The Interaction of the Flavonoid Fisetin with Human Glutathione Transferase A1-1

Abstract

Glutathione transferases (GSTs) are a family of Phase II detoxification enzymes that are involved in the development of the multidrug resistance (MDR) mechanism in cancer cells and therefore affect the clinical outcome of cancer chemotherapy. The discovery of nontoxic natural compounds as inhibitors for GSTs is a promising approach for chemosensitizing and reversing MDR. Fisetin (7,3′,4′-flavon-3-ol) is a plant flavonol present in many plants and fruits. In the present work, the interaction of fisetin with human glutathione transferase A1-1 (hGSTA1-1) was investigated. Kinetic analysis revealed that fisetin is a reversible inhibitor for hGSTA1-1 with IC50 1.2 ± 0.1 μΜ. It functions as a mixed-type inhibitor toward glutathione (GSH) and as a noncompetitive inhibitor toward the electrophile substrate 1-chloro-2,4-dinitrobenzene (CDNB). In silico molecular modeling and docking predicted that fisetin binds at a distinct location, in the solvent channel of the enzyme, and occupies the entrance of the substrate-binding sites. Treatment of proliferating human epithelial colorectal adenocarcinoma cells (CaCo-2) with fisetin causes a reduction in the expression of hGSTA1-1 at the mRNA and protein levels. In addition, fisetin inhibits GST activity in CaCo-2 cell crude extract with an IC50 (2.5 ± 0.1 μΜ), comparable to that measured using purified recombinant hGSTA1-1. These actions of fisetin can provide a synergistic role toward the suppression and chemosensitization of cancer cells. The results of the present study provide insights into the development of safe and effective GST-targeted cancer chemosensitizers.

Myricetin as a Potential Adjuvant in Chemotherapy: Studies on the Inhibition of Human Glutathione Transferase A1–1

“…Recombinant hGSTA1–1 was expressed in E. coli BL21 (DE3) cells and purified by affinity chromatography on immobilized GSH as described elsewhere [ 31 , 32 , 33 ]. Protein concentration was determined by the method of Bradford, using BSA as standard.…”

“…The activity of hGSTA1–1 was assessed by measuring the conjugating activity of the 1-chloro−2,4-dinitrobenzene (CDNB)/GSH system as described previously [ 31 , 32 , 33 ]. For the determination of the concentration of inhibitor at which 50% inhibition of enzyme activity was obtained (IC50), the reaction mixture contained different concentrations of MYR (0–2.3 μΜ).…”

“…The course of inactivation was followed by periodically removing samples for assaying the hGSTA1–1 activity. Initial rates of enzyme inactivation were determined from plots of log(% remaining activity) versus time (min) [ 32 , 33 , 35 , 36 ]. Irreversible inactivation of hGSTP1–1 by PEITC was also carried out in the presence of S-nitrobenzyl-glutathione (1 mM) or MYR (10–50 μΜ) as described above.…”

Targeting Drug Chemo-Resistance in Cancer Using Natural Products

“…Majidinia et al have also reported the suppression effect of emodin and quercetin on GSTπ to overcome MDR in cancer cells [191]. Moreover, fisetin, a plant flavonol, was significantly able to downregulate GST expression in colorectal adenocarcinoma cells (Caco-2), which made fisetin a promising GST-targeted chemosensitizer for modulating MDR [192]. Yu Ping Feng San (YPFS) is a popular Chinese herbal combination formula composed of Astragali Radix, Atractylodis Macrocephalea Rhizoma, and Saposhnikoviae Radix.…”

Ligandability Assessment of Human Glutathione Transferase M1-1 Using Pesticides as Chemical Probes

“…For example, the potent inhibitor, 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol (NBDHEX) showed high inhibition potency towards both GSTP1 and GSTM1 [ 16 ]. Furthermore, natural compounds such as curcumin and the flavonoid fisetin display high inhibitory potency towards human GSTA1 and GSTP1, respectively [ 24 , 25 ]. Georgakis et al [ 19 ], have synthesized and studied a series of 2,2’-dihydroxybenzophenone analogues that showed high inhibition potency towards hGSTM1-1.…”