Translocator
protein (TSPO), formerly known as the peripheral-type
benzodiazepine receptor, is an 18-kDa
drug- and
cholesterol-binding protein localized to the outer mitochondrial membrane and implicated in a variety of cell and mitochondrial functions. To determine the role of TSPO in
ischemia-reperfusion injury (IRI), we used both in vivo and in vitro porcine models: an in vivo renal
ischemia model where different conservation modalities were tested and an in vitro model where TSPO-transfected porcine proximal tubule LLC-PK(1) cells were exposed to
hypoxia and oxidative stress. The expression of TSPO and its partners in steroidogenic cells,
steroidogenic acute regulatory protein (StAR) and
cytochrome P-450 side chain cleavage
CYP11A1, as well as the impact of TSPO overexpression and exposure to TSPO
ligands in vitro in
hypoxia-
ischemia conditions were investigated.
Hypoxia induced
caspase activation, reduction of
ATP content, and LLC-PK(1) cell death. Transfection and overexpression of TSPO rescued the cells from the detrimental effects of
hypoxia and reoxygenation. Moreover, TSPO overexpression was accompanied by a reduction of H(2)O(2)-induced
necrosis. TSPO
drug ligands did not affect TSPO-mediated functions. In vivo, TSPO expression was modulated by IRI and during regeneration particularly in proximal tubule cells, which do not express this
protein at the basal level. Under the same conditions, StAR and
CYP11A1 protein and gene expression was reduced without apparent relation to TSPO changes.
Pregnenolone was identified and measured in the pig kidney.
Pregnenolone synthesis was not affected by the experimental conditions used. Taken together, these results indicate that changes in TSPO expression in kidney regenerating tissue could be important for renal protection and maintenance of kidney function.