Role of hyperbaric oxygen exposure in reduction of lipid peroxidation and in multiple organ failure induced by zymosan administration in the rat.

The aim of the present study was to evaluate the effects of hyperbaric oxygen (HBO) therapy on multiple organ failure induced by zymosan. Administration of zymosan (500 mg/kg) in the rat induced neutrophil infiltration in the lung, liver, and intestine as evaluated by increase in myeloperoxidase (MPO) activity. Therefore, lipid peroxidation was significantly increased in zymosan-treated rats. This inflammatory process coincided with the damage of lung, liver, and small intestine. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine in the lung, liver, and small intestine of zymosan-shocked rats. HBO (2 absolute Atmosphere) exposure attenuates the increase in the tissue levels of MPO and malondialdehyde (MDA) caused by zymosan in the lung, liver, and intestine. In addition, HBO (2 absolute Atmosphere) was effective in preventing the development of lung, liver, and intestine injury. Taken together, the present results demonstrate that HBO may also be an efficacious treatment in multiple organ failure induced by zymosan.

Effect of hyperbaric oxygen therapy in experimental subcutaneous and pulmonary infections due to Pseudomonas aeruginosa.

About 80% of nosocomial infections are caused by aerobic bacteria. Pseudomonas aeruginosa is a Gram-negative bacterium belonging to the Pseudomonadaceae family; P. aeruginosa is responsible for 6-22% of all hospital infections. The aim of this study was to evaluate the efficacy of hyperbaric oxygen (HBO2) therapy (2 atm abs x 55 min.day-1) alone for 8 days and combined with antibiotic chemotherapy (amikacin 15 mg.kg-1.day-1 for 8 days by intraperitoneal route) in rats infected subcutaneously and via the pulmonary route. In the rats infected by P. aeruginosa, HBO2 induced a reduction in mortality and morbidity with bacteria eradication in blood culture, bronchial aspirate, and skin biopsies when compared to control. These effects were increased by the use of amikacin, an antibiotic used for the treatment of sensitive Gram-negative bacteria.

Effects of hyperbaric oxygen exposure on a zymosan-induced shock model.

OBJECTIVE: To evaluate the effects of hyperbaric oxygen (HBO) therapy on zymosan-induced shock in rats. Zymosan, a cell wall component of the yeast Saccharomyces cerevisiae, induces inflammation by causing the production of various cytokines and pro-inflammatory mediators. The administration of zymosan to rats represents a new experimental shock model by inducing acute peritonitis, severe hypotension, and signs of systemic illness. However, it has been recently proposed that the zymosan-induced shock, like septic shock, may be mediated by overproduction of nitric oxide. DESIGN: Experimental study. SETTING: Institute of Pharmacology and Toxicology, 2nd University of Naples, Naples, Italy. SUBJECTS: Male rats were treated with zymosan (500 mg/kg) by intraperitoneal route, with HBO (2 Absolute Atmosphere) or with zymosan and HBO (2 Absolute Atmosphere). MEASUREMENTS AND MAIN RESULTS: Peritoneal exudate, plasma, and peritoneal nitric oxide metabolites (NOx) and zymosan determined a time-dependent increase in peritoneal and plasma NOx concentrations, and peritoneal leukocytes were determined. Moreover, symptomatology was observed. The administration of zymosan caused the appearance of a severe illness in the rats characterized by ruffled fur, lethargy, conjunctivitis, diarrhea, and a significant loss of body weight. All zymosan-treated rats developed an acute peritonitis, producing turbid exudate. Zymosan determined a time-dependent increase in peritoneal, plasma NOx, and tumor necrosis factor (TNF)-alpha concentrations. Morbidity of zymosan shocked rats has been attenuated and no mortality was observed by treatment with HBO. These findings were associated with a significant reduction either of peritoneal leukocytes and exudate, or plasma and peritoneal NOx concentrations. Moreover, TNF-alpha levels were significantly reduced in animals shocked by zymosan and treated with HBO.

Effects of hyperbaric oxygen exposure on non-adrenergic non-cholinergic responses of rat trachea.

The effects of prolonged (20 day) hyperbaric exposure (HBO) to oxygen on non adrenergic non cholinergic (NANC) contractile and relaxant responses of rat trachea were examined. The electrical field stimulation (EFS) of rat tracheal rings was performed at 30 Hz and contractile and relaxant responses were assessed in the absence or in the presence of pretreatment with L-nitro-arginine-methyl-ester (L-NAME), an inhibitor of NO synthase, and L-Arginine (L-ARG), a precursor of NO synthesis, plus L-NAME. Our data demonstrated that L-NAME significantly (p < 0.05) enhanced the contractile responses induced by EFS (controls 30.6 +/- 0.99%; L-NAME 76.07 +/- 2.00%) and statistically (p < 0.05) reduced the relaxant component of EFS (controls 31.10 +/- 0.46; L-NAME 15.00 +/- 0.12); these effects were reversed when tissues were pretreated with L-ARG plus L-NAME, suggesting that NO plays a modulatory role in cholinergic neurotransmission and participates in EFS relaxant responses. Moreover, prolonged HBO exposure (20 days) at 202.6 and 303.9 kPa did not modify the contractile or relaxant responses induced by EFS, nor modify the L-NAME or L-ARG effects on EFS responses.

[Effects of hyperbaric oxygenation in skin and pulmonary infections caused by Pseudomonas aeruginosa]. / Effetti dell'ossigenoterapia iperbarica nelle infezioni sperimentali cutanee e polmonari da Pseudomonas aeruginosa.

About 80% of nosocomial infections are caused by aerobic bacteria. The Pseudomonas aeruginosa is a Gram-negative bacterium pertaining to the Pseudomonadaceae family. P. aeruginosa is responsible for 6-22% of all hospital infections. The aim of this paper is to evaluate the efficacy of both hyperbaric oxygen-therapy (HBO 2 Atm x 35 min/day) alone for 8 days and when associated to the chemoantibiotic therapy (amikacine 15 mg/kg/day for 8 days intraperitoneal), in rats infected through pulmonary and subcutaneous intake. In rats affected by P. aeruginosa, HBO induces a significant reduction in mortality and morbility with bacteria eradication in blood culture findings, bronchial aspirate and skin biopsies. These effects were increased by the use of amikacine which is an antibiotic used for the treatment of Gram-negative bacteria.