Purpose

Acute increases in hydrostatic pressure activate endothelial signaling pathways that modulate barrier function and vascular permeability. We investigated the role the glycocalyx and established mechanotransduction pathways in pressure-induced albumin transport across rat lung microvascular endothelial cells.

Methods

Rat lung microvascular endothelial cells (RLMEC) were cultured on Costar Snapwell chambers. Cell morphology was assessed using silver nitrate staining. RLMEC were exposed to zero pressure (Control) or 30 cmH₂O (Pressure) for 30 or 60 min. Intracellular albumin uptake and transcellular albumin transport was quantified. Transcellular transport was reported as solute flux (J_s) and an effective permeability coefficient (P_e). The removal of cell surface heparan sulfates (heparinase), inhibition of NOS (L-NAME) and reactive oxygen species (apocynin, Apo) was investigated.

Results

Acute increase in hydrostatic pressure augmented albumin uptake by 30–40% at 60 min and J_s and P_e both increased significantly. Heparinase increased albumin uptake but attenuated transcellular transport while L-NAME attenuated both pressure-dependent albumin uptake and transport. Apo interrupted albumin uptake under both control and pressure conditions, leading to a near total lack of transcellular transport, suggesting a different mechanism and/or site of action.

Conclusion

Pressure-dependent albumin uptake and transcellular transport is another component of endothelial mechanotransduction and associated regulation of solute flux. This novel albumin uptake and transport pathway is regulated by heparan sulfates and eNOS. Albumin uptake is sensitive to ROS. The physiological and clinical implications of this albumin transport are discussed.

中文翻译：

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糖萼和压力依赖性跨细胞白蛋白转运

目的

静水压力的急剧增加会激活调节屏障功能和血管通透性的内皮信号通路。我们研究了糖萼的作用，并在压力诱导的白蛋白跨大鼠肺微血管内皮细胞转运中建立了机械转导途径。

方法

大鼠肺微血管内皮细胞 (RLMEC) 在 Costar Snapwell 室上培养。使用硝酸银染色评估细胞形态。RLMEC 暴露于零压力（对照）或 30 cmH ₂ O（压力）30 或 60 分钟。量化细胞内白蛋白摄取和跨细胞白蛋白转运。跨细胞转运报告为溶质通量 (J _s ) 和有效渗透系数 (P _e )。研究了细胞表面硫酸乙酰肝素（肝素酶）的去除、NOS（L-NAME）和活性氧（夹竹桃素，Apo）的抑制。

结果

60 分钟时静水压力的急剧增加使白蛋白摄取增加了 30-40%，并且 J _s和_Pe都显着增加。肝素酶增加白蛋白摄取但减弱跨细胞运输，而 L-NAME 减弱压力依赖性白蛋白摄取和运输。Apo 在控制和压力条件下中断白蛋白摄取，导致几乎完全缺乏跨细胞转运，表明不同的机制和/或作用位点。

结论

压力依赖性白蛋白摄取和跨细胞转运是内皮机械转导和溶质通量相关调节的另一个组成部分。这种新的白蛋白摄取和转运途径受硫酸乙酰肝素和 eNOS 的调控。白蛋白摄取对 ROS 敏感。讨论了这种白蛋白转运的生理和临床意义。