High-dimensional proteomic analysis for pathophysiological classification of Traumatic Brain Injury

ABSTRACT:

Pathophysiology and outcomes after Traumatic Brain Injury (TBI) are complex and highly heterogenous. Current classifications are uninformative about pathophysiology, which limits prognostication and treatment. Fluid-based biomarkers can identify pathways and proteins relevant to TBI pathophysiology. Proteomic approaches are well suited to exploring complex mechanisms of disease, as they enable sensitive assessment of an expansive range of proteins. We used novel high-dimensional, multiplex proteomic assays to study changes in plasma protein expression in acute moderate-severe TBI.

We analysed samples from 88 participants in the longitudinal BIO-AX-TBI cohort (n=38 TBI within 10 days of injury, n=22 non-TBI trauma, n=28 non-injured controls) on two platforms: Alamar NULISA™ CNS Diseases and OLINK® Target 96 Inflammation. Participants also had data available from Simoa® (neurofilament light, GFAP, total tau, UCHL1) and Millipore (S100B). The Alamar panel assesses 120 proteins, most of which have not been investigated before in TBI, as well as proteins, such as GFAP, which differentiate TBI from non-injured and non-TBI trauma controls. A subset (n=29 TBI, n=24 non-injured controls) also had subacute 3T MRI measures of lesion volume and white matter injury (fractional anisotropy, scanned 10 days to 6 weeks after injury).

Differential Expression analysis identified 16 proteins with TBI-specific significantly different plasma expression. These were neuronal markers (calbindin2, UCHL1, visinin-like protein1), astroglial markers (S100B, GFAP), tau and other neurodegenerative disease proteins (total tau, pTau231, PSEN1, amyloid beta42, 14-3-3γ), inflammatory cytokines (IL16, CCL2, ficolin2), cell signalling (SFRP1), cell metabolism (MDH1) and autophagy related (sequestome1) proteins. Acute plasma levels of UCHL1, PSEN1, total tau and pTau231 correlated with subacute lesion volume, while sequestome1 was correlated with whole white matter skeleton fractional anisotropy and CCL2 was inversely correlated with corpus callosum FA. Neuronal, astroglial, tau and neurodegenerative proteins correlated with each other, and IL16, MDH1 and sequestome1. Clustering (k means) by acute protein expression identified 3 TBI subgroups which had differential injury patterns, but did not differ in age or outcome. Proteins that overlapped on two platforms had excellent (r>0.8) correlations between values.

We identified TBI-specific changes in acute plasma levels of proteins involved in amyloid processing, inflammatory and cellular processes such as autophagy. These changes were related to patterns of injury, thus demonstrating that processes previously only studied in animal models are also relevant in human TBI pathophysiology. Our study highlights the potential of proteomic analysis to improve the classification and understanding of TBI pathophysiology, with implications for prognostication and treatment development.

AUTHORS & AFFILIATIONS:

Lucia M. Li1,2, Eleftheria Kodosaki3,4, Amanda Heselgrave3,4, Henrik Zetterberg4,5,6, Neil Graham1,2, Karl Zimmerman1,2, Eyal Soreq1,2, Thomas Parker1,2, Elena Garbero7, Federico Moro8, Sandra Magnoni9, Guido Bertolini7, David J. Loane10,11, David J Sharp1,2

1Department of Brain Sciences, Imperial College London, Sir Michael Uren Building, 86 Wood Lane, W12 0BZ 2 UKDRI Centre for Care Research & Technology, London, UK 3 Department of Neurodegenerative Disease, UCL Institute of Neurology, London, UK 4 Dementia Research Institute at UCL, London, UK 5 Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. 6 Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden. 7Department of Medical Epidemiology, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy 8 Department of Acute Brain and Cardiovascular Injury, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Milan, Italy 9Department of Medicine, Surgery and Pharmacy, University of Sassari, Sassari-Italy 10 School of Biochemistry and Immunology, Trinity College Dublin, Ireland 11 Department of Anesthesiology and Shock, Trauma and Anesthesiology (STAR) Research Center, University of Maryland School of Medicine, Baltimore, Maryland, USA