Developing an in vitro model of haemorrhagic shock to investigate the molecular mechanism of valproic acid in the treatment of massive blood loss

Haemorrhagic shock is a lethal condition caused by massive blood loss. Recent investigations in animal models have found that valproic acid (VPA), a well-established and widely used treatment for bipolar disorder and epilepsy, provides acute protection against haemorrhagic shock-induced mortality. Under these conditions, VPA prevents a decrease in glycogen synthase kinase 3β (GSK3β) Ser9 phosphorylation, an effect suggested to relate to histone deacetylase (HDAC) inhibition.

Here, the molecular signalling events during haemorrhagic shock-like conditions were investigated using a human liver cell line (Huh7). Cells exposed to hypoxia, hypercapnia, and hypothermia mimic the signalling changes seen in haemorrhagic shock, showing reduced GSK3β Ser9 phosphorylation. This in vitro reduction is blocked by VPA at physiologically relevant concentrations as it is in vivo. VPA treatment also prevents apoptotic signalling, improving cell survival in this model.

VPA-related compounds which are known activators of the peroxisome proliferator-activated receptor γ (PPARγ) were found to reproduce its protective effect independently of their HDAC inhibitory activity. PPARγ inhibition blocks this protection, demonstrating that PPARγ activity is essential for the therapeutic action of VPA in this model. This work therefore establishes an in vitro model for haemorrhagic shock signalling, identifies PPARγ regulation as a new molecular target in haemorrhagic shock, and provides novel candidate compounds for the development of life-saving treatment.