Downregulation of stromal interaction molecule-1 is implicated in the age-associated vasoconstriction dysfunction of aorta, intrarenal, and coronary arteries

The contractile function of vascular smooth muscle cells (VSMCs) typically undergoes significant changes with advancing age, leading to severe vascular aging-related diseases. The precise role and mechanism of stromal interaction molecule-1 (STIM1) in age-mediated Ca2+ signaling and vasocontraction remain unclear. The connection between STIM1 and age-related vascular dysfunction was investigated using a multi-myograph system, immunohistochemical analysis, protein blotting, and SA-β-gal staining. Results showed that vasoconstrictor responses in the thoracic aorta, intrarenal artery, and coronary artery decreased with age. STIM1 knockdown in the intrarenal and coronary arteries reduced vascular tone in young mice, while no change was observed in the thoracic aorta. A significant reduction in vascular tone occurred in the STIM1 knockout group with nifedipine. In the thoracic aorta, vasoconstriction significantly decreased with age following the use of nifedipine and thapsigargin and almost disappeared after STIM1 knockdown. The proportion of senescent VSMCs increased significantly in aged mice and further increased in sm-STIM1 KO aged mice. Moreover, the expression of senescence markers p21, p16, and IL-6 significantly increased with age, with p21 expression further increased in the STIM1 knockdown aged group, but not p16 or IL-6. These findings indicate that different arteries exhibit distinct organ-specific features and that STIM1 downregulation may contribute to age-related vasoconstrictive dysfunction through activation of the p21 pathway.

Contribution of calcium dysregulation to impaired coronary artery contraction in Zucker diabetic fatty rats

Diabetic coronary artery injury is closely associated with Ca²⁺ dysregulation, although the underlying mechanism remains unclear. This study explored the role and mechanism of Ca²⁺ handling in coronary artery dysfunction in type 2 diabetic rats. Zucker diabetic fatty (ZDF) rats were used as the type 2 diabetes mellitus model. The contractility of coronary artery rings induced by KCl, CaCl₂ , 5-HT and U46619 was significantly lower in ZDF rats than in Zucker lean rats. Vasoconstriction induced by 5-HT and U46619 was greatly inhibited by nifedipine. However, in the presence of 1 μM nifedipine or in the Ca²⁺ -free KH solution containing 1 μM nifedipine, there was no difference in the vasoconstriction between Zucker lean and ZDF rats. Store-operated calcium channels (SOCs) were not involved in coronary vasoconstriction. The downregulation of contractile proteins and the upregulation of synthesized proteins were in coronary artery smooth muscle cells (CASMCs) from ZDF rats. Metformin reversed the reduction of vasoconstriction in ZDF rats. Taken together, L-type calcium channel is important for regulating the excitation-contraction coupling of VSMCs in coronary arteries, and dysregulation of this channel contributes to the decreased contractility of coronary arteries in T2DM.

Signalling pathway of U46619-induced vascular smooth muscle contraction in mouse coronary artery

BACKGROUND

Thromboxane A2 (TXA2 ) participates in many pathophysiological processes of coronary artery disease. However, its mechanism of TXA2 -induced contraction in the coronary artery remains to be clarified. A multi myograph system was used to measure the isometric tension of the mouse coronary arteries and identify the effect and pathway of TXA2 analogues U46619. Confocal laser scanning microscopy was used to measure the intracellular calcium concentration ([Ca2+ ]i ) in mouse coronary artery smooth muscle cells. Results from the experiment had shown that contraction in coronary artery was generated by U46619 in a concentration-dependent manner, which was completely abolished by a specific TXA2 receptor blocker, GR32191. PI-PLC inhibitors U73122 and D609 and Rho-Kinase inhibitor Y-27632 can block the U46619 elicited coronary artery contraction in a dose-dependent manner. Then, the vasoconstriction response to U46619 was obviously inhibited by two pan-PKC inhibitors chelerythrine or Gӧ6983, and a selective PKCδ inhibitor rottlerin, but was not blocked by a selective PKCζ inhibitor PKC-PS or a selective PKCβ inhibitor hispidin. Meanwhile, the PKC activator PDBu-induced vasoconstriction was significantly inhibited by 1 μmol/L nifedipine, then mostly inhibited by 100 μmol/L 2-APB and 10 μmol/L Y27632. We further found that the response to U46619 was inhibited, respectively, by three calcium channel blockers nifedipine, SKF96356 or 2-APB in a concentration-dependent manner. Although Store-operated Ca2+ (SOC) channels generated the increase of [Ca2+ ]i in mouse coronary artery smooth muscle cells, SOC channels did not contribute to the vasoconstriction in mouse coronary arteries. Caffeine-induced sarcoplasmic reticulum (SR) Ca2+ release could obviously induce coronal vasoconstriction. In addition, NPPB, a cell membrane Ca2+ activated C1- channel blocker, could obviously inhibit the U46619-induced vasoconstriction. The U46619-induced mouse coronary artery contraction was involved in the increase in [Ca2+ ]i mediated by Cav1.2, TRPC channels and SR release through the activation of G-protein-coupled TP receptors and the kinases signalling pathway in TP downstream proteins, while SOC channels did not participate in the vasoconstriction.