Ginkgo biloba extracts prevent aortic rupture in angiotensin II-infused hypercholesterolemic mice

Abstract

Abdominal aortic aneurysms (AAAs) are a chronic vascular disease characterized by pathological luminal dilation. Aortic rupture is the fatal consequence of AAAs. Ginkgo biloba extracts (GBEs), a natural herb extract widely used as food supplements, drugs, and cosmetics, has been reported to suppress development of calcium chloride-induced AAAs in mice. Calcium chloride-induced AAAs do not rupture, while angiotensin II (AngII)-induced AAAs in mice have high rate of aortic rupture, implicating potentially different mechanisms from calcium chloride-induced AAAs. This study aimed to determine whether GBE would improve aortic dilation and rupture rate of AngII-induced AAAs. Male apolipoprotein E (apoE) -/- mice were infused with AngII and administered either GBE or its major active ingredients, flavonoids and ginkgolides, individually or in combination. To determine the effects of GBE in mice with established AAAs, male apoE-/- mice were firstly infused with AngII for 28 days to develop AAAs, and then administered either GBE or vehicle in mice with established AAAs, which were continuously infused with AngII for another 56 days. GBE, but not the two major active components separately or synergistically, prevented aortic rupture, but not aortic dilation. The protection of GBE from aortic rupture was independent of systolic blood pressure, lipid, and inflammation. GBE also did not attenuate either aortic rupture or progressive aortic dilation in mice with established AAAs. GBE did not reduce the atherosclerotic lesion areas, either. In conclusion, GBE prevents aortic rupture in AngII-infused hypercholesterolemic mice, but only in the early phase of the disease development.

Keywords: abdominal aortic aneurysm; angiotensin; flavonoids; ginkgo biloba extracts; ginkgolides; hypercholesterolemia.

Fig. 1

GBE reduced aortic rupture-induced death in AngII-infused mice. a Kaplan–Meier curves of survival. (log-rank analysis, *P = 0.015 vs. CTL). b Death due to aortic rupture was confirmed with necropsy (Fisher’s exact test, *P = 0.02 vs. CTL). c Incidence of AAAs defined by either (1) 50% or more increase of the maximal diameter in the suprarenal aortic region as compared to the baseline or (2) death due to abdominal aortic rupture. d Maximal external width of the suprarenal aortas was measured by Image-Pro Plus software. All values were presented as the means ± SEM. Values of individual mice were represented as circles, diamonds were means, and bars were SEM. GBE represented Ginkgo biloba extracts (n = 20), CTL represented the control (n = 19)

Fig. 2

GBE attenuated elastin breakdown in AngII-induced mice. The images shown are representative aneurysm sections with Verhoeff-van Gieson staining. Elastin disruption and medial rupture seen at arrows. GBE represented Ginkgo biloba extracts, CTL represented the  control

Fig. 3

GBE did not reduce serum concentrations of total cholesterol, proinflammatory cytokines, and MMPs. Serum concentrations of total cholesterol (a), MCP-1(b), IL-6 (c), MMP-2 (d), and MMP-9 (e) in apoE−/− mice infused with AngII for 28 days. All values were presented as the means ± SEM. Values of individual mice were represented as circles, diamonds were means, and bars were SEM. GBE represented Ginkgo biloba extracts (n = 15), CTL represented the control (n = 11)

Fig. 4

GBE major active ingredients did not prevent development of AngII-induced AAAs. a Kaplan–Meier curves of survival between vehicle and GBE major active ingredients. b Death due to aortic rupture was confirmed with necropsy. c Incidence of AAAs defined by either (1) 50% or more increase of the maximal diameter in the suprarenal aortic region as compared to the baseline or (2) death due to abdominal aortic rupture. d Maximal external width of the suprarenal aortas was measured by Image-Pro Plus software. All values were presented as the means ± SEM. Values of individual mice were represented as circles, diamonds are means, and bars were SEM. GBE1 represented flavonoids, GBE2 represented ginkgolides, and GBE1 + 2 represented the combined administration of flavonoids and ginkgolides (n = 10 per group). CTL represented the control (n = 19)

Fig. 5

GBE did not prevent aortic rupture and progressive aortic dilation in AngII-infused mice. a Kaplan–Meier curves of survival (n = 32). b Death due to aortic rupture was confirmed with necropsy. c Maximal diameter of suprarenal aortas was determined by in vivo ultrasound imaging and measured by Image-Pro Plus software (Mann–Whitney rank sum test, *P < 0.001 vs. day 0). All values were presented as the means ± SEM. d Maximal external width of the suprarenal aorta was measured by Image-Pro Plus software. GBE represented Ginkgo biloba extracts (n = 7), CTL represented the control (n = 7)