Giulio A. Cinotti

Effects of sulindac and ibuprofen in patients with chronic glomerular disease. Evidence for the dependence of renal function on prostacyclin.

We investigated whether the glomerular synthesis of prostacyclin modulates the renal blood flow and glomerular filtration rate in chronic glomerular disease. The urinary excretion of 6-keto-prostaglandin F1 alpha, a stable breakdown product of prostacyclin, was significantly (P less than 0.01) reduced in 20 women with chronic glomerular disease, as compared with 19 controls, whereas excretion of urinary prostaglandin E2 was unchanged. In 10 patients randomly assigned to one week of treatment with ibuprofen, excretion of urinary 6-keto-prostaglandin F1 alpha and prostaglandin E2 was reduced by 80 per cent, the level of serum creatinine was increased by 40 per cent, and creatinine and para-aminohippurate clearances were reduced by 28 and 35 per cent, respectively. The reduction of both clearances was inversely related (P less than 0.01) to the basal urinary excretion of 6-keto-prostaglandin F1 alpha but not of prostaglandin E2. No functional changes were detected in five healthy women, despite a similar suppression of renal prostacyclin synthesis by ibuprofen. In contrast, one week of treatment with sulindac did not affect renal prostacyclin synthesis or renal function in the other 10 patients, despite a marked inhibition of extrarenal cyclooxygenase activity. We conclude that in patients with mild impairment of renal function, the renal blood flow and glomerular filtration rate are critically dependent on prostacyclin production. In such patients sulindac may be a safe substitute for other nonsteroidal antiinflammatory drugs.

Evidence for a Direct Stimulatory Effect of Prostacyclin on Renin Release in Man

THE OBJECTIVES OF THIS INVESTIGATION WERE: (a) to characterize the time and dose dependence of the effects of prostacyclin (PGI(2)) on renin release in healthy men; (b) to define whether PGI(2)-induced renin release is secondary to hemodynamic changes; (c) to determine the plasma and urine concentrations of 6-keto-PGF(1alpha) (the stable breakdown product of PGI(2)) associated with renin release induced by exogenous or pharmacologically enhanced endogenous PGI(2). Intravenous PGI(2) or 6-keto-PGF(1alpha) infusions at nominal rates of 2.5, 5.0, 10.0, and 20.0 ng/kg per min were performed in each of six normal human subjects; in three of them, PGI(2) infusion was repeated after beta-adrenergic blockade and cyclooxygenase inhibition. PGI(2), but not 6-keto-PGF(1alpha), caused a time- and dose-dependent increase of plasma renin activity, which reached statistical significance at 5.0 ng/kg per min and was still significantly elevated 30 min after discontinuing the infusion. Although combined propranolol and indomethacin treatment significantly enhanced the hypotensive effects of infused PGI(2), it did not modify the dose-related pattern of PGI(2)-induced renin release. Plasma 6-keto-PGF(1alpha) levels rose from undetectable levels (<7.5 pg/ml) in a stepwise fashion during increasingly higher infusion rates of PGI(2) or 6-keto-PGF(1alpha). The threshold concentration of plasma 6-keto-PGF(1alpha) associated with a statistically significant stimulation of renin release was approximately 200 pg/ml. Upon discontinuing PGI(2) or 6-keto-PGF(1alpha) infusion, the disappearance of 6-keto-PGF(1alpha) from blood showed an identical biphasic behavior, the initial phase having an apparent t((1/2)) of 3.2 min. The intravenous infusion of furosemide, which is known to stimulate renin release via a cyclooxygenase-dependent mechanism, caused a three-to fourfold increase of urinary 6-keto-PGF(1alpha) excretion rate, concomitant with the elevation of plasma renin activity levels, in six healthy women. 6-Keto-PGF(1alpha) remained undetectable in peripheral venous plasma throughout the study. WE CONCLUDE THAT IN HUMAN SUBJECTS: (a) PGI(2)-induced renin release occurs with a dose and time dependence similar to its reported platelet effects; (b) PGI(2)-induced renin release is not mediated by adrenergic stimuli or cyclooxygenase-dependent mechanisms secondary to hemodynamic changes; (c) furosemide-induced renin release is associated with increased renal PGI(2) formation; and (d) PGI(2) appears to act as a local modulator rather than a circulating hormone in controlling juxtaglomerular function.

Improvement of Renal Function with Selective Thromboxane Antagonism in Lupus Nephritis

To test the hypothesis that the vasoconstrictor thromboxane A2 may affect renal hemodynamics in lupus nephritis, we examined the short-term effects of a selective thromboxane-receptor antagonist, BM 13,177, and of low-dose aspirin. In a randomized, double-blind, crossover study, 10 patients with biopsy-proved lupus nephritis were given a 48-hour continuous infusion of BM 13,177 or placebo. At base line, seven patients had markedly elevated urinary levels of thromboxane B2, the breakdown product of thromboxane A2. During the infusion of BM 13,177, the inulin clearance rate, which was 68 ml per minute per 1.73 m2 of body-surface area at base line, increased by an average of 24 percent (range, 12 to 47 percent; P less than 0.01). Para-aminohippurate clearance was increased to the same extent, with no change in the filtration fraction. The bleeding time doubled, indicating an occupancy of platelet thromboxane receptors of more than 95 percent. The hemodynamic changes were associated with a significant increase in sodium excretion from 76 to 118 mmol per day (P less than 0.01) but with no change in arterial blood pressure. In another study, 10 additional patients with lupus nephritis were randomly assigned to receive either placebo or 20 mg of aspirin twice daily for four weeks. The aspirin regimen produced a selective, cumulative inhibition of platelet cyclooxygenase activity and a doubling of bleeding time. However, there was no change in the inulin clearance rate and no change in urinary levels of thromboxane B2 or 6-keto-prostaglandin F1 alpha, which are indicators of renal synthesis of thromboxane A2 and prostacyclin, respectively. We conclude that in lupus nephritis, impairment of renal function is at least in part mediated hemodynamically and is reversible with a thromboxane antagonist. Platelets, however, are not a major source of thromboxane A2 synthesis and action within the kidney.

Characterization of furosemide-induced activation of the renal prostaglandin system

A detailed time course of changes in plasma renin activity (PRA), urinary prostaglandin (PG) E2, PGF2 alpha, thromboxane (TX) B2 and sodium excretion rates following furosemide was obtained in 7 women. PRA increased within the first 15 min and remained elevated all through the experiment. PGE2, PGF2 alpha, TXB2 and sodium increased simultaneously, reached a peak between 15 and 45 min after furosemide and declined thereafter. It is concluded that furosemide induces a generalized activation of the renal PG system temporally related to the increase of renin release and natriuresis.

Experimental posterolateral spinal fusion with porous ceramics and mesenchymal stem cells

Alternatives to autogenous bone graft for spinal fusion have been investigated for many years. It has been shown that osteoconductive materials alone do not give a rate of fusion which is comparable to that of autogenous bone graft. We analysed the effectiveness of porous ceramic loaded with cultured mesenchymal stem cells as a new graft material for spinal fusion in an animal model. Posterolateral fusion was carried out at the L4/L5 level in 40 White New Zealand rabbits using one of the following graft materials: porous ceramic granules plus cultured mesenchymal stem cells (group I); ceramic granules plus fresh autogenous bone marrow (group II); ceramic granules alone (group II); and autogenous bone graft (group IV). The animals were killed eight weeks after surgery and the spines were evaluated radiographically, by a manual palpation test and by histological analysis. The rate of fusion was significantly higher in group I compared with group III and higher, but not significantly, in group I compared with groups II and IV. In group I histological analysis showed newly formed bone in contact with the implanted granules and highly cellular bone marrow between the newly formed trabecular bone. In group II, thin trabeculae of newly formed bone were present in the peripheral portion of the fusion mass. In group III, there was a reduced amount of newly formed bone and abundant fibrous tissue. In group IV, there were thin trabeculae of newly formed bone close to the decorticated transverse processes and dead trabecular bone in the central portion of the fusion mass. In vitro cultured mesenchymal stem cells may be loaded into porous ceramic to make a graft material for spinal fusion which appears to be more effective than porous ceramic alone. Further studies are needed to investigate the medium- to long-term results of this procedure, its feasibility in the clinical setting and the most appropriate carrier for mesenchymal stem cells.

High glucose level inhibits capacitative Ca2 + influx in cultured rat mesangial cells by a protein kinase C-dependent mechanism

Summary In cultured mesangial cells (MC), capacitative Ca2 + influx via store-operated channels (SOC) is potentiated by agents that release Ca2 + from intracellular stores, and inhibited by protein kinase C (PKC). Cells grown under high glucose conditions, as a model of the diabetic microenvironment, display reduced Ca2 + signalling in response to vasoconstrictors, probably due to downregulation by elevated PKC activity. Since SOC might be relevant to this phenomenon, we assessed Ca2 + influx by microfluorometry of fura-2-loaded rat MC cultured for 5 days in normal (5.5 mmol/l, NG) or high glucose (30 mmol/l, HG). The addition of 1–10 mmol/l Ca2 + to NG cells equilibrated in Ca2 + -free media induced an immediate Ca2 + influx with a free cytosolic Ca2 + ([Ca2 + ]i) plateau of 155 ± 50 and 318 ± 114 nmol/l, respectively. Basal influx was reduced to 88 ± 8 and 145 ± 17 nmol/l [Ca2 + ]i (1–10 mmol/l Ca2 + , p < 0.01) by 30 mmol/l d-glucose. This effect of HG was confirmed by Mn2 + quenching of fura-2, indicating reduced entry of divalent cations via the capacitative pathway. Equimolar l-glucose had no effect on Ca2 + influx, consistent with a non-osmotic mechanism. Arginine vasopressin (10 μmol/l) elicited weaker release of stored Ca2 + and subsequent influx in HG cells (191 ± 33 vs 153 ± 24 nmol/l, 400 ± 76 vs 260 ± 33 nmol/l, 1–10 mmol/l Ca2 + , NG/HG, p < 0.05). To examine the involvement of PKC in the effect of HG on capacitative Ca2 + influx, the enzyme was activated or downregulated by treatment with 0.1 μmol/l phorbol myristate acetate (PMA) for 3 min or 24 h, respectively. PMA acutely inhibited Ca2 + influx in NG cells, while PKC downregulation restored it in HG cells. Similarly, the PKC inhibitors staurosporin or H-7 normalized SOC activity in HG cells. In summary, impairment of Ca2 + influx via SOC by HG is one mechanism of the reduced MC [Ca2 + ]i responsiveness to vasoconstrictors. This event is mediated by PKC and may contribute to the glomerular haemodynamic changes in the initial stages of diabetes mellitus. [Diabetologia (1997) 40: 521–527]

Renal Hemodynamics and Urinary Excretion of 6-Keto-Prostaglandin F1α and Thromboxane B2 in Newly Diagnosed Type I Diabetic Patients

We have studied the functional importance of renal eicosanoids in renal hemodynamics of seven newly diagnosed insulin-dependent diabetes mellitus (IDDM) patients by treatment with two structurally unrelated inhibitors of cyclooxygenase (i.e., piroxicam and sulindac). Glomerular filtration rate (GFR), renal plasma flow (RPF), daily urinary excretion of 6-keto-prostaglandin F1α (6-keto-PGF1α, the stable hydrolysis product of prostacyclin), and thromboxane B2 (TXB2, the stable hydrolysis product of thromboxane A2) were measured before, during, and after piroxicam (all patients) or sulindac (3 patients) treatment. Urinary excretion of 6-keto-PGF1α was significantly increased (P < .01) in diabetic patients compared with seven healthy subjects, whereas urinary excretion of TXB2 was unchanged. The baseline value of GFR was significantly (P < .01) higher in diabetic compared with normal volunteers, whereas baseline RPF was comparable in both groups. Piroxicam (20 mg/day) reduced urinary excretion of 6-keto-PGF1α and TXB2 by 65.7 ± 26 and 64.6 ± 33%, respectively. These biochemical changes were temporally associated with the ∼ 19% decrease in GFR (P < .01). A week after discontinuation of the drug, GFR and urinary excretion of 6-keto-PGF1α were still significantly (P < .05) reduced, whereas urinary excretion of TXB2 returned to control values. In contrast, urinary excretion of eicosanoids and renal function were not affected by sulindac (0.4 g/day) treatment. No functional changes were detected in healthy subjects despite a similar suppression of renal cyclooxygenase activity when they were treated with piroxicam.We conclude that altered GFR in newly diagnosed IDDM patients may depend, at least partially, on altered renal synthesis of vasodilator prostacyclin.

Angiotensin converting enzyme inhibition delays the progression of chronic renal failure in hypertensive patients with immunoglobulin A nephropathy

Ten hypertensive, non-nephrotic patients with immunoglobulin (IgA) nephropathy treated with conventional therapy (vasodilators, beta-blockers, diuretics) were observed for 21.4 +/- 9 months. Treatment was then changed to an angiotensin converting enzyme (ACE) inhibitor alone for an additional 22.6 +/- 9 months. The ACE inhibitor therapy was associated with a lower diastolic blood pressure and a slowing in the rate of decline in renal function, but no change in proteinuria.

Effects of Haemodialysis Session on Plasma Beta-Endorphin, ACTH and Cortisol in Patients with End-Stage Renal Disease

The effect of a regular haemodialysis session on the plasma concentrations of beta-endorphin, ACTH and cortisol was investigated in 14 patients with end-stage renal disease and 20 healthy controls. Blood for analysis of beta-endorphin, ACTH and cortisol was sampled before and immediately after haemodialysis. In four patients the dialysate was studied for presence of these hormones, but showed no specific activity. The predialysis beta-endorphin, ACTH and cortisol levels did not differ significantly from the control values. The postdialysis levels were significantly higher than the predialysis. Significant linear correlation was found between plasma ACTH and beta-endorphin values in the postdialysis samples. The similarity of plasma beta-endorphin, ACTH and cortisol levels in patients with end-stage renal disease before dialysis and in normal controls indicated integrity of the hypothalamic pituitary-adrenal axis. The significantly increased levels after the dialysis session and the significant correlation between postdialysis plasma beta-endorphin and ACTH suggest that the haemodialysis session was a stressful event.

Glomerular Hypertrophy and Chronic Renal Failure in Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis evolves toward chronic renal failure (CRF) with a highly variable rate; in particular, a group of patients with a much more rapid decline of renal function has been described. The purpose of this study was to evaluate the usefulness of morphometry in identifying those cases with a faster decline in renal function. Two groups of patients have been studied: six with rapid evolution toward CRF (group 1) and six without reduction in renal function during a follow-up of up to 10 years (group 2). The results of the morphometric analysis of glomeruli were as follows: mean glomerular area: 30,550 +/- 5,259 microns2 (group 1) versus 22,667 +/- 5,078 microns2 (group 2) (P = 0.01); maximum glomerular area: 40,827 +/- 9,508 microns2 (group 1) versus 30,445 +/- 7,224 microns2 (group 2) (P = 0.02); mean glomerular diameter: 193.9 +/- 15.8 microns (group 1) versus 161.8 +/- 16.8 microns (group 2) (P = 0.003); and caliper diameter: 328.6 +/- 20.6 microns (group 1) versus 260.6 +/- 36 microns (group 2) (P = 0.001). Values of body surface area were not different between the two groups (1.85 +/- 0.34 m2 v 1.6 +/- 0.13 m2) (P = NS). Our results suggest that glomerular hypertrophy in the course of focal segmental glomerulosclerosis is correlated with a faster decline toward CRF. It might represent a compensatory hypertrophy that would immediately precede a rapid decline in renal function or it might be the expression of the preexisting condition (meganephronia), which predisposes to the development of CRF.