Molecular mechanisms of apoptosis induction by 2-dodecylcyclobutanone, a radiolytic product of palmitic acid, in human lymphoma U937 cells

Abstract

The irradiation of fat-containing food forms 2-dodecylcyclobutanone (2-DCB) from palmitic acid (PA). In this study, we investigated whether 2-DCB and PA induce apoptosis in human lymphoma U937 cells. We found that cell viability decreased by 2-DCB and apoptosis was induced by 2-DCB and PA. 2-DCB and PA significantly enhanced the formation of intracellular reactive oxygen species (ROS). Apoptosis induced by 2-DCB and PA was strongly prevented by an antioxidant, N-acetyl-L: -cysteine. The treatment with 2-DCB and PA resulted in the loss of mitochondrial membrane potential, and Fas, caspase-8 and caspase-3 activation. Pretreatment with a pan-caspase inhibitor (z-VAD) significantly inhibited apoptosis induced by 2-DCB and PA. Moreover, 2-DCB and PA also induced Bax up-regulation, the reduction in Bcl-2 expression level, Bid cleavage and the release of cytochrome c from the mitochondria to the cytosol. In addition, an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) was observed after the treatment with 2-DCB and PA. Our results indicated that intracellular ROS generation, the modulation of the Fas-mitochondrion-caspase-dependent pathway and the increase in [Ca(2+)](i) involved in apoptosis are induced by 2-DCB and PA in U937 cells.

(−)-Epigallocatechingallate induces apoptosis in B lymphoma cells via caspase-dependent pathway and Bcl-2 family protein modulation

“…The death receptor pathway triggered by stimulation of the death receptor CD95 (APO-1/Fas) results in receptor aggregation, and FADD and caspase-8 recruitment; subsequently, caspase-8 becomes activated and directly leads to a cascade that activates the apoptosis executor caspase-3 (36). The role of EGCG and a radiolytic product in triggering the Fas-caspase-8-medicated pathway in lymphoma U937 cells has been demonstrated by others (37,38). The enhanced expression of Fas mRNA and cleavage of caspase-8 with increasing EGCG concentrations observed in this study demonstrated that EGCG initiates the death receptor pathway to induce apoptosis (Fig.…”

“…Whether this phenomenon is idiosyncratic requires further studies in other cell lines. Previous studies have revealed the means by which EGCG or other natural agents cause the mitochondria to release cytochrome c : one direct means is mediated by Bcl-2 family proteins; the other is through Fas aggregated caspase-8, not directly activating the caspase-3 cascade but followed by cleaving of Bid to tBid and subsequent cytochrome c release that activates caspase-9 and caspase-3 (37,43). Although our results suggested that EGCG induces apoptosis through both the extrinsic (death receptor) and intrinsic (mitochondrial) pathways, it is unclear whether the two pathways are linked by Bid cleavage in Jeko-1 and Raji cells.…”

3-O-trans-p-coumaroyl-alphitolic acid, a triterpenoid from Zizyphus jujuba, leads to apoptotic cell death in human leukemia cells through reactive oxygen species production and activation of the unfolded protein response

“…The secondary horseradish peroxidase (HRP)-conjugated antibodies (1:5000) were purchased from Cell Signaling Technology. The band signals were visualized using a luminescent image analyzer (LAS4000, Fujifilm Co., Tokyo, Japan) with the ECL chemiluminescence system (Amersham Biosciences) [ 17 ].…”

Modifications of azoxymethane-induced carcinogenesis and 90-day oral toxicities of 2-tetradecylcyclobutanone as a radiolytic product of stearic acid in F344 rats

“…It is well recognized that saturated fatty acids such as palmitic acid (C16:0) and stearic acid (C18:0) are cytotoxic to β-cells, and can induce apoptosis in vitro 22 , 23 . We found that 2-dDCB as well as its precursor to palmitic acid induced apoptosis in human lymphoma cells 24 . However, in vivo toxicity of dietary stearic acid has not been clearly demonstrated 25 , 26 , 27 .…”