Epistructured catechins, EGCG and EC facilitate apoptosis induction through targeting de novo lipogenesis pathway in HepG2 cells

Abstract

BackgroundAbnormally high expression of the mammalian de novo lipogenesis (DNL) pathway in various cancer cells promotes cell over-proliferation and resistance to apoptosis. Inhibition of key enzymes in the DNL pathway, namely, ATP citrate lyase, acetyl-CoA carboxylase, and fatty acid synthase (FASN) can increase apoptosis without cytotoxicity to non-cancerous cells, leading to the search for and presentation of novel selective and powerful targets for cancer therapy. Previous studies reported that epistructured catechins, epigallocatechin gallate (EGCG) and epicatechin (EC) exhibit different mechanisms regarding a strong inducer of apoptosis in various cancer cell lines. Thus, the current study investigated the growth inhibitory effect of EGCG and EC, on the enzyme expression and activity of the DNL pathway, which leads to the prominent activity of carnitine palmitoyl transferase-1 (CPT-1) mediating apoptosis in HepG2 cells.MethodsThe cytotoxicity on HepG2 cells of EGCG and EC was determined by MTT assay. Cell death caused by apoptosis, the dissipation of mitochondrial membrane potential (MMP), and cell cycle arrest were then detected by flow cytometry. We further investigated the decrease of fatty acid levels associated with DNL retardation, followed by evaluation of DNL protein expression. Then, the negative inhibitory effect of depleted fatty acid synthesis on malonyl-CoA synthesis followed by regulating of CPT-1 activity was investigated. Thereafter, we inspected the enhanced reactive oxygen species (ROS) generation, which is recognized as one of the causes of apoptosis in HepG2 cells.ResultsWe found that EGCG and EC decreased cancer cell viability by increasing apoptosis as well as causing cell cycle arrest in HepG2 cells. Apoptosis was associated with MMP dissipation. Herein, EGCG and EC inhibited the expression of FASN enzymes contributing to decreasing fatty acid levels. Notably, this decrease consequently showed a suppressing effect on the CPT-1 activity. We suggest that epistructured catechin-induced apoptosis targets CPT-1 activity suppression mediated through diminishing the DNL pathway in HepG2 cells. In addition, increased ROS production was found after treatment with EGCG and EC, indicating oxidative stress mechanism-induced apoptosis. The strong apoptotic effect of EGCG and EC was specifically absent in primary human hepatocytes.ConclusionOur supportive evidence confirms potential alternative cancer treatments by EGCG and EC that selectively target the DNL pathway.

Bridelia speciosa Müll.Arg. Stem bark Extracts as a Potential Biomedicine: From Tropical Western Africa to the Pharmacy Shelf

“…Conversely, the water extract of B. speciosa was able to reduce cell viability in the concentration range (300-500 µg/mL) throughout the 72 hour treatment (Figure 1), thus indicating significant anti-proliferative effects that are consistent with more than one speculation. On one side, the concentration-dependent anti-proliferative effects that were exerted by the water extract could be related to epicatechins [51]. This was, at least in part, confirmed by the mild anti-proliferative effect that was exerted by the sole epicatechin (100 µg/mL) (CTR: 100; Epicatechin: 87.88 ± 4.35).…”

<p>Cerebral protection of epigallocatechin gallate (EGCG) via preservation of mitochondrial function and ERK inhibition in a rat resuscitation model</p>

“…In addition, osteoclastic cell death was induced by ROS produced by EGCG (12.5–100 μm) 29. It had also been demonstrated that EGCG (0.5 mM) increased ROS generation, the mPTP opening as well as apoptosis level in HepG2 cells 30. We hold the opinion that the various and opposing effects of EGCG may depend on the different dosage, cellular condition and cell types.…”

Ethanolic Extract of Senna velutina Roots: Chemical Composition, In Vitro and In Vivo Antitumor Effects, and B16F10-Nex2 Melanoma Cell Death Mechanisms

“…Different studies report that catechins [41, 42], anthraquinones [39], and piceatannol [43, 44] induce apoptosis in tumor cells. Corroborating this is the analysis of the mechanism whereby ESVR-promoted B16F10-Nex2 cell death showed an increased number of apoptotic nuclei, which are characterized by chromatin condensation and DNA fragmentation, characteristic stages of death by apoptosis [45].…”