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Exploring the mechanism through which berberine (Ber) reverses the multidrug resistance (MDR) of breast cancer is of great importance. Herein, we used the methyl thiazolyl tetrazolium assay to determine the drug resistance and cytotoxicity of Ber and doxorubicin (DOX) alone or in combination on the breast cancer cell line MCF-7/DOXFluc. The results showed that Ber could synergistically enhance the inhibitory effect of DOX on tumor cell proliferation in vitro, and the optimal combination ratio was Ber/DOX = 2:1. Using a luciferase reporter assay system combined with the bioluminescence imaging technology, the efflux kinetics of d-luciferin potassium salt in MCF-7/DOXFluc cells treated with Ber in vivo was investigated. The results showed that Ber could significantly reduce the efflux of d-luciferin potassium salt in MCF-7/DOXFluc cells. In addition, western blot and immunohistochemistry experiments showed that the expression of P-glycoprotein (P-gp/ABCB1) and multidrug resistance protein 1 (MRP1/ABCC1) in MCF-7/DOXFluc cells was downregulated upon Ber treatment. Finally, high-performance liquid chromatography was used to investigate the effect of Ber on DOX tissue distribution in vivo, and the results showed that the uptake of DOX in tumor tissues increased significantly when combined with Ber (P < 0.05). Thus, the results illustrated that Ber can reverse MDR by inhibiting the efflux function of ATP-binding cassette transporters and downregulating their expression levels.

While elemene (ELE) can reverse tumor multidrug resistance (MDR), the mechanisms for ELE reversing MDR remain unclear. Numerous studies have suggested that the efflux functionality of ATP-binding cassette (ABC) transporters, not their quantity, is more relevant to tumor MDR. However, no appropriate methods exist for real-time detection of the intracellular drug efflux caused by ABC transporters in vitro, especially in vivo, which hinders the examination of MDR reversal mechanisms. This study directly investigates the correlation between efflux functionality of ABC transporters and MDR reversal via ELE, using D-luciferin potassium salt (D-luc) as the chemotherapeutic substitute to study the intracellular drug efflux. Here, a luciferase reporter assay system combined with bioluminescence imaging confirmed that the efflux of D-luc from MCF-7/DOXFluc cells in vitro and in vivo was significantly reduced by ELE and when combined with Doxorubicin (DOX), ELE showed a synergistically anti-tumor effect in vitro and in vivo. Additionally, the luminescence pharmacokinetics of D-luc in MCF-7/DOXFluc cells and pharmacodynamics of the combined ELE and DOX in vivo showed a great correlation, implying that D-luc might be used as a probe to study ABC transporters-mediated efflux in order to explore mechanisms of traditional Chinese medicines reversing MDR.

Exploring the mechanism through which berberine (Ber) reverses the multidrug resistance (MDR) of breast cancer is of great importance. Herein, we used the methyl thiazolyl tetrazolium assay to determine the drug resistance and cytotoxicity of Ber and doxorubicin (DOX) alone or in combination on the breast cancer cell line MCF-7/DOXFluc. The results showed that Ber could synergistically enhance the inhibitory effect of DOX on tumor cell proliferation in vitro, and the optimal combination ratio was Ber/DOX = 2:1. Using a luciferase reporter assay system combined with the bioluminescence imaging technology, the efflux kinetics of d-luciferin potassium salt in MCF-7/DOXFluc cells treated with Ber in vivo was investigated. The results showed that Ber could significantly reduce the efflux of d-luciferin potassium salt in MCF-7/DOXFluc cells. In addition, western blot and immunohistochemistry experiments showed that the expression of P-glycoprotein (P-gp/ABCB1) and multidrug resistance protein 1 (MRP1/ABCC1) in MCF-7/DOXFluc cells was downregulated upon Ber treatment. Finally, high-performance liquid chromatography was used to investigate the effect of Ber on DOX tissue distribution in vivo, and the results showed that the uptake of DOX in tumor tissues increased significantly when combined with Ber (P < 0.05). Thus, the results illustrated that Ber can reverse MDR by inhibiting the efflux function of ATP-binding cassette transporters and downregulating their expression levels.

Background: In this study, a liposomal gel based on a pH-gradient method was used to increase the skin-layer retention of monocrotaline (MCT) for topical administration. Methods: Using the Box-Behnken design, different formulations were designed to form liposome suspensions with optimal encapsulation efficiency (EE%) and stability factor (KE). In order to keep MCT in liposomes and accumulate in skin slowly and selectively, MCT liposome suspensions were engineered into gels. Results: A pH-gradient method was used to prepare liposome suspensions. The optimal formulation of liposome suspensions (encapsulation efficiency: 83.10 ± 0.21%) was as follows: MCT 12 mg, soybean phosphatidyl choline (sbPC) 200 mg, cholesterol (CH) 41 mg, vitamin E (VE) 5 mg, and citric acid buffer solution (CBS) 4.0 10 mL (pH 7.0). The final formulation of liposomal gels consisted of 32 mL liposome suspensions, 4.76 mL deionized water, 0.40 g Carbopol-940, 1.6 g glycerol, 0.04 g methylparaben, and a suitable amount of triethanolamine for pH value adjustment. The results of in vitro drug release showed that MCT in liposomal gels could be released in 12 h constantly in physiological saline as a Ritger-Peppas model. Compared with plain MCT in gel form, liposomal MCT in gel had higher skin retention in vitro. Conclusion: In this study, liposomal gels were formed for greater skin retention of MCT. It is potentially beneficial for reducing toxicities of MCT by topical administration with liposomal gel.

In order to explore the mechanism of the reversing multidrug resistance (MDR) phenotypes by β-elemene (β-ELE) in doxorubicin (DOX)-resistant breast cancer cells (MCF-7/DOX), both the functionality and quantity of the ABC transporters in MCF-7/DOX were studied. Bioluminescence imaging (BLI) was used to study the efflux of d-luciferin potassium salt, the substrate of ATP-binding cassette transporters (ABC transporters), in MCF-7/DOX cells treated by β-ELE. At the same time three major ABC transport proteins and genes-related MDR, P-glycoprotein (P-gp, ABCB1) and multidrug resistance-associated protein 1 (MRP, ABCC1) as well as breast cancer resistance protein (BCRP, ABCG2) were analyzed by q-PCR and Western blot. To investigate the efflux functionality of ABC transporters, MCF-7/DOXFluc cell line with stably-overexpressed luciferase was established. BLI was then used to real-time monitor the efflux kinetics of d-luciferin potassium salt before and after MCF-7/DOXFluc cells being treated with β-ELE or not. The results showed that the efflux of d-luciferin potassium salt from MCF-7/DOXFluc was lessened when pretreated with β-ELE, which means that β-ELE may dampen the functionality of ABC transporters, thus decrease the efflux of d-fluorescein potassium or other chemotherapies which also serve as the substrates of ABC transporters. As the effect of β-ELE on the expression of ABC transporters, the results of q-PCR and Western blot showed that gene and protein expression of ABC transporters such as P-gp, MRP, and BCRP were down-regulated after the treatment of β-ELE. To verify the efficacy of β-ELE on reversing MDR, MCF-7/DOX cells were treated with the combination of DOX and β-ELE. MTT assay showed that β-ELE increased the inhibitory effect of DOX on the proliferation of MCF-7/DOX, and the IC50 of the combination group was much lower than that of the single DOX or β-ELE treatment. In all, β-ELE may reverse MDR through the substrates of ABC transporters by two ways, to lessen the ABC protein efflux by weakening their functionality, or to reduce the quantity of ABC gene and protein expression.