The neuropeptide Rhopr CCHamide2 inhibits serotonin-stimulated transcellular Na+ transport across the anterior midgut of the vector of Chagas disease Rhodnius prolixus

CAPRIOTTI, NATALIA; GIOINO, PAULA; ONS, SHEILA; IANOWSKI, JUAN P.

JOURNAL OF EXPERIMENTAL BIOLOGY

COMPANY OF BIOLOGISTS LTD

Año: 2021

0022-0949

Rhodnius prolixus is a blood-feeding insect vector of Tripanosoma cruzi, aprotozoan parasite that causes Chagas´ disease. During each blood meal the animalsingest large volumes of blood, that may be up to 12 times the unfed body mass. Theseblood meals impose a significant osmotic stress for the animals due to the hyposmoticcondition of the ingested blood compared to the insect´s haemolymph. Thus, the insectundergoes a massive postprandial diuresis that allows for the excretion of the plasmafraction of the blood in less than two hours. Diuresis is performed by the excretorysystem, consisting of the Malpighian tubules and gut, under the control of diuretic andantidiuretic factors. We investigated the ion transport machinery triggered by stimulationwith the diuretic factor serotonin in the anterior midgut (i.e. crop) and the effect of thediuretic modulator RhoprCCHamide2. Ussing chamber assays revealed that serotoninstimulated increase in transepithelial short circuit current (Isc) was more sensitive to theblockage with amiloride than EIPA, suggesting the involvement of Na+ channels.Incubation in Na+-free, but not Cl--free saline, blocked the effect of serotonin on Isc.Moreover, treatment with NKCC and NCC blockers had no effect on fluid secretion butwas blocked by amiloride. Blockage of Na+/K+-ATPase with ouabain inhibit Isc but the H+-ATPase inhibitor bafilomycin had no effect. The neuropeptide RhoprCCHamide2diminished serotonin-stimulated Isc across the crop. The results suggest that Na+ undergoes active transport via an apical amiloride-sensitive Na+ channels and a basolateral ouabain-sensitive Na+/K+-ATPase while Cl- is transported through passive paracellular pathway