Toxic effects of intravenous and oral prostaglandin E therapy in patients with liver disease

Hypertrophic osteoarthropathy: estrogens, prostaglandinE2, prostaglandin A2, and the inflammatory reflex

It has been claimed that hyperestrogenism occurs in hypertrophic osteoarthropathy (HOA), but not in simple clubbing. However, one of our patients had simple clubbing and hyperestrogenism. We therefore measured estrogens, androgens, sex hormone-binding globulin (SHBG), and gonadotropins in five patients with HOA and in 18 patients with simple clubbing. Of the patients with HOA, 80% had a high urinary estriol concentration. In their serum, 80% had high estrone, 0% high estradiol, and 40% high SHBG. Of the patients with simple clubbing, 89% had a high urinary estriol concentration. In their serum, 76% had high estrone, 6% high estradiol, and 31% high SHBG. In all patients, urinary estriol concentration correlated positively with the degree of clubbing. Serum concentration of androstenedione, testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) was mostly normal, but androstenedione concentration correlated positively with the degree of clubbing. Spider angiomas were present in 74%, palmar erythema in 39%, and gynecomastia in 9%. Urinary creatinine concentration was low in 48% and correlated positively with the degree of clubbing. We reject the claim that hyperestrogenism occurs in HOA, but not in simple clubbing. Hyperestrogenism occurs both in HOA and in simple clubbing. Our results also support earlier reports that clubbing and HOA are associated with spider angiomas, palmar erythema, gynecomastia, adrenal cortical hyperfunction, muscle atrophy, and water retention. These results led to a new hypothesis on the pathogenesis of HOA, involving estrogens, prostaglandin E₂, prostaglandin A₂, and the inflammatory reflex.

Clubbing and hypertrophic osteoarthropathy: insights in diagnosis, pathophysiology, and clinical significance

BACKGROUND

Digital clubbing and hypertrophic osteoarthropathy (HOA) form a diagnostic challenge. Subtle presentations of clubbing are often missed. The underlying pathophysiology remains unclear. Establishing a differential diagnosis based on nonspecific signs can be cumbersome. Finally, the prognostic value of clubbing and HOA remains unclear.

OBJECTIVE

This article reviews clinical criteria and pathophysiology of clubbing and HOA. A diagnostic algorithm is proposed, based on etiology and current insights. The prognostic impact on associated diseases is discussed.

METHODS

The Internet databases Medline and Embase were searched. Articles were selected based on relevance of abstract, article type and impact of the journal.

RESULTS

Diagnostic criteria include Lovibond's profile sign, distal/interphalangeal depth ratio and Schamroth's sign. Three pathophysiological causes of clubbing can be distinguished: hypoxia, chronic inflammation and aberrant vascularization. A prominent role for vascular endothelial growth factor is suggested. Associated symptoms and clinical signs should guide the initial diagnostic evaluation. Finally, clubbing is a negative prognostic factor in certain pulmonary disorders, including cystic fibrosis.

Misoprostol modulates cytokine expression through a cAMP pathway: Potential therapeutic implication for liver disease

Dysregulated cytokine metabolism plays a critical role in the pathogenesis of many forms of liver disease, including alcoholic and non-alcoholic liver disease. In this study we examined the efficacy of Misoprostol in modulating LPS-inducible TNFα and IL-10 expression in healthy human subjects and evaluated molecular mechanisms for Misoprostol modulation of cytokines in vitro. Healthy subjects were given 14day courses of Misoprostol at doses of 100, 200, and 300μg four times a day, in random order. Baseline and LPS-inducible cytokine levels were examined ex vivo in whole blood at the beginning and the end of the study. Additionally, in vitro studies were performed using primary human PBMCs and the murine macrophage cell line, RAW 264.7, to investigate underlying mechanisms of misoprostol on cytokine production. Administration of Misoprostol reduced LPS inducible TNF production by 29%, while increasing IL-10 production by 79% in human subjects with no significant dose effect on ex vivo cytokine activity; In vitro, the effect of Misoprostol was largely mediated by increased cAMP levels and consequent changes in CRE and NFκB activity, which are critical for regulating IL-10 and TNF expression. Additionally, chromatin immunoprecipitation (ChIP) studies demonstrated that Misoprostol treatment led to changes in transcription factor and RNA Polymerase II binding, resulting in changes in mRNA levels. In summary, Misoprostol was effective at beneficially modulating TNF and IL-10 levels both in vivo and in vitro; these studies suggest a potential rationale for Misoprostol use in ALD, NASH and other liver diseases where inflammation plays an etiologic role.

Regulation of prostaglandin EP1 and EP4 receptor signaling by carrier-mediated ligand reuptake

After synthesis and release from cells, prostaglandin E₂ (PGE₂) undergoes reuptake by the prostaglandin transporter (PGT), followed by cytoplasmic oxidation. Although genetic inactivation of PGT in mice and humans results in distinctive phenotypes, and although experiments in localized environments show that manipulating PGT alters downstream cellular events, a direct mechanistic link between PGT activity and PGE₂ (EP) receptor activation has not been made. Toward this end, we created two reconstituted systems to examine the effect of PGT expression on PGE₂ signaling via two of its receptors (EP₁ and EP₄). In human embryonic kidney cells engineered to express the EP₁ receptor, exogenous PGE₂ induced a dose-dependent increase in cytoplasmic Ca²⁺. When PGT was expressed at the plasma membrane, the PGE₂ dose–response curve was right-shifted, consistent with reduction in cell surface PGE₂ availability; a potent PGT inhibitor acutely reversed this shift. When bradykinin was used to induce endogenous PGE₂ release, PGT expression similarly induced a reduction in Ca²⁺ responses. In separate experiments using Madin–Darby Canine Kidney cells engineered to express the PGE₂ receptor EP₄, bradykinin again induced autocrine PGE₂ signaling, as judged by an abrupt increase in intracellular cAMP. As in the EP₁ experiments, expression of PGT at the plasma membrane caused a reduction in bradykinin-induced cAMP accumulation. Pharmacological concentrations of exogenous PGE₂ induced EP₄ receptor desensitization, an effect that was mitigated by PGT. Thus, at an autocrine/paracrine level, plasma membrane PGT regulates PGE₂ signaling by decreasing ligand availability at cell surface receptors.

Prostaglandin transporter mutations cause pachydermoperiostosis with myelofibrosis

Pachydermoperiostosis, or primary hypertrophic osteoarthropathy (PHO), is an inherited multisystem disorder, whose features closely mimic the reactive osteoarthropathy that commonly accompanies neoplastic and inflammatory pathologies. We previously described deficiency of the prostaglandin-degrading enzyme 15-hydroxyprostaglandin dehydrogenase (HPGD) as a cause of this condition, implicating elevated circulating prostaglandin E(2) (PGE(2)) as causative of PHO, and perhaps also as the principal mediator of secondary HO. However, PHO is genetically heterogeneous. Here, we use whole-exome sequencing to identify recessive mutations of the prostaglandin transporter SLCO2A1, in individuals lacking HPGD mutations. We performed exome sequencing of four probands with severe PHO, followed by conventional mutation analysis of SLCO2A1 in nine others. Biallelic SLCO2A1 mutations were identified in 12 of the 13 families. Affected individuals had elevated urinary PGE(2), but unlike HPGD-deficient patients, also excreted considerable quantities of the PGE(2) metabolite, PGE-M. Clinical differences between the two groups were also identified, notably that SLCO2A1-deficient individuals have a high frequency of severe anemia due to myelofibrosis. These findings reinforce the key role of systemic or local prostaglandin excess as the stimulus to HO. They also suggest that the induction or maintenance of hematopoietic stem cells by prostaglandin may depend upon transporter activity.

Unilateral digital clubbing in a hemodialysis patient

We present an unusual case of a chronic hemodialysis patient with moderate diffuse acrocyanosis and prominent unilateral clubbing of his right hand fingers, with classic physical features of hypertrophic osteoarthropathy. The patient's left hand, which had a functioning arteriovenous fistula, did not show any evidence of clubbing. We briefly discuss the different theories in regards to the pathogenesis of clubbing, and the potential role of arteriovenous fistula in preventing its occurrence.

Review article: the current management of acute liver failure

BACKGROUND

Acute liver failure is a devastating clinical syndrome with a persistently high mortality rate despite critical care advances. Orthotopic liver transplantation (OLT) is a life-saving treatment in selected cases, but effective use of this limited resource requires accurate prognostication because of surgical risks and the requirement for subsequent life-long immunosuppression.

AIM

To review the aetiology of acute liver failure, discuss the evidence behind critical care management strategies and examine potential treatment alternatives to OLT.

METHODS

Literature review using Ovid, PubMed and recent conference abstracts.

RESULTS

Paracetamol remains the most common aetiology of acute liver failure in developed countries, whereas acute viral aetiologies predominate elsewhere. Cerebral oedema is a major cause of death, and its prevention and prompt recognition are vital components of critical care support, which strives to provide multiorgan support and 'buy time' to permit either organ regeneration or psychological and physical assessment prior to acquisition of a donor organ. Artificial liver support systems do not improve mortality in acute liver failure, whilst most other interventions have limited evidence bases to support their use.

CONCLUSION

Acute liver failure remains a truly challenging condition to manage, and requires early recognition and transfer of patients to specialist centres providing intensive, multidisciplinary input and, in some cases, OLT.

The role of endogenous bone morphogenetic proteins in normal skeletal repair

Bone morphogenetic proteins play a key role in the regulation of the three major phases of fracture healing; the inflammatory response, the chondrogenic stage and the osteogenic stage. BMP-2 and 4 show a rapid response during the initial inflammatory stage, and BMP-2 has been shown to be essential for fracture healing to occur. BMP-2 and 4 are also present in the chondrogenic stage, although expression levels of BMP-3b (GDF10) and BMP-6 seemingly have specific peaks at day 7, suggesting a crucial role in this process. BMP-3, 4 and 5 are also abundantly present during this stage. In the osteogenic stage studies have shown that BMPs 1, 2, 3, 3b, 4, 5, 6, 7 and 8A have high levels of expression. It is important to note that of these, BMP-3 and 4 have a peak in their expression and BMP-7 and 8A are almost exclusively expressed during day 14 and 21. The expression of the different BMPs in these stages is believed to be orchestrated by autoregulatory activation between the BMPs, negative feed back loops and external antagonists. Alterations of the BMP signaling pathway, either by direct targeting of the BMPs or by their inhibitors has been shown to interfere with embryologic skeletal development and a post natal regenerative repair following skeletal trauma.

Mutations in 15-hydroxyprostaglandin dehydrogenase cause primary hypertrophic osteoarthropathy

Digital clubbing, recognized by Hippocrates in the fifth century BC, is the outward hallmark of pulmonary hypertrophic osteoarthropathy, a clinical constellation that develops secondary to various acquired diseases, especially intrathoracic neoplasm. The pathogenesis of clubbing and hypertrophic osteoarthropathy has hitherto been poorly understood, but a clinically indistinguishable primary (idiopathic) form of hypertrophic osteoarthropathy (PHO) is recognized. This familial disorder can cause diagnostic confusion, as well as significant disability. By autozygosity methods, we mapped PHO to chromosome 4q33-q34 and identified mutations in HPGD, encoding 15-hydroxyprostaglandin dehydrogenase, the main enzyme of prostaglandin degradation. Homozygous individuals develop PHO secondary to chronically elevated prostaglandin E(2) levels. Heterozygous relatives also show milder biochemical and clinical manifestations. These findings not only suggest therapies for PHO, but also imply that clubbing secondary to other pathologies may be prostaglandin mediated. Testing for HPGD mutations and biochemical testing for HPGD deficiency in patients with unexplained clubbing might help to obviate extensive searches for occult pathology.

Exploring the Cause of the Most Ancient Clinical Sign of Medicine: Finger Clubbing

OBJECTIVE

Digital clubbing is regarded as the oldest clinical sign of medicine. The cause of this unique finger deformity has remained elusive throughout the centuries. For 3 decades our group has studied the etiology of this acropachy. This article reviews the current knowledge on the cause of digital clubbing.

METHODS

PubMed database (www.pubmed.gov) was accessed. In clinical queries/clinical study service we entered "clubbing" or "hypertrophic osteoarthropathy," choosing the "etiology" category with a "broad sensitive" search scope. The time span was from January 1975 to August 2006. Additionally, this article narrates the chronology of our research on the pathogenesis of clubbing.

RESULTS

The many dreadful internal illnesses associated with digital clubbing have in common enhanced platelet/endothelial cell activation. Emerging evidence suggests that, in hypoxic conditions with extrapulmonary shunting of blood, large megakaryocyte fragments fail to enter the pulmonary circulation. Instead they gain access to the systemic circulation impacting at the most distal sites, there releasing growth factors and thus inducing clubbing. In cases of lung cancer, the purported growth factor could gain direct entrance to the systemic circulation. Vascular endothelial growth factor (VEGF) may play a central role in the development of digital clubbing. It is a platelet-derived factor induced by hypoxia, and it is also abnormally produced by diverse malignant tumors fostering their uncontrolled growth. On the other hand VEGF produces vascular hyperplasia, edema, and fibroblast/osteoblast proliferation. Such are clubbing histologic characteristics. Enhanced VEGF expression has been reported in practically all internal illnesses associated with this type of finger deformity. Recent studies have demonstrated high circulating levels as well as increased local expression of VEGF in different groups of patients with digital clubbing.

CONCLUSION

Abnormal expression of VEGF may be the cause of digital clubbing.

New technologies for the enhancement of skeletal repair

Although fracture healing is a well-optimized biological process that leads to healing, approximately 10-20% of fractures result in impaired or delayed healing and these fractures may benefit from the use of biotechnologies to enhance skeletal repair. Peptide signaling molecules such as the bone morphogenetic proteins have been shown to stimulate the healing of fresh fractures, nonunions, and spinal fusions and side effects from their use appear to be minimal. Other growth factors currently being studied for local application include growth and differentiation factor-5 (GDF-5), vascular endothelial growth factor (VEGF), transforming growth factor beta (TGFbeta), and platelet-derived growth factor (PDGF). Molecules such as prostaglandin E receptor agonists and the thrombin-related peptide, TP508, have shown promise in animal models of fracture repair. Gene therapy using various growth factors or combinations of factors might also aid in fracture repair, particularly as new methods for delivery that do not require viral vectors are developed. Systemic therapy with agents such as parathyroid hormone (PTH), growth hormone (GH), and the HMG-CoA reductase inhibitors are also under investigation. As these and other technologies are shown to be safe and effective, their use will become a part of the standard of care in managing skeletal injuries.

Lactams as EP4 Prostanoid Receptor Agonists. 3. Discovery of N-Ethylbenzoic Acid 2-Pyrrolidinones as Subtype Selective Agents

Two distinct synthetic schemes were applied to access heteroatom-containing alpha-chain lactams or lactams terminated as aryl acids. The latter lactams were devised using a pharmacophore for EP(4) receptor activity. gamma-Lactams were characterized for their prostanoid EP receptor affinities and EP(4) activity and found to be selective for the EP(2) and EP(4) receptors or selective for the EP(4) subtype. Benzoic acid 17 displayed enhanced in vivo exposure relative to 3.

Nucleoside analogues and other antivirals for treatment of hepatitis B in the peritransplant period

Chronic HBV infection is a common cause of advanced liver disease that is associated with substantial mortality. Furthermore, chronic hepatitis B was historically a controversial indication for liver transplantation because of a low post-transplant survival, with graft infection being the major contributor to adverse outcomes. The initial use of hepatitis B immune globulin as prophylaxis, followed later by combined therapy with lamivudine, markedly reduced viral recurrence and improved the survival of patients transplanted for acute or chronic hepatitis B with liver failure. Lamivudine alone can also be used for long-term prophylaxis against de novo HBV infection that can be transmitted by organs from donors positive for anti-HBc or anti-HBs. When used in patients with decompensated chronic hepatitis B with cirrhosis, lamivudine has been shown to improve clinical manifestations, prolong pretransplant survival, and defer, or even obviate, the need for transplantation. Despite prophylaxis, viral mutations with breakthrough reinfection may occur and lead to liver failure. The recently approved adefovir dipivoxil, which is active against lamivudine-resistant mutation, and other nucleoside analogs that are in various phases of development, offer hope as rescue therapy for viral recurrence. Other therapeutic alternatives in the future may include gene therapy and immune interventions.

Raynaud's phenomenon in older adults: diagnostic considerations and management

Raynaud's phenomenon (RP) is characterised by sensitivity to cold temperatures associated with either biphasic or uniphasic change in colour of the digits. Since few studies are available which include older adults, the prevalence of RP in the older adult population is estimated from surveys or studies of the general population. The causes of RP in older adults may differ significantly from those in young adults and, therefore, so would the evaluation of RP. Because of comorbitis that accompany advancing age, the management of RP in older adult patients must take into consideration toxicity and adverse reactions that may develop, especially in the frail individual. Although nonpharmacological therapy is preferable, slow-release calcium antagonists provide a relatively well tolerated and effective treatment for moderate to severe RP in older adult patients. Aggressive treatment including hospitalisation is appropriate for older adult patients during periods of critical digital ischaemia associated with RP.

Oral prostaglandin (PGE2) therapy for chronic viral hepatitis B and C

The cytoprotective effects of prostaglandins have been utilized in the prevention of hepatitis B virus reactivation after liver transplantation. This pilot study evaluated the effects of oral prostaglandin E2 (PGE2) in chronic viral hepatitis B and C. Twenty patients with chronic hepatitis B and 20 patients with chronic hepatitis C received 4mg day-1 PGE2 for 6 months. The lymphocyte antiviral enzyme 2',5'-oligoadenylate synthetase (2',5'-OAS) and peripheral blood monocyte procoagulant activity (PCA) were measured before, during and after the treatment. Three of 20 hepatitis B and five of 20 hepatitis C patients withdrew from the study. Eight of 17 hepatitis B patients responded: in seven of these eight patients, serum alanine aminotransferase (ALT) levels normalized; loss of viral replication was sustained in all eight patients; and seroconversion from hepatitis Be antigen (HBeAg) to hepatitis Be antibody (HBeAb) positivity occurred in seven patients over the 48-week duration of this study. In 14 of the 15 hepatitis C patients, hepatitis C virus (HCV) RNA remained detectable and the serum ALT levels remained elevated. 2',5'-OAS levels and PCA values did not correlate with other markers of response to PGE2 therapy in either chronic hepatitis B or C. In summary, PGE2 was associated with sustained loss of viral replication in 47% of chronic hepatitis B patients; no beneficial effects were apparent in chronic hepatitis C.

Attenuation of ischemic liver injury by prostaglandin E1 analogue, misoprostol, and prostaglandin I2 analogue, OP-41483

BACKGROUND

Prostaglandin has been reported to have protective effects against liver injury. Use of this agent in clinical settings, however, is limited because of drug-related side effects. This study investigated whether misoprostol, prostaglandin E1 analogue, and OP-41483, prostaglandin I2 analogue, which have fewer adverse effects with a longer half-life, attenuate ischemic liver damage.

STUDY DESIGN

Thirty beagle dogs underwent 2 hours of hepatic vascular exclusion using venovenous bypass. Misoprostol was administered intravenously for 30 minutes before ischemia and for 3 hours after reperfusion. OP-41483 was administered intraportally for 30 minutes before ischemia (2 microg/kg/min) and for 3 hours after reperfusion (0.5 microg/kg/min). Animals were divided into five groups: untreated control group (n=10); high-dose misoprostol (total 100 microg/kg) group (MP-H, n=5); middle-dose misoprostol (50 microg/kg) group (MP-M, n=5); low-dose misoprostol (25 microg/kg) group (MP-L, n=5); and OP-41483 group (OP, n=5). Animal survival, hepatic tissue blood flow (HTBF), liver function, and histology were analyzed.

RESULTS

Two-week animal survival rates were 30% in control, 60% in MP-H, 100% in MP-M, 80% in MP-L, and 100% in OP. The treatments with prostaglandin analogues improved HTBF, and attenuated liver enzyme release, adenine nucleotrides degradation, and histologic abnormalities. In contrast to the MP-H animals that exhibited unstable cardiovascular systems, the MP-M, MP-L, and OP animals experienced only transient hypotension.

CONCLUSIONS

These results indicate that misoprostol and OP-41483 prevent ischemic liver damage, although careful dose adjustment of misoprostol is required to obtain the best protection with minimal side effects.

Effect of human milk prostaglandins and lactoferrin on respiratory syncytial virus and rotavirus

The effect of lactoferrin and prostaglandins E and F2 alpha on the growth of rotavirus and respiratory syncytial virus in cell culture was investigated. Lactoferrin inhibited the growth of respiratory syncytial virus at a concentration tenfold lower than that normally present in human milk. The prostaglandins had no effect on either virus growth, even at a concentration of 100-fold more than that found in human milk. Lactoferrin may have some antiviral properties in human milk in addition to its known antibacterial functions.

Plasma prostaglandin E1 concentrations and hemodynamics during intravenous infusions of prostaglandin E1 in humans and swine

Prostaglandin (PG) E1 administered intravenously has been used for the treatment of primary nonfunction of hepatic allografts and fulminant hepatic failure. It has been proposed that this therapy may improve hepatic blood flow via the vasodilating properties of PGE1. However, PGE1 undergoes extensive metabolic inactivation by the lung and the concentration of PGE1 reaching the liver during intravenous administration has not been determined. Thus, we measured plasma PGE1 concentrations in patients with hepatic dysfunction being treated with PGE1 and in a swine model of PGE1 infusion. We also determined the hemodynamic effects of PGE1 infusion in swine. Blood was sampled from the pulmonary artery, carotid artery, portal vein, and hepatic vein in swine infused with PGE1 (range, 0.67-4.9 microg/kg/hr) demonstrating: (1) a pulmonary extraction ratio of PGE1 of 0.78 +/- 0.12, (2) a splanchnic extraction ratio of PGE1 of 0.54 +/- 0.23, and (3) levels of PGE1 in the systemic circulation of </= 78 pg/ml, even at the highest infusion rates. Despite significant increases in body temperature and pulse rate, hepatic hemodynamics were not affected by the PGE1 infusions in healthy swine. Seven patients receiving intravenous PGE1 for hepatic dysfunction (0.11-1.30 microg/kg/hr) had a pulmonary extraction ratio of 0.69 +/- 0.17. Systemic arterial concentrations of PGE1 were </= 62 pg/ml. These results suggest that due to clearance of PGE2 in the pulmonary and splanchnic circulations, current clinical protocols for intravenous administration of PGE1 are not likely to affect perihepatic hemodynamics.