Chronic graft dysfunction in renal transplant patients: potential role of plasminogen activator inhibitor type 1

BACKGROUND: Chronic allograft nephropathy is the main cause of long-term kidney graft loss. The plasminogen activator inhibitor type 1 (PAI-1) is a potential fibrogenic molecule whose secretion is regulated by several metabolic, inflammatory, and genetic factors. We aimed to determine whether PAI-1 secretion in renal transplant patients is correlated with the decline in renal function after transplantation. METHODS: Renal transplant patients (145 male/71 female) were included in the study 1-27 years after transplantation (median of follow-up: 7.35 years). At inclusion, routine clinical and biological data were collected, the 4G/5G polymorphism of the recipient PAI-1 gene was determined, and the PAI-1 plasma level was measured. RESULTS: The mean rate of decline in renal function was -4.26+/-0.30 ml/min/year. By multiple linear regression analysis, the rate of decline in renal function was significantly correlated with proteinuria (P=0.0176), occurrence of late acute rejection episodes (P=0.0001), and PAI-1 plasma level (P=0.0051). In addition, PAI-1 plasma level was also significantly correlated with body mass index (P=0.038), insulin (P<0.0001), platelet count (P<0.0001), and fibrinogen (P=0.024). The PAI-1 gene polymorphism tested did not influence the rate of decline in renal function after transplantation nor the plasma level of PAI-1 antigen. CONCLUSION: We conclude that PAI-1, whose secretion is determined in large part by metabolic and inflammatory factors, may be implicated in the rate of decline in renal function after transplantation.     

Elevated plasminogen activator inhibitor levels in cyclosporin-treated renal allograft recipients

Atherosclerosis and thrombosis, two major causes of morbidityand mortality in renal transplant recipients, share the sameclinical risk factors including decreased fibrinolysis and lipiddisturbances. In a crosssectional study we have determined parametersof fibrinolysis in control subjects (n=23) and stable renalallograft recipients without cyclosporin CsA (n=10) and withCsA (n=87) in their immunosuppressive treatment. In CsA-treatedpatients, tissue-type plasminogen activator was moderately increasedcompared to patients without CsA (8.4±3.3 vs 5.5±2.8ng/ml). The plasminogen activator inhibitor (PAI) activity inplasma was clearly increased in CsA-treated patients: 14.5±8.8vs 7.2±3.2 in normal controls and 8.5±2.4 AU/mlin patients without CsA. Total cholesterol and LDL cholesterollevels were higher in CsA-treated patients (256±62 and169±60 mg/dl) than in patients without CsA (209±45and 136±44 mg/dl). The two groups did not differ in HDLcholesterol, triglycerides, and lipoprotein(a). Hypercholesterolaemia,obesity, and steroid-induced diabetes could be identified asrisk factors for elevated plasma PAI activity in CsA-treatedpatients. Hypofibrinolysis induced by elevated PAI levels andincreased LDL cholesterol may contribute to the increased thrombogenicityand accelerated atherosclerosis observed in cyclosporin-treatedpatients.     

Protease-activated receptor-2 expression in IgA nephropathy: a potential role in the pathogenesis of interstitial fibrosis

An increasing body of evidence suggests that proteases may play a key role in the pathogenesis of tissue fibrosis. Protease-activated receptor-2 (PAR-2) is cleaved and activated by trypsin-like proteolytic enzymes, including tryptase and activated coagulation factor X (FXa). Both these soluble mediators have been demonstrated, directly or indirectly, at the interstitial level in progressive renal diseases, including IgA nephropathy (IgAN). PAR-2 mRNA and protein levels were investigated by RT-PCR and immunohistochemistry, respectively, in 17 biopsies from IgAN patients and 10 normal kidneys. PAR-2 expression was also evaluated, by RT-PCR and western blotting, in cultured human mesangial and proximal tubular cells. Finally, gene expression of plasminogen activator inhibitor-1 (PAI-1) and TGF-beta, two powerful fibrogenic factors, was evaluated in FXa-, trypsin-, and PAR-2 activating peptide-stimulated human proximal tubular cells by Northern blot. In normal kidneys, PAR-2 gene expression was barely detectable, whereas in IgAN biopsies the mRNA levels for this protease receptor were strikingly increased and directly correlated with the extent of interstitial fibrosis. Immunohistochemical staining demonstrated that PAR-2 protein expression in IgAN biopsies was mainly localized in the proximal tubuli and within the interstitial infiltrate. Proximal tubular cells in culture expressed PAR-2. Activation of this receptor by FXa in tubular cells induced a striking increase in intracellular calcium concentration. In addition, incubation of both cell lines with trypsin, FXa, or PAR-2 activating peptide caused a marked upregulation of PAI-1 gene expression that was not counterbalanced by an increased expression of plasminogen activators. Finally, PAR-2 activation induced a significant upregulation of TGF-beta gene and protein expression in both mesangial and tubular cells. On the basis of our data, we can suggest that PAR-2 expressed by renal resident cells and activated by either mast cell tryptase or FXa may induce extracellular matrix deposition modifying the PAI-1/PA balance and inducing TGF-beta expression. These molecular mechanisms may underlie interstitial fibrosis in IgAN.     

Expression of urokinase plasminogen activator and its receptor during acute renal allograft rejection

BACKGROUND: In inflammation, urokinase plasminogen activator (uPA) and its receptor (uPAR) play an important role in fibrinolysis and in activation and chemotaxis of neutrophils and lymphocytes. Moreover, the uPA/uPAR system is involved in processes that affect turnover of the extracellular matrix (ECM). The aim of this study was to determine the local and systemic release of uPAR, and the expression of uPA and uPAR in renal tissues during acute renal allograft rejection. METHODS: Blood, urine, and tissue samples were collected from 33 patients diagnosed with acute allograft rejection and from 14 transplant patients without rejection. From 10 healthy volunteers, blood and urine were collected as a control. In urine and blood samples, the levels of uPAR were determined by enzyme-linked immunosorbent assay (ELISA). Immunostaining and in situ hybridization for uPA and uPAR were performed on renal biopsies. RESULTS: uPAR was detectable at low levels in serum and urine of healthy volunteers and was increased in nonrejecting allograft recipients. Serum and urine levels of uPAR were higher in transplant recipients with rejection compared to nonrejectors. The urine and serum levels of uPAR correlated with the renal function. Immunostaining and in situ hybridization showed an up-regulation of both uPA and uPAR in rejection biopsies. Nonrejected grafts displayed no expression of uPA and uPAR by immunostaining, or of uPAR by in situ hybridization. uPA was detected in a limited number of tubular epithelial cells by in situ hybridization. During rejection, lymphocytes as well as tubular epithelial cells showed uPA and uPAR expression. In the vascular types of rejection, strong expression of uPA was also seen in the entire vessel wall, while uPAR was expressed by the endothelium. CONCLUSION: This study shows that (1) uPA and uPAR are up-regulated during acute renal allograft rejection; (2) uPAR levels in urine and serum correlate with serum creatinine levels, and (3) uPA and uPAR are produced by inflammatory cells, tubular epithelium, and vascular endothelium during acute renal allograft rejection.     

ACEI联合钙通道抑制剂对慢性移植物肾病肾纤维化的影响

目的探讨血管紧张素转换酶抑制剂（ACEI）洛汀新和钙通道抑制剂洛活喜对慢性移植物肾病肾纤维化的影响。方法将26例慢性移植物肾病患者随机分为两组，治疗组14例和对照组12例，两组均调整免疫抑制剂，但治疗组另加服洛汀新10mg／d，洛活喜5mg／d；随访监测患者治疗前和治疗后的临床及生化指标，并于治疗后1年行移植肾穿刺活检。结果治疗组动脉血压、血肌酐、尿蛋白均较治疗前显著降低（均P〈0．01）。对照组血肌酐上升速度减慢，但仍上升，其他生化指标变化不明显。移植肾穿刺活检显示治疗组大部分病例肾间质纤维化程度无变化，而对照组大部分病例肾间质纤维化程度有所加重。结论洛汀新和洛活喜联合使用可减缓移植’肾纤维化过程。     

Rapamycin inhibits PAI-1 expression and reduces interstitial fibrosis and glomerulosclerosis in chronic allograft nephropathy

BACKGROUND: Chronic allograft nephropathy (CAN) is characterized by deposition of extracellular matrix (ECM) in all renal compartments. PAI-1 seems to play a pivotal role in ECM turnover in CAN. Rapamycin has been shown to improve long-term graft survival in patients with CAN. The aim of the study was to evaluate the molecular mechanisms underlying the beneficial effects of rapamycin on CAN progression at glomerular and tubulointerstitial level. METHODS: After a biopsy-proven CAN diagnosis (T0), 18 patients on calcineurin inhibitors (CNI) were randomly assigned in a 2:1 ratio to continue CNI (6 patients) or to receive rapamycin (RAPA; 12 patients). After 2 years of treatment (T24), all patients underwent a second renal biopsy. Morphometric analysis was conducted at T0 and at T24. PAI-1 expression was evaluated at T0 and T24 by immunohistochemistry. We evaluated the effect of rapamycin on PAI-1 gene expression in cultured proximal tubular cells incubated with CD40L or thrombin, two potential CAN pathogenic mediators. RESULTS: The RAPA group showed a significant regression of glomerulosclerotic lesions and only a 26% increase in interstitial fibrosis after 2 years compared to baseline, whereas the CNI group showed progression of glomerulosclerosis and 112% increase in fibrosis. Glomerular and tubulointerstitial PAI-1 expression was reduced compared to the baseline in the RAPA group, while they were unchanged in the CNI group. In vitro data showed that rapamycin significantly reduced PAI-1 gene expression induced by both CD40L and thrombin in proximal tubular epithelial cells. CONCLUSIONS: These data suggest that rapamycin may modulate ECM deposition in CAN reducing PAI-1 expression.     

TGF-beta1 in chronic allograft nephropathy following renal transplantation

BACKGROUND: Evidence from experimental models and clinical studies supports a major role for transforming growth factor-beta1 (TGF-beta1) in renal fibrosis. The aim of this study was to use repeated measurement of plasma TGF-beta1 as an indicator of persistent expression in a cohort of patients during the first 2 years post-renal transplantation and to correlate the findings with the development of chronic allograft nephropathy (CAN). METHODS: Active plasma TGF-beta1 was quantified in 100 consecutive renal allograft recipients (samples/patient = 35.6 +/- 12.9) under standard clinical management for a mean of 23 months (range 3.4-45 months). All patients were followed up for a minimum of 5 years. RESULTS: By 5 years, 23 patients had developed biopsy-proven CAN (CAN+), all of whom had been positive for plasma TGF-beta1. Demographic data were compared between patients who were CAN+ and CAN-negative (CAN-) and were not significantly different. TGF-beta1 exposure expressed as area under the curve / day (AUC/day) was correlated with the incidence of CAN. A Cox regression model was used to investigate the interrelationship of CAN, acute cellular rejection (ACR) and TGF-beta1 levels. ACR episodes were predictive of the development of CAN (log-rank test, p=0.003). After allowing for the effect of ACR (hazard ratio [HR]=3.6; 95% confidence ratio [95% CI], 1.5-8.7) between patients with and without ACR episodes, p=0.003), the independent effect of TGF-beta1 was confirmed (HR=1.7; 95% CI, 1.1-2.6; per quartile; p=0.008). CONCLUSION: The results demonstrate that episodes of ACR are highly predictive of chronic damage in the graft. Cumulative exposure to TGF-beta1 is identified as an independent predictor of CAN in the first 2 years posttransplantation.     

Inhibition of plasminogen activator inhibitor-1 by angiotensin II receptor blockers on cyclosporine-treated renal allograft recipients

INTRODUCTION: We previously showed that proteinuria from a renal graft was significantly decreased by administration of losartan potassium, an angiotensin II receptor blockers (ARB). To further evaluate the mechanism, we performed another clinical study focusing on the change in plasma plasminogen activator inhibitor-1 (PAI-1) levels among cyclosporine (CyA)-treated renal allograft recipients. METHODS: Among 12 hypertensive CyA-treated kidney transplant patients, four received 25 to 50 mg/day of losartan; four, 4 to 8 mg/day of candesartan cilexetil; and another four, 20 to 40 mg/day of nifedipine. Four CyA-treated kidney-transplanted patients without hypertension were selected as a control group. Informed consent was obtained from all participants. PAI-1 and serum creatinine (S-Cr) levels were monitored every 3 months for 1 year. RESULTS: Considering the pretreatment of PAI-1 as 100%, the mean percent of PAI-1 at 1 year after the onset of study for losartan, candesartan, nifedipine, and control groups were 78.6 +/- 6.7%, 81.4 +/- 8.0%, 96.7 +/- 7.6%, and 110.4 +/- 9.2%, respectively. The ARB groups demonstrated significant differences from the control group (P < .01), while the nifedipine group did not. S-Cr levels among ARB-administered groups were increased slightly but temporarily. As for S-Cr levels, no significant differences were seen among the four groups. CONCLUSIONS: Control of hypertension itself is important for all renal graft recipients; however, PAI-1 reduction by ARBs was thought to be a key for renal preservation. We expect that ARBs will contribute to prolonged renal allograft survival.     

Monocyte procoagulant activity and plasminogen activator. Role in human renal allograft rejection

Currently the mechanism of renal allograft rejection is not well understood. This study was designed to determine whether induction of monocyte procoagulant activity (MCPA) is important in the pathogenesis of renal allograft rejection. The MPCA assay was performed utilizing a one stage clotting assay both in normal and in factor-VII-deficient plasma. There was no increase in spontaneous MPCA in 20 patients with endstage renal failure and in 10 patients following abdominal or orthopedic operation, as compared with 20 normal controls. MPCA was assessed daily in 18 patients who had received renal allografts. Rejection episodes (RE) were predicted on the basis of persistent elevation in MPCA as compared with pretransplant levels. Rejection was diagnosed clinically and treated on the basis of standard criteria. Treated RE were compared with those predicted by elevated MPCA, and 3 patients were assessed as having no RE by MPCA and by standard criteria. In 8 RE, MPCA correlated temporally with RE (same day) when compared with standard criteria. In 12 RE, MPCA was predictive of rejection preceding standard criteria by at least 24 hr. There were 7 false-positive predictions on the basis of MPCA; however, there was only 1 false negative. MPCA was shown to be a prothrombinase by its dependence only on prothrombin and fibrinogen for full activity. MPCA may be important in the pathogenesis of allograft rejection, and additionally it may be a useful adjunct in the clinical management of this disease.     

Angiotensinogen and plasminogen activator inhibitor-1 gene polymorphism in relation to chronic allograft dysfunction

Chronic allograft dysfunction (CAD) is the most common cause of allograft failure in the long-term, and current immunologic strategies have little effect on this condition. The renin-angiotensin system (RAS) plays important roles progression of chronic renal disease. It is thought that plasminogen activator inhibitor-1 (PAI-1) functions in the RAS, in addition to involvement in thrombotic risk and fibrosis. This study investigated possible links between angiotensinogen (AGT) genotypes (M235T/MM, MT, TT) and PAI-1 genotypes (4G4G, 4G5G, 5G5G) and CAD assessments of both types of polymorphism were performed in 82 renal allograft recipients. One hundred healthy subjects were also investigated for AGT polymorphism, and 80 healthy subjects for PAI-1 polymorphism. Genotypes were determined using polymerase chain reaction (PCR) sequence-specific primers, and PCR followed by restriction fragment length polymorphism analysis. Kidney recipients with CAD had significantly lower frequencies of the MM genotype and the M allele than the recipients without CAD (p < 0.05 and <0.001). The transplant recipients with CAD also had significantly lower frequencies of the 5G5G genotype and the 5G allele than those without CAD (p < 0.001 and <0.05). Determination of AGT M235T and PAI-1 genotypes prior to transplantation may help identify patients who at risk for chronic renal transplant dysfunction.     

Possible involvement of urokinase-type plasminogen activator release from human peripheral blood lymphocytes in the pathophysiology of chronic allograft nephropathy

BACKGROUND: Little is known of the fibrinolytic host immune mechanisms responsible for induction of chronic allograft nephropathy (CAN), defined as a loss in glomerular filtration rate (GFR) caused by tubular atrophy and interstitial fibrosis, often with fibrous intimal thickening in the small arteries. However, chronic rejection has been reported to be associated with decreased activity of the fibrinolytic system. In our previous study, [Deamino-Cys1, D-Arg8]-vasopressin (dDAVP) induced urokinase-type plasminogen activator (uPA) release from human peripheral T lymphocytes via arginine vasopressin (AVP) V2-receptor-mediated reaction enhanced by an AVP V1-receptor antagonist. Therefore, we examined the level of uPA released from peripheral T lymphocytes by AVP in transplant patients with CAN in comparison with control groups. PATIENTS AND METHODS: In this study, we evaluated in vitro uPA releasing activity of lymphocytes obtained from renal allograft patients with well-functioning grafts (n = 9), CAN (n = 5), or acute rejection episodes (n = 5) compared with lymphocytes from healthy volunteers with normal renal function (n = 12) or patients with renal insufficiency (n = 5). RESULTS: Lymphocytes prepared from patients with chronic allograft nephropathy showed a significantly lower increase in uPA release induced by the combination of the V1-receptor antagonist and dDAVP compared with those from the other groups. CONCLUSION: This finding suggested that a decrease in uPA release from human peripheral blood lymphocytes by AVP-related peptides may be potentially involved in the pathophysiology of CAN.     

Enhanced expression of plasminogen activator inhibitor 1 in patients with nephrotic syndrome

Hypercoagulability is present in patients with nephrotic syndrome. However, alterations in coagulation and fibrinolysis reflected in the glomeruli and urine are not fully understood. We examined plasma and urine concentrations of tissue-type plasminogen activator (tPA) and type 1 plasminogen activator inhibitor (PAI-1) in 33 patients with nephrotic syndrome (nephrotic group). We compared these concentrations with the concentrations in 30 nonnephrotic patients with chronic glomerulonephritis (nonnephrotic group) and with the concentrations in 30 healthy volunteers (control group). We also examined fibrin/fibrinogen degradation products in serum and urine and plasma D-dimers. The expression of tPA and PAI-1 was examined in isolated glomeruli using RT-PCR methods. Deposition of fibrinogen/fibrin-related antigen was observed by direct immunofluorescence. The incidence of fibrinogen/fibrin-related antigen deposition in the nephrotic group was significantly higher than that in the nonnephrotic group. The concentrations of fibrin/fibrinogen degradation products in serum and urine and of plasma D-dimers were significantly elevated in the nephrotic group as compared with the nonnephrotic and control groups. The plasma concentrations of tPA in the nephrotic group were significantly higher than those in the control group. The urinary excretion of tPA in the nephrotic group was also significantly higher than in the nonnephrotic and control groups. The urinary excretion of PAI-1 in the nephrotic group was higher than that in the control group. The ratio of PAI-1 mRNA to tPA mRNA in glomeruli was increased in the nephrotic group as compared with the nonnephrotic group. These results indicate that the fibrinolytic activity is increased in patients with nephrotic syndrome despite urinary losses of tPA. However, a relatively enhanced expression of PAI-1 may be involved in the intraglomerular fibrinogen/fibrin-related antigen deposition seen in nephrotic syndrome.     

Ⅰ型纤溶酶原激活物抑制物在IgA肾病肾小管间质损伤中的作用研究

目的 探讨Ⅰ型纤溶酶原激活物抑制物（ＰＡＩ－１）在ＩｇＡ肾病肾小管间质损害中的作用。方法 采用原位杂交和免疫组织化学技术,分别在基因和蛋白质水平检测３８例ＩｇＡ肾病患者肾小管间质中的ＰＡＩ－１表达,同时观察α－平滑肌肌动蛋白和增殖细胞核抗原（ＰＣＮＡ）的表达变化。