Extracellular fluid, cerebrospinal fluid and plasma biomarkers of axonal and neuronal injury following intracerebral hemorrhage

Abstract

Spontaneous intracerebral hemorrhage (ICH) is the most devastating form of stroke. To refine treatments, improved understanding of the secondary injury processes is needed. We compared energy metabolic, amyloid and neuroaxonal injury biomarkers in extracellular fluid (ECF) from the perihemorrhagic zone (PHZ) and non-injured (NCX) brain tissue, cerebrospinal fluid (CSF) and plasma. Patients (n = 11; age 61 ± 10 years) undergoing ICH surgery received two microdialysis (MD) catheters, one in PHZ, and one in NCX. ECF was analysed at three time intervals within the first 60 h post- surgery, as were CSF and plasma samples. Amyloid-beta (Aβ) 40 and 42, microtubule associated protein tau (tau), and neurofilament-light (NF-L) were analysed using Single molecule array (Simoa) technology. Median biomarker concentrations were lowest in plasma, higher in ECF and highest in CSF. Biomarker levels varied over time, with different dynamics in the three fluid compartments. In the PHZ, ECF levels of Aβ40 were lower, and tau higher when compared to the NCX. Altered levels of Aβ peptides, NF-L and tau may reflect brain tissue injury following ICH surgery. However, the dynamics of biomarker levels in the different fluid compartments should be considered in the study of pathophysiology or biomarkers in ICH patients.

Figure 1

Energy-metabolic markers in extracellular fluid. (a) Extracellular fluid (ECF) level of glucose was significantly lower in the perihemorrhagic zone (PHZ) compared to non-injured cortex (NCX) during the initial 68 h of monitoring (p = 0.004), although both levels were above critical level in both locations. (b) Lactate pyruvate ratio (LPR) was significantly higher in the PHZ compared to the NCX (p = 0.001) as were the (c) extracellular levels of glutamate and (d) glycerol (p < 0.0001). In addition, ECF levels of lactate and pyruvate were significantly higher in PHZ compared to NCX (p < 0.0001; data not shown). Mean and S.E.M. presented for clarity. ** = p ≤ 0.01, *** = p ≤ 0.001, **** = p < 0.0001. ECF = extracellular fluid; LPR = lactate pyruvate ratio; PHZ = perihaemorrhagic zone; NCX = non-injured cortex.

Figure 2

Aβ40 levels were lower, and tau levels higher, in perihemorrhagic zone (PHZ) when compared to non-injured cortex (NCX). All biomarker levels were lower in plasma, and higher in cerebrospinal fluid (CSF), compared to the extracellular fluid (ECF). (a) There were significantly lower levels of Aβ40 in extracellular fluid (ECF) of perihemorrhagic tissue (ECF-PHZ) compared to non-injured cortex (ECF-NCX; p = 0.048). Levels of Aβ40 were higher in CSF than ECF and plasma. (b) ECF levels of Aβ42 did not differ significantly between the PHZ and NCX. CSF levels of Aβ42 were higher than ECF and plasma levels. (c) ECF levels of tau were significantly higher in PHZ compared to NCX (p = 0.031). CSF levels of tau were higher than ECF from NCX but not PHZ (p = 0.209), and were higher than plasma levels of tau. (d) There was no significant difference in levels of Neurofilament light (NF-L) in ECF from PHZ compared to NCX. CSF levels of NF-L were significantly higher than in ECF and plasma. Aβ = amyloid-beta; Tau = microtubule-associated protein tau; NF-L = neurofilament light; ECF-PHZ = extracellular fluid of perihemorrhagic zone; ECF-NCX = extracellular fluid of non-injured cortex; CSF = cerebrospinal fluid; ECF = extracellular fluid; ns = not significant. * = p < 0.05; *** = p < 0.001.

Figure 3

Dynamic changes in Aβ, tau and NF-L biomarkers in the different fluid compartments over time. In extracellular fluid (ECF), median levels of Aβ-40, Aβ42 or NF-L did not change over time, whereas the tau levels significantly decreased over time. In cerebrospinal fluid (CSF), Aβ40 and Aβ42 levels increased, whereas there was no significant difference in the levels of tau or NF-L over time. In plasma, levels of Aβ40 and Aβ42 increased over time, as did the levels of tau and NF-L. Tukey box plot. Note that, for visual clarity, ECF and CSF levels are displayed on the left Y-axis which is logarithmic whereas plasma levels are displayed on the right Y-axis which is linear. Ns = not significant; * = p < 0.05.

Figure 4

Correlations matrix between biomarkers in extracellular fluid (ECF), cerebrospinal fluid (CSF) and plasma. There was a strong correlation between levels of Aβ40 and Aβ -42 in ECF (ρ = 0.93, p < 0.05), plasma (ρ = 0.68, p < 0.05) and CSF (ρ = 0.93, p < 0.05), as for levels of tau and neurofilament light (NF-L) in ECF (ρ 0.64, p < 0.05) and CSF (ρ = 0.86, p < 0.05), whereas in plasma this correlation was moderate (ρ = 0.32, p < 0.05). ECF = extracellular fluid; LPR = lactate pyruvate ratio; Aβ = amyloid beta; NF-L = neurofilament light. Legend shows strong negative correlation in black and strong positive correlation in white.