THE ROLE OF pH AND TEMPERATURE IN THE DEVELOPMENT OF LEISHMANIA PARASITES

Abstract

Protozoans of the genus Leishmania are obligate intracellular parasites that cycle between the midgut of sandflies and the phagolysosomes of mammalian macrophages and therefore are exposed to extreme environmental changes. Recent evidence obtained from in vitro experiments indicate that such environmental changes trigger a developmental program in the parasites. Thus, following heat shock, promastigotes from certain Leishmania species differentiate to amastigotes. Promastigotes also respond to acidification of their environment by changing the expression of a number of genes. However, the combination of both low pH and high temperature induces the transformation of the promastigote to the amastigote in all Leishmania species examined to date. This review discusses the role of pH and heat shock in gene regulation and its contribution to the differentiation processes in Leishmania spp. Cycling between cold-blooded insect vectors and the warm-blooded mammalian host is not unique to Leishmania spp., but typical to most parasitic protozoa. It is therefore likely that the mechanism of stress-induced differentiation is shared by other mammalian parasites.

Sensitivity of Leishmania spp. to Glibenclamide and 4-Aminopiridine: A Tool for the Study of Drug Resistance Development

“…Their complex life cycles, their flexibility and their ability to adapt to diverse environments, where the membrane plays an important role in maintaining the cellular homeostasis, also justify the study of the membrane proteins implicated on structures such as ion channels, pores and membrane transporters (Zilberstein & Shapira 1994). The drug 4-AP has been used extensively for identifying a high variety of voltage-gated K + channels (Castle et al 1989) and GLIB which is a K + ATP channel blocker, has a widespread use to identify K + channels associated with insulin secretion (SchmidAntomarchi et al 1987, Panten et al 1989).…”

Efecto de la temperatura en la transformación de promastigotes en amastigotes de Leishmania amazonensis in vitra

“…El consenso que se desprende de estos ensayos afirma la importancia de estas dos variables en el procesode transformación (13,19).…”

“…Aun cuando los resultados arrojados por este estudio son consistentes con la hipótesis de que la temperatura es una variable necesaria en el proceso de transformación de promastigote a amastigote de Leishmania arnazonensis, no se puede concluir definitivamente que la temperatura es una variable suficiente en este proceso, ya que los ensayos de transformación en modelos axénicos mediante cambio en la temperatura, producen células similares a amastigotes, pero no reunen todas las características de éstos (24-26), y es solamente cuando se introducen otras variables, como pH, que se obtienen mejores resultados en la transformación (7, 13,19,26).…”

Leishmania, the phagosome, and host responses: The journey of a parasite

“…The signals that trigger the differentiation process are not fully understood and are believed to involve a temperature shift and acidification of the parasitophorous vacuole [63]. The effective differentiation into amatigotes has been shown to significantly up-regulate the Th2-associated cytokines while avirulent parasites failed to differentiate into amastigotes and to induce such an immune response [64].…”