Expression of sphingosine-1 phosphate receptor in rat renal ischemia-reperfusion injury

Sphingosine-1 phosphate receptor (S1PR) has come to the fore as a mediator of extracellular signaling through its interaction with G-protein-coupled receptors, which results in the induction of peripheral T-cell depletion. The mechanisms involved in renal ischemia-reperfusion (I/R) injury are complex, but appear to involve the early participation of bone marrow-derived cells, such as T lymphocytes. In this study, we investigated the expression of SIPR in a rat model of renal I/R injury. By means of a laparotomy, the right kidney was harvested and the left renal artery and vein were clamped. The kidney was reperfused after 90 min of ischemia, and rats were sacrificed at 0, 3, 6, 12 and 24 h after reperfusion. S1PR expression was analyzed by immunohistochemistry, and was observed only in endothelial cells of the normal kidneys. From 0 to 3 h after reperfusion, S1PR expression gradually became stronger in endothelial cells, reaching its peak intensity at 3 h after reperfusion. Twelve hours after reperfusion, necrosis had extended throughout the ischemic kidney, and nearly all the tubular epithelial cells had been destroyed. From 3 to 12 h after reperfusion, S1PR expression gradually weakened. At 24 h after reperfusion, levels of S1PR expression had almost reached those of the normal kidneys. In conclusion, S1PR was found to be expressed in a rat model of renal I/R injury. Several hours after achieving the maximum level of S1PR expression, the maximum level of renal I/R injury was observed. These results suggest a relationship between S1PR and renal I/R injury.