title: Stress response to high osmolarity in Trypanosoma cruzi epimastigotes.
abstract: Trypanosoma cruzi undergoes differentiation in the rectum of triatomine, where increased osmolarity is caused mainly by elevated content of NaCl from urine. Early biochemical events in response to high osmolarity in this parasite have not been totally elucidated. In order to clarify the relationship between these events and developmental stages of T. cruzi, epimastigotes were subjected to hyperosmotic stress, which caused activation of Na(+)/H(+) exchanger from acidic vacuoles and accumulation of inositol trisphosphate (InsP(3)). Suppression of InsP(3) levels was observed in presence of intracellular Ca(2+) chelator or pre-treatment with 5-(N-ethyl-N-isopropyl)-amiloride (EIPA), which also inhibited the alkalinization of acidic vacuoles via a Na(+)/H(+) exchanger and the consequent increase in cytosolic calcium. These effects were activated and inhibited by PMA and Chelerythrine respectively, suggesting regulation by protein kinase C. The T. cruzi Na(+)/H(+) exchanger, TcNHE1, has 11 transmembrane domains and is localized in acidic vacuoles of epimastigotes. The analyzed biochemical changes were correlated with morphological changes, including an increase in the size of acidocalcisomes and subsequent differentiation to an intermediate form. Both processes were delayed when TcNHE1 was inhibited by EIPA, suggesting that these early biochemical events allow the parasite to adapt to conditions faced in the rectum of the insect vector.
authors.affiliation: Química biológica, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, 5800 Río Cuarto, Córdoba, Argentina.
authors.forename: Sergio
authors.initials: S
authors.lastname: Bonansea
authors.forename: Melina
authors.initials: M
authors.lastname: Usorach
authors.forename: María Celeste
authors.initials: MC
authors.lastname: Gesumaría
authors.forename: Verónica
authors.initials: V
authors.lastname: Santander
authors.forename: Alba Marina
authors.initials: AM
authors.lastname: Gimenez
authors.forename: Mariana
authors.initials: M
authors.lastname: Bollo
authors.forename: Estela E
authors.initials: EE
authors.lastname: Machado
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D014355:Chagas Disease / Q000469:parasitology*; D004789:Enzyme Activation; D006801:Humans; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D015800:Protozoan Proteins / Q000032:analysis / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000032:analysis / Q000378:metabolism*; D014349:Trypanosoma cruzi / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: D015800:Protozoan Proteins; D017923:Sodium-Hydrogen Exchangers; D010738:Type C Phospholipases; D002118:Calcium