Multi-well plate immunoassays for measuring signaling protein activations/deactivations and membrane vs. intracellular receptor levels

Nongenomic effects of estradiol vs. the birth control estrogen ethinyl estradiol on signaling and cell proliferation in pituitary tumor cells, and differences in the ability of R-equol to neutralize or enhance these effects

Ethinyl estradiol (EE2, the active component of many birth control formulations) persists in treated waste waters and it has become a concerning endocrine-disrupting contaminant throughout the world. Previous studies have not examined the behavior of EE2 in nongenomic signaling pathways and the subsequent functional responses (either alone or in mixtures) or conducted comparisons with the physiological estrogen estradiol (E2). In this study, mitogen-activated protein kinases (MAPKs), ERK, and JNK were activated in pituitary tumor cells by fM EE2, but p38 activation was insensitive to Collapse

Key Words

• Calcium
• ERK JNK p38 activation
• Ethinyl estradiol
• G(α)i
• Kinase
• Membrane ERα
• Non-genomic effect
• Phytoestrogen
• Prolactin
• R-equol

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MESH Headings

• Cell Proliferation/drug effects
• Ethinyl Estradiol/pharmacology
• Pituitary Neoplasms/metabolism
• Pituitary Neoplasms/pathology
• Pituitary Neoplasms/drug therapy
• Estradiol/pharmacology
• Estradiol/metabolism
• Animals
• Signal Transduction/drug effects
• Cell Line, Tumor
• Rats
• Prolactin/metabolism
• Humans

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Grants

• R01 ES015292 NIEHS NIH HHS

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Affiliation(s)

Manish Kumar Saraf Department of Biochemistry & Molecular Biology, University of Texas Medical Branch Galveston, TX 77555-0645, United States
Yow-Jiun Jeng Department of Biochemistry & Molecular Biology, University of Texas Medical Branch Galveston, TX 77555-0645, United States
Cheryl S Watson Department of Biochemistry & Molecular Biology, University of Texas Medical Branch Galveston, TX 77555-0645, United States.

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Xenoestrogen interference with nongenomic signaling actions of physiological estrogens in endocrine cancer cells

Rapid nongenomic signaling by estrogens (Es), initiated near the cell membrane, provides new explanations for the potent actions of environmental chemicals that imperfectly mimic physiological Es. These pathways can affect tumor growth, stabilization, or shrinkage via a number of signaling streams such as activation/inactivation of mitogen-activated protein kinases and caspases, generation of second messengers, and phospho-triggering of cyclin instability. Though prostate cancers are better known for their responsiveness to androgen deprivation, ∼17% of late stage tumors regress in response to high dose natural or pharmaceutical Es; however, the mechanisms at the cellular level are not understood. More accurate recent measurements show that estradiol (E₂) levels decline in aging men, leading to the hypothesis that maintaining young male levels of E₂ may prevent the growth of prostate cancers. Major contributions to reducing prostate cancer cell numbers included low E₂ concentrations producing sustained ERK phospho-activation correlated with generation of reactive oxygen species causing cancer cell death, and phospho-activation of cyclin D1 triggering its rapid degradation by interrupting cell cycle progression. These therapeutic actions were stronger in early stage tumor cells (with higher membrane estrogen receptor levels), and E₂ was far more effective compared to diethylstilbestrol (the most frequently prescribed E treatment). Xenoestrogens (XEs) exacerbated the growth of prostate cancer cells, and as we know from previous studies in pituitary cancer cells, can interfere with the nongenomic signaling actions of endogenous Es. Therefore, nongenomic actions of physiological levels of E₂ may be important deterrents to the growth of prostate cancers, which could be undermined by the actions of XEs.