Renal eicosanoids as determinants of renal function in liver disease

Anti-leukotriene drugs in the prevention and treatment of hepatorenal syndrome

Hepatorenal syndrome (HRS) is a peculiar form of progressive renal failure complicating the course of cirrhosis and ascites. The renal impairment of HRS is merely functional and potentially reversible. Notwithstanding, in spite of several encouraging attempts, a satisfactory medical treatment for HRS is still expected. Several pathophysiological mechanisms are active in HRS. Arachidonate metabolism derangements are among these, and prostaglandins and thromboxane antagonists have been tried with variable outcomes. Also leukotrienes (LT) appear to be involved in HRS. Three drugs (zileuton, montelukast and zafirlukast) interfering with LT synthesis and receptor binding are currently available, but they have not yet been tried in HRS. Accordingly, the author would like to suggest physicians engaged in care of these critical patients to consider a trial with these drugs-as well as with any future innovative agent active on the arachidonate-derived metabolic pathways.

Effect of misoprostol on ibuprofen-induced renal dysfunction in patients with decompensated cirrhosis: results of a double-blind placebo-controlled parallel group study

OBJECTIVES

Patients with cirrhosis are prone to develop renal failure upon administration of nonsteroidal anti-inflammatory drugs. The aim of the present study was to determine the safety and efficacy of misoprostol (400 microg) in two repeated doses for the prevention of ibuprofen-induced decrements in renal function in decompensated cirrhotics.

METHODS

Patients were given ibuprofen (800 mg) with either misoprostol (n = 9) or a placebo (n = 10). Sixty minutes later another dose of misoprostol or the placebo was administered. Renal function tests were assessed by clearance techniques.

RESULTS

Administration of ibuprofen with a placebo caused significant decreases in urinary output, inulin clearance, sodium excretion, osmolar clearance, free water clearance, and urinary prostaglandin E2 excretion. Coadministration of ibuprofen and the first misoprostol dose maintained urinary output and sodium excretion, and caused an increase in free water clearance. These changes were maintained only for 1 h. Administration of the second dose of misoprostol temporarily improved inulin and creatinine clearances. Half the patients who received misoprostol suffered from episodes of chills, fever, and diarrhea.

CONCLUSION

Ibuprofen causes renal dysfunction in decompensated cirrhotics, whereas misoprostol may have some protective renal effects, which are, however, short lived and clinically insignificant. Because of side effects, misoprostol should be used with caution in these patients.

Pharmacokinetics of intravenously administered digoxin and histopathological picture in rabbits with experimental bile duct obstruction

This study aimed to examine the effect of obstructive cholestasis on the pharmacokinetics of digoxin. Eighteen male rabbits were randomly ascribed to the two study groups: the sham-operated control group and the examined group - with common and cystic bile duct ligations. Digoxin was administered intravenously as a single dose of 0.02 mg/kg, and blood samples were withdrawn for up to 24 h. Digoxin concentrations were determined by the FPIA method. The pharmacokinetic parameters were calculated using a noncompartmental analysis. During the whole observation period the blood serum concentrations of digoxin were statistically higher in animals with obstructive cholestasis versus the controls. A significant increase in the area under the plasma concentration-time curve, decrease in the total body clearance and in the volume of distribution on the 6th day after the bile ducts ligation as compared to the sham-operated controls, were observed. The obtained results suggest an impaired elimination of digoxin in obstructive cholestasis in rabbits.

Increased renal and vascular cytosolic phospholipase A2 activity in rats with cirrhosis and ascites

Indirect evidence suggests that the renal and vascular production of prostaglandins is increased in cirrhosis with ascites. However, the activity of the enzymes regulating the prostaglandin pathway has not been investigated in cirrhosis. The aim of the current study was to determine the activity of phospholipase A2 (PLA2), the key enzyme in the regulation of prostaglandin synthesis, in kidney and vascular tissue obtained from rats with carbon tetrachloride-induced cirrhosis and ascites (n = 9) and control rats (n = 6). PLA2 activity was assayed in vitro using [14C]arachidonyl-phosphatidylcholine (PC) and [14C]arachidonyl-phosphatidylethanolamine (PE) as substrates in the presence of Ca2+. Kidneys from cirrhotic rats had significantly higher PLA2 activity compared with control rats, with both PC and PE (35 +/- 5 and 40 +/- 6 vs. 21 +/- 2 and 26 +/- 3 pmol/mg/min, respectively; P < .05 for both). PLA2 activity was increased in the renal cortex as well as in the renal medulla. Fractionation of the kidney extracts by Mono-Q anion-exchange chromatography showed that the elution position of PLA2 activity corresponded to the cytosolic PLA2 isoform (cPLA2). Increased amounts of cPLA2 protein were found in kidney extracts immunoblotted with an anti-cPLA2 antibody However, reverse-transcriptase polymerase chain reaction (RT-PCR) analysis did not detect any difference in cPLA2 mRNA. PLA2 activity was also higher in aortic tissue from cirrhotic rats than in controls (PC 38 +/- 5 vs. 26 +/- 1 and PE 66 +/- 8 vs. 41 +/- 3 pmol/mg/min; P < .05 for both). Incubation of renal and aortic extracts from cirrhotic rats with anti-cPLA2 antibody reduced PLA2 activity by 64% and 88%, respectively. In conclusion, PLA2 activity is increased in kidneys and vascular tissue from cirrhotic rats with ascites. This can be accounted for by an induction of cPLA2, which would mediate, at least in part, the increased renal and vascular production of prostaglandins in cirrhosis.

Polyunsaturated fatty acid deficiency in liver diseases: pathophysiological and clinical significance

Polyunsaturated fatty acid (PUFA) deficiency occurs in advanced cirrhosis and other liver diseases (acute hepatitis, cholestasis). Long-chain PUFA deficit in cirrhosis is due to both essential fatty-acid (EFA) deficiency and impaired PUFA biosynthesis. Although hepatic insufficiency itself mostly accounts for this phenomenon, other factors such as associated malnutrition also play a role. PUFA deficiency in cirrhosis probably has a wide array of both cellular and clinical consequences, but, at present, they have been difficult to prove. In addition, the route, dosage, and safety of PUFA supplementation in these patients needs extensive investigation in the future.

Renal vasoactive mediator generation in portal hypertensive and bile duct ligated rats

BACKGROUND/METHODS

Vasoactive substances may have a role in the pathogenesis of functional renal abnormalities in patients with cirrhosis. We determined renal vasoactive mediators in rats with portal hypertension since the balance in each part of the kidney between the vasodilator activity of prostaglandin E2 and the vasospastic activity of thromboxane A2, leukotriene B4, leukotriene C4, endothelin-1 and platelet activating factor may determine renal function. Rats with partial portal vein ligation (n = 7), complete bile duct ligation (n = 6) and sham operated (n = 10) were studied. Three weeks following surgery renal function tests, including fractional excretion of sodium [Fe(Na)] were measured. Rats were anesthetized, splenic pulp pressure was measured, kidneys were removed, and cortex, medulla and papilla were separated and homogenized for determination of prostaglandin E2, thromboxane B2, leukotriene B4, leukotriene C4 and endothelin-1 by radioimmunoassay (ng/g) and platelet activating factor activity (pg/10 mg) by platelet aggregation.

RESULTS

Pulp pressure was > 13 mmHg in portal vein ligated and bile duct ligated and 6 mmHg in sham operated rats. In bile duct ligated rats there was a 70% decrease in Fe(Na) and a significant decrease in cortical and papillary prostaglandin E2, whereas cortical thromboxane B2 and platelet activating factor activity in the cortex, medulla and papilla were double that of sham operated rats. A similar but insignificant trend of changes was found in portal vein ligated rats. Medullary leukotriene B4 was significantly decreased in bile duct ligated rats. Papillary leukotriene B4 was not detected in bile duct ligated and portal vein ligated rats. Renal leukotriene C4 generation in the three groups was either unchanged (papilla) or beyond detection (cortex and medulla). Medullary and papillary endothelin-1 in portal vein ligated and bile duct ligated rats were 178%-130% higher than in sham operated rats. A significant negative correlation was found between Fe(Na) and cortical and medullary thromboxane B2 generation and medullary platelet activating factor activity.

CONCLUSIONS

1) In bile duct ligated rats enhanced intrarenal generation of thromboxane A2 and platelet activating factor may contribute to decreased renal sodium excretion. 2) The role of decreased intrarenal prostaglandin E2 and increased intrarenal endothelin-1 content in bile duct ligated rats is not yet understood. 3) Renal leukotriene generation is either decreased or undetected in portal vein ligated and bile duct ligated rats.

The effects of chronic administration of indomethacin and misoprostol on renal function in cirrhotic patients with and without ascites

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) often cause renal dysfunction in cirrhotic patients with ascites through inhibition of prostaglandin synthesis. However, their renal effects in cirrhotic patients without ascites are controversial. In addition, the role of prostaglandins in cirrhotic patients with ascites and in non-ascitic cirrhotic patients receiving NSAIDs also remains elusive. Thus we evaluated the chronic renal effects of indomethacin and misoprostol in 9 cirrhotic patients with ascites (protocol 1) and 21 cirrhotic patients without ascites (protocol 2).

METHODS

The patients of protocol 1 received 200 micrograms of misoprostol every 6 h for 7 consecutive days. In protocol 2, 11 patients received 25 mg indomethacin three times a day for 7 consecutive days. The other 10 patients received 25 mg indomethacin three times a day plus 200 micrograms misoprostol every 6 h for 7 consecutive days. Renal function tests, plasma renin activity, and plasma aldosterone concentration were measured before and after treatment.

RESULTS

In protocol 1, misoprostol tended to reduce the urinary sodium excretion (p = 0.08). In protocol 2, indomethacin alone greatly impaired renal plasma flow (p < 0.05), creatinine clearance (p < 0.05), blood urea nitrogen (p < 0.05), and serum creatinine (p = 0.06) in 11 patients. Similar magnitudes of renal dysfunction were observed in the other 10 patients despite the concomitant misoprostol treatment.

CONCLUSION

Chronic administration of misoprostol may have caused a negative natriuretic effect in cirrhotic patients with ascites. In cirrhotic patients without ascites chronic administration of indomethacin may induce a renal dysfunction that cannot be reversed by misoprostol.

Renal and hormonal responses to repeated treatment with enalapril in non-azotemic cirrhosis with ascites

Since a single dose of the angiotensin-converting enzyme inhibitor enalapril was shown to cause natriuresis in cirrhosis in a previous study, we investigated whether repeated doses of this substance would sustain a favorable renal effect in cirrhosis. Ten milligrams of enalapril maleate were administered once a day for 8 days to ten patients with non-azotemic cirrhosis and ascites. Enalapril reduced blood pressure significantly at 4 to 12 h (systolic blood pressure) and 2, 6, and 8 h (diastolic blood pressure) on day 2, compared to pretreatment (day 0) values, but this depressor effect decreased on day 8. No change in heart rate could be detected. Enalapril significantly suppressed serum angiotensin-converting enzyme activity and plasma aldosterone concentration (p < 0.001 to 0.01), which were elevated prior to treatment, with pretreatment values of 25.8 +/- 1.8 IU/l for serum angiotensin-converting enzyme activity and 241 +/- 67 pg/ml for plasma aldosterone concentration. This drug caused a 12 to 24% increase (p < 0.05 to 0.01) in mean daily urinary volume and a 40 to 54% increase (p < 0.001 to 0.01) in mean daily urinary sodium excretion from the respective pretreatment baselines during the 8-day period. Creatinine clearance was improved (p < 0.05) by the treatment, with mean improvement values from 24 to 34% above the pretreatment value of 47.4 +/- 4.3 ml/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of imidazole-salicylate on renal function and the diuretic action of furosemide in cirrhotic patients with ascites

Imidazole-salicylate is a non-steroidal anti-inflammatory drug with limited inhibitory effects on prostaglandin synthesis. The renal effects of this drug were investigated by a double-blind cross-over study in 10 patients with cirrhosis and ascites. Two therapeutic doses of imidazole-salicylate (750 mg each) were given at midnight and 08:00 h and 80 mg of furosemide were injected intravenously at 09:00 h. The same procedure was followed on another day but a placebo replaced imidazole-salicylate. Renal function (creatinine clearance, free water and electrolyte excretions) and urinary excretion of prostaglandin E, 6-keto-prostaglandin F1 alpha and thromboxane B2 were evaluated for 8 h after the first dose of the drug and for 2 h after furosemide injection. Platelet thromboxane production was also determined 9 h after the first administration of drug or placebo. Imidazole-salicylate did not affect renal function or inhibit kidney prostanoid production either under basal conditions or after the stimulating effect of furosemide. On the contrary, imidazole-salicylate significantly inhibited platelet thromboxane production (45.8 +/- 9 vs. 69.4 +/- 7.5 ng/ml, P < 0.05). These results suggest that imidazole-salicylate is an anti-inflammatory drug that can be given to patients with decompensated cirrhosis without risk of inhibiting kidney prostaglandin synthesis or the renal response to furosemide.

Plasma endothelin immunoreactivity in liver disease and the hepatorenal syndrome

BACKGROUND

Severe renal vasoconstriction is central to the pathogenesis of renal failure in the hepatorenal syndrome. Endothelin-1 and endothelin-3 are potent, long-acting vasoconstrictors, and endothelin-1 has selective potency as a renal vasoconstrictor. These properties suggest a role for endothelins in the hepatorenal syndrome.

METHODS

We measured plasma endothelin-1 and endothelin-3 concentrations using specific radioimmunoassays in subjects with hepatorenal syndrome, liver disease but normal renal function, chronic renal failure, acute renal failure, liver dysfunction and renal impairment, or normal liver and kidney function.

RESULTS

The patients with the hepatorenal syndrome had markedly elevated mean (+/- SE) plasma concentrations of endothelin-1 (36 +/- 5 ng per liter [14.5 +/- 1.8 pmol per liter]) and endothelin-3 (43 +/- 3 ng per liter [16.3 +/- 1.0 pmol per liter]) as compared with the normal subjects (endothelin-1, 4 +/- 1 ng per liter [1.7 +/- 0.2 pmol per liter]; and endothelin-3, 18 +/- 1 ng per liter [6.8 +/- 0.4 pmol per liter]; P < 0.001) and with the patients in the other four groups (P < 0.001 to P < 0.05). The plasma endothelin-1, but not endothelin-3, concentrations in these four patient groups were significantly higher than in the normal subjects (P < 0.001 to P < 0.05). The concentrations of endothelin-1 in renal arterial plasma and renal venous plasma, measured in five patients with the hepatorenal syndrome and three with chronic liver disease and normal renal function, were 20 +/- 4 ng per liter (7.9 +/- 1.8 pmol per liter) and 24 +/- 4 ng per liter (9.5 +/- 1.5 pmol per liter), respectively (P < 0.05).

CONCLUSIONS

The increase in plasma endothelin-1 and endothelin-3 concentrations in patients with the hepatorenal syndrome is consistent with the hypothesis that these substances have a role in the pathogenesis of the disease.

Do rat kidney cortex microsomes possess the enzymatic machinery to desaturate and chain elongate fatty acyl-CoA derivatives?

Rat kidney cortex microsomal preparations were unable to catalyze delta 9, delta 6 and delta 5 desaturation of stearoyl-coenzyme A (CoA), linoleoyl-CoA and dihomo-gamma-linolenoyl-CoA, respectively. The kidney cortex microsomal fraction, however, did catalyze the malonyl-CoA dependent fatty acyl-CoA elongation. The biochemical properties of palmitoyl-CoA elongation were studied as a function of protein concentration, time, reduced nicotinamide adenine dinucleotide phosphate (NADPH), malonyl-CoA and substrate concentrations; of the substrates investigated, delta 6,9,12-18:3 was the most active. Unlike what was observed in the hepatic system, a high-carbohydrate, fat-free diet did not induce kidney fatty acid chain elongation. All intermediate kidney cortex microsomal reactions, i.e., beta-ketoacyl-CoA reductase, beta-hydroxyacyl-CoA dehydrase and trans-2-enoyl-CoA reductase activities, were significantly higher (greater than one order of magnitude) than the condensing enzyme activity, suggesting that the rate-limiting step in total elongation is the initial condensation reaction. Contrary to other reports, the results suggest that the kidney cannot synthesize arachidonic acid needed for eicosanoid production.

Systemic and renal production of thromboxane A2 and prostacyclin in decompensated liver disease and hepatorenal syndrome

To assess the role of altered renal and systemic production of thromboxane A2 and prostacyclin in the hepatorenal syndrome, urinary excretion of their major renal and extrarenal metabolites was measured in patients with compensated and decompensated liver disease, chronic renal failure, and hepatorenal syndrome. Urinary excretion rates of all prostanoids (renal and extrarenal) were increased in subjects with liver disease compared with normal controls. Moreover, they were considerably higher in subjects with severe hepatic decompensation but good renal function compared with those with hepatorenal syndrome. In contrast, the excretion rate of all metabolites was reduced in patients with chronic renal failure. The excretion rate of all metabolites was markedly elevated during the early stages of hepatorenal syndrome and decreased in parallel with creatinine clearance. When corrected for creatinine clearance, there was a strong correlation between prostanoid excretion and serum bilirubin in subjects with liver disease; there was no difference, however, in the excretion of renal and extrarenal prostanoids between hepatorenal syndrome and severe hepatic decompensation. It is concluded that hepatic decompensation is associated with a progressive increase in prostanoid excretion but that changes in production of prostacyclin or thromboxane A2 are unlikely to be major factors in the pathogenesis of the hepatorenal syndrome.

Renal cytochrome P-450-dependent metabolism of arachidonic acid in cirrhotic rats

Cirrhosis was induced in Wistar-Kyoto rats by intragastric administration of carbon tetrachloride. Microsomes were obtained from the renal cortex and outer medulla and incubated with [14C]arachidonic acid (AA) (0.2-0.4 microCi) in the presence or absence of indomethacin, NADPH, and SKF-525A. Cytochrome P-450-dependent AA metabolites (those whose formation required NADPH, were inhibited by SKF-525A, but not by indomethacin) were separated by thin-layer chromatography and high-pressure liquid chromatography (HPLC). Compared to controls, total synthesis of cytochrome P-450-dependent AA metabolites was reduced in cirrhotic rats (renal cortex: cirrhotics 380 +/- 52 vs. controls 493 +/- 68 pg/mg protein per 30 min; p less than 0.05; renal outer medulla: cirrhotics 304 +/- 57 vs. controls 387 +/- 53 pg/mg protein per 30 min; p less than 0.05). The cytochrome P-450-dependent AA metabolites were composed of three peaks separated by HPLC. Peak I, which had a retention time of 16.3 +/- 0.3 min and comigrated with 11,12-dihydroxyeicosatrienoic acid, and peak II, which had a retention time of 18.7 +/- 0.4 min and comigrated with 19- and 20-hydroxyeicosatetraenoic acid, were not different in cirrhotics and controls. Peak III, which had a retention time of 26.8 +/- 0.3 min, and comigrated with 11,12-epoxyeicosatrienoic acid, was significantly decreased in the renal cortex of cirrhotic rats compared to controls (cirrhotics 316 +/- 40 vs. controls 473 +/- 89 pg/mg protein per 30 min; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal of hepatorenal syndrome in four patients by peroral misoprostol (prostaglandin E1 analogue) and albumin administration

Four consecutive patients with alcoholic cirrhosis and hepatorenal syndrome were treated with misoprostol, a synthetic methylester prostaglandin E1 analogue at twice the dosage advocated for anti-ulcer therapy (i.e., 0.4 mg four times per day orally) and albumin infusions. The mean urinary output obtained over the 3 days preceding misoprostol administration was 250, 315, 550 and 195 ml per 24 h, respectively, in the four patients, despite adequate volume expansion by plasma albumin to reach normal or high central venous pressure. Diuresis increased to 1450, 2440, 925 and 1300 ml, respectively, on days 2-4 after onset of therapy. Serum creatinine levels were 71, 51, 33 and 35 mg/l before and dropped to 26, 21, 13 and 17 mg/l during treatment. All patients had hyponatraemia (117-128 mequiv/l) which normalized, although they were continued on a low sodium intake of less than 10 mequiv per 24 h. Urinary sodium excretion increased from 0.4-3 mmol per 24 h, to 15-40 in the first two cases and only slightly to 3-5 in the last two patients. Three patients died after 10, 30 and 40 days due to oesophageal bleeding, encephalopathy or pulmonary infection, whereas one patient underwent an orthotopic liver transplantation when her serum creatinine attained a level of 13 mg/l. In the first patient, hepatorenal syndrome recurred 10 days after stopping the misoprostol treatment. High doses of misoprostol in the presence of adequate volume expansion thus seem to produce marked diuresis and creatininuria as well as mild natriuresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased bioavailability of enzymes of eicosanoid synthesis in hepatic and extrahepatic tissues after portacaval shunting

Metabolites of arachidonic acid have been attributed to severe circulatory, metabolic and hormonal alterations in patients with chronic liver disease. In order to study changes of the tissue-specific availability of enzymes of eicosanoid synthesis, we used portacaval-shunted rats, as this model exhibits many clinical and biochemical similarities to patients suffering from cirrhosis of the liver. Microsomal mass and maximal velocity of prostaglandin H synthase, the initial enzyme of prostaglandin synthesis, were markedly and permanently increased after shunting in both hepatic and extrahepatic tissues as compared to those of sham-operated rats. Maximal velocity of thromboxane synthase and prostacyclin synthase, two more peripheral enzymes of the arachidonic acid cascade, were tissue-specifically enhanced, whereas the apparent affinities (Km) remained unchanged. Determination of 5-lipoxygenase activity in tissue preparations disclosed a preferential increase in the liver, lung and renal cortex after portacaval shunting. Furthermore, exposure to endotoxin closely mimicked the shunting-induced changes. These results suggest that after portacaval shunting and possibly in patients with advanced liver disease, profound abnormalities at the level of local enzyme expression might play a pathophysiologically important role in the control of eicosanoid synthesis.