Identification of Serum Biomarkers in Brain-Injured Adults: Potential for Predicting Elevated Intracranial Pressure

Abstract

Brain injury biomarkers may have clinical utility in stratifying injury severity level, predicting adverse secondary events or outcomes, and monitoring the effectiveness of therapeutic interventions. As a biomarker source, serum offers several advantages over cerebrospinal fluid (CSF), including ease of accessibility and reduced risk to the patient. We screened pooled serum samples obtained from 11 severely injured traumatic brain injury (TBI) patients (Glasgow Coma Scale [GCS] <or= 8) and 11 age-, sex- and race-matched volunteers. Two time points-41.5 +/- 4.9 h and 66.3 +/- 6.6 h post-injury-were chosen for the initial screening analysis. Samples were immunodepleted for 12 highly abundant serum proteins, and then labeled with mass-balanced isobaric tags (iTRAQ), and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Identification and quantification of 2455 iTRAQ-labeled peptides that mapped to 160 proteins revealed 31 candidate biomarkers whose serum abundance was altered after injury. Changes in three candidate biomarkers (serum amyloid A, [SAA], c-reactive protein [CRP], retinol binding protein 4 [RBP4]) were verified using independent TBI and healthy volunteer serum samples. Receiver operating characteristic (ROC) curve analysis of CRP and SAA indicated they were robust indicators of injury even at very acute time points. Analysis of serum RBP4 levels at 24-36 h post-injury indicates it may predict subsequent increases in intracranial pressure (ICP) with a sensitivity of 86% and specificity of 88% at 11.6 mug/mL [n = 7, ICP < 20 mm Hg; n = 8, ICP > 25 mm Hg). Our results support the use of serum as a source for discovery of TBI biomarkers, and indicate that serum biomarkers may have utility for predicting secondary pathologies (e.g., elevated ICP) associated with TBI.

Biomarkers for the Diagnosis, Prognosis, and Evaluation of Treatment Efficacy for Traumatic Brain Injury

“…As an example of using serum samples from severely injured TBI patients and healthy volunteer controls, C-reactive protein and serum amyloid A have been reported to be capable of distinguishing between these two groups. 8 However, both of these proteins are general indicators of injury/infection, making them less likely to distinguish brain injury patients from persons with other bodily injuries. On the other hand, if brain injury alone is suspected, or if these markers were used in combination with other biomarkers, a rise in the levels of these proteins in serum may further support a brain injury diagnosis.…”

“…For example, it has been reported that the acute phase reactant proteins C-reactive protein and serum amyloid A are rapidly increased in the serum of brain trauma patients. 8 Using a multiplex approach to simultaneously evaluate a panel of chemokines and cytokines, Buttram et al 44 reported that severe TBI in children was associated with significant increases in the CSF levels of interleukin (IL)-1␤, IL-6, IL-12p70, IL-10, IL-8, and MIP-1␣. Because the injury to other organs can increase the serum level of these markers, these markers by themselves may not provide high specificity.…”

“…Using a "bottom-up" approach, it has been found that the serum concentration of retinol binding protein 4, measured between 24-and 36-h post injury, is predictive of subsequent increase of intracranial pressure (86% sensitivity; 88% specificity). 8 However, the transient nature and relatively small magnitude of this change likely limits its clinical usefulness. Ceruloplasmin, also called iron(II):oxygen oxidoreductase, is the major copper carrier protein in the blood and plays an important role in copper and iron metabolism.…”

C-reactive protein and vasospasm after aneurysmal subarachnoid hemorrhage1

“…Pathogenesis of vasospasm is due to smooth muscle contraction (entry and release of calcium and activation of calcium / calmodulin-dependent myosin light-chain kinase), endothelial injury (nitric oxide and endothelin-1 derangement), inflammation (inflammatory cytokines, intercellular adhesion molecules and genetic upregulation of inflammatory, proliferative and extracellular matrix-regulating genes) and vessel remodeling 1,3,[10][11][12][13] .…”

CE MALDI‐TOF/TOF MS for multiplexed quantification of proteins in human ventricular cerebrospinal fluid

“…The levels of hemoglobins were significantly increased over time, which correlates well with the expected increase of erythrocytes after intracranial bleeding 4-19 days after injury and their haemolysis that starts after approximately 12 h. Among the findings shown in Table 1, acute-phase, and thereto-related proteins, as well as other high abundant proteins such as albumin, immunoglobulins, hemoglobins and transferrin were detected. Acute-phase proteins have been described to be involved in the protection of the injured area as a response to prevent cell death [29,32] while increased levels of protease inhibitors, such as Cystatin C, have been related to an auto-protective brain response to protease hyper activation [29,33]. The fibrinogens identified in the vCSF sample could hypothetically be a blood contamination of CSF or a consequence of damage on the blood-CSF barrier.…”