Fluid proteomics of CSF and serum reveal important neuroinflammatory proteins in blood–brain barrier disruption and outcome prediction following severe traumatic brain injury: a prospective, observational study

Abstract

Background Severe traumatic brain injury (TBI) is associated with blood–brain barrier (BBB) disruption and a subsequent neuroinflammatory process. We aimed to perform a multiplex screening of brain enriched and inflammatory proteins in blood and cerebrospinal fluid (CSF) in order to study their role in BBB disruption, neuroinflammation and long-term functional outcome in TBI patients and healthy controls. Methods We conducted a prospective, observational study on 90 severe TBI patients and 15 control subjects. Clinical outcome data, Glasgow Outcome Score, was collected after 6–12 months. We utilized a suspension bead antibody array analyzed on a FlexMap 3D Luminex platform to characterize 177 unique proteins in matched CSF and serum samples. In addition, we assessed BBB disruption using the CSF-serum albumin quotient (QA), and performed Apolipoprotein E-genotyping as the latter has been linked to BBB function in the absence of trauma. We employed pathway-, cluster-, and proportional odds regression analyses. Key findings were validated in blood samples from an independent TBI cohort. Results TBI patients had an upregulation of structural CNS and neuroinflammatory pathways in both CSF and serum. In total, 114 proteins correlated with QA, among which the top-correlated proteins were complement proteins. A cluster analysis revealed protein levels to be strongly associated with BBB integrity, but not carriage of the Apolipoprotein E4-variant. Among cluster-derived proteins, innate immune pathways were upregulated. Forty unique proteins emanated as novel independent predictors of clinical outcome, that individually explained ~ 10% additional model variance. Among proteins significantly different between TBI patients with intact or disrupted BBB, complement C9 in CSF (p = 0.014, ΔR2 = 7.4%) and complement factor B in serum (p = 0.003, ΔR2 = 9.2%) were independent outcome predictors also following step-down modelling. Conclusions This represents the largest concomitant CSF and serum proteomic profiling study so far reported in TBI, providing substantial support to the notion that neuroinflammatory markers, including complement activation, predicts BBB disruption and long-term outcome. Individual proteins identified here could potentially serve to refine current biomarker modelling or represent novel treatment targets in severe TBI.

Quantitative Proteomics Reveals the Dynamic Pathophysiology Across Different Stages in a Rat Model of Severe Traumatic Brain Injury

“…By comparing the molecular pattern of cortex in focal and diffuse TBI, some specific proteomic biomarkers of diffuse TBI were obtained, including peptides related to neurodegeneration (Tau and Fascin) and antioxidant defense (Glutathione S -transferase Mu 3, Peroxiredoxin-6, Thioredoxin-dependent peroxide reductase) ( Abu Hamdeh et al, 2018 ). To harvest tissues conveniently, serum ( Anada et al, 2018 ; Huie et al, 2019 ; Lindblad et al, 2021 ), cerebrospinal fluid ( Lindblad et al, 2021 ), plasma ( Bao et al, 2018 ; Ojo et al, 2018 ), and exosomal samples ( Moyron et al, 2017 ) have been attempted for proteomics analysis. Thus, the yielded biomarkers in TBI were screened and verified from the differential proteins produced after comparison with various control groups.…”

Extracellular Fluid, Cerebrospinal Fluid and Plasma Biomarkers of Axonal and Neuronal Injury Following Intracerebral Hemorrhage

“…25,26 Our ndings of lower levels of biomarkers in the ECF than in the CSF may re ect a reduced relative recovery across the MD membrane, 24 reduced recovery due to biomarker adsorption to surfaces 5,27 , physiological factors including tissue clearance 28 and variability in blood-brain-barrier (BBB) integrity causing contamination by serum levels. [29][30][31] Peripheral plasma levels on the other hand, present the least invasive method although challenges include dilution effect of CNS derived biomarkers, and contamination by peripheral non-CNS production, re ected in our present study by signi cantly lower levels in plasma of all biomarkers. ECF concentrations of Aβ did not uctuate over time, implying a consistent production or release can a stable relative recovery be assumed.…”

Proteomic profiles in cerebrospinal fluid predicted death and disability in term infants with perinatal asphyxia: A pilot study

“…The selected proteins all provided high tissue enrichment in the central nervous system and were involved in different brain functions. 6 , 7 The FlexMap3D instrument (Luminex Corp, Texas, USA) was used to analyse cross‐linked interacting proteins in the antibody suspension bead. The relative abundance of proteins is reported as the median fluorescent intensities for each sample and bead identity.…”

“…Protein arrays have been used in preclinical and clinical studies of adults with traumatic brain injuiries. 6 , 7 They have also been used for protein profiling of cerebrospinal fluid (CSF) from preterm infants. 8 The present study used antibody suspension bead array technology to assess the levels of brain enriched proteins and known inflammatory mediators 9 in the CSF of infants with HIE.…”