ARDS neutrophils have a distinct phenotype and are resistant to phosphoinositide 3-kinase inhibition

Rationale: The acute respiratory distress syndrome is refractory to pharmacological intervention. Inappropriate activation of alveolar neutrophils is believed to underpin this disease’s complex pathophysiology, yet these cells have been little studied.

Objectives: To examine the functional and transcriptional profiles of patient blood and alveolar neutrophils compared to healthy volunteer cells, and define their sensitivity to phosphoinositide 3-kinase inhibition.

Methods: Twenty three ventilated patients underwent bronchoalveolar lavage. Alveolar and blood neutrophil apoptosis, phagocytosis and adhesion molecules were quantified by flow cytometry, and oxidase responses by chemiluminescence. Cytokine and transcriptional profiling utilized multiplex and GeneChip arrays.

Measurements and Main Results: Patient blood and alveolar neutrophils were distinct from healthy circulating cells, with increased CD11b and reduced CD62L expression, delayed constitutive apoptosis and primed oxidase responses. Incubating control cells with disease bronchoalveolar lavage recapitulated the aberrant functional phenotype and this could be reversed by phosphoinositide 3-kinase inhibitors. In contrast, the pro-survival phenotype of patient cells was resistant to phosphoinositide 3-kinase inhibition. RNA transcriptomic analysis revealed modified immune, cytoskeletal and cell death pathways in patient cells, aligning closely to sepsis and burns data sets but not phosphoinositide 3-kinase signatures.

Conclusions: Acute respiratory distress syndrome blood and alveolar neutrophils display a distinct primed, pro-survival profile and transcriptional signature. The enhanced respiratory burst was phosphoinositide 3-kinase-dependent, but delayed apoptosis and the altered transcriptional profile were not. These unexpected findings cast doubt over the utility of phosphoinositide 3-kinase inhibition in acute respiratory distress syndrome and highlight the importance of evaluating novel therapeutic strategies in patient-derived cells.