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Mechanisms regulating cytochrome c release in pancreatic mitochondria
  1. I V Odinokova1,2,
  2. K-F Sung1,3,
  3. O A Mareninova1,
  4. K Hermann1,
  5. Y Evtodienko2,
  6. A Andreyev4,
  7. I Gukovsky1,
  8. A S Gukovskaya1
  1. 1
    Veterans Affairs Greater Los Angeles Healthcare System and Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles, USA
  2. 2
    Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
  3. 3
    Department of Hepato-Gastroenterology, Chang Gung Memorial Hospital, Taipei, Taiwan
  4. 4
    Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California, USA
  1. Dr A S Gukovskaya, UCLA/VA Greater Los Angeles Healthcare System, West Los Angeles VA Healthcare Center, 11301 Wilshire Blvd, Blg 258, Rm 40, Los Angeles, CA 90073, USA; agukovsk{at}ucla.edu

Abstract

Background: 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 Ca2+, mitochondrial membrane potential (ΔΨm), 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).

Results: Micromolar amounts of Ca2+ depolarised isolated pancreatic mitochondria through a mechanism different from the “classical” (ie, liver) mitochondrial permeability transition pore (mPTP). In contrast with liver, Ca2+-induced mPTP opening caused a dramatic decrease in ROS and was not associated with pancreatic mitochondria swelling. Importantly, we found that Ca2+-induced depolarisation inhibited cytochrome c release from pancreatic mitochondria, due to blockade of ROS production. As a result, Ca2+ exerted two opposite effects on cytochrome c release: Ca2+ per se stimulated the release, whereas Ca2+-induced depolarisation inhibited it. This dual effect caused a non-monotonous dose-dependence of cytochrome c release on Ca2+. In intact acinar cells, cytochrome c release, caspase activation and apoptosis were all stimulated by ROS and Ca2+, and inhibited by depolarisation, corroborating the findings on isolated pancreatic mitochondria.

Conclusions: 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 Ca2+ and ROS on acinar cell death. They suggest that the extent of apoptosis in pancreatitis is regulated by the interplay between ROS, ΔΨm and Ca2+. Stabilising mitochondria against loss of ΔΨm may represent a strategy to mitigate the severity of pancreatitis.

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Footnotes

  • See Commentary, p 328

  • Supplementary methods and a figure are published online only at http://gut.bmj.com/content/vol58/issue3

  • Funding: This study was supported by NIH grant DK059936 (to ASG), an AGA Foundation Designated Research Scholar Award in Pancreatitis (to OAM) and by the Hirshberg Foundation.

  • Competing interests: None.

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