Background Aneurysmal subarachnoid hemorrhage induces proinflammatory and prothrombotic processes which have been associated with the development of delayed cerebral ischemia (DCI). Platelets appear to play a dominant role in the crosstalk of these processes. Platelet derived high-mobility-group-box-1 (HMGB1) activates neutrophils to release net-like chromatin structures (neutrophil extracellular traps, NETs). The enzymes protein-arginine deiminase type-4 (PAD4), DNase1 and myeloperoxidase (MPO), the citrullinated histone H3 (H3-Cit) and cell-free DNA (cfDNA) have been identified as markers of NET-release (NETosis). The role and interplay of the NETosis biomarkers in aSAH remain to be explored.

Methods A secondary analysis of a prospective, blinded, single-center biomarker observational study to investigate the role of HMGB1 was performed. The NETosis biomarkers H3-Cit, PAD4, cf-DNA and DNAse1 were assessed in patient serum obtained on admission and day 4. The association of these biomarkers with the development of DCI and clinical vasospasm (CVS) was analyzed. Treatment unrelated new infarction on CT after day 1 was defined as DCI. A composite variable of a delayed ischemic neurological deficits and/or pathologic transcranial doppler results were defined as CVS.

Results In 83/100 (83%) spontaneous non-traumatic subarachnoid hemorrhage patients, angiography confirmed a cerebral aneurysm. Five patients (5/83) died within 48h and DCI development could not be determined resulting in 78 aSAH patients for analysis. A total of 29/78 (37.2%) patients developed DCI and CVS. Among the CVS patients, 17/29 (58.6%) also developed DCI. In all serum samples on admission and day 4, H3-Cit, PAD4, cf-DNA and DNAse1 were detected. In all patients, H3-Cit levels significantly decreased from admission to day 4 (p=0.003-0.017). In contrast, in all patients, cf-DNA levels significantly increased from admission to day 4 (p<0.001). No differences were observed among patients who did or did not develop DCI or CVS. The PAD4 levels were similar among all subgroups and remained stable from admission to day 4 (p=ns). DNase1 levels significantly decreased from admission to day 4 in those patients who developed DCI (p=0.028) but not in the non-DCI, CVS or non-CVS subgroups.

Conclusion This exploratory analysis demonstrated presence of NETosis biomarkers in all aSAH patients. Differential dynamics of NETosis biomarkers were identified for DCI and CVS. Larger scaled studies are warranted to explore the role of NETosis in aSAH.

Disclosures P. Hendrix: None. J. Witsch: None. V. Spalart: None. H. Schneider: None. J. Oertel: None. J. Geisel: None. K. Martinod: 2; C; PEEL Therapeutics. 6; C; inventor US patent application 62-594,266. S. Hemmer: None.