Michele L Nealen

Johns Hopkins Medicine, Baltimore, Maryland, United States

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Publications (9)52.32 Total impact

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    ABSTRACT: Previous reports showed that 17beta-estradiol implants attenuate in vivo coronary hyperreactivity (CH), characterized by long-duration vasoconstrictions (in coronary angiographic experiments), in menopausal rhesus monkeys. Prolonged Ca2+ contraction signals that correspond with CH in coronary vascular muscle cells (VMC) to the same dual-constrictor stimulus, serotonin + the thromboxane analog U-46619, in estrogen-deprived VMC were suppressed by >72 h in 17beta-estradiol. The purpose of this study was to test whether an endogenous estrogen metabolite with estrogen receptor-beta (ER-beta) binding activity, estriol (E3), suppresses in vivo and in vitro CH. E3 treatment in vivo for 4 wk significantly attenuated the angiographically evaluated vasoconstrictor response to intracoronary serotonin + U-46619 challenge. In vitro treatment of rhesus coronary VMC for >72 h with nanomolar E3 attenuated late Ca2+ signals. This reduction of late Ca2+ signals also appeared after >72 h of treatment with subnanomolar 5alpha-androstane-3beta,17beta-diol (3beta-Adiol), an endogenous dihydrotestosterone metabolite with ER-beta binding activity. R,R-tetrahydrochrysene, a selective ER-beta antagonist, significantly blocked the E3- and 3beta-Adiol-mediated attenuation of late Ca2+ signal increases. ER-beta and thromboxane-prostanoid receptor (TPR) were coexpressed in coronary arteries and aorta. In vivo E3 treatment attenuated aortic TPR expression. Furthermore, in vitro treatment with E3 or 3beta-Adiol downregulated TPR expression in VMC, which was blocked for both agonists by pretreatment with R,R-tetrahydrochrysene. E3- and 3beta-Adiol-mediated reduction in persistent Ca2+ signals is associated with ER-beta-mediated attenuation of TPR expression and may partly explain estrogen benefits in coronary vascular muscle.
    No preview · Article · Jan 2006 · AJP Heart and Circulatory Physiology
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    ABSTRACT: TRPV1, the capsaicin receptor, is expressed not only in nociceptive neurons, but also in other locations, including the hypothalamus. Studies involving systemic or intrahypothalamic capsaicin administration have suggested a role for TRPV1 in body temperature control. To explore this possibility, we examined thermoregulatory responses in TRPV1-/- mice. These mutant animals exhibited no obvious changes in circadian body temperature fluctuation, tolerance to increased (35 degrees C) or decreased (4 degrees C) ambient temperature or ethanol-induced hypothermia. In contrast, fever production in response to the bacterial pyrogen, lipopolysaccharide (LPS) was significantly attenuated in TRPV1-/- mice. Despite this finding, we detected no significant differences between TRPV1-/- and control mice in the extent of LPS-induced c-Fos expression in numerous fever-related brain subregions. These results suggest that TRPV1 participates in the generation of polyphasic fever, perhaps at sites outside the brain.
    No preview · Article · May 2005 · Neuroscience Letters
  • S. Barrick · B. Chopra · M. Caterina · M. Nealen · H. Lee · L. Birder

    No preview · Article · Mar 2005 · Journal of Pain
  • Michele L Nealen · Michael S Gold · Paul D Thut · Michael J Caterina
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    ABSTRACT: Recent electrophysiological studies of cultured dorsal root and trigeminal ganglion neurons have suggested that multiple ionic mechanisms underlie the peripheral detection of cold temperatures. Several candidate "cold receptors," all of them ion channel proteins, have been implicated in this process. One of the most promising candidates is TRPM8, a nonselective cationic channel expressed in a subpopulation of sensory neurons that is activated both by decreases in temperature and the cooling compound menthol. However, evidence for the expression of TRPM8 in functionally defined cold-sensitive neurons has been lacking. Here, we combine fluorometric calcium imaging of cultured rat trigeminal neurons with single-cell RT-PCR to demonstrate that there are distinct subpopulations of cold responsive neurons and that TRPM8 likely contributes to cold transduction in one of them. TRPM8 is preferentially expressed within a subset of rapidly responsive, low-threshold (approximately 30 degrees C), cold-sensitive neurons. A distinct class of slowly responsive cold-sensitive neurons that is activated at lower temperatures (approximately 20 degrees C) generally lacks detectable TRPM8 mRNA. Together with previous findings, our data support the notion that cold responsive neurons are functionally heterogeneous.
    No preview · Article · Aug 2003 · Journal of Neurophysiology
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    ABSTRACT: We have investigated the intracellular signaling mechanisms underlying the release of nitric oxide (NO) evoked by beta-adrenoceptor (AR) agonists in urinary bladder strips and cultured bladder urothelial cells from adult rats. Reverse transcription-PCR revealed that inducible NO synthase and endothelial NOS but not neuronal NOS genes were expressed in urothelial cells. NO release from both urothelial cells and bladder strips was decreased (37-42%) in the absence of extracellular Ca2+ (100 microm EGTA) and was ablated after incubation with BAPTA-AM (5 microm) or caffeine (10 mm), indicating that the NO production is mediated in part by intracellular calcium stores. NO release was reduced (18-24%) by nifedipine (10 microm) and potentiated (29-32%) by incubation with the Ca2+ channel opener BAYK8644 (1-10 microm). In addition, beta-AR-evoked NO release (isoproterenol; dobutamine; terbutaline; 10(-9) to 10(-5) m) was blocked by the NOS inhibitors N(G)-nitro-L-arginine methyl ester (30 microm) or N(G)-monomethyl-L-arginine (50 microm), by beta-adrenoceptor antagonists (propranol, beta1/beta2; atenolol, beta1; ICI 118551; beta2; 100 microm), or by the calmodulin antagonist trifluoperazine (50 microm). Incubating cells with the nonhydrolyzable GTP analog GTPgammaS (1 microm) or the membrane-permeant cAMP analog dibutyryl-cAMP (10-100 microm) directly evoked NO release. Forskolin (10 microm) or the phosphodiesterase IBMX (50 microm) enhanced (39-42%) agonist-evoked NO release. These results indicate that beta-adrenoceptor stimulation activates the adenylate cyclase pathway in bladder epithelial cells and initiates an increase in intracellular Ca2+ that triggers NO production and release. These findings are considered in light of recent reports that urothelial cells may exhibit a number of "neuron-like" properties, including the expression of receptors/ion channels similar to those found in sensory neurons.
    No preview · Article · Oct 2002 · The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
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    Full-text · Article · Dec 2001 · Proceedings of the National Academy of Sciences
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    Michele L. Nealen · K. Vinod Vijayan · Everlie Bolton · Paul F. Bray
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    ABSTRACT: Platelets play an important role in the coronary thrombus formation that leads to myocardial ischemia and infarction. Gender differences in the development of coronary heart disease and its outcomes are partly regulated by estrogen and its receptors, but the roles of the latter in thrombogenicity are less well-defined. We previously demonstrated the presence of estrogen receptor (ER) beta in cells of the megakaryocytic lineage. In this study, we characterize human platelet ERbeta and its expression using biochemical and molecular biological techniques. Western immunoblotting showed that platelet ERbeta migrated with an apparent molecular mass approximately 3.7 kDa larger than ERbeta in a variety of cell lines (including those of prostate and breast origin). A rigorous investigation of platelet ERbeta mRNA by reverse transcriptase-polymerase chain reaction revealed normal transcripts and a single alternately spliced mRNA. However, this variant form was smaller, lacking exon 2, and could not account for the larger protein size seen in platelets. Treatment of ERbeta with N-glycosidase F, which removes core carbohydrate residues, caused a more rapid migration through polyacrylamide gels but had no effect on ERbeta from human cell lines. We conclude that the larger form of ERbeta in human platelets is not attributable to alternate mRNA splicing but primarily to tissue-specific glycosylation.
    Full-text · Article · Apr 2001 · Circulation Research
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    G Khetawat · N Faraday · M L Nealen · K V Vijayan · E Bolton · S J Noga · P F Bray
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    ABSTRACT: Gender differences in vascular thromboses are well known, and there is evidence that platelets may be involved in these differences and that sex hormones affect platelet function. We characterized the expression of the estrogen receptor alpha (ER alpha), estrogen receptor beta (ER beta), progesterone receptor (PR), and androgen receptor (AR) in the megakaryocyte lineage. Megakaryocytes generated ex vivo from normal human CD34(+) stem cells contained RNA for ER beta and AR, which increased with cell differentiation. Platelets and human erythroleukemia (HEL) cells also contained ER beta and AR transcripts. No ER alpha or PR messenger RNA or protein was detected in the megakaryocyte lineage. Immunofluorescence microscopy showed that ER beta protein was present in glycoprotein (GP) IIb(+) megakaryocytes and the HEL megakaryocytic cell line in a predominantly cytoplasmic location. AR showed a cytoplasmic and nuclear distribution in GPIIb(+) and GPIIb(-) cells derived from CD34(+) cells and in HEL cells. Western immunoblotting confirmed the presence of ER beta and AR in platelets. Megakaryocyte and HEL AR expression was up-regulated by 1, 5, and 10 nmol/L testosterone, but down-regulated by 100 nmol/L testosterone. These findings indicate a regulated ability of megakaryocytes to respond to testosterone and suggest a potential mechanism through which sex hormones may mediate gender differences in platelet function and thrombotic diseases.
    Full-text · Article · May 2000 · Blood
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    Full-text · Conference Paper · Sep 1999

Publication Stats

892 Citations
52.32 Total Impact Points

Institutions

  • 2003-2005
    • Johns Hopkins Medicine
      • Department of Biological Chemistry
      Baltimore, Maryland, United States
  • 2000-2001
    • Johns Hopkins University
      • • Department of Biological Chemistry
      • • Department of Medicine
      Baltimore, Maryland, United States