Dataset Information

Loss of Smooth Muscle ?-Actin Leads to NF-?B-Dependent Increased Sensitivity to Angiotensin II in Smooth Muscle Cells and Aortic Enlargement.

ABSTRACT: Mutations in ACTA2, encoding the smooth muscle isoform of ?-actin, cause thoracic aortic aneurysms, acute aortic dissections, and occlusive vascular diseases.We sought to identify the mechanism by which loss of smooth muscle ?-actin causes aortic disease.Acta2-/- mice have an increased number of elastic lamellae in the ascending aorta and progressive aortic root dilation as assessed by echocardiography that can be attenuated by treatment with losartan, an angiotensin II (AngII) type 1 receptor blocker. AngII levels are not increased in Acta2-/- aortas or kidneys. Aortic tissue and explanted smooth muscle cells from Acta2-/- aortas show increased production of reactive oxygen species and increased basal nuclear factor ?B signaling, leading to an increase in the expression of the AngII receptor type I a and activation of signaling at 100-fold lower levels of AngII in the mutant compared with wild-type cells. Furthermore, disruption of smooth muscle ?-actin filaments in wild-type smooth muscle cells by various mechanisms activates nuclear factor ?B signaling and increases expression of AngII receptor type I a.These findings reveal that disruption of smooth muscle ?-actin filaments in smooth muscle cells increases reactive oxygen species levels, activates nuclear factor ?B signaling, and increases AngII receptor type I a expression, thus potentiating AngII signaling in vascular smooth muscle cells without an increase in the exogenous levels of AngII.

SUBMITTER: Chen J

PROVIDER: S-EPMC5518614 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Loss of Smooth Muscle α-Actin Leads to NF-κB-Dependent Increased Sensitivity to Angiotensin II in Smooth Muscle Cells and Aortic Enlargement.

Chen Jiyuan J Peters Andrew A Papke Christina L CL Villamizar Carlos C Ringuette Lea-Jeanne LJ Cao Jiumei J Wang Shanzhi S Ma Shuangtao S Gong Limin L Byanova Katerina L KL Xiong Jian J Zhu Michael X MX Madonna Rosalinda R Kee Patrick P Geng Yong-Jian YJ Brasier Allan R AR Davis Elaine C EC Prakash Siddharth S Kwartler Callie S CS Milewicz Dianna M DM

Circulation research 20170501 12

<h4>Rationale</h4>Mutations in <i>ACTA2</i>, encoding the smooth muscle isoform of α-actin, cause thoracic aortic aneurysms, acute aortic dissections, and occlusive vascular diseases.<h4>Objective</h4>We sought to identify the mechanism by which loss of smooth muscle α-actin causes aortic disease.<h4>Methods and results</h4><i>Acta2</i><sup>-/-</sup> mice have an increased number of elastic lamellae in the ascending aorta and progressive aortic root dilation as assessed by echocardiography that ...[more]

PMID: 28461455

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Project description:AimTo investigate the effects of advanced glycation end products (AGEs) on calcification in human aortic smooth muscle cells (HASMCs) in vitro and the underlying mechanisms.MethodsAGEs were artificially prepared. Calcification of HASMCs was induced by adding inorganic phosphate (Pi, 2 mmol/L) in the media, and observed with Alizarin red staining. The calcium content in the supernatant was measured using QuantiChrome Calcium Assay Kit. Expression of the related mRNAs and proteins was analyzed using real-time PCR and Western blot, respectively. Chromatin immunoprecipitation (ChIP) assay was used to detect the binding of NF-κB to the putative IGF1R promoter.ResultsAGEs (100 μg/mL) significantly enhanced Pi-induced calcification and the levels of osteocalcin and Cbfα1 in HASMCs. Furthermore, the treatment decreased the expression of insulin-like growth factor 1 receptor (IGF1R). Over-expression of IGF1R in HASMCs suppressed the AGEs-induced increase in calcium deposition. When IGF1R expression was knocked down in HASMCs, AGEs did not enhance the calcium deposition. Meanwhile, AGEs time-dependently decreased the amounts of IκBα and Flag-tagged p65 in the cytoplasmic extracts, and increased the amount of nuclear p65 in HASMCs. In the presence of NF-κB inhibitor PDTC (50 μmol/L), the AGEs-induced increase in calcium deposition was blocked. Over-expression of p65 significantly enhanced Pi-induced mineralization, but suppressed IGF1R mRNA level. Knockdown of p65 suppressed the AGEs-induced increase in calcium deposition, and rescued the IGF1R expression. The ChIP analysis revealed that NF-κB bound the putative IGF1R promoter at position -230 to -219 bp. The inhibition of IGF1R by NF-κB was abolished when IGF1R reporter plasmid contained mutated binding sequence for NF-κB or an NF-κB reporter vector.ConclusionThe results demonstrate that AGEs promote calcification of human aortic smooth muscle cells in vitro via activation of NF-κB and down-regulation of IGF1R expression.

Project description:BackgroundAngiotensin II (Ang II) signaling, including matrix metalloproteinase type II (MMP2) activation, has been linked to an age-associated increase in migration capacity of vascular smooth muscle cells (VSMC), and to other proinflammatory features of arterial aging. Calpain-1 activation is required for MMP2 expression in fibroblasts and is induced in cardiomyocytes by Ang II. The consequences of engagement of calpain-1 with its substrates, however, in governing the age-associated proinflammatory status within the arterial wall, remains unknown.Methodology/principal findingsThe present findings demonstrate that transcription, translation, and activity of calpain-1 are significantly up-regulated in rat aortae or early-passage aortic VSMC from old (30-mo) rats compared to young (8-mo). Dual immunolabeling of the arterial wall indicates that colocalization of calpain-1 and Ang II increases within the aged arterial wall. To further explore the relationship of calpain-1 to Ang II, we chronically infused Ang II into young rats, and treated cultured aortic rings or VSMC with Ang II. We also constructed adenoviruses harboring calpain-1 (CANP1) or its endogenous inhibitor calpastatin (CAST) and infected these into VSMC. Ang II induces calpain-1 expression in the aortic walls in vivo and ex vivo and VSMC in vitro. The Ang II mediated, age-associated increased MMP2 activity and migration in VSMC are both blocked by calpain inhibitor 1 or CAST. Over-expression of calpain-1 in young VSMC results in cleavage of intact vimentin, and an increased migratory capacity mimicking that of old VSMC, which is blocked by the MMP inhibitor, GM6001.Conclusions/significanceCalpain-1 activation is a pivotal molecular event in the age-associated arterial Ang II/MMP2 signaling cascade that is linked to cytoskeleton protein restructuring, and VSMC migration. Therefore, targeting calpain-1 has the potential to delay or reverse the arterial remodeling that underlies age-associated diseases i.e. atherosclerosis.

Dataset Information

Loss of Smooth Muscle ?-Actin Leads to NF-?B-Dependent Increased Sensitivity to Angiotensin II in Smooth Muscle Cells and Aortic Enlargement.

Publications

Loss of Smooth Muscle α-Actin Leads to NF-κB-Dependent Increased Sensitivity to Angiotensin II in Smooth Muscle Cells and Aortic Enlargement.

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