Placental growth factor: New treatment target bringing hope for hepatopulmonary syndrome

Acute cytotoxicity and increased vascular endothelial growth factor after in vitro nitrogen mustard vapor exposure

Nitrogen mustard (NM) is a highly toxic alkylating agent. Inhalation exposure can cause acute and chronic lung injury. This study's aims were to develop an in vitro coculture model of mustard-induced airway injury and to identify growth factors contributing to airway pathology. Primary human bronchial epithelial cells cultured with pulmonary endothelial cells were exposed to NM (25, 50, 100, 250, or 500 μM) or PBS (control) for 1 hour. Lactate dehydrogenase (LDH) and transepithelial electrical resistance (TEER) were measured before and 24 h after NM exposure. Fixed cultures were stained for hematoxylin and eosin or live/dead staining. Culture media were analyzed for 11 growth factors. A 1-h vapor exposure to greater than or equal to 50 μM NM increased supernatant LDH, decreased TEER, and caused airway epithelial cell detachment. Endothelial cell death occurred at 500 μM NM. Vascular endothelial growth factor A (VEGF-A) and placental growth factor (PlGF) expression increased in 500 μM NM-exposed cultures compared with PBS-exposed control cultures. NM vapor exposure causes differential cytotoxicity to airway epithelial and endothelial injury in culture. Increased VEGF-A and PlGF expression occurred acutely in airway cocultures. Future studies are required to validate the role of VEGF signaling in mustard-induced airway pathology.

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.

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.