Determination of the Role of LOX‐1 during Escherichia coli Pneumonia

Abstract

Pneumonia is primarily caused by infection from bacteria, virus, and/or fungi and results in an acute lower respiratory tract inflammation. It is responsible for severe morbidity and mortality worldwide. Pneumonia is the foremost cause of children's hospitalizations in the United States and accounts for more than 935,000 deaths globally. In mice with severe bacterial pneumonia it is known that the pathophysiology of pneumonia is due to the overt activation and recruitment of host innate immune cells. Data generated in our lab has shown that there is an induction of the OLR1 gene that expresses lectin‐like oxidized low‐density lipoprotein receptor 1 (LOX‐1) in the lungs of mice during pneumonia. LOX‐1 is a receptor that is expressed in many cells, including host innate immune cells and it is commonly associated with atherosclerosis and inflammation. Herein, we aim to understand the role LOX‐1 plays during Gram‐negative bacterial pneumonia. Our recent results indicate that local neutralization of LOX‐1 within the lungs during pneumonia caused a significant increase in total tissue injury and inflammatory cytokines, indicating that LOX‐1 may have a protective effect.To determine the effect of LOX‐1 inhibition systemically, an intraperitoneal injection with 10 μg of anti‐LOX‐1 antibody was administered to neutralize LOX‐1 in C57BL/6J mice that were subsequently infected with Escherichia coli. Mice were euthanized 24 hours after infection and bronchoalveolar lavage fluid (BALF) samples were collected. In an ex vivo system, mouse lung epithelial (MLE‐12) cells were similarly treated with anti‐LOX‐1 antibody to observe the effect of neutralizing LOX‐1 on epithelial cell death. BALF from infected and uninfected mice was also added in the ex vivo model to more accurately recreate the conditions of the alveolar space. Total protein from MLE‐12 cells was then collected 24 hours after stimulation for analysis and characterization.Overall, the systemic neutralization of LOX‐1 in C57BL/6J mice during bacterial pneumonia did not significantly affect leukocyte recruitment or lung injury. In addition, ex vivo LOX‐1 neutralization in MLE‐12 cells did not affect apoptosis as measured by cleaved caspase‐3 on a western blot. In contrast with local inhibition of LOX‐1 in the lungs, systemic inhibition of LOX‐1 did not significantly limit tissue injury in mice with pneumonia. Blockade of LOX‐1 in ex vivo model did not remarkably affect epithelial cell death or apoptosis. Further studies involving measurement of resistance and resilience of lung tissue are underway and will more completely characterize the role of LOX‐1 during pneumonia.Support or Funding InformationNIH grants R01‐HL111449, R01‐GM120060, and T32‐HL007035.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.