Inhibition of the Renin-Angiotensin System Fails to Suppress ß-Aminopropionitrile-Induced Thoracic Aortopathy in Mice-Brief Report.

BACKGROUND: Cross-linking of lysine residues in elastic and collagen fibers is a vital process in aortic development. Inhibition of lysyl oxidase by BAPN (ß-aminopropionitrile) leads to thoracic aortopathies in mice. Although the renin-angiotensin system contributes to several types of thoracic aortopathies, it remains unclear whether inhibition of the renin-angiotensin system protects against aortopathy caused by the impairment of elastic fiber/collagen crosslinking. METHODS: BAPN (0.5% wt/vol) was started in drinking water to induce aortopathies in male C57BL/6J mice at 4 weeks of age for 4 weeks. Five approaches were used to investigate the impact of the renin-angiotensin system. Bulk RNA sequencing was performed to explore potential molecular mechanisms of BAPN-induced thoracic aortopathies. RESULTS: Losartan increased plasma renin concentrations significantly, compared with vehicle-infused mice, indicating effective angiotensin II type 1 receptor inhibition. However, losartan did not suppress BAPN-induced aortic rupture and dilatation. Since losartan is a surmountable inhibitor of the renin-angiotensin system, irbesartan, an insurmountable inhibitor, was also tested. Although increased plasma renin concentrations indicated effective inhibition, irbesartan did not ameliorate aortic rupture and dilatation in BAPN-administered mice. Thus, BAPN-induced thoracic aortopathies were refractory to angiotensin II type 1 receptor blockade. Next, we inhibited angiotensin II production by pharmacological or genetic depletion of AGT (angiotensinogen), the unique precursor of angiotensin II. However, neither suppressed BAPN-induced thoracic aortic rupture and dilatation. Aortic RNA sequencing revealed molecular changes during BAPN administration that were distinct from other types of aortopathies in which angiotensin II type 1 receptor inhibition protects against aneurysm formation. CONCLUSIONS: Inhibition of either angiotensin II action or production of the renin-angiotensin system does not attenuate BAPN-induced thoracic aortopathies in mice.

National Survey Identifying the Factors Affecting the Career Development of Cardiologists in Japan.

BACKGROUND: Equality in training opportunities, studying abroad, and satisfaction with work are not well investigated among Japanese cardiologists.Methods and Results: We studied cardiologists' career development using a questionnaire that was emailed to 14,798 cardiologists belonging to the Japanese Circulation Society (JCS) in September 2022. Feelings regarding equality in training opportunities, preferences for studying abroad, and satisfaction with work were evaluated with regard to cardiologists' age, sex, and other confounding factors. Survey responses were obtained from 2,566 cardiologists (17.3%). The mean (±SD) age of female (n=624) and male (n=1,942) cardiologists who responded to the survey was 45.6±9.5 and 50.0±10.6 years, respectively. Inequality in training opportunities was felt more by female than male cardiologists (44.1% vs. 33.9%) and by younger (<45 years old) than older (≥45 years old) (42.0% vs. 32.8%). Female cardiologists were less likely to prefer studying abroad (53.7% vs. 59.9%) and less satisfied with their work (71.3% vs. 80.8%) than male cardiologists. Increased feelings of inequality and lower work satisfaction were investigated among cardiologists who were young, had family care duties, and had no mentors. In the subanalysis, significant regional differences were found in cardiologists' career development in Japan. CONCLUSIONS: Female and younger cardiologists felt greater inequality in career development than male and older cardiologists. A diverse workplace may prompt equality in training opportunities and work satisfaction for both female and male cardiologists.

Authentication of In Situ Measurements for Thoracic Aortic Aneurysms in Mice.

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Deletion of AT1a (Angiotensin II Type 1a) Receptor or Inhibition of Angiotensinogen Synthesis Attenuates Thoracic Aortopathies in Fibrillin1C1041G/+ Mice.

Objective: A cardinal feature of Marfan syndrome is thoracic aortic aneurysm. The contribution of the renin-angiotensin system via AT1aR (Ang II [angiotensin II] receptor type 1a) to thoracic aortic aneurysm progression remains controversial because the beneficial effects of angiotensin receptor blockers have been ascribed to off-target effects. This study used genetic and pharmacological modes of attenuating angiotensin receptor and ligand, respectively, to determine their roles on thoracic aortic aneurysm in mice with fibrillin-1 haploinsufficiency (Fbn1C1041G/+). Approach and Results: Thoracic aortic aneurysm in Fbn1C1041G/+ mice was found to be strikingly sexual dimorphic. Males displayed aortic dilation over 12 months while aortic dilation in Fbn1C1041G/+ females did not differ significantly from wild-type mice. To determine the role of AT1aR, Fbn1C1041G/+ mice that were either +/+ or -/- for AT1aR were generated. AT1aR deletion reduced expansion of ascending aorta and aortic root diameter from 1 to 12 months of age in males. Medial thickening and elastin fragmentation were attenuated. An antisense oligonucleotide against angiotensinogen was administered to male Fbn1C1041G/+ mice to determine the effects of Ang II depletion. Antisense oligonucleotide against angiotensinogen administration attenuated dilation of the ascending aorta and aortic root and reduced extracellular remodeling. Aortic transcriptome analyses identified potential targets by which inhibition of the renin-angiotensin system reduced aortic dilation in Fbn1C1041G/+ mice. Conclusions: Deletion of AT1aR or inhibition of Ang II production exerted similar effects in attenuating pathologies in the proximal thoracic aorta of male Fbn1C1041G/+ mice. Inhibition of the renin-angiotensin system attenuated dysregulation of genes within the aorta related to pathology of Fbn1C1041G/+ mice.

High Salt Intake Worsens Aortic Dissection in Mice: Involvement of IL (Interleukin)-17A-Dependent ECM (Extracellular Matrix) Metabolism.

OBJECTIVE: Aortic dissection (AD) is a fatal disease that occurs suddenly without preceding clinical signs or symptoms. Although high salt intake is a proposed risk factor for cardiovascular diseases, the relationship between AD and high salt intake has not been clarified. We examined the effect of high-salt challenge on a mouse AD model. Approach and Results: AD was induced in male mice by continuous infusion of ß-aminopropionitrile and Ang II (angiotensin II). High-salt challenge exacerbated aortic wall destruction in AD. Deletion of Il17a (IL-17KO [IL (interleukin)-17A knockout]) did not affect the AD phenotype at baseline, but it abolished the high salt-induced worsening of the aortic destruction. Unexpectedly, aortas of IL-17KO mice exhibited global changes in ECM (extracellular matrix)-related genes without alteration of proinflammatory genes, altered architecture of collagen fibers, and reduced stiffness before AD induction. The aortas of IL-17KO mice were less sensitive to AD-inducing stimuli, as shown by the induction of phenotypic modulation markers SMemb and vimentin, suggesting a reduced stress response. The aortas of IL-17KO mice had a higher population of smooth muscle cells with nuclear-localized phosphorylated Smad2, indicative of TGFß (transforming growth factor-beta) signal activation. Consistently, pretreatment of smooth muscle cells in culture with IL-17A blunted the activation of Smad2 by TGFß1. CONCLUSIONS: These findings indicate that high salt intake has a worsening effect on AD in the context of high aortic wall stiffness, which is under the control of IL-17A through ECM metabolism. Therefore, salt restriction may represent a low-cost and practical way to reduce AD risk.

Therapeutic Effect of Rapamycin on Aortic Dissection in Mice.

Aortic dissection (AD) is a serious clinical condition that is unpredictable and frequently results in fatal outcome. Although rapamycin, an inhibitor of mechanistic target of rapamycin (mTOR), has been reported to be effective in preventing aortopathies in mouse models, its mode of action has yet to be clarified. A mouse AD model that was created by the simultaneous administration of ß-aminopropionitrile (BAPN) and angiotensin II (AngII) for 14 days. Rapamycin treatment was started either at day 1 or at day 7 of BAPN+AngII challenge, and continued throughout the observational period. Rapamycin was effective both in preventing AD development and in suppressing AD progression. On the other hand, gefitinib, an inhibitor of growth factor signaling, did not show such a beneficial effect, even though both rapamycin and gefitinib suppressed cell cycle activation in AD. Rapamycin suppressed cell cycle-related genes and induced muscle development-related genes in an AD-related gene expression network without a major impact on inflammation-related genes. Rapamycin augmented the activation of Akt1, Akt2, and Stat3, and maintained the contractile phenotype of aortic smooth muscle cells. These findings indicate that rapamycin was effective both in preventing the development and in suppressing the progression of AD, indicating the importance of the mTOR pathway in AD pathogenesis.

Ying and Yang of Stat3 in pathogenesis of aortic dissection.

Aortic dissection (AD) is a medical emergency, in which acute destruction of aortic wall occurs with unknown etiology. Recent studies have uncovered the critical role of inteleukin-6 (IL-6) and inflammatory cells including macrophages in the disease mechanism of AD. IL-6 activates janus kinase and signal transducer and activator of transcription 3 (STAT3) to alter the gene expression program in many cell types, thus regulating various aspects of inflammatory response. We found that in human AD tissue, STAT3 was activated in infiltrating macrophages and in medial smooth muscle cells (SMCs), suggesting that STAT3 may regulate the response of these cell types. However, it is unknown how Stat3 regulates the cell type-specific response in pathogenesis of AD. The role of STAT3 was examined in genetically modified mice in which STAT3 sensitivity was enhanced specifically in macrophages or in SMCs by tissue-specific deletion of suppressor of cytokine signaling 3 (Socs3), a negative regulator of STAT3. Macrophage-specific deletion of Socs3 caused acute enhancement of STAT3 activation, M1-dominant differentiation of macrophages, suppression of tissue repair response of SMCs, and exaggerated AD. In contrast, SMC-specific deletion of Socs3 caused chronic STAT3 activation and low-grade inflammatory response in aortic walls, activation of fibroblasts, M2-dominant differentiation of macrophages, increase in adventitial collagen deposition, resulting in the protection of aorta from AD by reinforcing the tensile strength of the aortic walls. Therefore, STAT3 regulates the balance between the destruction and the reinforcement of the aortic tissue, depending on the cell types and the time course of STAT3 activation, which ultimately regulates the development of AD. Elucidating such a dynamic mechanism to regulate the aortic tissue integrity would be essential to decipher the molecular pathogenesis of AD.

Genetic Deletion of Socs3 in Smooth Muscle Cells Ameliorates Aortic Dissection in Mice.

Aortic dissection (AD) is the acute destruction of aortic wall and is reportedly induced by inflammatory response. Here we investigated the role of smooth muscle Socs3 (a negative regulator of Janus kinases/signal transducer and activator of transcription signaling) in AD pathogenesis using a mouse model generated via ß-aminopropionitrile and angiotensin II infusion. Socs3 deletion specifically in smooth muscle cells yielded a chronic inflammatory response of the aortic wall, which was associated with increased fibroblasts, reinforced aortic tensile strength, and less-severe tissue destruction. Although an acute inflammatory response is detrimental in AD, smooth muscle-regulated inflammatory response seemed protective against AD.

MRTF-A promotes angiotensin II-induced inflammatory response and aortic dissection in mice.

Aortic dissection (AD) is a major cause of acute aortic syndrome with high mortality due to the destruction of aortic walls. Although recent studies indicate the critical role of inflammation in the disease mechanism of AD, it is unclear how inflammatory response is initiated. Here, we demonstrate that myocardin-related transcription factor A (MRTF-A), a signal transducer of humoral and mechanical stress, plays an important role in pathogenesis of AD in a mouse model. A mouse model of AD was created by continuous infusion of angiotensin II (AngII) that induced MRTF-A expression and caused AD in 4 days. Systemic deletion of Mrtfa gene resulted in a marked suppression of AD development. Transcriptome and gene annotation enrichment analyses revealed that AngII infusion for 1 day caused pro-inflammatory and pro-apoptotic responses before AD development, which were suppressed by Mrtfa deletion. AngII infusion for 1 day induced pro-inflammatory response, as demonstrated by expressions of Il6, Tnf, and Ccl2, and apoptosis of aortic wall cells, as detected by TUNEL staining, in an MRTF-A-dependent manner. Pharmacological inhibition of MRTF-A by CCG-203971 during AngII infusion partially suppressed AD phenotype, indicating that acute suppression of MRTF-A is effective in preventing the aortic wall destruction. These results indicate that MRTF-A transduces the stress of AngII challenge to the pro-inflammatory and pro-apoptotic responses, ultimately leading to AD development. Intervening this pathway may represent a potential therapeutic strategy.

Role of Macrophage Socs3 in the Pathogenesis of Aortic Dissection.

BACKGROUND: Aortic dissection (AD) is a life-threatening medical emergency caused by the abrupt destruction of the intimomedial layer of the aortic walls. Given that previous studies have reported the involvement of proinflammatory cytokine interleukin-6 in AD pathogenesis, we investigated the role of signal transduction and activator of transcription 3 signaling, a downstream pathway of interleukin-6 in macrophages in pathogenesis of AD. METHODS AND RESULTS: We characterized the pathological and molecular events triggered by aortic stress, which can lead to AD. Aortic stress on the suprarenal aorta because of infrarenal aorta stiffening and angiotensin II infusion for 1 week caused focal medial rupture at the branching point of the celiac trunk and superior mesenteric artery. This focal medial rupture healed in 6 weeks in wild-type (WT) mice, but progressed to AD in mice with macrophage-specific deletion of Socs3 gene (mSocs3-KO). mSocs3-KO mice showed premature activation of cell proliferation, an inflammatory response, and skewed differentiation of macrophages toward the tissue-destructive phenotype. Concomitantly, they showed aberrant phenotypic modulation of smooth muscle cells and transforming growth factor beta signaling, which are likely to participate in tissue repair. Human AD samples revealed signal transduction and activator of transcription 3 activation in adventitial macrophages adjacent to the site of tissue destruction. CONCLUSIONS: These findings suggest that AD development is preceded by focal medial rupture, in which macrophage Socs3 maintains proper inflammatory response and differentiation of SMCs, thus promoting fibrotic healing to prevent tissue destruction and AD development. Understanding the sequence of the pathological and molecular events preceding AD development will help predict and prevent AD development and progression.

Involvement of B Cells, Immunoglobulins, and Syk in the Pathogenesis of Abdominal Aortic Aneurysm.

BACKGROUND: Abdominal aortic aneurysm (AAA) is a potentially life-threatening disease that is common in older individuals. Currently, therapeutic options are limited to surgical interventions. Although it has long been known that AAA tissue is enriched in B cells and immunoglobulins, their involvement in AAA pathogenesis remains controversial. METHODS AND RESULTS: We investigated the role of B cells and immunoglobulins in a murine model of AAA, induced with a periaortic application of CaCl2, and in human AAA. Both human and mouse AAA tissue showed B-cell infiltration. Mouse AAA tissue showed deposition of IgG and activation of Syk, a key molecule in B-cell activation and immunoglobulin function, which were localized to infiltrating cells including B cells and macrophages. B-cell-deficient muMT mice showed suppression of AAA development that was associated with reduced activation of Syk and less expression of matrix metalloproteinase-9. Administration of exogenous immunoglobulins restored the blunted Syk activation and AAA development in muMT mice. Additionally, exogenous immunoglobulins induced interleukin-6 and metalloproteinase-9 secretions in human AAA tissue cultures. Furthermore, administration of R788, a specific Syk inhibitor, suppressed AAA expansion, reduced inflammatory response, and reduced immunoglobulin deposition in AAA tissue. CONCLUSIONS: From these results, we concluded that B cells and immunoglobulins participated in AAA pathogenesis by promoting inflammatory and tissue-destructive activities. Finally, we identified Syk as a potential therapeutic target.