Cytochrome P450 mRNA Expression Research Articles

Effects of fluoroquinolones on CYP4501A and 3A in male broilers

The inhibitory effects of fluoroquinolones on the enzyme activity, protein levels and mRNA expression of liver cytochrome P450 (CYP) 1A and 3A were investigated in male broiler chicks. Enrofloxacin (20 mg/kg), sarafloxacin (8 mg/kg) and marbofloxacin (5.5 mg/kg) were administrated in drinking water for 7 consecutive days. A cocktail of the probe drugs caffeine and dapsone was used to determine CYP1A and 3A activity. Western blot analysis and real-time PCR were used to determine the effects on protein levels of CYP1A and 3A, and on CYP1A4, 1A5, 3A37 mRNA levels. Enrofloxacin increased the half-life of elimination for both caffeine and dapsone, and decreased expression of CYP1A and 3A protein. Marbofloxacin decreased the metabolism of caffeine and expression of CYP1A protein. However, no change in mRNA expression was observed for any treatment group. This suggested that high doses of enrofloxacin and marbofloxacin, but not sarafloxacin, inhibit CYP in chick liver raising the possibility of drug–drug interaction when using these compounds.

NaHS ameliorates diabetic vascular injury by correcting depressed connexin 43 and 40 in the vasculature in streptozotocin-injected rats

Cardiovascular complication contributes an important role to morbidity and mortality in patients with diabetes. We hypothesized that these abnormalities are mainly mediated by oxidative stress, endothelial dysfunction and impaired intracellular communications. Thus, we examined vasoactivity and expression of connexin (Cx) 43 and 40, protein kinase C-epsilon (PKCepsilon) and NADPH oxidase of the vasculature of thoracic aorta in streptozotocin (STZ)-injected rats, and whether NaHS could reverse these abnormalities compared with aminoguanidine. Male Sprague-Dawley rats were administered with STZ (60 mg/kg, i.p.) to induce diabetes. Diabetic rats were divided into untreated and treated groups in the 5th-8th week and intervention with either NaHS (5 mg/kg daily, s.c.) or aminoguanidine (100 mg/kg daily, p.o.) was made. In rats with untreated diabetes, hyperglycaemia, increased activity of inducible nitric oxide (NO) synthase, increased NO, mild vascular spasm, reduced NO bioavailability and diminished vasorelaxation were found. These findings were accompanied by downregulated Cx43 and Cx40, and upregulated PKCepsilon and NADPH oxidase subunits p22(phox)/p47(phox)/p67(phox) in the thoracic aorta. NaHS appears to be as effective as aminoguanidine in attenuating these abnormalities. NaHS shows promise in relieving diabetic vascular abnormality by upregulating junctional connexin Cx40 and Cx43, via normalizing NADPH oxidase and PKCepsilon in the vasculature.

Dietary lycopene and tomato extract supplementations inhibit nonalcoholic steatohepatitis‐promoted hepatocarcinogenesis in rats

Epidemiological and experimental studies provide supportive evidence that lycopene (LY), a major carotenoid from tomatoes and tomato products, may act as a chemopreventive agent against certain types of cancers. We recently showed that high-fat diet (HFD)-induced nonalcoholic steatohepatitis (NASH) promoted diethylnitrosamine (DEN)-initiated hepatocarcinogenesis in a rat model. Using this model, we investigated the efficacy of an equivalent dosage of dietary LY from either a pure compound or a tomato extract (TE) against NASH-promoted hepatocarcinogenesis. Six groups of rats were injected with DEN and then fed either Lieber-DeCarli control diet or HFD with or without LY or TE for 6 weeks. Results showed that both LY and TE supplementations significantly decreased the number of altered hepatic foci expressing the placental form of glutathione S-transferase in the livers of HFD-fed rats. This was associated with significantly lower proliferating cell nuclear antigen positive hepatocytes and cyclinD1 protein, as well as decreased activation of extracellular signal-regulated kinase and nuclear NF-kappaB. Although both LY and TE supplementations reduced HFD-induced lipid peroxidation in the livers, we observed significantly decreased cytochrome P450 2E1, inflammatory foci and mRNA expression of proinflammatory cytokines (TNF-alpha, IL-1beta and IL-12) in the HFD+TE fed group but increased nuclear NF-E2-related factor-2 and heme oxygenase-1 proteins in the HFD+LY fed group, relative to HFD feeding alone. These data indicate that LY and TE can inhibit NASH-promoted hepatocarcinogenesis mainly as a result of reduced oxidative stress, which could be fulfilled through different mechanisms.

Acute inflammation and immunoresponses induced by ortho-phthalaldehyde in mice

ortho-Phthalaldehyde (OPA) has been used as a safe alternative disinfectant instead of glutaraldehyde; however, recently some adverse effects of OPA were reported in patients and medical professions. We examined the acute toxicity of OPA in male ICR mice injected with 0.125-0.5% OPA and killed some animals 1 day after a single OPA injection, and others 1 or 13 days after two OPA injections 5 days apart. Hematology, blood cell counts, specific antibody production, organ weights, hepatic enzymes, hepatic histopathology and gene expression of cytochrome P450 (CYP) mRNA in liver were examined. Single OPA injections elevated leukocyte counts, the proportion of neutrophils, alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Two OPA injections dose-dependently increased leukocyte counts, the proportion of neutrophils, ALT and AST, and decreased alkaline phosphatase. Leukocyte counts and proportions of neutrophils normalized 13 days after the second of two injections. However, both ALT and AST remained high in mice given higher OPA doses. Significant increased liver-to-body weight ratio and mild hepatic lesions were observed. Gene expression of CYP1a1 and CYP2e1 revealed a tendency of up-regulation 1 day after two OPA injections. However, expression of these genes was then down-regulated 13 days after OPA injections. OPA induced specific IgE and IgG significantly in the sera, suggesting that OPA acts as a hapten. Overall, OPA caused acute inflammation and acted as a haptenic allergen, although it caused only mild liver injury. Such evidence suggested that careful washing and prevention of exposure were needed after OPA disinfection of medical instruments.

High expression of the mRNA of cytochrome P450 and phase II enzymes in the lung and kidney tissues of cattle

The objective of this study was to investigate the tissue-specific mRNA expression of different cytochrome P450 (CYP) isoforms, UDP glucuronsyl transferase 1A1 (UGT1A1) and glutathione-S-transferase (GSTA1) in the different tissues (liver, mammary gland, lungs, spleen, kidney cortex, heart, masseter muscle and tongue) of cattle, using quantitative real-time polymerase chain reaction (qPCR). CYP1A1-like mRNA was expressed in all of the tissues examined, including the liver, with the highest expression level in the kidney. CYP1A2-, 2E1- and 3A4-like mRNAs were only expressed hepatically. Interestingly, significant expression of CYP2B6-like mRNA was recorded in the lung tissue, while CYP2C9-like mRNA was expressed in the liver and kidney tissues of the cattle examined. UGT1A1- and GSTA1-like mRNAs were expressed in all of the examined tissues, except the mammary glands, and the highest expression levels were recorded in the kidney. The high expression of UGT1A1 in the lung tissue and GSTA1 in the liver tissue was unique to cattle; this has not been reported for rats or mice. The findings of this study strongly suggest that the liver, kidneys and lungs of cattle are the major organs contributing to xenobiotics metabolism.

Regional Distribution of Cytochrome P450 mRNA Expression in the Liver and Small Intestine of Cynomolgus Monkeys

The cynomolgus monkey is used to study drug metabolism because of its evolutionary closeness to humans. Despite their importance, regional distribution of cytochrome P450 (CYP) enzymes including CYP3As in the liver and small intestine, the major sites of drug metabolism, has not been fully investigated in cynomolgus monkeys. In this study, we measured mRNA expression levels of 14 CYPs in the CYP1, 2, and 3 subfamilies, including orthologs of human CYP3A4 and CYP3A5, in the liver and small intestine of cynomolgus monkeys. Expression levels of each CYP mRNA in various regions of the liver were quantified and comparisons were made between the right lobe, quadrate lobe, left medial lobe, left lateral lobe, and caudate lobe and with four different sections of the right lobe. In the small intestine, the same mRNAs were measured in the duodenum and six different sections from the proximal jejunum to the distal ileum. Expression levels of the CYP mRNAs were not substantially different between liver samples, but varied between the different sections of the small intestine, including CYP3A4. These results suggest that analysis of distinct sections is required for a better understanding of cynomolgus monkey CYPs in the small intestine.

In Vitro Study of the Inhibition and Induction of Human Cytochromes P450 by Crystalline Glucosamine Sulfate

The induction and inhibition of human hepatic cytochrome P450 (CYP) isoforms by crystalline glucosamine sulfate (CGS) was investigated in vitro. Inhibition of CYP1A2, CYP2E1, CYP2C19, CYP2C9, CYP2D6, and CYP3A4 by CGS was assessed using recombinant human enzymes incubated with CGS (up to 3 mM expressed as free base). Induction of CYP1A2, CYP2B6, CYP2C9, CYP2C19 and CYP3A4 by CGS (0.01, 0.3 and 3 mM) was evaluated in cryopreserved human hepatocytes, by determining CYP mRNA expression using quantitative RT-PCR. CGS produced no inhibition or induction of any the CYP enzymes tested at concentrations hundred folds higher than the steady state peak plasma concentrations (approximately 10 microM) observed in man after therapeutic doses of CGS of 1500 mg once a day. Therefore, no clinically relevant metabolic interactions are expected between CGS and co-administered drugs that are substrates of the CYP enzymes investigated.

Aryl Hydrocarbon Receptor Is an Ozone Sensor in Human Skin

Ozone, one of the main components of photochemical smog, represents an important source of environmental oxidative stress to which the skin is exposed, especially during smoggy and ozone-alert days. However, very little is known about the effects of ozone exposure on human skin. Here, we used normal human epidermal keratinocytes (NHEKs) to determine the effects of attainable levels of ozone exposure on the family of cytochrome P450 (CYP) isoforms, which plays a determinant role in the biotransformation of many environmental pollutants. NHEK exposure to ozone (0.3 ppm) resulted in an increase in protein and messenger RNA (mRNA) expression of CYP1A1, CYP1A2, and CYP1B1. NHEK exposure to ozone also resulted in nuclear translocation of the aryl hydrocarbon receptor (AhR) and in phosphorylation of epidermal growth factor receptor (EGFR). The effect of ozone on events downstream of EGFR was an increased activation of phosphoinositide 3-kinase and phosphorylation of protein kinase B and mitogen-activated protein kinases. We found that AhR silencing by small interfering RNA abolished the capacity of these cells to increase the protein and mRNA expression of CYPs on ozone exposure. Thus, AhR signaling is an integral part of the induction of CYPs by ozone. These studies strongly suggest that there are toxicological consequences of ozone to human skin.

Modulation of Carcinogen Metabolism by Nitric Oxide-Aspirin 2 Is Associated with Suppression of DNA Damage and DNA Adduct Formation

Nitric oxide (NO)-donating non-steroidal anti-inflammatory drugs (NSAIDs) represent a promising new class of drugs developed to provide a safer alternative than their conventional NSAID counterparts in chemoprevention. We tested the effects of NO-aspirin 2 on Phase I and Phase II carcinogen-metabolizing enzymes. In HepG2 human hepatoma cells and in LS180 colonic adenocarcinoma cells, NO-aspirin 2 inhibited 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD)-induced cytochrome P450 (CYP) enzyme activity and CYP1A1 and CYP1A2 mRNA expression. These effects were further characterized as being mediated through transcriptional regulation: NO-aspirin 2 inhibited binding of ligand (TCDD)-activated aryl hydrocarbon receptor to the CYP1A1 enhancer sequence; additionally, NO-aspirin 2 suppressed carcinogen-induced expression of CYP1A heterogeneous nuclear RNA. The fate of carcinogen metabolites depends not only on activation by CYP enzymes but also detoxification by Phase II enzymes. Both HepG2 and LS180 cells treated with NO-aspirin 2 showed an increase in glutathione S-transferase-P1 (GST-P1), glutamate-cysteine ligase (GCL), and NAD(P)H:quinone oxidoreductase-1 (NQO1) expression. Compared with two other NO-releasing compounds, diethylenetriamine-NO and the organic nitrate, isosorbide dinitrate, the inhibitory effects of NO-aspirin 2 on TCDD-induced CYP activity and mRNA expression were considerably more potent. Furthermore, aspirin alone had no inhibitory effect on TCDD-induced CYP activity, nor did aspirin up-regulate GCL, GST-P1, or NQO1 expression. Consequent to the effects on carcinogen-metabolizing enzymes, NO-aspirin 2 inhibited [3H]benzo[a]pyrene-DNA adduct formation and DNA damage elicited by TCDD or benzo[a]pyrene. Our results demonstrate that NO-aspirin 2 may be an effective chemopreventive agent by favorably affecting the inhibitory and enhancing effects of Phase I and Phase II carcinogen metabolism, thereby protecting DNA from carcinogenic insult.

Expression and possible role of fibroblast growth factor family members in porcine antral follicles during final maturation

The aim of this study was to investigate the possible participation of fibroblast growth factor (FGF) family members (FGF1, FGF2 and FGF7 and their receptors) in porcine follicles (polyovulatory species) under special consideration for FGF2 during final growth. A classification of follicles was done by size and follicular fluid content of oestradiol-17beta, progesterone and prostaglandin F2alpha. The mRNA expression of examined factors was analysed by real-time PCR. The hormone concentration was estimated by enzyme immunoassay, protein characterisation by western blotting and localisation by immunohistochemistry. Follicle tissue separated in theca interna and granulosa cells was extracted and tested for mRNA of FGF1, FGF2, FGF7 and receptors (FGFR1IIIc, FGFRIIIb and FGFR2IIIc). Additionally, the mRNA expression of FSHR, LHR and aromatase cytochrome P450 for further characterisation of follicles was analysed. Significantly, higher FGF2 protein levels were measured in stroma when compared with total follicle or corpus luteum tissue. This result was confirmed by western blot with two strong bands. Immunological localisation of FGF2 only in stroma (fibroblasts) confirms the protein measurements. The results show a clear difference for FGF2 protein expression during final growth of follicles if monovulatory (bovine) and polyovulatory (porcine) species are compared. FGF2 protein in porcine ovary may be (due to localisation and concentration in stroma) important for support of angiogenesis of more follicles (polyovulatory species) and not of a single follicle like in cows.

Ginseng Extracts Facilitate Cytochrome P450 Xenobiotic Metabolism in Primary Cultures of Rat Hepatocytes

A 70% methanol extract from red ginseng (steamed and dried roots of Panax ginseng C. A. Meyer, a kind of Ginseng Radix) has been shown to have various actions on physiological functions. We investigated whether the ginseng extract (Ext.) affected the mRNA expression of cytochrome P450 (CYP) CYP1A1, 2B1, 2C11, 2D1, 3A1, and 3A2 in rat primary hepatocytes. After treatment with ginseng extract, the levels of CYP3A1 and 1A1 mRNA were significantly increased compared with those of the control. The increased protein levels of CYP3A1 were also observed after treatment with Ext. The mRNA levels of other examined CYPs exhibited little change. The mRNA levels of the pregnane X receptor, but not the constitutive androstane receptor, both transcription factors for CYPs, also significantly increased after treatment with ginseng extract. These results raise the possibility that ginseng Ext. promotes xenobiotic metabolism via an increase in CYP3A1 and 1A1 expression.

Time-Dependent Induction of Hepatic Cytochrome P450 Enzyme Activity and mRNA Expression by Bilobalide in Rats

A single dose by gavage of bilobalide (30 mg/kg) was found to produce a time-dependent induction of hepatic cytochrome P450 (CYP) enzyme activity and protein expression in rats. An RT-PCR study further showed that mRNA expression of CYP2B was maximal at 6 h. Plasma and liver bilobalide concentration in rats following administration of Ginkgo biloba extract equivalent to bilobalide of approximately 40 mg/kg showed a similar response to that exhibited by mRNA expression. These findings suggest that bilobalide markedly induced hepatic CYPs, but the induction could be mitigated due to rapid elimination from the liver.

Green tea extract increases cyclophosphamide-induced teratogenesis by modulating the expression of cytochrome P-450 mRNA

The effects of green tea extract (GTE) on the fetal development and external, visceral and skeletal abnormalities induced by cyclophosphamide were investigated in rats. Pregnant rats were daily administered GTE (100 mg/kg) by gavage for 7 d, from the 6th to 12th day of gestation, and intraperitoneally administered with cyclophosphamide (11 mg/kg) 1 h after the final treatment. On the 20th day of gestation, maternal and fetal abnormalities were determined by Cesarian section. Cyclophosphamide was found to reduce fetal and placental weights without increasing resorption or death. In addition, it induced malformations in live fetuses; 94.6%, 41.5% and 100% of the external (skull and limb defects), visceral (cleft palate and ureteric dilatation) and skeletal (acrania, vertebral/costal malformations and delayed ossification) abnormalities. When pre-treated with GTE, cyclophosphamide-induced body weight loss and abnormalities of fetuses were remarkably aggravated. Moreover, repeated treatment with GTE greatly increased mRNA expression and activity of hepatic cytochrome P-450 (CYP) 2B, which metabolizes cyclophosphamide into teratogenic acrolein and cytotoxic phosphoramide mustard, while reducing CYP3A expression (a detoxifying enzyme). The results suggest that repeated intake of GTE may aggravate cyclophosphamide-induced body weight loss and malformations of fetuses by modulating CYP2B and CYP3A.

Effects of Andrographis paniculata extract and Andrographolide on hepatic cytochrome P450 mRNA expression and monooxygenase activities after in vivo administration to rats and in vitro in rat and human hepatocyte cultures

The expression of cytochrome P450 (CYP) is regulated by both endogenous factors and foreign compounds including drugs and natural compounds such as herbs. When herbs are co-administrated with a given drug in modern medicine it can lead to drug–herb interaction that can be clinically significant. The ability of Andrographis paniculata extract (APE) and Andrographolide (AND), the most medicinally active phytochemical in the extract, to modulate hepatic CYP expression was examined in vivo in rats and in vitro in rat and human hepatocyte cultures. After in vivo administration, APE at dose levels of 0.5 g/kg/day (i.e. 5 mg/kg/day AND equivalents) and at 2.5 g/kg/day (i.e. 25 mg/kg/day AND equivalents) and AND at dose levels of 5 and 25 mg/kg/day significantly decreased CYP2C11 activity. In primary cultures of rat and human hepatocytes, treatment with AND 50 μM and APE-containing 50 μM AND also resulted in significant decreases in CYP2C expression and activity. In addition, in human hepatocytes, treatment with APE and AND 50 μM resulted in a decrease in CYP3A expression and activity. In conclusion, this study suggests that AND and APE could cause herb–drug interactions in humans through modulation of CYP2C9 and CYP3A4 expression and activities.

Resveratrol modulates pyrogallol-induced changes in hepatic toxicity markers, xenobiotic metabolizing enzymes and oxidative stress

Previously, we reported that pyrogallol, an anti-psoriatic agent, causes hepatotoxicity in experimental animals and silymarin, an herbal antioxidant, reduces pyrogallol-induced changes [Upadhyay, G., Kumar, A., Singh, M.P., 2007. Effect of silymarin on pyrogallol- and rifampicin-induced hepatotoxicity in mouse. Eur. J. Pharmacol. 565, 190–201.]. The present study was undertaken to assess the effect of resveratrol against pyrogallol-induced changes in hepatic damage markers, xenobiotic metabolizing enzymes and oxidative stress. Swiss albino mice were treated intraperitoneally, daily with pyrogallol (40 mg/kg), for one to four weeks, along with respective controls. In some set of experiments, animals were pre-treated with resveratrol (10 mg/kg), 2 h prior to pyrogallol treatment, along with respective controls. Alanine aminotransaminase, aspartate aminotransaminase and bilirubin were measured in blood plasma and mRNA expression of cytochrome P-450 (CYP) 1A1, CYP1A2, CYP2E1, glutathione-S-transferase (GST)-ya and GST-yc, catalytic activity of CYP1A1, CYP1A2, CYP2E1, GST, glutathione reductase and glutathione peroxidase, lipid peroxidation and reduced glutathione (GSH) level were measured in liver. Resveratrol reduced pyrogallol-mediated increase in alanine aminotransaminase, aspartate aminotransaminase, bilirubin, lipid peroxidation and mRNA expression and catalytic activity of CYP2E1 and CYP1A2. Pyrogallol-mediated decrease in GST-ya and GST-yc expressions, GST, glutathione peroxidase and glutathione reductase activities and GSH content was significantly attenuated in resveratrol co-treated animals. CYP1A1 expression and catalytic activity were not altered significantly in any treated groups. The results demonstrate that resveratrol modulates pyrogallol-induced changes in hepatic toxicity markers, xenobiotic metabolizing enzymes and oxidative stress.

Comparative analysis of family 1 cytochrome P-450 mRNA expression in human intestinal adenocarcinoma and intact portion of the intestine

The expression of mRNA of proteins involved in the transformations of cytostatics (cytochrome P-450 1A1 and 1B1 isoforms) and genes encoding proteins participating in their regulation (Ah receptor, AHRR and ARNT) in intestinal tumors and intact portions of the intestine were studied. The expression of cytochrome P-450 1A1 increased in poorly differentiated tumors in comparison with its expression in intact portions of the intestine (tumor/intact tissue=1.65). The expression of cytochrome P-450 1B1 was higher in well-differentiated tumors (tumor/intact tissue=1.62). The possibility of practical use of high expression of cytochrome P-450 isoforms in tumors in comparison with intact intestinal tissue is discussed.

Effects of Andrographis paniculata crude extract and Andrographolide on hepatic cytochrome P450 mRNA expression and monooxygenase activities

Effects of Andrographis paniculata crude extract and Andrographolide on hepatic cytochrome P450 mRNA expression and monooxygenase activities

Drug Transporter and Cytochrome P450 mRNA Expression in Human Ocular Barriers: Implications for Ocular Drug Disposition

Studies were designed to quantitatively assess the mRNA expression of 1) 10 cytochrome P450 (P450) enzymes in human cornea, iris-ciliary body (ICB), and retina/choroid relative to their levels in the liver, and of 2) 21 drug transporters in these tissues relative to their levels in human small intestine, liver, or kidney. Potential species differences in mRNA expression of PEPT1, PEPT2, and MDR1 were also assessed in these ocular tissues from rabbit, dog, monkey, and human. P450 expression was either absent or marginal in human cornea, ICB, and retina/choroid, suggesting a limited role for P450-mediated metabolism in ocular drug disposition. In contrast, among 21 key drug efflux and uptake transporters, many exhibited relative expression levels in ocular tissues comparable with those observed in small intestine, liver, or kidney. This robust ocular transporter presence strongly suggests a significant role that transporters may play in ocular barrier function and ocular pharmacokinetics. The highly expressed efflux transporter MRP1 and uptake transporters PEPT2, OCT1, OCTN1, and OCTN2 may be particularly important in absorption, distribution, and clearance of their drug substrates in the eye. Evidence of cross-species ocular transporter expression differences noted in these studies supports the conclusion that transporter expression variability, along with anatomic and physiological differences, should be taken into consideration to better understand animal ocular pharmacokinetic and pharmacodynamic data and the scalability to human for ocular drugs.

Inhibitory effects of a dietary phytochemical 3,3′-diindolylmethane on the phenobarbital-induced hepatic CYP mRNA expression and CYP-catalyzed reactions in female rats

3,3′-Diindolylmethane (DIM), derived from indole-3-carbinol (I3C), is used as a dietary supplement for its putative anticancer effects that include suppression of mammary tumor growth in female rats. The mechanism of action DIM may involve its interaction(s) with hepatic cytochromes P450 (CYPs) catalyzing oxidations of 17β-estradiol (E2). Our study showed that DIM added to hepatic microsomes of female Sprague–Dawley rats was primarily a competitive inhibitor of β-naphthoflavone (β-NF)- or I3C-induced CYP1A1 probe activity, and a potent mixed or uncompetitive inhibitor of phenobarbital (PB)-induced CYP2B1 or CYP2B2 probe activity, respectively. Microsomal metabolites of DIM were tentatively identified as two mono-hydroxy isomers of DIM, each formed preferentially by CYP1A1- or CYP2B1/2-catalyzed reaction. Evaluation of the effects of co-treatment of rats with PB and DIM by a full factorial ANOVA showed that DIM decreased the PB-induced CYP2B1 and CYP2B2 mRNA expression levels, and the rates of 2- and 4-hydroxylation of E2, and total E2 metabolite formation. The results suggest that interactions of DIM, and/or its mono-hydroxy metabolites, with CYP2B1 and CYP2B2 found to occur in hepatic microsomes upon addition of DIM or co-treatment of rats with DIM affect the rates of relevant oxidations of E2, and potentially protect against estrogen-dependent tumorigenesis.

Long-Term Feeding of Ginkgo biloba Extract Impairs Peripheral Circulation and Hepatic Function in Aged Spontaneously Hypertensive Rats

We previously demonstrated that Ginkgo biloba extract (GBE) produces an anti-hypertensive effect via enhanced vasodilation responses in young spontaneously hypertensive rats (SHR) and hepatic hypertrophy occurs with increased cytochrome P450 (CYP) mRNA expression in young rats. In the present study, to clarify whether these actions of GBE are observed in older rats, we investigated cardiovascular functions and hepatic CYP protein expressions in aged SHR fed a control diet or a diet containing 0.5% GBE for 4 weeks. In aged SHR, GBE feeding significantly increased liver weight per 100 g body weight without changing the body weight. Furthermore, significant increases in alanine aminotransferase level in serum and marked increase in CYP2B protein expression in the liver were observed in aged SHR fed GBE. On the other hand, GBE feeding did not affect blood pressure, but significantly reduced heart rate and blood flow velocity in tail arteries of aged SHR. Furthermore, GBE feeding did not affect contractile response to phenylephrine, relaxation responses to not only sodium nitroprusside but also acetylcholine, and protein levels of endothelium nitric oxide synthase and soluble guanylate cyclase in aortas of aged SHR. These results suggested that long-term GBE feeding impairs peripheral circulation due to bradycardia and hepatic function in aged SHR. Thus, in the elderly population with hypertension, the use of GBE may need to be assessed for effects on heart rate and liver function.