Decay accelerating factor (CD55) protects against lectin pathway-mediated AT2 cell dysfunction in cigarette smoke-induced emphysema

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Project summary The mechanisms by which cigarette smoke (CS) activates the complement cascade to cause distal lung sterile injury and progression to COPD are not completely understood. Considering the critical role of complement in pathogen-induced inflammation, selective inhibition of the lectin complement pathway may result in decreased CS-induced emphysema-like airspace enlargement without an indiscriminate inhibition of complement’s response to pathogens. In Aim 1 we propose to investigate a novel mechanism of CS-induced lung injury, focusing on members of the lectin complement pathway that are necessary to induce complement deposition in the lung, decreased type-2 alveolar epithelial (AT2) cell proliferation and differentiation into AT1 cells, resulting in emphysema. In Aim 2 we will investigate whether decay accelerating factor (CD55), a complement regulator is necessary and required to protect against lectin complement deposition on AT2, preventing cell injury and improving AT2 proliferation / differentiation. In Aim 3 we propose a translational approach to develop a plasma complement activity score encompassing complement proteins and their regulators that could identify emphysema progression in smokers at risk and early COPD individuals. My proposal addresses the clinically relevant question whether harnessing membrane CD55 expression and signaling in AT2 cells can prevent lectin complement deposition and improve AT2 proliferation and differentiation mitigating emphysema development. Our ex-vivo and in-vivo murine studies are accompanied by measurements of complement proteins and regulators levels and activity in plasma from active smokers with and without COPD enrolled in COPDGene using a multiplex proteomic platform, SomaScan. Multiple complement SomaScan proteins are used to develop a “complement activity score” to help predict emphysema progression. Completion of this project will provide compelling experimental evidences that targeting lectin pathway activation and preserving membrane CD55 expression on AT2 cells ameliorates distal lung injury in murine models of emphysema and it can be harnessed as next generation biomarkers in human COPD disease. Our newly complement activity score could identify smokers at risk and early COPD subjects in future research and pharmacological clinical trials. The complementary expertise of our team, the translational aspect of the proposal, and access to well-phenotyped human specimens increase the relevance and chance of successful completion of this project.