|
LDL ENDOCYTOSIS BY Leishmania chagasi AND Leishmania amazonensis.
*De Cicco, N.; *Ximenes, A.; #Corrêa, J.R.; #Soares, M.J. and *Atella, G.C.
*Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro; #Departamento de Ultraestrutura e Biologia Molecular, Fundação Oswaldo Cruz
Leishmania are the etiological agents of a variety of disease manifestations. Visceral leishmaniasis caused by Leishmania leishmania chagasi and cutaneous leishmaniais caused by Leishmania leishmania amazonensis are serious health problem in tropical and subtropical countries. During the life cycle it alternates between gut vector as an promastigote and macrophage as an intracellular amastigote. Trypanosomatids have incomplete de novo lipids synthesis. Therefore they avidly take up lipids from vertebrate blood stream presumably satisfying their requirements for growth and differentiation.
Low density lipoprotein (LDL) refers to a class and range of lipoprotein particles, varying in their size (18-25 nm in diameter) and contents, which carry cholesterol in the blood and around the body, for use by cells. Generally, LDL transports cholesterol and triglycerides away from cells and tissues that produce more than they use, towards cells and tissues which are taking up cholesterol and triglycerides. The objective of this work is to study the LDL endocytosis by Leishmania.
To examine the LDL endocytosis by L.amazonensis and L.chagasi, cells were incubated in the presence of LDL-I125. After 24h, cells were collected and the radioactivity was determined by gamma counting. The LDL was found associated with cells and endocytosis was significantly inhibited in assay with on excess of LDL, BSA or Transferrin.
To study if LDL endocytosis is lipids raft dependent process, L.chagasi cells were pretreated with MBCD (Methil-b-cyclodextrin) for 60 min and then incubated in the presence of LDL-I125. After 24h, cells were collected and the radioactivity was determined by gamma counting. It was observed that LDL endocytosis was significantly inhibited in cells treated with MBCD, suggesting that, in L. chagasi cells this process is dependent on the presence of lipid raft.
Supported by CNPq, FAPERJ, IFS
|