Connexin expression and conducted vasodilation along arteriolar endothelium in mouse skeletal muscle

Functional hyperemia requires the coordination of smooth muscle cell relaxation along and between branches of the arteriolar network. Vasodilation is conducted from cell to cell along the arteriolar wall through gap junction channels composed of connexin protein subunits. Within skeletal muscle, it is unclear whether arteriolar endothelium, smooth muscle, or both cell layers provide the cellular pathway for conduction. Furthermore, the constitutive profile of connexin expression within the microcirculation is unknown. We tested the hypothesis that conducted vasodilation and connexin expression are intrinsic to the endothelium of arterioles (17 ± 1 μm diameter) that supply the skeletal muscle fibers in the cremaster of anesthetized C57BL/6 mice. ACh delivered to an arteriole (500 ms, 1-μA pulse; 1-μm micropipette) produced local dilation of 17 ± 1 μm; conducted vasodilation observed 1 mm upstream was 9 ± 1 μm ( n = 5). After light-dye treatment to selectively disrupt endothelium (250-μm segment centered 500 μm upstream, confirmed by loss of local response to ACh while constriction to phenylephrine and dilation to sodium nitroprusside remained intact), we found that conducted vasodilation was nearly abolished (2 ± 1 μm; P < 0.05). Whole-mount immunohistochemistry for connexins revealed punctate labeling at borders of arteriolar endothelial cells, with connexin40 and connexin37 in all branches and connexin43 only in the largest branches. Immunoreactivity for connexins was not apparent in smooth muscle or in capillary or venular endothelium, despite robust immunolabeling for α-actin and platelet endothelial cell adhesion molecule-1, respectively. We conclude that vasodilation is conducted along the endothelium of mouse skeletal muscle arterioles and that connexin40 and connexin37 are the primary connexins forming gap junction channels between arteriolar endothelial cells.

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Functional sympatholysis in mouse skeletal muscle involves sarcoplasmic reticulum swelling in arterial smooth muscle cells

Physiological Reports ◽

10.14814/phy2.15133 ◽

2021 ◽

Vol 9 (23) ◽

Author(s):

Jennifer Horst ◽

Sophie Møller ◽

Sasha A. S. Kjeldsen ◽

Jørgen F. P. Wojtaszewski ◽

Ylva Hellsten ◽

...

Keyword(s):

Skeletal Muscle ◽

Smooth Muscle ◽

Sarcoplasmic Reticulum ◽

Smooth Muscle Cells ◽

Muscle Cells ◽

Arterial Smooth Muscle ◽

Mouse Skeletal Muscle ◽

Functional Sympatholysis ◽

Arterial Smooth Muscle Cells

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Expression of alpha 1 integrin, a laminin-collagen receptor, during myogenesis and neurogenesis in the avian embryo

Development ◽

10.1242/dev.116.3.585 ◽

1992 ◽

Vol 116 (3) ◽

pp. 585-600 ◽

Cited By ~ 2

Author(s):

J.L. Duband ◽

A.M. Belkin ◽

J. Syfrig ◽

J.P. Thiery ◽

V.E. Koteliansky

Keyword(s):

Skeletal Muscle ◽

Endothelial Cells ◽

Smooth Muscle ◽

Smooth Muscles ◽

Collagen Iv ◽

Integrin Subunit ◽

Avian Embryo ◽

Subunit Expression ◽

Capillary Endothelial Cells ◽

Collagen Receptor

In this study, we have examined the spatiotemporal distribution of the alpha 1 integrin subunit, a putative laminin and collagen receptor, in avian embryos, using immunofluorescence microscopy and immunoblotting techniques. We used an antibody raised against a gizzard 175 × 10(3) M(r) membrane protein which was described previously and which we found to be immunologically identical to the chicken alpha 1 integrin subunit. In adult avian tissues, alpha 1 integrin exhibited a very restricted pattern of expression; it was detected only in smooth muscle and in capillary endothelial cells. In the developing embryo, alpha 1 integrin subunit expression was discovered in addition to smooth muscle and capillary endothelial cells, transiently, in both central and peripheral nervous systems and in striated muscles, in association with laminin and collagen IV. alpha 1 integrin was practically absent from most epithelial tissues, including the liver, pancreas and kidney tubules, and was weakly expressed by tissues that were not associated with laminin and collagen IV. In the nervous system, alpha 1 integrin subunit expression occurred predominantly at the time of early neuronal differentiation. During skeletal muscle development, alpha 1 integrin was expressed on myogenic precursors, during myoblast migration, and in differentiating myotubes. alpha 1 integrin disappeared from skeletal muscle cells as they became contractile. In visceral and vascular smooth muscles, alpha 1 integrin appeared specifically during early smooth muscle cell differentiation and, later, was permanently expressed after cell maturation. These results indicate that (i) the expression pattern of alpha 1 integrin is consistent with a function as a laminin/collagen IV receptor; (ii) during avian development, expression of the alpha 1 integrin subunit is spatially and temporally regulated; (iii) during myogenesis and neurogenesis, expression of alpha 1 integrin is transient and correlates with cell migration and differentiation.

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Multiple Connexins Form Gap Junction Channels in Rat Basilar Artery Smooth Muscle Cells

Circulation Research ◽

10.1161/01.res.84.11.1277 ◽

1999 ◽

Vol 84 (11) ◽

pp. 1277-1284 ◽

Cited By ~ 41

Author(s):

Xing Li ◽

J. Marc Simard

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Gap Junction ◽

Basilar Artery ◽

Muscle Cells ◽

Gap Junction Channels

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Proteins of interstitial cells of Cajal and intestinal smooth muscle, colocalized with caveolin-1

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00222.2004 ◽

2005 ◽

Vol 288 (3) ◽

pp. G571-G585 ◽

Cited By ~ 35

Author(s):

Woo Jung Cho ◽

E. E. Daniel

Keyword(s):

Skeletal Muscle ◽

Smooth Muscle ◽

Gap Junction ◽

Interstitial Cells Of Cajal ◽

Smooth Muscles ◽

Circular Muscle ◽

Interstitial Cells ◽

Caveolin 1 ◽

Cells Of Cajal ◽

Junction Proteins

The murine jejunum and lower esophageal sphincter (LES) were examined to determine the locations of various signaling molecules and their colocalization with caveolin-1 and one another. Caveolin-1 was present in punctate sites of the plasma membranes (PM) of all smooth muscles and diffusely in all classes of interstitial cells of Cajal (ICC; identified by c-kit immunoreactivity), ICC-myenteric plexus (MP), ICC-deep muscular plexus (DMP), ICC-serosa (ICC-S), and ICC-intramuscularis (IM). In general, all ICC also contained the L-type Ca2+ (L-Ca2+) channel, the PM Ca2+ pump, and the Na+/Ca2+ exchanger-1 localized with caveolin-1. ICC in various sites also contained Ca2+-sequestering molecules such as calreticulin and calsequestrin. Calreticulin was present also in smooth muscle, frequently in the cytosol, whereas calsequestrin was present in skeletal muscle of the esophagus. Gap junction proteins connexin-43 and -40 were present in circular muscle of jejunum but not in longitudinal muscle or in LES. In some cases, these proteins were associated with ICC-DMP. The large-conductance Ca2+-activated K+ channel was present in smooth muscle and skeletal muscle of esophagus and some ICC but was not colocalized with caveolin-1. These findings suggest that all ICC have several Ca2+-handling and -sequestering molecules, although the functions of only the L-Ca2+ channel are currently known. They also suggest that gap junction proteins are located at sites where ultrastructural gap junctions are know to exist in circular muscle of intestine but not in other smooth muscles. These findings also point to the need to evaluate the function of Ca2+ sequestration in ICC.

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Expression of VEGF Receptors on Endothelial Cells in Mouse Skeletal Muscle

PLoS ONE ◽

10.1371/journal.pone.0044791 ◽

2012 ◽

Vol 7 (9) ◽

pp. e44791 ◽

Cited By ~ 38

Author(s):

Princess I. Imoukhuede ◽

Aleksander S. Popel

Keyword(s):

Skeletal Muscle ◽

Endothelial Cells ◽

Vegf Receptors ◽

Mouse Skeletal Muscle

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Sharing signals: connecting lung epithelial cells with gap junction channels

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00078.2002 ◽

2002 ◽

Vol 283 (5) ◽

pp. L875-L893 ◽

Cited By ~ 36

Author(s):

Michael Koval

Keyword(s):

Epithelial Cells ◽

Gap Junctions ◽

Gap Junction ◽

Alveolar Epithelial Cells ◽

Lung Epithelial Cells ◽

Cell Phenotype ◽

Connexin Expression ◽

Gap Junction Channels ◽

Alveolar Epithelial ◽

Junctional Communication

Gap junction channels enable the direct flow of signaling molecules and metabolites between cells. Alveolar epithelial cells show great variability in the expression of gap junction proteins (connexins) as a function of cell phenotype and cell state. Differential connexin expression and control by alveolar epithelial cells have the potential to enable these cells to regulate the extent of intercellular coupling in response to cell stress and to regulate surfactant secretion. However, defining the precise signals transmitted through gap junction channels and the cross talk between gap junctions and other signaling pathways has proven difficult. Insights from what is known about roles for gap junctions in other systems in the context of the connexin expression pattern by lung cells can be used to predict potential roles for gap junctional communication between alveolar epithelial cells.

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Gap Junction Localization and Connexin Expression in Cytochemically Identified Endothelial Cells of Arterial Tissue

Journal of Histochemistry & Cytochemistry ◽

10.1177/002215549704500406 ◽

1997 ◽

Vol 45 (4) ◽

pp. 539-550 ◽

Cited By ~ 74

Author(s):

Hung-I Yeh ◽

Emmanuel Dupont ◽

Steven Coppen ◽

Stephen Rothery ◽

Nicholas J. Severs

Keyword(s):

Endothelial Cells ◽

Coronary Artery ◽

Gap Junctions ◽

Gap Junction ◽

Vascular Endothelial Cells ◽

Rat Aorta ◽

Arterial System ◽

Connexin Expression ◽

Arterial Tissue ◽

Surrounding Areas

Vascular endothelial cells interact with one another via gap junctions, but information on the precise connexin make-up of endothelial gap junctions in intact arterial tissue is limited. One factor contributing to this lack of information is that standard immunocytochemical methodologies applied to arterial sections do not readily permit unequivocal localization of connexin immunolabeling to endothelium. Here we introduce a method for multiple labeling with specific endothelial cell markers and one or more connexin-specific antibodies which overcomes this limitation. Applying this method to localize connexins 43, 40, and 37 by confocal microscopy, we show that the three connexin types have quite distinctive labeling patterns in different vessels. Whereas endothelial cells of rat aorta and coronary artery characteristically show extensive, prominent connexin40, and heterogeneous scattered connexin37, the former, unlike the latter, also has abundant connexin43. The relative lack of connexin43 in coronary artery endothelium was confirmed in both rat and human using three alternative antibodies. In the aorta, connexins43 and 40 commonly co-localize to the same junctional plaque. Even within a given type of endothelium, zonal variation in connexin expression was apparent. In rat endocardium, a zone just below the mitral valve region is marked by expression of greater quantities of connexin43 than surrounding areas. These results are consistent with the idea that differential expression of connexins may contribute to modulation of endothelial gap junction function in different segments and subzones of the arterial system.

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Remodeling of Cardiac Gap Junctional Cell–Cell Coupling

Cells ◽

10.3390/cells10092422 ◽

2021 ◽

Vol 10 (9) ◽

pp. 2422

Author(s):

Stefan Dhein ◽

Aida Salameh

Keyword(s):

Gap Junctions ◽

Gap Junction ◽

Conduction System ◽

Cell Coupling ◽

Connexin Expression ◽

Gap Junction Channels ◽

Developmental States ◽

Gap Junction Channel ◽

Arrhythmogenic Substrate ◽

Cell Cell

The heart works as a functional syncytium, which is realized via cell-cell coupling maintained by gap junction channels. These channels connect two adjacent cells, so that action potentials can be transferred. Each cell contributes a hexameric hemichannel (=connexon), formed by protein subuntis named connexins. These hemichannels dock to each other and form the gap junction channel. This channel works as a low ohmic resistor also allowing the passage of small molecules up to 1000 Dalton. Connexins are a protein family comprising of 21 isoforms in humans. In the heart, the main isoforms are Cx43 (the 43 kDa connexin; ubiquitous), Cx40 (mostly in atrium and specific conduction system), and Cx45 (in early developmental states, in the conduction system, and between fibroblasts and cardiomyocytes). These gap junction channels are mainly located at the polar region of the cardiomyocytes and thus contribute to the anisotropic pattern of cardiac electrical conductivity. While in the beginning the cell–cell coupling was considered to be static, similar to an anatomically defined structure, we have learned in the past decades that gap junctions are also subject to cardiac remodeling processes in cardiac disease such as atrial fibrillation, myocardial infarction, or cardiomyopathy. The underlying remodeling processes include the modulation of connexin expression by e.g., angiotensin, endothelin, or catecholamines, as well as the modulation of the localization of the gap junctions e.g., by the direction and strength of local mechanical forces. A reduction in connexin expression can result in a reduced conduction velocity. The alteration of gap junction localization has been shown to result in altered pathways of conduction and altered anisotropy. In particular, it can produce or contribute to non-uniformity of anisotropy, and thereby can pre-form an arrhythmogenic substrate. Interestingly, these remodeling processes seem to be susceptible to certain pharmacological treatment.

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