Vassilis Minas

Neurosteroids as Endogenous Inhibitors of Neuronal Cell Apoptosis in Aging

Abstract:  The neuroactive steroids dehydroepiandrosterone (DHEA), its sulfate ester DHEAS, and allopregnanolone (Allo) are produced in the adrenals and the brain. Their production rate and levels in serum, brain, and adrenals decrease gradually with advancing age. The decline of their levels was associated with age‐related neuronal dysfunction and degeneration, most probably because these steroids protect central nervous system (CNS) neurons against noxious agents. Indeed, DHEA(S) protects rat hippocampal neurons against NMDA‐induced excitotoxicity, whereas Allo ameliorates NMDA‐induced excitotoxicity in human neurons. These steroids exert also a protective role on the sympathetic nervous system. Indeed, DHEA, DHEAS, and Allo protect chromaffin cells and the sympathoadrenal PC12 cells (an established model for the study of neuronal cell apoptosis and survival) against serum deprivation–induced apoptosis. Their effects are time‐ and dose‐dependent with EC50 1.8, 1.1, and 1.5 nM, respectively. The prosurvival effect of DHEA(S) appears to be NMDA‐, GABAA‐ sigma1‐, or estrogen receptor‐independent, and is mediated by G‐protein‐coupled‐specific membrane binding sites. It involves the antiapoptotic Bcl‐2 proteins, and the activation of prosurvival transcription factors CREB and NF‐κB, upstream effectors of the antiapoptotic Bcl‐2 protein expression, as well as prosurvival kinase PKCα/β, a posttranslational activator of Bcl‐2. Furthermore, they directly stimulate biosynthesis and release of neuroprotective catecholamines, exerting a direct transcriptional effect on tyrosine hydroxylase, and regulating actin depolymerization and submembrane actin filament disassembly, a fast‐response cellular system regulating trafficking of catecholamine vesicles. These findings suggest that neurosteroids may act as endogenous neuroprotective factors. The decline of neurosteroid levels during aging may leave the brain unprotected against neurotoxic challenges.

FSH receptor gene polymorphisms have a role for different ovarian response to stimulation in patients entering IVF/ICSI-ET programs

Purpose: To examine the frequency distribution of the Ser680Asn polymorphism of the follicle-stimulating hormone receptor (FSHR) gene in ovarian dysfunction (OD) infertile women, “poor responders” (PR) and “good responders” (GR). Methods: The hormonal profiles and treatment of all patients were analyzed and FSHR polymorphism was examined by PCR and RFLP. Women from all groups were classified as Asn/Asn, Asn/Ser, and Ser/Ser genotypes. Results: The frequency distribution of Ser/Ser, Asn/Ser and Asn/Asn variants in OD patients was 45.5, 22.7, and 31.8%, respectively. Day 3 FSH levels in OD and GR patients were higher in Ser/Ser and Asn/Asn subgroups. Asn/Ser carriers from OD and GR groups provided more follicles and oocytes compared to other allelic variants. Conclusions: GR patients carry more often the Asn/Ser genotype. The latter is correlated with more follicles and oocytes in both OD and GR patients. The Ser/Ser variant might be related to higher serum FSH levels, while the Asn/Ser with lower.

Hormonal and cytokine regulation of early implantation.

Implantation of the blastocyst into the endometrium is a delicately controlled process and a prerequisite for the furtherance of the mammalian species. A complex network of molecules is involved in preparing both the endometrium and blastocyst for a successful interaction. However, the exact molecular steps are poorly understood. Studies so far have shown that disruption of certain pathways results in fertility defects. Impaired implantation is currently considered to be the most important limiting factor for the establishment of viable pregnancies in assisted reproduction. It is expected that elucidating the molecular background of the process will enable accurate diagnosis and effective treatment of infertility.

The corticotropin-releasing factor (CRF) family of peptides as local modulators of adrenal function

Abstract.Corticotropin-releasing factor (CRF), also termed corticotropin-releasing hormone (CRH) or corticoliberin, is the major regulator of the adaptive response to internal or external stresses. An essential component of the adaptation mechanism is the adrenal gland. CRF regulates adrenal function indirectly through the central nervous system (CNS) via the hypothalamic-pituitary-adrenal (HPA) axis and via the autonomic nervous system by way of locus coeruleus (LC) in the brain stem. Accumulating evidence suggests that CRF and its related peptides also affect the adrenals directly, i.e. not through the CNS but from within the adrenal gland where they form paracrine regulatory loops. Indeed, CRF and its related peptides, the urocortins (UCNs: UCN1, UCN2 and UCN3), their receptors CRF type 1 (CRF1) and 2 (CRF2) as well as the endogenous pseudo-receptor CRF-binding protein (CRF-BP) are all expressed in adrenal cortical, medullary chromaffin and resident immune cells. The intra-adrenal CRF-based regulatory system is complex and depends on the balance between the local concentration of CRF ligands and the availability of their receptors.

Maternal serum corticotropin-releasing hormone and ACTH levels as predictive markers of premature labor

Objective: To investigate whether corticotropin‐releasing hormone (CRH) and corticotropin (ACTH) plasma concentrations in women diagnosed with preterm labor are of potential clinical value in the assessment of the risk of preterm birth. Method: Plasma samples of 79 women diagnosed with preterm labor were used in this study. Samples were divided into three groups based on the week of gestation (24th–28th, 29th–32nd, 33rd–37th). CRH and ACTH values were determined by ELISA. Result: Mean maternal peripheral plasma values of CRH and ACTH were significantly higher (p < 0.001) in women who were initially diagnosed with preterm labor and finally delivered a preterm birth, compared to women with the same diagnosis but with term birth. Conclusion: CRH and ACTH serum levels in women diagnosed with preterm labor could be used as predictors for the timing of parturition.

Peripheral Factors in the Metabolic Syndrome The Pivotal Role of Adiponectin

Abstract:  Several recently published reports, including ours, suggest that adiponectin is a strong proinflammatory agent. Indeed, exposure of human placenta and adipose tissue to adiponectin induces the production of interleukin‐1β (IL‐1β), IL‐6, tumor necrosis factor α (TNF‐α), and prostaglandin E2 (PGE2). We have previously shown that adiponectin is a powerful inducer of proinflammatory cytokines production by macrophages. The reported anti‐inflammatory effect of adiponectin may be due to the induction of macrophage tolerance to further adiponectin exposure or to other proinflammatory stimuli including the Toll‐like receptor (TLR) 3 ligand polyI:C and the TLR4 ligand lipopolysaccharide (LPS). We now present additional data supporting the hypothesis that adiponectin is a strong proinflammatory adipokine. More specifically, we demonstrate that adiponectin induces IL‐1β and IL‐8 from THP‐1 macrophage cell line. The effect of adiponectin is not restricted to differentiated THP‐1 macrophages but it is evident at lower levels in undifferentiated THP‐1 monocytes promoting TNF‐α, IL‐6, and IL‐8 production. Thus, its high levels in the circulation of lean subjects render their macrophages resistant to several proinflammatory stimuli including its own thus acting in effect as an anti‐inflammatory agent. Lowering of its high levels, as a consequence of increased body mass index (BMI), renders macrophages sensitive to any proinflammatory insult.

Mechanisms of implantation.

Successful embryo implantation in mammals requires the co-ordinated development of a blastocyst competent to implant and an adhesive endometrium. Given the indispensable role of implantation for the furtherance of the species, a number of molecular mechanisms have evolved to regulate the process. A variety of molecules, produced by embryo as well as maternal tissue participates in the cross-talk between the implanting blastocyst and the endometrium. The interplay between the various molecules and the routes in which they are involved is beginning to be elucidated. Because impaired implantation represents the most important limiting factor in the establishment of pregnancy, it is believed that research in the field will allow clinicians to improve the respective rates. This paper reviews certain groups of molecules that are considered to have key roles in the mechanisms of implantation.

Neuropeptide Urocortin and Its Receptors Are Expressed in Rat Kupffer Cells

The stress neuropeptides, corticotropin-releasing hormone (CRH) and urocortin (UCN), modulate the inflammatory response via the hypothalamus-pituitary-adrenal axis and locally, in a paracrine manner, act on mast and macrophage cells. Kupffer cells (KCs) are the resident macrophages of the liver. They represent the bulk of tissue macrophages in the body and they are the first to face invading noxious agents reaching the body via the portal circulation. The aim of the present report was to study the expression of the CRH system in rat KC and test its functionality. Our findings are as follows: (1) In highly purified KCs the transcripts of UCN, of its receptors CRHR1, CRHR2 and that of the pseudoreceptor CRH-binding protein (CRHBP) were present while that of CRH was not detectable. (2) Similarly, immunoreactive UCN, CRHR1, CRHR2 and CRHBP were easily detectable by immunohistochemistry and immunofluorescence in sections of whole rat liver (localized in KC) as well as in purified KC while CRH was again not detectable. (3) Exposure of purified KC to CRH or UCN suppressed lipopolysaccharide-induced tumor necrosis factor alpha production, an effect completely prevented by the CRHR1 and CRHR2 receptor antagonist astressin. Our data demonstrate the presence of UCN and its receptors in rat KC, the absence of CRH, and the functionality of these receptors. We propose that a UCN-based system may affect local inflammatory phenomena in the liver acting in a paracrine manner.

Aberrant expression of corticotropin-releasing hormone in pre-eclampsia induces expression of FasL in maternal macrophages and extravillous trophoblast apoptosis

Corticotropin-releasing hormone (CRH) and its receptors are expressed in human placenta. Recently, the impaired function of this system has been associated with a number of complications of pregnancy, including pre-eclampsia. The aim of the study was to test the hypothesis that CRH participates in the pathophysiology of pre-eclampsia through the induction of macrophage-mediated apoptosis of extravillous trophoblasts (EVTs). We found that the expression of CRH was increased in the EVT of the placental bed biopsy specimens from pre-eclamptic pregnancies (1.8-fold increase; P < 0.05). In addition, significantly larger numbers of apoptotic EVT were detected in pre-eclamptic placentas compared with normal ones (P < 0.05), and only in pre-eclamptic placentas, decidual macrophages were found to be Fas ligand (FasL)-positive. In vitro studies on the effect of CRH on human macrophages suggested that CRH induced the expression of the FasL protein in human macrophages and potentiated their ability to induce the apoptosis of a Fas-expressing EVT-based hybridoma cell line in co-cultures. These findings demonstrate a possible mechanism by which the aberrant expression of CRH in pre-eclampsia may activate the FasL-positive decidual macrophages, impair the physiological turnover of EVT and eventually disturb placentation.

CRF Receptor Antagonists: Utility in Research and Clinical Practice

CRF, CRF-related peptides and CRF receptors constitute a complex physiological system which has a key role in facilitating the adaptation of the organism to the stressful stimuli of the environment. The behavioral, endocrine, autonomic and immune branches of stress response are considered to be under the coordinating effects of CRF and its related peptides. The effects of these peptides are mediated through two distinct receptors, types 1 and 2 CRF receptors (CRF(1) and CRF(2)). The two receptors are encoded by separate genes and belong to the G-coupled receptor superfamily. The wide influence of the CRF system on physiological processes in both brain and periphery, suggests the implication of the respective peptides in the pathophysiology of numerous disorders which involve dysregulated stress responses. The potential use of CRF antagonists in such disorders is currently under intense investigation. Furthermore, such compounds have been invaluable in elucidating the physiology of the CRF system. This review will focus on existing data on the structural and pharmacological characteristics as well as the experimental and potential clinical uses of non-peptide, small molecule CRF antagonists.