Direct cytotoxicity of hypoxia-reoxygenation towards sinusoidal endothelial cells in the rat

Aims/Background Sinusoidal endothelial cells are the primary target of isch emia-reperfusion injury following liver preservation. The present study was undertaken to examine the susceptibility of sinusoidal endothelial cells t o hypoxia-reoxygenation and the potential role of oxygen free radicals in t he induction of cell injury. Methods: Sinusoidal endothelial cells were iso lated from rat liver. After 2-3 days of primary culture, the cells were exp osed to hypoxia (N-2/CO2 95/5) for 120 min and reoxygenation (O-2/CO2 95/5) for 90 min. Control cells were exposed to hypoxia alone, to 95% O-2 alone or were maintained under normoxic conditions. Human umbilical vein endothel ial cells were used as a model of vascular endothelial cells and submitted to the same protocol. Cell viability and lipid peroxidation were assessed b y LDH leakage and malondialdehyde production, respectively. In order to tes t the potential role of xanthine oxidase and mitochondrial dysfunction in c ell injury, the cells were treated with allopurinol and potassium cyanide ( KCN) respectively. Results: The different gaseous treatments did not affect LDH leakage in human umbilical vein endothelial cells. In sinusoidal endot helial cells, the sequential hypoxia-reoxygenation caused a significant inc rease in LDH release, malondialdehyde production and xanthine oxidase activ ity while hypoxia alone had no effect except on xanthine oxidase activity. Allopurinol inhibited xanthine oxidase without preventing cell injury or li pid peroxidation in this latter cell type. Conclusions: The results suggest that sinusoidal endothelial cells, as opposed to vascular endothelial cell s, are susceptible to a direct cytotoxic effect of hypoxia-reoxygenation. T his effect occurs in combination with an increase in xanthine oxidase activ ity and lipid peroxidation, although cell injury is mediated at least in pa rt by mechanisms independent of xanthine oxidase such as mitochondrial dysf unction.