Haem oxygenase-1 induction protects against tumour necrosis factor alpha impairment of endothelial-dependent relaxation in rat isolated pulmonary artery.
OBJECTIVE
Disturbances in pulmonary vascular reactivity are important components of inflammatory lung disease. Haem oxygenase-1 (HO-1) is an important homeostatic enzyme upregulated in inflammation. Here we have investigated the potentially protective effect of HO-1 against cytokine-induced impairment in pulmonary artery relaxation.


METHODS
Haem oxygenase-1 protein levels were assessed by immunofluorescence. HO activity was assessed by conversion of haemin to bilirubin. Rings of rat isolated pulmonary artery in organ baths were used to measure relaxant responses to the endothelium-dependent agent ACh and the endothelium-independent agent sodium nitroprusside (SNP). Production of nitric oxide (NO) and reactive oxygen species (ROS) was assessed by confocal fluorescence microscopy and fluorescent probes.


RESULTS
Haem oxygenase-1 protein expression was strongly induced in pulmonary artery after 24-h incubation with either haemin (5 microM) or curcumin (2 microM), accompanied by a significant increase in HO activity. Incubation with tumour necrosis factor alpha (TNFalpha, 1 ng.mL(-1), 2 h) significantly decreased relaxation of arterial rings to ACh, without affecting responses to SNP. Induction of HO-1 by curcumin or haemin protected against TNFalpha-induced hyporesponsiveness to ACh. The competitive HO inhibitor, tin protoporphyrin (20 microM), abolished the protective effect of haemin. HO-1 induction prevented a TNFalpha-induced increase in NO generation without affecting the TNFalpha-induced increase in ROS generation. HO-1 induction prevented the TNFalpha-induced decrease in ACh-stimulated NO generation.


CONCLUSIONS
Induction of HO-1 protected against TNFalpha impairment of endothelium-dependent relaxation in pulmonary artery, by a mechanism involving a reduction in inducible NO synthase-derived NO production.
Department of Pharmacy and Pharmacology, University of Bath, UK. helbassossy@zu.edu.eg
Hany M
HM
El-Bassossy
Nabila N
NN
El-Maraghy
Hassan M
HM
El-Fayoumi
Malcolm L
ML
Watson
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D003474:Curcumin / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology; D004790:Enzyme Induction / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D051547:Heme Oxygenase-1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006427:Hemin / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D011651:Pulmonary Artery / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects*
D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D006427:Hemin; D052247:Nitric Oxide Synthase Type II; D051547:Heme Oxygenase-1; D003474:Curcumin; D000109:Acetylcholine