Neutrophil cerebrovascular transmigration triggers rapid neurotoxicity through release of proteases associated with decondensed DNA.

Cerebrovascular inflammation contributes to diverse CNS disorders through mechanisms that are incompletely understood. The recruitment of neutrophils to the brain can contribute to neurotoxicity, particularly during acute brain injuries, such as cerebral ischemia, trauma, and seizures. However, the regulatory and effector mechanisms that underlie neutrophil-mediated neurotoxicity are poorly understood. In this study, we show that mouse neutrophils are not inherently toxic to neurons but that transendothelial migration across IL-1-stimulated brain endothelium triggers neutrophils to acquire a neurotoxic phenotype that causes the rapid death of cultured neurons. Neurotoxicity was induced by the addition of transmigrated neutrophils or conditioned medium, taken from transmigrated neutrophils, to neurons and was partially mediated by excitotoxic mechanisms and soluble proteins. Transmigrated neutrophils also released decondensed DNA associated with proteases, which are known as neutrophil extracellular traps. The blockade of histone-DNA complexes attenuated transmigrated neutrophil-induced neuronal death, whereas the inhibition of key neutrophil proteases in the presence of transmigrated neutrophils rescued neuronal viability. We also show that neutrophil recruitment in the brain is IL-1 dependent, and release of proteases and decondensed DNA from recruited neutrophils in the brain occurs in several in vivo experimental models of neuroinflammation. These data reveal new regulatory and effector mechanisms of neutrophil-mediated neurotoxicity (i.e., the release of proteases and decondensed DNA triggered by phenotypic transformation during cerebrovascular transmigration). Such mechanisms have important implications for neuroinflammatory disorders, notably in the development of antileukocyte therapies.

Assessment of Risk of Disease Progression in Pulmonary Arterial Hypertension: Insights from an International Survey of Clinical Practice.

INTRODUCTION: Current guidelines for the management of pulmonary arterial hypertension (PAH) recommend regular multi-parametric assessment of a patient's risk of clinical worsening or death, with the goal of achieving/maintaining a low-risk status. This international survey investigated how physicians currently assess risk and compared their clinical gestalt (judgement of risk) with the risk calculated using an algorithm based on the European Society of Cardiology (ESC)/European Respiratory Society (ERS) pulmonary hypertension guidelines and demonstrated to provide accurate mortality estimates. METHODS: PAH-treating physicians from Europe and the United States were surveyed on (1) how frequently they evaluated the recommended risk-assessment parameters and (2) to complete patient record forms (PRFs) with details on 5-7 recent adult PAH patients receiving treatment. For each PRF, physicians provided (1) their gestalt judgement of current risk and (2) details of the risk-assessment parameters measured. In accordance with the published method, measurements for ≥ 2 (of 6 selected) variables were required to calculate risk. Each variable was assigned a score of 1, 2 or 3 according to whether the measurement was within the thresholds for the low-, intermediate- or high-risk categories, as defined in the ESC/ERS guidelines. The average score represented the patient's calculated risk. RESULTS: In total, 90 physicians (52 cardiologists, 38 pulmonologists) completed the survey, providing a total of 623 PRFs; of these, 365 (59%) included ≥ 2 measurements required to calculate risk. Among these patients, the percentages assigned to low-, intermediate- and high-risk categories based on gestalt/calculation were 32%/15%, 45%/68% and 22%/17%, respectively. Overall, there was concordance between the gestalt and calculated risk category for 45% of patients. The greatest level of disparity was for patients judged to be at low risk, where 80% were assigned to higher risk categories based on their calculated risk. CONCLUSIONS: The results of this survey demonstrate that multi-parametric risk assessment is being performed in clinical practice, but not always to the extent recommended in the current guidelines. Further study on the utility of more regular measurement is required. FUNDING: Actelion Pharmaceuticals Ltd.