Clinical and Prognostic Factors in Patients with IgG4-Related Kidney Disease

BACKGROUND

IgG4-related kidney disease is a major manifestation of IgG4-related disease, a systemic fibroinflammatory disorder. However, the clinical and prognostic kidney-related factors in patients with IgG4-related kidney disease are insufficiently defined.

METHODS

We conducted an observational cohort study using data from 35 sites in two European countries. Clinical, biologic, imaging, and histopathologic data; treatment modalities; and outcomes were collected from medical records. Logistic regression was performed to identify the possible factors related to an eGFR ≤30 ml/min per 1.73 m 2 at the last follow-up. Cox proportional hazards model was performed to assess the factors associated with the risk of relapse.

RESULTS

We studied 101 adult patients with IgG4-related disease with a median follow-up of 24 (11-58) months. Of these, 87 (86%) patients were male, and the median age was 68 (57-76) years. Eighty-three (82%) patients had IgG4-related kidney disease confirmed by kidney biopsy, with all biopsies showing tubulointerstitial involvement and 16 showing glomerular lesions. Ninety (89%) patients were treated with corticosteroids, and 18 (18%) patients received rituximab as first-line therapy. At the last follow-up, the eGFR was below 30 ml/min per 1.73 m 2 in 32% of patients; 34 (34%) patients experienced a relapse, while 12 (13%) patients had died. By Cox survival analysis, the number of organs involved (hazard ratio [HR], 1.26; 95% confidence interval [CI], 1.01 to 1.55) and low C3 and C4 concentrations (HR, 2.31; 95% CI, 1.10 to 4.85) were independently associated with a higher risk of relapse, whereas first-line therapy with rituximab was protective (HR, 0.22; 95% CI, 0.06 to 0.78). At their last follow-up, 19 (19%) patients had an eGFR ≤30 ml/min per 1.73 m 2 . Age (odd ratio [OR], 1.11; 95% CI, 1.03 to 1.20), peak serum creatinine (OR, 2.74; 95% CI, 1.71 to 5.47), and serum IgG4 level ≥5 g/L (OR, 4.46; 95% CI, 1.23 to 19.40) were independently predictive for severe CKD.

CONCLUSIONS

IgG4-related kidney disease predominantly affected middle-aged men and manifested as tubulointerstitial nephritis with potential glomerular involvement. Complement consumption and the number of organs involved were associated with a higher relapse rate, whereas first-line therapy with rituximab was associated with lower relapse rate. Patients with high serum IgG4 concentrations (≥5 g/L) had more severe kidney disease.

A French Cohort Study of Kidney Retransplantation after Post-Transplant Lymphoproliferative Disorders

BACKGROUND AND OBJECTIVES

Post-transplant lymphoproliferative disorders arising after kidney transplantation portend an increased risk of morbidity and mortality. Retransplantation of patients who had developed post-transplant lymphoproliferative disorder remains questionable owing to the potential risks of recurrence when immunosuppression is reintroduced. Here, we investigated the feasibility of kidney retransplantation after the development of post-transplant lymphoproliferative disorder.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We reviewed the data from all patients who underwent kidney retransplantation after post-transplant lymphoproliferative disorder in all adult kidney transplantation centers in France between 1998 and 2015.

RESULTS

We identified a total of 52 patients with kidney transplants who underwent 55 retransplantations after post-transplant lymphoproliferative disorder. The delay from post-transplant lymphoproliferative disorder to retransplantation was 100±44 months (28-224); 98% of patients were Epstein-Barr virus seropositive at the time of retransplantation. Induction therapy for retransplantation was used in 48 patients (i.e., 17 [31%] patients received thymoglobulin, and 31 [57%] patients received IL-2 receptor antagonists). Six patients were also treated with rituximab, and 53% of the patients received an antiviral drug. The association of calcineurin inhibitors, mycophenolate mofetil, and steroids was the most common maintenance immunosuppression regimen. Nine patients were switched from a calcineurin inhibitor to a mammalian target of rapamycin inhibitor. One patient developed post-transplant lymphoproliferative disorder recurrence at 24 months after retransplantation, whereas post-transplant lymphoproliferative disorder did not recur in 51 patients.

CONCLUSIONS

The recurrence of post-transplant lymphoproliferative disorder among patients who underwent retransplantation in France is a rare event.

Post-transplantation lymphoproliferative disorder after kidney transplantation: report of a nationwide French registry and the development of a new prognostic score

PURPOSE

Post-transplantation lymphoproliferative disorder (PTLD) is associated with significant mortality in kidney transplant recipients. We conducted a prospective survey of the occurrence of PTLD in a French nationwide population of adult kidney recipients over 10 years.

PATIENTS AND METHODS

A French registry was established to cover a nationwide population of transplant recipients and prospectively enroll all adult kidney recipients who developed PTLD between January 1, 1998, and December 31, 2007. Five hundred patient cases of PTLD were referred to the French registry. The prognostic factors for PTLD were investigated using Kaplan-Meier and Cox analyses.

RESULTS

Patients with PTLD had a 5-year survival rate of 53% and 10-year survival rate of 45%. Multivariable analyses revealed that age > 55 years, serum creatinine level > 133 μmol/L, elevated lactate dehydrogenase levels, disseminated lymphoma, brain localization, invasion of serous membranes, monomorphic PTLD, and T-cell PTLD were independent prognostic indicators of poor survival. Considering five variables at diagnosis (age, serum creatinine, lactate dehydrogenase, PTLD localization, and histology), we constructed a prognostic score that classified patients with PTLD as being at low, moderate, high, or very high risk for death. The 10-year survival rate was 85% for low-, 80% for moderate-, 56% for high-, and 0% for very high-risk recipients.

CONCLUSION

This nationwide study highlights the prognostic factors for PTLD and enables the development of a new prognostic score. After validation in an independent cohort, the use of this score should allow treatment strategies to be better tailored to individual patients in the future.

Renal transplantation in HIV-infected patients: the Paris experience

Kidney transplantation is now considered as a reasonable option for HIV-infected patients with end-stage renal disease. We describe here a retrospective study conducted in five transplantation centers in Paris. Twenty-seven patients were included. Immunosuppressive protocol associated an induction therapy and a long-term treatment combining mycophenolate mofetil, steroids and either tacrolimus or cyclosporine. All the patients had protocol biopsies at 3 months and 1 year. Patient's survival was 100% at 1 year and 98% at 2 years. Graft survival at 1 and 2 years is 98% and 96% at 1 and 2 years, respectively. The mean glomerular filteration rate values at 12 and 24 months were 60.6 mL/min/1.73 m² (range 23-98) and 65.4 mL/min/1.73 m² (range 24-110), respectively. Acute cellular rejection was diagnosed in four cases (15%). Because of high trough levels of calcineurin inhibitor, protease-inhibitor therapies were withdrawn in 11 cases. HIV disease progression was not observed. One patient developed B-cell lymphoma. In conclusion, our study confirms the safety of renal transplantation in HIV-infected patients with few adverse events and a low incidence of acute rejection.

Prophylaxis of CMV disease by ganciclovir (DHPG) in seronegative recipients of renal allograft from seropositive donors

In an open-label randomized study of prophylactic treatment by ganciclovir, 23 seronegative recipients of kidney allograft from seropositive donors were randomized to receive from day 14 to day 28 after transplantation either no treatment (n = 11) or ganciclovir, 5 mg/kg twice daily (n = 12). Both groups were similar in age, immunosuppressive therapy, number of acute rejections and in steroid bolus. Seroconversion occurred in ten patients of the control group (91%) and in ten of the ganciclovir group (84%). CMV disease occurred in ten patients of the control group (91%) and in eight patients of the ganciclovir group (66%), three of whom had asymptomatic viraemia. The delay between transplantation and onset of CMV disease was significantly increased by ganciclovir prophylaxis (78.5 +/- 7.7 vs 46.5 +/- 7.5 days, P < 0.05). We conclude that in renal transplant recipients at risk of CMV disease, ganciclovir prophylaxis delays the onset of the disease and seems to decrease its incidence and its severity.

Prognostic value of plasminogen activator inhibitor type 1 mRNA in microdissected glomeruli from transplanted kidneys

BACKGROUND

Plasminogen activator inhibitor type 1 (PAI-1) exerts antifibrinolytic and profibrotic activities. Inside the glomerulus, PAI-1 is mainly synthesized by mesangial cells. We hypothesized that thrombin, via its receptor protease activated receptor type 1 (PAR-1), present on the membrane of glomerular cells, is an important mediator of PAI-1 synthesis.

METHODS

Using the technique of Peten et al., we microdissected the glomeruli of 23 kidney transplanted patients admitted in our department from 1993 to 1997, and we followed-up these patients for up to 5 years, with sometimes iterative renal biopsies. With this technique, we also microdissected the glomeruli of three patients who have had a nephrectomy for cancer (control patients). We investigated mRNA expression of the PAI-1, the thrombin receptor PAR-1, the alpha2 chain of type IV (alpha2 IV) collagen, and of a housekeeping gene (cyclophilin) by reverse transcription-polymerase chain reaction. The results were correlated with the renal function and the histological findings classified into acute rejection (9 biopsies), chronic rejection (22 biopsies), or normal (8 biopsies).

RESULTS

A significant up-regulation of PAI-1 and alpha2 IV collagen mRNA was observed in acute rejection (P<0.05) when compared to normal kidneys. A positive correlation exists between alpha2 IV collagen mRNA level and the degree of cellular infiltration. A negative correlation was found between the level of mRNA of PAR-1 and the degree of vascular thrombosis (P=0.005) and glomerulosclerosis (P=0.04). A positive correlation was found between the degradation of renal function and the mRNA level of PAI-1 at the time of the renal biopsy (P<0.05).

CONCLUSIONS

These results suggest that glomerular PAI-1 mRNA may be predictive of the long-term renal graft function.

Characteristics of sirolimus-associated interstitial pneumonitis in renal transplant patients

BACKGROUND

Sirolimus, a promising new immunosuppressive drug for organ transplantation, is currently associated with side effects, such as thrombocytopenia and hyperlipidemia.

METHODS

Eight renal transplant recipients, who developed unexplained interstitial pneumonitis during sirolimus therapy, were extensively re-screened for all causes of pneumonitis.

RESULTS

Interstitial pneumonitis was constantly characterized by bilateral interstitial infiltrates on chest x-rays and lung computed tomography scans, with marked general symptoms in all patients but one. Bronchoalveolar lavage (BAL) disclosed lymphocytic alveolitis (mainly of the CD4 type) in seven patients and alveolar hemorrhage in one. Transbronchial lung biopsies, performed in two patients, showed bronchiolitis obliterans with organizing pneumonia combined with lymphocytic interstitial pneumonitis. Pulmonary infections were ruled out by specific stainings and cultures of BAL, bronchial aspirates, and blood cultures. After the elimination of all possible causes, sirolimus-induced pneumonitis was considered probable. Discontinuation of sirolimus in seven cases and dose reduction in the remaining case dramatically improved clinical and radiological status within a few weeks and led to complete resolution within 3 months.

CONCLUSIONS

Sirolimus is very probably responsible for interstitial pneumonitis on the following grounds: (a) occurrence of pneumonitis during sirolimus therapy; (b) absence of any other causes; and (c) resolution within 3 months of sirolimus discontinuation or dose reduction. Sirolimus should now be added to the list of possible causes of pulmonary complications after renal transplantation. Discontinuation or dose reduction of sirolimus led to complete and lasting resolution of symptoms.

Acute renal failure in the course of HIV infection: a single-institution retrospective study of ninety-two patients and sixty renal biopsies

BACKGROUND

Acute renal failure syndromes are frequently encountered in patients with human immunodeficiency virus (HIV) infection. Most reported cases of acute renal failure are related to acute tubular necrosis, but many other causes of renal failure have been described in these patients.

METHODS

The present work is a single-institution retrospective study of 92 HIV-infected patients with acute or rapidly progressing renal failure. In 60 cases, a renal biopsy was performed. For each patient we analysed clinical and pathological data, as well as the short-term prognosis.

RESULTS

Ten different causes of acute or rapidly progressing renal failure were documented: (i) haemolytic uraemic syndrome (32 patients); (ii) acute tubular necrosis either of ischaemic-toxic origin (18 patients) or due to rhabdomyolysis (six patients); (iii) obstructive renal failure which was either extrinsic (two patients), drug-induced (13 patients) or secondary to paraprotein precipitation (one patient); (iv) HIV-associated nephropathy (14 patients); (v) acute interstitial nephritis (two patients); (vi) various glomerulonephritis (four patients). In most cases, renal failure was severe (the mean creatinine clearance at entry was 12 ml/min). Most patients had a significant improvement in renal function with only symptomatic treatment. Eighteen per cent of the patients died within 2 months of the diagnosis of renal failure. Renal biopsy seems important for the diagnosis but also for the prognosis, at least in the cases of haemolytic-uraemic syndrome, HIV-associated nephropathy and drug-induced micro-obstructive renal failure.

CONCLUSION

Vascular and glomerular diseases are frequent causes of acute or rapidly progressing renal failure in HIV-infected patients. Renal biopsy appears to be safe and useful for the diagnosis and the prognosis of the renal failure. High mortality rate is only observed in patients with ischaemic/toxic causes of acute renal failure.

Human herpes virus-8 and other risk factors for Kaposi's sarcoma in kidney transplant recipients. Groupe Cooperatif de Transplantation d' Ile de France (GCIF)

BACKGROUND

The exact reasons for the high incidence of Kaposi's sarcoma (KS) after kidney transplantation are still unknown. Immunosuppression is classically considered as the main risk factor, but the relative risk contributed by the patient's geographic origin and by human herpes virus (HHV)-8 infection still has to be determined.

METHODS

We carried out a retrospective and a prospective study among kidney transplant recipients (TP) to identify the risk factors for posttransplantation KS. Each of 30 KS patients was matched with two controls to investigate the association with geographic origin, immunosuppressive regimen, HHV-8 antibodies before and after transplantation, and other infections. Among TP with new onset of KS, we prospectively evaluated HHV-8 serology and viremia in response to decreased immunosuppression.

RESULTS

African and Middle East origins, past infection with hepatitis B, hemoglobin level <12 g/dl, lymphocyte count <750/mm3 at the time of diagnosis and initial use of polyclonal antilymphocyte sera were risk factors for KS. After multivariate analysis, origin in Africa or Middle East and use of antilymphocyte sera for induction remained as independent risk factors. Sixty-eight percent (17/25) of TP with HHV-8 antibodies before or after transplantation developed KS compared with 3% (1/33) of seronegative TP (P<0.00001). HHV-8 DNA was detectable in seven of nine peripheral blood mononuclear cells (PBMC) and in six of six KS lesions at diagnosis; it became negative in PBMC in three of five patients in parallel with tumor regression.

CONCLUSION

African and Middle East geographic origins, HHV-8 infection before and after kidney transplantation, and initial use of polyclonal antilymphocyte sera were independent risk factors for KS. The presence of HHV-8 antibodies before or after transplantation was highly predictive of the emergence of posttransplantation KS and conferred a 28-fold increased risk of KS (odds ratio=28.4; 95% confidence interval: 4.9-279). Detection of HHV-8 DNA within PBMC and KS lesions seems related to tumor burden and evolution.

Tissue-type plasminogen activator activity in HIV-associated HUS

BACKGROUND

In children, haemolytic uraemic syndrome (HUS) is associated with high plasma plasminogen activator inhibitor type 1 (PAI-1), which may contribute to the persistence of renal glomerular and arteriolar thrombi. HUS has been described in HIV-infected patients, but the pathophysiology of HUS in these patients is poorly understood. The aim of the study was to investigate plasma fibrinolytic activity in 18 patients with HIV-associated HUS.

METHODS

We measured tissue type plasminogen activator (t-PA) and PAI-1 activities in the plasma of 18 HIV-infected patients with biopsy-proven HUS (HIV+/HUS+) and 48 HIV-infected patients without HUS (HIV+/HUS-).

RESULTS

Patients with HUS had a significantly higher serum creatinine, a lower platelet count and an increased incidence of cytomegalovirus (CMV) infection (72% of patients HIV+/HUS+, vs 25% of patients HIV+/HUS-). Unexpectedly, plasma PAI-1 activity was similar in both groups. However, t-PA activity was significantly higher in HUS cases (11.5 vs 4.5 U/ml, P=0.001). Patients with CMV infection, with or without HUS, had significantly increased t-PA level (P=0.01). Multivariate analysis identified high t-PA (RR=9.21) and CMV infection (RR=3.36) as risk factors for HUS.

CONCLUSION

This study provides evidence that HIV-infected patients with HUS have high plasma t-PA activity. PAI-1 plasma activity is not significantly increased, as opposed to non-HIV-associated HUS. Thus, in the setting of HIV infection, HUS cannot be attributed to decreased fibrinolytic activity.

Retroperitoneal laparoscopic nephrectomy of native kidneys in renal transplant recipients

BACKGROUND

The purpose of this study was to compare retroperitoneal laparoscopic nephrectomy in transplant recipients and in other patients scheduled for nephrectomy.

METHODS

From February 1994 to July 1996, 15 transplant recipients and 17 other patients underwent a total of 36 retroperitoneal laparoscopic nephrectomies for various indications. Operative time, morbidity, and hospital stay were compared between the two groups.

RESULTS

The average operating time for the 36 procedures was 95+/-38 min (range, 35-180 min). It was shorter in transplant recipients (81+/-32 min) than in other patients (100+/-39 min, P<0.05). There was one postoperative complication in the transplant recipient group. The average length of the postoperative hospitalization was 3.7+/-1.4 days (range, 2-8 days).

CONCLUSIONS

The retroperitoneal laparoscopic approach for nephrectomy is as safe and effective in renal transplant recipients as in other patients. Postoperative stay and delay to resumption of oral immunotherapy are short. This approach has become our first-line approach for native nephrectomy in transplant recipients.

Renal cell carcinoma of native kidneys: prospective study of 129 renal transplant patients

PURPOSE

We evaluated the prevalence of renal cell carcinoma of the native kidneys in renal transplant recipients as well as possible risk factors.

MATERIALS AND METHODS

A total of 129 consecutive renal transplant recipients underwent ultrasound examination of the native kidneys as part of a routine evaluation. A record was made of acquired cystic kidney disease, defined as 3 cysts or more, and of suspicious masses. When a malignancy was suspected radical nephrectomy was performed.

RESULTS

The overall prevalence of renal cell carcinoma of the native kidney was 5 in 129 recipients (3.9%). All cancers were limited to the kidney. No significant relationship was detected between renal cell carcinoma occurrence and patient age, dialysis (when initiated, type and duration), transplantation, drug regimen or incidence of acquired cystic kidney disease.

CONCLUSIONS

The risk of renal cell carcinoma, a clinically significant cancer, was approximately 100 times greater in our renal transplant patients than in the general population but no significant risk factor could be identified. Routine ultrasonography for early diagnosis in asymptomatic patients on immunosuppressive therapy is strongly recommended to improve prognosis.

Long-term prognosis of renal transplantation after preemptive treatment of cytomegalovirus infection

A role for cytomegalovirus (CMV) infection in the etiologies of acute and chronic rejection in renal allograft recipients has been suggested. We previously reported that preemptive treatment of CMV infection with ganciclovir in kidney transplant patients was safe and effective. We now present a retrospective analysis of 169 consecutive renal transplant patients, of whom 87 (51.5%) received preemptive treatment with ganciclovir (CMV(+) group). No patient died of CMV infection. Actuarial graft and patient survival rates were not different between the CMV(+) and the CMV(-) groups (graft survival: 68% and 69%; patient survival: 89% and 88%, respectively). At the end of the study, the mean plasma creatinine levels were not statistically different between the two groups (185+/-13 and 166+/-12 micromol/L for the CMV(+) group and the CMV(-) group, respectively). These results suggest that preemptive treatment of CMV infection with ganciclovir may prevent the CMV-induced renal injury and graft loss.

Thrombotic microangiopathy and cytomegalovirus disease in patients infected with human immunodeficiency virus

Thrombotic microangiopathy (TMA) can occur during the course of human immunodeficiency virus (HIV) infection. Clinical and pathological data for 29 patients with TMA and HIV infection were recorded. In a retrospective case-control study, we analyzed the link between opportunistic infections or drug therapies and TMA. Twenty-five patients (mean CD4+ cell count +/- SD, 71.9 +/- 18.3/mm3) had renal impairment, and four had neurological dysfunction. In one-half the cases, the disease was progressive with isolated fragmentation anemia appearing several months before the clinical symptoms. The diagnosis of TMA was confirmed by histological examination of kidney biopsy specimens (18 cases). Endothelial cytomegalovirus (CMV) inclusions were associated with TMA in nine of 18 cases, whereas histological examination did not detect CMV in any control specimens (P < .001). The case-control study demonstrated a link between TMA and clinical CMV infection (odds ratio, 3.9; 95% confidence interval, 1.1-14). We conclude that TMA is a late complication of HIV infection and can be associated with systemic CMV infection in this setting.

Long-term benefit of intravenous immunoglobulins in cadaveric kidney retransplantation

Renal retransplantation can be hampered by the presence of anti-HLA alloantibodies. Previous studies have documented in vitro and in vivo suppression of these antibodies by intravenous immunoglobulins (IVIg). We conducted a randomized study in 41 patients, who have received a second cadaveric transplant between 1989 and 1994. They all were treated with a quadruple-immunosuppressive protocol. In addition, 21 patients received 0.4 g/kg/day of IVIg, on the first 5 days after transplantation. The two groups of patients were identical for age, sex, duration of the first graft, duration of cold ischemia, anti-HLA sensitization, HLA matching, the number of acute rejection episodes, and the incidence of cytomegalovirus infection. The 5-year survival rate was significantly higher in the group of patients treated with IVIg: 68% versus 50% in the control group. The only significant factor associated with IVIg infusion and better survival was a shorter delay of graft function (3.4 +/- 1.0 days versus 9.9 +/- 1.6 days). In conclusion, this randomized study demonstrates that IVIg treatment is associated with better long-term graft survival in retransplanted patients. This beneficial effect may be related to a long-lasting immunosuppressive effect of IVIg and/or to an early protective effect of the graft against ischemia.

Assessment of individual CYP2D6 activity in extensive metabolizers with renal failure: comparison of sparteine and dextromethorphan

OBJECTIVES

To examine whether the variability of CYP2D6 activity in patients with chronic renal failure can be assessed, particularly among subjects with the extensive metabolizer phenotype, by use of standard in vivo indexes of CYP2D6 activity derived from oral administration of dextromethorphan and sparteine.

METHODS

A single 100 mg oral dose of sparteine and a single 40 mg oral dose of dextromethorphan were administered on two occasions to 12 patients with chronic renal failure (creatinine clearance ranging from 20 to 70 ml/min) and 12 age- and sex-matched healthy subjects. Sparteine clearances, sparteine metabolic ratio, and urinary recovery of dextrorphan were calculated. Patients and healthy control subjects were not selected on the basis of their CYP2D6 phenotypes.

RESULTS

Chronic renal failure was associated with a decrease in sparteine partial metabolic clearance to dehydrosparteine (median of 322 ml/min and range of 62 to 670 ml/min in patients with renal failure versus median of 635 ml/min and range of 77 to 1276 ml/min in normal subjects; p < 0.02). Sparteine apparent oral clearance (p < 0.03) and renal clearance (p < 0.001) decreased in patients with renal failure. However, sparteine metabolic ratio was not significantly altered in patients with renal failure and showed that all patients were extensive metabolizers of sparteine. Although fractional urinary excretion of dextrorphan decreased in patients with renal failure (median, 24.4%; range, 9.7% to 55.9%) compared with control (median, 47.5%; range, 24.1% to 72.1%) (p = 0.02), it also showed that all subjects were extensive metabolizers of dextromethorphan. The amount of dextromethorphan excreted in urine correlated with creatinine clearance independently from CYP2D6 activity measured as sparteine partial metabolic clearance. However, it did not correlate with sparteine metabolic ratio or with fractional urinary excretion of dehydrosparteine.

CONCLUSION

Assessment of CYP2D6 activity by use of dextromethorphan and sparteine is possible in extensive metabolizer patients with chronic renal failure. However, in these subjects, dextromethorphan and sparteine do not reflect CYP2D6 activity in the same way.

[Experimental models of acute kidney failure]

Acute renal failure (ARF) is related to reversible tubular necrosis, usually caused by ischemia or toxic substances. Our knowledge of the pathophysiology of ARF stems from the study of animal models which reproduce either an ischemic or a toxic form of ARF. Classical studies using microdissection and micropuncture have characterized the salient mechanisms of ARF: vascular compromise with hypoperfusion and decrease in glomerular filtration rate, and tubular insult with cell necrosis and high intratubular pressure. More recent studies have emphasized the cellular and molecular events occurring during the course of ARF, including changes in cytoskeleton and matrix proteins, apoptosis and the role of Heat Shock Proteins. Endothelin and growth factors such as epidermal growth factor or hepatocyte growth factor seem to be important mediators in the regeneration phase of ARF. In various animal models, EGF, HGF or antagonists of endothelin receptors have a protective effect on renal function. These findings may be of clinical relevance, and suggest future therapeutic approaches in the treatment of ARF.

[Kidney surgery using lumbar endoscopy: initial experiences]

OBJECTIVES

To evaluate the feasibility, safety and clinical value of lumboscopy for the treatment of upper urinary tract diseases.

METHODS

Six nephrectomies, one renal biopsy and one renal cystectomy were performed by retroperitoneoscopy (lumboscopy) in 7 patients. These cases represent the beginning of our experience. The operating time, incidence of intraoperative or postoperative complications and length of hospital stay were studied.

RESULTS

The mean operating time was 134 min for nephrectomy, 180 min for cystectomy and 30 min for renal biopsy. No complications were observed. No conversion into laparotomy was required. The mean postoperative hospital stay was 3 days in the patients who were submitted to a single operation.

CONCLUSION

Lumboscopy is a relatively easy, safe and reliable technique, and its use in urology warrants further study and development. Dissection of the retroperitoneal space with low pressure CO2 is possible and simplifies the procedure, without increasing the risks for the patient. The indications, especially for nephrectomy, are currently under evaluation.

Constitutive expression and modulation of the functional thrombin receptor in the human kidney

Thrombin exerts procoagulant effects and has also many cellular effects mediated by cell surface receptors. A functional thrombin receptor from human platelets has been cloned and sequenced. In the present study, by reverse transcription and polymerase chain reaction, using specific primers designed from the thrombin receptor cDNA sequence, we show that the mRNA encoding for this receptor can be amplified from freshly isolated human glomeruli obtained by microdissection of normal kidney cortex. By immunohistochemistry using a specific monoclonal antibody, ATAP2, directed against the extracellular N-terminus of this receptor, we find that this functional thrombin receptor is constitutively expressed in the normal human kidney. The three glomerular cell types, endothelial, mesangial, and epithelial cells, were positively stained, as were the endothelial cells of renal arteries, arterioles, venules, and peritubular capillaries. Occasionally, interstitial cells and smooth muscle cells in the media of renal arteries were also stained. Proximal and distal tubular cells were not stained. By in situ hybridization, using a digoxigenin-labeled cDNA probe specific for thrombin receptor, the thrombin receptor mRNA was found to have the same distribution as the thrombin receptor protein detected by immunohistochemistry. A lighter staining of glomerular endocapillary cells was observed in cases of thrombotic microangiopathy and extracapillary glomerulonephritis, two renal diseases associated with in situ thrombin generation and fibrin formation. In one case of thrombotic microangiopathy, we observed an increase in thrombin receptor mRNA. This suggests that thrombin receptor protein is not always correlated with thrombin receptor mRNA level. Internalization and degradation of thrombin receptor protein have been demonstrated in vitro and could also occur after activation in vivo. This is the first demonstration of the constitutive expression of the functional thrombin receptor in the human kidney. These results suggest that thrombin may exert glomerular and vascular effects within the kidney in normal and in pathological conditions.

Heparin selectively inhibits synthesis of tissue type plasminogen activator and matrix deposition of plasminogen activator inhibitor 1 by human mesangial cells

BACKGROUND

Mesangial changes in a variety of pathologic conditions involve mesangial cell proliferation and mesangial matrix remodelling. Heparin has been shown to prevent these processes in vivo. In vitro, heparin interferes with cell growth, proto-oncogene expression, synthesis of specific proteins, and extracellular matrix composition. In some cell types, it seems to interact with intracellular protein kinase C-dependent pathways. The effect of heparin on the mesangial plasminogen activating system (tissue type plasminogen activator, t-PA, and plasminogen activator inhibitor type 1, PAI-1), which is thought to be involved in matrix remodelling, has not been previously reported.

EXPERIMENTAL DESIGN

Cultured human mesangial cells were stimulated by 10% fetal calf serum (FCS) or 16 nM phorbol myristate acetate (PMA) in the presence or absence of anticoagulant or nonanticoagulant heparins. Cell proliferation, synthesis of t-PA and PAI-1, cell morphology, and PAI-1 matrix deposition were studied using cell counting, [3H]thymidine incorporation, specific t-PA and PAI-1 enzyme-linked immunosorbent assay, Northern blot analysis, light microscopy, immunofluorescence and immunogold silver staining with combined bright-field and epipolarization microscopy.

RESULTS

Heparin partially inhibited FCS-stimulated cell growth but not PMA-induced thymidine incorporation. FCS and PMA stimulated t-PA (p < 0.05 and p < 0.01, respectively) and PAI-1 synthesis (p < 0.05 and p < 0.01 respectively). Heparin selectively and partially inhibited FCS-stimulated t-PA, but not PAI-1 synthesis. It has no effect on PMA-stimulated t-PA or PAI-1 synthesis but prevented cell shape-changes induced by PMA, suggesting that heparin inhibits some but not all protein kinase C (PKC)-dependent effects and that heparin block in t-PA synthesis is distal to PKC activation. Heparin decreased PAI-1 matrix accumulation. Similar distal to PKC activation. Heparin decreased PAI-1 matrix accumulation. Similar results were observed with anticoagulant and nonanticoagulant heparin fragments.

CONCLUSIONS

In human mesangial cells, anticoagulant and nonanticoagulant heparin exert an antiproliferative effect and may prevent mesangial matrix changes by decreasing FCS-stimulated t-PA synthesis and PAI-1 deposition in the matrix. Heparin is able to inhibit PKC-dependent cell shape changes but not PKC-dependent t-PA or PAI-1 synthesis. It also inhibits PKC-independent cell proliferation and t-PA synthesis. These results suggest multiple intracellular sites of action for heparin, unrelated or distal to PKC activation.

Induction of MHC class II molecules HLA-DR, -DP and -DQ and ICAM 1 in human podocytes by gamma-interferon

MHC class II-encoded molecules HLA-DR, -DP and -DQ play a pivotal role in the human immune response. Their constitutive expression is restricted to a number of immunocompetent cells referred to as antigen-presenting cells. However, gamma-interferon (gamma-IFN) has been shown to induce MHC class II molecule expression in several epithelia. Using flow cytometric analysis, we show here that normal and SV40-transformed human podocytes in culture constitutively expressed gamma-IFN receptors. We also show that MHC class I molecules are constitutively expressed in these cells and that HLA-DR, -DP and -DQ expression, which is not found in unstimulated cells, can be induced by gamma-IFN stimulation. This induction was a time-dependent event, a lag phase of 24-48 h being necessary for MHC class II molecules to become detectable at the cell surface by flow cytometric analysis. Induction of MHC class II molecules in human podocytes also showed a concentration dependence, a plateau being reached at a concentration of 500 IU of gamma-IFN/ml of culture medium. This effect was blunted by coincubation of the cells with an antihuman gamma-IFN receptor monoclonal antibody. HLA-DR expression was associated with specific mRNA accumulation, as detected by Northern blot analysis. By indirect immunofluorescence, the intercellular adhesion molecule 1 was also induced by gamma-IFN stimulation. Induction of DR, DP and DQ in human podocytes may be involved in the pathogenesis of immune glomerulonephritis in man.

Expression of plasminogen/plasmin receptors on human glomerular epithelial cells

The aim of the present study was to display plasminogen/plasmin receptors on human glomerular epithelial cell (HGEC) membranes and to determine the properties of receptor-bound plasminogen at the cell surface. Using an immortalized human glomerular epithelial cell line (E71-A1), we found a specific, saturable, and reversible binding of 125I-labeled plasminogen and 125I-labeled plasmin to HGEC that involved the lysine binding sites of both ligands. 125I-plasminogen and 125I-plasmin bound to the same receptors with different affinities: Kd = 1.20 +/- 0.08 and 0.30 +/- 0.05 microM, respectively (P < 0.001). The number of binding sites per cell was 6.00 +/- 0.56 x 10(6) for plasminogen and 2.00 +/- 0.47 x 10(6) for plasmin (P < 0.05). Similar receptor affinities were found on isolated glomeruli, on immortalized and nonimmortalized HGEC, and on purified HGEC membranes. The apparent kinetic constants of plasminogen activation by receptor-bound urokinase-type plasminogen activator (u-PA) compared with solution-phase u-PA [Michaelis constant (Km) = 0.80 +/- 0.54 vs. 3.15 +/- 0.78 microM, P < 0.0001; catalytic constant (kcat) = 0.39 +/- 0.17 vs. 0.50 +/- 0.29 s-1, not significant; kcat/Km = 0.57 +/- 0.35 vs. 0.16 +/- 0.11 microM-1.s-1, P < 0.05, respectively] showed a higher efficiency of plasminogen activation at the cell surface. When measured by a chromogenic assay using S22-51, receptor-bound plasmin activity on HGEC was partly protected from its inhibitor, alpha-2-antiplasmin, whereas solution-phase plasmin was not.(ABSTRACT TRUNCATED AT 250 WORDS)

Receptor binding and degradation of urokinase-type plasminogen activator by human mesangial cells

The binding of [125I] labeled urokinase-type plasminogen activator (u-PA) was studied on human mesangial cells (MC) in culture. The binding of active [125I]u-PA at 37 degrees C reached a plateau after 30 minutes of incubation and remained stable for at least four hours. When the supernatant was analyzed with trichloracetic acid (TCA), TCA soluble radioactive material could be detected after a lag phase of 30 minutes, and then increased linearly for four hours. Analysis by electrophoresis on SDS PAGE and autoradiography of the cell associated radioactivity and of the intracellular content showed that active u-PA and u-PA complexed to plasminogen activator inhibitor type-1 (PAI-1) were bound to the cell surface, but only u-PA/PAI-1 complexes were internalized and degraded. Therefore, the Kd and the number of binding sites were determined by competitive inhibition curves at 4 degrees C using diisopropyl-fluorophosphate (DFP) u-PA. Scatchard plots showed a Kd = 400 +/- 30 pM, and Bmax = 240,000 +/- 25,000 sites/cell. Excess of the amino terminal fragment of u-PA (ATF) completely blocked the specific binding of [125I]u-PA, confirming that the binding of u-PA was independent of the presence of the active site and/or of the formation of complexes with PAI-1. 3H thymidine incorporation by mesangial cells after stimulation with 100 nM active u-PA showed that u-PA had a moderate but significant mitogenic effect, in contrast to inactive u-PA and ATF. However, this mitogenic effect was not accompanied by a proliferative effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of the renin-angiotensin system on the renal functional reserve in renal transplant recipients

To determine the renal functional reserve in renal transplant recipients, we measured the glomerular filtration rate by inulin clearance and the renal plasma flow by PAH clearance before and during an amino acid infusion (Totamine, 6 to 8 mg/kg/min for 90 to 120 min) in 18 transplanted patients with stable renal function. To test the role of the renin-angiotensin system on the renal functional reserve, we performed a crossover placebo-controlled randomized trial of acute blockade of the renin-angiotensin system by injection of perindoprilat (2 mg i.v.), an inhibitor of angiotensin converting enzyme before amino acid infusion, each patient being studied twice at seven day intervals. Amino acid infusion induced a time-dependent increase in the glomerular filtration rate (P = 0.04), whether or not the renin-angiotensin system was blocked. Maximal increases were from 49.1 +/- 4.1 to 58.9 +/- 5.4, mean +/- SE (18.5%), in control conditions and from 52.4 +/- 5.6 to 62.1 +/- 5.5 ml/min/1.73 m2 (19.7%) after perindoprilat. The increase in glomerular filtration rate was less pronounced in patients taking cyclosporin A than in patients treated with steroid and azathioprine. Amino acid infusion also induced a significant and time-dependent increase (15.2 to 20.2%) in the renal plasma flow (P < 0.01) whether or not perindoprilat had been given. Furthermore, perindoprilat alone increased renal plasma flow by 13.6%, and this effect seemed additive with that of amino acids. Perindoprilat injection decreased filtration fraction (from 0.20 +/- 0.01 to 0.19 +/- 0.01). This parameter returned to basal values after amino acid infusion (0.20 +/- 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of neutral endopeptidase stimulates renal sodium excretion in patients with chronic renal failure

1. The acute effects of a single oral dose of sinorphan (100 mg), an inhibitor of neutral endopeptidase, on the plasma atrial natriuretic factor level and the fractional excretion of sodium were examined in 12 patients with severe chronic renal failure who were not on maintenance haemodialysis and who ingested a normal sodium diet. The drug was administered against placebo by a double-blind cross-over protocol. 2. Basal plasma atrial natriuretic factor level and fractional excretion of sodium were high (23.2 +/- 3.7 pmol/l and 2.64 +/- 0.38%, respectively). Sinorphan inhibited plasma neutral endopeptidase activity by 68-75% 30 min after ingestion. This effect persisted for at least 4 h. There were simultaneously increases in plasma atrial natriuretic factor and cyclic GMP levels to 1.9 and 1.4 times the basal values, respectively. Fractional excretion of sodium increased during the second and third hour periods after ingestion of the drug with a peak of 1.9 times the basal value in the second period. Changes in fractional excretion of sodium were significantly correlated with those in plasma atrial natriuretic factor and cyclic GMP levels. Plasma aldosterone level, creatinine clearance and mean blood pressure were unchanged, whereas plasma renin activity increased slightly. An increase in urinary cyclic GMP excretion was observed in parallel with the increase in plasma cyclic GMP level.(ABSTRACT TRUNCATED AT 250 WORDS)

Species-specific properties of the glomerular mesangium

Mesangial cells play a central role in the physiology and pathophysiology of the glomerulus. To date, most of the in vitro studies have been performed in cultured rat mesangial cells, with only 10% of them performed in human mesangial cells. In this article, the major differences between results obtained with these two types of cultured cells will be reviewed. In rats and in humans, most of the mesangial cells appear to be of smooth muscle origin. In the rat, some of the cultured cells also express a phenotype suggesting a monocyte/macrophage origin. Phagocytosis and synthesis of cytokines or proinflammatory proteins that have been described in cultured rat cells seem mostly linked to this monocyte/macrophage subtype of resident mesangial cells. In humans, macrophages are only detected in pathologic conditions, suggesting that they are not resident but rather infiltrating cells. Mesangial receptors, most notably angiotensin II receptors, are clearly present on mesangial cell membranes and are linked to prostaglandin E2 synthesis and to cell contraction. In humans, spontaneous prostanoid synthesis is low and is increased by the induction of cyclooxygenase by sodium butyrate in the medium. Even so, the amount of prostaglandin E2 synthesized by human mesangial cells is quantitatively low comparatively with that in rats. In rats, accordingly, mesangial cells play a role in the regulation of single-nephron GFR. In humans, angiotensin II also exerts a control on GFR but it is more difficult to demonstrate its contractile effect on human than on rat mesangial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of glomerular injury: overview and relation with hemostasis

The mechanisms of glomerular injury can be separated into nonimmunologically mediated glomerulonephritis (GN) such as diabetes, leading to glomerular hypertension and into immunologically mediated GN. The immunologically mediated GN may induce chronic glomerulopathy such as membranous GN or proliferative GN. The final pathway of these two types of GN is proteinuria and renal failure linked to glomerulosclerosis. In inflammatory GN, most of the mediators could be synthesized either by infiltrating cells or by resident glomerular cells. They include cytokines, lymphokines, complement activation, generation of superoxyde anions, arachidonic acid metabolites, and fibrin deposition. (a) We have investigated the interaction between isolated glomeruli and platelets and have demonstrated that lipidic and proteic extracts of glomeruli enhance thromboxane B2 platelet synthesis. This fact is related to the generation by isolated glomeruli of saturated fatty acids and tissue factor. (b) We investigated the interaction between rat isolated glomeruli and peritoneal macrophages. We have demonstrated that 12-HETE synthesized by isolated glomeruli induce macrophage prostaglandin synthesis which, in turn, inhibits the 12-HETE synthesis. (c) We have demonstrated, using human glomerular epithelial cells, that alpha-thrombin, the active form of thrombin, generated before fibrin formation, is able to induce cell proliferation and abolishes the profibrinolytic activity of these cells. In summary, the mechanisms of glomerular injury are complex, certainly acting by multiple pathways. So far, the mediators leading to proteinuria and renal failure after glomerular injury remain under investigation.

Methylprednisolone and cyclophosphamide pulse therapy in crescentic glomerulonephritis: safety and effectiveness

In a previous study, we found that aggressive immunosuppressive therapy with continuous high-dose oral steroid and cyclophosphamide combined with plasma exchanges for extracapillary crescentic glomerulonephritis gave controversial results since, although disease activity was controlled, iatrogenic complications had led to death in some aged patients. We then modified our therapeutic regimen, and we analyze here the evolution of 30 consecutive patients who were admitted for biopsy-proven crescentic glomerulonephritis between 1989 and 1991. The mean plasma creatinine level at admission was 393 +/- 59 mumol/L (range 70 to 1100), and 15 patients had crescent formation in more than 50% of glomeruli on initial renal biopsy. Ten patients did not receive any immunosuppressive treatment since they either had a normal renal function or they had terminal renal failure and no severe extrarenal manifestation. The 20 other patients received initial steroid pulses 500 mg x3 (n = 17), low oral steroid treatment (n = 20), cyclophosphamide pulses (n = 13), or oral cyclophosphamide (n = 3). In 4 cases plasma exchanges were also used. As a whole, 10 patients (33%) were discharged with a normal renal function, and 18 patients (60%) had chronic renal failure, 7 of them requiring dialysis or transplantation; only 2 patients died of pulmonary hemorrhage. No severe iatrogenic complication was observed. These results indicate that reduction in oral steroid dosage, cyclophosphamide pulse therapy rather than continuous oral treatment, and plasma exchanges do not induce overimmunosuppression and iatrogenic complication. It can be safe, well tolerated, and as effective as a more intensive immunosuppressive regimen for the treatment of crescentic extracapillary glomerulonephritis.

Necrotizing crescentic glomerulonephritis without significant immune deposits: a clinical and serological study

To determine the spectrum of systemic diseases associated with pauci-immune necrotizing crescentic glomerulonephritis, we have analysed extra-renal manifestations, occurrence of extra-glomerular vasculitis and incidence and specificity of antinuclear cytoplasmic antibodies (ANCA) in 40 patients selected only on renal histological criteria. Extra-renal symptoms were unexpectedly observed in all patients but one, and were suggestive of vasculitis in 24. Extra-glomerular vasculitis was seen in 18 kidney biopsies and four biopsies from other organs. Among the 33 patients with suspected or established vasculitis, 13 had presumed or biopsy-proven Wegener's granulomatosis, three had a macroscopic form of polyarteritis nodosa and 17 could not be adequately classified. An additional patient had clinical signs of Wegener's granulomatosis without clinical and histological evidence of vasculitis. ANCAs were detected in 28 of 33 and 25 of 34 sera tested by immunofluorescence and enzyme-linked immunoassay, respectively: 19 contained anti-myeloperoxidase antibodies and six had anti-proteinase 3 activity. Anti-myeloperoxidase and anti-proteinase 3 antibodies were present in all clinical subgroups but with various frequencies: anti-myeloperoxidase antibodies were more common (six of 12) than anti-proteinase 3 (four of 12) in patients with suspected or histologically proven Wegener's granulomatosis. Anti-proteinase 3 antibodies were 3- to 4-fold more common in patients with Wegener's granulomatosis than in those with systemic vasculitis of other causes (one of 12) or necrotizing crescentic glomerulonephritis without evidence of extra-renal vasculitis (one of 10). These results strongly suggest that pauci-immune necrotizing crescentic glomerulonephritis belongs to the broad spectrum of necrotizing vasculitides affecting glomerular capillaries. This study shows substantial improvement in renal prognosis and life expectancy with aggressive immunosuppressive therapy despite the older age of the patients, dissemination of the vasculitic process and often delayed diagnosis.

[Prophylaxis of cytomegalovirus infections with ganciclovir in kidney transplant recipients]

In an open-labeled randomized study, prophylactic treatment with ganciclovir (day 15 to day 29) was administered to 23 cytomegalovirus seronegative patients who received a kidney from a cytomegalovirus seropositive donor. Both groups (control = 11, ganciclovir = 12) were similar in age, immunosuppressive treatments, acute rejection episodes and number of steroid pulses. A seroconversion occurred in 10 control patients (91 percent) and in 10 patients of the ganciclovir group (84 percent). A cytomegalovirus disease was observed in 10 control patients (91 percent) and in 8 patients of the ganciclovir group (66 percent). The delay between grafting and cytomegalovirus disease was significantly longer in the ganciclovir than in the control group (78.5 +/- 7.7 vs 46.5 +/- 5.5 days, P < 0.05). In conclusion, in renal transplant recipients who are at high risk of cytomegalovirus disease, prophylactic treatment with ganciclovir delays the onset of the disease and seems to decrease slightly its frequency.

[Reduction of TNF-alpha release and clinical effects of the first injection of OKT3]

In order to prevent the adverse effects of a first OKT3 injection in renal transplant recipients, we administered polyclonal antilymphocyte globulins (ATG Fresenius, 4 mg/kg/j) for 3 days before OKT3 injection. Compared with a historical group of 5 patients who did not receive ATG pretreatment before OKT3 injection, the patients who were pretreated by ATG had a significantly lower absolute number of circulating lymphocytes before the first OKT3 injection (363 +/- 107 vs 1,230 +/- 80/mm3, P < 0.001), a lower raise in plasma TNF-alpha level 2 hours after OKT3 injection (178 +/- 42 vs 735 +/- 127 pg/ml, P < 0.005) and a significant decrease in frequency and intensity of clinical symptoms, mainly chills, dyspnea, and headaches. However, fever and peak creatinine level were similar in both groups. A 80 percent success rate of crisis treatment was achieved in both groups and there was no increase in infectious complications. In conclusion, pretreatment with ATG induces a lymphocyte depletion, and decreases the amounts of TNF-alpha released as well as the side-effects of a first OKT3 injection.

Transcriptional activation of the urokinase receptor gene by endothelin-1

Using an immortalized human glomerular epithelial cell line (E71 A1), we studied the effect of endothelin-1 (ET-1), a potent vasoconstrictor peptide, on the synthesis of urokinase type plasminogen activator (u-PA) and its receptor (u-PAR). The results show that ET-1 had no effect on u-PA synthesis but induced an increase in u-PAR number (2.8 +/- 0.6 x 10(4) vs 1.2 +/- 0.5 x 10(4) sites per cell, p less than 0.001) without change in receptor affinity (280 +/- 80 pM vs 250 +/- 50 pM, NS), maximal effect being observed at 10(-7) M. Time course shows that a plateau was reached after a 24 hour incubation. ET-1 induced-increase in binding capacity was abolished by cycloheximide. ET-1 also induced an increase in u-PAR mRNA level, which was completely blocked by alpha-amanitin (5 micrograms/ml). Cycloheximide (1 microgram/ml) alone induced an increase in u-PAR mRNA level and this effect was enhanced when cycloheximide was combined with ET-1. Our data show that ET-1 can induce an increase in membrane expression of u-PAR through activation of the transcription of the u-PAR gene and de novo protein synthesis.

Tumor necrosis factor alpha increases antifibrinolytic activity of cultured human mesangial cells

Tumor necrosis factor alpha (TNF alpha) is likely to exert a major influence in the pathogenesis of glomerulopathies. Besides its proinflammatory properties. TNF alpha interacts with cell growth and synthesis of components of the fibrinolytic system. In this study, we report the effects of recombinant human TNF alpha on the synthesis of tissue-type plasminogen activator (t-PA) and its inhibitor (PAI-1) by human mesangial cells in culture. We first demonstrate that TNF alpha binds specifically to a single class of high affinity receptors (Kd 5.10(-11) M; 1500 receptors/cell). TNF alpha has an antimitogenic effect on human mesangial cells since it decreased DNA synthesis, measured by 3H-thymidine incorporation, in a dose-dependent manner. Release of cytosolic LDH and incorporated 51Cr was not increased by 100 ng/ml TNF alpha as compared with control, indicating that this monokine is not cytotoxic for cultured human mesangial cells. Zymographic analysis and reverse fibrin autography disclosed a 120 kD t-PA-PAI-1 complex and a 50 kD free form of PAI-1 in the supernatants of both unstimulated and TNF-stimulated cells; PAI-1 was released in excess and free t-PA was not observed. TNF alpha (0 to 100 ng/ml) had no effect on t-PA synthesis, but enhanced PAI-1 release in a time- and dose-dependent manner (97% increase of PAI-1 synthesis after a 24 hour incubation). This effect was abolished by cycloheximide, suggesting that protein synthesis was required. Northern blot analysis showed that TNF alpha increased the steady-state PAI-1 mRNA levels in a time-dependent manner, with a maximal effect at two hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasminogen activator inhibitor-1 deposition in the extracellular matrix of cultured human mesangial cells

Human mesangial cells secrete tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1), the latter being secreted in large excess in vitro. We demonstrate that PAI-1 is a major component of the extracellular matrix of cultured human mesangial cells, where its deposition is dependent on cell density. By immunogold silver staining, epipolarization microscopy and dispersive X-ray spectrometry, we have shown that matrix-associated PAI-1 is synthesized by spreading human mesangial cells, as indicated by the time-dependent accumulation of PAI-1 and the inhibitory effect of cycloheximide. Furthermore, by in situ hybridization, PAI-1 mRNA was detected in cultured mesangial cells. t-PA is present inside the cells, or at the cell surface, but is never associated with the extracellular matrix. Exogenous t-PA can remove matrix-associated PAI-1 without affecting cell adhesion. A similar effect was obtained by addition of urokinase-type plasminogen activator (u-PA) but not with fibrinolysis unrelated enzymes. In conclusion, PAI-1 is synthesized by human cultured mesangial cells and is deposited in the extracellular matrix by nonconfluent cells, whereas less PAI-1 is seen between confluent cells. This can explain the absence of detectable PAI-1 in normal human kidney biopsies. t-PA released by mesangial cells can bind and detach matrix PAI-1.

Cell-specific regulation of plasminogen activator inhibitor 1 and tissue type plasminogen activator release by human kidney mesangial cells

Human mesangial cells in culture synthesize and secrete plasminogen activator inhibitor 1 (PAI-1) and tissue-type plasminogen activator (t-PA). Phorbol myristate acetate (PMA), a known activator of protein kinase C, induces a three to four-fold increase in t-PA and PAI-1 release over a period of 24 h, whereas cell-associated t-PA and PAI-1 levels remain relatively stable. A similar effect is obtained with oleylacetyl glycerol, a more physiologic protein kinase C activator. The effect of PMA is suppressed in the presence of H7, an inhibitor of cellular protein kinases, and by cycloheximide and actinomycin D, indicating a requirement for de novo protein and RNA synthesis, respectively. Northern blot analysis of PMA-treated cells reveals a rapid and transient increase in PAI-1 mRNA reaching a maximum after 4-8 h, whereas increase in t-PA mRNA levels requires 24 h. Activation of protein kinase A by addition of 8-bromocyclic AMP (8-bromo cAMP) has no significant effect on PAI-1 release but inhibits the PMA-mediated increases in PAI-1 antigen and mRNA. Addition of 8-bromo cAMP alone does not affect t-PA release. When added to PMA-stimulated cells, 8-bromo cAMP inhibits t-PA release in a dose-dependent manner, but causes a superinduction of t-PA mRNA. 8-bromo cAMP also induces a decrease in PMA-stimulated intracellular t-PA release. Similar inhibition is observed after stimulation of endogenous adenylate cyclase with prostaglandin E1 or isoproterenol. This indicates that protein kinase A activation may inhibit PMA-stimulated t-PA release via a post-transcriptional effect, e.g. inhibition of protein synthesis or activation of protein degradation. In conclusion, hormones or mediators which activate protein kinase C can stimulate t-PA and PAI-1 synthesis in human mesangial cells. Protein kinase A activation has no effect on the basal release of PAI-1 and t-PA by human mesangial cells, and, in contrast to endothelial cells, it inhibits both PMA-stimulated PAI-1 and t-PA releases. This cell-specific regulation of t-PA and PAI-1 seems to be mediated by differential transcriptional and post transcriptional mechanisms.

Thrombin signal transduction mechanisms in human glomerular epithelial cells

We have previously shown that alpha-thrombin exerted a mitogenic effect on human glomerular epithelial cells and stimulated the synthesis of urokinase-type (u-PA) and tissue-type plasminogen activator (t-PA) and of their inhibitor, plasminogen activator inhibitor 1 (PAI-1). In the present study, we investigate the signal transduction mechanisms of thrombin in these cultured cells. Thrombin induced an increase in intracellular free calcium concentrations ([Ca2+]i) in a dose-dependent manner, a plateau being reached at 1 U/ml thrombin. A 60% inhibition of this effect was produced by 300 nM nicardipine, a dihydroperidine agent, or by 4 mM EGTA, indicating that increase in [Ca2+]i was due in part to extracellular Ca2+ entry through L-type voltage-sensitive calcium channels. Thrombin also induced an increase in inositol trisphosphate (IP3), suggesting that phospholipase C activation and phosphatidylinositides breakdown were stimulated. Interestingly thrombin-stimulated cell proliferation measured by 3H thymidine incorporation was inhibited by 300 nM nicardipine, and restored by addition of 10(-8) M ionomycin, indicating that calcium entry was critical for the mitogenic signal of thrombin. Conversely, nicardipine did not modify thrombin-stimulated synthesis of u-PA, t-PA, and PAI-1. Both thrombin-stimulated cell proliferation and protein synthesis required protein kinase C activation since these effects were blocked by 10 microM H7, an inhibitor of protein kinases, and by desensitization of protein kinase C by phorbol ester pretreatment of the cells. Interestingly, DFP-inactivated thrombin which binds the thrombin receptor and gamma-thrombin, which has some enzymatic activity but does not bind to thrombin receptor, had no effect when used alone. Simultaneous addition of these two thrombin derivatives had no effect on [Ca2+]i, and 3H thymidine incorporation but stimulated u-PA, t-PA, and PAI-1 synthesis although to a lesser extent than alpha-thrombin. This effect also required protein kinase C activation to occur, presumably by a pathway distinct from phosphoinositoside turnover since it was not associated with IP3 generation. In conclusion, multiple signalling pathways can be activated by alpha-thrombin in glomerular epithelial cells: 1) Ca2+ influx through a dihydroperidine-sensitive calcium channel, which seems critical for mitogenesis; 2) protein kinase C activation by phosphoinositide breakdown, which stimulates both mitogenesis and synthesis of u-PA, t-PA, and PAI-1; 3) protein kinase C activation by other phospholipid breakdown can stimulate u-PA, t-PA, and PAI-1 synthesis but not mitogenesis.

Functional endothelin 1 receptors on human glomerular podocytes and mesangial cells

To determine if endothelin 1 (Et1) receptors are present in human glomeruli, and which glomerular cells possess these receptors, 125I Et1 binding to isolated glomeruli and cultured glomerular mesangial and epithelial cells was studied. The latter were identified as podocytes. We demonstrated that Et1 binds specifically and reversibly to isolated human glomeruli and to cultured glomerular mesangial and epithelial cells. Scatchard analysis of competitive inhibition of 125I Et1 binding gave the following results (m +/- SEM, n = 3): isolated glomeruli, Kd = 4.2 +/- 2.1 x 10(-10) M, Bmax = 8.1 +/- 1.2 x 10(10) sites/mg protein; mesangial cells, Kd = 5.2 +/- 1.5 x 10(-10) M, Bmax = 1.87 +/- 0.49 x 10(4) sites/cell; epithelial cells, Kd = 7.2 +/- 1.5 x 10(-10) M, Bmax = 2.46 +/- 0.15 x 10(4) sites/cell. These receptors seem to be functional, since in both mesangial and epithelial cells Et1 induces a rapid and transient increase in intracellular [Ca2+]i. All these results indicate that Et1 may regulate glomerular filtration rate through an autocrine-paracrine pathway on mesangial cells and on podocytes.