Kazumichi Nakamura

β2-glycoprotein I -dependent and -independent anticardiolipin antibody in patients with end-stage renal disease

Abstract We investigated whether anticardiolipin antibody (aCL), which is common in patients with end-stage renal disease (ESRD), was dependent on β2-glycoprotein I (GPI), a cofactor of aCL. Lupus anticoagulant (LA) was identified in 13/39 hemodialysis (HD) patients. GPI-independent aCL was positive in 12/39 of this group, five of whom had both GPI -independent aCL and LA. Three of the 20 patients on symptomatic and supportive treatment other than HD had LA, but none of them were aCL positive. When GPI was added to the assay system to allow for GPI-dependent aCL measurement, the optical density (OD) readings of 10/12 HD patients decreased, thus proving that they were negative for aCL. In contrast, the OD readings of 6 control patients with systemic lupus erythematosus (SLE) increased markedly (3/6) or decreased slightly to moderately (3/6), however, within the limits of positive range, indicating GPI-dependent cCL positivity. These results suggested that LA and GPI-independent aCL were produced in ESRD patients, especially those on HD, possibly through mechanisms related to the hemodialysis membrane. However, the significance of GPI-independent aCL in this clinical setting, which may differ from the GPI-dependent aCL detected in SLE patients, as well as the possible participation of serum GPI in the production of aCL remain to be clarified.

Source of Reactive Oxygen Species in Anti-Thy1 Nephritis

In proliferative glomerulonephritis, both macrophages and mesangial cells generate reactive oxygen species (ROS), contributing to the development of glomerular injury. We have attempted to determine which cell produces ROS during anti-Thy1 nephritis (ATN) in rats. The generation of ROS was studied using luminol amplified chemiluminescence (GCL) on isolated glomeruli. Immunohistochemical studies used avidin-biotin complex (ABC) to label macrophages and mesangial cells. Immediately after ATN induction, mesangiolysis and infiltration with ED-1 positive cells (referred to as macrophage) was noted with a peak at day 1. After day 4, mesangial proliferation appeared with a decrease of the ED-1 positive cells and a prominent increase of PCNA positive cells (regarded as mesangial cells). In the early phase of ATN, GCL, reflecting ROS generation, increased along with the appearance of ED-1 positive cells. GCL subsequently decreased as mesangial cells increased. This suggested that macrophage were the principal participants in ROS generation in the early phase of ATN although mesangial cells cannot be completely disregarded in the generation of ROS and development of glomerular injury.

Immunohistochemical and Biochemical Detection of Low Density Lipoprotein Receptors in Cultured Rat Mesangial Cells

The expression of low density lipoprotein (LDL) receptors by cultured rat mesangial cells was demonstrated using immunohistochemical and biochemical methods. Using a mouse monoclonal anti-human LDL receptor antibody, the immunofluorescence technique was applied to cultured mesangial cells and showed granular staining. Immunoblotting analysis of the membrane fraction of cultured mesangial cells showed a single band with a protein of approximately 130,000 molecular weight. In addition, [125I]LDL binding and the uptake of [125I]LDL by cultured mesangial cells were studied. Binding and uptake both reached an equilibrium after about 30 min of incubation. A 50% reduction in [125I]LDL (20 micrograms protein/ml) binding and uptake occurred when unlabelled LDL was added to cultures at 20-40 micrograms protein/ml. Addition of high density lipoprotein without apoE to the culture medium did not induce competitive inhibition of [125I]LDL binding and uptake by mesangial cells. These findings suggest that cultured mesangial cells have the capacity to express an LDL receptor that regulates the cellular uptake of LDL.

Do obesity and non-insulin dependent diabetes mellitus aggravate exercise-induced microproteinuria?

We evaluated the role of obesity in proteinuria by treadmill exercising of simple obese subjects and non-obese subjects with non-insulin dependent diabetes mellitus in whom the albumin excretion rate at rest was within normal range. Non-obese healthy volunteers were studied as the controls. The fractional renal clearances of four endogenous proteins, albumin, IgG, IgG4, and beta2-microglobulin were measured before, during, and after treadmill exercise in 17 simple obese and 15 non-obese diabetic subjects, and in 21 normal subjects. Exercise increased the fractional albumin clearance in all groups. In diabetic subjects, the fractional IgG4 clearance also increased: fractional beta2-microglobulin clearance increased in normal controls and in diabetics. In obese subjects, the fractional clearances of albumin, IgG, and IgG4 were similar to those in normal controls, but fractional beta2-microglobulin clearance was significantly lower. These results suggest that enhanced microalbuminuria in obese subjects is probably of glomerular origin. In normal subjects and diabetics, exercise-induced microproteinuria is probably of both glomerular and tubular origin. Defect in the charge-selective barrier of the glomerular capillary wall has been implicated in diabetics. Thus some additional factors relevant to obesity must be taken into account in the consideration of the mechanism of microalbuminuria in diabetics with obesity.

Post-prandial triglyceride-rich lipoprotein metabolism: possible role of sialilated apolipoprotein E isoproteins

Abstract. While serum concentrations of triglyceride (TG) and apolipoprotein (apo) E decreased significantly after 75 g glucose load, serum triglyceride concentration increased markedly and apoB concentration decreased significantly after 100 g fat load in 10 healthy men. Chylomicrons and very low density lipoproteins (VLDL) increased after the fat load but decreased after the glucose load. ApoB‐100/B‐48 ratio in VLDL fraction decreased slightly at 30 min and increased markedly at 60 min after the glucose load. On the other hand, the ratio decreased definitely at 30 min and then increased until 90 min after the fat load. Isoelectric focusing (IEF) and two‐dimensional gel electrophoresis revealed that the relative concentration of sialilated apoE in VLDL fraction decreased after the glucose load and increased after the fat load. In hypertriglyceridaemic patients, apoE3S1/E3 ratio in VLDL fraction was significantly higher than that in normal and hypercholesterolaemic patients. The results suggest that some structural changes in apoE, due probably to sialilation, may exert an influence on the hepatic uptake of the lipoproteins.

Serum osteocalcin level as an indication of parathyroidectomy for patients with renal hyperparathyroidism.

オステオカルシンはビタミンK依存性蛋白で骨回転の指標となっている. 著者らは腎性上皮小体機能亢進症 (RHP) 症例でオステオカルシン値を測定し, 上皮小体摘除術の有用な指標になりうるか否かを検討した. 手術後6か月以上経過観察しえたRHP症例37例を対象とし, 血液透析を3年以上受けている非手術透析症例46例を対照とした. 血清オステオカルシン値 (6.5ng/ml以下) は手術症例では278.8±159.8 (M±SD) (4.2-645) となり, 対照群では65.0±85.2ng/mlを示した (p<0.001). オステオカルシン高値例は激しい骨痛とX線上高度の線維性骨炎の所見を示した. また, オステオカルシン値はALP, m-PTH, 摘出上皮小体総重量と有意 (p<0.001) に相関した. 以上より, オステオカルシンは骨回転の増加をよく表現しており, 上皮小体摘除術の有用な指標となりうると考えられた.

Participation of Kallikrein, Coagulation/Fibrinolysis Parameters in the Development of Glomerulonephritis

Masugi nephritis was induced in dogs in which platelet count, fibrinogen, antithrombin activity, plasma prekallikrein and immediate plasmin inhibitors were coincidentally decreased immediately after the injection of nephrotoxin serum. It was found that the grade of decrease of urinary kallikrein excretion following these immediate reactions were parallel with the grade of renal damages. By the pretreatment with heparin or the defibrination with snake venom, however, the histological findings of Masugi nephritis showed rather severe damage. Based on the consumption of coagulation factors, kallikrein, kinin and their inhibitors in the development of this nephritis, it was postulated that inauguration of coagulation and activation of kallikrein contributed to the development of glomerulonephritis. The treatment or prevention of this coagulation process with heparin or snake venom, however, gave untoward effects on the pathological process in this experiment.