Molecular and Genetic Medicine

The Isoquinoline Alkaloid Berberine Augments Radiation Effect by Enhancing the DNA Damage at Molecular Level in HeLa Cells Irradiated with Various Doses of �Ž�³-Radiation: Correlation Between DNA Damage and Clonogenicity

Abstract

Jagetia GC and Rao SK

The passage of ionizing radiations through aqueous medium of biological material leads into the generation of a burst of free radicals owing to radiolysis of water. These free radicals are extremely reactive and interact with important macromolecules of cells resulting in the cytotoxicity. It is well known that ionizing radiation induce damage to the DNA triggering a cascade of events that result in eventual cell kill. Earlier we found that berberine chloride an isoquinoline alkaloid present in certain plants inflicts damage to the molecular DNA. Therefore we wanted to know whether berberine chloride will increase the effects of radiation in HeLa cells exposed to various doses of γ- radiation. HeLa cells were treated or not with 0, 1, 2, 4, 6 or 8 μg/ml of berberine chloride prior to 0, 0.5, 1, 2, 3 or 4 Gy γ-irrradiation and the molecular DNA damage was assessed immediately after irradiation (within 15 minute of irradiation) by single cell gel electrophoresis. The migration of fragmented DNA into comet tails was considered as a measure of molecular damage to DNA and has been expressed as Olive tail moment. Irradiation of HeLa cells to 0, 0.5, 1, 2, 3 or 4 Gy γ-irradiation caused a radiation dose-dependent rise in the Olive tail moment indicating an elevation in the DNA damage in HeLa cells. Treatment of HeLa cells with different concentrations of berberine chloride for 2 or 4 h before irradiation further raised the DNA damage denoted by a rise in the amount of tail DNA of the comets and Olive tail moment immediately after irradiation. The clonogenic assay revealed that clonogenic potential of HeLa cells alleviated with an increase in irradiation dose and treatment of HeLa cells with 1, 2 or 4 μg/ml berberine chloride further reduced the clonognenicity of cells. Our study indicates that berberine is a potent DNA damaging agent and could enhance radiation damage during cancer treatment in clinical conditions and clonogenicity of cells is directly related to the ability of berberine to inflict damage to DNA.