Genetic risk factors for hepatopulmonary syndrome in patients with advanced liver disease

Effects of Transjugular Intrahepatic Portosystemic Shunt on Renal and Pulmonary Function in Hepatic Decompensation with and without Hepatorenal and Hepatopulmonary Syndromes: A Review

Cirrhosis is often characterized by decreased liver function, ranging from a compensated, typically asymptomatic phase to a decompensated phase characterized by the appearance of ascites or variceal bleeding, and ultimately hepatorenal syndrome (HRS) or hepatopulmonary syndrome (HPS). The latter two complications are associated with a poor prognosis and limited treatment efficacy. In cases of ascites or variceal bleeding resistant to medical therapy, transjugular intrahepatic portosystemic shunt (TIPS) is effective and safe. Shunting blood by TIPS diverts portal blood to the systemic circulation, potentially increasing systemic blood volume and benefiting renal function. However, TIPS could also divert nitric oxide to the systemic circulation, potentially worsening systemic hypotension and perfusion, which could be detrimental to renal function. Available evidence indicates that TIPS often improves renal function in patients with portal hypertension, with or without HRS. No studies have shown persistently decreased renal function after TIPS. However, these data are insufficient to support a recommendation for the use of TIPS specifically for HRS. In patients without pre-existing HPS, TIPS does not appear to significantly affect pulmonary gas exchange. Results of TIPS in HPS have been inconsistent; some studies have shown improvement, but effects were transient. No studies have shown a persistent decline in pulmonary function after TIPS. The evidence supports the need for large randomized controlled trials to investigate the beneficial effects of TIPS for HRS. Similar pulmonary function data are less clear regarding TIPS for HPS. The aim of the current report was to review the literature regarding the effects of TIPS on renal and pulmonary function in hepatic decompensation, with or without the development of HRS or HPS.

HEPATOPULMONARY SYNDROME IN PEDIATRIC PATIENTS WITH PORTAL HYPERTENSION - AN INTEGRATIVE REVIEW

BACKGROUND

Hepatopulmonary syndrome (HPS) is characterized by the triad of abnormal arterial oxygenation caused by intrapulmonary vascular dilatations (IPVD) in the setting of advanced liver disease or portal hypertension, impacting the patient's quality of life and survival. There are still many gaps in the literature on this topic, especially in pediatrics, with practices frequently based on extrapolation of data obtained from adults.

OBJECTIVE

Provide a synthesis of the current knowledge about HPS in children.

METHODS

The research was carried out through narrative review. The databases used for the search include Medline, Embase, Elsevier, Lilacs and Scielo. The keywords used were "hepatopulmonary syndrome" AND child, children, infant, preschool, pediatric.

RESULTS

In cirrhotic children, the prevalence of HPS can reach up to 42.5%, and it is even more common in those whose underlying condition is biliary atresia, reaching up to 63%. Screening with pulse oximetry (O2 saturation <96%), unlike in adults, has low sensitivity in the pediatric age group. Management involves supportive care with oxygen therapy; liver transplantation is the only definitive treatment to reverse the condition and HPS is considered an exceptional criterion for waitlist. The waitlist mortality is similar among children listed by HPS as a special criterion when compared to those listed for other reasons. The reported rates of complete resolution of hypo-xemia after liver transplantation are close to 100% in children. The post-liver transplantation survival is similar or slightly lower in children with HPS when compared to those without HPS. Contrary to findings from adults, no differences were found in post- liver transplantation mortality between children of different hypoxemia ranges, although longer mechanical ventilation time and hospital stay were observed in children with PaO2 <50 mmHg.

CONCLUSION

HPS is not an uncommon complication of cirrhosis in children and adolescents, particularly when biliary atresia is the underlying condition. There are still many gaps to be filled regarding the condition, and this article demonstrates that not all data obtained in studies with adults reflects the disease's behavior in pediatrics, especially concerning prognosis.

Imaging in hepatopulmonary syndrome-case report. A multicenter approach during the coronavirus pandemic

A 60-year-old lady with alcoholic liver disease developed central cyanosis and orthodeoxia. A technetium-99m macro-aggregated albumin lung perfusion scan and contrast echocardiogram were performed. A 13% right to left shunt was calculated from the macro-aggregated albumin scan. There were more bubbles in the left heart than the right at the end of the contrast echocardiogram. Hepatopulmonary syndrome was therefore diagnosed. The patient had a liver transplant five days after these investigations. Further discussion about hepatopulmonary syndrome will be provided. Normally, macro-aggregated albumin scans are performed in few centers, however as this was at the height of the coronavirus pandemic, the scan needed to be performed locally to reduce the chance of the patient getting coronavirus. Local radiographers were remotely instructed on conducting the macro-aggregated albumin scan by a larger center to provide a timely and important investigation in a logistically difficult scenario.

Pulmonary Assessment of the Liver Transplant Recipient

Respiratory symptoms and hypoxemia can complicate chronic liver disease and portal hypertension. Various pulmonary disorders affecting the pleura, lung parenchyma, and pulmonary vasculature are seen in end-stage liver disease, complicating liver transplantation (LT). Approximately 8% of cirrhotic patients in an intensive care unit develop severe pulmonary problems. These disorders affect waiting list mortality and posttransplant outcomes. A thorough history, physical examination, and appropriate laboratory tests help diagnose and assess the severity to risk stratify pulmonary diseases before LT. Hepatopulmonary syndrome (HPS), portopulmonary hypertension (POPH), and hepatic hydrothorax (HH) are respiratory consequences specific to cirrhosis and portal hypertension. HPS is seen in 5-30% of cirrhosis cases and is characterized by impaired oxygenation due to intrapulmonary vascular dilatations and arteriovenous shunts. Severe HPS is an indication of LT. The majority of patients with HPS resolve their hypoxemia after LT. When pulmonary arterial hypertension occurs in patients with portal hypertension, it is called POPH. All other causes of pulmonary arterial hypertension should be ruled out before labeling as POPH. Since severe POPH (mean pulmonary artery pressure [mPAP] >50 mm Hg) is a relative contraindication for LT, it is crucial to screen for POPH before LT. Those with moderate POPH (mPAP >35 mm Hg), who improve with medical therapy, will benefit from LT. A transudative pleural effusion called hepatic hydrothorax (HH) is seen in 5-10% of people with cirrhosis. Refractory cases of HH benefit from LT. In recent years, increasing clinical expertise and advances in the medical field have resulted in better outcomes in patients with moderate to severe pulmonary disorders, who undergo LT.

Molecular Genetics of Abnormal Redox Homeostasis in Type 2 Diabetes Mellitus

Numerous studies have shown that oxidative stress resulting from an imbalance between the production of free radicals and their neutralization by antioxidant enzymes is one of the major pathological disorders underlying the development and progression of type 2 diabetes (T2D). The present review summarizes the current state of the art advances in understanding the role of abnormal redox homeostasis in the molecular mechanisms of T2D and provides comprehensive information on the characteristics and biological functions of antioxidant and oxidative enzymes, as well as discusses genetic studies conducted so far in order to investigate the contribution of polymorphisms in genes encoding redox state-regulating enzymes to the disease pathogenesis.

Portopulmonary Hypertension: Management and Liver Transplantation Evaluation

Portopulmonary hypertension (POPH) affects 5% to 6% of patients with advanced liver disease and accounts for 5% to 15% of pulmonary arterial hypertension (PAH) cases. Compared with idiopathic PAH, POPH is associated with significantly worse survival. Recent studies have improved our understanding of the role of both PAH therapy and liver transplantation (LT) in the management of POPH and their impact on overall prognosis. We performed a review of the published literature to summarize the available evidence and guidelines regarding the diagnosis and management of POPH. POPH is defined by the presence of precapillary PH in the context of portal hypertension. POPH is associated with increased perioperative risk at the time of LT, which can be stratified by mean pulmonary arterial pressure and pulmonary vascular resistance. Screening with echocardiography is recommended in all LT candidates to facilitate detection and treatment of POPH. Despite a paucity of evidence, POPH is treated similarly to idiopathic PAH with PAH therapy. These therapies are associated with improved pulmonary hemodynamics and facilitation of safe LT. LT can result in improvement or resolution of POPH in half of patients and has been associated with improved survival in highly selected patients. The prognosis in POPH is poor and is impacted by the severity of both PH and liver disease. Management with a combination of PAH therapy and LT in selected patients has been associated with improved pulmonary hemodynamics and survival.

Impact of hepatopulmonary syndrome in liver transplantation candidates and the role of angiogenesis

BACKGROUND

Hepatopulmonary syndrome affects 10-30% of patients with cirrhosis and portal hypertension. We evaluated the serum angiogenic profile of hepatopulmonary syndrome and assessed the clinical impact of hepatopulmonary syndrome in patients evaluated for liver transplantation.

METHODS

The Pulmonary Vascular Complications of Liver Disease 2 study was a multicentre, prospective cohort study of adults undergoing their first liver transplantation evaluation. Hepatopulmonary syndrome was defined as an alveolar-arterial oxygen gradient ≥15 mmHg (≥20 mmHg if age >64 years), positive contrast-enhanced transthoracic echocardiography and absence of lung disease.

RESULTS

We included 85 patients with hepatopulmonary syndrome and 146 patients without hepatopulmonary syndrome. Patients with hepatopulmonary syndrome had more complications of portal hypertension and slightly higher Model for End-Stage Liver Disease-Na score compared to those without hepatopulmonary syndrome (median (interquartile range) 15 (12-19) versus 14 (10-17), p=0.006). Hepatopulmonary syndrome patients had significantly lower 6-min walk distance and worse functional class. Hepatopulmonary syndrome patients had higher circulating angiopoietin 2, Tie2, tenascin C, tyrosine protein kinase Kit (c-Kit), vascular cell adhesion molecule 1 and von Willebrand factor levels, and lower E-selectin levels. Patients with hepatopulmonary syndrome had an increased risk of death (hazard ratio 1.80, 95% CI 1.03-3.16, p=0.04), which persisted despite adjustment for covariates (hazard ratio 1.79, 95% CI 1.02-3.15, p=0.04). This association did not vary based on levels of oxygenation, reflecting the severity of hepatopulmonary syndrome.

CONCLUSION

Hepatopulmonary syndrome was associated with a profile of abnormal systemic angiogenesis, worse exercise and functional capacity, and an overall increased risk of death.

Hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is a pulmonary vascular complication of liver disease, which adversely affects prognosis. The disease is characterised by intrapulmonary vascular dilatations and shunts, resulting in impaired gas exchange. A complex interaction between the liver, the gut and the lungs, predominately impacting pulmonary endothelial cells, immune cells and respiratory epithelial cells, is responsible for the development of typical pulmonary alterations seen in HPS. Liver transplantation is the only therapeutic option and generally reverses HPS. Since the implementation of the model for end-stage liver disease (MELD) standard exception policy, outcomes in patients with HPS have been significantly better than they were in the pre-MELD era. This review summarises current knowledge and highlights what’s new regarding the diagnosis and management of HPS, and our understanding of pathogenesis based on experimental models and translational studies.

Hepatopulmonary Syndrome and Portopulmonary Hypertension: Pulmonary Vascular Complications of Liver Disease

Pulmonary vascular disease is a frequent complication of chronic liver disease and portal hypertension, affecting up to 30% of patients. There are two distinct pulmonary vascular complications of liver disease: hepatopulmonary syndrome (HPS) and portopulmonary hypertension (POPH). HPS affects 25% of patients with chronic liver disease and is characterized by intrapulmonary vasodilatation and abnormal arterial oxygenation. HPS negatively impacts quality of life and is associated with a 2-fold increased risk of death compared to controls with liver disease without HPS. Angiogenesis, endothelin-1 mediated endothelial dysfunction, monocyte influx, and alveolar type 2 cell dysfunction seem to play important roles in disease pathogenesis but there are currently no effective medical therapies. Fortunately, HPS resolves following liver transplant (LT) with improvements in hypoxemia. POPH is a subtype of pulmonary arterial hypertension (PAH) characterized by an elevated mean pulmonary arterial pressure and pulmonary vascular resistance in the setting of normal left-sided filling pressures. POPH affects 5% to 6% of patients with chronic liver disease. Although the pathogenesis has not been fully elucidated, endothelial dysfunction, inflammation, and estrogen signaling have been identified as key pathways involved in disease pathogenesis. POPH is typically treated with PAH targeted therapy and may also improve with liver transplantation in selected patients. This article highlights what is currently known regarding the diagnosis, management, pathobiology, and outcomes of HPS and POPH. Ongoing research is needed to improve understanding of the pathophysiology and outcomes of these distinct and often misunderstood pulmonary vascular complications of liver disease. © 2021 American Physiological Society. Compr Physiol 11:1-22, 2021.

Roles of Genetic Predisposition in the Sex Bias of Pulmonary Pathophysiology, as a Function of Estrogens : Sex Matters in the Prevalence of Lung Diseases

In addition to studies focused on estrogen mediation of sex-different regulation of systemic circulations, there is now increasing clinical relevance and research interests in the pulmonary circulation, in terms of sex differences in the morbidity and mortality of lung diseases such as inherent-, allergic- and inflammatory-based events. Thus, female predisposition to pulmonary artery hypertension (PAH) is an inevitable topic. To better understand the nature of sexual differentiation in the pulmonary circulation, and how heritable factors, in vivo- and/or in vitro-altered estrogen circumstances and changes in the live environment work in concert to discern the sex bias, this chapter reviews pulmonary events characterized by sex-different features, concomitant with exploration of how alterations of genetic expression and estrogen metabolisms trigger the female-predominant pathological signaling. We address the following: PAH (Sect.7.2) is characterized as an estrogenic promotion of its incidence (Sect. 7.2.2), as a function of specific germline mutations, and as an estrogen-elicited protection of its prognosis (Sect.7.2.1). More detail is provided to introduce a less recognized gene of Ephx2 that encodes soluble epoxide hydrolase (sEH) to degrade epoxyeicosatrienic acids (EETs). As a susceptible target of estrogen, Ephx2/sEH expression is downregulated by an estrogen-dependent epigenetic mechanism. Increases in pulmonary EETs then evoke a potentiation of PAH generation, but mitigation of its progression, a phenomenon similar to the estrogen-paradox regulation of PAH. Additionally, the female susceptibility to chronic obstructive pulmonary diseases (Sect. 7.3) and asthma (Sect.7.4), but less preference to COVID-19 (Sect. 7.5), and roles of estrogen in their pathogeneses are briefly discussed.

Liver epigenome changes in patients with hepatopulmonary syndrome: A pilot study

The hepatopulmonary syndrome (HPS) is defined by the presence of pulmonary gas exchange abnormalities due to intrapulmonary vascular dilatations in patients with chronic liver disease. Changes in DNA methylation reflect the genomic variation. Since liver transplant (LT) reverts HPS we hypothesized that it may be associated with specific liver epigenetic changes. Thus, the aim of this study was to investigate the role of the liver epigenome in patients with HPS. We extracted DNA from paraffin embedded liver tissue samples from 10 patients with HPS and 10 age-, sex- and MELD (Model for End-stage Liver Disease)-matched controls. DNA methylation was determined using the 850K array (Illumina). Weighted Gene Co-expression Network Analysis (WGCNA) was used to identify modules related to defining physiologic characteristics of HPS. Only 12 out of the 20 liver biopsies (7 HPS and 5 controls) had sufficient quality to be analyzed. None of the 802,688 DNA probes analyzed in the case control comparison achieved a significant False Discovery Rate (FDR). WGCNA identified 5 co-methylated gene-modules associated to HPS markers, mainly related to nervous and neuroendocrine system, apoptotic processes, gut bacterial translocation, angiogenesis and vascular remodeling ontologies. To conclude, HPS is associated with nervous/neuroendocrine system and vascular remodeling related liver epigenetic changes.

Cardiovascular disorders in patients with congenital portosystemic shunts: 23 years of experience in a tertiary referral centre

BACKGROUND

Congenital portosystemic shunts are rare vascular malformations that may have an impact on the heart-lung system. Associated congenital and/or acquired heart diseases are poorly reported.

AIMS

To analyse cardiovascular disorders within a large congenital portosystemic shunt population, and develop a diagnostic strategy.

METHODS

Among the 168 consecutive fetuses and children referred for congenital portosystemic shunt (1996-2019), patients presenting with at least one cardiovascular disorder, including congenital heart disease, heart failure, portopulmonary hypertension and/or hepatopulmonary syndrome, were reviewed retrospectively. Cardiovascular disorders were detected using echocardiography and one or more of the following: right-sided heart catheterization; contrast-enhanced transthoracic echocardiography; or lung perfusion radionuclide scan.

RESULTS

Overall, 46/168 patients with a congenital portosystemic shunt (27.4%) had one or more clinically significant cardiovascular disorders. Congenital heart disease was present in 28 patients, including six with left heterotaxy. Heart failure was present in six fetuses and 21 neonates (eight without congenital heart disease, and 13 with congenital heart disease). In neonates without congenital heart disease, heart function recovered by the age of 3years. Portopulmonary hypertension was identified in 11 patients (mean age at diagnosis: 9years); it was fatal in one patient, and remained stable in five of six patients after congenital portosystemic shunt closure. In six patients, hepatopulmonary syndrome presented as hypoxia (mean age at diagnosis: 5.3years), which reversed after congenital portosystemic shunt closure.

CONCLUSIONS

Evaluation and monitoring of the cardiopulmonary status of patients with a congenital portosystemic shunt is mandatory to detect and prevent cardiovascular complications. Furthermore, congenital portosystemic shunts must be sought in patients with unexplained cardiovascular disorders, especially when malformations are present.

Pulmonary manifestations of chronic liver disease: a comprehensive review

Hepatopulmonary syndrome (HPS) and porto-pulmonary hypertension (PoPH) represent relatively common pulmonary vascular complications of advanced liver disease. Despite distinct differences in their pathogenetic background, both clinical states are characterized by impaired arterial oxygenation and limited functional status, and are associated with increased pre-transplantation mortality. Accumulation of ascitic fluid in the pleural cavity, known as hepatic hydrothorax (HH), is another frequent manifestation of decompensated cirrhosis, which may cause severe respiratory dysfunction, depending on the volume of the effusion, the rapidity of its development and its resistance to therapeutic measures. Orthotopic liver transplantation constitutes the only effective treatment able to resolve the pulmonary complications of liver disease. A prioritization policy for liver transplantation has evolved over the past years regarding advanced stages of HPS, yielding favorable outcomes regarding post-transplantation survival and HPS resolution. In contrast, severe PoPH is associated with poor post-transplantation survival. Hence, liver transplantation is recommended only for patients with PoPH and an acceptable reduction in pulmonary pressure values, after receiving PoPH-targeted vasodilating therapy. This review focuses on basic pathogenetic and diagnostic principles and discusses the current therapeutic approaches regarding HPS, PoPH, and HH.

Pulmonary Complications of Portal Hypertension

The most common pulmonary complications of chronic liver disease are hepatic hydrothorax, hepatopulmonary syndrome, and portopulmonary hypertension. Hepatic hydrothorax is a transudative pleural effusion in a patient with cirrhosis and no evidence of underlying cardiopulmonary disease. Hepatic hydrothorax develops owing to the movement of ascitic fluid into the pleural space. Hepatopulmonary syndrome and portopulmonary hypertension are pathologically linked by the presence of portal hypertension; however, their pathophysiologic mechanisms are significantly different. Hepatopulmonary syndrome is characterized by low pulmonary vascular resistance secondary to intrapulmonary vascular dilatations and hypoxemia; portopulmonary hypertension features elevated pulmonary vascular resistance and constriction/obstruction within the pulmonary vasculature.

Meta-analysis of massively parallel reporter assays enables prediction of regulatory function across cell types

Deciphering the potential of noncoding loci to influence gene regulation has been the subject of intense research, with important implications in understanding genetic underpinnings of human diseases. Massively parallel reporter assays (MPRAs) can measure regulatory activity of thousands of DNA sequences and their variants in a single experiment. With increasing number of publically available MPRA data sets, one can now develop data-driven models which, given a DNA sequence, predict its regulatory activity. Here, we performed a comprehensive meta-analysis of several MPRA data sets in a variety of cellular contexts. We first applied an ensemble of methods to predict MPRA output in each context and observed that the most predictive features are consistent across data sets. We then demonstrate that predictive models trained in one cellular context can be used to predict MPRA output in another, with loss of accuracy attributed to cell-type-specific features. Finally, we show that our approach achieves top performance in the Fifth Critical Assessment of Genome Interpretation "Regulation Saturation" Challenge for predicting effects of single-nucleotide variants. Overall, our analysis provides insights into how MPRA data can be leveraged to highlight functional regulatory regions throughout the genome and can guide effective design of future experiments by better prioritizing regions of interest.

Sorafenib in Hepatopulmonary Syndrome: A Randomized, Double-Blind, Placebo-Controlled Trial

The tyrosine kinase inhibitor sorafenib improves hepatopulmonary syndrome (HPS) in an experimental model. However, the efficacy and adverse effect profile in patients with HPS are unknown. We aimed to determine the effect of sorafenib on the alveolar-arterial oxygen gradient (AaPO₂ ) at 3 months in patients with HPS. We performed a randomized, double-blind, placebo-controlled parallel trial of sorafenib in patients with HPS at 7 centers. A total of 28 patients with HPS were randomized to sorafenib 400 mg by mouth daily or a matching placebo in a 1:1 ratio. We found no statistically significant difference in the median change in AaPO₂ from baseline to 12 weeks between the patients allocated to sorafenib (4.5 mm Hg; IQR, -3.8 to 7.0 mm Hg) and those allocated to placebo (-2.4 mm Hg; IQR, -4.8 to 8.2 mm Hg; P = 0.70). There was also no difference between the groups in terms of degree of intrapulmonary shunting by contrast echocardiography. Sorafenib significantly reduced circulating levels of angiogenic markers, including vascular endothelial growth factor receptors (P < 0.01) and TIE2-expressing M2 monocytes (P = 0.03), but it reduced the mental component scores of the Short Form 36 (P = 0.04), indicating a worse quality of life. In conclusion, sorafenib did not change the AaPO₂ or other disease markers at 3 months in patients with HPS. Alternative antiangiogenic therapies or treatments targeting other pathways should be investigated.

Association between Serum Urate and Risk of Hypertension in Menopausal Women with XDH Gene

Elevated serum urate (sUA) concentrations have been associated with an increased risk of hypertension. We aimed to examine the association of sUA concentration on the risk of hypertension in pre- and post-menopausal women and investigated the association between the polymorphism of the xanthine dehydrogenase gene and the risk of hypertension. Among 7294 women, 1415 premenopausal and 5879 postmenopausal women were recruited. Anthropometric parameters as risk factors of hypertension were identify by logistic regression models. In addition, we investigated an association between xanthine dehydrogenase gene and sUA and their combined associations on the risk of hypertension. Body mass index (BMI) and waist circumference (WC) were significantly increased in accordance to the increase of sUA levels (p < 0.001). Multivariate logistic regression analysis showed postmenopausal women with a high sUA and high BMI were 3.18 times more likely to have hypertension than in those with normal and lower sUA (Odds ratio: 3.18, 95% confidence interval: 2.54–3.96). Postmenopausal women with a high WC were 1.62 times more likely to have hypertension than in those with normal and lower sUA. Subjects with the AG genotype of rs206860 was found to be at lower risk of hypertension (odd ratio: 0.287, 95% confidence interval: 0.091–0.905, p = 0.033). This cross-sectional study indicated a high sUA is associated with a higher risk of hypertension in postmenopausal women. Further well-designed prospective studies in other populations are warranted to validate our results.

Vascular syndromes in liver cirrhosis

Liver cirrhosis is associated with multiple vascular syndromes affecting almost all body systems. Many of these syndromes are directly related to impaired liver function and sometimes reversible after liver transplantation while others arise secondary to portal hypertension and ascites. Altered expression of angiogenic and vasoactive compounds (most importantly nitric oxide), endothelial dysfunction, dysregulated neurohormonal control, and systemic inflammatory state play differential roles in mediating homeostatic instability and abnormal vasogenic response. Important vascular features encountered in liver disease include portal hypertension, splanchnic overflow, abnormal angiogenesis and shunts, portopulmonary syndrome, hepatopulmonary syndrome, and systemic hyperdynamic circulation. Redistribution of effective circulatory volume deviating from vital organs and pooling in splanchnic circulation is also encountered in liver patients which may lead to devastating outcomes as hepatorenal syndrome. Etiologically, vascular syndromes are not isolated phenomena and vascular dysfunction in one system may lead to the development of another in a different system. This review focuses on understanding the pathophysiological factors underlying vascular syndromes related to chronic liver disease and the potential links among them. Many of these syndromes are associated with high mortality, thus it is crucial to look for early biomarkers for these syndromes and develop novel preventive and therapeutic strategies.

Potential Clinical Targets in Hepatopulmonary Syndrome: Lessons From Experimental Models

Hepatopulmonary syndrome (HPS) is a relatively common and potentially severe pulmonary complication of cirrhosis with increased risk of mortality. In experimental models, a complex interaction between pulmonary endothelial cells, monocytes, and the respiratory epithelium, which produces chemokines, cytokines, and angiogenic growth factors, causes alterations in the alveolar microvasculature, resulting in impaired oxygenation. Model systems are critical for evaluating mechanisms and for preclinical testing in HPS, due to the challenges of evaluating the lung in the setting of advanced liver disease in humans. This review provides an overview of current knowledge and recent findings in the rodent common bile duct ligation model of HPS, which recapitulates many features of human disease. We focus on the concepts of endothelial derangement, monocyte infiltration, angiogenesis, and alveolar type II cell dysfunction as main contributors and potential targets for therapy.

A case report of hepatopulmonary syndrome in hereditary hemorrhagic telangiectasia (HHT): Not all right-to-left shunting in HHT is due to pulmonary arteriovenous malformations

RATIONALE

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by abnormal vessel growth that results in telangiectasias and arteriovenous malformations (AVMs) in the skin, mucosa, and viscera. Up to 30% of patients with HHT exhibit pulmonary AVMs (PAVMs), clinically manifesting as right-to-left shunting and hypoxemia.

PATIENT CONCERNS

We report an unusual and novel case of a patient with HHT who lacked clinical sequelae of portal hypertension but presented to clinic with hypoxemia without dyspnea.

DIAGNOSES

Diagnostic workup revealed noncardiac right-to-left shunting due to hepatopulmonary syndrome (HPS) from HHT-induced portal hypertension rather than PAVMs. The diagnosis was confirmed by the absence of PAVMs on chest computed tomography and evidence of elevated portal pressures as noted by the presence of small esophageal varices on upper endoscopy and histologic findings on liver biopsy.

INTERVENTION

Due to the patient's mild symptoms, no further intervention was required. He was closely followed up in the outpatient setting for changes in symptoms and underwent annual screening for development of PAVMs.

OUTCOMES

The patient continues to do well clinically. He has not experienced worsening hypoxemia or dyspnea and has not developed PAVMs.

LESSONS

Given that management of hypoxemia in HPS drastically differs from that of hypoxemia due to PAVMs, this case demonstrates the importance of evaluating HHT patients for HPS if they exhibit impaired oxygenation and noncardiac right-to-leftshunting in the setting of hepatic arteriovenous shunting.

Different forms of pulmonary hypertension in a family with clinical and genetic evidence for hereditary hemorrhagic teleangectasia type 2

Hereditary hemorrhagic telangiectasia (HTT) is an autosomal dominant disease, most frequently caused by a mutation in either ENG or ACVRL1, which can be associated with pulmonary arterial hypertension (PAH). In this report, we describe a new unpublished ACVRL1 mutation segregating in three members of the same family, showing three different types of pulmonary hypertension (PH) in the absence of BMPR2 mutations. The first patient has a form of heritable PAH (HPAH) in the absence of hepatic arteriovenous malformations (AVMs); the second one has a severe form of portopulmonary hypertension (PoPAH) associated with multiple hepatic AVMs; the third one has hepatopulmonary syndrome (HPS) with numerous hepatic arteriovenous fistulas and a form of post-capillary PH due to high cardiac output. In summary, a single mutation in the ACVRL1 gene can be associated, in the same family, with an extreme phenotypic variability regarding not only the clinical presentation of HHT but also the type of PH in the absence of BMPR2 mutations. More studies are needed to evaluate if this variability can be explained by the presence of additional variants in other genes relevant for the pathogenesis of HHT.

Isolated Intrapulmonary Vascular Dilatations and the Risk of Developing Hepatopulmonary Syndrome in Liver Transplant Candidates

BACKGROUND

The natural history of intrapulmonary vascular dilations (IPVD) and their impact on patient outcomes in the setting of portal hypertension has only been described in small series.

AIMS

To assess the development of hepatopulmonary síndrome (HPS) in patients with isolated IPVD and to evaluate outcomes of IPVD and HPS among patients evaluated for liver transplantation (LT).

MATERIAL AND METHODS

Data from a prospective cohort of patients evaluated for LT with standardized screening for HPS were analyzed. IPVDs were defined as the presence of microbubbles in the left atrium > 3 cycles following right atrial opacification. HPS was defined as the presence of IPVD and hypoxemia (Alveolar-arterial gradient ≥ 15 mmHg) in the absence of concomitant cardiopulmonary disease.

RESULTS

A total of 104 patients with negative contrast-enhanced echocardiogram (CE) were compared to 63 patients with IPVD and 63 patients with HPS. Only four patients were categorized as ‘severe’ HPS based on degree of hipoxemia (defined as PaO2 < 60 mmHg). Twenty IPVD patients were followed with ABG over a mean duration of 21 months (range 9-43), of whom 7 (35%) subsequently met HPS criteria. Overall unadjusted survival from the time of LT evaluation using multi-state survival models that accounted for pre- and post-LT time was not statistically different among the three groups (negative CE, IPVD, and HPS; p > 0.5).

CONCLUSIONS

Patients with IPVD appear to have a substantial risk of developing oxygenation impairment over time and progress to HPS. In our cohort, survival in patients with HPS and isolated IPVD is not different when compared to those without IPVDs.

A Case-Control Study of the Genetic Variability in Reactive Oxygen Species-Metabolizing Enzymes in Melanoma Risk

Recent studies have shown that ultraviolet (UV)-induced chemiexcitation of melanin fragments leads to DNA damage; and chemiexcitation of melanin fragments requires reactive oxygen species (ROS), as ROS excite an electron in the melanin fragments. In addition, ROS also cause DNA damages on their own. We hypothesized that ROS producing and metabolizing enzymes were major contributors in UV-driven melanomas. In this case-control study of 349 participants, we genotyped 23 prioritized single nucleotide polymorphisms (SNPs) in nicotinamide adenine dinucleotide phosphate (NADPH) oxidases 1 and 4 (NOX1 and NOX4, respectively), CYBA, RAC1, superoxide dismutases (SOD1, SOD2, and SOD3) and catalase (CAT), and analyzed their associated melanoma risk. Five SNPs, namely rs1049255 (CYBA), rs4673 (CYBA), rs10951982 (RAC1), rs8031 (SOD2), and rs2536512 (SOD3), exhibited significant genotypic frequency differences between melanoma cases and healthy controls. In simple logistic regression, RAC1 rs10951982 (odds ratio (OR) 8.98, 95% confidence interval (CI): 5.08 to 16.44; p < 0.001) reached universal significance (p = 0.002) and the minor alleles were associated with increased risk of melanoma. In contrast, minor alleles in SOD2 rs8031 (OR 0.16, 95% CI: 0.06 to 0.39; p < 0.001) and SOD3 rs2536512 (OR 0.08, 95% CI: 0.01 to 0.31; p = 0.001) were associated with reduced risk of melanoma. In multivariate logistic regression, RAC1 rs10951982 (OR 6.15, 95% CI: 2.98 to 13.41; p < 0.001) remained significantly associated with increased risk of melanoma. Our results highlighted the importance of RAC1, SOD2, and SOD3 variants in the risk of melanoma.

Differential diagnosis of hepatopulmonary syndrome (HPS): Portopulmonary hypertension (PPH) and hereditary hemorrhagic telangiectasia (HHT)

Hepatopulmonary syndrome (HPS) is a severe complication of advanced liver disease associated with an extremely poor prognosis. HPS is diagnosed in 4-47% of patients with cirrhosis and in 15-20% of candidates for liver transplantation. In addition, severe hypoxia is associated with a high risk of complications of liver transplantation (a 30% chance during the first 90 days) and increases the gap between transplantation and improving arterial oxygenation. The pathogenesis of HPS is not fully understood, and no effective pharmacological treatment has been developed yet. Currently, the treatment of choice for HPS is orthotopic liver transplantation. Non-specific clinical criteria and the lack of standardized diagnostic criteria for determining HPS can lead to diagnostic errors. Portopulmonary hypertension and hereditary hemorrhagic telangiectasia, also known as Osler-Weber-Rendu syndrome, are pulmonary complications of liver disease which should be differentially diagnosed from HPS.

Clinical Impact of Intrapulmonary Vascular Dilatation in Candidates for Liver Transplant

BACKGROUND

Intrapulmonary vascular dilatations (IPVD) frequently are detected in patients with liver disease by the delayed appearance of microbubbles at contrast-enhanced echocardiography. IPVD with an elevated alveolar-arterial (A-a) gradient define hepatopulmonary syndrome (HPS); however, the importance of IPVD in the absence of abnormal gas exchange is unknown. We aimed to determine the clinical impact of IPVD in patients with liver disease.

METHODS

We performed a cross-sectional study within the Pulmonary Vascular Complications of Liver Disease 2 Study, a multicenter, prospective cohort study of patients being evaluated for liver transplant. We excluded patients with obstructive or restrictive lung disease, HPS, or intracardiac shunting. We compared patients with and those without IPVD.

RESULTS

Forty-six patients with IPVD and 81 patients without IPVD were included. Patients with IPVD were more likely to have autoimmune hepatitis and less likely to have cryptogenic cirrhosis and hepatocellular carcinoma. Patients with IPVD had higher Child-Pugh scores (6 [interquartile range (IQR), 5-7] vs 5 [IQR, 4-7]; P = .04), possibly higher Model for End-Stage Liver Disease scores (14.5 [IQR, 11.6-15.8] vs 12.2 [IQR, 9.4-15.5]; P = .06), higher PaO₂ levels (97.9 [IQR, 92.0-103.0] vs 89.0 [IQR, 82.0-96.9] mm Hg; P < .001), and lower A-a gradients (9.9 [IQR, 6.2-13.5] vs 14.9 [IQR, 9.0-21.8] mm Hg; P < .001). Symptoms and quality of life were similar between the groups.

CONCLUSIONS

Autoimmune hepatitis and increased liver disease severity were associated with the presence of IPVD, which was characterized by higher PaO₂ levels. Future studies to better characterize IPVD pathogenesis and the relationship of IPVD to HPS are warranted.

Hepatopulmonary Syndrome and Portopulmonary Hypertension: Implications for Liver Transplantation

Hepatopulmonary syndrome (HPS) and portopulmonary hypertension (PoPH) represent serious pulmonary complications of advanced liver diseases. Orthotopic liver transplantation (OLT) is capable of completely resolving the underlying abnormalities associated with HPS. On the other hand, post-OLT response in patients with PoPH is less predictable, although heavily influenced by pre-OLT mean pulmonary arterial pressure. It remains the case that the opportunity to reverse 2 potentially fatal organ dysfunctions in the liver and the lung make HPS and PoPH more than worthy for further clinical investigations.

The Role of NOX4 and TRX2 in Angiogenesis and Their Potential Cross-Talk

The nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) family is the major source of reactive oxygen species (ROS) in the vascular system. In this family, NOX4, a constitutive active form of NOXs, plays an important role in angiogenesis. Thioredoxin 2 (TRX2) is a key mitochondrial redox protein that maintains normal protein function and also provides electrons to peroxiredoxin 3 (PRX3) to scavenge H₂O₂ in mitochondria. Angiogenesis, a process of new blood vessel formation, is involved in a variety of physiological processes and pathological conditions. It seems to be paradoxical for ROS-producing NOX4 and ROS-scavenging TRX2 to have a similar role in promoting angiogenesis. In this review, we will focus on data supporting the role of NOX4 and TRX2 in angiogenesis and their cross-talks and discuss how ROS can positively or negatively regulate angiogenesis, depending on their species, levels and locations. NOX4 and TRX2-mediated ROS signaling could be promising targets for the treatment of angiogenesis-related diseases.

International Liver Transplant Society Practice Guidelines: Diagnosis and Management of Hepatopulmonary Syndrome and Portopulmonary Hypertension

Two distinct pulmonary vascular disorders, hepatopulmonary syndrome (HPS) and portopulmonary hypertension (POPH) may occur as a consequence of hepatic parenchymal or vascular abnormalities. HPS and POPH have major clinical implications for liver transplantation. A European Respiratory Society Task Force on Pulmonary-Hepatic Disorders convened in 2002 to standardize the diagnosis and guide management of these disorders. These International Liver Transplant Society diagnostic and management guidelines are based on that task force consensus and should continue to evolve as clinical experience dictates. Based on a review of over 1000 published HPS and POPH articles identified via a MEDLINE search (1985-2015), clinical guidelines were based on, selected single care reports, small series, registries, databases, and expert opinion. The paucity of randomized, controlled trials in either of these disorders was noted. Guidelines are presented in 5 parts; I. Definitions/Diagnostic criteria; II. Hepatopulmonary syndrome; III. Portopulmonary hypertension; IV. Implications for liver transplantation; and V. Suggestions for future clinical research.

Pulmonary shunts in severe hepatosplenic schistosomiasis: Diagnosis by contrast echocardiography and their relationship with abdominal ultrasound findings

Background

Schistosomiasis is endemic to several parts of the world. Among the species that affect humans, Schistosoma mansoni is one of the most common causes of illness. In regions where schistosomiasis mansoni is endemic, reinfection is responsible for the emergence of hepatosplenic schistosomiasis (HSS) with portal hypertension in about 10% of infected individuals. Regardless of its etiology, portal hypertension may bring about the formation of arteriovenous fistulas and pulmonary vascular dilation, thus constituting a pulmonary shunt and its presence has been associated with the occurrence of neurological complications. The objective of this study was to identify pulmonary shunt using TTCE in patients with HSS and esophageal varices, and to compare the abdominal ultrasound and endoscopy findings among patients with and without pulmonary shunt.

Methodology/Principal findings

In this case series, a total of 461 patients with schistosomiasis mansoni were prospectively evaluated using abdominal ultrasound and endoscopy and 71 presented with HSS with esophageal varices. Fifty seven patients remained in the final analysis. The mean age of the patients was 55 ± 14 years, and 65% were female. Pulmonary shunts were observed in 19 (33.3%) patients. On comparing the groups with and without pulmonary shunt, no significant differences were observed in relation to the abdominal ultrasound and endoscopic findings. When comparing the two subgroups with pulmonary shunts (grade 1 vs grades 2 and 3), it was observed that the subgroup with shunt grades 2 and 3 presented with a significantly higher frequency of an enlarged splenic vein diameter (>0.9 cm), and an advanced pattern of periportal hepatic fibrosis (P = 0.041 and P = 0.005, respectively). None of the patients with pulmonary shunts had severe neurological complications.

Conclusions/Significance

Our findings suggest that in HSS with esophageal varices the pulmonary shunts may be present in higher grades and that in this condition it was associated with ultrasound findings compatible with advanced HSS.

Among the species of Schistosoma that infect humans Schistosoma mansoni is one of the most common causes of illness. In the areas where schistosomiasis mansoni is endemic, around 10% of infected individuals develop hepatosplenic schistosomiasis (HSS) with portal hypertension. Portal hypertension may promotes an imbalance in the hepatic production of vasoactive substances, which may act on the lungs promoting the formation of arteriovenous fistulas and pulmonary vascular dilation, a condition that is called a pulmonary shunt. When the pulmonary shunt is of higher grades, small thrombus or septic emboli that would normally be filtered through the pulmonary capillaries reach the left heart and the systemic circulation, which can lead to neurological complications. We found pulmonary shunts in patients with HSS and esophageal varices and we also found that patients with higher grades of pulmonary shunts presented with a significantly higher frequency of advanced periportal fibrosis and an enlarged splenic vein diameter. No neurological complications were observed. Our findings suggest that pulmonary shunts may be present in patients with HSS and esophageal varices. The abdominal ultrasound findings compatible with advanced HSS could be used as screening to investigate pulmonary shunt.

[Hepatopulmonary syndrome]

Hepatopulmonary syndrome (HPS) is defined by the association of portal hypertension, increased alveolar-arterial oxygen gradient and intrapulmonary vascular dilations. Pathophysiological mechanisms of hypoxemia are characterized by ventilation-perfusion mismatch, oxygen diffusion limitation between alveolus and the centre of the dilated capillary, and right-to-left shunting. An excess of vasodilator molecules (like nitric monoxide) and proangiogenic factors (like VEGF) play an important role in the occurrence of HPS. Symptoms of HPS are not specific and dominated by a progressive dyspnea in upright position. Pulse oximetry is a simple non-invasive screening test but only detect the most severe forms of HPS. Medical treatment is disappointing and only liver transplantation may lead to resolution of HPS. Survival following liver transplantation is promising when hypoxemia is not severely decreased.

Hepatopulmonary Syndrome in children: a comparative study of non-cirrhotic vs. cirrhotic portal hypertension

BACKGROUND & AIMS

Hepatopulmonary syndrome in children has not been extensively studied particularly in different subsets of portal hypertension. We prospectively studied hepatopulmonary syndrome in children with cirrhosis and extrahepatic portal venous obstruction. Their comparison might shed light on the pathogenesis of hepatopulmonary syndrome.

METHODS

Between 1 to 18 years of age, 135 children with portal hypertension (cirrhosis 35, extrahepatic portal venous obstruction 100) were studied. Hepatopulmonary syndrome was diagnosed by the presence intrapulmonary shunt using transthoracic contrast echocardiography and hypoxia/orthodeoxia (in arterial blood gas examination). Comparative analyses were done for both the groups, and also intra- and intergroups with and without hepatopulmonary syndrome.

RESULT

Of 135 children, hepatopulmonary syndrome occurred more frequently in cirrhosis (40%) than extrahepatic portal venous obstruction (13%) (P = 0.01). Cirrhotics with hepatopulmonary syndrome were symptomatic (85% vs. 14%, P < 0.001) and had longer disease duration [16(1-120) months vs. 28 (1-168) months, P = 0.01] as compared to cirrhotics without hepatopulmonary syndrome. Prevalence of hepatopulmonary syndrome among cirrhotics did not correlate with the severity of liver disease as assessed by both paediatric end-stage liver disease score and Child-Turcotte-Pugh score. Patients with extrahepatic portal venous obstruction and hepatopulmonary syndrome remain asymptomatic manifesting with clubbing alone (38%).

CONCLUSIONS

Hepatopulmonary syndrome occurs more frequently in cirrhosis, a majority being symptomatic with more severity in comparison to extrahepatic portal venous obstruction having no symptoms and less severity. There seems to be a role of liver dysfunction besides portal hypertension as an added factor in the pathogenesis of hepatopulmonary syndrome.

Variability of oxygenation in possible hepatopulmonary syndrome: effects of requiring two abnormal arterial blood gas results for diagnosis

BACKGROUND AND AIMS

Hepatopulmonary syndrome (HPS) affects 10-32 % of patients with cirrhosis and is defined by liver abnormalities, intrapulmonary vascular dilatations (IPVDs), and abnormal oxygenation. However, published criteria for abnormal oxygenation are inconsistent. We sought to evaluate variation in oxygenation over time and to compare various diagnostic criteria for validity, based on their diagnostic stability over time and ability to identify patients with clinically relevant findings.

METHODS

We retrospectively analyzed oxygenation and diffusion capacity in patients with liver abnormalities and IPVDs who had ≥ 2 arterial blood gases (ABGs) at the University of Toronto or Universite de Montreal. We compared the performance of nine possible oxygenation criteria for HPS and for each explored whether validity improved when requiring two consecutive abnormal ABGs on different days.

RESULTS

Mean PaO2 was 68.4 mmHg and annual within-patient coefficient of variation 6.3 % (58 patients). Applying published criteria, 8.6-15.5 % of patients initially diagnosed with HPS no longer met the criterion for HPS on a subsequent ABG (re-classified). Requiring two consecutive abnormal ABGs on different days: (1) reduced the proportion of re-classified patients (9/9 criteria); (2) identified patients with more rapid progression in hypoxemia and greater difference in rate of progression between HPS and non-HPS (7/9 criteria); and (3) identified patients with lower diffusion and a larger difference in diffusion between HPS and non-HPS (8/9 criteria).

CONCLUSIONS

Oxygenation is variable in this population, and requiring two abnormal results might reduce misdiagnosis and better differentiate patients with and without HPS according to clinically relevant markers of disease.

Effect of the oestrogen receptor antagonist fulvestrant on the cirrhotic rat lung

It has been postulated that cirrhosis-related lung vasodilatation and the subsequent hepatopulmonary syndrome are partly explained by an increased estradiol level through an enhanced endothelial formation of nitric oxide (NO). In this study, we assessed whether the oestrogen receptor antagonist fulvestrant (F) improves cirrhosis-related lung abnormalities. Cirrhosis was induced in rats by chronic bile duct ligation (CBDL). Four groups were studied: CBDL, CBDL+F, sham, and sham+F. Histological, immunohistochemical, and Western blot analyses were performed on lung samples. In the lung, the endothelial NO synthase and the nitrotyrosine protein expressions were increased in CBDL as compared to sham rats. Both parameters were significantly reduced by fulvestrant in the CBDL rats. Surprisingly, the level of pVASP (an indirect marker of NO formation and action) was decreased in CBDL rats, and fulvestrant had no effect on this parameter. The level of the vascular endothelial growth factor, the diameter of small lung vessels, and the number of macrophages were increased in CBDL lungs in comparison with sham lungs, and these parameters were unaffected by fulvestrant treatment. In conclusion, fulvestrant may not be relevant to improve lung abnormalities in cirrhosis because NO may not be biologically active and because key events contributing to the lung abnormalities are not affected by fulvestrant.

Familial hepatopulmonary syndrome in common variable immunodeficiency

Common Variable Immunodeficiency (CVID) comprises a heterogeneous group of primary antibody deficiencies which lead to a range of complications, including infectious, neoplastic and inflammatory disorders. This report describes monozygotic twin brothers with CVID who developed cryptogenic liver disease and subsequently hepatopulmonary syndrome (HPS). This is the second report of the association of HPS and CVID. Its occurrence in two identical twins implicates a genetic basis.

Alveolar type II epithelial cell dysfunction in rat experimental hepatopulmonary syndrome (HPS)

The hepatopulmonary syndrome (HPS) develops when pulmonary vasodilatation leads to abnormal gas exchange. However, in human HPS, restrictive ventilatory defects are also observed supporting that the alveolar epithelial compartment may also be affected. Alveolar type II epithelial cells (AT2) play a critical role in maintaining the alveolar compartment by producing four surfactant proteins (SPs, SP-A, SP-B, SP-C and SP-D) which also facilitate alveolar repair following injury. However, no studies have evaluated the alveolar epithelial compartment in experimental HPS. In this study, we evaluated the alveolar epithelial compartment and particularly AT2 cells in experimental HPS induced by common bile duct ligation (CBDL). We found a significant reduction in pulmonary SP production associated with increased apoptosis in AT2 cells after CBDL relative to controls. Lung morphology showed decreased mean alveolar chord length and lung volumes in CBDL animals that were not seen in control models supporting a selective reduction of alveolar airspace. Furthermore, we found that administration of TNF-α, the bile acid, chenodeoxycholic acid, and FXR nuclear receptor activation (GW4064) induced apoptosis and impaired SP-B and SP-C production in alveolar epithelial cells in vitro. These results imply that AT2 cell dysfunction occurs in experimental HPS and is associated with alterations in the alveolar epithelial compartment. Our findings support a novel contributing mechanism in experimental HPS that may be relevant to humans and a potential therapeutic target.

Von Willebrand factor antigen for detection of hepatopulmonary syndrome in patients with cirrhosis

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS) occurs in 20-30% of patients with liver cirrhosis and is associated with a >2 fold increased mortality. Endothelial dysfunction seems to play a central role in its pathogenesis. von Willebrand factor antigen (vWF-Ag), an established marker of endothelial dysfunction, is significantly elevated in patients with liver cirrhosis, portal hypertension, and in experimental HPS. Aim of the present study was to evaluate the impact of vWF-Ag as a screening marker for presence of HPS in patients with stable cirrhosis.

METHODS

145 patients with stable liver cirrhosis were screened for presence of HPS in this prospective cohort type cross sectional diagnostic study. vWF-Ag and SaO2 levels were assessed at time of screening for HPS. Criteria of HPS were fulfilled in 31 (21%) patients.

RESULTS

vWF-Ag levels were significantly higher in patients with HPS compared to patients without HPS (p<0.001). Furthermore, vWF-Ag correlated significantly with gas exchange in HPS positive patients (p<0.05). vWF-Ag is an independent predictor of HPS after correction for sex, age, model for endstage-liver disease (MELD), and hepatic venous pressure gradient (HVPG) (OR per 1% increase of vWF-Ag: 1.02, 95% CI: 1.00-1.04, p<0.05). The best cut-off was 328% at a sensitivity of 100% and specificity of 53.5%; positive predictive value: 36.9%; negative predictive value: 100%.

CONCLUSIONS

HPS is associated with elevated vWF-Ag levels. vWF-Ag may be a useful screening tool for early detection of HPS. Further studies investigating vWF-Ag in HPS will be needed to confirm our findings.

Hepatopulmonary syndrome

The hepatopulmonary syndrome (HPS) is a pulmonary complication of cirrhosis and/or portal hypertension whereby patients develop hypoxemia as a result of alterations in pulmonary microvascular tone and architecture. HPS occurs in up to 30% of patients with cirrhosis. Although the degree of hypoxemia does not reliably correlate with the severity of liver disease, patients with HPS have a higher mortality than do patients with cirrhosis without the disorder. There has been progress into defining the mechanisms that lead to hypoxemia in HPS, but to date there are no therapeutic options for HPS aside from liver transplantation.

Pathophysiology of lung injury induced by common bile duct ligation in mice

Background

Liver dysfunction and cirrhosis affect vasculature in several organ systems and cause impairment of organ functions, thereby increasing morbidity and mortality. Establishment of a mouse model of hepatopulmonary syndrome (HPS) would provide greater insights into the genetic basis of the disease. Our objectives were to establish a mouse model of lung injury after common bile duct ligation (CBDL) and to investigate pulmonary pathogenesis for application in future therapeutic approaches.

Methods

Eight-week-old Balb/c mice were subjected to CBDL. Immunohistochemical analyses and real-time quantitative reverse transcriptional polymerase chain reaction were performed on pulmonary tissues. The presence of HPS markers was detected by western blot and microarray analyses.

Results

We observed extensive proliferation of CD31-positive pulmonary vascular endothelial cells at 2 weeks after CBDL and identified 10 upregulated and 9 down-regulated proteins that were associated with angiogenesis. TNF-α and MMP-9 were highly expressed at 3 weeks after CBDL and were less expressed in the lungs of the control group.

Conclusions

We constructed a mouse lung injury model by using CBDL. Contrary to our expectation, lung pathology in our mouse model exhibited differences from that of rat models, and the mechanisms responsible for these differences are unknown. This phenomenon may be explained by contrasting processes related to TNF induction of angiogenic signaling pathways in the inflammatory phase. Thus, we suggest that our mouse model can be applied to pulmonary pathological analyses in the inflammatory phase, i.e., to systemic inflammatory response syndrome, acute lung injury, and multiple organ dysfunction syndrome.

Pulmonary complications in chronic liver disease

The association of chronic liver disease with respiratory symptoms and hypoxia is well recognized. Over the last century, three pulmonary complications specific to chronic liver disease have been characterized: hepatopulmonary syndrome (HPS), portopulmonary hypertension (POPH), and hepatic hydrothorax (HH). The development of portal hypertension is fundamental in the pathogenesis of each of these disorders. HPS is the most common condition, found in 5%-30% of cirrhosis patients, manifested by abnormal oxygenation due to the development of intrapulmonary vascular dilatations. The presence of HPS increases mortality and impairs quality of life, but is reversible with liver transplantation (LT). POPH is characterized by development of pulmonary arterial hypertension in the setting of portal hypertension, and is present in 5%-10% of cirrhosis patients evaluated for LT. Screening for POPH in cirrhosis patients eligible for LT is critical since severe POPH is a relative contraindication for LT. Patients with moderate POPH, who respond adequately to medical therapy, may benefit from LT, although sufficient controlled data are lacking. HH is a transudative pleural effusion seen in 5%-10% of cirrhosis patients, in the absence of cardiopulmonary disease. Diagnosis of HH should prompt consideration for LT, which is the ultimate treatment for HH. Conservative management includes salt restriction and diuretics, with thoracentesis and transjugular intrahepatic portosystemic shunt (TIPS) as second-line therapeutic options.

Paxillin suppresses the proliferation of HPS rat serum treated PASMCs by up-regulating the expression of cytoskeletal proteins

Hepatopulmonary syndrome (HPS) is a triad of advanced liver disease, intrapulmonary vasodilatation (IPVD), and arterial hypoxemia. The arterial hypoxemia induces pulmonary vascular remodelling (PVR). In recent studies, the role of the proliferation of pulmonary artery smooth muscle cells (PASMCs) in PVR associated with HPS has been established; the changes in cytoskeletal proteins play an essential role in the proliferation of PASMCs. Little is known about the relevance of cytoskeletal protein expression or the molecular mechanisms of PVR associated with HPS. In addition, it has been identified that paxillin could influence the cytoskeletal protein expression by some important signaling pathways in many diseases, including lung cancer and liver cancer. In this study, we found that HPS rat serum from a common bile duct ligation (CBDL) rat model decreased the expression of cytoskeletal proteins (α-actin, α-tubulin, and destrin) and enhanced the expression levels of paxillin mRNA and protein in PASMCs. After silencing paxillin with siRNA, we found that the down-regulation of cytoskeletal protein expression, induced by the HPS rat serum, was reversed. Additionally, we reported that HPS rat serum improved the proliferation of PASMCs and down-regulation of paxillin could significantly inhibit this variation. These findings suggest that the up-regulation of cytoskeletal protein expression, induced by the paxillin, may cause the dysregulation of PASMC proliferation as well as play a fundamental role in PVR associated with HPS. In conclusion, down-regulation of paxillin by siRNA results in the inhibition of the dysregulation of cytoskeletal proteins and proliferation of PASMCs, suggesting a potential therapeutic effect on PVR associated with HPS.

Pharmacological treatment for hepatopulmonary syndrome

AIM

Hepatopulmonary syndrome is a pulmonary dysfunction in the context of liver cirrhosis characterized by arterial deoxygenation. Affected patients have increased morbidity and mortality, and many of them expire before undergoing liver transplantation. Therefore, finding medical therapy as a bridge to transplantation or as a final treatment is necessary. In this study, we aimed to review the current literature about pharmacological options available for treatment of hepatopulmonary syndrome.

METHODS

A PubMED and Scopus search was conducted in January 2013 on the English literature published in any time period to find human and animal studies reporting pharmacological therapy of hepatopulmonary syndrome.

RESULTS

Out of 451 studies, 29 relevant articles were included. The number of patients, type, dose, duration, and mechanism of drugs in these studies was extracted and summarized separately. Most of pharmacologic agents act through inhibition of nitric oxide synthase and reduction in nitric oxide production, inactivation of endothelin-1, and treatment of bacterial translocation and pulmonary angiogenesis.

CONCLUSION

Several drugs have been applied for the treatment of HPS with conflicting results. However, no large randomized trial has been conducted probably due to low number of patients. Multicentered clinical trials are necessary to investigate these drugs.

Liver in cardiopulmonary disease

Hepatopulmonary syndrome (HPS) and portopulmonary hypertension (PoPH) are two fascinating and incompletely understood pulmonary vascular conditions seen in the setting of cirrhotic patients. Of the two HPS is more common and is primarily caused by pulmonary vasodilatation resulting in hypoxaemia and hyperdynamic circulation. PoPH is less common and conversely, pulmonary vasoconstriction and vascular remodelling occurs resulting in increased pulmonary vascular resistance. However, both conditions can co-exist and it is usually PoPH which develops in a patient with pre-existing HPS. Although these two pulmonary conditions are not common complications of chronic liver diseases, the treatment options are mainly limited to liver transplantation. Cirrhotic cardiomyopathy is closely related to haemodynamic changes in portal hypertension. The key features are normal cardiac pressures at rest, with reduced ability to compensate for physiological or iatrogenic stresses such as drug therapy or TIPSS. There is no effective therapy and outcomes after liver transplantation are variable.

Sorafenib treatment improves hepatopulmonary syndrome in rats with biliary cirrhosis

HPS (hepatopulmonary syndrome) is characterized by oxygen desaturation in patients with chronic liver disease. The initiation of HPS comes from abnormal pulmonary vasodilatation and/or angiogenesis. In the present study, we evaluated anti-angiogenesis therapy using sorafenib in experimental HPS animals. HPS was induced by CBDL (common bile duct ligation) in rats. A 2-week 10 mg·(kg of body weight)-1·day-1 treatment regimen of sorafenib or distilled water (control) was initiated 2 weeks after the surgical procedure. Haemodynamics, liver biochemistry, plasma VEGF (vascular endothelial growth factor) measurements and blood gas analysis of the CBDL rats were performed. The livers of the CBDL rats were dissected for histopathology examination, and the lungs were examined by immunohistochemical staining, real-time PCR and Western blot analysis. In another two parallel groups, intrapulmonary shunts were determined. The AaPO2 (alveolar-arterial O2 gradient) and plasma VEGF levels were reduced after sorafenib treatment [AaPO2, 7.2±3.4 mmHg in sorafenib-treated rats compared with 15.3±4.2 mmHg in controls (P=0.004); VEGF, 45.3±2.7 pg/ml in sorafenib-treated rats compared with 54.4±7.7 pg/ml in controls (P=0.021)]. Sorafenib attenuated pulmonary VEGF mRNA and VEGF, VEGFR-2 (VEGF receptor 2), phospho-VEGFR-2 and Akt protein expression. In addition, sorafenib significantly attenuated intrapulmonary angiogenesis and decreased the degree of intrapulmonary shunting by 33.7% (11.2±5.7% in sorafenib-treated rats compared with 16.9±5.9% in controls; P=0.003). Our findings suggest that sorafenib attenuates intrapulmonary shunting and decreases the AaPO2 in CBDL rats, implicating the improvement of HPS in this experimental animal model. The beneficial effect may be attributed to the reduction in intrapulmonary angiogenesis through inhibition of the VEGF/VEGFR-2/Akt pathway.