Celecoxib-mediated activation of endoplasmic reticulum stress induces de novo ceramide biosynthesis and apoptosis in hepatoma HepG2 cells

Abstract

Ceramides are the major sphingolipid metabolites involved in cell survival and apoptosis. When HepG2 hepatoma cells were treated with celecoxib, the expression of the genes in de novo sphingolipid biosynthesis and sphingomyelinase pathway was upregulated and cellular ceramide was elevated. In addition, celecoxib induced endoplasmic reticulum (ER) stress in a time-dependent manner. SPTLC2, a subunit of serine palmitoyltransferase, was overexpressed by adenovirus. Adenoviral overexpression of SPTLC2 (AdSPTLC2) decreased cell viability of HEK293 and HepG2 cells. In addition, AdSPTLC2 induced apoptosis via the caspase-dependent apoptotic pathway and elevated cellular ceramide, sphingoid bases, and dihydroceramide. However, overexpression of SPTLC2 did not induce ER stress. Collectively, celecoxib activates de novo sphingolipid biosynthesis and the combined effects of elevated ceramide and transcriptional activation of ER stress induce apoptosis. However, activation of de novo sphingolipid biosynthesis does not activate ER stress in hepatoma cells and is distinct from the celecoxib-mediated activation of ER stress.

C16‑ceramide and sphingosine�1‑phosphate/S1PR2 have opposite effects on cell growth through mTOR signaling pathway regulation

“…We found that CerS6 overexpression led to the elevation of C16 ceramide levels, and decreased both Akt/mTOR and ERK phosphorylation, which plays a critical role in the proliferation of breast cancer (2,33,34). In accordance with previous reports (24)(25)(26), which showed that several anticancer reagents such as doxorubicin, celecoxib and methotrexate increase C16-ceramide, increased C16-ceramide induced by CerS6 overexpression reduced breast cancer cell growth with concomitant inhibition of both the Akt/mTOR and ERK pathways. Because the Akt/mTOR pathway is highly dysregulated in breast cancer and it also mediates resistance to endocrine therapies, mTOR inhibition has received significant attention as a novel therapy against breast cancer (35).…”

“…CerS2 overexpression has been found to be correlated with breast cancer cell invasion and chemosensitivity (22,23). In addition, several anticancer drugs such as doxorubicin, celecoxib and methotrexate increase C16-ceramide levels and reduce cell growth (24)(25)(26). However, the precise molecular mechanisms and downstream signaling pathways of ceramide depending on the acyl chain length and S1P have not yet been elucidated in breast cancer.…”

“…Ceramide analyses were conducted as previously described (25,26). Briefly, lipids were extracted from 1x10 7 cells and introduced into a high-performance liquid chromatography (HPLC) system (Agilent 1,200 series; Agilent Technologies, Inc., Santa Clara, CA, USA) and separated through a reverse phase KINETEX C18 column (2.1x50 mm, ID: 2.6 µm) (Phenomenex Inc., St. Louis, MO, USA).…”

Elevated plasma ceramide levels in post-menopausal women: a cross-sectional study

“…The ceramides are key lipid constituents of mammalian cells. They regulate the structural properties of the lipid bilayer [1] along with its interaction with cellular proteins [2], and control many signalling processes, including cell survival [3], growth and proliferation [4], differentiation [5], senescence [6] and apoptosis [7,8]. Dysfunctions in ceramide-mediated signalling may contribute to the initiation and progression of a variety of age-dependent diseases.…”

Sphingomyelinases and Liver Diseases

“…Ceramide levels are markedly reduced in HCC tissues due to the increased expression of strategies that stimulate its degradation, and hence, raising ceramide levels specifically within the tumor may be a relevant therapeutic approach [104]. In this regard, the celecoxib-mediated activation of ER-stress has been shown to induce de novo ceramide biosynthesis, resulting in enhanced apoptosis in hepatoma HepG2 cells [105]. Targeting ACDase, an enzyme that hydrolyzes ceramide (Figure 1), with LCL521 or carmofur has been shown to be of potential relevance in cancer [106,107].…”