Experimental analysis of potential micrornas encoded during and after blood brain barrier disruption

MicroRNAs (miRNAs) regulate gene expression and have a critical role in many biological processes in health and disease conditions. Recent studies showed that Blood-brain barrier (BBB) break down is directly leading to brain dysfunction and damage. We thus hypothesized that miRNA expression profiles in brain subjected to different insults to the BBB would show common as well as unique miRNA expression profiles. Based on previously published aray data from BBB-injured or albumin-exposed brains (Cacheaux et aI., 2009) the top 50 3´UTR significant BBB genes that considered with all the known Rattus norvegicus mirna (249 miRNAs) downloded from Rfam database were chosen as potential targets. We used NBmiRTar target prediction tool (Yousef et aI., 2007) and the procedure predicted 357 target sites. In this study, rat´s brains were exposed to sodium deoxycholate - a known BBB opener, serum-derived albumin and vascular damage induced by Rose-bengal with focal laser exposure. Sham-operated animals were used as controls. From the prediction results, we validate the regulation of hsamiR-342, hsa-miR-326 candidates and hsa-mir-Iet-7c miRNAs as an internal control by using TaqMan miRNA Real Time PCR assay. MiRNAs changed more than 1.5-fold in brain after each experimental manipulation; hsa-mir-326 and hsa-miR-342 were significantly (pvalue = 0.0158 and 0.0017, respectively) upregulated in brains after sodium deoxycholate treatment and Rose-bengal with focal laser exposure, respectively. Our study revealed significant (pvalue = 0.0038) downregulation of hsa-miR-342 in brains treated with serumderived albumin compared to control brains. The results show the possible use of brain miRNAs as biomarkers for BBB injury; that selected brain miRNAs may be associated with common vascular injuries and that concerted changes in gene expression after brain injury are potentially accounted for by changes in miRNA expression.