Liver X receptors, lipids and their reproductive secrets in the male

International audienceLiver X receptor (LXR) a and LXRb belong to the nuclear receptor superfamily. For many years they have been called orphan receptors, as no natural ligand was identified. In the last decade the LXR natural ligands have been shown to be oxysterols, molecules derived from cholesterol. While these nuclear receptors have been abundantly studied for their roles in the regulation of lipid metabolism, it appears that they also present crucial activities in reproductive organs such as testis and epididymis, as well as prostate. Phenotypic analyses of mice lacking LXRs (−/−) pointed out their physiological activies in the various cells and organs regulating reproductive functions. This review summarizes the impact of LXR-deficiency in male reproduction, highlighting the novel information coming from the phenotypic analyses of −/−, −/− and −/− mice

Negative feedback regulation of the ERK1/2 MAPK pathway

The extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAPK) signalling pathway regulates many cellular functions, including proliferation, differentiation, and transformation. To reliably convert external stimuli into specific cellular responses and to adapt to environmental circumstances, the pathway must be integrated into the overall signalling activity of the cell. Multiple mechanisms have evolved to perform this role. In this review, we will focus on negative feedback mechanisms and examine how they shape ERK1/2 MAPK signalling. We will first discuss the extensive number of negative feedback loops targeting the different components of the ERK1/2 MAPK cascade, specifically the direct posttranslational modification of pathway components by downstream protein kinases and the induction of de novo gene synthesis of specific pathway inhibitors. We will then evaluate how negative feedback modulates the spatiotemporal signalling dynamics of the ERK1/2 pathway regarding signalling amplitude and duration as well as subcellular localisation. Aberrant ERK1/2 activation results in deregulated proliferation and malignant transformation in model systems and is commonly observed in human tumours. Inhibition of the ERK1/2 pathway thus represents an attractive target for the treatment of malignant tumours with increased ERK1/2 activity. We will, therefore, discuss the effect of ERK1/2 MAPK feedback regulation on cancer treatment and how it contributes to reduced clinical efficacy of therapeutic agents and the development of drug resistance

Nuclear receptors in physiology and pathophysiology

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Nuclear receptors as pharmacological targets, where are we now?

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Molecular and Cellular Endocrinology: Special issue hypothalomo - Pituitary axis: Roles in integrative physiology and pathophysiologies

International audienc

Bile acids, roles in integrative physiology and pathophysiology

International audienc

Perturbateurs endocriniens et fertilité

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Male fertility: Is spermiogenesis the critical step for answering biomedical issues?

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Endocrine disruptors and fertility: NR0B2, a new therapeutic target?

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Epigenetic: a molecular link between testicular cancer and environmental exposures?

In the last decades, studies in rodents have highlighted links between in utero and/or neonatal exposures to molecules that alter endocrine functions and the development of genital tract abnormalities, such as cryptorchidism, hypospadias, and impaired spermatogenesis. Most of these molecules, called endocrine disrupters (EDs) exert estrogenic and/or antiandrogenic activities. These data led to the hypothesis of the Testicular Dysgenesis Syndrome which postulates that these disorders are one clinical entity and are linked by epidemiological and pathophysiological relations. Futhermore, infertility has been stated as a risk factor for testicular cancer. The incidence of testicular cancer has been increasing over the past decades. Most of testicular germ cell cancers develop through a pre-invasive carcinoma in situ (CIS) from fetal germ cells (primordial germ cell or gonocyte). During their development, fetal germ cells undergo epigenetic modifications. Interestingly, several lines of evidence have shown that gene regulation through epigenetic mechanisms (DNA and histone modifications) plays an important role in normal development as well as in various diseases, including testicular cancer.Here we will review chromatin modifications which can affect testicular physiology leading to the development of testicular cancer; and highlight potential molecular pathways involved in these alterations in the context of environmental exposures