Neointimal hyperplasia following argon ion laser carotid endarterectomy: with and without endothelial cell seeding

Arsenite induces endothelial cytotoxicity by down-regulation of vascular endothelial nitric oxide synthase

Epidemiological studies have demonstrated a high association of inorganic arsenic exposure with vascular diseases. Recent research has also linked this vascular damage to impairment of endothelial nitric oxide synthase (eNOS) function by arsenic exposure. However, the role of eNOS in regulating the arsenite-induced vascular dysfunction still remains to be clarified. In our present study, we investigated the effect of arsenite on Akt1 and eNOS and its involvement in cytotoxicity of vascular endothelial cells. Our study demonstrated that arsenite decreased the protein levels of both Akt1 and eNOS accompanied with increased levels of ubiquitination of total cell lysates. We found that inhibition of the ubiquitin-proteasome pathway by MG-132 could partially protect Akt1 and eNOS from degradation by arsenite together with a proportional protection from the arsenite-induced cytoxicity. Moreover, up-regulation of eNOS protein expression significantly attenuated the arsenite-induced cytotoxicity and eNOS activity could be significantly inhibited after incubation with arsenite for 24 h in a cell-free system. Our study indicated that endothelial eNOS activity could be attenuated by arsenite via the ubiquitin-proteasome-mediated degradation of Akt1/eNOS as well as via direct inhibition of eNOS activity. Our study also demonstrated that eNOS actually played a protective role in arsenite-induced cytoxicity. These observations supported the hypothesis that the impairment of eNOS function by arsenite is one of the mechanisms leading to vascular changes and diseases.

Monocyte adhesion to balloon-injured arteries: the influence of endothelial cell seeding

OBJECTIVE

Deendothelialization of injuries of the artery disrupts normal vascular homeostasis, affecting both the structural integrity of the blood vessel wall, as well as the interaction of the arterial surface with blood components such as platelets, leukocytes, and circulating proteins. Leukocyte and, in particular, monocyte recruitment to damaged vessels has been implicated in the pathogenesis of intimal hyperplasia. We hypothesize that reendothelialization is an important modulator of monocyte adhesion to healing arterial surfaces.

METHODS

New Zealand white rabbits (n = 20) were subjected to bilateral iliofemoral artery balloon injury. Cultured, autologous venous endothelial cells (ECs) were immediately seeded onto one vessel, whereas the contralateral artery received medium alone, to accelerate endothelial relining. Vessels were harvested (5-9 days after injury) for analysis of permeability (Evans Blue dye exclusion), endothelial coverage (anti-CD31 immunohistochemistry), monocyte adhesion (ex vivo binding of 51Na2CrO4-labeled monocytic THP-1 cells), and monocyte recruitment (RAM-11 immunohistochemistry).

RESULTS

Improved EC coverage was evidenced by positive staining for CD31 in the seeded vessels. Vessel wall permeability was markedly reduced in EC-seeded arteries (29% +/- 10% vs 99% +/- 0% surface Evans blue staining, P <.005), consistent with restoration of a functional endothelial barrier. EC seeding significantly reduced ex vivo THP-1 binding to vessels explanted at a mean of 8 days after injury (45,170 +/- 8939 vs 85,994 +/- 16,500 cells/cm2, P <.05). However, RAM-11 staining revealed no significant difference in overall macrophage accumulation between seeded and control vessels 1 week after injury (111 +/- 22 vs 95 +/- 14 cells/section, P =.36).

CONCLUSIONS

Immediate seeding of a balloon-injured rabbit artery with cultured ECs results in accelerated restoration of the endothelial lining. At 1 week, barrier function is improved, and the seeded vessel surface is less adhesive to activated monocytes ex vivo, as compared with injured controls. Nonetheless, EC-seeded and nonseeded arteries demonstrate similar total macrophage accumulation over 1 week. These data suggest that after mechanical arterial injury, endothelial coverage may be one important variable influencing leukocyte adhesion.