Impact of Bacterial Translocation on Hepatopulmonary Syndrome: A Prospective Observational Study

Pathophysiological basis of hepatopulmonary syndrome

Circulatory changes with increased blood flow and vasodilatation/vasoconstriction imbalance are an integral consequence of liver cirrhosis and portal hypertension and can affect the pulmonary circulation with the development of vascular disorders, with hepatopulmonary syndrome (HPS) being the most common. HPS is a serious pulmonary complication of progressive liver disease, resulting in a poor clinical prognosis. Vascular tone decrease, monocytic infiltration of pulmonary vessels, formation of intrapulmonary arteriovenous shunts, dysfunction of alveolar type II cells, destruction of the endothelial glycocalyx are important in the pathogenesis of HPS. Abnormalities of pulmonary capillaries lead to hypoxemia caused by a violation of the ventilation/perfusion ratio, diffusion disorders, and the development of arteriovenous anastomoses. Infiltration of the pulmonary vessels by monocytes is one of the key factors of HPS. This migration is facilitated by the intestinal microbiota translocation into the portal bloodstream with increased expression of proinflammatory cytokines (tumor necrosis factor α, interleu­kins 1, 6), leading to the activation of monocytes. Monocytes located in the pulmonary circulation promote the vasodilation through the activation of inducible nitric oxide (NO) synthase and thus NO production. This is also associated with endothelial dysfunction due to a decreased hepatic secretion of bone morphogenetic protein 9 and increased endothelin 1, endothelial overexpression of endothelin B receptors, and increased endothelial NO production. Proangiogenic factors such as vascular endothelial growth factor, platelet-derived growth factor, and placental growth factor play an important role in the proliferation of pulmonary capillaries. Circulation of tumor necrosis factor α, bile acids and monocyte infiltration in the pulmonary circulation lead to increased apoptosis of alveolar type II cells and decreased surfactant synthesis. Chronic inflammation in HPS disrupts the continuity of the endothelial glycocalyx layer. This article provides an overview of the current knowledge on the pathogenesis of HPS, summarizes many features of the disease based on the literature research in MEDLINE database on the PubMed platform.

[Pulmonary Complications in Patients with Liver Cirrhosis]

Portal hypertension is a clinical syndrome defined by an increased portal venous pressure. The most frequent cause of portal hypertension is liver cirrhosis, and many of the complications of cirrhosis, such as ascites and gastroesophageal variceal bleeding, are related to portal hypertension. Portal hypertension is a pathological condition caused by the accumulation of blood flow in the portal system. This blood flow retention reduces the effective circulation volume. To compensate for these changes, neurotransmitter hormone changes and metabolic abnormalities occur, which cause complications in organs other than the liver. A hepatic hydrothorax is fluid accumulation in the pleural space resulting from increased portal pressure. Hepatopulmonary syndrome and portopulmonary hypertension are the pulmonary complications in cirrhosis by deforming the vascular structure. Symptoms, such as dyspnea and hypoxia, affect the survival and the quality of life of patients. These lung complications are usually underestimated in the management of cirrhosis. This review briefly introduces the type of lung complications of cirrhosis.

Combined exercise training improved exercise capacity and lung inflammation in rats with hepatopulmonary syndrome

AIM

Physical exercise training attenuates pulmonary inflammation, but its effects on impaired respiratory function caused by hepatopulmonary syndrome (HPS) have not been evaluated. We determined if the combination of moderate intensity aerobic and resistance training during HPS development modifies exercise capacity, respiratory system mechanics, and lung inflammation responses.

MAIN METHODS

Wistar rats were randomly divided into sham, HPS, and HPS + combined exercise training groups. Fifteen days after HPS induction, a moderate intensity aerobic plus resistance exercise training protocol was performed five times a week for 5 weeks on alternate days. Exercise capacity, respiratory system mechanics, lung inflammation, pulmonary morphology, and immunohistochemistry were evaluated.

KEY FINDINGS

Overall, our findings indicated that combined exercise training efficiently increased the maximal running and resistance capacity of HPS animals. The training regimen reduced the expression of P2X7 in parenchymal leukocytes (P < 0.01), partially restored the expression of interleukin-10 in airway epithelium (P < 0.01), and increased the expression of TFPI in the airway epithelium (P < 0.01) as well as reduced its expression in parenchymal leukocytes (P < 0.01). However, exercise training did not attenuate HPS-induced respiratory mechanical derangements or lung tissue remodeling.

SIGNIFICANCE

Combined exercise training can elicit adaptation with regard to both maximal running capacity and maximum strength and modify the expression of P2X7 and TFPI in parenchymal leukocytes and that of IL-10 in airway epithelium.

Hepatopulmonary syndrome is related to the development of acute-on-chronic liver failure and poor prognosis in cirrhotic patients

BACKGROUND AND AIMS

Long-term prospective data on hepatopulmonary syndrome (HPS) from a large number of patients, especially in Asian patients, are lacking. We evaluated the long-term prognosis of HPS and the development of acute-on-chronic liver failure (ACLF), and related factors.

METHODS

A total of 142 patients with cirrhosis who underwent saline-agitated contrast echocardiography for the diagnosis of HPS were enrolled and observed prospectively from 2014 to 2019.

RESULTS

A total of 59 patients (41%) were diagnosed with HPS (24 grade 1, 23 grade 2, 12 grade 3). Thirty-eight and 37 patients died in the HPS and non-HPS groups, respectively (p < 0.01). The 5-year survival rate was 47% in the HPS group and 62% in the non-HPS group. In the Cox proportional hazards model, HPS and Model for End-stage Liver Disease (MELD) score ≥ 18, and Child-Turcotte-Pugh (CTP) class B/C were significant risk factors for mortality after adjusting for other risk factors (HPS hazard ratio [HR] = 1.9, p = 0.01; MELD score ≥ 18 HR = 2.3, p < 0.01; CTP class B/C HR = 2.9, p < 0.01). Compared to that in non-HPS group, the HPS group had a significantly higher incidence of ACLF during follow-up (p < 0.01) and more frequently presented with lung involvement of ACLF (p = 0.03).

CONCLUSIONS

In the long-term follow-up cohort, patients with HPS showed poorer prognosis than that of patients without HPS. HPS was a risk factor for ACLF development independent of hepatic dysfunction, and lung involvement was significantly common than without ACLF.

Neglected Variables in the Interpretation of Serum Procalcitonin Levels in Patients With Septic Shock

The interpretation of serum procalcitonin (PCT) levels in septic patients is facilitated by reviewing the known stimuli that activate the PCT family of genes. Herein we describe 7 pathways that, alone or in combination, can increase serum PCT levels. As a marker of activation of innate immunity, high PCT levels affect clinical diagnosis, can be trended as a measure of "source" control, and can guide duration of antibacterial therapy in septic patients. Low PCT levels reflect little to no activation of an innate immune response, influence the differential diagnosis, and support the discontinuation of empiric antibiotic therapy. Understanding the pathways that result in elevated serum PCT levels is necessary for interpretation and subsequent clinical management.

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.

Analogies and differences between cirrhotic cardiomyopathy and hepatopulmonary syndrome

Cirrhotic cardiomyopathy and hepatopulmonary syndrome are two quite frequent clinical entities that may complicate the course of liver cirrhosis. The common pathophysiological origin and the same clinical presentation make them difficult to compare. Cirrhotic cardiomyopathy and hepatopulmonary syndrome may start with dyspnea and breathlessness but the former is characterized by a chronic cardiac dysfunction and the latter by a defect of oxygenation due to pulmonary shunts formation. The focus is to differentiate them as soon as possible since the treatment is different until the patient undergoes liver transplant that is the real unique cure for them.

Hepatocyte-derived exosomal MiR-194 activates PMVECs and promotes angiogenesis in hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is a serious vascular complication in the setting of liver disease. Factors produced by the liver are essential to regulate pulmonary angiogenesis in the pathogenesis of HPS; however, the pathogenic mechanisms of pulmonary angiogenesis are not fully understood. We investigated the role of HPS rat serum exosomes (HEs) and sham-operated rat serum exosomes (SEs) in the regulation of angiogenesis. We found that HEs significantly enhance PMVEC proliferation, migration, and tube formation. We further identified miR-194 was the most notably increased miRNA in HEs compared to SEs. Once released, hepatocyte-derived exosomal miR-194 was internalized by PMVECs, leading to the promotion of PMVEC proliferation, migration, and tube formation through direct targeting of THBS1, STAT1, and LIF. Importantly, the pathogenic role of exosomal miR-194 in initiating angiogenesis was reversed by P53 inhibition, exosome secretion inhibition or miR-194 inhibition. Additionally, high levels of miR-194 were found in serum exosomes and were positively correlated with P(A-a)O₂ in HPS patients and rats. Thus, our results highlight that the exosome/miR-194 axis plays a critical pathologic role in pulmonary angiogenesis, representing a new therapeutic target for HPS.