Research Paper
Subject Category: Cardiovascular and pulmonary pharmacology
British Journal of Pharmacology (2008) 153, 1399–1408; doi:10.1038/bjp.2008.12; published online 11 February 2008
Secretory PLA2 inhibitor indoxam suppresses LDL modification and associated inflammatory responses in TNF
-stimulated human endothelial cells
K Sonoki1, M Iwase1, N Sasaki1, S Ohdo2, S Higuchi2, Y Takata3 and M Iida1
- 1Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
- 2Department of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
- 3Division of General Internal Medicine, Department of Health Promotion, Science of Health Improvement, Kyushu Dental College, Kitakyushu, Japan
Correspondence: Dr M Iwase, Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812-8582, Japan. E-mail: iwase@intmed2.med.kyushu-u.ac.jp
Received 2 November 2007; Accepted 12 December 2007; Published online 11 February 2008.
Abstract
Background and purpose:
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).
Experimental approach:
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-
B) activity in HUVEC.
Key results:
Indoxam dose-dependently inhibited palmitoyl- and stearoyl-LPC production in LDL incubated with snake venom sPLA2 (IC50 1.2 
M for palmitoyl-LPC, 0.8 M for stearoyl-LPC). MCP-1 mRNA expression and NF-B 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 
(TNF) increased type V sPLA2 expression in HUVEC. Indoxam dose-dependently suppressed LPC production in native and glycoxidized LDL treated with TNF-stimulated HUVEC. Indoxam suppressed MCP-1 mRNA expression and NF-B activity in TNF-stimulated HUVEC incubated with native or glycoxidized LDL.
Conclusions and implications:
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.
Keywords:
secretory phospholipase A2, secretory phospholipase A2 inhibitor, indoxam, lysophosphatidylcholine, atherosclerosis, monocyte chemoattractant protein-1, nuclear factor-B, human umbilical vein endothelial cells, low-density lipoprotein, tumour-necrosis factor
Abbreviations:
GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HUVEC, human umbilical vein endothelial cell; LDL, low-density lipoprotein; LPC, lysophosphatidylcholine; MCP-1, monocyte chemoattractant protein-1; NF-B, nuclear factor-kappa B; PC, phosphatidylcholine; sPLA2, secretory PLA2; TNF, tumour-necrosis factor
