The metabolic bioactivation of caffeic acid phenethyl ester (CAPE) mediated by tyrosinase selectively inhibits glutathione S-transferase

Abstract

Glutathione S-transferase (GST) and multidrug resistance-associated proteins (MRPs) play major roles in drug resistance in melanoma. In this study, we investigated caffeic acid phenethyl ester (CAPE) as a selective GST inhibitor in the presence of tyrosinase, which is abundant in melanoma cells. Tyrosinase bioactivates CAPE to an o-quinone, which reacts with glutathione to form CAPE-SG conjugate. Our findings indicate that 90% CAPE was metabolized by tyrosinase after a 60-min incubation. LC–MS/MS analyses identified a CAPE-SG conjugate as a major metabolite. In the presence of tyrosinase, CAPE (10–25 µM) showed 70–84% GST inhibition; whereas in the absence of tyrosinase, CAPE did not inhibit GST. CAPE-SG conjugate and CAPE-quinone (25 µM) demonstrated ≥85% GST inhibition via reversible and irreversible mechanisms, respectively. Comparing with CDNB and GSH, the non-substrate CAPE acted as a weak, reversible GST inhibitor at concentrations >50 µM. Furthermore, MK-571, a selective MRP inhibitor, and probenecid, a non-selective MRP inhibitor, decrease the IC50 of CAPE (15 µM) by 13% and 21%, apoptotic cell death by 3% and 13%, and mitochondrial membrane potential in human SK-MEL-28 melanoma cells by 10% and 56%, respectively. Moreover, computational docking analyses suggest that CAPE binds to the GST catalytic active site. Caffeic acid, a hydrolyzed product of CAPE, showed a similar GST inhibition in the presence of tyrosinase. Although, as controls, 4-hydroxyanisole and l-tyrosine were metabolized by tyrosinase to form quinones and glutathione conjugates, they exhibited no GST inhibition in the absence and presence of tyrosinase. In conclusion, both CAPE and caffeic acid selectively inhibited GST in the presence of tyrosinase. Our results suggest that intracellularly formed quinones and glutathione conjugates of caffeic acid and CAPE may play major roles in the selective inhibition of GST in SK-MEL-28 melanoma cells. Moreover, the inhibition of MRP enhances CAPE-induced toxicity in the SK-MEL-28 melanoma cells.

Filamentous fungi from Plantago lanceolata L. leaves: Contribution to the pattern and stability of bioactive metabolites

“…Besides being powerful antioxidants that can be found in some functional food products (Bendini et al, 2007), several other possible uses were linked to these molecules, especially CA and its derivates. Caffeic acid and its phenylethyl ester (CAPE) are currently researched as possible anticancer agents -some metabolites of CA and CAPE were shown to inhibit cancer cell line development, via inhibition of glutathione-S-transferase (Kudugunti et al, 2011).…”

Caffeic acid phenethyl ester modulates aflatoxin B1‐induced hepatotoxicity in rats

“…An important role of GST is to biotransform xenobiotics and other endogenous toxic compounds. It initiates the conjunction of hydrophobic electrophilic toxic substances including carcinogenesis and aflatoxins with the GSH . CAPE exerts antioxidant effect by facilitating GSH biosynthesis .…”

“…It initiates the conjunction of hydrophobic electrophilic toxic substances including carcinogenesis and aflatoxins with the GSH. 28,29 CAPE exerts antioxidant effect by facilitating GSH biosynthesis. 11,15 In addition, Ilhan et al 30 reported that CAPE interferes with enzymes involved in GSH synthesis, because gamma-glutamyl cysteinyl synthetase and other GSH-related detoxifying enzymes were also increased.…”

Effect of Caffeic Acid and Low-Power Laser Light Co-Exposure on Viability of Pseudomonas aeruginosa

“…The application of a dye as a sensitizer has been the focus of some studies on photodynamic therapy (PDT), especially in mammalian cancer cells (27). The major objective of our study was to examine caffeic acid and its derivatives as an adjunct to other compounds for the treatment of skin disorders, in particular melanoma (28,29). Phenethyl caffeic acid esters, similar to frolic and chlorogenic acids show antibacterial, anti-mutageneic and antiviral activities and have no side effects (14).…”