Olle Söder

Science and policy on endocrine disrupters must not be mixed: a reply to a “common sense” intervention by toxicology journal editors

The “common sense” intervention by toxicology journal editors regarding proposed European Union endocrine disrupter regulations ignores scientific evidence and well-established principles of chemical risk assessment. In this commentary, endocrine disrupter experts express their concerns about a recently published, and is in our considered opinion inaccurate and factually incorrect, editorial that has appeared in several journals in toxicology. Some of the shortcomings of the editorial are discussed in detail. We call for a better founded scientific debate which may help to overcome a polarisation of views detrimental to reaching a consensus about scientific foundations for endocrine disrupter regulation in the EU.

Incidence in Sweden and Clinical Features of Familial Hemophagocytic Lymphohistiocytosis

ABSTRACT. We retrospectively studied the incidence of familial hemophagocytic lymphohistiocytosis (FHL) in children during the 16‐year period 1971–86. First, all departments of pediatrics, pathology, and infectious diseases were enquired for children with FHL or disorders resembling FHL. Secondly, the causes of death of all children who died during the study period in Sweden (n= 19 542) were also investigated. Files and histological specimens were further studied in selected children. By using a set of inclusion/exclusion criteria, we found 32 children with FHL. The incidence was 1.2/1000000 children per year. One child per 50 000 live borns developed FHL during this period. The sex ratio was close to 1:1. Prominent early clinical signs were fever (91%), splenomegaly (84%), hepatomegaly (90%), rash (43%), and lymph node enlargement (42%). Neurological symptoms, which developed in 47%, could totally dominate the clinical picture and develop prior to other symptoms and signs. Common laboratory findings were pancytopenia, hypertriglyceridemia, hypofibrinogenemia, elevated serum transaminases, hyperbilirubinemia, hyponatremia, hypoalbuminemia, and a moderate spinal fluid pleocytosis. Chest X‐ray often revealed mostly discrete pulmonary infiltrates. FHL is an underdiagnosed disease and in only 11/32 children was diagnosis made during their lifetime. It is important to be aware of the disorder as potential therapy now exists.

The Sertoli Cell – A Hormonal Target and ‘Super’ Nurse for Germ Cells That Determines Testicular Size

The somatic Sertoli cell plays an essential role in embryonic determination of male somatic sex and in spermatogenesis during adult life. One individual Sertoli cell supplies a clone of developing germ cells with nutrients and growth factors and it is well established that the number of Sertoli cells present is closely correlated to both testicular size and sperm output. Sertoli cells continue to proliferate and differentiate until the beginning of puberty, when they cease dividing and start nursing the germ cells. At this point in time, the future capacity of the testis for sperm production has thus been determined. Prior to puberty the Sertoli cells are immature and differ considerably with respect to morphology and biochemical activity from the mature cell. The several investigations that have focused on hormonal and paracrine regulation of the functions of the mature cell are reviewed here, but the mechanisms underlying the maturation and general maintenance of well-functioning Sertoli cells remain obscure. An alarming decline in male reproductive health has been observed in several Western countries during recent decades. Disturbance of Sertoli cell differentiation is thought to be involved in the pathogenesis of both a poor sperm count and testicular cancer. It is speculated that environmental agents that disrupt the estrogenic/androgenic balance in the testis may play a role in this connection.

Doxorubicin Induces Apoptosis in Germ Line Stem Cells in the Immature Rat Testis and Amifostine Cannot Protect against This Cytotoxicity

The underlying primary damage to the seminiferous epithelium caused by chemotherapeutic regimens at childhood is largely unknown. The present investigation was designed to identify acute cytotoxic events in the testis caused by a single dose of doxorubicin. Male rats at 6, 16, and 24 days of age were injected with doxorubicin (3 mg/kg, i.p.) or vehicle (saline) alone and 24 and 48 hours later, the germ cell types and apoptotic cells in the seminiferous epithelium were examined. As indicated by microscopy and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling staining, an 8-fold increase in the number of apoptotic germ cells in the testes of 6-day-old rats was observed 48 hours after doxorubicin treatment. Spermatogonia migrating to the basement membrane were the primary cell type undergoing this induced apoptosis. A single dose of amifostine (200 mg/kg) administered i.p. 15 minutes before injection of doxorubicin provided no protection against this enhanced apoptosis. Under the same conditions, testicular levels of p53 and activated caspase 8 were elevated, whereas the level of murine double minute-2 was lowered. In contrast, doxorubicin treatment did not result in any significant change in the physiologic, stage-specific germ cell apoptosis occurring in the testes of 16- and 24-day-old rats. These observations suggest that the initiation phase of spermatogenesis is highly sensitive to doxorubicin-induced apoptosis. Gonocytes and early spermatogonia are the cell types that are vulnerable to this p53-trigged apoptosis, which results in a decrease in the size of the pool of germ-line stem cells. Amifostine fails to protect the germ cells against this cytotoxic insult.

Increased Apoptosis Occurring During the First Wave of Spermatogenesis Is Stage-Specific and Primarily Affects Midpachytene Spermatocytes in the Rat Testis

Abstract The physiological apoptosis that occurs in immature testis appears to be necessary for the maturation of this tissue. Thus, inhibition of the early apoptotic wave associated with the first round of spermatogenesis is followed by accumulation of spermatogonia and infertility later in life. To identify the cell types undergoing apoptosis in immature rat testis and to characterize the relationship between this apoptosis and progression of the first wave of spermatogenesis, sequential viable segments of seminiferous tubules from 8-, 18-, and 26-day-old rats were examined under a phase-contrast microscope. One novel observation was the existence of pronounced stage-specificity during the peak of apoptosis at the very early postnatal ages of 18 and 26 days. Increased apoptosis of pachytene spermatocytes in stages VII–VIII was the major feature that distinguished immature spermatogenesis from the corresponding adult process. The frequency of apoptosis among type A spermatogonia in immature stages IX–I was also elevated in comparison to the corresponding mature stages. The age-related peak of apoptosis was mediated by caspase 3; furthermore, stage-dependent expression of Bax in midpachytene spermatocytes was observed in the 18- and 26-day-old testis. These observations suggest that this Bax-regulated, caspase 3-mediated, increased apoptosis of midpachytene spermatocytes during the first wave of immature spermatogenesis represents a major difference in comparison to apoptosis occurring in the mature testis, and it may play an important regulatory role in establishing spermatogenesis in the rat testis.

Origin, Development and Regulation of Human Leydig Cells

Sex steroids are crucial regulators of sexual differentiation and the proper development of secondary sex characteristics and patterns of sexual behavior. Since Leydig cells are the primary major producers of these steroid hormones, maintenance of the normal functions of these cells determines the reproductive capacity and fertility of males. The present minireview discusses recent findings concerning endocrine and paracrine regulation of the proliferation, differentiation and involution of human Leydig cells. The physiology and function of the two distinct fetal and adult populations of human Leydig cells are described, with particular focus on the paracrine environment that triggers their differentiation and functional maturation. The roles of established and more recently discovered paracrine regulators of this maturation, including insulin-like factor 3, platelet-derived growth factor-α, desert hedgehog, ghrelin and leptin are considered. A brief description of the origin, ontogenesis and functional markers of human fetal and adult Leydig cells is presented.

Age-dependent stimulation of Leydig cell steroidogenesis by interleukin-1 isoforms.

Different isoforms of testicular interleukin-1 (IL-1) were analysed to determine whether there were differences in the ability to modulate rat Leydig cell steroidogenesis in vitro. Rat 17K IL-1alpha and IL-1beta, 32K IL-1alpha precursor (32proIL-1alpha) and a 24K splice variant (24proIL-1alpha) stimulated testosterone production by Leydig cells from 40- but not 80-day-old rats. The potency of the isoforms was IL-1alpha>IL-1beta>32proIL-1alpha>24proIL-1alpha, IL-1alpha being 50-fold more potent than IL-1beta. IL-1 receptor antagonist reversed the effects and IL-1 receptor type I mRNA was expressed by the responding Leydig cells, indicating a receptor mediated action. Inhibition of PKA and Ca(2+) channels abolished IL-1-induced steroidogenesis, while inhibition of PKC had no significant effect. Except for 24proIL-1alpha which was stimulatory, all IL-1 isoforms suppressed hCG-driven testosterone production. This inhibitory effect was abolished by androstendione, suggesting that P450c17 was suppressed by IL-1. Our results indicate that IL-1 plays a paracrine role in the regulation of Leydig cell steroidogenesis.

The influence of di-(2-ethylhexyl) phthalate on steroidogenesis by the ovarian granulosa cells of immature female rats.

Phthalate esters are known to exert harmful effects on mammalian reproduction and fertility, but their potential adverse effects on the hormonal functions of the ovary have not yet been elucidated in detail. Here, we investigated the effects of di-(2-ethylhexyl) phthalate (DEHP) on the hypothalamic-pituitary-gonadal axis of young developing female rats, as well as on ex vivo steroidogenesis by granulosa cells (GCs) and secretion of LH by gonadotropes. Exposure of 20-day-old female rats to 500 mg DEHP by oral gavage once daily for 10 days reduced their serum levels of progesterone and estradiol, while tending to enhance levels of LH. Furthermore, primary cultures of GCs isolated from these rats exhibited an attenuated capacity to produce progesterone in response to stimulation by LH and FSH, as well as a lower degree of transport of endogenous cholesterol into mitochondria. Moreover, the ability of primary cultures of pituitary cells isolated from DEHP-treated rats to produce and secrete LH in response to GnRH was significantly enhanced. In addition, 2-ethylhexanoic acid, a metabolite of DEHP, significantly potentiated GnRH-stimulated production of LH by cultures of pituitary cells isolated from untreated 20-day-old female rats. Together, these data indicate that DEHP exerts dual effects on the pituitary-gonadal axis, stimulating the hormonal function of the pituitary and, at the same time, by inhibiting steroidogenesis by GCs.

Epididymal expression of the forkhead transcription factor Foxi1 is required for male fertility

An essential aspect of male reproductive capacity is the immediate availability of fertilization‐ready spermatozoa. To ensure this, most mammals rely on post‐testicular sperm maturation. In epididymis, germ cells are matured and stored in a quiescent state that readily can be altered to produce active spermatozoa. This depends on active proton secretion into the epididymal lumen. We have identified Foxi1 as an important regulator of gene expression in narrow and clear cells—the major proton secretory cells of epididymal epithelia. Foxi1 appears to be required for the expression of the B1‐subunit of the vacuolar H+‐ATPase proton pump and for carbonic anhydrase II as well as the chloride/bicarbonate transporter pendrin. Using transfection experiments, we have identified a Foxi1 binding cis‐element in the ATP6V1B1 (encoding the B1‐subunit) promoter that is critical for reporter gene activation. When this site is mutated to eliminate Foxi1 binding, activation is also abolished. As a consequence of defect Foxi1‐dependent epididymal sperm maturation, we demonstrate that spermatozoa from Foxi1 null males fail to reach the female genital tract in sufficient number to allow fertilization.

Constitutive Expression of Interleukin-1α Messenger Ribonucleic Acid in Rat Sertoli Cells Is Dependent upon Interaction with Germ Cells1

Interleukin-1 (IL-1), a proinflammatory cytokine originally isolated as a product of activated mononuclear phagocytes, consists of two distinct agonist proteins, IL-1α and IL-1β, of which IL-1β is the major inducible IL-1 protein produced by macrophages. We show here that mRNA of IL-1α, but not IL-1β, is constitutively expressed by the intact rat testis and localize the transcript to Sertoli cells as confirmed by a novel squash technique. The expression is developmentally regulated and appears only after postnatal day 20 in the rat testis, corresponding to onset of puberty. IL-1α mRNA shows a stage-dependent expression pattern during the cycle of the seminiferous epithelium. It is low or absent in stage VII, but present in all other stages of the cycle. The same stage-dependent distribution was also observed at the protein level when bioactive IL-1 was measured in extracts of accurately defined one millimeter segments of seminiferous tubules. No IL-1α mRNA was detected in adult rat testes after germ cell ...