Tumor necrosis factor-alpha-induced caspase activation mediates endotoxin-related cardiac dysfunction

Crit Care Med. 2005 May;33(5):1021-8. doi: 10.1097/01.ccm.0000163398.79679.66.

Abstract

Objective: Sepsis-induced cardiac dysfunction is a serious clinical syndrome characterized by hypotension, decreased systemic vascular resistance, and elevated cardiac index. Although cytokines such as tumor necrosis factor (TNF)-alpha have been shown to play a significant role early in this response, the downstream effects of TNF-alpha signaling on cardiac function, specifically its relationship to apoptosis, have not been fully elucidated.

Design: Previous studies from our laboratory have identified endotoxin-induced apoptosis in cardiac cells in vitro. To further determine the role of lipopolysaccharide-induced apoptosis in vivo, mice were injected intraperitoneally with lipopolysaccharide (4 mg/kg), and cardiac apoptosis was detected and inhibited using a broad-spectrum caspase inhibitor.

Setting: University research laboratory.

Subjects: Adult male wild-type (B6:129PF1/J) and TNF receptor 1/receptor 2 (TNFR-1/2) knockout mice (B6;129S-Tnfrsf1aTnfrsf1b).

Interventions: We sought to determine the dependence of cardiac apoptosis on TNF-alpha signaling and determine the physiologic role of caspase activation on lipopolysaccharide-induced cardiac dysfunction.

Measurements and main results: Cardiac apoptosis was determined at baseline and at 2, 4, 8, and 24 hrs by detection of capase-3 and -8 activity, cytoplasmic levels of Bax/Bcl-2, cleaved caspase-3 immunohistochemistry, and terminal deoxynucleotidyl transferase UTP nick-end labeling (TUNEL) staining of histologic sections in wild-type and TNFR-1/2 knockout mice. To determine the role of caspase activation in lipopolysaccharide-induced cardiac dysfunction, a broad-spectrum caspase inhibitor Z-Val-Ala-Asp (ome)-FMK (sad) was given, and cardiac function was determined in isolated beating hearts (Langendorff preparation). Our experiments determined that caspase-3-dependent apoptosis was active in cardiac tissue by 2 hrs and that this activation was completely mediated by TNFR-1/2. The Bax/Bcl-2 ratios supported the finding and time course of apoptosis, whereas TUNEL staining of cardiac tissue sections identified sporadic apoptotic ventricular cells. The administration of zVAD significantly inhibited myocardial caspase-3 activity and preserved cardiac physiologic function (Langendorff preparation).

Conclusions: Endotoxin induces a TNF-alpha-dependent apoptotic cascade in the myocardium, which contributes to the development of cardiac dysfunction.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Chloromethyl Ketones / pharmacology
  • Animals
  • Apoptosis
  • Caspase 3
  • Caspase 8
  • Caspase Inhibitors
  • Caspases / metabolism*
  • Endotoxins / toxicity
  • Enzyme Activation
  • Heart Diseases / enzymology*
  • Heart Diseases / microbiology
  • In Situ Nick-End Labeling
  • Lipopolysaccharides
  • Male
  • Mice
  • Mice, Knockout
  • Tumor Necrosis Factor-alpha / physiology*

Substances

  • Amino Acid Chloromethyl Ketones
  • Caspase Inhibitors
  • Endotoxins
  • Lipopolysaccharides
  • Tumor Necrosis Factor-alpha
  • z-Val-Ala-Asp(Ome)-fluoromethylketone
  • Casp3 protein, mouse
  • Casp8 protein, mouse
  • Caspase 3
  • Caspase 8
  • Caspases