Inhibiting HIF-1α Decreases Expression of TNF-α and Caspase-3 in Specific Brain Regions Exposed Kainic Acid-Induced Status Epilepticus

Abstract

Background/Aims: A recent study demonstrates that pro-inflammatory cytokines (PICs, i.e., IL-1β, IL-6 and TNF-α) in specific brain regions of rats play a role in regulating kainic acid (KA)-induced status epilepticus (SE) via a GABAergic mechanism. The purposes of this report were to examine contributions of hypoxia inducible factor subtype 1α (HIF-1α) to expression of PICs in these specific brain regions in epileptic rats. Particularly, we investigated the parietal cortex, hippocampus and amygdala. In addition, we further examined expression of Caspase-3 indicating cell apoptosis in those brain regions of epileptic rats after infusing 2-methoxyestradiol (2-MET, inhibitor of HIF-1α) and etanercept (TNF-α receptor antagonist). Methods: ELISA was used to determine the levels of HIF-1α and PICs and western blot analysis was used to examine Caspase-3 expression. Results: Our data show that HIF-1α was significantly increased in the parietal cortex, hippocampus and amygdala 1, 3 and 7 days after induction of SE (P<0.05 vs. control rats). Our results also show that inhibiting HIF-1α by central infusion of 2-MET significantly decreased the amplified TNF-α expression in these brain regions evoked by SE (P<0.05 vs. vehicle control), but did not modify IL-1β and IL-6. Our results demonstrate that 2-MET and etanercept attenuated an increase in Caspase-3 evoked by SE. Conclusion: Overall, we suggest that HIF-1α activated by SE is likely to contribute to epileptic activity via a TNF-α pathway, which has pharmacological implications to target specific HIF-1α and TNF-α pathways for neuronal dysfunction and vulnerability related to epilepsy.