Plasma leucine enkephalin is increased in liver disease

Evaluation of the Use of Naltrexone for Cholestatic Pruritus

OBJECTIVE

Pruritus is a common symptom of liver disease, managed with various medications including opioid antagonists like naltrexone. Current literature surrounding the safety and efficacy of naltrexone for cholestatic pruritus is limited. Our objective was to describe naltrexone prescribing practices for cholestatic pruritus.

METHODS

We conducted a single-center, retrospective review of inpatients who received naltrexone for cholestatic pruritus. We gathered information on naltrexone dosing, frequency, dose adjustments, duration, elevations in liver function tests (LFTs), and use of additional antipruritic agents.

RESULTS

Thirty-nine patients and 122 dosing regimens were included for analysis. Most patients were male (56.4%) with a median age of 6.32 years (range, 0.63-18.89). The median weight-based doses of naltrexone were 1.45 mg/kg/dose (IQR, 0.84-2.81) and 1.86 mg/kg/day (IQR, 0.97-3.37). The median flat doses were 25 mg/dose (IQR, 12.25-50) and 50 mg/day (IQR, 25-50). The median number of additional antipruritic agents used before and after naltrexone initiation was 3 (IQR, 2-4) and 4 (IQR, 3-5), respectively (p < 0.001). The most common elevated LFTs were total bilirubin and alanine aminotransferase (ALT), occurring in 15% of patients.

CONCLUSIONS

Naltrexone dosing ranged between 1 and 2 mg/kg/dose once or twice daily, with larger weight-based doses prescribed in younger and lower-weight patients. Naltrexone was commonly added as a fourth-line agent and did not lead to discontinuation of other antipruritic therapies. Larger, prospective, controlled studies are needed to assess the safety and efficacy of naltrexone for cholestatic pruritus.

Endogenous Opioid Levels Do Not Correlate With Itch Intensity and Therapeutic Interventions in Hepatic Pruritus

Background: Chronic pruritus affects up to 70% of patients with immune-mediated hepatobiliary disorders. Antagonists of the μ-opioid receptor (MOR) and agonists of the κ-opioid receptor (KOR) are used to treat hepatic itch, albeit with limited success. An imbalance between ligands of MOR and KOR receptors has recently been suggested as a potential mechanism of hepatic pruritus. In this study, we therefore investigated systemic levels of important endogenous opioids such as β-endorphin, dynorphin A, Leu- and Met-enkephalin in plasma of a large cohort of well-characterized patients with immune-mediated cholestatic disorders, including patients with liver cirrhosis, and during effective anti-pruritic therapy.

Methods: Plasma samples and clinical data were prospectively collected from well-characterized patients with primary/secondary sclerosing cholangitis (PSC/SSC), primary biliary cholangitis (PBC) and overlap syndromes suffering from pruritus (n = 29) and age-, gender- and disease-matched controls without pruritus (n = 27) as well as healthy controls (n = 20). General laboratory testing for hepatobiliary and renal function was performed. Levels of β-endorphin, dynorphin A, Leu- and Met-enkephalin were quantified in plasma by ELISA. Intensity of pruritus over the last week was evaluated using a visual analog scale (VAS, 0–10).

Results: PBC and PSC patients with or without pruritus did neither differ in disease entity, disease stage, nor in the presence of cirrhosis. While both dynorphin A and β-endorphin concentrations were lower in pruritic patients compared to those without pruritus and healthy controls, the MOR/KOR ligand ratio was unaltered. No significant differences were observed for Leu- and Met-enkephalin concentrations. Opioid levels correlated with neither itch intensity nor stage of disease. Cirrhotic patients displayed higher concentrations of MOR agonist Leu-enkephalin and KOR agonist dynorphin A. Endogenous opioid levels remained largely unchanged after successful treatment with the potent anti-pruritic drugs rifampicin and bezafibrate.

Conclusions: Endogenous opioid levels and the MOR/KOR ligand ratio neither correlate with itch intensity nor differentiate pruritic from non-pruritic patients with immune-mediated liver diseases. Thus, endogenous opioids may modulate signaling pathways involved in hepatic pruritus, but are unlikely to represent the major pruritogens in liver disease.

Cholestatic pruritus: Emerging mechanisms and therapeutics

Patients suffering from cholestasis often report experiencing a debilitating, unrelenting itch. In contrast to conditions, such as urticaria, in which histamine primarily drives itch (pruritus), cholestatic pruritus is multifactorial and more difficult to treat. Existing therapies are not always effective and have undesirable adverse effect profiles. Here, we conducted a systematic literature review to evaluate conventional treatment strategy, current pathophysiologic understanding, and the role of new therapies in the context of cholestatic pruritus. We discuss novel findings implicating bile acids, lysophosphatidic acid, and bilirubin as potential important mediators of cholestatic itch. New therapies that aim to remove or modulate pruritogens have been supported in observational cohort studies and randomized controlled trials. Although these new therapies show promise, further research is needed to confirm the pathophysiology of cholestatic pruritus so that targeted therapy can be developed.

Identification of a bilirubin receptor that may mediate a component of cholestatic itch

Various pathologic conditions result in jaundice, a yellowing of the skin due to a buildup of bilirubin. Patients with jaundice commonly report experiencing an intense non-histaminergic itch. Despite this association, the pruritogenic capacity of bilirubin itself has not been described, and no bilirubin receptor has been identified. Here, we demonstrate that pathophysiologic levels of bilirubin excite peripheral itch sensory neurons and elicit pruritus through MRGPRs, a family of G-protein coupled receptors expressed in primary sensory neurons. Bilirubin binds and activates two MRGPRs, mouse MRGPRA1 and human MRGPRX4. In two mouse models of pathologic hyperbilirubinemia, we show that genetic deletion of either Mrgpra1 or Blvra, the gene that encodes the bilirubin-producing enzyme biliverdin reductase, attenuates itch. Similarly, plasma isolated from hyperbilirubinemic patients evoked itch in wild-type animals but not Mrgpra1^-/- animals. Removing bilirubin decreased the pruritogenic capacity of patient plasma. Based on these data, targeting MRGPRs is a promising strategy for alleviating jaundice-associated itch.

Jaundice causes the skin to yellow as a result of a build-up of a pigment called bilirubin. Normally, bilirubin is made in the liver and removed from the body in digestive fluid called bile, but people with liver or gallbladder problems may end up with too much bilirubin that accumulates in their blood and skin. One side effect of jaundice is intense and uncontrollable itching. Researchers are not sure what causes this itching, and there are few treatments that help to relieve it.

At the molecular level, itching sensations occur when compounds bind to particular receptors on the surface of nerve cells. One family of receptors that can trigger itch is called the Mas-related G-protein Coupled Receptor (MRGPR). Could one of these receptors trigger jaundice-related itching?

Now, Meixiong, Vasavda et al. show that bilirubin binds to and activates MRGPRs to cause itch in mice. Whereas injecting bilirubin into normal mice causes them to scratch, mice that have been genetically engineered to lack MRGPRs do not itch when their own bilirubin levels rise, or when they are injected with bilirubin or with plasma from patients who experience jaundice-related itching. Furthermore, removing bilirubin from the plasma of patients before it was injected into normal mice reduced the amount of itching that the mice felt.

Overall, the results reported by Meixiong, Vasavda et al. suggest that drugs that prevent bilirubin from attaching to MRGPRs might help to alleviate jaundice-related itching. However, researchers must first verify that bilirubin interacts with MRGPRs in people to cause itch. If bilirubin causes itch in people like in mice, scientists could then evaluate existing drugs or make new ones to prevent bilirubin from attaching to the MRGPRs.

Chronic Pruritus in the Geriatric Population

Chronic pruritus (>6 week's duration) in the geriatric population (≥65 years old), is an increasing health care problem. The pathophysiologic predisposing factors are abnormalities of the epidermal barrier, immune system, and nervous system. Causes can be dichotomized into histaminergic and nonhistaminergic pruritus. Topical treatments are generally safe. Systemic treatments are chosen depending on the condition, comorbid diseases, and drug interactions. Treatment options are limited. Progress has been made in identifying itch-selective mediators over the last decade. Numerous new medications are currently undergoing clinical trials and they are anticipated to enter the clinics in the near future.

Neuropeptide proenkephalin A is associated with in-hospital mortality in patients with acute intracerebral hemorrhage

High plasma proenkephalin A (PENK-A) levels are associated with poor clinical outcome after ischemic stroke. However, not much is known regarding the change of its level in acute intracerebral hemorrhage. Thus, we sought to determine PENK-A in plasma of patients with acute spontaneous basal ganglia hemorrhage and evaluate its relation with disease severity and in-hospital mortality. One hundred and two patients and 100 healthy controls were recruited. Plasma samples were obtained on admission for patients and at study entry for controls. Its concentration was measured by chemoluminescence sandwich immunoassay. Plasma PENK-A levels were substantially higher in patients than in healthy controls (235.5±85.4 pmol/L vs. 90.1±31.3 pmol/L; P<0.0001). A forward stepwise logistic regression selected plasma PENK-A as an independent predictor for in-hospital mortality of patients (odds ratio 1.080, 95% confidence interval 1.018-1.147, P<0.001). A multivariate linear regression demonstrated that plasma PENK-A level was positively associated with National Institutes of Health Stroke Scale (NIHSS) score (t=6.189, P<0.001) and hematoma volume (t=5.388, P<0.001). A receiver operating characteristic curve identified a plasma PENK-A level>267.1 pmol/L predicted in-hospital mortality of patients with 80.0% sensitivity and 74.7% specificity (area under curve, 0.836; 95% confidence interval, 0.750-0.902). Its predictive value was similar to NIHSS score's and hematoma volume's (both P>0.05). However, it did not statistically significantly improve the predictive values of NIHSS score and hematoma volume (both P>0.05). Thus, increased plasma PENK-A levels are associated with disease severity and in-hospital mortality after acute intracerebral hemorrhage.

Prognostic value of neuropeptide proenkephalin A in patients with severe traumatic brain injury

High plasma proenkephalin A levels have been associated with poor clinical outcome of aneurysmal subarachnoid hemorrhage. This prospective observatory study was designed to investigate the relationship between plasma proenkephalin A levels and 1-week mortality, 6-month mortality and 6-month unfavorable outcome (defined as Glasgow Outcome Scale score of 1-3) in patients with severe traumatic brain injury. This study recruited 128 patients and 128 sex- and age-matched healthy controls. Plasma proenkephalin A levels, as measured by chemoluminescence sandwich immunoassay, were statistically significantly higher in patients than in healthy controls (239.1±93.0 pmol/L vs.81.3±22.1 pmol/L; P<0.001) and were correlated with Glasgow Coma Scale scores (r=-0.540, P<0.001). It was identified as an independent prognostic predictor of 1-week mortality [odds ratio (OR), 1.214; 95% confidence interval (CI), 1.103-1.425; P<0.001], 6-month mortality (OR, 1.162; 95% CI, 1.101-1.372; P<0.001) and 6-month unfavorable outcome (OR, 1.116; 95% CI, 1.097-1.281; P<0.001). Moreover, it had high predictive value for 1-week mortality [area under curve (AUC), 0.852; 95% CI, 0.778-0.908], 6-month mortality (AUC, 0.841; 95% CI, 0.766-0.899) and 6-month unfavorable outcome (AUC, 0.830; 95% CI, 0.754-0.891). Furthermore, its predictive value was similar to Glasgow Coma Scale score's (all P>0.05). Yet, a combined logistic-regression model did not show that it statistically significantly improved the predictive value of Glasgow Coma Scale score (all P>0.05). Thus, it was proposed that enhanced plasma proenkephalin A could be a useful, complementary tool to predict short- or long-term clinical outcome after severe traumatic brain injury.

Circulating levels of neuropeptide proenkephalin A predict outcome in patients with aneurysmal subarachnoid hemorrhage

High plasma proenkephalin A level has been associated with ischemic stroke severity and clinical outcomes. This study aimed to assess the relationship between proenkephalin A and disease severity as well as to investigate its ability to predict long-term clinical outcome in patients with aneurysmal subarachnoid hemorrhage. Plasma proenkephalin A concentrations of one hundred and eighty patients and 180 sex- and age-matched healthy controls were measured by chemoluminescence sandwich immunoassay. Plasma proenkephalin A level was substantially higher in patients than in healthy controls (205.5±41.6 pmol/L vs. 90.8±21.1 pmol/L, P<0.001), was highly associated with World Federation of Neurological Surgeons (WFNS) score (r=0.470, P<0.001) and Fisher score (r=0.488, P<0.001), was an independent predictor for 6-month mortality [odds ratio (OR), 1.183; 95% confidence interval (CI), 1.067-1.339; P=0.004] and unfavorable outcome (Glasgow Outcome Scale score of 1-3) (OR, 1.119; 95% CI, 1.046-1.332; P=0.005) using multivariate analysis, and had high area under receiver operating characteristic curve (AUC) for prediction of 6-month mortality (AUC, 0.831; 95% CI, 0.768-0.883) and unfavorable outcome (AUC, 0.821; 95% CI, 0.757-0.874). The predictive value of the plasma proenkephalin A concentration was also similar to those of WFNS score and Fisher score (both P>0.05). In a combined logistic-regression model, proenkephalin A improved the AUCs of WFNS score and Fisher score, but the differences were not significant (both P>0.05). Thus, proenkephalin A level may be a useful, complementary tool to predict mortality and functional outcome at 6 months after aneurysmal subarachnoid hemorrhage.

The TGR5 receptor mediates bile acid-induced itch and analgesia

Patients with cholestatic disease exhibit pruritus and analgesia, but the mechanisms underlying these symptoms are unknown. We report that bile acids, which are elevated in the circulation and tissues during cholestasis, cause itch and analgesia by activating the GPCR TGR5. TGR5 was detected in peptidergic neurons of mouse dorsal root ganglia and spinal cord that transmit itch and pain, and in dermal macrophages that contain opioids. Bile acids and a TGR5-selective agonist induced hyperexcitability of dorsal root ganglia neurons and stimulated the release of the itch and analgesia transmitters gastrin-releasing peptide and leucine-enkephalin. Intradermal injection of bile acids and a TGR5-selective agonist stimulated scratching behavior by gastrin-releasing peptide- and opioid-dependent mechanisms in mice. Scratching was attenuated in Tgr5-KO mice but exacerbated in Tgr5-Tg mice (overexpressing mouse TGR5), which exhibited spontaneous pruritus. Intraplantar and intrathecal injection of bile acids caused analgesia to mechanical stimulation of the paw by an opioid-dependent mechanism. Both peripheral and central mechanisms of analgesia were absent from Tgr5-KO mice. Thus, bile acids activate TGR5 on sensory nerves, stimulating the release of neuropeptides in the spinal cord that transmit itch and analgesia. These mechanisms could contribute to pruritus and painless jaundice that occur during cholestatic liver diseases.

Mediators of pruritus during cholestasis

PURPOSE OF REVIEW

Pruritus is a frequent symptom in patients with cholestatic liver diseases. Itching may be excruciating, may seriously impair quality of life and even induce suicidal ideation in the most severe cases.

RECENT FINDINGS

The molecular mechanism of itch signal transduction in cholestasis is largely unclear. It may be caused or potentiated by compounds that accumulate in the circulation during cholestasis, which either directly or indirectly affect signalling in itch fibres. In the past, bile salts and endogenous opioids have been proposed but never been proven to be key factors in itch perception during cholestasis. We have performed a screen for compounds in plasma from patients with various cholestatic conditions for their capacity to activate neuronal cell lines. In these sera, we could identify a potent neuronal activator as lysophosphatidic acid (LPA). LPA is a very potent signalling phospholipid that can activate cells through various LPA receptors. Quite strikingly, samples from itchy cholestatic patients contained higher amounts of LPA. These increased levels of LPA turned out to be caused by elevated levels of serum autotaxin, the enzyme that converts lysophosphatidylcholine into LPA. This is a striking finding, as autotaxin has never been connected to itch perception thus far. We have also shown that LPA, when injected intradermally, caused scratching behaviour in mice.

SUMMARY

On the basis of our results, we hypothesize that during cholestasis expression of autotaxin is induced, which gives rise to increased local formation of LPA near unmyelinated nerve endings of itch fibres. LPA activates these neurons through one of the LPA receptors, which in turn potentiates action potentials along itch fibres leading to the perception of pruritus.

Innovative management of pruritus

Pruritus remains a significant problem facing dermatologists and can be associated with various dermatoses and systemic derangements. At times, one can treat the underlying cutaneous or systemic process to alleviate itch. However, it is frequently challenging to identify the cause of a patient's itch and, in this situation, even more difficult to manage the symptom effectively. In this article, the authors discuss the approach to a patient with generalized pruritus without clinically obvious dermatoses. They also addresses mechanisms and management modalities of itch in common systemic diseases, including cholestasis, uremia, and neuropathic dysfunction.

Thyroid hormones alterations during acute liver failure: possible underlying mechanisms and consequences

Thyroid hormones are now recognized to change in different disease states with important consequences on severity and prognosis of disease. However, little is known about thyroid hormones' alterations in acute liver failure (ALF). To study the changes in thyroid hormones and cardiac thyroid receptors during ALF, we subjected seven female pigs to surgical liver devascularization. Liver function biochemical markers, thyroid hormones, endogenous opioids, malondialdehyde (MDA), and interleukins 1 and 6 were measured in serum for 24 h postoperatively. Heart biopsies were harvested at the end of the experiment. Baseline heart biopsies were taken from five additional animals. Serum thyroxin (T(4)) and triiodothyronine (T(3)) levels markedly decreased, whereas free-triiodothyronine and thyroxin-stimulating hormone levels did not change. T(4) and T(3) levels correlated with the degree of liver failure and with MDA and interleukin-6 levels. Beta-endorphin levels initially increased, whereas levels of leucine-enkephalin did not change. Thyroid hormone receptor-alpha1 protein expression in the heart decreased 1.6-fold after ALF, whereas myocardial myosin isoform expression remained unchanged. The downregulation of T(4) and T(3) levels during ALF seems to correlate well with the severity of disease. This downregulation related to inflammation and oxidative stress and resulted in changes in myocardial thyroid receptors.

The efficacy and safety of bile Acid binding agents, opioid antagonists, or rifampin in the treatment of cholestasis-associated pruritus

OBJECTIVES

The objective of this review was to evaluate the efficacy and safety of rifampin, opioid antagonists, or bile acid binding agents in the treatment of cholestasis-related pruritus (CAP) from available randomized controlled trial evidence.

METHODS

In addition to a comprehensive gray literature search, the Cochrane Library, MEDLINE, EMBASE, PubMed, and Web of Science were searched. Only full-text RCTs in participants (>75% adult) with CAP on at least one of the three medications were included. The primary outcome was change in pruritus score, recorded as a continuous or dichotomous outcome. Two independent reviewers performed trial selection and quality assessment.

RESULTS

From 487 citations, 12 RCTs were included. Rifampin (standardized mean difference [SMD]-1.62, 95% CI -3.05 to -0.18) and opioid antagonists (SMD -0.68, 95% CI -1.19 to -0.17) significantly reduced CAP. The two cholestyramine studies were too heterogeneous to pool. Although cholestyramine (P= 0.35) and rifampin (P= 0.96) were not associated with greater side effects compared with placebo, opioid antagonists were (number needed to harm = 2.6, 95% CI 1.4-25).

CONCLUSIONS

The available RCTs are small, few in number, and use varying scales for measuring pruritus. Although both opioid antagonists and rifampin demonstrated a reduction in pruritus, there were insufficient data to judge the efficacy of cholestyramine. Opioid antagonists were associated with transient side effects in a significant proportion of patients. A longer well-designed randomized controlled trial is needed to confirm the efficacy of bile acid binding agents and accurately assess adverse events.

Reduced susceptibility to epinephrine-induced arrhythmias in cirrhotic rats: the roles of nitric oxide and endogenous opioid peptides

BACKGROUND/AIMS

The clinical relevance of QT prolongation, the most widely recognized cardiac electrophysiological abnormality of cirrhosis, is still undefined. The aim of this study is to examine the susceptibility of chronic (4-week) bile duct-ligated rats to epinephrine-induced arrhythmias. The roles of nitric oxide and endogenous opioids were also evaluated.

METHODS

Sham-operated and cirrhotic rats were treated with daily subcutaneous administrations of normal saline (1 ml/kg/day), L-NAME (a non-selective nitric oxide synthase inhibitor, 3mg/kg/day), and naltrexone (20mg/kg/day) during the fourth week after operation. In order to evaluate the effects of acute nitric oxide synthesis inhibition, additional groups of animals were treated by acute intraperitoneal L-NAME injections (3mg/kg). Arrhythmias were induced by intravenous injections of 10 microg/kg epinephrine.

RESULTS

Despite QT prolongation (P<0.001), epinephrine induced fewer arrhythmias in cirrhotic rats compared to sham-operated animals (P<0.05). Chronic, but not acute, L-NAME administration corrected the QT prolongation in cirrhotic rats (P<0.001), and restored the susceptibility of cirrhotic rats to arrhythmias (P<0.05). Naltrexone injection without a significant effect on epinephrine-induced arrhythmias corrected QT interval in cirrhotic rats (P<0.001).

CONCLUSIONS

This study shows that despite QT prolongation, cirrhotic animals are resistant against epinephrine-induced arrhythmias. This resistance is mediated by chronic nitric oxide overproduction.

Involvement of endogenous opioid peptides and nitric oxide in the blunted chronotropic and inotropic responses to beta-adrenergic stimulation in cirrhotic rats

It is well known that chronotropic and inotropic responses to beta-adrenergic stimulation are impaired in cirrhosis, but the exact reason is not clear. Considering the inhibitory effect of endogenous opioid peptides and nitric oxide (NO) on beta-adrenergic pathway, we examined their roles in hyporesponsiveness of isolated atria and papillary muscles to isoproterenol stimulation in cirrhotic rats. Cirrhosis was induced by chronic bile duct ligation. Four weeks after ligation or sham operation, the responses of the isolated atria and papillary muscles to isoproterenol stimulation were evaluated in the absence and presence of naltrexone HCl (10(-6) m), N(omega)-nitro-L-arginine methyl ester (L-NAME, 10(-4) m), and naltrexone plus L-NAME in the organ bath. Considering the role of inducible NOS (iNOS) in hemodynamic abnormalities of cirrhotic rats, the chronotropic and inotropic responses of cirrhotic rats to isoproterenol stimulation were also assessed in the presence of aminoguanidine (a selective inhibitor of iNOS, 3 x 10(-4) m). Sham operation had no significant effect on basal atrial beating rate, contractile force, and maximal time derivatives for the development and the dissipation of papillary muscle tension. The basal atrial beating rate of cirrhotic rats did not show any significant difference compared with the sham-operated ones; however, the basal contractile parameters were significantly decreased in cirrhosis. Although the maximum effects of isoproterenol on chronotropic and inotropic responses were significantly reduced in cirrhotic rats, there was no difference in half-maximal effective concentrations of isoproterenol in these concentration-response curves. The basal abnormalities and the attenuated chronotropic and inotropic responses to isoproterenol were completely corrected by the administration of naltrexone, L-NAME and aminoguanidine. Concurrent administration of naltrexone and L-NAME also restored to normal the basal abnormalities and the blunted responses to isoproterenol in cirrhotic rats, and did not show any antagonistic effect. Based on these findings, both the endogenous opioid peptides and NO may be involved in the attenuated chronotropic and inotropic responses to beta-adrenergic stimulation in cirrhosis. It seems that the iNOS activity results in NO-induced hyporesponsiveness to beta-adrenergic stimulation in cirrhosis.

Effect of oral naltrexone on pruritus in cholestatic patients

AIM: To determine the efficacy and potential complications of oral naltrexone used in the treatment of pruritus in cholestatic patients and to compare them with other studies.

METHODS: Thirty-four enrolled cholestatic patients complaining of pruritus were studied. In the initial phase, pruritus scores during day and night were e v a l u a t e d . Subsequently, patients were given a placebo for one week followed by naltrexone for one week. In each therapeutic course (placebo or naltrexone) day and night pruritus scores were distinguished by a visual analogue scale (VAS) system and recorded in patients’ questionnaires.

RESULTS: Both naltrexone and placebo decreased VAS scores significantly. Naltrexone was more effective than placebo in decreasing VAS scores. Both day and night scores of pruritus decreased by half of the value prior to therapy in thirteen patients (38%). Daytime pruritus improved completely in two patients (5.9%), but no improvement in the nighttime values was observed in any patient.

Sixteen patients (47%) suffered from naltrexone complications, eleven (32%) of them were related to its withdrawal. Complications were often mild. In the case of withdrawal, the complication was transient (within the first 24-28 h of therapy) and self-limited. We had to cease the drug in two cases (5.9%) because of severe withdrawal symptoms.

CONCLUSION: Naltrexone can be used in the treatment of pruritus in cholestatic patients and is a safe drug showing few, mild and self-limited complications.

Obstructive cholestasis alters intestinal transit in mice: role of opioid system

Acute cholestasis is associated with increased activity of the endogenous opioid system. It is also known that opioid receptor agonists like morphine decrease the intestinal transit. The purpose of the present study was to investigate the effect of cholestasis on the small intestine transit and the possible involvement of opioid system in this phenomenon in mice. Cholestasis was induced by bile duct-ligation and intestinal transit was measured with charcoal meal and calculation of percent of transit through small intestine. The effect of chronic administration of naltrexone and acute pretreatment with morphine on intestinal transit was evaluated in bile duct-ligated (BDL) as well as unoperated (CTL) and sham-operated (SHAM) animals. The plasma alkaline phosphatase and alanine aminotransferase activities were also measured. A significant decrease in small intestine transit (%transit) was observed in BDL mice compared to SHAM animals, which was prominent even after 24 h of cholestasis. Chronic pretreatment with an opioid receptor antagonist, naltrexone, (10 mg/kg, i.p for 2, 4 or 6 days) completely restored the cholestasis-induced decrease in %transit to that of control animals. Although the acute administration of morphine (2 mg/kg, s.c.) 20 min before charcoal feeding caused a significant decrease in the intestinal transit of CTL and SHAM animals, it did not decrease the %transit of BDL animals on the day 5 after operation. Our findings show that acute cholestasis is associated with a prominent decrease in small intestine transit in mice and opioid receptors maybe involved in this phenomenon.

Efficacy and safety of oral naltrexone treatment for pruritus of cholestasis, a crossover, double blind, placebo-controlled study

BACKGROUND/AIMS

To assess the efficacy and safety of naltrexone for the short and long term treatment of pruritus of cholestasis.

METHODS

Twenty patients with pruritus and cholestasis were included. A baseline pruritus score was obtained over 1 week. Patients were then randomized to receive 50 mg/day of naltrexone or placebo for 2 weeks. Subsequently, a 1-week washout period ensued and patients were crossed over to the other therapy for 2 additional weeks. Pruritus was assessed daily with a visual analogue scale (VAS) from 0 to 10. Patients whose pruritus decreased >50% of basal with naltrexone received naltrexone 50 mg/day for 2 additional months.

RESULTS

Mean basal VAS was similar in both groups. VAS showed greater and more significant changes with naltrexone than with placebo (P<0.0003). In nine out of 20 patients (45%) receiving naltrexone, pruritus decreased >50% compared to basal value, including five whose pruritus disappeared completely. No significant changes were observed in serum biochemistry. Most of the adverse events that occurred during the first 48 h of naltrexone therapy were consistent with opioid withdrawal-like phenomena and spontaneously disappeared 2 days after starting treatment.

CONCLUSIONS

Naltrexone can be considered as an alternative option to treat pruritus of cholestasis. In the current study, side effects were transient and did not require specific medication.

Hepatic encephalopathy

In the last decade, a significant amount of research has been devoted to the pathogenesis and treatment of hepatic encephalopathy (HE). Non-invasive neuroimaging techniques such as magnetic resonance imaging and spectroscopy have become important research tools. The search for a suitable animal model of HE associated with cirrhosis is still ongoing. Moreover, consensus terminology and diagnostic criteria for HE in humans are badly needed.

Fosinopril-induced prolonged cholestatic jaundice and pruritus: first case report

We report a case of fosinopril-induced prolonged cholestatic jaundice and pruritus in a 61-year-old man, with no previous hepatobiliary disease, who presented with asthenia, jaundice and itching 3 weeks after starting fosinopril therapy. Other drugs taken by the patient were not considered probable causes. The diagnostic evaluation showed no biliary obstruction and other possible causes of intra-hepatic cholestasis were excluded. Liver biopsy showed cholestasis without bile duct damage. The disease ran a severe course during the 2 months of hospitalization, with prolonged itching for 6 months, eventually controlled with oral naltrexone. Jaundice subsided after 4 months, with anicteric cholestasis persisting for more than 18 months. Similar occurrences have been reported with other inhibitors of angiotensin-converting enzyme (mostly captopril), but this is the first case of an important adverse reaction to fosinopril.

Neurotropic and psychotropic drugs in dermatology

Several psychotropic and neurotropic agents are useful in treating patients with skin diseases such as obsessive compulsive skin manipulation, delusions of parasitosis, generalized pruritus, and post-herpetic neuralgia. The mechanism of action of these agents is based on their interaction with central and peripheral neuronal receptors. The medications discussed in this article include the tricyclic antidepressants, serotonin reuptake inhibitors, naltrexone, pimozide, and gabapentin. The pharmacology, mechanism of action, adverse effects, drug interactions, and monitoring guidelines are outlined for each of these drugs.

Further studies on aminopeptidase-M in blood in children with cholestatic liver diseases and viral hepatitis

Aim of this study was to determine and further characterize the serum aminopeptidase-M in children with liver diseases. Based on our new assay, we have shown two fractions of the enzyme. Activity of the first fraction is expressed in undiluted serum at pH adjusted from 8.5 (pH of storaged serum) to 7.4. Activity of the second fraction (cryptic activity) appears in the serum (pH 7.4) as a result of dilution and/or addition of aniline naphthalene sulfonic acid. In children with Alagille syndrome, extrahepatic biliary duct atresia, Byler's disease, and acute hepatitis due to hepatitis B virus infection, activities of both fractions are highly elevated as compared to healthy children or those with chronic viral hepatitis. Moreover, serum aminopeptidase-M seems to reflect other aspects of the pathological process than those reflected by the alanine aminotransferase and gamma-glutamyltranspeptidase. Due to increased activity and broad substrate specificity, the enzyme seems to be also a cofactor of cholestasis and hepatitis.

Basal total opioid peptide release in the striatum of rats with cholestasis from bile duct resection: a study by the use of in vivo microdialysis

The opiate withdrawal-like reaction experienced by patients with cholestatic liver disease after the ingestion of the opiate antagonist nalmefene led to the hypothesis that increased opioidergic neurotransmission/neuromodulation in the central nervous system (CNS) contributes to the pathophysiology of cholestasis. The state of antinociception, which is stereospecifically reversed by naloxone, documented in rats with cholestasis from bile duct resection supports this hypothesis. To further study the opioid system in this animal model of cholestasis, we studied the release of endogenous opioid peptides into the extracellular fluid of the dorso-lateral striatum by the technique of in-vivo microdialysis. Total opioid peptide concentration in the dialysate was measured by a solid phase radioimmunoassay with an antibody directed against the N-terminus of the Tyr-Gly-Gly-Phe-X amino acid sequence after acetylation. Basal total opioid peptide release was significantly higher after surgery in both sham resected and bile duct resected animals. However, basal (unstimulated) total opioid peptide release in the striatum of rats was not altered by cholestasis. It is inferred that the opioidergic abnormalities of cholestasis are not associated with an appreciable increase in the release of endogenous opioids into the extracellular fluid of the striatum. Abnormal processing of specific opioid peptides in cholestasis however, cannot be excluded.

Hepatic inactivation of Leu-enkephalin

Leu-enkephalin radiolabelled at the N-terminal tyrosine by two different methods was presented to isolated perfused rat livers. Approximately 10% of a pulse of tritiated Leu-enkephalin was taken up first-pass; this was increased to 62% when the peptide was iodinated with Bolton and Hunter reagent. Uptake of both forms of radiolabelled Leu-enkephalin was inhibited by taurocholate in a concentration-dependent manner. The proportion of internalised radioactivity secreted into bile also differed but in both cases showed a very rapid time-course similar to that of [24-(14)C]taurocholate and suggestive of non-endocytic transfer via membrane transport proteins. Pre-perfusion with the aminopeptidase inhibitor bestatin increased uptake of 3H-labelled Leu-enkephalin from 10% to 23%; no further increase occurred when the endopeptidase 24.11 inhibitor thiorphan was also present. On infusion of the native peptide into rat livers, 80% of Leu-enkephalin immunoreactivity was lost between the pre- and post-hepatic perfusate; this was reduced to 65% in the presence of 10(-5) M bestatin. The almost total release of the N-terminal tyrosine from 3H-labelled Leu-enkephalin which escaped first-pass uptake confirmed that substantial sinusoidal metabolism had occurred. Low levels of aminopeptidase N were visualised in the sinusoidal membrane using a specific monoclonal antibody coupled to peroxidase staining. Thus, hepatic inactivation of Leu-enkephalin is primarily via hydrolysis mediated by cell surface peptidase (including aminopeptidases) whilst uptake of the intact peptide, probably by a bile salt transport protein, is quantitatively minor unless the N-terminus is blocked by Bolton and Hunter reagent or peptidase inhibitors are present.

Pruritus--itching for a cause and relief?

The mechanisms of pruritus, an unpleasant irritation on the skin that provokes an urge to scratch, are reviewed. Whilst symptomatic treatment is only partially effective, antihistamines remain the first choice of treatment. However, recent novel treatment using opiate antagonists, propofol (subhypnotic doses) and serotonin antagonists offer attractive alternatives.

Hepatic concentrations of proenkephalin-derived opioids are increased in a rat model of cholestasis

The liver of adult rats with cholestasis secondary to bile duct resection has been shown to express the proenkephalin gene and, by immunohistochemical stains, to contain met-enkephalin. To further study hepatic opioids in cholestasis, concentrations of proenkephalin-derived endogenous opioids were measured in a rat model of cholestasis by the use of radioimmunoassays. The specificity of the immunoreactivity detected by the assays was confirmed by high performance liquid chromatography (HPLC). In adult male rats with cholestasis due to BDR, the concentrations of three proenkephalin-derived opioid peptides were increased. Specifically, the mean hepatic concentrations of met-enkephalin, Met-Enk-Arg6-Phe7 and leu-enkephalin were 2.5 (p < 0.005), 2.1 (p < 0.005) and 2.5 (p < 0.01) fold higher than the corresponding mean for controls. These findings provide further independent evidence that opioid peptides accumulate in the liver in a model of cholestasis and are consistent with de novo synthesis of opioid peptides occurring in the cholestatic liver. This phenomenon may have relevance to the altered function of the opioid system in cholestasis and to the role of the liver as a neuroendocrine organ.

Cholestasis in the male rat is associated with naloxone-reversible antinociception

Clinical observations have suggested that cholestasis is associated with increased neurotransmission mediated by the opioid system in the central nervous system. As opiate agonists (e.g. morphine) mediate analgesia, increased opioidergic tone in cholestasis should be associated with a decreased response to pain. To test this hypothesis, the response of rats with acute cholestasis to a nociceptive stimulus was measured by the use of the tail-flick test, an extensively validated assay for measuring opiate-induced antinociception. Five and 7 days after bile-duct resection, the mean tail-flick latency was longer than before surgery (p < 0.05), whereas the corresponding means for unoperated and sham-resected controls were not significantly different from their respective baseline values. The increase in the mean tail-flick latency in the bile-duct resection group was reversed by (-)-naloxone (1 mg/kg subcutaneously), but not by its enantiomer (+)-naloxone (10 mg/kg subcutaneously) (p < 0.001). The stereoselective reversal of antinociception in cholestasis by naloxone indicates that this phenomenon is opioid-receptor mediated. In contrast, prolongation of the mean TFL found in the rat model of thioacetamide-induced acute hepatocellular necrosis was not reversed by (-)-naloxone, indicating that antinociception in this model is not opioid mediated. These findings provide support for the hypothesis that cholestasis is associated with increased opioidergic tone.

Review article: the pathophysiology and pharmacological treatment of portal hypertension

The pathogenesis of portal hypertension remains poorly understood. Similarly, pharmacological manipulation for the prevention and treatment of variceal haemorrhage has not fulfilled the promise of the 1980s. This article reviews current concepts in the pathophysiology of portal hypertension and considers pharmacotherapy for the treatment of variceal bleeding.

A controlled trial of naloxone infusions for the pruritus of chronic cholestasis

To test the hypothesis that opioid agonist activity contributes to the pruritus of cholestasis, a placebo-controlled single-blinded trial of naloxone, an opioid antagonist, was conducted in eight patients with primary biliary cirrhosis. After discontinuation of all conventional antipruritic medications, one or two continuous (24-hour) IV infusions of naloxone (0.2 micrograms.kg-1.min-1) and placebo solution were administered consecutively in an order that was not predetermined. Pruritus was assessed subjectively by means of four hourly recordings of a visual analogue score. In addition, objective measurements of scratching activity that were independent of gross body movements were continuously recorded using an apparatus specifically designed to measure the frequencies associated with this activity. No side effects associated with naloxone infusions were observed. Only scratching activity data obtained for the same periods of day and night during both naloxone and placebo infusions were compared. Naloxone infusions were consistently associated with a decrease in values of the scratching activity index. In addition, in 50% of the patients the infusions were associated with a decrease in visual analogue score. The mean decrease in scratching activity ranged from 29% to 96% (mean, 50%; P less than 0.001). These findings imply that increased opioid agonist activity contributes to scratching activity in cholestatic patients.

Plasma beta endorphin in cirrhosis and renal failure

Whether the plasma concentration of beta endorphin was increased in hepatic cirrhosis like that of smaller opioid peptides methionine enkephalin and leucine enkephalin was determined. Its concentration in chronic renal failure was also measured. Plasma beta endorphin was not significantly raised in cirrhotic patients with or without ascites (medians 5.2 pmol/l and 4.7 pmol/l respectively) compared with disease control subjects (4.9 pmol/l) and healthy control subjects (4.9 pmol/l). In contrast, the peptide was increased 2.5 fold (p less than 0.001) in chronic renal failure (12.4 pmol/l) and was found in many of these patients' urine. The data are compatible with the hypothesis that the liver may play an important role in the elimination of opioid peptides of octapeptide size or less but not the larger peptides such as beta endorphin.