digoxin and hypericin

The use of herbal supplements and medicines is rapidly growing as most people consider them as being of natural origin and therefore being safe. However, a significant number of patients combine herbal remedies with prescription medications and there is a growing evidence for interactions of drugs with herbal remedies or single compounds originating from plants. Beside metabolic interactions particularly on the level of barrier tissues being equipped with a multitude of transport proteins such interactions are reason of rising concern. One barrier of particular interest is the blood brain barrier separating blood circulation and central nervous system and protecting the brain from potentially toxic metabolites and xenobiotics. The present review gives a condensed overview about structure and function of the blood-brain barrier and interactions of selected compounds originating from natural products with transport proteins in the barrier.

Topics: Animals; Anthracenes; Antineoplastic Agents, Phytogenic; Biological Transport; Blood-Brain Barrier; Digoxin; Flavonoids; Herb-Drug Interactions; Humans; Perylene

Continuous use of St. John's wort decreases the bioavailabilities of a variety of drugs. This interaction is attributed to the induction of cytochrome P450 3A4 and/or P-glycoprotein. In this study, we aimed to examine the chronic effects of St. John's wort and its constituents, hyperforin and hypericin, on the expression and function of P-glycoprotein in an intestinal cell line, LS 180. We also examined the acute inhibitory effect of St. John's wort on P-glycoprotein by using LLC-GA5-COL150 cells, which overexpress P-glycoprotein. St. John's wort and hyperforin but not hypericin increased the expression of P-glycoprotein in LS 180 cells. Removal of St. John's wort resulted in a restoration of P-glycoprotein level within 48 h. The content of hyperforin in St. John's wort extract was high enough to induce P-glycoprotein, suggesting that the induction of P-glycoprotein by St. John's wort can be almost attributable to hyperforin. The LS 180 cells chronically exposed to St. John's wort or hyperforin exhibited the increase in the function of P-glycoprotein assessed by the efflux of digoxin, and the activities correlated well with P-glycoprotein level. On the other hand, St. John's wort and its two constituents did not show any acute effect on P-glycoprotein-mediated transport of digoxin. St. John's wort induced P-glycoprotein in vitro that functions as a drug efflux pump. Hyperforin is considered to be a primary cause of the inductive effect of St. John's wort. Long-term administration of St. John's wort may cause clinically significant decrease in the plasma concentrations of P-glycoprotein substrates.

Topics: Adenocarcinoma; Animals; Anthracenes; ATP Binding Cassette Transporter, Subfamily B, Member 1; Biological Transport; Bridged Bicyclo Compounds; Cell Line, Tumor; Colonic Neoplasms; Digoxin; Humans; Hypericum; LLC-PK1 Cells; Perylene; Phloroglucinol; Plant Extracts; Rifampin; Swine; Terpenes; Transfection