Endotoxin Tolerance in Abdominal Aortic Aneurysm Macrophages, In Vitro: A Case-Control Study

Current understanding of macrophages in intracranial aneurysm: relevant etiological manifestations, signaling modulation and therapeutic strategies

Macrophages activation and inflammatory response play crucial roles in intracranial aneurysm (IA) formation and progression. The outcome of ruptured IA is considerably poor, and the mechanisms that trigger IA progression and rupture remain to be clarified, thereby developing effective therapy to prevent subarachnoid hemorrhage (SAH) become difficult. Recently, climbing evidences have been expanding our understanding of the macrophages relevant IA pathogenesis, such as immune cells population, inflammatory activation, intra-/inter-cellular signaling transductions and drug administration responses. Crosstalk between macrophages disorder, inflammation and cellular signaling transduction aggravates the devastating consequences of IA. Illustrating the pros and cons mechanisms of macrophages in IA progression are expected to achieve more efficient treatment interventions. In this review, we summarized the current advanced knowledge of macrophages activation, infiltration, polarization and inflammatory responses in IA occurrence and development, as well as the most relevant NF-κB, signal transducer and activator of transcription 1 (STAT1) and Toll-Like Receptor 4 (TLR4) regulatory signaling modulation. The understanding of macrophages regulatory mechanisms is important for IA patients' clinical outcomes. Gaining insight into the macrophages regulation potentially contributes to more precise IA interventions and will also greatly facilitate the development of novel medical therapy.

Abdominal Aortic Occlusion and the Inflammatory Effects in Heart and Brain

Background

Abdominal aortic occlusion (AAO) occurs frequently and causes ischemia/reperfusion (I/R) injury to distant organs. In this study, we aimed to investigate whether AAO induced I/R injury and subsequent damage in cardiac and neurologic tissue. We also aimed to investigate the how length of ischemic time in AAO influences reactive oxygen species (ROS) production and inflammatory marker levels in the heart, brain, and serum.

Methods

Sixty male C57BL/6 mice were used in this study. The mice were randomly divided into either sham group or AAO group. The AAO group was further subdivided into 1-4 hr groups of aortic occlusion times. The infrarenal abdominal aorta was clamped for 1-4 hr depending on the AAO group and was then reperfused for 24 hr after clamp removal. Serum, hippocampus, and left ventricle tissue samples were then subjected to biochemical and histopathological analyses.

Results

AAO-induced I/R injury had no effect on cell necrosis, cell apoptosis, or ROS production. However, serum and hippocampus levels of malondialdehyde (MDA) and lactate dehydrogenase (LDH) increased in AAO groups when compared to sham group. Superoxide dismutase and total antioxidant capacity decreased in the serum, hippocampus, and left ventricle. In the serum, AAO increased the level of inducible nitric oxide synthase (iNOS) and decreased the levels of anti-inflammatory factors (such as arginase-1), transforming growth factor- β1 (TGF-β1), interleukin 4 (IL-4), and interleukin 10 (IL-10). In the hippocampus, AAO increased the levels of tumor necrosis factor (TNF-α), interleukin 1β (IL-1β), interleukin 6 (IL-6), IL-4, and IL-6, and decreased the level of TGF-β1. In the left ventricle, AAO increased the level of iNOS and decreased the levels of TGF-β1, IL-4, and IL-10.

Conclusions

AAO did not induce cell necrosis or apoptosis in cardiac or neurologic tissue, but it can cause inflammation in the serum, brain, and heart.

Immune and inflammatory mechanisms of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease. Immune-mediated infiltration and a destruction of the aortic wall during AAA development plays significant role in the pathogenesis of this disease. While various immune cells had been found in AAA, the mechanisms of their activation and function are still far from being understood. A better understanding of mechanisms regulating the development of aberrant immune cell activation in AAA is essential for the development of novel preventive and therapeutic approaches. In this review we summarize current knowledge about the role of immune cells in AAA and discuss how pathogenic immune cell activation is regulated in this disease.

The physiological and clinical importance of cardiorespiratory fitness in people with abdominal aortic aneurysm

New Findings

What is the topic of this review?

This review focuses on the physiological impact of abdominal aortic aneurysm (AAA) on cardiorespiratory fitness and the negative consequences of low fitness on clinical outcomes in AAA. We also discuss the efficacy of exercise training for improving cardiorespiratory fitness in AAA.

What advances does it highlight?

We demonstrate the negative impact of low fitness on disease progression and clinical outcomes in AAA. We highlight potential mechanistic determinants of low fitness in AAA and present evidence that exercise training can be an effective treatment strategy for improving cardiorespiratory fitness, postoperative mortality and disease progression.

Abstract

An abdominal aortic aneurysm (AAA) is an abnormal enlargement of the aorta, below the level of the renal arteries, where the aorta diameter increases by >50%. As an aneurysm increases in size, there is a progressive increase in the risk of rupture, which ranges from 25 to 40% for aneurysms >5.5 cm in diameter. People with AAA are also at a heightened risk of cardiovascular events and associated mortality. Cardiorespiratory fitness is impaired in people with AAA and is associated with poor (postoperative) clinical outcomes, including increased length of hospital stay and postoperative mortality after open surgical or endovascular AAA repair. Although cardiorespiratory fitness is a well‐recognized prognostic marker of cardiovascular health and mortality, it is not assessed routinely, nor is it included in current clinical practice guidelines for the management of people with AAA. In this review, we discuss the physiological impact of AAA on cardiorespiratory fitness, in addition to the consequences of low cardiorespiratory fitness on clinical outcomes in people with AAA. Finally, we summarize current evidence for the effect of exercise training interventions on cardiorespiratory fitness in people with AAA, including the associated improvements in postoperative mortality, AAA growth and cardiovascular risk. Based on this review, we propose that cardiorespiratory fitness should be considered as part of the routine risk assessment and monitoring of people with AAA and that targeting improvements in cardiorespiratory fitness with exercise training might represent a viable adjunct treatment strategy for reducing postoperative mortality and disease progression.

Long Chain Omega-3 Polyunsaturated Fatty Acids Improve Vascular Stiffness in Abdominal Aortic Aneurysm: A Randomized Controlled Trial

Abdominal aortic aneurysm (AAA) is a vascular disease involving permanent focal dilation of the abdominal aorta (≥30 mm) that can lead to catastrophic rupture. Destructive remodeling of aortic connective tissue in AAA contributes to wall stiffening, a mechanical parameter of the arterial system linked to a heightened risk of cardiovascular morbidity and mortality. Since aortic stiffening is associated with AAA progression, treatment options that target vascular inflammation would appear prudent. Given this, and growing evidence indicating robust anti-inflammatory and vasoprotective properties for long chain omega-3 polyunsaturated fatty acids (LC n-3 PUFAs), this study evaluated the impact of these nutrients (1.8 g/day for 12 weeks) on indices of vascular stiffness in patients with AAA. At baseline, pulse wave velocity (PWV) and augmentation index normalized to a heart rate of 75 bpm (AIx75) were significantly higher in patients with AAA compared to control participants (PWV: 14.2 ± 0.4 m.s-1 vs. 12.6 ± 0.4 m.s-1, p = 0.014; AIx75: 26.4 ± 1.7% vs. 17.3 ± 2.7%, p = 0.005). Twelve-week LC n-3 PUFA supplementation significantly decreased PWV (baseline: 14.2 ± 0.6 m.s-1, week 12: 12.8 ± 0.7 m.s-1, p = 0.014) and heart rate (baseline: 63 ± 3 bpm, week 12: 58 ± 3 bpm, p = 0.009) in patients with AAA. No change was observed for patients receiving placebo capsules. While this raises the possibility that LC n-3 PUFAs provide improvements in aortic stiffness in patients with AAA, the clinical implications remain to be fully elucidated.