral iron therapy (OIT). However, data on lower doses of i.v. iron therapy are insufficient. Methods: A non-randomized, open-label study was performed to compare the efficacy of low-dose (≤50 mg/week of iron sucrose) i.v. iron therapy (LD-IVIT) with OIT in HD patients with 100–800 µg/L serum ferritin levels over 4 months. Results: Eighty-nine patients in the LD-IVIT group (40 men, 49 women; aged 61 ± 13 years) and 30 patients in the oral iron therapy group (17 men, 13 women; aged 59 ± 7 years) were evaluated. After 4 months of each treatment, serum ferritin levels increased from 398 ± 137 to 529 ± 234 µg/L in the LD-IVIT group ( P < 0.01) but decreased from 351 ± 190 to 294 ± 175 µg/L in the OIT group ( P < 0.01). In the LD-IVIT group, transferrin saturation (from 28% ± 11% to 30% ± 14%, P = 0.49), weekly doses of recombinant human erythropoietin (from 5822 ± 2354 to 5636 ± 2306 IU/week, P = 0.48) and haemoglobin (from 101 ± 9 to 103 ± 9 g/L, P = 0.15) levels remained stable. Conclusion: LD-IVIT may be one of the regimens that may be considered for maintaining iron status in HD patients. However, efficacy of LD-IVIT should be verified by further randomized study. [ABSTRACT FROM AUTHOR]

Background: Although several previous studies have reported that kidney donors are not at increased risk for adverse effects, some donors have been found to progress to chronic kidney disease (CKD). We retrospectively evaluated the risk factors for estimated glomerular filtration rate (GFR) from abbreviated Modification of Diet in Renal Disease (MDRD) equation (MDRD-GFR) of less than 60 mL/min per 1.73 m2 in kidney donors. Methods: Of the 756 individuals who underwent open donor nephrectomy between 27 June 1990 and 30 April 2001, 104 had follow-up records for 50 months or more. MDRD-GFR of 60 mL/min per 1.73 m2 at final follow up divided these individuals into a normal group ( n = 78) and a CKD-GFR group ( n = 26). We compared several clinical parameters between the two groups at baseline and follow up to evaluate the risk factors for MDRD-GFR of less than 60 mL/min per 1.73 m2 in kidney donors. Results: The CKD-GFR group was significantly older than the normal group at baseline (47 ± 12 vs 41 ± 11 years old, P = 0.02). Hypertension was more prevalent in the CKD-GFR group at baseline (15% vs 2%, P = 0.005). Binary logistic regression analysis showed that age (Odds ratio (OR) 1.06, 95% confidence interval (CI) 1.01–1.10) and hypertension (OR 7.91, 95% CI 1.13–55.2) at baseline were independent risk factors for MDRD-GFR of less than 60 mL/min per 1.73 m2. At final follow up, the prevalence rates of hypertension (31% vs 8%, P = 0.006) and proteinuria (15% vs 0%, P = 0.003) were significantly higher in the CKD-GFR group. Conclusion: Older kidney donors and those with hypertension were significantly more likely to have a MDRD-GFR of less than 60 mL/min per 1.73 m2. [ABSTRACT FROM AUTHOR]

Backgrounds: Immunological staining of the transplanted kidney for C4d in peritubular capillaries (C4dPTC) has emerged as a useful method to detect antibody-mediated rejection in situ. In this retrospective study, we evaluated the prevalence of C4dPTC deposition in allograft renal biopsies diagnosed of IgA nephropathy (IgAN) and analysed its clinical significance. Method: Sixty-six biopsy specimens of post-transplant IgAN, which were obtained to evaluate azotemia and/or heavy proteinuria, were examined by immunohistochemical staining of the paraffin sections with polyclonal antibody for C4d. Results: C4d was stained positively in peritubular capillaries in 16 (24%) of the 66 cases. The C4dPTC-negative (n=50) and C4dPTC-positive groups (n=16) were not different in recipient gender, age, donor age, type of donor (living vs. cadaveric), interval from transplantation to graft biopsy (41.6± 21.8 vs. 48.3±26.1 months) and post-biopsy follow-up period (60.3±23.3 vs. 56.9±25.4 months). During the follow-up period, 12 of 50 (24%) although the incidence of graft failure was not different by the C4d deposition in peritubular capillaries, intervals from renal biopsy to graft failure tended to be shorter in C4dPTC-positive cases than C4dPTC-negative cases. In Kaplan–Meier analysis, the renal allograft function of the C4dPTC-positive group deteriorated more rapidly than that of the C4dPTC-negative group (p<0.05). Histologically, the C4dPTC-positive group had findings suggestive of acute cellular rejection more commonly than the C4dPTC-negative group (p<0.01). Conclusions: Evidence of humoral rejection, as demonstrated by C4dPTC deposition, was concurrently present in significant portions of post-transplant IgAN biopsy specimens and was associated with more rapid deterioration of renal function. These results suggest that C4dPTC positivity needs to be determined at the time of biopsy even in cases of post-transplant glomerulonephritis and immunosuppression may need to be modified accordingly. [ABSTRACT FROM AUTHOR]

Background: C-reactive protein (CRP) is known to have a direct proinflammatory effect in endothelial cells. However, little is known about the effect of CRP in intrinsic renal cells. We investigated the effects of CRP on the nuclear factor-κB (NF-κB) activation and monocyte chemoattractant protein-1 (MCP-1) gene expression in human mesangial cells and also examined whether intracellular calcium and reactive oxygen species (ROS) were involved in the CRP- induced NF-κB activation. Methods: NF-κB binding activity and MCP-1 mRNA expression were measured by electrophoretic mobility shift assay and Northern blot analysis, respectively.Intracellular calcium was monitored by confocal microscopy using calcium sensitive dye, Fluo-3 and intracellular ROS production was determined, using 2′,7′-dichlorofluorescin diacetate. Results: CRP increased NF-κB binding activity in a dose-dependent manner (12.5–100 μg/ml), which was induced within 1 h after incubation and peaked around 3 h. CRP also increased the MCP-1 mRNA expression via activation of NF-κB. Both intracellular calcium and ROS was induced by CRP. Calcium chelator, BAPTA-AM and anti-oxidants such as N-acetylcysteine and tiron suppressed CRP-induced NF-κB activation. Conclusion: CRP exerted a proinflammatory effect in human mesangial cells by inducing MCP-1 gene expression via NF-κB activation, which was mediated, at least in part, through intracellular calcium and ROS. Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background/Aims: It is not clear whether a sublethal dose of myoglobin induces some pathophysiological changes in tubular cells, potentially affecting tubular injury or tubular regeneration. We investigated the effect of a low dose of myoglobin on vascular cell adhesion molecule-1 (VCAM-1) expression and elucidated the underlying signaling pathways. We further examined the effect of losartan and simvastatin on myoglobin-induced VCAM-1 expression and the signaling pathways. Methods: Activation of nuclear factor (NF)-κB and activator protein (AP)-1 was assessed by electrophoretic mobility shift assay. Phosphorylation of protein kinases was examined by Western blot analysis. VCAM-1 mRNA and protein were measured by Northern blot analysis and cell ELISA. Results: A sublethal dose of myoglobin (100 μg/ml) induced VCAM-1 expression via activation of AP-1 and NF-κB, which was mediated through activation of c-Src kinase, followed by mitogen-activated protein kinases (p38, ERK 1/2, JNK-1) and the IκB kinase – IκB-α. Inhibitors of protein kinase C and tyrosine kinase, antioxidants and intracellular calcium chelator suppressed myoglobin-induced activation of c-Src kinase. Losartan and simvastatin suppressed myoglobin-induced VCAM-1 expression via inhibition of c-Src kinase. Conclusion: VCAM-1 expression via c-Src kinase-AP-1/NF-κB pathways might be one of the possible mechanisms linking myoglobin to tubular injury. Losartan and simvastatin might be beneficial in attenuating myoglobin-induced tubular injury. Copyright © 2009 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background/Aims: Accurate measurement of glomerular filtration rate (GFR) is critical for the management of kidney transplant recipients. Comparison of creatinine and cystatin C in renal transplant recipients gave conflicting results. We aimed to compare the performance of creatinine- and cystatin C-based equations and creatinine clearance in 102 early postoperative Korean renal transplant patients. Methods: We measured 51Cr-EDTA clearance using a 2-compartment model and considered this the reference GFR. Then, we estimated GFR using 13 creatinine- and 7 cystatin C-based equations. Serum creatinine value was calibrated to isotope-dilution mass spectrometry (IDMS). Results: The mean reference GFR was 76.77 ± 17.01 ml/min/1.73 m2. The IDMS-traceable MDRD (IDMS-MDRD) equation had the highest accuracy (94.12 within 30% of the reference; 99.02 within 50% of the reference) with a bias of 0.33 ml/min/1.73 m2 and a precision of 12.57 ml/min/1.73 m2. The Mayo Clinic equation also performed well (92.16% within 30% of the reference; 99.02% within 50% of the reference; bias: –0.19 ml/min/1.73 m2). As for cystatin C-based equations, the Filler equation had the least bias (0.03 ml/min/1.73 m2) but low accuracy (78.43% within 30% of the reference). Conclusions: We conclude that the IDMS-MDRD equation provided the best estimate of GFR in our early postoperative Korean renal transplant patients. Copyright © 2009 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background/Aims: The development of renal injury in glomerulonephritis (GN) has been related to systemic inflammatory mediators. We investigated whether serum high-sensitivity C-reactive protein (hs-CRP) is a marker reflecting the inflammatory pathogenesis of primary GN. Methods: We compared serum hs-CRP levels in 192 patients with IgA nephropathy (IgAN), 43 patients with membranous nephropathy (MN), and 25 patients with minimal change disease (MCD) undergoing kidney biopsy and 638 matched controls. Results: There were no differences in hs-CRP levels between controls (median 0.08 mg/dl; range 0.03–1.87 mg/dl) and patients with IgAN (0.08 mg/dl; 0.03–3.13 mg/dl), MN (0.07 mg/dl; 0.03–0.99 mg/dl) or MCD (0.08 mg/dl; 0.03–1.75 mg/dl). In patients with IgAN, hs-CRP levels did not differ according to Haas’ pathological subclasses or subsequent renal outcomes. In the IgAN group, hs-CRP showed positive correlations with IgA, uric acid, systolic blood pressure, BMI and age. Hs-CRP level was significantly higher in male than in female IgAN patients. Serum IgA concentration was the strongest independent correlate with hs-CRP levels, and gender and BMI were also independently associated with hs-CRP. There were no correlations between hs-CRP and markers of disease activity. Conclusion: It is likely that hs-CRP does not closely reflect inflammatory pathogenesis in patients with IgAN, MN and MCD. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]