Inducible Depletion of Calpain-2 Mitigates Abdominal Aortic Aneurysm in Mice

Celastrol Supplementation Ablates Sexual Dimorphism of Abdominal Aortic Aneurysm Formation in Mice

BACKGROUND

Abdominal aortic aneurysms (AAAs) are permanent dilations of the abdominal aorta with 4-5 times greater prevalence in males than in females. The aim of this study is to define whether Celastrol, a pentacyclic triterpene from the root extracts of Tripterygium wilfordii, supplementation influences angiotensin II (AngII)-induced AAAs in hypercholesterolemic mice.

METHODS

Age-matched (8-12 weeks old) male and female low-density lipoprotein (Ldl) receptor-deficient mice were fed a fat-enriched diet supplemented with or without Celastrol (10 mg/kg/day) for five weeks. After one week of diet feeding, mice were infused with either saline (n = 5 per group) or AngII (500 or 1000 ng/kg/min, n = 12-15 per group) for 28 days.

RESULTS

Dietary supplementation of Celastrol profoundly increased AngII-induced abdominal aortic luminal dilation and external aortic width in male mice as measured by ultrasonography and ex vivo measurement, with a significant increase in incidence compared to the control group. Celastrol supplementation in female mice resulted in significantly increased AngII-induced AAA formation and incidence. In addition, Celastrol supplementation significantly increased AngII-induced aortic medial elastin degradation accompanied by significant aortic MMP9 activation in both male and female mice compared to saline and AngII controls.

CONCLUSIONS

Celastrol supplementation to Ldl receptor-deficient mice ablates sexual dimorphism and promotes AngII-induced AAA formation, which is associated with increased MMP9 activation and aortic medial destruction.

Mechanosignals in abdominal aortic aneurysms

Cumulative evidence has shown that mechanical and frictional forces exert distinct effects in the multi-cellular aortic layers and play a significant role in the development of abdominal aortic aneurysms (AAA). These mechanical cues collectively trigger signaling cascades relying on mechanosensory cellular hubs that regulate vascular remodeling programs leading to the exaggerated degradation of the extracellular matrix (ECM), culminating in lethal aortic rupture. In this review, we provide an update and summarize the current understanding of the mechanotransduction networks in different cell types during AAA development. We focus on different mechanosensors and stressors that accumulate in the AAA sac and the mechanotransduction cascades that contribute to inflammation, oxidative stress, remodeling, and ECM degradation. We provide perspectives on manipulating this mechano-machinery as a new direction for future research in AAA.

Edaravone Attenuated Angiotensin II-Induced Atherosclerosis and Abdominal Aortic Aneurysms in Apolipoprotein E-Deficient Mice

Background: The aim of the study was to define whether edaravone, a free-radical scavenger, influenced angiotensin II (AngII)-induced atherosclerosis and abdominal aortic aneurysms (AAAs) formation. Methods: Male apolipoprotein E-deficient mice (8–12 weeks old) were fed with a normal diet for 5 weeks. Either edaravone (10 mg/kg/day) or vehicle was injected intraperitoneally for 5 weeks. After 1 week of injections, mice were infused subcutaneously with either AngII (1000 ng/kg/min, n = 16–17 per group) or saline (n = 5 per group) by osmotic minipumps for 4 weeks. Results: AngII increased systolic blood pressure equivalently in mice administered with either edaravone or saline. Edaravone had no effect on plasma total cholesterol concentrations and body weights. AngII infusion significantly increased ex vivo maximal diameters of abdominal aortas and en face atherosclerosis but was significantly attenuated by edaravone administration. Edaravone also reduced the incidence of AngII-induced AAAs. In addition, edaravone diminished AngII-induced aortic MMP-2 activation. Quantitative RT-PCR revealed that edaravone ameliorated mRNA abundance of aortic MCP-1 and IL-1β. Immunostaining demonstrated that edaravone attenuated oxidative stress and macrophage accumulation in the aorta. Furthermore, edaravone administration suppressed thioglycolate-induced mice peritoneal macrophages (MPMs) accumulation and mRNA abundance of MCP-1 in MPMs in male apolipoprotein E-deficient mice. In vitro, edaravone reduced LPS-induced mRNA abundance of MCP-1 in MPMs. Conclusions: Edaravone attenuated AngII-induced AAAs and atherosclerosis in male apolipoprotein E-deficient mice via anti-oxidative action and anti-inflammatory effect.

Legumain Is an Endogenous Modulator of Integrin αvβ3 Triggering Vascular Degeneration, Dissection, and Rupture

BACKGROUND

The development of thoracic aortic dissection (TAD) is closely related to extracellular matrix degradation and vascular smooth muscle cell (VSMC) transformation from contractile to synthetic type. LGMN (legumain) degrades extracellular matrix components directly or by activating downstream signals. The role of LGMN in VSMC differentiation and the occurrence of TAD remains elusive.

METHODS

Microarray datasets concerning vascular dissection or aneurysm were downloaded from the Gene Expression Omnibus database to screen differentially expressed genes. Four-week-old male Lgmn knockout mice (Lgmn^-/-), macrophage-specific Lgmn knockout mice (Lgmn^F/F;LysM^Cre), and RR-11a-treated C57BL/6 mice were given BAPN (β-aminopropionitrile monofumarate; 1 g/kg/d) in drinking water for 4 weeks for TAD modeling. RNA sequencing analysis was performed to recapitulate transcriptome profile changes. Cell interaction was examined in macrophage and VSMC coculture system. The reciprocity of macrophage-derived LGMN with integrin αvβ3 in VSMCs was tested by coimmunoprecipitation assay and colocalization analyses.

RESULTS

Microarray datasets from the Gene Expression Omnibus database indicated upregulated LGMN in aorta from patients with TAD and mice with angiotensin II-induced AAA. Elevated LGMN was evidenced in aorta and sera from patients with TAD and mice with BAPN-induced TAD. BAPN-induced TAD progression was significantly ameliorated in Lgmn-deficient or inhibited mice. Macrophage-specific deletion of Lgmn alleviated BAPN-induced extracellular matrix degradation. Unbiased profiler polymerase chain reaction array and Gene Ontology analysis displayed that LGMN regulated VSMC phenotype transformation. Macrophage-specific deletion of Lgmn ameliorated VSMC phenotypic switch in BAPN-treated mice. Macrophage-derived LGMN inhibited VSMC differentiation in vitro as assessed by macrophages and the VSMC coculture system. Macrophage-derived LGMN bound to integrin αvβ3 in VSMCs and blocked integrin αvβ3, thereby attenuating Rho GTPase activation, downregulating VSMC differentiation markers and eventually exacerbating TAD development. ROCK (Rho kinase) inhibitor Y-27632 reversed the protective role of LGMN depletion in vascular dissection.

CONCLUSIONS

LGMN signaling may be a novel target for the prevention and treatment of TAD.