Serological and genetic characterization of newly isolated Peaton virus in Japan. Brief report

The viruses were isolated from the blood of sentinel cattle and Culicoides biting midges in the Kyushu district, southwestern Japan, in 1999 and identified by neutralization tests as Peaton (PEA) viruses. Before this study, PEA virus had been isolated in Australia only. The nucleotide identity of the nucleocapsid (N) protein encoded by the S segment ranged from 91.1 to 91.6% between the Australian and Japanese strains. A phylogenetic analysis of the N protein sequence revealed that the PEA virus strains are closely related to Aino (AIN) virus and suggested reassortment events for PEA and AIN viruses.

Regulation of aromatase by nuclear receptors

We investigated the effects of a nuclear receptor system constituted by retinoid X receptor (RXR) and its heterodimer partner on the aromatase activity in a cultured MCF-7 human breast cancer cell line and also in human ovarian granulosa cells, using each selective ligand for retinoic acid receptor, RAR (TTNPB), retinoid X receptor, RXR (LG100268), PPARgamma (troglitazone), and vitamin D3 receptor (cholecalciferol). In MCF-7 cells, the combined treatment with TTNPB and LG100268 caused a dramatic stimulation of the aromatase activity. The combined treatment with other ligand and LG100268 had little or no effect on the aromatase activity. The increase in the aromatase activity by TTNPB plus LG100268 was accompanied by an increase in the P450arom mRNA levels, which was also found to be related to the specific usage of promoter 1a of the CYP19 gene. These results suggest that a nuclear receptor system constituted by a RAR:RXR heterodimer is involved in the regulation of aromatase activity in MCF-7 breast cancer cells. In cultured human ovarian granulosa cells obtained from patients who underwent in vitro fertilization, troglitazone or LG100268 alone decreased the aromatase activity, while the combined treatment caused an even greater reduction in this activity. Little effect of other specific ligands for RXR heterodimer partners may support the notion that the effects of troglitazone and/or LG100268 in human granulosa cells may be mediated through the specific activation of PPARgamma:RXR heterodimer system. Since similar manners of effects of several PPARgamma ligands and/or LG100268 on the aromatase activity were observed in a newly established human ovarian granulosa cancer cell line, KGN, we performed the detailed analysis of the mechanisms of these effects using this cell line. As a result, the inhibitory effect of aromatase activity by troglitazone plus LG100268 was accompanied by the decrease of P450arom mRNA level. Furthermore, the loss of P450arom expression was considered to be due to both the decreased transcription and rapid degradation of its RNA based on the studies of nuclear run-on assay and RNA stability assay. In conclusion, RAR:RXR and PPARgamma:RXR heterodimer nuclear receptor systems may be other important modulators of estrogen production in human breast cancer cells and ovarian granulosa cells, respectively.

Tributyltin or triphenyltin inhibits aromatase activity in the human granulosa-like tumor cell line KGN

The superimposition of male sex organs (penis and vas deferens) in a female gastropod, called imposex, is widely attributed to the exposure to tributyltin (TBT) compounds, used world-wide in antifouling paints for ships. It has been hypothesized that the TBT-induced imposex is mediated by an increasing androgen level relative to the estrogen level, namely a decreased conversion of androgens to estrogens (i.e., aromatization). In the present study, we tested this hypothesis by examining the effects of TBT or triphenyltin (TPT) on the aromatase activity in a cultured human granulosa-like tumor cell line, KGN, which was recently established by our group. Treatment with more than 1000 ng/ml TBT compounds was very toxic to the cells and caused immediate cell death within 24 h, while 200 ng/ml was found to cause apoptosis of the cells. Treatment of the KGN cells for more than 48 h with 20 ng/ml TBT or TPT, which is a concentration level reported to cause imposex in marine species, did not affect cell proliferation but significantly suppressed the aromatase activity determined by a [(3)H]H(2)O release assay. Treatment with 20 ng/ml TBT compounds for 7 days also resulted in a reduction of the E2 production from Delta 4-androstenedione stimulated by db-cAMP. The changes in the aromatase activity by TBT compounds were associated with comparable changes in P450arom mRNA assessed by RT-PCR. The luciferase activity of the P450arom promoter II (1 kb) decreased after the addition of 20 ng/ml TBT compounds in transfected KGN cells either in a basic state or in states stimulated by db-cAMP. The Ad4BP-dependent increase in the luciferase activity of P450arom promoter II was also downregulated by such treatments. These results indicate that TBT compounds inhibited the aromatase activity and also decreased the P450arom mRNA level at the transcriptional level in KGN cells. The direct inhibitory effect of TBT compounds on the aromatase activity may therefore partly explain the induction of imposex by these compounds in female species.

Saturated FFAs, palmitic acid and stearic acid, induce apoptosis in human granulosa cells

Obesity is associated with insulin resistance and some reproductive abnormalities. Circulating FFAs are often elevated in obese subjects and are also closely linked to insulin resistance. In this study, we demonstrated that saturated FFAs, such as palmitic acid and stearic acid, markedly suppressed the granulosa cell survival in a time- and dose-dependent manner. Polyunsaturated FFA, arachidonic acid, had no effect on the cell survival, even at supraphysiological concentrations. The suppressive effect of saturated FFAs on cell survival was caused by apoptosis, as evidenced by DNA ladder formation and annexin V-EGFP/propidium iodide staining of the cells. The apoptotic effects of palmitic acid and stearic acid were unrelated to the increase of ceramide generation or nitric oxide production and were also completely blocked by Triacsin C, an inhibitor of acylcoenzyme A synthetase. In addition, acylcoenzyme A, pamitoylcoenzyme A, and stearylcoenzyme A markedly suppressed granulosa cell survival, whereas arachidonoylcoenzyme A had no such effect, and this finding was consistent with the effect of the respective FFA form. Surprisingly, arachidonic acid instead showed a protective effect on palmitic acid- and stearic acid-induced cell apoptosis. A Western blot analysis showed the apoptosis of the granulosa cells induced by palmitic acid to be accompanied by the down-regulation of an apoptosis inhibitor, Bcl-2, and the up-regulation of an apoptosis effector, Bax. These results indicate that saturated FFAs induce apoptosis in human granulosa cells caused by the metabolism of the respective acylcoenzyme A form, and the actual composition of circulating FFAs may thus play a critical role in the apoptotic events of human granulosa cells. These effects of FFAs on granulosa cell survival may be a possible mechanism for reproductive abnormalities, such as amenorrhea, which is frequently observed in obese women.

Combined treatment with specific ligands for PPARgamma:RXR nuclear receptor system markedly inhibits the expression of cytochrome P450arom in human granulosa cancer cells

Our previous study demonstrated that PPARgamma specific ligand troglitazone (TGZ) or RXR specific ligand LG100268 (LG) alone decreased the aromatase activity in cultured human ovarian granulosa cells from pre-ovulatory follicles, and combined treatment caused an even greater reduction in this activity. Since similar manners of effects of TGZ or/and LG on the aromatase activity in human ovarian granulosa cancer cell line were observed, we performed the detailed analysis of the mechanisms of these effects using this cell line. The changes in the aromatase activity were associated with comparable changes in the P450arom mRNA levels based on a RNase protection assay. A nuclear run-on assay indicated the P450arom transcript to decrease by 40 and 66% at 24 and 48 h, respectively, after TGZ plus LG treatment. An RNA stability analysis showed the half-life of P450arom mRNA to decrease from 13 to 9 h after the TGZ plus LG treatment. The inhibitory effect of TGZ plus LG on the aromatase activity and P450arom mRNA may not be mediated by the cAMP-PKA pathway that is usually implicated in the regulation of aromatase activity in granulosa cells: because (1) the aromatase activity stimulated by forskolin was not inhibited by TGZ plus LG; (2) the specific PKA inhibitor H89 could not block the inhibitory effect of TGZ plus LG on the aromatase activity; and (3) the luciferase activity of P450arom promoter II did not decrease by the addition of TGZ and LG in transfected cells either at a basic state or in the states stimulated by forskolin or PGE2, respectively. Taken together, these results indicate that TGZ plus LG inhibited the aromatase activity and also decreased the P450arom mRNA level in granulosa cancer cells, and the loss of P450arom mRNA expression was considered to be due to both the decreased transcription and rapid degradation of its RNA.

The Subnuclear Three-dimensional Image Analysis of Androgen Receptor Fused to Green Fluorescence Protein

To establish the novel approach in order to distinguish the transcriptionally active androgen receptor (AR) from the transcriptionally inactive AR, we performed the three-dimensional construction of confocal microscopic images of intranuclear AR. This method clearly distinguished the subnuclear localization of transcriptionally active AR tagged with green fluorescent protein (AR-GFP) from the transcriptionally inactive AR-GFP. Transcriptionally active AR-GFP mainly produced 250-400 fluorescence foci in the boundary region between euchromatin and heterochromatin. Although the AR-GFP bound to such antiandrogens as hydroxyflutamide or bicalutamide translocated to the nucleus, they homogeneously spread throughout the nucleus without producing any fluorescence foci. Antiandrogenic environmental disrupting chemicals, such as 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene, vinclozolin, or nitrofen, also disrupted the intranuclear fluorescence foci. A point mutation (T877A) resulted in the loss of ligand specificity in AR-GFP. Even in this mutant receptor, agonists, such as dihydrotestosterone, hydroxyflutamide, or progesterone, produced the fluorescence foci in the nucleus, whereas the transcriptionally inactive mutant binding bicalutamide was observed to be spread homogeneously in the nucleus. Taken together, our findings suggest that, after nuclear translocation, AR is possibly located in the specific region in the nucleus while demonstrating clustering tightly depending on the agonist-induced transactivation competence.

A case of fever of unknown origin with severe stomatitis in renal transplant recipient resulting in graft loss

We present a case of fever of unknown origin and life-threatening stomatitis developed about 60 months after renal transplantation. He was 15 yr old at the transplantation. Bacterial, fungal, and viral infections were not evident. Fever and stomatitis were resistant to acyclovir and to any anti-bacterial or anti-fungal treatment. Graft biopsy revealed a small focus of acute vascular rejection, but the findings were not severe enough to be an etiology of the fever in this case. The administration of cyclosporine (CYA) was stopped 19 d before graftectomy, but the clinical picture was unchanged. Fever and stomatitis was resolved immediately after graftectomy and the discontinuation of immunosuppressants such as mizoribine (MZ) and prednisolone. Pathological changes of the graft included chronic transplant glomerulopathy, acute glomerulitis, and lymphocyte infiltration in peritubular capillaries. Thus we suppose that immunosuppressants were the cause of both fever and stomatitis in this case. We speculate that a fever in this case might be due to the immunosuppressant itself, i.e., CYA or MZ, or viral infection probably herpes-simplex virus infection. It is probably the immunosuppressive state per se that may cause the resistance of his muco-cutaneous lesion to anti-viral agent.

No parallel relationship between nitric oxide production and wet dog shakes susceptible to nitric oxide synthase inhibitors following systemic administration of paraquat in rats

Shaking behavior, so-called wet dog shakes (WDS), in rats is characteristic behavior indicating morphine abstinence in morphine-dependence and central excitation in relation to seizures elicited by chemicals or electrical stimulation. We have found that paraquat (PQ), a nonselective herbicide, administered systemically to rats induces WDS in a dose-dependent manner. PQ-induced WDS are suppressed by nitric oxide (NO) synthase (NOS) inhibitors, but this suppression is not reversed by an NO precursor, L-arginine (L-Arg). The present study was performed to determine whether the NO system is associated with PQ-induced WDS in rats. A time-course study on the frequency of WDS for each 30-min period up to 120 min after PQ administration (70 mg/kg, s.c.) revealed that significant induction of WDS occurred during the first and second 30-min periods, that is within 60 min of PQ administration. A nonselective NOS inhibitor, Nomega-nitro-L-arginine (L-NA; 30 mg/kg, i.p.), reduced the frequency of the PQ-induced WDS during both of these periods, but the reduced frequency was not reversed by L-Arg (500 mg/kg, i.p.) in either period. Significant induction of WDS occurred when PQ (50 nmol) was administered directly into the ventral or dorsal hippocampus, but not when administered into the amygdala or the caudate putamen, indicating that the hippocampus plays an important role in PQ-induced WDS. The WDS after the administration of PQ into the dorsal hippocampus was significantly suppressed by pretreatment with L-NA (30 mg/kg, i.p.). The extracellular levels of nitrite (NO2-) and nitrate (NO3-), the oxidative products of NO, in the dorsal hippocampus determined by in vivo microdialysis, were stimulated after systemic PQ administration (70 mg/kg, s.c.) in urethane-anesthetized rats. The increases in extracellular NO2- and NO3- were inhibited by L-NA (30 mg/kg, i.p.), and this inhibition was partly reversed by L-Arg (500 mg/kg, i.p.). The increases in extracellular NO2- and NO3- in the dorsal hippocampus appeared 60 min after PQ administration, when the WDS had occurred and disappeared. These findings suggest that NO production in the hippocampus plays a minor role in PQ-induced WDS in rats and that the suppression of PQ-induced WDS by NOS inhibitors might be mediated though complex mechanisms in the brain.

Establishment and characterization of a steroidogenic human granulosa-like tumor cell line, KGN, that expresses functional follicle-stimulating hormone receptor

We established a steroidogenic human ovarian granulosa-like tumor cell line, designated KGN, from a patient with invasive ovarian granulosa cell carcinoma. KGN had a relatively long population doubling time of about 46.4 h and had an abnormal karyotype of 45,XX, 7q-, -22. A steroid analysis of the cultured medium by RIA performed 5 yr after the initiation of culture showed that KGN was able to secrete pregnenolone and progesterone, and both dramatically increased after stimulation with (Bu)(2)cAMP. However, little or no secretion of 17alpha-hydroxylated steroids, dehydroepiandrosterone, androstenedione, or estradiol was observed. The aromatase activity of KGN was relatively high and was further stimulated by (Bu)(2)cAMP or FSH. These findings showed a pattern similar to that of steroidogenesis in human granulosa cells, thus allowing analysis of naturally occurring steroidogenesis in human granulosa cells. Fas-mediated apoptosis of KGN was also observed, which mimicked the physiological regulation of apoptosis in normal human granulosa cells. Based on these findings, this cell line is considered to be a very useful model for understanding the regulation of steroidogenesis, cell growth, and apoptosis in human granulosa cells.

Identification of novel first exons in Ad4BP/SF-1 (NR5A1) gene and their tissue- and species-specific usage

It has been demonstrated that the mammalian Ad4BP/SF-1 (NR5A1) gene is regulated precisely in sex, tissue, and developmental stage specific manners. To clarify the complex transcriptional regulation, we investigated in the present study whether the gene transcription is regulated by multiple promoters accompanied by noncoding first exons. Novel first exons (Io and Ig) were identified downstream of the already identified exon Ia. Nucleotide sequences revealed that Ia and Ig exons were well conserved, whereas Io exon was less conserved among the mouse, rat, and human genes. Interestingly, the splice donor of the mouse and human Io and human Ig exons do not satisfy the consensus sequence. Transcripts containing Ia, Io, and Ig were detected in all rat tissues examined, while the transcript containing Io was undetectable in the corresponding tissues of mice. The lack of exon Io usage in the mouse was confirmed by transient transfection assays with cultured cells. Quantitative RT-PCR analysis revealed that the transcript containing Ig exon was the main product in the pituitary but significantly less in the spleen, suggesting that the regulation of Ad4BP/SF-1 gene transcription in the pituitary and spleen is distinct from that of other tissues. The above findings, together with the structural abnormality at the splice donor site, suggest that acquisition of the multiple first exons enables the Ad4BP/SF-1 gene to be regulated differentially in different animal species and in different tissues in the same animal.

Identification of insertion and deletion genes in Autographa californica nucleopolyhedrovirus variants isolated from Galleria mellonella, Spodoptera exigua, Spodoptera litura and Xestia c-nigrum

The genomic DNA of four Autographa californica multinucleocapsid nucleopolyhedrovirus (AcMNPV) variants isolated from Galleria mellonella, Spodoptera exigua, Spodoptera litura and Xestia c-nigrum was analyzed in comparison with the AcMNPV E2 strain. Restriction endonuclease analysis revealed a deletion and an insertion in collinear regions of the four variants. Polymerase chain reaction analysis indicated that, in the four variants, the deletion occurred in the region corresponding to AcMNPV C6 ORF86 (pnk/pnl). Also the insertion, with a length of approximately 1.1 kb, was commonly identified in the fragments corresponding to the PstI-J fragment (18.5 m.u.-21.2 m.u.) of AcMNPV E2. Sequencing analysis of the variant from S. litura showed that the insertion contains an additional open reading frame encoding 322 amino acids between homologues of AcMNPV ORF30 and ORF31 (the superoxide dismutase gene). This ORF has 82.8% amino acid identity to Bombyx mori NPV T3 ORF 22 (bro-a, one of the baculovirus repeated ORFs) and thus, it was named Splt-bro-a. Southern blot hybridization study indicated that the other three variants also contain Splt-bro-a homologue. In addition, the labeled Splt-bro-a gene weakly hybridized to the PstI-D fragment (99.0 m.u.-8.0 m.u.) of AcMNPV E2. This fragment contains AcMNPV ORF2, a member of bro family. The signal was also observed on the corresponding fragment of the four variants. This result suggested that two bro genes are present in the four variants, although AcMNPV E2 and C6 are known to contain a single bro gene.

Transcriptional regulation of the human FTZ-F1 gene encoding Ad4BP/SF-1

Ad4BP, also known as SF-1, is a steroidogenic tissue-specific transcription factor that is also essential for adrenal and gonadal development. Two mechanisms for the transcriptional regulation of the mammalian FTZ-F1 gene encoding Ad4BP in adrenocortical cells have been proposed in the previous studies: the crucial role of a cis-element, an E box for the steroidogenic cell-specific expression of mouse and rat FTZ-F1 genes, and a possible autoregulatory mechanism of the rFTZ-F1 gene by Ad4BP itself through binding to the Ad4 (or SF-1) site in the first intron. In the present study, the transcriptional regulation of the human FTZ-F1 gene in adrenocortical cells was investigated from several angles, including the above two mechanisms. Using a series of deletion analyses of the 5'-flanking region of the hFTZ-F1 gene and site-directed mutagenesis for transient transfection studies, an E box element, CACGTG at -87/-82 from the transcriptional start site, was also found to be essential for the transcription of the hFTZ-F1 gene in mouse or human adrenocortical cell lines as well as in non-steroidogenic CV-1 cells. Despite the presence of a corresponding Ad4 site, CCAAGGCC at +163/+156 in the first intron of the hFTZ-F1 gene, an autoregulatory mechanism through the Ad4 site was found to be unlikely in the hFTZ-F1 gene mainly due to site-directed mutagenesis. In addition, the forced expression of Ad4BP had little effect on hFTZ-F1 gene transcription in non-steroidogenic CV-1 cells. Such Ad4BP-independent regulation of the hFTZ-F1 gene was in striking contrast to the regulation of steroidogenic CYP genes, such as the human CYP11A gene, in which the proximal promoter activity is Ad4BP-dependent and the transactivation by Ad4BP is silenced by DAX-1. Even though the Ad4BP-dependent transcriptional regulation of the DAX-1 gene has been reported, DAX-1 did not affect the transcriptional activity of the hFTZ-F1 gene in our study. Taken together, these observations suggest that the E box is indeed required for the expression of the FTZ-F1 gene, at least in mammalian species, but may not determine the tissue-specific expression of the hFTZ-F1 gene, and that, unlike the steroidogenic CYP gene, the regulation of the hFTZ-F1 gene appears to be independent of both Ad4BP and DAX-1.

A nuclear receptor system constituted by RAR and RXR induces aromatase activity in MCF-7 human breast cancer cells

Estrogen is the most important endocrine hormone that stimulates the growth of hormone-dependent breast cancer. The biosynthesis of estrogens in breast tissue is catalyzed by cytochrome P450 aromatase (P450arom). The expression of P450arom is controlled by the tissue- or cell-specific promoters of CYP 19 gene. The roles of nuclear receptor systems for the aromatase activity in breast cancer cells have not yet been fully investigated. In the present study, we investigated the effects of a nuclear receptor system constituted by retinoid X receptor (RXR) and its heterodimer partner on the aromatase activity in a cultured MCF-7 human breast cancer cell line, using each selective ligand for retinoic acid receptor (RAR) (TTNPB), RXR (LG100268), PPARgamma (troglitazone), and vitamin D(3) receptor (vitamin D(3)). The treatment of the cells with TTNPB or LG100268 alone for 2 days increased slightly the aromatase activity, but the increases were not statistically significant in comparison to the control. However, the combined treatment with TTNPB (10(-7) M) and LG100268 (10(-7) M) caused a dramatic stimulation of the aromatase activity. The treatment with other ligands had little or no effect on the aromatase activity. The stimulation of the aromatase activity by TTNPB plus LG100268 was dose-dependent, and a maximum stimulation was observed at 10(-7) M in both compounds. In addition, the increase in the aromatase activity was accompanied by an increase in the P450arom mRNA levels determined by RT-PCR in MCF-7 cells. The increase in the P450arom transcript was also found to be related to the specific usage of promoter 1a of the CYP 19 gene based on the analysis using RT-PCR. This is the first demonstration that a nuclear receptor system constituted by a RAR:RXR heterodimer is involved in the regulation of aromatase activity in MCF-7 breast cancer cells.

A case of late onset cyclosporine-induced hemolytic uremic syndrome resulting in renal graft loss

A case of late onset hemolytic uremic syndrome (HUS) associated with cyclosporine (CYA) is described in this report. A 50-yr-old man with end-stage renal failure due to immunoglobulin A (IgA) nephropathy received a renal transplant from his wife. Human leucocyte antigen was completely unmatched. Immunosuppressant was a combination of prednisolone, azathioprine, and CYA. He was discharged 1 month after transplantation, with no episode of acute rejection. Twenty-one months after transplantation, his platelet count and hematocrit began to decrease and lactate dehydrogenase began to increase. Graft biopsy showed thrombotic microangiopathy and recurrent IgA nephropathy. Graft function was rapidly deteriorated and methylprednisolone pulse therapy was not effective. Twenty-five months after transplantation, he returned to a regular hemodialysis. Hemolysis was immediately improved after a reduction of the dose of CYA to 50 mg/d. The trough level of CYA was less than 200 ng/mL in most periods of his clinical course. Blood pressure was high throughout the clinical course. Although acute vascular rejection or malignant hypertension could also cause a thrombotic microangiopathy, CYA was most likely a cause of HUS in the present case because of the following reasons: neither anti-acute rejection therapy nor an adequate control of his blood pressure was effective in improving clinical features of HUS; hemolysis and thrombocytopenia disappeared immediately after the reduction of the dose of CYA to 50 mg/d. It has been reported that HUS carried poor prognosis only when occurring shortly after transplantation in cadaver kidney recipients. The present transplant was from a living donor and HUS occurred 21 months after transplantation and was severe enough to result in graft loss. High blood pressure might be one of the predisposing factors of HUS associated with CYA in the present case. CYA should be stopped and other alternative immunosuppressants should be given in cases of acute graft deterioration with hemolysis and thrombocytopenia, irrespective of the interval from transplantation, CYA dose, or CYA trough level.

Induction of endometrial cycles and ovulation in a woman with combined 17alpha-hydroxylase/17,20-lyase deficiency due to compound heterozygous mutations on the p45017alpha gene

OBJECTIVE

To describe the case of a Japanese woman with combined 17alpha-hydroxylase/17,20-lyase deficiency (congenital adrenal hyperplasia type V) and to discuss possible therapeutic procedures in such patients.

DESIGN

Case report.

SETTING

University hospital.

PATIENT(S)

A 26-year-old woman with secondary amenorrhea and primary sterility.

INTERVENTION(S)

Nucleotide sequencing of the P45017alpha gene (CYP17), induction of endometrial maturation with steroid hormone replacement, and ovulation induction with gonadotropin.

MAIN OUTCOME MEASURE(S)

Nucleotide sequence of CYP17, endometrial thickness and follicle diameter measured by transvaginal ultrasonography, and histologic evaluation of the endometrium.

RESULT(S)

Two different mutations were detected on CYP17: One was a deletion of the phenylalanine codon (TTC) at either amino acid 53 or 54 in exon 1, and the other was a missense mutation with the substitution of histidine (CAC) by leucine (CTC) at position 373 in exon 6. Repeated histologic evaluations performed during treatment with P consistently revealed an unripe endometrium with glands of the early secretory phase and markedly scanty stroma. Ultrasound examination revealed follicular growth and ovulation after gonadotropin administration, but insufficient thickness of the endometrium.

CONCLUSION(S)

Ovulation induction was possible in this patient with 17alpha-hydroxylase/17,20-lyase deficiency, but the endometrial response to steroid hormone replacement was extremely poor.

Insulin sensitizer, troglitazone, directly inhibits aromatase activity in human ovarian granulosa cells

Ovarian granulosa cells synthesize estrogens from androgens, which are catalyzed by aromatase cytochrome P450 (P450arom). Troglitazone (Tro), one of the insulin-sensitizing compounds, thiazolidinediones (TZDs), is a ligand for peroxisome proliferator activated receptor gamma (PPARgamma) and is effective in the treatment of both non-insulin-dependent diabetes mellitus (NIDDM) as well as polycystic ovary syndrome (PCOS). PPARgamma exerts a transcriptional activity as a PPARgamma:RXR heterodimer. In this study, we investigated the effects of Tro and/or RXR ligand, LG100268 (LG) on the aromatase activity in cultured human ovarian granulosa cells obtained from patients who underwent in vitro fertilization. Human ovarian granulosa cells expressed PPARgamma mRNA assessed by RT-PCR. The treatment of the granulosa cells with Tro for 24 h resulted in a dramatic inhibition of the aromatase activity in a dose-dependent manner. While the treatment with LG alone also inhibited the aromatase activity, the combined treatment with both Tro and LG caused a much more reduction in the aromatase activity. The changes in the aromatase activity by Tro and/or LG were associated with comparable changes in P450arom mRNA assessed by RT-PCR. These results suggest that Tro directly inhibit the aromatase activity in human granulosa cells probably via nuclear receptor system PPARgamma:RXR heterodimer. The findings may provide a biochemical basis for the decrease in the blood concentrations of estrogens which is observed after the in vivo administration of Tro and may also possibly be useful as a novel therapy for estrogen-dependent diseases.

Thiazolidinedione suppresses the expression of erythroid phenotype in erythroleukemia cell line K562

The activation of PPARgamma:RXR nuclear system induces monocytic differentiation of some myelogeneous leukemia cell lines. The present study was undertaken to examine the effect of PPARgamma ligand, TZD (troglitazone or pioglitazone) and/or RXR selective ligand, LG100268 on the erythroleukaemia cell line K562 which has both an erythroid character and a potential for differentiation into megakaryocytes. TZD suppressed cell proliferation and the erythroid phenotype of K562 cells. The suppression of erythroid phenotype of K562 cells by TZD was synergistically enhanced by the combined treatment with LG100268. Moreover, the marked suppression of erythroid phenotype in K562 cells was also accompanied by the downregulation of the erythroid lineage-transcription factor, GATA-1. These novel actions of troglitazone may provide a biochemical basis for anemia occasionally which is observed after the in vivo administration of TZD.

Suppression of paraquat-induced wet dog shakes by nitric oxide synthase inhibitors in rats

We have found that paraquat (PQ), a widely used herbicide, causes wet dog shakes (WDS), which involve the central opioid system, in rats. A non-selective nitric oxide (NO) synthase (NOS) inhibitor, N(omega)-nitro-L-arginine (L-NA), but not its less active enantiomer, N(omega)-nitro-D-arginine, decreased the PQ-induced WDS in a dose-related manner. A selective neuronal NOS inhibitor in vivo, 7-nitroindazole, also decreased the PQ-induced WDS. Although an opioid receptor antagonist, naloxone, reversed the suppressive effect of these NOS inhibitors on the PQ-induced WDS, L-arginine, an NO precursor, had no effect on it. These findings suggest that the suppression of the PQ-induced WDS by NOS inhibition is associated with the central opioid system and is insusceptible to exogenous L-arginine.

Inhibin-like immunoreactivity produced by the adrenal gland is circulating in vivo

To clarify the contribution of the inhibin-like immunoreactivity (inhibin-LI) produced by adrenal glands to the total circulating levels of inhibin-LI, we measured serum inhibin-LI in normal and hypogonadal subjects under ACTH-loading or dexamethasone-loading condition. The mean basal concentration of inhibin-LI in the peripheral serum of the hypogonadal cases was 3.6 +/- 1.3 IU/ml (mean +/- SD, n = 5), which corresponded to 19.5 +/- 5.8% of that of normal controls matched for age and sex. The low levels of inhibin-LI in hypogonadal subjects (n = 7) rose significantly (3.6 +/- 1.1 vs 8.1 +/- 1.7 IU/ml, p < 0.001) after the administration of synthetic 1-24ACTH (40 units/day intramuscular injection) for 2 days, while the levels of serum inhibin-LI were not increased in two cases of Addison's disease with hypogonadism after the administration of ACTH. After the oral administration of a low dose of dexamethasone (1 mg) the serum inhibin-LI level in normal subjects (eight males and eight females) decreased significantly (male, 16.2 +/- 3.3 vs 14.5 +/- 4.1 IU/ml; female, 12.9 +/- 6.3 vs 10.8 +/- 5.6 IU/ml; p < 0.01 each) without significant change in the levels of serum gonadotropin (LH and FSH) and those of gonadal steroid (testosterone or estradiol). These results indicate that a small; but significant amount of inhibin-LI is secreted from the adrenal gland and circulating in vivo, and that the proportion of adrenal-derived inhibin-LI is much higher in patients with hypogonadism.

Thiazolidinedione induces apoptosis and monocytic differentiation in the promyelocytic leukemia cell line HL60

Thiazolidinedione (TZD) is known to be a potent activator of peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor that constitutes a heterodimer with retinoid X receptor (RXR). Since a considerable amount of PPARgamma is expressed in various hematopoietic cells, the present study was undertaken to examine the effect of TZD in the absence or presence of LG100268, an RXR-selective ligand, on a cultured promyelocytic leukemia cell line, HL60. Treatment with TZD (25-50 microM troglitazone or pioglitazone) markedly suppressed cell proliferation of HL60. A cell cycle analysis revealed that the suppressive effect of troglitazone on HL60 cell proliferations was caused by G0/G1 cell cycle arrest as well as by an apoptotic effect. Treatment with the same concentration of troglitazone also induced the monocytic differentiation of HL60 cells. The apoptotic or the differentiating effect of TZD on HL60 cells was synergistically enhanced by the combined treatment with 1 microM LG100268, while LG100268 alone neither had an apoptotic nor a differentiating effect on HL60 cells. These results suggest that these actions are mediated through the nuclear receptor system constituted by the PPARgamma: RXR heterodimer.