title: Delayed inhaled carbon monoxide mediates the regression of established neointimal lesions.
abstract: OBJECTIVE
  Intimal hyperplasia (IH) contributes to the failure of vascular interventions. While many investigational therapies inhibit the development of IH in animal models, few of these potential therapies can reverse established lesions. Inhaled carbon monoxide (CO) dramatically inhibits IH in both rats and pigs when given perioperatively. It also prevented the development of pulmonary arterial hypertension in rodents. Interestingly, CO could reverse pulmonary artery structural changes and right heart hemodynamic changes when administered after the establishment of pulmonary hypertension. Thus, we hypothesize that inhaled CO may mediate the regression of established neointimal lesions.
  
  
  METHODS
  Rats underwent carotid artery balloon angioplasty injury. Carotid arteries were collected at 2 and 4 weeks after injury for morphometric analysis of the neointima. Another group was treated with inhaled CO (250 parts per million) for 1 hour daily from week 2 until week 4. Additional rats were sacrificed 3 days after initiating CO treatment, and the carotid arteries were examined for apoptosis by terminal deoxynucleotidyl transferase dUTP nick end-labeling, proliferation by Ki67 staining, and autophagy by microtubule-associated protein light chain 3 I/II staining.
  
  
  RESULTS
  At 2 weeks following injury, sizable neointimal lesions had developed (intimal/media = 0.92 ± 0.22). By 4 weeks, lesion size remained stable (0.80 ± 0.09). Delayed inhaled CO treatment greatly reduced neointimal lesion size vs the 2- and 4-week control mice (0.38 ± 0.05; P < .05). Arteries from the CO-treated rats exhibited significantly reduced apoptosis compared with control vessels (3.18% ± 1.94% vs 16.26% ± 5.91%; P = .036). Proliferation was also dramatically reduced in the CO-treated animals (2.98 ± 1.55 vs 10.37 ± 2.80; P = .036). No difference in autophagy between control and CO-treated rats was detected.
  
  
  CONCLUSIONS
  Delayed administration of inhaled CO reduced established neointimal lesion size. This effect was mediated by the antiproliferative effect of CO on medial and intimal smooth muscle cells without increases in arterial wall apoptosis or autophagy. Future studies will examine additional time points to determine if there is temporal variation in the rates of apoptosis and autophagy.
authors.affiliation: Department of Veterans Affairs Medical Center, University of Pittsburgh, Pittsburgh, Pa; Division of Vascular Surgery, University of Pittsburgh, Pittsburgh, Pa.
authors.forename: Michael
authors.initials: M
authors.lastname: Madigan
authors.affiliation: Department of Veterans Affairs Medical Center, University of Pittsburgh, Pittsburgh, Pa; Division of Vascular Surgery, University of Pittsburgh, Pittsburgh, Pa.
authors.forename: Fateh
authors.initials: F
authors.lastname: Entabi
authors.affiliation: Department of Veterans Affairs Medical Center, University of Pittsburgh, Pittsburgh, Pa; Department of Surgery, University of Pittsburgh, Pittsburgh, Pa.
authors.forename: Brian
authors.initials: B
authors.lastname: Zuckerbraun
authors.affiliation: Department of Surgery, University of Pittsburgh, Pittsburgh, Pa; Center of Biologic Imaging, University of Pittsburgh, Pittsburgh, Pa.
authors.forename: Patricia
authors.initials: P
authors.lastname: Loughran
authors.affiliation: Department of Veterans Affairs Medical Center, University of Pittsburgh, Pittsburgh, Pa; Division of Vascular Surgery, University of Pittsburgh, Pittsburgh, Pa. Electronic address: tzenge@upmc.edu.
authors.forename: Edith
authors.initials: E
authors.lastname: Tzeng
mesh_terms: D000280:Administration, Inhalation; D000800:Angioplasty, Balloon; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D002248:Carbon Monoxide / Q000008:administration & dosage*; D020212:Carotid Artery Injuries / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D002342:Carotid Artery, External / Q000187:drug effects / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects*; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D006965:Hyperplasia; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000473:pathology; D058426:Neointima; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D002248:Carbon Monoxide