title: Topical rapamycin suppresses the angiogenesis pathways induced by pulsed dye laser: molecular mechanisms of inhibition of regeneration and revascularization of photocoagulated cutaneous blood vessels.
abstract: OBJECTIVE
  Pulsed dye laser (PDL) is the most effective treatment for port wine stain (PWS) birthmarks. However, regeneration and revascularization of photocoagulated blood vessels may result in poor therapeutic outcome. We have recently shown that rapamycin (RPM), an angiogenesis inhibitor, can reduce the regeneration and revascularization of photocoagulated blood vessels. Herein, we attempt to further elucidate the molecular pathophysiology on the inhibition of the regeneration and revascularization of photocoagulated blood vessels by topical RPM in an animal model.
  
  
  METHODS
  Two separate skin areas on each hamster were irradiated by PDL. After PDL exposure, topical RPM was applied daily to one of the randomly selected test sites. PDL, PDL + RPM and normal skin test sites were biopsied on day 3 after PDL exposure. The total ribonucleic acid (RNA) and protein were extracted from biopsied skin samples and quantified. Real-time reverse transcription-polymerase chain reaction (RT-PCR) and immunoblot were subsequently performed to quantify the mRNA and protein levels of hypoxia-inducible factor-1alpha (HIF-1α), vascular endothelial growth factor (VEGF) and ribosomal protein S6 kinase (S6). The phosphorylation levels of S6 and AKT were also evaluated by immunoblot.
  
  
  RESULTS
  The mRNA and protein levels of HIF-1α, VEGF, and S6 significantly increased after PDL exposure as compared to the normal hamster skin. Topical application of 1% RPM suppressed the PDL-induced increase in mRNA and protein levels of those genes on day 3 post-PDL exposure. The phosphorylation levels of S6 and AKT increased after PDL exposure but the increases were suppressed by the topical application of RPM.
  
  
  CONCLUSIONS
  The increase in expression of HIF-1α, VEGF, and S6 after PDL-exposure suggests that angiogenesis pathways play very active roles in the process of skin blood vessel regeneration and revascularization. Topical application of 1% RPM can suppress the angiogenesis pathways and, therefore, reduce the regeneration and revascularization of photocoagulated blood vessels.
authors.affiliation: Department of Surgery, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, California 92617, USA. wenbint@uci.edu
authors.forename: Wenbin
authors.initials: W
authors.lastname: Tan
authors.forename: Wangcun
authors.initials: W
authors.lastname: Jia
authors.forename: Victor
authors.initials: V
authors.lastname: Sun
authors.forename: Martin C
authors.initials: MC
authors.lastname: Mihm
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Nelson
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000008:administration & dosage / Q000494:pharmacology*; D015415:Biomarkers / Q000378:metabolism; D006224:Cricetinae; D062109:Dermatologic Surgical Procedures; D004334:Drug Administration Schedule; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D015151:Immunoblotting; D017075:Laser Coagulation; D054025:Lasers, Dye; D008297:Male; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D020123:Sirolimus / Q000008:administration & dosage / Q000494:pharmacology*; D012867:Skin / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; D015415:Biomarkers; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D042461:Vascular Endothelial Growth Factor A; D019893:Ribosomal Protein S6 Kinases; D020123:Sirolimus