Effect of tacrolimus on energy metabolism in human umbilical endothelial cells

Tacrolimus has a wide spectrum of adverse effects, including neurotoxic and vascular events. Vascular dysfunction due to interference of tacrolimus with mitochondrial function in endothelial cells may contribute to these adverse reactions. We evaluated the impact of clinically relevant tacrolimus concentrations after 48 hours on energy metabolism in cultured human umbilical vein endothelial cells (HUVEC): Global fatty acid oxidation (FAO), activities of respiratory chain complexes I-V (RC), citratesynthase (CS), glycolytic enzymes and energy rich phosphates were measured. RC-complexes II+III were significantly compromised at 100 nmol/L and CS at 10, 25 and 50 nmol/L, while global FAO was not significantly impaired. Cellular lactate-dehydrogenase (LDH)-, hexokinase- and phosphofructokinase-activities were not altered; AMP levels increased after 48 hours at 200 nmol/L while energy charges remained stable. No cellular toxicity, assessed by light microscopy and LDH leakage was observed even at highest tacrolimus concentrations. Tacrolimus partially impaired mitochondrial function in HUVEC at the level of RC-complexes II+III and CS. Part of tacrolimus toxicity and vascular dysfunction may arise from these metabolic alterations. To some extent, energy balance could be maintained by FAO and cytosolic energy production; energy consumption might be economized. Although only demonstrated for endothelial cells, it is conceivable that such effects will alter energy metabolism in different tissues with high oxidative demands.