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

Abstract

Objective: Cytoskeletal structural proteins maintain cell structural integrity by bridging extracellular matrix with contractile filaments. During abdominal aortic aneurysm (AAA) development, (1) aortic medial degeneration is associated with loss of smooth muscle cell integrity and (2) fibrogenic mesenchymal cells mediate extracellular matrix remodeling. Calpains cleave cytoskeletal proteins that maintain cell structural integrity. Pharmacological inhibition of calpains exert beneficial effects on Ang II (angiotensin II)–induced AAAs in LDLR −/− (low-density receptor deficient) mice. Here, we evaluated the functional contribution of fibrogenic mesenchymal cells-derived calpain-2 on (1) cytoskeletal structural protein and extracellular matrix alterations and (2) AAA progression. Approach and Results: Calpain-2 protein and cytoskeletal protein (filamin and talin) fragmentation are significantly elevated in human and Ang II–induced AAAs in mice. To examine the relative contribution of calpain-2 in AAA development, calpain-2 floxed mice in an LDLr −/− background were bred to mice with a tamoxifen-inducible form of Cre under control of either the ubiquitous promoter, chicken β-actin, or fibrogenic mesenchymal cell-specific promoter, Col1α2. Ubiquitous or fibrogenic mesenchymal cell-specific depletion of calpain-2 in mice suppressed Ang II–induced AAAs, filamin/talin fragmentation, while promoting extracellular matrix protein, collagen in the aortas. Calpain-2 silencing in aortic smooth muscle cells or fibroblasts reduced Ang II–induced filamin fragmentation. In addition, silencing of filamin in aortic SMCs significantly reduced collagen protein. Furthermore, calpain-2 deficiency suppressed rupture of established Ang II–induced AAAs in mice. Conclusions: Our studies implicate that calpain-2 deficiency prevents (1) Ang II–induced cytoskeletal structural protein fragmentation and AAA development and (2) stabilize and suppress rupture of established AAAs in mice.

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

“…[32][33][34][35][36] Calpain-2 promoted AAA by mediating filamin/talin fragmentation and suppressing ECM protein, such as collagen in aorta. 33 Cathepsin L contributes to AAA formation by promoting lesion inflammatory cell accumulation, angiogenesis, and protease expression. 34 Cathepsin K plays an essential role in AAA formation by promoting T-cell proliferation, vascular smooth muscle cell apoptosis, and elastin degradation and by affecting vascular cell protease expression and activities.…”

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

“…This study followed the recommendations of The Guide for the Care and Use of Laboratory Animals (National Institutes of Health). Ldl receptor genotyping was performed as described previously [ 12 ]. The mice were randomly placed by Division of Laboratory Animal Research (DLAR) staff in cages ( n = 5/cage) upon weaning.…”

“…The concentration of Celastrol in a 2–3 g high-fat diet was 0.24–0.3 mg, which is equivalent to the dose of 10 mg/kg/day. After one week of diet feeding, mice were infused with either saline or AngII (500 or 1000 ng/kg/min, Bachem, Torrance, CA, USA) for 28 days by Alzet osmotic minipumps (Model 1004 and 2004, Durect Corporation, Cupertino, CA, USA) as described previously [ 12 ].…”

Mechanosignals in abdominal aortic aneurysms

“…Li et al ( 46 ) showed that the activation of calpain, calcium-dependent cysteine proteases, through shear stress-coupling could target the ECM cytoskeleton. Specifically, calpain-2 could fragment talin and filamin, disrupting endothelial organization and alignment that facilitates ECs and SMCs migration in AngII-induced AAA in LDLR –/– mice ( 47 ). Subramanian et al ( 48 ) later conducted in vivo pharmacological inhibition of a novel calpain inhibitor, BDA-410, which successfully reduced the incidence and development of AAA by attenuating the activation of MMP12, pro-inflammatory cytokines, and macrophage infiltration into the aorta using similar AAA mice models.…”