Secretory PLA2 inhibitor indoxam suppresses LDL modification and associated inflammatory responses in TNFalpha-stimulated human endothelial cells.
OBJECTIVE
Secretory phospholipase A2 (sPLA2) is implicated in atherosclerosis, although the effects of specific sPLA2 inhibitors have not been studied. We investigated the effects of the indole analogue indoxam on low-density lipoprotein (LDL) modification by sPLA2 enzymes of different types and on the associated inflammatory responses in human umbilical vein endothelial cells (HUVEC).


METHODS
LDL modification was assessed by measuring the contents of two major molecular species of lysophosphatidylcholine (LPC) using electrospray ionization-liquid chromatography/mass spectrometry. The proinflammatory activity of the modified LDL was evaluated by determining monocyte chemoattractant protein-1 (MCP-1) mRNA expression and transcriptional factor nuclear factor-kappaB (NF-kappaB) activity in HUVEC.


RESULTS
Indoxam dose-dependently inhibited palmitoyl- and stearoyl-LPC production in LDL incubated with snake venom sPLA2 (IC50 1.2 microM for palmitoyl-LPC, 0.8 microM for stearoyl-LPC). MCP-1 mRNA expression and NF-kappaB activity were enhanced by venom sPLA2-treated LDL, which was completely suppressed by indoxam but not by thioetheramide-PC, a competitive sPLA2 inhibitor. Indoxam also suppressed LPC production in LDL treated with human synovial type IIA sPLA2. Tumour necrosis factor alpha (TNFalpha) increased type V sPLA2 expression in HUVEC. Indoxam dose-dependently suppressed LPC production in native and glycoxidized LDL treated with TNFalpha-stimulated HUVEC. Indoxam suppressed MCP-1 mRNA expression and NF-kappaB activity in TNFalpha-stimulated HUVEC incubated with native or glycoxidized LDL.


CONCLUSIONS
Indoxam prevented sPLA2-induced LPC production in native and glycoxidized LDL as well as LDL-induced inflammatory activity in HUVEC. Our results suggest that indoxam may be a potentially useful anti-atherogenic agent.
Sonoki
K
K
Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Iwase
M
M
Sasaki
N
N
Ohdo
S
S
Higuchi
S
S
Takata
Y
Y
Iida
M
M
D002219:Carbamates / Q000008:administration & dosage / Q000494:pharmacology*; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007212:Indolizines / Q000008:administration & dosage / Q000494:pharmacology*; D008077:Lipoproteins, LDL / Q000187:drug effects / Q000378:metabolism; D008244:Lysophosphatidylcholines / Q000378:metabolism; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism; D064801:Phospholipase A2 Inhibitors; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects* / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology / Q000378:metabolism
D002219:Carbamates; D018932:Chemokine CCL2; D004791:Enzyme Inhibitors; D007212:Indolizines; D008077:Lipoproteins, LDL; D008244:Lysophosphatidylcholines; D016328:NF-kappa B; D064801:Phospholipase A2 Inhibitors; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; C119389:indoxam