Modulation of p-glycoprotein-mediated efflux pirarubicin in living multidrug-resistant K562/Dox cell lines by 4-hydroxybenzoic acid and 4-hydroxy-3-methoxybenzoic acid via impairment of the cellular energetic state

The objective was to investigate the effect of 4-hydroxybenzoic acid (4-HBA) and 4-hydroxy-3-methoxybenzoic acid (Vanillic acid, VA) on p-glycoprotein (P-gp) activity in multidrug-resistant K562/Dox cancer cells. The cytotoxic and co-treatment with pirarubicin (Pira) were analyzed using a resazurin assay. A noninvasive functional spectrofluorometric technique was used to determine the kinetics of Pira uptake in living multidrug-resistant K562/Dox cancer cells. The three biological endpoints for determination of cellular energetic state included the activity of mitochondria, mitochondrial membrane potential (ΔΨm), and ATP levels. The results revealed that 4-HBA (10 mM) and VA (5 and 10 mM) statistically decreased cell viability in K562 and multidrug-resistant K562/Dox cancer cells. In ways consistent with that result, 4-HBA and VA (0.01, 0.1, 1, and 10 mM) could statistically decrease the IC(50) of Pira in K562 and multidrug-resistant K562/Dox cancer cells at 48 and 72 h. The overall intracellular Pira concentration increased in 4-HBA- and VA-treated multidrug-resistant K562/Dox cancer cells when compared to control. The ratio of k(a)(i)/k(a)(0) in 4-HBA- and VA-treated multidrug-resistant K562/Dox cancer cells was significantly decreased when 4-HBA and VA concentration increased. The activity of mitochondria, ΔΨm, and ATP levels significantly reduced in multidrug-resistant K562/Dox cancer cells incubated with 0.01, 0.1, 1, and 10 mM 4-HBA and VA at all harvest time points. In conclusion, 4-HBA and VA were able to bring about cell death in multidrug-resistant K562/Dox cancer cell at high concentrations. The 4-HBA and VA could modify P-gp function via an impaired cellular energetic state, resulting in increased in intracellular drug concentration in multidrug-resistant K562/Dox cancer cells.