Abstract 3872: Transgenic HuR in Astrocytes Increases Ischemic Lesion Size in Mice
Introduction: Stroke is a serious neurological disorder that affects more than 800,000 Americans each year. HuR, an mRNA binding protein, regulates gene expression by modulating the stability and translational efficiency of mRNAs containing adenine-uridine rich elements in the 3’ untranslated region. Genes implicated in neuroprotection and post-ischemic repair may be regulated by HuR. The current investigation utilizes transgenic mice engineered to express Flag-HuR in astrocytes using the glial fibrillary acidic protein (GFAP) promoter. We hypothesized that modulation of mRNA stability in astrocytes would change the outcome from transient cerebral ischemia.
Methods: Four mouse cohorts were studied: male or female and transgenic (TG) or wild-type (WT). Mice underwent 30-minute transient right middle cerebral artery occlusion (MCAO) and survived for 24 or 72h. Neurological scores were recorded after ischemia and prior to euthanasia, and brain tissue was sectioned for histology and immunolabeling. In a blinded fashion, Flag-HuR expressing nuclei were counted in peri-lesional regions of interest (ROI) and contralateral mirror ROIs, and ischemic/contralateral indices were calculated. Representative lesion size was determined in hematoxylin-eosin sections at the level of Bregma 1.10 mm.
Results:HuR-Flag expression: The transgene was expressed in peri-lesional astrocytes. 24h after MCAO, hormonally intact female mice had higher levels of Flag-HuR expression: Flag-HuR index was 5.9 ± 1.9 in females (n = 7) vs. 2.0 ± 0.7 in males (n = 6), p = 0.002, Mann-Whitney rank sum test. 72h after MCAO, TG expression declined in females to levels comparable to those of males.
Lesion size: There was no difference in lesion size between sex-matched TG and WT mice 24h post-MCAO, but at 72h lesion size was larger in TG females than WT females: 47% ± 12 (n = 10) vs. 22% ± 11 (n = 5), respectively, p = 0.002, t-test. Analysis of neurological scores, sex hormone levels, and long term survival is ongoing.
Discussion: We hypothesized that altering mRNA stability in ischemic astrocytes would change outcome from cerebral ischemia. Initial characterization of TG mice in which HuR was expressed under control of the GFAP promoter showed that ischemia results in peri-lesional upregulation of the transgene, which is more robust in females than males 24h after MCAO and comparable to males 72h after MCAO. Transgene expression correlated with increased lesion size in females 72h after MCAO. While the mechanism of this effect requires elucidation, our results suggest that HuR is a viable novel target for further investigation in cerebral ischemia.
- © 2012 by American Heart Association, Inc.