• C Taillé, R Foresti, S Lanone, C Zedda, C Green, M Aubier, R Motterlini, and J Boczkowski.
• Institut National de la Santé et de la Recherche Médicale U408, Faculté Xavier Bichat, Paris, France.
• Am. J. Respir. Crit. Care Med. 2001 Mar 1; 163 (3 Pt 1): 753-61.

AbstractReactive oxygen species are strongly implicated in diaphragmatic dysfunction during sepsis. We investigated whether the heme oxygenase (HO) pathway, which is a powerful protective cellular system, protects the diaphragm against oxidative stress and contractile failure during sepsis. A basal expression of both the inducible and constitutive HO protein isoforms (HO-1 and HO-2, respectively) was found in the diaphragm. Enhanced HO-1 expression in diaphragmatic myocytes was observed 24 h after Escherichia coli endotoxin (lipopolysaccharide, LPS) inoculation and remained elevated for at least 96 h. Enhanced HO-1 expression was also observed in the rectus abdominis and soleus muscles and in the left ventricular myocardium of endotoxemic animals. Diaphragmatic HO-2 expression was not modified by endotoxin. Diaphragmatic HO activity exhibited a biphasic time course characterized by a transient decrease during the first 12 h followed by a significant increase at 24 h, corresponding to HO-1 induction. Diaphragmatic force was significantly reduced 24 h after LPS, concomitantly with muscular oxidative stress. Administation of an inhibitor of heme oxygenase activity, zinc protoporphyrin IX (ZnPP-IX), further impaired muscular oxidative stress and contractile failure. By contrast, increased levels of HO-1 expression obtained by pretreatment of rats with hemin, a powerful inducer of HO-1, completely prevented LPS-mediated diaphragmatic oxidative stress and contractile failure. This protective effect was reversed by ZnPP-IX. These results show an important protective role for the HO pathway against sepsis-induced diaphragmatic dysfunction, which could be related to its antioxidant properties.

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