Expression of beta2-microglobulin and c-fos mRNA: is there an influence of high- or low-flux dialyzer membranes?

BACKGROUND: Dialysis-related amyloidosis is an important complication of long-term hemodialysis (HD) therapy with several pathogenetic factors. One of them is the influence of the dialyzer membrane type on the synthesis of beta2-microglobulin (beta2m). In vitro results are controversial. Thus, the hypothesis of whether in vivo beta2m generation is induced by the HD procedure and whether this induction depends on the type of the used dialyzer membrane should be tested. The aim of the present study was to investigate the influence of "biocompatible" high-flux versus "bioincompatible" low-flux HD on in vivo beta2m generation as well as the induction of the early activation gene c-fos in peripheral blood cells. METHODS: Six nondiabetic HD patients [mean age 46 (21 to 69) years; Kt/V> 1.2] were included in a randomized crossover study using either a low-flux (cellulosic/cuprophan) or a high-flux (polyamide) dialyzer membrane. At the end of a four-week run-in period for each membrane, whole blood samples were taken before, immediately at, and four hours after the end of the dialysis session. MRNA was extracted, and after transcription to cDNA, quantitative polymerase chain reaction was performed for the beta2m gene, the early response gene c-fos, and the GAP-DH housekeeping gene. RESULTS: Based on the applied method for detection of specific mRNA, the results were given as ratio of beta2m or c-fos cDNA per GAP-DH cDNA. General cell activation during HD was indicated by increasing mRNA expression of c-fos related to the time course of the dialysis session, whereas beta2m did not change significantly. However, no difference was found when comparing the low-flux and the high-flux dialyzer membranes. Despite the evidence for activation of peripheral blood cells, as indicated by increasing c-fos message, no sign of beta2m mRNA induction during HD procedure with different dialyzer membranes was seen. CONCLUSIONS: Our results suggest that there is post-transcriptional regulation of beta2m generation and/or release as well as the influence of the dialyzer membrane type on post-translational processes, that is, advance glycation end products (AGE) or conformational modification of the beta2m protein. Furthermore, our data demonstrate that gene expression patterns during dialysis and/or uremia are not homogenous and need to be investigated further, especially with respect to the proinflammatory role of early leukocyte activation signals.

Elevated plasma TGF-beta1 in renal diseases: cause or consequence?

We previously reported elevated levels of TGF-beta1 in patients with renal carcinoma. Certain aspects led us to ask whether they might be caused by chronic damage to the kidney(s). Here we report on an extended set of patients with various renal diseases, lung cancer, humoral immunodeficiency and controls. For latent TGF-beta1 in plasma, we find that the control, immunodeficiency, lung cancer and kidney transplant groups do not differ significantly (means, 7.0-8.8 ng/ml). Also, acute short-term renal stress (extracorporal lithotrypsy) does not lead to an increase of TGF-beta1. However, the pyelonephritis patients present with levels of 19.0 ng/ml, chronic extracorporal dialysis patients with 15.5 ng/ml, and renal cell carcinoma patients with 22.8 ng/ml. For active TGF-beta1 these findings are exactly recovered. For serum levels, only the renal carcinoma group presents with significantly elevated levels of TGF-beta1. Kidney transplantation seems to normalize TGF-beta1 levels, while in the kidney cancer patients surgery has an effect only in part of the group. We conclude that elevated plasma TGF-beta1 levels are common in at least two chronic renal disease conditions, and that it normalizes with restoration of renal function. It is tempting to speculate that chronic elevation of TGF-beta1 in these patients may be critically involved in these conditions predisposing to renal cancer.

Progression of renal failure after subtotal nephrectomy in transgenic rats carrying an additional renin gene [TGR(mREN2)27].

OBJECTIVE: To study the evolution of glomerulosclerosis after renal ablation in a model with abnormal regulation of the renin gene. METHODS: Four-month-old female ovariectomized hypertensive heterozygous transgenic rats (TGR) harbouring the murine REN-2 gene were compared with pressure-matched, pair-fed, stroke-prone, spontaneously hypertensive rats (SHRsp). Both groups were followed for 6 weeks after 70% subtotal nephrectomy (SNX) or sham operation. RESULTS: Blood pressures in the SNX group at the end of the experiment were 193 +/- 3 mmHg in TGR and 199 +/- 5 mmHg in SHRsp. The final C(in) was 306 +/- 68 microliters/min per 100 g body weight in TGR that had undergone SNX and 550 +/- 93 microliters/min per 100 g body weight in SHR that had undergone SNX (P < 0.02), whereas inulin clearance (C(in)) in sham-operated pair-fed TGR and SHRsp controls did not differ from each other. The glomerulosclerosis index was 1.75 +/- 0.08 in perfusion-fixed TGR that had undergone SNX versus 1.21 +/- 0.03 in SHR that had undergone SNX (P < 0.005). In addition, the media thickness of preglomerular vessels was significantly greater in TGR that had undergone SNX (7.48 +/- 0.79 microns) than it was in SHRsp that had undergone SNX (5.27 +/- 1.38 microns, P < 0.02). Rat renal renin messenger RNA (mRNA) expression and, in parallel, mouse REN-2 gene expression were lower in TGR after SNX. Plasma renin and angiotensin II (ANG II) concentrations were reduced to a similar extent in both SNX groups, but plasma prorenin was higher in TGR that had undergone SNX than it was in SHRsp that had undergone SNX. The angiotensin II:I ratio in the kidney was significantly higher in TGR (P < 0.01). There was no significant difference between sham-operated or subtotally nephrectomized TGR and SHRsp with respect to angiotensin type 1 mRNA and angiotensinogen mRNA. The renal angiotensin converting enzyme activity, however, was significantly higher in sham operated and subtotally nephrectomized TGR than it was in sham operated SHRsp and in SHRsp that had undergone SNX. CONCLUSION: Deterioration of renal function is accelerated in subtotally nephrectomized transgenic rats [TGR(mREN2)27] compared with that in comparably hypertensive SHRsp despite suppressed circulating active mRNA and decreased renal renin mRNA. Although alternative explanations are possible, this observation is consistent with a role for local ANG II in the genesis of glomerulosclerosis.

Renin gene expression in human kidney biopsies from patients with glomerulonephritis or graft rejection.

The expression of renin mRNA was determined by a quantitative polymerase chain reaction assay in 27 human kidney samples: (1) 15 biopsies of patients with glomerulonephritis with or without angiotensin-converting enzyme inhibitor (ACEI) treatment; (2) biopsies of six renal allografts with graft rejection; and (3) six biopsy samples from unaffected parts of tumor nephrectomy specimens as controls. After isolation of RNA, 0.5 to 1 microgram of total RNA was used for reverse transcription to generate cDNA. The human renin gene was subsequently amplified by the use of two primers spanning the second and third exons. Renin expression was quantified with a renin cDNA mutant as the internal standard. It exhibited the same primer binding sites as the endogenous gene but carried a 155-basepair deletion, thus yielding a shorter amplification product. The number of glomeruli was counted by microscopic transillumination immediately after biopsy (median, 9 per biopsy; range, 2 to 23). Renin mRNA was expressed as femtograms of renin mRNA per glomerulus. Renin gene expression was lower in glomerulonephritic patients without ACEI treatment compared with that in control tumor nephrectomy samples, i.e., 63 +/- 20 (N = 7) versus 250 +/- 50 fg (N = 6) of renin mRNA/glomerulus, (P < 0.02), although plasma renin concentration in the glomerulonephritic patients was in the normal range. Significantly higher renin mRNA expression was found in glomerulonephritic patients treated with ACEI, i.e., 210 +/- 50 (N = 8) compared with 63 +/- 20 (N = 7) fg of renin mRNA/glomerulus in patient not treated with ACEI (P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

[Kidney function in hypertensive patients with chronic renal failure treated with the dual eliminated ACE-inhibitor spirapril]. / Renale Funktion bei hypertensiven Patienten mit chronischer Niereninsuffizienz unter Therapie mit dem dual eliminierbaren ACE-Hemmer Spirapril.

PATIENTS AND METHOD: Spirapril is a recent ACE inhibitor with a both renal and hepatic elimination pathway. In order to determine its tolerability, primarily the impact on renal function, Spirapril was tested in a single-blind trial with a 2-week placebo run-in phase and a 4-week active treatment period. Forty-nine patients (34 males and 15 females) with varying degrees of renal impairment were included. Their pretreatment diastolic blood pressure (DBP) ranged from 95 to 115 mm Hg. Spirapril was administered in oral doses of 6 mg once daily. RESULTS: Forty-four patients completed the study. Four patients dropped out due to side effects, 1 patient was withdrawn from the study due to lack of antihypertensive efficacy. 48% of the completers with renal failure achieved a normalized diastolic blood pressure (DBP < or = 90 mm Hg) or a reduction in DBP of > or = 10 mm Hg; the corresponding figure for patients with normal renal function was 31%. Renal function was assessed in the beginning and at the end of the active Spirapril treatment period using Tc-99m-DTPA-clearance (representing glomerular filtration rate), J-131-hippuran-clearance (representing renal plasma flow) and creatinine clearance. Particularly in patients with renal impairment, Spirapril did not deteriorate renal function as given by these parameters. Regression analysis revealed a linear correlation between total plasma clearance of the active metabolite Spiraprilate and creatinine clearance. There was no evidence for drug accumulation. CONCLUSION: In patients with renal impairment the pharmacokinetic results indicate a non-renal elimination of the drug. Spirapril 6 mg once daily is concluded to be a well tolerated antihypertensive therapy for patients with mild to moderate hypertension and varying degrees of chronic renal failure.

Pharmacokinetics of spirapril and spiraprilat in patients with chronic renal failure.

In this single-blind trial with a 2-week placebo run-in followed by a 4-week active-treatment period, patients were given 6 mg of spirapril once daily. Forty-nine hypertensive men and women were recruited; all had pretreatment diastolic blood pressures (DBP) of 95-115 mmHg with varying degrees of renal impairment. Regression analysis of pharmacokinetic parameters C(max)ss (the maximum steady-state drug concentration in plasma during a dosing interval), Cl/f (total plasma clearance) and k (elimination rate constant) of spirapril on creatinine clearance (Clcr) showed that the pharmacokinetics of spirapril were not significantly influenced by the degree of renal impairment. C(max)ss values of spiraprilat, however, increased with decreasing Clcr, and AUC(l)ss (area under the concentration-time curve during a dosing interval) values also increased. Regression analysis of the pharmacokinetic parameters C(max)ss, Clm/fm (total plasma clearance) and lambda 1 (rate constant of the first disposition phase) of spiraprilat on Clcr showed that Clm/fm as well as lambda 1 were linearly correlated with Clcr (p < 0.01). However, the results indicate that, even when renal elimination is completely blocked, there is significant elimination of spiraprilat through a non-renal pathway. In conclusion, the risk of drug accumulation after multiple dosing is minimal as the presence of a substantial non-renal spiraprilat elimination was consistently demonstrated.

Spirapril in chronic renal failure.

In a single-blind trial with a 2-week placebo run-in phase and a 4-week active-treatment period, spirapril at 6 mg once daily was administered to 49 consecutive hypertensive patients (34 men and 15 women). All had pretreatment diastolic blood pressures (DBP) of 95-115 mmHg and varying degrees of renal impairment. At the end of the placebo run-in and at the end of active treatment, renal function was assessed using the following procedures: technetium 99m-DTPA clearance [for glomerular filtration rate (GFR)]; radioiodine (131I)-labelled sodium iodohippurate (Hippuran) clearance [for renal plasma flow (RPF)]; creatinine clearance (Clcr). No statistically significant differences were found in GFR or Clcr during spirapril treatment. In renally impaired patients, RPF remained virtually unchanged whereas, in patients with normal Clcr, there was an increase of around 10% during active treatment. At the end of the study, 48% of the patients with renal failure achieved normalization of DBP (< or = 90 mmHg) and/or a DBP reduction of > or = 10 mmHg; the corresponding rate for patients with normal renal function was 31%. In conclusion, in patients with mild-to-moderate essential hypertension and varying degrees of renal impairment, spirapril at 6 mg once daily is an efficacious and well tolerated antihypertensive therapy.

Development and regulation of hepatocellular fatty acid synthesis towards term: studies in isolated fetal rat hepatocytes.

De novo fatty acid synthesis was studied in hepatocytes freshly isolated from rat fetuses on day 20 and 22 (term) of gestation by using the 3H2O incorporation method. Within 1 h, about 4 nmoles palmitate equivalents/10(6) cells were synthesized on day 20 of gestation. Towards term this rate decreases to about two thirds of this value. Both on day 20 and 22 of gestation, fetal hepatocellular de novo fatty acid synthesis is stimulated by the addition of lactate and octanoate, whereas a stimulating effect by the addition of pyruvate was found on day 20 of gestation only. These data provide evidence that both cytosolic and mitochondrially derived NADH2 is an adequate source of reducing equivalents required for NADPH2-dependent fatty acid synthesis. Insulin stimulates fetal hepatocellular de novo fatty acid synthesis at term, whereas db-cAMP remains ineffective on both gestational days under study.