Sphingolipids in models of kidney disease and injury.

Acute kidney injury (AKI), resulting from cisplatin, remains an obstacle in the treatment of cancer. Cisplatin-induced AKI involves cell death pathways regulated by sphingolipids such as ceramide and glucosylceramide. Results indicate that cisplatin-treated mice had increased levels of ceramide and hexosylceramide. Pre-treatment of mice with inhibitors of ceramide synthesis prevented accumulation of ceramide and hexosylceramide in the renal cortex and attenuated cisplatin-induced AKI. To determine the role of ceramide metabolism to hexosylceramides in kidney injury, we treated mice with an inhibitor of glycosphingolipid synthesis. Inhibition of glycosphingolipid synthesis attenuated the accumulation of the hexosylceramide and exacerbated ceramide accumulation in the renal cortex of cisplatin-treated mice and exacerbated cisplatin-induced AKI. Under conditions of high ceramide generation, data suggest that metabolism of ceramides to glucosylceramides buffers kidney ceramides and attenuate kidney injury. Neutral ceramidase (nCDase) is an enzyme responsible for the breakdown of ceramide. Loss of nCDase is protective in models of injury. Thus, we hypothesized that loss of nCDase would protect mice from cisplatin-induced AKI. In this study, we utilized a nCDase knockout mouse in combination with a mouse model of cisplatin-induced AKI. Data indicate that loss of nCDase protects the kidney from cisplatin-induced AKI as evidenced by improved markers of kidney function, reduced markers of kidney injury, and improved kidney pathology. Data presented indicate that loss of nCDase protects the kidney from the nephrotoxic effects of cisplatin treatment, which suggests that inhibition of this enzyme has potential for development as a renoprotective agent against cisplatin-induced AKI. To study the role of glycosphingolipids in kidney disease, we generated mice containing a doxycyline inducible shRNA that targets expression of UGCG (Tet-O-shUgCg). UCGC is the gene that encodes for glucosylceramide synthase, the enzyme that catalyzes synthesis of glucosylceramide from ceramide. Tet-O-shUgCg mice were bred with CAG+/-rtTA3 mice (CAG-rtTA3/Tet-O-shUgCg) for universal expression of the shRNA. Following UGCG knockdown (KD) renal tertiary lymphoid organ (TLOs) development was observed. TLOs are ectopic accumulations of lymphoid cells that can arise in areas of chronic inflammation via lymphoid neogenesis. UGCG KD mice were also shown to have altered renal N-glycan signatures, suggesting interplay between glycosphingolipid and N-glycan metabolism

Inhibiting glucosylceramide synthase exacerbates cisplatin-induced acute kidney injury

Acute kidney injury (AKI), resulting from chemotherapeutic agents such as cisplatin, remains an obstacle in the treatment of cancer. Cisplatin-induced AKI involves apoptotic and necrotic cell death, pathways regulated by sphingolipids such as ceramide and glucosylceramide. Results from this study indicate that C57BL/6J mice treated with cisplatin had increased ceramide and hexosylceramide levels in the renal cortex 72 h following cisplatin treatment. Pretreatment of mice with inhibitors of acid sphingomyelinase and de novo ceramide synthesis (amitriptyline and myriocin, respectively) prevented accumulation of ceramides and hexosylceramide in the renal cortex and protected from cisplatin-induced AKI. To determine the role of ceramide metabolism to hexosylceramides in kidney injury, we treated mice with a potent and highly specific inhibitor of glucosylceramide synthase, the enzyme responsible for catalyzing the glycosylation of ceramides to form glucosylceramides. Inhibition of glucosylceramide synthase attenuated the accumulation of the hexosylceramides and exacerbated ceramide accumulation in the renal cortex following treatment of mice with cisplatin. Increasing ceramides and decreasing glucosylceramides in the renal cortex sensitized mice to cisplatin-induced AKI according to markers of kidney function, kidney injury, inflammation, cell stress, and apoptosis. Under conditions of high ceramide generation, data suggest that metabolism of ceramides to glucosylceramides buffers kidney ceramides and helps attenuate kidney injury.-Dupre, T. V., M. A. Doll, P. P. Shah, C. N. Sharp, D. Siow, J. Megyesi, J. Shayman, A.Bielawska, J. Bielawski, L. J. Beverly, M. Hernandez-Corbacho, C. J. Clarke, A. J. Snider, R. G. Schnellmann, L. M. Obeid, Y. A. Hannun, and L. J. Siskind. Inhibiting glucosylceramide synthase exacerbates cisplatin-induced acute kidney injury.National Institute of Diabetes and Digestive and Kidney Diseases [R01-DK093462]; National Institutes of Health [P30 CA138313, P20RR017677, UH2NS092981, 1R01HD076004-04, GM097741, PO1CA097132]; Veterans Affairs Merit Awards [1I01BX002021-04, CAMM-011-13S]12 month embargo; Published online: May 10, 2017,This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]