Effects of a prostacyclin analog iloprost on kidney function, renin-angiotensin and kallikrein-kinin systems, prostanoids and catecholamines in man

12: Clinical Aspects of Prostaglandins and Leukotrienes in Migraine

Clinical, pathophysiological, pharmacological, and biochemical evidence support the concept that the prostanoid system may be involved in migraine. As a local defence system prostaglandins may best be linked with hyperalgesia and vascular events. The response to potent inhibitors of PG-synthesis like tolfenamic acid further supports the involvement of prostaglandins in the “inflammatory-like” aspects of migraine pain. The prostanoid system may be closely coupled with the monoaminergic mechanism; e.g. in stress reactions plasma thromboxane correlates with adrenaline levels. The possible participation of leukotrienes in migraine is only speculative. However, in cerebral hypoxia lipid peroxidation is increased and leukotrienes might participate in the cerebrovascular reactions. Prostaglandins may inhibit the formation of free radicals, antagonize some actions of leukotrienes and protect the tissues. The interplay between leukotrienes and prostaglandins may give new aspects to some cerebrovascular abnormalities in migraine.

Effect of iloprost on plasma asymmetric dimethylarginine and plasma and platelet serotonin in patients with peripheral arterial occlusive disease

BACKGROUND

Iloprost, a prostacyclin analogue, is used in the treatment of peripheral arterial occlusive disease at Leriche-Fontaine stages III-IV, through intravenous infusion for at least 21 days. Recently, iloprost has been shown to be safe and effective in critical limb ischemia patients when administered per 7 days. We investigated in patients at Leriche-Fontaine stages III-IV the effect of 1-week treatment with iloprost on plasma asymmetric dimethylarginine (ADMA), plasma and platelet serotonin, and on clinical response.

METHODS AND RESULTS

Twenty-four critical limb ischemia patients (16 men and 8 women, mean age 76+/-9.7 years) were included in the study and treated with intravenous iloprost (titrated from 0.5 up to 1.5 ng/kg/min) for 16 h a day for seven consecutive days. Blood samples were drawn before infusion on days 1, 4 and 8 of treatment, under the same conditions. Clinical assessment was performed by clinical evaluation, ankle/brachial pressure index and treadmill exercise test. During treatment with iloprost patients clinically improved and plasma levels of ADMA significantly decreased (p<0.001). We also observed a significant increase of serotonin (p<0.01) in platelets and a significant decrease of serotonin (p<0.001) in plasma. Similar variations of ADMA and serotonin were found in two subgroups of patients, diabetics and non-diabetics.

CONCLUSIONS

One-week treatment with iloprost in critical limb ischemia patients induced changes of peripheral markers of endothelial dysfunction and atherosclerosis, such as ADMA and serotonin, associated to a clinical improvement.

Effect of a prostacyclin analogue, iloprost, on urinary aquaporin-2 excretion in humans

The regulation of aquaporin-2 (AQP2) water channel excretion in the collecting duct depends mainly on the action of vasopressin (AVP). Recently, however, other regulatory factors have been identified: atrial natriuretic factor, oxytocin and prostaglandins. In healthy volunteers (5 males, 5 females; mean age 23 +/- 3 years) we therefore evaluated the effect of a stable analogue of prostacyclin-2 (PGI(2)), iloprost, on renal function and on the urinary excretion of AQP2 (U-AQP2). After 6 h of iloprost infusion, U-AQP2 increased from 0.8 +/- 0.15 to 1.8 +/- 0.2 pmol/mg creatinine (p < 0.001), while the urinary flow rate increased from 1.4 +/- 0.2 to 1.8 +/- 4 (p < 0.01). No significant change was found in the AVP serum concentration, with a basal value of 3.17 +/- 0.12 vs. 3.15 +/- 0.12 pg/ml after 6 h of prostacyclin infusion. All the values returned to pre-study levels after a recovery period of 6 h. In conclusion, the PGI(2) analogue, iloprost, can induce U-AQP2 excretion independent of AVP.

A randomized controlled trial of epoprostenol therapy for severe congestive heart failure: The Flolan International Randomized Survival Trial (FIRST)

This trial evaluated the effects of epoprostenol on patients with severe left ventricular failure. Patients with class IIIB/IV congestive heart failure and decreased left ventricular ejection fraction were eligible for enrollment if angiography documented severely compromised hemodynamics while the patient was receiving a regimen of digoxin, diuretics, and an angiotensin-converting enzyme inhibitor. We randomly assigned 471 patients to epoprostenol infusion or standard care. The primary end point was survival; secondary end points were clinical events, congestive heart failure symptoms, distance walked in 6 minutes, and quality-of-life measures. The median dose of epoprostenol was 4.0 ng/kg/min, resulting in a significant increase in cardiac index (1.81 to 2.61 L/min/m2), a decrease in pulmonary capillary wedge pressure (24.5 to 20.0 mm Hg), and a decrease in systemic vascular resistance (20.76 to 12.33 units). The trial was terminated early because of a strong trend toward decreased survival in the patients treated with epoprostenol. Chronic intravenous epoprostenol therapy is not associated with improvement in distance walked, quality of life, or morbid events and is associated with an increased risk of death.

Acute hemodynamic effects of the prostacyclin analog 15AU81 in severe congestive heart failure

This multicenter, open-label study provides the first assessment of the safety and acute hemodynamic effects of a short-term infusion of 15AU81, a chemically stable analog of prostacyclin, in patients with New York Heart Association class III or IV heart failure. Twelve patients underwent sequential dose escalation by increasing the rate of the infusion at 15-minute intervals until the drug was no longer tolerated. Patients then received a 90-minute infusion at their maximum tolerated dose. The infusion was then discontinued and the subjects were observed during a 90-minute washout segment. Serial hemodynamic measurements were made throughout the dose-ranging, maintenance, and washout segments. A significant decrease in systemic vascular resistance (1,935 +/- 774 vs 1,243 +/- 351 dynes.s.cm-5; p < 0.001) and pulmonary vascular resistance (395 +/- 335 vs 223 +/- 198 dynes.s.cm-5; p = 0.008) occurred from the infusion of vehicle to the maximum tolerated dose. During dose titration, there was a a significant increase in cardiac index (1.9 +/- 0.7 vs 2.6 +/- 0.6 liters/min/m2; p < 0.001) and a tendency for a mild reduction in pulmonary artery wedge pressure (18 +/- 7 vs 17 +/- 6; p = 0.055) for the 8 patients with values on vehicle and maximum tolerated dose. These hemodynamic changes persisted during the maintenance infusion and disappeared rapidly during the washout segment. The most common adverse event to limit dose-ranging was headache, which occurred at a mean maximum tolerated dose of 36 +/- 15 ng/kg/min. Administration of 15AU81 was associated with significant acute hemodynamic improvement in patients with severe heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Opposite renal effects of a PGE1 analog and prostacyclin in humans

Renal effects of prostaglandins have been widely investigated in anesthetized animals, but in contrast only few studies have been devoted to healthy and diseased humans. Recently, both prostacyclin and a stable analog of PGE1, misoprostol, have been available for therapeutic purposes in clinical conditions associated with peripheral or renal vasoconstriction; however, the renal effects have not been defined. We have therefore studied the acute renal effects of PGI2 5 ng.kg/min intravenously and of misoprostol, a stable PGE1 analogue, 400 micrograms orally in two groups of respectively 8 and 12 healthy supine subjects on normal sodium diet using sodium, lithium, inulin, PAH and neutral dextran clearances. PGI2 induced a slight natriuretic effect, a systemic and renal vasodilation with a decrease in mean arterial pressure from 85.3 +/- 1.1 to 80.2 +/- 1.6 mm Hg (P < 0.01) and in renal vascular resistance from 94 +/- 6 to 75 +/- 5 mm Hg.min/ml (P < 0.001). GFR did not change whereas fractional clearance of dextran decreased over the 34 to 48 A radius range. Applying these changes on a hydrodynamic model of filtration of macromolecules through water-filled pores, we calculated that PGI2 decreased the glomerular transcapillary pressure gradient from 35 +/- 1 to 32 +/- 1 mm Hg (P < 0.001), decreased nonsignificantly the ultrafiltration coefficient Kf and did not affect the membrane parameters r0 and omega 0. Misoprostol had no natriuretic effect, induced slight renal vasoconstriction and moderate decrease in GFR from 124 +/- 9 to 114 +/- 10 ml/min.1.73 m2 (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Iloprost decreases urinary albumin excretion rate in patients with diabetic nephropathy

We conducted an open clinical trial to determine whether administration of iloprost, a stable prostacyclin analog, has any effect on urinary albumin excretion and other parameters associated with non-insulin-dependent diabetes mellitus (NIDDM) patients. Twenty-three NIDDM patients with nephropathy were divided into groups A and B which were matched in terms of sex, age, duration of diabetes and blood glucose control. After 2 weeks of observation, 11 patients in group A received an intravenous infusion of iloprost (10 micrograms at a rate of 0.075 microgram/kg per h) once daily for 2 weeks, while 12 untreated diabetic patients in group B served as controls. In group A, iloprost significantly reduced the urinary albumin excretion rate, the urinary albumin-creatinine ratio and N-acetyl-beta-D-glucosaminidase without decreasing creatinine clearance during the treatment period (P < 0.05, respectively). However, none of these parameters changed significantly in group B. Urinary beta 2-microglobulin, blood pressure, heart rate, serum electrolytes, BUN and serum creatinine were not significantly altered by iloprost during the treatment period. Side effects associated with iloprost were mild and could be ameliorated by slowing the infusion rate. We conclude that iloprost appears to be safe and has an apparent effect on the urinary albumin excretion rate and N-acetyl-beta-D-glucosaminidase.

Thromboxane and prostacyclin differentially regulate murine extracellular matrix gene expression

Alterations in the arachidonic acid metabolites thromboxane and prostacyclin are known to contribute to hemodynamic changes observed in certain models of acute and chronic renal failure. We have previously shown that thromboxane may have an important role in mediating glomerulosclerosis by stimulating the expression of certain extracellular matrix proteins. In the present study, we compared the effects of thromboxane and prostacyclin on the expression of genes encoding basement membrane proteins using a murine teratocarcinoma cell line, that when differentiated to an endodermal phenotype synthesizes abundant extracellular matrix. Incubation of these cells with stable analogs of thromboxane and prostacyclin for four hours resulted in changes in basement membrane gene expression. Thromboxane increased steady-state mRNA levels for all three laminin chains, type IV collagen, and fibronectin, but decreased the level of mRNA for heparan sulfate proteoglycan. In contrast, incubation with carbo-prostacyclin, a stable analog of prostacyclin, decreased the steady-state mRNA level for the laminin A and B1 chains, type IV collagen and fibronectin, and increased the mRNA level for heparan sulfate proteoglycan and laminin B2. Carbo-prostacyclin did not affect cellular proliferation or thymidine incorporation. These results indicate that eicosanoids directly modulate matrix gene expression independently of hemodynamic influence, and independently of effects mediated by platelets, or mitogenesis. Furthermore, these findings suggest that the alterations in renal eicosanoid metabolism may directly participate in the pathogenesis of glomerulosclerosis and thus provide a rationale for therapy directed toward the specific inhibition of thromboxane in the treatment of progressive glomerular sclerosis.

Effect of prostacyclin on renal kallikrein release in man

The aim of this research was to study exogenous prostacyclin effect on urinary kallikrein excretion (UKK) in man, to define whether prostacyclin-induced renin release and/or endogenously released cyclooxygenase products were responsible for prostacyclin-induced enhancement of UKK, to determine furosemide effect on UKK. Prostacyclin was infused in eight healthy men and repeated after propranolol and indomethacin treatment. Prostacyclin caused a dose-dependent increase of UKK. Pretreatment with propranolol and indomethacin did not affect prostacyclin-induced enhancement of UKK, although it reduced absolute values of plasma renin activity. Furosemide increased UKK and simultaneously urinary 6-keto-prostaglandin F1 alpha. We conclude that prostacyclin induces an increase in UKK in a dose-dependent manner; furosemide-induced renal prostacyclin synthesis is temporally related to enhancement of UKK; partial dissociation of UKK from plasma renin activity under propranolol and indomethacin treatment and in response to furosemide might suggest a direct effect of prostacyclin on UKK.