Nitric oxide in shock

Mesenteric lymph duct ligation improves survival in a lethal shock model

The goal of this study was to test the hypothesis that factors released from the gut and carried in the mesenteric lymph contribute to mortality in a lethal gut I/R model. To test this hypothesis, a lethal splanchnic artery occlusion (SAO) shock model was used in male Sprague-Dawley rats. In the first set of experiments, ligation of the mesenteric lymph duct (LDL), which prevents gut-derived factors carried in the intestinal lymphatics from reaching the systemic circulation, significantly improved 24-h survival after a 20-min SAO insult (0% vs. 60% survival; P < 0.05). This increase in survival in the LDL-treated rats was associated with a blunted hypotensive response. Because increased iNOS-induced NO levels have been implicated in SAO-induced shock, we measured plasma nitrite/nitrate levels and liver iNOS protein levels in a second group of animals. Ligation of the mesenteric lymph duct significantly abrogated the SAO-induced increase in plasma nitrite/nitrate levels and the induction of hepatic iNOS (P < 0.05). In an additional series of studies, we documented that LDL increased not only 24-h but also long-term 7-day survival. During the course of these studies, we made the unexpected finding that Sprague-Dawley rats from different animal vendors had differential resistance to SAO, and that the time of the year that the experiments were carried out also influenced the results. Nonetheless, in conclusion, these studies support the hypothesis that factors carried in the mesenteric lymph significantly contribute to the development of irreversible shock after SAO.

Therapeutic effects of erythropoietin in murine models of endotoxin shock

OBJECTIVE

Erythropoietin has recently emerged as a cytoprotective cytokine, which possesses the ability to protect many tissues, including the brain, heart, and kidneys, against ischemia or traumatic injury. We investigated the therapeutic effects of erythropoietin in a murine model of endotoxin shock.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Male BALB/c mice.

INTERVENTIONS

Mice intraperitoneally received either lipopolysaccharide (LPS) from Escherichia coli or vehicle. Erythropoietin was administered at a dose of 1000 IU/kg subcutaneously at different time points after LPS administration. We also investigated the effect of erythropoietin on the development of septic shock caused by cecal perforation.

MEASUREMENTS AND MAIN RESULTS

Treatment of mice with erythropoietin, within 2 hours after LPS administration, improved the mortality rate. Treatment of cecal perforated mice with erythropoietin extended survival by 12 hours, but all animals died by 72 hours in both groups. Erythropoietin attenuated apoptosis in the lungs, liver, small intestine, thymus, and spleen, as assessed by terminal deoxynucleotidyl transferase-mediated nucleotide nick-end labeling staining, active caspase-3 immunostaining and immunoblotting, and measurements of caspase-3/7 activity. Erythropoietin also reduced inducible nitric oxide synthase expression, nitric oxide production, peroxynitrite formation, and tissue hypoxia. In contrast, erythropoietin did not affect the degree of LPS-induced inflammation, as assessed by measurements of blood levels of interleukin-1beta, interleukin-6, tumor necrosis factor-alpha, growth-related oncogene/keratinocyte-derived cytokine, and high mobility group box 1, the phosphorylation levels of nuclear factor kappaB, and the number of neutrophils infiltrating the lungs and the liver.

CONCLUSIONS

The results of the study demonstrate that administration of a large dose of erythropoietin after induction of experimental endotoxemia improved survival and that the beneficial effects of erythropoietin were associated with inhibition of apoptosis, nitric oxide production, and tissue hypoxia, without alterations in inflammatory responses.

Preconditioning with ozone/oxygen mixture induces reversion of some indicators of oxidative stress and prevents organic damage in rats with fecal peritonitis

OBJECTIVE AND DESIGN

Reactive oxygen and nitrogen species are involved in the pathogenesis of sepsis syndrome with peritonitis and the septic shock. The aim of this study was to determine whether ozone oxidative preconditioning (OOP) may exert beneficial effects in the prevention and treatment of sepsis syndrome in rats inoculated by the intraperitoneal route (i.p.) with fecal material and also to determine if antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) may exert protective effects against this systemic inflammatory disorder.

MATERIALS AND METHODS

Male Wistar rats were used. SOD and GPx activities were determined in erythrocytes. Thiobarbituric acid reactive substances (TBARS) content as biomarkers of oxidative stress, alanine amino transferase (ALT), aspartate amino transferase (AST) and creatinine (CRE) were measured in blood serum and myeloperoxidase (MPO) in lung tissue as markers of organs damage.

RESULTS

In rats submitted to OOP, SOD and GPx activities were significantly increased and it was accompanied by significant decrease of TBARS content in blood serum. OOP also significantly reduced levels of ALT, AST and CRE in blood serum as well as MPO in rat lung.

CONCLUSION

The results support the important role of SOD and GPx in the protective effects of OOP against organ damage induced by fecal peritonitis in rats.

Asymmetric dimethylarginine in hematological malignancies: a preliminary study

Asymmetric dimethylarginine (ADMA) is a product of protein hydrolysis and an endogenous competitive inhibitor of nitric oxide synthase. It is considered a new independent risk factor for endothelial dysfunction and cardiovascular diseases. Increased protein turnover, oxidative stress and impaired dimethylarginine dimethylaminohydrolase activity occurring in hematological malignancies may lead to increased dimethylarginines production. We have measured ADMA, symmetric dimethylarginine (SDMA) and L-arginine plasma levels in 43 patients with different types of hematological malignancies and in control group of 43 healthy volunteers. Mean ADMA and L-arginine plasma levels were higher in hematological group than in control group (1.59 vs 0.64; p<0.001 and 34.84 vs 28.35; p=0.044 respectively). Mean plasma levels of SDMA were not significantly different between the groups. Elevated ADMA plasma levels in patients with hematological malignancies interfere with nitric oxide metabolism and may influence their prognosis. Further prognostic studies are postulated to assess this phenomenon.

Is There NO Treatment For Severe Sepsis?

Sepsis is a systemic inflammatory response syndrome in the presence of suspected or proven infection, and it may progress to or encompass organ failure (severe sepsis) and hypotension (septic shock). Clinicians possess an arsenal of supportive measures to combat severe sepsis and septic shock, and some success, albeit controversial, has been achieved by using low doses of corticosteroids or recombinant human activated protein C. However, a truly effective mediator-directed specific treatment has not been developed yet. Treatment with low doses of corticosteroids or with recombinant human activated protein C remains controversial and its success very limited. Attempts to treat shock by blocking LPS, TNF or IL-1 were unsuccessful, as were attempts to use interferon-gamma or granulocyte colony stimulating factor. Inhibiting nitric oxide synthases held promise but met with considerable difficulties. Scavenging excess nitric oxide or targeting molecules downstream of inducible nitric oxide synthase, such as soluble guanylate cyclase or potassium channels, might offer other alternatives.

Dopamine modulates perioperative renal medulla aquaporin 2 expression in experimental obstructive jaundice

AIM: To investigate the changes in aquaporin 2 expression after bile duct recanalization and the effects of low-dose dopamine on perioperative renal aquaporin 2 expression.

METHODS: Seventy wistar rats were randomly allocated to 4 groups. Sixty rats underwent common bile duct ligation, while the other 10 underwent sham operation. The common duct was ligated on a silicon tube of 2 mm external diameter. Seven days later, the experimental rats were randomly allocated into another 3 groups. Rats in the obstructive jaundice group were injected with 9 g/L normal saline (NS), while those in the other 2 groups were injected with dopamine at 5 or 10 µg/(kg•min), respectively. After 2 h treatment, half in each group were killed and the others were killed 24 h later. Serum was collected from each rat to assess hepatic and renal functions. The right renal medulla was separated and kept at -80℃ until used to measure aquaporin 2 expressions by Western blotting.

RESULTS: In the early period of bile duct recanalization, serum bilirubin levels decreased. There were no significant changes in blood urine or creatine. Renal aquaporin 2 expression was detected by Western blotting. Aquaporin 2 expression in the experimental group treated with dopamine 5 µg/(kg•min) was nearly the same as that in the normal group, both at 0 and 24 h (16 010 ± 646 and 22 715 ± 575 vs 21 966 ± 1544 and 21 917 ± 2661), and better than the group treated with dopamine 10 µg/(kg•min).

CONCLUSION: Low-dose dopamine injection appears to modulate expression of aquaporin 2 in the renal collective tubule epithelium, and to have a positive effect on perioperative renal function in obstructive jaundice.