RESUMO
Lipids affect the membrane properties determining essential biological processes. Earlier studies have suggested a role of switch-activated protein 70 (SWAP-70) in lipid raft formation of dendritic cells. We used lipidomics combined with genetic and biochemical assays to analyze the role of SWAP-70 in lipid dynamics. TLR activation using LPS as a ligand represented a pathogenic immunogenic stimulus, physical disruption of cell-cell contacts a tolerogenic stimulus. Physical disruption, but not LPS, caused an increase of phosphatidylcholine ether and cholesteryl esters in CD11c+ immune cells. An increase of ceramide (Cer) was a hallmark for LPS activation. SWAP-70 was required for regulating the increase and localization of Cers in the cell membrane. SWAP-70 controls Cer accumulation through the regulation of pH-dependent acid-sphingomyelinase activity and of RhoA-dependent transport of endosomal contents to the plasma membrane. Poor accumulation of Cers in Swap70-/- cells caused decreased apoptosis. This shows that two different pathways of activation, immunogenic and tolerogenic, induce different changes in the lipid composition of cultured CD11c+ cells, and highlights the important role of SWAP-70 in Cer dynamics in dendritic cells.
Assuntos
Antígeno CD11c/imunologia , Ceramidas/metabolismo , Proteínas de Ligação a DNA/metabolismo , Células Dendríticas/imunologia , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Tolerância Imunológica , Lipídeos/imunologia , Antígenos de Histocompatibilidade Menor/metabolismo , Proteínas Nucleares/metabolismo , Animais , Apoptose , Linhagem Celular , Células Cultivadas , Ceramidas/imunologia , Ésteres do Colesterol/genética , Ésteres do Colesterol/imunologia , Meios de Cultura/química , Citocinas/biossíntese , Citocinas/imunologia , Proteínas de Ligação a DNA/genética , Células Dendríticas/efeitos dos fármacos , Células Dendríticas/metabolismo , Fatores de Troca do Nucleotídeo Guanina/genética , Lipídeos/análise , Lipopolissacarídeos/imunologia , Camundongos , Antígenos de Histocompatibilidade Menor/genética , Proteínas Nucleares/genética , Esfingomielina Fosfodiesterase/metabolismoRESUMO
BACKGROUND AND AIM OF WORK: The aim of the present study was to determine the TNFalpha release of cultured alveolar macrophages (AM) and the bronchoalveolar lavage (BAL) cellular profile in 35 patients suffering from long lasting sarcoidosis. METHODS: The AM TNFalpha release and the BAL cellular profile of 35 patients with a mean duration of sarcoidosis of 10.4 +/- 1.3 years at the time of BAL was compared to 35 healthy controls. RESULTS: The BAL profile of 12 sarcoid patients with a stable disease was similar to that known from acute sarcoidosis. Sarcoid patients with progressive disease (n = 12) and sarcoid patients with corticosteroid resistant disease (n = 11) were characterised by a normal CD4/CD8 ratio and a significant increase of BAL neutrophils (2.7 +/- 1.0% and 3.8 +/- 1.1%, respectively). The AM TNFalpha release of sarcoid patients with stable disease did not differ significantly from controls (523 +/- 124 pg/ml vs. 410 +/- 104 pg/ml). In contrast, we observed a significantly elevated TNFalpha release in sarcoid patients with progressive (2,124 +/- 550 pg/ml; p < 0.01) as well as in those with a corticosteroid resistant disease (1,585 +/- 520 pg/ml; p < 0.01) compared to controls. CONCLUSION: Chronic sarcoid patients in a progressive phase of the disease and those with a corticosteroid resistant disease are characterised by a significantly increased TNFalpha release of cultured AM. Our results support the usage of chimeric anti-TNFalpha antibodies as an alternative therapeutic regimen in chronic corticosteroid resistant sarcoidosis.