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.

Reduced synthesis of inflammatory cytokines by a free radical scavenger after hemorrhagic shock in rats.

OBJECTIVES: Intestinal ischemia/reperfusion during hemorrhage and resuscitation may be a major trigger for cytokine expression. To assess whether free radicals produced on tissue reperfusion may play a role in the inflammatory response after hemorrhage, we tested the effect of a free radical scavenger on the production of inflammatory cytokines in a rat model of hemorrhagic shock. DESIGN: A prospective, controlled animal study. SETTING: A university research laboratory. SUBJECTS: Male Wistar rats. INTERVENTIONS: Hemorrhage was induced in anesthetized rats. by bleeding the animal to achieve a mean arterial blood pressure of 40 mm Hg for 60 mins. Resuscitation was then induced by reinjecting shed blood followed by NaCl 0.9% to maintain arterial blood pressure within control values. Treated rats received the free radical scavenger N-2-mercaptopropionyl glycine (MPG; 20mg/kg iv bolus 30 mins before resuscitation followed by 20 mg/kg/hr). MEASUREMENTS AND MAIN RESULTS: MPG reduced the volume of saline necessary to restore blood pressure during resuscitation (untreated 85+/-6; MPG 35+/-5 mL/kg; p < .05). As compared with untreated rats, MPG markedly reduced the systemic and mesenteric plasma concentrations of tumor necrosis factor (TNF)-alpha (as measured by ELISA) and interleukin (IL)-6 (as measured by bioassay), assessed at the end of resuscitation. MPG also reduced TNF-alpha and IL-6 mRNA expression (as measured by reverse transcriptase-polymerase chain reaction) assessed in peritoneal macrophages isolated from shock rats. Finally, in vitro experiments showed that MPG also markedly reduced the mRNA expression and release of TNF-alpha and IL-6 in peritoneal macrophages isolated from normal rats and subjected to hypoxia and reoxygenation. CONCLUSION: Reactive oxygen species contribute to the production of proinflammatory cytokines during posthemorrhage resuscitation. Free radicals scavengers may be a useful treatment in the prevention of the systemic inflammatory response that occurs in shock states.

[Systemic and regional hemodynamic effects of a new angiotensin converting enzyme and neutral endopeptidase mixed inhibitor, alatriopril, in the dog]. / Effets hémodynamiques systémiques et régionaux d'un nouvel inhibiteur mixte de l'enzyme de conversion de l'angiotensine et de l'endopeptidase neutre, l'alatriopril, chez le chien.

Alatriopril is a dual inhibitor of two cell surface metallopeptidases which play important roles in the regulation of arterial blood pressure and renal function: the angiotensin I converting enzyme (ACE) which catalyses transformation of angiotensin I to angiotensin II, and the neutral endopeptidase (NEP; EC 3.4.24.11; atriopeptidase), responsible for the degradation of the atrial natriuretic factor (ANF). The purpose of the present study was to evaluate the systemic and regional hemodynamic effects of alatrioprilat, the active part of alatriopril, in 6 anesthetized, closed-chest beagle dogs instrumented for the measurement of arterial pressure (aortic catheter), cardiac output (thermodilution), as well as femoral and renal artery flows (Doppler). Animal received alatrioprilat at the doses of 1 and 10 mg/kg (i.v. bolus). Hemodynamic parameters were measured at baseline, then 15, 30, 45 and 60 min after administration of each dose. In addition, plasma ANF and ACE activity were determined at baseline and 30 min after administration. At the dose of 1 mg/kg, alatrioprilat dit not induce marked hemodynamic effects, except a transient hypotension which appeared within the first 10 min after administration and lasted less than 10 min. Neither plasma ANF nor angiotensin converting enzyme activity were affected by this dose.(ABSTRACT TRUNCATED AT 250 WORDS)