Priming of Peyer's patch lymphoid cells by hemorrhagic shock and resuscitation to produce superoxide radical

Rons formation under restrictive reperfusion does not affect organ dysfunction early after hemorrhage and trauma

Reactive oxygen species have been implicated in the pathophysiology of early reperfusion. We aimed to determine 1) reactive oxygen and nitrogen species (RONS) formation in organs of rats and 2) its pathophysiological relevance during a phase of restrictive reperfusion after hemorrhagic/traumatic shock (HTS). Fifty-seven male Sprague-Dawley rats were subjected to a clinically relevant HTS model, featuring laparotomy, bleeding, and a phase of restrictive reperfusion. The RONS scavenger 1-hydroxy-3-carboxy-2,2,5,5-tetramethyl-pyrrolidine hydrochloride (continuous i.v. infusion) and electron paramagnetic resonance spectroscopy were applied for RONS (primarily superoxide and peroxynitrite) detection. Compared with sham-operated animals, the organ-specific distribution of RONS changed during restrictive reperfusion after HTS. Reactive oxygen and nitrogen species formation increased during restrictive reperfusion in red blood cells and ileum only but decreased in the kidney and remained unchanged in other organs. Hemorrhagic traumatic shock followed by restrictive reperfusion resulted in metabolic acidosis, dysfunction of liver and kidney, and increased oxidative burst capacity in circulating cells. Plasma RONS correlated with shock severity and organ dysfunction. However, RONS scavenging neither affected organ dysfunction nor oxidative burst capacity nor myeloperoxidase activity in lung when compared with the shock controls. In summary, a phase of restrictive reperfusion does not increase RONS formation in most organs except in intestine and red blood cells. Moreover, scavenging of RONS does not affect the early organ dysfunction manifested at the end of a phase of restrictive reperfusion.

EFFECTS OF MANGANESE SUPEROXIDE DISMUTASE NEBULIZATION ON PULMONARY FUNCTION IN AN OVINE MODEL OF ACUTE LUNG INJURY

Smoke inhalation injury is a major cause of morbidity and mortality in thermally injured individuals. There is evidence of increased oxygen free radical activity, e.g., superoxide, in association with smoke inhalation injury. Because superoxide dismutase converts the reactive superoxide radical to peroxide, we hypothesized that nebulization of manganese superoxide dismutase (Mn-SOD) into the airway might attenuate pulmonary dysfunction secondary to smoke inhalation injury. The present study was designed as a prospective, controlled, and randomized laboratory experiment to determine the effects of aerosolized Mn-SOD on lung fluid balance, as indexed by changes in pulmonary microvascular permeability, lung lymph flow (Q(L)), and gas exchange in an established and clinically relevant ovine model of smoke inhalation injury. Fifteen female Merino sheep were chronically instrumented with a femoral arterial, a Swan-Ganz, and a left atrial catheter. In addition, the right caudal mediastinal lymph node was cannulated to measure Q(L) (mL.h(-1)). Pneumatic occluders were placed around the right pulmonary veins for the determination of the reflection coefficient (sigma). After 7 days of recovery, sheep were randomly allocated to (a) an untreated control group (4 groups of 12 breaths of cotton smoke), (b) an injured group treated with nebulized Mn-SOD (5 mg/kg), and (c) an injured group that received only the vehicle (nebulized saline). Nebulization was performed 1 h and 12 h after smoke inhalation. Mn-SOD nebulization attenuated the increase in both filtration coefficient and sigma and significantly decreased lung tissue conjugated dienes. However, there were no differences in Q(L), PaO2/FiO2 ratio, and bloodless lung wet/dry weight ratio between groups. Although Mn-SOD nebulization attenuated the loss of protein, it failed to improve lung edema and pulmonary gas exchange, thereby limiting its clinical use.

Comparative investigation of superoxide trapping by cyclic nitrone spin traps: the use of singular value decomposition and multiple linear regression analysis

The kinetics of the reaction between superoxide and the spin trapping agents 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide (DEPMPO), and 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO) were re-examined in the superoxide-generating xanthine/xanthine oxidase system, by competition with spontaneous dismutation. The approach used singular value decomposition (SVD), multiple linear regression, and spectral simulation. The experiments were carried out using a two-syringe mixing arrangement with fast scan acquisition of 100 consecutive EPR spectra. Using SVD analysis, the extraction of both temporal and spectral information could be obtained from in a single run. The superoxide spin adduct was the exclusive EPR active species in the case of DEPMPO and BMPO, and the major component when DMPO was used. In the latter case a very low concentration of hydroxyl adduct was also observed, which did not change during the decay of the DMPO-superoxide adduct. This indicates that the hydroxyl radical adduct is not formed from the spontaneous decay of the superoxide radical adduct, as has been previously suggested [correction]. It was established that in short-term studies (up to 100 s) DMPO was the superior spin trapping agent, but for reaction times longer than 100 s the other two spin traps were more advantageous. The second order rate constants for the spin trapping reaction were found to be DMPO (2.4 M(-1)s(-1)), DEPMPO (0.53 M(-1)s(-1)), and BMPO (0.24 M(-1)s(-1)) determined through competition with spontaneous dismutation of superoxide, at pH 7.4 and 20 degrees C.

The gastrointestinal tract: a major site of antioxidant action?

Diets rich in fruits and vegetables delay the onset of many age-related diseases, and contain a complex mixture of antioxidants (including ascorbate, carotenoids, vitamin E and other phenolics such as the flavonoids). However, diet also contains pro-oxidants, including iron, copper, H2O2, haem, lipid peroxides and aldehydes. Nitrite is frequently present in diet, leading to generation of reactive nitrogen species in the stomach. In considering the biological importance of dietary antioxidants, attention has usually focussed on those that are absorbed through the gastrointestinal tract into the rest of the body. In the present paper we develop the argument that the high levels of antioxidants present in certain foods (fruits, vegetables, grains) and beverages (e.g. green tea) play an important role in protecting the gastrointestinal tract itself from oxidative damage, and in delaying the development of stomach, colon and rectal cancer. Indeed, carotenoids and flavonoids do not seem to be as well absorbed as vitamins C and E. Hence their concentrations can be much higher in the lumen of the GI tract than are ever achieved in plasma or other body tissues, making an antioxidant action in the GI tract more likely. Additional protective mechanisms of these dietary constituents (e.g. effects on intercellular communication, apoptosis, cyclooxygenases and telomerase) may also be important.

Effects of blood resuscitation versus dextran resuscitation after hemorrhage on intrinsic myocardial function

BACKGROUND

Myocardial function is altered by many factors present in hemorrhaged and resuscitated animals. The purpose of this study was to determine whether resuscitation after a short period of hemorrhagic shock, which by itself did not alter intrinsic cardiac function, causes dysfunction.

METHODS

Guinea pigs were instrumented to measure blood pressure and cardiac output, and several days later 50% of their blood volume was removed at a rate of 1 mL/min. Some animals were resuscitated with the shed blood and some with 6% dextran. Hearts were studied 1 or 24 hours after resuscitation.

RESULTS

Isolated hearts from animals after 1 hour of resuscitation demonstrated dysfunction whether resuscitated with blood or dextran, although dysfunction was more severe with blood resuscitation. By 24 hours, dysfunction was essentially reversed.

CONCLUSIONS

Resuscitation after hemorrhagic shock caused injury to the myocardium independent of the hemorrhage. Blood resuscitation resulted in greater dysfunction than did resuscitation with dextran.

Activation of the superoxide-generating NADPH oxidase of intestinal lymphocytes produces highly reactive free radicals from sulfite

The objective of this study was to investigate the ability of immune cells of the small intestine to produce highly reactive free radicals from the food additive sulfites. These free radicals were characterized with a spin-trapping technique using the spin traps 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). In the presence of glucose, purified lymphocytes from intestinal Peyer's patches (PP) and mesenteric lymph nodes (MLN) were stimulated with phorbol 12-myristate 13-acetate (PMA) to produce superoxide and hydroxyl DEPMPO radical adducts. The formation of these adducts was inhibited by superoxide dismutase or diphenyleneiodonium chloride, indicating that these cells produced superoxide radical during reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation. With the treatment of sodium sulfite, PMA-stimulated PP lymphocytes produced a DEPMPO-sulfite radical adduct and an unknown radical adduct. When DEPMPO was replaced with DMPO, DMPO-sulfite and hydroxyl radical adducts were detected. The latter adduct resulted from DMPO oxidation by sulfate radical, which was capable of oxidizing formate or ethanol. Oxygen consumption rates were further increased after the addition of sulfite to PMA-stimulated lymphocytes, suggesting the presence of sulfiteperoxyl radical. Taken together, oxidants generated by stimulated lymphocytes oxidized sulfite to sulfite radical, which subsequently formed sulfiteperoxyl and sulfate radicals. The latter two radicals are highly reactive, contributing to increased oxidative stress, which may lead to sulfite toxicity, altered functions in intestinal lymphocytes, or both.