Microparticle derived proteins as potential biomarkers for cerebral vasospasm post subarachnoid hemorrhage. A preliminary study

Abstract

Objective: Cerebral vasospasm (CV) and associated secondary brain injury are major contributors to death and disability after aneurysmal subarachnoid hemorrhage (aSAH). Microparticles (MP) are small vesicular micro-molecules released by red and white blood cells, platelets and endothelial cells that can change rapidly and specifically depending on the type of cellular insult. They may serve as useful tools to target a specific pool of proteins associated with the development of CV post aSAH. In these studies, our goal was to use targeted MP-derived protein isolation to find reliable biomarkers indicating increased risk for the development of CV. We hypothesize that there are specific early changes in MP-derived protein expression in CV patients. These proteins may be useful as biomarkers for CV and may help us to further understand the mechanism for the development of CV. Patients Adult male and female patients with angiographically confirmed aSAH and an external ventricular drain (EVD) placed for medical or surgical needs were included in this study. Patients were closely monitored for CV development. Cerebrospinal fluid (CSF) was collected daily until EVD was removed.

Methods: Microparticles were isolated using serial ultra centrifugation. Differential protein expression in CSF microparticles was analyzed by a mass spectroscopy based system using isotopically-tagged peptides to profile proteins and determine their relative concentrations in individual patient samples. These proteins were correlated with the patient's clinical data and used to identify candidates for biomarkers predictive of CV.

Results: Over 140 proteins were isolated from CSF microparticles. Proteomic and molecular pathways analysis revealed marked differential expression of proteins in patients with CV. We identified specific candidate proteins that could potentially serve as early biomarkers for CV. ApoE, ApoD, synaptic nuclear envelope protein 1, clusterin, α-1-acid glycoprotein, plasma protease C1 inhibitor, and prostaglandin H2 D isomerase were downregulated in patients who developed CV post aSAH. Haptoglobin, fibrinogen α and γ chain, synaptic nuclear envelope protein 2, and hemoglobin subunits α and β were upregulated. Some of these proteins are associated with immune and metabolic processes and some have been specifically associated with cerebrovascular disease states.

Conclusions: This is the first preliminary demonstration that there is differential protein expression in CSF microparticles from CV patients. Alone or in combination, these and other proteins may be useful as reliable biomarkers to guide in stratifying patients into categories of risk to develop CV post aSAH. These results will deepen our understanding of the mechanisms of cerebral vasospasm and potentially facilitate the development of safer and more effective therapies therapies for cerebral vasospasm.

Keywords: Apolipoprotein; Biomarkers; Cerebro-spinal fluid; Haptoglobin; Microparticles; Prostaglandin isomerase.