P450arom gene expression in peripheral blood lymphocytes: identification of a cryptic splice site for exon-1 after Epstein-Barr virus transformation

Epigenetic regulation of steroidogenic enzymes expressed in peripheral blood mononuclear cells from healthy individuals and from patients with chronic lymphocytic leukemia

Sex hormone synthesis occurs in various organs and tissues besides the gonads, such as adrenal glands, brain, intestines, skin, fat, bone, and cells of the immune system. Regarding the latter, it is still not clear which pathways are active, and if they are modified in case of illness of the immune system. Our goal in this study was to determine mRNA expression of different steroidogenic enzymes in peripheral blood mononuclear cells (PBMCs) from healthy individuals of both sexes and of different ages, and then to compare their expression between healthy individuals and patients with Chronic Lymphocytic Leukemia (CLL). Furthermore, to elucidate possible mechanisms that regulate enzyme expression, we analyzed epigenetic events like promoter methylation. We determined that normal cells of the immune system, regardless of sex and age, expressed P450 side chain cleavage (P450scc), cytochrome P450 17α-hydroxylase/c17,20-lyase (P45017α), 3β-hydroxysteroid dehydrogenase/Δ5-Δ4-isomerase (3β-HSD), steroid 5 α reductase (5α-R) types 1, 2 and 3, 3α-hydroxysteroid dehydrogenase (3α-HSD) type 3, and 17β-hydroxysteroid dehydrogenase (17β-HSD) types 1, 3 and 5. We also established that 5α-R 1, 5α-R 3, 3α-HSD 3, 17β-HSD 1 and 17β-HSD 5 expression was altered in CLL patients, and that promoter regions of 5α-R 1, 17β-HSD 1 and 17β-HSD 5 were diferentially methylated. These results suggest that steroidogenic pathways may be affected in CLL cells, and this could be related to disease pathogenesis.

Aromatase expression in human peripheral blood leucocytes (PBLs) and in various tissues in primates: studies in elderly humans and cynomolgus monkeys

BACKGROUND

Previous analysis of aromatase gene and protein expression in peripheral blood leucocytes (PBLs), studied in children and adults, was extended to elderly subjects. In addition, we assessed whether aromatase expression in PBLs could be used as a parameter of aromatase expression in other tissues, using the cynomolgus monkey as model.

METHODS

Real-time PCR analysis of aromatase gene expression and protein evaluation by Western blot was performed in PBLs of human elderly subjects and in various tissues from cynomolgus monkeys.

RESULTS

No gender-related difference in CYP19A1 mRNA and protein expression in PBLs from human elderly women and men was found. In elderly male cynomolgus monkeys, CYP19A1 mRNA and protein were expressed in all cells and tissues analysed, with the lowest levels in PBLs but no clear-cut correlation with other tissues.

CONCLUSIONS

Aromatase expression in PBLs in elderly human subjects is not gender-related and cannot be a surrogate of aromatase expression for other tissues.

Sex hormones, acting on the TERT gene, increase telomerase activity in human primary hematopoietic cells

Androgens have been used in the treatment of bone marrow failure syndromes without a clear understanding of their mechanism of action. Blood counts of patients with dyskeratosis congenita or aplastic anemia with mutations in telomerase genes can improve with androgen therapy. Here we observed that exposure in vitro of normal peripheral blood lymphocytes and human bone marrow-derived CD34(+) cells to androgens increased telomerase activity, coincident with higher TERT mRNA levels. Cells from patients who were heterozygous for telomerase mutations had low baseline telomerase activity, which was restored to normal levels by exposure to androgens. Estradiol had an effect similar to androgens on TERT gene expression and telomerase enzymatic activity. Tamoxifen abolished the effects of both estradiol and androgens on telomerase function, and letrozole, an aromatase inhibitor, blocked androgen effects on telomerase activity. Conversely, flutamide, an androgen receptor antagonist, did not affect androgen stimulation of telomerase. Down-regulation by siRNA of estrogen receptor-alpha (ER alpha), but not ER beta, inhibited estrogen-stimulated telomerase function. Our results provide a mechanism for androgen therapy in bone marrow failure: androgens appear to regulate telomerase expression and activity mainly by aromatization and through ER alpha. These findings have potential implications for the choice of current androgenic compounds and the development of future agents for clinical use.

Aromatase is differentially expressed in peripheral blood leukocytes from children, and adult female and male subjects

OBJECTIVE

Aromatase, the key enzyme involved in estrogen synthesis, is expressed in a variety of cells and tissues including human peripheral blood leukocytes (PBLs). The present study was designed to evaluate PBL aromatase gene expression in male and female subjects of different age groups. In addition, differences in gene expression during the follicular and luteal phase of the menstrual cycle in women, and before and after testosterone administration in men, were estimated.

DESIGN

Aromatase mRNA and protein were measured in PBLs obtained from young (n = 10) and postmenopausal women (n = 10), men (n = 15), and prepubertal children (n = 10). Aromatase mRNA and protein were also measured during the follicular and luteal phases of the menstrual cycle in women, and before and after the intramuscular administration of 250 mg testosterone enanthate in men.

METHODS AND RESULTS

Aromatase mRNA measured by real-time PCR in PBLs from women during the follicular phase was significantly higher than during the luteal phase of the menstrual cycle (P < 0.05). In men, PBL aromatase mRNA values increased significantly following testosterone administration (P < 0.05). PBL mRNA aromatase levels in women during the follicular phase and men after testosterone administration were significantly higher (one-way ANOVA; P < 0.05) than in any other group. Children, postmenopausal women, and women during the luteal phase showed the lowest aromatase mRNA expression. The results of the immunoblot analysis confirmed the data obtained by real-time PCR. A positive correlation between PBL aromatase mRNA values and plasma estradiol and estrone levels during the follicular phase of the menstrual cycle was observed in the group of adult women. No other correlations were found.

CONCLUSIONS

The aromatase gene is differentially expressed in PBLs from women, men, and prepubertal children, indicating a sexual dimorphism in the enzyme expression and an important role of sex steroids in the modulation of aromatase gene expression.

Alterations of mRNA splicing in primary effusion lymphomas

Primary effusion lymphoma (PEL) is a unique form of malignant lymphoma associated with infection by the Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus-8 (HHV-8). The majority of PELs also contain the EBV genome. Although viral infection is believed to play a critical role in the pathogenesis of PEL, it has been suggested that additional molecular lesions are required for the development of PEL. Alternative splicing of pre-mRNA is an important mechanism in the regulation of cellular and viral gene expression. Deregulation of pre-mRNA splicing may shift the gene expression balance and lead to the development of cancer. In order to investigate mRNA splicing in PELs, we examined mRNA splicing of three genes, DNA polymerase beta (pol beta), Bcl-x and CD45, in eight PEL cell lines. We found that the average variant percentage of pol beta in PEL cell lines is two times higher than in peripheral blood mononuclear cells (PBMC) and that the variant pattern of genes bcl-x and CD45 is quite different in PEL cell lines than in PBMC. In addition, we also found that the percentage of variant pol beta increased two-fold in PBMC following Epstein-Barr virus (EBV) infection. Therefore, viral infection may contribute to mRNA alternative splicing in PEL. In order to explore the mechanism by which viral infection affects mRNA splicing, we also examined the roles of genes KS-SM, SM and EBERs and viral copies in mRNA splicing. Our findings indicate that various factors acting as positive or negative regulators may be involved in mRNA alternative splicing caused by viral infection. In conclusion, mRNA splicing in PEL can be altered by viral infection and this alteration may contribute to the pathogenesis of PEL.

Physical interaction of Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) with human oestrogen-related receptor 1 (hERR1): hERR1 interacts with a conserved domain of EBNA-LP that is critical for EBV-induced B-cell immortalization

Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) consists of W1W2 repeats and a unique C-terminal Y1Y2 domain and plays a critical role in EBV-induced transformation. To identify the cellular proteins associating with EBNA-LP, we performed a yeast two-hybrid screen using EBNA-LP cDNA containing a single W1W2 domain as bait and an EBV-transformed human peripheral blood lymphocyte cDNA library as the source of cellular genes. Our results were as follows. (i) A cDNA in the positive yeast colony was found to encode a cellular protein, human oestrogen-related receptor 1 (hERR1), which is a constitutive transcriptional activator of the various types of oestrogen response elements. (ii) A purified chimeric protein consisting of glutathione S-transferase (GST) fused to hERR1 specifically formed complexes with EBNA-LPs containing one (EBNA-LPR1), two (EBNA-LPR2) or four W1W2 repeats (EBNA-LPR4) transiently expressed in COS-7 cells. Reciprocally, GST fused to EBNA-LPR1 or EBNA-LPR2 pulled down hERR1 transiently expressed in COS-7 cells. (iii) Mutational analyses of EBNA-LP revealed that the Y2 domain of EBNA-LP is responsible for the interaction with hERR1 and two leucines in the Y2 domain (Leu-78 and -82), which are conserved among a subset of primate gammaherpesviruses, are interactive sites for hERR1. So far, it has been reported that the only domain of EBNA-LP critical for EBV-induced transformation is the Y1Y2 domain. Potential roles of hERR1 in EBV-induced transformation are discussed.

Aromatase expression in the human male

The role of estrogens produced by the testis may involve negative feedback regulation of androgen biosynthesis. Estrogens are also associated with contractile processes of seminiferous tubules, and might have mitogenic effects on Sertoli and Leydig cells. To investigate the location of aromatase (estrogen synthetase) in the testes, tissue from normal human subjects, aged 3 months to 72 years were studied using immunocytochemistry. In mature testes, aromatase immunostain was always associated with Leydig cells and was absent from Sertoli cells. Aromatase activity ranged from 0.014-0.55 pmol estrogen per mg/h and was significantly correlated with the immunostain intensity (P<0.02). Activity and immunostain intensity did not correlate with increasing age. Rather, the highest levels were measured in four of six testes of men aged 18-20 years, three of whom also had the strongest immunostain in larger and more prominent Leydig cell clusters than those in the other specimens. A low level of aromatase activity but no immunostain was detected in prepubertal testes. However, in several prepubertal patients with Peutz-Jegher's Syndrome (PJS) with bilateral multifocal sex cord tumors and enlarged seminiferous tubules and Sertoli cells, aromatase was expressed in these Sertoli cells, but absent from normal Sertoli and Leydig cells. Increased aromatase expression in these tissues involved activation of upstream regulatory elements of the gonadal P II promoter of P-450(arom). In a prepubertal boy with gynecomastia but without PJS, aromatase excess appeared to be due to increased aromatization in skin fibroblasts and lymphocytes. Several members of the patient's family including his sister also expressed high levels of aromatase. This condition appears to be inherited in an autosomal dominant manner.

Dual regulation of promoter II- and promoter 1f-derived cytochrome P450 aromatase transcripts in equine granulosa cells during human chorionic gonadotropin-induced ovulation: a novel model for the study of aromatase promoter switching

Estradiol biosynthesis is a key biochemical trait of developing follicles. To study its regulation in equine follicles, the objectives of this study were to clone and determine the structure of equine cytochrome P450 aromatase (P450AROM), and characterize the regulation of P450AROM and P450 17alpha-hydroxylase/C17-20 lyase (P45017alpha) messenger RNAs (mRNAs) in vivo in equine preovulatory follicles isolated during hCG-induced ovulation. Two distinct P450AROM complementary DNAs (cDNAs) were isolated from an equine preovulatory follicle cDNA library. One clone was 2682 bp in length and included 115 bp of 5'-untranslated region (UTR), 1509 bp of open reading frame encoding a well conserved 503-amino acid protein, and 1058 bp of 3'-UTR. Its 5'-most region represented the equine homolog of exon 1f, previously designated brain specific. The other cDNA clone encoded a truncated protein and contained a distinct 5'-UTR characteristic of transcripts derived from promoter II, previously identified as the predominant ovarian mRNA. Northern blot analyses were performed using preovulatory follicles obtained during estrus between 0-39 h after the administration of hCG and with corpora lutea isolated on day 8 of the estrous cycle (day 0 = day of ovulation). The results showed a biphasic regulation of P450AROM mRNA expression: levels were highest in follicles at 0 h post-hCG, decreased significantly during the ovulatory process at 12 and 24 h (P < 0.05), and increased again between 30-39 h post-hCG and in corpora lutea. When oligonucleotides specific for P450AROM mRNA variants were used as probes, a novel switching phenomenon was observed. Promoter II-derived transcripts accounted for the message present in follicles at 0 h post-hCG and in corpora lutea, whereas promoter 1f-derived mRNA was expressed exclusively during the ovulatory process (30-39 h post-hCG). Levels of P45017alpha mRNA were high in follicles at 0 h, but significantly decreased after hCG treatment (P < 0.05), with lowest levels in follicles at 36 and 39 h post-hCG and in corpora lutea. Northern blots performed on isolated cellular preparations revealed that P450AROM and P45017alpha transcripts were localized exclusively in granulosa cells and theca interna, respectively. Equine aromatase promoters II and 1f were cloned from a genomic library, and putative transcription start sites were characterized by primer extension assays. Sequence analyses identified distinct potential regulatory elements in each promoter. Thus, this study identifies a novel aromatase promoter-switching phenomenon in equine granulosa cells during follicular luteinization and provides a new model in which aromatase promoter switching is induced in vivo.