LPS pretreatment ameliorates multiple organ injuries and improves survival in a murine model of polymicrobial sepsis.

OBJECTIVE: The endotoxin tolerance phenotype is characterized with decreased inflammation and increased phagocytosis. We hypothesized that endotoxin tolerance would provide protective effects on experimental sepsis with multiple organ injuries induced by cecal ligation and puncture (CLP). METHODS: Endotoxin tolerance was induced in male Sprague-Dawley rats with daily intraperitoneal injection of either 0.6 mg/kg of lipopolysaccharide (LPS) or vehicle for four consecutive days before subsequent CLP. Biochemical parameters, histological changes, inflammatory cytokine production, and lung tissue nuclear factor-κB (NF-κB) activation were assessed post-CLP. In a separate experiment, survival rate was monitored for 7 days after CLP. RESULTS: In vehicle-treated animals, CLP caused multiple organ injuries confirmed by the biochemical variables and histological examination. This was accompanied by an early activation of NF-κB in the lung and a substantial increase in plasma levels of tumor necrosis factor-α, interleukin-6, and interleukin-10. In contrast, pretreatment with LPS not only alleviated the development of multiple organ injuries after CLP, but also decreased sepsis-induced activation of pulmonary NF-κB and reduced plasma cytokines production. In addition, LPS pretreatment improved the survival in rats subjected to CLP. CONCLUSIONS: The beneficial effects of endotoxin tolerance indicate the potential of immunomodulatory strategies in the management of severe sepsis.

[Anti-apoptotic effect of insulin in myocardial ischemia-reperfusion and its principal signaling pathway].

OBJECTIVE: To investigate the signaling pathway involved in the insulin-elicited anti-apoptotic effect during myocardial ischemia and reperfusion (MI/R) in vivo. METHODS: Male Sprague-Dawley rats were anesthetized and subjected to 30 min of myocardial ischemia followed by 4h-reperfusion. Rats were randomly treated with intravenous infusion of saline (vehicle, 4 ml.kg(-1).h(-1)), insulin (60 U/L), or insulin + wortmannin 5 min before reperfusion and continuing throughout the 4h-reperfusion period. Cardiac myocyte apoptosis was determined both qualitatively and quantitatively by DNA laddering and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) methods. Myocardial nitric oxide (NO) was measured by using NO-specific chemiluminescence detector. Activations of Akt and p38 mitogen-activated protein kinase (MAPK) were determined by kinase activity assays using corresponding kinase activity assay kits (Cell Signaling). RESULTS: In the vehicle-treated rats, MI/R caused significant cardiac myocyte apoptotic death. Treatment with insulin produced a significant anti-apoptotic effect as evidenced by a marked reduction of apoptotic index [(8.0 +/- 2.9)% vs. (19.3 +/- 4.6)% of vehicle, P < 0.01] and decreased formation of myocardial DNA fragmentation. In addition, insulin treatment produced 2.7-fold increase (P < 0.01) of myocardial Akt activity and 28% increase of myocardial NO production (P < 0.05), while p38 MAPK activity changed insignificantly as compared with that of vehicle (P > 0.05). Both insulin-induced Akt activation and anti-apoptotic effect could be abrogated by wortmannin, a phosphatidylinositol (PI) 3-kinase inhibitor. CONCLUSION: In vivo treatment with insulin at the initial of reperfusion significantly reduced postischemic apoptotic death via the PI3-kinase-Akt signaling pathway. Akt, but not p38 MAPK, activation plays a key role in the insulin-induced anti-apoptotic effect in MI/R.