Endovascular aneurysm repair reverses the increased titer and the inflammatory activity of interleukin-1α in the serum of patients with abdominal aortic aneurysm

Innovation in pathogenesis and management of aortic aneurysm

Aortic aneurysm (AA) refers to the persistent dilatation of the aorta, exceeding three centimeters. Investigating the pathophysiology of this condition is important for its prevention and management, given its responsibility for more than 25000 deaths in the United States. AAs are classified based on their location or morphology. various pathophysiologic pathways including inflammation, the immune system and atherosclerosis have been implicated in its development. Inflammatory markers such as transforming growth factor β, interleukin-1β, tumor necrosis factor-α, matrix metalloproteinase-2 and many more may contribute to this phenomenon. Several genetic disorders such as Marfan syndrome, Ehler-Danlos syndrome and Loeys-Dietz syndrome have also been associated with this disease. Recent years has seen the investigation of novel management of AA, exploring the implication of different immune suppressors, the role of radiation in shrinkage and prevention, as well as minimally invasive and newly hypothesized surgical methods. In this narrative review, we aim to present the new contributing factors involved in pathophysiology of AA. We also highlighted the novel management methods that have demonstrated promising benefits in clinical outcomes of the AA.

Blood immunological profile of abdominal aortic aneurysm based on autoimmune injury

Abdominal aortic aneurysm (AAA) occupies a large part of aorta aneurysm, and if there's no timely intervention or treatment, the risks of rupture and death would rise sharply. With the depth of research in AAA, more and more evidence showed correlations between AAA and autoimmune injury. Currently, a variety of bioactive peptides and cells have been confirmed to be related with AAA progression. Despite the tremendous progress, more than half researches were sampling from lesion tissues, which would be difficult to obtain. Given that the intrusiveness and convenience, serological test take advantages in initial diagnosis. Here we review blood biomarkers associated with autoimmune injury work in AAA evolution, aiming to make a profile on blood immune substances of AAA and provide a thought for potential clinical practice.

Multidisciplinary diagnosis and management of inflammatory aortic aneurysms

BACKGROUND

Inflammatory abdominal aortic aneurysms (IAAAs) are a variant involving a distinct immunoinflammatory process, with nearly one half believed to be associated with IgG4-related disease (IgG4-RD).

METHODS

MEDLINE and Google Scholar searches were conducted for English-language publications relevant to inflammatory aortic aneurysms from January 1970 onward. The search terms included inflammatory aortic aneurysms, aortitis, periaortitis, IgG4-related disease, and retroperitoneal fibrosis. Relevant studies were selected for review based on their relevance.

RESULTS

Morphologically, IAAAs are characterized by a thickened aneurysm wall often displaying contrast enhancement and elevated metabolic activity on fluorine-18 fluorodeoxyglucose-positron emission tomography imaging. A strong association exists with perianeurysmal and retroperitoneal fibrosis. Although the rupture risk appears lower with IAAAs than with noninflammatory abdominal aortic aneurysms (AAAs), the currently recommended diameter threshold for operative management is the same. Open repair has been associated with increased morbidity compared with noninflammatory AAAs, and a retroperitoneal approach or minimal dissection transperitoneal approach has been recommended to avoid duodenal and retroperitoneal structural injuries. Endovascular aneurysm repair has been increasingly used, especially for patients unfit for open surgery. It is important to exclude an infectious etiology before the initiation of immunosuppressive therapy or operative repair. Multimodality imaging follow-up is critical to monitor disease activity and secondary involvement of retroperitoneal structures by the associated fibrotic process. Maintenance of immunosuppressive therapy will be needed postoperatively for most patients with active systemic disease, especially those with IgG4-RD and those with persistent symptoms. Additional interventions aimed at ureteral decompression could also be required, and lifelong follow-up is mandatory.

CONCLUSIONS

Preoperative multimodality imaging is a diagnostic cornerstone for assessment of the disease extent and activity. IgG4-RD is an increasingly recognized category of IAAAs, with implications for tailoring adjunctive medical therapy. Open surgical repair remains the procedure of choice, although endovascular aneurysm repair is increasingly being offered. Maintenance immunosuppressive therapy can be offered according to the disease activity as assessed by follow-up imaging studies.

Biomarkers in EndoVascular Aneurysm Repair (EVAR) and Abdominal Aortic Aneurysm: Pathophysiology and Clinical Implications

Circulating biomarkers have been recently investigated among patients undergoing endovascular aortic aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA). Considering the plethora of small descriptive studies reporting potential associations between biomarkers and clinical outcomes, this review aims to summarize the current literature considering both the treated disease (post EVAR) and the untreated disease (AAA before EVAR). All studies describing outcomes of tissue biomarkers in patients undergoing EVAR and in patients with AAA were included, and references were checked for additional sources. In the EVAR scenario, circulating interleukin-6 (IL-6) is a marker of inflammatory reaction which might predict postoperative morbidity; cystatin C is a promising early marker of post-procedural acute kidney injury; plasma matrix metalloproteinase-9 (MMP-9) concentration after 3 months from EVAR might help in detecting post-procedural endoleak. This review also summarizes the current gaps in knowledge and future direction of this field of research. Among markers used in patients with AAA, galectin and granzyme appear to be promising and should be carefully investigated even in the EVAR setting. Larger prospective trials are required to establish and evaluate prognostic models with highest values with these markers.

Neutrophils as Regulators and Biomarkers of Cardiovascular Inflammation in the Context of Abdominal Aortic Aneurysms

Neutrophils represent up to 70% of circulating leukocytes in healthy humans and combat infection mostly by phagocytosis, degranulation and NETosis. It has been reported that neutrophils are centrally involved in abdominal aortic aneurysm (AAA) pathogenesis. The natural course of AAA is growth and rupture, if left undiagnosed or untreated. The rupture of AAA has a very high mortality and is currently among the leading causes of death worldwide. The use of noninvasive cardiovascular imaging techniques for patient screening, surveillance and postoperative follow-up is well established and recommended by the current guidelines. Neutrophil-derived biomarkers may offer clinical value to the monitoring and prognosis of AAA patients, allowing for potential early therapeutic intervention. Numerous promising biomarkers have been studied. In this review, we discuss neutrophils and neutrophil-derived molecules as regulators and biomarkers of AAA, and our aim was to specifically highlight diagnostic and prognostic markers. Neutrophil-derived biomarkers may potentially, in the future, assist in determining AAA presence, predict size, expansion rate, rupture risk, and postoperative outcome once validated in highly warranted future prospective clinical studies.

Interleukin 1α: a comprehensive review on the role of IL-1α in the pathogenesis and treatment of autoimmune and inflammatory diseases

The interleukin (IL)-1 family member IL-1α is a ubiquitous and pivotal pro-inflammatory cytokine. The IL-1α precursor is constitutively present in nearly all cell types in health, but is released upon necrotic cell death as a bioactive mediator. IL-1α is also expressed by infiltrating myeloid cells within injured tissues. The cytokine binds the IL-1 receptor 1 (IL-1R1), as does IL-1β, and induces the same pro-inflammatory effects. Being a bioactive precursor released upon tissue damage and necrotic cell death, IL-1α is central to the pathogenesis of numerous conditions characterized by organ or tissue inflammation. These include conditions affecting the lung and respiratory tract, dermatoses and inflammatory skin disorders, systemic sclerosis, myocarditis, pericarditis, myocardial infarction, coronary artery disease, inflammatory thrombosis, as well as complex multifactorial conditions such as COVID-19, vasculitis and Kawasaki disease, Behcet's syndrome, Sjogren Syndrome, and cancer. This review illustrates the clinical relevance of IL-1α to the pathogenesis of inflammatory diseases, as well as the rationale for the targeted inhibition of this cytokine for treatment of these conditions. Three biologics are available to reduce the activities of IL-1α; the monoclonal antibody bermekimab, the IL-1 soluble receptor rilonacept, and the IL-1 receptor antagonist anakinra. These advances in mechanistic understanding and therapeutic management make it incumbent on physicians to be aware of IL-1α and of the opportunity for therapeutic inhibition of this cytokine in a broad spectrum of diseases.

Platelet activation and prothrombotic mediators at the nexus of inflammation and atherosclerosis: Potential role of antiplatelet agents

Platelets are central to inflammation-related manifestations of cardiovascular diseases (CVD) such as atherosclerosis. Platelet-activating factor (PAF), thrombin, thromboxane A₂ (TxA₂), and adenosine diphosphate (ADP) are some of the key agonists of platelet activation that are at the intersection between a plethora of inflammatory pathways that modulate pro-inflammatory and coagulation processes. The aim of this article is to review the role of platelets and the relationship between their structure, function, and the interactions of their constituents in systemic inflammation and atherosclerosis. Antiplatelet therapies are discussed with a view to primary prevention of CVD by the clinical reduction of platelet reactivity and inflammation. Current antiplatelet therapies are effective in reducing cardiovascular risk but increase bleeding risk. Novel therapeutic antiplatelet approaches beyond current pharmacological modalities that do not increase the risk of bleeding require further investigation. There is potential for specifically designed nutraceuticals that may become safer alternatives to pharmacological antiplatelet agents for the primary prevention of CVD but there is serious concern over their efficacy and regulation, which requires considerably more research.

Survival, cardiovascular morbidity, and reinterventions after elective endovascular aortic aneurysm repair in patients with and without diabetes: A nationwide propensity-adjusted analysis

Epidemiological data indicate decreased risk for development and growth of abdominal aortic aneurysm (AAA) among patients with diabetes mellitus (DM). On the other hand, DM adds to increased cardiovascular (CV) morbidity and mortality. In a nationwide observational cohort study of patients registered in the Swedish Vascular Register and the Swedish National Diabetes Register, we evaluated potential effects of DM on total mortality, CV morbidity, and the need for reintervention after elective endovascular aneurysm repair (EVAR) for AAA. We compared 748 patients with and 2630 without DM with propensity score-adjusted analysis, during a median 4.22 years of follow-up for patients with DM, and 4.05 years for those without. In adjusted analysis, diabetic patients showed higher rates of acute myocardial infarction (AMI) during follow-up (relative risk (RR) 1.44, 95% CI 1.06-1.95; p = 0.02), but lower need for reintervention (RR 0.12, CI 0.02-0.91; p = 0.04). There were no differences in total (RR 0.88, CI 0.74-1.05; p = 0.15) or CV (RR 1.58, CI 0.87-2.86; p = 0.13) mortality, or stroke (RR 0.95, CI 0.68-1.32; p = 0.75) during follow-up. In conclusion, patients with DM had higher rates of AMI and lower need for reintervention after elective EVAR than those without DM, whereas neither total nor CV mortality differed between groups. The putative protective effects of DM towards further AAA enlargement and late sac rupture may help explain the lower need for reintervention and absence of excess mortality.

The Coagulation and Immune Systems Are Directly Linked through the Activation of Interleukin-1α by Thrombin

Ancient organisms have a combined coagulation and immune system, and although links between inflammation and hemostasis exist in mammals, they are indirect and slower to act. Here we investigated direct links between mammalian immune and coagulation systems by examining cytokine proproteins for potential thrombin protease consensus sites. We found that interleukin (IL)-1α is directly activated by thrombin. Thrombin cleaved pro-IL-1α at a site perfectly conserved across disparate species, indicating functional importance. Surface pro-IL-1α on macrophages and activated platelets was cleaved and activated by thrombin, while tissue factor, a potent thrombin activator, colocalized with pro-IL-1α in the epidermis. Mice bearing a mutation in the IL-1α thrombin cleavage site (R114Q) exhibited defects in efficient wound healing and rapid thrombopoiesis after acute platelet loss. Thrombin-cleaved IL-1α was detected in humans during sepsis, pointing to the relevance of this pathway for normal physiology and the pathogenesis of inflammatory and thrombotic diseases.

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Mammalian IL-1α contains a highly conserved thrombin consensus site

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Thrombin cleavage leads to IL-1α activation and shedding from the cell surface

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Thrombin activates IL-1α after epidermal wounding and after acute platelet loss

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Thrombin-cleaved IL-1α is also detected in humans during sepsis

The Relationship Between Serum Interleukin-1α and Asymptomatic Infrarenal Abdominal Aortic Aneurysm Size, Morphology, and Growth Rates

OBJECTIVE/BACKGROUND

In a pilot study, a relationship between abdominal aortic aneurysm (AAA) diameter and serum interleukin (IL)-1α levels was reported, and that endothelial cell (EC) activation in vitro in response to serum from patients with AAA was blocked by anti-IL-1α antibodies. The aim of the present study was to further investigate the relationship between serum IL-1α and asymptomatic infrarenal AAA size, morphology, and growth rates.

METHODS

Serum IL-1α was measured using enzyme linked immunosorbent assay in 101 patients with asymptomatic, infrarenal AAA and related to aneurysm size, morphology, and growth rates.

RESULTS

IL-1α was measured in 101 patients. There was no statistically significant difference in mean age between men and women. IL-1α was detectable in 62.4% of patients; median IL-1α titre was 3.26 pg/mL. There was no statistically significant relationship between IL-1α and maximum AAA antero-posterior diameter as measured by ultrasound (p = .649), AAA morphology (aortic length [p = .394], sac [p = .369], and thrombus volume [p = .629]) as measured on computed tomography, absolute increase in AAA diameter (p = .214), or AAA growth rate (p = .230).

CONCLUSION

IL-1α is detectable in the majority of patients with infrarenal AAA, but the cause and clinical significance of this novel observation remains unknown.

Comparison of 2 Sample Processing Methods and 9 Commercial Immunoassays for the Detection of Interleukin-1α in the Serum of Patients with Abdominal Aortic Aneurysm

BACKGROUND

For a cytokine to have a role as a clinically useful biomarker, it must be measureable in a practical, reliable, and reproducible manner. Furthermore, assays from different manufacturers should produce comparable results. The aim of this paper was to examine the effect of 2 sample processing methodologies and compare 9 commercially available immunoassays for their measurement of serum interleukin (IL)-1α in patients with abdominal aortic aneurysm.

METHODS

Two sample processing methodologies and 9 manufacturers' immunoassays were compared. Each immunoassay was also tested for detection of both IL-1α isoforms.

RESULTS

A positive signal for IL-1α was found in all serum samples, in all immunoassays, using both processing methods. In the majority, titer concentrations were unquantifiable with values below manufacturers' detectable range. Variability in titer concentrations was seen across all immunoassays. With the exception of 1 immunoassay, all were able to detect both IL-1α isoforms.

CONCLUSIONS

Researchers wishing to measure serum cytokines levels should be aware that differences in sample processing methods and manufacturers' immunoassays can affect the results. This may result in misleading conclusions being drawn about biological processes underpinning a wide range of inflammatory diseases.

High-density lipoprotein therapy inhibits Porphyromonas gingivalis-induced abdominal aortic aneurysm progression

Clinical and experimental studies have highlighted the potential implication of periondontal bacteria contamination in the pathogenesis of abdominal aortic aneurysms (AAA). In addition to their role in reverse cholesterol transport, high-density lipoproteins (HDLs) display multiple functions, including anti-inflammatory and lipopolysaccharide scavenging properties. Low plasma levels of HDL-cholesterol have been reported in AAA patients. We tested the effect of a HDL therapy in Sprague-Dawley rat model of AAA, obtained by intraluminal elastase infusion followed by repeated injections of Porphyromonas gingivalis (Pg). HDLs, isolated by ultracentrifugation of plasma from healthy human volunteers, were co-injected intravenously (10 mg/kg) with Pg (1.107 Colony Forming Unit) one, eight and 15 days after elastase perfusion. Rats were sacrificed one week after the last injection. Our results show that Pg injections promote the formation of a persistent neutrophil-rich thrombus associated with increased aortic diameter in this AAA model. HDLs significantly reduced the increased AAA diameter induced by Pg. Histology showed the onset of a healing process in the Pg/HDL group. HDL injections also reduced neutrophil activation in Pg-injected rats associated with decreased cytokine levels in conditioned media and plasma. Scintigraphic analysis showed an intense uptake of 99mTc-HDL by the AAA suggesting that HDLs could exert their beneficial effect by acting directly on the thrombus components. HDL supplementation may therefore constitute a new therapeutic tool for AAA treatment.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Inhibition of the mTOR pathway in abdominal aortic aneurysm: implications of smooth muscle cell contractile phenotype, inflammation, and aneurysm expansion

The development of effective pharmacological treatment of abdominal aortic aneurysm (AAA) potentially offers great benefit to patients with preaneurysmal aortic dilation by slowing the expansion of aneurysms and reducing the need for surgery. To date, therapeutic targets for slowing aortic dilation have had low efficacy. Thus, in this study, we aim to elucidate possible mechanisms driving aneurysm progression to identify potential targets for pharmacological intervention. We demonstrate that mechanistic target of rapamycin (mTOR) signaling is overactivated in aortic smooth muscle cells (SMCs), which contributes to murine AAA. Rapamycin, a typical mTOR pathway inhibitor, dramatically limits the expansion of the abdominal aorta following intraluminal elastase perfusion. Furthermore, reduction of aortic diameter is achieved by inhibition of the mTOR pathway, which preserves and/or restores the contractile phenotype of SMCs and downregulates macrophage infiltration, matrix metalloproteinase expression, and inflammatory cytokine production. Taken together, these results highlight the important role of the mTOR cascade in aneurysm progression and the potential application of rapamycin as a therapeutic candidate for AAA.

NEW & NOTEWORTHY This study provides novel observations that mechanistic target of rapamycin (mTOR) signaling is overactivated in aortic smooth muscle cells and contributes to mouse abdominal aortic aneurysm (AAA) and that rapamycin protects against aneurysm development. Our data highlight the importance of preservation and/or restoration of the smooth muscle cell contractile phenotype and reduction of inflammation by mTOR inhibition in AAA.

Sex- and disease-specific inflammasome signatures in circulating blood leukocytes of patients with abdominal aortic aneurysm

Male sex is a risk factor for abdominal aortic aneurysm (AAA). Within the AAA adventitia, infiltrating leukocytes express high levels of inflammasome components. To further elucidate the role of inflammatory cells in the pathogenesis of AAA, we here addressed expression and functionality of inflammasome components in peripheral blood mononuclear cells (PBMC) of AAA patients in association with sex. PBMC and plasma were isolated from 100 vascular patients, including 34 pairs of AAA patients and age/sex-matched non-AAA patients. Male PBMC were found to express significantly higher mRNA levels of AIM2, NLRP3, ASC (PYCARD), CASP1, CASP5, and IL1B (all P < 0.0001) than female PBMC. Within the male patients, PBMC of AAA patients displayed increased mRNA levels of NLRP3 (P = 0.044), CASP1 (P = 0.032) and IL1B (P = 0.0004) compared to matched non-AAA PBMC, whereas there was no difference between female AAA and non-AAA patients. The relative protein level of NLRP3 was significantly lower in PBMC lysates from all AAA patients than in matched controls (P = 0.038), whereas AIM2 and active Caspase-1 (p10) protein levels were significantly increased (P = 0.014 and P = 0.049). ELISA revealed significantly increased IL-1α (mean = 6.34 vs 0.01 pg/ml) and IL-1β plasma levels (mean = 12.07 vs. 0.04 pg/ml) in AAA patients. The data indicate that male PBMC display a systemic proinflammatory state with primed inflammasomes that may contribute to AAA-pathogenesis. The AAA-specific inflammasome activation pattern suggests differential regulation of the sensors AIM2 and NLRP3 in inflammatory cells of AAA patients.

Role of Interleukin-1 Signaling in a Mouse Model of Kawasaki Disease-Associated Abdominal Aortic Aneurysm

OBJECTIVE

Kawasaki disease (KD) is the most common cause of acquired cardiac disease in US children. In addition to coronary artery abnormalities and aneurysms, it can be associated with systemic arterial aneurysms. We evaluated the development of systemic arterial dilatation and aneurysms, including abdominal aortic aneurysm (AAA) in the Lactobacillus casei cell-wall extract (LCWE)-induced KD vasculitis mouse model.

METHODS AND RESULTS

We discovered that in addition to aortitis, coronary arteritis and myocarditis, the LCWE-induced KD mouse model is also associated with abdominal aorta dilatation and AAA, as well as renal and iliac artery aneurysms. AAA induced in KD mice was exclusively infrarenal, both fusiform and saccular, with intimal proliferation, myofibroblastic proliferation, break in the elastin layer, vascular smooth muscle cell loss, and inflammatory cell accumulation in the media and adventitia. Il1r(-/-), Il1a(-/-), and Il1b(-/-) mice were protected from KD associated AAA. Infiltrating CD11c(+) macrophages produced active caspase-1, and caspase-1 or NLRP3 deficiency inhibited AAA formation. Treatment with interleukin (IL)-1R antagonist (Anakinra), anti-IL-1α, or anti-IL-1β mAb blocked LCWE-induced AAA formation.

CONCLUSIONS

Similar to clinical KD, the LCWE-induced KD vasculitis mouse model can also be accompanied by AAA formation. Both IL-1α and IL-1β play a key role, and use of an IL-1R blocking agent that inhibits both pathways may be a promising therapeutic target not only for KD coronary arteritis, but also for the other systemic arterial aneurysms including AAA that maybe seen in severe cases of KD. The LCWE-induced vasculitis model may also represent an alternative model for AAA disease.

Periostin links mechanical strain to inflammation in abdominal aortic aneurysm

AIMS

Abdominal aortic aneurysms (AAAs) are characterized by chronic inflammation, which contributes to the pathological remodeling of the extracellular matrix. Although mechanical stress has been suggested to promote inflammation in AAA, the molecular mechanism remains uncertain. Periostin is a matricellular protein known to respond to mechanical strain. The aim of this study was to elucidate the role of periostin in mechanotransduction in the pathogenesis of AAA.

METHODS AND RESULTS

We found significant increases in periostin protein levels in the walls of human AAA specimens. Tissue localization of periostin was associated with inflammatory cell infiltration and destruction of elastic fibers. We examined whether mechanical strain could stimulate periostin expression in cultured rat vascular smooth muscle cells. Cells subjected to 20% uniaxial cyclic strains showed significant increases in periostin protein expression, focal adhesion kinase (FAK) activation, and secretions of monocyte chemoattractant protein-1 (MCP-1) and the active form of matrix metalloproteinase (MMP)-2. These changes were largely abolished by a periostin-neutralizing antibody and by the FAK inhibitor, PF573228. Interestingly, inhibition of either periostin or FAK caused suppression of the other, indicating a positive feedback loop. In human AAA tissues in ex vivo culture, MCP-1 secretion was dramatically suppressed by PF573228. Moreover, in vivo, periaortic application of recombinant periostin in mice led to FAK activation and MCP-1 upregulation in the aortic walls, which resulted in marked cellular infiltration.

CONCLUSION

Our findings indicated that periostin plays an important role in mechanotransduction that maintains inflammation via FAK activation in AAA.