Gonzalez Bosc Laura V, Osmond Jessica M, Giermakowska Wieslawa K, Pace Carolyn E, Riggs Jennifer L, Jackson-Weaver Olan, Kanagy Nancy L
Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
Am J Physiol Heart Circ Physiol. 2017 Apr 1;312(4):H791-H799. doi: 10.1152/ajpheart.00952.2015. Epub 2017 Jan 27.
Sleep apnea is a risk factor for cardiovascular disease, and intermittent hypoxia (IH, 20 episodes/h of 5% O-5% CO for 7 h/day) to mimic sleep apnea increases blood pressure and impairs hydrogen sulfide (HS)-induced vasodilation in rats. The enzyme that produces HS, cystathionine γ-lyase (CSE), is decreased in rat mesenteric artery endothelial cells (EC) following in vivo IH exposure. In silico analysis identified putative nuclear factor of activated T cell (NFAT) binding sites in the CSE promoter. Therefore, we hypothesized that IH exposure reduces Ca concentration ([Ca]) activation of calcineurin/NFAT to lower CSE expression and impair vasodilation. In cultured rat aortic EC, inhibiting calcineurin with cyclosporine A reduced CSE mRNA, CSE protein, and luciferase activity driven by a full-length but not a truncated CSE promoter. In male rats exposed to sham or IH conditions for 2 wk, [Ca] in EC in small mesenteric arteries from IH rats was lower than in EC from sham rat arteries (Δfura 2 ratio of fluorescence at 340 to 380 nm from Ca free: IH = 0.05 ± 0.02, sham = 0.17 ± 0.03, < 0.05), and fewer EC were NFATc3 nuclear positive in IH rat arteries than in sham rat arteries (IH = 13 ± 3, sham = 59 ± 11%, < 0.05). HS production was also lower in mesenteric tissue from IH rats vs. sham rats. Endothelium-dependent vasodilation to acetylcholine (ACh) was lower in mesenteric arteries from IH rats than in arteries from sham rats, and inhibiting CSE with β-cyanoalanine diminished ACh-induced vasodilation in arteries from sham but not IH rats but did not affect dilation to the HS donor NaHS. Thus, IH lowers EC [Ca], NFAT activity, CSE expression and activity, and HS production while inhibiting NFAT activation lowers CSE expression. The observations that IH exposure decreases NFATc3 activation and CSE-dependent vasodilation support a role for NFAT in regulating endothelial HS production. This study identifies the calcium-regulated transcription factor nuclear factor of activated T cells as a novel regulator of cystathionine γ-lyase (CSE). This pathway is basally active in mesenteric artery endothelial cells, but, after exposure to intermittent hypoxia to mimic sleep apnea, nuclear factor of activated T cells c3 nuclear translocation and CSE expression are decreased, concomitant with decreased CSE-dependent vasodilation.
睡眠呼吸暂停是心血管疾病的一个危险因素，模拟睡眠呼吸暂停的间歇性低氧（IH，每天7小时，20次/小时，5%氧气-5%二氧化碳）会升高大鼠血压并损害硫化氢（HS）诱导的血管舒张。体内IH暴露后，大鼠肠系膜动脉内皮细胞（EC）中产生HS的酶——胱硫醚γ-裂解酶（CSE）减少。计算机分析确定了CSE启动子中假定的活化T细胞核因子（NFAT）结合位点。因此，我们推测IH暴露会降低钙调神经磷酸酶/NFAT的钙浓度（[Ca]）激活，从而降低CSE表达并损害血管舒张。在培养的大鼠主动脉EC中，用环孢素A抑制钙调神经磷酸酶可降低CSE mRNA、CSE蛋白以及由全长而非截短的CSE启动子驱动的荧光素酶活性。在暴露于假手术或IH条件2周的雄性大鼠中，IH大鼠小肠系膜动脉EC中的[Ca]低于假手术大鼠动脉EC中的[Ca]（游离钙条件下340至380 nm处的fura 2荧光比值：IH = 0.05±0.02，假手术 = 0.17±0.03，P<0.05），且IH大鼠动脉中NFATc3核阳性的EC比假手术大鼠动脉中的少（IH = 13±3，假手术 = 59±11%，P<0.05）。与假手术大鼠相比，IH大鼠肠系膜组织中的HS产生也较低。IH大鼠肠系膜动脉对乙酰胆碱（ACh）的内皮依赖性血管舒张低于假手术大鼠的动脉，用β-氰基丙氨酸抑制CSE可减弱假手术大鼠动脉中ACh诱导的血管舒张，但对IH大鼠动脉无影响，且不影响对HS供体硫氢化钠的舒张反应。因此，IH降低EC中的[Ca]、NFAT活性、CSE表达和活性以及HS产生，而抑制NFAT激活可降低CSE表达。IH暴露会降低NFATc3激活和CSE依赖性血管舒张的观察结果支持了NFAT在调节内皮HS产生中的作用。本研究确定钙调节转录因子活化T细胞核因子是胱硫醚γ-裂解酶（CSE）的一种新型调节因子。该途径在肠系膜动脉内皮细胞中基本活跃，但在暴露于间歇性低氧以模拟睡眠呼吸暂停后，活化T细胞核因子c3核转位和CSE表达降低，同时CSE依赖性血管舒张也降低。
