J LIU1, K TAYLOR1, A AU1, Z ENDRE1, J ERLICH1
1Renal Research Laboratory, Department of Nephrology, Prince of Wales Hospital and Prince of Wales Clinical School, Faculty of Medicine, UNSW Sydney, Randwick, Australia
Aim To investigate factors downstream of protease-activated receptor-1 (PAR-1) that may mediate ischaemia-reperfusion injury (IRI).
Background: IRI is a common cause of acute kidney injury (AKI) and occurs post-kidney transplantation. We have previously reported that post-IRI, PAR-1 deficiency reduces histological injury and loss of glomerular filtration rate (GFR). PAR-1 may regulate a number of inflammatory mediators via regulating the sphingosine 1-phosphate (S1P) pathway. S1P is actively exported from cells to act on external S1P receptors (S1Pr1-5) to have a diverse range of effects. We hypothesise that PAR-1 deficiency attenuates renal IRI in part by reducing the injurious S1Pr3 pathway.
Methods Renal IRI was induced by clamping of the renal pedicles for 25 minutes. Sham-operated mice underwent surgery without clamping of the renal pedicles. Mice were culled at 2, 5 and 24 hours post-reperfusion. Blood, urine and kidney tissue was taken for further analysis. Gene expression was performed by real-time PCR.
Results: We assessed S1Pr3, Spinster 2 (SPNS2) a major S1P membrane channel, and Hes1, a downstream product of S1Pr3 activation. Compared to WT, PAR-1 deficiency resulted in reduced SPNS2 expression in both mice undergoing IRI and sham surgery. PAR-1 deficient mice had reduced S1Pr3 levels compared to WT and S1Pr3 levels were not induced at 5 and 24 hours compared to sham operated mice. This supports a functional effect of reduced S1Pr3 and SPNS2 expression in PAR-1 mice as there was reduced Hes1.
Conclusion: Taken together the data supports a potential role of reduced S1Pr3 signalling contributing to protection of PAR-1 deficient mice following IRI. This may occur via both reduced export of S1P to the cell surface and reduced S1Pr3 expression and signalling.
Medical student, Renal Research Laboratory, Prince of Wales Hospital and Faculty of Medicine, UNSW