Negative Effect of Ellagic Acid on Cytosolic pH Regulation and Glycolytic Flux in Human Endometrial Cancer Cells

Abstract

Background/Aims: Key properties of tumor cells include enhanced glycolytic flux with excessive consumption of glucose and formation of lactate. As glycolysis is highly sensitive to cytosolic pH, maintenance of glycolysis requires export of H⁺ ions, which is in part accomplished by Na⁺/H⁺ exchangers, such as NHE1. The carrier is sensitive to oxidative stress. Growth of tumor cells could be suppressed by the polyphenol Ellagic acid, which is found in various fruits and vegetables. An effect of Ellagic acid on transport processes has, however, never been reported. The present study thus elucidated an effect of Ellagic acid on cytosolic pH (pHi), NHE1 transcript levels, NHE1 protein abundance, Na⁺/H⁺ exchanger activity, and lactate release. Methods: Experiments were performed in Ishikawa cells without or with prior Ellagic acid (20 µM) treatment. NHE1 transcript levels were determined by qRT-PCR, NHE1 protein abundance by Western blotting, pH_i utilizing (2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein [BCECF] fluorescence, Na⁺/H⁺ exchanger activity from Na⁺ dependent realkalinization after an ammonium pulse, cell volume from forward scatter in flow cytometry, reactive oxygen species (ROS) from 2’,7’-dichlorodihydrofluorescein fluorescence, glucose uptake utilizing 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose, and lactate concentration in the supernatant utilizing a colorimetric (570 nm)/ fluorometric enzymatic assay. Results: A 48 hour treatment with Ellagic acid (20 µM) significantly decreased NHE1 transcript levels by 75%, NHE1 protein abundance by 95%, pHi from 7.24 ± 0.01 to 7.02 ± 0.01, Na⁺/H⁺ exchanger activity by 77%, forward scatter by 10%, ROS by 82%, glucose uptake by 58%, and lactate release by 15%. Conclusion: Ellagic acid (20µM) markedly down-regulates ROS formation and NHE1 expression leading to decreased Na⁺/H⁺ exchanger activity, pHi, glucose uptake and lactate release in endometrial cancer cells. Those effects presumably contribute to reprogramming and growth inhibition of tumor cells.

Expressional and Functional Characterization of Intracellular pH Regulators and Effects of Ethanol in Human Oral Epidermoid Carcinoma Cells

“…Such low pH e inside solid tumors is mainly attributable to the pH i extruders, such as Na + -H + exchanger (NHE) and Na + -HCO 3 -exchanger (NBC) [6,7]. Indeed, NHE activation has been found to enhance tumor cell migration and invasion by creating a distinct cell surface pH gradient and invadopodial-dependent extracellular matrix degradation in human endometrial cancer cells, human breast carcinoma and melanoma cells [8][9][10][11][12]. On the other hand, change of pH i affects many mammalian cellular functions, such as ion channel permeability [13], cell volume [14], proliferation, apoptosis, differentiation and metastasis [15,16].…”

Ellagic Acid Inhibits Extracellular Acidity-Induced Invasiveness and Expression of COX1, COX2, Snail, Twist 1, and c-myc in Gastric Carcinoma Cells

“…Therefore, increased expression of COX1 and COX2 seemed to be involved in the acidity-enhanced gastric cancer cell invasion, and the anti-invasive role of ellagic acid may be associated with suppression of COX1 and COX2 induction, although inhibition of COX activity was not sufficient for complete prevention of cell invasion. On the other hand, in endometrial cancer cells, high concentration of ellagic acid was shown to reduce the expression of the Na/H+ exchanger NHE1, a regulator of extracellular acidity often overexpressed in cancer cells [18]. To determine if the inhibitory role of ellagic acid on acidity-induced gastric cancer cell invasion is associated with the regulation of NHE1 expression, we detected the effect of ellagic acid on NHE1 expression; however, low concentration of ellagic acid hardly affected NHE1 protein expression in these cells.…”

Enhanced anticancer activity and oral bioavailability of ellagic acid through encapsulation in biodegradable polymeric nanoparticles

“…[10][11][12] Therapeutically, EA has been proclaimed to be effective in the regression of various kinds of tumors, involving but not limited to lung cancer, colorectal carcinoma, esophageal cancer, metastatic melanoma, hepatocellular carcinoma, tongue cancer, breast cancer, bladder cancer, endometrial carcinoma, and prostate cancer. 4,16,[18][19][20][21][22][23][24][25] Whereas the pharmacological effect of EA has been broadly considered and permitted for the management of a vast spectrum of cancer, it still has poor aqueous solubility and poor bioavailability that offer minimal therapeutic benefit and restrict its full clinical use. 26 Oral administration showed a poor absorption, metabolism in gastrointestinal tract, first-pass effect, and rapid elimination, 19,27,28 which are reported as the main causes of its low bioavailability.…”