title: Mechanism of the delay phenomenon: tissue protection is mediated by heme oxygenase-1.
abstract: Induction of the "delay phenomenon" by chronic ischemia is an established clinical procedure, but the mechanisms conferring tissue protection are still incompletely understood. To elucidate the role of heme oxygenase-1 [HO-1 or heat shock protein-32 (HSP-32)] in delay, we examined in the skin-flap model of the ear of the hairless mouse, 1) whether chronic ischemia (delay) is capable to induce expression of HO-1, and 2) whether delay-induced HO-1 affects skin-flap microcirculation and survival by either its carbon monoxide-associated vasodilatory action or its biliverdin-associated anti-oxidative mechanism. Chronic ischemia was induced by transsection of the central feeding vessel of the ear 7 days before flap creation. The flap was finally raised by an incision through four-fifths of the base of the ear. Microcirculatory dysfunction and tissue necrosis were studied with the use of laser Doppler fluxmetry and intravital fluorescence microscopy. HO-1 protein expression was determined with Western blot analysis. Seven days of chronic ischemia (delay) induced a marked expression of HO-1. This was paralleled by a significant improvement (P <0.05) of microvascular perfusion and a reduction (P <0.05) of flap necrosis when compared with nondelayed controls. Importantly, blockade of HO-1 activity by tin protoporhyrin-IX completely blunted the protection of microcirculation and the improvement of tissue survival. Additional administration of the vitamin E analog trolox after blockade of HO-1 to mimic exclusively the anti-oxidative action of the heat shock protein did not restore the HO-1-associated microcirculatory improvement and only transiently attenuated the manifestation of flap necrosis. Thus our data indicate that the delay-induced protection from tissue necrosis is mediated by HO-1, predominantly through its carbon monoxide-associated action of adequately maintaining nutritive capillary perfusion.
authors.affiliation: Dept. of Anesthesiology and Intensive Care Medicine, Univ. of Saarland, D-66421 Homburg/Saar, Germany. darius.kubulus@uniklinik-saarland.de
authors.forename: Darius
authors.initials: D
authors.lastname: Kubulus
authors.forename: Frank
authors.initials: F
authors.lastname: Roesken
authors.forename: Michaela
authors.initials: M
authors.lastname: Amon
authors.forename: Martin
authors.initials: M
authors.lastname: Rücker
authors.forename: Michael
authors.initials: M
authors.lastname: Bauer
authors.forename: Inge
authors.initials: I
authors.lastname: Bauer
authors.forename: Michael D
authors.initials: MD
authors.lastname: Menger
mesh_terms: D000818:Animals; D000975:Antioxidants; D001664:Biliverdine; D002248:Carbon Monoxide / Q000378:metabolism; D003213:Conditioning, Psychological; D019610:Cytoprotection; D004423:Ear; D005260:Female; D015870:Gene Expression; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1; D007150:Immunohistochemistry; D007511:Ischemia / Q000201:enzymology / Q000473:pathology; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008819:Mice, Nude; D008833:Microcirculation; D009336:Necrosis; D012867:Skin / Q000098:blood supply / Q000473:pathology*; D013524:Surgical Flaps; D013997:Time Factors; D014664:Vasodilation
chemical_list: D000975:Antioxidants; D008565:Membrane Proteins; D002248:Carbon Monoxide; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D001664:Biliverdine