The diagnosis and treatment of hepatopulmonary syndrome

The ET-1-mediated carbonylation and degradation of ANXA1 induce inflammatory phenotype and proliferation of pulmonary artery smooth muscle cells in HPS

Hepatopulmonary syndrome (HPS) is a serious complication of advanced liver disease, which markedly increases mortality. Pulmonary vascular remodelling (PVR) induced by circulating mediators plays an important role in the pathogenesis of HPS, while the underlying mechanism remains undefined. In the present study, we reported that endothelin-1 (ET-1) is up-regulated and annexin A1(ANXA1) is down-regulated in HPS rat, and ET-1 decreases the ANXA1 expression in a dose-dependent manner in rat pulmonary arterial smooth muscle cells (PASMCs). Then, we showed that ANXA1 can decrease nuclear p-ERK1/2 accumulation and decrease the cyclin D1 expression, thus resulting in the subsequent inhibition of PASMCs proliferation. As previously reported, we confirmed that ET-1 decreases the ANXA1 protein levels by the carbonylation and degradation of ANXA1. In conclusion, our research links the signaling cascade of ET1-ANXA1-cell proliferation to a potential therapeutic strategy for blocking IPS-associated PVR.

Annexin A1 protein regulates the expression of PMVEC cytoskeletal proteins in CBDL rat serum-induced pulmonary microvascular remodeling

Background

Hepatopulmonary syndrome (HPS) is characterized by advanced liver disease, hypoxemia and intrapulmonary vascular dilatation (IPVD). The pathogenesis of HPS is not completely understood. Recent findings have established the role of proliferation and phenotype differentiation of pulmonary microvascular endothelial cells (PMVECs) in IPVD of HPS; the change in cytoskeletal proteins and their molecular mechanism play an essential role in the proliferation, phenotype modulation and differentiation of PMVECs. However, little is known about the relevance of cytoskeletal protein expression and its molecular mechanism in IPVD of HPS. In addition, ANX A1 protein has been identified as a key regulator in some important signaling pathways, which influences cytoskeletal remodeling in many diseases, such as lung cancer, liver cancer, etc.

Methods

PMVECs were cultured from the normal rats and then divided into three groups(Ad-ANXA1-transfected group, a non-transfected group, and an adenovirus empty vector group) and incubated by nomal rat serum or hepatopulmonary syndrome rat serum respectively. mRNA level was evaluated by real time reverse transcription polymerase chain reaction, and protein expression was detected by western blot. Cell proliferation was determined by the MTT and thymidine incorporation assay.

Results

In this study, we found that the serum from a common bile duct ligation(CBDL) Rat model decreased the expression levels of the ANX A1 mRNA and protein by at least two-fold in human PMVECs. We also found the expression of cytoskeletal proteins (Destrin, a1-actin, and a1-tubulin) in PMVECs significantly increased. After stimulating ANX A1 over-expression in PMVECs by adenovirus-mediated ANX A1 (Ad-ANXA1) transfection, we found the expression levels of cytoskeletal proteins were significantly suppressed in PMVECs at all time points. Additionally, we report here that serum from a CBDL Rat model increases the proliferation of PMVECs by nearly two-fold and that over-expression of Ad-ANXA1 significantly inhibits HPS-rat-serum-induced PMVEC proliferation (p <0.05). These findings suggest that the ANX A1 down-regulation of PMVEC proliferation in the presence of HPS-rat-serum may be the major cause of aberrant dysregulation of cytoskeletal proteins (Destrin, a1-actin, and a1-tubulin) and may, therefore, play a fundamental role in the proliferation and phenotype differentiation of PMVECs in the PVD of HPS.

Conclusion

Finally, the fact that transfection with Ad-ANXA1 results in inhibition of the aberrant dysregulation of cytoskeletal proteins and proliferation of PMVECs suggests a potential therapeutic effect on PVD of HPS.

Pulmonary artery embolotherapy in a patient with type I hepatopulmonary syndrome after liver transplantation

Although liver transplantation (LT) is the only effective treatment option for hepatopulmonary syndrome (HPS), the post-LT morbidity and mortality have been high for patients with severe HPS. We performed post-LT embolotherapy in a 10-year-old boy who had severe type I HPS preoperatively, but he failed to recover early from his hypoxemic symptoms after an LT. Multiple embolizations were then successfully performed on the major branches that formed the abnormal vascular structures. After the embolotherapy, the patient had symptomatic improvement and he was discharged without complications.

Hepatopulmonary syndrome: use of extracorporeal life support for life-threatening hypoxia following liver transplantation

Hepatopulmonary syndrome is an uncommon complication of nonacute liver failure, and in rare cases, hypoxia may be the presenting sign of liver dysfunction. The condition, once thought to be a contraindication, is improved in most cases by transplantation. There is a significant risk of postoperative, hypoxia-related morbidity and mortality in patients with hepatopulmonary syndrome. We present a case of life-threatening hypoxia following liver transplantation for liver failure and associated hepatopulmonary syndrome, with successful management using extracorporeal membrane oxygenation.

Prevalence of hepatopulmonary syndrome in children

OBJECTIVE

The hepatopulmonary syndrome is defined as a triad of liver disease, hypoxemia, and intrapulmonary vascular dilation. The reported prevalence of hepatopulmonary syndrome in adults with cirrhosis ranges from 4% to 29%; however, the prevalence of hepatopulmonary syndrome and its outcome in children is unknown. The objective of this study was to describe prospectively the prevalence of intrapulmonary vascular dilation and hepatopulmonary syndrome in children with liver disease.

METHODS

Pulse oximetry was undertaken in children with liver disease, and those with oxygen saturation < or = 97%, those with cirrhosis, and those with clinically severe portal hypertension from other causes underwent contrast-enhanced echocardiography for detection of intrapulmonary vascular dilations. Patients with intrapulmonary vascular dilation underwent arterial blood gas analysis and technetium-99m-labeled macroaggregated albumin scan.

RESULTS

Oxygen saturation was measured in 301 children and was < or = 97% in 8. These 8 and an additional 18 patients with cirrhosis or portal hypertension underwent contrast-enhanced echocardiography. Seven (27%) patients had intrapulmonary vascular dilation detected by contrast-enhanced echocardiography; 2 of these patients had abnormal arterial blood gas analysis and thus met diagnostic criteria for hepatopulmonary syndrome (representing 8% of patients with cirrhosis or severe portal hypertension). Both patients with hepatopulmonary syndrome had abnormal pulse oximetry. Technetium-99m-labeled macroaggregated albumin scans for 6 patients showed a median 6.5% (range: 4%-12%) tracer uptake outside the lungs.

CONCLUSIONS

Hepatopulmonary syndrome occurs in an important minority of children with cirrhosis or severe portal hypertension. Additional studies should be undertaken to determine the importance of intrapulmonary vascular dilation without hepatopulmonary syndrome and the impact of hepatopulmonary syndrome on the outcomes of affected children.

Therapy Insight: hepatopulmonary syndrome and orthotopic liver transplantation

Hepatopulmonary syndrome (HPS)--a pulmonary complication observed in patients who have chronic liver disease and/or portal hypertension--is attributed to intrapulmonary vascular dilatation and induces severe hypoxemia. HPS is mainly detected when patients are included on the waiting list for orthotopic liver transplantation (OLT) and can be diagnosed by blood gas analysis, transthoracic contrast-enhanced echocardiography or body scan with (99m)Tc-labeled macroaggregated albumin perfusion. When the partial pressure of arterial oxygen (PaO(2)) is >or=80 mmHg, it is unlikely that the patient has HPS. When the PaO(2) is <80 mmHg, imaging techniques should be used to confirm or exclude pulmonary vascular dilatation. When a diagnosis of HPS is confirmed, knowing the degree of hypoxemia is crucial for optimum patient management. Patients who have a PaO(2) >or=50 mmHg but <60 mmHg should be prioritized for OLT. This procedure is not indicated for patients with a PaO(2) between 60 mmHg and 80 mmHg, although follow-up every 3 months is recommended to detect any deterioration of the PaO(2). A PaO(2) of <50 mmHg might preclude OLT, because mortality and morbidity after OLT are greatly increased in these patients.

Hepatopulmonary syndrome and portopulmonary hypertension

The incidence of pulmonary vascular disorders is significantly increased in patients with liver disease. Intrapulmonary shunting with hypoxemia in patients with liver disease is diagnosed as hepatopulmonary syndrome (HPS), whereas precapillary pulmonary vessel obliteration is identified as portopulmonary hypertension (PPHTN). Because the symptoms of liver disease can mimic those of pulmonary vascular disease, all patients with hepatic failure should be screened for these two diseases. Pulse oximetry effectively screens for hypoxemia associated with HPS, whereas an elevated right ventricular systolic pressure estimated by echocardiography identifies patients at risk of having PPHTN. Liver transplantation is the only effective medical therapy for HPS. However, those who have a resting arterial oxygenation less than 50 mm Hg or a shunt measured by scintigraphic perfusion greater than 20% have an unacceptably high mortality rate following surgery. Compared with HPS, there are more therapeutic options that can bridge patients with PPHTN to transplantation. Drugs used to manage idiopathic pulmonary hypertension have shown promise in the treatment of PPHTN. Prostanoids, endothelin receptor antagonists, and phosphodiesterase-5 inhibitors have improved transplant survival. Despite treatment, however, perioperative mortality for patients with PPHTN remains high. Even with successful transplantation, HPS and PPHTN can persist or develop de novo. Long-term follow-up and surveillance of liver transplant recipients is thus indicated to identify HPS and PPHTN following surgery.

Deleterious effect of nitric oxide inhibition in chronic hepatopulmonary syndrome

On the basis of limited experimental and clinical studies, increased activity of the vasodilatory nitric oxide-cyclic guanosine monophosphate pathway is considered to play a key role in the pathogenesis of hepatopulmonary syndrome. We report a 46-year-old woman with Child-Pugh class C cirrhosis and progressive dyspnoea for 12 months. Investigations revealed elevated circulating concentrations of nitric oxide metabolites and exhaled nitric oxide levels, an hyperdynamic circulation with low systemic vascular resistance and mean arterial pressure, a large right to left intrapulmonary shunt fraction on radiolabelled macroaggregated albumin perfusion scanning, positive contrast-enhanced echocardiography, reduced diffusion capacity of carbon monoxide, hypoxaemia and orthodeoxyia, all in keeping with severe hepatopulmonary syndrome. Sequential inhibition of the nitric oxide-cyclic guanosine monophosphate pathway using curcumin (diferuloylmethane), terlipressin and methylene blue was associated with substantial improvements in vascular tone and the hyperdynamic circulation. No improvement, however, in the intrapulmonary shunt was demonstrated. Both hypoxaemia and orthodeoxia were substantially, reproducibly and reversibly worsened with all three treatments. Our findings argue against the contention that intrapulmonary shunting and impairment in arterial oxygenation in hepatopulmonary syndrome are necessarily the consequence of on-going, nitric oxide-cyclic guanosine monophosphate-mediated vasodilatation, at least in the chronic stage, and, given the possibility of substantial worsening of pulmonary oxygen exchange, suggest that inhibition of the nitric oxide-cyclic guanosine monophosphate pathway should be avoided in this setting.