TY - JOUR T1 - α- and ϵ-Protein Kinase C Activity during Smooth Muscle Cell Apoptosis in Response to γ-Radiation JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 964 LP - 972 DO - 10.1124/jpet.107.125930 VL - 322 IS - 3 AU - Sandra Claro AU - Celia Akemi Kanashiro AU - Maria Etsuko Miyamoto Oshiro AU - Alice Teixeira Ferreira AU - Raouf Ali Khalil Y1 - 2007/09/01 UR - http://jpet.aspetjournals.org/content/322/3/964.abstract N2 - The use of γ-radiation in treatment of pelvic cancer is associated with injury of healthy surrounding tissues and disorders of intestinal motility; however, the cellular mechanisms involved are unclear. We tested the hypothesis that exposure of visceral smooth muscle cells (SMCs) to γ-radiation induces apoptosis via activation of specific protein kinase C (PKC) isoforms. Cultured SMCs and slices from guinea pig ileum smooth muscle longitudinal layer (GPISMLL) were exposed to 10 to 50 Gy. Flow cytometry in γ-radiated SMCs showed increased percentage of cells in the sub-G0/G1 phase, a hallmark of apoptosis. γ-Radiation-induced reduction in cell survival was partially but significantly alleviated with the PKC inhibitors. Sections of γ-irradiated GPISMLL showed DNA fragmentation and apoptotic bodies analyzed by the terminal deoxynucleotidyl transferase dUTP nick-end labeling method, whereas the plasma and nuclear membranes were preserved. Confocal microscopy in γ-radiated SMCs labeled with annexin V-fluorescein showed an increase in apoptotic cells and phosphatidylserine externalization. Contraction of GPISMLL strips in response to KCl and acetylcholine was reduced in tissues exposed to 30 and 50 Gy. γ-Radiation of GPISMLL caused an increase in PKC activity in the particulate fraction, a decrease in the cytosolic fraction, and increased particulate/cytosolic PKC activity ratio. Western blot analysis revealed significant amounts of α- and ϵ-PKC in the cytosolic fraction of control GPISMLL. γ-Radiation caused an increase in the amount of α- and ϵ-PKC in the particulate fraction and a decrease in the cytosolic fraction. Data suggest that γ-radiation induces apoptosis, growth arrest, and contractile dysfunction in visceral SMCs of GPISMLL via activation and translocation of α- and ϵ-PKC isoforms. ER -