Background: Neuroinflammation plays an important role in the pathogenesis of various neurodegenerative
diseases including Alzheimer’s disease (AD). Suppressor of cytokine signaling 3 (SOCS3) is an anti-inflammatory
molecule that suppresses cytokine signaling and inflammatory gene expression in different cells including microglia.
Objective: The pathways through which SOCS3 could be upregulated are poorly described. Cinnamic acid is a metabolite
of cinnamon, a natural compound that is being widely used all over the world as a spice or flavoring agent.
Here, we examined if cinnamic acid could upregulate SOCS3 in microglia.
Method: Microglia and astroglia isolated from mouse brain as well as BV-2 microglial cells were treated with cinnamic
acid followed by monitoring the level of SOCS3 and different proinflammatory molecules by RT-PCR and
real-time PCR. To nail down the mechanism, we also performed ChIP analysis to monitore the recruitment of cAMP
response element binding (CREB) to the socs3 gene promoter and carried out siRNA knockdown of CREB.
Results: Cinnamic acid upregulated the expression of SOCS3 mRNA and protein in mouse BV-2 microglial cells in
dose- and time-dependent manner. Accordingly, cinnamic acid also increased the level of SOCS3 and suppressed the
expression of inducible nitric oxide synthase and proinflammatory cytokines (TNFα, IL-1β and IL-6) in LPSstimulated
BV-2 microglial cells. Similar to BV-2 microglial cells, cinnamic acid also increased the expression of
SOCS3 in primary mouse microglia and astrocytes. We have seen that cAMP response element is present in the promoter
of socs3 gene, that cinnamic acid induces the activation of CREB, that siRNA knockdown of CREB abrogates
cinnamic acid-mediated upregulation of SOCS3, and that cinnamic acid treatment leads to the recruitment of CREB
to the socs3 gene.
Conclusions: These studies suggest that cinnamic acid upregulates the expression of SOCS3 in glial cells via CREB
pathway, which may be of importance in neuroinflammatory and neurodegenerative disorders.