Effects of Resolvin D1 on blood-brain barrier disruption induced by Angiotensin II

Chronic hypertension is a major contributor to cerebrovascular dysfunction and the progression of neurodegenerative disease through disruption of the blood-brain barrier (BBB) and neurovascular unit (NVU). Although hypertension can be controlled by antihypertensive medications, therapeutic approaches cannot fully ameliorate the damage to the cardiovascular and cerebrovascular structures. Specialized pro-resolving mediators such as Resolvin D1 (RvD1) have emerged as a promising candidate for improving neuroinflammation and restoring BBB integrity under hypertensive conditions. In this study, we investigated the therapeutic potential of RvD1 in attenuating BBB disruption induced by chronic hypertension. An in vitro BBB model was established using mouse brain microvascular endothelial cells (bEnd.3) and following Ang (Angiotensin) II and/or RvD1 administration, cell viability, transendothelial electrical resistance (TEER), paracellular permeability of sodium fluorescein (NaFl), and expression of claudin-5, caveolin-1 (Cav-1), and major facilitator superfamily domain 2a (Mfsd2a) were assessed. In parallel, chronic hypertension was induced in mice via Ang II (1000 ng/kg/min) infusion using osmotic mini pumps. Then, hypertensive animals were intraperitoneally treated with RvD1 (3 μg/kg/day) for 5 days. BBB integrity was evaluated via quantification of Alexa Fluor 594 conjugated bovine serum albumin (BSA) leakage and, claudin-5, Cav-1, and Mfsd2a expressions. In addition, Prussian blue staining was performed to assess microvascular damage, and glial fibrillary acidic protein (GFAP) immunofluorescence staining was conducted to evaluate astrogliosis. Ang II administration resulted in a significant decrease in cell viability and TEER values, accompanied by an increase in NaFl permeability (p<0.01). Furthermore, Ang II caused alterations in the paracellular pathway by decreasing claudin-5 and in the transcellular pathway by increasing Cav-1 and decreasing Mfsd2a expression (p<0.001). RvD1 treatment remarkably increased TEER values (p<0.001), reduced NaFl permeability (p<0.001), downregulated Cav-1 (p<0.01), and upregulated claudin-5 (p<0.05) and Mfsd2a expressions (p<0.001) in Ang II-treated cells. In vivo, subcutaneous Ang II-infusion elevated arterial blood pressure, increased Alexa Fluor 594-conjugated BSA leakage, exacerbated microhemorrhages, and astrogliosis as evidenced by increased GFAP intensity in the brain (p<0.01). In addition, Cav-1 was upregulated (p<0.0001) along with the downregulation of claudin-5 (p<0.01) and Mfsd2a (p<0.05) in these animals. Following RvD1 administration, arterial blood pressure and BBB permeability of Alexa Fluor-594 conjugated tracer were decreased, and microhemorrhage burden was reduced along with the attenuation of reactive astrocytes (p<0.01). Moreover, RvD1 restored tight junctions by increasing claudin-5, and reversed transcytotic shift by decreasing Cav-1 (p<0.0001) and increasing Mfsd2a expressions (p<0.0001). In conclusion, our results demonstrate that RvD1 protects BBB integrity under hypertensive conditions. Thus, RvD1 can be a promising therapeutic agent against hypertension-associated cerebrovascular pathologies.