Ascaris intestine calcium fluorescence dataset showing synergism of levamisole and Cry5B

A novel class of biocidal compounds are the Crystal 3D (Cry) and Cytolytic
(Cyt) proteins produced by Bacillus thuringiensis (Bt). Some Bt Cry
proteins have a selective nematocidal activity, with Cry5B being the most
studied. Cry5B kills nematode parasites by binding selectively to membrane
glycosphingolipids, then forming pores in the cell membranes of the
intestine leading to damage. Cry5B selectively targets multiple species of
nematodes from different clades and has no effect against mammalian hosts.
Levamisole is a cholinomimetic anthelmintic that acts by selectively
opening L-subtype nicotinic acetylcholine receptor ion-channels (L-AChRs)
that have been found on muscles of nematodes.  A synergistic
nematocidal interaction between levamisole and Cry5B has been described
previously on whole worms, but the location, mechanism and time-course of
this synergism is not known. In this study we follow the timeline of the
effects of levamisole and Cry5B on the Ca2+ levels of enterocyte cells of
the intestine of Ascaris suum using fluorescence imaging.
 The peak Ca2+ responses to levamisole were observed
after approximately 10 minutes and the peak responses to activated Cry5B
were seen after approximately 80 minutes.  When levamisole and
Cry5B were applied simultaneously, we observed that the responses to Cry5B
were bigger and occurred sooner than when it was applied by itself. It is
proposed that there is an irreversible cytoplasmic Ca2+ overload that
leads to cell-death in the enterocyte that is induced by levamisole
opening Ca2+ permeable L-subtype nAChRs and the development of Ca2+
permeable Cry5B toxin pores in enterocyte plasma membranes. The effects of
levamisole potentiate and speed the actions of Cry5B.