Although estrogen is known to protect against β-amyloid (Aβ)-induced neurotoxicity, the mechanisms responsible for this effect are only beginning to be elucidated. In addition, the effect of raloxifene on Aβ-induced neuro-toxicity remains unknown. Here we investigated whether raloxifene exhibits similar neuro-protective effects to estrogen against Aβ-induced neurotoxicity and the mechanism of the effects of these agents in PC12 cells transfected with the full-length human estrogen receptor (ER) α gene (PCER). Raloxifene, like 17β-estradiol (E2), significantly inhibited Aβ-induced apoptosis in PCER cells, but not in a control line of cells transfected with vector DNA alone (PCCON). Since telomerase activity, the level of which is modulated by regulation of telomerase catalytic subunit (TERT) at both the transcriptional and post-transcriptional levels, is known to be involved in suppressing apoptosis in neurons, we examined the effect of E2 and raloxifene on telomerase activity. Although both E2 and raloxifene induced telomerase activity in PCER cells, but not in PCCON cells, treated with Aβ, they had no effect on the level of TERT expression. These results suggest that neither E2 nor raloxifene affects the telomerase activity at the transcriptional level. We therefore studied the mechanism by which E2 and raloxifene induce the telomerase activity at the post-transcriptional level. Both E2 and raloxifene induced the phosphorylation of Akt, and pre-treatment with a phosphatidylinositol 3-kinase inhibitor, LY294002, attenuated both E2 − and raloxifene-induced activation of the telomerase activity. Moreover, both E2 and raloxifene induced both the phosphorylation of TERT at a putative Akt phosphorylation site and the association of nuclear factor κB with TERT. Our findings suggest that and raloxifene exert neuroprotective effects by E2 telomerase activation via a post-transcriptional cascade in an experimental model relevant to Alzheimer’s disease.
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Botao Du, Masahide Ohmichi, Kazuhiro Takahashi, Jun Kawagoe, Chika Ohshima, Hideki Igarashi, Akiko Mori-Abe, Maki Saitoh, Tsuyoshi Ohta, Akira Ohishi, Masakazu Doshida, Naohiro Tezuka, Toshifumi Takahashi, and Hirohisa Kurachi
Ryo Morimoto, Fumitoshi Satoh, Osamu Murakami, Takuo Hirose, Kazuhito Totsune, Yutaka Imai, Yoichi Arai, Takashi Suzuki, Hironobu Sasano, Sadayoshi Ito, and Kazuhiro Takahashi
Adrenomedullin 2/intermedin (AM2/IMD) is a new member of calcitonin/calcitonin gene-related peptide family. AM is expressed in various tumors including adrenocortical tumors and modulates tumor growth. The AM2/IMD expression has not been studied, however, in adrenal tumors. The expression of AM2/IMD and AM was therefore studied in human adrenal tumors and attached non-neoplastic adrenal tissues by immunocytochemistry (ICC). Immunoreactive (IR)–AM2/IMD was measured by RIA. Furthermore, the expression of AM2/IMD and its receptor components, calcitonin receptor-like receptor (CRLR), and receptor activity-modifying proteins (RAMPs) 1, 2, and 3 mRNA in these tissues was studied by reverse transcription PCR (RT-PCR). ICC showed that AM2/IMD and AM immunoreactivities were localized in adrenocortical tumors and pheochromocytomas. AM2/IMD and AM immunoreactivities were detected in medulla of attached non-neoplastic tissues, while the degree of immunoreactivity for AM2/IMD and AM in cortices of attached adrenals was relatively weak or undetectable. RIA detected IR-AM2/IMD in adrenal tumors (0.414±0.12 to 0.786±0.27 pmol/g wet weight, mean±s.e.m.) and attached adrenal tissues (0.397±0.052 pmol/g wet weight). Reverse-phase high-performance liquid chromatography showed one broad peak eluted in the similar position to synthetic AM2/IMD with several minor peaks. RT-PCR showed expression of AM2/IMD, CRLR, and RAMP1, RAMP2, and RAMP3 mRNA in tissues of adrenal tumors and attached adrenal glands. In conclusion, AM2/IMD is expressed in human adrenal tumors and attached non-neoplastic adrenal tissues and may play (patho-)physiological roles in normal and neoplastic adrenals as an autocrine/paracrine regulator.
Seiji Tsutsumi, Xi Zhang, Keiko Takata, Kazuhiro Takahashi, Richard H Karas, Hirohisa Kurachi, and Michael E Mendelsohn
Estrogen has both rapid and longer term direct effects on cardiovascular tissues mediated by the two estrogen receptors, ESR1 and ESR2. Previous work identified that estrogen regulates the expression of inducible nitric oxide synthase (NOS2A) in vascular smooth muscle cells (VSMC). ESR2 knockout mice have vascular dysfunction due to dysregulation of NOS2A expression and these mice are hypertensive (Zhu et al. Science 2002 295 505–508). Here, we report studies to examine the differential regulation of NOS2A gene expression by ESR1 and 2. Immunoblotting and RT-PCR studies revealed that different VSMC lines expressed different levels of ESR1 and ESR2 protein and mRNA. VSMC from different vascular beds were studied, including aortic VSMC expressing ESR1 and radial (Rad) VSMC expressing ESR2. E2 inhibited NO production and NOS2A protein expression in aortic VSMC. Human NOS2A promoter–reporter studies revealed suppression of NOS2A reporter activity by E2 in aortic VSMC, and stimulation of NOS2A reporter activity by E2 in Rad arterial VSMC. In heterologous expression studies of COS-7 cells lacking endogenous ER, E2 treatment of COS-7 cells did not alter NOS2A reporter activity in the presence of ESR1, while reporter activity increased 2.3-fold in the presence of ESR2. Similar experiments in COS-7 cells using the selective estrogen receptor modulator raloxifene showed that raloxifene caused a reduction in NOS2A reporter activity with ESR1 coexpression and an increase with ESR2 coexpression. Rat VSMC expressing ESR2 but not ESR1 also showed increased NOS2A reporter activity with E2 treatment, an effect lost when ESR1 was introduced into the cells. Taken together, these data support that hNOS2A transcription is regulated positively by ESR2 and negatively by ESR1 in VSMC, supporting differential actions of these two estrogen receptors on a physiologically relevant gene in VSMC.