Hiroshi Egawa

Decreased Fluidity of Polymorphonuclear Leukocyte Membrane in Streptozocin-Induced Diabetic Rats

Using flow cytometry with the excimer-forming lipid technique with pyrenedecanoic acid, we measured membrane fluidity of polymorphonuclear leukocytes (PMNs) from 20 streptozocin (STZ)-induced diabetic rats. Diabetes mellitus was induced in male Sprague-Dawley rats (body wt 243 ± 11 g) with an injection of 25 mg/kg i.v. STZ. Membrane fluidity of PMNs was significantly lower at 2 wk after the STZ injection when serum glucose reached the plateau (31.1 ± 5.8 mM), and after 3 wk, membrane fluidity remained unchanged. In 7 STZ-resistant rats for which serum glucose was <10 mM at 2 wk after the STZ injection, gradual normalization in membrane fluidity was observed. PMN membrane fluidity at each week correlated inversely with respective serum glucose levels 1 wk previously (r = −0.76) but not with serum lipid levels. Cross-incubation studies ascribed this observation to factors in the diabetic rat serum. Glycosylated protein, which was separated from diabetic rat serum, decreased membrane fluidity of control rat PMNs. Human diabetic subjects have an increased risk for infection, which may be due partly to altered membrane fluidity of their PMNs.

PURIFICATION OF FACTOR XIa INHIBITOR FROM HUMAN PLATELETS

An inhibitor of activated factor XI (FXIa) in human platelets was recently identified as an amyloid beta-protein precursor (APP). We purified an FXIa inhibitor (XIaI) from the supernatant of activated human platelets, and assessed its inhibitor activity toward FXIa amidolytic activity. Approximately 90 micrograms of XIaI that cross-reacted with anti-APP antibody was obtained from two hundred units of platelet suspension by employing a six-step column chromatography procedure. The molecular weight of the purified XIaI was 94,000. The Ki value of XIaI to factor XIa was 526 +/- 120 pM, and the inhibition was enhanced by the addition of ZnCl2. The amino-terminal sequence of XIaI was L-E-V-P-T-D-G-N-A-, which is identical to that for the leucine (N18) to alanine (N26) sequence of APP751 and the amino-terminal sequence of protease nexin-2.

Measurement of membrane fluidity of polymorphonuclear leukocytes by flow cytometry

A method was established for measuring membrane fluidity of polymorphonuclear leukocytes (PMN) by the excimer-forming lipid technique with pyrenedecanoic acid in flow cytometry. When cells were labeled, the use of 2-25 microM of pyrenedecanoic acid provided similar results. Neither the removal of the unincorporated pyrenedecanoic acid nor adjustment of PMN counts exhibited any effect. By the gate analysis method, membrane fluidity of PMN could be measured with 100 microliters of heparinized whole blood in a short time and results with PMN in whole blood was similar to those with purified PMN. Therefore, purification and count adjustment of PMN could be omitted. By this method, membrane fluidity of PMN, which were treated with membrane fluidizer, was measured successfully. This method could be applied to the study of PMN function in various diseases.

Murine monoclonal antibodies to human factor XI

Murine monoclonal antibodies to human factor XI (F.XI) are described. The monoclonal antibodies (2-1, 4-1, 7-1 and 10-1) consisted of IgG1. 4-1 inhibited the activation of F.XI completely in the presence of high molecular weight kininogen and kaolin and the others did so partially, whereas these antibodies had no effect on the activation of F.XI with activated factor XII (beta-XIIa). Four antibodies had no effect directly on the amidolytic activity of activated F.XI (F.XIa). 10-1 inhibited the activation of factor IX in coagulant assay for F.XIa by Mannhalter. And 4-1 and 7-1 did so partially, whereas 2-1 did not. In immunoblotting analysis, all antibodies bound to F.XI, its reduced form and F.XIa. All were directed against the heavy chain of F.XI. All antibodies recognized F.XIa-alpha 1 antitrypsin complex.

Increased accumulation of nonenzymatically glycated fibrinogen in the renal cortex in rats

We have determined that the nonenzymatic glycation of fibrinogen altered its biological functions in vitro. Thrombin clottability of rat fibrinogen incubated with glucose decreased with increasing incubation time, but was not affected by the glucose concentration. Fibrin prepared from glycated fibrinogen showed a significant resistance in susceptibility to plasmin degradation. We also examined the in vivo distribution of glycated fibrinogen in renal cortex. Iodine labeled rat glycated or unglycated fibrinogen was injected into streptozocin-induced diabetic and control rats. No appreciable difference in the plasma disappearance rate in control rats was observed (half-lives in hours for glycated, 25.6 +/- 0.37; unglycated, 26.1 +/- 0.74). The radioactivity of fibrinogen retained to the renal cortex was calculated 24-hours after injection. In both control and diabetic rats, the retention rate of glycated fibrinogen in renal cortex was significantly higher than that of the unglycated. These results suggest that glycated fibrinogen may occur in a more resistant form to plasmin digestion with fibrin deposition as confirmed in in vitro studies. Therefore, we suggest that glycated fibrinogen may partly contribute to the development of diabetic microangiopathic lesions such as glomerulosclerosis.

Determination of main inhibitor of activated factor XI

To study the contribution of alpha 1 antitrypsin (alpha 1AT) and antithrombin III (AT III) to the inactivation of F.XIa in plasma, we developed the assay system of F.XIa-AT III complex according to our method of F.XIa-alpha 1AT complex, and measured the levels of both complexes in the patients with disseminated intravascular coagulation (DIC) derived from various triggers. F.XIa-alpha 1AT complex level was always higher than F.XIa-AT III complex level in each patient, independently on the trigger of DIC, the administration of heparin and the levels of F.XI, alpha 1AT and AT III. These results indicate that alpha 1AT is the main inhibitor of F.XIa in plasma.

Factor XIa-α1antitrypsin complex — Elevation in the patients with DIC —

We developed an assay for the factor XIa-α1antitrypsin complex (F.XIa-α1AT complex) in plasma. The purified factor XI (F.XI) activated with β-XIIa and treated with α1antitrypsin (α1AT) served as the standard complex. The assay is an enzyme-linked differential antibody immunosorbent assay. The complex level of tested plasma was measured with peroxidase-labeled anti-α1AT Fab′ after the addition of 10-fold diluted test plasma (200 μl) to the anti-F.XI monoclonal antibody beads. To eliminate the effects of plasma, the standard F.XIa-α1AT complex was diluted with F.XI-deficient plasma (10-fold diluted) which did not contain the complex. Purified F.XI (0.08 μg/assay, i.e. 100%) was added to the standard F.XIa-α1AT complex, because the absorbance of the standard complex containing F.XI (0.016-0.12 μg/assay, i.e. 20–150%) was a little lower than that of the complex alone. The recovery of the F.XIa-α1AT complex added was over 90%. Neither F.XI nor α1AT alone had the color development. The complex level of 25 normal individuals was below the detectable limit (<0.18 ng/assay), whereas the 30 patients with disseminated intravascular coagulation (DIC) had a high level complex (0.18-4.2 ng/assay). This assay may be helpful for the diagnosis of DIC.

New rapid assay for factor XIa-α1antitrypsin complex — application to dic —

We developed a new rapid assay for the factor XIa-alpha 1 antitrypsin in complex (F.XIa-alpha 1 AT) in plasma with the use of a newly produced anti-F.XI monoclonal antibody (KMXI-1). This assay was completed within about 5 hours, and the minimum assay range extended sensitivity about 5-fold over the former assay (Thromb. Res. 44, 489-501, 1986). In 20-fold diluted plasma samples, this assay was not affected by co-existing F.XI or nonspecific color development of the plasma. Normal levels of F.XIa-alpha 1 AT (11 +/- 4.1 ng/ml plasma [n = 96]) increased with the aging of healthy adults. The F.XIa-alpha 1 AT levels of patients with disseminated intravascular coagulation (DIC) rose along with the progression of the disease, and the appearance of high levels and the peak of F.XIa-alpha 1 AT developed faster than FDP-E or alpha 2 plasmin inhibitor-plasmin-complex in most patients. These results indicate that, in addition to FDP, F.XIa-alpha 1 AT is a useful molecular marker for DIC.

Microdetermination of unbound tryptophan in plasma by a combination of ultrafiltration and high-performance liquid chromatography.

Abstract Previous methods for measuring unbound plasma tryptophan are not completely satisfactory, and therefore we have developed an improved method for this purpose. Unbound tryptophan is separated from bound tryptophan by centrifugation through Amicon ultrafiltration membrane cones in a short period (within 2 min). The first fraction of filtrate is obtained in 30 s by centrifugation at 3000 g at controlled pH and is assayed with a high-performance liquid chromatography system. The first filtrate has a higher tryptophan concentration than that obtained by prolonged centrifugation. We propose that the tryptophan concentration in the first filtrate is the value nearest that of the plasma, since a change of equilibrium between bound and unbound tryptophan during the separation procedure is quite small. The method is also simple and convenient for clinical application.

Accumulation of 125I-factor XI in atheroma of rabbit with hereditary hyperlipidemia (WHHL-rabbit)

We have studied the turnover and accumulation of rabbit factor XI (F.XI) in atherosclerotic lesion in Watanabe-hereditable hyperlipidemic rabbit (WHHL rabbit) to reveal the participation of blood coagulation in atherosclerotic lesion. Rabbit F.XI was iodinated and administered intravenously to WHHL rabbits and Japanese white rabbits. The turnover of 125I-rabbit F.XI was significantly faster in WHHL rabbits (T1/2 = 2.84 +/- 0.44 days) than in normal rabbits (T1/2 = 4.44 +/- 0.42 days). The thoracic aorta of WHHL rabbit was strongly labelled with 125I-rabbit F.XI, in sections obtained after 5 days by en-face autoradiography, whereas no radioactivity was detected in normal aorta. By an immunohistochemical study of WHHL rabbit aorta, we confirmed that many F.XI- and fibrin-related compounds existed in the atheroma, whereas albumin did not in these area. These results suggest that the activation of F.XI proceeds on the atherosclerotic lesions of WHHL rabbits.