Plasma metalloproteinase‐9 (MMP9) changes in acute mild traumatic brain injury (mTBI) and correlates with quantitative EEG

Abstract

Background and ObjectivesWe aim to explore blood plasma levels of matrix metalloproteinase‐9 (MMP9) in acute mild traumatic brain injury (mTBI), and test if MMP9 levels correlate with quantitative electroencephalography (qEEG) during working memory (WM) testing.MethodsStudy participants were recruited from the emergency department of Huntington Memorial Hospital in Pasadena, CA, consisting of thirteen acute mTBI civilian patients and seven controls who were trauma patients without head injury ranging between 18–50 years of age. Blood samples were collected from three time points: within 1 week, 14 days, and 30 days after the injury. To study blood‐brain‐barrier (BBB) integrity, we quantified three MMP9 peptides (SLGPALLLLQK, QLSLPETGELDSATLK, and LGLGADVAQVTGALR) using liquid chromatography and mass spectrometry with stable isotope standards. We also employed qEEG at each visit to investigate alpha frequency power during N‐back WM processing.Results & DiscussionWe detected the presence of all three MMP9 peptides in blood plasma. We observed that MMP9 peptide levels in both mTBI and controls were decreasing in abundance in the 2–4 weeks after injury compared to the first week. Importantly, the MMP9 levels of the LGLGADVAQVTGALR peptide but not the peptides from the pre‐protein, were significantly higher in the mTBI group 2–4 weeks after the injury, consistent with known “secondary injury” phenomena. MMP9 levels correlated with alpha power during WM testing, at the first visit for the controls but not for the mTBI patients, at specific brain regions during different WM load. Elevated MMP9 levels indicate the BBB integrity is compromised acutely after mTBI. The correlations between MMP9 and alpha power during WM that we only found in the trauma controls need further investigation.Support or Funding InformationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.