title: SGK-1 protects kidney cells against apoptosis induced by ceramide and TNF-α.
abstract: Ceramide regulates several different cellular responses including mechanisms leading to apoptosis. Serum- and glucocorticoid-inducible protein kinase (SGK)-1 is a serine threonine kinase, which activates survival pathways in response to stress stimuli. Recently, we demonstrated an anti-apoptotic role of SGK-1 in human umbilical endothelial cells treated with high glucose. In the present study, since ceramide induces apoptosis by multiple mechanisms in diabetes and its complication such as nephropathy, we aimed to investigate whether SGK-1 may protect even against apoptosis induced by ceramide in kidney cells. Human embryonic kidney (HEK)-293 cells stable transfected with SGK-1 wild type (SGK-1wt) and its dominant negative gene (SGK-1dn) have been used in this study. Apoptotic stimuli were induced by C2-ceramide and TNF-α to increase endogenous synthesis of ceramide. Upon activation with these stimuli, SGK-1wt transfected cells have a statistically significant reduction of apoptosis compared with SGK-1dn cells (P<0.001). This protection was dependent on activation of caspase-3 and Poly-ADP-ribose-polymerase-1 (PARP-1) cleavage. SGK-1 and AKT-1 two highly homologous kinases differently reacted to ceramide treatment, since SGK-1 increases in response to apoptotic stimulus while AKT-1 decreases. This enhancement of SGK-1 was dependent on p38-mitogen-activated-protein kinases (p38MAPK), cyclic-adenosine-monophosphate/protein kinase A (cAMP/PKA) and phosphoinositide-3-kinase (PI3K) pathways. Especially, by using selective LY294002 inhibitor, we demonstrated that the most involved pathway in the SGK-1 mediated process of protection was PI3K. Treatment with inhibitor of SGK-1 (GSK650394) significantly enhanced TNF-α-dependent apoptosis in HEK-293 cells overexpressing SGK-1wt. Caspase-3, -8 and -9 selective inhibitors confirmed that SGK-1 reduced the activation of caspase-dependent apoptosis, probably by both intrinsic and extrinsic pathways. In conclusion, we demonstrated that in kidney cells, overexpression of SGK-1 is protective against ceramide-induced apoptosis and the role of SGK-1 can be potentially explored as a therapeutic target in conditions like diabetes, where ceramide levels are increased.
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Pastore
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.|IRCCS San Raffaele Pisana, Rome, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Della-Morte
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Coppola
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Capuani
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: M F
authors.initials: MF
authors.lastname: Lombardo
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Pacifici
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Ferrelli
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Arriga
authors.affiliation: Laboratory of Cardiovascular Endocrinology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), San Raffaele Pisana, Rome, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Mammi
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.|Department of Medicine, University Hospital 'Fondazione Policlinico di Tor Vergata', Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Federici
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.|Department of Medicine, University Hospital 'Fondazione Policlinico di Tor Vergata', Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Bellia
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.|Department of Medicine, University Hospital 'Fondazione Policlinico di Tor Vergata', Rome, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Di Daniele
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.|Department of Medicine, University Hospital 'Fondazione Policlinico di Tor Vergata', Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Tesauro
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Donadel
authors.affiliation: Department of Internal Medicine and Biomedical Specialist (DIBIMIS), University of Palermo, Palermo, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Noto
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.|Department of Medicine, University Hospital 'Fondazione Policlinico di Tor Vergata', Rome, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Sbraccia
authors.affiliation: Department of Biomedicine, Institute of Translational Pharmacology, National Research Council, Rome, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Sconocchia
authors.affiliation: Laboratory of Molecular Medicine, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.|Department of Medicine, University Hospital 'Fondazione Policlinico di Tor Vergata', Rome, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Lauro
mesh_terms: D017209:Apoptosis; D002518:Ceramides; D057809:HEK293 Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D002518:Ceramides; D017874:Immediate-Early Proteins; D017346:Protein Serine-Threonine Kinases; D014409:Tumor Necrosis Factor-alpha; D000099184:Serum-Glucocorticoid Regulated Kinases