Vitamin D deficiency has been clearly linked to major chronic diseases associated with oxidative stress, inflammation, and aging, including cardiovascular and neurodegenerative diseases, diabetes, and cancer. In particular, the cardiovascular system appears to be highly sensitive to vitamin D deficiency, as this may result in endothelial dysfunction and vascular defects via multiple mechanisms. Accordingly, recent research developments have led to the proposal that pharmacological interventions targeting either vitamin D deficiency or its key downstream effects, including defective autophagy and abnormal pro-oxidant and pro-inflammatory responses, may be able to limit the onset and severity of major cerebrovascular diseases, such as stroke and cerebrovascular malformations. Here we review the available evidence supporting the role of vitamin D in preventing or limiting the development of these cerebrovascular diseases, which are leading causes of disability and death all over the world.

Cellular apoptosis is a key pathological mechanism contributing to neuronal death following ischemic stroke. The pro-apoptotic Bcl-2 family protein, Bim, is an important regulator of apoptosis. In this study we investigated the effect of Bim expression on post-stroke functional outcomes, brain injury and inflammatory mechanisms. Wild type (WT) and Bim-deficient mice underwent 1-h middle cerebral artery occlusion (MCAO) followed by 23 h of reperfusion. At 24-h post-stroke, we assessed functional deficit, infarct volume, immune cell death, as well as the number of infiltrating immune cells in the brain and circulating immune cells. Bim deficiency did not affect infarct volume (P > 0.05), but resulted in less motor impairment (~ threefold greater latency to fall in hanging grip strength test, P < 0.05) and a lower median clinical score than WT mice (P < 0.05). Additionally following MCAO, Bim-deficient mice exhibited fewer myeloid cells (particularly neutrophils) in the ischemic brain hemisphere and less apoptosis of CD3⁺ T cells in the spleen and thymus compared with WT (all P < 0.05). After MCAO, Bim-deficient mice also tended to have more M2-polarised macrophages in the brain than WT mice. In sham-operated mice, we found that Bim deficiency resulted in greater numbers of circulating total CD45⁺ leukocytes, Ly6C^lo+ monocytes and CD3⁺ T cells, although MCAO did not affect the number of circulating cells at 24 h in either genotype. Our findings suggest that Bim deficiency modulates post-stroke outcomes, including reductions in motor impairment, brain inflammation and systemic post-stroke leukocyte apoptosis. Bim could therefore serve as a potential therapeutic target for stroke.

Hypertension increases the risk for cognitive impairment and promotes vascular and renal inflammation. We tested if immune cell infiltration occurs in the brain during hypertension and if it is associated with cognitive impairment. Male C57Bl/6 mice were administered vehicle, angiotensin II (0.7 mg/kg/d S.C.) or aldosterone (0.72 mg/kg/d S.C.) via osmotic minipumps. A subset of mice also received hydralazine (50 mg/kg) in their drinking water after minipump implantation. We measured systolic blood pressure, markers of inflammation, working memory and transcriptomic changes in the brain. Administration of angiotensin II or aldosterone increased blood pressure and promoted blood-brain barrier dysfunction, leukocyte accumulation and impairment of working memory in mice. When co-administered with angiotensin II, hydralazine prevented the development of these changes. In a separate cohort of mice in which angiotensin II-induced changes were first established, intervention with hydralazine lowered blood pressure but did not reverse brain inflammation or cognitive impairment. Finally, angiotensin II infusion altered the transcriptomic profile of the whole brain, as well as specifically within the hippocampus, and co-treatment with hydralazine modulated these changes. Experimental hypertension leads to brain inflammation and was associated with impaired working memory. Cognitive impairment that develops during hypertension can be inhibited, but not readily reversed, by anti-hypertensive therapy.