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Background: The purpose of these experiments was to test the hypothesis that dietary phytoestrogens would diminish experimental aortic aneurysm formation. Materials and methods: Six-wk-old C57BL/6 mice were divided into groups, fed either a diet with minimal phytoestrogen content or a regular commercial rodent diet with high phytoestrogen content for 2 wk. At the age of 8 wk, aortic aneurysms were induced by infusing the isolated infrarenal abdominal aorta with 0.4% elastase for 5 min. Mice were recovered and the diameter of the infused aorta was measured at postoperative days 3, 7, and 14. Abdominal aorta samples were collected for histology, cytokine array, and gelatin zymography after aortic diameter measurement. Blood samples were also collected to determine serum phytoestrogens and estradiol levels. Multiple-group comparisons were done using an analysis of variance with post hoc Tukey tests. Results: Compared with mice on a minimal phytoestrogen diet, mice on a regular rodent diet had higher levels of serum phytoestrogens (male, 1138 ± 846 ng/dL; female, 310 ± 295 ng/dL). These serum phytoestrogen levels were also much higher than their own endogenous estradiol levels (109-fold higher for males and 35.5-fold higher for females). Although aortic diameters of female mice were unaffected by the phytoestrogen concentration in the diets, male mice on the regular rodent diet (M+ group) developed smaller aortic aneurysms than male mice on the minimal phytoestrogen diet (M− group) on postoperative day 14 (M+ 54.8 ± 8.8% versus M− 109.3 ± 37.6%; P < 0.001). During aneurysm development (postoperative days 3 and 7), there were fewer neutrophils, macrophages, and lymphocytes in the aorta from the M+ group than from the M− group. Concentrations of multiple proinflammatory cytokines (matrix metalloproteinases [MMPs]; interleukin 1β [IL-1β]; IL-6; IL-17; IL-23; monocyte chemoattractant protein-1; regulated on activation, normal T cell expressed and secreted; interferon γ; and tumor necrosis factor α) from aortas of the M+ group were also lower than those from the aortas of the M− group. Zymography also demonstrated that the M+ group had lower levels of aortic MMP-9s than the M− group on postoperative day 14 (P < 0.001 for pro-MMP-9, P < 0.001 for active MMP-9). Conclusions: These results suggest that dietary phytoestrogens inhibit experimental aortic aneurysm formation in male mice via a reduction of the inflammatory response in the aorta wall. The protective effect of dietary phytoestrogens on aneurysm formation warrants further investigation. [ABSTRACT FROM AUTHOR]

Introduction: Abdominal aortic aneurysm (AAA) formation involves vascular remodeling and inflammation. Recent reports indicate that Pannexin-1 (Panx1) channels are expressed on endothelial cells and modulate cellular ATP release. Hypothesis: This study investigates the role of Panx1 inhibition in mitigation of AAA formation. Methods: Human AAA tissue was analyzed for Panx1 expression by western blot compared to normal controls. AAAs were induced in 8- to 12-week old male C57BL/6 (WT), VECadCreERT2+/Panx1fl/fl (endothelial cell-specific Panx1 inducible knockout (KO) and SMMHC-CreERT2+/Panx1fl/fl (smooth muscle cell-specific Panx1 inducible KO) mice using topical (0.4 U/mL type 1 porcine pancreatic elastase) treatment or deactivated elastase as control. WT mice were also treated with probenecid (PBN, 1.1 mg/kg i.p.), a Panx1 specific inhibitor on days 1, 3, 5 and 7 and analyzed on day 14. Also, male apolipoprotein E (ApoE-/-) knockout mice were treated with angiotensin II (Ang II; 1000 ng/kg) and were similarly administered PBN or vehicle. Aortic diameter was measured and tissue was harvested on post-operative day 28. Cytokine expression in aortic tissue was analyzed by ELISA and immunohistochemistry was performed. Groups were compared using ANOVA followed by Tukey's test. Results: A significant increase in Panx1 expression was observed in aortic tissue from male AAA patients compared to controls. Aortic diameter was significantly decreased in elastase-treated WT mice treated with PBN compared to untreated controls (69.5±5.6% vs. 123.3±2.7%; mean +/- S.E.; n=5-8/group, p<0.001) on day 14. Elastase-treated endothelial-specific Panx1 KO mice, but not the smooth muscle-specific Panx1 KO mice, had a significant attenuation in AAA formation compared to elastase-treated WT mice (72±5.4%* and 100±6.0% vs. 123.3±2.7%, respectively; *p<0.001; n=7-10/group). Similarly, there was a significant decrease in aortic diameter in ApoE-/- mice treated with PBN compared to vehicle (0.73±0.1 vs. 1.1±0.2 mm; n=8/group; p<0.01) on day 28. A significant mitigation of inflammatory cytokines (IL-17, HMGB1, MCP1, TNF-α), cell infiltration (CD3+ T cells, macrophages and neutrophils) and decrease in elastic fiber disruption occurred in elastase-treated endothelial-specific Panx1 knockout mice as well as in PBN treated WT mice compared to elastase-treated WT mice. Conclusions: Pharmacologic inhibition and endothelial-specific deletion of Panx1 channels modulate inflammation, leukocyte trafficking and AAA formation. [ABSTRACT FROM AUTHOR]

Our previous studies showed that neutrophil infiltration and activation plays an important role in the pathogenesis of abdominal aortic aneurysms (AAA). However, there is a lack of noninvasive, inflammatory cell-specific molecular imaging methods to provide early diagnosis of AAA formation. Formyl peptide receptor 1 (FPR1) is rapidly upregulated on neutrophils during inflammation. Therefore, it is hypothesized that the use of cinnamoyl-F-(D)L-F-(D)L-F-K (cFLFLF), a PEGylated peptide ligand that binds FPR1 on activated neutrophils, would permit accurate and noninvasive diagnosis of AAA via single-photon emission computed tomography (SPECT) imaging. Male C57BL/6 (wild-type) mice were treated with topical elastase (0.4 U/mL type 1 porcine pancreatic elastase) or heat-inactivated elastase (control), and aortic diameter was measured by video micrometry. Comparative histology was performed on Day 14 to assess neutrophil infiltration in aortic tissue. We performed near-infrared fluorescence imaging using c-FLFLF-Cy7 probe on Days 7 and 14 postelastase treatment and measured fluorescence intensity ex vivo in excised aortic tissue. A separate group of animals were injected with 99mTc-c-FLFLF 2 h before SPECT imaging on Day 14 using a SPECT/computed tomography/positron emission tomography trimodal scanner. Coexpression of neutrophils with c-FLFLF was also performed on aortic tissue by immunostaining on Day 14. Aortic diameter was significantly increased in the elastase group compared with controls on Days 7 and 14. Simultaneously, a marked increase in neutrophil infiltration and elastin degradation as well as decrease in smooth muscle integrity were observed in aortic tissue after elastase treatment compared with controls. Moreover, a significant increase in fluorescence intensity of c-FLFLF-Cy7 imaging probe was also observed in elastase-treated mice on Day 7 (approximately twofold increase) and Day 14 (approximately 2.5-fold increase) compared with respective controls. SPECT imaging demonstrated a multifold increase in signal intensity for 99mTc-cFLFLF radiolabel probe in mice with AAA compared with controls on Day 14. Immunostaining of aortic tissue with c-FLFLF-Cy5 demonstrated a marked increase in coexpression with neutrophils in AAA compared with controls. cFLFLF, a novel FPR1 ligand, enables quantifiable, noninvasive diagnosis and progression of AAAs. Clinical application of this inflammatory, cell-specific molecular probe using SPECT imaging may permit early diagnosis of AAA formation, enabling targeted therapeutic interventions and preventing impending aortic rupture. [ABSTRACT FROM AUTHOR]

Male gender is a well-established risk factor for abdominal aortic aneurysm (AAA), whereas estrogen is hypothesized to play a protective role. Although rupture rates are higher in women, these reasons remain unknown. In the present study, we sought to determine if female mice are protected from AAA rupture. Apolipoprotein E–deficient male and female mice (aged 7 wk; n = 25 per group) were infused with angiotensin II (AngII; 2000 ng/kg/min) plus β-aminopropionitrile (BAPN) in the drinking water for 28 d to test the effects of gender on AAA rupture. Separately, a second group of male apolipoprotein E–deficient mice underwent AngII infusion + BAPN while being fed high-fat phytoestrogen free or a high-fat phytoestrogen diet to assess effects of phytoestrogens on rupture. In a third group, female mice either underwent oophorectomy or sham operation 4 wk before infusion of AngII and BAPN to further test the effects of female hormones on AA rupture. Surviving mice abdominal aorta were collected for histology, cytokine array, and gelatin zymography on postoperative day 28. Female mice had decreased AAA rupture rates (16% versus 46%; P = 0.029). Female mice expressed fewer elastin breaks (P = 0.0079) and decreased smooth muscle cell degradation (P = 0.0057). Multiple cytokines were also decreased in the female group. Gelatin zymography demonstrated significantly decreased pro-matrix metalloproteinase 2 in female mice (P = 0.001). Male mice fed a high dose phytoestrogen diet failed to decrease AAA rupture. Female mice undergoing oophorectomy did not have accelerated aortic rupture. These data are the first to attempt to tease out hormonal effects on AAA rupture and the possible role of gender in rupture. [ABSTRACT FROM AUTHOR]

Background No medical therapies are yet available to slow abdominal aortic aneurysm (AAA) growth. This study sought to investigate the effect of different genders of bone marrow-derived mesenchymal stem cells (MSC) on AAA growth in a murine AAA model. Given the decreased rate of AAA in women, it is hypothesized that female MSC would attenuate AAA growth more so than male MSC. Materials and methods Aortas of 8–10-wk-old male C57Bl/6 mice were perfused with purified porcine pancreatic elastase to induce AAA formation. Bone marrow-derived MSC from male and female mice were dosed via tail vein injection (3 million cells per dose, 500 μL of volume per injection) on postaortic perfusion days 1, 3, and 5. Aortas were harvested after 14 d. Results Mean aortic dilation in the elastase group was 121 ± 5.2% (mean ± standard error of the mean), while male MSC inhibited AAA growth (87.8 ± 6.9%, P = 0.008) compared with that of elastase. Female MSC showed the most marked attenuation of AAA growth (75.2 ± 8.3% P = 0.0004). Proinflammatory cytokines tumor necrosis factor α, interleukin 1β, and monocyte chemotactic protein-1 (MCP-1) were only decreased in tissues treated with female MSC ( P = 0.017, P = 0.001, and P < 0.0001, respectively, when compared with elastase). Conclusions These data exhibit that female MSC more strongly attenuate AAA growth in the murine model. Furthermore, female MSC and male MSC inhibit proinflammatory cytokines at varying levels. The effects of MSC on aortic tissue offer a promising insight into biologic therapies for future medical treatment of AAAs in humans. [ABSTRACT FROM AUTHOR]