Vidya Hebbar

Metabolism, oral bioavailability and pharmacokinetics of chemopreventive kaempferol in rats

The purpose of this study was to compare the hepatic and small intestinal metabolism, and to examine bioavailability and gastro-intestinal first-pass effects, of kaempferol in rats. Liver and small intestinal microsomes fortified with either NADPH or UDPGA were incubated with varying concentrations of kaempferol for up to 120 min. Based on the values of the kinetic constants (K(m) and V(max)), the propensity for UDPGA-dependent conjugation compared with NADPH-dependent oxidative metabolism was higher for both hepatic and small intestinal microsomes. Male Sprague-Dawley rats were administered kaempferol intravenously (i.v.) (10, 25 mg/kg) or orally (100, 250 mg/kg). Gastro-intestinal first-pass effects were observed by collecting portal blood after oral administration of 100 mg/kg kaempferol. Pharmacokinetic parameters were obtained by non-compartmental analysis using WinNonlin. After i.v. administration, the plasma concentration-time profiles for 10 and 25 mg/kg were consistent with high clearance (approximately 3 L/hr/kg) and large volumes of distribution (8-12 L/hr/kg). The disposition was characterized by a terminal half-life value of 3-4 h. After oral administration the plasma concentration-time profiles demonstrated fairly rapid absorption (t(max) approximately 1-2 h). The area under the curve (AUC) values after i.v. and oral doses increased approximately proportional to the dose. The bioavailability (F) was poor at approximately 2%. Analysis of portal plasma after oral administration revealed low to moderate absorption. Taken together, the low F of kaempferol is attributed in part to extensive first-pass metabolism by glucuronidation and other metabolic pathways in the gut and in the liver.

Modulation of activator protein-1 (AP-1) and MAPK pathway by flavonoids in human prostate cancer PC3 cells

In last couple of decades the use of natural compounds like flavonoids as chemopreventive agents has gained much attention. Our current study focuses on identifying chemopreventive flavonoids and their mechanism of action on human prostate cancer cells. Human prostate cancer cells (PC3), stably transfected with activator protein 1 (AP-1) luciferase reporter gene were treated with four main classes of flavonoids namely flavonols, flavones, flavonones, and isoflavones. The maximum AP-1 luciferase induction of about 3 fold over control was observed with 20 μM concentrations of quercetin, chrysin and genistein and 50 μM concentration of kaempferol. At higher concentrations, most of the flavonoids demonstrated inhibition of AP-1 activity. The MTS assay for cell viability at 24 h showed that even at a very high concentration (500 μM), cell death was minimal for most of the flavonoids. To determine the role of MAPK pathway in the induction of AP-1 by flavonoids, Western blot of phospho MAPK proteins was performed. Four out of the eight flavonoids namely kaempferol, apigenin, genistein and naringenin were used for the Western Blot analysis. Induction of phospho-JNK and phospho-ERK activity was observed after two hour incubation of PC3-AP1 cells with flavonoids. However no induction of phospho-p38 activity was observed. Furthermore, pretreating the cells with specific inhibitors of JNK reduced the AP-1 luciferase activity that was induced by genistein while pretreatment with MEK inhibitor reduced the AP-1 luciferase activity induced by kaempferol. The pharmacological inhibitors did not affect the AP-1 luciferase activity induced by apigenin and naringenin. These results suggest the possible involvement of JNK pathway in genistein induced AP-1 activity while the ERK pathway seems to play an important role in kaempferol induced AP-1 activity.

Differential expression of MUC genes in endometrial and cervical tissues and tumors

BackgroundMucin glycoproteins are major components of mucus and are considered an important class of tumor associated antigens. The objective of this study was to investigate the expression of human MUC genes (MUC1, MUC2, MUC5B, MUC5AC and MUC8) in human endometrium and cervix, and to compare and quantitate the expression of MUC genes in normal and cancerous tissues.MethodsSlot blot techniques were used to study the MUC gene expression and quantitation.ResultsOf the five-mucin genes studied, MUC1, MUC5B and MUC8 showed high expression levels in the normal and cancerous endometrial and cervical tissues, MUC2 and MUC5AC showed considerably lower expression. Statistically, higher levels of MUC1, MUC5B and MUC8 were observed in endometrial adenocarcinomas compared to normal tissues. In contrast, only MUC1 levels increased with no significant changes in expression of MUC5B and MUC8 in cervical tumors over normal cervical tissues.ConclusionEndometrial tumors showed increased expression of MUC1, MUC5B and MUC8 over normal tissues. Only MUC1 appears to be increase, in cervical tumors. All the studied tissues showed high and consistent expression of MUC8 mRNA. Low to neglible levels of MUC2 and MUC5AC were observed in all studied endometrial and cervical tissues.