Intrahepatic modulation of portal pressure and its role in portal hypertension. Role of nitric oxide

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Overexpression of beta-catenin is responsible for the development of portal hypertension during liver cirrhosis

beta-catenin functions as both a structural protein and a transcriptional activator. In this study, we examined the expression of beta-catenin in human cirrhotic livers, and administered adenoviruses carrying the beta-catenin or DeltaTCF4 genes to cirrhotic rats to investigate the role of beta-catenin in the development of liver cirrhosis development. beta-catenin expression was associated with liver cirrhosis development in cirrhotic human and rat liver. beta-catenin adenovirus was capable of accelerating cirrhosis progress but this progression was unaffected by administration of DeltaTCF4 adenovirus. beta-catenin was mainly located in the intercellular regions between liver cells and was highly concentrated in the hepatic sinusoid wall, where alpha-smooth muscle actin (SMA) was also mainly distributed. The binding of beta-catenin to alpha-SMA was also increased in cirrhotic liver. Portal vein blood pressure was significantly increased in the group administered beta-catenin adenovirus, but not in that receiving DeltaTCF4 adenovirus. These results suggest that high concentrations of beta-catenin at the hepatic intercellular membrane and the hepatic sinusoid wall contribute to hepatic hyperpiesia in liver cirrhosis patients. beta-catenin functions as a structural molecule, but not as a signaling molecule, during liver cirrhosis development.

Pathophysiologic basis for the medical management of portal hypertension

BACKGROUND

Portal hypertension is a potentially life-threatening complication of cirrhosis, resulting from increased intrahepatic resistance and portal inflow.

OBJECTIVE

Given the complex nature of this disorder, a more complete understanding of the pathophysiology of portal hypertension is necessary to develop new therapies that target specific pathways that regulate portal pressure.

METHODS

This review is based on a literature search of published articles and abstracts on the pathophysiology of portal hypertension, its complications and its treatment.

RESULTS/CONCLUSION

A number of therapies have been developed or are under investigation for the treatment of portal hypertension and its complications. These agents may reduce mortality and improve quality of life for patients with advanced liver disease.

Treatment of bile duct-ligated rats with the nitric oxide synthase transcription enhancer AVE 9488 ameliorates portal hypertension

AIM

Nitric oxide levels are decreased in the cirrhotic liver and increased in the systemic vasculature. We investigated whether the nitric oxide synthase (NOS) transcription enhancer AVE 9488 ameliorates portal hypertension in cirrhotic rats.

METHODS

Rats with secondary biliary cirrhosis [bile duct ligation (BDL)] were treated with AVE 9488. BDL animals without treatment served as controls. Blood flow was determined with the microsphere technique. Intrahepatic resistance was measured by in situ perfusion. NOS-3 mRNA and protein levels in the liver, aorta and superior mesenteric artery (SMA) were measured.

RESULTS

Arterial pressure did not differ between treated and non-treated animals. Portal pressure, hepatic portal-vascular resistance and perfusion pressure of the in situ perfused liver were lower in the AVE 9488-treated animals. Arterial splanchnic resistance, portal venous inflow and shunt volume were increased by AVE 9488. N (G)-nitro-l-arginine methyl ester abolished the effect of AVE 9488. AVE 9488-treated rats had higher liver NOS-3 mRNA and protein levels, whereas NOS-3 mRNA and protein in the aorta and the SMA did not vary between groups. Phosphorylation of liver vasodilator-stimulated phosphoprotein (VASP) and NOS-3 as well as hepatic nitrite/nitrate was increased by AVE 9488.

CONCLUSIONS

Treatment of BDL rats with the NOS transcription enhancer AVE 9488 induces an increase in NOS-3 mRNA and protein in the liver. This is associated with an amelioration of portal hypertension.

Hemodynamics in the isolated cirrhotic liver

Increased intrahepatic resistance is the initial event to the increased portal pressure and development portal hypertension in cirrhosis. Narrowing of the sinusoids due to anatomic changes is the main component of the increased intrahepatic resistance. However, a dynamic component is also involved in the increased vascular tone in cirrhosis. The imbalance between the hyperresponsiveness and overproduction of vasoconstrictors (mainly endothelin-1 and cyclooxygenase-derived prostaglandins) and the hyporesponsiveness and impaired production of vasodilators [mainly nitric oxide (NO)] are the mechanisms responsible of the increased vascular tone in the sinusoidal/postsinusoidal area. In contrast, the vascular resistance in the hepatic artery, which is determined in the presinusoidal area, is decreased due to increased vasodilators (NO and adenosine). This suggests different availabilities of NO in the intrahepatic circulation with preserved production in the presinusoidal area and impaired production in the sinusoidal/postsinusoidal area.

Effects of primary metronidazole and clarithromycin resistance to Helicobacter pylori on omeprazole, metronidazole, and clarithromycin triple-therapy regimen in a region with high rates of metronidazole resistance

The aim of this study was to investigate the effect of metronidazole resistance (MtzR) and clarithromycin resistance (ClaR) on the eradication rate for omeprazole, clarithromycin, and metronidazole triple-therapy regimen and on the development of posttherapy drug resistance in a region of high rates of MtzR. One hundred ninety-six Helicobacter pylori isolates were recovered from patients with duodenal ulcer, gastric ulcer, or nonulcer dyspepsia during upper endoscopy. The prevalences of MtzR, ClaR, and dual resistance were 37.8%, 13.8%, and 8.7%, respectively. The intention-to-treat eradication rates for metronidazole-susceptible (87.2% vs. 67.6%; P=.001) and clarithromycin-susceptible (86.4% vs. 40.7%; P<.001) strains were significantly higher than the rates for resistant strains. Multiple logistic regression analysis implicated younger age (<40 years old), MtzR, ClaR, and the diagnosis of nonulcer dyspepsia as independent factors that predicted treatment failure. The rates of posttreatment MtzR, ClaR, and dual resistance were 88%, 88%, and 75%, respectively. MtxR and ClaR significantly affected the success of eradication therapy. Posttreatment rates of resistance were high and were related to the presence of pretreatment antibiotic resistance.

Nitric oxide-releasing drugs

Pharmacological compounds that release nitric oxide (NO) have been useful tools for evaluating the broad role of NO in physiology and therapeutics. NO deficiency has been implicated in the genesis and evolution of several disease states. Both medical needs and commercial opportunities have fostered attempts to modulate NO in the human body for therapeutic gain. Strategies for NO modulation encompass antiinflammatory, sexual dysfunction, and cardiovascular indications. Apart from newly developed drugs, several commonly used cardiovascular drugs exert their beneficial action, at least in part, by modulating the NO pathway. This review discusses the fundamental pharmacological properties and mechanisms of action of NO-releasing drugs. Some of these compounds may enter in the clinical arena providing important therapeutic benefits in human diseases.

Nitric oxide donors and cardiovascular agents modulating the bioactivity of nitric oxide: an overview

Nitric oxide (NO) mediates multiple physiological and pathophysiological processes in the cardiovascular system. Pharmacological compounds that release NO have been useful tools for evaluating the pivotal role of NO in cardiovascular physiology and therapeutics. These agents constitute two broad classes of compounds, those that release NO or one of its redox congeners spontaneously and those that require enzymatic metabolism to generate NO. In addition, several commonly used cardiovascular drugs exert their beneficial action, in part, by modulating the NO pathway. Here, we review these classes of agents, summarizing their fundamental chemistry and pharmacology, and provide an overview of their cardiovascular mechanisms of action.

Helicobacter pylori eradication therapy is more effective in peptic ulcer than in non-ulcer dyspepsia

AIM

To evaluate whether eradication therapy is more effective in peptic ulcer disease (PUD) than in non-ulcer dyspepsia (NUD).

METHODS

We retrospectively studied 481 patients with NUD (183 patients) or PUD (298 patients) infected with Helicobacter pylori included in several prospective clinical trials. Three eradication regimens were given: (1) proton pump inhibitor (PPI) plus clarithromycin, plus either amoxycillin or metronidazole for 7 days (297 patients); (2) ranitidine bismuth citrate (RBC) plus clarithromycin plus amoxycillin for 7 days (79 patients); and (3) RBC plus clarithromycin plus amoxycillin plus metronidazole for 5 days (105 patients). H. pylori eradication was defined as a negative 13C-urea breath test 4 weeks after completing treatment.

RESULTS

H. pylori eradication rates were 82% (95% CI 78-87%) with PPI plus two antibiotics for 7 days, 85% (95% CI 75-91%) with RBC plus two antibiotics for 7 days, and 91% (95% CI 86-97%) with RBC plus three antibiotics for 5 days (P < 0.05 compared with the first regimen). Overall, the H. pylori eradication rate in patients with NUD was 78% (95% CI 71-84%), while in patients with PUD it was 89% (95% CI 86-93%) (P < 0.001). Both the combination of PPI plus two antibiotics for 7 days and the combination of RBC plus three antibiotics for 5 days were more effective in PUD than in NUD patients. However, RBC plus clarithromycin plus amoxycillin for 7 days was equally effective in both diseases. RBC plus two antibiotics for 7 days achieved better results than the same therapy with PPI only in NUD patients (84% v. 59%, P < 0.01), but both regimens were similar when prescribed in PUD patients (86% v. 88%). In the multivariate analysis, the type of therapy, the diagnosis (NUD v. PUD), and the product variable of therapy (with RBC plus 2 antibiotics for 7 days) and diagnosis (interaction variable) were the only variables that influenced H. pylori eradication. The odds ratio (OR) for the effect of RBC versus PPI plus two antibiotics for 7 days in patients with NUD was 4 (95% CI 1.7-9.7; P < 0.01), whereas in patients with PUD no statistical significance was achieved (OR 0.79; 95% CI 0.2-3.9).

CONCLUSION

Overall, H. pylori eradication therapy is more effective in PUD than in NUD patients. This advantage of eradication therapies in PUD patients seems to be observed with 7-day PPI-based triple regimens, and with 5-day RBC-based quadruple therapy, while the 7-day RBC-based triple regimen seems to be equally effective in both diseases.

Regional and systemic hemodynamic disturbances in cirrhosis

In cirrhosis of the liver there is an imbalance between factors mediating vasodilatation such as nitric oxide and factors mediating vasoconstriction such as endothelins. These imbalances result in portal hypertension, hepatorenal syndrome, portopulmonary hypertension, hepatopulmonary syndrome, as well as alterations in cerebral blood flow.

High efficacy of ranitidine bismuth citrate, amoxicillin, clarithromycin and metronidazole twice daily for only five days in Helicobacter pylori Eradication

AIM

The combination of a proton pump inhibitor (PPI) or ranitidine-bismuth-citrate (Rbc) and two antibiotics for 7-10 days are, at present, the preferred treatments in Helicobacter pylori eradication. However, therapies for fewer than 7 days have been scarcely evaluated and it is unknown whether the length of treatment can be shortened, without a lost of efficacy, if three instead of two antibiotics are used. The aim of our study was to evaluate the efficacy of Rbc plus three antibiotics for only 5 days in H. pylori eradication.

METHODS

We prospectively studied 80 patients (34% duodenal ulcer, 66% functional dyspepsia) infected by H. pylori. At endoscopy, biopsies were obtained for histological study and rapid urease test, and a 13C-urea breath test was carried out. Urea breath test was repeated 4 weeks after completing eradication treatment with Rbc [400 mg twice a day (bid)], amoxicillin (1 g bid), clarithromycin (500 mg bid) and metronidazole (500 mg bid). All drugs were administered together after breakfast and dinner for 5 days only, and no treatment was administered thereafter. Compliance with therapy was determined from the interrogatory and the recovery of empty envelopes of medications.

RESULTS

In 79 out of the 80 patients, H. pylori eradication success or failure was assessed after therapy (one patient was lost from follow-up). All but one of these 79 patients took all the medications (one patient stopped treatment on the day 3 due to nausea/vomiting). Per protocol eradication was achieved in 72/78 (92%; 95% CI, 84-96%) and in 72/80 (90%; 81-95%) by intention-to-treat. Therapy was more effective in patients with duodenal ulcer than in those with functional dyspepsia [100% (87-100%) vs. 85% (73-92%) by intention-to-treat; p <.05]. Adverse effects were described in ten patients (12%), and included the perception of a metallic taste (eight patients), nausea/vomiting (two patients, one of them abandoned the treatment due to this), and diarrhea (two patients).

CONCLUSION

The combination of Rbc, amoxicillin, clarithromycin and metronidazole for only 5 days represents a promising therapy for H. pylori infection, due to its high efficacy, simple posology, low cost and excellent tolerance.

Strategy for retreatment of therapeutic failure of eradication of Helicobacter pylori infection

BACKGROUND AND AIM

A proton pump inhibitor (PPI)-based triple therapy consisting of a PPI, amoxicillin (A) and clarithromycin (C) or metronidazole (M) provides an eradication rate ranging from 80 to 90%. However, there have been few controlled studies with regard to the most effective regimen to re-treat patients after failure of the first-line therapy. Accordingly, we retrospectively reviewed our experiences and compared regimens with different combinations of antimicrobials to determine the optimal retreatment regimen.

METHODS

Out of 133 patients who had received second-line therapy after failure of first-line PPI/AC therapy, we selected, for review, patients who took the prescribed drugs for first-line therapy equal to, or more than 80%. As a result, data on 114 patients (83 males and 31 females; mean age 49.1 +/- 13.0 years; peptic ulcer n = 89; non-ulcer dyspepsia, n = 25) were eligible for evaluation. They had either repeated the PPI/AC regimen (n = 34; 5-14 days), or had been administered the PPI/AM regimen (n = 80; 10 days). The cure rates of the two regimens were compared.

RESULTS

The eradication rates for second-line therapy with the PPI/AC regimen versus the PPI/AM regimen were 52.9% (95% CI, 35-70) versus 81.3% (95% CI, 71-89) by intention-to-treat analysis (P < 0.01), and 62.1% (95% CI, 42-79) versus 91.4% (95% CI, 81-97) by per-protocol analysis (P < 0.01).

CONCLUSION

The eradication rate for the PPI/AM retreatment regimen was significantly higher than for the repeated PPI/AC regimen, suggesting that a 10-day PPI/AM regimen can be recommended as a retreatment regimen for patients who had first-line eradication therapy by PPI/AC regimens.

Retreatment of Helicobacter pylori infection after initial treatment failure

OBJECTIVES

Helicobacter pylori treatment regimens fail to cure the infection in at least 10-20% of patients undergoing initial treatment. Retreatment strategies for patients who have failed initial treatment for H. pylori infection remain poorly described.

METHODS

The literature describing the frequency of H. pylori treatment failure and factors leading to failure is reviewed. The role of antibiotic resistance is discussed and clinical studies assessing success rates according to antibiotic resistance are described. Clinical trials evaluating the treatment success rates for a second episode of treatment are discussed.

RESULTS

The literature describing retreatment of failed H. pylori infection remains limited. The existing data support the use of bismuth-based quadruple therapy or ranitidine bismuth citrate (RBC)-based triple therapy as the preferred agents after initial treatment failure.

CONCLUSION

Further studies are needed to better define the optimal second treatment regimen after failed H. pylori treatment.

The pharmacological basis of contemporary pain management

Pain management has become an increasingly well researched area in medicine over recent years, and there have been advances in a number of areas. While opioids remain an integral part of pain-management strategies, there is now an emphasis on the use of adjuvant drugs, such as paracetamol and anti-inflammatory agents, which through physiological or pharmacological synergism, both enhance pain control and reduce opioid use. The management of neuropathic pain continues to be a challenge. Anti-epileptics and antidepressants, together with clonidine and ketamine, provide the foundations for treatment. Another area of interest has been the widespread use of patient-controlled analgesia and the administration of some drugs, especially opioids, by means other than traditional oral and parenteral routes. The number of new drugs that have reached the stage of clinical trials has been small, yet they offer exciting possibilities. The epibatidine analogue ABT-594 and zinconitide both offer novel approaches to the management of neuropathic pain states, while selective cyclo-oxygenase-2 inhibitors and nitroaspirins may see advances in the management of nociceptive pain states.

Helicobacter pylori

Helicobacter pylori infection is a major cause of peptic ulcer disease, and its detection and eradication are now an important part of gastroenterology. Effective regimes are available which will eliminate the organism in about 90% of cases in developed countries.

Treatment of Helicobacter pylori infection

Combination antimicrobial therapies for the effective eradication of Helicobacter pylori infection have been identified and are commercially available. Ongoing studies to improve eradication rates are based on modification of currently approved treatments. Management of H. pylori infection now focuses on which patients should be treated and, by extension, which should be tested, because all patients should have a positive test result for H. pylori before starting antimicrobial therapy. Peptic ulcer disease was believed to be caused by acid abnormalities until about two decades ago, when H. pylori was successfully cultured; the clinical records of an early proponent of an infectious cause of peptic ulcer disease were recently discovered. The role of H. pylori infection in gastroesophageal disease and in ulcer disease associated with nonsteroidal anti-inflammatory drugs have become intensely investigated topics. Consensus conferences among pediatric physicians are establishing practice guidelines for H. pylori management in children and adolescents.

Liver fibrogenesis and the role of hepatic stellate cells: new insights and prospects for therapy

Hepatic fibrosis is a wound-healing response to chronic liver injury, which if persistent leads to cirrhosis and liver failure. Exciting progress has been made in understanding the mechanisms of hepatic fibrosis. Major advances include: (i) characterization of the components of extracellular matrix (ECM) in normal and fibrotic liver; (ii) identification of hepatic stellate cells as the primary source of ECM in liver fibrosis; (iii) elucidation of key cytokines, their cellular sources, modes of regulation, and signalling pathways involved in liver fibrogenesis; (iv) characterization of key matrix proteases and their inhibitors; (v) identification of apoptotic mediators in stellate cells and exploration of their roles during the resolution of liver injury. These advances have helped delineate a more comprehensive picture of liver fibrosis in which the central event is the activation of stellate cells, a transformation from quiescent vitamin A-rich cells to proliferative, fibrogenic and contractile myofibroblasts. The progress in understanding fibrogenic mechanisms brings the development of effective therapies closer to reality. In the future, targeting of stellate cells and fibrogenic mediators will be a mainstay of antifibrotic therapy. Points of therapeutic intervention may include: (i) removing the injurious stimuli; (ii) suppressing hepatic inflammation; (iii) down-regulating stellate cell activation; and (iv) promoting matrix degradation. The future prospects for effective antifibrotic treatment are more promising than ever for the millions of patients with chronic liver disease worldwide.