A Comparison of Gene Expression Profiles in Rat Brains Following Ischemic Stroke and Neuregulin Treatment

Stroke is a serious cardiovascular disease that can cause long-term disability or even death. About 87% of all strokes are ischemic strokes. Previous studies have shown that neuregulin-1 (NRG-1) was neuroprotective and improved neurological function in rat models of ischemic stroke. In this study, we analyzed early gene expression profiles after stroke and NRG-1 treatment over time. Ischemic stroke was induced by Middle Cerebral Artery Occlusion (MCAO). Rats were randomly allocated into 3 groups: Sham (Control), MCAO + vehicle and MCAO + NRG-1. Cortical brain tissues were collected 3 hours, 6 hours and 12 hours following MCAO and NRG-1 treatment and were subjected to microarray analysis. Gene expression analysis and ontology associations were performed using a series of bioinformatic tools namely Transcriptome Analysis Console (TAC), Short Time-series Expression Miner (STEM), Enrichr and STRING. TAC revealed several genes differentially expressed in a temporal manner. STEM organized these genes into 10 significant temporal expression profiles and similarly behaving genes into clusters using the novel STEM clustering method. Enrichr displayed the top gene ontologies associated with these clusters. Temporally upregulated genes were associated with cytokine-mediated signaling pathways, chemokine signaling and inflammatory responses post ischemic stroke. Temporally downregulated genes were associated with nervous system development and synaptic transmission post MCAO. STEM also revealed that genes exhibiting similar behavioral patterns over time, differed in terms of their magnitude of expression on comparison of MCAO and MCAO + NRG-1 profiles. Inflammation and stress-related genes such as IL-1B, CD44, HMOX1, HSP-70B, ICAM1, IL-6 and JAK2 were upregulated post ischemic stroke but were decreased between 1- and 2-fold upon NRG-1 treatment. For the profiles analyzed in this study, NRG-1 had the maximum effect at 12 hours in reducing damage post ischemic stroke. STRING highlighted known protein-protein interactions and identified IL-6 and IL-1B as central regulators or potential ‘Hub’ genes associated with the JAK/STAT signaling pathway. These results explore NRG-1’s role as a potent neuroprotectant and identify NRG-1 as a potential therapeutic target for the treatment of ischemic stroke