[Albumin in sepsis]

Human serum albumin is a small (66kD) globular protein representing over 60 % of the total plasma protein content. It is made up of 585 amino 6 acids and contains 35 cysteine residues forming disulfide bridges that contribute to its overall tertiary structure. It has a free cysteine-derived thiol group at Cys-34, which accounts for 80 % of its redox activity. Physiologically, serum albumin exists in a reduced form with a free thiol contributing to its antioxidant properties. It is synthesized primarily in the liver and is an acute-phase protein. It is a multifunctional plasma protein ascribed ligand-binding and transport properties as well as antioxidants and enzymatic functions. It maintains colloid osmotic pressure, modulates inflammatory response and may influence oxidative damage. Hypoalbuminemia is common in the intensive care unit and may be due to decreased synthesis by the liver and/or to increased losses or increased proteolysis and clearance. Although albumin was long used to control vascular collapse in critically ill patients, the evidence suggests that it does not offer a benefit over crystalloid solutions in vascular collapse. However, human serum albumin is an important circulating antioxidant and it may be beneficial in critically ill patients to limit oxidative damage. A number of studies suggest that in specific groups of hypoalbuminemic critically ill patients, albumin administration may have beneficial effects on organ function, although the exact mechanisms remain undefined. Further trials are needed to confirm theses observations and to clearly demonstrate whether albumin should be administered in critically ill patients with hypoalbuminemia.

[Aortic bioprosthesis implanted percutaneously: three year follow up]

Percutaneous implantation of a bioprosthesis for the treatment of degenerative aortic stenosis ushered in a new era for interventional cardiology, and now represents the best therapeutic option for a growing number of patients for whom surgical aortic replacement would be too risky. This is the case in about a third of symptomatic patients affected. Between 2003 and 2005, we performed initial feasibility studies (I-REVIVE and RECAST) in Rouen, on non-operable patients in a critical state, included for purely compassionate reasons. The valve used was a pericardial bioprosthesis mounted in an expandable balloon stent. The mean age of the patients was 80 years, all had multiple co-morbidity and had been turned down by the cardiac surgeons. In 33 of the 36 included patients, the technique was attempted by the anterograde trans-septal approach (n=27, success rate 80%) or by the retrograde arterial route (n=7, success rate 57%). Echocardiography following implantation revealed a final aortic surface area of 1.70 cm2 and a transvalvular gradient of 9 mmHg. A significant paravalvular aortic leak was noted in 5 cases. There were 6 deaths by 1 month, related to the procedure, and 10 deaths by 6 months, from non-cardiac causes and not related to the procedure. There was no occurrence of coronary occlusion, secondary displacement or dysfunction of the prosthesis. In December 2006, 8 patients reached 2 years of follow up, and two others reached 3 years, symptom free and still with an unchanged valvular function. Significant technological improvements have made the technique simpler, quicker and safer, with very much improved short and long term results. The new trans-apical approach is under evaluation with some promising initial results. More than 280 patients have been implanted to date. Other implantable prostheses are under evaluation. This therapeutic modality looks likely to develop rapidly, and in the near future it should offer a new and optimal solution for all high surgical risk or non-operable patients.

[Interest of D-lactate as a colic hypoperfusion marker during aortic abdominal aneurysm surgery]

OBJECTIVE

D-lactate is the dextrogyre form of the lactate usually measured in intensive care. Its bacterial origin should make it a marker of translocation during gut ischemia. The aim was to test D-lactate as a postoperative marker of colic hypoperfusion measured during aortic surgery.

STUDY DESIGN

Prospective observational cohort study.

PATIENTS AND MEASUREMENTS

Patients operated for abdominal aortic aneurysm. Two groups were stratified on inferior mesenteric arterial residual pressure (IMArP) measured during the surgery: Colic hypoperfusion during surgery (CHs) group: patients with an IMArP < 40 mmHg.

CONTROL GROUP

patients with an IMArP > or = 40 mmHg. Baseline data such as age, duration of aortic clamping and severity score (IGS II) were collected. The D-lactate was measured in postoperative at admission time in ICU and then daily. D-lactate(max) defined the maximum value of D-lactate for one patient.

MAIN RESULTS

Twenty-nine patients were included, 23 in the control group and 6 in the CHs group. Groups were comparable at baseline. D-lactate(max) was significantly higher in the CHs group (median: 0.13 mmol/l; min-max: 0.03-0.9 mmol/l) than in the control group (0.03; 0-0.26 mmol/l, p=0.007).

CONCLUSION

D-lactate could be postoperative marker of colic hypoperfusion measured during surgery for abdominal aortic aneurysm.

Changes in severity and organ failure scores as prognostic factors in onco-hematological malignancy patients admitted to the ICU

OBJECTIVE

To determine whether severity and organ failure scores over the first 3 days in an ICU predict in-hospital mortality in onco-hematological malignancy patients.

DESIGN AND SETTING

Retrospective study in a 22-bed medical ICU.

PATIENTS

92 consecutive patients with onco-hematological malignancies including 20 hematopoietic stem cell transplantation (HSCT) patients (11 with allogenic HSCT).

MEASUREMENTS

Simplified Acute Physiology Score (SAPS) II, Organ Dysfunction and/or Infection (ODIN) score, Logistic Organ Dysfunction System (LODS), and Sequential Organ Failure Assessment (SOFA) score were recorded on admission. The change in each score (Delta score) during the first 3 days in the ICU was calculated as follows: severity or organ failure score on day 3 minus severity or organ failure score on day 1, divided by severity or organ failure score on day 1.

RESULTS

In-hospital mortality was 58%. Using multivariate analysis in-hospital mortality was predicted by all scores on day 1 and all Delta scores. Areas under the receiver operating characteristics curves were similar for SAPS II (0.78), ODIN (0.78), LODS (0.83), and SOFA (0.78) scores at day 1. They were also similar for DeltaSAPS II, DeltaODIN, DeltaLODS, and DeltaSOFA. Similar results were observed when excluding patients with allogenic HSCT.

CONCLUSION

Severity and three organ failure scores on day 1 and Delta scores perform similarly in predicting in-hospital mortality in ICU onco-hematological malignancy patients but do not predict individual outcome. Decision to admit such patients to the ICU or to forgo life-sustaining therapies should not be based on these scores.

[Quality of care assessment and nosocomial pneumonia in the intensive care unit]

INTRODUCTION

Nosocomial pneumonia (NP) is a major cause of infection in the intensive care unit and is responsible for a significant increase in morbidity, mortality and healthcare costs. Ventilator-associated pneumonia is the most frequent and severe form of NP.

STATE OF ART

Assessment of the quality of care and healthcare practices relating to the prevention and treatment of nosocomial pneumonia represents a potentially vast area but has been little studied in the literature. Difficulties include the lack of either a "gold standard" for diagnosis, or standardization of techniques for microbiological sampling and, therefore, the lack of reliable indicators of performance in the management of NP. Currently, published data mainly involve diagnostic strategies, preventive measures and antibiotic therapy.

PERSPECTIVES AND CONCLUSIONS

In line with the latest published recommendations, clinicians should continue their efforts in this field to improve the management and reduce the impact of NP in the intensive care unit.

Serum erythropoietin levels in septic shock

Erythropoietin is a glycoprotein hormone mainly released by the kidney, which stimulates red blood cell production. However, in sepsis, the mechanisms responsible for the final increase in circulating erythropoietin remain unclear Seventeen critically ill patients with Simplified Acute Physiologic Score average 66 (range 43 to 103) were included in this study. Ten patients survived and seven died within 28 days. Blood samples obtained at different times were assayed for erythropoietin, cytokine levels and lactate measurements. PCO2 gap was assessed to detect the presence of gastric mucosal acidosis. Erythropoietin decreased in the patients who survived while it remained high or increased in non-survivors (37+/-6.5 vs 147+/-6. 7 UI/l respectively, P<0.05). Erythropoietin plasma levels were correlated with IL-6 levels (r=0.84, P<0.05) and TNFalpha levels (r=0.84, P<0.05). We observed a significant positive relationship between erythropoietin plasma levels and lactate concentrations (r= 0.89, P< 0. 05) and with PCO2 gap (r=0.9, P < 0.05). No correlation was found between erythropoietin concentration and the other parameters. High serum erythropoietin levels in non-survivors were observed with septic shock despite an increase in the levels of proinflammatory cytokines. We found a relationship between erythropoietin concentration and biological markers of tissue hypoperfusion i.e. lactate levels or PCO2 gap. This relationship could suggest tissue hypoperfusion as the stimulating factor for erythropoietin production in septic shock.

[Bickerstaff's brainstem encephalitis]

INTRODUCTION

Bickerstaff's brainstem encephalitis represents a differential diagnostic that must be discuss with meningoencephalitis with ophtalmoplegia, ataxia and confusion.

EXEGESE

A 26 year-old woman presented a Bickerstaff syndrome. A severe disturbance of consciousness had lead to admission in intensive care unit with mechanical ventilation. Electrophysiological tests and the brain magnetic resonance were normal. We have not observed systemic anti-G1Qb antibody in our patient. Nevertheless, 66% of patients with Bickerstaff syndrome have anti-GQ1b antibody during the acute phase period. We observed a beneficial effect of IV Ig treatment although no significant improvement was observed with corticosteroids.

CONCLUSION

Controlled clinical trials are needed to established the efficacy of IV Ig or plasmapheresis as a specific therapy for this pathology.

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.

A shock associated with adult-onset Still's disease

Only two cases of adult-onset Still's disease associated with shock have been previously described. We report a case of shock in a man with adult-onset Still's disease and discuss the relationship between the two processes by assessing tumor necrosis factor-alpha, procalcitonin and interleukin-6 concentrations.

Improvement of endothelial function by chronic angiotensin-converting enzyme inhibition in heart failure : role of nitric oxide, prostanoids, oxidant stress, and bradykinin

BACKGROUND-Chronic heart failure (CHF) impairs the endothelium-dependent, flow-mediated dilation (FMD) of small arteries. However, whether chronic angiotensin-converting enzyme (ACE) inhibition affects the impairment of FMD in CHF is unknown. We investigated the effects of long-term ACE inhibition on the FMD of peripheral arteries in rats with CHF and the mechanism(s) involved. METHODS AND RESULTS-FMD was assessed in isolated, perfused gracilis muscle arteries from sham-operated, and untreated or ACE inhibitor-treated (perindopril 2 mg. kg(-1). day(-1) for 10 weeks) rats with CHF (coronary artery ligation). The role of nitric oxide (NO), prostaglandins, and free radicals was assessed by pretreating the vessels with the NO synthase inhibitor N(W)-nitro-L-arginine, the cyclooxygenase inhibitor diclofenac, or the free radical scavenger N-2-mercaptopropionyl-glycine (MPG). Endothelial NO synthase mRNA expression was determined by reverse transcriptase polymerase chain reaction. In animals with hemodynamic and echographic signs of CHF, FMD was converted into vasoconstriction, and this was prevented by ACE inhibition. FMD of arteries from sham-operated or ACE inhibitor-treated CHF rats was abolished by N(W)-nitro-L-arginine. In untreated CHF rats, FMD was increased by diclofenac and MPG. In contrast, in arteries from ACE inhibitor-treated rats, neither diclofenac nor MPG affected FMD. In parallel, ACE inhibition prevented the reduction of endothelial NO synthase mRNA by CHF. CONCLUSIONS-In CHF, ACE inhibition normalized NO-dependent dilatation and suppressed the production of vasoconstrictor prostanoid(s), resulting in improved FMD. The improvement of FMD might contribute to the beneficial effects of ACE inhibition during CHF.

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.

Fomepizole (4-methylpyrazole) in fatal methanol poisoning with early CT scan cerebral lesions

BACKGROUND

Methanol poisoning, potentially fatal, is generally treated with the combination of ethanol as antidote, and hemodialysis. Fomepizole, a competitive inhibitor of alcohol dehydrogenase, has more recently been used, and is capable of blocking the toxic metabolism of methanol. To our knowledge, its use has never been reported as an antidote in severe methanol poisoning requiring hemodialysis.

CASE REPORT

We report a case of fatal methanol poisoning (1.9 g/L on admission) suspected due to the combined presence of coma and severe metabolic acidosis with normokalaemia.

CONCLUSION

The fomepizole treatment protocol (10 mg/kg by i.v. infusion over 1 hour before dialysis, repeated 12 hours later in combination with 1.5 mg/kg/h during dialysis) was simple to use and appeared effective in eliminating methanol in combination with hemodialysis. The case is also unusual in terms of severity and the early onset of cerebral lesions demonstrated by computed tomography (CT) scan.

Protective effects of preconditioning in cultured rat endothelial cells: effects on neutrophil adhesion and expression of ICAM-1 after anoxia and reoxygenation

BACKGROUND

Preconditioning with brief periods of ischemia protects the coronary endothelium against acute and chronic reperfusion injury, but the mechanisms of this endothelial protection remain unknown. We hypothesized that preconditioning protects endothelial cells through a decreased production of endothelial adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1), leading to a lesser adhesion of neutrophils to the endothelium.

METHODS AND RESULTS

Cultured rat aortic endothelial cells were subjected to 6-hour anoxia followed by various durations of reoxygenation. Preconditioning was induced by 1-hour anoxia and 1-hour reoxygenation. ICAM-1 gene expression was measured by polymerase chain reaction, and the percentage of cells expressing ICAM-1 was assessed by confocal laser fluorescence microscopy. Anoxia/reoxygenation increased expression of ICAM-1, with a peak occurring after 6 hours of reoxygenation for mRNA and 9 hours for protein. Preconditioning prevented the increase in ICAM-1. Similar reductions were observed with the free radical scavenger N-2 mercaptopropionyl glycine (MPG). The inhibitory effect of preconditioning on ICAM-1 expression was abolished by an inhibitor of protein kinase C, an inhibitor of nitric oxide synthesis, and by MPG but was not affected by an adenosine receptor antagonist. Finally, both preconditioning and MPG partially prevented the increased adhesion of human neutrophils to reoxygenated endothelial cells.

CONCLUSIONS

Preconditioning prevented reoxygenation-induced, free radical-mediated expression of ICAM-1 by a mechanism involving activation of protein kinase C and production of nitric oxide and free radicals, and this is associated with a lesser adhesion of neutrophils to endothelial cells. Such prevention of neutrophil adhesion may contribute to the protective effect of preconditioning against reperfusion-induced endothelial injury.

Noninvasive ventilation as a systematic extubation and weaning technique in acute-on-chronic respiratory failure: a prospective, randomized controlled study

Prolonged duration of endotracheal mechanical ventilation (ETMV) is associated with an increased morbidity and mortality in intensive care unit (ICU) patients. The aim of this study was to assess the usefulness of noninvasive ventilation (NIV) as a systematic extubation and weaning technique to reduce the duration of ETMV in acute-on-chronic respiratory failure (ACRF). Among 53 consecutively intubated patients admitted for ACRF, we conducted a prospective, randomized controlled trial of weaning in 33 patients who failed a 2-h T-piece weaning trial (2 h-WT) although they met simple criteria for weaning. Conventional invasive pressure support ventilation (IPSV) was used as the control weaning technique in 16 patients (IPSV group), and NIV was applied immediately after extubation in 17 patients (NIV group). The two weaning groups were similar for type of chronic respiratory failure (CRF), pulmonary function data, age, Simplified Acute Physiology Score (SAPS II), and severity of ACRF on admission. The characteristics of the two groups were also similar at randomization. In the IPSV group, 12 of 16 patients (75%) were successfully weaned and extubated, versus 13 of 17 (76.5%) in the NIV group (p = NS). NIV like IPSV significantly and similarly improved gas exchange in relation to that achieved during 2 h-WT (p < 0.05). The duration of ETMV was significantly shorter in the NIV (4.56 +/- 1.85 d) than in the IPSV group (7.69 +/- 3.79 d) (p = 0. 004). NIV also reduced the mean period of daily ventilatory support, but increased the total duration of ventilatory support related to weaning (3.46 +/- 1.42 d, versus 11.54 +/- 5.24 d with NIV; p = 0. 0001). Most patients in the IPSV group developed complications related to ETMV and/or the weaning process, but the difference was not significant (nine of 16 versus six of 17). The durations of ICU and hospital stays and the 3-mo survival were similar in the two groups. In conclusion, NIV permits earlier removal of the endotracheal tube than with conventional IPSV, and reduces the duration of daily ventilatory support without increasing the risk of weaning failures. NIV should be considered as a new and useful systematic approach to weaning in patients with ACRF who are difficult to wean.

Exercise improves flow-mediated vasodilatation of skeletal muscle arteries in rats with chronic heart failure. Role of nitric oxide, prostanoids, and oxidant stress

BACKGROUND

Flow-mediated dilatation (FMD) of the peripheral arteries may be impaired in chronic heart failure (CHF), and this could contribute to the increased peripheral resistance and exercise intolerance that occur with this disease. Physical exercise improves the FMD of large conduit arteries in CHF, but whether a similar impairment also occurs in smaller arteries is unknown. The mechanisms of the changes in FMD after CHF or exercise are also unknown.

METHODS AND RESULTS

FMD was assessed in isolated, perfused, and preconstricted gracilis muscle arteries from sham-operated rats or CHF rats (coronary artery ligation) who were either sedentary or exercised (30-minute swimming period twice a day for 10 weeks, starting 7 days after ligation). In animals with hemodynamic and echographic signs of CHF, FMD was abolished and converted into vasoconstriction (percent change in diameter after 370 microL/min flow: sham, 42+/-5%; CHF, -4+/-3%; P<0.05). Exercise partially restored FMD (18+/-3%; P<0.05 versus CHF). In sham rats, FMD was abolished by the nitric oxide-synthase inhibitor Nomega-nitro-L-arginine (L-NA) but unaffected by the cyclooxygenase inhibitor diclofenac or the free radical scavenger N-(2-mercaptopropionyl)-glycine (MPG). In arteries from sedentary CHF rats, FMD was not modified by L-NA, but it was partially restored by diclofenac or MPG. In exercised CHF rats, FMD was abolished by L-NA and only moderately improved by diclofenac or MPG. Likewise, endothelial nitric oxide synthase mRNA expression (determined by reverse transcription polymerase chain reaction at the level of the gracilis muscle) was reduced by CHF, and this was prevented by exercise.

CONCLUSIONS

CHF abolishes the FMD of small arteries by impairing the nitric oxide pathway, increasing oxidant stress, and releasing a prostanoid-contracting factor. Exercise partially restores FMD by increasing expression of endothelial nitric oxide synthase and preventing the production of vasoconstrictor prostanoids and free radicals. Such restoration of FMD might contribute to the increase in exercise capacity after physical exercise in CHF.

Induction of haem oxygenase contributes to the synthesis of pro-inflammatory cytokines in re-oxygenated rat macrophages: role of cGMP

Macrophage activation and the resulting inflammatory response may be a major component of tissue injury upon hypoxia and re-oxygenation. Activation of the haem oxygenase (HO)/carbon monoxide (CO) pathway may be an important regulator of the inflammatory response, through production of cyclic 3', 5'-monophosphate (cGMP). We have assessed whether HO contributes to the increased production of the pro-inflammatory cytokines TNF-alpha and IL-6 in re-oxygenated rat peritoneal macrophages.Hypoxia/re-oxygenation markedly increased levels of HO-1 mRNA and cGMP. The increase in cGMP was reduced by the HO-1 inhibitor tin-protoporphyrin (SnPP-9) given during re-oxygenation. Hypoxia and re-oxygenation also increased IL-6 and TNF-alpha mRNA expression, as well as IL-6 and TNF-alpha concentrations in the cell supernatant. These increases were nullified by SnPP-9 and by Methylene Blue, an inhibitor of guanylate cyclase, but were not affected by L-NNA, an inhibitor of NO synthesis. The inhibitory effect of SnPP on the synthesis of cytokines was reversed by co-administration of the stable analogue of cGMP, 8-Br-cGMP. Our results indicate that activation of haem oxygenase and of the CO/cGMP pathway is a major stimulus for the synthesis and release of pro-inflammatory cytokines in re-oxygenated macrophages. This pathway may play a central role in pathological situations in which local tissue hypoxia/re-oxygenation triggers a systemic inflammatory response, for example in patients with shock.

Heme and acute inflammation role in vivo of heme in the hepatic expression of positive acute-phase reactants in rats

Acute-phase protein synthesis in the liver during inflammation is regulated via cytokines and glucocorticoids. Using quantitative reverse transcription (RT)-PCR analysis and immunoassay, we explored, in the rat, the response of the acute-phase protein, alpha-2 macroglobulin (A2M), after systemic inflammation induced by lipopolysaccharide (LPS) or localized inflammation induced by turpentine oil (TO). The results indicate that synthesis of A2M is higher following TO-induced inflammation than LPS-induced inflammation and is not correlated with interleukin (IL)-6 or glucocorticoid levels. We studied the putative role of heme in this differential A2M expression following localized vs. systemic inflammation; addition of heme during LPS-induced inflammation can boost the expression of A2M, whereas blocking heme synthesis (by succinyl acetone) or enhancing its consumption in parallel biosynthetic pathways (cytochrome P450 induction by phenobarbital) decreases A2M expression. This decrease was abolished by exogenous heme supplementation. Finally, we demonstrate that heme supplementation is also able to increase the A2M response in female rats to a level similar to that in male rats providing a new insight into the puzzling sexual dimorphism observed previously during localized inflammation. We propose that heme should be considered a new regulatory element in controlling liver A2M expression during inflammation.

Nitric oxide synthase inhibition and the induction of cytochrome P-450 affect heme oxygenase-1 messenger RNA expression after partial hepatectomy and acute inflammation in rats

OBJECTIVES

a) To evaluate in vivo, in rat liver, heme oxygenase-1 (HO-1) messenger RNA (mRNA) expression level and the regulation of 3',5'-cyclic guanosine monophosphate (cGMP) production during hepatic regeneration, localized inflammation, and systemic inflammation; and b) to investigate the effect of the induction of cytochrome P-450 and nitric oxide synthase (NOS) inhibition on HO-1 mRNA level and cGMP production in the liver.

DESIGN

Experimental, comparative study.

SETTING

Biochemical and molecular biology laboratory.

SUBJECTS

Six-wk-old male Sprague-Dawley rats (n = 60).

INTERVENTIONS

We randomly divided the rats into four groups: a) saline controls; b) animals receiving lipopolysaccharide (600 microg/kg) for systemic inflammation; c) animals receiving turpentine oil (5 mL/kg) for localized inflammation obtained by sterile abscess; and d) partially hepatectomized animals (two-thirds removal of the parenchyma) for hepatic regeneration.

MEASUREMENTS AND MAIN RESULTS

Hepatic regeneration induced HO-1 mRNA expression, as shown by quantitative reverse transcription-polymerase chain reaction analysis. The time course of liver HO-1 mRNA induction after partial hepatectomy and localized and systemic inflammation showed a similar and gradual increase, with a maximum at 6 hrs and a return to a minimal level 48 hrs after treatments. Liver HO-1 mRNA was overexpressed during localized vs. systemic inflammation. This overexpression was not correlated with either serum IL-6 or corticosterone concentrations, but is related to increased cGMP production. The administration of phenobarbital, a cytochrome P-450 inducer and of nitro-L-arginine methyl ester, a NOS inhibitor, prevented cGMP production and abolished the overexpression of HO-1 mRNA.

CONCLUSIONS

The results of this study indicate that HO-1 mRNA is induced during hepatic regeneration with a similar time course to that observed during acute inflammation. In addition, we demonstrated that: a) HO-1 mRNA is overexpressed during localized vs. systemic inflammation; b) this overexpression is not correlated with IL-6 or corticosterone concentrations but is related to intrahepatic cGMP production; c) induction of cytochromes P-450 and/or inhibition of NOS both reduce liver cGMP production and HO-1 mRNA expression. These results suggest that in rat liver, a cGMP-transducing pathway may control HO-1 mRNA expression. Thus, there may be a role for HO-1 mRNA in the modulation of the hepatic stress response.