[Effect of mild moxibustion on vascular aging in senescence rats based on local MCP-1/MMP-2/TGF-β1 pro-inflammatory signal loop]

OBJECTIVE

To observe the effect of mild moxibustion on monocyte chemotaxis protein 1 (MCP-1)/matrix metalloproteinase 2 (MMP-2)/transforming growth factor β1 (TGF-β1) pro-inflammatory signal loop in senile rats, so as to explore its mechanisms underlying improving vascular aging (VA).

METHODS

Twenty-four male VA SD rats were randomized into senium (VA) control, medication and moxibustion groups, and other 8 young SD rats (aged 2 months) were used as the young control group. The VA model was established by intraperitoneal injection of D-galactose (300 mg·kg^-1·d^-1) once daily for 4 weeks, and verified by serum total testosterone (TT) and free testosterone (FT) levels. For rats of the moxibustion group, mild moxibustion was applied to bilateral "Shenshu"(BL23) and "Guanyuan"(CV4) for 20 min, once a day, 5 days a week for 8 weeks. Rats of the medication group were treated by intraperitoneal injection of testosterone propionate (7 mg·kg^-1·[3 d]^-1) once daily for 8 weeks except weekends, and rats of the senium control and young control groups treated by intraperitoneal injection of the same dose of normal saline, once daily for 8 weeks except weekends. The duration of exhausted swimming (DES) before and after the treatment was recorded. H.E. staining and Masson staining were used to observe histopathological changes and collagen fiber content of the thoracic aortic tissue, respectively. The contents of serum TT, FT and angiotensin 2 (Ang Ⅱ) were determined by ELISA. The immunoactivity of aortic MCP-1 was detected by immunohistochemistry, and the expression levels of aortic MCP-1, MMP-2 and TGF-β1 were detected by Western blot.

RESULTS

Compared with the young control group, the levels of DES, serum TT and FT contents were significantly decreased (P<0.01), while those of serum AngⅡ and collagen fiber contents, aortic MCP-1 immunoactivity and MMP-2, TGF-β1 and MCP-1 protein expression considerably increased in the senium control group (P<0.01). After the interventions, the decreased levels of DES, serum TT and FT contents and the increased levels of serum AngⅡ, collagen fiber contents, aortic MCP-1 immunoactivity and MMP-2, TGF-β1 and MCP-1 protein expression were reversed in both medication and moxibustion groups (P<0.01, P<0.05). The therapeutic effect of mild moxibustion was significantly superior to that of medication in down-regulating the aortic collagen fiber, serum AngⅡ contents and MCP-1 immunoactivity and protein expression (P<0.05). H.E. staining showed thickened endometrium and disordered arrangement of vascular smooth muscles of the aorta in the senium group, and thinner endometrium and regular and ordered arrangement of aortic vascular smooth muscles in both moxibustion and medication groups.

CONCLUSION

Mild moxibustion may improve vascular aging in senescence rats, which is possibly by suppressing vascular MCP-1/MMP-2/TGF-β1 pro-inflammatory signal loop.

[Electroacupuncture intervention increases testosterone level of aged rats by activating ERK/Nrf2/HO-1 signaling of Leydig cells]

OBJECTIVE

To observe the effect of electroacupuncture (EA) on anti-oxidant function of Leydig cells in aged rats with low testosterone, so as to reveal its underlying mechanism of anti-aging of male reproduction.

METHODS

Eighteen 20 months old SD rats were divided into aged control, medication and EA groups(n=6 in each group), and other 6 young male SD rats (2 months of age) were used as the youth control group. The rats of the youth and the aged control groups received subcutaneous injection of 0.9% normal saline (7 mg·kg^-1·3 d^-1) for 8 weeks, and those of the medication group received abdominal subcutaneous injection of Testosterone Propionate (7 mg·kg^-1·3 d^-1) for 8 weeks. EA (2 Hz/100 Hz, 1 mA) was applied to bilateral "Shenshu" (BL23) and "Guanyuan" (CV4) for 15 min, once daily for 8 weeks except the weekends. The levels of serum total testosterone (TT) and free testosterone (FT) were determined by enzyme linked immune sorbent assay (ELISA), the immunoactivity of phosphorylated extracellular signal-regulated protein kinase (p-ERK) was detected by immunohistochemistry, and the expression levels of ERK, p-ERK, nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) proteins in the testis tissues were determined by Western blot.

RESULTS

Before and after the treatment, the levels of serum TT and FT in the aged control group were significantly lower than those of the youth control group (P<0.01). After the treatment, the serum TT and FT contents in the EA and medication groups were obviously higher than those in the aged control group (P<0.01). Compared with the youth control group, the expression levels of ERK, p-ERK, Nrf2 and HO-1 proteins were significantly down-regulated in the aged control group (P<0.01), while in comparison with the aged control group, the expression levels of ERK, p-ERK, Nrf2 and HO-1 proteins were significantly up-regulated in the medication and EA groups (P<0.01). The therapeutic effect of EA was notably superior to that of medication in up-regulating the immunoactivity of p-ERK, and the expression levels of ERK, p-ERK, Nrf2 and HO-1 proteins (P<0.01). No significant differences were found between the EA and medication groups in the increased levels of serum TT and FT after the intervention (P>0.05).

CONCLUSION

EA intervention may increase testosterone level of the aged rats, which may be related to its effects in triggering ERK /Nrf2 /HO-1 signaling (anti-oxidative stress signal pathway) in the testis.

[Electroacupuncture Combined with Intracerebral Injection of VEGF Improves Neurological Dysfunction Possibly by Down-regulating Expression of Endoplasmic Reticulum Stress Related Proteins ATF 6, etc. in Cerebral Ischemia-reperfusion Injury Rats]

OBJECTIVE

To observe the effect of electroacupuncture (EA) and EA combined with intracerebral injection of vascular endothelial growth factor (VEGF) on endoplasmic reticulum stress (ERS) related proteins and genes as activating transcription factor (ATF 6), inositol requiring enzyme-1 (IRE 1), CCAAT/enhancer binding protein homologous protein (CHOP), X box-binding protein-1 (XBP 1) of cerebral ischemia reperfusion injury (CIRI) rats, so as to study its repair effect for CIRI.

METHODS

Forty male SD rats were equally and randomly divided into 5 groups: sham operation, model, EA, VEGF and EA+VEGF groups (n=8). The CIRI model was established by occlusion of the middle cerebral artery (MCAO) with thread embolism method. For rats of the sham operation group, the right common carotid artery was isolated without MCAO. EA (2 Hz/100 Hz, 1-3 mA) was applied to "Baihui" (GV 20), left "Quchi" (LI 11) and left "Zusanli" (ST 36) for 30 min, once a day for 14 days. For rats of the VEGF and EA+VEGF groups, 10 µL VEGF (0.025 µg/µL) was injected into the lateral ventricle 24 h after successful modeling. The rats' neurological function was assessed by using the modified neurological severity score (mNSS), and the histopathological changes of cerebral tissue were observed by Nissl staining method. The expression levels of ERS related proteins and genes ATF 6, IRE 1, XBP 1 and CHOP were determined by western blot (WB) and fluorescent quantitative PCR, separately.

RESULTS

After modeling, the level of mNSS was significantly higher in the model group than in the sham operation group (P<0.05), and the number of Nissl bodies was markedly lower in the model group than in the sham operation group (P<0.05). Following the treatment, the mNSS was significantly lower in the EA, VEGF and EA+VEGF groups than in the model group (P<0.05), and the numbers of Nissl bodies were obviously higher in the EA, VEGF and EA+VEGF groups than in the model group (P<0.05), suggesting an improvement of neurological dysfunction and a repair of the injured cerebral tissue after the treatment. The levels of CIRI-induced increase of mNSS and CIRI-induced decrease of the number of Nissl bodies in the EA+VEGF group were respectively remarkably lower or higher than those of the simple EA and simple VEGF groups (P<0.05). WB and PCR showed that the expression levels of ATF 6, IRE 1, XBP1 and CHOP proteins and genes were notably higher in the model group than in the sham operation group (P<0.05), and considerably lower in the EA, VEGF and EA+VEGF groups than in the model group (P<0.05). Comparison among the three treatment groups showed that after the treatment, the expression levels of ATF 6, IRE 1, XBP1 and CHOP proteins and genes were obviously lower in the EA+VEGF group than in the EA and VEGF groups (P<0.05).

CONCLUSION

EA and EA plus intracerebral microinjection of VEGF can improve neurological function and promote cerebral tissue repair in CIRI rats, which is associated with their effects in down-regulating the expression of ERS related proteins ATF 6, IRE 1, XBP1 and CHOP. The effect of EA+VEGF is superior to that of simple EA and simple VEGF.

[Electroacupuncture Intervention Improves Physical Power of Aged Rats with Low Testosterone by Reducing Chronic Inflammatory Response of Leydig Cells]

OBJECTIVE

To assess the effect of electroacupuncture (EA) on chronic inflammatory response of Leydig cells in aged rats with low testosterone, so as to investigate its underlying mechanism of anti-male reproductive aging.

METHODS

Twenty-four 20 months old SD rats were randomly divided into EA, medication and aged control groups (n＝ 8 in each), and other 8 young SD rats (2 months of age) were used as the youth control group. EA (2 Hz/100 Hz, 1 mA) was applied to "Guanyuan"(CV 4) and bilate-ral "Shenshu"(BL 23) for 15 min, once daily for 8 weeks except the weekends. The medication group received abdominal subcutaneous injection of testosterone propionate (7 mg• kg^－1• 3 d^－1) for 8 weeks. The aged control group and the youth control group received subcutaneous injection of 0.9% normal saline, with the same dose and same treatment frequency as those of the medication group. The rats' physical power was assessed according to the exhausted swimming duration, and the levels of serum total testosterone (TT) and free testosterone(FT) were determined by ELISA. The pathological changes of the testis tissue were detected by using H．E.staining, and the immunoactivity of cyclooxygenase-2 (COX-2) in Leydig cells was detected by immunohisto-chemistry. The expression levels of nuclear factor-κB p 65 (NF-κB p 65), COX-2, interleukin-1 β (IL-1 β) and tumor necrosis factor-α (TNF-α) proteins in the testis tissues were determined by Western blot.

RESULTS

Before and after treatment, the exhaustive swimming duration and the levels of serum TT and FT in the aged control group were significantly lower than those of the youth control group (P < 0.01). After the treatment, the exhaustive swimming duration and serum TT and FT in the EA and medication groups were notably higher than those in the aged control group (P<0.01). HE staining showed that the incompleteness of basement membrane of spermatogenic tubules, reduction of spermatogenic cells and supporting cells and irregularity of Leydig cells in the testis tissue of the aged rats were relatively milder after EA intervention. Compared with the youth control group, the expression levels of NF-κB p 65 and COX-2, IL-1 β and TNF-α in the testicular tissue were significantly higher in the aged control group (P<0.01),while in compared with the aged control group, the expression levels of NF-κB p 65, COX-2, IL-1 β and TNF-α proteins were significantly down-regulated in the EA group (P<0.01).

CONCLUSION

EA intervention can improve the physical power of the aged rats with low testosterone, which may be related to its effects in up-regulating TT and FT levels, and in reducing chronic inflammatory response in the testis tissue.

[Warm needle moxibustion, mild moxibustion and electroacupuncture interventions have an anti-aging effect possibly by regulating hypothalamus-pituitary-testis axis in aged male rats]

OBJECTIVE

To observe the effect of warm needle moxibustion (WNM), mild moxibustion and electroacupuncture (EA) of "Shenshu" (BL23) and "Guanyuan" (CV4) on serum gonadal hormone levels and related gene expression in the hypothalamus and testis in aged rats, so as to explore their underlying mechanisms in anti-aging.

METHODS

Forty male SD male rats were randomly divided into aged control, WNM, mild moxibustion, EA and medication groups (n ＝ 8 in each group), and other 8 male young adult SD rats were used as the youth control group. WNM (acupuncture plus moxibustion), mild moxibustion or EA (2 Hz /100 Hz, 1 mA) was separately applied to CV4 and bilateral BL23 for 15 min, once daily, 5 days a week for 8 weeks. Rats of the medication group received subcutaneous injection of testosterone propionate injection (7 mg/kg), once every 3 days, and those of the aged and youth groups received the same dose of 0.9% NaCl solution for 8 weeks. The levels of serum testoste-rone (T) and gonadotropin-releasing hormone (GnRH) were measured by ELISA. The expression of Kisspeptin (KISS-1), G protein-coupled receptors 54 (GPR54), RFamide-related peptide-3 (RFRP-3) and GPR147 mRNAs in the hypothalamus and GnRH-R, GPR54 and GPR147 mRNAs in the testis tissues were detected by quantitative real-time PCR.

RESULTS

The levels of serum T and GnRH, and the expressions of KISS-1, GPR54, RFRP-3 and GPR147 mRNAs in the hypothalamus and GnRH-R and GPR54 mRNAs in the testis in the aged rats were significantly lower than those in the youth rats (P<0.05), while the expression level of GPR147 mRNA of the testis tissue was obviously higher in the aged group than that in the youth group (P<0.05). Follo-wing the treatment, the lowered serum T and GnRH contents, the down-regulated expression levels of hypothalamic KISS-1, GPR54, RFRP-3 and GPR147 mRNAs and testicle GnRH-R and GPR54 mRNAs, as well as the up-regulated testicle GPR147 mRNA expression in the aged rats were reversed in the WNM, mild moxibustion and EA groups (not the medication group except serum T) in comparison with the aged control group (P<0.05). The therapeutic effects of WNM, mild moxibustion and EA were significantly superior to those of medication in up-regulating serum GnRH content and expression levels of KISS-1, GPR54, RFRP-3 and GPR147 mRNAs in the hypothalamus and GnRH-R, GPR54 and GPR147 mRNAs in the testis (P<0.05). No significant differences were found among the WNM, mild moxibustion and EA groups in serum T and GnRH contents, and the expression levels of KISS-1, GPR54, RFRP-3 and GPR147 mRNAs in the hypothalamus and GnRH-R and GPR54 and GPR147 mRNAs in the testis (P>0.05)．.

CONCLUSION

The WNM, mild moxibustion and EA therapies have an anti-aging effect by increasing serum T and GnRH levels in aged rats, which is possibly related to their effects in up-regulating the expression of hypothalamic KISS-1, GPR54, RFRP-3 and GPR147 mRNAs and testicle GnRH-R and GPR54 mRNAs, as well as down-regulating testicle GPR147 mRNA expression. The therapeutic effect of WNM, mild moxibustion and EA is evidently superior to that of medication.

[Effects of Electroacupuncture and Intracerebral Injection of VEGF on Caspase12, Caspase3, and GRP78 Genes in Rats with Cerebral Ischemia-Reperfusion Injury]

OBJECTIVE

To determine the effects of electroacupuncture (EA) and intracerebral injection of vascular endothelial growth factor (VEGF) on caspase12, caspase3, and glucose regulated protein 78 kD (GRP78) genes of rats with cerebral ischemia reperfusion injury.

METHODS

60 SD rats were randomly divided into sham-operation group, model group, EA group and EA+VEGF group with 15 rats in each group. Middle cerebral artery occlusion (MCAO) method was used to establish the model of cerebral ischemia reperfusion injury. Electro-acupuncture intervention was introduced 1 day after the injury in the EA group and EA+VEGF group: 30 minutes each session and once a day for a total of 14 d [acupoint selection: Baihui (GV 20), Quchi(Li 11), Zusanli (ST36)]. The rats in the EA+VEGF group were also injected with 10 μL of VEGF165 (0.025 μg/μL) into the lateral ventricle after the first session of EA. Five rats in each group were sacrificed after obtaining a neurological function score (mNSS) at day 0 (1 d after modeling, before EA intervention), day 7 and day 14, respectively. Nissl staining was used to observe the histomorphology of cerebral infarction areas. Immunohistochemistry was used to CM(155mm]detect GRP78 activity in the ischemic brain tissues. Real-time fluorescence quantitative PCR (real-time PCR) was used to detect the expressions of caspase12, caspase3 and GRP78 mRNA in the ischemic brain tissues.

RESULTS

Compared with the sham-operation group, rats in the model group had higher mNSS scores ( P<0.05), showed signs of cerebral infarction (with reduced numbers of and disordered Nissl bodies and unclear structure), increased GRP78 immunopositive cells, increased expression of GRP78 mRNA ( P<0.05), and increased expressions of caspase12 and caspase3 mRNA ( P<0.05). Compared with the model group, EA and EA+VEGF decreased mNSS scores at day 7 and 14 ( P<0.05), showing alleviated signs of cerebral infarction, increased GRP78 immunopositive cells ( P<0.05), increased GRP78 mRNA expression ( P<0.05), and decreased caspase12 and caspase3 mRNA expressions ( P<0.05). The most obvious changes were found in the EA+VEGF group ( P<0.05). No significant changes were observed in the sham-operation group over time ( P<0.05). In comparison, mNSS scores, the signs of cerebral infarction, and the expressions of caspase12 and caspase3 decreased over time in the other groups ( P<0.05), accompanied with increased GRP78 immunopositive cells and the expression of GRP78 gene ( P<0.05).

CONCLUSION

Electroacupuncture and intracerebral injection of VEGF promote tissue repair of rats with cerebral ischemic injury, possibly through down-regulating the expressions of caspase12 and caspase3 genes and up-regulating the expression of GRP78 gene. The effect of electroacupuncture in combination with intracerebral injection of VEGF is superior to that of the single use of electroacupuncture.

Inhibitive effect of diphenytriazol on rat cytochrome P450 enzyme in vitro

The inhibiting effect of diphenytriazol, a non-hormonal early pregnancy-terminating agent, towards cytochrome P450 (CYP) enzymes in rat liver microsomes was studied in vitro. The inhibiting effect of diphenytriazol on CYP was investigated by coincubating diphenytriazol with the specific CYP1A substrates, ethoxyresorufin and phenacetin, in microsome induced by beta-naphthoflavone, with the specific CYP2B substrates, pentoxyresorufin and aminopyrine, in the microsome induced by phenobarbital, and with the specific CYP3A substrates, diazepam, testosterone, nifedipine and quinine sulfate in microsome induced by dexamethasone. The results showed that diphenytriazol inhibited the metabolism of ethoxyresorufin and phenacetin significantly, and its inhibition potential on CYP1A was higher than the typical inhibitor fluvoxamine. Diphenytriazol also inhibited the metabolism of diazepam, testosterone, nifedipine and quinine sulfate to different degrees, but its inhibition potential was relatively weaker than that of the typical inhibitor, ketoconazole. No inhibiting effect of diphenytriazol was seen on the metabolism of pentoxyresorufin and aminopyrine. The ability of diphenytriazol to inhibit rat liver CYP1A and CYP3A suggests that in human patients complex interactions may result from co-adiministration of diphenytriazol with other agents which are also substrates for CYP1A or CYP3A enzymes.

Structural elucidation of metabolites of ginkgolic acid in rat liver microsomes by ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry and hydrogen/deuterium exchange

Ginkgolic acids have been shown to possess allergenic as well as genotoxic and cytotoxic properties. The question arises whether the metabolism of ginkgolic acids in the liver could decrease or increase their toxicity. In this study, the in vitro metabolism of ginkgolic acid (15:1, GA), one component of ginkgo acids, was investigated as a model compound in Sprague-Dawley rat liver microsomes. The metabolites were analyzed by ultra-performance liquid chromatography coupled with photodiode array detector/negative-ion electrospray ionization tandem mass spectrometry (UPLC-PDA/ESI-MS/MS) and hydrogen/deuterium (H/D) exchange. The result showed that the benzene ring remained unchanged and the oxidations occurred at the side alkyl chain in rat liver microsomes. At least eight metabolites were found. Among them, six phase I metabolites were tentatively identified. This study might be useful for the investigation of toxicological mechanism of ginkgolic acids.

An enantiospecific HPLC method for the determination of (S)-enantiomer impurities in (R)-tolterodine tartarate

A high-performance liquid chromatographic method was developed for the separation of the enantiomers of tolterodine tartarate. The proposed method was applied to the determination of (S)-isomer in (R)-tolterodine tartarate, and satisfactory results were obtained. The enantiomers of tolterodine tartarate were separated on a Chiralpak AD-H (250 mm x 4.6 mm) column containing amylose tris-(3,5-dimethylphenyl-carbamate) at room temperature. The mobile phase consisted of n-hexane and isopropyl alcohol in the ratio of 85:15 (v/v) with 0.075% triethylamine (TEA) and 0.05% trifluoroacetic acid (TFA) as the additive. The flow rate was kept at 0.5 ml/min, and UV detection wavelength was set at 283 nm. The calibration curves of (S)-enantiomer in the concentration range from 0.05 microg/ml to 1 microg/ml range were linear. The relative standard deviations of within-day and between-day were less than 2% (n = 3). The limit of detection (LOD) was 0.75 ng (S/N = 3) and the limit of quantification (LOQ) was 0.05 microg/ml (RSD < 4.1%, n = 3). The determination recoveries of the (S)-enantiomer were in the range of 98.2-104.8%. The results demonstrated that the developed HPLC method was a reliable, simple technique and was applicable to the purity determination of (R)- tolterodine tartarate.

Zolmitriptan uptake by human intestinal epithelial Caco-2 cells

The oral uptake of zolmitriptan, a novel and highly selectively 5-HT 1B/1D receptor agonist, was evaluated in the human epithelial cell line caco-2 that possesses intestinal enterocyte-like properties when cultured in vitro. The study demonstrated that zolmitriptan uptake significantly depended upon the extracelluar temperature and pH in the Caco-2 cell. The zolmitriptan uptake at 39 degrees C was 2.1 fold as that at 23 degrees C and the zolmitriptan uptake at pH 8.0 was 2.7 fold as that at pH 6.0. The uptake rates of zolmitriptan on both sides increased with increasing zolmitriptan concentration from 0.1 to 10 mmol x L(-1), and it shows concave concentration-dependency at high concentration. The uptake rates of zolmitriptan on the basolateral side (BL) were 3-7 times higher than that on the apical side (AP). Verapamil, nimodipine, nifedipine, flunarizine, amiloride and sumatriptan significantly increased the uptake rates of zolmitriptan on the apical sides. Propafenone significantly inhibited the uptake rate of zolmitriptan on both sides. Propranolol and aspirin have no significant effect. The results indicated that the zolmitriptan uptake in Caco-2 cells was temperature, pH and concentration dependent, and was partially counteracted by the action of an outwardly directed efflux pump, presumably p-glycoprotein. Absorption interactions should be considered when P-gp substrates or inhibitors, Na+ -H+ exchange inhibitors, P-gp ATPase agonists or inhibitors are co-administered with zomitriptan in clinical practice.

Analysis of luteolin in Elsholtzia blanda Benth. by RP-HPLC

The total luteolin content in Elsholtzia blanda Benth. extracts (EBBE) was determined using reversed phase HPLC. C18 was used as the packing material and 0.01 M phosphate buffer (pH 2)-tetrahydrofuran-isopropanol (70:30:5) as the mobile phase with detection wavelength 360 nm. The recovery of the method was 96.4%-101.8%, and the assay was linear at concentrations from 5 to 200 microg/ml (r = 0.9999). The results indicated that the content of luteolin in EBBE extracted under different conditions varied significantly. This method can be used to optimize the extraction procedure and determine the content of luteolin in Elsholtzia blanda Benth. extracts.

Disposition of quercetin and kaempferol in human following an oral administration of Ginkgo biloba extract tablets

Ten adult volunteers with an average age 28 years were given a single oral dose of six tablets of Ginkgo biloba extract. Quercetin and kaempferol in different period of human urine were determined by using RP-HPLC. The results showed the elimination rate constant k and the absorption rate constant ka of quercetin were slightly more than that of kaempferol; and the absorption half-life (t(1/2a)), the elimination half-life (t(1/2)) and t(max) of quercetin were less than that of kaempferol, the differences were, however, not statistically significant. The mean values of ka were 0.61 h(-1) and 0.55 h(-1), t(1/2a) 1.51 h and 1.56 h, k 0.37 h(-1) and 0.30 h(-1), t(1/2) 2.17 h and 2.76 h, T(max) 2.30 h and 2.68 h for quercetin and kaempferol, respectively, which mean absorption and elimination of quercetin and kaempferol are 0.17% and 0.22%, respectively. Quercetin and kaempferol are excreted in the human urine mainly as glucuronides.

Determination of quercetin and kaempferol in human urine after orally administrated tablet of ginkgo biloba extract by HPLC

A sensitive, simple and accurate method was developed for determination of quercetin and kaempferol in human urine by reversed phase high performance liquid chromatography. The urine samples were analyzed on C18 column. Quercetin and kaempferol were analyzed simultaneously with good separation. UV detector was set at 380 nm. There was a linear relationship between chromatographic area of analytes and concentration of analytes over the concentration range 1.638-81.90 and 1.872-93.60 ng/ml for quercetin and kaempferol, respectively. The recovery of the assay was 99.7+/-6.2 and 97.4+/-7.2% for quercetin and kaempferol, respectively. The within-day and between-day coefficients of variation were less than 9.7 and 16.5% (RSD), respectively. The limit of detection was 1.0 ng/ml for quercetin and 1.1 ng/ml for kaempferol. The limit of quantitation was 1.61+/-0.11 ng/ml (n=5) for quercetin and 1.85+/-0.11 ng/ml (n=5) for kaempferol. The method developed has been applied to determine quercetin and kaempferol after orally administrated tablet of Ginkgo biloba extract in human urine.

Concentration dependent stereoselectivity of propafenone N-depropylation metabolism with human hepatic recombinant CYP1A2

Concentration dependency of stereoselective N-depropylation metabolism of propafenone was studied by using transgenic cell line expressing human CYP1A2. Enantiomers of propafenone and N-depropylpropafenone were separated and assayed simultaneously by RP-HPLC with precolumn GITC chiral derivatization. The experimental results showed that CYP1A2 was involved in enantioselective N-depropylation of propafenone and that the metabolic stereoselectivity depends on substrate concentration. For racemic propafenone, stereoselectivity was observed at low substrate concentration and was not seen at high substrate concentration. For individual isomers, S-(+)-propafenone was metabolized faster than its antipode at higher enantiomer concentrations and R-(-)-propafenone was eliminated faster than its antipode at lower enantiomer concentrations. There is interaction between S- and R-propafenone. R-(-)-propafenone inhibited the metabolism of S-(+)-propafenone with IC50 0.225 mmol/L for human CYP1A2.

Chiral reversed phase high-performance liquid chromatography for determining propranolol enantiomers in transgenic Chinese hamster CHL cell lines expressing human cytochrome P450

An enantioselective assay for S-(-)- and R-(+)-propranolol in transgenic Chinese hamster CHL cell lines, expressing human cytochrome P450 (CYP), was developed. The method involves extraction of propranolol from the S(9) incubates, using S-(+)-propafenone as internal standard, chiral derivatization with 2,3,4,6-tetra-O-beta-D-glucopranosyl isothiocyanate and quantitation by reversed phase high-performance liquid chromatography system with UV detection (lambda=220 nm). A baseline separation of propranolol enantiomers was achieved on a 5-microm reverse-phase ODS column, with a mixture of methanol/water/glacial acetic acid (67:33:0.05, v/v) as mobile phase. The assay is linear from 5 to 500 microM for each enantiomer. The analytical method affords average recoveries of 99.2% and 98.8% for S-(-)- and R-(+)-propranolol, respectively. The limit of quantitation for the method is 5 microM for both S-(-)- and R-(+)-propranolol. The reproducibility of the assay is satisfactory (RSD < 10%). The method allowed study of the depletion of S-(-)- and R-(+)-propranolol in transgenic Chinese hamster CHL cell lines expressing CYP3A4, CYP2C18 and CYP2C9.

Chiral metabolism of propafenone in rat hepatic microsomes treated with two inducers

AIM: To study the influence of inducers of drug metabolism enzyme, β-naphthoflavone (BNF) and dexamethasone (DEX), on the stereoselective metabolism of propafenone in the rat hepatic microsomes.

METHODS: Phase I metabolism of propafenone was studied using the microsomes induced by BNF and DEX and the non-induced microsome was used as the control. The enzymatic kinetics parameters of propafenone enantiomers were calculated by regress analysis of Eadie-Hofstee Plots. Propafenone enantiomer concentrations were assayed by a chiral HPLC.

RESULTS: The metabolite of propafenone, N-desalkylpropafenone, was found after incubation of propafenone with the rat hepatic microsomes induced by BNF and DEX. In these two groups, the stereoselectivity favoring R (-) isomer was observed in metabolism at low substrate concentrations of racemic propafenone, but lost the stereoselectivity at high substrate concentrations. However, in control group, no stereoselectivity was observed. The enzyme kinetic parameters were: ① K_m. Control group: R (-) 83 ± 6, S (+) 94 ± 7; BNF group: R (-) 105 ± 6, S (+) 128 ± 14; DEX group: R (-) 86 ± 11, S (+) 118 ± 16; ② υ_max. Control group: R (-) 0.75 ± 0.16, S (+) 0.72 ± 0.07; BNF group: R (-)1.04 ± 0.15, S (+)1.0 7 ± 14; DEX group: R (-) 0.93 ± 0.06, S (+) 1.04 ± 0.09; ③ Cl_int. Control group: R (-) 8.9 ± 1.1, S (+) 7.6 ± 0.7; BNF group: R (-)9.9 ± 0.9, S (+)8.3 ± 0.7; DEX group: R (-) 10.9 ± 0.8, S (+) 8.9 ± 0.9. The enantiomeric differences in K_m and Cl_int were both significant, but not in υ_max, in BNF and DEX group. Whereas enantiomeric differences in three parameters were all insignificant in control group. Furthermore, K_m and υ max were both significantly less than those in BNF or DEX group. In the rat liver microsome in duced by DEX, nimodipine (NDP) decreased the stereoselectivity in propafenone metabolism at low substrate concentration. The inhibition of NDP on the metabolism of propafenone was stereo selective with R (-)-isomer being impaired more than S (+)-isomer. The inhibition constant (Ki) of S (+)- and R (-)-propafenone, calculated from Dixon plots, was 15.4 and 8.6 mg•L¯¹, respectively.

CONCLUSION: CYP1A subfamily (induced by BNF) and CYP3A4 (induced by DEX) have pronounced contribution to propafenone N-desalkylation which exhibited stereose lectivity depending on substrate concentration. The molecular base for this phenomenon is the stereo selectivity in affinity of substrate to the enzyme activity centers instead of at the catalyzing sites.

Stereoselective metabolism of propafenone by human liver CYP3A4 expressed in transgenic Chinese hamster CHL cells lines

AIM

To investigate the stereoselective metabolism of propafenone (PPF) by human liver CYP3A4.

METHODS

A chiral and an achiral HPLC were combined to determine the enantiomer of PPF in S9 incubates prepared from transgenic Chinese hamster CHL cells lines expressing CYP3A4. The time-dependent study was performed using individual enantiomer or racemate at low or high substrate concentration. Kinetic parameters were determined employing individual enantiomers as substrates. Enantiomeric inhibition experiments were performed by using R(-)-PPF as an inhibitor and S(+)-PPF as a substrate.

RESULTS

Stereoselectivity was found in metabolism of racemic PPF at low substrate concentration (10 mg/L) (S < R), and lost at high substrate concentration (400 mg/L) When an individual enantiomer of high concentration (200 mg/L) was used as a substrate, S(+)-PPF was eliminated faster than its isomer (S < R). However, the opposite situation was observed at low concentration (5 mg/L) (S < R). The Vmax of S(+)-PPF was significantly greater than that of R(-)-PPF [(2.66 +/- 0.32) vs (1.71 +/- 0.19) micromol . mg-1 . min-1]. The Km of R(-)-PPF was significantly lower than that of S(+)-PPF [(73 +/- 11) vs (185 +/- 17) micromol/L]. R(-)-PPF inhibited S(+)-isomer with an IC50 value of 125 micromol . L-1.

CONCLUSION

It is concluded that stereoselectivity in metabolism of propafenone via CYP3A4 depend on substrate concentration. Enantiomer/enantiomer interaction of PPF occurred at high concentration of substrate, and resulted in the loss of stereoselectivity. There maybe no enantiomer/enantiomer interaction at low concentration thus keeping the superiority of R(-)-PPF in metabolism.

Stereoselective determination of p-hydroxyphenyl-phenylhydantoin enantiomers in rat liver microsomal incubates by reversed-phase high-performance liquid chromatography using beta-cyclodextrin as chiral mobile phase additives

An analytical method was developed for determination of p-hydroxyphenylphenylhydantoin enantiomers in rat liver microsome by using reversed-phase high-performance liquid chromatography. A 50 mm C(8) column was used as the analytical column. The mobile phase was made up of 8.8 mmol/L beta-cyclodextrin, 0.25 mol/L urea and 0.05 mol/L ammonium acetate in water. The assay was linear from 2.05 to 410.0 micromol/L for each enantiomer. The limits of detection and of quantitation for the method were 0.90 and 2.05 micromol/L for each enantiomer, respectively. The analytical method afforded average recoveries of 93.59 +/- 2.75% and 94.72 +/- 1.78% for S- and R-p-hydroxyphenylphenylhydantoin, respectively. The method allowed study of the in vitro glucuronidation of p-hydroxyphenylphenylhydantoin in rat liver microsomal incubates. The stereoselectivity of p-hydroxyphenylphenylhydantoin phase II metabolism was observed.

Phenotype analysis of cytochrome P450 2C19 in Chinese subjects with mephenytoin S/R enantiomeric ratio in urine measured by chiral GC

A chiral gas chromatographic method with FID was developed for the determination of S- and R-mephenytoin in human urine. The assay is linear from 25 to 800 ng/mL for each enantiomer and the limit of detection and limit of quantitation were 12 and 25ng/mL for each enantiomer, respectively. The method affords average recoveries of 74.41 +/- 3.93% and 73.78 +/- 3.02% for S- and R-mephenytoin, respectively. The method allows the phenotype study of CYP2C19 in Chinese subjects. The phenotype pattern of 90 Chinese volunteers was determined, in which 26 volunteers received phenotyping and genotyping tests. The results of phenotype analysis showed that the interindividual variation was marked. The mephenytoin S/R enantiomeric ratios in urine of 11 volunteers were > or = 0.95 and identified as poor metabolizers. The frequency of poor metabolizers was 12.2% in the Chinese subjects tested. A good relationship between phenotype and genotype analysis of CYP2C19 was observed.

Stereoselective determination of propafenone enantiomers in transgenic Chinese hamster CHL cells expressing human cytochrome P450

An enantioselective assay for S(+)- and R(-)-propafenone in transgenic Chinese hamster CHL cells expressing human cytochrome P450 was developed. The method involved extraction of propafenone from the S9s incubates, and formation of propafenone diastereomeric derivatives with the chiral reagent 2,3,4, 6-tetra-O-beta-D-glucopranosyl isothiocyanate. Separation and quantitation of diastereomeric propafenone derivatives were carried out in a reverse-phase-HPLC system with UV detection. The assay was linear from 2 to 200 microg/mL for each enantiomer. The analytical method gave average recoveries of 97.5% and 97.0% for S(+)- and R(-)-propafenone, respectively. The limits of detection and quantitation for the method are 0.1 and 2.0 microg/mL for both S(+)- and R(-)-propafenone, respectively. The reproducibility of the assay was good (RSD <10%). The method allowed study of the depletion of S(+)- and R(-)-propafenone in transgenic Chinese hamster CHL cells expressing human cytochrome P450. The stereoselectivity of propafenone phase I metabolism via cDNA-expressed CYP3A4 was observed.

Stereoselective determination of propafenone enantiomers in transgenic Chinese hamster CHL cells expressing human cytochrome P450

An enantioselective assay for S(+)- and R(-)-propafenone in transgenic Chinese hamster CHL cells expressing human cytochrome P450 was developed. The method involved extraction of propafenone from the S9s incubates, and formation of propafenone diastereomeric derivatives with the chiral reagent 2,3,4, 6-tetra-O-beta-D-glucopranosyl isothiocyanate. Separation and quantitation of diastereomeric propafenone derivatives were carried out in a reverse-phase-HPLC system with UV detection. The assay was linear from 2 to 200 microg/mL for each enantiomer. The analytical method gave average recoveries of 97.5% and 97.0% for S(+)- and R(-)-propafenone, respectively. The limits of detection and quantitation for the method are 0.1 and 2.0 microg/mL for both S(+)- and R(-)-propafenone, respectively. The reproducibility of the assay was good (RSD <10%). The method allowed study of the depletion of S(+)- and R(-)-propafenone in transgenic Chinese hamster CHL cells expressing human cytochrome P450. The stereoselectivity of propafenone phase I metabolism via cDNA-expressed CYP3A4 was observed.

Reversed-phase high-performance liquid chromatographic analysis of atenolol enantiomers in rat hepatic microsome after chiral derivatizaton with 2,3,4,6,-tetra-O-acetyl-beta-D-glycopyranosyl isothiocyanate

A reversed-phase high-performance liquid chromatographic method for the determination of the enantiomers of atenolol in rat hepatic microsome has been developed. Racemic atenolol was extracted from alkalinized rat hepatic microsome by ethyl acetate. The organic layer was dried with anhydrous sodium sulfate and evaporated using a gentle stream of air. Atenolol racemic compound was derivatized with 2,3,4,6-tetra-O-acetyl-beta-D-glycopyranosyl isothiocyanate at 35 degrees C for 30 min to form diastereomers. After removal of excess solvent, the diastereomers were dissolved in phosphate buffer (pH 4.6)-acetonitrile (50:30). The diastereomers were separated on a Shimadzu CLC-C18 column (10 microm particle size, 10 cm x 0.46 cm I.D.) with a mobile phase of phosphate buffer-methanol-acetonitrile (50:20:30, v/v) at a flow-rate of 0.5 ml/min. A UV-VIS detector was operated at 254 nm. For each enantiomer, the limit of detection was 0.055 microg/ml (signal-to-noise ratio 3) and the limit of quantification (signal-to-noise ratio 10) was 0.145 microg/ml (RSD <10%). In the range 0.145-20 microg/ml, intra-day coefficients of variation were 1.0-7.0% and inter-day coefficients of variation were 0.4-16.5% for each enantiomer. The assay was applied to determine the concentrations of atenolol enantiomers in rat hepatic microsome as a function of time after incubation of racemic atenolol.