Povećanje letalnog učinka bleomicina na stanice HeLa i V79 s pomoću pčelinjeg otrova

This study investigated possible growth-inhibiting effects of bee venom applied alone or in combination with a cytotoxic drug bleomycin on HeLa and V79 cells in vitro based on clone formation, cell counting, and apoptosis. Melittin, the key component of bee venom, is a potent inhibitor of calmodulin activity, and also a potent inhibitor cell growth and clonogenicity. Intracellular accumulation of melittin correlates with the cytotoxicity of antitumour agents. Previous studies indicated that some calcium antagonists and calmodulin inhibitors enhanced intracellular levels of antitumor agents by inhibiting their outward transport. In this study, treatment of exponentially growing HeLa and V79 cells with bleomycin caused a dose-dependent decrease in cell survival due to DNA damage. This lethal effect was potentiated by adding a non-lethal dose of the bee venom. By preventing repair of damaged DNA, bee venom inhibited recovery from potentially lethal damage induced by bleomycin in V79 and HeLa cells. Apoptosis, necrosis, and lysis were presumed as possible mechanisms by which bee venom inhibited growth and clonogenicity of V79 cells. HeLa cells, on the other hand, showed greater resistance to bee venom. Our findings suggest that bee venom might find a therapeutic use in enhancing cytotoxicity of antitumour agent bleomycin.U uvjetima in vitro istražen je inhibitorni učinak pčelinjeg otrova, samog ili združenog s citostatikom bleomicinom, na rast stanica HeLa i V79. Rabljene su sljedeće metode: brojenje stanica, metoda klonskog rasta i apoptoza. Poznato je da neki antagonisti kalcija i kalmodulinski inhibitori povisuju unutarstaničnu razinu protutumorskih lijekova inhibirajući njihov prijenos iz stanice. Unutarstanična akumulacija melitina izravno povećava citotoksični učinak protutumorskog lijeka. Obrada stanica HeLa i V79 u eksponencijalnoj fazi rasta bleomicinom uzrokuje oštećenje DNA ovisno o dozi te smanjenje broja živih stanica. Uočeno je da se letalni učinak bleomicina može pojačati dodatkom neletalne doze pčelinjeg otrova. Pčelinji otrov pritom inhibira popravak nastalih oštećenja u stanicama HeLa i V79 te sprječava oporavak stanica tretiranih bleomicinom. Apoptoza, nekroza i liza mogući su mehanizmi kojima pčelinji otrov inhibira rast i stvaranje kolonija stanica V79, dok HeLa-stanice pokazuju pojačanu otpornost na pčelinji otrov. Istraživanje također potvrđuje mogućnost uporabe pčelinjeg otrova u povećanju citotoksičnosti bleomicina

Human neutrophil phosphodiesterase

Extracts of human neutrophils were examined for phosphodiesterase activity using a radiochemical assay. As reported by other investigators, both high- and low- K m forms of the enzyme were found. Although calmodulin could be measured in these extracts, human neutrophil phosphodiesterase proved not to be calmodulin dependent. Activity of the neutrophil phosphodiesterase was also not altered by physiologic concentrations of indomethacin, p -bromophenacyl bromide, eicosatetraenoic acid, or eicosatetraynoic acid, all inhibitors of arachidonic acid metabolism. These results are relevant to stimulus-secretion coupling in neutrophils, wherein calmodulin-dependent reactions play a vital role.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44535/1/10753_2004_Article_BF00916094.pd