Mn is an abundant element required for normal mammalian physiological processes, but both excesses and deficiencies can cause serious health problems. Our recent studies have shown that prepubertal Mn exposure activates the neuroendocrine hypothalamus to stimulate LHRH secretion, an action that generated precocious pubertal development. Thus, this seemingly beneficial effect of Mn to activate the reproductive system may be harmful if an individual is exposed to low, but elevated levels of the metal too early in life. Therefore, the long- term goal of this study is to obtain information which will allow us to better understand the effects and mechanisms of action of manganese (Mn) on the induction of precocious puberty. Molecular and physiological approaches will be utilized to address four specific aims.
Aim 1 will assess the effects of prepubertal Mn exposure on the expressions of specific puberty related genes and proteins in the hypothalamus. One of these is KiSS-1, a gene vital for the onset of puberty as it is responsible for the production of the kisspeptins (Kp), which are potent stimulators of hypothalamic luteinizing hormone-releasing hormone (LHRH).
Aim 2 will assess upstream actions of Mn on KiSS-1/Kp functions and evaluate its effects on potential upper echelon genes suggested as regulators of KiSS-1 gene expression.
Aim 3 will use cultured rat hypothalamic astrocytes to assess the effects of Mn on downstream glial to glial communications involved in the pubertal process.
Aim 4 will assess the puberty-related effects of Mn in developing female pups exposed to Mn through their mothers during gestation, lactation or both.
This aim will enable us to determine which exposure time caused the most significant insult, and discern whether the effects and underlining mechanisms are similar or different compared to pups in the previous aims that were exposed to Mn during postnatal development. Understanding the involvement of Mn in precocious puberty is clearly important as it relates to adolescent health and development. Because Mn affects humans and its actions on puberty are mediated through normal neuroendocrine channels that apply to all mammals, the proposed study should provide information that will translate to research using primates and human epidemiological studies to further investigate the actions of Mn on precocious puberty and its health related effects.

Public Health Relevance

Normal pubertal development is an important child health concern. Recently, we have shown that prepubertal exposure to low, but elevated levels of manganese chloride (MnCl2) can induce precocious puberty, a serious endocrine disorder. In this study we will assess the molecular and physiological mechanisms of action by which early developmental exposure to this element activates the reproductive hypothalamus;hence, in accordance with the NIEHS Strategic Plan, the information gained from this research will provide insights into the effects of an environmental substance on normal physiology and disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
2R01ES013143-05A1
Application #
8233842
Study Section
Neurotoxicology and Alcohol Study Section (NAL)
Program Officer
Heindel, Jerrold
Project Start
2004-09-30
Project End
2016-10-31
Budget Start
2011-12-01
Budget End
2012-11-30
Support Year
5
Fiscal Year
2012
Total Cost
$329,344
Indirect Cost
$104,344
Name
Texas Agrilife Research
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
847205713
City
College Station
State
TX
Country
United States
Zip Code
77843
Dees, William L; Hiney, Jill K; Srivastava, Vinod K (2017) Influences of manganese on pubertal development. J Endocrinol 235:R33-R42
Hiney, Jill K; Srivastava, Vinod K; Dees, William L (2016) Manganese protects against the effects of alcohol on hypothalamic puberty-related hormones. Life Sci 148:106-11
Srivastava, Vinod K; Hiney, Jill K; Dees, William L (2016) Manganese-Stimulated Kisspeptin Is Mediated by the IGF-1/Akt/Mammalian Target of Rapamycin Pathway in the Prepubertal Female Rat. Endocrinology 157:3233-41
Dearth, Robert K; Hiney, Jill K; Srivastava, Vinod K et al. (2014) Prepubertal exposure to elevated manganese results in estradiol regulated mammary gland ductal differentiation and hyperplasia in female rats. Exp Biol Med (Maywood) 239:871-882
Hiney, Jill K; Srivastava, Vinod K; Volz, Claire E et al. (2014) Alcohol alters insulin-like growth factor-1-induced transforming growth factor ?1 synthesis in the medial basal hypothalamus of the prepubertal female rat. Alcohol Clin Exp Res 38:2572-8
Srivastava, Vinod K; Hiney, Jill K; Dees, William L (2013) Early life manganese exposure upregulates tumor-associated genes in the hypothalamus of female rats: relationship to manganese-induced precocious puberty. Toxicol Sci 136:373-81
Hiney, Jill K; Srivastava, Vinod K; Dees, William Les (2011) Manganese induces IGF-1 and cyclooxygenase-2 gene expressions in the basal hypothalamus during prepubertal female development. Toxicol Sci 121:389-96
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Pine, Michelle; Lee, Boyeon; Dearth, Robert et al. (2005) Manganese acts centrally to stimulate luteinizing hormone secretion: a potential influence on female pubertal development. Toxicol Sci 85:880-5