Attenuation of vascular permeability by methylnaltrexone: Role of mOP-R and S1P3 transactivation

Patrick A. Singleton, Liliana Moreno-Vinasco, Saad Sammani, Sherry L. Wanderling, Jonathan Moss, Joe G.N. Garcia

Research output: Contribution to journalArticlepeer-review

107 Scopus citations


Endothelial cell (EC) barrier dysfunction (i.e., increased vascular permeability) is observed in inflammatory states, tumor angiogenesis, atherosclerosis, and both sepsis and acute lung injury. Therefore, agents that preserve vascular integrity have important clinical therapeutic implications. We examined the effects of methylnaltrexone (MNTX), a mu opioid receptor (mOP-R) antagonist, on human pulmonary EC barrier disruption produced by edemagenic agents including morphine, the endogenous mOP-R agonist DAMGO, thrombin, and LPS. Pretreatment of EC with MNTX (0.1 μM, 1 h) or the uncharged mOP-R antagonist naloxone attenuated morphine- and DAMGO-induced barrier disruption in vitro. However, MNTX, but not naloxone, pretreatment of EC inhibited thrombin-and LPS-induced barrier disruption, indicating potential mOP-R-independent effects of MNTX. In addition, intravenously delivered MNTX attenuated LPS-induced vascular hyperpermeability in the murine lung. We next examined the mechanistic basis for this MNTX barrier protection and observed that silencing of mOP-R attenuated the morphine- and DAMGO-induced EC barrier disruption, but not the permeability response to either thrombin or LPS. Because activation of the sphingosine 1-phosphate receptor, S1P3, is key to a number of barrier-disruptive responses, we examined the role of this receptor in the permeability response to mOP-R ligation. Morphine, DAMGO, thrombin, and LPS induced RhoA/ROCK-mediated threonine phosphorylation of S1P3, which was blocked by MNTX, suggesting S1P3 transactivation. In addition, silencing of S1P3 receptor expression (siRNA) abolished the permeability response to each edemagenic agonist. These results indicate that MNTX provides barrier protection against edemagenic agonists via inhibition of S1P3 receptor activation and represents a potentially useful therapeutic agent for syndromes of increased vascular permeability.

Original languageEnglish (US)
Pages (from-to)222-231
Number of pages10
JournalAmerican journal of respiratory cell and molecular biology
Issue number2
StatePublished - Aug 2007


  • EC barrier regulation
  • Methylnaltrexone
  • S1P3 receptor
  • Vascular permeability
  • mu opioid receptor

ASJC Scopus subject areas

  • Molecular Biology
  • Pulmonary and Respiratory Medicine
  • Clinical Biochemistry
  • Cell Biology


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