TY - JOUR
T1 - Influence of immunologic activation and cellular fatty acid levels on the catabolism of platelet-activating factor within the murine mast cell (PT-18)
AU - Triggiani, Massimo
AU - Chilton, Floyd H.
N1 - Funding Information:
lent technical assistanced uring this project, and to Madeline Mattheu and Bonnie Hebdcn for excellent secretarial assistance in the preparation of this manuscriptI.n addition,t he authorsw ould i~ket o thank Dr. B.J. Undem, Dr. G.K. Adams III and Dr. R.P. Schleimerf or their helpful commentsd uring t~s pro-jeer. This work wass upportedi n part by NIH Grants AI24985 and A126771a nd by an award of the American Lung Association( Dr. Chilton~.M .T. is the recipient of a Fogarty International Fellowship Research Award (NIH, Bethesda).
PY - 1989/11/6
Y1 - 1989/11/6
N2 - The present study has examined the catabolism of 1-O-[3H]hexadecyl-2-acetyl-GPC (C16-PAF) and of 1-O-octadecyl-acetyl-GPC (C18-PAF) in spleen-derived PT-18 murine mast cells (mast cells). Mast cells catabolized exogenous PAF into two inactive metabolites, 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine (lysoPAF) and 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine(1-O-alkyl-2-acyl-GPC). The rate of conversion of C16-PAF to metabolites was more rapid than that of C18-PAF. Analysis of the acyl composition of 1-O-alkyl-2-acyl-GPC formed during the metabolism of PAF revealed that arachidonic acid (20:4) was the major fatty acyl chain incorporated at the sn-2 position. However, 25% of newly formed 1-O-alkyl-2-acyl-GPC was reacylated with docosahexaenoic acid (22:6). The influence of cellular fatty acid content on PAF catabolism was further explored in mast cells in which the ratio of fatty acids within cellular phosphoglycerides had been altered by supplementing the cells with various fatty acids in culture. Mast cells supplemented with 20:4 or 22:6 converted PAF to 1-O-alkyl-2-acyl-GPC at a significantly higher rate than non-supplemented cells. In contrast, cells supplemented with linoleic acid (18:2) metabolized PAF at rates similar to non-supplemented cells. Analysis of the acyl composition of 1-O-alkyl-2-acyl-GPC derived from the metabolism of PAF in 20:4-supplemented cells indicated that 20:4 was incorporated exclusively into the sn-2 position. Conversely, 22:6-supplemented cells incorporated predominantly 22:6 at the sn-2 position of 1-alkyl-2-lyso-GPC. Supplementation with 18:2 had no effect on the acylation pattern seen in newly formed 1-O-alkyl-2-acyl-GPC. Activation of passively sensitized mast cells with antigen or with ionophore A23187 significantly enhanced the rate of catabolism of exogenously-provided PAF but had no effect on the acylation pattern of 1-O-alkyl-2-acyl-GPC. Experiments performed with the soluble fraction of the cells showed that acetyl hydrolase activity was increased in mast cells stimulated with antigen. In addition, supernatant fluids from antigen or ionophore-treated mast cells converted PAF to lysoPAF, suggesting that acetyl hydrolase activity was released during cell activation. These data indicate that the ability of mast cells to catabolize PAF to inactive metabolites is influenced by cell activation and by the cellular levels of certain fatty acids.
AB - The present study has examined the catabolism of 1-O-[3H]hexadecyl-2-acetyl-GPC (C16-PAF) and of 1-O-octadecyl-acetyl-GPC (C18-PAF) in spleen-derived PT-18 murine mast cells (mast cells). Mast cells catabolized exogenous PAF into two inactive metabolites, 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine (lysoPAF) and 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine(1-O-alkyl-2-acyl-GPC). The rate of conversion of C16-PAF to metabolites was more rapid than that of C18-PAF. Analysis of the acyl composition of 1-O-alkyl-2-acyl-GPC formed during the metabolism of PAF revealed that arachidonic acid (20:4) was the major fatty acyl chain incorporated at the sn-2 position. However, 25% of newly formed 1-O-alkyl-2-acyl-GPC was reacylated with docosahexaenoic acid (22:6). The influence of cellular fatty acid content on PAF catabolism was further explored in mast cells in which the ratio of fatty acids within cellular phosphoglycerides had been altered by supplementing the cells with various fatty acids in culture. Mast cells supplemented with 20:4 or 22:6 converted PAF to 1-O-alkyl-2-acyl-GPC at a significantly higher rate than non-supplemented cells. In contrast, cells supplemented with linoleic acid (18:2) metabolized PAF at rates similar to non-supplemented cells. Analysis of the acyl composition of 1-O-alkyl-2-acyl-GPC derived from the metabolism of PAF in 20:4-supplemented cells indicated that 20:4 was incorporated exclusively into the sn-2 position. Conversely, 22:6-supplemented cells incorporated predominantly 22:6 at the sn-2 position of 1-alkyl-2-lyso-GPC. Supplementation with 18:2 had no effect on the acylation pattern seen in newly formed 1-O-alkyl-2-acyl-GPC. Activation of passively sensitized mast cells with antigen or with ionophore A23187 significantly enhanced the rate of catabolism of exogenously-provided PAF but had no effect on the acylation pattern of 1-O-alkyl-2-acyl-GPC. Experiments performed with the soluble fraction of the cells showed that acetyl hydrolase activity was increased in mast cells stimulated with antigen. In addition, supernatant fluids from antigen or ionophore-treated mast cells converted PAF to lysoPAF, suggesting that acetyl hydrolase activity was released during cell activation. These data indicate that the ability of mast cells to catabolize PAF to inactive metabolites is influenced by cell activation and by the cellular levels of certain fatty acids.
KW - Acetyl hydrolase
KW - Mast cell
KW - Platelet activating factor
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U2 - 10.1016/0005-2760(89)90321-4
DO - 10.1016/0005-2760(89)90321-4
M3 - Article
C2 - 2572273
AN - SCOPUS:0024385112
SN - 0005-2760
VL - 1006
SP - 41
EP - 51
JO - Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
JF - Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
IS - 1
ER -