Hyperbaric oxygen protects against lipopolysaccharide-stimulated oxidative stress and mortality in rats

https://doi.org/10.1016/j.ejphar.2004.12.021Get rights and content

Abstract

Free radicals and proinflammatory mediators have been implicated in the pathogenesis of endotoxic shock, a disease with high mortality caused by Gram-negative bacterial endotoxin. Hyperbaric oxygen is used as an adjuvant therapy for various inflammatory diseases and shows beneficial effects in lipopolysaccharide-induced shock syndrome. However, the underlying mechanisms for these effects are still to be defined. In this study, we investigated the effect of hyperbaric oxygen on inflammatory mediators, free radicals, and mortality in endotoxic rats. Wistar–Kyoto rats were injected with lipopolysaccharide (10 mg/kg) and then exposed to aminoguanidine, an inhibitor of inducible nitric oxide (NO) synthase (bolus injection 2 h after lipopolysaccharide), or hyperbaric oxygen (2 ATA for 60 min 1, 4, 9, and 24 h after lipopolysaccharide). Plasma tumor necrosis factor alpha (TNF-α), NO, and superoxide anion were detected and the vasorelaxation response and survival rate were assessed. The results demonstrated that increases in plasma TNF-α and NO, and the vasohyporeactivity induced by lipopolysaccharide treatment were significantly inhibited by hyperbaric oxygen and aminoguanidine. Mortality and vascular superoxide anion production of lipopolysaccharide treatment were also markedly reduced by hyperbaric oxygen treatment, but were not restored by aminoguanidine. None of the parameters was changed by hyperbaric oxygen treatment alone. Thus, repeated hyperbaric oxygen exposure significantly attenuated the inflammatory mediators, free radicals, and mortality in endotoxic rats.

Introduction

Septic shock is a serious progressive failure of the circulation with a high mortality rate of 30–90% (Rangel-Frausto et al., 1995). Lipopolysaccharide evokes a septic shock-like state characterized by fever, hypotension, vasohyporeactivity to vasoactive agents, myocardial dysfunction, hypoglycemia, and multiple organ failure. It has become clear that lipopolysaccharide does not injure host tissues directly, but acts through a variety of inflammatory mediators, such as tumor necrosis factor alpha (TNF-α), interleukins, and nitric oxide (NO) (Chorinchath et al., 1996, Zhao et al., 1997). However, recent studies using antibodies to inflammatory mediators do not show reduced mortality in patients with septic shock (Fukumoto et al., 1996, Volman et al., 2002b). Notably, lipopolysaccharide also increases production of reactive oxygen species such as superoxide anions (Tsao et al., 2003, Victor and De La Fuente, 2003). Recently, pretreatment with hyperbaric oxygen has shown some beneficial effects on lipopolysaccharide-induced sepsis shock (Sunakawa and Yusa, 1997, Pedoto et al., 2003), but the underlying protective mechanism remains to be examined.

Hyperbaric oxygen therapy provides 100% inhaled oxygen at increased atmospheric pressure. It is used as an adjuvant therapy for many disorders, including several types of inflammatory conditions and ischemic tissue injury (Tibbles and Edelsberg, 1996, Nighoghossian and Trouillas, 1997). Hyperbaric oxygen successfully protects mice with aerobic septicemia and significantly prolongs survival of the infected host through its antibacterial activity (Ross and McAllister, 1965). Luongo and coworkers have reported that hyperbaric oxygen significantly decreases symptoms, reduces TNF-α and NO levels, and improves survival of animals shocked by zymosan, a nonbacterial and nonendotoxic agent (Luongo et al., 1998). Recently, in vitro studies show that hyperbaric oxygen inhibits the endotoxin lipopolysaccharide-induced proinflammatory cytokines in monocyte-macrophages (Benson et al., 2003). Furthermore, the beneficial effect of hyperbaric oxygen is mediated by increased superoxide dismutase and glutathione peroxidase activities in experimental acute necrotizing pancreatitis (Yasar et al., 2003). In this study, we investigated the relevance of the reduction of TNF-α, NO, and superoxide anion formation to improvement of vasohyporeactivity and mortality after hyperbaric oxygen treatment in endotoxic rats.

Section snippets

Materials

Eight- to ten-week-old male Wistar–Kyoto rats weighing 230–280 g were obtained from the National Animal Breeding and Research Center, Taipei, Taiwan. All reagents were obtained from Sigma Chemicals (St. Louis, MO) unless otherwise specified. The main reagents used include lipopolysaccharide from Escherichia coli, serotype 0127:B8, and aminoguanidine. Drugs and chemicals were dissolved in sterile normal saline for experimental use.

Hyperbaric oxygen treatment and experimental protocol

Animals were anaesthetized with pentobarbital sodium (50 mg/kg

Effect of hyperbaric oxygen and aminoguanidine treatment on TNF-α and NOx release

Plasma TNF-α and NOx concentrations for the five rat groups are shown in Fig. 1. Significant increases in plasma TNF-α (from 0.8±1.3 to 780±87 pg/ml; P<0.05) at 2 h and NOx (from 31.2±1.3 to 435±16 μM; P<0.05) at 9 h were noted in lipopolysaccharide-treated rats compared with the control group. In lipopolysaccharide-treated rats, administration of aminoguanidine significantly decreased plasma TNF-α production by 54% (P<0.05) and NOx by 46% (P<0.05), and exposure to hyperbaric oxygen

Discussion

Previous studies have shown that hyperbaric oxygen has beneficial effects on experimental acute necrotizing pancreatitis and zymosan-induced shock models (Luongo et al., 1998, Pedoto et al., 2003, Yasar et al., 2003). Our study further demonstrated that TNF-α and NOx release, vascular superoxide anion production, hypovasoreactivity and survival rate in lipopolysaccharide-treated rats were improved by serial exposure to hyperbaric oxygen (2 ATA). The effects of aminoguanidine, an inhibitor of

Acknowledgments

This work was supported by NSC 91-2314-B-016-036 Grants from National Science Council and C.Y. Foundation for Advancement of Education, Sciences and Medicine, Taiwan.

References (29)

  • S.A. Jerrett et al.

    Seizures, H2O2 formation and lipid peroxides in brain during exposure to oxygen under high pressure

    Aerosp. Med.

    (1973)
  • B. Juttner et al.

    Lack of toxic side effects in neutrophils following hyperbaric oxygen

    Undersea Hyperb. Med.

    (2003)
  • H.C. Lin et al.

    Systemic administration of lipopolysaccharide induces release of nitric oxide and glutamate and c-fos expression in the nucleus tractus solitarii of rats

    Hypertension

    (1999)
  • C. Luongo et al.

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

    Crit. Care Med.

    (1998)
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