TY - JOUR

T1 - Bestrophin is important for the rhythmic but not the tonic contraction in rat mesenteric small arteries

AU - Broegger, Torbjoern

AU - Jacobsen, Jens Christian Brings

AU - Secher Dam, Vibeke

AU - Boedtkjer, Donna M Briggs

AU - Kold-Petersen, Henrik Houmann

AU - Pedersen, Finn Skou

AU - Aalkjaer, Christian

AU - Matchkov, Vladimir

PY - 2011

Y1 - 2011

N2 - Aims We have previously characterized a cGMP-dependent Ca2+-activated Cl– current in vascular smooth muscle cells (SMCs) and have shown its dependence on bestrophin-3 expression. We hypothesize that this current is important for synchronization of SMCs in the vascular wall. In the present study, we aimed to test this hypothesis by transfecting rat mesenteric small arteries in vivo with siRNA specifically targeting bestrophin-3. Methods and results The arteries were tested 3 days after transfection in vitro for isometric force development and for intracellular Ca2+ in SMCs. Bestrophin-3 expression was significantly reduced compared with arteries transfected with mutated siRNA. mRNA levels for bestrophin-1 and -2 were also significantly reduced by bestrophin-3 down-regulation. This is suggested to be secondary to specific bestrophin-3 down-regulation since siRNAs targeting different exons of the bestrophin-3 gene had identical effects on bestrophin-1 and -2 expression. The transfection affected neither the maximal contractile response nor the sensitivity to norepinephrine and arginine-vasopressin. The amplitude of agonist-induced vasomotion was significantly reduced in arteries down-regulated for bestrophins compared with controls, and asynchronous Ca2+ waves appeared in the SMCs. The average frequency of vasomotion was not different. 8Br-cGMP restored vasomotion in arteries where the endothelium was removed, but oscillation amplitude was still significantly less in bestrophin-down-regulated arteries. Thus, vasomotion properties were consistent with those previously characterized for rat mesenteric small arteries. Data from our mathematical model are consistent with the experimental results. Conclusion This study demonstrates the importance of bestrophins for synchronization of SMCs and strongly supports our hypothesis for generation of vasomotion.

AB - Aims We have previously characterized a cGMP-dependent Ca2+-activated Cl– current in vascular smooth muscle cells (SMCs) and have shown its dependence on bestrophin-3 expression. We hypothesize that this current is important for synchronization of SMCs in the vascular wall. In the present study, we aimed to test this hypothesis by transfecting rat mesenteric small arteries in vivo with siRNA specifically targeting bestrophin-3. Methods and results The arteries were tested 3 days after transfection in vitro for isometric force development and for intracellular Ca2+ in SMCs. Bestrophin-3 expression was significantly reduced compared with arteries transfected with mutated siRNA. mRNA levels for bestrophin-1 and -2 were also significantly reduced by bestrophin-3 down-regulation. This is suggested to be secondary to specific bestrophin-3 down-regulation since siRNAs targeting different exons of the bestrophin-3 gene had identical effects on bestrophin-1 and -2 expression. The transfection affected neither the maximal contractile response nor the sensitivity to norepinephrine and arginine-vasopressin. The amplitude of agonist-induced vasomotion was significantly reduced in arteries down-regulated for bestrophins compared with controls, and asynchronous Ca2+ waves appeared in the SMCs. The average frequency of vasomotion was not different. 8Br-cGMP restored vasomotion in arteries where the endothelium was removed, but oscillation amplitude was still significantly less in bestrophin-down-regulated arteries. Thus, vasomotion properties were consistent with those previously characterized for rat mesenteric small arteries. Data from our mathematical model are consistent with the experimental results. Conclusion This study demonstrates the importance of bestrophins for synchronization of SMCs and strongly supports our hypothesis for generation of vasomotion.

KW - Animals

KW - Arginine Vasopressin

KW - Calcium

KW - Chloride Channels

KW - Male

KW - Mesenteric Arteries

KW - Norepinephrine

KW - RNA, Messenger

KW - RNA, Small Interfering

KW - Rats

KW - Rats, Wistar

KW - Transfection

KW - Vasoconstriction

U2 - 10.1093/cvr/cvr111

DO - 10.1093/cvr/cvr111

M3 - Journal article

C2 - 21498420

VL - 91

SP - 685

EP - 693

JO - Cardiovascular Research

JF - Cardiovascular Research

SN - 0008-6363

IS - 4

ER -