Plasma cholesterol lowering in an AngII‑infused atherosclerotic mouse model with moderate hypercholesterolemia

Sox17 protects human brain microvascular endothelial cells from AngII-induced injury by regulating autophagy and apoptosis

Intracranial aneurysm (IA), is a localized dilation of the intracranial arteries, the rupture of which is catastrophic. Hypertension is major IA risk factor that mediates endothelial cell damage. Sox17 is highly expressed in intracranial vascular endothelial cells, and GWAS studies indicate that its genetic alteration is one of the major genetic risk factors for IA. Vascular endothelial cell injury plays a vital role in the pathogenesis of IA. The genetic ablation of Sox17 plus hypertension induced by AngII can lead to an increased incidence of intracranial aneurysms had tested in the previous animal experiments. In order to study the underlying molecular mechanisms, we established stable Sox17-overexpressing and knockdown cell lines in human brain microvascular endothelial cells (HBMECs) first. Then flow cytometry, western blotting, and immunofluorescence were employed. We found that the knockdown of Sox17 could worsen the apoptosis and autophagy of HBMECs caused by AngII, while overexpression of Sox17 had the opposite effect. Transmission electron microscopy displayed increased autophagosomes after the knockdown of Sox17 in HBMECs. The RNA-sequencing analysis shown that dysregulation of the Sox17 gene was closely associated with the autophagy-related pathways. Our study suggests that Sox17 could protect HBMECs from AngII-induced injury by regulating autophagy and apoptosis.

Pemafibrate Prevents Rupture of Angiotensin II-Induced Abdominal Aortic Aneurysms

Background

Abdominal aortic aneurysm (AAA) is a life-threatening disease that lacks effective preventive therapies. This study aimed to evaluate the effect of pemafibrate, a selective peroxisome proliferator-activated receptor alpha (PPARα) agonist, on AAA formation and rupture.

Methods

Experimental AAA was induced by subcutaneous angiotensin II (AngII) infusion in ApoE ^{- / -} mice for 4 weeks. Pemafibrate (0.1 mg/kg/day) was administered orally. Dihydroethidium staining was used to evaluate the reactive oxygen species (ROS).

Results

The size of the AngII-induced AAA did not differ between pemafibrate- and vehicle-treated groups. However, a decreased mortality rate due to AAA rupture was observed in pemafibrate-treated mice. Pemafibrate ameliorated AngII-induced ROS and reduced the mRNA expression of interleukin-6 and tumor necrosis factor-α in the aortic wall. Gelatin zymography analysis demonstrated significant inhibition of matrix metalloproteinase-2 activity by pemafibrate. AngII-induced ROS production in human vascular smooth muscle cells was inhibited by pre-treatment with pemafibrate and was accompanied by an increase in catalase activity. Small interfering RNA-mediated knockdown of catalase or PPARα significantly attenuated the anti-oxidative effect of pemafibrate.

Conclusion

Pemafibrate prevented AAA rupture in a murine model, concomitant with reduced ROS, inflammation, and extracellular matrix degradation in the aortic wall. The protective effect against AAA rupture was partly mediated by the anti-oxidative effect of catalase induced by pemafibrate in the smooth muscle cells.

Inhibition of angiotensin-induced aortic aneurysm by metformin in apolipoprotein E-deficient mice

Objective

Metformin is associated with a reduced incidence and growth of abdominal aortic aneurysms (AAAs). The aim of the present study was to investigate the inhibitory effects of metformin on AAA development and possible underlying mechanisms in experimentally induced AAAs in mice, along with the possible synergistic effects of metformin and imatinib.

Methods

Angiotensin II was used to induce AAAs in apolipoprotein E knockout (ApoE ^-/- ) mice for 28 days. The mice were treated with metformin (n = 11), metformin combined with imatinib (n = 7), or vehicle (n = 12), starting 3 days before angiotensin II infusion. Ultrasound examination was used to analyze aneurysm formation. Cholesterol and blood pressure levels were measured at the start and end of the study. Gene array and quantitative polymerase chain reaction were used to analyze the changes in gene expression in the aorta. Wire myography was used to study vascular function.

Results

Metformin (n = 11) suppressed the formation and progression of AAAs by 50% compared with the vehicle controls (n = 12), with no further effects from imatinib (n = 7). Metformin reduced total cholesterol and mRNA expression of SPP1 (encoding osteopontin), MMP12, and the glycoprotein genes Gpnmb and Clec7a. Furthermore, metformin inhibited blood pressure increases and reduced vascular contractions, as determined by wire myography, and restored the anticontractile function of perivascular adipose tissue.

Conclusion

Metformin inhibited aneurysm formation and progression and normalized vascular function in ApoE ^-/- mice with no additional effect of imatinib. This might be mediated by the protective effects on vascular endothelial function and perivascular adipose tissue via reduced expression of genes promoting inflammation, including SPP1, MMP12, Gpnmb, and Clec7a.

Clinical relevance

Retrospective studies of the effects of metformin in patients with aneurysm have so far only been performed of those with type 2 diabetes. The present study shows that metformin has effects on nondiabetic mice and revealed the mechanistic effects mediated by the drug that could also be important to study as outcomes in humans. Future clinical trials using metformin are warranted in patients without diabetes with abdominal aortic aneurysms.