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Abstract
Thirty years ago, Robert F. Furchgott concluded that nitric oxide, a compound traditionally known to be a toxic component of fuel exhaust, is in fact released from the endothelium, and in a paracrine fashion, induces relaxation of underlying vascular smooth muscle resulting in vasodilation. This discovery has helped pave the way for a more thorough understanding of vascular intercellular and intracellular communication that supports the process of regulating regional perfusion to match the local tissue oxygen demand. Vasoregulation is controlled not only by endothelial release of a diverse class of vasoactive compounds such as nitric oxide, arachidonic acid metabolites, and reactive oxygen species, but also by physical forces on the vascular wall and through electrotonic conduction through gap junctions. Although the endothelium is a critical source of vasoactive compounds, paracrine mediators can also be released from surrounding parenchyma such as perivascular fat, myocardium, and cells in the arterial adventitia to exert either local or remote vasomotor effects. The focus of this review will highlight the various means by which intercellular communication contributes to mechanisms of vasodilation. Paracrine signaling and parenchymal influences will be reviewed as well as regional vessel communication through gap junctions, connexons, and myoendothelial feedback. More recent modes of communication such as vesicular and microRNA signaling will also be discussed.
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Sancho M, Samson NC, Hald BO, Hashad AM, Marrelli SP, Brett SE, Welsh DG. K IR channels tune electrical communication in cerebral arteries. J Cereb Blood Flow Metab 2017; 37:2171-2184. [PMID: 27466375 PMCID: PMC5464710 DOI: 10.1177/0271678x16662041] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The conducted vasomotor response reflects electrical communication in the arterial wall and the distance signals spread is regulated by three factors including resident ion channels. This study defined the role of inward-rectifying K+ channels (KIR) in governing electrical communication along hamster cerebral arteries. Focal KCl application induced a vasoconstriction that conducted robustly, indicative of electrical communication among cells. Inhibiting dominant K+ conductances had no attenuating effect, the exception being Ba2+ blockade of KIR. Electrophysiology and Q-PCR analysis of smooth muscle cells revealed a Ba2+-sensitive KIR current comprised of KIR2.1/2.2 subunits. This current was surprisingly small and when incorporated into a model, failed to account for the observed changes in conduction. We theorized a second population of KIR channels exist and consistent with this idea, a robust Ba2+-sensitive KIR2.1/2.2 current was observed in endothelial cells. When both KIR currents were incorporated into, and then inhibited in our model, conduction decay was substantive, aligning with experiments. Enhanced decay was ascribed to the rightward shift in membrane potential and the increased feedback arising from voltage-dependent-K+ channels. In summary, this study shows that two KIR populations work collaboratively to govern electrical communication and the spread of vasomotor responses along cerebral arteries.
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Affiliation(s)
- Maria Sancho
- 1 Department of Physiology and Pharmacology, University of Western Ontario, London, Canada.,2 Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Libin Cardiovascular Institute, University of Calgary, Calgary, Canada
| | - Nina C Samson
- 2 Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Libin Cardiovascular Institute, University of Calgary, Calgary, Canada
| | - Bjorn O Hald
- 3 Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ahmed M Hashad
- 2 Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Libin Cardiovascular Institute, University of Calgary, Calgary, Canada
| | - Sean P Marrelli
- 4 Department of Anesthesiology, Baylor College of Medicine, Houston, USA
| | - Suzanne E Brett
- 1 Department of Physiology and Pharmacology, University of Western Ontario, London, Canada.,2 Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Libin Cardiovascular Institute, University of Calgary, Calgary, Canada
| | - Donald G Welsh
- 1 Department of Physiology and Pharmacology, University of Western Ontario, London, Canada.,2 Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Libin Cardiovascular Institute, University of Calgary, Calgary, Canada
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Rai A, Cross JC. Development of the hemochorial maternal vascular spaces in the placenta through endothelial and vasculogenic mimicry. Dev Biol 2014; 387:131-41. [PMID: 24485853 DOI: 10.1016/j.ydbio.2014.01.015] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 01/14/2014] [Accepted: 01/19/2014] [Indexed: 11/27/2022]
Abstract
The maternal vasculature within the placenta in primates and rodents is unique because it is lined by fetal cells of the trophoblast lineage and not by maternal endothelial cells. In addition to trophoblast cells that invade the uterine spiral arteries that bring blood into the placenta, other trophoblast subtypes sit at different levels of the vascular space. In mice, at least five distinct subtypes of trophoblast cells have been identified which engage maternal endothelial cells on the arterial and venous frontiers of the placenta, but which also form the channel-like spaces within it through a process analogous to formation of blood vessels (vasculogenic mimicry). These cells are all large, post-mitotic trophoblast giant cells. In addition to assuming endothelial cell-like characteristics (endothelial mimicry), they produce dozens of different hormones that are thought to regulate local and systemic maternal adaptations to pregnancy. Recent work has identified distinct molecular pathways in mice that regulate the morphogenesis of trophoblast cells on the arterial and venous sides of the vascular circuit that may be analogous to specification of arterial and venous endothelial cells.
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Affiliation(s)
- Anshita Rai
- Department of Biochemistry and Molecular Biology, University of Calgary, HSC Room 2279, 3330 Hospital Drive NW, Calgary, Alta., Canada; Department of Comparative Biology and Experimental Medicine, Obstetrics and Gynecology, and Medical Genetics, University of Calgary, HSC Room 2279, 3330 Hospital Drive NW, Calgary, Alta., Canada T2N 4N1
| | - James C Cross
- Department of Biochemistry and Molecular Biology, University of Calgary, HSC Room 2279, 3330 Hospital Drive NW, Calgary, Alta., Canada; Department of Comparative Biology and Experimental Medicine, Obstetrics and Gynecology, and Medical Genetics, University of Calgary, HSC Room 2279, 3330 Hospital Drive NW, Calgary, Alta., Canada T2N 4N1.
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