Cyclosporin A induced toxicity in mouse liver slices is only slightly aggravated by Fxr-deficiency and co-occurs with upregulation of pro-inflammatory genes and downregulation of genes involved in mitochondrial functions.
BACKGROUND
The transcription factor farnesoid X receptor (FXR) governs bile acid and energy homeostasis, is involved in inflammation, and has protective functions in the liver. In the present study we investigated the effect of Fxr deficiency in mouse precision cut liver slices (PCLS) exposed to a model hepatotoxicant cyclosporin A (CsA). It was anticipated that Fxr deficiency could aggravate toxicity of CsA in PCLS and pinpoint to novel genes/processes regulated by FXR.


METHODS
To test this hypothesis, PCLS obtained from livers of wild type mice (WT-PCLS) and Fxr-knockout mice (FXRKO-PCLS) were treated with 40 μM CsA for 24 h and 48 h. ATP and histological assays were applied to assess the viability of PCLS. DNA microarrays combined with bioinformatics analysis were used to identify genes and processes that were affected by CsA in WT-PCLS and/or FXRKO-PCLS. In addition, WT-PCLS and FXRKO-PCLS were exposed to the endogenous FXR ligand chenodeoxycholic acid (CDCA) and subjected to q-PCR to determine whether subsets of known FXR-targets and the identified genes were regulated upon FXR activation in an FXR-dependent manner.


RESULTS
No difference in viability was observed between WT-PCLS and FXRKO-PCLS upon CsA treatment. Transcriptomics data analysis revealed that CsA significantly upregulated stress-response and inflammation and significantly downregulated processes involved in lipid and glucose metabolism in WT-PCLS and FXRKO-PCLS. However, only in FXRKO-PCLS, CsA upregulated additional pro-inflammatory genes and downregulated genes related to mitochondrial functions. Furthermore, only in WT-PCLS, CDCA upregulated a subset of known FXR-target genes as well as the regulator of inflammation and mitochondrial functions peroxisome proliferator- activated receptor delta (Ppar delta).


CONCLUSIONS
Although FXR governs energy metabolism, no major differences in response to CsA could be observed between WT-PCLS and FXRKO-PCLS in regulation of processes involved in lipid and glucose metabolism. This finding indicates that CsA does not directly affect FXR functions in relation to the above mentioned processes. However, the more pronounced induction of pro-inflammatory genes and the downregulation of genes involved in mitochondrial functions only in FXRKO-PCLS suggest that FXR deficiency aggravates CsA-induced inflammation and impairs mitochondrial functions. Therefore, FXR can exert its hepatoprotective functions by controlling inflammation and mitochondrial functions, possibly involving an FXR-PPAR delta cross-talk.
RIKILT - Institute of Food Safety/Wageningen UR, Akkermaalsbos 2, P.O. Box 230, 6700 AE, Wageningen, The Netherlands. eszalow@gmail.com.|RIKILT-Institute of Food Safety/Wageningen UR, Akkermaalsbos 2, 6708 WB, Wageningen, The Netherlands. eszalow@gmail.com.
Ewa
E
Szalowska
Centre for Health Protection, National Institute for Public Health and the Environment (GZB, RIVM), Antonie van Leeuwenhoeklaan 9, 3721 MA, Bilthoven, The Netherlands. tessa.pronk@gmail.com.
Tessa E
TE
Pronk
RIKILT - Institute of Food Safety/Wageningen UR, Akkermaalsbos 2, P.O. Box 230, 6700 AE, Wageningen, The Netherlands. ad.peijnenburg@wur.nl.
Ad Acm
AA
Peijnenburg
D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism; D016572:Cyclosporine / Q000633:toxicity*; D004734:Energy Metabolism / Q000235:genetics; D005947:Glucose / Q000378:metabolism; D050356:Lipid Metabolism / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D047494:PPAR delta / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency / Q000235:genetics*; D015533:Transcriptional Activation / Q000235:genetics; D000099150:Receptor, Farnesoid X-Activated
D001647:Bile Acids and Salts; D016572:Cyclosporine; D005947:Glucose; D047494:PPAR delta; D018160:Receptors, Cytoplasmic and Nuclear; D000099150:Receptor, Farnesoid X-Activated