Ressource pédagogique : Prof. Richard Martin - Calcium imaging in the intestine of Ascaris suum, TRP channels and diethylcarbamazine

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The intestine of nematode parasites is involved in more than digestion, absorption and storage of nutrients. It is involved in vesicular trafficking, ageing, innate immunity, drug metabolism and excretion making it a sensitive tissue for drugs to target. We used Fluo-3 AM, a calcium sensitive dye that is taken up into the cytoplasm of the columnar cells of isolated Ascaris suum intestine flaps, to determine the effects of diethylcarbamazine. One of the possible modes of action of diethylcarbamazine is it is a TRP channel agonist. We used PCR and detected the presence of TRP channel message in the Ascaris intestine strips and found: Asu-gon-2, Asu-trp-1(2), Asu-ocr-1, and Asu-trpa-1. As a control we Increased calcium in the bathing solution to 10mM which produces a sharp and reversible rise in cytosolic calcium. 10 M diethylcarbamazine produced a characteristic ‘step-like’ slow increase in calcium that persisted after removal of diethylcarbamazine before returning slowly towards base levels. 2-APB, a TRP channel antagonist inhibited the effect of 10 M diethylcarbamazine. Interestingly, in the absence of added calcium in the bathing solution, 10 M diethylcarbamazine produced a fall in cytosolic calcium as it was leached from the intestinal cells and 100 M lanthanum, a TRP channel blocker, prevented this leaching. These observations suggest a direct effect of diethylcarbamazine on TRP channels of Ascaris intestines, an effect that is not predicted by effects mediated by host immune systems or effects on host arachidonic acid metabolism. The observations emphasize the intestine as a tissue that is sensitive to anthelmintic drugs. Supported by NIH R01AI047194 and R01AI155413 to RJM and the EA Benbrook Foundation  

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• Sciences de la vie. Biologie (570)

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