AIMS: Bacterial endotoxin lipopolysaccharide (LPS) is responsible for the multi-organ dysfunction that characterizes septic shock and is causal in the myocardial depression that is a common feature of endotoxemia in patients. In this setting the myocardial dysfunction appears to be due, in part, to the production of pro-inflammatory cytokines. A line of evidence also indicates that LPS stimulates autophagy in cardiomyocytes. However, the signal transduction pathway leading to autophagy and its role in the heart are incompletely characterized. In this work, we wished to determine the effect of LPS on autophagy, and the physiologic significance of the autophagic response. METHODS: Autophagy was monitored morphologically and biochemically in HL-1 cardiomyocytes, neonatal rat cardiomyocytes, and in transgenic mouse hearts after administration of bacterial LPS or TNF-RESULTS: We observed that autophagy was increased after exposure to LPS or TNF-, which is induced by LPS. Inhibition of TNF- production by AG126 significantly reduced the accumulation of autophagosomes both in cell culture and in vivo. Inhibition of p38 MAPK or NOS by pharmacological inhibitors also reduced autophagy. Nitric oxide (NO) or H₂O₂ induced autophagy in cardiomyocytes while N-acetyl-cysteine (NAC), a potent antioxidant, suppressed autophagy. LPS resulted in increased ROS production and decreased total glutathione. To test the hypothesis that autophagy might serve as a damage control mechanism to limit further ROS production we induced autophagy with rapamycin before LPS exposure. Activation of autophagy by rapamycin suppressed LPS-mediated ROS production and protected cells against LPS toxicity. CONCLUSIONS: These findings support the notion that autophagy is a cytoprotective response to LPS- induced cardiomyocyte injury; additional studies are needed to determine the therapeutic implications.