Post-Stroke Learning Impairment and Brain Hemorrhage are Augmented in Hypertensive Mice

Hypertension is a major risk factor for both stroke and cognitive impairment, but it is unclear whether it may specifically affect post-stroke cognitive impairment. We assessed the effect of hypertension and/or stroke on brain injury, cognitive outcome, and the brain transcriptomic profile. C57BL/6J mice (n=117; 3-5 mo.) received s.c. infusion of either saline or angiotensin II (for 14 d or 28 d) followed by sham surgery or photothrombotic stroke targeting the prefrontal cortex seven days later. Cognitive function was assessed with the Barnes maze. RNA sequencing was used to quantify transcriptomic changes in the brain. Angiotensin II treatment produced spontaneous hemorrhaging on the stroke brain. In the Barnes maze, hypertensive mice that received stroke surgery had an increased escape latency compared to other groups (day 3: hypertensive + stroke=166.6±6.0 s vs. hypertensive + sham=122.8±13.8 s vs. normotensive + stroke=139.9±10.1 s vs. normotensive + sham=101.9±16.7 s), consistent with a greater learning impairment. RNA sequencing revealed >800 differentially expressed genes related to neuroinflammation in hypertensive + stroke vs. hypertensive + sham, which included genes associated with apoptosis, microRNAs, autophagy, anti-cognitive biomarkers and Wnt signaling. The combination of hypertension and stroke resulted in greater learning impairment and brain injury.