Transport Characteristics of Tryptanthrin and its Inhibitory Effect on P-gp and MRP2 in Caco-2 Cells

Abstract

Purpose. Tryptanthrin, an indole quinazoline alkaloid with multiple medical activities, has been recently under preclinical development as an anti-tuberculosis and anti-tumor drug. The aims of this study are to characterize the intestinal transport of tryptanthrin in Caco-2 cells, to determine whether P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (MRP2) are involved in this issue, and to evaluate the potential influence of tryptanthrin on the function of P-gp and MRP2. Methods. Transport assays of tryptanthrin were performed in Caco-2 monolayers with or without the supplement of P-gp and MRP2 inhibitors. Transport assays of P-gp and MRP2 substrates were also performed in the presence of tryptanthrin. The effect of tryptanthrin on the expression of P-gp and MRP2 was analyzed by reverse transcriptase-PCR. Results. Both absorption and secretion of tryptanthrin were concentration-independent at a low concentration range of 0.8–20 µM. The apparent permeability (Papp) for the apical (AP) to basolateral (BL) was 6.138 ± 0.291 × 10-5. The ratio of Papp (BL→AP) to Papp (AP→BL) was 0.77, suggesting greater permeability in the absorptive direction. Both the P-gp inhibitor, verapamil, and the MRP2 inhibitor, glibenclamide, didn’t affect the efflux transport of tryptanthrin. The efflux transport of the P-gp substrate, digoxin, and the MRP2 substrate, pravastatin sodium, decreased when tryptanthrin was present. However, tryptanthrin didn’t change the expression of P-gp and MRP2. Conclusions. Tryptanthrin was well absorbed across the Caco-2 monolayers, and its transepithelial transports were dominated by passive diffusion. Tryptanthrin was not a substrate, but a potential inhibitor of P-gp and MRP2.
 
 This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

Tryptanthrin Inhibits Angiogenesis by Targeting the VEGFR2-Mediated ERK1/2 Signalling Pathway

“…Tryptanthrin, a weakly basic alkaloid isolated from the dried roots of medicinal indigo plants (Banlangen), has been found to possess anti-cancer properties on various cancer cell lines in vitro [25]–[27], [35]. However, its inhibitory effect on angiogenesis in endothelial cells and the underlying molecular action mechanisms have not yet been examined.…”

Benzo[b]tryptanthrin Inhibits MDR1, Topoisomerase Activity, and Reverses Adriamycin Resistance in Breast Cancer Cells

“…Additionally, the apoptotic markers, cleaved caspase-3 and cleaved PARP, [30] were monitored by Western blot analysis of HCT15 cells treat- Tryptanthrin was reported to have MDR-reversing effects through down-regulation of the MDR1 gene expression and protein synthesis. [31][32][33] Benzo[b]tryptanthrin has one more benzene ring attached to tryptanthrin (Figure 1). According to the previously reported results, benzo-annulation did not change the topo I inhibition activity, but noticeably enhanced the topo II inhibitory activity and cytotoxicity against HCT15 cells.…”

“…Therefore, overexpression of MDR1 in cancer cells causes multidrug resistance by pumping out drugs. [31][32][33] In the case of co-treatment with adriamycin and verapamil, the growth percentage decreased from 78.2 % to 18.1 % in MCF7adr cells. Although it was not as effective as verapamil, benzo[b]tryptanthrin decreased the growth percentage to 59.0 %, showing the MDR1-reversing effect.…”

“…[33] This inconsistency in tryptanthrin activity as an MDR1 inhibitor may be attributed to different experimental designs, such as compound treatment time, concentration, and cell line used. In the present study, benzo[b]tryptanthrin showed better potency than tryptanthrin for reversing adriamycin resistance and down-regulating the level of MDR1 mRNA and protein in MCF7adr cells.…”

Quercetin and Tryptanthrin

“…An extension study by the same group revealed that tryptanthrin is inducing JNK-mediated apoptosis in doxorubicin-resistant MCF-7 cells through the downregulation of GSTpi [97]. Additionally, the intestinal transport profile of tryptanthrin in human epithelial colorectal adenocarcinoma cells was studied in correlation with the potential inhibition of the two proteins involved in drug absorption, namely, the P-glycoprotein (P-gp encoded by MDR1) and multidrug resistance-associated protein 2 (MRP2) [98].…”