Imaging mass spectrometry reveals loss of polyunsaturated cardiolipins in the cortical contusion, hippocampus, and thalamus after traumatic brain injury

Abstract

Traumatic brain injury (TBI) leads to changes in ion fluxes, alterations in mitochondrial function and increased generation of reactive oxygen species, resulting in secondary tissue damage. Mitochondria play important signaling roles in coordination of multiple metabolic platforms in addition to their well-known role in bioenergetics. Mitochondrial signaling strongly depends on cardiolipin (CL), a mitochondria-specific structurally unusual anionic phospholipid containing four fatty acyl chains. While our previous reports indicated that CL is selectively oxidized and presents itself as a target for the redox therapy following TBI, the topography of changes of CL in the injured brain remained to be defined. Here we present a MALDI imaging study which reports regio-specific changes in CL, in a controlled cortical impact (CCI) model of TBI in rats. MALDI imaging revealed that TBI caused early decreases in CL in the contusional cortex, ipsilateral hippocampus and thalamus with the most highly unsaturated CL species being most susceptible to loss. Phosphatidylinositol was the only other lipid species that exhibited a significant decrease, albeit to a lesser extent than CL. Signals for other lipids remained unchanged. This is the first study evaluating the spatial distribution of CL loss after acute brain injury. We propose that the CL loss may constitute an upstream mechanism for CL-driven signaling in different brain regions as an early response mechanism and may also underlie the bioenergetic changes that occur in hippocampal, cortical and thalamic mitochondria after TBI.

Gas Cluster Ion Beam Time-of-Flight Secondary Ion Mass Spectrometry High-Resolution Imaging of Cardiolipin Speciation in the Brain: Identification of Molecular Losses after Traumatic Injury

“…This enhancement of CL signals from EDC/PLC tissue treatment is consistent with our previous results with MALDI imaging. 9,10 Recently, Angerer et al have shown that frozen hydrated tissue and dried tissue exposed to various reactive vapors aids in the analysis of brain lipids by TOF-SIMS. Enhanced high-mass species were observed, but no CL species were reported in that study.…”

“…However, since our previous studies indicated that the tissue treatment protocol enhanced the signals for gangliosides in MALDI imaging, 9,10 we examined the higher mass region for indications of them by GCIB-SIMS. 9,10 Interestingly, signals for several brain ganglioside species were also enhanced by EDC/PLC treatment (Figure 1f).…”

“…However, since our previous studies indicated that the tissue treatment protocol enhanced the signals for gangliosides in MALDI imaging, 9,10 we examined the higher mass region for indications of them by GCIB-SIMS. 9,10 Interestingly, signals for several brain ganglioside species were also enhanced by EDC/PLC treatment (Figure 1f). Without treatment, Ganglioside GM1 with putative 18:0 and 20:0 fatty acyl chains (d36:1 and d38:1, respectively) was hardly detectable by GCIB-SIMS as [M − H] − ions ( m / z 1544.9 and 1572.9, respectively) and the spectrum was devoid of higher-order gangliosides (Figure 1c).…”

PEBP1 Wardens Ferroptosis by Enabling Lipoxygenase Generation of Lipid Death Signals

“…Kidney sections for high spatial resolution analysis were coated with 40 mg/ml DHB in 50 % methanol using a TM Imaging Sprayer (HTX Technologies). Brain and lung sections were coated with DHB as a 0.5 M solution in 2:1 chloroform (HPLC grade, Sigma-Aldrich) to methanol (LC/MS grade, ThermoFisher Scientific) according to our previously published protocol (Sparvero et al, 2016). In brief, the matrix solution was loaded into a capillary-sprayer aerosol device.…”

“…Lung images were acquired at 50 μm lateral resolution in both positive and negative polarity, brain in positive polarity at 200 μm, and kidney in positive polarity at 5 μm. MALDI-MS images from Bruker instruments were produced using FlexImaging 4.0 software (Bruker Daltonics), and those from the AB Sciex with MSI Reader v0.06 software (www.msireader.com) using our previously published protocol (Sparvero et al, 2016). Heat maps for a given mass/charge ( m / z ) value ± 0.25 Da were generated either as a rainbow display (for single species) or red/green (for co-localization of two different species).…”