Leydig Cell Adenomas Research Articles

Environmental explanation of prostate cancer progression based on the comprehensive analysis of perfluorinated compounds

Perfluorinated compounds (PFCs) are man-made chemicals used in the manufacture of many products with water and dirt repellent properties. Many diseases have been proved to be related to the exposure of PFCs, including breast fibroadenoma, hepatocellular carcinoma, breast cancer and leydig cell adenoma. However, whether the PFCs promote the progression of prostate cancer remains unclear. In this work, through comprehensive bioinformatics analysis, we discovered the correlation between the prostate cancer and five PFCs using Comparative Toxicogenomics Database (CTD), Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. In addition, further analysis showed that several PFCs-related genes demonstrated strong prognostic value for prostate cancer patients. The survival analysis and receiver operating characteristic (ROC) curves revealed that PFCs-related genes based prognostic model held great predictive value for the prognosis of prostate cancer, which could potentially serve as an independent risk factor in the future. In vitro experiments verified the promotive role of perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) in the growth of prostate cancer cells. This study provided novel insights into understanding the role of PFCs in prostate cancer and brought attention to the environmental association with cancer risks and progression.

Developmental, behavioral and endocrine alterations in male rats at early and late postnatal life following in utero exposure to low dose di-n-butylphthalate.

Environmental chemical pollutants that interfere with hormonal homeostasis or hormone signaling are the relevant agents inducing congenital or postnatally developed reproductive abnormalities in human beings, wild and domestic animals. In this study, we are examining reproductive effects of prenatal exposure of male rats to a low dose di-n-butylphthalate (DBP). Wistar female rats were given intragastrically DBP at a daily dose of 100mg/kg b.w. during 15th-21st days of pregnancy. Anogenital distance(AGD) in male offspring decreased on postnatal day (PND) 2 followed by its normalization on PND 7 and 10. There were no other visible teratogenic lesions in the newborns. The testicle descent into scrotum of control males occurred on PND 38.5 ± 0.1, while in DBP group it accelerated by 5.3days on the average. At the age of 6months, DBP-exposed animals exhibited double increase of blood plasma testosterone level as compared to controls, and hyperactive male sexual behavior in the presence of receptive female. The duration of latent periods of the first mount and the first intromission, as well as post-ejaculatory refractory period, have been shortened; the number of mounts with intromission and the number of ejaculations increased significantly. Histological examination of the testes indicated activation of Leydig cells. The female-type sexual behavior as evaluated by appearance of lordosis of orchidectomized and primed with estradiol and progesterone 10-month-old males in response to mount or approach of sexually active normal male was enhanced in DBP-group. Both 10-month-old and aging males (18months), castrated and hormone-primed, displayed homosexual type of behavior. Prenatal low dose DBP caused in 18-month-old males premature atrophy of the testes and accessory sexual glands, increased number of Leydig cell adenomas, a twice decrease of plasma testosterone level and exhausting of sexual potency. We concluded that prenatal exposition of male rats to low dose DBP determines epigenetic alterations of programming of sex brain differentiation and regulation of testicular steroidogenesis that leads to reproductive disorders and accelerated aging of reproductive system.

Testotoxicosis without Testicular Mass: Revealed by Peripheral Precocious Puberty and Confirmed by Somatic LHCGR Gene Mutation

ABSTRACTPurpose: Testotoxicosis is an autosomal dominant form of limited gonadotropin-independent precocious puberty in boys. It is caused by a heterozygous constitutively activating mutation of the LHCGR gene encoding the luteinizing/hormone receptor (LHR). Some twenty mutations of the LHCGR gene have been reported. Most of them are constitutive mutations isolated from blood leukocyte DNA, although others are somatic, found only in testicular tumoural tissue. In all the previously reported cases of these somatic mutations, the tumour, whether a nodular Leydig cell adenoma or hyperplasia, was easily visible on testicular ultrasonography. The aim of this study was to describe an unusual presentation of a patient with the clinical and hormonal characteristics of testotoxicosis but no well-circumscribed lesion at testicular ultrasonography.Materials and Methods: Molecular analysis of the LHCGR gene was performed by direct sequencing of DNA extracted from peripheral leucocytes and testicular biopsy.Results: Molecular analysis didn’t find any LHR mutation in blood, whereas it revealed for the first time a somatic D578H mutation in testicular tissue despite no evidence of a nodular aspect at testis ultrasonography.Conclusions: This observation underlines the need to look for a somatic LHCGR gene mutation from the testicular biopsies of all boys with testotoxicosis with no constitutive LHCGR gene mutation identified from blood DNA, even in the absence of circumscribed testicular lesion at ultrasonography. In addition, based on the known link between LHR mutations and testicular tumourigenesis, yearly ultrasound monitoring of the testes should be considered for these patients.

CASE REPORT: UNILATERAL ECTOPIC TESTIS IN THE TUNICA ALBUGINEA CONCURS WITH EPIDIDYMAL HYPERPLASIA IN THE ATROPHIC TESTIS IN A DOG

A 10-year-old male Fox Terrier presented with two descended testes of different sizes. The left testis was normal, while the right one was atrophic. The tunica albuginea (TA) of the right testis was distributed with brown spots of less than 1[Formula: see text]mm in diameter, and was microscopically determined to be ectopic testis which consists of Leydig cell adenoma, primitive seminiferous tubules (STs), intratubular seminoma, and reduplication of arterioles. At the junction of the TA with the spermatic cord, units of testis primordia were present. The STs of the remaining atrophic (not ectopic) right testis were populated not by germ cells but by ciliated pseudostratified cells mimicking those of the epididymis, as supported by the immunohistochemistry results. During the adaptation process, multiple smaller tubules combined into fewer but larger less convoluted tubules. This is a case of concurrent ectopic testis and arterial malformation in the TA with hypoxia, subsequent testicular atrophy, and epididymal hyperplasia in a dog.

Germ Cell Neoplasia in Situ and Preserved Fertility Despite Suppressed Gonadotropins in a Patient With Testotoxicosis

Testotoxicosis is an autosomal-dominant, male-limited disorder. Activating mutations in the luteinizing hormone receptor gene (LHCGR) cause high autonomous testosterone secretion, resulting in early-onset peripheral precocious puberty. Little is known about long-term consequences of testotoxicosis. We present a rare case of a patient followed for 25 years with two remarkable outcomes: preserved fertility and germ cell neoplasia in situ (GCNIS). He presented with precocious puberty at 10 months of age and was diagnosed with testotoxicosis due to a de novo heterozygous Asp578Tyr mutation in LHCGR. Testicular biopsy in childhood showed Leydig cell hyperplasia with altered cell maturation. From infancy throughout adulthood, elevated testosterone and estradiol, low inhibin B and anti-Müllerian hormone, and completely suppressed follicle-stimulating hormone and luteinizing hormone were noted. Height acceleration and advanced bone age resulted in a reduced final height. Semen analysis revealed ongoing spermatogenesis, and the patient fathered a child by natural conception. Ketoconazole treatment decreased circulating testosterone in childhood, supported by experimental suppression of testosterone production in his adult testis tissue cultured ex vivo. At 25 years of age, ultrasound revealed a testicular tumor, identified as a Leydig cell adenoma, but unexpectedly with GCNIS present in adjacent seminiferous tubules. The case illustrates that absence of gonadotropins but high intratesticular testosterone concentration is sufficient for spermatogenesis and to allow fatherhood. Our study is also the first description, to our knowledge, of GCNIS in a patient with testotoxicosis. We recommend regular clinical examination and ultrasonic evaluation of the testes in these patients due to potential increased risk of malignancy.

Mammary gland tumors in a male Cocker Spaniel

BackgroundMammary gland tumors are the most common tumors in sexually intact female dogs; however, they are rare in male dogs. This study was conducted to investigate the relationship between sexual hormones and mammary gland tumors in a male dog.Case presentationA 13-year-old, intact male Cocker Spaniel presented to the Veterinary Teaching Hospital of Kangwon National University, Republic of Korea, with an acute right ruptured caudal abdominal mass. Physical examination revealed a 14 × 14 cm ruptured mass in the right caudal abdomen, as well as a 1.5 × 1.5 cm mass in the first right mammary gland. The estrogen and progesterone concentrations in serum were within normal levels. Total mastectomy was done on the right side mammary glands. Following surgery, the site was fully recovered; however, a mass that had grown to 2 × 2 cm was found in the left fifth mammary gland and a testis tumor was also found over the period of 4 months. Mastectomy was performed on the left caudal mammary gland and castration was also performed. After the final surgery, the dog fully recovered. Histopathological examination of all three masses revealed high grade mammary adenocarcinoma in the mammary gland and the testis was diagnosed as Leydig cell adenoma. Immunohistochemical analysis revealed that the estrogen and progesterone receptors were expressed on limited cells in mammary and testis tumors.ConclusionThe results of this study suggest that mammary tumors and testes tumors can occur in male dogs without relationship to female sexual hormone.

Constitutive luteinizing hormone receptor signaling causes sexual dysfunction and Leydig cell adenomas in male mice.

The luteinizing hormone receptor (LHCGR) is necessary for fertility, and genetic mutations cause defects in reproductive development and function. Activating mutations in LHCGR cause familial male-limited precocious puberty (FMPP). We have previously characterized a mouse model (KiLHRD582G) for FMPP that exhibits the same phenotype of precocious puberty, Leydig cell hyperplasia, and elevated testosterone as boys with the disorder. We observed that KiLHRD582G male mice became infertile by 6 months of age, although sperm count and motility were normal. In this study, we sought to determine the reason for the progressive infertility and the long-term consequences of constant LHCGR signaling. Mating with superovulated females showed that infertile KiLHRD582G mice had functional sperm and normal accessory gland function. Sexual behavior studies revealed that KiLHRD582G mice mounted females, but intromission was brief and ejaculation was not achieved. Histological analysis of the reproductive tract showed unique metaplastic changes resulting in pseudostratified columnar epithelial cells with cilia in the ampulla and chondrocytes in the penile body of the KiLHRD582G mice. The infertile KiLHRD582G exhibited enlarged sinusoids and a decrease in smooth muscle content in the corpora cavernosa of the penile body. However, collagen content was unchanged. Leydig cell adenomas and degenerating seminiferous tubules were seen in 1-year-old KiLHRD582G mice. We conclude that progressive infertility in KiLHRD582G mice is due to sexual dysfunction likely due to functional defects in the penis.

Effects of the Janus Kinase Inhibitor, Tofacitinib, on Testicular Leydig Cell Hyperplasia and Adenoma in Rats, and on Prolactin Signaling in Cultured Primary Rat Leydig Cells.

Tofacitinib is an oral Janus kinase (JAK) inhibitor for the treatment of rheumatoid arthritis. Tofacitinib preferentially inhibits receptor signaling through JAK3 and JAK1, relative to JAK2. In the 2-year rat carcinogenicity study, there were tofacitinib, dose-related increases in the incidences of testicular Leydig cell hyperplasia and benign adenomas in male rats, and decreased incidences of mammary tumors and duct dilatation/galactocele in female rats. Such findings in rats are typical of agents, such as dopamine agonists, which decrease prolactin (PRL) activity. Since prolactin signals through the JAK2 pathway, we hypothesized that these findings were off-target effects due to inhibition of PRL signaling via JAK2. The studies reported here were designed to investigate the interruption of PRL signaling pathways in Leydig cells. In isolated primary rat Leydig cells, PRL increased phosphorylated Signal Transducer and Activator of Transcription-5 protein, and mRNA levels for luteinizing hormone receptor. Tofacitinib, at concentrations observed in the rat carcinogenicity study, dose-dependently inhibited these effects. These observations illustrate a novel mechanism, the inhibition of prolactin signaling by which modulation of JAK activity can modulate PRL signaling pathways to induce Leydig cell tumors in rats. Since human Leydig cells lack this PRL dependence for normal function, these rodent tumors do not indicate a health risk to human patients.

NNT mutations: a cause of primary adrenal insufficiency, oxidative stress and extra-adrenal defects.

Nicotinamide nucleotide transhydrogenase (NNT), one of the several genes recently discovered in familial glucocorticoid deficiencies (FGD), is involved in reactive oxygen species detoxification, suggesting that extra-adrenal manifestations may occur, due to the sensitivity to oxidative stress of other organs rich in mitochondria. Here, we sought to identify NNT mutations in a large cohort of patients with primary congenital adrenal insufficiency without molecular etiology and evaluate the degree of adrenal insufficiency and onset of extra-adrenal damages. Sanger or massive parallel sequencing of NNT and patient monitoring. Homozygous or compound heterozygous NNT mutations occurred frequently (26%, 13 unrelated families, 18 patients) in our cohort. Seven new mutations were identified: p.Met337Val, p.Ala863Glu, c.3G>A (p.Met1?), p.Arg129*, p.Arg379*, p.Val665Profs*29 and p.Ala704Serfs*19. The most frequent mutation, p.Arg129*, was found recurrently in patients from Algeria. Most patients were diagnosed belatedly (8-18 months) after presenting severe hypoglycemia; others experiencing stress conditions were diagnosed earlier. Five patients also had mineralocorticoid deficiency at onset. One patient had congenital hypothyroidism and two cryptorchidism. In follow-up, we noticed gonadotropic and genitalia impairments (precocious puberty, testicular inclusions, interstitial Leydig cell adenoma, azoospermia), hypothyroidism and hypertrophic cardiomyopathy. Intrafamilial phenotype heterogeneity was also observed. NNT should be sequenced, not only in FGD, but also in all primary adrenal insufficiencies for which the most frequent etiologies have been ruled out. As NNT is involved in oxidative stress, careful follow-up is needed to evaluate mineralocorticoid biosynthesis extent, and gonadal, heart and thyroid function.

Loss of Smad4 in Sertoli and Leydig Cells Leads to Testicular Dysgenesis and Hemorrhagic Tumor Formation in Mice1

As the central component of canonical TGFbeta superfamily signaling, SMAD4 is a critical regulator of organ development, patterning, tumorigenesis, and many other biological processes. Because numerous TGFbeta superfamily ligands are expressed in developing testes, there may exist specific requirements for SMAD4 in individual testicular cell types. Previously, we reported that expansion of the fetal testis cords requires expression of SMAD4 by the Sertoli cell lineage. To further uncover the role of Smad4 in murine testes, we produced conditional knockout mice lacking Smad4 in either Leydig cells or in both Sertoli and Leydig cells simultaneously. Loss of Smad4 concomitantly in Sertoli and Leydig cells led to underdevelopment of the testis cords during fetal life and mild testicular dysgenesis in young adulthood (decreased testis size, partially dysgenic seminiferous tubules, and low sperm production). When the Sertoli/Leydig cell Smad4 conditional knockout mice aged (56- to 62-wk old), the testis phenotypes became exacerbated with the appearance of hemorrhagic tumors, Leydig cell adenomas, and a complete loss of spermatogenesis. In contrast, loss of Smad4 in Leydig cells alone did not appreciably alter fetal and adult testis development. Our findings support a cell type-specific requirement of Smad4 in testis development and suppression of testicular tumors.

Precocious Puberty, Elevated Steroidogenesis, and Leydig Cell Hyperplasia in Male Mice with a Gain of Function Mutation in the Luteinizing Hormone Receptor Gene.

The activation of the luteinizing hormone receptor (LHR) in the gonads by luteinizing hormone (LH) is critical for steroidogenesis and gametogenesis. Several activating mutations in human LHR have been identified in boys with sporadic or familial male limited precocious puberty (FMPP) or testotoxicosis. Boys with this mutation present with elevated levels of testosterone in the context of prepubertal LH levels, the onset of puberty by age four or earlier and Leydig cell hyperplasia. The majority of the activating mutations are in transmembrane helix 6 of the 7 transmembrane G protein-coupled receptor, the most common being a mutation of aspartic acid 578 to glycine. We have created a knock-in mouse (KiLHR) with an activating point mutation, caused by substitution of glycine for aspartic acid at position 582 (D582G) in mouse LHR, corresponding to the common D578G mutation in human LHR. In this study, we have examined the effects of the mutated LHR on reproductive and metabolic function in male KiLHR mice. RT-PCR analysis of RNA from multiple tissues of heterozygous KiLHR mice demonstrated expression of the WT and mutant alleles only in the gonads and brain. Male KiLHR mice exhibited precocious puberty as evidenced by premature balanopreputial separation at postnatal day 14.5 compared to 22.4 days for WT mice and presence of major urinary proteins (MUPs), which are secreted at the onset of puberty, in KiLHR mice at postnatal day 15 compared to day 22 in WT mice. KiLHR mice were fertile. Male KiLHR mice were analyzed at neonatal (7 and10d), prepubertal (2 and 3 weeks), pubertal (6 weeks) and adult (12 and 24 weeks) ages. Hormonal analysis indicated that the KiLHR mice had significantly elevated serum and testicular testosterone levels as early as postnatal day 7 and remained elevated through adulthood. No significant difference was seen in serum estradiol levels; however testicular estradiol levels were elevated in KiLHR mice compared to WT mice. Gonadotropin levels were decreased in KiLHR compared to WT mice. Expression of the steroidogenic enzyme genes was upregulated as early as 7 days consistent with the elevated testosterone levels. The levels of LHR mRNA were significantly upregulated at all ages, but not those of the follicle stimulating hormone or steroid hormone receptors. Histological analysis revealed premature Leydig cell proliferation and the presence of Leydig cell hyperplasia as early as 7 days of age. Gene expression analysis suggested the precocious development of adult Leydig cells. At 24 weeks, Leydig cell adenomas were apparent is some of the KiLHR mice. However, there were no apparent differences in testicular germ cell or Sertoli cell development. KiLHR mice at 24 weeks of age exhibited impaired glucose tolerance compared to WT mice although there was no difference in fasting glucose or insulin levels. No changes in body weight or body fat were measured between the genotypes. The overall phenotype of precocious puberty, elevated testosterone and Leydig cell hyperplasia in the KiLHR male mice is similar to that seen in humans with FMPP. These studies suggest that the KiLHR mice will be a novel model to understand the effects of premature LHR activation during early Leydig cell development as well as the consequences of chronic elevated testosterone levels on adult testicular and metabolic function. Supported by NIH HD044119.

Mutation Analysis of the LH Receptor Gene in Leydig Cell Adenoma and Hyperplasia and Functional and Biochemical Studies of Activating Mutations of the LH Receptor Gene

Germline and somatic activating mutations in the LH receptor (LHR) gene have been reported. Our objective was to perform mutation analysis of the LHR gene of patients with Leydig cell adenoma or hyperplasia. Functional studies were conducted to compare the D578H-LHR mutant with the wild-type (WT)-LHR and the D578G-LHR mutant, a classic cause of testotoxicosis. The three main signal transduction pathways in which LHR is involved were studied. We describe eight male patients with gonadotropin-independent precocious puberty due to Leydig cell adenoma or hyperplasia. The D578H-LHR mutation was found in the adenoma or nodule with hyperplasia in all but two patients. D578H-LHR displayed a constitutively increased but noninducible production of cAMP, led to a very high production of inositol phosphates, and induced a slight phosphorylation of p44/42 MAPK in the absence of human chorionic gonadotropin. The D578G-LHR showed a response intermediate between WT-LHR and the D578H-LHR. Subcellular localization studies showed that the WT-LHR was almost exclusively located at the cell membrane, whereas the D578H-LHR showed signs of internalization. D578H-LHR was the only receptor to colocalize with early endosomes in the absence of human chorionic gonadotropin. Although several LHR mutations have been reported in testotoxicosis, the D578H-LHR mutation, which has been found only as a somatic mutation, appears up until now to be specifically responsible for Leydig cell adenomas. This is reflected by the different activation of the signal transduction pathways, when compared with the WT-LHR or D578G-LHR, which may explain the tumorigenesis in the D578H mutant.

Toxicity and carcinogenicity of androstenedione in F344/N rats and B6C3F1 mice

Androstenedione was marketed as a dietary supplement to increase muscle mass during training. Due to concern over long-term use, the NTP evaluated the subchronic and chronic toxicity and carcinogenicity of androstenedione in male and female F344/N rats and B6C3F1 mice. In subchronic studies, dose limiting effects were not observed. A chronic (2-year) exposure by gavage at 10, 20, or 50mg/kg in rats and male mice, and 2, 10, or 50mg/kg in female mice (50mg/kg, maximum feasible dose) was conducted. Increased incidences of lung alveolar/bronchiolar adenoma and carcinoma occurred in the 20mg/kg male rats and increases in mononuclear cell leukemia occurred in the 20 and 50mg/kg female rats, which may have been related to androstenedione administration. In male and female mice, androstenedione was carcinogenic based upon a significant increase in hepatocellular tumors. A marginal increase in pancreatic islet cell adenomas in male (50mg/kg) and female (2, 10, 50mg/kg) mice was considered to be related to androstenedione administration. Interestingly, incidences of male rat Leydig cell adenomas and female rat mammary gland fibroadenomas decreased. In conclusion, androstenedione was determined to be carcinogenic in male and female mice, and may have been carcinogenic in rats.

RITA—Registry of Industrial Toxicology Animal data: The application of historical control data for Leydig cell tumors in rats

Historical data for Leydig cell tumors from untreated or vehicle treated rats from carcinogenicity studies collected in the RITA database are presented. Examples are given for analyses of these data for dependency on variables considered to be of possible influence on the spontaneous incidence of Leydig cell tumors. In the 7453 male rats available for analysis, only one case of a Leydig cell carcinoma was identified. The incidence of Leydig cell adenomas differed markedly between strains. High incidences of close to 100% have been found in F344 rats, while the mean incidence was 4.2% in Sprague–Dawley rats and 13.7% in Wistar rats. Incidences in Wistar rats were highly variable, primarily caused by different sources of animals. Mean incidences per breeder varied from 2.8 to 39.9%. Analyses for the dependency on further parameters have been performed in Wistar rats. In breeders G and I, the Leydig cell tumor incidence decreased over the observation period and with increasing mean terminal body weight. The incidence of Leydig cell tumors increased with mean age at necropsy and was higher in studies with dietary admixture compared to gavage studies. These parameters had no effect on Leydig cell tumor incidence in breeders A and B. Animals from almost all breeders had a considerably higher mean age at necropsy when bearing a Leydig cell adenoma than animals without a Leydig cell adenoma. Studies with longitudinal trimming of the testes had a higher incidence than studies with transverse trimming. The observed dependencies and breeder differences are discussed and explanations are given. Consequences for the use of historical control data are outlined. With the retrospective analyses presented here we were able to confirm the published features of Leydig cell adenomas and carcinomas. This indicates that the RITA database is a valuable tool for analyses of tumors for their biological features. Furthermore, it demonstrates that the RITA database is highly beneficial for the definition of reliable historical control data for carcinogenicity studies on a scientifically solid basis.

Slide Seminar Case 7: Leydig cell tumors in rats: The application of RITA Historical Control Data

The RITA (Registry of Industrial Toxicology Animal Data) database is a proprietary database for the collection of Historical Control Data of rodent carcinogenicity studies. A number of study- and animal-related variables are collected in addition to the quality and peer reviewed histological diagnoses. Standardization of nomenclature, diagnostic criteria as well as technical procedures like tissue sampling and trimming are prerequisites for the long-term comparability of the Historical Control data. The benefits/advantages of the RITA historical control data will be shown for Leydig cell tumors in rats. In a first step, the “reliable historical control data” for a given case (Leydig cell carcinoma and its differential diagnosis of Leydig cell adenoma) will be defined by analysing the influence of strain, breeder and years of study conduct. Secondly, the historical data will be set into relation to other variables like age at necropsy, body weight or caging and feeding conditions. This example shows the value that RITA Historical Control Data can add to the interpretation of rodent carcinogenicity studies. It will also demonstrate that the analysis of RITA data may give new insights into the biology of a given neoplastic entity and discover variables with influence on its spontaneous incidence.

Hypogonadotropism with elevated serum testosterone: reversible causes of secondary infertility

A 33-year-old man presented with secondary infertility, increased libido, and extreme oligospermia. Testicular volumes were reduced, but no gynecomastia was apparent and androgen abuse was denied. Physical examination, semen-volume and sperm-density assessment, laboratory tests for serum levels of luteinizing hormone, follicle-stimulating hormone, testosterone, and dehydroepiandrosterone sulfate, karyotyping, testicular ultrasound, pelvic and abdominal CT, assessment for serum testicular tumor markers (alpha-fetoprotein and human chorionic gonadotropin), and histologic examination of testicular tissue. Benign Leydig-cell adenoma. Left orchidectomy.

Methyl tertiary-Butyl Ether: Studies for Potential Human Health Hazards

When methyl tertiary-butyl ether (MTBE) in gasoline was first introduced to reduce vehicle exhaust emissions and comply with the Clean Air Act, in the United States, a pattern of complaints emerged characterised by seven “key symptoms.” Later, carefully controlled volunteer studies did not confirm the existence of the specific key symptoms, although one study of self-reported sensitive (SRS) people did suggest that a threshold at about 11–15% MTBE in gasoline may exist for SRSs in total symptom scores. Neurobehavioral and psychophysiological studies on volunteers, including SRSs, found no adverse responses associated with MTBE at likely exposure levels. MTBE is well and rapidly absorbed following oral and inhalation exposures. Cmax values for MTBE are achieved almost immediately after oral dosing and within 2 h of continuous inhalation. It is rapidly eliminated, either by exhalation as unchanged MTBE or by urinary excretion of its less volatile metabolites. Metabolism is more rapid humans than in rats, for both MTBE and tert-butyl alcohol (TBA), its more persistent primary metabolite. The other primary metabolite, formaldehyde, is detoxified at a rate very much greater than its formation from MTBE. MTBE has no specific effects on reproduction or development, or on genetic material. Neurological effects were observed only at very high concentrations. In carcinogenicity studies of MTBE, TBA, and methanol (included as an endogenous precursor of formaldehyde, without the presence of TBA), some increases in tumor incidence have been observed, but consistency of outcome was lacking and even some degree of replication was observed in only three cases, none of which had human relevance: α2 u-globulin nephropathy-related renal tubule cell adenoma in male rats; Leydig-cell adenoma in male rats, but not in mice, which provide the better model of the human disease; and B-cell-derived lymphoma/leukemia of doubtful pathogenesis that arose mainly in lungs of orally dosed female rats. In addition, hepatocellular adenomas were significantly higher in female CD-1 mice and thyroid follicular-cell adenomas were increased in female B6C3F1 mice treated with TBA, but these results lack any independent confirmation, which would have been possible from a number of other studies.

Transgenic Mice Expressing P450 Aromatase as a Model for Male Infertility Associated with Chronic Inflammation in the Testis

Our previous studies have shown that transgenic male mice expressing human P450 aromatase (AROM+) are infertile. In the present study, we followed the testis phenotype up to 15 months of age in these mice. The testes of the old AROM+ mice showed Leydig cell hypertrophy and hyperplasia, as indicated by the staining for steroidogenic enzymes and androgen and estrogen receptors. However, the Leydig cell adenomas did not show signs of malignization. In contrast, we observed a marked increase in the number of activated macrophages in the testicular interstitium of the aging AROM+ mice. The macrophages were further shown to express high levels of CD68 (a monocyte/macrophage marker) and secrete TNFalpha, indicating strong activation, presumably by estrogen exposure. The increased activity of the macrophages was associated with Leydig cell depletion (analyzed at the age of 9 and 15 months) and an increased number of mast cells and fibrosis in the testicular interstitium. Interestingly, similar findings have been made in testes of infertile men. Hence, the aging AROM+ males present with a phenocopy of inflammation-associated infertility in men, providing a model for further studies on the putative link among estrogens, orchitis, and infertility.

Fetal but not adult Leydig cells are susceptible to adenoma formation in response to persistently high hCG level: a study on hCG overexpressing transgenic mice

We have previously demonstrated that male transgenic (TG) mice overexpressing human chorionic gonadotropin (hCG+) develop reproductive organ defects, but no tumors, in adult age. In this study, the effects of persistently elevated hCG were followed in TG males between day 5 postpartum and adulthood. Leydig cell (LC) adenomas were found in prepubertal mice, most prominently at the age of 10 days, but not in adult age. Serum testosterone concentrations were significantly increased in TG males at all ages studied. The phenotype of the prepubertal hCG+ males resembled that found in boys upon expression of constitutively activating luteinizing hormone (LH) receptor mutations. The temporal expression patterns of the fetal LC marker gene, thrombospondin 2, and those of adult LCs, hydroxysteroid dehydrogenase-6, delta5-3-beta and prostaglandin D synthase, were similar in wild-type and hCG+ males. Hence, the postnatal adenomas resemble functionally fetal LCs, and only these cells are susceptible to hCG-induced tumorigenesis. Our findings demonstrate a novel intriguing difference between the fetal and adult LC populations and provide further insight into the potential tumorigenic effects of gonadotropins.

Characterization of risk for general population exposure to perfluorooctanoate

Perfluorooctanoate (PFOA), an environmentally and metabolically stable perfluorinated carboxylic acid, has been detected in the serum of children, adults and the elderly from the United States with the upper bound of the 95th percentile estimate in the range of 0.011–0.014 μg/mL (ppm). In this risk characterization, margins of exposure (MOE), which can provide a realistic perspective on potential for human risk, were determined by comparison of general population serum PFOA concentrations with serum concentrations from toxicological studies that are associated with the lower 95% confidence limit of a modeled 10 percent response or incidence level (LBMIC 10) using USEPA BMDS software. The LBMIC 10 was estimated using surrogate data from other studies or pharmacokinetic relationships if serum PFOA data were not available. Modeled dose–responses (with resulting LBMIC 10 values) included post-natal effects in rats (29 μg/mL), liver-weight increase (23 μg/mL), and body-weight change (60 μg/mL) in rats and monkeys, and incidence of Leydig cell adenoma (125 μg/mL) in rats. MOE values based on the upper bound 95th percentile population serum PFOA concentration were large, ranging from 1600 (liver-weight increase) to 8900 (Leydig cell adenoma). These MOE values represent substantial protection of children, adults, and the elderly.