Microsomal Research Articles

Effects of species of origin and mode of induction of microsomes on carbamazepine-induced cell toxicity

Standardization and validation of in vitro drug metabolism is essential for pre-clinical drug development as well as for in vitro toxicity assays including the lymphocyte toxicity assay (LTA) and the in vitro platelet toxicity assay (iPTA). Use of isolated liver microsomes (MIC) in in vitro testing has been utilized for a long time; however, the effect of species of origin and induction agents on the metabolic capacities of MIC is not adequately evaluated. In this study we investigated the impact of species of origin and induction agent on the capacity of MICs to bioactivate carbamazepine (CBZ) using cytotoxicity as a gross endpoint to measure the levels of cytotoxic metabolites generated by each type of MICs. Jurkat E6.1 cell line was used and MICs from human, rat, mouse, minipig and rabbit origin as well as rat MICs that is either non-induced or induced by phenobarbitone (PHB), dexamethasone (DEXA), 3-methylcholanthrene (3MC), clofibrate (CLOF) and isoniazid (INH) were investigated. MICs from minipig and rat MICs induced with 3MC exhibited the highest capacity to produce cytotoxic metabolites of CBZ. These findings will help optimize and standardize in vitro toxicity assays and provide guidance to pre-clinical investigation of drugs.

Differential expression and activities of cytochrome P450 3A in the rat brain microsomes and mitochondria.

Midazolam (MDZ), a benzodiazepine derivative, is metabolized to 1'- and 4-hydroxylated metabolites (1'-OH-MDZ and 4-OH-MDZ, respectively) by cytochrome P450 3A (CYP3A). The purpose of this study was to investigate the CYP3A-mediated hydroxylation of MDZ in the rat brain mitochondria (MT). Brain microsomes (MC) and MT fractions were prepared from rats (n = 8) using differential and density gradient centrifugations, and the purity of the fractions was evaluated using VDAC1 and calreticulin as markers of MT and MC, respectively. The formation rates of 1'-OH-MDZ and 4-OH-MDZ in the rat brain MC and MT samples were determined using an LC-MS/MS method after validation. Subsequently, Michaelis-Menten kinetics of 1'- and 4-hydroxylation of MDZ were estimated. Western blot (WB) analysis was used to determine the protein expression of CYP3A in the rat brain MC and MT. The MC fractions had 5.93% ± 3.01% mitochondrial impurity, and the MT fractions had 19.3% ± 7.8% microsomal impurity (mean ± SD). The maximum velocity (Vmax ) values of the formation of the hydroxylated metabolites in the brain MT were 2.4-9-fold higher than those in MC. Further, the Vmax values of 4-OH-MDZ in both MC and MT fractions were substantially higher than those of 1'-OH-MDZ. The WB analysis showed that the intensity of the CYP3A immunoreactive band in MT was more than twofold higher than that in MC. It is concluded that compared with MC, rat brain MT contains substantial CYP3A, which may affect the pharmacology or toxicology of centrally acting xenobiotic and endogenous substrates of this enzyme.

Plasma and vacuolar membrane sphingolipidomes: composition and insights on the role of main molecular species.

Lipid structures affect membrane biophysical properties such as thickness, stability, permeability, curvature, fluidity, asymmetry, and interdigitation, contributing to membrane function. Sphingolipids are abundant in plant endomembranes and plasma membranes (PMs) and comprise four classes: ceramides, hydroxyceramides, glucosylceramides, and glycosylinositolphosphoceramides (GIPCs). They constitute an array of chemical structures whose distribution in plant membranes is unknown. With the aim of describing the hydrophobic portion of sphingolipids, 18 preparations from microsomal (MIC), vacuolar (VM), PM, and detergent-resistant membranes (DRM) were isolated from Arabidopsis (Arabidopsis thaliana) leaves. Sphingolipid species, encompassing pairing of long-chain bases and fatty acids, were identified and quantified in these membranes. Sphingolipid concentrations were compared using univariate and multivariate analysis to assess sphingolipid diversity, abundance, and predominance across membranes. The four sphingolipid classes were present at different levels in each membrane: VM was enriched in glucosylceramides, hydroxyceramides, and GIPCs; PM in GIPCs, in agreement with their key role in signal recognition and sensing; and DRM in GIPCs, as reported by their function in nanodomain formation. While a total of 84 sphingolipid species was identified in MIC, VM, PM, and DRM, only 34 were selectively distributed in the four membrane types. Conversely, every membrane contained a different number of predominant species (11 in VM, 6 in PM, and 17 in DRM). This study reveals that MIC, VM, PM, and DRM contain the same set of sphingolipid species but every membrane source contains its own specific assortment based on the proportion of sphingolipid classes and on the predominance of individual species.

Correction: In vitro hepatic metabolism of mefloquine using microsomes from cats, dogs and the common brush-tailed possum (Trichosurus vulpecula).

[This corrects the article DOI: 10.1371/journal.pone.0230975.].

Effects of cyclosporin A on the pharmacokinetics and toxicities of irinotecan mediated by UGT1A1 in vitro and in vivo.

Irinotecan (CPT-11) is a broad spectrum agent for the treatment of solid tumor malignancies, despite severe diarrhea is limiting its widespread usage. The local effects of SN-38 in the small intestine were considered to be responsible for the irinotecan-induced delayed diarrhea. It was proposed that cyclosporin A (CsA) inhibiting biliary excretion could attenuate this side effect, but in fact, it could not improve the therapeutic index of irinotecan. At present, most studies focused on the inhibition of bile excretion by cyclosporin A through the transporters MRP2 and MDR1 and its effect the irinotecan treatment in vivo. However, UDP glucuronyltransferase-1 polypeptide A1 (UGT1A1) was related to a significantly altered disposition of irinotecan and its metabolites, and was therefore associated with irinotecan-induced toxicity. This study focused on UGT1A1-mediated conversion of SN-38 to SN-38G, and systematically investigated the CsA-irinotecan interactions in vitro and in vivo. After treatment with 10 mg·kg-1 CsA for 7 days, the bile excretion of irinotecan and its metabolites decreased and AUC0-∞ increased significantly. The AUC0-∞ (SN-38G)/AUC0-∞ (SN-38) was significantly reduced when compared with that in vehicle-treated rats. In the liver microsome incubation system, the IC50 of CsA for UGT1A1 enzyme was 9.4 μM. Furthermore, the UGT1A1 mRNA and protein expression levels were significantly reduced. The present study indicated that CsA treatment could enhance the systemic exposure and toxicity of SN-38 by inhibiting the UGT1A1 enzyme. The inhibition of UGT1A1 enzyme might be a critical factor in the failure of CsA improving irinotecan's treatment index.

Effects of Thioacetamide—Induced Cirrhosis, after a Drug Washout Period, on the Michaelis–Menten Kinetics of Major Cytochrome P450 Enzymes in the Rat Liver Microsomes

PurposeThioacetamide (TAA) is used to induce liver cirrhosis in rodents. However, the drug itself directly inhibits cytochrome P450 (CYP450) enzymes. The purpose of this study was to determine the effects of TAA‐induced liver cirrhosis, after a washout period to eliminate TAA, on the Michaelis‐Menten (MM) kinetics and protein contents of the major CYP450 enzymes CYP2D, CYP2E1, and CYP3A in rat liver microsomes.MethodsAdult, male Sprague‐Dawley rats were treated for 10 weeks with either TAA (200 mg/kg ip, 3 days per week) or vehicle (n = 7/each group). After a 10‐day washout period, animals were euthanized, and the liver was collected after cardiac perfusion with cold saline. Liver microsomes (MC) were prepared by differential centrifugation. The activities of the liver microsomal CYP2D (dextromethorphan O‐demethylation), CYP2E1 (chlorzoxazone 6‐hydroxylation) and CYP3A (midazolam 1′‐hydroxylation) were estimated by measurement of the metabolites by LC‐MS/MS. The microsomal CYP450 reductase (CPR) activity was analyzed spectrophotometry. Furthermore, the protein expressions of the isoenzymes were determined using Western blot analysis. The MM kinetic parameters maximum velocity (Vmax) and MM constant (Km) were determined using nonlinear regression analysis. Unpaired t‐test was used for statistical analysis of data, with a p value of < 0.05 as significant.ResultsWhereas the MM kinetics of dextromethorphan demethylation (CYP2D) were best fit by a two‐enzyme equation, those of chlorzoxazone hydroxylation (CYP2E1) and midazolam 1′‐hydroxylation (CYP3A) were best fit by a single‐enzyme equation. Cirrhosis resulted in significant reductions in the Vmax values for all the tested microsomal activities. The microsomal high‐ and low‐capacity Vmax values for CYP2D demethylase activity were significantly reduced by 74% (p value < 0.0001) and 51% (p < 0.05), respectively, in the TAA group. This was associated with a significant (p < 0.001) reduction (71%) in the protein contents of CYP2D in the TAA group. However, Km values were not affected by cirrhosis. For CYP2E1, cirrhosis caused a significant reduction (52%) in the Vmax value (p < 0.0001) for the chlorzoxazone hydroxylation activity. However, the Km values and protein contents of CYP2E1 remained unchanged. The Vmax and Km values of microsomal CYP3A hydroxylase activity, resulting in 1′‐hydroxylation of midazolam, were significantly reduced by 71% (p < 0.001) and 46% (p < 0.05), respectively, which was associated with a 30% reduction (p < 0.05) in the protein contents of CYP3A. Cirrhotic animals also showed a 31% decline (p < 0.05) in the microsomal CPR activity.ConclusionsTAA‐induced cirrhosis in rats resulted in a decreased liver microsomal activity of CPR and major CYP450 enzymes (CYP2D, CYP2E1, and CYP3A). Except for CYP2E1, the decreased isoenzyme activities were also associated with decreases in the protein concentrations of the isoenzymes. However, the cirrhosis‐induced decrease in the CYP2E1 activity, which was in the absence of a change in its protein levels, is possibly due to a decrease in the microsomal CPR activity.Support or Funding InformationFunding: Chapman University School of Pharmacy

Analysis of the autoantibodies characteristics of 77 anti-soluble liver antigen positive patients with liver diseases

Objective To understand the characteristics and clinical significance of anti-soluble liver antigen antibody (anti-SLA) in patients with liver diseases. Methods Serum samples from seventy-seven patients with anti-SLA were collected from Beijing You'An Hospital during the period between January 2010 and December 2018. Anti-SLA, anti-liver cytosol type 1 antibody (anti-LC1), anti-glycoprotein 210 antibody(anti-gp210) and anti-nuclear body protein sp100 antibody(anti-sp100) were detected by immunoblotting; indirect immunofluorescence assay used for detecting anti-nuclear antibody (ANA), anti-mitochondrial antibody (AMA), anti-smooth muscle antibody (SMA), and anti-liver kidney microsome antibody (anti-LKM). One-way analysis of variance was used to compare the ages of different anti-SLA groups. The non-parametric rank sum test was used to compare the liver function indexes and immunoglobulins in different intensity groups of anti-SLA. P<0.05 was considered statistically significant. Further comparisons were made between the two groups, the correction level α′=0.008 3, P<0.008 3 was considered statistically significant. Results The average age of 77 anti-SLA positive patients was (52.50±1.25) years old, 70 females (90.9%) and 7 males (9.1%). 80.5% of anti-SLA-positive patients (62/77 cases) were strongly positive at the time of initial diagnosis (+++ to ++++).The Alanine aminotransferase (ALT) level in the SLA++ group was higher than that in the SLA++++ group (232.7 U/L vs 65.6 U/L,χ2=7.751,P=0.005) and the immunoglobulin M(IgM) level in the SLA+++ group was lower than that in the SLA++++ group (1 270 mg/L vs 2 270 mg/L,χ2=8.337,P=0.004).There was no significant difference in age, other liver function and immunological indicators among the different groups.Seventy cases (90.9%) were both anti-SLA and ANA positive, 13 cases (16.9%) were positive with SMA, and none positive with anti-LKM and anti-LC1. Among anti-SLA positive patients, 58 cases were diagnosed with autoimmune hepatitis (AIH), 12 were AIH/primary biliary cholangitis (PBC) overlap syndrome (OS), 2 were drug-induced liver injury, 2 were chronic hepatitis B, and 3 were hepatitis A, hepatitis E and acquired immune deficiency syndrome (AIDS) with liver injury, respectively.Cases of AIH and AIH/PBC OS accounted for 90.9% (70/77 cases) of anti-SLA-positive patients, and 5 of 7 patients diagnosed with non-AIH (and OS) had elevated IgG, showing AIH feature.92.3% (12/13 cases) of anti-SLA with high titers of AMA were diagnosed as AIH/PBC overlap syndrome. Of the 77 anti-SLA-positive patients, 28 (36.4%) had advanced or end-stage liver disease, including decompensated cirrhosis (22 cases), chronic acute liver failure (4 cases), and liver transplantation (1 case) and death from liver failure (1 case). Conclusions Anti-SLA has high diagnostic specificity for AIH;anti-SLA positive in patients with PBC should be an important biomarker for the diagnosis of AIH/PBC overlap syndrome. Key words: Liver diseases; Hepatitis, autoimmune; Autoantibodies

Circulating microsome proteins in the pathogenesis of preeclampsia

Objective In this study, we aimed to detect the level of total circulating microparticles (MPs) in pregnant women with preeclampsia (PE) and analyze the proteome of MPs to explore their roles in the pathogenesis and progression of PE. Methods 98 pregnant women with PE, 54 healthy pregnant women, and 51 healthy non-pregnant women were enrolled from December 2016 to June 2018, whose MP levels were detected by flow cytometry and compared. Proteins extracted from the MPs were analyzed by high performance liquid chromatography mass spectrometry. Results The total MP level of the healthy pregnant group was significantly higher than thatof the non-pregnant group [159.87 (113.25, 218.18)/μl vs 94.10 (53.35, 140.23)/μl, P=0.004], but was not significantly different from that of the PE group. By proteomic profiling, 30 differential proteins were obtained between healthy pregnant women and healthy non-pregnant women, which were closely related to biological processes such as complements, coagulation cascades, angiogenesis and so on; 14 differential proteins were found between PE patients and healthy pregnant women, which were closely related to biological processes such as coagulation cascades, complements and inflammatory reactions, angiogenesis and so forth. Conclusions The level of circulating MPs may reflect the hypercoagulability of preeclampsia. In addition, circulating MPs may be involved in the pathogenesis of PE through various pathways by carrying different proteins, which indicates their potential value in the intervention of PE. Key words: Pre-eclampsia; Cell-derived microparticles; Thrombophilia; Proteomics

Molecular diagnosis of glycogen storage disease type I: a review.

Glycogen storage disease type I (GSD I) is a relatively rare metabolic disease with variable clinical intensity. It is caused by deficient activity of the glucose 6-phosphatase enzyme (GSD Ia) or a deficiency in the microsomal transport proteins for glucose 6-phosphate (GSD Ib). We searched the most recent English literature (1997-2017) regarding any article with the key word of "glycogen storage disease type I" in PubMed, Science Direct, Scopus, EMBASE, and Google Scholar. We will present all of the published articles about the molecular genetic characteristics and old-to-new diagnostic methods used to identify GSD I in regard of methodology, advantages and disadvantages. Diagnosis of GSD type I and its variants is challenging because it is a genetically heterogeneous disorder. Many molecular methods have been used to diagnose GSD I most of which have been based on mutation detection. Therefore, we discuss complete aspects of all of the molecular diagnostic tests, which have been used in GSD type I so far. With the advent of high throughput advanced molecular tests, molecular diagnosis is going to be an important platform for the diagnosis of storage and metabolic diseases such as GSD type I. Next-generation sequencing, in combination with the biochemical tests and clinical signs and symptoms create an accurate, reliable and feasible method. It can overcome the difficulties by the diagnosis of diseases with broad clinical and genetic heterogeneity.

Advances in coagulation compensation mechanisms of patients with immune thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired autoimmune hemorrhagic disease involving increased platelet destruction and insufficient platelet production, leading to thrombocytopenia, with or without clinical manifestations of bleeding. Although thrombocytopenia may cause coagulation dysfunction and hemorrhagic complications, the bleeding severity is not certainly proportional to the number of platelets. In some cases, there is no significant bleeding symptom even the platelet count is extremely low, which suggests there are additional compensatory mechanisms to control or ameliorate the bleeding complications in ITP patients. The present article aims to review recent investigations on the compensatory mechanisms of coagulation function in the patients with ITP. Key words: Thrombocytopenia; Microsomes; Phosphatidylserines; Thromboplastin; Platelet membrane glycoproteins; Thrombin; Interleukin-6

Effect of miR-758-3p on invasion and proliferation of gastric cancer cell line MGC803 by targeting MDM2

Objective To observe the regulation of microRNA (miRNA, miR)-758-3p on the expression of murine double microsomal gene 2 (MDM2) and its effect on invasion and proliferation of gastric cancer cell line MGC803. Methods The bioinformatics software was used to predict MDM2 as target gene of miR-758-3p. The wild type MDM2 gene 3 ′untranslated region luciferase reporter gene vector and miR-758-3p target sequence mutated vector and the corresponding miRNA were transfected into gastric cancer cells MGC803 by lipofectamine. Dual luciferase reporter system detects luciferase activity. The miR-758-3p mimics were transfected into gastric cancer cell MGC803 by lipofectamine. Real-time PCR was used to detect the transfection efficiency. Real-time PCR and Western blot were used to detect miR- MDM2 expression level in cells after transfection. Transwell assay and CCK-8 assay were used to detect cell invasion and proliferation. SPSS 20.0 was used to conduct the statistical analysis. Results Dual luciferase reporter assay confirmed that miR-758-3p could target MDM2 gene(P<0.05). The expression level of miR-758-3p in MGC803 cells transfected with miR-758-3p mimics was significantly higher than that in miR-NC cells [(6.68±0.53) vs (0.84±0.12), P<0.01]. Compared with miR-NC group, MDM2 expression was down-regulated in MGC803 cells transfected with miR-758-3p mimics (P<0.05). The number of invasive cells in miR-NC group and miR-758-3p group were (136.00 ±16.62)and (79.49±6.42). After knockdown MDM2, the invasiveness of cells was significantly decreased (P<0.05). The results of CCK-8 showed that the proliferation of MGC803 cells transfected with miR-758-3p group was significantly lower than that of miR-NC group (P<0.01). Conclusion miR-758-3p can reduce the invasion and proliferation of MGC803 cells by targeting MDM2. Key words: Stomach neoplasms; MicroRNAs; Neoplasm invasiveness; Cell proliferation; Murine double micro-gene 2

Correction: Microsomal prostaglandin E synthase-1 gene deletion impairs neuro-immune circuitry of the cholinergic anti-inflammatory pathway in endotoxaemic mouse spleen.

[This corrects the article DOI: 10.1371/journal.pone.0193210.].

Carbamazepine 10,11-epoxidation in human liver microsomes: influence of the CYP3A5*3 polymorphism.

Carbamazepine (CBZ) is a commonly prescribed antiepileptic drug, and is mainly metabolized to 10,11-CBZ epoxide in humans. Its biotransformation is catalyzed by cytochrome P450 (CYP) enzymes, with the predominant isoforms being CYP3A4 and CYP3A5. In the present study, the effects of the CYP3A5*3 (rs776746) polymorphism on CBZ 10,11-epoxidation in human liver microsomes genotyped as CYP3A5*3 were examined using a kinetic analysis. The kinetics for CBZ 10,11-epoxidation fit the Hill model with n of approximately 1.9-2.1 in all liver microsomes of the wild-type (CYP3A5*1/*1) and heterozygous (CYP3A5*1/*3) and homozygous (CYP3A5*3/*3) variants. The S50, Vmax, and CLmax values of wild-type liver microsomes were 263-327 μM, 793-1590 pmol/min/mg protein, and 1.51-2.95 μL/min/mg protein, respectively. The Vmax and CLmax values of liver microsomes of the heterozygous variant were approximately 15-40% those of wild-type liver microsomes. On the other hand, the Vmax and CLmax values of liver microsomes of the homozygous variant were more similar to those of the wild-type than the heterozygous variant. These results suggest that the CYP3A5*3 polymorphism has a negligible effect on CBZ 10,11-epoxidation in an in vitro system using human liver microsomes.

Purification and Characterization of LTC 4 Synthase from Sheep Uterus

Purification and Characterization of LTC 4 Synthase from Sheep UterusPurification and Characterization of LTC 4 Synthase from Sheep UterusEicosanoids, the oxygenated metabolites of eicosapolyenoic fatty acids such as arachidonic acid via the cyclooxygenase (COX), lipoxygenase (LOX) and epoxygenase (EPOX) pathways, are generated in response to specific stimuli, elicit the response and are then quickly metabolized. Hence, these are rightly termed as “local hormones” or “autocoids”. They are involved in the regulation of a variety of physiological as well as pathological processes, including reproduction. While there are extensive studies on the role of COX metabolites, such as prostaglandins, in reproduction, not much is known on the role of LOX metabolites in reproduction. Earlier, we have identified abundant LOX activity in sheep uterus and the highly purified enzyme was found to be a homo-dimeric protein with a molecular weight of 66 kDa. When incubated with arachidonic acid, the enzyme showed two lipoxygenase activities producing both 12- and 15-Hydroxyeicosatetraenoic acid (15-HPETEs) at the optimum pH of 5.5. The relative concentration of 12- and 15-HPETEs, however, changed with the pH of the reaction, 12-Hydroxyeicosatetraenoic acid (HETE) being higher in the alkaline range and 15-HETE being the abundant in the acidic range. Furthermore, the enzyme showed the dual lipoxygenase based 14,15-LTA 4 synthase activity as evidenced by the formation of 8,15-diHETEs, the hydrolysis products of 14,15-LTA 4 . In the present study, leukotriene C 4 synthase (LTC 4 S) enzyme was purified on Q-Sepharose column after solubilization of microsomes utilizing a combination of CHAPS and taurocholate. The purified enzyme showed activity with 5, 6-LTA 4 and 14, 15-LTA 4 , with slight preference towards the latter, and converting them to corresponding LTC 4 s. Both methyl esters and free acids of LTA 4 served as substrates, though the activity was more with methyl esters. However, the enzyme showed no activity with I-chloro-2, 4-dinitrobenzene (CDNB), the conventional substrate of glutathione S-transferases. Western blot analysis of sheep uterine microsomal proteins with LTC 4 synthase specific-peptide as well as whole protein antibodies showed strong cross reactivity with two closely migrating 70 kDa proteins. While showing similarity with the known LTC 4 synthases, sheep uterine LTC 4 synthase thus appears to be quite different in terms of molecular weight, as most LTC 4 synthases reported are 18 kDa proteins. In view of its association with the microsomal membranes and involvement in eicosanoid and glutathione metabolism, sheep uterine LTC 4 synthase may form a member of MAPEG (Membrane Associated Proteins in Eicosanoid and Glutathione metabolism) superfamily.

Effect of microsomal triglyceride transfer protein gene variants (-493G > T, Q95H and H297Q) on plasma lipid levels in healthy middle-aged UK men.

Microsomal triglyceride transfer protein (MTP) plays a central role in the synthesis of lipoproteins by shuttling lipids between phospholipid membranes to apoB. We have examined the effect of three MTP gene variants, -493G > T, Q95H and H297Q, in 2831 healthy UK middle-aged men. The rare allele frequencies were: 0.25 (95% CI 0.24-0.26) for -493T, 0.054 (95% CI 0.05-0.06) for 95H and 0.32 (95% CI 0.31-0.33) for 297Q. The three variants were in strong allelic association in all pairwise combinations (p < 0.001). None of the variant sites were associated with significant differences in cholesterol, triglyceride, apoB or apoAI levels. When stratified by tertiles of triglycerides for the H297Q variant alone there was a significant effect on apoB levels in men in the top tertile (p = 0.01). Considering the -493G > T and H297Q genotype in combination on baseline levels, individuals with three or four rare alleles had 6.6% higher mean apoB levels compared to the rest (p = 0.007). Therefore, homozygosity for 297Q at higher triglyceride (Tg) levels, or in combination with -493G > T, is associated with a raising effect on apoB levels, suggesting the importance of modest differences in MTP activity in determining hepatic secretion of lipoproteins in healthy men.

Effect of neonatal overfeeding on associated enzymes of lipid metabolism in rat liver

Objective To investigate the effect of neonatal overfeeding on the expression of lipid metabolic associated enzymes and molecular mechanisms in the livers of rats. Methods Male Sprague-Dawley rats were randomly assigned to litter sizes of three group (small litters, SL group) or ten (normal litters, NL group) on postnatal day 3.Body weight, milk intake, liver and fat pad (epididymal and retroperitonea) weight, and hepatic histological analysis were recorded in week 2 and week 3, respectively.The levels of lipids were detected by the automatic biochemical analyzer.The mRNA expressions of acetyl-CoA carboxylase (ACC), lipoprotein lipase (LPL), liver-type fatty acid-binding protein (L-FABP), carnitine palmitoyltransferase 1(CPT1), microsomal triglyceride transfer protein (MTP), sterol regulatory element-binding protein-1c (SREBP-1c) and peroxisome proliferator activated receptor α (PPARα)in liver were determined by real time PCR; the protein expressions of SREBP-1c and PPARα were determined by Western lot. Results As early as week 2, the body weight of rats in SL group began to elevate (t=-5.997, P<0.001) and food intake (t=-3.462, P=0.002) compared with the rats in NL group, and persistent to weaning (body weight: t=-17.019, P<0.001; food intake: t=-2.276, P=0.031). By the time of 3 weeks old, SL rats increased visceral fat pad [retroperitonea (t=-7.643, P<0.001), epididymal (t=5.997, P=0.001)], liver weight (t=-7.812, P<0.001), hepatosomatic index (t=-3.829, P=0.003) and serum triglyceride (TG) level (t=-2.703, P=0.022) compared with those of NL rats, as well as the level of hepatic ACC mRNA (t=-3.751, P=0.007), LPL (t=-2.721, P=0.017) and L-FABP mRNA (t=-2.521, P=0.026) .While CPT1 mRNA (t=-1.531, P=0.155) and MTP mRNA (t=-1.741, P=0.098) levels remained unchanged in both groups.Hepatic SREBP-1c mRNA expression increased in SL rats after 2 to 3 weeks (t=-2.836, P=0.016), paralleled with ACC and LPL mRNA expression; while the mRNA and protein expression of PPARα remained unchanged (t=-0.854, P=0.411). Conclusions Postnatal overfeeding can promote higher liver pad and dyslipidemia at the time of weaning.The process may be regulated by up-regulated expression of ACC, LPL and L-FABP.SREBP-1c may be participated in the regulation of ACC, a rate-limiting enzyme involved in lipogenesis. Key words: Nutritional programming; Liver; Lipid metabolism; Rat

Gene variance in microsomal epoxide hydrolase and the susceptibility of coal workers' pneumoconiosis

To explore whether the tagging single nucleotide polymorphisms (SNPs) within EPHX1 gene were involved in the genetic susceptibility to coal worker's pneumoconiosis (CWP) by case-control study. This study consisted of 697 CWP patients and 694 controls. All the subjects were Han Chinese, underground coal miners and recruited from coal mines of Xuzhou Mining Business Group Co Ltd.. The venous blood samples were obtained from all subjects and extracted genome DNA from the isolated leucocytes. Three SNPs were selected from the HapMap and the genotyping was done by the TaqMan method with the ABI 7900HT Real Time PCR system. The Single SNP analyses showed that the genotype frequencies of EPHX1 (rs2234922) was significantly associated with decreased risk of CWP under co-dominant model (OR = 0.22, 95% CI = 0.06~0.79, P = 0.020), recessive model (OR = 0.23, 95% CI = 0.06~0.82, P = 0.023), and addictive model (OR = 0.75, 95% CI = 0.58~0.96, P = 0.022). The further stratification analysis showed that the risk of CWP will significantly decreased in non-smoking groups (OR = 0.10, 95% CI = 0.01~0.83, P = 0.033). Our results suggest that individuals with the EPHX1 (rs223492) GG genotype was associated with a dereased risk of CWP, and it has a protective effect on the developing CWP.

Screening for endogenous substrates reveals that CYP2D6 is a 5-methoxyindolethylamine O-demethylase.

The objective of this investigation was to screen for potential endogenous substrates for CYP2D6. Using recombinant CYP2D6, together with hepatic microsomes from CYP2D6-transgenic mice, human liver microsomes, and a specific anti-CYP2D6 monoclonal antibody, it was ascertained that CYP2D6 does not significantly metabolize the endogenous phenylethylamines 2-phenylethylamine, octopamine, synephrine, 3-methoxy-p-tyramine, 4-methoxy-m-tyramine, metanephrine, and normetanephrine, nor the indolethylamines tryptamine, serotonin, 6-methoxytryptamine, and melatonin, nor the beta-carbolines harman, norharman and tryptoline. However, the indolethylamines 5-methoxy-N,N-dimethyltryptamine (5-MDMT) and pinoline (6-methoxy-1,2,3,4-tetrahydro-beta-carboline) showed relatively high affinity for CYP2D6 in a spectral binding assay (K(s) 28 +/- 5, and 0.5 +/- 0.3 microm (mean +/- SEM), respectively) and were O-demethylated only by CYP2D6 in a panel of 15 recombinant common human P450s. Pinoline and 5-MDMT O-demethylase activities were 35- and 11-fold greater in liver microsomes from CYP2D6-humanized mice, respectively, than those in liver microsomes from control mice. Moreover, the increased activities were completely inhibited by an anti-CYP2D6 monoclonal antibody. Kinetic analysis with recombinant CYP2D6 gave K(m) and k(cat) values for 5-MDMT and pinoline O-demethylations of 12 +/- 1 microm and 65 +/- 1 min(-1) and 1.8 +/- 0.3 microm and 26 +/- 1 min(-1), respectively. These two substrates can be added to 5-methoxytryptamine, which we have recently reported to be an endogenous CYP2D6 substrate. CYP2D6 is therefore a relatively highly specific, high-affinity, high-capacity 5-methoxyindolethylamine O-demethylase. Polymorphic cytochrome CYP2D6 may therefore exert an influence on mood and behavior by the O-demethylation of these 5-methoxyindolethylamines found in the brain and pineal gland. These processes may also impact on mental and neurological health. The findings may open new vistas for the determination of CYP2D6 phenotype.

Regeneration of serotonin from 5-methoxytryptamine by polymorphic human CYP2D6.

Polymorphic cytochrome P450 2D6 (CYP2D6) is expressed in several types of central neurons but its function in human brain is currently unknown. Using recombinant enzymes and CYP2D6-transgenic mice, we established that 5-methoxytryptamine (5-MT), a metabolite and precursor of melatonin, is a specific and high-turnover endogenous substrate of CYP2D6. This potent serotonergic neuromodulator in numerous physiological systems binds tightly to recombinant CYP2D6 enzyme with an equilibrium dissociation constant (K(s)) of 23.4 micromol/l, and is O-demethylated to serotonin (5-hydroxytryptamine, 5-HT) with a high turnover of 51.7 min(-1) and low Michaelis-Menten constant of 19.5 micromol/l. The production of 5-HT from 5-MT catalyzed by CYP2D6 was inhibited by selective serotonin reuptake inhibitors, and their inhibition potency (K(i), micromol/l) decreased in the order of fluoxetine (0.411) > norfluoxetine (1.38) > fluvoxamine (10.1) > citalopram (10.9). Liver microsomes prepared from CYP2D6-transgenic mice showed about 16-fold higher 5-MT O-demethylase activity than that from wild-type mice. After the intravenous co-administration of 5-MT (10 mg/kg) and pargyline (20 mg/kg), serum 5-HT level was about 3-fold higher in CYP2D6-transgenic mice than wild-type mice. When dosed with alpha,alpha,beta,beta-d -5-MT, alpha,alpha,beta,beta-d4-5-HT was detected in transgenic mouse serum, and its content was much higher than wild-type mouse. alpha,alpha,beta,beta-d4-5-HT was not produced in CYP2D6-transgenic mice pretreated with quinidine. The regeneration of 5-HT from 5-MT provides the missing link in the serotonin-melatonin cycle. Up to 10% of the population lacks this enzyme. It is proposed that this common inborn error in 5-MT O-demethylation to serotonin influences a range of neurophysiologic and pathophysiologic events.

Highly Efficient Preparation of Resorufin-β-D-glucuronide†

Resorufin-beta-o-glucuronide(keg) is a substrate of the beta-glucuronidase enzyme which exhibited almost no fluorescence, upon addition of beta-glucuronidase a high fluorescent compound resorufin will be released. resorufin, is a fluorescent compound possessing good optical properties. on the basis of the off-on type fluorescent reaction, reg can be served as the good fluorescent substrate of beta-glucuronidase. however, commercial available keg is rather expensive due to the difficulty for preparation of reg and the studies on reg are very limited. this study aimed to adopt the mild biosynthesis approach to efficiently prepare reg, based on resorufin can be extensively metabolized to keg by udp-glucuronosyltransferases(ugts). reg was prepared using resorufin as the starting material and liver microsomes from cynomolgus monkeys(cylm) as the enzyme source. resorufin(re, 100 mu mol/l) was incubated in tris-hcl(50 mmol/l, ph = 7.4, with 1% dmso) with cylm(0.5 mg/ml) at 37 degrees c for 4 h. after the optimization of the incubation conditions, the conversion of reg was more than 80%. a unique solid-phase extraction column(spe) packed with c18wax was used to enrich and purify the product keg with high yield. the product was then identified by both lc-ms and nmr techniques. finally, a high throughput screening method for beta-glucuronidase inhibitors was well established, based on the accurate kinetic parameters of reg towards beta-glucuronidase and the absorption and emission spectrum of reg.