Bioactive products generated by group V sPLA(2) hydrolysis of LDL activate macrophages to secrete pro-inflammatory cytokines.
OBJECTIVE
Previous studies have established that hydrolysis of LDL by Group V secretory phospholipase A(2) (GV sPLA(2)) generates a modified particle capable of inducing macrophage foam cell formation. The aim of the present study was to determine whether GV sPLA(2)-hydrolyzed LDL (GV-LDL) produces pro-atherogenic effects in macrophages independent of cholesterol accumulation.


RESULTS
J-774 cells incubated with GV-LDL produced more TNF-alpha and IL-6 compared to cells incubated with control-LDL. Indirect immunofluorescence showed that GV-LDL but not control-LDL induced nuclear translocation of NFkappaB. Inhibitors of NFkappaB activation, effectively blocked cytokine production induced by GV-LDL. Control-LDL and GV-LDL were separated from albumin present in reaction mixtures by ultracentrifugation. The albumin fraction derived from GV-LDL contained 80% of the FFA generated and was more potent than the re-isolated GV-LDL in inducing pro-inflammatory cytokine secretion. Linoleic acid (18:2) and oleic acid (18:1) were the most abundant FFAs generated, whereas newly formed lyso-PCs contained 14:0 (myristic), 16:1 (palmitic), and 18:2 fatty acyl groups. Experiments with synthetic FFA showed that 18:1 induced J-774 cells to secrete TNF-alpha and IL-6.


CONCLUSIONS
These results indicate that in addition to promoting atherosclerotic lipid accumulation in macrophages, GV sPLA(2) hydrolysis of LDL leads to activation of NFkappaB, a key regulator of inflammation.
Department of Internal Medicine Endocrinology Division, University of Kentucky, Lexington, 40536, USA. bbboya2@uky.edu
Boris B
BB
Boyanovsky
Xia
X
Li
Preetha
P
Shridas
Manjula
M
Sunkara
Andrew J
AJ
Morris
Nancy R
NR
Webb
D000418:Albumins / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D008078:Cholesterol, LDL / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D054505:Group V Phospholipases A2 / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D018836:Inflammation Mediators / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism*; D008066:Lipolysis; D008262:Macrophage Activation; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D011485:Protein Binding; D021381:Protein Transport; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D000418:Albumins; D008078:Cholesterol, LDL; D005227:Fatty Acids; D018836:Inflammation Mediators; D015850:Interleukin-6; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D054505:Group V Phospholipases A2