Effects of menthol and Akt inhibitors on the gene expression of MRP2.

HepG2 cells were exposed to 10–100 μM menthol, 5 μM MK-2206, 40 μM perifosine, or 40 μM ipatasertib for 24 hr. Total RNA was extracted and purified from HepG2 cells, and the expression level of MRP2 was measured by real-time PCR. The results represent the mean ± SD of three independent experiments. ***: pver. Control group).</p

Effect of menthol on intracellular accumulation and efflux of EPI.

HepG2 cells were exposed to 100 μM menthol for 24 hr. (A) Cells were preincubated for 10 min at 37°C and then incubated with 5 μM EPI for 10 or 30 min. (B) After the cells had been loaded with 5 μM EPI for 30 min at 37°C, they were incubated in drug-free HBSS for 3 min at 37°C. The results represent the mean ± SD of three independent experiments. **: pver. Control group), ***: pver. Control group).</p

Effects of menthol on cytotoxicity of EPI and CIS.

The cells were exposed to 5 μM EPI or 80 μM CIS 24 hr after treatment with 100 μM menthol, and cell viability was then evaluated by the MTT method 24 hr later. The results are shown as means ± SD of three independent experiments. **: pp<0.001, NS: not significant.</p

Effect of MK-571 and verapamil on decreased intracellular accumulation of EPI after menthol exposure.

HepG2 cells were exposed to 100 μM menthol for 24 hr. Cells were preincubated for 10 min at 37°C with or without 100 μM MK-571, and 100 μM verapamil, and then incubated with 5 μM EPI for 30 min under the same conditions as for preincubation. The results represent the mean ± SD of three independent experiments. **: pp<0.001.</p