Abstract

AIMS:
Carotid artery disease (CAD) is an important risk factor for stroke. We first evaluated CAD and stroke pathology in elderly post-stroke survivors. To simulate CAD, we assessed long-term consequences of bilateral common carotid artery stenosis (BCAS) in mice and exposed them to environmental enrichment (EE).

METHODS:
Histopathological methods were used to determine degrees of CAD (% area stenosis), brain infarct types, sizes and distribution in post-stroke survivors and BCAS mice. Adult male C57BL/6J mice after BCAS or sham surgery were randomly assigned to standard housing (Std) or limited (3hrs) or full-time (Full) exposure to EE per day for 12 weeks.

RESULTS:
High frequencies of moderate carotid artery stenosis (51-75%) were evident in post-stroke survivors whereas those with severe CAD (>75% stenosis) exhibited greater numbers of cortical rather than subcortical infarcts and, were at higher risk of developing dementia. BCAS in mice reduced cerebral blood flow by 52% (P<0.01) and thickened carotid artery walls, regardless of EE duration. Remarkably, the total and cortical infarcts declined by >50% in BCAS mice exposed to EE compared with BCAS-Std (P<0.01). Frontal lobe and cortical strokes were associated with worsening working memory tested in a radial maze paradigm. Proteomic analysis revealed EE, both BCAS-3hrs and BCAS-Full attenuated coagulation cascade factors including fibrinogen and von Willebrand factor, markers of blood-brain barrier damage.

CONCLUSION:
Small cortical and subcortical infarcts were evident in both post-stroke survivors with CAD and BCAS mice. Experimental evidence suggested that moderate exposure to EE is sufficient to reduce subsequent stroke lesions.