HYPOXIA INDUCES LYSYL OXIDASE (LOX) EXPRESSION IN ENDOTELIAL CELLS

Introduction. Hypoxia actively participates in the pathogenesis of cardiovascular diseases through the coordinate regulation of several genes including those involved in extracellular matrix (ECM) synthesis/repair. Lysyl oxidase (LOX) is an enzyme involved in the maturation of ECM that seems to play a key role in the maintenance of endothelial homeostasis. Our aim was to determine if hypoxia could modulate endothelial LOX expression. Methods. LOX expression in bovine aortic endothelial cells (BAEC) and human umbilical cord vein endothelial cells (HUVEC) was assessed by real time PCR. LOX activity was evaluated by a fluorimetric method and LOX transcriptional activity by means of transient transfection studies. Results. Hypoxia (1% O-2) increased LOX expression in both BAEC and HUVEC in conditions in which HIF-1 alpha levels, VEGF expression and neovessel formation were induced. We observed that this effect was associated to a significant increase in LOX enzymatic activity. Similarly, stimulation of endothelial cells with dimethyl-oxal-glycine, an inhibitor of prolyl hydroxylases, augmented mRNA LOX levels. Transcription inhibition with 5,6-dichlorobenzimidazole prevented this effect, suggesting the involvement of a transcripcional mechanism. In agreement, transient transfection studies demonstrated that both hypoxia and HIF-1 alpha over-expression induced LOX transcripcional activity to a similar extent. Conclusions. Hypoxia induces LOX expression and activity in endothelial cells through an HIF-1-dependent transcriptional mechanism.