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

• Published in: Critical care medicine Vol. 33; no. 5; pp. 1021 - 1028
• Main Authors: Carlson, Deborah L, Willis, Monte S, White, D Jean, Horton, Jureta W, Giroir, Brett P
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD by the Society of Critical Care Medicine and Lippincott Williams & Wilkins 01-05-2005; Lippincott
• Subjects: Amino Acid Chloromethyl Ketones - pharmacology; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Animals; Apoptosis; Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Caspase 3; Caspase 8; Caspase Inhibitors; Caspases - metabolism; Diseases of the peripheral vessels. Diseases of the vena cava. Miscellaneous; Emergency and intensive cardiocirculatory care. Cardiogenic shock. Coronary intensive care; Endotoxins - toxicity; Enzyme Activation; Heart Diseases - enzymology; Heart Diseases - microbiology; In Situ Nick-End Labeling; Intensive care medicine; Lipopolysaccharides; Male; Medical sciences; Mice; Mice, Knockout; Tumor Necrosis Factor-alpha - physiology; Intensive care; Enzyme; Cysteine endopeptidases; Transferases; Cytokine; Caspase; terminal deoxynucleotidyl transferase UTP nick-end labeling; Endotoxin; Peptidases; Toxin; Lipopolysaccharide; Hydrolases; Tumor necrosis factor β; cardiac dysfunction; Tumor necrosis factor α; Resuscitation; Apoptosis
• ISSN: 0090-3493; 1530-0293
• DOI: 10.1097/01.CCM.0000163398.79679.66

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)-α have been shown to play a significant role early in this response, the downstream effects of TNF-α 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-α 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-α-dependent apoptotic cascade in the myocardium, which contributes to the development of cardiac dysfunction.