miR-124-3p is a chronic regulator of gene expression after brain injury

Abstract

Traumatic brain injury (TBI) initiates molecular and cellular pathologies that underlie post-injury morbidities, including hippocampus-related memory decline and epileptogenesis. Non-coding small RNAs are master regulators of gene expression with the potential to affect multiple molecular pathways. To evaluate whether hippocampal gene expression networks are chronically regulated by microRNAs after TBI, we sampled the dentate gyrus of rats with severe TBI induced by lateral fluid-percussion injury 3 months earlier. Ingenuity pathway analysis revealed 30 upregulated miR-124-3p targets, suggesting that miR-124-3p is downregulated post-TBI (z-score = - 5.146, p < 0.05). Droplet digital polymerase chain reaction (ddPCR) and in situ hybridization confirmed the chronic downregulation of miR-124-3p (p < 0.05). Quantitative PCR analysis of two targets, Plp2 and Stat3, indicated that their upregulation correlated with the miR-124-3p downregulation (r = - 0.647, p < 0.05; r = - 0.629, p < 0.05, respectively). Immunohistochemical staining of STAT3 confirmed the increased protein expression. STRING analysis showed that 9 of the 30 miR-124-3p targets belonged to a STAT3 network. Reactome analysis and data mining connected the targets especially to inflammation and signal transduction. L1000CDS2 software revealed drugs (e.g., importazole, trichostatin A, and IKK-16) that could reverse the observed molecular changes. The translational value of our data was emphasized by in situ hybridization showing chronic post-traumatic downregulation of miR-124-3p in the dentate gyrus of TBI patients. Analysis of another brain injury model, status epilepticus, highlighted the fact that chronic downregulation of miR-124 is a common phenomenon after brain injury. Together, our findings indicate that miR-124-3p is a chronic modulator of molecular networks relevant to post-injury hippocampal pathologies in experimental models and in humans.

Discovery and validation of blood microRNAs as molecular biomarkers of epilepsy: Ways to close current knowledge gaps

“…Neuroinflammatory signaling is in part controlled by miR‐146a, and overexpression of miR‐146a following status epilepticus potently suppresses spontaneous recurrent seizures in mice . In addition, reduced levels of miR‐124 have been proposed to promote epileptogenesis through inflammatory and epigenetic targets in models of status epilepticus and traumatic brain injury . Thus, miRNAs also provide direct targets for antiepileptogenesis and disease‐modifying therapy development.…”

Chronic Regulation of miR-124-3p in the Perilesional Cortex after Experimental and Human TBI

“…miR-124-3p drive cells towards neuronal identity [35,36], and regulates gene expression by promoting neuron-specific splicing [37]. Our previous study on post-TBI downregulation of miR-124-3p in the dentate gyrus suggested a link between miR-124-3p and post-injury hippocampal pathologies such as epileptogenesis and memory decline [19]. To explore the role of miR-124-3p in the progression of cortical damage, we investigated the post-TBI expression pattern of miR-124-3p in the perilesional cortex in experimental and human TBI.…”

“…miRNA-based treatments show potential as disease-modifying network therapies after experimental TBI [9][10][11].Despite an increasing number of reports describing alterations in the regulation of miRNAs after TBI, our understanding of the regulation of the miRNome and its cellular localization after TBI is still in its infancy [12,13]. TBI regulates brain miRNA expression acutely [14][15][16][17], and some miRNAs remain regulated chronically-months to years after TBI [18,19]. Dysregulated miRNA levels are reported in the cortex [9,14,[20][21][22], hippocampus [15,16,18,19,[23][24][25][26][27], and plasma [28][29][30].…”

“…TBI regulates brain miRNA expression acutely [14][15][16][17], and some miRNAs remain regulated chronically-months to years after TBI [18,19]. Dysregulated miRNA levels are reported in the cortex [9,14,[20][21][22], hippocampus [15,16,18,19,[23][24][25][26][27], and plasma [28][29][30]. Only a few studies, however, have addressed miRNA expression in patients with TBI [13,19,23,28], highlighting the gap between preclinical and clinical studies.…”

“…Dysregulated miRNA levels are reported in the cortex [9,14,[20][21][22], hippocampus [15,16,18,19,[23][24][25][26][27], and plasma [28][29][30]. Only a few studies, however, have addressed miRNA expression in patients with TBI [13,19,23,28], highlighting the gap between preclinical and clinical studies. Our previous study showed that TBI results in miR-124-3p downregulation in both rat and human dentate gyrus, making this miRNA an interesting subject for further study.miR-124 is the most abundant microRNA in the brain, accounting for 25-48% of all brain miRNA pool [31].…”