Investigation of heme-induced lung injury in human precision cut lung slices using a proteomics approach.

<bold>Background:</bold> Acute Respiratory Distress Syndrome (ARDS) patients have increased levels of heme in the blood and alveolar spaces. Elevated systemic heme levels have been associated with unfavorable clinical outcomes in sepsis related ARDS (Janz DR.J Intensive Care.2015). ARDS have also raised cytokines like IL-6, IL-8 associated with higher mortality.(Jabaudon M, Curr Opin Crit Care.2021). We used Precision Cut Lung Slices (PCLS)-an advanced ex vivo model to study heme-induced acute lung injury and its effects on the proteome and the transcriptome to develop a new model for ARDS research. <bold>Methods:</bold> PCLS (400µm thickness and 4 mm diameter) were obtained from 7 human donors undergoing lung resection surgery for various reasons (e.g. tumor resection). PCLS were cultured and stimulated with 100 µM heme for 24h. The PCLS were collected and protein extraction was done by tissue lysis. We performed proteomic profiling with the tissue lysates. We also performed bulk RNA sequencing to investigate transcriptomics from the same donors. <bold>Results:</bold> Heme stimulation induced pro-inflammatory and injury signals. The proteomic analysis after heme stimulation showed upregulation of 34 proteins, including mostly inflammatory markers such as IL-6, IL-8, and IL-1β. Comparative analyses of lung transcriptomic and plasma proteomic signatures identified a set of 27 differentially expressed common markers. <bold>Conclusion:</bold> Heme raises the production of inflammatory cytokines in human PCLS, comparable to findings from ARDS patients. PCLS treated with heme might be a new translational model to study mechanisms causing acute lung injury.