Effects of molsidomine, a long acting venous dilator, on portal hypertension. A hemodynamic study in patients with cirrhosis

Atorvastatin lowers portal pressure in cirrhotic rats by inhibition of RhoA/Rho-kinase and activation of endothelial nitric oxide synthase

In cirrhosis, increased RhoA/Rho-kinase signaling and decreased nitric oxide (NO) availability contribute to increased intrahepatic resistance and portal hypertension. Hepatic stellate cells (HSCs) regulate intrahepatic resistance. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) inhibit synthesis of isoprenoids, which are necessary for membrane translocation and activation of small GTPases like RhoA and Ras. Activated RhoA leads to Rho-kinase activation and NO synthase inhibition. We therefore investigated the effects of atorvastatin in cirrhotic rats and isolated HSCs. Rats with secondary biliary cirrhosis (bile duct ligation, BDL) were treated with atorvastatin (15 mg/kg per day for 7 days) or remained untreated. Hemodynamic parameters were determined in vivo (colored microspheres). Intrahepatic resistance was investigated in in situ perfused livers. Expression and phosphorylation of proteins were analyzed by RT-PCR and immunoblots. Three-dimensional stress-relaxed collagen lattice contractions of HSCs were performed after incubation with atorvastatin. Atorvastatin reduced portal pressure without affecting mean arterial pressure in vivo. This was associated with a reduction in intrahepatic resistance and reduced responsiveness of in situ-perfused cirrhotic livers to methoxamine. Furthermore, atorvastatin reduced the contraction of activated HSCs in a 3-dimensional stress-relaxed collagen lattice. In cirrhotic livers, atorvastatin significantly decreased Rho-kinase activity (moesin phosphorylation) without affecting expression of RhoA, Rho-kinase and Ras. In activated HSCs, atorvastatin inhibited the membrane association of RhoA and Ras. Furthermore, in BDL rats, atorvastatin significantly increased hepatic endothelial nitric oxide synthase (eNOS) mRNA and protein levels, phospho-eNOS, nitrite/nitrate, and the activity of the NO effector protein kinase G (PKG).

CONCLUSION

In cirrhotic rats, atorvastatin inhibits hepatic RhoA/Rho-kinase signaling and activates the NO/PKG-pathway. This lowers intrahepatic resistance, resulting in decreased portal pressure. Statins might represent a therapeutic option for portal hypertension in cirrhosis.

Aortic hyporeactivity to norepinephrine induced by lipopolysaccharide in cirrhotic rats: beneficial effects of a non-steroidal anti-inflammatory drug coupled with a nitric oxide donor

BACKGROUND AND AIMS

Cirrhosis is associated with a hyperdynamic syndrome and arterial vasodilation that is related to nitric oxide (NO) synthase 3 overactivity. Septic shock is frequently associated with cirrhosis and with a vascular induction of NO synthase 2. The aims of this study were to compare the effects of lipopolysaccharide (LPS) in normal and cirrhotic rats, and to test the effects of a nonsteroidal anti-inflammatory drug (NSAID) coupled with a (NO) donor.

METHODS

Cirrhotic rats received NO-flurbiprofen, flurbiprofen or vehicle followed by LPS or placebo 15 min later. The heart rate and mean arterial pressure of rats were monitered for 5 h. Thoracic aortic rings were removed and contracted with the use of norepinephrine. Nitric oxide synthase activity was measured in the aorta and stomach of cirrhotic rats.

RESULTS

Arterial pressure decreased in cirrhotic rats in the vehicle/LPS and flurbiprofen/LPS groups. After LPS administration, the heart rate of rats increased in all groups. In the aortic rings, LPS induced hyporeactivity to norepinephrine in all groups except the NO-flurbiprofen group. This hyporeactivity was abolished after preincubation with Nw-nitro-L-arginine (L-NNA). Nw-nitro-L-arginine had no effect on norepinephrine-induced vasoconstriction in the NO-flurbiprofen/LPS group. Nitric oxide synthase 2 activity in the stomach and aorta of cirrhotic rats was increased in each group except in the NO-flurbiprofen group after LPS administration. Pretreatment with NO NSAID prevented aortic hyporeactivity to norepinephrine in cirrhotic rats treated with LPS as it probably inhibited the NO synthase 2 induction.

CONCLUSIONS

These findings suggest that NO-flurbiprofen has a beneficial hemodynamic effect in cirrhotic rats and may help to prevent LPS aortic hyporeactivity.

Intraportal administration of glyceryl trinitrate or nitroprusside exerts more systemic than intrahepatic effects in anaesthetised cirrhotic rats

BACKGROUND/AIMS

Increased intrahepatic vascular tone can be pharmacologically manipulated in isolated cirrhotic livers. Intrahepatic endothelial dysfunction may lead to a decreased production of the potent endogenous vasodilator nitric oxide in cirrhotic livers. The aims of the study were to determine whether portal pressure can be lowered in vivo by injecting nitric oxide donors glyceryl trinitrate or nitroprusside directly in the portal vein and whether this is related to a decrease in intrahepatic resistance.

METHODS

In anaesthetised CCl4 cirrhotic rats, intraportal doses of glyceryl trinitrate 0.5, 1 or 5 microg/kg/ min or nitroprusside 1, 5 or 10 microg/kg/min did not decrease portal pressure but only arterial pressure. Systemic and splanchnic haemodynamics were measured before and during 15 min intraportal infusion of glyceryl trinitrate 10 microg/kg/min or nitroprusside 20 microg/kg/min.

RESULTS

Glyceryl trinitrate decreased portal pressure from 14.0+/-1.1 to 11.8+/-1.4 mm Hg, splanchnic perfusion pressure from 102+/-10 to 74+/-5 mm Hg and portal sinusoidal flow from 2.11+/-0.38 to 1.70+/-0.35 ml/min/g liver (all p<0.05). Nitroprusside did not decrease portal pressure significantly but led to a reduction of the splanchnic perfusion pressure (104+/-9 to 66+/-7 mm Hg) and the portal sinusoidal flow (2.39+/-0.50 to 1.77+/-0.31 ml/min/g liver; all p<0.05). Portal sinusoidal resistance was not altered by either drug.

CONCLUSIONS

Intraportal infusion of nitric oxide donors decreased arterial pressure more than portal pressure. Portal sinusoidal resistance remained unaffected, but the liver parenchyma became less perfused with high doses. The systemic effects of nitric oxide donating drugs prevailed.

Haemodynamic effects of combined treatment with molsidomine and propranolol on portal hypertension in conscious and unrestrained cirrhotic rats

We investigated the systemic and splanchnic haemodynamic effects of combined treatment with molsidomine and propranolol on cirrhotic rats. Liver cirrhosis was produced by repeated intraperitoneal injections of thioacetamide. The blood flow of each organ was measured serially using the radioactive microsphere method in the awake state before and after the administration of each agent. Cirrhotic rats received molsidomine (0-.5 mg/kg), propranolol (0.1 or 0.2 mg/min), both agents or placebo. Combination treatment with molsidomine and 0.1 mg/min propranolol significantly reduced portal pressure compared with molsidomine or propranolol alone (21 +/- 4 vs 15 +/- 3 or 11 +/- 2% P < 0.05). Systemic haemodynamic changes with this combined treatment were mild. This combined treatment slightly inhibited the molsidomine-induced decrease in portal vascular resistance (27 +/- 9 vs 31 +/- 6; NS) and markedly inhibited the molsidomine-induced decrease in splanchnic arterial resistance (7 +/- 6 vs 27 +/- 5% P < 0.05). Compared with low-dose propranolol administration, the combined treatment was associated with a significant decrease in portal vascular resistance (27 +/- 9% decrease vs 2 +/- 2% increase; P < 0.001) and a significant decrease in splanchnic arterial resistance (7 +/- 6% decrease vs 5 +/- 4% increase P < 0.05). The combination of molsidomine and high-dose propranolol (0.2 mg/min) caused a marked reduction in portal venous inflow, mean arterial pressure and cardiac index. We conclude that propranolol enhances the molsidomine-induced decrease in portal pressure by splanchnic vasoconstriction in association with a slight decrease in portal vascular resistance. The combination therapy with molsidomine and low-dose propranolol combination had more beneficial and less harmful effects on systemic and splanchnic haemodynamics and thus appears to be a superior method for treating portal hypertension.

Propranolol plus molsidomine vs propranolol alone in the treatment of portal hypertension in patients with cirrhosis

BACKGROUND/AIMS

Effective protection from the risk of variceal bleeding is achieved when the hepatic venous pressure gradient is reduced to 12 mmHg or at least by 20% of baseline values. Such a marked decrease is rarely achieved with propranolol, and new agents or combinations of them are now being explored. The present randomized study investigated whether chronic treatment with the combination of propranolol plus molsidomine, a preferential venous dialator that reduces hepatic venous pressure gradient and does not cause pharmacological tolerance, achieves greater reduction in hepatic venous pressure gradient than propranolol alone.

METHODS

A hemodynamic study was performed in 34 patients with cirrhosis with portal hypertension in baseline conditions and after 3 months of chronic oral treatment with propranolol alone (n = 19) or propranolol plus molsidomine (n = 15).

RESULTS

Propranolol produced a significant reduction in hepatic venous pressure gradient (-16%, p < 0.01). Propranolol plus molsidomine also caused a slight but significant decrease in hepatic venous pressure gradient (-9%, p < 0.05). Hepatic blood flow and the hepatic and intrinsic clearance of indocyanine green were significantly reduced by propranolol. The combined administration of propranolol+molsidomine significantly reduced hepatic blood flow but not hepatic and intrinsic clearance of indocyanine green. Both treatment groups produced similar reduction in azygos blood flow, heart rate and cardiac output. However, contrary to propranolol alone, propranolol plus molsidomine did not increase cardiopulmonary pressures.

CONCLUSIONS

The current study shows that although the combined administration of propranolol plus molsidomine prevents some of the adverse effects of propranolol on liver function and cardiopulmonary pressures, it does not achieve a greater reduction in hepatic venous pressure gradient than propranolol alone and therefore, does not support the use of this combined therapy for the pharmacological treatment of portal hypertension.

Pharmacological treatment of portal hypertension: hemodynamic effects and prevention of bleeding

In the past 10 years, it has been clearly shown that vasoactive substances reduce portal pressure in patients or animals with portal hypertension. Some of these substances act by inducing splanchnic vasoconstriction, while others reduce hepatic and porto-systemic collateral vascular resistance and, thus, induce a portal hypotensive effect. Still others induce arterial hypotension, which causes a vasoconstrictive effect in the splanchnic territory. Since these drugs act on different vascular receptors, their combination should have a more marked effect on portal hypertension. Up to now, only nonselective beta-blockers have been used in the prevention of first gastrointestinal bleeding in patients with portal hypertension and esophageal varices and in the prevention of recurrent gastrointestinal bleeding. These trials have shown that propranolol or nadolol significantly reduce either a first episode of bleeding or recurrent bleeding. This pharmacological treatment also improves the survival rate in these patients. All of these studies have helped us to understand, in part, why gastrointestinal hemorrhage occurs in certain patients. Additional studies of beta-blockers or other substances are, nevertheless, necessary to select patients who will respond to this type of treatment. Finally, it is possible that the pharmacological treatment of portal hypertension may also be used before esophageal varices occur.

New approaches in the pharmacologic treatment of portal hypertension

To alleviate the risk of variceal bleeding, the portal pressure gradient--usually evaluated as the hepatic venous pressure gradient (HVPG)--must be reduced to < or = 12 mmHg. Although beta-blocking agents are accepted therapy for preventing first or subsequent bleeding episodes, propranolol therapy decreases final HVPG to < or = 12 mmHg in only 12% of patients, while only 24% of patients have a > or = 20% reduction in HVPG and nearly 40% show no reduction in HVPG. This has stimulated research on alternative or additional treatments. Nitrates such as isosorbide dinitrate reduce portal pressure by decreasing resistance to portal and collateral blood flow and by promoting reflex splanchnic vasoconstriction. However, while nitrates are effective in the acute situation, tolerance leading to refractoriness develops over the long term unless they are combined with diuretics or other agents in the treatment of portal hypertension. Propranolol and isosorbide-5-mononitrate combined cause a substantially greater reduction in HVPG than monotherapy with either drug in both acute and long-term use. Presumably concomitant isosorbide-5-mononitrate administration opposes the increase in portal resistance induced by propranolol. Spironolactone, which has been shown to lower HVPG in patients with cirrhosis, produces a reduction in plasma volume that attenuates the increased cardiac output associated with cirrhosis and triggers vasoactive mechanisms that decrease splanchnic blood flow. Potentially, spironolactone may maintain and enhance the decrease in portal pressure achieved by nitrates or propranolol. Triple therapy with a beta-blocker, a nitrate and spironolactone may be feasible.(ABSTRACT TRUNCATED AT 250 WORDS)