ß-Glucuronidase- and OATP2B1-mediated drug interaction of scutellarin in Dengzhan Xixin Injection: A formulation aspect.

Scutellarin is the major and active constituent of Dengzhan Xixin Injection (DZXX), a traditional Chinese medicine prepared from the aqueous extract of Erigeron breviscapus and widely used for the treatment of various cerebrovascular diseases in clinic. In present study, the possible pharmacokinetic differences of scutellarin after intravenous administration of scutellarin alone or DZXX were explored. Additional, the potential roles of ß-glucuronidase (GLU) and OATP2B1 in drug-drug interaction (DDI) between scutellarin and constituents of DZXX were further evaluated in vitro. The plasma concentration, urinary and biliary excretion of scutellarin in rats after administration of DZXX, were significantly higher than those received scutellarin, while pharmacokinetic profile of Apigenin 7-O-glucuronide (AG) in rats was similar no matter AG or DZXX group. Furthermore, higher concentration in brain and plasma, however, lower level of scutellarin in intestine were observed after intravenous administration of DZXX. Finally, AG and caffeoylquinic acid esters were found to significantly inhibit GLU and OATP2B1 in vitro, which might explain, at least in part, the pharmacokinetic DDI between scutellarin and other chemical constituents in DZXX. The findings provided deep insight into the prescription-formulating principle in DZXX for treating the cerebrovascular diseases.

Organic anion transporter 3 (OAT3)-mediated transport of dicaffeoylquinic acids and prediction of potential drug-drug interaction.

Dicaffeoylquinic acids (DCQAs) are widely distributed in daily food and herb medicine (such as Dengzhanxiyin injection) with multiple health benefits and pharmacological activities. However, drug-drug Interactions (DDIs) between DCQAs and possible concomitant drugs were not fully understood in clinic. The purpose of present study was to investigate the role of organic anion transporters (OATs) in the transport of DCQAs and to explore the potential clinical DDIs using in vitro transporter assays. Uptake study using hOAT1/hOAT3-transfected HEK293 cells revealed that none of DCQAs was OAT1 substrate, while 3,4-DCQA, 3,5-DCQA, and 4,5-DCQA were substrates of OAT3 with Km values of 119.7 ±â€¯28.8, 269.3 ±â€¯129.5 and 53.2 ±â€¯32.1 µM, respectively. The docking analysis revealed that 3,4-DCQA, 3,5-DCQA, and 4,5-DCQA were effectively embedded in the active site of OAT3 and fitted well with the cavity in three-dimensional space. Moreover, the classical substrates/inhibitors of OAT decreased the accumulation of 3,4-DCQA, 3,5-DCQA, and 4,5-DCQA in kidney slices, suggesting potential DDI risks with co-administration of substrate drugs of OAT. In fact, antivirals, antibiotics, neuroprotective agents, and PPIs (proton pump inhibitors) all showed varying degrees of inhibition of OAT3-mediated uptake of 3,4-DCQA, 3,5-DCQA, and 4,5-DCQA in vitro. For cefaclor, ceftizoxime, pantoprazole, and zidovudine, in particular, their IC50 values were <10 times the maximal free plasma concentration, indicating potential clinically relevant DDIs when used together with DCQAs. These findings provided useful information for the prediction of DDIs between DCQAs and OAT3 inhibitors, and rational application of herbal medicines containing DCQAs in clinic.

Increase in DPP-IV in the intestine, liver and kidney of the rat treated with high fat diet and streptozotocin.

High fat diet or insulin deficiency is commonly seen in Type II diabetes, while the mechanism remains unclear. To test our hypothesis that DPP-IV contributes to Type II diabetes, we examined the expression and activity of DPP-IV in rats (n=8 to each group) treated for 12 weeks with 3 separate diets: a) normal control; b) a high fat diet; and c) a high fat diet plus streptozotocin, a chemical for induction of insulin-deficient diabetes. Compared to rats on the normal diet, the rats with a high fat diet significantly increased DPP-IV's expression and activity about 142-152% in the intestine (P<0.05) and 153-240% in kidneys (P<0.05), but there was no change in the liver. Administration of streptozotocin to the rats treated with the high fat diet showed an insufficient insulin secretion and higher blood glucose in response to glucose/insulin tolerance test, and an increase in expression of DPP-IV and activity by 188-242% in the intestine (P<0.01); 191-225% in liver (P<0.01); and 211-321% in the kidneys (P<0.01). Immunohistochemistry studies confirmed the above results, showing increased DPP-IV immunostaining localized primarily in intestinal epithelium, hepatocytes and renal tubular cells. This study, for the first time reports an increase in DPP-IV associated with a high fat diet, as well as in the combination of a high fat diet with an insulin deficiency. Since both high fat diet and insulin deficiency are closely linked with etiology of Type II diabetes, the evidence in this study suggests a role of DPP-IV in development of Type II diabetes.