Nitric oxide mediates down regulation of lipoprotein lipase activity induced by tumor necrosis factor-alpha in brown adipocytes.
We previously reported that tumor necrosis factor-alpha (TNF-alpha)/cachectin suppresses lipoprotein lipase activity and its gene expression in brown adipocytes differentiated in culture. Recent evidence suggests that the effect of TNF-alpha over various cells is related to the enhanced production of nitric oxide (NO). The present study examined whether the suppressive effect of TNF-alpha on lipoprotein lipase activity is mediated by production of NO in the brown adipocytes. A reverse transcription-polymerase chain reaction (RT-PCR) assay revealed that TNF-alpha caused a concentration- and time-dependent expression of inducible NO synthase in brown adipocytes. Increasing concentrations of TNF-alpha (0.5-50 ng/ml) for 24 h resulted in a concentration-dependent decrease in lipoprotein lipase activity with reciprocal increase in nitrite production in the medium. The suppressive effect of TNF-alpha on lipoprotein lipase activity was significantly prevented by NO synthase inhibitors, NG-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine, but not by D-NAME, an inactive isomer. Furthermore, 8-bromoguanosine 3',5'-cyclic monophosphate, cell permeant cGMP, suppressed lipoprotein lipase activity and 1 H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one, a selective inhibitor for soluble guanylate cyclase, restored the TNF-alpha-suppressed lipoprotein lipase activity. These results suggest that TNF-alpha stimulates brown adipocytes to express inducible NO synthase, followed by production of NO, which in turn mediates the suppressive effect of TNF-alpha on lipoprotein lipase activity. The effect of NO is mediated, at least partly, through production of cGMP.
Uchida
Y
Y
Department of Pharmacology, Tokyo Women's Medical College, Japan. uchiy@research.twmc.ac.jp
Tsukahara
F
F
Ohba
K
K
Ogawa
A
A
Irie
K
K
Fujii
E
E
Yoshimoto
T
T
Yoshioka
T
T
Muraki
T
T
D017667:Adipocytes / Q000201:enzymology*; D002001:Adipose Tissue, Brown / Q000166:cytology / Q000201:enzymology*; D000818:Animals; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000096:biosynthesis; D015536:Down-Regulation; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000235:genetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D012995:Solubility; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology*
D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D008071:Lipoprotein Lipase; D006162:Guanylate Cyclase; D006152:Cyclic GMP