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Induction of ER stress-mediated apoptosis by ceramide via disruption of ER Ca(2+) homeostasis in human adenoid cystic carcinoma cells.

Liu Z, Xia Y, Li B, Xu H, Wang C, Liu Y, Li Y, Li C, Gao N, Li L - Cell Biosci (2014)

Bottom Line: Up-regulation of the ER stress-associated apoptosis promoting transcription factor CHOP and p-JNK suggested that the antitumor activity of ceramide is owing to activation of apoptotic ER stress.The chemical chaperone TUDCA inhibited ceramide-induced ER stress and cell death.In addition, the downstream metabolite of ceramide, S1P, cannot activate ER stress.

View Article: PubMed Central - PubMed

Affiliation: Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China.

ABSTRACT

Background: Ceramides are a class of sphingolipids that form the structural component of the cell membrane and also act as second messengers in cell signaling pathways. Emerging results suggest that ceramide induces growth arrest and apoptosis in various human cancer cells. However, the mechanisms underlying its antitumor activity are yet to be identified. Endoplasmic reticulum stress (ER stress), a cellular adaptive response, is believed to initially compensate for damage but can eventually trigger cell death if the stimulus is severe or prolonged. In this study, we investigated whether ceramide induces cell death in human salivary adenoid cystic carcinoma (ACCs) through activation of the apoptotic ER stress.

Results: RT-PCR, real-time PCR and western blot demonstrated that exogenous ceramide treatment up-regulated GRP78 and p-eIF2α expression and XBP1 splicing. Moreover, the ceramide synthase inhibitor FB1 abolished ceramide-induced ER stress. Up-regulation of the ER stress-associated apoptosis promoting transcription factor CHOP and p-JNK suggested that the antitumor activity of ceramide is owing to activation of apoptotic ER stress. Mechanistically, [Ca(2+)]ER depletion and SERCA inhibition by ceramide treatment suggested that it induces ER stress by disrupting [Ca(2+)]ER homeostasis. The chemical chaperone TUDCA inhibited ceramide-induced ER stress and cell death. In addition, the downstream metabolite of ceramide, S1P, cannot activate ER stress.

Conclusions: These results demonstrated that exogenous ceramide induces cancer cell death through a mechanism involving severe ER stress triggered by the disruption of ER Ca(2+) homeostasis.

No MeSH data available.


Related in: MedlinePlus

Ceramide triggers ER stress is independent of its downstream metabolite S1P. (A) ACC-M and ACC-2 cells were seeded into 60 mm culture dishes and the next day cells were treated with 5–10 μM S1P. The level of phosphorylated eIF2α and ERK was analyzed. Unphosphorylated eIF2α and ERK were measured and actin were used as loading control. The experiment was repeated several times and the representative result is shown. (B) Proposed mechanism of ceramide-mediated activation of ER stress response in ACCs. Ceramide induces SERCA inhibition and ER calcium depletion. This leads to increase GRP78 and activate PERK/eIF2α and IRE1α/XBP1 arm of ER stress. FB1 inhibits ceramide-induced ER stress. Prolonged ER stress eventually induces apoptosis through activates pro-apoptotic proteins CHOP and JNK.
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Fig7: Ceramide triggers ER stress is independent of its downstream metabolite S1P. (A) ACC-M and ACC-2 cells were seeded into 60 mm culture dishes and the next day cells were treated with 5–10 μM S1P. The level of phosphorylated eIF2α and ERK was analyzed. Unphosphorylated eIF2α and ERK were measured and actin were used as loading control. The experiment was repeated several times and the representative result is shown. (B) Proposed mechanism of ceramide-mediated activation of ER stress response in ACCs. Ceramide induces SERCA inhibition and ER calcium depletion. This leads to increase GRP78 and activate PERK/eIF2α and IRE1α/XBP1 arm of ER stress. FB1 inhibits ceramide-induced ER stress. Prolonged ER stress eventually induces apoptosis through activates pro-apoptotic proteins CHOP and JNK.

Mentions: Ceramide is catalyzed by ceramidase and sphingosine kinase to produce the downstream metabolite S1P, and treating HL-60 cells with exogenous C2-ceramide increases S1P production[24]. Intracellular and extracellular S1P are both reported to trigger ER stress[25]. We further investigated whether increased levels of the downstream metabolite S1P are responsible for ceramide-induced ER stress. Western blot showed that treatment of ACC-M and ACC-2 cells with 5–10 μM exogenous S1P induced ERK1/2 phosphorylation. However, treatment of the cells with 5–10 μM S1P had no significant effect on eIF2α phosphorylation (Figure 7A). These results indicate that ceramide-induced ER stress is independent of its downstream metabolite S1P.Figure 7


Induction of ER stress-mediated apoptosis by ceramide via disruption of ER Ca(2+) homeostasis in human adenoid cystic carcinoma cells.

Liu Z, Xia Y, Li B, Xu H, Wang C, Liu Y, Li Y, Li C, Gao N, Li L - Cell Biosci (2014)

Ceramide triggers ER stress is independent of its downstream metabolite S1P. (A) ACC-M and ACC-2 cells were seeded into 60 mm culture dishes and the next day cells were treated with 5–10 μM S1P. The level of phosphorylated eIF2α and ERK was analyzed. Unphosphorylated eIF2α and ERK were measured and actin were used as loading control. The experiment was repeated several times and the representative result is shown. (B) Proposed mechanism of ceramide-mediated activation of ER stress response in ACCs. Ceramide induces SERCA inhibition and ER calcium depletion. This leads to increase GRP78 and activate PERK/eIF2α and IRE1α/XBP1 arm of ER stress. FB1 inhibits ceramide-induced ER stress. Prolonged ER stress eventually induces apoptosis through activates pro-apoptotic proteins CHOP and JNK.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC4417540&req=5

Fig7: Ceramide triggers ER stress is independent of its downstream metabolite S1P. (A) ACC-M and ACC-2 cells were seeded into 60 mm culture dishes and the next day cells were treated with 5–10 μM S1P. The level of phosphorylated eIF2α and ERK was analyzed. Unphosphorylated eIF2α and ERK were measured and actin were used as loading control. The experiment was repeated several times and the representative result is shown. (B) Proposed mechanism of ceramide-mediated activation of ER stress response in ACCs. Ceramide induces SERCA inhibition and ER calcium depletion. This leads to increase GRP78 and activate PERK/eIF2α and IRE1α/XBP1 arm of ER stress. FB1 inhibits ceramide-induced ER stress. Prolonged ER stress eventually induces apoptosis through activates pro-apoptotic proteins CHOP and JNK.
Mentions: Ceramide is catalyzed by ceramidase and sphingosine kinase to produce the downstream metabolite S1P, and treating HL-60 cells with exogenous C2-ceramide increases S1P production[24]. Intracellular and extracellular S1P are both reported to trigger ER stress[25]. We further investigated whether increased levels of the downstream metabolite S1P are responsible for ceramide-induced ER stress. Western blot showed that treatment of ACC-M and ACC-2 cells with 5–10 μM exogenous S1P induced ERK1/2 phosphorylation. However, treatment of the cells with 5–10 μM S1P had no significant effect on eIF2α phosphorylation (Figure 7A). These results indicate that ceramide-induced ER stress is independent of its downstream metabolite S1P.Figure 7

Bottom Line: Up-regulation of the ER stress-associated apoptosis promoting transcription factor CHOP and p-JNK suggested that the antitumor activity of ceramide is owing to activation of apoptotic ER stress.The chemical chaperone TUDCA inhibited ceramide-induced ER stress and cell death.In addition, the downstream metabolite of ceramide, S1P, cannot activate ER stress.

View Article: PubMed Central - PubMed

Affiliation: Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China.

ABSTRACT

Background: Ceramides are a class of sphingolipids that form the structural component of the cell membrane and also act as second messengers in cell signaling pathways. Emerging results suggest that ceramide induces growth arrest and apoptosis in various human cancer cells. However, the mechanisms underlying its antitumor activity are yet to be identified. Endoplasmic reticulum stress (ER stress), a cellular adaptive response, is believed to initially compensate for damage but can eventually trigger cell death if the stimulus is severe or prolonged. In this study, we investigated whether ceramide induces cell death in human salivary adenoid cystic carcinoma (ACCs) through activation of the apoptotic ER stress.

Results: RT-PCR, real-time PCR and western blot demonstrated that exogenous ceramide treatment up-regulated GRP78 and p-eIF2α expression and XBP1 splicing. Moreover, the ceramide synthase inhibitor FB1 abolished ceramide-induced ER stress. Up-regulation of the ER stress-associated apoptosis promoting transcription factor CHOP and p-JNK suggested that the antitumor activity of ceramide is owing to activation of apoptotic ER stress. Mechanistically, [Ca(2+)]ER depletion and SERCA inhibition by ceramide treatment suggested that it induces ER stress by disrupting [Ca(2+)]ER homeostasis. The chemical chaperone TUDCA inhibited ceramide-induced ER stress and cell death. In addition, the downstream metabolite of ceramide, S1P, cannot activate ER stress.

Conclusions: These results demonstrated that exogenous ceramide induces cancer cell death through a mechanism involving severe ER stress triggered by the disruption of ER Ca(2+) homeostasis.

No MeSH data available.


Related in: MedlinePlus