Valproic acid protects against haemorrhagic shock-induced signalling changes via PPARγ activation in an in vitro model.
OBJECTIVE
Valproic acid (VPA), a widely used epilepsy and bipolar disorder treatment, provides acute protection against haemorrhagic shock-induced mortality in a range of in vivo models through an unknown mechanism. In the liver, this effect occurs with a concomitant protection against a decrease in GSK3β-Ser(9) phosphorylation. Here, we developed an in vitro model to investigate this protective effect of VPA and define a molecular mechanism.


METHODS
The human hepatocarcinoma cell line (Huh7) was exposed to conditions occurring during haemorrhagic shock (hypoxia, hypercapnia and hypothermia) to investigate the changes in GSK3β-Ser(9) phosphorylation for a 4 h period following treatment with VPA, related congeners, PPAR agonists, antagonists and siRNA.


RESULTS
Huh7 cells undergoing combined hypoxia, hypercapnia, and hypothermia reproduced the reduced GSK3β-Ser(9) phosphorylation shown in vivo during haemorrhagic shock, and this change was blocked by VPA. The protective effect occurred through upstream PTEN and Akt signalling, and prevented downstream β-catenin degradation while increasing histone 2/3 acetylation. This effect was reproduced by several VPA-related compounds with known PPARγ agonist activity, independent of histone deacetylase (HDAC) inhibitory activity. Specific pharmacological inhibition (by T0070907) or knockdown of PPARγ blocked the protective effect of VPA against these signalling changes and apoptosis. In addition, specific activation of PPARγ using ciglitazone reproduced the changes induced by VPA in haemorrhagic shock-like conditions.


CONCLUSIONS
Changes in GSK3β-Ser(9) phosphorylation in in vivo haemorrhagic shock models can be modelled in vitro, and this has identified a role for PPARγ activation in the protective role of VPA.
Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK.
Alexandra M E
AM
Zuckermann
School of Veterinary Medicine, University of Surrey, Guildford Surrey, GU2 7XH, UK.
Roberto M
RM
La Ragione
Institute for Infection and Immunity, St George's University of London, London, SW17 0RE, UK.
Deborah L
DL
Baines
Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK.
Robin S B
RS
Williams
D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D006935:Hypercapnia / Q000378:metabolism; D007035:Hypothermia / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D047495:PPAR gamma / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D020011:Protective Agents / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000235:genetics; D012771:Shock, Hemorrhagic / Q000378:metabolism*; D015398:Signal Transduction; D014635:Valproic Acid / Q000494:pharmacology*
D047495:PPAR gamma; D020011:Protective Agents; D034741:RNA, Small Interfering; D014635:Valproic Acid; D007770:L-Lactate Dehydrogenase; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3