Endothelial nuclear factor-κB translocation and vascular cell adhesion molecule-1 induction by complement inhibition with anti-human C5 therapy or cGMP analogues

We have previously shown that reoxygenation of hypoxic human umbilical vein endothelial cells (HUVECs) leads to the activation and deposition of complement. In the present study, we investigated whether the terminal complement complex (C5b-9) influences HUVEC nuclear factor-kappa B (NF-kappa B) translocation and vascular cell adhesion molecule-1 (VCAM-1) protein expression after hypoxia/reoxygenation by decreasing endothelial cGMP. Additionally, we investigated the action of anti-human C5 therapy on endothelial cGMP, NF-kappa B translocation, and VCAM-1 protein expression. Reoxygenation (0.5 to 3 hours, 21% O-2) of hypoxic (12 hours, 1% O-2) HUVECs in human serum (HS) significantly increased C5b-9 deposition, VCAM-1 expression, and NF-kappa B translocation compared with hypoxic/reoxygenated HUVECs treated with the recombinant human C5 inhibitor h5G1.1scFv. Acetylcholine (ACh)-induced cGMP synthesis was significantly higher in normoxic HUVECs compared with hypoxic HUVECs reoxygenated in HS but did not differ from hypoxic HUVECs reoxygenated in buffer or HS treated with h5G1.1-scFv. Treatment of hypoxic/reoxygenated HUVECs with h5G1.1-scFv or cGMP analogues significantly attenuated NF-kappa B translocation and VCAM-1 protein expression, Treatment with NO analogues, but not a cAMP analogue, cGMP antagonists, or an NO antagonist, also significantly attenuated VCAM-1 expression. We conclude that (1) C5b-9 deposition, NF-kappa B translocation, and VCAM-1 protein expression are increased in hypoxic HUVECs reoxygenated in HS; (2) reoxygenation of hypoxic HUVECs in HS, but not buffer alone, attenuates ACh-induced cGMP synthesis; and (3) treatment of hypoxic/reoxygenated HUVECs with h5G1.1-scFv attenuates C5b-9 deposition, NF-kappa B translocation, and VCAM-1 expression while preserving ACh-induced cGMP synthesis, C5b-9-induced VCAM-1 expression may thus involve an NO/cGMP-regulated NF-kappa B translocation mechanism.