Bol, Mélissa

De Bock, Marijke

De Vuyst, Elke

Decaluwé, Kelly

Decrock, Elke

Leybaert, Luc

Monsalvo Casta, Jhon Jairo

Van de Voorde, Johan

Vanheel, Bert

Wang, Nan

English

Ghent University Academic Bibliography

HEMICHANNEL INVOLVEMENT IN CA2+ DYNAMICS AND CONTRACTILITY OF SMOOTH MUSCLE CELLS IN ACUTELY ISOLATED SMALL MESENTERIC ARTERIES  Bol1 M., De Bock1 M., De Vuyst1 E., Wang1 N., Decrock1 E., Monsalvo1 J., Decaluwe2 K., Vanheel1 B., Van de Voorde2 J., Leybaert1 L. Intracellular Ca2+ mediates a variety of vascular endothelial and smooth muscle cell functions. Smooth muscle cells (SMC) respond to biological activators with oscillatory and propagating rises in [Ca2+]i that are highly organized in both time and space. Gap junctions (GJs) play a crucial role in the communication between vascular cells and in the synchronization of Ca2+ signals thereby tightly controlling the level of vasoconstriction. Before being incorporated into GJs, connexin (Cx) hemichannels reside in the plasma membrane in a closed state. Recent evidence suggests that hemichannels can be opened by various messengers and conditions, thereby forming a pore that allows the passage of ATP and ions. Using confocal microscopy and the Ca2+ sensitive dye Fluo-3, we examined the role of hemichannels in dynamic Ca2+ responses of SMC in intact acutely isolated small rat mesenteric arteries. Furthermore, we assessed the involvement of these signalling partners in contractile responses of small mesenteric arteries using a wire myograph for isometric tension measurements. Importantly, the experimental conditions were such that vasomotion, characterized by synchronized Ca2+ signals, was avoided because in that case gap junctions between SMC and myo-endothelial gap junctions are expected to contribute. Norepinephrine (NOR, 3 M) induced Ca2+ oscillations that were reduced in frequency by 98.4 % (p< 0.05) when exposed to carbenoxolone (CBX, 50 M), a none specific Cx channel inhibitor. Gap27 (200 M), a Cx mimetic peptide that blocks hemichannel responses (assayed by ATP release and dye uptake) after short incubation, reduced the spiking frequency by 96.4 % (p< 0.05). Suramin (200 M) and PPADS (75 M), two P2Y receptor antagonists, decreased the spiking frequency by 90.5 % (p<0.05) and 96.4% (p<0.01) respectively. Apyrase (5 U/ml), an enzyme that rapidly degrades extracellular ATP, reduced the spiking frequency by 71.4 % (p<0.01). None of these agents affected the amplitude of the Ca2+ oscillations. Both gap27 (56.6 %, p<0.01) and CBX (53.4 %, p<0.05) reduced the NOR-induced contractions. Incubation with suramin decreased the NOR-induced contractions by 31.6 % (p<0.001). Our results suggest a role for Cx hemichannels and purinergic signaling in Ca2+ oscillations and contractility.  

Hemichannel involvement in CA2+ dynamics and contractility of smooth muscle cells in acutely isolated small mesenteric arteries

https://biblio.ugent.be/publication/1151716/file/1221510

Hemichannel involvement in CA2+ dynamics and contractility of smooth muscle cells in acutely isolated small mesenteric arteries

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Ghent University Academic Bibliography