Abstract
The aim of this study was to assess the in vivo effects of quercetin on pial microvascular responses during transient bilateral common carotid artery occlusion (BCCAO) and reperfusion. Rat pial microcirculation was visualized by fluorescence microscopy through a closed cranial window. Pial arterioles were classified in five orders of branchings. Capillaries were assigned order 0, the smallest arterioles order 1, and the largest ones order 5. In ischemic rats, 30 min BCCAO and 60 min reperfusion caused arteriolar diameter decrease (by 14.5 ± 3.3% of baseline in order 2), microvascular leakage [0.47 ± 0.04, normalized gray levels (NGL)], leukocyte adhesion in venules (9 ± 2/100 μm venular length, v.l./30 s), and reduction of capillary perfusion (by 40 ± 7% of baseline). Moreover, at the end of BCCAO and reperfusion there was a significant increase in reactive oxygen species (ROS) formation when compared with baseline. Quercetin highest dose determined dilation in all arteriolar orders (by 40 ± 4% of baseline in order 2) and prevented microvascular permeability (0.15 ± 0.02 NGL), leukocyte adhesion (3 ± 1/100 μm v.l./30 s) as well as ROS formation, while capillary perfusion was protected. Inhibition of endothelial nitric oxide synthase (NOS) prior to quercetin reduced arteriolar dilation (order 2 diameter increase by 10.3 ± 2.5% of baseline) and caused permeability increase (0.29 ± 0.03 NGL); inhibition of neuronal NOS or inducible NOS did not affect quercetin-induced effects. Inhibition of guanylyl cyclase prior to quercetin reversed the quercetin’s effects on pial arteriolar diameter and leakage. In conclusion, quercetin was able to protect pial microcirculation from ischemia–reperfusion damage inducing arteriolar dilation likely by nitric oxide release. Moreover, quercetin scavenger activity blunted ROS formation preserving the blood–brain barrier integrity.
Highlights
The cerebral transient hypoperfusion, induced in experimental models by bilateral common carotid artery occlusion (BCCAO) and followed by reperfusion, causes significant microvascular alterations
Our suggestion was that quercetin could induce vasodilation through the NO pathway; we studied the effects of inhibiting endothelial nitric oxide synthase by N G-nitro-l-arginine-methyl ester (L-NAME), or neuronal NOS by 7-nitroindazole, or inducible NOS by l-N 6-(1iminoethyl) lysine hydrochloride
Three animals were treated with artificial cerebrospinal fluid containing 250 mM 2 -7 dichlorofluorescein-diacetate (DCFH-DA), five animals were used for microvascular observations, five animals were utilized to evaluate the endothelial nitric oxide synthase (eNOS) expression by Western blotting and five animals were used to determine neuronal damage by 2,3,5-Triphenyltetrazolium Chloride (TTC) Staining
Summary
The cerebral transient hypoperfusion, induced in experimental models by bilateral common carotid artery occlusion (BCCAO) and followed by reperfusion, causes significant microvascular alterations. These are characterized by disruption of the blood– brain barrier, edema, and swelling of perivascular astrocyte foot processes, decrease in arteriolar endothelium-dependent relaxation, altered expression of proteases, and matrix metalloproteinases, increase in inflammatory mediators (Chan, 1996; Nakashima et al, 1999; Cho et al, 2006; Lapi et al, 2008a). The cerebral tissue is vulnerable to the effects of ROS, because under oxidative stress superoxide anion and hydrogen peroxide cannot be readily neutralized due to the low catalase, superoxide dismutase (SOD) and glutathione peroxidase activities present in the brain. Brain membrane lipids are very rich in polyunsaturated fatty acids, which are sensitive to free radical-induced peroxidation, likely one of the most important events in cerebral cell damage (Del Zoppo, 1994; Pietta, 2000)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
