• James Jm Loan, Caoimhe Kirby, Katherine Emelianova, Owen R Dando, Michael Tc Poon, Leisan Pimenova, Giles E Hardingham, Barry W McColl, Catharina Jm Klijn, Rustam Al-Shahi Salman, Floris Hbm Schreuder, and Neshika Samarasekera.
• Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK.
• J. Neurol. Neurosurg. Psychiatr. 2022 Feb 1; 93 (2): 126132126-132.

BackgroundInflammatory responses to intracerebral haemorrhage (ICH) are potential therapeutic targets. We aimed to quantify molecular markers of inflammation in human brain tissue after ICH compared with controls using meta-analysis.MethodsWe searched OVID MEDLINE (1946-) and Embase (1974-) in June 2020 for studies that reported any measure of a molecular marker of inflammation in brain tissue from five or more adults after ICH. We assessed risk of bias using a modified Newcastle-Ottawa Scale (mNOS; mNOS score 0-9; 9 indicates low bias), extracted aggregate data, and used random effects meta-analysis to pool associations of molecules where more than two independent case-control studies reported the same outcome and Gene Ontology enrichment analysis to identify over-represented biological processes in pooled sets of differentially expressed molecules (International Prospective Register of Systematic Reviews ID: CRD42018110204).ResultsOf 7501 studies identified, 44 were included: 6 were case series and 38 were case-control studies (median mNOS score 4, IQR 3-5). We extracted data from 21 491 analyses of 20 951 molecules reported by 38 case-control studies. Only one molecule (interleukin-1β protein) was quantified in three case-control studies (127 ICH cases vs 41 ICH-free controls), which found increased abundance of interleukin-1β protein after ICH (corrected standardised mean difference 1.74, 95% CI 0.28 to 3.21, p=0.036, I2=46%). Processes associated with interleukin-1β signalling were enriched in sets of molecules that were more abundant after ICH.ConclusionInterleukin-1β abundance is increased after ICH, but analyses of other inflammatory molecules after ICH lack replication. Interleukin-1β pathway modulators may optimise inflammatory responses to ICH and merit testing in clinical trials.© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY. Published by BMJ.

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