PFI-3 induces vasorelaxation with potency to reduce extracellular calcium influx in rat mesenteric artery.

Background: PFI-3 is a small-molecule inhibitor that targets the bromodomains (BRDs) of Brahma-related gene 1 (BRG1). This monomeric compound, which has high selectivity and potent cellular effects, has recently been developed. Although PFI-3 has been reported as a potential therapeutic agent targeting thrombomodulin, its role in the regulation of vascular function remains unknown. Therefore, we aimed to investigate the impact of PFI-3 on arterial vessel tone. Methods: A microvascular tension measurement device (DMT) was utilized to identify alterations in vascular tension within the mesenteric artery. To detect variations in cytosolic [Ca2+]i, a Fluo-3/AM fluorescent probe and fluorescence microscope were employed. Additionally, whole-cell patch clamp techniques were utilized to evaluate the activity of L-type voltage-dependent calcium channels (VDCCs) in cultured arterial smooth muscle cells (A10 cells). Results: PFI-3 exerted a dose-dependent relaxation effect on rat mesenteric arteries with both intact and denuded endothelium after phenylephrine (PE)- and high-K+-induced constriction. PFI-3-induced vasorelaxation was not affected by the presence of L-NAME/ODQ or K+ channel blockers (Gli/TEA). PFI-3 abolished Ca2+-induced contraction on endothelium-denuded mesenteric arteries preincubated by PE in Ca2+-free solution. Incubation with TG had no impact on PFI-3-induced vasorelaxation pre-contracted by PE. PFI-3 reduced Ca2+-induced contraction on endothelium-denuded mesenteric arteries pre-incubated by KCl (60 mM) in Ca2+-free solution. PFI-3 declined extracellular calcium influx in A10 cells detected by Fluo-3/AM fluorescent probe and fluorescence microscope. Furthermore, we observed that PFI-3 decreased the current densities of L-type VDCC by whole-cell patch clamp techniques. Conclusions: PFI-3 blunted PE and high K+-induced vasoconstriction independent of endothelium on rat mesenteric artery. The vasodilatory effect of PFI-3 may be attributed to its inhibition of VDCCs and receptor-operated calcium channels (ROCCs) on vascular smooth muscle cells (VSMCs).

Transient receptor potential melastatin 4 contributes to early-stage endothelial injury induced by arsenic trioxide.

BACKGROUND/AIMS: To investigate the effect of Arsenic Trioxide (ATO) on endothelial cells injury and explore the role of transient receptor potential melastatin 4 channel (TRPM4) in ATO-induced endothelial injury. METHODS: qRT-PCR was used to examine the mRNA expression of TRPM4 in human umbilical vein endothelial cells (HUVECs). The protein levels were measured by Western blot and immunostaining. The MTT, TUNEL, and transwell assays were used to evaluate the cell viability, apoptosis, and migration, respectively. The ultrastructural changes were observed by scanning electron microscopy. The membrane potential, cytosolic [Na+]i, cytosolic [Ca2+]i and reactive oxygen species (ROS) levels were detected by fluorescent probes. Isometric tension of mesenteric artery was recorded by using a multiwire myograph system. RESULTS: ATO induced HUVEC cells injury, the significant upregulation of TRPM4 in this process was inhibited by 9-phenanthrol or siRNA. ATO-induced apoptosis and decrease in the cell viability/ migration were all partially reversed upon the treatment with 9-phenanthrol. Whereas, ATO-mediated increase in membrane potential, cytosolic [Na+]i, cytosolic [Ca2+]i and the ROS levels were also abolished by 9-phenanthrol or siRNA, suggesting that oxidative stress may be the potential mechanisms underlying ATO-induced endothelial injury. Additionally, 9-phenanthrol treatment prevented ATO-mediated impairment of acetylcholine-induced endothelium-dependent relaxations. CONCLUSION: TRPM4 is involved in endothelial injury induced by ATO and may be a promising therapeutic target for endothelial injury.