Research Paper

Mechanical and Pharmacological Approaches to Investigate the Pathogenesis of Marfan Syndrome in the Abdominal Aorta
Ada W.Y. Chung, H.H. Clarice Yang, Karen Au Yeung, Cornelis van Breemen

Department of Cardiovascular Science, Child and Family Research Institute and Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, B.C., Canada

Address of Corresponding Author

J Vasc Res 2008;45:314-322 (DOI: 10.1159/000113603)

 Outline

• Key Words
• Abstract
• Introduction
• Materials and Methods
• Drugs
• Experimental Animals and Tissue Preparation
• Measurement of Isometric Force
• Mechanical Properties
• Western Immunoblotting
• Histology
• Statistics
• Results
• Disorganization and Degradation of Elastic Fiber in the Marfan Abdominal Aortic Media
• Increase in Abdominal Aortic Stiffness in Marfan Syndrome
• Preserved Contractile Capacity in Marfan Abdominal Aorta
• Decreased Synthesis of TXA₂ in Marfan Abdominal Aorta
• Discussion
• Acknowledgements
• References

• Author Contacts
• Article Information
• Publication Details
• Drug Dosage / Copyright

  Key Words

• Marfan syndrome
• Abdominal aorta
• Cyclooxygenase
• Elastic fiber
• Aortic stiffness
• Vasomotor function

  Abstract

Background: Occurrence of disease complications in the abdominal aorta in Marfan syndrome, a connective tissue disorder caused by mutations in the gene encoding fibrillin-1, is relatively rare. We hypothesized that Marfan syndrome could affect the structure, vasomotor function and mechanical property of the abdominal aorta. Methods and Results: Abdominal aorta from mice at 3, 6, 9 and 12 months of age, heterozygous for the Fbn1 allele encoding a cysteine substitution (Fbn1^C1039G/+, Marfan mice, n = 50), were compared with those from age-matched control littermates (n = 50). Marfan abdominal aorta demonstrated pronounced elastic fiber degradation and disorganization, concomitant with an increased aortic stiffness during aging. In the isometric force measurement, vasoconstriction in response to membrane depolarization or phenylephrine stimulation was similar in both Marfan and control abdominal aorta. However, Marfan abdominal aorta was less sensitive to the inhibition of the phenylephrine-induced contraction by indomethacin and SQ-29548, during which the release of thromboxane A₂ was one half of that of the controls. Nevertheless, the protein expression of cyclooxygenase-1 and cyclooxygenase-2 detected by Western immunoblotting was not different between the 2 strains. Conclusions: We demonstrated that Marfan syndrome affected abdominal aorta with respect to matrix elastic fiber organization, aortic stiffness and release of thromboxane A₂.

Copyright © 2008 S. Karger AG, Basel

 Introduction

Marfan syndrome, an autosomal dominant disorder of connective tissue caused by mutations in the gene encoding fibrillin-1 [1], affects multiple systems including the cardiovascular, skeletal, ocular and pulmonary. However, the most life-threatening complication is progressive thoracic aortic aneurysm [2]. Fibrillin-1-rich microfibrils are essential in the formation and maturation of elastic fibers in large arteries. Patients with Marfan syndrome display increased aortic stiffness, reduced aortic distensibility, as well as elevated pulse wave velocity, which have been suggested as an indicator of dissection and rupture [3, 4]. Ninety percent of patients develop severe aneurysm in the aortic root and the ascending thoracic aorta, and a smaller population has complications in the abdominal aorta [2, 5]. The investigation of the relatively low disease vulnerability in the abdominal aorta in Marfan syndrome could be an interesting research area and might suggest potential treatment strategies for aneurysm along the whole aorta. However, the research regarding the abdominal aorta in Marfan syndrome is minimal. A reduction in aortic elastin content and a decrease in distensibility have been observed in the abdominal aorta of patients with Marfan syndrome [6,7,8,9]. Information about the elastic fiber organization in the abdominal aorta of Marfan syndrome is not elucidated, though elastic fiber disarray is often reported in the thoracic aorta [9,10,11,12,13].

Formation of aneurysm involves a multifactorial process influenced by both extracellular and cellular mechanisms. It has been suggested that the regulation of vascular tone controls the susceptibility of aneurysm development and that impairment of vasoconstriction would promote the dilatation of vessel wall [14]. Vascular endothelium regulates vasoconstriction and vasorelaxation through the synthesis and release of vasoactive mediators [15]. Nitric oxide constitutively synthesized from the endothelial nitric oxide synthase causes relaxation of the underlying smooth muscle cells [16]. In the vasculature under normal physiological conditions, thromboxane (TXA₂), one of the primary mediators of vasoconstriction, is synthesized by cyclooxygenase (COX)-1 and COX-2, which are abundantly expressed in the endothelial cells compared with the smooth muscle cells [15, 17, 18]. We have recently shown the impairment of nitric oxide-mediated endothelial-dependent relaxation and the reduced synthesis of TXA₂ in the thoracic aorta during disease progression of Marfan syndrome [19, 20]. However, the regulation of the COX-derived TXA₂ in vasomotor function has never been investigated in the abdominal aorta in Marfan syndrome.

Using a validated mouse model of Marfan syndrome [11,19,20,21,22,23], in the present study we elucidated the pathogenesis of Marfan syndrome in the abdominal aorta by comparing it with age-matched controls with respect to elastic fiber integrity, aortic stiffness and vasomotor function. We conclude that Marfan syndrome affects both functional and mechanical properties of the abdominal aorta.

 Materials and Methods

 Drugs

Ketamine hydrochloride and xylazine hydrochloride (Research Biochemicals International, Natick, Mass., USA), TXA₂ and/or prostaglandin H₂ receptor antagonist SQ-29548 (Cayman Chemical, Ann Arbor, Mich., USA), phenylephrine, potassium chloride, indomethacin, 9,11-dideoxy-11,9-epoxymethanoprostaglandin F₂ (TXA₂ receptor agonist, U-46619) and chemicals for preparing Krebs solution (Sigma-Aldrich, Oakville, Canada) were used.

 Experimental Animals and Tissue Preparation

Heterozygous (Fbn1^C1039G/+) mice were mated to C57BL/6 mice to produce equal numbers of Fbn1^C1039G/+ Marfan subjects (n = 60) and wild-type controls (n = 60) as described previously [19, 20]. Both strains were housed in the institutional animal facility (Child and Family Research Institute, University of British Columbia) under standard animal room conditions, and all animal procedures were approved by the institutional Animal Ethics Board. Mice at ages of 3 (n = 40), 6 (n = 30), 9 (n = 30) and 12 (n = 20) months were anesthetized with a mixture of ketamine hydrochloride (80 mg/kg) and xylazine hydrochloride (12 mg/kg) intraperitoneally for experimentation. The abdominal aorta (between the diaphragm and the common iliac arteries) was isolated and cleaned of connective tissues and blood, with special care taken to preserve the endothelium [19, 20].

 Measurement of Isometric Force

Abdominal aortic segments (2 mm) were mounted isometrically in a small vessel myograph (A/S Danish Myotechnology, Aarhus, Denmark) for measuring generated force [19, 20]. Aortic segments were stretched to the optimal tension (3.5 mN) for 20 min. The vessels were thereafter challenged twice with 80 mM potassium chloride (KCl) before the continuation of experiments. To investigate the possible participation of prostanoids in the reduction of contraction in the Marfan aorta, aortic segments were incubated with the COX-1/COX-2 inhibitor indomethacin (10 µM) for 30 min before the addition of phenylephrine (1 nM to 3 µM). Concentration-response curve of phenylephrine-induced contraction was constructed. The negative logarithm (pD2) of the concentration of phenylephrine giving half-maximum response (EC₅₀) was assessed by linear interpolation on the semilogarithm concentration-response curve [pD2 = -log(EC₅₀)]. To evaluate the possible participation of vasoconstrictor prostanoids, aortic segments were preincubated with SQ-29548 (TXA₂/PGH₂ receptor antagonist; 1 µM) before the addition of phenylephrine.

 Mechanical Properties

Vessel stiffness was deduced from the stress-strain curves. In a small-vessel myograph (A/S Danish Myotechnology), a 2-mm aortic segment was stretched by increasing the distance between the 2 stainless wires, and held at each length for 3 min. Initially, 2 wires were adjusted to L₀, at which the vessel was not stretched. The distance between the 2 wires was then increased by 100 µm, and the new length was noted as L. The developed force (mN) was divided by the surface area (length × 2 × thickness; mm²) to calculate wall stress (mN/mm²). Thickness = initial thickness × (initial circumference/current circumference)^0.5. The procedure was repeated until the vessel was unable to maintain its tone. The stress at which rupture occurred was reported as breaking stress. L/L₀ and the wall stress were fitted on an exponential curve.

 Western Immunoblotting

The procedures of protein homogenization and Western immunoblotting were previously described [19, 20]. Protein sample (40 µg) was separated on 9% sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and then transferred to polyvinyldifluoride membranes (Bio-Rad, Hercules, Calif., USA). Membranes were first incubated with primary antibodies, rabbit polyclonal anti-COX-1 or anti-COX-2 antibodies (dilution 1:200; Cayman Chemical), then with IgG peroxidase-conjugated secondary antibodies (dilution 1:2,500; Sigma-Aldrich). Immunoreactive proteins were visualized by enhanced chemiluminescence kit (Amersham Life Sciences, Arlington Heights, Ill., USA). To ensure equal protein loading, membranes were stripped and reprobed with antibodies against -actin.

 Histology

Representative aortic segments (4 mm in length) were formalin fixed, embedded in paraffin, and 3-µm cross sections were prepared. Image acquisition, processing and analysis were performed as described previously [24]. Computerized morphometry was performed to determine medial thickness and inner vessel circumference from the Movat-stained slides. Medial thickness was measured between the internal elastic lamina and the edge of the compact collagenous outer layer of the vessel. The thickness of each vessel was averaged from at least 15 images captured from the same vessel on the same slide. Lumen diameter in vivo was calculated assuming circular geometry: diameter = inner vessel circumference/.

 Statistics

Data were reported as means ± SEM from at least 3 independent experiments. Statistical analysis and construction of concentration-response curves were performed using GraphPad Prism software (San Diego, Calif., USA). Differences between control and Marfan groups were studied by 2-tailed Student's t test. Differences between stress-strain curves were analyzed by 2-way ANOVA. Statistical significance was defined as p < 0.05.

 Results

 Disorganization and Degradation of Elastic Fiber in the Marfan Abdominal Aortic Media

On Movat-stained histological slides, elastic fibers are laid down in concentric layers, interspersed with collagen and circumferentially arranged smooth muscle cells (fig. 1a-d). Marfan abdominal aorta demonstrated breakage and disarray of elastic fibers at 3 months, and these changes became more pronounced with age. At 9 and 12 months, the elastin content in the Marfan aorta was about 80% of the control (fig. 1e). Occasionally, broken elastic fibers were also visible in aged control aorta, but elastin content remained constant (about 50% of the total medial area) during aging (fig. 1e).

Fig. 1. Representative Movat-stained histological slides showing the elastic fiber organization in the control and Marfan abdominal aorta (a-d). The bar graph presents the percent area of aortic media covered by elastic fiber in 2 strains at different ages (e). n = 5-10. * p < 0.05 vs. control.

 Increase in Abdominal Aortic Stiffness in Marfan Syndrome

Disorganization of elastin fibers would alter structural integrity and stiffness in large vessels. We therefore investigated whether the aortic stiffness would be modified in abdominal aorta in Marfan syndrome. In the measurement of stiffness, stress increases exponentially as a function of the vessel diameter, eliciting a J-shaped curve. At 6 months, the fitted curves for the stress-strain relationship from control and Marfan aorta were not significantly different (fig. 2a). At 9 and 12 months, the slope of stress-strain curves from Marfan abdominal aorta was markedly increased, indicating increased vessel stiffness (fig. 2b, c).

Fig. 2. Stress-strain relationship for abdominal aorta from control and Marfan mice at 6 (a), 9 (b) and 12 (c) months of age. n = 8-12. * p < 0.05 vs. control.

The gradual increase in vessel stiffness during aging was observed only in the Marfan abdominal aorta, but not in the control (fig. 3).

Fig. 3. Stress-strain relationship exponential curves showing the gradual changes of vessel stiffness with aging in the Marfan abdominal aorta. n = 3-8.

Unexpectedly, the breaking stress of the Marfan abdominal aorta at 6 months of age was 30% higher than the control (control = 47.2 mN/mm²; Marfan = 61.4 mN/mm²). These effects were not seen in other age groups.

 Preserved Contractile Capacity in Marfan Abdominal Aorta

Contractile properties of blood vessel could be related to the susceptibility of aneurysm formation [14]. The contractions induced by membrane depolarization (80 mM KCl) in the abdominal aorta from Marfan and control were similar (fig. 4a). There was also no difference in the pEC₅₀ and E_max values of phenylephrine-induced contraction between the 2 groups, regardless of age (fig. 4b; table 1).

Table 1. Diameter and medial thickness of aortas from control and Marfan mice

Fig. 4. Maximal force generated in the abdominal aorta in response to 80 mM KCl (a) and EC95 of phenylephrine (b) during the isometric force measurement. n = 10-12.

 Decreased Synthesis of TXA₂ in Marfan Abdominal Aorta

We have previously shown that endothelial-dependent relaxation and nitric oxide-mediated downstream signaling were impaired only in the thoracic aorta of Marfan syndrome [19, 20], which also displayed a decreased synthesis of COX-derived TXA₂ [20]. To investigate the involvement of COX in vasomotor function, we preincubated the abdominal aorta with indomethacin (10 µM) before contraction. Indomethacin diminished the phenylephrine-induced contraction in the control abdominal aorta by about 50% at 3 and 6 months, and significantly decreased the phenylephrine-induced sensitivity (pEC₅₀) at 6 and 9 months (table 1), indicating the production of basal COX-synthesized vasoconstrictors. In the Marfan strain, however, this observation was not obvious in most age groups (table 1).

Inhibiting the TXA₂/PGH₂ with SQ-29548 greatly suppressed the phenylephrine-induced contraction in the abdominal aorta of both strains at 3 and 9 months of age (table 1). However, the percent of inhibition by SQ-29548 pretreatment on contraction was greater in the control (3 months = 58%; 9 months = 67%) compared with the Marfan aorta (3 months = 47%; 9 months = 42%).

To investigate if Marfan aorta also has downregulated TXA₂/PGH₂-mediated signaling, we directly stimulated the TXA₂/PGH₂ contraction pathway by using TXA₂ analogue, U46619.

Marfan aorta, at both 3 and 9 months of age, displayed an increase in U46619-induced contraction compared with the age-matched control (fig. 5). This was not observed at 6 months.

Fig. 5. Bar graphs present the values of Emax and pEC50 of U46616-induced contraction in the control and Marfan abdominal aorta at different ages. U46616 was added in a cumulative concentration (10-11 to 10-8M). Concentration-response curves were constructed as described in Materials and Methods and Emax and pEC50 values were determined. n = 6-10. * p < 0.05 vs. control.

In Marfan aorta at 3 months of age, the release of TXA₂ during phenylephrine-induced vasoconstriction was only 50% of that in the controls (fig. 6). However, this difference was not observed from 6 months on (data not shown).

Fig. 6. Bar graph showing the release of TXB2 (a stable metabolite of TXA2) from the abdominal aorta (3 months of age) during phenylephrine (1 µM) stimulation with or without indomethacin (10 µM) preincubation. n = 3. * p < 0.05 vs. control.

The reduction in TXA₂ release in the Marfan aorta could not be attributed to the differential expression of COX-1 and COX-2 of 2 strains at any age groups (fig. 7) table 2.

Table 2. Summary of Emax and pEC50 values of phenylephrine-induced contraction in the abdominal aorta from control and Marfan mice at different ages

Fig. 7. Western immunoblotting showing the protein expression of COX-1 and COX-2 in the abdominal aorta from control and Marfan mice at different ages. Because of the limited aortic samples from each mouse, abdominal aorta was pooled from at least 10 mice from each group of animals at different ages. Expression of -actin served as loading control. Bar graphs showing the changing trend of the ratios of COX/-actin expression.

 Discussion

In the present study, we showed the disorganization and degradation of elastic fiber in the abdominal aorta during the progression of Marfan syndrome (fig. 1, 2). The gradual increase in aortic stiffness during aging was only observed in the Marfan group, but not in the controls (fig. 3). In Marfan syndrome, the abnormality in fibrillin-1 protein affects the formation and maturation of elastic fiber that normally provides reversible extensibility and recoil during systole and diastole [25]. After prolonged mechanical loading, the lack of structural integrity of elastic fiber would affect the stiffness of the large artery [6, 9] and lead to aortic aneurysm and dilatation [26]. Since thoracic aortic aneurysm is the most common and life-threatening complication, most basic science and clinical research on Marfan syndrome is mainly focused on the pathogenesis in the thoracic aorta. In this study, the concurrence of elastin fiber degradation and increased stiffness in Marfan abdominal aorta suggest a causal relationship between elastic fiber integrity and mechanical property. It has been well established that elastin degradation has a strong correlation with aneurysm formation [27,28,29], and it likely contributes to the reduced distensibility and compliance in abdominal aortic aneurysm [28]. However, the loss of elastic fiber integrity and increase in stiffness unexpectedly resulted in a significantly higher breaking stress in the abdominal aorta. The increase in breaking stress explained the low incidence of dissection and rupture of the abdominal aorta in Marfan syndrome. The underlying reasons could be due to the modifications in the integrity of collagen which gives rise to the vessel tensile strength. An increase in collagen content has been reported in Marfan aorta [30]. Indeed, it has been demonstrated that while elastase causes human vessels to dilate, collagenase causes their rupture [31].

During aging, the absolute elastin content did not change in the thoracic aorta and in the control abdominal aorta in our present study (fig. 1) [32,33,34]. However, increased stiffness in the thoracic and abdominal aorta with age has been suggested to be associated with the relative decrease in elastin/collagen ratio [32,33,34,35,36,37]. In human abdominal aorta, the stiffness of the aneurysmal aorta increases significantly faster with age than that of the control [38]. It is possible that while the more drastic change in the stiffness in Marfan abdominal aorta was observed, the more subtle increase in aged control aorta was not distinguished.

In the thoracic aorta in Marfan syndrome, vasoconstriction regardless of any means of stimulation was markedly impaired [19]. However, we did not observe any difference in the force generation in the abdominal aorta of 2 strains in the present study (fig. 4), implicating the differential influence of Marfan syndrome along the aorta. It has been suggested that responsiveness to vasoconstricting agonists is beneficial to prevent uncontrolled aortic dilatation. In abdominal aortic aneurysm, the inhibition of active and tonic contraction of vascular smooth muscle was believed to reduce the ability of the aortic wall to withstand the pulsatile hemodynamic force generated during systole, consequently resulting in progressive aortic dilatation and aneurysm [14]. Therefore, the preserved contracting capacity of the abdominal aorta in Marfan syndrome might indicate the low incidence of aneurysm.

Vasomotor function is tightly regulated by both contractile and relaxing mediators. We have demonstrated the impairment of nitric oxide-mediated endothelial-dependent relaxation and a reduced synthesis of COX-derived TXA₂ in the thoracic aorta [19, 20]. In this study, the blockade of the COX pathway with indomethacin did not affect contraction in the Marfan abdominal aorta (table 1). In the presence of TXA₂/PGH₂ receptor antagonist SQ-29548, the percent of inhibition of contraction in the Marfan abdominal aorta was lower compared with the controls. These results altogether showed that in the Marfan aorta, the TXA₂/PGH₂-mediated pathway was less essential in mediating vasoconstriction, which could be due to the impairment of TXA₂/PGH₂ downstream signaling. However, this was ruled out since the contractile responses evoked by the TXA₂/PGH₂ receptor agonist U46619 in the Marfan aorta were similar to those in the control at 6 months of age. At 3 and 9 months, such contraction responses were indeed much greater in the Marfan aorta, which may be a compensatory effect for the reduced constricting prostanoid production (fig. 5). In addition, the release of TXA₂ during phenylephrine-induced vasoconstriction was greatly decreased in the Marfan aorta. However, the reduction was only observed at 3 months of age and not later on (fig. 6). During aging (that is, 9 months), indomethacin reduced sensitivity to phenylephrine-induced contraction (pEC₅₀; table 1) in the control, but not in the Marfan strain, though little difference was observed in TXA₂ release between the 2 groups (fig. 6). This may be due to a decrease in production of constricting prostanoids other than TXA₂, such as constricting prostaglandins (that is, PGF₂) [39] in the Marfan abdominal aorta.

The reduction in TXA₂ release in the Marfan aorta was not owing to the differential protein expressions of COX-1 and COX-2 between the 2 groups (fig. 7). However, COX-2 expression is significantly elevated in patients with abdominal aortic aneurysm [40]. In COX-2-deficient mice, the incidence and severity of abdominal aortic aneurysm was greatly reduced [41]. The lack of difference in COX-2 expression in Marfan and control abdominal aorta may help to explain the lower incidence of aneurysm formation in the abdominal aorta.

In conclusion, we demonstrated that Marfan syndrome could affect the abdominal aorta particularly with respect to the elastic fiber structural integrity, vessel stiffness and TXA₂ release. We suggest that Marfan syndrome should be considered as a vascular disorder affecting the whole aorta. The low susceptibility of disease complication in the abdominal aorta could be due to the preserved contractile capacity and COX protein expression.

 Acknowledgements

This work was partly funded by the Canadian Marfan Association. A.W.Y.C. is the recipient of a Michael Smith Foundation for Health Research/St. Paul's Hospital Foundation Trainee Award.

  References

1.

Dietz HC, Cutting GR, Pyeritz RE, Maslen CL, Sakai LY, Corson GM, Puffenberger EG, Hamosh A, Nanthakumar EJ, Curristin SM, et al: Marfan syndrome caused by a recurrent de novo missense mutation in the fibrillin gene. Nature 1991;352:337-339.

2.

Judge DP, Dietz HC: Marfan syndrome. Lancet 2000;366:1965-1976.

3.

Vitarelli A, Conde Y, Cimino E, D'Angeli I, D'Orazio S, Stellato S, Padella V, Caranci F: Aortic wall mechanics in the Marfan syndrome assessed by transesophageal tissue Doppler echocardiography. Am J Cardiol 2006;97:571-577.

4.

Yin FC, Brin KP, Ting CT, Pyeritz RE: Arterial hemodynamic indexes in Marfan's syndrome. Circulation 1989;79:854-862.

5.

Wolfgarten B, Kruger I, Gawenda M: Rare manifestation of abdominal aortic aneurysm and popliteal aneurysm in a patient with Marfan's syndrome. Vasc Surg 2001;35:81-84.

6.

Hirata K, Triposkiadis F, Sparks E, Bowen J, Wooley CF, Boudoulas H: The Marfan syndrome: abnormal aortic elastic properties. J Am Coll Cardiol 1991;18:57-63.

7.

Scheck M, Siegel RC, Parker J, Chang YH, Fu JC: Aortic aneurysm in Marfan's syndrome: changes in the ultrastructure and composition of collagen. J Anat 1979;129:645-657.

8.

Sonesson B, Hansen F, Lanne T: Abnormal mechanical properties of the aorta in Marfan's syndrome. Eur J Vasc Surg 1994;8:595-601.

9.

Perejda AJ, Abraham PA, Carnes WH, Coulson WF: Marfan's syndrome: structural, biochemical, and mechanical studies of the aortic media. J Lab Clin Med 1985;106:376-383.

10.

Bunton TE, Biery NJ, Myers L, Gayraud B, Ramirez F, Dietz HC: Phenotypic alteration of vascular smooth muscle cells precedes elastolysis in a mouse model of Marfan syndrome. Circ Res 2001;88:37-43.

11.

Judge DP, Biery NJ, Keene DR, Geubtner J, Myers L, Huso DL, Sakai LY, Dietz HC: Evidence for a critical contribution of haploinsufficiency in the complex pathogenesis of Marfan syndrome. J Clin Invest 2004;114:172-181.

12.

Marque V, Kieffer P, Gayraud B, Lartaud-Idjouadiene I, Ramirez F, Atkinson J: Aortic wall mechanics and composition in a transgenic mouse model of Marfan syndrome. Arterioscler Thromb Vasc Biol 2001;21:1184-1189.

13.

Recchia D, Sharkey AM, Bosner MS, Kouchoukos NT, Wickline SA: Sensitive detection of abnormal aortic architecture in Marfan syndrome with high-frequency ultrasonic tissue characterization. Circulation 1995;91:1036-1043.

14.

Chew DKW, Conte MS, Khalil RA: Matrix metalloproteinase-specific inhibition of Ca²⁺ entry mechanisms of vascular contraction. J Vasc Surg 2004;40:1001-1100.

15.

Furchgott RF, Vanhoutte PM: Endothelium-derived relaxing and contracting factors. FASEB J 1989;3:2007-2018.

16.

Cohen RA, Adachi T: Nitric-oxide-induced vasodilatation: regulation by physiologic s-glutathiolation and pathologic oxidation of the sarcoplasmic endoplasmic reticulum calcium ATPase. Trends Cardiovasc Med 2006;16:109-114.

17.

DeWitt DL, Day JS, Sonnenburg WK, Smith, WL: Concentrations of prostaglandin endoperoxide synthase and prostaglandin I2 synthase in the endothelium and smooth muscle of bovine aorta. J Clin Invest 1983;72:1882-1888.

18.

Smith WL, DeWitt DL, Garavito RM: Cyclooxygenases: structural, cellular, and molecular biology. Annu Rev Biochem 2000;69:145-182.

19.

Chung AW, Au Yeung K, Cortes SF, Sandor GS, Judge DP, Dietz HC, van Breemen C: Endothelium dysfunction and compromised Akt/eNOS signaling in the thoracic aorta during the progression of Marfan syndrome. Br J Pharmacol 2007;150:1075-1083.

20.

Chung AW, Yang HHC, van Breemen C: Imbalanced synthesis of cyclooxygenase-derived thromboxane A₂ and prostacyclin compromises vasomotor function of the thoracic aorta in Marfan syndrome. Br J Pharmacol 2007;152:305-312.

21.

Habashi JP, Judge DP, Holm TM, Cohn RD, Loeys BL, Cooper TK, Myers L, Klein EC, Liu G, Calvi C, et al: Losartan, an AT1 antagonist, prevents aortic aneurysm in a mouse model of Marfan syndrome. Science 2006;312:117-121.

22.

Ng CM, Cheng A, Myers LA, Martinez-Murillo F, Jie C, Bedja D, Gabrielson KL, Hausladen JM, Mecham RP, Judge DP, Dietz HC: TGF--dependent pathogenesis of mitral valve prolapse in a mouse model of Marfan syndrome. J Clin Invest 2004;114:1586-1592.

23.

Neptune ER, Frischmeyer PA, Arking DE, Myers L, Bunton TE, Gayraud B, Ramirez F, Sakai LY, Dietz HC: Dysregulation of TGF- activation contributes to pathogenesis in Marfan syndrome. Nat Genet 2003;33:407-411.

24.

Chung AW, Rauniyar P, Luo H, Hsiang YN, van Breemen C, Okon EB: Pressure distention compared with pharmacologic relaxation in vein grafting upregulates matrix metalloproteinase-2 and -9. J Vasc Surg 2005;42:747-756.

25.

Wagenseil JE, Nerurkar NL, Knutsen RH, Okamoto RJ, Li DY, Mechan RP: Effects of elastin haploinsufficiency on the mechanical behavior of mouse arteries. Am J PhysiolHeart Circ Physiol 2005;289:H1209-H1217.

26.

Lillie MA, Gosline JM: Limits to the durability of arterial elastic tissue. Biomaterials 2007;28:2021-2031.

27.

Campa JS, Greenhalgh RM, Powell JT: Elastin degradation in abdominal aortic aneurysms. Atherosclerosis 1987;65:13-21.

28.

He CM, Roach MR: The composition and mechanical properties of abdominal aortic aneurysms. J Vasc Surg 1994;20:6-13.

29.

Sumner DS, Hokanson DE, Strandness DE: Stress-strain characteristics and collagen-elastin content of abdominal aortic aneurysms. Surg Gynecol Obstet 1970;130:459-466.

30.

Parsons JC, Hoffman Y, Potter KA, Besser TE: Normal elastin content of aorta in bovine Marfan syndrome. Exp Mol Pathol 1992;57:145-152.

31.

Dobrin PB, Baker WH, Gley WC: Elastolytic and collagenolytic studies of arteries. Implications for the mechanical properties of aneurysms. Arch Surg 1984;119:405-409.

32.

Michel JB, Heudes D, Michel O, Poitevin P, Philippe M, Scalbert E, Corman B, Levy BI: Effect of chronic ANG I-converting enzyme inhibition on aging processes. II. Large arteries. Am J Physiol 1994;267:R124-R135.

33.

Fitch RM, Rutledge JC, Wang YX, Powers AF, Tseng JL, Clary T, Rubanyi GM: Synergistic effect of angiotensin II and nitric oxide synthase inhibitor in increasing aortic stiffness in mice. Am J Physiol Heart Circ Physiol 2006;290:H1190-H1198.

34.

Safar ME, Levy BI, Struiiker-Boudier H: Current perspectives on arterial stiffness and pulse pressure in hypertension and cardiovascular diseases.Circulation 2003;107:2864-2869.

35.

Brüel A, Oxlund H: Changes in biomechanical properties, composition of collagen and elastin, and advanced glycation end products of the rat aorta in relation to age.Atherosclerosis 1996;127:155-165.

36.

Lanne T, Hansen F, Mangell P, Sonesson B: Differences in mechanical properties of the common carotid artery and abdominal aorta in healthy males. J Vasc Surg 1994;20:218-225.

37.

Ahlgren AR, Hansen F, Sonesson B, Lanne T: Stiffness and diameter of the common carotid artery and abdominal aorta in women. Ultrasound Med Biol 1997;23:983-988.

38.

Lanne T, Sonesson B, Bergqvist D, Bengtsson H, Gustafsson D: Diameter and compliance in the male human abdominal aorta: influence of age and aortic aneurysm. Eur J Vasc Surg 1992;6:178-184.

39.

Lamb VL, Schwartz AJ, Rohn WR, Kaiser L: Cyclooxygenase inhibitors depress norepinephrine constriction of rat abdominal, but not thoracic, aorta. Eur J Pharmacol 1994;256:221-226.

40.

Holmes DR, Wester W, Thompson RW, Reilly JM: Prostaglandin E2 synthesis and cyclooxygenase expression in abdominal aortic aneurysms. J Vasc Surg 1997;25:810-815.

41.

Gitlin JM, Trivedi DB, Langenbach R, Loftin CD: Genetic deficiency of cyclooxygenase-2 attenuates abdominal aortic aneurysm formation in mice. Cardiovasc Res 2007;73:227-236.

  Author Contacts

Dr. Ada W.Y. Chung
Department of Cardiovascular Science, University of British Columbia
Room 2099, 950 28th W Ave
Vancouver, BC V5Z 4H4 (Canada)
Tel. +1 604 875 3852, Fax +1 604 875 3120, E-Mail achung@mrl.ubc.ca

  Article Information

Received: July 12, 2007
Accepted after revision: October 19, 2007
Published online: January 22, 2008
Number of Print Pages : 9
Number of Figures : 7, Number of Tables : 2, Number of References : 41

  Publication Details

Journal of Vascular Research (Incorporating 'International Journal of Microcirculation')

Vol. 45, No. 4, Year 2008 (Cover Date: June 2008)

Journal Editor: Pohl, U. (Munich)
ISSN: 1018-1172 (Print), eISSN: 1423-0135 (Online)

For additional information: http://www.karger.com/JVR

  Drug Dosage / Copyright

Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.