Lectin-like oxidized low-density receptor-1 attenuates pneumonia-induced lung injury

Identifying host factors that contribute to pneumonia incidence and severity are of utmost importance to guiding the development of more effective therapies. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a scavenger receptor known to promote vascular injury and inflammation, but it is unknown whether and how LOX-1 functions in the lung. Here, we provide evidence of substantial accumulation of LOX-1 in the lungs of ARDS patients and in mice with pneumonia. Unlike previously described injurious contributions of LOX-1, we found that LOX-1 is uniquely protective in the pulmonary airspaces, limiting proteinaceous edema and inflammation. We also identified alveolar macrophages and recruited neutrophils as two prominent sites of LOX-1 expression in the lungs, whereby macrophages are capable of further induction during pneumonia and neutrophils exhibit a rapid, but heterogenous elevation of LOX-1 in the infected lung. Blockade of LOX-1 led to dysregulated immune signaling in alveolar macrophages, marked by alterations in activation markers and a concomitant elevation of inflammatory gene networks. However, bone marrow chimeras also suggested a prominent role for neutrophils in LOX-1-mediated lung protection, further supported by LOX-1+ neutrophils exhibiting transcriptional changes consistent with reparative processes. Taken together, this work establishes LOX-1 as a tissue-protective factor in the lungs during pneumonia, possibly mediated by its influence on immune signaling in alveolar macrophages (AMs) and LOX-1+ airspace neutrophils. 1. An assessment of transcriptional differences in alveolar macrophages isolated from mice with pneumonia + anti-LOX-1 or control antibody treatment 2. An assessment of transcriptional differences in LOX-1+ v LOX-1- neutrophils isolated from mice with pneumonia