Isoliquiritigenin induces growth inhibition and apoptosis through downregulating arachidonic acid metabolic network and the deactivation of PI3K/Akt in human breast cancer.

Arachidonic acid (AA)-derived eicosanoids and its downstream pathways have been demonstrated to play crucial roles in growth control of breast cancer. Here, we demonstrate that isoliquiritigenin, a flavonoid phytoestrogen from licorice, induces growth inhibition and apoptosis through downregulating multiple key enzymes in AA metabolic network and the deactivation of PI3K/Akt in human breast cancer. Isoliquiritigenin diminished cell viability, 5-bromo-2'-deoxyuridine (BrdU) incorporation, and clonogenic ability in both MCF-7 and MDA-MB-231cells, and induced apoptosis as evidenced by an analysis of cytoplasmic histone-associated DNA fragmentation, flow cytometry and hoechst staining. Furthermore, isoliquiritigenin inhibited mRNA expression of multiple forms of AA-metabolizing enzymes, including phospholipase A2 (PLA2), cyclooxygenases (COX)-2 and cytochrome P450 (CYP) 4A, and decreased secretion of their products, including prostaglandin E2 (PGE2) and 20-hydroxyeicosatetraenoic acid (20-HETE), without affecting COX-1, 5-lipoxygenase (5-LOX), 5-lipoxygenase activating protein (FLAP), and leukotriene B4 (LTB4). In addition, it downregulated the levels of phospho-PI3K, phospho-PDK (Ser(241)), phospho-Akt (Thr(308)), phospho-Bad (Ser(136)), and Bcl-xL expression, thereby activating caspase cascades and eventually cleaving poly(ADP-ribose) polymerase (PARP). Conversely, the addition of exogenous eicosanoids, including PGE2, LTB4 and a 20-HETE analog (WIT003), and caspase inhibitors, or overexpression of constitutively active Akt reversed isoliquiritigenin-induced apoptosis. Notably, isoliquiritigenin induced growth inhibition and apoptosis of MDA-MB-231 human breast cancer xenografts in nude mice, together with decreased intratumoral levels of eicosanoids and phospho-Akt (Thr(308)). Collectively, these data suggest that isoliquiritigenin induces growth inhibition and apoptosis through downregulating AA metabolic network and the deactivation of PI3K/Akt in human breast cancer.

Effects of 18alpha-glycyrrhizin on the pharmacodynamics and pharmacokinetics of glibenclamide in alloxan-induced diabetic rats.

This paper investigated the effects of 18alpha-glycyrrhizin (18alpha-GL) on the pharmacodynamics and pharmacokinetics of glibenclamide in experimental diabetic rats. 18alpha-GL (25 mg/kg) and/or glibenclamide (1 mg/kg) were given to alloxan-induced diabetic rats for consecutive 5 days. When the rats were co-treated with 18alpha-GL and glibenclamide, fasting plasma glucose concentration was further reduced, plasma insulin content and liver glycogen level were increased markedly as compared with glibenclamide-treated animals. Meanwhile, in co-treated group, elimination rate constant (Ke) of glibenclamide was reduced while peak plasma concentration (C(max)), area under the plasma concentration vs time curve (AUC(0-14 h)) and elimination half-life (T(1/2Ke)) were increased significantly vs glibenclamide alone administered rats. The activities of hepatic CYP3A and the markers of liver injury, plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST), were significantly decreased in rats treated with 18alpha-GL alone and in combination with glibenclamide. Results of immunohistochemistry showed that 18alpha-GL improved the effects of glibenclamide on the pathological morphology of pancreatic islet beta cells and the intensities of positive immunostaining for insulin. Our results revealed that 18alpha-GL led to the enhancement of the hypoglycemic effect of glibenclamide by inhibiting the activity of CYP3A; on the other hand, 18alpha-GL protected the pancreatic islet beta cells and liver from damage in diabetes which suggested that 18alpha-GL might be beneficial as an adjuvant drug of glibenclamide in a proper dose, especially to the diabetic patients associated with liver dysfunction.

Segment-specific proximal tubule injury in tripterygium glycosides intoxicated rats.

Tripterygium glycosides (TG), extracted from the Chinese herb Tripterygium wilfordii Hook. f, is a widely used anti-inflammatory and immunosuppressive agent with definite nephrotoxicity. However, its toxic mechanism remained undiscovered. The aim of this study was to characterize the potential toxicity of TG on segments of proximal tubule in rats. Six hundred and 1200 mg/kg of TG was administered by daily intragastric instillation for 16 days. A significant reduction of p-aminohippurate accumulation by renal cortical slices indicated that TG damaged organic anion transporter (OAT) system that localized at the proximal tubule, especially S(2) segment. A dramatic loss of kidney glutamine synthetase (GS) activity induced by TG reflected S(3) segment damage. Because mRNA expression of OAT1, OAT3, and GS was decreased substantially, we ascribe the fall of p-aminohippurate accumulation and GS activity to alterations at the transcriptional level. A dose-related diminution of kidney glutathione S-transferase activity was noted simultaneously, suggesting oxidative stress involvement. Histopathological lesions were observed in the TG intoxicated rat kidney even though there were no obvious changes of serum urea and creatinine at this dose level. In summary, we provided evidences supporting that TG caused segment-specific dysfunction in the kidney proximal tubule.

Expression of epoxygenases belonging to CYP2 family in rat myocardial ischemia/reperfusion injury in vivo.

OBJECTIVE: To elucidate the expression of epoxygenases belonging to cytochrome P-450 mono-oxygenases (CYP2) family in rat ischemic myocardium at varying reperfusion periods, and the effect of epoxygenase inhibition on the post-ischemic heart. METHODS: The current study was conducted in the Department of Pharmacology, Medical College of Wuhan University, China, between September 2004 and June 2005. Rats were subjected to 40 minutes of myocardial ischemia, followed by 0, 15, 60, and 180 minutes of reperfusion. Superoxide generation was assayed by confocal microscopy, CYP2B1/2, 2C6, 2E1, 2J3 gene expressions were determined by reverse transcriptase polymerase chain reaction. Fourteen, 15-dihydroxyeicosatrienoic acid (DHET) concentration was measured by enzyme-linked immunosorbent assay. The effects of the CYP epoxygenase inhibitor N-methylsulphonyl-6-(2-propargyloxyphenyl) hexanamide (MS-PPOH) on myocardial damage and superoxide generation caused by 60 minutes of reperfusion were also evaluated. RESULTS: During myocardial ischemia/reperfusion, CYP2C6 and 2J3 mRNA expression were up-regulated with the peak level at 15 minutes of reperfusion; CYP2E1 gene expression decreased in a time dependent manner and reached the minimum level at 180 minutes of post-ischemia. Meanwhile, no obvious variations of CYP2B1/2 gene expression were detected during different reperfusion periods. Fourteen, 15-DHET significantly increased during reperfusion in ischemic hearts. The MS-PPOH pretreatment (15 mg/kg) effectively reduced myocardial damage and superoxide production. CONCLUSION: There are changes in gene expression of individual isozymes and an elevation of CYP epoxygenase activity involved in myocardial reperfusion injury in vivo. Epoxygenase inhibition plays a protective role in cardiac post-ischemic damage.

Fast evaluation of oxidative DNA damage by liquid chromatography-electrospray tandem mass spectrometry coupled with precision-cut rat liver slices.

OBJECTIVE: To establish a fast and sensitive method for the detection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in precision-cut rat liver slices by HPLC-MS/MS and to investigate isoniazid (INH) -induced oxidative DNA damage. METHODS: Precision-cut liver slices (300 microm) were prepared from male rats, and incubated with INH (0.018 mol/L) for 2 h after 1 h preincubation. DNA in the slices was extracted and digested into free nucleosides at 37 degrees C. The samples were injected into HPLC-MS/MS after the proteins were removed. The level of oxidative DNA damage was estimated using the ratio of 8-OHdG to deoxyguanosine (dG). RESULTS: The limit of detection of 8-OHdG was 1 ng/mL (S/N=3) and the intra-assay relative standard variation was 3.38% when one transition 284.3/168.4 was used as a quantifier and another two transitions 284.3/140.2, 306.1/190.2 as qualifiers. 8-OHdG and dG were well separated, as indicated by elution at 10.02 and 7.37 min, respectively. INH significantly increased the ratio of 8-OHdG to dG in rat liver slices (P<0.05). CONCLUSION: 8-OHdG in precision-cut liver slices could be sensitively determined by HPLC-MS/MS. HPLC-MS/MS coupled with precision-cut tissue slices is a fast and reliable analytical technique to evaluate oxidative DNA damage of target tissues caused by procarcinogens and cytotoxins.

Effects of Kupffer cell inhibition on liver function and hepatocellular activity in mice.

Kupffer cells are the tissue macrophages in the liver and play an important role in the defense mechanisms of the body. However, their role in liver function and hepatocellular activity remains unclear. This study was therefore undertaken to investigate the effect of gadolinium chloride-induced Kupffer cell dysfunction on liver function and hepatocellular signaling activity in mice and to establish an animal model for studying the role of Kupffer cells in vivo. Kunming mice were intraperitoneally injected with different doses of gadolinium chloride (GdCl3), a selective inhibitor of Kupffer cells, and the mice were sacrificed at different time periods following the drug administration. Hepatotoxicity and Kupffer cell function, as well as the levels of signaling molecules and inflammatory mediators in liver tissue, were measured. We demonstrated that the administration of 10-20 mg/kg GdCl3 caused apoptosis of Kupffer cells and blocked the Kupffer cell effector function, as shown by a decrease in CD68 expression and phagocytic activity. In addition, the NO, PGE2 and cAMP levels in the liver were also reduced significantly. Furthermore, 20 mg/kg GdCl3 decreased the levels of cNOS, PKC and NF-kappaB p65 expression by 26.6, 68 and 64%, respectively. In contrast, hepatotoxicity was not observed when the same doses of GdCl3 were used. Moreover, we found that Kupffer cell function and the NO, PGE2 and cAMP contents, as well as PKC and NF-kappaB p65 levels in the liver were only partially, but not fully recovered in up to six days following 20 mg/kg GdCl3 injection. However, the administration of higher doses of GdCl3 (40 mg/kg) caused both hepatotoxicity and Kupffer cell necrosis, as well as an increased release of TNF, NO, and PGE2 in the liver. These results indicate that administration of suitable doses of GdCl3 blocked the effector function of Kupffer cells selectively, but did not cause liver parenchymal cell toxicity, and provide a frame-work for the establishment of an animal model for studying the role of Kupffer cells in signaling in the liver. Lastly, the present study also provides evidence that shows there is a positive association between the expression of cAMP, PKC, or NF-kappaB and the levels of NO, PGE2 and TNF in the liver of Kupffer-cell-blocked mice, and suggests that Kupffer cells may play a part in mediating liver function and hepatocellular activity.

[Activation of the immunologic function of rat Kupffer cells by the polysaccharides of Angelica sinensis].

AIM: To observe the influence of polysaccharides of Angelica sinensis (ASP) on the immunologic function of rat Kupffer cells. METHODS: Normal rat Kupffer cells were treated with ASP in vitro. Absorbance at 540 nm ( A540) of neutral red absorption and supernatant NO, TNF-alpha in the cells were measured to evaluate the immunologic function of Kupffer cells; LDH leakage was measured to estimate the severity of cellular damage; Rats were given ASP 0.025, 0.1, 0.25 and 1.0 g x kg(-1) ig (qd x 7 d) in vivo. The above indices and ACP of Kupffer cells were measured, sGST and sALT activity were detected as indices of hepatotoxicity. RESULTS: ASP markedly enhanced the phagocytic activity, ACP and supernatant NO, TNF-alpha of Kupffer cells both in vitro and in vivo . The increase of sGST was observed after administration of ASP 1.0 g x kg(-1), but the LDH leakage of the hepatocytes was not increased in vitro. CONCLUSION: ASP with suitable dose could activate the function of Kupffer cells. Slight liver injury was caused by ASP 1.0 g x kg(-1) in vivo, which was likely caused by factors, such as NO, TNF-alpha, indirectly.

[Antagonistic effect of sodium ferulate on glycerol-induced renal oxidative injury in mice].

AIM: To investigate the effect of sodium ferulate (SF) on glycerol-induced renal injury. METHODS: Glycerol solution 50% was injected intramuscularly to establish a model of acute tubular necrosis in mice. SF was administered intraperitoneally at the dose of 100-200 mg.kg-1 at the beginning of establishing the model and its effect was observed by monitoring renal function, antioxidative functions and renal pathologic histology. RESULTS: At 6 and 72 h after glycerol injection, SF treatment (100-200 mg.kg-1) showed significant and dose-dependent antagonistic actions on the increment of blood urea nitrogen (BUN), creatinine (Cr), and N-acetyl-beta-glucosaminidase (NAG) induced by glycerol. The increase of renal malondialdehyde (MDA) content and the decrease of glutathione content, glutathione peroxidase (GSH-Px), glutathione S-transferase (GST), catalase (Cat) and superoxide dismutase (SOD) activities resulting from glycerol injection were remarkably inversed by SF at the dose of 200 mg.kg-1. Meanwhile, improvement of the renal histology was observed as well. CONCLUSION: SF showed beneficial effect on glycerol-induced acute tubular necrosis due to its antioxidative action.

[Studies on nano-particle sols of hydroxyaptite and titanium dioxide for haemo-compatibility].

A biological evaluation is conducted for two types of nano-particle sols, hydroxyaptite(HAP) and titanium dioxide(TiO2). The results show that HAP sol significnatly prolongs the bleeding time and coagulation time of mice as well as the prothrombin time(PT) and partial thromboplastin time(PTT) of rats while TiO2 sol exhibits no such effects. Neither HAP sol nor TiO2 sol instigated in-vitro hemolysis of rabbit erythrocyte. However, both of the materials caused in-vitro aggregation of rabbit erythrocytes. The reason underlying the different results as to the two types of material is their specific stabilizer, heparin for HAP sol and PVC for TiO2 sol. We came to the conclusion that a biologically inert stablizer has no less significance than the nano-particle's very own nature in a nano-material's application prospect.

[Effects of L yaojiu of invigorating blood circulation and eliminating blood stasis in old rats].

L Yaojiu was investigated for its effects of invigorating blood circulation and eliminating blood stasis using old rats (aged over ten months) as the model of blood stasis. Three different dosages of L Yao Jiu (14.3, 28.5, 57.0 mg crude drugs/kg) had been administrated orally per day to rats for 12 consecutive days. The changes of the mesenteric microcirculation and the hemorrheology were observed. The content of serum malondialdehyde (MDA) and the activities of serum monoamine oxidase (MAO) and superoxide dismutase (SOD) were determined. The results showed L Yao Jiu could accelerate the blood streams, dilate the capillaries and inhibit erythrocyte aggregations. It also reduced blood viscosity, inhibited platelet aggregations and improved the function of erythrocytes. On the other hand, the activities of total-SOD and Cu-SOD were increased and the content of MDA was decreased. These results suggests that L Yao Jiu could invigorate blood circulation and eliminate blood stasis in old rats.

[Application of precision-cut liver slice to the study of the effect of glutathione on cadmium chloride hepatotoxicity].

In order to evaluate the feasibility of application of precision cut liver slice(PCLS) to the study of the effect of glutathione on cadmium chloride hepatotoxicity, slices were cultured with CdCl2 and GSH. Slices activity and drug metabolic function was estimated by assay of slice viability, NO secretion, and phase I and phase II enzyme activity. Results showed that the slices activity was significantly inhibited by CdCl2. Various phase I and phase II enzymes activity of slices were obviously reduced by CdCl2, but aniline hydroxidase activity was enhanced. GSH could distinctly reversed the change of slices induced by CdCl2. Therefore, it could be concluded that PCLS culture system was sensitive and steady, and was a good model for pharmacological and toxicological investigation of liver in vitro.

[The effects of silymarin on hepatic microsomal and mitochondrial membrane fluidity in mice].

OBJECTIVE: To observe the effects of silymarin on hepatic microsomal and mitochondrial membrane fluidity in mice. METHOD: Liver microsomal and mitochondrial membranes were labled by ANS and DPH. Membrane fluorensent intensity (F), fluorensent polarization(P) and microviscosily(eta) of liver microsome and mitochondria were determined. RESULT: Sil increased the external membrane fluidities of liver microsome and mitochondria, and decreased the internal membrane fluidities of liver microsome and mitochondria. Pretreatment with CCl4, the external membrane fluidity of liver microsome and mitochondria were increased, and the internal membrane fluidities of liver microsome and mitochondria were decreased. After given sil 140,280 mg.kg-1, the increased external membrane fluidities of liver microsome and mitochondria were lowered, and the decreased internal membrane fluidities of liver microsome and mitochondria were enhanced in a dose-dependent manner. CONCLUSION: The protective effects of sil on liver injury may be related to the recovery of the membrane fluidities of liver microsome and mitochondria.

[Effects of Angelica sinensis polysaccharides on hepatic drug metabolism enzymes activities in mice].

OBJECTIVE: To study the effects of Angelica sinensis Polysaccharides (ASP) on the hepatic drug metabolism enzymes activities in normal mice and those prednisolone (PSL)-induced liver injury. METHOD: The activities of phase II enzymes (GSH-related enzymes) and cytochrome P450 enzymes were measured by biochemical method. RESULT: ASP increased the activities of glutathione S-transferase in liver microsomes and mitochondria. The cytochrome P450 content, NADPH-cytochrome c reductase, aminopyrine N-demethylase, and aniline hydroxylase activities in liver microsomes were also increased. PSL significantly increased serum ALT levels, and decreased the liver mitochondrial glutathione content. At the same time, other enzymes activities were all increased. When mice were treated with ASP 2.0 g.kg-1, the PSL-induced changes on cytochrome P450 enzymes, glutathione S-transferase, and GSH content were restored. CONCLUSION: ASP can modulate the activities of drug metabolism enzymes.

Antitumor and immunostimulatory activity of a polysaccharide-protein complex from Scolopendra subspinipes mutilans L. Koch in tumor-bearing mice.

Scolopendra subspinipes mutilans L. Koch has been used for cancer treatment in traditional Chinese medicine for hundreds of years. In this study, the effects of a polysaccharide-protein complex from Scolopendra subspinipes mutilans L. Koch (SPPC) on the tumor growth and immune function were assessed in sarcoma S180 and hepatoma H22 bearing mice. Results showed that SPPC significantly inhibited the growth of S180 transplanted in mice and prolonged the survival time of H22- bearing mice. In S180-bearing mice, it promoted specific and nonspecific immune response as evidenced by enhancing the activities of natural killer (NK) cells, cytotoxic T lymphocytes (CTL) and the ratio of Th1/Th2 cytokines, and increasing the percentages of CD4(+) T cells, B cells and NK cells. Furthermore, SPPC not only significantly inhibited mRNA expression and production of the immunosuppressive cytokines (IL-10 and TGF-ß), but also diminished arachidonic acid (AA)-metabolizing enzymes (COX-2 and CYP4A) and their products (PGE(2) and 20-HETE) in tumor-associated macrophages (TAMs). Taken together, our results indicate that SPPC inhibits tumor growth in vivo by improving antitumor immune responses at least partly via downregulating AA-metabolic pathways in TAMs, and could act as an anti-tumor agent with immunomodulatory activity.

Does CYP2E1 play a major role in the aggravation of isoniazid toxicity by rifampicin in human hepatocytes?

Isoniazid and rifampicin are first-line anti-tubercular drugs. In a recent paper, Shen et al. provided interesting findings that rifampicin exacerbated isoniazid toxicity in human hepatocytes but not in rat hepatocytes. The main conclusion was that the difference in cytochrome P450 2E1 (CYP2E1) induction by rifampicin between rat and human hepatocytes accounted for the difference in exacerbation of isoniazid hepatotoxicity by rifampicin. 4-Nitrophenol hydroxylase (4-NP) activity was the only probe of CYP2E1 activity used in the paper. The authors presented data showing that rifampicin enhanced 4-NP activity and CYP2E1 mRNA expression in human hepatocytes, but not in rat hepatocytes. However, CYP3A also makes a significant contribution to 4-NP activity in humans and rats, which has been confirmed by both CYP3A-specific inducer and inhibitors. Rifampicin is a strong inducer of human CYP3A; thus, the increase in 4-NP activity in human hepatocytes could be due to the induction of CYP3A. Rifampicin did not increase 4-NP activities in rat hepatocytes, which could reflect a lack of the induction of rat CYP3A by rifampicin. Additionally, more experiments are needed to support the conclusion that rifampicin increased CYP2E1 mRNA expression in human hepatocytes because of the small sample size and the limitations of semi-quantitative RT-PCR. The study by Shen et al. suggests that another drug-metabolizing enzyme rather than CYP2E1 could be involved in the aggravation of isoniazid toxicity by rifampicin in human hepatocytes.

Protective effects of thiopronin against isoniazid-induced hepatotoxicity in rats.

Isoniazid is a widely used drug for the treatment of tuberculosis, but hepatotoxicity is a major concern during treatment. Thiopronin contains an SH-group and is generally considered an antioxidant. The aim of the present study was to investigate the effects of thiopronin during liver injury and DNA damage induced by isoniazid. Rats were injected daily with isoniazid (100 mg/kg, i.p.) for 21 days with or without thiopronin co-administration (60 mg/kg, i.p.) from day 11 to day 21. The influence of thiopronin on isoniazid-induced DNA oxidative damage was analyzed in precision-cut rat liver slices by HPLC-MS/MS. Thiopronin prevented isoniazid-induced hepatotoxicity, indicated by both diagnostic indicators of liver damage (alanine aminotransferase and aspartate aminotransferase) and histopathological analysis. In vivo, thiopronin significantly inhibited isoniazid-induced CYP2E1 activity as assessed by both chlorzoxazone hydroxylase and aniline hydroxylase (p<0.001). Thiopronin concentration-dependently inhibited CYP2E1-dependent aniline hydroxylation, and the Dixon plots suggest that thiopronin is a competitive inhibitor of CYP2E1. Thiopronin markedly attenuated isoniazid-induced inhibition of the detoxification system through cytosolic glutathione S-transferases (GSTs), including mu GST and alpha GST. In precision-cut liver slices, the free radical scavenging activity of thiopronin reduced the generation of DNA adducts induced by isoniazid (p<0.05). Altogether, these results suggest that thiopronin exerts its hepatoprotective activity against isoniazid-induced hepatotoxicity by inhibiting the production of free radicals in addition to its role as a scavenger. Thiopronin may reduce free radical generation via inhibition of hepatic CYP2E1 and increase the removal of free radicals directly or through the induction of cytosolic GSTs.

Effects of rifampin on CYP2E1-dependent hepatotoxicity of isoniazid in rats.

Isoniazid and rifampin are first line drugs used to prevent and treat tuberculosis. The effects of rifampin co-administration on isoniazid-induced oxidative stress were investigated by the determination of the changes in hepatic metabolizing enzymes and DNA damage. Rats were treated with isoniazid alone (100 mg/kg, i.p.) or co-treated with rifampin (100 mg/kg, i.g.) for 10 or 21 days. Activities of CYP2E1, CYP1A1, CYP3A and glutathione S-transferases (GSTs) were analyzed by specific substrates. DNA oxidative damage by drug treatments was analyzed in precision-cut liver slices by HPLC-MS/MS. Isoniazid significantly increased CYP2E1 activities above control levels after 10 or 21 days treatment (2.25-4.59-fold), indicated by both chlorzoxazone hydroxylase and aniline hydroxylase (p<0.01). Isoniazid treatment decreased activities of cytosolic total GST, alpha GST and mu GST after 21 days (p<0.01). No change in activities of CYP1A1, CYP3A, and CYP3A1 mRNA expression was observed after isoniazid treatment. Rifampin co-administration significantly attenuated isoniazid-induced CYP2E1 levels (p<0.01) and inhibition of mu GST (p<0.01). Rifampin did not increase the formation of DNA adducts induced by isoniazid. These results suggest that rifampin co-administration does not increase isoniazid-induced oxidative stress through hepatic CYP2E1 during short-term treatment in experimental rats.

Changes of multiple biotransformation phase I and phase II enzyme activities in human fetal adrenals during fetal development.

AIM: Fetal adrenal, which synthesizes steroid hormones, is critical to fetal growth and development. Our recent research showed that some xenobiotics could interfere with steroidogenesis and induce intrauterine growth retardation in rats. The study on the characteristics of biotransformation enzymes in fetal adrenals still seems to be important with respect to possible significance in xenobiotic-induced fetal development toxicity. In this study, the activities of several important xenobiotic-related phase I and phase II enzymes in human fetal adrenals were examined and compared with those in fetal livers. METHODS: The activity and mRNA expression were determined by enzymatic analysis and RT-PCR. RESULTS: The levels of cytochrome (CYP)2A6, CYP2E1, and CYP3A7 isozymes in fetal adrenals were 82%, 92%, and 33% of those in fetal livers, respectively. There was a good positive correlation between adrenal CYP2A6 activity and gestational time. The values of alpha glutathione S-transferase (GST), pi-GST, and microGST in adrenals were 0.5, 4.4, and 8.3-fold of those in the livers, respectively, and the activity of adrenal pi-GST was negatively correlated with gestational time. The uridine diphosphoglucuronyl transferase activities, which were measured using p-hydroxy-biphenyl and 7-hydroxy-4-methylcoumarin as substrates, were 9% and 3%, respectively, of those in the fetal livers. CONCLUSION: Our investigation suggested that adrenal could be an important xenobiotic-metabolizing organ in fetal development and may play a potential role in xenobiotic-induced fetal development toxicity.

Influences of 3-methylcholanthrene, phenobarbital and dexamethasone on xenobiotic metabolizing-related cytochrome P450 enzymes and steroidogenesis in human fetal adrenal cortical cells.

AIM: To explore the influence and possible mechanism of xenobiotics on adrenal steroidogenesis during fetal development. METHODS: Primary human fetal adrenal cortical cells were prepared, cultured and treated with 3-methylcholanthrene, phenobarbital and dexamethasone. The activities of 7-ethoxyresorufin O-dealkylase, benzphetamine, aminopyrine and erythromycin N-demethylases were measured by enzyme assays. At the same time, quantitative analysis of steroid hormones cortisol, aldosterone, testosterone and progesterone were carried out in cultural medium by radioimmunoassays. RESULTS: The activities of benzphetamine and aminopyrine N-demethylase were increased in the cultural fetal adrenal cells treated with phenobarbital (0.25-1 mmol/L) for 24 h. Dexamethasone (25-100 micromol/L) also increased the activity of erythromycin N-demethylase. The activity of 7-ethoxyresorufin O-dealkylase was undetected in the cells treated without and with 3-methylcholanthrene (0.5-2 micromol/L). Meanwhile, the contents of medium cortisol, aldosterone and progesterone were decreased after treatment with 3-methylcholanthrene. Cortisol, aldosterone and progesterone concentrations were also slightly decreased with phenobarbital. Dexamethasone enhanced the productions of cortisol and progesterone remarkably. The trend of testosterone concentration was uncertain after 3-methylcholanthrene, phenobarbital or dexamethasone treatment. CONCLUSION: 3-Methylcholanthrene, phenobarbital or dexamethasone could interfere with the synthesis of cortisol, aldosterone and progesterone in primary human fetal adrenal cortical cells, which likely act through xenobiotic metabolizing-related cytochrome P450 isoform activation.