Submitted on July 18, 2008
Revised on March 30, 2009
Accepted on April 17, 2009
Expression and Modulation of Translocator Protein and its partners by Hypoxia Re-oygenation or Ischemia and Reperfusion in Porcine Renal Models
Frederic Favreau1, Ludivine Rossard2, Keqiang Zhang, Thibault Desurmont2, Emilie Manguy, Aude Belliard2, Stephane Fabre3, Jun Liu4, Zeqiu Han4, Raphael Thuillier2, Vassilios Papadopoulos5, and Thierry Hauet6*
1 CHU de Poitiers
2 Inserm U927
3 INRA
4 georgetown university
5 Georgetown university
6 CHU
* To whom correspondence should be addressed. E-mail: t.hauet{at}chu-poitiers.fr.
h2Translocator protein (TSPO), formerly known as 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 TSPO-transfected porcine proximal tubule LLC-PK1 cells exposed to hypoxia and oxidative stress. The expression of TSPO and its partners in steroidogenic cells, steroidogenic acute regulatory protein (StAR) and cytochrome P450 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-PK1 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 H2O2-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 basal level. Under the same conditions, StAR and CYP11A1 protein and gene expression were 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.
