Background-Doxycycline has been shown to effectively inhibit aneurysm formation in animal models of abdominal aortic aneurysm. Although this effect is ascribed to matrix metalloproteinase-9 inhibition, such an effect is unclear in human studies. We reevaluated the effect of doxycycline on aortic wall protease content in a clinical trial and found that doxycycline selectively reduces neutrophil-derived proteases. We thus hypothesized that doxycycline acts through an effect on vascular inflammation. Methods and Results-Sixty patients scheduled for elective open aneurysmal repair were randomly assigned to 2 weeks of low-, medium-, or high-dose doxycycline (50, 100, or 300 mg/d, respectively) or no medication (control group). Aortic wall samples were collected at the time of operation, and the effect of doxycycline treatment on vascular inflammation was evaluated. Independently of its dose, doxycycline treatment resulted in a profound but selective suppression of aortic wall inflammation as reflected by a selective 72% reduction of the aortic wall neutrophils and a 95% reduction of the aortic wall cytotoxic T-cell content (median values; PϽ0.00003). Evaluation of major inflammatory pathways suggested that doxycycline treatment specifically quenched AP-1 and C/EBP proinflammatory transcription pathways (PϽ0.0158, NS) and reduced vascular interleukin-6 (PϽ0.00115), interleukin-8 (PϽ0.00246, NS), interleukin-13 (PϽ0.0184, NS), and granulocyte colony-stimulating factor (PϽ0.031, NS) protein levels. Doxycycline was well tolerated; there were no adverse effects. Conclusions-A brief period of doxycycline treatment has a profound but selective effect on vascular inflammation and reduces aortic wall neutrophil and cytotoxic T-cell content. Results of this study are relevant for pharmaceutical stabilization of the abdominal aneurysm and possibly for other inflammatory conditions that involve neutrophils and/or cytotoxic T cells.

An aneurysm of the aorta is a common pathology characterized by segmental weakening of the artery. Although it is generally accepted that the vessel-wall weakening is caused by an impaired collagen metabolism, a clear association has been demonstrated only for rare syndromes such as the vascular type Ehlers-Danlos syndrome. Here we show that vessel-wall failure in growing aneurysms of patients who have aortic abdominal aneurysm (AAA) or Marfan syndrome is not related to a collagen defect at the molecular level. On the contrary our findings indicate similar (Marfan) or even higher collagen concentrations (AAA) and increased collagen cross-linking in the aneurysms. Using 3D confocal imaging we show that the two conditions are associated with profound defects in collagen microarchitecture. Reconstructions of normal vessel wall show that adventitial collagen fibers are organized in a loose braiding of collagen ribbons. These ribbons encage the vessel, allowing the vessel to dilate easily but preventing overstretching. AAA and aneurysms in Marfan syndrome show dramatically altered collagen architectures with loss of the collagen knitting. Evaluations of the functional characteristics by atomic force microscopy showed that the wall has lost its ability to stretch easily and revealed a second defect: although vascular collagen in normal aortic wall behaves as a coherent network, in AAA and Marfan tissues it does not. As result, mechanical forces loaded on individual fibers are not distributed over the tissue. These studies demonstrate that the mechanical properties of tissue are strongly influenced by collagen microarchitecture and that perturbations in the collagen networks may lead to mechanical failure.A ortic aneurysms are localized dilatations of the aortic wall that are caused by segmental weakening of the vessel wall. Although aneurysms generally are without clinical symptoms, larger aneurysms may rupture, and bleeding from a ruptured aneurysm is responsible for more than 15,000 annual deaths in the United States alone (1).Aneurysm formation relates to a primary or secondary (acquired) defect in the matrix structures supporting the vessel wall resulting in attenuation and ultimate failure of the vessel wall (2). Although extensive loss of medial elastin traditionally is considered the hallmark of aneurysm formation, it now is acknowledged that aneurysmal growth and ultimate rupture relate to impaired collagen homeostasis (2). Remarkably, although numerous studies have looked for putative quantitative changes in aortic collagen, results reported to date are controversial (3-5). With the exception of rare mutations in the collagen III gene such as the vascular type of Ehlers-Danlos syndrome, no clear association between impaired collagen homeostasis and aneurysm growth and/or rupture has been identified.In search of the collagen defect(s) underlying aneurysm formation, we applied an integrated approach of biochemical analyses, multiple imaging modalities, and functional analysis by atomic force microscopy (AFM) to...

Inflammation plays a key role in the pathogenesis of an AAA (abdominal aortic aneurysm); however, the nature of the inflammatory factors and cellular response(s) involved in AAA growth is controversial. In the present study, we set out to determine the aortic levels of inflammatory cytokines in relation to downstream inflammatory transcription factors and cellular responses. A comparison of AAA wall samples with atherosclerotic wall samples taken from the same aortic region allowed AAA-specific inflammatory parameters to be identified that distinguish AAAs from ASD (aortic atherosclerotic disease). RT-PCR (real-time PCR), ELISA, Western blotting and immunohistochemistry were combined to assess cytokines and transcription factors at the mRNA and protein level, and their activation status. Compared with ASD, inflammatory parameters associated with Th1-type [T-bet, IL (interleukin)-2, IFN-gamma (interferon-gamma), TNF-alpha (tumour necrosis factor-alpha), IL-1alpha and cytotoxic T-cells] and Th2-type [GATA3, IL-4, IL-10, IL-13 and B-cells] responses were all increased in AAA samples. Evaluation of major downstream inflammatory transcription factors revealed higher baseline levels of C/EBP (CCAAT/enhancer-binding protein) alpha, beta and delta in the AAA samples. Baseline p65 NF-kappaB (nuclear factor kappaB) and c-Jun [AP-1 (activator protein-1)] levels were comparable, but their activated forms were strongly increased in the AAA samples. Downstream target genes of p65 NF-kappaB, c-Jun, IL-6 and IL-8 were hyperexpressed. Molecular and cellular processes associated with IL-6 and IL-8 hyperactivation were enhanced in the AAA samples, i.e. the expression of phospho-STAT-3 (signal transducer and activator of transcription-3) and perforin were elevated, and the content of plasma cells, neutrophils and vasa vasorum was increased. In conclusion, our findings demonstrate that an AAA is a general inflammatory condition which is characterized by enhanced expression and activation of pro-inflammatory transcription factors, accompanied by IL-6 and IL-8 hyperexpression and exaggerated downstream cellular responses, which together clearly distinguish an AAA from ASD.

Growth and rupture of abdominal aortic aneurysms (AAAs) result from increased collagen turnover . Collagen turnover critically depends on specific collagenases that cleave the triple helical region of fibrillar collagen. As yet , the collagenases responsible for collagen degradation in AAAs have not been identified. Increased type I collagen degradation products confirmed collagen turnover in AAAs (median values: <1 , 43 , and 108 ng/mg protein in control , growing , and ruptured AAAs , respectively). mRNA and protein analysis identified neutrophil collagenase [matrix metalloproteinase (MMP)-8] and cysteine collagenases cathepsin K , L , and S as the principle collagenases in growing and ruptured AAAs. Except for modestly increased MMP-14 mRNA levels , collagenase expression was similar in growing and ruptured AAAs (anteriorlateral wall). Evaluation of posttranslational regulation of protease activity showed a threefold increase in MMP-8 , a fivefold increase in cathepsins K and L , and a 30-fold increase in cathepsin S activation in growing and ruptured AAAs. The presence of the osteoclastic proton pump indicated optimal conditions for extracellular cysteine protease activity. Protease inhibitor mRNA expression was similar in AAAs and controls, but AAA protein levels of cystatin C, the principle cysteine protease inhibitor, were profoundly reduced (>80%). We found indications that this secondary deficiency relates to cystatin C degradation by (neutrophil-derived) proteases. Abdominal aortic aneurysm (AAA) is a common pathology and a major cause of death because of rupture. 1,2 The hallmark pathology of AAA is a persistent proteolytic imbalance that results in excess matrix destruction and progressive weakening of the arterial wall. A number of matrix metalloproteinases (MMPs) (in particular the gelatinases MMP-2 and -9) 1,3 have been implicated as primary proteolytic culprits in the disease, but it is dubious whether these proteases are directly responsible for the weakening and ultimate failure of the aortic wall. Biomechanical studies invariably show that the mechanical stability of the arterial wall essentially relies on fibrillar collagens in media and adventitia. 4 -6 These structural collagens are highly resistant toward proteolytic degradation, and the only mammalian proteases that have been shown to cleave the native triple helical region of fibrillar collagen are the classic collagenases of the MMP family 7 [ie, MMP-1, -8, and -13 and the membrane type-1 MMP (MT-1 MMP or MMP-14 8 )], as well as selected members of the cysteine protease family (ie, cathepsin K, 9,10 L, 11 and possibly S 12 ).Several reports indicate expression of these collagenases in AAA on an individual basis, but comparative data regarding expression of the collagenases, and their possible relationship to rupture of the aneurysm, 13,14 are not available. Moreover, available studies 15 do not address the critical and complex posttranslational regulation of protease activity that involves controlled secretion of an inactive proenzyme,...

This explorative study characterizes degenerative aneurysmal disease general inflammatory conditions that are dominated by profound activation of the NF-kappaB and AP-1 pathways, hyperexpression of IL-6 and IL-8, and neutrophil involvement. Discordant findings for interferon gamma, cytotoxic T cells, B cells, and plasma cells challenge a critical role for these factors in the process of aneurysm growth. Pharmaceutic strategies targeting the common components in AAA and PAA may prove effective for the stabilization of AAA.