title: Suppression of cell membrane permeability by suramin: involvement of its inhibitory actions on connexin 43 hemichannels.
abstract: OBJECTIVE
  Suramin is a clinically prescribed drug for treatment of human African trypanosomiasis, cancer and infection. It is also a well-known pharmacological antagonist of P2 purinoceptors. Despite its clinical use and use in research, the biological actions of this molecule are still incompletely understood. Here, we investigated the effects of suramin on membrane channels, as exemplified by its actions on non-junctional connexin43 (Cx43) hemichannels, pore-forming α-haemolysin and channels involved in ATP release under hypotonic conditions.
  
  
  METHODS
  Hemichannels were activated by removing extracellular Ca(2+) . The influences of suramin on hemichannel activities were evaluated by its effects on influx of fluorescent dyes and efflux of ATP. The membrane permeability and integrity were assessed through cellular retention of preloaded calcein and LDH release.
  
  
  RESULTS
  Suramin blocked Cx43 hemichannel permeability induced by removal of extracellular Ca(2+) without much effect on Cx43 expression and gap junctional intercellular communication. This action of suramin was mimicked by its analogue NF023 and NF449 but not by another P2 purinoceptor antagonist PPADS. Besides hemichannels, suramin also significantly blocked intracellular and extracellular exchanges of small molecules caused by α-haemolysin from Staphylococcus aureus and by exposure of cells to hypotonic solution. Furthermore, it prevented α-haemolysin- and hypotonic stress-elicited cell injury.
  
  
  CONCLUSIONS
  Suramin blocked membrane channels and protected cells against toxin- and hypotonic stress-elicited injury. Our finding provides novel mechanistic insights into the pharmacological actions of suramin. Suramin might be therapeutically exploited to protect membrane integrity under certain pathological situations.
authors.affiliation: Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Chi
authors.forename: Kun
authors.initials: K
authors.lastname: Gao
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takeda
authors.forename: Jian
authors.initials: J
authors.lastname: Yao
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects*; D018031:Connexin 43 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D051381:Rats; D013329:Structure-Activity Relationship; D013498:Suramin / Q000494:pharmacology*; D013552:Swine
chemical_list: D018031:Connexin 43; D013498:Suramin; D002118:Calcium
keywords: channel permeability; connexin 43; hemichannels; hypotonic stress; suramin; α-haemolysin