Synergistic effect of electric pulses and bleomycin on cultured rabbit subconjunctival fibroblasts

Background: The combined effect of electric pulses (EP) and antiproliferative agents on the proliferation of rabbit Tenon's capsule fibroblasts was investigated. Methods. Rabbit Tenon's capsule fibroblasts were cultured. Some of these cells were exposed to various intensities of EP alone (500-2500 V/cm). Other cells were then exposed for 30 min to an antiproliferative agent: bleomycin (BLM; 0.0005-50 μmol/l), mitomycin C (MMC; 0.0005-50 μmol/l), 5-fluorouracil (5-FU; 0.05-5000 μmol/l), or streptomycin (SM; 0.0005-50 μmol/l) with or without EP (2000 V/cm, 99 μs, eight pulses). Cell proliferation was assessed by cell counting on day 3 and by a ³H-thymidine uptake assay. DNA fragmentation was assessed by flow-cytometric analysis and agarose gel electrophoresis. Results: A significant reduction in the cell number was observed only at 2500 V/cm (P < 0.05). BLM, MMC and 5-FU treatment inhibited cell proliferation in a dose-dependent manner either with or without EP (ID₅₀: BLM alone, 0.029 μmol/l; BLM and EP, 0.00022 μmol/l; MMC alone, 41.6 μmol/l; MMC and EP, 27.5 μmol/l; 5-FU alone, 1045 μmol/l; 5-FU and EP, 690.2 μmol/l; P < 0.05). EP treatment induced an inhibitory effect of BLM on cell proliferation which was 100 times more prominent than BLM alone (0.0005 μmol/l of BLM alone 103.4 ± 4.4%, 0.0005 μmol/l of BLM and EP 26.0 ± 4.4%; P = 0.021). BLM treatment with EP also augmented the apoptotic-like DNA fragmentation in both a flow-cytometric DNA histogram and agarose gel electrophoresis. Conclusion: EP treatment enhanced the inhibitory effect of BLM on the cell proliferation of Tenon's capsule fibroblasts of rabbits. The combination of electric pulses and antiproliferative drug treatments may therefore reduce the necessary dose of antiproliferative agents in filtering surgery.