Autophagy in chronically ischemic myocardium

Lin Yan, Dorothy E. Vatner, Song Jung Kim, Hui Ge, Malthi Masurekar, William H. Massover, Guiping Yang, Yutaka Matsui, Junichi Sadoshima, Stephen F. Vatner

Research output: Contribution to journalArticlepeer-review

441 Scopus citations

Abstract

We tested the hypothesis that chronically ischemic (IS) myocardium induces autophagy, a cellular degradation process responsible for the turnover of unnecessary or dysfunctional organelles and cytoplasmic proteins, which could protect against the consequences of further ischemia. Chronically instrumented pigs were studied with repetitive myocardial ischemia produced by one, three, or six episodes of 90 min of coronary stenosis (30% reduction in baseline coronary flow followed by reperfusion every 12 h) with the non-IS region as control. In this model, wall thickening in the IS region was chronically depressed by ≈37%. Using a nonbiased proteomic approach combining 2D gel electrophoresis with in-gel proteolysis, peptide mapping by MS, and sequence database searches for protein identification, we demonstrated increased expression of cathepsin D, a protein known to mediate autophagy. Additional autophagic proteins, cathepsin B, heat shock cognate protein Hsc73 (a key protein marker for chaperone-mediated autophagy), beclin 1 (a mammalian autophagy gene), and the processed form of microtubule-associated protein 1 light chain 3 (a marker for autophagosomes), were also increased. These changes, not evident after one episode, began to appear after two or three episodes and were most marked after six episodes of ischemia, when EM demonstrated autophagic vacuoles in chronically IS myocytes. Conversely, apoptosis, which was most marked after three episodes, decreased strikingly after six episodes, when autophagy had increased. Immunohistochemistry staining for cathepsin B was more intense in areas where apoptosis was absent. Thus, autophagy, triggered by ischemia, could be a homeostatic mechanism, by which apoptosis is inhibited and the deleterious effects of chronic ischemia are limited.

Original languageEnglish (US)
Pages (from-to)13807-13812
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number39
DOIs
StatePublished - Sep 27 2005

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Apoptosis
  • Hibernating myocardium
  • Lyposomal proteins
  • Myocardial protection
  • Proteomics

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