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

Réalisation : 29 novembre 2021 Mise en ligne : 29 novembre 2021
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Theintestine of nematode parasites is involved in more than digestion, absorptionand storage of nutrients. It is involved in vesicular trafficking, ageing,innate immunity, drug metabolism and excretion making it a sensitive tissue fordrugs to target. We used Fluo-3 AM, a calcium sensitive dye that is taken upinto the cytoplasm of the columnar cells of isolated Ascaris suum intestineflaps, to determine the effects of diethylcarbamazine. One of the possiblemodes of action of diethylcarbamazine is it is a TRP channel agonist. We usedPCR and detected the presence of TRP channel message in the Ascaris intestinestrips 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 whichproduces a sharp and reversible rise in cytosolic calcium. 10 Mdiethylcarbamazine produced a characteristic ‘step-like’ slow increase incalcium that persisted after removal of diethylcarbamazine before returningslowly towards base levels. 2-APB, a TRP channel antagonist inhibited theeffect of 10 Mdiethylcarbamazine. Interestingly, in the absence of added calcium in thebathing solution, 10 Mdiethylcarbamazine produced a fall in cytosolic calcium as it was leached fromthe intestinal cells and 100 Mlanthanum, a TRP channel blocker, prevented this leaching. These observationssuggest a direct effect of diethylcarbamazine on TRP channels of Ascaris intestines,an effect that is not predicted by effects mediated by host immune systems oreffects on host arachidonic acid metabolism. The observations emphasize theintestine as a tissue that is sensitive to anthelmintic drugs.

Supportedby NIH R01AI047194and R01AI155413 to RJM and the EA Benbrook Foundation  


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