Risk of overestimation of kidney function using GFR-estimating equations in patients with low inulin clearance.

BACKGROUND: Accurate estimation of the glomerular filtration rate (GFR) is very important in clinical practice. Although renal inulin clearance (Cin) is the gold standard for measuring GFR, the procedure for Cin measurement is complicated. Use of GFR-estimating equations has been increasing recently due to their simplicity. The objectives of the present study are to analyze the correlation between Cin and other GFR-estimating parameters and to investigate their clinical usefulness and limitation. METHODS: Seventy-two Japanese patients were enrolled in this study. Cin was measured by the continuous infusion method. Serum creatinine (s-Cr), cystatin C, uric acid (UA), and hemoglobin (Hb) were measured. The Japanese formula of estimated GFR (eGFR) was as follows: eGFR (ml/min/1.73m(2) ) = 194 × s-Cr(-1.094) × Age(-0.287) × 0.739 (if female). The endogenous creatinine clearance test was also performed. RESULTS: Levels of Cin were highly correlated with those of endogenous creatinine clearance (Ccr) (R(2) = 0.7585) and eGFR (R(2) = 0.5659). However, patients with lower Cin showed unexpectedly elevated levels of endogenous Ccr and eGFR. Moreover, the levels of eGFR tended to be unexpectedly increased in patients with low body surface area. CONCLUSION: Although GFR-estimating equations are useful for estimating GFR accurately, they pose a risk of overestimation of kidney function in patients with decreased GFRor a poor physique.

One-year results of an open-label study on antiproteinuric effect of benidipine in elderly patients with chronic kidney disease.

BACKGROUND: The long-term antiproteinuric effects of benidipine, a calcium channel blocker (CCB), have not been evaluated in detail in hypertensive patients with chronic kidney disease (CKD). METHODS: Benidipine (4 mg/day) was administered to previously untreated hypertensive patients with CKD, or hypertensive patients with CKD not achieving target blood pressure (BP) despite taking an angiotensin II receptor blocker (ARB). The patients were followed up for 1 year. If target BP was not achieved by 2 weeks after the start of benidipine treatment, the dosage was increased to 8 mg/day. The urinary protein to creatinine (UP/cre) ratio was evaluated before and after benidipine treatment. RESULTS: This study evaluated 65 hypertensive patients with CKD. BP (systolic/diastolic) decreased from 154 ± 19 / 91 ± 12 mm Hg before treatment to 134 ± 16 / 78 ± 10 mm Hg at 1 year after treatment (p<0.001). The UP/cre ratio decreased significantly from 2.21 ± 2.47 g/g creatinine (g/g cre) before treatment to 1.43 ± 2.21 g/g cre after treatment (p<0.001). In both the untreated and ARB-treated groups, the BP and UP/cre ratio decreased significantly at 1 year after treatment. The percentage change in the UP/cre ratio was significantly greater in patients aged 65 years or older than in those less than 65 years (79.1% vs. 48.7%, p=0.038). CONCLUSIONS: Benidipine treatment reduced the UP/cre ratio in hypertensive patients with CKD, and the percentage decrease of the UP/cre ratio was greater in elderly patients, suggesting that benidipine may have more potent antiproteinuric effects in elderly hypertensive patients with CKD.

Three cases of PR3-ANCA positive subacute endocarditis caused by attenuated bacteria (Propionibacterium, Gemella, and Bartonella) complicated with kidney injury.

Subacute bacterial endocarditis (SBE) associated with antiproteinase-3 antineutrophil cytoplasmic antibodies (PR3-ANCA) has previously been reported in 10 cases of Streptococcus viridans and in 1 case of Escherichia faecalis infection. Most of these patients had hypocomplementemia and were positive for several autoantibodies. The infections in most of these patients showed good responses to antibiotic treatment. We report three patients with ANCA-positive SBE, which was induced by attenuated slow-growing intracellular pathogens; these patients had severe complications, such as acute kidney injury, cerebral embolism, and aortic valve destruction.

Down-regulation of core 1 beta1,3-galactosyltransferase and Cosmc by Th2 cytokine alters O-glycosylation of IgA1.

BACKGROUND: Patients with IgA nephropathy (IgAN) have an increased amount of abnormally O-glycosylated IgA1 in circulation, in glomerular deposits and produced by tissue cells in vitro. Although increased production of Th2 cytokines by peripheral blood lymphocytes and a functional abnormality of core 1 ß1,3-galactosyltransferase (C1ß3Gal-T) have been proposed as mechanisms underlying pathogenesis of IgAN, they are still obscure and are not connected. METHODS: To clarify the effect of T-cell cytokines, we analysed the mRNA levels of C1ß3Gal-T and its molecular chaperone Cosmc, C1ß3Gal-T activity and subsequent O-glycosylation of IgA1 in a human B-cell line stimulated with these cytokines. The surface IgA1-positive human B-cell line was cultured with recombinant human IFN-γ, IL-2, IL-4 or IL-5. The production and glycosylation of IgA1 were determined by sandwich ELISA and enzyme-linked lectin binding assay, respectively. The mRNA levels of C1ß3Gal-T and Cosmc were quantitatively measured by real-time PCR. C1ß3Gal-T activity was analysed using high-performance liquid chromatography. RESULTS: IgA1 production by IL-4-stimulated cells was significantly higher than controls or after IFN-γ or IL-5. The terminal glycosylation of secreted IgA1 was altered in response to IL-4. IL-4 stimulation significantly decreased the mRNA levels of both C1ß3Gal-T and Cosmc and of C1ß3Gal-T activity. IL-4 stimulation was clearly blocked by recombinant human IL-4 soluble receptor. CONCLUSIONS: It appears that Th2 cytokine IL-4 may play a key role in controlling glycosylation of the IgA1 hinge region.

Analysis of innate immune responses in a model of IgA nephropathy induced by Sendai virus.

In a model of IgA nephropathy (IgAN) induced by Sendai virus (SeV) without Th1/Th2 polarizing immunization, Th2-prone BALB/c mice develop more severe nephritis with acute renal insufficiency than Th1-prone C3H mice. To determine whether Th1 or Th2 predominance influences the severity of experimental IgAN in mice, we employed polarizing immunizations in a SeV-induced IgAN model in Th1-prone C57Bl/6 mice and Th2-prone BALB/c mice. C57Bl/6 mice, immunized with SeV +CFA or +IFA, showed: (1) clear cytokine polarity by splenocytes in recall assays. (2) Total serum IgA and especially SeV-specific IgA from the IFA group showed a selective defect in galactosylation, not seen in the CFA group, and (3) serum creatinine in the IFA group was higher than in the CFA group or nonimmune controls. However, BALB/c mice did not show clear cytokine polarity with CFA/IFA adjuvant. Moreover, spleen cells from naive BALB/c mice produce IFN-gamma (but not IL-2, -4, -5, or -13) upon stimulation with inactivated SeV in vitro. By flow cytometry, IFN-gamma producing cells are CD3(-), CD19(-), CD49b(+) natural killer cells. IFN-gamma production by naive splenocytes is blocked partially by anti-IL12 blocking Abs, and completely by anti-IL18R blocking Abs. In conclusion, C57Bl/6 mice with polarizing priming with SeV showed clear cytokine polarity and distinct kidney injuries. However, BALB/c mice did not show clear cytokine polarity in the same immunizing system, presumably due to the effects of innate responses to SeV upon antigen-specific lymphocytes. Natural IFN-gamma production may influence the risk of renal failure in IgAN.

Changes in plasma interleukin-18 by direct hemoperfusion with polymyxin B-immobilized fiber in patients with septic shock.

BACKGROUND/AIMS: Polymyxin B-immobilized fiber (PMX-F) treatment is reported to be safe and effective in patients with severe sepsis and septic shock. The aim of the present study was to determine whether plasma levels of interleukin (IL)-18, which is linked with sepsis, are associated with plasma endotoxin levels and sepsis-related scores and whether PMX-F treatment affects these variables in patients with septic shock. PATIENTS AND METHODS: Twenty-six patients with septic shock (15 men and 11 women; mean age 56.5 years) and 20 age-matched healthy subjects (12 men and 8 women; mean age 54.0 years) were included in this study. Septic shock patients were divided into 2 groups: a PMX-F treatment group (9 men and 5 women; mean age 57.5 years) and a conventional treatment group (7 men and 5 women; mean age 55.3 years). Standard supportive care was continued without change during PMX-F treatment. Plasma endotoxin, plasma IL-18, and clinical variables were measured before, immediately after the first and second PMX-F treatment, and the following day. RESULTS: The plasma IL-18 levels were significantly higher in septic shock patients (1,320+/- 360 pg/ml) than in healthy volunteers (140+/- 60 pg/ml; p< 0.001). The IL-18 level was significantly correlated with the plasma endotoxin level (p < 0.001), the Acute Physiology and Chronic Health Evaluation II score (p<0.01), the Sepsis Severity Score (p<0.01), the number of failed organs (p<0.01), and the Goris score (p<0.01). PMX-F treatment reduced the plasma endotoxin and IL-18 levels significantly after the first treatment (p<0.05), after the second treatment (p<0.01), and on the following day (p<0.001). However, these variables did not change significantly during conventional treatment. CONCLUSIONS: IL-18 may be associated with the severity of septic shock, and PMX-F treatment is effective in reducing the IL-18 level in patients with septic shock.

Differential effects of Sendai virus infection on mediator synthesis by mesangial cells from two mouse strains.

BACKGROUND: Recently, we observed that the severity of glomerulonephritis in an experimental model of immunoglobulin A nephropathy (IgAN) induced by Sendai virus differs between C57BL/6 and BALB/c mouse strains. The determinants of differing renal insufficiency are not understood. In the present study, we examine the capacity for mesangial cells to support Sendai viral replication and assess the direct effects of Sendai virus on the production of selected cytokines, chemokines, and eicosanoids by mesangial cells, comparing C57BL/6 to BALB/c mouse strains. METHODS: Sendai virus replication was measured by viral plaque assay using LLCMK2 cells. Production of cytokines [interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha)], chemokines (JE and KC), and eicosanoids [prostaglandin E2 (PGE2) and thromboxane B2 (TxB2)] in culture medium was evaluated by sandwich enzyme-linked immunosorbent assay (ELISA) or competitive enzyme immunoassay (EIA) after 48 hours' incubation with infectious or inactivated Sendai virus. RESULTS: Sendai virus replicates equally well in mesangial cells from both strains, and infection evokes increased IL-6, JE, KC, and PGE2 production in relation to viral dose. BALB/c mesangial cells produce significantly more IL-6 and JE than those from C57BL/6, and the dose response for KC is steeper in BALB/c mesangial cells than those from C57BL/6. Synthesis of PGE2 in BALB/c mesangial cells is higher than that of C57BL/6 mesangial cells, both under basal conditions and in response to infectious Sendai virus, again in a dose-dependent manner. There is no TNF-alpha or thromboxane response to viral stimulation. CONCLUSION: We conclude that different mesangial cell responses to this common mucosal viral pathogen might influence the severity of IgAN in our model system.

Serum cystatin C is a more sensitive marker of glomerular function than serum creatinine.

We determined the relationship between the levels of serum cystatin C or creatinine (s-Cr) and the grade of creatinine clearance (CCr) in patients with various glomerular diseases. Serum samples from 96 patients with glomerular diseases were obtained from our hospital. The levels of serum cystatin C were measured using the Dade Behring Cystatin C assay with the automated Dade Behring Nephelometer II (BNII). CCr levels were classified into six groups according to the Guidelines of the Japanese Society of Nephrology as follows: grade 1 (normal renal function); grade 2 (slight decrease of renal function); grade 3 (moderate decrease of renal function); grade 4 (severe decrease of renal function); grade 5 (renal failure), and grade 6 (uremia). The mean levels of serum cystatin C in grade 3 patients were significantly higher than those in grade 1. The mean levels of serum cystatin C in grades 4, 5 and 6 patients were also significantly higher than those in grade 1. However, the mean levels of serum Cr in grade 3 patients were not significantly higher than those in grade 1. The levels of s-Cr in grades 4, 5 or 6 patients were significantly higher than those in grade 1. In this study, an increase of serum cystatin C levels occurred earlier than that of s-Cr in various glomerular diseases. It appears that the levels of serum cystatin C may provide early prognostic marker of patients with various glomerular diseases rather than the levels of s-Cr.

Effects of oral adsorbent AST-120 (Kremezin) on renal function and glomerular injury in early-stage renal failure of subtotal nephrectomized rats.

The aim of the present study was to determine if treatment with an oral adsorbent (AST-120, Kremezin) might decrease the urinary albumin excretion and serum indoxyl sulfate (s-IS), and prevent glomerular sclerosis in early-stage renal failure, i.e. 0.9-1.2 mg/dl of serum creatinine (s-Cr) and 60-95 mg/dl of blood urea nitrogen (BUN), in subtotal (3/4) nephrectomized rats. Levels of s-Cr and s-IS in the AST-120-treated rats were significantly lower than those in the untreated control rats. The AST-120-treated rats showed an increase of creatinine clearance. Urinary protein and indoxyl sulfate excretion in the AST-120-treated rats were also significantly lower than those in the untreated control rats. The ratio of glomerular tuft area to the area of Bowman's capsules (GT/BC) in the AST-120-treated rats was significantly lower than that in the untreated control rats. The degree of glomerular sclerosis and tubulointerstitial fibrosis in the AST-120-treated rats was significantly lower than that in the untreated control rats. Furthermore, there was a significant relationship among the degree of GT/BC, glomerular sclerosis, tubulointerstitial fibrosis and the levels of urinary protein excretion. It appears that AST-120 might decrease the accumulation of s-Cr and s-IS, and prevent glomerular sclerosis in early stage renal failure in the subtotal nephrectomized rats.

Temocapril, a long-acting non-SH group angiotensin converting enzyme inhibitor, modulates glomerular injury in chronic puromycin aminonucleoside nephrosis.

The purpose of the present study was to determine whether chronic administration of temocapril, a long-acting non-SH group angiotensin converting enzyme (ACE) inhibitor, reduced proteinuria, inhibited glomerular hypertrophy and prevented glomerulosclerosis in chronic puromycin aminonucleoside (PAN) - induced nephrotic rats. Nephrosis was induced by injection of PAN (15mg/100g body weight) in male Sprague-Dawley (SD) rats. Four groups were used, i) the PAN group (14), ii) PAN/temocapril (13), iii) temocapril (14) and iv) untreated controls (15). Temocapril (8 mg/kg/day) was administered to the rats which were killed at weeks 4, 14 or 20. At each time point, systolic blood pressure (BP), urinary protein excretion and renal histopathological findings were evaluated, and morphometric image analysis was done. Systolic BP in the PAN group was significantly high at 4, 14 and 20 weeks, but was normal in the PAN/temocapril group. Urinary protein excretion in the PAN group increased significantly, peaking at 8 days, then decreased at 4 weeks, but rose again significantly at 14 and 20 weeks. Temocapril did not attenuate proteinuria at 8 days, but it did markedly lower it from weeks 4 to 20. The glomerulosclerosis index (GSI) was 6.21 % at 4 weeks and respectively 25.35 % and 30.49 % at 14 and 20 weeks in the PAN group. There was a significant correlation between urinary protein excretion and GSI (r = 0.808, p < 0.0001). The ratio of glomerular tuft area to the area of Bowman's capsules (GT/BC) in the PAN group was significantly increased, but it was significantly lower in the PAN/temocapril group. It appears that temocapril was effective in retarding renal progression and protected renal function in PAN neprotic rats.

FcRn-mediated transcytosis of immunoglobulin G in human renal proximal tubular epithelial cells.

In the kidney, proteins filtered through glomeruli are reabsorbed by endocytosis along the proximal tubules to avoid renal loss of large amounts of proteins. Recently, neonatal Fc receptor (FcRn), which is involved in the transport of IgG across several epithelial and endothelial cells, was reported to be expressed in renal proximal tubular epithelial cells (RPTECs). However, there has been no direct evidence for receptor-mediated endocytosis of IgG in human RPTECs. To explore physiological roles of FcRn in the proximal tubules, we used the human RPTECs to examine IgG transport. FcRn was expressed in RPTECs and physically associated with beta(2)-microglobulin, preserving the capacity of specific pH-dependent IgG binding. Human IgG was bound to the cell surface of RPTECs in a pH-dependent manner. The human IgG transport assay revealed that receptor-mediated transepithelial transport of intact IgG in RPTECs is bidirectional and that it requires the formation of acidified intracellular compartments. With the use of double immunofluorescence, the internalized human IgG was marked in cytoplasm of RPTECs and colocalized with FcRn. These data define the mechanisms of FcRn-associated IgG transport in RPTEC monolayers. It was suggested that the intact pathway for human IgG transepithelial transport may avoid lysosomal degradation of IgG.