Caffeine induction of sulfotransferases in rat liver and intestine

Influence of methylxanthines isolated from Bancha green tea on the pharmacokinetics of sildenafil in rats

BACKGROUND

Sildenafil is used to treat erectile dysfunction and pulmonary arterial hypertension and is metabolized in the liver mainly by CYP3A4, thus co-administration with drugs or herbal extracts that affect CYP3A4 activity may lead to drug-drug or drug-herb interactions, respectively. The aim of the present study was to evaluate the influence of single and multiple oral doses of methylxanthine fraction, isolated from Bancha green tea leaves on the pharmacokinetics of sildenafil in rats.

METHODS

Rats were given sildenafil alone as well as simultaneously with methylxanthines or ketoconazole. The plasma concentrations of sildenafil were measured with high-performance liquid chromatography method with ultraviolet detection. The pharmacokinetic parameters of sildenafil were calculated by non-compartmental analysis.

RESULTS

Concomitant use of sildenafil with a single oral dose of methylxanthines resulted in a decrease in C_max (p > 0.05), AUC_0-t (p < 0.05) and AUC_0-inf (p < 0.05), while the administration of sildenafil after methylxanthines pretreatment resulted in an increase in C_max (p < 0.0001), AUC_0-t (p < 0.0001) and AUC_0-inf (p < 0.001) compared to the sildenafil group. After co-administration of sildenafil and ketoconazole, a significant increase in C_max, AUC_0-t and AUC_0-inf was observed in both of the experiments.

CONCLUSION

Drug-herb interactions were observed when sildenafil was co-administered with Bancha methylxanthines in rats. Further in vivo studies about the potential drug interactions between sildenafil and methylxanthines, especially caffeine, are needed to clarify mechanisms underlying the observed changes in sildenafil pharmacokinetics.

Innovation in bioanalytical strategies and in vitro drug-drug interaction study approaches in drug discovery

Failure to evaluate actual toxicities of investigational molecules in drug discovery is majorly due to inadequate evaluation of their pharmacokinetics. Limitation of conventional drug metabolism profiling procedure demands advancement of existing approaches. Various techniques such as 3D cell culture system, bio microfluidic OoC model, sandwich culture model is in pipeline to be employed at their full potential in drug discovery phase. Although they outweigh the conventional techniques in various aspects, a more detailed exploration of applicability in terms of automation and high throughput analysis is required. This review extensively discusses various ongoing innovations in bioanalytical techniques. The review also proposed various scientific strategies to be adopted for prior assessment of interaction possibilities in translational drug discovery research.

The Relative Importance of the Small Intestine and the Liver in Phase II Metabolic Transformations and Elimination of p-Nitrophenol Administered in Different Doses in the Rat

Intestinal and hepatic function have been investigated in phase II metabolic reactions and elimination of p-nitrophenol (PNP) in the rat. A jejunal loop was cannulated and recirculated with isotonic solutions containing PNP in different concentrations (0, 20, 100, 500, 1000 µM). Samples were obtained from the perfusate at given intervals. To investigate the metabolic and excretory functions of the liver, the bile duct was cannulated, and the bile was collected. Metabolites of PNP were determined by validated HPLC (high pressure liquid chromatography) methods. The results demonstrated the relative importance of the small intestine and the liver in phase II metabolic transformations and elimination of PNP. There were significant differences between the luminal and biliary appearances of p-nitrophenol-glucuronide (PNP-G) and p-nitrophenol–sulfate (PNP-S). The PNP-G appeared in the intestinal lumen at the lower PNP concentrations (20 µM and 100 µM) at higher rate than in the bile. No significant difference was found between the intestinal and the biliary excretion of PNP-G when PNP was administered at a concentration of 500 µM. However, a reverse ratio of these parameters was observed at the administration of 1000 µM PNP. The results indicated that both the small intestine and the liver might play an important role in phase II metabolic reactions and elimination of PNP. However, the relative importance of the small intestine and the liver can be dependent on the dose of drugs.

Sexual Dimorphism in Drug Metabolism and Pharmacokinetics

Background:

Sex and gender-based differences are observed well beyond the sex organs and affect several physiological and biochemical processes involved in the metabolism of drug molecules. It is essential to understand not only the sex and gender-based differences in the metabolism of the drug but also the molecular mechanisms involved in the regulation of drug metabolism for avoiding sex-related adverse effects of drugs in the human.

Method:

The articles on the sex and gender-based differences in the metabolism of drug molecules were retrieved from the Pub Med database. The articles were classified into the metabolism of the drug molecule, gene expression regulation of drug-metabolizing enzymes, the effect of sex hormones on the metabolism of drug, expression of drugmetabolizing enzymes, etc.

Result:

Several drug molecules are known, which are metabolized differently in males and females. These differences in metabolism may be due to the genomic and non-genomic action of sex hormones. Several other drug molecules still require further evaluation at the molecular level regarding the sex and gender-based differences in their metabolism. Attention is also required at the effect of signaling cascades associated with the metabolism of drug molecules.

Conclusion:

Sex and gender-based differences in the metabolism of drugs exist at various levels and it may be due to the genomic and non-genomic action of sex hormones. Detailed understanding of the effect of sex and related condition on the metabolism of drug molecules will help clinicians to determine the effective therapeutic doses of drugs dependingon the condition of patient and disease.

The effects of oral administration of Cola nitida on the pharmacokinetic profile of metoclopramide in rabbits

BACKGROUND

Cola nitida is commonly chewed in many West African cultures to ease hunger pangs and sometimes for their stimulant and euphoriant qualities. Metoclopramide is a known substrate for P-gp, SULT2A1 and CYP2D6 and studies have revealed that caffeine- a major component of Cola nitida can induce P-glycoprotein (P-gp), SULT2A1 and SULT1A1, hence a possible drug interaction may occur on co-administration. The aim of this study was to investigate the pharmacokinetic interactions of Cola nitida and metoclopramide in rabbits.

METHODS

The study was performed in two stages using five healthy male rabbits with a 1-week washout period between treatments. Stage one involved oral administration of metoclopramide (0.5 mg/kg) alone while in the second stage, metoclopramide (0.5 mg/kg) was administered concurrently with Cola nitida (0.7 mg/kg). Blood samples were collected after each stage at predetermined intervals and analyzed for plasma metoclopramide concentration using HPLC.

RESULTS

Compared with control, the metoclopramide/Cola nitida co-administration produced a decrease in plasma concentration of metoclopramide at all the time intervals except at the 7th hour. The following pharmacokinetic parameters were also decreased: area under the curve (51%), peak plasma concentration (39%), half-life (51%); while an increase in elimination rate constant (113%) and clearance rate (98%) were noted indicating rapid elimination of the drug. A minimal decrease in absorption rate (10%) was also observed.

CONCLUSIONS

The results of this study reveal a possible herb-drug interaction between Cola nitida and metoclopramide.

Identification of Catalposide Metabolites in Human Liver and Intestinal Preparations and Characterization of the Relevant Sulfotransferase, UDP-glucuronosyltransferase, and Carboxylesterase Enzymes

Catalposide, an active component of Veronica species such as Catalpa ovata and Pseudolysimachion lingifolium, exhibits anti-inflammatory, antinociceptic, anti-oxidant, hepatoprotective, and cytostatic activities. We characterized the in vitro metabolic pathways of catalposide to predict its pharmacokinetics. Catalposide was metabolized to catalposide sulfate (M1), 4-hydroxybenzoic acid (M2), 4-hydroxybenzoic acid glucuronide (M3), and catalposide glucuronide (M4) by human hepatocytes, liver S9 fractions, and intestinal microsomes. M1 formation from catalposide was catalyzed by sulfotransferases (SULTs) 1C4, SULT1A1*1, SULT1A1*2, and SULT1E1. Catalposide glucuronidation to M4 was catalyzed by gastrointestine-specific UDP-glucuronosyltransferases (UGTs) 1A8 and UGT1A10; M4 was not detected after incubation of catalposide with human liver preparations. Hydrolysis of catalposide to M2 was catalyzed by carboxylesterases (CESs) 1 and 2, and M2 was further metabolized to M3 by UGT1A6 and UGT1A9 enzymes. Catalposide was also metabolized in extrahepatic tissues; genetic polymorphisms of the carboxylesterase (CES), UDP-glucuronosyltransferase (UGT), and sulfotransferase (SULT) enzymes responsible for catalposide metabolism may cause inter-individual variability in terms of catalposide pharmacokinetics.

Repeated restraint stress upregulates rat sulfotransferase 1A1

BackgroundSulfotransferases (SULTs) are phase II drug-metabolizing enzymes. SULTs also regulate the biological activities of biological signaling molecules, such as various hormones, bile acids, and monoamine neurotransmitters; therefore, they play critical roles in the endocrine and nervous systems. People are subject to various kinds of physical, chemical, toxicological, physiological, and psychological stresses at one time or another. The study of the effects produced by stress may lead to finding novel remedies for many disease conditions. The effect of repeated restraint stress on rat SULT expression has not been studied. MethodsThis study involves the effect of repeated restraint stress on SULT1A1 expressions. Male Sprague-Dawley rats (n=4) were subjected to repeated restraint stress 2 h/day for 7 days. Protein and RNA expression of SULT1A1 were analyzed by western blot and quantitative real time reverse transcription polymerase chain reaction, respectively, in important tissues. ResultsWe observed that repeated restraint stress increased the expression of SULT1A1 in the liver, adrenal glands, cerebellum, hypothalamus, and cerebral cortex in male rats. Patterns of enhanced expression were observed at both mRNA and protein level, indicating that repeated restraint stress stimulates enzyme expression at the transcriptional level. ConclusionsChanges of SULT1A1 expression in important tissues caused by repeated restraint stress will have a significant effect on drug metabolism and xenobiotics detoxification. The significant changes in endocrine glands and brain sections may also cause disturbances in hormone homeostasis, therefore leading to disease conditions. This report provides clues for the understanding of the effect of stresses on health.

Multiple UDP-Glucuronosyltransferase and Sulfotransferase Enzymes are Responsible for the Metabolism of Verproside in Human Liver Preparations

Verproside, an active iridoid glycoside component of Veronica species, such as Pseudolysimachion rotundum var. subintegrum and Veronica anagallis-aquatica, possesses anti-asthma, anti-inflammatory, anti-nociceptive, antioxidant, and cytostatic activities. Verproside is metabolized into nine metabolites in human hepatocytes: verproside glucuronides (M1, M2) via glucuronidation, verproside sulfate (M3) via sulfation, picroside II (M4) and isovanilloylcatalpol (M5) via O-methylation, M4 glucuronide (M6) and M4 sulfate (M8) via further glucuronidation and sulfation of M4, and M5 glucuronide (M7) and M5 sulfate (M9) via further glucuronidation and sulfation of M5. Drug-metabolizing enzymes responsible for verproside metabolism, including sulfotransferase (SULT) and UDP-glucuronosyltransferase (UGT), were characterized. The formation of verproside glucuronides (M1, M2), isovanilloylcatalpol glucuronide (M7), and picroside II glucuronide (M6) was catalyzed by commonly expressed UGT1A1 and UGT1A9 and gastrointestinal-specific UGT1A7, UGT1A8, and UGT1A10, consistent with the higher intrinsic clearance values for the formation of M1, M2, M6, and M7 in human intestinal microsomes compared with those in liver microsomes. The formation of verproside sulfate (M3) and M5 sulfate (M9) from verproside and isovanilloylcatalpol (M5), respectively, was catalyzed by SULT1A1. Metabolism of picroside II (M4) into M4 sulfate (M8) was catalyzed by SULT1A1, SULT1E1, SULT1A2, SULT1A3, and SULT1C4. Based on these results, the pharmacokinetics of verproside may be affected by the co-administration of relevant UGT and SULT inhibitors or inducers.

Guarana (Paullinia cupana Mart.) attenuates methylmercury-induced toxicity in Caenorhabditis elegans

The influence of routine guarana (Paullinia cupana) consumption on apparent tolerance to mercury intoxication has been proposed. The present study investigated this hypothesis in Caenorhabditis elegans, a suitable experimental model for studies in toxicology. Wild type (WT) and skn-1 (ok2315) worm strains were pretreated with guarana ethanolic extract (GEE) from larvae 1 (L1) to L4 stage and then exposed for 6 hours to methylmercury (MeHg). The analyses included evaluation of GEE's effects on lethality, developmental delay, feeding, locomotion, gene expression (sod-3, gst-4, sir-2.1, hsf-1, snn-1, mtl-1, mtl-2, aat-1, aat-2 and aat-3) and antioxidant activity. GEE pre-treatment had no aberrant effects on WT worms exposed to MeHg, and protected skn-1 (ok2315) worms, which are more susceptible to environmental stresses. Protective effects of GEE might be dependent on modulation of genes other than those directly involved in antioxidant activity. GEE increased the expression of genes involved in metal transport (aat-2), metal detoxification (mtl-1 and mtl-2) and antioxidant responses (sir-2.1 and sod-3). Thus, routine consumption of guarana might be beneficial in protecting against MeHg-induced toxicity.

Gender-Dependent Pharmacokinetics of Veratramine in Rats: In Vivo and In Vitro Evidence

Veratramine, a major alkaloid from Veratrum nigrum L., has distinct anti-tumor and anti-hypertension effects. Our previous study indicated that veratramine had severe toxicity toward male rats. In order to elucidate the underling mechanism, in vivo pharmacokinetic experiments and in vitro mechanistic studies have been conducted. Veratramine was administrated to male and female rats intravenously via the jugular vein at a dose of 50 μg/kg or orally via gavage at 20 mg/kg. As a result, significant pharmacokinetic differences were observed between male and female rats after oral administration with much lower concentrations of veratramine and 7-hydroxyl-veratramine and higher concentrations of veratramine-3-O-sulfate found in the plasma and urine of female rats. The absolute bioavailability of veratramine was 0.9% in female rats and 22.5% in male rats. Further experiments of veratramine on Caco-2 cell monolayer model and in vitro incubation with GI content or rat intestinal subcellular fractions demonstrated that its efficient passive diffusion mediated absorption with minimal intestinal metabolism, suggesting no gender-related difference during its absorption process. When veratramine was incubated with male or female rat liver microsomes/cytosols, significant male-predominant formation of 7-hydroxyl-veratramine and female-predominant formation of veratramine-3-O-sulfate were observed. In conclusion, the significant gender-dependent hepatic metabolism of veratramine could be the major contributor to its gender-dependent pharmacokinetics.

Modulation of Metabolic Detoxification Pathways Using Foods and Food-Derived Components: A Scientific Review with Clinical Application

Research into human biotransformation and elimination systems continues to evolve. Various clinical and in vivo studies have been undertaken to evaluate the effects of foods and food-derived components on the activity of detoxification pathways, including phase I cytochrome P450 enzymes, phase II conjugation enzymes, Nrf2 signaling, and metallothionein. This review summarizes the research in this area to date, highlighting the potential for foods and nutrients to support and/or modulate detoxification functions. Clinical applications to alter detoxification pathway activity and improve patient outcomes are considered, drawing on the growing understanding of the relationship between detoxification functions and different disease states, genetic polymorphisms, and drug-nutrient interactions. Some caution is recommended, however, due to the limitations of current research as well as indications that many nutrients exert biphasic, dose-dependent effects and that genetic polymorphisms may alter outcomes. A whole-foods approach may, therefore, be prudent.

Ethanol up-regulates phenol sulfotransferase (SULT1A1) and hydroxysteroid sulfotransferase (SULT2A1) in rat liver and intestine

Ethanol-consumption impairs physiological-efficiency/endurance, expedites senescence. Impaired-regulations of steroids/biomolecules link these processes. Steroids are catabolized by cytosolic-sulfotransferases (SULTs). Ethanol-induction of eukaryotic-SULTs-expression is scanty. Plant (Brassica-napus) steroid-sulfotransferase; BNST3/BNST4 (gene/BNST) is highly ethanol-inducible (protein/mRNA). Resembling mammalian-SULTs catalytic-mechanism BNSTs show broad substrate-specificities (mammalian-steroids; estradiol/dehydroepiandrosterone/pregnanolone). Recently, ethanol-regulation of SULTs-expression is verified in rat liver/intestine/cultured human-hepatocarcinoma (Hep-G2) cells at enzyme-activity/protein-expression (Western-blot) level. Here, two week's ethanol ingestion by male rat significantly increased SULT2A1 in their liver/intestine (p < 0.05-p < 0.001) and phenol-sulfotransferase (SULT1A1) in intestine (p < 0.001) at enzyme-activity/protein levels. In human cells, ethanol significantly (2-fold) increased hSULT1A1/hSULT1E (2-3 fold) protein expressions paralleling their enzymatic-activities (p < 0.05-p < 0.01). The earlier finding of alcohol-association to the physiological impairment may be corroborated by our present findings. Inductions of SULT-expressions by ethanol have significant physiological/pharmacological consequences.

Toward systems epidemiology of coffee and health

PURPOSE OF REVIEW

Coffee is one of the most widely consumed beverages in the world and has been associated with many health conditions. This review examines the limitations of the classic epidemiological approach to studies of coffee and health, and describes the progress in systems epidemiology of coffee and its correlated constituent, caffeine. Implications and applications of this growing body of knowledge are also discussed.

RECENT FINDINGS

Population-based metabolomic studies of coffee replicate coffee-metabolite correlations observed in clinical settings but have also identified novel metabolites of coffee response, such as specific sphingomyelin derivatives and acylcarnitines. Genome-wide analyses of self-reported coffee and caffeine intake and serum levels of caffeine support an overwhelming role for caffeine in modulating the coffee consumption behavior. Interindividual variation in the physiological exposure or response to any of the many chemicals present in coffee may alter the persistence and magnitude of their effects. It is thus imperative that future studies of coffee and health account for this variation.

SUMMARY

Systems epidemiological approaches promise to inform causality, parse the constituents of coffee responsible for health effects, and identify the subgroups most likely to benefit from increasing or decreasing coffee consumption.

Pharmacogenomics, pharmacokinetics and pharmacodynamics: interaction with biological differences between men and women

Pharmacological response depends on multiple factors and one of them is sex-gender. Data on the specific effects of sex-gender on pharmacokinetics, as well as the safety and efficacy of numerous medications, are beginning to emerge. Nevertheless, the recruitment of women for clinical research is inadequate, especially during the first phases. In general, pharmacokinetic differences between males and females are more numerous and consistent than disparities in pharmacodynamics. However, sex-gender pharmacodynamic differences are now increasingly being identified at the molecular level. It is now even becoming apparent that sex-gender influences pharmacogenomics and pharmacogenetics. Sex-related differences have been reported for several parameters, and it is consistently shown that women have a worse safety profile, with drug adverse reactions being more frequent and severe in women than in men. Overall, the pharmacological status of women is less well studied than that of men and deserves much more attention. The design of clinical and preclinical studies should have a sex-gender-based approach with the aim of tailoring therapies to an individual's needs and concerns.