Characterization of gap junction channels in A7r5 vascular smooth muscle cells

1991 ◽  
Vol 260 (5) ◽  
pp. C975-C981 ◽  
Author(s):  
L. K. Moore ◽  
E. C. Beyer ◽  
J. M. Burt
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Gap Junctions ◽  
Gap Junction ◽  
Second Messengers ◽  
Protein Composition ◽  
Cell Coupling ◽  
Cyclic Monophosphate ◽  
A7r5 Cells ◽  
Immunohistochemical Studies

Recent evidence suggest that coordination of blood flow in the microcirculation involves cell-to-cell coupling via gap junctions. In this study, using A7r5 cells as a model of vascular smooth muscle, we have characterized the gap junctions in terms of the unitary conductances of the observed channels, the responses to second messengers, and subunit protein composition. The cells were typically well coupled several hours after plating, with junctional conductances on the order 20-40 nS. Channels with mean conductances of 36 and 89 pS were observed in low-conductance cell pairs and in cell pairs whose macroscopic conductance was reduced by exposure to halothane. Connexin43 was the only known gap junction sequence detected by Northern blots (low and high stringency), immunoblots, or immunohistochemical studies. Junctional conductance was reduced 15% by 8-bromoadenosine 3',5'-cyclic monophosphate; 8-bromoguanosine 3',5'-cyclic monophosphate had no effect. The results suggest that connexin43 can form stable channels of at least two distinct conductances and gap junctions with differing responses to second messengers.

Gap junction permeability is diminished in proliferating vascular smooth muscle cells

1998 ◽  
Vol 275 (6) ◽  
pp. C1674-C1682 ◽  
Author(s):  
David T. Kurjiaka ◽  
Timothy D. Steele ◽  
Mary V. Olsen ◽  
Janis M. Burt
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Gap Junction ◽  
Vascular Smooth Muscle Cells ◽  
Electrical Coupling ◽  
Proliferating Cells ◽  
Tetraethylammonium Chloride ◽  
A7r5 Cells ◽  
Anions And Cations

In atherosclerosis and hypertension, vascular smooth muscle cells (SMCs) are stimulated to proliferate and exhibit enhanced gap junction protein expression. Our goal was to determine whether gap junction function differs in proliferating vs. growth-arrested SMCs. A7r5 cells (embryonic rat aortic SMCs) did not proliferate in media with reduced serum (∼90% of cells in G0/G1phase after 48–96 h in 1% fetal bovine serum). Dye coupling was less but electrical coupling was comparable in proliferating vs. growth-arrested A7r5 cells, suggesting differences in junctional permselectivity. In growth-arrested cells, junctional conductances measured with potassium glutamate, tetraethylammonium chloride, and KCl were well predicted by the conductivities of these solutions. In contrast, junctional conductances measured with potassium glutamate and tetraethylammonium chloride in proliferating cells were significantly greater than predicted by the conductivities of these solutions. These results suggest that junctions between growth-arrested cells are permeated equally well and simultaneously by anions and cations, whereas junctions between proliferating cells are poorly permeated by large molecules of either charge and equally well but not simultaneously by small anions and cations. The data indicate that A7r5 cells regulate chemical coupling independent of electrical coupling, a capacity that could facilitate growth control while protecting vasomotor responsiveness of vessels.

scholarly journals Effects of Hyperglycemia on Vascular Smooth Muscle Ca2+Signaling

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Nahed El-Najjar ◽  
Rashmi P. Kulkarni ◽  
Nancy Nader ◽  
Rawad Hodeify ◽  
Khaled Machaca
Keyword(s):  
Insulin Resistance ◽  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Vascular Smooth Muscle ◽  
Complex Disease ◽  
Prolonged Exposure ◽  
In Vitro System ◽  
A7r5 Cells

Diabetes is a complex disease that is characterized with hyperglycemia, dyslipidemia, and insulin resistance. These pathologies are associated with significant cardiovascular implications that affect both the macro- and microvasculature. It is therefore important to understand the effects of various pathologies associated with diabetes on the vasculature. Here we directly test the effects of hyperglycemia on vascular smooth muscle (VSM) Ca2+signaling in an isolated in vitro system using the A7r5 rat aortic cell line as a model. We find that prolonged exposure of A7r5 cells to hyperglycemia (weeks) is associated with changes to Ca2+signaling, including most prominently an inhibition of the passive ER Ca2+leak and the sarcoplasmic reticulum Ca2+-ATPase (SERCA). To translate these findings to the in vivo condition, we used primary VSM cells from normal and diabetic subjects and find that only the inhibition of the ER Ca2+leaks replicates in cells from diabetic donors. These results show that prolonged hyperglycemia in isolation alters the Ca2+signaling machinery in VSM cells. However, these alterations are not readily translatable to the whole organism situation where alterations to the Ca2+signaling machinery are different.

scholarly journals Intercellular calcium signalling between chondrocytes and synovial cells in co-culture

1998 ◽  
Vol 329 (3) ◽  
pp. 681-687 ◽  
Author(s):  
Paola D'ANDREA ◽  
Alessandra CALABRESE ◽  
Micaela GRANDOLFO
Keyword(s):  
Gap Junctions ◽  
Intercellular Communication ◽  
Structural Changes ◽  
Articular Chondrocytes ◽  
Cell Metabolism ◽  
Second Messengers ◽  
Calcium Signalling ◽  
Cell Types ◽  
Synovial Cells ◽  
Cell Coupling

Intercellular communication allows the co-ordination of cell metabolism between tissues as well as sensitivity to extracellular stimuli. Paracrine stimulation and cell-to-cell coupling through gap junctions induce the formation of complex cellular networks that favour the intercellular exchange of nutrients and second messengers. Heterologous intercellular communication was studied in co-cultures of articular chondrocytes and HIG-82 synovial cells by measuring mechanically induced cytosolic changes in Ca2+ ion levels by digital fluorescence video imaging. In confluent co-cultures, mechanical stimulation induced intercellular Ca2+ waves that propagated to both cell types with similar kinetics. Intercellular wave spreading was inhibited by 18α-glycyrrhetinic acid and by treatments inhibiting the activation of purinoreceptors, suggesting that intercellular signalling between these two cell types occurs both through gap junctions and ATP-mediated paracrine stimulation. In rheumatoid arthritis the formation of the synovial pannus induces structural changes at the chondrosynovial junction, where chondrocyte and synovial cells come into close apposition: these results provide the first evidence for direct intercellular communication between these two cell types.

Are gap junctions necessary for cell-to-cell coupling of smooth muscle?: an update

1992 ◽  
Vol 70 (4) ◽  
pp. 481-490 ◽  
Author(s):  
R. E. Garfield ◽  
G. Thilander ◽  
M. G. Blennerhassett ◽  
N. Sakai
Keyword(s):  
Smooth Muscle ◽  
Gap Junctions ◽  
Current Knowledge ◽  
Smooth Muscles ◽  
Cell Communication ◽  
Circular Muscle ◽  
Cell Coupling ◽  
And Function ◽  
Longitudinal Layer ◽  
Cell Cell

Earlier, it was questioned whether gap junctions (GJs) were necessary for cell–cell communication in smooth muscle, and GJs were not seen in some smooth muscles. We reexamined this question in the myometrium and in intestinal smooth muscle, in light of current knowledge of the presence and function of GJs. In the uterus, numerous studies show that an increase in GJ number is associated with the onset of delivery and is required for effective parturition. In all cases, this increase in GJ number and the changes in uterine contractility were correlated with increased electrical and metabolic coupling. Evidence for the much smaller, but detectable, degree of electrical coupling in the preterm uterus is explained by the small (but again detectable) number of GJs present. In the intestine, GJs are readily detected in the circular muscle layer but have not been described in the adjacent longitudinal layer. While our immunohistochemical studies failed to detect GJs in the longitudinal layer, this may not be adequate to prove their absence. Therefore, current knowledge of GJ number and function is adequate to explain cell–cell coupling in the uterus. Although it remains uncertain whether GJs are absent from the longitudinal muscle of the intestine, there is no definitive evidence that cell–cell coupling can occur by means other than GJs.Key words: gap junctions, myometrium, connexins, smooth muscle, cell communication.

Regulation of calcium channel current in A7r5 vascular smooth muscle cells by cyclic nucleotides

1994 ◽  
Vol 266 (6) ◽  
pp. C1656-C1663 ◽  
Author(s):  
J. N. Lorenz ◽  
D. R. Bielefeld ◽  
N. Sperelakis
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase ◽  
Vascular Smooth Muscle ◽  
Calcium Channel ◽  
Reversal Potential ◽  
Outward Current ◽  
Water Soluble ◽  
Control Group ◽  
Cyclic Monophosphate ◽  
Time Control

In vascular smooth muscle (VSM) cells, the slow inward calcium current (ICa) may be regulated by phosphorylation of the calcium channel protein or of associated regulatory proteins. We investigated the role of several protein kinase systems in the regulation of ICa in cultured A7r5 cells, a clonal cell line derived from rat aorta. The perforated-patch voltage-clamp technique was used to record whole cell ICa. To isolate the ICa, the pipette contained high Cs+ and the bath contained 140 mM tetraethylammonium to block potassium currents. Ba2+ was used as the charge carrier. In control experiments, ICa was stable for at least 15 min. Compared with 23 +/- 3% in the time-control group (i.e., run-down; n = 10), 3 mM 8-bromo-adenosine 3',5'-cyclic monophosphate (8-BrcAMP) inhibited peak ICa by 53 +/- 3% (n = 9) within 15 min. Similarly, 3 mM 8-bromo-guanosine 3',5'-cyclic monophosphate (8-BrcGMP) inhibited ICa by 59 +/- 4 (n = 11). Application of 30 microM forskolin inhibited ICa by 58 +/- 9% (n = 6) within 5 min (compared with 4 +/- 3% for the 5-min time control). Forskolin also shifted the reversal potential to the left, suggesting a stimulation of an outward current. In the presence of the protein kinase inhibitor, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, the same dose of forskolin had no effect (n = 7). The water-soluble analogue of forskolin (L-858051, 30 microM) decreased ICa by 72 +/- 11% (n = 9) and reduced the outward current component.(ABSTRACT TRUNCATED AT 250 WORDS)

Seaweed Porphyra yezoensis polysaccharides with different molecular weights inhibit hydroxyapatite damage and osteoblast differentiation of A7R5 cells

2020 ◽  
Vol 11 (4) ◽  
pp. 3393-3409
Author(s):  
Ling-Hong Huang ◽  
Hong Liu ◽  
Jia-Yun Chen ◽  
Xin-Yuan Sun ◽  
Zhi-hui Yao ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Osteoblast Differentiation ◽  
Cell Damage ◽  
Porphyra Yezoensis ◽  
Molecular Weights ◽  
A7r5 Cells ◽  
Hydroxyapatite Crystals

Porphyra yezoensis polysaccharide could effectively reduce the cell damage and osteogenic transformation of vascular smooth muscle cells induced by hydroxyapatite crystals.

Interactions between nitroglycerin and endothelium in vascular smooth muscle relaxation

1991 ◽  
Vol 260 (3) ◽  
pp. H698-H701 ◽  
Author(s):  
J. L. Dinerman ◽  
D. L. Lawson ◽  
J. L. Mehta
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Muscle Relaxation ◽  
Smooth Muscle Relaxation ◽  
No Production ◽  
Cyclic Monophosphate ◽  
The Mean ◽  
Smooth Muscle Relaxant ◽  
Vascular Smooth Muscle Relaxation

To evaluate the role of endothelium in nitroglycerin (NTG)-mediated vascular relaxation, epinephrine-contracted rat thoracic aortic segments with and without intact endothelium were exposed to NTG (10(-10) to 10(-5) M). Aortic segments with intact (endo+, n = 15) and denuded endothelium (endo-, n = 9) exhibited typical NTG-induced relaxation. However, the mean effective concentration of NTG was lower for endo- than for endo+ segments (P less than 0.001). To determine if this phenomenon related to nitric oxide (NO) generation by endothelium, six endo+ segments were treated with NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO production. These endo+ segments exhibited greater (P less than 0.001) relaxation in response to NTG than the untreated endo+ segments. Oxyhemoglobin, an inhibitor of guanylate cyclase activation, greatly diminished NTG-mediated relaxation of all aortic segments. To determine if the enhanced NTG-mediated relaxation of endo- segments was unique to the guanosine 3',5'-cyclic monophosphate-dependent vasodilator NTG, other endo+ and endo- segments were exposed to adenosine 3',5'-cyclic monophosphate-dependent vasodilator papaverine (10(-8) to 10(-4) M), and no difference in EC50 was noted between endo+ and endo- segments. Thus endothelium attenuates NTG-mediated vasorelaxation, and this attenuation is abolished by inhibition of endothelial NO production with L-NMMA. These observations indicate that endothelium is a dynamic modulator of vascular smooth muscle relaxant effects of NTG. This modulation appears to result from a competitive interaction between endothelial NO and NTG.

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