Acute lethal crush-injured rats can be successfully rescued by a single injection of high-dose dexamethasone through a pathway involving PI3K-Akt-eNOS signaling

Abstract

Crush syndrome (CS) is characterized by ischemia/reperfusion-induced rhabdomyolysis and the subsequent onset of systemic inflammation. CS is associated with a high mortality, even when patients are treated with conventional therapy. We hypothesized that treatment of lethal CS rat model with dexamethasone (DEX) have therapeutic effects on the laboratory findings and clinical course and outcome. To create a CS model, anesthetized rats were subjected to bilateral hind limb compression with rubber tourniquets for 5 hours and randomly divided into three groups as follows: saline-treated CS group, CS groups treated with low (0.1 mg/kg) and high doses (5.0 mg/kg) of DEX. Saline for the CS group or DEX for the DEX-treated CS groups was intravenously administered immediately before reperfusion. Under continuous monitoring and recording of arterial blood pressures, blood and tissue samples were collected for histologic and biochemical analysis at designated period before and after reperfusion. Ischemic compression of rat hind limbs reduced the nitrite content in the crushed muscle, and the subsequent reperfusion induced reactive oxygen species-mediated circulatory collapse and systemic inflammation, finally resulting in a mortality rate of 76% by 48 hours after reperfusion. A single injection of high-dose DEX immediately before reperfusion activated endothelial nitric oxide synthase (eNOS) by sequential phosphorylation through the nongenomic phosphoinositide 3-kinase (PI3K)-Akt-eNOS signaling pathway. DEX also exhibited anti-inflammatory effects by modulating proinflammatory and anti-inflammatory mediators, consequently suppressing myeloperoxidase activities and subsequent systemic inflammation, showing a complete recovery of the rats from lethal CS. These results indicate that high-dose DEX reduces systemic inflammation and contributes to the improved survival rate in a rat CS model.