Department of Medicine, Cardiovascular Medicine, University of Wisconsin-Madison, Madison, WI, USA.
Department of Pediatrics, Pediatric Cardiology, University of Wisconsin-Madison, Madison, WI, USA.
J Physiol. 2024 Sep;602(18):4387-4407. doi: 10.1113/JP284807. Epub 2023 Oct 27.
Cardiovascular disease is the leading cause of death in the USA and is known to be exacerbated by elevated mechanical stress from hypertension. Caveolae are plasma membrane structures that buffer mechanical stress but have been found to be reduced in pathological conditions associated with chronically stretched myocardium. To explore the physiological implications of the loss of caveolae, we used human engineered cardiac tissue (ECT) constructs, composed of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes and hiPSC-derived cardiac fibroblasts, to develop a long-term cyclic stretch protocol that recapitulates the effects of hypertension on caveolae expression, membrane tension, and the β-adrenergic response. Leveraging this new stretch protocol, we identified neutral sphingomyelinases (nSMase) as mechanoregulated mediators of caveolae loss, ceramide production and the blunted β-adrenergic response in this human cardiac model. Specifically, in our ECT model, nSMase inhibition via GW4869 prevented stretch-induced loss of caveolae-like structures, mitigated nSMase-dependent ceramide production, and maintained the ECT contractile kinetic response to isoprenaline. These findings are correlated with a blood lipidomic analysis in middle-aged and older adults, which revealed an increase of the circulating levels of ceramides in adults with hypertension. Furthermore, we found that conduction slowing from increased pressure loading in mouse left ventricle was abolished in the context of nSMase inhibition. Collectively, these findings identify nSMase as a potent drug target for mitigating stretch-induced effects on cardiac function. KEY POINTS: We have developed a new stretch protocol for human engineered cardiac tissue that recapitulates changes in plasma membrane morphology observed in animal models of pressure/volume overload. Stretch of engineered cardiac tissue induces activation of neutral sphingomyelinase (nSMase), generation of ceramide, and disassembly of caveolae. Activation of nSMase blunts cardiac β-adrenergic contractile kinetics and mediates stretch-induced slowing of conduction and upstroke velocity. Circulating ceramides are increased in adults with hypertension, highlighting the clinical relevance of stretch-induced nSMase activity.
心血管疾病是美国的主要死亡原因，已知其会因高血压引起的机械应力升高而加剧。陷窝是一种缓冲机械应力的质膜结构，但在与慢性拉伸心肌相关的病理条件下发现其减少。为了探索陷窝丧失的生理意义，我们使用了由人诱导多能干细胞（hiPSC）衍生的心肌细胞和 hiPSC 衍生的心脏成纤维细胞组成的人工程心脏组织（ECT）构建体，开发了一种长期循环拉伸方案，该方案可模拟高血压对陷窝表达、膜张力和β-肾上腺素能反应的影响。利用这种新的拉伸方案，我们确定了中性鞘磷脂酶（nSMase）作为机械调节因子，可介导该人类心脏模型中陷窝的丧失、神经酰胺的产生和β-肾上腺素能反应的钝化。具体而言，在我们的 ECT 模型中，nSMase 抑制通过 GW4869 防止了拉伸诱导的陷窝样结构丧失，减轻了 nSMase 依赖性神经酰胺的产生，并维持了 ECT 对异丙肾上腺素的收缩动力学反应。这些发现与中年和老年人的血脂组学分析相关，该分析显示高血压成年人的循环神经酰胺水平增加。此外，我们发现，在 nSMase 抑制的情况下，来自左心室压力负荷增加的传导减慢被消除。总之，这些发现确定 nSMase 是一种潜在的药物靶点，可减轻心脏功能的拉伸诱导作用。关键点：我们开发了一种新的用于人工程心脏组织的拉伸方案，该方案可再现动物模型中压力/容积超负荷时质膜形态的变化。工程心脏组织的拉伸会激活中性鞘磷脂酶（nSMase），产生神经酰胺，并使陷窝解体。nSMase 的激活会使心脏β-肾上腺素能收缩动力学变钝，并介导拉伸诱导的传导减慢和上升速度减慢。高血压成年人的循环神经酰胺增加，突出了拉伸诱导的 nSMase 活性的临床相关性。
