3-Ketosphinganine provokes the accumulation of dihydroshingolipids and induces autophagy in cancer cells

Abstract

Although several reports describe the metabolic fate of sphingoid bases and their analogs, as well as their action and that of their phosphates as regulators of sphingolipid metabolizing-enzymes, similar studies for 3-ketosphinganine (KSa), the product of the first committed step in de novo sphingolipid biosynthesis, have not been reported. In this article we show that 3-ketosphinganine (KSa) and its dideuterated analog at C4 (d2KSa) are metabolized to produce high levels of dihydrosphingolipids in HGC27, T98G and U87MG cancer cells. In contrast, either direct C1 O-phosphorylation or N-acylation of d2KSa to produce dideuterated ketodihydrosphingolipids does not occur. We also show that cells respond to d2KSa treatment with induction of autophagy. Time-course experiments agree with sphinganine, sphinganine 1-phosphate and dihydroceramides being the mediators of autophagy stimulated by d2KSa. Enzyme inhibition studies support that inhibition of Des1 by 3-ketobases is caused by their dihydroceramide metabolites. However, this effect contributes to increasing dihydrosphingolipid levels only at short incubation times, since cells respond to long time exposure to 3-ketobases with Des1 overexpression. The translation of these overall effects into cell fate is discussed.

Deciphering the Differential Effective and Toxic Responses of Bupleuri Radix following the Induction of Chronic Unpredictable Mild Stress and in Healthy Rats Based on Serum Metabolic Profiles

“…Sphingolipids are a major lipid class that constitute a significant proportion of brain membrane lipids, including ceramides, sphingomyelins, cerebrosides, gangliosides, and sphingosines (Abe and Norton, 1974 ; Müller et al, 2015 ; Dinoff et al, 2017 ). Ceramides (N-acylsphingosine), the central molecule in sphingolipid metabolism, are generated by hydrolysis of the major membrane sphingolipid, sphingomyelin, by acid or neutral sphingomyelinases (aSMase), by degradation of complex glycosphingolipids and by de novo synthesis from palmitoyl-CoA and serine (Jernigan et al, 2015 ; Ordóñez et al, 2016 ). They can be degraded by the catabolic route to sphingosine by ceramidases, and further phosphorylation to sphingosine 1-phosphate (S1P) (Ordóñez et al, 2016 ).…”

“…Ceramides (N-acylsphingosine), the central molecule in sphingolipid metabolism, are generated by hydrolysis of the major membrane sphingolipid, sphingomyelin, by acid or neutral sphingomyelinases (aSMase), by degradation of complex glycosphingolipids and by de novo synthesis from palmitoyl-CoA and serine (Jernigan et al, 2015 ; Ordóñez et al, 2016 ). They can be degraded by the catabolic route to sphingosine by ceramidases, and further phosphorylation to sphingosine 1-phosphate (S1P) (Ordóñez et al, 2016 ). Sphinganine, which can also be phosphorylated to sphinganine 1-phosphate, is an intermediate in the de novo synthesis from palmitoyl-CoA and serine, and is further transformed into ceramides (Ordóñez et al, 2016 ).…”

“…They can be degraded by the catabolic route to sphingosine by ceramidases, and further phosphorylation to sphingosine 1-phosphate (S1P) (Ordóñez et al, 2016 ). Sphinganine, which can also be phosphorylated to sphinganine 1-phosphate, is an intermediate in the de novo synthesis from palmitoyl-CoA and serine, and is further transformed into ceramides (Ordóñez et al, 2016 ). An elevated level of sphingolipids has been implicated in depression (Dinoff et al, 2017 ).…”

“…Moreover, many antidepressants inhibit acid sphingomyelinases, such as tricyclic antidepressants, fluoxetine and sertraline, further suggesting a role of aSMase and ceramides in depression and depression treatment (Kornhuber et al, 2008 , 2010 ). In addition, sphingolipids are major constituents of eukaryotic cell membranes (Ordóñez et al, 2016 ) and, in addition to a structural role, some sphingolipids are bioactive and control vital biological functions by regulating signal transduction pathways involved in several processes (i.e., apoptosis, adhesion, autophagy, cell proliferation, differentiation, migration, and senescence)(Ordóñez et al, 2016 ). Kolesnick has reported that aSMase is activated in response to tumor necrosis factor (TNF-α) and other cytokines (Kolesnick and Kronke, 1998 ).…”

Ceramide Metabolism Enzymes—Therapeutic Targets against Cancer

“…Furthermore, 3-ketosphinganine and its dideuterated analog at C4 (d2KSa) are metabolized to produce high levels of dihydrosphingolipids (dhSLs) in HGC27, T98G and U87MG cancer cells. d2KSa provokes the accumulation of dhCer and other dhSLs by inhibition of Des1 and induces autophagy in cancer cells [ 92 ]. Fenretinide, which is an agonist of SPT, also inhibits Des1 and, combined with Foscan-mediated photodynamic therapy, enhances apoptosis in SCC19 cells, a human head and neck squamous cell carcinoma [ 93 ].…”