Heterogeneous Gene Expression and Functional Activity of Ryanodine Receptors in Resistance and Conduit Pulmonary as well as Mesenteric Artery Smooth Muscle Cells

Abstract

Background: Hypoxia causes heterogeneous contractile responses in resistance and conduit pulmonary as well as systemic (mesenteric) artery smooth muscle cells (RPASMCs, CPASMCs and MASMCs), but the underlying mechanisms are largely unknown. In this study, we aimed to investigate whether the gene expression and functional activity of ryanodine receptors (RyRs) would be different in these 3 cell types. Methods: RyR mRNA expression, Ca²⁺ sparks and [Ca²⁺]_i were measured by real-time quantitative RT-PCR, laser scanning confocal microscopy and wide-field fluorescence microscopy, respectively. Results: All 3 RyR subtype (RyR1, RyR2 and RyR3) mRNAs are expressed in RPASMCs, CPASMCs and MASMCs, but their expression levels are different. Spontaneous Ca²⁺ sparks (functional events of RyRs) show distinct frequency, amplitude, duration, size and kinetics in these 3 cell types. Similarly, activation of RyRs by caffeine, 4-chloro-m-cresol or high K⁺ induces differential Ca²⁺ release. Moreover, hypoxia-induced increase in [Ca²⁺]_i is largest in MASMCs relative to CPSAMCs and smallest in RPASMCs. Conclusion: This study provides comprehensive evidence that RyRs are heterogeneous in gene expression and functional activity in RPASMCs, CPASMCs and MASMCs, which may contribute to the diversity of excitation-contraction coupling and hypoxic Ca²⁺ responses in different vascular smooth muscle cells.

ROS-Dependent Signaling Mechanisms for Hypoxic Ca2+Responses in Pulmonary Artery Myocytes

“…By using real-time quantitative RT-PCR, we showed that RyR1, RyR2, and RyR3 are all expressed in freshly isolated rat and mouse PASMCs (121,122). In support of our findings, other investigators reported that all three RyR subtype mRNAs are …”

Stimulation of the adenosine A3 receptor reverses vascular hyporeactivity after hemorrhagic shock in rats

“…Consistent with others' reports, our results showed that RyR-mediated Ca 2+ release is over-activated in hypoxic VSMCs, which might be owing to the increased expression of RyR and the increased sensitivity of RyR to Ca 2+ [25,26] . Furthermore, the over-activation of RyRmediated Ca 2+ release is closely associated with the occurrence of vascular hyporeactivity to NE in hemorrhagic shock rats.…”

CD38 Mediates Angiotensin II–Induced Intracellular Ca2+ Release in Rat Pulmonary Arterial Smooth Muscle Cells

“…CD38 activation mobilizes intracellular Ca 21 through cADPR-dependent Ca 21 release from RyR-gated stores and NAADP-dependent Ca 21 release from the acidic endo-lysosomes. Previous work by our and other laboratories have identified all three RyR subtypes in PASMCs, with RyR2 being the most abundant subtype (23,39). RyR1 and RyR2 are associated mainly with SR in the subsarcolemmal region, whereas RyR3 is localized predominantly in the perinuclear SR (23,40 There is substantial evidence suggesting that Ang II enhances ROS production through activation of NOX, contributing to Ca 21 response in VSMCs (17).…”