Complement C3a/C3aR inhibition alleviates the formation of aortic aneurysm in Marfan syndrome mice.

Mutations in fibrillin 1 (FBN1) is the main cause of Marfan syndrome (MFS) with thoracic aortic aneurysm (TAA) as the main complication. Activation of the complement system plays a key role in the formation of thoracic and abdominal aortic aneurysms. However, the role of the complement system in MFS-associated aortic aneurysms remains unclear. In this study, we observed increased levels of complement C3a and C5a in the plasma of MFS patients and mouse, and the increased deposition of the activated complement system product C3b/iC3b was also observed in the elastic fiber rupture zone of 3-month-old MFS mice. The expression of C3a receptor (C3aR) was increased in MFS aortas, and recombinant C3a promoted the expression of cytokines in macrophages. The administration of a C3aR antagonist (C3aRA) attenuated the development of thoracic aortic aneurysms in MFS mice. The increased inflammation response and matrix metalloproteinases activities were also attenuated by C3aRA treatment in MFS mice. Therefore, these findings indicate that the complement C3a/C3aR inhibition alleviates the formation of aortic aneurysm in Marfan syndrome mice.

Redox Dysregulation of Vascular Smooth Muscle Sirtuin-1 in Thoracic Aortic Aneurysm in Marfan Syndrome.

BACKGROUND: Thoracic aortic aneurysms (TAAs) are abnormal aortic dilatations and a major cardiovascular complication of Marfan syndrome. We previously demonstrated a critical role for vascular smooth muscle (VSM) SirT1 (sirtuin-1), a lysine deacetylase, against maladaptive aortic remodeling associated with chronic oxidative stress and aberrant activation of MMPs (matrix metalloproteinases). METHODS: In this study, we investigated whether redox dysregulation of SirT1 contributed to the pathogenesis of TAA using fibrillin-1 hypomorphic mice (Fbn1mgR/mgR), an established model of Marfan syndrome prone to aortic dissection/rupture. RESULTS: Oxidative stress markers 3-nitrotyrosine and 4-hydroxynonenal were significantly elevated in aortas of patients with Marfan syndrome. Moreover, reversible oxidative post-translational modifications (rOPTM) of protein cysteines, particularly S-glutathionylation, were dramatically increased in aortas of Fbn1mgR/mgR mice, before induction of severe oxidative stress markers. Fbn1mgR/mgR aortas and VSM cells exhibited an increase in rOPTM of SirT1, coinciding with the upregulation of acetylated proteins, an index of decreased SirT1 activity, and increased MMP2/9 activity. Mechanistically, we demonstrated that TGFß (transforming growth factor beta), which was increased in Fbn1mgR/mgR aortas, stimulated rOPTM of SirT1, decreasing its deacetylase activity in VSM cells. VSM cell-specific deletion of SirT1 in Fbn1mgR/mgR mice (SMKO-Fbn1mgR/mgR) caused a dramatic increase in aortic MMP2 expression and worsened TAA progression, leading to aortic rupture in 50% of SMKO-Fbn1mgR/mgR mice, compared with 25% of Fbn1mgR/mgR mice. rOPTM of SirT1, rOPTM-mediated inhibition of SirT1 activity, and increased MMP2/9 activity were all exacerbated by the deletion of Glrx (glutaredoxin-1), a specific deglutathionylation enzyme, while being corrected by overexpression of Glrx or of an oxidation-resistant SirT1 mutant in VSM cells. CONCLUSIONS: Our novel findings strongly suggest a causal role of S-glutathionylation of SirT1 in the pathogenesis of TAA. Prevention or reversal of SirT1 rOPTM may be a novel therapeutic strategy to prevent TAA and TAA dissection/ruptures in individuals with Marfan syndrome, for which, thus far, no targeted therapy has been developed.

Urate-Lowering Therapy Inhibits Thoracic Aortic Aneurysm and Dissection Formation in Mice.

BACKGROUND: Thoracic aortic aneurysm and dissection (TAAD) is a highly lethal vascular disease without effective drug therapy. Whether elevated serum concentrations of uric acid are involved in TAAD development remains unclear. METHODS: Serum uric acid levels were detected in different TAAD mouse models and patients. The urate-lowering drug allopurinol was administered in the drinking water of TAAD mice. Adenine diet-induced mice were established to investigate the role of hyperuricemia in TAAD formation and RNA-sequencing of thoracic aortas from these mice was performed. RESULTS: We found serum uric acid levels were elevated in various mouse TAAD models, including mice fed a ß-aminopropionitrile diet, Marfan mice with fibrillin-1 haploinsufficiency (Fbn1C1041G/+), and ApoE-/- mice infused with Ang II (angiotensin II), as well as in patients with TAAD. Administration of urate-lowering drug allopurinol in the drinking water significantly alleviated TAAD formation in ß-aminopropionitrile-treated mice, Fbn1C1041G/+ mice, and Ang II-infused ApoE-/- mice. Moreover, an adenine diet was used to induce hyperuricemia in mice. Intriguingly, a 4-week adenine diet feeding directly induced TAAD formation characterized by increased maximal thoracic aortic diameters and severe elastin degradation, which were ameliorated by allopurinol. Unbiased RNA-sequencing in mouse thoracic aortas suggested that FcγR (Fc gamma receptor) was upregulated upon adenine diet, but reciprocally repressed by allopurinol. Mechanistically, hyperuricemia activated FcγR-mediated ERK1/2 (extracellular signal-regulated kinase 1/2) phosphorylation to induce macrophage inflammation and TAAD development, which was abrogated by allopurinol or FcγR deficiency. CONCLUSIONS: This study uncovered an important and previously unrecognized role of hyperuricemia in mediating the pathogenesis of TAAD, and uric acid-lowering drug may represent a promising therapeutic approach for TAAD.

Lineage-Specific Induced Pluripotent Stem Cell-Derived Smooth Muscle Cell Modeling Predicts Integrin Alpha-V Antagonism Reduces Aortic Root Aneurysm Formation in Marfan Syndrome Mice.

BACKGROUND: The role of increased smooth muscle cell (SMC) integrin αv signaling in Marfan syndrome (MFS) aortic aneurysm remains unclear. Herein, we examine the mechanism and potential efficacy of integrin αv blockade as a therapeutic strategy to reduce aneurysm progression in MFS. METHODS: Induced pluripotent stem cells (iPSCs) were differentiated into aortic SMCs of the second heart field (SHF) and neural crest (NC) lineages, enabling in vitro modeling of MFS thoracic aortic aneurysms. The pathological role of integrin αv during aneurysm formation was confirmed by blockade of integrin αv with GLPG0187 in Fbn1C1039G/+ MFS mice. RESULTS: iPSC-derived MFS SHF SMCs overexpress integrin αv relative to MFS NC and healthy control SHF cells. Furthermore, integrin αv downstream targets (FAK [focal adhesion kinase]/AktThr308/mTORC1 [mechanistic target of rapamycin complex 1]) were activated, especially in MFS SHF. Treatment of MFS SHF SMCs with GLPG0187 reduced p-FAK/p-AktThr308/mTORC1 activity back to control SHF levels. Functionally, MFS SHF SMCs had increased proliferation and migration compared to MFS NC SMCs and control SMCs, which normalized with GLPG0187 treatment. In the Fbn1C1039G/+ MFS mouse model, integrin αv, p-AktThr308, and downstream targets of mTORC1 proteins were elevated in the aortic root/ascending segment compared to littermate wild-type control. Mice treated with GLPG0187 (age 6-14 weeks) had reduced aneurysm growth, elastin fragmentation, and reduction of the FAK/AktThr308/mTORC1 pathway. GLPG0187 treatment reduced the amount and severity of SMC modulation assessed by single-cell RNA sequencing. CONCLUSIONS: The integrin αv-FAK-AktThr308 signaling pathway is activated in iPSC SMCs from MFS patients, specifically from the SHF lineage. Mechanistically, this signaling pathway promotes SMC proliferation and migration in vitro. As biological proof of concept, GLPG0187 treatment slowed aneurysm growth and p-AktThr308 signaling in Fbn1C1039G/+ mice. Integrin αv blockade via GLPG0187 may be a promising therapeutic approach to inhibit MFS aneurysmal growth.

Satralizumab, Novel Interleukine-6 Inhibitor for Preventing Descending Thoracic Aorta Aneurysm Development.

BACKGROUND: Descending thoracic aorta aneurysm (dTAA) has increasing incidence and, if left untreated, could lead to death. There is not any study of satralizumab treatment for preventing dTAA formation and progression. MATERIALS AND METHODS: Forty male 10-week-old Rattus norvegicus were enrolled in the experiment. They were divided into four equal groups: dTAA treated with saline (dTAA-P) and dTAA treated with satralizumab (dTAA-S). One of the control groups was treated with saline (C-P), and the other was treated with satralizumab (C-S). Satralizumab and saline were used once every 2 weeks, subcutaneously 120 mg for 4 weeks. dTA diameter was measured at days 0, 3, 7, 14, 21, and 28. RESULTS: IL-6 level was measured on the 7th day that showed significantly increased IL-6 serum level in dTAA-P rats compared to C-P. Maximal dTA diameter (%MAD) was obtained at day 14, which was scientifically matched to the aorta aneurysm definition (>50% increase in diameter). From the seventh day, a significant difference in %MAD was observed between dTAA-P and dTAA-S groups. However, the %MAD of these two groups was significantly higher than control groups till the end of the 28th day. CONCLUSION: Using an IL-6 inhibitor agent to prevent dTAA formation and progression showed promising results. It suggests that using the IL-6 inhibitors in susceptible persons can be considered a lifesaving therapeutic approach.

Aortic Stress Activates an Adaptive Program in Thoracic Aortic Smooth Muscle Cells That Maintains Aortic Strength and Protects Against Aneurysm and Dissection in Mice.

BACKGROUND: When aortic cells are under stress, such as increased hemodynamic pressure, they adapt to the environment by modifying their functions, allowing the aorta to maintain its strength. To understand the regulation of this adaptive response, we examined transcriptomic and epigenomic programs in aortic smooth muscle cells (SMCs) during the adaptive response to AngII (angiotensin II) infusion and determined its importance in protecting against aortic aneurysm and dissection (AAD). METHODS: We performed single-cell RNA sequencing and single-cell sequencing assay for transposase-accessible chromatin (scATAC-seq) analyses in a mouse model of sporadic AAD induced by AngII infusion. We also examined the direct effects of YAP (yes-associated protein) on the SMC adaptive response in vitro. The role of YAP in AAD development was further evaluated in AngII-infused mice with SMC-specific Yap deletion. RESULTS: In wild-type mice, AngII infusion increased medial thickness in the thoracic aorta. Single-cell RNA sequencing analysis revealed an adaptive response in thoracic SMCs characterized by upregulated genes with roles in wound healing, elastin and collagen production, proliferation, migration, cytoskeleton organization, cell-matrix focal adhesion, and PI3K-PKB/Akt (phosphoinositide-3-kinase-protein kinase B/Akt) and TGF-ß (transforming growth factor beta) signaling. ScATAC-seq analysis showed increased chromatin accessibility at regulatory regions of adaptive genes and revealed the mechanical sensor YAP/transcriptional enhanced associate domains as a top candidate transcription complex driving the expression of these genes (eg, Lox, Col5a2, Tgfb2). In cultured human aortic SMCs, cyclic stretch activated YAP, which directly bound to adaptive gene regulatory regions (eg, Lox) and increased their transcript abundance. SMC-specific Yap deletion in mice compromised this adaptive response in SMCs, leading to an increased AAD incidence. CONCLUSIONS: Aortic stress triggers the systemic epigenetic induction of an adaptive response (eg, wound healing, proliferation, matrix organization) in thoracic aortic SMCs that depends on functional biomechanical signal transduction (eg, YAP signaling). Our study highlights the importance of the adaptive response in maintaining aortic homeostasis and preventing AAD in mice.

mTOR inhibition prevents angiotensin II-induced aortic rupture and pseudoaneurysm but promotes dissection in Apoe-deficient mice.

Aortic dissection and rupture are triggered by decreased vascular wall strength and/or increased mechanical loads. We investigated the role of mTOR signaling in aortopathy using a well-described model of angiotensin II-induced dissection, aneurysm, or rupture of the suprarenal abdominal aorta in Apoe-deficient mice. Although not widely appreciated, nonlethal hemorrhagic lesions present as pseudoaneurysms without significant dissection in this model. Angiotensin II-induced aortic tears result in free rupture, contained rupture with subadventitial hematoma (forming pseudoaneurysms), dilatation, or healing, while the media invariably thickens regardless of mural tears. Medial thickening results from smooth muscle cell hypertrophy and extracellular matrix accumulation, including matricellular proteins. Angiotensin II activates mTOR signaling in vascular wall cells, and inhibition of mTOR signaling by rapamycin prevents aortic rupture but promotes dissection. Decreased aortic rupture correlates with decreased inflammation and metalloproteinase expression, whereas extensive dissection correlates with induction of matricellular proteins that modulate adhesion of vascular cells. Thus, mTOR activation in vascular wall cells determines whether aortic tears progress to dissection or rupture. Previous mechanistic studies of aortic aneurysm and dissection by angiotensin II in Apoe-deficient mice should be reinterpreted as clinically relevant to pseudoaneurysms, and mTOR inhibition for aortic disease should be explored with caution.

Meta-analysis Examining the Usefulness of Angiotensin Receptor blockers for the Prevention of Aortic Root Dilation in Patients With the Marfan Syndrome.

The Marfan syndrome (MFS) patients are highly predisposed to thoracic aortic aneurysm and/or dissection, with virtually every patient having evidence of aortic disease at some point during their lifetime. We conducted a meta-analysis to investigate the efficacy of angiotensin receptor blockers (ARBs) in slowing down the progression of aortic dilatation in MFS patients. PUBMED, EMBASE, and COCHRANE databases were searched for relevant articles published from inception to February 1, 2020. We included randomized clinical trials evaluating the effect of ARBs on aortic root size in patients with MFS with a follow-up period of at least 2.5 years. Seven studies were included with a total of 1,510 patients. Our analysis demonstrated a significantly smaller change in aortic root and ascending aorta dilation in the ARBs treated group when compared with placebo (mean difference 0.68; 95% confidence interval [CI] -1.31 to -0.04; p = 0.04, I2 = 94%, and mean difference -0.13, 95% CI -0.17 to -0.09; p < 0.00001, I2 = 0%, respectively). ARBs as an add-on therapy to beta-blockers resulted in a significantly smaller change in aortic root dilation when compared with the arm without ARBs (mean difference -2.06, 95% CI -2.54 to -1.58; p < 0.00001, I2 = 91%). However, there was no statistically significant difference in the number of clinical events (aortic complications/surgery) observed in the ARBs arm when compared with placebo (Risk ratio of 1.01, 95% CI 0.74 to 1.38; p = 0.94, I2 = 0%). In conclusion, ARBs therapy is associated with a slower progression of aortic root dilation when compared with placebo and as an addition to beta-blocker therapy.

Targeting the NLRP3 Inflammasome With Inhibitor MCC950 Prevents Aortic Aneurysms and Dissections in Mice.

Background Aortic aneurysms and dissections are highly lethal diseases for which an effective treatment strategy is critically needed to prevent disease progression. The nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3)-caspase-1 inflammasome cascade was recently shown to play an important role in aortic destruction and disease development. In this study, we tested the effects of MCC950, a potent, selective NLRP3 inhibitor, on preventing aortic destruction and aortic aneurysm and dissection formation. Methods and Results In a model of sporadic aortic aneurysm and dissection induced by challenging wild-type mice with a high-fat, high-cholesterol diet and angiotensin II infusion, MCC950 treatment significantly inhibited challenge-induced aortic dilatation, dissection, and rupture in different thoracic and abdominal aortic segments in both male and female mice. Aortic disease reduction by MCC950 was associated with the prevention of NLRP3-caspase-1 upregulation, smooth muscle cell contractile protein degradation, aortic cell death, and extracellular matrix destruction. Further investigation revealed that preventing matrix metallopeptidase 9 (MMP-9) expression and activation in macrophages is an important mechanism underlying MCC950's protective effect. We found that caspase-1 directly activated MMP-9 by cleaving its N-terminal inhibitory domain. Moreover, the genetic knockdown of Nlrp3 or Casp-1 in mice or treatment of mice with MCC950 diminished the challenge-induced N-terminal cleavage of MMP-9, MMP-9 activation, and aortic destruction. Conclusions Our findings suggest that the NLRP3-caspase-1 inflammasome directly activates MMP-9. Targeting the inflammasome with MCC950 is a promising approach for preventing aortic destruction and aortic aneurysm and dissection development.

PKM2 Activator TEPP-46 Attenuates Thoracic Aortic Aneurysm and Dissection by Inhibiting NLRP3 Inflammasome-Mediated IL-1ß Secretion.

BACKGROUND: The development of thoracic aortic aneurysm and dissection (TAAD) is mediated by inflammasome activation, which exacerbates the secretion of pro-inflammatory cytokines, chemokines, matrix metalloproteinases (MMPs), and reactive oxygen species (ROS). The glycolytic enzyme pyruvate kinase M2 (PKM2) has shown a protective role against various disorders with an inflammatory basis, such as sepsis, tumorigenesis, and diabetic nephropathy. However, its potential role in TAAD has not been investigated so far. APPROACH AND RESULTS: We analyzed aortic tissues from TAAD patients and the ß-aminopropionitrile fumarate (BAPN)-induced mouse model of TAAD and observed elevated levels of PKM2 in the aortic lesions of both. Treatment with the PKM2 activator TEPP-46 markedly attenuated the progression of TAAD in the mouse model as demonstrated by decreased morbidity and luminal diameter of the aorta. In addition, the thoracic aortas of the BAPN-induced mice showed reduced monocytes and macrophages infiltration and lower levels of IL-1ß, MMPs, and ROS when treated with TEPP-46. Furthermore, TEPP-46 treatment also suppressed the activation of the NOD-like receptor (NLR) family and pyrin domain-containing protein 3 (NLRP3) inflammasome by downregulating p-STAT3 and HIF1-α. CONCLUSION: Pyruvate kinase M2 plays a protective role in TAAD development, and its activation is a promising therapeutic strategy against the progression of TAAD.

MiR-26b Suppresses the Development of Stanford Type A Aortic Dissection by Regulating HMGA2 and TGF-ß/Smad3 Signaling Pathway.

PURPOSE: Stanford type A aortic dissection (TAAD) is one of the most dangerous cardiovascular diseases. MicroRNAs (miRNAs) have been considered as potential therapeutic targets for TAAD. In this present study, we aimed to investigate the functional role and regulatory mechanism of miR-26b in TAAD development. MATERIALS AND METHODS: MiR-26b mRNA expression was detected by real-time polymerase chain reaction (RT-PCR) and protein levels were measured by Western blot. Verifying the direct target of miR-26b was used by dual luciferase assay, RT-PCR, and Western blot. Cell Counting Kit-8 (CCK-8) and TUNEL staining assays were applied for detecting rat aortic vascular smooth muscle cells (VSMCs) viability and apoptosis, respectively. RESULTS: We found that miR-26b was under-expressed in TAAD patients and closely associated with the poor prognosis of TAAD patients. Re-expression of miR-26b facilitated while knockdown of miR-26b inhibited VSMC proliferation. However, miR-26b showed the opposite effect on cell apoptosis. More importantly, high-mobility group AT-hook 2 (HMGA2) was verified as the direct target of miR-26b. Furthermore, transforming growth factor beta (TGF-ß)/Smad3 signaling pathway was involved in the development of TAAD modulated by miR-26b. CONCLUSION: miR-26b impeded TAAD development by regulating HMGA2 and TGF-ß/Smad3 signaling pathway, which provided a potential biomarker for TAAD treatment.

Aortic pathology from protein kinase G activation is prevented by an antioxidant vitamin B12 analog.

People heterozygous for an activating mutation in protein kinase G1 (PRKG1, p.Arg177Gln) develop thoracic aortic aneurysms and dissections (TAAD) as young adults. Here we report that mice heterozygous for the mutation have a three-fold increase in basal protein kinase G (PKG) activity, and develop age-dependent aortic dilation. Prkg1R177Q/+ aortas show increased smooth muscle cell apoptosis, elastin fiber breaks, and oxidative stress compared to aortas from wild type littermates. Transverse aortic constriction (TAC)-to increase wall stress in the ascending aorta-induces severe aortic pathology and mortality from aortic rupture in young mutant mice. The free radical-neutralizing vitamin B12-analog cobinamide completely prevents age-related aortic wall degeneration, and the unrelated anti-oxidant N-acetylcysteine ameliorates TAC-induced pathology. Thus, increased basal PKG activity induces oxidative stress in the aorta, raising concern about the widespread clinical use of PKG-activating drugs. Cobinamide could be a treatment for aortic aneurysms where oxidative stress contributes to the disease, including Marfan syndrome.

Update on Clinical Trials of Losartan With and Without ß-Blockers to Block Aneurysm Growth in Patients With Marfan Syndrome: A Review.

Importance: Thoracic aortic aneurysms leading to acute aortic dissections are a major cause of morbidity and mortality despite significant advances in surgical treatment, which remains the main intervention to prevent type A dissections. In the past 2 decades progress has been made toward a better understanding of molecular mechanisms that lead to aneurysm formation and dissections of the thoracic aorta. This focused review emphasizes the results of clinical trials using ß-blocker, losartan potassium, and irbesartan in patients with Marfan syndrome and comments briefly on mechanisms of aortic remodeling, including fibrosis and transforming growth factor ß signaling. Observation: The major risk factors for the disease are increased hemodynamic forces, typically owing to poorly controlled hypertension, and heritable genetic variants. The altered genes predisposing to thoracic aortic disease have been shown or are predicted to decrease vascular smooth muscle cell contraction, decrease transforming growth factor ß signaling, or alter the extracellular matrix. Preclinical models of Marfan syndrome showed promising results for losartan as a potential therapy to attenuate aortic dilation in mice. However, several clinical trials did not conclusively confirm that losartan attenuated aortic aneurysm expansion better than ß-blockers. Most importantly, clinical trials assessing whether losartan therapy not only reduces aortic growth but also improves adverse aortic outcomes, including dissection, need for surgery, and death, have not been conducted. The largest trial to date to our knowledge, the Pediatric Heart Network trial, sponsored by the National Heart, Lung, and Blood Institute, showed a nonsignificant increase in adverse aortic outcomes, with almost a doubling of adverse events in patients randomized to losartan treatment compared with ß-blockers, suggesting that this study was underpowered to assess adverse aortic outcomes. On the other hand, the evidence for ß-blocker therapy to reduce morbidity and mortality in Marfan syndrome is limited to a single small, prospective randomized and nonblinded clinical trial. Conclusions and Relevance: Taken together, these data emphasize the need for clinical trials adequately powered to assess both aortic aneurysm growth and adverse aortic outcomes to identify effective medical therapies for Marfan syndrome and other aortopathies.

Aortic dissection and prophylactic surgery in congenital heart disease.

BACKGROUND: Proximal aortic dilatation in certain congenital heart diseases (CHD) prompts concerns about dissection and consideration of prophylactic surgery. To evaluate contemporary prophylactic practice, we determined incidence of aortic dissection and prophylactic surgery in aortopathy-associated CHD, compared to Marfan syndrom (MFS) and controls. METHODS AND RESULTS: We followed patients from the CONCOR adult CHD registry (2002-2015), with a native proximal aorta and aortopathy-associated CHD, comprising bicuspid aortic valve/aortic stenosis ('BAV/AS'; n = 2239) and aortic coarctation/conotruncal defects/univentricular heart/ventricular septal defect ('At-risk CHD'; n = 5439). As reference, we selected MFS (n = 356) and 'Control' (atrial septal defect, pulmonary stenosis; n = 2940) patients. Cumulative incidences of dissection and prophylactic proximal aortic replacement - considered competing events - were determined, and compared corrected for age and sex. Median follow-up was 6.7 years. Ten-year dissection-incidence was 0.3% (95%CI: 0.0-0.7) in BAV/AS and 0.2% (0.0-0.3) in At-risk CHD, both significantly lower than in MFS (4.1%; 1.8-6.4) and similar to Controls (0.1%; 0.0-0.3). Ten-year prophylactic-surgery incidence was 9.3% (7.6-11.0) in BAV/AS and 0.7% (0.5-1.0) in At-risk CHD, both significantly lower than in MFS (21.3%; 16.3-26.3) and higher than in Controls (0.1%; 0.0-0.3). CONCLUSIONS: In contemporary practice, aortic-dissection incidence is low in adults with aortopathy-associated CHDs, while prophylactic-surgery incidence is high in BAV/AS. To reduce surgical burden, BAV/AS patients could benefit from more individualised prophylactic-surgery algorithms.

Rapamycin prevents thoracic aortic aneurysm and dissection in mice.

OBJECTIVE: The purpose of this study was to investigate whether rapamycin inhibits the development of thoracic aortic aneurysm and dissection (TAAD) in mice. METHODS: Three-week-old C57BL/6J male mice were fed a normal diet and randomized into a control group (n = 6), ß-aminopropionitrile fumarate (BAPN) group (Gp A; n = 15), BAPN plus rapamycin (5 mg) group (Gp B; n = 8), and BAPN plus rapamycin (10 mg) group (Gp C; n = 8). Gp A, Gp B, and Gp C were administered BAPN (1 g/kg/d) for 4 weeks. One week after BAPN administration, Gp B and Gp C were treated with rapamycin (5 mg/kg/d or 10 mg/kg/d) through gavage for 21 days. Thoracic aortas were harvested for Western blot and immunofluorescence staining at day 14 and for morphologic and histologic analyses at day 28. RESULTS: BAPN treatment induced TAAD formation in mice. The incidence of TAAD in control, Gp A, Gp B, and Gp C mice was 0%, 80%, 25%, and 37.5%, respectively. Smaller thoracic aortic diameters (ascending aorta and arch) were observed in Gp B and Gp C mice than in Gp A mice (Gp B vs Gp A: ascending aorta, ex vivo, 1.07 ± 0.21 mm vs 1.80 ± 0.67 mm [P < .05]; aortic arch, ex vivo, 1.51 ± 0.40 mm vs 2.70 ± 1.06 mm [P < .05]; Gp C vs Gp A: ascending aortas, ex vivo, 1.10 ± 0.33 mm vs 1.80 ± 0.67 mm [P < .05]; aortic arch, ex vivo, 1.55 ± 0.56 mm vs 2.70 ± 1.06 mm [P < .05]). TAAD mice exhibited elastin fragmentation, abundant inflammatory cell infiltration, and significantly increased matrix metalloproteinase production in the aorta, and rapamycin treatment alleviated these changes. The protein levels of p-S6K and p-S6 in TAAD aortic tissues increased significantly, whereas they were suppressed by rapamycin. CONCLUSIONS: Rapamycin suppressed TAAD formation, probably by inhibition of mechanistic target of rapamycin signaling and reduction of inflammatory cell infiltration and matrix metalloproteinase 9 production. Targeting of the mechanistic target of rapamycin signaling pathway using rapamycin may be a favorable modulation for the clinical treatment of TAAD.

Effect of irradiation and bone marrow transplantation on angiotensin II-induced aortic inflammation in ApoE knockout mice.

BACKGROUND AND AIMS: Angiotensin II (Ang II) infusion promotes the development of aortic aneurysms and accelerates atherosclerosis in ApoE-/- mice. In order to elucidate the role of hematopoietic cells in these pathologies, irradiation and bone marrow transplantation (BMT) are commonly utilized. The aim of this study was to investigate the effects of irradiation and BMT on abdominal and thoracic aortic aneurysm formation and acute leukocyte recruitment in the aortic root and descending aorta, in an experimental mouse model of aortic aneurysm formation. METHODS: ApoE-/- mice were either lethally irradiated and reconstituted with ApoE-/- bone marrow or non-irradiated. Following engraftment, mice were treated with Ang II to induce aortic inflammation and accelerate atherosclerosis. RESULTS: Ang II infusion (0.8 mg/kg/day) in BMT mice resulted in reduced aortic aneurysms and atherosclerosis with decreased leukocyte infiltration in the aorta compared to non-BMT mice, when receiving the same dose of Ang II. Furthermore, the reduced aortic infiltration in BMT mice was accompanied by increased levels of monocytes in the spleen and bone marrow. A dose of 3 mg/kg/day Ang II was required to achieve a similar incidence of aneurysm formation as achieved with 0.8 mg/kg/day in non-BMT mice. CONCLUSIONS: This study provides evidence that BMT can alter inflammatory cell recruitment in experimental mouse models of aortic aneurysm formation and atherosclerosis and suggests that irradiation and BMT have a considerably more complex effect on vascular inflammation, which should be evaluated.

Diabetes and aortic aneurysm: current state of the art.

Aortic aneurysm is a life-threatening disease due to the risk of aortic rupture. The only curative treatment available relies on surgical approaches; drug-based therapies are lacking, highlighting an unmet need for clinical practice. Abdominal aortic aneurysm (AAA) is frequently associated with atherosclerosis and cardiovascular risk factors including male sex, age, smoking, hypertension, and dyslipidaemia. Thoracic aortic aneurysm (TAA) is more often linked to genetic disorders of the extracellular matrix and the contractile apparatus but also share similar cardiovascular risk factors. Intriguingly, a large body of evidence points to an inverse association between diabetes and both AAA and TAA. A better understanding of the mechanisms underlying the negative association between diabetes and aortic aneurysm could help the development of innovative diagnostic and therapeutic approaches to tackle the disease. Here, we summarize current knowledge on the relationship between glycaemic parameters, diabetes, and the development of aortic aneurysm. Cellular and molecular pathways that underlie the protective effect of diabetes itself and its treatment are reviewed and discussed, along with their potential implications for clinical translation.