• Biomolecules & Therapeutics
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• v.16 no.3
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• pp.243-248
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• 2008

In the present study, we investigated activity change of sphingomyelin anabolic enzymes such as sphingomyelin synthase and ceramide synthase. Sprague-Dawley male rats treated with 10 mg/kg of DMN intraperitoneally were used as a hepatic fibrosis model. Sphingomyelin synthase and ceramide synthase activities were measured in 1-week, 2-week, 3-week and 4-week DMN-treated rats along with respective control group rats. We found the increased sphingomyelin synthase activity in 4-week DMN-treated liver but not in kidney. Ceramide synthase activity was significantly increased in DMN-treated kidney after 2-week treatment and in DMN-treated liver after 3-week treatment. Although further investigation is necessary to elucidate meanings of sphingolipid metabolites during the liver fibrosis, activity change of sphingolipid anabolic enzymes may imply that sphingolipid metabolism and sphingolipid metabolites could be involved in liver fibrosis especially under oxidative stress.

• Toxicological Research
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• v.27 no.3
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• pp.185-190
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• 2011

Di-(2-ethylhexyl)-phthalate (DEHP), the most widely utilized industrial plastizer and a ubiquitous environmental contaminant, can act on peroxisome proliferators-activated nuclear hormone receptor family (PPAR) isoforms. To understand the contribution of sphingolipid metabolism to DEHP-induced hepatotoxicity, effect of DEHP exposure on activities of sphingolipid metabolic enzymes in rat liver was investigated. DEHP (250, 500 or 750 mg/kg) was administered to the rats through oral gavage daily for 28 days. The activities of acidic and alkaline ceramidases were slightly increased in 250 mg/kg DEHP-administered rat livers and significantly elevated in 500 mg/kg DEHP-administered ones, although the level of 750 mg/kg DEHP-administered ones was not increased. Neutral ceramidase, acidic and neutral sphingomyelinases, sphingomyeline synthase and ceramide syhthase were not changed at all by DEHP exposure. Therefore, acidic and alkaline ceramidases might play important roles in DEHP-induced hepatotoxicity.

• Molecules and Cells
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• v.46 no.11
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• pp.688-699
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• 2023

We set up this study to understand the underlying mechanisms of reduced ceramides on immune cells in acute rejection (AR). The concentrations of ceramides and sphingomyelins were measured in the sera from hepatic transplant patients, skin graft mice and hepatocyte transplant mice by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Serum concentrations of C24 ceramide, C24:1 ceramide, C16:0 sphingomyelin, and C18:1 sphingomyelin were lower in liver transplantation (LT) recipients with than without AR. Comparisons with the results of LT patients with infection and cardiac transplant patients with cardiac allograft vasculopathy in humans and in mouse skin graft and hepatocyte transplant models suggested that the reduced C24 and C24:1 ceramides were specifically involved in AR. A ceramide synthase inhibitor, fumonisin B₁ exacerbated allogeneic immune responses in vitro and in vivo, and reduced tolerogenic dendritic cells (tDCs), while increased P3-like plasmacytoid DCs (pDCs) in the draining lymph nodes from allogeneic skin graft mice. The results of mixed lymphocyte reactions with ceranib-2, an inhibitor of ceramidase, and C24 ceramide also support that increasing ceramide concentrations could benefit transplant recipients with AR. The results suggest increasing ceramides as novel therapeutic target for AR, where reduced ceramides were associated with the changes in DC subsets, in particular tDCs.

• Biomolecules & Therapeutics
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• v.23 no.6
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• pp.525-530
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• 2015

Ceramide is the most abundant lipid in the epidermis and plays a critical role in maintaining epidermal barrier function. Overall ceramide content in keratinocyte increases in parallel with differentiation, which is initiated by supplementation of calcium and/or vitamin C. However, the role of metabolic enzymes responsible for ceramide generation in response to vitamin C is still unclear. Here, we investigated whether vitamin C alters epidermal ceramide content by regulating the expression and/or activity of its metabolic enzymes. When human keratinocytes were grown in 1.2 mM calcium with vitamin C ($50{\mu}g/ml$) for 11 days, bulk ceramide content significantly increased in conjunction with terminal differentiation of keratinocytes as compared to vehicle controls (1.2 mM calcium alone). Synthesis of the ceramide fractions was enhanced by increased de novo ceramide synthesis pathway via serine palmitoyltransferase and ceramide synthase activations. Moreover, sphingosine-1-phosphate (S1P) hydrolysis pathway by action of S1P phosphatase was also stimulated by vitamin C supplementation, contributing, in part, to enhanced ceramide production. However, activity of sphingomyelinase, a hydrolase enzyme that converts sphingomyelin to ceramide, remained unaltered. Taken together, we demonstrate that vitamin C stimulates ceramide production in keratinocytes by modulating ceramide metabolicrelated enzymes, and as a result, could improve overall epidermal barrier function.