title: Sensitization to hyperthermia by intracellular acidification of C6 glioma cells.
abstract: Hyperthermia has been introduced as a new modality of treatment for glioma. In these experiments, the cytotoxicity of hyperthermia in C6 glioma cells was enhanced by increasing the intracellular acidity with amiloride and/or 4,4'-diisothiocyanatostilbene-2,2' disulfonic acid (DIDS). Intracellular pH (pHi) is regulated mainly by Na+/H+ and HCO3-/Cl- antiports through the cell membrane, and amiloride acts on the former, DIDS on the latter to lower pHi. The cellular thermosensitivity to clinically achievable brain hyperthermia at 42 degrees C was enhanced by 0.5 mM amiloride (Na+/H+ antiport inhibitor). T0 values (T0 = the heating period required to reduce experimental survival rate by 1/e) at 42 degrees C without and with amiloride was 192 and 81 min, respectively. The addition of DIDS (HCO3-/Cl- antiport inhibitor) further enhanced. T0 value was 25 min. Fluorophotometric measurement of pHi was employed using the pH sensitive dye, bis(carboxyethyl)carboxyfluorescein, which is trapped in viable cells. The average pHi in control C6 glioma cells in pH 7.2 media was 7.21. In the untreated cells heated at 42 degrees C for 1 hour, the pHi was 7.12. The pHi of the cells heated in the presence of amiloride was decreased to 6.83. The pHi was further lowered to 6.67 by the treatment with amiloride in combination with DIDS for 2 hours. Hyperthermia with amiloride and DIDS may be a more effective treatment for malignant gliomas.
authors.affiliation: Department of Neurosurgery, Fukui Medical School, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Kitai
authors.forename: M
authors.initials: M
authors.lastname: Kabuto
authors.forename: T
authors.initials: T
authors.lastname: Kubota
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.forename: H
authors.initials: H
authors.lastname: Matsumoto
authors.forename: S
authors.initials: S
authors.lastname: Hayashi
authors.forename: H
authors.initials: H
authors.lastname: Shioura
authors.forename: T
authors.initials: T
authors.lastname: Ohtsubo
authors.forename: K
authors.initials: K
authors.lastname: Katayama
authors.forename: E
authors.initials: E
authors.lastname: Kano
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000627:therapeutic use*; D000143:Acids; D000584:Amiloride / Q000627:therapeutic use*; D000818:Animals; D001932:Brain Neoplasms / Q000188:drug therapy / Q000628:therapy*; D002470:Cell Survival / Q000187:drug effects; D005910:Glioma / Q000188:drug therapy / Q000628:therapy*; D006863:Hydrogen-Ion Concentration; D006979:Hyperthermia, Induced / Q000379:methods*; D051381:Rats; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured
chemical_list: D000143:Acids; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid