Neutrophil-epithelial microRNA shuttling in acute lung injury (ALI)

• Applicant: Dr. Catharina Conrad
• Subject Area: Anaesthesiology
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 415286639

The acute respiratory distress syndrome (ARDS) is a life-threating condition that can develop following major surgery or as a complication of critical illness. ARDS is characterized by acute diffuse lung injury (ALI) with increased pulmonary vascular permeability and loss of aerated lung tissue, clinically resulting in acute hypoxemic respiratory failure and bilateral pulmonary edema. Although mortality rates have been progressively decreased due to advances in supportive care and improved ventilation strategies in the last decade, the outcome of ARDS patients remains unfavorable with mortality rates ranging from 35-60%. Currently, there are no specific pharmacotherapies available.Dysregulated inflammation and alveolar barrier disruption are the central pathophysiological hallmarks of ALI/ARDS. Once recruited into the lung, inflammatory cells come into close spatial contact with the alveolar epithelium and release cytotoxic mediators, resulting in increased vascular permeability and a sustained loss of normal endothelial barrier function. Recently, there is increasing evidence for regulatory roles of microRNAs (miR) in the pathogenesis of ARDS. microRNAs are small non-coding RNAs involved in the post-transcriptional regulation of target genes. The microRNA-223 is considered a negative regulator of inflammation and is upregulated in pulmonary epithelial cells in acute lung injury. In a mouse model of ARDS, miR-223 deficiency resulted in severe lung inflammation, whereas the induction of pulmonary miR-223 overexpression was protective. Interestingly, it has been demonstrated that neutrophil granulocytes transfer miR-223 via exosomes to lung epithelial cells (microRNA shuttling) inducing an anti-inflammatory response that may be targeted for ARDS treatment. Thus, the ultimate goal of this project is to understand the underlying molecular mechanisms of neutrophil-epithelial microRNA shuttling in the pathophysiological phases of ARDS to evaluate the modulation of miR-223 expression as a therapeutic strategy. Consequently, we aim to characterize the kinectics of neutrophil miR-223 release and subsequent uptake in lung epithelia in vitro using co-culture models of human neutrophils and pulmonary epithelial cells. Based on a microarray screening of lung epithelial cells overexpressing miR-223, we intend to identify miR-223-regulated signaling pathways and investigate the functional role of potential miR-223 target genes in attenuating pulmonary epithelial inflammation. Furthermore, we will examine the impact of specific miR-223 deletion in neutrophils in ARDS induction and resolution in vivo using mice with a conditional miR-223 knock-out. In these animals, miR-223 will be reinduced by intratracheal and systemical administration of miR-223 containing nanoparticles during onset and resolution of ARDS. The knowledge of these studies can be utilised to develop a rational strategy for targeted micro-RNA-based therapy of ARDS.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Holger Klaus Eltzschig, Ph.D.