CSF neutrophils are implicated in the development of vasospasm in subarachnoid hemorrhage

Abstract

Background: Cerebral vasospasm is a significant cause of morbidity in patients after aneurysmal subarachnoid hemorrhage (aSAH). There are few effective treatments. The search for new treatments has focused predominantly on dilating cerebral blood vessels. Growing evidence supports a role for inflammation in its pathogenesis but no potential target for intervention has emerged.

Methods: CSF and clinical information from patients with aSAH were collected. Additionally, tyrosine modifications by stable isotope dilution HPLC with online tandem mass spectrometry were quantified in CSF samples.

Results: We report an association between neutrophil accumulation in the cerebrospinal fluid of patients with aSAH and the development of vasospasm. In particular, CSF neutrophil content of >62% on the third day after aSAH is an independent predictor of the later development of vasospasm (OR 6.8, 95% CI 2.0-23.3, P = 0.002). Further, activity of myeloperoxidase and NADPH oxidase is elevated in aSAH suggesting a role for modification of CSF proteins by reactive oxidant species.

Conclusions: Neutrophil percentage is an independent predictor of vasospasm in aSAH patients, days prior to its onset suggesting a role of neutrophils in vasospasm. The activity of neutrophil enzymes is also increased suggesting a mechanism for blood vessel damage. Inflammation mediated by neutrophils is a potential target for therapies in vasospasm. More study is necessary to determine the mechanism by which neutrophils damage cerebral blood vessels.

Fig. 1

CSF neutrophil percentage is associated with vasospasm after SAH. a In a cohort of 70 patients, there is an increased median neutrophil percentage in CSF 3 days after aSAH in patients who later develop vasospasm. Boxes denote interquartile range; whiskers are 90–10% intervals. b The receiver operator characteristic (ROC) identifies a cutoff of 62% neutrophils in the CSF as having the best predictive value for vasospasm (sensitivity 0.8, specificity 0.58)

Fig. 2

Levels of modifications to tyrosine residues that predict the source of ROS in CSF of patients with SAH (n = 17) and controls (n = 17). a, b Chlorotyrosine and bromotyrosine levels are significantly greater in patients with SAH supporting the action of the neutrophil enzyme myeloperoxidase in the production of ROS in SAH. c, d Orthotyrosine and nitrotyrosine level elevation suggests the specific actions of the neutrophil enzyme NADPH oxidase and myeloid cell iNOS. e Di-tyrosine levels were greatly elevated in SAH compared to controls although the levels varied greatly in SAH patients. Di-tyrosine levels may reflect the action of MPO and NADPH oxidase but also reflects the reactive oxidant milieu of the CSF after SAH. Boxes denote interquartile range; whiskers are 90–10% intervals