Serum lipid profile and plasma fatty acid composition in hemodialysis patients--comparison with chronic kidney disease patients

Polyunsaturated fatty acids (PUFA) are reported to be associated with atherosclerotic and inflammatory diseases because they are the major components of the cytoplasmic membrane and are the precursor fatty acids for prostaglandins and leukotrienes. In the present study, the serum lipid profile and plasma fatty acid composition in hemodialysis (HD) patients were determined and compared with those in chronic kidney disease (CKD) patients. Seventeen HD patients (HD group) and 36 CKD patients (CKD group) were entered in the present study. The estimated glomerular filtration ratio (eGFR) in the CKD group was under 60 ml/min/1.73m2. In the analysis of the serum lipid profile, triglyceride concentrations in the HD group were significantly lower than those in the CKD group (90.9 +/- 41.0 mg/dl vs. 136.2 +/- 64.9 mg.dl, p = 0.011). In the analysis of the plasma fatty acid composition, alpha-linolenic acids (0.81 +/- 0.28% vs. 0.99 +/- 0.22%, p = 0.016), eicosapentaenoic acids (EPA) (2.31 +/- 0.89% vs. 3.24 +/- 1.79%, p = 0.048), docosahexaenoic acids (4.10 +/- 1.09% vs. 5.15 +/- 1.65%, p = 0.021), the ratios of EPA to arachidonic acids (0.458 +/- 0.195 vs. 0.727 +/- 0.438, p = 0.019), and the ratios of n-3 PUFA to n-6 PUFA (0.219 +/- 0.062 vs. 0.320 +/- 0.162, p = 0.017) in the HD group were significantly lower than those in the CKD group. These results suggest that there might be disorders not only in serum lipid metabolism but also in plasma fatty acid metabolism in HD patients.

Beneficial effect of neutrophil elastase inhibitor on anti-Thy1.1 nephritis in rats

BACKGROUND

Neutrophil elastase, one of the proteinases released by neutrophils, plays an important role at the sites of inflammation and was reported to be involved in the pathogenesis of glomerulonephritis. Sivelestat is a selective neutrophil elastase inhibitor used for acute lung injury associated with systemic inflammatory response syndrome. There have been few reports on the effects of sivelestat on renal disease.

METHODS

In male Wistar rats, anti-Thy1.1 nephritis was induced by the injection of anti-Thy1.1 antibody. The rats were divided into four groups: nephritic rats treated with low- (group A) and high-dose sivelestat (group B), those not treated with sivelestat (group C) and control rats (group D). Urine samples were obtained every day during the experiment. The rats were killed on day 6 in order to obtain the blood plasma and kidneys. Measurement of urine protein levels, blood biochemical values and histological examination of the kidneys were carried out.

RESULTS

Increased levels of proteinuria were observed in the nephritic rats (groups A, B and C) compared with group D. The proteinuria level was significantly suppressed by sivelestat in groups A and B in a dose-dependent fashion compared with group C. The light microscopy revealed an increased glomerular cell count in group C, which was significantly suppressed in group B. In the electron microscopic study, sivelestat suppressed the fusion of epithelial foot process, especially in group B.

CONCLUSION

Neutrophil elastase is suggested to be involved in the development of anti-Thy1.1 nephritis, and the neutrophil elastase inhibitor sivelestat reduces the tissue injury of anti-Thy1.1 nephritis in rats.

Pancreatic B-cell function is altered by oxidative stress induced by acute hyperglycaemia

AIMS

Type 2 diabetes is preceded by a symptom-free period of impaired glucose tolerance (IGT). Pancreatic B-cell function decreases as glucose intolerance develops. In many patients with IGT, fasting blood glucose is within normal limits and hyperglycaemia occurs only postprandially. We examined whether pancreatic B-cell function changes during acute hyperglycaemia induced by oral glucose loading.

METHODS

We calculated the insulinogenic index (I.I.) as an indicator of pancreatic B-cell function and measured serum levels of thioredoxin, a marker of cellular redox state, and 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative stress, during a 75-g oral glucose tolerance test (OGTT) in 45 subjects [24 patients with normal glucose tolerance (NGT), 14 with IGT and seven with Type 2 diabetes].

RESULTS

Thioredoxin levels decreased after glucose loading [66.1 +/- 23.7, *59.3 +/- 22.4, *49.3 +/- 21.2 and *37.7 +/- 18.0 ng/ml, fasting (0 min) and at 30, 60 and 120 min, respectively; *P < 0.001 vs. fasting]. In contrast, concentrations of 8-OHdG peaked at 30 min and then gradually decreased (0.402 +/- 0.123, *0.440 +/- 0.120, 0.362 +/- 0.119 and 0.355 +/- 0.131 ng/ml, *P < 0.05 vs. fasting, P < 0.01 vs. 30 min). The insulinogenic index correlated with the change in thioredoxin levels (r = 0.34, P < 0.05). However, there was no relationship with the change in 8-OHdG levels from 0 to 30 min.

CONCLUSIONS

Hyperglycaemia in response to oral glucose impairs pancreatic B-cell function with decreasing thioredoxin levels. The augmented oxidative stress induced by hyperglycaemia may affect the cellular redox state. These findings strongly suggest that repeated postprandial hyperglycaemia may play an important role in the development and progression of diabetes mellitus.

Fatty acid composition of plasma and kidney in rats with anti-Thy1.1 nephritis

BACKGROUND

n-3 Polyunsaturated fatty acids (PUFA) are reported to ameliorate atherosclerotic and inflammatory diseases because they compete with arachidonic acid and reduce its inflammatory metabolites. In the present study, the fatty acid composition of plasma and kidney in rats with anti-Thy1.1 nephritis was investigated.

MATERIALS AND METHODS

A group of male Wister rats weighing about 200 g was injected with anti-Thy1.1 antibody (1.25 mL/kg) through their tail veins (nephritis group). Rats in the control group were injected with saline. Five days after the injection, urinary protein levels were determined. All rats were then sacrificed and fatty acid composition of plasma and kidney were analyzed.

RESULTS

Eicosapentaenoic acids (EPA) levels in the kidney phospholipid (PL) fraction in the nephritis group were significantly lower than those in the control group (0.67 +/- 0.06 mol% vs. 0.96 +/- 0.06 mol%, p < 0.05). EPA levels in the plasma PL fraction in the nephritis group were also significantly lower than those in the control group (0.38 +/- 0.05 mol% vs. 0.59 +/- 0.03 mol%, p < 0.05). Urinary protein levels 5 days after the injection were inversely correlated with EPA levels in the kidney PL fraction (r2 = 0.65, p = 0.01). These results suggested that decreased EPA levels in the kidney PL fraction might play an important role in anti-Thy1.1 nephritis.

Nephrotic syndrome associated with interferon-beta-1b therapy for multiple sclerosis

A 43-year-old woman with multiple sclerosis (MS) had nephrotic syndrome 21 months after starting treatment with interferon (IFN)-beta-1b (subcutaneous administration). She had taken no drug except for the IFN-beta-1b. Because nephrotic syndrome may be induced by IFN therapy, the IFN was stopped. Percutaneous renal biopsy revealed that she had minimal change nephrotic syndrome. As nephrotic-range proteinuria, hypoalbuminemia, and general edema were worsening even 2 weeks after cessation of the drug, oral corticosteroid therapy (prednisolone 40 mg/day) was started. The nephrotic syndrome was treated successfully with prednisolone. The dosage of prednisolone was tapered, without a relapse, and then the corticosteroid therapy was stopped. IFN-beta-1b therapy was then resumed, and the patient is in remission for both nephrotic syndrome and MS. Though proteinuria and nephrotic syndrome is a rare adverse effect of IFN-beta-1b therapy, physicians treating MS patients with this agent should pay careful attention to new clinical symptoms and laboratory findings.

Roxithromycin inhibits transforming growth factor-? production by cultured human mesangial cells

BACKGROUND

Transforming growth factor-beta (TGF-beta) plays an important role in progression of renal injury. However, few materials which inhibit TGF-beta have been known. Roxithromycin (ROX), macrolide antibiotics, is known to have anti-inflammatory, immunomodulatory and tissue reparative effects besides its bacteriostatic activity, although the exact mechanism of its anti-inflammatory and immunomodulatory effects was not defined. We examined the effect of ROX on production of TGF-beta and type IV collagen by cultured human mesangial cells (HMC).

METHODS

Human mesangial cells were incubated with several concentrations of ROX and TGF-beta and type IV collagen levels in the culture supernatants were measured by enzyme-linked immunoassay. Amount of TGF-beta mRNA was also quantified by using a colourimetric mRNA quantification kit and semiquantitative reverse transcriptase polymerase chain reaction. We also examined the effect of ROX on tyrosine kinase, MAP kinase and NF-kappaB stimulated by thrombin.

RESULTS

Roxithromycin (0.1-10.0 microg/mL) inhibited TGF-beta production by HMC in a dose- and time-dependent manner without inducing cell injury. ROX (10.0 microg/mL) also inhibited mRNA expression of TGF-beta in HMC. Thrombin (5 U/mL) stimulated TGF-beta production by HMC and ROX significantly inhibited the stimulating effect of thrombin on TGF-beta production. ROX also inhibited the increment of type IV collagen production stimulated by thrombin. ROX (10.0 microg/mL) suppressed the thrombin-induced NF-kappaB activation, although ROX did not inhibit the activation of tyrosine kinase and MAP kinase by thrombin.

CONCLUSION

Roxithromycin has an inhibitory effect on TGF-beta production by HMC possibly via inhibition of NF-kappaB. ROX may be a potential agent for the treatment of glomerulosclerosis.

Comparison of lipid and fatty acid metabolism between minimal change nephrotic syndrome and membranous nephropathy

Polyunsaturated fatty acids have been reported to be associated with atherosclerotic and inflammatory diseases, as they are the major components of cytoplasmic membranes and the precursor fatty acids for prostaglandins and leukotrienes. Nephrotic syndrome is associated with serum lipid disorders, such as hypercholesterolemia due to the increased production of lipoproteins by the liver. However, there are few reports regarding the fatty acid metabolism in patients with nephrotic syndrome. In the present study, serum lipid concentrations and plasma fatty acid composition were measured in patients with minimal change nephritic syndrome (MCNS) and membranous nephropathy (MN). Seven patients with MCNS (MCNS group), 11 patients with MN (MN group) and 8 healthy subjects (control group) were enrolled in the study. All patients were diagnosed by percutaneous renal biopsy. Fasting blood samples were obtained and the serum lipid profile was measured enzymatically. The fatty acid composition of plasma was analyzed by gas-chromatography after transmethylation. There were no significant differences in serum urea nitrogen and creatinine levels among the three groups. Patients with MN were older than those with MCNS. In the serum lipid profile, hypercholesterolemia was observed both in the MCNS and MN groups. Regarding the plasma fatty acid composition, alpha-linolenic acid levels in the MCNS group were significantly higher than those in the control group (1.06 +/- 0.08 wt% vs. 0.77 +/- 0.16 wt%, p = 0.008) and docosahexaenoic acid levels in the MN group were significantly higher than those in the control group (5.51 +/- 1.17 wt% vs. 3.96 +/- 1.07 wt%, p = 0.005). These results suggest that nephrotic syndrome might not only disrupt lipid metabolism but also fatty acid metabolism.

Hypoxic conditions stimulate the production of angiogenin and vascular endothelial growth factor by human renal proximal tubular epithelial cells in culture

BACKGROUND

Chronic low oxygen in the tubulointerstitial area is a crucial cause of renal degradation and tubulointerstitial damage. Previous reports have suggested that the maintenance of renal blood flow plays a role in the suppression of progressive renal damage. Neovascularization is important for the maintenance of blood flow. We studied the production of angiogenic factors by culturing renal proximal tubular epithelial cells (PTEC) under hypoxic conditions.

METHODS

Cultured PTEC were exposed to normal and low-oxygen conditions. The levels of angiogenin (ANG) and vascular endothelial growth factor (VEGF) in the cell supernatants were measured by enzyme-linked immunosorbent assay. The messenger RNAs (mRNAs) of ANG and VEGF in the PTEC were examined by real-time reverse transcriptase polymerase chain reaction (real-time RT-PCR). The presence of ANG, VEGF and hypoxia-inducible factor-1 (HIF-1) was studied by immunofluorescence techniques. The effect of cobalt chloride (CoCl(2)), which is an HIF-1 inducer, on the production of ANG and VEGF was also examined in order to elucidate the contribution of the HIF-1 pathway to the production of these cytokines.

RESULTS

ANG and VEGF were demonstrated to exist in the cell supernatants, and ANG and VEGF mRNAs were detected in the PTEC. Hypoxic conditions stimulated the secretion of ANG (2.5-fold vs normoxia, P<0.001) and VEGF (3.2-fold vs normoxia, P<0.001) by PTEC. Hypoxic conditions increased the mRNA expression of ANG for 6 h (1.38-fold vs normoxia, P<0.05) and VEGF for 24 h (2.04-fold vs normoxia, P<0.01). Hypoxic conditions also enhanced ANG, VEGF and HIF-1 protein expression in PTEC. The CoCl(2) increased the secretion of ANG (5.2-fold vs control, P<0.0001) and VEGF (2.3-fold vs control, P<0.0001) by PTEC.

CONCLUSION

Under hypoxic conditions, the ANG and VEGF secreted by PTEC may modulate angiogenesis and vascular remodeling in the renal interstitium via an increase in the production of HIF-1.

Losartan, an Angiotensin-II Receptor Antagonist, Retards the Progression of Advanced Renal Insufficiency

Chronic renal disease with elevated level of serum creatinine (Cr) often progresses to end-stage renal disease. Although blockade of the renin-angiotensin system has been shown to slow the progression of chronic renal disease, it remains uncertain whether one could expect such a renoprotective effect even when the treatment is initiated late in the course of renal disease. The purpose of the present study was to examine the effect of losartan, an angiotensin-II receptor antagonist, on the progression of advanced renal insufficiency. We retrospectively analyzed eight hypertensive patients, whose baseline Cr levels exceeded 2.0 mg/dl (2.2-5.5); the subjects included 6 non-diabetic glomerular diseases, 1 diabetic nephropathy and 1 polycystic kidney disease. Losartan was given at the dosage of 25-50 mg/day. Changes in mean blood pressure (MBP) and serum levels of Cr, potassium (K) and uric acid were evaluated after treatment for 24 weeks. Slopes of reciprocal of serum Cr plotted against time (1/sCr slope), which indicate the rate of renal function loss before and after the treatment period, were compared. There was a significant reduction of 1/sCr slope after losartan (-0.004 +/- 0.002 dl/mg/week before and -0.001 +/- 0.002 dl/mg/week after the treatment, p < 0.05). MBP and serum levels of Cr, K and uric acid were not changed significantly by losartan treatment. However, improvement of 1/sCr slope was correlated to the degree of MBP changes. Based on the available data from 4 patients, proteinuria was decreased in 3 patients. These results suggest that losartan may retard the progression of advanced renal insufficiency.

Hepatitis C virus-associated glomerulonephritis without hepatitis C virus in the blood

An 82-year-old woman with nephrotic syndrome and a 61-year-old woman with proteinuria and purpura on the lower extremities are reported. Both patients had test results positive for hepatitis C virus (HCV) antibody, but HCV RNA was not detected in the blood of either patient. The kidney biopsy showed membranoproliferative glomerulonephritis with capillary deposition of C3 and immunoglobulin M, indicating HCV-associated glomerulonephritis. These cases are suggestive to study the pathogenesis of this disease.

Roxithromycin is an inhibitor of human coronary artery smooth muscle cells proliferation: a potential ability to prevent coronary heart disease

Roxithromycin (RXM), a macrolide antibiotic, is used in clinical trials to address secondary prevention of coronary heart disease. However, the effects of RXM on human coronary artery smooth muscle cells (CASMC) proliferation remain unclear. Human CASMC were stimulated with growth medium containing 5% fetal bovine serum and growth factors. RXM at 1 or 10 microg/ml, which are relevant to the therapeutic plasma levels, significantly suppressed mitogen-induced CASMC proliferation, assessed by WST-1 assay and cell counting. Flow cytometry analysis demonstrated that RXM suppressed mitogen-induced G1 to S progression on cell cycle. Western blot showed that RXM inhibited phosphorylation of retinoblastoma gene products, reduced protein levels of cyclin D1 and A, and restored downregulation of cyclin-dependent kinase (CDK) inhibitor p27kip1. The activities of CDK4 and CDK2 were suppressed by RXM without affecting their protein levels. When transfected with both IkappaB kinase alpha and beta constructs as nuclear factor-kappa B (NF-kappaB) activator, CASMC entered S phase at 24 h, and RXM inhibited it. Electrophoretic mobility shift assay and immunostaining of NF-kappaB p65 demonstrated that RXM inhibited mitogen-induced NF-kappaB activation. These results indicate that RXM is an inhibitor of human CASMC proliferation through modulating cell cycle regulatory proteins and inhibiting NF-kappaB signaling pathway.

Effects of eicosapentaenoic acids on oxidative stress and plasma fatty acid composition in patients with lupus nephritis

Eicosapentaenoic acid (EPA) is one of the major components of fish oil, which was reported to have antiatherogenic, anti-inflammatory and immune suppressive effects. In the present study, highly purified EPA was administered to patients with lupus nephritis and the effects of EPA on urinary 8-isoprostane, a reliable marker of oxidative stress, were investigated in these patients. Six outpatients (1 man and 5 women), with lupus nephritis diagnosed by renal biopsy, were entered in the study. We administered 1800 mg EPA ethyl-ester (purity > 95%) daily and examined the urinary 8-isoprostane levels and plasma fatty acid composition before and 3 months after EPA treatment. The urinary 8-isoprostane levels were significantly decreased after the treatment compared with those before the treatment (from 530 +/- 113 pg/mg x Cr to 235 +/- 49 pg/mg x Cr, p = 0.02). The EPA levels in the plasma phospholipid (PL) fraction were significantly increased after the treatment (from 3.30 +/- 0.64 mol% to 8.01 +/- 0.47 mol%, p < 0.001). Arachidonic acid (AA) levels in the plasma PL fraction were significantly decreased after the treatment (from 9.47 +/- 0.28 mol% to 7.33 +/- 0.43 mol%, p < 0.001). The ratios of EPA to AA were significantly increased after the treatment (from 0.35 +/- 0.07 to 1.14 +/- 0.16, p < 0.001). Thus, this preliminary study indicated that EPA might exert beneficial effects on lupus nephritis by decreasing the oxidative stress.

Effects of cilostazol on lipid and fatty acid metabolism

Cilostazol is a selective inhibitor of phosphodiesterase III with anti-platelet-aggregatory and vasodilating properties. Randomised, double-blind, placebo-controlled trials in 2702 patients with intermittent claudication demonstrated that cilostazol significantly increased walking distances compared with placebo. Furthermore, the agent has beneficial effects on the serum lipid profile and fatty acid composition in plasma. Consequently, cilostazol may be useful to prevent atherosclerosis from progressing by ameliorating lipid and fatty acid metabolism.

Involvement of tonsils in IgA nephropathy

This study was intended to clarify the involvement of tonsils in the pathogenesis of IgA nephropathy. In 62 patients with IgA nephropathy and 20 patients with other renal diseases, their tonsils were stimulated by an ultra short wave. Forty of 62 patients with IgA nephropathy (65%) showed a deterioration of urinary findings after the stimulation compared with six of 20 patients with other renal diseases (30%). Previous episodes of gross hematuria following upper respiratory tract infections existed in 17 of 40 patients (Group A) who showed a deterioration of urinary findings after tonsil stimulation (43%) as against in four of 22 (Group B) without the deterioration (18%). The level of serum secretory IgA was higher in Group A than in Group B. It is suggested that chronic tonsillitis may play an important role in the development of IgA nephropathy. Thirty-six patients received tonsillectomy from 1980-2002. The frequency of gross hematuria at upper respiratory infection decreased in 56% of the patients The amount of urinary protein decreased in 33% of the patients and RBC counts decreased in 56% of the patients Eight patients with tonsillectomy were followed up longer than 16 years Two of them went to hemodialysis and five of them showed no urinary abnormalities at present. The effect of tonsillectomy in the long term was not clarified in this study.

Plasma concentration of coupling factor 6 and cardiovascular events in patients with end-stage renal disease

BACKGROUND

Plasma asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), is an independent predictor of overall mortality and cardiovascular outcome in hemodialysis patients. However, not only ADMA but also traditional risk factors account for only part of the high cardiovascular morbidity and mortality in these patients. We investigated cross-sectionally the association between coupling factor 6 (CF6), an endogenous inhibitor of prostacyclin synthesis, and cardiovascular events in 95 hemodialysis patients.

METHODS

Plasma CF6 level was measured by radioimmunoassay, whereas plasma ADMA level by high-performance liquid chromatography (HPLC).

RESULTS

Plasma levels of CF6 and ADMA were threefold higher in hemodialysis patients than in control individuals, and there was a positive correlation between these two compounds (r=0.25, P < 0.05). Plasma CF6 level was positively correlated with serum creatinine level (r=0.36, P < 0.01) and was reduced after dialysis (P < 0.05). Plasma CF6 and ADMA levels were both higher in hemodialysis patients complicating ischemic heart disease (myocardial infarction and/or angina) than in those free of cardiovascular events. In a multiple regression model, plasma CF6 level (r=0.24, P=0.023) and ADMA level (r=0.26, P=0.023) were independently related to the occurrence of ischemic heart disease in hemodialysis patients.

CONCLUSION

CF6 is a novel risk factor for ischemic heart disease in end-stage renal disease (ESRD). Synergism of this peptide and ADMA might contribute to its occurrence presumably by inhibition of prostacyclin and nitric oxide production. A prospective study is needed to evaluate this issue more precisely.

A randomized open-label comparative study of conventional therapy versus mizoribine onlay therapy in patients with steroid-resistant nephrotic syndrome (postmarketing survey)

BACKGROUND

A previous double-blind 24-week clinical trial of mizoribine (MZ) vs placebo in steroid-resistant primary nephrotic syndrome (SRPNS) showed that MZ was more effective than placebo in reducing the rate of deterioration of renal function. The present study was conducted to evaluate the efficacy and safety of MZ in patients with SRPNS after 2 years' treatment.

METHODS

A multicenter randomized open-label controlled trial in patients with SRPNS was conducted as a 2-year prospective postmarketing study.

RESULTS

There was a significant imbalance in the baseline serum albumin level (s-Alb) between the conventional therapy (CT) and MZ onlay therapy groups. Early dropouts were more frequent in the subset of patients in the CT group having a baseline s-Alb < or =3 g/dl. Therefore, the primary analysis (urinary protein level (UP)-improving effect) was performed using a mixed-effects model, with stratification according to the baseline s-Alb value. The analysis revealed that, in the subset of 34 patients with membranous nephropathy (MN) within the stratum of patients with baseline s-Alb < or =3 g/dl (n = 52), the rate of change (slope of change in the UP level/month), in terms of the log (UP+0.2), was -0.0577 in those allocated to the MZ group and -0.0227 in those allocated to the CT group (P = 0.058). In the stratum of patients with a baseline s-Alb >3 g/dl (n = 97), there were no significant differences in the UP between the two treatment groups. Hence, MZ onlay therapy was not considered to be efficacious in this group of patients. No serious adverse reactions to the drug were observed.

CONCLUSIONS

The present study yielded significant results, in that it suggested the possibility that long-term MZ therapy may afford further reduction of the UP, in addition to that obtained following CT, in particular, in MN patients in a severe nephrotic state.

Thrombin stimulates production of fibronectin by human proximal tubular epithelial cells via a transforming growth factor-beta-dependent mechanism

BACKGROUND

Tubulointerstitial fibrosis contributes to the progression of many forms of glomerular disease and to end-stage renal failure. Inflammatory mediators generated during glomerular injury may induce tubulointerstitial lesions by stimulating tubular cells. Thrombin has multiple biological functions in addition to its role in haemostasis and has been detected in the urine of patients with glomerular diseases. The present study investigated whether thrombin can modulate the production of fibronectin (FN) in cultured human proximal tubular epithelial cells (PTEC).

METHODS

Cultured PTEC were incubated with or without thrombin to examine the effect of thrombin on FN production in PTEC. FN and transforming growth factor-beta (TGF-beta) levels were measured in culture supernatants by enzyme-linked immunosorbent assay (ELISA). Expression of FN mRNA was analysed by reverse transcriptase-polymerase chain reaction. Effects of thrombin on matrix metabolism were examined by enzyme immunoassay for the detection of secreted matrix metalloproteinase (MMP) and its inhibitors (TIMPs) as well as by zymography.

RESULTS

Thrombin stimulated FN secretion in PTEC. Thrombin also stimulated TGF-beta secretion in PTEC in a dose-dependent manner. Expression of FN mRNA by PTEC was augmented by thrombin. The stimulatory effect of thrombin on FN secretion was inhibited by neutralizing antibodies against TGF-beta but not by an irrelevant antibody. Thrombin-induced FN secretin was also inhibited by thrombin inhibitors, such as antithrombin III, hirudin and argatroban. Although thrombin stimulated TIMP-1 and -2 secretion by PTEC, the stimulatory effect of thrombin on MMP-2 was not statistically significant. Thrombin did not affect the expression of MMP-2 in zymography studies.

CONCLUSIONS

We found that thrombin stimulates FN production in PTEC without causing matrix degradation, an effect that may contribute to the formation of tubulointerstitial fibrosis associated with glomerular disease. The stimulatory effect of thrombin on FN production in PTEC is, at least in part, mediated by TGF-beta.

Relationship between salt intake, nitric oxide and asymmetric dimethylarginine and its relevance to patients with end-stage renal disease

Patients with essential hypertension (n = 24) were administered a low-salt diet (2 g NaCl/day), a high-salt diet (20-23 g) and then a low-salt diet for 7 days, and plasma levels of nitrate and nitrite (NOx) and asymmetric dimethylarginine (ADMA) were examined. There was a negative correlation between the percent changes in mean blood pressure and the plasma NOx concentration after salt loading and restriction. The percent change in plasma ADMA concentration was negatively correlated with that in the plasma NOx concentration after salt loading and restriction. In patients with end-stage renal disease (n = 51), the plasma ADMA concentration was positively correlated with the duration of dialysis treatment. The frequency of cardiovascular events was greater in patients with a plasma ADMA level of >/=3 microM than in those with a plasma AMDA level of <3 microM. The results indicate that ADMA is not only a modulator of salt sensitivity in hypertension but also a cardiovascular risk factor in end-stage renal disease.

Tissue factor pathway inhibitor production by human proximal tubular epithelial cells in culture

Fibrin deposition in the peritubular capillaries and along the tubular basement membrane is commonly observed in several renal diseases and suggests the involvement of blood coagulation in tubulointerstitial damage. It has been demonstrated that tissue factor (TF) is present in tubular epithelial cells of animal models of nephritis. Tissue factor pathway inhibitor (TFPI) regulates the extrinsic pathway of blood coagulation through its ability to inhibit TF activity and it is now thought to be produced mainly by the vascular endothelial cells. We examined whether human proximal tubular epithelial cells (PTEC) could produce TFPI and attempted to clarify the regulatory factors affecting TFPI production. Cultured human PTEC were used. The procoagulant activity (PCA) in PTEC lysate was quantified by measurement of the one-stage recalcification time. TFPI in the cell supernatants was measured by ELISA. The mRNA of TF and TFPI in PTEC was analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). PCA which is compatible with TF activity was present in the PTEC lysate. TF mRNA and TFPI mRNA were detected in PTEC. The amount of TFPI increased over time in the cell supernatants. Immnoblot analysis revealed 40 kD protein of TFPI, and TFPI antigen was demonstrated in PTEC by immunofluorescence. The concentration of TFPI was significantly increased following incubation with thrombin and heparin in a dose- and time-dependent manner, although the amount of TFPI mRNA was not changed. Our study showed that TFPI is produced in cultured PTEC and added one more cell type that produced TFPI other than endothelial cells. Thrombin and heparin stimulated TFPI secretion from PTEC. TFPI of PTEC may act against generation of thrombin and tubular fibrin formation induced by tissue factor activation. The augmentation of TFPI secretion by heparin may play an important role in the modulation of anticoagulant properties of PTEC.