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  1. Article ; Online: β3 Receptor Signaling in Pregnant Human Myometrium Suggests a Role for β3 Agonists as Tocolytics.

    Buxton, Iain L O / Asif, Hazik / Barnett, Scott D

    Biomolecules

    2023  Volume 13, Issue 6

    Abstract: Preterm labor leading to preterm birth is the leading cause of infant morbidity and mortality. At the present time, nothing can reliably halt labor once it begins. The knowledge that agonists of the β2 adrenergic receptor relax airway smooth muscle and ... ...

    Abstract Preterm labor leading to preterm birth is the leading cause of infant morbidity and mortality. At the present time, nothing can reliably halt labor once it begins. The knowledge that agonists of the β2 adrenergic receptor relax airway smooth muscle and are effective in the treatment of asthma led to the notion that β2 mimetics would prevent preterm birth by relaxing uterine smooth muscle. The activation of cAMP-dependent protein kinase by β2 receptors is unable to provide meaningful tocolysis. The failure of β2 agonists such as ritodrine and terbutaline to prevent preterm birth suggests that the regulation of uterine smooth muscle is disparate from that of airway. Other smooth muscle quiescent-mediating molecules, such as nitric oxide, relax vascular smooth muscle in a cGMP-protein kinase G-dependent manner; however, nitric oxide activation of protein kinase G fails to explain the relaxation of the myometrium to nitric oxide. Moreover, nitric oxide-mediated relaxation is blunted in preterm labor, and thus, for this reason and because of the fall in maternal blood pressure, nitric oxide cannot be employed as a tocolytic. The β3 adrenergic receptor-mediated relaxation of the human myometrium is claimed to be cAMP-dependent protein kinase-dependent. This is scientifically displeasing given the failure of β2 agonists as tocolytics and suggests a non-canonical signaling role for β3AR in myometrium. The addition of the β3 agonist mirabegron to pregnant human myometrial strips in the tissue bath relaxes oxytocin-induced contractions. Mirabegron stimulates nitric oxide production in myometrial microvascular endothelial cells, and the relaxation of uterine tissue in vitro is partially blocked by the addition of the endothelial nitric oxide synthase blocker Nω-Nitro-L-arginine. Recent data suggest that both endothelial and smooth muscle cells respond to β3 stimulation and contribute to relaxation through disparate signaling pathways. The repurposing of approved medications such as mirabegron (Mybetriq™) tested in human myometrium as uterine tocolytics can advance the prevention of preterm birth.
    MeSH term(s) Infant, Newborn ; Pregnancy ; Female ; Humans ; Myometrium/metabolism ; Tocolytic Agents/pharmacology ; Tocolytic Agents/metabolism ; Tocolytic Agents/therapeutic use ; Premature Birth/prevention & control ; Nitric Oxide/metabolism ; Endothelial Cells/metabolism ; Obstetric Labor, Premature/drug therapy ; Obstetric Labor, Premature/prevention & control ; Obstetric Labor, Premature/metabolism ; Cyclic AMP-Dependent Protein Kinases/metabolism ; Receptors, Adrenergic/metabolism
    Chemical Substances Tocolytic Agents ; mirabegron (MVR3JL3B2V) ; Nitric Oxide (31C4KY9ESH) ; Cyclic AMP-Dependent Protein Kinases (EC 2.7.11.11) ; Receptors, Adrenergic
    Language English
    Publishing date 2023-06-17
    Publishing country Switzerland
    Document type Journal Article ; Review ; Research Support, N.I.H., Extramural
    ZDB-ID 2701262-1
    ISSN 2218-273X ; 2218-273X
    ISSN (online) 2218-273X
    ISSN 2218-273X
    DOI 10.3390/biom13061005
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Novel identification and modulation of the mechanosensitive Piezo1 channel in human myometrium.

    Barnett, Scott D / Asif, Hazik / Buxton, Iain L O

    The Journal of physiology

    2022  Volume 601, Issue 9, Page(s) 1675–1690

    Abstract: Approximately 10% of US births deliver preterm before 37 weeks of completed gestation. Premature infants are at risk for life-long debilitating morbidities and death, and spontaneous preterm labour explains 50% of preterm births. In all cases existing ... ...

    Abstract Approximately 10% of US births deliver preterm before 37 weeks of completed gestation. Premature infants are at risk for life-long debilitating morbidities and death, and spontaneous preterm labour explains 50% of preterm births. In all cases existing treatments are ineffective, and none are FDA approved. The mechanisms that initiate preterm labour are not well understood but may result from dysfunctional regulation of quiescence mechanisms. Human pregnancy is accompanied by large increases in blood flow, and the uterus must enlarge by orders of magnitude to accommodate the growing fetus. This mechanical strain suggests that stretch-activated channels may constitute a mechanism to explain gestational quiescence. Here we identify for the first time that Piezo1, a mechanosensitive cation channel, is present in the uterine smooth muscle and microvascular endothelium of pregnant myometrium. Piezo is downregulated during preterm labour, and stimulation of myometrial Piezo1 in an organ bath with the agonist Yoda1 relaxes the tissue in a dose-dependent fashion. Further, stimulation of Piezo1 while inhibiting protein kinase A, AKT, or endothelial nitric oxide synthase mutes the negative inotropic effects of Piezo1 activation, intimating that actions on the myocyte and endothelial nitric oxide signalling contribute to Piezo1-mediated contractile dynamics. Taken together, these data highlight the importance of stretch-activated channels in pregnancy maintenance and parturition, and identify Piezo1 as a tocolytic target of interest. KEY POINTS: Spontaneous preterm labour is a serious obstetric dilemma without a known cause or effective treatments. Piezo1 is a stretch-activated channel important to muscle contractile dynamics. Piezo1 is present in the myometrium and is dysregulated in women who experience preterm labour. Activation of Piezo1 by the agonist Yoda1 relaxes the myometrium in a dose-dependent fashion, indicating that Piezo1 modulation may have therapeutic benefits to treat preterm labour.
    MeSH term(s) Pregnancy ; Infant, Newborn ; Humans ; Female ; Myometrium/physiology ; Obstetric Labor, Premature/metabolism ; Uterus ; Muscle, Smooth/metabolism ; Premature Birth ; Ion Channels/metabolism
    Chemical Substances PIEZO1 protein, human ; Ion Channels
    Language English
    Publishing date 2022-08-08
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 3115-x
    ISSN 1469-7793 ; 0022-3751
    ISSN (online) 1469-7793
    ISSN 0022-3751
    DOI 10.1113/JP283299
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Title: β3 Adrenergic Receptor Signaling in the Human Myometrium.

    Asif, Hazik / Barnett, Scott D / Buxton, Iain L O

    Reproductive sciences (Thousand Oaks, Calif.)

    2022  Volume 30, Issue 1, Page(s) 124–134

    Abstract: Preterm labor leading to preterm birth is the leading cause of infant morbidity and mortality. Although β2 adrenergic agonists fail to provide adequate tocolysis, the expression of the β3 adrenergic receptor in myometrium and its unique signaling suggest ...

    Abstract Preterm labor leading to preterm birth is the leading cause of infant morbidity and mortality. Although β2 adrenergic agonists fail to provide adequate tocolysis, the expression of the β3 adrenergic receptor in myometrium and its unique signaling suggest a role for β3 agonist in the management of preterm labor. Western blot analysis showed that the β3 adrenergic receptor expression increased in human pregnancy myometrium compared to nonpregnant tissues (p < 0.0001). There was no difference in β3 adrenergic receptor expression throughout pregnancy (p > 0.05). The addition of the β3 agonist mirabegron in the tissue bath relaxed oxytocin contracted myometrium with an EC
    MeSH term(s) Infant, Newborn ; Pregnancy ; Female ; Humans ; Myometrium/metabolism ; Premature Birth/metabolism ; Nitric Oxide/metabolism ; Endothelial Cells/metabolism ; Tocolytic Agents/pharmacology ; Obstetric Labor, Premature/metabolism ; Arginine/metabolism ; Receptors, Adrenergic/metabolism
    Chemical Substances mirabegron (MVR3JL3B2V) ; Nitric Oxide (31C4KY9ESH) ; Tocolytic Agents ; Arginine (94ZLA3W45F) ; Receptors, Adrenergic
    Language English
    Publishing date 2022-04-04
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 2276411-2
    ISSN 1933-7205 ; 1933-7191
    ISSN (online) 1933-7205
    ISSN 1933-7191
    DOI 10.1007/s43032-022-00917-y
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: β3 adrenergic receptor activation modulates connexin 43 activity to relax human myometrium.

    Asif, Hazik / Barnett, Scott D / Saxon, Dylan / Younis, Hazar / Buxton, Iain L O

    Cellular signalling

    2023  Volume 106, Page(s) 110640

    Abstract: Preterm labor, delivery prior to 37 completed weeks of gestation, is the leading cause of infant morbidity and mortality. β3 adrenergic receptor protein expression is increased in the myometrium during pregnancy, and the agonist, mirabegron, relaxes the ... ...

    Abstract Preterm labor, delivery prior to 37 completed weeks of gestation, is the leading cause of infant morbidity and mortality. β3 adrenergic receptor protein expression is increased in the myometrium during pregnancy, and the agonist, mirabegron, relaxes the myometrium making the β3 adrenergic receptor a potential therapeutic target in PTL. β3 adrenergic receptor has been shown to activate the tyrosine kinase, Src, which can down regulate connexin 43, a contractile associated protein which promotes the formation of gap junctions that create an electrical syncytium. We hypothesize that mirabegron downregulates connexin 43, imparting quiescence effects on the myometrium. Employing contractile studies, we demonstrate that Src is involved in the mirabegron-induced relaxation of contracting pregnant human myometrial tissue strips. Western blot analysis demonstrates that Src kinase expression is decreased in both preterm and term laboring myometrial tissue. Imaging revealed that mirabegron stimulation of the β3 adrenergic receptor phosphorylates tyrosine at position Y265 on connexin 43 in pregnant human uterine myocytes. Western blot analysis and immunofluorescent imaging indicate that mirabegron decreases the expression of connexin 43 and mediates relaxation over a 24-h exposure period, suggesting that mirabegron has long lasting quiescent effects on the human myometrium. The relationship between the β3 adrenergic receptor and down regulation of the contractile associated protein connexin 43 through activation of Src kinase suggests that mirabegron may be useful in combination tocolysis.
    MeSH term(s) Pregnancy ; Female ; Infant, Newborn ; Humans ; Myometrium/metabolism ; Connexin 43/metabolism ; src-Family Kinases/metabolism ; Receptors, Adrenergic/metabolism
    Chemical Substances mirabegron (MVR3JL3B2V) ; Connexin 43 ; src-Family Kinases (EC 2.7.10.2) ; Receptors, Adrenergic
    Language English
    Publishing date 2023-02-24
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 1002702-6
    ISSN 1873-3913 ; 0898-6568
    ISSN (online) 1873-3913
    ISSN 0898-6568
    DOI 10.1016/j.cellsig.2023.110640
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Novel Tocolytic Strategy: Modulating Cx43 Activity by

    Barnett, Scott D / Asif, Hazik / Anderson, Mitchell / Buxton, Iain L O

    The Journal of pharmacology and experimental therapeutics

    2020  Volume 376, Issue 3, Page(s) 444–453

    Abstract: Currently available tocolytics are ineffective at significantly delaying preterm birth. This is due in part to our failure to better understand the mechanisms that drive spontaneous preterm labor (sPTL). Cyclic nucleotides are not the primary ... ...

    Abstract Currently available tocolytics are ineffective at significantly delaying preterm birth. This is due in part to our failure to better understand the mechanisms that drive spontaneous preterm labor (sPTL). Cyclic nucleotides are not the primary contributors to myometrial quiescence, but instead nitric oxide (NO)-mediated protein
    MeSH term(s) Animals ; Connexin 43/metabolism ; Drug Discovery ; Drug Interactions ; Enzyme Inhibitors/pharmacology ; Female ; Gap Junctions/drug effects ; Guinea Pigs ; HEK293 Cells ; Humans ; Nitric Oxide/pharmacology ; Nitric Oxide Synthase/antagonists & inhibitors ; Nitrosation/drug effects ; Pregnancy ; Tocolytic Agents/pharmacology
    Chemical Substances Connexin 43 ; Enzyme Inhibitors ; Tocolytic Agents ; Nitric Oxide (31C4KY9ESH) ; Nitric Oxide Synthase (EC 1.14.13.39)
    Language English
    Publishing date 2020-12-31
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 3106-9
    ISSN 1521-0103 ; 0022-3565
    ISSN (online) 1521-0103
    ISSN 0022-3565
    DOI 10.1124/jpet.120.000427
    Database MEDical Literature Analysis and Retrieval System OnLINE

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