Leptin-mediated reactive oxygen species production does not significantly affect primary mouse hepatocyte functions in vitro.
OBJECTIVE
Direct and indirect effects of leptin on hepatic stellate cells (HSCs) have been documented in the literature, whereas little is known about leptin's actions on hepatocytes. Leptin mediates its profibrogenic and proinflammatory effects on HSCs in part through the production of intracellular reactive oxygen species (ROS). In this study, we focus our analysis on leptin-induced ROS production in hepatocytes.


METHODS
The expression of leptin receptor isoforms on primary mouse liver cells was examined by real-time quantitative-PCR and western blotting. Cultures were exposed to leptin in combination with inhibitors for reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, MAP kinase/ERK kinase 1 (MEK1) or janus kinase 2 (JAK2). ROS levels were quantified by measuring fluorescence. The effects of leptin on hepatocyte functions and programmed cell death were evaluated by fluorescent or luminescent assays.


RESULTS
Leptin induced ROS production in primary hepatocytes by 150-450%, compared with a 20-30% increase in HSCs and liver sinusoidal endothelial cells (LSECs). This ROS production could be inhibited by NADPH oxidase, MEK1 and JAK2 inhibitors. Western blotting indicated that mouse HSCs and LSECs mainly express short leptin receptor isoforms, whereas hepatocytes appeared to express both short and long isoform(s). Leptin-induced ROS production in db/db hepatocytes did not differ from wild-type mice. Finally, leptin had no negative influence on primary hepatocyte functions.


CONCLUSIONS
Leptin induced higher ROS levels in primary hepatocytes than in LSECs and HSCs, depending on NADPH oxidase, MEK1 and JAK2 signalling but not on the long leptin receptor isoform. Furthermore, leptin exposure did not influence primary hepatocyte functionality negatively.
Liver Cell Biology Lab, Department of Cell Biology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium.
Ben
B
Schroyen
Eduardo L
EL
Guimarães
Laurent
L
Dollé
Stephanie
S
Coulon
Christophe
C
Empsen
Marc
M
Nyssen
Anja
A
Geerts
Isabelle
I
Colle
Albert
A
Geerts
Leo A
LA
van Grunsven
D000418:Albumins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002478:Cells, Cultured; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020738:Leptin / Q000378:metabolism*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D054411:Receptors, Leptin / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors; D014508:Urea / Q000378:metabolism
D000418:Albumins; D004791:Enzyme Inhibitors; D020738:Leptin; D008565:Membrane Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D054411:Receptors, Leptin; C515447:leptin receptor, mouse; D014508:Urea; D019388:Cytochrome P-450 CYP1A2; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D019255:NADPH Oxidases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse