6
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Apoptosis of Lactotrophs Induced by D2 Receptor Activation Is Estrogen Dependent

      Read this article at

      ScienceOpenPublisherPubMed
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Background/Aims: Dopamine (DA) inhibits prolactin release and reduces lactotroph proliferation by activating D2 receptors. DA and its metabolite, 6-hydroxydopamine (6-OHDA), induce apoptosis in different cell types. DA receptors and DA transporter (DAT) were implicated in this action. Considering that estradiol sensitizes anterior pituitary cells to proapoptotic stimuli, we investigated the effect of estradiol on the apoptotic action of DA and 6-OHDA in anterior pituitary cells, and the involvement of the D2 receptor and DAT in the proapoptotic effect of DA. Methods: Viability of cultured anterior pituitary cells from ovariectomized rats was determined by MTS assay. Apoptosis was evaluated by Annexin-V/flow cytometry and TUNEL. Lactotrophs were identified by immunocytochemistry. Results: DA induced apoptosis of lactotrophs in an estrogen-dependent manner. In contrast, estradiol was not required to trigger the apoptotic action of 6-OHDA. Cabergoline, a D2 receptor agonist, induced lactotroph apoptosis, while sulpiride, a D2 receptor antagonist, blocked DA-induced cell death. The blockade of DAT by GBR12909 did not affect the apoptotic action of DA, but inhibited 6-OHDA-induced apoptosis. Conclusion: These data show that DA, through D2 receptor activation, induces apoptosis of estrogen-sensitized anterior pituitary cells, and suggest that DA contributes to the control of lactotroph number not only by inhibiting proliferation but also by inducing apoptosis.

          Related collections

          Most cited references 31

          • Record: found
          • Abstract: found
          • Article: not found

          Molecular pathways involved in the neurotoxicity of 6-OHDA, dopamine and MPTP: contribution to the apoptotic theory in Parkinson's disease.

          Parkinson's disease (PD) is a neurodegenerative disorder characterized by a preferential loss of the dopaminergic neurons of the substantia nigra pars compacta. Although the etiology of PD is unknown, major biochemical processes such as oxidative stress and mitochondrial inhibition are largely described. However, despite these findings, the actual therapeutics are essentially symptomatical and are not able to block the degenerative process. Recent histological studies performed on brains from PD patients suggest that nigral cell death could be apoptotic. However, since post-mortem studies do not allow precise determination of the sequence of events leading to this apoptotic cell death, the molecular pathways involved in this process have been essentially studied on experimental models reproducing the human disease. These latter are created by using neurotoxic compounds such as 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or dopamine (DA). Extensive study of these models have shown that they mimick, in vitro and in vivo, the histological and/or the biochemical characteristics of PD and thus help to define important cellular actors of cell death presumably critical for the nigral degeneration. This review reports recent data concerning the biochemical and molecular apoptotic mechanisms underlying the experimental models of PD and correlates them to the phenomena occurring in human disease.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Advances in the treatment of prolactinomas.

            Prolactinomas account for approximately 40% of all pituitary adenomas and are an important cause of hypogonadism and infertility. The ultimate goal of therapy for prolactinomas is restoration or achievement of eugonadism through the normalization of hyperprolactinemia and control of tumor mass. Medical therapy with dopamine agonists is highly effective in the majority of cases and represents the mainstay of therapy. Recent data indicating successful withdrawal of these agents in a subset of patients challenge the previously held concept that medical therapy is a lifelong requirement. Complicated situations, such as those encountered in resistance to dopamine agonists, pregnancy, and giant or malignant prolactinomas, may require multimodal therapy involving surgery, radiotherapy, or both. Progress in elucidating the mechanisms underlying the pathogenesis of prolactinomas may enable future development of novel molecular therapies for treatment-resistant cases. This review provides a critical analysis of the efficacy and safety of the various modes of therapy available for the treatment of patients with prolactinomas with an emphasis on challenging situations, a discussion of the data regarding withdrawal of medical therapy, and a foreshadowing of novel approaches to therapy that may become available in the future.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Pituitary lactotroph hyperplasia and chronic hyperprolactinemia in dopamine D2 receptor-deficient mice.

              Dopamine secreted from hypophysial hypothalamic neurons is a principal inhibitory regulator of pituitary hormone secretion. Mice with a disrupted D2 dopamine receptor gene had chronic hyperprolactinemia and developed anterior lobe lactotroph hyperplasia without evidence of adenomatous transformation. Unexpectedly, the mutant mice had no hyperplasia of the intermediate lobe melanotrophs. Aged female D2 receptor -/- mice developed uterine adenomyosis in response to prolonged prolactin exposure. These data reveal a critical role of hypothalamic dopamine in controlling pituitary growth and support a multistep mechanism for the induction and perpetuation of lactotroph hyperplasia, involving the lack of dopamine signaling, a low androgen/estrogen ratio, and a final autocrine or paracrine "feed-forward" stimulation of mitogenesis, probably by prolactin itself.
                Bookmark

                Author and article information

                Journal
                NEN
                Neuroendocrinology
                10.1159/issn.0028-3835
                Neuroendocrinology
                S. Karger AG
                0028-3835
                1423-0194
                2008
                July 2008
                06 February 2008
                : 88
                : 1
                : 43-52
                Affiliations
                Instituto de Investigaciones en Reproducción, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
                Article
                116117 Neuroendocrinology 2008;88:43–52
                10.1159/000116117
                18259092
                © 2008 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 6, References: 41, Pages: 10
                Categories
                Cellular Communication, Receptors and Signalling

                Comments

                Comment on this article