Visit our Expo - Redox and Inflammation signaling 2012

VIII. Inflammation specific signaling Poster VIII, 2
A role for TNF-alpha in VLDL apoB but not lipid secretion modulation in primary rat
hepatocytes under non-promoting triacylglycerol production conditions
Nerea Bartolomé, Lorena Rodríguez, Cristina López, Virginia Martínez, Begoña Ochoa,
María J. Martínez and Yolanda Chico
Department of Physiology, Faculty of Medicine and Dentistry, University of the Basque
Country, P. Box 669, Bilbao, Bizkaia, Spain. ofbbaesn@lg.ehu.es
The cytokine TNF-alpha has been reported to play a pivotal role in the septic inflammatory
response. It is rapidly liberated to bloodstream triggering the production of other cytokines
and initiating the liver acute phase reaction. Hipertriglyceridemia is an early hallmark of
sepsis associated to high levels of VLDL particles, due to both enhanced secretion by the liver
and decreased peripheral clearance, but the time response of hepatocytes and the underlying
mechanisms are not completely understood. The biogenesis of VLDL is a complex and timerequiring
process that depends on lipid availability and the activity of microsomal triglyceride
transfer protein (MTP) for correct apoB lipidation. The aim of this work was to asses in vitro
whether TNF-alpha has a sustained role in VLDL production regulation and the putative
implication of apoB and MTP transcription. Rat primary hepatocytes were cultured in
conditions mimicking the fed situation, with 5, 20 or 100 ng/ml TNF-alpha for 8 or 16 h.
VLDL were isolated from the medium and apoB-48, apoB-100 and lipids were quantified.
Total RNA was extracted from cells and apoB and MTP mRNA levels measured by Northern
blotting. At 8 h, there was an increase of 17%, 22% and 24% in the secretion of VLDL
particles by 5, 20 or 100 ng/ml TNF-alpha-treated hepatocytes, respectively. However, basal
secretion was recorded after 16 h. Cell apoB mRNA content increased by 1.88-, 1.54- and
1.44-fold in cells at 8 h of TNF-alpha treatment with 5, 20 or 100 ng/ml, and 1.43 and 1.38
fold after 16 h of treatment with 20 or 100 ng/ml. The total amount of lipids secreted into
VLDL, as well as the lipid composition of each particle and the MTP transcript levels did not
change significantly with any of the TNF-alpha doses and periods of treatment tested. In
conclusion, this is another finding supporting for a correlation between the hepatocyte level of
apoB mRNA and the secretion of its protein without enhanced lipid secretion vinculated to a
sepsis-promoted cytokine.
Supported by grants G03/015, PE02UN04 and a personal grant to N.B.
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