Infection of neutrophil granulocytes with Leishmania major activates ERK 1/2 and modulates multiple apoptotic pathways to inhibit apoptosis.
Neutrophil granulocytes provide the first line of defense against bacterial, fungal, and parasitic infections. They phagocytose and kill many invading pathogens. Certain pathogenic microorganisms such as the intracellular protozoan parasite Leishmania major (L. major) can survive inside neutrophils. Mature neutrophils have a very short life span due to spontaneous apoptosis. Previously, we have reported that infections with L. major are able to delay spontaneous apoptosis. In the present study, we addressed the underlying mechanisms of regulation of both extrinsic and intrinsic apoptosis. We show that interaction with L. major transiently activates ERK1/2 phosphorylation. Pharmacological inhibition of ERK1/2 phosphorylation reversed the apoptosis delay. Moreover, infection leads to the enhanced and sustainable expression of the anti-apoptotic proteins Bcl-2 and Bfl-1, respectively. As downstream events, the release of cytochrome c from mitochondria and processing of caspase-6 were inhibited. We also confirm that infection with L. major results in reduced FAS expression on the surface of neutrophils. The presented data indicate that infection with L. major affects both intrinsic as well as extrinsic pathways of neutrophil apoptosis. Enhanced life span of host neutrophils enables the parasite to survive within neutrophils.
Institute for Medical Microbiology and Hygiene, University of Lübeck, Lübeck, Germany.
Arup
A
Sarkar
Eresso
E
Aga
Uta
U
Bussmeyer
Asima
A
Bhattacharyya
Sonja
S
Möller
Lars
L
Hellberg
Martina
M
Behnen
Werner
W
Solbach
Tamás
T
Laskay
D017209:Apoptosis; D053178:Caspase 6 / Q000378:metabolism; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D006801:Humans; D018320:Leishmania major / Q000472:pathogenicity*; D020935:MAP Kinase Signaling System / Q000276:immunology*; D008928:Mitochondria / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology* / Q000469:parasitology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D019014:fas Receptor / Q000096:biosynthesis
D019253:Proto-Oncogene Proteins c-bcl-2; D019014:fas Receptor; D045304:Cytochromes c; D053178:Caspase 6