Institute of Physiology & Pathophysiology, University of Witten/Herdecke, Witten, Germany.
Pancreas. 2012 May;41(4):596-604. doi: 10.1097/MPA.0b013e318239c6e5.
The immunosuppressant tacrolimus (FK506) has improved pancreas allograft survival compared with cyclosporin A (CsA), possibly because of reduced acute pancreatitis following ischemia-reperfusion injury. Ion permeabilities in zymogen granule (ZG) membranes, including a KCNQ1 K channel, promote hormone-stimulated enzyme secretion. We investigated whether a differential modulation of ZG and lysosomal ion permeabilities and enzyme secretion by CsA/FK506 contributes to pancreatitis.
Rat ZGs and lysosomes were isolated by gradient centrifugation, ion permeabilities assayed by osmotic lysis, and single-channel currents recorded in a planar lipid bilayer. Amylase release was measured in permeabilized acini and lysosomal cathepsin B release detected by immunoblotting.
CsA (1-10 μM), but not FK506, enhanced ZGs osmotic lysis by selectively increasing K permeability up to 5-fold. Zymogen granule membrane K channels showed ∼2-fold increased single-channel open probability with CsA only. Cyclosporin A selectively increased basal (∼2-fold), but not cholecystokinin-octapeptide (1 nM)-induced amylase secretion in K medium only. Cyclosporin A (5 μM), but not FK506, increased cathepsin B release from lysosomes.
Cyclosporin A selectively opens the ZG K channel and induces cathepsin B release from lysosomes, which cause increased in situ lysis of ZGs and may aggravate or fuel acute allograft pancreatitis following hypoxia-reperfusion injury.
免疫抑制剂他克莫司（FK506）与环孢素 A（CsA）相比，可提高胰腺移植体的存活率，这可能是因为缺血再灌注损伤后胰腺炎的发生率降低。酶原颗粒（ZG）膜中的离子通透性，包括 KCNQ1 K 通道，可促进激素刺激的酶分泌。我们研究了 CsA/FK506 是否通过调节 ZG 和溶酶体离子通透性和酶分泌来导致胰腺炎。
通过梯度离心分离大鼠 ZG 和溶酶体，通过渗透裂解测定离子通透性，并在平面脂质双层中记录单通道电流。在通透的腺泡中测量淀粉酶释放，通过免疫印迹检测溶酶体组织蛋白酶 B 的释放。
CsA（1-10 μM），而不是 FK506，通过选择性增加 K 通透性将 ZG 渗透裂解增加高达 5 倍。只有 CsA 才能使酶原颗粒膜 K 通道的单通道开放概率增加约 2 倍。CsA 仅选择性增加基础（约 2 倍），但不增加 K 介质中胆囊收缩素八肽（1 nM）诱导的淀粉酶分泌。CsA（5 μM），而不是 FK506，增加了溶酶体中的组织蛋白酶 B 释放。
CsA 选择性地打开 ZG K 通道并诱导溶酶体中的组织蛋白酶 B 释放，这会导致 ZG 原位溶解增加，可能会加重或引发缺氧再灌注损伤后的急性同种异体移植胰腺炎。
