SPHK1 and hemolytic-uremic syndrome: Therefore, decreased levels of long-chain and very-long-chain ceramide species in the kidneys of the SphK2−/− mice with experimental HUS compared to the WT and SphK1−/− mice with experimental HUS might have protected them from the induction of severe damage of proximal tubule epithelial cells, whereas in the SphK1−/− mice with experimental HUS, increased long-chain ceramide levels might have contributed to enhanced proximal tubule epithelial damage.