Effects of the anthelmintic drug PF1022A on mammalian tissue and cells

Nematode infections cause human morbidity and enormous economic loss in livestock. Since resistance against currently available anthelmintics is a worldwide problem, there is a continuous need for new compounds. The cyclooctadepsipeptide PF1022A is a novel anthelmintic that binds to the latrophilin-like transmembrane receptor important for pharyngeal pumping in nematodes. Furthermore, PF1022A binds to GABA receptors, which might contribute to the anthelmintic effect. Like other cyclodepsipeptides, PF1022A acts as an ionophore. However, no correlation between ionophoric activity and anthelmintic properties was found. This is the first study describing the effect of PF1022A on mammalian cells and tissues. While channel-forming activity was observed already at very low concentrations, changes in intracellular ion concentrations and reduction of contractility in isolated guinea pig ileum occurred at multiples of anthelmintically active concentrations. PF1022A did not induce necrotic cell death indicated by complete lack of cellular lactate dehydrogenase release. In contrast, apoptosis induction via the mitochondrial pathway was suggested for long-term drug treatment at high concentrations due to numerous apoptotic morphological changes as well as mitochondrial membrane depolarisation. Short time effects were based on cell cycle blockade in G(0)/G(1) phase. Additionally, the cell cycle and apoptosis regulating proteins p53, p21 and bax, but not Bcl-2 were shown to impact on PF1022A-induced cytotoxicity. However, since PF1022A-induced cytotoxicity was found at drug concentrations higher than those used in anthelmintic treatment, it can be suggested that PF1022A intake might not impair human or animal health. Thus, PF1022A seems to be a safe alternative to other anthelmintic drugs.