European Respiratory Journal

Nuria Roldan, Giulia Raggi, Kleanthis Fytianos, Jessica Petracca, Janick Stucki, Fabian Käsermann, Nina Hobi


Disruption of the alveolar barrier is one of the main features of Acute Respiratory Distress Syndrome (ARDS), a devastating disease with no pharmacological treatments available at present. Sepsis is also a common risk factor for the development of ARDS, associated with 30% of the cases. During sepsis, hemolysis takes place, leading to the release of haemoglobin and heme in the bloodstream, which have been shown to contritube to cytotoxicity and inflammation. We aimed to develop an in vitro alveolar barrier disruption model that mimics some of the sepsis-induced ARDS main characteristics. For this purpose, epithelial and endothelial co-cultures on an in vitro micro-physiological system (MPS) were exposed to lipopolysaccharide (LPS) and hemin (i.e. the oxidized form of heme) and the effects on barrier disruption and inflammation were investigated.

Hemin led to barrier disruption (>90% transbarrier resistance reduction) regardless of the presence of LPS or Peripheral Blood Mononuclear Cells (PBMCs). This was accompanied by an increase in the gene expression of Heme Oxygenase – 1 (> 80-fold) and endothelial damage, indicated by disruption of the cell layers. LPS treatment increased pro-inflammatory cytokine secretion (IL-8, TNF-α and IL1-β) in PBMCs. Hemin combined with LPS also induced pro-inflammatory responses but to a lower extent.

In conclusion, our human alveolar barrier disruption model appears to be appropriate to study heme-induced toxicity and inflammation and thus may be a relevant tool for preclinical drug testing.