ABSTRACT: Introduction: Brain plasticity, synaptic regeneration and neuroinflammation are crucial mechanisms that play important roles in the recovery from acute brain injuries, such as aneurysmal subarachnoid hemorrhage (aSAH), ischemic stroke (IS), and traumatic brain injury (TBI). The p75 neurotrophic receptor (p75NTR) is a significant receptor that modulates brain plasticity, neuroinflammation and apoptosis, making it an interesting target for therapeutic interventions. However, despite the progress made in understanding the molecular mechanisms involved in brain plasticity and neuroinflammation, there are still significant knowledge gaps in identifying protein biomarkers and microRNAs (miRNAs) associated with different types of acute brain injuries. Addressing these gaps will be critical in advancing our understanding of the underlying mechanisms involved in brain injury and developing effective therapies or prognostic strategies for recovery. Hypotheses: We hypothesized that changes in serum levels of p75NTR and its linked neuroinflammatory signaling proteins could predict recovery from acute brain injuries, regardless of injury type. Differentially expressed (DE) circulating miRNAs following acute brain injuries may regulate studied protein targets and overall injury outcome. Methods: A prospective cohort of 74 patients with ischemic stroke (n=30), aneurysmal subarachnoid hemorrhage (n=31), and traumatic brain injury (n=13) was evaluated. Serum samples were collected at two time points after the injury (early at 1.9 ± 1.0 days and late at 5.9 ± 2.2 days) and outcome evaluation was performed after three months. Six proteins were measured using ELISAs: p75NTR, NGF, sortilin, IL1, TNF, and cyclophilin A. A 2-tailed 2-sample t-test, univariate, and multivariate linear discriminant analysis (LDA) was used to compare serum molecules between patients with favorable (modified Rankin Scale (mRS) 0-3) and unfavorable outcome (mRS 4-6). Additionally, circulating miRNAs were extracted from the samples (n=48, early and late) and DE miRNAs were identified using DESeq2. The miRNA putative target genes were predicted and LDA was performed using the normalized expression values of identified DE miRNAs. Results: In this study, p75NTR (p < 0.01) and IL1 (p < 0.05) were found to be independently associated with outcome among the six circulating protein biomarkers studied. Combinatory LDA analysis of all six biomarkers showed significant predictive value for favorable outcome (OR 2.95 (1.46-5.98); area under the curve (AUC)= 71.2%, 95% CI = (0.590-0.833), p = 0.003). Temporal alterations of miRNA expression were observed in the aSAH, TBI, and IS groups (p<0.05, FDR corrected). Twenty-three common miRNAs were identified that differentiated favorable and unfavorable outcome (p<0.05) in all three groups. LDA of four identified miRNAs with predicted targets to studied proteins showed high predictive accuracy (OR (95% CI) 11.7 (2.39-226)); AUC = 94.1%, 95% CI = (0.849 - 1.00), p = 0.016). Conclusions This study indicates that assessing serum levels of p75NTR and its mechanistically linked proteins can predict recovery outcome in patients with different types of acute brain injuries. The combined miRNA and protein biomarker models demonstrated accurate outcome prediction across diverse injury types, implying the presence of a common recovery mechanism. DE miRNAs were found to target the studied molecules, suggesting a potential mechanistical role in recovery. The identified common miRNAs may provide new targets for mechanistic validation in disease models. Further investigation is warranted to validate and explore the potential of these proteins and miRNAs in prognostication and as therapeutic targets for enhancing recovery from acute brain injuries.
