Department of Pediatrics, Northwestern University, Chicago, IL 60611, USA.
Int J Mol Sci. 2013 Feb 21;14(2):4334-48. doi: 10.3390/ijms14024334.
In the pulmonary vasculature, mechanical forces such as cyclic stretch induce changes in vascular signaling, tone and remodeling. Nitric oxide is a potent regulator of soluble guanylate cyclase (sGC), which drives cGMP production, causing vasorelaxation. Pulmonary artery smooth muscle cells (PASMCs) express inducible nitric oxide synthase (iNOS), and while iNOS expression increases during late gestation, little is known about how cyclic stretch impacts this pathway. In this study, PASMC were subjected to cyclic stretch of 20% amplitude and frequency of 1 Hz for 24 h and compared to control cells maintained under static conditions. Cyclic stretch significantly increased cytosolic oxidative stress as compared to static cells (62.9 ± 5.9% vs. 33.3 ± 5.7% maximal oxidation), as measured by the intracellular redox sensor roGFP. Cyclic stretch also increased sGCβ protein expression (2.5 ± 0.9-fold), sGC activity (1.5 ± 0.2-fold) and cGMP levels (1.8 ± 0.2-fold), as well as iNOS mRNA and protein expression (3.0 ± 0.9 and 2.6 ± 0.7-fold, respectively) relative to control cells. An antioxidant, recombinant human superoxide dismutase (rhSOD), significantly decreased stretch-induced cytosolic oxidative stress, but did not block stretch-induced sGC activity. Inhibition of iNOS with 1400 W or an iNOS-specific siRNA inhibited stretch-induced sGC activity by 30% and 68% respectively vs. static controls. In conclusion, cyclic stretch increases sGC expression and activity in an iNOS-dependent manner in PASMC from fetal lambs. The mechanism that produces iNOS and sGC upregulation is not yet known, but we speculate these effects represent an early compensatory mechanism to counteract the effects of stretch-induced oxidative stress. A better understanding of the interplay between these two distinct pathways could provide key insights into future avenues to treat infants with pulmonary hypertension.
在肺血管中，机械力如周期性拉伸会引起血管信号、张力和重塑的变化。一氧化氮是可溶性鸟苷酸环化酶（sGC）的有效调节剂，可促进 cGMP 的产生，从而引起血管舒张。肺动脉平滑肌细胞（PASMCs）表达诱导型一氧化氮合酶（iNOS），虽然 iNOS 在妊娠晚期表达增加，但对于周期性拉伸如何影响该途径知之甚少。在这项研究中，将 PASMC 置于 20%幅度和 1Hz 频率的周期性拉伸下 24 小时，并与维持在静态条件下的对照细胞进行比较。与静态细胞相比，周期性拉伸显著增加了细胞浆氧化应激（通过细胞内氧化还原传感器 roGFP 测量为 62.9±5.9%与 33.3±5.7%的最大氧化），如 roGFP 测量的，与静态细胞相比，周期性拉伸还增加了 sGCβ 蛋白表达（2.5±0.9 倍）、sGC 活性（1.5±0.2 倍）和 cGMP 水平（1.8±0.2 倍），以及 iNOS mRNA 和蛋白表达（分别为 3.0±0.9 和 2.6±0.7 倍）。抗氧化剂重组人超氧化物歧化酶（rhSOD）显著降低了拉伸诱导的细胞浆氧化应激，但并未阻断拉伸诱导的 sGC 活性。用 1400W 或 iNOS 特异性 siRNA 抑制 iNOS，可使 sGC 活性分别降低 30%和 68%，与静态对照相比。总之，周期性拉伸以 iNOS 依赖的方式增加了来自胎羊 PASMC 的 sGC 表达和活性。产生 iNOS 和 sGC 上调的机制尚不清楚，但我们推测这些效应代表了一种早期的代偿机制，以抵消拉伸诱导的氧化应激的影响。更好地理解这两种不同途径之间的相互作用，可能为治疗患有肺动脉高压的婴儿提供新的途径。
