Regulation of steroidogenesis and steroidogenic acute regulatory protein in R2C cells by DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1)

In the present study, steroidogenesis in two different Leydig tumor cell lines was compared. One, the MA-10 mouse tumor cell line, produces steroids and the steroidogenic acute regulatory (StAR) protein only when stimulated by trophic hormones and cAMP analogs. The other, the R2C rat tumor cell line, produces steroids and the StAR protein constitutively without stimulation. We observed that high levels of DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1), a repressor of steroidogenesis and StAR gene expression, were present in MA-10 cells but not in R2C cells. Based upon this observation, we hypothesized that the absence of DAX-1 might result in constitutive steroidogenesis in R2C cells. To test this hypothesis, DAX-1 was overexpressed in the R2C cells using the Tet-on inducible gene expression system and resulted in a 45% decrease in steroid production, a 35% decrease in StAR protein, and a 39% decrease in cytochrome P450 side chain cleavage expression. Further, using retroviral infection with DAX-1, StAR expression and steroidogenesis were decreased 50-60% and 60% in R2C cells, respectively. These results corroborate previous findings that DAX-1 negatively regulates steroid synthesis through the inhibition of StAR expression and indicate that the absence of DAX-1 in R2C cells is, at least in part, responsible for the constitutive steroidogenesis and StAR expression observed.     

Four Japanese patients with adrenal hypoplasia congenita and hypogonadotropic hypogonadism caused by DAX-1 gene mutations: mutant DAX-1 failed to repress steroidogenic acute regulatory protein (StAR) and luteinizing hormone beta-subunit gene promoter activity

Mutations of DSS (dosage sensitive sex reversal)-AHC critical region on the X chromosome, gene 1 DAX-1(NROB1)] results in X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HHG). Here we report four Japanese patients with AHC and HHG caused by the mutations of the DAX-1 gene. All patients manifested adrenal crisis at early childhood. Three patients did not show any pubertal sign and were diagnosed as having HHG. One patient manifested spontaneous pubertal development at 17 years of age. Nevertheless, his puberty did not develop further and his gonadotropin and testosterone levels decreased thereafter. Therefore, he was also diagnosed as having HHG. We performed testicular biopsy in another patient with HHG. Histological examination demonstrated Sertoli cell hypoplasia and no sperm formation in the seminiferous tubules. Molecular analysis demonstrated two novel point mutations (V269D and L278R) in two patients. Transient transfection assays showed that all these mutations (V269D, L271X, L278R, and Q395X) abolished the repression activity to both StAR and LHbeta gene promoter activation. In conclusion, we reported patients with AHC and HHG caused by the loss of function mutations of the DAX-1 gene.     

Differential effects of high and low steroidogenic factor-1 expression on CYP11B2 expression and aldosterone production in adrenocortical cells

Steroidogenic factor-1 (SF-1/Ad4BP/NR5A1) plays a major role in regulating steroidogenic enzymes. We have previously shown that SF-1 inhibits aldosterone synthase (CYP11B2) reporter gene activity. Herein, we used the H295R/TR/SF-1 adrenal cells that increase SF-1 in a doxycycline-dependent fashion. Cells were incubated with or without doxycycline to induce SF-1 and then treated with angiotensin II (Ang II). Aldosterone was measured by immunoassay. SF-1 mRNA was silenced by small interfering RNA (siRNA) by Nucleofector technology. mRNA levels were measured by real-time RT-PCR. Ang II treatment without doxycycline increased aldosterone production by 11.3-fold and CYP11B2 mRNA by 116-fold. Doxycycline treatment increased SF-1 mRNA levels by 3.7-fold and inhibited Ang II-induced aldosterone by 84%. Doxycycline treatment inhibited Ang II-stimulated CYP11B2 mRNA levels by 86%. Doxycycline decreased basal CYP11B2 promoter activity by 68%. Doxycycline inhibited Ang II stimulation by 85%. Ang II increased CYP21 mRNA expression by 4.6-fold, whereas doxycycline inhibited induction by 69%. In contrast, doxycycline treatment increased CYP11B1 mRNA by 1.7-fold in basal cells and increased Ang II induction by 3.6-fold. SF-1-specific siRNA significantly reduced SF-1 mRNA expression as compared with cells treated with control siRNA. SF-1 siRNA reversed doxycycline stimulation of CYP B1 and its inhibition of CYP11B2. However, in H295R/TR/SF-1 cells without doxycycline treatment, both CYP11B1 and CYP11B2 mRNAs were significantly decreased, suggesting that both enzymes require a minimal level of SF-1 for basal expression. In summary, SF-1 overexpression dramatically inhibited CYP11B2 expression and decreased aldosterone production. The opposing effects of SF-1 on CYP11B1 and CYP11B2 suggest that the regulation of SF-1 activity may play a role that determines the relative ability to produce mineralocorticoid and glucocorticoid.     

Role of CYP2D6, CYP1A1, CYP2E1, GSTT1, and GSTM1 genes in the susceptibility to acute leukemias

Acute leukemias (ALs) are heterogeneous diseases. Functional polymorphisms in the genes encoding detoxification enzymes cause inter-individual differences, which contribute to leukemia susceptibility. The CYP2D6, CYP1A1, CYP2E1, GSTT1, and GSTM1 polymorphisms in ALL (n = 156) and AML (n = 94) patients and 140 healthy controls were genotyped by PCR and/or PCR-RFLP using blood or bone marrow samples. No association was observed between the GSTT1 gene deletion and patients (OR = 0.8, 95% CI = 0.4-1.7 for AMLs and OR = 0.9, 95% CI = 0.5-1.6 for ALLs). Patients with ALL and AML had a higher prevalence of the GSTM1 deletions compared to controls but only the difference among adult AML patients (OR = 2.1, 95% CI = 1.0-4.2) was statistically significant. The CYP2D6*3 variant allele frequency was lower in the overall acute leukemia patients (0.6%) compared to controls (P = 0.03). CYP2D6*1/*3 genotype frequency also showed a protective association in AML patients (OR = 0.09, 95% CI = 0.01-1.7; P = 0.04). We also found a risk association for CYP2E1*5 in ALL and AML (OR = 3.6, 95% CI = 1.4-9.4 and OR = 3.9, 95% CI = 1.4-10.5, respectively). No association was found for the studied CYP2D6*4, CYP1A1*2A, and GSTT1"null" variants and the risk of acute leuke-mia (ALL or AML). This case-control study suggests a contribution of CYP2E1, CYP2D6, and GSTM1 "null" variants to the development of acute leukemias.     

Familial pericentric inversion chromosome 3 and R448C mutation of CYP11B1 gene in Turkish kindred with 11beta-hydroxylase deficiency

11beta-hydroxylase deficiency is the second most common cause of congenital adrenal hyperplasia (CAH). This isoenzyme is coded by two highly homologous genes of cytochrome P450: CYP11B1 and CYP11B2 which were mapped to the chromosomal band 8q24. The aim of this study was to perform a series of molecular and cytogenetic analyses in two families with 11beta-hydroxylase deficiency of the Turkish kindred. Mutational analysis was carried out by directly sequencing the PCR products of CYP11B1 gene. We performed fluorescence in situ hybridisation (FISH) experiments with consecutive bacterial artificial chromosome (BAC) clones to map the breakpoints of the inversion of chromosome 3 which was detected during the karyotypic analysis of the propositus. Homozygous R448C mutations were detected in 2 individuals with 11beta-hydroxylase deficiency. Interestingly, karyotypic change of pericentric inversion [inv(3)(p13q24)] was detected in both individuals who are cousins, one transmitted paternally and the other maternally. The breakpoint at 3p included one interesting gene PPP4R2. Here we present the data of two Turkish families' members having 11beta-hydroxylase deficiency coupled with the familial chromosomal aberration of inv(3)(p13q24). Our data suggest that codon 448, which is a mutational hot spot in CYP11B1 causing 11beta-hydroxylase deficiency, is not restricted to Jews of Moroccan origin. Phenotypic variations observed in former studies in patients homozygous for R448H were stated to be due to other factors outside the CYP11B1 locus. The breakpoint in 3p might be a candidate region affecting variations in phenotypes of 11beta-hydroxylase deficiency.     

The expression of the sex steroid-synthesizing enzymes CYP11A1, 3beta-HSD, CYP17, and CYP19 in gonads and adrenals of adult and developing zebra finches

Songbirds have emerged as important animal models for understanding how sex steroids influence brain and behavior, particularly how they direct the sexually dimorphic development of the neural circuits controlling song and then activate adult song behavior. Presumably, sex steroids synthesized in the gonads are responsible for these actions on brain. However, experiments do not always reveal a direct relationship between gonadal function, circulating sex steroids, and activation and/or organization of song. Thus, it is critical that we understand more about the sites and mechanisms of sex steroid synthesis in this group of birds. Toward this end, we have established the use in zebra finches of chicken cDNA probes to the principal androgen synthetic enzymes, CYP11A1, 3beta-HSD, and CYP17. On Northern blots, these probes recognized bands of the appropriate size and in tissues similar to those seen in chickens. With these probes, and a probe to CYP19 specific to the zebra finch, we used in situ hybridization to examine the cellular expression of these enzymes in gonads and adrenals of adult and developing zebra finches (1 to 20 days posthatching). In adults, we identified significant expression of CYP11A1 and CYP17 in large ovarian follicles, particularly the thecal cell layer and over the testicular interstitial area. 3beta-HSD was expressed by both theca and granulosa and in testicular interstitial and seminiferous tubular cells. In adrenals, CYP11A1 and 3beta-HSD are abundant with lesser amounts of CYP17. Developmentally, we identified high expression of CYP11A1 and 3beta-HSD in the adrenals, CYP17 in both testes and ovaries, and CYP19 in ovaries only. These results suggest that the ovaries but not the testes may secrete estrogen developmentally and the adrenals may contribute precursors for gonadal steroidogensis.     

Interactive stimulation by luteinizing hormone and insulin of the steroidogenic acute regulatory (StAR) protein and 17alpha-hydroxylase/17,20-lyase (CYP17) genes in porcine theca cells

LH and insulin are postulated to jointly stimulate theca-cell androgen biosynthesis in patients with hyperthecosis or polycystic ovarian syndrome. To explore the mechanisms of putative LH and insulin steroidogenic synergy in primary culture of normal theca cells, we have implemented an in vitro serum-free monolayer culture system of Percoll-purified, porcine theca cells harvested from immature ovaries. Initial dose and time course analyses revealed that a maximally effective concentration of LH (100 ng/ml) or insulin (100 ng/ml) individually will drive androstenedione production (at 6 to 48 h) by 1.5- to 2.6- and 1.1- to 1.7-fold, respectively, while combined agonists act synergistically over the interval 12 to 48 h yielding a 3- to 4-fold joint effect. Coadministration of LH and insulin can augment theca-cell concentrations of CYP17 and StAR messenger RNA (mRNA) resulting in 3.4- to 3.9- and 3.8- to 4.1-fold increases at 24 to 48 h, respectively (P < 0.01). Combined LH and insulin stimulation also amplified the nuclear content of intron-specific heterogeneous nuclear (hn)RNAs encoding CYP17 and StAR. Insulin significantly enhanced LH-driven but not basal cAMP accumulation (14-18 vs. 3-5.5 pmol/microg DNA/12-48 h) (P < 0.01). A stable exogenous analog of cAMP, 8 Br-cAMP, mimicked LH's effect on steroidogenesis and StAR and CYP17 gene expression and with insulin stimulated StAR mRNA and hnRNA accumulation synergistically. However, unlike LH, 8 Br-cAMP did not synergize with insulin on theca-cell androstenedione biosynthesis or CYP17 mRNA and hnRNA expression. In summary, the present in vitro data identify molecular interactions of LH and insulin on StAR and CYP17 gene expression, thus establishing potent signaling interfaces between these distinct hormonal agonists in regulating theca-cell steroidogenesis.     

Expression and regulation of plasminogen activators,plasminogen activator inhibitor type-1, and steroidogenic acute regulatory protein in the rhesus monkey corpus luteum

The corpus luteum (CL) is a transient endocrine organ that secretes progesterone to support early pregnancy. Using primate materials obtained from rhesus monkeys, we have in this study investigated the expression and regulation of the plasminogen activators (PAs) and PA inhibitor type 1 (PAI-1) during CL development and regression. Adult (5-7 yr old) female rhesus monkeys were treated with pregnant mare serum gonadotropin/human chorionic gonadotropin to induce ovulation and follicular luteinization. At various luteal developmental stages, CL or whole ovaries were obtained for preparing luteal cells, Northern blot, in situ hybridization, and immunohistochemistry. We demonstrated that luteal cells from the rhesus monkey were able to produce both tissue type PA (tPA) and urokinase type PA, as well as the physiological PAI-1. During luteal development in the monkey, urokinase type PA was the major PA species taking part in the active angiogenesis and tissue remodeling processes in the forming CL. However, the mRNA as well as the enzymatic activity levels of tPA increased dramatically in monkey CL with the advent of luteolysis. This change of tPA levels was in a temporal coordination with the regulation of PAI-1 expression, resulting in an increased tPA activity at the initiation of luteolysis. Therefore, we suggest that tPA might be a luteolytic factor to the monkey CL. A PAI-1 modulated tPA activity might be important for the initiation of luteolysis in the monkey. In addition, we have also demonstrated that the expression of steroidogenic acute regulatory protein in the monkey CL was in accordance with the changes of progesterone production, suggesting that steroidogenic acute regulatory protein expression may be considered as a reliable marker for CL function in primates.     

Relationship between genetic polymorphisms of drug-metabolizing enzymes (CYP1A1, CYP2E1, GSTM1, and NAT2), drinking habits, histological subtypes, and p53 gene point mutations in Japanese patients with gastric cancer

Background Genetic polymorphisms of drug-metabolizing enzymes have recently been shown to affect susceptibility to chemical carcinogenesis. However, the molecular mechanisms of individual susceptibility to gastric cancer have not been fully understood. Therefore, we studied the relationship between the genetic polymorphisms of drug-metabolizing enzymes, drinking habits, histological subtypes, and p53 gene point mutations in Japanese patients with gastric cancer.Methods The genotypes of cytochromes P450 (CYP) 1A1 and 2E1, glutathione S-transferase (GST) M1, and N-acetyltransferase (NAT) were investigated by polymerase chain reaction (PCR), allele-specific PCR, or restriction fragment length polymorphism (RFLP) following PCR in 146 Japanese patients with gastric cancer (67 intestinal-type and 79 diffuse-type carcinomas) and 177 autopsied controls. In addition, p53 gene point mutations of exons 5 through 9 in gastric cancer tissues were determined.Results The frequency of either being a habitual drinker or having a CYP2E1^*1A/^*1A genotype was significantly higher in patients with intestinal-type gastric cancer than in control subjects. The difference between the frequencies of habitual drinkers with the CYP2E1^*1A/^*1A genotype and non-drinkers with the CYP2E1^*5B allele was much more significant in the intestinal-type cancer versus the control group. Among intestinal-type cancer patients with the CYP2E1^*1A/^*1A genotype, p53 point mutations were significantly more frequent in the group of habitual drinkers than in that of non-drinkers. On the other hand, the combination of GSTM1 null and CYP2E1^*1A/^*1A genotypes increased the risk for diffuse-type gastric cancer, but had no influence on the frequency of p53 gene mutations.Conclusions The present study suggests that individuals with both the CYP2E1^*1A/^*1A genotype and a history of habitual drinking have an increased risk of intestinal-type gastric cancer with a high frequency of p53 gene point mutations in the gastric mucosa.     

细胞色素P4501A1基因多态性和谷胱甘肽硫转移酶基因缺失及烹调油烟暴露与非吸烟女性肺癌易感性的关系

目的 探讨细胞色素P4501 A1(CYP1A1)MspI位点多态性、谷胱甘肽硫转移酶(GSTM1)基因缺失及烹调油烟暴露与非吸烟女性肺癌易感性的关系.方法 2009年3一12月选择中南大学湘雅医院女性非吸烟的原发性肺癌患者及对照各160例,应用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)及聚合酶链反应(PCR)技术分别检测CYP1A1 MspI多态性及GSTM1基因型,分析基因的多态性、分型及烹调油烟暴露与肺癌遗传易感性的关系.结果 肺癌组及对照组烹调油烟暴露的频率分别为51.9%(83例)及33.7%(54例),差异有统计学意义(x2=10.734,P＜0.01);肺癌组MspI位点突变的等位基因频率为44.4%(71例),高于对照组(36.9%,59例),差异无统计学意义(X2=3.731,P＞0.05);携带突变型或杂合型基因同时又有油烟暴露个体患肺癌的风险明显增高,OR(odds ratio)值分别为3.032(95%CI为1.291～7.124)和2.769(95%CI为1.341～5.552);肺癌组GSTM1缺失型的频率为58.1%(93例),与对照组(45.0%,72例)比较,差异有统计学意义(X2=0.518,P＜0.05),GSTM1缺失型的个体患肺癌的风险明显增高,OR值为1.697(95%CI为1.090～2.640);携带GSTM1缺失型且有烹调油烟暴露的个体肺癌的易感性明显增加,其OR值为3.617(95%CI为1.899～6.891);GSTM1缺失型与CYP1A1 MspI杂合型或突变型联合作用时,个体患肺癌的风险亦增高,OR值分别为1.966(95%CI为1.007～3.836)和2.402(95%CI为1.023～5.640),差异明显.结论 烹调油烟暴露是非吸烟女性肺癌的危险因素;CYP1A1 MspI基因多态性与烹调油烟联合作用可增加肺癌发病的风险;GSTM1基因缺失可能是非吸烟女性肺癌的遗传易感因素,其与烹调油烟暴露联合作用可明显增加肺癌发病的风险,且GSTM1基因缺失与CYP1A1基因多态性存在交互作用.