Nonionic contrast agents produce thrombotic effect by inducing adhesion of leukocytes on human endothelium

Recent advances of oxidative stress in thromboangiitis obliterans: biomolecular mechanisms, biomarkers, sources and clinical applications

Oxidative stress (OS) has been identified as a key factor in the development of Thromboangiitis Obliterans (TAO). The detection of OS levels in clinical and scientific research practice is mainly based on the measurement of oxidative stress such as reactive oxygen species (ROS), reactive nitrogen species (RNS) and lipid peroxides. These markers are typically assessed through a combination of physical and chemical methods. Smoking is known to the state of OS in TAO, and OS levels are significantly increased in smokers due to inadequate antioxidant protection, which leads to the expression of apoptotic proteins and subsequent cell injury, thrombosis and limb ischemia. There, understanding the role of OS in the pathogenesis of TAO may provide insights into the etiology of TAO and a basis for its prevention and treatment.

Spinal vascular malformations: Angiographic evaluation and endovascular management

Spinal vascular malformations (SVM) are classified based on their location (intramedullary, perimedullary, radicular, extradural) and flow pattern (high-flow, low-flow, no arteriovenous shunt). High-flow SVMs are generally congenital lesions diagnosed in children and young patients without gender predominance. They present with hemodynamic disturbances, mass effect, or hemorrhages, but may also be discovered incidentally. Low-flow SVMs tend to be acquired lesions presenting in older men with progressive myelopathy caused by spinal venous hypertension. They are rarely associated with vascular syndromes but may accompany prothrombotic conditions. The sensitivity and specificity of conventional MRI are excellent for high-flow SVMs but poor for low-flow lesions, which are frequently diagnosed with extensive delays reducing the potential for favorable outcomes. The sensitivity of advanced MRI techniques remains unclear, notably for the detection of low-flow shunts without flow voids on conventional MRI. Catheter angiography remains the gold standard modality for the evaluation of the spinal vasculature and its disorders. SVMs can be treated by surgical or endovascular means. Initially plagued by high recurrence rates due to inadequate embolization material, endovascular techniques represent nowadays a valid alternative to surgery, thanks notably to the introduction of liquid embolic agents.

Heme oxygenase-1 counteracts contrast media-induced endothelial cell dysfunction

Endothelial cell (EC) dysfunction is involved in the pathogenesis of contrast-induced acute kidney injury, which is a major adverse event following coronary angiography. In this study, we evaluated the effect of contrast media (CM) on human EC proliferation, migration, and inflammation, and determined if heme oxygenase-1 (HO-1) influences the biological actions of CM. We found that three distinct CM, including high-osmolar (diatrizoate), low-osmolar (iopamidol), and iso-osmolar (iodixanol), stimulated the expression of HO-1 protein and mRNA. The induction of HO-1 was associated with an increase in NF-E2-related factor-2 (Nrf2) activity and reactive oxygen species (ROS). CM also stimulated HO-1 promoter activity and this was prevented by mutating the antioxidant responsive element or by overexpressing dominant-negative Nrf2. In addition, the CM-mediated induction of HO-1 and activation of Nrf2 was abolished by acetylcysteine. Finally, CM inhibited the proliferation and migration of ECs and stimulated the expression of intercellular adhesion molecule-1 and the adhesion of monocytes on ECs. Inhibition or silencing of HO-1 exacerbated the anti-proliferative and inflammatory actions of CM but had no effect on the anti-migratory effect. Thus, induction of HO-1 via the ROS-Nrf2 pathway counteracts the anti-proliferative and inflammatory actions of CM. Therapeutic approaches targeting HO-1 may provide a novel approach in preventing CM-induced endothelial and organ dysfunction.

The N-terminal domain of thrombomodulin sequesters high-mobility group-B1 protein, a novel antiinflammatory mechanism

Thrombomodulin (TM) is an endothelial anticoagulant cofactor that promotes thrombin-mediated formation of activated protein C (APC). We have found that the N-terminal lectin-like domain (D1) of TM has unique antiinflammatory properties. TM, via D1, binds high-mobility group-B1 DNA-binding protein (HMGB1), a factor closely associated with necrotic cell damage following its release from the nucleus, thereby preventing in vitro leukocyte activation, in vivo UV irradiation-induced cutaneous inflammation, and in vivo lipopolysaccharide-induced lethality. Our data also demonstrate antiinflammatory properties of a peptide spanning D1 of TM and suggest its therapeutic potential. These findings highlight a novel mechanism, i.e., sequestration of mediators, through which an endothelial cofactor, TM, suppresses inflammation quite distinctly from its anticoagulant cofactor activity, thereby preventing the interaction of these mediators with cell surface receptors on effector cells in the vasculature.

The N-terminal domain of thrombomodulin sequesters high-mobility group-B1 protein, a novel antiinflammatory mechanism

Thrombomodulin (TM) is an endothelial anticoagulant cofactor that promotes thrombin-mediated formation of activated protein C (APC). We have found that the N-terminal lectin-like domain (D1) of TM has unique antiinflammatory properties. TM, via D1, binds high-mobility group-B1 DNA-binding protein (HMGB1), a factor closely associated with necrotic cell damage following its release from the nucleus, thereby preventing in vitro leukocyte activation, in vivo UV irradiation-induced cutaneous inflammation, and in vivo lipopolysaccharide-induced lethality. Our data also demonstrate antiinflammatory properties of a peptide spanning D1 of TM and suggest its therapeutic potential. These findings highlight a novel mechanism, i.e., sequestration of mediators, through which an endothelial cofactor, TM, suppresses inflammation quite distinctly from its anticoagulant cofactor activity, thereby preventing the interaction of these mediators with cell surface receptors on effector cells in the vasculature.

Cytokine activation and intestinal mucosal and renal dysfunction are reduced in endovascular AAA repair compared to surgery

PURPOSE

To compare endovascular (EVR) to open repair (OR) of abdominal aortic aneurysm (AAA) for cytokine activation, changes in the intestinal mucosal barrier, and renal dysfunction.

METHODS

In a prospective nonrandomized study, 15 patients admitted to a university hospital for elective infrarenal AAA repair (8 OR and 7 EVR) were recruited. Intestinal permeability was assessed preoperatively (PO), at day 1 (D1), and at day 3 (D3) after surgery using the lactulose/mannitol differential excretion (LMR) test. Renal damage was assessed from measurements of the urinary albumin:creatinine ratio (ACR); cytokine activation was based on the urinary concentration of tumor necrosis factor receptor p55 (TNF-Rp55) at the same time points. Serum creatinine and urea concentrations were measured preoperatively and daily for 5 days postoperatively.

RESULTS

A significant increase in LMR was found in the OR group at D1 and D3 compared to PO (p<0.05). The LMR increase at D3 was significantly greater in the OR group (p<0.01). A significant difference was observed in the percentage rise in ACR on D1 in the OR group compared to the EVR group (p<0.005). The urinary TNF-Rp55 concentration was significantly elevated in the OR group at D1 (p<0.05) and D3 (p<0.05) compared to baseline; in the EVR group, it was elevated at D1 (p<0.05) compared to PO. The difference was also significant for this marker between the 2 groups at D1 (p<0.01). No significant change was observed in the serum creatinine or urea concentrations in either group perioperatively.

CONCLUSIONS

Endovascular AAA repair is associated with less cytokine production and less intestinal and renal dysfunction compared to the open approach.

The inflammatory response following treatment of abdominal aortic aneurysms: a comparison between open surgery and endovascular repair

OBJECTIVES

to compare the inflammatory response following endovascular and conventional AAA repair.

DESIGN

prospective study.

PATIENTS AND METHODS

ten patients were selected for open surgery (OPEN) and ten for endovascular (ENDO) AAA repair. Leukocytes, platelets, myeloperoxidase, lactoferrin, beta-thromboglobulin, C-reactive protein (CRP), interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-alpha) and complement activation products were measured before, during and after surgery.

RESULTS

in the OPEN group the median hospital stay was longer (6 vs. 12 days, p=0.001) and more patients required transfusion (p=0.02). IL-6 and CRP increased postoperatively, most in OPEN (p<0.01). Platelet counts decreased after the first angiography in ENDO (p<0.01) and before aortic cross-clamping in OPEN (p<0.05). The decrease was larger in OPEN (p=0.02). Leukocyte counts decreased after the first angiography in ENDO, and thereafter increased (p=0.001). An equivalent increase was observed in OPEN after declamping (p=0.001). Leukocyte and platelet degranulation products increased after the first angiography in ENDO and after declamping in OPEN. Changes in complement activation products were small. TNF-alpha did not change significantly.

CONCLUSION

endovascular AAA repair caused significant leukocyte and platelet activation. Based on the timing of activation this could be caused by radiographic contrast media.

In vivo effects of contrast media on coronary thrombolysis

OBJECTIVES

The aim of the present study was to evaluate the influence of radiographic contrast media (CM) on alteplase-induced coronary thrombolysis.

BACKGROUND

Contrast media inhibit fibrinolysis in vitro and interact with endothelial cells, platelets and the coagulation system. The in vivo effects of CM on thrombolysis are not known.

METHODS

Occlusive coronary artery thrombosis was induced in 4 groups of 10 dogs by the copper coil technique. After 70 min of occlusion the dogs were randomized to intracoronary injection of 2 ml kg(-1) of either saline, a low-osmolar ionic CM (ioxaglate), a low-osmolar nonionic CM (iohexol) or a high-osmolar ionic CM (amidotrizoate). Thrombolysis with alteplase and co-therapy with aspirin and heparin was initiated after 90 min of occlusion. The coronary artery flow was monitored with an electromagnetic flowmeter throughout the experiment.

RESULTS

Iohexol and amidotrizoate, but not ioxaglate, were associated with longer reperfusion delays (time to optimal reperfusion: 67+/-48 min and 65+/-49 min, respectively, vs. 21+/-11 min after placebo; p < 0.05) and shorter periods of coronary perfusion (optimal perfusion time: 21+/-26 min and 21+/-28 min, respectively, vs. 58+/-40 min after placebo; p < 0.05). No significant differences were observed between groups with regard to activated partial thromboplastin times, circulating thrombin-antithrombin III complex concentrations and fibrinogen.

CONCLUSIONS

In this animal model administration of iohexol and amidotrizoate before thrombolysis significantly delayed reperfusion. This interaction should be considered in the design of clinical trials of thrombolytic therapy that evaluate coronary artery patency and in patients receiving local infusions of fibrinolytic agents.

Effect of iodinated contrast media on neutrophil adhesion to cultured endothelial cells

PURPOSE

To investigate the influence of contrast media (CM) on endothelial cells (ECs) with respect to cytotoxicity and to neutrophil adhesion.

MATERIALS AND METHODS

Human umbilical vein ECs were incubated with chromium-51-labeled human neutrophils in the presence of CM (diatrizoate, ioxaglate, iopamidol, and iodixanol) in three concentrations: 2, 20, and 50 mg I/mL. CM was compared with glucose solutions prepared from plain, buffered glucose solutions, iso-osmolar to the corresponding CM solution. Neutrophil adhesion to the EC monolayer, EC morphology, and cytotoxicity were evaluated.

RESULTS

The effect of CM on neutrophil adhesion was dependent on dose, with increased adhesion at low CM concentrations (2 and 20 mg I/mL) and decreased adhesion at high CM concentration (50 mg I/mL). The response was observed only if ECs and neutrophils were exposed to CM simultaneously in a shared environment. Glucose solutions with the same osmolarity did not show similar effect. Both diatrizoate and ioxaglate had a greater cytotoxic effect on ECs and neutrophils than did iodixanol and iopamidol.

CONCLUSION

The altered neutrophil adhesion to ECs may be due to CM-induced cytotoxicity or CM-induced EC activation because the glucose solutions did not cause a similar change at equal osmolality. The lack of cell death, combined with altered neutrophil adhesion implies modulation of cell adhesion molecules by CM. The results could be pertinent to the pathogenesis of peripheral vascular lesions and the endothelial response in immunosuppressed or septic patients receiving CM during imaging studies.

The differential effect of contrast agents on endothelial cell and smooth muscle cell growth in vitro

PURPOSE

This study was designed to evaluate the effects of ionic and nonionic contrast agents on endothelial cell (EC) and smooth muscle cell (SMC) proliferation, and to determine the role of osmolality as the etiology of these effects.

METHODS

Cultured bovine aorta EC and SMC were exposed to ionic (iothalamate meglumine) or nonionic (ioversol or iopamidol) contrast, or varying osmolar solutions of mannitol, for periods of 1, 3, 5, 10, or 20 minutes. Cells were then incubated in growth media at 37 degrees C and proliferation and structure were assessed 1, 3, 5, and 7 days later.

RESULTS

Both EC and SMC showed decreased proliferation after brief exposure to both ionic and nonionic contrast. Proliferation was markedly decreased at 24 hours after exposure, and began to recover by day 3 after exposure. EC showed a significant decrease up to 7 days after exposure to ionic contrast (p < 0.03), whereas SMC showed a significant decrease up to 7 days after exposure to nonionic contrast (p < 0.001). The decrease in proliferation was directly dependent on the length of exposure to the contrast and the concentration of the contrast. EC proliferation decreased in proportion to increasing osmolality of the test solution (p < 0.05). SMC proliferation did not show a decrease proportional to osmolality. No change was observed in cell viability as assessed by LDH activity studies. After contrast exposure, bare areas with no cells present were noted in the previously confluent EC and SMC culture wells. Cell structure was altered immediately after exposure to contrast, with normal structure recovered by 24 hours after exposure.

CONCLUSION

This study demonstrates that brief exposure to contrast agents injures EC and SMC, altering their structure and decreasing proliferation for up to 7 days in vitro. This response is both dose and time dependent. EC are more severely affected by ionic contrast, and SMC are more severely affected by nonionic contrast. EC injury appears to be mediated by the osmolar effect of the contrast, but the effects of contrast on SMC seem to be due to a different mechanism.

Modulation of ADPase and t-PA release by radiographic contrast media in bovine aortic endothelium

Vascular endothelial injuries induced by intravascular administration of radiographic contrast agents may be clinically relevant to the development of thrombosis and platelet activation. In this connection, we investigated the in vitro effects induced by iodamide, iopamidol, and ioxaglate on vascular endothelial ADPase activity and tissue plasminogen activator (t-PA) release in bovine aortic endothelium, in order to extend knowledge required to evaluate endothelial compatibility of radiographic contrast media. Undiluted and Tris-diluted contrast agent formulations were employed, and mannitol and sucrose hyperosmolar solutions were used as comparison. Results demonstrated that the high-osmolar ionic contrast agent iodamide, and to a lesser extent, the low-osmolar nonionic agent iopamidol, stimulated endothelial ADPase activity of the aortic endothelium; the low-osmolar ionic agent ioxaglate left endothelial ADPase activity unchanged. Furthermore, the diluted formulations of iodamide and iopamidol, as well as high-osmolar mannitol and sucrose solutions, were devoid of activity in ADPase. This suggests that the endothelial ADPase stimulation induced by both radiographic contrast media was a hyperosmolar-independent pharmacodynamic activity. Iopamidol and ioxaglate reduced endogenous t-PA release from bovine aortic endothelium only in undiluted formulation, while iodamide showed this inhibiting action in both diluted and undiluted formulations. No effect was observed when using mannitol solutions at different osmolarity values. Our in vitro findings agree with published data on the different thrombotic tendency attributed to the contrast agents used, suggesting endothelial enzymatic activities (ADPase and t-PA release) as suitable tools for evaluating endothelial vessel wall compatibility with radiographic contrast media.

Effect of iodixanol on in vitro bleeding time

RATIONALE AND OBJECTIVES

Both monomeric and dimeric ionic radio contrast media (CM) have been shown to be more anticoagulant than nonionic monomeric CM. Iodixanol is a relatively new nonionic dimeric contrast medium. We investigated whether the dimeric structure of iodixanol would produce the same level of anticoagulation that has been observed using nonionic monomeric CM.

METHODS

We used a global screening device that operates under physiologic flow conditions to monitor the effects of iodixanol on in vitro bleeding time (IVBT). This flow dynamic technique perfuses nonanticoagulated whole blood through a hollow fiber device. A leak in the fiber is created by a precision needle, and the resulting pressure fluctuations within the fiber are monitored to examine the ability of the hemostatic system to close the leak by forming a stable platelet plug.

RESULTS

In 20 donors, iodixanol (25% CM/blood, v/v) was shown to lengthen the mean IVBT (18.74 min) compared with the normal blood mean IVBT (4.24 min).

CONCLUSION

The addition of dimeric iodixanol to normal blood affects the IVBT in the same manner as nonionic monomeric CM (ioversol, iopamidol, and iohexol).