The itch of liver disease

Sleep disorders in dermatology - a comprehensive review

Sleep is a normal physiological process that accounts for approximately one third of a person's life. Disruption of the normal sleep cycle, which maintains physiological homeostasis, can lead to pathology. It is not known whether sleep disturbance causes skin disease or skin disease causes sleep impairment, but a bidirectional influence is suspected. We have compiled the data from published articles on "sleep disorders in dermatology" in PubMed Central from July 2010 to July 2022 (with the option "full text available") and provide an overview of sleep disorders associated with dermatological conditions and certain drugs used in dermatology as well as sleep disturbances for which some drugs used can cause itch or dermatological issues. Atopic dermatitis, eczema and psoriasis have been shown to be exacerbated by sleep problems and vice versa. Sleep deprivation, night-time pruritus and disrupted sleep cycles are often used to assess treatment response and quality of life in these conditions. Some medications used primarily for dermatological conditions have also been associated with alterations in the sleep-wake cycle. Addressing patients sleep disorders should be an integral part of the management of dermatological conditions. More studies are needed to further investigate the influence of sleep and skin disorders.

Mechanisms of pruritus in cholestasis: understanding and treating the itch

Pruritus in cholestatic liver diseases can be a major burden and dramatically impair the quality of life of those affected. Here, we provide an update on the latest insights into the molecular pathogenesis of and novel therapeutic approaches for cholestasis-associated itch. Endogenous and exogenous small-molecule pruritogen candidates bind to their receptors on unmyelinated itch C-fibres in the skin. Candidate pruritogens in cholestasis include certain lysophospholipids and sulfated progesterone metabolites, among others, whereas total bile acid or bilirubin conjugates seem unlikely to have a dominant role in the pathogenesis of cholestasis-associated pruritus. Transmission of itch signals via primary, secondary and tertiary itch neurons to the postcentral gyrus and activation of scratch responses offer various targets for therapeutic intervention. At present, evidence-based treatment options for pruritus in fibrosing cholangiopathies, such as primary biliary cholangitis and primary sclerosing cholangitis, are the peroxisome proliferator-associated receptor (PPAR) agonist bezafibrate and the pregnane X receptor (PXR) agonist rifampicin. In pruritus of intrahepatic cholestasis of pregnancy, ursodeoxycholic acid is recommended and might be supported in the third trimester by rifampicin if needed. Alternatively, non-absorbable anion exchange resins, such as cholestyramine, can be administered, albeit with poor trial evidence. Liver transplantation for intolerable refractory pruritus has become an extremely rare therapeutic strategy.

Evaluation and Management of Pruritus in Primary Biliary Cholangitis

Chronic pruritus is a classic symptom in patients with primary biliary cholangitis. It affects up to two-thirds of patients in the course of the disease. Efficient therapy consists of topical treatment combined with systemic options such as anion exchangers, rifampicin, bezafibrate, μ-opioid receptor antagonists, selective-serotonin receptor uptake inhibitors, and gabapentinoids. Future therapeutic approaches may contain the selective blockade of the enterohepatic cycle by inhibiting the ileal bile acid transporter, the agonism at κ-opioid receptors, and antagonism of the mas-related G protein-coupled receptor X4. As nondrug treatment, ultraviolet B therapy, albumin dialysis, and biliary drainage are available at specialized centers.

Pruritus: A Sensory Symptom Generated in Cutaneous Immuno-Neuronal Crosstalk

Pruritus or itch generated in the skin is one of the most widespread symptoms associated with various dermatological and systemic (immunological) conditions. Although many details about the molecular mechanisms of the development of both acute and chronic itch were uncovered in the last 2 decades, our understanding is still incomplete and the clinical management of pruritic conditions is one of the biggest challenges in daily dermatological practice. Recent research revealed molecular interactions between pruriceptive sensory neurons and surrounding cutaneous cell types including keratinocytes, as well as resident and transient cells of innate and adaptive immunity. Especially in inflammatory conditions, these cutaneous cells can produce various mediators, which can contribute to the excitation of pruriceptive sensory fibers resulting in itch sensation. There also exists significant communication in the opposite direction: sensory neurons can release mediators that maintain an inflamed, pruritic tissue-environment. In this review, we summarize the current knowledge about the sensory transduction of pruritus detailing the local intercellular interactions that generate itch. We especially emphasize the role of various pruritic mediators in the bidirectional crosstalk between cutaneous non-neuronal cells and sensory fibers. We also list various dermatoses and immunological conditions associated with itch, and discuss the potential immune-neuronal interactions promoting the development of pruritus in the particular diseases. These data may unveil putative new targets for antipruritic pharmacological interventions.

Pediatric COVID-19 and Gastrointestinal Symptoms in Africa

One year into the coronavirus disease 2019 (COVID-19) pandemic, the African continent still seems to be spared from the devastating effects the disease had in other continents. Africa's COVID-19 seems to be of a milder nature both in adults and children. However, lack of data from Africa is significant, and more studies are needed to validate the disease status, clinical manifestations, and future implications for Africa. In this study, we report pediatric COVID-19 features in Africa represented by 8 countries.

Gastrointestinal Manifestations, Clinical Characteristics and Outcomes of COVID-19 in Adult and Pediatric Patients

BACKGROUND

Italy was the first country in Europe to report a SARS-CoV-2 case. Since then, the country has suffered a large number of COVID-19 infections both in adults and children. This disease has been shown to lead to different outcomes in these two groups, which often present varying symptoms and comorbidities.

AIM

Therefore, we aimed to evaluate the symptoms, comorbidities and laboratory values in adults and children.

METHODS

We present the characteristics of 1,324 adults and 563 pediatric COVID-19 Italian patients. The data was retrieved from studies published in Italy and found via PubMed and Google Scholar.

RESULTS

The virus appeared to affect adults more than children and men more than women, and to result in more severe outcomes in patients with abnormal laboratory values and a higher number of comorbidities. Adults are at higher risk for complications and death, and they usually present with fever, respiratory symptoms, cough, fatigue, diarrhea, myalgia, and/or loss of taste, smell, or appetite. Children usually have a milder disease progression and usually present with fever, cough, rhinorrhea, pharyngitis, sore throat, pneumonia, GI symptoms (diarrhea, vomiting, abdominal pain), fatigue, and dyspnea.

CONCLUSION

Our findings support early reports that showed that SARS-CoV-2 is associated with more common asymptomatic cases and milder clinical outcome in children than in adults. Acute respiratory distress syndrome and Multisystem inflammatory syndrome in children (systemic vasculitis) are the most severe disease progressions for adults and children, respectively.

Newer Approaches to the Management of Pruritus in Cholestatic Liver Disease

Purpose of Review

Chronic pruritus represents a burdensome symptom in cholestatic liver disease. This review recommends a stepwise therapeutic approach, alongside with providing information on epidemiology, pathophysiology, and novel drug targets.

Recent Findings

Current epidemiological data emphasize chronic itch as a major symptom in immune-mediated liver diseases such as primary biliary cholangitis affecting up to 70% of patients with a significant number suffering from long-lasting and severe pruritus. κ-opioid receptor (KOR) agonists, PPAR agonists, and ileal bile acid transporter (IBAT) inhibitors are currently investigated for their anti-pruritic efficacy in clinical trials. Future therapies may target the autotaxin-lysophosphatidic acid-axis or the Mas-related GPCR MRGPRX4.

Summary

Cholestatic pruritus still remains a challenging symptom for patients and physicians. Using a stepwise approach including cholestyramine, rifampicin, bezafibrate, naltrexone, and sertraline, pruritus is often adequately manageable. KOR agonists and IBAT inhibitors are currently the most promising anti-pruritic drugs for cholestatic pruritus in development.

Activation of pruritogenic TGR5, MrgprA3, and MrgprC11 on colon-innervating afferents induces visceral hypersensitivity

Itch induces scratching that removes irritants from the skin, whereas pain initiates withdrawal or avoidance of tissue damage. While pain arises from both the skin and viscera, we investigated whether pruritogenic irritant mechanisms also function within visceral pathways. We show that subsets of colon-innervating sensory neurons in mice express, either individually or in combination, the pruritogenic receptors Tgr5 and the Mas-gene-related GPCRs Mrgpra3 and Mrgprc11. Agonists of these receptors activated subsets of colonic sensory neurons and evoked colonic afferent mechanical hypersensitivity via a TRPA1-dependent mechanism. In vivo intracolonic administration of individual TGR5, MrgprA3, or MrgprC11 agonists induced pronounced visceral hypersensitivity to colorectal distension. Coadministration of these agonists as an "itch cocktail" augmented hypersensitivity to colorectal distension and changed mouse behavior. These irritant mechanisms were maintained and enhanced in a model of chronic visceral hypersensitivity relevant to irritable bowel syndrome. Neurons from human dorsal root ganglia also expressed TGR5, as well as the human ortholog MrgprX1, and showed increased responsiveness to pruritogenic agonists in pathological states. These data support the existence of an irritant-sensing system in the colon that is a visceral representation of the itch pathways found in skin, thereby contributing to sensory disturbances accompanying common intestinal disorders.

Treatment of Pruritus Secondary to Liver Disease

PURPOSE OF REVIEW

Pruritus is a common extrahepatic symptom in various liver disorders, in particularly those with cholestatic features. This review summarizes epidemiology, pathophysiology, evidence-based therapeutic recommendations and currently investigated drugs for pruritus in hepatobiliary disorders.

RECENT FINDINGS

Recent epidemiological data suggest pruritus as a common and relevant symptom in immune-mediated liver diseases, i.e., primary biliary cholangitis (PBC) with over 70% affected patients, up to 56% suffering from chronic pruritus. The better pathophysiological understanding of hepatic pruritus has led to the identification of novel therapeutic targets, addressed in drug trials using KOR agonists, PPAR agonists, and ileal bile acid transporter inhibitors. Hepatic itch remains among the most agonizing symptoms for affected patients and a clinical challenge for physicians. Therapeutic recommendations include a guideline-based stepwise approach starting with cholestyramine, followed by rifampicin, naltrexone, and sertraline. Bezafibrate and ileal bile acid transporter inhibitors represent promising future anti-pruritic treatment options.

BAM8-22 and its receptor MRGPRX1 may attribute to cholestatic pruritus

Pruritus is an unexpected symptom observed in cholestasis and its mechanism is still unclear. Here, we show that bovine adrenal medulla (BAM) 8-22, an endogenous itch-inducing peptide, could be involved in cholestatic pruritus. It was found that bile duct ligation (BDL) mice, an obstructive cholestasis model, showed increased spontaneous scratching behaviour. Importantly, the mRNA level of proenkephalin, a precursor polypeptide of BAM8-22, was significantly increased in the skin of BDL mice. Furthermore, the mRNA level of Mrgprx1, which encodes a receptor for BAM8-22, was significantly increased in the dorsal root ganglia (DRG) of BDL mice. This was further confirmed by elevation of intracellular calcium levels upon BAM8-22 treatment in primarily-cultured DRG neurons. In addition, BDL mice showed augmented scratching behaviour by BAM8-22, indicating enhanced activity of MRGPRX1. Moreover, the skin homogenate of BDL mice induced elevation of intracellular calcium levels through MRGPRX1. Finally, among the various bile acids, chenodeoxycholic acid significantly increased proenkephalin transcription in a human keratinocyte cell line (HaCaT). In conclusion, cholestatic pruritus could be attributed in part to enhanced action of both BAM8-22 in the skin and its receptor MRGPRX1 in sensory neurons.

A Randomized, Controlled, Phase 2 Study of Maralixibat in the Treatment of Itching Associated With Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is typically associated with elevated serum bile acid levels and pruritus, but pruritus is often refractory to treatment with existing therapies. This phase 2 study assessed the efficacy and safety of maralixibat, a selective, ileal, apical, sodium‐dependent, bile acid transporter inhibitor, in adults with PBC and pruritus. Adults with PBC and pruritus who had received ursodeoxycholic acid (UDCA) for ≥6 months or were intolerant to UDCA were randomized 2:1 to maralixibat (10 or 20 mg/day) or placebo for 13 weeks in combination with UDCA (when tolerated). The primary outcome was change in Adult Itch Reported Outcome (ItchRO™) average weekly sum score (0, no itching; 70, maximum itching) from baseline to week 13/early termination (ET). The study enrolled 66 patients (maralixibat [both doses combined], n = 42; placebo, n = 24). Mean ItchRO™ weekly sum scores decreased from baseline to week 13/ET with maralixibat (–26.5; 95% confidence interval [CI], –31.8, –21.2) and placebo (–23.4; 95% CI, –30.3, –16.4). The difference between groups was not significant (P = 0.48). In the maralixibat and placebo groups, adverse events (AEs) were reported in 97.6% and 70.8% of patients, respectively. Gastrointestinal disorders were the most frequently reported AEs (maralixibat, 78.6%; placebo, 50.0%). Conclusion: Reductions in pruritus did not differ significantly between maralixibat and placebo. However, a large placebo effect may have confounded assessment of pruritus. Lessons learned from this rigorously designed and executed trial are indispensable for understanding how to approach trials assessing pruritus as the primary endpoint and the therapeutic window of bile acid uptake inhibition as a therapeutic strategy in PBC.

Lysophosphatidic acid activates satellite glia cells and Schwann cells

Pruritus is a common and disabling symptom in patients with hepatobiliary disorders, particularly in those with cholestatic features. Serum levels of lysophosphatidic acid (LPA) and its forming enzyme autotaxin were increased in patients suffering from hepatic pruritus, correlated with itch severity and response to treatment. Here we show that in a culture of dorsal root ganglia LPA 18:1 surprisingly activated a large fraction of satellite glia cells, and responses to LPA 18:1 correlated inversely with responses to neuronal expressed transient receptor potential channels. LPA 18:1 caused only a marginal activation of heterologously expressed TRPV1, and responses in dorsal root ganglion cultures from TRPV1-deficient mice were similar to controls. LPA 18:1 desensitized subsequent responsiveness to chloroquine and TGR5 agonist INT-777. The LPA 18:1-induced increase in cytoplasmatic calcium stems from the endoplasmatic reticulum. LPA receptor expression in dorsal root ganglia and Schwann cells, LPAR1 immunohistochemistry, and pharmacological results indicate a signaling pathway through LPA receptor 1. Peripheral rat Schwann cells, which are of glial lineage as the satellite glia cells, were also responsive to LPA 18:1. Summarizing, LPA 18:1 primarily activates rather glial cells than neurons, which may subsequently modulate neuronal responsiveness and sensory sensations such as itch and pain.

Fibrates for the treatment of cholestatic itch (FITCH): study protocol for a randomized controlled trial

BACKGROUND

Pruritus (itch) is a frequent, burdensome and difficult-to-treat symptom in patients with cholestasis. Fibrates are currently under investigation for the treatment of primary biliary cholangitis in patients with a suboptimal response to ursodeoxycholic acid. Moreover, there is empirical evidence for a possible antipruritic effect. We aim to prove this in a randomized controlled trial, including patients with cholestatic liver diseases other than primary biliary cholangitis that are accompanied by pruritus.

METHODS

A multicenter investigator-initiated, double-blind, randomized placebo-controlled trial to evaluate the effect of bezafibrate on cholestatic pruritus in 84 adult patients with primary biliary cholangitis or primary/secondary sclerosing cholangitis. Primary outcome is the proportion of patients with a reduction of itch intensity of 50% or more (measured on a Visual Analog Scale) after 21 days of treatment with bezafibrate 400 mg qid or placebo. Secondary outcomes include the effect of bezafibrate on a five-dimensional itch score, liver disease-specific quality of life, serum liver tests and autotaxin activity. Safety will be evaluated through serum parameters for kidney function and rhabdomyolysis as well as precise recording of (serious) adverse events. We provide a schematic overview of the study protocol and describe the methods used to recruit and randomize patients, collect and handle data and perform statistical analyses.

DISCUSSION

Given its favorable safety profile and anticholestatic properties, bezafibrate may become the new first-line treatment option for treating cholestatic pruritus.

TRIAL REGISTRATION

Netherlands Trial Register, ID: NCT02701166 . Registered on 2 March 2016; Netherlands Trial Register, ID: NTR5436 . Registered on 3 August 2015.

Serum Autotaxin Activity Correlates With Pruritus in Pediatric Cholestatic Disorders

OBJECTIVE

Pruritus is a common symptom of cholestatic liver disorders. The present study aimed at evaluating autotaxin (ATX), a lysophospholipase recently identified as potential cause for cholestatic pruritus, in pediatric cholestatic diseases presenting with or without itching.

METHODS

A cohort of 45 children consisting of 14 patients experiencing itching (Alagille syndrome [n = 10], complete extrahepatic biliary atresia [n = 2], neonatal sclerosing cholangitis (n = 1), progressive familial intrahepatic cholestasis type 2 [n = 1]), 9 patients with bile acid synthesis defects (3β-hydroxy-C27-steroid-oxidoreductase [n = 7] and Δ-3-oxosteroid-5β-reductase deficiency [n = 2]), and 22 healthy children were studied. Serum ATX activity and total serum bile salt were determined enzymatically, ATX protein content was semiquantified by Western blotting. Using real-time polymerase chain reaction, ATX mRNA expression was studied in HepG2 cells treated with farnesoid-X-receptor agonists or vehicle.

RESULTS

Serum ATX activity was increased in pruritic children with Alagille and other cholestatic syndromes (mean ± standard deviation: 16.1 ± 4.3 nmol · mL · min) compared with children with nonpruritic cholestatic diseases with bile acid synthesis defects (10.4 ± 4.7 nmol · mL · min; P < 0.01) and healthy controls (7.6 ± 2.3 nmol · mL · min; P < 0.001). ATX protein levels closely correlated with serum ATX activity. Serum ATX activity and total serum bile salt showed a linear correlation with itch intensity (r = 0.66, P < 0.001 and r = 0.80, P < 0.001, respectively). No correlation was observed between ATX activity and bilirubin. ATX mRNA expression in HepG2 cells was not induced by farnesoid-X-receptor ligands.

CONCLUSIONS

Serum ATX activity correlated with itch intensity in children with cholestatic diseases. Bile salts did not increase ATX expression in vitro. ATX inhibitors may be useful antipruritic agents in pediatric cholestatic disorders.

Pruritus in Systemic Diseases: A Review of Etiological Factors and New Treatment Modalities

Pruritus is the most frequently described symptom in dermatology and can significantly impair the patient's quality of life. In 10–50% of adults with persistent pruritus, it can be an important dermatologic clue for the presence of a significant underlying systemic disease such as renal insufficiency, cholestasis, hematologic disorder, or malignancy (Etter and Myers, 2002; Zirwas and Seraly, 2001). This review describes the presence of pruritus in different systemic diseases. It is quite important to discover the cause of pruritus for providing relief for the patients experiencing substantial morbidity caused by this condition.

Use of transcutaneous electrical nerve stimulation for chronic pruritus

Pruritus is a distressing symptom in many dermatological as well as systemic conditions, and it is sometimes very chronic and relapsing. Transcutaneous electrical nerve stimulation (TENS) is an inexpensive form of analgesia that could also ameliorate itching. This study aimed to evaluate TENS efficacy in patients with pruritus due to some types of chronic eczema, and in patients with chronic hepatic disease. Ten patients with atopic dermatitis (AD), 20 patients with lichen simplex chronicus (LSC), and 16 patients with chronic liver disease having chronic distressing pruritus received three sessions of TENS weekly for 12 sessions, and the effect on the visual analogue scale (VAS) scores was recorded after 2 weeks of therapy, at treatment end, and after an additional month for follow up. There was a statistically significant decline in the mean VAS score for studied groups at weeks 2 and 4 of therapy compared to baseline, but the improvement was more significant in patients with AD, and LSC (p < 0.001 for both) than in those with chronic liver disease (p < 0.01) who also showed an early re-elevation of VAS score on follow up. TENS therapy holds promise as a palliative, alternative, safe and inexpensive treatment for patients with some chronic pruritic conditions.

The bile acid receptor TGR5 activates the TRPA1 channel to induce itch in mice

BACKGROUND & AIMS

Patients with cholestatic disease have increased systemic concentrations of bile acids (BAs) and profound pruritus. The G-protein-coupled BA receptor 1 TGR5 (encoded by GPBAR1) is expressed by primary sensory neurons; its activation induces neuronal hyperexcitability and scratching by unknown mechanisms. We investigated whether the transient receptor potential ankyrin 1 (TRPA1) is involved in BA-evoked, TGR5-dependent pruritus in mice.

METHODS

Co-expression of TGR5 and TRPA1 in cutaneous afferent neurons isolated from mice was analyzed by immunofluorescence, in situ hybridization, and single-cell polymerase chain reaction. TGR5-induced activation of TRPA1 was studied in in HEK293 cells, Xenopus laevis oocytes, and primary sensory neurons by measuring Ca(2+) signals. The contribution of TRPA1 to TGR5-induced release of pruritogenic neuropeptides, activation of spinal neurons, and scratching behavior were studied using TRPA1 antagonists or Trpa1(-/-) mice.

RESULTS

TGR5 and TRPA1 protein and messenger RNA were expressed by cutaneous afferent neurons. In HEK cells, oocytes, and neurons co-expressing TGR5 and TRPA1, BAs caused TGR5-dependent activation and sensitization of TRPA1 by mechanisms that required Gβγ, protein kinase C, and Ca(2+). Antagonists or deletion of TRPA1 prevented BA-stimulated release of the pruritogenic neuropeptides gastrin-releasing peptide and atrial natriuretic peptide B in the spinal cord. Disruption of Trpa1 in mice blocked BA-induced expression of Fos in spinal neurons and prevented BA-stimulated scratching. Spontaneous scratching was exacerbated in transgenic mice that overexpressed TRG5. Administration of a TRPA1 antagonist or the BA sequestrant colestipol, which lowered circulating levels of BAs, prevented exacerbated spontaneous scratching in TGR5 overexpressing mice.

CONCLUSIONS

BAs induce pruritus in mice by co-activation of TGR5 and TRPA1. Antagonists of TGR5 and TRPA1, or inhibitors of the signaling mechanism by which TGR5 activates TRPA1, might be developed for treatment of cholestatic pruritus.

GPBA: a GPCR for bile acids and an emerging therapeutic target for disorders of digestion and sensation

Bile acids (BAs) are digestive secretions that are necessary for the emulsification and absorption of dietary fats. Given the episodic nature of BA secretion and intestinal re-absorption, the circulating and tissue levels of BAs, like those of the gut hormones, fluctuate in fasting and fed states, and BA levels and forms are markedly affected by disease. BAs exert widespread hormonal-like effects by activating receptors in the nucleus and at the plasma membrane. The nuclear steroid receptors mediate the genomic actions of BAs on BA, glucose and lipid homeostasis. GPBA (TGR5) is a G-protein coupled plasma membrane receptor for BAs that mediates many of the rapid, non-genomic actions of BAs. GPBA has been implicated in the control of glucose homeostasis, inflammation and liver functions. Recent observations have revealed an unexpected role for GPBA in the nervous system. GPBA is expressed by enteric neurons and enterochromaffin cells that control peristalsis, and GPBA mediates the prokinetic actions of BAs in the colon that have been known for millennia. GPBA is also present on primary spinal afferent and spinal neurons that are necessary for sensory transduction. BA-induced activation of GPBA in the sensory nervous system promotes scratching behaviours and analgesia, which may contribute to the pruritus and painless jaundice that are observed in some patients with chronic cholestatic disease, where circulating BA concentrations are markedly increased. Thus, GPBA has emerged as an intriguing target for diverse metabolic, inflammatory, digestive and sensory disorders, where agonists and antagonists may be of value.

Pruritus in cholestasis: facts and fiction

Pruritus is a common symptom in patients with cholestatic liver diseases such as primary biliary cirrhosis, primary sclerosing cholangitis, intrahepatic cholestasis of pregnancy, or hereditary pediatric cholestatic disorders and may accompany, although less frequently, many other liver diseases. Recent findings indicate that lysophosphatidic acid (LPA), a potent neuronal activator, and autotaxin (ATX; ectonucleotide pyrophosphatase/phosphodiesterase 2), the enzyme which forms LPA, may form a key element of the long-sought pruritogenic signaling cascade in cholestatic patients suffering from itch. Serum ATX, but no other pruritogen candidate studied so far, correlates with pruritus intensity and responds to therapeutic interventions. In this comprehensive review, we provide a short update on actual insights in signal transmission related to pruritus and discuss pruritogen candidates in cholestasis. We also summarize evidence-based and guideline-approved as well as experimental therapeutic approaches for patients suffering from pruritus in cholestasis.

Bile acids reach out to the spinal cord: new insights to the pathogenesis of itch and analgesia in cholestatic liver disease

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.

Review article: controversies in the management of primary biliary cirrhosis and primary sclerosing cholangitis

BACKGROUND

Despite considerable advances over the last two decades in the molecular understanding of cholestasis and cholestatic liver disease, little improvement has been made in diagnostic tools and therapeutic strategies.

AIMS

To critically review controversial aspects of the scientific basis for common clinical practice in primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) and to discuss key ongoing challenges to improve patient management.

METHODS

We performed a literature search using PubMed and by examining the reference lists of relevant review articles related to the clinical management of PBC and PSC. Articles were considered on the background of the European Association for the Study of the Liver (EASL) and the American Association for the Study of Liver Diseases (AASLD) practice guidelines and clinical experience of the authors.

RESULTS

Ongoing challenges in PBC mainly pertain to the improvement of medical therapy, particularly for patients with a suboptimal response to ursodeoxycholic acid. In PSC, development of medical therapies and sensitive screening protocols for cholangiocarcinoma represent areas of intense research. To rationally improve patient management, a better understanding of pathogenesis, including complications like pruritis and fatigue, is needed and there is a need to identify biomarker end-points for treatment effect and prognosis. Timing of liver transplantation and determining optimal regimens of immunosuppression post-liver transplantation will also benefit from better appreciation of pre-transplant disease mechanisms.

CONCLUSION

Controversies in the management of PBC and PSC relate to topics where evidence for current practice is weak and further research is needed.

Advanced aging skin and itch: addressing an unmet need

Itch is the most common skin disorder in the elderly and frequently diminishes quality of life in this population. The high prevalence of pruritus in elderly patients is attributed in part to the decline in the normal physiology of the advanced aging skin, and reflects poor hydration, impaired skin barrier, and altered neural function, all ultimately contributing to inflammation and pruritus. As the elderly population continues to grow, practitioners need to be aware of how to evaluate and manage pruritus, recognizing the common conditions contributing to itch in elderly patients as well as the challenges of treatment in this group. Ultimately, management of pruritus will require an individually tailored approach that is guided by a patient's general health, severity of symptoms, and the potential adverse effects of itch therapies.

Ondansetron to treat pruritus due to cholestatic jaundice

Intractable itching is a symptom of cholestatic liver disease of various causes that is bothersome and difficult to manage. Although treatment of the primary cause of cholestasis is paramount in resolving the issue, given the debilitating consequences of pruritus, symptomatic treatment is frequently necessary. Although many medications including cholestyramine, rifampin, opioid antagonists (i.e., naloxone, naltrexone), phenobarbital, and antihistamines have been used to treat cholestatic-induced pruritus, none has resulted in uniform success. We report anecdotal success with the use of ondansetron to treat pruritus associated with cholestasis following prolonged intensive care unit course of a 16-year-old. The theories accounting for pruritus with cholestasis are presented, treatment options are reviewed, and the role of ondansetron in the treatment of pruritus is discussed.

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.

Pathogenesis and management of pruritus in cholestatic liver disease

Patients with cholestatic liver diseases such as primary biliary cirrhosis, primary sclerosing cholangitis and intrahepatic cholestasis of pregnancy commonly complain of pruritus. The underlying pathogenesis remains obscure with several mediators possibly playing an important role; these include lysophosphatidic acid, bile salts, opioids, histamine and progesterone metabolites. We describe in this review novel insights into the pathogenesis and management of pruritus in patients with cholestasis.