Odinokova I V, Sung K-F, Mareninova O A, Hermann K, Evtodienko Y, Andreyev A, Gukovsky I, Gukovskaya A S
Veterans Affairs Greater Los Angeles Healthcare System and Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles, CA 90073, USA.
Gut. 2009 Mar;58(3):431-42. doi: 10.1136/gut.2007.147207. Epub 2008 Jul 2.
Mechanisms of acinar cell death in pancreatitis are poorly understood. Cytochrome c release is a central event in apoptosis in pancreatitis. Here, we assessed the regulation of pancreatic cytochrome c release by Ca(2+), mitochondrial membrane potential (Delta Psi m), and reactive oxygen species (ROS), the signals involved in acute pancreatitis. We used both isolated rat pancreatic mitochondria and intact acinar cells hyperstimulated with cholecystokinin-8 (CCK-8; in vitro model of acute pancreatitis).
Micromolar amounts of Ca(2+) depolarised isolated pancreatic mitochondria through a mechanism different from the "classical" (ie, liver) mitochondrial permeability transition pore (mPTP). In contrast with liver, Ca(2+)-induced mPTP opening caused a dramatic decrease in ROS and was not associated with pancreatic mitochondria swelling. Importantly, we found that Ca(2+)-induced depolarisation inhibited cytochrome c release from pancreatic mitochondria, due to blockade of ROS production. As a result, Ca(2+) exerted two opposite effects on cytochrome c release: Ca(2+) per se stimulated the release, whereas Ca(2+)-induced depolarisation inhibited it. This dual effect caused a non-monotonous dose-dependence of cytochrome c release on Ca(2+). In intact acinar cells, cytochrome c release, caspase activation and apoptosis were all stimulated by ROS and Ca(2+), and inhibited by depolarisation, corroborating the findings on isolated pancreatic mitochondria.
These data implicate ROS as a key mediator of CCK-induced apoptotic responses. The results indicate a major role for mitochondria in the effects of Ca(2+ )and ROS on acinar cell death. They suggest that the extent of apoptosis in pancreatitis is regulated by the interplay between ROS, Delta Psi m and Ca(2+). Stabilising mitochondria against loss of Delta Psi m may represent a strategy to mitigate the severity of pancreatitis.
胰腺炎中腺泡细胞死亡的机制尚不清楚。细胞色素c释放是胰腺炎细胞凋亡的核心事件。在此，我们评估了Ca(2+)、线粒体膜电位（ΔΨm）和活性氧（ROS）对胰腺细胞色素c释放的调节作用，这些信号参与了急性胰腺炎的发生。我们使用了分离的大鼠胰腺线粒体和用胆囊收缩素-8（CCK-8；急性胰腺炎的体外模型）过度刺激的完整腺泡细胞。
微摩尔浓度的Ca(2+)通过一种不同于“经典”（即肝脏）线粒体通透性转换孔（mPTP）的机制使分离的胰腺线粒体去极化。与肝脏不同，Ca(2+)诱导的mPTP开放导致ROS显著减少，且与胰腺线粒体肿胀无关。重要的是，我们发现Ca(2+)诱导的去极化抑制了胰腺线粒体细胞色素c的释放，这是由于ROS产生受阻。因此，Ca(2+)对细胞色素c释放产生了两种相反的作用：Ca(2+)本身刺激释放，而Ca(2+)诱导的去极化则抑制释放。这种双重作用导致细胞色素c释放对Ca(2+)呈现非单调的剂量依赖性。在完整的腺泡细胞中，细胞色素c释放、半胱天冬酶激活和细胞凋亡均受到ROS和Ca(2+)的刺激，并被去极化所抑制，这与分离的胰腺线粒体的研究结果一致。
这些数据表明ROS是CCK诱导的凋亡反应的关键介质。结果表明线粒体在Ca(2+)和ROS对腺泡细胞死亡的影响中起主要作用。它们提示胰腺炎中细胞凋亡的程度受ROS、ΔΨm和Ca(2+)之间相互作用的调节。稳定线粒体防止ΔΨm丧失可能是减轻胰腺炎严重程度的一种策略。
