HYPOXIA-REOXYGENATION POTENTIATES ZYMOSAN ACTIVATED PLASMA-INDUCED ENDOTHELIAL INJURY

The pathophysiology of ischemia-reperfusion injury and the role played by the interaction of plasma proteins, including complement, with rep erfused endothelium remains incompletely understood. Venular endotheli al changes due to hypoxia followed by reoxygenation (H-R) are vital be cause venules are the primary site of fluid accumulation and polymorph onuclear leukocyte deposition due to inflammation. This investigation focused on whether H-R potentiates the response to permeability induci ng agents found in activated plasma. Activated complement was studied by using zymosan activated plasma (ZAP). Permeability changes were ass essed by quantitating rate of clearance of albumin across the monolaye rs. H-R alone did not change permeability relative to the normoxic con dition, ZAP at 2% in normoxic cells increased albumin clearance from 2 +/- 0.2 to 9 +/- 1.0 mu L/h, which increased significantly to 13.5 +/ - 2.0 mu L/h when given to hypoxia-reoxygenation challenged monolayers . The permeability response to ZAP was dose related and not present wi th heat inactivated ZAP. ZAP at 2% altered the structure of the cytosk eleton of the human umbilical vein endothelial cells (HUVEC). However, addition of monoclonal anti-complement antibodies or addition of solu ble complement receptor-1 did not attenuate ZAP-induced HUVEC permeabi lity. Addition of zymosan-activated serum did not alter the permeabili ty and addition of heparin inhibited the ZAP-induced changes in permea bility, suggesting that these changes were mediated via thrombin and n ot complement. The increase in monolayer permeability due to ZAP was p revented by increasing intracellular adenosine-3',5'-cyclic monophosph ate, These findings suggest that HUVEC monolayers challenged with H-R are more susceptible to increases in permeability induced by activated plasma components. (C) 1998 Academic Press.