A cellular model of endothelial cell ischemia

Abstract

Endothelial cell dysfunction in ischemia may cause increased capillary permeability. We examined the effect of failing ATP synthesis, a major consequence of ischemia, on microfilaments—important structural determinants of the endothelial cell. Glycolytic and mitochondrial ATP synthesis in bovine pulmonary artery endothelial cells was inhibited by glucose depletion and 650 picomole (pmole) oligomycin/μg DNA, respectively. ATP levels were monitored with the luciferase-luciferin assay over a 2-hr time course followed by recovery for 1 hr after removal of the oligomycin and addition of 5.5 m M glucose. ATP levels fell to 83.6 ± 63.8 pmole/μg DNA ( n = 11) by 30 min, 26.9 ± 13.8 pmole/μg DNA ( n = 11) by 60 min, and 17.2 ± 3.8 pmole/μg DNA ( n = 6) by 120 min, whereas control uninjured cells had 541.3 ± 196.8 pmole/μg DNA ( n = 6) at 120 min. Fluorescence microscopy of microfilaments stained with rhodamine-phalloidin revealed progressive disassembly and shortening of the microfilaments in >90% of cells over 60 min which correlated with the fall in ATP. Ultrastructural examination revealed that side to side aggregation of microfilaments had occurred over the 120-min time course. Two hours of glucose depletion (305.5 ± 130.8 pmole ATP/μg DNA, n = 6) or oligomycin alone (480.0 ± 90.1 pmole ATP/μg DNA, n = 6) failed to produce the dramatic fall in ATP or the microfilament changes. During cell recovery, there was a rapid reassembly of microfilaments, detected by fluorescence microscopy, which was nearly complete in 85–90% of cells by 45–60 min. ATP levels increased significantly ( P = 0.002) to 96.1 ± 36.8 pmole/μg DNA ( n = 6) by 30 min. This model should provide insight into the pathogenesis and treatment of the capillary leak seen with ischemia.