Iron reduction was associated with lower cancer risk and mortality. Further studies are needed to define the role of body iron in cancer risk.

Background-Platelet-rich arterial thrombi are resistant to lysis by plasminogen activators. However, the mechanisms underlying thrombolysis resistance are poorly defined. Plasminogen activator inhibitor-1 (PAI-1), which is present in plasma, platelets, and vascular endothelium, may be an important determinant of the resistance of arterial thrombi to lysis. However, in vitro studies examining the regulation of platelet-rich clot lysis by PAI-1 have yielded inconsistent results. Methods and Results-We developed a murine arterial injury model and applied it to wild-type (PAI-1 ϩ/ϩ) and PAI-1-deficient (PAI-1 Ϫ/Ϫ) animals. FeCl 3 was used to induce carotid artery thrombosis. Thrombi consisted predominantly of dense platelet aggregates, consistent with the histology of thrombi in large-animal arterial injury models and human acute coronary syndromes. To examine the role of PAI-1 in regulating endogenous clearance of platelet-rich arterial thrombi, thrombi were induced in 22 PAI-1 ϩ/ϩ mice 14 PAI-1 Ϫ/Ϫ mice. Twenty-four hours later, the amount of residual thrombus was determined by histological analysis of multiple transverse sections of each artery. Residual thrombus was detected in 55 of 85 sections (64.7%) obtained from PAI-1 ϩ/ϩ mice compared with 19 of 56 sections (33.9%) from PAI-1 Ϫ/Ϫ mice (Pϭ.009). Computer-assisted planimetry analysis revealed that mean thrombus cross-sectional area was 0.033Ϯ0.027 mm 2 in PAI-1 ϩ/ϩ mice versus 0.016Ϯ0.015 mm 2 in PAI-1 Ϫ/Ϫ mice (Pϭ.048). Conclusions-PAI-1 is an important determinant of thrombolysis at sites of arterial injury. Application of this model to other genetically altered mice should prove useful for studying the molecular determinants of arterial thrombosis and thrombolysis.

CCUMULATION OF IRON IN EX-cess of physiologic requirements has been implicated in the risk of several chronic diseases through increased ironcatalyzed free radical-mediated oxidative stress. [1][2][3][4][5][6][7][8] Common diseases of aging that have been attributed to this mechanism include cardiovascular disease and cancer. 1,5,[8][9][10][11][12][13][14] Sullivan 15 formulated the ironheart hypothesis of atherosclerotic cardiovascular disease to explain the agerelated increase in risk of myocardial infarction (MI) in women following menopause. Serum ferritin levels average about 25 ng/mL in children and in women prior to menopause but increase in concert with increasing MI risk in women with cessation of menstrual blood loss. 15 Rates of MI increase earlier in men, in whom ferritin levels begin to increase from childhood levels in the late teens. 1,15 Increasing levels of body iron might be causative, a hypoth-For editorial comment see p 639.

Staged extra-anatomic bypass grafting (with axillofemoral bypass graft) and aortic graft removal for treatment of aortic graft infection are associated with acceptable early and long-term outcomes and should remain a primary approach in selected patients with this grave problem.

Monocyte adhesion to shear stress-activated endothelium stands as an important initial step during arteriogenesis (collateral artery growth). Using multiple approaches, we tested the hypothesis that monocyte adhesion via intercellular adhesion molecule-1 (ICAM-1) and selectin interactions is essential for adaptive arteriogenesis. Forty-eight New Zealand White rabbits received either solvent, monocyte chemoattractant protein-1 (MCP-1) alone, MCP-1 plus ICAM-mab, or MCP-1 plus an IgG2a isotype control via osmotic minipumps. After 7 days, collateral conductance was evaluated: solvent 4.01 (mL/min per 100 mm Hg), MCP-1 plus ICAM-mab 8.04 (versus solvent P=NS), and MCP-1 alone 33.11 (versus solvent P<0.05). Furthermore, the right femoral arteries of ICAM-1-/-, Mac-1-/- and mice having defective selectin interactions (FT4/7-/-) as well as their corresponding controls were ligated. One week later, perfusion ratios were determined by the use of fluorescent microspheres. FT4/7-/- mice did not show any significant difference in perfusion restoration whereas ICAM-1-/- and Mac-1-/- mice had a significant reduction in arteriogenesis as compared with matching controls (FT4/7-WT 37+/-9%, FT4/7-/- 32+/-3%, P=0.31; C57BL/6J 59+/-9%, ICAM-1-/- 36+/-8%, P<0.05; Mac-1-/- 42+/-3%, P<0.05). ICAM-1/Mac-1-mediated monocyte adhesion to the endothelium of collateral arteries is an essential step for arteriogenesis, whereas this process can proceed via selectin interaction independent mechanisms. Furthermore, in vivo treatment with monoclonal antibodies against ICAM-1 totally abolishes the stimulatory effect of MCP-1 on collateral artery growth, suggesting that the mechanism of the MCP-1-induced arteriogenesis proceeds via the localization of monocytes rather than the action of the MCP-1 molecule itself.

Background-Tumor necrosis factor-␣ (TNF-␣) and interleukin 1 (IL-1) are proximal inflammatory cytokines that stimulate expression of adhesion molecules and induce synthesis of other proinflammatory cytokines. In addition, TNF-␣ and IL-1 influence vascular smooth muscle cell migration and proliferation in vitro. In view of the inflammatory nature of neointimal hyperplasia (NIH), we tested the hypothesis that endogenous TNF-␣ and IL-1 modulate low shear stress-induced NIH. Methods and Results-Mice underwent unilateral common carotid artery (CCA) ligation. Low shear stress in the patent ligated CCA has previously been shown to result in remodeling and NIH. Reverse transcriptase-polymerase chain reaction for TNF-␣ and IL-1␣ mRNA demonstrated both TNF-␣ and IL-1␣ mRNA in ligated CCAs, whereas normal and sham-operated CCAs had none. Mice lacking functional TNF-␣ (TNFϪ/Ϫ) developed 14-fold less neointimal area than WT controls (PϽ0.05). p80 IL-1 type I receptor knockout (IL-1RIϪ/Ϫ) mice tended to develop less (7-fold, PϾ0.05) neointimal area than WT controls. Furthermore, no IL-1␣ mRNA expression was detected in CCAs from TNFϪ/Ϫ mice; however, TNF-␣ mRNA expression was found in the IL-1RIϪ/Ϫ mice. Mice that overexpress membrane-bound TNF-␣ but produce no soluble TNF-␣ display an accentuated fibroproliferative response to low shear stress (PϽ0.05). Conclusions-These results directly demonstrate that TNF-␣ and IL-1 modulate NIH induced by low shear stress. NIH can proceed by way of soluble TNF-␣-independent mechanisms. Specific anti-TNF-␣ and anti-IL-1 therapies may lessen

Background-Arteriogenesis serves as an efficient mechanism for flow restoration after arterial occlusion. This process is associated with inflammatory mediators such as tumor necrosis factor-␣ (TNF-␣), although their role in arteriogenesis remains unclear. We hypothesized that arteriogenesis is reduced in mice lacking functional TNF-␣ or p55 receptor. To test this hypothesis, we developed a novel microsphere-based murine model of hindlimb perfusion measurement. Methods and Results-Unilateral femoral arteries of nude (nϭ9), TNF-␣ Ϫ/Ϫ (nϭ9), TNF-␣ receptor p55 Ϫ/Ϫ (nϭ8), and p75 Ϫ/Ϫ (nϭ8) mice as well as their appropriate genetic background controls were occluded. The nude mice underwent laser Doppler hindlimb flux measurements preoperatively, postoperatively, and after 7 days. Seven days after ligation, all animals underwent tissue perfusion determinations using fluorescent microspheres. Laser Doppler findings confirmed acute decrease in flux with falsely normal values after 1 week. Microsphere results from control mice showed perfusion restoration to values Ϸ50% of normal within 7 days. Key Words: collateral circulation Ⅲ inflammation Ⅲ microspheres Ⅲ blood flow Ⅲ remodeling A rteriogenesis (remodeling of preexistent arteriolar collateral networks into large collateral conductance arteries) serves as the most efficient mechanism to restore flow after arterial occlusion. 1 Perivascular inflammation and monocyte/macrophage accumulation accompany this process. 2 Tumor necrosis factor-␣ (TNF-␣) is an important proximal mediator of inflammation. Most prototypical inflammatory TNF-␣ signaling occurs by TNF-␣ binding to its p55 receptor. 3 Previous studies have associated TNF-␣ with arteriogenesis. 2 We hypothesized that arteriogenesis proceeds by way of TNF-␣ signaling via the p55 receptor. Specifically, we hypothesized that arteriogenesis is reduced in mice lacking functional TNF-␣ or p55 receptor. We developed and validated a novel model of perfusion measurement in the mouse hindlimb to test this hypothesis. Methods Animal ModelThis study conforms to the Guide for the Care and Use of Laboratory Animals (NIH publication No. 85-23, revised 1996). Nine athymic nude, 8 TNF-␣ receptor p55Ϫ/Ϫ3,4 (N5 backcross onto C57BL/6J, maintained by brother/sister matings) and 9 TNF-␣ Ϫ/Ϫ5(on B6x129 F1 background, maintained by sister/brother matings) (both provided by Dr Carl K. Edwards III, Amgen, Inc, Thousand Oaks, Calif), 8 TNF-␣ receptor p75 Ϫ/Ϫ , 7 B6x129, and 9 C57BL/6J (Jackson Laboratory, Bar Harbor, Maine) mice underwent unilateral femoral artery ligation. The right femoral artery was ligated immediately distal to the inguinal ligament. Because collateral arteries develop from preexisting arteriolar connections spanning from the profunda femoris and circumflexa femoris to the genualis and saphena parva arteries, 4 the femoral artery was not excised to leave these vessels intact. In rabbits, this technique does not lead to ischemia in the region of collateral artery growth or distal to the site of ligation. 5 Wounds were cl...

Accelerated intimal hyperplasia in response to altered flow environment is critical to the process of vein bypass graft failure. Lack of a reproducible animal model for dissecting the mechanisms of vein graft (VG) remodeling has limited progress toward solving this clinically significant problem. Combining a cuffed anastomotic technique with other surgical manipulations, we developed a well-defined, more robust method for studying hemodynamic factors in VG arterialization. VG with fistula placement, complete occlusion, or partial distal branch ligation (DBL) was performed in the carotid artery of 56 rabbits. Extensive hemodynamic and physiological analyses were performed to define the hemodynamic forces and histological adaptations of the wall at 1-28 days. Anastomotic time averaged 12 min, with 100% patency of bilateral grafts and unilateral grafts plus no adjunct or delayed fistula. Bilateral VG-DBL resulted in an immediate disparity in wall shear (0.8 +/- 0.1 vs. 12.4 +/- 1.1 dyn/cm2, ligated vs. contralateral graft). Grafts exposed to low shear stress responded primarily through enhanced intimal thickening (231 +/- 35 vs. 36 +/- 18 microm, low vs. high shear). High-shear-stress grafts adapted through enhanced outward remodeling, with a 24% increase in lumen diameter at 28 days (3.0 +/- 0.1 vs. 3.7 +/- 0.2 mm, low vs. high shear). We have taken advantage of the cuffed anastomotic technique and combined it with a bilateral VG-DBL model to dissect the impact of hemodynamic forces on VG arterialization. This novel model offers a robust, clinically relevant, statistically powerful small animal model for evaluation of high- and low-shear-regulated VG remodeling.