Authors :
Peravina Thergarajan, PhD – Monash University
Margaret L. Hibbs, PhD – Monash University
Terence J. O'Brien, MBBS, MD – Alfred Health
Nigel Jones, Professor – Monash University
Evelyn Tsantikos, PhD – Monash University
Presenting Author: Idrish Ali, PhD – Monash University
Rationale:
Neuroinflammation plays a critical role in the pathogenesis of epilepsy. In addition to brain resident glia, such as microglia, peripheral immune cells can also influence epilepsy outcomes. Granulocyte-colony-stimulating factor (G-CSF), which regulates the development, survival and activation of peripheral myeloid cells, can promote chronic inflammatory diseases as well as regulate neuroinflammation. Here, we tested whether G-CSF deficiency influenced susceptibility to status epilepticus (SE) in a mouse model of temporal lobe epilepsy.
Methods:
G-CSF-deficient (n=21) and wild-type control mice (n=22) were subjected to surgical implantation of a bipolar electrode in the ventral hippocampus and three subdural electrodes as active, reference and ground. Self-sustained SE was induced after 1-week, comprising a 90 min stimulation with 100 ms trains of 50 Hz stimulations at the after-discharge threshold (ADT), or sham stimulations. The animals developed SE within this period, which was allowed to continue for another 150 minutes, when a diazepam injection (5 mg/kg i.p.) was administered to terminate the SE. The ADT, and the severity of the SE i.e. the number of convulsive seizures during the SE period, were compared between groups. Animals were euthanised 1-week after SE, and the hippocampus was dissected for qPCR-based evaluation of neuroinflammatory genes.
Results: Analysis of the ADT using a Mann-Whitney test, revealed that a significantly higher (p=0.01) ADT was required to induce a hippocampal seizure in G-CSF-deficient mice. G-CSF deficient mice exhibited less severe SE i.e. they displayed significantly (p=0.01) fewer convulsive seizures, when compared to wild type mice. Contingency analysis showed no difference in mortality between the G-CSF deficient (n=3/15) vs wild-type controls (n=4/13). SE led to significantly increased levels of several neuroinflammatory genes such as IL-1β, IL-1α, CD86, TNFα, TREM2 and CD45, but these did not differ by genotype.
Conclusions:
Our results show that G-CSF deficiency reduced susceptibility to SE development and resulted in a less severe SE phenotype and may represent a novel anti-seizure strategy. The follow up neuroinflammatory reaction was unaltered by the G-CSF phenotype. Future investigations are needed to establish whether the observed anti-seizure effects are due to developmental compensation of G-CSF deficiency or acute loss in G-CSF signalling.
Funding:
This study was funded by the GIN Discovery Program at Monash University, awarded to I. Ali & E. Tsantikos, and a NHMRC Investigator Grant to T.J. O’Brien.