Sertraline inhibits the transport of PAT1 substrates in vivo and in vitro.

BACKGROUND AND PURPOSE: Intestinal nutrient transporters may mediate the uptake of drugs. The aim of this study was to investigate whether sertraline interacts with the intestinal proton-coupled amino acid transporter 1 PAT1 (SLC36A1). EXPERIMENTAL APPROACH: In vitro investigations of interactions between sertraline and human (h)PAT1, hSGLT1 (sodium-glucose linked transporter 1) and hPepT1 (proton-coupled di-/tri-peptide transporter 1) were conducted in Caco-2 cells using radiolabelled substrates. In vivo pharmacokinetic investigations were conducted in male Sprague-Dawley rats using gaboxadol (10 mg·kg(-1), p.o.) as a PAT1 substrate and sertraline (0-30.6 mg·kg(-1)). Gaboxadol was quantified by hydrophilic interaction chromatography followed by MS/MS detection. KEY RESULTS: Sertraline inhibited hPAT1-mediated L-[(3)H]-Pro uptake in Caco-2 cells. This interaction between sertraline and PAT1 appeared to be non-competitive. The uptake of the hSGLT1 substrate [(14)C]-α-methyl-D-glycopyranoside and the hPepT1 substrate [(14)C]-Gly-Sar in Caco-2 cells was also decreased in the presence of 0.3 mM sertraline. In rats, the administration of sertraline (0.1-10 mM, corresponding to 0.3-30.6 mg·kg(-1), p.o.) significantly reduced the maximal gaboxadol plasma concentration and AUC after its administration p.o. CONCLUSIONS AND IMPLICATIONS: Sertraline is an apparent non-competitive inhibitor of hPAT1-mediated transport in vitro. This inhibitory effect of sertraline is not specific to hPAT1 as substrate transport via hPepT1 and hSGLT1 was also reduced in the presence of sertraline. In vivo, sertraline reduced the amount of gaboxadol absorbed, suggesting that the inhibitory effect of sertraline on PAT1 occurs both in vitro and in vivo. Hence, sertraline could alter the bioavailability of drugs absorbed via PAT1.

Function and expression of the proton-coupled amino acid transporter PAT1 along the rat gastrointestinal tract: implications for intestinal absorption of gaboxadol.

BACKGROUND AND PURPOSE: Intestinal absorption via membrane transporters may determine the pharmacokinetics of drug compounds. The hypothesis is that oral absorption of gaboxadol (4,5,6,7-tetrahydroisoxazolo [5,4-c] pyridine-3-ol) in rats occurs via the proton-coupled amino acid transporter, rPAT1 (encoded by the gene rSlc36a1). Consequently, we aimed to elucidate the in vivo role of rPAT1 in the absorption of gaboxadol from various intestinal segments obtained from Sprague-Dawley rats. EXPERIMENTAL APPROACH: The absorption of gaboxadol was investigated following its administration into four different intestinal segments. The intestinal expression of rSlc36a1 mRNA was measured by quantitative real-time PCR. Furthermore, the hPAT1-/rPAT1-mediated transport of gaboxadol or L-proline was studied in hPAT1-expressing Xenopus laevis oocytes, Caco-2 cell monolayers and excised segments of the rat intestine. KEY RESULTS: The absorption fraction of gaboxadol was high (81.3-91.3%) following its administration into the stomach, duodenum and jejunum, but low (4.2%) after administration into the colon. The pharmacokinetics of gaboxadol were modified by the co-administration of L-tryptophan (an hPAT1 inhibitor) and L-proline (an hPAT1 substrate). The in vitro carrier-mediated uptake rate of L-proline in the excised intestinal segments was highest in the mid jejunum and lowest in the colon. The in vitro uptake and the in vivo absorption correlated with the expression of rSlc36a1 mRNA along the rat intestine. CONCLUSIONS AND IMPLICATIONS: These results suggest that PAT1 mediates the intestinal absorption of gaboxadol and therefore determines its oral bioavailability. This has implications for the in vivo role of PAT1 and may have an influence on the design of pharmaceutical formulations of PAT1 substrates.

Green tea extract only affects markers of oxidative status postprandially: lasting antioxidant effect of flavonoid-free diet.

Epidemiological studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease and cancer. The objective of the present study was to investigate the effect of green tea extract (GTE) used as a food antioxidant on markers of oxidative status after dietary depletion of flavonoids and catechins. The study was designed as a 2 x 3 weeks blinded human cross-over intervention study (eight smokers, eight non-smokers) with GTE corresponding to a daily intake of 18.6 mg catechins/d. The GTE was incorporated into meat patties and consumed with a strictly controlled diet otherwise low in flavonoids. GTE intervention increased plasma antioxidant capacity from 1.35 to 1.56 (P<0.02) in postprandially collected plasma, most prominently in smokers. The intervention did not significantly affect markers in fasting blood samples, including plasma or haemoglobin protein oxidation, plasma oxidation lagtime, or activities of the erythrocyte superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase. Neither were fasting plasma triacylglycerol, cholesterol, alpha-tocopherol, retinol, beta-carotene, or ascorbic acid affected by intervention. Urinary 8-oxo-deoxyguanosine excretion was also unaffected. Catechins from the extract were excreted into urine with a half-life of less than 2 h in accordance with the short-term effects on plasma antioxidant capacity. Since no long-term effects of GTE were observed, the study essentially served as a fruit and vegetables depletion study. The overall effect of the 10-week period without dietary fruits and vegetables was a decrease in oxidative damage to DNA, blood proteins, and plasma lipids, concomitantly with marked changes in antioxidative defence.

Optimised extraction of folic acid from multivitamin-mineral preparations for liquid chromatographic analysis.

Degradation of folic acid may occur during extraction of multivitamin-mineral preparations. The degradation may be caused by presence of ions such as Fe3+ and Cu2+, however, the buffer composition may also be critical. This study presents an optimised extraction procedure tested on 24 different products of multivitamin-mineral tablets. The present method yielded mean recoveries of 97% (n = 20) for folic acid and prevented degradation of folic acid in at least 24 h in extracts from multivitamin-mineral tablets.

Improved method for simultaneous determination of ascorbic acid and dehydroascorbic acid, isoascorbic acid and dehydroisoascorbic acid in food and biological samples.

The total vitamin C amount in different food and plasma samples was determined by a dual detection system, after HPLC separation, with direct detection of ascorbic acid and indirect fluorimetric detection of dehydroascorbic acid after a post-column O-phenyldiamine derivatisation. The two active forms of vitamin C and their D-isomers were separated within 10 min. The repeatability was determined by measurement of several fruits and vegetables and ranged from 0.3 to 1.9% (relative standard deviation) for vitamin C. The reproducibility, based on double determinations, ranged from 1.9 to 3.6% for vitamin C, depending on the matrix. The reproducibility, based on several determinations of reference materials, ranged from 2.4 to 3.7% for ascorbic acid and from 4.3 to 5.8% for dehydroascorbic acid, again depending on the matrix.

Effects of dietary broccoli on human drug metabolising activity.

Eighteen volunteers received 500 g fresh broccoli every day for 12 days after a 6-day period of standard diet. The activity of CYP1A2, CYP2E1 and the estrone 2 and 16alpha-hydroxylation were determined prior to and after the broccoli diet. The average activity of CYP1A2 and the average 2/16alpha-hydroxyestrone ratio were increased 19% (P < 0.0005) and 29.5% (P < 0.05), respectively; however, no effects were observed on the CYP2E1 activity.

Effects of dietary broccoli on human in vivo drug metabolizing enzymes: evaluation of caffeine, oestrone and chlorzoxazone metabolism.

Ingestion of cruciferous vegetables may prevent chemically induced carcinogenesis by their influence on specific cytochrome P450 enzymes (CYP) and phase II drug metabolizing enzymes in humans and rodents. Thus CYP enzymes are involved in transformation of procarcinogens, mutagens, steroid hormones and a large variety of other endogenous and exogenous components. In order to learn more about the influence of cruciferous vegetables on drug metabolizing enzymes in man two CYP enzymes previously suggested to be induced by vegetables were selected in an in vivo experiment in humans. Sixteen healthy non-smoking subjects, two females and 14 males, were exposed to three different types of diets and afterwards assayed for CYP1A2 catalysed caffeine metabolites and for CYP2E1 catalysed 6-hydroxylation of chlorzoxazone. Further, 2-hydroxyoestrone:16 alpha-hydroxylation ratios were determined in urine by means of a monoclonal antibody-based enzyme immunoassay. The three dietary periods were: (A) a customary home diet; (B) a 6 day standard diet avoiding well-known dietary inducers and inhibitors of CYP; (C) a 12 day dietary supplement to the standard diet of 500 g/day broccoli. The average 6-hydroxychlorzoxazone:chlorzoxazone ratio decreased by 21% (P < 0.05) after diet B compared with diet A in a 2 h plasma sample after ingestion of 500 mg chlorzoxazone. The ratio increased by 19% after diet C, however, this was not statistically significant. The caffeine metabolic ratio (CMR) was determined in urine 6 h after ingestion of 100 mg caffeine. The mean CMR increased by 5.5% when changing from diet A to diet B. When shifting to diet C the mean CMR increased a further 19% (P < 0.0005). The average 2-hydroxyoestrone:16 alpha-hydroxyoestrone ratio decreased by 1.3% when comparing diet A with diet B. Daily broccoli intake increased the ratio by 29.5% (P < 0.05). A low correlation of CMR with the 2-hydroxyoestrone:16 alpha-hydroxyoestrone ratio indicates that human CYP1A2 and other CYP enzymes involved in oestrone 2-hydroxylation are induced by dietary broccoli. On the other hand, the catalytic activity of CYP2E1 is not affected to the same degree by dietary broccoli.

Dietary effect on mixed function P450 1A2 activity assayed by estimation of caffeine metabolism in man.

Two studies were performed in order to evaluate cytochrome P450 1A2 mediated caffeine metabolism during different nutritional conditions. 1. In the first study, 23 healthy male non-smokers, mean age 25, changed from a customary mixed diet to a standard diet in 6 days. The 6 day's standard diet was based on bread, potatoes, rice and boiled meat. Thus, broccoli, cabbage and other cruciferous vegetables, spinach, leeks, onion, parsley, grapefruit, toasted bread, fried and charcoal grilled food, smoked fish and meat, ham and sausages were avoided. 2. In the second study, 33 healthy non-smoking subjects, 24 men and nine women mean age 25 years, volunteered. The study was designed to compare a customary home dietary period with the 6 day period of low dietary P450 induction and with a 5 day supplementary dietary period, i.e. ingestion of known dietary inducers. None of the women were using oral contraceptives or were pregnant during the experimental period. In the period of diet supplementation, the volunteers received charcoal grilled hamburger as a supplement to the standard low induction diet for lunch for 5 days. The hamburgers were made with 150 g beef (18-20% fat) and were grilled on charcoal for 10 min on each side until they were 'well done'. In the present study P450 1A2 activity was estimated from the caffeine metabolic ratio, the so-called CYP 1A2 index:(AFMU + 1-MX + 1-MU/ 17 -DMU) of the caffeine metabolites formed after oral ingestion of 200 mg caffeine. Urine was collected 4-8 h after caffeine ingestion in study 1 and 5 h after caffeine ingestion in study 2. In study 1 the CYP 1A2 index decreased from 4.28 +/- 0.98 in the customary home dietary period to 3.87 +/- 0.69 in the standard dietary period corresponding to 10.6% (P < 0.06) decrease in the CYP 1A2 index. In study 2 the CYP 1A2 index decreased from 4.47 +/- 1.76 in the customary home dietary period to 3.90 +/- 1.12 in the standard dietary period corresponding to a 14.6% decrease (P < 0.2) in P450 1A2 activity. The female subjects had a mean index value of 3.89 +/- 1.14 which was 16.8% (P = 0.09) lower than the mean male index value of 4.68 +/- 1.76 during the home dietary period. After the 5 day period with charcoal grilled hamburgers as a dietary supplement, the CYP 1A2 index increased to almost the same level as in the customary home dietary period. The index increased to 4.45 +/- 1.57 in the whole group of volunteers, corresponding to a 14.1% (P < 0.05) increase. The mean increase in the CYP 1A2 index covered a large inter-individual variation in response to ingestion of charcoal grilled meat ranging from a 29% decrease to a 147% increase.

Studies on immunity to mouse sarcomas using the tumor-cell neutralization test.

Statistical analysis of the results of tumor-cell neutralization (Winn) tests has been presented in a refined manner using three variables: tumor incidence, time to palpable tumor, and growth rate. The concept of relative risk and the Z statistic were used to describe the latter two variables. This analysis is then applied to a particular experiment. Lymphocytes sensitized in vitro were compared with specifically immune lymphocytes and were found to facilitate the growth rate. Further applications of this analysis are discussed.

In vitro generation of primary and secondary cytotoxic cell-mediated immune responses to chemically induced mouse sarcomas.

Mixtures of lymph node and spleen cells from normal (untreated) BALB/c mice and from BALB/c mice whose syngeneic tumors had been excised 7-28 days previously ("tumor-excised mice"), were sensitized in vitro by cultivation for 9 days with cells from syngeneic, methylcholanthrene-induced sarcomas. The in vitro-sensitized lymphoid cells were tested in a 36-h microcytotoxicity assay for reactivity against target cells carrying the sensitizing tumor antigens, as well as against control target cells lacking these antigens. After co-cultivation with tumor cells, lymphoid cells from both normal and tumor-excised mice were cytotoxic to tumor cells carrying the sensitizing antigens. The cytotoxicity was generally specific, and occurred at low effector: target cell ratios (in some experiments down to 1:1). When lymphoid cells from tumor-excised mice were exposed in vitro for 9 days to cells carrying the same antigens as those which were originally present on the surgical excised tumors, the effector cells obtained gave a dose-dependent cytotoxic response suggestive of a linear relationship. When lymphoid cells from normal mice were similarly sensitized for 9 days, specifically cytotoxic lymphoid cells were generated but no linear dose-dependent response was detected.

Different responses of lymphoid cells from tumor-bearing as compared to tumor-immunized mice when sensitized to tumor specific antigens in vitro.

Lymphoid cells from spleen and lymph nodes of BALB/c mice were sensitized in vitro by cocultivation with cells from syngeneic methylcholanthrene-induced sarcomas. The donor mice were either immunized in vivo by tumor transplantation followed by excision ("tumor-excised mice") or were carrying a progressively growing tumor ("tumor-bearing mice"). The cell-mediated immune response of the sensitized cells was compared by a 36-hr microcytotoxicity assay. Lymphoid cells from tumor-excised mice were cytotoxic when tested after 3 days and also after 6 days of sensitization in vitro. Lymphoid cells from tumor-bearing mice were cytotoxic to cells of the tumor borne when tested after 3 days in culture. However, the cytotoxic effect was lost after 6 days of contact with the sensitizing tumor in vitro. Preliminary data suggest that the cultured lymphoid cells of tumor-bearing mice which have lost cytotoxicity, can suppress the reactivity of in vitro sensitized lymphoid cells from tumor-excised mice.

Specific stimulatory and cytotoxic effects of lymphocytes sensitized in vitro to either alloantigens or tumor antigens.

Lymph node cells (LNC) or spleen cells from normal BALB/c mice were sensitized in vitro by co-cultivation with mitomycin C-treated allogeneic sarcoma cells, and their reactivity measured with a microcytotoxicity assay. Following 5 days of sensitization, a specific cytotoxic effect against tumor cells carrying the sensitizing alloantigens was observed; this is in agreement with previously published findings. Lymphoid cells tested after 3 days of sensitization, however, specifically increased the number of target cells remaining in the Microtest plates at the conclusion of the microcytotoxicity assays. LNC from normal BALB/c mice were also sensitized in vitro against tumor specific antigens using four different methylcholanthrene-induced sarcomas of BALB/c origin. After 6 days of sensitization the LNC were specifically cytotoxic for the immunizing tumor cell line. After 3 days of sensitization, however, the LNC gave a specific increase of the number of remaining target tumor cells.