Systematic Review Examining the Association Between Angiotensin Converting Enzyme Inhibitor or Angiotensin Receptor Blocker Prescription and Abdominal Aortic Aneurysm Growth and Events

OBJECTIVE

Whether angiotensin II blockade is an effective medical treatment for abdominal aortic aneurysms (AAAs) has not been established. This systematic review and meta-analysis aimed to determine the association between angiotensin converting enzyme inhibitor (ACEi) or angiotensin receptor blocker (ARB) prescription and AAA growth and events.

DATA SOURCES

MEDLINE, Embase, Scopus, Web of Science, and the Cochrane Library databases were searched from their inception to 4 January 2024, with no language restrictions.

REVIEW METHODS

The five databases were searched for randomised controlled trials (RCTs) and observational studies reporting the association between ACEi or ARB prescription and AAA growth, repair, or rupture. The primary outcome was AAA growth, with secondary outcomes of AAA rupture, AAA repair, and AAA related events (rupture and repair combined). Risk of bias was assessed using the Risk of Bias 2 tool for RCTs and with a modified Newcastle-Ottawa scale for observational studies. Certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE). Random effects models were used for meta-analyses.

RESULTS

Eleven studies (two RCTs, eight observational studies, and one meta-analysis of individual patient data from seven populations) involving 58 022 patients were included. ACEi prescription was not associated with a statistically significant reduction in AAA growth (standard mean difference 0.01 mm/year, 95% confidence interval [CI] -0.26 - 0.28; p = .93; I2 = 98%) or AAA repair (odds ratio [OR] 0.73, 95% CI 0.50 - 1.09; p = .65; I2 = 61%), but was associated with a statistically significantly lower risk of AAA rupture (OR 0.87, 95% CI 0.81 - 0.93; p < .001; I2 = 26%) and AAA related events (OR 0.82, 95% CI 0.72 - 0.95; p = .006; I2 = 80%). ARB prescription was not associated with significantly reduced AAA growth or a lower risk of AAA related events. The two RCTs had a low risk of bias, with one observational study having low, seven moderate, and one high risk of bias. All of the findings had a very low certainty of evidence based on the GRADE analysis.

CONCLUSION

There was no association between ACEi or ARB prescription and AAA growth, but ACEi prescription was associated with a reduced risk of AAA rupture and AAA related events with very low certainty of evidence.

Magnetically-responsive, multifunctional drug delivery nanoparticles for elastic matrix regenerative repair

Arresting or regressing growth of abdominal aortic aneurysms (AAAs), localized expansions of the abdominal aorta are contingent on inhibiting chronically overexpressed matrix metalloproteases (MMPs)-2 and -9 that disrupt elastic matrix within the aortic wall, concurrent with providing a stimulus to augmenting inherently poor auto-regeneration of these matrix structures. In a recent study we demonstrated that localized, controlled and sustained delivery of doxycycline (DOX; a tetracycline-based antibiotic) from poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs), enhances elastic matrix deposition and MMP-inhibition at a fraction of the therapeutically effective oral dose. The surface functionalization of these NPs with cationic amphiphiles, which enhances their arterial uptake, was also shown to have pro-matrix regenerative and anti-MMP effects independent of the DOX. Based on the hypothesis that the incorporation of superparamagnetic iron oxide NPs (SPIONs) within these PLGA NPs would enhance their targetability to the AAA site under an applied external magnetic field, we sought to evaluate the functional effects of NPs co-encapsulating DOX and SPIONs (DOX-SPION NPs) on elastic matrix regeneration and MMP synthesis/activity in vitro within aneurysmal smooth muscle cell (EaRASMC) cultures. The DOX-SPION NPs were mobile under an applied external magnetic field, while enhancing elastic matrix deposition 1.5-2-fold and significantly inhibiting MMP-2 synthesis and MMP-2 and -9 activities, compared to NP-untreated control cultures. These results illustrate that the multifunctional benefits of NPs are maintained following SPION co-incorporation. Additionally, preliminary studies carried out demonstrated enhanced targetability of SPION-loaded NPs within proteolytically-disrupted porcine carotid arteries ex vivo, under the influence of an applied external magnetic field. Thus, this dual-agent loaded NP system proffers a potential non-surgical option for treating small growing AAAs, via controlled and sustained drug release from multifunctional, targetable nanocarriers.

STATEMENT OF SIGNIFICANCE

Proactive screening of high risk elderly patients now enables early detection of abdominal aortic aneurysms (AAAs). There are no established drug-based therapeutic alternatives to surgery for AAAs, which is unsuitable for many elderly patients, and none which can achieve restore disrupted and lost elastic matrix in the AAA wall, which is essential to achieve growth arrest or regression. We have developed a first generation design of polymer nanoparticles (NPs) for AAA tissue localized delivery of doxycycline, a modified tetracycline drug at low micromolar doses at which it provides both pro-elastogenic and anti-proteolytic benefits that can augment elastic matrix regenerative repair. The nanocarriers themselves are also uniquely chemically functionalized on their surface to also provide them pro-elastin-regenerative & anti-matrix degradative properties. To provide an active driving force for efficient uptake of intra-lumenally infused NPs to the AAA wall, in this work, we have rendered our polymer NPs mobile in an applied magnetic field via co-incorporation of super-paramagnetic iron oxide NPs. We demonstrate that such modifications significantly improve wall uptake of the NPs with no significant changes to their physical properties and regenerative benefits. Such NPs can potentially stimulate structural repair in the AAA wall following one time infusion to delay or prevent AAA growth to rupture. The therapy can provide a non-surgical treatment option for high risk AAA patients.

Viral Anti-Inflammatory Proteins Target Diverging Immune Pathways with Converging Effects on Arterial Dilatation, Plaque and Apoptosis

Abdominal aortic aneurysms are often fatal due to atherosclerosis, thromboembolism, rupture, and hemorrhage, however, treatment is limited to expectant monitoring and surgical intervention. Inflammation is detected in aneurysms and in plaque with associated increased apoptosis, chemokines, cytokines, hemorrhage, and thrombosis. We compared treatment with three different myxomavirus-derived anti-inflammatory proteins targeting apoptosis, thrombosis, and chemokine pathways. The effect of each protein on aortic dilatation and plaque growth was assessed after angioplasty in Apolipoprotein Enull mice. Four myxomavirus-derived proteins were studied; Serp-1 a serine protease inhibitor (serpin) targeting thrombotic and thrombolytic proteases, Serp-2 a cross-class serpin inhibiting granzyme B and caspases 1 and 8, M-T7 a broad spectrum C, CC, and CXC chemokine inhibitor, and R171E, an inactive M-T7 mutant. Cell invasion, elastin breaks, plaque progression, and aortic dilatation were significantly reduced by Serp-1, Serp-2, or M-T7 protein treatment, but not by R171E. PCR array analysis detected altered expression of a group of shared 40 apoptotic genes in monocytes after treatment with each active protein, but not R171E. Interference with inflammatory cell responses, through highly divergent inflammatory response pathways, produces similar reductions in monocyte invasion, arterial dilatation, and plaque growth potentially through modified expression of apoptotic genes.

Aortic volume as an indicator of disease progression in patients with untreated infrarenal abdominal aneurysm

OBJECTIVE

The maximal diameter of an abdominal aortic aneurysm (AAA) and the change in diameter over time reflect rupture risk and are used for surgical planning. However, evidence has emerged that aneurysm volume may be a better indicator of AAA remodeling. The purpose of this study was to assess the relationship between the volume and maximal diameter of the abdominal aorta in patients with untreated infrarenal AAA.

MATERIALS AND METHODS

This was a retrospective study of 100 patients with infrarenal AAA who were followed for more than 6 months. We examined 2 sets of computed tomography images for each patient, acquired ≥ 6 months apart. The maximal diameter and volume of the infrarenal abdominal aorta were determined by semiautomated segmentation software.

RESULTS

At baseline, mean maximal infrarenal diameter was 5.1 ± 1.0 cm and mean aortic volume was 139 ± 72 mL. There was good correlation between the maximal diameter and aortic volume at baseline (r(2) = 0.55; P<0.001). The mean change in maximal diameter between studies was 0.2 ± 0.3 cm and the mean volume change was 19 ± 19 mL. However, the correlation between diameter change and volume change was modest (r(2) = 0.34; P=0.001). Most patients (n = 64) had no measurable change in maximal diameter between studies (≤ 2 mm), but the change in volume was found to vary widely (-2 to 69 mL).

CONCLUSION

In patients with untreated infrarenal AAA, a change in aortic volume can occur in the absence of a significant change in maximal diameter. Additional work is needed to examine the relationship between change in AAA volume and outcomes in this patient group.

Safety and Efficacy Review of Doxycycline

Doxycycline is a member of the tetracycline class of antibiotics and has been used clinically for more than 40 years. It is a well-tolerated drug that is bacteriostatic and acts via the inhibition of bacterial ribosomes. It is generally given at a dose of 100-mg daily or twice daily. It is well absorbed and has generally good tissue penetration. The serum half-life is 18-22 hours and dosage does not need to be adjusted in the presence of renal or hepatic impairment. Major side effects are gastro-intestinal and dermatological and it is generally contra-indicated in pregnancy or childhood because of concerns about discolouration of developing teeth and potential effects on growing bones. Drug interactions are not common although can occur with the concomitant use of methotrexate and the oral contraceptive pill, and its absorption can be reduced by the co-administration with some antacids and iron preparations. It has activity against many organisms, including Gram-positives, Gram-negatives and atypical bacteria. In addition, it appears to have some potentially clinically useful anti-inflammatory properties.