Mechanisms of blood-vascular reactions of the primate lung to acute endotoxemia

Mechanisms of bacterial lipopolysaccharide-induced endothelial apoptosis

Gram-negative bacterial sepsis remains a common, life-threatening event. The prognosis for patients who develop sepsis-related complications, including the development of acute respiratory distress syndrome (ARDS), remains poor. A common finding among patients and experimental animals with sepsis and ARDS is endothelial injury and/or dysfunction. A component of the outer membrane of gram-negative bacteria, lipopolysaccharide (LPS) or endotoxin, has been implicated in the pathogenesis of much of the endothelial cell injury and/or dysfunction associated with these disease states. LPS is a highly proinflammatory molecule that elicits a wide array of endothelial responses, including the upregulation of cytokines, adhesion molecules, and tissue factor. In addition to activation, LPS induces endothelial cell death that is apoptotic in nature. This review summarizes the evidence for LPS-induced vascular endothelial injury and examines the molecular signaling pathways that activate and inhibit LPS-induced endothelial apoptosis. Furthermore, the role of apoptotic signaling molecules in mediating LPS-induced activation of endothelial cells will be considered.

Extracorporeal membrane oxygenation therapy in neonates with septic shock

Neonatal septic shock has significant morbidity and mortality with current therapeutic measures. At Children's National Medical Center, from June 1984 to October 1986, 10 of 100 patients treated with venoarterial extracorporeal membrane oxygenation (ECMO) had a documented diagnosis of septic shock. All of these infants fulfilled criteria consistent with 80% mortality using conventional intensive medical management. However, the survival rate for the septic neonates in this study was 100%. Compared with other groups of infants treated with ECMO, these septic neonates required significantly more ventilatory support after ECMO and had a higher incidence of chronic lung disease (30% v 12%). The septic neonates were also at higher risk for intracranial hemorrhage than the other infants treated with ECMO (40% v 26%). The necessity for prolonged intubation after ECMO for patients with septic shock suggests that this condition may be associated with additional structural damage not seen with meconium aspiration syndrome or respiratory distress syndrome. Nevertheless, for neonatal patients with septic shock unresponsive to conventional medical management, ECMO must be considered a viable alternative treatment.

Sinusoidal circulatory disturbance by microthrombosis as a cause of endotoxin-induced hepatic injury

The present study was undertaken in rats to examine the significance of sinusoidal circulatory disturbance by microthrombosis in the pathogenesis of hepatic damage and dysfunction due to endotoxin. Administration of endotoxin induced fibrin deposits and infiltration of polymorphonuclear leukocytes in the sinusoids, focal random coagulative hepatocellular necrosis and elevation of serum transaminase activities. When heparin was given simultaneously with endotoxin, the formation of fibrin thrombus in the sinusoids was prevented, and the endotoxin-induced morphological and functional changes in the liver were markedly inhibited. Infusion of thrombin into the portal vein induced a large amount of fibrin thrombi in the sinusoids, focal random necrotic foci resembling the lesions produced by endotoxin and elevation of levels of serum transaminases. These experimental data suggest that disturbance of hepatic microcirculation by sinusoidal thrombosis is the necessary and sufficient condition for the development of endotoxin-induced hepatic injury.

Current perspectives on septic shock

Although septic shock may be initiated by invading microbes, it is the metabolic and immunologic host responses that determine the true pathophysiology of this common critical care illness. Currently, septic shock therapeutics emphasize empiric and symptomatic treatment. Biochemical elucidation of the septic process will ultimately result in specific interventions for this ominous intensive care syndrome.

Lung cyclic 3',5'-adenosine monophosphate and adenylate cyclase in endotoxic shock

Cyclic 3',5'-adenosine monophosphate (cyclic AMP) and adenylate cyclase activity were measured in lungs from guinea pigs in endotoxic shock induced by an intravenous injection of Salmonella enteritidis endotoxin (10 mg/kg body weight). Both cyclic AMP content and adenylate cyclase activity were significantly elevated in lung tissue from the endotoxic guinea pigs. There was no apparent change in the affinity of adenylate cyclase for its substrate (ATP); however, the maximum velocity of the enzyme reaction was increased in lungs from the endotoxic group. Endotoxin, in the concentration range of 10(-4) to 10(-2) micrograms/ml, added to lung homogenates did not affect adenylate cyclase activity. Prostaglandins do not seem to mediate the effects of endotoxin in vivo on lung cyclic AMP since treatment of guinea pigs with indomethacin (10 mg/kg body weight) 30 min prior to endotoxin administration did not alter the endotoxin-induced increase in lung cyclic AMP.

Protection against endotoxin-induced mortality in mice treated with transition metal salts

Administration of manganese or chromium chloride 1 h before challenge with a single bolus of Salmonella typhosa endotoxin completely obviated death in endotoxin-challenged mice.