Superoxide dismutase (SOD) prevents hypotension after hemorrhagic shock and aortic cross clamping

Monocyte deactivation correlates with injury severity score, but not with heme oxygenase-1 levels in trauma patients

Traumatic injury induces a local and systemic release of pro-inflammatory cytokines, acute phase proteins, hormones, and other inflammatory mediators. The excessive release of these mediators plays an important role in the pathogenesis of shock. In parallel to this pro-inflammatory response, there is a regulatory response characterized by the release of anti-inflammatory mediators, which is thought to represent the host's attempt to restore immunological equilibrium. Studies in septic patients have suggested the compensatory anti-inflammatory response may result in an "immunodeficient state" that leaves the host susceptible to further infectious insults. A key feature of the anti-inflammatory state in septic patients is a change in the responsiveness of monocytes that has been termed "monocyte deactivation." This is supported by data that link monocyte deactivation to increased mortality in septic patients. Monocytes with reduced HLA-DR expression have been described in trauma patients. We collected blood from 25 severely injured patients and evaluated peripheral blood mononuclear cells (PBMC) for HLA-DR expression and TNF-α response to LPS stimulation as markers of monocyte deactivation. Levels of intracellular HO-1 were determined in each patient, as HO-1 has been implicated in monocyte deactivation in patients with severe systemic inflammatory response syndrome (SIRS). HLA-DR expression correlated inversely with Injury Severity Scores and TNF-α response to LPS stimulation, but failed to correlate with HO-1 levels in these patients. HLA-DR expression was decreased in normal monocytes stimulated with patient plasma, but this treatment had no effect on HO-1 levels. These results suggest monocyte deactivation in trauma patients is unlikely to be mediated by HO-1.

A superoxide dismutase mimetic with catalase activity (EUK-8) reduces the organ injury in endotoxic shock

Reactive oxygen species contribute to the multiple organ failure in endotoxic shock. Here, we investigate the effects of a salen-manganese complex, which exhibits both superoxide dismutase and catalase activity (EUK-8), on the circulatory failure, renal and liver injury and dysfunction caused by endotoxin in the anaesthetised rat. Endotoxaemia (6 mg/kg i.v., Escherichia coli lipopolysaccharide) for 6 h caused hypotension, renal dysfunction and liver injury. Treatment of rats with EUK-8 (0.3 or 1 mg/kg bolus injection followed by an infusion of 0.3 or 1 mg/kg/h) attenuated the renal and liver injury and dysfunction in a dose-related fashion. In addition, the higher dose of EUK-8 attenuated the delayed hypotension caused by endotoxin in the rat. Thus, an enhanced formation of reactive oxygen species importantly contributes to the circulatory failure, as well as the organ injury and dysfunction associated with endotoxic shock. We propose that small molecules, which have the catalytic activity of both superoxide dismutase and catalase, may represent a novel therapeutic approach for the therapy of endotoxic shock.

Superoxide dismutase mimetics with catalase activity reduce the organ injury in hemorrhagic shock

Reactive oxygen species (ROS) contribute to the multiple organ failure (MOF) in hemorrhagic shock. Here we investigate the effects of two superoxide dismutase (SOD) mimetics with catalase activity (EUK-8 and EUK-134) on the circulatory failure and the organ injury and dysfunction associated with hemorrhagic shock in the anesthetised rat. Hemorrhage (sufficient to lower mean arterial blood pressure to 45 mmHg for 90 min) and subsequent resuscitation with shed blood resulted (within 4 h after resuscitation) in a delayed fall in blood pressure, liver injury and renal dysfunction as well as pancreatic injury. Treatment of rats on resuscitation with EUK-8 (3 mg/kg i.v. bolus followed by 3 mg/kg/h i.v. infusion) significantly attenuated liver injury, renal dysfunction and pancreatic injury caused by hemorrhage and resuscitation. Administration of EUK-134 (3 mg/kg i.v. bolus followed by 3 mg/kg/h) reduced the liver injury and renal dysfunction (but not the pancreatic injury) caused by hemorrhagic shock. However, neither EUK-8 nor EUK-134 reduced the delayed circulatory failure associated with hemorrhagic shock. Thus, we propose that an enhanced formation of ROS contributes to the MOF in hemorrhagic shock, and that membrane-permeable SOD-mimetics with catalase activity, such as EUK-8 or EUK-134, may represent a novel therapeutic approach for the therapy of hemorrhagic shock.

Induction of heme-oxygenase-1 prevents the systemic responses to hemorrhagic shock

Oxidant-mediated reperfusion injury of the gut is a major contributor of the systemic inflammatory response in hemorrhagic shock. Recent studies have suggested that heme-oxygenase-1 (HO-1) represents an endogenous protective mechanism against oxidant stress. We assessed whether HO-1 induction modulates the synthesis of tumor necrosis factor-alpha (TNF-alpha) in hemorrhagic shock. In rats submitted to hemorrhagic shock, pretreatment with hemoglobin (Hb) increased HO-1 mRNA expression in macrophages. This increased expression was associated with a decreased expression of TNF-alpha mRNA, as well as decreased plasma concentrations of TNF-alpha. These effects of Hb were reduced by the HO-1 inhibitor tin-protoporphyrin (Sn-PP 20 micromol/kg), while Sn-PP had no effect in the absence of Hb. In parallel, Hb pretreatment reduced pulmonary edema, vascular injury, and increased mesenteric blood flow, and these effects were reduced by Sn-PP. Thus, induction of HO-1 is protective in hemorrhagic shock, possibly through its antioxidant properties. Interventions that induce HO-1 may be beneficial in the treatment of shock states, leading to a reduced systemic inflammatory response.

Extracellular superoxide dismutase attenuates lung injury after hemorrhage

Reperfusion of the lung after hemorrhage generates free radicals such as superoxide (O(2)(.)) that may injure the lung; however, the relative importance of intracellular versus extracellular free radicals is unclear. The superoxide dismutases (SOD) are the primary enzymatic method to reduce superoxide. We examined whether lung-specific overexpression of extracellular superoxide dismutase (EC-SOD) would attenuate hemorrhage-induced lung injury. Wild-type mice and mice overexpressing the human EC-SOD gene with a lung-specific promoter were hemorrhaged by removing 30% of blood volume. After hemorrhage, the lung wet to dry weight ratios increased from 5.4 +/- 0.11 in unmanipulated control mice to 6.3 +/- 0.16 in wild-type mice, but to only 5.60 +/- 0.17 in the EC-SOD transgenic mice (p < 0.05 compared with hemorrhaged wild-type). Hemorrhage-induced lipid peroxidation, as assessed by lung F(2) isoprostanes, was lower in the EC-SOD transgenic mice (3.4 +/- 0.3 microg/lung) compared with wild-type mice (1.9 +/- 0.2 microg/lung; p < 0.05). Compared with wild-type, EC-SOD transgenic mice had attenuated the hemorrhage-induced increase in both pulmonary nuclear factor kappa B (NK-kappaB) activation (relative absorbance 1.1 +/- 0.2 for EC-SOD transgenic versus 2.5 +/- 0.1 for wild-type; p < 0.05) and myeloperoxidase activity (5.1 +/- 0.87 units/g for EC-SOD transgenic versus 11.3 +/- 1.8 units/g for wild-type; p < 0.01). Thus, overexpression of pulmonary EC-SOD in the mouse lung attenuates lung injury after hemorrhage.

Systemic and mesenteric hemodynamics, metabolism, and intestinal tonometry in a rat model of supraceliac aortic cross-clamping and declamping

OBJECTIVE

To describe systemic and mesenteric hemodynamics, metabolism, and intestinal tonometry in a rat model of supraceliac aortic cross-clamping and declamping.

DESIGN

Prospective, randomized, experimental study.

SETTING

University cardiovascular research laboratory.

PARTICIPANTS

Twelve male anesthetized and ventilated Sprague-Dawley rats.

INTERVENTION

Supraceliac aortic cross-clamping was performed for 30 minutes, followed by declamping and reperfusion for 180 minutes or sham clamping and sham declamping.

MEASUREMENTS AND MAIN RESULTS

Mean arterial blood pressure; abdominal aortic, superior mesenteric, and carotid artery blood flow; intestinal mucosal tonometry; hemoglobin; lactate; and blood gases were measured before and after 30 minutes of aortic cross-clamping and 15, 30, 60, 120, and 180 minutes after declamping during reperfusion. Aortic cross-clamping induced an increase in mean arterial pressure (117+/-20 mm Hg to 147+/-12 mm Hg), an increase in right atrial hemoglobin saturation(66%+/-11% to 81%+/-6%), an increase in lactate levels (1.7+/-0.7 mmol/L to 4.3+/-1.3 mmol/L), and an increase in tonometric PCO2 (49.6+/-5.0 mm Hg to 75.6+/-8.6 mm Hg). Three hours of reperfusion after declamping resulted in significantly decreased mean arterial pressure (38+/-10 mm Hg); decreased aortic (101+/-12 mL/min/kg to 57+/-32 mL/min/kg), mesenteric (19+/-4 to 13+/-6 mL/min/kg), and carotid (12+/-4 mL/min/kg to 5+/-3 mL/min/ kg) blood flows; and elevated lactate levels (4.2+/-2.0 mmol/L). Tonometric PCO2 had normalized to baseline levels (51.9+/-3.8 mm Hg), but PCO2 gap was significantly higher than in sham clamped rats (17.9+/-7.8 mm Hg v. 7.0+/-2.6 mm Hg).

CONCLUSIONS

Hemodynamic and metabolic effects of aortic cross-clamping and declamping known from large animal models are reproducible using a rat model. Intestinal tonometry indicated mesenteric ischemia during aortic cross-clamping, which was reversible to preclamp values within 30 minutes of reperfusion after declamping.

Effects of inhibitors of the activity of poly (ADP-ribose) synthetase on the organ injury and dysfunction caused by haemorrhagic shock

1 Poly (ADP-ribose) synthetase (PARS) is a nuclear enzyme activated by strand breaks in DNA, which are caused by reactive oxygen species (ROS). Here we investigate the effects of the PARS inhibitors 3-aminobenzamide (3-AB), nicotinamide and 1,5-dihydroxyisoquinoline (ISO) on the circulatory failure and the organ injury/dysfunction caused by haemorrhage and resuscitation in the anaesthetized rat. 2 Haemorrhage (sufficient to lower mean arterial blood pressure to 50 mmHg for 90 min) and subsequent resuscitation with shed blood resulted (within 4 h after resuscitation) in a delayed fall in blood pressure to 66+/-4 mmHg (control, n=13). This circulatory failure was not affected by administration (5 min prior to resuscitation) of 3-AB (10 mg kg-1 i.v., n=7), nicotinamide (10 mg kg-1 i.v., n=6) or ISO (3 mg kg-1 i.v., n=6). 3 Haemorrhage and resuscitation also resulted in rises in the serum levels of urea and creatinine. This renal dysfunction was attenuated by 3-AB and nicotinamide, but not by nicotinic acid (n=7), an inactive analogue of nicotinamide. Although ISO (n=6) also attenuated the renal dysfunction caused by haemorrhage and resuscitation, its vehicle (10% DMSO, n=4) had the same effect. 4 Haemorrhagic shock resulted in enhanced serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lipase, indicating the development of hepatocellular and pancreatic injury, respectively. Similarly, haemorrhagic shock also resulted in an increase in the serum levels of creatine kinase (CK) indicating the development of neuromuscular injury. This was attenuated by 3-AB and nicotinamide, but not by nicotinic acid. Although ISO also attenuated the liver, pancreatic and neuromuscular injury caused by haemorrhagic shock, its vehicle had the same effect. 5 Thus, activation of PARS contributes to the organ injury and dysfunction caused by haemorrhage and resuscitation in the rat.