Cell-cell contacts via N-cadherin induce a regulatory renin secretory phenotype in As4.1 cells.

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.

Febuxostat, a novel inhibitor of xanthine oxidase, reduces ER stress through upregulation of SIRT1-AMPK-HO-1/thioredoxin expression.

BACKGROUND: Endoplasmic reticulum (ER) stress has been implicated in the development of various renal diseases. Thus, inhibition of ER stress using pharmacological agents may serve as a promising therapeutic approach. We postulated that febuxostat, a novel xanthine oxidase inhibitor, could suppress the ER stress through upregulation of SIRT1 (silent mating type information regulation 2 homolog 1)-AMPK (AMP activated protein kinase)-HO-1 (heme oxygenase-1)/thioredoxin expression. METHODS: We examined the effect of febuxostat on the ER stress induced by a chemical inducer, tunicamycin and non-chemical agents such as angiotensin II, aldosterone, high glucose, and albumin in renal tubular cells. We further examined the in vivo effects of febuxostat using mouse model of kidney disease induced by unilateral ureteral obstruction (UUO). Expression of ER stress was measured by western blot analysis and immunohistochemical stain. RESULTS: Febuxostat suppressed the ER stress induced by tunicamycin and non-chemical agents, as shown by inhibition of increased GRP78 (glucose-related protein78) and p-eIF2α (phosphospecific-eukaryotic translation initiation factor 2α) expression. Inhibitory effect of febuxostat was mediated through upregulation of SIRT1-AMPK followed by induction of HO-1 and thioredoxin. In animal model of UUO, febuxostat reduced the UUO-induced ER stress, which was abolished by pretreatment with SIRT1 inhibitor (sirtinol) and AMPK inhibitor (compound C). CONCLUSION: Febuxostat could suppress the ER stress caused by various ER stress inducers through upregulation of SIRT1-AMPK-HO-1/thioredoxin expression. Targeting these pathways might serve as one of the possible therapeutic approaches in kidney diseases under excessive ER stress.

Outcomes of arteriovenous access among cancer patients requiring chronic haemodialysis.

BACKGROUND: There are limited data focusing specifically on the types of arteriovenous (AV) access used and outcomes of AV access among cancer patients as a consequence of cancer. We aimed to describe outcomes of AV access among cancer patients requiring chronic haemodialysis, and also to compare outcomes between patients with and without cancer. METHODS: In this single-centre, retrospective, observational cohort study, 84 patients diagnosed with cancer before AV access placement were included; we analysed outcomes of AV access among these patients and compared these outcomes with our previous results. The study endpoints were AV access patency and early failure, defined as AV access abandonment within 12 months after AV access placement. RESULTS: Various cancer types, stages, and treatments were identified in our analysis. Autologous arteriovenous fistulas (AVFs) were used for 92.9% of this study population. Using our previous results for comparison, we found no significant difference in death-censored primary (P = 0.546) and secondary (P = 0.266) patency of AV access between patients with and without cancer; however, the rate of early AVF failure was statistically significantly higher among cancer patients (25.6% vs 13.9%; P = 0.008), and the most common cause of AVF failure was patient death. The rate of early failure was significantly higher among patients with advanced-stage cancer (59.1%) than among those with early-stage cancer (12.9%) (P <  0.001). CONCLUSIONS: Although AV access patency rates were similar among patients with and without cancer in the death-censored analysis, cancer patients were more prone to early AVF failure, mainly due to cancer-associated deaths, and this consideration needs to be carefully balanced against individual patients' life expectancies, according to cancer type and stage.

Effects of patient age on patency of chronic hemodialysis vascular access.

BACKGROUND: In this single-center, retrospective observational study, we assessed the long-term patency of vascular access (VA) after first VA placement to uncover independent risk factors associated with VA patency in Asian hemodialysis (HD) patients stratified by age. We also investigated factors associated with VA patency among older HD patients according to the type of VA in the overall study population. METHODS: The study period was from January 2011 to December 2013. A total of 651 chronic HD patients with confirmed first upper-extremity VA placement were enrolled, and their records were analyzed retrospectively. A total of 445 patients (68.4%) made up the nonelderly group (< 65 years), and 206 patients (31.6%) were in the elderly group (≥ 65 years). Study outcomes were defined as primary or secondary VA patency. RESULTS: Autologous arteriovenous fistula (AVF) was more common in the nonelderly group (P <  0.01). Kaplan-Meier curve survival analysis indicated that primary patency was longer in the nonelderly group (P <  0.01); secondary patency, however, was similar between groups (P = 0.37). The multivariate analysis of factors associated with primary VA patency revealed that increased age (hazard ratio [HR], 1.02; 95% confidence interval [CI], 1.01-1.03; P <  0.01) was associated with shorter primary patency, and AVF (HR, 0.38; 95% CI, 0.28-0.51; P <  0.01) was associated with longer primary patency. AVF (HR, 0.57; 95% CI, 0.37-0.87; P = 0.010) and diabetes mellitus (HR, 1.56; 95% CI, 1.07-2.29; P = 0.02) were independently associated with longer and shorter secondary patency periods, respectively; however, increased age was not a risk factor for decreased secondary patency. CONCLUSIONS: Increased age was associated with shorter primary patency but not secondary patency, whereas AVF placement was associated with longer primary and secondary patency. Considering the similar rates of secondary patency between groups and the superior patency of AVF compared to arteriovenous graft, a fistula-first strategy should be applied to appropriate older patients.

Impact of transvenous cardiac implantable electronic devices in chronic hemodialysis patients: a single-center, observational comparative study.

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.

Change in alkaline phosphatase activity associated with intensive care unit and hospital length of stay in patients with septic acute kidney injury on continuous renal replacement therapy.

BACKGROUND: Evidence suggests that alkaline phosphatase attenuates inflammatory response in sepsis by lipopolysaccharide detoxification and adenosine triphosphate dephosphorylation. We sought to determine changes in alkaline phosphatase (AP) activity during septic acute kidney injury (AKI) and clinical parameters associated with AP activity. METHODS: In this retrospective study, we investigated baseline (when initiating CRRT) and follow-up AP activity on day 3, and associated outcomes in patients who underwent continuous renal replacement therapy (CRRT) due to septic AKI. RESULTS: We analyzed the baseline AP activity of 155 patients and day 3 AP activity in 123 patients. Baseline AP activity was not associated with renal or inflammatory biomarkers, or outcomes. It did not significantly differ between the 75 survivors and 80 non-survivors (p = 0.155). AP activity was higher on day 3 than at baseline (105 U/L [interquartile range, 79-156] vs 90 U/L [interquartile range, 59-133]). In particular, liver and bone isoforms increased significantly (p < 0.05), but intestine isoforms did not reach statistical significance (p = 0.367). In addition, day 3 AP activity showed a weak correlation with length of ICU stay (r = 0.213, p = 0.018) and length of hospital stay (r = 0.216, p = 0.017), but not with survival (r = - 0.035, p = 0.698). CONCLUSION: Endogenous AP activity significantly increased in patients with septic AKI. However, neither baseline nor follow-up AP activity was associated with survival.

Anti-Fibrotic Effect of Losartan, an Angiotensin II Receptor Blocker, Is Mediated through Inhibition of ER Stress via Up-Regulation of SIRT1, Followed by Induction of HO-1 and Thioredoxin.

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 by Western blot analysis and immunohistochemical stain. ER stress was induced by chemical ER stress inducer, tunicamycin, and non-chemical inducers such as TGF-ß, 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.

Clinical Outcomes of Cryopreserved Arterial Allograft Used as a Vascular Conduit for Hemodialysis.

This single center cohort study aimed to test the hypothesis that use of a cryopreserved arterial allograft could avoid the maturation or healing process of a new vascular access and to evaluate the patency of this technique compared with that of vascular access using a prosthetic graft. Between April 2012 and March 2013, 20 patients underwent an upper arm vascular access using a cryopreserved arterial allograft for failed or failing vascular accesses and 53 using a prosthetic graft were included in this study. The mean duration of catheter dependence, calculated as the time interval from upper arm access placement to removal of the tunneled central catheter after successful cannulation of the access, was significantly longer for accesses using a prosthetic graft than a cryopreserved arterial allograft (34.4 ± 11.39 days vs. 4.9 ± 8.5 days, P < 0.001). In the allograft group, use of vascular access started within 7 days in 16 patients (80%), as soon as from the day of surgery in 10 patients. Primary (unassisted; P = 0.314) and cumulative (assisted; P = 0.673) access survivals were similar in the two groups. There were no postoperative complications related to the use of a cryopreserved iliac arterial allograft except for one patient who experienced wound hematoma. In conclusion, upper arm vascular access using a cryopreserved arterial allograft may permit immediate hemodialysis without the maturation or healing process, resulting in access survival comparable to that of an access using a prosthetic graft.

AMP-activated protein kinase inhibits TGF-ß-, angiotensin II-, aldosterone-, high glucose-, and albumin-induced epithelial-mesenchymal transition.

The epithelial-mesenchymal transition (EMT) is a novel mechanism that promotes renal fibrosis. Transforming growth factor-ß (TGF-ß), 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-ß (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 α-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-1ß riboside (AICAR)] exerted the same effects as metformin. In conclusion, AMPK activation might be beneficial in attenuating the tubulointerstitial fibrosis induced by TGF-ß, angiotensin II, aldosterone, high glucose, and urinary albumin.

Spleen tyrosine kinase mediates high glucose-induced transforming growth factor-ß1 up-regulation in proximal tubular epithelial cells.

The role of spleen tyrosine kinase (Syk) in high glucose-induced intracellular signal transduction has yet to be elucidated. We investigated whether Syk is implicated in high glucose-induced transforming growth factor-ß1 (TGF-ß1) up-regulation in cultured human proximal tubular epithelial cells (HK-2 cell). High glucose increased TGF-ß1 gene expression through Syk, extracellular signal-regulated kinase (ERK), AP-1 and NF-κB. High glucose-induced AP-1 DNA binding activity was decreased by Syk inhibitors and U0126 (an ERK inhibitor). Syk inhibitors suppressed high glucose-induced ERK activation, whereas U0126 had no effect on Syk activation. High glucose-induced NF-κB DNA binding activity was also decreased by Syk inhibitors. High glucose increased nuclear translocation of p65 without serine phosphorylation of IκBα and without degradation of IκBα, but with an increase in tyrosine phosphorylation of IκBα that may account for the activation of NF-κB. Both Syk inhibitors and Syk-siRNA attenuated high glucose-induced IκBα tyrosine phosphorylation and p65 nuclear translocation. Depletion of p21-activated kinase 2 (Pak2) by transfection of Pak2-siRNA abolished high glucose-induced Syk activation. In summary, high glucose-induced TGF-ß1 gene transcription occurred through Pak2, Syk and subsequent ERK/AP-1 and NF-κB pathways. This suggests that Syk might be implicated in the diabetic kidney disease.

Hepatorenal syndrome: Current concepts and future perspectives.

Hepatorenal syndrome (HRS), a progressive but potentially reversible deterioration of kidney function, remains a major complication in patients with advanced cirrhosis, often leading to death before liver transplantation (LT). Recent updates in the pathophysiology, definition, and classification of HRS have led to a complete revision of the nomenclature and diagnostic criteria for HRS type 1, which was renamed HRS-acute kidney injury (AKI). HRS is characterized by severe impairment of kidney function due to increased splanchnic blood flow, activation of several vasoconstriction factors, severe vasoconstriction of the renal arteries in the absence of kidney histologic abnormalities, nitric oxide dysfunction, and systemic inflammation. Diagnosis of HRS remains a challenge because of the lack of specific diagnostic biomarkers that accurately distinguishes structural from functional AKI, and mainly involves the differential diagnosis from other forms of AKI, particularly acute tubular necrosis. The optimal treatment of HRS is LT. While awaiting LT, treatment options include vasoconstrictor drugs to counteract splanchnic arterial vasodilation and plasma volume expansion by intravenous albumin infusion. In patients with HRS unresponsive to pharmacological treatment and with conventional indications for kidney replacement therapy (KRT), such as volume overload, uremia, or electrolyte imbalances, KRT may be applied as a bridging therapy to transplantation. Other interventions, such as transjugular intrahepatic portosystemic shunt, and artificial liver support systems have a very limited role in improving outcomes in HRS. Although recently developed novel therapies have potential to improve outcomes of patients with HRS, further studies are warranted to validate the efficacy of these novel agents.

Activation of AMP-activated protein kinase inhibits albumin-induced endoplasmic reticulum stress and apoptosis through inhibition of reactive oxygen species.

BACKGROUND: Endoplasmic reticulum (ER) stress induced by urinary albumin plays an important role in tubulointerstitial injury. We have shown that albumin-induced ER stress is regulated through reactive oxygen species (ROS)-c-Src kinase-mTOR signaling pathways. We postulated that peroxisome proliferator-activated receptor-γ (PPAR-γ) might also act as an upstream signaling molecule between c-Src kinase and mTOR. It has been suggested that AMP-activated protein kinase (AMPK) is involved in attenuation of ER stress. We examined whether and how activation of AMPK suppressed the albumin-induced ER stress and apoptosis in tubular epithelial cells. METHOD: HK-2 cells, a proximal tubular cell line, were used. Protein expressions were measured by Western blot analysis. Intracellular ROS and apoptosis were analyzed by flow cytometry. RESULTS: Albumin-induced PPAR-γ expression and PPAR-γ inhibitor (GW9662) suppressed the albumin-induced ER stress. c-Src kinase inhibitor and GW9662 reduced the albumin-induced PPAR-γ and mTOR, respectively. Metformin (the best known clinical activator of AMPK) and another AMPK activator (AICAR) suppressed the albumin-induced ER stress via inhibition of ROS through induction of endogenous antioxidant thioredoxin. AMPK inhibitor blocked the effect of metformin and AICAR. Our in vivo animal study showed that metformin reduced the renal cortical expression of ER stress protein (GRP78) in protein-overload proteinuria rats. Metformin also reduced the caspase 3-dependent apoptosis induced by albumin. CONCLUSION: PPAR-γ was involved in albumin-induced ER stress as an upstream signaling molecule between c-Src kinase and mTOR. AMPK activation might be beneficial in attenuating the tubulointerstitial injury induced by albumin.

Assessment of the influence of severe renal impairment on the pharmacokinetics of mirodenafil in Korean male volunteers.

OBJECTIVE: To evaluate and compare the pharmacokinetics and tolerability of a single oral dose of mirodenafil in volunteer patients with severe renal impairment and healthy volunteers. METHODS AND MATERIALS: This open-label, single-dose, parallel group clinical study enrolled a total 12 volunteers (6 healthy volunteers and 6 volunteer patients with severe renal impairment). Each volunteer was orally administered 50 mg mirodenafil and serial blood samples were obtained after drug administration to determine the plasma concentration of mirodenafil using LC-MS/MS. The measured individual plasma concentrations were used to calculate the pharmacokinetic parameters using noncompartmental methods. Tolerability was also assessed using measurements of vital signs, clinical chemistry tests, and interviews. RESULTS: All of the volunteers completed the study with no serious adverse events (AEs). A total of 4 AEs were reported, but all were of mild or moderate intensity and not considered to be related to the study drug. The geometric mean (95% CI) of the terminal half-life (t1/2ß) and the apparent clearance (CL/F) values of mirodenafil were 2.2 (1.4 - 3.4) h and 127.2 (95.1 - 170.2) l/h in the volunteer patients, and 3.0 (2.1 - 4.4) h and 136.1 (74.4 - 249.2) l/h in the healthy volunteers, respectively. The geometric mean of the AUC0-t of the volunteer patients was 8% higher and the geometric mean for clearance was 7% lower compared with the healthy volunteers. However, the geometric mean of the Cmax of the volunteer patients was 38% higher than that of the healthy volunteers. CONCLUSIONS: A single oral 50-mg dose of mirodenafil was well tolerated. Exposure (AUC0-t) to mirodenafil was similar in both healthy volunteers and volunteer patients with severe renal impairment and healthy volunteers.

Albumin-induced epithelial-mesenchymal transition and ER stress are regulated through a common ROS-c-Src kinase-mTOR pathway: effect of imatinib mesylate.

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)-ß1, 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.

Uncertain Clinical Effect of Polymyxin B Hemoperfusion in Patients with Septic Acute Kidney Injury Requiring Continuous Renal Replacement Therapy.

ABSTRACT: Polymyxin B hemoperfusion (PMX-HP) may improve the clinical outcomes of patients with sepsis and gram-negative bacteremia by reducing endotoxin levels. However, the recent studies with the variable degree of renal support have shown that the improvement of survival rate by PMX-HP remains unclear in such patients. Therefore, we investigated whether the addition of PMX-HP to continuous renal replacement therapy (CRRT) could improve the survival rate than CRRT alone. This study included 231 patients with sepsis undergoing CRRT alone or PMX-HP with CRRT. Primary outcomes were 28-day and 90-day all-cause mortality. Urine output, ventilator support, and Sequential Organ Failure Assessment (SOFA) score were not significantly different between the two groups. Crude 28-day and 90-day mortality rates were higher in the PMX-HP with CRRT group than in the CRRT-alone group. To correct for disease severity, propensity score (PS) matching was performed with acute respiratory distress syndrome, mechanical ventilation support, extracorporeal membrane oxygenation, infection source (abdomen), age, inotropic score, SOFA score, C-reactive protein, and procalcitonin levels. Sixty-six PS-matched pairs revealed significantly higher 28-day and 90-day mortality rates in the PMX-HP with CRRT group than in the CRRT-alone group. Considering the mortality rates after PS matching, the additional use of PMX-HP does not improve the clinical outcomes of patients with sepsis and acute kidney injury requiring CRRT.

Renal Recovery After Liver Transplantation Alone in Patients With Liver Cirrhosis and Severe Chronic Kidney Disease With Normal Kidney Size.

BACKGROUND: Most guidelines recommend simultaneous liver-kidney transplantation (SLKT) in patients with liver cirrhosis (LC) and severe chronic kidney disease (CKD) over liver transplantation alone (LTA). CKD, however, is not irreversible. This study evaluates the reversibility of kidney disease after LTA based on kidney size. MATERIALS AND METHODS: In this single-center retrospective study, we classified 90 patients with LC and severe CKD into 3 groups: the normal kidney (NK)-LTA group (n=39), small kidney (SK)-LTA group (both kidneys <9 cm at the time of LTA, n=40), and SK-SLKT group (n=11). RESULTS: The NK-LTA group had a lower percentage of hepatocellular carcinoma and a higher pre-liver transplantation (LT) estimated glomerular filtration rate. This group, however, was older, received livers from a higher percentage of deceased donors, and had a higher Child-Pugh score. Renal recovery, defined as the return of creatinine to their baseline, or a persistent change from baseline but not persistent (≥3 months) need for renal replacement therapy after LT, was found in 79% in the NK-LTA group, which was higher than 7.5% in the SK-LTA group. Renal and patient survival was found in 56% of the NK-LTA group, which was higher than 2.5% of the SK-LTA group. CONCLUSIONS: There is a high percentage of renal recovery in the NK-LTA group, and accordingly, this does not justify SLKT, since this would result in a "waste" of kidneys. Therefore, KT after LT is recommended over SLKT for the LC patients with NK size.

Myoglobin induces vascular cell adhesion molecule-1 expression through c-Src kinase-activator protein-1/nuclear factor-kappaB pathways.

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)-kappaB 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 microg/ml) induced VCAM-1 expression via activation of AP-1 and NF-kappaB, which was mediated through activation of c-Src kinase, followed by mitogen-activated protein kinases (p38, ERK 1/2, JNK-1) and the I kappaB kinase - I kappaB-alpha. 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-kappaB 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.

Fatty acid-bearing albumin induces VCAM-1 expression through c-Src kinase-AP-1/NF-kB pathways: effect of L-carnitine.

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-kappaB 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-kappaB, which was mediated through activation of c-Src kinase, followed by MAP kinases (p38, ERK 1/2, JNK-1) and IkappaB kinase and IkappaB-alpha, 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/NFkappaB 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.

Suitability of the IDMS-traceable MDRD equation method to estimate GFR in early postoperative renal transplant recipients.

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 (51)Cr-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 m(2). 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 m(2) and a precision of 12.57 ml/min/1.73 m(2). 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 m(2)). As for cystatin C-based equations, the Filler equation had the least bias (0.03 ml/min/1.73 m(2)) 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.

Urine podocyte mRNAs mark progression of renal disease.

Because loss of podocytes associates with glomerulosclerosis, monitoring podocyte loss by measuring podocyte products in urine may be clinically useful. To determine whether a single episode of podocyte injury would cause persistent podocyte loss, we induced limited podocyte depletion using a diphtheria toxin receptor (hDTR) transgenic rat. We monitored podocyte loss by detecting nephrin and podocin mRNA in urine particulates with quantitative reverse transcriptase-PCR. Aquaporin 2 mRNA served as a kidney reference gene to account for variable kidney contribution to RNA amount and quality. We found that a single injection of diphtheria toxin resulted in an initial peak of proteinuria and podocyte mRNAs (podocin and nephrin) followed 8 d later by a second peak of proteinuria and podocyte mRNAs that were podocin positive but nephrin negative. Proteinuria that persisted for months correlated with podocin-positive, nephrin-negative mRNAs in urine. Animals with persistent podocyte mRNA in urine progressed to ESRD with global podocyte depletion and interstitial scarring. Podocytes in ectatic tubules expressed podocalyxin and podocin proteins but not nephrin, compatible with detached podocytes' having an altered phenotype. Parallel human studies showed that biopsy-proven glomerular injury associated with increased urinary podocin:aquaporin 2 and nephrin:aquaporin 2 molar ratios. We conclude that a single episode of podocyte injury can trigger glomerular destabilization, resulting in persistent podocyte loss and an altered phenotype of podocytes recovered from urine. Podocyte mRNAs in urine may be a useful clinical tool for the diagnosis and monitoring of glomerular diseases.