Thermodynamic interference with bile acid demicelleization reduces systemic entry and injury during cholestasis
Thermodynamic interference with bile acid demicelleization reduces systemic entry and injury during cholestasis
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DOI：
10.1038/s41598-020-65451-w
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发表时间：
2020-05-21
影响因子：
4.6
通讯作者：
Singh, Vijay P.
中科院分区：
文献类型：
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作者：
de Oliveira, Cristiane;Khatua, Biswajit;Singh, Vijay P.
胆汁酸（BA）具有较大的疏水类固醇核和极性基团，是两亲性分子。在胆汁中，当浓度高于临界胶束浓度（CMC）时，它们以胶束形式存在。在血液中浓度较低时，它们以单体形式存在，并引发细胞信号。这种从胶束到单体的转变可能涉及胆汁盐单独之间或与磷脂（即混合胶束）以及水环境之间复杂的热力学相互作用。因此，我们接着测试了在治疗相关的温度变化是否会影响胆汁盐的胶束行为，进而是否会影响细胞和体内的生物学反应。牛磺胆酸钠（STC）属于一类主要的胆汁盐。STC的临界胶束浓度在5 - 8mM范围内，将其注入胰管通常用于研究胰腺炎。因此，我们使用等温滴定量热法（ITC）、动态光散射和低温透射电子显微镜研究了STC的胶束分解。在与体内环境相关的条件下（pH 7.4，Na⁺ 0.15M），ITC显示STC在37℃到15℃之间胶束分解呈U形减少，在25℃时达到最低点，接近约90%的抑制率。这种温度依赖性与单体STC诱导的胰腺腺泡损伤平行。STC和1 - 棕榈酰 - 2 - 油酰磷脂酰胆碱（一种在胆汁中高比例存在的磷脂）的混合胶束表现相似，与37℃相比，在25℃时胶束分解减少约75%。在体内将胰腺冷却到25℃，可减少在向胰管注入120mM（5%）STC并结扎胰管后循环胆汁酸的增加。较低的胆汁酸水平与心脏功能改善、心肌损伤减轻、休克缓解、肺损伤减轻以及生存率提高相关，且与胰腺损伤无关。因此，胆汁盐的胶束分解对于它们进入体循环至关重要，对其进行热力学干扰可能会减少它们在胆汁淤积（如胆源性胰腺炎）期间进入体循环以及由此导致的损伤。
Bile acids (BA), with their large hydrophobic steroid nucleus and polar groups are amphipathic molecules. In bile, these exist as micelles above their critical micellar concentration (CMC). In blood at low concentrations, these exist as monomers, initiating cellular signals. This micellar to monomer transition may involve complex thermodynamic interactions between bile salts alone or with phospholipids, i.e. mixed micelles and the aqueous environment. We therefore went on to test if therapeutically relevant changes in temperature could influence micellar behavior of bile salts, and in turn whether this affected the biological responses in cells, and in vivo. Sodium taurocholate (STC) belongs to a major class of bile salts. STC has a CMC in the 5-8mM range and its infusion into the pancreatic duct is commonly used to study pancreatitis. We thus studied micellar breakdown of STC using isothermal titration calorimetry (ITC), dynamic light scattering and cryogenic transmission electron microscopy. Under conditions relevant to the in vivo environment (pH 7.4, Na 0.15M), ITC showed STC to have a U shaped reduction in micellar breakdown between 37 degrees C and 15 degrees C with a nadir at 25 degrees C approaching approximate to 90% inhibition. This temperature dependence paralleled pancreatic acinar injury induced by monomeric STC. Mixed micelles of STC and 1-palmitoyl, 2-oleyl phosphatidylcholine, a phospholipid present in high proportions in bile, behaved similarly, with approximate to 75% reduction in micellar breakdown at 25 degrees C compared to 37 degrees C. In vivo pancreatic cooling to 25 degrees C reduced the increase in circulating BAs after infusion of 120mM (5%) STC into the pancreatic duct, and duct ligation. Lower BA levels were associated with improved cardiac function, reduced myocardial damage, shock, lung injury and improved survival independent of pancreatic injury. Thus micellar breakdown of bile salts is essential for their entry into the systemic circulation, and thermodynamic interference with this may reduce their systemic entry and consequent injury during cholestasis, such as from biliary pancreatitis.